Soil Taxonomy

A Basic System of Soil Classification for

Making and Interpreting Soil Surveys

Second Edition, 1999

United States Department of Agriculture

Natural Resources Conservation Service

Soil Taxonomy

A Basic System of Soil Classification for Making

and Interpreting Soil Surveys

Second Edition, 1999

By Soil Survey Staff

United States Department of Agriculture Agriculture Handbook

Natural Resources Conservation Service Number 436
4

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5

Table of Contents

Foreword .................................................................................................................................... 7

Chapter 1: The Soils That We Classify ...................................................................................9

Chapter 2: Soil Taxonomy and Soil Classification ................................................................. 15

Chapter 3: Differentiae for Mineral Soils and Organic Soils ................................................. 19

Chapter 4: Horizons and Characteristics Diagnostic for the Higher Categories ................... 21

Chapter 5: Application of Soil Taxonomy to Soil Surveys .................................................. 115

Chapter 6: The Categories of Soil Taxonomy ...................................................................... 119

Chapter 7: Nomenclature .................................................................................................... 125

Chapter 8: Identification of the Taxonomic Class of a Soil.................................................. 159

Chapter 9: Alfisols .............................................................................................................. 163

Chapter 10: Andisols.............................................................................................................. 271

Chapter 11: Aridisols ............................................................................................................ 329

Chapter 12: Entisols.............................................................................................................. 389

Chapter 13: Gelisols .............................................................................................................. 445

Chapter 14: Histosols ........................................................................................................... 473

Chapter 15: Inceptisols ......................................................................................................... 489

Chapter 16: Mollisols ........................................................................................................... 555

Chapter 17: Oxisols............................................................................................................... 655

Chapter 18: Spodosols ......................................................................................................... 695

Chapter 19: Ultisols .............................................................................................................. 721

Chapter 20: Vertisols............................................................................................................. 783

Chapter 21: Family and Series Differentiae and Names ........................................................ 819

Chapter 22: Soils of the United States .................................................................................. 837

Chapter 23: World Distribution of Orders and Suborders .................................................... 851

Appendix ................................................................................................................................ 857

Index ....................................................................................................................................... 863

Maps of the United States and of the World

7

The second edition of Soil Taxonomy: A Basic System of

Soil Classification for Making and Interpreting Soil Surveys is

the result of the collective experience and contributions of

thousands of pedologists from around the world.

This new edition includes many improvements. Two new

soil orders, Andisols and Gelisols, are added. Low-activity

clays are defined, and taxa are developed. The Aridisol,

Alfisol, Histosol, Inceptisol, Mollisol, Oxisol, Spodosol, and

Vertisol orders are updated. Aquic conditions, episaturation,

and oxyaquic subgroups are defined. Additions and

improvements are made at the family level.

We are indebted to our many colleagues throughout the

world who contributed soil descriptions and data, comments,

suggestions, and criticisms. We are especially grateful to all of

those who organized and hosted workshops and training

sessions. Many pedologists provided input to the International

Committees (ICOM’s), and we are thankful for their

participation. Although we cannot list everyone who offered

assistance, we do want to acknowledge the chairpersons of the

various ICOM’s.

ICOM Chairperson Institute

Low Activity

Clays ................ Frank Moormann............. Univ. of Utrecht

Oxisols ............... Stan Buol ......................... North Carolina

 State Univ.

Andisols ............. Frank Leamy .................... Soil Bureau,

Lower Hutt

Aquic Soils ........ Johan Bouma ................... Agricultural Univ.,

Wageningen

Spodosols ........... Robert Rouke ................... Univ. of Maine

Vertisols ............. Juan Comerma ................. Univ. Centro

Venezuela

Aridisols ............ Ahmed Osman ................. Arab Center for

the Studies of

Arid Zones and

Dry Lands

Soil Families ...... Ben Hajek ........................ Auburn Univ.

Gelisols .............. James Bockheim .............. Univ. of Wisconsin

Although many improvements have been made since

Dr. Guy Smith headed the effort to publish the first edition of

Soil Taxonomy, there are still areas that will require a

concerted effort to improve. The taxonomic system will

continue to evolve as the science matures.

The taxonomic system does not adequately address the

anthropogenic effects on soils. Soils in urban/industrial areas

can be drastically altered by landfills, farming, earth

movement, and heavy metal contamination. Agricultural areas

have undergone erosion, ripping, and land leveling. Drastically

disturbed soils are common in regions where precious metals,

rock aggregate, and fossil fuels have been mined. The

International Committee on Anthropogenic Soils

(ICOMANTH), chaired by Dr. Ray Bryant, is currently

meeting the challenge of developing appropriate taxa for these

unique soils.

Soil moisture regimes and intergrades of soil moisture

regimes need to be better defined. Some of the temperature

regimes need refinement. The International Committee on Soil

Moisture and Temperature Regimes (ICOMMOTR), chaired by

Dr. Ron Paetzold, is gathering data to make needed

improvements.

The system of soil taxonomy currently does not provide for

paleosols formed under remarkably different

paleoenvironments. With age, the properties of soils from

paleo and contemporaneous environments become welded.

Yet, when paleosols are well preserved, they are valuable

proxies of the biological and physiochemical evolution of the

earth. Many paleosols are deeper than the 2 m limit set by the

current system of soil taxonomy. There is now and will

continue to be pressure to observe and classify soils beyond the

2 m limit.

Many pedologists developed proposals, made comments and

suggestions, and reviewed chapters for this second edition.

Because of the concerted effort of many, the author of this

publication is identified as the “Soil Survey Staff.”

We would like to acknowledge those who helped write

chapters or provide data for figures, maps, and tables. They

include Dr. Arnt Bronger, Dr. Hari Eswaran, Dr. Samuel

Indorante, Dr. John Kimble, Henry Mount, Loyal Quandt, Paul

Reich, Sharon Waltman, and Dr. John Witty. Dr. Stanley

Anderson had the arduous task of editing the second edition.

Suzann Meierdierks and Dr. Patricia West provided their able

assistance in the editing and formatting process. Adrian Smith,

Foreword
8

Christopher Roll, and Nathan Kress provided invaluable GIS

expertise. Lastly, Dr. Robert Ahrens coordinated the effort. He

and Robert Engel worked tirelessly during the past few years to

prepare this edition.

Assistance in acquiring photographs for this publication was

provided by the Kentucky Association of Soil Classifiers; the

Washington Society of Professional Soil Scientists; the

University of Nebraska Press and Andrew A. Aandahl; the

Alaska/Yukon Society of Professional Soil Scientists; the

Florida Association of Professional Soil Classifiers; the Society

of Soil Scientists of Southern New England—Massachusetts;

the Kansas Association of Professional Soil Classifiers; the Soil

Classifiers Association of Michigan; the Professional Soil

Classifiers Association of Alabama; the Professional Soil

Scientists Association of Texas; and members of the National

Cooperative Soil Survey.

Horace Smith

Director, Soil Survey Division
9

The word “soil,” like many common words, has severalmeanings. In its traditional meaning, soil is the natural

medium for the growth of land plants, whether or not it has

discernible soil horizons. This meaning is still the common

understanding of the word, and the greatest interest in soil is

centered on this meaning. People consider soil important

because it supports plants that supply food, fibers, drugs, and

other wants of humans and because it filters water and recycles

wastes. Soil covers the earth’s surface as a continuum, except on

bare rock, in areas of perpetual frost or deep water, or on the

bare ice of glaciers. In this sense, soil has a thickness that is

determined by the rooting depth of plants.

About 1870, a new concept of soil was introduced by the

Russian school led by Dokuchaiev (Glinka, 1927). Soils were

conceived to be independent natural bodies, each with a unique

morphology resulting from a unique combination of climate,

living matter, earthy parent materials, relief, and age of

landforms. The morphology of each soil, as expressed by a

vertical section through the differing horizons, reflects the

combined effects of the particular set of genetic factors

responsible for its development.

This was a revolutionary concept. One did not need to

depend wholly on inferences from the underlying rocks, the

climate, or other environmental factors, considered singly or

collectively; rather, the soil scientist could go directly to the soil

itself and see the integrated expression of all these in its

morphology. This concept made it not only possible but also

necessary to consider all soil characteristics collectively, in

terms of a complete, integrated, natural body, rather than

individually. Thus, the effect of any one characteristic or a

difference in any one depends on the others in the combination.

Experience has shown that no useful generalizations about

single characteristics can be made for all soils. Characteristics

are given weight according to the knowledge gained through

research and experience in soil genesis and the responses of soil

to management or manipulation. Both research in genesis and

the responses of soils have vital roles, but they are themselves

one step removed from the taxonomy of the soil, which is based

on combinations of soil characteristics. In short, the new

concept made pedology possible.

The Russian view of soils as independent natural bodies that

have genetic horizons led to a concept of soil as the part of the

earth’s crust that has properties reflecting the effects of local

and regional soil-forming agents. The solum in that concept is

the set of genetic horizons developed by soil-building forces,

but the parent material beneath is nonsoil. This concept has

limitations. If a solum is 1 or 2 m thick, there is little conflict

between the concept of soil as solum and the concept of soil as

the natural medium for the growth of terrestrial plants. If genetic

horizons are thin or absent and unconsolidated parent material

lies at or only a few centimeters below the surface, there is

serious conflict between the concepts. Dokuchaiev realized this

conflict and, despite the lack of horizons, included young

alluvium and peat in his classification of soil.

Soil in this text is a natural body comprised of solids

(minerals and organic matter), liquid, and gases that occurs on

the land surface, occupies space, and is characterized by one or

both of the following: horizons, or layers, that are

distinguishable from the initial material as a result of additions,

losses, transfers, and transformations of energy and matter or

the ability to support rooted plants in a natural environment.

This definition is expanded from the previous version of Soil

Taxonomy to include soils in areas of Antarctica where

pedogenesis occurs but where the climate is too harsh to

support the higher plant forms.

The upper limit of soil is the boundary between soil and air,

shallow water, live plants, or plant materials that have not begun

to decompose. Areas are not considered to have soil if the

surface is permanently covered by water too deep (typically

more than 2.5 m) for the growth of rooted plants. The horizontal

boundaries of soil are areas where the soil grades to deep water,

barren areas, rock, or ice. In some places the separation between

soil and nonsoil is so gradual that clear distinctions cannot be

made.

The lower boundary that separates soil from the nonsoil

underneath is most difficult to define. Soil consists of the

horizons near the earth’s surface that, in contrast to the

underlying parent material, have been altered by the

interactions of climate, relief, and living organisms over time.

Commonly, soil grades at its lower boundary to hard rock or to

earthy materials virtually devoid of animals, roots, or other

marks of biological activity. The lowest depth of biological

activity, however, is difficult to discern and is often gradual.

For purposes of classification, the lower boundary of soil is

arbitrarily set at 200 cm. In soils where either biological

activity or current pedogenic processes extend to depths greater

than 200 cm, the lower limit of the soil for classification

purposes is still 200 cm. In some instances the more weakly

cemented bedrocks (paralithic materials, defined later) have

been described and used to differentiate soil series (series

The Soils That We Classify

CHAPTER 1
10 Soil Taxonomy

control section, defined later), even though the paralithic

materials below a paralithic contact are not considered soil in

the true sense. In areas where soil has thin cemented horizons

that are impermeable to roots, the soil extends as deep as the

deepest cemented horizon, but not below 200 cm. For certain

management goals, layers deeper than the lower boundary of the

soil that is classified (200 cm) must also be described if they

affect the content and movement of water and air or other

interpretative concerns.

In the humid tropics, earthy materials may extend to a depth

of many meters with no obvious changes below the upper 1 or 2

m, except for an occasional stone line. In many wet soils, gleyed

soil material may begin a few centimeters below the surface and,

in some areas, continue down for several meters apparently

unchanged with increasing depth. The latter condition can arise

through the gradual filling of a wet basin in which the A horizon

is gradually added to the surface and becomes gleyed beneath.

Finally, the A horizon rests on a thick mass of gleyed material

that may be relatively uniform. In both of these situations, there

is no alternative but to set the lower limit of soil at the arbitrary

limit of 200 cm.

Soil, as defined in this text, does not need to have discernible

horizons, although the presence or absence of horizons and

their nature are of extreme importance in soil classification.

Plants can be grown under glass in pots filled with earthy

materials, such as peat or sand, or even in water. Under proper

conditions all these media are productive for plants, but they are

nonsoil here in the sense that they cannot be classified in the

same system that is used for the soils of a survey area, county,

or even nation. Plants even grow on trees, but trees are regarded

as nonsoil.

Soil has many properties that fluctuate with the seasons. It

may be alternately cold and warm or dry and moist. Biological

activity is slowed or stopped if the soil becomes too cold or too

dry. The soil receives flushes of organic matter when leaves fall

or grasses die. Soil is not static. The pH, soluble salts, amount of

organic matter and carbon-nitrogen ratio, numbers of microorganisms, soil fauna, temperature, and moisture all change with

the seasons as well as with more extended periods of time. Soil

must be viewed from both the short-term and long-term

perspective.

Buried Soils

A buried soil is covered with a surface mantle of new soil

material that either is 50 cm or more thick or is 30 to 50 cm thick

and has a thickness that equals at least half the total thickness

of the named diagnostic horizons that are preserved in the

buried soil. A surface mantle of new material that does not have

the required thickness for buried soils can be used to establish a

phase of the mantled soil or even another soil series if the mantle

affects the use of the soil.

Any horizons or layers underlying a plaggen epipedon are

considered to be buried.

A surface mantle of new material, as defined here, is largely

unaltered, at least in the lower part. It may have a diagnostic

surface horizon (epipedon) and/or a cambic horizon, but it has

no other diagnostic subsurface horizons, all defined later.

However, there remains a layer 7.5 cm or more thick that fails the

requirements for all diagnostic horizons, as defined later,

overlying a horizon sequence that can be clearly identified as

the solum of a buried soil in at least half of each pedon. The

recognition of a surface mantle should not be based only on

studies of associated soils.

The Pedon, a Unit of Sampling

Few soil properties can be determined from the surface. To

determine the nature of a soil, one must study its horizons, or

layers. This study requires pits or some means of extracting

samples of material from the surface to the base of the soil. The

visible and tactile properties of samples can be studied in the

field. Soil moisture and temperature regimes are studied by

observations of changes over time at points selected to be

representative. Other properties of a soil must be learned by

studies of samples in an appropriate place, usually a laboratory.

In other words, one learns about most of the properties of a soil

by studying samples extracted to represent a sampling unit, not

by study of the whole soil body that is classified. A concept of

what to sample must be developed before soils can be classified

in a manner that meets the needs of the soil survey, and different

concepts might lead to different classifications. The concept

presented in this text is not the only one possible, and, in fact,

its logic has been scrutinized (Holmgren, 1988).

A soil commonly is not uniform in all its properties. Variability

may be due to accidents; events that lack definite order, such as

the development of fractures in a hard rock; variations in

deposits left by running water; or the placement of seeds by

wind or by animals. The influence of the biotic factors tends to

produce many examples of variability in a soil. Burrowing

animals, taprooted plants, falling trees, and plants that collect

different elements do not operate uniformly over large areas. A

filled burrow or a trace left by a taproot can result in holes in

horizons filled by contrasting materials. Salts collected by a

desert shrub remain concentrated below the shrub until it dies.

Shrink-swell and freeze-thaw processes are other factors that

contribute to soil variability.

The transition between two soils that differ in a particular

property or set of properties may be of at least two kinds.

Normally, a given horizon of one soil disappears over

horizontal distance by a gradual weakening of its expression.

However, in some places the horizons become intermittent

either with or without a marked decrease in the strength of

expression. The transitional forms having discontinuous

horizons or horizons that vary greatly in thickness or other

properties are not the rule, but the soils have been troublesome

to classify. One must decide whether the area is one soil in

which a horizon is discontinuous or variable, or two soils.
The Soils That We Classify 11

Trouble cannot be avoided by arbitrarily saying that two soils

are present if a diagnostic property or horizon is present in

some spots and not present in others. Some limit of area must

be set. If one sets no limit, a vertical hole made by a burrowing

animal would be considered “nonsoil.” It would become a soil

when filled or, if a coating were present, the coating would be

considered a soil. This would be absurd. Such a soil could not

support plants, could not have structure, and could not be

sampled for determination of its properties. The view that a

minimum areal limit of “a soil” cannot be set, if carried to the

extreme, leads to other odd conclusions. For example, if

columns or prisms were present, the exteriors of the prisms

would be different soils from the interiors wherever there are

coatings on the exteriors. In a structureless soil, a definition of

the smallest area of “a soil” as equivalent to the size of the

largest ped would have no meaning. No escape from a

minimum limit to the area of “a soil” seems possible. The

concept of the pedon (Gr. pedon, ground; rhymes with head on)

offers a partial solution to this problem and provides a clear

basis for soil descriptions and for the selection of soil samples.

A pedon has the smallest volume for which one should

describe and sample the soil to represent the nature and

arrangement of its horizons and variability in the properties that

are preserved in samples. A pedon is comparable in some ways

to the unit cell of a crystal. It has three dimensions. Its lower

limit is the somewhat vague limit between the soil and “nonsoil”

below. Its lateral dimensions are large enough to represent the

nature of any horizons and variability that may be present. A

horizon may vary in thickness or in composition, or it may be

discontinuous. The minimal horizontal area of a pedon is

arbitrarily set at 1 m2

, but it ranges to 10 m2, depending on the

variability in the soil.

In the usual situation, where all horizons are continuous and

of nearly uniform thickness and composition, the pedon has a

horizontal area of about 1 m2. Photo 1 shows the normal

situation in which horizons are continuous and relatively

Photo 1.—A soil that has continuous horizons, in an area of Wyoming.
12 Soil Taxonomy

uniform in thickness over considerable areas. The mollic

epipedon and calcic horizon extend for hundreds of meters in

areas of this Wyoming landscape. Each pedon includes the

range of variability that is present in a small volume. The pedon

is roughly polygonal. One lateral dimension does not differ

greatly from any other. The size of a pedon can be determined

only by examination of a volume that is appreciably larger than

the pedon.

Where horizons are intermittent or cyclic and recur in linear

intervals of 2 to 7 m (roughly 7 to 23 ft), the pedon includes onehalf the cycle. Thus, each pedon includes the range of variability

that occurs within these small areas, but not necessarily the total

variability included in other similar pedons studied over a large

area. Where the cycle is less than 2 m, the horizontal area of a

pedon is the minimum size, 1 m2.

Depending on the concept of soil and of the pedon, there

could be different classifications of the soils. With the concept

of soil and of the pedon that is outlined here, the pedons of

some soils may include markedly differing sequences of

horizons. The following examples clarify the concept of a pedon

that has intermittent horizons.

Photo 2 illustrates a soil near Brugge, Belgium, in an area that

is covered by eolian sand of Wisconsin (Wurm) age. The plow

layer, 35 cm thick, is very dark brown fine sand or loamy fine

sand. Most sand grains are free of visible coatings. The lower

boundary of the plow layer is abrupt and irregular and shows

many clear spade marks.

The next layer is a discontinuous B horizon that consists of

at least three materials. The first of these is dark brown (7.5YR

3/4, moist) fine sand with nodules. The nodules range from

about 5 to 20 cm in diameter and are firm or friable in the interior

but have a very firm crust about one-half cm thick. The crust has

stronger chroma and redder hue than the interior, suggesting the

segregation of iron. The interiors of the nodules are free of

roots.

The second material is very friable, massive, grayish brown

(10YR 5/2, moist) fine sand that has many fine fibrous roots. It

would normally be considered parent material, the C horizon,

Photo 2.—A sandy soil near Brugge, Belgium.
The Soils That We Classify 13

where it underlies the nodules of the B horizon; however, it

surrounds the nodules and continues down with little change to

a thin layer of buried muck that has been dated by radiocarbon

as Allerod (Two Creeks), about 11,000 years B.P.

The third material is very friable, massive fine sand that is

present in gross, more or less tubular forms as much as 60 cm in

diameter. The sand is similar to the second material in color but

has many weak, fine dark gray and very dark gray lamellae or

fibers that are comparable to those in or below the B horizon of

the sandy soils formed under heath.

The history of this soil has been studied by the staff of the

Institute for Soil Survey, IRSIA, Ghent.1 While under forest,

the soil was brown and had no clearly expressed eluvial or

illuvial horizons. After clearing of the forest and invasion of

the heather (Calluna vulgaris), a dark colored illuvial horizon

that contained amorphous compounds or mixtures of organic

matter, iron, and aluminum (see spodic horizon) formed.

During the 17th and 18th centuries, flax became an important

crop in Flanders, and the linen was woven in the farm homes

1

 Personal communication from R. Tavernier.

Photo 3.—A soil in the Yukon Territory of Canada.

in the winter. To obtain high yields of high-quality flax, large

amounts of manure and chalk were applied to the fields. The

influence of the calcium and nitrogen was to destroy the B

horizon of amorphous materials, first in spots and then

completely. Photo 2 shows that the B horizon has been partly

destroyed. Because discontinuous horizons recur at intervals of

less than 1 m, the pedon has an area of 1 m2.

The processes of either formation or destruction of many

horizons may not operate uniformly and may first produce

intermittent horizons. In places the forces operate with

remarkable uniformity and produce faint but continuous

horizons. Genetically, therefore, the discontinuous horizons can

have significance equivalent to weakly expressed but

continuous horizons.

Many cold soils are subject to physical disturbance as a

result of freezing and thawing. The forces generated through

freezing often produce cyclic or intermittent horizons. Photo 3

shows a soil from the Yukon Territory of Canada. The small

orange squares mark the boundary between permafrost and the

active layer. The organic layer is about 40 cm thick in the lowlying areas and about 20 cm thick in the areas of higher
14

microrelief. This pattern is repeated at linear intervals of about

1 m. The pedon in photo 3 is 1 m2

. Soil taxonomy has taxa at

the subgroup level of Gelisols to deal with the range in

thickness of the organic layers.

Although every pedon can be classified, not every pedon

need be classified. The pedon should represent a segment of the

landscape. Sometimes, pedons that represent a segment of the

landscape are referred to as polypedons. Soil scientists should

try to sample, characterize, and classify representative pedons.

Soil taxonomy provides a means of comparing, describing, and

differentiating these various pedons.

Summary

Since the genesis of a soil may not be understood or may be

disputed, it can be used only as a guide to our thinking in

selecting criteria and forming concepts. Generally, a more or

less arbitrary definition of a pedon serves the purpose of

classification better at this time than a genetic one. For that

reason, the following definition is used: A pedon is a threedimensional body of soil that has lateral dimensions large

enough to include representative variations in the shape and

relation of horizons and in the composition of the soil. Its

horizontal area ranges from 1 to 10 m2, depending on the

nature of the variability in the soil, and its volume varies,

depending on the depth of the soil. Where the cycle of

variations is less than 2 m long and where all horizons are

continuous and of nearly uniform thickness, the pedon has a

horizontal area of approximately 1 m2. Where horizons or

other properties are intermittent or cyclic and recur at linear

intervals of 2 to 7 m, the pedon includes one-half of the cycle.

If horizons are cyclic but recur at intervals of more than 7 m,

the pedon reverts to an area of approximately 1 m2 and more

than one soil is usually represented in each cycle.

Literature Cited

Glinka, K.D. 1927. Dokuchaiev’s Ideas in the Development

of Pedology and Cognate Sciences. 32 p. In Russian Pedology.

Invest. I. Acad. Sci. USSR, Leningrad.

Holmgren, G.G.S. 1988. The Point Representation of Soil.

Soil Sci. Soc. Am. J. 52: 712-716.
15

The primary objective of soil taxonomy is to establishhierarchies of classes that permit us to understand, as

fully as possible, the relationship among soils and between

soils and the factors responsible for their character. A second

objective is to provide a means of communication for the

discipline of soil science. Soil taxonomy was originally

developed to serve the purposes of soil survey. During the last

few decades, it has evolved into a means of communication in

soil science.

Taxonomy is a narrower term than classification.

Classification includes taxonomy, but it also includes the

grouping of soils according to limitations that affect specific

practical purposes, such as the soil limitations affecting the

foundations of buildings. Taxonomy is the part of classification

that is concerned primarily with relationships. Classifications

are contrivances made by humans to suit their purposes. They

are not themselves truths that can be discovered. A perfect

classification would have no drawbacks when used for the

purpose intended. Each distinctly different purpose, to be

served best, demands a different classification.

For the different purposes of the soil survey, classes are

needed that can be grouped or subdivided and regrouped to

permit the largest number and the most precise predictions

possible about responses to management and manipulation.

Consequently, not one but many classifications can be drawn

from the basic taxonomy. Flexibility in the classes of the

taxonomic system is achieved by the use of phases and by the

nomenclature. The phases are used to subdivide taxa according

to the practical needs for the purposes of a particular survey or

interpretation. They are discussed later in this chapter.

Flexibility in the hierarchy permits grouping taxa into

successively smaller numbers as one goes from lower to higher

categories. For some purposes it is useful to group taxa that

have been separated at a higher level in the system. For

example, one might want a group that includes all soils that

are waterlogged for extended periods. For other purposes one

might want a group comprised of all soils that have a B

horizon affected by sodium or of all soils that have a fragipan

or permafrost. Some soils might be in several of these groups,

so that no matter how a single hierarchy is arranged, it is not

possible to have all desired groups. Therefore, no single

hierarchy can best serve all our purposes. The way we attain

flexibility in the hierarchy is explained in the discussion of the

nomenclature.

As knowledge expands, new facts or closer approximations

of truths not only make improvements in classification possible

but also make some changes imperative. Thus, classifications

are not static but require change as knowledge expands.

Since the original edition of Soil Taxonomy was published in

1975, eight international committees have made proposals

that have been approved and incorporated. These committees

include the International Committee on Low Activity Clays

(ICOMLAC), the International Committee on Oxisols

(ICOMOX), the International Committee on Andisols

(ICOMAND), the International Committee on Spodosols

(ICOMOD), the International Committee on Aquic Moisture

Regimes (ICOMAQ), the International Committee on Vertisols

(ICOMERT), the International Committee on Aridisols

(ICOMID), the International Committee on Families

(ICOMFAM), and the International Committee on PermafrostAffected Soils (ICOMPAS).

Taxonomy of soils is a controversial subject. In part,

controversy reflects differences in the purposes for which

taxonomic classifications are made and differences in concepts

of soil as well as differences in opinion about the taxonomy of

soils. One cannot say that one taxonomic classification is better

than another without reference to the purposes for which both

were made, and comparisons of the merits of taxonomies made

for different purposes can be useless.

The Attributes of Soil Taxonomy

Soil surveys require many nontaxonomic classifications that

can be related to the real bodies of soil and that facilitate

comparisons of both similarities and differences among them

for a great variety of purposes. These classifications are used to

determine whether experience at one location is applicable to

the soils of other locations. The classifications may have to be

used by a pedologist to apply the experience of others for soils

that are unfamiliar. Many persons with diverse backgrounds

and training are expected to use the classifications accurately to

transfer experience with the behavior of soils under a variety of

uses. These intended uses of the classifications impose some

specific requirements on the taxonomy that stands behind the

classifications. The attributes of soil taxonomy are described in

the following paragraphs.

First, the definition of each taxon carries as nearly as

possible the same meaning to each user. Definitions in soil

taxonomy are operational. It is insufficient to say that the soils

in one taxon are differentiated from others by high organicCHAPTER 2

Soil Taxonomy and Soil Classification
16 Soil Taxonomy

matter content because what is considered high in one place

may be considered low in another. The disadvantage of

definitions, of course, is that distinctions are made that may

not be meaningful for every conceivable use of the soil. Only by

operational definitions can competent pedologists with diverse

backgrounds arrive at the same classification of the same kind

of soil.

Second, soil taxonomy is a multicategoric system. Many

taxa are needed in the lower categories because many

properties are important to the use of a soil. Specific properties

can vary independently of others, and their importance depends

on their combination with other properties. Taxa in the lower

categories, therefore, must be defined as specifically as possible

in terms of many properties. This requirement results in more

taxa in the lower categories than the mind can comprehend.

Consequently, the taxa must be grouped on some rational basis

into progressively smaller numbers of classes of higher

categories in a manner that permits the mind to grasp the

concepts and relationships of all taxa. The mind readily grasps

5 to 12 items, but it cannot deal simultaneously with 100 to

1,000 items without some ordering principle. Higher categories

are necessary for organizing and understanding the lower

categories and, in addition, they can be useful in comparing

soils of large areas. They have only limited value for

transferring experience to a specific site for a specific use.

Third, the taxa represent real bodies of soil that are known to

occupy geographic areas. Pedologists are concerned with

mapping real bodies of soil, and a classification related to these

real bodies facilitates the mapping (Cline, 1963). Soil taxonomy

does not try to provide for all possible combinations of

properties because the classification of kinds of soil that have

not been studied should not be prejudiced by a closed system

that covers all contingencies. Rather, soil taxonomy provides a

means to recognize new taxa when discovery leads to new

combinations of properties important to our purposes.

Fourth, differentiae are soil properties that can be observed

in the field or that can be inferred either from other properties

that are observable in the field or from the combined data of

soil science and other disciplines. Some of the most important

properties of the soil are chemical properties, and soil

taxonomy uses criteria in some taxa based on laboratory

measurements. Often data from laboratory measurements can

be interpolated to other areas, or pedologists discover physical

or morphological properties that reflect chemical

characteristics. Soil temperature, soil moisture, and other

properties that fluctuate with the seasons are difficult to use in

taxonomy unless they can be inferred by reasoning from the

combined data of soil science and other disciplines, such as

meteorology. Soil mineralogy can usually be inferred by

reasoning from the combined data of soil science and geology.

If there are no data that permit inferences about important but

invisible soil properties, it is probably best to defer classifying a

soil until some knowledge of its important properties is

available. A classification that is based on extremely limited

knowledge of an object has little utility.

Fifth, soil taxonomy is capable of modification to

accommodate new knowledge with a minimum of disturbance.

Taxa can be added or combined in any category without

disturbance of the rest of the system at the same or a higher

categorical level. If the highest category includes a number of

taxa defined by a variety of properties, the number can be

increased or decreased by combining or subdividing taxa

whenever experience convinces us that this is advisable. If one

taxon in the highest category is divided, no others in that

category need be affected. If two or parts of two are combined,

only those two or those parts are affected. Obviously,

combining taxa at a high level changes classes of lower

categories if they are members of those taxa. Adding taxa may

have no effect on the lower categories if the soils concerned

were not previously included in the system. If the addition is a

consequence of combining classes, it affects the lower

categories.

Sixth, the differentiae keep an undisturbed soil and its

cultivated or otherwise human-modified equivalents in the

same taxon insofar as possible. Changes produced by a single

or repeated plowing that mixes the surface soil to a depth of 18

to 25 cm (7 to 10 in), for example, have the least possible effect

on the placement of a soil in soil taxonomy. Truncation by

erosion does not change the classification of a soil until

horizons or diagnostic features important to the use or

identification of the soil have been lost. Consequently, insofar

as possible, the diagnostic horizons and features should be

those below the part of the soil affected by human activities.

However, significant changes in the nature of the soil by

humans cannot be ignored.

Seventh, soil taxonomy is capable of providing taxa for all

soils on a landscape. Soils form a continuum. The continuum

is broken into a reasonable number of segments that have

limited and defined ranges in properties so that quantitative

interpretations of soil behavior can be made.

Eighth, soil taxonomy provides for all soils that are known,

wherever they may be. Many kinds of soil are poorly

represented or are unknown in the United States. A system that

includes all known soils helps us to see the soils of the United

States in better perspective, particularly if a kind of soil is

poorly represented or is very extensive. It also helps us to draw

on experience in other countries with kinds of soil that are

poorly represented or are not extensive in the United States as a

whole but that are extensive locally.

Selection of Differentiae

To serve the purpose of the soil survey, the pedon should be

classified by its own properties and the taxa defined strictly in

terms of soil properties. In soil definitions, a given property,

such as particle-size distribution or pH, cannot be treated in an
Soil Taxonomy and Soil Classification 17

identical way for all soils. The significance of a difference in any

one property depends on the others in the combination that

makes a soil of a certain kind.

Soil color and the soil horizons are obvious properties that

have been used as differentiating characteristics at high

categoric levels in most taxonomies. Color per se seems to

have no accessory characteristics. For example, if one

considers all the soils that have brown color, no statement can

be made about them except that they are brown. There are

accessory characteristics for some colors in combination with

other properties, and the use of color as a differentiating

characteristic should be limited to these situations. A more

useful classification can be devised if properties that have more

accessory properties than color are used as differentiae in the

highest categories.

Soil horizons are the result of the dominance of one or more

sets of processes over other processes through time. The

processes themselves are not now suitable for use as

differentiae. The illuviation of clay, for example, cannot be

observed or measured in a soil. If illuviation has been a

significant process in the genesis of a soil, however, there

should be marks in the soil that indicate this process. These

marks need not be the same everywhere, but if the proper

marks are selected, the classification can reflect the dominance

of illuviation over other processes, such as those that mix

horizons and those that prevent the movement of clay.

The nature of the horizons is useful in defining the taxa of

soils that have horizons but is useless for soils that do not have

them. Of course, the absence of horizons is itself a mark of

significance. Many important properties of soils, however, are

not necessarily reflected by the combinations of horizons, and

many important processes do not themselves produce horizons.

Intensive mixing of soil by animals can destroy horizons. The

leaching of bases, particularly calcium, and the cycling of bases

by plants in humid climates can be reflected by changes in base

status with increasing depth but can be independent of the

kinds of horizons in a soil. The horizons, therefore, are not the

sole differentiating characteristics in defining taxa.

Some soil properties influence or control specific processes

and, through them, the genesis of the soil. Silicate clays cannot

form in a soil composed entirely of quartz, and apparently they

do not form if a soil is too cold. The soil moisture regime

influences the base status of a soil and the formation of

horizons with an accumulation of illuvial clay or of carbonates.

These are examples of soil properties that are causes of other

properties and that require consideration when properties are

selected to be used as differentiae for taxa.

The differentiae should be soil properties, but the most

useful properties for the higher categories may be either those

that result from soil genesis or those that affect soil genesis

because they have the greatest number of accessory properties.

For example, the clay percentage in soils commonly increases

and then decreases with increasing depth. In many soils

differences in the content of clay are the result of eluviation

and illuviation. In other soils they may be only the result of

stratification of the materials in which the soils developed. If

the horizons are genetic, they have accessory properties,

although the accessory properties may vary with the kind of

soil. If the climate is humid, the eluvial horizons and at least

part of the illuvial horizons are free of finely divided

carbonates because carbonates tend to immobilize clay and

because the leaching required to form an illuvial horizon is

greater than the leaching required to dissolve and remove the

carbonates. Time of the order of some thousands of years

without significant erosion is required. During this time there

is opportunity for nutrients used by plants to be systematically

concentrated in various horizons. In soils that formed under

grass in humid temperate regions, phosphorus seems to be

concentrated in the surface horizons, a considerable part of it

in organic compounds.

If the clay distribution in a soil is due solely to stratification

of parent materials, few other statements can be made about

that soil. The soil may be calcareous or acid. This example

illustrates why properties that are the result of soil genesis or

that affect soil genesis are important. They have accessory

properties. Some of the accessory properties are known, but it

is likely that many are still unknown.

In soil surveys the pedologist is commonly concerned with

finding the boundaries between map units. The boundaries are

in places where there has been or is a difference in one or more

of the factors that control soil genesis. The mapper learns to

look for these places and uses a knowledge of soil genesis to

improve the accuracy and efficiency of mapping. Genesis is

fundamental to soil taxonomy and to the soil survey. Genesis

itself, however, is unsuitable for direct use in soil taxonomy.

Because the genesis of a soil cannot be observed or measured,

pedologists may have widely differing opinions about it, and

the classification of a given pedon is affected by the

background of the pedologist.

Forming and Defining Taxa

When forming and defining the taxa, one must consider all

the known properties, although only a few can be

differentiating. The differentiating properties should be the

ones that are the most important for our purposes or that have

the most important accessory characteristics.

Research and experience indicate that some properties are

important to plant growth. Soil taxonomy attempts to make the

most important statements possible about the taxa. Those

properties that are important to plant growth and that result

from or influence soil genesis are considered in the higher

categories. Those that are important to plant growth but are

unrelated to genesis should be considered only for the lowest

categories. For example, in soils that are only slightly

weathered, the nature and amount of clay may be the result of

geologic accidents. If the differences are not extreme, the

course of soil genesis is not necessarily affected. Although the
18

difference between illite and smectite is important to plant

growth, it is used as a differentiating characteristic only at a

low category in the system, the family.

Determining the similarities among soils is not always a

simple matter. There may be similarity in particle-size

distribution to the members of one taxon and in base status to

the members of another. One must decide which property is the

more important, and this decision must rest on the nature of

the statements that one can make about the classes if the kind

of soil is grouped one way or the other. The best grouping

determines the definition; the definition does not determine the

grouping. If the grouping has imperfections, so does the

definition. The statements are about the nature of the soils and

the interpretations that can be made for the various phases of a

taxon. Interpretations are predictions of the consequences of

specific uses of soils, commonly in terms of plant growth under

specified systems of management but also in terms of

engineering soil behavior after a given manipulation.

Interpretations of the soils indicate the reasonable alternatives

for their use and management and the expected results. The

best grouping is one that helps us to make the most precise and

most important interpretations. Soil taxonomy must continue to

be tested by the nature of the interpretations that can be made.

The taxonomic classification used in soil surveys requires

flexibility in the classes. It is commonly necessary to subdivide

taxa and regroup those subdivisions into new classes of another

classification for the greatest number and most precise

interpretations possible. Soil taxonomy was designed to

facilitate interpretations, but the interpretations themselves

require at least one additional step of reasoning (Cline, 1963).

The interpretations may also require information that is not

available from the taxonomy. Slope and stoniness are soil

characteristics that must be known or assumed for one to

predict consequences of farming with heavy machinery.

Invasions of locusts, hurricanes, or frequent hailstorms are not

soil characteristics, but their probability must be known or

assumed when crop yields are predicted. These and other

important characteristics may be used as bases for defining

phases of taxa that are necessary for interpretations for

specific fields or farms. The phases are not a part of the

taxonomy. Their nature is determined by the foreseeable

uses of the soils in a particular survey area. Quite different

phases might be differentiated for the same soils in an area of

general farming in contrast to a national forest or an area

being developed for housing and in an irrigated area in

contrast to the desert grazing land that is above the irrigation

canal. The phases represent a number of classifications

superimposed on the taxonomic classification to give part of

the flexibility that is needed for the wide variety of uses made

of soil.

Inevitably, the conclusions of a large group of scientists

include some compromises of divergent points of view.

Members of a group representing unlike interests and

experience are likely to see soils differently. Different points

of view about soil produce different ideas about its

classification. Consequently, compromises between the

conflicting desires of a number of individuals not only are

necessary but also are likely to produce a system that has more

general utility than a system that represents a single point of

view. Compromise may not be the exact word. The truth has

many facets; each person has a somewhat different view of the

truth, and no person can see the whole truth clearly. Soil

taxonomy allows changes in the system as new information

about soils becomes available. Since its inception, soil

taxonomy has been amended many times. Probably, no one

person will approve of all the details of these changes; few will

be able to agree on all the changes.

Literature Cited

Cline, M.G. 1963. Logic of the New System of Soil

Classification. Soil Sci. 96: 17-22.
19

Soil taxonomy differentiates between mineral soils andorganic soils. To do this, first, it is necessary to

distinguish mineral soil material from organic soil material.

Second, it is necessary to define the minimum part of a soil

that should be mineral if a soil is to be classified as a mineral

soil and the minimum part that should be organic if the soil is

to be classified as an organic soil.

Nearly all soils contain more than traces of both mineral

and organic components in some horizons, but most soils are

dominantly one or the other. The horizons that are less than

about 20 to 35 percent organic matter, by weight, have

properties that are more nearly those of mineral than of organic

soils. Even with this separation, the volume of organic matter

at the upper limit exceeds that of the mineral material in the

fine-earth fraction.

Mineral Soil Material

Mineral soil material (less than 2.0 mm in diameter) either:

1. Is saturated with water for less than 30 days (cumulative)

per year in normal years and contains less than 20 percent (by

weight) organic carbon; or

2. Is saturated with water for 30 days or more cumulative in

normal years (or is artificially drained) and, excluding live

roots, has an organic carbon content (by weight) of:

a. Less than 18 percent if the mineral fraction contains 60

percent or more clay; or

b. Less than 12 percent if the mineral fraction contains no

clay; or

c. Less than 12 + (clay percentage multiplied by 0.1)

percent if the mineral fraction contains less than 60 percent

clay.

Organic Soil Material

Soil material that contains more than the amounts of

organic carbon described above for mineral soil material is

considered organic soil material.

In the definition of mineral soil material above, material

that has more organic carbon than in item 1 is intended to

include what has been called litter or an O horizon. Material

that has more organic carbon than in item 2 has been called

peat or muck. Not all organic soil material accumulates in or

under water. Leaf litter may rest on a lithic contact and support

forest vegetation. The soil in this situation is organic only in

the sense that the mineral fraction is appreciably less than half

the weight and is only a small percentage of the volume of the

soil.

Distinction Between Mineral Soils and Organic

Soils

Most soils are dominantly mineral material, but many

mineral soils have horizons of organic material. For simplicity

in writing definitions of taxa, a distinction between what is

meant by a mineral soil and an organic soil is useful. To apply

the definitions of many taxa, one must first decide whether the

soil is mineral or organic. An exception is the Andisols

(defined later). These generally are considered to consist of

mineral soils, but some may be organic if they meet other

criteria for Andisols. Those that exceed the organic carbon

limit defined for mineral soils have a colloidal fraction

dominated by short-range-order minerals or aluminum-humus

complexes. The mineral fraction in these soils is believed to

give more control to the soil properties than the organic

fraction. Therefore, the soils are included with the Andisols

rather than the organic soils defined later as Histosols.

If a soil has both organic and mineral horizons, the relative

thickness of the organic and mineral soil materials must be

considered. At some point one must decide that the mineral

horizons are more important. This point is arbitrary and

depends in part on the nature of the materials. A thick layer of

sphagnum has a very low bulk density and contains less

organic matter than a thinner layer of well-decomposed muck.

It is much easier to measure the thickness of layers in the field

than it is to determine tons of organic matter per hectare. The

definition of a mineral soil, therefore, is based on the thickness

of the horizons, or layers, but the limits of thickness must vary

with the kinds of materials. The definition that follows is

intended to classify as mineral soils those that have both thick

mineral soil layers and no more organic material than the

amount permitted in the histic epipedon, which is defined in

chapter 4.

In the determination of whether a soil is organic or mineral,

the thickness of horizons is measured from the surface of the

CHAPTER 3

Differentiae for Mineral Soils1 and Organic Soils

1 Mineral soils include all soils except the suborder Histels and the order Histosols.
20

soil whether that is the surface of a mineral or an organic

horizon, unless the soil is buried as defined in chapter 1. Thus,

any O horizon at the surface is considered an organic horizon

if it meets the requirements of organic soil material as defined

later, and its thickness is added to that of any other organic

horizons to determine the total thickness of organic soil

materials.

Definition of Mineral Soils

Mineral soils are soils that have either of the following:

1. Mineral soil materials that meet one or more of the

following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or have voids2 that are filled with 10 percent or less

organic materials and directly below these materials have

either a densic, lithic, or paralithic contact; or

b. When added with underlying cindery, fragmental, or

pumiceous materials, total more than 10 cm between the soil

surface and a depth of 50 cm; or

c. Constitute more than one-third of the total thickness of

the soil to a densic, lithic, or paralithic contact or have a

total thickness of more than 10 cm; or

d. If they are saturated with water for 30 days or more per

year in normal years (or are artificially drained) and have

organic materials with an upper boundary within

40 cm of the soil surface, have a total thickness of either:

(1) Less than 60 cm if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3; or

(2) Less than 40 cm if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more; or

2. More than 20 percent, by volume, mineral soil materials

from the soil surface to a depth of 50 cm or to a glacic layer or

a densic, lithic, or paralithic contact, whichever is shallowest;

and

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface.

Definition of Organic Soils

Organic soils have organic soil materials that:

1. Do not have andic soil properties in 60 percent or more of

the thickness between the soil surface and either a depth of 60

cm or a densic, lithic, or paralithic contact or duripan if

shallower; and

2. Meet one or more of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices2 and directly below these

materials have a densic, lithic, or paralithic contact; or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more per year in

normal years (or are artificially drained), have an upper

boundary within 40 cm of the soil surface, and have a total

thickness of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more; or

e. Are 80 percent or more, by volume, from the soil

surface to a depth of 50 cm or to a glacic layer or a densic,

lithic, or paralithic contact, whichever is shallowest.

It is a general rule that a soil is classified as an organic soil

(Histosol) if more than half of the upper 80 cm (32 in) of the

soil is organic or if organic soil material of any thickness rests

on rock or on fragmental material having interstices filled with

organic materials.

2 Materials that meet the definition of cindery, fragmental, or pumiceous but have more

than 10 percent, by volume, voids that are filled with organic soil materials are considered to be

organic soil materials.
21

This chapter defines the horizons and characteristics ofboth mineral and organic soils. It is divided into three

parts—horizons and characteristics diagnostic for mineral soils,

characteristics diagnostic for organic soils, and horizons and

characteristics diagnostic for both mineral and organic soils.

The four highest categories of this taxonomy, in order of

decreasing rank and increasing numbers of taxa, are

distinguished by the presence or absence or a variety of

combinations of diagnostic horizons and characteristics. The

categories themselves are described in chapter 6.

The horizons and characteristics defined below are not in a

key format. Some diagnostic horizons are mutually exclusive,

and some are not. An umbric epipedon, for example, could not

also be a mollic epipedon. A kandic horizon with clay films,

however, could also meet the definition of an argillic horizon.

A soil horizon is a layer that is commonly parallel to the soil

surface. In some orders, such as Gelisols, Vertisols, and

Spodosols, however, horizons are not always parallel to the

surface. A horizon has some set of properties that have been

produced by soil-forming processes, and it has some properties

that are not like those of the layers directly above and beneath

it (USDA, SCS, 1993). A soil horizon commonly is differentiated

from the horizons adjacent to it partly by characteristics that can

be seen or measured in the field, such as color, structure, texture,

rupture-resistance class, and the presence or absence of

carbonates. In identifying a soil horizon, however, measurements

in the laboratory are sometimes required to supplement field

observations. According to the criteria we use, horizons are

identified partly by their own morphology and partly by

properties that differ from those of the overlying and underlying

horizons.

Many of the layers that are differentiae for organic soils do

not meet the definition of soil horizons. Unlike the layers of

soil that are commonly called horizons, they are layers that

formed in differing environments during the period when the

materials that now constitute the soils accumulated. Some of

the layers that serve as differentiae are soil horizons, but there

are no operational methods that can always distinguish

between “horizons” and “layers” that have similar properties.

The importance of making a distinction between horizons and

layers of organic soils is unknown. In the discussion that

follows, the term “soil material” is commonly used as a

broader term that includes both horizons and layers in organic

soils.

The horizon designations used in this chapter are defined in

the Soil Survey Manual (USDA, SCS, 1993) and the Keys to Soil

Taxonomy (USDA, NRCS, 1998).

Horizons and Characteristics

Diagnostic for Mineral Soils

The criteria for some of the following horizons and

characteristics, such as histic and folistic epipedons, can be met

in organic soils. They are diagnostic, however, only for the

mineral soils.

Diagnostic Surface Horizons: The

Epipedon

The epipedon (Gr. epi, over, upon, and pedon, soil) is a

horizon that forms at or near the surface and in which most of

the rock structure has been destroyed. It is darkened by organic

matter or shows evidence of eluviation, or both. Rock structure

as used here and in other places in this taxonomy includes fine

stratification (less than 5 mm) in unconsolidated sediments

(eolian, alluvial, lacustrine, or marine) and saprolite derived

from consolidated rocks in which the unweathered minerals

and pseudomorphs of weathered minerals retain their relative

positions to each other.

Any horizon may be at the surface of a truncated soil. The

following section, however, is concerned with eight diagnostic

horizons that have formed at or near the soil surface. These

horizons can be covered by a surface mantle of new soil

material. If the surface mantle has rock structure, the top of the

epipedon is considered the soil surface unless the mantle meets

the definition of buried soils in chapter 1. If the soil includes a

buried soil, the epipedon, if any, is at the soil surface and the

epipedon of the buried soil is considered a buried epipedon and

is not considered in selecting taxa unless the keys specifically

indicate buried horizons, such as those in Thapto-Histic

subgroups. A soil with a mantle thick enough to have a buried

soil has no epipedon if the soil has rock structure to the

surface or has an Ap horizon less than 25 cm thick that is

underlain by soil material with rock structure. The melanic

epipedon (defined below) is unique among epipedons. It forms

commonly in volcanic deposits and can receive fresh deposits of

ash. Therefore, this horizon is permitted to have layers within

and above the epipedon that are not part of the melanic

epipedon.

CHAPTER 4

Horizons and Characteristics Diagnostic for the Higher Categories
22 Soil Taxonomy

A recent alluvial or eolian deposit that retains stratifications

(5 mm or less thick) or an Ap horizon directly underlain by such

stratified material is not included in the concept of the epipedon

because time has not been sufficient for soil-forming processes

to erase these transient marks of deposition and for diagnostic

and accessory properties to develop.

An epipedon is not the same as an A horizon. It may

include part or all of an illuvial B horizon if the darkening by

organic matter extends from the soil surface into or through the

B horizon.

Anthropic Epipedon

The anthropic epipedon has the same limits as the mollic

epipedon in color, structure, and organic-carbon content. It

formed during long-continued use of the soil by humans, either

as a place of residence or as a site for growing irrigated crops.

In the former case, disposal of bones and shells has supplied

calcium and phosphorus and the level of phosphorus in the

epipedon is too high for a mollic epipedon. Such epipedons

occur in the humid parts of Europe, the United States, and

South America and probably in other parts of the world, mostly

in kitchen middens. The high level of phosphorus in the

anthropic epipedons is not everywhere accompanied by a base

saturation of 50 percent or more, but it is accompanied by a

relatively high base saturation if compared with the adjacent

soils.

In arid regions some long-irrigated soils have an epipedon

that is like the mollic epipedon in most chemical and physical

properties. The properties of the epipedon in these areas are

clearly the consequence of irrigation by humans. Such an

epipedon is grouped with the anthropic epipedons, which

developed under human habitation. If not irrigated, such an

epipedon is dry in all its parts for more than 9 months in

normal years. Additional data about anthropic epipedons from

several parts of the world may permit future improvements in

this definition.

Required Characteristics

In summary, the anthropic epipedon shows some evidence of

disturbance by human activity and meets all of the

requirements for a mollic epipedon, except for one or both of

the following:

1. 1,500 milligrams per kilogram or more P2

O5 soluble in 1

percent citric acid and a regular decrease in P2O5 to a depth of

125 cm; or

2. If the soil is not irrigated, all parts of the epipedon are dry

for 9 months or more in normal years.

Folistic Epipedon

The folistic epipedon consists of organic material (defined in

chapter 3), unless the soil has been plowed. This epipedon

normally is at the soil surface, although it can be buried. If the

soil has been plowed, the organic-carbon requirements are lower

than the requirements for organic soil material because of the

need to accommodate the oxidation that occurs when the soil is

plowed. Folistic epipedons occur primarily in cool, humid

regions of the world. They differ from histic epipedons because

they are saturated with water for less than 30 days (cumulative)

in normal years (and are not artificially drained). Taxa for soils

with folistic epipedons above the series level are not currently

recognized in this taxonomy. The folistic epipedon is used only

with mineral soils.

Required Characteristics

The folistic epipedon is defined as a layer (one or more

horizons) that is saturated for less than 30 days (cumulative) in

normal years (and is not artificially drained) and either:

1. Consists of organic soil material that:

a. Is 20 cm or more thick and either contains 75 percent or

more (by volume) Sphagnum fibers or has a bulk density,

moist, of less than 0.1; or

b. Is 15 cm or more thick; or

2. Is an Ap horizon that, when mixed to a depth of 25 cm,

has an organic-carbon content (by weight) of:

a. 16 percent or more if the mineral fraction contains 60

percent or more clay; or

b. 8 percent or more if the mineral fraction contains no

clay; or

c. 8 + (clay percentage divided by 7.5) percent or more

if the mineral fraction contains less than 60 percent

clay.

Most folistic epipedons consist of organic soil material

(defined in chapter 3). Item 2 provides for a folistic epipedon

that is an Ap horizon consisting of mineral soil material.

Histic Epipedon

The histic epipedon consists of organic soil material (peat or

muck) if the soil has not been plowed. If the soil has been

plowed, the epipedon normally has a high content of organic

matter that results from mixing organic soil material with some

mineral material. The histic epipedon either is characterized by

saturation and reduction for some time in normal years or has

been artificially drained. It is normally at the soil surface,

although it can be buried.

Photo 4 shows a very dark histic epipedon that is saturated

for long periods and meets criterion 1 below.

Required Characteristics

The histic epipedon is a layer (one or more horizons) that is

characterized by saturation (for 30 days or more, cumulative)
Horizons and Characteristics Diagnostic for the Higher Categories 23

and reduction for some time during normal years (or is artificially

drained) and either:

1. Consists of organic soil material that:

a. Is 20 to 60 cm thick and either contains 75 percent or

more (by volume) Sphagnum fibers or has a bulk density,

moist, of less than 0.1; or

b. Is 20 to 40 cm thick; or

2. Is an Ap horizon that, when mixed to a depth of 25 cm,

has an organic-carbon content (by weight) of:

a. 16 percent or more if the mineral fraction contains 60

percent or more clay; or

b. 8 percent or more if the mineral fraction contains no

clay; or

c. 8 + (clay percentage divided by 7.5) percent or more if

the mineral fraction contains less than 60 percent clay.

Most histic epipedons consist of organic soil material

(defined in chapter 3). Item 2 provides for a histic epipedon

that is an Ap horizon consisting of mineral soil material. A

histic epipedon consisting of mineral soil material can also be

part of a mollic or umbric epipedon.

Melanic Epipedon

The melanic epipedon is a thick, dark colored (commonly

black) horizon at or near the soil surface (photo 5). It has high

concentrations of organic carbon, generally associated with

short-range-order minerals or aluminum-humus complexes.

The intense dark colors are attributed to the accumulation of

organic matter from which “Type A” humic acids are

extracted. This organic matter is thought to result from large

amounts of root residues supplied by a gramineous vegetation

and can be distinguished from organic matter formed under

forest vegetation by the melanic index.

The suite of secondary minerals generally is dominated by

allophane, and the soil material has a low bulk density and a

high anion adsorption capacity.

Required Characteristics

The melanic epipedon has both of the following:

1. An upper boundary at, or within 30 cm of, either the

mineral soil surface or the upper boundary of an organic layer

with andic soil properties (defined below), whichever is

shallower; and

2. In layers with a cumulative thickness of 30 cm or more

within a total thickness of 40 cm, all of the following:

a. Andic soil properties throughout; and

b. A color value, moist, and chroma (Munsell

designations) of 2 or less throughout and a melanic index of

1.70 or less throughout; and

c. 6 percent or more organic carbon as a weighted average

and 4 percent or more organic carbon in all layers.

Mollic Epipedon

The mollic epipedon is a relatively thick, dark colored,

humus-rich surface horizon (or horizons) in which bivalent

cations are dominant on the exchange complex and the grade

of structure is weak to strong (photos 6 and 7). These properties

are common in the soils of the steppes in the Americas, Europe,

and Asia.

Properties

The mollic epipedon is defined in terms of its morphology

rather than its genesis. It consists of mineral soil material and

is at the soil surface, unless it underlies a histic epipedon or

thin surface mantle, as explained earlier in this chapter. If the

surface layer of organic material is so thick that the soil is

recognized as a Histosol (defined below), the horizon that at one

time was a mollic epipedon is considered to be buried and no

longer meets the definition of an epipedon.

The mollic epipedon has soil structure strong enough that

less than one-half of the volume of all parts has rock structure

and one-half or more of the horizon is not both hard, very

hard, or harder and massive when dry. In this definition very

coarse prisms, with a diameter of 30 cm or more, are treated as

if they were the same as massive unless there is secondary

structure within the prisms. The restriction against hardness

and structure applies only to those epipedons that become dry.

A mollic epipedon can directly overlie deposits with rock

structure, including fine stratifications, if the epipedon is 25

cm or more thick. The epipedon does not include any layer in

which one-half or more of the volume has rock structure,

including fine stratifications.

The mollic epipedon has dark color and low chroma in 50

percent or more of its matrix. It typically has a Munsell color

value of 3 or less when moist and of 5 or less when dry and

chroma of 3 or less when moist. If its structure is fine granular

or fine blocky, the sample, when broken, may show only the

color of the coatings of peds. The color of the matrix in such

situations can be determined only by crushing or briefly

rubbing the sample. Prolonged rubbing should be avoided

because it may cause darkening of a sample if soft ironmanganese concretions are present. Crushing should be just

sufficient to mix the coatings with the matrix. The dry color

value should be determined after the crushed sample is dry

enough for continued drying to produce no further change and

the sample has been smoothed to eliminate shadows.

Normally, the color value is at least 1 Munsell unit lower or

the chroma at least 2 units lower (both moist and dry) than that

of the 1C horizon (if one occurs). Some parent materials, such
24 Soil Taxonomy

as loess, cinders, basalt, or carbonaceous shale, can also have

dark color and low chroma. Soils that formed in such materials

can accumulate appreciable amounts of organic matter but

commonly have no visible darkening in the epipedon. In these

dark colored materials, the requirement that the mollic

epipedon have a lower color value or chroma than the C

horizon is waived if the surface horizon(s) meets all of the

other requirements for a mollic epipedon and, in addition, has

at least 0.6 percent more organic carbon than the C horizon.

Finely divided CaCO3

 acts as a white pigment and causes

soils to have a high color value, especially when dry. To

compensate for the color of the carbonates, the mollic epipedon

is allowed to have lighter color than normal if the epipedon

averages more than 15 percent carbonates.

If the fine-earth fraction has a calcium carbonate equivalent

of 15 to 40 percent, the limit for the dry color value is waived.

If it has a calcium carbonate equivalent of 40 percent or more,

the limit for the dry color value is waived and the moist color

value is 5 or less.

The mollic epipedon forms in the presence of bivalent

cations, particularly calcium. The base saturation by the

NH4OAc method is required to be 50 percent or more

throughout the epipedon.

The mollic epipedon is thought to be formed mainly through

the underground decomposition of organic residues in the

presence of these cations. The residues that are decomposed are

partly roots and partly organic residues from the surface that

have been taken underground by animals. Accumulation and

turnover of the organic matter in the mollic epipedon probably

are rapid. The radiocarbon age (mean residence time) of the

organic carbon is mostly 100 to 1,000 years. A high percentage

of the organic matter is so-called “humic acid.” The minimum

organic-carbon content throughout the thickness of the mollic

epipedon is 0.6 percent in most mollic epipedons. Exceptions

are (1) a minimum of 2.5 percent organic carbon in epipedons

that have a color value, moist, of 4 or 5 and a fine-earth

fraction with a calcium carbonate equivalent of 40 percent or

more and (2) a minimum of 0.6 percent more organic carbon

than in the C horizon in epipedons in which the C horizon has

a color as dark as or darker than the color of the epipedon.

The maximum organic-carbon content of a mollic epipedon

is the same as for mineral soil material. Some Ap horizons that

approach the lower limit of a histic epipedon can be part of the

mollic epipedon.

The minimum thickness of the mollic epipedon depends on

the depth and texture of the soil. The minimum thickness is for

soils with an epipedon that is loamy very fine sand or finer and

that is directly above a densic, lithic, or paralithic contact, a

petrocalcic horizon, or a duripan. These soils have a minimum

thickness of 10 cm. Soils that are 10 to 18 cm deep have a

mollic epipedon if the whole soil meets all of the criteria for a

mollic epipedon when mixed.

The minimum thickness is 25 cm for: (1) all soils with a

texture throughout the epipedon of loamy fine sand or coarser;

(2) all soils that have no diagnostic horizons or features below

the epipedon; and (3) soils that are 75 cm or more deep to a

densic, lithic, or paralithic contact, a petrocalcic horizon, or a

duripan, are more than 75 cm deep to the upper boundary of

any identifiable secondary carbonates, and are more than 75

cm deep to the lower boundary of any argillic, cambic, kandic,

natric, oxic, or spodic horizon (all defined below).

The minimum thickness is one-third of the thickness from

the mineral soil surface to any of the features described in the

paragraph above if (1) the texture throughout the epipedon is

loamy very fine sand or finer and (2) depth to the feature

described in the paragraph above is between 54 and 75 cm.

The minimum thickness is 18 cm for all other soils.

The mollic epipedon has less than 1,500 milligrams per

kilogram of P2

O5 soluble in 1 percent citric acid or has an

irregular decrease in the amounts of P2O5 with increasing depth

below the epipedon, or there are phosphate nodules within the

epipedon. This restriction is intended to exclude plow layers of

very old arable soils and kitchen middens that, under use, have

acquired the properties of a mollic epipedon and to include the

epipedon of a soil developed in highly phosphatic parent

material.

Some part of the epipedon is moist for 90 days or more

(cumulative) in normal years during times when the soil

temperature at a depth of 50 cm is 5 oC or higher and the soil is

not irrigated.

Sediments that have been continuously under water since

they were deposited have a very high water content and are

unable to support livestock. Although many soils that have a

mollic epipedon are very poorly drained, the mollic epipedon is

required to have an n value (defined below) of less than 0.7.

Several accessory properties are common in soils that have a

mollic epipedon. Most natural environments (not made by

humans) that produce a mollic epipedon also produce 2:1

lattice clays from minerals that can be altered, preclude serious

toxicity from aluminum or manganese, and ensure a reasonable

reserve of calcium, magnesium, and potassium and of nitrogen

if the soil has not been cultivated for a long time. These are

accessory properties that are important to plant growth.

Permeability is another accessory property important to most

uses of the soil. The structure of the mollic epipedon facilitates

the movement of moisture and air whenever the soil is not

saturated with water.

The content of organic matter indicates that the soil has

received enough moisture to support fair to luxuriant plant

growth in normal years. The mollic epipedon must be moist in

at least some part for 90 days or more (cumulative) in normal

years at times when the soil temperature is 5 o

C or higher at a

depth of 50 cm and when the soil is not irrigated.

Although the mollic epipedon is a surface horizon that can

be truncated by erosion, its many important accessory

properties suggest its use as a diagnostic horizon at a high

categoric level. Some soils have eroded to the extent that the

epipedon is no longer thick enough to meet the requirements
Horizons and Characteristics Diagnostic for the Higher Categories 25

for a mollic epipedon. In this case human activities have altered

the surface horizon, changing a mollic epipedon into an ochric

epipedon (defined below).

Required Characteristics

The mollic epipedon consists of mineral soil materials and has

the following properties:

1. When dry, either or both:

a. Structural units with a diameter of 30 cm or less

or secondary structure with a diameter of 30 cm or less;

or

b. A moderately hard or softer rupture-resistance class;

and

2. Rock structure, including fine (less than 5 mm)

stratifications, in less than one-half of the volume of all parts;

and

3. One of the following:

a. All of the following:

(1) Colors with a value of 3 or less, moist, and of 5 or

less, dry; and

(2) Colors with chroma of 3 or less, moist; and

(3) If the soil has a C horizon, the mollic epipedon has

a color value at least 1 Munsell unit lower or chroma at

least 2 units lower (both moist and dry) than that of the C

horizon or the epipedon has at least 0.6 percent more

organic carbon than the C horizon; or

b. A fine-earth fraction that has a calcium carbonate

equivalent of 15 to 40 percent and colors with a value and

chroma of 3 or less, moist; or

c. A fine-earth fraction that has a calcium carbonate

equivalent of 40 percent or more and a color value, moist, of

5 or less; and

4. A base saturation (by NH4OAc) of 50 percent or more; and

5. An organic-carbon content of:

a. 2.5 percent or more if the epipedon has a color value,

moist, of 4 or 5; or

b. 0.6 percent more than that of the C horizon (if one

occurs) if the mollic epipedon has a color value less than 1

Munsell unit lower or chroma less than 2 units lower (both

moist and dry) than the C horizon; or

c. 0.6 percent or more; and

6. After mixing of the upper 18 cm of the mineral soil or of

the whole mineral soil if its depth to a densic, lithic, or

paralithic contact, petrocalcic horizon, or duripan (all defined

below) is less than 18 cm, the minimum thickness of the

epipedon is as follows:

a. 10 cm or the depth of the noncemented soil if the

epipedon is loamy very fine sand or finer and is directly

above a densic, lithic, or paralithic contact, a petrocalcic

horizon, or a duripan that is within 18 cm of the mineral

soil surface; or

b. 25 cm or more if the epipedon is loamy fine sand or

coarser throughout or if there are no underlying diagnostic

horizons (defined below) and the organic-carbon content of

the underlying materials decreases irregularly with

increasing depth; or

c. 25 cm or more if all of the following are 75 cm or more

below the mineral soil surface:

(1) The upper boundary of any pedogenic lime that is

present as filaments, soft coatings, or soft nodules; and

(2) The lower boundary of any argillic, cambic, natric,

oxic, or spodic horizon (defined below); and

(3) The upper boundary of any petrocalcic horizon,

duripan, or fragipan; or

d. 18 cm if the epipedon is loamy very fine sand or finer in

some part and one-third or more of the total thickness

between the top of the epipedon and the shallowest of any

features listed in item 6-c is less than 75 cm below the

mineral soil surface; or

e. 18 cm or more if none of the above conditions apply;

and

7. Phosphate:

a. Content less than 1,500 milligrams per kilogram

soluble in 1 percent citric acid; or

b. Content decreasing irregularly with increasing depth

below the epipedon; or

c. Nodules are within the epipedon; and

8. Some part of the epipedon is moist for 90 days or more

(cumulative) in normal years during times when the soil

temperature at a depth of 50 cm is 5 o

C or higher, if the soil is

not irrigated; and

9. The n value (defined below) is less than 0.7.

Ochric Epipedon

The ochric epipedon fails to meet the definitions for any of

the other seven epipedons because it is too thin or too dry, has

too high a color value or chroma, contains too little organic

carbon, has too high an n value or melanic index, or is both

massive and hard or harder when dry (photos 8 and 9). Many

ochric epipedons have either a Munsell color value of 4 or

more, moist, and 6 or more, dry, or chroma of 4 or more, or

they include an A or Ap horizon that has both low color values

and low chroma but is too thin to be recognized as a mollic or
26 Soil Taxonomy

umbric epipedon (and has less than 15 percent calcium

carbonate equivalent in the fine-earth fraction). Ochric

epipedons also include horizons of organic materials that are

too thin to meet the requirements for a histic or folistic

epipedon.

The ochric epipedon includes eluvial horizons that are at or

near the soil surface, and it extends to the first underlying

diagnostic illuvial horizon (defined below as an argillic,

kandic, natric, or spodic horizon). If the underlying horizon is

a B horizon of alteration (defined below as a cambic or oxic

horizon) and there is no surface horizon that is appreciably

darkened by humus, the lower limit of the ochric epipedon is

the lower boundary of the plow layer or an equivalent depth

(18 cm) in a soil that has not been plowed. Actually, the same

horizon in an unplowed soil may be both part of the epipedon

and part of the cambic horizon; the ochric epipedon and the

subsurface diagnostic horizons are not all mutually exclusive.

The ochric epipedon does not have rock structure and does not

include finely stratified fresh sediments, nor can it be an Ap

horizon directly overlying such deposits.

The ochric epipedon by itself has few or no accessory

characteristics, but an ochric epipedon in combination with

other diagnostic horizons and features has many accessory

characteristics. For example, if there is an underlying horizon

in which clay has accumulated (defined later as an argillic

horizon) and if the epipedon is seldom or never dry, carbonates

are absent and base saturation is moderate or low in the major

part of the epipedon unless the soil has been limed. If the

texture is loamy, the structure breaks down easily when the soil

is cultivated.

Plaggen Epipedon

The plaggen epipedon is a human-made surface layer 50 cm

or more thick that has been produced by long-continued

manuring (photo 10). In medieval times, sod or other materials

commonly were used for bedding livestock and the manure was

spread on fields being cultivated. The mineral materials

brought in by this kind of manuring eventually produced an

appreciably thickened Ap horizon (as much as 1 m or more

thick). In northwestern Europe this custom was associated with

the poorly fertile, sandy Spodosols. The practice more or less

ceased at the turn of the 19th century, when fertilizers became

available.

The color of a plaggen epipedon and its organic-carbon

content depend on the materials used for bedding. If the sod

was cut from the heath, the plaggen epipedon tends to be black

or very dark gray, to be rich in organic matter, and to have a

wide carbon-nitrogen ratio. If the sod came from forested soils,

the plaggen epipedon tends to be brown, to have less organic

matter, and to have a narrower carbon-nitrogen ratio.

Commonly, the organic-carbon content ranges from 1.5 to 4

percent. Values commonly range from 1 to 4, moist, and

chromas are 2 or less.

A plaggen epipedon can be identified by several means.

Commonly, it contains artifacts, such as bits of brick and

pottery, throughout its depth. There may be chunks of diverse

materials, such as black sand and light gray sand, as large as

the size held by a spade. The plaggen epipedon normally shows

spade marks throughout its depth and also remnants of thin

stratified beds of sand that were probably produced on the soil

surface by beating rains and were later buried by spading. A

map unit delineation of soils with plaggen epipedons would

tend to have straight-sided rectangular bodies that are higher

than the adjacent soils by as much as or more than the

thickness of the plaggen epipedon.

Umbric Epipedon

The umbric epipedon is a relatively thick, dark colored,

humus-rich surface horizon or horizons (photo 11). It cannot be

distinguished by the eye from a mollic epipedon, but laboratory

studies show that the base saturation is less than 50 percent (by

NH4OAc) in some or all parts.

The umbric epipedon is used for defining taxa at different

levels. For those soils in which the content of organic matter is

roughly proportional to the darkness of the color, the most

satisfactory groupings appear to be those that assign soils with

a thick, dark colored surface horizon and soils with a light

colored or thin surface horizon to different suborders.

Structure, bulk density, cation-exchange capacity, and other

properties are related to the amount and type of organic matter

in these soils. In those kinds of soil where dark color is not

related to the content of organic matter, the soils that have light

colored epipedons are separated from the soils that have dark

colored epipedons only at lower categoric levels, if at all.

Properties

The umbric epipedon consists of mineral soil material and is

at the soil surface, unless it underlies either a recent deposit

that is less than 50 cm thick and has fine stratification if not

plowed or a thin layer of organic soil material. If the surface

layer of organic material is so thick that the soil is recognized

as a Histosol (defined below), the umbric epipedon is considered

to be buried.

The umbric epipedon has soil structure strong enough so

that one-half or more of the horizon is not both hard, very

hard, or harder and massive when dry. Very coarse prisms,

with a diameter of 30 cm or more, are treated as if they were

the same as massive if there is no secondary structure within

the prisms. The restriction against massive and hardness

applies only to those epipedons that become dry.

The umbric epipedon has dark color and low chroma in 50

percent or more of its matrix. It has a Munsell color value of 3

or less, moist, and of 5 or less, dry, and chroma of 3 or less. If

its structure is fine granular or fine blocky, the sample when

broken may show only the color of the coatings of peds. The

color of the matrix in such situations can be determined only
Horizons and Characteristics Diagnostic for the Higher Categories 27

by crushing or briefly rubbing the sample. Prolonged rubbing

should be avoided because it may cause darkening of a sample

if soft iron-manganese concretions are present. Crushing

should be just sufficient to mix the coatings with the matrix.

The dry color value should be determined after the crushed

sample is dry enough for continued drying to produce no

further change and the sample has been smoothed to eliminate

shadows.

Normally, the color value is at least 1 Munsell unit lower or

the chroma at least 2 units lower (both moist and dry) than that

of the C horizon (if present). Some parent materials, such as

loess, cinders, alluvium, or shale, can also have dark color and

low chroma. Soils that formed in such materials can

accumulate appreciable amounts of organic matter but

commonly show no visible darkening in the epipedon. In these

dark colored materials, the requirement that the umbric

epipedon have a lower color value or chroma than the C

horizon is waived if the surface horizon(s) meets all of the

other requirements for an umbric epipedon and, in addition,

has at least 0.6 percent more organic carbon than the C

horizon.

Base saturation by the NH4

OAc method is required to be

less than 50 percent in some or all parts of the epipedon.

The umbric epipedon is thought to be formed mainly by the

decomposition of organic residues. The residues that are

decomposed are partly roots and partly organic residues from

the surface that have been taken underground by animals.

Accumulation and turnover of the organic matter in the umbric

epipedon probably are slower than in the mollic epipedon. The

aluminum ions may be somewhat toxic to some kinds of soil

micro-organisms. The minimum organic-carbon content

throughout the thickness of the umbric epipedon is 0.6 percent.

The minimum thickness of the umbric epipedon is

dependent on the depth and texture of the soil. The minimum

thickness is for soils with an epipedon that is loamy very fine

sand or finer (when mixed) and that is directly above a densic,

lithic, or paralithic contact, a petrocalcic horizon, or a duripan.

These soils have a minimum thickness of 10 cm. Soils that are

10 to 18 cm deep have an umbric epipedon if the whole soil

meets all of the criteria for an umbric epipedon when mixed.

The minimum thickness is 25 cm for (1) all soils with a

texture throughout the epipedon of loamy fine sand or coarser;

(2) all soils that have no diagnostic horizons or features below

the epipedon; and (3) soils that are 75 cm or more deep to a

densic, lithic, or paralithic contact or a duripan and are more

than 75 cm deep to the lower boundary of any argillic, cambic,

kandic, natric, oxic, or spodic horizon (all defined below).

The minimum thickness is one-third of the thickness from

the mineral soil surface to any of the features in the paragraph

above if (1) the texture in some or all parts of the epipedon is

loamy very fine sand or finer and (2) depth to the feature listed

in the paragraph above is between 54 and 75 cm below the

mineral soil surface.

The minimum thickness is 18 cm for all other soils.

The umbric epipedon has less than 1,500 milligrams per

kilogram of P2

O5 soluble in 1 percent citric acid or has an

irregular decrease in the amounts of P2O5 with increasing depth

below the epipedon, or there are phosphate nodules within the

epipedon. This restriction is intended to exclude plow layers of

very old arable soils and kitchen middens that, under use, have

acquired the properties of an umbric epipedon and to include

the epipedon of a soil developed in highly phosphatic parent

material.

Some part of the epipedon is moist for 90 days or more

(cumulative) in normal years during times when the soil

temperature at a depth of 50 cm is 5 oC or higher and the soil is

not irrigated.

Sediments that have been continuously under water since

deposition have a very high water content and are unable to

support livestock. Although some soils that have an umbric

epipedon are very poorly drained, the umbric epipedon is

required to have an n value (defined below) of less than 0.7.

Several accessory properties are common in soils that have

an umbric epipedon. These soils have the potential for toxicity

from aluminum, and they are commonly low in calcium,

magnesium, and potassium if lime and fertilizer have not been

applied. These are accessory properties important to plant

growth. The structure of the umbric epipedon facilitates the

movement of moisture and air whenever the soil is not

saturated with water.

The content of organic matter indicates that the soil has

received enough moisture to support fair to luxuriant plant

growth in normal years. The umbric epipedon must be moist in

at least some part for 3 months or more (cumulative) in normal

years at times when the soil temperature is 5 oC or higher at a

depth of 50 cm and when the soil is not irrigated.

Although the umbric epipedon is a surface horizon that can

be truncated by erosion, its many important accessory

properties suggest its use as a diagnostic horizon at a high

categoric level.

Some plaggen epipedons meet all of the requirements for an

umbric epipedon but also show evidence of a gradual addition

of materials during cultivation, whereas the umbric epipedon

does not have the artifacts, spade marks, and raised surfaces

that are characteristic of the plaggen epipedon.

Required Characteristics

The umbric epipedon consists of mineral soil materials and

has the following properties:

1. When dry, either or both:

a. Structural units with a diameter of 30 cm or less or

secondary structure with a diameter of 30 cm or less; or

b. A moderately hard or softer rupture-resistance class;

and
28 Soil Taxonomy

2. All of the following:

a. Colors with a value of 3 or less, moist, and of 5 or less,

dry; and

b. Colors with chroma of 3 or less, moist; and

c. If the soil has a C horizon, the umbric epipedon has a

color value at least 1 Munsell unit lower or chroma at least

2 units lower (both moist and dry) than that of the C

horizon or the epipedon has at least 0.6 percent more

organic carbon than that of the C horizon; and

3. A base saturation (by NH4

OAc) of less than 50 percent in

some or all parts; and

4. An organic-carbon content of:

a. 0.6 percent more than that of the C horizon (if one

occurs) if the umbric epipedon has a color value less than 1

Munsell unit lower or chroma less than 2 units lower (both

moist and dry) than the C horizon; or

b. 0.6 percent or more; and

5. After mixing of the upper 18 cm of the mineral soil or of

the whole mineral soil if its depth to a densic, lithic, or

paralithic contact or a duripan (all defined below) is less than

18 cm, the minimum thickness of the epipedon is as follows:

a. 10 cm or the depth of the noncemented soil if the

epipedon is loamy very fine sand or finer and is directly

above a densic, lithic, or paralithic contact or a duripan that

is within 18 cm of the mineral soil surface; or

b. 25 cm or more if the epipedon is loamy fine sand or

coarser throughout or if there are no underlying diagnostic

horizons (defined below) and the organic-carbon content of

the underlying materials decreases irregularly with

increasing depth; or

c. 25 cm or more if the lower boundary of any argillic,

cambic, natric, oxic, or spodic horizon (defined below) is 75

cm or more below the mineral soil surface; or

d. 18 cm if the epipedon is loamy very fine sand or finer in

some part and one-third or more of the total thickness

between the top of the epipedon and the shallowest of any

features listed in item 5-c is less than 75 cm below the

mineral soil surface; or

e. 18 cm or more if none of the above conditions apply;

and

6. Phosphate:

a. Content less than 1,500 milligrams per kilogram

soluble in 1 percent citric acid; or

b. Content decreasing irregularly with increasing depth

below the epipedon; or

c. Nodules are within the epipedon; and

7. Some part of the epipedon is moist for 90 days or more

(cumulative) in normal years during times when the soil

temperature at a depth of 50 cm is 5 oC or higher, if the soil is

not irrigated; and

8. The n value (defined below) is less than 0.7; and

9. The umbric epipedon does not have the artifacts, spade

marks, and raised surfaces that are characteristic of the

plaggen epipedon.

Diagnostic Subsurface Horizons

The horizons described in this section form below the surface

of the soil, although in some areas they form directly below a

layer of leaf litter. They may be exposed at the surface by

truncation of the soil. Some of these horizons are generally

regarded as B horizons, some are considered B horizons by

many but not all pedologists, and others are generally regarded

as parts of the A horizon.

Agric Horizon

The agric horizon is an illuvial horizon that has formed

under cultivation and contains significant amounts of illuvial

silt, clay, and humus. When a soil is brought under cultivation,

the vegetation and the soil fauna as a rule are changed

drastically. The plow layer is mixed periodically, and, in effect,

a new cycle of soil formation is started. Even where the

cultivated crops resemble the native vegetation, stirring of the

plow layer and the use of amendments, especially lime,

nitrogen, and phosphate, normally produce significant changes

in soil structure, flora, and fauna.

After a soil has been cultivated for a long time, changes in

the horizon directly below the plow layer become apparent and

cannot be ignored in classifying the soil. The large pores in the

plow layer and the absence of vegetation immediately after

plowing permit a turbulent flow of muddy water to the base of

the plow layer. The water can enter wormholes or fine cracks

between peds at the base of the plow layer, and the suspended

materials are deposited as the water is withdrawn into capillary

pores. The worm channels, root channels, and surfaces of peds

in the horizon underlying the plow layer become coated with a

dark colored mixture of organic matter, silt, and clay. The

accumulations on the sides of wormholes become thick and can

eventually fill the holes. If worms are scarce, the accumulations

may take the form of lamellae that range in thickness from a

few millimeters to about 1 cm. The lamellae and the coatings

on the sides of wormholes always have a lower color value and

chroma than the soil matrix.

The agric horizon can have somewhat different forms in

different climates if there are differences in soil fauna. In areas

of a humid, temperate climate where soils have a udic moisture

regime and a mesic soil temperature regime (defined below),

earthworms can become abundant. If there are wormholes that,
Horizons and Characteristics Diagnostic for the Higher Categories 29

including their coatings, constitute 5 percent or more (by

volume) of the horizon and if the coatings are 2 mm or more

thick and have a color value, moist, of 4 or less and chroma of

2 or less, the horizon is an agric horizon. After long

cultivation, the content of organic matter in the agric horizon

is not likely to be high, but the carbon-nitrogen ratio is low

(generally less than 8). The pH value of the agric horizon is

close to neutral (6 to 6.5).

In areas of a Mediterranean climate where soils have a xeric

soil moisture regime (defined below), earthworms are less

common and the illuvial materials accumulate as lamellae

directly below the Ap horizon. If these lamellae are 5 mm or

more thick, have a color value, moist, of 4 or less and chroma

of 2 or less, and constitute 5 percent or more (by volume) of a

horizon 10 cm or more thick, this horizon is an agric horizon.

The agric horizon in these xeric soils is also part of an

argillic horizon. An agric horizon may form in several of the

other diagnostic horizons, but not in a mollic or anthropic

epipedon. A soil in which an illuvial horizon has formed in the

mollic epipedon is distinguished by other means.

Required Characteristics

The agric horizon is directly below an Ap horizon and has the

following properties:

1. A thickness of 10 cm or more and either:

a. 5 percent or more (by volume) wormholes, including

coatings that are 2 mm or more thick and have a value,

moist, of 4 or less and chroma of 2 or less; or

b. 5 percent or more (by volume) lamellae that have a

thickness of 5 mm or more and have a value, moist, of 4 or

less and chroma of 2 or less.

Albic Horizon

The albic horizon (photo 12) is an eluvial horizon, 1.0 cm or

more thick, that has 85 percent or more (by volume) albic

materials (defined below). It generally occurs below an A

horizon but may be at the mineral soil surface. Under the albic

horizon there generally is an argillic, cambic, kandic, natric, or

spodic horizon or a fragipan (defined below). The albic horizon

may lie between a spodic horizon and either a fragipan or an

argillic horizon, or it may be between an argillic or kandic

horizon and a fragipan. It may lie between a mollic epipedon

and an argillic or natric horizon or between a cambic horizon

and an argillic, kandic, or natric horizon or a fragipan. The

albic horizon may separate horizons that, if they were together,

would meet the requirements for a mollic epipedon. It may

separate lamellae that together meet the requirements for an

argillic horizon. These lamellae are not considered to be part of

the albic horizon.

In some soils the horizon underlying the albic horizon is too

sandy or too weakly developed to have the levels of

accumulation required for an argillic, kandic, natric, or spodic

horizon. Some soils have, directly below the albic horizon, either

a densic, lithic, or paralithic contact or another relatively

impervious layer that produces a perched water table with

stagnant or moving water.

Argillic Horizon

An argillic horizon is normally a subsurface horizon with a

significantly higher percentage of phyllosilicate clay than the

overlying soil material (photo 13). It shows evidence of clay

illuviation. The argillic horizon forms below the soil surface,

but it may be exposed at the surface later by erosion.

Genesis

Because there is little or no evidence of illuvial clay

movement in soils on the youngest landscapes, soil scientists

have concluded that the formation of an argillic horizon

requires at least a few thousand years. On some latePleistocene landscapes, argillic horizons are more strongly

expressed in soils under forest vegetation than in soils under

grass. Therefore, the kind of flora and associated fauna is

thought to have an influence on the rate of development or

degree of expression of the argillic horizon. Climate also is a

factor. There are few or no examples of clay films in soils with

perudic soil moisture regimes, such as the soils in parts of

southeastern Alaska, the Olympic Peninsula of Washington,

and the British highlands where water percolates through the

soils during all seasons. Argillic horizons are common on the

adjacent lowlands in Great Britain, under climates where the

soils undergo wetting and drying cycles.

Textural differentiation in soils with argillic horizons results

from one or more processes acting simultaneously or

sequentially, affecting surface horizons, subsurface horizons, or

both. The degree to which a process or several processes

operate varies widely from soil to soil. In some soils clay

illuviation is significant, while in others clay illuviation is

overshadowed by in situ weathering. Not all of the processes

are completely understood. The ones thought to be most

important are summarized in the following paragraphs.

1. Clay eluviation and illuviation.—Some suspended clay

is carried downward in the soil water. The movement of clay

can take place from one horizon to another or within a horizon.

There is a strong mineralogical similarity between the fine clay

in an eluvial horizon and that in a deeper illuvial horizon. This

similarity supports the idea that clay migrates dominantly as

clay rather than as the products of decomposition that were

later synthesized to form clay-sized particles.

Clay mobility is influenced by a number of factors. If clay

platelets are aggregated by sesquioxides or other cementing

agents, the cement must be dissolved prior to clay movement.

Phyllosilicates with thick, diffuse double layers of adsorbed

cations are dispersed more easily than those with thin double

layers. If the ionic strength of the soil solution is high, clays

tend to flocculate. Wetting a dry soil seems to lead to
30 Soil Taxonomy

disruption of the fabric and to dispersion of clay unless the ionic

concentration is high. Sodium ions in solution, between critical

limits of activity, increase clay dispersion. Optimal clay

dispersion occurs when the pH at the zero point of net charge

on the clay particle is distinctly different from the pH of the

soil solution. This dispersion commonly occurs between pH

values of 4.5 and 6.5.

In soils that are periodically dry, the clay suspension moves

downward and stops in the dry subsoil as the soil solution is

absorbed. During absorption of the soil solution, the surface of

the ped acts as a filter and keeps clays from entering the

interior of the ped. The clay platelets then coat the surface of

the ped or void wall and are oriented with their long axes

parallel to the surface on which they were deposited. They are

called clay films. These layers of oriented clay can be

distinguished from the rest of the clay through the use of a

petrographic microscope.

As soil solution enters unsaturated subsoils, water

movement occurs in fine pores. Pore water velocity is reduced

as a function of pore wall friction. Some clay deposition may

occur simply because fluid velocity is too low to keep the clay

suspended.

Capillarity affects water movement both downward and into

the peds. If a soil horizon is underlain by a horizon of

considerably coarser texture (i.e., larger pores), capillary

continuity is broken and water tends to remain in the fine

capillaries above the zone of contact. When water evaporates or

is withdrawn by roots, suspended and/or dissolved materials,

including clay, are left. This action accentuates the original

difference in pore-size distribution, and clay is deposited

directly above the coarse textured strata or lenses.

Clays that are deposited from suspension in sediments, such

as shale or glacial till, are commonly oriented parallel to the

depositional or stress surface. In contrast, clays formed in place

within the soil generally are oriented according to the crystal

structure of the original mineral grains from which they

formed. Neither the mineral grains nor the planes in the shale

or till are consistently oriented with respect to any pedogenic

features. Consequently, the thin sections of many soils indicate

layers of oriented clays in peds and on the surfaces of pores and

peds.

Accumulation of clay in some soils occurs predominantly

through flocculation. The dispersed clay stops moving

downward if a layer with different pH or electrolyte

concentration, or both, is present in the subsoil. The

flocculated clays will have little or no orientation with respect

to the features of the microfabric. Thus, distinguishing

flocculated clays from clays formed in situ is difficult.

The above discussion is not intended to imply that all of the

clay increase in an argillic horizon is the result of illuviation.

The conclusions of many studies range from those indicating

that most of the clay increase is the result of translocation to

those indicating that most of the clay formed in situ with

minimal translocation.

2. Clay dissolution in the epipedon.—Dissolution of claysized phyllosilicates can lead to a loss of clay in soils. The loss

generally is greatest in the upper horizons, where weathering

processes are most intense. Because this process generally

affects surface horizons more than subsurface horizons, a

vertical textural differentiation can result.

3. Selective erosion.—Raindrop splash and subsequent

surface soil erosion cause the smaller soil particles to be moved

farther downslope than the larger particles. Eventually, part of

the fine fraction is eliminated from the surface layer of sloping

soils, leaving a concentration of the coarser textured part. The

speed of this process depends on many factors. In areas where

highly erosive rain falls on soils with little surface cover, the

process can occur rapidly. The surficial movement of clay

downslope seems to be widespread, and selective erosion likely

is a process that contributes to textural differentiation in some

soils.

4. In situ clay formation.—Vertical textural

differentiation is enhanced in some soils when the surface

horizon dries and evaporation ceases but the subsoil remains

moist. The presence of water allows hydrolysis in the subsoil

and the subsequent production of clay. This process is

important in many soils.

5. Clay destruction in a subsurface horizon.—Clay

destruction may occur in a soil through the process of

ferrolysis. Ferrolysis causes loss of clay from the upper

horizons by decomposition from the upper layers. The process

consists of a sequence of repetitive cycles involving an

oxidative phase and a reductive phase. During the reductive

phase, the ferrous iron displaces exchangeable cations, which

are then removed by leaching. During the oxidative stage,

oxidation of exchangeable ferrous iron produces exchangeable

hydrogen, part of which attacks the phyllosilicate. In every

cycle, cations are removed by leaching and part of the

phyllosilicate is destroyed. With continued ferrolysis, a

seasonally wet soil, even if base saturated, can develop a gray,

silty or sandy horizon with a low clay content and a low cationexchange capacity. Ferrolysis is the process that may help to

develop albic material in a number of soils, including Albolls

and Albaqualfs.

Regardless of the process responsible for textural

differentiation, clay illuviation in one form or another is

common to all argillic horizons.

Significance to Soil Classification

The argillic horizon represents a time-landscape

relationship that is locally and regionally important. A taxon

that includes all soils that have an argillic horizon would have

very few other common properties. Yet, the horizon is a mark

of landscape stability with respect to the formation and

preservation of a finer textured subsurface horizon, as opposed

to processes that destroy or remove clay from the horizon or

that mix horizons. Because an argillic horizon forms at a

relatively slow rate, its presence indicates that the geomorphic
Horizons and Characteristics Diagnostic for the Higher Categories 31

surface has been relatively stable and that the period of stability

has been long.

If the argillic horizon occurs in an area of an aridic moisture

regime (defined below) and is rarely moist or has free carbonates

throughout, it probably indicates an old soil and stable

geomorphic surface of such great age that the climate has

changed since the formation of the horizon. In the present

environment, the precipitation is not sufficient to remove

carbonates from the soil or to translocate clay to the base of the

argillic horizon.

On the steppes, savannas, and grasslands in areas of

subhumid climates, the argillic horizon is a useful means of

distinguishing between surfaces of Holocene or late-Pleistocene

age and older surfaces.

In cool, humid regions the argillic horizon seems to be

impermanent. It forms slowly, but there is evidence that with

time it is moved to a greater depth in the soil and is finally

destroyed. In its place, a glossic or spodic horizon may form.

In humid, temperate and tropical regions, the presence of an

argillic horizon has other meanings. In humid, temperate

regions that are forested, the argillic horizon is mainly a mark

of a stable surface. In the humid tropics the clay fraction of the

argillic horizon commonly is low in silicon because of intense

weathering. The high degree of weathering is reflected by a

dominance of 1:1 layer lattice clays and oxyhydroxides of iron

and by a general absence of 2:1 layer lattice clays, except for

hydroxy-interlayered vermiculite. Gibbsite can occur in the

most weathered argillic horizons. In humid, temperate and

tropical regions where cycling of bases by plants is the chief

mechanism by which basic cations are retained against

leaching from the soils, the available nutrients of ped exteriors

relative to ped interiors are significant to root development. In

some of these soils, the roots do not enter the peds of the

argillic horizon but occur along faces of the peds. The peds are

coated by continuous clay films with significantly more

nitrogen, phosphorus, and potassium than the available

nutrients in the interior of the peds.

Identification

Since the argillic horizon can result from one or more

processes acting simultaneously or sequentially and affecting

surface horizons, subsurface horizons, or both, one or more sets

of properties can be used for its identification. Positive

identification of the argillic horizon is difficult in some

situations. No one feature is common to all argillic horizons

and absent from all other horizons. Nearly all argillic horizons

have at least two of the following features:

1. There is more silicate clay in the argillic horizon than in an

overlying horizon. The boundary between the eluvial horizon

and the argillic horizon is generally clear or abrupt, and

commonly it is irregular. The clay content (percent, by weight,

less than 2 micrometers, excluding clay-sized carbonates) of the

argillic horizon must be at least 1.2 times the clay content of an

overlying eluvial horizon, and generally the increase must be

larger to be consistently detected in the field. The required

increase in clay content occurs within a vertical distance of 15

cm in most pedons, but it can occur within a vertical distance as

great as 30 cm and still meet the requirements for an argillic

horizon.

2. There are coatings of oriented clay on the surfaces of pores

and peds or orientated clay as coatings or as bridges between

sand grains somewhere within many argillic horizons. An

experienced pedologist can often identify the layers of oriented

clay on the surfaces of peds and in pores, called clay films,

with a 10 X hand lens. The clay films used to identify an

argillic horizon should occur on more than just the vertical

sides of peds. Examination of the surfaces of peds and pores

under a 10- to 20-power hand lens usually discloses one or

more of the features common to most clay films. The films may

differ from the interiors of the peds in color as well as texture.

Clay films should also have an observable thickness, whereas

many pressure faces do not. Pores that are open on the lower

side of a ped can have irregular lips where the clay protrudes.

Commonly, the surfaces have an irregular shape and show

channels and flow lines that apparently were formed by soil

solution moving through the soil. Photo 14 shows a prominent

clay film in a pore and a faint clay film on the surface of a ped

of an argillic horizon in a medium textured soil under

magnification. The pore has a prominent, dark gray coating,

and the surface of the ped has a distinct, brownish coating. The

broken surface that reveals the interior of the ped, on the right,

has no coating. The scale is 2 mm. Photo 15 shows illuvial clay

in sand. The clay coats the sand grains, and an occasional pore

has a clay film. Very commonly, the coatings occur only in part

of the horizon. Some argillic horizons have clay films only

toward the base of the argillic horizon.

3. The ratio of fine clay (particles less than 0.2 micrometer in

diameter) to total clay can be larger in an argillic horizon than

in the overlying horizons. This difference is more common in

soils with higher amounts of 2:1 phyllosilicates than 1:1

phyllosilicates. The table “Clay Distribution and Ratio of Fine

Clay to Total Clay in Two Soils That Have Argillic Horizons”

illustrates the difference in the size of clay particles in the

various horizons. The ratio of fine clay to total clay is typically,

but not always, highest in the argillic horizons with 2:1

phyllosilicates.

4. Rock structure is evident in less than half of the volume of

the argillic horizon. In this context rock structure includes fine

stratification (less than 10 mm) in unconsolidated sediments

(eolian, alluvial, lacustrine, or marine) and saprolite derived

from consolidated rocks in which unweathered minerals and

pseudomorphs of weathered minerals retain their relative

positions to each other.
32 Soil Taxonomy

5. The argillic horizon is commonly parallel or nearly parallel to

the surface. If the epipedon has been truncated, the argillic

horizon can occur at the soil surface.

Special Problems

This section is divided into five parts: (1) soils that formed in

uniform parent materials with clay illuviation; (2) truncated soils,

cultivated soils, and soils that formed in stratified parent

materials; (3) problems associated with determining the top of

the argillic horizon; (4) problems associated with determining

the base of the argillic horizon; and (5) destruction of the

argillic horizon.

1. Soils that formed in uniform parent materials with

clay illuviation.—It is believed that many soils are derived

from multiple parent materials rather than a single, uniform

material. Argillic horizons forming in uniform parent

materials are described first because they are the least

complicated. In soils that formed in uniform parent material

and have 15 to 40 percent clay in the overlying eluvial horizon,

no truncation, and no Ap horizon directly above the illuvial

horizon, the clay content in the illuviated horizon is at least 1.2

times greater than the clay content in the eluvial horizon. The

thickness of the illuvial horizon must be at least one-tenth that

of the overlying horizons, but as a minimum an illuvial

horizon must be at least 7.5 cm thick before it is considered an

argillic horizon. The thickness of the transition zone from the

eluvial horizon to the argillic horizon must be 30 cm or less.

The ratio of fine clay to total clay in the argillic horizon is

commonly at least 1.2 times greater than the ratio in the eluvial

horizon.

In soils with less than 15 percent clay in any part of the

overlying eluvial horizon, the illuvial horizon can be either

continuous vertically or composed of lamellae (photo 16). The

required ratio of clay in the illuvial horizon to that in the

eluvial horizon is somewhat higher than is required in both

medium textured and clayey soils. Soils that have less than 15

percent clay in any part of the eluvial horizon must have at

least 3 percent (absolute) more clay in the illuvial horizon. For

example, if the eluvial horizon has 4 percent clay, then the

illuvial horizon must have at least 7 percent clay.

In soils with less than 15 percent clay, the illuvial horizon

must be 15 cm or more thick to be an argillic horizon. If the

argillic horizon is composed of lamellae, which can be spaced

at intervals ranging from a few centimeters to a few decimeters

or more, only the lamellae 0.5 cm or more thick are considered

in determining whether the horizon meets the clay content and

thickness requirements for an argillic horizon.

In soils that have at least 40 percent clay in the eluvial

horizon, that formed in uniform material, and have no

truncation, the difference in clay content between the eluvial

horizon and the illuvial horizon must be 8 percent (absolute

difference) or more. For example, if the eluvial horizon has 42

percent clay, the illuvial horizon must have at least 50 percent

clay before it can be considered an argillic horizon. The

thickness of the illuvial horizon should be at least one-tenth

that of the overlying horizons. As a minimum, the illuvial

horizon must be at least 7.5 cm thick.

In areas where climates have distinct wet and dry seasons

and illuvial horizons have clayey textures and expansive 2:1

phyllosilicates, appreciable interped pressures are generated as

the clays swell. The pressures produce irregular but smooth

surfaces of peds and a strong degree of stress orientation of

clay throughout the ped. In many such clayey horizons,

identifying clay films is difficult or impossible.

If the coefficient of linear extensibility of the horizon

exceeds 0.04 and there are periods with distinct differences in

moisture content, the evidence of clay illuviation is satisfied if

the ratio of fine clay to total clay in the illuvial horizon is

greater by 1.2 times or more than the ratio in an overlying

horizon.

2. Truncated soils, cultivated soils, and soils that

formed in stratified parent materials.—Soils that formed in

stratified parent materials and truncated soils in which the

eluvial horizon has been removed or the illuvial horizon has

been mixed into an Ap horizon present special problems in the

identification of the argillic horizon. If both the eluvial

Clay Distribution and Ratio of Fine Clay to Total Clay in Two

Soils That Have Argillic Horizons

(Data for the argillic horizons are printed in italic type)

Clay distribution

Depth (cm)

Less than

0.002 mm

0.002 to

0.0002 mm

Less than

0.0002 mm

Fine clay:

total clay

Percent Percent Percent Ratio

0-18 ......... 22.6 15.8 6.8 0.30

18-25 ......... 26.2 18.8 7.4 .28

25-36 ......... 45.3 25.1 20.2 .45

36-58 ......... 42.8 26.6 16.2 .38

58-74 ......... 34.7 25.2 9.5 .27

74-89 ......... 32.9 24.0 8.9 .27

0-18 ......... 33.1 24.6 8.5 .26

18-25 ......... 32.4 23.2 9.2 .28

25-40 ......... 40.4 24.6 15.8 .39

40-53 ......... 45.0 25.0 20.0 .45

53-71 ......... 41.4 23.3 18.1 .44

71-120 ....... 38.0 23.3 14.7 .39

120-140 ....... 20.5 15.6 4.9 .23

140-205 ....... 20.3 15.3 5.0 .25

205-250 ....... 12.3 9.5 2.8 .23
Horizons and Characteristics Diagnostic for the Higher Categories 33

horizons and the illuvial horizons formed in materials with

different amounts of clay initially, differences in clay content

between the horizons cannot always be used to identify the

argillic horizon. Likewise, in soils that have been cultivated

and in which the Ap horizon is directly above the argillic

horizon, the argillic horizon may not be recognizable on the

basis of a clay increase. The plow layer may contain the most

clayey part of the original argillic horizon.

For soils that have an Ap horizon and do not have a

sufficient clay increase between the Ap horizon and the illuvial

horizon (as described above), the argillic horizon is determined

by the identification of evidence of clay illuviation, such as clay

films, clay linings on pores, or oriented clay in thin sections of

the matrix in some subhorizon.

In soils that have a lithologic discontinuity at the boundary

between the eluvial horizon and the illuvial horizon, clay

illuviation is evidence of an argillic horizon. Since it is critical

in these soils, clay illuviation must be prominent enough to

obscure fine sand grains on at least 10 percent of the surfaces

of peds, the clay illuviation must be nearly continuous in some

pores, or thin sections must show oriented clay coatings on at

least 1 percent of the horizon before the horizon is considered

to be an argillic horizon.

3. The top of the argillic horizon.—The top of the

argillic horizon in soils that are not truncated and that have no

lithologic discontinuity between the eluvial and illuvial

horizons occurs at the depth where the requirement for clay

increase is met. Soils that have an abrupt or clear boundary

between the eluvial and illuvial horizons have an argillic

horizon that starts near the top of the illuvial layer. If

properties of an argillic horizon are present but the upper

boundary is gradual, the top of the argillic horizon is the depth

at which the percentage of clay exceeds that of a horizon

higher in the profile by the appropriate amount after fitting a

smooth curve. Although the top of the argillic horizon is

defined on the basis of a clay increase, there are other

properties that provide clues to its identification. In many soils

the argillic horizon has stronger chroma, redder hue, or larger

structural units than the eluvial horizon. Clay films may or

may not be present at the depth designated as the top of the

argillic horizon.

In soils where the argillic horizon is degrading, such as soils

that have a glossic horizon, the top of the argillic horizon is the

point where the clay increase is met after mixing. For example,

an E/Bt horizon may be part of the argillic horizon if its clay

content, after mixing, exceeds the clay content of the overlying

horizon by the required amount. More commonly, Bt/E

horizons rather than E/Bt horizons have the required clay

increase.

The top of the argillic horizon in truncated soils that do not

exhibit the required clay increase and that do not have a

lithologic discontinuity is the bottom of the Ap horizon.

For soils that have a lithologic discontinuity between the

eluvial horizon and the illuvial horizon and that do not have

the required clay increase described above, the top of the argillic

horizon is considered to be at the contact between the two

materials.

4. The base of the argillic horizon.—The base of the

argillic horizon is obvious in many soils that overlie rootlimiting layers, such as duripans or bedrock. In other soils the

lower boundary of the argillic horizon is gradual and

commonly is irregular. In these soils describing the base of the

argillic horizon is difficult, but a definition is needed for

identification of proper taxa.

The bottom of argillic horizons that have clay films is at the

depth where the combination of both structure with mean

horizontal dimensions of 10 cm or less and clay illuviation are

no longer identifiable. In sandy soils that have argillic horizons

without structure, the bottom of the argillic horizon is at the

depth where clay bridging of the sand grains is no longer

identifiable. The base of the argillic horizon is allowed to have

less total clay than the eluvial horizon.

Argillic horizons that do not have clay films, such as some

of the argillic horizons with a high shrink-swell potential, have

different criteria. The base of the argillic horizon in soils with

a high shrink-swell potential and no clay films is at the depth

where both the pressure faces and structure with mean

horizontal dimensions of 10 cm or less are no longer

identifiable.

5. Destruction of the argillic horizon.—An argillic

horizon can be formed and later destroyed. Destruction of

argillic horizons can occur in many ways and is by no means

limited to the following examples.

Argillic horizons that formed in paleoenvironments with

more effective precipitation than that in the present

environment can be engulfed by carbonates and more soluble

salts. This process commonly occurs in areas that are presently

arid. As the argillic horizon is engulfed, salt crystals grow and

plug the horizon. Concurrently, the salt crystals disrupt the soil

fabric and the cutans, including the clay films. In time, the

entire argillic horizon could be engulfed by salts and all

evidence of clay illuviation could be destroyed.

Mixing of horizons by animals, by frost, or by shrinking and

swelling can destroy argillic horizons or inhibit their

formation. Humans can rapidly change a soil and in some cases

destroy an argillic horizon.

Detailed studies of the micromorphology of some soils that

have an argillic horizon (e.g., Glossudalfs) provide evidence of

the destruction of argillic horizons. Clay films are absent from

the surfaces of peds, and skeletans, which are bleached silt or

sand grains that result from the loss of clay and iron, are

common. Oriented clay within the peds apparently persists. In

a degrading argillic horizon, the clay films on surfaces of peds

or in pores commonly are most abundant in the lower part of

the argillic horizon and in the underlying transitional horizon.

In advanced stages of degradation, there may be no clay films

within or on peds in the upper part of the argillic horizon.

Normally, a degrading argillic horizon also has an irregular
34 Soil Taxonomy

upper boundary that is marked by narrow to broad penetrations

of the eluvial horizon. Small nodular remnants of the argillic

horizon commonly occur in the lower part of the present

eluvial horizon.

An argillic layer that is being degraded or is subject to

pedoturbation must meet the requirements for clay increase

outlined above before it is considered an argillic horizon.

Required Characteristics

1. All argillic horizons must meet both of the following

requirements:

a. One of the following:

(1) If the argillic horizon is coarse-loamy, fine-loamy,

coarse-silty, fine-silty, fine, or very-fine or is loamy or

clayey, including skeletal counterparts, it must be at least

7.5 cm thick or at least one-tenth as thick as the sum of

the thickness of all overlying horizons, whichever is

greater. For example, if the overlying horizons are more

than 150 cm thick, then the argillic horizon must be 15

cm or more thick; or

(2) If the argillic horizon is sandy or sandy-skeletal, it

must be at least 15 cm thick; or

(3) If the argillic horizon is composed entirely of

lamellae, the combined thickness of the lamellae that are

0.5 cm or more thick must be 15 cm or more; and

b. Evidence of clay illuviation in at least one of the

following forms:

(1) Oriented clay bridging the sand grains; or

(2) Clay films lining pores; or

(3) Clay films on both vertical and horizontal surfaces

of peds; or

(4) Thin sections with oriented clay bodies that are

more than 1 percent of the section; or

(5) If the coefficient of linear extensibility is 0.04 or

higher and the soil has distinct wet and dry seasons, then

the ratio of fine clay to total clay in the illuvial horizon is

greater by 1.2 times or more than the ratio in the eluvial

horizon; and

2. If an eluvial horizon remains and there is no lithologic

discontinuity between it and the illuvial horizon and no plow

layer directly above the illuvial layer, then the illuvial horizon

must contain more total clay than the eluvial horizon within a

vertical distance of 30 cm or less, as follows:

a. If any part of the eluvial horizon has less than 15

percent total clay in the fine-earth fraction, the argillic

horizon must contain at least 3 percent (absolute) more clay

(10 percent versus 13 percent, for example); or

b. If the eluvial horizon has 15 to 40 percent total clay in

the fine-earth fraction, the argillic horizon must have at least

1.2 times more clay than the eluvial horizon; or

c. If the eluvial horizon has 40 percent or more total clay in

the fine-earth fraction, the argillic horizon must contain at

least 8 percent (absolute) more clay (42 percent versus 50

percent, for example).

Calcic Horizon

The calcic horizon is an illuvial horizon in which secondary

calcium carbonate or other carbonates have accumulated to a

significant extent (photo 17). Calcic horizons must be 15 cm or

more thick. They must have 15 percent calcium carbonate

equivalent and either have at least 5 percent more calcium

carbonate equivalent than the underlying horizon or have 5

percent or more identifiable secondary carbonates unless the

particle-size class is sandy, sandy-skeletal, coarse-loamy, or

loamy-skeletal and the clay content is less than 18 percent. If

the clay content is less than 18 percent and the particle-size

class is sandy, sandy-skeletal, coarse-loamy, or loamy-skeletal,

there must be at least 5 percent more calcium carbonate

equivalent than in an underlying horizon. In order to indicate

pedogenic accumulations of calcium carbonate, calcic horizons

require either identifiable secondary carbonates or more

calcium carbonate equivalent than an underlying horizon. If a

horizon with secondary carbonates is indurated or cemented to

such a degree that it meets the requirements for a petrocalcic

horizon, it is considered a petrocalcic horizon (defined below).

A calcic horizon may occur in conjunction with various other

horizons, such as a mollic epipedon, an argillic horizon, or a

natric horizon.

Most calcic horizons have identifiable secondary carbonates.

For reasons not fully understood, accumulations of carbonate in

some soils do not form filaments but are disseminated.

Disseminated carbonates have been observed in soils that are

high in gypsum or sodium and in soils where accumulations of

carbonate form through capillary rise.

The genetic implications of a calcic horizon vary. In arid

and semiarid regions with parent materials, including the dust

that falls, high in calcium carbonate, the precipitation is

insufficient to leach bases and salts. In these situations

carbonates accumulate in the larger voids, often first as

filaments along root channels and as thin, discontinuous

coatings on the bottom of rock fragments. With time,

continuous coatings of carbonate form on the rock fragments,

the carbonate filaments enlarge, and carbonate nodules and

concretions can form. With continued deposition of carbonates,

the horizon becomes plugged with carbonates. Finally, some

parts of a calcic horizon may become cemented or indurated,

though typically air-dry fragments of a calcic horizon slake in

water, except for disconnected carbonate concretions and

pendants under rock and pararock fragments.

In soils where ground water near the surface contains

appreciable amounts of calcium bicarbonate, capillary rise and
Horizons and Characteristics Diagnostic for the Higher Categories 35

evaporation and transpiration cause precipitation of calcium

carbonate. Depending on the depth from the surface to the

capillary fringe, the top of the zone of calcium carbonate

accumulation may be from the surface to a depth of about 60

cm. In such soils, the accumulation of calcium carbonate is

comparable to the accumulation of more soluble salts in desert

playas. Depending on the position of the water table, these soils

may occupy depressions. If water was ponded, a soil that has a

calcic horizon commonly forms a circular outline around the

deeper depressions and can also occur on microhighs in the

depressions.

In the situations above, one might attach a high genetic

significance to a calcic horizon. In some other circumstances,

however, one can attach little genetic significance to the

absolute amount of carbonates in a horizon or layer of

carbonate accumulation. Deposition from ground water at a

depth of 3 m or more is likely a geologic rather than a

pedologic process. In soils that formed in calcareous materials

on steppes, the amount of calcium carbonate in horizons that

contain secondary calcium carbonate is a partial function of the

amount of calcium carbonate in the parent materials.

Some plant species growing in soils with calcic horizons

often exhibit “lime-induced chlorosis,” in which

micronutrients, such as iron, manganese, and zinc, are

rendered unavailable to the plants. Plant species that occur

naturally in arid environments frequently do not exhibit this

chlorosis, but many agriculturally grown plant species, such as

citrus, avocados, corn, and beans, are susceptible to

micronutrient deficiencies in calcareous soils.

Required Characteristics

The calcic horizon has all of the following properties:

1. Is 15 cm or more thick; and

2. Is not indurated or cemented to such a degree that it meets

the requirements for a petrocalcic horizon; and

3. Has one or more of the following:

a. 15 percent or more CaCO3

 equivalent (see below), and

its CaCO3 equivalent is 5 percent or more (absolute) higher

than that of an underlying horizon; or

b. 15 percent or more CaCO3 equivalent and 5 percent or

more (by volume) identifiable secondary carbonates; or

c. 5 percent or more calcium carbonate equivalent and

has:

(1) Less than 18 percent clay in the fine-earth fraction;

and

(2) A sandy, sandy-skeletal, coarse-loamy, or loamyskeletal particle-size class; and

(3) 5 percent or more (by volume) identifiable

secondary carbonates or a calcium carbonate equivalent

(by weight) that is 5 percent or more (absolute) higher

than that of an underlying horizon.

Cambic Horizon

A cambic horizon (photo 18) is the result of physical

alterations, chemical transformations, or removals or of a

combination of two or more of these processes.

Physical alterations are the result of the movement of soil

particles by freezing and thawing, shrinking and swelling, root

proliferation, wetting and drying, or animal activities

(including human activities) to such an extent as to destroy

one-half or more of the original rock structure or to form

aggregations of the soil particles into peds, or both. Rock

structure in this context includes fine stratification (less than 5

mm thick) in unconsolidated sediments (eolian, alluvial,

lacustrine, or marine) and saprolite or residuum derived from

bedrock in which the unweathered minerals and pseudomorphs

of weathered minerals retain their relative positions to each

other.

Chemical transformations in the cambic horizon are the

result of (1) hydrolysis of primary minerals, which forms clays

and liberates sesquioxides; (2) solution and redistribution or

removal of carbonates or gypsum; (3) reduction and

segregation or removal of iron; or (4) a combination of these

processes.

Alteration by the accumulation of silicate clay, sesquioxides,

or organic matter or by the removal of calcium carbonate or

gypsum can also produce a cambic horizon. The accumulation

of clay and sesquioxides can be identified by field or laboratory

tests. The accumulation must be too little or the layer too thin

to meet the requirements for any other diagnostic subsurface

horizon. The cambic horizon also excludes layers that are part

of an anthropic, plaggen, folistic, histic, melanic, mollic, or

umbric epipedon but can include parts of some ochric

epipedons in unplowed soils. The cambic horizon and the

ochric horizon are not necessarily mutually exclusive.

The cambic horizon is commonly a subsurface horizon. It

normally lies in the position of a B horizon and in most pedons

is considered to be a B horizon, but it can include some A, E,

and transitional horizons. The cambic horizon is considered

part of the solum, and it normally occurs within the zone that

is reached by the roots of native plants. Some truncated soils

have a cambic horizon at the surface. Otherwise, the cambic

horizon is below one of the diagnostic epipedons. Regardless of

its mode of formation or position in a soil, the cambic horizon

must be 15 cm or more thick. The thickness requirement can

be met by combining lamellae that are 0.5 cm or more thick if

the other required criteria are met. The cambic horizon can

also include the illuvial materials that occur between the

lamellae. Although a cambic horizon requires a thickness of

only 15 cm, the base of the horizon must be 25 cm for most

taxa. (See the “Key to Soil Orders” in chapter 8.)
36 Soil Taxonomy

Below many argillic and spodic horizons, there are BC and CB

horizons that are transitional to the C horizon and in which

weathering and alteration have occurred. The alteration of

these transitional horizons in many soils is comparable to that

of other cambic horizons. There are also transitional horizons,

such as AB, EB, or BA horizons between an A or E horizon

and an argillic or kandic horizon, that may have the diagnostic

properties of a cambic horizon. Such transitional horizons are

considered cambic horizons. These cambic horizons are not

considered diagnostic above the series level in this taxonomy.

Identification

Cambic horizons may have several somewhat contrasting

forms, but each of these grades in places imperceptibly into the

others. The genetic significance of the cambic horizon varies

somewhat with the kind of soil. The properties of a cambic

horizon consistently carry the implication of a horizon that has

been altered. One could define several kinds of cambic

horizons and give them distinctive names, but understanding

the limits of the transitional forms would be difficult. The

possible benefits of separating the contrasting forms do not

seem to justify the complications that would result if one tried

to distinguish clearly the transitional forms. Nevertheless, it is

important to understand that cambic horizons vary in

appearance and in genetic significance. The typical forms that

the cambic horizon may have under varying combinations of

the soil-forming factors are described in the following

paragraphs.

1. A cambic horizon can form in the presence of aquic

conditions. If the level of ground water fluctuates near the soil

surface, free iron generally is removed from the individual

particles of sand, silt, and clay. Either this iron is lost from the

horizon, or some of it is concentrated, forming redoximorphic

concentrations. Gray redox depletions and red, brown, and

black redox concentrations are associated with the fluctuating

ground water. Because these features can develop rapidly in a

wet soil, they alone do not indicate sufficient alteration for the

identification of a cambic horizon. The processes of reduction

or of reduction and segregation of the iron must have been

intense enough to produce a horizon dominated by low chroma.

In addition, there must be soil structure or rock structure in less

than one-half of the volume before a layer can be identified as a

cambic horizon.

A cambic horizon normally does not form if aquic

conditions are present in a horizon at all times. Soils that

formed under these conditions have a reduced matrix with

colors that are commonly neutral or consist of shades of green

or blue. Soils with a reduced matrix change color on exposure

to air. Ordinarily, these changes are visible within a few

minutes if a moist clod is briefly exposed to the air and then is

broken so that the colors of the interior and the exterior can be

compared. Horizons with a reduced matrix are excluded from

the concept of the cambic horizon on the assumption that losses

of iron have been negligible.

A horizon forming under aquic conditions is a cambic horizon

if it has fluctuating aquic conditions within 50 cm of the surface

or the soil is artificially drained and the dominant colors (moist)

on faces of peds or in the matrix are characterized by the

following:

a. No change in hue on exposure to air; and

b. A value of 3 or less and chroma of 0; or

c. A value of 4 or more and chroma of 1 or less; or

d. Any value, chroma of 2 or less, and redox

concentrations.

2. Cambic horizons that are in subhumid and humid,

temperate regions and do not have aquic conditions near the

surface normally are brownish. Because free iron oxides have

been liberated, the chroma commonly is higher or the hue is

redder in the cambic horizon than in the C horizon or the

overlying horizon. Feldspars, volcanic glass, and easily

weatherable minerals, such as biotite, some pyroxenes, and

some amphiboles, show evidence of alteration under the

microscope. Oxides of iron derived from iron removed from

primary minerals can form coatings on individual soil paticles.

These coatings may be responsible for brownish and reddish

colors in the horizon. In humid, tropical regions the colors

commonly are more reddish than brownish.

Considerable time is required for the partial destruction of

iron-bearing minerals necessary for the development of color or

for the formation of clay. Structure, however, can form in short

periods. If there is sufficient clay and the soil material has a

relatively high coefficient of linear extensibility, expression of

structure takes place within a few years of the deposition of

sediment. Illuviation is insufficient to meet the requirements

for diagnostic horizons, and the peds generally do not show

distinctive coatings. In thin sections the microfabric

characteristics may include some distinctive features, such as

stress-oriented plasma domains. Illuviation argillans are

generally rare in cambic horizons. If there is a marked change

in pH because of the presence of calcareous materials

underlying the horizon or there is saprolitic material

underlying the cambic horizon, however, these underlying

materials may have significant amounts of translocated clay.

The presence of this clay implies that clay movement has taken

place in the soil, but the B horizon is not characterized by an

accumulation of translocated clay.

3. A cambic horizon that forms under a humid or subhumid

climate and from highly calcareous material commonly has

granular structure produced by soil fauna. In areas of temperate

and warm climates, earthworms, in particular, are ordinarily

active in mixing material from different horizons.

Consequently, the soil commonly is calcareous throughout its
Horizons and Characteristics Diagnostic for the Higher Categories 37

thickness, even though there has been a considerable loss of

carbonates. In calcareous materials there may be little or no

evidence of the weathering of feldspars and other silicate

materials. Evidence of the loss of carbonates is furnished by

weathered remnants of limestone fragments, by solution pitting

that can be seen on the faces of limestone pebbles, or by an

increasing content of carbonates with increasing depth. In

addition, the percentage of silicate clay commonly decreases

gradually with increasing depth.

4. In areas of arid and semiarid climates, the cambic horizon

commonly has still other forms. Gypsum and, especially,

calcium carbonate are common but are not present everywhere.

Except in areas that have Cicadidae or other burrowing

insects, the soil fauna are less significant to soil structure than

in humid regions. Changes in volume accompanying seasonal

changes in moisture content tend to produce prismatic

structure, and in some soils the prisms are very coarse. In arid

regions the tops of the prisms commonly lie only a very few

centimeters below a platy surface horizon. Other things being

equal, it appears that, up to a point, the lower the mean annual

precipitation, the closer the prisms are to the surface. Rock

structure, including fine stratification of sediments, is absent in

at least one-half of the volume of the cambic horizon, primarily

because the materials have been moved by roots and by

animals. In addition to soil structure or the absence of rock

structure, the cambic horizon shows evidence of the

redistribution of carbonates or gypsum. The mere redistribution

of salts more soluble than gypsum is insufficient evidence of a

cambic horizon because salt removal and accumulation can

occur very rapidly and change with the season. Calcium

carbonate and/or gypsum in transit through the cambic horizon

may be reprecipitated there, particularly on the undersides of

rock fragments, in pores, and on the faces of peds.

If calcium carbonate and gypsum are absent from the parent

material and from the dust that falls, there may be no

secondary carbonates or gypsum in the soil. In this situation,

the cambic horizon is identified by soil structure or the absence

of rock structure in more than one-half of the volume of the

horizon and any combination of redder hues and higher

chromas than in the underlying material or accumulations of

clays or sesquioxides. The clay content commonly decreases

with increasing depth in cambic horizons. Because of the

presence of lithologic discontinuities, however, determining

whether clay has been formed in the soil is difficult.

Features Common to Cambic Horizons

In spite of the diversity in appearance of cambic horizons,

there are some common features.

The degree of alteration of primary minerals may be slight

to very strong, but some weatherable minerals are present in

most cambic horizons. These include the clay minerals that

have a 2:1 lattice and amorphous clays as well as the various

alterable minerals that yield bases or iron to the soil solution.

Cambic horizons normally have soil structure, but some are

structureless.

A cambic horizon does not include layers that are part of the

following diagnostic horizons—an anthropic, histic, folistic,

melanic, mollic, plaggen, or umbric epipedon; an argillic,

calcic, gypsic, natric, oxic, petrocalcic, petrogypsic, placic, or

spodic horizon; or a duripan or fragipan (all defined in this

chapter).

A cambic horizon can include layers that are part of the

following diagnostic horizons—an ochric epipedon and an

agric, albic, glossic, or sombric horizon.

Required Characteristics

In summary, the cambic horizon is an altered horizon 15 cm

or more thick. If it is composed of lamellae, the combined

thickness of the lamellae must be 15 cm or more. In addition,

the cambic horizon must meet all of the following:

1. Has a texture of very fine sand, loamy very fine sand, or

finer; and

2. Shows evidence of alteration in one of the following forms:

a. Aquic conditions within 50 cm of the soil surface or

artificial drainage and all of the following:

(1) Soil structure or the absence of rock structure in

more than one-half of the volume; and

(2) Colors that do not change on exposure to air; and

(3) Dominant color, moist, on faces of peds or in the

matrix as follows:

(a) Value of 3 or less and chroma of 0; or

(b) Value of 4 or more and chroma of 1 or less; or

(c) Any value, chroma of 2 or less, and redox

concentrations; or

b. Does not have the combination of aquic conditions

within 50 cm of the soil surface or artificial drainage and

colors, moist, as defined in item 2-a-(3) above, and has soil

structure or the absence of rock structure in more than onehalf of the volume and one or more of the following

properties:

(1) Higher chroma, higher value, redder hue, or higher

clay content than the underlying horizon or an overlying

horizon; or

(2) Evidence of the removal of carbonates or gypsum;

and

3. Has properties that do not meet the requirements for an

anthropic, histic, folistic, melanic, mollic, plaggen, or umbric

epipedon, a duripan or fragipan, or an argillic, calcic, gypsic,

natric, oxic, petrocalcic, petrogypsic, placic, or spodic horizon;

and
38 Soil Taxonomy

4. Is not part of an Ap horizon and does not have a brittle

manner of failure in more than 60 percent of the matrix.

Duripan

A duripan (L. durus, hard; meaning hardpan) is a subsurface

horizon that is cemented by illuvial silica to the degree that less

than 50 percent of the volume of air-dry fragments slake in water

or during prolonged soaking in acid (HCl). See photos 19 and 20.

Duripans vary in the degree of cementation by silica. In addition,

they commonly contain accessory cements, chiefly calcium

carbonate. As a consequence, duripans vary in appearance.

They generally are very firm or firmer and are always brittle, even

after prolonged wetting. They grade into and can occur in

conjunction with petrocalcic horizons, mostly in semiarid and

arid regions. They also grade into noncemented earthy materials

and into the fragipans of humid regions.

Genesis

Duripans occur mostly in soils with a xeric or aridic moisture

regime (defined later), that is, in soils that are seasonally dry or

are usually dry. Most soils that have a duripan have a moisture

regime in which soluble silica might be expected to be

translocated into lower horizons but not out of the soils.

Geographically, duripans are largely in areas affected by

volcanism. Soils may show evidence of recent ash deposition,

or they may be forming in sediments derived from pyroclastic

materials, such as tuffs and ignimbrites. Many duripans occur

in soils that contain an appreciable amount of volcanic glass in

the overlying horizons, which suggests the importance of

soluble silica to the genesis. Glass tends to weather readily, and

the weathering can liberate soluble silicates at a rapid rate.

Duripans are not limited to soils derived from volcanic

materials. Weathering of ferromagnesian minerals and

feldspars may also contribute to the formation of a duripan.

The parent materials of many soils that have a duripan

contain only a small amount of calcium. If calcium is

abundant, a calcic or petrocalcic horizon tends to occur with

the duripan.

In the initial stages of duripan formation, much of the silica

cementation appears to occur at or close to the weathering site

of the mineral grain or glass chard. Monosilicic acid in the

solution is adsorbed on soil grains, polymerizes, and

precipitates as the soil dries. Silt- and clay-sized particles can

then be cemented to the grains by the precipitated silica,

forming microaggregates. These microaggregates can grow in

size.

Alternatively, silica is adsorbed to the surface of the soil

particles, forming bridges that cement grains without

completely plugging small voids between the grains. This

process continues until roots and the downward movement of

the soil solution are stopped. At this point laminar caps

composed dominantly of silica and calcite can develop.

Once formed, a duripan may become broken into blocky

fragments, perhaps by earthquakes or slight volume changes

resulting from wetting and drying. Before a layer can be

considered a duripan, the lateral spacing of cracks wide enough

to allow the entry of feeder roots must average 10 cm or more.

Appearance in an Arid Climate

The strongly cemented to indurated duripans in areas of arid

climates (an aridic moisture regime, defined later) have an abrupt

upper boundary and are commonly platy. The plates are roughly

1 to 15 cm thick. In many of these pans, the pores and the

surfaces of the plates are coated with opal and with some

birefringent material that is probably a microcrystalline form of

silica. Carbonates generally are present in small to large

amounts. Roots commonly are between the plates. More than

50 percent of the cementation can be destroyed by alternately

soaking fragments of the pan in acid and concentrated alkali.

The acid is used to destroy any cementation by carbonates. If

some of the cements are carbonates or if a petrocalcic horizon

is present, less than 50 percent of the cementation is destroyed

by soaking the fragments in acid, but more than 50 percent is

destroyed by soaking the fragments in concentrated alkali,

either as a single treatment or by alternating treatments with

acid. The presence of a thin, continuous layer of opal, which is

insoluble in acid, indicates enough cementation by silica to

satisfy the requirements for a duripan. A duripan and a

petrocalcic horizon can occur together within the same

horizon. If a horizon is cemented and meets the criteria for a

petrocalcic horizon, any continuous horizon within the

cemented layers that does not slake, in 50 percent or more of

the volume, in acid is also considered a duripan. Commonly, a

nearly continuous layer of secondary silica occurs in the part of

the horizon that does not slake in acid.

The forms of a duripan that are transitional to regolith in

arid regions are mostly massive and firm or very firm when

moist and are brittle at all moisture states. Laminar caps of

silica and coatings of silica on plates are uncommon. For a

horizon to be a duripan, more than 50 percent of the horizon

must not slake in water or in HCl and the horizon must have at

least (1) a few vertical opal coatings, (2) some opal or other

forms of silica partly filling interstices or forming bridges

between sand-sized mineral grains, or (3) some silica coatings

or pendants on the undersides of rock and pararock fragments.

Moistened specimens of these forms of the duripan commonly

show a dull glassy luster when viewed under a hand lens. The

most weakly cemented forms of these transitional duripans can

be penetrated with some difficulty by a hand-powered soil

auger. Under irrigation, such horizons commonly are slowly

permeable to water, and, except in cracks, they are virtually

impenetrable to the roots of most plants.
Horizons and Characteristics Diagnostic for the Higher Categories 39

Appearance in a Mediterranean Climate

In areas of Mediterranean climates (a xeric moisture regime,

defined later), the pan commonly has an abrupt upper boundary

and is broken into very coarse prisms or into polyhedrons that

are roughly 30 cm to 3 m or more in diameter. Coatings of opal

partly line the faces of the prisms and many of the pores. Roots

are absent in the prisms, except in cracks, and are commonly

matted on the upper boundary of the pan and on the sides of the

prisms. The prisms may have been formed by the slight volume

changes that result from wetting and drying. This process of

formation is suggested by the absence of prisms in the duripans

of arid regions.

The more strongly cemented pans of Mediterranean regions

have opal coatings over the tops of the polyhedrons as well as

on the sides, and the coatings are thicker than in the more

weakly cemented pans. Water often perches on top of the pan

during the rainy season. Coatings of iron, manganese, and

oriented clay may be observed on many of these pans.

Subsequent deposits of opal could engulf such coatings and

give rise to a cementation that can be broken down only by

repeated alternating treatments with solutions of acid and

concentrated alkali. Carbonates may be present above the pan

or in any part of it, or they may be completely absent. These

observations indicate that carbonates are not an essential part

of the pans.

The most weakly cemented forms of the duripans in a

Mediterranean region are mostly transitional to regolith.

Brittleness is pronounced at all moisture states, but most of the

pans can be penetrated with some difficulty by a hand-powered

soil auger. When dry, most of the pans are very hard and are

slowly permeable.

In areas of more humid climates (a udic moisture regime,

defined later), many of the duripans are in soils that have andic

soil properties (defined later) in some overlying horizons. Some

have characteristics transitional to a fragipan (described

later). Some have redoximorphic features of gray and strong

brown. Secondary carbonates and salts are absent in these

pans. The cementation in the pan must be strong enough for

less than 50 percent of dry pan fragments to slake when placed

in water. Some horizons meet the requirements for a fragipan if

more than 50 percent of dry pan fragments slake when placed in

water.

Required Characteristics

A duripan is a silica-cemented subsurface horizon with or

without auxiliary cementing agents. It can occur in conjunction

with a petrocalcic horizon.

A duripan must meet all of the following requirements:

1. The pan is cemented or indurated in more than 50 percent

of the volume of some horizon; and

2. The pan shows evidence of the accumulation of opal or

other forms of silica, such as laminar caps, coatings, lenses,

partly filled interstices, bridges between sand-sized grains, or

coatings on rock and pararock fragments; and

3. Less than 50 percent of the volume of air-dry fragments

slakes in 1N HCl even during prolonged soaking, but more

than 50 percent slakes in concentrated KOH or NaOH or in

alternating acid and alkali; and

4. Because of lateral continuity, roots can penetrate the pan

only along vertical fractures with a horizontal spacing of 10 cm

or more.

Fragipan

A fragipan (modified from L. fragilis, brittle, and pan;

meaning brittle pan) is an altered subsurface horizon, 15 cm or

more thick, that restricts the entry of water and roots into the

soil matrix. It may, but does not necessarily, underlie an

argillic, cambic, albic, or spodic horizon. It is commonly

within an argillic horizon, but some are within an albic

horizon. The fragipan has strongly developed fragic properties

(defined below). Commonly, it has a relatively low content of

organic matter and a high bulk density relative to the horizons

above it. The fragipan has a hard or harder rupture-resistance

class when dry. When moist, it has a brittle manner of failure

in 60 percent or more of the volume. The term “manner of

failure” refers to the tendency of a ped or clod to rupture

suddenly rather than to undergo slow deformation when

pressure is applied. Air-dried fragments slake when submerged

in water.

Most fragipans have redoximorphic features, show evidence

of translocation of clay, and have low or very low saturated

hydraulic conductivity. Some fragipans consist of albic

materials (defined below).

Most fragipans have very coarse prismatic structure. Some

have weak to strong, thick platy or lenticular structure within

the prisms. In others, the secondary structure is more nearly

weak coarse blocky than platy. Some fragipans have

transitional structure between platy and blocky. Some have no

secondary structure, and some appear to be massive. Many

have bleached, roughly vertical faces or borders of prisms that

look like seams in vertical cross section. The spacing of any

separations or bleached seams that are between the structural

units and allow the entry of roots averages 10 cm or more on

the horizontal dimensions.

The seams commonly have less clay in the upper part than

in the lower part. They form a polygonal pattern in horizontal

cross section. Most commonly, a fragipan has an abrupt or

clear upper boundary at a depth of 50 to 100 cm below the

original soil surface. The pan ranges from about 15 to 200 cm

in thickness. The lower boundary commonly is gradual or

diffuse. A fragipan is virtually free of roots, except in the

bleached seams and on the faces of prisms. In many fragipans

the bleached materials are not brittle when moist, although
40 Soil Taxonomy

they may be hard when dry. Photo 21 shows a fragipan that

begins at a depth of about 50 cm and has bleached seams

between peds. Clay films are on the faces of peds or on pore

fillings. Oriented clay is in the matrix of some fragipans.

Fragipans consisting of albic materials commonly do not have

bodies of oriented clay.

Significance to Soil Classification

Any continuous horizon that impedes movement of water

and the growth of roots is important to soil classification,

particularly for interpretations of soils for plant growth and for

engineering manipulations. Water stands above the pan in a

level soil and moves laterally along the top of the pan in a

sloping soil. Even though the processes that produce fragipans

are imperfectly known, these pans are restricted in their

climatic range and natural vegetation and are believed to be

genetic.

Genesis

The genesis of fragipans is obscure (Grossman and Carlisle,

1969). The formation of the density and brittleness of a fragipan

has been variously attributed to physical ripening, the weight of

glaciers, permafrost processes, and other events during the

Pleistocene. Some of the properties of some fragipans are

inherited from buried paleosols. The authors cited in the review

by Grossman and Carlisle all consider fragipans to be pedogenic

soil horizons, regardless of whether or not the density and

brittleness are pedogenic, on the basis of the following

evidence:

1. Fragipans show evidence of pedogenesis, other than

density and brittleness, including one or more of the

following—oriented clay in the matrix or on the faces of peds,

albic materials or coatings of albic materials on the faces of

peds or in seams, soil structure, and redoximorphic features in

the matrix or on the faces of peds.

2. The fragipan is roughly parallel to the soil surface.

3. The upper boundary of most fragipans has a narrow depth

range of about 50 to 100 cm below the surface, if the soil is not

eroded. This range in depth has been observed in northern

Michigan, in southern Mississippi, in New Zealand, in

Scotland, and in Italy. The extreme range in depth from the

surface in soils that have not been eroded or buried seems to be

from about 25 to 150 cm. This narrow range would be a

remarkable coincidence if the fragipans were not soil horizons.

4. The parent materials have common features, including a

loamy texture, few or no carbonates, and an appreciable

content of silt or very fine sand.

5. Fragipans of similar morphology underlie a variety of

horizons, including spodic, argillic, cambic, and albic

horizons.

6. Fragipans form only in soils in which water moves

downward through the profile. They are commonly at depths

that rarely freeze.

7. If a soil has an E ́ horizon and a B ́t horizon, the fragipan

may be in the lower part of an argillic horizon or even in the

eluvial horizon that separates the two B horizons. Thus, it

occurs in otherwise eluvial or illuvial horizons.

8. Fragipans most commonly occur in soils that formed under

forest vegetation.

The polygonal network of bleached materials is formed by

reduction of free iron after water has saturated the cracks. The

bleached materials commonly are bounded by a thin zone in

which iron has been concentrated. Other things being equal,

the structural units are smallest in the finest textured materials.

For a given texture, structure tends to be larger if the dry

season is short or mild rather than long or intense. Structural

units, with bleached surfaces, are rare or absent in the coarsest

textured materials.

If an argillic horizon overlies a fragipan, movement of clay

down the faces of structural units generally is indicated by

relatively thick clay films on the lower parts of the structural

units and by pedotubules within the peds.

Examination of the interiors of prisms shows close packing

of the mineral grains and bodies of oriented clay. The close

packing is consistent with the high bulk density of the fragipan

relative to the density of the overlying horizons.

The hardness of the fragipan when dry is largely attributed

to the close packing and to binding by clay. Binding by clay

alone, however, does not account for the brittleness of the pan

when it is moist. The brittleness may be the result of weak

chemical binding by one or more agents, not necessarily the

same in all kinds of soil. The higher pH of a fragipan that

underlies a spodic horizon suggests some consistent difference.

Hydrogen bonding with amorphous aluminosilicates has been

suggested in the literature. One piece of field evidence

supporting the hypothesis of weak chemical binding is that one

can find fragipans in which the brittleness appears to have

been partly or completely destroyed. Some soils in very old

arable fields in Belgium lack brittleness, but they retain the

color pattern. A weak fragipan is present in the adjacent fields.

The patterns of polygonal bleaching can be very well

developed, but the brittleness may be observable in only a small

part of the horizon near the center of the prisms. Fine feeder

roots ramify the nonbrittle parts of the prisms. The amount of

nonbrittle materials ranges from none to well over two-thirds

of the volume of the horizon.

A second piece of field evidence for weak chemical binding

is that, when exposed on streambanks, at least some fragipans

seem more stable than either the overlying horizons or the

underlying materials. The overlying and underlying materials

commonly slump in the exposures, and the fragipan protrudes.

The bleached materials on the sides of the prisms in the

protruding fragipan are commonly washed out by rain, after

which the brittle parts are exposed as separated prisms. At this
Horizons and Characteristics Diagnostic for the Higher Categories 41

time, the evidence about the cause of the brittleness is

conflicting.

Where a fragipan formed in till, its relatively high bulk density

may be attributed partly to the weight of the glaciers, to physical

ripening, or to consolidation within a layer of permafrost. Yet,

many if not all of the fragipans seem to reflect the influence of

other factors. One factor is presumed to be pressure generated

by very slight shrinking and swelling. When dry, a pan normally

has very fine cracks between the prisms, and very fine sand, silt,

and clay might be washed into these cracks when the dry

season ends. Then, when the pan is remoistened, it swells very

slightly. The force of swelling, however, is opposed by the

materials that have moved into the cracks between the prisms

and by the weight of the soil above. The internal pressure thus

generated may be responsible for part of the compaction. A

second factor is the inertness of the pan. Swelling and shrinking

produce little soil movement. Soil fauna seem to be absent, and

roots, restricted to the bleached zones between the prisms, are

mostly oriented vertically and do not lift the soil as they grow.

The pressure generated by the growth of the woody tree roots is

lateral, not vertical. The common flattened shape of the roots

attests to the pressure. Freezing and thawing are minimal. In

areas that support native vegetation, it is doubtful that many

fragipans ever freeze. Freezing is unlikely because of the depth

of the fragipan and the insulation provided by the O horizons

and by snow.

Identification

Four factors are important in identifying a fragipan.

First, a fragipan must have a minimum thickness. A

thickness of 15 cm or more is thought to be thick enough to

impart the interpretations for plant growth and for engineering

manipulations and to separate the fragipan from plowpans,

other compacted surface layers, or compacted layers near the

surface.

Second, a fragipan shows evidence of pedogenesis, in

addition to density and brittleness. This evidence, in the

matrix, on faces of peds, or in seams, is in the form of bodies of

oriented clay, clay films, albic materials, and/or both

redoximorphic features and soil structure. The evidence of

pedogenesis is needed to separate the fragipan from dense

parent materials (densic materials), such as dense till and

volcanic mudflow material.

Third, a fragipan has a combination of properties that

restrict the penetration of roots and water from 60 percent or

more of the volume of the horizon. Roots are restricted, except

in nearly vertical zones that form the boundaries between very

coarse structural units. The structural units are commonly

polyhedral in horizontal cross section and average 10 cm or

more across. Material within the structural units is massive, is

platy, or has weak blocky structure and has a firm or firmer

rupture-resistance class and a brittle manner of failure at or

near field capacity. Some fragipans are massive and are

restrictive throughout the horizon.

Fourth, air-dry fragments of the natural soil fabric, 5 to 10

cm in diameter, from more than 50 percent of the horizon slake

when they are submerged in water. This property separates

fragipans from duripans and other cemented horizons.

In the United States, soils that have a small amount of

plinthite normally are brittle in at least some parts of the

horizons that contain the plinthite. Some of these horizons

meet the requirements for a fragipan. At this stage of

knowledge, it is not clear that such horizons should be

considered fragipans. Where they are at depths comparable to

those of fragipans in other soils, however, the effects on plants

and on engineering uses of the soils are the same. For

pragmatic reasons, therefore, such horizons that have an upper

boundary within 100 cm of the mineral soil surface are

considered fragipans.

Required Characteristics

To be identified as a fragipan, a layer must have all of the

following characteristics:

1. The layer is 15 cm or more thick; and

2. The layer shows evidence of pedogenesis within the

horizon or, at a minimum, on the faces of structural units; and

3. The layer has very coarse prismatic, columnar, or blocky

structure of any grade, has weak structure of any size, or is

massive. Separations between structural units that allow roots

to enter have an average spacing of 10 cm or more on the

horizontal dimensions; and

4. Air-dry fragments of the natural soil fabric, 5 to 10 cm in

diameter, from more than 50 percent of the horizon slake when

they are submerged in water; and

5. The layer has, in 60 percent or more of the volume, a firm

or firmer rupture-resistance class, a brittle manner of failure at

or near field capacity, and virtually no roots.

Glossic Horizon

The glossic horizon (Gr. glossa, tongue) develops as a result

of the degradation of an argillic, kandic, or natric horizon from

which clay and free iron oxides are removed (photo 22). The

material between the peds resulting from this removal is albic

material (defined below). The process of eluviation gradually

progresses from the exteriors of the peds to their interiors. In

the early stages of development, the peds of the remnant

argillic, kandic, or natric horizon still form structural units that

extend throughout the glossic horizon, constituting close to 85

percent of its volume. In this early stage, the albic materials,

when viewed in vertical cross section, resemble tongues

extending into the horizon from the top. In the later stages,

some of these structural units no longer extend throughout the

horizon, and in the most advanced stages of the degradation

process, remnant peds constitute little more than 15 percent (by
42 Soil Taxonomy

volume) of the glossic horizon and are completely surrounded

by albic materials. The boundary between the illuvial and eluvial

parts of the glossic horizon may be either abrupt or clear and

either irregular or broken.

A glossic horizon generally occurs between an overlying

albic horizon and an underlying argillic, kandic, or natric

horizon or fragipan. It can lie between an argillic, cambic, or

kandic horizon and a fragipan. In the early stages of the

degradation process described above, a glossic horizon can be

within an argillic, kandic, or natric horizon or within a

fragipan if the fragipan shows evidence of the degradation of

an argillic horizon. An albic horizon may be below, or between

subhorizons of, the glossic horizon.

Argillic horizons consisting of lamellae and intervening

albic materials are not within the concept of the glossic

horizon.

Required Characteristics

The glossic horizon is 5 cm or more thick and consists of:

1. An eluvial part, i.e., albic materials (defined below), which

constitute 15 to 85 percent (by volume) of the glossic horizon;

and

2. An illuvial part, i.e., remnants (pieces) of an argillic,

kandic, or natric horizon (defined below).

Gypsic Horizon

The gypsic horizon is an illuvial horizon in which

secondary gypsum has accumulated to a significant extent

(photo 23). Most gypsic horizons occur in arid environments

where the parent materials are rich in gypsum. In soils that

have ground water near the surface, capillary rise and

evaporation plus transpiration can result in significant

accumulations of gypsum.

Gypsum may accumulate uniformly throughout a matrix of

sand and finer textured material or as masses or clusters of

crystals. In gravelly or stony material, it may accumulate in

pendants below the rock fragments.

Because of its solubility, gypsum can dissolve in soils and

cause damage to buildings, roads, irrigation delivery systems,

earthen dams, and other structures.

Required Characteristics

A gypsic horizon has all of the following properties:

1. Is 15 cm or more thick; and

2. Is not cemented or indurated to such a degree that it meets

the requirements for a petrogypsic horizon; and

3. Is 5 percent or more gypsum and 1 percent or more (by

volume) secondary visible gypsum; and

4. Has a product of thickness, in cm, multiplied by the

gypsum content percentage of 150 or more.

Thus, a horizon 30 cm thick that is 5 percent gypsum

qualifies as a gypsic horizon if it is 1 percent or more (by

volume) visible gypsum and is not cemented or indurated to

such a degree that it meets the requirements for a petrogypsic

horizon.

The gypsum percentage can be calculated by multiplying the

milliequivalents of gypsum per 100 g soil by the

milliequivalent weight of CaSO4

.2H2

O, which is 0.086.

Kandic Horizon1

Genesis

A kandic horizon is a subsurface horizon that has a

significantly higher percentage of clay than the overlying

horizon or horizons and has an apparent CEC of 16 cmol(+) or

less per kg clay (by 1N NH4OAc pH 7) and an apparent ECEC

of 12 cmol(+) or less per kg clay (sum of bases extracted with

1N NH4OAc pH 7 plus 1N KCl-extractable Al) in 50 percent or

more of the soil volume in the upper 100 cm or to a densic,

lithic, paralithic, or petroferric contact if shallower. The claysized fraction is composed predominantly of 1:1 layer silicate

clays, mainly kaolinite, with varying amounts of oxyhydroxides

of iron and aluminum. Clay films may or may not be present.

(The percentage of clay is either measured by the pipette

method or estimated to be 2.5 times [percent water retained at

1500 kPa tension minus percent organic carbon], whichever

value is higher, but no more than 100.)

Textural differentiation in pedons with kandic horizons may

result from one or more processes acting simultaneously or

sequentially, affecting surface horizons, subsurface horizons, or

both. These processes are not all clearly understood, although

the most important ones can be summarized as follows:

1. Clay eluviation and illuviation.—In some soils it is

often difficult to find clear evidence, even by

micromorphological analysis, that the higher clay content in

the B horizon is a result of accumulation by illuviation of layer

silicate clays. Specifically, clay films (cutans) may be

completely absent, or they may be present only at depths below

the control section used in classification. In other soils clay

films may have been destroyed by biological activity or

pedoturbation processes. High concentrations and strong

activity of soil fauna in soils of tropical and subtropical areas,

where kandic horizons are common, may cause the partial or

total disappearance of clay films to a considerable depth over

time.

Many of the soils with kandic horizons that probably have

formed by illuvial processes occur on stable geomorphic

surfaces. On stable surfaces the illuviation process may no

longer be operative or at least may be acting so slowly that

mixing by soil organisms is more rapid than the formation of

1The concept of the kandic horizon and the “kandi” and “kanhapli” great groups of soils

represent the work of the International Committee on the Classification of Low Activity Clays

(ICOMLAC), chaired by Dr. Frank R. Moormann.
Horizons and Characteristics Diagnostic for the Higher Categories 43

clay films. Under these conditions, clay films may be evident in

some pedons but not in other nearby pedons that otherwise

have similar morphology. Even within the same horizon of a

single pedon, some peds may have clay films while others do

not.

2. Clay destruction in the epipedon.—Weathering of

layer silicates may lead to a relative loss of clay in soils. The

loss generally is greatest in the upper horizons, where

weathering processes are most intense. Elimination of bases

and some silica is enhanced by high surface soil temperatures

in well drained soils with high rates of leaching. Because this

process affects surface horizons more than subsoil horizons, a

vertical textural differentiation may result. This process may

also have resulted in the absence of clay films in the lower

horizons of highly weathered soils on old stable surfaces. A

related process that occurs in surface horizons that are

periodically wet may also result in similar textural

differentiation.

3. Selective erosion.—Raindrop splash and subsequent

surface soil erosion cause the smallest soil particles to be

moved farther downslope than the larger particles. Eventually,

part of the fine fraction may be eliminated from the surface

layer of sloping soils, leaving a coarser textured surface layer.

The speed of this process depends on many factors. It may be

very rapid in climates with highly erosive rains or on soils with

little plant cover. The surficial movement of clay downslope

seems to be widespread, and selective erosion probably is a

major process leading to textural differentiation. The process

appears to be enhanced by periodic fire or by intermittent

cultivation, such as the shifting cultivation practiced for

thousands of years in areas where these soils occur.

4. Sedimentation of coarse textured surface

materials.—Lithologic discontinuities are probable on stable

landscapes in many intertropical areas. In many of the soils of

these areas, the surface layer is coarser textured than the

subsoil. Because all of the soil material is highly weathered,

however, stratification is not evident. If the finer textured

subsoil fulfills the requirements for the kandic horizon and the

surface layer is not composed of fine strata of recent material,

the subsoil horizon is classified as a kandic horizon.

Significance to Soil Classification

The kandic horizon provides a basis for differentiation

among soils with clay accumulation in the subsoil. The argillic

horizon alone does not provide an adequate diagnostic criterion

to differentiate all Ultisols and Alfisols from Oxisols and

Inceptisols. The kandic horizon is a diagnostic horizon that

separates Ultisols and Alfisols in which the clay fraction has

clay minerals with low CEC, comparable to Oxisols, from

Ultisols and Alfisols that have clay minerals with high CEC.

Textural differentiation in most low-activity clay soils by itself

is believed to be sufficiently important for the understanding of

soil development and use and should be recognized at a high

level of the classification system. In soils with clayey surface

horizons, however, the textural differentiation loses much of its

significance. Most low-activity clay (LAC) soils that have, after

mixing of the upper 18 cm, more than 40 percent clay in the

surface horizon will be Oxisols, although a few that have LAC

and the clay increase necessary for an argillic or kandic

horizon but have significant amounts of weatherable minerals

will remain “kandi” Ultisols or Alfisols.

The presence of a kandic horizon indicates a high degree of

weathering of the mineral soil material, such as that in soils on

old surfaces where weathering has taken place under warm

climatic conditions with moderate to high precipitation. The

high degree of weathering is reflected by a dominance of 1:1

layer silicate clays and oxyhydroxides of iron and aluminum,

although small amounts of 2:1 layer silicate clays may also be

present. There is a general absence of short-range-order

minerals, such as allophane or imgolite. The composition of

the 0.02 to 0.2 mm fraction does not always reflect the same

degree of weathering, especially in soils that formed in

weathering products of crystalline rocks. Thus, no weatherable

mineral content is specified in the definition of the kandic

horizon.

Identification

The kandic horizon is a vertically continuous subsurface

horizon (not composed of lamellae) with a significantly finer

texture than the overlying horizon or horizons. It may underlie

an ochric, umbric, anthropic, or mollic epipedon. The upper

boundary normally is clear or gradual, although it may be

abrupt. It is never diffuse. The increase in clay content is

reached within a vertical distance of 15 cm or less.

The top of the kandic horizon is within one of the following

depths:

1. If the particle-size class throughout the upper 100 cm is

sandy, the upper boundary is at a depth between 100 and 200

cm from the soil surface in most of the pedon.

2. If the clay content of the surface horizon is less than 20

percent and the particle-size class (of part or all of the upper

100 cm) is finer than sandy, the upper boundary is at a depth of

less than 125 cm from the soil surface.

3. If the clay content of the surface horizon is 20 percent or

more, the upper boundary is at a depth of less than 100 cm

from the mineral soil surface.

Textures coarser than loamy very fine sand are excluded

from the definition of the kandic horizon. The presence or

absence of clay films, identified by field examination, or cutans

in thin sections, is not a differentiating characteristic for

kandic horizons.

Other field characteristics of kandic horizons are not

normally diagnostic, since these horizons may have properties

of the argillic, cambic, or oxic horizon. Some soils with kandic

horizons resemble those with argillic horizons in that they have

a well developed subangular blocky structure, while bleached
44 Soil Taxonomy

grains of sand and silt may be present in the overlying coarser

textured horizon or horizons. The ratio of fine clay (particles

smaller than 0.2 micrometer) to total clay may be larger in the

kandic horizon than in the overlying coarser textured horizon or

horizons but is not diagnostic.

Other kandic horizons have one or more properties of oxic

horizons and would be called oxic horizons if they did not have

a distinct increase in content of clay at the upper boundary.

This rationale is comparable to that used for pedons dominated

by more active clays where an argillic horizon would be called

a cambic horizon if it did not have the characteristic increase

in content of clay at the upper boundary.

A kandic horizon is not overlain by layers more than 30 cm

thick that show fine stratification and/or have an organiccarbon content that decreases irregularly with increasing depth,

unless it is a buried horizon. The kandic horizon also does not

show fine stratification and/or have an organic-carbon content

that decreases irregularly with increasing depth.

Required Characteristics

The kandic horizon:

1. Is a vertically continuous subsurface horizon that underlies

a coarser textured surface horizon. The minimum thickness of

the surface horizon is 18 cm after mixing or 5 cm if the

textural transition to the kandic horizon is abrupt and there is

no densic, lithic, paralithic, or petroferric contact (defined

below) within 50 cm of the mineral soil surface; and

2. Has its upper boundary:

a. At the point where the clay percentage in the fine-earth

fraction, increasing with depth within a vertical distance of

15 cm or less, is either:

(1) 4 percent or more (absolute) higher than that in the

surface horizon if that horizon has less than 20 percent

total clay in the fine-earth fraction; or

(2) 20 percent or more (relative) higher than that in the

surface horizon if that horizon has 20 to 40 percent total

clay in the fine-earth fraction; or

(3) 8 percent or more (absolute) higher than that in the

surface horizon if that horizon has more than 40 percent

total clay in the fine-earth fraction; and

b. At a depth:

(1) Between 100 cm and 200 cm from the mineral soil

surface if the particle-size class is sandy or sandy-skeletal

throughout the upper 100 cm; or

(2) Within 100 cm from the mineral soil surface if the

clay content in the fine-earth fraction of the surface

horizon is 20 percent or more; or

(3) Within 125 cm from the mineral soil surface for all

other soils; and

3. Has a thickness of either:

a. 30 cm or more; or

b. 15 cm or more if there is a densic, lithic, paralithic, or

petroferric contact within 50 cm of the mineral soil surface

and the kandic horizon constitutes 60 percent or more of the

vertical distance between a depth of 18 cm and the contact;

and

4. Has a texture of loamy very fine sand or finer; and

5. Has an apparent CEC of 16 cmol(+) or less per kg clay (by

1N NH4

OAc pH 7) and an apparent ECEC of 12 cmol(+) or

less per kg clay (sum of bases extracted with 1N NH4OAc pH 7

plus 1N KCl-extractable Al) in 50 percent or more of its

thickness between the point where the clay increase

requirements are met and either a depth of 100 cm below that

point or a densic, lithic, paralithic, or petroferric contact if

shallower. (The percentage of clay is either measured by the

pipette method or estimated to be 2.5 times [percent water

retained at 1500 kPa tension minus percent organic carbon],

whichever is higher, but no more than 100); and

6. Has a regular decrease in organic-carbon content with

increasing depth, no fine stratification, and no overlying layers

more than 30 cm thick that have fine stratification and/or an

organic-carbon content that decreases irregularly with

increasing depth.

Natric Horizon

The natric (modified from natrium, sodium; implying the

presence of sodium) horizon is a special kind of argillic

horizon (photo 24). The dispersive properties of sodium

accelerate clay illuviation. Research has shown that natric

horizons form in Holocene-age soils, even in arid or semiarid

environments.

The effect of sodium on dispersion of clay and on the

formation of a B horizon of illuvial clay has long been

recognized. The effect of magnesium ions on dispersion of clay,

however, is still inconclusive. Laboratory studies seem to show

but slight difference between the effects of magnesium and the

effects of calcium. Yet, it is common for soils with a large

amount of exchangeable magnesium to have poor physical

properties. The reasons for the poor physical condition are

uncertain. Magnesium is considered in the definition of the

natric horizon because, as sodium is removed, magnesium

follows in the leaching sequence if chlorides are low and

sulfates high. If leaching continues, the magnesium is

eventually replaced. When replacement reaches the point

where the amount of exchangeable sodium is less than 15

percent and the amount of magnesium and sodium is less than

that of calcium and exchange acidity in upper subhorizons that

have a total thickness of 40 cm or more, the horizon is no

longer considered natric. The remains of such former natric

horizons are evident in soils in which the columnar structure is
Horizons and Characteristics Diagnostic for the Higher Categories 45

clearly evident but all other properties have been altered

because of a greatly changed environment or continued

leaching.

Required Characteristics

The natric horizon has, in addition to the properties of the

argillic horizon:

1. Either:

a. Columns or prisms in some part (generally the upper

part), which may break to blocks; or

b. Both blocky structure and eluvial materials, which

contain uncoated silt or sand grains and extend more than

2.5 cm into the horizon; and

2. Either:

a. An exchangeable sodium percentage (ESP) of 15

percent or more (or a sodium adsorption ratio [SAR] of 13

or more) in one or more horizons within 40 cm of its upper

boundary; or

b. More exchangeable magnesium plus sodium than

calcium plus exchange acidity (at pH 8.2) in one or more

horizons within 40 cm of its upper boundary if the ESP is

15 or more (or the SAR is 13 or more) in one or more

horizons within 200 cm of the mineral soil surface.

Ortstein

Ortstein is a cemented horizon that consists of spodic

materials.

Ortstein has one of the following orientations:

1. As a relatively horizontal layer. This type of orientation

tends to be root restrictive and occurs primarily in Aquods.

2. As vertical to irregular columns, tongues, pillars, or

bridges. This orientation tends to be less root restrictive than

the horizontal orientation. Vertical orientation occurs primarily

in Orthods.

3. As nodules. These may be remnants of one of the

orientations listed above.

Ortstein is 25 mm or more thick and 50 percent or more (by

volume) cemented. Continuous ortstein is 90 percent or more

cemented and has lateral continuity. Because of this continuity,

roots can penetrate only along vertical fractures with a

horizontal spacing of 10 cm or more.

Ortstein is differentiated from a placic horizon within

spodic materials solely on the basis of thickness. Placic

horizons within spodic materials are less than 25 mm thick,

and ortstein is 25 mm or more thick.

Required Characteristics

Ortstein has all of the following:

1. Consists of spodic materials; and

2. Is in a layer that is 50 percent or more cemented; and

3. Is 25 mm or more thick.

Oxic Horizon

The oxic horizon is a mineral subsurface horizon of sandy

loam or a finer texture with a low cation-exchange capacity

and a low content of weatherable minerals. It is at least 30 cm

(12 in) thick. The clay-sized fraction generally is dominated by

kaolinite with or without iron and aluminum oxyhydrates and

with few or no other lattice silicate minerals, except for

hydroxy interlayered vermiculites. The silt and sand fraction of

the oxic horizon is generally dominated by quartz with some

other resistant minerals. Weatherable minerals that are

potential sources of plant nutrients (K, Ca, and Mg) may be

present only if they do not exceed 10 percent of the 50- to 200-

micron fraction. Rock fragments or lithorelicts may be present

only if they are coated with sesquioxides or if the included

weatherable minerals are completely altered.

Where dispersion is a problem, 3 times (percent water

retained at 1500 kPa tension minus percent organic carbon) is

used to estimate clay content. The apparent CEC, by the 1N

NH4OAc pH 7 method, is equal to or less than 16 cmol(+) per

kg of clay, and the apparent effective CEC (ECEC), as

determined by the sum of NH4OAc displaced bases plus 1N

KCl-extractable aluminum, is equal to or less than 12 cmol(+)

per kg of clay. The mineralogy and charge characteristics

exclude horizons containing significant quantities of shortrange-order minerals. The oxic horizon does not have andic

soil properties. Some oxiclike horizons may have high amounts

of low-charge illite, but they have more than 10 percent

muscovite in the 50- to 200-micron fraction and are thus

excluded from oxic horizons because muscovite is considered a

weatherable mineral.

The upper boundary of the oxic horizon is either 18 cm

below the mineral soil surface or at the lower boundary of an

Ap horizon, whichever is deeper, or it is at a greater depth

where mineralogical and charge characteristics meet the

requirements for the oxic horizon. Any increase in clay content

at the upper boundary must be diffuse. The lower boundary of

the oxic horizon is also defined by its mineralogical and charge

requirements and may, in addition, be defined by the presence

of saprolite with rock structure.

Significance to Soil Classification and Use

One important attribute of the oxic horizon is that it is

almost devoid of primary weatherable minerals. Thus, further

weathering will release few plant nutrients.

Another important attribute is that in many soils with oxic

horizons the clay content is relatively constant with increasing

depth, indicating little or no clay mobility, which suggests a

high order of stability in the clay fraction of these soils. This
46 Soil Taxonomy

stability has been attributed to cementation by sesquioxides.

Oxic horizons generally have only traces of water-dispersible

clay if their net charge is near zero, but this characteristic is

also shared by some other horizons.

A third attribute of most oxic horizons is a stable fine and

very fine granular structure and thus the friable and porous

nature of the horizon. Bulk densities are generally low,

commonly near 1 g/cm3

 in fine and very-fine particle-size

classes. Macrostructure may be angular or subangular blocky,

but the grade of blocky structure is generally weak.

These and other attributes directly or indirectly influence

the performance of soils having oxic horizons. The very low

cation-exchange capacity is an important consideration in soil

management. In addition, some oxic horizons have a high

capacity to adsorb anions and make some of the anions,

especially phosphates, unavailable to plants. Large amounts of

phosphate may need to be added as an initial amendment to

overcome the fixation capacity. Cations may need to be added

frequently and in small amounts to compensate for leaching

losses. The low CEC, where dominated by exchangeable Al, is

often an advantage in that only small amounts of basic cations

are needed to increase the base saturation percentage. Further,

the ease with which basic cations are leached makes the

chemical deepening of the root zone feasible via continued

applications of lime or gypsum.

Although oxic horizons commonly contain high amounts of

clay, their tendency to form a strong grade of very fine or fine

granular structure may give them characteristics similar to

those of sands. The horizons have a low available waterholding capacity because most of the pores are either very large

between the granules (and thus do not retain water against the

forces of gravity) or are very small within the granules (and

thus retain water at too great a tension to be extracted by

plants). Plants may show evidence of moisture stress after only

a week without rain. Although the low available water-holding

capacity is most limiting to shallow-rooted plants, yields of

deep-rooted trees, such as rubbertree and oil palm, are also

known to decline because of moisture stress.

It is considered desirable to identify soil horizons that are

nearly sterile mineralogically because they are unable to supply

basic cations through the continued weathering of primary

minerals. As such, the oxic horizon can be considered a

counterpart of the cambic horizon, which has a greater content

of weatherable minerals. As with the cambic horizon, the

exclusion of certain sandy textures is admittedly arbitrary. In

the case of the oxic horizon, however, it is considered

necessary to preserve the uniformity of the horizon with

materials that have enough clay to reflect the low CEC nature

and structural tendencies.

When considered in the vertical sequence of a soil profile,

an increase in clay content with increasing depth may be

associated with increased grades of blocky structure not

common to the central concept of the oxic horizon. Where the

increase in clay content is below coarser textured surface

horizons, a small increase in the amount of clay appears more

significant to moisture relationships than where the surface

horizon is clayey. This increase is especially significant in the

interpretation of soils that have been subject to accelerated

erosion. Where the coarser textured surface horizons are

eroded in cultivated areas and finer textured subsoil material

becomes incorporated into the plow layer, spatial heterogeneity

with respect to the characteristics of the plow layer develops.

Thus, this pattern is considered more closely related to soils

that have argillic horizons than to soils that do not have rather

abrupt increases in clay content with increasing depth.

Therefore, some horizons with many oxic horizon properties,

such as low CEC and an absence of weatherable minerals, are

classified as kandic horizons and may be part of Ultisols and

Alfisols rather than Oxisols if there is less than 40 percent clay

in the upper 18 cm.

The identification of an oxic horizon in most soils requires

that the increase in clay content with increasing depth not

exceed 1.2 times the clay content in the overlying horizons

within a vertical distance of 15 cm (gradual boundary limit) if

the surface horizon contains 20 to 40 percent clay. If the

surface horizon contains more than 40 percent clay, an oxic

horizon must have an absolute clay content increase of less

than 8 percent within a vertical distance of 15 cm. If the

surface horizon contains less than 20 percent clay, the oxic

horizon must have an absolute clay content increase of less

than 4 percent in a vertical distance of 15 cm. These are

admittedly arbitrary limits, but they lend themselves to

consistent identification in the field and rather easy verification

by laboratory techniques.

Genesis

Oxic horizons are generally in soils on very old stable

geomorphic surfaces. They may occur in soils on younger

surfaces if the parent rock is basalt, serpentine, or other easily

weathered rock or if the parent material is preweathered. Oxic

horizons are not common in soils on steep slopes where

rejuvenation of the soils takes place through erosion,

truncation, or lateral flow of base-enriched subsurface water.

Soils on old geomorphic surfaces that may date to the mid

or late Tertiary generally have been reworked. Many of the

surficial deposits are preweathered, transported over short

distances, and deposited, perhaps several times. After

deposition and stabilization of the landscape, weathering and

soil formation start anew. Stone lines composed of quartz or

petroplinthite are common in some of these soils if the original

material could supply the stones. Quartz veins may be traced

through the saprolite but end abruptly or taper off at the stone

line, indicating that the material above the stone line has been

transported. Particle-size sorting may take place during

transport and deposition, and lithologic discontinuities are

common, although materials are very similar.
Horizons and Characteristics Diagnostic for the Higher Categories 47

As was indicated earlier, the parent materials may be

strongly preweathered. Weathering continues after deposition.

The intensity of the weathering is a function of environmental

conditions. In areas of aridic climates, this is minimal, and it is

supposed that the oxic properties were attained during

previous, more humid phases of the climate or in poorly

drained environments or developed as the material weathered

in transport.

In the more easily weathered parent materials and when

climatic conditions are favorable, oxic horizons form in soils

on young surfaces and over a relatively short period. Leaching

and desilicification are the most important processes, resulting

in a deep solum. The weathering front moves rapidly down the

soils, and on many basic and ultrabasic rocks, there is no real

saprolitic zone because the oxic horizon rests on rock or on a

thin weathering crust. Primary minerals are altered to

kaolinite, and, simultaneously or at a later stage, gibbsite and

geothite also accumulate. Accidents of nature may occur,

leaving behind some partially weathered rock or mineral

fragments in the oxic horizon. These fragments are generally

rare and, if present, are frequently coated with sesquioxides.

Pseudomorphs of olivine and augite may be present in some

oxic horizons, but these are not considered indicators of a lack

of weathering.

On stable surfaces time has permitted homogenization of the

soil material by pedoturbation processes. It is also possible that

the active pedoturbation has disrupted and assimilated any

evidence of lessivage, such as clay films. Consequently, most

oxic horizons are uniform in color, texture, and other

mineralogical or chemical properties to great depths in the soil.

The pedoturbation processes have also disrupted any rock

structure. In some saprolites weathering results in a

pseudomorphic alteration of feldspar phenocrysts to gibbsite,

the aggregates of which retain the original fabric.

Mineralogically and chemically, the saprolite may meet the

requirements for an oxic horizon, but it is not considered an

oxic horizon if it retains more than 5 percent rock fabric.

Booklets of kaolinite that formed through the pseudomorphic

alteration of biotite are considered weatherable minerals. In an

oxic horizon, these are disrupted and assimilated in the soil

material.

Soils with oxic horizons frequently occupy the upper part of

the landscape. The silica potential is very low in such soils.

These soils have a leaching environment in which there is no

possibility for synthesis of 2:1 clay minerals. Even in the wet

soils with oxic horizons, the recharging water may be so low in

bases and silica that, despite a high water table, the soils are

continuously flushed and leached. Isohyperthermic soil

temperature regimes and udic or perudic soil moisture regimes

are often considered optimal for the formation of oxic horizons,

but soils with oxic horizons are common in areas with ustic

soil moisture regimes or with isothermic soil temperature

regimes. They are rare in areas with aridic soil moisture

regimes and isomesic soil temperature regimes. Some oxic

horizons are present in areas of soil temperature regimes other

than iso regimes, and, although paleoclimatic factors have been

attributed to their formation, parent material is also probably a

major contributor.

Required Characteristics

In summary, the oxic horizon is a subsurface horizon that

does not have andic soil properties (defined below) and has all

of the following characteristics:

1. A thickness of 30 cm or more; and

2. A texture of sandy loam or finer in the fine-earth fraction;

and

3. Less than 10 percent weatherable minerals in the 50-

to 200-micron fraction; and

4. Rock structure in less than 5 percent of its volume, unless

the lithorelicts with weatherable minerals are coated with

sesquioxides; and

5. A diffuse upper boundary, i.e., within a vertical distance

of 15 cm, a clay increase with increasing depth of:

a. Less than 4 percent (absolute) in its fine-earth fraction

if the fine-earth fraction of the surface horizon contains less

than 20 percent clay; or

b. Less than 20 percent (relative) in its fine-earth fraction

if the fine-earth fraction of the surface horizon contains 20

to 40 percent clay; or

c. Less than 8 percent (absolute) in its fine-earth fraction

if the fine-earth fraction of the surface horizon contains 40

percent or more clay); and

6. An apparent CEC of 16 cmol(+) or less per kg clay (by 1N

NH4

OAc pH 7) and an apparent ECEC of 12 cmol(+) or less

per kg clay (sum of bases extracted with 1N NH4OAc pH 7 plus

1N KCl-extractable Al). (The percentage of clay is either

measured by the pipette method or estimated to be 3 times

[percent water retained at 1500 kPa tension minus percent

organic carbon], whichever value is higher, but no more than

100).

Petrocalcic Horizon

The petrocalcic horizon is an illuvial horizon in which

secondary calcium carbonate or other carbonates have

accumulated to the extent that the horizon is cemented or

indurated (photo 25).

In some soils forming in parent materials that are rich in

carbonates or that receive regular additions of carbonates in

dust, the calcic horizon tends in time to become plugged with

carbonates and cemented into a massive, continuous horizon.

There is also evidence that a petrocalcic horizon can form

through a process of limestone alteration by in situ dissolution
48 Soil Taxonomy

and reprecipitation of carbonates. Petrocalcic horizons are

mainly in soils older than the Holocene and seem to be a mark

of advanced soil evolution.

In areas with an abundant source of carbonates and silica,

petrocalcic horizons and duripans can occur within the same

pedon.

The petrocalcic horizon is indurated or cemented

throughout each pedon by calcium carbonate or, less

commonly, by calcium and magnesium carbonate, with or

without accessory silica, to such a degree that dry fragments do

not slake in water and roots cannot enter, except in cracks that

have a horizontal spacing of 10 cm or more. If the fragments

are soaked in acid, cementation of the petrocalcic horizon is

destroyed in half or more of its lateral extent in each pedon.

The horizon is commonly massive or platy and is very hard or

harder when dry and very firm or firmer when moist. Its

saturated hydraulic conductivity commonly is moderately low

to very low unless the horizon is fractured.

A laminar cap may be present but is not required. If one is

present, carbonates normally constitute half or more, by

weight, of the laminar horizon. Gravel, sand, and silt grains

have been separated by the crystallization of carbonates in at

least parts of the laminar subhorizon. Sand and gravel have

been largely pushed aside by crystallization of calcium

carbonate at the surface of the laminar horizon. Radiocarbon

dates of the organic and inorganic carbon indicate that this

laminar horizon is late Wisconsinan to Holocene in age and

that the cementation of the underlying gravel took place during

the late Pleistocene.

Required Characteristics

A petrocalcic horizon must meet the following

requirements:

1. The horizon is cemented or indurated by carbonates, with or

without silica or other cementing agents; and

2. Because of lateral continuity, roots can penetrate only

along vertical fractures with a horizontal spacing of 10 cm or

more; and

3. The horizon has a thickness of:

a. 10 cm or more; or

b. 1 cm or more if it consists of a laminar cap directly

underlain by bedrock.

Petrogypsic Horizon

The petrogypsic horizon is an illuvial horizon, 10 cm or

more thick, in which secondary gypsum has accumulated to the

extent that the horizon is cemented or indurated (photo 26). Dry

fragments do not slake in water, and roots cannot enter, except in

vertical fractures that have a horizontal spacing of 10 cm or

more. The minimum gypsum content is 5 percent, and the

product of the thickness, in cm, multiplied by the gypsum

content percentage is 150 or more. Commonly, the gypsum

content is far greater than the minimum requirements. In many

pedons it is 60 percent or more. Petrogypsic horizons are known

to occur only in arid regions and develop in parent materials that

are rich in gypsum. They are rare in the United States but are

common in parts of Africa and Asia

Required Characteristics

A petrogypsic horizon must meet the following

requirements:

1. The horizon is cemented or indurated by gypsum, with or

without other cementing agents; and

2. Because of lateral continuity, roots can penetrate only

along vertical fractures with a horizontal spacing of 10 cm or

more; and

3. The horizon is 10 cm or more thick; and

4. The horizon is 5 percent or more gypsum, and the product

of its thickness, in cm, multiplied by the gypsum content

percentage is 150 or more.

Placic Horizon

The placic horizon (Gr. base of plax, flat stone; meaning a

thin cemented pan) is a thin, black to dark reddish pan that is

cemented by iron (or iron and manganese) and organic matter.

It is generally between 2 and 10 mm thick but may be as thin

as 1 mm. The placic horizon has a maximum thickness of 25

mm where it is associated with spodic materials. Where not

associated with spodic materials, it has no maximum thickness.

It is often associated with stratification in parent materials,

such as an abrupt discontinuity of hydraulic conductivity

associated with different particle sizes in ash layers. The placic

horizon is commonly within 50 cm of the mineral soil surface

and is roughly parallel with the mineral soil surface. It has a

pronounced wavy or even convoluted form. Commonly, it

occurs as a single pan rather than as multiple sheets (one

underlying another), but it may be bifurcated. It is a barrier to

water and roots. Placic horizons have been described in

Andisols, Histosols, Inceptisols, and Spodosols. In New

Zealand they also have been reported in young alluvial soils.

Most placic horizons occur in areas of cool, moist climates

with low evapotranspiration. They are known to occur in the

British Isles, New Zealand, Canada, and southeastern Alaska.

They also have been reported in the Tropics.

Placic horizons range in color from dark red to black.

Chemical data indicate that carbon and iron are major

components and aluminum and manganese minor components

in most placic horizons. In some areas, however, manganese is

a significant constituent of the horizons. There appears to be

little relationship between the chemical composition and the

color of the placic horizon.
Horizons and Characteristics Diagnostic for the Higher Categories 49

Research on genesis suggests that placic horizons form from

iron that is reduced and mobilized in the surface horizons and

oxidized and precipitated in the B horizon, where it can adsorb

soluble organic matter. The iron, however, does not form organometallic complexes. The most common forms of iron in the placic

horizon are ferrihydrite and poorly crystalline goethite. These

minerals have a large capacity for adsorbing anions, including

humic substances.

Conditions for the reduction and mobilization of iron are

favored in strongly leached, acid soils with organic surface

horizons containing anaerobic micro-organisms. In some soils

placic horizons form at the boundary between layers with

contrasting particle-size classes, which restrict the soil

solution. Placic horizons also can form above lithic, densic, or

paralithic contacts. They are by no means restricted to the

conditions described above.

Most placic horizons in the British Isles have formed within

the last 3,000 years, but there is evidence to support incipient

formation of placic horizons within 100 years.

Placic horizons form in material with a variety of textures

ranging from sands to clays. The native vegetation in the

different climates includes tropical rain forest, Sphagnum, and

other rain-loving plants. In the British Isles placic horizons

occur under peat-forming ericaceous or grassy seminatural

vegetation, which is subject to periodic burns and was likely

forest within the last 3,000 years.

Unless the thickness of the placic horizon is minimal,

identification of the horizon is seldom difficult because the

hard, brittle pan differs so much from the material in which it

occurs and is so close to the mineral soil surface. The presence

of organic carbon and the shape and position of the placic

horizon distinguish the horizon from the ironstone sheets that

may form where water hangs, or moves laterally, at a lithologic

discontinuity. Where placic horizons occur within spodic

materials, they are arbitrarily differentiated from ortstein by

thickness. Ortstein has a minimum thickness of 25 mm.

Required Characteristics

A placic horizon must meet the following requirements:

1. The horizon is cemented or indurated with iron or iron and

manganese and organic matter, with or without other cementing

agents; and

2. Because of lateral continuity, roots can penetrate only

along vertical fractures with a horizontal spacing of 10 cm or

more; and

3. The horizon has a minimum thickness of 1 mm and, where

associated with spodic materials, is less than 25 mm thick.

Salic Horizon

A salic horizon is a horizon of accumulation of salts that are

more soluble than gypsum in cold water (photo 27). A common

salt is halite, the crystalline form of sodium chloride. In some

areas soluble sulfates may also accumulate with the crystalline

forms, such as thernadite, hexahydrite, epsomite, and mirabilite.

Two of the commonly occurring bicarbonates are trona and

natron. Under extreme aridic conditions and at low temperatures,

evaporites of calcium chloride, nitrates, and other soluble salts

may accumulate. Identification of the kinds of crystalline salts

requires detailed mineralogical analyses.

In extremely arid areas, such as parts of Chile and

Antarctica, where measurable precipitation is rare, salic

horizons have a hard or rigid rupture-resistance class. These

types of salic horizons are physical barriers to roots, but they

slake in water and, therefore, are not considered cemented.

Required Characteristics

A salic horizon is 15 cm or more thick and has, for 90

consecutive days or more in normal years:

1. An electrical conductivity (EC) equal to or greater than 30

dS/m in the water extracted from a saturated paste; and

2. A product of the EC, in dS/m, and thickness, in cm,

equal to 900 or more.

Sombric Horizon

A sombric horizon (F. sombre, dark) is a subsurface horizon

in mineral soils that has formed under free drainage. It

contains illuvial humus that is neither associated with

aluminum, as is the humus in the spodic horizon, nor dispersed

by sodium, as is common in the natric horizon. Consequently,

the sombric horizon does not have the high cation-exchange

capacity in its clay that characterizes a spodic horizon and does

not have the high base saturation of a natric horizon. It does

not underlie an albic horizon.

Sombric horizons are thought to be restricted to the cool,

moist soils of high plateaus and mountains in tropical or

subtropical regions. Because of strong leaching, their base

saturation is low (less than 50 percent by NH4OAc).

The sombric horizon has a lower color value or chroma, or

both, than the overlying horizon and commonly contains more

organic matter. It may have formed in an argillic, cambic, or

oxic horizon. If peds are present, the dark colors are most

pronounced on surfaces of peds.

In the field a sombric horizon is easily mistaken for a buried

A horizon. It can be distinguished from some buried epipedons

by lateral tracing. In thin sections the organic matter of a

sombric horizon appears more concentrated on peds and in

pores than uniformly dispersed throughout the matrix.

Spodic Horizon

A spodic horizon is an illuvial layer with 85 percent or more

spodic materials (defined below). Spodic materials contain

illuvial active amorphous materials composed of organic matter

and aluminum, with or without iron. The term “active” is used
50 Soil Taxonomy

here to describe materials that have a high pH-dependent

charge, a large surface area, and high water retention. In

uncultivated soils the spodic horizon normally lies below an

albic horizon (a light colored eluvial horizon defined earlier).

Less commonly, it either is under an ochric epipedon that does

not meet the color requirements for an albic horizon or is in or

under an umbric epipedon. In some soils the spodic horizon is

at the surface of the mineral soil, directly below a thin O

horizon. In cultivated soils it generally occurs directly below

the Ap horizon. Spodic materials may remain in some

cultivated soils where the spodic horizon has been destroyed. If

85 percent of the spodic materials remain in the Ap horizon

and the soil meets the other criteria listed in the “Key to Soil

Orders” in chapter 8, the soil is considered a Spodosol.

Genesis

Spodic horizons form only in a humid environment. They are

commonly associated with cold or temperate climates but also

occur in hot climates. They do not occur in an arid environment,

although some occur in Mediterranean climates that have long,

dry summers.

The types of vegetation and litter covering the surface are

important in the formation of spodic horizons. In cool climates

spodic horizons occur in soils that have had a heath vegetation

(Erica and Calluna) or forest (broadleaf or coniferous)

vegetation. In a mixed forest, the spodic horizon generally is

more strongly expressed under certain species, such as hemlock

(Tsuga canadensis) or kauri (Agathis australis), than under

other species. In warm climates spodic horizons occur under

savanna, palm trees, and mixed forests.

A spodic horizon forms mostly in sandy, sandy-skeletal,

coarse-loamy, loamy-skeletal, or coarse-silty materials or in

andic soil materials (defined below), but it occasionally

develops in finer textured material. Some spodic horizons that

are not associated with an albic horizon may have been

overlooked in the past. If the parent materials are rich in clay,

the formation of a spodic horizon is likely to be delayed until

eluviation or weathering has reduced the clay content below a

critical level. A spodic horizon then forms in the eluvial horizon,

and the underlying argillic horizon is either destroyed or moved

to a greater depth as the spodic horizon thickens. There seems

to be an antagonism between a spodic horizon and

phyllosilicates. If a spodic horizon and an argillic horizon occur

in the same soil, they generally are separated by an eluvial

horizon (E ́), but under heath vegetation a spodic horizon may

rest directly on, and may tongue into, an argillic horizon. In

calcareous parent material, a spodic horizon does not begin to

develop until carbonates have been leached from the upper part

of the soil. A spodic horizon can form either in relatively fresh

parent material containing abundant weatherable minerals or in

nearly pure quartz sand.

A spodic horizon can form either in a well drained soil or in a

soil with a shallow, fluctuating level of ground water. If the

water table remains within the spodic horizon for long periods,

the horizon may contain little or no iron. A spodic horizon does

not seem to develop in a soil that is permanently saturated with

water.

Under optimum conditions, a spodic horizon can form within

a few hundred years. Its biological destruction can be equally

rapid, at least in some cultivated soils where lime and fertilizers

are applied.

Most spodic horizons are horizons in which organic matter,

aluminum, and iron have accumulated. As far as is known,

aluminum is always present and may be essential. Almost all

spodic horizons have a maximum content of organic matter,

iron, or aluminum in their upper few centimeters, although

iron may be absent in some, or the iron and aluminum maxima

may be below the organic-matter maximum, and the aluminum

maximum may be below the iron maximum. Most spodic

horizons have hue of 7.5YR or redder. The presence of hue of

7.5YR or redder in a spodic horizon that does not contain iron,

the persistence of the hue after reduction if iron is present, and,

if iron is absent, the destruction of the color by ignition suggest

that organic compounds are important to the color of the spodic

horizon.

The mobile sesquioxides in spodic horizons can result from

the dissolution of primary minerals and from cycling by plants.

In eluvial horizons that overlie spodic horizons, the

aluminosilicates appear pitted as if by solution. Pitting is

particularly evident on mafic minerals. In some soils a well

developed spodic horizon is the upper mineral horizon,

overlain only by an O horizon. Although mixing of horizons by

animals or by falling trees generally can be demonstrated in

such soils, more than one source of the materials accumulated

in the spodic horizon is possible.

Some older theories concerning the formation of spodic

horizons postulated a mutual flocculation of positively charged

colloidal sesquioxides and negatively charged colloidal organic

matter. Others assumed a flocculation of sesquioxides or of

organic matter by changes in the redox potential or pH with

increasing depth.

According to newer theories, an association between organic

matter and iron and aluminum is formed by chelation and

electrostatic bonding. The compounds thus formed are soluble

if the sesquioxide concentration is low, but they are

precipitated when the sesquioxide concentration reaches a

critical level. Other research has demonstrated that large

amounts of inorganic aluminum and iron in a Spodosol can be

translocated as a sol from an A horizon to a B horizon before

complexing with organic matter.

Consequently, if solutions of organic compounds or sols that

are moving through the soil pick up sesquioxides from primary

minerals and from part of the spodic horizon, the compounds

are eventually precipitated somewhere in the spodic horizon.

The movement either can be downward (as a result of gravity)

or can be lateral or upward. Upward movement resulting from

capillary forces is suggested by the black, humus-rich

subhorizon above and on the sides of tongues of the E horizon
Horizons and Characteristics Diagnostic for the Higher Categories 51

that commonly penetrate at various angles into the spodic

horizon. Immobilization of sesquioxides may also be the result of

a hydrolysis of the organometallic complex induced by changes

in pH or by biological destruction of organic ligands. Two of the

specific properties of the immobilized material that becomes the

active fraction of a spodic horizon are (1) high concentrations of

carboxyl and hydroxyl sites that are destroyed on heating and

(2) solubilization of organic matter and sesquioxides on

treatment with a strong complexing agent, such as ammonium

oxalate.

Distinctions Between Spodic Horizons and Andic Soil

Materials

The central concept of andic soil materials is that of a soil

developing in weatherable, silica-rich parent materials, such as

volcanic ejecta or volcaniclastic materials, which have a

colloidal fraction dominated by short-range-order minerals or

aluminum-humus complexes. Under some environmental

conditions, weathering of primary aluminosilicates in parent

materials of nonvolcanic origin may also lead to the formation

of short-range-order minerals. The dominant process in most

soils with andic soil materials is one of weathering and mineral

transformation. Translocation within the soils and

accumulation of the translocated compounds are normally

minimal.

The central concept of soils with spodic horizons is one of

aluminum, or aluminum and iron, and organic matter

illuviating and precipitating when critical levels are reached.

Some areas, for example some areas in Alaska, periodically

receive volcanic ejecta (photo 28). These areas also have

climatic and vegetative conditions conducive to the formation

of spodic materials. The soils in these areas of Alaska exhibit

features of both andic and spodic materials. Because it

represents evidence of eluviation, the albic horizon is used to

separate Andisols from Spodosols; however, a layer of volcanic

ash should not be mistaken for an albic horizon.

Distinctions Between Spodic and Argillic Horizons

Argillic horizons are illuvial, and so are spodic horizons. As

an argillic horizon forms, discrete crystalline clay particles are

moved from an eluvial horizon to an illuvial horizon.

Consequently, the clays in the eluvial and illuvial horizons of a

soil that has an argillic horizon are similar, except where one

kind of clay mineral has moved in preference to others. The

silica-sesquioxide (SiO2 to R2O3) ratio of the whole soil is at a

minimum in the argillic horizon, but that of the clay fraction

remains virtually constant throughout the profile.

In soils that have a spodic horizon, the dominant processes

are dissolution of primary minerals in any eluvial horizon;

movement of iron, aluminum, and organic matter; and

precipitation of complexes of amorphous organic matter and

metal. Typically, the clay mineralogy in the eluvial horizon

differs greatly from that in the illuvial horizons, and the ratio

of SiO2 to R2O3 both in the whole soil and in the clay fraction is

at a minimum in the spodic horizon.

In a particle-size separation, at least some of the illuviated

iron and aluminum is dispersed and becomes part of the

measured clay fraction. Consequently, data commonly show a

clay maximum in the spodic horizon. Both the spodic horizon

and the argillic horizon may be a horizon of accumulation of

free iron. In well drained soils that have an argillic horizon,

the ratio of free iron to clay tends to be constant in all horizons.

In soils that have a spodic horizon, however, this ratio tends to

vary.

There are large differences in micromorphology between an

argillic horizon and a spodic horizon. The birefringent

crystalline clay coatings of the argillic horizon differ sharply

from the isotropic amorphous coatings of the spodic horizon.

Most spodic horizons, however, contain some illuviated

crystalline clay.

Distinctions Between Spodic and Cambic Horizons

A cambic horizon can be formed either by alteration of

parent materials in place, resulting in the release of iron and

the formation of structure, or by solution and removal or

accumulation of carbonates or gypsum. There is not enough

illuviation to form a spodic horizon. Two situations in which a

spodic horizon and a cambic horizon might be confused in the

field are possible. A cambic horizon may grade laterally by

imperceptible stages into a spodic horizon as a result of

increasing accumulation of complexes of organic matter and

sesquioxides. A very weakly developed spodic horizon,

however, contains more of these complexes relative to

phyllosilicates than a cambic horizon, and the two kinds of

horizons can be separated either on the basis of their

morphology or by chemical techniques described below, in the

section on spodic materials.

It may be difficult to distinguish a spodic horizon from a

cambic horizon in a soil that has developed in pyroclastic

materials in a cool, perhumid climatic region. Under those

conditions, part of the amorphous mineral material in a cambic

horizon may form complexes with organic matter that are

similar to those of a spodic horizon. In this situation, a

distinction may be made on the basis of evidence of eluviation

and the typical color pattern of a spodic horizon. If an

overlying eluvial (albic) horizon is present in more than 50

percent of the pedon, it can be inferred that the underlying

horizon is illuvial. Likewise, the presence of a spodic horizon

is suggested if, in a freely drained soil, there is an abrupt

boundary between an Ap horizon and an underlying horizon

that contains 85 percent or more spodic materials.

Morphology

A typical spodic horizon is easily recognized in the field by

its color and structure. Commonly, it has a sandy, sandyskeletal, coarse-loamy, loamy-skeletal, or coarse-silty particle-
52 Soil Taxonomy

size class. The upper boundary of the horizon is commonly

abrupt, and the hue, color value, and chroma of the horizon

change markedly with increasing depth within a few centimeters

of its upper boundary. The lowest color value, the reddest hue,

and the lowest chroma occur in the upper part of the horizon.

The lower part of the spodic horizon, or the horizon directly

below it, has a higher chroma or a yellower hue than the main

part, or it has some combination of these colors. Structure is

either absent or is granular, platy, blocky, or prismatic. Cracked

coatings of an isotropic amorphous mixture of organic matter,

iron, and aluminum can be detected on mineral sand grains in a

sandy or coarse-loamy spodic horizon viewed under a 40- to 60-

power lens.

Commonly, cracked coatings are dominant in the lower part

of the spodic horizon. If the coatings are very thick, the

horizon may be ortstein. In a dry soil the coatings may be

cracked. Clay films are not present on peds or in pores within a

spodic horizon. Coatings on sand grains in a spodic horizon

may not be distinguishable under a hand lens, however, from

thin clay coatings in an argillic horizon.

If an albic horizon overlies a spodic horizon, there is seldom

any difficulty in determining that the spodic horizon is of

illuvial origin. Commonly, there is a second maximum of

organic carbon in the spodic horizon. In some tropical and

subtropical areas, the albic horizon may be extremely thick and

the spodic horizon may occur at a depth of 200 cm or more

below the mineral soil surface. The presence of organic carbon

and the characteristics of the exchange complex distinguish a

cemented spodic horizon (ortstein) from the ironstone layer

(petroferric contact, defined below) at a lithologic discontinuity

below many soils. In undisturbed soils without an albic

horizon, there is commonly a thin, dark eluvial horizon in

which many of the sand grains are free of humus and of

sesquioxide coatings. Many spodic horizons, however, are so

close to the mineral soil surface that the horizons overlying

them are easily destroyed by plowing or even by the

disturbances associated with logging. In some soils the albic or

other overlying horizons seem to have been mixed with the

spodic horizon by falling trees or by animals or may never have

existed. In a disturbed soil it may be difficult or impossible to

establish the illuvial nature of the spodic horizon, although it

has all of the morphological, chemical, and physical properties

of a spodic horizon, which is clearly illuvial. The presence of

an overlying eluvial horizon is not required in the definition of

a spodic horizon, although its identification is facilitated by the

presence of an eluvial horizon.

Identification

A spodic horizon normally underlies an O, A, Ap, or E

horizon. The hue and chroma may remain constant with

increasing depth if the horizon is thin and overlies a densic,

lithic, or paralithic contact (defined below). Generally, the

subhorizon with the reddest hue or the lowest chroma, or both,

is near the top of the spodic horizon. The hue becomes

yellower or the chroma higher, or both, within subhorizons of

the spodic horizon or in an underlying BC, C, E ́, or Bx

horizon.

Spodic horizons must contain at least 85 percent spodic

materials. There are many useful clues from field evidence to

help identify spodic materials. Among these are an albic horizon

in 50 percent or more of the pedon and amorphous aluminum (or

aluminum and iron), which, when present in sufficient amounts,

provides color clues to the existence of spodic materials. These

colors are listed in the section on spodic materials. Spodic

materials cannot be positively identified from field evidence

alone. They must also have a pH value of 5.9 or less and an

organic-carbon content of 0.6 percent or more. Not all soils with

spodic materials have albic horizons. When albic horizons are

absent, spodic materials must still meet specific color

requirements and have at least one additional feature. Such

features can be morphological or chemical, or both. The

additional morphological features include (1) ortstein that has a

horizontal continuity through 50 percent or more of the pedon

and a very firm or firmer rupture-resistance class and (2) cracked

coatings on 10 percent or more of the sand grains. In some soils

the presence of isotropic cracked coatings may have to be

confirmed with the aid of a petrographic microscope. Optical

identification may not be feasible if there are significant

inclusions of mica or of other anisotropic clay or if the presence

of volcanic glass or other pyroclastic materials leads one to

suspect that the horizon is a cambic horizon containing

amorphous clay.

If a pedon does not have an albic horizon, ortstein, or sand

grains with cracked coatings, then the definition of spodic

materials requires that specific color and chemical criteria be

met. Two chemical criteria are used to evaluate spodic

materials. If at least one of these, in addition to the color

requirements, is satisfied, the definition of spodic materials is

met.

The first chemical criterion is that the percentages of

ammonium-oxalate-extractable aluminum plus one-half the

ammonium-oxalate-extractable iron in spodic materials must

total 0.50 or more and must be 2 times or more the amounts

present in an overlying umbric (or subhorizon of an umbric)

epipedon or in an ochric epipedon or albic horizon. The

increase in ammonium-oxalate-extractable iron and aluminum

from an A and/or E horizon to a B horizon is indicative of the

illuvial process. Ammonium oxalate will extract both iron and

aluminum associated with humus and inorganic amorphous

compounds, and it will also dissolve magnetite and

ferrihydrite, both of which contribute to the ammoniumoxalate-extractable iron values. Ferrihydrite is believed to be

associated with both spodic and nonspodic materials in soils

associated with wetness.

The second chemical criterion is that the optical-density-ofoxalate-extract (ODOE) value should be 0.25 or more and at

least double from an eluvial horizon to the spodic horizon. The

ODOE is assumed to result mostly from extracted fulvic acids.
Horizons and Characteristics Diagnostic for the Higher Categories 53

Photo 4.—A histic epipedon.
54 Soil Taxonomy

Photo 5.—A melanic epipedon approximately 90 cm thick in a

Melanudand from Japan.

Photo 6.—A mollic epipedon approximately 25 cm thick over a

calcic horizon in a soil from Idaho.
Horizons and Characteristics Diagnostic for the Higher Categories 55

Photo 7.—A mollic epipedon approximately 57 cm thick in an

Argiustoll from Kansas.

Photo 8.—An ochric epipedon from an Oxisol in Hawaii. The

ochric epipedon has high value and chroma.
56 Soil Taxonomy

Photo 10.—A soil that has a plaggen epipedon about 90 cm (3 ft)

thick. The sod presumably came from the heath. Variations

caused by mixing of materials can be seen. This map unit has

straight boundaries, and it is higher than the surrounding

landscape. Plaggen epipedons are not known to occur in the

United States but are common in parts of Western Europe.

Photo 9.—A soil with an ochric epipedon about 15 cm thick. The

dark colored ochric epipedon is too thin to be a mollic or

umbric epipedon.
Horizons and Characteristics Diagnostic for the Higher Categories 57

Photo 11.—An umbric epipedon in an Xerept from Spain. Photo 12.—An albic horizon in an Argialboll from North Dakota.
58 Soil Taxonomy

Photo 13.—An argillic horizon that begins at about 5 cm in a

Haplustalf from Texas. This argillic horizon has strong

prismatic structure.

Photo 14.—A prominent clay film in a pore and a faint clay film

on the surface of a ped in an argillic horizon.
Horizons and Characteristics Diagnostic for the Higher Categories 59

Photo 15.—Clay films and bridges on sand grains, which

commonly occur in argillic horizons with associated eluvial

horizons that have less than 15 percent clay.

Photo 16.—An argillic horizon that consists of lamellae.
60 Soil Taxonomy

Photo 17.—A partially cemented Ustic Haplocalcid from New

Mexico.

Photo 18.—A cambic horizon below a mollic epipedon in an Ustoll

from Nebraska.
Horizons and Characteristics Diagnostic for the Higher Categories 61

Photo 19.—A duripan underlain by cinders in a Durustoll from Arizona.
62 Soil Taxonomy

Photo 20.—Close-up of a calcareous duripan.
Horizons and Characteristics Diagnostic for the Higher Categories 63

Photo 21.—A fragipan beginning at a depth of about 50 cm.

Bleached seams are between the peds.

Photo 22.—A glossic horizon that has more than 15 percent albic

material between the peds of a degrading argillic horizon.
64 Soil Taxonomy

Photo 23.—A gypsic horizon between depths of 26 and 165 cm in a

Gypsid from New Mexico.
Horizons and Characteristics Diagnostic for the Higher Categories 65

Photo 24.—A natric horizon with columnar structure in a Natrudoll from Argentina.
66 Soil Taxonomy

Photo 25.—A petrocalcic horizon that begins at a depth of about

63 cm in an Argic Petrocalcid from New Mexico.

Photo 26.—A petrogypsic horizon beginning at a depth of about 50

cm in a Petrogypsid from New Mexico.
Horizons and Characteristics Diagnostic for the Higher Categories 67

Photo 28.—A spodic horizon in a Haplocryod from Alaska. This

soil receives periodic deposits of volcanic ash.

Photo 27.—A salic horizon in an Aquisalid from Nevada.
68 Soil Taxonomy

Photo 29.—A pedon with andic soil properties between depths of

about 48 and 100 cm. The material above 48 cm is from the

1980 eruption of Mount St. Helens and has not weathered

sufficiently to meet the criteria for andic soil properties.
Horizons and Characteristics Diagnostic for the Higher Categories 69

Photo 30.—Identifiable secondary carbonates that have engulfed a calcic horizon.
70 Soil Taxonomy

Photo 31.—Lamellae below an argillic horizon.
Horizons and Characteristics Diagnostic for the Higher Categories 71

Photo 32.—Close-up of lamellae.
72 Soil Taxonomy

Photo 33.—Continuous plinthite in a Plinthic Paleudalf from

Texas.

Photo 34.—Slickensides.
Horizons and Characteristics Diagnostic for the Higher Categories 73

Photo 35.—A pedon with aquic conditions close to the surface.
74 Soil Taxonomy

Photo 36.—Peds from a gleyed horizon and the horizon directly below.
Horizons and Characteristics Diagnostic for the Higher Categories 75

Photo 37.—A Turbel from the Yukon Territory with cryoturbation in the subsoil.
76 Soil Taxonomy

Photo 38.—A Glacistel from the Yukon Territory with a glacic layer beginning at a depth of about 50 cm.
Horizons and Characteristics Diagnostic for the Higher Categories 77

Photo 39.—Fractured lithic contact. Vertical fractures are greater than 10 cm. Sandstone is below the lithic contact.
78 Soil Taxonomy

Photo 40.—Differential weathering in grus from a soil in South Africa. The paralithic contact is highly irregular in this pedon.
Horizons and Characteristics Diagnostic for the Higher Categories 79

When there are significantly higher quantities in an illuvial

horizon than in an eluvial horizon, it is concluded that spodic

materials are present.

Thickness of the Spodic Horizon

For a variety of reasons, some spodic horizons are thin or

otherwise weakly developed. Some soils, particularly those that

formed in calcareous parent materials in areas of cool, humid

climates, have two horizons of accumulation, the upper of

which contains an accumulation of amorphous materials,

whereas the lower contains phyllosilicates. The two are

separated by an eluvial horizon. This sequence of horizons is

defined as a bisequum. In this situation, a spodic horizon has

formed, or begun to form, in a clay-depleted eluvial horizon.

Other spodic horizons are thin because they rest on a fragipan

or on a densic, lithic, or paralithic contact. In areas of very

cold, humid climates, any illuvial horizon is normally

dominated by organic matter and amorphous sesquioxides and

may be thin. Very thin horizons of accumulation are easily

destroyed by plowing, trampling by livestock, or logging. To

prevent such minor disturbances from changing the

classification of a soil, a minimum depth to the lower boundary

of the spodic horizon is required for the Spodosol order,

depending on the soil temperature regime (defined below). If the

soil temperature regime is mesic or warmer, the spodic horizon

must extend to a depth of 25 cm from the mineral soil surface,

unless the soil is less than 25 cm deep. For soils that have either

a cryic or a pergelic soil temperature regime, or a frigid soil

temperature regime and a spodic horizon with a coarse-loamy,

loamy-skeletal, or finer particle-size class, depth limits are waived

because in these soils there is less prospect of a serious

disturbance of significant areas than in sandy and warmer soils.

Depth limits also are waived for soils that have a duripan or

fragipan or a petroferric, paralithic, densic, or lithic contact

within 25 cm of the mineral soil surface. If these soils are

disturbed, the whole soil is altered and the classification is likely

to be affected.

Required Characteristics

A spodic horizon is normally a subsurface horizon underlying

an O, A, Ap, or E horizon. It may, however, meet the definition of

an umbric epipedon.

A spodic horizon must have 85 percent or more spodic

materials (described below) in a layer 2.5 cm or more thick that

is not part of any Ap horizon.

Other Diagnostic Soil Characteristics

(Mineral Soils)

Diagnostic soil characteristics are features of the soil that

are used in various places in the keys or in definitions of

diagnostic horizons.

Abrupt Textural Change

An abrupt textural change is a specific kind of change that

may occur between an ochric epipedon or an albic horizon and

an argillic horizon. It is characterized by a considerable increase

in clay content within a very short vertical distance in the zone

of contact. If the clay content in the fine-earth fraction of the

ochric epipedon or albic horizon is less than 20 percent, it

doubles within a vertical distance of 7.5 cm or less. If the clay

content in the fine-earth fraction of the ochric epipedon or the

albic horizon is 20 percent or more, there is an increase of 20

percent or more (absolute) within a vertical distance of 7.5 cm or

less (e.g., an increase from 22 to 42 percent) and the clay content

in some part of the argillic horizon is 2 times or more the amount

contained in the overlying horizon.

Normally, there is no transitional horizon between an ochric

epipedon or an albic horizon and an argillic horizon, or the

transitional horizon is too thin to be sampled. Some soils,

however, have a glossic horizon or interfingering of albic

materials (defined below) in parts of the argillic horizon. The

upper boundary of such a horizon is irregular or even

discontinuous. Sampling this mixture as a single horizon

might create the impression of a relatively thick transitional

horizon, whereas the thickness of the actual transition at the

contact may be no more than 1 mm.

Albic Materials

Albic (L. albus, white) materials are soil materials with a color

that is largely determined by the color of primary sand and silt

particles rather than by the color of their coatings. This

definition implies that clay and/or free iron oxides have been

removed from the materials or that the oxides have been

segregated to such an extent that the color of the materials is

largely determined by the color of the primary particles.

Required Characteristics

Albic materials have one of the following colors:

1. Chroma of 2 or less; and either

a. A color value, moist, of 3 and a color value, dry, of 6 or

more; or

b. A color value, moist, of 4 or more and a color value,

dry, of 5 or more; or

2. Chroma of 3 or less; and either

a. A color value, moist, of 6 or more; or

b. A color value, dry, of 7 or more; or

3. Chroma that is controlled by the color of uncoated grains

of silt or sand, hue of 5YR or redder, and the color values listed

in item 1-a or 1-b above.
80 Soil Taxonomy

Relatively unaltered layers of light colored sand, volcanic

ash, or other materials deposited by wind or water are not

considered albic materials, although they may have the same

color and apparent morphology. These deposits are parent

materials that are not characterized by the removal of clay

and/or free iron and do not overlie an illuvial horizon or other

soil horizon, except for a buried soil. Light colored krotovinas

or filled root channels should be considered albic materials

only if they have no fine stratifications or lamellae, if any

sealing along the krotovina walls has been destroyed, and if

these intrusions have been leached of free iron oxides and/or

clay after deposition.

Andic Soil Properties

Andic soil properties result mainly from the presence of

significant amounts of allophane, imogolite, ferrihydrite, or

aluminum-humus complexes in soils (photo 29). These materials,

originally termed “amorphous” (but understood to contain

allophane) in the 1975 edition of Soil Taxonomy, are commonly

formed during the weathering of tephra and other parent

materials with a significant content of volcanic glass. Although

volcanic glass is or was a common component in many

Andisols, it is not a requirement of the Andisol order. Some soils

develop andic soil properties without the influence of volcanic

glass.

Volcanic glass is a significant component of fresh tephra. In

most environments the volcanic glass weathers to short-rangeorder minerals. The concept of Andisols includes weakly

weathered soils with much volcanic glass as well as more

strongly weathered soils rich in short-range-order minerals.

Hence, the content of volcanic glass is one of the

characteristics used in defining andic soil properties. Volcanic

glass is defined as optically isotropic translucent glass or

pumice of any color, including glassy aggregates and glass

coatings on other mineral grains. Composite grains must have

at least 50 percent (by volume) volcanic glass to be counted as

volcanic glass. In most cases the method used to determine

volcanic glass is not critical. When accurate measurement is

required, however, the standard method, use of a polarizing

microscope, is recommended.

Most horizons that have andic soil properties consist of

mineral soil materials. Some consist of organic soil materials.

A layer or horizon must have less than 25 percent organic

carbon, however, before it is considered to have andic soil

properties.

Required Characteristics

To be recognized as having andic soil properties, soil

materials must contain less than 25 percent (by weight) organic

carbon and meet one or both of the following requirements:

1. In the fine-earth fraction, all of the following:

a. Aluminum plus 1

/2 iron percentages (by ammonium

oxalate) totaling 2.0 percent or more; and

b. A bulk density, measured at 33 kPa water retention, of

0.90 g/cm3 or less; and

c. A phosphate retention of 85 percent or more; or

2. In the fine-earth fraction, a phosphate retention of 25

percent or more, 30 percent or more particles 0.02 to 2.0 mm

in size, and one of the following:

a. Aluminum plus 1/2 iron percentages (by ammonium

oxalate) totaling 0.40 or more and, in the 0.02 to 2.0 mm

fraction, 30 percent or more volcanic glass; or

b. Aluminum plus 1/2 iron percentages (by ammonium

oxalate) totaling 2.0 or more and, in the 0.02 to 2.0 mm

fraction, 5 percent or more volcanic glass; or

c. Aluminum plus 1/2 iron percentages (by ammonium

oxalate) totaling between 0.40 and 2.0 and, in the 0.02 to

2.0 mm fraction, enough volcanic glass so that the glass

percentage, when plotted against the value obtained by

adding aluminum plus 1/2 iron percentages in the fine-earth

fraction, falls within the shaded area of diagram 1.

Anhydrous Conditions

Anhydrous conditions (Gr. anydros, waterless) refer to the

active layer in soils of cold deserts and other areas with

permafrost (often dry permafrost) and low precipitation

(usually less than 50 mm water equivalent). Anhydrous soil

conditions are similar to the aridic (torric) soil moisture

regimes, except that the soil temperature is less than 0 oC.

Coefficient of Linear Extensibility (COLE)

The coefficient of linear extensibility (COLE) is the ratio of

the difference between the moist length and dry length of a

clod to its dry length. It is (Lm - Ld)/Ld, where Lm is the

length at 33 kPa tension and Ld is the length when dry. COLE

can be calculated from the differences in bulk density of the

clod when moist and when dry. An estimate of COLE can be

calculated in the field by measuring the distance between two

pins in a clod of undisturbed soil at field capacity and again

after the clod has dried. COLE does not apply if the shrinkage

is irreversible.

Durinodes

Durinodes (L. durus, hard, and nodus, knot) are weakly

cemented to indurated nodules with a diameter of 1 cm or

more. The cement is SiO2, presumably opal and

microcrystalline forms of silica. Durinodes break down in hot

concentrated KOH after treatment with HCl to remove
Horizons and Characteristics Diagnostic for the Higher Categories 81

carbonates but do not break down with concentrated HCl alone.

Dry durinodes do not slake appreciably in water, but prolonged

soaking can result in spalling of very thin platelets. Durinodes

are firm or firmer and brittle when wet, both before and after

treatment with acid. Most durinodes are roughly concentric

when viewed in cross section, and concentric stringers of opal

are visible under a hand lens.

Fragic Soil Properties

Fragic soil properties are the essential properties of a

fragipan. They have neither the layer thickness nor volume

requirements for the fragipan. Fragic soil properties are in

subsurface horizons, although they can be at or near the surface

in truncated soils. Aggregates with fragic soil properties have a

firm or firmer rupture-resistance class and a brittle manner of

failure when soil water is at or near field capacity. Air-dry

fragments of the natural fabric, 5 to 10 cm in diameter, slake when

they are submerged in water. Aggregates with fragic soil

properties show evidence of pedogenesis, including one or more

of the following: oriented clay within the matrix or on faces of

peds, redoximorphic features within the matrix or on faces of

peds, strong or moderate soil structure, and coatings of albic

materials or uncoated silt and sand grains on faces of peds or in

seams. Peds with these properties are considered to have fragic

soil properties regardless of whether or not the density and

brittleness are pedogenic.

Soil aggregates with fragic soil properties must:

1. Show evidence of pedogenesis within the aggregates or, at a

minimum, on the faces of the aggregates; and

2. Slake when air-dry fragments of the natural fabric, 5 to 10 cm

in diameter, are submerged in water; and

3. Have a firm or firmer rupture-resistance class and a brittle

manner of failure when soil water is at or near field capacity;

and

4. Restrict the entry of roots into the matrix when soil water

is at or near field capacity.

Identifiable Secondary Carbonates

The term “identifiable secondary carbonates” is used in the

definitions of a number of taxa. It refers to translocated

authigenic calcium carbonate that has been precipitated in

place from the soil solution rather than inherited from a soil

parent material, such as a calcareous loess or till (photo 30).

Identifiable secondary carbonates either may disrupt the soil

structure or fabric, forming masses, nodules, concretions, or

spheroidal aggregates (white eyes) that are soft and powdery

when dry, or may be present as coatings in pores, on structural

faces, or on the undersides of rock or pararock fragments. If

present as coatings, the secondary carbonates cover a

significant part of the surfaces. Commonly, they coat all of the

surfaces to a thickness of 1 mm or more. If little calcium

carbonate is present in the soil, however, the surfaces may be

only partially coated. The coatings must be thick enough to be

visible when moist. Some horizons are entirely engulfed by

carbonates. The color of these horizons is largely determined

by the carbonates. The carbonates in these horizons are within

the concept of identifiable secondary carbonates.

The filaments commonly seen in a dry calcareous horizon

are within the meaning of identifiable secondary carbonates if

the filaments are thick enough to be visible when the soil is

moist. Filaments commonly branch on structural faces.

Interfingering of Albic Materials

The term “interfingering of albic materials” refers to albic

materials that penetrate 5 cm or more into an underlying

argillic, kandic, or natric horizon along vertical and, to a lesser

Diagram 1.—Soils that are plotted in the shaded area have andic

soil properties. A soil has these properties if the fraction less

than 2.0 mm in size has phosphate retention of more than 25

percent and the 0.02 to 2.0 mm fraction is at least 30 percent

of the fraction less than 2.0 mm in size.
82 Soil Taxonomy

degree, horizontal faces of peds. There need not be a

continuous overlying albic horizon. The albic materials

constitute less than 15 percent of the layer that they penetrate,

but they form continuous skeletans (ped coatings of clean silt or

sand defined by Brewer, 1976) 1 mm or more thick on the vertical

faces of peds, which means a total width of 2 mm or more

between abutting peds. Because quartz is such a common

constituent of silt and sand, these skeletans are usually light

gray when moist and nearly white when dry, but their color is

determined in large part by the color of the sand or silt

fraction.

Required Characteristics

Interfingering of albic materials is recognized if albic

materials:

1. Penetrate 5 cm or more into an underlying argillic or

natric horizon; and

2. Are 2 mm or more thick between vertical faces of abutting

peds; and

3. Constitute less than 15 percent (by volume) of the layer

that they penetrate.

Lamellae

A lamella is an illuvial horizon less than 7.5 cm thick

(photos 31 and 32). Each lamella contains an accumulation of

oriented silicate clay on or bridging sand and silt grains (and

rock fragments if any are present). A lamella has more silicate

clay than the overlying eluvial horizon.

The significance of lamellae to soil classification is not in the

single lamella but in the multiple number of lamellae, each with

an overlying eluvial horizon in a single pedon. A single lamella

may occur in a pedon, but more commonly there are several

lamellae separated by eluvial horizons.

A lamella 0.5 cm or more thick can be part of a cambic

horizon unless it is sandy (loamy fine sand or coarser). It can

be part of an argillic horizon. A lamella is required to have an

accumulation of oriented silicate clay, but no specific amount

of clay is required. A single lamella is too thin to be either a

cambic or an argillic horizon. A combination of lamellae 15

cm or more thick, however, can be either a cambic or an

argillic horizon if all of the other criteria are met.

Identification

A lamella typically has (but is not required to have) a higher

chroma, redder hue, or lower color value, or any combination

of these, than the overlying eluvial horizon. Some lamellae

have no color differences. All lamellae are required to have

more silicate clay than the overlying eluvial horizon.

In a vertical cross section of a pedon, a lamella appears as a

thin horizon and is often called a “band.” It actually is an

undulating layer, and it is not always continuous. The upper

and lower boundaries may be wavy, and the thickness may vary

from one point to another.

Lamellae commonly occur in sandy and sandy-skeletal

sediments and less commonly in coarse-loamy, loamy-skeletal,

and coarse-silty sediments. The texture of the fine-earth

fraction in lamellae is mostly loamy sand or sandy loam, but it

is known to range from sand to sandy clay loam, silt loam, and

clay loam. The content of rock fragments ranges from 0 to

more than 65 percent. Lamellae commonly are single grained

or granular, but in some pedons they are massive.

Laboratory data show that, in addition to silicate clay

accumulations, silt (particularly fine silt), sesquioxides, and

organic carbon accumulate in some lamellae. Where there is

recharge of carbonates, there may also be accumulations of

carbonates in lamellae.

Although lamellae most commonly occur in eolian and

alluvial sediments, they have also been observed in coarse

grained residuum, such as grus. It is likely that there were very

thin layers with finer soil particles and smaller pore spaces

than in the residuum either above or below them. These thin

layers would then be similar to the bedding planes in the eolian

or alluvial sediments. It is logical that lamellae in residuum

form in the same way as described below.

Origin

Lamellae form in coarse textured sediments (coarse silt or

coarser) of eolian or alluvial deposits that include very small

amounts of silicate clay. Evidence indicates that they form

initially in the bedding planes. The bedding planes, as used

here, are very thin layers with finer soil particles and smaller

pore spaces than the materials either above or below them.

These were deposited during a lull in the wind or a reduction

in the velocity of water. Before a wetting front can move

through these bedding planes to the larger pores in the

underlying strata, the finer pores must be nearly saturated. This

pause in the percolation flow may be sufficient for plant roots

to capture water leaving suspended clay. As a result, silicate

clay suspended in the soil solution can be deposited in the

pores and on the surfaces of the particles. This deposition

further reduces the pore size. With the passing of each

succeeding wetting front, the pore size is reduced even further

and lamellae form.

The lamellae thicken as additional fine particles are

deposited. It is thought that the lamellae may also begin to act

as a filter at this point in their development.

In a close examination of pedons with a large number of

lamellae, the lamellae nearer the soil surface generally have the

least concentration of clay and have the faintest color contrast

from the overlying eluvial horizon. Some sand grains are

devoid of clay, and some have only thin coatings. These

lamellae are generally more wavy and less continuous than

those in the other parts of the lamellae zone (the zone in which

lamellae form). The eluvial horizons overlying these lamellae

are generally the thickest of those in the lamellae zone.
Horizons and Characteristics Diagnostic for the Higher Categories 83

Lamellae in the middle part of the lamellae zone appear to

have the highest concentration of clay at the upper edge of the

lamellae, and the clay content decreases with increasing depth.

The color contrast is greatest at the upper edge of the lamellae,

adjacent to the overlying eluvial horizon. In the lower part of

these lamellae, some sand grains are devoid of clay and some

have only thin clay coatings. The lower part of these lamellae

appear to be very similar to the lamellae closest to the soil

surface. The lamellae in the middle part of the lamellae zone

are wavy but commonly are not so wavy as those in the upper

part of the lamellae zone.

The deepest lamellae are commonly very thin. They have a

color contrast that is nearly as great as that at the upper edge of

the lamellae in the middle part of the lamellae zone. The

deepest lamellae are not very wavy and are commonly parallel

with each other. The thickness of the overlying eluvial

horizons varies more than that in the other parts of the

lamellae zone.

These observations suggest that clay is being moved from

the upper few lamellae to the lower lamellae. Also, in the

lamellae in the middle part of the layer containing lamellae,

clay is being stripped from the lower part of one lamella and is

being redeposited in the top part of the next lower lamella. The

lamellae thicken as clay is added to the top of the lamellae. At

this point, a lamella begins to move away from the bedding

plane from which it originated. The stripping of clay from the

lower part of a lamella and the redeposition in the top part of

the next lower lamella continue this movement upward and

away from the bedding plane.

The movement upward of each lamella is not uniform

throughout its extent. Consequently, lamellae are wavy rather

than smooth, like the bedding planes from which they

originated. Occasionally, some lamellae appear to be branched.

This branching occurs where part of a lamella has moved up

more rapidly than the overlying part of the next higher lamella

and they become joined in this part. The branching is further

evidence that lamellae form upward and that the movement is

not uniform.

Required Characteristics

A lamella is an illuvial horizon less than 7.5 cm thick

formed in unconsolidated regolith more than 50 cm thick.

Each lamella contains an accumulation of oriented silicate clay

on or bridging the sand and silt grains (and coarse fragments if

any are present). Each lamella is required to have more silicate

clay than the overlying eluvial horizon.

Lamellae occur in a vertical series of two or more, and each

lamella must have an overlying eluvial horizon. (An eluvial

horizon is not required above the uppermost lamella if the soil

is truncated.)

Lamellae may meet the requirements for either a cambic or an

argillic horizon. A combination of two or more lamellae 15 cm or

more thick is a cambic horizon if the texture is very fine sand,

loamy very fine sand, or finer. A combination of two or more

lamellae meets the requirements for an argillic horizon if there is

15 cm or more cumulative thickness of lamellae that are 0.5 cm or

more thick and that have a clay content of either:

1. 3 percent or more (absolute) higher than in the overlying

eluvial horizon (e.g., 13 percent versus 10 percent) if any part

of the eluvial horizon has less than 15 percent clay in the fineearth fraction; or

2. 20 percent or more (relative) higher than in the overlying

eluvial horizon (e.g., 24 percent versus 20 percent) if all parts

of the eluvial horizon have more than 15 percent clay in the

fine-earth fraction.

Linear Extensibility (LE)

Linear extensibility (LE) helps to predict the potential of a

soil to shrink and swell. The LE of a soil layer is the product of

the thickness, in cm, multiplied by the COLE of the layer in

question. The LE of a soil is the sum of these products for all

soil horizons.

Lithologic Discontinuities

Lithologic discontinuities are significant changes in particlesize distribution or mineralogy that represent differences in

lithology within a soil. A lithologic discontinuity can also

denote an age difference. For information on using horizon

designations for lithologic discontinuities, see the Soil Survey

Manual (USDA, SCS, 1993).

Not everyone agrees on the degree of change required for a

lithologic discontinuity. No attempt is made to quantify

lithologic discontinuities. The discussion below is meant to

serve as a guideline.

Several lines of field evidence can be used to evaluate

lithologic discontinuities. In addition to mineralogical and

textural differences that may require laboratory studies, certain

observations can be made in the field. These include but are

not limited to the following:

1. Abrupt textural contacts.—An abrupt change in

particle-size distribution, which is not solely a change in clay

content resulting from pedogenesis, can often be observed.

2. Contrasting sand sizes.—Significant changes in sand

size can be detected. For exampe, if material containing mostly

medium sand or finer sand abruptly overlies material containing

mostly coarse sand and very coarse sand, one can assume that

there are two different materials. Although the materials may be

of the same mineralogy, the contrasting sand sizes result from

differences in energy at the time of deposition by water and/or

wind.

3. Bedrock lithology vs. rock fragment lithology in the

soil.—If a soil with rock fragments overlies a lithic contact,

one would expect the rock fragments to have a lithology

similar to that of the material below the lithic contact. If many

of the rock fragments do not have the same lithology as the
84 Soil Taxonomy

underlying bedrock, the soil is not derived completely from the

underlying bedrock.

4. Stone lines.—The occurrence of a horizontal line of rock

fragments in the vertical sequence of a soil indicates that the soil

may have developed in more than one kind of parent material.

The material above the stone line is most likely transported, and

the material below may be of different origin.

5. Inverse distribution of rock fragments.—A lithologic

discontinuity is often indicated by an erratic distribution of

rock fragments. The percentage of rock fragments decreases

with increasing depth. This line of evidence is useful in areas

of soils that have relatively unweathered rock fragments.

6. Rock fragment weathering rinds.—Horizons

containing rock fragments with no rinds that overlie horizons

containing rocks with rinds suggest that the upper material is

in part depositional and not related to the lower part in time

and perhaps in lithology.

7. Shape of rock fragments.—A soil with horizons

containing angular rock fragments overlying horizons

containing well rounded rock fragments may indicate a

discontinuity. This line of evidence represents different

mechanisms of transport (colluvial vs. alluvial) or even

different transport distances.

8. Soil color.—Abrupt changes in color that are not the

result of pedogenic processes can be used as indicators of

discontinuity.

9. Micromorphological features.—Marked differences in

the size and shape of resistant minerals in one horizon and not

in another are indicators of differences in materials.

Use of Laboratory Data

Discontinuities are not always readily apparent in the field.

In these cases laboratory data are necessary. Even with

laboratory data, detecting discontinuities may be difficult. The

decision is a qualitative or perhaps a partly quantitative

judgment. General concepts of lithology as a function of depth

might include:

1. Laboratory data—visual scan.—The array of

laboratory data is assessed in an attempt to determine if a fielddesignated discontinuity is corroborated and if any data show

evidence of a discontinuity not observed in the field. One must

sort changes in lithology from changes caused by pedogenic

processes. In most cases the quantities of sand and coarser

fractions are not altered significantly by soil-forming processes.

Therefore, an abrupt change in sand size or sand mineralogy is

a clue to lithologic change. Gross soil mineralogy and the

resistant mineral suite are other clues.

2. Data on a clay-free basis.—A common manipulation

in assessing lithologic change is computation of sand and silt

separates on a carbonate-free, clay-free basis (percent fraction,

e.g., fine sand and very fine sand, divided by percent sand plus

silt, times 100). Clay distribution is subject to pedogenic

change and may either mask inherited lithologic differences or

produce differences that are not inherited from lithology. The

numerical array computed on a clay-free basis can be inspected

visually or plotted as a function of depth.

Another aid used to assess lithologic changes is computation

of the ratios of one sand separate to another. The ratios can be

computed and examined as a numerical array, or they can be

plotted. The ratios work well if sufficient quantities of the two

fractions are available. Low quantities magnify changes in

ratios, especially if the denominator is low.

n Value

The n value (Pons and Zonneveld, 1965) characterizes the

relation between the percentage of water in a soil under field

conditions and its percentages of inorganic clay and humus.

The n value is helpful in predicting whether a soil can be

grazed by livestock or can support other loads and in

predicting what degree of subsidence would occur after

drainage.

For mineral soil materials that are not thixotropic, the n

value can be calculated by the following formula:

n = (A - 0.2R)/(L + 3H)

In this formula, A is the percentage of water in the soil in

field condition, calculated on a dry-soil basis; R is the

percentage of silt plus sand; L is the percentage of clay; and H

is the percentage of organic matter (percent organic carbon

multiplied by 1.724).

This formula is based on experience with soil materials that

have humified organic matter and in which illite and other

nonexpanding clay minerals are predominant. There are

indications that the factor by which the organic matter is

multiplied should exceed 3 if the organic matter is

incompletely humified. The correction for the water held by the

organic matter becomes an increasing source of uncertainty as

the ratio of clay to organic matter becomes narrow. In this

taxonomy, the n value is used only to characterize mineral

soils.

Few data for calculations of the n value are available in the

United States, but the critical n value of 0.7 can be

approximated closely in the field by a simple test of squeezing

a soil sample in the hand. If the soil flows between the fingers

with difficulty, the n value is between 0.7 and 1.0 (slightly fluid

manner of failure class); if the soil flows easily between the

fingers, the n value is 1 or more (moderately fluid or very fluid

manner of failure class).

Soils in which the moisture content is periodically reduced

below field capacity seldom have an n value of 0.7 or more.

Most of the soils that have been permanently saturated are

likely to have a high n value. Consequently, high n values are

primarily in soils of tidal marshes, swamps, and shallow lakes.

The sediments in these areas have never been above the

capillary fringe during drought cycles. A high calculated n

value may also be characteristic of some soils that formed in
Horizons and Characteristics Diagnostic for the Higher Categories 85

volcanic ash in areas of a perhumid climate. These soils are

thixotropic, and the field test is more reliable than the formula

for estimating their bearing value.

Petroferric Contact

A petroferric (Gr. petra, rock, and L. ferrum, iron; implying

ironstone) contact is a boundary between soil and a continuous

layer of indurated material in which iron is an important

cement and organic matter is either absent or present only in

traces. The indurated layer must be continuous within the

limits of each pedon, but it may be fractured if the average

lateral distance between fractures is 10 cm or more. The fact

that this ironstone layer contains little or no organic matter

distinguishes it from a placic horizon and an indurated spodic

horizon (ortstein), both of which contain organic matter.

The purpose in choosing a petroferric contact as a

diagnostic feature distinct from a lithic contact is to identify

the shallow layers of hard ironstone that may have been called

hardened laterite and those that may have accumulated in a

hard form. Petroferric contacts are extensive in tropical and

subtropical regions. There may be shallow sandstone that is

cemented by iron in any climatic region. The contact with such

a layer is a lithic contact, not a petroferric contact.

Several features can aid in making the distinction between a

lithic contact and a petroferric contact. First, a petroferric

contact is roughly horizontal. Second, the material directly

below a petroferric contact contains a high amount of iron

(normally 30 percent or more Fe2

O3). Third, the ironstone

sheets below a petroferric contact are thin; their thickness

ranges from a few centimeters to very few meters. Sandstone,

on the other hand, may be thin or very thick, may be levelbedded or tilted, and may contain only a small percentage of

Fe2O3. In the Tropics, the ironstone is generally more or less

vesicular.

Plinthite

Plinthite (Gr. plinthos, brick) is an iron-rich, humus-poor

mixture of clay with quartz and other minerals (photo 33). It

commonly occurs as dark red redox concentrations that usually

form platy, polygonal, or reticulate patterns. Plinthite changes

irreversibly to an ironstone hardpan or to irregular aggregates

on exposure to repeated wetting and drying, especially if it is

also exposed to heat from the sun. The lower boundary of a

zone in which plinthite occurs generally is diffuse or gradual,

but it may be abrupt at a lithologic discontinuity.

Plinthite may occur as a constituent of a number of

horizons, such as an epipedon, a cambic horizon, an argillic

horizon, an oxic horizon, or a C horizon. It is one form of the

material that has been called laterite. It normally forms in a

horizon below the surface, but it may form at the surface in a

seepy area at the base of a slope.

From a genetic viewpoint, plinthite forms by segregation of

iron. In many places iron probably has been added from other

horizons or from the higher adjacent soils. Generally, plinthite

forms in a horizon that is saturated with water for some time

during the year. Initially, iron is normally segregated in the

form of soft, more or less clayey, red or dark red redox

concentrations. These concentrations are not considered

plinthite unless there has been enough segregation of iron to

permit their irreversible hardening on exposure to repeated

wetting and drying. Plinthite is firm or very firm when the soil

moisture content is near field capacity and hard when the

moisture content is below the wilting point. Plinthite does not

harden irreversibly as a result of a single cycle of drying and

rewetting. After a single drying, it will remoisten and then can

be dispersed in large part if one shakes it in water with a

dispersing agent.

In a moist soil, plinthite is soft enough to be cut with a

spade. After irreversible hardening, it is no longer considered

plinthite but is called ironstone. Indurated ironstone materials

can be broken or shattered with a spade but cannot be dispersed

if one shakes them in water with a dispersing agent.

A small amount of plinthite in the soil does not form a

continuous phase; that is, the individual redox concentrations

or aggregates are not connected with each other. If a large

amount of plinthite is present, it may form a continuous phase.

If a continuous layer becomes indurated, it is a massive

ironstone layer that has irregular, somewhat tubular inclusions

of yellowish, grayish, or white, clayey material. If the layer is

exposed, these inclusions may be washed out, leaving an

ironstone that has many coarse, tubular pores.

Much that has been called laterite is included in the

meaning of plinthite. Doughy and concretionary laterite that

has not hardened is an example. Hardened laterite, whether it

is vesicular or pisolitic, is not included in the definition of

plinthite.

Resistant Minerals

Several references are made to resistant minerals in this

taxonomy. Obviously, the stability of a mineral in the soil is a

partial function of the soil moisture regime. Where resistant

minerals are referred to in the definitions of diagnostic

horizons and of various taxa, a humid climate, past or present,

is always assumed.

Resistant minerals are durable minerals in the 0.02 to 2.0

mm fraction. Quartz is the most common resistant mineral in

soils. The less common ones include sphene, rutile, zircon,

tourmaline, and beryl.

Slickensides

Slickensides are polished and grooved surfaces and

generally have dimensions exceeding 5 cm (photo 34). They

are produced when one soil mass slides past another. Some

slickensides occur at the lower boundary of a slip surface where
86 Soil Taxonomy

a mass of soil moves downward on a relatively steep slope.

Slickensides result directly from the swelling of clay minerals

and shear failure. They are very common in swelling clays that

undergo marked changes in moisture content.

Spodic Materials

Spodic materials form in an illuvial horizon that normally

underlies a histic, ochric, or umbric epipedon or an albic

horizon. In most undisturbed areas, spodic materials underlie

an albic horizon. They may occur within an umbric epipedon

or an Ap horizon.

A horizon consisting of spodic materials normally has an

optical-density-of-oxalate-extract (ODOE) value of 0.25 or

more, and that value is commonly at least 2 times as high as

the ODOE value in an overlying eluvial horizon. This increase

in ODOE value indicates an accumulation of translocated

organic materials in an illuvial horizon. Soils with spodic

materials show evidence that organic materials and aluminum,

with or without iron, have been moved from an eluvial horizon

to an illuvial horizon.

Definition of Spodic Materials

Spodic materials are mineral soil materials that do not have

all of the properties of an argillic or kandic horizon; are

dominated by active amorphous materials that are illuvial and

are composed of organic matter and aluminum, with or without

iron; and have both of the following:

1. A pH value in water (1:1) of 5.9 or less and an organiccarbon content of 0.6 percent or more; and

2. One or both of the following:

a. An overlying albic horizon that extends horizontally

through 50 percent or more of each pedon and, directly

under the albic horizon, colors, moist (crushed and

smoothed sample), as follows:

(1) Hue of 5YR or redder; or

(2) Hue of 7.5YR, color value of 5 or less, and chroma

of 4 or less; or

(3) Hue of 10YR or neutral and a color value and

chroma of 2 or less; or

(4) A color of 10YR 3/1; or

b. With or without an albic horizon and one of the colors

listed above or hue of 7.5YR, color value, moist, of 5 or less,

chroma of 5 or 6 (crushed and smoothed sample), and one

or more of the following morphological or chemical

properties:

(1) Cementation by organic matter and aluminum, with

or without iron, in 50 percent or more of each pedon and

a very firm or firmer rupture-resistance class in the

cemented part; or

(2) 10 percent or more cracked coatings on sand grains;

or

(3) Aluminum plus 1

/2 iron percentages (by ammonium

oxalate) totaling 0.50 or more, and half that amount or

less in an overlying umbric (or subhorizon of an umbric)

epipedon, ochric epipedon, or albic horizon; or

(4) An optical-density-of-oxalate-extract (ODOE) value

of 0.25 or more, and a value half as high or lower in an

overlying umbric (or subhorizon of an umbric) epipedon,

ochric epipedon, or albic horizon.

Weatherable Minerals

Several references are made to weatherable minerals in this

taxonomy. Obviously, the stability of a mineral in a soil is a

partial function of the soil moisture regime. Where weatherable

minerals are referred to in the definitions of diagnostic

horizons and of various taxa in this taxonomy, a humid

climate, either present or past, is always assumed. The

minerals that are included in the meaning of weatherable

minerals are as follows:

1. Clay minerals: All 2:1 lattice clays, except for one that is

currently considered to be an aluminum-interlayered chlorite.

Sepiolite, talc, and glauconite are also included in this group of

weatherable clay minerals, although they are not everywhere of

clay size.

2. Silt- and sand-sized minerals (0.02 to 0.2 mm in

diameter): Feldspars, feldspathoids, ferromagnesian minerals,

glass, micas, zeolites, and apatite.

Obviously, this definition of the term “weatherable

minerals” is restrictive. The intent is to include, in the

definitions of diagnostic horizons and various taxa, only those

weatherable minerals that are unstable in a humid climate

compared to other minerals, such as quartz and 1:1 lattice

clays, but that are more resistant to weathering than calcite.

Characteristics Diagnostic for

Organic Soils

Following is a description of the characteristics that are

used only with organic soils.

Kinds of Organic Soil Materials

Three different kinds of organic soil materials are

distinguished in this taxonomy, based on the degree of

decomposition of the plant materials from which the organic

materials are derived. The three kinds are (1) fibric, (2) hemic,

and (3) sapric. Because of the importance of fiber content in

the definitions of these materials, fibers are defined before the

kinds of organic soil materials.
Horizons and Characteristics Diagnostic for the Higher Categories 87

Fibers

Fibers are pieces of plant tissue in organic soil materials

(excluding live roots) that:

1. Are large enough to be retained on a 100-mesh sieve

(openings 0.15 mm across) when the materials are screened;

and

2. Show evidence of the cellular structure of the plants from

which they are derived; and

3. Either are 2 cm or less in their smallest dimension or are

decomposed enough to be crushed and shredded with the

fingers.

Pieces of wood that are larger than 2 cm in cross section and

are so undecomposed that they cannot be crushed and shredded

with the fingers, such as large branches, logs, and stumps, are

not considered fibers but are considered coarse fragments

(comparable to gravel, stones, and boulders in mineral soils).

The degree of decomposition of organic materials is

indicated by the content of fibers. If the organic materials are

highly decomposed, fibers are nearly absent. If the organic

materials are only slightly decomposed, more of the volume,

exclusive of the coarse fragments, normally consists of fibers.

If the organic materials are moderately decomposed, the fibers

may be largely preserved but are easily broken down by

rubbing between the thumb and fingers. The percentage of

fibers that do not break down when rubbed gives the most

realistic field estimate of the degree of decomposition. In

addition, the bulk density (and hence the amount of subsidence

after drainage) is more closely related to the content of fiber

after rubbing than to the content of fiber before rubbing. A

small volume of the wet material is rubbed between the thumb

and fingers about 10 times with firm pressure. In the laboratory

the material, after rubbing, is washed on a screen. In the field

the rubbed material may be molded into a spherical or rodshaped mass and broken for examination under a hand lens of

10 power or more to estimate the fiber content.

The definitions of fibric, hemic, and sapric soil materials

that follow are based in part on the content of fibers after

rubbing and in part on the solubility of the materials in sodium

pyrophosphate.

Fibric Soil Materials

Fibric soil materials (L. fibra, fiber) are the least

decomposed of all of the organic soil materials. They contain

large amounts of fibers that are well preserved and can be

linked to botanical origin. They have a low bulk density and a

high water content when saturated. Fibric soil materials have a

wide geographic distribution, and they occur in environments

that are not conducive to processes of alteration and

decomposition. Examples of such environments are the cool or

cold, perhumid, boreal forest zones, where raised bogs and hill

peats are dominated by Sphagnum; land-locked depressions

that have Hypnum moss; and very flat, undrained areas that

support a variety of reeds, sedges, and grasses. Wet flatlands

occur in glaciated areas in the higher latitudes. Also, very wet

flatlands are in some semitropical and tropical areas. An

example is the sawgrass (sedge) bogs of the Everglades in

Florida. Fibric materials commonly have a bulk density of less

than 0.1; a fiber content (unrubbed) exceeding two-thirds of the

volume; and a water content, when saturated, ranging from

about 850 to more than 3,000 percent of the weight of ovendry

material. Fibric materials commonly are light yellowish brown,

dark brown, or reddish brown.

Fibric soil materials are organic soil materials that either:

1. Contain three-fourths or more (by volume) fibers after

rubbing, excluding coarse fragments; or

2. Contain two-fifths or more (by volume) fibers after

rubbing, excluding coarse fragments, and yield color values

and chromas of 7/1, 7/2, 8/1, 8/2, or 8/3 (diagram 2) on white

chromatographic or filter paper that is inserted into a paste

made of the soil materials in a saturated sodium-pyrophosphate

solution.

Hemic Soil Materials

Hemic soil materials (Gr. hemi, half; implying intermediate

decomposition) are intermediate in their degree of

decomposition between the less decomposed fibric and more

decomposed sapric materials. Their morphological features

give intermediate values for fiber content, bulk density, and

water content. Hemic soil materials are partly altered both

physically and biochemically. Their geographic distribution is

widespread. Colors are commonly dark grayish brown to dark

reddish brown. The fibers are largely destroyed when the wet

organic material is rubbed. The bulk density commonly is

between 0.07 and 0.18, the fiber content normally is between

one-third and two-thirds of the volume before rubbing, and the

maximum water content at saturation commonly ranges from

about 450 to 850 percent. Hemic materials do not meet both the

fiber content (after rubbing) and the sodium-pyrophosphate

solubility requirements for either fibric or sapric materials

(diagram 2).

Sapric Soil Materials

Sapric soil materials (Gr. sapros, rotten) are the most highly

decomposed of the three kinds of organic soil materials. They

have the smallest amount of plant fiber, the highest bulk

density, and the lowest water content on a dry-weight basis at

saturation. Sapric soil materials are commonly very dark gray

to black. They are relatively stable; i.e., they change very little

physically and chemically with time in comparison to other

organic soil materials. Sapric materials have been exposed to

aerobic decomposition either naturally or because of artificial
88 Soil Taxonomy

drainage. In undrained bogs sapric materials occur at the

present surface or were previously at the surface and are now

buried. The bulk density of these materials commonly is 0.2 or

more, the fiber content averages less than one-third of the

volume before rubbing, and the maximum water content at

saturation normally is less than 450 percent on an ovendry

basis.

Sapric materials have the following characteristics:

1. The fiber content, after rubbing, is less than one-sixth (by

volume), excluding coarse fragments; and

2. The color of the sodium-pyrophosphate extract on white

chromatographic or filter paper is below or to the right of a

line drawn to exclude blocks 5/1, 6/2, and 7/3 (Munsell

designations, diagram 2). If few or no fibers can be detected

and the color of the pyrophosphate extract is to the left of or

above this line, the possibility that the material is limnic must be

considered.

Humilluvic Material

Humilluvic material, i.e., illuvial humus, accumulates in the

lower parts of some organic soils that are acid and have been

drained and cultivated. The humilluvic material has a C14 age

that is not older than the overlying organic materials. It has

very high solubility in sodium pyrophosphate and rewets very

slowly after drying. Most commonly, it accumulates near a

contact with a sandy mineral horizon.

To be recognized as a differentia in classification, the

humilluvic material must constitute one-half or more (by

volume) of a layer 2 cm or more thick. Because humilluvic

materials are recognized in few soils, there are not enough data

to develop a precise definition. Taxa with humilluvic material

are recognized in Histosols but not Histels.

Limnic Materials

The presence or absence of limnic deposits is taken into

account in the higher categories of Histosols but not Histels.

The nature of such deposits is considered in the lower

categories of Histosols. Limnic materials include both organic

and inorganic materials that were either (1) deposited in water

by precipitation or through the action of aquatic organisms,

such as algae or diatoms, or (2) derived from underwater and

floating aquatic plants and subsequently modified by aquatic

animals. They include coprogenous earth (sedimentary peat),

diatomaceous earth, and marl. Except for some of the

coprogenous earths that contain 30 percent or more organic

matter, most of these limnic materials are inorganic. Diatomite

is highly siliceous; marl is mainly calcium carbonate. Limnic

materials generally occur in the lower part of an organic soil

and were formed during an open-water stage of bog

development.

Coprogenous Earth

A layer of coprogenous earth (sedimentary peat) is a limnic

layer that:

1. Contains many fecal pellets with diameters between a few

hundredths and a few tenths of a millimeter; and

2. Has a color value, moist, of 4 or less; and

3. Either forms a slightly viscous water suspension and is

nonplastic or slightly plastic but not sticky, or shrinks upon

drying, forming clods that are difficult to rewet and often tend

to crack along horizontal planes; and

4. Either yields a saturated sodium-pyrophosphate extract on

Diagram 2.—Value and chroma of pyrophosphate solution of

fibric and sapric materials.
Horizons and Characteristics Diagnostic for the Higher Categories 89

white chromatographic or filter paper that has a color value of

7 or more and chroma of 2 or less (diagram 2) or has a cationexchange capacity of less than 240 cmol(+) per kg organic

matter (measured by loss on ignition), or both.

Normally, layers of coprogenous earth contain almost no

visible fragments of plants. These layers have a range in

particle size and a C-N ratio (12 to 20) that are consistent with

advanced decomposition. Yet, they have both a low and a

narrow range in cation-exchange capacity (80 to 160 cmol(+)

per kg of organic matter), which indicates little decomposition

influenced by exposure to air. In places these layers have what

appears to be platy structure. The individual plates are a little

more than 0.5 mm thick and may be increments of annual

deposition. Such structure certainly is not pedogenic. Olive or

olive brown colors in organic layers of organic soils are

characteristic of coprogenous earth layers. The most common

colors are those with hue of 2.5Y or 5Y, value of 3 or 4, and

chroma of 2.

Diatomaceous Earth

A layer of diatomaceous earth is a limnic layer that:

1. If not previously dried, has a matrix color value of 3, 4,

or 5, which changes irreversibly on drying as a result of the

irreversible shrinkage of organic-matter coatings on diatoms

(identifiable by microscopic, 440 X, examination of dry

samples); and

2. Either yields a saturated sodium-pyrophosphate extract on

white chromatographic or filter paper that has a color value of

8 or more and chroma of 2 or less or has a cation-exchange

capacity of less than 240 cmol(+) per kg organic matter (by

loss on ignition), or both.

Layers of diatomaceous earth normally are more nearly

mineral than organic in composition.

Marl

A layer of marl is a limnic layer that:

1. Has a color value, moist, of 5 or more; and

2. Reacts with dilute HCl to evolve CO2

.

The color of marl usually does not change irreversibly

on drying because a layer of marl contains too little organic

matter, even before it has been shrunk by drying, to coat

the carbonate particles. Most of the samples of marl from

the United States studied to date have an organic-matter

content between 4 and 20 percent, inclusive, and, after

treatment with dilute HCl, some disintegrated plant remains

are evident.

Thickness of Organic Soil Materials

(Control Section of Histosols and Histels)

The thickness of organic materials over limnic materials,

mineral materials, water, or permafrost is used to define the

Histosols and Histels.

For practical reasons, an arbitrary control section has been

established for the classification of Histosols and Histels.

Depending on the kinds of soil material in the surface layer,

the control section has a thickness of either 130 cm or 160 cm

from the soil surface if there is no densic, lithic, or paralithic

contact, thick layer of water, or permafrost within the

respective limit. The thicker control section is used if the

surface layer to a depth of 60 cm either contains three-fourths

or more fibers derived from Sphagnum, Hypnum, or other

mosses or has a bulk density of less than 0.1. Layers of water,

which may be between a few centimeters and many meters

thick in these soils, are considered to be the lower boundary of

the control section only if the water extends below a depth of

130 or 160 cm, respectively. A densic, lithic, or paralithic

contact, if shallower than 130 or 160 cm, constitutes the lower

boundary of the control section. In some soils the lower

boundary is 25 cm below the upper limit of permafrost. An

unconsolidated mineral substratum shallower than those limits

does not change the lower boundary of the control section.

The control section of Histosols and Histels is divided

somewhat arbitrarily into three tiers—surface, subsurface, and

bottom tiers.

Surface Tier

The surface tier of a Histosol or Histel extends from the soil

surface to a depth of 60 cm if either (1) the materials within

that depth are fibric and three-fourths or more of the fiber

volume is derived from Sphagnum or other mosses or (2) the

materials have a bulk density of less than 0.1. Otherwise, the

surface tier extends from the soil surface to a depth of 30 cm.

Some organic soils have a mineral surface layer less than 40

cm thick as a result of flooding, volcanic eruptions, additions

of mineral materials to increase soil strength or reduce the

hazard of frost, or other causes. If such a mineral layer is less

than 30 cm thick, it constitutes the upper part of the surface

tier; if it is 30 to 40 cm thick, it constitutes the whole surface

tier and part of the subsurface tier.

Subsurface Tier

The subsurface tier is normally 60 cm thick. If the control

section ends at a shallower depth (at a densic, lithic, or

paralithic contact or a water layer or in permafrost), however,
90 Soil Taxonomy

the subsurface tier extends from the lower boundary of the

surface tier to the lower boundary of the control section. It

includes any unconsolidated mineral layers that may be present

within those depths.

Bottom Tier

The bottom tier is 40 cm thick unless the control section has

its lower boundary at a shallower depth (at a densic, lithic, or

paralithic contact or a water layer or in permafrost).

Thus, if the organic materials are thick, there are two

possible thicknesses of the control section, depending on the

presence or absence and the thickness of a surface mantle of

fibric moss or other organic material that has a low bulk

density (less than 0.1). If the fibric moss extends to a depth of

60 cm and is the dominant material within this depth (threefourths or more of the volume), the control section is 160 cm

thick. If the fibric moss is thin or absent, the control section

extends to a depth of 130 cm.

Horizons and Characteristics

Diagnostic for Both Mineral and

Organic Soils

Following are descriptions of the horizons and

characteristics diagnostic for both mineral and organic soils.

Aquic Conditions2

Soils with aquic (L. aqua, water) conditions are those that

currently undergo continuous or periodic saturation and

reduction. The presence of these conditions is indicated by

redoximorphic features, except in Histosols and Histels, and

can be verified by measuring saturation and reduction, except

in artificially drained soils. Artificial drainage is defined here

as the removal of free water from soils having aquic conditions

by surface mounding, ditches, or subsurface tiles to the extent

that water table levels are changed significantly in connection

with specific types of land use. In the keys, artificially drained

soils are included with soils that have aquic conditions.

Elements of aquic conditions are as follows:

1. Saturation is characterized by zero or positive pressure in

the soil water and can generally be determined by observing

free water in an unlined auger hole. Problems may arise,

however, in clayey soils with peds, where an unlined auger

hole may fill with water flowing along faces of peds while the

soil matrix is and remains unsaturated (bypass flow). Such free

water may incorrectly suggest the presence of a water table,

while the actual water table occurs at greater depth. Use of well

sealed piezometers or tensiometers is therefore recommended

for measuring saturation. Problems may still occur, however, if

water runs into piezometer slits near the bottom of the

piezometer hole or if tensiometers with slowly reacting

manometers are used. The first problem can be overcome by

using piezometers with smaller slits and the second by using

transducer tensiometry, which reacts faster than manometers.

Soils are considered wet if they have pressure heads greater

than -1 kPa. Only macropores, such as cracks between peds or

channels, are then filled with air, while the soil matrix is

usually still saturated. Obviously, exact measurements of the

wet state can be obtained only with tensiometers. For

operational purposes, the use of piezometers is recommended

as a standard method.

The duration of saturation required for creating aquic

conditions varies, depending on the soil environment, and is

not specified.

Three types of saturation are defined:

a. Endosaturation.—The soil is saturated with water in all

layers from the upper boundary of saturation to a depth of

200 cm or more from the mineral soil surface.

b. Episaturation.—The soil is saturated with water in one

or more layers within 200 cm of the mineral soil surface and

also has one or more unsaturated layers, with an upper

boundary above a depth of 200 cm, below the saturated

layer. The zone of saturation, i.e., the water table, is perched

on top of a relatively impermeable layer.

c. Anthric saturation.—This term refers to a special kind

of aquic conditions that occur in soils that are cultivated and

irrigated (flood irrigation). Soils with anthraquic conditions

must meet the requirements for aquic conditions and in

addition have both of the following:

(1) A tilled surface layer and a directly underlying

slowly permeable layer that has, for 3 months or more in

normal years, both:

(a) Saturation and reduction; and

(b) Chroma of 2 or less in the matrix; and

(2) A subsurface horizon with one or more of the

following:

(a) Redox depletions with a color value, moist, of 4

or more and chroma of 2 or less in macropores; or

(b) Redox concentrations of iron; or

(c) 2 times or more the amount of iron (by dithionite

citrate) contained in the tilled surface layer.

2. The degree of reduction in a soil can be characterized by

the direct measurement of redox potentials. Direct

measurements should take into account chemical equilibria as

expressed by stability diagrams in standard soil textbooks.

2 In 1992, the term “aquic conditions” was introduced and other changes were made

throughout this taxonomy as a result of recommendations submitted to NRCS by the

International Committee on Aquic Moisture Regime (ICOMAQ), which was established in

1982 and was chaired initially by Dr. Frank Moormann, then by Dr. Johan Bouma.
Horizons and Characteristics Diagnostic for the Higher Categories 91

Reduction and oxidation processes are also a function of soil

pH. Obtaining accurate measurements of the degree of reduction

in a soil is difficult. In the context of this taxonomy, however,

only a degree of reduction that results in reduced iron is

considered, because it produces the visible redoximorphic

features that are identified in the keys. A simple field test is

available to determine if reduced iron ions are present. A freshly

broken surface of a field-wet soil sample is treated with

alpha,alpha-dipyridyl in neutral, 1-normal ammonium-acetate

solution. The appearance of a strong red color on the freshly

broken surface indicates the presence of reduced iron ions. A

positive reaction to the alpha,alpha-dipyridyl field test for

ferrous iron (Childs, 1981) may be used to confirm the existence

of reducing conditions and is especially useful in situations

where, despite saturation, normal morphological indicators of

such conditions are either absent or obscured (as by the dark

colors characteristic of melanic great groups). A negative

reaction, however, does not imply that reducing conditions are

always absent. It may only mean that the level of free iron in the

soil is below the sensitivity limit of the test or that the soil is in

an oxidized phase at the time of testing. Use of alpha,alphadipyridyl in a 10 percent acetic-acid solution is not

recommended because the acid is likely to change soil

conditions, for example, by dissolving CaCO3.

The duration of reduction required for creating aquic

conditions is not specified.

3. Redoximorphic features associated with wetness result

from alternating periods of reduction and oxidation of iron and

manganese compounds in the soil. Reduction occurs during

saturation with water, and oxidation occurs when the soil is not

saturated. The reduced iron and manganese ions are mobile

and may be transported by water as it moves through the soil.

Certain redox patterns occur as a function of the patterns in

which the ion-carrying water moves through the soil and as a

function of the location of aerated zones in the soil. Redox

patterns are also affected by the fact that manganese is reduced

more rapidly than iron, while iron oxidizes more rapidly upon

aeration. Characteristic color patterns are created by these

processes. The reduced iron and manganese ions may be

removed from a soil if vertical or lateral fluxes of water occur,

in which case there is no iron or manganese precipitation in

that soil. Wherever the iron and manganese are oxidized and

precipitated, they form either soft masses or hard concretions

or nodules. Movement of iron and manganese as a result of

redox processes in a soil may result in redoximorphic features

that are defined as follows:

a. Redox concentrations.—These are zones of apparent

accumulation of Fe-Mn oxides, including:

(1) Nodules and concretions, which are cemented

bodies that can be removed from the soil intact.

Concretions are distinguished from nodules on the basis

of internal organization. A concretion typically has

concentric layers that are visible to the naked eye.

Nodules do not have visible organized internal structure.

Boundaries commonly are diffuse if formed in situ and

sharp after pedoturbation. Sharp boundaries may be relict

features in some soils; and

(2) Masses, which are noncemented concentrations of

substances within the soil matrix; and

(3) Pore linings, i.e., zones of accumulation along

pores that may be either coatings on pore surfaces

or impregnations from the matrix adjacent to the

pores.

b. Redox depletions.—These are zones of low chroma

(chromas less than those in the matrix) where either Fe-Mn

oxides alone or both Fe-Mn oxides and clay have been

stripped out, including:

(1) Iron depletions, i.e., zones that contain low amounts

of Fe and Mn oxides but have a clay content similar to

that of the adjacent matrix (often referred to as albans or

neoalbans); and

(2) Clay depletions, i.e., zones that contain low

amounts of Fe, Mn, and clay (often referred to as silt

coatings or skeletans).

c. Reduced matrix.—This is a soil matrix that has low

chroma in situ but undergoes a change in hue or chroma

within 30 minutes after the soil material has been exposed

to air.

d. In soils that have no visible redoximorphic features, a

reaction to an alpha,alpha-dipyridyl solution satisfies the

requirement for redoximorphic features.

Photo 35 shows a pedon from Alaska with aquic conditions

close to the surface. When snow begins to melt in the spring,

the subsoil remains frozen and perches water in the gleyed

zone. Photo 36 shows peds from the gleyed horizon and the

horizon directly below. The gleyed horizon has redoximorphic

concentrations lining pores and redoximorphic depletions in

the matrix. The horizon below has redoximorphic depletions

lining pores and redoximorphic concentrations in the matrix.

Field experience indicates that it is not possible to define a

specific set of redoximorphic features that is uniquely

characteristic of all of the taxa in one particular category.

Therefore, color patterns that are unique to specific taxa are

referenced in the keys.

Anthraquic conditions are a variant of episaturation and

are associated with controlled flooding (for such crops as

wetland rice and cranberries), which causes reduction

processes in the saturated, puddled surface soil and oxidation
92 Soil Taxonomy

of reduced and mobilized iron and manganese in the unsaturated

subsoil.

Cryoturbation

Cryoturbation (frost churning) is the mixing of the soil matrix

within the pedon that results in irregular or broken horizons,

involutions, accumulation of organic matter on the permafrost

table, oriented rock fragments, and silt caps on rock fragments

(photo 37).

Densic Contact

A densic contact (L. densus, thick) is a contact between soil

and densic materials (defined below). It has no cracks, or the

spacing of cracks that roots can enter is 10 cm or more.

Densic Materials

Densic materials are relatively unaltered materials (do not

meet the requirements for any other named diagnostic horizons

or any other diagnostic soil characteristic) that have a

noncemented rupture-resistance class. The bulk density or the

organization is such that roots cannot enter, except in cracks.

These are mostly earthy materials, such as till, volcanic

mudflows, and some mechanically compacted materials, for

example, mine spoils. Some noncemented rocks can be densic

materials if they are dense or resistant enough to keep roots

from entering, except in cracks.

Densic materials are noncemented and thus differ from

paralithic materials and the material below a lithic contact,

both of which are cemented.

Densic materials have, at their upper boundary, a densic

contact if they have no cracks or if the spacing of cracks that

roots can enter is 10 cm or more. These materials can be used

to differentiate soil series if the materials are within the series

control section.

Gelic Materials

Gelic materials are mineral or organic soil materials that

show evidence of cryoturbation (frost churning) and/or ice

segregation in the active layer (seasonal thaw layer) and/or the

upper part of the permafrost. Cryoturbation is manifested by

irregular and broken horizons, involutions, accumulation of

organic matter on top of and within the permafrost, oriented

rock fragments, and silt-enriched layers. The characteristic

structures associated with gelic materials include platy, blocky,

or granular macrostructures; the structural results of sorting;

and orbiculic, conglomeric, banded, or vesicular microfabrics.

Ice segregation is manifested by ice lenses, vein ice, segregated

ice crystals, and ice wedges. Cryopedogenic processes that lead

to gelic materials are driven by the physical volume change of

water to ice, moisture migration along a thermal gradient in

the frozen system, or thermal contraction of the frozen material

by continued rapid cooling.

Glacic Layer

A glacic layer is massive ice or ground ice in the form of ice

lenses or wedges (photo 38). The layer is 30 cm or more thick

and contains 75 percent or more visible ice.

Lithic Contact

A lithic contact is the boundary between soil and a coherent

underlying material (photo 39). Except in Ruptic-Lithic

subgroups, the underlying material must be virtually

continuous within the limits of a pedon. Cracks that can be

penetrated by roots are few, and their horizontal spacing is 10

cm or more. The underlying material must be sufficiently

coherent when moist to make hand-digging with a spade

impractical, although the material may be chipped or scraped

with a spade. The material below a lithic contact must be in a

strongly cemented or more cemented rupture-resistance class.

Commonly, the material is indurated. The underlying material

considered here does not include diagnostic soil horizons, such

as a duripan or a petrocalcic horizon.

A lithic contact is diagnostic at the subgroup level if it is

within 125 cm of the mineral soil surface in Oxisols and within

50 cm of the mineral soil surface in all other mineral soils. In

organic soils the lithic contact must be within the control

section to be recognized at the subgroup level.

Paralithic Contact

A paralithic (lithiclike) contact is a contact between soil and

paralithic materials (defined below) where the paralithic

materials have no cracks or the spacing of cracks that roots can

enter is 10 cm or more (photo 40).

Paralithic Materials

Paralithic materials are relatively unaltered materials (do

not meet the requirements for any other named diagnostic

horizons or any other diagnostic soil characteristic) that have

an extremely weakly cemented to moderately cemented

rupture-resistance class. Cementation, bulk density, and the

organization are such that roots cannot enter, except in cracks.

Paralithic materials have, at their upper boundary, a paralithic

contact if they have no cracks or if the spacing of cracks that

roots can enter is 10 cm or more. Commonly, these materials

are partially weathered bedrock or weakly consolidated

bedrock, such as sandstone, siltstone, or shale. Paralithic

materials can be used to differentiate soil series if the materials

are within the series control section. Fragments of paralithic

materials 2.0 mm or more in diameter are referred to as

pararock fragments.
Horizons and Characteristics Diagnostic for the Higher Categories 93

Permafrost

Permafrost is defined as a thermal condition in which a

material (including soil material) remains below 0 oC for 2 or

more years in succession. Those gelic materials having

permafrost contain the unfrozen soil solution that drives

cryopedogenic processes. Permafrost may be cemented by ice

or, in the case of insufficient interstitial water, may be dry. The

frozen layer has a variety of ice lenses, vein ice, segregated ice

crystals, and ice wedges. The permafrost table is in dynamic

equilibrium with the environment.

Soil Moisture Regimes

It has been conventional to identify three soil moisture

regimes. In one, the soil is saturated. In another, the amount of

water is enough to cause leaching. In the third, no leaching

occurs. In the leaching regime, some water moves through the

soil at some time during the year and moves on down to the

moist substratum. In the nonleaching regime, water moves into

the soil but is withdrawn by evapotranspiration, leaving

precipitated carbonates and more soluble salts. Between these

two regimes, there is another possible one in which there is

alternation from year to year; leaching occurs in some years but

not in all. For consideration of the losses of soluble materials

or their accumulation in horizons with k, y, or z suffixes, these

concepts are adequate. For the understanding of biological

processes, they leave much to be desired. A soil can be subject

to leaching during winter, when it is too cold for optimum

biological activity, and it can be too dry during most of the

summer for significant biological activity. The result is a

relatively wide carbon-nitrogen ratio.

The term “soil moisture regime” refers to the presence or

absence either of ground water or of water held at a tension of

less than 1500 kPa in the soil or in specific horizons during

periods of the year. Water held at a tension of 1500 kPa or

more is not available to keep most mesophytic plants alive. The

availability of water is also affected by dissolved salts. If a soil

is saturated with water that is too salty to be available to most

plants, it is considered salty rather than dry. Consequently, a

horizon is considered dry when the moisture tension is 1500

kPa or more and is considered moist if water is held at a

tension of less than 1500 kPa but more than zero. A soil may

be continuously moist in some or all horizons either throughout

the year or for some part of the year. It may be either moist in

winter and dry in summer or the reverse. In the Northern

Hemisphere, summer refers to June, July, and August and

winter refers to December, January, and February.

Significance to Soil Classification

The moisture regime of a soil is an important property of the

soil as well as a determinant of processes that can occur in the

soil. During geologic time there have been significant changes

in climate. Soils that could have formed only in a humid

climate are now preserved in an arid climate in some areas.

Such soils have relict features that reflect the former moisture

regime and other features that reflect the present moisture

regime.

The soil moisture regime is only partially a function of

climate. Most deep, permeable soils under high and well

distributed rainfall have water that is available to plants most

of the time. Soils in areas of an arid climate, however, are not

necessarily dry. They may be dry, moist, or saturated,

depending on their position on the landscape, because they

may receive water from sources other than the rain that falls on

them. The extra water may be runoff from rainfall on an

adjacent slope or on distant mountains, or it may come from

melting snow, seepage, or even natural artesian sources. In the

Northern Hemisphere, precipitation is more effective in soils

on north aspects than in soils on south aspects. In some areas

this difference is significant enough for there to be different

soil moisture regimes on north and south aspects. Soils may

also lose part or most of the water that falls on them,

particularly if they are sloping and the surface horizon has few

noncapillary pores. On any given landscape that has uniform

climate, adjacent soils may have different moisture regimes.

Each of the moisture regimes in the history of a soil is a

factor in the genesis of that soil and is the cause of many

accessory characteristics. Most of the accessory characteristics,

however, and those most important for interpretations are

associated with the present moisture regime, even if the present

regime differs widely from some of the earlier regimes. For

example, before an argillic horizon forms, enough water has to

pass through the soil to remove soluble materials, such as

finely divided carbonates. If the leaching and formation of the

argillic horizon took place under climatic conditions with more

effective precipitation than that of today, the present argillic

horizon is not necessarily free from carbonates or other soluble

materials. Soils with soluble salts or carbonates above and

within the argillic horizon have characteristics that reflect both

past and present climates. The argillic horizon formed under a

past climate, and the soluble salts and carbonates accumulated

under the present climate. Both climates have left markers that

can be observed in the soils today. The argillic horizon that

formed under more effective moisture may have formed under

precipitation similar to that of today but under cooler

temperatures, or it may have formed under temperatures

similar to those of today but under higher precipitation. There

is no precise measure of past climates, and an accurate

reconstruction of past climates is difficult. More importantly,

the present climate determines use and management of the soil.

It is a property of the soil. Furthermore, the moisture regimes

of most soils are inferred from the present climate, and smallscale maps can be interpreted in terms of the many accessory
94 Soil Taxonomy

characteristics that are common to most of the soils that have a

common climate. These characteristics include the amount,

nature, and distribution of organic matter, the base status of the

soil, and the presence or absence of salts.

The most important of the soil interpretations are the

potentials for growing different plants and the cultural

practices required to grow them. Without soil climate as a

criterion at some level in the taxonomic system, for example,

Vertisols from Texas could be in the same taxonomic class as

Vertisols from North Dakota.

Normal Years

In the discussions that follow and throughout the keys, the

term “normal years” is used. A normal year is defined as a year

that has plus or minus one standard deviation of the long-term

mean annual precipitation. (Long-term refers to 30 years or

more.) Also, the mean monthly precipitation during a normal

year must be plus or minus one standard deviation of the longterm monthly precipitation for 8 of the 12 months. For the

most part, normal years can be calculated from the mean

annual precipitation. When catastrophic events occur during a

year, however, the standard deviations of the monthly means

should also be calculated. The term “normal years” replaces

the terms “most years” and “6 out of 10 years,” which were

used in the previous edition of Soil Taxonomy (USDA, SCS,

1975).

Estimation

The landscape position of every soil is subject to extremes in

climate. While no 2 years have exactly the same weather

conditions, the moisture status of the soil must be characterized

by probability. Weather probabilities can be determined from

long-term weather records and observations of how each soil

responds to weather conditions as modified by its landscape

position.

A number of methods have been devised to relate soil

moisture to meteorological records. To date, all of these

methods have some shortcomings, even for gently sloping soils

that depend primarily on precipitation for their moisture. Dew

and fog can add appreciable amounts of moisture to some soils,

but quantitative data are rare.

The graphs in diagrams 3 to 16 are based on the average

values for precipitation, temperature, and potential

evapotranspiration. They give an oversimplified picture of the

moisture regime of the whole soil rather than of the moisture

control section. The data are based on the monthly

climatological values of temperature and precipitation for the

indicated number of years and the monthly potential

evapotranspiration (PE) normals taken from the large

Thornthwaite collection covering the world (Mather, 1964,

1965). No reduction from potential evapotranspiration was

made.

The following legend helps to explain the graphs in

diagrams 3 to 16. Numbers at the bottom of the graphs indicate

months of the year.

In diagram 3 the area between the line that joins all of the

precipitation normals and the one that joins all of the PE

normals indicates the status of soil moisture. Beginning at the

point where precipitation becomes greater than PE, the area to

the right shows recharge, the amount of moisture stored in the

soil. This area commonly extends to the extreme right of the

diagram. The amount of recharge is limited either by the

available water capacity (AWC) of the soil, in which case a

vertical line delimits the area as surplus, or by the fact that PE

again exceeds precipitation before the AWC has been filled.

The point where PE exceeds precipitation is utilization.

Utilization shows the amount of PE necessary to remove the

water held at a tension of less than 1500 kPa. Excess PE, if

any, before the time that recharge begins is called deficit and is

delimited by a vertical line.

The discussion of recharge, surplus, utilization, and deficit

in the preceding paragraph has implied the moisture regime of

a cool, moist region in the Northern Hemisphere, but many

other combinations of recharge, surplus, utilization, and deficit

can occur, including all surplus and all deficit.

For definitions of taxa, it is recognized that the accretion of

daily or monthly precipitation is depleted, linearly or

nonlinearly, by daily or monthly potential evapotranspiration.

An initial condition is set, and the sequence of subsequent

water balances shows whether critical parts of the soil profile

are likely to be moist, partly dry, or completely dry as the

seasons advance. Depending on one’s purposes, an assumption

of linear or of nonlinear depletion of soil moisture might be

best. To represent the probable soil moisture regime, the

estimate of evapotranspiration should be reduced as the soil

dries. To represent irrigation needs, evapotranspiration at the

full potential rate would give a better picture. Either procedure

gives a crude picture of both.

Soil Moisture Control Section

The intent in defining the soil moisture control section is to

facilitate estimation of soil moisture regimes from climatic

data. The upper boundary of this control section is the depth to

which a dry (tension of more than 1500 kPa, but not air-dry)
Horizons and Characteristics Diagnostic for the Higher Categories 95

soil will be moistened by 2.5 cm of water within 24 hours. The

lower boundary is the depth to which a dry soil will be

moistened by 7.5 cm of water within 48 hours. These depths do

not include the depth of moistening along any cracks or animal

burrows that are open to the surface.

The boundaries for the soil moisture control section

correspond to the rooting depths for many crops; however,

there are natural plant communities that have their roots either

above or below the control section. Attempts are currently

being made to improve the parameters of the soil moisture

control section.

If 7.5 cm of water moistens the soil to a densic, lithic,

paralithic, or petroferric contact or to a petrocalcic or

petrogypsic horizon or a duripan, the contact or the upper

boundary of the cemented horizon constitutes the lower

boundary of the soil moisture control section. If a soil is

moistened to one of these contacts or horizons by 2.5 cm of

water, the soil moisture control section is the boundary or the

contact itself. The control section of such a soil is considered

moist if the contact or upper boundary of the cemented horizon

has a thin film of water. If that upper boundary is dry, the

control section is considered dry.

The concept of the soil moisture control section does not

apply well to the cracking clays, because these clays remoisten

from both the surface and the bases of the cracks. The soil

moisture patterns of these soils are defined in terms of the

pattern of cracking over time.

Dry soils can remoisten unevenly for a variety of reasons

other than microrelief or the presence of cracks or holes that

are open at the surface. Water can be suspended by capillary

forces in a dry sandy soil (Rode, 1965). When the suspended

water exceeds a critical limit, it drains rapidly at some points

into lower soil layers. Water can be suspended in a dry or moist

soil if pore sizes increase with increasing depth, and similar

leaks may occur. Uneven moistening may result from

interception of rain by plants. Part of the rain reaches the soil

by flowing down the stem of the plant. Some plants, such as

mulga (Acacia aneura) in Australia, intercept virtually all of

the rain falling on them. In this situation, the soil is moistened

deeply around the stem but remains extremely dry under the

canopy of the mulga. In areas between the plants, rain

generally falls directly on the soil. Thus, within a very short

distance, there are three contrasting moisture regimes. In one,

the soil is deeply moistened; in the second, which surrounds

the first, the soil receives virtually no moisture; and in the

third, the soil is intermittently moist and dry.

If moistening occurs unevenly, the weighted average depth

of moistening in a pedon is used for the limits of the moisture

control section.

The moisture control section of a soil extends approximately

(1) from 10 to 30 cm below the soil surface if the particle-size

class of the soil is fine-loamy, coarse-silty, fine-silty, or clayey;

(2) from 20 to 60 cm if the particle-size class is coarse-loamy;

and (3) from 30 to 90 cm if the particle-size class is sandy. If

the soil contains rock and pararock fragments that do not

absorb and release water, the limits of the moisture control

section are deeper. The limits of the soil moisture control

section are affected not only by the particle-size class but also

by differences in soil structure or pore-size distribution or by

other factors that influence the movement and retention of

water in the soil.

The classification of the soil series in the United States

was determined in part by knowledge of the moisture

regimes. The definitions of soil moisture regimes that follow

were fitted to the boundaries. If future studies show that the

classifications of the soils are not in agreement with these

definitions, we are more likely to change the definitions than

the classifications. Over time, changes in both will doubtless

be made.

Classes of Soil Moisture Regimes

The soil moisture regimes are defined in terms of the level

of ground water and in terms of the seasonal presence or

absence of water held at a tension of less than 1500 kPa in the

moisture control section. It is assumed in the definitions that

the soil supports whatever vegetation it is capable of

supporting, i.e., crops, grass, or native vegetation, and that the

amount of stored moisture is not being increased by irrigation

Diagram 3.—Udic, frigid; St. Petersburg, Russia (formerly

Leningrad, U.S.S.R.).
96 Soil Taxonomy

or fallowing. These cultural practices affect the soil moisture

conditions as long as they are continued.

Aquic moisture regime.—The aquic (L. aqua, water)

moisture regime is a reducing regime in a soil that is virtually

free of dissolved oxygen because it is saturated by water. Some

soils are saturated with water at times while dissolved oxygen

is present, either because the water is moving or because the

environment is unfavorable for micro-organisms (e.g., if the

temperature is less than 1 o

C); such a regime is not considered

aquic.

It is not known how long a soil must be saturated before it is

said to have an aquic moisture regime, but the duration must

be at least a few days, because it is implicit in the concept that

dissolved oxygen is virtually absent. Because dissolved oxygen

is removed from ground water by respiration of microorganisms, roots, and soil fauna, it is also implicit in the

concept that the soil temperature is above biologic zero for

some time while the soil is saturated. Biologic zero is defined

as 5 oC in this taxonomy. In some of the very cold regions of

the world, however, biological activity occurs at temperatures

below 5 oC.

Very commonly, the level of ground water fluctuates with

the seasons; it is highest in the rainy season or in fall, winter,

or spring if cold weather virtually stops evapotranspiration.

There are soils, however, in which the ground water is always

at or very close to the surface. Examples are soils in tidal

marshes or in closed, landlocked depressions fed by perennial

streams. Such soils are considered to have a peraquic moisture

regime. The distinction between the aquic moisture regime and

the peraquic moisture regime is not closely defined because

neither regime is used as a criterion for taxa above the series

level. These terms can be used in descriptions of taxa. Some

soils with an aquic moisture regime also have a xeric, ustic, or

aridic (torric) regime.

Although the aquic and peraquic moisture regimes are

not used as either criteria or formative elements for taxa,

they are used in taxon descriptions as an aid in understanding

genesis. The formative term “aqu” refers to aquic conditions,

not an aquic moisture regime. Some soils included in the

“Aqu” suborders may have aquic or peraquic moisture

regimes.

Aridic and torric (L. aridus, dry, and L. torridus, hot

and dry) moisture regimes.—These terms are used for the

same moisture regime but in different categories of the

taxonomy.

In the aridic (torric) moisture regime, the moisture control

section is, in normal years:

1. Dry in all parts for more than half of the cumulative days

per year when the soil temperature at a depth of 50 cm from the

soil surface is above 5 o

C; and

2. Moist in some or all parts for less than 90 consecutive

days when the soil temperature at a depth of 50 cm is above

8 oC.

Soils that have an aridic (torric) moisture regime

normally occur in areas of arid climates. A few are in areas

of semiarid climates and either have physical properties that

keep them dry, such as a crusty surface that virtually

precludes the infiltration of water, or are on steep slopes where

runoff is high. There is little or no leaching in this moisture

regime, and soluble salts accumulate in the soils if there is a

source.

Diagrams 4 to 7 illustrate climatic data in a region where the

soils have an aridic (torric) moisture regime. Diagram 4 is an

example of an area with an aridic soil moisture regime and a

hyperthermic soil temperature regime. Diagram 5 is an

Diagram 4.—Aridic, hyperthermic; Jodhpur, India.
Horizons and Characteristics Diagnostic for the Higher Categories 97

example of an area with an aridic soil moisture regime and a

thermic temperature regime. Diagram 6 is an example of an area

with an aridic soil moisture regime and a mesic soil temperature

regime. Diagram 7 is an example of an area with an aridic soil

moisture regime that grades towards an ustic soil moisture

regime.

The limits set for soil temperature exclude from these moisture

regimes soils in the very cold and dry polar regions and in areas

at high elevations. Such soils are considered to have anhydrous

conditions (defined earlier).

Udic moisture regime.—The udic (L. udus, humid)

moisture regime is one in which the soil moisture control

section is not dry in any part for as long as 90 cumulative days

in normal years. If the mean annual soil temperature is lower

than 22 oC and if the mean winter and mean summer soil

temperatures at a depth of 50 cm from the soil surface differ by

6 oC or more, the soil moisture control section, in normal

years, is dry in all parts for less than 45 consecutive days

in the 4 months following the summer solstice. In addition,

the udic moisture regime requires, except for short periods, a

three-phase system, solid-liquid-gas, in part or all of the soil

moisture control section when the soil temperature is above

5 o

C.

The udic moisture regime is common to the soils of humid

climates that have well distributed rainfall; have enough rain

in summer so that the amount of stored moisture plus rainfall

is approximately equal to, or exceeds, the amount of

evapotranspiration; or have adequate winter rains to recharge

the soils and cool, foggy summers, as in coastal areas. Water

moves downward through the soils at some time in normal

years.

In climates where precipitation exceeds evapotranspiration in

all months of normal years, the moisture tension rarely reaches

100 kPa in the soil moisture control section, although there are

occasional brief periods when some stored moisture

Diagram 5.—Aridic, thermic; Las Vegas, Nevada, United States. is used. The water moves through the soil in all months when

Diagram 6.—Aridic, mesic; Lanzhou, China.
98 Soil Taxonomy

it is not frozen. Such an extremely wet moisture regime is

called perudic (L. per, throughout in time, and L. udus,

humid). In the names of most taxa, the formative element “ud”

is used to indicate either a udic or a perudic regime; the

formative element “per” is used in selected taxa. The

distinction between perudic and udic can always be made

at the series level.

Diagram 8 illustrates an area with a udic soil moisture regime

and an isohyperthermic soil temperature regime. Diagram 9

illustrates an area with a udic soil moisture regime and a thermic

temperature regime. Diagrams 10 and 11 are examples of areas

with a udic soil moisture regime and mesic and frigid temperature

regimes, respectively.

Diagram 12 illustrates a perudic soil moisture regime. Note

that the perudic regime shows a surplus every month of the

year. Obviously, if calculations were made on a daily basis,

there would be short periods of withdrawal.

Ustic moisture regime.—The ustic (L. ustus, burnt;

implying dryness) moisture regime is intermediate between

the aridic regime and the udic regime. Its concept is one of

moisture that is limited but is present at a time when

conditions are suitable for plant growth. The concept of

the ustic moisture regime is not applied to soils that have

permafrost or a cryic soil temperature regime (defined

below).

If the mean annual soil temperature is 22 oC or higher or if

the mean summer and winter soil temperatures differ by less

than 6 oC at a depth of 50 cm below the soil surface, the soil

moisture control section in areas of the ustic moisture regime is

dry in some or all parts for 90 or more cumulative days in

normal years. It is moist, however, in some part either for more

than 180 cumulative days per year or for 90 or more

consecutive days.

If the mean annual soil temperature is lower than 22 oC and

Diagram 7.—Aridic, mesic; Odessa, Ukraine.

Diagram 8.—Udic, isohyperthermic; Rio de Janeiro, Brazil.
Horizons and Characteristics Diagnostic for the Higher Categories 99

if the mean summer and winter soil temperatures differ by 6 o

C

or more at a depth of 50 cm from the soil surface, the soil

moisture control section in areas of the ustic moisture regime is

dry in some or all parts for 90 or more cumulative days in

normal years, but it is not dry in all parts for more than half of

the cumulative days when the soil temperature at a depth of 50

cm is higher than 5 oC. If in normal years the moisture control

section is moist in all parts for 45 or more consecutive days in

the 4 months following the winter solstice, the moisture control

section is dry in all parts for less than 45 consecutive days in

the 4 months following the summer solstice. Diagram 13

illustrates an area with an ustic soil moisture regime and a

thermic soil temperature regime. Diagram 14 illustrates an

area with an ustic soil moisture regime and a mesic soil

temperature regime.

In tropical and subtropical regions that have a monsoon

climate with either one or two dry seasons, summer and winter

seasons have little meaning. In those regions the moisture

regime is ustic if there is at least one rainy season of 3 months

or more. In temperate regions of subhumid or semiarid

climates, the rainy seasons are usually spring and summer or

spring and fall, but never winter. Native plants are mostly

annuals or plants that have a dormant period while the soil is

dry.

Xeric moisture regime.—The xeric (Gr. xeros, dry)

moisture regime is the typical moisture regime in areas of

Mediterranean climates, where winters are moist and cool and

summers are warm and dry. The moisture, which falls during

the winter, when potential evapotranspiration is at a minimum,

is particularly effective for leaching. In areas of a xeric

moisture regime, the soil moisture control section, in normal

years, is dry in all parts for 45 or more consecutive days in the

4 months following the summer solstice and moist in all parts

for 45 or more consecutive days in the 4 months following the

Diagram 9.—Udic, thermic; Buenos Aires, Argentina.

Diagram 10.—Udic, mesic; Sapporo, Japan.
100 Soil Taxonomy

winter solstice. Also, in normal years, the moisture control

section is moist in some part for more than half of the

cumulative days per year when the soil temperature at a depth

of 50 cm from the soil surface is higher than 6 o

C or for 90 or

more consecutive days when the soil temperature at a depth of

50 cm is higher than 8 oC. The mean annual soil temperature is

lower than 22 oC, and the mean summer and mean winter soil

temperatures differ by 6 oC or more either at a depth of 50 cm

from the soil surface or at a densic, lithic, or paralithic contact

if shallower.

Diagram 15 illustrates an area with a xeric soil moisture regime

and a thermic soil temperature regime. Diagram 16 illustrates an

area with a xeric soil moisture regime and a mesic soil

temperature regime.

Soil Temperature Regimes

The temperature of a soil is one of its important properties.

Within limits, temperature controls the possibilities for plant

growth and for soil formation. Below the freezing point, there

is no biotic activity, water no longer moves as a liquid, and,

unless there is frost heaving, time stands still for the soil.

Between temperatures of 0 and 5 o

C, root growth of most plant

species and germination of most seeds are impossible. A

horizon as cold as 5 oC is a thermal pan to the roots of most

plants.

Biological processes in the soil are controlled in large

measure by soil temperature and moisture. Each plant species

has its own temperature requirements. In the Antarctic, for

example, there is a microscopic plant that grows only at

temperatures below 7 oC, temperatures at which most other

plants are inactive. At the other extreme, germination of seeds

of many tropical plant species requires a soil temperature of

24 oC or higher. Plant species have one or more soil

temperature requirements that are met by the soils of their

native environment. Similarly, soil fauna have temperature

requirements for survival. Soil temperature, therefore, has an

important influence on biological, chemical, and physical

processes in the soil and on the adaptation of introduced plant

species.

Diagram 11.—Udic, frigid; Harbin, China. At any moment the temperature within a soil varies from

Diagram 12.—Perudic, mesic; Zeehan, Australia (Tasmania) .
Horizons and Characteristics Diagnostic for the Higher Categories 101

horizon to horizon. The temperature near the surface fluctuates

with the hours of the day and with the seasons of the year. The

fluctuations may be very small or very large, depending on the

environment. Because temperature is so variable, or perhaps

because it is not preserved in samples, some pedologists have

thought that it is not a property of a soil. One is inclined to

notice the properties that differ among soils and to focus

attention on them.

Each pedon has a characteristic temperature regime that can

be measured and described. For most practical purposes, the

temperature regime can be described by the mean annual soil

temperature, the average seasonal fluctuations from that mean,

and the mean warm or cold seasonal soil temperature gradient

within the main root zone, which is the zone from a depth of 5

to 100 cm.

Mean Annual Soil Temperature

Each pedon has a mean annual temperature that is

essentially the same in all horizons at all depths in the soil and

at depths considerably below the soil. The measured mean

annual soil temperature is seldom the same in successive

depths at a given location, but the differences are so small that it

seems valid and useful to take a single value as the mean annual

temperature of a soil.

The mean annual soil temperature is related most closely

to the mean annual air temperature, but this relationship is

affected to some extent by the amount and distribution of

rain, the amount of snow, the protection provided by shade

and by O horizons in forests, the slope aspect and gradient,

and irrigation. Other factors, such as soil color, texture,

and content of organic matter, have negligible effects (Smith

et al., 1964).

Fluctuations of Soil Temperature

The mean annual temperature of a soil is not a single

reading but the average of a series of readings. Near the

surface, the readings may fluctuate from the mean fully as

much as those of the air temperature, especially if there is no

insulating cover. The fluctuations occur as daily and annual

cycles, which in most places are made somewhat irregular by

weather events. The fluctuations decrease with increasing

Diagram 13.—Ustic, thermic; Haskell, Texas, United States. depth and are ultimately damped out in the substrata in a zone

Diagram 14.—Ustic, mesic; Halle, Germany.
102 Soil Taxonomy

where the temperature is constant and is the same as the mean

annual soil temperature.

Daily fluctuations.—Daily changes in air temperature

have a significant effect on the temperature of soil horizons

to a depth of about 50 cm. The fluctuations may be very

large, particularly in soils of dry climates where the daily

range in temperature of the upper 2.5 cm of the soils may

approach 55 o

C. At the other extreme, under melting snow,

the temperature at the soil surface may be constant

throughout the day. In a few places in high mountains

very near the Equator, the soils have virtually constant

temperature.

Daily fluctuations in soil temperature are affected by

clouds, vegetation, length of day, soil color, slope, soil

moisture, air circulation near the ground, and the temperature

of any rain that falls. Moisture can be exceedingly important

in reducing fluctuations in soil temperature. The specific heat

of water is roughly 4 times that of a dry surface horizon, and the

specific heat of a medium textured surface horizon at field

capacity is roughly one-half more than that at the wilting

point. Water increases the thermal conductivity of soils, and

it can also absorb or liberate heat by freezing and thawing

or by evaporating and condensing. All of these effects of

soil water reduce fluctuations in soil temperature at the

surface.

Fluctuations caused by changes in weather.—Soil

temperatures also fluctuate during short periods of belowaverage or above-average air temperatures. The fluctuations

caused by weather extend to a greater depth than those of the

diurnal cycle. Periods of high or low temperature tend to last

a few days to a week in most of the United States. Like

weather patterns in general, however, they occur at irregular

intervals.

The soil temperature at a depth of 50 cm shows almost no

Diagram 15.—Xeric, thermic; Athens, Greece.

Diagram 16.—Xeric, mesic; Portland, Oregon, United States.
Horizons and Characteristics Diagnostic for the Higher Categories 103

daily fluctuation, but it reflects short-time weather patterns. Data

indicate that at shallow depths soil temperatures reflect daily

fluctuations in temperature.

Cold or warm rains may bring about rapid and marked

changes in the temperature of surface horizons. Generally, the

direct effect of a rain on soil temperature is not measurable 48

hours after the rain ends.

Seasonal fluctuations and soil temperature gradients in the

Tropics.—Seasonal fluctuations of soil temperature are

generally small in the intertropical regions between the Tropic of

Capricorn and the Tropic of Cancer. Mean annual soil

temperatures vary with elevation, but seasonal temperatures

vary primarily with clouds and rain. The warmest seasons may

be the dry seasons, for the effects of clouds and rain may

outweigh those of the angle of the sun’s rays.

Diagram 17 shows the soil temperature, air temperature,

rainfall, and percentage of possible sunshine at Yangambi, Zaire,

at an elevation of about 365 m (I.N.E.A.C., 1953). These data

indicate that the soil temperature is higher in winter than in

summer. Actually, the soil temperature fluctuates with cloud

cover and rain and appears to be most closely correlated with

the amount of sunshine. In the Tropics, differences between

summer and winter temperatures are small and may be in

either direction. The average temperature over a 3-month

season is virtually the same at all depths within the upper m of

the soil.

As the temperate region is approached, near the Tropic of

Cancer, for example, soil temperatures in summer are likely to be

higher than those in winter, but the differences between the

mean summer temperature and the mean winter temperature in

the upper m of the soil are usually less than 6 o

C.

Seasonal fluctuation and soil temperature gradients in

midlatitudes.—Soil temperatures in the 48 conterminous

States of the United States generally show marked seasonal

Diagram 17.—Mean monthly soil temperature at a depth of 50 cm for 1952 at Yangambi, Zaire, and the major factors that affect the soil

temperature.
104 Soil Taxonomy

fluctuations. To illustrate seasonal changes under a midlatitude

continental climate, such as that in much of the United States,

a good record of soil temperatures from Belgrade, Yugoslavia

(Chang, 1958b), has been selected. This record is shown

graphically in diagram 18. The annual cooling and heating

waves extend to a depth of 12 m, but the amplitude of variation

at this depth is only 0.1 oC. At a depth of 14 m, the temperature

is constant and is the same as the mean annual soil temperature.

These records clearly show that seasonal temperature

fluctuations penetrate deeply into the earth, well below the limit

of soil.

The depth to the stratum that has constant temperature is not

the same in all soils. It is reduced by shallow ground water

because water has high specific heat. Records of well-water

temperature in the 48 conterminous States of the United States

show that, in the presence of ground water, the stratum of

constant soil temperature occurs at a depth of about 9 m.

Chang (1958a) has estimated that, in the absence of ground

water, seasonal fluctuations of soil temperature penetrate to a

depth of 20 m in Alaska, 15 m in midlatitudes, and 10 m in the

Tropics. In dry soils, thermal conductivity is low and, although

seasonal fluctuations in temperature may be very large, the

depth of penetration is no greater than in moist soils. At Jaipur,

India (lat. 27o N.), the seasonal range in soil temperature at a

depth of 6 m was 2.7 oC, but at a depth of 14 m, it was only

0.2 oC (Chang, 1958b).

The amplitude of seasonal fluctuations and the timing of

periods of warm and cool soil temperature are primarily

functions of latitude and climate. In midlatitudes the angle of

the sun’s rays is most important, but clouds, rain, irrigation

water, snow cover, bodies of water, direction and angle of

slope, and presence or absence of shallow ground water and of

thick O horizons can all affect the amplitude of fluctuation.

Seasonal fluctuations in midlatitudes are generally in excess of

Diagram 18.—Mean monthly isotherms of ground temperature at Belgrade, Yugoslavia.
Horizons and Characteristics Diagnostic for the Higher Categories 105

6 o

C. That is, the average summer soil temperature is more

than 6 oC higher than the average winter soil temperature in

the upper m of the soil.

Since the temperatures of soils at high elevations tend to

resemble those of soils at high latitudes, the discussion in this

section is confined to soils having mean annual temperatures of

8 oC or higher. The cold soils at high elevations in the

midlatitudes are discussed with the soils of high latitudes.

Effect of depth.—In a given soil, the closer to the surface,

the greater the amplitude of fluctuation. Seasonal variations

of soil temperature are greatest at the surface and decrease

with increasing depth until, at a depth of 9 m or more, they

disappear (diagram 18). The mean summer, winter, and

annual soil temperatures (Chang, 1958b) are plotted in

diagram 19 as a function of depth together with air

temperatures for Ames, Iowa, which is in the midlatitudes. If

we disregard the upper few cm, the changes in the mean

seasonal soil temperature with increasing depth are nearly

linear, so nearly so that one must conclude that the mean

seasonal temperature of soil to any depth within the main

zone of rooting is very closely approximated by the mean

temperature at the midpoint in depth. The temperature gradient

is positive in winter and negative in summer. It is

approximately 0.5 oC per 10 cm. The gradients seem very

similar in most midlatitude soils where records are available,

even in undrained peats.

Effect of vegetative cover.—In the humid midlatitudes, the

plant cover can have an important influence on seasonal

fluctuations of soil temperature. The differences among kinds

of plant cover, such as grass, crops, and trees, in shading or

insulating the soil are minor if O horizons are transient or

absent.

Diagram 19.—Soil temperature gradients with air temperatures for winter and summer in relation to mean annual temperatures at Ames,

Iowa.
106 Soil Taxonomy

Effect of irrigation.—Irrigation of dry soils can have a

marked effect on the soil temperature in summer. Both

evaporation and shade affect the temperature, but evaporation

is probably the more important. The reduction may exceed 8 o

C

in places.

Effect of ground water.—Because of its large latent and

specific heat, shallow ground water greatly affects seasonal

fluctuations of soil temperature in midlatitudes. The principal

effects occur during periods when the soil is freezing or

thawing because the latent heat of the freezing of water is

about 80 times the specific heat.

Effect of aspect and gradient of slope.—The aspect

(direction) and gradient of slope may affect the deviation of the

mean monthly soil temperatures from the annual mean. The

effect in winter is large compared to that in summer. In the

Northern Hemisphere, south-facing slopes have smaller

seasonal fluctuations from the annual mean than north-facing

slopes. The effects of aspect increase sharply in high latitudes.

Diagram 20 shows the relationship between soil temperature and

elevation on north and south aspects in the Great Basin of

Nevada (Jensen et al., 1989).

Seasonal fluctuations in high latitudes.—Soils in high

latitudes are cold, and the seasonal soil temperature fluctuations

do not approximate a simple sine curve as do those in

midlatitudes. Diagram 21 shows the mean monthly soil and air

temperatures at Mustiala, Finland (Chang, 1958b). The air

temperature follows a simple sine curve and is above the mean

for only 5 months and below it for 7 months. The asymmetrical

soil temperature fluctuations reflect the combined influence of

snow as an insulator during winter and the relatively high

insolation during summer months, when the sun is above the

horizon all or most of the time

Diagram 22 shows the mean annual seasonal soil

temperature at Mustiala, Finland, as a function of depth

Diagram 20.—Relationship between soil temperature and elevation on south and north aspects.
Horizons and Characteristics Diagnostic for the Higher Categories 107

(Chang, 1958b). The skewed seasonal fluctuations are indicated

by the closeness of the lines that show winter temperature and

mean annual temperature

In these latitudes, the soil temperature in summer is lower

than the air temperature. The temperature gradients with

increasing depth are similar to those in midlatitudes.

Effect of snow cover.—Diagram 23 shows the effect of

snow cover on soil temperature at various depths (Molga, 1958).

It indicates the difference in temperature between bare soil and

soil covered with snow (snow-covered plot minus bare plot).

From November through March, the snow-covered plot was

warmer at all depths. The average temperature difference for the

winter months, December through February, was 4 oC

at a depth of 50 cm. In April, when the air temperature was

rising and snow was melting, the bare soil warmed more

rapidly and was warmer than the snow-covered plot to a depth

of 40 cm.

The effect of snow on soil temperature is not limited to high

latitudes and high altitudes. Snow cover is common but

intermittent for the most part in midlatitudes where the mean

annual soil temperature is less than 13 oC.

Effect of vegetative cover.—The cover of litter and of moss in

areas of cold climates commonly is thicker than the cover in

areas of warm climates. As the cover thickens, it reduces the

amplitude of seasonal fluctuations of soil temperature because

it insulates the soil during the entire year.

Diagram 24 shows the mean monthly soil temperatures for a

cleared field versus a forested site at Delta Junction, Alaska

(Shur et al., 1993). Without the shade from trees and insulation

from litter and organic matter, the cleared field is colder in

winter and warmer in summer.

Differences in the type of vegetation can result in variations

in soil temperature. Diagram 25 illustrates differences between a

climax spruce forest with a thick organic layer and a less

insulated aspen forest in the Copper River area of Alaska

(Moore and Ping, 1989).

Diagram 21.—Mean monthly and annual soil and air temperatures at Mustiala, Finland.
108 Soil Taxonomy

Effect of ground water.—Because of its specific and latent

heat, ground water reduces seasonal fluctuations of soil

temperature. In diagram 26 the soil temperature at a depth of 50

cm is plotted for two soils at Flahult, Sweden (Chang, 1958b),

where the mean annual soil temperature is about 6 o

C. The soil in

the wet bog was warmer in winter and cooler in summer than the

sandy soil. The amplitude of fluctuations at a depth of 50 cm

was 4 oC less in the wet bog than in the sandy soil.

Estimation of Soil Temperature

Soil temperature often can be estimated from climatological

data with a precision that is adequate for the present needs of

soil surveys. If we cannot make reasonably precise estimates,

the measurement of soil temperature need not be a difficult or a

time-consuming task.

Frequently, the mean annual soil temperature for much

of the United States is estimated by adding 1 oC to the

mean annual air temperature. The table “Mean Annual

Soil Temperature (MAST) and Mean Annual Air Temperature

(MAAT)” shows the mean annual soil temperature from

various sites in the United States. It also shows the

difference between the mean annual soil temperature and

the mean annual air temperature at these sites. These data

indicate that for some areas in the United States the mean

annual soil temperature should be estimated by adding 2 or

even 3 o

C (rather than 1 oC) to the mean annual air

temperature.

The mean summer soil temperature at a specific depth

also can be estimated. To make this estimate, we can take

the average summer temperatures of the upper 100 cm and

correct for the temperature-depth gradient by adding or

subtracting 0.6 oC for each 10 cm above or below a depth of

50 cm. The mean winter temperature of many midlatitude

soils can be estimated from the difference between the mean

annual temperatures and the mean summer temperatures

because the differences are of the same magnitude but have

opposite signs.

The cooling wave at Belgrade extends to a depth of 12 m,

and at this depth the minimum temperature is reached about 10

months later than at a depth of 1 m (diagram 18). The amplitude

of variation at a depth of 12 m is less than 0.1 oC. Thus, the

mean annual temperature of a soil in midlatitudes can be

Diagram 22.—Soil temperature gradients with air temperatures for winter and summer in relation to mean annual temperatures at

Mustiala, Finland.
Horizons and Characteristics Diagnostic for the Higher Categories 109

determined at any time by a single reading at a depth of 13 m. A

single reading at a depth of 10 m is within 0.1 o

C of the mean

annual soil temperature. A single reading at a depth of 6 m is

within 1 oC of the mean annual temperature.

The mean annual temperature of soils underlain by deep

regolith can therefore be very closely approximated at any

season by measurement in a deep auger boring. In some areas

an even simpler method of determining the mean annual soil

temperature can be used. Dug wells generally range from 6 to

18 m in depth. If the water table stands between 9 and 18 m

and water is drawn from the well frequently, the temperature of

water in the well, which is in equilibrium with the soil

temperature, gives the mean annual soil temperature within a

margin of error of less than 1 oC. The well must be in use, so

that water is moving into it from the ground. Unfortunately,

this method is suited only to humid regions where ground

water is shallow and is not frozen. Extensive records of wellwater temperature have shown that the water temperature

between depths of 9 and 18 m is essentially constant

throughout the year.

If the soil is shallow and there are no wells, the mean

annual soil temperature can be measured over the four seasons

only by taking several readings at regular intervals of time. If

the soil is expected to be frozen deeply at the time of one or

Diagram 23.—Monthly soil temperature differences between bare and snow-covered plots at Leningrad, U.S.S.R. (now St. Petersburg,

Russia), and mean monthly air temperature and snow thickness.

Site name MAST

(50 cm)

MAST

minus

MAAT

o

C oC

Adams Ranch, New Mexico ............. 14.67 2.94

Crescent City, Minnesota ................. 7.30 1.39

Ellicott City, Maryland ..................... 12.23 1.14

Geneva, New York ............................ 9.60 1.20

Lind, Washington ............................. 11.12 1.70

Mandan, North Dakota..................... 7.13 2.84

Molly Caren, Ohio ............................ 11.72 2.19

Nunn, Colorado ................................ 10.43 2.89

Prairie View, Texas ........................... 21.17 1.79

Rogers Farm, Nebraska .................... 11.25 1.84

Tidewater, North Carolina ............... 16.29 .72

Torrington, Wyoming ....................... 9.96 2.40

Wabeno, Wisconsin .......................... 6.14 2.10

Watkinsville, Georgia ....................... 17.20 2.14

Mean Annual Soil Temperature (MAST) and Mean Annual Air

Temperature (MAAT)
110 Soil Taxonomy

more readings, a special thermometer or a thermocouple can be

buried. If the temperature of a soil is measured at a depth

below the influence of the daily cycle of fluctuations, such as a

depth of 50 cm, four readings equally spaced throughout

the year give a very close approximation of the mean annual

temperature. For example, the average of readings taken

at a depth of 50 cm at Vauxhall, Alberta, on January 1,

April 1, July 1, and October 1, 1962, differs from the

average of two readings each day of the year by only 0.3 o

C.

Greater precision can be achieved by increasing either the

number or the depth of the readings. The mean annual soil

temperature computed for any one year will be close to the longterm mean annual temperature, that is, the normal temperature.

At Ames, Iowa, for example, the standard deviation of the yearly

mean for a 13-year record at a depth of 50 cm is only 0.6 oC.

Seasonal temperatures bear an almost linear relation to

depth within the limits of depth that usually concern soil

scientists. By selecting a suitable depth and measuring the

temperature on the 15th of June, July, and August, we can

derive the average soil temperature for the 3-month summer

period. The margin of error will be small only if measurements are

made at a depth below the daily temperature fluctuations, that is,

Diagram 24.—Mean monthly soil temperatures measured at 50 cm below the mineral soil surface during 1992 near Delta Junction,

Alaska, United States.

Diagram 25.—Relationship of mean annual soil temperature

(MAST) and vegetative cover for the Copper River series.

Sites are in close proximity on the same landform. The

spruce site is in a late seral stage. The aspen site is in an

early seral stage because of wildfire.
Horizons and Characteristics Diagnostic for the Higher Categories 111

at a depth of 50 cm or more. Measurements made at a depth of 50

cm give the average temperature in the upper m of the soil. A

test of this method at Vauxhall, Alberta, shows that the average

of three measurements taken at a depth of 50 cm on June 15, July

15, and August 15, 1962, is within 0.6 o

C of the mean summer

temperature computed from daily readings.

Greater precision can be achieved mainly by increasing the

number of readings. Readings of soil temperature at depths as

shallow as 50 cm should be deferred for at least 48 hours after a

heavy rain.

Classes of Soil Temperature Regimes

Following is a description of the soil temperature regimes

used in defining classes at various categoric levels in this

taxonomy.

Cryic (Gr. kryos, coldness; meaning very cold soils).—Soils

in this temperature regime have a mean annual temperature lower

than 8 oC but do not have permafrost.

1. In mineral soils the mean summer soil temperature (June,

July, and August in the Northern Hemisphere and December,

January, and February in the Southern Hemisphere) either at a

depth of 50 cm from the soil surface or at a densic, lithic, or

paralithic contact, whichever is shallower, is as follows:

a. If the soil is not saturated with water during some part of

the summer and

(1) If there is no O horizon: lower than 15 oC; or

(2) If there is an O horizon: lower than 8 oC; or

b. If the soil is saturated with water during some part of the

summer and

(1) If there is no O horizon: lower than 13 oC; or

(2) If there is an O horizon or a histic epipedon: lower

than 6 oC.

2. In organic soils the mean annual soil temperature is lower

than 6 oC.

Cryic soils that have an aquic moisture regime commonly are

churned by frost.

Isofrigid soils could also have a cryic temperature regime. A

few with organic materials in the upper part are exceptions.

The concepts of the soil temperature regimes described

Diagram 26.—Mean monthly and mean annual soil temperatures in a soil in a wet bog and in a sandy soil at Flahult, Sweden.
112 Soil Taxonomy

below are used in defining classes of soils in the low

categories.

Frigid.—A soil with a frigid temperature regime is

warmer in summer than a soil with a cryic regime, but its

mean annual temperature is lower than 8 o

C and the difference

between mean summer (June, July, and August) and mean

winter (December, January, and February) soil temperatures is

more than 6 oC either at a depth of 50 cm from the soil surface

or at a densic, lithic, or paralithic contact, whichever is

shallower.

Mesic.—The mean annual soil temperature is 8 oC or higher

but lower than 15 oC, and the difference between mean summer

and mean winter soil temperatures is more than 6 oC either at a

depth of 50 cm from the soil surface or at a densic, lithic, or

paralithic contact, whichever is shallower.

Thermic.—The mean annual soil temperature is 15 oC or

higher but lower than 22 oC, and the difference between mean

summer and mean winter soil temperatures is more than 6 oC

either at a depth of 50 cm from the soil surface or at a densic,

lithic, or paralithic contact, whichever is shallower.

Hyperthermic.—The mean annual soil temperature is

22 oC or higher, and the difference between mean summer and

mean winter soil temperatures is more than 6 oC either at a

depth of 50 cm from the soil surface or at a densic, lithic, or

paralithic contact, whichever is shallower.

If the name of a soil temperature regime has the prefix iso,

the mean summer and mean winter soil temperatures differ by

less than 6 oC at a depth of 50 cm or at a densic, lithic, or

paralithic contact, whichever is shallower.

Isofrigid.—The mean annual soil temperature is lower than

8 oC.

Isomesic.—The mean annual soil temperature is 8 oC or

higher but lower than 15 oC.

Isothermic.—The mean annual soil temperature is 15 oC or

higher but lower than 22 oC.

Isohyperthermic.—The mean annual soil temperature is

22 oC or higher.

Sulfidic Materials

Sulfidic materials contain oxidizable sulfur compounds. They

are mineral or organic soil materials that have a pH value of more

than 3.5 and that, if incubated as a layer 1 cm thick under moist

aerobic conditions (field capacity) at room temperature, show a

drop in pH of 0.5 or more units to a pH value of 4.0 or less (1:1

by weight in water or in a minimum of water to permit

measurement) within 8 weeks.

Sulfidic materials accumulate as a soil or sediment that is

permanently saturated, generally with brackish water. The

sulfates in the water are biologically reduced to sulfides as the

materials accumulate. Sulfidic materials most commonly

accumulate in coastal marshes near the mouth of rivers that

carry noncalcareous sediments, but they may occur in

freshwater marshes if there is sulfur in the water. Upland sulfidic

materials may have accumulated in a similar manner

in the geologic past.

If a soil containing sulfidic materials is drained or if sulfidic

materials are otherwise exposed to aerobic conditions, the

sulfides oxidize and form sulfuric acid. The pH value, which

normally is near neutrality before drainage or exposure, may

drop below 3. The acid may induce the formation of iron and

aluminum sulfates. The iron sulfate, jarosite, may segregate,

forming the yellow redoximorphic concentrations that

commonly characterize a sulfuric horizon. The transition from

sulfidic materials to a sulfuric horizon normally requires very

few years and may occur within a few weeks. A sample of

sulfidic materials, if air-dried slowly in shade for about 2

months with occasional remoistening, becomes extremely acid.

Sulfuric Horizon

Brackish water sediments frequently contain pyrite (rarely

marcasite), which is an iron sulfide. Pyrite forms from the

microbial decomposition of organic matter. Sulfur released

from the organic matter combines with the iron to crystallize

FeS. Characteristically, the pyrite crystals occur as nests or

framboids composed of bipyramidal crystals of pyrite. In an

oxidizing environment, pyrite oxidizes and the products of

oxidation are jarosite and sulfuric acid. The jarosite may

undergo slow hydrolysis, leading to further production of

sulfuric acid. Iron is precipitated as a reddish ochre precipitate,

commonly ferrihydrite, which later may crystallize as

maghemite, goethite, and even hematite. If free aluminum is

present, alunite may crystallize in addition to jarosite. The

jarosite has a straw-yellow color and frequently lines pores in

the soil. Jarosite concentrations are among the indicators of a

sulfuric horizon.

In some soils, the hydrolysis of jarosite is rapid and the

yellow redoximorphic concentrations may not be evident, even

though the soils are extremely acid (pH less than 3.5) or the

soil solution is high in soluble sulfur. The low pH and high

amount of soluble sulfur are indicators of a sulfuric horizon. A

soil can develop low pH values, however, from highly acidic

materials from other sources. Therefore, low pH and sulfuric

materials in the underlying layers also are indicators of a

sulfuric horizon. A quick test of sulfidic materials is a rapid

fall in pH on drying or after treatment with an oxidizing agent,

such as hydrogen peroxide.

A sulfuric horizon forms as a result of drainage (most

commonly artificial drainage) and oxidation of sulfide-rich or

organic soil materials. It can form in areas where sulfidic

materials have been exposed as a result of surface mining,

dredging, or other earth-moving operations. A sulfuric horizon

is detrimental to most plants.

Required Characteristics

The sulfuric (L. sulfur) horizon is 15 cm or more thick and is

composed of either mineral or organic soil material that has a pH
Horizons and Characteristics Diagnostic for the Higher Categories 113

value of 3.5 or less (1:1 by weight in water or in a minimum of

water to permit measurement) and shows evidence that the low

pH value is caused by sulfuric acid. The evidence is one or more

of the following:

1. Jarosite concentrations; or

2. Directly underlying sulfidic materials (defined above);

or

3. 0.05 percent or more water-soluble sulfate.

Literature Cited

Brewer, R. 1976. Fabric and Mineral Analysis of Soils.

Second edition. John Wiley and Sons, Inc. New York, New

York.

Chang, Jen Hu. 1958a. Ground Temperature. I. Blue Hill

Meteorol. Observ. Harvard Univ.

Chang, Jen Hu. 1958b. Ground Temperature. II. Blue Hill

Meteorol. Observ. Harvard Univ.

Childs, C.W. 1981. Field Test for Ferrous Iron and FerricOrganic Complexes (on Exchange Sites or in Water-Soluble

Forms) in Soils. Austr. J. of Soil Res. 19: 175-180.

Grossman, R.B., and F.J. Carlisle. 1969. Fragipan Soils of the

Eastern United States. Advan. Agron. 21: 237-279.

Institut National pour l’etude Agronomique du Congo Belge

(I.N.E.A.C.). 1953. Bulletin Climatologique annuel du Congo

Belge et du Duanda-Urundi. Annee. Bur. Climatol. 7.

Jensen, M.E., G.H. Simonson, and R.E. Keane. 1989. Soil

Temperature and Moisture Regime Relationships Within Some

Rangelands of the Great Basin. Soil Sci. 147: 134-139.

Mather, J.R., ed. 1964. Average Climatic Water Balance Data

of the Continents, Parts V-VII. C.W. Thornthwaite Assoc. Lab.

Climatol. Publ., Vol. XVII, No. 1-3.

Mather, J.R., ed. 1965. Average Climatic Water Balance Data

of the Continents, Part VIII. C.W. Thornthwaite Assoc. Lab.

Climatol. Publ., Vol. XVIII, No. 2.

Molga, M. 1958. Agricultural Meteorology. Part II. Outline

of Agrometeorological Problems. Translated (from Polish)

reprint of Part II, pp. 218-517, by Centralny Instytut

Informacji. Naukowo-Technicznej i Ekonomicznej, Warsaw.

1962.

Moore, J.P., and C.L. Ping. 1989. Classification of Permafrost

Soils. Soil Surv. Horiz. 30: 98-104.

Pons, L.J., and I.S. Zonneveld. 1965. Soil Ripening and Soil

Classification. Initial Soil Formation in Alluvial Deposits and

a Classification of the Resulting Soils. Int. Inst. Land Reclam.

and Impr. Pub. 13. Wageningen, The Netherlands.

Rode, A.A. 1965. Theory of Soil Moisture. Vol. 1. Moisture

Properties of Soils and Movement of Soil Moisture. pp. 159-

202. (Translated from Russian, 1969). Israel Program Sci.

Transl., Jerusalem.

Shur, Y.L., G.J. Michaelson, and C.L. Ping. 1993. International

Correlation Meeting on Permafrost-Affected Soils. Suppl. Data

to the Guidebook—Alaska Portion.

Smith, G.D., D.F. Newhall, and L.H. Robbins. 1964. SoilTemperature Regimes, Their Characteristics and Predictability.

U.S. Dep. Agric., Soil Conserv. Serv, SCS-TP-144.

United States Department of Agriculture, Natural Resources

Conservation Service. 1998. Keys to Soil Taxonomy. Eighth

edition. Soil Surv. Staff.

United States Department of Agriculture, Soil Conservation

Service. 1975. Soil Taxonomy: A Basic System of Soil

Classification for Making and Interpreting Soil Surveys. Soil

Surv. Staff. U.S. Dep. Agric. Handb. 436.

United States Department of Agriculture, Soil Conservation

Service. 1993. Soil Survey Manual. Soil Surv. Div. Staff. U.S.

Dep. Agric. Handb. 18.

115

The fundamental purposes of a soil survey are to showthe geographic distribution of soils and to make

predictions about the soils (USDA, SCS, 1951 and 1993). To

this end, a soil survey includes soil maps, map unit

descriptions, soil series descriptions, taxonomic classifications,

and interpretations for the use and management of the soils.

Soil surveys are made at several intensities and for many

uses. The procedures, standards, and uses are described in the

most recent revision of the Soil Survey Manual (USDA, SCS,

1993) and the most recent version of the National Soil Survey

Handbook (USDA, NRCS, 1997). The applications of soil survey

are numerous. They include interpretations for the growth of

plants, such as crops, forage species, trees, and ornamental

shrubs. They also include interpretations for urban, rural, and

recreational development and for conservation and wildlife

habitat planning.

Soil mapping and classification have evolved, and the

conceptual framework for mapping and classifying soils has

changed and will continue to change. Over the years soil

science literature has documented numerous concepts and

approaches to mapping, classifying, and interpreting soils at

various scales. The purpose of this chapter is not to present the

numerous concepts and approaches but to outline the

application of widely used and accepted soil-landscape models

and taxonomic models for mapping and labeling soil

geographic order in soil surveys at scales of 1:12,000 to

1:100,000 and in soil surveys at scales smaller than 1:100,000.

Mapping and Labeling Soil Geographic Order at

Large (1:12,000 to 1:31,680) and Intermediate

(1:31,680 to 1:100,000) Scales

Mapping Soil Geographic Order

A landscape is a portion of the land surface that the eye can

comprehend in a single view and is a collection of landforms

(Ruhe, 1969). Understanding landscapes and landforms and

their influence on soil distribution is critical in observing and

mapping soil geographic order (Peterson, 1981; Ruhe, 1969).

The tasks of a soil scientist who sets out to map soils and

produce a soil survey are to perceive a meaningful soil

geographic pattern at the landscape, landform, and landform

component levels and to record that pattern in a form that can

be retained and conveyed to others. The most common scales

for a large-scale soil map range from 1:12,000 to 1:31,680

(USDA, SCS, 1993). With intensive field investigation of areas

mapped within this scale range, soil geographic variation can

be readily observed and recorded cartographically at the

landscape, landform, and landform component levels. The

minimum-size delineation is commonly between 0.6 and 4 ha

(USDA, SCS, 1993).

Intermediate-scale soil maps range from 1:31,680 to

1:100,000 and are commonly associated with lower intensity

field soil surveys (USDA, SCS, 1993). At this map scale and

with the lower intensity of field investigation, soil geographic

variation can be observed and recorded cartographically at the

multiple landscape, landscape, or landform level. The

minimum-size delineation for intermediate soil maps is

commonly between 4 and 250 ha (USDA, SCS, 1993).

In mapping soils at any scale, it is necessary to assume that

there is a pattern of order in the spatial distribution of soil

characteristics. The soil genesis model, which defines soil as a

function of parent material, climate, living organisms, relief,

and time, provides a basis for predicting order. A soil surveyor

quickly learns that the geographic distribution of soils is

related to the five soil-forming factors. A soil surveyor observes

and maps a geographic pattern of soils by grouping soils with

similar genesis and by separating soils where there is a change

in one or more of the soil-forming factors. Hudson (1990 and

1992) outlined the application of the catena concept (Milne,

1936) and the soil factor equation (Jenny, 1941) to soil survey as

a general model of perceiving and mapping soil geographic

order. Hudson (1992) has also summarized the soil-landscape

paradigm that has guided field soil surveys in the United States

for almost a century.

The Soil-Landscape Paradigm and Soil Survey

Soils are landscapes as well as profiles (USDA, SCS, 1951,

pp. 5-8; USDA, SCS, 1993, pp. 9-11). In soil survey, a soillandscape unit can be thought of as a landscape unit

(landscape, landform, or landform component) further modified

by one or more of the soil-forming factors. Within a soillandscape unit, the five factors of soil formation interact in a

distinctive manner. As a result, areas of a soil-landscape unit

have a relatively homogeneous soil pattern. A soil surveyor

perceives soil patterns by first conceptually dividing the

landscape into soil-landscape units. The boundaries between

dissimilar soil-landscape units are placed where one or more of

the soil-forming factors change within a short lateral distance.

The more rapid the change between one or more of the soilCHAPTER 5

Application of Soil Taxonomy to Soil Surveys
116 Soil Taxonomy

forming factors, the more abrupt the boundary between the

soil-landscape units and the easier it is for one to locate the

boundary. The slower the change between one or more of the

soil-forming factors, the more gradual the boundary between

the soil-landscape units and the more difficult it is for one to

locate the boundary. Generally, the closer the similarities

between two landscape units, the more gradual the change

between the landscape units and the more similar their

associated soils tend to be. Conversely, very dissimilar

landscape units tend to have abrupt boundaries between them

and have very dissimilar soils.

Identifying soil-landscape units provides the basis for

recognizing soils and then designing soil map units, which are

the basic units for identifying soil geographic order in a soil

survey. Soil-landscape units can be combined to form map

units that encompass broader ranges of soils, or subdividing

the soil-landscape units can identify the soils and soil

distribution within a map unit in greater detail. The degree to

which soil-landscape units are combined or subdivided to form

soil map units is primarily a function of the complexity of the

soil-landscape units, the detail required for the intended use of

the soil survey, and the ability of the soil scientist to

consistently identify the soils and map units through

application of the available knowledge and tools and within the

constraints of cost and time.

Labeling Soil Geographic Order With Soil Taxonomy

A soil delineation (soil map unit delineation) is an

individual polygon identified on a soil map by a map unit

symbol and/or name that defines a three-dimensional soil body

of a specified area, shape, and location on the landscape (Soil

Science Society of America, 1997). A map unit is an aggregate

of all soil delineations in a soil survey area that have a defined

set of similar soil characteristics (Van Wambeke and Forbes,

1986).

Once soil-landscape units and soil map units have been

delineated, some means of labeling and representing the kinds

of soil that occur in the map units is needed. The classification

system described in Soil Taxonomy (USDA, SCS, 1975) has

been used for many years in identifying and labeling soils that

occur within soil-landscape units and soil map units. Following

is a description of the application of the taxonomic system to

soil survey.

A class is a group of individuals or other units similar in

selected properties and distinguished from all other classes of

the same population by differences in these properties. Taxon

(pl. taxa) is a name used in classifications for a single class. It

may be broadly or narrowly defined according to the category.

A soil order is a taxon, as is a soil series, a family, or a great

group (Smith, 1963). The taxa of this soil classification are

conceptual and are defined as precisely as our present

knowledge permits. They give us common standards for soil

correlation, which includes the mapping, naming, and

interpretation of soils. In practice, soil scientists map soillandscape units. Properties of these soil-landscape units

correspond to the concepts of the taxa. Relating the soil bodies

(soil-landscape units or soil delineations) represented on maps

to taxonomic classes at some level in a classification system is

accomplished through soil correlation (Simonson, 1963).

In large- and intermediate-scale soil surveys, if the concept of

a named series or other taxon corresponds to the properties of

the soil expected in a soil-landscape unit or soil map unit, we

normally use the name of that series or taxon to help identify the

soil properties of the delineation. If there is no named series or

taxon available and we believe that such a series or other taxon

would be useful, we define and establish a new series or other

taxon. Also, for the practical purposes of a soil survey, another

classification is superimposed on the series or taxa to identify

significant differences in slope, erosion, stoniness, or other

characteristics. The assignment of taxonomic names, such as the

name of a soil series, to label a map unit means that if we examine

the soil-landscape unit or soil map unit, we expect most

locations within the delineation to meet the criteria of the taxon

or taxa (Holmgren, 1988). The designing, naming, and describing

of soil map units, which are covered elsewhere (USDA, SCS,

1993; USDA, NRCS, 1997; Van Wambeke and Forbes, 1986), are

all critical elements in the understanding of soil geographic

patterns.

Soil Geographic Order and Soil Taxonomy in Soil Survey

It is commonly acknowledged that there is a disparity

between the entity that soil surveyors map and the entity that

they classify. Soil surveyors map soil bodies (soil-landscape

units and soil map units). Soil taxonomy, however, effectively

utilizes properties from samples taken within the soillandscape units and soil map units to establish taxon

boundaries and classify soils (Holmgren, 1988). Time and the

fiscal constraints of a soil survey necessitate minimizing the

number of samples taken. In the past, this disparity between

sampling units and mapping units and the need for minimizing

the sampling effort was rationalized with the pedon and

polypedon. The pedon served as the sampling unit and was

defined as a three-dimensional soil volume with an area of 1 to

10 m2 and a depth that includes the entire solum (USDA, SCS,

1975). The polypedon was defined as a set of contiguous

pedons (USDA, SCS, 1975). It was intended to be used to

establish series level taxa and the map units delineated in the

soil survey.

Applying the pedon and polypedon concepts to mapping

and classification has been the subject of debate and a source of

misunderstanding in soil survey for decades (Hudson, 1990 and

1992; Holmgren, 1988). Some notable problems are that in

reality soil profiles rather than pedons (i.e., three-dimensional

volumes) are really sampled and classified (Holmgren, 1988),

that soil property variation prohibits the selection of one profile

or a few profiles to represent variation within delineated soil

bodies (Hudson, 1990), and that soil-landscape units and soil

map units are composed of more than one polypedon (as
Application of Soil Taxomony to Soil Surveys 117

defined by USDA, SCS, 1975) and contain soils with properties

outside the ranges of established taxa. Application of the soillandscape paradigm (Hudson, 1990 and 1992), however, can

identify soil-landscape boundaries and soil map unit boundaries,

and then, through careful selection of soil profiles that best

represent soil conditions within soil-landscape and soil map unit

delineations, the soil map units can be labeled and described

and useful soil surveys can be produced.

Large- and intermediate-scale soil surveys can be used to

provide general information about soil properties within each

soil-landscape unit and soil map unit. These soil surveys,

however, cannot be used in predicting exact soil properties at

any particular location with statistical confidence, and soil

properties may exceed the ranges defined for the taxa used to

represent soil-landscape units and soil map units.

Recognizing Established Series and Establishing

New Series in a Soil Survey Area at Scales of

1:12,000 to 1:100,000

The standards for establishing series, recognizing

established series, and naming the map units within a soil

survey area have changed in the past and can be expected to

change in the future. The current standards are presented

elsewhere (USDA, SCS, 1993; USDA, NRCS, 1997; Van

Wambeke and Forbes, 1986), and the results of the various

international classification committees are readily available.

The factors that should be considered when recognizing

established soil series, establishing new soil series, and naming

the map units within a soil survey area are described in the

following paragraphs.

The soil series is the basic taxonomic class in soil survey

areas mapped at large and intermediate scales. As a taxonomic

class, a series is a group of soils that have horizons similar in

arrangement and in differentiating characteristics (USDA, SCS,

1993). When recognizing established series and establishing

new series in the field, we must consider the scale and the

degree of accuracy and precision at which we observe and plot

boundaries between soil-landscape units and soil map units. We

must also consider the ability of soil scientists to consistently

observe, determine, and record soil similarities and differences in

the field; the purpose of the soil survey; the nature of the

variability of the soils within a delineation; the importance of the

variations to planning; and the probable uses of the soils. An

example of the application of series differentiae is given in

chapter 21 of this publication.

The representation of soil distribution on a map is imperfect

to varying degrees. In the field, at large and intermediate

scales, soil scientists observe the boundaries between soillandscape units and soil map units and then record the

boundaries on an aerial photo or an appropriate map base.

Inevitably, there are errors in the observation and placement of

these lines, in the sampling and identification of soils at the

boundaries, and in the sampling and identification of soils within

the boundaries of soil-landscape units and soil map units.

Because series have narrow ranges in their properties, most

soils within a soil-landscape unit or soil map unit can be sampled

and identified with reasonable accuracy, even though the

locations of some of the boundaries may be obscure or difficult

to place. There commonly are areas in which a soil in a

delineation does not fit an established series. In this case the

range in characteristics of the existing series could be

expanded, a new series could be established, or the soil could

be handled as a taxadjunct (USDA, SCS, 1993; Van Wambeke

and Forbes, 1986). There are also cases in which soils within a

soil-landscape unit or soil map unit occur as areas too small or

too intermingled to be delineated at the selected scale or in

which differences between soils are subtle and cannot be

consistently observed and mapped in the field. These cases can

be handled within the definitions of kinds of soil map units,

which include consociations, complexes, associations, and

undifferentiated groups, and in the map unit descriptions

(USDA, SCS, 1993; Van Wambeke and Forbes, 1986).

Labeling Soil Maps at Scales Smaller Than

1:100,000

As map scales become smaller, the degree of detail and

precision of the soil map decreases. This decrease is reflected

in the naming of map units and in the map unit descriptions.

Small-scale or general soil maps of individual survey areas in

published soil surveys in the United States commonly have

scales that range from about 1:100,000 to 1:250,000. The map

units delineated on these maps have been named as

associations of series. These generalized maps usually are

made by combining the delineations of detailed soil survey

maps to form broader map units (USDA, SCS, 1993). These

broader map units group similar map unit delineations and are

commonly named for the two or three most dominant soil

series or taxa. The map unit descriptions for these smaller scale

maps should reflect the greater degree of map generalization.

State and regional soil maps commonly are produced at

scales of 1:250,000 to 1:1,000,000. State and regional general

soil maps can be produced by further generalizing county soil

maps. These state and regional maps are typically at scales of

about 1:500,000, and the map units delineated on these maps

are associations of the dominant soil series or taxa on the

county general soil maps.

Schematic soil maps commonly are at a scale of 1:1,000,000

or smaller (USDA, SCS, 1993). These maps can be compiled from

information on more detailed soil maps, county and state general

soil maps, and regional soil maps. Other sources of soil

geographic information can also be used where little or no soil

mapping information is available. At these small scales, map

units commonly are associations or consociations of taxa at the

higher categories, such as Oxisols, Udalfs, and Epiaquepts.
118

Literature Cited

Holmgren, G.G.S. 1988. The Point Representation of Soil. Soil

Sci. Soc. Amer. J. 52: 712-716.

Hudson, B.D. 1990. Concepts of Soil Mapping and

Interpretation. Soil Surv. Horiz. 31: 63-72.

Hudson, B.D. 1992. The Soil Survey as Paradigm-Based

Science. Soil Sci. Soc. Amer. J. 56: 836-841.

Jenny, H. 1941. Factors of Soil Formation. McGraw-Hill, New

York.

Milne, G. 1936. A Provisional Map of East Africa. East

African Agric. Res. Stn. Amani Memoirs.

Peterson, F.F. 1981. Landforms of the Basin and Range

Province Defined for Soil Survey. Nevada Agric. Exp. Stn.

Tech. Bull. 28.

Ruhe, R.V. 1969. Quaternary Landscapes in Iowa. Iowa State

Univ. Press.

Simonson, R.W. 1963. Soil Correlation and the New

Classification System. Soil Sci. 96: 23-30.

Smith, G.D. 1963. Objectives and Basic Assumptions of the

New Classification System. Soil Sci. 96: 6-16.

Soil Science Society of America. 1997. Glossary of

Soil Science Terms.

United States Department of Agriculture, Natural

Resources Conservation Service. 1997. National Soil

Survey Handbook. Soil Surv. Staff.

United States Department of Agriculture, Soil

Conservation Service. 1951. Soil Survey Manual. Soil

Surv. Staff. U.S. Dep. Agric. Handb. 18.

United States Department of Agriculture, Soil

Conservation Service. 1975. Soil Taxonomy: A Basic

System of Soil Classification for Making and Interpreting

Soil Surveys. Soil Surv. Staff. U.S. Dep. Agric. Handb.

436.

United States Department of Agriculture, Soil

Conservation Service. 1993. Soil Survey Manual. Soil

Surv. Div. Staff. U.S. Dep. Agric. Handb. 18.

Van Wambeke, A., and T.R. Forbes, eds. 1986.

Guidelines for Using “Soil Taxonomy” in the Names

of Soil Map Units. Soil Manage. Support Serv. Tech.

Monogr. 10. U.S. Dep. Agric., Soil Conserv. Serv., and

Cornell Univ., Agron. Dep.
119

A category of soil taxonomy is a set of classes that isdefined approximately at the same level of

generalization or abstraction and that includes all soils. There

are six categories in soil taxonomy. In order of decreasing rank

and increasing number of differentiae and classes, the

categories are order, suborder, great group, subgroup, family,

and series.

In one sense, soil taxonomy is a sorting process. In the

highest category, one sorts all kinds of soil into a small number

of classes. The number of classes is small enough for one to

comprehend and remember them and to understand the

distinctions among them. The sorting must make distinctions

that are meaningful for our purposes. When all soils are sorted

into a very few classes, such as the 12 orders, each order is very

heterogeneous with respect to properties that are not considered

in the sorting and that are not accessory to the properties that

are considered. For some purposes, however, the order level

may provide sufficient information. As one continues to

classify a soil at lower and lower levels of soil taxonomy, more

information is conveyed about the soil. This method of

conveying information is one of the advantages of a

multicategoric classification system.

Reducing the heterogeneity requires another sorting in the

next lower category, the suborder. Again, the sorting must be

meaningful, but the sorting in one order may have little

meaning in another order. In soil taxonomy there are 64

suborders, a number larger than can be remembered

conveniently along with all the properties of the suborders. If

we focus on the suborders of a single order, however, we have,

at the most, seven suborders to understand and remember.

Each of the suborders in an order has the properties common to

the order plus the properties used for sorting into that suborder.

In each of the 64 suborders, there is still great heterogeneity, so

we must sort again to obtain, at the next lower level, a set of

meaningful great groups. There are more than 300 great

groups, more than one can remember. One need focus,

however, on only one suborder at a time.

The sorting process continues in the remaining categories

down to the soil series. The soils in any one series are nearly

homogeneous in that their range of properties is small and can

be readily understood. Collectively, the thousands of soil series

are far beyond our powers of comprehension, but they can be

sorted category by category, and one seldom needs to

comprehend more than a few of them at any one time.

Orders

There are 12 orders. They are differentiated by the presence

or absence of diagnostic horizons or features that reflect soilforming processes. If the soils in a given taxon are thought to

have had significantly different genesis, the intent has been to

sort out the differences in the next lower category.

Soil properties are the consequences of a variety of processes

acting on parent materials over time. Distinctions among

orders aid in understanding soils and remembering them on a

grand scale. The processes that occur in soils must be orderly

in relation to the soil-forming factors, which are climate and

living organisms acting on parent materials over time, as

conditioned by relief. These factors, in turn, have geographic

order. The features of the soil-forming processes are clearly

visible, but the details of the processes can only be inferred.

The distinctions made in classifying soils cannot be based on

the processes themselves because new knowledge is certain to

change our ideas about the processes, but the features of the

processes are facts that can be observed and measured and used

as a basis for distinctions. Thus, the distinctions between

orders are based on the markers left by processes that

experience indicates are dominant forces in shaping the

character of the soil. In this framework, the lack of features or

the zero degree also is a logical criterion.

The 12 orders and the major properties that differentiate

them illustrate the nature of this category. Complete definitions

are given later in this publication.

These orders are not the only possible orders in the

taxonomy. In fact, two new orders, Andisols and Gelisols, have

been established since the first edition of Soil Taxonomy. The

hierarchy is flexible, and other ad hoc orders may be defined to

emphasize properties not considered in the 12 orders. The

method of defining ad hoc orders is described in connection

with nomenclature later in this publication.

Alfisols

The soils in this order have markers of processes that

translocate silicate clays without excessive depletion of bases

and without dominance of the processes that lead to the

formation of a mollic epipedon. The unique properties of

Alfisols are a combination of an ochric or umbric epipedon, an

argillic or natric horizon, a medium to high supply of bases in

the soils, and water available to mesophytic plants for more

CHAPTER 6

The Categories of Soil Taxonomy
120 Soil Taxonomy

than half the year or more than 3 consecutive months during a

warm season. Because these soils have water and bases, they

are, as a whole, intensively used.

Andisols

The unique property of Andisols is a dominance of shortrange-order minerals or Al-humus complexes that result from

weathering and mineral transformation with a minimum of

translocation. The characteristics common to most Andisols

include a high phosphorus retention, available water capacity,

and cation-exchange capacity. Most Andisols formed in

volcanic ejecta or volcaniclastic materials. Andisols can form

in almost any environment, however, as long as suitable

temperature and adequate moisture are available to permit

weathering and the formation of short-range-order minerals.

The soils can have any diagnostic epipedon or subsurface

horizon as long as the unique property of Andisols is in 60

percent of the upper 60 cm of the soils, disregarding O

horizons that have 25 percent or more organic carbon.

Prior to 1989, the soils now classified as Andisols were

included with Inceptisols, mainly as Andepts and Andaquepts,

which were discontinued with the acceptance of Andisols as an

order in soil taxonomy.

Aridisols

The unique properties common to Aridisols are a

combination of a lack of water available to mesophytic plants

for very extended periods, one or more pedogenic horizons, a

surface horizon or horizons not significantly darkened by

humus, and absence of deep, wide cracks (see Vertisols) and

andic soil properties (see Andisols). Aridisols have no

available water during most of the time that the soils are warm

enough for plant growth (warmer than 5 o

C [41 oF]), and they

never have water continuously available for as long as 90 days

when the soil temperature is above 8 oC (47 oF).

Aridisols are primarily soils of arid areas. They are in areas

that preclude much entry of water into the soils at present,

either under extremely scanty rainfall or under slight rainfall

that for one reason or another does not enter the soils. The

vegetation in many areas consists of scattered ephemeral

grasses and forbs, cacti, and xerophytic shrubs. Some Aridisols

furnish limited grazing. If irrigated, many of them are suitable

for a wide variety of crops.

Entisols

The unique properties common to Entisols are dominance of

mineral soil materials and absence of distinct pedogenic

horizons. The absence of features of any major set of soilforming processes is itself an important distinction. There can

be no accessory characteristics. Entisols are soils in the sense

that they support plants, but they may be in any climate and

under any vegetation. The absence of pedogenic horizons may

be the result of an inert parent material, such as quartz sand, in

which horizons do not readily form; slowly soluble, hard rock,

such as limestone, which leaves little residue; insufficient time

for horizons to form, as in recent deposits of ash or alluvium;

occurrence on slopes where the rate of erosion exceeds the rate

of formation of pedogenic horizons; recent mixing of horizons

by animals or by plowing to a depth of 1 or 2 m; or the spoils

from deep excavations.

Gelisols

The unique property of Gelisols is the presence of

permafrost and soil features and properties associated with

freezing and thawing. These features include irregular or

broken horizons and incorporation of organic materials in the

lower horizons, especially along the top of the permafrost table.

Freezing and thawing produce granular, platy, and vesicular

structures in surface and subsurface horizons. The increases in

soil volume on freezing are considered a major soil-forming

process in Gelisols. These soils are confined to the higher

latitudes or high elevations, but they make up about 13 percent

of the soils in the world, second only to Aridisols.

Histosols

The unique properties of Histosols are a very high content of

organic matter in the upper 80 cm (32 in) of the soils and no

permafrost. The amount of organic matter is at least 20 to 30

percent in more than half of this thickness, or the horizon that

is rich in organic matter rests on rock or rock rubble. Most

Histosols are peats or mucks, which consist of more or less

decomposed plant remains that accumulated in water, but some

formed from forest litter or moss, or both, and are freely

drained. The freely drained Histosols are described in chapter

14.

Inceptisols

Inceptisols have a wide range in characteristics and occur in

a wide variety of climates. They can form in almost any

environment, except for an arid environment, and the

comparable differences in vegetation are great. Inceptisols can

grade toward any other soil order and occur on a variety of

landforms. The unique properties of Inceptisols are a

combination of water available to plants for more than half the

year or more than 3 consecutive months during a warm season

and one or more pedogenic horizons of alteration or

concentration with little accumulation of translocated materials

other than carbonates or amorphous silica. In addition,

Inceptisols do not have one or more of the unique properties of

Mollisols, which are a thick, dark surface horizon and a high

calcium supply, or the unique property of Andisols, which is

the dominance of short-range-order minerals or Al-humus

complexes.

Mollisols

The unique properties of Mollisols are a combination of a

very dark brown to black surface horizon (mollic epipedon)

that makes up more than one-third of the combined thickness
The Categories of Soil Taxonomy 121

of the A and B horizons or that is more than 25 cm thick and

that has structure or is not hard or very hard when dry; a

dominance of calcium among the extractable cations in the A

and B horizons; a dominance of crystalline clay minerals of

moderate or high cation-exchange capacity; and less than 30

percent clay in some horizon above 50 cm if the soils have

deep, wide cracks (1 cm or more wide) above this depth at

some season.

Mollisols characteristically form under grass in climates

that have a moderate to pronounced seasonal moisture deficit.

Some Mollisols, however, formed under a forest ecosystem, and

a few formed in marshes or in marls in humid climates.

Mollisols are extensive soils on the steppes of Europe, Asia,

North America, and South America.

Oxisols

The unique properties of Oxisols are extreme weathering of

most minerals other than quartz to kaolin and free oxides, very

low activity of the clay fraction, and a loamy or clayey texture

(sandy loam or finer).

Oxisols characteristically occur in tropical or subtropical

regions, on land surfaces that have been stable for a long time.

Generally, the surfaces are early Pleistocene or much older, but

Oxisols can occur on relatively young surfaces when weathered

soil material is redeposited. Oxisols developed in a humid

climate. Because climates change, however, some are now in

an arid environment.

Spodosols

Spodosols have markers in at least an upper sequum of

dominant processes that translocate humus and aluminum, or

humus, aluminum, and iron, as amorphous materials. The

unique property of Spodosols is a B horizon consisting of an

accumulation of black or reddish amorphous materials that

have a high cation-exchange capacity. This horizon is the

spodic horizon. In most undisturbed soils, an albic horizon

overlies the B horizon. The spodic horizon has accessory

characteristics of coarse texture, high pH-dependent charge,

and few bases. Commonly, the cation-exchange capacity is

related to the amount of organic carbon rather than to the clay.

Ultisols

Ultisols, like Alfisols, have markers of clay translocation,

but they also have markers of intensive leaching that are absent

in Alfisols. The unique properties common to Ultisols are an

argillic horizon and a low supply of bases, particularly in the

lower horizons.

The cation-exchange capacity in Ultisols is mostly moderate

or low. The decrease in base saturation with increasing depth

reflects cycling of bases by plants or additions in fertilizers. In

soils that have not been cultivated, the highest base saturation

is normally in the few centimeters directly beneath the surface.

Like Alfisols, Ultisols have water, but they have few bases.

Without applications of fertilizer, they can be used for shifting

cultivation. Because they are commonly warm and moist,

however, they can be made highly productive if fertilizer is

applied.

Vertisols

These soils have markers of processes related to the failure

of soil materials along shear planes (slickensides). Because the

soil material moves, the diagnostic properties have many

accessory properties. Among them are a high bulk density

when the soils are dry, low or very low hydraulic conductivity

when the soils are moist, an appreciable rise and fall of the soil

surface as the soils become moist and then dry, and rapid

drying as a result of open cracks. The unique properties

common to Vertisols are a high content of clay, pronounced

changes in volume with changes in moisture, cracks that open

and close periodically, and evidence of soil movement in the

form of slickensides and of wedge-shaped structural aggregates

that are tilted at an angle from the horizontal. The

development of eluvial/illuvial horizons in some Vertisols

suggests that pedoturbation is not rapid enough to preclude

long-term translocation processes.

Suborders

Sixty-four suborders currently are recognized. The

differentiae for the suborders vary with the order but can be

illustrated by examples from two orders. The Entisol order has

five suborders that distinguish the major reasons for absence of

horizon differentiation. One suborder includes soils that have

aquic conditions. These are the soils in areas of marshy recent

alluvium and the soils of coastal marshes that are saturated

with water and have a blue or green hue close to the surface.

This suborder segregates the wet varieties. A second suborder

includes soils that are not wet and that consist of recent

alluvium, which generally is stratified. This suborder

segregates the very young soils that do not have horizons

because there is continuing deposition of new sediments. A

third suborder includes soils on recently eroded slopes. This

suborder segregates soils that are kept young by removal of soil

materials at a rate that is more rapid than that of horizon

differentiation. A fourth suborder includes sands that may

range from recent to old. If old, they either lack the building

blocks for pedogenic horizons or do not have enough moisture.

Although the reasons for absence of horizons in the sands vary,

the sands have many common physical properties, such as a

low capacity for moisture retention, high hydraulic

conductivity, and susceptibility to soil blowing. The sorting of

these differences is continued in the lower categories. The fifth

suborder of Entisols includes soils in which horizons have been

mixed by deep plowing or other human activities that have

destroyed the pedogenic horizons as such but not the fragments

of the horizons.

Alfisols has five suborders. As in Entisols, one suborder

includes wet soils in which the colors are dominantly gray. A
122 Soil Taxonomy

second suborder includes Alfisols that are cold and have a

short growing season. A third suborder includes soils that have

a udic moisture regime and rarely do not have water available

for plants. A fourth suborder has an ustic moisture regime and

has extended or frequent periods when the soils do not have

water that is available to mesophytic plants in some or all

horizons. The fifth suborder includes the Alfisols that have a

xeric moisture regime. These soils are cool and moist in winter,

but they are dry for extended periods in summer.

The differentiae used in defining the suborders of Alfisols

include important properties that influence genesis and that are

extremely important to plant growth. The differentiae in six of

the other orders closely parallel those of Alfisols. In the

remaining orders, differentiae were selected to reflect what

seemed to be the most important variables within the orders.

Great Groups

There are more than 300 great groups. At as high a

categoric level as possible, it is desirable to consider all the

horizons and their nature collectively as well as the

temperature and moisture regimes. The moisture and

temperature regimes are causes of properties, and they also are

properties of the whole soil rather than of specific horizons. At

the order and suborder levels, only a few of the most important

horizons could be considered because there are few taxa in

those categories. At the great group level, the assemblage of

horizons and the most significant properties of the whole soil

are considered. Although the definition of a great group may

involve only a few differentiae, the accessory properties are

many times that number.

Differentiae in the great group category segregate soils that

have the following properties in common:

Close similarities in kind, arrangement, and degree of

expression of horizons.—Exceptions are made for some thin

surface horizons that would be mixed by plowing or lost by

erosion and for horizons that indicate transitions to other great

groups. For example, an argillic horizon that underlies the

spodic horizon is permitted in the Spodosol order because that

combination is considered to represent a kind of transition

between Spodosols on the one hand and Alfisols and Ultisols

on the other. Emphasis is placed on the upper sequum in the

great group category because it is thought to reflect the current

processes and is more critical to plant growth than the deeper

horizons.

Similarities in base status.—If the base status varies widely

within a suborder, the range is narrowed at the great group

level.

The suborders of Alfisols were defined on the basis of

moisture regimes. In addition to the argillic horizon that is

common to all Alfisols, other kinds of horizons may occur. A

fragipan or duripan restricts root development and water

movement, which in turn affect current processes of soil

formation. These horizons are used as one basis for defining

great groups. The argillic horizon may have a fine texture and

may be abruptly separated from an overlying albic horizon.

This combination also affects root development and water

movement, inducing shallow perched ground water and

intermittent reducing conditions in the soils. The horizons may

be thick as a result of very long periods of development. They

may be undergoing destruction, and the soils may have

developed a glossic horizon. These features also are used as

differentiae for great groups.

In contrast to Alfisols, emphasis in the Entisols was placed

on soil moisture and temperature regimes when the great

groups were differentiated. Because the various suborders occur

in all parts of the world, they have extreme ranges in moisture

and temperature regimes, and those regimes affect pedogenesis

as well as use and management of the soils.

Subgroups

There are more than 2,400 subgroups. Through the

categories of order, suborder, and great group, emphasis has

been placed on features or processes that appear to dominate

the course or degree of soil development. In addition to these

dominant features, many soils have properties that, although

apparently subordinate, are still markers of important sets of

processes. Some of these appear to be features of processes that

are dominant in some other great group, suborder, or order. In

a particular soil, however, they only modify the traits of other

processes. For example, some soils have aquic conditions and

have, throughout their depth, gray colors with reddish or

brownish redox concentrations. Other soils have aquic

conditions only in their lower horizons, and in those horizons

the dominant colors may be shades of brown, red, or yellow

with some gray redox depletions. The effects of ground water

are apparent in both sets of soils, but they have less importance

in the latter set.

Other properties are features of processes that are not used

as criteria of any taxon above the subgroup level. For example,

a Mollisol at the foot of a slope, where there has been a slow

accumulation of materials washed from the higher parts of the

slope, may have a greatly overthickened mollic epipedon.

Thus, there are three kinds of subgroups:

Typic subgroups.—These are not necessarily the most

extensive subgroups, nor do they necessarily represent the

central concept of the great group. In some taxa typic

subgroups simply represent the soils that do not have the

characteristics defined for the other subgroups.

Intergrades or transitional forms to other orders,

suborders, or great groups.—The properties may be the result

of processes that cause one kind of soil to develop from or

toward another kind of soil or otherwise to have intermediate

properties between those of two or three great groups. The

properties used to define the intergrades may be:

1. Horizons in addition to those definitive of the great

group, including an argillic horizon that underlies a spodic
The Categories of Soil Taxonomy 123

horizon and a buried horizon, such as a thick layer of

organic materials that is buried by a thin mineral soil; or

2. Intermittent horizons, such as those described in the

section of chapter 1 that deals with the pedon; or

3. Properties of one or more other great groups that are

expressed in part of the soils but are subordinate to the

properties of the great group of which the subgroup is a

member. One example of different depths of saturation and

reduction was given earlier. Another example might be an

Alfisol that has an ochric epipedon a little too thin or a little

too light in color to be a mollic epipedon. This feature could

result from an invasion of grassland by forest or the reverse,

from the coexistence of both grass and forest, or from the

erosion caused by human activities.

Extragrades.—These subgroups have some properties that

are not representative of the great group but that do not

indicate transitions to any other known kind of soil. One

example of an overthickened mollic epipedon was given

earlier. Other examples are soils that are very shallow over

rock (Lithic) or soils that have high amounts of organic carbon

(Humic).

Families

In this category, the intent has been to group the soils within

a subgroup having similar physical and chemical properties

that affect their responses to management and manipulation for

use. In some cases soil properties are used in this category

without regard to their significance as indicators of soilforming processes.

The following are defined primarily to provide groupings of

mineral soils with restricted ranges in:

1. Particle-size classes in horizons of major biologic

activity below plow depth;

2. Mineralogy classes in the same horizons that are

considered in naming particle-size classes;

3. Cation-exchange activity classes of certain particle-size

and mineralogy classes in the same horizons that are

considered in naming particle-size classes;

4. Calcareous and reaction classes in horizons directly

below plow depth;

5. Soil temperature classes;

6. Thickness of the soil penetrable by roots; and

7. Classes of coatings, cracks, and rupture resistance used

in defining some families to produce the needed

homogeneity.

These properties carry important interpretive information,

including aeration and the movement and retention of water,

both of which affect the growth of plants and engineering

uses. The differentiae are described in more detail in chapter

21.

Series

The series is the lowest category in this system. More

than 19,000 series have been recognized in the United States.

The differentiae used for series generally are the same as

those used for classes in other categories, but the range

permitted for one or more properties is narrower than the

range permitted in a family or in some other higher category.

For several properties, a series may have virtually the full

range that is permitted in a family, but for one or more

properties, the range is restricted. The purpose of the series

category, like that of the family, is mainly pragmatic, and the

taxa in the series category are closely allied to interpretive uses

of the system.

Two kinds of distinctions, therefore, are made among series.

First, the distinctions among families and among classes of all

higher categories also are distinctions among series. A series

cannot range across the limits between two families or between

two classes of any higher category. Second, distinctions among

similar series within a family are restrictions in one or more

but not necessarily all of the ranges in properties of the family.

Taken collectively, the number of the latter kind of distinctions

is too large to be comprehended readily. One can only state the

basis for separating individual series. Diagnostic horizons and

features provide a framework for differentiating series, but

series differentiae need not be limited to the defined diagnostic

horizons and features.

The differentiae for series in the same family are expected to

meet three tests. The first is that properties serving as

differentiae can be observed or can be inferred with reasonable

assurance. The second is that the differentiae must create soil

series having a unique range of properties that is significantly

greater than the normal margin of errors made by qualified

pedologists when they measure, observe, or estimate the

properties. The third is that the differentiae must reflect a

property of the soils. This significance can be reflected in the

nature or degree of expression of one or more horizons. The

nature of horizons includes mineralogy, structure, ruptureresistance class, texture of the subhorizons, and moisture and

temperature regimes. If color is accessory to some other

property, it too is included. Degree of horizon expression

includes thickness, contrast between horizons or subhorizons,

and the nature of boundaries. If horizons are absent, the nature

of the whole zone of major biologic activity is considered. The

series control section is defined in chapter 21.

Important differences, shown by experience or research to

condition or influence the nature of the statements that we can

make about the behavior of the soil, should be considered as

series differentiae.
124

A number of soil properties condition the statements made

about a soil or its use but are not series differentiae. A steep

slope or stones on the surface may be very important to the use

of a soil in mechanized farming, but they may have virtually no

importance to the growth of a forest, although they can hinder

timber harvesting. If it is assumed that these soil characteristics

are not reflected in the nature of the soil, or in the nature or

degree of expression of horizons explained earlier, then they

may be used as one of the bases of phases of soil series. The

phases provide for a utilitarian classification that can be

superimposed on soil taxonomy at any categoric level to permit

more precise interpretations and predictions of the consequence

of the various alternative uses of the soil.

The primary use of soil series in the classification system is

to relate the map units represented on detailed soil maps to the

taxa and to the interpretations that may follow. Map units are

named for one or more soil series. Map units are real things,

but series are conceptual. The Miami series, for example,

cannot be seen or touched, but the map units that are identified

as physical entities expressing the concept of the Miami series

can be seen and touched.

The names of soil series have several meanings that must be

kept in mind. First, the Miami series is a taxonomic class, a

concept of a narrowly defined kind of soil. Second, one may

examine a pedon and say, “This is Miami,” meaning that the

properties in the pedon are those of the Miami series and that

the pedon is a proper example. Third, “Miami” is used as part

of the name of a map unit in an area that is shown on a soil

map if the Miami series is dominant in that area. An example

of such a map unit is Miami silt loam, 2 to 6 percent slopes.

These are three common meanings of “Miami,” or of any series

name, and all are proper. It is essential, however, to keep in

mind that a series, as used in this taxonomy, is conceptual; the

meaning is not identical with the meaning intended on soil

maps because an area of Miami soil has inclusions of soils of

other series. Inclusions of Miami soil also are permitted in

areas named for other series. The application of this taxonomy

to soil surveys is described in chapter 5.
125

The nomenclature of soil taxonomy is based on thefollowing premises: Each taxon requires a name if it is

to be used in speech; a good name is short, easy to pronounce,

and distinctive in meaning; a name is connotative, that is,

capable of mnemonic attachment to the concept of the thing

itself (Heller, 1963); and it is useful if the name of a taxon

indicates its position in the classification, if similarities in

important properties are reflected by similarities in names, if

the mnemonic attachments hold in many languages, and if the

name fits into many languages without translation.

The name of each taxon above the category of series

indicates its class in all categories of which it is a member.

The name of a soil series indicates only the category of series.

Thus, a series name may be recognized as a series, but it does

not indicate the order, suborder, great group, subgroup, or

family.

The table “Example of Names of Taxa” shows the names of

taxa in each category from order to series for two soil series.

Because the assigned names are connotative and because most

formative elements carry the same meaning in any

combination, a name can convey a great deal of information

about a soil.

Recognition of Names

Orders

The names of orders can be recognized as such because the

name of each order ends in sol (L. solum, soil) with the

connecting vowel o for Greek roots and i for other roots, as is

indicated in the table “Formative Elements in Names of Soil

Orders.” Each name of an order contains a formative element

that begins with the vowel directly preceding the connecting

vowel and ends with the last consonant preceding the

connecting vowel. In the order name “Entisol,” the formative

element is ent. In the name “Aridisol,” it is id. These formative

elements are used as endings for the names of suborders, great

groups, and subgroups. Thus, the names of all taxa higher than

the series that are members of the Entisol order end in ent and

can be recognized as belonging to that order. Names ending in

id are the names of taxa belonging to the Aridisol order.

Suborders

The names of suborders have exactly two syllables. The first

syllable connotes something about the diagnostic properties of

the soils. The second is the formative element from the name of

the order. The 28 formative elements shown in the table

“Formative Elements in Names of Suborders” are used with the

12 formative elements from names of the orders to make the

names of 64 suborders. The suborder of Entisols that has aquic

conditions throughout is called Aquents (L. aqua, water, plus

ent from Entisol). The formative element aqu is used with this

meaning in 9 of the 12 orders. The suborder of Entisols that

consists of very young sediments is called Fluvents (L. fluvius,

river, plus ent from Entisol).

Great Groups

The name of a great group consists of the name of a

suborder and a prefix that consists of one or two formative

elements suggesting something about the diagnostic properties.

The formative elements are shown in the table “Formative

Elements in Names of Great Groups.” The names of great

groups, therefore, have three or four syllables and end with the

name of a suborder. Fluvents that have a cryic temperature

regime are called Cryofluvents (Gr. kryos, icy cold, plus

fluvent). Fluvents that have a torric moisture regime are called

Torrifluvents (L. toridus, hot and dry).

Subgroups

The name of a subgroup consists of the name of a great

group modified by one or more adjectives. In some instances,

the adjective Typic represents what is thought to typify the

great group. In other instances, Typic subgroups simply do not

have any of the characteristics used to define the other

subgroups in a great group. Each Typic subgroup has, in

clearly expressed form, all the diagnostic properties of the

order, suborder, and great group to which it belongs. Typic

subgroups also have no additional properties indicating a

transition to another great group. A Typic subgroup is not

necessarily the most extensive subgroup of a great group.

CHAPTER 7

Nomenclature1

1 This chapter was developed with the assistance of the late Prof. A.L. Leemans, Classic

Language Department, State University of Ghent, and the late Prof. John L. Heller, Department

of the Classics, University of Illinois.
126 Soil Taxonomy

Intergrade subgroups are those that belong to one great

group but have some properties of another order, suborder, or

great group. They are named by use of the adjectival form of

the name of the appropriate taxon as a modifier of the great

group name. Thus, the Torrifluvents that have some of the

properties of Vertisols or the properties closely associated with

Vertisols are called Vertic Torrifluvents. Vertic Torrifluvents

have some of the properties of Vertisols superimposed on the

complete set of diagnostic properties of Torrifluvents.

Extragrade subgroups are those that have important

properties that are not representative of the great group but that

do not indicate transitions to any other known kind of soil.

They are named by modifying the great group name with an

adjective that connotes something about the nature of the

aberrant properties. Thus, a Cryorthent that has bedrock that is

at least strongly cemented within 50 cm of the mineral soil

surface is called a Lithic Cryorthent (lithic, Gr. lithos, stone).

This subgroup is listed as an example in the table “Names of

Orders, Suborders, Great Groups, and Subgroups.”

Families

The names of families are polynomial. Each consists of the

name of a subgroup and descriptive terms, generally three or

more, that indicate the particle-size class (or combinations

thereof if strongly contrasting), the mineralogy (26 classes), the

cation-exchange activity (4 classes), the calcareous and

reaction class (4 classes), the temperature (8 classes), and, in a

few families, depth of the soil (3 classes), rupture resistance (2

classes), and classes of coatings and classes of cracks (3

classes). The names of most families have three to five

descriptive terms that modify the subgroup name, but a few

have only one or two and a few have as many as six. The

example given in the table “Example of Names of Taxa” is a

family of fine-loamy (particle-size class), mixed (mineralogy),

superactive (cation-exchange activity), calcareous (calcareous

and reaction), mesic (soil temperature) Typic Torrifluvents.

Series

The names of series as a rule are abstract place names. The

name generally is taken from a place near the one where the

series was first recognized. It may be the name of a town, a

county, or some local feature. Some series have coined names.

Many of the series names have been carried over from earlier

classifications. Some have been in use since 1900. The name of

a series carries no meaning to people who have no other source

of information about the soils in the series.

Entisols ...................... Fluvents .................... Torrifluvents............. Typic Torrifluvents ... Fine-loamy, Jocity, Youngston.

mixed, superactive,

calcareous, mesic.

Example of Names of Taxa

Order Suborder Great Group Subgroup Family Series

Alfisols ........................................ Alf ............................................... Meaningless syllable .................. Pedalfer.

Andisols....................................... And ............................................. Modified from ando ................... Ando.

Aridisols ...................................... Id................................................. L. aridus, dry .............................. Arid.

Entisols ........................................ Ent .............................................. Meaningless syllable .................. Recent.

Gelisols ........................................ El ................................................ L. gelare, to freeze ..................... Jell.

Histosols ...................................... Ist ................................................ Gr. histos, tissue ......................... Histology.

Inceptisols .................................... Ept .............................................. L. inceptum, beginning .............. Inception.

Mollisols ...................................... Oll ............................................... L. mollis, soft ............................. Mollify.

Oxisols ......................................... Ox ............................................... F. oxide, oxide ............................ Oxide.

Spodosols..................................... Od ............................................... Gr. spodos, wood ash ................. Odd.

Ultisols ......................................... Ult ............................................... L. ultimus, last ............................ Ultimate.

Vertisols ....................................... Ert ............................................... L. verto, turn .............................. Invert.

Formative Elements in Names of Soil Orders

Name of order Formative element in name Derivation of formative element Pronunciation of formative

element
Nomenclature 127

Meanings in the Names

The Jocity and Youngston series shown in the table

“Example of Names of Taxa” are two members of the fineloamy, mixed, superactive, calcareous, mesic family of Typic

Torrifluvents. The meaning of each of these terms is defined as

follows:

Fine-loamy means that from a depth of 25 to 100 cm there

is no marked contrast in particle-size class, the content of clay

is between 18 and 35 percent, 15 percent or more of the

material is coarser than 0.1 mm in diameter (fine sand to very

coarse sand plus gravel), but less than 35 percent of the

material, by volume, is rock fragments 2.0 mm or more in

diameter (less than about 50 percent by weight). The average

texture, then, is likely to be loam, clay loam, or sandy clay

loam.

Mixed indicates a mixed mineralogy, that is, there is less

than 40 percent any one mineral other than quartz in the

fraction between 0.02 and 2.0 mm in diameter, less than 20

percent (by weight) glauconitic pellets in the fine-earth

fraction, a total of 5 percent or less iron plus gibbsite (by

weight) in the fine-earth fraction, and a fine-earth fraction that

has at least one of the following: free carbonates, pH of a

suspension of 1 g soil in 50 ml 1 M NaF of 8.4 or less after 2

minutes, or a ratio of 1500 kPa water to measured clay of 0.6

or less.

Superactive means that the cation-exchange capacity

divided by the percent clay is 0.60 or more.

Calcareous means that the soils have free carbonates in all

parts from a depth of 25 to 50 cm and that, in this setting, they

probably are calcareous throughout.

Mesic indicates a mesic temperature regime, that is, the

mean annual soil temperature is between 8 and 15 oC (47 and

59 oF) and the soil temperature fluctuates more than 8 oC

between summer and winter. In other words, the soils are

somewhere in the midlatitudes, summer is warm or hot, and

winter is cool or cold.

No term for soil depth is included in the family name of

Alb ........................... L. albus, white ................................................................. Presence of an albic horizon.

Anthr ....................... Modified from Gr. anthropos, human ............................. Modified by humans.

Aqu .......................... L. aqua, water .................................................................. Aquic conditions.

Ar ............................. L. arare, to plow .............................................................. Mixed horizon.

Arg ........................... Modified from argillic horizon; L. argilla, white clay ... Presence of an argillic horizon.

Calc .......................... L. calcis, lime .................................................................. Presence of a calcic horizon.

Camb........................ L. cambiare, to exchange ................................................ Presence of a cambic horizon.

Cry ........................... Gr. kryos, icy cold ............................................................ Cold.

Dur ........................... L. durus, hard .................................................................. Presence of a duripan.

Fibr .......................... L. fibra, fiber ................................................................... Least decomposed stage.

Fluv .......................... L. fluvius, river ................................................................ Flood plain.

Fol ............................ L. folia, leaves .................................................................. Mass of leaves.

Gyps......................... L. gypsum, gypsum .......................................................... Presence of a gypsic horizon.

Hem ......................... Gr. hemi, half ................................................................... Intermediate stage of decomposition.

Hist .......................... Gr. histos, tissue .............................................................. Presence of organic materials.

Hum ......................... L. humus, earth ................................................................ Presence of organic matter.

Orth ......................... Gr. orthos, true ................................................................ The common ones.

Per ............................ L. per, throughout in time ............................................... Perudic moisture regime.

Psamm ..................... Gr. psammos, sand........................................................... Sandy texture.

Rend ......................... Modified from Rendzina ................................................. High carbonate content.

Sal ............................ L. base of sal, salt ............................................................ Presence of a salic horizon.

Sapr.......................... Gr. saprose, rotten ........................................................... Most decomposed stage.

Torr .......................... L. torridus, hot and dry ................................................... Torric moisture regime.

Turb ......................... L. turbidus, disturbed ...................................................... Presence of cryoturbation.

Ud ............................ L. udus, humid................................................................. Udic moisture regime.

Ust ............................ L. ustus, burnt .................................................................. Ustic moisture regime.

Vitr ........................... L. vitrum, glass ................................................................ Presence of glass.

Xer ........................... Gr. xeros, dry ................................................................... Xeric moisture regime.

Formative Elements in Names of Suborders

Formative element Derivation Connotation
128 Soil Taxonomy

Acr ........................... Modified from Gr. arkos, at the end ............................... Extreme weathering.

Al ............................. Modified from aluminum ................................................ High aluminum, low iron.

Alb ........................... L. albus, white ................................................................. Presence of an albic horizon.

Anhy ........................ Gr. anydros, waterless ..................................................... Very dry.

Anthr ....................... Modified from Gr. anthropos, human ............................. An anthropic epipedon.

Aqu .......................... L. aqua, water .................................................................. Aquic conditions.

Argi .......................... Modified from argillic horizon; L. argilla, white clay ... Presence of an argillic horizon.

Calci, calc ................ L. calcis, lime .................................................................. A calcic horizon.

Cry ........................... Gr. kryos, icy cold ............................................................ Cold.

Dur ........................... L. durus, hard .................................................................. A duripan.

Dystr, dys ................. Modified from Gr. dys, ill; dystrophic, infertile ............. Low base saturation.

Endo......................... Gr. endon, endo, within................................................... Implying a ground water table.

Epi ........................... Gr. epi, on, above ............................................................ Implying a perched water table.

Eutr .......................... Modified from Gr. eu, good; eutrophic, fertile ............... High base saturation.

Ferr .......................... L. ferrum, iron ................................................................. Presence of iron.

Fibr .......................... L. fibra, fiber ................................................................... Least decomposed stage.

Fluv .......................... L. fluvius, river ................................................................ Flood plain.

Fol ............................ L. folia, leaf ..................................................................... Mass of leaves.

Fragi ........................ Modified from L. fragilis, brittle .................................... Presence of a fragipan.

Fragloss ................... Compound of fra(g) and gloss ......................................... See the formative elements “frag” and “gloss.”

Fulv .......................... L. fulvus, dull brownish yellow ....................................... Dark brown color, presence of organic carbon.

Glac.......................... L. glacialis, icy ................................................................ Ice lenses or wedges.

Gyps......................... L. gypsum, gypsum .......................................................... Presence of a gypsic horizon.

Gloss ........................ Gr. glossa, tongue ............................................................ Presence of a glossic horizon.

Hal ........................... Gr. hals, salt..................................................................... Salty.

Hapl ......................... Gr. haplous, simple ......................................................... Minimum horizon development.

Hem ......................... Gr. hemi, half ................................................................... Intermediate stage of decomposition.

Hist .......................... Gr. histos, tissue .............................................................. Presence of organic materials.

Hum ......................... L. humus, earth ................................................................ Presence of organic matter.

Hydr ......................... Gr. hydor, water ............................................................... Presence of water.

Kand, kan ................ Modified from kandite..................................................... 1:1 layer silicate clays.

Luv ........................... Gr. louo, to wash ............................................................. Illuvial.

Melan ....................... Gr. melasanos, black ....................................................... Black, presence of organic carbon.

Moll ......................... L. mollis, soft ................................................................... Presence of a mollic epipedon.

Natr .......................... Modified from natrium, sodium ...................................... Presence of a natric horizon.

Pale .......................... Gr. paleos, old ................................................................. Excessive development.

Petr........................... Gr. comb. form of petra, rock ......................................... A cemented horizon.

Plac .......................... Gr. base of plax, flat stone ............................................... Presence of a thin pan.

Plagg ........................ Modified from Ger. plaggen, sod .................................... Presence of a plaggen epipedon.

Plinth ....................... Gr. plinthos, brick............................................................ Presence of plinthite.

Psamm ..................... Gr. psammos, sand........................................................... Sandy texture.

Quartz ...................... Ger. quarz, quartz ............................................................ High quartz content.

Rhod ........................ Gr. base of rhodon, rose .................................................. Dark red color.

Sal ............................ L. base of sal, salt ............................................................ Presence of a salic horizon.

Sapr.......................... Gr. saprose, rotten ........................................................... Most decomposed stage.

Somb ........................ F. sombre, dark ................................................................ Presence of a sombric horizon.

Sphagn ..................... Gr. sphagnos, bog ............................................................ Presence of sphagnum.

Sulf .......................... L. sulfur, sulfur ................................................................ Presence of sulfides or their oxidation products.

Torr .......................... L. torridus, hot and dry ................................................... Torric moisture regime.

Formative Elements in Names of Great Groups

Formative element Derivation Connotation
Nomenclature 129

these Typic Torrifluvents, indicating that the soils are 50 cm or

more deep.

The meaning of Typic varies with the great group. Torri

indicates a torric (dry) moisture regime. Fluv indicates that the

sediments are probably alluvial rather than eolian because fresh

eolian sediments may be sandy, silty, or clayey but are rarely

fine-loamy. Ent, the final syllable, indicates that the soils are

Entisols. As such, they have no fragipan, duripan, permafrost,

or cambic, argillic, calcic, petrocalcic, gypsic, oxic,

petrogypsic, placic, salic, or spodic horizon within 100 cm of

the mineral soil surface; have no sulfuric horizon within 150

cm of the mineral soil surface; and have no histic, mollic,

plaggen, or umbric epipedon.

The terms describing these Typic Torrifluvents allow us to

visualize soils on flood plains or alluvial fans in an arid,

temperate climate. Although the soils may be a bit salty, they

cannot be extremely salty. They probably have stratification but

have no severe limitation for irrigation. Under irrigation, iron

chlorosis may be a problem in sensitive plants. Unless

irrigated, the soils can be used only for limited grazing.

Forming Names

Names of Orders, Suborders, and Great Groups

The names of the orders, suborders, and great groups that

are currently recognized are shown in the table “Names of

Orders, Suborders, Great Groups, and Subgroups.” The

formative elements used in these names are shown in the tables

“Formative Elements in Names of Soil Orders,” “Formative

Elements in Names of Suborders,” and “Formative Elements in

Names of Great Groups.”

Names of Subgroups

The name of a subgroup consists of the name of a great

group modified by one or more adjectives. As was explained

earlier, the adjective Typic is used for the subgroup that is

thought to typify the central concept of the great group or for

soils that fail to meet the criteria of the other subgroups defined

for a great group.

Intergrade subgroups that have, in addition to the properties

of their great group, some properties of another taxon carry the

name of the other taxon in the form of an adjective. The names

of orders, suborders, or great groups or any of the prior (first)

formative elements of those names may be used in the form of

an adjective in subgroup names. A few soils may have aberrant

properties of two great groups that belong in different orders or

suborders. For these, it is necessary to use two names of taxa as

adjectives in the subgroup name.

The names of extragrade subgroups include one or more

special descriptive adjectives that modify the name of the great

group and connote the nature of aberrant properties.

Names of Intergrades Toward Other Great Groups in the

Same Suborder

If the aberrant property of a soil is one that is characteristic

of another great group in the same suborder, only the

distinctive formative element of the great group name is used

to indicate the aberrant property. Thus, a Typic Argidurid is

defined in part as having an indurated or very strongly

cemented duripan. If the only aberrant feature of an Argidic

Argidurid is that the duripan is strongly cemented or less

cemented throughout, the soil is considered to intergrade

toward Argids. The name, however, is Argidic Argidurids, not

Haplargidic Argidurids. Only the prior (first) formative

element is used in adjectival form if the two great groups are in

the same suborder.

Names of Intergrades Toward a Great Group in the Same

Order but in a Different Suborder

Two kinds of names have been chosen to indicate

intergrades toward a great group in the same order but in a

different suborder. If the only aberrant features are color and

moisture regime and hue is too yellow or chroma is too high or

too low for the Typic subgroup, the adjectives Aeric and Aquic

are used.

If an Epiaquult has chroma too high for the Typic subgroup

but has no other aberrant feature, it is assigned to an Aeric

Ud ............................ L. udus, humid................................................................. Udic moisture regime.

Umbr ........................ L. umbra, shade ............................................................... Presence of an umbric epipedon.

Ust ............................ L. ustus, burnt .................................................................. Ustic moisture regime.

Verm ......................... L. base of vermes, worms ................................................. Wormy or mixed by animals.

Vitr ........................... L. vitrum, glass ................................................................ Presence of glass.

Xer ........................... Gr. xeros, dry ................................................................... Xeric moisture regime.

Formative Elements in Names of Great Groups--Continued

Formative element Derivation Connotation
130 Soil Taxonomy

Alfisols ........ Aqualfs ........Cryaqualfs ........ Typic.

Plinthaqualfs .... Typic.

Duraqualfs ........ Typic.

Natraqualfs ....... Vertic,

Vermic,

Albic Glossic,

Albic,

Glossic,

Mollic,

Typic.

Fragiaqualfs ..... Vermic,

Aeric,

Plinthic,

Humic,

Typic.

Kandiaqualfs .... Arenic,

Grossarenic,

Plinthic,

Aeric Umbric,

Aeric,

Umbric,

Typic.

Vermaqualfs ..... Natric,

Typic.

Albaqualfs ........ Arenic,

Aeric Vertic,

Chromic Vertic,

Vertic,

Udollic,

Aeric,

Aquandic,

Mollic,

Umbric,

Typic.

Glossaqualfs ..... Histic,

Arenic,

Aeric Fragic,

Fragic,

Aeric,

Mollic,

Typic.

Epiaqualfs ........ Aeric Chromic

Vertic,

Aeric Vertic,

Chromic Vertic,

Vertic,

Aquandic,

Aeric Fragic,

Fragic,

Arenic,

Grossarenic,

Aeric Umbric,

Udollic,

Aeric,

Mollic,

Umbric,

Typic.

Endoaqualfs...... Aquandic,

Chromic Vertic,

Vertic,

Aeric Fragic,

Fragic,

Arenic,

Grossarenic,

Udollic,

Aeric Umbric,

Aeric,

Mollic,

Umbric,

Typic.

Cryalfs.........Palecryalfs ........ Andic,

Vitrandic,

Aquic,

Oxyaquic,

Xeric,

Ustic,

Mollic,

Umbric,

Typic.

Glossocryalfs .... Lithic,

Vertic,

Andic,

Vitrandic,

Aquic,

Oxyaquic,

Fragic,

Xerollic,

Umbric Xeric,

Ustollic,

Xeric,

Ustic,

Mollic,

Umbric,

Eutric,

Typic.

Haplocryalfs ..... Lithic,

Vertic,

Andic,

Names of Orders, Suborders, Great Groups, and Subgroups

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 131

Vitrandic,

Aquic,

Oxyaquic,

Lamellic,

Psammentic,

Inceptic,

Xerollic,

Umbric Xeric,

Ustollic,

Xeric,

Ustic,

Mollic,

Umbric,

Eutric,

Typic.

Ustalfs ....... Durustalfs .......... Typic.

Plinthustalfs ...... Typic.

Natrustalfs ......... Salidic,

Leptic Torrertic,

Torrertic,

Aquertic,

Aridic Leptic,

Vertic,

Aquic Arenic,

Aquic,

Arenic,

Petrocalcic,

Leptic,

Haplargdic,

Aridic,

Mollic,

Typic.

Kandiustalfs ...... Grossarenic,

Aquic Arenic,

Plinthic,

Aquic,

Arenic Aridic,

Arenic,

Aridic,

Udic,

Rhodic,

Typic.

Kanhaplustalfs .. Lithic,

Aquic,

Aridic,

Udic,

Rhodic,

Typic.

Paleustalfs.......... Aquertic,

Oxyaquic Vertic,

Udertic,

Vertic,

Aquic Arenic,

Aquic,

Oxyaquic,

Lamellic,

Psammentic,

Arenic Aridic,

Grossarenic,

Arenic,

Plinthic,

Petrocalcic,

Calcidic,

Aridic,

Kandic,

Rhodic,

Ultic,

Udic,

Typic.

Rhodustalfs....... Lithic,

Kanhaplic,

Udic,

Typic.

Haplustalfs ....... Lithic,

Aquertic,

Oxyaquic Vertic,

Torrertic,

Udertic,

Vertic,

Aquic Arenic,

Aquultic,

Aquic,

Oxyaquic,

Vitrandic,

Lamellic,

Psammentic,

Arenic Aridic,

Arenic,

Calcidic,

Aridic,

Kanhaplic,

Inceptic,

Calcic Udic,

Ultic,

Calcic,

Udic,

Typic.

Xeralfs ........Durixeralfs ....... Natric,

Order Suborder Great Group Subgroup Suborder Great Group Subgroup Order

Names of Orders, Suborders, Great Groups, and Subgroups--Continued
132 Soil Taxonomy

Durixeralfs

(continued) ..... Vertic,

Aquic,

Abruptic Haplic,

Abruptic,

Haplic,

Typic.

Natrixeralfs ...... Vertic,

Aquic,

Typic.

Fragixeralfs ...... Andic,

Vitrandic,

Mollic,

Aquic,

Inceptic,

Typic.

Plinthoxeralfs ... Typic.

Rhodoxeralfs .... Lithic,

Vertic,

Petrocalcic,

Calcic,

Inceptic,

Typic.

Palexeralfs ........ Vertic,

Aquandic,

Andic,

Vitrandic,

Fragiaquic,

Aquic,

Petrocalcic,

Lamellic,

Psammentic,

Arenic,

Natric,

Fragic,

Calcic,

Plinthic,

Ultic,

Haplic,

Mollic,

Typic.

Haploxeralfs ..... Lithic Mollic,

Lithic RupticInceptic,

Lithic,

Vertic,

Aquandic,

Andic,

Vitrandic,

Fragiaquic,

Aquultic,

Aquic,

Natric,

Fragic,

Lamellic,

Psammentic,

Plinthic,

Calcic,

Inceptic,

Ultic,

Mollic,

Typic.

Udalfs ..........Natrudalfs ......... Vertic,

Glossaquic,

Aquic,

Typic.

Ferrudalfs ......... Aquic,

Typic.

Fraglossudalfs .. Andic,

Vitrandic,

Aquic,

Oxyaquic,

Typic.

Fragiudalfs ....... Andic,

Vitrandic,

Aquic,

Oxyaquic,

Typic.

Kandiudalfs ...... Plinthaquic,

Aquic,

Oxyaquic,

Arenic Plinthic,

Grossarenic

Plinthic,

Arenic,

Grossarenic,

Plinthic,

Rhodic,

Mollic,

Typic.

Kanhapludalfs .. Lithic,

Aquic,

Oxyaquic,

Rhodic,

Typic.

Paleudalfs ......... Vertic,

Andic,

Vitrandic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 133

Fragiaquic,

Plinthaquic,

Glossaquic,

Albaquic,

Aquic,

Anthraquic,

Oxyaquic,

Fragic,

Arenic Plinthic,

Grossarenic

Plinthic,

Lamellic,

Psammentic,

Arenic,

Grossarenic,

Plinthic,

Glossic,

Rhodic,

Mollic,

Typic.

Rhodudalfs ....... Typic.

Glossudalfs ....... Aquertic,

Oxyaquic Vertic,

Vertic,

Aquandic,

Andic,

Vitrandic,

Fragiaquic,

Aquic,

Oxyaquic,

Fragic,

Arenic,

Haplic,

Typic.

Hapludalfs ........ Lithic,

Aquertic

Chromic,

Aquertic,

Oxyaquic Vertic,

Chromic Vertic,

Vertic,

Andic,

Vitrandic,

Fragiaquic,

Fragic Oxyaquic,

Aquic Arenic,

Albaquultic,

Albaquic,

Glossaquic,

Aquultic,

Aquollic,

Aquic,

Anthraquic,

Oxyaquic,

Fragic,

Lamellic,

Psammentic,

Arenic,

Glossic,

Inceptic,

Ultic,

Mollic,

Typic.

Andisols ....... Aquands ......Cryaquands ...... Lithic,

Histic,

Thaptic,

Typic.

Placaquands ..... Lithic,

Duric Histic,

Duric,

Histic,

Thaptic,

Typic.

Duraquands ...... Histic,

Acraquoxic,

Thaptic,

Typic.

Vitraquands ...... Lithic,

Duric,

Histic,

Thaptic,

Typic.

Melanaquands .. Lithic,

Acraquoxic,

Hydric Pachic,

Hydric,

Pachic,

Thaptic,

Typic.

Epiaquands....... Duric,

Histic,

Alic,

Hydric,

Thaptic,

Typic.

Endoaquands.... Lithic,

Duric,

Histic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
134 Soil Taxonomy

Xerands ..... Vitrixerands....... Lithic,

Aquic,

Thaptic,

Alfic Humic,

Ultic,

Alfic,

Humic,

Typic.

Melanoxerands .. Pachic,

Typic.

Haploxerands..... Lithic,

Aquic,

Thaptic,

Calcic,

Ultic,

Alfic Humic,

Alfic,

Humic,

Typic.

Vitrands .... Ustivitrands ....... Lithic,

Aquic,

Thaptic,

Calcic,

Humic,

Typic.

Udivitrands ........ Lithic,

Aquic,

Thaptic,

Ultic,

Alfic,

Humic,

Typic.

Ustands ..... Durustands ........ Aquic,

Thaptic,

Humic,

Typic.

Haplustands ....... Lithic,

Aquic,

Dystric Vitric,

Vitric,

Pachic,

Thaptic,

Calcic,

Dystric,

Oxic,

Ultic,

Alfic,

Humic,

Typic.

Endoaquands

(continued) ..... Alic,

Hydric,

Thaptic,

Typic.

Cryands .......Duricryands ...... Aquic,

Typic.

Hydrocryands .... Lithic,

Placic,

Aquic,

Thaptic,

Typic.

Melanocryands .. Lithic,

Vitric,

Typic.

Fulvicryands ...... Lithic,

Pachic,

Vitric,

Typic.

Vitricryands ....... Lithic,

Aquic,

Oxyaquic,

Thaptic,

Humic Xeric,

Xeric,

Ultic,

Alfic,

Humic,

Typic.

Haplocryands ..... Lithic,

Alic,

Aquic,

Acrudoxic,

Vitric,

Thaptic,

Xeric,

Typic.

Torrands.... Duritorrands ...... Petrocalcic,

Vitric,

Typic.

Vitritorrands...... Lithic,

Duric,

Aquic,

Calcic,

Typic.

Haplotorrands .... Lithic,

Duric,

Calcic,

Typic.

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 135

Udands ...... Placudands ........ Lithic,

Aquic,

Acrudoxic,

Hydric,

Typic.

Durudands ........ Aquic,

Acrudoxic,

Hydric,

Pachic,

Typic.

Melanudands.... Lithic,

Anthraquic,

Aquic,

Acrudoxic Vitric,

Acrudoxic

Hydric,

Acrudoxic,

Pachic Vitric,

Vitric,

Hydric Pachic,

Pachic,

Hydric,

Thaptic,

Ultic,

Eutric,

Typic.

Hydrudands ...... Lithic,

Aquic,

Acrudoxic

Thaptic,

Acrudoxic,

Thaptic,

Eutric,

Ultic,

Typic.

Fulvudands ....... Eutric Lithic,

Lithic,

Aquic,

Hydric,

Acrudoxic,

Ultic,

Eutric Pachic,

Eutric,

Pachic,

Thaptic,

Typic.

Hapludands ...... Lithic,

Anthraquic,

Aquic Duric,

Duric,

Alic,

Aquic,

Acrudoxic

Hydric,

Acrudoxic

Thaptic,

Acrudoxic Ultic,

Acrudoxic,

Vitric,

Hydric Thaptic,

Hydric,

Eutric Thaptic,

Thaptic,

Eutric,

Oxic,

Ultic,

Alfic,

Typic.

Aridisols ...... Cryids ..........Salicryids .......... Aquic,

Typic.

Petrocryids........ Xereptic,

Duric Xeric,

Duric,

Petrogypsic,

Xeric,

Ustic,

Typic.

Gypsicryids....... Calcic,

Vitrixerandic,

Vitrandic,

Typic.

Argicryids......... Lithic,

Vertic,

Natric,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Calcicryids ....... Lithic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Haplocryids ...... Lithic,

Vertic,

Vitrixerandic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
136 Soil Taxonomy

Haplocryids

(continued) ..... Vitrandic,

Xeric,

Ustic,

Typic.

Salids ..........Aquisalids ........ Gypsic,

Calcic,

Typic.

Haplosalids ....... Duric,

Petrogypsic,

Gypsic,

Calcic,

Typic.

Durids .........Natridurids ....... Vertic,

Aquic

Natrargidic,

Aquic,

Natrixeralfic,

Natrargidic,

Vitrixerandic,

Vitrandic,

Xeric,

Typic.

Argidurids ........ Vertic,

Aquic,

Abruptic Xeric,

Abruptic,

Haploxeralfic,

Argidic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Haplodurids ...... Aquicambidic,

Aquic,

Xereptic,

Cambidic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Gypsids .......Petrogypsids ..... Petrocalcic,

Calcic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Natrigypsids ..... Lithic,

Vertic,

Petronodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Argigypsids ...... Lithic,

Vertic,

Calcic,

Petronodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Calcigypsids ..... Lithic,

Petronodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Haplogypsids .... Lithic,

Leptic,

Sodic,

Petronodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Argids .........Petroargids ....... Petrogypsic Ustic,

Petrogypsic,

Duric Xeric,

Duric,

Natric,

Xeric,

Ustic,

Typic.

Natrargids ........ Lithic Xeric,

Lithic Ustic,

Lithic,

Vertic,

Aquic,

Durinodic Xeric,

Durinodic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 137

Petronodic,

Glossic Ustic,

Haplic Ustic,

Haploxeralfic,

Haplic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Glossic,

Typic.

Paleargids ......... Vertic,

Aquic,

Arenic Ustic,

Arenic,

Calcic,

Durinodic Xeric,

Durinodic,

Petronodic Ustic,

Petronodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Gypsiargids ...... Aquic,

Durinodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Calciargids ....... Lithic,

Xerertic,

Ustertic,

Vertic,

Aquic,

Arenic Ustic,

Arenic,

Durinodic Xeric,

Durinodic,

Petronodic Xeric,

Petronodic Ustic,

Petronodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Haplargids ........ Lithic RupticEntic,

Lithic Xeric,

Lithic Ustic,

Lithic,

Xerertic,

Ustertic,

Vertic,

Aquic,

Arenic Ustic,

Arenic,

Durinodic Xeric,

Durinodic,

Petronodic Ustic,

Petronodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Calcids ........Petrocalcids ...... Aquic,

Natric,

Xeralfic,

Ustalfic,

Argic,

Calcic Lithic,

Calcic,

Xeric,

Ustic,

Typic.

Haplocalcids ..... Lithic Xeric,

Lithic Ustic,

Lithic,

Vertic,

Aquic Durinodic,

Aquic,

Duric Xeric,

Duric,

Durinodic Xeric,

Durinodic,

Petronodic Xeric,

Petronodic Ustic,

Petronodic,

Sodic Xeric,

Sodic Ustic,

Sodic,

Vitrixerandic,

Vitrandic,

Xeric,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
138 Soil Taxonomy

Haplocalcids

(continued) ..... Ustic,

Typic.

Cambids ......Aquicambids .... Sodic,

Durinodic Xeric,

Durinodic,

Petronodic,

Vitrixerandic,

Vitrandic,

Fluventic,

Xeric,

Ustic,

Typic.

Petrocambids .... Sodic,

Vitrixerandic,

Vitrandic,

Xeric,

Ustic,

Typic.

Anthracambids .. Typic.

Haplocambids .... Lithic Xeric,

Lithic Ustic,

Lithic,

Xerertic,

Ustertic,

Vertic,

Durinodic Xeric,

Durinodic,

Petronodic Xeric,

Petronodic Ustic,

Petronodic,

Sodic Xeric,

Sodic Ustic,

Sodic,

Vitrixerandic,

Vitrandic,

Xerofluventic,

Ustifluventic,

Fluventic,

Xeric,

Ustic,

Typic.

Entisols ........ Aquents ..... Sulfaquents ........ Haplic,

Histic,

Thapto-Histic,

Typic.

Hydraquents ...... Sulfic,

Sodic,

Thaptic-Histic,

Typic.

Cryaquents......... Aquandic,

Typic.

Psammaquents ... Lithic,

Sodic,

Spodic,

Humaqueptic,

Mollic,

Typic.

Fluvaquents ....... Sulfic,

Vertic,

Thapto-Histic,

Aquandic,

Aeric,

Humaqueptic,

Mollic,

Typic.

Epiaquents ......... Aeric,

Humaqueptic,

Mollic,

Typic.

Endoaquents ..... Sulfic,

Lithic,

Sodic,

Aeric,

Humaqueptic,

Mollic,

Typic.

Arents .........Ustarents .......... Haplic.

Xerarents .......... Sodic,

Duric,

Alfic,

Haplic.

Torriarents........ Sodic,

Duric,

Haplic.

Udarents ........... Alfic,

Ultic,

Mollic,

Haplic.

Psamments ..Cryopsamments ..... Lithic,

Aquic,

Oxyaquic,

Vitrandic,

Spodic,

Lamellic,

Typic.

Subgroup

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group
Nomenclature 139

Torripsamments ..... Lithic,

Vitrandic,

Haploduridic,

Ustic,

Xeric,

Rhodic,

Typic.

Quartzipsamments ..... Lithic,

Aquodic,

Aquic,

Oxyaquic,

Ustoxic,

Udoxic,

Plinthic,

Lamellic Ustic,

Lamellic,

Ustic,

Xeric,

Spodic,

Typic.

Ustipsamments ..... Lithic,

Aquic,

Oxyaquic,

Aridic,

Lamellic,

Rhodic,

Typic.

Xeropsamments ..... Lithic,

Aquic Durinodic,

Aquic,

Oxyaquic,

Vitrandic,

Durinodic,

Lamellic,

Dystric,

Typic.

Udipsamments ..... Lithic,

Aquic,

Oxyaquic,

Spodic,

Lamellic,

Plagganthreptic,

Typic.

Fluvents ......Cryofluvents ..... Andic,

Vitrandic,

Aquic,

Oxyaquic,

Mollic,

Typic.

Xerofluvents ..... Vertic,

Aquandic,

Andic,

Vitrandic,

Aquic,

Oxyaquic,

Durinodic,

Mollic,

Typic.

Ustifluvents ...... Aquertic,

Torrertic,

Vertic,

Anthraquic,

Aquic,

Oxyaquic,

Aridic,

Udic,

Mollic,

Typic.

Torrifluvents ..... Ustertic,

Vertic,

Vitrixerandic,

Vitrandic,

Aquic,

Oxyaquic,

Duric Xeric,

Duric,

Ustic,

Xeric,

Anthropic,

Typic.

Udifluvents ....... Aquertic,

Vertic,

Andic,

Vitrandic,

Aquic,

Oxyaquic,

Mollic,

Typic.

Orthents ......Cryorthents ----- Lithic,

Vitrandic,

Aquic,

Oxyaquic,

Lamellic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
140 Soil Taxonomy

Cryorthents

(continued) ..... Typic.

Torriorthents .... Lithic Ustic,

Lithic Xeric,

Lithic,

Xerertic,

Ustertic,

Vertic,

Vitrandic,

Aquic,

Oxyaquic,

Duric,

Ustic,

Xeric,

Typic.

Xerorthents ...... Lithic,

Vitrandic,

Aquic,

Oxyaquic,

Durinodic,

Dystric,

Typic.

Ustorthents ....... Aridic Lithic,

Lithic,

Torrertic,

Vertic,

Anthraquic,

Aquic,

Oxyaquic,

Durinodic,

Vitritorrandic,

Vitrandic,

Aridic,

Udic,

Vermic,

Typic.

Udorthents ........ Lithic,

Vitrandic,

Aquic,

Oxyaquic,

Vermic,

Typic.

Gelisols ........ Histels .........Folistels ............ Lithic,

Glacic,

Typic.

Glacistels .......... Hemic,

Sapric,

Typic.

Fibristels ........... Lithic,

Terric,

Fluvaquentic,

Sphagnic,

Typic.

Hemistels ........... Lithic,

Terric,

Fluvaquentic,

Typic.

Sapristels ........... Lithic,

Terric,

Fluvaquentic,

Typic.

Turbels ........Histoturbels ....... Lithic,

Glacic,

Ruptic,

Typic.

Aquiturbels ........ Lithic,

Glacic,

Sulfuric,

Ruptic-Histic,

Psammentic,

Typic.

Anhyturbels ....... Lithic,

Glacic,

Petrogypsic,

Gypsic,

Nitric,

Salic,

Calcic,

Typic.

Molliturbels ....... Lithic,

Glacic,

Vertic,

Andic,

Vitrandic,

Cumulic,

Aquic,

Typic.

Umbriturbels ..... Lithic,

Glacic,

Vertic,

Andic,

Vitrandic,

Cumulic,

Aquic,

Typic.

Psammoturbels .. Lithic,

Glacic,

Spodic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 141

Typic.

Haploturbels ..... Lithic,

Glacic,

Aquic,

Typic.

Orthels ........Historthels ........ Lithic,

Glacic,

Ruptic,

Typic.

Aquorthels ........ Lithic,

Glacic,

Sulfuric,

Ruptic-Histic,

Andic,

Vitrandic,

Salic,

Psammentic,

Typic.

Anhyorthels ...... Lithic,

Glacic,

Petrogypsic,

Gypsic,

Nitric,

Salic,

Calcic,

Typic.

Mollorthels ....... Lithic,

Glacic,

Vertic,

Andic,

Vitrandic,

Cumulic,

Aquic,

Typic.

Umbrorthels ..... Lithic,

Glacic,

Vertic,

Andic,

Vitrandic,

Cumulic,

Aquic,

Typic.

Argiorthels ....... Lithic,

Glacic,

Natric,

Typic.

Psammorthels ... Lithic,

Glacic,

Spodic,

Typic.

Haplorthels ....... Lithic,

Glacic,

Aquic,

Typic.

Histosols ...... Folists ..........Cryofolists ........ Lithic,

Typic.

Torrifolists ........ Lithic,

Typic.

Ustifolists ......... Lithic,

Typic.

Udifolists .......... Lithic,

Typic.

Fibrists ........Cryofibrists ....... Hydric,

Lithic,

Terric,

Fluvaquentic,

Sphagnic,

Typic.

Sphagnofibrists............. Hydric,

Lithic,

Limnic,

Terric,

Fluvaquentic,

Hemic,

Typic.

Haplofibrists ..... Hydric,

Lithic,

Limnic,

Terric,

Fluvaquentic,

Hemic,

Typic.

Saprists .......Sulfosaprists ..... Typic.

Sulfisaprists ...... Terric,

Typic.

Cryosaprists ...... Lithic,

Terric,

Fluvaquentic,

Typic.

Haplosaprists .... Lithic,

Limnic,

Halic Terric,

Halic,

Terric,

Fluvaquentic,

Hemic,

Typic.

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
142 Soil Taxonomy

Hemists .......Sulfohemists ..... Typic.

Sulfihemists...... Terric,

Typic.

Luvihemists ...... Typic.

Cryohemists ..... Hydric,

Lithic,

Terric,

Fluvaquentic,

Typic.

Haplohemists .... Hydric,

Lithic,

Limnic,

Terric,

Fluvaquentic,

Fibric,

Sapric,

Typic.

Inceptisols .... Aquepts .......Sulfaquepts ....... Salidic,

Hydraquentic,

Typic.

Petraquepts ....... Histic Placic,

Placic,

Plinthic,

Typic.

Halaquepts ........ Vertic,

Aquandic,

Duric,

Aeric,

Typic.

Fragiaquepts ..... Aeric,

Humic,

Typic.

Cryaquepts ....... Sulfic,

Histic Lithic,

Lithic,

Vertic,

Histic,

Aquandic,

Fluvaquentic,

Aeric Humic,

Aeric,

Humic,

Typic.

Vermaquepts ..... Sodic,

Typic.

Humaquepts ..... Hydraquentic,

Histic,

Aquandic,

Cumulic,

Fluvaquentic,

Aeric,

Typic.

Epiaquepts ........ Vertic,

Aquandic,

Fluvaquentic,

Fragic,

Aeric,

Humic,

Mollic,

Typic.

Endoaquepts ..... Sulfic,

Lithic,

Vertic,

Aquandic,

Fluvaquentic,

Fragic,

Aeric,

Humic,

Mollic,

Typic.

Anthrepts ....Plagganthrepts......... Typic.

Haplanthrepts ... Typic.

Cryepts ........Eutrocryepts ..... Humic Lithic,

Lithic,

Andic,

Vitrandic,

Aquic,

Oxyaquic,

Lamellic,

Xeric,

Ustic,

Humic,

Typic.

Dystrocryepts.... Humic Lithic,

Lithic,

Andic,

Vitrandic,

Aquic,

Oxyaquic,

Lamellic,

Spodic,

Xeric,

Ustic,

Humic,

Typic.

Ustepts ........Durustepts ........ Typic.

Calciustepts ...... Lithic Petrocalcic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 143

Lithic,

Torrertic,

Vertic,

Petrocalcic,

Gypsic,

Aquic,

Aridic,

Udic,

Typic.

Dystrustepts ...... Lithic,

Andic,

Vitrandic,

Aquic,

Fluventic,

Oxic,

Humic,

Typic.

Haplustepts ....... Aridic Lithic,

Lithic,

Udertic,

Torrertic,

Vertic,

Andic,

Vitrandic,

Anthraquic,

Aquic,

Oxyaquic,

Oxic,

Lamellic,

Torrifluventic,

Udifluventic,

Fluventic,

Gypsic,

Haplocalcidic,

Calcic Udic,

Calcic,

Aridic,

Dystric,

Udic,

Typic.

Xerepts ........Durixerepts....... Aquandic,

Andic,

Vitrandic,

Aquic,

Entic,

Typic.

Calcixerepts...... Lithic,

Vertic,

Petrocalcic,

Sodic,

Vitrandic,

Aquic,

Typic.

Fragixerepts ..... Andic,

Vitrandic,

Aquic,

Humic,

Typic.

Dystroxerepts ... Humic Lithic,

Lithic,

Aquandic,

Andic,

Vitrandic,

Fragiaquic,

Fluvaquentic,

Aquic,

Oxyaquic,

Fragic,

Fluventic Humic,

Fluventic,

Humic,

Typic.

Haploxerepts .... Humic Lithic,

Lithic,

Vertic,

Aquandic,

Andic,

Vitrandic,

Gypsic,

Aquic,

Lamellic,

Fragic,

Fluventic,

Calcic,

Humic,

Typic.

Udepts .........Sulfudepts ......... Typic.

Durudepts ......... Aquandic,

Andic,

Vitrandic,

Aquic,

Typic.

Fragiudepts....... Andic,

Vitrandic,

Aquic,

Humic,

Typic.

Eutrudepts ........ Humic Lithic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
144 Soil Taxonomy

Eutrudepts

(continued) ..... Lithic,

Aquertic,

Vertic,

Andic,

Vitrandic,

Anthraquic,

Fragiaquic,

Fluvaquentic,

Aquic Dystric,

Aquic,

Oxyaquic,

Fragic,

Lamellic,

Dystric Fluventic,

Fluventic,

Arenic,

Dystric,

Rendollic,

Humic,

Ruptic-Alfic,

Typic.

Dystrudepts ...... Humic Lithic,

Lithic,

Vertic,

Aquandic,

Andic,

Vitrandic,

Fragiaquic,

Fluvaquentic,

Aquic Humic,

Aquic,

Oxyaquic,

Fragic,

Lamellic,

Humic

Psammentic,

Fluventic Humic,

Fluventic,

Spodic,

Oxic,

Humic Pachic,

Humic,

Ruptic-Alfic,

Ruptic-Ultic,

Typic.

Mollisols ...... Albolls.........Natralbolls ........ Leptic,

Typic.

Argialbolls ........ Xerertic,

Vertic,

Argiaquic Xeric,

Argiaquic,

Xeric,

Aquandic,

Typic.

Aquolls........Cryaquolls ........ Vertic,

Histic,

Thapto-Histic,

Aquandic,

Argic,

Calcic,

Cumulic,

Typic.

Duraquolls ........ Natric,

Vertic,

Argic,

Typic.

Natraquolls ....... Vertic,

Typic.

Calciaquolls...... Petrocalcic,

Aeric,

Typic.

Argiaquolls ....... Arenic,

Grossarenic,

Vertic,

Abruptic,

Typic.

Epiaquolls ........ Cumulic Vertic,

Fluvaquentic

Vertic,

Vertic,

Histic,

Thapto-Histic,

Aquandic,

Duric,

Cumulic,

Fluvaquentic,

Typic.

Endoaquolls ..... Lithic,

Cumulic Vertic,

Fluvaquentic

Vertic,

Vertic,

Histic,

Thapto-Histic,

Aquandic,

Duric,

Cumulic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 145

Fluvaquentic,

Typic.

Rendolls ......Cryrendolls ....... Lithic,

Typic.

Haprendolls ...... Lithic,

Vertic,

Inceptic,

Entic,

Typic.

Cryolls.........Duricryolls ....... Argic,

Typic.

Natricryolls ...... Typic.

Palecryrolls....... Aquic,

Oxyaquic,

Abruptic,

Pachic,

Ustic,

Xeric,

Typic.

Argicryolls........ Lithic,

Vertic,

Andic,

Vitrandic,

Abruptic,

Aquic,

Oxyaquic,

Pachic,

Alfic,

Ustic,

Xeric,

Typic.

Calcicryolls ...... Lithic,

Petrocalcic,

Pachic,

Ustic,

Xeric,

Typic.

Haplocryolls ..... Lithic,

Vertic,

Andic,

Vitrandic,

Aquic Cumulic,

Cumulic,

Fluvaquentic,

Aquic,

Oxyaquic,

Calcic Pachic,

Pachic,

Fluventic,

Calcic,

Ustic,

Xeric,

Typic.

Xerolls ........Durixerolls ....... Vertic,

Vitritorrandic,

Vitrandic,

Aquic,

Paleargidic,

Abruptic

Argiduridic,

Cambidic,

Haploduridic,

Argidic,

Argiduridic,

Haplic

Palexerollic,

Palexerollic,

Haplic

Haploxerollic,

Haploxerollic,

Haplic,

Typic.

Natrixerolls ...... Vertic,

Aquic Duric,

Aquic,

Aridic,

Duric,

Typic.

Palexerolls ........ Vertic,

Vitrandic,

Aquic,

Pachic,

Petrocalcidic,

Duric,

Aridic,

Petrocalcic,

Ultic,

Haplic,

Typic.

Calcixerolls ...... Lithic,

Vertic,

Aquic,

Oxyaquic,

Pachic,

Vitrandic,

Aridic,

Vermic,

Typic.

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
146 Soil Taxonomy

Argixerolls ....... Lithic Ultic,

Lithic,

Torrertic,

Vertic,

Andic,

Vitritorrandic,

Vitrandic,

Aquultic,

Aquic,

Oxyaquic,

Alfic,

Calcic Pachic,

Pachic Ultic,

Pachic,

Argiduridic,

Duric,

Calciargidic,

Aridic,

Calcic,

Ultic,

Typic.

Haploxerolls ..... Lithic Ultic,

Lithic,

Torrertic,

Vertic,

Vitritorrandic,

Vitrandic,

Aquic Cumulic,

Cumulic Ultic,

Cumulic,

Fluvaquentic,

Aquic Duric,

Aquultic,

Aquic,

Oxyaquic,

Calcic Pachic,

Pachic Ultic,

Pachic,

Torrifluventic,

Duridic,

Calcidic,

Torripsammentic,

Torriorthentic,

Aridic,

Duric,

Psammentic,

Fluventic,

Vermic,

Calcic,

Entic Ultic,

Ultic,

Entic,

Typic.

Ustolls .........Durustolls ......... Natric,

Haploduridic,

Argiduridic,

Entic,

Haplic,

Typic.

Natrustolls ........ Leptic Torrertic,

Torrertic,

Leptic Vertic,

Glossic Vertic,

Vertic,

Aridic Leptic,

Leptic,

Aquic,

Aridic,

Duric,

Glossic,

Typic.

Calciustolls ....... Salidic,

Lithic

Petrocalcic,

Lithic,

Torrertic,

Udertic,

Vertic,

Petrocalcic,

Gypsic,

Pachic,

Aquic,

Oxyaquic,

Aridic,

Udic,

Typic.

Paleustolls ........ Torrertic,

Udertic,

Vertic,

Pachic,

Aquic,

Petrocalcic,

Calcidic,

Aridic,

Udic,

Calcic,

Entic,

Typic.

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 147

Argiustolls ........ Aridic Lithic,

Alfic Lithic,

Lithic,

Torrertic,

Udertic,

Vertic,

Andic,

Vitritorrandic,

Vitrandic,

Pachic,

Aquic,

Oxyaquic,

Alfic,

Calcidic,

Aridic,

Udic,

Duric,

Typic.

Vermustolls ...... Lithic,

Aquic,

Pachic,

Entic,

Typic.

Haplustolls ....... Salidic,

Ruptic-Lithic,

Lithic,

Torrertic,

Pachic Udertic,

Udertic,

Vertic,

Torroxic,

Oxic,

Andic,

Vitritorrandic,

Vitrandic,

Aquic Cumulic,

Cumulic,

Anthraquic,

Fluvaquentic,

Pachic,

Aquic,

Oxyaquic,

Torrifluventic,

Torriorthentic,

Aridic,

Fluventic,

Duric,

Udorthentic,

Udic,

Entic,

Typic.

Udolls ..........Natrudolls......... Petrocalcic,

Leptic Vertic,

Glossic Vertic,

Vertic,

Leptic,

Glossic,

Calcic,

Typic.

Calciudolls ....... Lithic,

Vertic,

Aquic,

Fluventic,

Typic.

Paleudolls ......... Vertic,

Petrocalcic,

Aquic,

Pachic,

Oxyaquic,

Calcic,

Typic.

Argiudolls ........ Lithic,

Aquertic,

Oxyaquic Vertic,

Pachic Vertic,

Alfic Vertic,

Vertic,

Andic,

Vitrandic,

Aquic,

Pachic,

Oxyaquic,

Lamellic,

Psammentic,

Arenic,

Abruptic,

Alfic,

Oxic,

Calcic,

Typic.

Vermudolls ....... Lithic,

Haplic,

Typic.

Hapludolls ........ Lithic,

Aquertic,

Vertic,

Andic,

Vitrandic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
148 Soil Taxonomy

Hapludolls

(continued) ..... Aquic Cumulic,

Cumulic,

Fluvaquentic,

Aquic,

Pachic,

Oxyaquic,

Fluventic,

Vermic,

Calcic,

Entic,

Typic.

Oxisols ......... Aquox .........Acraquox .......... Plinthic,

Aeric,

Typic.

Plinthaquox ...... Aeric,

Typic.

Eutraquox ......... Histic,

Plinthic,

Aeric,

Humic,

Typic.

Haplaquox ........ Histic,

Plinthic,

Aeric,

Humic,

Typic.

Torrox .........Acrotorrox ........ Petroferric,

Lithic,

Typic.

Eutrotorrox ....... Petroferric,

Lithic,

Typic.

Haplotorrox ...... Petroferric,

Lithic,

Typic.

Ustox ...........Sombriustox ..... Petroferric,

Lithic,

Humic,

Typic.

Acrustox ........... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Anionic Aquic,

Anionic,

Plinthic,

Aquic,

Eutric,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Eutrustox .......... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aquic,

Kandiustalfic,

Humic Inceptic,

Inceptic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Kandiustox ....... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aquic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Haplustox ......... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aqueptic,

Aquic,

Oxyaquic,

Inceptic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 149

Xanthic,

Typic.

Perox ...........Sombriperox ..... Petroferric,

Lithic,

Humic,

Typic.

Acroperox ......... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Anionic,

Plinthic,

Aquic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Eutroperox........ Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aquic,

Kandiudalfic,

Humic Inceptic,

Inceptic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Kandiperox....... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aquic,

Andic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Haploperox ....... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aquic,

Andic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Udox............Sombriudox ...... Petroferric,

Lithic,

Humic,

Typic.

Acrudox ............ Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Anionic Aquic,

Anionic,

Plinthic,

Aquic,

Eutric,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Eutrudox........... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aquic,

Kandiudalfic,

Humic Inceptic,

Inceptic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
150 Soil Taxonomy

Kandiudox ........ Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aquic,

Andic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Hapludox .......... Aquic Petroferric,

Petroferric,

Aquic Lithic,

Lithic,

Plinthaquic,

Plinthic,

Aquic,

Inceptic,

Andic,

Humic Rhodic,

Humic Xanthic,

Humic,

Rhodic,

Xanthic,

Typic.

Spodosols ..... Aquods ........Cryaquods ........ Lithic,

Placic,

Duric,

Andic,

Entic,

Typic.

Alaquods .......... Lithic,

Duric,

Histic,

Alfic Arenic,

Arenic Ultic,

Arenic Umbric,

Arenic,

Grossarenic,

Alfic,

Ultic,

Aeric,

Typic.

Fragiaquods ...... Histic,

Plagganthreptic,

Argic,

Typic.

Placaquods ....... Andic,

Typic.

Duraquods ........ Histic,

Andic,

Typic.

Epiaquods ......... Lithic,

Histic,

Andic,

Alfic,

Ultic,

Umbric,

Typic.

Endoaquods ...... Lithic,

Histic,

Andic,

Argic,

Umbric,

Typic.

Cryods .........Placocryods ...... Andic,

Humic,

Typic.

Duricryods ........ Aquandic,

Andic,

Aquic,

Oxyaquic,

Humic,

Typic.

Humicryods ...... Lithic,

Aquandic,

Andic,

Aquic,

Oxyaquic,

Typic.

Haplocryods...... Lithic,

Aquandic,

Andic,

Aquic,

Oxyaquic,

Entic,

Typic.

Humods .......Placohumods .... Andic,

Typic.

Durihumods ..... Andic,

Typic.

Fragihumods .... Typic.

Haplohumods ... Lithic,

Andic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
Nomenclature 151

Plagganthreptic,

Typic.

Orthods .......Placorthods ....... Typic.

Durorthods ....... Andic,

Typic.

Fragiorthods ..... Aquic,

Alfic Oxyaquic,

Oxyaquic,

Plagganthreptic,

Alfic,

Ultic,

Entic,

Typic.

Alorthods.......... Oxyaquic,

Arenic Ultic,

Arenic,

Entic

Grossarenic,

Entic,

Grossarenic,

Plagganthreptic,

Alfic,

Ultic,

Typic.

Haplorthods ...... Entic Lithic,

Lithic,

Fragiaquic,

Aqualfic,

Aquentic,

Aquic,

Alfic Oxyaquic,

Oxyaquic Ultic,

Fragic,

Lamellic,

Oxyaquic,

Andic,

Alfic,

Ultic,

Entic,

Typic.

Ultisols ......... Aquults .......Plinthaquults .... Kandic,

Typic.

Fragiaquults ..... Aeric,

Plinthic,

Umbric,

Typic.

Albaquults ........ Vertic,

Kandic,

Aeric,

Typic.

Kandiaquults .... Acraquoxic,

Arenic Plinthic,

Arenic Umbric,

Arenic,

Grossarenic,

Plinthic,

Aeric,

Umbric,

Typic.

Kanhaplaquults ............ Aquandic,

Plinthic,

Aeric Umbric,

Aeric,

Umbric,

Typic.

Paleaquults ....... Vertic,

Arenic Plinthic,

Arenic Umbric,

Arenic,

Grossarenic,

Plinthic,

Aeric,

Umbric,

Typic.

Umbraquults ..... Plinthic,

Typic.

Epiaquults ........ Vertic,

Aeric Fragic,

Arenic,

Grossarenic,

Fragic,

Aeric,

Typic.

Endoaquults ..... Arenic,

Grossarenic,

Aeric,

Typic.

Humults ......Sombrihumults........... Typic.

Plinthohumults........... Typic.

Kandihumults... Andic

Ombroaquic,

Ustandic,

Andic,

Aquic,

Ombroaquic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup
152 Soil Taxonomy

Kandihumults

(continued) ..... Plinthic,

Ustic,

Xeric,

Anthropic,

Typic.

Kanhaplohumults........... Lithic,

Ustandic,

Andic,

Aquic,

Ombroaquic,

Ustic,

Xeric,

Anthropic,

Typic.

Palehumults ...... Aquandic,

Andic,

Aquic,

Plinthic,

Oxyaquic,

Ustic,

Xeric,

Typic.

Haplohumults ... Lithic,

Aquandic,

Aquic,

Andic,

Plinthic,

Oxyaquic,

Ustic,

Xeric,

Typic.

Udults ..........Plinthudults...... Typic.

Fragiudults ....... Arenic,

Plinthaquic,

Glossaquic,

Aquic,

Plinthic,

Glossic,

Humic,

Typic.

Kandiudults ...... Arenic

Plinthaquic,

Aquic Arenic,

Arenic Plinthic,

Arenic Rhodic,

Arenic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup

Grossarenic

Plinthic,

Grossarenic,

Acrudoxic

Plinthic,

Acrudoxic,

Plinthaquic,

Aquandic,

Andic,

Aquic,

Plinthic,

Ombroaquic,

Oxyaquic,

Sombric,

Rhodic,

Typic.

Kanhapludults .. Lithic,

Plinthaquic,

Arenic Plinthic,

Arenic,

Acrudoxic,

Fragiaquic,

Andic,

Aquic,

Ombroaquic,

Oxyaquic,

Plinthic,

Fragic,

Rhodic,

Typic.

Paleudults ......... Vertic,

Spodic,

Arenic

Plinthaquic,

Aquic Arenic,

Plinthaquic,

Fragiaquic,

Aquic,

Anthraquic,

Oxyaquic,

Lamellic,

Arenic Plinthic,

Psammentic,

Grossarenic

Plinthic,

Plinthic,

Arenic Rhodic,

Arenic,
Nomenclature 153

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup

Grossarenic,

Fragic,

Rhodic,

Typic.

Rhodudults ....... Lithic,

Psammentic,

Typic.

Hapludults ........ Lithic RupticEntic,

Lithic,

Vertic,

Fragiaquic,

Aquic Arenic,

Aquic,

Fragic,

Oxyaquic,

Lamellic,

Psammentic,

Arenic,

Grossarenic,

Inceptic,

Humic,

Typic.

Ustults .........Plinthustults ..... Haplic,

Typic.

Kandiustults ..... Acrustoxic,

Aquic,

Arenic Plinthic,

Arenic,

Udandic,

Andic,

Plinthic,

Aridic,

Udic,

Rhodic,

Typic.

Kanhaplustults ............. Lithic,

Acrustoxic,

Aquic,

Arenic,

Udandic,

Andic,

Plinthic,

Ombroaquic,

Aridic,

Udic,

Rhodic,

Typic.

Paleustults ........ Typic.

Rhodustults ...... Lithic,

Psammentic,

Typic.

Haplustults ....... Lithic,

Petroferric,

Aquic,

Arenic,

Ombroaquic,

Plinthic,

Kanhaplic,

Typic.

Xerults ........Palexerults ........ Aquandic,

Aquic,

Andic,

Typic.

Haploxerults ..... Lithic RupticInceptic,

Lithic,

Aquic,

Andic,

Lamellic,

Psammentic,

Arenic,

Grossarenic,

Typic.

Vertisols ....... Aquerts........Salaquerts ......... Aridic,

Ustic,

Leptic,

Entic,

Chromic,

Typic.

Duraquerts ........ Aridic,

Xeric,

Ustic,

Aeric,

Chromic,

Typic.

Natraquerts ....... Typic.

Calciaquerts ..... Aeric,

Typic.

Dystraquerts ..... Sulfaqueptic,

Aridic,

Ustic,

Aeric,

Leptic,

Entic,

Chromic,

Typic.
154 Soil Taxonomy

Epiaquerts ........ Halic,

Sodic,

Aridic,

Xeric,

Ustic,

Aeric,

Leptic,

Entic,

Chromic,

Typic.

Endoaquerts ..... Halic,

Sodic,

Aridic,

Xeric,

Ustic,

Aeric,

Leptic,

Entic,

Chromic,

Typic.

Cryerts ........Humicryerts ...... Sodic,

Typic.

Haplocryerts ..... Sodic,

Chromic,

Typic.

Xererts ........Durixererts ....... Halic,

Sodic,

Aquic,

Aridic,

Udic,

Haplic,

Chromic,

Typic.

Calcixererts ...... Lithic,

Petrocalcic,

Aridic,

Leptic,

Entic,

Chromic,

Typic.

Haploxererts ..... Lithic,

Halic,

Sodic,

Aridic,

Aquic,

Udic,

Leptic,

Entic,

Chromic,

Names of Orders, Suborders, Great Groups, and Subgroups--Continued

Order Suborder Great Group Subgroup Order Suborder Great Group Subgroup

Typic.

Torrerts .......Salitorrerts........ Aquic,

Leptic,

Entic,

Chromic,

Typic.

Gypsitorrerts .... Chromic,

Typic.

Calcitorrerts ..... Petrocalcic,

Leptic,

Entic,

Chromic,

Typic.

Haplotorrerts .... Halic,

Sodic,

Leptic,

Entic,

Chromic,

Typic.

Usterts .........Dystrusterts ...... Lithic,

Aquic,

Aridic,

Udic,

Leptic,

Entic,

Chromic,

Typic.

Salusterts .......... Lithic,

Sodic,

Aquic,

Aridic,

Leptic,

Entic,

Chromic,

Typic.

Gypsiusterts ...... Lithic,

Halic,

Sodic,

Aridic,

Udic,

Leptic,

Entic,

Chromic,

Typic.

Calciusterts....... Lithic,

Halic,

Sodic,

Petrocalcic,

Aridic,
Nomenclature 155

Names of Orders, Suborders, Great Groups,

and Subgroups--Continued

Order Suborder Great Group Subgroup

subgroup. Using an adjective taken from the suborder (“Udic”)

would not suggest that the difference is one of aeration alone.

If the only aberrant feature of a Hapludult is redoximorphic

features that are too shallow for a Typic Hapludult, the

adjective Aquic is used in the subgroup name. If redox

depletions (accompanied by aquic conditions unless the soils

are artificially drained) appear within the upper 60 cm of the

argillic horizon, the soil is called an Aquic Hapludult, not an

Aquultic Hapludult.

In other instances, the adjective in the subgroup name is

made from the first two formative elements of the appropriate

Udic,

Leptic,

Entic,

Chromic,

Typic.

Haplusterts ....... Lithic,

Halic,

Sodic,

Petrocalcic,

Gypsic,

Calcic,

Aridic Leptic,

Aridic,

Leptic Udic,

Entic Udic,

Chromic Udic,

Udic,

Leptic,

Entic,

Chromic,

Typic.

Uderts ..........Dystruderts ....... Aquic,

Oxyaquic,

Leptic,

Entic,

Chromic,

Typic.

Hapluderts ........ Lithic,

Aquic,

Oxyaquic,

Leptic,

Entic,

Chromic,

Typic.

great group name in that suborder. For example, if a Paleudult

has both shallow redoximorphic features and some plinthite, it

is called a Plinthaquic Paleudult, not a Plinthaquultic

Paleudult. Note that the formative element for the order is not

repeated in the adjective if the two great groups are in the same

order.

Names of Intergrades Toward Great Groups in Other

Orders

If a Hapludalf has a surface horizon that is too dark for a

Typic subgroup and approaches the properties of the surface

horizons of Mollisols, the soil is considered to intergrade to

one of the great groups of Mollisols. If the only aberrant feature

is the nature of the surface horizon, the soil is called a Mollic

Hapludalf. This soil has the feature that is common to all

Mollisols, and only the prior formative element of the order

name is used. If, in addition, the soil has gray redox depletions

in the upper part of the argillic horizon, it is considered an

intergrade toward Aquolls and is called an Aquollic Hapludalf.

Note that this name is simpler than “Aquic Mollic Hapludalf.”

The general rule is that the simplest possible name is used. If

there are several aberrant features, the adjectival forms of one

or more great group names may be required. An exception is

the adjective Argic when used in great groups of Aquods.

Rather than intergrading to one specific taxon, Argic

subgroups intergrade to orders that have argillic horizons,

specifically Alfisols and Ultisols.

Names of Subgroups not Intergrading Toward Any Known

Kind of Soil (Extragrades)

Some soils have aberrant properties that are not

characteristic of a class in a higher category of any order,

suborder, or great group. One example might be taken from the

concave pedons that are at the base of slopes, in depressions, or

in other areas where new soil material accumulates slowly on

the surface. In these soils material is added to the A horizon.

The presence of an overthickened A horizon is not used to

define any great group, but the soils lie outside the range of the

Typic subgroup and there is no class toward which they

intergrade. Hence, a descriptive adjective is required. For this

particular situation, the adjective Cumulic (L. cumulus, heap,

plus ic, Gr. ikos) is used to form the subgroup names. Pachic is

used to indicate an overthickened epipedon if there is no

evidence of new material at the surface.

Other soils lie outside the range of Typic subgroups in an

opposite direction. Such soils are, in effect, truncated by hard

rock and are shallow or are intermittent between rock outcrops.

They are, in effect, intergrades to nonsoil and are called Lithic

subgroups. The names of formative elements in groups of this

sort, which are called extragrades, are listed together with their

derivation in the table “Adjectives in Names of Extragrades and

Their Meaning.”
156 Soil Taxonomy

Adjectives in Names of Extragrades and Their Meaning

Adjective Derivation Connotation

Abruptic ................... L. abruptus, torn off ......................................................... Abrupt textural change.

Aeric1 ....................... Gr. aerios, air .................................................................. Aeration.

Albic ........................ L. albus, white ................................................................. Presence of an albic horizon.

Alic .......................... Modified from aluminum ................................................ High Al3+ status.

Anionic .................... Gr. anion .......................................................................... Positively charged colloid.

Anthraquic ............... Modified from Gr. anthropos, human, and

L. aqua, water ................................................................ Controlled flooding.

Anthropic................. Modified from Gr. anthropos, human ............................. An anthropic epipedon.

Arenic ...................... L. arena, sand .................................................................. Sandy material between 50 and 100 cm thick.

Calcic ....................... L. calis, lime .................................................................... Presence of a calcic horizon.

Chromic ................... Gr. chroma, color ............................................................. High chroma.

Cumulic ................... L. cumulus, heap.............................................................. Thickened epipedon.

Durinodic ................. L. durus, hard .................................................................. Presence of durinodes.

Eutric ....................... Modified from Gr. eu, good; eutrophic, fertile ............... High base status.

Fragic ....................... Modified from L. fragilis, brittle .................................... Presence of fragic properties.

Glacic ....................... L. glacialis, icy ................................................................ Presence of ice lenses or wedges.

Glossic ..................... Gr. glossa, tongue ............................................................ Tongued horizon boundaries.

Grossarenic .............. L. grossus, thick, and L. arena, sand .............................. Thick sandy layer.

Gypsic ...................... L. gypsum, gypsum .......................................................... Presence of a gypsic horizon.

Halic ........................ Gr. hals, salt..................................................................... Salty.

Humic ...................... L. humus, earth ................................................................ Presence of organic matter.

Hydric ...................... Gr. hydor, water ............................................................... Presence of water.

Kandic ..................... Modified from kandite..................................................... Presence of 1:1 layer silicate clays.

Lamellic ................... L. lamella, dim ................................................................ Presence of lamellae.

Leptic ....................... Gr. leptos, thin ................................................................. A thin soil.

Limnic ..................... Modified from Gr. limn, lake .......................................... Presence of a limnic layer.

Lithic ....................... Gr. lithos, stone ............................................................... Presence of a shallow lithic contact.

Natric ....................... Modified from natrium, sodium ...................................... Presence of sodium.

Nitric ........................ Modified from nitron ....................................................... Presence of nitrate salts.

Ombroaquic ............. Gr. ombros, rain, and aquic ............................................. Surface wetness.

Oxyaquic .................. Oxy, representing oxygen, and aquic .............................. Aerated.

Pachic ...................... Gr. pachys, thick.............................................................. A thick epipedon.

Petrocalcic ............... Gr. petra, rock, and calcic from calcium ........................ Presence of a petrocalcic horizon.

Petroferric ................ Gr. petra, rock, and L. ferrum, iron ................................ Presence of a petroferric contact (ironstone).

Petrogypsic .............. Gr. petra, rock, and L. gypsum, gypsum ......................... Presence of a petrogypsic horizon.

Petronodic ................ Modified from petra, rock, and nodulus, a little knot .... Presence of concretions and/or nodules.

Placic ....................... Gr. base of plax, flat stone ............................................... Presence of a thin pan (placic horizon).

Plinthic .................... Modified from Gr. plinthos, brick ................................... Presence of plinthite.

Rhodic...................... Gr. base of rhodon, rose .................................................. Dark red color.

Ruptic1 ..................... L. ruptum, broken ............................................................ Intermittent or broken horizons.

Sodic ........................ Modified from sodium ..................................................... Presence of sodium salts.

Sombric.................... F. sombre, dark ................................................................ Presence of a sombric horizon.

Sulfic........................ L. sulfur, sulfur ................................................................ Presence of sulfides or their oxidation products.

Terric ....................... L. terra, earth .................................................................. A mineral substratum.

Thapto(ic)1 ............... Gr. thapto, buried ............................................................ A buried soil.

Umbric ..................... L. base of umbra, shade ................................................... Presence of an umbric epipedon.

Xanthic .................... Gr. xanthos ...................................................................... Yellow.

1 Not strictly an extragrade. Name used to indicate a special departure from the Typic subgroup.
Nomenclature 157

Names of Multiple Subgroups Intergrading Between Two Given

Great Groups

Two or more subgroups in a given great group may be

intergrades to the same class of soil or even to nonsoil. In one

area, for example, the horizons may be continuous; in another,

discontinuous; and in a third, buried. Also, the properties of

two classes may be mixed in a single horizon in one area but

may be in separate horizons in another area. A soil of class X

may be developing from or toward class Y, producing subgroups

that have different properties.

If the intergrade is one in which horizons are intermittent,

the adjective Ruptic (L. ruptum, broken) is used in the

subgroup name. The substantive in the name is the one for the

kind of soil having the greatest area in the pedon; the

adjectives are formed from the names of the kinds that have the

lesser area, preceded by the adjective Ruptic and connected by

hyphens. Thus, if X is dominant and Y is minor, the soil is

named Ruptic-Yic X. For example, Ruptic-Lithic Haplustolls

have a lithic contact only in part of each pedon. If the entire

pedon were lithic and the argillic horizon of the Haploxerult

were intermittent, the name would be Lithic Ruptic-Inceptic

Haploxerults. The general rule is that modifiers are hyphenated

if they apply to only part of the pedon. No hyphens are used if

the modifier applies to the entire pedon.

If the subgroup is one in which a buried soil is an important

part of the present soil, the name includes Thapto (Gr. thapto,

buried) as a modifier of the name of the buried soil. Hyphens

are used to connect Thapto with the name of the buried soil,

except in the order Andisols, where the name of the buried soil

is omitted. In Thaptic subgroups of Andisols, the buried soil is

normally an Andisol. Thus, soil X that includes a buried soil,

Y, is called Thapto-Yic X. A Humaquept that has a histic

epipedon is called a Histic Humaquept, but a Fluvaquent in

which a Histosol or Histic epipedon has been buried is called a

Thapto-Histic Fluvaquent.

Arrangement of modifiers.—Modifiers are arranged

alphabetically, for example, Aquic Arenic Hapludults.

Names of Families

Each family requires one or more names. The technical

family name consists of a series of descriptive terms modifying

the subgroup name. For these terms we take the class names

that are given in chapter 21 for particle-size class, mineralogy,

and so on, in family differentiae. The descriptive terms in the

names of families are given in a consistent order, which is as

follows: particle-size class, mineralogy class, cation-exchange

activity class, calcareous and reaction class, soil temperature

class, soil depth class, rupture resistance class, classes of

coatings, and classes of cracks.

Redundancy in the names of families should be avoided.

Particle-size class and temperature classes should not be used

in the family name if they are specified above the family level.

Psamments, by definition, all have a sand or loamy sand texture

and are in a sandy particle-size class, unless they are ashy. It is

therefore redundant to specify a particle-size class for

Psamments, unless they are ashy.

Rules of Nomenclature

For uniformity, certain rules are followed.

First, the names are considered to be modern vernacular

nouns. They are treated as masculine nouns in languages that

have grammatical gender. While only the names of the orders

have a suffix meaning “soil,” this meaning is understood to be

included in all names. Thus, the names are not to be converted

to adjectives that modify the word “soil.” The prior (first)

formative elements of the names of suborders and great groups

can be converted to adjectives that modify the name of the

category. Thus, one may speak of Aquic great groups, referring

to all taxa of that rank with names that include the formative

element aqu.

Second, plural forms of the nouns conform to the rules of

the language in which the names are used. If a final vowel or

suffix allows the name to fit better into a particular language, it

can be added as needed.

Third, adjectives are formed by adding the suffix ikos (Gr.),

shortened or adapted to the modern vernaculars according to

the rules of the language used. For example, in English the

ending is ic; in French, ique; and in German, isch. Adjectival

forms are placed in the position that is normal for the language

in which they are used.

Fourth, the names of the orders, suborders, and great groups

are treated as proper nouns, and the first letter is capitalized.

The adjectival forms of these names may be capitalized or not,

depending on the conventions of printing in the language in

which they are used. In the United States, each word in a

subgroup name is capitalized.

Fifth, pronunciation of the names follows the rules of the

modern vernacular in the language in which the words are

used.

Use of Single Formative Elements

The names in the tables “Formative Elements in Names of Soil

Orders,” “Formative Elements in Names of Suborders,” and

“Formative Elements in Names of Great Groups” are not the only

possible names or uses of the formative elements. There is

considerable repetition in the use of a number of formative

elements. Aqu, for example, is the prior (first) formative element

in the names of nine suborders. In this position, it implies that

the soils are completely saturated with water at some season and

that they show the effects of permanent or periodic reduction of

iron to the ferrous state. If one wishes to specify all mineral soils

that are permanently or periodically wet, one may use the

appropriate formative element to modify the name of a category
158

and speak of Aquic suborders or Aquic great groups. Such a

use of Aquic is equivalent to creating an order with all these

suborders.

It is necessary, however, to specify the categoric level of the

taxa. Aquic also is used to define subgroups of soils that are not

in Aquic suborders but that have shallow ground water at some

period and have the required redox criteria at a depth generally

of more than 50 cm. Aquic subgroups are not so wet as Aquic

suborders. One should not speak of aquic soils if one means

Aquic suborders or Aquic subgroups.

If it serves one’s purpose, many formative elements that are

repeated in the names of taxa can be used to alter the hierarchy

for the moment and to call to mind all the soils with the

property one wishes to consider. The soils in the Cryic suborder

and Gelisol order bring together all the cold soils. Calcic great

groups bring together all the soils that have a horizon of

appreciable accumulation of carbonates, and so on. The

nomenclature permits a flexible classification in which

emphasis can be shifted as needed to any of a number of

important properties that are subordinated in the arrangement

shown in the table “Names of Orders, Suborders, Great

Groups, and Subgroups.”

Literature Cited

Heller, J.L. 1963. The Nomenclature of Soils or What’s in a

Name? Soil Sci. Soc. Amer. Proc. 27: 216-220.
159

The taxonomic class of a specific soil can be determinedby using the keys that follow in this and other chapters.

It is assumed that the reader is familiar with the definitions of

diagnostic horizons and properties that are given in chapters 3

and 4 of this publication and with the meanings of the terms

used for describing soils given in the Soil Survey Manual. The

Index at the back of this publication indicates the pages on

which definitions of terms are given.

Standard rounding conventions should be used to determine

numerical values.

Soil colors (hue, value, and chroma) are used in many of

the criteria that follow. Soil colors typically change value and

some change hue and chroma, depending on the water state.

In many of the criteria of the keys, the water state is specified.

If no water state is specified, the soil is considered to meet

the criterion if it does so when moist or dry or both moist and

dry.

All of the keys in this taxonomy are designed in such a way

that the user can determine the correct classification of a soil

by going through the keys systematically. The user must start at

the beginning of the “Key to Soil Orders” and eliminate, one

by one, all classes that include criteria that do not fit the soil in

question. The soil belongs to the first class listed for which it

meets all the required criteria.

In classifying a specific soil, the user of soil taxonomy

begins by checking through the “Key to Soil Orders” to

determine the name of the first order that, according to the

criteria listed, includes the soil in question. The next step is

to go to the page indicated to find the “Key to Suborders” of

that particular order. Then the user systematically goes through

the key to identify the suborder that includes the soil, i.e., the

first in the list for which it meets all the required criteria. The

same procedure is used to find the great group class of the soil

in the “Key to Great Groups” of the identified suborder.

Likewise, going through the “Key to Subgroups” of that great

group, the user selects as the correct subgroup name the name

of the first taxon for which the soil meets all of the required

criteria.

The family level is determined, in a similar manner, after

the subgroup has been determined. Chapter 21 can be used, as

one would use other keys in this taxonomy, to determine which

components are part of the family. The family, however,

typically has more than one component, and therefore the entire

chapter must be used. The keys to control sections for classes

used as components of a family must be used to determine the

control section before use of the keys to classes.

The descriptions and definitions of individual soil series are

not included in this text. Definitions of the series and of the

control section and examples of the application are given in

chapter 21. The classification of the series and the list of

families and their included series for the soils of the 50 States,

Puerto Rico, and the Virgin Islands are given in another

publication (Soil Series of the United States, Including Puerto

Rico and the Virgin Islands: Their Taxonomic Classification).

That publication does not include the descriptions or

definitions of the series, but descriptions of specific series are

available on request from the Natural Resources Conservation

Service. No one publication includes descriptions of all the

series.

In the “Key to Soil Orders” and the other keys that follow,

the diagnostic horizons and the properties mentioned do not

include those below any densic, lithic, paralithic, or petroferric

contact. The properties of buried soils and the properties of a

surface mantle are considered on the basis of whether or not

the soil meets the meaning of the term “buried soil” given in

chapter 1.

If a soil has a surface mantle and is not a buried soil, the top

of the original surface layer is considered the “soil surface” for

determining depth to and thickness of diagnostic horizons and

most other diagnostic soil characteristics. The only properties

of the surface mantle that are considered are soil temperature,

soil moisture (including aquic conditions), any andic or vitrandic

properties, and family criteria.

If a soil profile includes a buried soil, the present soil

surface is used to determine soil moisture and temperature as

well as depth to and thickness of diagnostic horizons and other

diagnostic soil characteristics. Diagnostic horizons of the

buried soil are not considered in selecting taxa unless the

criteria in the keys specifically indicate buried horizons, such

as in Thapto-Histic subgroups. Most other diagnostic soil

characteristics of the buried soil are not considered, but organic

carbon if of Holocene age, andic soil properties, base

saturation, and all properties used to determine family and

series placement are considered.

CHAPTER 8

Identification of the Taxonomic Class of a Soil
160 Soil Taxonomy

Key to Soil Orders

A. Soils that have:

1. Permafrost within 100 cm of the soil surface; or

2. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface.

Gelisols, p. 445

B. Other soils that:

1. Do not have andic soil properties in 60 percent or more

of the thickness between the soil surface and either a depth

of 60 cm or a densic, lithic, or paralithic contact or duripan

if shallower; and

2. Have organic soil materials that meet one or more of

the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices1 and directly below these

materials, have a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery,

fragmental, or pumiceous materials, total 40 cm or more

between the soil surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness

of the soil to a densic, lithic, or paralithic contact and

have no mineral horizons or have mineral horizons with

a total thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more per

year in normal years (or are artificially drained), have an

upper boundary within 40 cm of the soil surface, and

have a total thickness of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk

density, moist, of 0.1 g/cm3 or more.

Histosols, p. 473

C. Other soils that do not have a plaggen epipedon or an

argillic or kandic horizon above a spodic horizon, and have

one or more of the following:

1. A spodic horizon, an albic horizon in 50 percent or

more of each pedon, and a cryic soil temperature regime;

or

2. An Ap horizon containing 85 percent or more spodic

materials; or

3. A spodic horizon with all of the following

characteristics:

a. One or more of the following:

(1) A thickness of 10 cm or more; or

(2) An overlying Ap horizon; or

(3) Cementation in 50 percent or more of each

pedon; or

(4) A coarse-loamy, loamy-skeletal, or finer particlesize class and a frigid temperature regime in the soil;

or

(5) A cryic temperature regime in the soil; and

b. An upper boundary within the following depths from

the mineral soil surface: either

(1) Less than 50 cm; or

(2) Less than 200 cm if the soil has a sandy

particle-size class in at least some part between

the mineral soil surface and the spodic horizon;

and

c. A lower boundary as follows:

(1) Either at a depth of 25 cm or more below the

mineral soil surface or at the top of a duripan or

fragipan or at a densic, lithic, paralithic, or petroferric

contact, whichever is shallowest; or

(2) At any depth,

(a) If the spodic horizon has a coarse-loamy,

loamy-skeletal, or finer particle-size class and the

soil has a frigid temperature regime; or

(b) If the soil has a cryic temperature regime;

and

d. Either:

(1) A directly overlying albic horizon in 50 percent

or more of each pedon; or

(2) No andic soil properties in 60 percent or more of

the thickness either:

(a) Within 60 cm either of the mineral soil

surface or of the top of an organic layer with andic

soil properties, whichever is shallower, if there is

no densic, lithic, or paralithic contact, duripan, or

petrocalcic horizon within that depth; or

(b) Between either the mineral soil surface or the

top of an organic layer with andic soil properties,

whichever is shallower, and a densic, lithic, or

1 Materials that meet the definition of cindery, fragmental, or pumiceous but have more

than 10 percent, by volume, voids that are filled with organic soil materials are considered to be

organic soil materials.
Identification of the Taxonomic Class of a Soil 161

paralithic contact, a duripan, or a petrocalcic

horizon.

Spodosols, p. 695

D. Other soils that have andic soil properties in 60 percent or

more of the thickness either:

1. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

2. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Andisols, p. 271

E. Other soils that have either:

1. An oxic horizon that has its upper boundary within 150

cm of the mineral soil surface and no kandic horizon that

has its upper boundary within that depth; or

2. 40 percent or more (by weight) clay in the fine-earth

fraction between the mineral soil surface and a depth of 18

cm (after mixing) and a kandic horizon that has the

weatherable-mineral properties of an oxic horizon and has

its upper boundary within 100 cm of the mineral soil

surface.

Oxisols, p. 655

F. Other soils that have:

1. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides or wedge-shaped peds that have their long axes

tilted 10 to 60 degrees from the horizontal; and

2. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon if shallower; and

3. Cracks2 that open and close periodically.

Vertisols, p. 783

G. Other soils that:

1. Have:

a. An aridic soil moisture regime; and

b. An ochric or anthropic epipedon; and

c. One or more of the following with the upper

boundary within 100 cm of the soil surface: a cambic

horizon with a lower depth of 25 cm or more; a cryic

temperature regime and a cambic horizon; a calcic,

gypsic, petrocalcic, petrogypsic, or salic horizon; or a

duripan; or

d. An argillic or natric horizon; or

2. Have a salic horizon; and

a. Saturation with water in one or more layers within

100 cm of the soil surface for 1 month or more during a

normal year; and

b. A moisture control section that is dry in some or all

parts at some time during normal years; and

c. No sulfuric horizon that has its upper boundary

within 150 cm of the mineral soil surface.

Aridisols, p. 329

H. Other soils that have either:

1. An argillic or kandic horizon, but no fragipan, and a

base saturation (by sum of cations) of less than 35 percent at

one of the following depths:

a. If the epipedon has a sandy or sandy-skeletal

particle-size class throughout, either:

(1) 125 cm below the upper boundary of the argillic

horizon (but no deeper than 200 cm below the mineral

soil surface) or 180 cm below the mineral soil surface,

whichever is deeper; or

(2) At a densic, lithic, paralithic, or petroferric

contact if shallower; or

b. The shallowest of the following depths:

(1) 125 cm below the upper boundary of the argillic

or kandic horizon; or

(2) 180 cm below the mineral soil surface; or

(3) At a densic, lithic, paralithic, or petroferric

contact; or

2. A fragipan and both of the following:

a. Either an argillic or a kandic horizon above, within,

or below it or clay films 1 mm or more thick in one or

more of its subhorizons; and

b. A base saturation (by sum of cations) of less than

35 percent at the shallowest of the following depths:

2 A crack is a separation between gross polyhedrons. If the surface is strongly selfmulching, i.e., a mass of granules, or if the soil is cultivated while cracks are open, the cracks

may be filled mainly by granular materials from the surface, but they are open in the sense that

the polyhedrons are separated. A crack is regarded as open if it controls the infiltration and

percolation of water in a dry, clayey soil.
162

(1) 75 cm below the upper boundary of the fragipan;

or

(2) 200 cm below the mineral soil surface; or

(3) At a densic, lithic, paralithic, or petroferric

contact.

Ultisols, p. 721

I. Other soils that have both of the following:

1. Either:

a. A mollic epipedon; or

b. Both a surface horizon that meets all the

requirements for a mollic epipedon except thickness after

the soil has been mixed to a depth of 18 cm and a

subhorizon more than 7.5 cm thick, within the upper part

of an argillic, kandic, or natric horizon, that meets the

color, organic-carbon content, base saturation, and

structure requirements of a mollic epipedon but is

separated from the surface horizon by an albic horizon;

and

2. A base saturation of 50 percent or more (by NH4

OAc) in

all horizons either between the upper boundary of any

argillic, kandic, or natric horizon and a depth of 125 cm

below that boundary, or between the mineral soil surface

and a depth of 180 cm, or between the mineral soil surface

and a densic, lithic, or paralithic contact, whichever depth is

shallowest.

Mollisols, p. 555

J. Other soils that do not have a plaggen epipedon and that

have either:

1. An argillic, kandic, or natric horizon; or

2. A fragipan that has clay films 1 mm or more thick in

some part.

Alfisols, p. 163

K. Other soils that have either:

1. One or more of the following:

a. A cambic horizon with its upper boundary within

100 cm of the mineral soil surface and its lower boundary

at a depth of 25 cm or more below the mineral soil surface;

or

b. A calcic, petrocalcic, gypsic, petrogypsic, or

placic horizon or a duripan with an upper boundary within

a depth of 100 cm of the mineral soil surface; or

c. A fragipan or an oxic, sombric, or spodic horizon with

an upper boundary within 200 cm of the mineral soil

surface; or

d. A sulfuric horizon that has its upper boundary within

150 cm of the mineral soil surface; or

e. A cryic temperature regime and a cambic horizon; or

2. No sulfidic materials within 50 cm of the mineral soil

surface; and both:

a. In one or more horizons between 20 and 50 cm

below the mineral soil surface, either an n value of 0.7 or

less or less than 8 percent clay in the fine-earth fraction;

and

b. One or both of the following:

(1) A salic horizon or a histic, mollic, plaggen, or

umbric epipedon; or

(2) In 50 percent or more of the layers between the

mineral soil surface and a depth of 50 cm, an

exchangeable sodium percentage of 15 or more (or a

sodium adsorption ratio of 13 or more), which

decreases with increasing depth below 50 cm, and also

ground water within 100 cm of the mineral soil

surface at some time during the year when the soil is

not frozen in any part.

Inceptisols, p. 489

L. Other soils.

Entisols, p. 389

Literature Cited

United States Department of Agriculture, Soil Conservation

Service. 1990. Soil Series of the United States, Including Puerto

Rico and the Virgin Islands: Their Taxonomic Classification.

Misc. Pub. 1483.
163

The central concept of Alfisols is that of soils that havean ochric epipedon, an argillic horizon, and moderate to

high base saturation and in which water is held at less than

1500 kPa tension during at least 3 months each year when the

soils are warm enough for plants to grow. Alfisols may also

have a fragipan, a duripan, a kandic horizon, a natric horizon,

a petrocalcic horizon, plinthite, or other features, and these

features are used in defining the great groups within the order.

A very few Alfisols that are very wet during part of the year

have an umbric epipedon.

Alfisols that have a thermic or warmer soil temperature

regime tend to form a belt between the Aridisols of arid regions

and the Inceptisols, Ultisols, and Oxisols in areas of warm,

humid climates. Where the soil temperature regime is mesic or

cooler, the Alfisols in the United States tend to form a belt

between the Mollisols of the grasslands and the Spodosols and

Inceptisols in areas of very humid climates.

In regions of mesic and frigid soil temperature regimes,

Alfisols are mostly on late-Pleistocene deposits or surfaces. In

warmer regions, they are on late-Pleistocene or older surfaces if

there are only infrequent years when the soils lose bases by

leaching or if there is an external source of bases, such as

calcareous dust from a desert.

Most Alfisols have a udic, ustic, or xeric moisture regime,

and many have aquic conditions. Alfisols are not known to

have a perudic moisture regime. Leaching of bases from the

soils may occur almost every year or may be infrequent.

Definition of Alfisols and Limits Between

Alfisols and Soils of Other Orders

The definition of Alfisols must provide criteria that separate

Alfisols from all other orders. The aggregate of these criteria

defines the limits of Alfisols in relation to all other known

soils.

Alfisols are mineral soils that meet all of the following:

1. Unlike Histosols, Alfisols do not have organic soil

materials that meet one or more of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices1 and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more in normal

years (or are artificially drained), have an upper boundary

within 40 cm of the soil surface, and have a total thickness

of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3

; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more;

2. Unlike Spodosols, Alfisols do not have a spodic horizon or

an Ap horizon containing 85 percent or more spodic materials

above the argillic, kandic, or natric horizon and do not have

one or more of the following:

a. An albic horizon in 50 percent or more of each pedon

and a cryic soil temperature regime; or

b. A spodic horizon with all of the following

characteristics:

(1) One or more of the following:

(a) A thickness of 10 cm or more; or

(b) An overlying Ap horizon; or

(c) Cementation in 50 percent or more of each

pedon; or

(d) A coarse-loamy, loamy-skeletal, or finer

particle-size class and a frigid soil temperature

regime; or

(e) A cryic soil temperature regime;

and

CHAPTER 9

Alfisols

1 Materials that meet the definition of cindery, fragmental, or pumiceous but have more

than 10 percent, by volume, voids that are filled with organic soil materials are considered to be

organic soil materials.
164 Soil Taxonomy

(2) An upper boundary within the following depths

from the mineral soil surface: either

(a) Less than 50 cm; or

(b) Less than 200 cm if the soil has a sandy particlesize class between the mineral soil surface and the

spodic horizon; and

(3) A lower boundary as follows:

(a) Either at a depth of 25 cm or more below the

mineral soil surface or at the top of a duripan or

fragipan or at a densic, lithic, paralithic, or petroferric

contact, whichever is shallowest; or

(b) At any depth if the spodic horizon has a coarseloamy, loamy-skeletal, or finer particle-size class and

the soil has a frigid temperature regime, or if the soil

has a cryic temperature regime;

3. Unlike Andisols, Alfisols have andic soil properties in less

than 60 percent of the thickness either:

a. Within 60 cm of either the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon;

4. Unlike Gelisols, Alfisols do not have:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface;

5. Unlike Oxisols, Alfisols do not have:

a. An oxic horizon that has its upper boundary within 150

cm of the mineral soil surface, unless the soil also has both

an argillic or kandic horizon that has its upper boundary

within that depth and less than 40 percent (by weight) clay

in the fine-earth fraction between the mineral soil surface

and a depth of 18 cm (after mixing) or more than 10 percent

weatherable minerals; and

b. Both of the following: (1) a kandic horizon that has less

than 10 percent weatherable minerals and has an upper

boundary within 150 cm of the mineral soil surface and (2)

40 percent or more (by weight) clay in the fine-earth

fraction between the mineral soil surface and a depth of 18

cm (after mixing);

6. Unlike Vertisols, Alfisols do not have all of the following:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

aggregates that have their long axes tilted 10 to 60 degrees

from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon if shallower; and

c. Cracks2

 that open and close periodically;

7. Unlike Aridisols, Alfisols do not have an aridic soil

moisture regime;

8. Unlike Ultisols, Alfisols have either:

a. An argillic or kandic horizon, but no fragipan, and a

base saturation (by sum of cations) of 35 percent or more at

one of the following depths:

(1) In an epipedon that has a sandy or sandy-skeletal

particle-size class throughout, either:

(a) 125 cm below the upper boundary of the argillic

or kandic horizon (but no deeper than 200 cm below

the mineral soil surface) or 180 cm below the mineral

soil surface, whichever is deeper; or

(b) At a densic, lithic, paralithic, or petroferric

contact if shallower; or

(2) The shallowest of the following depths:

(a) 125 cm below the upper boundary of the argillic

or kandic horizon; or

(b) 180 cm below the mineral soil surface; or

(c) At a densic, lithic, paralithic, or petroferric

contact; or

b. A fragipan and a base saturation (by sum of cations) of

35 percent or more at the shallowest of the following

depths:

(1) 75 cm below the upper boundary of the fragipan; or

(2) 200 cm below the mineral soil surface; or

(3) At a densic, lithic, paralithic, or petroferric contact;

9. Unlike Mollisols, Alfisols do not have both:

a. A mollic epipedon or both a surface horizon that meets

2 A crack is a separation between gross polyhedrons. If the surface is strongly selfmulching, i.e., a mass of granules, or if the soil is cultivated while cracks are open, the cracks

may be filled mainly by granular materials from the surface, but they are open in the sense that

the polyhedrons are separated. A crack is regarded as open if it controls the infiltration and

percolation of water in a dry, clayey soil.
Alfisols 165

all of the requirements for a mollic epipedon except thickness

after the surface soil has been mixed to a

depth of 18 cm, and a subhorizon more than 7.5 cm thick,

within the upper part of an argillic, kandic, or natric

horizon, that meets the color, organic-carbon content, base

saturation, and structure requirements of a mollic epipedon

but is separated from the surface horizon by an albic

horizon; and

b. A base saturation of 50 percent or more (by NH4

OAc) in

all horizons either between the upper boundary of any

argillic, kandic, or natric horizon and a depth of 125 cm

below that boundary, or between the mineral soil surface

and a depth of 180 cm, or between the mineral soil surface

and a densic, lithic, or paralithic contact, whichever depth is

shallowest;

10. Unlike Inceptisols and Entisols, Alfisols have either:

a. An argillic, kandic, or natric horizon; or

b. A fragipan that has clay films 1 mm or more thick in

some part.

Representative Pedon and Data

Following is a description of a representative Alfisol. Data

for the pedon identified in this description are given in the

table “Characterization Data for an Alfisol.”

Classification: Fine, mixed, semiactive, isohyperthermic Typic

Haplustalf

Site identification number: 90P0621

Location: Killikulam Agriculture College, India

Latitude: 09 degrees, 00 minutes 00 seconds N.

Longitude: 78 degrees 00 minutes 00 seconds E.

Landscape: Plains

Microrelief: Land leveled or smooth

Slope: Plane

Elevation: 23 m above m.s.l.

Permeability class: Moderate

Drainage class: Well drained

Land use: Cropland

Vegetation: Foxtail millet

Hazard of erosion or deposition: Slight

Parent material: Alluvium derived from igneous material over

igneous rock

Diagnostic horizons: An ochric epipedon from a depth of 0 to

23 cm and an argillic horizon from a depth of 23 to 115

cm

Described by: M. Janakiraman, S. Ramu, and R.J. Engel

In the following pedon description, colors are for dry soil

unless otherwise indicated.

Ap—0 to 13 cm; yellowish red (5YR 5/6) sandy clay loam,

yellowish red (5YR 4/6) moist; weak fine subangular

blocky structure; hard, firm, sticky and plastic; common

fine roots throughout; many very fine and fine interstitial

and tubular pores; common medium rounded ironmanganese concretions; 5 percent igneous pebbles; clear

smooth boundary.

BAt—13 to 23 cm; red (2.5YR 4/6) gravelly sandy clay loam,

dark red (2.5YR 3/6) moist; moderate fine subangular

blocky structure; slightly hard, friable, sticky and plastic;

few fine roots throughout; many fine and medium

interstitial and tubular pores; few faint clay films on faces

of peds and in pores; common medium rounded ironmanganese concretions; 30 percent igneous pebbles;

abrupt smooth boundary.

Bt1—23 to 36 cm; dark reddish brown (2.5YR 3/4) sandy clay,

dark reddish brown (2.5YR 3/4) moist; strong fine

subangular blocky structure; friable, very sticky and

plastic; few fine roots throughout; common fine interstitial

and tubular pores; few faint clay films on faces of peds and

in pores; common medium rounded iron-manganese

concretions; 5 percent igneous pebbles; clear wavy

boundary.

Bt2—36 to 48 cm; dark reddish brown (2.5YR 3/4) sandy clay,

dark red (2.5YR 3/6) moist; strong medium angular blocky

structure; very friable, very sticky and plastic; few fine

roots throughout; common fine interstitial and tubular

pores; few faint clay films on faces of peds and in pores;

common medium rounded iron-manganese concretions; 10

percent igneous pebbles; clear smooth boundary.

Bt3—48 to 81 cm; dark reddish brown (2.5YR 3/4) very

gravelly sandy clay, dark red (2.5YR 3/6) moist; strong

medium subangular blocky structure; friable, very sticky

and plastic; few fine roots throughout; common fine and

medium interstitial and tubular pores; few faint clay films

on faces of peds and in pores; common medium rounded

iron-manganese concretions; 40 percent igneous pebbles;

gradual broken boundary.

BCt—81 to 115 cm; yellowish red (5YR 5/6) extremely

gravelly sandy clay and weathered bedrock, 50 percent

yellowish red (5YR 4/6) and 50 percent reddish yellow

(5YR 6/8) moist; moderate fine subangular blocky

structure; very friable, very sticky and plastic; few fine

roots throughout; common fine and medium interstitial

and tubular pores; few faint clay films on faces of peds and

in pores; common medium rounded iron-manganese

concretions; 65 percent igneous pebbles; clear broken

boundary.

Cr—115 to 130 cm; reddish yellow (5YR 6/8), moist,

weathered bedrock; massive.

Key to Suborders

JA. Alfisols that have, in one or more horizons within 50 cm

of the mineral soil surface, aquic conditions (other than

anthraquic conditions) for some time in normal years (or

artificial drainage) and have one or both of the following:
166 Soil Taxonomy

Characterization Data for an Alfisol

 SITE IDENTIFICATION NO.: 90P0621

 CLASSIFICATION: FINE, MIXED, SEMIACTIVE, ISOHYPERTHERMIC TYPIC HAPLUSTALF

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 90P3691 0- 13 Ap 28.0 12.3 59.7 21.4 6.6 5.7 12.5 15.8 12.4 11.5 7.5 8 TR -- 51 8

 90P3692 13- 23 BAt 17.9 8.6 73.5 12.8 3.4 5.2 11.6 18.5 14.9 14.3 14.2 13 TR -- 67 13

 90P3693 23- 36 Bt1 36.9 8.5 54.6 28.1 3.5 5.0 7.4 13.6 12.4 11.7 9.5 6 TR -- 50 6

 90P3694 36- 48 Bt2 48.2 9.1 42.7 39.5 4.8 4.3 7.3 10.0 9.1 7.9 8.4 8 1 -- 41 9

 90P3695 48- 81 Bt3 44.7 9.7 45.6 35.3 5.3 4.4 7.0 8.2 7.4 7.7 15.3 24 2 -- 55 26

 90P3696 81-115 BCt 45.5 12.6 41.9 30.5 7.3 5.3 6.4 9.4 6.2 5.5 14.4 32 20 1 70 53

 90P3697 115-130 Cr1 16.9 13.3 69.8 10.2 6.9 6.4 15.5 24.3 13.9 8.7 7.4 11 2 -- 60 13

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 13 0.68 0.60 0.37 1.62 1.77 0.028 15.7 10.4 0.08

 13- 23 0.15 0.40 0.37 1.67 1.77 0.018 13.2 6.7 0.10

 23- 36 0.23 0.35 0.33 1.63 1.73 0.019 15.3 12.3 0.05

 36- 48 0.22 0.35 0.34 1.59 1.77 0.034 20.5 16.3 0.06

 48- 81 0.13 0.39 0.32 14.3

 81-115 0.09 0.50 0.37 1.58 1.70 0.015 19.1 16.7 0.02

 115-130 0.02 1.24 0.63 1.70 1.78 0.014 15.6 10.6 0.08

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)

 Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9b 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1f 8C1f

 <- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1

 0- 13 12.5 5.5 0.2 0.6 18.8 2.5 21.3 16.8 88 100 TR 0.22 7.1 7.7

 13- 23 5.8 2.3 0.2 0.2 8.5 1.4 9.9 7.2 86 100 TR 0.14 7.1 7.8

 23- 36 10.0 4.1 0.4 0.2 14.7 2.5 17.2 12.9 85 100 TR 0.11 7.0 7.5

 36- 48 13.1 6.3 0.6 0.3 20.3 2.7 23.0 16.7 88 100 -- 0.17 7.1 7.8

 48- 81 12.5 6.3 0.6 0.3 19.7 2.3 22.0 17.6 90 100 TR 0.16 7.0 7.7

 81-115 15.3 8.2 0.7 0.5 24.7 3.0 27.7 22.8 89 100 0.16 6.8 7.5

 115-130 16.9 6.1 0.5 0.2 23.7 2.1 25.8 20.9 92 100 0.11 6.8 7.7

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA-

 < - - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION

 NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->

 90P3693 TCLY KK 3 MI 1 GE 1 HE 1 29.0 13.3 0.9

 90P3695 TCLY KK 4 MT 2 GE 2 MI 1 HE 1 26.0 11.4 1.0

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.

 Fraction interpretation: TCLY, total clay, <0.002 mm.

 Mineral interpretation: KK, kaolinite; MI, mica; GE, goethite; HE, hematite; MT, montmorillonite.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.

 Pedon mineralogy based on clay: Mixed.

 Family mineralogy: Mixed.
Alfisols 167

1. Redoximorphic features in all layers between either the

lower boundary of an Ap horizon or a depth of 25 cm below

the mineral soil surface, whichever is deeper, and a depth of

40 cm; and one of the following within the upper 12.5 cm of

the argillic, natric, glossic, or kandic horizon:

a. 50 percent or more redox depletions with chroma of 2

or less on faces of peds and redox concentrations within

peds; or

b. Redox concentrations and 50 percent or more redox

depletions with chroma of 2 or less in the matrix; or

c. 50 percent or more redox depletions with chroma of

1 or less on faces of peds or in the matrix, or both; or

2. In the horizons that have aquic conditions, enough

active ferrous iron to give a positive reaction to alpha,alphadipyridyl at a time when the soil is not being irrigated.

Aqualfs, p. 167

JB. Other Alfisols that have a cryic or isofrigid temperature

regime.

Cryalfs, p. 189

JC. Other Alfisols that have an ustic moisture regime.

Ustalfs, p. 228

JD. Other Alfisols that have a xeric moisture regime.

Xeralfs, p. 253

JE. Other Alfisols.

Udalfs, p. 200

Aqualfs

Aqualfs are the Alfisols that have aquic conditions for some

time in normal years (or artificial drainage) at or near the soil

surface. Their appearance is normally controlled by gray redox

depletions and higher chroma redox concentrations. In some of

these soils, ground water is near the surface during a

considerable part of the year but drops to depths below the

argillic or kandic horizon in another part of the year. In others,

the ground water may be deep most of the year but horizons

that have low hydraulic conductivity restrict the downward

movement of water and extend the period of saturation.

Aqualfs occur in many parts of the world, mostly in small

areas of late-Pleistocene deposits. In either of these situations,

the fluctuating water table that seems essential to the genesis of

Aqualfs does not occur. The wetness of a few Aqualfs is the

result of seepage.

Most Aqualfs, except for those that have a frigid or cryic

temperature regime, have some artificial drainage or other

water control and are cultivated. Rice is a common crop on the

Aqualfs that have a thermic or warmer temperature regime.

Before they were cultivated, some of the Aqualfs were under

forest vegetation and others were under grass. Nearly all

Aqualfs are believed to have supported forest vegetation at

some time in the past.

Definition

Aqualfs are the Alfisols that have, within 50 cm of the

mineral soil surface, aquic conditions for some time in normal

years (or artificial drainage) and have one or both of the

following:

1. Redoximorphic features in all layers between either the lower

boundary of an Ap horizon or a depth of 25 cm below the

mineral soil surface, whichever is deeper, and a depth of 40 cm

or more; and one of the following:

a. 50 percent or more redox depletions with chroma of 2

or less on faces of peds, and redox concentrations within

peds, of the argillic, natric, or kandic horizon; or

b. 50 percent or more redox depletions with chroma of 2

or less, and redox concentrations, in the matrix of the

argillic, natric, or kandic horizon; or

c. 50 percent or more redox depletions with chroma of 1

or less either on faces of peds or in the matrix of the argillic,

natric, or kandic horizon; or

2. In the horizons that have aquic conditions, enough active

ferrous iron to give a positive reaction to alpha,alpha-dipyridyl

at a time when the soil is not being irrigated.

Key to Great Groups

JAA. Aqualfs that have a cryic temperature regime.

Cryaqualfs, p. 171

JAB. Other Aqualfs that have one or more horizons, at a

depth between 30 and 150 cm from the mineral soil surface, in

which plinthite either forms a continuous phase or constitutes

one-half or more of the volume.

Plinthaqualfs, p. 188

JAC. Other Aqualfs that have a duripan.

Duraqualfs, p. 171

JAD. Other Aqualfs that have a natric horizon.

Natraqualfs, p. 186

JAE. Other Aqualfs that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragiaqualfs, p. 181

JAF. Other Aqualfs that have a kandic horizon.

Kandiaqualfs, p. 184

JAG. Other Aqualfs that have one or more layers, at least 25
168 Soil Taxonomy

cm thick (cumulative) within 100 cm of the mineral soil surface,

that have 50 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts.

Vermaqualfs, p. 188

JAH. Other Aqualfs that have an abrupt textural change

between the ochric epipedon or the albic horizon and the

argillic horizon and have a moderately low or lower saturated

hydraulic conductivity in the argillic horizon.

Albaqualfs, p. 168

JAI. Other Aqualfs that have a glossic horizon.

Glossaqualfs, p. 182

JAJ. Other Aqualfs that have episaturation.

Epiaqualfs, p. 175

JAK. Other Aqualfs.

Endoaqualfs, p. 171

Albaqualfs

These are the Aqualfs with ground water seasonally perched

above a slowly permeable argillic horizon. Commonly, an albic

horizon rests abruptly on the argillic horizon, with virtually no

transitional horizon between the two. The soil temperature

regime is frigid, isomesic, mesic, or warmer. Albaqualfs do not

have a kandic horizon, a natric horizon, a fragipan, or a

duripan. They have no horizon at a depth between 30 and 150

cm from the mineral soil surface in which plinthite either

forms a continuous phase or constitutes one-half or more of the

volume. Recognizable bioturbation, such as filled animal

burrows, wormholes, or casts, is less than 50 percent (by

volume) in all layers at least 25 cm thick (cumulative) within

100 cm of the mineral soil surface. In the United States, most

Albaqualfs have a mesic, thermic, or hyperthermic temperature

regime and, unless the soils are irrigated, the albic horizon is

dry for short periods in summer in normal years. The dryness

seems essential to the genesis. Thus, Aqualfs in which the albic

horizon is rarely dry are in great groups other than Albaqualfs.

Definition

Albaqualfs are the Aqualfs that:

1. Have an abrupt textural change between an ochric

epipedon or, more commonly, an albic horizon and the argillic

horizon and have moderately low or lower saturated hydraulic

conductivity in the argillic horizon;

2. Have a frigid, mesic, isomesic, or warmer temperature

regime;

3. Have no fragipan, no duripan, no kandic horizon, and no

natric horizon;

4. Do not have one or more layers, at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, that

have 50 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts;

5. Have, in all horizons at a depth between 30 and 150 cm from

the mineral soil surface, less than 50 percent (by volume)

plinthite.

Key to Subgroups

JAHA. Albaqualfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more below the mineral soil surface.

Arenic Albaqualfs

JAHB. Other Albaqualfs that have both of the following:

1. One or both:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. Chroma of 3 or more in 40 percent or more of the

matrix between the lower boundary of the A or Ap horizon

and a depth of 75 cm from the mineral soil surface.

Aeric Vertic Albaqualfs

JAHC. Other Albaqualfs that have both of the following:

1. One or both:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. An Ap horizon or materials between the mineral soil

surface and a depth of 18 cm that, after mixing, have one or

more of the following:

a. A color value, moist, of 4 or more; or

b. A color value, dry, of 6 or more; or
Alfisols 169

c. Chroma of 4 or more.

Chromic Vertic Albaqualfs

JAHD. Other Albaqualfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Albaqualfs

JAHE. Other Albaqualfs that have both:

1. Chroma of 3 or more in 40 percent or more of the

matrix between the lower boundary of the A or Ap horizon

and a depth of 75 cm from the mineral soil surface; and

2. A mollic epipedon, an Ap horizon that meets all of the

requirements for a mollic epipedon except thickness, or

materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing.

Udollic Albaqualfs

JAHF. Other Albaqualfs that have chroma of 3 or more in 40

percent or more of the matrix between the lower boundary of

the A or Ap horizon and a depth of 75 cm from the mineral

soil surface.

Aeric Albaqualfs

JAHG. Other Albaqualfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Albaqualfs

JAHH. Other Albaqualfs that have a mollic epipedon, an

Ap horizon that meets all of the requirements for a mollic

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements

after mixing.

Mollic Albaqualfs

JAHI. Other Albaqualfs that have an umbric epipedon, an Ap

horizon that meets all of the requirements for an umbric

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Umbric Albaqualfs

JAHJ. Other Albaqualfs.

Typic Albaqualfs

Definition of Typic Albaqualfs

Typic Albaqualfs are the Albaqualfs that:

1. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

2. Have chroma of 2 or less in 60 percent or more of the mass

between the bottom of the A or Ap horizon and a depth of 75

cm;

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density of 1.0 g/cm3

 or less, measured at 33 kPa

water retention, in the fraction less than 2.0 mm in size and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and
170 Soil Taxonomy

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more; and

5. Do not have a mollic or umbric epipedon, an Ap horizon

that meets all of the requirements for a mollic or umbric

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements

after mixing.

Description of Subgroups

Typic Albaqualfs.—The central concept or Typic subgroup of

Albaqualfs is fixed on soils that have dominantly low chroma

throughout the upper part to a depth of 75 cm or more; that have

relatively high color value in the plow layer, too high for a mollic

epipedon; that do not have a thick epipedon with a sandy or

sandy-skeletal particle-size class throughout; and that do not

have slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks. Chroma of 3 or more, if dominant in

the horizons directly below the A or Ap horizon, indicates

saturation with water for only short periods and is a defining

feature for Aeric Albaqualfs and other subgroups that

intergrade to freely drained soils.

An Ap horizon that has the color of a mollic epipedon and

similar upper horizons that would be mixed by plowing are

associated in some parts of the United States with a native

prairie vegetation. Horizons with such colors are used to define

intergrades to the Mollisols. Soils that have slickensides,

wedge-shaped aggregates, a high linear extensibility, or wide

cracks are assigned to Vertic or combination Vertic subgroups

because these properties are shared with Vertisols. Typic

Albaqualfs do not have a surface mantle or layer in the upper

75 cm that has both a low bulk density and a high content of

weakly crystalline minerals or that consists of slightly or

moderately weathered pyroclastic materials because these

properties are shared with Andisols. Typic Albaqualfs are

extensive in parts of the Mississippi Valley in Illinois,

Missouri, Arkansas, and Louisiana and in part of Oregon and

Florida. They are uncommon elsewhere in the United States.

These soils are nearly level and are difficult to drain. Some are

cultivated, but many are used as pasture or are in forests.

Aeric Albaqualfs.—Chroma in these soils is more than 2 in

more than 40 percent of the mass between the bottom of the A

or Ap horizon and a depth of 75 cm. Most commonly, the

chroma in the matrix of the argillic horizon is 3 or more. The

period of saturation with water in these soils is shorter than the

one characteristic of Typic Albaqualfs. Aeric Albaqualfs are

intergrades between Albaqualfs and Hapludalfs. They generally

are steep enough for water to run off the surface rather than

stand on the surface. They genarally are either cultivated or

used as pasture. If they are cultivated, erosion is commonly a

problem. These soils are not extensive. They occur mostly in

Louisiana and Missouri.

Aeric Vertic Albaqualfs.—These soils are like Typic

Albaqualfs, but they are high in content of expanding clays and

have cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

These soils also have chroma of more than 2 in more than 40

percent of the mass between the bottom of the A or Ap horizon

and a depth of 75 cm. Most commonly, the chroma in the

matrix of the argillic horizon is 3 or more. These soils are

permitted, but not required, to have upper horizons that have a

color value of 3 or less, moist, and 5 or less, dry, or have these

colors after mixing to a depth of 15 cm. The period of

saturation with water in these soils is shorter than the one

characteristic of Typic Albaqualfs. Aeric Vertic Albaqualfs are

considered to be transitional to Uderts and are not extensive in

the United States.

Aquandic Albaqualfs.—These soils are like Typic Albaqualfs,

but they have a surface mantle or layer in the upper 75 cm that

has both a low bulk density and a high content of weakly

crystalline minerals or that consists of slightly or moderately

weathered pyroclastic materials. These soils are not known to

occur in the United States.

Arenic Albaqualfs.—Arenic Albaqualfs have a sandy or

sandy-skeletal particle-size class throughout a layer extending

from the mineral soil surface to the top of an argillic horizon at

a depth of 50 cm or more below the mineral soil surface. They

may have chroma of more than 2 in more than 40 percent of

the mass between the A or Ap horizon and a depth of 75 cm.

They may also either have an Ap horizon in which the color

value, moist, is less than 4 and the value, dry, is less than 6

after the soils have been crushed and smoothed or, if not

disturbed, have these colors to a depth of 18 cm, after mixing.

These soils are not extensive. They are most common in

Florida.

Chromic Vertic Albaqualfs.—These soils are like Typic

Albaqualfs, but they are high in content of expanding clays and

have cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

These soils are one kind of intergrade between Albaqualfs and

Aquerts. Chromic Vertic Albaqualfs are not extensive.

Mollic Albaqualfs.—These soils are like Typic Albaqualfs,

but they have either a mollic epipedon or an Ap horizon that

meets all of the requirements for a mollic epipedon except

thickness or have materials between the soil surface and a

depth of 18 cm that meet these requirements after mixing.

Many of these soils had a prairie vegetation before they were

cultivated. Mollic Albaqualfs are intergrades between

Albaqualfs and Argialbolls or Argiaquolls. They are nearly

level and cannot be easily drained. They are most extensive in

Florida and are rare elsewhere in the United States. Most of

them are cultivated.

Udollic Albaqualfs.—These soils are like Typic Albaqualfs,
Alfisols 171

but they have either a mollic epipedon or an Ap horizon that

meets all of the requirements for a mollic epipedon except

thickness or have materials between the soil surface and a

depth of 18 cm that meet these requirements after mixing.

These soils also have chroma of more than 2 in more than 40

percent of the mass between the bottom of the A or Ap horizon

and a depth of 75 cm. Most commonly, the chroma in the

matrix of the argillic horizon is 3 or more. The period of

saturation with water in these soils is shorter than the one

characteristic of Typic Albaqualfs. Udollic Albaqualfs are

intergrades between Albaqualfs and Argiudolls and are of

very small extent in the United States.

Umbric Albaqualfs.—These soils are like Typic

Albaqualfs, but they have either an umbric epipedon or an Ap

horizon that meets all of the requirements for an umbric

epipedon except thickness or have materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing. They are nearly level and cannot be easily drained.

They are most common in Florida and are rare elsewhere in the

United States.

Vertic Albaqualfs.—These soils are like Typic Albaqualfs,

but they are high in content of expanding clays and have

cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

They also have upper horizons that have a color value of 3 or

less, moist, and 5 or less, dry, or have these colors after mixing

to a depth of 15 cm. These soils are one kind of intergrade

between Albaqualfs and Aquerts. Vertic Albaqualfs are mostly

in the central part of the United States and are common in

parts of Illinois and Missouri. Their slopes are gentle. Most of

these soils have been cleared and are used as cropland. Some of

the soils are used as woodland or pasture.

Cryaqualfs

Cryaqualfs are the Aqualfs that have a cryic or isofrigid

temperature regime. These soils are not known to occur in the

United States. The group has been proposed for other

countries, but definitions of subgroups have not been

suggested.

Key to Subgroups

JAAA. All Cryaqualfs (provisionally).

Typic Cryaqualfs

Duraqualfs

Duraqualfs are the Aqualfs that have a duripan and a frigid,

mesic, isomesic, or warmer temperature regime. These soils

have no horizon at a depth between 30 and 150 cm from the

mineral soil surface in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume.

Duraqualfs are not known to occur in the United States. The

group has been proposed for other countries, but definitions of

subgroups have not been suggested.

Key to Subgroups

JACA. All Duraqualfs (provisionally).

Typic Duraqualfs

Endoaqualfs

Endoaqualfs are the Aqualfs that have an epipedon that rests

on an argillic horizon without an abrupt textural change

if the argillic horizon has moderately low or lower saturated

hydraulic conductivity. These soils do not have a kandic

horizon, a natric horizon, a fragipan, or a duripan. The soil

temperature regime is frigid, isomesic, mesic, or warmer.

Endoaqualfs have no horizon at a depth between 30 and 150

cm from the mineral soil surface in which plinthite either

forms a continuous phase or constitutes one-half or more of

the volume. Recognizable bioturbation, such as filled animal

burrows, wormholes, or casts, is less than 50 percent (by

volume) in all layers at least 25 cm thick (cumulative)

within 100 cm of the mineral soil surface. Endoaqualfs

are characterized by endoaquic saturation. The ground

water fluctuates from a level near the soil surface to below

the argillic horizon and is sometimes below a depth of

200 cm.

Before cultivation, most Endoaqualfs supported either a

deciduous broadleaf or a coniferous forest. Generally,

Endoaqualfs are nearly level, and their parent materials are

typically late-Pleistocene sediments.

Definition

Endoaqualfs are the Aqualfs that:

1. Have endosaturation and a frigid, mesic, isomesic, or

warmer soil temperature regime; and

2. Do not have a glossic, kandic, or natric horizon or a

duripan; and

3. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface; and

4. Do not have an abrupt textural change between the albic

and argillic horizons if the saturated hydraulic conductivity of

the argillic horizon is moderately low or lower; and

5. Do not have one or more layers, at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, that

have 50 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts; and

6. Have, in all horizons at a depth between 30 and 150 cm

from the mineral soil surface, less than 50 percent (by volume)

plinthite.
172 Soil Taxonomy

Key to Subgroups

JAKA. Endoaqualfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or more of the

following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Endoaqualfs

JAKB. Other Endoaqualfs that have both of the following:

1. One or both:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. An Ap horizon or materials between the mineral soil

surface and a depth of 18 cm that, after mixing, have one or

more of the following:

a. A color value, moist, of 4 or more; or

b. A color value, dry, of 6 or more; or

c. Chroma of 4 or more.

Chromic Vertic Endoaqualfs

JAKC. Other Endoaqualfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Endoaqualfs

JAKD. Other Endoaqualfs that have:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, one or

a combination of the following colors:

a. Hue of 7.5YR or redder in 50 percent or more of the

matrix; and

(1) If peds are present, chroma of 2 or more on 50

percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. In 50 percent or more of the matrix, hue of 10YR or

yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more (moist and dry); or

(2) Chroma of 2 or more if there are no redox

concentrations.

Aeric Fragic Endoaqualfs

JAKE. Other Endoaqualfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Endoaqualfs

JAKF. Other Endoaqualfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm below the mineral soil surface.

Arenic Endoaqualfs

JAKG. Other Endoaqualfs that have a sandy or sandyskeletal particle-size class throughout a layer extending from
Alfisols 173

the mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more below the mineral soil surface.

Grossarenic Endoaqualfs

JAKH. Other Endoaqualfs that have both:

1. A mollic epipedon, an Ap horizon that meets all of the

requirements for a mollic epipedon except thickness, or

materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, one or

a combination of the following colors:

a. Hue of 7.5YR or redder in 50 percent or more of the

matrix; and

(1) If peds are present, chroma of 2 or more on 50

percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. In 50 percent or more of the matrix, hue of 10YR or

yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more; or

(2) Chroma of 2 or more if there are no redox

concentrations.

Udollic Endoaqualfs

JAKI. Other Endoaqualfs that have both:

1. An umbric epipedon, an Ap horizon that meets all of

the requirements for an umbric epipedon except thickness,

or materials between the soil surface and a depth of 18 cm

that meet these requirements after mixing; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, one or

a combination of the following colors:

a. Hue of 7.5YR or redder in 50 percent or more of the

matrix; and

(1) If peds are present, chroma of 2 or more on 50

percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. In 50 percent or more of the matrix, hue of 10YR or

yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more; or

(2) Chroma of 2 or more if there are no redox

concentrations.

Aeric Umbric Endoaqualfs

JAKJ. Other Endoaqualfs that have, in one or more horizons

between the A or Ap horizon and a depth of 75 cm below the

mineral soil surface, in 50 percent or more of the matrix, one

or a combination of the following colors:

1. Hue of 7.5YR or redder; and

a. If peds are present, chroma of 2 or more (both moist

and dry) on 50 percent or more of ped exteriors or no

redox depletions with chroma of 2 or less (both moist and

dry) in ped interiors; or

b. If peds are absent, chroma of 2 or more (both moist

and dry); or

2. Hue of 10YR or yellower and either:

a. Both a color value of 3 or more (moist) and chroma

of 3 or more (moist and dry); or

b. Chroma of 2 or more (both moist and dry) and no

redox concentrations.

Aeric Endoaqualfs

JAKK. Other Endoaqualfs that have a mollic epipedon, an

Ap horizon that meets all of the requirements for a mollic

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Mollic Endoaqualfs

JAKL. Other Endoaqualfs that have an umbric epipedon, an

Ap horizon that meets all of the requirements for an umbric

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Umbric Endoaqualfs

JAKM. Other Endoaqualfs.

Typic Endoaqualfs

Definition of Typic Endoaqualfs

Typic Endoaqualfs are the Endoaqualfs that:

1. Do not have, in any horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following: either

a. Hue of 7.5YR or redder; and

(1) If peds are present, either chroma of 2 or more on

50 percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or
174 Soil Taxonomy

(2) If peds are absent, chroma of 2 or more in 50 percent

or more of the matrix; or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and chroma of

3 or more (moist and dry); or

(2) Chroma of 2 or more (both moist and dry) and no

redox concentrations;

2. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

4. Do not have a mollic or umbric epipedon, an Ap horizon

that meets all of the requirements for a mollic or umbric

epipedon except thickness, or materials between the mineral

soil surface and a depth of 18 cm that meet these requirements

after mixing;

5. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more;

6. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Endoaqualfs.—The Typic subgroup of Endoaqualfs

is fixed on soils that have dominantly low chroma throughout

the upper part to a depth of 75 cm or more; that have relatively

high color value in the plow layer, too high for a mollic or

umbric epipedon; that do not have a thick epipedon with a

sandy or sandy-skeletal particle-size class throughout; and that

do not have slickensides, wedge-shaped aggregates, a high

linear extensibility, or wide cracks. Chroma of 3 or more, if

dominant in the horizons directly below the A or Ap horizon,

indicates saturation with water for only short periods and is a

defining feature for Aeric Endoaqualfs and other subgroups

that intergrade to freely drained soils.

Soils with a mollic or umbric epipedon, or an Ap horizon

and similar upper horizons that, when mixed, have the color of

a mollic or umbric epipedon, are associated in some parts of

the United States with a native prairie vegetation. Horizons

with such colors are used to define intergrades to Mollisols and

to define Umbric extragrades. Soils that have slickensides,

wedge-shaped aggregates, a high linear extensibility, or wide

cracks are assigned to Vertic or combination Vertic subgroups

because these properties are shared with Vertisols. Soils that

have fragic soil properties in a significant volume are assigned

to Fragic or combination Fragic subgroups because these

properties are shared with Fragiaqualfs and Fragiudalfs. Typic

Endoaqualfs do not have a surface mantle or layer in the upper

75 cm that has both a low bulk density and a high content of

weakly crystalline minerals or that consists of slightly or

moderately weathered pyroclastic materials because these

properties are shared with Andisols. A thick layer of sand or

loamy sand, starting at the mineral soil surface, is the basis for

defining the Arenic and Grossarenic subgroups. Typic

Endoaqualfs are moderately extensive. They are not extensive

in any one State but occur throughout a large part of the

Eastern United States and in Oregon and Washington. These

soils are nearly level. Most have been cleared and are used as

cropland, but some are used as pasture or are in forests.

Aeric Endoaqualfs.—Below the A or Ap horizon, these

soils have chroma that is too high for the Typic subgroup, but

they are otherwise like Typic Endoaqualfs in their defined

properties and in most other properties. The high chroma

commonly occurs in the matrix of the peds in the argillic

horizon. Aeric Endoaqualfs are moderately extensive in the

north-central part of the United States, which was covered by

Wisconsinan glaciers and their valley trains. Nearly all of the

soils have been cleared and are used as cropland.

Aeric Fragic Endoaqualfs.—These soils have fragic soil

properties in a significant volume but do not have a fragipan

unless it has its upper boundary at a depth of more than 100

cm below the mineral soil surface. Below the A or Ap horizon,

these soils have chroma that is too high for the Typic subgroup.
Alfisols 175

The high chroma commonly occurs in the matrix of the peds in

the argillic horizon. The soils are otherwise like Typic

Endoaqualfs in their defined properties and in most other

properties. Aeric Fragic Endoaqualfs are rare in the United

States.

Aeric Umbric Endoaqualfs.—These soils have an umbric

epipedon or a surface horizon that meets all of the

requirements for an umbric epipedon except thickness. Below

the A or Ap horizon, these soils have chroma that is too high

for the Typic subgroup. The high chroma commonly occurs in

the matrix of the peds in the argillic horizon. The soils are

otherwise like Typic Endoaqualfs in their defined properties

and in most other properties. Aeric Umbric Endoaqualfs are

rare in the United States.

Aquandic Endoaqualfs.—These soils are like Typic

Endoaqualfs, but they have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils are rare in the United States and are known to occur only

in the Pacific Northwest. They are in forests or have been

cleared and are used as cropland or pasture.

Arenic Endoaqualfs.—These soils have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of an argillic horizon at a

depth of 50 to 100 cm below the mineral soil surface. The

upper part of the argillic horizon or the lower part of the

epipedon is permitted to have, in 50 percent or more of the

matrix, chroma that is too high for Typic Endoaqualfs. Arenic

Endoaqualfs may also have either an Ap horizon with a color

value, moist, of 3 or less and a color value, dry, of 5 or less

(crushed and smoothed sample) or, if undisturbed, materials

between the soil surface and a depth of 18 cm that have these

colors after mixing. These soils are otherwise like those of the

Typic subgroup in their defined properties, but their argillic

horizon generally is sandier than that of the Typic

Endoaqualfs. In the United States, Arenic Endoaqualfs occur

principally in Florida. Many have been cleared and drained

and are used as cropland.

Chromic Vertic Endoaqualfs.—These soils are like Typic

Endoaqualfs, but they are high in content of expanding clays

and have cracks 5 mm or more wide, slickensides, wedgeshaped aggregates, or a high linear extensibility. These soils

may also have a somewhat higher chroma in the upper part of

the argillic horizon than Typic Endoaqualfs. Chromic Vertic

Endoaqualfs are rare in the United States.

Fragic Endoaqualfs.—These soils have fragic soil

properties in a significant volume but do not have a fragipan

unless it has its upper boundary at a depth of more than 100

cm below the mineral soil surface. The soils are otherwise like

Typic Endoaqualfs in their defined properties and in most other

properties. Fragic Endoaqualfs are rare in the United States.

Grossarenic Endoaqualfs.—The sandy or sandy-skeletal

layer is thicker in these soils than in Arenic Endoaqualfs.

Grossarenic Endoaqualfs are not known to occur in the United

States.

Mollic Endoaqualfs.—These soils have a mollic epipedon

or a surface horizon that meets all of the requirements for a

mollic epipedon except thickness but have a base saturation of

less than 50 percent (by NH4

OAc) in some part of the argillic

horizon. In the United States, the dark colored surface horizon

generally is too thin to be a mollic epipedon. These soils are

intergrades between Endoaqualfs and Argiaquolls. They are

extensive in the glaciated parts of the United States. Most of

them have been cleared and drained and are used as cropland.

Udollic Endoaqualfs.—These soils are like Typic

Endoaqualfs, but they have chroma in the upper part of the

argillic horizon that is too high for the Typic subgroup and

have a mollic epipedon or a surface horizon that meets all of

the requirements for a mollic epipedon except thickness. The

high chroma commonly occurs in the matrix of the peds in the

argillic horizon. Udollic Endoaqualfs are widely scattered in

the glaciated parts of the United States, particularly in the

north-central region. Most of them have been cleared and

drained and are used as cropland.

Umbric Endoaqualfs.—These soils are like Typic

Endoaqualfs, but they have an umbric epipedon or a surface

horizon that meets all of the requirements for an umbric

epipedon except thickness. These soils are rare in the United

States.

Vertic Endoaqualfs.—These soils are like Typic

Endoaqualfs, but they are high in content of expanding clays

and have cracks 5 mm or more wide, slickensides, wedgeshaped aggregates, or a high linear extensibility. In addition,

because Vertisols can have a mollic epipedon, the soils in this

subgroup may have either an Ap horizon with a color value,

moist, of 3 or less and a color value, dry, of 5 or less or, if

undisturbed, materials between the mineral soil surface and a

depth of 18 cm that have these color values after mixing. A

mollic epipedon is permitted if some subhorizon of the argillic

horizon has a base saturation of less than 50 percent (by

NH4

OAc). Vertic Endoaqualfs may also have a somewhat higher

chroma than Typic Endoaqualfs.

Epiaqualfs

Epiaqualfs are the Aqualfs that have an epipedon that rests

on an argillic horizon without an abrupt textural change if the

argillic horizon has low saturated hydraulic conductivity. These

soils do not have a kandic horizon, a natric horizon, a

fragipan, or a duripan. The soil temperature regime is frigid,

isomesic, mesic, or warmer. The soils have no horizon at a

depth between 30 and 150 cm from the mineral soil surface in

which plinthite either forms a continuous phase or constitutes

one-half or more of the volume. Recognizable bioturbation,

such as filled animal burrows, wormholes, or casts, is less than

50 percent (by volume) in all layers at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface. The
176 Soil Taxonomy

soils have epiaquic saturation during some part of the year.

Ground water is commonly perched on horizons below the

argillic horizon. It fluctuates from a level near the soil surface to

below the argillic horizon and sometimes is not evident.

Before cultivation, most Epiaqualfs supported either a

deciduous broadleaf or a coniferous forest. Generally,

Epiaqualfs are nearly level, and their parent materials are

typically late-Pleistocene sediments.

Definition

Epiaqualfs are the Aqualfs that:

1. Have episaturation and a frigid, mesic, isomesic, or

warmer temperature regime;

2. Do not have a glossic, kandic, or natric horizon or a

duripan;

3. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

4. Do not have an abrupt textural change between the albic

and argillic horizons if the saturated hydraulic conductivity of

the argillic horizon is moderately low or lower;

5. Do not have one or more layers, at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, that

have 50 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts; and

6. Have, in all horizons at a depth between 30 and 150 cm

from the mineral soil surface, less than 50 percent (by volume)

plinthite.

Key to Subgroups

JAJA. Epiaqualfs that have all of the following:

1. One or both:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following colors:

a. Hue of 7.5YR or redder; and

(1) If peds are present, chroma of 2 or more (both

moist and dry) on 50 percent or more of ped exteriors or

no redox depletions with chroma of 2 or less (both

moist and dry) in ped interiors; or

(2) If peds are absent, chroma of 2 or more (both

moist and dry); or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more (moist and dry); or

(2) Chroma of 2 or more (both moist and dry) and

no redox concentrations; and

3. An Ap horizon or materials between the mineral soil

surface and a depth of 18 cm that, after mixing, have one or

more of the following:

a. A color value, moist, of 4 or more; or

b. A color value, dry, of 6 or more; or

c. Chroma of 4 or more.

Aeric Chromic Vertic Epiaqualfs

JAJB. Other Epiaqualfs that have both of the following:

1. One or both:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following colors:

a. Hue of 7.5YR or redder; and

(1) If peds are present, chroma of 2 or more (both

moist and dry) on 50 percent or more of ped exteriors

or no redox depletions with chroma of 2 or less (both

moist and dry) in ped interiors; or

(2) If peds are absent, chroma of 2 or more (both

moist and dry); or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more (moist and dry); or
Alfisols 177

(2) Chroma of 2 or more (both moist and dry) and no

redox concentrations.

Aeric Vertic Epiaqualfs

JAJC. Other Epiaqualfs that have both of the following:

1. One or both:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. An Ap horizon or materials between the mineral soil

surface and a depth of 18 cm that, after mixing, have one or

more of the following:

a. A color value, moist, of 4 or more; or

b. A color value, dry, of 6 or more; or

c. Chroma of 4 or more.

Chromic Vertic Epiaqualfs

JAJD. Other Epiaqualfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Epiaqualfs

JAJE. Other Epiaqualfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or more of the

following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Epiaqualfs

JAJF. Other Epiaqualfs that have:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following colors:

a. Hue of 7.5YR or redder; and

(1) If peds are present, chroma of 2 or more (both

moist and dry) on 50 percent or more of ped exteriors

or no redox depletions with chroma of 2 or less (both

moist and dry) in ped interiors; or

(2) If peds are absent, chroma of 2 or more (both

moist and dry); or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more (moist and dry); or

(2) Chroma of 2 or more (both moist and dry) and

no redox concentrations.

Aeric Fragic Epiaqualfs

JAJG. Other Epiaqualfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Epiaqualfs

JAJH. Other Epiaqualfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm below the mineral soil surface.

Arenic Epiaqualfs
178 Soil Taxonomy

JAJI. Other Epiaqualfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more below the mineral soil surface.

Grossarenic Epiaqualfs

JAJJ. Other Epiaqualfs that have:

1. An umbric epipedon, an Ap horizon that meets all of

the requirements for an umbric epipedon except thickness,

or materials between the soil surface and a depth of 18 cm

that meet these requirements after mixing; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following colors:

a. Hue of 7.5YR or redder; and

(1) If peds are present, chroma of 2 or more (both

moist and dry) on 50 percent or more of ped exteriors

or no redox depletions with chroma of 2 or less (both

moist and dry) in ped interiors; or

(2) If peds are absent, chroma of 2 or more (both

moist and dry); or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more (moist and dry); or

(2) Chroma of 2 or more (both moist and dry) and

no redox concentrations.

Aeric Umbric Epiaqualfs

JAJK. Other Epiaqualfs that have both:

1. A mollic epipedon, an Ap horizon that meets all of the

requirements for a mollic epipedon except thickness, or

materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing; and

2. In 50 percent or more of the matrix in one or more

horizons between the A or Ap horizon and a depth of 75 cm

below the mineral soil surface, one or a combination of the

following colors:

a. Hue of 7.5YR or redder; and

(1) If peds are present, chroma of 2 or more on 50

percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more; or

(2) Chroma of 2 or more if there are no redox

concentrations.

Udollic Epiaqualfs

JAJL. Other Epiaqualfs that have, in one or more horizons

between the A or Ap horizon and a depth of 75 cm below the

mineral soil surface, in 50 percent or more of the matrix, one

or a combination of the following colors:

1. Hue of 7.5YR or redder; and

a. If peds are present, chroma of 2 or more (both moist

and dry) on 50 percent or more of ped exteriors or no

redox depletions with chroma of 2 or less (both moist and

dry) in ped interiors; or

b. If peds are absent, chroma of 2 or more (both moist

and dry); or

2. Hue of 10YR or yellower and either:

a. Both a color value of 3 or more (moist) and chroma

of 3 or more (moist and dry); or

b. Chroma of 2 or more (both moist and dry) and no

redox concentrations.

Aeric Epiaqualfs

JAJM. Other Epiaqualfs that have a mollic epipedon, an Ap

horizon that meets all of the requirements for a mollic

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Mollic Epiaqualfs

JAJN. Other Epiaqualfs that have an umbric epipedon, an Ap

horizon that meets all of the requirements for an umbric

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Umbric Epiaqualfs

JAJO. Other Epiaqualfs.

Typic Epiaqualfs

Definition of Typic Epiaqualfs

Typic Epiaqualfs are the Epiaqualfs that:

1. Do not have, in any horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following: either

a. Hue of 7.5YR or redder; and

(1) If peds are present, either chroma of 2 or more

on 50 percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors;

or
Alfisols 179

(2) If peds are absent, chroma of 2 or more in 50 percent

or more of the matrix; or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and chroma of

3 or more (moist and dry); or

(2) Chroma of 2 or more (both moist and dry) and no

redox concentrations;

2. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

3. Do not have a mollic or umbric epipedon, an Ap horizon

that meets all of the requirements for a mollic or umbric

epipedon except thickness, or materials between the mineral

soil surface and a depth of 18 cm that meet these requirements

after mixing;

4. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more;

5. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

6. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Epiaqualfs.—The central concept or Typic subgroup

of Epiaqualfs is fixed on soils that (1) have dominantly low

chroma between the A or Ap horizon and a depth of 75 cm or

more from the mineral soil surface; (2) have a lighter color

value, moist, in the plow layer, or in comparable horizons if

undisturbed, than in a mollic epipedon; and (3) do not have a

thick epipedon with a sandy or sandy-skeletal particle-size

class throughout. In addition, the soils have no surface mantle

affected by pyroclastic materials, have no cracks and

slickensides or wedge-shaped aggregates, and do not have a

linear extensibility of 6.0 cm or more to a depth of 100 cm

from the mineral soil surface.

Chroma higher than that of Typic Epiaqualfs is

characteristic of soils that are saturated for shorter periods and

serves to define intergrades to freely drained soils. Soils that

have slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks are assigned to Vertic or

combination Vertic subgroups because these properties are

shared with Vertisols. Soils that have fragic soil properties in a

significant volume are assigned to Fragic or combination

Fragic subgroups because these properties are shared with

Fragiaqualfs and Fragiudalfs. Typic Epiaqualfs do not have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals

or that consists of slightly or moderately weathered pyroclastic

materials because these properties are shared with Andisols.

Color values, moist, of 2 or 3 in a plow layer indicate a higherthan-normal content of organic matter and form the basis for

defining intergrades to other great groups. A thick layer of

sand or loamy sand, starting at the mineral soil surface, is the

basis for defining the Arenic subgroup. Typic Epiaqualfs are

moderately extensive. They are not extensive in any one State

but occur throughout a large part of the Eastern United States

and in California and Texas. These soils are nearly level. Most

have been cleared and are used as cropland, but some are used

as pasture or are in forests.

Aeric Chromic Vertic Epiaqualfs.—These soils are like

Typic Epiaqualfs, but they are high in content of expanding

clays and have cracks 5 mm or more wide, slickensides,

wedge-shaped aggregates, or a high linear extensibility. Below

the A or Ap horizon, they have higher chroma than that in

Typic Epiaqualfs. The high chroma commonly occurs in the

matrix of the peds in the argillic horizon. Aeric Chromic Vertic

Epiaqualfs are rare in the United States.

Aeric Epiaqualfs.—Below the A or Ap horizon, these soils

have chroma that is too high for the Typic subgroup, but they
180 Soil Taxonomy

are otherwise like Typic Epiaqualfs in their defined properties

and in most other properties. The high chroma commonly

occurs in the matrix of the peds in the argillic horizon. In the

United States, Aeric Epiaqualfs are extensive in the northcentral region, which was covered by Wisconsinan glaciers, but

are of small extent elsewhere. Nearly all have been cleared and

are used as cropland, but some are used as pasture or are in

forests.

Aeric Fragic Epiaqualfs.—These soils have fragic soil

properties in a significant volume but do not have a fragipan

unless it has its upper boundary at a depth of more than 100

cm below the mineral soil surface. Below the A or Ap horizon,

these soils have chroma that is too high for the Typic subgroup.

The high chroma commonly occurs in the matrix of the peds in

the argillic horizon. The soils are otherwise like Typic

Epiaqualfs in their defined properties and in most other

properties. Aeric Fragic Epiaqualfs are rare in the United

States.

Aeric Umbric Epiaqualfs.—These soils have an umbric

epipedon or a surface horizon that meets all of the

requirements for an umbric epipedon except thickness. Below

the A or Ap horizon, these soils have chroma that is too high

for the Typic subgroup. The high chroma commonly occurs in

the matrix of the peds in the argillic horizon. The soils are

otherwise like Typic Epiaqualfs in their defined properties and

in most other properties. Aeric Umbric Epiaqualfs are rare in

the United States.

Aeric Vertic Epiaqualfs.—These soils are like Typic

Epiaqualfs, but they are high in content of expanding clays and

have cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a high linear extensibility. Below the A or Ap

horizon, these soils have chroma that is too high for the Typic

subgroup. The high chroma commonly occurs in the matrix of

the peds in the argillic horizon. Aeric Vertic Epiaqualfs are

rare in the United States.

Aquandic Epiaqualfs.—These soils are like Typic

Epiaqualfs, but they have a surface mantle or layer in the upper

75 cm that has both a low bulk density and a high content of

weakly crystalline minerals or that consists of slightly or

moderately weathered pyroclastic materials. These soils are

rare in the United States and are known to occur only in the

Pacific Northwest. They are in forests or have been cleared and

are used as cropland or pasture.

Arenic Epiaqualfs.—These soils have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of an argillic horizon at a

depth of 50 to 100 cm below the mineral soil surface. The

upper part of the argillic horizon or the lower part of the

epipedon is permitted to have, in 50 percent or more of the

matrix, chroma that is too high for Typic Epiaqualfs. Arenic

Epiaqualfs may also have either an Ap horizon with a color

value, moist, of 3 or less and a color value, dry, of 5 or less

(crushed and smoothed sample) or, if undisturbed, materials

between the soil surface and a depth of 18 cm that have these

colors after mixing. These soils are otherwise like those of the

Typic subgroup in their defined properties. They are of small

extent in the United States and occur principally in Minnesota.

Chromic Vertic Epiaqualfs.—These soils are like Typic

Epiaqualfs, but they are high in content of expanding clays and

have cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a high linear extensibility. In the upper part of

the argillic horizon, they may also have somewhat higher

chroma than that in Typic Epiaqualfs. Chromic Vertic

Epiaqualfs are rare in the United States.

Fragic Epiaqualfs.—These soils have fragic soil properties

in a significant volume but do not have a fragipan unless it has

its upper boundary at a depth of more than 100 cm below the

mineral soil surface. The soils are otherwise like Typic

Epiaqualfs in their defined properties and in most other

properties. Fragic Epiaqualfs are rare in the United States.

Grossarenic Epiaqualfs.—These soils have a sandy or

sandy-skeletal particle-size class throughout a layer extending

from the mineral soil surface to the top of an argillic horizon at

a depth of 100 cm or more below the mineral soil surface.

These soils are not known to occur in the United States.

Mollic Epiaqualfs.—These soils have a mollic epipedon or

a surface horizon that meets all of the requirements for a

mollic epipedon except thickness. Soils with a mollic epipedon

have a base saturation of less than 50 percent (by NH4

OAc) in

some part of the argillic horizon. In the United States, the dark

colored surface horizon of these soils generally is too thin to be

a mollic epipedon. These soils are intergrades between

Epiaqualfs and Argiaquolls. They are moderately extensive in

the Great Lakes region of the United States. Most of them have

been cleared and drained and are used as cropland, but some

are used as pasture or are in forests.

Udollic Epiaqualfs.—These soils are like Typic Epiaqualfs,

but they have (1) in 50 percent or more of the matrix of some

horizon between the A or Ap horizon and a depth of 75 cm

from the mineral soil surface, chroma that is too high for Typic

Epiaqualfs, and (2) either a mollic epipedon or a surface

horizon that meets all of the requirements for a mollic

epipedon except thickness. A mollic epipedon is permitted in

this subgroup only if the base saturation in some part of the

argillic horizon is less than 50 percent (by NH4OAc).

Udollic Epiaqualfs are moderately extensive in the Great

Lakes region of the United States. Most of them have been

cleared and drained and are used as cropland, but some are

used as pasture or are in forests.

Umbric Epiaqualfs.—These soils are like Typic Epiaqualfs,

but they have either an umbric epipedon, an Ap horizon that

meets all of the requirements for an umbric epipedon except

thickness, or materials between the soil surface and a depth of

18 cm that meet these requirements after mixing. These soils

are rare in the United States.

Vertic Epiaqualfs.—These soils are like Typic Epiaqualfs,

but they are high in content of expanding clays and have

cracks 5 mm or more wide, slickensides, wedge-shaped
Alfisols 181

aggregates, or a high linear extensibility. In addition, because

Typic Vertisols have a dark colored epipedon, Vertic Epiaqualfs

have either an Ap horizon with a color value, moist, of 3 or

less and a color value, dry, of 5 or less or, if undisturbed,

materials between the mineral soil surface and a depth of 18

cm that have these color values after mixing. A mollic

epipedon is permitted if some subhorizon of the argillic

horizon has a base saturation of less than 50 percent (by

NH4

OAc).

Vertic Epiaqualfs are moderately extensive. They are most

extensive in the Midwest but occur throughout a large part of

the Eastern United States. These soils are nearly level. Most

have been cleared and are used as cropland, but some are used

as pasture or are in forests.

Fragiaqualfs

Fragiaqualfs are the Aqualfs that have a fragipan within 100

cm of the mineral soil surface. Most of them have ground water

that is perched above a fragipan at some period and saturates

the soils at another period. These soils have no duripan or

natric horizon and do not have plinthite that forms a

continuous phase or constitutes more than one-half of the

matrix within some subhorizon at a depth between 30 and 150

cm from the soil surface. The soil temperature regime is frigid,

isomesic, mesic, or warmer. In the United States, the soils

generally have frigid to thermic temperature regimes. In

normal years, the albic horizon generally does not become dry,

but the ground water drops below the base of the fragipan

during summer and the soil moisture content is below field

capacity at some period. Most Fragiaqualfs in the United States

formed in Wisconsinan deposits of late-Pleistocene age and had

a broadleaf deciduous forest vegetation before they were

cultivated. Most of the soils are nearly level. Fragiaqualfs as a

group have lower base saturation than other Aqualfs.

Definition

Fragiaqualfs are the Aqualfs that:

1. Have a fragipan with an upper boundary within 100 cm of

the mineral soil surface;

2. Have a frigid, mesic, isomesic, or warmer temperature

regime;

3. Have no duripan or natric horizon;

4. Have, in all horizons at a depth between 30 and 150 cm

from the mineral soil surface, less than 50 percent (by volume)

plinthite.

Key to Subgroups

JAEA. Fragiaqualfs that have one or more layers, at least 25

cm thick (cumulative) within 100 cm of the mineral soil

surface, that have 25 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts.

Vermic Fragiaqualfs

JAEB. Other Fragiaqualfs that have, between the A or Ap

horizon and a fragipan, a horizon with 50 percent or more

chroma of 3 or more if hue is 10YR or redder or of 4 or more if

hue is 2.5Y or yellower.

Aeric Fragiaqualfs

JAEC. Other Fragiaqualfs that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Fragiaqualfs

JAED. Other Fragiaqualfs that have an Ap horizon with a

color value, moist, of 3 or less and a color value, dry, of 5 or

less (crushed and smoothed sample) or materials between the

soil surface and a depth of 18 cm that have these color values

after mixing.

Humic Fragiaqualfs

JAEE. Other Fragiaqualfs.

Typic Fragiaqualfs

Definition of Typic Fragiaqualfs

Typic Fragiaqualfs are the Fragiaqualfs that:

1. Have, in all horizons between the A or Ap horizon and

the fragipan, more than 50 percent chroma of 2 or less if

hue is 10YR or redder or of 3 or less if hue is 2.5Y or

yellower;

2. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface;

3. Have an Ap horizon that has either or both a color value,

moist, of 4 or more or a color value, dry, of 6 or more after the

soil has been crushed and smoothed or have these color values

in the upper 18 cm after mixing; and

4. Do not have one or more layers, at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, that

have 25 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts.

Description of Subgroups

Typic Fragiaqualfs.—The central concept or Typic

subgroup of Fragiaqualfs is fixed on soils that have dominantly

low chroma in all horizons between the fragipan and the plow

layer, if one occurs, and that have a color value in the plow

layer that is lighter than that of an umbric epipedon. Typic

Fragiaqualfs have less than 5 percent (by volume) plinthite in

all subhorizons within 150 cm of the mineral soil surface and
182 Soil Taxonomy

have less than 25 percent (by volume) recognizable bioturbation,

such as filled animal burrows, wormholes, or casts, in all

subhorizons at least 25 cm thick (cumulative) within 100 cm of

the mineral soil surface. These soils are nearly level and are

saturated for long periods in winter and early spring. Most Typic

Fragiaqualfs in the United States are in the Central and

Northeastern States. Typic Fragiaqualfs are of moderate extent.

Most of them have been cleared and are used as cropland.

Artificial drainage is difficult, however, and some of the soils are

used as pasture or are in forests.

Aeric Fragiaqualfs.—These soils are like Typic Fragiaqualfs,

but, in some subhorizon between the A or Ap horizon and the

fragipan, they have chroma of 3 or more if hue is 10YR or redder

or chroma of 4 or more if hue is 2.5Y or yellower. The period of

saturation with water in these soils is shorter than that in the

Typic subgroup. In most areas the slope is slightly greater in

areas of Aeric Fragiaqualfs than in areas of Typic Fragiaqualfs.

Aeric Fragiaqualfs are considered intergrades between

Fragiaqualfs and Fragiudalfs.

Aeric Fragiaqualfs generally are steep enough for water to

run off the surface rather than stand on the surface. They are

extensive locally in the glaciated areas of the north-central

region of the United States but are rare elsewhere in the United

States. Most Aeric Fragiaqualfs in the United States have been

cleared and are used as cropland, but some are used as pasture

or are in forests.

Plinthic Fragiaqualfs.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 150 cm of

the mineral soil surface. These soils are not known to occur in

the United States.

Humic Fragiaqualfs.—These soils have a mollic or umbric

epipedon or a plow layer or A horizon that meets all of the

requirements for a mollic or umbric epipedon except thickness.

These soils are known to occur only in Missouri. They had a

prairie vegetation before they were cultivated. Most of them are

now used as cropland.

Vermic Fragiaqualfs.—These soils have one or more

layers, at least 25 cm thick (cumulative) within 100 cm of the

mineral soil surface, that have 25 percent or more (by volume)

recognizable bioturbation, such as filled animal burrows,

wormholes, or casts. These soils are known to occur only in

Texas.

Glossaqualfs

Glossaqualfs are the Aqualfs that have a frigid, mesic,

isomesic, or warmer temperature regime and have a glossic

horizon. These soils do not have a fragipan, a duripan, a

kandic horizon, or a natric horizon. Plinthite constitutes less

than one-half of the volume of the matrix in all subhorizons at

a depth between 30 and 150 cm from the soil surface. The

glossic horizon is interpreted as evidence that the argillic

horizon has been partly destroyed. Tubular intrusions of albic

materials into the argillic horizon may be formed by filling of

burrows made by crayfish or of traces of taproots. Light colored

krotovinas or filled root channels should be considered albic

materials only if they have no fine stratifications and no

lamellae, if all sealing along krotovina walls has been

destroyed, and if these intrusions have, after deposition, been

leached of some free iron oxides and/or clay.

Characteristically, these soils have the most humid climates

of the Alfisols and the most water passing through the profile

and have a relatively low base saturation for soils of this order.

Before the soils were cultivated, the vegetation was mostly

deciduous hardwood forest. The parent materials are largely

basic or calcareous sediments of late-Pleistocene age. Slopes

are nearly level or concave.

Glossaqualfs are mostly in the most northern and southern

parts of the range of Aqualfs. They generally are in the Great

Lakes area and on the gulf coast. A few are in the Pacific

Northwest. Except where the temperature regime is frigid,

most of these soils have been drained and are used for

cultivated crops.

Definition

Glossaqualfs are the Aqualfs that:

1. Have a glossic horizon;

2. Have a frigid, mesic, isomesic, or warmer temperature

regime;

3. Have, in all horizons at a depth between 30 and 150 cm

from the mineral soil surface, less than 50 percent (by volume)

plinthite;

4. Do not have a fragipan, a duripan, a kandic horizon, or a

natric horizon;

5. Do not have one or more layers, at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, that

have 50 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts;

6. Do not have both an abrupt textural change between the

ochric epipedon or albic horizon and the argillic horizon and a

moderately low or lower saturated hydraulic conductivity in the

argillic horizon.

Key to Subgroups

JAIA. Glossaqualfs that have a histic epipedon.

Histic Glossaqualfs

JAIB. Other Glossaqualfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more below the mineral soil surface.

Arenic Glossaqualfs

JAIC. Other Glossaqualfs that have:
Alfisols 183

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of

the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm or

more thick; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, one or

a combination of the following colors:

a. Hue of 7.5YR or redder in 50 percent or more of the

matrix; and

(1) If peds are present, chroma of 2 or more on 50

percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. In 50 percent or more of the matrix, hue of 10YR or

yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more (moist and dry); or

(2) Chroma of 2 or more if there are no redox

concentrations.

Aeric Fragic Glossaqualfs

JAID. Other Glossaqualfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Glossaqualfs

JAIE. Other Glossaqualfs that have, in one or more horizons

between the A or Ap horizon and a depth of 75 cm below the

mineral soil surface, in 50 percent or more of the matrix, one

or a combination of the following colors:

1. Hue of 7.5YR or redder; and

a. If peds are present, chroma of 2 or more (both moist

and dry) on 50 percent or more of ped exteriors or no

redox depletions with chroma of 2 or less (both moist and

dry) in ped interiors; or

b. If peds are absent, chroma of 2 or more (both moist

and dry); or

2. Hue of 10YR or yellower and either:

a. Both a color value of 3 or more (moist) and chroma

of 3 or more (moist and dry); or

b. Chroma of 2 or more (both moist and dry) and no

redox concentrations.

Aeric Glossaqualfs

JAIF. Other Glossaqualfs that have a mollic epipedon, an Ap

horizon that meets all of the requirements for a mollic

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Mollic Glossaqualfs

JAIG. Other Glossaqualfs.

Typic Glossaqualfs

Definition of Typic Glossaqualfs

Typic Glossaqualfs are the Glossaqualfs that:

1. Do not have a histic epipedon;

2. Do not have, in any horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following: either

a. Hue of 7.5YR or redder; and

(1) If peds are present, either chroma of 2 or more on

50 percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and chroma

of 3 or more (moist and dry); or

(2) Chroma of 2 or more (both moist and dry) and no

redox concentrations;

3. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

4. Do not have a mollic epipedon, an Ap horizon that meets

all of the requirements for a mollic epipedon except thickness,

or materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing;

5. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Glossaqualfs.—The central concept or Typic

subgroup of Glossaqualfs is fixed on soils that have dominantly
184 Soil Taxonomy

low chroma throughout the horizons below the A or Ap

horizon, to a depth of 75 cm or more. These soils do not have a

mollic epipedon, nor do they have a plow layer or an

equivalent horizon that meets all of the requirements for a

mollic epipedon except thickness. Soils that have a thick

epipedon with a sandy or sandy-skeletal particle-size class

throughout are assigned to the Arenic subgroup. Soils that

have fragic soil properties in a significant volume are assigned

to Fragic or combination Fragic subgroups because these

properties are shared with Fragiaqualfs and Fragiudalfs. Typic

Glossaqualfs are the wettest Glossaqualfs.

Higher chroma than that of Typic Glossaqualfs is

characteristic of the somewhat better drained Glossaqualfs and

is used to define the Aeric subgroup, which consists of

intergrades to Glossudalfs. Typic Glossaqualfs occur

throughout the areas of Glossaqualfs in the United States. Most

of them are cultivated.

Aeric Fragic Glossaqualfs.—These soils have fragic soil

properties in a significant volume but do not have a fragipan

unless it has its upper boundary at a depth of more than 100

cm below the mineral soil surface. Below the A or Ap horizon,

these soils have chroma that is too high for the Typic subgroup.

The high chroma commonly occurs in the matrix of the peds in

the argillic horizon. The soils are otherwise like Typic

Glossaqualfs in their defined properties and in most other

properties. Aeric Fragic Glossaqualfs are rare in the United

States.

Aeric Glossaqualfs.—These soils have some subhorizon

between the A or Ap horizon and a depth of 75 cm that has

chroma that is too high for Typic Glossaqualfs. The period of

saturation is somewhat shorter than that in soils of the Typic

subgroup. Aeric Glossaqualfs occur throughout the areas of

Glossaqualfs in the United States. Most of them are cultivated.

Arenic Glossaqualfs.—These soils have a sandy or sandyskeletal layer, starting at the mineral soil surface, that is 50 cm

or more thick. The epipedon overlies an argillic horizon. The

chroma may or may not be higher than that in the Typic

subgroup. These soils occur in Florida but are not extensive in

the United States.

Fragic Glossaqualfs.—These soils have fragic soil

properties in a significant volume but do not have a fragipan

unless it has its upper boundary at a depth of more than 100

cm below the mineral soil surface. The soils are otherwise like

Typic Glossaqualfs in their defined properties and in most

other properties. Fragic Glossaqualfs are rare in the United

States.

Histic Glossaqualfs.—These soils have a Histic epipedon.

They occur near sea level and are thought to have had a lower

water table at the time the argillic horizon formed than they

have now. They are known to occur only in Florida in the

United States.

Mollic Glossaqualfs.—These soils have a mollic epipedon or

a plow layer or its equivalent, if not plowed, that meets all of the

requirements for a mollic epipedon except thickness. These

soils are known to occur only in Minnesota in the United

States.

Kandiaqualfs

These are the Aqualfs that have a frigid, mesic, isomesic, or

warmer temperature regime and a kandic horizon. These soils

do not have a fragipan, a duripan, or a natric horizon. Plinthite

constitutes less than half of the volume of the matrix in all

subhorizons at a depth between 30 and 150 cm from the soil

surface. The soils are allowed, but not required, to have a

glossic horizon. Characteristically, they have the most warm

and humid climates of the Aqualfs and the most water passing

through the profile and have a relatively low base saturation for

soils of this order. The vegetation is mostly tropical or

subtropical hardwood forest. Slopes are nearly level or concave.

Kandiaqualfs are mostly in tropical and subtropical areas.

They are rare in the United States.

Definition

Kandiaqualfs are the Aqualfs that:

1. Have a kandic horizon;

2. Have a frigid, mesic, isomesic, or warmer temperature

regime;

3. Do not have a natric horizon or a duripan;

4. Have, in all horizons at a depth between 30 and 150 cm

from the mineral soil surface, less than 50 percent (by volume)

plinthite;

5. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface.

Key to Subgroups

JAFA. Kandiaqualfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a kandic horizon at a depth of

50 to 100 cm below the mineral soil surface.

Arenic Kandiaqualfs

JAFB. Other Kandiaqualfs that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 100 cm or more below the mineral soil surface.

Grossarenic Kandiaqualfs

JAFC. Other Kandiaqualfs that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kandiaqualfs

JAFD. Other Kandiaqualfs that have both:

1. An Ap horizon with a color value, moist, of 3 or less
Alfisols 185

and a color value, dry, of 5 or less (crushed and smoothed

sample) or materials between the soil surface and a depth of

18 cm that have these color values after mixing; and

2. In one or more horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following colors:

a. Hue of 7.5YR or redder; and

(1) If peds are present, chroma of 2 or more (both

moist and dry) on 50 percent or more of ped exteriors

or no redox depletions with chroma of 2 or less (both

moist and dry) in ped interiors; or

(2) If peds are absent, chroma of 2 or more (both

moist and dry); or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and

chroma of 3 or more (moist and dry); or

(2) Chroma of 2 or more (both moist and dry) and

no redox concentrations.

Aeric Umbric Kandiaqualfs

JAFE. Other Kandiaqualfs that have, in one or more horizons

between the A or Ap horizon and a depth of 75 cm below the

mineral soil surface, in 50 percent or more of the matrix, one

or a combination of the following colors:

1. Hue of 7.5YR or redder; and

a. If peds are present, chroma of 2 or more (both moist

and dry) on 50 percent or more of ped exteriors or no

redox depletions with chroma of 2 or less (both moist and

dry) in ped interiors; or

b. If peds are absent, chroma of 2 or more (both moist

and dry); or

2. Hue of 10YR or yellower and either:

a. Both a color value of 3 or more (moist) and chroma

of 3 or more (moist and dry); or

b. Chroma of 2 or more (both moist and dry) and no

redox concentrations.

Aeric Kandiaqualfs

JAFF. Other Kandiaqualfs that have an umbric epipedon, an

Ap horizon that meets all of the requirements for an umbric

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Umbric Kandiaqualfs

JAFG. Other Kandiaqualfs.

Typic Kandiaqualfs

Definition of Typic Kandiaqualfs

Typic Kandiaqualfs are the Kandiaqualfs that:

1. Do not have, in any horizons between the A or Ap horizon

and a depth of 75 cm below the mineral soil surface, in 50

percent or more of the matrix, one or a combination of the

following: either

a. Hue of 7.5YR or redder; and

(1) If peds are present, either chroma of 2 or more on

50 percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. Hue of 10YR or yellower and either:

(1) Both a color value of 3 or more (moist) and chroma

of 3 or more (moist and dry); or

(2) Chroma of 2 or more (both moist and dry) and no

redox concentrations;

2. Have an Ap horizon that has either a color value, moist, of

4 or more or a color value, dry, of 6 or more after the soil has

been crushed or have these color values in the upper 18 cm

after mixing;

3. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

4. Do not have a horizon within 150 cm of the soil surface

that has 5 percent or more plinthite, by volume.

Description of Subgroups

Typic Kandiaqualfs.—The central concept or Typic

subgroup of Kandiaqualfs is fixed on soils that (1) have

dominantly low chroma between the A or Ap horizon and a

depth of 75 cm or more from the mineral soil surface; (2) have

a lighter color value, moist, in the plow layer, or in comparable

horizons if undisturbed, than in an umbric epipedon; and (3)

do not have a thick epipedon with a sandy or sandy-skeletal

particle-size class throughout.

Chroma higher than that of Typic Kandiaqualfs is

characteristic of soils that are saturated for shorter periods and

serves to define intergrades to freely drained soils. Color

values, moist, of 2 or 3 in a plow layer indicate a higher-thannormal content of organic matter and form the basis for

defining intergrades to other great groups. A thick layer of

sand or loamy sand, starting at the mineral soil surface, is the

basis for defining the Arenic and Grossarenic subgroups. Typic

Kandiaqualfs are not known to occur in the United States.

Aeric Kandiaqualfs.—Below the A or Ap horizon, these

soils have chroma that is too high for the Typic subgroup, but

they are otherwise like Typic Kandiaqualfs in their defined

properties and in most other properties. Aeric Kandiaqualfs are

not known to occur in the United States.
186 Soil Taxonomy

Aeric Umbric Kandiaqualfs.—These soils have an umbric

epipedon or a surface horizon that meets all of the

requirements for an umbric epipedon except thickness. Below

the A or Ap horizon, these soils have chroma that is too high for

the Typic subgroup. They are otherwise like Typic Kandiaqualfs

in their defined properties and in most other properties. Aeric

Umbric Kandiaqualfs are not known to occur in the United

States.

Arenic Kandiaqualfs.—These soils have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 50 to 100 cm below the mineral soil surface. The

upper part of the kandic horizon or the lower part of the

epipedon is permitted to have, in 50 percent or more of the

matrix, chroma that is too high for Typic Kandiaqualfs. Arenic

Kandiaqualfs may also have either an Ap horizon with a color

value, moist, of 3 or less and a color value, dry, of 5 or less

(crushed and smoothed sample) or, if undisturbed, materials

between the soil surface and a depth of 18 cm that have these

colors after mixing. These soils are otherwise like those of the

Typic subgroup in their defined properties. Arenic

Kandiaqualfs are not known to occur in the United States.

Grossarenic Kandiaqualfs.—These soils have a sandy or

sandy-skeletal particle-size class throughout a layer extending

from the mineral soil surface to the top of a kandic horizon at a

depth of 100 cm or more below the mineral soil surface. These

soils are not known to occur in the United States.

Plinthic Kandiaqualfs.—These soils have 5 percent or

more (by volume) plinthite in one or more horizons within 150

cm of the mineral soil surface. These soils are not known to

occur in the United States.

Umbric Kandiaqualfs.—These soils have an umbric

epipedon or a plow layer or its equivalent, if not plowed, that

meets all of the requirements for an umbric epipedon except

thickness. These soils are not known to occur in the United

States.

Natraqualfs

Natraqualfs are the Aqualfs that have a natric horizon and

have a frigid, mesic, isomesic, or warmer temperature regime.

These soils do not have a duripan, and plinthite constitutes less

than one-half of the volume of the matrix in all subhorizons at

a depth between 30 and 150 cm from the soil surface.

Typically, ground water perches above the natric horizon at one

period and saturates the soils at another period. Natraqualfs are

allowed, but not required, to have a glossic horizon. In the

United States, most of these soils have a mesic, thermic, or

hyperthermic temperature regime, but a few are frigid. If

undisturbed, Natraqualfs commonly have a thin A horizon

overlying a thin albic horizon that, in turn, overlies the natric

horizon. If the soils are plowed, the two upper horizons and

part of the natric horizon or only part of the two upper

horizons may be mixed.

In the United States, the vegetation on Natraqualfs before

cultivation most commonly was grass or mixed grass and

drought-tolerant trees. In humid regions where the precipitation

is 100 cm or more, the presence of sodium generally is attributed

to very slow permeability in the natric horizon. The permeability

is so slow that there is thought to

be less leaching of sodium than there is release of sodium by

the weathering of feldspars. Many Natraqualfs in the United

States formed in loess or alluvium of Wisconsinan age.

Some Natraqualfs are in basins or on lowlands and are

subject to flooding, and the sodium in them may be supplied by

salty ground water or sea water. Characteristically, areas of

Natraqualfs are small.

Definition

Natraqualfs are the Aqualfs that:

1. Have a natric horizon;

2. Have a frigid, mesic, isomesic, or warmer temperature

regime;

3. Do not have a duripan;

4. Have, in all horizons at a depth between 30 and 150 cm

from the mineral soil surface, less than 50 percent (by volume)

plinthite.

Key to Subgroups

JADA. Natraqualfs that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Natraqualfs

JADB. Other Natraqualfs that have one or more layers, at

least 25 cm thick (cumulative) within 100 cm of the mineral

soil surface, that have 25 percent or more (by volume)

recognizable bioturbation, such as filled animal burrows,

wormholes, or casts.

Vermic Natraqualfs

JADC. Other Natraqualfs that have both:

1. A glossic horizon or interfingering of albic materials

into the natric horizon; and

2. An exchangeable sodium percentage of less than 15 and

less magnesium plus sodium than calcium plus extractable

acidity either throughout the upper 15 cm of the natric
Alfisols 187

horizon or in all horizons within 40 cm of the mineral soil

surface, whichever is deeper.

Albic Glossic Natraqualfs

JADD. Other Natraqualfs that have an exchangeable sodium

percentage of less than 15 and less magnesium plus sodium than

calcium plus extractable acidity either throughout the upper 15

cm of the natric horizon or in all horizons within 40 cm of the

mineral soil surface, whichever is deeper.

Albic Natraqualfs

JADE. Other Natraqualfs that have a glossic horizon or

interfingering of albic materials into the natric horizon.

Glossic Natraqualfs

JADF. Other Natraqualfs that have a mollic epipedon, an Ap

horizon that meets all of the requirements for a mollic

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Mollic Natraqualfs

JADG. Other Natraqualfs.

Typic Natraqualfs

Definition of Typic Natraqualfs

Typic Natraqualfs are the Natraqualfs that:

1. Do not have a glossic horizon or interfingering of albic

materials more than 2.5 cm into the natric horizon;

2. Do not have a mollic epipedon, an Ap horizon that meets

all of the requirements for a mollic epipedon except thickness,

or materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing;

3. Have, in some horizon within 40 cm of the soil surface or

within the upper 15 cm of the natric horizon, whichever is

deeper, 15 percent or more saturation with sodium or more

magnesium plus sodium than calcium plus extractable acidity;

4. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

5. Do not have one or more layers, at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, that

have 25 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts.

Description of Subgroups

Typic Natraqualfs.—The central concept or Typic

subgroup of Natraqualfs is fixed on soils that (1) have high

saturation with sodium or more magnesium and sodium than

calcium and extractable acidity in the upper part; (2) have

dominantly low chroma between the A or Ap horizon and a

depth of 75 cm or more from the mineral soil surface; (3) do

not have a glossic horizon or interfingering of albic materials

more than 2.5 cm into the natric horizon; (4) have an ochric

epipedon and do not meet any of the requirements for a mollic

epipedon, except for thickness, in the plow layer or in

comparable horizons if undisturbed; and (5) do not have both

cracks and slickensides, wedge-shaped aggregates, or a linear

extensibility of 6.0 cm or more to a depth of 100 cm from the

mineral soil surface.

Chroma higher than that of Typic Natraqualfs is characteristic

of soils that are saturated for shorter periods and serves to

define intergrades to freely drained soils. Soils that have

slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks are assigned to Vertic subgroups

because these properties are shared with Vertisols. Natraqualfs

that have a mollic epipedon or an epipedon that meets all of

the requirements for a mollic epipedon except thickness are

considered intergrades to Natraquolls and form the basis for

defining the Mollic subgroup. Typic Natraqualfs are not

extensive. The Typic subgroup is not necessarily the most

extensive, but it provides what seems to be the best base for

defining other subgroups. Many of these soils are in Texas, and

others are widely distributed in the United States. Because the

area of Typic Natraqualfs is small, their use generally is

determined by the use of the associated soils. Many Typic

Natraqualfs have been cleared and are used as cropland, but

some are used as pasture or are in forests. Some of these soils

are used for rice. The amount of calcium in some of these soils

is inadequate for some plants.

Albic Glossic Natraqualfs.—These soils have less than 15

percent sodium and less sodium plus magnesium than calcium

plus exchangeable acidity in the upper part of the natric

horizon or the upper part of the soils if the top of the natric

horizon is deep. These soils also have a glossic horizon or albic

materials interfingering into the natric horizon. There are

fewer problems of plant nutrition in these soils than in soils of

the Typic subgroup. Nevertheless, moisture relations as a rule

negatively affect the productivity of Albic Glossic Natraqualfs.

These soils are of small extent in the United States and are

mostly near the gulf coast. Commonly, they occur in small

areas, and the use of these soils is closely associated with the

use of the surrounding soils.

Albic Natraqualfs.—These soils have less than 15 percent

sodium and less sodium plus magnesium than calcium plus

exchangeable acidity in the upper part of the natric horizon or
188 Soil Taxonomy

the upper part of the soils if the top of the natric horizon is deep.

These soils are otherwise much like Typic Natraqualfs in defined

properties. There are fewer problems of plant nutrition in Albic

Natraqualfs than in soils of the Typic subgroup. Nevertheless,

moisture relations as a rule negatively affect the productivity of

Albic Natraqualfs. Commonly, the extent of these soils is small,

and the use of the soils is closely associated with the use of the

surrounding soils.

Glossic Natraqualfs.—These soils have a glossic horizon

or interfingering of albic materials in the upper part of the

natric horizon but are otherwise like Typic Natraqualfs in

defined properties. In general, the natric horizon is deeper in

soils of this subgroup than in Typic Natraqualfs. In the United

States, Glossic Natraqualfs are of only small extent. They occur

principally in the Mississippi River Valley, California, and

Montana. Their use generally is determined by the use of the

associated soils.

Mollic Natraqualfs.—These soils have a mollic epipedon

or a surface horizon that meets all of the requirements for a

mollic epipedon except thickness. The soils are intergrades to

Natraquolls. They are of very small extent in the United States.

Vermic Natraqualfs.—These soils have one or more layers,

at least 25 cm thick within 100 cm of the mineral soil surface,

that have 25 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts. The soils are intergrades to Vermaqualfs. They are of

very small extent in the United States and are mainly in Texas.

Vertic Natraqualfs.—These soils are like Typic Natraqualfs,

but they are high in content of expanding clays and have cracks

5 mm or more wide, slickensides, wedge-shaped aggregates, or a

high linear extensibility. These soils are not extensive. They are

nearly level. Most have been cleared and are used as cropland,

but some are used as pasture or are in forests.

Plinthaqualfs

Plinthaqualfs are the Aqualfs that have a frigid, mesic,

isomesic, or warmer temperature regime. Plinthite constitutes

one-half or more of the volume of the matrix in some

subhorizon at a depth between 30 and 150 cm from the soil

surface. These soils are mainly in depressions in areas of wetdry tropical and subtropical climates. They are not known to

occur in the United States, but they are reported to be extensive

in Africa south of the Sahara. They are perhaps the least used

of the Alfisols, at least in part because they tend to be too wet

in the rainy season and too dry in the dry season for most

crops. On most of these soils, the vegetation is or was savanna

or a deciduous broadleaf forest.

Definition

Plinthaqualfs are the Aqualfs that:

1. Have one or more horizons at a depth between 30 and 150

cm from the mineral soil surface in which plinthite either

forms a continuous phase or constitutes one-half or more of the

volume;

2. Have a frigid, mesic, isomesic, or warmer temperature regime.

Key to Subgroups

JABA. All Plinthaqualfs (provisionally).

Typic Plinthaqualfs

Vermaqualfs

Vermaqualfs are the Aqualfs that have one or more layers,

at least 25 cm thick (cumulative) within 100 cm of the

mineral soil surface, that have 50 percent or more (by volume)

recognizable bioturbation, such as filled animal burrows,

wormholes, or casts. Bioturbation has destroyed less than

one-half of the volume of some part of the argillic horizon.

Krotovinas restrict water movement because they are dense,

massive, compact, and stratified. Soil horizons are obliterated

where the krotovinas occur. Significant amounts of krotovinas

in a soil affect soil morphology, soil hydrology, and soil

behavior. These soils are known to in areas occur along the

coastal plain of Texas where the bioturbation is caused by

crayfish.

Definition

Vermaqualfs are the Aqualfs that:

1. Have one or more layers, at least 25 cm thick (cumulative)

within 100 cm of the mineral soil surface, that have 50 percent

or more (by volume) recognizable bioturbation, such as filled

animal burrows, wormholes, or casts;

2. Have a frigid, mesic, isomesic, or warmer temperature

regime;

3. Have, in all horizons at a depth between 30 and 150 cm

from the mineral soil surface, less than 50 percent (by volume)

plinthite;

4. Do not have a duripan, a kandic horizon, or a natric

horizon;

5. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface.

Key to Subgroups

JAGA. Vermaqualfs that have an exchangeable sodium

percentage of 7 or more (or a sodium adsorption ratio of 6 or

more) either or both:

1. Throughout the upper 15 cm of the argillic horizon;

and/or

2. Throughout all horizons within 40 cm of the mineral

soil surface.

Natric Vermaqualfs
Alfisols 189

JAGB. Other Vermaqualfs.

Typic Vermaqualfs

Definition of Typic Vermaqualfs

Typic Vermaqualfs are the Vermaqualfs that have an

exchangeable sodium percentage of less than 7 throughout the

upper 15 cm of the argillic horizon and throughout all horizons

within 40 cm of the mineral soil surface.

Description of Subgroups

Typic Vermaqualfs.—Typic Vermaqualfs are the

Vermaqualfs that have an exchangeable sodium percentage of

less than 7 (and a sodium adsorption ratio of less than 6) both

in some part of the upper 15 cm of the argillic horizon and in

some horizon within 40 cm of the mineral soil surface.

Natric Vermaqualfs.—Natric Vermaqualfs are the

Vermaqualfs that have an exchangeable sodium percentage of 7

or more (and a sodium adsorption ratio of 6 or more) either in

some part of the upper 15 cm of the argillic horizon or in some

horizon within 40 cm of the mineral soil surface.

Cryalfs

Cryalfs are the more or less freely drained Alfisols of cold

regions. Nearly all of these soils have a cryic temperature

regime and normally have a udic moisture regime.

Cryalfs are not extensive. They formed in North America,

Eastern Europe, and Asia above 49o N. latitude and in some

high mountains south of that latitude. In the mountains, they

tend to form below the Spodosols or Inceptisols. Most Cryalfs

are or have been under a coniferous forest. In North America

they are mainly in forests because of their short, cool growing

season.

Characteristically, Cryalfs have an O horizon, an albic

horizon, and an argillic horizon. In some areas they have a thin

A horizon. In regions of the least rainfall, they are neutral or

slightly acid in all horizons and a Bk horizon may underlie the

argillic horizon. In many of the more humid areas of their

occurrence, the lower part of the albic horizon and the upper

part of the argillic horizon are strongly or very strongly acid.

Cryalfs in the United States generally developed in

Pleistocene deposits, mostly of Wisconsinan age.

Definition

Cryalfs are the Alfisols that:

1. Do not have both aquic conditions and the colors defined

for Aqualfs; and

2. Have a cryic temperature regime.

Key to Great Groups

JBA. Cryalfs that have all of the following:

1. An argillic, kandic, or natric horizon that has its upper

boundary 60 cm or more below both:

a. The mineral soil surface; and

b. The lower boundary of any surface mantle containing

30 percent or more vitric volcanic ash, cinders, or other

vitric pyroclastic materials; and

2. A texture (in the fine-earth fraction) finer than loamy fine

sand in one or more horizons above the argillic, kandic, or

natric horizon; and

3. Either a glossic horizon or interfingering of albic materials

into the argillic, kandic, or natric horizon.

Palecryalfs, p. 198

JBB. Other Cryalfs that have a glossic horizon.

Glossocryalfs, p. 189

JBC. Other Cryalfs.

Haplocryalfs, p. 193

Glossocryalfs

Glossocryalfs are the Cryalfs that have a glossic horizon and

normally have an argillic horizon that has an upper boundary

within 60 cm of the mineral soil surface. The argillic, kandic,

or natric horizon has its upper boundary within 60 cm of the

soil surface, unless there is either a sandy or sandy-skeletal

particle-size class throughout the layers above the argillic,

kandic, or natric horizon or there is a surface mantle or layer in

the upper 75 cm consisting of slightly or moderately weathered

pyroclastic materials.

The glossic horizon commonly has tonguelike projections of

albic materials extending into the argillic horizon. These

projections are thought to indicate that the argillic horizon is

being moved deeper into the soils. In the areas where the soils

are transitional between Spodosols and Alfisols, some

Glossocryalfs have a cambic horizon that appears to be an

incipient spodic horizon. The cambic horizon is commonly

separated from the argillic horizon by an albic horizon. The

vegetation is mostly coniferous trees. A few Glossocryalfs have

been cleared and are used mostly as pasture.

Definition

Glossocryalfs are the Cryalfs that have:

1. A glossic horizon; and

2. One or more of the following:

a. An argillic, kandic, or natric horizon that has its upper

boundary at less than 60 cm below the mineral soil surface;

or

b. An argillic, kandic, or natric horizon that has its upper
190 Soil Taxonomy

boundary at less than 60 cm below the lower boundary of

any surface mantle containing 30 percent or more vitric

volcanic ash, cinders, or other vitric pyroclastic materials;

or

c. No texture (in the fine-earth fraction) finer than loamy fine

sand in any horizon above the argillic, kandic, or natric

horizon.

Key to Subgroups

JBBA. Glossocryalfs that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Glossocryalfs

JBBB. Other Glossocryalfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Glossocryalfs

JBBC. Other Glossocryalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Glossocryalfs

JBBD. Other Glossocryalfs that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Glossocryalfs

JBBE. Other Glossocryalfs that have, in one or more

subhorizons within the upper 25 cm of the argillic, kandic, or

natric horizon, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years

(or artificial drainage).

Aquic Glossocryalfs

JBBF. Other Glossocryalfs that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Glossocryalfs

JBBG. Other Glossocryalfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Glossocryalfs

JBBH. Other Glossocryalfs that have:

1. A xeric moisture regime; and

2. An Ap horizon with a color value, moist, of 3 or

less and a color value, dry, of 5 or less (crushed and

smoothed sample) or materials between the soil surface

and a depth of 18 cm that have these color values after

mixing; and

3. A base saturation of 50 percent or more (by NH4

OAc)

in all parts from the mineral soil surface to a depth of 180

cm or to a densic, lithic, or paralithic contact, whichever is

shallower.

Xerollic Glossocryalfs

JBBI. Other Glossocryalfs that have:

1. A xeric moisture regime; and

2. An Ap horizon with a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed

sample) or materials between the soil surface and a depth of

18 cm that have these color values after mixing.

Umbric Xeric Glossocryalfs

JBBJ. Other Glossocryalfs that:

1. Are dry in some part of the moisture control section for

45 or more days (cumulative) in normal years; and

2. Have an Ap horizon with a color value, moist, of 3 or

less and a color value, dry, of 5 or less (crushed and

smoothed sample) or materials between the soil surface and

a depth of 18 cm that have these color values after mixing;

and
Alfisols 191

3. Have a base saturation of 50 percent or more (by

NH4

OAc) in all parts from the mineral soil surface to a depth

of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower.

Ustollic Glossocryalfs

JBBK. Other Glossocryalfs that have a xeric moisture

regime.

Xeric Glossocryalfs

JBBL. Other Glossocryalfs that are dry in some part of the

moisture control section for 45 or more days (cumulative) in

normal years.

Ustic Glossocryalfs

JBBM. Other Glossocryalfs that:

1. Have an Ap horizon with a color value, moist, of 3 or

less and a color value, dry, of 5 or less (crushed and

smoothed sample) or materials between the soil surface and

a depth of 18 cm that have these color values after mixing;

and

2. Have a base saturation of 50 percent or more (by

NH4OAc) in all parts from the mineral soil surface to a

depth of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower.

Mollic Glossocryalfs

JBBN. Other Glossocryalfs that have an Ap horizon with a

color value, moist, of 3 or less and a color value, dry, of 5 or

less (crushed and smoothed sample) or materials between the

soil surface and a depth of 18 cm that have these color values

after mixing.

Umbric Glossocryalfs

JBBO. Other Glossocryalfs that have a base saturation of 50

percent or more (by NH4OAc) in all parts from the mineral soil

surface to a depth of 180 cm or to a densic, lithic, or paralithic

contact, whichever is shallower.

Eutric Glossocryalfs

JBBP. Other Glossocryalfs.

Typic Glossocryalfs

Definition of Typic Glossocryalfs

Typic Glossocryalfs are the Glossocryalfs that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have one or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

3. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

4. In any subhorizon within the upper 25 cm of the argillic,

kandic, or natric horizon, do not have redox depletions with

chroma of 2 or less and also aquic conditions;

5. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 7 or more consecutive days or 20 or

more cumulative days in normal years;

6. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick;

7. Have a udic moisture regime;

8. Are dry in some part of the moisture control section for

less than 45 days (cumulative) in normal years;

9. Have an Ap horizon with a color value, moist, of 4 or more

or a color value, dry, of 6 or more (crushed and smoothed

sample) or materials between the soil surface and a depth of 18

cm that have these color values after mixing;

10. Have a base saturation of less than 50 percent (by
192 Soil Taxonomy

NH4

OAc) in some part between the mineral soil surface and a

depth of 180 cm or a densic, lithic, or paralithic contact,

whichever is shallower.

Description of Subgroups

Typic Glossocryalfs.—The central concept or Typic

subgroup of Glossocryalfs is fixed on freely drained soils that

are deep or moderately deep to hard rock and that have a high

color value to a depth comparable to that of an Ap horizon.

The soils have a glossic horizon and are moist in all but short

periods during the growing season.

These soils do not have slickensides, wedge-shaped

aggregates, a high linear extensibility, or wide cracks because

these properties are shared with Vertisols. Soils that have both

a low bulk density and a high content of weakly crystalline

minerals or that have a high content of volcanic glass are

excluded from Typic Glossocryalfs because these properties are

shared with Andisols. Soils that have both redox depletions

with low chroma in the upper 25 cm of the argillic, kandic, or

natric horizon and ground water within this depth are excluded

from Typic Glossocryalfs because these properties are shared

with Aqualfs. Other soils that are saturated with water within

100 cm of the mineral soil surface for 20 or more consecutive

days or 30 or more cumulative days in normal years are

excluded because of importance to the use of these soils. Soils

with a layer having fragic soil properties also are excluded

because these properties are shared with Fraglossudalfs and

Fragiudalfs. Typic Glossocryalfs do not have a surface mantle

or layer in the upper 75 cm that has both a low bulk density

and a high content of weakly crystalline minerals or that

consists of slightly or moderately weathered pyroclastic

materials because these properties are shared with Andisols.

Soils that have a xeric moisture regime and other soils that are

dry for more than 45 days also are excluded because they share

properties with Xeralfs and Ustalfs. Soils that have a surface

horizon as thick as 15 cm that is dark enough to be near or

within the range of a mollic or umbric epipedon are recognized

as Mollic intergrades or Umbric extragrades.

Typic Glossocryalfs are in the mountains in the Western

United States. They generally are under a coniferous forest.

They have gentle to very steep slopes. They are of small extent

in the United States and are rare elsewhere.

Andic and Vitrandic Glossocryalfs.—These soils are like

Typic Glossocryalfs, but they have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the high mountains of the Western United States.

They are permitted, but not required, to have redox depletions

and also a color value of 3 or less, moist, and 5 or less, dry, in

surface horizons, after mixing to a depth of 15 cm. They also

are permitted to be dry for more than 45 days. They are not

extensive. Most of them have moderate or strong slopes and

are used for limited summer grazing, as forest, or as wildlife

habitat.

Aquic Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they have redox depletions with chroma of 2

or less and have horizons, within 75 cm of the surface, that are

saturated with water at some time during the year. The gray

redox depletions should not be confused with low chroma of

the glossic horizon. In addition to the redox depletions, Aquic

Glossocryalfs are permitted to have a color value of 3 or less,

moist, and 5 or less, dry, in surface horizons, after mixing to a

depth of 15 cm. The wetness is caused mainly by slowly

permeable materials in the lower horizons or the substratum.

These soils are rare in the United States.

Eutric Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they have a base saturation of 50 percent or

more (by NH4

OAc) in all parts between the mineral soil surface

and a depth of 180 cm or a densic, lithic, or paralithic contact,

whichever is shallower. These soils formed mostly in

calcareous materials. They support range or coniferous forest

vegetation and have gentle to very steep slopes. They are of

small extent in the United States and are rare elsewhere.

Fragic Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they have a fragipan or at least 30 percent

(by volume) peds with fragic soil properties in the upper part of

the argillic horizon. Fragic Glossocryalfs have not been

recognized in the United States.

Lithic Glossocryalfs.—These soils are permitted to have

any of the properties of Glossocryalfs. They are required to

have a lithic contact within 50 cm of the surface. These soils

are of small extent in the Western United States.

Mollic Glossocryalfs.—These soils are like Typic

Glossocryalfs, but their upper horizons have a color value of 3

or less, moist, and 5 or less, dry, after mixing to a depth of 15

cm. Mollic Glossocryalfs have a base saturation of 50 percent

or more (by NH4

OAc) in all parts from the mineral soil surface

to a depth of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower. These soils commonly support a

coniferous forest in which the trees are more widely spaced

than is typical for Glossocryalfs. Mollic Glossocryalfs are not

extensive in the United States except very locally.

Oxyaquic Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they are saturated with water within 100 cm

of the mineral soil surface for 20 or more consecutive days or

30 or more cumulative days in normal years. Oxyaquic

Glossocryalfs are permitted to have a color value of 3 or less,

moist, and 5 or less, dry, in surface horizons, after mixing to a

depth of 15 cm. The wetness is caused mainly by slowly

permeable materials in the lower horizons or the substratum.

These soils are rare in the United States.

Umbric Glossocryalfs.—These soils are like Typic

Glossocryalfs, but their upper horizons have a color value of 3

or less, moist, and 5 or less, dry, after mixing to a depth of 15

cm. These soils have a base saturation of less than 50 percent
Alfisols 193

(by NH4

OAc) in some part between the mineral soil surface and

a depth of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower. The soils commonly support coniferous

forest. Some forests have widely spaced trees. In some areas

these soils are used as rangeland. The soils are not extensive in

the United States.

Umbric Xeric Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they have a xeric moisture regime and their

upper horizons have a color value of 3 or less, moist, and 5 or

less, dry, after mixing to a depth of 15 cm. These soils have a

base saturation of less than 50 percent (by NH4OAc) in some

part between the mineral soil surface and a depth of 180 cm or

a densic, lithic, or paralithic contact, whichever is shallower.

Umbric Xeric Glossocryalfs commonly support coniferous

forest. Some forests have widely spaced trees. In some areas

these soils are used as rangeland. They are not extensive in the

United States.

Ustic Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they are dry in some part of the moisture

control section for 45 or more days (cumulative) in normal

years. They are considered to be transitional to Ustalfs. Ustic

Glossocryalfs commonly support a sparse coniferous forest with

widely spaced trees or are used as rangeland. They are not

extensive in the United States except very locally.

Ustollic Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they are dry in some part of the moisture

control section for 45 or more days (cumulative) in normal

years and their upper horizons have a color value of 3 or less,

moist, and 5 or less, dry, after mixing to a depth of 15 cm.

These soils have a base saturation of 50 percent or more (by

NH4

OAc) in all parts from the mineral soil surface to a depth

of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower. They are considered to be transitional

to Ustolls. They commonly support rangeland vegetation or a

sparse coniferous forest with widely spaced trees. They are not

extensive in the United States.

Vertic Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they are high in content of expanding clays

and have cracks 5 mm or more wide, slickensides, wedgeshaped aggregates, or a linear extensibility of 6.0 cm or more

between the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is shallower.

These soils are considered to be transitional to Vertisols. Vertic

Glossocryalfs support coniferous forest or are used as

rangeland. They are not extensive in the United States.

Xeric Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they have a xeric moisture regime. They are

considered to be transitional to Xeralfs. Xeric Glossocryalfs

commonly support coniferous forest. Some forests have widely

spaced trees. In some areas Xeric Glossocryalfs are used as

rangeland. These soils are not extensive in the United States.

Xerollic Glossocryalfs.—These soils are like Typic

Glossocryalfs, but they have a xeric moisture regime and their

upper horizons have a color value of 3 or less, moist, and 5 or

less, dry, after mixing to a depth of 15 cm. These soils have a

base saturation of 50 percent or more (by NH4

OAc) in all parts

from the mineral soil surface to a depth of 180 cm or to a densic,

lithic, or paralithic contact, whichever is shallower. They are

considered to be transitional to Xerolls. Xerollic Glossocryalfs

commonly support a sparse coniferous forest with widely

spaced trees or support rangeland vegetation. They are not

extensive in the United States.

Haplocryalfs

These are the Cryalfs with no glossic horizon. Most of these

soils have no interfingering of albic materials into the argillic,

kandic, or natric horizon. Most have an argillic horizon that

has an upper boundary within 60 cm of the mineral soil

surface. The common sequence of horizons is an O horizon, an

albic horizon, and an argillic horizon. There also are

transitional horizons and a Bw, Btk, or Bk horizon in some

pedons.

The Haplocryalfs of the United States are in the mountains

of the Western States and have a cryic temperature regime.

Most support coniferous forest vegetation. Virtually none of

them are cultivated because their slopes are steep and the

growing season is short and cool. In other countries,

Haplocryalfs occur on mountains and also on plains nearly as

far north as the line of continuous permafrost. Some of the

associated soils on these landscapes are Gelisols on northfacing slopes and Histosols.

Definition

Haplocryalfs are the Cryalfs that:

1. Do not have a glossic horizon; and

2. Have one or more of the following:

a. An argillic, kandic, or natric horizon that has its upper

boundary at less than 60 cm below the mineral soil surface;

or

b. An argillic, kandic, or natric horizon that has its upper

boundary at less than 60 cm below the lower boundary of

any surface mantle containing 30 percent or more vitric

volcanic ash, cinders, or other vitric pyroclastic materials;

or

c. No texture (in the fine-earth fraction) finer than loamy

fine sand in any horizon above the argillic, kandic, or natric

horizon; or

d. No interfingering of albic materials into the argillic or

natric horizon.

Key to Subgroups

JBCA. Haplocryalfs that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplocryalfs
194 Soil Taxonomy

JBCB. Other Haplocryalfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haplocryalfs

JBCC. Other Haplocryalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Haplocryalfs

JBCD. Other Haplocryalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Haplocryalfs

JBCE. Other Haplocryalfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Haplocryalfs

JBCF. Other Haplocryalfs that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplocryalfs

JBCG. Other Haplocryalfs that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or more

subhorizons with a thickness of 7.5 to 20 cm, each layer with

an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Haplocryalfs

JBCH. Other Haplocryalfs that have a sandy or sandy-skeletal

particle-size class throughout the upper 75 cm of the argillic,

kandic, or natric horizon or throughout the entire argillic,

kandic, or natric horizon if it is less than 75 cm thick.

Psammentic Haplocryalfs

JBCI. Other Haplocryalfs that have:

1. An argillic, kandic, or natric horizon that is 35 cm or

less thick; and

2. No densic, lithic, or paralithic contact within 100 cm of

the mineral soil surface.

Inceptic Haplocryalfs

JBCJ. Other Haplocryalfs that have:

1. A xeric moisture regime; and

2. An Ap horizon with a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed

sample) or materials between the soil surface and a depth of

18 cm that have these color values after mixing; and

3. A base saturation of 50 percent or more (by NH4

OAc)

in all parts from the mineral soil surface to a depth of 180

cm or to a densic, lithic, or paralithic contact, whichever is

shallower.

Xerollic Haplocryalfs

JBCK. Other Haplocryalfs that have:

1. A xeric moisture regime; and

2. An Ap horizon with a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed

sample) or materials between the soil surface and a depth of

18 cm that have these color values after mixing.

Umbric Xeric Haplocryalfs
Alfisols 195

JBCL. Other Haplocryalfs that:

1. Are dry in some part of the moisture control section for

45 or more days (cumulative) in normal years; and

2. Have an Ap horizon with a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed

sample) or materials between the soil surface and a depth of

18 cm that have these color values after mixing; and

3. Have a base saturation of 50 percent or more (by

NH4

OAc) in all parts from the mineral soil surface to a

depth of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower.

Ustollic Haplocryalfs

JBCM. Other Haplocryalfs that have a xeric moisture regime.

Xeric Haplocryalfs

JBCN. Other Haplocryalfs that are dry in some part of the

moisture control section for 45 or more days (cumulative) in

normal years.

Ustic Haplocryalfs

JBCO. Other Haplocryalfs that:

1. Have an Ap horizon with a color value, moist, of 3 or

less and a color value, dry, of 5 or less (crushed and

smoothed sample) or materials between the soil surface and

a depth of 18 cm that have these color values after mixing;

and

2. Have a base saturation of 50 percent or more (by

NH4

OAc) in all parts from the mineral soil surface to a

depth of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower.

Mollic Haplocryalfs

JBCP. Other Haplocryalfs that have an Ap horizon with a

color value, moist, of 3 or less and a color value, dry, of 5 or

less (crushed and smoothed sample) or materials between the

soil surface and a depth of 18 cm that have these color values

after mixing.

Umbric Haplocryalfs

JBCQ. Other Haplocryalfs that have a base saturation of 50

percent or more (by NH4OAc) in all parts from the mineral soil

surface to a depth of 180 cm or to a densic, lithic, or paralithic

contact, whichever is shallower.

Eutric Haplocryalfs

JBCR. Other Haplocryalfs.

Typic Haplocryalfs

Definition of Typic Haplocryalfs

Typic Haplocryalfs are the Haplocryalfs that:

1. Do not have a lithic contact within 50 cm of the mineral soil

surface;

2. Do not have one or both of the following:

a. Cracks within 125 cm of the mineral soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is

shallower;

3. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

4. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

5. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 7 or more consecutive days or 20 or

more cumulative days in normal years;

6. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness of 5
196 Soil Taxonomy

cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon;

7. Have an argillic, kandic, or natric horizon that is finer

than the sandy or sandy-skeletal particle-size class in some part

of the upper 75 cm if the argillic, kandic, or natric horizon is

more than 75 cm thick or in any part if the argillic, kandic, or

natric horizon is less than 75 cm thick;

8. Have an argillic, kandic, or natric horizon that is more

than 35 cm thick;

9. Have a udic moisture regime;

10. Are dry in some part of the moisture control section for

less than 45 days (cumulative) in normal years;

11. Have an Ap horizon with a color value, moist, of 4 or

more or a color value, dry, of 6 or more (crushed and smoothed

sample) or materials between the soil surface and a depth of 18

cm that have these color values after mixing; and

12. Have a base saturation of less than 50 percent (by

NH4

OAc) in some part between the mineral soil surface and a

depth of 180 cm or a densic, lithic, or paralithic contact,

whichever is shallower.

Description of Subgroups

Typic Haplocryalfs.—The central concept or Typic

subgroup of Haplocryalfs is fixed on freely drained soils that

are deep or moderately deep to hard rock and that do not have

a glossic horizon. These soils have a high color value in an Ap

horizon or in a layer of comparable depth after mixing and

have a loamy or finer textured argillic horizon not composed

entirely of thin lamellae.

These soils do not have slickensides, wedge-shaped

aggregates, a high linear extensibility, or wide cracks because

these properties are shared with Vertisols. Soils with both a low

bulk density and a high content of weakly crystalline minerals

or that consist of thin layers of pyroclastic materials are

excluded from Typic Haplocryalfs because they have properties

that are shared with the Andisols. Redox depletions and

saturation with water within 100 cm of the surface for extended

periods cause a soil to be excluded from the Typic subgroup

because they are properties shared with Aqualfs. A shallow

lithic contact defines the Lithic subgroup, a convention used

throughout this taxonomy.

Soils that have a xeric moisture regime and other soils that

are dry for more than 45 days also are excluded because they

share properties with Xeralfs and Ustalfs. Soils that have a

surface horizon as thick as 15 cm that is dark enough to be

near or within the range of a mollic or umbric epipedon are

excluded from the Typic subgroup because the thick, dark

horizon is believed to indicate a transitional form to Mollisols or

an Umbric extragrade.

Haplocryalfs with an argillic, kandic, or natric horizon that has

a sandy or sandy-skeletal particle-size class are excluded from

the Typic subgroup and are assigned to the Psammentic

subgroup. Soils that have a base saturation of 50 percent or

more (by NH4

OAc) in all parts from the mineral soil surface to

a depth of 180 cm or to a root-limiting layer are considered

atypical and are assigned to the Eutric subgroup.

Typic Haplocryalfs are not extensive in the United States.

They are in the mountains of the Western States. Most of them

are under a coniferous forest. Slopes generally are moderately

steep to very steep.

Andic and Vitrandic Haplocryalfs.—These soils are like

Typic Haplocryalfs, but they have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the high mountains of the Western United States.

They are permitted, but not required, to have redox depletions

and also color value of 3 or less, moist, and 5 or less, dry, in

surface horizons, after mixing to a depth of 15 cm. They also

are permitted to be dry for more than 45 days. They are not

extensive. Most of them have moderate or strong slopes and are

used for limited summer grazing, as forest, or as wildlife

habitat.

Aquic Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they have redox depletions with chroma of 2

or less and have, within 75 cm of the surface, horizons that are

saturated with water at some time during the year. In addition

to the redox depletions, Aquic Haplocryalfs are permitted to

have a color value of 3 or less, moist, and 5 or less, dry, in

surface horizons, after mixing to a depth of 15 cm. The

wetness is caused mainly by slowly permeable materials in the

lower horizons or the substratum. These soils are rare in the

United States.

Eutric Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they have a base saturation of 50 percent or

more (by NH4

OAc) in all parts between the mineral soil surface

and a depth of 180 cm or a densic, lithic, or paralithic contact,

whichever is shallower. Most of these soils formed in

calcareous materials. Eutric Haplocryalfs support range or

coniferous forest vegetation and have gentle to very steep

slopes. They are of small extent in the United States and are

rare elsewhere.

Inceptic Haplocryalfs.—These soils are like Typic

Haplocryalfs in defined properties, but they have an argillic,

kandic, or natric horizon that is 35 cm or less thick and have

no densic, lithic, or paralithic contact within 100 cm of the

mineral soil surface. These soils may also have an Ap horizon

that has a color value, moist, of 3 or less or upper horizons that
Alfisols 197

have a color value, moist, of less than 4 after the surface soil has

been mixed to a depth of 15 cm. These soils are not extensive in

the United States.

Lamellic Haplocryalfs.—These soils are like Typic

Haplocryalfs in defined properties, but they have an argillic

horizon that consists entirely or partially of lamellae. Most of

these soils have a sandy particle-size class, and the upper

boundary of the argillic horizon or the upper lamella may be

below a depth of 60 cm. The upper several lamellae are

commonly broken or discontinuous horizontally. These soils

may also have a glossic horizon, and they are allowed to have

an Ap horizon that has a color value, moist, of 3 or less or

upper horizons that have a color value, moist, of less than 4

after the surface soil has been mixed to a depth of 15 cm. These

soils are not extensive in the United States.

Lithic Haplocryalfs.—These soils are permitted to have

any of the properties of Haplocryalfs. They are required to have

a lithic contact within 50 cm of the surface. They are of small

extent in the Western United States.

Mollic Haplocryalfs.—These soils are like Typic

Haplocryalfs, but their upper horizons have a color value of 3

or less, moist, and 5 or less, dry, after mixing to a depth of 15

cm. These soils have a base saturation of 50 percent or more

(by NH4

OAc) in all parts from the mineral soil surface to a

depth of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower. Mollic Haplocryalfs commonly support

a coniferous forest in which the trees are more widely spaced

than in areas of the Typic subgroup. These soils are not

extensive in the United States except very locally.

Oxyaquic Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they are saturated with water within 100 cm

of the mineral soil surface for 20 or more consecutive days or

30 or more cumulative days in normal years. They are

permitted to have a color value of 3 or less, moist, and 5 or

less, dry, in surface horizons, after mixing to a depth of 15 cm.

The wetness is caused mainly by slowly permeable materials in

the lower horizons or the substratum. These soils are rare in

the United States.

Psammentic Haplocryalfs.—These soils are like Typic

Haplocryalfs in defined properties, but they have a sandy or

sandy-skeletal particle-size class throughout the upper 75 cm of

the argillic, kandic, or natric horizon or throughout the entire

argillic, kandic, or natric horizon if it is less than 75 cm thick.

These soils may also have a glossic horizon and an Ap horizon

that has a color value, moist, of 3 or less or upper horizons that

have a color value, moist, of less than 4 after the surface soil

has been mixed to a depth of 15 cm. These soils are not

extensive in the United States.

Umbric Haplocryalfs.—These soils are like Typic

Haplocryalfs, but their upper horizons have a color value of 3

or less, moist, and 5 or less, dry, after mixing to a depth of 15

cm. These soils have a base saturation of less than 50 percent

(by NH4

OAc) in some part between the mineral soil surface

and a depth of 180 cm or a root-limiting layer, whichever is

shallower. Umbric Haplocryalfs commonly support coniferous

forest. Some forests have widely spaced trees. In some areas

these soils are used as rangeland. The soils are not extensive in

the United States.

Umbric Xeric Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they have a xeric moisture regime and their

upper horizons have a color value of 3 or less, moist, and 5 or

less, dry, after mixing to a depth of 15 cm. They also have a

base saturation of less than 50 percent (by NH4

OAc) in some

part between the mineral soil surface and a depth of 180 cm or

a densic, lithic, or paralithic contact, whichever is shallower.

Umbric Xeric Haplocryalfs commonly support coniferous

forest. Some forests have widely spaced trees. In some areas

these soils are used as rangeland. The soils are not extensive in

the United States.

Ustic Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they are dry in some part of the moisture

control section for 45 or more days (cumulative) in normal

years. They are considered to be transitional to Ustalfs. Ustic

Haplocryalfs commonly support a sparse coniferous forest with

widely spaced trees or are used as rangeland. They are not

extensive in the United States except very locally.

Ustollic Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they are dry in some part of the moisture

control section for 45 or more days (cumulative) in normal

years and their upper horizons have a color value of 3 or less,

moist, and 5 or less, dry, after mixing to a depth of 15 cm.

These soils have a base saturation of 50 percent or more (by

NH4

OAc) in all parts from the mineral soil surface to a depth

of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower. They are considered to be transitional

to Ustolls. Ustollic Haplocryalfs commonly support rangeland

vegetation or a sparse coniferous forest with widely spaced

trees. They are not extensive in the United States.

Vertic Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they are high in content of expanding clays

and have cracks 5 mm or more wide, slickensides, wedgeshaped aggregates, or a linear extensibility of 6.0 cm or more

between the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is shallower.

These soils are considered to be transitional to Vertisols. They

support coniferous forest or are used as rangeland. They are not

extensive in the United States.

Xeric Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they have a xeric moisture regime. They are

considered to be transitional to Xeralfs. Xeric Haplocryalfs

commonly support coniferous forest. Some forests have widely

spaced trees. In some areas these soils are used as rangeland.

The soils are not extensive in the United States.

Xerollic Haplocryalfs.—These soils are like Typic

Haplocryalfs, but they have a xeric moisture regime and their

upper horizons have a color value of 3 or less, moist, and 5 or
198 Soil Taxonomy

less, dry, after mixing to a depth of 15 cm. These soils have a

base saturation of 50 percent or more (by NH4

OAc) in all parts

from the mineral soil surface to a depth of 180 cm or to a densic,

lithic, or paralithic contact, whichever is shallower. They are

considered to be transitional to Xerolls. Xerollic Haplocryalfs

commonly support a sparse coniferous forest with widely

spaced trees or support rangeland vegetation. They are not

extensive in the United States.

Palecryalfs

Palecryalfs are the Cryalfs that have a thick epipedon and a

glossic horizon or interfingering of albic materials into the

argillic, kandic, or natric horizon. Most of these soils have an

albic horizon and a glossic horizon. The soils are thought to be

restricted to relatively stable surfaces in the mountains, many

of which are older than the Wisconsinan Glaciation. The

stability may be the result of stoniness. The vegetation on these

soils is mostly coniferous forest. The temperature regimes are

mostly cryic. The moisture regimes are mostly udic.

Definition

Palecryalfs are the Cryalfs that:

1. Have an argillic, kandic, or natric horizon that has its

upper boundary 60 cm or more below both:

a. The mineral soil surface; and

b. The lower boundary of any surface mantle containing

60 percent or more vitric volcanic ash, cinders, or other

vitric pyroclastic materials; and

2. Have a glossic horizon or interfingering of albic materials

in the argillic, kandic, or natric horizon; and

3. Have texture (in the fine-earth fraction) finer than loamy

fine sand in some subhorizon above the argillic, kandic, or

natric horizon.

Key to Subgroups

JBAA. Palecryalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Palecryalfs

JBAB. Other Palecryalfs that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the

following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Palecryalfs

JBAC. Other Palecryalfs that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Palecryalfs

JBAD. Other Palecryalfs that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Palecryalfs

JBAE. Other Palecryalfs that have a xeric moisture regime.

Xeric Palecryalfs

JBAF. Other Palecryalfs that are dry in some part of the

moisture control section for 45 or more days (cumulative) in

normal years.

Ustic Palecryalfs

JBAG. Other Palecryalfs that:

1. Have an Ap horizon with a color value, moist, of 3 or

less and a color value, dry, of 5 or less (crushed and

smoothed sample) or materials between the soil surface and

a depth of 18 cm that have these color values after mixing;

and

2. Have a base saturation of 50 percent or more (by

NH4

OAc) in all parts from the mineral soil surface to a

depth of 180 cm or to a densic, lithic, or paralithic contact,

whichever is shallower.

Mollic Palecryalfs

JBAH. Other Palecryalfs that have an Ap horizon with a

color value, moist, of 3 or less and a color value, dry, of 5 or

less (crushed and smoothed sample) or materials between the

soil surface and a depth of 18 cm that have these color values

after mixing.

Umbric Palecryalfs

JBAI. Other Palecryalfs.

Typic Palecryalfs
Alfisols 199

Definition of Typic Palecryalfs

Typic Palecryalfs are the Palecryalfs that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size, of

1.0 g/cm3

 or less, measured at 33 kPa water retention, and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 7 or more consecutive days or 20 or

more cumulative days in normal years;

4. Have a udic moisture regime;

5. Are dry in some part of the moisture control section for

less than 45 days (cumulative) in normal years; and

6. Have an Ap horizon that has a color value, moist, of 4 or

more or a color value, dry, of 6 or more when crushed and

smoothed or have materials to a depth of 18 cm that have these

colors after mixing.

Description of Subgroups

Typic Palecryalfs.—The central concept or Typic subgroup

of Palecryalfs is fixed on freely drained soils that are deep to

the top of the argillic horizon and that have a glossic horizon.

These soils have a high color value in an Ap horizon or in a

layer of comparable depth after mixing and have a loamy or

finer texture above the argillic horizon.

Soils with both a low bulk density and a high content of

weakly crystalline minerals or that consist of thin layers of

pyroclastic materials are excluded from Typic Palecryalfs

because they have properties that are shared with Andisols.

Redox depletions and saturation with water within 100 cm of

the surface for extended periods cause a soil to be excluded from

the Typic subgroup because they are properties shared with

Aqualfs.

Soils that have a xeric moisture regime and other soils that

are dry for more than 45 days also are excluded because they

share properties with Xeralfs and Ustalfs. Soils that have a

surface horizon as thick as 15 cm that is dark enough to be

near or within the range of a mollic or umbric epipedon are

excluded from the Typic subgroup because the thick, dark

horizon is believed to indicate a transitional form to Mollisols

or an Umbric extragrade.

Typic Palecryalfs are not extensive in the United States.

They are in the mountains of the Western States. Most are

under a coniferous forest. Slopes generally are moderately steep

to very steep.

Andic and Vitrandic Palecryalfs.—These soils are like

Typic Palecryalfs, but they have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the high mountains of the Western United States.

They are permitted, but not required, to have redox depletions

and also color value of 3 or less, moist, and 5 or less, dry, in

surface horizons, after mixing to a depth of 15 cm. They also

are permitted to be dry for more than 45 days. They are not

extensive. Most of them are moderately steep to very steep and

are used for limited summer grazing, as forest, or as wildlife

habitat.

Aquic Palecryalfs.—These soils are like Typic Palecryalfs,

but they have redox depletions with chroma of 2 or less and

have, within 75 cm of the surface, horizons that are saturated

with water at some time during the year. In addition to the

redox depletions, Aquic Palecryalfs are permitted to have a

color value of 3 or less, moist, and 5 or less, dry, in surface

horizons, after mixing to a depth of 15 cm. The wetness is

caused mainly by slowly permeable materials in the lower

horizons or the substratum. These soils are rare in the United

States.

Mollic Palecryalfs.—These soils are like Typic Palecryalfs,

but their upper horizons have a color value of 3 or less, moist,

and 5 or less, dry, after mixing to a depth of 15 cm. These soils

have a base saturation of 50 percent or more (by NH4

OAc) in

all parts from the mineral soil surface to a depth of 180 cm or

to a densic, lithic, or paralithic contact, whichever is shallower.

The soils commonly support a coniferous forest in which the

trees are more widely spaced than is typical for Palecryalfs.

Mollic Palecryalfs are not extensive in the United States.

Oxyaquic Palecryalfs.—These soils are like Typic

Palecryalfs, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. They are permitted

to have a color value of 3 or less, moist, and 5 or less, dry, in
200 Soil Taxonomy

surface horizons, after mixing to a depth of 15 cm. The wetness

is caused mainly by slowly permeable materials in the lower

horizons or the substratum. These soils are rare in the United

States.

Umbric Palecryalfs.—These soils are like Typic

Palecryalfs, but their upper horizons have a color value of 3 or

less, moist, and 5 or less, dry, after mixing to a depth of 15 cm.

These soils have a base saturation of less than 50 percent (by

NH4

OAc) in some part between the mineral soil surface and a

depth of 180 cm or a root-limiting layer, whichever is

shallower. They commonly support a coniferous forest. Some

forests have widely spaced trees. In some areas Umbric

Palecryalfs are used as rangeland. The soils are not extensive

in the United States.

Ustic Palecryalfs.—These soils are like Typic Palecryalfs,

but they are dry in some part of the moisture control section for

45 or more days (cumulative) in normal years. They are

considered to be transitional to Ustalfs. Ustic Palecryalfs

commonly support a sparse coniferous forest with widely

spaced trees or are used as rangeland. They are not extensive in

the United States.

Xeric Palecryalfs.—These soils are like Typic Palecryalfs,

but they have a xeric moisture regime. They are considered to

be transitional to Xeralfs. Xeric Palecryalfs commonly support

a coniferous forest. Some forests have widely spaced trees. In

some areas these soils are used as rangeland. The soils are not

extensive in the United States.

Udalfs

Udalfs are the more or less freely drained Alfisols that have a

udic moisture regime and a frigid, mesic, isomesic, or warmer

temperature regime. These soils are principally but not entirely in

areas of late-Pleistocene deposits and erosional surfaces of

about the same age. Some of the Udalfs that are on the older

surfaces are underlain by limestone or other calcareous

sediments.

Udalfs are very extensive in the United States and in

Western Europe. All of them are believed to have supported

forest vegetation at some time during development. Most

Udalfs with a mesic or warmer temperature regime have or had

deciduous forest vegetation, and many with a frigid

temperature regime have or had mixed coniferous and

deciduous forest vegetation.

Many Udalfs have been cleared of trees and are intensively

farmed. As a result of erosion, many now have only an argillic

or kandic horizon below an Ap horizon that is mostly material

once part of the argillic or kandic horizon. Other Udalfs are on

stable surfaces and retain most of their eluvial horizons above

the argillic or kandic horizon. Normally, the undisturbed soils

have a thin A horizon darkened by humus. A few Udalfs have a

natric horizon. Others have a fragipan in or below the argillic

or kandic horizon.

Definition

Udalfs are the Alfisols that:

1. Have a frigid, mesic, isomesic, or warmer temperature

regime;

2. Have a udic moisture regime; and

3. Have, in no horizon within 50 cm of the mineral soil surface,

both aquic conditions (other than anthraquic conditions) for

some time in normal years (or artificial drainage) and either of

the following:

a. Redoximorphic features in all layers between either the

lower boundary of an Ap horizon or a depth of 25 cm below

the mineral soil surface, whichever is deeper, and a depth of

40 cm; and one of the following within the upper 12.5 cm of

the argillic, kandic, natric, or glossic horizon:

(1) 50 percent or more redox depletions with chroma of

2 or less on faces of peds and redox concentrations

within peds; or

(2) Redox concentrations and 50 percent or more redox

depletions with chroma of 2 or less in the matrix; or

(3) 50 percent or more redox depletions with chroma of

1 or less on faces of peds or in the matrix, or both; or

b. In a horizon that has aquic conditions, enough active

ferrous iron to give a positive reaction to alpha,alphadipyridyl at a time when the soil is not being irrigated.

Key to Great Groups

JEA. Udalfs that have a natric horizon.

Natrudalfs, p. 221

JEB. Other Udalfs that have:

1. A glossic horizon; and

2. In the argillic or kandic horizon, discrete nodules, 2.5

to 30 cm in diameter, that:

a. Are enriched with iron and extremely weakly

cemented to indurated; and

b. Have exteriors with either a redder hue or a higher

chroma than the interiors.

Ferrudalfs, p. 201

JEC. Other Udalfs that have both:

1. A glossic horizon; and

2. A fragipan with an upper boundary within 100 cm of

the mineral soil surface.

Fraglossudalfs, p. 203
Alfisols 201

JED. Other Udalfs that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragiudalfs, p. 202

JEE. Other Udalfs that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Have a kandic horizon; and

3. Within 150 cm of the mineral soil surface, either:

a. Do not have a clay decrease with increasing depth of

20 percent or more (relative) from the maximum clay

content [Clay is measured noncarbonate clay or based on

the following formula: Clay % = 2.5(% water retained at

1500 kPa tension - % organic carbon), whichever value is

greater, but no more than 100]; or

b. Have 5 percent or more (by volume) skeletans on

faces of peds in the layer that has a 20 percent lower clay

content and, below that layer, a clay increase of 3 percent

or more (absolute) in the fine-earth fraction.

Kandiudalfs, p. 217

JEF. Other Udalfs that have a kandic horizon.

Kanhapludalfs, p. 219

JEG. Other Udalfs that:

1. Do not have a densic, lithic, or paralithic contact within

150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface, either:

a. Do not have a clay decrease with increasing depth of

20 percent or more (relative) from the maximum clay

content [Clay is measured noncarbonate clay or based on

the following formula: Clay % = 2.5(% water retained at

1500 kPa tension - % organic carbon), whichever value is

greater, but no more than 100]; or

b. Have 5 percent or more (by volume) skeletans on

faces of peds in the layer that has a 20 percent lower clay

content and, below that layer, a clay increase of 3 percent

or more (absolute) in the fine-earth fraction; and

3. Have an argillic horizon with one or more of the

following:

a. In 50 percent or more of the matrix of one or more

subhorizons in its lower one-half, hue of 7.5YR or redder

and chroma of 5 or more; or

b. In 50 percent or more of the matrix of horizons that

total more than one-half the total thickness, hue of

2.5YR or redder, value, moist, of 3 or less, and value,

dry, of 4 or less; or

c. Many coarse redox concentrations with hue of 5YR or

redder or chroma of 6 or more, or both, in one or more

subhorizons; or

4. Have a frigid temperature regime and all of the

following:

a. An argillic horizon that has its upper boundary 60 cm

or more below both:

(1) The mineral soil surface; and

(2) The lower boundary of any surface mantle

containing 30 percent or more vitric volcanic ash,

cinders, or other vitric pyroclastic materials; and

b. A texture (in the fine-earth fraction) finer than

loamy fine sand in one or more horizons above the

argillic horizon; and

c. Either a glossic horizon or interfingering of albic

materials into the argillic horizon.

Paleudalfs, p. 222

JEH. Other Udalfs that have, in all subhorizons in the upper

100 cm of the argillic horizon or throughout the entire argillic

horizon if less than 100 cm thick, more than 50 percent colors

that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodudalfs, p. 228

JEI. Other Udalfs that have a glossic horizon.

Glossudalfs, p. 205

JEJ. Other Udalfs.

Hapludalfs, p. 208

Ferrudalfs

Ferrudalfs are the Udalfs that do not have a natric horizon

and have both a glossic horizon and an argillic or kandic

horizon that has been partially cemented by iron. In some areas

these soils formed under a heath vegetation. The heath

vegetation may have succeeded a forest following many years

of collection and removal of forest litter. Under the heath,

which is efficient in complexing iron and aluminum, the upper

part of the argillic horizon was destroyed and fragments of the

argillic horizon became coated and weakly cemented with iron.

Some Ferrudalfs have a fragipan at some depth, commonly

about 100 cm. Ferrudalfs are not known to occur in the United

States and are rare elsewhere. Only two subgroups are

provided.
202 Soil Taxonomy

Definition

Ferrudalfs are the Udalfs that:

1. Do not have a natric horizon;

2. Have a glossic horizon; and

3. In the argillic or kandic horizon, have discrete nodules, 2.5

to about 30 cm in diameter, that are enriched with iron, that

are extremely weakly cemented to indurated, and that have

exteriors with either a redder hue and/or a higher chroma than

the interiors.

Key to Subgroups

JEBA. Ferrudalfs that have, in one or more horizons within 60

cm of the mineral soil surface, redox depletions with chroma of 2

or less and also aquic conditions for some time in normal years

(or artificial drainage).

Aquic Ferrudalfs

JEBB. Other Ferrudalfs.

Typic Ferrudalfs

Definition of Typic Ferrudalfs

Typic Ferrudalfs are the Ferrudalfs that do not have, in one

or more horizons within 60 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions for some time in normal years.

Description of Subgroups

Typic Ferrudalfs.—These soils are the Ferrudalfs that do

not have, in any horizon within 60 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions. These soils are not known to occur in the

United States.

Aquic Ferrudalfs.—These soils are like Typic Ferrudalfs,

but they have, in one or more horizons within 40 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). These soils are intergrades between

Aqualfs and Ferrudalfs. They are not known to occur in the

United States.

Fragiudalfs

Fragiudalfs are the Udalfs that have a fragipan within 100

cm of the soil surface but do not have a glossic or natric

horizon. They commonly have an argillic or cambic horizon

above the fragipan. Redoximorphic features are in many

pedons, starting at a depth 50 to 100 cm below the mineral

soil surface. Ground water is perched seasonally above the

fragipan, and a thin eluvial horizon commonly is directly above

the fragipan.

Most Fragiudalfs in the United States are on gentle slopes

and formed, at least in part, in silty or loamy deposits. The

deposits are largely of late-Pleistocene age. The duripan formed

in an older buried soil in some areas. A duripan seems to form if

the burial was to a depth of about 50 to 75 cm. Temperature

regimes are mostly frigid, mesic, or thermic. In the United

States, the native vegetation on these soils was primarily a

broadleaf deciduous forest.

Definition

Fragiudalfs are the Udalfs that:

1. Have a fragipan with an upper boundary within 100 cm of

the mineral soil surface;

2. Do not have a natric horizon; and

3. Do not have a glossic horizon.

Key to Subgroups

JEDA. Fragiudalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Fragiudalfs

JEDB. Other Fragiudalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Fragiudalfs

JEDC. Other Fragiudalfs that have, in one or more horizons

within 40 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Fragiudalfs

JEDD. Other Fragiudalfs that are saturated with water in one

or more layers above the fragipan in normal years for either or

both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Fragiudalfs
Alfisols 203

JEDE. Other Fragiudalfs.

Typic Fragiudalfs

Definition of Typic Fragiudalfs

Typic Fragiudalfs are the Fragiudalfs that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size, of

1.0 g/cm3

 or less, measured at 33 kPa water retention, and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any subhorizon within the upper 25 cm of

the argillic or kandic horizon, redox depletions with chroma of

2 or less and also aquic conditions; and

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 7 or more consecutive days or 20 or

more cumulative days in normal years.

Description of Subgroups

Typic Fragiudalfs.—The central concept or Typic subgroup

of Fragiudalfs is fixed on the most freely drained soils of this

great group. Typic Fragiudalfs are not the most extensive

subgroup, but they furnish the best basis for definition of

subgroups. No Fragiudalfs are freely drained because in all of

them ground water is perched above the fragipan in many

years. The perched water table is a probable cause of the very

common albic materials and bleached clay depletions directly

above the fragipan. Soils that have these features and also

redox depletions with low chroma at a shallow depth, normally

along with redox concentrations of high chroma or of reddish

hue, are considered to be intergrades toward Aqualfs. Typic

Fragiudalfs do not have a surface mantle or layer in the upper

75 cm that has both a low bulk density and a high content of

weakly crystalline minerals or that consists of slightly or

moderately weathered pyroclastic materials because these

properties are shared with Andisols.

Andic and Vitrandic Fragiudalfs.—These soils are like

Typic Fragiudalfs, but they have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the foothills and mountains of the Western

United States. They are permitted, but not required, to have

redox depletions and to be saturated with water within 100 cm

of the mineral soil surface for 7 or more consecutive days or 20

or more cumulative days in normal years. They are not

extensive. They are used mainly as forest, but some have been

cleared and are used as cropland or pasture.

Aquic Fragiudalfs.—These soils are like Typic Fragiudalfs,

but they have, in one or more horizons within 40 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). They are intergrades between Fragiaqualfs

and Fragiudalfs. In the United States, they are widely scattered

from Pennsylvania to Illinois and from Illinois to Louisiana.

They are moderately extensive locally within this area. They

have gentle slopes, and most of them are farmed.

Oxyaquic Fragiudalfs.—These soils are like Typic

Fragiudalfs, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. The wetness is

caused by slow permeability in the fragipan. These soils are

common in the United States. Most of them have been cleared

and are used for crops or pasture.

Fraglossudalfs

Fraglossudalfs have both a fragipan within 100 cm of the

soil surface and a glossic horizon. They do not have a natric

horizon or discrete iron-cemented nodules 2.5 to 30 cm in

diameter in an argillic or kandic horizon. The upper boundary

of the argillic or kandic horizon generally is broken. These

soils are not extensive in the United States. They are more

extensive in Europe.

Definition

Fraglossudalfs are the Udalfs that:

1. Have a glossic horizon;

2. Have a fragipan with an upper boundary within 100 cm of

the mineral soil surface;

3. Do not have a natric horizon; and

4. Do not have, in the argillic or kandic horizon, discrete

nodules, 2.5 to 30 cm in diameter, that have exteriors with

either a redder hue or a higher chroma than the interiors, that

are enriched with iron, and are extremely weakly cemented to

indurated.

Key to Subgroups

JECA. Fraglossudalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm
204 Soil Taxonomy

of the mineral soil surface, a fine-earth fraction with both a bulk

density of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0.

Andic Fraglossudalfs

JECB. Other Fraglossudalfs that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Fraglossudalfs

JECC. Other Fraglossudalfs that have, in one or more

subhorizons within the upper 25 cm of the argillic or kandic

horizon, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage).

Aquic Fraglossudalfs

JECD. Other Fraglossudalfs that are saturated with water in

one or more layers above the fragipan in normal years for

either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Fraglossudalfs

JECE. Other Fraglossudalfs.

Typic Fraglossudalfs

Definition of Typic Fraglossudalfs

Typic Fraglossudalfs are the Fraglossudalfs that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more; and

2. Do not have, in any subhorizon within the upper 25 cm of

the argillic or kandic horizon, redox depletions with chroma of

2 or less and also aquic conditions; and

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 7 or more consecutive days or 20 or

more cumulative days in normal years.

Description of Subgroups

Typic Fraglossudalfs.—The central concept or Typic

subgroup of Fraglossudalfs is fixed on moderately well drained

soils that have a fragipan at a depth of 50 to 100 cm from the

mineral soil surface. These soils are more freely drained than

most soils in this great group. Typic Fraglossudalfs do not have

a surface mantle or layer in the upper 75 cm that has both a

low bulk density and a high content of weakly crystalline

minerals or that consists of slightly or moderately weathered

pyroclastic materials because these properties are shared with

Andisols. Typic Fraglossudalfs are rare in the United States.

Andic and Vitrandic Fraglossudalfs.—These soils are like

Typic Fraglossudalfs, but they have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the foothills and mountains of the Western

United States. They are permitted, but not required, to have

redox depletions and to be saturated with water within 100 cm

of the mineral soil surface for 7 or more consecutive days or 20

or more cumulative days in normal years. They are not

extensive. They are used mainly as forest, but some have been

cleared and are used as cropland or pasture.

Aquic Fraglossudalfs.—These soils are like Typic

Fraglossudalfs, but they have, in one or more horizons within

40 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage). These soils are

intergrades between Fragiaqualfs and Fraglossudalfs. In the

United States, they are widely scattered from New York to

Louisiana and some are in Idaho. These soils are moderately

extensive locally within this area. They have gentle slopes, and

most of them are farmed.

Oxyaquic Fraglossudalfs.—These soils are like Typic

Fraglossudalfs, but they are saturated with water within 100
Alfisols 205

cm of the mineral soil surface for 20 or more consecutive days or

30 or more cumulative days in normal years. The wetness is

caused by slow permeability in the fragipan. These soils are

common in the United States. Most of them have been cleared

and are used for crops or pasture.

Glossudalfs

Glossudalfs do not have a fragipan, a kandic horizon, or a

natric horizon. They have an argillic horizon that shows

evidence of destruction in the form of a glossic horizon, but

they do not have discrete iron-cemented nodules 2.5 to 30 cm

in diameter. The glossic horizon extends through the argillic

horizon in some of these soils. Glossudalfs do not have very

dark red colors throughout the argillic horizon. They are more

extensive in Europe than in the United States.

Definition

Glossudalfs are the Udalfs that:

1. Have a glossic horizon;

2. Do not have, in the argillic horizon, discrete nodules, 2.5

to 30 cm in diameter, that have enriched exteriors and are

cemented or indurated with iron;

3. Do not have a natric or kandic horizon;

4. Do not have a fragipan within 100 cm of the soil surface;

5. Have an argillic horizon that in some part has hue of

5YR or yellower, a color value, moist, of 3.5 or more, or

a color value, dry, more than 1 unit higher than the moist

value.

Key to Subgroups

JEIA. Glossudalfs that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below the

mineral soil surface.

Aquertic Glossudalfs

JEIB. Other Glossudalfs that have both:

1. Saturation with water in one or more layers within 100

cm of the mineral soil surface in normal years for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Oxyaquic Vertic Glossudalfs

JEIC. Other Glossudalfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Glossudalfs

JEID. Other Glossudalfs that have both:

1. In one or more subhorizons within the upper 25 cm of

the argillic horizon, redox depletions with chroma of 2 or

less and also aquic conditions for some time in normal years

(or artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or
206 Soil Taxonomy

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Glossudalfs

JEIE. Other Glossudalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Glossudalfs

JEIF. Other Glossudalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Glossudalfs

JEIG. Other Glossudalfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface.

Fragiaquic Glossudalfs

JEIH. Other Glossudalfs that have, in one or more

subhorizons within the upper 25 cm of the argillic horizon,

redox depletions with chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Glossudalfs

JEII. Other Glossudalfs that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Glossudalfs

JEIJ. Other Glossudalfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Glossudalfs

JEIK. Other Glossudalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more below the mineral soil surface.

Arenic Glossudalfs

JEIL. Other Glossudalfs that have a glossic horizon less than

50 cm in total thickness.

Haplic Glossudalfs

JEIM. Other Glossudalfs.

Typic Glossudalfs

Definition of Typic Glossudalfs

Typic Glossudalfs are the Glossudalfs that:

1. Do not have cracks within 125 cm of the mineral soil

surface that are 5 mm or more wide through a thickness of 30

cm or more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the mineral soil

surface;

2. Have a linear extensibility of less than 6.0 cm between the

mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower;
Alfisols 207

3. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

4. Do not have, in any subhorizon within the upper 25 cm of

the argillic horizon, redox depletions with chroma of 2 or less

and also aquic conditions;

5. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 7 or more consecutive days or 20 or

more cumulative days in normal years;

6. Do not have fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm or

more thick;

7. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more below

the mineral soil surface;

8. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick; and

9. Have a glossic horizon that is 50 cm or more thick.

Description of Subgroups

Typic Glossudalfs.—The central concept or Typic subgroup

of Glossudalfs is fixed on freely drained soils that have a

glossic horizon that is at least 50 cm in total thickness. These

soils do not have slickensides, wedge-shaped aggregates, a

high linear extensibility, or wide cracks because these properties

are shared with Vertisols.

Soils with both a low bulk density and a high content of

weakly crystalline minerals or that consist of thin layers of

pyroclastic materials are excluded from Typic Glossudalfs

because they have properties that are shared with Andisols.

Redox depletions and saturation with water within 100 cm of

the surface for extended periods cause a soil to be excluded

from the Typic subgroup because these properties are shared

with Aqualfs. Typic Glossudalfs do not have fragic soil

properties in a large volume in any layer 15 cm or more thick

because these are properties shared with Fragiudalfs and

Fraglossudalfs. Typic Glossudalfs do not have a layer, starting

at the mineral soil surface, that has a texture of loamy fine sand

or coarser in all parts and that is more than 50 cm thick

because this property is used to define the Arenic subgroup.

Typic Glossudalfs are of small extent in the United States.

They occur in areas from Texas to Michigan.

Andic and Vitrandic Glossudalfs.—These soils are like

Typic Glossudalfs, but they have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the foothills and mountains of the Western

United States. They are not extensive. Most of them have

gently sloping to steep slopes and are used as cropland, forest,

or pasture.

Aquandic Glossudalfs.—These soils are like Typic

Glossudalfs, but they have redox depletions with low chroma

and also aquic conditions at a shallow depth for some time in

normal years. In addition, they a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the foothills and mountains of the Western

United States. They are not extensive. Most of them are level to

gently sloping and are used as cropland, forest, or pasture.

Aquertic Glossudalfs.—These soils have redox depletions

with low chroma and also aquic conditions at a shallow depth

for some time in normal years. In addition, they have an

appreciable amount of swelling clays. The aquic conditions,

swelling clays, and low saturated hydraulic conductivity seem

to be the most important properties of the soils in this

subgroup. Most of the soils formed in clayey parent materials.

Aquertic Glossudalfs are of small extent. Slopes are gentle, but

the soils are highly erodible. Most of the soils are farmed, but

some of them are used as pasture or forest.

Aquic Glossudalfs.—These soils have redox depletions

with low chroma and also aquic conditions at a shallow depth

for some time in normal years. In addition, they are permitted

to have fragic soil properties. These soils are permitted, but not

required, to have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more. In
208 Soil Taxonomy

the United States, these soils are moderately extensive on the

lower coastal plain along the Gulf of Mexico and are known to

occur elsewhere. Many of them are in forests, but much of the

acreage of these soils has been cleared and is used as cropland

or pasture.

Arenic Glossudalfs.—These soils have a layer that has a

sandy or sandy-skeletal particle-size class throughout and

extends from the mineral soil surface to the top of an argillic

horizon at a depth of 50 cm or more below the mineral soil

surface. These soils are known to occur only in Texas and

Michigan in the United States.

Fragiaquic Glossudalfs.—These soils are like Typic

Glossudalfs, but they have redox depletions with low chroma

and also aquic conditions at a shallow depth for some time in

normal years. In addition, they have fragic soil properties in 30

percent or more of the volume of a layer 15 cm or more thick

that has its upper boundary within 100 cm of the mineral soil

surface or in 60 percent or more of the volume of a layer 15 cm

or more thick anywhere in the soils. These soils are not

extensive in the United States.

Fragic Glossudalfs.—These soils are like Typic

Glossudalfs, but they have fragic soil properties in 30 percent

or more of the volume of a layer 15 cm or more thick that has

its upper boundary within 100 cm of the mineral soil surface or

in 60 percent or more of the volume of a layer 15 cm or more

thick anywhere in the soils. These soils are not extensive in the

United States.

Haplic Glossudalfs.—These soils are like Typic

Glossudalfs, but the glossic horizon is less than 50 cm thick.

Thus, the soils have some characteristics of Hapludalfs. They

occur locally in Michigan and Wisconsin and in the central

part of the Southern United States.

Oxyaquic Glossudalfs.—These soils are like Typic

Glossudalfs, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. The wetness is

caused mainly by slowly permeable materials in the lower

horizons or the substratum. These soils are of small extent and

are mostly in the south-central and north-central parts of the

United States.

Oxyaquic Vertic Glossudalfs.—These soils are like Typic

Glossudalfs, but they are high in content of expanding clays

and have cracks 5 mm or more wide, slickensides, wedgeshaped aggregates, or a linear extensibility of 6.0 cm or more

between the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is shallower.

The soils also are saturated with water within 100 cm of the

mineral soil surface for 20 or more consecutive days or 30 or

more cumulative days in normal years. The wetness is caused

mainly by slowly permeable materials in the lower horizons or

the substratum. These soils are rare in the United States and

are considered to be transitional to Vertisols.

Vertic Glossudalfs.—These soils are like Typic

Glossudalfs, but they are high in content of expanding clays

and have cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower. These soils

are rare in the United States and are considered to be transitional

to Vertisols.

Hapludalfs

Hapludalfs are the Udalfs that do not have a glossic, kandic,

or natric horizon or a fragipan within 100 cm of the mineral

soil surface. They do not have very dark red colors throughout

the argillic horizon. The base of the argillic horizon is

normally less than 150 cm below the soil surface and, in many

areas, is less than 100 cm below the surface. In an undisturbed

soil, there generally is a thin, very dark brown A horizon, 5 to

10 cm thick, over a lighter colored brownish eluvial horizon.

The eluvial horizon grades into a finer textured argillic

horizon, generally at a depth of about 30 to 45 cm in loamy

materials. Because the Hapludalfs have been cultivated

extensively, many of those on slopes have lost their eluvial

horizons.

These soils formed principally in late-Pleistocene deposits

or on a surface of comparable age. They are extensive soils in

the Northeastern States, excluding New England, and in

Europe, excluding most of Scandinavia.

The vegetation on Hapludalfs in the United States was a

deciduous broadleaf forest, but the soils are now mostly

farmed. Temperature regimes are mesic or thermic.

Definition

Hapludalfs are the Udalfs that:

1. Do not have a glossic, kandic, or natric horizon;

2. Have an argillic horizon that in some part has hue of 5YR

or yellower, a color value, moist, of 3.5 or more, or a color

value, dry, more than 1 unit higher than the moist value;

3. Do not have a fragipan within 100 cm of the mineral soil

surface;

4. Either have a densic, lithic, or paralithic contact within

150 cm of the soil surface or have a clay distribution in which

the clay content decreases with increasing depth by 20 percent

or more from its maximum within 150 cm of the soil surface

and, if there is a clay increase of 3 percent or more (absolute)

below that layer, less than 5 percent of the volume in the layer

where the clay content decreases consists of skeletans on faces

of peds, if:

a. Hue is redder than 10YR and chroma of more than 4 is

dominant;

b. Hue is 2.5YR or redder, the value, moist, is less than 4,

and the value, dry, is less than 5 throughout the major part

of the argillic horizon; or
Alfisols 209

c. There are many coarse redox concentrations that have

hue redder than 7.5YR or chroma of more than 5.

Key to Subgroups

JEJA. Hapludalfs that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Hapludalfs

JEJB. Other Hapludalfs that have all of the following:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface; and

3. An Ap horizon or materials between the mineral soil

surface and a depth of 18 cm that, after mixing, have one or

more of the following:

a. A color value, moist, of 4 or more; or

b. A color value, dry, of 6 or more; or

c. Chroma of 4 or more.

Aquertic Chromic Hapludalfs

JEJC. Other Hapludalfs that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface.

Aquertic Hapludalfs

JEJD. Other Hapludalfs that have both:

1. Saturation with water in one or more layers within 100

cm of the mineral soil surface in normal years for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Oxyaquic Vertic Hapludalfs

JEJE. Other Hapludalfs that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. An Ap horizon or materials between the mineral soil
210 Soil Taxonomy

surface and a depth of 18 cm that, after mixing, have one or

more of the following:

a. A color value, moist, of 4 or more; or

b. A color value, dry, of 6 or more; or

c. Chroma of 4 or more.

Chromic Vertic Hapludalfs

JEJF. Other Hapludalfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or

a densic, lithic, or paralithic contact, whichever is

shallower.

Vertic Hapludalfs

JEJG. Other Hapludalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Hapludalfs

JEJH. Other Hapludalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Hapludalfs

JEJI. Other Hapludalfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm or

more thick; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface.

Fragiaquic Hapludalfs

JEJJ. Other Hapludalfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. Saturation with water in one or more layers within 100

cm of the mineral soil surface in normal years for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Fragic Oxyaquic Hapludalfs

JEJK. Other Hapludalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface

to the top of an argillic horizon at a depth of 50 cm or

more.

Aquic Arenic Hapludalfs

JEJL. Other Hapludalfs that have:

1. An abrupt textural change; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper
Alfisols 211

boundary of the argillic horizon is 50 cm or more below the

mineral soil surface; and

3. A base saturation (by sum of cations) of less than 60

percent at a depth of 125 cm from the top of the argillic

horizon, at a depth of 180 cm from the mineral soil surface,

or directly above a densic, lithic, or paralithic contact,

whichever is shallowest.

Albaquultic Hapludalfs

JEJM. Other Hapludalfs that have both:

1. An abrupt textural change; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface.

Albaquic Hapludalfs

JEJN. Other Hapludalfs that have both:

1. Interfingering of albic materials in the upper part of the

argillic horizon; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface.

Glossaquic Hapludalfs

JEJO. Other Hapludalfs that have both:

1. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface; and

2. A base saturation (by sum of cations) of less than 60

percent at a depth of 125 cm from the top of the argillic

horizon, at a depth of 180 cm from the mineral soil surface, or

directly above a densic, lithic, or paralithic contact, whichever

is shallowest.

Aquultic Hapludalfs

JEJP. Other Hapludalfs that have both:

1. An Ap horizon that has a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed

sample) or materials between the soil surface and a depth of

18 cm that have these color values after mixing; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface.

Aquollic Hapludalfs

JEJQ. Other Hapludalfs that have redox depletions with

chroma of 2 or less in layers that also have aquic conditions in

normal years (or artificial drainage) either:

1. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil surface;

or

2. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below the

mineral soil surface.

Aquic Hapludalfs

JEJR. Other Hapludalfs that have anthraquic conditions.

Anthraquic Hapludalfs

JEJS. Other Hapludalfs that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Hapludalfs

JEJT. Other Hapludalfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Hapludalfs
212 Soil Taxonomy

JEJU. Other Hapludalfs that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or more

subhorizons with a thickness of 7.5 to 20 cm, each layer with

an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Hapludalfs

JEJV. Other Hapludalfs that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Hapludalfs

JEJW. Other Hapludalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more.

Arenic Hapludalfs

JEJX. Other Hapludalfs that have interfingering of

albic materials in one or more subhorizons of the argillic

horizon.

Glossic Hapludalfs

JEJY. Other Hapludalfs that have:

1. An argillic, kandic, or natric horizon that is 35 cm or

less thick; and

2. No densic, lithic, or paralithic contact within 100 cm of

the mineral soil surface.

Inceptic Hapludalfs

JEJZ. Other Hapludalfs that have a base saturation (by sum

of cations) of less than 60 percent at a depth of 125 cm below

the top of the argillic horizon, at a depth of 180 cm below the

mineral soil surface, or directly above a densic, lithic, or

paralithic contact, whichever is shallowest.

Ultic Hapludalfs

JEJZa. Other Hapludalfs that have a mollic epipedon, an Ap

horizon that meets all of the requirements for a mollic

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Mollic Hapludalfs

JEJZb. Other Hapludalfs.

Typic Hapludalfs

Definition of Typic Hapludalfs

Typic Hapludalfs are the Hapludalfs that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

3. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

4. Do not have redox depletions with chroma of 2 or less in

layers that also have aquic conditions in normal years (or

artificial drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil surface;

or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below the

mineral soil surface;
Alfisols 213

5. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 7 or more consecutive days or 20 or

more cumulative days in normal years;

6. Do not have anthraquic conditions;

7. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

8. Do not have a mollic epipedon, an Ap horizon that meets

all of the requirements for a mollic epipedon except thickness,

or materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing;

9. Have an argillic horizon that is finer than the sandy

particle-size class in some part of the upper 75 cm if the

argillic horizon is more than 75 cm thick or in any part if the

argillic horizon is less than 75 cm thick;

10. Have a base saturation (by sum of cations) of 60 percent

or more at a depth of 125 cm below the top of the argillic

horizon, at a depth of 180 cm below the soil surface, or directly

above a densic, lithic, or paralithic contact, whichever is

shallowest;

11. Do not have interfingering of albic materials in any

subhorizon of the argillic horizon;

12. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon;

13. Have an argillic horizon that is more than 35 cm thick;

and

14. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Hapludalfs.—The central concept or Typic subgroup of

Hapludalfs is fixed on freely drained soils that have an argillic

horizon that does not have an abrupt upper boundary, that does

not have interfingering of albic materials, that has a relatively

high base saturation, and that has a loamy or clayey texture and

is not composed entirely of thin lamellae. In addition, these soils

are deep or moderately deep to hard rock, have a light colored

plow layer, and do not have a thick epipedon with a sandy or

sandy-skeletal particle-size class throughout. They do not have

slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks.

An abrupt upper boundary of the argillic horizon and redox

concentrations in the argillic horizon are properties shared

with Albaqualfs and Albaquults and define intergrades to those

great groups.

If the upper 25 cm of the argillic horizon has aquic

conditions for some time in normal years (or artificial

drainage) and redox depletions with chroma of 2 or less, or

saturation with water within 100 cm of the surface for extended

periods, the soil is excluded from Typic Hapludalfs because

these properties are shared with Aqualfs.

A thick layer, starting at the mineral soil surface, that has a

sandy or sandy-skeletal particle-size class is considered

atypical and defines the Arenic subgroup. Interfingering of

albic materials in the argillic horizon causes a soil to be

excluded because this property is shared with Glossudalfs.

Typic Glossudalfs do not have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials because

these properties are shared with Andisols.

A shallow lithic contact defines the Lithic subgroup, a

convention used throughout this taxonomy. Surface horizons

above a depth of 18 cm that, after mixing, have the color of a

mollic epipedon and a plow layer that has this color are

believed to indicate a transition to Mollisols.

An argillic horizon that has a sandy particle-size class or

that is composed entirely of thin lamellae is the basis for

defining the Lamellic and Psammentic subgroups. A relatively

low base saturation in the deeper horizons is a property shared

with Ultisols and is used to define the intergrades to that order.

Soils that have slickensides, wedge-shaped aggregates, a

high linear extensibility, or wide cracks are excluded from the

Typic Hapludalfs because these properties are shared with

Vertisols.

Albaquic Hapludalfs.—These soils have an abrupt textural

change between an eluvial horizon, commonly an albic

horizon, and the argillic horizon. They also have, in one or

more subhorizons within the upper 25 cm of the argillic

horizon, redox depletions with chroma of 2 or less and aquic

conditions for some time in normal years (or artificial
214 Soil Taxonomy

drainage). These soils are intergrades between Albaqualfs and

Hapludalfs. They are mostly in the Southern United States and

are widely distributed. Most of them are used as forest, but

some have been cleared and are used as pasture or cropland.

Some of them developed under grass and are used as

rangeland, pasture, or cropland.

Albaquultic Hapludalfs.—These soils are like Typic

Hapludalfs, but they have an abrupt textural change between an

eluvial horizon, commonly an albic horizon, and the argillic

horizon and have, in one or more subhorizons within the upper

25 cm of the argillic horizon, redox depletions with chroma of

2 or less and aquic conditions for some time in normal years

(or artificial drainage). They also have a base saturation (by

sum of cations) of less than 60 percent at a depth of 125 cm

below the top of the argillic horizon, at a depth of 180 cm

below the soil surface, or directly above a densic, lithic, or

paralithic contact, whichever is shallowest. They differ from

soils of the Albaquic subgroup because they have a lower base

saturation and from soils of the Aquultic subgroup because

they have an abrupt textural change at the top of the argillic

horizon. Albaquultic Hapludalfs are intergrades between

Albaquults and Hapludalfs. They are mostly on the coastal

plain bordering the Gulf of Mexico and are not extensive.

Nearly all of these soils are in forests.

Andic and Vitrandic Hapludalfs.—These soils are like

Typic Hapludalfs, but they have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the foothills and mountains of the Western

United States. They are permitted, but not required, to have

redox depletions and to be saturated with water within 100 cm

of the mineral soil surface for 7 or more consecutive days or 20

or more cumulative days in normal years. These soils are of

very small extent but are locally important. They are used

mainly as forest, but some areas have been cleared and are used

as cropland or pasture.

Anthraquic Hapludalfs.—These soils are like Typic

Hapludalfs, but they have been irrigated for paddy rice

production for many years and have developed anthraquic

conditions. They are permitted, but not required, to have redox

depletions with chroma of 2 or less in layers that also have

aquic conditions in normal years either within the upper 25 cm

of the argillic horizon if its upper boundary is within 50 cm of

the mineral soil surface or within 75 cm of the mineral soil

surface if the upper boundary of the argillic horizon is deeper

than 50 cm. These soils are not extensive and are rare in the

United States. They have level or nearly level slopes.

Aquertic Hapludalfs.—These soils are like Typic

Hapludalfs, but they have redox depletions with low chroma,

aquic conditions at a shallow depth for some time in normal

years, and an appreciable amount of swelling clays. The Ap

horizon or the surface soil to a depth of 18 cm after mixing has

a color value of 3 or less, moist, and 5 or less, dry. A few of

these soils have a mollic epipedon, but the base saturation is

less than 50 percent (by NH4

OAc) in at least part of the argillic

horizon. The aquic conditions, swelling clays, and low

saturated hydraulic conductivity seem to be the most important

properties of the soils in this subgroup. Most of the soils

formed in clayey parent materials. Aquertic Hapludalfs are of

small extent. Slopes are gentle. Most of the soils have been

cleared and are used as cropland or pasture, but some of them

are used as forest. Some of the soils developed under grass

vegetation and are used as cropland or rangeland.

Aquertic Chromic Hapludalfs.—These soils are like Typic

Hapludalfs, but they have redox depletions with low chroma

and also have aquic conditions at a shallow depth for some

time in normal years. In addition, they have an appreciable

amount of swelling clays. The aquic conditions, swelling clays,

and low saturated hydraulic conductivity seem to be the most

important properties of the soils in this subgroup. Most of the

soils formed in clayey parent materials. Aquertic Chromic

Hapludalfs are of small extent. Slopes are gentle. Most of the

soils have been cleared and are used as cropland or pasture, but

some are used as forest.

Aquic Arenic Hapludalfs.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). They

also have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more. The

plow layer or the surface soil to a depth of 18 cm after mixing

is permitted, but not required, to have a color value of 3 or less,

moist, and 5 or less, dry. There is no restriction on the base

saturation other than that imposed by the definition of Alfisols.

Aquic Arenic Hapludalfs are not extensive in the United States.

They are mostly on the lake plains adjacent to the Great Lakes.

Their slopes are very gentle. Most of the soils have been

cleared and are used as cropland, but some of them are used as

pasture or forest.

Aquic Hapludalfs.—These soils are like Typic Hapludalfs,

but they have redox depletions with chroma of 2 or less in

layers that also have aquic conditions in normal years (or

artificial drainage) either within the upper 25 cm of the argillic

horizon if its upper boundary is within 50 cm of the mineral

soil surface or within 75 cm of the mineral soil surface if the

upper boundary of the argillic horizon is deeper than 50 cm.

These soils are intergrades between Aqualfs and Hapludalfs.

They are moderately extensive in the United States,

particularly in the glaciated areas of the north-central region.

Most of the soils have gentle slopes and have been cleared and

are used as cropland, but some of them are used as pasture or

forest.

Aquollic Hapludalfs.—These soils have, in one or more

subhorizons within the upper 25 cm of the argillic horizon,

redox depletions with chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial
Alfisols 215

drainage). In addition, the Ap horizon or the surface soil to a

depth of 18 cm after mixing has a color value of 3 or less,

moist, and 5 or less, dry. These soils are intergrades between

Argiaquolls and Hapludalfs. They are moderately extensive in

the United States, particularly in the glaciated parts of the

north-central region. Slopes are very gentle. Nearly all of the

soils have been cleared and are used as cropland, but some of

them are used as pasture or forest.

Aquultic Hapludalfs.—These soils have, in one or more

subhorizons within the upper 25 cm of the argillic horizon,

redox depletions with chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial

drainage). In addition, the base saturation (by sum of cations)

is less than 60 percent at a depth of 125 cm below the top of

the argillic horizon, at a depth of 180 cm below the soil

surface, or directly above a densic, lithic, or paralithic contact,

whichever is shallowest. The Ap horizon or the surface soil to

a depth of 18 cm after mixing may have any color value when

moist. These soils are intergrades between Aquults and

Hapludalfs. They are not extensive in the United States and are

known to occur only on the low Atlantic Coastal Plain. Their

slopes are very gentle. Many of the soils have been cleared and

are used as cropland, but some of them are used as pasture or

forest.

Arenic Hapludalfs.—These soils have a sandy or sandyskeletal particle-size class in all subhorizons to the top of an

argillic horizon at a depth of 50 cm or more. The plow layer or

the surface soil to a depth of 18 cm after mixing is permitted,

but not required, to have a color value of 3 or less, moist, and 5

or less, dry. There is no restriction on the base saturation other

than that imposed by the definition of Alfisols. Arenic

Hapludalfs are not extensive in the United States. They occur

mostly in the glaciated parts of the north-central region of the

United States and in Florida. Their slopes are mostly gentle.

Where slopes are suitable, the soils have been cleared and are

used as cropland. Some of the soils are used as pasture or

forest.

Chromic Vertic Hapludalfs.—These soils are like Typic

Hapludalfs, but they have an appreciable amount of swelling

clays. The swelling clays and low saturated hydraulic

conductivity seem to be the most important properties of the

soils in this subgroup. Most of the soils formed in clayey parent

materials. Chromic Vertic Hapludalfs are of small extent.

Slopes are gentle to steep. Most of the less sloping soils have

been cleared and are used as cropland or pasture. Some of the

soils are used as forest.

Fragiaquic Hapludalfs.—These soils are like Typic

Hapludalfs, but they have redox depletions with low chroma

and also aquic conditions at a shallow depth for some time in

normal years. In addition, they have fragic soil properties in 30

percent or more of the volume of a layer 15 cm or more thick

that has its upper boundary within 100 cm of the mineral soil

surface or in 60 percent or more of the volume of a layer 15 cm

or more thick anywhere in the soils. These soils are considered

intergrades to Fraqiaqualfs. They are not extensive in the United

States.

Fragic Hapludalfs.—These soils are like Typic Hapludalfs,

but they have fragic soil properties in 30 percent or more of the

volume of a layer 15 cm or more thick that has its upper

boundary within 100 cm of the mineral soil surface or in 60

percent or more of the volume of a layer 15 cm or more thick

anywhere in the soils. These soils are considered intergrades to

Fraqiudalfs. They are not extensive in the United States.

Fragic Oxyaquic Hapludalfs.—These soils are like Typic

Hapludalfs, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. In addition, they

have fragic soil properties in 30 percent or more of the volume

of a layer 15 cm or more thick that has its upper boundary

within 100 cm of the mineral soil surface or in 60 percent or

more of the volume of a layer 15 cm or more thick anywhere in

the soils. These soils are considered intergrades to

Fraqiaqualfs. They are not extensive in the United States.

Glossaquic Hapludalfs.—These soils have, in one or more

subhorizons within the upper 25 cm of the argillic horizon,

redox depletions with chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial

drainage). In addition, there is evidence of destruction of the

argillic horizon in the form of albic materials interfingering in

or into the argillic horizon. The Ap horizon or the surface soil

to a depth of 18 cm after mixing is permitted, but not required,

to have a color value, moist, of 3 or less. These soils are

intergrades between Glossaqualfs and Hapludalfs. They are

primarily in cool areas that were glaciated and along the gulf

coast of the United States. Where they have gentle slopes, most

of these soils have been cleared and are used as cropland or

pasture. Some of the soils are used as forest.

Glossic Hapludalfs.—These soils show evidence of

destruction of the argillic horizon in the form of albic materials

interfingering in or into the argillic horizon. The soils are

intergrades between Glossudalfs and Hapludalfs. The Ap

horizon or the surface soil to a depth of 18 cm after mixing is

permitted, but not required, to have a color value, moist, of 3 or

less. In most undisturbed areas of Glossic Hapludalfs, the color

value is 4 or more after the upper layers to a depth of 18 cm

have been mixed, but the cultivated soils have a darker Ap

horizon. Glossic Hapludalfs are moderately extensive in the

United States. They are primarily in cool areas that were

glaciated. Where they have gentle slopes, many of these soils

have been cleared and are used as cropland or pasture. Some of

the soils are used as forest.

Inceptic Hapludalfs.—These soils have an argillic horizon

that is less than 35 cm thick and have no densic, lithic, or

paralithic contact within 100 cm of the mineral soil surface.

They are permitted, but not required, to have a color value,

moist, of 3 or less in the Ap horizon or in the surface soil to a

depth of 18 cm after mixing and to have a base saturation (by

sum of cations) that is less than 60 percent. These soils are not
216 Soil Taxonomy

extensive in the United States. They are considered intergrades

between Udepts and Hapludalfs. They are of small extent in the

United States. Where slopes are suitable, many of these soils

have been cleared and are used as cropland or pasture. Some of

the soils, mostly the more sloping ones, are used as forest.

Lamellic Hapludalfs.—These soils are like Typic

Hapludalfs, but they have an argillic horizon that consists

entirely of lamellae or is a combination of two or more

lamellae and one or more subhorizons with a thickness of 7.5

to 20 cm, each layer with an overlying eluvial horizon. In some

of the soils, the argillic horizon consists of one or more

subhorizons that are more than 20 cm thick, each with an

overlying eluvial horizon, and above these horizons there are

either two or more lamellae with a combined thickness of 5 cm

or more or a combination of lamellae and one or more parts of

the argillic horizon 7.5 to 20 cm thick, each with an overlying

eluvial horizon. Lamellic Hapludalfs are permitted, but not

required, to have a color value, moist, of 3 or less in the Ap

horizon or in the surface soil to a depth of 18 cm after mixing

and to have a base saturation (by sum of cations) that is less

than 60 percent. The soils are not extensive in the United

States. They are intergrades between Psamments and

Hapludalfs. Many of the Lamellic Hapludalfs in the United

States are on lake plains adjacent to the Great Lakes. Where

they have gentle slopes, many of these soils have been cleared

and are used as cropland or pasture. Some of the soils are used

as forest.

Lithic Hapludalfs.—These soils have a lithic contact

within 50 cm of the mineral soil surface. They are permitted to

have any other property that is allowed in Hapludalfs. They can

have redox depletions with low chroma and aquic conditions at

a shallow depth for some time in normal years. There can be

evidence of destruction of the argillic horizon in the form of

albic materials interfingering in or into the argillic horizon.

The Ap horizon or the surface soil to a depth of 18 cm after

mixing is permitted, but not required, to have a color value,

moist, of 3 or less. These soils are not extensive in the United

States, and they are widely distributed. Their slopes range from

gentle to very steep. Most of the soils are used as pasture or

forest.

Mollic Hapludalfs.—These soils are like Typic Hapludalfs,

but they have a mollic epipedon, an Ap horizon that meets all

of the requirements for a mollic epipedon except thickness, or

materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing. The soils that have a

mollic epipedon also have a base saturation of less than 50

percent (by NH4

OAc) in at least part of the argillic horizon.

Mollic Hapludalfs are mostly transitional in morphology and in

location to Udolls. They are moderately extensive in the United

States. Their slopes range from gentle to strong. Where slopes

are suitable, nearly all of these soils have been cleared and are

used as cropland or pasture. Some of the soils, mainly the most

sloping ones, are used as forest.

Oxyaquic Hapludalfs.—These soils are like Typic

Hapludalfs, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. In addition, the soils

are permitted, but not required, to have a color value, moist, of

3 or less in the Ap horizon or in the surface soil to a depth of

18 cm after mixing and to have a base saturation (by sum of

cations) that is less than 60 percent. These soils are moderately

extensive in the United States. They are considered intergrades

to Aqualfs. Slopes are gentle. Most Oxyaquic Hapludalfs have

been cleared and are used as cropland or pasture, but some of

them are used as forest.

Oxyaquic Vertic Hapludalfs.—These soils are like Typic

Hapludalfs, but they have an appreciable amount of swelling

clays and are saturated with water within 100 cm of the

mineral soil surface for 20 or more consecutive days or 30 or

more cumulative days in normal years. In addition, the soils

are permitted, but not required, to have a color value, moist, of

3 or less in the Ap horizon or in the surface soil to a depth of

18 cm after mixing and to have a base saturation (by sum of

cations) that is less than 60 percent. A few of these soils have a

mollic epipedon, but the base saturation is less than 50 percent

(by NH4

OAc) in at least part of the argillic horizon. The

swelling clays, saturation, and low saturated hydraulic

conductivity seem to be the most important properties of the

soils in this subgroup. Most of the soils formed in clayey parent

materials. Oxyaquic Vertic Hapludalfs are considered

intergrades to Aquerts. They are not extensive in the United

States. Slopes are gentle. Most of the soils have been cleared

and are used as cropland or pasture, but some of them are used

as forest.

Psammentic Hapludalfs.—These soils have a sandy

particle-size class throughout the upper 75 cm of the argillic

horizon or throughout the entire argillic horizon if it is less

than 75 cm thick. Depth to the argillic horizon may be more

than 100 cm. Generally, the depth is more than 50 cm, and all

horizons above the argillic horizon have a texture of loamy fine

sand or coarser. These soils are permitted, but not required, to

have a color value, moist, of 3 or less in the Ap horizon or in

the surface soil to a depth of 18 cm after mixing and to have a

base saturation (by sum of cations) that is less than 60 percent.

The soils are not extensive in the United States. They are

intergrades between Psamments and Hapludalfs. Most

Psammentic Hapludalfs are in the parts of the United States

that were glaciated, but a few are in Florida. Slopes generally

are gentle. Most of these soils have been cleared and are used

as cropland or pasture, but some of them are used as forest.

Ultic Hapludalfs.—These soils have a base saturation (by

sum of cations) that is less than 60 percent at a depth of 125

cm below the top of the argillic horizon, at a depth of 180 cm

below the soil surface, or directly above a densic, lithic, or

paralithic contact, whichever is shallowest. In addition, the Ap

horizon or the surface soil to a depth of 18 cm after mixing is

permitted, but not required, to have a color value, moist, of 3 or

less. Commonly, the argillic horizon has hue of 7.5YR or
Alfisols 217

redder or has chroma of more than 4. Some Typic Hapludalfs

have these same colors. Ultic Hapludalfs are intergrades

between Hapludults and Hapludalfs. They are moderately

extensive in the United States. Most of them developed from

weathered country rocks but not from acid rocks. Ultic

Hapludalfs are mostly in highly dissected areas where the

landscape is hilly or mountainous. Their slopes range from

gentle to strong. Where slopes are suitable, most of the soils

have been cleared and are used as cropland or pasture. Some of

the soils, mostly the most sloping ones, are used as forest.

Vertic Hapludalfs.—These soils have deep cracks and

appreciable amounts of swelling clays. The swelling clays and

low saturated hydraulic conductivity seem to be the most

important properties of the soils in this subgroup. Most of the

soils formed in clayey parent materials. Vertic Hapludalfs are

moderately extensive. Slopes are gentle to steep, and the soils

are highly erodible. Some of these soils have been cleared and

are used as cropland or pasture, and some, mainly the most

sloping ones, are used as forest.

Kandiudalfs

Kandiudalfs are the Udalfs that have a kandic horizon. These

soils have a clay distribution in which the content of clay does

not decrease from its maximum amount by 20 percent or more

within 150 cm of the soil surface or the layer with the decrease

has at least 5 percent of the volume consisting of skeletans on

faces of peds and there is at least a 3 percent (absolute) increase

in content of clay below this layer. Kandiudalfs do not have a

natric horizon, nor do they have a fragipan within 100 cm of the

mineral soil surface. They do not have both a glossic horizon

and discrete nodules, 2.5 to 30 cm in diameter, that are enriched

with iron and cemented to indurated. These soils are 150 cm or

more deep to a densic, lithic, paralithic, or petroferric contact.

The base of the kandic horizon is commonly more than 150 cm

below the soil surface and in some areas is more than 200 cm

below the surface. Most of these soils have a thermic or warmer

soil temperature regime. The natural vegetation was forest,

mostly deciduous, but many of the soils are now cleared and

used as cropland.

Definition

Kandiudalfs are the Udalfs that:

1. Have a kandic horizon;

2. Do not have a densic, lithic, paralithic, or petroferric contact

within 150 cm of the mineral soil surface;

3. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within 150 cm of the soil surface, or the layer in which

the clay percentage decreases by more than 20 percent has at

least 5 percent of the volume consisting of skeletans on faces of

peds and there is at least a 3 percent (absolute) increase in

content of clay below this layer;

4. Do not have a natric horizon;

5. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

6. Do not have both a glossic horizon and, in the kandic

horizon, discrete nodules, 2.5 to 30 cm in diameter, that have

enriched exteriors, are weakly cemented with iron, and have

exteriors with redder hue or higher chroma than the interiors.

Key to Subgroups

JEEA. Kandiudalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Plinthaquic Kandiudalfs

JEEB. Other Kandiudalfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Kandiudalfs

JEEC. Other Kandiudalfs that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Kandiudalfs

JEED. Other Kandiudalfs that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 to 100 cm; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthic Kandiudalfs

JEEE. Other Kandiudalfs that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 100 cm or more; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Grossarenic Plinthic Kandiudalfs
218 Soil Taxonomy

JEEF. Other Kandiudalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a kandic horizon at a depth of

50 to 100 cm.

Arenic Kandiudalfs

JEEG. Other Kandiudalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a kandic horizon at a depth of

100 cm or more.

Grossarenic Kandiudalfs

JEEH. Other Kandiudalfs that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kandiudalfs

JEEI. Other Kandiudalfs that have, in all subhorizons in the

upper 100 cm of the kandic horizon or throughout the entire

kandic horizon if less than 100 cm thick, more than 50 percent

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodic Kandiudalfs

JEEJ. Other Kandiudalfs that have a mollic epipedon, an Ap

horizon that meets all of the requirements for a mollic

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Mollic Kandiudalfs

JEEK. Other Kandiudalfs.

Typic Kandiudalfs

Definition of Typic Kandiudalfs

Typic Kandiudalfs are the Kandiudalfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years;

3. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

4. Do not have, in all subhorizons in the upper 100 cm of the

kandic horizon or throughout the entire kandic horizon if less

than 100 cm thick, more than 50 percent colors that have all of

the following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value;

5. Have a kandic horizon that has a color value, dry, of 5 or

more in some subhorizon, or a color value, moist, that is less

than the value, dry, by more than 1 unit unless hue in some

part of the kandic horizon is 5YR or yellower;

6. Do not have a horizon within 150 cm of the surface that

has 5 percent or more plinthite, by volume; and

7. Do not have a mollic epipedon, an Ap horizon that meets

all of the requirements for a mollic epipedon except thickness,

or materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing.

Description of Subgroups

Typic Kandiudalfs.—The central concept or Typic

subgroup of Kandiudalfs is fixed on freely drained soils that do

not have a thick epipedon with a sandy or sandy-skeletal

particle-size class throughout and that do not have the color of

a mollic epipedon in any Ap horizon or in subhorizons of

comparable thickness if the soils are undisturbed. The kandic

horizon has a color value, dry, of 4.5 or more in some

subhorizon, or the color values, moist and dry, differ by more

than 1 unit unless hue in some part of the kandic horizon is

5YR or yellower. The kandic horizon does not have an

appreciable amount of plinthite.

Soils that have shallow redox depletions with low chroma in

horizons that also have aquic conditions for some time in

normal years (or artificial drainage) are excluded from Typic

Kandiudalfs because these properties are shared with

Kandiaqualfs. A thick epipedon with a sandy or sandy-skeletal

particle-size class throughout is considered atypical and defines

the Arenic and Grossarenic subgroups. The color of a mollic

epipedon in the plow layer or, if the soils are undisturbed, in

surface horizons of comparable thickness is not typical and

defines the Mollic subgroup. Plinthite in appreciable volume

defines the Plinthic subgroup. Typic Kandiudalfs are rare in

the United States.

Aquic Kandiudalfs.—These soils are like Typic Kandiudalfs,

but they have, in one or more horizons within

75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time

in normal years (or artificial drainage). The soils are

permitted, but not required, to have a color value, moist, of

less than 4 and a color value, dry, of less than 6 in the Ap

horizon or in the upper 18 cm after mixing and to have a

sandy or sandy-skeletal particle-size class throughout a layer

extending from the mineral soil surface to the top of a kandic

horizon at a depth of 50 cm or more below the mineral soil

surface. The soils also are permitted to have 5 percent or

more (by volume) plinthite in some subhorizon within 150 cm
Alfisols 219

of the surface. They are not known to occur in the United

States.

Arenic Kandiudalfs.—These soils are like Typic Kandiudalfs,

but they have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to the

top of a kandic horizon at a depth of 50 to 100 cm below the

mineral soil surface. These soils are not known to occur in the

United States.

Arenic Plinthic Kandiudalfs.—These soils are like Typic

Kandiudalfs, but they have a sandy or sandy-skeletal particlesize class throughout a layer extending from the mineral soil

surface to the top of a kandic horizon at a depth of 50 to 100

cm below the mineral soil surface. They also have 5 percent or

more (by volume) plinthite in some subhorizon within 150 cm

of the surface. During rainy seasons ground water tends to

perch above the horizon that contains plinthite. These soils are

not known to occur in the United States.

Grossarenic Kandiudalfs.—These soils are like Typic

Kandiudalfs, but they have a sandy or sandy-skeletal particlesize class throughout a layer extending from the mineral soil

surface to the top of a kandic horizon at a depth of 100 cm or

more below the mineral soil surface. These soils are not known

to occur in the United States.

Grossarenic Plinthic Kandiudalfs.—These soils are like

Typic Kandiudalfs, but they have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a kandic horizon at a depth of

100 cm or more below the mineral soil surface. They also have

5 percent or more (by volume) plinthite in some subhorizon

within 150 cm of the surface. During rainy seasons ground

water tends to perch above the horizon that contains plinthite.

These soils are not known to occur in the United States.

Mollic Kandiudalfs.—These soils are like Typic

Kandiudalfs, but they have a mollic epipedon, an Ap horizon

that meets all of the requirements for a mollic epipedon except

thickness, or materials between the soil surface and a depth of

18 cm that meet these requirements after mixing. These soils

are considered intergrades between Paleudolls and

Kandiudalfs. They are not known to occur in the United States.

Oxyaquic Kandiudalfs.—These soils are like Typic

Kandiudalfs, but they are saturated with water within 100 cm

of the mineral soil surface for 20 or more consecutive days or

30 or more cumulative days in normal years. In addition, the

soils are permitted, but not required, to have a color value,

moist, of 3 or less in the Ap horizon or in the surface soil to a

depth of 18 cm after mixing and to have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 50 cm or more below the mineral soil surface. They

also are permitted to have 5 percent or more (by volume)

plinthite in some subhorizon within 150 cm of the surface.

These soils are considered intergrades to Aqualfs.

Plinthaquic Kandiudalfs.—These soils are like Typic

Kandiudalfs, but they have, in one or more horizons within 75

cm of the mineral soil surface, redox depletions with chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). They have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of

the mineral soil surface. In addition, the soils are permitted,

but not required, to have a color value, moist, of 3 or less in

the Ap horizon or in the surface soil to a depth of 18 cm, after

mixing. These soils are intergrades between Plinthaqualfs and

Kandiudalfs. They are not known to occur in the United

States.

Plinthic Kandiudalfs.—These soils have 5 percent or more

(by volume) plinthite in some subhorizon within 150 cm of the

surface. In addition, they are permitted, but not required, to

have a color value, moist, of 3 or less in the Ap horizon or in

the surface soil to a depth of 18 cm, after mixing. During rainy

seasons ground water tends to perch above the horizons that

contain plinthite. These soils are not known to occur in the

United States.

Rhodic Kandiudalfs.—These soils are like Typic Kandiudalfs,

but all parts of the kandic horizon have a color value, moist, of

less than 3.5 and a dry color value no more than 1 unit higher

than the moist value and hue in the kandic horizon is redder than

5YR. In addition, the Ap horizon or the upper 18 cm after mixing

commonly has a color value, moist, of less than 3.5 and value,

dry, no more than 1 unit higher than the moist value. These soils

are rare in the United States.

Kanhapludalfs

Kanhapludalfs are the Udalfs that have a kandic horizon.

They do not have a natric horizon, nor do they have a fragipan

with an upper boundary within 100 cm of the mineral soil

surface. They do not have both a glossic horizon and discrete

nodules, 2.5 to 30 cm in diameter, that are enriched with iron

and cemented to indurated. The base of the kandic horizon is

less than 150 cm below the soil surface, or the kandic horizon

has a clay distribution in which the content of clay decreases

from its maximum amount by 20 percent or more within 150

cm of the soil surface, and the layer in which the percentage of

clay is less than the maximum has less than 5 percent of the

volume consisting of skeletans on faces of peds or there is less

than a 3 percent (absolute) increase in content of clay below

this layer. Most of these soils have a thermic or warmer soil

temperature regime. The natural vegetation on Kanhapludalfs

was forest, mostly deciduous, but many of the soils are now

cleared and used as cropland.

Definition

Kanhapludalfs are the Udalfs that:

1. Have a kandic horizon;

2. Have a clay distribution in which the content of clay

decreases from its maximum amount by 20 percent or more

within 150 cm of the soil surface, and the layer in which the
220 Soil Taxonomy

percentage of clay is less than the maximum has less than 5

percent of the volume consisting of skeletans on faces of peds

or there is less than a 3 percent (absolute) increase in content of

clay below this layer;

3. Do not have a natric horizon;

4. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface; and

5. Do not have both a glossic horizon and, in the kandic

horizon, discrete nodules, 2.5 to about 30 cm in diameter, that

are enriched with iron, are extremely weakly cemented to

indurated, and have exteriors with either redder hue and/or

higher chroma than the interiors.

Key to Subgroups

JEFA. Kanhapludalfs that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Kanhapludalfs

JEFB. Other Kanhapludalfs that have, in one or

more horizons within 75 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Kanhapludalfs

JEFC. Other Kanhapludalfs that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Kanhapludalfs

JEFD. Other Kanhapludalfs that have, in all subhorizons in

the upper 100 cm of the kandic horizon or throughout the

entire kandic horizon if less than 100 cm thick, more than 50

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodic Kanhapludalfs

JEFE. Other Kanhapludalfs.

Typic Kanhapludalfs

Definition of Typic Kanhapludalfs

Typic Kanhapludalfs are the Kanhapludalfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

conditions;

2. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30 or

more cumulative days in normal years;

3. Do not have a lithic contact within 50 cm of the soil surface;

and

4. Do not have, in all subhorizons in the upper 100 cm of the

kandic horizon or throughout the entire kandic horizon if less

than 100 cm thick, more than 50 percent colors that have all of

the following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value.

Description of Subgroups

Typic Kanhapludalfs.—The central concept or Typic

subgroup of Kanhapludalfs is fixed on freely drained soils that

are more than 50 cm deep to a lithic contact.

Soils with a kandic horizon that has 50 percent or more

colors with hue of 2.5YR or redder, value, dry, of 3 or less, and

color values, moist and dry, that differ by 1 or less than 1 unit

are excluded from Typic Kanhapludalfs because these

properties are shared with Rhodudalfs. Soils that have shallow

redox depletions with low chroma in horizons that also have

aquic conditions for some time in normal years (or artificial

drainage) are excluded from Typic Kanhapludalfs because

these properties are shared with Kandiaqualfs. Typic

Kanhapludalfs are rare in the United States.

Aquic Kanhapludalfs.—These soils are like Typic

Kanhapludalfs, but they have, in one or more horizons within

75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time

in normal years (or artificial drainage). The soils are

permitted, but not required, to have a kandic horizon that has

50 percent or more colors with hue of 2.5YR or redder, value,

dry, of 3 or less, and color values, moist and dry, that differ by

1 or less than 1 unit, and they are excluded from Typic

Kanhapludalfs because these properties are shared with

Rhodudalfs. Aquic Kanhapludalfs are not known to occur in

the United States.

Lithic Kanhapludalfs.—These soils have a lithic contact

within 50 cm of the mineral soil surface. In addition, they are

permitted to have any color, saturation, or redox feature

allowed in Kanhapludalfs. Lithic Kanhapludalfs are not known

to occur in the United States.

Oxyaquic Kanhapludalfs.—These soils are like Typic

Kanhapludalfs, but they are saturated with water within 100

cm of the mineral soil surface for 20 or more consecutive days

or 30 or more cumulative days in normal years. In addition,

these soils are permitted, but not required, to have a kandic

horizon that has 50 percent or more colors with hue of 2.5YR

or redder, value, dry, of 3 or less, and color values, moist and
Alfisols 221

dry, that differ by 1 or less than 1 unit, and they are excluded

from Typic Kanhapludalfs because these properties are shared

with Rhodudalfs. Oxyaquic Kanhapludalfs are considered

intergrades to Aqualfs. They are not known to occur in the

United States.

Rhodic Kanhapludalfs.—These soils are like Typic

Kanhapludalfs, but all parts of the kandic horizon have a color

value, moist, of less than 3.5 and a dry color value no more

than 1 unit higher than the moist value and hue in the kandic

horizon is redder than 5YR. In addition, the Ap horizon or the

upper 18 cm after mixing commonly has a color value, moist,

of less than 3.5 and value, dry, no more than 1 unit higher than

the moist value. These soils are considered intergrades to

Rhodudalfs. They are rare in the United States.

Natrudalfs

Natrudalfs are the Udalfs that have a natric horizon. Because

the natric horizon is slowly permeable, perched ground water is

common for short periods and the natric horizon commonly has

redoximorphic features. These soils are of small extent in the

United States. Some of the soils were forested. Some supported

open forests, and some supported grass. Most of the soils have

been cleared and are used as cropland or pasture. The soils are

not so productive as most Udalfs, but they generally are farmed

if they occur in very small areas and the associated soils are

productive.

Key to Subgroups

JEAA. Natrudalfs that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Natrudalfs

JEAB. Other Natrudalfs that have:

1. Either a glossic horizon or interfingering of albic

materials into the natric horizon; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the natric horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the natric horizon is 50 cm or more below the

mineral soil surface.

Glossaquic Natrudalfs

JEAC. Other Natrudalfs that have redox depletions with

chroma of 2 or less in layers that also have aquic conditions in

normal years (or artificial drainage) either:

1. Within the upper 25 cm of the natric horizon if its

upper boundary is within 50 cm of the mineral soil surface;

or

2. Within 75 cm of the mineral soil surface if the upper

boundary of the natric horizon is 50 cm or more below the

mineral soil surface.

Aquic Natrudalfs

JEAD. Other Natrudalfs.

Typic Natrudalfs

Definition of Typic Natrudalfs

Typic Natrudalfs are the Natrudalfs that:

1. Do not have redox depletions with chroma of 2 or less in

layers that also have aquic conditions in normal years (or

artificial drainage) either:

a. Within the upper 25 cm of the natric horizon if its

upper boundary is within 50 cm of the mineral soil surface;

or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the natric horizon is 50 cm or more below the

mineral soil surface; and

2. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Natrudalfs.—Typic Natrudalfs are not the most

extensive subgroup, but they furnish the best basis for

definition of subgroups. Most Natrudalfs are not freely drained

because the ground water is perched above the natric horizon

in many years. The perched water table is a probable cause of

the very common albic materials and glossic horizon at the

upper boundary of the natric horizon. Soils that have redox

depletions with low chroma at a shallow depth and also have

aquic conditions are considered to be intergrades toward
222 Soil Taxonomy

Aqualfs. Soils that have cracks and slickensides or wedgeshaped aggregates are excluded from the Typic subgroup

because these properties are shared with Vertisols.

Aquic Natrudalfs.—Aquic Natrudalfs are not so well

drained as Typic Natrudalfs because the natric horizon

commonly has low or very low saturated hydraulic

conductivity. Soils that have a glossic horizon and

interfingering of albic materials into the upper part of the

natric horizon are excluded from the aquic subgroup because

these properties are shared with Glossaqualfs.

Glossaquic Natrudalfs.—These soils are not so well

drained as Typic Natrudalfs because the natric horizon

commonly has low or very low saturated hydraulic

conductivity. Glossaquic Natrudalfs also have a glossic horizon

or albic materials that interfinger into the natric horizon,

mostly between columns or prisms, commonly to a depth of 10

to 20 cm below their tops. These soils are not extensive in the

United States.

Vertic Natrudalfs.—These soils are like Typic Natrudalfs, but

they are high in content of expanding clays and have cracks 5

mm or more wide, slickensides, wedge-shaped aggregates, or a

linear extensibility of 6.0 cm or more between the mineral soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact, whichever is shallower. Vertic Natrudalfs are

considered intergrades between Natrudalfs and Vertisols. They

are rare in the United States.

Paleudalfs

Paleudalfs are the Alfisols that have a thick solum. These

soils do not have a kandic or natric horizon, nor do they have a

fragipan within 100 cm of the mineral soil surface. Some have

an argillic horizon that shows evidence of destruction in the

form of a glossic horizon, but they do not have both a glossic

horizon and discrete iron-cemented nodules 2.5 to 30 cm in

diameter. Paleudalfs are on relatively stable surfaces. Most of

them are older than the Wisconsinan Glaciation. The time of

soil formation dates from the Sangamon interglacial period or

earlier. Base saturation commonly is lower than that in many

other Alfisols. Before cultivation, most Paleudalfs in the

United States had a vegetation of mixed deciduous hardwood

forest.

Definition

Paleudalfs are the Udalfs that:

1. Do not have a kandic or natric horizon;

2. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

3. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within 150 cm of the soil surface, or the layer in which

the clay percentage decreases by more than 20 percent has at

least 5 percent of the volume consisting of skeletans on faces of

peds and there is at least a 3 percent (absolute) increase in

content of clay below this layer;

4. Do not have a densic, lithic, or paralithic contact within

150 cm of the soil surface;

5. Have an argillic horizon with one or more of the

following:

a. In 50 percent or more of the matrix of one or more

subhorizons in its lower one-half, hue of 7.5YR or redder

and chroma of 5 or more; or

b. In 50 percent or more of the matrix of horizons that

total more than one-half the total thickness, hue of 2.5YR or

redder, value, moist, of 3 or less, and value, dry, of 4 or less;

or

c. Many coarse redox concentrations with hue of 5YR or

redder or chroma of 6 or more, or both, in one or more

subhorizons;

6. Do not have both a glossic horizon and, in the argillic

horizon, discrete nodules, 2.5 to 30 cm in diameter, that are

cemented or indurated with iron and that have exteriors with

redder hue or higher chroma than the interiors; and

7. Have a frigid temperature regime and all of the following:

a. An argillic horizon that has its upper boundary 60 cm

or more below both:

(1) The mineral soil surface; and

(2) The lower boundary of any surface mantle

containing 30 percent or more vitric volcanic ash,

cinders, or other vitric pyroclastic materials; and

b. A texture (in the fine-earth fraction) finer than loamy

fine sand in one or more horizons above the argillic

horizon; and

c. Either a glossic horizon or interfingering of albic

materials into the argillic horizon.

Key to Subgroups

JEGA. Paleudalfs that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Paleudalfs
Alfisols 223

JEGB. Other Paleudalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Paleudalfs

JEGC. Other Paleudalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Paleudalfs

JEGD. Other Paleudalfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic horizon if its

upper boundary is within 50 cm of the mineral soil

surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface.

Fragiaquic Paleudalfs

JEGE. Other Paleudalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Plinthaquic Paleudalfs

JEGF. Other Paleudalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A glossic horizon or, in the upper part of the argillic

horizon, one or more subhorizons that have 5 percent or

more (by volume) clay depletions with chroma of 2 or less.

Glossaquic Paleudalfs

JEGG. Other Paleudalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A clay increase of 15 percent or more (absolute) in the

fine-earth fraction within a vertical distance of 2.5 cm at the

upper boundary of the argillic horizon.

Albaquic Paleudalfs

JEGH. Other Paleudalfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Paleudalfs

JEGI. Other Paleudalfs that have anthraquic conditions.

Anthraquic Paleudalfs

JEGJ. Other Paleudalfs that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Paleudalfs

JEGK. Other Paleudalfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Paleudalfs
224 Soil Taxonomy

JEGL. Other Paleudalfs that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 to 100 cm; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthic Paleudalfs

JEGM. Other Paleudalfs that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 100 cm or more; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Grossarenic Plinthic Paleudalfs

JEGN. Other Paleudalfs that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Paleudalfs

JEGO. Other Paleudalfs that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Paleudalfs

JEGP. Other Paleudalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm.

Arenic Paleudalfs

JEGQ. Other Paleudalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more.

Grossarenic Paleudalfs

JEGR. Other Paleudalfs that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Paleudalfs

JEGS. Other Paleudalfs that have either:

1. A glossic horizon; or

2. In the upper part of the argillic horizon, one or more

subhorizons that have 5 percent or more (by volume)

skeletans with chroma of 2 or less; or

3. 5 percent or more (by volume) albic materials in some

subhorizon of the argillic horizon.

Glossic Paleudalfs

JEGT. Other Paleudalfs that have, in all subhorizons in the

upper 100 cm of the argillic horizon or throughout the entire

argillic horizon if less than 100 cm thick, more than 50 percent

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodic Paleudalfs

JEGU. Other Paleudalfs that have a mollic epipedon, an Ap

horizon that meets all of the requirements for a mollic

epipedon except thickness, or materials between the soil

surface and a depth of 18 cm that meet these requirements after

mixing.

Mollic Paleudalfs

JEGV. Other Paleudalfs.

Typic Paleudalfs

Definition of Typic Paleudalfs

Typic Paleudalfs are the Paleudalfs that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and
Alfisols 225

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions and do not have an increase of 15 percent or

more (absolute) clay within a vertical distance of 2.5 cm at the

upper boundary of the argillic horizon;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years;

4. Do not have anthraquic conditions;

5. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

6. Do not have, in all subhorizons in the upper 100 cm of the

argillic horizon or throughout the entire argillic horizon if less

than 100 cm thick, more than 50 percent colors that have all of

the following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value;

7. Have an argillic horizon that has a color value, dry, of 4.5

or more in some subhorizon, or a color value, moist, that is less

than the value, dry, by more than 1 unit unless hue in some

part of the argillic horizon is 5YR or yellower;

8. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

9. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the surface;

10. Have an argillic horizon that is finer than the sandy

particle-size class in some part of the upper 75 cm if the

argillic horizon is more than 75 cm thick or in any part if the

argillic horizon is less than 75 cm thick;

11. Do not have a glossic horizon or subhorizons in the upper

part of the argillic horizon that have clay depletions that:

a. Have moist chroma of 2 or less; and

b. Occupy 5 percent or more of the volume of the

subhorizon;

12. Do not have albic materials that constitute as much as 5

percent of any subhorizon of the argillic horizon;

13. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon;

14. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick;

15. Do not have a mollic epipedon, an Ap horizon that meets

all of the requirements for a mollic epipedon except thickness,

or materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing.

Description of Subgroups

Typic Paleudalfs.—The central concept or Typic subgroup

of Paleudalfs is fixed on freely drained soils that do not have a

thick epipedon with a sandy or sandy-skeletal particle-size

class throughout. These soils do not have a mollic epipedon or

an Ap horizon or subhorizons of comparable thickness that

meet all of the requirements for a mollic epipedon except

thickness. The argillic horizon has a color value, dry, of 5 or

more in some subhorizon, or the color values, moist and dry,

differ by more than 1 unit unless hue in some part of the

argillic horizon is 5YR or yellower. The argillic horizon does

not have cracks and slickensides or wedge-shaped aggregates,

and it does not have an appreciable amount of plinthite or a

sandy texture throughout. These soils do not have albic

materials that constitute as much as 5 percent of any

subhorizon of the argillic horizon.

Soils that have shallow redox depletions with low chroma in
226 Soil Taxonomy

horizons that also have aquic conditions for some time in normal

years (or artificial drainage) are excluded from Typic Paleudalfs

because these properties are shared with Aqualfs. A thick

epipedon with a sandy or sandy-skeletal particle-size class

throughout is considered atypical and defines the Arenic and

Grossarenic subgroups. Typic Paleudalfs do not have a surface

mantle or layer in the upper 75 cm that has both a low bulk

density and a high content of weakly crystalline minerals or that

consists of slightly or moderately weathered pyroclastic

materials because these properties are shared with Andisols.

Soils that have a mollic epipedon or that meet all of the

requirements for a mollic epipedon, except for thickness, in the

plow layer or in surface horizons of comparable thickness are

considered atypical, and these properties define the Mollic

subgroup. Plinthite in appreciable volume defines the Plinthic

subgroup. An argillic horizon that has a sandy particle-size

class throughout its upper 75 cm is the basis for defining the

Psammentic subgroup. An argillic horizon that is composed

entirely of lamellae is the basis for defining the Lamellic

subgroup.

Typic Paleudalfs are moderately extensive in the United

States. Many are in the unglaciated areas of the Southern

States. Most of the soils that have gentle or moderate slopes

have been cleared of the original forests and are used as

cropland.

Albaquic Paleudalfs.—These soils are like Typic

Paleudalfs, but they have, in one or more horizons within 75

cm of the mineral soil surface, redox depletions with chroma of

2 or less and also aquic conditions for some time in normal

years (or artificial drainage). They have an increase of 15

percent or more in the amount of clay (absolute) within a

vertical distance of 2.5 cm at the top of the argillic horizon.

They are intergrades between Albaqualfs and Paleudalfs. They

are mainly in Oklahoma and are not extensive in the United

States.

Andic and Vitrandic Paleudalfs.—These soils are like

Typic Paleudalfs, but they have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur in the foothills and mountains of the Western

United States. They are permitted, but not required, to have

redox depletions and to be saturated with water within 100 cm

of the mineral soil surface for 7 or more consecutive days or 20

or more cumulative days in normal years. The soils are

permitted, but not required, to have a mollic epipedon or an Ap

horizon or other subhorizons of comparable thickness that meet

all of the requirements for a mollic epipedon, except for

thickness, after mixing. These soils are of very small extent but

are locally important. They generally have a frigid temperature

regime and are used as forest. Some areas have been cleared

and are used as cropland or pasture.

Anthraquic Paleudalfs.—These soils are like Typic

Paleudalfs, but they have been irrigated for paddy rice

production for many years and have developed anthraquic

conditions. They are permitted, but not required, to have redox

depletions with chroma of 2 or less in layers that also have

aquic conditions in normal years either within the upper 25 cm

of the argillic horizon if its upper boundary is within 50 cm of

the mineral soil surface or within 75 cm of the mineral soil

surface if the upper boundary of the argillic horizon is deeper

than 50 cm. These soils are permitted, but not required, to have

a mollic epipedon or an Ap horizon that meets all of the

requirements for a mollic epipedon except thickness. They

have level or nearly level slopes. They are not extensive and

are not known to occur in the United States. They have been

cleared of the original forests and are used mostly for paddy

rice.

Aquic Paleudalfs.—These soils are like Typic Paleudalfs,

but they have, in one or more horizons within 75 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). A gray, sandy albic horizon is not adequate

evidence of wetness. These soils are permitted, but not

required, to have a mollic epipedon or an Ap horizon or other

subhorizons of comparable thickness that meet all of the

requirements for a mollic epipedon, except for thickness, after

mixing. The soils are not extensive in the United States. Most

of them are in the Southern States. Slopes are gentle, and most

of the soils have been cleared of the original forests and are

used as cropland.

Arenic Paleudalfs.—These soils have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of an argillic horizon at a

depth of 50 to 100 cm below the mineral soil surface. The

argillic horizons are mostly loamy and tend to have more sand

than those in Typic Paleudalfs. Arenic Paleudalfs are rare in

the United States. They occur on plains and high terraces,

mostly in Texas and Oklahoma. Slopes are mostly gentle. Most

of these soils are used as pasture, but some are used as

cropland.

Arenic Plinthic Paleudalfs.—These soils have a sandy or

sandy-skeletal particle-size class throughout a layer extending

from the mineral soil surface to the top of an argillic horizon at

a depth of 50 to 100 cm below the mineral soil surface. They

have 5 percent or more (by volume) plinthite in some

subhorizon within 150 cm of the surface. During rainy seasons

ground water tends to perch above the horizon that contains

plinthite. These soils are rare in the United States. They are

mostly on the coastal plain in Texas. Most of the soils are in

forests.

Fragiaquic Paleudalfs.—These soils are like Typic

Paleudalfs, but they have redox depletions with low chroma

and also aquic conditions at a shallow depth for some time in

normal years. In addition, they have fragic soil properties in 30

percent or more of the volume of a layer 15 cm or more thick

that has its upper boundary within 100 cm of the mineral soil

surface or in 60 percent or more of the volume of a layer 15 cm
Alfisols 227

or more thick anywhere in the soils. These soils are permitted,

but not required, to have a mollic epipedon or an Ap horizon or

other subhorizons of comparable thickness that meet all of the

requirements for a mollic epipedon, except for thickness, after

mixing. These soils are considered intergrades to Fraqiaqualfs.

They are not extensive in the United States.

Fragic Paleudalfs.—These soils are like Typic Paleudalfs,

but they have fragic soil properties in 30 percent or more of the

volume of a layer 15 cm or more thick that has its upper

boundary within 100 cm of the mineral soil surface or in 60

percent or more of the volume of a layer 15 cm or more thick

anywhere in the soils. These soils are considered intergrades to

Fraqiudalfs. They are not extensive in the United States.

Glossaquic Paleudalfs.—These soils are like Typic

Paleudalfs, but they have, in one or more horizons within 75

cm of the mineral soil surface, redox depletions with chroma of

2 or less and also aquic conditions for some time in normal

years (or artificial drainage). In addition, they have a glossic

horizon or a subhorizon within the argillic horizon, commonly

25 cm or more below its upper boundary, that has thick

skeletans of low chroma. These soils are permitted, but not

required, to have a mollic epipedon or an Ap horizon or other

subhorizons of comparable thickness that meet all of the

requirements for a mollic epipedon, except for thickness, after

mixing. These soils are of minor extent in the central part of

the Southern United States.

Glossic Paleudalfs.—These soils have a glossic horizon or

a subhorizon within the argillic horizon, commonly 25 cm or

more below its upper boundary, that has thick skeletans of low

chroma that occupy an appreciable part of the mass of the

subhorizon. These soils are permitted, but not required, to have

a mollic epipedon or an Ap horizon or other subhorizons of

comparable thickness that meet all of the requirements for a

mollic epipedon, except for thickness, after mixing. The soils

are otherwise like Typic Paleudalfs in defined properties and in

accessory properties. They are not extensive in the United

States. They occur mostly in the central part of the Southern

United States. Slopes are very gentle, and most of the soils are

used as cropland.

Grossarenic Paleudalfs.—These soils have a sandy or

sandy-skeletal particle-size class throughout a layer extending

from the mineral soil surface to the top of an argillic horizon at

a depth of 100 cm or more below the mineral soil surface. The

argillic horizons are mostly loamy and tend to have more sand

than those in Typic Paleudalfs. Grossarenic Paleudalfs are of

small extent in the United States. They occur on the coastal

plain in Texas and Florida. Slopes are gentle. The soils are

used mainly as pasture, but some are used as cropland.

Grossarenic Plinthic Paleudalfs.—These soils have a

sandy or sandy-skeletal particle-size class throughout a layer

extending from the mineral soil surface to the top of an argillic

horizon at a depth of 100 cm or more below the mineral soil

surface. The argillic horizon contains some plinthite, and

ground water may be perched above the plinthite during rainy

seasons. These soils are rare in the United States. They are

mostly on the coastal plain in Texas. Slopes are gentle. Most of

these soils are used as forest.

Lamellic Paleudalfs.—These soils are like Typic

Paleudalfs, but they have an argillic horizon that consists

entirely of lamellae or is a combination of two or more

lamellae and one or more subhorizons with a thickness of 7.5

to 20 cm, each layer with an overlying eluvial horizon. In some

of the soils, the argillic horizon consists of one or more

subhorizons that are more than 20 cm thick, each with an

overlying eluvial horizon, and above these horizons there are

either two or more lamellae with a combined thickness of 5 cm

or more or a combination of lamellae and one or more parts of

the argillic horizon 7.5 to 20 cm thick, each with an overlying

eluvial horizon These soils are permitted, but not required, to

have a color value, moist, of 3 or less in the Ap horizon or in

the surface soil to a depth of 18 cm, after mixing. They are not

extensive in the United States.

Mollic Paleudalfs.—These soils are like Typic Paleudalfs,

but they have a mollic epipedon, an Ap horizon that meets all

of the requirements for a mollic epipedon except thickness, or

materials between the soil surface and a depth of 18 cm that

meet these requirements after mixing. Many of the Mollic

Paleudalfs in the United States had grass vegetation or open

forest vegetation before they were cultivated. Mollic Paleudalfs

are considered intergrades between Paleudalfs and Paleudolls.

They are not extensive in the United States. Most of them are

in the center of the country, from Wisconsin to Oklahoma and

the adjacent states. Slopes are mainly gentle, and most of the

soils are used as cropland.

Oxyaquic Paleudalfs.—These soils are like Typic

Paleudalfs, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. These soils are

permitted, but not required, to have a mollic epipedon or an Ap

horizon or other subhorizons of comparable thickness that meet

all of the requirements for a mollic epipedon, except for

thickness, after mixing. The soils are not extensive in the

United States.

Plinthaquic Paleudalfs.—These soils have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). They

also have 5 percent or more (by volume) plinthite in some

subhorizon within 150 cm of the soil surface. These soils are

permitted, but not required, to have a mollic epipedon or an Ap

horizon or other subhorizons of comparable thickness that meet

all of the requirements for a mollic epipedon, except for

thickness, after mixing. They are of small extent, mostly in

Texas, in the United States.

Plinthic Paleudalfs.—These soils have 5 percent or more

(by volume) plinthite in some subhorizon within 150 cm of the

soil surface. During rainy seasons ground water tends to perch

for short periods above the horizons that contain plinthite.
228 Soil Taxonomy

These soils are not extensive in the United States. They occur

mainly along the gulf coast in Texas. Their slopes are mostly

gentle. Many of the soils are used as cropland, but some are in

forests.

Psammentic Paleudalfs.—These soils have an argillic

horizon that has a sandy particle-size class throughout the

upper 75 cm or throughout the entire thickness if it is less than

75 cm thick. The clay content of the argillic horizon

approaches that of a sandy loam in most of the soils.

Psammentic Paleudalfs commonly have an epipedon that has a

texture of loamy fine sand or coarser throughout its thickness

and that may be either more or less than 50 cm thick. The soils

are permitted, but not required, to have a mollic epipedon or an

Ap horizon or other subhorizons of comparable thickness that

meet all of the requirements for a mollic epipedon, except for

thickness, after mixing. These soils are considered intergrades

between Udipsamments and Paleudalfs. They are of small

extent in the United States. Most of them are used as forest, but

some have been cleared of trees and are used as pasture or

cropland.

Rhodic Paleudalfs.—These soils are like Typic Paleudalfs,

but all parts of the argillic horizon have a color value, moist, of

less than 3.5 and a dry color value no more than 1 unit higher

than the moist value and hue in the argillic horizon is 2.5YR

or redder. In addition, the Ap horizon or the upper 18 cm after

mixing normally has a color value, moist, of less than 3.5 and

value, dry, no more than 1 unit higher than the moist value.

These soils are of small extent in the United States. They occur

in the Southeastern States. Their slopes are mainly gentle.

Most of the soils have been cleared of trees and are used as

cropland or pasture.

Vertic Paleudalfs.—These soils are high in content of

expanding clays and have cracks 5 mm or more wide,

slickensides, wedge-shaped aggregates, or a linear extensibility

of 6.0 cm or more between the mineral soil surface and either a

depth of 100 cm or a densic, lithic, or paralithic contact,

whichever is shallower. They are permitted, but not required, to

have redox depletions and to be saturated with water within

100 cm of the mineral soil surface for 7 or more consecutive

days or 20 or more cumulative days in normal years. These

soils also are permitted, but not required, to have a mollic

epipedon or an Ap horizon or other subhorizons of comparable

thickness that meet all of the requirements for a mollic

epipedon, except for thickness, after mixing. The soils are of

small extent in the United States. Most of them are used as

forest or pasture, but some are used as cropland.

Rhodudalfs

Rhodudalfs are dark red Udalfs that have a thinner solum

than that of Paleudalfs. Rhodudalfs do not have a kandic or

natric horizon. They do not have a fragipan with an upper

boundary within 100 cm of the mineral soil surface. They do

not have both a glossic horizon and discrete nodules, 2.5 to 30

cm in diameter, that are enriched with iron and cemented to

indurated. Their parent materials are mostly basic. These soils

are rare in the United States, and definitions of subgroups have

not been developed.

Definition

Rhodudalfs are the Udalfs that:

1. Have, in all subhorizons in the upper 100 cm of the argillic

horizon or throughout the entire argillic horizon if less than 100

cm thick, more than 50 percent colors that have all of the

following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value;

2. Do not have a kandic or natric horizon;

3. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

4. Do not have both a glossic horizon and, in the argillic

horizon, discrete nodules, 2.5 to about 30 cm in diameter, that

are enriched with iron, are extremely weakly cemented to

indurated, and that have exteriors with either redder hue

and/or higher chroma than the interiors; and

5. Have either a densic, lithic, or paralithic contact within

150 cm of the soil surface; or

a. Within 150 cm of the mineral soil surface, have both:

(1) A clay decrease with increasing depth of 20 percent

or more (relative) from the maximum clay content; and

(2) Less than 5 percent (by volume) skeletans on faces

of peds in the layer that has a 20 percent lower clay

content or, below that layer, a clay increase of less than 3

percent (absolute) in the fine-earth fraction.

Key to Subgroups

JEHA. All Rhodudalfs (provisionally).

Typic Rhodudalfs

Ustalfs

Ustalfs are the Alfisols of subhumid to semiarid regions.

They have an ustic moisture regime and a frigid, mesic,

isomesic, or warmer temperature regime. They do not have,

near the soil surface, both redoximorphic features with low

chroma and aquic conditions (other than anthraquic

conditions) for some time in normal years. Moisture moves

through most of these soils to deeper layers only in occasional

years. If there are carbonates in the parent materials or in the

dust that settles on the surface, the soils tend to have a Bk or

calcic horizon below or in the argillic or kandic horizon. The
Alfisols 229

dry season or seasons are pronounced enough that trees are

either deciduous or xerophytic. Many of these soils have or

have had a savanna vegetation, and some were grasslands.

Most of the soils are used as cropland or for grazing. Some are

used as irrigated cropland. Sorghum, wheat, and cotton are the

most common crops. Droughts are common.

Ustalfs tend to form a belt between the Aridisols of arid

regions and the Udalfs, Ultisols, Oxisols, and Inceptisols of

humid regions. The temperature regimes of Ustalfs are mostly

thermic, isothermic, or warmer. These soils are extensive in the

world. In the United States, their area is moderate, but the soils

are extensive in the southern part of the Great Plains.

Ustalfs may be in areas of erosional surfaces or deposits of

late-Wisconsinan age, but a great many, and characteristically

those of warm regions, are on old surfaces. In the Ustalfs on

old surfaces, the minerals have been strongly weathered,

possibly in an environment more humid than the present one.

At least, the clays in many of these older soils are kaolinitic.

The base saturation in them at present probably reflects

additions of bases in dust and rain.

Definition

Ustalfs are the Alfisols that:

1. Have an ustic moisture regime;

2. Have chroma too high for Aqualfs or do not have aquic

conditions within 50 cm of the mineral soil surface for some

time in normal years; and

3. Have a frigid, mesic, isomesic, or warmer temperature

regime.

Key to Great Groups

JCA. Ustalfs that have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Durustalfs, p. 230

JCB. Other Ustalfs that have one or more horizons within

150 cm of the mineral soil surface in which plinthite either

forms a continuous phase or constitutes one-half or more of the

volume.

Plinthustalfs, p. 252

JCC. Other Ustalfs that have a natric horizon.

Natrustalfs, p. 241

JCD. Other Ustalfs that:

1. Have a kandic horizon; and

2. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

3. Within 150 cm of the mineral soil surface, either:

a. Do not have a clay decrease with increasing depth of

20 percent or more (relative) from the maximum clay

content [Clay is measured noncarbonate clay or based on

the following formula: Clay % = 2.5(% water retained at

1500 kPa tension - % organic carbon), whichever value is

greater, but no more than 100]; or

b. Have 5 percent or more (by volume) skeletans on

faces of peds in the layer that has a 20 percent lower clay

content and, below that layer, a clay increase of 3 percent

or more (absolute) in the fine-earth fraction.

Kandiustalfs, p. 237

JCE. Other Ustalfs that have a kandic horizon.

Kanhaplustalfs, p. 240

JCF. Other Ustalfs that have one or more of the following:

1. A petrocalcic horizon that has its upper boundary

within 150 cm of the mineral soil surface; or

2. No densic, lithic, or paralithic contact within 150 cm of

the mineral soil surface and an argillic horizon that has

both:

a. Within 150 cm of the mineral soil surface, either:

(1) With increasing depth, no clay decrease of 20

percent or more (relative) from the maximum clay

content [Clay is measured noncarbonate clay or based

on the following formula: Clay % = 2.5(% water

retained at 1500 kPa tension - % organic carbon),

whichever value is greater, but no more than 100]; or

(2) 5 percent or more (by volume) skeletans on faces

of peds in the layer that has a 20 percent lower clay

content and, below that layer, a clay increase of 3

percent or more (absolute) in the fine-earth fraction;

and

b. In the lower one-half of the argillic horizon, one or

more subhorizons with either or both:

(1) Hue of 7.5YR or redder and chroma of 5 or more

in 50 percent or more of the matrix; or

(2) Common or many coarse redox concentrations

with hue of 7.5YR or redder or chroma of 6 or more,

or both; or

3. No densic, lithic, or paralithic contact within 50 cm of

the mineral soil surface and an argillic horizon that has

both:

a. A clayey or clayey-skeletal particle-size class

throughout one or more subhorizons in its upper part;

and

b. At its upper boundary, a clay increase (in the fineearth fraction) of either 20 percent or more (absolute)
230 Soil Taxonomy

within a vertical distance of 7.5 cm or of 15 percent or more

(absolute) within a vertical distance of 2.5 cm.

Paleustalfs, p. 246

JCG. Other Ustalfs that have, in all subhorizons in the upper

100 cm of the argillic horizon or throughout the entire argillic

horizon if less than 100 cm thick, more than 50 percent colors

that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodustalfs, p. 252

JCH. Other Ustalfs.

Haplustalfs, p. 230

Durustalfs

Durustalfs are the Ustalfs that have a duripan that has its

upper boundary within 100 cm of the mineral soil surface.

They are not known to occur in the United States, but the great

group has been provided for use in other countries. Subgroups

have not been developed.

Key to Subgroups

JCAA. All Durustalfs (provisionally).

Typic Durustalfs

Haplustalfs

Haplustalfs are the Ustalfs that have an argillic horizon. They

do not have a kandic or natric horizon, do not have a duripan

that has its upper boundary within 100 cm of the surface, do not

have a petrocalcic horizon within 150 cm of the surface, and do

not have much plinthite. Many of these soils are relatively thin,

are reddish to yellowish brown, or have a significant clay

decrease within 150 cm of the surface. They are not dark red or

dusky red throughout the argillic horizon. The argillic horizon

does not have both a clayey or clayey-skeletal particle-size class

in some subhorizon in its upper part and an abrupt upper

boundary.

Haplustalfs are commonly in areas of relatively recent

erosional surfaces or deposits, most of them late Pleistocene in

age. Some of the soils have a monsoon climate. Others have

two more or less marked dry seasons during the year.

Definition

Haplustalfs are the Ustalfs that:

1. Have an argillic horizon but do not have a kandic or natric

horizon;

2. Do not have a duripan that has an upper boundary within

100 cm of the mineral soil surface;

3. Do not have a petrocalcic horizon that has an upper

boundary within 150 cm of the mineral soil surface;

4. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix within any subhorizon

of the argillic horizon within 125 cm of the mineral soil

surface;

5. Have an argillic horizon that in some part has hue no

redder than 5YR or value, moist, of 4 or more or value, dry,

more than 1 unit higher than the moist value;

6. Have a densic, lithic, or paralithic contact at a depth of less

than 150 cm below the mineral soil surface, or the argillic

horizon has either:

a. Within 150 cm of the mineral soil surface: either

(1) A clay decrease with increasing depth of 20 percent

or more (relative) from the maximum clay content; or

(2) Less than 5 percent (by volume) skeletans on faces

of peds in the layer that has a 20 percent lower clay

content or, below that layer, no clay increase of as much

as 3 percent (absolute) in the fine-earth fraction; or

b. All of the following:

(1) In 50 percent or more of the matrix of all

subhorizons in its lower one-half, hue of 10YR or

yellower or chroma of 4 or less; and

(2) In less than one-half of the total thickness,

subhorizons that have, in 50 percent or more of the

matrix, hue of 7.5YR or redder, a color value, moist, of 3

or less, and a color value, dry, of 4 or less; and

(3) In the matrix of all subhorizons in its lower onehalf, few or no coarse redox concentrations with hue of

7.5YR or redder or chroma of 6 or more, or both;

7. Have a densic, lithic, or paralithic contact at a depth of less

than 50 cm below the mineral soil surface, or the argillic

horizon either:

a. Does not have a clayey or clayey-skeletal particle-size

class in some subhorizon in its upper part; or

b. At its upper boundary, has a clay increase, in the fineearth fraction, of less than 15 percent (absolute) within a

vertical distance of 2.5 cm, and less than 20 percent

(absolute) within a vertical distance of 7.5 cm.

Key to Subgroups

JCHA. Haplustalfs that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplustalfs
Alfisols 231

JCHB. Other Haplustalfs that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage).

Aquertic Haplustalfs

JCHC. Other Haplustalfs that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. Saturation with water in one or more layers within 100

cm of the mineral soil surface in normal years for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Oxyaquic Vertic Haplustalfs

JCHD. Other Haplustalfs that have both of the following:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days per

year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC;

2. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower.

Torrertic Haplustalfs

JCHE. Other Haplustalfs that have both:

1. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth

of 50 cm below the soil surface is higher than 8 oC; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a
232 Soil Taxonomy

densic, lithic, or paralithic contact, whichever is

shallower.

Udertic Haplustalfs

JCHF. Other Haplustalfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haplustalfs

JCHG. Other Haplustalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 to 100 cm.

Aquic Arenic Haplustalfs

JCHH. Other Haplustalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. An argillic horizon that has a base saturation (by sum

of cations) of less than 75 percent throughout.

Aquultic Haplustalfs

JCHI. Other Haplustalfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Haplustalfs

JCHJ. Other Haplustalfs that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplustalfs

JCHK. Other Haplustalfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm of

the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Haplustalfs

JCHL. Other Haplustalfs that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Haplustalfs

JCHM. Other Haplustalfs that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Haplustalfs

JCHN. Other Haplustalfs that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 cm or more; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or
Alfisols 233

b. A mesic or thermic soil temperature regime

and a moisture control section that in normal years

is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature

at a depth of 50 cm below the soil surface is higher

than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Arenic Aridic Haplustalfs

JCHO. Other Haplustalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more.

Arenic Haplustalfs

JCHP. Other Haplustalfs that have both:

1. A calcic horizon with its upper boundary within 100 cm

of the mineral soil surface; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 o

C; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 o

C.

Calcidic Haplustalfs

JCHQ. Other Haplustalfs that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Haplustalfs

JCHR. Other Haplustalfs that have a CEC of less than 24

cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more

either of the argillic horizon if less than 100 cm thick or of its

upper 100 cm.

Kanhaplic Haplustalfs

JCHS. Other Haplustalfs that have:

1. An argillic, kandic, or natric horizon that is 35 cm or

less thick; and

2. No densic, lithic, or paralithic contact within 100 cm of

the mineral soil surface.

Inceptic Haplustalfs

JCHT. Other Haplustalfs that have both:

1. A calcic horizon with its upper boundary within 100 cm

of the mineral soil surface; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in some or all parts for

less than 105 cumulative days per year when the
234 Soil Taxonomy

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth

of 50 cm below the soil surface is higher than 8 oC.

Calcic Udic Haplustalfs

JCHU. Other Haplustalfs that have an argillic horizon with a

base saturation (by sum of cations) of less than 75 percent

throughout.

Ultic Haplustalfs

JCHV. Other Haplustalfs that have a calcic horizon with its

upper boundary within 100 cm of the mineral soil surface.

Calcic Haplustalfs

JCHW. Other Haplustalfs that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in some or all parts for

less than 105 cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for four-tenths or less of the cumulative days per year

when the temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Udic Haplustalfs

JCHX. Other Haplustalfs.

Typic Haplustalfs

Definition of Typic Haplustalfs

Typic Haplustalfs are the Haplustalfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30 or

more cumulative days in normal years;

3. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

4. Do not have a lithic contact within 50 cm of the soil

surface;

5. Have a CEC of 24 or more cmol(+)/kg clay (by 1N

NH4

OAc pH 7) in the major part of the argillic horizon or in

the major part of its upper 100 cm if the argillic horizon is

more than 100 cm thick;

6. Do not have a sandy particle-size class throughout the

upper 75 cm of the argillic horizon or throughout the entire

argillic horizon if it is less than 75 cm thick;

7. When neither irrigated nor fallowed to store moisture:

a. Have a frigid soil temperature regime and both are dry

in some or all parts of the soil moisture control section for

105 or more cumulative days and are dry in all parts of the

soil moisture control section for less than four-tenths of the

cumulative days per year in normal years and during a

period when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

b. Have a mesic or thermic soil temperature regime and

both are dry for more than four-tenths of the cumulative

days per year in some part of the moisture control section

and are dry for less than six-tenths of the time in some part

of the moisture control section (not necessarily the same

part) in normal years and during a period when the soil

temperature at a depth of 50 cm exceeds 5 oC; or

c. Have a hyperthermic, isomesic, or warmer soil

temperature regime and:

(1) Are dry in some or all parts of the moisture control

section for 120 or more cumulative days per year; and

(2) Are moist in some or all parts of the moisture

control section for 90 or more consecutive days per year

both in normal years and during a period when the soil

temperature at a depth of 50 cm exceeds 8 oC; and

(3) Are moist in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC;

8. Have an argillic horizon that has a base saturation (by sum

of cations) of 75 percent or more in some part;

9. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick
Alfisols 235

that has its upper boundary within 125 cm of the mineral soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

10. Do not have a calcic horizon with its upper boundary

within 100 cm of the mineral soil surface;

11. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon;

12. Have an argillic horizon more than 35 cm thick; and

13. Do not have, throughout one or more horizons with a

total thickness of 18 cm or more within 75 cm of the mineral

soil surface, one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Haplustalfs.—The central concept or Typic subgroup

of Haplustalfs is fixed on freely drained soils that are

moderately deep or deep to hard rock; that have an argillic

horizon that has a loamy or clayey particle-size class, some 2:1

lattice clay, and high base saturation; that do not have deep,

wide cracks in normal years; that do not have a calcic horizon

at a moderate depth; and that are moist for an appreciable part

of a growing season.

Soils that have redox depletions with low chroma near the

surface in one or more horizons that also have aquic conditions

for some time in normal years (or artificial drainage) are

excluded from Typic Haplustalfs because these properties are

shared with Aqualfs. Soils that are saturated with water in one

or more layers within 100 cm of the mineral soil surface for 20

or more consecutive days or 30 or more cumulative days in

normal years are considered atypical and define the Oxyaquic

subgroup. A thick layer, starting at the mineral soil surface, of

sand or loamy sand is not considered normal and defines

Arenic subgroups, a convention used elsewhere in this

taxonomy. A shallow lithic contact defines the Lithic subgroup,

another convention used throughout this taxonomy. Clays that

have low activity suggest strong weathering and are used to

define the Kanhaplic subgroup. An argillic horizon that has a

texture of loamy fine sand or coarser is not considered normal

and defines the Psammentic subgroup. An argillic horizon that

is composed entirely of thin lamellae defines the Lamellic

subgroup.

A soil moisture regime that approaches the udic regime is

considered more moist than normal and defines the Udic

subgroup. A moderately low base saturation throughout the

argillic horizon is considered atypical and defines the Ultic

subgroup.

Cracks and slickensides or wedge-shaped aggregates are

properties shared with Vertisols and define Vertic subgroups. A

soil moisture regime that approaches the aridic regime is

considered drier than normal and defines Aridic subgroups.

Typic Haplustalfs are moderately extensive in the United

States. They are used mainly for grazing or as cropland.

Aquertic Haplustalfs.—These soils have a clayey texture

and have expanding clay in the argillic horizon. They also

have redox depletions with low chroma within 75 cm of the

mineral soil surface that are caused by periods of wetness.

These soils are in nearly level areas and may or may not have

calcic horizons or relatively low base saturation. They are rare

in the United States.

Aquic Arenic Haplustalfs.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). In

addition, they have a layer, starting at the mineral soil surface,

that is between 50 and 100 cm thick and has a texture of loamy

fine sand or coarser. The presence or absence of a calcic

horizon or of relatively low base saturation is not definitive of

this subgroup. These soils are on gentle slopes and are rare in

the United States.

Aquic Haplustalfs.—These soils are like Typic Haplustalfs,

but they have redox depletions with low chroma within 75 cm

of the mineral soil surface that are caused by periods of

wetness. These soils are in nearly level areas and may or may

not have calcic horizons or relatively low base saturation. They

are locally important in the central part of the Southern United

States. They are used as cropland or for grazing.

Aquultic Haplustalfs.—These soils are like Typic
236 Soil Taxonomy

Haplustalfs, but they have redox depletions with low chroma

within 75 cm of the mineral soil surface that are caused by

periods of wetness. These soils are in nearly level areas and

have relatively low base saturation. They are rare in the United

States.

Arenic Aridic Haplustalfs.—These soils are like Typic

Haplustalfs, but they have a layer, 50 cm or more thick,

starting at the mineral soil surface, that has a texture of loamy

fine sand or coarser throughout its thickness. In addition, they

are drier than the Typic Haplustalfs and, because they have a

thick epipedon with a sandy or sandy-skeletal particle-size

class throughout, they are permitted, but not required, to have a

calcic horizon within the depths required for the Typic

subgroup. Arenic Aridic Haplustalfs are rare in the United

States.

Arenic Haplustalfs.—These soils are like Typic

Haplustalfs, but they have a layer, 50 cm or more thick,

starting at the mineral soil surface, that has a texture of loamy

fine sand or coarser throughout its thickness. There is no

restriction on base saturation in the argillic horizon, except for

the limit imposed by the definition of Alfisols. A calcic horizon

may be present at any depth but is not required. These soils are

of small extent but are locally important in the southern part of

the Great Plains in the United States. Their slopes are gentle.

Most of the soils are used as cropland.

Aridic Haplustalfs.—These soils are drier than Typic

Haplustalfs. They are intergrades between Haplargids and

Haplustalfs. They are extensive in the southern part of the

Great Plains of the United States. Slopes generally are gentle or

moderate. Many of these soils are used for grazing, and others

are used as cropland. Some of the cropland is irrigated, and

some is used for drought-tolerant crops.

Calcic Haplustalfs.—These soils are like Typic Haplustalfs,

but they have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface. They are rare in the

United States.

Calcic Udic Haplustalfs.—These soils are like Typic

Haplustalfs, but they are dry in some part of the moisture

control section for less than four-tenths of the cumulative days

when the soil temperature at a depth of 50 cm exceeds 5 o

C if

the soil temperature regime is mesic or thermic and are dry in

some or all parts of the moisture control section for less than

90 days during a period when the soil temperature at a depth of

50 cm exceeds 8 oC if the soil temperature regime is

hyperthermic, isomesic, or warmer. These soils also have a

calcic horizon that has its upper boundary within 100 cm of the

mineral soil surface. They are rare in the United States.

Calcidic Haplustalfs.—These soils are drier than Typic

Haplustalfs. They have a calcic horizon that has its upper

boundary within 100 cm of the mineral soil surface. These soils

are intergrades between Calcids or Calciargids and Haplustalfs.

They are rare in the United States.

Inceptic Haplustalfs.—These soils have an argillic horizon 35

cm or less thick and have no densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface. In addition,

the base saturation of all parts of the argillic horizon is

permitted, but not required, to be lower than that in Typic

Haplustalfs. A calcic horizon also is permitted. These soils are

considered intergrades to Ustepts. They are rare in the United

States.

Kanhaplic Haplustalfs.—These soils are like Typic

Haplustalfs, but they have a cation-exchange capacity (by 1N

NH4

OAc pH 7) of less than 24 cmol(+)/kg clay. They are

permitted, but not required, to have a base saturation (by sum

of cations) that is less than 75 percent in all parts of the argillic

horizon and to have a calcic horizon or soft, powdery

secondary lime at any depth. The upper boundary of the argillic

horizon in these soils generally is gradual. Kanhaplic

Haplustalfs are intergrades between Haplustalfs and Ustox.

They are not known to occur on the United States mainland or

in Puerto Rico, but the subgroup is provided for use in other

countries.

Lamellic Haplustalfs.—These soils are like Typic

Haplustalfs in defined properties, but they have an argillic

horizon that consists of lamellae or partially of lamellae. Most

of these soils have a sandy particle-size class, and the upper

boundary of the argillic horizon or the upper lamella may be

below a depth of 60 cm. The upper several lamellae are

commonly broken or discontinuous horizontally. These soils

are not extensive in the United States.

Lithic Haplustalfs.—These soils have a lithic contact

within 50 cm of the soil surface. They are permitted to have

any of the other properties allowed in Haplustalfs. They are

common in the southwestern part of the United States. Their

slopes are moderate or strong. Most of the soils are used for

grazing.

Oxyaquic Haplustalfs.—These soils are like Typic

Haplustalfs, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. In addition, these

soils are permitted, but not required, to have a base saturation

(by sum of cations) that is less than 75 percent. They are

considered intergrades to Aqualfs. These soils are rare in the

United States.

Oxyaquic Vertic Haplustalfs.—These soils have a clayey

texture and have expanding clay in the argillic horizon. They

also have deep, wide cracks in normal years. In addition, they

are saturated with water within 100 cm of the mineral soil

surface for 20 or more consecutive days or 30 or more

cumulative days in normal years. These soils are not extensive

in the United States.

Psammentic Haplustalfs.—These soils have a sandy

particle-size class throughout the upper 75 cm of the argillic

horizon or throughout the entire argillic horizon if it is less

than 75 cm thick. In addition, the base saturation of the argillic

horizon is permitted, but not required, to be lower than that in

Typic Haplustalfs. A calcic horizon is permitted. These soils

are considered intergrades to Ustipsamments. They are of small
Alfisols 237

extent in the United States. Their slopes are mostly gentle. Most

of these soils are grazed, but some are used for drought-tolerant

crops.

Torrertic Haplustalfs.—These soils are drier than Typic

Haplustalfs. They also have a clayey texture and have

expanding clay in the argillic horizon. They have deep, wide

cracks in normal years. They are not extensive in the United

States.

Udertic Haplustalfs.—These soils are like Typic

Haplustalfs, but they have a clayey texture and have expanding

clay in the argillic horizon. They are dry in some part of the

moisture control section for less than four-tenths of the

cumulative days when the soil temperature at a depth of 50 cm

exceeds 5 o

C if the soil temperature regime is mesic or thermic

and are dry in some or all parts of the moisture control section

for less than 90 days during a period when the soil temperature

at a depth of 50 cm exceeds 8 oC if the soil temperature regime

is hyperthermic, isomesic, or warmer. These soils are

intergrades between Uderts and Haplustalfs. They are of small

extent but are locally important in Texas and Oklahoma in the

United States. Their slopes are mostly gentle. Most of these

soils are used as cropland.

Udic Haplustalfs.—These soils are like Typic Haplustalfs,

but they are dry in some part of the moisture control section for

less than four-tenths of the cumulative days when the soil

temperature at a depth of 50 cm exceeds 5 oC if the soil

temperature regime is mesic or thermic and are dry in some or

all parts of the moisture control section for less than 90 days

during a period when the soil temperature at a depth of 50 cm

exceeds 8 oC if the soil temperature regime is hyperthermic,

isomesic, or warmer. These soils are intergrades between

Hapludalfs and Haplustalfs. They are extensive locally on the

Great Plains in the United States. Their slopes range from

gentle to strong. Where slopes are suitable, most of these soils

are used as cropland.

Ultic Haplustalfs.—These soils are like Typic Haplustalfs,

but they have a base saturation (by sum of cations) that is less

than 75 percent in all parts of the argillic horizon. These soils

are intergrades between Hapludults and Haplustalfs. They are

moderately extensive in California and Oklahoma in the

United States and are extensive in some parts of the world.

Their slopes are gentle to strong in the United States. Where

slopes are suitable, most of these soils are used as cropland.

Vertic Haplustalfs.—These soils have a clayey texture and

have expanding clay in the argillic horizon. They also have

deep, wide cracks in normal years. They are not extensive in

the United States. Their slopes are gentle or moderate. Most of

these soils are used for grazing.

Vitrandic Haplustalfs.—These are the Haplustalfs that

have significant amounts of volcanic ash, pumice, or glass in

one or more layers 18 cm or more thick within 75 cm of the

mineral soil surface. These soils do not have a high shrinkswell potential and are not saturated within 100 cm of the

mineral soil surface for extended periods. They occur in New

Mexico and are used as rangeland or woodland.

Kandiustalfs

Kandiustalfs are the Ustalfs with thick argillic horizons that

have relatively high base saturation but a low cation-exchange

capacity. Many of these soils occur on the older surfaces in

warm, humid or semihumid areas. Kandiustalfs occur in Africa

and South America. They are commonly used as rangeland or

cropland.

Definition

Kandiustalfs are the Ustalfs that:

1. Have a kandic horizon;

2. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface and do not

have a duripan within 100 cm of the mineral soil surface;

3. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within 150 cm of the soil surface, or the layer in which

the clay percentage decreases by more than 20 percent has at

least 5 percent of the volume consisting of skeletans on faces of

peds and there is at least a 3 percent (absolute) increase in

content of clay below this layer;

4. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the mineral soil surface; and

5. Do not have a natric horizon.

Key to Subgroups

JCDA. Kandiustalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a kandic horizon at a depth of

100 cm or more.

Grossarenic Kandiustalfs

JCDB. Other Kandiustalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 to 100 cm.

Aquic Arenic Kandiustalfs

JCDC. Other Kandiustalfs that have 5 percent or more (by
238 Soil Taxonomy

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kandiustalfs

JCDD. Other Kandiustalfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Kandiustalfs

JCDE. Other Kandiustalfs that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 to 100 cm; and

2. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Arenic Aridic Kandiustalfs

JCDF. Other Kandiustalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a kandic horizon at a depth of

50 to 100 cm.

Arenic Kandiustalfs

JCDG. Other Kandiustalfs that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 o

C;

and

b. Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Kandiustalfs

JCDH. Other Kandiustalfs that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for 135 cumulative days or less per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Udic Kandiustalfs

JCDI. Other Kandiustalfs that have, in all subhorizons in the

upper 100 cm of the kandic horizon or throughout the entire

kandic horizon if less than 100 cm thick, more than 50 percent

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodic Kandiustalfs

JCDJ. Other Kandiustalfs.

Typic Kandiustalfs

Definition of Typic Kandiustalfs

Typic Kandiustalfs are the Kandiustalfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

3. Have, in all horizons within 150 cm of the mineral soil

surface, less than 5 percent plinthite, by volume;

4. When neither irrigated nor fallowed to store moisture:

a. Have a mesic or thermic soil temperature regime and

both are dry in some part less than six-tenths of the time
Alfisols 239

and are dry for more than 135 cumulative days per year in

some part of the moisture control section (not necessarily the

same part) in normal years and during a period when the soil

temperature at a depth of 50 cm exceeds 5 o

C; or

b. Have a hyperthermic, isomesic, or warmer soil

temperature regime and:

(1) Are dry in some or all parts of the moisture control

section for 120 or more cumulative days per year; and

(2) Are moist in some or all parts of the moisture

control section for 90 or more consecutive days per year

both in normal years and during a period when the soil

temperature at a depth of 50 cm exceeds 8 oC; and

(3) Are moist in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC;

5. Do not have, in all subhorizons in the upper 100 cm of the

kandic horizon or throughout the entire kandic horizon if less

than 100 cm thick, more than 50 percent colors that have all of

the following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value.

Description of Subgroups

Typic Kandiustalfs.—The central concept or Typic

subgroup of Kandiustalfs is fixed on freely drained soils that

are moderately deep or deep to hard rock, that have an argillic

horizon that has a loamy or clayey particle-size class and high

base saturation, and that are moist for an appreciable part of a

growing season.

Soils that have redox depletions with low chroma near the

surface in one or more horizons that also have aquic conditions

for some time in normal years (or artificial drainage) are

excluded from Typic Kandiustalfs because these properties are

shared with Aqualfs. A thick layer, starting at the mineral soil

surface, of sand or loamy sand is not considered normal and

defines Arenic and Grossarenic subgroups, a convention used

elsewhere in this taxonomy.

A soil moisture regime that approaches the udic regime is

considered more moist than normal and defines the Udic

subgroup.

A soil moisture regime that approaches the aridic regime is

considered drier than normal and defines Aridic subgroups.

Typic Kandiustalfs are not known to occur in the United

States. They are defined for use in other parts of the world.

Aquic Arenic Kandiustalfs.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). In addition,

they have a layer, starting at the mineral soil surface, that is 50 to

100 cm thick and has a sandy or sandy-skeletal particle-size

class throughout. These soils are on gentle slopes. They are not

known to occur in the United States. They are defined for use in

other parts of the world.

Aquic Kandiustalfs.—These soils are like Typic

Kandiustalfs, but they have redox depletions with low chroma

within 75 cm of the mineral soil surface that are caused by

periods of wetness. The soils are in nearly level areas. They are

not known to occur in the United States. They are defined for

use in other parts of the world.

Arenic Aridic Kandiustalfs.—These soils are like Typic

Kandiustalfs, but they have a layer, 50 to 100 cm thick, starting

at the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class throughout its thickness. In addition, they

are drier than the Typic Kandiustalfs. Arenic Aridic

Kandiustalfs are on gentle slopes. They are not known to occur

in the United States. They are defined for use in other parts of

the world.

Arenic Kandiustalfs.—These soils are like Typic

Kandiustalfs, but they have a layer, 50 to 100 cm thick, starting

at the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class throughout its thickness. These soils are not

known to occur in the United States. They are defined for use

in other parts of the world.

Aridic Kandiustalfs.—These soils are drier than Typic

Kandiustalfs. They are intergrades between Argids and

Kandiustalfs. They are not known to occur in the United

States. They are defined for use in other parts of the world.

Grossarenic Kandiustalfs.—These soils are like Typic

Kandiustalfs, but they have a layer, 100 cm or more thick,

starting at the mineral soil surface, that has a sandy or sandyskeletal particle-size class throughout its thickness. These soils

are not known to occur in the United States. They are defined

for use in other parts of the world.

Plinthic Kandiustalfs.—These soils are like Typic

Kandiustalfs, but they have 5 percent or more (by volume)

plinthite in one or more horizons within 150 cm of the mineral

soil surface. These soils are not known to occur in the United

States. They are defined for use in other parts of the world.

Rhodic Kandiustalfs.—These soils are like Typic

Kandiustalfs, but they have, in all subhorizons in the upper 100

cm of the kandic horizon or throughout the entire kandic

horizon if less than 100 cm thick, more than 50 percent colors

that have hue of 2.5YR or redder, value, moist, of 3 or less, and

dry value no more than 1 unit higher than the moist value.

These soils are not known to occur in the United States. They

are defined for use in other parts of the world.

Udic Kandiustalfs.—These soils are like Typic

Kandiustalfs, but they are dry in some part of the moisture

control section for less than four-tenths of the cumulative days

when the soil temperature at a depth of 50 cm exceeds 5 o

C if

the soil temperature regime is mesic or thermic and are dry in
240 Soil Taxonomy

some or all parts of the moisture control section for less than 90

days during a period when the soil temperature at a depth of 50

cm exceeds 8 o

C if the soil temperature regime is hyperthermic,

isomesic, or warmer. These soils are intergrades between

Kandiudalfs and Kandiustalfs. They are not known to occur in

the United States. They are defined for use in other parts of the

world.

Kanhaplustalfs

Kanhaplustalfs are the Ustalfs that have relatively high base

saturation but have a low cation-exchange capacity. These soils

do not have the thick argillic horizon characteristic of the

Kandiustalfs. Kanhaplustalfs commonly occur on the older

surfaces in warm, humid or semihumid areas. They are used

for livestock grazing or crop production.

Definition

Kanhaplustalfs are the Ustalfs that:

1. Have a kandic horizon;

2. Are more than 150 cm deep and have a clay distribution

in which the content of clay decreases from its maximum

amount by 20 percent or more within 150 cm of the soil

surface, and the layer in which the percentage of clay is less

than the maximum has less than 5 percent of the volume

consisting of skeletans on faces of peds or there is less than

a 3 percent (absolute) increase in content of clay below this

layer;

3. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the soil surface;

4. Do not have a natric horizon; and

5. Do not have a duripan within 100 cm of the mineral soil

surface.

Key to Subgroups

JCEA. Kanhaplustalfs that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Kanhaplustalfs

JCEB. Other Kanhaplustalfs that have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Kanhaplustalfs

JCEC. Other Kanhaplustalfs that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Kanhaplustalfs

JCED. Other Kanhaplustalfs that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for 135 cumulative days or less per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Udic Kanhaplustalfs

JCEE. Other Kanhaplustalfs that have, in all subhorizons in

the upper 100 cm of the kandic horizon or throughout the

entire kandic horizon if less than 100 cm thick, more than 50

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodic Kanhaplustalfs

JCEF. Other Kanhaplustalfs.

Typic Kanhaplustalfs

Definition of Typic Kanhaplustalfs

Typic Kanhaplustalfs are the Kanhaplustalfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Do not have a lithic contact within 50 cm of the soil

surface;

3. When neither irrigated nor fallowed to store moisture:
Alfisols 241

a. Have a mesic or thermic soil temperature regime and, in

one-half or more of the years, both are dry less than sixtenths of the time and are dry for more than 135 cumulative

days in some part of the moisture control section (not

necessarily the same part) during a period when the soil

temperature at a depth of 50 cm exceeds 5 o

C; or

b. Have a hyperthermic, isomesic, or warmer soil

temperature regime and:

(1) Are dry in some or all parts of the moisture control

section for 120 or more cumulative days per year; and

(2) Are moist in some or all parts of the moisture

control section for 90 or more consecutive days per year

both in normal years and during a period when the soil

temperature at a depth of 50 cm exceeds 8 oC; and

(3) Are moist in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; and

4. Have, in all subhorizons in the upper 100 cm of the kandic

horizon or throughout the entire kandic horizon if less than

100 cm thick, more than 50 percent colors that have all of the

following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value.

Description of Subgroups

Typic Kanhaplustalfs.—The central concept or Typic

subgroup of Kanhaplustalfs is fixed on freely drained soils that

are moderately deep or deep to hard rock and that are moist for

an appreciable part of a growing season.

Soils that have redox depletions with low chroma near the

surface in one or more horizons that also have aquic conditions

for some time in normal years (or artificial drainage) are

excluded from Typic Kanhaplustalfs because these properties

are shared with Aqualfs. A shallow lithic contact defines the

Lithic subgroup, a convention used throughout this taxonomy.

A soil moisture regime that approaches the udic regime is

considered more moist than normal and defines the Udic

subgroup. A soil moisture regime that approaches the aridic

regime is considered drier than normal and defines the Aridic

subgroup.

Typic Kanhaplustalfs are not known to occur in the United

States. They are defined for use in other parts of the world.

Aquic Kanhaplustalfs.—These soils are like Typic

Kanhaplustalfs, but they have redox depletions with low

chroma within 75 cm of the mineral soil surface that are

caused by periods of wetness. The soils are in nearly level areas

and may or may not have calcic horizons or relatively low base

saturation. Aquic Kanhaplustalfs are not known to occur in the

United States. They are defined for use in other parts of the

world.

Aridic Kanhaplustalfs.—These soils are drier than Typic

Kanhaplustalfs. They are intergrades between Haplargids and

Kanhaplustalfs. Aridic Kanhaplustalfs are not known to occur

in the United States. They are defined for use in other parts of

the world.

Lithic Kanhaplustalfs.—These soils have a lithic contact

within 50 cm of the soil surface. They are permitted to have

any of the other properties allowed in Kanhaplustalfs. They are

not known to occur in the United States. They are defined for

use in other parts of the world.

Rhodic Kanhaplustalfs.—These soils are like Typic

Kanhaplustalfs, but all of the kandic horizon or the upper 100

cm of the kandic horizon has a color with hue of 2.5YR or

redder, value, moist, of 3 or less, and a dry color value no more

than 1 unit higher than the moist value. Rhodic Kanhaplustalfs

are not known to occur in the United States. They are defined

for use in other parts of the world.

Udic Kanhaplustalfs.—These soils are like Typic

Kanhaplustalfs, but they are dry in some part of the moisture

control section for 135 or fewer cumulative days per year when

the soil temperature at a depth of 50 cm exceeds 5 o

C if the soil

temperature regime is mesic or thermic and are dry in some or

all parts of the moisture control section for less than 120

cumulative days per year during a period when the soil

temperature at a depth of 50 cm exceeds 8 oC if the soil

temperature regime is hyperthermic, isomesic, or warmer.

These soils are intergrades between Kanhapludalfs and

Kanhaplustalfs. Udic Kanhaplustalfs are not known to occur in

the United States. They are defined for use in other parts of the

world.

Natrustalfs

Natrustalfs are the Ustalfs that have a natric horizon. They do

not have a duripan within 100 cm of the mineral soil surface, nor

do they have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the soil surface. The epipedon is normally 10 to

20 cm thick. The natric horizon generally is underlain by a Bk or

calcic horizon at a depth between about 25 and 40 cm.

Natrustalfs were considered Solonetz soils, Soloth soils, and

transitional forms in the 1938 classification. Except for a few

parts of the Great Plains and mountain basins, they are not

extensive in the United States.

Definition

Natrustalfs are the Ustalfs that:

1. Have a natric horizon;

2. Do not have a duripan within 100 cm of the mineral soil

surface;
242 Soil Taxonomy

3. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the soil surface.

Key to Subgroups

JCCA. Natrustalfs that have a salic horizon that has its upper

boundary within 75 cm of the mineral soil surface.

Salidic Natrustalfs

JCCB. Other Natrustalfs that have all of the following:

1. Visible crystals of gypsum or other salts more soluble

than gypsum, or both, within 40 cm of the soil surface; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC; and

3. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Leptic Torrertic Natrustalfs

JCCC. Other Natrustalfs that have both of the following:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Torrertic Natrustalfs

JCCD. Other Natrustalfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or
Alfisols 243

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Aquertic Natrustalfs

JCCE. Other Natrustalfs that have both of the following:

1. Visible crystals of gypsum or other salts more soluble

than gypsum, or both, within 40 cm of the mineral soil

surface; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Aridic Leptic Natrustalfs

JCCF. Other Natrustalfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or

a densic, lithic, or paralithic contact, whichever is

shallower.

Vertic Natrustalfs

JCCG. Other Natrustalfs that have both:

1. In one or more horizons within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage); and

2. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 cm or more.

Aquic Arenic Natrustalfs

JCCH. Other Natrustalfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Natrustalfs

JCCI. Other Natrustalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more.

Arenic Natrustalfs

JCCJ. Other Natrustalfs that have a petrocalcic horizon that

has its upper boundary within 150 cm of the mineral soil

surface.

Petrocalcic Natrustalfs

JCCK. Other Natrustalfs that have visible crystals of gypsum

or other salts more soluble than gypsum, or both, within 40 cm

of the mineral soil surface.

Leptic Natrustalfs

JCCL. Other Natrustalfs that have both of the following:

1. An exchangeable sodium percentage of less than 15 (or

a sodium adsorption ratio of less than 13) in 50 percent or

more of the natric horizon; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90
244 Soil Taxonomy

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 o

C; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Haplargidic Natrustalfs

JCCM. Other Natrustalfs that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Natrustalfs

JCCN. Other Natrustalfs that have an Ap horizon with a

color value, moist, of 3 or less and a color value, dry, of 5 or

less (crushed and smoothed sample) or materials between the

soil surface and a depth of 18 cm that have these color values

after mixing.

Mollic Natrustalfs

JCCO. Other Natrustalfs.

Typic Natrustalfs

Definition of Typic Natrustalfs

Typic Natrustalfs are the Natrustalfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Have an Ap horizon that has a color value, moist, of more

than 3, or the surface soil to a depth of 18 cm, after mixing, has a

color value, moist, of more than 3;

3. Do not have a salic horizon that has its upper boundary

within 75 cm of the soil surface;

4. Do not have a petrocalcic horizon that has its upper

boundary within 150 cm of the surface;

5. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

6. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

7. When neither irrigated nor fallowed to store moisture,

meet one of the following:

a. Have a frigid temperature regime and a moisture

control section that in normal years is dry in all parts for

less than four-tenths of the cumulative days per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. Have a mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for less than six-tenths of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

c. Have a hyperthermic, isomesic, or warmer soil

temperature regime and:

(1) Are dry in some or all parts of the moisture control

section for 120 or more cumulative days per year; and

(2) Are moist in some or all parts of the moisture

control section for 90 or more consecutive days per year

both in normal years and during a period when the soil

temperature at a depth of 50 cm exceeds 8 oC; and

(3) Are moist in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC;

8. Have an exchangeable sodium percentage of 15 or more

(or a sodium adsorption ratio of 13 or more) in more than 50

percent of the natric horizon; and

9. Do not have visible crystals of gypsum or other salts more
Alfisols 245

soluble than gypsum, or both, within 40 cm of the mineral soil

surface.

Description of Subgroups

Typic Natrustalfs.—The central concept or Typic subgroup

of Natrustalfs is fixed on soils that are not so well drained as

most other Ustalfs because the natric horizon has virtually no

hydraulic conductivity. The plow layer, if one occurs, or the

equivalent subhorizons have a color value, moist, of more than

3, and there is no salic horizon within 75 cm and no

petrocalcic horizon within 150 cm of the surface. A thick

epipedon with a sandy or sandy-skeletal particle-size class

throughout is considered atypical and is used to define Arenic

subgroups. Visible crystals of gypsum or other salts more

soluble than gypsum are not within 40 cm of the mineral soil

surface. Surface horizons above a depth of 18 cm that, after

mixing, have the color of a mollic epipedon or a plow layer

that has this color is believed to indicate a transition to

Mollisols and define the Mollic subgroup.

Soils that have shallow redox depletions with low chroma in

horizons that also have aquic conditions for some time in

normal years (or artificial drainage) are excluded from the

Typic subgroup because these properties are shared with

Aqualfs. Soils that have a shallow salic horizon are excluded

because such a horizon is shared with Salids. A petrocalcic

horizon is considered atypical and is the basis for defining the

Petrocalcic subgroup.

The Typic Natrustalfs in the United States are most

commonly in depressions or on the margins of lakes or playas.

Their slopes are nearly level. Most of these soils are used for

grazing.

Aquertic Natrustalfs.—These soils are like Typic

Natrustalfs, but they have a clayey texture and have expanding

clay in the argillic horizon. They also have redox depletions

with low chroma within 75 cm of the mineral soil surface that

are caused by periods of wetness. In addition, the surface soil to

a depth of 18 cm after mixing or the Ap horizon is permitted,

but not required, to have a color value, moist, of 3 or less.

These soils are in nearly level areas. They are rare in the

United States.

Aquic Arenic Natrustalfs.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). In

addition, they have a layer, starting at the mineral soil surface,

that is between 50 and 100 cm thick and has a texture of

loamy fine sand or coarser. The soils in this subgroup are

known to be locally extensive only in Texas in the United

States. Most are used for grazing. Slopes are nearly level to

gently undulating, suggesting some reworking by wind in the

late Pleistocene.

Aquic Natrustalfs.—These soils are like Typic Natrustalfs,

but they have, in one or more horizons within 75 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). In addition, the surface soil to a depth of

18 cm after mixing or the Ap horizon is permitted, but not

required, to have a color value, moist, of 3 or less. These soils

are rare in the United States. Most of them are used for

grazing.

Arenic Natrustalfs.—These soils are like Typic Natrustalfs,

but they have a layer, starting at the mineral soil surface, 50 cm

or more thick, with a sandy or sandy-skeletal particle-size class

throughout its thickness. These soils are not extensive in the

United States. Their slopes are nearly level to gently

undulating, suggesting some reworking by wind.

Aridic Leptic Natrustalfs.—These soils are drier than

Typic Natrustalfs. In addition, they have visible crystals of

gypsum or other salts more soluble than gypsum within 40 cm

of the mineral soil surface. These soils are intergrades between

Natrargids and Natrustalfs. They are rare in the United States.

Aridic Natrustalfs.—These soils are drier than Typic

Natrustalfs. They are intergrades between Natrargids and

Natrustalfs. They are rare in the United States.

Haplargidic Natrustalfs.—These soils are drier than Typic

Natrustalfs. They also have an exchangeable sodium

percentage of less than 15 (or a sodium adsorption ratio of less

than 13) in 50 percent or more of the natric horizon. These

soils are intergrades between Haplargids and Natrustalfs. They

are rare in the United States.

Leptic Natrustalfs.—These soils have visible crystals of

gypsum or other salts more soluble than gypsum within 40 cm

of the mineral soil surface. They are rare in the United States.

Leptic Torrertic Natrustalfs.—These soils are drier than

Typic Natrustalfs. They have a clayey texture and have

expanding clay in the argillic horizon. They have deep, wide

cracks in normal years. These soils also have visible crystals of

gypsum or other salts more soluble than gypsum within 40 cm

of the mineral soil surface. They are rare in the United States.

Mollic Natrustalfs.—These soils are like Typic Natrustalfs,

but the Ap horizon or the upper 18 cm after mixing has a color

value, moist, of 3 or less, generally 3. These soils are of small

extent in the United States. Their slopes are nearly level, and

most of the soils are used for grazing.

Petrocalcic Natrustalfs.—These soils have a petrocalcic

horizon that is normally about 50 to 75 cm below the soil

surface but is very thin, about 5 to 10 cm thick. They are rare

in the United States.

Salidic Natrustalfs.—These soils are like Typic Natrustalfs,

but they have a salic horizon within 75 cm of the surface but in

or below the natric horizon. They are rare in the United States.

Ground water in these soils is relatively shallow and is salty.

The soils are used only for limited grazing.

Torrertic Natrustalfs.—These soils are drier than Typic

Natrustalfs. They have a clayey texture and have expanding

clay in the argillic horizon. They have deep, wide cracks in

normal years. They are rare in the United States.

Vertic Natrustalfs.—These soils are like Typic Natrustalfs,
246 Soil Taxonomy

but they have a clayey texture and have expanding clay in the

argillic horizon. In addition, the surface soil to a depth of 18 cm

after mixing or the Ap horizon is permitted, but not required, to

have a color value, moist, of 3 or less. These soils are in nearly

level areas. They are rare in the United States.

Paleustalfs

Paleustalfs are the reddish or red Ustalfs that are on old

surfaces. Many of them have some plinthite in their lower

horizons. Paleustalfs occur in relatively stable landscape

positions, their slopes are mostly gentle, and their genesis

began before the late Pleistocene. In the United States, they

typically have a Bk or calcic horizon in or below the argillic

horizon as a result of additions of atmospheric carbonates.

Commonly, secondary lime coats the surfaces of peds that have

noncalcareous interiors and the soils may be noncalcareous at a

depth of less than 200 cm. A few of these soils, near the

boundary where they join Aridisols, have received enough

calcareous dust to have a petrocalcic horizon. A few others,

near the boundary where they join Udults or Udalfs, do not

have a Bk horizon. Before cultivation, the vegetation on the

Paleustalfs in the United States included a mixture of grasses

and woody plants. These soils are moderately extensive in the

southern part of the Great Plains in the United States, and they

probably are extensive in Africa and southern Asia.

Definition

Paleustalfs are the Ustalfs that:

1. Do not have a duripan within 100 cm of the soil surface

and do not have a natric horizon;

2. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix within any subhorizon of

the argillic horizon within 150 cm of the soil surface; and

3. Meet one or more of the following:

a. Have a petrocalcic horizon that is in or below an argillic

horizon but that has an upper boundary within 150 cm of

the soil surface; or

b. Do not have a densic, lithic, or paralithic contact within

150 cm of the soil surface and have an argillic horizon that

has:

(1) A clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much

as 20 percent from the soil surface to a depth of 150 cm,

or the layer in which the clay percentage decreases by

more than 20 percent has at least 5 percent of the volume

consisting of skeletans on faces of peds and there is at

least a 3 percent (absolute) increase in content of clay

below this layer; and

(2) One or more of the following:

(a) Hue of 7.5YR or redder and chroma of 5 or more in

50 percent or more of the matrix of one or more horizons

in its lower one-half;

(b) In 50 percent or more of the matrix of horizons that

total more than one-half the total thickness, hue of

7.5YR or redder, value, moist, of 3 or less, and value,

dry, of 4 or less; or

(c) In one or more horizons in its lower one-half,

common coarse redox concentrations that have hue of

7.5YR or redder or chroma of 6 or more, or both; or

c. Do not have a densic, lithic, or paralithic contact within

50 cm of the surface and have an argillic horizon that has:

(1) A clayey or clayey-skeletal particle-size class in its

upper part; and

(2) At its upper boundary, a clay increase of at least 20

percent (absolute) within a vertical distance of 7.5 cm or

of 15 percent (absolute) within a distance of 2.5 cm, in

the fine-earth fraction.

Although the restriction on depth to a densic, lithic, or

paralithic contact in the Paleustalfs is only 50 cm, it is rare that

such a contact is within a depth of 150 cm. A few of these

soils, however, have rock at a depth of less than 100 cm.

Key to Subgroups

JCFA. Paleustalfs that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage).

Aquertic Paleustalfs

JCFB. Other Paleustalfs that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick
Alfisols 247

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

2. Saturation with water in one or more layers within 100

cm of the mineral soil surface in normal years for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Oxyaquic Vertic Paleustalfs

JCFC. Other Paleustalfs that have both:

1. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the time (cumulative)

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth

of 50 cm below the soil surface is higher than 8 oC; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Udertic Paleustalfs

JCFD. Other Paleustalfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower.

Vertic Paleustalfs

JCFE. Other Paleustalfs that have both:

1. In one or more horizons within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage); and

2. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 to 100 cm.

Aquic Arenic Paleustalfs

JCFF. Other Paleustalfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Paleustalfs

JCFG. Other Paleustalfs that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Paleustalfs

JCFH. Other Paleustalfs that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Paleustalfs

JCFI. Other Paleustalfs that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Paleustalfs
248 Soil Taxonomy

JCFJ. Other Paleustalfs that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 to 100 cm; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the time (cumulative) per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the time (cumulative)

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Arenic Aridic Paleustalfs

JCFK. Other Paleustalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more.

Grossarenic Paleustalfs

JCFL. Other Paleustalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm.

Arenic Paleustalfs

JCFM. Other Paleustalfs that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Paleustalfs

JCFN. Other Paleustalfs that have a petrocalcic horizon that

has its upper boundary within 150 cm of the mineral soil

surface.

Petrocalcic Paleustalfs

JCFO. Other Paleustalfs that have both:

1. When neither irrigated nor fallowed to store moisture,

either:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the time (cumulative) per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the time (cumulative)

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC; and

2. A calcic horizon either within 100 cm of the mineral

soil surface if the weighted average particle-size class of the

upper 50 cm of the argillic horizon is sandy, or within 60

cm if it is loamy, or within 50 cm if it is clayey, and

carbonates in all horizons above the calcic horizon.

Calcidic Paleustalfs

JCFP. Other Paleustalfs that, when neither irrigated nor

fallowed to store moisture, have:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the time (cumulative) per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the time (cumulative) per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for less than 90

consecutive days per year when the temperature at a
Alfisols 249

depth of 50 cm below the soil surface is higher than 8 o

C;

and

b. Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Paleustalfs

JCFQ. Other Paleustalfs that have a CEC of less than 24

cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more

either of the argillic horizon if less than 100 cm thick or of its

upper 100 cm.

Kandic Paleustalfs

JCFR. Other Paleustalfs that have, in all subhorizons in the

upper 100 cm of the argillic horizon or throughout the entire

argillic horizon if less than 100 cm thick, more than 50 percent

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodic Paleustalfs

JCFS. Other Paleustalfs that have an argillic horizon with a

base saturation (by sum of cations) of less than 75 percent

throughout.

Ultic Paleustalfs

JCFT. Other Paleustalfs that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for four-tenths or less of the time (cumulative) per year

when the temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Udic Paleustalfs

JCFU. Other Paleustalfs.

Typic Paleustalfs

Definition of Typic Paleustalfs

Typic Paleustalfs are the Paleustalfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years;

3. Have a texture finer than loamy fine sand in one or more

subhorizons within 50 cm of the mineral soil surface;

4. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the soil surface;

5. When neither irrigated nor fallowed to store moisture:

a. Have a frigid temperature regime and a moisture

control section that in normal years is dry in all parts for

less than four-tenths of the time (cumulative) per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

b. Have a mesic or thermic soil temperature regime and a

moisture control section that is dry in some part for more

than four-tenths but less than six-tenths of the time

(cumulative) when the soil temperature at a depth of 50 cm

exceeds 5 oC; or

c. Have a hyperthermic, isomesic, or warmer soil

temperature regime and:

(1) Are dry in some or all parts of the moisture control

section for 120 or more cumulative days per year; and

(2) Are moist in some or all parts of the moisture

control section for 90 or more consecutive days per year

both in normal years and during a period when the soil

temperature at a depth of 50 cm exceeds 8 oC; and

(3) Are moist in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC;

6. Have an argillic horizon that has a base saturation (by sum

of cations) of 75 percent or more in some part;

7. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

8. Do not have a petrocalcic horizon that has its upper

boundary within 150 cm of the soil surface;

9. Do not have a calcic horizon that has an upper boundary

within 100 cm of the soil surface if the weighted average
250 Soil Taxonomy

particle-size class of the upper 50 cm of the argillic horizon is

sandy, or 60 cm if it is loamy, or 50 cm if it is clayey;

10. Have a CEC of 24 or more cmol(+)/kg clay (by 1N NH4

OAc

pH 7) in the major part of the argillic horizon or in the major part

of its upper 100 cm if it is thicker than 100 cm;

11. Have, in all subhorizons in the upper 100 cm of the argillic

horizon or throughout the entire argillic horizon if less than 100

cm thick, more than 50 percent colors that have all of the

following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value;

12. Have an argillic horizon that is finer than the sandy

particle-size class in some part of the upper 75 cm if the

argillic horizon is more than 75 cm thick or in any part if the

argillic horizon is less than 75 cm thick;

13. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Description of Subgroups

Typic Paleustalfs.—The central concept or Typic subgroup

of Paleustalfs is fixed on freely drained soils that have a thin or

loamy epipedon; that do not have cracks and slickensides or

wedge-shaped aggregates; that are moist for an appreciable

part of the growing season; and that have an argillic horizon

that contains some 2:1 lattice clays, has a loamy or clayey

particle-size class and high base saturation in at least some

part, and is not composed entirely of thin lamellae.

Soils that have shallow redox depletions with low chroma in

horizons that also have aquic conditions for some time in

normal years (or artificial drainage) are excluded from Typic

Paleustalfs because these properties are shared with Aqualfs. A

thick epipedon with a sandy or sandy-skeletal particle-size

class throughout is not considered normal and defines Arenic

and Grossarenic subgroups, a convention used elsewhere in

this taxonomy. Soils that have an appreciable amount of

plinthite are excluded because the presence of plinthite is a

property of Plinthustalfs. A soil moisture regime that is ustic

but borders on udic is more moist than normal and defines the

Udic subgroup. A moderately low base saturation throughout

the argillic horizon is considered atypical and defines the Ultic

subgroup.

Cracks and slickensides or wedge-shaped aggregates are

properties shared with Vertisols and define intergrades to that

order. A petrocalcic horizon causes a soil to be excluded from

the Typic subgroup, even though one is very common in

Paleustalfs, and its presence defines the Petrocalcic subgroup.

A soil moisture regime that approaches the aridic regime is

considered drier than normal and defines Aridic subgroups.

Clays that have low activity are considered evidence of

strong weathering, and their dominance is the basis for

defining the Kandic subgroup.

Typic Paleustalfs are not the most extensive subgroup of

Paleustalfs in the United States. They are mostly in Texas.

Some of them are used as cropland, and many of them are used

for grazing. The Typic subgroup was selected to provide a basis

for defining subgroups, and it is thought to be extensive in

some parts of the world.

Aquertic Paleustalfs.—These soils are like Typic

Paleustalfs, but they have, in one or more horizons within 75

cm of the mineral soil surface, redox depletions with chroma of

2 or less and also aquic conditions for some time in normal

years (or artificial drainage). In addition, they have cracks and

slickensides or wedge-shaped aggregates. The base saturation

(by sum of cations) may be less than 75 percent throughout the

argillic horizon. These soils are not extensive in the United

States. Their slopes are gentle, and most of the soils are used as

cropland.

Aquic Arenic Paleustalfs.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). In

addition, they have a layer, starting at the mineral soil surface,

that is between 50 and 100 cm thick and has a sandy or sandyskeletal particle-size class throughout its thickness. The base

saturation (by sum of cations) may be less than 75 percent

throughout the argillic horizon. These soils are moderately

extensive in some areas in the southern part of the Great

Plains in the United States. Their slopes are gentle or

moderate.

Aquic Paleustalfs.—These soils are like Typic Paleustalfs,

but they have, in one or more horizons within 75 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). Skeletans with low chroma should not be

mistaken for redox depletions with low chroma, which are

caused by wetness. The base saturation (by sum of cations) may

be less than 75 percent throughout the argillic horizon. These
Alfisols 251

soils are of moderate extent in the United States. Most of them

are in Texas. Their slopes are gentle, and most of the soils are

used as cropland.

Arenic Aridic Paleustalfs.—These soils have a layer,

starting at the mineral soil surface, that is between 50 and 100

cm thick and has a sandy or sandy-skeletal particle-size class

throughout its thickness. They are drier than Typic Paleustalfs.

Some Arenic Aridic Paleustalfs have a calcic horizon or a

horizon that has identifiable secondary carbonates. Arenic

Aridic Paleustalfs are of small extent in the southern part of the

Great Plains in the United States. Their slopes are gentle. These

soils are used mainly for grazing.

Arenic Paleustalfs.—These soils have a layer, starting at

the mineral soil surface, that is between 50 and 100 cm thick

and has a sandy or sandy-skeletal particle-size class throughout

its thickness. These soils are not extensive in the United States.

Their slopes are mostly gentle or moderate. Some of the soils

are used as cropland, but most of them are used for grazing.

Aridic Paleustalfs.—These soils are like Typic Paleustalfs,

but they are drier. In addition, they do not have a calcic

horizon or are noncalcareous in some subhorizon above the

calcic horizon, or, if calcareous throughout, the calcic horizon

is deeper than 100 cm if the weighted average particle-size

class of the upper 50 cm of the argillic horizon is sandy, deeper

than 60 cm if the particle-size class is loamy, or 50 cm if the

particle-size class is clayey. The calcic horizon is normally in

the thick argillic horizon. These soils are thought to have been

recalcified since the argillic horizon formed. In the United

States, dust from the Aridisols to the west is a probable source

of some of the carbonates. Aridic Paleustalfs are extensive in

some areas in the southern part of the Great Plains. Their

slopes are gentle. Many of the soils are used as cropland. Some

are used for irrigated crops, mainly cotton, sorghum, and

wheat. Others are used for drought-tolerant crops or for

grazing.

Calcidic Paleustalfs.—These soils are calcareous in all

subhorizons; have a calcic horizon within 100 cm of the soil

surface, commonly within 50 cm; and are drier than Typic

Paleustalfs. The argillic horizon appears to have been largely

but not entirely disrupted by the deposition of carbonates, but it

is preserved in part below the calcic horizon. Calcidic

Paleustalfs are not extensive in the United States. They are

used mainly for grazing.

Grossarenic Paleustalfs.—These soils have an epipedon

that has a sandy or sandy-skeletal particle-size class throughout

and is more than 100 cm thick. The argillic horizon commonly

is sandy loam or sandy clay loam. The soils of this subgroup

are extensive only locally in Texas in the United States. Most

of them are used for grazing. Their slopes are gentle but

commonly are billowy, suggesting some reworking by wind at

some time during the late Pleistocene.

Kandic Paleustalfs.—These soils have an argillic horizon

that has a CEC (by 1N NH4

OAc pH 7) of less than 24 cmol(+)/

kg clay in the major part. The base saturation (by sum of

cations) is less than 75 percent in all parts of the argillic horizon

in some pedons. These soils are intergrades between Paleustalfs

and Kandiustalfs. They are not known to occur in the United

States but probably are moderately extensive in some other

countries.

Lamellic Paleustalfs.—These soils are like Typic

Paleustalfs in defined properties, but they have an argillic

horizon that consists of lamellae or partially of lamellae. Most

of these soils have a sandy particle-size class, and the upper

boundary of the argillic horizon or the upper lamella may be

below a depth of 60 cm. The upper several lamellae are

commonly broken or discontinuous horizontally. These soils

are not extensive in the United States.

Oxyaquic Paleustalfs.—These soils are like Typic

Paleustalfs, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. In addition, the soils

are permitted, but not required, to have a base saturation (by

sum of cations) that is less than 75 percent. They are

considered intergrades to Aqualfs. They are rare in the United

States.

Oxyaquic Vertic Paleustalfs.—These soils are like Typic

Paleustalfs, but they have a clayey texture and have expanding

clay in the argillic horizon. They also have deep, wide cracks

in normal years and are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. These soils are not

extensive in the United States.

Petrocalcic Paleustalfs.—These soils have a petrocalcic

horizon, most commonly at a depth about 75 cm below the

surface, and are drier than Typic Paleustalfs. The upper part of

the argillic horizon is noncalcareous. Petrocalcic Paleustalfs

are locally extensive in the southern part of the Great Plains in

the United States. Some of them are used for crops, mainly

cotton, sorghum, and wheat. A few of the soils are irrigated.

Many are used for grazing.

Plinthic Paleustalfs.—These soils are like Typic

Paleustalfs, but they have 5 percent or more (by volume)

plinthite in one or more horizons within 150 cm of the mineral

soil surface. In addition, the soils are permitted, but not

required, to have a base saturation (by sum of cations) that is

less than 75 percent. These soils are rare in the United States.

Psammentic Paleustalfs.—These soils are like Typic

Paleustalfs, but they have a sandy particle-size class throughout

the upper 75 cm of the argillic horizon or throughout the entire

argillic horizon if it is less than 75 cm thick. In addition, the

epipedon is permitted to be, and generally is, more than 50 cm

thick, and its texture is permitted to be loamy fine sand or

coarser throughout its thickness. These soils are not extensive

in the United States. Their slopes are gentle to strong. Most of

the soils are used for grazing.

Rhodic Paleustalfs.—These soils are like Typic Paleustalfs,

but the argillic horizon has hue of 2.5YR or redder and has a

color value, moist, of 3 or less and a dry color value 1 unit or
252 Soil Taxonomy

less higher than the moist value. In addition, the base saturation

(by sum of cations) may be less than 75 percent throughout the

argillic horizon. These soils are not extensive in the United

States. Their slopes are gentle, and most of the soils are used for

grazing.

Udertic Paleustalfs.—These soils are like Typic Paleustalfs,

but they have cracks and slickensides or wedge-shaped

aggregates and are moist for longer periods. They are

intergrades between Hapluderts and Paleustalfs. They are

locally extensive in some areas in the southern part of the Great

Plains in the United States. Their slopes are gentle, and most of

the soils are used as cropland.

Udic Paleustalfs.—These soils are like Typic Paleustalfs,

but they are moist for longer periods. They are intergrades

between Paleudalfs and Paleustalfs. They are extensive in parts

of the United States. Their slopes are gentle, and most of the

soils are used as cropland.

Ultic Paleustalfs.—These soils are like Typic Paleustalfs,

but they have a base saturation (by sum of cations) that is less

than 75 percent in all subhorizons of the argillic horizon. Most

Ultic Paleustalfs do not have a calcic horizon or a horizon that

contains identifiable secondary carbonates. Ultic Paleustalfs are

intergrades between Paleudults or Paleustults and Paleustalfs.

They are locally extensive in Texas and Oklahoma in the

United States. Their slopes are gentle, and most of the soils are

used as cropland.

Vertic Paleustalfs.—These soils are like Typic Paleustalfs,

but they have cracks and slickensides or wedge-shaped

aggregates. Vertic Paleustalfs are intergrades between

Haplusterts and Paleustalfs. They are moderately extensive

locally in some areas in the southern part of the Great Plains

and in the southwestern part of the United States. Their slopes

are gentle, and most of the soils are used as cropland.

Plinthustalfs

Plinthustalfs are the Ustalfs that have one or more horizons

within 150 cm of the mineral soil surface in which plinthite

either forms a continuous phase or constitutes one-half or more

of the volume. These soils do not have a duripan that has its

upper boundary within 100 cm of the soil surface. There are no

soil series in the United States that are presently classified in

this great group, but the group is provided for use in other

parts of the world. Subgroups have not been developed.

Key to Subgroups

JCBA. All Plinthustalfs (provisionally).

Typic Plinthustalfs

Rhodustalfs

Rhodustalfs are dark red Ustalfs that have a thinner solum

than that in Paleustalfs. Rhodustalfs generally formed on

erosional surfaces or in deposits of late-Pleistocene age. In the

United States, their vegetation was mostly grass and scattered

woody shrubs and trees before the soils were cultivated. The

parent materials are basic. These soils are rare in the United

States.

Definition

Rhodustalfs are the Ustalfs that:

1. Have, in all subhorizons in the upper 100 cm of the

argillic horizon or throughout the entire argillic horizon if less

than 100 cm thick, more than 50 percent colors that have all of

the following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value;

2. Do not have a natric or kandic horizon;

3. Do not have a duripan that has an upper boundary within

100 cm of the soil surface or a petrocalcic horizon that has an

upper boundary within 150 cm of the soil surface;

4. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix within any subhorizon of

the argillic horizon within 150 cm of the soil surface;

5. Either have a densic, lithic, or paralithic contact within

150 cm of the soil surface or have a clay distribution in the

argillic horizon in which the clay content decreases with

increasing depth by 20 percent or more from its maximum

within 150 cm of the soil surface and, if there is a clay increase

of 3 percent or more (absolute) below that layer, less than 5

percent of the volume in the layer where the clay content

decreases consists of skeletans on faces of peds; and

6. Have either:

a. A densic, lithic, or paralithic contact within 50 cm of

the soil surface; or

b. A particle-size class other than fine, very-fine, or

clayey-skeletal in the upper part of the argillic horizon; or

c. A fine, very-fine, or clayey-skeletal particle-size class in

the upper part of the argillic horizon and an increase of less

than 20 percent clay (absolute) within a vertical distance of

7.5 cm and of less than 15 percent within 2.5 cm of the

upper boundary of the argillic horizon.

Key to Subgroups

JCGA. Rhodustalfs that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Rhodustalfs

JCGB. Other Rhodustalfs that have a CEC of less than 24

cmol(+)/kg clay (by 1N NH4

OAc pH 7) in 50 percent or more
Alfisols 253

either of the argillic horizon if less than 100 cm thick or of its

upper 100 cm.

Kanhaplic Rhodustalfs

JCGC. Other Rhodustalfs that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for four-tenths or less of the time (cumulative) per year

when the temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Udic Rhodustalfs

JCGD. Other Rhodustalfs.

Typic Rhodustalfs

Definition of Typic Rhodustalfs

Typic Rhodustalfs are the Rhodustalfs that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have a CEC of 24 or more cmol(+)/kg clay (by 1N

NH4OAc pH 7) in the major part of the argillic horizon or the

major part of the upper 100 cm of the argillic horizon if the

argillic horizon is thicker than 100 cm; and

3. When neither irrigated nor fallowed to store moisture,

have:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for more than four-tenths of the time (cumulative)

when the soil temperature at a depth of 50 cm exceeds 5 oC;

or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for 120 or more days

(cumulative) during a period when the soil temperature at a

depth of 50 cm exceeds 8 oC.

Description of Subgroups

Typic Rhodustalfs.—The central concept or Typic subgroup

of Rhodustalfs is fixed on soils that are deep or moderately

deep to hard rock and that have some 2:1 lattice clays.

A shallow lithic contact defines the Lithic subgroup, a

convention used throughout this taxonomy. Low activity in the

clay fraction is thought to indicate stronger weathering than

normal and is used to define the Kanhaplic subgroup.

Rhodustalfs that are moist for longer periods than are described

for the Typic subgroup are assigned to the Udic subgroup.

Typic Rhodustalfs are rare in the United States. Their slopes

range from gentle to strong. Most of them are used for grazing.

Kanhaplic Rhodustalfs.—These soils are like Typic

Rhodustalfs, but their CEC is less than 24 cmol(+)/kg clay.

They are permitted, but not required, to have a calcic or Bk

horizon that contains identifiable secondary carbonates. These

soils are rare in the United States and are known to occur only in

Hawaii. Their slopes are strong, and most of the soils are used

for grazing.

Lithic Rhodustalfs.—These soils have a lithic contact

within 50 cm of the soil surface. They may have any of the

other properties allowed in Rhodustalfs. Lithic Rhodustalfs are

rare in the United States and are known to occur only in Texas.

Udic Rhodustalfs.—These soils are like Typic Rhodustalfs,

but they are moist for longer periods. They are rare in the

United States. Their slopes are moderate or strong, and most of

the soils are used for grazing.

Xeralfs

Xeralfs are the Alfisols in regions that have a

Mediterranean climate. As their name implies, they have a

xeric moisture regime. They are dry for extended periods in

summer, but in winter moisture moves through the soils to

deeper layers in at least occasional years, if not in normal

years. Small grain and other winter annuals are common crops

where there is no irrigation. Grapes and olives also are

common crops where the climate is thermic. With irrigation, a

wide variety of crops can be grown.

Xeralfs formed not only in the area around the

Mediterranean Sea but also in parts of South Africa, Chile,

western and southern Australia, and in the Western United

States. Most of these soils border the Mediterranean Sea or lie

to the east of an ocean at midlatitudes. The temperature regime

is thermic, mesic, or frigid. In the world as a whole, Xeralfs

are not extensive soils, but in the regions where they occur,

they are extensive. In the United States, they are moderately

extensive. Before the soils were farmed, the vegetation was a

mixture of annual grasses, forbs, and woody shrubs on the

warmest and driest Xeralfs and coniferous forest on the coolest

and most moist Xeralfs.

Xeralfs formed on surfaces that are of different ages. Some

formed on erosional surfaces or in deposits of late-Wisconsinan

age, and some, such as those in Australia, are on old surfaces

and have characteristics that probably reflect an environment

greatly different from the present one. In the oldest Xeralfs, the

boundary between the A and B horizons commonly is very

abrupt. The epipedon of some Xeralfs is hard and massive

when dry.
254 Soil Taxonomy

Definition

Xeralfs are the Alfisols that:

1. Have a xeric moisture regime;

2. Have a frigid, mesic, or thermic temperature regime;

3. Have, in no horizon within 50 cm of the mineral soil surface,

both aquic conditions (other than anthraquic conditions) for

some time in normal years (or artificial drainage) and either of

the following:

a. Redoximorphic features in all layers between either the

lower boundary of an Ap horizon or a depth of 25 cm below

the mineral soil surface, whichever is deeper, and a depth of

40 cm; and one of the following within the upper 12.5 cm of

the argillic, kandic, natric, or glossic horizon:

(1) 50 percent or more redox depletions with chroma of

2 or less on faces of peds and redox concentrations

within peds; or

(2) Redox concentrations and 50 percent or more redox

depletions with chroma of 2 or less in the matrix; or

(3) 50 percent or more redox depletions with chroma of

1 or less on faces of peds or in the matrix, or both; or

b. In a horizon that has aquic conditions, enough active

ferrous iron to give a positive reaction to alpha,alphadipyridyl at a time when the soil is not being irrigated.

Key to Great Groups

JDA. Xeralfs that have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Durixeralfs, p. 254

JDB. Other Xeralfs that have a natric horizon.

Natrixeralfs, p. 263

JDC. Other Xeralfs that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragixeralfs, p. 256

JDD. Other Xeralfs that have one or more horizons within

150 cm of the mineral soil surface in which plinthite either

forms a continuous phase or constitutes one-half or more of the

volume.

Plinthoxeralfs, p. 269

JDE. Other Xeralfs that have, in all subhorizons in the upper

100 cm of the argillic or kandic horizon or throughout the

entire argillic or kandic horizon if less than 100 cm thick,

more than 50 percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

3. Dry value no more than 1 unit higher than the moist

value.

Rhodoxeralfs, p. 269

JDF. Other Xeralfs that have one or more of the following:

1. A petrocalcic horizon that has its upper boundary within

150 cm of the mineral soil surface; or

2. No densic, lithic, or paralithic contact within 150 cm of

the mineral soil surface and an argillic or kandic horizon

that has both:

a. Within 150 cm of the mineral soil surface, either:

(1) With increasing depth, no clay decrease of 20

percent or more (relative) from the maximum clay

content [Clay is measured noncarbonate clay or based

on the following formula: Clay % = 2.5(% water

retained at 1500 kPa tension - % organic carbon),

whichever value is greater, but no more than 100]; or

(2) 5 percent or more (by volume) skeletans on faces

of peds in the layer that has a 20 percent lower clay

content and, below that layer, a clay increase of 3

percent or more (absolute) in the fine-earth fraction;

and

b. A base at a depth of 150 cm or more; or

3. No densic, lithic, or paralithic contact within 50 cm of

the mineral soil surface and an argillic or kandic horizon

that has within 15 cm of its upper boundary both:

a. A clayey, clayey-skeletal, fine, or very-fine particlesize class; and

b. A clay increase, in the fine-earth fraction, of either

20 percent or more (absolute) within a vertical distance

of 7.5 cm or of 15 percent or more (absolute) within a

vertical distance of 2.5 cm.

Palexeralfs, p. 264

JDG. Other Xeralfs.

Haploxeralfs, p. 258

Durixeralfs

Durixeralfs are the Xeralfs that have a duripan that has an

upper boundary within 100 cm of the soil surface but below an

argillic or natric horizon. These soils are known to have

formed in California, Idaho, Nevada, Oregon, Chile, and Italy,

in areas of Pleistocene or earlier vulcanism. Some of the

Durixeralfs in the United States appear to be on very old

surfaces and have complex horizons that indicate polygenesis.

The oldest soils are commonly reddish and have kaolinitic
Alfisols 255

mineralogy. Other Durixeralfs appear to have formed in latePleistocene sediments and are yellowish brown and have 2:1

lattice clays. The pan commonly has an upper boundary about

50 cm below the soil surface and has very coarse polyhedrons,

the tops and sides of which are coated with opal or chalcedony.

In undisturbed areas in the United States, a microrelief of about

10 to 100 cm or more is common. The microrelief is mainly

the result of differences in the thickness of horizons that are

above the duripan.

Durixeralfs are moderately extensive only in California and

Idaho in the United States.

Definition

Durixeralfs are the Xeralfs that have a duripan that has an

upper boundary within 100 cm of the mineral soil surface.

Key to Subgroups

JDAA. Durixeralfs that have a natric horizon.

Natric Durixeralfs

JDAB. Other Durixeralfs that have, above the duripan, one

or both of the following:

1. Cracks that are 5 mm or more wide through a thickness

of 30 cm or more for some time in normal years, and

slickensides or wedge-shaped aggregates in a layer 15 cm or

more thick; or

2. A linear extensibility of 6.0 cm or more.

Vertic Durixeralfs

JDAC. Other Durixeralfs that have, in one or more

subhorizons within the argillic horizon, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Durixeralfs

JDAD. Other Durixeralfs that have both:

1. An argillic horizon that has both:

a. A clayey, clayey-skeletal, fine, or very-fine particlesize class throughout some subhorizon 7.5 cm or more

thick; and

b. At its upper boundary or within some part, a clay

increase either of 20 percent or more (absolute) within a

vertical distance of 7.5 cm or of 15 percent or more

(absolute) within a vertical distance of 2.5 cm, in the

fine-earth fraction; and

2. A duripan that is strongly cemented or less cemented in

all subhorizons.

Abruptic Haplic Durixeralfs

JDAE. Other Durixeralfs that have an argillic horizon that

has both:

1. A clayey, clayey-skeletal, fine, or very-fine particle-size

class throughout some subhorizon 7.5 cm or more thick;

and

2. At its upper boundary or within some part, a clay

increase either of 20 percent or more (absolute) within a

vertical distance of 7.5 cm or of 15 percent or more

(absolute) within a vertical distance of 2.5 cm, in the fineearth fraction.

Abruptic Durixeralfs

JDAF. Other Durixeralfs that have a duripan that is strongly

cemented or less cemented in all subhorizons.

Haplic Durixeralfs

JDAG. Other Durixeralfs.

Typic Durixeralfs

Definition of Typic Durixeralfs

Typic Durixeralfs are the Durixeralfs that:

1. Have an argillic horizon that meets one or more of the

following:

a. Has less than 35 percent clay in all subhorizons that are

7.5 cm or thicker; or

b. Has an increase in clay content that is less than 15

percent (absolute) within a vertical distance of 2.5 cm and is

less than 20 percent (absolute) within a vertical distance of

7.5 cm at the upper boundary and within all parts;

2. Do not have, in any subhorizon within the argillic horizon,

redox depletions with chroma of 2 or less and also aquic

conditions;

3. Have a duripan that is very strongly cemented or indurated

in some part;

4. Do not have a natric horizon; and

5. Above the duripan, do not have either:

a. Cracks that are 5 mm or more wide through a thickness

of 30 cm or more for some time in normal years, and

slickensides or wedge-shaped aggregates in a layer 15 cm or

more thick; or

b. A linear extensibility of 6.0 cm or more.

Description of Subgroups

Typic Durixeralfs.—The central concept or Typic subgroup

is fixed on the most freely drained Durixeralfs that have a very

strongly cemented or indurated duripan and do not have a

natric horizon. These soils have an argillic horizon that either

has less than 35 percent clay or, if it has 35 percent or more

clay, has a relatively small increase in clay content or a

relatively thick transitional horizon between the epipedon and

the argillic horizon.
256 Soil Taxonomy

The Typic subgroup is not the most extensive subgroup, but

it was selected to provide what seems the best basis for

definition of the others.

An abrupt textural change at the upper boundary of the

argillic horizon or within the argillic horizon is very common,

and it defines Abruptic subgroups. Soils that have redox

depletions with low chroma and aquic conditions for some time

in normal years (or artificial drainage) in the argillic horizon are

excluded from the Typic subgroup. A duripan that does not

have a very strongly cemented or indurated subhorizon is

considered weakly expressed and is the basis for definition of

Haplic subgroups. A natric horizon is considered atypical and

is used to define the Natric subgroup.

Abruptic Durixeralfs.—These soils are like Typic

Durixeralfs, but the argillic horizon has a fine, very-fine,

clayey, or clayey-skeletal particle-size class in some

subhorizon, and at the upper boundary of the argillic horizon

or within the argillic horizon, there is a marked increase in

content of clay. These soils are moderately extensive in

California. In many of the soils, the argillic horizon appears to

have formed since the duripan developed. Slopes are gentle or

moderate. Most of the soils are used for grazing or for small

grain.

Abruptic Haplic Durixeralfs.—These soils have an argillic

horizon that has a fine, very-fine, clayey, or clayey-skeletal

particle-size class in some subhorizon and, at the upper

boundary of the argillic horizon or within the argillic horizon,

there is a marked increase in content of clay. In addition, the

duripan is strongly cemented or less cemented in all

subhorizons. It is not known whether the duripan is forming, is

being destroyed, or is only weakly developed. These soils are

not extensive. Their slopes are gentle. Most of the soils are

used for grazing.

Aquic Durixeralfs.—These soils are like Typic Durixeralfs,

but they have, in one or more horizons within 75 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). These soils are not known to occur in the

United States.

Haplic Durixeralfs.—These soils are like Typic

Durixeralfs, but the duripan is strongly cemented or less

cemented in all subhorizons. It is not known whether the

duripan is forming, is being destroyed, or is only weakly

developed. In the United States, Haplic Durixeralfs are not

extensive, except locally in California. Their slopes are gentle

or moderate. Some of the soils are used for irrigated citrus

crops, some are used for small grain, and some are used as

pasture.

Natric Durixeralfs.—These soils have a natric horizon.

The duripan may or may not be indurated, and there may be

redox depletions with low chroma in the natric horizon, which

in some years may be saturated or may have ground water

perched above it. In the United States, these soils are extensive

only in the Central Valley of California. Commonly, they are

saline. After reclamation, they may be used for cultivated

crops. Otherwise, they provide only limited grazing unless

irrigated.

Vertic Durixeralfs.—These soils have, above the duripan,

cracks that are 5 mm or more wide through a thickness of 30

cm or more in normal years and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick or have a linear

extensibility of 6.0 cm or more. These soils are not known to

occur in the United States.

Fragixeralfs

Fragixeralfs are the Xeralfs that have a fragipan with an upper

boundary within 100 cm below the mineral soil surface.

Commonly, these soils have a brown argillic or kandic horizon

and have redoximorphic features and a perched water table that

is seasonally above the pan. Above the pan, some Fragixeralfs

have a thin eluvial horizon with peds that have gray clay

depletions.

Most Fragixeralfs in the United States are on gentle or

moderate slopes and formed, at least in part, in silty or loamy

late-Pleistocene deposits. Some are strongly sloping.

Temperature regimes are mesic or frigid. In the United States,

the native vegetation was primarily a coniferous forest. These

soils are of small extent in Idaho and Oregon.

Definition

Fragixeralfs are the Xeralfs that:

1. Have a fragipan with an upper boundary within 100 cm of

the mineral soil surface;

2. Do not have a duripan with an upper boundary within 100

cm of the mineral soil surface;

3. Do not have a natric horizon.

Key to Subgroups

JDCA. Fragixeralfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Fragixeralfs

JDCB. Other Fragixeralfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and
Alfisols 257

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Fragixeralfs

JDCC. Other Fragixeralfs that have an Ap horizon with a color

value, moist, of 3 or less and a color value, dry, of 5 or less

(crushed and smoothed sample) or materials between the soil

surface and a depth of 18 cm that have these color values after

mixing.

Mollic Fragixeralfs

JDCD. Other Fragixeralfs that have, in one or more horizons

within 40 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Fragixeralfs

JDCE. Other Fragixeralfs that, above the fragipan, do not

have an argillic or kandic horizon with clay films on both

vertical and horizontal faces of any peds.

Inceptic Fragixeralfs

JDCF. Other Fragixeralfs.

Typic Fragixeralfs

Definition of Typic Fragixeralfs

Typic Fragixeralfs are the Fragixeralfs that:

1. Above the fragipan, have an argillic or kandic horizon that

has clay films on at least some vertical and horizontal faces of

primary or secondary peds, or both;

2. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more;

3. Either have an Ap horizon that has a color value, moist, of 4

or more or a color value, dry, of 6 or more, when crushed and

smoothed, or have materials to a depth of 18 cm that have

these colors after mixing; and

4. Do not have, in any horizon within 40 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions.

Description of Subgroups

Typic Fragixeralfs.—The central concept or Typic

subgroup of Fragixeralfs is fixed on the soils of this great

group that are the most freely drained, that have an argillic or

kandic horizon above the fragipan, and that have a high color

value in an Ap horizon or in comparable layers if the soils are

undisturbed.

Typic Fragixeralfs are not the most extensive subgroup, but

they furnish the best basis for definition of subgroups. No

Fragixeralfs are freely drained because in all of them ground

water is perched above the fragipan in many years. The

perched water table is a probable cause of the very common

albic materials and gray clay depletions directly above the

fragipan. Soils that have these features and also redox

depletions with low chroma at a shallow depth together with

redox concentrations of high chroma or of reddish hue are

considered to be intergrades toward Aqualfs.

Typic Fragixeralfs do not have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. An Ap

horizon or subhorizons of comparable thickness that have the

color of a mollic epipedon are considered atypical and define

the Mollic subgroup.

In many Fragixeralfs the fragipan is in the argillic horizon;

above the fragipan, there is a cambic horizon that is separated

from the pan by an eluvial horizon. These extra horizons form

the basis for defining intergrades to Fragixerepts.

Andic and Vitrandic Fragixeralfs.—These soils are like

Typic Fragixeralfs, but they have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. In the

United States, these soils occur in Idaho. They are permitted,

but not required, to have redox depletions and also color value

of 3 or less, moist, and 5 or less, dry, in surface horizons, after

mixing to a depth of 15 cm. These soils are not extensive.

Aquic Fragixeralfs.—These soils are like Typic

Fragixeralfs, but they have, in one or more horizons within 40

cm of the mineral soil surface, redox depletions with chroma of

2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Fragixeralfs are
258 Soil Taxonomy

intergrades between Fragiaqualfs and Fragixeralfs. They are rare

in the United States.

Inceptic Fragixeralfs.—These soils are like Typic

Fragixeralfs, but, above the fragipan, they do not have a distinct

argillic horizon that has clay films on some vertical and

horizontal faces of peds. They have, above the fragipan, a

brown or strong brown, unmottled horizon that seems more

like a cambic horizon than an argillic horizon. Directly above

the fragipan, there may be a thin eluvial horizon. The prism

faces of the fragipan have thick (more than 1 mm) clay films, or

the fragipan itself also is an argillic horizon.

Mollic Fragixeralfs.—These soils have an Ap horizon that

has a color value, moist, darker than 4 and a color vaue, dry,

darker than 6, or they have these color values to a depth of 18

cm, after mixing. These soils are permitted, but not required, to

have redox depletions that have chroma of 2 or less within 40

cm of the soil surface. The epipedon is mollic or approaches

the properties of a mollic epipedon.

Haploxeralfs

These are the Xeralfs that have an argillic or kandic horizon

that is relatively thin, has a clear or gradual upper boundary, or

has a loamy particle-size class throughout. These soils are not

dark red or dusky red throughout. They do not have a natric

horizon and do not have a duripan or fragipan with an upper

boundary within 100 cm of the mineral soil surface. They have

neither a petrocalcic horizon nor one or more horizons in

which plinthite either forms a continuous phase or constitutes

one-half or more of the volume within 150 cm of the soil

surface. Many Haploxeralfs formed in late-Pleistocene deposits

or on erosional surfaces of that age. Their parent materials may

be either acidic or basic. These soils are extensive in the areas

of Xeralfs in the Western United States.

Definition

Haploxeralfs are the Xeralfs that:

1. Do not have a natric horizon;

2. Do not have a duripan or fragipan with an upper boundary

within 100 cm of the mineral soil surface;

3. Do not have plinthite that forms a continuous phase or that

constitutes more than half the matrix within one or more

horizons within 150 cm of the mineral soil surface;

4. Do not have a petrocalcic horizon with its upper boundary

within 150 cm of the soil surface;

5. Have a densic, lithic, or paralithic contact within 150 cm

of the mineral soil surface or have an argillic or kandic horizon

that has either:

a. Within 150 cm of the mineral soil surface, either:

(1) A clay decrease with increasing depth of 20 percent

or more (relative) from the maximum clay content; or

(2) Less than 5 percent (by volume) skeletans on faces

of peds in the layer that has a 20 percent lower clay

content or, below that layer, a clay increase of less than 3

percent (absolute) in the fine-earth fraction; or

b. A base at a depth of less than 150 cm;

6. Have a densic, lithic, or paralithic contact within 50 cm of

the mineral soil surface or have an argillic or kandic horizon

that has:

a. Less than 35 percent clay in all parts; or

b. At its upper boundary, a clay increase, in the fine-earth

fraction, of both less than 20 percent (absolute) within a

vertical distance of 7.5 cm and of less than 15 percent

(absolute) within a vertical distance of 2.5 cm;

7. Have, in the upper 100 cm of the argillic or kandic horizon

or throughout the entire argillic or kandic horizon if less than

100 cm thick, less than 50 percent colors that have hue of

2.5YR or redder or one of the following:

a. Value, moist, of 4 or more; or

b. Dry value 2 or more units higher than the moist value.

Key to Subgroups

JDGA. Haploxeralfs that have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. A color value, moist, of 3 or less and 0.7 percent or

more organic carbon either throughout an Ap horizon or

throughout the upper 10 cm of an A horizon.

Lithic Mollic Haploxeralfs

JDGB. Other Haploxeralfs that have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. An argillic or kandic horizon that is discontinuous

horizontally in each pedon.

Lithic Ruptic-Inceptic Haploxeralfs

JDGC. Other Haploxeralfs that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Haploxeralfs

JDGD. Other Haploxeralfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or
Alfisols 259

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower.

Vertic Haploxeralfs

JDGE. Other Haploxeralfs that have both:

1. In one or more horizons within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Haploxeralfs

JDGF. Other Haploxeralfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Haploxeralfs

JDGG. Other Haploxeralfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more.

Vitrandic Haploxeralfs

JDGH. Other Haploxeralfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of

the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm or

more thick; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic or kandic

horizon if its upper boundary is within 50 cm of the

mineral soil surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic or kandic horizon is 50 cm or

more below the mineral soil surface.

Fragiaquic Haploxeralfs

JDGI. Other Haploxeralfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. An argillic or kandic horizon that has a base saturation

(by sum of cations) of less than 75 percent in one or more

subhorizons within its upper 75 cm or above a densic, lithic,

or paralithic contact, whichever is shallower.

Aquultic Haploxeralfs

JDGJ. Other Haploxeralfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Haploxeralfs

JDGK. Other Haploxeralfs that have an exchangeable sodium

percentage of 15 or more (or a sodium adsorption ratio of 13 or

more) in one or more subhorizons of the argillic or kandic

horizon.

Natric Haploxeralfs

JDGL. Other Haploxeralfs that have fragic soil properties:
260 Soil Taxonomy

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Haploxeralfs

JDGM. Other Haploxeralfs that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or more

subhorizons with a thickness of 7.5 to 20 cm, each layer with

an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Haploxeralfs

JDGN. Other Haploxeralfs that have a sandy particle-size

class throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Haploxeralfs

JDGO. Other Haploxeralfs that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Haploxeralfs

JDGP. Other Haploxeralfs that have a calcic horizon that has

its upper boundary within 100 cm of the mineral soil surface.

Calcic Haploxeralfs

JDGQ. Other Haploxeralfs that have:

1. An argillic, kandic, or natric horizon that is 35 cm or

less thick; and

2. No densic, lithic, or paralithic contact within 100 cm of

the mineral soil surface.

Inceptic Haploxeralfs

JDGR. Other Haploxeralfs that have an argillic or kandic

horizon that has a base saturation (by sum of cations) of less

than 75 percent in one or more subhorizons within its upper 75

cm or above a densic, lithic, or paralithic contact, whichever is

shallower.

Ultic Haploxeralfs

JDGS. Other Haploxeralfs that have a color value, moist, of 3

or less and 0.7 percent or more organic carbon either

throughout an Ap horizon or throughout the upper 10 cm of an

A horizon.

Mollic Haploxeralfs

JDGT. Other Haploxeralfs.

Typic Haploxeralfs

Definition of Typic Haploxeralfs

Typic Haploxeralfs are the Haploxeralfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Have an A horizon that, throughout its upper 10 cm, has a

color value, moist, of 4 or more or has less than 0.7 percent

organic carbon in some part or have an Ap horizon that has a

color value, moist, of 4 or more or contains less than 0.7

percent organic carbon;

3. Do not have a lithic contact within 50 cm of the soil

surface;

4. Have exchangeable sodium that is less than 15 percent of

the CEC (at pH 8.2) throughout the argillic horizon;

5. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the soil surface;

6. Have an argillic or kandic horizon that has a base

saturation (by sum of cations) of 75 percent or more throughout

the upper 75 cm or to a densic, lithic, or paralithic contact,

whichever is shallower;

7. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

8. Have an argillic or kandic horizon that is finer than the

sandy particle-size class in some part of the upper 75 cm if the

argillic or kandic horizon is more than 75 cm thick or in any

part if the argillic or kandic horizon is less than 75 cm thick;

9. Do not have a calcic horizon that has its upper boundary

within the upper 100 cm of the mineral soil surface;
Alfisols 261

10. Have an exchangeable sodium percentage of less than 15

(or a sodium adsorption ratio of less than 13) in all subhorizons

of the argillic or kandic horizon;

11. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention, and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

12. Do not have an argillic horizon that:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon;

13. Have an argillic or kandic horizon that is more than 35

cm thick; and

14. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Haploxeralfs.—The central concept or Typic subgroup

of Haploxeralfs is fixed on freely drained soils that are deep or

moderately deep to hard rock, that have high base saturation but

little sodium on the exchange complex, and that have little or no

plinthite. In addition, the argillic horizon is 35 cm or more thick,

does not consist of lamellae, and has a particle-size class finer

than sandy. Typic Haploxeralfs do not have cracks and

slickensides or wedge-shaped aggregates or a linear extensibility

of 6.0 cm or more.

Soils that have redox depletions with low chroma at a

shallow depth and that have ground water during the growing

season are excluded from Typic Haploxeralfs because these

properties are shared with Aqualfs. Soils that have a large

volume of fragic soil properties are excluded because they are

considered intergrades to Fragixeralfs. Soils that have an Ap

horizon or a moderately thick A horizon that has the color and

organic-matter content of a mollic epipedon are excluded

because these properties are shared with Mollisols. A shallow

lithic contact defines the Lithic subgroups, a convention used

throughout this taxonomy.

Soils that contain exchangeable sodium in the amount

adequate for a natric horizon are excluded from Typic

Haploxeralfs because this important property is shared with

Natrixeralfs. Soils that contain plinthite are excluded because

plinthite is a property of Plinthoxeralfs. A base saturation that

is only moderately high is considered atypical and defines the

Ultic subgroup. Soils that have cracks and slickensides or

wedge-shaped aggregates are excluded because these properties

are shared with Vertisols. An argillic horizon composed

entirely of thin lamellae is considered atypical and defines the

Psammentic subgroup. A moderately shallow calcic horizon

also is considered atypical and defines the Calcic subgroup.

Typic Haploxeralfs are extensive in the central and coastal

valleys and adjacent foothills of California in the United States.

They are on late-Pleistocene terraces and fans or dissected

upland surfaces. Where slopes are suitable, the soils are

irrigated and intensively farmed. Other areas are used for

grazing or woodland.

Andic and Vitrandic Haploxeralfs.—These soils are like

Typic Haploxeralfs, but they have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. They

are permitted, but not required, to have a color value of 3 or

less, moist, and 5 or less, dry, in surface horizons, after mixing

to a depth of 15 cm. In the United States, these soils occur

mostly in Washington, Idaho, Oregon, and California. The

temperature regimes are mostly mesic or frigid. The native

vegetation was primarily a coniferous forest. These soils are

moderately extensive in the United States. They are used
262 Soil Taxonomy

mostly as forest, but some have been cleared and are used as

cropland or pasture.

Aquandic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. They

have, in one or more horizons within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage). They are permitted, but not required, to have a color

value of 3 or less, moist, and 5 or less, dry, in surface horizons,

after mixing to a depth of 15 cm. Aquandic Haploxeralfs are not

extensive.

Aquic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have, in one or more horizons within 75

cm of the mineral soil surface, redox depletions with chroma of

2 or less and also aquic conditions for some time in normal

years (or artificial drainage). In addition, they are permitted,

but not required, to have an A horizon that, throughout the

upper 10 cm, has a color value, moist, of 3 or less and has more

than 0.7 percent organic carbon or to have an Ap horizon that

has a color value, moist, of 3 or less and has more than 0.7

percent organic carbon. These soils are not extensive. They are

mostly in California and Washington. Most of them have a

clayey argillic horizon that has low hydraulic conductivity.

Slopes range considerably. The native vegetation was primarily

a coniferous forest in Washington and grass and shrubs in

California. The soils that have suitable slopes are used mainly

as cropland.

Aquultic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have, in one or more horizons within 75

cm of the mineral soil surface, redox depletions with chroma of

2 or less and also aquic conditions for some time in normal

years (or artificial drainage). They have a base saturation (by

sum of cations) that is less than 75 percent in some subhorizon

within 75 cm of the upper boundary of the argillic or kandic

horizon. In addition, they are permitted, but not required, to

have an A horizon that, throughout the upper 10 cm, has a

color value, moist, of 3 or less and has more than 0.7 percent

organic carbon or to have an Ap horizon that has a color value,

moist, of 3 or less and has more than 0.7 percent organic

carbon. These soils are of small extent, mostly in Oregon. They

are intergrades between Haploxeralfs and Aquults. Most

Aquultic Haploxeralfs have a clayey argillic horizon that has

low hydraulic conductivity. The native vegetation was

primarily forest. Slopes are mostly gentle, and many of the

soils have been cleared and are used as cropland.

Calcic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have a calcic horizon that has its upper

boundary within 100 cm of the soil surface. They are known to

occur in Idaho and Utah in the United States. They are not

extensive.

Fragiaquic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have redox depletions with low chroma

and aquic conditions at a shallow depth for some time in normal

years. In addition, they have fragic soil properties in 30 percent

or more of the volume of a layer 15 cm or more thick that has its

upper boundary within 100 cm of the mineral soil surface or in 60

percent or more of the volume of a layer 15 cm or more thick

anywhere in the soils. These soils are not extensive in the

United States.

Fragic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have fragic soil properties in 30 percent

or more of the volume of a layer 15 cm or more thick that has

its upper boundary within 100 cm of the mineral soil surface or

in 60 percent or more of the volume of a layer 15 cm or more

thick anywhere in the soils. These soils are not extensive in the

United States.

Inceptic Haploxeralfs.—These soils are like Typic

Haploxeralfs in defined properties, but they have an argillic or

kandic horizon that is 35 cm or less thick and have no densic,

lithic, or paralithic contact within 100 cm of the soil surface.

They may also have an A horizon that, throughout its upper 10

cm, has a color value, moist, of 3 or less and has 0.7 percent or

more organic carbon or an Ap horizon that has both a color

value, moist, of 3 or less and 0.7 percent or more organic

carbon. These soils are not extensive in the United States.

Lamellic Haploxeralfs.—These soils are like Typic

Haploxeralfs in defined properties, but they have an argillic

horizon that consists of lamellae or partially of lamellae. Most

Lamellic Haploxeralfs have a sandy particle-size class. The

upper several lamellae are commonly broken or discontinuous

horizontally. Lamellic Haploxeralfs are allowed to have an Ap

horizon that has a color value, moist, of 3 or less or upper

horizons that have a color value, moist, of less than 4 after the

surface soil has been mixed to a depth of 15 cm. These soils are

not extensive in the United States.

Lithic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have a lithic contact within 50 cm of the

soil surface. In addition, they are permitted, but not required,

to have a base saturation (by sum of cations) that is less than

75 percent in some subhorizon within 75 cm of the upper

boundary of the argillic or kandic horizon. These soils are not

extensive in the United States. They are mostly in California

and Idaho. The vegetation is mostly grasses and shrubs. Some

areas support widely spaced trees. These soils are used as

rangeland.

Lithic Mollic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have a lithic contact within 50 cm of the

soil surface and also have an A horizon that, throughout its

upper 10 cm, has a color value, moist, of 3 or less and has 0.7

percent or more organic carbon; rarely, they have an Ap

horizon that has a color value, moist, of 3 or less and has 0.7

percent or more organic carbon. These soils are permitted, but

not required, to have a base saturation (by sum of cations) that
Alfisols 263

is less than 75 percent in some subhorizon within 75 cm of the

upper boundary of the argillic or kandic horizon. They are

mostly in California and Idaho in the United States. The

vegetation is mostly grasses and shrubs. Some areas support

widely spaced trees. These soils are used mainly as rangeland.

Lithic Ruptic-Inceptic Haploxeralfs.—These soils are like

Typic Haploxeralfs, but they have a lithic contact within 50 cm

of the soil surface. The upper boundary of the contact is

irregular. The major part of the pedon has an argillic or kandic

horizon. Where the lithic contact is closest to the soil surface,

however, only a cambic horizon is evident. These soils are rare

in the United States.

Mollic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have an A horizon that, throughout its

upper 10 cm, has a color value, moist, of 3 or less and has 0.7

percent or more organic carbon; rarely, they have an Ap

horizon that has both a color value, moist, of 3 or less and 0.7

percent or more organic carbon. The epipedon of these soils

meets all of the requirements for a mollic epipedon as a rule,

but it is both massive and hard or very hard when dry. These

soils are extensive in the United States. They are intergrades

between Haploxeralfs and Argixerolls. Their slopes range from

nearly level to very strong. Where slopes are suitable, many of

the soils are cultivated. The soils that have strong slopes are

mainly under forest vegetation.

Natric Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have 15 percent or more saturation with

sodium in some part of the argillic horizon. The argillic

horizon would be a natric horizon if it had prismatic or

columnar structure or if it had blocky structure and albic

materials extending more than 2.5 cm into the horizon. These

soils are not extensive in the United States.

Plinthic Haploxeralfs.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 150 cm of

the mineral soil surface. These soils are not known to occur in

the United States.

Psammentic Haploxeralfs.—These soils have an argillic

horizon that has a sandy particle-size class (loamy fine sand or

coarser) throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick. These soils are rare in the United States. Most formed on

old stabilized sand dunes, and their slopes are gentle or

moderate. Most of the soils are used for grazing.

Ultic Haploxeralfs.—These soils are like Typic

Haploxeralfs, but they have a base saturation (by sum of

cations) that is less than 75 percent in some subhorizon within

75 cm of the upper boundary of the argillic or kandic horizon.

In addition, they are permitted, but not required, to have an A

horizon that, throughout its upper 10 cm, has a color value,

moist, of 3 or less and has 0.7 percent or more organic carbon

or to have an Ap horizon that has a color value, moist, of 3 or

less and has 0.7 percent or more organic carbon. These soils

are extensive. They are mostly in California, Oregon,

Washington, and Idaho. They occur in areas where Xeralfs

intergrade toward Ultisols and in areas where the parent

materials have a component of volcanic ash. Slopes range from

gentle to very strong. Most Ultic Haploxeralfs with strong or

very strong slopes are in forests and in some areas are grazed

for short periods. Many Ultic Haploxeralfs with gentle slopes

have been cleared and are used as cropland, but some are used

as pasture or are in forests.

Vertic Haploxeralfs.—These soils are like Typic Haploxeralfs,

but they are high in content of expanding clays and have cracks

5 mm or more wide, slickensides, wedge-shaped aggregates, or a

linear extensibility of 6.0 cm or more between the mineral soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact, whichever is shallower. These soils are rare in

the United States and are considered to be transitional to

Vertisols.

Natrixeralfs

Natrixeralfs are the Xeralfs that have a natric horizon but do

not have a duripan. They are not extensive. They support a

sparse vegetation that commonly consists of salt-tolerant

grasses and forbs. They were considered Solonetz soils, Soloth

soils, and transitional forms in the 1938 classification.

Definition

Natrixeralfs are the Xeralfs that:

1. Have a natric horizon;

2. Do not have a duripan within 100 cm of the soil surface.

Key to Subgroups

JDBA. Natrixeralfs that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Natrixeralfs

JDBB. Other Natrixeralfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Natrixeralfs

JDBC. Other Natrixeralfs.

Typic Natrixeralfs
264 Soil Taxonomy

Definition of Typic Natrixeralfs

Typic Natrixeralfs are the Natrixeralfs that:

1. Do not have, in any horizon within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also aquic

conditions; and

2. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the mineral soil surface; or

b. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or

a densic, lithic, or paralithic contact, whichever is

shallower.

Description of Subgroups

Typic Natrixeralfs.—The central concept or Typic

subgroup of Natrixeralfs is fixed on the most freely drained

soils of this great group. None of these soils are freely drained

because their low hydraulic conductivity results in perched

ground water above the natric horizon in many years. Some

Natrixeralfs have ground water below as well as above the

natric horizon and have redox depletions with low chroma.

These features cause the soils to be excluded from the Typic

subgroup because they are properties shared with Aqualfs.

Typic Natrixeralfs are not extensive in the United States.

They are mostly in California and Montana. Their slopes are

mostly gentle. The soils developed under grass, shrubs, and

forbs. Some of the soils, mostly those in California, are

reclaimed and used as cropland. The native plants are used for

grazing.

Aquic Natrixeralfs.—These soils are like Typic

Natrixeralfs, but they have, in one or more horizons within 75

cm of the mineral soil surface, redox depletions with chroma of

2 or less and also aquic conditions for some time in normal

years (or artificial drainage). These soils are rare in the United

States. Their slopes are mostly nearly level. The soils

developed under grass, shrubs, and forbs. Some of the soils,

mostly those in California, are reclaimed and used as cropland.

The native plants are used for grazing.

Vertic Natrixeralfs.—These soils are like Typic

Natrixeralfs, but they are high in content of expanding clays

and have cracks 5 mm or more wide, slickensides, wedgeshaped aggregates, or a linear extensibility of 6.0 cm or more

between the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is shallower.

These soils are rare in the United States. They are considered

to be transitional to Vertisols.

Palexeralfs

Palexeralfs are the Xeralfs that have a petrocalcic horizon or

an argillic or kandic horizon that is thick or that has, at its

upper boundary, both a clayey, clayey-skeletal, fine, or veryfine particle-size class and a large clay increase. Many of these

soils have some plinthite in their lower horizons, but this

feature is rare in the United States. Palexeralfs are in relatively

stable landscape positions on gentle slopes, and most began

their genesis before the late Pleistocene. During pluvial periods

of the Pleistocene, carbonates appear to have been almost

completely removed from the argillic or kandic horizon of most

of these soils, but some of the soils appear to have been

recalcified later.

Most Palexeralfs formed in acid or in moderately basic parent

materials, but some formed in materials as basic as basalt. The

native vegetation on the warmest Palexeralfs in the United States

was a mixture of annual grasses, forbs, and woody shrubs. The

native vegetation on the coolest Palexeralfs was mostly a

coniferous forest. Palexeralfs are moderately extensive both in

the United States and in some other parts of the world.

Definition

Palexeralfs are the Xeralfs that:

1. Have a petrocalcic horizon that has its upper boundary

within 150 cm of the mineral soil surface;

2. Have no densic, lithic, or paralithic contact within 150 cm

of the mineral soil surface and have an argillic or kandic

horizon that has both:

a. Within 150 cm of the mineral soil surface, either:

(1) With increasing depth, no clay decrease of 20

percent or more (relative) from the maximum clay

content; or

(2) 5 percent or more (by volume) skeletans on faces of

peds in the layer that has a 20 percent lower clay content

and, below that layer, a clay increase of 3 percent or

more (absolute) in the fine-earth fraction; and

b. A base at a depth of 150 cm or more;

3. Have no densic, lithic, or paralithic contact within 50 cm

of the mineral soil surface and have an argillic or kandic

horizon that has within 15 cm of its upper boundary both:

a. A clayey, clayey-skeletal, fine, or very-fine particle-size

class; and

b. A clay increase, in the fine-earth fraction, of either 20

percent or more (absolute) within a vertical distance of 7.5

cm or of 15 percent or more (absolute) within a vertical

distance of 2.5 cm; and
Alfisols 265

4. Do not have a duripan or fragipan with an upper boundary

within 100 cm of the mineral soil surface;

5. Do not have a natric horizon;

6. Do not have plinthite that forms a continuous phase

or that constitutes more than one-half the matrix within

one or more horizons within 150 cm of the mineral soil

surface;

7. Have, in the upper 100 cm of the argillic or kandic horizon or

throughout the entire argillic or kandic horizon if less than 100

cm thick, less than 50 percent colors that have hue of 2.5YR or

redder or one of the following:

a. Value, moist, of 4 or more; or

b. Dry value 2 or more units higher than the moist value.

Key to Subgroups

JDFA. Palexeralfs that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Palexeralfs

JDFB. Other Palexeralfs that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Palexeralfs

JDFC. Other Palexeralfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Palexeralfs

JDFD. Other Palexeralfs that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Palexeralfs

JDFE. Other Palexeralfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. Redox depletions with chroma of 2 or less in layers that

also have aquic conditions in normal years (or artificial

drainage) either:

a. Within the upper 25 cm of the argillic or kandic

horizon if its upper boundary is within 50 cm of the

mineral soil surface; or

b. Within 75 cm of the mineral soil surface if the upper

boundary of the argillic or kandic horizon is 50 cm or

more below the mineral soil surface.

Fragiaquic Palexeralfs

JDFF. Other Palexeralfs that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with
266 Soil Taxonomy

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Palexeralfs

JDFG. Other Palexeralfs that have a petrocalcic horizon that

has its upper boundary within 150 cm of the mineral soil

surface.

Petrocalcic Palexeralfs

JDFH. Other Palexeralfs that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Palexeralfs

JDFI. Other Palexeralfs that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Palexeralfs

JDFJ. Other Palexeralfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic or kandic horizon

at a depth of 50 cm or more.

Arenic Palexeralfs

JDFK. Other Palexeralfs that have an exchangeable sodium

percentage of 15 or more (or a sodium adsorption ratio of 13 or

more) in one or more horizons within 100 cm of the mineral

soil surface.

Natric Palexeralfs

JDFL. Other Palexeralfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Palexeralfs

JDFM. Other Palexeralfs that have a calcic horizon within 150

cm of the mineral soil surface.

Calcic Palexeralfs

JDFN. Other Palexeralfs that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Palexeralfs

JDFO. Other Palexeralfs that have an argillic or kandic

horizon that has a base saturation (by sum of cations) of less

than 75 percent throughout.

Ultic Palexeralfs

JDFP. Other Palexeralfs with an argillic or kandic horizon

that has, in the fine-earth fraction, either or both:

1. Less than 35 percent clay throughout all subhorizons

within 15 cm of its upper boundary; or

2. At its upper boundary, a clay increase of less than 20

percent (absolute) within a vertical distance of 7.5 cm and of

less than 15 percent (absolute) within a vertical distance of

2.5 cm.

Haplic Palexeralfs

JDFQ. Other Palexeralfs that have a color value, moist, of 3

or less and 0.7 percent or more organic carbon either

throughout an Ap horizon or throughout the upper 10 cm of an

A horizon.

Mollic Palexeralfs

JDFR. Other Palexeralfs.

Typic Palexeralfs

Definition of Typic Palexeralfs

Typic Palexeralfs are the Palexeralfs that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Have neither a calcic nor a petrocalcic horizon within 150

cm of the soil surface;

3. Have an A horizon that, throughout its upper 10 cm, has a

color value, moist, of 4 or more or contains less than 0.7

percent organic carbon or have an Ap horizon that has a color

value, moist, of 4 or more or contains less than 0.7 percent

organic carbon;

4. Have an argillic or kandic horizon that has at least 75

percent base saturation (by sum of cations) in some part;

5. Have an argillic or kandic horizon in which some

subhorizon in the upper 15 cm has 35 percent or more

clay and there is an increase of at least 20 percent clay

(absolute) within a vertical distance of 7.5 cm or of at least
Alfisols 267

15 percent clay (absolute) within 2.5 cm at the upper

boundary;

6. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the soil surface;

7. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

8. Have less than 15 percent saturation with sodium in all

subhorizons within 100 cm of the soil surface;

9. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

10. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an overlying

eluvial horizon; and

11. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Palexeralfs.—The central concept or Typic subgroup

of Palexeralfs is fixed on moderately deep or deep, freely

drained soils that have an argillic or kandic horizon that has an

abrupt upper boundary, 35 percent or more clay in the upper

part, and high base saturation. These soils have neither a calcic

nor a petrocalcic horizon within 150 cm of the mineral soil

surface. They also have little or no plinthite, and they do not

have cracks and slickensides or wedge-shaped aggregates.

Soils that have redox depletions with low chroma and

ground water at a moderate depth are excluded from the Typic

subgroup because these properties are shared with Aqualfs.

Soils that have a calcic or petrocalcic horizon are excluded

because these horizons are interpreted to be evidence of

recalcification of the soils. Soils that have a moderately thin A

horizon or an Ap horizon that has the color and organic-matter

content of a mollic epipedon are excluded because they

approach the properties of Mollisols. A moderately low base

saturation is associated with relatively high precipitation,

either past or present, and is used to define the Ultic subgroup.

A clear or gradual upper boundary of the argillic or kandic

horizon is considered atypical in Palexeralfs, and a soil that

has one is excluded from the Typic subgroup. Plinthite is a

property shared with Plinthoxeralfs, and a soil that contains

plinthite is excluded from the Typic subgroup, unless the

amount is very small. Cracks and slickensides or wedge-shaped

aggregates are properties shared with Vertisols and define the

Vertic subgroup. A thick epipedon with a sandy or sandyskeletal particle-size class throughout is considered atypical

and causes soils to be excluded from the Typic subgroup, a

convention that is used elsewhere in this taxonomy.

Typic Palexeralfs are moderately extensive. They are on old

terraces and on foothills, mostly in California in the United

States. Slopes are gentle to steep. Most of these soils are used

as rangeland. Some are used as cropland.

Andic and Vitrandic Palexeralfs.—These soils are like

Typic Palexeralfs, but they have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils are permitted, but not required, to have a color value of 3

or less, moist, and 5 or less, dry, in surface horizons, after

mixing to a depth of 15 cm. In the United States, these soils
268 Soil Taxonomy

occur mostly in Washington and California. The temperature

regimes are mostly mesic or frigid. The native vegetation was

primarily a coniferous forest. These soils are moderately

extensive in the United States. They are used mostly as forest,

but some have been cleared and are used as cropland or

pasture.

Aquandic Palexeralfs.—These soils are like Typic

Palexeralfs, but they have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils have, in one or more horizons within 75 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). They are permitted, but not required, to

have a color value of 3 or less, moist, and 5 or less, dry, in

surface horizons, after mixing to a depth of 15 cm. Aquandic

Palexeralfs are not extensive.

Arenic Palexeralfs.—These soils have a layer, starting at

the mineral soil surface, that is 50 cm or more thick and has a

sandy or sandy-skeletal particle-size class throughout its

thickness. These soils are not known to occur in the United

States. The subgroup has been established for use in other

countries.

Aquic Palexeralfs.—These soils are like Typic Palexeralfs,

but they have, in one or more horizons within 75 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). In addition, they are permitted to have an

A horizon that, throughout its upper 10 cm, has a color value,

moist, of 3 or less and contains more than 0.7 percent organic

carbon or to have an Ap horizon that has a color value, moist,

of 3 or less and contains more than 0.7 percent organic

carbon. Aquic Palexeralfs are of small extent, mostly in

Washington and Oregon in the United States. Their slopes are

nearly level. The native vegetation is primarily a coniferous

forest.

Calcic Palexeralfs.—These soils are like Typic Palexeralfs,

but they have a calcic horizon that has its upper boundary

within 150 cm of the mineral soil surface. They are rare in the

United States and are known to occur only in California. The

subgroup may also be needed for use in other countries.

Fragiaquic Palexeralfs.—These soils are like Typic

Palexeralfs, but they have redox depletions with low chroma

and aquic conditions at a shallow depth for some time in

normal years. In addition, they have fragic soil properties in 30

percent or more of the volume of a layer 15 cm or more thick

that has its upper boundary within 100 cm of the mineral soil

surface or in 60 percent or more of the volume of a layer 15 cm

or more thick anywhere in the soils. These soils are not

extensive in the United States.

Fragic Palexeralfs.—These soils are like Typic Palexeralfs,

but they have fragic soil properties in 30 percent or more of the

volume of a layer 15 cm or more thick that has its upper

boundary within 100 cm of the mineral soil surface or in 60

percent or more of the volume of a layer 15 cm or more thick

anywhere in the soils. These soils are not extensive in the

United States.

Haplic Palexeralfs.—These soils are like Typic Palexeralfs,

but they do not have an argillic or kandic horizon that has an

abrupt upper boundary and 35 percent or more clay in the upper

part. These soils are not extensive in the United States.

Lamellic Palexeralfs.—These soils are like Typic Palexeralfs,

but they have an argillic horizon that consists of lamellae or

partially of lamellae. Most of these soils do not have an argillic

or kandic horizon that has an abrupt upper boundary and 35

percent or more clay in the upper part. The upper several

lamellae are commonly broken or discontinuous horizontally.

These soils are not extensive in the United States.

Mollic Palexeralfs.—These soils are like Typic Palexeralfs,

but they have an A horizon that, throughout its upper 10 cm,

has a color value, moist, of 3 or less and contains more than

0.7 percent organic carbon or have an Ap horizon that has a

color value, moist, of 3 or less and contains more than 0.7

percent organic carbon. Mollic Palexeralfs have an argillic or

kandic horizon that has an abrupt upper boundary, 35 percent

or more clay in the upper part, and high base saturation. They

are intergrades between Palexeralfs and Palexerolls. Their

slopes are gentle or moderate. The native vegetation is

primarily rangeland or savanna with widely spaced oak or

coniferous trees. Mollic Palexeralfs are of moderate extent in

the United States. Where slopes are suitable, some of these

soils are used as cropland. Many of the soils are used for

grazing.

Natric Palexeralfs.—These soils have 15 percent or more

saturation with sodium in one or more horizons within 100 cm

of the mineral soil surface. Some of these soils have columnar

or prismatic structure in the argillic horizon, but the horizon

that contains sodium is too deep in the soils to be a natric

horizon. Natric Palexeralfs are rare in the United States.

Petrocalcic Palexeralfs.—These soils are like Typic

Palexeralfs, but they have a petrocalcic horizon that has an

upper boundary within 150 cm of the soil surface. In addition,

the argillic or kandic horizon is permitted, but not required, to

have less than 35 percent clay in all subhorizons, and there

may be, at the upper boundary, an increase in clay content of

less than 20 percent (absolute) within a vertical distance of 7.5

cm and an increase of less than 15 percent clay (absolute)

within a vertical distance of 2.5 cm. These soils are rare in the

United States. The subgroup has been established for use in

other countries.

Plinthic Palexeralfs.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 150 cm of

the mineral soil surface. They are not known to occur in the

United States.

Psammentic Palexeralfs.—These soils have an argillic
Alfisols 269

horizon that has a sandy particle-size class throughout the

upper 75 cm or throughout the entire argillic horizon if it is less

than 75 cm thick. They are rare in the United States.

Ultic Palexeralfs.—These soils are like Typic Palexeralfs,

but they have a base saturation that is less than 75 percent in

all parts of the argillic or kandic horizon. In addition, the

argillic or kandic horizon is permitted, but not required, to

have less than 35 percent clay in all subhorizons, and there

may be, at the upper boundary, an increase of less than 20

percent (absolute) in clay content within a vertical distance of

7.5 cm and an increase of less than 15 percent clay (absolute)

within a vertical distance of 2.5 cm. These soils also are

permitted to have an A horizon that, throughout its upper 10

cm, has a color value, moist, of 3 or less and contains more than

0.7 percent organic carbon or to have an Ap horizon that has a

color value, moist, of 3 or less and contains more than 0.7

percent organic carbon. Ultic Palexeralfs are moderately

extensive in California, Oregon, and Washington in the United

States. The native vegetation is primarily a coniferous forest but

is rangeland or savanna with widely spaced oak or coniferous

trees on the warmest and driest sites. Slopes are gentle to steep.

The primary uses of these soils are timber production and

grazing. Some of the soils are used as cropland, much of which

is irrigated.

Vertic Palexeralfs.—These soils are high in content of

expanding clays and have cracks 5 mm or more wide,

slickensides, wedge-shaped aggregates, or a linear extensibility

of 6.0 cm or more between the mineral soil surface and either a

depth of 100 cm or a densic, lithic, or paralithic contact,

whichever is shallower. These soils are considered to be

transitional to Vertisols. They are rare in the United States. The

subgroup has been established mainly for use in other

countries.

Plinthoxeralfs

Plinthoxeralfs are the Xeralfs that have one or more horizons

within 150 cm of the mineral soil surface in which plinthite either

forms a continuous phase or constitutes one-half or more of the

volume. There are few of these soils in the United States, but the

soils are moderately extensive in other parts of the world.

Subgroups have not been developed.

Definition

Plinthoxeralfs are the Xeralfs that:

1. Have one or more horizons within 150 cm of the mineral soil

surface in which plinthite either forms a continuous phase or

constitutes one-half or more of the volume;

2. Have neither a fragipan nor a duripan with an upper

boundary within 100 cm of the mineral soil surface;

3. Do not have a natric horizon.

Key to Subgroups

JDDA. All Plinthoxeralfs (provisionally).

Typic Plinthoxeralfs

Rhodoxeralfs

Rhodoxeralfs are the more or less dark red Xeralfs that formed

in areas of limestone, basalt, and other highly basic parent

materials. As a group, these soils are remarkably uniform in

virtually all properties, except for depth to rock. A few that are

receiving carbonates may have a calcic or petrocalcic horizon

below the argillic or kandic horizon. Rhodoxeralfs are rare in the

United States.

Definition

Rhodoxeralfs are the Xeralfs that:

1. Have, in all subhorizons in the upper 100 cm of the argillic

or kandic horizon or throughout the entire argillic or kandic

horizon if less than 100 cm thick, more than 50 percent colors

that have all of the following:

a. Hue of 2.5YR or redder; and

b. Value, moist, of 3 or less; and

c. Dry value no more than 1 unit higher than the moist

value;

2. Have neither a fragipan nor a duripan that has its upper

boundary within 100 cm of the mineral soil surface;

3. Do not have a natric horizon;

4. Do not have, within 150 cm of the mineral soil surface,

plinthite forming a continuous phase or constituting one-half

or more of the volume.

Key to Subgroups

JDEA. Rhodoxeralfs that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Rhodoxeralfs

JDEB. Other Rhodoxeralfs that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Rhodoxeralfs
270

JDEC. Other Rhodoxeralfs that have a petrocalcic horizon

that has its upper boundary within 150 cm of the mineral soil

surface.

Petrocalcic Rhodoxeralfs

JDED. Other Rhodoxeralfs that have a calcic horizon that

has its upper boundary within 150 cm of the mineral soil

surface.

Calcic Rhodoxeralfs

JDEE. Other Rhodoxeralfs that have an argillic or kandic

horizon that is either less than 15 cm thick or is discontinuous

horizontally in each pedon.

Inceptic Rhodoxeralfs

JDEF. Other Rhodoxeralfs.

Typic Rhodoxeralfs

Definition of Typic Rhodoxeralfs

Typic Rhodoxeralfs are the Rhodoxeralfs that:

1. Have an argillic or kandic horizon that is more than 15 cm

thick and is horizontally continuous in each pedon;

2. Do not have a lithic contact within 50 cm of the mineral

soil surface;

3. Do not have a petrocalcic horizon that has an upper

boundary within 150 cm of the mineral soil surface;

4. Do not have a calcic horizon that has an upper boundary

within 150 cm of the mineral soil surface; and

5. Do not have one or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Rhodoxeralfs.—The central concept or Typic

subgroup of Rhodoxeralfs is fixed on moderately deep or

deep soils that have an argillic or kandic horizon that is

horizontally continuous throughout each pedon and that do

not have a calcic or petrocalcic horizon shallow enough to be

diagnostic.

Soils in which an argillic horizon is discontinuous

horizontally are excluded from the Typic subgroup because

such a horizon represents weak development. A shallow lithic

contact is used to define the Lithic subgroup, a convention

used throughout this taxonomy. Soils that have a calcic or

petrocalcic horizon are excluded from this subgroup because

these horizons are thought to indicate recalcification

through addition of carbonates that originated outside of the

soils.

Most of the Typic Rhodoxeralfs in the United States

are moderately sloping or strongly sloping and are in

forests or are used for grazing. A few are irrigated and

farmed.

Calcic Rhodoxeralfs.—These soils are like Typic

Rhodoxeralfs, but they have a calcic horizon that has an upper

boundary within 150 cm of the mineral soil surface. They are

not known to occur in the United States. The subgroup is

provided for use in other countries.

Inceptic Rhodoxeralfs.—These soils are like Typic

Rhodoxeralfs in defined properties, but they have an argillic or

kandic horizon that is 35 cm or less thick. They are not known

to occur in the United States. The subgroup is provided for use

in other countries.

Lithic Rhodoxeralfs.—These soils are like Typic

Rhodoxeralfs, but they have a lithic contact within 50 cm of

the mineral soil surface. They are not known to occur in the

United States. The subgroup is provided for use in other

countries.

Petrocalcic Rhodoxeralfs.—These soils are like Typic

Rhodoxeralfs, but they have a petrocalcic horizon that has an

upper boundary within 150 cm of the mineral soil surface.

They are not known to occur in the United States. The

subgroup is provided for use in other countries.

Vertic Rhodoxeralfs.—These soils are high in content of

expanding clays and have cracks 5 mm or more wide,

slickensides, wedge-shaped aggregates, or a linear extensibility

of 6.0 cm or more between the mineral soil surface and either a

depth of 100 cm or a densic, lithic, or paralithic contact,

whichever is shallower. These soils are considered to be

transitional to Vertisols. They are rare in the United States. The

subgroup has been established mainly for use in other

countries.
271

The central concept of an Andisol is that of a soildeveloping in volcanic ejecta (such as volcanic ash,

pumice, cinders, and lava) and/or in volcaniclastic materials,

the colloidal fraction of which is dominated by short-rangeorder minerals or Al-humus complexes. Under some

environmental conditions, weathering of primary aluminosilicates in parent materials of nonvolcanic origin may also

lead to the formation of short-range-order minerals. Some of

these soils also are included in Andisols.

The dominant processes in most Andisols are weathering

and mineral transformation. Translocation within the soils and

accumulation of the translocated compounds are normally

minimal. The accumulation of organic matter, complexed with

aluminum, however, is characteristic of Andisols in some

regimes.

Weathering of primary alumino-silicates has proceeded only

to the point of formation of short-range-order minerals, such as

allophane, imogolite, and ferrihydrite. Commonly, this state

has been perceived as a stage in the transition from

unweathered to the more weathered volcanic material

characteristic of some other soil orders. Under some

conditions, however, the short-range-order minerals achieve a

stability that allows them to persist with little or only very slow

further alteration over long periods.

Andisols may have any diagnostic epipedon, provided that

the minimum requirements for the order are met in and/or

below the epipedon. Andisols may also have any soil moisture

regime and any soil temperature regime. They can occupy any

position on the landscape and can occur at any elevation.

Andisols have andic soil properties in 60 percent of a layer

in the upper part of the soils. The upper part is considered to

start at the mineral soil surface or at the surface of organic soil

materials with andic soil properties and end at a point 60 cm

below the starting point or at a densic, lithic, or paralithic

contact, a duripan, or a petrocalcic horizon, whichever is

shallowest. These soils may have many kinds of diagnostic

horizons below this layer. The soils are considered Andisols if

the criteria for thickness and position of the andic layer or

layers are met, irrespective of the nature of the underlying

material or horizons.

Cultivation of the soils, as in puddling of the surface layer

in areas used for rice paddies, may change some of the

physical properties of the upper part of the soils, such as bulk

density. A soil that, below this disturbed zone, has a layer, at

least 36 cm thick, with andic soil properties meets the

requirements for Andisols. Many Andisols, such as those that

formed in some loess or alluvium, are stratified. Before the

soils are considered Andisols, the layers that meet the

requirements for andic soil properties must have a cumulative

thickness of at least 36 cm within the upper 60 cm.

One of the outstanding features of Andisols is their high

natural productivity. There are exceptions to this very general

statement, but the dominance of physical properties that favor

the growth of most plants, allied to the most common

occurrence of the soils in areas of considerable rainfall, has

resulted in volcanic soils being generally regarded as highly

fertile soils.

Andisols cover more than 124 million hectares, or

approximately 0.8 percent of the earth’s surface. By far, the

most striking pattern in the distribution of Andisols follows the

circum-Pacific Ring of Fire—that concentration of active

tectonic zones and volcanoes along the western coast of the

American continents, both North and South, across the

Aleutian Islands, down the Kamchatka peninsula of Russia,

through Japan, the Philippine Islands, and Indonesia, across

Papua New Guinea, the Solomon Islands, and Vanuatu and

other Pacific Islands to New Zealand. Other distinctive patterns

are associated with the Rift Valley of Africa, the west coast of

Italy, the Hawaiian Islands, the West Indies, Iceland, the

Canary Islands, and other island locations.

Definition of Andisols and Limits Between

Andisols and Soils of Other Orders

Andisols are soils that:

1. Have andic soil properties in 60 percent or more of the

thickness either:

a. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

b. Between either the mineral soil surface or the top of an

CHAPTER 10

Andisols1

1This chapter builds on the preliminary Andisol Proposal (1978) by Guy D. Smith (New

Zealand Soil Bureau Record 96) and represents the work of the International Committee on the

Classification of Andisols (ICOMAND), chaired by Michael L. Leamy, New Zealand Soil

Bureau.
272 Soil Taxonomy

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon;

2. Do not have organic soil materials that meet one or more

of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices2 and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more in normal

years (or are artificially drained), have an upper boundary

within 40 cm of the soil surface, and have a total thickness

of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more;

3. Do not have both a spodic horizon and an albic horizon in

50 percent or more of each pedon;

4. Do not have an Ap horizon containing 85 percent or more

spodic materials; and

5. Do not have:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface.

Limits Between Andisols and Other Soil Orders

The definition of Andisols must provide criteria that

separate Andisols from all other soil orders. The aggregate of

these criteria defines the limits of Andisols in relation to all

other known kinds of soil.

1. Unlike Andisols, Gelisols have:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface.

2. Unlike Andisols, Histosols are soils that:

a. Do not have andic soil properties in 60 percent or more

of the thickness between the soil surface and either a depth

of 60 cm or a densic, lithic, or paralithic contact or duripan

if shallower; and

b. Have organic soil materials that meet one or more of

the following:

(1) Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices2 and directly below these

materials have either a densic, lithic, or paralithic

contact; or

(2) When added with the underlying cindery,

fragmental, or pumiceous material, total 40 cm or more

between the soil surface and a depth of 50 cm; or

(3) Constitute two-thirds or more of the total thickness

of the soil to a densic, lithic, or paralithic contact and

have no mineral horizons or have mineral horizons with

a total thickness of 10 cm or less; or

(4) Are saturated with water for 30 days or more in

normal years (or are artificially drained), have an upper

boundary within 40 cm of the soil surface, and have a

total thickness of either:

(a) 60 cm if three-fourths or more of their volume

consists of moss fibers or if their bulk density, moist,

is less than 0.1 g/cm3; or

(b) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk

density, moist, of 0.1 g/cm3 or more.

3. Unlike Andisols, Spodosols have:

a. Both a spodic horizon and an albic horizon in 50

percent or more of each pedon; or

b. An Ap horizon containing 85 percent or more spodic

materials.

4. Andisols differ from Alfisols, Aridisols, Entisols,

Inceptisols, Mollisols, Oxisols, Ultisols, and Vertisols because

they have andic soil properties in 60 percent or more of the

thickness either:

a. Within 60 cm either of the mineral soil surface or the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

2 Materials that meet the definition of cindery, fragmental, or pumiceous but have more

than 10 percent, by volume, voids that are filled with organic soil materials are considered to be

organic soil materials.
Andisols 273

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Representative Pedon and Data

Following is a description of a representative Andisol. Data

for the pedon identified in this description are given in the

table “Characterization Data for an Andisol.”

Classification: Medial, amorphic, mesic Eutric Fulvudand

Site identification number: 83P0481

Location: Chile

Landform: Terrace

Slope: 1 percent, plane

Elevation: 17 m above m.s.l.

Annual precipitation: 205 cm

Soil moisture regime: Udic

Average annual air temperature: 13 oC

Permeability class: Moderately rapid

Drainage class: Well drained

Depth to water table: More than 200 cm

Land use: Pasture

Stoniness class: 1

Particle-size control section: 0 to 100 cm

Parent material: Ejecta ash

Diagnostic features: An umbric epipedon from a depth of

0 to 27 cm, a cambic horizon from a depth of 27 to

98 cm, and andic soil properties from a depth of 0 to

200 cm

Field moisture: From a depth of 0 to 39 cm—dry; from a depth

of 39 to 200 cm—slightly moist

Described by: T. Cook, W. Luzio, R. Honorato, G. Galindo, W.

Vera, and R. Grez

In the following pedon description, colors are for moist soil

unless otherwise indicated. Field reaction was determined by

use of paper test strips.

Ap1—0 to 4 cm; very dark grayish brown (10YR 3/2) silt

loam, brown (10YR 4/3) dry; strong medium and coarse

granular structure; friable, weakly smeary, slightly sticky

and slightly plastic; many very fine and fine roots; many

very fine and fine interstitial pores; strongly acid (pH 5.3);

abrupt smooth boundary.

Ap2—4 to 27 cm; very dark brown (10YR 2/2) silt loam,

brown (10YR 4/3) dry; moderate very coarse subangular

blocky structure parting to weak coarse granular; friable,

moderately smeary, slightly sticky and slightly plastic;

many very fine and few medium roots; many very fine and

fine interstitial pores; strongly acid (pH 5.3); abrupt

smooth boundary.

2BA—27 to 39 cm; dark yellowish brown (10YR 3/4) silt

loam, brown (10YR 5/3) dry; weak coarse prismatic

structure; very friable, moderately smeary, slightly sticky

and slightly plastic; common very fine and few medium

roots; common coarse and common very fine tubular

pores; few fine cylindrical insect casts; moderately acid

(pH 5.7); 1 percent ejecta pebbles; clear smooth boundary.

2Bw1—39 to 73 cm; dark brown (7.5YR 3/4) silt loam; weak

coarse prismatic structure parting to moderate medium

and coarse subangular blocky; very friable, moderately

smeary, slightly sticky and slightly plastic; common very

fine roots; many very fine and few fine tubular pores;

few fine cylindrical insect casts; moderately acid (pH 5.7);

1 percent ejecta pebbles; clear smooth boundary.

2Bw2—73 to 98 cm; dark brown (10YR 3/3) silt loam;

moderate coarse prismatic structure parting to weak

medium subangular blocky; friable, moderately smeary,

slightly sticky and slightly plastic; few very fine roots;

many fine and medium tubular pores; patchy skeletans

(sand or silt) in root channels and/or pores; moderately

acid (pH 5.7); 1 percent ejecta pebbles; gradual smooth

boundary.

2C1—98 to 160 cm; dark yellowish brown (10YR 3/4) silt

loam; massive; friable, moderately smeary, slightly sticky

and slightly plastic; few very fine roots; many fine and

medium tubular pores; patchy skeletans (sand or silt) in

root channels and/or pores; moderately acid (pH 5.7); clear

irregular boundary.

3C2—160 to 200 cm; dark yellowish brown (10YR 4/4) silt

loam; massive; firm, moderately smeary, sticky and

slightly plastic; few very fine roots; many very fine and

fine and many medium tubular pores; a few thin seams

and masses of uncoated fine sand; moderately acid (pH

5.7).

Key to Suborders

DA. Andisols that have either:

1. A histic epipedon; or

2. In a layer above a densic, lithic, or paralithic contact or in

a layer at a depth between 40 and 50 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallowest, aquic

conditions for some time in normal years (or artificial

drainage) and one or more of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on

faces of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction

to alpha,alpha-dipyridyl at a time when the soil is not

being irrigated.

Aquands, p. 275
274 Soil Taxonomy

Characterization Data for an Andisol

 SITE IDENTIFICATION NO.: 83P0481

 CLASSIFICATION: MEDIAL, AMORPHIC, MESIC EUTRIC FULVUDAND

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 83P2246 0- 4 Ap1 10.4 68.8 20.8 44.4 24.4 10.5 5.1 2.2 2.7 0.3 TR -- -- 10 --

 83P2247 4- 27 Ap2 5.9 72.7 21.4 45.1 27.6 13.7 5.4 1.2 0.9 0.2 TR TR -- 8 --

 83P2248 27- 39 2BA 1.0 56.1 42.9 30.4 25.7 21.5 14.2 4.6 1.9 0.7 TR -- -- 21 --

 83P2249 39- 73 2Bw1 -- 42.7 57.3 17.7 25.0 24.9 21.7 6.7 3.1 0.9 TR -- -- 32 --

 83P2250 73- 98 2Bw2 3.6 36.7 59.7 17.4 19.3 20.9 21.6 10.4 5.7 1.1 TR TR -- 39 --

 83P2251 98-129 2C1 4.7 35.0 60.3 16.7 18.3 21.8 20.8 10.9 6.2 0.6 TR -- -- 38 --

 83P2252 129-160 2C1 2.2 29.0 68.8 13.5 15.5 24.9 24.3 11.6 6.6 1.4 TR -- -- 44 --

 83P2253 160-200 3C2 3.7 46.9 49.4 27.7 19.2 11.4 8.9 7.0 10.1 12.0 TR -- -- 38 --

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 4 12.4 1.076 3.2 1.9 3.97 4.38 36.9

 4- 27 8.61 0.668 3.8 2.3 5.37 5.78 0.70 0.81 0.050 55.5 29.4 0.15

 27- 39 4.03 0.302 4.6 2.0 22.00 44.10 0.68 0.80 0.056 27.9

 39- 73 2.43 4.9 1.8 0.87 0.87 24.9

 73- 98 1.07 5.1 1.6 3.89 12.67 0.74 0.84 0.043 54.5 24.0 0.07

 98-129 0.91 4.9 1.7 2.62 9.49 0.84 0.96 0.046 54.0 22.9 0.08

 129-160 0.72 4.1 1.3 5.68 21.36 0.80 0.93 0.051 57.0 21.4 0.08

 160-200 1.69 4.6 1.7 6.57 16.54 0.90 1.09 0.066 60.8 26.2

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)

 Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos NaF CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9a 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1d 8C1f 8C1f

 <- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1

 0- 4 11.4 3.0 0.8 0.6 15.8 47.5 0.3 63.3 41.3 16.1 2 25 38 10.4 5.2 5.6

 4- 27 1.7 0.2 0.1 0.1 2.1 49.5 1.3 51.6 31.7 3.4 38 4 7 10.9 4.8 5.2

 27- 39 0.9 0.1 0.1 -- 1.1 39.7 TR 40.8 22.0 3 5 11.1 5.4 5.7

 39- 73 3.4 0.4 0.1 0.1 4.0 31.2 TR 35.2 18.6 11 22 10.7 5.6 5.9

 73- 98 2.5 0.7 TR -- 3.2 23.6 -- 26.8 14.0 12 23 10.6 5.8 6.1

 98-129 2.9 0.8 -- -- 3.7 22.4 -- 26.1 12.3 14 30 10.4 5.8 6.2

 129-160 2.3 0.7 TR -- 3.0 23.7 TR 26.7 12.5 11 24 10.6 5.8 6.2

 160-200 1.5 0.3 -- -- 1.8 33.2 0.1 35.0 24.3 1.9 5 5 7 10.8 5.7 5.9

 -----------------------------------------------------------------------------------------------------------------------------------

 ACID OXALATE EXTRACTION PHOSPHORUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT

 OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL

 DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm

 SAMPLE HZ 8J 6C9a 6V2 6G12 6S4 6S5 6D3 6A2d 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1

 NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>

 83P2246 1 1.40 1.08 3.01 94 45.6

 83P2247 2 1.39 1.18 3.54 99 34.1

 83P2248 3 1.84 1.95 4.55 98 44.1

 83P2249 4 2.13 2.13 4.68 98 51.7

 83P2250 5 2.01 1.27 2.86 98 45.6

 83P2251 6 2.01 1.27 2.64 97 44.6

 83P2252 7 1.69 1.48 2.97 98 47.0

 83P2253 8 2.50 2.83 5.77 98 61.2

 -----------------------------------------------------------------------------------------------------------------------------------
Andisols 275

DB. Other Andisols that have a cryic soil temperature

regime.

Cryands, p. 285

DC. Other Andisols that have an aridic moisture regime.

Torrands, p. 294

DD. Other Andisols that have a xeric moisture regime.

Xerands, p. 323

DE. Other Andisols that have a 1500 kPa water retention of

less than 15 percent on air-dried samples and less than 30

percent on undried samples throughout 60 percent or more of

the thickness either:

1. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

2. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Vitrands, p. 319

DF. Other Andisols that have an ustic moisture regime.

Ustands, p. 315

DG. Other Andisols.

Udands, p. 297

Aquands

Aquands are the Andisols with aquic conditions at or near

the surface. Commonly, these soils have dark colored surface

horizons that meet the requirements for a histic, umbric, or

mollic epipedon. They occur in the lower landscape positions

and support forest or grass vegetation. Some have been drained

and are used for small grain or grass for livestock. Aquands

occur in the Pacific Northwest and in other areas that have a

volcanic influence.

Definition

Aquands are the Andisols that have either:

1. A histic epipedon; or

2. In a layer above a densic, lithic, or paralithic contact or in

a layer at a depth between 40 and 50 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, aquic conditions

for some time in normal years (or artificial drainage) and one

or more of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

Characterization Data for an Andisol--Continued

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA-

 < - - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION

 NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->

 83P2247 TCLY VR 1 NX 6 6.3 0.2

 83P2248 TCLY GI 1 VR 1 NX 6 GI 1 5.7

 83P2250 TCLY GI 2 KK 1 VR 1 NX 6 GI13 KK 2 10.2 0.1

 83P2253 TCLY KK 1 GI 1 NX 6 KK 4 GI 3 9.7 0.2

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA-

 < - - - - 7A2i - - - - >< - 7A3b - >< - 7A4b - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION

 NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->

 83P2248 VFS OT96 GS 4 GAtr

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.

 Fraction interpretation: TCLY, total clay, <0.002 mm; VFS, very fine sand, 0.05-0.10 mm.

 Mineral interpretation: VR, vermiculite; NX, noncrystalline; GA, glass aggregate; GI, gibbsite; OT, other; GS, glass; KK,

 kaolinite.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
276 Soil Taxonomy

more chroma of 2 or less either in redox depletions on faces of

peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Key to Great Groups

DAA. Aquands that have a cryic soil temperature regime.

Cryaquands, p. 276

DAB. Other Aquands that have, in half or more of each

pedon, a placic horizon within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Placaquands, p. 282

DAC. Other Aquands that have, in 75 percent or more of

each pedon, a cemented horizon that has its upper boundary

within 100 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower.

Duraquands, p. 277

DAD. Other Aquands that have a 1500 kPa water retention

of less than 15 percent on air-dried samples and less than 30

percent on undried samples throughout 60 percent or more of

the thickness either:

1. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact within that depth; or

2. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact.

Vitraquands, p. 283

DAE. Other Aquands that have a melanic epipedon.

Melanaquands, p. 281

DAF. Other Aquands that have episaturation.

Epiaquands, p. 279

DAG. Other Aquands.

Endoaquands, p. 278

Cryaquands

Cryaquands are the more or less poorly drained Andisols of

cold regions. They are not extensive. They formed in the

western part of North America and the northeastern part of

Asia above 49o north latitude and in mountains south of that

latitude. Most of these soils formed under grassy meadow or

coniferous forest vegetation.

Characteristically, Cryaquands have a thin O horizon, a

mollic or umbric epipedon, and a cambic horizon with many

redox concentrations.

The Cryaquands in the United States generally developed in

late-Pleistocene or Holocene deposits.

Definition

Cryaquands are the Aquands that have a cryic soil

temperature regime.

Key to Subgroups

DAAA. Cryaquands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Cryaquands

DAAB. Other Cryaquands that have a histic epipedon.

Histic Cryaquands

DAAC. Other Cryaquands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Cryaquands

DAAD. Other Cryaquands.

Typic Cryaquands

Definition of Typic Cryaquands

Typic Cryaquands are the Cryaquands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a histic epipedon; and

3. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value 1 unit or more higher and an organic-carbon content 1

percent or more lower.

Description of Subgroups

Typic Cryaquands.—The central concept or Typic

subgroup of Cryaquands is fixed on soils that are moderately

deep or deeper and have a mollic or umbric epipedon and a

cambic horizon. Typic Cryaquands do not have a histic
Andisols 277

epipedon; a lithic contact within a depth of 50 cm; or, between

depths of 25 and 100 cm, a buried, dark colored layer 10 cm or

more thick.

These soils commonly support wet meadow vegetation, but

some support coniferous forest vegetation. Some forests have

widely spaced trees. Typic Cryaquands are not extensive in the

United States.

Histic Cryaquands.—These soils are like Typic

Cryaquands, but they have a histic epipedon. They are

considered intergrades to Histosols. They are rare in the United

States.

Lithic Cryaquands.—These soils are like Typic

Cryaquands, but they have a lithic contact within a depth of 50

cm. They are rare in the United States.

Thaptic Cryaquands.—These soils are like Typic

Cryaquands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons, 10 cm or more thick, with

a lower content of organic carbon. Thaptic Cryaquands are rare

in the United States.

Duraquands

Duraquands are the more or less poorly drained Andisols

that have, in 75 percent or more of each pedon, a cemented

horizon that has its upper boundary within 100 cm of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower. Duraquands are not

known to occur in the United States. They are established for

use in other countries.

Definition

Duraquands are the Aquands that:

1. In 75 percent or more of each pedon, have a cemented

horizon with its upper boundary within 100 cm of the mineral

soil surface or of the top of an organic layer that has andic soil

properties, whichever is shallower;

2. Do not have a cryic soil temperature regime; and

3. Do not have, in half or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface or of the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower.

Key to Subgroups

DACA. Duraquands that have a histic epipedon.

Histic Duraquands

DACB. Other Duraquands that have extractable bases (by

NH4OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower.

Acraquoxic Duraquands

DACC. Other Duraquands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Duraquands

DACD. Other Duraquands.

Typic Duraquands

Definition of Typic Duraquands

Typic Duraquands are the Duraquands that:

1. Do not have a histic epipedon;

2. Do not have, between depths of 25 and 100 cm, a layer 10 cm

or more thick with more than 3.0 percent organic carbon and the

colors of a mollic epipedon throughout, occurring below a

horizon or horizons 10 cm or more thick with a color value 1 unit

or more higher and an organic-carbon content 1 percent or more

lower; and

3. Have extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick between depths

of 25 and 100 cm.

Description of Subgroups

Typic Duraquands.—The central concept or Typic

subgroup of Duraquands is fixed on soils that do not have a

histic epipedon, have extractable bases plus 1N KCl-extractable

Al3+ totaling 2.0 or more cmol(+)/kg, and do not have, between

depths of 25 and 100 cm, a buried, dark colored layer 10 cm or

more thick below a lighter colored horizon or horizons 10 cm

or more thick with a lower content of organic carbon.

These soils are not known to occur in the United States.

They are established for use in other countries.

Acraquoxic Duraquands.—These soils are like Typic

Duraquands, but they have very low extractable bases plus 1N

KCl-extractable Al3+ in the fine-earth fraction of one or more

horizons with a total thickness of 30 cm or more at a depth

between 25 and 100 cm either from the mineral soil surface or

from the top of an organic layer with andic soil properties,

whichever is shallower. Acraquoxic Duraquands are not known

to occur in the United States. They are established for use in

other countries.

Histic Duraquands.—These soils are like Typic
278 Soil Taxonomy

Duraquands, but they have a histic epipedon. They are not

known to occur in the United States. They are established for

use in other countries.

Thaptic Duraquands.—These soils are like Typic

Duraquands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. Thaptic Duraquands are not

known to occur in the United States. They are established for

use in other countries.

Endoaquands

Endoaquands are the more or less poorly drained Andisols

with no slowly permeable layers that cause unsaturated layers

to underlie saturated layers within 200 cm of the mineral soil

surface. Most of these soils formed under grassy meadow

vegetation, but some formed under coniferous forest vegetation.

Characteristically, Endoaquands have a thin O horizon, a

mollic or umbric epipedon, and a cambic horizon with many

redox concentrations.

The Endoaquands in the United States generally developed

in late-Pleistocene or Holocene deposits.

Definition

Endoaquands are the Aquands that:

1. Do not have, in 75 percent or more of each pedon, a

cemented horizon that has its upper boundary within 100 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower;

2. Do not have, in half or more of each pedon, a placic

horizon within 100 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower;

3. Do not have a melanic epipedon;

4. Do not have a cryic soil temperature regime;

5. Have a 1500 kPa water retention either of 15 percent or

more on air-dried samples or of 30 percent or more on undried

samples throughout one or more layers with a total thickness of

more than 25 cm within 60 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

6. Have endosaturation.

Key to Subgroups

DAGA. Endoaquands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Endoaquands

DAGB. Other Endoaquands that have a horizon 15 cm or

more thick that has 20 percent or more (by volume)

cemented soil material and has its upper boundary within

100 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower.

Duric Endoaquands

DAGC. Other Endoaquands that have a histic epipedon.

Histic Endoaquands

DAGD. Other Endoaquands that have more than 2.0

cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one or

more horizons with a total thickness of 10 cm or more at a depth

between 25 and 50 cm either from the mineral soil surface or from

the top of an organic layer with andic soil properties, whichever

is shallower.

Alic Endoaquands

DAGE. Other Endoaquands that have, on undried samples, a

1500 kPa water retention of 70 percent or more throughout a

layer 35 cm or more thick within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Hydric Endoaquands

DAGF. Other Endoaquands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Endoaquands

DAGG. Other Endoaquands.

Typic Endoaquands

Definition of Typic Endoaquands

Typic Endoaquands are the Endoaquands that:

1. Do not have a lithic contact within 50 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower;

2. Do not have a horizon with an upper boundary within 100

cm either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower, that is

more than 15 cm thick and has 20 percent or more (by volume)

cemented soil material;

3. Do not have a histic epipedon;

4. Do not have, at a depth between 25 and 100 cm either from

the mineral soil surface or from the top of an organic layer with
Andisols 279

andic soil properties, whichever is shallower, a layer 10 cm or

more thick with more than 3.0 percent organic carbon and the

colors of a mollic epipedon throughout, underlying one or more

horizons with a total thickness of 10 cm or more that have a color

value, moist, 1 unit or more higher and an organic-carbon

content 1 percent or more (absolute) lower;

5. Have 2.0 cmol(+)/kg or less Al3+ (by 1N KCl) in the fine-earth

fraction throughout a layer 10 cm or more thick at a depth

between 25 and 50 cm either from the mineral soil surface or from

the top of an organic layer with andic soil properties, whichever

is shallower; and

6. Have, on undried samples, a 1500 kPa water retention of less

than 70 percent throughout a layer 35 cm or more thick within

100 cm either of the mineral soil surface or of the upper

boundary of an organic layer with andic soil properties,

whichever is shallower.

Description of Subgroups

Typic Endoaquands.—The central concept or Typic

subgroup of Endoaquands is fixed on soils that do not have a

histic epipedon, that are moderately deep or deeper, and that do

not have, between depths of 25 and 100 cm, a buried, dark

colored layer 10 cm or more thick below a lighter colored

horizon or horizons 10 cm or more thick with a lower content

of organic carbon. Soils that have a horizon 15 cm or more

thick with 20 percent or more cemented soil material also are

excluded.

Endoaquands that have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick in the upper part are assigned to the Hydric

subgroup. Soils with more than 2.0 cmol(+)/kg Al3+ (by 1N

KCl) in the fine-earth fraction of one or more horizons with a

total thickness of 10 cm or more also are excluded from the

Typic subgroup. Soils that have a lithic contact within a depth

of 50 cm are assigned to the Lithic subgroup. Soils that have a

histic epipedon are excluded from the Typic subgroup because

they are considered intergrades to Histosols.

Typic Endoaquands are not extensive in the United States.

They commonly support wet meadow vegetation, but some

support coniferous forest vegetation. Most Typic Endoaquands

are used as rangeland, but some have been drained and are

used as cropland or pasture.

Alic Endoaquands.—These soils are like Typic

Endoaquands, but they have more than 2.0 cmol(+)/kg Al3+ (by

1N KCl) in the fine-earth fraction of one or more horizons with

a total thickness of 10 cm or more at a depth between 25 and

50 cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower. These soils are rare in the United States.

Duric Endoaquands.—These soils are like Typic

Endoaquands, but they have a horizon 15 cm or more thick

that has 20 percent or more (by volume) cemented soil material

and has its upper boundary within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils have not been

recognized in the United States.

Histic Endoaquands.—These soils are like Typic

Endoaquands, but they have a histic epipedon. They have not

been recognized in the United States.

Hydric Endoaquands.—These soils are like Typic

Endoaquands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States.

Lithic Endoaquands.—These soils are like Typic

Endoaquands, but they have a lithic contact within a depth of

50 cm. They have not been recognized in the United States.

Thaptic Endoaquands.—These soils are like Typic

Endoaquands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils are rare in the

United States.

Epiaquands

Epiaquands are the more or less poorly drained Andisols with

a slowly permeable layer that causes unsaturated layers to

underlie saturated layers within 200 cm of the mineral soil

surface. Most of these soils formed under grassy meadow

vegetation, but some formed under coniferous forest vegetation.

Characteristically, Epiaquands have a thin O horizon, a

mollic or umbric epipedon, and a cambic horizon with many

redox concentrations.

The Epiaquands in the United States generally developed in

late-Pleistocene or Holocene deposits.

Definition

Epiaquands are the Aquands that:

1. Do not have, in 75 percent or more of each pedon, a

cemented horizon that has its upper boundary within 100 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower;

2. Do not have, in half or more of each pedon, a placic

horizon within 100 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower;

3. Do not have a melanic epipedon;

4. Do not have a cryic soil temperature regime;

5. Have a 1500 kPa water retention either of 15 percent or more

on air-dried samples or of 30 percent or more on undried samples

throughout one or more layers with a total thickness of more
280 Soil Taxonomy

than 25 cm within 60 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties, whichever

is shallower; and

6. Have episaturation.

Key to Subgroups

DAFA. Epiaquands that have a horizon 15 cm or more thick

that has 20 percent or more (by volume) cemented soil material

and has its upper boundary within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Duric Epiaquands

DAFB. Other Epiaquands that have a histic epipedon.

Histic Epiaquands

DAFC. Other Epiaquands that have more than 2.0

cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one or

more horizons with a total thickness of 10 cm or more at a depth

between 25 and 50 cm either from the mineral soil surface or from

the top of an organic layer with andic soil properties, whichever

is shallower.

Alic Epiaquands

DAFD. Other Epiaquands that have, on undried samples, a

1500 kPa water retention of 70 percent or more throughout a

layer 35 cm or more thick within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Hydric Epiaquands

DAFE. Other Epiaquands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Epiaquands

DAFF. Other Epiaquands.

Typic Epiaquands

Definition of Typic Epiaquands

Typic Epiaquands are the Epiaquands that:

1. Do not have a horizon with an upper boundary

within 100 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower, that is more than 15 cm thick

and has 20 percent or more (by volume) cemented soil

material;

2. Do not have a histic epipedon;

3. Do not have, at a depth between 25 and 100 cm either from

the mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, a layer 10 cm or

more thick with more than 3.0 percent organic carbon and the

colors of a mollic epipedon throughout, underlying one or more

horizons with a total thickness of 10 cm or more that have a color

value, moist, 1 unit or more higher and an organic-carbon

content 1 percent or more (absolute) lower;

4. Have 2.0 cmol(+)/kg or less Al3+ (by 1N KCl) in the fine-earth

fraction throughout a layer 10 cm or more thick at a depth

between 25 and 50 cm either from the mineral soil surface or from

the top of an organic layer with andic soil properties, whichever

is shallower; and

5. Have, on undried samples, a 1500 kPa water retention of less

than 70 percent throughout a layer 35 cm or more thick within

100 cm either of the mineral soil surface or of the upper

boundary of an organic layer with andic soil properties,

whichever is shallower.

Description of Subgroups

Typic Epiaquands.—The central concept or Typic

subgroup of Epiaquands is fixed on moderately deep or deeper

soils that do not have a histic epipedon and do not have,

between depths of 25 and 100 cm, a buried, dark colored layer

10 cm or more thick below a lighter colored horizon or

horizons 10 cm or more thick with a lower content of organic

carbon. Soils that have a horizon 15 cm or more thick with 20

percent or more cemented soil material also are excluded.

Epiaquands that have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick in the upper part are assigned to the Hydric

subgroup. Soils with more than 2.0 cmol(+)/kg Al3+ (by 1N

KCl) in the fine-earth fraction of one or more horizons with a

total thickness of 10 cm or more also are excluded from the

Typic subgroup. Soils that have a histic epipedon are excluded

from the Typic subgroup because they are considered

intergrades to Histosols.

Typic Epiaquands are rare in the United States. They

commonly support wet meadow vegetation, but some support

coniferous forest vegetation.

Alic Epiaquands.—These soils are like Typic Epiaquands,

but they have more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in

the fine-earth fraction of one or more horizons with a total

thickness of 10 cm or more at a depth between 25 and 50 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower. These soils are rare in the United States.
Andisols 281

Duric Epiaquands.—These soils are like Typic

Epiaquands, but they have a horizon 15 cm or more thick that

has 20 percent or more (by volume) cemented soil material and

has its upper boundary within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils have not been

recognized in the United States.

Histic Epiaquands.—These soils are like Typic

Epiaquands, but they have a histic epipedon. They have not

been recognized in the United States.

Hydric Epiaquands.—These soils are like Typic

Epiaquands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States.

Thaptic Epiaquands.—These soils are like Typic

Epiaquands, but they have, between depths of 25 and 100 cm, a

buried, dark colored layer 10 cm or more thick below a lighter

colored horizon or horizons 10 cm or more thick with a lower

content of organic carbon. These soils are rare in the United

States.

Melanaquands

Melanaquands are the more or less poorly drained Andisols

with a melanic epipedon. Most of these soils formed under

forest vegetation.

Characteristically, Melanaquands have a thin O horizon, a

thick melanic epipedon, and a cambic horizon with many

redox concentrations.

Definition

Melanaquands are the Aquands that:

1. Have a melanic epipedon;

2. Do not have, in 75 percent or more of each pedon, a

cemented horizon with its upper boundary within 100 cm

of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower;

3. Do not have a cryic soil temperature regime;

4. Do not have, in half or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface or of the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower; and

5. Have a 1500 kPa water retention of 15 percent or more

on air-dried samples or 30 percent or more on undried samples

throughout a thickness of more than 25 cm within 60 cm of

the mineral soil surface or of the upper boundary of an

organic layer with andic soil properties, whichever is

shallower.

Key to Subgroups

DAEA. Melanaquands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic layer

with andic soil properties, whichever is shallower.

Lithic Melanaquands

DAEB. Other Melanaquands that have extractable bases (by

NH4

OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower.

Acraquoxic Melanaquands

DAEC. Other Melanaquands that have both:

1. On undried samples, a 1500 kPa water retention of 70

percent or more throughout a layer 35 cm or more thick

within 100 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower; and

2. More than 6.0 percent organic carbon and the colors of

a mollic epipedon throughout a layer 50 cm or more thick

within 60 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower.

Hydric Pachic Melanaquands

DAED. Other Melanaquands that have, on undried samples,

a 1500 kPa water retention of 70 percent or more throughout a

layer 35 cm or more thick within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Hydric Melanaquands

DAEE. Other Melanaquands that have more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

a layer 50 cm or more thick within 60 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Pachic Melanaquands

DAEF. Other Melanaquands that have, at a depth between 40

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total
282 Soil Taxonomy

thickness of 10 cm or more that have a color value, moist, 1 unit

or more higher and an organic-carbon content 1 percent or more

(absolute) lower.

Thaptic Melanaquands

DAEG. Other Melanaquands.

Typic Melanaquands

Definition of Typic Melanaquands

Typic Melanaquands are the Melanaquands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. On undried samples, have a 1500 kPa water retention of

less than 70 percent throughout any continuous thickness of 35

cm or more within the upper 100 cm;

3. Do not have both more than 6.0 percent organic carbon

and the colors of a mollic epipedon throughout at least 50 cm

of the upper 60 cm;

4. Do not have, between depths of 40 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value 1 unit or more higher and an organic-carbon content 1

percent or more lower; and

5. Have extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick between depths

of 25 and 100 cm.

Description of Subgroups

Typic Melanaquands.—The central concept or Typic

subgroup of Melanaquands is fixed on soils that have a melanic

epipedon less than 50 cm thick, are moderately deep or deeper,

and do not have, between depths of 25 and 100 cm, a buried,

dark colored layer 10 cm or more thick below a lighter colored

horizon or horizons 10 cm or more thick with a lower content

of organic carbon. Soils that have, on undried samples, a 1500

kPa water retention of 70 percent or more throughout a layer

35 cm or more thick in the upper part are assigned to the

Hydric subgroup. Soils that have a lithic contact within a depth

of 50 cm are assigned to the Lithic subgroup.

Typic Melanaquands are not extensive in the United States.

They commonly support coniferous forest vegetation. Most of

these soils are used as woodland or have been drained and are

used as cropland or pasture.

Acraquoxic Melanaquands.—These soils are like Typic

Melanaquands, but they have very low extractable bases plus

1N KCl-extractable Al3+ in the fine-earth fraction of one or

more horizons with a total thickness of 30 cm or more at a

depth between 25 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower. These soils are not known

to occur in the United States. They are established for use in

other countries.

Hydric Melanaquands.—These soils are like Typic

Melanaquands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States.

Hydric Pachic Melanaquands.—These soils are like Typic

Melanaquands, but they have both more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

at least 50 cm of the upper 60 cm of the andic materials and,

on undried samples, a 1500 kPa water retention of 70 percent

or more throughout a layer 35 cm or more thick within 100 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower. Hydric

Pachic Melanaquands have not been recognized in the United

States.

Lithic Melanaquands.—These soils are like Typic

Melanaquands, but they have a lithic contact within a depth of

50 cm. They have not been recognized in the United States.

Pachic Melanaquands.—These soils are like Typic

Melanaquands, but they have more than 6.0 percent organic

carbon and the colors of a mollic epipedon throughout at least

50 cm of the upper 60 cm below the mineral soil surface or

below the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States.

Thaptic Melanaquands.—These soils are like Typic

Melanaquands, but they have, between depths of 25 and 100

cm, a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States.

Placaquands

Placaquands are the more or less poorly drained Andisols

that have, in half or more of each pedon, a placic horizon

within 100 cm of the mineral soil surface or of the upper

boundary of an organic layer that has andic soil properties,

whichever is shallower. Most of these soils formed under

coniferous forest vegetation.

Characteristically, Placaquands have a thin O horizon and

an umbric or histic epipedon above the placic horizon. They

are rare in the United States.

Definition

Placaquands are the Aquands that:

1. In half or more of each pedon, have a placic horizon

within 100 cm of the mineral soil surface or of the upper

boundary of an organic layer that has andic soil properties,

whichever is shallower; and
Andisols 283

2. Do not have a cryic soil temperature regime.

Key to Subgroups

DABA. Placaquands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Placaquands

DABB. Other Placaquands that have both:

1. A histic epipedon; and

2. A horizon 15 cm or more thick that has 20 percent or

more (by volume) cemented soil material and has its upper

boundary within 100 cm either of the mineral soil surface or

of the top of an organic layer with andic soil properties,

whichever is shallower.

Duric Histic Placaquands

DABC. Other Placaquands that have a horizon 15 cm or

more thick that has 20 percent or more (by volume) cemented

soil material and has its upper boundary within 100 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Duric Placaquands

DABD. Other Placaquands that have a histic epipedon.

Histic Placaquands

DABE. Other Placaquands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Placaquands

DABF. Other Placaquands.

Typic Placaquands

Definition of Typic Placaquands

Typic Placaquands are the Placaquands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a horizon with its upper boundary within 100

cm of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower, that is more than 15 cm thick and that has 20

percent or more (by volume) cemented soil material;

3. Do not have a histic epipedon; and

4. Do not have, between depths of 25 and 100 cm, a layer 10 cm

or more thick with more than 3.0 percent organic carbon and the

colors of a mollic epipedon throughout, occurring below a

horizon or horizons 10 cm or more thick with a color value 1 unit

or more higher and an organic-carbon content 1 percent or more

lower.

Description of Subgroups

Typic Placaquands.—The central concept or Typic

subgroup of Placaquands is fixed on soils that do not have a

histic epipedon, are moderately deep or deeper, and do not

have, between depths of 25 and 100 cm, a buried, dark colored

layer 10 cm or more thick below a lighter colored horizon or

horizons 10 cm or more thick with a lower content of organic

carbon. Soils that average 20 percent or more (by volume)

cemented soil material in a layer 15 cm or more thick are

assigned to the Duric subgroup. Soils that have a lithic contact

within a depth of 50 cm are assigned to the Lithic subgroup.

Typic Placaquands have not been recognized in the United

States.

Duric Histic Placaquands.—These soils are like Typic

Placaquands, but they have both a histic epipedon and a

horizon 15 cm or more thick that has 20 percent or more (by

volume) cemented soil material and has its upper boundary

within 100 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower. These soils have not been recognized in the United

States.

Duric Placaquands.—These soils are like Typic

Placaquands, but they have a horizon 15 cm or more thick that

has 20 percent or more (by volume) cemented soil material and

has its upper boundary within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils have not been

recognized in the United States.

Histic Placaquands.—These soils are like Typic

Placaquands, but they have a histic epipedon. They are rare in

the United States.

Lithic Placaquands.—These soils are like Typic

Placaquands, but they have a lithic contact within a depth of 50

cm. They have not been recognized in the United States.

Thaptic Placaquands.—These soils are like Typic

Placaquands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States.

Vitraquands

Vitraquands are the more or less poorly drained Andisols

with relatively coarse textures. Most of these soils have no

slowly permeable layer that causes unsaturated layers to

underlie saturated layers within 200 cm of the mineral soil
284 Soil Taxonomy

surface. Many of the soils formed under grassy or brushy

meadow vegetation, but some formed under coniferous forest

vegetation.

Characteristically, Vitraquands have a thin O horizon, a

mollic or umbric epipedon, and a cambic horizon with many

redox concentrations.

Most Vitraquands in the United States developed in

Holocene deposits.

Definition

Vitraquands are the Aquands that:

1. Have a 1500 kPa water retention of less than 15 percent on

air-dried samples and less than 30 percent on undried samples

throughout 60 percent or more of the thickness either:

a. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no lithic or paralithic contact,

duripan, or petrocalcic horizon within that depth; or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon;

2. Do not have a cryic soil temperature regime;

3. Do not have, in half or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface or of the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower; and

4. Do not have, in 75 percent or more of each pedon, a

cemented horizon with its upper boundary within 100 cm of

the mineral soil surface or of the upper boundary of an organic

layer that has andic soil properties, whichever is shallower.

Key to Subgroups

DADA. Vitraquands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Vitraquands

DADB. Other Vitraquands that have a horizon 15 cm or

more thick that has 20 percent or more (by volume) cemented

soil material and has its upper boundary within 100 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Duric Vitraquands

DADC. Other Vitraquands that have a histic epipedon.

Histic Vitraquands

DADD. Other Vitraquands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Vitraquands

DADE. Other Vitraquands.

Typic Vitraquands

Definition of Typic Vitraquands

Typic Vitraquands are the Vitraquands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a horizon with its upper boundary within 100

cm of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower, that is more than 15 cm thick and that has 20

percent or more (by volume) cemented soil material;

3. Do not have a histic epipedon; and

4. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value 1 unit or more higher and an organic-carbon content 1

percent or more lower.

Description of Subgroups

Typic Vitraquands.—The central concept or Typic

subgroup of Vitraquands is fixed on soils that do not have a

histic epipedon, are moderately deep or deeper, and do not

have, between depths of 25 and 100 cm, a buried, dark colored

layer 10 cm or more thick below a lighter colored horizon or

horizons 10 cm or more thick with a lower content of organic

carbon. Soils that average 20 percent or more (by volume)

cemented soil material in a layer 15 cm or more thick are

assigned to the Duric subgroup. Soils that have a lithic

contact within a depth of 50 cm are assigned to the Lithic

subgroup. Typic Vitraquands are of small extent in the United

States.

Duric Vitraquands.—These soils are like Typic

Vitraquands, but they have a horizon 15 cm or more thick that

has 20 percent or more (by volume) cemented soil material and

has its upper boundary within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils have not been

recognized in the United States.

Histic Vitraquands.—These soils are like Typic

Vitraquands, but they have a histic epipedon. They are of small

extent in the United States.

Lithic Vitraquands.—These soils are like Typic
Andisols 285

Vitraquands, but they have a lithic contact within a depth of 50

cm. They have not been recognized in the United States.

Thaptic Vitraquands.—These soils are like Typic

Vitraquands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States.

Cryands

Cryands are the more or less well drained Andisols of cold

regions. These soils are moderately extensive. They formed in

the western part of North America and the northeastern part of

Asia above 49o north latitude and in mountains south of that

latitude. Most of the soils formed under coniferous forest

vegetation.

Characteristically, Cryands have a thin O horizon and a

cambic horizon. The epipedon ranges from ochric to melanic.

The Cryands in the United States generally developed in

late-Pleistocene or Holocene deposits.

Definition

Cryands are the Andisols that:

1. Have a cryic soil temperature regime; and

2. Do not have a histic epipedon or the aquic conditions

characteristic of Aquands.

Key to Great Groups

DBA. Cryands that have, in 75 percent or more of each

pedon, a cemented horizon that has its upper boundary within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower.

Duricryands, p. 285

DBB. Other Cryands that have, on undried samples, a 1500

kPa water retention of 100 percent or more, by weighted

average, throughout either:

1. One or more layers with a total thickness of 35 cm

between the mineral soil surface or the top of an organic

layer with andic soil properties, whichever is shallower,

and 100 cm from the mineral soil surface or from the top

 of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

2. 60 percent or more of the horizon thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a

densic, lithic, or paralithic contact, a duripan, or a petrocalcic

horizon.

Hydrocryands, p. 289

DBC. Other Cryands that have a melanic epipedon.

Melanocryands, p. 291

DBD. Other Cryands that have a layer that meets the depth,

thickness, and organic-carbon requirements for a melanic

epipedon.

Fulvicryands, p. 286

DBE. Other Cryands that have a 1500 kPa water retention of

less than 15 percent on air-dried samples and less than 30

percent on undried samples throughout 60 percent or more of

the thickness either:

1. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

2. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Vitricryands, p. 292

DBF. Other Cryands.

Haplocryands, p. 287

Duricryands

Duricryands are the Cryands that have, in 75 percent or

more of each pedon, a cemented horizon that has its upper

boundary within 100 cm either of the mineral soil surface or

of the top of an organic layer with andic soil properties,

whichever is shallower. Characteristically, Duricryands have a

thin O horizon and a cambic horizon above the cemented

horizon.

The Duricryands in the United States generally developed in

late-Pleistocene or Holocene deposits. Most formed under

coniferous forest vegetation.

Definition

Duricryands are the Cryands that have, in 75 percent or

more of each pedon, a cemented horizon that has its upper

boundary within 100 cm of either the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower.

Key to Subgroups

DBAA. Duricryands that have, in some subhorizon at a depth

between 50 and 100 cm either from the mineral soil surface or
286 Soil Taxonomy

from the top of an organic layer with andic soil properties,

whichever is shallower, aquic conditions for some time in

normal years (or artificial drainage) and one or more of the

following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or more

chroma of 2 or less either in redox depletions on faces of peds

or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Duricryands

DBAB. Other Duricryands.

Typic Duricryands

Definition of Typic Duricryands

Typic Duricryands are the Duricryands that do not have, in

any horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, both aquic

conditions and any of the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Description of Subgroups

Typic Duricryands.—The central concept or Typic

subgroup of Duricryands is fixed on soils that have relatively

high amounts of aluminum and low cation-exchange capacities

and do not have both aquic conditions and redox features in

any horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower.

These soils are not extensive in the United States. They

commonly support coniferous forest vegetation. Most of the

soils are used for timber production, but some are used as

recreational areas.

Aquic Duricryands.—These soils are like Typic

Duricryands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are rare in the United States. Most are

used for timber production, but some are used as recreational

areas.

Fulvicryands

Fulvicryands are the Cryands that do not have a melanic

epipedon but have a layer that meets the depth, thickness, and

organic-carbon requirements for a melanic epipedon. They do

not have, in 75 percent or more of each pedon, a cemented

horizon that has its upper boundary within 100 cm of either the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower.

Characteristically, Fulvicryands have a thin O horizon, an

umbric epipedon, and a cambic horizon.

The Fulvicryands in the United States generally developed

in late-Pleistocene or Holocene deposits. Most formed under

coniferous forest vegetation.

Definition

Fulvicryands are the Cryands that:

1. Have, in less than 75 percent of each pedon, a cemented

horizon that has its upper boundary within 100 cm of either the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower;

2. Do not have a melanic epipedon but have a layer that

meets the depth, thickness, and organic carbon requirements

for a melanic epipedon; and

3. Do not have, on undried samples, a 1500 kPa water

retention of 100 percent or more, by weighted average,

throughout either:

a. One or more layers with a total thickness of 35 cm

between the mineral soil surface or the top of an organic

layer with andic soil properties, whichever is shallower, and

100 cm from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no densic, lithic, or paralithic contact,

duripan, or petrocalcic horizon within that depth; or

b. 60 percent or more of the horizon thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a

densic, lithic, or paralithic contact, a duripan, or a

petrocalcic horizon.

Key to Subgroups

DBDA. Fulvicryands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Fulvicryands

DBDB. Other Fulvicryands that have, throughout a layer 50

cm or more thick within 60 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower:
Andisols 287

1. More than 6.0 percent organic carbon, by weighted

average; and

2. More than 4.0 percent organic carbon in all parts.

Pachic Fulvicryands

DBDC. Other Fulvicryands that have a 1500 kPa water

retention of less than 15 percent on air-dried samples and less

than 30 percent on undried samples throughout one or more

layers that have andic soil properties and have a total thickness

of 25 cm or more within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Vitric Fulvicryands

DBDD. Other Fulvicryands.

Typic Fulvicryands

Definition of Typic Fulvicryands

Typic Fulvicryands are the Fulvicryands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have a 1500 kPa water retention of 15 percent or more on

air-dried samples or 30 percent or more on undried samples in

all subhorizons that meet the requirements for andic soil

properties and that are 25 cm or more thick and are within 100

cm of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower; and

3. Do not have throughout a layer 50 cm or more thick within

60 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower:

a. More than 6.0 percent organic carbon, by weighted

average; and

b. More than 4.0 percent organic carbon in all parts.

Description of Subgroups

Typic Fulvicryands.—The central concept or Typic

subgroup of Fulvicryands is fixed on moderately deep or

deeper, more or less well drained soils that have a 1500 kPa

water retention of 15 percent or more on air-dried samples or

30 percent or more on undried samples in all subhorizons that

meet the requirements for andic soil properties and that are 25

cm or more thick and are within 100 cm of the mineral soil

surface or of the upper boundary of an organic layer that has

andic soil properties, whichever is shallower.

Typic Fulvicryands commonly have relatively high amounts

of aluminum and low cation-exchange capacities. These soils

are not extensive in the United States. They commonly support

coniferous forest vegetation. Most are used for timber

production, but some are used as recreational areas.

Lithic Fulvicryands.—These soils are like Typic

Fulvicryands, but they have a lithic contact within a depth of

50 cm. They have not been recognized in the United States.

Pachic Fulvicryands.—These soils are like Typic

Fulvicryands, but they have thicker, darker layers or horizons

at or near the surface. These soils are not extensive in the

United States. They commonly support coniferous forest

vegetation. Most are used for timber production, but some are

used as recreational areas.

Vitric Fulvicryands.—These soils are like Typic

Fulvicryands, but they have a 1500 kPa water retention of less

than 15 percent on air-dried samples and less than 30 percent

on undried samples in all subhorizons that meet the

requirements for andic soil properties and that are 25 cm or

more thick and are within 100 cm of the mineral soil surface or

of the upper boundary of an organic layer that has andic soil

properties, whichever is shallower. These soils are rare in the

United States. Most of the soils are used for timber production,

but some are used as recreational areas.

Haplocryands

Haplocryands are the Cryands that do not have a melanic

epipedon or a layer that meets the depth, thickness, and

organic-carbon requirements for a melanic epipedon. They do

not have, in 75 percent or more of each pedon, a cemented

horizon that has its upper boundary within 100 cm of either the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower. They have, on undried

samples, a 1500 kPa water retention of less than 100 percent,

by weighted average, throughout 60 percent or more of the

upper 60 cm of the andic materials. They also have a 1500 kPa

water retention of 30 percent or more on undried samples or of

15 percent or more on air-dried samples, by weighted average,

throughout 60 percent or more of the upper 60 cm of the andic

materials.

Characteristically, Haplocryands have a thin O horizon, an

umbric epipedon, and a cambic horizon.

The Haplocryands in the United States generally developed

in late-Pleistocene or Holocene deposits. Most formed under

coniferous forest vegetation.

Definition

Haplocryands are the Cryands that:

1. Have, in less than 75 percent of each pedon, a cemented

horizon that has its upper boundary within 100 cm of either the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower;

2. Do not have a melanic epipedon or an epipedon meeting

the depth, thickness, and organic-carbon requirements for a

melanic epipedon;

3. Have, on undried samples, a 1500 kPa water retention of
288 Soil Taxonomy

less than 100 percent, by weighted average, throughout more

than 40 percent of the horizon thickness between either the

mineral soil surface or the top of an organic layer with andic soil

properties, whichever is shallower, and a densic, lithic, or

paralithic contact, a duripan, a petrocalcic horizon, or a depth of

60 cm, whichever is shallowest; and

4. Have a 1500 kPa water retention of 30 percent or more on

undried samples or 15 percent or more on air-dried samples in

all subhorizons that meet the requirements for andic soil

properties and that are at least 25 cm thick and are within 100

cm of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower.

Key to Subgroups

DBFA. Haplocryands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Haplocryands

DBFB. Other Haplocryands that have more than 2.0

cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one

or more horizons with a total thickness of 10 cm or more at a

depth between 25 and 50 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower.

Alic Haplocryands

DBFC. Other Haplocryands that have, in some subhorizon at

a depth between 50 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower, aquic conditions for some

time in normal years (or artificial drainage) and one or more of

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Haplocryands

DBFD. Other Haplocryands that have extractable bases (by

NH4OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower.

Acrudoxic Haplocryands

DBFE. Other Haplocryands that have a 1500 kPa water

retention of less than 15 percent on air-dried samples and less

than 30 percent on undried samples throughout one or more

layers that have andic soil properties and have a total thickness

of 25 cm or more within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Vitric Haplocryands

DBFF. Other Haplocryands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Haplocryands

DBFG. Other Haplocryands that have a xeric moisture

regime.

Xeric Haplocryands

DBFH. Other Haplocryands.

Typic Haplocryands

Definition of Typic Haplocryands

Typic Haplocryands are the Haplocryands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50

and 100 cm either from the mineral soil surface or from

the top of an organic layer with andic soil properties,

whichever is shallower, both aquic conditions and any of

the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Have, on undried samples, 30 percent or more 1500 kPa

water retention in all subhorizons that meet the requirements

for andic soil properties and that are at least 25 cm thick and

are within 100 cm of the mineral soil surface or of the upper

boundary of an organic layer that has andic soil properties,

whichever is shallower;

4. Have 1N KCl-extractable Al3+ of 2.0 or less cmol(+) kg-1 in
Andisols 289

the fine-earth fraction throughout all layers 10 cm or more thick

between depths of 25 and 50 cm;

5. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value 1 unit or more higher and an organic-carbon content 1

percent or more lower;

6. Have extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick between depths

of 25 and 100 cm; and

7. Do not have a xeric soil moisture regime.

Description of Subgroups

Typic Haplocryands.—The central concept or Typic

subgroup of Haplocryands is fixed on moderately deep or deep

soils that have a 1500 kPa water retention of 15 percent or

more on air-dried samples or 30 percent or more on undried

samples in all subhorizons that meet the requirements for andic

soil properties and that are 25 cm or more thick and are within

100 cm of the mineral soil surface or of the upper boundary of

an organic layer that has andic soil properties, whichever is

shallower.

Soils with more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in

the fine-earth fraction of one or more horizons with a total

thickness of 10 cm or more are excluded from the Typic

subgroup. Soils that have a lithic contact within a depth of 50

cm are assigned to the Lithic subgroup. Soils that have both

aquic conditions (or artificial drainage) and redox features in

any horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, are excluded

from the Typic subgroup and are considered intergrades to

Aquands.

Typic Haplocryands are moderately extensive in the United

States. They commonly support coniferous forest vegetation.

Most are used for timber production, but some are used as

recreational areas.

Acrudoxic Haplocryands.—These soils are like Typic

Haplocryands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more at a depth between 25 and 100 cm either from

the mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower. These soils have

not been recognized in the United States.

Alic Haplocryands.—These soils are like Typic

Haplocryands, but they have more than 2.0 cmol(+)/kg Al3+ (by

1N KCl) in the fine-earth fraction of one or more horizons with

a total thickness of 10 cm or more at a depth between 25 and

50 cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower. These soils are mostly in Oregon and Washington

and are of small extent in the United States. Most of the soils

are used for timber production, but some are used as

recreational areas.

Aquic Haplocryands.—These soils are like Typic

Haplocryands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are rare in the United States. Most of the

soils are used for timber production, but some are used as

recreational areas.

Lithic Haplocryands.—These soils are like Typic

Haplocryands, but they have a lithic contact within a depth of

50 cm. They are mostly in Oregon and Washington and are of

small extent in the United States. Most of the soils are used for

timber production or as recreational areas.

Thaptic Haplocryands.—These soils are like Typic

Haplocryands, but they have, between depths of 25 and 100

cm, a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States.

Vitric Haplocryands.—These soils are like Typic

Haplocryands, but they have a 1500 kPa water retention of less

than 15 percent on air-dried samples and less than 30 percent

on undried samples in some subhorizon that meets the

requirements for andic soil properties and that is 25 cm or

more thick and is within 100 cm of the mineral soil surface or

of the upper boundary of an organic layer that has andic soil

properties, whichever is shallower. These soils are mostly in

Idaho, Oregon, and Washington and are of small extent in the

United States. Most of the soils are used for timber production,

but some are used as recreational areas.

Xeric Haplocryands.—These soils are like Typic

Haplocryands, but they have a xeric moisture regime. They are

mostly in California and Idaho and are of small extent in the

United States. Most of the soils are used for timber production,

but some are used as recreational areas.

Hydrocryands

Hydrocryands have, on undried samples, a 1500 kPa water

retention of 100 percent or more, by weighted average,

throughout 60 percent or more of the upper part of the pedon.

They do not have, in 75 percent or more of each pedon, a

cemented horizon that has its upper boundary within 100 cm of

either the mineral soil surface or of the top of an organic layer

with andic soil properties, whichever is shallower.

Hydrocryands have not been recognized in the United

States. Most formed under coniferous forest vegetation.
290 Soil Taxonomy

Definition

Hydrocryands are the Cryands that:

1. Have, in less than 75 percent of each pedon, a cemented

horizon that has its upper boundary within 100 cm of either the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower; and

2. Have, on undried samples, a 1500 kPa water retention of

100 percent or more, by weighted average, throughout either:

a. One or more layers with a total thickness of 35 cm

between the mineral soil surface or the top of an organic

layer with andic soil properties, whichever is shallower, and

100 cm from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no densic, lithic, or paralithic contact,

duripan, or petrocalcic horizon within that depth; or

b. 60 percent or more of the horizon thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a

densic, lithic, or paralithic contact, a duripan, or a

petrocalcic horizon.

Key to Subgroups

DBBA. Hydrocryands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Hydrocryands

DBBB. Other Hydrocryands that have a placic horizon within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower.

Placic Hydrocryands

DBBC. Other Hydrocryands that have, in one or more

horizons at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, aquic conditions

for some time in normal years (or artificial drainage) and one

or more of the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Hydrocryands

DBBD. Other Hydrocryands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Hydrocryands

DBBE. Other Hydrocryands.

Typic Hydrocryands

Definition of Typic Hydrocryands

Typic Hydrocryands are the Hydrocryands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Do not have a placic horizon within 100 cm of the soil

surface; and

4. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value 1 unit or more higher and an organic-carbon content 1

percent or more lower.

Description of Subgroups

Typic Hydrocryands.—The central concept or Typic

subgroup of Hydrocryands is fixed on moderately deep or deep

soils that do not have a placic horizon within a depth of 100

cm and do not have, between depths of 25 and 100 cm, a

buried, dark colored layer 10 cm or more thick below a lighter

colored horizon or horizons 10 cm or more thick with a lower

content of organic carbon.

Soils that have a lithic contact within a depth of 50 cm are

assigned to the Lithic subgroup. Soils that have both aquic

conditions (or artificial drainage) and redox features in any

horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, are excluded
Andisols 291

from the Typic subgroup and are considered intergrades to

Aquands.

Typic Hydrocryands are not known to occur in the United

States.

Aquic Hydrocryands.—These soils are like Typic

Hydrocryands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are not known to occur in the United

States.

Lithic Hydrocryands.—These soils are like Typic

Hydrocryands, but they have a lithic contact within a depth of

50 cm. They are not known to occur in the United States.

Placic Hydrocryands.—These soils are like Typic

Hydrocryands, but they have a placic horizon within 100 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower. These

soils are not known to occur in the United States.

Thaptic Hydrocryands.—These soils are like Typic

Hydrocryands, but they have, between depths of 25 and 100

cm, a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States.

Melanocryands

Melanocryands are the Cryands that have a melanic

epipedon but do not have, in 75 percent or more of each pedon,

a cemented horizon that has its upper boundary within 100 cm

of either the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower. These

soils also do not have the high water retention associated with

Hydrocryands. Melanocryands have not been recognized in the

United States.

Definition

Melanocryands are the Cryands that:

1. Have, in less than 75 percent of each pedon, a cemented

horizon that has its upper boundary within 100 cm of either the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower;

2. Have a melanic epipedon; and

3. Do not have, on undried samples, a 1500 kPa water

retention of 100 percent or more, by weighted average,

throughout either:

a. One or more layers with a total thickness of 35 cm

between the mineral soil surface or the top of an organic

layer with andic soil properties, whichever is shallower, and

100 cm from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no densic, lithic, or paralithic contact,

duripan, or petrocalcic horizon within that depth; or

b. 60 percent or more of the horizon thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a

densic, lithic, or paralithic contact, a duripan, or a

petrocalcic horizon.

Key to Subgroups

DBCA. Melanocryands that have a lithic contact within

50 cm either of the mineral soil surface or of the top of an

organic layer that has andic soil properties, whichever is

shallower.

Lithic Melanocryands

DBCB. Other Melanocryands that have a 1500 kPa water

retention of less than 15 percent on air-dried samples and less

than 30 percent on undried samples throughout one or more

layers that have andic soil properties and have a total thickness

of 25 cm or more within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Vitric Melanocryands

DBCC. Other Melanocryands.

Typic Melanocryands

Definition of Typic Melanocryands

Typic Melanocryands are the Melanocryands that:

1. Do not have a lithic contact within 50 cm of the soil

surface; and

2. Have, on undried samples, 30 percent or more 1500 kPa

water retention in all subhorizons that meet the requirements

for andic soil properties and that are at least 25 cm thick and

are within 100 cm of the mineral soil surface or of the upper

boundary of an organic layer that has andic soil properties,

whichever is shallower.

Description of Subgroups

Typic Melanocryands.—The central concept or Typic

subgroup of Melanocryands is fixed on moderately deep or

deeper soils that have a 1500 kPa water retention of 15 percent

or more on air-dried samples or 30 percent or more on undried

samples in all subhorizons that meet the requirements for andic

soil properties and that are 25 cm or more thick and are within

100 cm of the mineral soil surface or of the upper boundary of

an organic layer that has andic soil properties, whichever is

shallower.

Typic Melanocryands commonly have relatively high

amounts of aluminum. They have been recognized in the

Pacific Northwest.

Lithic Melanocryands.—These soils are like Typic
292 Soil Taxonomy

Melanocryands, but they have a lithic contact within a depth

of 50 cm. They have not been recognized in the United

 States.

Vitric Melanocryands.—These soils are like Typic

Melanocryands, but they have a 1500 kPa water retention

of less than 15 percent on air-dried samples and less than

30 percent on undried samples in all subhorizons that meet

the requirements for andic soil properties and that are 25

cm or more thick and are within 100 cm of the mineral

soil surface or of the upper boundary of an organic layer

that has andic soil properties, whichever is shallower.

Vitric Melanocryands have not been recognized in the United

States.

Vitricryands

Vitricryands are the Cryands that have a 1500 kPa water

retention of less than 15 percent on air-dried samples and less

than 30 percent on undried samples throughout 60 percent or

more of the upper 60 cm of the andic materials. These soils do

not have a melanic epipedon or a layer that meets the depth,

thickness, and organic-carbon requirements for a melanic

epipedon. They do not have, in 75 percent or more of each

pedon, a cemented horizon that has its upper boundary within

100 cm of either the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower.

Characteristically, Vitricryands have a thin O horizon; an

ochric, mollic, or umbric epipedon; and a cambic horizon.

The Vitricryands in the United States generally developed in

Holocene deposits. Most formed under coniferous forest

vegetation.

Definition

Vitricryands are the Cryands that:

1. Have, in less than 75 percent of each pedon, a cemented

horizon that has its upper boundary within 100 cm of either the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower;

2. Do not have a melanic epipedon or an epipedon meeting

the depth, thickness, and organic-carbon requirements for a

melanic epipedon; and

3. Have a 1500 kPa water retention of less than 15 percent on

air-dried samples and less than 30 percent on undried samples

throughout 60 percent or more of the thickness either:

a. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a duripan,

or a petrocalcic horizon.

Key to Subgroups

DBEA. Vitricryands that have a lithic contact within

50 cm either of the mineral soil surface or of the top of an

organic layer that has andic soil properties, whichever is

shallower.

Lithic Vitricryands

DBEB. Other Vitricryands that have, in one or more horizons

at a depth between 50 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower, aquic conditions for some

time in normal years (or artificial drainage) and one or more of

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Vitricryands

DBEC. Other Vitricryands that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Vitricryands

DBED. Other Vitricryands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Vitricryands

DBEE. Other Vitricryands that have a xeric moisture regime

and a mollic or umbric epipedon.

Humic Xeric Vitricryands

DBEF. Other Vitricryands that have a xeric moisture regime.

Xeric Vitricryands

DBEG. Other Vitricryands that have an argillic or kandic

horizon that has both:
Andisols 293

1. An upper boundary within 125 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

2. A base saturation (by sum of cations) of less than 35

percent throughout the upper 50 cm or throughout the entire

argillic or kandic horizon if it is less than 50 cm thick.

Ultic Vitricryands

DBEH. Other Vitricryands that have an argillic or kandic

horizon that has its upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower.

Alfic Vitricryands

DBEI. Other Vitricryands that have a mollic or umbric

epipedon.

Humic Vitricryands

DBEJ. Other Vitricryands.

Typic Vitricryands

Definition of Typic Vitricryands

Typic Vitricryands are the Vitricryands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value 1 unit or more higher and an organic-carbon content 1

percent or more lower;

4. Do not have a xeric moisture regime;

5. Do not have an argillic or kandic horizon with its upper

boundary within 125 cm of the mineral soil surface or of the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower;

6. Do not have a mollic or umbric epipedon; and

7. Are not saturated with water in one or more layers within

100 cm of the mineral soil surface for 20 or more consecutive

days or 30 or more cumulative days in normal years.

Description of Subgroups

Typic Vitricryands.—The central concept or Typic

subgroup of Vitricryands is fixed on moderately deep or deep,

more or less well drained soils that have an ochric epipedon

and a udic moisture regime. These soils do not have an argillic

horizon. They do not have, between depths of 25 and 100 cm, a

buried, dark colored layer 10 cm or more thick below a lighter

colored horizon or horizons 10 cm or more thick with a lower

content of organic carbon.

Soils that have a lithic contact within a depth of 50 cm are

assigned to the Lithic subgroup. Soils that are saturated with

water in one or more layers within 100 cm of the mineral soil

surface for 20 or more consecutive days or 30 or more

cumulative days in normal years are excluded from the Typic

subgroup and are considered intergrades to Aquands. Soils that

have both aquic conditions (or artificial drainage) and redox

features in any horizon at a depth between 50 and 100 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, also are excluded from the Typic subgroup and are

considered intergrades to Aquands.

Typic Vitricryands are moderately extensive in the United

States. They are mainly in Washington, Oregon, and Idaho.

They commonly support coniferous forest vegetation. Most are

used for timber production, but some are used as recreational

areas.

Alfic Vitricryands.—These soils are like Typic

Vitricryands, but they have both an argillic or kandic horizon

within 125 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower, and a base saturation (by sum of cations) of 35

percent or more in some part of the argillic or kandic horizon.

These soils are of small extent in the United States. They are

mainly in Washington, Oregon, and Idaho. They commonly

support coniferous forest vegetation. Most are used for timber

production, but some are used as recreational areas.

Aquic Vitricryands.—These soils are like Typic

Vitricryands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are rare in the United States. Most are

used for timber production, but some are used as recreational

areas.

Humic Vitricryands.—These soils are like Typic

Vitricryands, but they have a mollic or umbric epipedon. They

are of small extent in the United States. They are mainly in

Alaska, Idaho, and Washington. They commonly support

grassy vegetation in Alaska and coniferous forest vegetation

elsewhere. Most of the soils are used as recreational areas or

for timber production.
294 Soil Taxonomy

Humic Xeric Vitricryands.—These soils are like Typic

Vitricryands, but they have both a mollic or umbric epipedon

and a xeric moisture regime. These soils are of small extent in

the United States. They are mainly in Washington. They

commonly support coniferous forest vegetation. Most are used

for timber production, but some are used as recreational areas.

Lithic Vitricryands.—These soils are like Typic

Vitricryands, but they have a lithic contact within a depth of 50

cm. They are mostly in Alaska and Washington and are of

small extent in the United States. They commonly support

grassy vegetation in Alaska and coniferous forest vegetation

elsewhere. Most of the soils are used as recreational areas or

for timber production.

Oxyaquic Vitricryands.—These soils are like Typic

Vitricryands, but they are saturated with water in one or more

layers within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. These soils are rare in the United States.

Thaptic Vitricryands.—These soils are like Typic

Vitricryands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States.

Ultic Vitricryands.—These soils are like Typic

Vitricryands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of less than 35 percent throughout the

upper 50 cm or throughout the entire horizon if it is less than

50 cm thick. These soils have not been recognized in the

United States.

Xeric Vitricryands.—These soils are like Typic Vitricryands,

but they have a xeric moisture regime. They are moderately

extensive in the United States. They are mainly in Washington

and Oregon. They commonly support coniferous forest

vegetation. Most are used for timber production, but some are

used as recreational areas.

Torrands

Torrands are the more or less well drained Andisols of dry

regions. These soils are not extensive. Some formed in the

western part of North America, and some are known to occur

in Hawaii and other Pacific islands. Most of the soils formed

under grassy or shrub vegetation.

Characteristically, Torrands have an ochric or mollic

epipedon and a cambic horizon. Some have a duripan or a

petrocalcic horizon.

The Torrands in the United States generally developed in

late-Pleistocene or Holocene deposits.

Definition

Torrands are the Andisols that:

1. Have an aridic soil moisture regime;

2. Have a frigid or warmer soil temperature regime; and

3. Do not have a histic epipedon or the aquic conditions

characteristic of Aquands.

Key to Great Groups

DCA. Torrands that have, in 75 percent or more of each

pedon, a cemented horizon that has its upper boundary within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower.

Duritorrands, p. 294

DCB. Other Torrands that have, on air-dried samples, a 1500

kPa water retention of less than 15 percent throughout 60

percent or more of the thickness either:

1. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

2. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Vitritorrands, p. 296

DCC. Other Torrands.

Haplotorrands, p. 295

Duritorrands

Duritorrands are the Torrands that have, in 75 percent or

more of each pedon, a cemented horizon that has its upper

boundary within 100 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties, whichever

is shallower.

Characteristically, these soils have an ochric or mollic

epipedon and a cambic horizon above the cemented horizon.

The Duritorrands in the United States generally developed

in late-Pleistocene deposits. Most formed under grass or shrub

vegetation, and some have widely spaced trees.

Definition

Duritorrands are the Torrands that have, in 75 percent or

more of each pedon, a cemented horizon that has its upper
Andisols 295

boundary within 100 cm of either the mineral soil surface or of

the top of an organic layer with andic soil properties, whichever

is shallower.

Key to Subgroups

DCAA. Duritorrands that have a petrocalcic horizon that has

its upper boundary within 100 cm of the mineral soil surface.

Petrocalcic Duritorrands

DCAB. Other Duritorrands that have, on air-dried samples, a

1500 kPa water retention of less than 15 percent throughout 60

percent or more of the thickness either:

1. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no paralithic contact or duripan within

that depth, and a point 60 cm below that depth; or

2. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a paralithic contact or a duripan.

Vitric Duritorrands

DCAC. Other Duritorrands.

Typic Duritorrands

Definition of Typic Duritorrands

Typic Duritorrands are the Duritorrands that:

1. Do not have a petrocalcic horizon with its upper boundary

within 100 cm of the mineral soil surface;

2. Do not have, on air-dried samples, a 1500 kPa water

retention of less than 15 percent throughout 60 percent or more

of the thickness either:

a. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no paralithic contact or duripan within

that depth, and a point 60 cm below that depth; or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a paralithic contact or a duripan.

Description of Subgroups

Typic Duritorrands.—The central concept or Typic

subgroup of Duritorrands is fixed on soils that have a cemented

horizon, other than a petrocalcic horizon, that has its upper

boundary within 100 cm of the mineral soil surface.

Commonly, the cemented horizon is a duripan. These soils do

not have, on air-dried samples, a 1500 kPa water retention of

less than 15 percent throughout 60 percent or more of the

thickness between either the mineral soil surface or the top of

an organic layer with andic soil properties and a point 60 cm

below that depth, a paralithic contact, or a duripan, whichever

is shallowest.

These soils are known to occur only in Hawaii and are of

small extent in the United States. They commonly support

grassy or shrub vegetation. Most are used as rangeland, but

some are used as recreational areas.

Petrocalcic Duritorrands.—These soils are like Typic

Duritorrands, but they have a petrocalcic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

These soils are known to occur only in Hawaii and are of small

extent in the United States. They commonly support grassy or

shrub vegetation. Most are used as rangeland, but some are

used as recreational areas.

Vitric Duritorrands.—These soils are like Typic

Duritorrands, but they have, on air-dried samples, a 1500 kPa

water retention of less than 15 percent throughout 60 percent

or more of the thickness between either the mineral soil surface

or the top of an organic layer with andic soil properties and a

point 60 cm below that depth, a paralithic contact, or a

duripan, whichever is shallowest.

These soils are known to occur only in Oregon and are of

small extent in the United States. They support grassy or shrub

vegetation, and some have widely spaced trees. Most of the

soils are used as rangeland, but some are used as recreational

areas.

Haplotorrands

Haplotorrands are the Torrands that do not have a cemented

horizon that has its upper boundary within 100 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower. These soils have, on

air-dried samples, a 1500 kPa water retention of 15 percent or

more throughout less than 60 percent of the thickness between

the mineral soil surface or the top of an organic layer with

andic soil properties, whichever is shallower, and a point 60

cm below the starting point or a densic, lithic, or paralithic

contact, whichever is shallower.

Characteristically, Haplotorrands have an ochric or mollic

epipedon and a cambic horizon.

The Haplotorrands in the United States generally developed

in late-Pleistocene deposits. Most formed under grass or shrub

vegetation, and some have widely spaced trees.

Definition

Haplotorrands are the Torrands that:

1. Do not have, in 75 percent or more of each pedon, a

cemented horizon that has its upper boundary within 100 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower;

2. Have, on air-dried samples, a 1500 kPa water retention of

15 percent or more throughout less than 60 percent of the

thickness either:

a. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever
296 Soil Taxonomy

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Key to Subgroups

DCCA. Haplotorrands that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Haplotorrands

DCCB. Other Haplotorrands that have a horizon 15 cm or

more thick that has 20 percent or more (by volume) cemented

soil material and has its upper boundary within 100 cm of the

mineral soil surface.

Duric Haplotorrands

DCCC. Other Haplotorrands that have a calcic horizon that

has its upper boundary within 125 cm of the mineral soil

surface.

Calcic Haplotorrands

DCCD. Other Haplotorrands.

Typic Haplotorrands

Definition of Typic Haplotorrands

Typic Haplotorrands are the Haplotorrands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have 20 percent or more (by volume) cemented soil

material in a horizon that has its upper boundary within 100

cm of the mineral soil surface and is more than 15 cm thick;

3. Do not have a calcic horizon with its upper boundary

within 125 cm of the mineral soil surface.

Description of Subgroups

Typic Haplotorrands.—The central concept or Typic

subgroup of Haplotorrands is fixed on moderately deep or deep

soils that have no horizon 15 cm or more thick that has 20

percent or more (by volume) cemented soil material and has its

upper boundary within 100 cm of the mineral soil surface.

These soils do not have a calcic horizon that has its upper

boundary within 125 cm of the mineral soil surface. Soils that

have a lithic contact within a depth of 50 cm are assigned to

the Lithic subgroup.

Typic Haplotorrands are known to occur only in Hawaii and

are of small extent in the United States. They commonly

support grassy or shrub vegetation. Most are used as rangeland,

but some are used as recreational areas.

Calcic Haplotorrands.—These soils are like Typic

Haplotorrands, but they have a calcic horizon that has its upper

boundary within 125 cm of the mineral soil surface. They are

known to occur only in Hawaii and are of small extent in the

United States. They commonly support grassy or shrub

vegetation. Most of the soils are used as rangeland, but some

are used as recreational areas.

Duric Haplotorrands.—These soils are like Typic

Haplotorrands, but they have 20 percent or more (by volume)

cemented soil material in a horizon that has its upper boundary

within 100 cm of the mineral soil surface and is more than 15

cm thick. These soils are known to occur only in Hawaii and

are of small extent in the United States. They commonly

support grassy or shrub vegetation. Most of the soils are used

as rangeland, but some are used as recreational areas.

Lithic Haplotorrands.—These soils are like Typic

Haplotorrands, but they have a lithic contact within a depth of

50 cm. They have not been recognized in the United States.

Vitritorrands

Vitritorrands are the Torrands that do not have a cemented

horizon that has its upper boundary within 100 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower. They have, on air-dried

samples, a 1500 kPa water retention of less than 15 percent

throughout 60 percent or more of the thickness between the

mineral soil surface or the top of an organic layer with andic

soil properties, whichever is shallower, and a point 60 cm

below the starting point or a densic, lithic, or paralithic

contact, whichever is shallower.

Characteristically, Vitritorrands have an ochric or mollic

epipedon and a cambic horizon.

The Vitritorrands in the United States generally developed

in Holocene deposits. Most formed under grass or shrub

vegetation, and some have widely spaced trees.

Definition

Vitritorrands are the Torrands that:

1. Have, on air-dried samples, a 1500 kPa water retention of

less than 15 percent throughout 60 percent or more of the

thickness either:

a. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no paralithic contact or duripan within

that depth, and a point 60 cm below that depth; or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a paralithic contact or a duripan; and

2. Do not have, in 75 percent or more of each pedon, a

cemented horizon that has its upper boundary within 100 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.
Andisols 297

Key to Subgroups

DCBA. Vitritorrands that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Vitritorrands

DCBB. Other Vitritorrands that have a horizon 15 cm or

more thick that has 20 percent or more (by volume) cemented

soil material and has its upper boundary within 100 cm of the

mineral soil surface.

Duric Vitritorrands

DCBC. Other Vitritorrands that have, in one or more

horizons at a depth between 50 and 100 cm from the mineral

soil surface, aquic conditions for some time in normal years (or

artificial drainage) and one or more of the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Vitritorrands

DCBD. Other Vitritorrands that have a calcic horizon that

has its upper boundary within 125 cm of the mineral soil

surface.

Calcic Vitritorrands

DCBE. Other Vitritorrands.

Typic Vitritorrands

Definition of Typic Vitritorrands

Typic Vitritorrands are the Vitritorrands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have 20 percent or more (by volume) cemented soil

material in a horizon that has its upper boundary within 100

cm of the mineral soil surface and is more than 15 cm thick;

3. Do not have, in any horizon at a depth between 50 and 100

cm from the mineral soil surface, both aquic conditions and

any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated; and

4. Do not have a calcic horizon with its upper boundary within

125 cm of the mineral soil surface.

Description of Subgroups

Typic Vitritorrands.—The central concept or Typic

subgroup of Vitritorrands is fixed on moderately deep or deep

soils that have no horizon 15 cm or more thick that has 20

percent or more (by volume) cemented soil material and has its

upper boundary within 100 cm of the mineral soil surface.

These soils do not have a calcic horizon that has its upper

boundary within 125 cm of the mineral soil surface. Soils that

have a lithic contact within a depth of 50 cm are assigned to

the Lithic subgroup.

Typic Vitritorrands are known to occur only in Oregon and

are of small extent in the United States. They commonly

support grassy or shrub vegetation and some widely spaced

trees. Most of the soils are used as rangeland, but some are

used as recreational areas.

Aquic Vitritorrands.—These soils are like Typic

Vitritorrands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are not known to occur in the United

States.

Calcic Vitritorrands.—These soils are like Typic

Vitritorrands, but they have a calcic horizon that has its upper

boundary within 125 cm of the mineral soil surface. These soils

are not known to occur in the United States.

Duric Vitritorrands.—These soils are like Typic

Vitritorrands, but they have 20 percent or more (by volume)

cemented soil material in a horizon that has its upper boundary

within 100 cm of the mineral soil surface and is more than 15

cm thick. These soils are not known to occur in the United

States.

Lithic Vitritorrands.—These soils are like Typic

Vitritorrands, but they have a lithic contact within a depth of

50 cm. They have not been recognized in the United States.

Udands

Udands are the more or less well drained Andisols of moist

regions. These soils are moderately extensive. They are mostly

on the Pacific rim, mainly in the western part of North

America and in Japan, New Zealand, the Philippines, and

Indonesia. Most of the Udands in the United States are in

Washington and Oregon, but some are in Hawaii. Most Udands

formed under forest vegetation.

Characteristically, Udands have an ochric or umbric

epipedon and a cambic horizon. Some have a duripan.
298 Soil Taxonomy

Most of the Udands in the United States developed in latePleistocene or Holocene deposits.

Definition

Udands are the Andisols that:

1. Have a udic soil moisture regime;

2. Have a frigid or warmer soil temperature regime;

3. Do not have a histic epipedon or the aquic conditions

characteristic of Aquands; and

4. Have a 1500 kPa water retention of 15 percent or more on

air-dried samples and 30 percent or more on undried samples

throughout more than 40 percent of the thickness either:

a. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Key to Great Groups

DGA. Udands that have, in half or more of each pedon, a

placic horizon within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower.

Placudands, p. 314

DGB. Other Udands that have, in 75 percent or more of each

pedon, a cemented horizon that has its upper boundary within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower.

Durudands, p. 298

DGC. Other Udands that have a melanic epipedon.

Melanudands, p. 310

DGD. Other Udands that have, on undried samples, a 1500

kPa water retention of 100 percent or more, by weighted

average, throughout either:

1. One or more layers with a total thickness of 35 cm

between the mineral soil surface or the top of an organic

layer with andic soil properties, whichever is shallower, and

100 cm from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no densic, lithic, or paralithic contact,

duripan, or petrocalcic horizon within that depth; or

2. 60 percent or more of the horizon thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a

densic, lithic, or paralithic contact, a duripan, or a

petrocalcic horizon.

Hydrudands, p. 308

DGE. Other Udands that have a layer that meets the depth,

thickness, and organic-carbon requirements for a melanic

epipedon.

Fulvudands, p. 300

DGF. Other Udands.

Hapludands, p. 303

Durudands

Durudands are moderately deep or shallow Udands that do

not have a placic horizon. In 75 percent or more of each pedon,

they have a cemented horizon that has its upper boundary

within 100 cm of the mineral soil surface or of the upper

boundary of an organic layer that has andic soil properties,

whichever is shallower.

Characteristically, Durudands have a thin O horizon, an

ochric or umbric epipedon, a cambic horizon, and a cemented

horizon.

The Durudands in the United States generally developed in

late-Pleistocene deposits. Most formed under coniferous forest

vegetation.

Definition

Durudands are the Udands that:

1. Do not have, in half or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface or of the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower; and

2. Have, in 75 percent or more of each pedon, a cemented

horizon with its upper boundary within 100 cm of the mineral

soil surface or of the upper boundary of an organic layer that

has andic soil properties, whichever is shallower.

Key to Subgroups

DGBA. Durudands that have, in one or more horizons above

the cemented horizon, aquic conditions for some time in

normal years (or artificial drainage) and one or more of the

following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to
Andisols 299

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Durudands

DGBB. Other Durudands that have extractable bases (by

NH4

OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, and the cemented horizon.

Acrudoxic Durudands

DGBC. Other Durudands that have, on undried samples, a

1500 kPa water retention of 70 percent or more throughout a

layer 35 cm or more thick above the cemented horizon.

Hydric Durudands

DGBD. Other Durudands that have more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

a layer 50 cm or more thick within 60 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Pachic Durudands

DGBE. Other Durudands.

Typic Durudands

Definition of Typic Durudands

Typic Durudands are the Durudands that:

1. Do not have, in any horizon at a depth between 50 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, and the cemented horizon, both aquic conditions

and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

2. Do not have, on undried samples, a 1500 kPa water

retention of 70 percent or more throughout a continuous

thickness of 35 cm or more above the cemented horizon;

3. Have extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick at a depth

between either 25 cm from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower, and the cemented horizon; and

4. Do not have more than 6.0 percent organic carbon and the

colors of a mollic epipedon throughout a layer 50 cm or more

thick within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Description of Subgroups

Typic Durudands.—The central concept or Typic subgroup

of Durudands is fixed on moderately deep or shallow soils that

have, on undried samples, a 1500 kPa water retention of less

than 70 percent throughout all layers 35 cm or more thick

above the cemented horizon.

Soils that have both aquic conditions (or artificial drainage)

and redox features in any horizon at a depth between 50 and

100 cm either from the mineral soil surface or from the top of

an organic layer with andic soil properties, whichever is

shallower, are excluded from the Typic subgroup and are

considered intergrades to Aquands. Soils that have more than

6.0 percent organic carbon and the colors of a mollic epipedon

throughout a layer 50 cm or more thick within 60 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower, also are

excluded.

Typic Durudands are moderately extensive in the United

States. They commonly support coniferous forest vegetation.

Most of these soils are used for timber production, but some are

used as recreational areas.

Acrudoxic Durudands.—These soils are like Typic

Durudands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more at a depth between 25 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, and the cemented

horizon. These soils have not been recognized in the United

States.

Aquic Durudands.—These soils are like Typic Durudands,

but they have both aquic conditions (or artificial drainage) and

redox features in a horizon at a depth between 50 cm either

from the mineral soil surface or from the top of an organic

layer with andic soil properties, whichever is shallower, and

the cemented horizon. These soils are of small extent in the

State of Washington. Most of the soils are used for timber

production.

Hydric Durudands.—These soils are like Typic

Durudands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick above the cemented horizon. These soils are rare

and are known to occur only in Hawaii.

Pachic Durudands.—These soils are like Typic Durudands,

but they have more than 6.0 percent organic carbon and the

colors of a mollic epipedon throughout a layer 50 cm or more

thick within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is
300 Soil Taxonomy

shallower. These soils are not known to occur in the United

States.

Fulvudands

Fulvudands are the Udands that do not have a melanic

epipedon but have a layer that meets the depth, thickness, and

organic-carbon requirements for a melanic epipedon. These

soils can have a lithic contact. In 75 percent or more of each

pedon, however, they do not have a placic horizon or any other

cemented horizon with its upper boundary within 100 cm of

the mineral soil surface or of the upper boundary of an organic

layer that has andic soil properties, whichever is shallower.

The soils have, on undried samples, a 1500 kPa water retention

of less than 100 percent, by weighted average, throughout the

major part of the andic materials.

Characteristically, Fulvudands have a thin O horizon, an

umbric epipedon, and a cambic horizon.

The Fulvudands in the United States generally developed in

late-Pleistocene deposits. Most formed under coniferous forest

vegetation.

Definition

Fulvudands are the Udands that:

1. Do not have, within 100 cm of the mineral soil surface or

of the upper boundary of an organic layer that has andic soil

properties, whichever is shallower, the upper boundary of a

placic horizon that occurs in half or more of each pedon and

can have a lithic contact but do not have any other cemented

horizon that occurs in 75 percent or more of each pedon within

these depths;

2. Do not have, on undried samples, a 1500 kPa water

retention of 100 percent or more, by weighted average,

throughout either:

a. One or more layers with a total thickness of 35 cm

between the mineral soil surface or the top of an organic

layer with andic soil properties, whichever is shallower, and

100 cm from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no densic, lithic, or paralithic contact,

duripan, or petrocalcic horizon within that depth; or

b. 60 percent or more of the horizon thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a

densic, lithic, or paralithic contact, a duripan, or a

petrocalcic horizon; and

3. Do not have a melanic epipedon but have a layer that

meets the depth, thickness, and organic-carbon requirements

for a melanic epipedon.

Key to Subgroups

DGEA. Fulvudands that have both:

1. A lithic contact within 50 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

2. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N

KCl) in the fine-earth fraction and with a total thickness of

10 cm or more at a depth between 25 cm from the mineral

soil surface or from the top of an organic layer with andic

soil properties, whichever is shallower, and the lithic

contact.

Eutric Lithic Fulvudands

DGEB. Other Fulvudands that have a lithic contact within 50

cm either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Fulvudands

DGEC. Other Fulvudands that have, in one or more horizons

at a depth between 50 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower, aquic conditions for some

time in normal years (or artificial drainage) and one or more of

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Fulvudands

DGED. Other Fulvudands that have, on undried samples, a

1500 kPa water retention of 70 percent or more throughout a

layer 35 cm or more thick within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Hydric Fulvudands

DGEE. Other Fulvudands that have extractable bases (by

NH4

OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower.

Acrudoxic Fulvudands

DGEF. Other Fulvudands that have an argillic or kandic

horizon that has both:

1. An upper boundary within 125 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and
Andisols 301

2. A base saturation (by sum of cations) of less than 35

percent throughout its upper 50 cm.

Ultic Fulvudands

DGEG. Other Fulvudands that have both:

1. No horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N

KCl) in the fine-earth fraction and with a total thickness of

10 cm or more at a depth between 25 and 50 cm either from

the mineral soil surface or from the top of an organic layer

with andic soil properties, whichever is shallower; and

2. Throughout a layer 50 cm or more thick within 60 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower:

a. More than 6.0 percent organic carbon, by weighted

average; and

b. More than 4.0 percent organic carbon in all parts.

Eutric Pachic Fulvudands

DGEH. Other Fulvudands that have no horizons with more

than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction

and with a total thickness of 10 cm or more at a depth between

25 and 50 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower.

Eutric Fulvudands

DGEI. Other Fulvudands that have, throughout a layer 50 cm

or more thick within 60 cm either of the mineral soil surface or

of the top of an organic layer with andic soil properties,

whichever is shallower:

1. More than 6.0 percent organic carbon, by weighted

average; and

2. More than 4.0 percent organic carbon in all parts.

Pachic Fulvudands

DGEJ. Other Fulvudands that have, at a depth between 40

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Fulvudands

DGEK. Other Fulvudands.

Typic Fulvudands

Definition of Typic Fulvudands

Typic Fulvudands are the Fulvudands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Do not have throughout a layer 50 cm or more thick within

60 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower, both:

a. More than 6.0 percent organic carbon, by weighted

average; and

b. More than 4.0 percent organic carbon in all parts;

4. On undried samples, have a 1500 kPa water retention of

less than 70 percent throughout all layers 35 cm or more thick

within the upper 100 cm;

5. Do not have, between depths of 40 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value 1 unit or more higher and an organic-carbon content 1

percent or more lower;

6. Have an Al3+ (1N KCl extractable) of 2.0 cmol(+)/kg in the

fine-earth fraction throughout all layers 10 cm or more thick

between depths of 25 and 50 cm;

7. Have extractable bases (by NH4OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick between depths

of 25 and 100 cm; and

8. Do not have an argillic or kandic horizon that has its

upper boundary within 125 cm of the mineral soil surface or of

the upper boundary of an organic layer with andic soil

properties, whichever is shallower, and base saturation (by sum

of cations) of less than 35 percent throughout the upper 50 cm

of that horizon.

Description of Subgroups

Typic Fulvudands.—The central concept or Typic subgroup

of Fulvudands is fixed on moderately deep or deep soils that

have a relatively high amount of aluminum. These soils have,

on undried samples, a 1500 kPa water retention of less than 70
302 Soil Taxonomy

percent throughout all layers 35 cm or more thick within 100

cm either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower. Soils

that have, at a depth between 40 and 100 cm either from the

mineral soil surface or from the top of an organic layer with andic

soil properties, whichever is shallower, a dark colored layer 10

cm or more thick with more than 3.0 percent organic carbon,

underlying one or more lighter colored horizons with a total

thickness of 10 cm or more and a lower content of organic

carbon, are excluded from the Typic subgroup. The upper part

of Typic Fulvudands has extractable bases plus 1N KClextractable Al3+ that total more than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more.

Soils that have both aquic conditions (or artificial drainage)

and redox features in any horizon at a depth between 50 and

100 cm either from the mineral soil surface or from the top of

an organic layer with andic soil properties, whichever is

shallower, are excluded from the Typic subgroup and are

considered intergrades to Aquands. Soils that average more

than 6.0 percent organic carbon throughout a layer 50 cm or

more thick in the upper part also are excluded.

Typic Fulvudands are moderately extensive in the United

States. They commonly support coniferous forest vegetation.

Most of these soils are used for timber production, but some are

used as cropland.

Acrudoxic Fulvudands.—These soils are like Typic

Fulvudands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more at a depth between 25 and 100 cm either from

the mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower. These soils are

not known to occur in the United States. They are established

for use in other countries.

Aquic Fulvudands.—These soils are like Typic Fulvudands,

but they have both aquic conditions (or artificial drainage) and

redox features in a horizon at a depth between 50 and 100 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower. These soils are of small extent and are known to

occur only in the State of Washington in the United States.

Most of the soils are used for timber production.

Eutric Fulvudands.—These soils are like Typic

Fulvudands, but they do not have one or more horizons with

more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth

fraction and with a total thickness of 10 cm or more at a depth

between 25 and 50 cm either from the mineral soil surface or

from the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States. They are established for use in other

countries.

Eutric Lithic Fulvudands.—These soils are like Typic

Fulvudands, but they have a lithic contact within 50 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower. They do not have

one or more horizons with more than 2.0 cmol(+)/kg Al3+ (by 1N

KCl) in the fine-earth fraction and with a total thickness of 10 cm

or more at a depth between 25 and 50 cm either from the mineral

soil surface or from the top of an organic layer with andic soil

properties, whichever is shallower. These soils are of small

extent and are known to occur only in the State of Washington

in the United States. Most of the soils are used for timber

production, but some are used as recreational areas.

Eutric Pachic Fulvudands.—These soils are like Typic

Fulvudands, but they do not have horizons with more than 2.0

cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction and with

a total thickness of 10 cm or more at a depth between 25 and

50 cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower. They have, throughout a layer 50 cm or more thick

within 60 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower, both more than 6.0 percent organic carbon, by

weighted average, and more than 4.0 percent organic carbon in

all parts.

Hydric Fulvudands.—These soils are like Typic

Fulvudands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States. They are established for use in other

countries.

Lithic Fulvudands.—These soils are like Typic

Fulvudands, but they have a lithic contact within 50 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower. These soils are of

small extent and are known to occur only in the State of

Washington. Most of the soils are used for timber production,

but some are used as recreational areas.

Pachic Fulvudands.—These soils are like Typic

Fulvudands, but they have, throughout a layer 50 cm or more

thick within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower, both more than 6.0 percent organic carbon, by

weighted average, and more than 4.0 percent organic carbon in

all parts. These soils are not known to occur in the United

States.

Thaptic Fulvudands.—These soils are like Typic

Fulvudands, but they have, between depths of 25 and 100 cm, a

buried, dark colored layer 10 cm or more thick below a lighter

colored horizon or horizons 10 cm or more thick with a lower

content of organic carbon. These soils have not been

recognized in the United States.

Ultic Fulvudands.—These are the Fulvudands that have an

argillic or kandic horizon with a base saturation of less than 35

percent throughout the upper 50 cm. These soils do not have a
Andisols 303

lithic contact within 50 cm of the mineral soil surface or aquic

conditions within 100 cm of the mineral soil surface. They occur

in the Pacific Northwest, where they formed under forest

vegetation.

Hapludands

Hapludands are the Udands that do not have a melanic

epipedon or a layer that meets the depth, thickness, and

organic-carbon requirements for a melanic epipedon. They do

not have a placic horizon with its upper boundary within 100

cm of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower. They can have a lithic contact but do not have any

other cemented horizon in 75 percent or more of each pedon

within these depths. They have, on undried samples, a 1500

kPa water retention of less than 100 percent, by weighted

average, throughout the major part of the andic materials.

Commonly, Hapludands have a thin O horizon, an ochric or

umbric epipedon, and a cambic horizon.

Most of the Hapludands in the United States developed in

late-Pleistocene or Holocene deposits. Most formed under

coniferous forest vegetation.

Definition

Hapludands are the Udands that:

1. Do not have, in half or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface or of the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower;

2. Do not have, in 75 percent or more of each pedon, a

cemented horizon with its upper boundary within 100 cm of

the mineral soil surface or of the upper boundary of an organic

layer that has andic soil properties, whichever is shallower;

3. Do not have a melanic epipedon or an epipedon meeting

the depth, thickness, and organic-carbon requirements for a

melanic epipedon; and

4. Have, on undried samples, a 1500 kPa water retention of

less than 100 percent, by weighted average, throughout all

layers 35 cm or more thick within 100 cm of the mineral soil

surface or of the upper boundary of an organic layer that has

andic soil properties, whichever is shallower.

Key to Subgroups

DGFA. Hapludands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Hapludands

DGFB. Other Hapludands that have anthraquic conditions.

Anthraquic Hapludands

DGFC. Other Hapludands that have both:

1. A horizon 15 cm or more thick that has 20 percent or more

(by volume) cemented soil material and has its upper

boundary within 100 cm either of the mineral soil surface or

of the top of an organic layer with andic soil properties,

whichever is shallower; and

2. In one or more horizons at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, aquic conditions for some time in normal years

(or artificial drainage) and one or more of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on

faces of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction

to alpha,alpha-dipyridyl at a time when the soil is not

being irrigated.

Aquic Duric Hapludands

DGFD. Other Hapludands that have a horizon 15 cm or more

thick that has 20 percent or more (by volume) cemented soil

material and has its upper boundary within 100 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Duric Hapludands

DGFE. Other Hapludands that have more than 2.0

cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one

or more horizons with a total thickness of 10 cm or more at a

depth between 25 and 50 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower.

Alic Hapludands

DGFF. Other Hapludands that have, in one or more horizons

at a depth between 50 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower, aquic conditions for some

time in normal years (or artificial drainage) and one or more of

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Hapludands
304 Soil Taxonomy

DGFG. Other Hapludands that have both:

1. Extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the

fine-earth fraction of one or more horizons with a total

thickness of 30 cm or more at a depth between 25 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower; and

2. On undried samples, a 1500 kPa water retention of 70

percent or more throughout a layer 35 cm or more thick

within 100 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower.

Acrudoxic Hydric Hapludands

DGFH. Other Hapludands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, both:

1. Extractable bases (by NH4OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the

fine-earth fraction of one or more horizons with a total

thickness of 30 cm or more; and

2. A layer 10 cm or more thick with more than 3.0 percent

organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent

or more (absolute) lower.

Acrudoxic Thaptic Hapludands

DGFI. Other Hapludands that have both:

1. Extractable bases (by NH4OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the

fine-earth fraction of one or more horizons with a total

thickness of 30 cm or more at a depth between 25 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower; and

2. An argillic or kandic horizon that has both:

a. An upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower; and

b. A base saturation (by sum of cations) of less than 35

percent throughout its upper 50 cm.

Acrudoxic Ultic Hapludands

DGFJ. Other Hapludands that have extractable bases (by

NH4

OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

and 100 cm either from the mineral soil surface or from the top of

an organic layer with andic soil properties, whichever is

shallower.

Acrudoxic Hapludands

DGFK. Other Hapludands that have a 1500 kPa water

retention of less than 15 percent on air-dried samples and less

than 30 percent on undried samples throughout one or more

layers that have andic soil properties and have a total thickness

of 25 cm or more within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Vitric Hapludands

DGFL. Other Hapludands that have both:

1. On undried samples, a 1500 kPa water retention of 70

percent or more throughout a layer 35 cm or more thick

within 100 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower; and

2. At a depth between 25 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, a layer 10 cm

or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, underlying

one or more horizons with a total thickness of 10 cm or

more that have a color value, moist, 1 unit or more higher

and an organic-carbon content 1 percent or more (absolute)

lower.

Hydric Thaptic Hapludands

DGFM. Other Hapludands that have, on undried samples, a

1500 kPa water retention of 70 percent or more throughout a

layer 35 cm or more thick within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Hydric Hapludands

DGFN. Other Hapludands that have both:

1. A sum of extractable bases of more than 25.0

cmol(+)/kg in the fine-earth fraction throughout one or

more horizons with a total thickness of 15 cm or more at a

depth between 25 and 75 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower; and

2. At a depth between 25 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, a layer 10 cm

or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, underlying

one or more horizons with a total thickness of 10 cm or
Andisols 305

more that have a color value, moist, 1 unit or more higher

and an organic-carbon content 1 percent or more (absolute)

lower.

Eutric Thaptic Hapludands

DGFO. Other Hapludands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Hapludands

DGFP. Other Hapludands that have a sum of extractable

bases of more than 25.0 cmol(+)/kg in the fine-earth fraction

throughout one or more horizons with a total thickness of 15

cm or more at a depth between 25 and 75 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower.

Eutric Hapludands

DGFQ. Other Hapludands that have an oxic horizon that has

its upper boundary within 125 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Oxic Hapludands

DGFR. Other Hapludands that have an argillic or kandic

horizon that has both:

1. An upper boundary within 125 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

2. A base saturation (by sum of cations) of less than 35

percent throughout its upper 50 cm.

Ultic Hapludands

DGFS. Other Hapludands that have an argillic or kandic

horizon that has its upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower.

Alfic Hapludands

DGFT. Other Hapludands.

Typic Hapludands

Definition of Typic Hapludands

Typic Hapludands are the Hapludands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a horizon with its upper boundary within 100

cm of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower, that is more than 15 cm thick and that has 20 percent

or more (by volume) cemented soil material;

3. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

4. Do not have anthraquic conditions;

5. Have, on undried samples, a 1500 kPa water retention of

less than 70 percent throughout all layers 35 cm or more thick

within 100 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower;

6. Have a 1500 kPa water retention of 15 percent or more on

air-dried samples or 30 percent or more on undried samples

throughout all layers that have andic soil properties and have a

total thickness of 25 cm or more within 100 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower;

7. Have 1N KCl-extractable Al3+ of 2.0 or less cmol(+) kg-1 in

the fine-earth fraction throughout all layers 10 cm or more

thick between depths of 25 and 50 cm;

8. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value, moist, 1 unit or more higher and an organic-carbon

content 1 percent or more lower;

9. Have a sum of bases of 25.0 or less cmol(+) kg-1 in the

fine-earth fraction of one or more subhorizons 35 cm or more

thick between depths of 25 and 75 cm;

10. Have extractable bases (by NH4OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick between depths

of 25 and 100 cm; and

11. Do not have an argillic, kandic, or oxic horizon with its

upper boundary within 125 cm of the mineral soil surface or of

the upper boundary of an organic layer that has andic soil

properties, whichever is shallower.
306 Soil Taxonomy

Description of Subgroups

Typic Hapludands.—The central concept or Typic

subgroup of Hapludands is fixed on moderately deep or deep

soils that have 2.0 or less cmol(+)/kg Al3+ (by 1N KCl) in the

fine-earth fraction of a layer 10 cm or more thick at a depth

between 25 and 50 cm either from the mineral soil surface or

from the top of an organic layer with andic soil properties,

whichever is shallower. These soils have, within 100 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower, a 1500 kPa water

retention of 15 percent or more on air-dried samples

throughout all layers 25 cm or more thick and between 30 and

70 percent on undried samples throughout all layers 35 cm or

more thick. The sum of extractable bases is 25.0 cmol(+)/kg or

less throughout horizons with a total thickness of 15 cm or more

in the upper part of the soils.

Soils that have, at a depth between 40 and 100 cm either from

the mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, a dark colored layer

10 cm or more thick with more than 3.0 percent organic carbon,

underlying one or more lighter colored horizons with a total

thickness of 10 cm or more and a lower content of organic

carbon, are excluded from the Typic subgroup. Typic

Hapludands do not have a horizon 15 cm or more thick with 20

percent or more (by volume) cemented soil material in the upper

part. Extractable bases plus 1N KCl-extractable Al3+ total more

than 2.0 cmol(+)/kg in the fine-earth fraction of one or more

horizons with a total thickness of 30 cm or more in the upper part

of these soils.

Soils that have anthraquic conditions and soils with both

aquic conditions (or artificial drainage) and redox features in

any horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, are excluded

from the Typic subgroup and are considered intergrades to

Aquands. Soils that have a lithic contact within a depth of 50

cm are assigned to the Lithic subgroup.

Typic Hapludands are moderately extensive in the United

States. They commonly support coniferous forest vegetation.

Most of these soils are used for timber production, but some

have been cleared and are used as cropland.

Acrudoxic Hapludands.—These soils are like Typic

Hapludands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more at a depth between 25 and 100 cm either from

the mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower. These soils are

not known to occur in the United States. They are established

for use in other countries.

Acrudoxic Hydric Hapludands.—These soils are like

Typic Hapludands, but they have extractable bases plus 1N

KCl-extractable Al3+ totaling less than 2.0 cmol(+)/kg in the

fine-earth fraction of one or more horizons with a total

thickness of 30 cm or more at a depth between 25 and 100 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower. They also have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States. They are established for use in other

countries.

Acrudoxic Thaptic Hapludands.—These soils are like

Typic Hapludands, but they have, between depths of 25 and

100 cm, a buried, dark colored layer 10 cm or more thick

below a lighter colored horizon or horizons 10 cm or more

thick with a lower content of organic carbon. They also have

extractable bases plus 1N KCl-extractable Al3+ totaling less

than 2.0 cmol(+)/kg in the fine-earth fraction of one or more

horizons with a total thickness of 30 cm or more at a depth

between 25 and 100 cm either from the mineral soil surface or

from the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States. They are established for use in other

countries.

Acrudoxic Ultic Hapludands.—These soils are like Typic

Hapludands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more at a depth between 25 and 100 cm either from

the mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower. They also have

an argillic or kandic horizon that has both an upper boundary

within 125 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower, and a base saturation (by sum of cations) of less

than 35 percent throughout the upper 50 cm or throughout the

entire horizon if it is less than 50 cm thick. These soils are not

known to occur in the United States. They are established for

use in other countries.

Alfic Hapludands.—These soils are like Typic Hapludands,

but they have an argillic or kandic horizon that has both an

upper boundary within 125 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower, and a base saturation (by

sum of cations) of 35 percent or more in some part of the upper

50 cm or in the entire horizon if it is less than 50 cm thick.

These soils are not known to occur in the United States. They

are established for use in other countries.

Alic Hapludands.—These soils are like Typic Hapludands,

but they have more than 2.0 cmol(+)/kg Al3+ (by 1N KCl) in

the fine-earth fraction of one or more horizons with a total

thickness of 10 cm or more at a depth between 25 and 50 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is
Andisols 307

shallower. These soils are moderately extensive in the United

States. They commonly support coniferous forest vegetation.

Most of the soils are used for timber production, but some have

been cleared and are used as cropland.

Anthraquic Hapludands.—These soils are like Typic

Hapludands, but they have anthraquic conditions. They are

used for the production of paddy rice. These soils are not

known to occur in the United States. They are established for

use in other countries.

Aquic Duric Hapludands.—These soils are like Typic

Hapludands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are not known to occur in the United

States. They are established for use in other countries.

Aquic Hapludands.—These soils are like Typic

Hapludands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are of small extent and are known to

occur only in the State of Washington. Most of the soils are

used for timber production.

Duric Hapludands.—These soils are like Typic

Hapludands, but they have a horizon 15 cm or more thick that

has 20 percent or more (by volume) cemented soil material and

has its upper boundary within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils have not been

recognized in the United States.

Eutric Hapludands.—These soils are like Typic

Hapludands, but they have a sum of extractable bases of more

than 25.0 cmol(+)/kg in the fine-earth fraction throughout one

or more horizons with a total thickness of 15 cm or more at a

depth between 25 and 75 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower. These soils are not known

to occur in the United States. They are established for use in

other countries.

Eutric Thaptic Hapludands.—These Hapludands have a

sum of extractable bases of more than 25.0 cmol(+)/kg in the

fine-earth fraction throughout one or more horizons with a

total thickness of 15 cm or more at a depth between 25 and 75

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower. These soils also have a buried mineral layer. They

do not have aquic conditions within a depth of 100 cm or high

amounts of aluminum. They are not known to occur in the

United States. They are established for use in other countries.

Hydric Hapludands.—These soils are like Typic

Hapludands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower. They also have, between depths of 25

and 100 cm, a buried, dark colored layer 10 cm or more thick

below a lighter colored horizon or horizons 10 cm or more

thick with a lower content of organic carbon. These soils are

rare and are known to occur only in Hawaii in the United

States.

Hydric Thaptic Hapludands.—These soils are like Typic

Hapludands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States. They are established for use in other

countries.

Lithic Hapludands.—These soils are like Typic

Hapludands, but they have a lithic contact within 50 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower. These soils are of

small extent in Washington and Oregon in the United States.

Most are used for timber production, but some are used as

recreational areas.

Oxic Hapludands.—These soils are like Typic Hapludands,

but they have an oxic horizon that has its upper boundary

within 125 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower. These soils are not known to occur in the United

States.

Thaptic Hapludands.—These soils are like Typic

Hapludands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States.

Ultic Hapludands.—These soils are like Typic Hapludands,

but they have an argillic or kandic horizon that has both an

upper boundary within 125 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower, and a base saturation (by

sum of cations) of less than 35 percent throughout the upper 50

cm or throughout the entire horizon if it is less than 50 cm

thick. These soils are not known to occur in the United States.

They are established for use in other countries.

Vitric Hapludands.—These soils are like Typic Hapludands,

but they have a 1500 kPa water retention of less than 15 percent

on air-dried samples and less than 30 percent on undried

samples throughout one or more layers that have andic soil

properties and have a total thickness of 25 cm or more within 100

cm either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower. These

soils are of small extent in Washington and Oregon in the United

States. Most are used for timber production. Some have been

cleared and are used as cropland, and some are used as

recreational areas.
308 Soil Taxonomy

Hydrudands

Hydrudands are the Udands that have, on undried samples,

a 1500 kPa water retention of 100 percent or more, by

weighted average, throughout the major part of the andic

materials. These soils do not have, in 75 percent or more of

each pedon, a melanic epipedon or a placic horizon or any

other cemented horizon with its upper boundary within 100 cm

of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower.

Commonly, Hydrudands have a thin O horizon, an ochric or

umbric epipedon, and a cambic horizon.

Most of the Hydrudands in the United States developed in

late-Pleistocene deposits and formed under forest vegetation.

Definition

Hydrudands are the Udands that:

1. Do not have, in half or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface or of the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower;

2. Do not have, in 75 percent or more of each pedon, a

cemented horizon with its upper boundary within 100 cm of

the mineral soil surface or of the upper boundary of an organic

layer that has andic soil properties, whichever is shallower;

3. Do not have a melanic epipedon; and

4. Have, on undried samples, a 1500 kPa water retention of

100 percent or more, by weighted average, throughout either:

a. One or more layers with a total thickness of 35 cm

between the mineral soil surface or the top of an organic

layer with andic soil properties, whichever is shallower, and

100 cm from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, if there is no densic, lithic, or paralithic contact,

duripan, or petrocalcic horizon within that depth; or

b. 60 percent or more of the horizon thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a

densic, lithic, or paralithic contact, a duripan, or a

petrocalcic horizon.

Key to Subgroups

DGDA. Hydrudands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Hydrudands

DGDB. Other Hydrudands that have, in one or more

horizons at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, aquic conditions

for some time in normal years (or artificial drainage) and one or

more of the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or more

chroma of 2 or less either in redox depletions on faces of peds

or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Hydrudands

DGDC. Other Hydrudands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, both:

1. Extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the

fine-earth fraction of one or more horizons with a total

thickness of 30 cm or more; and

2. A layer 10 cm or more thick with more than 3.0 percent

organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent

or more (absolute) lower.

Acrudoxic Thaptic Hydrudands

DGDD. Other Hydrudands that have extractable bases (by

NH4OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower.

Acrudoxic Hydrudands

DGDE. Other Hydrudands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Hydrudands

DGDF. Other Hydrudands that have a sum of extractable

bases of more than 25.0 cmol(+)/kg in the fine-earth fraction

throughout one or more horizons with a total thickness of 15

cm or more at a depth between 25 and 75 cm either from the
Andisols 309

mineral soil surface or from the top of an organic layer with andic

soil properties, whichever is shallower.

Eutric Hydrudands

DGDG. Other Hydrudands that have an argillic or kandic

horizon that has both:

1. An upper boundary within 125 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

2. A base saturation (by sum of cations) of less than 35

percent throughout its upper 50 cm.

Ultic Hydrudands

DGDH. Other Hydrudands.

Typic Hydrudands

Definition of Typic Hydrudands

Typic Hydrudands are the Hydrudands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value, moist, 1 unit or more higher and an organic-carbon

content 1 percent or more lower;

4. Have a sum of bases of 25.0 or less cmol(+) kg-1 in the

fine-earth fraction of one or more subhorizons 35 cm or more

thick at a depth between 25 and 75 cm from the mineral soil

surface or from the upper boundary of an organic layer that has

andic soil properties, whichever is shallower;

5. Have extractable bases (by NH4OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick between depths

of 25 and 100 cm; and6. Do not have an argillic or kandic

horizon with its upper boundary within 125 cm of the mineral

soil surface or of the upper boundary of an organic layer that

has andic soil properties, whichever is shallower.

Description of Subgroups

Typic Hydrudands.—The central concept or Typic

subgroup of Hydrudands is fixed on more or less well drained,

moderately deep or deep soils that have extractable bases plus

1N KCl-extractable Al3+ totaling 2.0 or more cmol(+)/kg in the

fine-earth fraction of horizons with a total thickness of 30 cm

or more at a depth between 25 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower. These soils do

not have an argillic horizon with a base saturation (by sum of

cations) of less than 35 percent throughout its upper 50 cm.

The sum of extractable bases is 25.0 cmol(+)/kg or less

throughout horizons with a total thickness of 15 cm or more in

the upper part of the soils.

Soils that have, at a depth between 40 and 100 cm either

from the mineral soil surface or from the top of an organic

layer with andic soil properties, whichever is shallower, a dark

colored layer 10 cm or more thick with more than 3.0 percent

organic carbon, underlying one or more lighter colored

horizons with a total thickness of 10 cm or more and a lower

content of organic carbon, are excluded from the Typic

subgroup.

Soils that have both aquic conditions (or artificial drainage)

and redox features in any horizon at a depth between 50 and

100 cm either from the mineral soil surface or from the top of

an organic layer with andic soil properties, whichever is

shallower, are excluded from the Typic subgroup and are

considered intergrades to Aquands. Soils that have a lithic

contact within a depth of 50 cm are assigned to the Lithic

subgroup.

Typic Hydrudands are of moderate extent in Hawaii in

the United States. They supported forest vegetation. Most

of these soils have been cleared and are used as cropland or

pasture.

Acrudoxic Hydrudands.—These soils are like Typic

Hydrudands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more at a depth between 25 and 100 cm either from

the mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower. These soils are

not known to occur in the United States. They are established

for use in other countries.

Acrudoxic Thaptic Hydrudands.—These soils are like

Typic Hydrudands, but they have, between depths of 25 and

100 cm, a buried, dark colored layer 10 cm or more thick

below a lighter colored horizon or horizons 10 cm or more thick

with a lower content of organic carbon. They also have

extractable bases plus 1N KCl-extractable Al3+ totaling less

than 2.0 cmol(+)/kg in the fine-earth fraction of one or more

horizons with a total thickness of 30 cm or more at a depth

between 25 and 100 cm either from the mineral soil surface or

from the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in
310 Soil Taxonomy

the United States. They are established for use in other

countries.

Aquic Hydrudands.—These soils are like Typic

Hydrudands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are of small extent and are known to

occur only in Hawaii in the United States. Most of the soils

have been cleared and are used as cropland or pasture.

Eutric Hydrudands.—These soils are like Typic

Hydrudands, but they have a sum of extractable bases of more

than 25.0 cmol(+)/kg in the fine-earth fraction throughout one

or more horizons with a total thickness of 35 cm or more at a

depth between 25 and 75 cm either from the mineral soil surface

or from the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States. They are established for use in other

countries.

Lithic Hydrudands.—These soils are like Typic Hydrudands,

but they have a lithic contact within 50 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils are of small

extent in Hawaii in the United States. Most have been cleared

and are used as cropland or pasture, but some are used as

recreational areas.

Thaptic Hydrudands.—These soils are like Typic

Hydrudands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States. They are established for use in

other countries.

Ultic Hydrudands.—These soils are like Typic

Hydrudands, but they have an argillic or kandic horizon

that has both an upper boundary within 125 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower, and a base

saturation (by sum of cations) of less than 35 percent

throughout the upper 50 cm or throughout the entire horizon if it

is less than 50 cm thick. These soils are not known to occur in

the United States. They are established for use in other

countries.

Melanudands

These are the Udands that have a melanic epipedon. They

can have a lithic contact but do not have, in 75 percent or more

of each pedon, a placic horizon or any other cemented horizon

with its upper boundary within 100 cm of the mineral soil

surface or of the upper boundary of an organic layer with andic

soil properties, whichever is shallower. Characteristically,

Melanudands have a melanic epipedon and a cambic horizon.

The Melanudands in the United States generally developed

in late-Pleistocene deposits. Most formed under forest or

savanna vegetation.

Definition

Melanudands are the Udands that:

1. Do not have, in half or more of each pedon, a placic horizon

within 100 cm of the mineral soil surface or of the upper

boundary of an organic layer that has andic soil properties,

whichever is shallower;

2. Do not have, in 75 percent or more of each pedon, a

cemented horizon with its upper boundary within 100 cm of

the mineral soil surface or of the upper boundary of an organic

layer that has andic soil properties, whichever is shallower;

and

3. Have a melanic epipedon.

Key to Subgroups

DGCA. Melanudands that have a lithic contact within

50 cm either of the mineral soil surface or of the top of an

organic layer that has andic soil properties, whichever is

shallower.

Lithic Melanudands

DGCB. Other Melanudands that have anthraquic conditions.

Anthraquic Melanudands

DGCC. Other Melanudands that have, in one or more

horizons at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, aquic conditions

for some time in normal years (or artificial drainage) and one

or more of the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Melanudands

DGCD. Other Melanudands that have both:

1. Extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the

fine-earth fraction of one or more horizons with a total

thickness of 30 cm or more at a depth between 25 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower; and

2. A 1500 kPa water retention of less than 15 percent on
Andisols 311

air-dried samples and less than 30 percent on undried

samples throughout one or more layers that have andic soil

properties and have a total thickness of 25 cm or more within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower.

Acrudoxic Vitric Melanudands

DGCE. Other Melanudands that have both:

1. Extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the

fine-earth fraction of one or more horizons with a total

thickness of 30 cm or more at a depth between 25 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower; and

2. On undried samples, a 1500 kPa water retention of 70

percent or more throughout a layer 35 cm or more thick

within 100 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower.

Acrudoxic Hydric Melanudands

DGCF. Other Melanudands that have extractable bases (by

NH4OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower.

Acrudoxic Melanudands

DGCG. Other Melanudands that have both:

1. More than 6.0 percent organic carbon and the colors of

a mollic epipedon throughout a layer 50 cm or more thick

within 60 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower; and

2. A 1500 kPa water retention of less than 15 percent on

air-dried samples and less than 30 percent on undried

samples throughout one or more layers that have andic soil

properties and have a total thickness of 25 cm or more

within 100 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower.

Pachic Vitric Melanudands

DGCH. Other Melanudands that have a 1500 kPa water

retention of less than 15 percent on air-dried samples and less

than 30 percent on undried samples throughout one or more

layers that have andic soil properties and have a total thickness

of 25 cm or more within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower.

Vitric Melanudands

DGCI. Other Melanudands that have both:

1. On undried samples, a 1500 kPa water retention of 70

percent or more throughout a layer 35 cm or more thick

within 100 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower; and

2. More than 6.0 percent organic carbon and the colors of

a mollic epipedon throughout a layer 50 cm or more thick

within 60 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower.

Hydric Pachic Melanudands

DGCJ. Other Melanudands that have more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

a layer 50 cm or more thick within 60 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Pachic Melanudands

DGCK. Other Melanudands that have, on undried samples, a

1500 kPa water retention of 70 percent or more throughout a

layer 35 cm or more thick within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Hydric Melanudands

DGCL. Other Melanudands that have, at a depth between 40

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Melanudands

DGCM. Other Melanudands that have an argillic or kandic

horizon that has both:

1. An upper boundary within 125 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

2. A base saturation (by sum of cations) of less than 35

percent throughout its upper 50 cm.

Ultic Melanudands
312 Soil Taxonomy

DGCN. Other Melanudands that have a sum of extractable

bases of more than 25.0 cmol(+)/kg in the fine-earth fraction

throughout one or more horizons with a total thickness of 15

cm or more at a depth between 25 and 75 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower.

Eutric Melanudands

DGCO. Other Melanudands.

Typic Melanudands

Definition of Typic Melanudands

Typic Melanudands are the Melanudands that:

1. Do not have a lithic contact within 50 cm of the soil surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Have, on undried samples, a 1500 kPa water retention of

less than 70 percent throughout all layers 35 cm or more thick

within 100 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower;

4. Have a 1500 kPa water retention of 15 percent or more on

air-dried samples or 30 percent or more on undried samples

throughout all layers that have andic soil properties and have a

total thickness of 25 cm or more within 100 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower;

5. Do not have both more than 6.0 percent organic carbon

and the colors of a mollic epipedon throughout at least 50 cm

of the upper 60 cm, excluding any overlying layers that do not

have andic soil properties;

6. Do not have a sum of bases of more than 25.0 cmol(+) kg-1 in

the fine-earth fraction throughout some subhorizon 15 cm or

more thick at a depth between 25 and 75 cm either from mineral

soil surface or from the upper boundary of an organic layer that

has andic soil properties, whichever is shallower;

7. Do not have, between depths of 40 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon and

the colors of a mollic epipedon throughout, occurring below a

horizon or horizons 10 cm or more thick with a color value, moist,

1 unit or more higher and an organic-carbon content 1 percent or

more lower;

8. Have extractable bases (by NH4OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick at a depth

between 25 and 100 cm from the mineral soil surface or from

the upper boundary of an organic layer that has andic soil

properties, whichever is shallower;

9. Do not have an argillic or kandic horizon with a base

saturation (by sum of cations) of less than 35 percent

throughout its upper 50 cm and its upper boundary within 125

cm of the mineral soil surface or of the upper boundary of an

organic layer that has andic soil properties, whichever is

shallower; and

10. Do not have anthraquic conditions.

Description of Subgroups

Typic Melanudands.—The central concept or Typic

subgroup of Melanudands is fixed on moderately deep or

deeper soils that commonly have relatively high amounts of

aluminum. These soils have, within 100 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, a 1500 kPa water

retention of 15 percent or more on air-dried samples

throughout all layers 25 cm or more thick and between 30 and

70 percent on undried samples throughout all layers 35 cm or

more thick. The sum of extractable bases is 25.0 cmol(+)/kg or

less throughout horizons with a total thickness of 15 cm or

more in the upper part of the soils.

Soils that have, at a depth between 40 and 100 cm either

from the mineral soil surface or from the top of an organic

layer with andic soil properties, whichever is shallower, a dark

colored layer 10 cm or more thick with more than 3.0 percent

organic carbon, underlying one or more lighter colored

horizons with a total thickness of 10 cm or more and a lower

content of organic carbon, are excluded from the Typic

subgroup. Extractable bases plus 1N-KCl-extractable Al3+ total

more than 2.0 cmol(+)/kg in the fine-earth fraction of one or

more horizons with a total thickness of 30 cm or more in the

upper part of the Typic Melanudands.

Soils that have anthraquic conditions and soils with both

aquic conditions (or artificial drainage) and redox features in

any horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, are excluded

from the Typic subgroup and are considered intergrades to

Aquands. Soils that have a lithic contact within a depth of 50

cm are assigned to the Lithic subgroup.

Typic Melanudands are not known to occur in the Pacific

Northwest.

Acrudoxic Hydric Melanudands.—These soils are like Typic
Andisols 313

Melanudands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth

fraction of one or more horizons with a total thickness of 30 cm

or more at a depth between 25 and 100 cm either from the mineral

soil surface or from the top of an organic layer with andic soil

properties, whichever is shallower. They also have, on undried

samples, a 1500 kPa water retention of 70 percent or more

throughout a layer 35 cm or more thick within 100 cm of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower. These soils are not

known to occur in the United States. They are established for

use in other countries.

Acrudoxic Melanudands.—These soils are like Typic

Melanudands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more at a depth between 25 and 100 cm either from

the mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower. These soils are

not known to occur in the United States. They are established

for use in other countries.

Acrudoxic Vitric Melanudands.—These soils are like Typic

Melanudands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fine-earth

fraction of one or more horizons with a total thickness of 30 cm

or more at a depth between 25 and 100 cm either from the mineral

soil surface or from the top of an organic layer with andic soil

properties, whichever is shallower. They also have a 1500 kPa

water retention of less than 15 percent on air-dried samples and

less than 30 percent on undried samples throughout one or more

layers that have andic soil properties and have a total thickness

of 25 cm or more within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States. They are established for use in other

countries.

Anthraquic Melanudands.—These soils are like Typic

Melanudands, but they have anthraquic conditions. They are

used for the production of paddy rice. These soils are not

known to occur in the United States. They are established for

use in other countries.

Aquic Melanudands.—These soils are like Typic

Melanudands, but they have both aquic conditions (or

artificial drainage) and redox features in a horizon at a depth

between 50 and 100 cm either from the mineral soil surface or

from the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States. They are established for use in other

countries.

Eutric Melanudands.—These soils are like Typic

Melanudands, but they have a sum of extractable bases of more

than 25.0 cmol(+)/kg in the fine-earth fraction throughout one

or more horizons with a total thickness of 35 cm or more at a

depth between 25 and 75 cm either from the mineral soil surface

or from the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States. They are established for use in other

countries.

Hydric Melanudands.—These soils are like Typic

Melanudands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States. They are established for use in other

countries.

Hydric Pachic Melanudands.—These soils are like Typic

Melanudands, but they have, on undried samples, a 1500 kPa

water retention of 70 percent or more throughout a layer 35 cm

or more thick within 100 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower. These soils also have both more than

6.0 percent organic carbon and the colors of a mollic epipedon

throughout at least 50 cm of the upper 60 cm of the andic

materials and have, on undried samples, a 1500 kPa water

retention of 70 percent or more throughout a layer 35 cm or

more thick within 100 cm either of the mineral soil surface or

of the top of an organic layer with andic soil properties,

whichever is shallower. The soils have not been recognized in

the United States. They are established for use in other

countries.

Lithic Melanudands.—These soils are like Typic

Melanudands, but they have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower. These

soils have not been recognized in the United States. They are

established for use in other countries.

Pachic Melanudands.—These soils are like Typic

Melanudands, but they have both more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

at least 50 cm of the upper 60 cm of the andic materials and

have, on undried samples, a 1500 kPa water retention of 70

percent or more throughout a layer 35 cm or more thick within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower. These soils have not been recognized in the United

States. They are established for use in other countries.

Pachic Vitric Melanudands.—These soils are like Typic

Melanudands, but they have a 1500 kPa water retention of less

than 15 percent on air-dried samples and less than 30 percent

on undried samples throughout one or more layers that have

andic soil properties and have a total thickness of 25 cm or

more within 100 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower. These soils also have both more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

at least 50 cm of the upper 60 cm of the andic materials and

have, on undried samples, a 1500 kPa water retention of 70
314 Soil Taxonomy

percent or more throughout a layer 35 cm or more thick within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is shallower.

The soils have not been recognized in the United States. They

are established for use in other countries.

Thaptic Melanudands.—These soils are like Typic

Melanudands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a lighter

colored horizon or horizons 10 cm or more thick with a lower

content of organic carbon. These soils have not been

recognized in the United States. They are established for use in

other countries.

Ultic Melanudands.—These soils are like Typic

Melanudands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of less than 35 percent throughout the

upper 50 cm or throughout the entire horizon if it is less than

50 cm thick. These soils are not known to occur in the United

States. They are established for use in other countries.

Vitric Melanudands.—These soils are like Typic

Melanudands, but they have a 1500 kPa water retention of less

than 15 percent on air-dried samples and less than 30 percent

on undried samples throughout one or more layers that have

andic soil properties and have a total thickness of 25 cm or

more within 100 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are not known to occur in the United

States. They are established for use in other countries.

Placudands

Placudands are the more or less well drained Udands that

have, in half or more of each pedon, a placic horizon within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is shallower.

Characteristically, Placudands have a thin O horizon and an

ochric or umbric epipedon above the placic horizon.

Placudands are rare in the United States. Most formed under

forest vegetation.

Definition

Placudands are the Udands that have, in half or more of

each pedon, a placic horizon within 100 cm of the mineral soil

surface or of the upper boundary of an organic layer that has

andic soil properties, whichever is shallower.

Key to Subgroups

DGAA. Placudands that have a lithic contact within

50 cm either of the mineral soil surface or of the top of an

organic layer that has andic soil properties, whichever is

shallower.

Lithic Placudands

DGAB. Other Placudands that have, in one or more

horizons at a depth between 50 cm either from the mineral

soil surface or from the top of an organic layer with andic

soil properties, whichever is shallower, and the placic

horizon, aquic conditions for some time in normal years

(or artificial drainage) and one or more of the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent

or more chroma of 2 or less either in redox depletions

on faces of peds or in the matrix if peds are absent;

or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Placudands

DGAC. Other Placudands that have extractable bases (by

NH4

OAc) plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, and the placic horizon.

Acrudoxic Placudands

DGAD. Other Placudands that have, on undried samples, a

1500 kPa water retention of 70 percent or more throughout a

layer 35 cm or more thick within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Hydric Placudands

DGAE. Other Placudands.

Typic Placudands

Definition of Typic Placudands

Typic Placudands are the Placudands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is shallower,

and the placic horizon, both aquic conditions and any of the

following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or more

chroma of 2 or less either in redox depletions on faces of peds

or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to
Andisols 315

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Have extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ of 2.0 or more cmol(+) kg-1 in the fine-earth

fraction of all subhorizons 30 cm or more thick at a depth

between 25 cm from the mineral soil surface or from the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower, and the placic horizon;

and

4. Do not have, on undried samples, a 1500 kPa water

retention of 70 percent or more throughout a layer 35 cm or more

thick within 100 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower.

Description of Subgroups

Typic Placudands.—The central concept or Typic subgroup

of Placudands is fixed on moderately deep or shallow soils that

have, on undried samples, a 1500 kPa water retention of less

than 70 percent throughout all layers 35 cm or more thick

above the cemented horizon.

Soils that have both aquic conditions (or artificial drainage)

and redox features in any horizon at a depth between 50 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, are excluded from the Typic subgroup and are

considered intergrades to Aquands. Soils that have extractable

bases plus 1N KCl-extractable Al3+ totaling less than 2.0

cmol(+)/kg in the fine-earth fraction of one or more horizons

with a total thickness of 30 cm or more at a depth between 25

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, and the placic horizon also are excluded.

Typic Placudands are of very small extent in the United

States.

Acrudoxic Placudands.—These soils are like Typic

Placudands, but they have extractable bases plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness of

30 cm or more at a depth between 25 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, and the placic

horizon. These soils have not been recognized in the United

States.

Aquic Placudands.—These soils are like Typic Placudands,

but they have both aquic conditions (or artificial drainage) and

redox features in a horizon at a depth between 50 cm either

from the mineral soil surface or from the top of an organic

layer with andic soil properties, whichever is shallower, and

the placic horizon. These soils have not been recognized in the

United States.

Hydric Placudands.—These soils are like Typic Placudands,

but they have, on undried samples, a 1500 kPa water retention

of 70 percent or more throughout a layer 35 cm or more thick

within 100 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower. These soils have not been recognized in the United

States.

Lithic Placudands.—These soils are like Typic Placudands,

but they have a lithic contact within 50 cm of the mineral soil

surface.

Ustands

Ustands are the more or less well drained Andisols of

subhumid to semiarid regions. These soils are of relatively small

extent. They are mostly in Mexico, the western part of the United

States, the Pacific Islands, and the eastern part of Africa. Most

Ustands in the United States are in Hawaii, Arizona, and New

Mexico. Most formed under grass, shrub, or forest vegetation.

Characteristically, Ustands have an ochric or mollic epipedon

and a cambic horizon. Some have a duripan.

The Ustands in the United States generally developed in latePleistocene or Holocene deposits.

Definition

Ustands are the Andisols that:

1. Have an ustic soil moisture regime;

2. Have a frigid or warmer soil temperature regime;

3. Do not have a histic epipedon or the periods of saturation

and reduction that are defined for Aquands; and

4. Do not have a 1500 kPa water retention of less than 15

percent on air-dried samples and less than 30 percent on

undried samples throughout 60 percent or more of the

thickness from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, to a point 60 cm below the starting point or to any

densic, lithic, or paralithic contact, duripan, or petrocalcic

horizon within that depth.

Key to Great Groups

DFA. Ustands that have, in 75 percent or more of each pedon,

a cemented horizon that has its upper boundary within 100 cm

either of the mineral soil surface or of the top of an organic layer

with andic soil properties, whichever is shallower.

Durustands, p. 316

DFB. Other Ustands.

Haplustands, p. 317
316 Soil Taxonomy

Durustands

Durustands are the Ustands that have, in 75 percent or more

of each pedon, a cemented horizon with its upper boundary

within 100 cm either of the mineral soil surface or of the top of

an organic layer with andic soil properties, whichever is

shallower.

Characteristically, Durustands have an ochric epipedon and a

cambic horizon above the cemented horizon.

The Durustands in the United States generally developed in

late-Pleistocene or Holocene deposits. Most formed under

coniferous/grass or shrub vegetation.

Definition

Durustands are the Ustands that have, in 75 percent or more

of each pedon, a cemented horizon with its upper boundary

within 100 cm of the mineral soil surface.

Key to Subgroups

DFAA. Durustands that have, in one or more horizons at a

depth between 50 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower, aquic conditions for some

time in normal years (or artificial drainage) and one or more of

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Durustands

DFAB. Other Durustands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Durustands

DFAC. Other Durustands that have a melanic, mollic, or

umbric epipedon.

Humic Durustands

DFAD. Other Durustands.

Typic Durustands

Definition of Typic Durustands

Typic Durustands are the Durustands that:

1. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is shallower,

both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or more

chroma of 2 or less either in redox depletions on faces of peds

or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

2. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value, moist, 1 unit or more higher and an organic-carbon

content 1 percent or more lower; and

3. Do not have a melanic, mollic, or umbric epipedon.

Description of Subgroups

Typic Durustands.—The central concept or Typic subgroup

of Durustands is fixed on moderately deep or shallow soils with

an ochric epipedon. These soils do not have both aquic

conditions (or artificial drainage) and redox features in any

horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower. They do not have,

between depths of 25 and 100 cm, a buried, dark colored layer

10 cm or more thick below a lighter colored horizon or

horizons 10 cm or more thick with a lower content of organic

carbon. These soils are not known to occur in the United

States. They are established for use in other countries.

Aquic Durustands.—These soils are like Typic Durustands,

but they have both aquic conditions (or artificial drainage) and

redox features in a horizon at a depth between 50 and 100 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower. These soils are not known to occur in the United

States. They are established for use in other countries.

Humic Durustands.—These soils are like Typic

Durustands, but they have a melanic, mollic, or umbric

epipedon. They are rare in the United States. Most of these

soils are used as rangeland, but some are used for timber

production or as recreational areas.

Thaptic Durustands.—These soils are like Typic

Durustands, but they have, between depths of 25 and 100 cm, a

buried, dark colored layer 10 cm or more thick below a lighter
Andisols 317

colored horizon or horizons 10 cm or more thick with a lower

content of organic carbon. These soils are not known to occur in

the United States. They are established for use in other

countries.

Haplustands

Haplustands are the Ustands that do not have, in 75 percent

or more of each pedon, a cemented horizon that has its upper

boundary within 100 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower. Characteristically, Haplustands have an

ochric epipedon and a cambic horizon above the cemented

horizon.

The Haplustands in the United States generally developed in

late-Pleistocene or Holocene deposits. Most formed under

coniferous/grass or shrub vegetation.

Definition

Haplustands are the Ustands that do not have, in 75 percent

or more of each pedon, a cemented horizon with its upper

boundary within 100 cm of the mineral soil surface.

Key to Subgroups

DFBA. Haplustands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Haplustands

DFBB. Other Haplustands that have, in one or more horizons

at a depth between 50 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower, aquic conditions for some

time in normal years (or artificial drainage) and one or more of

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Haplustands

DFBC. Other Haplustands that have both:

1. Extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ totaling less than 15.0 cmol(+)/kg in the

fine-earth fraction throughout one or more horizons with a

total thickness of 60 cm or more within 75 cm either of the

mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower; and

2. A 1500 kPa water retention of less than 15 percent on

air-dried samples and less than 30 percent on undried

samples throughout one or more layers that have andic soil

properties and have a total thickness of 25 cm or more within

100 cm either of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower.

Dystric Vitric Haplustands

DFBD. Other Haplustands that have a 1500 kPa water

retention of less than 15 percent on air-dried samples and less

than 30 percent on undried samples throughout one or more

layers that have andic soil properties and have a total thickness

of 25 cm or more within 100 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Vitric Haplustands

DFBE. Other Haplustands that have more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

a layer 50 cm or more thick within 60 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Pachic Haplustands

DFBF. Other Haplustands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Haplustands

DFBG. Other Haplustands that have a calcic horizon that has

its upper boundary within 125 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Calcic Haplustands

DFBH. Other Haplustands that have extractable bases (by

NH4

OAc) plus 1N KCl-extractable Al3+ totaling less than 15.0

cmol(+)/kg in the fine-earth fraction throughout one or more

horizons with a total thickness of 60 cm or more within 75 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Dystric Haplustands
318 Soil Taxonomy

DFBI. Other Haplustands that have an oxic horizon that has its

upper boundary within 125 cm either of the mineral soil surface

or of the top of an organic layer with andic soil properties,

whichever is shallower.

Oxic Haplustands

DFBJ. Other Haplustands that have an argillic or kandic

horizon that has both:

1. An upper boundary within 125 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

2. A base saturation (by sum of cations) of less than 35

percent throughout the upper 50 cm or throughout the entire

argillic or kandic horizon if it is less than 50 cm thick.

Ultic Haplustands

DFBK. Other Haplustands that have an argillic or kandic

horizon that has its upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower.

Alfic Haplustands

DFBL. Other Haplustands that have a melanic, mollic, or

umbric epipedon.

Humic Haplustands

DFBM. Other Haplustands.

Typic Haplustands

Definition of Typic Haplustands

Typic Haplustands are the Haplustands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Have, on undried samples, 30 percent or more 1500 kPa

water retention in all subhorizons that meet the requirements

for andic soil properties and that are at least 25 cm thick and

are within 100 cm of the mineral soil surface or of the upper

boundary of an organic layer that has andic soil properties,

whichever is shallower;

4. Do not have both more than 6.0 percent organic carbon and

the colors of a mollic epipedon throughout at least 50 cm of the

upper 60 cm, excluding any overlying layers that do not have

andic soil properties;

5. Do not have, between depths of 25 and 100 cm, a layer 10 cm

or more thick with more than 3.0 percent organic carbon and the

colors of a mollic epipedon throughout, occurring below a

horizon or horizons 10 cm or more thick with a color value, moist,

1 unit or more higher and an organic-carbon content 1 percent or

more lower;

6. Do not have a calcic horizon with its upper boundary within

125 cm of the mineral soil surface;

7. Have extractable bases (by NH4

OAc) plus 1N KClextractable Al3+ of 15.0 or more cmol(+) kg-1 in the fine-earth

fraction throughout at least 60 cm of the upper 75 cm;

8. Do not have an oxic horizon with its upper boundary

within 125 cm of the mineral soil surface;

9. Do not have an argillic or kandic horizon with its upper

boundary within 125 cm of the mineral soil surface; and

10. Do not have a melanic, mollic, or umbric epipedon.

Description of Subgroups

Typic Haplustands.—The central concept or Typic

subgroup of Haplustands is fixed on moderately deep or deeper

soils that have an ochric epipedon and do not have a calcic,

argillic, or oxic horizon. These soils have extractable bases

plus 1N KCl-extractable Al3+ of 15.0 or more cmol(+) kg-1 in

the fine-earth fraction throughout at least 60 cm of the upper

75 cm. They have a 1500 kPa water retention of 15 percent or

more on air-dried samples and 30 percent or more on undried

samples throughout all layers 25 cm or more thick within 100

cm either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower. Soils

that have, at a depth between 40 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, a dark colored

layer 10 cm or more thick with more than 3.0 percent organic

carbon, underlying one or more lighter colored horizons with a

total thickness of 10 cm or more and a lower content of organic

carbon, are excluded from the Typic subgroup.

Soils that have both aquic conditions (or artificial drainage)

and redox features in any horizon at a depth between 50 and

100 cm either from the mineral soil surface or from the top of

an organic layer with andic soil properties, whichever is

shallower, are excluded from the Typic subgroup and are

considered intergrades to Aquands. Soils that have a lithic
Andisols 319

contact within a depth of 50 cm are assigned to the Lithic

subgroup.

Typic Haplustands are of small extent in the United States.

They commonly support grassland or forest vegetation. Most

are used as rangeland or for timber production, but some have

been cleared and are used as cropland.

Alfic Haplustands.—These soils are like Typic

Haplustands, but they have an argillic or kandic horizon that has

both an upper boundary within 125 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower, and a base saturation (by

sum of cations) of 35 percent or more in some part of the upper

50 cm or in the entire horizon if it is less than 50 cm thick. These

soils are not known to occur in the United States. They are

established for use in other countries.

Aquic Haplustands.—These soils are like Typic

Haplustands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are not known to occur in the United

States. They are established for use in other countries.

Calcic Haplustands.—These soils are like Typic

Haplustands, but they have a calcic horizon that has its upper

boundary within 125 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States.

Dystric Haplustands.—These soils are like Typic

Haplustands, but they have a sum of extractable bases plus

aluminum of less than 15.0 cmol(+)/kg in the fine-earth

fraction throughout one or more horizons with a total thickness

of 60 cm or more within 75 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils are not known

to occur in the United States. They are established for use in

other countries.

Dystric Vitric Haplustands.—These soils are like Typic

Haplustands, but they have a sum of extractable bases plus

aluminum of less than 15.0 cmol(+)/kg in the fine-earth

fraction throughout one or more horizons with a total thickness

of 60 cm or more within 75 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower. They also have a 1500 kPa

water retention of less than 15 percent on air-dried samples

and less than 30 percent on undried samples throughout one or

more layers that have andic soil properties and have a total

thickness of 25 cm or more within 100 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils are not known

to occur in the United States. They are established for use in

other countries.

Humic Haplustands.—These soils are like Typic

Haplustands, but they have a melanic, mollic, or umbric

epipedon. They are rare and are known to occur only in Hawaii

and Arizona in the United States.

Lithic Haplustands.—These soils are like Typic

Haplustands, but they have a lithic contact within 50 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower. These soils are of

small extent and occur mostly in Hawaii in the United States.

Most of the soils are used as cropland or as recreational areas.

Oxic Haplustands.—These soils are like Typic

Haplustands, but they have an oxic horizon that has its upper

boundary within 125 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower. These soils are not known to occur in

the United States.

Pachic Haplustands.—These soils are like Typic

Haplustands, but they have more than 6.0 percent organic

carbon and the colors of a mollic epipedon throughout a layer

50 cm or more thick within 60 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils have not been

recognized in the United States.

Thaptic Haplustands.—These soils are like Typic

Haplustands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States.

Ultic Haplustands.—These soils are like Typic

Haplustands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of less than 35 percent throughout the

upper 50 cm or throughout the entire horizon if it is less than

50 cm thick. These soils are not known to occur in the United

States. They are established for use in other countries.

Vitric Haplustands.—These soils are like Typic

Haplustands, but they have a 1500 kPa water retention of less

than 15 percent on air-dried samples and less than 30 percent

on undried samples throughout one or more layers that have

andic soil properties and have a total thickness of 25 cm or

more within 100 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are of small extent in Washington and

Oregon. Most are used for timber production. Some have been

cleared and are used as cropland, and some are used as

recreational areas.

Vitrands

Vitrands are the more or less well drained, coarse textured

Andisols. These are relatively young soils that occur mostly
320 Soil Taxonomy

near volcanoes. Most of the Vitrands in the United States are in

Oregon, Washington, and Idaho. Vitrands formed mainly under

coniferous forest vegetation.

Characteristically, Vitrands have an ochric or mollic epipedon

and a cambic horizon.

Most of the Vitrands in the United States developed in

Holocene deposits.

Definition

Vitrands are the Andisols that:

1. Have a frigid or warmer soil temperature regime;

2. Do not have a histic epipedon or the periods of saturation

and reduction that are defined for Aquands;

3. Have an ustic or udic moisture regime; and

4. Have a 1500 kPa water retention of less than 15 percent

on air-dried samples and less than 30 percent on undried

samples throughout 60 percent or more of the thickness

either:

a. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Key to Great Groups

DEA. Vitrands that have an ustic moisture regime.

Ustivitrands, p. 322

DEB. Other Vitrands.

Udivitrands, p. 320

Udivitrands

Udivitrands are the more or less well drained Vitrands that

have a udic moisture regime. Characteristically, these soils

have an ochric epipedon and a cambic horizon. Some have an

argillic horizon.

Most of the Udivitrands in the United States developed in

Holocene deposits under coniferous forest vegetation.

Definition

Udivitrands are the Vitrands that have a udic soil moisture

regime.

Key to Subgroups

DEBA. Udivitrands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Udivitrands

DEBB. Other Udivitrands that have, in one or more horizons

at a depth between 50 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower, aquic conditions for some

time in normal years (or artificial drainage) and one or more of

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Udivitrands

DEBC. Other Udivitrands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Udivitrands

DEBD. Other Udivitrands that have both:

1. An argillic or kandic horizon that has its upper

boundary within 125 cm of the mineral soil surface or of the

upper boundary of an organic layer with andic soil

properties, whichever is shallower; and

2. A base saturation (by sum of cations) of less than 35

percent throughout the upper 50 cm of the argillic or kandic

horizon.

Ultic Udivitrands

DEBE. Other Udivitrands that have an argillic or kandic

horizon that has its upper boundary within 125 cm of the

mineral soil surface or of the upper boundary of an organic

layer with andic soil properties, whichever is shallower.

Alfic Udivitrands

DEBF. Other Udivitrands that have a melanic, mollic, or

umbric epipedon.

Humic Udivitrands
Andisols 321

DEBG. Other Udivitrands.

Typic Udivitrands

Definition of Typic Udivitrands

Typic Udivitrands are the Udivitrands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is shallower,

both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or more

chroma of 2 or less either in redox depletions on faces of peds

or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value, moist, 1 unit or more higher and an organic-carbon

content 1 percent or more lower;

4. Do not have an argillic or kandic horizon that has its

upper boundary within 125 cm of the mineral soil surface or of

the upper boundary of an organic layer with andic soil

properties, whichever is shallower; and

5. Do not have a melanic, mollic, or umbric epipedon.

Description of Subgroups

Typic Udivitrands.—The central concept or Typic

subgroup of Udivitrands is fixed on moderately deep or deeper

soils that have an ochric epipedon and do not have an argillic

horizon.

Soils that have both aquic conditions (or artificial drainage)

and redox features in any horizon at a depth between 50 and

100 cm either from the mineral soil surface or from the top of

an organic layer with andic soil properties, whichever is

shallower, are excluded from the Typic subgroup and are

considered intergrades to Aquands. Soils that have, at a depth

between 40 and 100 cm either from the mineral soil surface or

from the top of an organic layer with andic soil properties,

whichever is shallower, a dark colored layer 10 cm or more

thick with more than 3.0 percent organic carbon, underlying

one or more lighter colored horizons with a total thickness of

10 cm or more and a lower content of organic carbon, also are

excluded. Soils that have a lithic contact within a depth of 50

cm are assigned to the Lithic subgroup.

Typic Udivitrands are moderately extensive in the States of

Washington and Idaho. They commonly support coniferous

forest vegetation. Most of these soils are used for timber

production, but some have been cleared and are used as

cropland.

Alfic Udivitrands.—These soils are like Typic Udivitrands,

but they have an argillic or kandic horizon that has both an

upper boundary within 125 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower, and a base saturation (by

sum of cations) of 35 percent or more in some part of the upper

50 cm or in the entire horizon if it is less than 50 cm thick. These

soils are moderately extensive in Idaho and Oregon. They

commonly support coniferous forest vegetation. Most of the

soils are used for timber production, but some have been cleared

and are used as cropland.

Aquic Udivitrands.—These soils are like Typic

Udivitrands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are not known to occur in the United

States. They are established for use in other countries.

Humic Udivitrands.—These soils are like Typic

Udivitrands, but they have a melanic, mollic, or umbric

epipedon. They are of small extent and are known to occur

only in the State of Washington. They commonly support

coniferous forest vegetation. Most of the soils are used for

timber production, but some have been cleared and are used as

cropland.

Lithic Udivitrands.—These soils are like Typic

Udivitrands, but they have a lithic contact within 50 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower. These soils are of

small extent and occur mostly in Oregon, Montana, and

Washington. They commonly support coniferous forest

vegetation. Most of the soils are used for timber production, but

some are used as recreational areas.

Thaptic Udivitrands.—These soils are like Typic

Udivitrands, but they have, between depths of 25 and 100 cm, a

buried, dark colored layer 10 cm or more thick below a lighter

colored horizon or horizons 10 cm or more thick with a lower

content of organic carbon. These soils have not been

recognized in the United States.

Ultic Udivitrands.—These soils are like Typic Udivitrands,

but they have an argillic or kandic horizon that has both an

upper boundary within 125 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower, and a base saturation (by

sum of cations) of less than 35 percent throughout the upper 50

cm or throughout the entire horizon if it is less than 50 cm

thick. These soils are not known to occur in the United States.

They are established for use in other countries.
322 Soil Taxonomy

Ustivitrands

Ustivitrands are the more or less well drained Vitrands that

have an ustic moisture regime. Characteristically, Ustivitrands

have an ochric epipedon and a cambic horizon.

Ustivitrands are rare in the United States.

Definition

Ustivitrands are the Vitrands that have an ustic soil

moisture regime.

Key to Subgroups

DEAA. Ustivitrands that have a lithic contact within 50 cm

either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Lithic Ustivitrands

DEAB. Other Ustivitrands that have, in one or more horizons

at a depth between 50 and 100 cm either from the mineral soil

surface or from the top of an organic layer with andic soil

properties, whichever is shallower, aquic conditions for some

time in normal years (or artificial drainage) and one or more of

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Ustivitrands

DEAC. Other Ustivitrands that have, at a depth between 25

and 100 cm either from the mineral soil surface or from the top

of an organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Ustivitrands

DEAD. Other Ustivitrands that have a calcic horizon that has

its upper boundary within 125 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Calcic Ustivitrands

DEAE. Other Ustivitrands that have a melanic, mollic, or

umbric epipedon.

Humic Ustivitrands

DEAF. Other Ustivitrands.

Typic Ustivitrands

Definition of Typic Ustivitrands

Typic Ustivitrands are the Ustivitrands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or more

chroma of 2 or less either in redox depletions on faces of peds

or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value, moist, 1 unit or more higher and an organic-carbon

content 1 percent or more lower;

4. Do not have a calcic horizon with its upper boundary

within 125 cm of the mineral soil surface; and

5. Do not have a melanic, mollic, or umbric epipedon.

Description of Subgroups

Typic Ustivitrands.—The central concept or Typic

subgroup of Ustivitrands is fixed on moderately deep or deep

soils that have an ochric epipedon and do not have an argillic

or calcic horizon. Soils that have, at a depth between 40 and

100 cm either from the mineral soil surface or from the top of

an organic layer with andic soil properties, whichever is

shallower, a dark colored layer 10 cm or more thick with more

than 3.0 percent organic carbon, underlying one or more

lighter colored horizons with a total thickness of 10 cm or

more and a lower content of organic carbon, are excluded from

the Typic subgroup.

Soils that have a lithic contact within a depth of 50 cm are

assigned to the Lithic subgroup. Soils that have both aquic

conditions (or artificial drainage) and redox features in any

horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, are excluded

from the Typic subgroup and are considered intergrades to

Aquands.

Typic Ustivitrands are of moderate extent. They are mostly

in California and Washington.
Andisols 323

Aquic Ustivitrands.—These soils are like Typic Ustivitrands,

but they have both aquic conditions (or artificial drainage) and

redox features in a horizon at a depth between 50 and 100 cm

either from the mineral soil surface or from the top of an organic

layer with andic soil properties, whichever is shallower. These

soils are not known to occur in the United States. They are

established for use in other countries.

Calcic Ustivitrands.—These soils are like Typic

Ustivitrands, but they have a calcic horizon that has its upper

boundary within 125 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States. They are established for use in other

countries.

Humic Ustivitrands.—These soils are like Typic

Ustivitrands, but they have a melanic, mollic, or umbric

epipedon. They are not known to occur in the United States.

They are established for use in other countries.

Lithic Ustivitrands.—These soils are like Typic

Ustivitrands, but they have a lithic contact within 50 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower. These soils are

not known to occur in the United States. They are established

for use in other countries.

Thaptic Ustivitrands.—These soils are like Typic

Ustivitrands, but they have, between depths of 25 and 100 cm,

a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States. They are established for use in

other countries.

Xerands

Xerands are the more or less well drained Andisols that

have a xeric moisture regime and a frigid, mesic, or thermic

temperature regime. Most of the Xerands in the United States

are in Oregon, Washington, Idaho, and California. Most

Xerands have a frigid or mesic temperature regime and formed

under coniferous forest vegetation. Some formed under grass or

shrub vegetation.

Characteristically, Xerands have an ochric or mollic epipedon

and a cambic horizon.

Most of the Xerands in the United States developed in latePleistocene or Holocene deposits.

Definition

Xerands are the Andisols that:

1. Have a xeric soil moisture regime;

2. Have a frigid, mesic, or thermic soil temperature regime;

and

3. Do not have a histic epipedon or the aquic conditions

characteristic of Aquands.

Key to Great Groups

DDA. Xerands that have a 1500 kPa water retention of less

than 15 percent on air-dried samples and less than 30 percent

on undried samples throughout 60 percent or more of the

thickness either:

1. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

2. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Vitrixerands, p. 326

DDB. Other Xerands that have a melanic epipedon.

Melanoxerands, p. 325

DDC. Other Xerands.

Haploxerands, p. 323

Haploxerands

Haploxerands are the more or less well drained Xerands that

do not have a melanic epipedon. These soils have a 1500 kPa

water retention of 15 percent or more on air-dried samples and

30 percent or more on undried samples throughout more than

30 percent of the upper part.

Characteristically, Haploxerands have a thin O horizon, an

ochric or mollic epipedon, and a cambic horizon.

The Haploxerands in the United States generally developed

in late-Pleistocene or Holocene deposits. Most formed under

coniferous forest vegetation, but some formed under grass or

shrub vegetation.

Definition

Haploxerands are the Xerands that:

1. Do not have a 1500 kPa water retention of less than 15

percent on air-dried samples and less than 30 percent on

undried samples throughout 60 percent or more of the

thickness either:

a. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon; and
324 Soil Taxonomy

2. Do not have a melanic epipedon.

Key to Subgroups

DDCA. Haploxerands that have a lithic contact within 50 cm of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Lithic Haploxerands

DDCB. Other Haploxerands that have, in one or more

horizons at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with andic

soil properties, whichever is shallower, aquic conditions for

some time in normal years (or artificial drainage) and one or more

of the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or more

chroma of 2 or less either in redox depletions on faces of peds

or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Haploxerands

DDCC. Other Haploxerands that have, at a depth between 25

and 100 cm from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Haploxerands

DDCD. Other Haploxerands that have a calcic horizon that

has its upper boundary within 125 cm of the mineral soil

surface.

Calcic Haploxerands

DDCE. Other Haploxerands that have an argillic or kandic

horizon that has both:

1. An upper boundary within 125 cm of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

2. A base saturation (by sum of cations) of less than 35

percent throughout its upper 50 cm.

Ultic Haploxerands

DDCF. Other Haploxerands that have both:

1. A mollic or umbric epipedon; and

2. An argillic or kandic horizon that has its upper

boundary within 125 cm of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower.

Alfic Humic Haploxerands

DDCG. Other Haploxerands that have an argillic or kandic

horizon that has its upper boundary within 125 cm of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower.

Alfic Haploxerands

DDCH. Other Haploxerands that have a mollic or umbric

epipedon.

Humic Haploxerands

DDCI. Other Haploxerands.

Typic Haploxerands

Definition of Typic Haploxerands

Typic Haploxerands are the Haploxerands that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Do not have, between depths of 25 and 100 cm, a layer 10

cm or more thick with more than 3.0 percent organic carbon

and the colors of a mollic epipedon throughout, occurring

below a horizon or horizons 10 cm or more thick with a color

value, moist, 1 unit or more higher and an organic-carbon

content 1 percent or more lower;

4. Do not have a calcic horizon with its upper boundary

within 125 cm of the mineral soil surface;

5. Do not have an argillic or kandic horizon with its upper

boundary within 125 cm of the mineral soil surface or of the

upper boundary of an organic layer that has andic soil

properties, whichever is shallower; and

6. Do not have either a mollic or umbric epipedon.

Description of Subgroups

Typic Haploxerands.—The central concept or Typic

subgroup of Haploxerands is fixed on moderately deep or deep
Andisols 325

soils that have an ochric epipedon and do not have an argillic

horizon. Soils that have both aquic conditions (or artificial

drainage) and redox features in any horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower, are excluded from the Typic subgroup and are

considered intergrades to Aquands. Soils that have, at a depth

between 40 and 100 cm either from the mineral soil surface or

from the top of an organic layer with andic soil properties,

whichever is shallower, a dark colored layer 10 cm or more

thick with more than 3.0 percent organic carbon, underlying one

or more lighter colored horizons with a total thickness of 10 cm

or more and a lower content of organic carbon, also are

excluded. Soils that have a lithic contact within a depth of 50

cm are assigned to the Lithic subgroup.

Typic Haploxerands commonly support coniferous forest

vegetation. Most of these soils are used for timber production,

but some have been cleared and are used as cropland.

Alfic Haploxerands.—These soils are like Typic

Haploxerands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of 35 percent or more in some part of the

upper 50 cm or in the entire horizon if it is less than 50 cm

thick. These soils are rare in the United States.

Alfic Humic Haploxerands.—These soils are like Typic

Haploxerands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of 35 percent or more in some part of the

upper 50 cm or in the entire horizon if it is less than 50 cm

thick. They also have a melanic, mollic, or umbric epipedon.

They are rare in the United States.

Aquic Haploxerands.—These soils are like Typic

Haploxerands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the

top of an organic layer with andic soil properties, whichever is

shallower. These soils are rare in the United States. They are

known to occur in Washington and Oregon.

Calcic Haploxerands.—These soils are like Typic

Haploxerands, but they have a calcic horizon that has its upper

boundary within 125 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower. These soils have not been recognized

in the United States. They are established for use in other

countries.

Humic Haploxerands.—These soils are like Typic

Haploxerands, but they have a melanic, mollic, or umbric

epipedon. They are of small extent in the United States. They

are known to occur in California and Washington.

Lithic Haploxerands.—These soils are like Typic

Haploxerands, but they have a lithic contact within 50 cm either

of the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower. These soils are of

small extent in the United States. They are known to occur in

California and Oregon.

Thaptic Haploxerands.—These soils are like Typic

Haploxerands, but they have, between depths of 25 and 100

cm, a buried, dark colored layer 10 cm or more thick below a

lighter colored horizon or horizons 10 cm or more thick with a

lower content of organic carbon. These soils have not been

recognized in the United States. They are established for use in

other countries.

Ultic Haploxerands.—These soils are like Typic

Haploxerands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of less than 35 percent throughout the

upper 50 cm or throughout the entire horizon if it is less than

50 cm thick. These soils are of small extent in the United

States. They are known to occur in California.

Melanoxerands

Melanoxerands are the Xerands that have a melanic epipedon

and a 1500 kPa water retention of 15 percent or more on air-dried

samples and 30 percent or more on undried samples throughout

more than 30 percent of the upper part.

Melanoxerands have a melanic epipedon and commonly

have a cambic horizon.

Most of the Melanoxerands in the United States developed

in late-Pleistocene or Holocene deposits. Most formed under

forest or savanna vegetation.

Definition

Melanoxerands are the Xerands that:

1. Have a melanic epipedon; and

2. Do not have a 1500 kPa water retention of less than 15

percent on air-dried samples and less than 30 percent on

undried samples throughout 60 percent or more of the

thickness either:

a. Within 60 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever

is shallower, if there is no densic, lithic, or paralithic

contact, duripan, or petrocalcic horizon within that depth;

or

b. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.
326 Soil Taxonomy

Key to Subgroups

DDBA. Melanoxerands that have more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

a layer 50 cm or more thick within 60 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Pachic Melanoxerands

DDBB. Other Melanoxerands.

Typic Melanoxerands

Definition of Typic Melanoxerands

Typic Melanoxerands are the Melanoxerands that do not

have both more than 6.0 percent organic carbon and the colors

of a mollic epipedon throughout at least 50 cm of the upper 60

cm, excluding any overlying layers that do not have andic soil

properties.

Description of Subgroups

Typic Melanoxerands.—The central concept or Typic

subgroup of Melanoxerands is fixed on soils that have a

melanic epipedon and do not have both more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

at least 50 cm of the upper 60 cm below the mineral soil

surface or below the top of an organic layer with andic soil

properties, whichever is shallower.

These soils commonly support coniferous forest vegetation.

They are not extensive in the United States. They are known to

occur in Washington and California. Most of the soils are used

as woodland or have been cleared and are used as cropland or

pasture.

Pachic Melanoxerands.—These soils are like Typic

Melanoxerands, but they have both more than 6.0 percent

organic carbon and the colors of a mollic epipedon throughout

at least 50 cm of the upper 60 cm below the mineral soil

surface or below the top of an organic layer with andic soil

properties, whichever is shallower. These soils are of small

extent in the United States. They are known to occur in

Washington and California.

Vitrixerands

Vitrixerands are the relatively coarse textured Xerands. These

are relatively young soils that in many areas occur

near volcanoes. The soils are moderately extensive in the

United States. They are mostly in Oregon, Washington, and

Idaho. These soils formed mainly under coniferous forest

vegetation.

Commonly, Vitrixerands have an ochric or mollic epipedon

and a cambic horizon.

Most of the Vitrixerands in the United States developed in

Holocene or late-Pleistocene deposits.

Definition

Vitrixerands are the Xerands that have a 1500 kPa water

retention of less than 15 percent on air-dried samples and less

than 30 percent on undried samples throughout 60 percent or

more of the thickness either:

1. Within 60 cm either of the mineral soil surface or of

the top of an organic layer with andic soil properties,

whichever is shallower, if there is no densic, lithic, or

paralithic contact, duripan, or petrocalcic horizon within that

depth; or

2. Between either the mineral soil surface or the top of an

organic layer with andic soil properties, whichever is shallower,

and a densic, lithic, or paralithic contact, a duripan, or a

petrocalcic horizon.

Key to Subgroups

DDAA. Vitrixerands that have a lithic contact within 50 cm of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Lithic Vitrixerands

DDAB. Other Vitrixerands that have, in one or more

horizons at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, aquic conditions

for some time in normal years (or artificial drainage) and one

or more of the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Vitrixerands

DDAC. Other Vitrixerands that have, at a depth between 25

and 100 cm from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, a layer 10 cm or more thick with more than 3.0

percent organic carbon and the colors of a mollic epipedon

throughout, underlying one or more horizons with a total

thickness of 10 cm or more that have a color value, moist, 1

unit or more higher and an organic-carbon content 1 percent or

more (absolute) lower.

Thaptic Vitrixerands

DDAD. Other Vitrixerands that have both:

1. A melanic, mollic, or umbric epipedon; and
Andisols 327

2. An argillic or kandic horizon that has its upper boundary

within 125 cm of the mineral soil surface or of the top of an

organic layer with andic soil properties, whichever is

shallower.

Alfic Humic Vitrixerands

DDAE. Other Vitrixerands that have an argillic or kandic

horizon that has both:

1. An upper boundary within 125 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower; and

2. A base saturation (by sum of cations) of less than 35

percent throughout the upper 50 cm or throughout the entire

argillic or kandic horizon if it is less than 50 cm thick.

Ultic Vitrixerands

DDAF. Other Vitrixerands that have an argillic or kandic

horizon that has its upper boundary within 125 cm of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower.

Alfic Vitrixerands

DDAG. Other Vitrixerands that have a melanic, mollic, or

umbric epipedon.

Humic Vitrixerands

DDAH. Other Vitrixerands.

Typic Vitrixerands

Definition of Typic Vitrixerands

Typic Vitrixerands are the Vitrixerands that:

1. Do not have a lithic contact within 50 cm of the soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower;

2. Do not have, in any horizon at a depth between 50 and 100

cm either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, both aquic conditions and any of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or

more chroma of 2 or less either in redox depletions on faces

of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated;

3. Do not have, at a depth between 25 and 100 cm from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, a layer 10 cm or

more thick with more than 3.0 percent organic carbon and the

colors of a mollic epipedon throughout, occurring below a

horizon or horizons 10 cm or more thick with a color value, moist,

1 unit or more higher and an organic-carbon content 1 percent or

more lower;

4. Do not have an argillic or kandic horizon that has its upper

boundary within 125 cm of the mineral soil surface or of the

upper boundary of an organic layer with andic soil properties,

whichever is shallower; and

5. Do not have a melanic, mollic, or umbric epipedon.

Description of Subgroups

Typic Vitrixerands.—The central concept or Typic

subgroup of Vitrixerands is fixed on moderately deep or deep

soils that have an ochric epipedon and do not have an argillic

horizon. Soils that have, at a depth between 40 and 100 cm

either from the mineral soil surface or from the top of an

organic layer with andic soil properties, whichever is

shallower, a dark colored layer 10 cm or more thick with more

than 3.0 percent organic carbon, underlying one or more lighter

colored horizons with a total thickness of 10 cm or more and a

lower content of organic carbon, are excluded from the Typic

subgroup.

Soils that have a lithic contact within a depth of 50 cm are

assigned to the Lithic subgroup. Soils that have both aquic

conditions (or artificial drainage) and redox features in any

horizon at a depth between 50 and 100 cm either from the

mineral soil surface or from the top of an organic layer with

andic soil properties, whichever is shallower, are excluded

from the Typic subgroup and are considered intergrades to

Aquands.

Typic Vitrixerands commonly support coniferous forest

vegetation. Most are used for timber production, but some have

been cleared and are used as cropland.

Alfic Vitrixerands.—These soils are like Typic

Vitrixerands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of 35 percent or more in some part of the

upper 50 cm or in the entire horizon if it is less than 50 cm

thick. These soils are rare in the United States.

Alfic Humic Vitrixerands.—These soils are like Typic

Vitrixerands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of 35 percent or more in some part of the

upper 50 cm or in the entire horizon if it is less than 50 cm

thick. They also have a melanic, mollic, or umbric epipedon.

These soils are rare in the United States.

Aquic Vitrixerands.—These soils are like Typic

Vitrixerands, but they have both aquic conditions (or artificial

drainage) and redox features in a horizon at a depth between

50 and 100 cm either from the mineral soil surface or from the
328

top of an organic layer with andic soil properties, whichever is

shallower. These soils are rare in the United States. They are

known to occur in Washington and Oregon.

Humic Vitrixerands.—These soils are like Typic

Vitrixerands, but they have a melanic, mollic, or umbric

epipedon. They are moderately extensive in the United States.

They are known to occur in Oregon, California, and

Washington.

Lithic Vitrixerands.—These soils are like Typic Vitrixerands,

but they have a lithic contact within 50 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower. These soils are of small

extent in the United States. They are known to occur in

California and Oregon.

Thaptic Vitrixerands.—These soils are like Typic

Vitrixerands, but they have, between depths of 25 and 100 cm, a

buried, dark colored layer 10 cm or more thick below a lighter

colored horizon or horizons 10 cm or more thick with a lower

content of organic carbon. These soils have not been

recognized in the United States. They are established for use in

other countries.

Ultic Vitrixerands.—These soils are like Typic

Vitrixerands, but they have an argillic or kandic horizon that

has both an upper boundary within 125 cm either of the

mineral soil surface or of the top of an organic layer with andic

soil properties, whichever is shallower, and a base saturation

(by sum of cations) of less than 35 percent throughout the upper

50 cm or throughout the entire horizon if it is less than 50 cm

thick. These soils are of small extent in the United States. They

are known to occur in California.
329

Aridisols, as their name implies, are soils in which wateris not available to mesophytic plants for long periods.

During most of the time when the soils are warm enough for

plants to grow, soil water is held at potentials less than the

permanent wilting point or has a content of soluble salts great

enough to limit the growth of plants other than halophytes, or

both. There is no period of 90 consecutive days when moisture

is continuously available for plant growth.

The concept of Aridisols is based on limited soil moisture

available for the growth of most plants. In areas bordering

deserts, the absolute precipitation may be sufficient for the

growth of some plants. Because of runoff or a very low storage

capacity of the soils, or both, however, the actual soil moisture

regime is aridic.

Soil moisture and to a lesser extent soil temperature regimes

control processes in soils. In the other soil orders, soil moisture

regimes are used at the suborder level or the lower categories,

but in the Aridisols they are used to define the order category.

The result is a rather homogeneous class in the sense that

additions, removals, transfers, and transformations within the

soils are strongly influenced by the lack of moisture. Aridisols

require a minimum degree of soil formation. This is commonly

expressed as a cambic horizon. Because the soil moisture

regime is the single most important constraint in the utilization

of these soils, this order delineates geographic areas that have

relatively uniform use.

Because of an extreme imbalance between

evapotranspiration and precipitation, many Aridisols contain

salts. The dominant process is one of accumulation and

concentration of weathering products. The accumulation of

salts is the second most important constraint to land use. Many

soluble precipitates may be eliminated or changed in

concentration through irrigation. In Aridisols, however, the

availability of adequate quality irrigation water is a

fundamental problem. Together with irrigation, a mechanism

for evacuation of the soluble precipitates must be provided or

there is a rapid buildup of salinity and/or sodicity. Irrigation

and drainage systems must be well maintained to keep the soils

from reverting to their original state.

The classification of Aridisols must include consideration of

these constraints or performance restrictive qualities at a high

categoric level. Some Aridisols are also situated on geologic

evaporites. It is frequently difficult to bring these substratum

conditions into a classification system, but care must be taken

to evaluate these deep-seated salt accumulations, particularly in

irrigation projects.

Some Aridisols have inherited features, such as an argillic

horizon, that may be attributed to past wetter paleoclimatic

conditions. There is evidence, however, that clay illuviation

has also occurred during the Holocene. These attributes, and

specifically an argillic horizon, significantly affect the use and

management of the soils.

In the definition of suborders, emphasis is given to the

redistribution of soluble materials and their accumulation. Four

of the seven suborders are defined on the basis of the

composition and accumulation of the soluble fraction.

Weathering and clay translocation also take place in Aridisols.

Two suborders reflect these processes. The seven suborders are:

1. Cryids—Aridisols in cold areas

2. Salids—accumulation of salts more soluble than

gypsum

3. Durids—accumulation of silica

4. Gypsids—accumulation of gypsum

5. Argids—accumulation of clay

6. Calcids—accumulation of carbonates

7. Cambids—translocation and/or transformation of

material

The great group level reflects the degree of expression of the

horizons of accumulation and/or the results of other processes

that are considered subordinate to the particular suborder. The

defining element is the degree of expression of the diagnostic

horizon.

Definition of Aridisols and Limits Between

Aridisols and Soils of Other Orders

1. Unlike Inceptisols and Entisols, Aridisols have:

a. An aridic soil moisture regime; and

b. An ochric or anthropic epipedon; and

c. One or more of the following with the upper boundary

within 100 cm of the soil surface: a cambic horizon with its

lower boundary at a depth of 25 cm or more; a cryic

CHAPTER 11

Aridisols1

1 This chapter was rewritten in 1994 following recommendations of the International

Committee on Aridisols (ICOMID), chaired by Dr. A. Osman. Major contributions were made

by Dr. H. Eswaran, J. Nichols, and Dr. Mohammad Ilaiwi.
330 Soil Taxonomy

temperature regime and a cambic horizon; a calcic, gypsic,

petrocalcic, petrogypsic, or salic horizon; or a duripan; or

d. An argillic or natric horizon; or

e. A salic horizon; and

(1) Saturation with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years; and

(2) A moisture control section that is dry in some or all

parts at some time in normal years; and

(3) No sulfuric horizon that has its upper boundary

within 150 cm of the mineral soil surface;

2. Unlike Histosols, Aridisols do not have organic soil

materials that meet one or more of following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more in normal

years (or are artificially drained), have an upper boundary

within 40 cm of the soil surface, and have a total thickness

of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3

; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more;

3. Unlike Gelisols, Aridisols do not have:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface;

4. Unlike Spodosols, Aridisols do not have either:

a. A spodic horizon and an albic horizon in 50 percent or

more of each pedon; or

b. An Ap horizon containing 85 percent or more spodic

materials;

5. Unlike Andisols, Aridisols do not have andic soil

properties in 60 percent or more of the thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a depth

of 60 cm or a densic, lithic, or paralithic contact, a duripan, or

a petrocalcic horizon, whichever is shallower;

6. Unlike Oxisols, Aridisols do not have within 150 cm of the

mineral soil surface either an oxic horizon or a kandic horizon

that meets the weatherable-mineral requirements for an oxic

horizon and also do not have 40 percent or more clay in the

surface 18 cm after mixing;

7. Unlike Vertisols, Aridisols do not have all of the following:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides or wedge-shaped aggregates that have their

long axes tilted 10 to 60 degrees from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon if shallower; and

c. Cracks that open and close periodically;

8. Unlike Alfisols and Ultisols, Aridisols have an aridic soil

moisture regime;

9. Unlike Mollisols, Aridisols do not have a mollic epipedon.

Representative Pedon and Data

Following is a description of a representative Aridisol. Data

for the pedon identified in this description are given in the

table “Characterization Data for an Aridisol.”

Classification: Coarse-loamy, carbonatic, thermic Ustic

Haplocalcid

Site identification number: 40A3562

Location: Cochise County, Arizona; 5.6 km east and 22.5 km

south of Willcox, Arizona; 320 m north and 180 m east of

the S1/4 corner of sec. 11, T. 16 S., R. 24 E.

Slope: 3 percent

Elevation: 1,293 m above m.s.l.

Annual precipitation: 280 mm

Soil moisture regime: Aridic

Air temperature: Average annual—14 oC; summer—17 oC;

winter—12 oC

Drainage class: Well drained

Land use: Cropland

Runoff class: Low

Particle-size control section: 56 to 100 cm

Parent material: Mixed alluvium derived from andesite,

limestone, and quartzite
Aridisols 331

Diagnostic horizons: An ochric epipedon from a depth of 0 to 56

cm and a calcic horizon from a depth of 56 to 269 cm

Described by: J. Jay and M.L. Richardson

In the following pedon description, colors are for dry soil

unless otherwise indicated. Field determination of pH was

made by a colormetric method.

Ap1—0 to 33 cm; light brownish gray (10YR 6/2) loam, brown

(10YR 4/3) moist; moderate fine granular structure;

slightly hard, friable, slightly plastic; many fine to coarse

roots; many fine interstitial pores; continuous violent

effervescence; moderately alkaline (pH 8.2); gradual

smooth boundary.

Ap2—33 to 56 cm; light brownish gray (10YR 6/2) loam,

brown (10YR 4/3) moist; weak fine subangular blocky

structure; slightly hard, friable, slightly sticky and slightly

plastic; many fine to coarse roots; many fine interstitial

pores; continuous violent effervescence; moderately

alkaline (pH 8.2); abrupt irregular boundary.

Bk1—56 to 81 cm; pale brown (10YR 6/3) and white (10YR

8/2) loam, brown (10YR 5/3) and 1 percent pale brown

(10YR 6/3) moist; massive; extremely hard, firm,

nonsticky and slightly plastic; many fine to coarse roots;

many very fine and fine tubular pores; continuous violent

effervescence; 50 to 60 percent medium and large

carbonate masses that are extremely hard and slightly

rigid; strongly alkaline (pH 8.8); gradual smooth

boundary.

Bk2—81 to 107 cm; white (10YR 8/2) and pinkish gray

(7.5YR 7/2) clay loam, light brown (7.5YR 6/4) moist;

weak fine subangular blocky structure; very hard, friable,

slightly sticky and slightly plastic; many fine to coarse

roots; many very fine and fine tubular pores; continuous

violent effervescence; approximately 9 percent carbonate

masses that are extremely hard and slightly rigid; strongly

alkaline (pH 8.6); gradual smooth boundary.

Bk3—107 to 135 cm; pinkish white (7.5YR 8/2) loam, light

brown (7.5YR 6/4) and pink (7.5YR 7/4) moist; weak fine

subangular blocky structure parting to weak fine granular;

slightly hard, friable, slightly sticky and slightly plastic;

many fine to coarse roots; many very fine and fine tubular

pores; continuous violent effervescence; 50 to 60 percent

5- to 25-mm, rounded and irregularly shaped carbonate

masses; strongly alkaline (pH 8.6); clear smooth

boundary.

Bk4—135 to 269 cm; white (10YR 8/2) and pink (7.5YR 7/4)

clay loam, light brown (7.5YR 6/4) moist; weak fine

subangular blocky structure; very hard, extremely firm,

slightly sticky and plastic; many fine to coarse roots; many

very fine to medium tubular pores; continuous violent

effervescence; 10 to 15 percent 6- to 30-mm carbonate

masses; strongly alkaline (pH 8.8); clear irregular

boundary.

2C—269 to 279 cm; light brown (7.5YR 6/4) clay, brown (7.5YR

4/4) moist; common coarse distinct pink (7.5YR 7/4) mottles;

weak fine and medium subangular blocky structure; hard,

very firm, very plastic; many fine to coarse roots; common

medium and many very fine and fine tubular pores;

continuous violent effervescence; strongly alkaline (pH

8.6).

Key to Suborders

GA. Aridisols that have a cryic soil temperature regime.

Cryids, p. 365

GB. Other Aridisols that have a salic horizon that has its

upper boundary within 100 cm of the soil surface.

Salids, p. 387

GC. Other Aridisols that have a duripan that has its upper

boundary within 100 cm of the soil surface.

Durids, p. 372

GD. Other Aridisols that have a gypsic or petrogypsic horizon

that has its upper boundary within 100 cm of the soil surface

and do not have a petrocalcic horizon overlying these horizons.

Gypsids, p. 379

GE. Other Aridisols that have an argillic or natric 

horizon (deleted text) and do not have a petrocalcic horizon

than has an upper boundary within 100 cm of the soil 

surface.

Argids, p. 331

GF. Other Aridisols that have a calcic or petrocalcic horizon

that has its upper boundary within 100 cm of the soil surface.

Calcids, p. 351

GG. Other Aridisols.

Cambids, p. 357

Argids

These are the Aridisols that have an argillic or natric

horizon but do not have a duripan or a gypsic, petrocalcic,

petrogypsic, or salic horizon within 100 cm of the soil surface.

The low water flux and high concentration of salts in many

Aridisols hinder clay illuviation. The presence of an argillic

horizon commonly is attributed to a moister paleoclimate,

although there is evidence that clay illuviation occurred during

the Holocene in arid soils. Where the soil moisture regime

grades to ustic or xeric, evidence of clay translocation

commonly is more readily established. Most of the Argids

occur in North America. A few have been recognized in the

deserts of North Africa or the Near East.
332 Soil Taxonomy

Characterization Data for an Aridisol

 SITE IDENTIFICATION NO.: 40A3562

 CLASSIFICATION: COARSE-LOAMY, CARBONATIC, THERMIC USTIC HAPLOCALCID

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 4027472 0- 33 Ap1 17.2 32.4 50.4 5.0 17.9 14.5 10.9 17.2 8.4 9.8 4.1 -- -- -- 39 --

 4027473 33- 56 Ap2 18.3 34.5 47.2 6.0 17.9 16.6 11.9 16.3 7.5 8.1 3.4 -- -- -- 35 --

 4027474 56- 81 Bk1 29.2 32.9 37.9 15.0 19.8 13.1 9.2 11.6 5.5 7.5 4.1 -- -- -- 29 --

 4027475 81-107 Bk2 38.1 36.2 25.7 24.0 23.7 12.5 7.3 8.4 3.5 4.1 2.4 -- -- -- 18 --

 4027476 107-135 Bk3 45.1 31.6 23.3 29.0 20.4 11.2 6.1 8.8 3.2 3.4 1.8 -- -- -- 17 --

 4027477 135-269 Bk4 50.2 29.4 20.4 33.0 21.1 8.3 5.9 6.6 2.7 3.5 1.7 -- -- -- 14 --

 4027478 269-279 2C 40.2 34.1 25.7 13.0 24.6 9.5 10.3 9.3 2.8 2.3 1.0 -- -- 2 17 2

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B4a 6S3 6R3b 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A5 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 33 0.90 0.093 0.88 0.86 14.8

 33- 56 0.60 0.067 0.79 0.85 15.6

 56- 81 0.34 0.32 0.52 58 28 15.3

 81-107 0.18 0.29 0.40 45 23 15.3

 107-135 0.16 0.26 0.33 14.7

 135-269 0.11 0.19 0.32 16.3

 269-279 0.03 0.38 0.36 14.6

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- (- -CEC- -) EXCH SAR BASE CARBONATE CaSO4 AS (- - - -PH - - -)

 Ca Mg Na K SUM ITY SUM NH4- Na SATURATION AS CaCO3 GYPSUM SAT CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc SUM NH4OAc <2mm <20mm <2mm <20mm PASTE .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 5A3a 5A8b 55D2 5E 5C3 5C1 6E1g 6E4 6F1a 6F4 8C1b 8C1f 8C1f

 <- - - - - - - - - -meq / 100 g - - - - - - - - - -> Pct <- -Pct- > <- -Pct -> <- -Pct -> 1:2 1:1

 0- 33 3.2 1.0 1.7 15.1 4 2 100 100 27 7.8

 33- 56 3.3 0.8 2.0 14.5 4 2 100 100 29 8.0

 56- 81 3.9 0.8 1.6 9.4 7 2 100 100 46 8.1

 81-107 3.6 1.0 1.3 10.9 8 2 100 100 60 8.1

 107-135 3.9 1.1 1.5 11.5 7 2 100 100 55 8.1

 135-269 4.7 0.9 1.5 9.6 7 2 100 100 58 8.1

 269-279 4.7 0.9 2.0 15.4 5 2 100 100 29 8.0

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - - - - - - - - - -WATER EXTRACTED FROM SATURATED PASTE- - - - - - - - - - - - - )PRED.

 TOTAL ELEC. ELEC.

 Ca Mg Na K CO3 HCO3 F Cl SO4 NO2 NO3 H2O SALTS COND. COND.

 DEPTH EST. 8A3a 8I

 (cm) 6N1b 6O1b 6P1b 6Q1b 6I1b 6J1b 6U1a 6K1c 6L1c 6W1a 6M1c 8A 8D5 mmhos mmhos

 < - - - - - - - - - - - - - -meq / liter - - - - - - - - - - - -> <- -Pct- -> /cm /cm

 0- 33 18.6 4.0 6.9 0.8 -- 2.2 5.0 51.8 0.1 2.83

 33- 56 6.4 1.5 3.4 0.4 -- 2.3 2.5 54.3 TR 1.17

 56- 81 5.4 2.0 3.2 0.8 -- 2.8 2.2 53.8 TR 1.13

 81-107 2.8 2.2 3.4 0.8 -- 2.0 2.2 49.2 TR 1.13

 107-135 5.5 2.6 5.0 1.0 -- 2.2 2.2 49.6 TR 1.40

 135-269 5.6 2.2 4.4 1.2 -- 2.2 2.1 52.3 TR 1.37

 269-279 4.9 2.0 3.2 0.8 -- 1.8 1.7 59.9 TR 1.09

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.
Aridisols 333

Definition

Argids are the Aridisols that:

1. Have a natric or argillic horizon (deleted text);

2. Have a soil temperature regime warmer than cryic;

3. Do not have a duripan or a gypsic, petrocalcic, petrogypsic,

or salic horizon that has its upper boundary within 100 cm of the

soil surface.

Key to Great Groups

GEA. Argids that have a duripan or a petrocalcic or

petrogypsic horizon that has its upper boundary within 150 cm

of the soil surface.

Petroargids, p. 350

GEB. Other Argids that have a natric horizon.

Natrargids, p. 343

GEC. Other Argids that do not have a densic, lithic, or

paralithic contact within 50 cm of the soil surface and have

either:

1. A clay increase of 15 percent or more (absolute) within

a vertical distance of 2.5 cm either within the argillic

horizon or at its upper boundary; or

2. An argillic horizon that extends to 150 cm or more

from the soil surface, that does not have a clay decrease with

increasing depth of 20 percent or more (relative) from the

maximum clay content, and that has, in 50 percent or more

of the matrix in some part between 100 and 150 cm, either:

a. Hue of 7.5YR or redder and chroma of 5 or more; or

b. Hue of 7.5YR or redder and value, moist, of 3 or less

and value, dry, of 4 or less.

Paleargids, p. 346

GED. Other Argids that have a gypsic horizon that has its

upper boundary within 150 cm of the soil surface.

Gypsiargids, p. 337

GEE. Other Argids that have a calcic horizon that has its

upper boundary within 150 cm of the soil surface.

Calciargids, p. 333

GEF. Other Argids.

Haplargids, p. 339

Calciargids

These are the Argids that, below the argillic horizon, have a

calcic horizon within 150 cm of the soil surface. These soils

have been recharged with calcium carbonate from dust.

Calciargids are commonly on late-Pleistocene erosional

surfaces or on gentle to steep slopes. Before the International

Committee on Aridisols (ICOMID) was established, these soils

were classified as Haplargids.

Definition

Calciargids are the Argids that:

1. Have a calcic horizon that has its upper boundary within 150

cm of the soil surface;

2. Do not have a natric horizon;

3. Do not have a duripan or a gypsic, petrocalcic, or

petrogypsic horizon that has its upper boundary within 150 cm

of the soil surface;

4. Have a densic, lithic, or paralithic contact within 50 cm of

the soil surface; or

a. A clay increase of less than 15 percent (absolute) within

a vertical distance of 2.5 cm either within the argillic

horizon or at its upper boundary; or

b. An argillic horizon that does not extend to 150 cm from

the soil surface, has a clay decrease with increasing depth of

20 percent or more (relative) from the maximum clay

content, or has either:

(1) Hue of 10YR or yellower or chroma of 4 or less in

the matrix of all horizons between depths of 100 and 150

cm; or

(2) Hue of 10YR or yellower and value, moist, of 4 or

more or value, dry, of 4 or less in less than 50 percent of

the matrix.

Key to Subgroups

GEEA. Calciargids that have a lithic contact within 50 cm of

the soil surface.

Lithic Calciargids

GEEB. Other Calciargids that have both:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact if shallower; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the
334 Soil Taxonomy

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Xerertic Calciargids

GEEC. Other Calciargids that have both:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact if shallower; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Ustertic Calciargids

GEED. Other Calciargids that have one or both of the

following:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide through a thickness of 30 cm or more for some

time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact if shallower.

Vertic Calciargids

GEEE. Other Calciargids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years.

Aquic Calciargids

GEEF. Other Calciargids that have:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the soil surface to the top of an

argillic horizon at a depth of 50 cm or more; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 oC or higher and a

soil moisture regime that borders on ustic.

Arenic Ustic Calciargids

GEEG. Other Calciargids that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the soil

surface to the top of an argillic horizon at a depth of 50 cm or

more.

Arenic Calciargids

GEEH. Other Calciargids that have the following

combination of characteristics:

1. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,

that contain 20 percent or more (by volume) durinodes or

are brittle and have at least a firm rupture-resistance class

when moist; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and

have a soil moisture regime that borders on xeric.

Durinodic Xeric Calciargids

GEEI. Other Calciargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes or are brittle and have at least a firm

rupture-resistance class when moist.

Durinodic Calciargids

GEEJ. Other Calciargids that:

1. Are dry in all parts of the moisture control section

for less than three-fourths of the time (cumulative) when

the soil temperature at a depth of 50 cm is 5 oC or higher

and have a soil moisture regime that borders on xeric;

and

2. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,

that contain 20 percent or more (by volume) nodules or

concretions.

Petronodic Xeric Calciargids

GEEK. Other Calciargids that:

1. Are dry in all parts of the moisture control section

for less than three-fourths of the time (cumulative) when

the soil temperature at a depth of 50 cm is 5 oC or higher

and have a soil moisture regime that borders on ustic;

and

2. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,
Aridisols 335

that contain 20 percent or more (by volume) nodules or

concretions.

Petronodic Ustic Calciargids

GEEL. Other Calciargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) nodules or concretions.

Petronodic Calciargids

GEEM. Other Calciargids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Calciargids

GEEN. Other Calciargids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Calciargids

GEEO. Other Calciargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

xeric.

Xeric Calciargids

GEEP. Other Calciargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

ustic.

Ustic Calciargids

GEEQ. Other Calciargids.

Typic Calciargids

Definition of Typic Calciargids

Typic Calciargids are the Calciargids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years;

3. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes,

nodules, or concretions or are brittle and have at least a firm

rupture-resistance class when moist;

4. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm;

5. Do not have a sandy or sandy-skeletal particle-size class in

all layers extending from the soil surface to the top of an

argillic horizon at a depth of 50 cm or more;

6. Have either:

a. No cracks within 125 cm of the soil surface that are

5 mm or more wide through a thickness of 30 cm or more

for some time in normal years, and no slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of less than 6.0 cm between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower;

7. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.
336 Soil Taxonomy

Description of Subgroups

Typic Calciargids.—These soils are among the driest of the

Calciargids. Soils in which the soil moisture regime borders on

ustic or xeric are more moist and are the basis for the Ustic and

Xeric subgroups. Typic Calciargids do not have a high shrinkswell potential or a lithic contact within 50 cm of the soil

surface. They do not have a significant amount of durinodes,

nodules, concretions, volcanic glass, cinders, pumice, or

pumicelike fragments. They do not have a layer that is partially

cemented by silica. They do not have a thick sandy surface

horizon and are not saturated for 1 month in normal years.

These soils occur in the deserts of the western part of the

United States and are used for grazing.

Aquic Calciargids.—These are the Calciargids that are

saturated within 100 cm of the soil surface for short periods but

are dry enough to meet the requirements of an aridic soil

moisture regime. These soils do not have a high shrink-swell

potential or a lithic contact within 50 cm of the soil surface.

They are rare in the world.

Arenic Calciargids.—These are the Calciargids that have a

sandy or sandy-skeletal particle-size class from the soil surface

to a depth of 50 cm or more and have a soil moisture regime

that does not border on ustic. These soils do not have a lithic

contact within 50 cm of the surface and are not saturated

within 100 cm of the soil surface. They are known to occur in

the desert of California.

Arenic Ustic Calciargids.—These are the Calciargids that

have a sandy or sandy-skeletal particle-size class from the

surface to a depth of 50 cm or more and have a soil moisture

regime that borders on ustic. These soils do not have a lithic

contact within 50 cm of the soil surface or aquic conditions for

more than 1 month per year within 100 cm of the soil surface.

Durinodic Calciargids.—These are the Calciargids that

have a horizon with 20 percent or more durinodes or are brittle

and have at least a firm rupture-resistance class. These soils do

not have a lithic contact within 50 cm of the soil surface and

are not saturated within 100 cm of the soil surface for 1 month

or more in normal years. Durinodic Calciargids do not have

thick sandy horizons from the surface to a depth of 50 cm or

more, nor do they have a high shrink-swell potential. These

soils occur in Nevada and Idaho and are used primarily for

grazing by livestock.

Durinodic Xeric Calciargids.—These are the Calciargids

that have a horizon with 20 percent or more durinodes or are

brittle and have at least a firm rupture-resistance class. These

soils have a soil moisture regime that borders on xeric. They do

not have a lithic contact within 50 cm of the soil surface and

are not saturated within 100 cm of the soil surface for 1 month

or more in normal years. Durinodic Xeric Calciargids do not

have thick sandy horizons from the surface to a depth of 50 cm

or more, nor do they have a high shrink-swell potential. These

soils occur in Nevada and Idaho and are used primarily for

grazing by livestock.

Lithic Calciargids.—These are the Calciargids that have a

lithic contact within 50 cm of the soil surface. These soils

occur in several States in the southwestern part of the United

States. They are commonly used for grazing by livestock.

Petronodic Calciargids.—These are the Calciargids that

have one or more horizons, 15 cm or more thick, that have 20

percent or more (by volume) nodules or concretions. The

nodules and concretions are not cemented by silica (durinodes).

These soils do not have a lithic contact within 50 cm of the soil

surface or a high shrink-swell potential. They are not saturated

within 100 cm of the soil surface, nor do they have thick sandy

layers starting at the soil surface. Petronodic Calciargids do not

have a soil moisture regime that borders on ustic or xeric.

These soils occur in California, Arizona, and New Mexico and

are used as rangeland.

Petronodic Ustic Calciargids.—These are the Calciargids

that have, in one or more horizons with a combined thickness

of 15 cm or more, 20 percent or more (by volume) nodules or

concretions and that have a soil moisture regime that borders

on ustic. These soils do not have a lithic contact within 50 cm

of the soil surface, a high shrink-swell potential, saturation

with water for 1 month or more within 100 cm of the soil

surface, or durinodes or brittleness. Petronodic Ustic

Calciargids occur in Arizona and New Mexico.

Petronodic Xeric Calciargids.—These are the Calciargids

that have a soil moisture regime that borders on xeric and have

one or more horizons, 15 cm or more thick, that have 20

percent or more (by volume) nodules or concretions. The

nodules and concretions are not cemented by silica (durinodes).

These soils do not have a lithic contact within 50 cm of the soil

surface or a high shrink-swell potential. Petronodic Xeric

Calciargids are not saturated within 100 cm of the soil surface,

nor do they have thick sandy layers starting at the soil surface.

These soils are moderately extensive in Idaho and are used as

irrigated cropland, pasture, or rangeland.

Ustertic Calciargids.—These are the Calciargids that have

a high shrink-swell potential and a soil moisture regime that

borders on ustic. These soils do not have a lithic contact within

50 cm of the soil surface. They occur in the southwestern part

of the United States and are commonly used as rangeland.

Ustic Calciargids.—These are the Calciargids that have a

soil moisture regime that borders on ustic. These soils do not

have many other distinguishing characteristics, such as a lithic

contact within 50 cm of the soil surface; a high shrink-swell

potential; an accumulation of durinodes, concretions, or

nodules; or a significant amount of volcanic glass, pumice,

cinders, or pumicelike fragments near the surface. These soils

occur in various States throughout the southwestern part of the

United States. They are extensive and are used as irrigated

cropland, pasture, or rangeland.

Vertic Calciargids.—These are the Calciargids that have

a high shrink-swell potential but do not have a soil moisture

regime that borders on ustic or xeric. These soils also do not

have a lithic contact within 50 cm of the soil surface. Vertic
Aridisols 337

Calciargids occur in the southwestern part of the United

States.

Vitrandic Calciargids.—These are the Calciargids that

have a layer 18 cm or more thick in the upper 75 cm with a

significant amount of volcanic glass, pumice, cinders, and

pumicelike fragments. These soils do not have a lithic contact

within 50 cm of the soil surface; a high shrink-swell potential;

an accumulation of nodules, concretions, or durinodes; or a soil

moisture regime that borders on xeric. These soils occur in the

southwestern part of the United States, in areas that have a

volcanic influence.

Vitrixerandic Calciargids.—These are the Calciargids that

have a layer 18 cm or more thick in the upper 75 cm with a

significant amount of volcanic glass, pumice, cinders, and

pumicelike fragments and have a soil moisture regime that

borders on xeric. These soils do not have a lithic contact within

50 cm of the soil surface; a high shrink-swell potential; or an

accumulation of nodules, concretions, or durinodes. They occur

in the southwestern part of the United States, in areas that have

a volcanic influence.

Xerertic Calciargids.—These are the Calciargids that have

a high shrink-swell potential and have a soil moisture regime

that borders on xeric. These soils do not have a lithic contact

within 50 cm of the soil surface.

Xeric Calciargids.—These are the Calciargids that have a

soil moisture regime that borders on xeric. These soils do not

have many other distinguishing characteristics, such as a lithic

contact within 50 cm of the soil surface; a high shrink-swell

potential; an accumulation of durinodes, concretions, or

nodules; or a significant amount of volcanic glass, pumice,

cinders, or pumicelike fragments near the surface. These soils

occur in various States throughout the western part of the

United States. They are extensive and are used as irrigated

cropland, pasture, or rangeland.

Gypsiargids

Gypsiargids are the Argids that have a gypsic horizon within

150 cm of the soil surface. Most of these soils are on latePleistocene surfaces. In the United States, they are of minor

extent and are known to occur in northwestern New Mexico and

possibly in other States in the Four Corners area.

Definition

Gypsiargids are the Argids that:

1. Have a gypsic horizon that has its upper boundary within

150 cm of the soil surface;

2. Do not have a duripan or a petrocalcic or petrogypsic

horizon that has its upper boundary within 150 cm of the soil

surface;

3. Do not have a natric horizon;

4. Have a densic, lithic, or paralithic contact within 50 cm of the

soil surface; or

a. A clay increase of less than 15 percent (absolute) within

a vertical distance of 2.5 cm either within the argillic

horizon or at its upper boundary; or

b. An argillic horizon that does not extend to 150 cm from

the soil surface, has a clay decrease with increasing depth of

20 percent or more (relative) from the maximum clay

content, or has either:

(1) Hue of 10YR or yellower or chroma of 4 or less in

the matrix of all horizons between depths of 100 and 150

cm; or

(2) Hue of 10YR or yellower and value, moist, of 4 or

more or value, dry, of 4 or less in less than 50 percent of

the matrix.

Key to Subgroups

GEDA. Gypsiargids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Are saturated with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years.

Aquic Gypsiargids

GEDB. Other Gypsiargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that either contain 20 percent or

more (by volume) durinodes or are brittle and have at least a

firm rupture-resistance class when moist.

Durinodic Gypsiargids

GEDC. Other Gypsiargids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more
338 Soil Taxonomy

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Gypsiargids

GEDD. Other Gypsiargids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Gypsiargids

GEDE. Other Gypsiargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

xeric.

Xeric Gypsiargids

GEDF. Other Gypsiargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Gypsiargids

GEDG. Other Gypsiargids.

Typic Gypsiargids

Definition of Typic Gypsiargids

Typic Gypsiargids are the Gypsiargids that:

1. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years;

2. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes or

are brittle and have at least a firm rupture-resistance class

when moist;

3. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Gypsiargids.—The Typic subgroup is centered on

the soils that are not saturated for 1 month or more within 100

cm of the soil surface in normal years, that do not have a soil

moisture regime that borders on ustic or xeric, that do not have

durinodes or brittleness, and that do not have a significant

amount of volcanic glass, pumice, cinders, or pumicelike

fragments close to the surface.

Aquic Gypsiargids.—These are the Gypsiargids that are

saturated for 1 month or more within 100 cm of the soil surface

in normal years. These soils are very rare in the world.

Durinodic Gypsiargids.—These are the Gypsiargids that

have one or more horizons, 15 cm or more thick, that have 20

percent or more durinodes or are brittle and firm when moist.

The brittleness and firm rupture-resistance class in these soils

are attributed to partial cementation by silica.

Ustic Gypsiargids.—These are the Gypsiargids that have a

soil moisture regime that borders on ustic. Because of the

added moisture, these soils are more productive than soils in

the Typic subgroup. Ustic Gypsiargids do not have an

accumulation of durinodes or brittleness; a significant amount

of volcanic glass, cinders, pumice, or pumicelike fragments

near the surface; or saturation for 1 month or more within 100

cm of the soil surface in normal years.

Vitrandic Gypsiargids.—These are the Gypsiargids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric. These soils are not saturated for 1 month

or more within 100 cm of the soil surface in normal years and

do not have brittleness or an accumulation of durinodes.

Vitrixerandic Gypsiargids.—These are the Gypsiargids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments and have a soil moisture

regime that borders on xeric. These soils are not saturated for 1

month or more within 100 cm of the soil surface in normal

years and do not have brittleness or durinodes.

Xeric Gypsiargids.—These are the Gypsiargids that have a

soil moisture regime that borders on xeric. These soils are not

saturated for 1 month or more within 100 cm of the soil surface

in normal years and do not have brittleness or an accumulation
Aridisols 339

of durinodes. They also do not have a significant amount of

volcanic glass, cinders, pumice, or pumicelike fragments.

Haplargids

These are the Argids that have an argillic horizon but do not

have a duripan or a petrocalcic, petrogypsic, calcic, gypsic, or

natric horizon. These soils commonly have calcium carbonate

accumulations within or below the argillic horizon. Haplargids

commonly occur on late-Pleistocene surfaces or sediments.

Definition

Haplargids are the Argids that:

1. Do not have a duripan or a petrocalcic, petrogypsic,

gypsic, or calcic horizon that has an upper boundary within

150 cm of the soil surface;

2. Do not have a natric horizon;

3. Have a densic, lithic, or paralithic contact within 50 cm of

the soil surface; or

a. A clay increase of less than 15 percent (absolute) within

a vertical distance of 2.5 cm either within the argillic

horizon or at its upper boundary; or

b. An argillic horizon that does not extend to 150 cm from

the soil surface, has a clay decrease with increasing depth of

20 percent or more (relative) from the maximum clay

content, or has either:

(1) Hue of 10YR or yellower or chroma of 4 or less in

the matrix of all horizons between depths of 100 and 150

cm; or

(2) Hue of 10YR or yellower and value, moist, of 4 or

more or value, dry, of 4 or less in less than 50 percent of

the matrix.

Key to Subgroups

GEFA. Haplargids that have:

1. A lithic contact within 50 cm of the soil surface; and

2. An argillic horizon that is discontinuous throughout

each pedon.

Lithic Ruptic-Entic Haplargids

GEFB. Other Haplargids that have:

1. A lithic contact within 50 cm of the soil surface;

and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Lithic Xeric Haplargids

GEFC. Other Haplargids that have:

1. A lithic contact within 50 cm of the soil surface; and

2. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm and a soil

moisture regime that borders on ustic.

Lithic Ustic Haplargids

GEFD. Other Haplargids that have a lithic contact within 50

cm of the soil surface.

Lithic Haplargids

GEFE. Other Haplargids that have both:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact if shallower; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Xerertic Haplargids

GEFF. Other Haplargids that have both:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact if shallower; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Ustertic Haplargids

GEFG. Other Haplargids that have one or both of the

following:

1. Cracks within 125 cm of the soil surface that are 5 mm
340 Soil Taxonomy

or more wide through a thickness of 30 cm or more for some

time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact if shallower.

Vertic Haplargids

GEFH. Other Haplargids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within 100

cm of the soil surface for 1 month or more in normal years.

Aquic Haplargids

GEFI. Other Haplargids that have:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the soil surface to the top of an

argillic horizon at a depth of 50 cm or more; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and a

soil moisture regime that borders on ustic.

Arenic Ustic Haplargids

GEFJ. Other Haplargids that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the soil

surface to the top of an argillic horizon at a depth of 50 cm or

more.

Arenic Haplargids

GEFK. Other Haplargids that have:

1. One or more horizons, within 100 cm of the soil surface

and with a combined thickness of 15 cm or more, that

contain 20 percent or more (by volume) durinodes or are

brittle and have at least a firm rupture-resistance class when

moist; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Durinodic Xeric Haplargids

GEFL. Other Haplargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes or are brittle and have at least a firm

rupture-resistance class when moist.

Durinodic Haplargids

GEFM. Other Haplargids that:

1. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,

that contain 20 percent or more (by volume) nodules or

concretions; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and

have a soil moisture regime that borders on ustic.

Petronodic Ustic Haplargids

GEFN. Other Haplargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) nodules or concretions.

Petronodic Haplargids

GEFO. Other Haplargids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplargids

GEFP. Other Haplargids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Haplargids

GEFQ. Other Haplargids that are dry in all parts of the

moisture control section for less than three-fourths of the time
Aridisols 341

(cumulative) when the soil temperature at a depth of 50 cm is

5 o

C or higher and have a soil moisture regime that borders on

xeric.

Xeric Haplargids

GEFR. Other Haplargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Haplargids

GEFS. Other Haplargids.

Typic Haplargids

Definition of Typic Haplargids

Typic Haplargids are the Haplargids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have an argillic horizon that is continuous throughout

each pedon;

3. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 oC or higher at a depth of 50 cm;

4. Have:

a. No cracks within 125 cm of the soil surface that are

5 mm or more wide through a thickness of 30 cm or more

for some time in normal years, and no slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; and

b. A linear extensibility of less than 6.0 cm between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact if shallower;

5. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years;

6. Do not have a sandy or sandy-skeletal particle-size class in

all layers extending from the soil surface to the top of an

argillic horizon at a depth of 50 cm or more;

7. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes,

nodules, or concretions or are brittle and have at least a firm

rupture-resistance class when moist;

8. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Haplargids.—The Typic subgroup is centered on

soils that are moderately deep or deeper and have a soil

moisture regime that borders on neither ustic nor xeric. These

soils do not have a high shrink-swell potential; saturation

within 100 cm of the soil surface for 1 month or more in

normal years; horizons with a sandy or sandy-skeletal particlesize class from the soil surface to a depth of 50 cm; or horizons

with significant accumulations of durinodes, concretions,

nodules, volcanic glass, pumice, cinders, or pumicelike

fragments.

Aquic Haplargids.—These are the Haplargids that are

saturated within 100 cm of the soil surface for 1 month or more

in normal years but are dry for most of the year. These soils do

not have a lithic contact within 50 cm of the soil surface or a

high shrink-swell potential. They occur on stream terraces in

Idaho and California.

Arenic Haplargids.—These are the Haplargids that have a

sandy or sandy-skeletal particle-size class from the surface to a

depth of 50 cm or more and do not have a soil moisture regime

that borders on ustic. These soils do not have a lithic contact

within 50 cm of the soil surface or a high shrink-swell

potential. They are not saturated with water for 1 month or

more within 100 cm of the soil surface in normal years. These

soils occur in California and are used as rangeland.

Arenic Ustic Haplargids.—These are the Haplargids that

have a sandy or sandy-skeletal particle-size class from the

surface to a depth of 50 cm or more and have a soil moisture

regime that borders on ustic. These soils do not have a lithic

contact within 50 cm of the soil surface or a high shrink-swell

potential. They are not saturated with water for 1 month or

more within 100 cm of the soil surface in normal years. These

soils occur in Texas, New Mexico, and Colorado and are used

as rangeland.

Durinodic Haplargids.—These are the Haplargids that

have one or more horizons, at least 15 cm thick, that have 20

percent or more durinodes or are brittle and at least firm when

moist. These soils do not have a soil moisture regime that

borders on xeric and do not have a high shrink-swell potential.

They do not have a lithic contact within 50 cm of the soil

surface or thick sandy horizons from the soil surface to a depth
342 Soil Taxonomy

of 50 cm or more. They are not saturated for 1 month or more

within 100 cm of the soil surface in normal years. These soils

occur in Nevada and California. They are used primarily as

rangeland, but in some areas they are used for urban

development or irrigated cropland.

Durinodic Xeric Haplargids.—These are the Haplargids

that have one or more horizons, at least 15 cm thick, that have

20 percent or more durinodes or are brittle and at least firm

when moist. These soils have a soil moisture regime that

borders on xeric. They do not have a lithic contact within 50

cm of the soil surface; thick sandy horizons from the soil

surface to a depth of 50 cm or more; or a high shrink-swell

potential. They are not saturated for 1 month or more within

100 cm of the soil surface in normal years. These soils occur in

Nevada, Idaho, and California. They are used primarily as

rangeland, but in some areas they are used for urban

development or irrigated cropland.

Lithic Haplargids.—These are the Haplargids that have a

lithic contact within 50 cm of the soil surface. These soils have

a continuous argillic horizon and do not have a soil moisture

regime that borders on ustic or xeric. They occur in the hot to

cool deserts in the western part of the United States and are

used primarily as rangeland.

Lithic Ruptic-Entic Haplargids.—These are the

Haplargids that have a lithic contact within 50 cm of the soil

surface and have a discontinuous argillic horizon. These soils

occur in Nevada and are used primarily as rangeland.

Lithic Ustic Haplargids.—These are the Haplargids that

have a lithic contact within 50 cm of the soil surface, a

continuous argillic horizon, and a soil moisture regime that

borders on ustic. These soils occur in the deserts of the

southwestern part of the United States and are used primarily

as rangeland.

Lithic Xeric Haplargids.—These are the Haplargids that

have a lithic contact within 50 cm of the soil surface, a

continuous argillic horizon, and a soil moisture regime that

borders on xeric. These soils occur in Nevada, California, and

Idaho and are used primarily as rangeland.

Petronodic Haplargids.—These are the Haplargids that

have one or more horizons, 15 cm or more thick, that have 20

percent or more, by volume, nodules and concretions. These

soils do not have durinodes or brittleness and at least a firm

rupture-resistance class when moist. They do not have a lithic

contact within 50 cm of the surface or a high shrink-swell

potential. They are not sandy or sandy-skeletal from the soil

surface to a depth of 50 cm or more, do not have a soil

moisture regime that borders on ustic, and are not saturated for

1 month or more within 100 cm of the soil surface in normal

years. These soils occur in Arizona and New Mexico and are

used primarily as rangeland.

Petronodic Ustic Haplargids.—These are the Haplargids

that have, in one or more horizons with a total thickness of 15

cm or more, 20 percent or more nodules and concretions and

that have a soil moisture regime that borders on ustic. These

soils do not have a lithic contact within 50 cm of the mineral soil

surface, are not saturated with water for 1 month or more within

100 cm of the soil surface in normal years, and do not have

durinodes or brittleness. They occur in Arizona and New

Mexico.

Ustertic Haplargids.—These are the Haplargids that have

a high shrink-swell potential and have a soil moisture regime

that borders on ustic. These soils do not have a lithic contact

within 50 cm of the soil surface. They occur in the deserts of

the southwestern part of the United States and are used

primarily as rangeland.

Ustic Haplargids.—These are the Haplargids that have a

soil moisture regime that borders on ustic. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; a sandy or sandy-skeletal particle-size

class from the soil surface to a depth of 50 cm or more; or a

significant amount of volcanic glass, cinders, pumice,

pumicelike fragments, durinodes, concretions, or nodules.

Ustic Haplargids are not saturated for 1 month or more within

100 cm of the soil surface in normal years. These soils are

extensive in the southwestern part of the United States.

Vertic Haplargids.—These are the Haplargids that have a

high shrink-swell potential but do not have a soil moisture

regime that borders on xeric or ustic. These soils also do not

have a lithic contact within 50 cm of the soil surface. They

occur in the western part of the United States.

Vitrandic Haplargids.—These are the Haplargids that have

a significant amount of volcanic glass, pumice, cinders, or

pumicelike fragments in one or more horizons with a total

thickness of 18 cm within 75 cm of the soil surface. These soils

do not have a soil moisture regime that borders on xeric; a

lithic contact within 50 cm of the soil surface; a high shrinkswell potential; a significant amount of durinodes, nodules, or

concretions; or a sandy or sandy-skeletal particle-size class

from the soil surface to a depth of 50 cm or more. These soils

are rare but occur in the western part of the United States, in

areas with a volcanic influence.

Vitrixerandic Haplargids.—These are the Haplargids that

have a significant amount of volcanic glass, pumice, cinders, or

pumicelike fragments in one or more horizons with a total

thickness of 18 cm within 75 cm of the soil surface and have a

soil moisture regime that borders on xeric. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; a significant amount of durinodes,

nodules, or concretions; or a sandy or sandy-skeletal particlesize class from the soil surface to a depth of 50 cm or more.

They are rare but occur in the western part of the United States,

in areas with a volcanic influence.

Xerertic Haplargids.—These are the Haplargids that have

a high shrink-swell potential and have a soil moisture regime

that borders on xeric. These soils do not have a lithic contact

within 50 cm of the soil surface. They occur in Nevada and

Idaho and are used primarily as rangeland.

Xeric Haplargids.—These are the Haplargids that have a
Aridisols 343

soil moisture regime that borders on xeric. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; a sandy or sandy-skeletal particle-size

class from the soil surface to a depth of 50 cm or more; or a

significant amount of volcanic glass, durinodes, concretions, or

nodules. Xeric Haplargids are not saturated for 1 month or more

within 100 cm of the soil surface in normal years. They are

extensive in Oregon, Nevada, and Idaho.

Natrargids

These are the Argids that have a natric horizon but do not

have a duripan or a petrocalcic or petrogypsic horizon within

150 cm of the soil surface. Commonly, the natric horizon has

prismatic or columnar structure. Natrargids commonly contain

carbonates, soluble salts, or both. These soils formed in

sediments that range in age from Holocene to late-Pleistocene.

Most of them are nearly level to gently sloping. These soils

occur in the western part of the United States and on the

western edge of the Great Plains.

Definition

Natrargids are the Argids that:

1. Have a natric horizon;

2. Do not have a duripan or a petrocalcic or petrogypsic

horizon that has its upper boundary within 150 cm of the soil

surface.

Key to Subgroups

GEBA. Natrargids that have both of the following:

1. A lithic contact within 50 cm of the soil surface; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Lithic Xeric Natrargids

GEBB. Other Natrargids that have both of the following:

1. A lithic contact within 50 cm of the soil surface; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Lithic Ustic Natrargids

GEBC. Other Natrargids that have a lithic contact within 50

cm of the soil surface.

Lithic Natrargids

GEBD. Other Natrargids that have one or both of the

following:

1. Cracks within 125 cm of the soil surface that are 5 mm or

more wide through a thickness of 30 cm or more for some time

in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower.

Vertic Natrargids

GEBE. Other Natrargids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years.

Aquic Natrargids

GEBF. Other Natrargids that meet both of the following:

1. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,

that contain 20 percent or more (by volume) durinodes or

are brittle and have at least a firm rupture-resistance class

when moist; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and

have a soil moisture regime that borders on xeric.

Durinodic Xeric Natrargids

GEBG. Other Natrargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes or are brittle and have at least a firm

rupture-resistance class when moist.

Durinodic Natrargids

GEBH. Other Natrargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) nodules or concretions.

Petronodic Natrargids

GEBI. Other Natrargids that have:

1. Skeletans covering 10 percent or more of the surfaces of
344 Soil Taxonomy

peds at a depth 2.5 cm or more below the upper boundary of

the natric horizon; and

2. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm and a soil

moisture regime that borders on ustic.

Glossic Ustic Natrargids

GEBJ. Other Natrargids that have:

1. An exchangeable sodium percentage of less than 15 (or

an SAR of less than 13) in 50 percent or more of the natric

horizon; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Haplic Ustic Natrargids

GEBK. Other Natrargids that have:

1. An exchangeable sodium percentage of less than 15

(or an SAR of less than 13) in 50 percent or more of the

natric horizon; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Haploxeralfic Natrargids

GEBL. Other Natrargids that have an exchangeable sodium

percentage of less than 15 (or an SAR of less than 13) in 50

percent or more of the natric horizon.

Haplic Natrargids

GEBM. Other Natrargids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Natrargids

GEBN. Other Natrargids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm of

the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Natrargids

GEBO. Other Natrargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

xeric.

Xeric Natrargids

GEBP. Other Natrargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

ustic.

Ustic Natrargids

GEBQ. Other Natrargids that have skeletans covering 10

percent or more of the surfaces of peds at a depth 2.5 cm or

more below the upper boundary of the natric horizon.

Glossic Natrargids

GEBR. Other Natrargids.

Typic Natrargids

Definition of Typic Natrargids

Typic Natrargids are the Natrargids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have either:

a. No cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and no slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has

its upper boundary within 125 cm of the soil surface; or

b. A linear extensibility of less than 6.0 cm between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower;

3. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with
Aridisols 345

water in one or more layers within 100 cm of the soil surface for 1

month or more in normal years;

4. Do not have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of more than 15 cm, that

contain 20 percent or more (by volume) durinodes, nodules, or

concretions or are brittle and have at least a firm ruptureresistance class when moist;

5. Are dry in all parts of the moisture control section for threefourths or more of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm;

6. Have skeletans covering less than 10 percent of the

surfaces of peds at a depth 2.5 cm or more below the upper

boundary of the natric horizon;

7. Have an exchangeable sodium percentage of 15 or more

(or an SAR of 13 or more) in more than 50 percent of the

natric horizon;

8. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Natrargids.—The Typic subgroup is centered on

soils that are moderately deep or deeper and have a soil

moisture regime that borders on neither ustic nor xeric. These

soils have an exchangeable sodium percentage of 15 or more in

more than 50 percent of the natric horizon but do not have

more than 10 percent skeletans at a depth 2.5 cm or more

below the upper boundary of the natric horizon. They also do

not have a high shrink-swell potential; saturation within 100

cm of the soil surface for 1 month or more in normal years; or

horizons with significant accumulations of durinodes,

concretions, nodules, volcanic glass, pumice, cinders, or

pumicelike fragments. These soils occur in the southwestern

part of the United States as well as southern Argentina.

Aquic Natrargids.—These are the Natrargids that are

saturated within 100 cm of the soil surface for 1 month or more

in normal years but are dry for most of the year. These soils do

not have a lithic contact within 50 cm of the soil surface or a

high shrink-swell potential. They occur on stream terraces in

Nevada, Oregon, Colorado, Montana, Utah, and California.

Durinodic Natrargids.—These are the Natrargids that have

one or more horizons, at least 15 cm thick, that have 20

percent or more durinodes or are brittle and at least firm when

moist. These soils do not have a soil moisture regime that

borders on xeric and do not have a high shrink-swell potential.

They do not have a lithic contact within 50 cm of the soil

surface. These soils are not saturated for 1 month or more

within 100 cm of the soil surface in normal years. They occur

in Nevada and California. They are used primarily as

rangeland, but in some areas they are used for urban

development or irrigated cropland.

Durinodic Xeric Natrargids.—These are the Natrargids

that have one or more horizons, at least 15 cm thick, that have

20 percent or more durinodes or are brittle and at least firm

when moist. These soils have a soil moisture regime that

borders on xeric but do not have a high shrink-swell potential.

They do not have a lithic contact within 50 cm of the soil

surface. These soils are not saturated for 1 month or more

within 100 cm of the soil surface in normal years. They occur

in Nevada, Idaho, and California. They are used primarily as

rangeland, but in some areas they are used for urban

development or irrigated cropland.

Glossic Natrargids.—These are the Natrargids that have

skeletans covering 10 percent or more of the surfaces of peds at

a depth 2.5 cm or more below the upper boundary of the natric

horizon and have an exchangeable sodium percentage of 15 or

more in more than 50 percent of the natric horizon. These soils

do not have a soil moisture regime that borders on ustic or

xeric. They do not have a lithic contact within 50 cm of the soil

surface or a high shrink-swell potential. They are not saturated

for 1 month or more within 100 cm of the soil surface in

normal years. These soils do not have a significant amount of

volcanic glass, pumice, cinders, pumicelike fragments,

durinodes, nodules, or concretions.

Glossic Ustic Natrargids.—These are the Natrargids that

have skeletans covering 10 percent or more of the surfaces of

peds at a depth 2.5 cm or more below the upper boundary of

the natric horizon and have a soil moisture regime that borders

on ustic. These soils do not have a lithic contact within 50 cm

of the soil surface or a high shrink-swell potential. They are

not saturated for 1 month or more within 100 cm of the soil

surface in normal years. These soils do not have a significant

amount of durinodes, nodules, or concretions. They occur in

Montana. They are used as rangeland or irrigated cropland.

Haplic Natrargids.—These are the Natrargids that have an

exchangeable sodium percentage of less than 15 in 50 percent

or more of the natric horizon but do not have a soil moisture

regime that borders on ustic or xeric. These soils do not have a

lithic contact within 50 cm of the soil surface or a high shrinkswell potential. They are not saturated for 1 month or more

within 100 cm of the soil surface. These soils do not have a

significant amount of durinodes, nodules, or concretions. They

occur in Nevada, New Mexico, and Arizona. They are used

primarily as rangeland.

Haplic Ustic Natrargids.—These are the Natrargids that

have an exchangeable sodium percentage of less than 15 in 50
346 Soil Taxonomy

percent or more of the natric horizon and have a soil moisture

regime that borders on ustic. These soils do not have a lithic

contact within 50 cm of the soil surface, a high shrink-swell

potential, or skeletans covering 10 percent or more of the

surfaces of peds at a depth 2.5 cm or more below the upper

boundary of the natric horizon. Haplic Ustic Natrargids are not

saturated for 1 month or more within 100 cm of the soil

surface. These soils do not have a significant amount of

durinodes, nodules, or concretions. They occur in Wyoming

and the Four Corners area of northwestern New Mexico,

northeastern Arizona, southeastern Utah, and southwestern

Colorado. They are used primarily as rangeland.

Haploxeralfic Natrargids.—These are the Natrargids that

have an exchangeable sodium percentage of less than 15 in 50

percent or more of the natric horizon and have a soil moisture

regime that borders on xeric. These soils do not have a lithic

contact within 50 cm of the soil surface, a high shrink-swell

potential, or skeletans covering 10 percent or more of the

surfaces of peds at a depth 2.5 cm or more below the upper

boundary of the natric horizon. Haploxeralfic Natrargids are

not saturated for 1 month or more within 100 cm of the soil

surface. They do not have a significant amount of durinodes,

nodules, or concretions. They occur in California and possibly

in Nevada. They are used primarily as rangeland.

Lithic Natrargids.—These are the Natrargids that have a

lithic contact within 50 cm of the soil surface. These soils do

not have a soil moisture regime that borders on ustic or xeric.

They occur in the hot to cool deserts in the western part of the

United States and are used primarily as rangeland.

Lithic Ustic Natrargids.—These are the Natrargids that

have a lithic contact within 50 cm of the soil surface and have

a soil moisture regime that borders on ustic. These soils occur

in the deserts of the southwestern part of the United States and

are used primarily as rangeland.

Lithic Xeric Natrargids.—These are the Natrargids that

have a lithic contact within 50 cm of the soil surface and have

a soil moisture regime that borders on xeric. These soils occur

in Nevada, California, and Idaho and are used primarily as

rangeland.

Petronodic Natrargids.—These are the Natrargids that

have one or more horizons, 15 cm or more thick, that have 20

percent or more, by volume, nodules and concretions. These

soils do not have durinodes or brittleness and at least a firm

rupture-resistance class when moist. They do not have a lithic

contact within 50 cm of the surface or a high shrink-swell

potential. Petronodic Natrargids are not saturated for 1 month

or more within 100 cm of the soil surface in normal years.

These soils occur in Arizona and New Mexico and are used

primarily as rangeland.

Ustic Natrargids.—These are the Natrargids that have a

soil moisture regime that borders on ustic. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; skeletans covering 10 percent or more

of the surfaces of peds at a depth 2.5 cm or more below the

upper boundary of the natric horizon; an exchangeable sodium

percentage of 15 or more in more than 50 percent of the natric

horizon; or a significant amount of volcanic glass, pumice,

cinders, pumicelike fragments, durinodes, concretions, or

nodules. Ustic Natrargids are not saturated for 1 month or

more within 100 cm of the soil surface in normal years. These

soils occur in the southwestern part of the United States as well

as southern Argentina.

Vertic Natrargids.—These are the Natrargids that have a

high shrink-swell potential. These soils do not have a lithic

contact within 50 cm of the soil surface. Because of a high

percentage of clay and sodium, these soils are difficult to

reclaim and manage. Most of the soils are used as rangeland.

Vitrandic Natrargids.—These are the Natrargids that have

a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments in one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface.

These soils do not have a soil moisture regime that borders on

xeric; a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; an exchangeable sodium percentage of

15 or more in more than 50 percent of the natric horizon; or a

significant amount of durinodes, concretions, or nodules.

Vitrandic Natrargids are not saturated for 1 month or more

within 100 cm of the soil surface in normal years.

Vitrixerandic Natrargids.—These are the Natrargids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments in one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface

and have a soil moisture regime that borders on xeric. These

soils do not have a lithic contact within 50 cm of the soil

surface; a high shrink-swell potential; an exchangeable sodium

percentage of 15 or more in more than 50 percent of the natric

horizon; or a significant amount of durinodes, concretions, or

nodules. Vitrixerandic Natrargids are not saturated for 1 month

or more within 100 cm of the soil surface in normal years.

Xeric Natrargids.—These are the Natrargids that have a soil

moisture regime that borders on xeric. These soils do not have a

lithic contact within 50 cm of the soil surface; a high shrink-swell

potential; an exchangeable sodium percentage of 15 or more in

more than 50 percent of the natric horizon; or a significant

amount of volcanic glass, pumice, cinders, pumicelike fragments,

durinodes, concretions, or nodules. Xeric Natrargids are not

saturated for 1 month or more within 100 cm of the soil surface in

normal years. These soils occur in Nevada, Utah, and Idaho and

in southern Argentina.

Paleargids

These are the Argids that are on stable land surfaces and

have an abrupt textural change or a clay distribution that does

not decrease significantly. Most of these soils formed in

sediments appreciably older than the late-Pleistocene. If

calcareous dust is present, some of these soils may be

calcareous in all horizons. Slopes are normally gentle.
Aridisols 347

Definition

Paleargids are the Argids that:

1. Do not have a densic, lithic, or paralithic contact within 50

cm of the soil surface and that have either:

a. A clay increase of 15 percent or more (absolute) within

a vertical distance of 2.5 cm either within the argillic

horizon or at its upper boundary; or

b. An argillic horizon that extends to 150 cm or more

from the soil surface, that does not have a clay decrease with

increasing depth of 20 percent or more (relative) from the

maximum clay content and has, in 50 percent or more of the

matrix in some part between depths of 100 and 150 cm,

either:

(1) Hue of 7.5YR or redder and chroma of 5 or more;

or

(2) Hue of 7.5YR or redder and value, moist, of 3 or

less and value, dry, of 4 or less; and

2. Do not have a duripan or a petrocalcic or petrogypsic

horizon that has its upper boundary within 150 cm of the soil

surface; and

3. Do not have a natric horizon.

Key to Subgroups

GECA. Paleargids that have one or both of the following:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide through a thickness of 30 cm or more for some

time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower.

Vertic Paleargids

GECB. Other Paleargids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within 100

cm of the soil surface for 1 month or more in normal years.

Aquic Paleargids

GECC. Other Paleargids that have:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 cm or more; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Arenic Ustic Paleargids

GECD. Other Paleargids that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more.

Arenic Paleargids

GECE. Other Paleargids that have a calcic horizon that has

its upper boundary within 150 cm of the soil surface.

Calcic Paleargids

GECF. Other Paleargids that have:

1. One or more horizons, within 100 cm of the soil surface

and with a combined thickness of 15 cm or more, that

contain 20 percent or more (by volume) durinodes or are

brittle and have at least a firm rupture-resistance class when

moist; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Durinodic Xeric Paleargids

GECG. Other Paleargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes or are brittle and have at least a firm

rupture-resistance class when moist.

Durinodic Paleargids

GECH. Other Paleargids that:

1. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,

that contain 20 percent or more (by volume) nodules or

concretions; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and

have a soil moisture regime that borders on ustic.

Petronodic Ustic Paleargids

GECI. Other Paleargids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) nodules or concretions.

Petronodic Paleargids

GECJ. Other Paleargids that have both:
348 Soil Taxonomy

1. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm and a soil

moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Paleargids

GECK. Other Paleargids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Paleargids

GECL. Other Paleargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Paleargids

GECM. Other Paleargids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Paleargids

GECN. Other Paleargids.

Typic Paleargids

Definition of Typic Paleargids

Typic Paleargids are the Paleargids that:

1. Have both of the following:

a. No cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and no slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has

its upper boundary within 125 cm of the soil surface; and

b. A linear extensibility of less than 6.0 cm between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower;

2. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years;

3. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more;

4. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm;

5. Do not have a calcic horizon that has its upper boundary

within 150 cm of the soil surface;

6. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes,

nodules, or concretions or are brittle and have at least a firm

rupture-resistance class when moist;

7. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Paleargids.—The Typic subgroup is centered on the

concept of dry soils that do not have a soil moisture regime that

borders on ustic or xeric. These soils do not have a high

shrink-swell potential; saturation with water for 1 month or

more within 100 cm of the soil surface; a sandy or sandyskeletal particle-size class from the soil surface to a depth of 50

cm; a calcic horizon; or a significant amount of durinodes,

nodules, concretions, volcanic glass, pumice, cinders, or

pumicelike fragments. These soils are not the dominant

subgroup of Paleargids. They occur in the deserts of the

southwestern part of the United States and in southern

Argentina.
Aridisols 349

Aquic Paleargids.—These are the Paleargids that are

saturated for 1 month or more within 100 cm of the soil surface

in normal years. These soils do not have a high shrink-swell

potential. They commonly have some sodium associated with

them. They are rare in the world.

Arenic Paleargids.—These are the Paleargids that have a

sandy or sandy-skeletal particle-size class from the soil surface

to a depth of 50 cm or more. These soils do not have a soil

moisture regime that borders on ustic, do not have a high

shrink-swell potential, and are not saturated with water for 1

month or more within 100 cm of the soil surface in normal

years. They are rare in the world.

Arenic Ustic Paleargids.—These are the Paleargids that

have a sandy or sandy-skeletal particle-size class from the soil

surface to a depth of 50 cm or more and have a soil moisture

regime that borders on ustic. These soils do not have a high

shrink-swell potential and are not saturated with water for 1

month or more within 100 cm of the soil surface in normal

years. They are rare in the world.

Calcic Paleargids.—These are the Paleargids with a calcic

horizon that has its upper boundary within 150 cm of the soil

surface. These soils do not have a high shrink-swell potential,

a sandy or sandy-skeletal particle-size class from the soil

surface to a depth of 50 cm or more, or saturation with water

for 1 month or more within 100 cm of the soil surface in

normal years. These soils occur in Arizona, New Mexico, and

Texas.

Durinodic Paleargids.—These are the Paleargids that have

one or more horizons, with a combined thickness of 15 cm or

more, that contain 20 percent or more durinodes or are brittle

and have at least a firm rupture-resistance class. These soils do

not have a high shrink-swell potential, saturation with water

for 1 month or more within 100 cm of the soil surface in

normal years, a calcic horizon, a soil moisture regime that

borders on xeric, or a sandy or sandy-skeletal particle-size class

from the soil surface to a depth of 50 cm or more.

Durinodic Xeric Paleargids.—These are the Paleargids

that have one or more horizons, with a combined thickness of

15 cm or more, that contain 20 percent or more durinodes or

are brittle and have at least a firm rupture-resistance class.

These soils also have a soil moisture regime that borders on

xeric. They do not have a high shrink-swell potential,

saturation with water for 1 month or more within 100 cm of

the soil surface in normal years, a calcic horizon, or a sandy or

sandy-skeletal particle-size class from the soil surface to a

depth of 50 cm or more. These soils occur in Oregon.

Petronodic Paleargids.—These are the Paleargids that have

one or more horizons, with a combined thickness of 15 cm or

more, that contain 20 percent or more nodules or concretions

but do not have durinodes. These soils do not have a high

shrink-swell potential, a soil moisture regime that borders on

ustic, saturation with water for 1 month or more within 100 cm

of the soil surface in normal years, a calcic horizon, or a sandy

or sandy-skeletal particle-size class from the soil surface to a

depth of 50 cm or more. These soils occur in Arizona.

Petronodic Ustic Paleargids.—These are the Paleargids

that have, in one or more horizons with a combined thickness

of 15 cm or more, 20 percent or more nodules or concretions

and that have a soil moisture regime that borders on ustic.

These soils do not have a high shrink-swell potential,

saturation with water for 1 month or more within 100 cm of

the soil surface in normal years, a calcic horizon within 150

cm of the soil surface, or durinodes or brittleness within 100

cm of the soil surface. The soils occur mostly in Arizona and

New Mexico.

Ustic Paleargids.—These are the Paleargids that have a soil

moisture regime that borders on ustic. These soils do not have

a high shrink-swell potential; saturation with water for 1

month or more within 100 cm of the soil surface in normal

years; a calcic horizon; a sandy or sandy-skeletal particle-size

class from the soil surface to a depth of 50 cm or more; or a

significant amount of volcanic glass, pumice, cinders,

pumicelike fragments, durinodes, nodules, and concretions.

These soils occur in desert areas of the United States and

Argentina.

Vertic Paleargids.—These are the Paleargids that have a

high shrink-swell potential. They are known to occur in

California, Arizona, Nevada, Oregon, and Colorado.

Vitrandic Paleargids.—These are the Paleargids that have

a significant amount of volcanic glass, pumice, cinders, or

pumicelike fragments in one or more horizons with a total

thickness of 18 cm within 75 cm of the soil surface. These soils

do not have a soil moisture regime that borders on xeric; a high

shrink-swell potential; saturation with water for 1 month or

more within 100 cm of the soil surface in normal years; a

calcic horizon; a sandy or sandy-skeletal particle-size class

from the soil surface to a depth of 50 cm or more; or a

significant amount of durinodes, nodules, and concretions.

Vitrixerandic Paleargids.—These are the Paleargids that

have a significant amount of volcanic glass, pumice, cinders, or

pumicelike fragments in one or more horizons with a total

thickness of 18 cm within 75 cm of the soil surface and have a

soil moisture regime that borders on xeric. These soils do not

have a high shrink-swell potential; saturation with water for 1

month or more within 100 cm of the soil surface in normal

years; a calcic horizon; a sandy or sandy-skeletal particle-size

class from the soil surface to a depth of 50 cm or more; or a

significant amount of durinodes, nodules, and concretions.

Xeric Paleargids.—These are the Paleargids that have a

soil moisture regime that borders on xeric. These soils do not

have a high shrink-swell potential; saturation with water for 1

month or more within 100 cm of the soil surface in normal

years; a calcic horizon; a sandy or sandy-skeletal particle-size

class from the soil surface to a depth of 50 cm or more; or a

significant amount of volcanic glass, pumice, cinders,

pumicelike fragments, durinodes, nodules, and concretions.
350 Soil Taxonomy

These soils occur in desert areas of the United States and

Argentina.

Petroargids

These are the Argids that have a duripan or a petrocalcic or

petrogypsic horizon that has its upper boundary at a depth

between 100 and 150 cm from the soil surface. These soils

occur on stable landscapes in the western part of the United

States and in southern Argentina and western South Africa.

Definition

These are the Argids that have a duripan or a petrocalcic or

petrogypsic horizon that has its upper boundary within 150 cm

of the soil surface.

Key to Subgroups

GEAA. Petroargids that meet both of the following:

1. Have a petrogypsic horizon that has its upper boundary

within 150 cm of the soil surface; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and

have a soil moisture regime that borders on ustic.

Petrogypsic Ustic Petroargids

GEAB. Other Petroargids that have a petrogypsic horizon

that has its upper boundary within 150 cm of the soil surface.

Petrogypsic Petroargids

GEAC. Other Petroargids that have:

1. A duripan that has its upper boundary within 150 cm of

the soil surface; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Duric Xeric Petroargids

GEAD. Other Petroargids that have a duripan that has its

upper boundary within 150 cm of the soil surface.

Duric Petroargids

GEAE. Other Petroargids that have a natric horizon.

Natric Petroargids

GEAF. Other Petroargids that have a moisture control section

that is dry in all parts for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Petroargids

GEAG. Other Petroargids that have a moisture control section

that is dry in all parts for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Petroargids

GEAH. Other Petroargids.

Typic Petroargids

Definition of Typic Petroargids

Typic Petroargids are the Petroargids that:

1. Have a petrocalcic horizon that has its upper boundary

within 150 cm of the soil surface;

2. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 oC or higher at a depth of 50 cm;

3. Do not have a duripan or a petrogypsic horizon that has its

upper boundary within 150 cm of the soil surface;

4. Do not have a natric horizon.

Description of Subgroups

Typic Petroargids.—These are the Petroargids that have a

petrocalcic horizon that has its upper boundary within 150 cm

of the soil surface. These soils do not have a soil moisture

regime that borders on ustic or xeric. They occur in the

southwestern part of the United States and in South Africa and

Argentina.

Duric Petroargids.—These are the Petroargids that have a

duripan. These soils do not have a soil moisture regime that

borders on xeric. Many of the soils occur in areas that have a

volcanic influence. Duric Petroargids occur in Nevada, New

Mexico, and Arizona in the United States and in Australia and

South Africa.

Duric Xeric Petroargids.—These are the Petroargids that

have a duripan and a soil moisture regime that borders on

xeric. Many of these soils occur in areas that have a volcanic

influence. Duric Xeric Petroargids occur in Nevada and Idaho.

Natric Petroargids.—These are the Petroargids that have

natric and petrocalcic horizons. These soils occur in Argentina

and are used mostly for grazing by livestock.

Petrogypsic Petroargids.—These are the Petroargids that

have a petrogypsic horizon but do not have a soil moisture

regime that borders on ustic. These soils occur in very dry parts

of the world where the parent materials are rich in gypsum.

They are known to occur in New Mexico as well as Iran and

Iraq.

Petrogypsic Ustic Petroargids.—These are the Petroargids

that have a petrogypsic horizon and have a soil moisture

regime that borders on ustic. These soils are rare in the world.

Ustic Petroargids.—These are the Petroargids that have a

petrocalcic horizon and have a soil moisture regime that
Aridisols 351

borders on ustic. These soils occur in Arizona and New Mexico

as well as Argentina.

Xeric Petroargids.—These are the Petroargids that have a

petrocalcic horizon and have a soil moisture regime that borders

on xeric. They are known to occur in Idaho.

Calcids

Calcids are the Aridisols with calcium carbonate that was in

the parent materials or was added as dust, or both.

Precipitation is insufficient to leach or even move the

carbonates to great depths. The upper boundary of the calcic or

petrocalcic horizon is normally within 50 cm of the soil

surface. If the soils are irrigated and cultivated, micronutrient

deficiencies are normal. These soils are extensive in the

western part of the United States and in other arid regions of

the world.

Definition

Calcids are the Aridisols that:

1. Have a petrocalcic or calcic horizon that has its upper

boundary within 100 cm of the soil surface and do not have an

argillic or natric horizon with its upper boundary within 100

cm of the soil surface, unless a petrocalcic horizon is within

100 cm of the soil surface;

2. Have a temperature regime warmer than cryic;

3. Do not have a duripan or a salic, gypsic, or petrogypsic

horizon that has its upper boundary within 100 cm of the soil

surface.

Key to Great Groups

GFA. Calcids that have a petrocalcic horizon that has its

upper boundary within 100 cm of the soil surface.

Petrocalcids, p. 355

GFB. Other Calcids.

Haplocalcids, p. 351

Haplocalcids

Haplocalcids are the Calcids that have a calcic horizon with

its upper boundary within 100 cm of the soil surface. These

soils do not have a duripan or an argillic, natric, or petrocalcic

horizon within 100 cm of the soil surface. Some of the soils

have a cambic horizon above the calcic horizon. Haplocalcids

are extensive.

Definition

Haplocalcids are the Calcids that:

1. Have a calcic horizon that has its upper boundary within 100

cm of the soil surface;

2. Do not have a petrocalcic horizon that has its upper

boundary within 100 cm of the soil surface.

Key to Subgroups

GFBA. Haplocalcids that have:

1. A lithic contact within 50 cm of the soil surface; and

2. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 oC or higher at a depth of 50 cm and a soil

moisture regime that borders on xeric.

Lithic Xeric Haplocalcids

GFBB. Other Haplocalcids that have:

1. A lithic contact within 50 cm of the soil surface; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Lithic Ustic Haplocalcids

GFBC. Other Haplocalcids that have a lithic contact within

50 cm of the soil surface.

Lithic Haplocalcids

GFBD. Other Haplocalcids that have:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide through a thickness of 30 cm or more for some

time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower.

Vertic Haplocalcids

GFBE. Other Haplocalcids that:

1. Are either:

a. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the

soil surface; or

b. Saturated with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years; and

2. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,
352 Soil Taxonomy

that contain 20 percent or more (by volume) durinodes or are

brittle and have at least a firm rupture-resistance class when

moist.

Aquic Durinodic Haplocalcids

GFBF. Other Haplocalcids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within 100

cm of the soil surface for 1 month or more in normal years.

Aquic Haplocalcids

GFBG. Other Haplocalcids that have:

1. A duripan that has its upper boundary within 150 cm of

the surface; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Duric Xeric Haplocalcids

GFBH. Other Haplocalcids that have a duripan that has its

upper boundary within 150 cm of the surface.

Duric Haplocalcids

GFBI. Other Haplocalcids that have:

1. One or more horizons, within 100 cm of the soil surface

and with a combined thickness of 15 cm or more, that

contain 20 percent or more (by volume) durinodes or are

brittle and have at least a firm rupture-resistance class when

moist; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Durinodic Xeric Haplocalcids

GFBJ. Other Haplocalcids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes or are brittle and have at least a firm

rupture-resistance class when moist.

Durinodic Haplocalcids

GFBK. Other Haplocalcids that have:

1. One or more horizons, within 100 cm of the soil surface

and with a combined thickness of 15 cm or more, that

contain 20 percent or more (by volume) nodules or

concretions; and

2. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 oC or higher at a depth of 50 cm and a soil

moisture regime that borders on xeric.

Petronodic Xeric Haplocalcids

GFBL. Other Haplocalids that:

1. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,

that contain 20 percent or more (by volume) nodules or

concretions; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 oC or higher and

have a soil moisture regime that borders on ustic.

Petronodic Ustic Haplocalcids

GFBM. Other Haplocalcids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) nodules or concretions.

Petronodic Haplocalcids

GFBN. Other Haplocalcids that have both:

1. A horizon at least 25 cm thick within 100 cm of the soil

surface that has an exchangeable sodium percentage of 15

or more (or an SAR of 13 or more) during at least 1 month

in normal years; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and a

soil moisture regime that borders on xeric.

Sodic Xeric Haplocalcids

GFBO. Other Haplocalcids that meet both of the following:

1. Have, in a horizon at least 25 cm thick within 100 cm

of the soil surface, an exchangeable sodium percentage of 15

or more (or an SAR of 13 or more) during at least 1 month

in normal years; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and

have a soil moisture regime that borders on ustic.

Sodic Ustic Haplocalcids

GFBP. Other Haplocalcids that have, in a horizon at least 25

cm thick within 100 cm of the mineral soil surface, an

exchangeable sodium percentage of 15 or more (or an SAR of

13 or more) during at least 1 month in normal years.

Sodic Haplocalcids
Aridisols 353

GFBQ. Other Haplocalcids that have both:

1. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm and a soil

moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplocalcids

GFBR. Other Haplocalcids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Haplocalcids

GFBS. Other Haplocalcids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Haplocalcids

GFBT. Other Haplocalcids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Haplocalcids

GFBU. Other Haplocalcids.

Typic Haplocalcids

Definition of Typic Haplocalcids

Typic Haplocalcids are the Haplocalcids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Are dry in all parts of the moisture control section for threefourths or more of the time (cumulative) when the soil

temperature is 5 oC or higher at a depth of 50 cm;

3. Have both of the following:

a. No cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and no slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has

its upper boundary within 125 cm of the soil surface; and

b. A linear extensibility of less than 6.0 cm between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower;

4. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years;

5. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes,

nodules, or concretions or are brittle and have at least a firm

rupture-resistance class when moist;

6. Do not have, in one or more horizons within 100 cm of the

mineral soil surface, an exchangeable sodium percentage of 15

or more (or an SAR of 13 or more) for 1 month or more in

normal years;

7. Do not have a duripan that has its upper boundary within

150 cm of the surface;

8. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Haplocalcids.—The Typic subgroup is centered on dry

soils that lack the features that define the other subgroups.

These soils do not have a lithic contact with its upper boundary

within 50 cm of the soil surface; a high shrink-swell potential;

saturation with water for 1 month or more within 100 cm of
354 Soil Taxonomy

the soil surface; a duripan within 150 cm of the soil surface; a

significant amount of durinodes or brittleness, nodules,

concretions, volcanic glass, pumice, cinders, or pumicelike

fragments; an accumulation of sodium; or a soil moisture regime

that borders on xeric or ustic. These soils are common in the

desert areas of the world.

Aquic Durinodic Haplocalcids.—These are the

Haplocalcids that are saturated with water for 1 month or more

within 100 cm of the soil surface in normal years and have a

significant amount of durinodes or brittleness. These soils do

not have a lithic contact within 50 cm of the soil surface or a

high shrink-swell potential. They are known to occur in

California and Nevada.

Aquic Haplocalcids.—These are the Haplocalcids that are

saturated with water for 1 month or more within 100 cm of the

soil surface in normal years. These soils do not have a lithic

contact within 50 cm of the soil surface, a high shrink-swell

potential, or a significant amount of durinodes or brittleness.

These soils occur in California, Nevada, Idaho, and Utah.

Duric Haplocalcids.—These are the Haplocalcids that have

a duripan with an upper boundary between depths of 100 and

150 cm but do not have a soil moisture regime that borders on

xeric. These soils do not have a lithic contact within 50 cm of

the soil surface or a high shrink-swell potential. They are not

saturated with water for 1 month or more within 100 cm of the

soil surface in normal years and do not have a significant

amount of durinodes or brittleness. These soils are rare in the

world.

Duric Xeric Haplocalcids.—These are the Haplocalcids

that have a duripan at a depth of 100 to 150 cm and have a soil

moisture regime that borders on xeric. These soils do not have

a lithic contact within 50 cm of the soil surface or a high

shrink-swell potential. Duric Haplocalcids are not saturated

with water for 1 month or more within 100 cm of the soil

surface in normal years and do not have a significant amount

of durinodes or brittleness. These soils are rare in the world.

Durinodic Haplocalcids.—These are the Haplocalcids that

have one or more horizons, within 100 cm of the soil surface

and with a combined thickness of 15 cm or more, that contain

20 percent or more durinodes or are brittle and have at least a

firm rupture-resistance class when moist. These soils do not

have a soil moisture regime that borders on xeric, a duripan

within 150 cm of the soil surface, a lithic contact within 50 cm

of the soil surface, or a high shrink-swell potential. They are

not saturated with water for 1 month or more within 100 cm of

the soil surface. They occur in Nevada, California, and

Arizona.

Durinodic Xeric Haplocalcids.—These are the

Haplocalcids that have one or more horizons, within 100 cm of

the soil surface and with a combined thickness of 15 cm or

more, that contain 20 percent or more durinodes or are brittle

and have at least a firm rupture-resistance class when moist.

These soils have a soil moisture regime that borders on xeric.

They do not have a duripan within 150 cm of the soil surface, a

lithic contact within 50 cm of the soil surface, a high shrink-swell

potential, or saturation with water for 1 month or more within 100

cm of the soil surface. They occur in Nevada, California, Idaho,

and Utah.

Lithic Haplocalcids.—These are the Haplocalcids that have

a lithic contact within 50 cm of the soil surface but do not have

a soil moisture regime that borders on either xeric or ustic.

These soils occur throughout the deserts of the world.

Lithic Ustic Haplocalcids.—These are the Haplocalcids

that have a lithic contact within 50 cm of the soil surface and a

soil moisture regime that borders on ustic. These soils are

common in the semiarid regions of the world. In the United

States, they occur in Texas, Utah, and Arizona.

Lithic Xeric Haplocalcids.—These are the Haplocalcids

that have a lithic contact within 50 cm of the soil surface and a

soil moisture regime that borders on xeric. In the United

States, these soils occur in Nevada, Utah, and Idaho.

Petronodic Haplocalcids.—These are the Haplocalcids that

have, in one or more horizons with a combined thickness of 15

cm or more, 20 percent or more nodules and concretions but do

not have a soil moisture regime that borders on ustic or xeric.

These soils do not have a lithic contact within 50 cm of the soil

surface, a high shrink-swell potential, saturation with water for

1 month or more within 100 cm of the soil surface, a duripan

within 150 cm of the soil surface, or durinodes or brittleness.

These soils occur in California, Arizona, Nevada, New Mexico,

and Idaho.

Petronodic Ustic Haplocalcids.—These are the

Haplocalcids that have, in one or more horizons with a

combined thickness of 15 cm or more, 20 percent or more

nodules and concretions and that have a soil moisture regime

that borders on ustic. These soils do not have a lithic contact

within 50 cm of the soil surface, a high shrink-swell potential,

saturation with water for 1 month or more within 100 cm of

the soil surface, a duripan within 150 cm of the soil surface, or

durinodes or brittleness. The soils occur in Arizona, New

Mexico, and Texas.

Petronodic Xeric Haplocalcids.—These are the

Haplocalcids that have, in one or more horizons with a

combined thickness of 15 cm or more, 20 percent or more

nodules and concretions and have a soil moisture regime that

borders on xeric. These soils do not have a lithic contact within

50 cm of the soil surface, a high shrink-swell potential,

saturation with water for 1 month or more within 100 cm of

the soil surface, a duripan within 150 cm of the soil surface, or

durinodes or brittleness. The soils occur in Nevada, Oregon,

and Idaho.

Sodic Haplocalcids.—These are the Haplocalcids that have,

in a horizon at least 25 cm thick within 100 cm of the soil

surface, an exchangeable sodium percentage of 15 or more

during at least 1 month in normal years and have a soil

moisture regime that does not border on either ustic or xeric.

These soils do not have a lithic contact within 50 cm of the soil

surface; a high shrink-swell potential; saturation with water for
Aridisols 355

1 month or more within 100 cm of the soil surface; a duripan

within 150 cm of the soil surface; or a significant amount of

durinodes, nodules, concretions, or brittleness. These soils

occur in California, Nevada, and Texas.

Sodic Ustic Haplocalcids.—These are the Haplocalcids that

have, in a horizon at least 25 cm thick within 100 cm of the

soil surface, an exchangeable sodium percentage of 15 or more

during at least 1 month in normal years and have a soil

moisture regime that borders on ustic. These soils do not have

a lithic contact within 50 cm of the soil surface; a high shrinkswell potential; saturation with water for 1 month or more

within 100 cm of the soil surface; a duripan within 150 cm of

the soil surface; or a significant amount of durinodes, nodules,

concretions, or brittleness. These soils occur in Utah.

Sodic Xeric Haplocalcids.—These are the Haplocalcids

that have, in a horizon at least 25 cm thick within 100 cm of

the soil surface, an exchangeable sodium percentage of 15 or

more during at least 1 month in normal years and have a soil

moisture regime that borders on xeric. These soils do not have

a lithic contact within 50 cm of the soil surface; a high shrinkswell potential; saturation with water for 1 month or more

within 100 cm of the soil surface; a duripan within 150 cm of

the soil surface; or a significant amount of durinodes, nodules,

concretions, or brittleness. These soils are known to occur in

Idaho, Oregon, and Utah.

Ustic Haplocalcids.—These are the Haplocalcids that have

a soil moisture regime that borders on ustic. These soils do not

have, in a horizon at least 25 cm thick within 100 cm of the

soil surface, an exchangeable sodium percentage of 15 or more

during at least 1 month in normal years and do not have a

lithic contact within 50 cm of the soil surface; a high shrinkswell potential; saturation with water for 1 month or more

within 100 cm of the soil surface; a duripan within 150 cm of

the soil surface; or a significant amount of volcanic glass,

pumice, cinders, pumicelike fragments, durinodes, nodules,

concretions, or brittleness. These soils are common in the

semiarid deserts of the world.

Vertic Haplocalcids.—These are the Haplocalcids that have

a high shrink-swell potential. These soils do not have a lithic

contact within 50 cm of the soil surface. They are relatively

rare in the world.

Vitrandic Haplocalcids.—These are the Haplocalcids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments throughout one or more horizons with a

total thickness of 18 cm or more within 75 cm of the soil

surface and have a soil moisture regime that does not border on

xeric. These soils do not have, in a horizon at least 25 cm thick

within 100 cm of the soil surface, an exchangeable sodium

percentage of 15 or more during at least 1 month in normal

years and do not have a lithic contact within 50 cm of the soil

surface; a high shrink-swell potential; saturation with water for

1 month or more within 100 cm of the soil surface; a duripan

within 150 cm of the soil surface; or a significant amount of

durinodes, nodules, concretions, or brittleness. These soils are

not common in the world but occur in areas that have a volcanic

influence.

Vitrixerandic Haplocalcids.—These are the Haplocalcids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface and have a soil moisture regime that borders

on xeric. These soils do not have, in a horizon at least 25 cm

thick within 100 cm of the soil surface, an exchangeable

sodium percentage of 15 or more during at least 1 month in

normal years and do not have a lithic contact within 50 cm of

the soil surface; a high shrink-swell potential; saturation with

water for 1 month or more within 100 cm of the soil surface; a

duripan within 150 cm of the soil surface; or a significant

amount of durinodes, nodules, concretions, or brittleness.

These soils are not common in the world but occur in areas

that have a volcanic influence.

Xeric Haplocalcids.—These are the Haplocalcids that have a

soil moisture regime that borders on xeric. These soils do not

have, in a horizon at least 25 cm thick within 100 cm of the

soil surface, an exchangeable sodium percentage of 15 or more

during at least 1 month in normal years and do not have a

lithic contact within 50 cm of the soil surface; a high shrinkswell potential; saturation with water for 1 month or more

within 100 cm of the soil surface; a duripan within 150 cm of

the soil surface; or a significant amount of volcanic glass,

pumice, cinders, pumicelike fragments, durinodes, nodules,

concretions, or brittleness. These soils are common in the

semiarid deserts of the world where summers are dry and

winters are moist.

Petrocalcids

Petrocalcids are the Calcids that have a petrocalcic horizon

that has its upper boundary within 100 cm of the soil surface.

Normally, the upper boundary of the petrocalcic horizon is

close to the soil surface. Some of these soils show evidence of

former argillic horizons that are now engulfed with carbonates.

Generally, Petrocalcids are on gentle slopes that have been

stable for long periods. They occur on old landscapes in the

southwestern part of the United States and in other deserts of

the world.

Definition

Petrocalcids are the Calcids that have a petrocalcic

horizon that has its upper boundary within 100 cm of the

soil surface.

Key to Subgroups

GFAA. Petrocalcids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or
356 Soil Taxonomy

2. Saturated with water in one or more layers within 100 cm

of the soil surface for 1 month or more in normal years.

Aquic Petrocalcids

GFAB. Other Petrocalcids that have a natric horizon.

Natric Petrocalcids

GFAC. Other Petrocalcids that have both of the following:

1. An argillic horizon that has its upper boundary within

100 cm of the soil surface; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Xeralfic Petrocalcids

GFAD. Other Petrocalcids that have both of the following:

1. An argillic horizon that has its upper boundary within

100 cm of the soil surface; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Ustalfic Petrocalcids

GFAE. Other Petrocalcids that have an argillic horizon that

has its upper boundary within 100 cm of the soil surface.

Argic Petrocalcids

GFAF. Other Petrocalcids that have:

1. A calcic horizon overlying the petrocalcic horizon; and

2. A lithic contact within 50 cm of the soil surface.

Calcic Lithic Petrocalcids

GFAG. Other Petrocalcids that have a calcic horizon

overlying the petrocalcic horizon.

Calcic Petrocalcids

GFAH. Other Petrocalcids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 o

C or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Petrocalcids

GFAI. Other Petrocalcids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Petrocalcids

GFAJ. Other Petrocalcids.

Typic Petrocalcids

Definition of Typic Petrocalcids

Typic Petrocalcids are the Petrocalcids that:

1. Are not both irrigated and characterized by aquic conditions

for some time in normal years in one or more layers within 100 cm

of the soil surface and are not saturated with water in one or

more layers within 100 cm of the soil surface for 1 month or more

in normal years;

2. Do not have a natric horizon;

3. Do not have an argillic horizon that has its upper boundary

within 100 cm of the soil surface;

4. Do not have a calcic horizon overlying the petrocalcic

horizon;

5. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 oC or higher at a depth of 50 cm.

Description of Subgroups

Typic Petrocalcids.—The Typic subgroup is centered on

dry soils that do not have any of the features associated with

the other subgroups. These soils do not have a natric, argillic,

or calcic horizon. They also do not have a soil moisture regime

that borders on xeric or ustic. They are saturated with water for

1 month or more in one or more layers within 100 cm of the

soil surface. These soils are widespread in the desert areas of

the world.

Aquic Petrocalcids.—These are the Petrocalcids that are

saturated with water for 1 month or more within 100 cm of the

soil surface in normal years. These soils can have other

diagnostic horizons. They are saturated for short periods and

dry for most of the year. They are rare but occur in Nevada.

Argic Petrocalcids.—These are the Petrocalcids that have

an argillic horizon and have a soil moisture regime that does

not border on ustic or xeric. These soils do not have a natric

horizon. They occur in the desert areas of several States in the

western part of the United States.

Calcic Lithic Petrocalcids.—These are the Petrocalcids

that have a calcic horizon, do not have an argillic or natric

horizon, and have a lithic contact within 50 cm of the soil

surface. These soils are not saturated for 1 month or more

within 100 cm of the soil surface in normal years. They occur

in Arizona, New Mexico, Texas, and other Western States.

Most of these soils are used as rangeland.

Calcic Petrocalcids.—These are the Petrocalcids that have

a calcic horizon but do not have an argillic or natric horizon.

These soils are not saturated for 1 month or more within 100

cm of the soil surface in normal years. They occur in Arizona,

California, Nevada, New Mexico, Texas, and Utah.

Natric Petrocalcids.—These are the Petrocalcids that have
Aridisols 357

a natric horizon. These soils are not saturated for 1 month or

more within 100 cm of the soil surface in normal years. They are

rare in the world.

Ustalfic Petrocalcids.—These are the Petrocalcids that have

an argillic horizon and have a soil moisture regime that borders

on ustic. These soils do not have a natric horizon and are not

saturated for 1 month or more within 100 cm of the soil surface

during the growing season. They occur in Nevada, New Mexico,

Arizona, and Utah.

Ustic Petrocalcids.—These are the Petrocalcids that have a

soil moisture regime that borders on ustic. These soils do not

have an argillic, calcic, or natric horizon. They are not

saturated for 1 month or more in normal years. These soils

occur in Arizona, Utah, and New Mexico and in other semiarid

areas of the world.

Xeralfic Petrocalcids.—These are the Petrocalcids that

have an argillic horizon and have a soil moisture regime that

borders on xeric. The soils do not have a natric horizon and are

not saturated with water for 1 month or more within 100 cm of

the soil surface. They are moist in winter and dry in summer.

Xeric Petrocalcids.—These are the Petrocalcids that have a

soil moisture regime that borders on xeric. These soils do not

have an argillic, calcic, or natric horizon. They are not

saturated for 1 month or more in normal years. These soils

occur in California, Utah, and Nevada.

Cambids

These are the Aridisols with the least degree of soil

development. These soils have a cambic horizon within 100 cm

of the soil surface. They may have other diagnostic horizons,

such as a petrocalcic, gypsic, or calcic horizon, but the upper

boundary of these horizons must be below 100 cm of the soil

surface. These soils are the most common Aridisols in the

United States.

Definition

Cambids are the Aridisols that:

1. Have a cambic horizon that has its upper boundary within

100 cm of the soil surface;

2. Have a soil temperature regime warmer than cryic;

3. Do not have a duripan or an argillic, calcic, natric,

petrocalcic, gypsic, petrogypsic, or salic horizon that has its

upper boundary within 100 cm of the soil surface.

Key to Great Groups

GGA. Cambids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within 100 cm

of the soil surface for 1 month or more in normal years.

Aquicambids, p. 357

GGB. Other Cambids that have a duripan or a petrocalcic or

petrogypsic horizon that has its upper boundary within 150 cm

of the soil surface.

Petrocambids, p. 364

GGC. Other Cambids that have an anthropic epipedon.

Anthracambids, p. 357

GGD. Other Cambids.

Haplocambids, p. 359

Anthracambids

These are the Cambids that have an anthropic epipedon.

These soils generally have been irrigated for many centuries.

They are not known to occur in large areas of the United

States. The great group is provided for use elsewhere.

Definition

Anthracambids are the Cambids that:

1. Have an anthropic epipedon.

2. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years.

3. Do not have a duripan or a petrocalcic or petrogypsic

horizon that has its upper boundary within 150 cm of the soil

surface.

Key to Subgroups

GGCA. All Anthracambids.

Typic Anthracambids

Definition of Typic Anthracambids

All Anthracambids are considered Typic.

Description of Subgroups

Typic Anthracambids.—All Anthracambids are considered

Typic. Few data are available for these soils. No soil series have

been established for these taxa in the United States. These soils

occur in small areas adjacent to Native American ruins.

Aquicambids

These are the Cambids that are saturated with water for

short periods in normal years. These soils commonly are

adjacent to playas and have accumulations of salts.
358 Soil Taxonomy

Aquicambids commonly have high pH values, which inhibit the

formation of redoximorphic features.

Definition

Aquicambids are the Cambids that are either irrigated and

have redoximorphic features in one or more layers within 100

cm of the soil surface or are saturated with water in one or

more layers within 100 cm of the soil surface for 1 month or

more in normal years.

Key to Subgroups

GGAA. Aquicambids that have, in a horizon at least 25 cm

thick within 100 cm of the soil surface, an exchangeable

sodium percentage of 15 or more (or an SAR of 13 or more)

during at least 1 month in normal years.

Sodic Aquicambids

GGAB. Other Aquicambids that:

1. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,

that contain 20 percent or more (by volume) durinodes r are

brittle and have at least a firm rupture-resistance class when

moist; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and

have a soil moisture regime that borders on xeric.

Durinodic Xeric Aquicambids

GGAC. Other Aquicambids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes or are brittle and have at least a firm

rupture-resistance class when moist.

Durinodic Aquicambids

GGAD. Other Aquicambids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) nodules or concretions.

Petronodic Aquicambids

GGAE. Other Aquicambids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Aquicambids

GGAF. Other Aquicambids that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Aquicambids

GGAG. Other Aquicambids that have an irregular decrease in

content of organic carbon from a depth of 25 cm either to a

depth of 125 cm or to a densic, lithic, or paralithic contact if

shallower.

Fluventic Aquicambids

GGAH. Other Aquicambids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Aquicambids

GGAI. Other Aquicambids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Aquicambids

GGAJ. Other Aquicambids.

Typic Aquicambids

Definition of Typic Aquicambids

Typic Aquicambids are the Aquicambids that:

1. Do not have, in a horizon at least 25 cm thick within 100

cm of the soil surface, an exchangeable sodium percentage of

15 or more (or an SAR of 13 or more) during at least 1 month

in normal years;
Aridisols 359

2. Do not have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of more than 15 cm, that

contain 20 percent or more (by volume) durinodes, nodules, or

concretions or are brittle and have at least a firm ruptureresistance class when moist;

3. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more;

5. Have a regular decrease in content of organic carbon from

a depth of 25 cm either to a depth of 125 cm or to a densic,

lithic, or paralithic contact if shallower.

Description of Subgroups

Typic Aquicambids.—The Typic subgroup is centered on

Aquicambids that do not have any of the features defined for

the other subgroups. These soils do not have an accumulation

of sodium; durinodes or brittleness; a significant amount of

nodules, concretions, volcanic glass, pumice, cinders, or

pumicelike fragments; an irregular decrease in content of

organic carbon below the cambic horizon; or a soil moisture

regime that borders on ustic or xeric.

Durinodic Aquicambids.—These are the Aquicambids that

have one or more horizons, within 100 cm of the soil surface

and with a cumulative thickness of 15 cm or more, that contain

20 percent or more durinodes or are brittle and have at least a

firm rupture-resistance class. These soils do not have, in a

horizon at least 25 cm thick, an exchangeable sodium

percentage of 15 or more. The soil moisture regime does not

border on xeric.

Durinodic Xeric Aquicambids.—These are the

Aquicambids that have a soil moisture regime that borders on

xeric and have one or more horizons, within 100 cm of the soil

surface and with a cumulative thickness of 15 cm or more, that

contain 20 percent or more durinodes or are brittle and have at

least a firm rupture-resistance class. These soils do not have, in

a horizon at least 25 cm thick, an exchangeable sodium

percentage of 15 or more.

Fluventic Aquicambids.—These are the Aquicambids that

have an irregular decrease in content of organic carbon below

the cambic horizon. These soils do not have a significant

amount of sodium, durinodes, nodules, concretions, volcanic

glass, pumice, cinders, or pumicelike fragments and are not

brittle.

Petronodic Aquicambids.—These are the Aquicambids

that have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more, that

contain 20 percent or more nodules and concretions. These soils

do not have a significant amount of sodium, durinodes, or

brittleness.

Sodic Aquicambids.—These are the Aquicambids that have,

in one or more horizons at least 25 cm thick within 100 cm of the

soil surface, an exchangeable sodium percentage of 15 or more

for at least 1 month in normal years. These soils occur in New

Mexico.

Ustic Aquicambids.—These are the Aquicambids that have

a soil moisture regime that borders on ustic. These soils do not

have a significant amount of sodium, durinodes, nodules,

concretions, volcanic glass, pumice, cinders, or pumicelike

fragments and are not brittle. They also do not have an

irregular decrease in content of organic carbon below the

cambic horizon.

Vitrandic Aquicambids.—These are the Aquicambids that

have a significant amount of volcanic glass, pumice, cinders, or

pumicelike fragments in one or more horizons 18 cm thick

within 75 cm of the soil surface but do not have a soil moisture

regime that borders on xeric. These soils do not have a

significant amount of sodium, durinodes, concretions, or

nodules and are not brittle.

Vitrixerandic Aquicambids.—These are the Aquicambids

that have a significant amount of volcanic glass, pumice,

cinders, or pumicelike fragments in one or more horizons 18

cm thick within 75 cm of the soil surface and have a soil

moisture regime that borders on xeric. These soils do not have

a significant amount of sodium, durinodes, concretions, or

nodules and are not brittle.

Xeric Aquicambids.—These are the Aquicambids that have a

soil moisture regime that borders on xeric. These soils do not

have a significant amount of sodium, durinodes, nodules,

concretions, volcanic glass, pumice, cinders, or pumicelike

fragments and are not brittle. They also do not have an

irregular decrease in content of organic carbon below the

cambic horizon.

Haplocambids

Haplocambids are the most commonly occurring of the

Cambids. These soils are characterized by minimal horizon

expression. Most Haplocambids have a redistribution of

carbonates below the cambic horizon. The amount of

carbonates, however, is insufficient to meet the definition of a

calcic horizon, or the upper boundary is more than 100 cm

below the soil surface. These soils occur on a variety of

landscapes, commonly on those that are younger than latePleistocene in age.
360 Soil Taxonomy

Definition

Haplocambids are the Cambids that:

1. Are not both irrigated and characterized by aquic conditions

for some time in normal years in one or more layers within 100 cm

of the soil surface and are not saturated with water in one or

more layers within 100 cm of the soil surface for 1 month or more

in normal years;

2. Do not have a duripan or a petrocalcic or petrogypsic

horizon that has its upper boundary within 150 cm of the soil

surface;

3. Do not have an anthropic epipedon.

Key to Subgroups

GGDA. Haplocambids that have:

1. A lithic contact within 50 cm of the soil surface;

and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Lithic Xeric Haplocambids

GGDB. Other Haplocambids that have:

1. A lithic contact within 50 cm of the soil surface; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Lithic Ustic Haplocambids

GGDC. Other Haplocambids that have a lithic contact within

50 cm of the soil surface.

Lithic Haplocambids

GGDD. Other Haplocambids that have:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact if shallower; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the soil

temperature is 5 oC or higher at a depth of 50 cm and a soil

moisture regime that borders on xeric.

Xerertic Haplocambids

GGDE. Other Haplocambids that have:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact if shallower; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on ustic.

Ustertic Haplocambids

GGDF. Other Haplocambids that have at least one of the

following:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide through a thickness of 30 cm or more for some

time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower.

Vertic Haplocambids

GGDG. Other Haplocambids that have both of the following:

1. One or more horizons, within 100 cm of the soil surface

and with a combined thickness of 15 cm or more, that

contain 20 percent or more (by volume) durinodes or are

brittle and have at least a firm rupture-resistance class when

moist; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and a

soil moisture regime that borders on xeric.

Durinodic Xeric Haplocambids

GGDH. Other Haplocambids that have one or more horizons,

within 100 cm of the soil surface and with a combined
Aridisols 361

thickness of 15 cm or more, that contain 20 percent or more (by

volume) durinodes or are brittle and have at least a firm ruptureresistance class when moist.

Durinodic Haplocambids

GGDI. Other Haplocambids that have:

1. One or more horizons, within 100 cm of the soil surface

and with a combined thickness of 15 cm or more, that

contain 20 percent or more (by volume) nodules or

concretions; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and a

soil moisture regime that borders on xeric.

Petronodic Xeric Haplocambids

GGDJ. Other Haplocambids that:

1. Have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more,

that contain 20 percent or more (by volume) nodules or

concretions; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 oC or higher and

have a soil moisture regime that borders on ustic.

Petronodic Ustic Haplocambids

GGDK. Other Haplocambids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) nodules or concretions.

Petronodic Haplocambids

GGDL. Other Haplocambids that have both:

1. A horizon at least 25 cm thick within 100 cm of the soil

surface that has an exchangeable sodium percentage of 15

or more (or an SAR of 13 or more) during at least 1 month

in normal years; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and a

soil moisture regime that borders on xeric.

Sodic Xeric Haplocambids

GGDM. Other Haplocambids that meet both of the following:

1. Have, in a horizon at least 25 cm thick within 100 cm

of the soil surface, an exchangeable sodium percentage of 15

or more (or an SAR of 13 or more) during at least 1 month

in normal years; and

2. Are dry in all parts of the moisture control section

for less than three-fourths of the time (cumulative) when

the soil temperature at a depth of 50 cm is 5 oC or higher

and have a soil moisture regime that borders on ustic.

Sodic Ustic Haplocambids

GGDN. Other Haplocambids that have, in a horizon at least 25

cm thick within 100 cm of the soil surface, an exchangeable

sodium percentage of 15 or more (or an SAR of 13 or more)

during at least 1 month in normal years.

Sodic Haplocambids

GGDO. Other Haplocambids that have both:

1. A moisture control section that is dry in all parts

for less than three-fourths of the time (cumulative) when

the soil temperature is 5 oC or higher at a depth of 50

cm and a soil moisture regime that borders on xeric;

and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplocambids

GGDP. Other Haplocambids that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Haplocambids

GGDQ. Other Haplocambids that:

1. Are dry in all parts of the moisture control section

for less than three-fourths of the time (cumulative) when

the soil temperature at a depth of 50 cm is 5 oC or higher

and have a soil moisture regime that borders on xeric;

and

2. Have an irregular decrease in content of organic carbon
362 Soil Taxonomy

from a depth of 25 cm either to a depth of 125 cm or to a

densic, lithic, or paralithic contact if shallower.

Xerofluventic Haplocambids

GGDR. Other Haplocambids that:

1. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature at a depth of 50 cm is 5 o

C or higher and

have a soil moisture regime that borders on ustic; and

2. Have an irregular decrease in content of organic carbon

from a depth of 25 cm either to a depth of 125 cm or to a

densic, lithic, or paralithic contact if shallower.

Ustifluventic Haplocambids

GGDS. Other Haplocambids that have an irregular decrease

in content of organic carbon from a depth of 25 cm either to a

depth of 125 cm or to a densic, lithic, or paralithic contact if

shallower.

Fluventic Haplocambids

GGDT. Other Haplocambids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

xeric.

Xeric Haplocambids

GGDU. Other Haplocambids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

ustic.

Ustic Haplocambids

GGDV. Other Haplocambids.

Typic Haplocambids

Definition of Typic Haplocambids

Typic Haplocambids are the Haplocambids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes,

nodules, or concretions or are brittle and have at least a firm

rupture-resistance class when moist;

3. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm;

4. Have either:

a. No cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and no slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has

its upper boundary within 125 cm of the soil surface; or

b. A linear extensibility of less than 6.0 cm between the soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact, whichever is shallower;

5. Do not have, in a horizon at least 25 cm thick within 100 cm

of the soil surface, an exchangeable sodium percentage of 15 or

more (or an SAR of 13 or more) during at least 1 month in normal

years;

6. Have a regular decrease in content of organic carbon from a

depth of 25 cm either to a depth of 125 cm or to a densic, lithic,

or paralithic contact if shallower;

7. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Haplocambids.—These are the Haplocambids that

do not have any of the features defined for the other subgroups.

These soils do not have any of the following: a lithic contact

within 50 cm of the soil surface; a high shrink-swell potential;

brittleness; a significant amount of sodium, durinodes, nodules,

concretions, volcanic glass, cinders, pumice, or pumicelike

fragments; a soil moisture regime that borders on ustic or

xeric; or an irregular decrease in content of organic carbon

below the cambic horizon.

Durinodic Haplocambids.—These are the Haplocambids

that have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more, that

contain 20 percent or more, by volume, durinodes or are brittle.

These soils do not have a soil moisture regime that borders on

xeric. They also do not have a lithic contact within 50 cm of

the soil surface or a high shrink-swell potential. They occur in

Nevada and California as well as other areas that have a source

of silica.

Durinodic Xeric Haplocambids.—These are the

Haplocambids that have one or more horizons, within 100 cm

of the soil surface and with a combined thickness of 15 cm or

more, that contain 20 percent or more, by volume, durinodes or

are brittle. These soils have a soil moisture regime that borders

on xeric. They do not have a lithic contact within 50 cm of the
Aridisols 363

soil surface or a high shrink-swell potential. They occur in

Nevada, Idaho, Oregon, and Washington as well as other areas

that have a source of silica.

Fluventic Haplocambids.—These are the Haplocambids

that have an irregular decrease in content of organic carbon

below the cambic horizon. These soils do not have a lithic

contact within 50 cm of the soil surface; a high shrink-swell

potential; a significant amount of sodium, durinodes, nodules,

concretions, volcanic glass, cinders, pumice, or pumicelike

fragments; or brittleness. These soils occur in Arizona and

New Mexico.

Lithic Haplocambids.—These are the Haplocambids that

have a lithic contact within 50 cm of the soil surface. These

soils do not have a soil moisture regime that borders on ustic or

xeric. They are common in the desert areas of the world.

Lithic Ustic Haplocambids.—These are the Haplocambids

that have a lithic contact within 50 cm of the soil surface and

have a soil moisture regime that borders on ustic.

Lithic Xeric Haplocambids.—These are the Haplocambids

that have a lithic contact within 50 cm of the soil surface and

have a soil moisture regime that borders on xeric.

Petronodic Haplocambids.—These are the Haplocambids

that have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of 15 cm or more, that

contain 20 percent or more nodules and concretions. These

soils do not have a soil moisture regime that borders on ustic or

xeric, a lithic contact within 50 cm of the soil surface, a high

shrink-swell potential, a significant amount of durinodes, or

brittleness.

Petronodic Ustic Haplocambids.—These are the

Haplocambids that have one or more horizons, within 100 cm

of the soil surface and with a combined thickness of 15 cm or

more, that contain 20 percent or more nodules and concretions.

These soils have a soil moisture regime that borders on ustic.

They do not have a lithic contact within 50 cm of the soil

surface, a high shrink-swell potential, a significant amount of

durinodes, or brittleness. The soils occur in Arizona and New

Mexico.

Petronodic Xeric Haplocambids.—These are the

Haplocambids that have one or more horizons, within 100 cm

of the soil surface and with a combined thickness of 15 cm or

more, that contain 20 percent or more nodules and concretions.

These soils have a soil moisture regime that borders on xeric.

They do not have a lithic contact within 50 cm of the soil

surface, a high shrink-swell potential, a significant amount of

durinodes, or brittleness.

Sodic Haplocambids.—These are the Haplocambids that

have, in a horizon at least 25 cm thick within 100 cm of the

soil surface, an exchangeable sodium percentage of 15 or more

during at least 1 month in normal years but do not have a soil

moisture regime that borders on xeric or ustic. These soils do

not contain a significant amount of durinodes, nodules, or

concretions, nor are they brittle. They do not have a lithic

contact within 50 cm of the soil surface or a high shrink-swell

potential. They occur in Nevada, New Mexico, and California.

Sodic Ustic Haplocambids.—These are the Haplocambids

that have, in a horizon at least 25 cm thick within 100 cm of

the soil surface, an exchangeable sodium percentage of 15 or

more during at least 1 month in normal years and have a soil

moisture regime that borders on ustic. These soils do not

contain a significant amount of durinodes, nodules, or

concretions and are not brittle. They do not have a lithic

contact within 50 cm of the soil surface or a high shrink-swell

potential. They occur in Arizona, New Mexico, and Utah.

Sodic Xeric Haplocambids.—These are the Haplocambids

that have, in a horizon at least 25 cm thick within 100 cm of

the soil surface, an exchangeable sodium percentage of 15 or

more during at least 1 month in normal years and have a soil

moisture regime that borders on xeric. These soils do not

contain a significant amount of durinodes, nodules, or

concretions, nor are they brittle. They do not have a lithic

contact within 50 cm of the soil surface or a high shrink-swell

potential. They occur in Oregon, California, and Nevada.

Ustertic Haplocambids.—These are the Haplocambids that

have a high shrink-swell potential and have a soil moisture

regime that borders on ustic. Most of these soils formed in

parent materials rich in smectitic clays. These soils do not have

a lithic contact within 50 cm of the soil surface. They are

known to occur in Wyoming.

Ustic Haplocambids.—These are the Haplocambids that

have a soil moisture regime that borders on ustic. These soils

do not have a lithic contact within 50 cm of the soil surface; a

high shrink-swell potential; brittleness; a significant amount of

sodium, durinodes, nodules, concretions, volcanic glass,

cinders, pumice, or pumicelike fragments; or an irregular

decrease in content of organic carbon below the cambic

horizon. They occur in the deserts of the western part of the

United States and in other deserts of the world.

Ustifluventic Haplocambids.—These are the

Haplocambids that have a soil moisture regime that borders on

ustic and have an irregular decrease in content of organic

carbon below the cambic horizon. These soils do not have a

lithic contact within 50 cm of the soil surface; a high shrinkswell potential; brittleness; or a significant amount of sodium,

durinodes, nodules, concretions, volcanic glass, cinders,

pumice, or pumicelike fragments. They are known to occur in

Arizona, Wyoming, New Mexico, and Texas.

Vertic Haplocambids.—These are the Haplocambids that

have a high shrink-swell potential but do not have a soil

moisture regime that borders on xeric or ustic. These soils do

not have a lithic contact within 50 cm of the soil surface.

Vitrandic Haplocambids.—These are the Haplocambids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime that

borders on xeric. These soils do not have a lithic contact within

50 cm of the soil surface; a high shrink-swell potential;
364 Soil Taxonomy

brittleness; or a significant amount of sodium, durinodes,

nodules, or concretions.

Vitrixerandic Haplocambids.—These are the Haplocambids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments and have a soil moisture regime

that borders on xeric. These soils do not have a lithic contact

within 50 cm of the soil surface; a high shrink-swell potential;

brittleness; or a significant amount of sodium, durinodes,

nodules, or concretions. These soils occur in California, Oregon,

Nevada, and Washington.

Xerertic Haplocambids.—These are the Haplocambids that

have a high shrink-swell potential and have a soil moisture

regime that borders on xeric. These soils do not have a lithic

contact within 50 cm of the soil surface. They occur in

Washington and Idaho.

Xeric Haplocambids.—These are the Haplocambids that

have a soil moisture regime that borders on xeric. These

soils do not have a lithic contact within 50 cm of the soil

surface; a high shrink-swell potential; brittleness; a significant

amount of sodium, durinodes, nodules, concretions, volcanic

glass, cinders, pumice, or pumicelike fragments; or an

irregular decrease in content of organic carbon below the

cambic horizon. They occur in many of the deserts in the

western part of the United States and in other deserts of the

world.

Xerofluventic Haplocambids.—These are the Haplocambids

that have a soil moisture regime that borders on xeric and have

an irregular decrease in content of organic carbon below the

cambic horizon. These soils do not have a lithic contact within

50 cm of the soil surface; a high shrink-swell potential;

brittleness; or a significant amount of sodium, durinodes,

nodules, concretions, volcanic glass, cinders, pumice, or

pumicelike fragments.

Petrocambids

These soils have a duripan or a petrocalcic or petrogypsic

horizon that has its upper boundary at a depth between 100 and

150 cm from the soil surface. These soils are not extensive

because most Aridisols have these diagnostic horizons at

shallower depths. Because of their importance to water

movement as well as interpretations, however, classes for these

types of soils are provided.

Definition

Petrocambids are the Cambids that:

1. Have a duripan or a petrocalcic or petrogypsic horizon

with an upper boundary within 150 cm of the soil surface;

2. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years.

Key to Subgroups

GGBA. Petrocambids that have, in a horizon at least 25 cm

thick within 100 cm of the soil surface, an exchangeable

sodium percentage of 15 or more (or an SAR of 13 or more)

during at least 1 month in normal years.

Sodic Petrocambids

GGBB. Other Petrocambids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Petrocambids

GGBC. Other Petrocambids that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Petrocambids

GGBD. Other Petrocambids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

xeric.

Xeric Petrocambids

GGBE. Other Petrocambids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 oC or higher and have a soil moisture regime that borders on

ustic.

Ustic Petrocambids
Aridisols 365

GGBF. Other Petrocambids.

Typic Petrocambids

Definition of Typic Petrocambids

Typic Petrocambids are the Petrocambids that:

1. Do not have, in a horizon at least 25 cm thick within 100 cm

of the soil surface, an exchangeable sodium percentage of 15 or

more (or an SAR of 13 or more) during at least 1 month in normal

years;

2. Are dry in all parts of the moisture control section for threefourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

3. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Petrocambids.—These are the Petrocambids that do

not have a soil moisture regime that borders on ustic or xeric or

a significant amount of sodium, volcanic glass, cinders,

pumice, or pumicelike fragments.

Sodic Petrocambids.—These are the Petrocambids that

have, in a horizon at least 25 cm thick within 100 cm of the

soil surface, an exchangeable sodium percentage of 15 or more

during at least 1 month in normal years.

Ustic Petrocambids.—These are the Petrocambids that

have a soil moisture regime that borders on ustic. These soils

do not have a significant amount of sodium, volcanic glass,

cinders, pumice, or pumicelike fragments.

Vitrandic Petrocambids.—These are the Petrocambids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments throughout one or more horizons with a

total thickness of 18 cm or more within 75 cm of the soil

surface and do not have a soil moisture regime that borders on

xeric. These soils also do not have a significant amount of

sodium.

Vitrixerandic Petrocambids.—These are the Petrocambids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface and have a soil moisture regime that borders

on xeric. These soils do not have a significant amount of

sodium.

Xeric Petrocambids.—These are the Petrocambids that

have a soil moisture regime that borders on xeric. These soils

do not have a significant amount of sodium, volcanic glass,

cinders, pumice, or pumicelike fragments. They occur in

Nevada.

Cryids

Cryids are the Aridisols of cold deserts. Short growing

seasons combined with arid conditions limit the use of these

soils. The soils are characteristically at high elevations,

dominantly in the mountain and basin areas in the United

States and Asia and in other parts of the world.

The cold deserts commonly have undergone alternating

periods of colder and warmer climates, which have resulted in

the expansion and contraction of alpine glaciers in the adjacent

mountains. The consequent variations in the sediment load

carried by mountain streams have resulted in relict landforms,

such as pediments, terraces, and alluvial fans. Cryids

commonly show evidence of periglacial features, such as icewedged casts, ground wedges, and mounds.

Cryids may have a duripan or an argillic, calcic, cambic,

gypsic, natric, petrocalcic, petrogypsic, or salic horizon. These

horizons are the basis for great groups. Haplocryids are

characterized by minimal development. Some Cryids occur

near ustic or xeric soil moisture regimes, which are the basis

for subgroups.

Definition

Cryids are the Aridisols that have a cryic temperature

regime.

Key to Great Groups

GAA. Cryids that have a salic horizon that has its upper

boundary within 100 cm of the soil surface.

Salicryids, p. 372

GAB. Other Cryids that have a duripan or a petrocalcic or

petrogypsic horizon that has its upper boundary within 100 cm

of the soil surface.

Petrocryids, p. 371

GAC. Other Cryids that have a gypsic horizon that has its

upper boundary within 100 cm of the soil surface.

Gypsicryids, p. 368

GAD. Other Cryids that have an argillic or natric horizon.

Argicryids, p. 366

GAE. Other Cryids that have a calcic horizon that has its

upper boundary within 100 cm of the soil surface.

Calcicryids, p. 367
366 Soil Taxonomy

GAF. Other Cryids.

Haplocryids, p. 369

Argicryids

These are the Cryids that have an illuvial horizon in which

silicate clays have accumulated. In general, the Argicryids

without a natric horizon formed in areas of late-Pleistocene or

older sediments or surfaces. Many of these soils receive

increments of dust, which may be a source of clay-sized

particles. Argicryids may be on gentle or steep slopes. These

soils are not extensive.

Definition

Argicryids are the Cryids that:

1. Have an argillic or natric horizon;

2. Do not have a duripan or a gypsic, petrocalcic,

petrogypsic, or salic horizon with an upper boundary within

100 cm of the soil surface.

Key to Subgroups

GADA. Argicryids that have a lithic contact within 50 cm of

the soil surface.

Lithic Argicryids

GADB. Other Argicryids that have one or both of the

following:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide throughout a thickness of 30 cm or more for

some time in normal years, and slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has

its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Argicryids

GADC. Other Argicryids that have a natric horizon that has

its upper boundary within 100 cm of the soil surface.

Natric Argicryids

GADD. Other Argicryids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Argicryids

GADE. Other Argicryids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Argicryids

GADF. Other Argicryids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Argicryids

GADG. Other Argicryids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Argicryids

GADH. Other Argicryids.

Typic Argicryids

Definition of Typic Argicryids

Typic Argicryids are the Argicryids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have either:

a. No cracks within 125 cm of the soil surface that are

5 mm or more wide through a thickness of 30 cm or more

for some time in normal years, and no slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of less than 6.0 cm between the
Aridisols 367

soil surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact, whichever is shallower;

3. Do not have a natric horizon that has its upper boundary

within 100 cm of the soil surface;

4. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 o

C at a depth of 50 cm;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Argicryids.—The Typic subgroup is centered on soils

that do not have a soil moisture regime that borders on ustic or

xeric. These soils also do not have a high shrink-swell

potential; a lithic contact within 50 cm of the soil surface; a

natric horizon; or a significant amount of volcanic glass,

cinders, pumice, or pumicelike fragments.

Lithic Argicryids.—These are the Argicryids that have a

lithic contact within 50 cm of the soil surface. These soils can

have other features, such as a soil moisture regime that borders

on ustic or xeric or a natric horizon, but the lithic contact keys

first.

Natric Argicryids.—These are the Argicryids that have a

natric horizon that has its upper boundary within 100 cm of the

soil surface. These soils do not have a lithic contact within 50

cm of the soil surface or a high shrink-swell potential.

Ustic Argicryids.—These are the Argicryids that have a

soil moisture regime that borders on ustic. These soils do not

have a high shrink-swell potential; a lithic contact within 50

cm of the soil surface; a natric horizon; or a significant amount

of volcanic glass, cinders, pumice, or pumicelike fragments.

Vertic Argicryids.—These are the Argicryids that have a

high shrink-swell potential. These soils do not have a lithic

contact within 50 cm of the soil surface. They can have a soil

moisture regime that borders on ustic or xeric.

Vitrandic Argicryids.—These are the Argicryids that have

a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments. These soils do not have a soil moisture

regime that borders on xeric, a lithic contact within 50 cm of

the soil surface, a high shrink-swell potential, or a natric

horizon. They are associated with areas that have a volcanic

influence.

Vitrixerandic Argicryids.—These are the Argicryids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments and have a soil moisture regime that

borders on xeric. These soils do not have a lithic contact within

50 cm of the soil surface, a natric horizon, or a high shrink-swell

potential.

Xeric Argicryids.—These are the Argicryids that have a soil

moisture regime that borders on xeric. These soils do not have a

significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments; a lithic contact within 50 cm of the soil

surface; a natric horizon; or a high shrink-swell potential.

Calcicryids

These are the Cryids that are derived from parent materials

high in content of lime or that have had lime added as dust.

Precipitation is unable to remove the calcium carbonate to

substantial depths. These soils typically have an ochric

epipedon and a calcic horizon. Some have a cambic horizon

overlying the calcic horizon.

Definition

Calcicryids are the Cryids that:

1. Have a calcic horizon that has its upper boundary within

100 cm of the soil surface;

2. Do not have a duripan or a gypsic, petrocalcic,

petrogypsic, or salic horizon with an upper boundary within

100 cm of the soil surface;

3. Do not have an argillic or natric horizon.

Key to Subgroups

GAEA. Calcicryids that have a lithic contact within 50 cm of

the soil surface.

Lithic Calcicryids

GAEB. Other Calcicryids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Calcicryids
368 Soil Taxonomy

GAEC. Other Calcicryids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm of

the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Calcicryids

GAED. Other Calcicryids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Calcicryids

GAEE. Other Calcicryids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Calcicryids

GAEF. Other Calcicryids.

Typic Calcicryids

Definition of Typic Calcicryids

Typic Calcicryids are the Calcicryids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm;

3. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Calcicryids.—The Typic subgroup is centered on the

Calcicryids that do not have the properties associated with the

other subgroups. These soils do not have a lithic contact within

50 cm of the soil surface; a soil moisture regime that borders

on ustic or xeric, or a significant amount of volcanic glass,

cinders, pumice, or pumicelike fragments.

Lithic Calcicryids.—These are the Calcicryids that have a

lithic contact within 50 cm of the soil surface.

Ustic Calcicryids.—These are the Calcicryids that have a

soil moisture regime that borders on ustic. These soils do not

have a lithic contact within 50 cm of the soil surface or a

significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments.

Vitrandic Calcicryids.—These are the Calcicryids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric. These soils do not have a lithic contact

within 50 cm of the soil surface.

Vitrixerandic Calcicryids.—These are the Calcicryids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments and have a soil moisture regime that

borders on xeric. These soils do not have a lithic contact within

50 cm of the soil surface.

Xeric Calcicryids.—These are the Calcicryids that have a

soil moisture regime that borders on xeric. These soils do not

have a lithic contact within 50 cm of the soil surface or a

significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments. They are known to occur in Idaho.

Gypsicryids

Gypsicryids are the Cryids that have a gypsic horizon. An

ochric epipedon and a cambic horizon commonly occur above

the gypsic horizon. These soils formed in parent materials rich

in gypsum. They are rare in the world.

Definition

Gypsicryids are the Cryids that:

1. Have a gypsic horizon that has its upper boundary within

100 cm of the soil surface;

2. Do not have a duripan or a petrocalcic, petrogypsic, or

salic horizon with an upper boundary within 100 cm of the soil

surface.

Key to Subgroups

GACA. Gypsicryids that have a calcic horizon.

Calcic Gypsicryids

GACB. Other Gypsicryids that have both:
Aridisols 369

1. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm and a soil

moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Gypsicryids

GACC. Other Gypsicryids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Gypsicryids

GACD. Other Gypsicryids.

Typic Gypsicryids

Definition of Typic Gypsicryids

Typic Gypsicryids are the Gypsicryids that:

1. Do not have a calcic horizon;

2. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Gypsicryids.—These are the Gypsicryids that do not

have a calcic horizon or a significant amount of volcanic glass,

cinders, pumice, or pumicelike fragments.

Calcic Gypsicryids.—These are the Gypsicryids that have a

calcic horizon. These soils can have other diagnostic horizons

or features, but the calcic horizon keys first.

Vitrandic Gypsicryids.—These are the Gypsicryids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric.

Vitrixerandic Gypsicryids.—These are the Gypsicryids

that have a significant amount of volcanic glass, cinders,

pumice, and pumicelike fragments and have a soil moisture

regime that borders on xeric.

Haplocryids

These are the Cryids that have a cambic horizon. An ochric

epipedon is common. Other diagnostic horizons may occur

below a depth of 100 cm. These soils commonly have

accumulations of calcium carbonate below the cambic horizon.

They are rare in the world.

Definition

Haplocryids are the Cryids that:

1. Do not have an argillic or natric horizon;

2. Do not have a duripan or a calcic, gypsic, petrocalcic,

petrogypsic, or salic horizon that has an upper boundary within

100 cm of the soil surface.

Key to Subgroups

GAFA. Haplocryids that have a lithic contact within 50 cm of

the soil surface.

Lithic Haplocryids

GAFB. Other Haplocryids that have one or both of the

following:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide throughout a thickness of 30 cm or more for

some time in normal years, and slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has

its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haplocryids
370 Soil Taxonomy

GAFC. Other Haplocryids that have both:

1. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm and a soil

moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplocryids

GAFD. Other Haplocryids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Haplocryids

GAFE. Other Haplocryids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Haplocryids

GAFF. Other Haplocryids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Haplocryids

GAFG. Other Haplocryids.

Typic Haplocryids

Definition of Typic Haplocryids

Typic Haplocryids are the Haplocryids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have either:

a. No cracks within 125 cm of the soil surface that are

5 mm or more wide through a thickness of 30 cm or more

for some time in normal years, and no slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of less than 6.0 cm between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower;

3. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 o

C at a depth of 50 cm;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Haplocryids.—The Typic subgroup of Haplocryids is

centered on features that are not defined for the other

subgroups. These soils do not have a lithic contact within 50

cm of the soil surface; a significant amount of volcanic glass,

cinders, pumice, and pumicelike fragments; a high shrinkswell potential; or a soil moisture regime that borders on ustic

or xeric.

Lithic Haplocryids.—These are the Haplocryids that have

a lithic contact within 50 cm of the soil surface. These soils can

have other characteristics, but the lithic contact keys first.

Ustic Haplocryids.—These are the Haplocryids that have a

soil moisture regime that borders on ustic. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; or a significant amount of volcanic

glass, cinders, pumice, or pumicelike fragments.

Vertic Haplocryids.—These are the Haplocryids that have

a high shrink-swell potential. These soils do not have a lithic

contact within 50 cm of the soil surface.

Vitrandic Haplocryids.—These are the Haplocryids that

have a significant amount of volcanic glass, cinders, pumice,

and pumicelike fragments but do not have a soil moisture
Aridisols 371

regime that borders on xeric. These soils also do not have a lithic

contact within 50 cm of the soil surface or a high shrink-swell

potential.

Vitrixerandic Haplocryids.—These are the Haplocryids

that have a significant amount of volcanic glass, cinders,

pumice, and pumicelike fragments and have a soil moisture

regime that borders on xeric. These soils do not have a lithic

contact within 50 cm of the soil surface or a high shrink-swell

potential.

Xeric Haplocryids.—These are the Haplocryids that have a

soil moisture regime that borders on xeric. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; or a significant amount of volcanic

glass, cinders, pumice, or pumicelike fragments.

Petrocryids

These are the Cryids that have a duripan or a petrocalcic or

petrogypsic horizon. An argillic, cambic, or natric horizon may

occur above the cemented layer. These soils occur in the

mountains of Idaho and possibly Wyoming.

Definition

Petrocryids are the Cryids that:

1. Have a duripan or a petrocalcic or petrogypsic horizon

with an upper boundary within 100 cm of the soil surface;

2. Do not have a salic horizon that has its upper boundary

within 100 cm of the soil surface.

Key to Subgroups

GABA. Petrocryids that:

1. Have a duripan that is strongly cemented or less

cemented in all subhorizons and has its upper boundary

within 100 cm of the soil surface; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and

have a soil moisture regime that borders on xeric.

Xereptic Petrocryids

GABB. Other Petrocryids that:

1. Have a duripan that has its upper boundary within 100

cm of the soil surface; and

2. Are dry in all parts of the moisture control section for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and

have a soil moisture regime that borders on xeric.

Duric Xeric Petrocryids

GABC. Other Petrocryids that have a duripan that has its upper

boundary within 100 cm of the soil surface.

Duric Petrocryids

GABD. Other Petrocryids that have a petrogypsic horizon that

has its upper boundary within 100 cm of the soil surface.

Petrogypsic Petrocryids

GABE. Other Petrocryids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 o

C or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Petrocryids

GABF. Other Petrocryids that are dry in all parts of the

moisture control section for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Petrocryids

GABG. Other Petrocryids.

Typic Petrocryids

Definition of Typic Petrocryids

Typic Petrocryids are the Petrocryids that:

1. Have a petrocalcic horizon that has its upper boundary

within 100 cm of the soil surface;

2. Do not have a duripan or a petrogypsic horizon that has an

upper boundary within 100 cm of the soil surface;

3. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 oC at a depth of 50 cm.

Description of Subgroups

Typic Petrocryids.—The central concept of the Typic

subgroup is that of dry soils with a petrocalcic horizon. These

soils do not have a duripan, a petrogypsic horizon, or a soil

moisture regime that borders on ustic or xeric.

Duric Petrocryids.—These are the Petrocryids that have a

duripan that is very strongly cemented or indurated in at least

some part. These soils do not have a soil moisture regime that

borders on xeric.

Duric Xeric Petrocryids.—These are the Petrocryids that

have a duripan that is very strongly cemented or indurated and

have a soil moisture regime that borders on xeric. These soils

occur in Idaho.

Petrogypsic Petrocryids.—These are the Petrocryids that

have a petrogypsic horizon. These soils do not have a duripan.
372 Soil Taxonomy

Ustic Petrocryids.—These are the Petrocryids that have a

petrocalcic horizon and have a soil moisture regime that borders

on ustic. These soils do not have a petrogypsic horizon or a

duripan.

Xeric Petrocryids.—These are the Petrocryids that have a

petrocalcic horizon and have a soil moisture regime that

borders on xeric. These soils do not have a petrogypsic horizon

or a duripan.

Xereptic Petrocryids.—These are the Petrocryids that have a

duripan that is strongly cemented or less cemented and have a

soil moisture regime that borders on xeric. These soils occur in

Idaho.

Salicryids

Salicryids are the Cryids that have a salic horizon. These soils

can have other diagnostic horizons and characteristics, but the

presence of soluble salts is considered important to

interpretations. The soils occur in extremely arid, cold regions

of the world.

Definition

Salicryids are the Cryids that have a salic horizon that has

its upper boundary within 100 cm of the soil surface.

Key to Subgroups

GAAA. Salicryids that are saturated with water in one or

more layers within 100 cm of the soil surface for 1 month or

more in normal years.

Aquic Salicryids

GAAB. Other Salicryids.

Typic Salicryids

Definition of Typic Salicryids

Typic Salicryids are the Salicryids that are not saturated

with water in any layer within 100 cm of the soil surface for 1

month or more in normal years.

Description of Subgroups

Typic Salicryids.—These are the Salicryids that are not

saturated with water in one or more horizons within 100 cm of

the soil surface for at least 1 month in normal years.

Aquic Salicryids.—These are the Salicryids that are

saturated with water in one or more horizons for 1 month or

more in normal years.

Durids

Durids are the Aridisols that have a duripan that has an

upper boundary within 100 cm of the soil surface. In many

areas the duripan is within 50 cm of the soil surface. These

soils occur dominantly on gentle slopes and formed in

sediments that contain pyroclastics. The duripan is cemented

partly with opal or chalcedony. The soils commonly have

calcium carbonate. The duripan is a barrier to both roots and

water.

Some Durids have an argillic or natric horizon above

the duripan, and these horizons are the basis for great

groups. Where these soils occur in areas adjacent to an ustic

or xeric soil moisture regime, intergrades are recognized at

the subgroup level. Most of these soils are used for grazing.

The amount of forage is low where the duripan is shallow.

These soils occur in the western part of the United States,

particularly in Nevada. They are not known to occur outside

the United States.

Definition

Durids are the Aridisols that:

1. Have a duripan that has its upper boundary within 100 cm of

the surface;

2. Have a soil temperature regime warmer than cryic;

3. Do not have a salic horizon that has its upper boundary

within 100 cm of the soil surface.

Key to Great Groups

GCA. Durids that have a natric horizon above the duripan.

Natridurids, p. 377

GCB. Other Durids that have an argillic horizon above the

duripan.

Argidurids, p. 372

GCC. Other Durids.

Haplodurids, p. 375

Argidurids

These are the Durids with an argillic horizon above the

duripan. Commonly, the duripan is within 50 cm of the soil

surface. These soils are close to volcanic areas or formed in

eolian or alluvial sediments derived from pyroclastics.

Definition

Argidurids are the Durids that:

1. Have an argillic horizon above the duripan;

2. Do not have a natric horizon above the duripan.

Key to Subgroups

GCBA. Argidurids that have, above the duripan, one or both

of the following:

1. Cracks between the soil surface and the top of the
Aridisols 373

duripan that are 5 mm or more wide through a thickness of

30 cm or more for some time in normal years, and

slickensides or wedge-shaped aggregates in a layer 15 cm

or more thick that has its upper boundary above the duripan;

or

2. A linear extensibility of 6.0 cm or more between the soil

surface and the top of the duripan.

Vertic Argidurids

GCBB. Other Argidurids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within 100

cm of the soil surface for 1 month or more in normal years.

Aquic Argidurids

GCBC. Other Argidurids that have the following combination

of characteristics:

1. An argillic horizon that has 35 percent or more clay in

the fine-earth fraction of some part; and either

a. A clay increase of 15 percent or more (absolute)

within a vertical distance of 2.5 cm either within the

argillic horizon or at its upper boundary; or

b. If there is an Ap horizon directly above the argillic

horizon, a clay increase of 10 percent or more (absolute)

at the upper boundary of the argillic horizon; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Abruptic Xeric Argidurids

GCBD. Other Argidurids that have an argillic horizon that

has 35 percent or more clay in the fine-earth fraction of some

part; and either

1. A clay increase of 15 percent or more (absolute) within

a vertical distance of 2.5 cm within the argillic horizon or at

its upper boundary; or

2. If there is an Ap horizon directly above the argillic

horizon, a clay increase of 10 percent or more (absolute) at

the upper boundary of the argillic horizon.

Abruptic Argidurids

GCBE. Other Argidurids that have:

1. A duripan that is strongly cemented or less cemented in

all subhorizons; and

2. A moisture control section that is dry in all parts for less

than three-fourths of the time (cumulative) when the soil

temperature is 5 oC or higher at a depth of 50 cm and a soil

moisture regime that borders on xeric.

Haploxeralfic Argidurids

GCBF. Other Argidurids that have a duripan that is strongly

cemented or less cemented in all subhorizons.

Argidic Argidurids

GCBG. Other Argidurids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Argidurids

GCBH. Other Argidurids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Argidurids

GCBI. Other Argidurids that have a moisture control section

that is dry in all parts for less than three-fourths of the time

(cumulative) when the soil temperature is 5 oC or higher at a

depth of 50 cm and have a soil moisture regime that borders on

xeric.

Xeric Argidurids

GCBJ. Other Argidurids that have a moisture control section
374 Soil Taxonomy

that is dry in all parts for less than three-fourths of the time

(cumulative) when the soil temperature at a depth of 50 cm is

5 o

C or higher and have a soil moisture regime that borders on

ustic.

Ustic Argidurids

GCBK. Other Argidurids.

Typic Argidurids

Definition of Typic Argidurids

Typic Argidurids are the Argidurids that:

1. Do not have either of the following:

a. Cracks between the soil surface and the top of the

duripan that are 5 mm or more wide through a thickness of

30 cm or more for some time in normal years, or

slickensides or wedge-shaped aggregates in a layer 15 cm or

more thick that has its upper boundary above the duripan;

or

b. A linear extensibility of 6.0 cm or more between the soil

surface and the top of the duripan;

2. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years;

3. Have an argillic horizon that has less than 35 percent clay

in the fine-earth fraction of some part; or

a. A clay increase of less than 15 percent (absolute) within

a vertical distance of 2.5 cm both within the argillic horizon

and at its upper boundary; or

b. If there is an Ap horizon directly above the argillic

horizon, a clay increase of less than 10 percent (absolute) at

the upper boundary of the argillic horizon;

4. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more;

6. Have a duripan that is strongly cemented or less cemented

in all subhorizons.

Description of Subgroups

Typic Argidurids.—The Typic subgroup of Argidurids is

defined in terms of characteristics that are not evident. It does

not have the following: a high shrink-swell potential;

saturation with water for 1 month or more within 100 cm of

the soil surface in normal years; a significant increase in

content of clay either within the argillic horizon or at its upper

boundary; a soil moisture regime that borders on ustic or xeric;

or a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments. These soils have a duripan that is very

strongly cemented or indurated in at least some part.

Abruptic Argidurids.—These are the Argidurids that have

a significant increase in content of clay within a short distance

either within the argillic horizon or at its upper boundary but

do not have a soil moisture regime that borders on xeric. The

abrupt increase in content of clay is important to water

movement. These soils do not have a high shrink-swell

potential and are not saturated with water for 1 month or more

within 100 cm of the soil surface in normal years. They are

known to occur in Arizona and Nevada.

Abruptic Xeric Argidurids.—These are the Argidurids

that have a significant increase in content of clay within a short

distance either within the argillic horizon or at its upper

boundary and have a soil moisture regime that borders on

xeric. The abrupt increase in content of clay is important to

water movement. These soils do not have a high shrink-swell

potential and are not saturated with water for 1 month or more

within 100 cm of the soil surface in normal years. They occur

in California, Oregon, and Nevada.

Aquic Argidurids.—These are the Argidurids that are

saturated with water for 1 month or more within 100 cm of the

soil surface in normal years. These soils are commonly

saturated by runoff from melting snow or from heavy rains.

They are dry for most of the year. They do not have a high

shrink-swell potential.

Argidic Argidurids.—These are the Argidurids that have a

duripan that is strongly cemented or less cemented in all

subhorizons and do not have a soil moisture regime that

borders on xeric. These soils do not have a high shrink-swell

potential, saturation with water for 1 month or more within

100 cm of the soil surface in normal years, or a significant

increase in content of clay within the argillic horizon or at its

upper boundary. These soils are known to occur in Nevada,

Oregon, and California.

Haploxeralfic Argidurids.—These are the Argidurids that

have a duripan that is strongly cemented or less cemented in

all subhorizons and have a soil moisture regime that borders on

xeric. These soils do not have a high shrink-swell potential,

saturation with water for 1 month or more within 100 cm of

the soil surface in normal years, or a significant increase in
Aridisols 375

content of clay within the argillic horizon or at its upper

boundary. These soils are known to occur in Nevada, Oregon,

Utah, Idaho, and California.

Ustic Argidurids.—These are the Argidurids that have a

soil moisture regime that borders on ustic and have a duripan

that is very strongly cemented or indurated in at least some

part. These soils do not have a high shrink-swell potential;

saturation with water for 1 month or more within 100 cm of

the soil surface in normal years; a significant increase in

content of clay either within the argillic horizon or at its upper

boundary; or a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments. These soils occur in Nevada.

Vertic Argidurids.—These are the Argidurids that have a

high shrink-swell potential. These soils occur in Nevada.

Vitrandic Argidurids.—These are the Argidurids that have

a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric. These soils have a duripan that is very

strongly cemented or indurated in at least some part. They do

not have an abrupt change in content of clay within the argillic

horizon or at its upper boundary, a high shrink-swell potential,

or saturation with water for 1 month or more within 100 cm of

the soil surface during the growing season.

Vitrixerandic Argidurids.—These are the Argidurids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments and have a soil moisture regime that

borders on xeric. These soils have a duripan that is very

strongly cemented or indurated in at least some part. They do

not have an abrupt change in content of clay within the argillic

horizon or at its upper boundary, a high shrink-swell potential,

or saturation with water for 1 month or more within 100 cm of

the soil surface during the growing season. These soils are

known to occur in Oregon.

Xeric Argidurids.—These are the Argidurids that have a soil

moisture regime that borders on xeric and have a duripan that is

very strongly cemented or indurated in at least some part. These

soils do not have a high shrink-swell potential; saturation with

water for 1 month or more within 100 cm of the soil surface in

normal years; a significant increase in content of clay either

within the argillic horizon or at its upper boundary; or a

significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments. These soils occur in Nevada, Oregon,

Idaho, Utah, and California.

Haplodurids

These are the Durids that do not have a natric or argillic

horizon. These soils formed in materials that have a pyroclastic

influence. Most Haplodurids are used for grazing.

Definition

Haplodurids are the Durids that do not have an argillic or

natric horizon above the duripan.

Key to Subgroups

GCCA. Haplodurids that:

1. Have a duripan that is strongly cemented or less

cemented in all subhorizons; and

2. Are either:

a. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the

soil surface; or

b. Saturated with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years.

Aquicambidic Haplodurids

GCCB. Other Haplodurids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within 100

cm of the soil surface for 1 month or more in normal years.

Aquic Haplodurids

GCCC. Other Haplodurids that have:

1. A duripan that is strongly cemented or less cemented in

all subhorizons; and

2. A mean annual soil temperature lower than 22 o

C, a

difference of 5 oC or more between mean summer and mean

winter soil temperatures at a depth of 50 cm, and a soil

moisture regime that borders on xeric.

Xereptic Haplodurids

GCCD. Other Haplodurids that have a duripan that is

strongly cemented or less cemented in all subhorizons.

Cambidic Haplodurids

GCCE. Other Haplodurids that have:

1. A moisture control section that is dry in all parts for

three-fourths of the time (cumulative) or less when the soil

temperature at a depth of 50 cm is 5 o

C or higher and a soil

moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent
376 Soil Taxonomy

or more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplodurids

GCCF. Other Haplodurids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Haplodurids

GCCG. Other Haplodurids that have a mean annual soil

temperature lower than 22 oC, a difference of 5 oC or more

between mean summer and mean winter soil temperatures at a

depth of 50 cm, and a soil moisture regime that borders on

xeric.

Xeric Haplodurids

GCCH. Other Haplodurids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on ustic.

Ustic Haplodurids

GCCI. Other Haplodurids.

Typic Haplodurids

Definition of Typic Haplodurids

Typic Haplodurids are the Durids that:

1. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years;

2. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

3. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more;

4. Have a duripan that is indurated or very strongly cemented

in at least one subhorizon.

Description of Subgroups

Typic Haplodurids.—These are the Haplodurids that have

a duripan that is very strongly cemented or indurated in at least

some part. These soils do not have a soil moisture regime that

borders on ustic or xeric; saturation with water for 1 month or

more within 100 cm of the soil surface in normal years; or a

significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments.

Aquicambidic Haplodurids.—These are the Haplodurids

that are saturated with water for 1 month or more within 100

cm of the soil surface in normal years and have a duripan that

is strongly cemented or less cemented in all subhorizons. These

soils occur in California, Oregon, and Nevada.

Aquic Haplodurids.—These are the Haplodurids that are

saturated with water for 1 month or more within 100 cm of the

soil surface in normal years and have a duripan that is very

strongly cemented or indurated in at least some part. These

soils occur in California, Oregon, and Washington.

Cambidic Haplodurids.—These are the Haplodurids that

have a duripan that is strongly cemented or less cemented in

all subhorizons but do not have a soil moisture regime that

borders on xeric. These soils are not saturated with water for 1

month or more within 100 cm of the soil surface in normal

years. They occur in Nevada and California.

Ustic Haplodurids.—These are the Haplodurids that have a

soil moisture regime that borders on ustic and have a duripan

that is very strongly cemented or indurated in at least some

part. These soils are not saturated with water for 1 month or

more within 100 cm of the soil surface in normal years, nor do

they have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments.

Vitrandic Haplodurids.—These are the Haplodurids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric. These soils have a duripan that is very

strongly cemented or indurated in at least some part. They are

not saturated with water for 1 month or more within 100 cm of

the soil surface in normal years. These soils are known to occur

in California.

Vitrixerandic Haplodurids.—These are the Haplodurids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments and have a soil moisture

regime that borders on xeric. These soils also have a duripan

that is very strongly cemented or indurated in at least some

part. They are not saturated with water for 1 month or more
Aridisols 377

within 100 cm of the soil surface in normal years. These soils are

known to occur in California and Oregon.

Xeric Haplodurids.—These are the Haplodurids that have

a soil moisture regime that borders on xeric and have a duripan

that is very strongly cemented or indurated in at least some

part. These soils are not saturated with water for 1 month or

more within 100 cm of the soil surface in normal years, nor do

they have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments. They occur in a number of

Western States.

Xereptic Haplodurids.—These are the Haplodurids that

have a soil moisture regime that borders on xeric and have a

duripan that is strongly cemented or less cemented in all

subhorizons. These soils are not saturated with water for 1

month or more within 100 cm of the soil surface in normal

years. They occur in Nevada, Utah, Oregon, Washington, and

Idaho.

Natridurids

These are the Durids that have a natric horizon above the

duripan. Commonly, the duripan is within 50 cm of the soil

surface. In many areas it is plugged by calcium carbonate.

These soils are commonly on gently sloping landscapes and

formed in materials derived from pyroclastics. They are not

extensive and are used mostly for grazing.

Definition

Natridurids are the Durids that have a natric horizon above

the duripan.

Key to Subgroups

GCAA. Natridurids that have, above the duripan, one or both

of the following:

1. Cracks between the soil surface and the top of the

duripan that are 5 mm or more wide through a thickness of

30 cm or more for some time in normal years, and

slickensides or wedge-shaped aggregates in a layer 15 cm or

more thick that has its upper boundary above the duripan;

or

2. A linear extensibility of 6.0 cm or more between the

soil surface and the top of the duripan.

Vertic Natridurids

GCAB. Other Natridurids that meet both of the following:

1. Have a duripan that is strongly cemented or less

cemented in all subhorizons; and

2. Are either:

a. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the

soil surface; or

b. Saturated with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years.

Aquic Natrargidic Natridurids

GCAC. Other Natridurids that are either:

1. Irrigated and have aquic conditions for some time in

normal years in one or more layers within 100 cm of the soil

surface; or

2. Saturated with water in one or more layers within 100

cm of the soil surface for 1 month or more in normal years.

Aquic Natridurids

GCAD. Other Natridurids that have the following

combination of characteristics:

1. A duripan that is strongly cemented or less cemented in

all subhorizons; and

2. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Natrixeralfic Natridurids

GCAE. Other Natridurids that have a duripan that is strongly

cemented or less cemented in all subhorizons.

Natrargidic Natridurids

GCAF. Other Natridurids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Natridurids

GCAG. Other Natridurids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser
378 Soil Taxonomy

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Natridurids

GCAH. Other Natridurids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature is 5 oC or higher

at a depth of 50 cm and have a soil moisture regime that

borders on xeric.

Xeric Natridurids

GCAI. Other Natridurids.

Typic Natridurids

Definition of Typic Natridurids

Typic Natridurids are the Durids that:

1. Do not have either of the following:

a. Cracks between the soil surface and the top of the

duripan that are 5 mm or more wide through a thickness of

30 cm or more for some time in normal years, and

slickensides or wedge-shaped aggregates in a layer 15 cm or

more thick that has its upper boundary above the duripan;

or

b. A linear extensibility of 6.0 cm or more between the soil

surface and the top of the duripan;

2. Are not both irrigated and characterized by aquic

conditions for some time in normal years in one or more layers

within 100 cm of the soil surface and are not saturated with

water in one or more layers within 100 cm of the soil surface

for 1 month or more in normal years;

3. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature is 5 o

C or higher at a depth of 50 cm;

4. Have a duripan that is either indurated or very strongly

cemented in at least one subhorizon;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Natridurids.—These are the Natridurids that have a

duripan that is very strongly cemented or indurated in at least

some part. These soils do not have a soil moisture regime that

borders on xeric, a high shrink-swell potential, or saturation

with water for 1 month or more within 100 cm of the soil

surface in normal years.

Aquic Natrargidic Natridurids.—These are the

Natridurids that are saturated with water for at least 1 month

within 100 cm of the soil surface in normal years and have a

duripan that is strongly cemented or less cemented in all

subhorizons. These soils do not have a high shrink-swell

potential. They occur in Nevada.

Aquic Natridurids.—These are the Natridurids that have a

duripan that is very strongly cemented or indurated in at least

some part and are saturated with water for at least 1 month

within 100 cm of the soil surface in normal years. These soils

do not have a high shrink-swell potential.

Natrargidic Natridurids.—These are the Natridurids that

have a duripan that is strongly cemented or less cemented in

all subhorizons and have a soil moisture regime that does not

border on xeric. These soils do not have a high shrink-swell

potential and are not saturated with water for 1 month or more

within 100 cm of the soil surface in normal years. They occur

in Nevada.

Natrixeralfic Natridurids.—These are the Natridurids that

have a duripan that is strongly cemented or less cemented in

all subhorizons and have a soil moisture regime that borders on

xeric. These soils do not have a high shrink-swell potential and

are not saturated with water for 1 month or more within 100

cm of the soil surface in normal years. They occur in Nevada

and California.

Vertic Natridurids.—These are the Natridurids that have a

high shrink-swell potential.

Vitrandic Natridurids.—These are the Natridurids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments and have a soil moisture regime that

does not border on xeric. These soils have a duripan that is

very strongly cemented or indurated in at least some part. They

do not have a high shrink-swell potential and are not saturated

with water for 1 month or more within 100 cm of the soil

surface in normal years.

Vitrixerandic Natridurids.—These are the Natridurids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments and have a soil moisture regime that

borders on xeric. These soils also have a duripan that is very

strongly cemented or indurated in at least some part. They do

not have a high shrink-swell potential and are not saturated

with water for 1 month or more within 100 cm of the soil

surface in normal years.

Xeric Natridurids.—These are the Natridurids that have a
Aridisols 379

duripan that is very strongly cemented or indurated in at least

some part and have a soil moisture regime that borders on xeric.

These soils do not have a high shrink-swell potential and are not

saturated with water for 1 month or more within 100 cm of the

soil surface in normal years.

Gypsids

Gypsids are the Aridisols that have a gypsic or petrogypsic

horizon within 100 cm of the soil surface. Accumulation of

gypsum takes place initially as crystal aggregates in the voids

of the soils. These aggregates grow by accretion, displacing the

enclosing soil material. When the gypsic horizon occurs as a

cemented impermeable layer, it is recognized as the

petrogypsic horizon. Each of these forms of gypsum

accumulation implies processes in the soils, and each presents

a constraint to soil use. One of the largest constraints is

dissolution of the gypsum, which plays havoc with structures,

roads, and irrigation delivery systems.

The presence of one or more of these horizons, with or

without other diagnostic horizons, defines the great groups of

the Gypsids. Gypsids occur in Iraq, Syria, Saudi Arabia, Iran,

Somalia, West Asia, and some of the most arid areas of the

western part of the United States.

Gypsids are on many segments of the landscape. Some of

them have calcic or related horizons that overlie the gypsic

horizon.

Definition

Gypsids are the Aridisols that:

1. Have a gypsic or petrogypsic horizon that has an upper

boundary within 100 cm of the soil surface;

2. Do not have a petrocalcic horizon overlying the gypsic or

petrogypsic horizon;

3. Have a soil temperature regime warmer than cryic;

4. Do not have a duripan or a salic horizon that has an upper

boundary within 100 cm of the soil surface.

Key to Great Groups

GDA. Gypsids that have a petrogypsic or petrocalcic horizon

that has its upper boundary within 100 cm of the soil surface.

Petrogypsids, p. 386

GDB. Other Gypsids that have a natric horizon that has its

upper boundary within 100 cm of the soil surface.

Natrigypsids, p. 384

GDC. Other Gypsids that have an argillic horizon that has its

upper boundary within 100 cm of the soil surface.

Argigypsids, p. 379

GDD. Other Gypsids that have a calcic horizon that has its

upper boundary within 100 cm of the soil surface.

Calcigypsids, p. 381

GDE. Other Gypsids.

Haplogypsids, p. 382

Argigypsids

Argigypsids are the Gypsids that have an argillic horizon.

These soils are known to occur in the Four Corners area of the

western part of the United States and in Texas. They are used

primarily for grazing.

Definition

Argigypsids are the Gypsids that:

1. Have an argillic horizon that has its upper boundary

within 100 cm of the soil surface;

2. Do not have a natric, petrocalcic, or petrogypsic horizon

with an upper boundary within 100 cm of the soil surface.

Key to Subgroups

GDCA. Argigypsids that have a lithic contact within 50 cm of

the soil surface.

Lithic Argigypsids

GDCB. Other Argigypsids that have:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide through a thickness of 30 cm or more for some

time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower.

Vertic Argigypsids

GDCC. Other Argigypsids that have a calcic horizon

overlying the gypsic horizon.

Calcic Argigypsids

GDCD. Other Argigypsids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes, nodules, or concretions.

Petronodic Argigypsids

GDCE. Other Argigypsids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and
380 Soil Taxonomy

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or both

of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Argigypsids

GDCF. Other Argigypsids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 percent or more.

Vitrandic Argigypsids

GDCG. Other Argigypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on xeric.

Xeric Argigypsids

GDCH. Other Argigypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on ustic.

Ustic Argigypsids

GDCI. Other Argigypsids.

Typic Argigypsids

Definition of Typic Argigypsids

Typic Argigypsids are the Argigypsids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have either:

a. No cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and no slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has its

upper boundary within 125 cm of the soil surface; or

b. A linear extensibility of less than 6.0 cm between the soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact, whichever is shallower;

3. Do not have a calcic horizon overlying the gypsic horizon;

4. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 oC or higher;

5. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes,

nodules, or concretions;

6. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Argigypsids.—These are the Argigypsids that do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; a calcic horizon above the gypsic

horizon; a soil moisture regime that borders on xeric or ustic; a

significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments; or a significant amount of durinodes,

concretions, or nodules.

Calcic Argigypsids.—These are the Argigypsids that have

a calcic horizon over the gypsic horizon. These soils do not

have a lithic contact within 50 cm of the soil surface or a high

shrink-swell potential. They are known to occur in Arizona.

Lithic Argigypsids.—These are the Argigypsids that have a

lithic contact within 50 cm of the soil surface. They can have a

soil moisture regime that borders on ustic or xeric.

Petronodic Argigypsids.—These are the Argigypsids that

have a significant amount of durinodes, nodules, or

concretions. These soils do not have a calcic horizon above the

gypsic horizon, a lithic contact within 50 cm of the soil

surface, or a high shrink-swell potential.

Ustic Argigypsids.—These are the Argigypsids that have a

soil moisture regime that borders on ustic. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; a calcic horizon above the gypsic
Aridisols 381

horizon; a significant amount of volcanic glass, cinders, pumice,

or pumicelike fragments; or a significant amount of durinodes,

concretions, or nodules.

Vertic Argigypsids.—These are the moderately deep to

very deep Argigypsids that have a high shrink-swell potential.

They occur in Texas, where they are used as rangeland.

Vitrandic Argigypsids.—These are the Argigypsids that

have a significant amount of volcanic glass, cinders, pumice,

or pumicelike fragments but do not have a soil moisture

regime that borders on xeric. These soils also do not have

a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; a calcic horizon above the gypsic

horizon; or a significant amount of durinodes, nodules, or

concretions.

Vitrixerandic Argigypsids.—These are the Argigypsids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments and have a soil moisture

regime that borders on xeric. Vitrixerandic Argigypsids do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; a calcic horizon above the gypsic

horizon; or a significant amount of durinodes, nodules, or

concretions.

Xeric Argigypsids.—These are the Argigypsids that have a

soil moisture regime that borders on xeric. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; a calcic horizon above the gypsic

horizon; or a significant amount of volcanic glass, cinders,

pumice, pumicelike fragments, durinodes, concretions, or

nodules.

Calcigypsids

Calcigypsids are the Gypsids that have a calcic horizon.

Commonly, the calcic horizon is above the gypsic horizon

because of differences in the solubility of gypsum and calcium

carbonate. These soils are known to occur in New Mexico.

Most Calcigypsids are used for grazing.

Definition

Calcigypsids are the Gypsids that:

1. Have both a gypsic and calcic horizon that have their

upper boundary within 100 cm of the soil surface;

2. Do not have an argillic, natric, petrogypsic, or petrocalcic

horizon that has an upper boundary within 100 cm of the soil

surface.

Key to Subgroups

GDDA. Calcigypsids that have a lithic contact within 50 cm

of the soil surface.

Lithic Calcigypsids

GDDB. Other Calcigypsids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more (by

volume) durinodes, nodules, or concretions.

Petronodic Calcigypsids

GDDC. Other Calcigypsids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Calcigypsids

GDDD. Other Calcigypsids that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Calcigypsids

GDDE. Other Calcigypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on xeric.

Xeric Calcigypsids

GDDF. Other Calcigypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on ustic.

Ustic Calcigypsids

GDDG. Other Calcigypsids.

Typic Calcigypsids
382 Soil Taxonomy

Definition of Typic Calcigypsids

Typic Calcigypsids are the Calcigypsids that:

1. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

2. Do not have a lithic contact within 100 cm of the soil

surface;

3. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes,

nodules, or concretions;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Calcigypsids.—These are the Calcigypsids that do

not have a lithic contact within 50 cm of the soil surface; a

significant amount of volcanic glass, cinders, pumice,

pumicelike fragments, durinodes, nodules, or concretions; or a

soil moisture regime that borders on ustic or xeric. These soils

are known to occur in Arizona, Texas, and New Mexico.

Lithic Calcigypsids.—These are the Calcigypsids that have

a lithic contact within 50 cm of the soil surface. These soils

occur in New Mexico and Arizona.

Petronodic Calcigypsids.—These are the Calcigypsids that

have a significant amount of durinodes, concretions, or

nodules. These soils do not have a lithic contact within 50 cm

of the soil surface. They occur in Arizona.

Ustic Calcigypsids.—These are the Calcigypsids that have

a soil moisture regime that borders on ustic. These soils do not

have a lithic contact within 50 cm of the soil surface or a

significant amount of volcanic glass, cinders, pumice,

pumicelike fragments, durinodes, nodules, or concretions.

These soils are known to occur in New Mexico and Texas.

Vitrandic Calcigypsids.—These are the Calcigypsids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric. These soils do not have a lithic contact

within 50 cm of the soil surface or a significant amount of

durinodes, concretions, or nodules.

Vitrixerandic Calcigypsids.—These are the Calcigypsids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments and have a soil moisture regime

that borders on xeric. These soils do not have a lithic contact

within 50 cm of the soil surface or a significant amount of

durinodes, concretions, or nodules.

Xeric Calcigypsids.—These are the Calcigypsids that have a

soil moisture regime that borders on xeric. These soils do not

have a lithic contact within 50 cm of the soil surface or a

significant amount of volcanic glass, cinders, pumice,

pumicelike fragments, durinodes, nodules, or concretions.

These soils are known to occur in Utah.

Haplogypsids

Haplogypsids are the Gypsids that have no petrogypsic,

natric, argillic, or calcic horizon that has an upper boundary

within 100 cm of the soil surface. Some Haplogypsids have a

cambic horizon overlying the gypsic horizon. These soils are

commonly very pale in color. They are not extensive in the

United States. The largest concentrations in the United States

are in New Mexico and Texas. The soils are more common in

other parts of the world.

Definition

Haplogypsids are the Gypsids that:

1. Do not have a petrogypsic or calcic horizon that has an

upper boundary within 100 cm of the soil surface;

2. Do not have an argillic or natric horizon that has an upper

boundary within 100 cm of the soil surface.

Key to Subgroups

GDEA. Haplogypsids that have a lithic contact within 50 cm

of the soil surface.

Lithic Haplogypsids

GDEB. Other Haplogypsids that have a gypsic horizon that

has its upper boundary within 18 cm of the soil surface.

Leptic Haplogypsids

GDEC. Other Haplogypsids that have, in a horizon at least

25 cm thick within 100 cm of the mineral soil surface, an

exchangeable sodium percentage of 15 or more (or an SAR of

13 or more) during at least 1 month in normal years.

Sodic Haplogypsids

GDED. Other Haplogypsids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes, nodules, or concretions.

Petronodic Haplogypsids

GDEE. Other Haplogypsids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the
Aridisols 383

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplogypsids

GDEF. Other Haplogypsids that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Haplogypsids

GDEG. Other Haplogypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on xeric.

Xeric Haplogypsids

GDEH. Other Haplogypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on ustic.

Ustic Haplogypsids

GDEI. Other Haplogypsids.

Typic Haplogypsids

Definition of Typic Haplogypsids

Typic Haplogypsids are the Haplogypsids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a gypsic horizon that has its upper boundary

within 18 cm of the soil surface;

3. Do not have, in one or more horizons within 100 cm of the

soil surface, an exchangeable sodium percentage of 15 or more

(or an SAR of 13 or more) for 1 month or more in normal

years;

4. Have a moisture control section that is dry in all parts for

three-fourths of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

5. Do not have one or more horizons, within 100 cm of the

soil surface and with a combined thickness of more than 15

cm, that contain 20 percent or more (by volume) durinodes,

nodules, or concretions;

6. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Haplogypsids.—These are the Haplogypsids that do

not have a lithic contact within 50 cm of the soil surface; a

gypsic horizon within 18 cm of the soil surface; a significant

amount of sodium, durinodes, concretions, nodules, volcanic

glass, cinders, pumice, or pumicelike fragments; or a soil

moisture regime that borders on xeric or ustic. These soils

occur in California, New Mexico, Arizona, Texas, and Nevada.

Leptic Haplogypsids.— These are the Haplogypsids that

have a gypsic horizon with its upper boundary within 18 cm of

the soil surface. These soils do not have a lithic contact within

50 cm of the soil surface. They occur in Nevada, Arizona, and

New Mexico.

Lithic Haplogypsids.—These are the Haplogypsids that

have a lithic contact within 50 cm of the soil surface. These

soils can have characteristics that are common in the other

subgroups.

Petronodic Haplogypsids.—These are the Haplogypsids

that have a significant amount of durinodes, concretions, or

nodules. These soils do not have a lithic contact within 50 cm

of the soil surface, a gypsic horizon with its upper boundary

within 18 cm of the soil surface, or a significant amount of

sodium.

Sodic Haplogypsids.—These are the Haplogypsids that

have, in a horizon at least 25 cm thick within 100 cm of the

soil surface, an exchangeable sodium percentage of 15 or more.

These soils do not have a lithic contact within 50 cm of the soil

surface or a gypsic horizon that has its upper boundary within

18 cm of the soil surface.
384 Soil Taxonomy

Ustic Haplogypsids.—These are the Haplogypsids that

have a soil moisture regime that borders on ustic. These soils

do not have a lithic contact within 50 cm of the soil surface; a

gypsic horizon within 18 cm of the soil surface; or a significant

amount of sodium, durinodes, concretions, nodules, volcanic

glass, cinders, pumice, or pumicelike fragments. Ustic

Haplogypsids occur in Utah, Arizona, Colorado, New Mexico,

and Wyoming.

Vitrandic Haplogypsids.—These are the Haplogypsids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric. These soils do not have a lithic contact

within 50 cm of the soil surface; a gypsic horizon within 18 cm

of the soil surface; or a significant amount of sodium,

durinodes, concretions, or nodules.

Vitrixerandic Haplogypsids.—These are the Haplogypsids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments and have a soil moisture

regime that borders on xeric. These soils do not have a lithic

contact within 50 cm of the soil surface; a gypsic horizon

within 18 cm of the soil surface; or a significant amount of

sodium, durinodes, concretions, or nodules.

Xeric Haplogypsids.—These are the Haplogypsids that have

a soil moisture regime that borders on xeric. These soils do not

have a lithic contact within 50 cm of the soil surface; a gypsic

horizon within 18 cm of the soil surface; or a significant amount

of sodium, durinodes, concretions, nodules, volcanic glass,

cinders, pumice, or pumicelike fragments. Xeric Haplogypsids

occur in Utah and California.

Natrigypsids

Natrigypsids are the Gypsids that have a natric horizon and

have no petrogypsic or petrocalcic horizon within 100 cm of

the soil surface. The gypsic horizon is commonly below the

natric horizon. These soils formed in parent materials high in

content of gypsum and sodium, such as sedimentary materials

that were deposited in a marine environment. The soils are rare

but are known to occur in the Four Corners area of the western

part of the United States (northwestern New Mexico,

northeastern Arizona, southeastern Utah, and southwestern

Colorado). The soils are used primarily for grazing.

Definition

Natrigypsids are the Gypsids that:

1. Have a natric horizon that has its upper boundary within

100 cm of the soil surface;

2. Do not have a petrogypsic or petrocalcic horizon with an

upper boundary within 100 cm of the soil surface.

Key to Subgroups

GDBA. Natrigypsids that have a lithic contact within 50 cm of

the soil surface.

Lithic Natrigypsids

GDBB. Other Natrigypsids that have:

1. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the soil surface;

or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower.

Vertic Natrigypsids

GDBC. Other Natrigypsids that have one or more horizons,

within 100 cm of the soil surface and with a combined

thickness of 15 cm or more, that contain 20 percent or more

(by volume) durinodes, nodules, or concretions.

Petronodic Natrigypsids

GDBD. Other Natrigypsids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Natrigypsids

GDBE. Other Natrigypsids that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or
Aridisols 385

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Natrigypsids

GDBF. Other Natrigypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on xeric.

Xeric Natrigypsids

GDBG. Other Natrigypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on ustic.

Ustic Natrigypsids

GDBH. Other Natrigypsids.

Typic Natrigypsids

Definition of Typic Natrigypsids

Typic Natrigypsids are the Natrigypsids that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have either:

a. No cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and no slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has

its upper boundary within 125 cm of the soil surface; or

b. A linear extensibility of less than 6.0 cm between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower;

3. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more;

5. Do not have one or more horizons, within 100 cm of the soil

surface and with a combined thickness of more than 15 cm, that

contain 20 percent or more (by volume) durinodes, nodules, or

concretions.

Description of Subgroups

Typic Natrigypsids.—The Typic subgroup of Natrigypsids is

defined in terms of characteristics that are not evident. These

soils do not have a lithic contact within 50 cm of the soil

surface; a high shrink-swell potential; a soil moisture regime

that borders on xeric or ustic; or a significant amount of

durinodes, nodules, concretions, volcanic glass, cinders,

pumice, or pumicelike fragments.

Lithic Natrigypsids.—These are the Natrigypsids that have

a lithic contact within 50 cm of the soil surface. These soils can

have the characteristics defined for the other subgroups. The

presence of a lithic contact is considered important to

interpretations and keys first.

Petronodic Natrigypsids.—These are the Natrigypsids that

have a significant amount of durinodes, nodules, or

concretions. These soils do not have a lithic contact within 50

cm of the soil surface or a high shrink-swell potential.

Ustic Natrigypsids.—These are the Natrigypsids that have

a soil moisture regime that borders on ustic. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; or a significant amount of durinodes,

concretions, nodules, volcanic glass, cinders, pumice, or

pumicelike fragments.

Vertic Natrigypsids.—These are the Natrigypsids that have

a high shrink-swell potential. These soils do not have a lithic

contact within 50 cm of the soil surface.

Vitrandic Natrigypsids.—These are the Natrigypsids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric. These soils also do not have a lithic

contact within 50 cm of the soil surface; a high shrink-swell

potential; or a significant amount of durinodes, nodules, and

concretions.

Vitrixerandic Natrigypsids.—These are the Natrigypsids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments and have a soil moisture

regime that borders on xeric. These soils do not have a lithic

contact within 50 cm of the soil surface; a high shrink-swell

potential; or a significant amount of durinodes, nodules, and

concretions.

Xeric Natrigypsids.—These are the Natrigypsids that have

a soil moisture regime that borders on xeric. These soils do not

have a lithic contact within 50 cm of the soil surface; a high

shrink-swell potential; or a significant amount of durinodes,

concretions, nodules, volcanic glass, cinders, pumice, or

pumicelike fragments.
386 Soil Taxonomy

Petrogypsids

Petrogypsids are the Gypsids that have a petrogypsic or

petrocalcic horizon that has its upper boundary within 100 cm

of the soil surface. These soils occur in very arid areas of the

world where the parent material is high in content of gypsum.

When the petrogypsic horizon is close to the surface, crusting

forms pseudohexagonal patterns on the soil surface.

Petrogypsids occupy old surfaces. In Syria and Iraq, they are on

the highest terraces along the Tigris and Euphrates Rivers.

These soils are not extensive in the United States but are

extensive in other countries.

Definition

Petrogypsids are the Gypsids that have a petrogypsic or

petrocalcic horizon that has its upper boundary within 100 cm

of the soil surface.

Key to Subgroups

GDAA. Petrogypsids that have a petrocalcic horizon that has

its upper boundary within 100 cm of the soil surface.

Petrocalcic Petrogypsids

GDAB. Other Petrogypsids that have a calcic horizon

overlying the petrogypsic horizon.

Calcic Petrogypsids

GDAC. Other Petrogypsids that have both:

1. A moisture control section that is dry in all parts for

less than three-fourths of the time (cumulative) when the

soil temperature is 5 oC or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the soil surface, one or

both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Petrogypsids

GDAD. Other Petrogypsids that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Petrogypsids

GDAE. Other Petrogypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on xeric.

Xeric Petrogypsids

GDAF. Other Petrogypsids that have a moisture control

section that is dry in all parts for less than three-fourths of the

time (cumulative) when the soil temperature at a depth of 50

cm is 5 oC or higher and have a soil moisture regime that

borders on ustic.

Ustic Petrogypsids

GDAG. Other Petrogypsids.

Typic Petrogypsids

Definition of Typic Petrogypsids

Typic Petrogypsids are the Petrogypsids that:

1. Do not have a petrocalcic horizon within 100 cm of the

soil surface;

2. Do not have a calcic horizon overlying the petrogypsic

horizon;

3. Have a moisture control section that is dry in all parts for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 oC or higher;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Description of Subgroups

Typic Petrogypsids.—These are the Petrogypsids that have

a petrogypsic horizon. These soils do not have a calcic or

petrocalcic horizon above the petrogypsic horizon or a

significant amount of volcanic glass, cinders, pumice, or
Aridisols 387

pumicelike fragments. The moisture regime does not border on

ustic or xeric.

Calcic Petrogypsids.—These are the Petrogypsids that have

a calcic horizon above the petrogypsic horizon. These soils do

not have a petrocalcic horizon.

Petrocalcic Petrogypsids.—These are the Petrogypsids that

have a petrocalcic horizon. These soils are known to occur in

Nevada.

Ustic Petrogypsids.—These are the Petrogypsids that

have a petrogypsic horizon and have a soil moisture regime

that borders on ustic. These soils do not have a calcic or

petrocalcic horizon above the petrogypsic horizon or a

significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments.

Vitrandic Petrogypsids.—These are the Petrogypsids that

have a significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments but do not have a soil moisture regime

that borders on xeric. These soils do not have a calcic horizon

overlying the petrogypsic horizon and do not have a petrocalcic

horizon.

Vitrixerandic Petrogypsids.—These are the Petrogypsids

that have a significant amount of volcanic glass, cinders,

pumice, or pumicelike fragments and have a soil moisture

regime that borders on xeric. These soils do not have a calcic

horizon overlying the petrogypsic horizon and do not have a

petrocalcic horizon.

Xeric Petrogypsids.—These are the Petrogypsids that have

a petrogypsic horizon and have a soil moisture regime that

borders on xeric. These soils do not have a calcic horizon

above the petrogypsic horizon; a petrocalcic horizon; or a

significant amount of volcanic glass, cinders, pumice, or

pumicelike fragments.

Salids

Salids are most common in depressions (playas) in the

deserts or in closed basins in the wetter areas bordering the

deserts. In North Africa and in the Near East, such depressions

are referred to as Sebkhas or Chotts, depending on the presence

or absence of surface water for prolonged periods.

Under the arid environment and hot temperatures,

accumulation of salts commonly occurs when there is a supply

of salts and a net upward movement of water in the soils. In

some areas a salic horizon has formed in salty parent materials

without the presence of ground water. The most common form

of salt is sodium chloride (halite), but sulfates (thenardite,

mirabilite, and hexahydrite) and other salts may also occur.

The concept of Salids is one of accumulation of an excessive

amount of salts that are more soluble than gypsum. This is

implicit in the definition, which requires a minimum absolute

EC of 30 dS/m in 1:1 extract (about 2 percent salt) and a

product of EC and thickness of at least 900.

As a rule, Salids are unsuitable for agricultural use, unless

the salts are leached out. Leaching the salts is an expensive

undertaking, particularly if there is no natural outlet for the

drainage water.

Two great groups are recognized—Aquisalids, which are

saturated with water for 1 month or more during the year, and

Haplosalids, which are drier.

Definition

Salids are the Aridisols that have:

1. A salic horizon that has its upper boundary within 100 cm of

the soil surface;

2. A soil temperature regime warmer than cryic.

Key to Great Groups

GBA. Salids that are saturated with water in one or more layers

within 100 cm of the mineral soil surface for 1 month or more in

normal years.

Aquisalids, p. 387

GBB. Other Salids.

Haplosalids, p. 388

Aquisalids

These are the salty soils in wet areas in the deserts where

capillary rise and evaporation of water concentrate the salts

near the surface. Some of these soils have redoximorphic

depletions and concentrations. In other soils redoximorphic

features may not be evident because of a high pH and the

associated low redox potential, which inhibit iron and

manganese reduction. These soils occur dominantly in

depressional areas where ground water saturates the soils at

least part of the year. The vegetation on these soils generally is

sparse, consisting of salt-tolerant shrubs, grasses, and forbs.

Although these soils may hold water at a tension less than

1500 kPa, the dissolved salt content makes the soils

physiologically dry.

Definition

Aquisalids are the Salids that are saturated with water in

one or more layers within 100 cm of the mineral soil surface

for 1 month or more in normal years.

Key to Subgroups

GBAA. Aquisalids that have a gypsic or petrogypsic horizon

that has its upper boundary within 100 cm of the soil surface.

Gypsic Aquisalids

GBAB. Other Aquisalids that have a calcic or petrocalcic
388

horizon that has an upper boundary within 100 cm of the soil

surface.

Calcic Aquisalids

GBAC. Other Aquisalids.

Typic Aquisalids

Definition of Typic Aquisalids

Typic Aquisalids are the Aquisalids that do not have a calcic,

gypsic, petrocalcic, or petrogypsic horizon that has its upper

boundary within 100 cm of the soil surface.

Description of Subgroups

Typic Aquisalids.—These are the Aquisalids that do not

have a calcic, petrocalcic, gypsic, or petrogypsic horizon.

These soils occur in most States in the West.

Calcic Aquisalids.—These are the Aquisalids that have a

calcic or petrocalcic horizon within 100 cm of the soil surface.

These soils do not have a gypsic or petrogypsic horizon with an

upper boundary within 100 cm of the soil surface. They occur

in Nevada and Texas.

Gypsic Aquisalids.—These are the Aquisalids that have a

gypsic or petrogypsic horizon with an upper boundary within

100 cm of the soil surface. These soils occur in Texas and

Colorado.

Haplosalids

These are the Salids that have a high concentration of salts

but do not have the saturation that is associated with the

Aquisalids. Haplosalids may be saturated for shorter periods

than Aquisalids or may have had a water table associated with

a past climate. In the Four Corners area of the United States,

salic horizons have formed without the influence of a water

table in saline parent materials.

Definition

Haplosalids are the Salids that are not saturated with water

in one or more layers within 100 cm of the mineral soil surface

for 1 month or more in normal years.

Key to Subgroups

GBBA. Haplosalids that have a duripan that has its upper

boundary within 100 cm of the soil surface.

Duric Haplosalids

GBBB. Other Haplosalids that have a petrogypsic

horizon that has its upper boundary within 100 cm of

the soil surface.

Petrogypsic Haplosalids

GBBC. Other Haplosalids that have a gypsic horizon that has

its upper boundary within 100 cm of the soil surface.

Gypsic Haplosalids

GBBD. Other Haplosalids that have a calcic horizon that has

its upper boundary within 100 cm of the soil surface.

Calcic Haplosalids

GBBE. Other Haplosalids.

Typic Haplosalids

Definition of Typic Haplosalids

Typic Haplosalids are the Haplosalids that do not have a

calcic, gypsic, or petrogypsic horizon or a duripan that has an

upper boundary within 100 cm of the soil surface.

Description of Subgroups

Typic Haplosalids.—These are the Haplosalids that do not

have a calcic, gypsic, or petrogypsic horizon or a duripan with

an upper boundary within 100 cm of the soil surface. Before

1994, these soils were identified as Torriorthents if a salic

horizon was the only diagnostic horizon. These soils occur in

California.

Calcic Haplosalids.—These are the Haplosalids that have a

calcic horizon that has its upper boundary within 100 cm of the

soil surface. These soils do not have a gypsic or petrogypsic

horizon or a duripan with an upper boundary within 100 cm of

the soil surface. They occur in Arizona.

Duric Haplosalids.—These are the Haplosalids that have a

duripan with its upper boundary within 100 cm of the soil

surface.

Gypsic Haplosalids.—These are the Haplosalids that have

a gypsic horizon with its upper boundary within 100 cm of the

soil surface. These soils do not have a duripan. They occur in

California.

Petrogypsic Haplosalids.—These are the Haplosalids

that have a petrogypsic horizon that has its upper boundary

within 100 cm of the soil surface. These soils do not have a

duripan.
389

The central concept of Entisols is that of soils that havelittle or no evidence of the development of pedogenic

horizons. Most Entisols have no diagnostic horizons other than

an ochric epipedon. Very few have an anthropic epipedon. A

few that have a sandy or sandy-skeletal particle-size class have

a horizon that would be a cambic horizon were it not for the

particle-size class exclusion. Very few Entisols have an albic

horizon. In coastal marshes some Entisols that have sulfidic

materials within 50 cm of the mineral soil surface have a histic

epipedon.

On many landscapes the soil material is not in place long

enough for pedogenic processes to form distinctive horizons.

Some of these soils are on steep, actively eroding slopes, and

others are on flood plains or glacial outwash plains that receive

new deposits of alluvium at frequent intervals. Some Entisols

are old enough to have formed diagnostic horizons, but they

consist mostly of quartz or other minerals that are resistant to

the weathering needed to form diagnostic horizons. Buried

diagnostic horizons are permitted in Entisols if they meet the

requirements for buried soil defined in chapter 1.

Entisols may have any mineral parent material, vegetation,

age, or moisture regime and any temperature regime, but they

do not have permafrost. The only features common to all soils

of the order are the virtual absence of diagnostic horizons and

the mineral nature of the soils.

Definition of Entisols and Limits Between

Entisols and Soils of Other Orders

Entisols are mineral soils that:

1. Do not have an Ap horizon containing 85 percent or more

spodic materials;

2. Do not have a fragipan or an argillic, kandic, natric, oxic,

or spodic horizon;

3. Do not have andic soil properties in 60 percent or more of

the thickness, whether buried or not, between either the

mineral soil surface or the top of an organic layer with andic

soil properties, whichever is shallower, and either a depth of 60

cm from the shallower of the above or a densic, lithic, or

paralithic contact if shallower than 60 cm;

4. Do not have permafrost within 100 cm of the soil surface

or both gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface;

5. Do not have all of the following:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

aggregates that have their long axes tilted 10 to 60 degrees

from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon if shallower; and

c. Cracks that open and close periodically;

6. Do not have both a salic horizon and an aridic moisture

regime;

7. Do not have all of the following:

a. A salic horizon; and

b. A moisture control section that is dry at some time in

normal years; and

c. Saturation with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years;

8. Do not have both a mollic epipedon and a base saturation

(by NH4

OAc) of 50 percent or more in all horizons either

between the mineral soil surface and a depth of 180 cm or

between the mineral soil surface and a densic, lithic, or

paralithic contact, whichever is shallower;

9. Do not have a cambic horizon with its upper boundary

within 100 cm of the mineral soil surface or its lower boundary

at a depth of 25 cm or more below the mineral soil surface;

10. Do not have both a cambic horizon and a cryic

temperature regime;

11. Do not have a duripan or a calcic, petrocalcic, gypsic,

petrogypsic, or placic horizon unless its upper boundary is

more than 100 cm below the mineral soil surface;

CHAPTER 12

Entisols
390 Soil Taxonomy

12. Do not have a sulfuric horizon unless its upper boundary

is more than 150 cm below the mineral soil surface; and

13. Unless the soil has either sulfidic materials within 50 cm

of the mineral soil surface or has, in one or more horizons at a

depth between 20 and 50 cm below the mineral soil surface,

both an n value of more than 0.7 and 8 percent or more clay in

the fine-earth fraction, do not have:

a. In 50 percent or more of the layers between the mineral

soil surface and a depth of 50 cm, an exchangeable sodium

percentage of 15 or more (or a sodium adsorption ratio of 13

or more), which decreases with increasing depth below 50

cm, and also ground water within 100 cm of the mineral

soil surface at some time during the year when the soil is

not frozen in any part; or

b. A histic, mollic, plaggen, or umbric epipedon.

Limits Between Entisols and Soils of Other Orders

The definition of Entisols must provide criteria that separate

Entisols from all other orders. These criteria define the limits

of Entisols in relation to all other known kinds of soil.

1. Unlike Alfisols, Entisols must not have an argillic, natric,

or kandic horizon.

2. Unlike Andisols, Entisols must not have andic soil

properties in 60 percent or more of the thickness, whether

buried or not, between either the mineral soil surface or the top

of an organic layer with andic soil properties, whichever is

shallower, and either a depth of 60 cm from the shallower of

the above or a densic, lithic, or paralithic contact if shallower

than 60 cm.

3. Unlike Aridisols, Entisols must not have:

a. All of the following:

(1) A salic horizon; and

(2) A moisture control section that is dry at some time

in normal years; and

(3) Saturation with water in one or more layers within

100 cm of the soil surface for 1 month or more in normal

years; or

b. Both an anthropic or ochric epipedon and an aridic

moisture regime; and

(1) An argillic or natric horizon; or

(2) A cambic horizon with its lower boundary below 25

cm or its upper boundary within 100 cm of the soil

surface; or

(3) A calcic, petrocalcic, gypsic, petrogypsic, or salic

horizon or a duripan with its upper boundary within 100

cm of the soil surface.

4. Unlike Gelisols, Entisols do not have permafrost within

100 cm of the soil surface, nor do they have both gelic

materials within 100 cm of the soil surface and permafrost

within 200 cm of the soil surface.

5. Unlike Inceptisols, Entisols:

a. Must not have any of the following:

(1) A cambic horizon with its upper boundary within

100 cm of the mineral soil surface or its lower boundary

at a depth of 25 cm or more below the mineral soil

surface;

(2) A duripan or a calcic, petrocalcic, gypsic,

petrogypsic, or placic horizon unless its upper boundary

is more than 100 cm below the mineral soil surface;

(3) A fragipan or an oxic or spodic horizon;

(4) A sulfuric horizon unless its upper boundary is

more than 150 cm below the mineral soil surface;

(5) Both a cambic horizon and a cryic temperature

regime; and

b. Have either sulfidic materials within 50 cm of the

mineral soil surface or have, in one or more horizons at a

depth between 20 and 50 cm below the mineral soil surface,

both an n value of more than 0.7 and 8 percent or more clay

in the fine-earth fraction, if they have:

(1) In 50 percent or more of the layers between the

mineral soil surface and a depth of 50 cm, an

exchangeable sodium percentage of 15 or more (or a

sodium adsorption ratio of 13 or more), which decreases

with increasing depth below 50 cm, and also ground

water within 100 cm of the mineral soil surface at some

time during the year when the soil is not frozen in any

part; or

(2) A histic, mollic, plaggen, or umbric epipedon.

6. Unlike Histosols, Entisols must meet the definition of

mineral soils.

7. Unlike Mollisols, Entisols must not have a mollic

epipedon unless they also either have sulfidic materials within

50 cm of the mineral soil surface or have, in one or more

horizons at a depth between 20 and 50 cm below the mineral

soil surface, both an n value of more than 0.7 and 8 percent or

more clay in the fine-earth fraction.

8. Unlike Oxisols, Entisols must not have an oxic or kandic

horizon.

9. Unlike Spodosols, Entisols must not have a spodic horizon

or an Ap horizon consisting of 85 percent or more spodic

materials.

10. Unlike Ultisols, Entisols must not have an argillic or

kandic horizon.
Entisols 391

11. Unlike Vertisols, Entisols must not have all of the

following:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

aggregates that have their long axes tilted 10 to 60 degrees

from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in all horizons between

a depth of 18 cm and either a depth of 50 cm or a densic,

lithic, or paralithic contact, a duripan, or a petrocalcic

horizon if shallower; and

c. Cracks that open and close periodically.

Representative Pedon and Data

Following is a description of a representative Entisol. Data

for the pedon identified in this description are given in the

table “Characterization Data for an Entisol.”

Classification: Mixed, mesic Typic Ustipsamment

Site identification number: 87P0168

Location: Blaine County, Nebraska; 520 m north and 90 m

west of the southeast corner of sec. 9, T. 22 N., R. 22 E.

Landscape: Sandhills

Landform: Dune

Slope: 19 percent, north facing

Elevation: 778 m above m.s.l.

Soil moisture regime: Ustic

Soil temperature regime: Mesic

Permeability class: Rapid

Drainage class: Excessively drained

Depth to water table: More than 150 cm

Land use: Rangeland (grazed)

Hazard of erosion or deposition: Slight

Parent material: Sandy eolian material

Described by: Shurtliff

In the following pedon description, colors are for dry soil

unless otherwise indicated.

A—0 to 13 cm; grayish brown (10YR 5/2) fine sand, very dark

grayish brown (10YR 3/2) moist; weak fine granular

structure; soft, very friable; many fine and medium roots;

slightly acid (pH 6.3); clear smooth boundary.

AC—13 to 28 cm; light brownish gray (10YR 6/2) fine sand,

dark grayish brown (10YR 4/2) moist; single grain; loose;

common fine and medium roots; neutral (pH 7.0); clear

smooth boundary.

C1—28 to 64 cm; pale brown (10YR 6/3) fine sand, brown

(10YR 5/3) moist; single grain; loose; few or common fine

roots; neutral (pH 7.0); clear smooth boundary.

C2—64 to 152 cm; very pale brown (10YR 7/3) fine sand, pale

brown (10YR 6/3) moist; single grain; loose; few fine

roots; neutral (pH 7.0).

Key to Suborders

LA. Entisols that have one or more of the following:

1. Aquic conditions and sulfidic materials within 50 cm of

the mineral soil surface; or

2. Permanent saturation with water and a reduced

matrix in all horizons below 25 cm from the mineral soil

surface; or

3. In a layer above a densic, lithic, or paralithic contact or

in a layer at a depth between 40 and 50 cm below the

mineral soil surface, whichever is shallower, aquic

conditions for some time in normal years (or artificial

drainage) and one or more of the following:

a. A texture finer than loamy fine sand and, in 50

percent or more of the matrix, one or more of the

following:

(1) Chroma of 0; or

(2) Chroma of 1 or less and a color value, moist,

of 4 or more; or

(3) Chroma of 2 or less and redox concentrations;

or

b. A texture of loamy fine sand or coarser and, in 50

percent or more of the matrix, one or more of the

following:

(1) Chroma of 0; or

(2) Hue of 10YR or redder, a color value, moist, of 4

or more, and chroma of 1; or

(3) Hue of 10YR or redder, chroma of 2 or less, and

redox concentrations; or

(4) Hue of 2.5Y or yellower, chroma of 3 or less, and

distinct or prominent redox concentrations; or

(5) Hue of 2.5Y or yellower and chroma of 1; or

(6) Hue of 5GY, 5G, 5BG, or 5B; or

(7) Any color if it results from uncoated sand grains;

or

c. Enough active ferrous iron to give a positive reaction

to alpha,alpha-dipyridyl at a time when the soil is not

being irrigated.

Aquents, p. 393

LB. Other Entisols that have, in one or more layers at a depth

between 25 and 100 cm below the mineral soil surface, 3
392 Soil Taxonomy

Characterization Data for an Entisol

 SITE IDENTIFICATION NO.: 87P0168

 CLASSIFICATION: MIXED, MESIC TYPIC USTIPSAMMENT

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 87P 904 0- 13 A 3.5 3.2 93.3 0.7 2.5 19.9 66.0 7.1 0.3 -- -- -- -- 73 --

 87P 905 13- 28 AC 2.8 2.1 95.1 0.5 1.6 18.8 67.6 8.5 0.2 -- -- -- -- 76 --

 87P 906 28- 64 C1 2.5 1.2 96.3 0.2 1.0 16.4 72.4 7.3 0.2 -- -- -- -- 80 --

 87P 907 64-152 C2 2.5 1.0 96.5 -- 1.0 13.0 73.0 10.2 0.3 -- -- -- -- 83 --

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 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 13 0.58 0.049 1.20 0.86 3.0

 13- 28 0.35 0.033 1.29 0.79 2.2

 28- 64 0.09 1.20 0.64 1.6

 64-152 0.06 1.00 0.56 1.4

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 (- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)

 Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9b 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1f 8C1f

 <- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1

 0- 13 3.0 0.6 TR 0.3 3.9 1.5 5.4 4.2 72 93 5.2 5.8

 13- 28 2.7 0.5 TR 0.2 3.4 0.8 4.2 3.6 81 94 5.4 6.1

 28- 64 2.2 0.5 TR 0.1 2.8 0.7 3.5 3.0 80 93 5.6 6.3

 64-152 1.8 0.4 TR 0.1 2.3 0.3 2.6 2.5 88 92 5.6 6.4

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 < - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA-

 < - - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION

 NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->

 87P 905 FS 66 QZ61 FK20 FP 9 AR 6 CD 5 PRtr

 87P 905 FS TMtr FEtr HNtr GStr GNtr

 87P 906 FS 76 QZ68 FK12 CD 8 FP 7 AR 5 GStr

 87P 906 FS PRtr OPtr HNtr

 87P 907 FS 68 QZ63 FK18 FP10 CD 5 AR 4 PRtr

 87P 907 FS HNtr GNtr POtr

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 The chemical data are based on the fraction less than 2 mm in size.

 Fraction interpretation: FS, fine sand, 0.1-0.25 mm.

 Mineral interpretation: QZ, quartz; FK, potassium feldspar; FP, plagioclase feldspar; AR, weathered aggregate; CD, chalcedony;

 PR, pyroxene; TM, tourmaline; FE, iron oxides; HN, hornblende; GS, glass; GN, garnet; OP, opaques; PO, plant opal.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
Entisols 393

2. Permanent saturation with water and a reduced matrix in all

horizons below 25 cm from the mineral soil surface; or

3. In a layer above a densic, lithic, or paralithic contact or in a

layer at a depth between 40 and 50 cm below the mineral soil

surface, whichever is shallower, aquic conditions for some time

in normal years (or artificial drainage) and either:

a. A texture finer than loamy fine sand and, in 50 percent

or more of the matrix, either:

(1) Chroma of 0; or

(2) Chroma of 2 or less if there are redox

concentrations; or

(3) Chroma of 1 or less and a color value, moist, of 4 or

more if there are no redox concentrations; or

b. A texture of loamy fine sand or coarser and, in 50

percent or more of the matrix, either:

(1) Chroma of 0; or

(2) Hue of 10YR or redder, a color value, moist, of 4 or

more, and chroma of 1; or

(3) Hue of 10YR or redder and chroma of 2 or less if

there are redox concentrations; or

(4) Hue of 2.5Y or yellower and chroma of 3 or less if

there are distinct or prominent redox concentrations; or

(5) Hue of 2.5Y or yellower and chroma of 1; or

(6) Hue of 5GY, 5G, 5BG, or 5B; or

(7) Any color if it results from uncoated sand grains; or

c. Enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Key to Great Groups

LAA. Aquents that have sulfidic materials within 50 cm of

the mineral soil surface.

Sulfaquents, p. 403

LAB. Other Aquents that have, in all horizons at a depth

between 20 and 50 cm below the mineral soil surface, both an

n value of more than 0.7 and 8 percent or more clay in the fineearth fraction.

Hydraquents, p. 400

LAC. Other Aquents that have a cryic soil temperature

regime.

Cryaquents, p. 394

LAD. Other Aquents that have less than 35 percent (by

volume) rock fragments and a texture of loamy fine sand or

percent or more (by volume) fragments of diagnostic horizons

that are not arranged in any discernible order.

Arents, p. 403

LC. Other Entisols that have less than 35 percent (by volume)

rock fragments and a texture of loamy fine sand or coarser in all

layers (sandy loam lamellae are permitted) within the particle-size

control section.

Psamments, p. 432

LD. Other Entisols that do not have a densic, lithic, or

paralithic contact within 25 cm of the mineral soil surface and

have:

1. A slope of less than 25 percent; and

2. Either 0.2 percent or more organic carbon of Holocene

age at a depth of 125 cm below the mineral soil surface or

an irregular decrease in content of organic carbon from a

depth of 25 cm to a depth of 125 cm or to a densic, lithic, or

paralithic contact if shallower; and

3. A soil temperature regime:

a. That is warmer than cryic; or

b. That is cryic and the soil has:

(1) No gelic material; and

(2) Either a slope of less than 5 percent or less than

15 percent volcanic glass in the 0.02 to 2.0 mm

fraction in some part of the particle-size control

section.

Fluvents, p. 406

LE. Other Entisols.

Orthents, p. 420

Aquents

These are the wet Entisols. They may be in tidal marshes,

on deltas, on the margins of lakes where the soils are

continuously saturated with water, on flood plains along

streams where the soils are saturated at some time of the year,

or in areas of wet, sandy deposits. Many Aquents have bluish

or grayish colors and redoximorphic features. They may have

any temperature regime. Most of them formed in recent

sediments, and they support vegetation that tolerates

permanent or periodic wetness.

Definition

Aquents are the Entisols that have one or more of the

following:

1. Aquic conditions and sulfidic materials within 50 cm of

the mineral soil surface; or
394 Soil Taxonomy

coarser in all layers (sandy loam lamellae are permitted) within

the particle-size control section.

Psammaquents, p. 401

LAE. Other Aquents that have either 0.2 percent or more

organic carbon of Holocene age at a depth of 125 cm below the

mineral soil surface or an irregular decrease in content of

organic carbon from a depth of 25 cm to a depth of 125 cm or

to a densic, lithic, or paralithic contact if shallower.

Fluvaquents, p. 397

LAF. Other Aquents that have episaturation.

Epiaquents, p. 396

LAG. Other Aquents.

Endoaquents, p. 395

Cryaquents

These are the cold, wet soils in high mountains or of high

latitudes. Cryaquents are on flood plains, in depressional areas,

and in coastal marshes. Many are grayish and stratified. Those

in coastal marshes commonly have greenish to bluish hues.

Because they are both cold and wet, Cryaquents have low

potential for farming. The major areas of these soils in the

United States are in Alaska, where they are in coastal marshes,

on outwash plains, and on flood plains. The soils formed in

recent sediments and are extensive in Alaska south of the

permafrost zone. Most Cryaquents support mixed forest,

shrub, or grassy vegetation. Many are nearly level, and their

parent materials are typically Holocene or late-Pleistocene

sediments.

Definition

Cryaquents are the Aquents that:

1. Have a cryic soil temperature regime;

2. Do not have sulfidic materials within 50 cm of the mineral

soil surface;

3. Do not have, in all horizons at a depth between 20 and

50 cm below the mineral soil surface, both an n value of

more than 0.7 and 8 percent or more clay in the fine-earth

fraction.

Key to Subgroups

LACA. Cryaquents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Cryaquents

LACB. Other Cryaquents.

Typic Cryaquents

Definition of Typic Cryaquents

Typic Cryaquents are the Cryaquents that do not have,

throughout a cumulative thickness of 18 cm or more and

within a depth of 75 cm, one or more of the following:

1. A bulk density, in the fraction less than 2.0 mm in size, of

1.0 g/cm3 or less, measured at 33 kPa water retention, and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

2. Fragments coarser than 2.0 mm constituting more than 35

percent of the whole soil and cinders, pumice, and pumicelike

fragments making up more than 66 percent of these fragments;

or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more.

Description of Subgroups

Typic Cryaquents.—More variability in properties is

permitted in this subgroup than in most Typic subgroups

because the soils are both cold and wet. There are no

restrictions on particle size, organic carbon, and other

properties that are used to distinguish taxa in many places in

this taxonomy. These soils are of moderate extent in the United

States, occurring mostly on wet flood plains in Alaska and in

the high mountains of the Western States. Most of the Typic

Cryaquents are under their native vegetation and have a thin O

horizon.

Aquandic Cryaquents.—These soils have a layer in the

upper 75 cm that is 18 cm or more thick and is rich in

pyroclastics. The clays in this layer normally do not disperse

well and have a high pH-dependent charge. These soils are rare

in the United States and are known to occur only on wet flood

plains in Alaska.
Entisols 395

Endoaquents

Endoaquents are the Aquents that have an isofrigid, frigid, or

warmer temperature regime and endoaquic saturation. The

ground water fluctuates from a level near or above the soil

surface to about 100 cm below the soil surface and is

sometimes below 200 cm.

Many Endoaquents support either a deciduous or coniferous

forest. Some have been cleared and are used as cropland or

pasture. Generally, Endoaquents are nearly level, and their

parent materials are typically late-Pleistocene or Holocene

sediments.

Definition

Endoaquents are the Aquents that:

1. Do not have sulfidic materials within 50 cm of the mineral

soil surface;

2. Do not have a cryic soil temperature regime;

3. Have either an n value of 0.7 or less or less than 8 percent

clay in some or all horizons at a depth between 20 and 50 cm

below the mineral soil surface;

4. In some part of the particle-size control section, have

either:

a. A texture finer than loamy fine sand; or

b. 35 percent or more (by volume) rock fragments;

5. Have less than 0.2 percent organic carbon of Holocene age

at a depth of 125 cm below the mineral soil surface and a

regular decrease in content of organic carbon from a depth of

25 cm to a depth of 125 cm or to a densic, lithic, or paralithic

contact if shallower; and

6. Have endosaturation.

Key to Subgroups

LAGA. Endoaquents that have, within 100 cm of the mineral

soil surface, one or both of the following:

1. Sulfidic materials; or

2. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

value between 3.5 and 4.0.

Sulfic Endoaquents

LAGB. Other Endoaquents that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Endoaquents

LAGC. Other Endoaquents that have, in one or more

horizons within 100 cm of the mineral soil surface, an

exchangeable sodium percentage of 15 or more (or a sodium

adsorption ratio of 13 or more) for 6 or more months in normal

years.

Sodic Endoaquents

LAGD. Other Endoaquents that have, in one or more

horizons between either the Ap horizon or a depth of 25 cm

from the mineral soil surface, whichever is deeper, and a depth

of 75 cm, colors in 50 percent or more of the matrix as follows:

1. Hue of 2.5Y or redder, a color value, moist, of 6 or

more, and chroma of 3 or more; or

2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,

and chroma of 2 or more; or

3. Hue of 5Y and chroma of 3 or more; or

4. Hue of 5Y or redder and chroma of 2 or more if there

are no redox concentrations.

Aeric Endoaquents

LAGE. Other Endoaquents that have both:

1. An Ap horizon that has a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed)

or materials in the upper 15 cm that have these colors after

mixing; and

2. A base saturation (by NH4

OAc) of less than 50 percent

in some part within 100 cm of the mineral soil surface.

Humaqueptic Endoaquents

LAGF. Other Endoaquents that have either an Ap horizon

that has a color value, moist, of 3 or less and a color value, dry,

of 5 or less (crushed and smoothed) or materials in the upper

15 cm that have these colors after mixing.

Mollic Endoaquents

LAGG. Other Endoaquents.

Typic Endoaquents

Definition of Typic Endoaquents

Typic Endoaquents are the Endoaquents that:

1. Have, in one or more horizons between either the Ap

horizon or a depth of 25 cm from the mineral soil surface,

whichever is deeper, and a depth of 75 cm, colors in 50 percent

or more of the matrix as follows:

a. If there are redox concentrations, either:

(1) Hue of 2.5Y or redder, a color value, moist, of 6 or

more, and chroma of 2 or less; or

(2) Hue less yellow and less red than 5Y; or

(3) Hue of 5Y and chroma of 2 or less; or

b. Chroma of 1 or less;
396 Soil Taxonomy

2. Have an Ap horizon that has a color value, moist, of 4 or

more or a color value, dry, of 6 or more (crushed and

smoothed) and materials in the upper 15 cm that have one or

more of these colors after mixing;

3. Do not have a lithic contact within 50 cm of the mineral

soil surface;

4. Do not have, within 100 cm of the mineral soil surface,

either:

a. Sulfidic materials; or

b. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

value between 3.5 and 4.0; and

5. Do not have, in one or more horizons within 100 cm of the

mineral soil surface, an exchangeable sodium percentage of 15

or more (or a sodium adsorption ratio of 13 or more) for 6 or

more months in normal years.

Description of Subgroups

Typic Endoaquents.—The central concept or Typic

subgroup of Endoaquents is centered on moderately deep or

deeper soils with low chroma throughout the layer at a depth

between 25 and 75 cm below the mineral soil surface. These

soils have an Ap horizon that has a color value, moist, of 4 or

more or a color value, dry, of 6 or more (crushed and

smoothed) or have materials in the upper 15 cm that have these

colors after mixing. The soils do not have, within 100 cm of

the mineral soil surface, a horizon with an exchangeable

sodium percentage of 15 or more, sulfidic materials, or any

horizon 15 cm or more thick that has all of the characteristics

of a sulfuric horizon, except that it has a pH value between 3.5

and 4.0.

Soils that have a shallow lithic contact are excluded from

the Typic subgroup. Typic Endoaquents are of small extent in

the United States. They are widely distributed, mostly in the

humid parts of the country.

Aeric Endoaquents.—These soils are like Typic

Endoaquents, but they have some subhorizon at a depth

between 25 and 75 cm in which hue is redder or chroma is

higher than is typical for Endoaquents or there are no redox

concentrations. These colors are thought to reflect a level of

ground water that is not so shallow as the level in the Typic

subgroup or is shallow for a shorter period. These soils are of

small extent in the United States. They are widely distributed,

mostly in the humid parts of the country.

Humaqueptic Endoaquents.—These soils are like Typic

Endoaquents, but they have an Ap horizon that has a color

value, moist, of 3 or less and a color value, dry, of 5 or less

(crushed and smoothed) or have materials in the upper 15 cm

that have these colors after mixing. These soils are considered

intergrades to Humaquepts. They are mainly in the northcentral part of the United States. They are of small extent in

the United States.

Lithic Endoaquents.—These soils are like Typic

Endoaquents, but they have a lithic contact within 50 cm of the

soil surface. They are of small extent in the United States.

Mollic Endoaquents.—These soils are like Typic

Endoaquents, but they have an Ap horizon that has a color

value, moist, of 3 or less and a color value, dry, of 5 or less

(crushed and smoothed) or have materials in the upper 15 cm

that have these colors after mixing. These soils are considered

intergrades to Aquolls. They are mainly in the north-central

part of the United States.

Sodic Endoaquents.—These soils are like Typic

Endoaquents, but they have, within 100 cm of the mineral soil

surface, an exchangeable sodium percentage of 15 or more for

6 or more months in normal years. These soils are of small

extent and are known to occur only in tidal-influenced areas on

the gulf coast in the United States. They support mostly grassy

vegetation.

Sulfic Endoaquents.—These soils are like Typic

Endoaquents, but they have sulfidic materials at a depth

between 50 and 100 cm below the mineral soil surface. These

soils are not known to occur in the United States. The subgroup

has been established for use in other countries.

Epiaquents

Epiaquents are the Aquents that have an isofrigid, frigid,

isomesic, mesic, or warmer temperature regime and epiaquic

saturation. The ground water is perched during some periods

in these soils and fluctuates from a level near or above the soil

surface in wet seasons. The water table does not occur in the

upper 200 cm during some periods in some of these soils.

Many Epiaquents support either a deciduous or a coniferous

forest. Some have been cleared and are used as cropland or

pasture. Generally, Epiaquents are nearly level, and their

parent materials are typically late-Pleistocene or Holocene

sediments.

Definition

Epiaquents are the Aquents that:

1. Do not have sulfidic materials within 50 cm of the mineral

soil surface;

2. Do not have a cryic soil temperature regime;

3. Have either an n value of 0.7 or less or less than 8 percent

clay in some or all horizons at a depth between 20 and 50 cm

below the mineral soil surface;

4. In some part of the particle-size control section, have

either:

a. A texture finer than loamy fine sand; or

b. 35 percent or more (by volume) rock fragments;

5. Have less than 0.2 percent organic carbon of Holocene age

at a depth of 125 cm below the mineral soil surface and a
Entisols 397

regular decrease in content of organic carbon from a depth of 25

cm to a depth of 125 cm or to a densic, lithic, or paralithic contact

if shallower; and

6. Have episaturation.

Key to Subgroups

LAFA. Epiaquents that have, in one or more horizons between

either the Ap horizon or a depth of 25 cm from the mineral soil

surface, whichever is deeper, and a depth of 75 cm, colors in 50

percent or more of the matrix as follows:

1. Hue of 2.5Y or redder, a color value, moist, of 6 or more,

and chroma of 3 or more; or

2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,

and chroma of 2 or more; or

3. Hue of 5Y and chroma of 3 or more; or

4. Chroma of 2 or more if there are no redox

concentrations.

Aeric Epiaquents

LAFB. Other Epiaquents that have both:

1. An Ap horizon that has a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed)

or materials in the upper 15 cm that have these colors after

mixing; and

2. A base saturation (by NH4

OAc) of less than 50 percent

in some part within 100 cm of the mineral soil surface.

Humaqueptic Epiaquents

LAFC. Other Epiaquents that have either an Ap horizon that

has a color value, moist, of 3 or less and a color value, dry, of 5

or less (crushed and smoothed) or materials in the upper 15 cm

that have these colors after mixing.

Mollic Epiaquents

LAFD. Other Epiaquents.

Typic Epiaquents

Definition of Typic Epiaquents

Typic Epiaquents are the Epiaquents that have:

1. In one or more horizons between either the Ap horizon or

a depth of 25 cm from the mineral soil surface, whichever is

deeper, and a depth of 75 cm, colors in 50 percent or more of

the matrix as follows:

a. If there are redox concentrations, either:

(1) Hue of 2.5Y or redder, a color value, moist, of 6 or

more, and chroma of 2 or less; or

(2) Hue less yellow or less red than 5Y; or

(3) Hue of 5Y and chroma of 2 or less; or

b. Chroma of 1 or less; and

2. An Ap horizon that has a color value, moist, of 4 or more or

a color value, dry, of 6 or more (crushed and smoothed) or

materials in the upper 15 cm that have these colors after

mixing.

Description of Subgroups

Typic Epiaquents.—The Typic subgroup of Epiaquents is

centered on soils with low chroma throughout the layer at a

depth between 25 and 75 cm below the mineral soil surface.

These soils have an Ap horizon that has a color value, moist, of

4 or more or a color value, dry, of 6 or more (crushed and

smoothed) or have materials in the upper 15 cm that have these

colors after mixing. The soils are of small extent in the United

States. They are widely distributed, mostly in the humid parts

of the country.

Aeric Epiaquents.—These soils are like Typic Epiaquents,

but they have some subhorizon at a depth between 25 and 75

cm in which hue is redder or chroma is higher than is typical

for Epiaquents or there are no redox concentrations. These

colors are thought to reflect a level of ground water that is not

so shallow as the level in the Typic subgroup or is shallow for a

shorter period. These soils are of small extent in the United

States. They are widely distributed, mostly in the humid parts

of the country.

Humaqueptic Epiaquents.—These soils are like Typic

Epiaquents, but they have an Ap horizon that has a color value,

moist, of 3 or less and a color value, dry, of 5 or less (crushed

and smoothed) or have materials in the upper 15 cm that have

these colors after mixing. These soils are considered

intergrades to Humaquepts. They are of small extent in the

United States. They occur mainly in the north-central part of

the country.

Mollic Epiaquents.—These soils are like Typic Epiaquents,

but they have an Ap horizon that has a color value, moist, of 3

or less and a color value, dry, of 5 or less (crushed and

smoothed) or have materials in the upper 15 cm that have these

colors after mixing. These soils are considered intergrades to

Aquolls. They are mainly in the north-central part of the

United States.

Fluvaquents

Fluvaquents are primarily the stratified, wet soils on flood

plains and deltas of middle and low latitudes. The stratification

reflects deposition of sediments under changing currents and in

shifting channels. The sediments are of Holocene age and have

a relatively high content of organic carbon at a considerable

depth when compared with many other wet, mineral soils. The

materials have dried or have partially dried from time to time

as they accumulated, and the n values are low. These soils are

extensive along large rivers, particularly in humid areas. The

ground water fluctuates from a level near or above the soil

surface to about 100 cm below the soil surface and is
398 Soil Taxonomy

sometimes below 200 cm. Generally, Fluvaquents are nearly

level.

Many Fluvaquents support either a deciduous or a

coniferous forest. Some have been cleared and protected from

flooding and are used as cropland or pasture.

Definition

Fluvaquents are the Aquents that:

1. Have a soil temperature regime warmer than cryic;

2. Have an n value of 0.7 or less or have less than 8 percent

clay in some or all subhorizons between depths of 20 and 50

cm;

3. Have either a texture finer than loamy fine sand or 35

percent or more (by volume) rock fragments in some or in all

parts of the particle-size control section;

4. Have a content of Holocene-age organic carbon that

decreases irregularly with increasing depth below 25 cm or that

remains more than 0.2 percent to a depth of 125 cm (thin strata

of sand may have less organic carbon if the finer sediments at a

depth of 125 cm or below have 0.2 percent organic carbon or

more); and

5. Do not have sulfidic materials within 50 cm of the mineral

soil surface.

Key to Subgroups

LAEA. Fluvaquents that have, within 100 cm of the mineral

soil surface, one or both of the following:

1. Sulfidic materials; or

2. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

value between 3.5 and 4.0.

Sulfic Fluvaquents

LAEB. Other Fluvaquents that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Fluvaquents

LAEC. Other Fluvaquents that have a buried layer of organic

soil materials, 20 cm or more thick, that has its upper boundary

within 100 cm of the mineral soil surface.

Thapto-Histic Fluvaquents

LAED. Other Fluvaquents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm of

the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Fluvaquents

LAEE. Other Fluvaquents that have, in one or more horizons

between either the Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and a depth of 75

cm, colors in 50 percent or more of the matrix as follows:

1. Hue of 2.5Y or redder, a color value, moist, of 6 or

more, and chroma of 3 or more; or

2. Hue of 2.5Y or redder, a color value, moist, of 5 or less,

and chroma of 2 or more; or

3. Hue of 5Y and chroma of 3 or more; or

4. Chroma of 2 or more if there are no redox

concentrations.

Aeric Fluvaquents

LAEF. Other Fluvaquents that have both:

1. An Ap horizon that has a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed)

or materials in the upper 15 cm that have these colors after

mixing; and

2. A base saturation (by NH4OAc) of less than 50 percent

in some part within 100 cm of the mineral soil surface.

Humaqueptic Fluvaquents

LAEG. Other Fluvaquents that have either an Ap horizon

that has a color value, moist, of 3 or less and a color value, dry,

of 5 or less (crushed and smoothed) or materials in the upper

15 cm that have these colors after mixing.

Mollic Fluvaquents

LAEH. Other Fluvaquents.

Typic Fluvaquents
Entisols 399

Definition of Typic Fluvaquents

Typic Fluvaquents are the Fluvaquents that:

1. Have, in all horizons between either the Ap horizon

or a depth of 25 cm from the mineral soil surface, whichever

is deeper, and a depth of 75 cm, colors in 50 percent or more

of the matrix as follows:

a. If there are redox concentrations, either:

(1) Hue of 2.5Y or redder, a color value, moist, of 6 or

more, and chroma of 2 or less; or

(2) Hue less yellow and less red than 5Y; or

(3) Hue of 5Y and chroma of 2 or less; or

b. Chroma of 1 or less;

2. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

4. Have an Ap horizon that has a color value, moist, of 4 or

more or a color value, dry, of 6 or more (crushed and

smoothed) or materials in the upper 15 cm that have these

colors after mixing;

5. Do not have a buried layer of organic soil materials, 20 cm

or more thick, that has its upper boundary within 100 cm of the

soil surface; and

6. Do not have, within 100 cm of the mineral soil surface,

either:

a. Sulfidic materials; or

b. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

value between 3.5 and 4.0.

Description of Subgroups

Typic Fluvaquents.—The concept of Typic Fluvaquents is

centered almost exclusively on very young water-laid deposits

that are mostly in wet areas on flood plains. These soils have

fine strata at a shallow depth, or they show too little evidence

of alteration to have a cambic horizon. Redoximorphic features

in the soils extend downward from a point very close to the

surface, and the water table is at or close to the surface most of

the year unless artificial drainage has been provided. The soils

do not have a layer of fine pyroclastic materials that is as thick

as or thicker than 18 cm and that is within 75 cm of the

surface. They do not have a buried Histosol or a buried histic

epipedon within a depth of 100 cm. They do not have a dark

surface horizon or, if one occurs, it is thin. These

characteristics were selected for the Typic subgroup not

because they are most common but because they represent the

wettest and most recent Fluvaquents. As horizons begin to

develop, the soils are classified in intergrade subgroups that

indicate their nature.

Most Typic Fluvaquents are nearly level, and their parent

materials are Holocene sediments. Many support forest

vegetation, but some support shrub or grassy vegetation. Some

areas have been cleared, drained, and protected from flooding

and are used as cropland or pasture.

Aeric Fluvaquents.—These soils are like Typic

Fluvaquents, but they have some subhorizon at a depth between

25 and 75 cm in which chroma is higher than that of soils in

the Typic subgroup, reflecting a level of ground water that is

not so shallow as in the Typic subgroup or is shallow a shorter

period.

Most Aeric Fluvaquents are nearly level. Most support forest

vegetation, but some support shrub or grassy vegetation. Many

areas have been cleared, drained, and protected from flooding

and are used as cropland or pasture.

Aquandic Fluvaquents.—These soils are similar to Typic

Fluvaquents, but they have a layer of pyroclastic materials that

is 18 cm or more thick and that is in the upper 75 cm. In the

United States, these soils occur in western Washington but are

not extensive. Most Aquandic Fluvaquents are nearly level and

support forest vegetation. Many areas have been cleared,

drained, and protected from flooding and are used as hayland

or pasture.

Humaqueptic Fluvaquents.—These soils have a surface
400 Soil Taxonomy

horizon that has the color and other properties of an umbric

epipedon, except for thickness. In the United States, these soils

occur on nearly level flood plains in areas where Ultisols or

other soils that have low base saturation are the dominant

upland soils. Most Humaqueptic Fluvaquents are forested.

Some are pastured, and a few have been drained and are

cultivated. Humaqueptic Fluvaquents are not extensive soils.

Mollic Fluvaquents.—These soils have a surface horizon

that has the color and other properties of a mollic epipedon,

except for thickness. The epipedon is less than 25 cm thick.

These soils are otherwise like Typic Fluvaquents in defined

properties. They have high base saturation, and some of them

are calcareous. Many of them are on flood plains along streams

in areas where Mollisols are extensive soils on uplands. Mollic

Fluvaquents are moderately extensive soils in the United

States. Nearly all have been cleared, drained, and protected

from flooding and are used as cropland or pasture.

Sulfic Fluvaquents.—These soils have sulfidic materials at

a depth between 50 and 100 cm below the mineral soil surface.

They are of small extent in the States of Washington and

California in the United States.

Thapto-Histic Fluvaquents.—These soils are similar to

Typic Fluvaquents, but they have a buried Histosol or a buried

histic epipedon that has its upper boundary within 100 cm of

the soil surface. Many Thapto-Histic Fluvaquents in the United

States formed within the last 100 to 150 years as a result of

erosion on hillsides and the deposition of sediment on a

Histosol. In the United States, Thapto-Histic Fluvaquents are of

moderately small extent and in many areas are farmed or

pastured. In other parts of the world, these soils occur near

streams in coastal marshes.

Vertic Fluvaquents.—These soils are like Typic Fluvaquents,

but they either have cracks and slickensides or wedge-shaped

aggregates or have a linear extensibility of 6.0 or more within 100

cm of the mineral soil surface. These soils are mainly in

backswamps on flood plains where water stands for long

periods unless the soils have been artificially drained. Because

there are no restrictions on the color value of Vertisols, Vertic

Fluvaquents are permitted, but not required, to have a lower

color value than the soils of the Typic subgroup. Vertic

Fluvaquents have fine strata near the surface. They are of

moderate extent in the United States. They are nearly level and

support forest, shrub, or grassy vegetation. Many areas have

been cleared, drained, and protected from flooding and are

used as cropland or pasture.

Hydraquents

These are loamy and clayey soils in tidal marshes that are

permanently saturated with water. Hydraquents formed in

sediments that were deposited under water and have a low bulk

density, commonly about 0.6 g/cc, and a high water content,

commonly more than 100 percent of the dry weight. If the soils

are drained, the loss of water is irreversible and the bulk

density increases as water is withdrawn. The soils deposited in

tidal marshes retain their high water content. Hydraquents

never have been dry, and consequently the bulk density is low

and the water content is very high. The soils typically have

reduced matrices, and their colors mostly are bluish gray to

greenish gray and change to shades of brown when the soils

are exposed to air. A color change normally can be seen within

a matter of seconds or a few minutes but may not be complete

until some weeks have passed.

Because the water content is high, the soil strength is low,

commonly too low for the soils to support grazing animals.

Nevertheless, some Hydraquents may be grazed if the water

content in the surface layer is relatively low or if vegetation

adds strength to the surface layer.

Hydraquents are extensive in tidal marshes. In the United

States, they are largely confined to the Atlantic and gulf coasts,

although a few are on the northern Pacific coast and near San

Francisco Bay.

Definition

Hydraquents are the Aquents that:

1. Do not have sulfidic materials within 50 cm of the mineral

soil surface; and

2. Have, in all subhorizons at a depth between 20 and 50 cm

below the mineral soil surface, both an n value of more than

0.7 and 8 percent or more clay.

Key to Subgroups

LABA. Hydraquents that have, within 100 cm of the mineral

soil surface, one or both of the following:

1. Sulfidic materials; or

2. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

value between 3.5 and 4.0.

Sulfic Hydraquents

LABB. Other Hydraquents that have, in one or more

horizons within 100 cm of the mineral soil surface, an

exchangeable sodium percentage of 15 or more (or a sodium

adsorption ratio of 13 or more) for 6 or more months in normal

years.

Sodic Hydraquents

LABC. Other Hydraquents that have a buried layer of organic

soil materials, 20 cm or more thick, that has its upper boundary

within 100 cm of the mineral soil surface.

Thapto-Histic Hydraquents

LABD. Other Hydraquents.

Typic Hydraquents
Entisols 401

Definition of Typic Hydraquents

Typic Hydraquents are the Hydraquents that:

1. Do not have, within 100 cm of the mineral soil surface, one

or both of the following:

a. Sulfidic materials; or

b. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

value between 3.5 and 4.0;

2. Do not have, in one or more horizons within 100 cm of the

mineral soil surface, an exchangeable sodium percentage of 15

or more (or a sodium adsorption ratio of 13 or more) for 6 or

more months in normal years; and

3. Do not have a buried layer of organic soil materials, 20 cm

or more thick, that has its upper boundary within 100 cm of the

mineral soil surface.

Description of Subgroups

Typic Hydraquents.—These are the Hydraquents that,

within 100 cm of the soil surface, do not have any horizon 15

cm or more thick that has all of the characteristics of a sulfuric

horizon, except that it has a pH value between 3.5 and 4.0, and

do not have sulfidic materials or an exchangeable sodium

percentage of 15 or more. These soils have neither a buried

Histosol nor a buried histic epipedon that has its upper

boundary within 100 cm of the mineral soil surface.

Typic Hydraquents are of moderate extent in the United

States. They are nearly level and support swamp forest, shrub,

or grassy vegetation. Most of these soils are used as wildlife

habitat.

Sodic Hydraquents.—These are the Hydraquents that,

within 100 cm of the soil surface, have an exchangeable

sodium percentage of 15 or more. They do not have, within

100 cm of the soil surface, any sulfidic materials or any

horizon 15 cm or more thick that has a pH value of 3.5 to 4.0

and any other characteristics of a sulfuric horizon.

Sodic Hydraquents are of small extent in the United States,

occurring mostly in the Mississippi delta and westward along

the gulf coast. They are nearly level and support mostly grassy

and forb vegetation. Most of these soils are used as wildlife

habitat.

Sulfic Hydraquents.—These are the Hydraquents that,

within 100 cm of the soil surface, have sulfidic materials or a

horizon 15 cm or more thick that has all of the characteristics

of a sulfuric horizon, except that it has a pH value between 3.5

and 4.0. The soils are of small extent in the United States.

They are nearly level and support mostly grassy and forb

vegetation. Most of these soils are used as wildlife habitat.

Thapto-Histic Hydraquents.—These soils are like Typic

Hydraquents, but they have a buried Histosol or a buried histic

epipedon that has its upper boundary within 100 cm of the

mineral soil surface. Within 100 cm of the soil surface, they do

not have any sulfidic materials or any horizon 15 cm or more

thick that has a pH value of 3.5 to 4.0 and any other

characteristics of a sulfuric horizon and do not have an

exchangeable sodium percentage of 15 or more.

Thapto-Histic Hydraquents are of small extent in the United

States. They are nearly level and support swamp forest, shrub,

or grassy vegetation. Most of these soils are used as wildlife

habitat.

Psammaquents

These Aquents have a sandy texture and commonly are gray,

with or without redox concentrations. The water table is at or

near the surface for long periods unless artificial drainage has

been provided. Most of these soils formed in late-Pleistocene to

recent sediments. Most do not have distinctive features, but a

few have a B horizon that is similar to the one in Spodosols but

is too weakly developed to be a spodic horizon. Others show

some darkening and accumulation of organic matter in an A

horizon but too little for a mollic or umbric epipedon.

Definition

Psammaquents are the Aquents that:

1. Do not have sulfidic materials within 50 cm of the mineral

soil surface;

2. Do not have, in any horizon at a depth between 20 and 50

cm below the mineral soil surface, both an n value of more

than 0.7 and 8 percent or more clay in the fine-earth fraction;

3. Do not have a cryic soil temperature regime;

4. Have less than 35 percent (by volume) rock fragments and

a texture of loamy fine sand or coarser in all layers within the

control section for the family particle-size class.

Key to Subgroups

LADA. Psammaquents that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Psammaquents

LADB. Other Psammaquents that have, in one or more

horizons within 100 cm of the mineral soil surface, an

exchangeable sodium percentage of 15 or more (or a sodium

adsorption ratio of 13 or more) for 6 or more months in normal

years.

Sodic Psammaquents

LADC. Other Psammaquents that have a horizon, 5 cm or

more thick, either below an Ap horizon or at a depth of 18 cm

or more from the mineral soil surface, whichever is deeper, that

has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or
402 Soil Taxonomy

2. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Psammaquents

LADD. Other Psammaquents that have both:

1. An Ap horizon that has a color value, moist, of 3 or less

and a color value, dry, of 5 or less (crushed and smoothed)

or materials in the upper 15 cm that have these colors after

mixing; and

2. A base saturation (by NH4OAc) of less than 50 percent

in some part within 100 cm of the mineral soil surface.

Humaqueptic Psammaquents

LADE. Other Psammaquents that have either an Ap horizon

that has a color value, moist, of 3 or less and a color value, dry,

of 5 or less (crushed and smoothed) or materials in the upper

15 cm that have these colors after mixing.

Mollic Psammaquents

LADF. Other Psammaquents.

Typic Psammaquents

Definition of Typic Psammaquents

Typic Psammaquents are the Psammaquents that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Have an Ap horizon that has a color value, moist, of 4 or

more or a color value, dry, of 6 or more (crushed and

smoothed) and materials in the upper 15 cm that have these

colors after mixing;

3. Do not have a horizon, 5 cm or more thick, either below

an Ap horizon or at a depth of 18 cm or more from the mineral

soil surface, whichever is deeper, that has one or more of the

following:

a. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

b. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

c. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon; and

4. Do not have, in one or more horizons within 100 cm of the

mineral soil surface, an exchangeable sodium percentage of 15

or more (or a sodium adsorption ratio of 13 or more) for 6 or

more months in normal years.

Description of Subgroups

Typic Psammaquents.—The central concept or Typic

subgroup of Psammaquents is fixed on moderately deep or

deeper soils that have an Ap horizon that has a color value,

moist, of 4 or more or a color value, dry, of 6 or more or that

have materials in the upper 15 cm that have these colors after

mixing. These soils do not have an exchangeable sodium

percentage of 15 or more within 100 cm of the mineral soil

surface. They do not have a horizon that approaches the

criteria for a spodic horizon. They are saturated with water part

of the time. A range in the length of the periods of saturation is

permitted.

Typic Psammaquents are locally extensive in the United

States, particularly on the coastal plains and in areas covered

by Wisconsinan outwash. Few of them are farmed. Most are

used for grazing or forest, depending on their natural

vegetation.

Humaqueptic Psammaquents.—These soils are like Typic

Psammaquents, but the A or Ap horizon resembles an umbric

epipedon but is less than 25 cm thick. The base saturation (by

NH4

OAc) is less than 50 percent in some part of the soils

within the upper 100 cm. In the United States, these soils are

of small extent. Most support mixed forest vegetation. Some

have been cleared and drained and are used as cropland,

hayland, or pasture.

Lithic Psammaquents.—These soils are like Typic

Psammaquents, but they have a lithic contact within 50 cm of

the soil surface. They are of small extent in the United States.

Mollic Psammaquents.—These soils are like Typic

Psammaquents, but the A or Ap horizon resembles a mollic

epipedon but is less than 25 cm thick. They have a base

saturation of 50 percent or more in all horizons within 100 cm

of the soil surface. These soils are moderately extensive in the

United States, mostly in areas of Wisconsinan outwash. The A

horizon generally is black or very dark gray but is too thin to

meet the requirements for a mollic epipedon, which in sands

must be at least 25 cm thick. Many of these soils support

hardwood forest, and some support grass or grass and widely

scattered trees. Mollic Psammaquents are used for grazing or

forest, depending on their natural vegetation. Some of the soils

have been cleared and drained and are used as cropland or

pasture.

Sodic Psammaquents.—These soils have, in one or more

horizons within 100 cm of the mineral soil surface, an

exchangeable sodium percentage of 15 or more. They are not

extensive in the United States. They are mostly on the low

coastal plains in Texas. Most of them support their native

vegetation of grasses and forbs and are used as rangeland.

Spodic Psammaquents.—These soils have a weak

accumulation of amorphous materials, mostly humus. They are

not extensive in the United States. They are in Florida, on the

low coastal plains along the Atlantic Ocean and the Gulf of

Mexico. Most of them still have their native vegetation of
Entisols 403

forest or shrubs and grasses. Some have been cleared and

drained and are used as cropland or pasture.

Sulfaquents

These are the Aquents that have an appreciable amount of

sulfides close to the mineral soil surface and have few or no

carbonates. The sulfides are close enough to the surface for the

soils to become extremely acid and virtually sterile if drained.

These soils are largely restricted to coastal marshes where the

water is brackish. Tidal marshes at the mouth of rivers

normally have areas of these soils unless the river sediments

are rich in carbonates. Coastal marshes that are not near rivers

also may have areas of these soils if storms periodically flood

them with salt water.

Sulfaquents are permanently saturated at or near the

surface, and many are nearly neutral in reaction. The n value

typically is high, commonly more than 1 in most horizons. A

histic epipedon composed of organic soil materials is common.

These soils can have any mineral particle-size class, but those

with less than 8 percent clay are not considered typical. If the

soils are drained, the sulfides oxidize and the soils change

rapidly to Sulfaquepts.

Sulfaquents commonly are not used as cropland, but some

are used for the production of rice. The areas used for rice are

kept flooded at all times, except for a very brief period while

the crop is harvested.

Sulfaquents are extensive along coasts and bays from the

Equator to high latitudes. They are moderately extensive on the

east coast of the United States, where they border the Atlantic

Ocean in areas not protected by barrier islands.

Definition

Sulfaquents are the Aquents that have sulfidic materials

within 50 cm of the mineral soil surface.

Key to Subgroups

LAAA. Sulfaquents that have, in some horizons at a depth

between 20 and 50 cm below the mineral soil surface, either or

both:

1. An n value of 0.7 or less; or

2. Less than 8 percent clay in the fine-earth fraction.

Haplic Sulfaquents

LAAB. Other Sulfaquents that have a histic epipedon.

Histic Sulfaquents

LAAC. Other Sulfaquents that have a buried layer of organic

soil materials, 20 cm or more thick, that has its upper boundary

within 100 cm of the mineral soil surface.

Thapto-Histic Sulfaquents

LAAD. Other Sulfaquents.

Typic Sulfaquents

Definition of Typic Sulfaquents

Typic Sulfaquents are the Sulfaquents that:

1. Do not have, in one or more horizons at a depth between 20

and 50 cm below the mineral soil surface, either or both:

a. Less than 8 percent clay in the fine-earth fraction; or

b. An n value of 0.7 or less;

2. Do not have a histic epipedon;

3. Do not have a buried layer of organic soil materials, 20 cm or

more thick, that has its upper boundary within 100 cm of the

mineral soil surface.

Description of Subgroups

Typic Sulfaquents.—The central concept or Typic subgroup

of Sulfaquents is fixed on soils that have, in all horizons at a

depth between 20 and 50 cm below the mineral soil surface,

both an n value of more than 0.7 and 8 percent or more clay in

the fine-earth fraction. These soils do not have a histic

epipedon or a buried histic epipedon. They are extensive in the

coastal marshes along the Atlantic seaboard but are not

extensive elsewhere in the United States. They are nearly level

and support mostly grassy and forb vegetation. Most of the

soils are used as wildlife habitat.

Haplic Sulfaquents.—These are the Sulfaquents that have,

in one or more horizons at a depth between 20 and 50 cm

below the mineral soil surface, either or both less than 8

percent clay in the fine-earth fraction or an n value of 0.7 or

less. These soils are of small extent in the United States. They

are nearly level and support mostly grassy and forb vegetation.

Most of these soils are used as wildlife habitat.

Histic Sulfaquents.—These soils are like Typic

Sulfaquents, but they have a histic epipedon. They are of small

extent in the United States. They are nearly level and support

mostly grassy and forb vegetation. Most of these soils are used

as wildlife habitat.

Thapto-Histic Sulfaquents.—These are the Sulfaquents

that have a buried Histosol or a buried histic epipedon with its

upper boundary within 100 cm of the soil surface. These soils have

both n values of more than 0.7 and 8 or more percent clay in the 

fine-earth fraction. They are in New Jersey, Maryland, and Delaware.

Arents

These are the Entisols that do not have horizons because

they have been deeply mixed by plowing, spading, or other

methods of moving by humans. The soils retain fragments that

can be identified as parts of a former spodic or argillic horizon,
404 Soil Taxonomy

a duripan, and so on, but the fragments do not themselves form

horizons. Rather, they are scattered through the soils and are

mixed with the materials of other horizons. Some of these soils

are the result of deliberate soil modification intended to break

or remove a pan. Some are the result of replacing the soil

profile after strip-mining. Others have resulted from cuts and

fills made to shape the surface or even from the accident of

location in an area of intensive bombardment during a war.

Arents are not extensive in the United States. Their area is

increasing, however, because of increased use of modern power

machinery to modify soils for high-intensity crop production.

Arents form a unique suborder in that there are no Typic

subgroups. Subgroups of Arents are intergrades to other orders,

suborders, or great groups, according to the nature of the

fragments that can be identified. The Arents that do not meet

other subgroup criteria are assigned to the Haplic subgroup.

Definition

Arents are the Entisols that:

1. Have 3 percent or more, by volume, fragments of diagnostic

horizons in one or more subhorizons at a depth between 25 and

100 cm below the soil surface, and the fragments are not

arranged in a discernible order; and

2. Do not have, within 50 cm of the mineral soil surface, aquic

conditions; and

a. The colors defined for Aquents; or

b. Sulfidic materials; or

c. A positive reaction to alpha,alpha-dipyridyl when the soil

is not being irrigated.

Key to Great Groups

LBA. Arents that have an ustic moisture regime.

Ustarents, p. 405

LBB. Other Arents that have a xeric moisture regime.

Xerarents, p. 406

LBC. Other Arents that have an aridic (or torric) moisture

regime.

Torriarents, p. 404

LBD. Other Arents.

Udarents, p. 404

Torriarents

These are the Arents of arid regions. They have an aridic (or

torric) moisture regime. Generally, they are neutral or more

alkaline, and many are calcareous. Many have gentle slopes.

Most have been modified for irrigated agriculture. Torriarents

are extensive in California but occur throughout the Western

United States.

Definition

Torriarents are the Arents that have an aridic soil moisture

regime.

Key to Subgroups

LBCA. Torriarents that have, in one or more horizons within

100 cm of the mineral soil surface, 3 percent or more

fragments of a natric horizon.

Sodic Torriarents

LBCB. Other Torriarents that have, within 100 cm of the

mineral soil surface, 3 percent or more fragments of a duripan

or a petrocalcic horizon;

Duric Torriarents

LBCC. Other Torriarents.

Haplic Torriarents

Description of Subgroups

Haplic Torriarents.—The Haplic subgroup of Torriarents

is centered on soils that have 3 percent or more fragments of an

argillic or cambic horizon. These soils are permitted to have

fragments of any diagnostic horizon, but they cannot have, in

any horizon within 100 cm of the mineral soil surface,

fragments of a duripan or a petrocalcic or natric horizon. Many

of the soils have gentle slopes. Most have been modified for

irrigated agriculture. Haplic Torriarents are used as irrigated

cropland. They are of moderately small extent. They are mostly

in California but occur throughout the Western United States.

Duric Torriarents.—The Duric subgroup of Torriarents is

centered on soils that have, in some horizon within 100 cm of

the mineral soil surface, 3 percent or more fragments of a

duripan or a petrocalcic horizon. Many of these soils have

gentle slopes. Most have been modified for irrigated

agriculture. Duric Torriarents are used as irrigated cropland.

They are of moderate extent. They are mostly in California but

occur throughout the Western United States.

Sodic Torriarents.—The Sodic subgroup of Torriarents is

centered on soils that have, in some horizon within 100 cm of

the mineral soil surface, 3 percent or more fragments of a

natric horizon. Many of these soils have gentle slopes. Most

have been modified for irrigated agriculture. Sodic Torriarents

are used as irrigated cropland. They are of small extent. They

are known to occur only in California in the United States.

Udarents

These are the Arents of moist regions. They have a udic

moisture regime. Many have gentle slopes. Many have been

modified in the process of strip-mining. The top part of the soil

profile was removed and then replaced after the mining was
Entisols 405

completed. Some of these soils have a densic contact with

compacted layers of soil materials. Some formed in fill

material. Udarents are moderately extensive in the United

States. They are used mostly as pasture, but some are used as

woodland, cropland, or homesites.

Definition

Udarents are the Arents that have a udic soil moisture

regime.

Key to Subgroups

LBDA. Udarents that have 3 percent or more fragments of an

argillic horizon in some horizon within 100 cm of the mineral

soil surface and have a base saturation (by sum of cations) of

35 percent or more in all parts within 100 cm of the mineral

soil surface.

Alfic Udarents

LBDB. Other Udarents that have 3 percent or more

fragments of an argillic horizon in some horizon within 100

cm of the mineral soil surface.

Ultic Udarents

LBDC. Other Udarents that have 3 percent or more

fragments of a mollic epipedon in some horizon within 100 cm

of the mineral soil surface and have a base saturation (by sum

of cations) of 35 percent or more in all parts within 100 cm of

the mineral soil surface.

Mollic Udarents

LBDD. Other Udarents.

Haplic Udarents

Description of Subgroups

Haplic Udarents.—The Haplic subgroup of Udarents is

centered on soils that have 3 percent or more fragments of a

cambic horizon in some horizon within 100 cm of the mineral

soil surface. These soils are permitted to have fragments of

other diagnostic horizons, but they cannot have, in any horizon

within 100 cm of the mineral soil surface, 3 percent or more

fragments of an argillic horizon. They cannot have 3 percent or

more fragments of a mollic epipedon unless some horizon

within 100 cm of the mineral soil surface has a base saturation

of less than 35 percent. Commonly, these soils have gentle

slopes. They formed in a number of ways. Some have been

modified in the process of strip-mining. The top part of the soil

profile was removed and then replaced after the mining was

completed. Some of the soils have a densic contact with

compacted layers of soil materials. Haplic Udarents are of

small extent in the United States.

Alfic Udarents.—The Alfic subgroup of Udarents is fixed

on soils that have 3 percent or more fragments of an argillic

horizon in some horizon and have a base saturation (by sum of

cations) of 35 percent or more in all parts within 100 cm of the

mineral soil surface. These soils are permitted to have

fragments of other diagnostic horizons. Many of the soils have

gentle slopes. Alfic Udarents formed in a number of ways.

Many have been modified in the process of strip-mining. The

top part of the soil profile was removed and then replaced after

the mining was completed. Some of these soils have a densic

contact with compacted layers of soil materials. Alfic Udarents

are moderately extensive in the United States. They are used

mostly as pasture or cropland. Some are used as woodland and

some as homesites.

Mollic Udarents.—The Mollic subgroup of Udarents is

fixed on soils that have 3 percent or more fragments of a mollic

epipedon in some horizon within 100 cm of the mineral soil

surface and have a base saturation (by sum of cations) of 35

percent or more in all parts within 100 cm of the mineral soil

surface. These soils are permitted to have fragments of other

diagnostic horizons, but they cannot have, in any horizon

within 100 cm of the mineral soil surface, 3 percent or more

fragments of an argillic horizon. Many of the soils have gentle

slopes. Mollic Udarents formed in a number of ways. Some

have been modified in the process of strip-mining. The top

part of the soil profile was removed and then replaced after

the mining was completed. Some of the soils have a densic

contact with compacted layers of soil materials. Mollic

Udarents are of small extent in the United States. They are

used mostly as pasture or cropland, but some are used as

homesites.

Ultic Udarents.—The Ultic subgroup of Udarents is fixed

on soils that have 3 percent or more fragments of an argillic

horizon and have a base saturation (by sum of cations) of less

than 35 percent in some part within 100 cm of the mineral soil

surface. These soils are permitted to have fragments of other

diagnostic horizons. Many have gentle slopes. Ultic Udarents

formed in a number of ways. A few have been modified in the

process of strip-mining. The top part of the soil profile was

removed and then replaced after the mining was completed.

Some of these soils have a densic contact with compacted

layers of soil materials. Ultic Udarents are of small extent in the

United States. They are used mostly as pasture, woodland, or

cropland.

Ustarents

These are the Arents that have an ustic moisture regime.

Many of these soils have gentle slopes. Most formed in fill

material. Some have a densic contact with compacted layers of

soil materials. Ustarents are of small extent in the United

States. They are used mostly as pasture or are idle.

Definition

Ustarents are the Arents that have an ustic soil moisture

regime.
406 Soil Taxonomy

Key to Subgroups

LBAA. All Ustarents.

Haplic Ustarents

Description of Subgroups

Haplic Ustarents.—The Haplic subgroup of Ustarents is

the only subgroup recognized. These soils have, in some

horizon within 100 cm of the mineral soil surface, 3 percent or

more fragments of a diagnostic horizon. They are permitted to

have fragments of any diagnostic horizon. Commonly, they

have gentle slopes. Most formed in fill material. Some have a

densic contact with compacted layers of soil materials. Haplic

Ustarents are of small extent in the United States. They are

used mostly as pasture or are idle.

Xerarents

These are the Arents that have a xeric moisture regime. Most

of these soils have been modified for irrigated agriculture. Many

have gentle slopes. Xerarents occur mostly in California in the

United States.

Definition

Xerarents are the Arents that have a xeric soil moisture

regime.

Key to Subgroups

LBBA. Xerarents that have, in one or more horizons within

100 cm of the mineral soil surface, 3 percent or more

fragments of a natric horizon.

Sodic Xerarents

LBBB. Other Xerarents that have, within 100 cm of the

mineral soil surface, 3 percent or more fragments of a duripan

or a petrocalcic horizon.

Duric Xerarents

LBBC. Other Xerarents that have fragments of an argillic

horizon with a base saturation (by sum of cations) of 35 percent

or more within 100 cm of the mineral soil surface.

Alfic Xerarents

LBBD. Other Xerarents.

Haplic Xerarents

Description of Subgroups

Haplic Xerarents.—The Haplic subgroup of Xerarents is

centered on soils that have 3 percent or more fragments of a

cambic horizon or another diagnostic horizon. These soils are

not permitted to have, in any horizon within 100 cm of the

mineral soil surface, 3 percent or more fragments of a duripan

or an argillic or natric horizon. Many of the soils have gentle

slopes. Most have been modified for irrigated agriculture.

Haplic Xerarents are used as irrigated cropland. They are of

small extent, mostly in California.

Alfic Xerarents.—The Alfic subgroup of Xerarents is

centered on soils that have 3 percent or more fragments of an

argillic horizon in some horizon and have a base saturation (by

sum of cations) of 35 percent or more in all parts within 100

cm of the mineral soil surface. These soils are not permitted to

have, in any horizon within 100 cm of the mineral soil surface,

3 percent or more fragments of a duripan or a petrocalcic or

natric horizon. They are permitted to have fragments of other

diagnostic horizons. Many of the soils have gentle slopes. Most

have been modified for irrigated agriculture. Alfic Xerarents

are used as irrigated cropland. They are of moderate extent,

mostly in California.

Duric Xerarents.—The Duric subgroup of Xerarents is

centered on soils that have, in some horizon within 100 cm of

the mineral soil surface, 3 percent or more fragments of a

duripan or a natric or petrocalcic horizon. Many of these soils

have gentle slopes. Most have been modified for irrigated

agriculture. Duric Xerarents are used as irrigated cropland.

They are of moderate extent, mostly in California.

Sodic Xerarents.—The Sodic subgroup of Xerarents is

centered on soils that have, in some horizon within 100 cm of

the mineral soil surface, 3 percent or more fragments of a

natric horizon. Many of these soils have gentle slopes. Most

have been modified for irrigated agriculture. Sodic Xerarents

are used as irrigated cropland. They are of small extent and are

known to occur only in California in the United States.

Fluvents

These are mostly brownish to reddish soils that formed in

recent water-deposited sediments, mainly on flood plains, fans,

and deltas of rivers and small streams but not in backswamps

where drainage is poor. The age of the sediments in humid

regions commonly is a few years or decades or a very few

hundred years. In arid regions it may be somewhat more. Many

Fluvents are frequently flooded unless they are protected by

dams or levees. Stratification of the materials is normal. Most

of the alluvial sediments are derived from eroding soils or

streambanks and contain an appreciable amount of organic

carbon, which is mainly in the clay fraction. Strata of clayey or

loamy materials commonly have more organic carbon than the

overlying more sandy strata. Thus, the percentage of organic

carbon of Holocene age decreases irregularly with increasing

depth if the materials are stratified. If the texture is

homogeneous, the content of organic carbon decreases

regularly with increasing depth. Because the deposits generally

are loamy and recent, however, the percentage of carbon in the

deep layers is higher than in soils that formed in parent

materials other than alluvium. This difference in content of

organic carbon is the basis for the definition of Fluvents that

follows. Fluvents can have any vegetation and any temperature

regime. They can have any moisture regime that does not meet
Entisols 407

the criteria for Aquents. Soils that formed in recent alluvium

and have a permanently frozen substratum are grouped with

Gelisols. Some soils that formed in volcanic tephra and some

that have gelic materials are excluded from Fluvents because

they have a different mode of formation and different

interpretations.

Definition

Fluvents are the Entisols that:

1. Have 35 percent or more (by volume) rock fragments or a

texture of loamy very fine sand or finer in some part of the

particle-size control section;

2. Do not have, in one or more layers at a depth between 25

and 100 cm below the mineral soil surface, 3 percent or more

(by volume) fragments of diagnostic horizons that can be

identified and that occur more or less without a discernible

order;

3. Have a slope of less than 25 percent;

4. Have a content of Holocene-age organic carbon that

decreases irregularly with increasing depth or that is 0.2

percent or more at a depth of 125 cm or at a densic, lithic, or

paralithic contact if shallower;

5. Do not have, within 50 cm of the mineral soil surface,

aquic conditions; and

a. The colors defined for Aquents; or

b. Sulfidic materials; or

c. A positive reaction to alpha,alpha-dipyridyl when the

soil is not being irrigated;

6. Do not have both permanent saturation with water and a

reduced matrix in all horizons below 25 cm from the mineral

soil surface;

7. Have a soil temperature regime:

a. That is warmer than cryic; or

b. That is cryic and the soil has:

(1) No gelic material; and

(2) Either a slope of less than 5 percent or less than 15

percent volcanic glass in the 0.02 to 2.0 mm fraction in

some part of the particle-size control section; and

8. Do not have a densic, lithic, or paralithic contact within 25

cm of the soil surface.

Key to Great Groups

LDA. Fluvents that have a cryic soil temperature regime.

Cryofluvents, p. 407

LDB. Other Fluvents that have a xeric moisture regime.

Xerofluvents, p. 417

LDC. Other Fluvents that have an ustic moisture regime.

Ustifluvents, p. 414

LDD. Other Fluvents that have an aridic (or torric) moisture

regime.

Torrifluvents, p. 408

LDE. Other Fluvents.

Udifluvents, p. 411

Cryofluvents

These are the cold Fluvents. They do not have permafrost or

gelic materials, but the growing season is short and cool. The

vegetation typically is a coniferous or mixed forest. In the

United States, these soils are mostly in Alaska, but some are in

mountain valleys in the West. Cryofluvents are moderately

extensive.

Definition

Cryofluvents are the Fluvents that have a cryic temperature

regime.

Key to Subgroups

LDAA. Cryofluvents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and percent aluminum plus 1/2 the iron percentage

(by ammonium oxalate) totaling more than 1.0.

Andic Cryofluvents

LDAB. Other Cryofluvents that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Cryofluvents

LDAC. Other Cryofluvents that have, in one or more

horizons within 50 cm of the mineral soil surface, redox
408 Soil Taxonomy

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Cryofluvents

LDAD. Other Cryofluvents that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Cryofluvents

LDAE. Other Cryofluvents that have either an Ap horizon

that has a color value, moist, of 3 or less and a color value, dry,

of 5 or less (crushed and smoothed) or materials in the upper

15 cm that have these colors after mixing.

Mollic Cryofluvents

LDAF. Other Cryofluvents.

Typic Cryofluvents

Definition of Typic Cryofluvents

Typic Cryofluvents are the Cryofluvents that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 1 month or more in normal years;

and

4. Have an A or Ap horizon that has a color value, moist,

of 4 or more or a color value, dry, of 6 or more when crushed

and smoothed or that is less than 15 cm thick.

Description of Subgroups

Typic Cryofluvents.—The Typic subgroup of Cryofluvents

is centered on soils without ground water within the upper 100

cm, except for short periods following floods. When these soils

thaw in spring, the soil above the layer that remains frozen

may be saturated and very soft, but the water drains out rapidly

when the frozen layer thaws. Redox depletions with chroma of

2 or less do not occur within 50 cm of the mineral soil surface.

The soils do not have, in the upper 75 cm, a deposit of

pyroclastic materials that is as thick as 18 cm. An O horizon at

the surface is normal, but the A horizon is thin or faint. Both

fine and coarse strata are common below a depth of a few

centimeters.

Andic and Vitrandic Cryofluvents.—These soils are like

Typic Cryofluvents, but they have a layer of pyroclastic

materials that is 18 cm or more thick and that is in the upper

75 cm. Andic and Vitrandic Cryofluvents have slopes of less

than 5 percent. They are of very minor extent, but they have

been observed in the State of Washington.

Aquic Cryofluvents.—These soils are like Typic

Cryofluvents, but they have some redox depletions with low

chroma (2 or less) within the upper 50 cm of the mineral soil

surface in horizons that also have aquic conditions for some

time in normal years (or artificial drainage). These soils are

intergrades to Aquents. They are not extensive even in Alaska.

Mollic Cryofluvents.—These soils have a surface horizon

that meets the criteria for a mollic epipedon, except that it is

too thin or finely stratified. The soils are not extensive. They

are along streams in areas where Cryolls occur, mainly at

intermediate elevations in the mountains of the Western United

States.

Oxyaquic Cryofluvents.—These soils are like Typic

Cryofluvents, but they are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both 20 or more consecutive days or 30 or more cumulative

days in normal years. Some of the soils have redox depletions

with low chroma (2 or less) below 50 cm from the mineral soil

surface. Oxyaquic Cryofluvents are considered intergrades to

Aquents. They are not extensive.

Torrifluvents

These are the Fluvents of arid climates. They have an aridic

(or torric) moisture regime and a temperature regime warmer

than cryic. Most of them have a high pH value and are

calcareous, and a few are somewhat salty. The soils are subject

to flooding, but most are not flooded frequently or for long

periods. The larger areas that have a favorable topography and

are close to a source of water commonly are irrigated. The

natural vegetation on the Torrifluvents in the United States

consisted mostly of grasses, xerophytic shrubs, and cacti, but in

some parts of the world the only vegetation on the soils has

been irrigated crops because the sediments accumulated while

the soils were being cultivated.
Entisols 409

Definition

Torrifluvents are the Fluvents that have an aridic (or torric)

moisture regime and a soil temperature regime warmer than

cryic.

Key to Subgroups

LDDA. Torrifluvents that have:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 o

C or higher; and

3. An aridic (or torric) moisture regime that borders on

ustic.

Ustertic Torrifluvents

LDDB. Other Torrifluvents that have one or both of the

following:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide through a thickness of 30 cm or more for some

time in most normal years, and slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has

its upper boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower.

Vertic Torrifluvents

LDDC. Other Torrifluvents that have:

1. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 o

C or higher; and

2. A thermic, mesic, or frigid soil temperature regime and

an aridic (or torric) moisture regime that borders on xeric;

and

3. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrixerandic Torrifluvents

LDDD. Other Torrifluvents that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Torrifluvents

LDDE. Other Torrifluvents that have, in one or more

horizons within 100 cm of the soil surface, both redox

depletions with chroma of 2 or less and aquic conditions for

some time in normal years (or artificial drainage).

Aquic Torrifluvents

LDDF. Other Torrifluvents that are saturated with water in

one or more layers within 150 cm of the soil surface in normal

years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Torrifluvents

LDDG. Other Torrifluvents that have:

1. A horizon within 100 cm of the mineral soil surface

that is 15 cm or more thick and that either has 20 percent or

more (by volume) durinodes or is brittle and has a firm

rupture-resistance class when moist; and

2. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 oC or higher; and
410 Soil Taxonomy

3. A thermic, mesic, or frigid soil temperature regime and an

aridic (or torric) moisture regime that borders on xeric.

Duric Xeric Torrifluvents

LDDH. Other Torrifluvents that have a horizon within 100

cm of the mineral soil surface that is 15 cm or more thick and

that either has 20 percent or more (by volume) durinodes or is

brittle and has a firm rupture-resistance class when moist.

Duric Torrifluvents

LDDI. Other Torrifluvents that have both:

1. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 o

C or higher; and

2. An aridic (or torric) moisture regime that borders on

ustic.

Ustic Torrifluvents

LDDJ. Other Torrifluvents that have both:

1. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 oC or higher; and

2. A thermic, mesic, or frigid soil temperature regime and

an aridic (or torric) moisture regime that borders on xeric.

Xeric Torrifluvents

LDDK. Other Torrifluvents that have an anthropic epipedon.

Anthropic Torrifluvents

LDDL. Other Torrifluvents.

Typic Torrifluvents

Definition of Typic Torrifluvents

Typic Torrifluvents are the Torrifluvents that:

1. Do not have a horizon within 100 cm of the surface that is

more than 15 cm thick and that either has as much as 20

percent durinodes in a nonbrittle matrix or is brittle and has a

firm rupture-resistance class when moist;

2. Have neither:

a. Cracks within 125 cm of the soil surface that are 5 mm

or more wide through a thickness of 30 cm or more for some

time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; nor

b. A linear extensibility of 6.0 cm or more between the soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact, whichever is shallower;

3. Do not have an anthropic epipedon;

4. Are dry in all parts of the moisture control section for threefourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or more;

5. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

6. Do not have, in any horizon within 100 cm of the soil

surface, both redox depletions with chroma of 2 or less and

aquic conditions; and

7. Are not saturated with water in any layer within 150 cm of

the soil surface for either or both 30 or more cumulative days

or 20 or more consecutive days in normal years.

Description of Subgroups

Typic Torrifluvents.—These are the driest Fluvents. They

are subject to flooding, but flooding is rare in some areas of the

soils.

Weak cementation by silica is excluded from the Typic

subgroup because it is considered to indicate the initial

development of a duripan. Cracks and slickensides or wedgeshaped aggregates are properties shared with Vertisols and are

the basis for defining the Vertic subgroup. Typic Torrifluvents

do not have an anthropic epipedon or a water table within a

depth of 150 cm. They do not have, in the upper 75 cm, a

deposit of pyroclastic materials that is as thick as 18 cm.

The concept of the Typic subgroup is that of the drier part of

the range of Torrifluvents. Extra moisture coming as summer

rain or during summer floods is the basis for defining the Ustic

subgroup. Extra moisture coming as cool-season rain or during

winter floods is the basis for defining the Xeric subgroups.

Typic Torrifluvents are extensive soils in the intermountain

States of the United States. Many of them are irrigated. The

others furnish only a small amount of forage for grazing.

Anthropic Torrifluvents.—These soils are like Typic

Torrifluvents, but they have an anthropic epipedon. They have

been irrigated for many years or even many centuries. They are

not known to occur in the United States. They are mainly along

rivers flowing through deserts in parts of the world with a long

irrigation history.

Aquic Torrifluvents.—These soils have a water table
Entisols 411

within a depth of 100 cm. They have some redox depletions with

chroma of 2 or less within 100 cm of the mineral soil surface,

although chroma of 3 or more is commonly dominant to this

depth or deeper. These soils are intergrades between

Ustifluvents and Aquents. They are not extensive in the United

States as a whole but are locally important on the flood plains

along the larger rivers. Many Aquic Torrifluvents in the United

States are irrigated and cultivated. Some have a water table

that is partly or fully a result of excess irrigation water.

Duric Torrifluvents.—These soils have, within the upper

meter, a horizon that is partially cemented by silica. This

horizon is at least 15 cm thick. It has at least 20 percent

durinodes, by volume, or it is both brittle and firm when moist.

Either of these characteristics causes some interference with

water movement and root penetration. These soils are

intergrades between Fluvents and Durids. They are not

extensive in the United States, but they occur in Nevada. They

are used only as rangeland.

Duric Xeric Torrifluvents.—These soils have a moisture

regime that is marginal to xeric. The moisture control section

is regularly moist in winter and early in spring but is very dry

in summer. These soils have, within the upper meter, a horizon

that is partially cemented by silica. This horizon is 15 cm or

more thick. It has at least 20 percent durinodes, by volume, or

it is both brittle and firm when moist. Either of these

characteristics causes some interference with water movement

and root penetration. These soils are intergrades between

Fluvents and Durixerolls.

The moisture that is stored in winter results in better plant

growth on these soils than on the related Duric Torrifluvents,

which have a lower and less reliable supply of moisture. Duric

Xeric Torrifluvents are rare in the United States. They are used

mainly for winter and spring grazing.

Oxyaquic Torrifluvents.—These soils are like Typic

Torrifluvents, but they are saturated with water in one or more

layers within 150 cm of the mineral soil surface for either or

both 20 or more consecutive days or 30 or more cumulative

days in normal years. Some of the soils have redox depletions

with low chroma (2 or less) at a depth below 100 cm from the

mineral soil surface. Oxyaquic Torrifluvents are considered

intergrades to Aquents. They are not extensive. Some of the

soils have a water table that is partly or fully a result of excess

irrigation water. Oxyaquic Torrifluvents are used mainly as

cropland.

Ustertic Torrifluvents.—These soils have a high linear

extensibility and deep cracks. The moisture that closes the

cracks comes during a growing season when the soils are

warm. These soils are not extensive in the United States, but

they are widely scattered along the rivers in the drier parts of

the northern Great Plains. Some of the soils are irrigated and

used as cropland, and others are used for summer grazing.

Ustic Torrifluvents.—These soils are like Typic

Torrifluvents, but they have more available moisture during

summer or, in tropical regions, during rainy seasons. They

either receive more rainfall or are flooded more frequently than

the soils in the Typic subgroup. Ustic Torrifluvents are moist in

some or all parts of the moisture control section for more than

one-fourth of the time (cumulative) when the soil temperature

at a depth of 50 cm is 5 o

C or higher. These soils are extensive

along the rivers in the drier parts of the Great Plains in the

United States. Many of the soils are irrigated and used as

cropland, and the others are used for summer grazing.

Vertic Torrifluvents.—These soils are like Typic

Torrifluvents, but they have cracks and slickensides or wedgeshaped aggregates and have many of the properties of Vertisols.

Vertic Torrifluvents are not extensive in the United States.

Some that have a low content of salts are irrigated. Others,

particularly those that are salty, furnish only a small amount of

forage for grazing.

Vitrandic Torrifluvents.—These soils are like Typic

Torrifluvents, but they have a layer of pyroclastic materials that

is 18 cm or more thick and that is in the upper 75 cm. These

soils are of minor extent, mostly in California.

Vitrixerandic Torrifluvents.—These soils are like Typic

Torrifluvents, but they have a moisture regime that is marginal

to xeric. The moisture control section is regularly moist in

winter and early in spring but is very dry in summer. These

soils have a layer of pyroclastic materials that is 18 cm or more

thick and that is in the upper 75 cm. The moisture stored in

winter results in better plant growth on these soils than on the

soils in the Typic subgroup. Vitrixerandic Torrifluvents are of

minor extent in the United States. They are used as rangeland

or cropland.

Xeric Torrifluvents.—These soils are like Typic

Torrifluvents, but they have a moisture regime that is marginal

to xeric. The moisture control section is regularly moist in

winter and early in spring but is very dry in summer. The

moisture stored in winter results in better plant growth on these

soils than on the soils in the Typic subgroup.

Xeric Torrifluvents are moderately extensive in the northern

intermountain States of the United States. Many of the soils are

irrigated and used as cropland, and the others are used for

winter and spring grazing.

Udifluvents

These are the Fluvents that have a udic moisture regime and

a temperature regime warmer than cryic. They are on flood

plains along streams and rivers, and they may be flooded

during almost any season. There is little or no evidence of

alteration of the fine stratification in the alluvium, although in

some Udifluvents that have a fine-silty or fine particle-size

class, identifying the stratification may be difficult. Some

Udifluvents formed under forest vegetation, but many have had

no vegetation other than pasture or cultivated crops because the

sediments in which the soils formed were deposited while the

soils were being used. Udifluvents are extensive in the United

States.
412 Soil Taxonomy

Definition

Udifluvents are the Fluvents that:

1. Have a udic moisture regime; and

2. Have a temperature regime warmer than cryic.

Key to Subgroups

LDEA. Udifluvents that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. Either or both of the following:

a. In one or more horizons within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years

(or artificial drainage); or

b. In one or more horizons within 100 cm of the

mineral soil surface, a color value, moist, of 4 or more

and either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B

and also aquic conditions for some time in normal years

(or artificial drainage).

Aquertic Udifluvents

LDEB. Other Udifluvents that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is

shallower.

Vertic Udifluvents

LDEC. Other Udifluvents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling more than 1.0.

Andic Udifluvents

LDED. Other Udifluvents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Udifluvents

LDEE. Other Udifluvents that have either:

1. In one or more horizons within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); or

2. In one or more horizons within 100 cm of the mineral

soil surface, a color value, moist, of 4 or more and either

chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Udifluvents

LDEF. Other Udifluvents that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Udifluvents

LDEG. Other Udifluvents that have either an Ap horizon that

has a color value, moist, of 3 or less and a color value, dry, of 5

or less (crushed and smoothed) or materials in the upper 15 cm

that have these colors after mixing.

Mollic Udifluvents

LDEH. Other Udifluvents.

Typic Udifluvents

Definition of Typic Udifluvents

Typic Udifluvents are the Udifluvents that:
Entisols 413

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size, of

1.0 g/cm3

 or less, measured at 33 kPa water retention, and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have either:

a. In any horizon within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less or aquic

conditions; or

b. In any horizon within 100 cm of the mineral soil

surface, a color value, moist, of 4 or more and either chroma

of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for either or both 20 or more

consecutive days or 30 or more cumulative days;

4. Have either an Ap horizon that has a color value, moist,

of 4 or more or a color value, dry, of 6 or more when crushed

and smoothed or materials in the upper 15 cm thick that have

these colors after mixing; and

5. Do not have either of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Udifluvents.—These are the Udifluvents that have

moderately good or good drainage. They occur in relatively

high areas on flood plains, and the water table is deeper than

50 cm all of the time or enough of the time for there to be no

redox depletions with chroma of 2 or less or aquic conditions

within 50 cm of the mineral soil surface and no chroma of 0 or

hue bluer than 10Y or aquic conditions within a depth of 100

cm. The Typic subgroup excludes soils that have either cracks

and slickensides or wedge-shaped aggregates or a linear

extensibility of 6.0 or more within 100 cm of the mineral soil

surface. Typic Udifluvents are considered intergrades to

Vertisols. They do not have, in the upper 75 cm, a deposit of

pyroclastic materials that is as thick as 18 cm. They are

extensive along the rivers in the humid parts of the United

States and in many other countries. If redox depletions are

shallow, the soils are excluded from the Typic subgroup and are

considered intergrades to Aquents. Most of the Typic

Udifluvents in the United States are used as cropland if the

areas of the soils are large enough.

Andic and Vitrandic Udifluvents.—These soils are like

Typic Udifluvents, but they have a layer of pyroclastic

materials that is 18 cm or more thick and that is in the upper

75 cm. They are of minor extent, mostly in the States of

Washington and Oregon.

Aquertic Udifluvents.—These soils have either cracks and

slickensides or wedge-shaped aggregates or a linear

extensibility of 6.0 or more within 100 cm of the mineral soil

surface. They also have a water table that is shallower than the

one in Typic Udifluvents or that persists for longer periods

within a depth of 50 cm. They have some redox depletions with

chroma of 2 or less within 50 cm of the mineral soil surface,

although chroma of 3 or more is dominant to this depth or

deeper, or they have chroma of 0 or hue bluer than 10Y in one

or more horizons at a depth between 50 and 100 cm below the

mineral soil surface. In either situation, they have aquic

conditions for some time in normal years within these depths

(or artificial drainage). These soils are intergrades between

Udifluvents and Aquerts. They are not extensive in the United

States as a whole but are locally important on the flood plains

along some of the larger rivers. Most of the Aquertic

Udifluvents in the United States have been cleared and are used

as cropland.

Aquic Udifluvents.—These soils have a water table that is

shallower than the one in Typic Udifluvents or that persists for

longer periods within a depth of 50 cm. They have some redox

depletions with chroma of 2 or less within 50 cm of the

mineral soil surface, although chroma of 3 or more is dominant

to this depth or deeper, or they have chroma of 0 or hue bluer

than 10Y in one or more horizons at a depth between 50 and

100 cm below the mineral soil surface. In either situation, they

have aquic conditions for some time in normal years within

these depths (or artificial drainage). These soils are intergrades

between Udifluvents and Aquents. They are not extensive in

the United States as a whole but are locally extensive on the

flood plains along the larger rivers. Nearly all of the Aquic

Udifluvents in the United States are used as cropland.

Mollic Udifluvents.—These soils differ from Typic
414 Soil Taxonomy

Udifluvents in that the Ap horizon or the upper 15 cm, after

mixing, has colors as dark as those of a mollic epipedon. The

sediments below this depth are finely stratified and may have

dark colors. The soils have not been in place long enough for

mixing by roots and by burrowing animals and insects, volume

changes on wetting and drying, and frost action to have

obliterated the fine strata below the Ap horizon or a depth of

15 cm. Mollic Udifluvents are associated with Udolls in the

central part of the Northern United States. They are adjacent to

streams and are not extensive. Most of them are used as

cropland.

Oxyaquic Udifluvents.—These soils are like Typic

Udifluvents, but they are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both 20 or more consecutive days or 30 or more cumulative

days in normal years. Some of these soils have redox depletions

with low chroma (2 or less) at a depth below 100 cm from the

mineral soil surface. Oxyaquic Udifluvents are considered

intergrades to Aquents. They are not extensive.

Vertic Udifluvents.—These soils have either cracks

and slickensides or wedge-shaped aggregates or a linear

extensibility of 6.0 or more within 100 cm of the mineral

soil surface. The soils are intergrades between Udifluvents

and Uderts. They are not extensive in the United States as

a whole but are locally important on the flood plains along

some of the larger rivers. Most of the Vertic Udifluvents

in the United States have been cleared and are used as

cropland.

Ustifluvents

These are the Fluvents that have an ustic moisture regime

and a temperature regime warmer than cryic. These soils are

on flood plains along rivers and streams in areas of middle or

low latitudes. Flooding can occur in any season but is most

common in summer in the middle latitudes and during the

rainy season in the Tropics. A few of the soils are flooded

regularly in summer because of melting snow in high

mountains, even though the summer is rainless.

Definition

Ustifluvents are the Fluvents that:

1. Have an ustic moisture regime; and

2. Have a temperature regime warmer than cryic.

Key to Subgroups

LDCA. Ustifluvents that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. Either or both of the following:

a. In one or more horizons within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years

(or artificial drainage); or

b. In one or more horizons within 150 cm of the

mineral soil surface, a color value, moist, of 4 or more

and either chroma of 0 or hue of 5GY, 5G, 5BG, or 5B

and also aquic conditions for some time in normal years

(or artificial drainage).

Aquertic Ustifluvents

LDCB. Other Ustifluvents that have both of the following:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that, in normal years, is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that,

in normal years, remains moist in some or all parts for

less than 90 consecutive days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 8 oC; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Torrertic Ustifluvents
Entisols 415

LDCC. Other Ustifluvents that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Ustifluvents

LDCD. Other Ustifluvents that have anthraquic conditions.

Anthraquic Ustifluvents

LDCE. Other Ustifluvents that have either:

1. In one or more horizons within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); or

2. In one or more horizons within 150 cm of the mineral

soil surface, a color value, moist, of 4 or more and either

chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Ustifluvents

LDCF. Other Ustifluvents that are saturated with water in

one or more layers within 150 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Ustifluvents

LDCG. Other Ustifluvents that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime and a moisture control

section that, in normal years, is dry in all parts for fourtenths or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for six-tenths or more of the cumulative days per

year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 5 o

C; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that, in

normal years, is moist in some or all parts for less than 180

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 o

C.

Aridic Ustifluvents

LDCH. Other Ustifluvents that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime and a moisture control

section that, in normal years, is dry in some or all parts for

less than 105 cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for less than four-tenths of the cumulative days

per year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that, in

normal years, is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Udic Ustifluvents

LDCI. Other Ustifluvents that have either an Ap horizon that

has a color value, moist, of 3 or less and a color value, dry, of 5

or less (crushed and smoothed) or materials in the upper 15 cm

that have these colors after mixing.

Mollic Ustifluvents

LDCJ. Other Ustifluvents.

Typic Ustifluvents

Definition of Typic Ustifluvents

Typic Ustifluvents are the Ustifluvents that:

1. Do not have either:

a. In any horizon within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less or aquic

conditions; or

b. In any horizon within 150 cm of the mineral soil

surface, a color value, moist, of 4 or more and either chroma

of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic conditions;

2. Are not saturated with water in any layer within 150 cm of

the mineral soil surface for either or both 20 or more

consecutive days or 30 or more cumulative days;

3. Do not have anthraquic conditions;

4. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or
416 Soil Taxonomy

wedge-shaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the mineral soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

5. Have either an Ap horizon that has a color value, moist, of

4 or more or a color value, dry, of 6 or more when crushed and

smoothed or materials in the upper 15 cm that have these

colors after mixing; and

6. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid soil temperature regime and a moisture control

section that, in normal years, is dry in some or all parts for

105 or more cumulative days per year but is not dry in all

parts for four-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for four- to six-tenths of the cumulative days per

year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that, in

normal years, is dry in some or all parts for 120 or more

cumulative days and moist for 180 or more cumulative days

per year when the temperature at a depth of 50 cm below the

soil surface is higher than 8 oC.

Description of Subgroups

Typic Ustifluvents.—These are the Ustifluvents that have

good or moderately good drainage and that do not have a fine

particle-size class and clay of a swelling type in a major part of

the upper 125 cm. These soils occur in relatively high areas on

flood plains, and the water table is deeper than 100 cm, except

for very brief periods. There are no redox depletions with

chroma of 2 or less or aquic conditions within 50 cm of the

mineral soil surface and no chroma of 0 or hue bluer than 10Y

or aquic conditions within a depth of 100 cm.

There normally is little or no evidence of alteration of the

fine stratification in the alluvium. In some Typic Ustifluvents

that have a fine-silty or fine particle-size class, however,

stratification cannot be easily identified. Typic Ustifluvents are

extensive along streams in the subhumid or semiarid parts of

the Great Plains in the United States and also are extensive in

many other countries. Many of these soils are used as cropland,

with or without irrigation. Others are used for summer grazing.

Anthraquic Ustifluvents.—These soils are like Typic

Ustifluvents, but they have a human-made perched water table

near the soil surface. They commonly have some redox

depletions with chroma of 2 or less in the Ap horizon. They are

intergrades between Ustifluvents and Aquents. Anthraquic

Ustifluvents may or may not have an Ap horizon or material in

the upper 15 cm that would be a mollic epipedon, except that

the layer rests on finely stratified sediment. These soils are not

known to occur in the United States. They are irrigated and are

used for paddy rice.

Aquertic Ustifluvents.—These soils have aquic conditions

within 50 cm of the mineral soil surface for some time in

normal years and have a high shrink-swell potential. They are

of limited extent in the West and on the Great Plains in the

United States. They commonly are used as grazing land.

Aquic Ustifluvents.—These soils have a shallower water

table than that in Typic Ustifluvents or one that persists for

long periods within a depth of 150 cm. They commonly have

some redox depletions with chroma of 2 or less within 50 cm of

the mineral soil surface, or they have chroma of 0 or hue bluer

than 10Y at some depth between 50 and 150 cm. They are

intergrades between Ustifluvents and Aquents. Aquic

Ustifluvents may or may not have an Ap horizon or material in

the upper 15 cm that would be a mollic epipedon, except that

the layer rests on finely stratified sediment. These soils are not

extensive in the United States. Most of them are used as

cropland, some of which is irrigated.

Aridic Ustifluvents.—These soils are drier than Typic

Ustifluvents. They are intergrades between Ustifluvents and

Torrifluvents. They are moderately extensive in the southern

part of the Great Plains of the United States. Slopes in general

are gentle or moderate. Many of these soils are used for

grazing, and others are used as cropland. Some of the cropland

is irrigated, and some is used for drought-tolerant crops.

Mollic Ustifluvents.—These soils differ from Typic

Ustifluvents in that the Ap horizon or the upper 15 cm, after

mixing, has colors as dark as those of a mollic epipedon. The

sediments below this depth are finely stratified and may have

dark colors. The soils have not been in place long enough for

mixing by roots and by burrowing animals and insects, volume

changes on wetting and drying, and frost action to have

obliterated the fine strata below the Ap horizon or a depth of

15 cm. Mollic Ustifluvents are associated with Ustolls on the

Great Plains and in areas to the west in the United States. They

are adjacent to streams and are not extensive. They are used as

cropland or grazing land.

Oxyaquic Ustifluvents.—These soils have a shallower

water table than that in Typic Ustifluvents. The water table

persists for either or both 20 or more consecutive days or 30 or

more cumulative days within a depth of 150 cm. The soils

commonly have some redox depletions with chroma of 2 or less

at a depth between 50 and 150 cm below the mineral soil

surface. They are intergrades between Ustifluvents and

Aquents. They may or may not have an Ap horizon or material

in the upper 15 cm that would be a mollic epipedon, except
Entisols 417

that the layer rests on finely stratified sediment. These soils are

not extensive in the United States. Most of them are used as

cropland, with or without irrigation.

Torrertic Ustifluvents.—These soils are drier than Typic

Ustifluvents. They have cracks and high COLE values, which

are properties shared with Vertisols. They do not yet have the

properties that are diagnostic for Vertisols. Because there are

no restrictions on the color value of Vertisols, Torrertic

Ustifluvents are permitted, but not required, to have a lower

color value than the soils in the Typic subgroup. Torrertic

Ustifluvents are rare in the United States. Some of them are

used as cropland, with or without irrigation, and the others are

used as grazing land.

Udic Ustifluvents.—These soils are like Typic Ustifluvents,

but they are less dry. They are dry in some part of the moisture

control section for less than four-tenths of the cumulative days

when the soil temperature at a depth of 50 cm exceeds 5 o

C if

the soil temperature regime is mesic or thermic. They are dry

in some or all parts of the moisture control section for less than

90 days during a period when the soil temperature at a depth of

50 cm exceeds 8 oC if the soil temperature regime is

hyperthermic, isomesic, or warmer. These soils are intergrades

between Ustifluvents and Udifluvents. They are moderately

extensive on the Great Plains in the United States. Their slopes

are gentle. Where areas are large, most of these soils are used

as cropland.

Vertic Ustifluvents.—These soils are like Typic

Ustifluvents, but they have cracks and high COLE values,

which are properties shared with Vertisols. They do not yet

have the properties that are diagnostic for Vertisols. Because

there are no restrictions on the color value of Vertisols, Vertic

Ustifluvents are permitted, but not required, to have a lower

color value than the soils in the Typic subgroup. Vertic

Ustifluvents are rare in the United States. Some of them are

used as cropland, with or without irrigation, and the others are

used as grazing land.

Xerofluvents

These are the Fluvents that have a xeric moisture regime

and a frigid, mesic, or thermic temperature regime. These soils

are on flood plains along rivers or streams or on alluvial fans,

mostly in areas with Mediterranean climates. Flooding is most

common in winter, but some of the soils are flooded in spring

because of melting snow in the nearby mountains. Not all

Fluvents in Mediterranean climates are Xerofluvents. Some are

flooded during summer because of melting snow in high

mountains. This flooding can supply moisture during the

summer. The vegetation on Xerofluvents is commonly mixed

forest or grass and shrubs. The Xerofluvents in the United

States are mostly in California and the Northwestern States.

The soils are moderately extensive.

Definition

Xerofluvents are the Fluvents that have a xeric moisture

regime and a frigid, mesic, or thermic soil temperature

regime.

Key to Subgroups

LDBA. Xerofluvents that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Xerofluvents

LDBB. Other Xerofluvents that have:

1. In one or more horizons within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); or

2. In one or more horizons within 150 cm of the mineral

soil surface, a color value, moist, of 4 or more and either

chroma of 0 or hue bluer than 10Y and also aquic

conditions for some time in normal years (or artificial

drainage); and

3. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Xerofluvents
418 Soil Taxonomy

LDBC. Other Xerofluvents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm of

the mineral soil surface, a fine-earth fraction with both a bulk

density of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0.

Andic Xerofluvents

LDBD. Other Xerofluvents that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Xerofluvents

LDBE. Other Xerofluvents that have either:

1. In one or more horizons within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); or

2. In one or more horizons within 150 cm of the mineral

soil surface, a color value, moist, of 4 or more and either

chroma of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic

conditions for some time in normal years.

Aquic Xerofluvents

LDBF. Other Xerofluvents that are saturated with water in

one or more layers within 150 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Xerofluvents

LDBG. Other Xerofluvents that have a horizon within 100

cm of the mineral soil surface that is 15 cm or more thick and

that either has 20 percent or more (by volume) durinodes or is

brittle and has a firm rupture-resistance class when moist.

Durinodic Xerofluvents

LDBH. Other Xerofluvents that have either an Ap horizon

that has a color value, moist, of 3 or less and a color value, dry,

of 5 or less (crushed and smoothed) or materials in the upper 15

cm that have these colors after mixing.

Mollic Xerofluvents

LDBI. Other Xerofluvents.

Typic Xerofluvents

Definition of Typic Xerofluvents

Typic Xerofluvents are the Xerofluvents that:

1. Do not have either:

a. In any horizon within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less or aquic

conditions; or

b. In any horizon within 150 cm of the mineral soil

surface, a color value, moist, of 4 or more and either chroma

of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic conditions;

2. Are not saturated with water in any layer within 150 cm of

the mineral soil surface in normal years for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have a horizon within 100 cm of the surface that is

more than 15 cm thick and that either has 20 percent or more

durinodes or is brittle and has a firm rupture-resistance class

when moist;

4. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

5. Have either an Ap horizon that has a color value, moist,

of 4 or more or a color value, dry, of 6 or more when crushed

and smoothed or materials in the upper 15 cm that have these

colors after mixing; and

6. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser
Entisols 419

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Xerofluvents.—The central concept or Typic

subgroup of Xerofluvents is fixed on soils that have good or

moderately good drainage, that show little or no evidence of

cementation by silica, and that do not have a fine particle-size

class and clay of a swelling type in the upper 100 cm. These

soils do not have, in the upper 75 cm, a deposit of pyroclastic

materials that is as thick as 18 cm. They are in relatively high

areas on flood plains, and the water table is deeper than 150

cm in normal years.

Partial cementation by silica causes soils to be excluded

from the Typic subgroup because this feature is considered to

indicate an intergrade to Durids or Durixerepts. Soils that have

cracks and slickensides or wedge-shaped aggregates are

excluded from the Typic subgroup because they have most of

the properties of Xererts. Presumably, the deposits are too

recent to have the evidence of movement that is necessary in

Vertisols.

Typic Xerofluvents are moderately extensive in the Western

United States. They are nearly level and are used mostly as

pasture or irrigated cropland.

Andic and Vitrandic Xerofluvents.—These soils are like

Typic Xerofluvents, but they have a surface mantle or layer in

the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. These

soils occur on flood plains in the Western United States. They

are permitted, but not required, to have color value of 3 or less,

moist, and 5 or less, dry, in surface horizons, after mixing to a

depth of 15 cm. These soils are of small extent. Most have

gentle slopes, have been cleared and protected from flooding,

and are used as cropland. Some are used as forest or pasture.

Aquandic Xerofluvents.—These soils have, in one or more

horizons within 50 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage), or they

have, in one or more horizons within 150 cm of the mineral

soil surface, a color value, moist, of 4 or more and either

chroma of 0 or hue bluer than 10Y and also aquic conditions

for some time in normal years (or artificial drainage). The soils

have a surface mantle or layer in the upper 75 cm that has both

a low bulk density and a high content of weakly crystalline

minerals or that consists of slightly or moderately weathered

pyroclastic materials. These soils occur on flood plains in the

Western United States. They are permitted, but not required, to

have a color value of 3 or less, moist, and 5 or less, dry, in

surface horizons, after mixing to a depth of 15 cm. The soils

are not extensive. Most have gentle slopes, have been cleared

and protected from flooding, and are used as cropland. Some

are used as pasture or forest.

Aquic Xerofluvents.—These soils have, in one or more

horizons within 50 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage), or they

have, in one or more horizons within 150 cm of the mineral

soil surface, a color value, moist, of 4 or more and either

chroma of 0 or hue bluer than 10Y and also aquic conditions

for some time in normal years (or artificial drainage). The soils

are otherwise like Typic Xerofluvents in defined properties, but

they tend to have more salts bacause of capillary rise and

evapotranspiration. Aquic Xerofluvents are on nearly level

flood plains. They are used mostly as irrigated cropland or

pasture. Some are used for native pasture, hay, or grazing.

These soils are moderately extensive in the Western United

States.

Durinodic Xerofluvents.—These soils differ from Typic

Xerofluvents in that they are partially cemented by silica. They

are in relatively high areas on flood plains, and the water table

is deeper than 150 cm in normal years. Durinodic Xerofluvents

are intergrades to Durids or Durixerepts. They are nearly level

and are used for native pasture or irrigated crops. They are not

extensive in the United States.

Mollic Xerofluvents.—These soils differ from Typic

Xerofluvents in that the Ap horizon or the upper 15 cm, after

mixing, has colors as dark as those of a mollic epipedon. The

sediments below this depth are finely stratified and may have

dark colors. The soils have not been in place long enough for

mixing by roots and by burrowing animals and insects, wetting

and drying, and frost action to have obliterated the fine strata

below the Ap horizon or a depth of 15 cm. Mollic Xerofluvents

are associated with Xerolls in the Western United States. They

are adjacent to streams and are not extensive.

Oxyaquic Xerofluvents.—These soils are like Typic

Xerofluvents, but they are saturated with water in one or more

layers within 150 cm of the mineral soil surface for either or

both 20 or more consecutive days or 30 or more cumulative

days in normal years. Some of the soils have redox depletions

with low chroma (2 or less) at a depth below 100 cm from the

mineral soil surface. Oxyaquic Xerofluvents are considered

intergrades to Aquents. They are not extensive. Some have a

water table that is partly or fully a result of excess irrigation

water.

Vertic Xerofluvents.—These soils have a fine texture and

deep, wide cracks, but they do not yet have all of the properties

that are diagnostic for Vertisols. There is no restriction on the

presence of ground water above a depth of 150 cm. Vertic
420 Soil Taxonomy

Xerofluvents generally are in low areas on flood plains. They

are rare in the United States.

Orthents

These are primarily Entisols on recent erosional surfaces. The

erosion may be geologic or may have been induced by

cultivation, mining, or other factors. Any former soil that was

on the landscape has been completely removed or so truncated

that the diagnostic horizons for all other orders do not occur. A

few Orthents are in areas of recent loamy or fine eolian

deposits, in areas of solifluction or glacial deposits, or in areas

of debris from recent landslides and mudflows.

Orthents occur in any climate and under any vegetation.

They are do not occur in areas that have aquic conditions, a

high water table, and the colors defined for Aquents or on

shifting or stabilized sand dunes.

Definition

Orthents are the Entisols that:

1. Have a texture of loamy very fine sand or finer or 35

percent (by volume) or more rock fragments in some layer

within the particle-size control section;

2. Do not have fragments of diagnostic horizons that can be

identified and that occur more or less without a discernible

order below any Ap horizon but above a depth of 100 cm or

above a densic, lithic, or paralithic contact that is shallower

than 100 cm;

3. Have a slope of more than 25 percent or have a content of

Holocene-age organic carbon that decreases regularly with

increasing depth and reaches a level of 0.2 percent or less

within a depth of 125 cm; and

4. Do not have, within 50 cm of the mineral soil surface,

aquic conditions; and

a. The colors defined for Aquents; or

b. Sulfidic materials; or

c. A positive reaction to alpha,alpha-dipyridyl when the

soil is not being irrigated.

Key to Great Groups

LEA. Orthents that have a cryic soil temperature regime.

Cryorthents, p. 420

LEB. Other Orthents that have an aridic (or torric) moisture

regime.

Torriorthents, p. 421

LEC. Other Orthents that have a xeric moisture regime.

Xerorthents, p. 430

LED. Other Orthents that have an ustic moisture regime.

Ustorthents, p. 426

LEE. Other Orthents.

Udorthents, p. 425

Cryorthents

These are the Orthents of high mountains or high latitudes.

Most of them are sandy-skeletal, are on slopes where rock is

very shallow, or are in areas of recent solifluction or volcanic

deposits. The vegetation may be coniferous forest, tundra, or

even the sparse vegetation of very cold, dry areas. Few areas

are cultivated. These soils are of small extent in high

mountains and in areas of tundra vegetation in the United

States. Some of the soils are cold and dry, have a thin

efflorescence of salt on the surface during summer, and may be

dry in all horizons during some periods. Most of the

Cryorthents in the United States still support their native

vegetation.

Definition

Cryorthents are the Orthents that have a cryic soil

temperature regime.

Key to Subgroups

LEAA. Cryorthents that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Cryorthents

LEAB. Other Cryorthents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Cryorthents

LEAC. Other Cryorthents that have, in one or more horizons

within 50 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Cryorthents

LEAD. Other Cryorthents that are saturated with water in
Entisols 421

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Cryorthents

LEAE. Other Cryorthents that have lamellae within 200 cm

of the mineral soil surface.

Lamellic Cryorthents

LEAF. Other Cryorthents.

Typic Cryorthents

Definition of Typic Cryorthents

Typic Cryorthents are the Cryorthents that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface in normal years for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

4. Do not have a lithic contact within 50 cm of the soil

surface; and

5. Do not have lamellae within 200 cm of the mineral soil

surface.

Description of Subgroups

Typic Cryorthents.—These are the Cryorthents that are not

saturated with water within a depth of 100 cm and that, in the

upper 75 cm, do not have a deposit of pyroclastic materials that

is as thick as 18 cm. Most of the soils are sandy-skeletal or

very shallow to a paralithic or densic contact. Most are in

forests, and they have an O horizon, a thin or sandy A horizon,

and a B horizon too sandy or too thin to be a cambic horizon.

Typic Cryorthents do not have diagnostic horizons other than

an ochric epipedon. Because cultivation is not likely in the

foreseeable future, the soils cannot have a cambic horizon even

if the base is at a depth of less than 25 cm below the mineral

soil surface. Typic Cryorthents are of small extent.

Aquic Cryorthents.—These soils are saturated with water

within 50 cm of the surface at some time during normal years

and have redox depletions with chroma of 2 or less within that

depth. The dominant chroma, however, is more than 2. These

soils are considered intergrades to Cryaquents. They are rare in

the United States.

Lamellic Cryorthents.—These soils have lamellae within

200 cm of the soil surface. The uppermost lamellae commonly

are within 75 cm of the soil surface, but other lamellae may be

as deep as 200 cm. These soils are of very small extent, mostly

in the mountains of the Western United States. They formed

under coniferous forest vegetation.

Lithic Cryorthents.—These soils have a lithic contact

within 50 cm of the soil surface and commonly at a depth

appreciably less than 50 cm. The soils may be saturated with

water above the lithic contact when snow melts. They are of

small extent, mostly in the mountains of the Western United

States. Some are in Alaska, and some are in the mountains of

the Northeastern United States. Lithic Cryorthents formed

under forest vegetation or under grasses and shrubs.

Oxyaquic Cryorthents.—These soils are saturated with

water within 100 cm of the surface at some time during normal

years. They can have redox depletions that have chroma of 2 or

less below a depth of 50 cm. These soils are considered

intergrades to Cryaquents. They are rare in the United States.

Vitrandic Cryorthents.—These soils formed in volcanic

deposits or have a deposit of fine pyroclastic materials near the

surface. Most of these deposits are of Holocene or historic age.

These soils are considered intergrades to Vitricryands. They are

of small extent, mostly in the mountains of the Western United

States.

Torriorthents

These are the dry Orthents of cool to hot, arid regions. They

have an aridic (or torric) moisture regime and a temperature

regime warmer than cryic. Generally, they are neutral or

calcareous and are on moderate to very steep slopes. A few are

on gentle slopes. Many of the gently sloping soils are on rock

pediments, are very shallow, have a sandy-skeletal particle-size

class, or are salty. Others are on fans where sediments are

recent but have little organic carbon. The vegetation on

Torriorthents commonly is sparse and consists mostly of

xerophytic shrubs and ephemeral grasses and forbs. The

vegetation on a few of the soils is saltgrass. Torriorthents are
422 Soil Taxonomy

used mainly for grazing. They are extensive in the Western

United States.

Definition

Torriorthents are the Orthents that have an aridic (or torric)

moisture regime and have a soil temperature regime warmer

than cryic.

Key to Subgroups

LEBA. Torriorthents that have:

1. A lithic contact within 50 cm of the soil surface; and

2. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 o

C or higher; and

3. A hyperthermic, thermic, mesic, frigid, or iso soil

temperature regime and an aridic (or torric) moisture

regime that borders on ustic.

Lithic Ustic Torriorthents

LEBB. Other Torriorthents that have:

1. A lithic contact within 50 cm of the soil surface; and

2. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 oC or higher; and

3. A thermic, mesic, or rigid soil temperature regime and

an aridic (or torric) moisture regime that borders on xeric.

Lithic Xeric Torriorthents

LEBC. Other Torriorthents that have a lithic contact within

50 cm of the soil surface.

Lithic Torriorthents

LEBD. Other Torriorthents that have:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower; and

2. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 o

C or higher; and

3. A thermic, mesic, or frigid soil temperature regime and an

aridic (or torric) moisture regime that borders on xeric.

Xerertic Torriorthents

LEBE. Other Torriorthents that have:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5

mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower; and

2. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 o

C or higher; and

3. An aridic (or torric) moisture regime that borders on

ustic.

Ustertic Torriorthents

LEBF. Other Torriorthents that have one or both of the

following:

1. Cracks within 125 cm of the soil surface that are 5 mm

or more wide through a thickness of 30 cm or more for some

time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the

soil surface and either a depth of 100 cm or a densic, lithic,

or paralithic contact, whichever is shallower.

Vertic Torriorthents

LEBG. Other Torriorthents that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Torriorthents
Entisols 423

LEBH. Other Torriorthents that have, in one or more horizons

within 100 cm of the soil surface, redox depletions with chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage).

Aquic Torriorthents

LEBI. Other Torriorthents that are saturated with water in

one or more layers within 150 cm of the soil surface in normal

years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Torriorthents

LEBJ. Other Torriorthents that have a horizon within 100 cm

of the soil surface that is 15 cm or more thick and that either

has 20 percent or more (by volume) durinodes or is brittle and

has a firm rupture-resistance class when moist.

Duric Torriorthents

LEBK. Other Torriorthents that have both:

1. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 o

C or higher; and

2. A hyperthermic, thermic, mesic, frigid, or iso soil

temperature regime and an aridic (or torric) moisture

regime that borders on ustic.

Ustic Torriorthents

LEBL. Other Torriorthents that have both:

1. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 oC or higher; and

2. A thermic, mesic, or frigid soil temperature regime

and an aridic (or torric) moisture regime that borders on

xeric.

Xeric Torriorthents

LEBM. Other Torriorthents.

Typic Torriorthents

Definition of Typic Torriorthents

Typic Torriorthents are the Torriorthents that:

1. Do not have a horizon within 100 cm of the surface that is

more than 15 cm thick and that either has 20 percent or more

durinodes or is brittle and has a firm rupture-resistance class

when moist;

2. Do not have a lithic contact within 50 cm of the surface;

3. Do not have either:

a. Cracks within 125 cm of the soil surface that are 5 mm or

more wide through a thickness of 30 cm or more for some time

in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the soil surface; or

b. A linear extensibility of 6.0 cm or more between the soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact, whichever is shallower;

4. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

5. Do not have, in any horizon within 100 cm of the soil

surface, redox depletionswith chroma of 2 or less and also

aquic conditions;

6. Are not saturated with water in any layer within 150 cm of

the soil surface for either or both 30 or more cumulative days

or 20 or more consecutive days in normal years; and

7. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Torriorthents.—The Typic subgroup is fixed on the

driest Torriorthents. Many of these soils are shallow to weakly

cemented rock. Some are moderately deep or deep to hard rock.

Soils that are partially cemented by silica are excluded from

the Typic subgroup because this feature is considered to

indicate the initial development of a duripan. The Torriorthents

that have a high linear extensibility or cracks and slickensides

or wedge-shaped aggregates also are excluded because they

share so many properties with Torrerts. Typic Torriorthents do

not have, in the upper 75 cm, a deposit of pyroclastic materials

that is as thick as 18 cm.

Typic Torriorthents are extensive soils in the intermountain

States of the United States. Most of them have moderate or

strong slopes and are used only for grazing. Others that have

gentle slopes are irrigated. The gently sloping soils are mostly

on fans or piedmont slopes where the sediments are recent and

have little organic carbon.
424 Soil Taxonomy

Aquic Torriorthents.—These soils have, in one or more

horizons within 100 cm of the soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage). The soils formed

mostly in recent alluvium, but they have too little organic

matter to meet the requirements for Fluvents. Ground water is

evident mostly during the high-water stages of streams. Most

Aquic Torriorthents have conductivity well in excess of 2 dS/m

as a result of salts that accumulate through capillary rise and

evapotranspiration. Soil moisture depends greatly on

subirrigation and is unpredictable, and there are no restrictions

on it in the definition. These soils are rare in the United States.

They have gentle slopes, and many of them are irrigated.

Duric Torriorthents.—These soils are partially cemented

by silica. In the soils in the United States, the cementation is in

the form of durinodes. Duric Torriorthents formed mostly in

rather recent alluvium, but they have too little organic matter

to meet the requirements for Fluvents. Most of the soils have

conductivity well in excess of 2 dS/m. The parent materials

were derived from rocks rich in pyroclastic materials. Duric

Torriorthents are rare in the United States.

Lithic Torriorthents.—These soils have a lithic contact

that is within 50 cm of the surface and commonly is at a depth

of less than 25 cm. They have a low moisture-storage capacity,

and they occur mostly in association with soils of other orders

or subgroups that have more moisture available to plants.

Lithic Torriorthents are of moderate extent in the United

States. They are used mostly for winter or spring grazing.

Lithic Ustic Torriorthents.—These soils have more

available moisture than Lithic Torriorthents during summer or,

if located in the Tropics, during the rainy seasons. They are

moist in some or all parts of the moisture control section for

more than one-fourth of the time (cumulative) when the soil

temperature at a depth of 50 cm exceeds 5 o

C. They have a

shallow or very shallow lithic contact, which limits the

moisture-storage capacity. Consequently, the soils commonly

are associated with the Ustalfs and Ustolls on more stable

surfaces. Lithic Ustic Torriorthents are of moderate extent in

the United States. They are used mostly for winter or spring

grazing.

Lithic Xeric Torriorthents.—These soils have a lithic

contact within 50 cm of the surface and have more available

moisture than the soils of the Lithic subgroup. They are in

regions that have enough winter precipitation for the moisture

control section to be moist in all parts during late winter or

early spring, but they are continuously dry in all parts of the

moisture control section for most of the summer in normal

years. The lithic contact commonly limits the moisture-storage

capacity of the moisture control section. Lithic Xeric

Torriorthents are of moderate extent in the United States. They

are used mostly for winter or spring grazing.

Oxyaquic Torriorthents.—These soils are like Typic

Torriorthents, but they are saturated with water in one or more

layers within 150 cm of the mineral soil surface for either or

both 20 or more consecutive days or 30 or more cumulative

days in normal years. Some of the soils have redox depletions

with low chroma (2 or less) at a depth below 100 cm from the

mineral soil surface. Oxyaquic Torriorthents are considered

intergrades to Aquents. They are not extensive. Some have a

water table that is partly or fully a result of excess irrigation

water.

Ustertic Torriorthents.—These soils have a high linear

extensibility or cracks and slickensides or wedge-shaped

aggregates. In the soils in the United States, the cracks are

closed in spring and periodically in summer. Most of the soils

have cracks and a high linear extensibility. Some have all of

the properties of Vertisols but have a densic or paralithic

contact at a shallow depth. Most are on flood plains on the

Great Plains. Ustertic Torriorthents are not extensive. Many of

them are used for summer grazing, and some are used as

cropland.

Ustic Torriorthents.—These soils have more available

moisture than Typic Torriorthents during summer or during

rainy seasons in the Tropics. They are moist in some or all

parts of the moisture control section for more than one-fourth

of the time (cumulative) when the soil temperature at a depth

of 50 cm exceeds 5 o

C. These soils can support somewhat more

vegetation than the soils in the Typic subgroup. They

commonly are associated with the Ustolls or Ustalfs on the

gentler slopes of the more stable surfaces. In many areas Ustic

Torriorthents lose an appreciable part of their precipitation as

runoff. These soils are extensive in the United States. They are

used mostly for grazing, but some are used as cropland.

Vertic Torriorthents.—These soils have a high linear

extensibility or cracks and slickensides or wedge-shaped

aggregates. They commonly have two short, undependable

rainy seasons. Slopes of the soils in the United States range

from nearly level to strong. Where slopes are suitable and

water is available, most of the soils are irrigated. Others are

used for grazing. Vertic Torriorthents are of small extent in the

Southwestern United States.

Vitrandic Torriorthents.—These soils are like Typic

Torriorthents, but they formed in volcanic deposits or have a

layer of pyroclastic materials that is 18 cm or more thick and

that is in the upper 75 cm. These soils are of small extent,

mostly in California, Oregon, and Nevada.

Xerertic Torriorthents.—These soils have a high linear

extensibility and cracks that regularly close during a cool or

cold season. They are in areas of winter precipitation and have

a moisture regime that approaches xeric. These soils can

produce more vegetation than the soils of the Typic or Ustic

subgroup because of the reliable supply of moisture stored in

winter. Xerertic Torriorthents are of small extent, mostly in

Utah. Most of these soils are used for grazing, but some are

used as irrigated cropland.

Xeric Torriorthents.—These soils are moist in some part of

the moisture control section for more than one-fourth of the

time when the soil temperature at a depth of 50 cm is 5 o

C or
Entisols 425

higher. They are in areas of winter precipitation and have a

moisture regime that approaches xeric. These soils can produce

more vegetation than the soils of the Typic or Ustic subgroup

because of the reliable supply of moisture stored in winter.

Xeric Torriorthents are extensive in the intermountain and

Pacific States of the United States. Some have moderate to very

steep slopes and formed mostly in weakly cemented country

rock. Others have gentle slopes and formed in alluvium that

had little organic matter. The gently sloping soils are mostly on

fans and piedmont slopes. Where slopes are suitable and water

is available, most of the Xeric Torriorthents are irrigated and

used as cropland. Those that are not irrigated are used mainly

for winter and spring grazing.

Udorthents

These are the Orthents of cool to hot, moist regions. They

have a udic moisture regime and a temperature regime warmer

than cryic. Generally, they are acid to neutral, but some are

calcareous. Slopes generally are moderate to steep but are

gentle in a few areas. Udorthents commonly occur in areas of

very recently exposed regolith, such as loess or till; in areas of

weakly cemented rocks, such as shale; or in areas of thin

regolith over hard rocks. Many of the gently sloping soils are

the result of mining or other earth-moving activities. Some

have a sandy-skeletal particle-size class. The vegetation is

commonly a deciduous forest, or the soils are used as pasture.

Udorthents are extensive soils on steep slopes in the humid

parts of the United States.

Definition

Udorthents are the Orthents that:

1. Have a udic moisture regime; and

2. Have a soil temperature regime warmer than cryic.

Key to Subgroups

LEEA. Udorthents that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Udorthents

LEEB. Other Udorthents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more.

Vitrandic Udorthents

LEEC. Other Udorthents that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Udorthents

LEED. Other Udorthents that are saturated with water in one

or more layers within 150 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Udorthents

LEEE. Other Udorthents that have 50 percent or more (by

volume) wormholes, wormcasts, and filled animal burrows

between either the Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and either a depth of

100 cm or a densic, lithic, paralithic, or petroferric contact,

whichever is shallower.

Vermic Udorthents

LEEF. Other Udorthents.

Typic Udorthents

Definition of Typic Udorthents

Typic Udorthents are the Udorthents that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Are not saturated with water in any layer within 150

cm of the mineral soil surface for either or both 30 or more
426 Soil Taxonomy

cumulative days or 20 or more consecutive days in normal

years;

4. Do not have a lithic contact within 50 cm of the mineral soil

surface; and

5. Have less than 50 percent (by volume) wormholes,

wormcasts, and filled animal burrows between the bottom of

the Ap horizon or a depth of 25 cm, whichever is deeper, and

either a depth of 100 cm or a densic, lithic, paralithic, or

petroferric contact if one occurs above a depth of 100 cm.

Description of Subgroups

Typic Udorthents.—The central concept or Typic subgroup

of Udorthents is fixed on soils that are shallow to weakly

cemented rock or deep or moderately deep to rock and that

have deep ground water and low animal activity. Many of these

soils formed in mine spoil or fill material. Some have a densic

contact with compacted layers of soil materials. Typic

Udorthents do not have, in the upper 75 cm, a deposit of

pyroclastic materials that is as thick as 18 cm. These soils are

used mostly as pasture or forest. A few are used as cropland,

and a few are idle.

Aquic Udorthents.—These soils have, in one or more

horizons within 100 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). The soils

are not extensive in the United States. They have slopes that

range from nearly level to steep. They are used mostly for

grazing or forest, but some that are gently sloping are used for

cultivated crops.

Lithic Udorthents.—These soils have a lithic contact

within 50 cm of the surface. The lithic contact is at a depth of

less than 25 cm in most of the soils. Lithic Udorthents are

otherwise like Typic Udorthents, except that possibly some of

them have very high biological activity above the lithic contact.

Lithic Udorthents are of small extent in the United States.

They are used mostly as pasture or forest. A few of these soils

are used as wildlife habitat.

Oxyaquic Udorthents.—These soils are saturated with

water for 20 consecutive days and/or 30 cumulative days within

150 cm of the mineral soil surface during normal years. They

may or may not have redoximorphic features, but they do not

have redox depletions with chroma of 2 or less within 100 cm

of the mineral soil surface. These soils occur in the

Midwestern and Northeastern United States. The soils in the

Northeast commonly are forested, but some are used for hay

and pasture. The soils in the Midwest are used mostly for crop

production.

Vermic Udorthents.—These soils have been so completely

reworked by animals, generally by earthworms, that distinct

horizons cannot be identified. The soils have not been

identified in the United States but have been observed in other

countries.

Vitrandic Udorthents.—These soils formed in volcanic

deposits or have a deposit of fine pyroclastic material 18 cm

thick or thicker within the upper 75 cm and generally at the

surface. Most of these deposits are of Holocene or historic age.

These soils are considered intergrades to Vitrands. They are of

small extent, mostly in the mountains of the Western United

States.

Ustorthents

These are the Orthents of cool to hot regions. They have an

ustic moisture regime and a temperature regime warmer than

cryic. Generally, they are neutral to calcareous, but some are

acid. Slopes generally are moderate to steep but are gentle in a

few areas. Ustorthents commonly occur in areas of very

recently exposed regolith, mostly weakly cemented sedimentary

deposits, or in areas of thin regolith over hard rocks. The

vegetation in warm regions commonly is a deciduous forest or

savanna. The soils that have a mesic or frigid temperature

regime commonly support scattered grasses mixed with

xerophytic shrubs. Some of the soils that have been cultivated

for a long time probably now consist of what was the C horizon

of other soils, particularly Ustalfs. The cultivated soils probably

never had any vegetation, except for cultivated crops. A few of

the soils that are in areas of loamy-skeletal or sandy-skeletal

sediments, mostly alluvium, have gentle slopes. Ustorthents are

extensive in the United States, particularly on the Great Plains.

Definition

Ustorthents are the Orthents that:

1. Have a soil temperature regime warmer than cryic; and

2. Have an ustic soil moisture regime.

Key to Subgroups

LEDA. Ustorthents that have:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that, in normal years, is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or
Entisols 427

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that,

in normal years, remains moist in some or all parts for

less than 90 consecutive days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 8 o

C.

Aridic Lithic Ustorthents

LEDB. Other Ustorthents that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Ustorthents

LEDC. Other Ustorthents that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that, in normal years, is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that,

in normal years, remains moist in some or all parts for

less than 90 consecutive days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 8 oC.

Torrertic Ustorthents

LEDD. Other Ustorthents that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Ustorthents

LEDE. Other Ustorthents that have anthraquic conditions.

Anthraquic Ustorthents

LEDF. Other Ustorthents that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Ustorthents

LEDG. Other Ustorthents that are saturated with water in

one or more layers within 150 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Ustorthents

LEDH. Other Ustorthents that have a horizon within 100

cm of the mineral soil surface that is 15 cm or more thick

and that either has 20 percent or more (by volume) durinodes

or is brittle and has a firm rupture-resistance class when

moist.

Durinodic Ustorthents

LEDI. Other Ustorthents that have both:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that, in normal years, is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that,

in normal years, remains moist in some or all parts for

less than 90 consecutive days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 8 o

C; and

2. Throughout one or more horizons with a total thickness
428 Soil Taxonomy

of 18 cm or more within 75 cm of the soil surface, one or both

of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitritorrandic Ustorthents

LEDJ. Other Ustorthents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Ustorthents

LEDK. Other Ustorthents that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime and a moisture control

section that, in normal years, is dry in all parts for fourtenths or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for six-tenths or more of the cumulative days per

year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that, in

normal years, is moist in some or all parts for less than 180

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 o

C.

Aridic Ustorthents

LEDL. Other Ustorthents that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime and a moisture control

section that, in normal years, is dry in some or all parts for

less than 105 cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for less than four-tenths of the cumulative days

per year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that, in

normal years, is dry in some or all parts for less than 120

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Udic Ustorthents

LEDM. Other Ustorthents that have 50 percent or more (by

volume) wormholes, wormcasts, and filled animal burrows

between either the Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and either a depth of

100 cm or a densic, lithic, paralithic, or petroferric contact,

whichever is shallower.

Vermic Ustorthents

LEDN. Other Ustorthents.

Typic Ustorthents

Definition of Typic Ustorthents

Typic Ustorthents are the Ustorthents that:

1. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Are not saturated with water in any layer within 150 cm of

the mineral soil surface for either or both 30 or more

cumulative days or 20 or more consecutive days in normal

years;

3. Do not have anthraquic conditions;

4. Do not have a horizon within 100 cm of the surface that is

more than 15 cm thick and that either has 20 percent or more

durinodes or is brittle and has a firm rupture-resistance class

when moist;

5. Do not have a lithic contact within 50 cm of the surface;

6. Have less than 50 percent (by volume) wormholes,

wormcasts, and filled animal burrows between the bottom of

the Ap horizon or a depth of 25 cm, whichever is deeper, and a
Entisols 429

depth of 100 cm or a densic, lithic, or paralithic or petroferric

contact, whichever is shallower;

7. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

8. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid soil temperature regime and a moisture control

section that, in normal years, is dry in some or all parts for

105 or more cumulative days per year but is not dry in all

parts for four-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for four- to six-tenths of the cumulative days per

year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that, in

normal years, is dry in some or all parts for 120 or more

cumulative days and moist for 180 or more cumulative days

per year when the temperature at a depth of 50 cm below the

soil surface is higher than 8 oC; and

9. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the soil surface,

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Ustorthents.—The central concept or Typic subgroup

of Ustorthents is fixed on soils that are deep or moderately deep

to hard rock and that do not have ground water within a depth

of 150 cm, do not have appreciable cementation by silica, do

not have high biologic activity, do not have a clayey texture

and a swelling type of clay, and do not have, in the upper 75

cm, a deposit of pyroclastic materials that is as thick as 18 cm.

The most common of these soils have a thin or very thin ochric

epipedon resting on weakly cemented rock or on sediments.

Some Typic Ustorthents formed in mine spoil or fill material.

Soils that have a shallow lithic contact are excluded from the

Typic subgroup, a convention used throughout this taxonomy.

Slopes of Typic Ustorthents range from nearly level to very

steep. These soils are used mostly for grazing, forest, or

catchments, but some are used for nonirrigated grain and a few

that have gentle slopes are used as irrigated cropland. Typic

Ustorthents are of moderate extent on the Great Plains in the

United States.

Anthraquic Ustorthents.—These soils are like Typic

Ustorthents, but they have a human-made perched water table

near the soil surface. They commonly have some redox

depletions with chroma of 2 or less in the Ap horizon. They are

intergrades between Ustorthents and Aquents. Anthraquic

Ustorthents are not known to occur in the United States. They

are irrigated and are used for paddy rice.

Aquic Ustorthents.—These soils have, in one or more

horizons within 100 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). The soils

are on low terraces or fans, in areas of sediments that are partly

sandy and partly loamy. Ground water is shallow during wet

periods or during periods when snow melts on the adjacent

mountains. The water has a very low salt content. These soils

either are nearly level or are in depressions. They commonly

have been drained and are used for irrigated crops. They are

not extensive in the United States.

Aridic Lithic Ustorthents.—These are the Ustorthents that

are drier than the soils in the Typic subgroup and have a lithic

contact within 50 cm of the mineral soil surface. Aridic Lithic

Ustorthents occur in the more arid regions of the Great Plains

in the United States. They range from gently sloping to steep.

Most are used as rangeland and wildlife habitat.

Aridic Ustorthents.—These soils are drier than Typic

Ustorthents and do not have a lithic contact within 50 cm of

the mineral soil surface. They are intergrades between

Ustorthents and Torriorthents. They are moderately extensive

in the southern part of the Great Plains in the United States.

Slopes are gentle to steep. Many Aridic Ustorthents are used

for grazing. Some of the less sloping soils are used as cropland.

Some of the cropland is irrigated, and some is used for

drought-tolerant crops.

Durinodic Ustorthents.—These soils differ from Typic

Ustorthents in that they are partially cemented by silica. They

are intergrades to Durids or Durustepts. They are not known to

occur in the United States.

Lithic Ustorthents.—These soils have a lithic contact
430 Soil Taxonomy

within 50 cm of the soil surface. Generally, the lithic contact is

appreciably shallower than 50 cm and is most commonly at a

depth of less than 25 cm. These soils are otherwise like those

of the Typic subgroup in defined characteristics. Slopes range

from gentle to very steep. Lithic Ustorthents are used mostly as

grazing land and watersheds, but some areas are used as forest.

These soils are moderately extensive in parts of the Western

United States.

Oxyaquic Ustorthents.—These soils are like Typic

Ustorthents, but they are saturated with water in one or more

layers within 150 cm of the mineral soil surface for either or

both 20 or more consecutive days or 30 or more cumulative

days in normal years. Some of these soils have redox depletions

with low chroma (2 or less) at a depth of more than 100 cm

below the mineral soil surface. Oxyaquic Ustorthents are

considered intergrades to Aquents. They are not extensive.

Some of the soils have a water table that is partly or fully a

result of excess irrigation water.

Torrertic Ustorthents.—These soils have a high shrinkswell potential and a soil moisture regime that borders on

aridic. They do not have a lithic contact within 50 cm of the

mineral soil surface. They occur in the western Dakotas as well

as Montana, Wyoming, Colorado, Arizona, and New Mexico.

They are used mostly as rangeland.

Udic Ustorthents.—These soils are like Typic Ustorthents,

but they are dry in some part of the moisture control section for

less than four-tenths of the cumulative days when the soil

temperature at a depth of 50 cm exceeds 5 oC if the soil

temperature regime is mesic or thermic and are dry in some or

all parts of the moisture control section for less than 90 days

during a period when the soil temperature at a depth of 50 cm

exceeds 8 oC if the soil temperature regime is hyperthermic,

isomesic, or warmer. These soils are intergrades between

Ustorthents and Udorthents. They are of very small extent in

the United States.

Vermic Ustorthents.—These soils have been so completely

reworked by animals, such as rodents, earthworms, and insects,

that diagnostic horizons cannot be identified. The soils have

not been identified in the United States but have been observed

in other countries.

Vertic Ustorthents.—These soils have high linear

extensibility or cracks and slickensides or wedge-shaped

aggregates. Slopes of the soils in the United States range from

nearly level to strong. Vertic Ustorthents are of small extent in

the United States. They are used mostly for grazing.

Vitrandic Ustorthents.—These soils are like Typic

Ustorthents, but they are composed of volcanic deposits or have

a layer of pyroclastic materials that is 18 cm or more thick and

is in the upper 75 cm. These soils are of minor extent, mostly

in the States of Arizona and New Mexico.

Vitritorrandic Ustorthents.—These soils are like Typic

Ustorthents, but they are composed of volcanic deposits or have

a layer of pyroclastic materials that is 18 cm or more thick and

is in the upper 75 cm. The soils have a moisture regime that is

marginal to aridic. They are of minor extent, mostly in the

States of Arizona and New Mexico.

Xerorthents

These are the Orthents of Mediterranean climates. They

have a xeric moisture regime and a frigid, mesic, or thermic

soil temperature regime. Generally, they are neutral to

moderately alkaline, but some are acid. Slopes are mostly

moderate to steep but are gentle in a few areas. Because many

of the soils are strongly sloping and lose water through runoff,

not all Orthents in a Mediterranean climate have a xeric

moisture regime, particularly if the regolith is thin. Winter

rains usually are gentle, summer drought is certain, and most

of the Orthents in a Mediterranean climate are Xerorthents.

The Xerorthents commonly are in sandy-skeletal families or

occur in areas of very recently exposed regolith, such as loess

or till; in areas of weakly cemented rocks, such as shale; or in

areas of very thin regolith over hard rocks. Some of these soils,

particularly those that have been cultivated for a long time or

reshaped for irrigation, consist of what was the C horizon of

other Xeric great groups, chiefly Xeralfs and Xerolls. The

vegetation is commonly trees or shrubs, or the soils are used

as pasture.

Definition

Xerorthents are the Orthents that have a xeric moisture

regime and a frigid, mesic, or thermic soil temperature regime.

Key to Subgroups

LECA. Xerorthents that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Xerorthents

LECB. Other Xerorthents that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Xerorthents

LECC. Other Xerorthents that have, in one or more horizons
Entisols 431

within 100 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Xerorthents

LECD. Other Xerorthents that are saturated with water in

one or more layers within 150 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Xerorthents

LECE. Other Xerorthents that have a horizon within 100 cm

of the mineral soil surface that is 15 cm or more thick and that

either has 20 percent or more (by volume) durinodes or is

brittle and has a firm rupture-resistance class when moist.

Durinodic Xerorthents

LECF. Other Xerorthents that have a base saturation (by

NH4

OAc) of less than 60 percent in all horizons at a depth

between 25 and 75 cm below the mineral soil surface.

Dystric Xerorthents

LECG. Other Xerorthents.

Typic Xerorthents

Definition of Typic Xerorthents

Typic Xerorthents are the Xerorthents that:

1. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Are not saturated with water in any layer within 150 cm of

the mineral soil surface for either or both 30 or more

cumulative days or 20 or more consecutive days in normal

years;

3. Do not have a horizon within 100 cm of the surface that is

more than 15 cm thick and that either has 20 percent or more

durinodes or is brittle and has a firm rupture-resistance class

when moist;

4. Do not have a lithic contact within 50 cm of the soil

surface;

5. Have a base saturation (by NH4

OAc) of 60 percent or more

in some part at a depth between 25 and 75 cm below the soil

surface; and

6. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Xerorthents.—The central concept or Typic

subgroup of Xerorthents is fixed on soils that are moderately

deep or deep to hard rock, do not have ground water within a

depth of 150 cm, and are not partially cemented by silica.

These soils have a base saturation (by NH4OAc) of 60 percent

or more in some part at a depth of between 25 and 75 cm below

the soil surface. Soils that have a shallow lithic contact are

excluded from the Typic subgroup, a convention used

throughout this taxonomy. Soils that are partially cemented by

silica are excluded because such soils are thought to represent

intergrades to Durixerepts.

Commonly, Typic Xerorthents are in a sandy-skeletal family

or have a thin ochric epipedon that rests on a densic or

paralithic contact with weakly cemented rock or dense

sediments. Some of these soils have been cultivated for a long

time or have been reshaped for irrigation and consist of what

was the C horizon of other soils, chiefly Xeralfs and Xerolls.

Typic Xerorthents are used mostly as forest or grazing land.

A few of these soils are used as cropland, and a few are idle.

Aquic Xerorthents.—These soils have, in one or more

horizons within 100 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). The soils

are on low terraces in the western part of the United States and

are not extensive.

Durinodic Xerorthents.—These soils differ from the soils

in the Typic subgroup because they have, within 100 cm of the

mineral soil surface, a horizon that is more than 15 cm thick

and that either has 20 percent or more (by volume) durinodes

or is brittle and has a firm rupture-resistance class when moist.

The Durinodic Xerorthents in the United States occur mainly

in eastern Washington, where there is appreciable volcanic ash

in the loess. The soils are used for small grain or as grazing

land.

Dystric Xerorthents.—These are the Xerorthents that occur

in areas of relatively high rainfall. The soils have a base

saturation (by NH4

OAc) of less than 60 percent in some part at

a depth between 25 and 75 cm below the surface. They have

coarse textures, but they are excluded from Psamments because

they have a high content of rock fragments and from Xerepts
432 Soil Taxonomy

because the textures are coarser than is permitted in cambic

horizons. Dystric Xerorthents are of moderate extent in the

Western United States, mostly in California, Washington, and

Oregon. They are used mostly as forest, but some are used as

cropland.

Lithic Xerorthents.—These soils have a lithic contact

within 50 cm of the soil surface, normally within 25 cm of the

surface. Slopes range from gentle to very steep. Lithic

Xerorthents are used mostly as grazing land and watersheds,

but some areas are used as forest. These soils are moderately

extensive in parts of the Western United States.

Oxyaquic Xerorthents.—These soils are saturated with

water for 20 or more consecutive days and/or 30 or more

cumulative days within 100 cm of the mineral soil surface

during normal years. They do not have redox depletions with

chroma of 2 or less within 100 cm of the mineral soil surface.

These soils are of limited extent in California, Idaho, and

eastern Oregon. They are used as grazing land.

Vitrandic Xerorthents.—These soils are like Typic

Xerorthents, but they are composed of volcanic deposits or

have a layer of pyroclastic materials that is 18 cm or more

thick and is in the upper 75 cm. The soils are of minor

extent, mostly in the States of California, Oregon, and

Washington.

Psamments

These are the sandy Entisols. They are sandy in all layers

within the particle-size control section. Some formed in poorly

graded (well sorted) sands on shifting or stabilized sand dunes,

in cover sands, or in sandy parent materials that were sorted in

an earlier geologic cycle. Some formed in sands that were

sorted by water and are on outwash plains, lake plains, natural

levees, or beaches. A few Psamments formed in material

weathered from sandstone or granitic bedrock. Psamments

occur under any climate, but they cannot have permafrost

within 100 cm of the soil surface. They can have any

vegetation and are on surfaces of virtually any age from

recent historic to Pliocene or older. The Psamments on old

stable surfaces commonly consist of quartz sand. Ground

water typically is deeper than 50 cm and commonly is much

deeper.

Psamments have a relatively low water-holding capacity.

Those that are bare and become dry are subject to soil blowing

and drifting and cannot easily support wheeled vehicles.

Because very gravelly sands do not have the two qualities just

described, they are excluded from Psamments and are grouped

with Orthents. Thus, not all Entisols that have a sandy texture

are Psamments.

Definition

Psamments are the Entisols that:

1. Have have less than 35 percent (by volume) rock fragments

and a texture of loamy fine sand or coarser in all layers within

the particle-size control section;

2. Do not have, within 50 cm of the mineral soil surface, aquic

conditions; and

a. The colors defined for Aquents; or

b. Sulfidic materials; or

c. A positive reaction to alpha,alpha-dipyridyl when the soil

is not being irrigated;

3. Do not have fragments of diagnostic horizons that can be

identified and that occur more or less without a discernible

order below any Ap horizon but within the particle-size control

section; and

4. Do not have sulfidic materials within 50 cm of the mineral

soil surface or both the aquic conditions and colors defined for

Aquents.

Key to Great Groups

LCA. Psamments that have a cryic soil temperature

regime.

Cryopsamments, p. 432

LCB. Other Psamments that have an aridic (or torric)

moisture regime.

Torripsamments, p. 436

LCC. Other Psamments that have, in the 0.02 to 2.0 mm

fraction within the particle-size control section, a total of more

than 90 percent (by weighted average) resistant minerals.

Quartzipsamments, p. 434

LCD. Other Psamments that have an ustic moisture regime.

Ustipsamments, p. 439

LCE. Other Psamments that have a xeric moisture regime.

Xeropsamments, p. 441

LCF. Other Psamments.

Udipsamments, p. 438

Cryopsamments

These are the Psamments of cold areas. In the United States,

they are primarily in high mountains of the West and in

Alaska. Generally, they have, or had before they were

disturbed, a coniferous forest vegetation. They are of small

extent. Most of them formed in material weathered from

granitic rocks or in deposits of late-Pleistocene or recent age.

Some formed in recent volcanic deposits.
Entisols 433

Definition

Cryopsamments are the Psamments that have a cryic soil

temperature regime.

Key to Subgroups

LCAA. Cryopsamments that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Cryopsamments

LCAB. Other Cryopsamments that have, in one or more

horizons within 50 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Cryopsamments

LCAC. Other Cryopsamments that are saturated with water

in one or more layers within 100 cm of the mineral soil surface

in normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Cryopsamments

LCAD. Other Cryopsamments that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction

containing 5 percent or more volcanic glass, and [(Al plus 1

/2

Fe, percent extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrandic Cryopsamments

LCAE. Other Cryopsamments that have a horizon 5 cm or

more thick that has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

2. Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Cryopsamments

LCAF. Other Cryopsamments that have lamellae within 200

cm of the mineral soil surface.

Lamellic Cryopsamments

LCAG. Other Cryopsamments.

Typic Cryopsamments

Definition of Typic Cryopsamments

Typic Cryopsamments are the Cryopsamments that:

1. Do not have lamellae within 200 cm of the soil surface;

2. Do not have, in any horizon within 50 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also aquic

conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for either or both 20 or more

consecutive days or 30 or more cumulative days in normal

years;

4. Do not have a lithic contact within 50 cm of the soil

surface;

5. Do not have a horizon, 5 cm or more thick, either below

an Ap horizon or at a depth of 18 cm or more from the mineral

soil surface, whichever is deeper, that has one or more of the

following:

a. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

b. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

c. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon; and

6. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction containing 5 percent or more

volcanic glass, and [(Al plus 1/2 Fe, percent extracted by

ammonium oxalate) times 60] plus the volcanic glass (percent)

is less than 30.

Description of Subgroups

Typic Cryopsamments.—The central concept or Typic

subgroup of Cryopsamments is fixed on deep sands that have

ground water deeper than 100 cm, that do not have a weak

accumulation of amorphous materials, and do not have

lamellae within 200 cm of the soil surface.

These soils do not have, in the upper 75 cm, a deposit of

pyroclastic materials that is as thick as 18 cm. Lamellae with

illuvial clay are considered to represent a transition to Cryalfs.

Shallow mottles with low chroma and short periods of

saturation in the mottled horizon are considered features of the

intergrades to Psammaquents. Soils that have a weak

accumulation of amorphous materials are considered

intergrades to Spodosols.

Typic Cryopsamments are of small extent. Most are in

Alaska, but some are in the mountains of other Western States.

Aquic Cryopsamments.—These soils have aquic

conditions for some time in normal years (or artificial

drainage) and redox depletions with chroma of 2 or less within

50 cm of the mineral soil surface. The soils have not been

identified as series in the United States, but the subgroup is

provided for use if needed.

Lamellic Cryopsamments.—These soils have lamellae

within 200 cm of the soil surface. An albic horizon normally is
434 Soil Taxonomy

below an O horizon or a thin A or Ap horizon in these soils.

The soils are rare in the United States and are at elevations

above 1,200 m. They are used as forest.

Lithic Cryopsamments.—These soils have a lithic contact

within a depth of 50 cm. They are permitted to have redox

depletions with low chroma (2 or less) above the lithic contact.

These soils are not known to occur in the United States.

Oxyaquic Cryopsamments.—These soils are like Typic

Cryopsamments, but they are saturated with water in one or

more layers within 100 cm of the mineral soil surface for either

or both 20 or more consecutive days or 30 or more cumulative

days in normal years. Some of these soils have redox depletions

with low chroma (2 or less) at a depth below 50 cm from the

mineral soil surface. Oxyaquic Cryopsamments are considered

intergrades to Aquents. They are not known to occur in the

United States.

Spodic Cryopsamments.—These soils have a weak

accumulation of amorphous materials. They are presumed to be

developing toward Spodosols, mainly Cryods, but are too

weakly developed to be classified as Spodosols. No series has

been established, but the subgroup is provided for use if

needed.

Vitrandic Cryopsamments.—These soils formed in volcanic

deposits or have a deposit of fine pyroclastic materials near the

surface. The soils are considered intergrades to Vitricryands.

They are of small extent, mostly in the mountains of the Western

United States.

Quartzipsamments

These are the freely drained Psamments that have more than

90 percent resistant minerals. They are in humid to semiarid,

cool to hot regions. They can have any temperature regime,

except for cryic, and any moisture regime, except for aridic (or

torric). These soils are high in content of quartz sand and are

white or stained with shades of brown, yellow, or red. Because

they commonly have virtually no minerals that can weather,

they can occur on some extremely old land surfaces. They also

occur on late-Pleistocene and younger surfaces. A spodic

horizon is known to lie beneath white sand, particularly in

tropical areas, at a depth of several meters, so deep that

determination of its presence or absence is not practical. The

most important properties in such areas are those of the upper

2 m or so that consists of uncoated quartz sand.

The vegetation on Quartzipsamments varies widely with

climate. Few of these soils are cultivated, except in Florida.

Quartzipsamments are extensive on the coastal plains in the

United States.

Definition

Quartzipsamments are the Psamments that:

1. Have a temperature regime warmer than cryic;

2. Have a moisture regime other than aridic (or torric); and

3. Average more than 90 percent resistant minerals in

the 0.02 to 2.0 mm fraction within the particle-size control

section.

Key to Subgroups

LCCA. Quartzipsamments that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Quartzipsamments

LCCB. Other Quartzipsamments that have both:

1. In one or more horizons within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A horizon, 5 cm or more thick, either below an Ap

horizon or at a depth of 18 cm or more from the mineral soil

surface, whichever is deeper, that has one or more of the

following:

a. In 25 percent or more of each pedon, cementation

by organic matter and aluminum, with or without iron;

or

b. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

c. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Aquodic Quartzipsamments

LCCC. Other Quartzipsamments that have, in one or more

horizons within 100 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Quartzipsamments

LCCD. Other Quartzipsamments that are saturated with

water in one or more layers within 100 cm of the mineral soil

surface in normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Quartzipsamments

LCCE. Other Quartzipsamments that meet all of the

following:

1. Have an ustic moisture regime; and

2. Have a clay fraction with a CEC of 16 cmol(+) or less

per kg clay (by NH4OAc pH 7); and

3. The sum of the weighted average silt plus 2 times

the weighted average clay (both by weight) is more than 5.

Ustoxic Quartzipsamments
Entisols 435

LCCF. Other Quartzipsamments that meet all of the

following:

1. Have a udic moisture regime; and

2. Have a clay fraction with a CEC of 16 cmol(+) or less per

kg clay (by NH4

OAc pH 7); and

3. The sum of the weighted average silt plus 2 times the

weighted average clay (both by weight) is more than 5.

Udoxic Quartzipsamments

LCCG. Other Quartzipsamments that have 5 percent or more

(by volume) plinthite in one or more horizons within 100 cm of

the mineral soil surface.

Plinthic Quartzipsamments

LCCH. Other Quartzipsamments that have both:

1. Lamellae within 200 cm of the mineral soil surface; and

2. An ustic moisture regime.

Lamellic Ustic Quartzipsamments

LCCI. Other Quartzipsamments that have lamellae within

200 cm of the mineral soil surface.

Lamellic Quartzipsamments

LCCJ. Other Quartzipsamments that have an ustic moisture

regime.

Ustic Quartzipsamments

LCCK. Other Quartzipsamments that have a xeric moisture

regime.

Xeric Quartzipsamments

LCCL. Other Quartzipsamments that have a horizon, 5 cm or

more thick, either below an Ap horizon or at a depth of 18 cm

or more from the mineral soil surface, whichever is deeper, that

has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

2. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Quartzipsamments

LCCM. Other Quartzipsamments.

Typic Quartzipsamments

Definition of Typic Quartzipsamments

Typic Quartzipsamments are the Quartzipsamments that:

1. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 30 or more cumulative days or 20

or more consecutive days in normal years;

3. Do not have a horizon, 5 cm or more thick, either below

an Ap horizon or at a depth of 18 cm or more from the mineral

soil surface, whichever is deeper, that has one or more of the

following:

a. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

b. Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

c. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon;

4. Do not have a lithic contact within 50 cm of the soil

surface;

5. Have a clay fraction with a CEC of more than 16 than

cmol(+) per kg clay (by NH4OAc pH 7) if the sum of the

weighted average silt plus 2 times the weighted clay (both by

weight) is more than 5;

6. Have less than 5 percent plinthite in all horizons above a

depth of 100 cm;

7. Have a udic or perudic moisture regime; and

8. Do not have lamellae within 200 cm of the soil surface.

Description of Subgroups

Typic Quartzipsamments.—The Typic subgroup of

Quartzipsamments is centered on soils that have a udic or

perudic moisture regime, have deep ground water in all

seasons, do not have distinct color horizons, have a moderately

thick or thicker regolith, and have at least moderately active

clays or very little clay. These soils are extensive in the United

States. They are mostly in the Southeastern States. Most are

used as forest, but some are used as cropland or pasture.

Aquic Quartzipsamments.—These soils have, in one or

more horizons within 100 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). The soils

are considered intergrades to Psammaquents. They are of small

extent in the United States.

Aquodic Quartzipsamments.—These soils have weak

accumulations of amorphous materials. They also have, in one

or more horizons within 100 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and aquic conditions

for some time in normal years (or artificial drainage). These

soils are considered intergrades to Aquods. They are of small

extent in the United States.
436 Soil Taxonomy

Lamellic Quartzipsamments.—These soils have lamellae

within 200 cm of the soil surface. The Lamellic

Quartzipsamments in the United States have a udic moisture

regime, although the subgroup also allows soils with a xeric

regime. Because of the lamellae, Lamellic Quartzipsamments

have more moisture available for deep-rooted plants, such as

trees and perennial grasses, than Typic Quartzipsamments.

Lamellic Quartzipsamments are of small extent in the United

States.

Lamellic Ustic Quartzipsamments.—These soils have an

ustic moisture regime and have lamellae within 200 cm of the

soil surface. Because of the lamellae, these soils have more

moisture available for deep-rooted plants, such as trees and

perennial grasses, than other Quartzipsamments with an ustic

moisture regime. Lamellic Ustic Quartzipsamments are of

small extent in the United States.

Lithic Quartzipsamments.—These soils are shallow to a

lithic contact. They are of small extent in the United States.

Oxyaquic Quartzipsamments.—These soils are saturated

with water in one or more layers within 150 cm of the mineral

soil surface for either or both 20 or more consecutive days or

30 or more cumulative days in normal years. Some of the soils

have redox depletions with low chroma (2 or less) at a depth

below 100 cm from the mineral soil surface. Oxyaquic

Quartzipsamments are considered intergrades to Aquents. They

are of small extent in the United States.

Plinthic Quartzipsamments.—These soils have 5 percent

or more (by volume) plinthite in one or more horizons within

100 cm of the mineral soil surface. They are not known to

occur in the United States.

Spodic Quartzipsamments.—These soils are like Typic

Quartzipsamments, but they have a weak accumulation of

amorphous materials. The ground water is deeper than 100 cm

most of the year in the soils of this subgroup. These soils are of

small extent in the United States.

Udoxic Quartzipsamments.—These soils are like Typic

Quartzipsamments, but they have a clay fraction that meets the

CEC requirements for an oxic horizon, but the amount of clay

is too small for an oxic horizon. Udoxic Quartzipsamments are

not known to occur in the United States, but they are extensive

in the equatorial regions of Africa and South America.

Ustic Quartzipsamments.—These soils are like Typic

Quartzipsamments, but they have an ustic moisture regime.

They are of small extent in the United States.

Ustoxic Quartzipsamments.—These soils are like Typic

Quartzipsamments, but they have an ustic moisture regime and

have a clay fraction that meets the CEC requirements of clay in

an oxic horizon. The amount of clay is too small to meet the

requirements for an oxic horizon. These soils are not known to

occur in the United States, but they are extensive in Africa and

South America.

Xeric Quartzipsamments.—These soils are like Typic

Quartzipsamments, but they have a xeric moisture regime.

They are not known to occur in the United States.

Torripsamments

These are the cool to hot Psamments of arid climates. They

have an aridic (or torric) moisture regime and a temperature

regime warmer than cryic. Many of these soils are on stable

surfaces, some are on dunes, some are stabilized, and some are

moving. Torripsamments consist of quartz, mixed sands,

volcanic glass, or even gypsum and may have any color.

Generally, they are neutral or calcareous and are nearly level to

steep. The vegetation consists mostly of xerophytic shrubs,

grasses, and forbs. Many of these soils support more vegetation

than other soils with an aridic moisture regime, presumably

because they lose less water as runoff. Some of the soils on

dunes support a few ephemeral plants or have a partial cover of

xerophytic and ephemeral plants. The shifting dunes may be

devoid of plants in normal years. Most of the deposits are of

late-Pleistocene or younger age. These soils are used mainly for

grazing. They are extensive in the Western United States.

Definition

Torripsamments are the Psamments that have an aridic (or

torric) moisture regime and a soil temperature regime warmer

than cryic.

Key to Subgroups

LCBA. Torripsamments that have a lithic contact within 50

cm of the soil surface.

Lithic Torripsamments

LCBB. Other Torripsamments that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction

containing 5 percent or more volcanic glass, and [(Al plus 1

/2

Fe, percent extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrandic Torripsamments

LCBC. Other Torripsamments that have a horizon within

100 cm of the soil surface that is 15 cm or more thick and that

either has 20 percent or more (by volume) durinodes or is

brittle and has a firm rupture-resistance class when moist.

Haploduridic Torripsamments

LCBD. Other Torripsamments that have both:

1. A moisture control section that, in normal years, is dry

in all its parts for less than three-fourths of the cumulative

days per year when the soil temperature at a depth of 50 cm

from the soil surface is 5 o

C or higher; and

2. An aridic (or torric) moisture regime that borders on

ustic.

Ustic Torripsamments

LCBE. Other Torripsamments that have both:
Entisols 437

1. A moisture control section that, in normal years, is dry in

all its parts for less than three-fourths of the cumulative days

per year when the soil temperature at a depth of 50 cm from

the soil surface is 5 o

C or higher; and

2. A thermic, mesic, or frigid soil temperature regime and an

aridic (or torric) moisture regime that borders on xeric.

Xeric Torripsamments

LCBF. Other Torripsamments that have, in all horizons from

a depth of 25 to 100 cm, more than 50 percent colors that have

all of the following:

1. Hue of 2.5YR or redder; and

2. A color value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Rhodic Torripsamments

LCBG. Other Torripsamments.

Typic Torripsamments

Definition of Typic Torripsamments

Typic Torripsamments are the Torripsamments that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a horizon within 100 cm of the surface that is

more than 15 cm thick and that either has 20 percent or more

durinodes or is brittle and has a firm rupture-resistance class

when moist;

3. Are dry in all parts of the moisture control section for

three-fourths or more of the time (cumulative) when the soil

temperature at a depth of 50 cm is 5 o

C or higher;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction containing 5 percent or more

volcanic glass, and [(Al plus 1/2 Fe, percent extracted by

ammonium oxalate) times 60] plus the volcanic glass (percent)

is 30 or more; and

5. Do not have, in all horizons from a depth of 25 to 100 cm,

more than 50 percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A color value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Description of Subgroups

Typic Torripsamments.—The Typic subgroup consists of

the Torripsamments that are dry for more than three-fourths of

the time when the soil temperature is 5 o

C or higher. These

soils do not have evident cementation by silica and are

moderately deep or deep to a lithic contact. The limitation on

moisture restricts the subgroup to the drier part of the range of

the great group. The restriction against a lithic contact is the

same one that is applied in Typic subgroups throughout most of

this taxonomy. Many of these soils support more vegetation

than other soils with an aridic moisture regime, perhaps

because of rapid infiltration and a low available water capacity,

which cause the precipitation to moisten the soils to a greater

depth than in most other soils with an aridic moisture regime.

Some water is stored below the soil moisture control section.

Typic Torripsamments are moderately extensive in the Western

United States. They are used mainly for grazing.

Haploduridic Torripsamments.—These soils have, within

100 cm of the surface, a horizon that is more than 15 cm thick

and that either has 20 percent or more durinodes or is brittle

and has a firm rupture-resistance class when moist. The soils

are permitted to have a moisture regime that is not so dry as

that of the Typic subgroup. Some volcanic ash and other

pyroclastic materials are in some of these soils. Haploduridic

Torripsamments are not known to occur in the United States.

Lithic Torripsamments.—These soils are less than 50 cm

deep to a lithic contact. Because the soils are shallow, a wider

range in the moisture regime is permitted than in other

Torripsamments. Small areas of Lithic Torripsamments are in

the mountains in the Western United States and are used for

grazing.

Rhodic Torripsamments.—These soils have dark red

colors. They do not have a lithic contact within 50 cm of the

soil surface or a moisture regime that borders on ustic or xeric.

They are in areas of an isohyperthermic soil temperature

regime in India. Some of these soils are used for the production

of cashews.

Ustic Torripsamments.—These soils have an aridic

moisture regime that borders on ustic. Most of the soils in this

subgroup have two short rainy seasons and two long dry

seasons each year. The longer rainy season is less than 3

months, or it has only showers of erratic distribution, so that

the moisture control section dries between rains. Many of these

soils support more vegetation than other soils with an aridic

moisture regime that borders on ustic, perhaps because of rapid

infiltration and a low available water capacity, which cause the

precipitation to moisten the soils to a greater depth than in

most other soils with an aridic moisture regime. Some water is

stored below the soil moisture control section. Ustic

Torripsamments are extensive in the Western United States.

They are used mainly for grazing.

Vitrandic Torripsamments.—These soils have a

significant volcanic influence in one or more layers 18 cm or

more thick within 75 cm of the mineral soil surface. They are

in California and Oregon. Most are used as rangeland, but

some are mined for pumice or are irrigated and used for alfalfa.

Xeric Torripsamments.—These soils have an aridic

moisture regime that borders on xeric. The rainy season is in
438 Soil Taxonomy

winter, and summer is very dry. The supply of winter moisture

 is dependable, however, and the soils can support more

vegetation than the soils of the Typic subgroup. The level of

organic matter may be higher than in Typic Torripsamments

but does not need to be higher in the soils on shifting dunes.

Many of the Xeric Torripsamments support more brushy

vegetation than other soils with an aridic moisture regime that

borders on xeric, perhaps because of rapid infiltration and a

low available water capacity, which cause the precipitation to

moisten the soils to a greater depth than in most other soils

with an aridic moisture regime. Some water is stored deep

below the soil moisture control section. Xeric Torripsamments

are moderately extensive in the Western United States. They

are used mainly for grazing. Some of the soils are used as

irrigated cropland.

Udipsamments

These are the Psamments that are of humid regions and have

a temperature regime warmer than cryic. The soils have a udic

moisture regime, and they average more than 10 percent

weatherable minerals (in the 0.02 to 2.0 mm fraction) in the

particle-size control section. They are predominantly in areas

of late-Pleistocene or more recent deposits and are mostly

brownish and freely drained. Most of the soils have supported

forest vegetation, but a few have been cultivated ever since the

sands were deposited. Others have been cultivated for a very

long time. Udipsamments are extensive in the United States.

Many are used as forest. Large areas, mostly with mesic or

warmer temperature regimes, have been cleared and are used

as cropland or pasture.

Definition

Udipsamments are the Psamments that:

1. Have a soil temperature regime warmer than cryic;

2. Have a udic moisture regime; and

3. Average less than 90 percent resistant minerals in the 0.02

to 2.0 mm fraction within the particle-size control section.

Key to Subgroups

LCFA. Udipsamments that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Udipsamments

LCFB. Other Udipsamments that have, in one or more

horizons within 100 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Udipsamments

LCFC. Other Udipsamments that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Udipsamments

LCFD. Other Udipsamments that have a horizon, 5 cm or

more thick, either below an Ap horizon or at a depth of 18 cm

or more from the mineral soil surface, whichever is deeper, that

has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

2. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Udipsamments

LCFE. Other Udipsamments that have lamellae within 200

cm of the mineral soil surface.

Lamellic Udipsamments

LCFF. Other Udipsamments that have a surface horizon

between 25 and 50 cm thick that meets all of the requirements

for a plaggen epipedon except thickness.

Plagganthreptic Udipsamments

LCFG. Other Udipsamments.

Typic Udipsamments

Definition of Typic Udipsamments

Typic Udipsamments are the Udipsamments that:

1. Do not have lamellae within 200 cm of the soil surface;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 30 or more cumulative days or 20

or more consecutive days in normal years;

4. Do not have a lithic contact within a depth of 50 cm;

5. Do not have a horizon, 5 cm or more thick, either below

an Ap horizon or at a depth of 18 cm or more from the mineral

soil surface, whichever is deeper, that has one or more of the

following:

a. In 25 percent or more of each pedon, cementation

by organic matter and aluminum, with or without iron;

or

b. Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or
Entisols 439

c. An ODOE value of 0.12 or more, and a value half as high

or lower in an overlying horizon; and

6. Do not have a surface horizon between 25 and 50 cm thick

that meets all of the requirements for a plaggen epipedon

except thickness.

Description of Subgroups

Typic Udipsamments.—The Typic subgroup of

Udipsamments is centered on soils that are moderately deep or

deeper to a lithic contact, have deep ground water, do not have

a weak accumulation of amorphous materials, do not have

lamellae within 200 cm of the soil surface, and do not have an

epipedon (less than 50 cm thick) that meets all of the

requirements for a plaggen epipedon except thickness.

Soils that have a lithic contact within 50 cm of the soil

surface are excluded from the Typic subgroup, a convention

used throughout this taxonomy. Soils that are saturated with

water within a depth of 100 cm and have redox depletions with

low chroma (2 or less) are considered intergrades to

Psammaquents. Soils that have weak accumulations of

amorphous materials are considered intergrades to Spodosols.

In the United States, such soils are mostly intergrades to

Orthods. Lamellae are used as criteria for the Lamellic

subgroup and indicate a transition to Alfisols or Ultisols. A

thin surface mantle that meets all of the requirements for a

plaggen epipedon except thickness is considered a transition to

Plagganthrepts.

Typic Udipsamments are extensive in the Eastern United

States. They are used mainly as forest, but large areas have

been cleared and are used as cropland or pasture.

Aquic Udipsamments.—These soils are saturated with

water at some time of the year and have redox depletions with

low chroma (2 or less) within 100 cm of the soil surface, and

they are permitted, but not required, to have lamellae within

200 cm of the surface. They are otherwise like Typic

Udipsamments. Aquic Udipsamments are of moderate extent in

the Eastern United States. They are used mainly as forest, but

some areas have been cleared and are used as cropland or

pasture.

Lamellic Udipsamments.—These soils have lamellae in

which clay has accumulated as oriented coatings on sand

grains. These soils are of moderate extent in the Eastern

United States. They are used mainly as forest, but some have

been cleared and are used as cropland or pasture.

Lithic Udipsamments.—These soils have a lithic contact

within 50 cm of the soil surface but are otherwise like Typic

Udipsamments. Lithic Udipsamments are of very small extent

in the Eastern United States. They are used mainly as forest.

Oxyaquic Udipsamments.—These soils are saturated with

water for 20 or more consecutive days or 30 or more

cumulative days in normal years; do not have redox depletions

with low chroma (2 or less) within 100 cm of the soil surface;

and are permitted, but not required, to have lamellae within

200 cm of the surface. They are otherwise like Typic

Udipsamments. Oxyaquic Udipsamments are of moderately small

extent in the Eastern United States. They are used mainly as

forest, but some have been cleared and are used as cropland or

pasture.

Plagganthreptic Udipsamments.—These soils have a

surface horizon between 25 and 50 cm thick that meets all of

the requirements for a plaggen epipedon except thickness.

They are not known to occur in the United States, but the

subgroup is provided for use in other countries.

Spodic Udipsamments.—These soils have weak

accumulations of amorphous materials. They are considered to

be developing toward Spodosols or to be more or less in

equilibrium between Psamments and Spodosols, generally

Orthods in the United States. Spodic Udipsamments are of

small extent in the Eastern United States. They are used

mainly as forest, but some have been cleared and are used as

cropland or pasture.

Ustipsamments

These are the Psamments that have an ustic moisture

regime. They can have any temperature regime warmer than

cryic. These soils support mostly grass or savanna vegetation.

A few are in drought-tolerant forests of small, scattered trees.

Many support as much vegetation as or more vegetation than

other soils with an ustic moisture regime, perhaps because of

rapid infiltration and a low available water capacity, which cause

the precipitation to moisten the soils to a greater depth than in

most other soils with an ustic moisture regime. Some water is

stored below the soil moisture control section. Ustipsamments

are used mainly for grazing. Few of them are cultivated because

they are subject to soil blowing if they are cultivated.

Ustipsamments are extensive soils on the Great Plains in the

United States.

Definition

Ustipsamments are the Psamments that:

1. Have a soil temperature regime warmer than cryic;

2. Have an ustic soil moisture regime; and

3. Average less than 90 percent resistant minerals (in

the 0.02 to 2.0 mm fraction) in the particle-size control

section.

Key to Subgroups

LCDA. Ustipsamments that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Ustipsamments

LCDB. Other Ustipsamments that have, in one or more

horizons within 100 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time in normal years (or artificial drainage).

Aquic Ustipsamments
440 Soil Taxonomy

LCDC. Other Ustipsamments that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Ustipsamments

LCDD. Other Ustipsamments that, when neither irrigated

nor fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime and a moisture control

section that, in normal years, is dry in all parts for fourtenths or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for six-tenths or more of the cumulative days per

year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that, in

normal years, is moist in some or all parts for less than 180

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Aridic Ustipsamments

LCDE. Other Ustipsamments that have lamellae within 200

cm of the mineral soil surface.

Lamellic Ustipsamments

LCDF. Other Ustipsamments that have, in all horizons from

a depth of 25 to 100 cm, more than 50 percent colors that have

all of the following:

1. Hue of 2.5YR or redder; and

2. A color value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Rhodic Ustipsamments

LCDG. Other Ustipsamments.

Typic Ustipsamments

Definition of Typic Ustipsamments

Typic Ustipsamments are the Ustipsamments that:

1. Do not have lamellae within 200 cm of the soil surface;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 30 or more cumulative days or 20 or

more consecutive days in normal years;

4. Do not have a lithic contact within 50 cm of the surface;

5. Are either irrigated or fallowed to store moisture or have one

of the following:

a. A frigid soil temperature regime and a moisture control

section that, in normal years, is dry in all parts for less than

four-tenths of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a

moisture control section that, in normal years, is dry in

some part for less than six-tenths of the cumulative days per

year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that, in

normal years, is moist in some or all parts for 180 or more

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC; and

6. Do not have, in all horizons from a depth of 25 to 100 cm,

more than 50 percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A color value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Description of Subgroups

Typic Ustipsamments.—The central concept or Typic

subgroup of Ustipsamments is fixed on sands that have deep

ground water and a thick regolith and do not have lamellae

within 200 cm of the soil surface. Some of these soils are

shallow to a paralithic contact. Commonly, the sands are a

mixture of quartz and feldspars.

Soils that have lamellae in which silicate clays have

accumulated are excluded from the Typic subgroup because the

lamellae are considered to indicate intergrades to soils that

have an argillic horizon. Soils that have a lithic contact within

50 cm of the surface are excluded from the Typic subgroup, a

convention used throughout this taxonomy. Redoximorphic

features and the presence of ground water within 100 cm of the

surface at some time of the year cause soils to be excluded

because these features are considered to indicate intergrades to

Psammaquents.

Typic Ustipsamments are freely drained sands. They support

mostly grass or savanna vegetation. A few are in droughttolerant forests of small, scattered trees. Many support as much
Entisols 441

vegetation as or more vegetation than other soils with an ustic

moisture regime, perhaps because of rapid infiltration and a

low available water capacity, which cause the precipitation to

moisten the soils to a greater depth than in most other soils

with an ustic moisture regime. Some water is stored below the

soil moisture control section. Typic Ustipsamments are

extensive on the Great Plains in the United States. They are

used mainly for grazing. Few of them are cultivated because

they are subject to soil blowing if they are cultivated.

Aquic Ustipsamments.—These soils are saturated with

water at some time of the year and have redoximorphic features

of low or high chroma within 100 cm of the soil surface. The

soils are otherwise like the soils of the Typic subgroup. They

are of small extent in the United States.

Aridic Ustipsamments.—These soils are drier than Typic

Ustipsamments. They are intergrades between Ustipsamments

and Torripsamments. They are moderately extensive in the

southern part of the Great Plains in the United States. Slopes

are gentle to steep. These soils are freely drained sands. They

support mostly grass or savanna vegetation. A few are in

drought-tolerant forests of small, scattered trees. Many support

as much vegetation as or more vegetation than other soils with

an ustic moisture regime, perhaps because of rapid infiltration

and a low available water capacity, which cause the

precipitation to moisten the soils to a greater depth than in

most other soils with an ustic moisture regime. Some water is

stored below the soil moisture control section. Most of the

Aridic Ustipsamments are used for grazing. Few of them are

cultivated because they are subject to soil blowing if they are

cultivated.

Lamellic Ustipsamments.—These soils have lamellae

within 200 cm of the soil surface. They are of small extent in

the United States. They are used mainly as rangeland. Few of

them are cultivated because they are subject to soil blowing if

they are cultivated.

Lithic Ustipsamments.—These soils have a lithic contact

within 50 cm of the soil surface. They support grass or savanna

vegetation. Small areas of these soils are known to occur in the

United States.

Oxyaquic Ustipsamments.—These soils are saturated

with water for 20 or more consecutive days or 30 or more

cumulative days in normal years; do not have redox

depletions with low chroma (2 or less) within 100 cm of the

soil surface; and are permitted, but not required, to have

lamellae within 200 cm of the surface. They are otherwise

like Typic Ustipsamments. Oxyaquic Ustipsamments are of

small extent in the United States. They are used mainly as

rangeland.

Rhodic Ustipsamments.—These soils have dark red colors.

They do not have a lithic contact within 50 cm of the soil

surface, lamellae, or a moisture regime that borders on aridic.

They are known to occur only in areas of an isohyperthermic

soil temperature regime in India. These soils commonly are

used for the production of cashews.

Xeropsamments

These are the Psamments that are of Mediterranean climates

and that have weatherable minerals, commonly feldspars, in

the sand fraction. These soils are moist in winter and dry in

summer. They have a frigid, mesic, or thermic temperature

regime. Most Xeropsamments formed in deposits of lateWisconsinan or more recent age. Some are on terraces and

glacial outwash plains. Others are on dunes. Because the

supply of winter moisture is reliable, few of the dunes are

shifting. Some of these soils have supported a coniferous

vegetation, but most have supported and still support a mixture

of grasses and xerophytic shrubs or trees. Xeropsamments are

moderately extensive in parts of the Western United States.

Definition

Xeropsamments are the Psamments that:

1. Have a xeric moisture regime and a frigid, mesic, or

thermic soil temperature regime; and

2. Have, in the 0.02 to 2.0 mm fraction within the particlesize control section, 90 percent or less (by weighted average)

resistant minerals.

Key to Subgroups

LCEA. Xeropsamments have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Xeropsamments

LCEB. Other Xeropsamments that have both:

1. In one or more horizons within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A horizon within 100 cm of the mineral soil surface

that is 15 cm or more thick and that either has 20 percent or

more (by volume) durinodes or is brittle and has a firm

rupture-resistance class when moist.

Aquic Durinodic Xeropsamments

LCEC. Other Xeropsamments that have, in one or more

horizons within 100 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time in normal years (or artificial drainage).

Aquic Xeropsamments

LCED. Other Xeropsamments that are saturated with water

in one or more layers within 100 cm of the mineral soil surface

in normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Xeropsamments
442 Soil Taxonomy

LCEE. Other Xeropsamments that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction

containing 5 percent or more volcanic glass, and [(Al plus 1

/2

Fe, percent extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrandic Xeropsamments

LCEF. Other Xeropsamments that have a horizon within

100 cm of the mineral soil surface that is 15 cm or more thick

and that either has 20 percent or more (by volume) durinodes

or is brittle and has a firm rupture-resistance class when

moist.

Durinodic Xeropsamments

LCEG. Other Xeropsamments that have lamellae within 200

cm of the mineral soil surface.

Lamellic Xeropsamments

LCEH. Other Xeropsamments that have a base saturation (by

NH4OAc) of less than 60 percent in all horizons at a depth

between 25 and 75 cm below the mineral soil surface.

Dystric Xeropsamments

LCEI. Other Xeropsamments.

Typic Xeropsamments

Definition of Typic Xeropsamments

Typic Xeropsamments are the Xeropsamments that:

1. Do not have lamellae within 200 cm of the soil surface;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 30 or more cumulative days or 20

or more consecutive days in normal years;

4. Do not have a horizon within 100 cm of the surface that is

more than 15 cm thick and that either has 20 percent or more

durinodes or is brittle and has a firm rupture-resistance class

when moist;

5. Do not have a lithic contact within 50 cm of the soil

surface;

6. Have a base saturation (by NH4

OAc) of 60 percent or more

in some part at a depth between 25 and 75 cm below the soil

surface; and

7. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction containing 5 percent or more

volcanic glass, and [(Al plus 1

/2 Fe, percent extracted by

ammonium oxalate) times 60] plus the volcanic glass (percent)

is less than 30.

Description of Subgroups

Typic Xeropsamments.—The Typic subgroup of

Xeropsamments is centered on sands that have no ground

water within a depth of 100 cm, that do not have evident

cementation with silica, and that do not have lamellae in which

silicate clay has accumulated. These soils are more than 50 cm

deep to any lithic contact. Normally, the sands are deep and are

a mixture of quartz and feldspars and little volcanic glass.

These soils have no lamellae within 200 cm of the soil

surface because the lamellae are considered to indicate

intergrades to soils that have an argillic horizon, generally

Xeralfs. Soils that have a lithic contact within a depth of 50 cm

are excluded from the Typic subgroup, a convention used

throughout this taxonomy. Soils that have ground water within

100 cm of the surface at some time of the year are excluded

because they are considered to indicate intergrades to

Psammaquents. Partial cementation by silica is considered to

indicate intergrades to great groups that have duripans.

Typic Xeropsamments are of moderate extent in the Western

United States, mostly in California, Washington, and Nevada.

The soils that are frigid or mesic are used mostly as forest, but

some areas have been cleared and are used as cropland. The

soils that are thermic are used mostly as cropland or rangeland.

Aquic Durinodic Xeropsamments.—These soils show

evidence of weak cementation by silica in the form of

durinodes or of a horizon more than 15 cm thick that is brittle

and has a firm rupture-resistance class when moist. The soils

normally have an appreciable amount of pyroclastics in the

sand fraction. In addition, they are saturated with water at

some time during the year and have distinct or prominent

redox concentrations within 100 cm of the soil surface.

Aquic Xeropsamments.—These soils are saturated with

water at some time during the year and have distinct or

prominent redox concentrations within 100 cm of the soil

surface. They are not extensive soils in the United States.

Durinodic Xeropsamments.—These soils show evidence of

weak cementation by silica in the form of durinodes or of a

horizon more than 15 cm thick that is brittle and has a firm

rupture-resistance class when moist. The soils are not known to

occur in the United States.

Dystric Xeropsamments.—These soils receive relatively

high amounts of rainfall during the winter months. As a

consequence, the base saturation is lower than that in the soils

of the Typic subgroup. Dystric Xeropsamments are not

extensive. In the United States, they are mostly in California

and Washington, where they support forest vegetation.

Lamellic Xeropsamments.—These soils have lamellae

within 200 cm of the soil surface. They are not extensive. They

are mostly in California, Washington, and Idaho in the United

States. They are used mainly as forest.

Lithic Xeropsamments.—These soils have a lithic contact

within 50 cm of the surface. They are not extensive. They are

mostly in California, Oregon, and Idaho in the United States.

They are used mainly as forest.
Entisols 443

Oxyaquic Xeropsamments.—These soils are saturated with

water at some time during the year. The saturation occurs

within 100 cm of the soil surface. These soils are not extensive

in the United States.

Vitrandic Xeropsamments.—These soils consist of volcanic

deposits or have a layer of pyroclastic materials, 18 cm or more

thick, in the upper 75 cm. The soils are of minor extent, mostly in

California. They are used mainly as forest.

445

The central concept of Gelisols is that of soils with gelicmaterials underlain by permafrost. Freezing and

thawing are important processes in Gelisols. Diagnostic

horizons may or may not be present. Permafrost influences

pedogenesis by acting as a barrier to the downward movement

of the soil solution.

Cryoturbation (frost mixing) is an important process in

many Gelisols and results in irregular or broken horizons,

involutions, organic matter accumulation on the permafrost

table, oriented rock fragments, and silt caps on rock fragments.

Cryoturbation occurs when two freezing fronts, one from the

surface and the other from the permafrost, merge during

freeze-back in the autumn. Ice segregation is an important

property of gelic materials and occurs when the soil solution

migrates toward ice, increasing the volume of ice. Volume

changes also occur as the water freezes. In the drier areas,

cryoturbation is less pronounced or does not occur, but the soils

still have gelic materials, as manifested by sand wedges and ice

crystals.

Diagnostic horizons, including ochric, mollic, umbric, and

histic epipedons and argillic, salic, gypsic, and calcic horizons,

have been observed in Gelisols. The importance of these

diagnostic horizons, however, is overshadowed by the

properties of the gelic materials and the associated permafrost.

In some Gelisols the effects of cryoturbation are so well

expressed that no diagnostic horizons are observed.

Definition of Gelisols and Limits Between

Gelisols and Soils of Other Orders

Gelisols are soils that have one or more of the following:

1. Permafrost within 100 cm of the soil surface; or

2. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface.

Limits Between Gelisols and Other Soil Orders

The definition of Gelisols must provide criteria that separate

Gelisols from all other orders. The aggregate of these criteria

defines the limits of Gelisols in relation to all other known

soils.

Unlike the other soil orders, Gelisols have one or both of the

following:

1. Permafrost within 100 cm of the soil surface; or

2. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface.

Representative Pedon and Data

Following is a description of a representative Gelisol. Data

for the pedon identified in this description are given in the

table “Characterization Data for a Gelisol.”

Classification: Loamy, mixed, superactive Typic Molliorthel

Site identification number: 94P0668

Location: Lower Kolymar, Russia

Latitude: 68 degrees 43 minutes 56 seconds N.

Longitude: 161 degrees 31 minutes 49 seconds E.

Slope: 3 percent

Aspect: 270 degrees

Horizontal shape: Convex

Vertical shape: Convex

Total slope length: 200 m, 30 m of which is above the sample

site

Elevation: 140 m

Landscape: Plains

Landform: Pediment

Annual precipitation: 190 mm

Soil moisture regime: Udic

Land use: Forest land (not grazed)

Permeability class: Moderate

Natural drainage class: Well drained

Parent material: Loess and moderately weathered local

colluvium derived from acidic schist and diorite

Particle-size control section: 25 to 100 cm

Diagnostic features: An mollic epipedon from a depth of 0 to

38 cm and permafrost at a depth of 94 cm

Notes: An ice-rich permafrost table is at a depth of 94 cm.

The frozen layer from a depth of 78 to 94 cm is thought to be

part of the active layer in some years. Charcoal is mixed to a

depth of 25 cm. Rock fragments are diorite.

CHAPTER 13

Gelisols1

1 This chapter is based on recommendations by the International Committee on

Permafrost-Affected Soils (ICOMPAS), chaired by Dr. James G. Bockheim, University of

Wisconsin.
446 Soil Taxonomy

Characterization Data for a Gelisol

 SITE IDENTIFICATION NO.: 94P0668

 CLASSIFICATION: LOAMY, MIXED, SUPERACTIVE TYPIC MOLLORTHEL

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 94P5015 0- 7 A 23.7 61.3 15.0 11.2 31.1 30.2 8.4 3.3 0.6 0.4 2.3 4 2 3V 15 9

 94P5016 7- 12 AB 8.7 72.9 18.4 4.5 34.4 38.5 12.1 1.7 1.4 1.5 1.7 2 1 5V 14 8

 94P5017 12- 38 Bw1 13.0 70.1 16.9 5.6 33.1 37.0 13.4 1.3 0.9 0.7 0.6 1 1 5V 10 7

 94P5018 38- 59 Bw2 15.5 68.3 16.2 9.6 31.9 36.4 14.1 1.1 0.4 0.4 0.2 TR 1 5V 8 6

 94P5019 59- 78 Bw3 15.4 68.9 15.7 8.1 29.8 39.1 14.0 1.1 0.2 0.3 0.1 TR TR 5V 7 5

 94P5020 78- 94 Bw4 15.2 70.3 14.5 7.3 29.8 40.5 12.5 1.0 0.3 0.3 0.4 TR TR 5V 7 5

 94P5021 94-110 Cf 13.5 75.6 10.9 6.7 29.1 46.5 9.7 0.6 0.2 0.2 0.2 TR 1 5V 7 6

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B4a 6S3 6R3c 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A5 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 7 7.54 0.331 TR 1.25 0.95 0.73 1.04 0.121 38.3 22.5 0.11

 7- 12 0.65 0.064 1 -- 1.4 0.1 TR 1.31 0.67 1.65 1.65 -- 18.5 5.8 0.20

 12- 38 0.56 0.065 TR -- 1.6 0.1 TR 0.97 0.50 6.5

 38- 59 0.48 0.065 1 -- 1.8 0.1 TR 0.95 0.57 8.8

 59- 78 0.44 0.066 2 -- 1.7 0.1 TR 0.88 0.54 1.54 1.66 0.024 20.8 8.3 0.19

 78- 94 0.44 0.068 1 -- 1.6 0.1 TR 0.86 0.51 1.73 1.79 0.011 18.3 7.7 0.18

 94-110 0.39 0.059 1 -- 1.5 0.1 TR 0.83 0.51 6.9

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)

 Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos KCl CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm IN .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9d 5A3a 5A8c 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1g 8C1f 8C1f

 <- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1

 0- 7 11.1 4.9 0.6 0.4 17.0 28.0 45.0 29.7 38 57 3.8 4.6 5.2

 7- 12 6.0 2.8 0.3 0.1 9.2 7.5 0.3 16.7 11.4 9.5 3 55 81 4.1 4.9 5.7

 12- 38 7.4 3.7 0.2 0.1 11.4 5.4 TR 16.8 12.6 68 90 4.7 5.6 6.6

 38- 59 9.5 4.9 0.4 0.2 15.0 5.1 20.1 14.7 75 100 5.4 6.1 6.8

 59- 78 9.2 4.6 0.2 0.2 14.2 3.8 18.0 13.5 79 100 5.6 6.3 6.8

 78- 94 8.0 4.1 0.2 0.2 12.5 3.7 16.2 13.1 77 95 5.8 6.4 7.3

 94-110 7.5 3.8 0.2 0.2 11.7 2.4 14.1 11.2 83 100 5.8 6.5 7.3

 -----------------------------------------------------------------------------------------------------------------------------------

 ACID OXALATE EXTRACTION PHOSPHORUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT

 OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL

 DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm

 SAMPLE HZ 8J 6C9b 6V2b 6G12b 6S4 6S5 6D3b 6A2e 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1

 NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>

 94P5015 1 30.8 90

 94P5016 2 0.06 0.48 0.03 0.13 32 0.5 11.0

 94P5017 3 0.05 0.42 0.05 0.14 31 0.6 12.3

 94P5018 4 0.04 0.37 0.05 0.15 28 12.7

 94P5019 5 0.04 0.36 0.06 0.15 23 12.5

 94P5020 6 0.04 0.33 0.06 0.12 28 14.1

 94P5021 7 0.03 0.28 0.06 0.11 28 10.7

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA-

 < - - - - - 7A2i - - - - - ->< - 7A6b - >< - 7A4c - >< - - - - - - - - - 7C4a- - - - - - - - ->< > 7D2 TION

 NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->

 94P5017 TCLY VR 3 MI 3 KK 2 QZ 2 FD 2

 94P5017 VM 1

 94P5019 TCLY MI 3 VR 3 KK 2 QZ 1 FD 1

 94P5021 TCLY MI 3 VR 2 KK 2 QZ 1 FD 1

 -----------------------------------------------------------------------------------------------------------------------------------
Gelisols 447

Characterization Data for a Gelisol--Continued

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA-

 < - - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION

 NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->

 94P5017 CSi 39 QZ38 FK25 AR19 FP 5 MS 4 CM 4

 94P5017 CSi PR 2 HN 1 FE 1 OPtr POtr BYtr

 94P5017 CSi GNtr RUtr GStr ZRtr APtr BYtr

 94P5018 CSi 48 QZ46 FK22 AR17 FP 7 PR 2 HN 2

 94P5018 CSi FE 2 MS 1 BT 1 CM 1 OPtr APtr

 94P5018 CSi MZtr BYtr ZRtr RUtr GNtr GStr

 94P5018 CSi FZtr ZEtr

 94P5019 CSi 43 QZ42 AR24 FK15 FP 5 HN 4 MS 2

 94P5019 CSi CM 2 FE 1 BT 1 PRtr OPtr FZtr

 94P5019 CSi GNtr ZEtr CTtr BYtr ZRtr APtr

 94P5019 CSi RUtr

 94P5020 CSi 46 QZ46 AR19 FK17 FP 6 MS 4 CM 3

 94P5020 CSi HN 3 PR 1 FEtr BTtr BYtr RUtr

 94P5020 CSi OPtr APtr TMtr POtr GStr ZRtr

 94P5020 CSi GNtr

 94P5021 CSi 46 QZ45 FK20 AR20 FP 5 CM 4 HU 2

 94P5021 CSi MS 1 BT 1 PR 1 FE 1 OPtr RUtr

 94P5021 CSi ZRtr BYtr APtr GNtr

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.

 V in tier 1, column 18, indicates volume estimates.

 Fraction interpretation: TCLY, total clay, <0.002 mm; CSi, coarse silt, 0.02-0.05 mm.

 Mineral interpretation: VR, vermiculite; MI, mica; KK, kaolinite; QZ, quartz; FD, feldspar; VM, vermiculite-mica; FK, potassium

 feldspar; AR, weathered aggregate; FP, plagioclase feldspar; MS, muscovite; CM, chlorite-mica; PR, pyroxene; HN, hornblende;

 FE, iron oxides; OP, opaques; PO, plant opal; BY, beryl; GN, garnet; RU, rutile; GS, glass; ZR, zircon; AP, apatite;

 BT, biotite; MZ, monazite; FZ, feldspathoid; ZE, zeolite; CT cassiterite; TM, tourmaline.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.

 Family mineralogy: Mixed.

In the following pedon description, colors are for moist soil

unless otherwise indicated.

A—0 to 7 cm; dark reddish brown (5YR 2/2) silt loam, dark

reddish brown (5YR 3/2) dry; weak thin platy and

moderate very fine subangular blocky structure; many very

fine roots throughout; 1 percent angular gravel; very

strongly acid; abrupt wavy boundary.

AB—7 to 12 cm; dark grayish brown (10YR 4/2) silt loam,

light olive brown (2.5Y 5/3) dry; weak thin platy and

moderate very fine subangular blocky structure; firm,

slightly sticky and slightly plastic; common very fine to

medium roots throughout; common fine high-continuity

tubular pores; 9.0 percent clay; 3 percent angular gravel;

very strongly acid; abrupt wavy boundary.

Bw1—12 to 38 cm; dark brown (10YR 3/3) silt loam, light

olive brown (2.5Y 5/3) dry; moderate thin platy and

moderate fine subangular blocky structure; friable, slightly

sticky and slightly plastic; common very fine to medium

roots throughout; many medium vesicular and many very

fine high-continuity tubular pores; 10.0 percent clay; 3

percent angular gravel; very strongly acid; clear wavy

boundary.

Bw2—38 to 59 cm; very dark grayish brown (10YR 3/2) silt loam,

light olive brown (2.5Y 5/3) dry; strong very fine subangular

blocky structure; very friable, slightly sticky and plastic;

common very fine to medium roots throughout; many very

fine and fine high-continuity tubular pores; 15.0 percent

clay; 3 percent angular gravel; very strongly acid; clear

wavy boundary.

Bw3—59 to 78 cm; very dark grayish brown (2.5Y 3/2) silt

loam, light olive brown (2.5Y 5/3) dry; moderate very thin

platy and moderate very fine subangular blocky structure;

friable, slightly sticky and plastic; 15.0 percent clay; 3

percent angular gravel; strongly acid; gradual wavy

boundary.

Bw4—78 to 94 cm; dark grayish brown (2.5Y 4/2) silt loam,

grayish brown (2.5Y 5/2) dry; strong medium platy and

moderate fine subangular blocky structure; extremely

firm, sticky and plastic; few very fine and fine roots;

common very fine and fine moderate-continuity tubular

pores; 17.0 percent clay; 2 percent angular cobbles and 3

percent angular gravel; strongly acid; clear wavy boundary.
448 Soil Taxonomy

Cf—94 to 110 cm; dark grayish brown (2.5Y 4/2) silt loam;

massive; extremely firm, sticky and plastic; 17.0 percent

clay; 2 percent angular cobbles and 3 percent angular

gravel; strongly acid.

Key to Suborders

AA. Gelisols that have organic soil materials that meet one or

more of the following:

1. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices and directly below these

materials have either a densic, lithic, or paralithic contact;

or

2. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

3. Are saturated with water for 30 or more cumulative

days during normal years (or are artificially drained) and

have 80 percent or more, by volume, organic soil materials

from the soil surface to a depth of 50 cm or to a glacic layer

or a densic, lithic, or paralithic contact, whichever is

shallowest.

Histels, p. 448

AB. Other Gelisols that have one or more horizons showing

cryoturbation in the form of irregular, broken, or distorted

horizon boundaries, involutions, the accumulation of organic

matter on top of the permafrost, ice or sand wedges, and

oriented rock fragments.

Turbels, p. 462

AC. Other Gelisols.

Orthels, p. 452

Histels

These are the Gelisols with large amounts of organic carbon

that commonly accumulate under anaerobic conditions, or the

organic matter at least partially fills voids in fragmental,

cindery, or pumiceous materials. Cold temperatures contribute

to the accumulation of organic matter.

Definition

Histels are the Gelisols that have organic soil materials that

meet one or more of the following:

1. Overlie cindery, fragmental, or pumiceous materials and/or

fill their interstices and directly below these materials have

either a densic, lithic, or paralithic contact; or

2. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

3. Are saturated with water for 30 or more cumulative

days during normal years (or are artificially drained) and

have 80 percent or more, by volume, organic soil materials

from the soil surface to a depth of 50 cm or to a glacic layer

or a densic, lithic, or paralithic contact, whichever is

shallowest.

Key to Great Groups

AAA. Histels that are saturated with water for less than 30

cumulative days during normal years (and are not artificially

drained).

Folistels, p. 449

AAB. Other Histels that are saturated with water for 30 or

more cumulative days during normal years and that have both:

1. A glacic layer with its upper boundary within 100 cm of

the soil surface; and

2. Less than three-fourths (by volume) Sphagnum fibers in

the organic soil materials to a depth of 50 cm or to a densic,

lithic, or paralithic contact, whichever is shallower.

Glacistels, p. 450

AAC. Other Histels that have more thickness of fibric soil

materials than any other kind of organic soil material to a

depth of 50 cm or to a densic, lithic, or paralithic contact,

whichever is shallowest.

Fibristels, p. 448

AAD. Other Histels that have more thickness of hemic soil

materials than any other kind of organic soil material to a

depth of 50 cm or to a densic, lithic, or paralithic contact,

whichever is shallowest.

Hemistels, p. 450

AAE. Other Histels.

Sapristels, p. 451

Fibristels

These are wet Histels in which the organic materials are

slightly decomposed. Most of the fiber is not destroyed by

rubbing between the thumb and fingers. The botanical origin of

much of the materials can be readily determined.

Many Fibristels have ground water near the surface nearly

all the time. These soils are of small extent in Alaska, Canada,

and Siberia. They occur in depressional or level areas,

commonly to adjacent water bodies.
Gelisols 449

Definition

Fibristels are the Histels that:

1. Are saturated with water for 30 or more cumulative days

during normal years;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the soil surface; and

3. Have more thickness of fibric soil materials than any other

kind of organic soil material to a depth of 50 cm or to a densic,

lithic, or paralithic contact, whichever is shallowest.

Key to Subgroups

AACA. Fibristels that have a lithic contact within 100 cm of

the soil surface.

Lithic Fibristels

AACB. Other Fibristels that have a mineral layer 30 cm or

more thick within 100 cm of the soil surface.

Terric Fibristels

AACC. Other Fibristels that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more layers of any thickness within 100 cm of the soil

surface.

Fluvaquentic Fibristels

AACD. Other Fibristels in which three-fourths or more of the

fibric material is derived from Sphagnum to a depth of 50 cm

or to a densic, lithic, or paralithic contact, whichever is

shallowest.

Sphagnic Fibristels

AACE. Other Fibristels.

Typic Fibristels

Definition of Typic Fibristels

Typic Fibristels are the Fibristels that:

1. Do not have a lithic contact within 100 cm of the soil

surface;

2. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within 100 cm of

the soil surface;

3. Do not have a mineral layer 30 cm or more thick that has

its upper boundary within 100 cm of the soil surface; and

4. Have less than three-fourths of their fibric material derived

from Sphagnum to a depth of 50 cm or to a densic, lithic, or

paralithic contact, whichever is shallowest.

Description of Subgroups

Typic Fibristels.—The Typic subgroup is fixed on soils that

do not have a lithic contact within 100 cm of the soil surface

and are not composed largely of Sphagnum. A lithic contact is

used in classifying soils in lithic subgroups. Thick or thin

mineral layers as well as intermittent layers that are within 100

cm of the soil surface cause soils to be excluded from the Typic

subgroup. Typic Fibristels are of small extent in the world but

are known to occur in northern Russia and in Alaska and

Canada.

Fluvaquentic Fibristels.—These soils differ from the Typic

Fibristels because they have, within 100 cm of the soil surface,

either one mineral layer 5 to 30 cm thick or two or more

mineral layers of any thickness. These soils are relatively rare

but occur in Canada and Siberia.

Lithic Fibristels.—These soils differ from Typic Fibristels

because they have a lithic contact within 100 cm of the soil

surface.

Sphagnic Fibristels.—These soils differ from Typic

Fibristels because three-fourths or more of their fibric materials

is derived from Sphagnum to a depth of 50 cm. These soils

occur in Alaska, Siberia, and Canada.

Terric Fibristels.—These soils differ from Typic Fibristels

because they have a mineral layer 30 cm or more thick within

100 cm of the soil surface. These soils occur in Alaska,

Canada, and Siberia.

Folistels

These are the more or less freely drained Histels that consist

primarily of O horizons derived from plant litter resting on

rock or on fragmental materials that consist of gravel or larger

rock fragments in which the interstices are partly filled or

filled with organic materials. Plant roots grow in the organic

materials. These soils are rare in the world.

Definition

Folistels are the Histels that are saturated with water for less

than 30 cumulative days during normal years (and are not

artificially drained).

Key to Subgroups

AAAA. Folistels that have a lithic contact within 50 cm of

the soil surface.

Lithic Folistels

AAAB. Other Folistels that have a glacic layer with its upper

boundary within 100 cm of the soil surface.

Glacic Folistels

AAAC. Other Folistels.

Typic Folistels

Definition of Typic Folistels

Typic Folistels are the Folistels that:

1. Do not have a lithic contact within 50 cm of the soil

surface; and
450 Soil Taxonomy

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the soil surface.

Description of Subgroups

Typic Folistels.—The concept of the Typic Folistels is that of

soils with organic materials that are filling or partially filling

interstices in fragmental materials. Typic Folistels do not have

either a glacic layer within 100 cm of the soil surface or a lithic

contact within 50 cm of the soil surface.

Glacic Folistels.—These are the Folistels that have a

layer of ice 30 cm or more thick within 100 cm of the soil

surface.

Lithic Folistels.—These are the Folistels that have organic

materials resting on a lithic contact within 50 cm of the soil

surface.

Glacistels

Glacistels are the Histels that have 30 cm or more of ice within

100 cm of the soil surface. Disturbance of the surface-insulating

layer causes the ice layer to melt and the soils to collapse. These

soils occur in Alaska, Canada, and Siberia.

Definition

Glacistels are the Histels that:

1. Are saturated with water for 30 or more cumulative days

during normal years;

2. Have a glacic layer with its upper boundary within 100 cm

of the soil surface; and

3. Have less than three-fourths (by volume) Sphagnum fibers

to a depth of 50 cm or to a densic, lithic, or paralithic contact,

whichever is shallowest.

Key to Subgroups

AABA. Glacistels that have more thickness of hemic

materials than any other kind of organic soil material in the

upper 50 cm.

Hemic Glacistels

AABB. Other Glacistels that have more thickness of sapric

materials than any other kind of organic soil material in the

upper 50 cm.

Sapric Glacistels

AABC. Other Glacistels

Typic Glacistels

Definition of Typic Glacistels

Typic Glacistels are the Glacistels that have more thickness

of fibric material than any other kind of organic material in the

upper 50 cm.

Description of Subgroups

Typic Glacistels.—These are the Glacistels that are

dominated by fibric materials. The Typic concept of Glacistels

is centered on a dominance of fibric material. The cold

temperature and high water tables associated with these soils

inhibit the breakdown of organic matter.

Hemic Glacistels.—These are the Glacistels that are

dominated by hemic materials. The botanical origin of much of

the material cannot be readily determined. Water is at or very

close to the surface of these soils much of the time, unless

drainage has been provided.

Sapric Glacistels.—These are the Glacistels that are

dominated by sapric materials. Although water is at or near the

surface for much of the year, the organic material is

decomposed to the degree that the original plant material is

unrecognizable.

Hemistels

These are wet Histels in which the organic materials are

moderately decomposed. The botanical origin of much of the

organic material is between one-sixth and two-thirds after

rubbing between the fingers. Water is at or very close to the

surface of these soils much of the time, unless artificial

drainage has been provided. The level of ground water may

fluctuate but seldom drops much below the surface tier.

Hemistels occur in depressional areas or the adjacent water

bodies. These soils are known to occur in Siberia, Canada, and

Alaska.

Definition

Hemistels are the Histels that:

1. Are saturated with water for 30 or more cumulative days

during normal years (and are not artificially drained);

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the soil surface; and

3. Have more thickness of hemic soil materials than any

other kind of organic soil material to a depth of 50 cm or to a

densic, lithic, or paralithic contact, whichever is shallowest.

Key to Subgroups

AADA. Hemistels that have a lithic contact within 100 cm of

the soil surface.

Lithic Hemistels

AADB. Other Hemistels that have a mineral layer 30 cm or

more thick within 100 cm of the soil surface.

Terric Hemistels

AADC. Other Hemistels that have, within the organic

materials, either one mineral layer 5 cm or more thick or two
Gelisols 451

or more layers of any thickness within 100 cm of the soil

surface.

Fluvaquentic Hemistels

AADD. Other Hemistels.

Typic Hemistels

Definition of Typic Hemistels

Typic Hemistels are the Hemistels that:

1. Do not have a lithic contact within 100 cm of the soil

surface;

2. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within 100 cm of

the soil surface; and

3. Do not have a mineral layer 30 cm or more thick that has

its upper boundary within 100 cm of the soil surface.

Description of Subgroups

Typic Hemistels.—These are the Hemistels that do not

have a lithic contact within 100 cm of the soil surface. These

soils also do not have thick or thin mineral layers within 100

cm of the soil surface. Typic Hemistels occur in Alaska,

Siberia, and Canada.

Fluvaquentic Hemistels.—These are the Hemistels that

have one or more thin layers of mineral soil material within

100 cm of the soil surface. The mineral soil material commonly

is deposited by floodwaters or ponded waters. These soils occur

in Alaska, Canada, and Siberia.

Lithic Hemistels.—These are the Hemistels that have a

lithic contact within 100 cm of the soil surface. These soils are

relatively rare in the world.

Terric Hemistels.—These are the Hemistels that have a

thick mineral layer within 100 cm of the soil surface. The thick

mineral layer may have been deposited under hydrologic

conditions that differ from those of the present. These soils

occur in Alaska, Canada, and Siberia.

Sapristels

These are wet Histels in which the organic materials are well

decomposed. The botanical origin of the organic material is

difficult to determine in most of these soils. The fiber content of

most of the organic material is less than one-sixth after rubbing

between the fingers.

Sapristels occur in areas where ground water tables tend to

fluctuate within the soils or where the soils were aerobic during

drier periods in the past. When drained, fibric and hemic

materials commonly decompose to form sapric materials.

Definition

Sapristels are the Histels that:

1. Are saturated with water for 30 or more cumulative days

during normal years (and are not artificially drained);

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the soil surface; and

3. Have more thickness of sapric soil materials than any other

kind of organic soil material to a depth of 50 cm or to a densic,

lithic, or paralithic contact, whichever is shallowest.

Key to Subgroups

AAEA. Sapristels that have a lithic contact within 100 cm of

the soil surface.

Lithic Sapristels

AAEB. Other Sapristels that have a mineral layer 30 cm or

more thick within 100 cm of the soil surface.

Terric Sapristels

AAEC. Other Sapristels that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more layers of any thickness within 100 cm of the soil

surface.

Fluvaquentic Sapristels

AAED. Other Sapristels.

Typic Sapristels

Definition of Typic Sapristels

Typic Sapristels are the Sapristels that:

1. Do not have a lithic contact within 100 cm of the soil

surface;

2. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within 100 cm of

the soil surface; and

3. Do not have a mineral layer 30 cm or more thick that has

its upper boundary within 100 cm of the soil surface.

Description of Subgroups

Typic Sapristels.—These are the Sapristels that do not have

a lithic contact within 100 cm of the soil surface. These soils

also do not have thick or thin mineral layers within 100 cm of

the soil surface. Typic Sapristels occur in Alaska, Siberia, and

Canada.

Fluvaquentic Sapristels.—These are the Sapristels that

have one or more thin layers of mineral soil material within

100 cm of the soil surface. The mineral soil material commonly

is deposited by floodwaters or ponded waters. These soils occur

in Alaska, Canada, and Siberia.

Lithic Sapristels.—These are the Sapristels that have a

lithic contact within 100 cm of the soil surface. These soils are

relatively rare in the world.
452 Soil Taxonomy

Terric Sapristels.—These are the Sapristels that have a thick

mineral layer within 100 cm of the soil surface. The thick mineral

layer may have been deposited under hydrologic conditions that

differ from those of the present. These soils occur in Alaska,

Canada, and Siberia.

Orthels

Orthels are the Gelisols that show little or no evidence of

cryoturbation and are the second most abundant suborder of

Gelisols. These soils occur primarily within the zone of

widespread permafrost or in areas of coarse textured materials

in the continuous zone of permafrost. Orthels are generally

drier than Turbels and Histels. They occur in the southern

Andes and the high latitudes of the Northern Hemisphere.

Definition

Orthels are the Gelisols that:

1. Do not have organic soil materials that meet any of the

following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Are saturated with water for 30 or more cumulative

days during normal years (or are artificially drained) and

have 80 percent or more, by volume, organic soil materials

from the soil surface to a depth of 50 cm or to a glacic layer

or a densic, lithic, or paralithic contact, whichever is

shallowest; and

2. Do not have any horizons showing cryoturbation in the

form of irregular, broken, or distorted horizon boundaries,

involutions, the accumulation of organic matter on top of the

permafrost, ice or sand wedges, and oriented rock fragments.

Key to Great Groups

ACA. Orthels that have in 30 percent or more of the pedon

more than 40 percent, by volume, organic materials from the

soil surface to a depth of 50 cm.

Historthels, p. 457

ACB. Other Orthels that have, within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions during normal years (or artificial drainage).

Aquorthels, p. 453

ACC. Other Orthels that have anhydrous conditions.

Anhyorthels, p. 452

ACD. Other Orthels that have a mollic epipedon.

Mollorthels, p. 457

ACE. Other Orthels that have an umbric epipedon.

Umbrorthels, p. 460

ACF. Other Orthels that have an argillic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

Argiorthels, p. 455

ACG. Other Orthels that have, below the Ap horizon or below

a depth of 25 cm, whichever is deeper, less than 35 percent (by

volume) rock fragments and have a texture of loamy fine sand or

coarser in the particle-size control section.

Psammorthels, p. 459

ACH. Other Orthels.

Haplorthels, p. 456

Anhyorthels

These are the Orthels that have anhydrous conditions. They

often have dry permafrost (i.e., insufficient moisture for

interstitial ice to occur). The cold deserts commonly receive

less than 30 mm of annual precipitation. These soils support

little or no vegetation.

These soils are limited in extent but are known to occur in

continental Antarctica, the High Arctic (northern Greenland

and Ellesmere Island), and the cold, dry mountains of Eurasia

at elevations of more than 3,700 m.

Definition

Anhyorthels are the Orthels that:

1. Have anhydrous conditions;

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm; and

3. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years.

Key to Subgroups

ACCA. Anhyorthels that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Anhyorthels

ACCB. Other Anhyorthels that have a glacic layer that has

its upper boundary within 100 cm of the mineral soil surface.

Glacic Anhyorthels
Gelisols 453

ACCC. Other Anhyorthels that have a petrogypsic horizon

that has its upper boundary within 100 cm of the mineral soil

surface.

Petrogypsic Anhyorthels

ACCD. Other Anhyorthels that have a gypsic horizon that

has its upper boundary within 100 cm of the mineral soil

surface.

Gypsic Anhyorthels

ACCE. Other Anhyorthels that have a horizon 15 cm or

more thick that contains 12 cmol(-)/L in 1:5 soil:water nitrate

and in which the product of its thickness (in cm) and its nitrate

concentration is 3,500 or more.

Nitric Anhyorthels

ACCF. Other Anhyorthels that have a salic horizon that has

its upper boundary within 100 cm of the mineral soil surface.

Salic Anhyorthels

ACCG. Other Anhyorthels that have a calcic horizon with its

upper boundary within 100 cm of the mineral soil surface.

Calcic Anhyorthels

ACCH. Other Anhyorthels.

Typic Anhyorthels

Definition of Typic Anhyorthels

These are the Anhyorthels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer or a petrogypsic, gypsic, salic,

or calcic horizon with its upper boundary within 100 cm of the

mineral soil surface; and

3. Do not have a horizon 15 cm or more thick that has 12

cmol(-)/L nitrate in 1:5 soil:water extract and in which the

product of its thickness (in cm) and its nitrate concentration is

3,500 or more.

Description of Subgroups

Typic Anhyorthels.—These are the Anhyorthels that

commonly have accumulations of salts, including gypsum and

calcium carbonate, but insufficient quantities to meet the

criteria for a calcic, gypsic, petrogypsic, or salic horizon. These

soils also do not contain large amounts of nitrate. Typic

Anhyorthels do not have a lithic contact within 50 cm of the

mineral soil surface or a glacic layer with its upper boundary

within 100 cm of the mineral soil surface.

Calcic Anhyorthels.—These are the Anhyorthels that have

a calcic horizon within 100 cm of the mineral soil surface.

These soils commonly have other more soluble salts, but not in

sufficient quantity to meet the criteria for a petrogypsic, gypsic,

or salic horizon. These soils also lack sufficient quantities of

nitrate, a glacic layer, and a lithic contact.

Glacic Anhyorthels.—These are the Anhyorthels that have

a glacic layer with its upper boundary within 100 cm of the

mineral soil surface. These soils commonly have accumulations

of salts, including calcium carbonate and gypsum, but do not

have a lithic contact within 50 cm of the mineral soil surface.

Gypsic Anhyorthels.—These are the Anhyorthels that have

a gypsic horizon within 100 cm of the mineral soil surface.

They commonly have other salts, including calcium carbonate.

These soils do not have a lithic contact within 50 cm or a

glacic layer with its upper boundary within 100 cm of the

mineral soil surface.

Lithic Anhyorthels.—These are the Anhyorthels that have

a lithic contact within 50 cm of the mineral soil surface. They

commonly have accumulations of salts, including calcium

carbonate and gypsum.

Nitric Anhyorthels.—These are the Anhyorthels that have

large accumulations of nitrate. They commonly have

accumulations of other salts, but do not have gypsic or

petrogypsic horizons. Nitric Anhyorthels also do not have a

lithic contact within 50 cm or a glacic layer with an upper

boundary within 100 cm of the mineral soil surface.

Petrogypsic Anhyorthels.—These are the Anhyorthels that

have a petrogypsic horizon within 100 cm of the mineral soil

surface. They can have accumulations of other salts, but they

do not have a lithic contact within 50 cm or a glacic layer with

its upper boundary within 100 cm of the mineral soil surface.

Salic Anhyorthels.—These are the Anhyorthels that have a

salic horizon with or without a calcic horizon. These soils do

not have a lithic contact within 50 cm or a glacic layer with its

upper boundary within 100 cm of the mineral soil surface.

They also do not have gypsic or petrogypsic horizons or large

accumulations of nitrates within 100 cm of the mineral soil

surface.

Aquorthels

These are the Orthels that are saturated and reduced close to

the surface for at least part of the year. These soils have redox

depletions with chroma of 2 or less. Aquorthels do not have

high amounts of organic carbon at the surface. These soils are

common in the centers of large-scale, low-centered polygons

along the North Slope of the Brooks Range in Alaska.

Definition

Aquorthels are the Orthels that:

1. Have, within 50 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

during normal years; and

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the

mineral soil surface to a depth of 50 cm.
454 Soil Taxonomy

Key to Subgroups

ACBA. Aquorthels that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Aquorthels

ACBB. Other Aquorthels that have a glacic layer that has its

upper boundary within 100 cm of the mineral soil surface.

Glacic Aquorthels

ACBC. Other Aquorthels that have a sulfuric horizon or

sulfidic materials with an upper boundary within 100 cm of the

mineral soil surface.

Sulfuric Aquorthels

ACBD. Other Aquorthels that have either:

1. Organic soil materials that are discontinuous at the

surface; or

2. Organic soil materials at the surface that change in

thickness fourfold or more within a pedon.

Ruptic-Histic Aquorthels

ACBE. Other Aquorthels that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Aquorthels

ACBF. Other Aquorthels that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Aquorthels

ACBG. Other Aquorthels that have a salic horizon that

has its upper boundary within 100 cm of the mineral soil

surface.

Salic Aquorthels

ACBH. Other Aquorthels that have less than 35 percent (by

volume) rock fragments and a texture of loamy fine sand or

coarser in all layers within the particle-size control section.

Psammentic Aquorthels

ACBI. Other Aquorthels.

Typic Aquorthels

Definition of Typic Aquorthels

These are the Aquorthels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface;

3. Do not have either:

a. Organic soil materials that are discontinuous at the

surface; or

b. Organic soil materials at the surface that change in

thickness fourfold or more within a pedon;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al plus 1

/2 Fe percentages (by ammonium oxalate) totaling more than

1.0;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

6. Do not have a salic or sulfuric horizon or sulfidic materials

with an upper boundary within 100 cm of the mineral soil

surface; and

7. Have 35 percent (by volume) or more rock fragments or a

texture finer than loamy fine sand in at least one layer within

the particle-size control section.

Description of Subgroups

Typic Aquorthels.—The concept of Typic Aquorthels is

centered on soils without special characteristics. The Typic
Gelisols 455

subgroup does not have a lithic contact within 50 cm or a glacic

layer with an upper boundary within 100 cm of the mineral soil

surface. These soils also do not have salic or sulfuric horizons

or sulfidic materials within 100 cm of the mineral soil surface.

Textures are finer than loamy fine sand or are skeletal in at least

some layers of the particle-size control section. If these soils

have organic soil materials at the surface, the layer is continuous

and does not change much in thickness within a pedon. These

soils do have the andic soil properties or volcanic glass

associated with the Vitrandic Aquorthels.

Andic Aquorthels.—These are the Aquorthels that have,

throughout one or more horizons with a total thickness of 18

cm or more within 75 cm of the mineral soil surface, a fineearth fraction with both a bulk density of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0.

These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. Andic Aquorthels are commonly in areas

that receive volcanic ejecta, but this is not required.

Glacic Aquorthels.—These are the Aquorthels that have a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. Commonly, these soils have organic soil

materials at the surface. Disturbance of the surface horizon

removes the insulating layer; the glacic layer then melts, and

the soil collapses.

Lithic Aquorthels.—These are the Aquorthels that have a

lithic contact within 50 cm of the mineral soil surface. These

soils are rare in the world.

Psammentic Aquorthels.—These are the sandy Aquorthels

that do not have a lithic contact within 50 cm of the mineral

soil surface or a glacic layer with its upper boundary within

100 cm of the mineral soil surface. They also do not have a

salic or sulfuric horizon or sulfidic materials with an upper

boundary within 100 cm of the mineral soil surface. These soils

commonly have thin organic layers and do not have andic soil

properties.

Ruptic-Histic Aquorthels.—These are the Aquorthels that

have an organic layer at the surface that is either discontinuous

or thins and thickens because of periglacial microrelief. These

soils are common in Alaska, Canada, and Siberia.

Salic Aquorthels.—These are the Aquorthels that have a

salic horizon with its upper boundary within 100 cm of the

mineral soil surface. These soils do not have a glacic layer, a

sulfuric horizon, or sulfidic materials with an upper boundary

within 100 cm or a lithic contact within 50 cm of the mineral

soil surface. Salic Aquorthels do not have an organic layer at

the surface that thins and thickens in relationship to

microrelief. These soils do not have andic soil properties.

Sulfuric Aquorthels.—These are the Aquorthels that have

a sulfuric horizon or sulfidic materials within 100 cm of the

mineral soil surface. They do not have a lithic contact within

50 cm of the mineral soil surface and do not have a glacic layer

within 100 cm of the mineral soil surface. These soils occur in

cold coastal areas of the world.

Vitrandic Aquorthels.—These are Aquorthels that have,

throughout one or more horizons with a total thickness of 18

cm or more within 75 cm of the mineral soil surface, one or

both of the following:

1. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Aquorthels are not so weathered as the Andic

Aquorthels. They do not have a lithic contact within 50 cm or a

glacic layer, a sulfuric horizon, or sulfidic materials with an

upper boundary within 100 cm of the mineral soil surface.

Argiorthels

These are the Orthels that have an argillic horizon. These

soils do not have a mollic or umbric epipedon or anhydrous

conditions. Argiorthels do not have the wet conditions

conducive to the accumulation of organic matter close to the

surface. The argillic horizon in these soils commonly is weakly

expressed. These soils are rare in the world but are known to

occur in northern Siberia.

Definition

Argiorthels are the Orthels that:

1. Have an argillic horizon that has its upper boundary

within 100 cm of the mineral soil surface;

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm;

3. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years;

4. Do not have anhydrous conditions; and

5. Do not have a mollic or umbric epipedon.

Key to Subgroups

ACFA. Argiorthels that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Argiorthels
456 Soil Taxonomy

ACFB. Other Argiorthels that have a glacic layer that has its

upper boundary within 100 cm of the mineral soil surface.

Glacic Argiorthels

ACFC. Other Argiorthels that have a natric horizon.

Natric Argiorthels

ACFD. Other Argiorthels.

Typic Argiorthels

Definition of Typic Argiorthels

Typic Argiorthels are the Orthels that:

1. Do not have a lithic contact within 50 cm of the mineral soil

surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface; and

3. Do not have a natric horizon.

Description of Subgroups

Typic Argiorthels.—These are the Argiorthels that have no

special characteristics. Commonly, the argillic horizon is

weakly developed in these soils. Typic Argiorthels do not have

a lithic contact within 50 cm or a glacic layer with an upper

boundary within 100 cm of the mineral soil surface. These

soils also do not have the sodium associated with natric

horizons. Typic Argiorthels are on stable surfaces with tundra

vegetation.

Glacic Argiorthels.—These are the Argiorthels that have a

glacic layer with its upper boundary within 100 cm of the

mineral soil surface. Glacic Argiorthels do not have a lithic

contact within 50 cm of the mineral soil surface. Disturbance

of the insulating surface layer causes the ice to melt and the

soil to collapse.

Lithic Argiorthels.—These are the Argiorthels that have a

lithic contact within 50 cm of the mineral soil surface. Lithic

Argiorthels are associated with stable, bedrock-controlled

landscapes.

Natric Argiorthels.—These are the Argiorthels that have a

natric horizon. Natric Argiorthels do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface. These soils commonly are

derived from sodium-rich marine deposits.

Haplorthels

Haplorthels are the Orthels that have an ochric epipedon and

commonly a cambic horizon but have insufficient moisture prior

to freezing to produce cryoturbation. These soils are not

sufficiently wet for the development of thick organic layers at

the surface. They are not sandy throughout the particle-size

control section. They occur in Alaska, Canada, and Siberia.

Definition

Haplorthels are the Orthels that:

1. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm;

2. Do not have anhydrous conditions;

3. Do not have a mollic or umbric epipedon;

4. Do not have an argillic horizon that has its upper boundary

within 100 cm of the mineral soil surface;

5. Have 35 percent or more (by volume) rock fragments or a

texture finer than loamy fine sand in at least one layer within

the particle-size control section; and

6. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years.

Key to Subgroups

ACHA. Haplorthels that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplorthels

ACHB. Other Haplorthels that have a glacic layer that has its

upper boundary within 100 cm of the mineral soil surface.

Glacic Haplorthels

ACHC. Other Haplorthels that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time

during normal years (or artificial drainage).

Aquic Haplorthels

ACHD. Other Haplorthels.

Typic Haplorthels

Definition of Typic Haplorthels

Typic Haplorthels are the Orthels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface; and

3. Do not have, in one or more horizons within 100 cm of the

mineral soil surface, distinct or prominent redox

concentrations and also aquic conditions for some time during

normal years.

Description of Subgroups

Typic Haplorthels.—These are the Haplorthels that do not

have a lithic contact within 50 cm or a glacic layer with an
Gelisols 457

upper boundary within 100 cm of the mineral soil surface. The

Typic subgroup does not have the redoximorphic features

associated with the Aquic subgroup.

Aquic Haplorthels.—These are the Haplorthels that are

saturated and reduced for some time during normal years. They

do not have a lithic contact within 50 cm of the mineral soil

surface or a glacic layer with an upper boundary within 100 cm

of the mineral soil surface. These soils commonly have well

expressed features related to cryoturbation.

Glacic Haplorthels.—These are the Haplorthels that have

a glacic layer with an upper boundary within 100 cm of the

mineral soil surface. They do not have a lithic contact within

50 cm of the mineral soil surface. Disturbance of the surface

can cause the ice layer to melt and the soil to collapse.

Lithic Haplorthels.—These are the Haplorthels that have a

lithic contact within 50 cm of the mineral soil surface. These

soils are rare in the world.

Historthels

Historthels are the Orthels that have organic materials at the

surface. Commonly, the organic materials are thicker in the

lower positions on the landscape and thinner in the higher

positions. These soils are commonly saturated at or near the

surface for some time during normal years and have

redoximorphic features.

Definition

Historthels are the Orthels that have in 30 percent or more

of the pedon more than 40 percent, by volume, organic

materials from the soil surface to a depth of 50 cm.

Key to Subgroups

ACAA. Historthels that have a lithic contact within 50 cm of

the soil surface.

Lithic Historthels

ACAB. Other Historthels that have a glacic layer that has its

upper boundary within 100 cm of the soil surface.

Glacic Historthels

ACAC. Other Historthels that have more than 40 percent, by

volume, organic soil materials from the soil surface to a depth

of 50 cm in 75 percent or less of the pedon.

Ruptic Historthels

ACAD. Other Historthels.

Typic Historthels

Definition of Typic Historthels

Typic Historthels are the Orthels that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the soil surface; and

3. Have more than 40 percent, by volume, organic soil

materials from the soil surface to a depth of 50 cm in more

than 75 percent of the pedon.

Description of Subgroups

Typic Historthels.—These are the Historthels that do not

have a glacic layer with an upper boundary within 100 cm or a

lithic contact within 50 cm of the soil surface. Commonly,

these soils have an organic layer at the surface that varies in

thickness and are saturated for at least brief periods during

normal years.

Glacic Historthels.—These are the Historthels that have a

glacic layer with an upper boundary within 100 cm of the soil

surface. These soils do not have a lithic contact within 50 cm

of the mineral soil surface. Disturbance of the insulating

organic layer causes the ice to melt and the soil to collapse.

Lithic Historthels.—These are the Historthels that have a

lithic contact within 50 cm of the soil surface. These soils are

rare in the world.

Ruptic Historthels.—These are the Historthels that have

organic layers at the surface that vary in thickness. Commonly,

the thickness is related to the position on the landscape. A

pattern of high and low areas repeats itself over relatively short

distances. These soils do not have a lithic contact within 50 cm

or a glacic layer with an upper boundary within 100 cm of the

soil surface.

Mollorthels

Mollorthels are the Orthels that have a mollic epipedon.

These soils are not wet for long periods and, unlike Historthels,

do not have organic materials at the surface. They are known to

occur in Alaska, Canada, and Siberia. On the North Slope of

the Brooks Range in Alaska, they support vegetation that

differs from that on Umbrorthels.

Definition

Mollorthels are the Orthels that:

1. Have a mollic epipedon;

2. Do not have anhydrous conditions;

3. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm; and

4. Do not have, within 50 cm of the mineral soil surface,
458 Soil Taxonomy

redox depletions with chroma of 2 or less and aquic conditions

during normal years.

Key to Subgroups

ACDA. Mollorthels that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Mollorthels

ACDB. Other Mollorthels that have a glacic layer that has its

upper boundary within 100 cm of the mineral soil surface.

Glacic Mollorthels

ACDC. Other Mollorthels that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time during normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallowest.

Vertic Mollorthels

ACDD. Other Mollorthels that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Mollorthels

ACDE. Other Mollorthels that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Mollorthels

ACDF. Other Mollorthels that have:

1. A mollic epipedon 40 cm or more thick with a texture

finer than loamy fine sand; and

2. A slope of less than 25 percent.

Cumulic Mollorthels

ACDG. Other Mollorthels that have, in one or more horizons

within 100 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time during normal years (or artificial drainage).

Aquic Mollorthels

ACDH. Other Mollorthels.

Typic Mollorthels

Definition of Typic Mollorthels

Typic Mollorthels are the Mollorthels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface;

3. Do not have either of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time during normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallowest;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al plus 1

/2 Fe percentages (by ammonium oxalate) totaling more than

1.0;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

6. Have either:
Gelisols 459

a. A mollic epipedon that is less than 40 cm thick, unless

the texture is loamy fine sand or coarser; or

b. A slope of 25 percent or more; and

7. Do not have, in any horizon within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions for some time during normal years.

Description of Subgroups

Typic Mollorthels.—These are the Mollorthels without any

special features. These soils do not have a lithic contact within

50 cm or a glacic layer with an upper boundary within 100 cm

of the mineral soil surface. They do not have the potential to

shrink and swell characteristic of the Vertic Mollorthels and do

not have the volcanic glass or ammonium-extractable iron and

aluminum characteristic of the Andic and Vitrandic

Mollorthels. Typic Mollorthels have a mollic epipedon that is

less than 40 cm thick, unless they are on steep slopes or are

sandy, or both, and do not have evidence of wetness and

distinct or prominent redox concentrations within 100 cm of

the mineral soil surface.

Andic Mollorthels.—These are the Mollorthels that have,

throughout one or more horizons with a total thickness of 18

cm or more within 75 cm of the mineral soil surface, a fineearth fraction with both a bulk density of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0.

These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. They also do not have the high shrinkswell potential associated with the Vertic Mollorthels. Andic

Mollorthels are commonly in areas that receive volcanic ejecta,

but this is not required.

Aquic Mollorthels.—These are the Mollorthels with aquic

conditions and distinct or prominent redox concentrations

within 100 cm of the mineral soil surface. These soils do not

have a lithic contact within 50 cm or a glacic layer with an

upper boundary within 100 cm of the mineral soil surface.

They do not have the potential to shrink and swell

characteristic of the Vertic Mollorthels or the volcanic glass or

ammonium-extractable iron and aluminum characteristic of the

Andic and Vitrandic Mollorthels. Aquic Mollorthels have a

mollic epipedon that is less than 40 cm thick, unless they are

on steep slopes or are sandy, or both.

Cumulic Mollorthels.—These are the Mollorthels that have

a mollic epipedon that is 40 cm or more thick, a texture finer

than loamy fine sand, and a slope of less than 25 percent.

These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. Cumulic Mollorthels do not have the

potential to shrink and swell characteristic of the Vertic

Mollorthels or the volcanic glass or ammonium-extractable

iron and aluminum characteristic of the Andic and Vitrandic

Mollorthels.

Glacic Mollorthels.—These are the Mollorthels that have a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. These soils do not have a lithic contact

with its upper boundary within 50 cm of the mineral soil

surface. Disturbance of the insulating surface layer causes the

ice to melt and the soil to collapse.

Lithic Mollorthels.—These are the Mollorthels that have a

lithic contact within 50 cm of the mineral soil surface.

Vertic Mollorthels.—These are the Mollorthels that show

physical evidence of high shrink-swell in the form of cracks

and slickensides or wedge-shaped aggregates or have the

potential to shrink and swell. This potential is determined by

the linear extensibility. These soils do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface.

Vitrandic Mollorthels.—These are the Mollorthels that

have, throughout one or more horizons with a total thickness of

18 cm or more within 75 cm of the mineral soil surface, one or

both of the following:

1. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Mollorthels are not so weathered as the Andic

Mollorthels, do not have the shrink-swell potential associated

with the Vertic Mollorthels, and do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface.

Psammorthels

Psammorthels are the Orthels that have less than 35 percent

(by volume) rock fragments and a texture of loamy fine sand or

coarser in all layers within the particle-size control section.

These soils commonly have an ochric epipedon but not an

umbric or mollic epipedon or an argillic horizon. Unlike

Historthels, Psammorthels do not have organic materials close

to the surface. They also do not have aquic conditions within

50 cm of the mineral soil surface or anhydrous conditions.

Definition

Psammorthels are the Orthels that:

1. Have less than 35 percent (by volume) rock fragments and

a texture of loamy fine sand or coarser in all layers within the

particle-size control section;
460 Soil Taxonomy

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm;

3. Do not have an argillic horizon with its upper boundary

within 100 cm of the mineral soil surface;

4. Do not have anhydrous conditions;

5. Do not have a mollic or umbric epipedon; and

6. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years.

Key to Subgroups

ACGA. Psammorthels that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Psammorthels

ACGB. Other Psammorthels that have a glacic layer that

has its upper boundary within 100 cm of the mineral soil

surface.

Glacic Psammorthels

ACGC. Other Psammorthels that have a horizon 5 cm or

more thick that has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

2. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Psammorthels

ACGD. Other Psammorthels.

Typic Psammorthels

Definition of Typic Psammorthels

Typic Psammorthels are the Psammorthels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface; and

3. Do not have a horizon 5 cm or more thick that has any of

the following:

a. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

b. Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

c. An ODOE value of 0.12 or more, and a value half as high

or lower in an overlying horizon.

Description of Subgroups

Typic Psammorthels.—These are the Psammorthels that do

not have a lithic contact within 50 cm or a glacic layer with its

upper boundary within 100 cm of the mineral soil surface.

Typic Psammorthels do not have accumulations of

sesquioxides.

Glacic Psammorthels.—These are the Psammorthels that

have a glacic layer with its upper boundary within 100 cm of

the mineral soil surface but do not have a lithic contact within

50 cm of the mineral soil surface. Disturbance of the surface

commonly thaws the ice layer, after which the soil collapses.

Lithic Psammorthels.—These are the Psammorthels that

have a lithic contact within 50 cm of the mineral soil surface.

Spodic Psammorthels.—These are the Psammorthels that

grade toward Spodosols. Spodic Psammorthels have an E

horizon and a B horizon with accumulations of organic matter,

aluminum, and iron. They do not have a lithic contact within

50 cm of the mineral soil surface or a glacic layer with an

upper boundary within 100 cm of the mineral soil surface.

Umbrorthels

Umbrorthels are the Orthels that have an umbric epipedon.

These soils are not wet for long periods, nor are they dry

throughout the growing season. Unlike Historthels,

Umbrorthels do not have organic materials at the surface. They

are known to occur in Alaska, Canada, and Siberia. On the

North Slope of the Brooks Range in Alaska, they support

vegetation that differs from that on Mollorthels.

Definition

Umbrorthels are the Orthels that:

1. Have an umbric epipedon;

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm;

3. Do not have anhydrous conditions; and

4. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years.

Key to Subgroups

ACEA. Umbrorthels that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Umbrorthels

ACEB. Other Umbrorthels that have a glacic layer that has

its upper boundary within 100 cm of the mineral soil surface.

Glacic Umbrorthels
Gelisols 461

ACEC. Other Umbrorthels that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time during normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallowest.

Vertic Umbrorthels

ACED. Other Umbrorthels that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3

 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Umbrorthels

ACEE. Other Umbrorthels that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Umbrorthels

ACEF. Other Umbrorthels that have:

1. An umbric epipedon 40 cm or more thick with a texture

finer than loamy fine sand; and

2. A slope of less than 25 percent.

Cumulic Umbrorthels

ACEG. Other Umbrorthels that have, in one or more

horizons within 100 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time during normal years (or artificial drainage).

Aquic Umbrorthels

ACEH. Other Umbrorthels.

Typic Umbrorthels

Definition of Typic Umbrorthels

Typic Umbrorthels are the Umbrorthels that:

1. Do not have a lithic contact within 50 cm of the mineral soil

surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface;

3. Have neither of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time during normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; nor

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallowest;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al plus 1

/2 Fe percentages (by ammonium oxalate) totaling more than

1.0;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

6. Have either:

a. An umbric epipedon that is less than 40 cm thick,

unless the texture is loamy fine sand or coarser; or

b. A slope of 25 percent or more; and

7. Do not have, in any horizon within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions for some time during normal years.

Description of Subgroups

Typic Umbrorthels.—These are the Umbrorthels without

any special features. These soils do not have a lithic contact
462 Soil Taxonomy

within 50 cm or a glacic layer with its upper boundary within

100 cm of the mineral soil surface. They do not have the

potential to shrink and swell characteristic of the Vertic

Umbrorthels or the volcanic glass or ammonium-extractable

iron and aluminum characteristic of the Andic and Vitrandic

Umbrorthels. Typic Umbrorthels have an umbric epipedon that

is less than 40 cm thick, unless they are on steep slopes or are

sandy, or both, and do not have evidence of wetness and

distinct or prominent redox concentrations within 100 cm of

the mineral soil surface.

Andic Umbrorthels.—These are the Umbrorthels that

have, throughout one or more horizons with a total thickness of

18 cm or more within 75 cm of the mineral soil surface, a fineearth fraction with both a bulk density of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0.

These soils do not have a lithic contact within 50 cm or a

glacic layer with its upper boundary within 100 cm of the

mineral soil surface. They also do not have the high shrinkswell potential associated with the Vertic Umbrorthels. Andic

Umbrorthels are commonly in areas that receive volcanic

ejecta, but this is not required.

Aquic Umbrorthels.—These are the Umbrorthels with aquic

conditions and distinct or prominent redox concentrations

within 100 cm of the mineral soil surface. These soils do not

have a lithic contact within 50 cm or a glacic layer with its upper

boundary within 100 cm of the mineral soil surface. They do not

have the potential to shrink and swell characteristic of the Vertic

Umbrorthels or the volcanic glass or ammonium-extractable iron

and aluminum characteristic of the Andic and Vitrandic

Umbrorthels. Aquic Umbrorthels have an umbric epipedon that

is less than 40 cm thick, unless they are on steep slopes or are

sandy, or both.

Cumulic Umbrorthels.—These are the Umbrorthels that

have an umbric epipedon that is 40 cm or more thick, a texture

finer than loamy fine sand, and a slope of less than 25 percent.

These soils do not have a lithic contact within 50 cm or a

glacic layer with its upper boundary within 100 cm of the

mineral soil surface. Cumulic Umbrorthels do not have the

potential to shrink and swell characteristic of the Vertic

Umbrorthels or the volcanic glass or ammonium-extractable

iron and aluminum characteristic of the Andic and Vitrandic

Umbrorthels.

Glacic Umbrorthels.—These are the Umbrorthels that have

a glacic layer with an upper boundary within 100 cm of the

mineral soil surface. These soils do not have a lithic contact

with its upper boundary within 50 cm of the mineral soil

surface. Disturbance of the insulating surface layer causes the

ice to melt and the soil to collapse.

Lithic Umbrorthels.—These are the Umbrorthels that have

a lithic contact within 50 cm of the mineral soil surface.

Vertic Umbrorthels.—These are the Umbrorthels that show

physical evidence of high shrink-swell in the form of cracks

and slickensides or wedge-shaped aggregates or have the

potential to shrink and swell. This potential is determined by the

linear extensibility. These soils do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within 100

cm of the mineral soil surface.

Vitrandic Umbrorthels.—These are the Umbrorthels that

have, throughout one or more horizons with a total thickness of

18 cm or more within 75 cm of the mineral soil surface, one or

both of the following:

1. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Umbrorthels are not so weathered as the Andic

Umbrorthels, do not have the shrink-swell potential associated

with the Vertic Umbrorthels, and do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface.

Turbels

These are the Gelisols that have one or more horizons with

evidence of cryoturbation in the form of irregular, broken, or

distorted horizon boundaries, involutions, the accumulation of

organic matter on top of the permafrost, ice or sand wedges,

and oriented rock fragments.

Cryoturbation occurs only in soils with sufficient moisture.

Cryoturbated horizons in soils that are dry for most of the year

likely were more moist in the past.

Turbels are the dominant suborder of Gelisols. They

account for about half the Gelisols on a global basis. These

soils are common in the High and Middle Arctic vegetation

regions of North America and Eurasia at latitudes of 65o

 N. or

more.

Definition

Turbels are the Gelisols that:

1. Do not have organic soil materials that meet one or more

of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or
Gelisols 463

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Are saturated with water for 30 or more cumulative days

during normal years (or are artificially drained) and have 80

percent or more, by volume, organic soil materials from the

soil surface to a depth of 50 cm or to a glacic layer or a

densic, lithic, or paralithic contact, whichever is shallowest;

and

2. Have one or more horizons with evidence of cryoturbation

in the form of irregular, broken, or distorted horizon

boundaries, involutions, the accumulation of organic matter on

top of the permafrost, ice or sand wedges, and oriented rock

fragments.

Key to Great Groups

ABA. Turbels that have in 30 percent or more of the pedon

more than 40 percent, by volume, organic materials from the

soil surface to a depth of 50 cm.

Histoturbels, p. 466

ABB. Other Turbels that have, within 50 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions during normal years (or artificial drainage).

Aquiturbels, p. 464

ABC. Other Turbels that have anhydrous conditions.

Anhyturbels, p. 463

ABD. Other Turbels that have a mollic epipedon.

Molliturbels, p. 466

ABE. Other Turbels that have an umbric epipedon.

Umbriturbels, p. 469

ABF. Other Turbels that have less than 35 percent (by

volume) rock fragments and a texture of loamy fine sand or

coarser in all layers within the particle-size control section.

Psammoturbels, p. 468

ABG. Other Turbels.

Haploturbels, p. 465

Anhyturbels

These are the Turbels that have anhydrous conditions and

may have dry permafrost (i.e., insufficient moisture for

interstitial ice to occur). The cold deserts commonly receive

less than 30 mm of annual precipitation. These soils support

little or no vegetation.

Anhyturbels are limited in extent but occur in continental

Antarctica, northern Greenland, and the cold, dry mountains of

Eurasia at elevations of more than 3,700 m.

These soils have undergone climatic periods in the past when

more moisture was available.

Definition

Anhyturbels are the Turbels that:

1. Have anhydrous conditions;

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm; and

3. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years.

Key to Subgroups

ABCA. Anhyturbels that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Anhyturbels

ABCB. Other Anhyturbels that have a glacic layer with its

upper boundary within 100 cm of the mineral soil surface.

Glacic Anhyturbels

ABCC. Other Anhyturbels that have a petrogypsic horizon

with its upper boundary within 100 cm of the mineral soil

surface.

Petrogypsic Anhyturbels

ABCD. Other Anhyturbels that have a gypsic horizon with

its upper boundary within 100 cm of the mineral soil surface.

Gypsic Anhyturbels

ABCE. Other Anhyturbels that have a horizon 15 cm or more

thick that contains 12 cmol(-)/L nitrate in 1:5 soil:water extract

and in which the product of its thickness (in cm) and its nitrate

concentration is 3,500 or more.

Nitric Anhyturbels

ABCF. Other Anhyturbels that have a salic horizon that has

its upper boundary within 100 cm of the mineral soil surface.

Salic Anhyturbels

ABCG. Other Anhyturbels that have a calcic horizon that has

its upper boundary within 100 cm of the mineral soil surface.

Calcic Anhyturbels

ABCH. Other Anhyturbels.

Typic Anhyturbels

Definition of Typic Anhyturbels

These are the Anhyturbels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;
464 Soil Taxonomy

2. Do not have a glacic layer or a petrogypsic, gypsic, salic, or

calcic horizon with its upper boundary within 100 cm of the

mineral soil surface; and

3. Do not have a horizon 15 cm or more thick that has 12

cmol(-)/L nitrate in 1:5 soil:water extract and in which the

product of its thickness (in cm) and its nitrate concentration is

3,500 or more.

Description of Subgroups

Typic Anhyturbels.—These are the Anhyturbels that

commonly have accumulations of salts, including gypsum and

calcium carbonate, but insufficient quantities to meet the

criteria for a calcic, gypsic, petrogypsic, or salic horizon. These

soils also do not contain large amounts of nitrate. They do not

have a lithic contact within 50 cm of the mineral soil surface or

a glacic layer with its upper boundary within 100 cm of the

mineral soil surface.

Calcic Anhyturbels.—These are the Anhyturbels that have

a calcic horizon within 100 cm of the mineral soil surface.

These soils commonly have other more soluble salts, but not in

sufficient quantity to meet the criteria for a petrogypsic, gypsic,

or salic horizon. The soils also lack sufficient quantities of

nitrate, a glacic layer, and a lithic contact.

Glacic Anhyturbels.—These are the Anhyturbels that have

a glacic layer with an upper boundary withi 100 cm of the

mineral soil surface. These soils commonly have accumulations

of salts, including calcium carbonate and gypsum, but do not

have a lithic contact within 50 cm of the mineral soil surface.

Gypsic Anhyturbels.—These are the Anhyturbels that have

a gypsic horizon within 100 cm of the mineral soil surface.

They commonly have other salts, including calcium carbonate.

These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface.

Lithic Anhyturbels.—These are the Anhyturbels that have

a lithic contact within 50 cm of the mineral soil surface. They

commonly have accumulations of salts, including calcium

carbonate and gypsum.

Nitric Anhyturbels.—These are the Anhyturbels that have

large accumulations of nitrate. They commonly have

accumulations of other salts, but they do not have gypsic or

petrogypsic horizons. They also do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface.

Petrogypsic Anhyturbels.—These are the Anhyturbels that

have a petrogypsic horizon within 100 cm of the mineral soil

surface. They can have accumulations of other salts, but they

do not have a lithic contact within 50 cm or a glacic layer with

an upper boundary within 100 cm of the mineral soil surface.

Salic Anhyturbels.—These are the Anhyturbels that have a

salic horizon with or without a calcic horizon. These soils do

not have a lithic contact within 50 cm or a glacic layer with an

upper boundary within 100 cm of the mineral soil surface. They

also do not have gypsic or petrogypsic horizons or large

accumulations of nitrates within 100 cm of the mineral soil

surface.

Aquiturbels

These are the Turbels that are saturated with water close to

the surface. Saturation commonly occurs in spring, when water

perches on the permafrost and temperatures are warm enough

for iron reduction to occur. These soils can have mollic,

umbric, or ochric epipedons. They occur in depressional areas

in Alaska, Canada, and Eurasia.

Definition

Aquiturbels are the Turbels that:

1. Have, within 50 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

during normal years (or artificial drainage); and

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm.

Key to Subgroups

ABBA. Aquiturbels that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Aquiturbels

ABBB. Other Aquiturbels that have a glacic layer with its

upper boundary within 100 cm of the mineral soil surface.

Glacic Aquiturbels

ABBC. Other Aquiturbels that have a sulfuric horizon or

sulfidic materials with an upper boundary within 100 cm of the

mineral soil surface.

Sulfuric Aquiturbels

ABBD. Other Aquiturbels that have either:

1. Organic soil materials that are discontinous at the

surface; or

2. Organic soil materials at the surface that change in

thickness fourfold or more within a pedon.

Ruptic-Histic Aquiturbels

ABBE. Other Aquiturbels that have less than 35 percent (by

volume) rock fragments and a texture of loamy fine sand or

coarser in all layers within the particle-size control section.

Psammentic Aquiturbels

ABBF. Other Aquiturbels.

Typic Aquiturbels
Gelisols 465

Definition of Typic Aquiturbels

Typic Aquiturbels are the Turbels that:

1. Do not have a lithic contact within 50 cm of the mineral soil

surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface;

3. Have neither of the following:

a. Organic soil materials that are discontinous at the

surface; nor

b. Organic soil materials at the surface that change in

thickness fourfold or more within a pedon;

4. Have neither a sulfuric horizon nor sulfidic materials with

an upper boundary within 100 cm of the mineral soil surface;

and

5. Have either 35 percent or more (by volume) rock

fragments or a texture finer than loamy fine sand in one or

more layers within the particle-size control section.

Description of Subgroups

Typic Aquiturbels.—The concept of Typic Aquiturbels is

centered on Aquiturbels without special characteristics. The

Typic subgroup does not have a lithic contact within 50 cm, a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface, or a sulfuric horizon or sulfidic materials

within 100 cm of the mineral soil surface. Textures are finer

than loamy fine sand or are skeletal in at least some part of the

particle-size control section. If these soils have organic soil

materials at the surface, the layer is continuous and does not

change much in thickness within a pedon.

Glacic Aquiturbels.—These are the Aquiturbels that have a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. Commonly, these soils have organic soil

materials at the surface. Disturbance of the surface horizon

removes the insulating layer; the glacic layer then melts, and

the soil collapses.

Lithic Aquiturbels.—These are the Aquiturbels that have a

lithic contact within 50 cm of the mineral soil surface. These

soils are rare in the world.

Psammentic Aquiturbels.—These are the sandy

Aquiturbels that do not have a lithic contact within 50 cm of

the mineral soil surface or a glacic layer with an upper

boundary within 100 cm of the mineral soil surface. These soils

commonly have thin organic layers.

Ruptic-Histic Aquiturbels.—These are the Aquiturbels

that have an organic layer at the surface that is either

discontinuous or thins and thickens because of periglacial

microrelief. These soils are common in Alaska, Canada, and

Siberia.

Sulfuric Aquiturbels.—These are the Aquiturbels that have

a sulfuric horizon or sulfidic materials within 100 cm of the

mineral soil surface. These soils occur in cold coastal areas of

the world.

Haploturbels

Haploturbels are the Turbels that have an ochric epipedon

and have sufficient moisture to produce cryoturbation. These

soils are not sufficiently wet for the development of thick

organic layers at the surface or redox features. Haploturbels are

not sandy throughout the particle-size control section.

Commonly, the cryoturbation is not well expressed. These soils

occur in Alaska, Canada, and Siberia.

Definition

Haploturbels are the Turbels that:

1. Do not have in 30 percent or more of the pedon more than

40 percent, by volume, organic materials from the soil surface

to a depth of 50 cm;

2. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years;

3. Do not have anhydrous conditions;

4. Do not have a mollic or umbric epipedon; and

5. Have 35 percent or more (by volume) rock fragments or a

texture finer than loamy fine sand in at least one layer within

the particle-size control section.

Key to Subgroups

ABGA. Haploturbels that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Haploturbels

ABGB. Other Haploturbels that have a glacic layer that has

an upper boundary within 100 cm of the mineral soil surface.

Glacic Haploturbels

ABGC. Other Haploturbels that have, in one or more

horizons within 100 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time during normal years (or artificial drainage).

Aquic Haploturbels

ABGD. Other Haploturbels.

Typic Haploturbels

Definition of Typic Haploturbels

Typic Haploturbels are the Turbels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface; and
466 Soil Taxonomy

3. Do not have, in one or more horizons within 100 cm

of the mineral soil surface, distinct or prominent redox

concentrations and also aquic conditions for some time

during normal years.

Description of Subgroups

Typic Haploturbels.—These are the Haploturbels that do not

have a lithic contact within 50 cm or a glacic layer with an upper

boundary within 100 cm of the mineral soil surface. The Typic

subgroup does not have the redoximorphic features associated

with the Aquic subgroup.

Aquic Haploturbels.—These are the Haploturbels that are

saturated and reduced for some time during normal years.

These soils commonly have well expressed features related to

cryoturbation.

Glacic Haploturbels.—These are the Haploturbels that

have a glacic layer with an upper boundary within 100 cm of

the mineral soil surface. Disturbance of the surface can cause

the ice layer to melt and the soil to collapse.

Lithic Haploturbels.—These are the Haploturbels that have

a lithic contact within 50 cm of the mineral soil surface. These

soils are rare in the world.

Histoturbels

Histoturbels are the Turbels that have organic materials at the

surface. Commonly, the organic materials are thicker in the lower

positions on the landscape and thinner in the higher positions.

These soils are commonly saturated at or near the surface for

some time during normal years. They commonly have

redoximorphic features.

Definition

Histoturbels are the Turbels that have in 30 percent or more

of the pedon more than 40 percent, by volume, organic

materials from the soil surface to a depth of 50 cm.

Key to Subgroups

ABAA. Histoturbels that have a lithic contact within 50 cm

of the soil surface.

Lithic Histoturbels

ABAB. Other Histoturbels that have a glacic layer with its

upper boundary within 100 cm of the soil surface.

Glacic Histoturbels

ABAC. Other Histoturbels that have more than 40 percent,

by volume, organic soil materials from the soil surface to a

depth of 50 cm in 75 percent or less of the pedon.

Ruptic Histoturbels

ABAD. Other Histoturbels.

Typic Histoturbels

Definition of Typic Histoturbels

Typic Histoturbels are the Turbels that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the soil surface; and

3. Have more than 40 percent, by volume, organic soil

materials from the soil surface to a depth of 50 cm in more

than 75 percent of the pedon.

Description of Subgroups

Typic Histoturbels.—These are the Histoturbels that do not

have a glacic layer with an upper boundary within 100 cm or a

lithic contact within 50 cm of the soil surface. Commonly,

these soils have an organic layer at the surface that varies in

thickness. These soils are saturated for at least brief periods

during normal years.

Glacic Histoturbels.—These are the Histoturbels that have

a glacic layer with an upper boundary within 100 cm of the soil

surface. They do not have a lithic contact within 50 cm of the

mineral soil surface. Disturbance of the insulating organic

layer causes the ice to melt and the soil to collapse.

Lithic Histoturbels.—These are the Histoturbels that have

a lithic contact within 50 cm of the soil surface. These soils are

rare in the world.

Ruptic Histoturbels.—These are the Histoturbels that have

organic layers at the surface that vary in thickness. Commonly,

the thickness is related to the position on the landscape. A

pattern of high and low areas repeats itself over relatively short

distances. These soils do not have a lithic contact within 50 cm

or a glacic layer with an upper boundary within 100 cm of the

soil surface.

Molliturbels

Molliturbels are the Turbels that have a mollic epipedon.

These soils are not wet for long periods and do not have the

redoximorphic features associated with Aquiturbels or the

organic materials at the surface associated with Histoturbels.

They are known to occur in Alaska, Canada, and Siberia. On

the North Slope of the Brooks Range in Alaska, they support

vegetation that differs from that on the more acid

Umbriturbels.

Definition

Molliturbels are the Turbels that:

1. Have a mollic epipedon;

2. Do not have anhydrous conditions;

3. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm; and
Gelisols 467

4. Do not have, within 50 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

during normal years.

Key to Subgroups

ABDA. Molliturbels that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Molliturbels

ABDB. Other Molliturbels that have a glacic layer that has

its upper boundary within 100 cm of the mineral soil surface.

Glacic Molliturbels

ABDC. Other Molliturbels that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time during normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallowest.

Vertic Molliturbels

ABDD. Other Molliturbels that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Molliturbels

ABDE. Other Molliturbels that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Molliturbels

ABDF. Other Molliturbels that have:

1. A mollic epipedon 40 cm or more thick with a texture finer

than loamy fine sand; and

2. A slope of less than 25 percent.

Cumulic Molliturbels

ABDG. Other Molliturbels that have, in one or more

horizons within 100 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time during normal years (or artificial drainage).

Aquic Molliturbels

ABDH. Other Molliturbels.

Typic Molliturbels

Definition of Typic Molliturbels

Typic Molliturbels are the Molliturbels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface;

3. Do not have either of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time during normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallowest;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al plus 1

/2 Fe percentages (by ammonium oxalate) totaling more than

1.0;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium
468 Soil Taxonomy

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more;

6. Have either:

a. A mollic epipedon that is less than 40 cm thick, unless

the texture is loamy fine sand or coarser; or

b. A slope of 25 percent or more; and

7. Do not have, in any horizon within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions for some time during normal years.

Description of Subgroups

Typic Molliturbels.—These are the Molliturbels without

any special features. These soils do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface. They do not have the

potential to shrink and swell characteristic of the Vertic

subgroup and do not have the volcanic glass or ammoniumextractable iron and aluminum characteristic of the Andic and

Vitrandic subgroups. Typic Molliturbels have a mollic

epipedon that is less than 40 cm thick, unless they are on steep

slopes or are sandy, or both, and do not have evidence of

wetness and distinct or prominent redox concentrations within

100 cm of the mineral soil surface.

Andic Molliturbels.—These are the Molliturbels that have,

throughout one or more horizons with a total thickness of 18

cm or more within 75 cm of the mineral soil surface, a fineearth fraction with both a bulk density of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and Al plus

1

/2 Fe percentages (by ammonium oxalate) totaling more than

1.0. These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. They also do not have the high shrinkswell potential associated with the Vertic subgroup. Andic

Molliturbels are commonly in areas that receive volcanic

ejecta, but this is not required.

Aquic Molliturbels.—These are the Molliturbels with aquic

conditions and distinct or prominent redox concentrations

within 100 cm of the mineral soil surface. These soils do not

have a lithic contact within 50 cm or a glacic layer with an

upper boundary within 100 cm of the surface. They do not have

the potential to shrink and swell characteristic of the Vertic

subgroup or the volcanic glass or ammonium-extractable iron

and aluminum characteristic of the Andic and Vitrandic

subgroups. Aquic Molliturbels have a mollic epipedon that is

less than 40 cm thick, unless they are sandy or on steep slopes.

Cumulic Molliturbels.—These are the Molliturbels that

have a mollic epipedon that is 40 cm or more thick, a texture

finer than loamy fine sand, and a slope of less than 25 percent.

These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

surface. Cumulic Molliturbels do not have the potential to

shrink and swell characteristic of the Vertic subgroup or the

volcanic glass or ammonium-extractable iron and aluminum

characteristic of the Andic and Vitrandic subgroups.

Glacic Molliturbels.—These are the Molliturbels that have

a glacic layer with an upper boundary within 100 cm of the

mineral soil surface. These soils do not have a lithic contact

with its upper boundary within 50 cm of the mineral soil

surface. Disturbance of the insulating surface layer causes the

ice to melt and the soil to collapse.

Lithic Molliturbels.—These are the Molliturbels that have

a lithic contact within 50 cm of the mineral soil surface.

Vertic Molliturbels.—These are the Molliturbels that show

physical evidence of high shrink-swell in the form of cracks

and slickensides or wedge-shaped aggregates or have the

potential to shrink and swell. This potential is determined by

the linear extensibility. These soils do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface.

Vitrandic Molliturbels.—These are the Molliturbels that

have, throughout one or more horizons with a total thickness of

18 cm or more within 75 cm of the mineral soil surface, one or

both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more.

Vitrandic Molliturbels are not so weathered as the Andic

subgroup, do not have the shrink-swell potential associated

with the Vertic subgroup, and do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface.

Psammoturbels

Psammoturbels are the Turbels that have less than 35 percent

(by volume) rock fragments and a texture of loamy fine sand or

coarser in all layers within the particle-size control section.

These soils commonly have an ochric epipedon but not an

umbric or mollic epipedon or anhydrous conditions.

Psammoturbels do not have the redoximorphic features

associated with Aquiturbels or the organic materials close to

the surface associated with Histoturbels.

Definition

Psammoturbels are the Turbels that:

1. Have less than 35 percent (by volume) rock fragments and
Gelisols 469

a texture of loamy fine sand or coarser in all layers within the

particle-size control section;

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm;

3. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years;

4. Do not have anhydrous conditions; and

5. Do not have a mollic or umbric epipedon.

Key to Subgroups

ABFA. Psammoturbels that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Psammoturbels

ABFB. Other Psammoturbels that have a glacic layer that

has its upper boundary within 100 cm of the mineral soil

surface.

Glacic Psammoturbels

ABFC. Other Psammoturbels that have a horizon 5 cm or

more thick that has one or more of the following:

1. In 25 percent or more of each pedon, cementation

by organic matter and aluminum, with or without iron; or

2. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Psammoturbels

ABFD. Other Psammoturbels.

Typic Psammoturbels

Definition of Typic Psammoturbels

Typic Psammoturbels are the Psammoturbels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface; and

3. Do not have a horizon 5 cm or more thick that has any of

the following:

a. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

b. Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

c. An ODOE value of 0.12 or more, and a value half as high

or lower in an overlying horizon.

Description of Subgroups

Typic Psammoturbels.—These are the Psammoturbels that

do not have a lithic contact within 50 cm or a glacic layer with

an upper boundary within 100 cm of the mineral soil surface.

Typic Psammoturbels do not have the accumulations of

sesquioxides that are associated with the Spodic intergrade.

Glacic Psammoturbels.—These are the Psammoturbels

that have a glacic layer with an upper boundary within 100 cm

of the mineral soil surface but do not have a lithic contact

within 50 cm of the mineral soil surface. Disturbance of the

surface commonly thaws the ice layer, after which the soil

collapses.

Lithic Psammoturbels.—These are the Psammoturbels

that have a lithic contact within 50 cm of the mineral soil

surface.

Spodic Psammoturbels.—These are the Psammoturbels

that grade toward the Spodosols. They have an E horizon and a

B horizon with accumulations of organic matter, aluminum,

and iron. These soils do not have a lithic contact within 50 cm

or a glacic layer with an upper boundary within 100 cm of the

soil surface.

Umbriturbels

Umbriturbels are the Turbels that have an umbric epipedon.

These soils are not wet for long periods and do not have the

redoximorphic features associated with Aquiturbels, the

organic materials at the surface associated with Histoturbels, or

the anhydrous conditions associated with Anhyturbels.

Umbriturbels are known to occur in Alaska, Canada,

Greenland, and Siberia. On the North Slope of the Brooks

Range in Alaska, they support vegetation that differs from that

on Molliturbels.

Definition

Umbriturbels are the Turbels that:

1. Have an umbric epipedon;

2. Do not have in 30 percent or more of the pedon more

than 40 percent, by volume, organic materials from the soil

surface to a depth of 50 cm;

3. Do not have, within 50 cm of the mineral soil surface,

redox depletions with chroma of 2 or less and also aquic

conditions during normal years; and

4. Do not have anhydrous conditions.

Key to Subgroups

ABEA. Umbriturbels that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Umbriturbels
470 Soil Taxonomy

ABEB. Other Umbriturbels that have a glacic layer that has its

upper boundary within 100 cm of the mineral soil surface.

Glacic Umbriturbels

ABEC. Other Umbriturbels that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time during normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or

a densic, lithic, or paralithic contact, whichever is

shallowest.

Vertic Umbriturbels

ABED. Other Umbriturbels that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3

 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Umbriturbels

ABEE. Other Umbriturbels that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the

following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Umbriturbels

ABEF. Other Umbriturbels that have:

1. An umbric epipedon 40 cm or more thick with a texture

finer than loamy fine sand; and

2. A slope of less than 25 percent.

Cumulic Umbriturbels

ABEG. Other Umbriturbels that have, in one or more

horizons within 100 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time during normal years (or artificial drainage).

Aquic Umbriturbels

ABEH. Other Umbriturbels.

Typic Umbriturbels

Definition of Typic Umbriturbels

Typic Umbriturbels are the Umbriturbels that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a glacic layer that has its upper boundary

within 100 cm of the mineral soil surface;

3. Have neither of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time during normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; nor

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallowest;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al plus 1

/2 Fe percentages (by ammonium oxalate) totaling more than

1.0;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, either of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

6. Have either:

a. An umbric epipedon that is less than 40 cm thick,

unless the texture is loamy fine sand or coarser; or

b. A slope of 25 percent or more; and
Gelisols 471

7. Do not have, in any horizon within 100 cm of the mineral soil

surface, distinct or prominent redox concentrations and also

aquic conditions for some time during normal years.

Description of Subgroups

Typic Umbriturbels.—These are the Umbriturbels without

any special features. These soils do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface. They do not have the

potential to shrink and swell characteristic of the Vertic

subgroup or the volcanic glass or ammonium-extractable iron

and aluminum characteristic of the Andic and Vitrandic

subgroups. Typic Umbriturbels have an umbric epipedon that is

less than 40 cm thick, unless they are on steep slopes or are

sandy, or both, and do not have evidence of wetness and

distinct or prominent redox concentrations within 100 cm of

the mineral soil surface.

Andic Umbriturbels.—These are the Umbriturbels that

have, throughout one or more horizons with a total thickness of

18 cm or more within 75 cm of the mineral soil surface, a fineearth fraction with both a bulk density of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and Al plus

1

/2 Fe percentages (by ammonium oxalate) totaling more than

1.0. These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. They also do not have the high shrinkswell potential associated with the Vertic subgroup. Andic

Umbriturbels are commonly in areas that receive volcanic

ejecta, but this is not required.

Aquic Umbriturbels.—These are the Umbriturbels with

aquic conditions and distinct or prominent redox

concentrations within 100 cm of the mineral soil surface.

These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. They do not have the potential to shrink

and swell characteristic of the Vertic subgroup or the volcanic

glass or ammonium-extractable iron and aluminum

characteristic of the Andic and Vitrandic subgroups. Aquic

Umbriturbels have an umbric epipedon that is less than 40 cm

thick, unless they are on steep slopes or are sandy, or both.

Cumulic Umbriturbels.—These are the Umbriturbels that

have an umbric epipedon that is 40 cm or more thick, a texture

finer than loamy fine sand, and a slope of less than 25 percent.

These soils do not have a lithic contact within 50 cm or a

glacic layer with an upper boundary within 100 cm of the

mineral soil surface. Cumulic Umbriturbels do not have the

potential to shrink and swell characteristic of the Vertic

subgroup or the volcanic glass or ammonium-extractable iron

and aluminum characteristic of the Andic and Vitrandic

subgroups.

Glacic Umbriturbels.—These are the Umbriturbels that have

a glacic layer with an upper boundary within 100 cm of the

mineral soil surface. These soils do not have a lithic contact with

its upper boundary within 50 cm of the mineral soil surface.

Disturbance of the insulating surface layer causes the ice to melt

and the soil to collapse.

Lithic Umbriturbels.—These are the Umbriturbels that

have a lithic contact within 50 cm of the mineral soil surface.

Vertic Umbriturbels.—These are the Umbriturbels that

show physical evidence of high shrink-swell in the form of

cracks and slickensides or wedge-shaped aggregates or have

the potential to shrink and swell. This potential is determined

by the linear extensibility. These soils do not have a lithic

contact within 50 cm or a glacic layer with an upper boundary

within 100 cm of the mineral soil surface.

Vitrandic Umbriturbels.—These are the Umbriturbels that

have, throughout one or more horizons with a total thickness of

18 cm or more within 75 cm of the mineral soil surface, one or

both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Umbriturbels are not so weathered as the Andic

subgroup, do not have the shrink-swell potential associated

with the Vertic subgroup, and do not have a lithic contact

within 50 cm or a glacic layer with an upper boundary within

100 cm of the mineral soil surface.

473

The central concept of Histosols is that of soils formingin organic soil materials. The general rule is that a soil

without permafrost is classified as a Histosol if half or more of

the upper 80 cm is organic. A soil is also classified as a

Histosol if the organic materials rest on rock or fill or partially

fill voids in fragmental, cindery, or pumiceous materials. If the

bulk density is very low, less than 0.1, three-fourths or more of

the upper 80 cm must be organic.

Definition of Histosols and Limits Between

Histosols and Soils of Other Orders

Histosols are soils that:

1. Do not have either of the following:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface; and

2. Do not have andic soil properties in 60 percent or more of

the thickness between the soil surface and either a depth of 60

cm or a densic, lithic, or paralithic contact or duripan if

shallower; and

3. Have organic soil materials that meet one or more of the

following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 30 or more cumulative

days during normal years (or are artificially drained), have

an upper boundary within 40 cm of the soil surface, and

have a total thickness of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3

; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more.

Limits Between Histosols and Soils of Other

Orders

The definition of Histosols must provide criteria that

separate Histosols from all other orders. The aggregate of these

criteria defines the limits of Histosols in relation to all other

known soils.

1. Unlike Gelisols, Histosols do not have:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface;

2. Unlike Andisols, Histosols do not have andic soil

properties in 60 percent or more of the thickness between the

soil surface and either a depth of 60 cm, or a densic, lithic, or

paralithic contact or duripan if shallower;

3. Unlike all other mineral soil orders, Histosols have organic

soil materials that meet one or more of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices1 and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Constitute two-thirds or more of the total thickness of

CHAPTER 14

Histosols

1 Materials that meet the definition of cindery, fragmental, or pumiceous but have more

than 10 percent, by volume, voids that are filled with organic soil materials are considered to be

organic soil materials.
474 Soil Taxonomy

the soil from the soil surface to 25 cm below the upper

boundary of permafrost and have no mineral horizons or

have mineral horizons with a total thickness of 10 cm or

less within that depth; or

e. Are saturated with water for 30 or more cumulative days

during normal years (or are artificially drained), have an upper

boundary within 40 cm of the soil surface, and have a total

thickness of either:

(1) 60 cm or more if three-fourths or more of their volume

consists of moss fibers or if their bulk density, moist, is

less than 0.1 g/cm3

; or

(2) 40 cm or more if they consist either of sapric or hemic

materials, or of fibric materials with less than three-fourths

(by volume) moss fibers and a bulk density, moist, of 0.1

g/cm3 or more.

Key to Suborders

BA. Histosols that are saturated with water for less than 30

cumulative days during normal years (and are not artificially

drained).

Folists, p. 478

BB. Other Histosols that:

1. Have more thickness of fibric soil materials than any

other kind of organic soil material either:

a. In the organic parts of the subsurface tier if there is

no continuous mineral layer 40 cm or more thick that has

its upper boundary within the subsurface tier; or

b. In the combined thickness of the organic parts

of the surface and subsurface tiers if there is a

continuous mineral layer 40 cm or more thick that

has its upper boundary within the subsurface tier;

and

2. Do not have a sulfuric horizon that has its upper

boundary within 50 cm of the soil surface; and

3. Do not have sulfidic materials within 100 cm of the soil

surface.

Fibrists, p. 474

BC. Other Histosols that have more thickness of sapric

soil materials than any other kind of organic soil materials

either:

1. In the organic parts of the subsurface tier if there is no

continuous mineral layer 40 cm or more thick that has its

upper boundary within the subsurface tier; or

2. In the combined thickness of the organic parts of the

surface and subsurface tiers if there is a continuous mineral

layer 40 cm or more thick that has its upper boundary within

the subsurface tier.

Saprists, p. 484

BD. Other Histosols.

Hemists, p. 480

Fibrists

These are the wet Histosols in which the organic materials are

only slightly decomposed. More than two-fifths or more than

three-fourths (depending on solubility in a sodiumpyrophosphate solution) of the soil consists of fibers that

remain after rubbing between the thumb and fingers. The

botanic origin of the materials can be readily determined. The

bulk density is commonly less than 0.1 g/cm3. Many Fibrists

have ground water near the soil surface nearly all the time. A few

areas of Fibrists are artificially drained. The level of the ground

water fluctuates but seldom drops much below the bottom of the

surface tier.

Fibrists are of relatively small extent but occur from the

Equator to latitudes with a cryic temperature regime. They are

in closed depressions and in broad flat areas, such as coastal

plains. Most are under natural vegetation.

Definition

Fibrists are the Histosols that:

1. Are saturated for 30 or more cumulative days or are

artificially drained; and

2. Have fibric soil materials that are:

a. Dominant in the organic part of the control section if

there is a mineral layer (or layers) 40 cm or more thick that

has its upper boundary in the subsurface tier, or if a densic,

lithic, or paralithic contact occurs in the subsurface tier; or

b. Dominant in the subsurface tier if there is no continuous

mineral layer 40 cm or more thick that has its upper boundary

in that tier; and

3. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the soil surface; and

4. Do not have sulfidic materials within 100 cm of the soil

surface.

Key to Great Groups

BBA. Fibrists that have a cryic soil temperature regime.

Cryofibrists, p. 475

BBB. Other Fibrists in which fibric Sphagnum constitutes

three-fourths or more of the volume to either a depth of 90 cm

from the soil surface or to a densic, lithic, or paralithic contact,
Histosols 475

fragmental materials, or other mineral soil materials if at a depth

of less than 90 cm.

Sphagnofibrists, p. 477

BBC. Other Fibrists.

Haplofibrists, p. 476

Cryofibrists

These are cold Fibrists. The fibers may be derived from any

plant, woody or herbaceous. These soils may freeze during the

winter, or they may have a climate in which the soils do not

freeze during winter in normal years but are cold in summer.

In either situation, the low temperatures limit the use of the

soils. Most of these soils support native vegetation.

Definition

Cryofibrists are the Fibrists that have a cryic soil

temperature regime.

Key to Subgroups

BBAA. Cryofibrists that have a layer of water within the

control section, below the surface tier.

Hydric Cryofibrists

BBAB. Other Cryofibrists that have a lithic contact within

the control section.

Lithic Cryofibrists

BBAC. Other Cryofibrists that have a mineral layer 30 cm or

more thick that has its upper boundary within the control

section, below the surface tier.

Terric Cryofibrists

BBAD. Other Cryofibrists that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more mineral layers of any thickness in the control section,

below the surface tier.

Fluvaquentic Cryofibrists

BBAE. Other Cryofibrists in which three-fourths or more of

the fiber volume in the surface tier is derived from Sphagnum.

Sphagnic Cryofibrists

BBAF. Other Cryofibrists.

Typic Cryofibrists

Definition of Typic Cryofibrists

Typic Cryofibrists are the Cryofibrists that:

1. Do not have a layer of water within the control section,

below the surface tier;

2. Have less than three-fourths of their fiber volume derived

from Sphagnum in the surface tier;

3. Do not have a lithic contact within the control section;

4. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within the organic

materials in the control section, below the surface tier; and

5. Do not have a mineral layer 30 cm or more thick that has

its upper boundary below the surface tier and within the control

section.

Description of Subgroups

Typic Cryofibrists.—The central concept or Typic

subgroup of Cryofibrists is fixed on soils that do not have a

lithic contact and have less than three-fourths of the fiber

volume in the surface tier derived from Sphagnum.

A lithic contact is used in classifying lithic subgroups, as it

is throughout this taxonomy. In addition, thick or thin mineral

layers as well as intermittent mineral layers that are within the

control section, below the surface tier, cause soils to be

excluded from the Typic subgroup. The presence of layers that

are more decomposed than fibric materials is considered less

important in cold soils than in the warmer soils. The cold soils

are mostly in the State of Alaska in the United States and are

used as woodland or wildlife habitat.

Fluvaquentic Cryofibrists.—These soils differ from Typic

Cryofibrists because they have, within the organic materials,

either one mineral layer 5 to 30 cm thick or two or more

mineral layers of any thickness in the control section, below

the surface tier. These soils are not known to occur in the

United States.

Hydric Cryofibrists.—These soils differ from Typic

Cryofibrists because they have a layer of water within the

control section, below the surface tier. These soils are of small

extent, mostly in the State of Alaska in the United States, and

are used as wildlife habitat.

Lithic Cryofibrists.—These soils differ from Typic

Cryofibrists because they have a lithic contact within the

control section. These soils are not known to occur in the

United States.

Sphagnic Cryofibrists.—These soils differ from Typic

Cryofibrists because three-fourths or more of the fiber volume

in their surface tier is derived from Sphagnum. These soils are

of small extent, mostly in the State of Alaska in the United

States, and are used as woodland or wildlife habitat. The soils

are an important source of mulch for gardening, and some are

used as fuel.

Terric Cryofibrists.—These soils differ from Typic

Cryofibrists because they have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier. These soils are of small extent, mostly in
476 Soil Taxonomy

the State of Alaska in the United States, and are used as

woodland or wildlife habitat.

Haplofibrists

These are the Fibrists in which the temperature regime is

warmer than cryic and less than three-fourths of the fiber

volume is derived from Sphagnum. The fibers may have been

derived from wood, grasses, sedges, mosses, and other

herbaceous plants or from some combination of these. If these

soils are drained and cultivated under the present technology,

the organic materials will decompose either slowly or rapidly,

depending on the management used and the temperature.

Eventually, within some decades, the Haplofibrists that are

drained and cultivated will be replaced first by Hemists and

Saprists and then by mineral soils. Most of these soils in the

United States support native vegetation.

Definition

Haplofibrists are the Fibrists that:

1. Have a soil temperature regime warmer than cryic;

2. Have less than three-fourths of their fiber volume derived

from Sphagnum either in the upper 90 cm or more of the

control section or in the soil above a densic, lithic, or paralithic

contact, fragmental materials, or mineral soil materials

shallower than 90 cm.

Key to Subgroups

BBCA. Haplofibrists that have a layer of water within the

control section, below the surface tier.

Hydric Haplofibrists

BBCB. Other Haplofibrists that have a lithic contact within

the control section.

Lithic Haplofibrists

BBCC. Other Haplofibrists that have one or more limnic

layers with a total thickness of 5 cm or more within the control

section.

Limnic Haplofibrists

BBCD. Other Haplofibrists that have a mineral layer 30 cm

or more thick that has its upper boundary within the control

section, below the surface tier.

Terric Haplofibrists

BBCE. Other Haplofibrists that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more mineral layers of any thickness in the control section,

below the surface tier.

Fluvaquentic Haplofibrists

BBCF. Other Haplofibrists that have one or more layers of

hemic and sapric materials with a total thickness of 25 cm or

more in the control section, below the surface tier.

Hemic Haplofibrists

BBCG. Other Haplofibrists.

Typic Haplofibrists

Definition of Typic Haplofibrists

Typic Haplofibrists are the Haplofibrists that:

1. Have a total of less than 25 cm hemic and sapric materials

below the surface tier;

2. Do not have a limnic layer(s) 5 cm or more thick within

the control section;

3. Do not have a lithic contact within the control section;

4. Do not have a mineral layer between 5 and 30 cm thick

or two or more thin, continuous mineral layers within the

organic materials in the control section, below the surface

tier;

5. Do not have a mineral layer 30 cm or more thick that has

its upper boundary within the control section, below the surface

tier; and

6. Do not have a layer of water within the control section,

below the surface tier.

Description of Subgroups

Typic Haplofibrists.—The central concept or Typic

subgroup of Haplofibrists is fixed on soils that do not have a

lithic contact and do not have a layer of water within the

control section, below the surface tier.

A lithic contact is used in classifying lithic subgroups, as it

is throughout this taxonomy. In addition, thick or thin mineral

layers as well as intermittent mineral layers that are within the

surface tier cause soils to be excluded from the Typic

subgroup. The presence of limnic materials and layers that

are more decomposed than fibric materials also excludes

soils from the Typic subgroup. Typic Haplofibrists are of

small extent in the United States and are used mostly as

wildlife habitat.

Fluvaquentic Haplofibrists.—These soils differ from Typic

Haplofibrists because they have, within the organic materials,

either one mineral layer 5 to 30 cm thick or two or more

mineral layers of any thickness in the control section, below

the surface tier. These soils are not known to occur in the

United States.

Hemic Haplofibrists.—These soils differ from Typic

Haplofibrists because they have one or more layers of hemic

and sapric materials with a total thickness of 25 cm or more

below the surface tier. These soils are not known to occur in

the United States.

Hydric Haplofibrists.—These soils differ from Typic

Haplofibrists because they have a layer of water within the
Histosols 477

control section, below the surface tier. These soils are of small

extent, mostly in the State of Alaska in the United States, and

are used as wildlife habitat.

Limnic Haplofibrists.—These soils differ from Typic

Haplofibrists because they have one or more limnic layers

with a total thickness of 5 cm or more within the control

section. These soils are not known to occur in the United

States.

Lithic Haplofibrists.—These soils differ from Typic

Haplofibrists because they have a lithic contact within the

control section. These soils are not known to occur in the

United States.

Terric Haplofibrists.—These soils differ from Typic

Haplofibrists because they have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier. These soils are of small extent, mostly in

the State of Alaska in the United States, and are used as

woodland or wildlife habitat.

Sphagnofibrists

These are the Fibrists that were derived mainly from the

various species of Sphagnum and associated herbaceous plants.

At least three-fourths of the fibers, by volume, are Sphagnum in

at least the upper 90 cm of the soil or throughout the soil if

there is a densic, lithic, or paralithic contact shallower than 90

cm. A few of these soils have a mesic soil temperature regime

that borders on frigid, but in general the soils are cool. Most of

them have a frigid temperature regime. The structure of

Sphagnum, with its water-holding cells, makes these soils

unique, and for that reason they are grouped as

Sphagnofibrists.

Definition

Sphagnofibrists are the Fibrists that:

1. Have three-fourths or more of their fiber volume

derived from Sphagnum in the upper 90 cm or more of

the control section, or above a densic, lithic, or paralithic

contact, fragmental materials, or mineral soil shallower than

90 cm;

2. Have a mean annual soil temperature that is warmer than

cryic.

Key to Subgroups

BBBA. Sphagnofibrists that have a layer of water within the

control section, below the surface tier.

Hydric Sphagnofibrists

BBBB. Other Sphagnofibrists that have a lithic contact

within the control section.

Lithic Sphagnofibrists

BBBC. Other Sphagnofibrists that have one or more limnic

layers with a total thickness of 5 cm or more within the control

section.

Limnic Sphagnofibrists

BBBD. Other Sphagnofibrists that have a mineral layer 30

cm or more thick that has its upper boundary within the control

section, below the surface tier.

Terric Sphagnofibrists

BBBE. Other Sphagnofibrists that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more mineral layers of any thickness in the control section,

below the surface tier.

Fluvaquentic Sphagnofibrists

BBBF. Other Sphagnofibrists that have one or more layers of

hemic and sapric materials with a total thickness of 25 cm or

more in the control section, below the surface tier.

Hemic Sphagnofibrists

BBBG. Other Sphagnofibrists.

Typic Sphagnofibrists

Definition of Typic Sphagnofibrists

Typic Sphagnofibrists are the Sphagnofibrists that:

1. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within the organic

materials in the control section, below the surface tier;

2. Have a total of less than 25 cm hemic and sapric materials

below the surface tier;

3. Do not have a layer of water within the control section,

below the surface tier;

4. Do not have a limnic layer(s) 5 cm or more thick within

the control section;

5. Do not have a lithic contact within the control section; and

6. Do not have a mineral layer 30 cm or more thick that has

its upper boundary in the control section, below the surface tier.

Description of Subgroups

Typic Sphagnofibrists.—The central concept or Typic

subgroup of Sphagnofibrists is fixed on thick, continuous fibric

organic materials that were derived primarily from Sphagnum.

These soils do not have a lithic contact and do not have a layer

of water within the control section, below the surface tier. At

least three-fourths of the fibric materials, by volume, were

derived from Sphagnum. These soils occur as raised bogs or

high moors in closed depressions and as blanket bogs on more

or less dissected landscapes.

Layers of organic material more decomposed than fibric

materials affect the movement of water and indicate an

intergrade to Hemists. Thin mineral layers normally affect the
478 Soil Taxonomy

movement of water drastically. These layers normally are alluvial

and define the Fluvaquentic subgroup. Thick mineral layers,

rock, limnic layers, and water within the control section are used

as bases for classifying terric, lithic, limnic, and hydric

extragrades, respectively.

Typic Sphagnofibrists are used mostly as wildlife habitat. A

few have been cleared and are used for specialty crops. These

soils are of small extent in the United States.

Fluvaquentic Sphagnofibrists.—These soils differ from

Typic Sphagnofibrists because they have, within the organic

materials, either one mineral layer 5 to 30 cm thick or two or

more mineral layers of any thickness in the control section,

below the surface tier. These soils are not known to occur in

the United States.

Hemic Sphagnofibrists.—These soils differ from Typic

Sphagnofibrists because they have one or more layers of hemic

and sapric materials with a total thickness of 25 cm or more

below the surface tier. These soils are of small extent in the

United States.

Hydric Sphagnofibrists.—These soils differ from Typic

Sphagnofibrists because they have a layer of water within the

control section, below the surface tier. These soils are not

known to occur in the United States.

Limnic Sphagnofibrists.—These soils differ from Typic

Sphagnofibrists because they have one or more limnic layers

with a total thickness of 5 cm or more within the control

section. These soils are not known to occur in the United

States.

Lithic Sphagnofibrists.—These soils differ from Typic

Sphagnofibrists because they have a lithic contact within the

control section. These soils are not known to occur in the

United States.

Terric Sphagnofibrists.—These soils differ from Typic

Sphagnofibrists because they have a mineral layer 30 cm

or more thick with its upper boundary within the control

section, below the surface tier. These soils are of small extent

in the United States and are used as woodland or wildlife

habitat.

Folists

These are the more or less freely drained Histosols that

consist primarily of O horizons derived from leaf litter, twigs,

and branches resting on rock or on fragmental materials that

consist of gravel, stones, and boulders in which the interstices

are filled or partly filled with organic materials. Plant roots

grow only in the organic materials. Many of these soils are in

very humid climates from the Tropics to high latitudes and

high elevations. Some have an ustic or aridic (or torric) soil

moisture regime. Most of the Folists in the United States are

in Hawaii and Alaska. There are some Folists in the

mountains in the western part of the United States, in the

northern Lake States, and in the northeastern part of the

United States.

Definition

Folists are the Histosols that are saturated with water for less

than 30 cumulative days during normal years (and are not

artificially drained).

Key to Great Groups

BAA. Folists that have a cryic soil temperature regime.

Cryofolists, p. 478

BAB. Other Folists that have an aridic (or torric) soil moisture

regime.

Torrifolists, p. 479

BAC. Other Folists that have an ustic or xeric soil moisture

regime.

Ustifolists, p. 479

BAD. Other Folists.

Udifolists, p. 479

Cryofolists

These are the cold Folists. In the United States they occur

mostly in southeastern Alaska, where the climate is cool,

oceanic, and very humid. They are on gentle to very steep

slopes. Their vegetation is primarily coniferous forests, and the

only part of the soils in which there are plant roots is the O

horizon. Beneath the O horizon, there may be a few

centimeters of mineral soil material or none on hard rock or

there may be fragmental materials consisting of gravel, stones,

and boulders with the interstices filled or partly filled with

organic materials.

Definition

Cryofolists are the Folists that have a cryic temperature

regime.

Key to Subgroups

BAAA. Cryofolists that have a lithic contact within 50 cm of

the soil surface.

Lithic Cryofolists

BAAB. Other Cryofolists.

Typic Cryofolists

Definition of Typic Cryofolists

Typic Cryofolists are the Cryofolists that do not have a lithic

contact within 50 cm of the surface.

Description of Subgroups

Typic Cryofolists.—The central concept or Typic subgroup

of Cryofolists is fixed on soils that have organic materials

resting on fragmental materials and filling or partly filling
Histosols 479

interstices in the fragmental materials, which consist of gravel,

stones, and boulders. The soils on fragmental materials are not

necessarily the most common in the great group, but they are

classified as the Typic subgroup because the presence of

shallow hard rock is used throughout this taxonomy to define

lithic subgroups.

Lithic Cryofolists.—The Lithic subgroup of Cryofolists

has organic materials that rest on a lithic contact within

50 cm of the soil surface. Lithic Cryofolists are of small

extent. They occur on the Olympic Peninsula in the United

States. These soils are used as either woodland or wildlife

habitat.

Torrifolists

These are the Folists that have a temperature regime warmer

than cryic and an aridic (or torric) soil moisture regime. They

occur in Hawaii, chiefly on lava flows in areas that receive little

rainfall. The vegetation is mostly fountaingrass mixed with

shrubs.

Definition

Torrifolists are the Folists that have a temperature regime

warmer than cryic and an aridic (or torric) soil moisture

regime.

Key to Subgroups

BABA. Torrifolists that have a lithic contact within 50 cm of

the soil surface.

Lithic Torrifolists

BABB. Other Torrifolists.

Typic Torrifolists

Definition of Typic Torrifolists

Typic Torrifolists are the Torrifolists that do not have a

lithic contact within 50 cm of the soil surface.

Description of Subgroups

Typic Torrifolists.—The central concept or Typic subgroup

of Torrifolists is fixed on soils that have organic materials

resting on fragmental materials and filling or partly filling

interstices in the fragmental materials, which consist of

gravel, stones, and boulders. The soils on fragmental materials

are not necessarily the most common in the great group, but

they are classified as the Typic subgroup because the presence

of shallow hard rock is used throughout this taxonomy to

define lithic subgroups. These soils are of small extent in the

State of Hawaii in the United States and are used as wildlife

habitat.

Lithic Torrifolists.—The Lithic subgroup of Torrifolists has

organic materials resting on a lithic contact within 50 cm of

the soil surface. These soils are of small extent in the State of

Hawaii in the United States and are used as wildlife habitat.

Udifolists

These are the Folists that have a temperature regime warmer

than cryic and a udic (or perudic) soil moisture regime. They

occur in Hawaii, chiefly on lava flows in areas that receive very

high amounts of well-distributed rainfall. The vegetation is

mostly forest mixed with tree ferns.

Definition

Udifolists are the Folists that have:

1. A temperature regime warmer than cryic;

2. A udic (or perudic) soil moisture regime.

Key to Subgroups

BADA. Udifolists that have a lithic contact within 50 cm of the

soil surface.

Lithic Udifolists

BADB. Other Udifolists.

Typic Udifolists

Definition of Typic Udifolists

Typic Udifolists are the Udifolists that do not have a lithic

contact within 50 cm of the surface.

Description of Subgroups

Typic Udifolists.—The central concept or Typic subgroup

of Udifolists is fixed on soils that have organic materials

resting on fragmental materials and filling or partly filling

interstices in the fragmental materials, which consist of gravel,

stones, and boulders. The soils on fragmental materials are not

necessarily the most common in the great group, but they are

classified as the Typic subgroup because the presence of

shallow hard rock is used throughout this taxonomy to define

lithic subgroups. These soils are of small extent in the State of

Hawaii in the United States and are used as wildlife habitat.

Lithic Udifolists.—The Lithic subgroup of Udifolists has

organic materials resting on a lithic contact within 50 cm of

the soil surface. These soils are of small extent in the State of

Hawaii and on the Olympic Peninsula of Washington in the

United States and are used as wildlife habitat.

Ustifolists

These are the Folists that have a temperature regime

warmer than cryic and an ustic or xeric soil moisture regime.

These soils have an O horizon overlying or in fragmental

materials or directly overlying bedrock that is less than 50 cm

from the surface.

Definition

Ustifolists are the Folists that have a temperature regime

warmer than cryic and an ustic or xeric soil moisture regime.
480 Soil Taxonomy

Key to Subgroups

BACA. Ustifolists that have a lithic contact within 50 cm of the

soil surface.

Lithic Ustifolists

BACB. Other Ustifolists.

Typic Ustifolists

Definition of Typic Ustifolists

Typic Ustifolists are the Ustifolists that do not have a lithic

contact within 50 cm of the surface.

Description of Subgroups

Typic Ustifolists.—The central concept or Typic subgroup

of Ustifolists is fixed on soils that have organic materials

resting on fragmental materials and filling or partly filling

interstices in the fragmental materials, which consist of gravel,

stones, and boulders. The soils on fragmental materials are not

necessarily the most common in the great group, but they are

classified as the Typic subgroup because the presence of

shallow hard rock is used throughout this taxonomy to define

lithic subgroups. These soils are of small extent in the State of

Hawaii in the United States and are used as wildlife habitat.

Lithic Ustifolists.—The Lithic subgroup of Ustifolists has

organic materials resting on a lithic contact within 50 cm of

the soil surface. These soils are of small extent in the State of

Hawaii in the United States and are used as wildlife habitat.

Hemists

These are wet Histosols in which the organic materials are

moderately decomposed. The botanic origin of much of the

organic material cannot be readily determined. The fiber

content of much of the organic material is between one-sixth

and two-thirds after rubbing between the thumb and fingers.

The bulk density commonly is between 0.1 and 0.2 g/cm3.

Ground water is at or very close to the surface of these soils

much of the time unless artificial drainage has been provided.

The level of ground water may fluctuate but seldom drops

much below the bottom of the surface tier.

Hemists occur from the Equator to latitudes with a cryic

temperature regime. They are in closed depressions and in

broad flat areas, such as coastal plains and outwash plains.

Most Hemists are under natural vegetation and are used as

woodland, rangeland, or wildlife habitat. Some large areas of

Hemists are cleared, drained, and used as cropland.

Definition

Hemists are the Histosols that:

1. Are saturated with water for 30 or more cumulative days

during normal years (unless artificially drained);

2. Do not have more thickness of fibric soil materials and do

not have more thickness of sapric soil materials than any other

kind of organic soil material either:

a. In the organic parts of the subsurface tier if there is no

continuous mineral layer 40 cm or more thick that has its

upper boundary within the subsurface tier; or

b. In the combined thickness of the organic parts of the

surface and subsurface tiers if there is a continuous mineral

layer 40 cm or more thick that has its upper boundary

within the subsurface tier; or

3. Have a sulfuric horizon that has its upper boundary within

50 cm of the soil surface, or sulfidic materials within 100 cm

of the soil surface, and more thickness of fibric soil material

than any other kind of organic soil material either:

a. In the organic parts of the subsurface tier if there is no

continuous mineral layer 40 cm or more thick that has its

upper boundary within the subsurface tier; or

b. In the combined thickness of the organic parts of the

surface and subsurface tiers if there is a continuous mineral

layer 40 cm or more thick that has its upper boundary

within the subsurface tier.

Key to Great Groups

BDA. Hemists that have a sulfuric horizon that has its upper

boundary within 50 cm of the soil surface.

Sulfohemists, p. 483

BDB. Other Hemists that have sulfidic materials within 100

cm of the soil surface.

Sulfihemists, p. 483

BDC. Other Hemists that have a horizon 2 cm or more thick

in which humilluvic materials constitute one-half or more of

the volume.

Luvihemists, p. 483

BDD. Other Hemists that have a cryic temperature regime.

Cryohemists, p. 480

BDE. Other Hemists.

Haplohemists, p. 481

Cryohemists

These are the cold Hemists that do not have a sulfuric

horizon with its upper boundary within 50 cm of the soil

surface or sulfidic materials within 100 cm of the soil surface.

They have a cryic temperature regime. The fibers in these soils

are from many kinds of plant materials, including wood, moss,

grass, and herbaceous materials. Some of these soils freeze

during the winter, and some do not freeze. Those that do not
Histosols 481

freeze are insulated by snow cover or have a marine climate in

which winters are mild and summers are very cool. Low soil

temperatures in the summer limit the suitable crops where

these soils are used as cropland. Most of these soils support

native coniferous forest vegetation.

Definition

Cryohemists are the Hemists that:

1. Have a cryic temperature regime;

2. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the surface;

3. Do not have sulfidic materials within 100 cm of the

surface;

4. Do not have a horizon 2 cm or more thick in which

humilluvic materials constitute one-half or more of the volume.

Key to Subgroups

BDDA. Cryohemists that have a layer of water within the

control section, below the surface tier.

Hydric Cryohemists

BDDB. Other Cryohemists that have a lithic contact within

the control section.

Lithic Cryohemists

BDDC. Other Cryohemists that have a mineral layer 30 cm

or more thick that has its upper boundary within the control

section, below the surface tier.

Terric Cryohemists

BDDD. Other Cryohemists that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more mineral layers of any thickness in the control section,

below the surface tier.

Fluvaquentic Cryohemists

BDDE. Other Cryohemists.

Typic Cryohemists

Definition of Typic Cryohemists

Typic Cryohemists are the Cryohemists that:

1. Do not have a layer of water within the control section,

below the surface tier;

2. Do not have a lithic contact within the control section;

3. Do not have a mineral layer 30 cm or more thick that has

its upper boundary in the control section, below the surface

tier; and

4. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within the organic

materials in the control section, below the surface tier.

Description of Subgroups

Typic Cryohemists.—The central concept or Typic subgroup

of Cryohemists is fixed on soils that do not have a lithic contact

and do not have a layer of water within the control section,

below the surface tier.

A lithic contact is used in classifying the Lithic subgroup, as

it is throughout this taxonomy. In addition, thick or thin

mineral layers as well as intermittent mineral layers that are

below the surface tier cause soils to be excluded from the Typic

subgroup. The presence or absence of layers of materials either

more or less decomposed than hemic materials is considered

less important in the very cold soils than in other great groups

of Hemists. These soils are mostly in the State of Alaska in the

United States and are used mainly as woodland or wildlife

habitat.

Fluvaquentic Cryohemists.—These soils differ from Typic

Cryohemists because they have, within the organic materials,

either one mineral layer 5 to 30 cm thick or two or more

mineral layers of any thickness in the control section, below

the surface tier. These soils are not known to occur in the

United States.

Hydric Cryohemists.—These soils differ from Typic

Cryohemists because they have a layer of water within the

control section, below the surface tier. These soils are not

known to occur in the United States.

Lithic Cryohemists.—These soils differ from Typic

Cryohemists because they have a lithic contact within the

control section. These soils are of small extent, mostly in the

State of Alaska in the United States, and are used as woodland

or wildlife habitat.

Terric Cryohemists.—These soils differ from Typic

Cryohemists because they have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier. These soils are of small extent, mostly in

the State of Alaska in the United States, and are used as

woodland or wildlife habitat.

Haplohemists

These are the Hemists that have a temperature regime

warmer than cryic and that do not have a sulfuric horizon with

its upper boundary within 50 cm of the soil surface or sulfidic

materials within 100 cm of the soil surface. They are wet at the

base of the surface tier for more than 30 cumulative days during

normal years unless they have been drained. Most

Haplohemists are saturated for considerably longer than 30

days per year. The organic materials in these soils are from

many kinds of plant materials, including wood, moss, grass,

and herbaceous materials. These soils do not have a layer of

humilluvic materials 2 cm or more thick within 130 cm of the soil

surface.

If these soils are drained and cultivated under the present

technology, the organic materials decompose and disappear

slowly or rapidly, depending on the management used and the
482 Soil Taxonomy

temperature. Eventually, within some decades, the

Haplohemists that are drained and cultivated will be replaced

by Saprists and then by mineral soils. Most Haplohemists

support native vegetation, mostly forest plants or shrubs and

grasslike plants. Some large areas are cleared, drained, and used

as cropland.

Definition

Haplohemists are the Hemists that:

1. Have a soil temperature regime warmer than cryic;

2. Do not have a layer of humilluvic materials 2 cm or more

thick;

3. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the soil surface; and

4. Do not have sulfidic materials within 100 cm of the soil

surface.

Key to Subgroups

BDEA. Haplohemists that have a layer of water within the

control section, below the surface tier.

Hydric Haplohemists

BDEB. Other Haplohemists that have a lithic contact within

the control section.

Lithic Haplohemists

BDEC. Other Haplohemists that have one or more limnic

layers with a total thickness of 5 cm or more within the control

section.

Limnic Haplohemists

BDED. Other Haplohemists that have a mineral layer 30 cm

or more thick that has its upper boundary within the control

section, below the surface tier.

Terric Haplohemists

BDEE. Other Haplohemists that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more mineral layers of any thickness in the control section,

below the surface tier.

Fluvaquentic Haplohemists

BDEF. Other Haplohemists that have one or more layers of

fibric materials with a total thickness of 25 cm or more in the

control section, below the surface tier.

Fibric Haplohemists

BDEG. Other Haplohemists that have one or more layers of

sapric materials with a total thickness of 25 cm or more below

the surface tier.

Sapric Haplohemists

BDEH. Other Haplohemists.

Typic Haplohemists

Definition of Typic Haplohemists

Typic Haplohemists are the Haplohemists that:

1. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within the organic

materials in the control section, below the surface tier;

2. Have:

a. Less than 25 cm of fibric materials below the surface

tier; and

b. Less than 25 cm of sapric materials below the surface

tier;

3. Do not have a mineral layer 30 cm or more thick that has

its upper boundary in the control section, below the surface

tier;

4. Do not have a layer of water within the control section,

below the surface tier;

5. Do not have a limnic layer(s) 5 cm or more thick within

the control section; and

6. Do not have a lithic contact within the control section.

Description of Subgroups

Typic Haplohemists.—The central concept or Typic

subgroup of Haplohemists is fixed on soils that do not have a

lithic contact and do not have a layer of water within the

control section, below the surface tier.

A lithic contact is used in classifying the Lithic subgroup, as

it is throughout this taxonomy. In addition, thick or thin

mineral layers as well as intermittent mineral layers that are

below the surface tier cause soils to be excluded from the Typic

subgroup. The presence of layers of materials either more or

less decomposed than hemic materials is used as differentia for

the Fibric and Sapric subgroups, respectively. These soils are

widely distributed in the United States, mostly in the Eastern

States. They are used mainly as woodland, cropland, or wildlife

habitat.

Fibric Haplohemists.—These soils differ from Typic

Haplohemists because they have one or more layers of fibric

materials with a total thickness of 25 cm or more below the

surface tier. These soils are of very small extent in the United

States.

Fluvaquentic Haplohemists.—These soils differ from Typic

Haplohemists because they have, within the organic materials,

either one mineral layer 5 to 30 cm thick or two or more

mineral layers of any thickness in the control section, below

the surface tier. These soils are of very small extent in the

United States.

Hydric Haplohemists.—These soils differ from Typic
Histosols 483

Haplohemists because they have a layer of water within the

control section, below the surface tier. These soils are of small

extent in the United States.

Limnic Haplohemists.—These soils differ from Typic

Haplohemists because they have one or more limnic layers with

a total thickness of 5 cm or more within the control section.

These soils are of small extent but occur in a broad geographic

range from Puerto Rico to the Pacific Northwest. Many of the

soils support natural vegetation, but some are used as cropland

or for hay and pasture.

Lithic Haplohemists.—These soils differ from Typic

Haplohemists because they have a lithic contact within the

control section. These soils are of very small extent in the

United States.

Sapric Haplohemists.—These soils differ from Typic

Haplohemists because they have one or more layers of sapric

materials with a total thickness of 25 cm or more below the

surface tier. These soils are of very small extent in the United

States.

Terric Haplohemists.—These soils differ from Typic

Haplohemists because they have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier. These soils are widely distributed in the

United States, mostly in the Eastern States. They are used

mainly as woodland, cropland, or wildlife habitat.

Luvihemists

Luvihemists are not known to occur in the United States, but

the great group is provided tentatively for use in other countries

if needed. These are the Hemists that have, within the control

section, a horizon 2 cm or more thick in which humilluvic

materials constitute one-half or more of the volume. Because

Luvihemists cannot be studied in the United States, a precise

definition of these soils is not attempted here. It should be

noted, however, that they are normally acid and have been

cultivated for a long time.

Key to Subgroups

BDCA. All Luvihemists (provisionally).

Typic Luvihemists

Sulfihemists

These are the Hemists that have sulfidic materials within 100

cm of the surface. They are potentially extremely acid or ultra

acid. Most Sulfihemists will develop a sulfuric horizon and

become Sulfohemists if they are artificially drained to an extent

that allows oxygen to reach the sulfidic materials. These soils are

permitted to have more fiber than other Hemists. They are mainly

in coastal marshes near the mouths of rivers or in the deltas of

rivers that carry sediments having a low content of carbonates

and are locally extensive. Most Sulfihemists support native

vegetation, mainly forbs and grasslike plants.

Definition

Sulfihemists are the Hemists that:

1. Have sulfidic materials within 100 cm of the surface; and

2. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the soil surface.

Key to Subgroups

BDBA. Sulfihemists that have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier.

Terric Sulfihemists

BDBB. Other Sulfihemists.

Typic Sulfihemists

Definition of Typic Sulfihemists

Typic Sulfihemists are the Sulfihemists that do not have a

mineral layer 30 cm or more thick that has its upper boundary

in the control section, below the surface tier.

Description of Subgroups

Typic Sulfihemists.—The central concept or Typic

subgroup of Sulfihemists is fixed on soils that do not have a

mineral layer 30 cm or more thick that has its upper boundary

in the control section, below the surface tier. These soils are

widely distributed in the United States, mostly in the Eastern

States. They generally support native vegetation, mostly sparse

forbs and grasslike plants. They are used mainly as recreational

areas or wildlife habitat.

Terric Sulfihemists.—These soils differ from Typic

Sulfihemists because they have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier. They are mainly in coastal marshes near

the mouths of rivers or in the deltas of rivers on the east coast

of the United States. They are locally extensive. These soils

support native vegetation, mostly forbs and grasslike plants.

They are used mainly as recreational areas or wildlife habitat.

Sulfohemists

These are the Hemists that have a sulfuric horizon within 50

cm of the surface. The sulfuric horizon formed as a

consequence of draining the sulfidic materials. These soils are

extremely acid and are toxic to most plants. Most are nearly

black and have straw-colored redoximorphic concentrations of

iron sulfate (jarosite) within 50 cm of the surface. The soils are

mainly in drained coastal marshes or deltas near the mouths of

rivers that carry sediments having a low content of carbonates.

Most of the soils have an appreciable amount of mineral

material within the control section. These soils support sparse

vegetation, mostly forbs and grasslike plants. They are used

mainly as recreational areas or wildlife habitat.
484 Soil Taxonomy

Definition

Sulfohemists are the Hemists that have a sulfuric horizon that

has its upper boundary within 50 cm of the surface.

Key to Subgroups

BDAA. All Sulfohemists (provisionally).

Typic Sulfohemists

Saprists

These are the wet Histosols in which the organic materials

are well decomposed. The botanic origin of the organic

material is difficult to determine in most of these soils. The

fiber content is less than one-sixth after rubbing between the

thumb and fingers. Most of these soils have a bulk density of

more than 0.2 g/cm3.

Saprists occur in areas where the ground water table tends

to fluctuate within the soils or in areas where the soils were

aerobic during drier periods in the past. They consist of the

residue that remains after the aerobic decomposition of organic

matter. When drained, fibric and hemic materials commonly

decompose to form sapric materials. If the organic materials

are deep and are drained either artificially or naturally, the

Fibrists and Hemists are converted after some decades to

Saprists.

Definition

Saprists are the Histosols that:

1. Are saturated with water for 30 or more cumulative days

during normal years (unless artificially drained); and

2. Have more thickness of sapric soil materials than any other

kind of organic soil materials either:

a. In the organic parts of the subsurface tier if there is no

continuous mineral layer 40 cm or more thick that has its

upper boundary within the subsurface tier; or

b. In the combined thickness of the organic parts of the

surface and subsurface tiers if there is a continuous mineral

layer 40 cm or more thick that has its upper boundary

within the subsurface tier.

Key to Great Groups

BCA. Saprists that have a sulfuric horizon that has its upper

boundary within 50 cm of the soil surface.

Sulfosaprists, p. 487

BCB. Other Saprists that have sulfidic materials within 100

cm of the soil surface.

Sulfisaprists, p. 486

BCC. Other Saprists that have a cryic temperature regime.

Cryosaprists, p. 484

BCD. Other Saprists.

Haplosaprists, p. 485

Cryosaprists

These are the cold Saprists that do not have a sulfuric

horizon with its upper boundary within 50 cm of the soil

surface and do not have sulfidic materials within 100 cm of the

soil surface. They have a cryic temperature regime. These soils

formed from many kinds of plant materials, including wood,

moss, grass, and herbaceous materials. Some of these soils

freeze during the winter, and some do not freeze. Those that do

not freeze are insulated by snow cover or have a marine climate

in which winters are mild and summers are very cool. Low soil

temperatures in the summer limit the suitable crops where

these soils are used as cropland. Most of these soils support

native coniferous forest vegetation.

Definition

Cryosaprists are the Saprists that:

1. Have a cryic temperature regime; and

2. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the soil surface; and

3. Do not have sulfidic materials within 100 cm of the soil

surface.

Key to Subgroups

BCCA. Cryosaprists that have a lithic contact within the

control section.

Lithic Cryosaprists

BCCB. Other Cryosaprists that have a mineral layer 30 cm or

more thick that has its upper boundary within the control

section, below the surface tier.

Terric Cryosaprists

BCCC. Other Cryosaprists that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more mineral layers of any thickness in the control section,

below the surface tier.

Fluvaquentic Cryosaprists

BCCD. Other Cryosaprists.

Typic Cryosaprists

Definition of Typic Cryosaprists

Typic Cryosaprists are the Cryosaprists that:

1. Do not have a lithic contact within the control section;
Histosols 485

2. Do not have a mineral layer 30 cm or more thick that has its

upper boundary in the control section, below the surface tier;

and

3. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within the organic

materials in the control section, below the surface tier.

Description of Subgroups

Typic Cryosaprists.—The central concept or Typic

subgroup of Cryosaprists is fixed on soils that do not have a

lithic contact and do not have thick or thin mineral layers or

intermittent mineral layers below the surface tier.

A lithic contact is used in classifying the Lithic subgroup, as

it is throughout this taxonomy. In addition, thick or thin

mineral layers as well as intermittent mineral layers that are

below the surface tier cause soils to be excluded from the Typic

subgroup. The presence of layers of materials less decomposed

than sapric materials is considered less important in these cold

Saprists than in the other great groups. These soils are of small

extent, mostly in the State of Alaska in the United States, and

are used as woodland or wildlife habitat.

Fluvaquentic Cryosaprists.—These soils differ from Typic

Cryosaprists because they have, within the organic materials,

either one mineral layer 5 to 30 cm thick or two or more

mineral layers of any thickness in the control section, below

the surface tier. These soils are of small extent, mostly in the

State of Alaska in the United States, and are used as woodland

or wildlife habitat.

Lithic Cryosaprists.—These soils differ from Typic

Cryosaprists because they have a lithic contact within the

control section. These soils are of small extent, mostly in the

State of Alaska in the United States, and are used as woodland

or wildlife habitat.

Terric Cryosaprists.—These soils differ from Typic

Cryosaprists because they have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier. These soils are of small extent, mostly in

the State of Alaska in the United States, and are used as

woodland or wildlife habitat.

Haplosaprists

These are the Saprists that have a temperature regime

warmer than cryic and that do not have a sulfuric horizon with

its upper boundary within 50 cm of the soil surface or sulfidic

materials within 100 cm of the soil surface. These soils are wet

at the base of the surface tier for more than 30 cumulative days

during normal years unless they have been drained. The

organic materials in these soils are from many kinds of plant

materials, including wood, moss, grass, and herbaceous

materials.

If these soils are drained and cultivated under the present

technology, the organic materials decompose and disappear

slowly or rapidly, depending on the management used and the

temperature. Eventually, within some decades, the Haplosaprists

that are drained and cultivated will be replaced by mineral soils.

This conversion of some of the soils has been observed in the

United States. Many Haplosaprists support native vegetation,

mostly forest plants or shrubs and grasslike plants. Many areas

are cleared, drained, and used as cropland.

Definition

Haplosaprists are the Saprists that:

1. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the soil surface;

2. Do not have sulfidic materials within 100 cm of the soil

surface; and

3. Have a temperature regime warmer than cryic.

Key to Subgroups

BCDA. Haplosaprists that have a lithic contact within the

control section.

Lithic Haplosaprists

BCDB. Other Haplosaprists that have one or more limnic

layers with a total thickness of 5 cm or more within the control

section.

Limnic Haplosaprists

BCDC. Other Haplosaprists that have both:

1. Throughout a layer 30 cm or thick that has its upper

boundary within the control section, an electrical

conductivity of 30 dS/m or more (1:1 soil:water) for 6

months or more during normal years; and

2. A mineral layer 30 cm or more thick that has its upper

boundary within the control section, below the surface tier.

Halic Terric Haplosaprists

BCDD. Other Haplosaprists that have throughout a layer 30

cm or more thick within the control section, an electrical

conductivity of 30 dS/m or more (1:1 soil:water) for 6 months

or more during normal years.

Halic Haplosaprists

BCDE. Other Haplosaprists that have a mineral layer 30 cm

or more thick that has its upper boundary within the control

section, below the surface tier.

Terric Haplosaprists

BCDF. Other Haplosaprists that have, within the organic

materials, either one mineral layer 5 cm or more thick or two

or more mineral layers of any thickness in the control section,

below the surface tier.

Fluvaquentic Haplosaprists
486 Soil Taxonomy

BCDG. Other Haplosaprists that have one or more layers of

fibric or hemic materials with a total thickness of 25 cm or more in

the control section, below the surface tier.

Hemic Haplosaprists

BCDH. Other Haplosaprists.

Typic Haplosaprists

Definition of Typic Haplosaprists

Typic Haplosaprists are the Haplosaprists that:

1. Do not have a mineral layer between 5 and 30 cm thick or

two or more thin, continuous mineral layers within the organic

materials in the control section, below the surface tier;

2. Have a total of less than 25 cm fibric and hemic materials

below the surface tier;

3. Do not have a mineral layer 30 cm or more thick that has

its upper boundary in the control section, below the surface

tier;

4. Do not have throughout a layer 30 cm or more thick within

the control section, an electrical conductivity of 30 dS/m or

more (1:1 soil:water) for 6 months or more during normal

years;

5. Do not have a limnic layer(s) 5 cm or more thick within

the control section; and

6. Do not have a lithic contact within the control section.

Description of Subgroups

Typic Haplosaprists.—The central concept or Typic

subgroup of Haplosaprists is fixed on soils that do not have a

lithic contact and do not have thick or thin mineral layers or

intermittent mineral layers below the surface tier.

A lithic contact is used in classifying the Lithic subgroup, as

it is throughout this taxonomy. In addition, thick or thin

mineral layers as well as intermittent mineral layers that are

below the surface tier cause soils to be excluded from the Typic

subgroup. The presence of layers of materials less decomposed

than sapric materials is used as differentia for the Hemic

subgroup. These soils are widely distributed in the United

States, mostly in the Eastern States. They are used mainly as

woodland, cropland, or wildlife habitat.

Fluvaquentic Haplosaprists.—These soils differ from

Typic Haplosaprists because they have, within the organic

materials, either one mineral layer 5 to 30 cm thick or two or

more mineral layers of any thickness in the control section,

below the surface tier. These soils are of very small extent in

the United States.

Halic Haplosaprists.—These are the Haplosaprists that

have an electrical conductivity of 30 dS/m or more in a layer

30 cm or more thick within 130 cm of the soil surface. These

soils do not have a lithic contact within a depth of 130 cm or

limnic layers. Halic Haplosaprists commonly occur near coastal

areas that are inundated by the ocean.

Halic Terric Haplosaprists.—These are the Haplosaprists

that have an electrical conductivity of 30 dS/m or more in a layer

30 cm or more thick within 130 cm of the soil surface and have a

mineral layer 30 cm or more thick. These soils do not have a lithic

contact within a depth of 130 cm or limnic layers. Halic Terric

Haplosaprists commonly occur near coastal areas that are

inundated by the ocean.

Hemic Haplosaprists.—These soils differ from Typic

Haplosaprists because they have one or more layers of fibric or

hemic materials with a total thickness of 25 cm or more below

the surface tier. These soils are of small extent, mostly in the

Lake States in the United States.

Limnic Haplosaprists.—These soils differ from Typic

Haplosaprists because they have one or more limnic layers with

a total thickness of 5 cm or more within the control section.

These soils are of small extent, mostly in the Lake States in the

United States.

Lithic Haplosaprists.—These soils differ from Typic

Haplosaprists because they have a lithic contact within the

control section. These soils are of very small extent in the

United States.

Terric Haplosaprists.—These soils differ from Typic

Haplosaprists because they have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier. These soils are widely distributed in the

United States, mostly in the Eastern States. They are used

mainly as woodland, cropland, or wildlife habitat.

Sulfisaprists

These are the potentially acid sulfate soils (cat clays) that

consist of organic soil materials. They have sulfidic materials

within 100 cm of the soil surface and have not been drained.

They occur mainly in coastal marshes near the mouths of rivers

or in the deltas of rivers that carry sediments with a low

content of carbonates. The soils are locally extensive in the

coastal marshes and deltas of some large rivers that drain

humid regions.

Definition

Sulfisaprists are the Saprists that:

1. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the soil surface; and

2. Have sulfidic materials within 100 cm of the soil surface.

Key to Subgroups

BCBA. Sulfisaprists that have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier.

Terric Sulfisaprists
Histosols 487

BCBB. Other Sulfisaprists.

Typic Sulfisaprists

Definition of Typic Sulfisaprists

Typic Sulfisaprists are the Sulfisaprists that do not have a

mineral layer 30 cm or more thick that has its upper boundary

in the control section, below the surface tier.

Description of Subgroups

Typic Sulfisaprists.—The central concept or Typic

subgroup of Sulfisaprists is fixed on soils that do not have a

mineral layer 30 cm or more thick that has its upper boundary

in the control section, below the surface tier. These soils are of

small extent in the United States, mostly in the Eastern States.

They generally support native vegetation, mostly sparse forbs

and grasslike plants. They are used mainly as recreational

areas or wildlife habitat.

Terric Sulfisaprists.—These soils differ from Typic

Sulfisaprists because they have a mineral layer 30 cm or more

thick that has its upper boundary within the control section,

below the surface tier. They are mainly in coastal marshes near

the mouths of rivers or in the deltas of rivers on the east coast

of the United States. They are of small extent. These soils

support native vegetation, mostly forbs and grasslike plants.

They are used mainly as recreational areas or wildlife habitat.

Sulfosaprists

These are the acid sulfate soils (cat clays) that consist of

organic soil materials. They have a sulfuric horizon that

formed as a consequence of draining the sulfidic materials.

They are extremely acid and are toxic to most plants. They are

mainly in drained coastal marshes or deltas near the mouths of

rivers that carry sediments containing few or no carbonates.

Most of these soils have an appreciable amount of mineral

material within the control section.

Definition

Sulfosaprists are the Saprists that have a sulfuric horizon

that has its upper boundary within 50 cm of the soil surface.

Key to Subgroups

BCAA. All Sulfosaprists (provisionally).

Typic Sulfosaprists

489

The central concept of Inceptisols is that of soils that areof cool to very warm, humid and subhumid regions and

that have a cambic horizon and an ochric epipedon. The order

of Inceptisols includes a wide variety of soils. In some areas

Inceptisols are soils with minimal development, while in other

areas they are soils with diagnostic horizons that merely fail

the criteria of the other soil orders.

Inceptisols have many kinds of diagnostic horizons and

epipedons. They can have an anthropic, histic, mollic, ochric,

plaggen, or umbric epipedon. Only a very few Inceptisols,

however, have a mollic epipedon. The mollic epipedon is

restricted to soils with low base saturation below the epipedon.

The most common diagnostic horizons are ochric and umbric

epipedons, a cambic horizon, and a fragipan. The most

common horizon sequence is an ochric epipedon over a cambic

horizon, with or without an underlying fragipan. Some

Inceptisols have an umbric epipedon overlying a cambic

horizon, with or without an underlying duripan or fragipan. A

calcic or petrocalcic horizon or a duripan is common in

subhumid areas. All soils that have a plaggen epipedon are

Inceptisols, and any soil underlying the plaggen epipedon is

considered to be buried.

The definition of Inceptisols is necessarily complicated.

These soils range from very poorly drained to excessively

drained. If the epipedon is ochric or anthropic, a diagnostic

subsurface horizon or high exchangeable sodium also is

required. Inceptisols typically have a cambic horizon, but one

is not required if the soil has a mollic, umbric, histic, or

plaggen epipedon or if there is a fragipan or duripan or any

placic, calcic, petrocalcic, gypsic, petrogypsic, salic, or sulfuric

horizon. Inceptisols cannot have an argillic, kandic, or natric

horizon unless it is buried. An oxic horizon is permitted only if

the upper boundary is deeper than 150 cm. A spodic horizon is

permitted only if it is less than 10 cm thick or if the upper

boundary is deeper than 50 cm below the mineral soil surface

and none of the overlying layers have a sandy or sandy-skeletal

particle-size class.

Inceptisols occur from equatorial to tundra regions. Soils

that have permafrost within 100 cm of the soil surface are now

classified as Gelisols. Inceptisols cannot have an aridic (torric)

moisture regime. Soils with an aridic (torric) moisture regime

are recognized as Aridisols if they have a cambic or other

diagnostic horizon. Inceptisols commonly occur on landscapes

that are relatively active, such as mountain slopes, where

erosional processes are actively exposing unweathered

materials, and river valleys, where relatively unweathered

sediments are being deposited. Many of the Inceptisols in the

United States formed in late-Pleistocene glacial drift. If the

precipitation exceeds the potential evapotranspiration every

month, Inceptisols occur in areas of old as well as young

surfaces or deposits. If the soil temperature regime is frigid or

cryic in these humid regions, Inceptisols form mainly in the

more loamy and clayey parent materials and Spodosols and

Entisols (Psamments) form in the sandy materials.

Definition of Inceptisols and Limits

Between Inceptisols and Soils of Other

Orders

The definition of Inceptisols provides criteria that separate

Inceptisols from all other orders. The aggregate of these

criteria defines the limits of Inceptisols in relation to other soil

orders.

Inceptisols are mineral soils that meet all of the following:

1. Unlike Gelisols, Inceptisols do not have either of the

following:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface;

2. Unlike Andisols, Inceptisols do not have andic soil

properties in 60 percent or more of the thickness between the

soil surface and either a depth of 60 cm or a densic, lithic, or

paralithic contact or duripan if shallower;

3. Unlike Histosols, Inceptisols do not have organic soil

materials that meet one or more of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

CHAPTER 15

Inceptisols
490 Soil Taxonomy

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more in normal

years (or are artificially drained), have an upper boundary

within 40 cm of the soil surface, and have a total thickness

of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3

; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more;

4. Unlike Spodosols, Inceptisols do not have one or more of

the following:

a. A spodic horizon, an albic horizon in 50 percent or

more of each pedon, and a cryic or pergelic soil temperature

regime; or

b. An Ap horizon containing 85 percent or more spodic

materials; or

c. A spodic horizon with all of the following

characteristics:

(1) One or more of the following:

(a) A thickness of 10 cm or more; or

(b) An overlying Ap horizon; or

(c) Cementation in 50 percent or more of each

pedon; or

(d) A coarse-loamy, loamy-skeletal, or finer particlesize class and a frigid temperature regime; or

(e) A cryic or pergelic temperature regime; and

(2) An upper boundary within the following depths

from the mineral soil surface: either

(a) Less than 50 cm; or

(b) Less than 200 cm if the soil has a sandy or

sandy-skeletal particle-size class in at least some part

between the mineral soil surface and the spodic

horizon; and

(3) A lower boundary as follows:

(a) Either at a depth of 25 cm or more below the

mineral soil surface, or at the top of a duripan or

fragipan, or at a densic, lithic, paralithic, or

petroferric contact, whichever is shallowest; or

(b) At any depth:

1) If the spodic horizon has a coarse-loamy,

loamy-skeletal, or finer particle-size class and the

soil has a frigid temperature regime; or

2) If the soil has a cryic or pergelic temperature

regime;

5. Unlike Oxisols, Inceptisols do not have an oxic horizon

that has its upper boundary within 150 cm of the mineral soil

surface;

6. Unlike Vertisols, Inceptisols do not have all of the

following:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

aggregates that have their long axes tilted 10 to 60 degrees

from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon if shallower; and

c. Cracks that open and close periodically;

7. Unlike Aridisols, Inceptisols do not have an aridic soil

moisture regime and meet all of the following criteria:

a. Do not have a salic horizon; and

b. Are not saturated with water in one or more layers

within 100 cm of the soil surface for 1 month or more in

normal years; and

c. Do not have a moisture control section that is dry in

some or all parts at some time in normal years; and

d. Have a sulfuric horizon that has its upper boundary

within 150 cm of the mineral soil surface;

8. Unlike Alfisols and Ultisols, Inceptisols do not have an

argillic, kandic, or natric horizon and do not have a fragipan

with clay films 1 mm or more thick in one or more of its

subhorizons;

9. Unlike Mollisols, Inceptisols do not have both of the

following:

a. Either:

(1) A mollic epipedon; or

(2) Both a surface horizon that meets all of the

requirements for a mollic epipedon, except for thickness,
Inceptisols 491

after the soil has been mixed to a depth of 18 cm, and a

subhorizon more than 7.5 cm thick, within the upper part

of an argillic, kandic, or natric horizon, that meets the

color, organic-carbon content, base saturation, and

structure requirements for a mollic epipedon but is

separated from the surface horizon by an albic horizon;

and

b. A base saturation of 50 percent or more (by NH4

OAc) in

all horizons either between the upper boundary of any

argillic, kandic, or natric horizon and a depth of 125 cm

below that boundary, or between the mineral soil surface

and a depth of 180 cm, or between the mineral soil surface

and a densic, lithic, or paralithic contact, whichever depth is

shallower; and

10. Unlike Entisols, Inceptisols have either:

a. One or more of the following:

(1) A cambic horizon with its upper boundary

within 100 cm of the mineral soil surface and its lower

boundary at a depth of 25 cm or more below the mineral

soil surface; or

(2) A calcic, petrocalcic, gypsic, petrogypsic, or placic

horizon or a duripan with an upper boundary within 100

cm of the mineral soil surface; or

(3) A fragipan or an oxic, sombric, or spodic horizon

with an upper boundary within 200 cm of the mineral

soil surface; or

(4) A sulfuric horizon that has its upper boundary

within 150 cm of the mineral soil surface; or

(5) A cryic or pergelic temperature regime and a

cambic horizon; or

b. No sulfidic materials within 50 cm of the mineral soil

surface; and both

(1) In one or more horizons at a depth between 20

and 50 cm below the mineral soil surface, either an n

value of 0.7 or less or less than 8 percent clay in the fineearth fraction; and

(2) One or both of the following:

(a) A salic horizon or a histic, mollic, plaggen, or

umbric epipedon; or

(b) In 50 percent or more of the layers between the

mineral soil surface and a depth of 50 cm, an

exchangeable sodium percentage of 15 or more (or a

sodium adsorption ratio of 13 or more), which

decreases with increasing depth below 50 cm, and also

ground water within 100 cm of the mineral soil

surface at some time during the year when the soil is

not frozen in any part.

Representative Pedon and Data

Following is a description of a representative Inceptisol. Data

for the pedon identified in this description are given in the table

“Characterization Data for an Inceptisol.”

Classification: Coarse-loamy, isotic, frigid Typic Dystrudept

Site identification number: 87P0581

Location: Windsor County, Vermont; town of West Windsor;

30 m south of the Hartland town line and 2,280 m east of

the Reading town line

Latitude: 43 degrees 31 minutes 41 seconds N.

Longitude: 72 degrees 30 minutes 15 seconds W.

Landscape: Hills

Slope: 12 percent, complex, east facing

Elevation: 417 m above m.s.l.

Annual precipitation: 100 cm

Soil moisture regime: Udic

Average annual air temperature: 6 oC

Average annual soil temperature: 7 oC

Permeability class: Moderate

Drainage class: Well drained

Depth to water table: More than 150 cm

Land use: Pasture

Stoniness class: 1

Hazard of erosion: Slight

Runoff class: Medium

Particle-size control section: 25 to 73 cm

Parent material: Glacial till derived from schist and phyllite

Vegetation: Natural—mixed forest; cleared—native pasture

Diagnostic features: An ochric epipedon from a depth of 0 to

22 cm, a cambic horizon from a depth of 22 to 73 cm, and

a lithic contact at a depth of 73 cm

Described by: Villars, McLeese, Gourley, and Wheeler

In the following pedon description, colors are for moist soil

unless otherwise indicated.

Ap1—0 to 10 cm; very dark gray (10YR 3/1) silt loam, gray

(10YR 5/1) dry; moderate medium granular structure; very

friable, nonsticky and nonplastic; many very fine and

many fine roots throughout; common very fine interstitial

and tubular pores; neutral (pH 6.6); 1 percent

metamorphic pebbles; abrupt smooth boundary.

Ap2—10 to 22 cm; very dark grayish brown (10YR 3/2) silt

loam, light brownish gray (10YR 6/2) dry; weak fine

subangular blocky structure parting to weak fine granular;

friable, nonsticky and nonplastic; many very fine and

common fine roots throughout; common very fine

interstitial and tubular pores; common continuous faint

iron stains on sand grains and pebbles; sand grains are

coated with sesquioxides and have very few black

micropellets when viewed with a 10X and 20X hand lens

and a 100X microscope; slightly acid (pH 6.4); 1 percent

metamorphic pebbles; abrupt wavy boundary.
492 Soil Taxonomy

Characterization Data for an Inceptisol

 SITE IDENTIFICATION NO: 87P0581

 CLASSIFICATION: COARSE-LOAMY, ISOTIC, FRIGID TYPIC DYSTRUDEPT

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 87P3045 0- 10 Ap1 4.9 39.5 55.6 1.6 27.2 12.3 14.5 20.0 10.3 6.8 4.0 3 2 -- 44 5

 87P3046 10- 22 Ap2 3.4 38.3 58.3 0.6 24.3 14.0 13.1 18.6 10.3 8.0 8.3 9 7 2 55 18

 87P3047 22- 40 Bw 1.6 44.5 53.9 0.7 28.9 15.6 13.2 16.8 9.4 7.1 7.4 7 4 1 48 12

 87P3048 40- 55 Bt 1.7 45.4 52.9 0.2 29.1 16.3 13.4 17.3 9.3 7.1 5.8 5 7 -- 47 15

 87P3049 55- 73 BCt 1.0 39.6 59.4 -- 24.2 15.4 14.5 18.4 10.0 8.3 8.2 8 8 1 54 20

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 10 5.16 0.457 1.7 0.4 0.1 4.51 8.00 0.91 1.04 0.045 27.1 25.9 11.5

 10- 22 2.17 0.186 1.7 0.5 0.1 3.09 2.18 1.38 1.38 -- 26.1 24.6 6.4 0.21

 22- 40 1.29 0.100 1.7 0.5 0.1 4.50 6.00 1.24 1.26 0.005 33.1 28.1 5.6 0.22

 40- 55 1.02 1.5 0.5 0.1 3.29 4.00 1.25 1.25 -- 29.8 25.1 4.6 0.22

 55- 73 0.81 1.4 0.3 TR 4.90 3.70 3.7

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)

 Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos NaF CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9b 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1d 8C1f 8C1f

 <- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1

 0- 10 15.1 0.4 0.1 0.1 15.7 14.7 TR 30.4 22.1 52 71 9.7 5.3 5.6

 10- 22 4.7 TR TR -- 4.7 11.0 15.7 10.5 30 45 10.4 5.3 5.8

 22- 40 0.9 TR -- -- 0.9 11.6 1.1 12.5 7.2 2.0 55 7 13 10.9 4.8 5.4

 40- 55 0.9 -- 0.1 -- 1.0 8.8 9.8 5.6 10 18 10.8 5.0 5.7

 55- 73 1.2 TR TR -- 1.2 7.4 8.6 4.9 14 24 10.6 5.0 5.7

 -----------------------------------------------------------------------------------------------------------------------------------

 ACID OXALATE EXTRACTION PHOSPHORUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT

 OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL

 DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm

 SAMPLE HZ 8J 6C9a 6V2 6G12 6S4 6S5 6D3 6A2d 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1

 NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>

 87P3045 1 0.27 0.72 0.05 0.44 52 5.30 39.2 95

 87P3046 2 0.21 0.71 0.05 0.47 47 2.42 26.1 7.4 86

 87P3047 3 0.16 0.65 0.08 0.59 56 1.63 33.1 9.6

 87P3048 4 0.09 0.46 0.07 0.50 52 1.34 29.8 6.8

 87P3049 5 0.09 0.49 0.05 0.37 44 1.08 39

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA-

 < - - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION

 NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->

 87P3045 TCLY KK 1 VR 1 MI 1 7.1 0.8

 87P3047 TCLY VR 1 KK 1 MI 1 GE 1 13.9 1.0

 87P3049 TCLY MI 1 KK 1 VR 1 7.1 0.7

 -----------------------------------------------------------------------------------------------------------------------------------
Inceptisols 493

Characterization Data for an Inceptisol--Continued

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA-

 < - - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION

 NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->

 87P3047 FS 66 QZ66 MS16 BT13 AR 2 FK 2 FP 1

 87P3047 FS FEtr GNtr OPtr MZtr PRtr

 87P3048 FS 72 QZ68 BT15 MS 7 FP 4 GN 3 AR 1

 87P3048 FS OP 1 FK 1 PR 1 HNtr SPtr

 87P3049 FS 64 QZ61 BT16 MS14 AR 3 FP 3 GN 2

 87P3049 FS OP 1 FKtr PRtr HNtr SPtr

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.

 Fraction interpretation: TCLY, total clay, <0.002 mm; FS, fine sand, 0.1-0.25 mm.

 Mineral interpretation: KK, kaolinite; VR, vermiculite; MI, mica; GE, goethite; QZ, quartz; MS, muscovite; BT, biotite;

 AR, weathered aggregate; FK, potassium feldspar; FP, plagioclase feldspar; FE, iron oxides; GN, garnet; OP, opaques;

 MZ, monazite; PR, pyroxene; HN, hornblende; SP, sphene.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.

Bw—22 to 40 cm; dark brown (10YR 3/3) silt loam, pale brown

(10YR 6/3) dry; weak fine subangular blocky structure;

friable, weakly smeary, nonsticky and nonplastic; few fine

roots throughout; few very fine interstitial and tubular

pores; many continuous faint iron stains on sand grains

and pebbles; slightly acid (pH 6.0);

1 percent metamorphic pebbles; sand grains are thinly

coated with sesquioxides and have a few black

micropellets; clear wavy boundary.

Bt—40 to 55 cm; dark grayish brown (2.5Y 4/2) silt loam;

weak fine and medium subangular blocky structure;

friable, nonsticky and nonplastic; few fine and few

medium roots throughout; few very fine interstitial and

tubular pores; few faint clay films on sand grains and

pebbles; moderately acid (pH 5.8); 1 percent metamorphic

pebbles and 2 percent metamorphic cobbles; coated sand

grains; abrupt wavy boundary.

BCt—55 to 73 cm; dark grayish brown (2.5Y 4/2) silt loam;

weak medium subangular blocky structure; friable,

nonsticky and nonplastic; few fine roots throughout;

few very fine interstitial and tubular pores; very few

faint clay films on sand grains and pebbles; slightly acid

(pH 6.0); 1 percent metamorphic pebbles and 2 percent

metamorphic cobbles; coated sand grains; abrupt wavy

boundary.

2R—73 cm; schist or phyllite.

Key to Suborders

KA. Inceptisols that have one or more of the following:

1. In a layer above a densic, lithic, or paralithic contact or

in a layer at a depth between 40 and 50 cm from the mineral

soil surface, whichever is shallower, aquic conditions for

some time in normal years (or artificial drainage) and one or

more of the following:

a. A histic epipedon; or

b. A sulfuric horizon that has its upper boundary within

50 cm of the mineral soil surface; or

c. A layer directly under the epipedon, or within 50 cm

of the mineral soil surface, that has, on faces of peds or

in the matrix if peds are absent, 50 percent or more

chroma of either:

(1) 2 or less if there are redox concentrations; or

(2) 1 or less; or

d. Within 50 cm of the mineral soil surface, enough

active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated; or

2. An exchangeable sodium percentage (ESP) of 15 or

more (or a sodium adsorption ratio [SAR] of 13 or more) in

half or more of the soil volume within 50 cm of the mineral

soil surface, a decrease in ESP (or SAR) values with

increasing depth below 50 cm, and ground water within 100

cm of the mineral soil surface for some time during the year.

Aquepts, p. 494

KB. Other Inceptisols that have a plaggen or anthropic

epipedon.

Anthrepts, p. 494

KC. Other Inceptisols that have a cryic soil temperature

regime.

Cryepts, p. 512
494 Soil Taxonomy

KD. Other Inceptisols that have an ustic soil moisture

regime.

Ustepts, p. 530

KE. Other Inceptisols that have a xeric soil moisture regime.

Xerepts, p. 542

KF. Other Inceptisols that have a udic soil moisture regime.

Udepts, p. 516

Anthrepts

These are the more or less freely drained Inceptisols that

have either an anthropic or plaggen epipedon. Most of these

soils have been used as cropland or as sites for human

occupation for many years. Anthrepts can have almost any

temperature regime and almost any vegetation. Most have a

cambic horizon.

Definition

Anthrepts are the Inceptisols that:

1. Have an anthropic or plaggen epipedon; and

2. Do not have, in a layer above a densic, lithic, or paralithic

contact or in a layer at a depth between 40 and 50 cm from the

mineral soil surface, whichever is shallower, aquic conditions

for some time in normal years and one or more of the

following:

a. A histic epipedon; or

b. A sulfuric horizon that has its upper boundary within

50 cm of the mineral soil surface; or

c. A layer directly under the epipedon, or within 50 cm of

the mineral soil surface, that has, on faces of peds or in the

matrix if peds are absent, 50 percent or more chroma of

either:

(1) 2 or less if there are redox concentrations; or

(2) 1 or less; and

3. Do not have an exchangeable sodium percentage (ESP)

of 15 or more (or a sodium adsorption ratio [SAR] of 13 or

more) in half or more of the soil volume within 50 cm of the

mineral soil surface, an ESP (or SAR) below 50 cm that

decreases with increasing depth, and ground water within 100

cm of the mineral soil surface during some time of the year;

and

4. Do not have, within 50 cm of the mineral soil surface,

enough active ferrous iron to give a positive reaction to

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Key to Great Groups

KBA. Anthrepts that have a plaggen epipedon.

Plagganthrepts, p. 494

KBB. Other Anthrepts.

Haplanthrepts, p. 494

Haplanthrepts

Haplanthrepts are the Anthrepts that have an anthropic

epipedon. Because Haplanthrepts are not extensive, their

classification has not been developed. Subgroups based on soil

moisture regimes may be needed. Most of these soils are in

Asia and North Africa. Haplanthrepts have gentle slopes and

are either farmed or used as homesites.

Key to Subgroups

KBBA. All Haplanthrepts (provisionally).

Typic Haplanthrepts

Plagganthrepts

Plagganthrepts are the Anthrepts that have a plaggen

epipedon. Because Plagganthrepts are not extensive, their

classification has not been developed beyond their grouping

into a single great group. These soils are known to occur only

in Europe, including the British Isles. They have a udic

moisture regime. They have gentle slopes and are used either

as cropland or as homesites. The buried soils under the plaggen

epipedon vary appreciably in morphology, but few of them had

high natural fertility.

Key to Subgroups

KBAA. All Plagganthrepts (provisionally).

Typic Plagganthrepts

Aquepts

These are the wet Inceptisols. The natural drainage is poor or

very poor and, if the soils have not been artificially drained,

ground water is at or near the soil surface at some time during

normal years but typically not at all seasons. These soils

generally have a gray to black surface horizon and a gray

subsurface horizon with redox concentrations that begins at a

depth of less than 50 cm. A few of the soils have a brownish

surface horizon that is less than 50 cm thick.

Most Aquepts formed in late-Pleistocene or younger

deposits in depressions, on nearly level plains, or on flood

plains. They occur from the Equator to latitudes with

discontinuous permafrost. The common features of most of

these soils are the grayish and reddish colors of redoximorphic

features at a depth of 50 cm or less and, unless the soils have
Inceptisols 495

been artificially drained, shallow ground water. Aquepts may

have almost any particle-size class except fragmental, any

reaction class, any temperature regime, and almost any

vegetation. Most of the soils have a cambic horizon, and some

have a fragipan. It is possible that some have a plaggen

epipedon.

Definition

Aquepts are the Inceptisols that have:

1. In a layer above a densic, lithic, or paralithic contact or in a

layer at a depth between 40 and 50 cm from the mineral soil

surface, whichever is shallower, aquic conditions for some time

in normal years (or artificial drainage) and one or more of the

following:

a. A histic epipedon; or

b. A sulfuric horizon that has its upper boundary within

50 cm of the mineral soil surface; or

c. A layer directly under the epipedon, or within 50 cm of

the mineral soil surface, that has, on faces of peds or in the

matrix if peds are absent, 50 percent or more chroma of

either:

(1) 2 or less if there are redox concentrations; or

(2) 1 or less; or

2. An exchangeable sodium percentage (ESP) of 15 or more

(or a sodium adsorption ratio [SAR] of 13 or more) in half or

more of the soil volume within 50 cm of the mineral soil

surface, an ESP (or SAR) below 50 cm that decreases with

increasing depth, and ground water within 100 cm of the

mineral soil surface during some time of the year; or

3. Within 50 cm of the mineral soil surface, enough active

ferrous iron to give a positive reaction to alpha,alpha-dipyridyl

at a time when the soil is not being irrigated.

Key to Great Groups

KAA. Aquepts that have a sulfuric horizon that has its upper

boundary within 50 cm of the mineral soil surface.

Sulfaquepts, p. 510

KAB. Other Aquepts that have, within 100 cm of the

mineral soil surface, one or more horizons in which plinthite

or a cemented or indurated diagnostic horizon either forms a

continuous phase or constitutes one-half or more of the

volume.

Petraquepts, p. 509

KAC. Other Aquepts that have either:

1. A salic horizon; or

2. In one or more horizons with a total thickness of 25 cm

or more within 50 cm of the mineral soil surface, an

exchangeable sodium percentage (ESP) of 15 or more (or a

sodium adsorption ratio [SAR] of 13 or more) and a

decrease in ESP (or SAR) values with increasing depth

below 50 cm.

Halaquepts, p. 505

KAD. Other Aquepts that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragiaquepts, p. 504

KAE. Other Aquepts that have a cryic soil temperature

regime.

Cryaquepts, p. 495

KAF. Other Aquepts that have, in one or more layers at least

25 cm thick (cumulative) within 100 cm of the mineral soil

surface, 25 percent or more (by volume) recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts.

Vermaquepts, p. 511

KAG. Other Aquepts that have a histic, melanic, mollic, or

umbric epipedon.

Humaquepts, p. 507

KAH. Other Aquepts that have episaturation.

Epiaquepts, p. 502

KAI. Other Aquepts.

Endoaquepts, p. 498

Cryaquepts

These are the cold Aquepts. They are of moderate extent in

the high mountains and subarctic regions of North America

and Eurasia. They typically have an ochric or histic epipedon

over a cambic horizon. Cryaquepts are on flood plains, in

depressional areas, and on plains. Most have grayish subsoils,

and some are stratified. The major areas of the Cryaquepts in

the United States are on the outwash plains and flood plains of

Alaska. Cryaquepts formed mostly in late-Pleistocene or recent

sediments south of the continuous permafrost zone. Most

support mixed forest, shrub, or grassy vegetation. Many are

nearly level, but some in areas of high precipitation have

strong slopes. Because Cryaquepts are both cold and wet, they

have low potential for cropping.

Definition

Cryaquepts are the Aquepts that:

1. Have a cryic soil temperature regime;
496 Soil Taxonomy

2. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface;

3. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the soil surface;

4. Do not have a cemented or indurated diagnostic horizon

within 100 cm of the mineral soil surface in half or more of

each pedon; and

5. Do not have either:

a. A salic horizon; or

b. In one or more horizons with a total thickness of 25 cm

or more within 50 cm of the mineral soil surface, an

exchangeable sodium percentage (ESP) of 15 or more (or a

sodium adsorption ratio [SAR] of 13 or more) and a

decrease in ESP (or SAR) values with increasing depth

below 50 cm.

Key to Subgroups

KAEA. Cryaquepts that have, within 150 cm of the mineral

soil surface, one or more of the following:

1. A sulfuric horizon; or

2. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

between 3.5 and 4.0; or

3. Sulfidic materials.

Sulfic Cryaquepts

KAEB. Other Cryaquepts that have both a histic epipedon

and a lithic contact within 50 cm of the mineral soil surface.

Histic Lithic Cryaquepts

KAEC. Other Cryaquepts that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Cryaquepts

KAED. Other Cryaquepts that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Cryaquepts

KAEE. Other Cryaquepts that have a histic epipedon.

Histic Cryaquepts

KAEF. Other Cryaquepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or more of the

following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Cryaquepts

KAEG. Other Cryaquepts that have a slope of less than 25

percent; and

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluvaquentic Cryaquepts

KAEH. Other Cryaquepts that have both:

1. Chroma of 3 or more in 40 percent or more of the

matrix of one or more horizons at a depth between 15 and

50 cm from the mineral soil surface; and

2. A mollic or umbric epipedon.

Aeric Humic Cryaquepts

KAEI. Other Cryaquepts that have chroma of 3 or more in

40 percent or more of the matrix of one or more horizons at a

depth between 15 and 50 cm from the mineral soil surface.

Aeric Cryaquepts

KAEJ. Other Cryaquepts that have a mollic or umbric

epipedon.

Humic Cryaquepts

KAEK. Other Cryaquepts.

Typic Cryaquepts
Inceptisols 497

Definition of Typic Cryaquepts

Typic Cryaquepts are the Cryaquepts that:

1. Do not have, within 150 cm of the mineral soil surface, any

of the following:

a. A sulfuric horizon; or

b. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

between 3.5 and 4.0; or

c. Sulfidic materials;

2. Do not have a lithic contact within 50 cm of the mineral

soil surface;

3. Do not have a histic, umbric, or mollic epipedon;

4. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

5. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

6. Do not have both:

a. Either 0.2 percent or more organic carbon (Holocene

age) at a depth of 125 cm below the mineral soil surface or

an irregular decrease in organic-carbon content (Holocene

age) between a depth of 25 cm and either a depth of 125 cm

below the mineral soil surface or a densic, lithic, or paralithic

contact, whichever is shallower; and

b. A slope of less than 25 percent; and

7. Have chroma of 2 or less in 60 percent or more of the mass

of all horizons between depths of 15 and 50 cm.

Description of Subgroups

Typic Cryaquepts.—The central concept or Typic subgroup

of Cryaquepts is fixed on soils that have a thick, gray regolith

and an ochric epipedon and do not have a layer of materials

with andic soil properties that is as thick as 18 cm and is near

the surface.

Soils that have a lithic contact within a depth of 50 cm are

assigned to the Lithic subgroup. Soils that have a histic

epipedon are excluded from the Typic subgroup because they

are considered intergrades to Histosols. Soils that have an

umbric or mollic epipedon are excluded from the Typic

subgroup because they are considered intergrades to

Humaquepts and Aquolls, respectively. Soils that either have

0.2 percent or more organic carbon (Holocene age) at a depth

of 125 cm below the mineral soil surface or have an irregular

decrease in organic-carbon content (Holocene age) between a

depth of 25 cm and either a depth of 125 cm below the mineral

soil surface or a densic, lithic, or paralithic contact, whichever

is shallower, are considered intergrades to Fluvaquents.

Typic Cryaquepts are of moderate extent in the United

States. They occur mostly in southern Alaska, but some are in

the high mountains of the Western States. Most Typic

Cryaquepts support native vegetation and have a thin O

horizon.

Aeric Cryaquepts.—These soils have chroma of 3 or more

in 40 percent or more of some subhorizon within 50 cm of the

mineral soil surface. The high chroma is thought to reflect

either deeper ground water or a shorter period of saturation

than that in the Typic subgroup. The soils are otherwise like

Typic Cryaquepts. Aeric Cryaquepts are of small extent in the

United States and occur mostly in southern Alaska and in the

high mountains of the Western and Northern States. Most of

these soils support their native vegetation and have a thin O

horizon. Most support forest vegetation, but some support

water-tolerant grasses. Aeric Cryaquepts are used mainly as

forest and wildlife habitat. Some are used as pasture and some

as hayland.

Aeric Humic Cryaquepts.—These soils have a mollic or

umbric epipedon and also have chroma of 3 or more in 40

percent or more of some subhorizon within 50 cm of the

mineral soil surface. The high chroma is thought to reflect

either deeper ground water or a shorter period of saturation

than that in the Typic subgroup. The soils are otherwise like

Typic Cryaquepts. Aeric Humic Cryaquepts are of very small

extent in the United States and are known to occur only in

southern Alaska. They support native vegetation and have a

thin O horizon. The vegetation consists of water-tolerant trees,
498 Soil Taxonomy

shrubs, and grasses. These soils are used mainly as wildlife

habitat.

Aquandic Cryaquepts.—These soils have a layer in the

upper 75 cm that has some andic soil properties. This layer is

18 cm or more thick. The clays in this layer normally do not

disperse well and have a high pH-dependent charge. In the

Aquandic Cryaquepts in the United States, this layer normally

is at or very close to the soil surface. The epipedon commonly

is umbric, but this is not required. These soils are of small

extent in the United States and are known to occur in Alaska

and Oregon. Most support native vegetation. Most support

water-tolerant grasses, and some support forest vegetation.

Aquandic Cryaquepts are used mainly as wildlife habitat. Some

are used as pasture and some as hayland.

Fluvaquentic Cryaquepts.—These soils have either 0.2

percent or more organic carbon (Holocene age) at a depth of

125 cm below the mineral soil surface or an irregular decrease

in organic-carbon content (Holocene age) between a depth of

25 cm and either a depth of 125 cm below the mineral soil

surface or a densic, lithic, or paralithic contact, whichever is

shallower. They also have slopes of less than 25 percent. These

soils are of small extent in the United States. They are on flood

plains. Most support a native vegetation of water-tolerant trees

and grasses. Fluvaquentic Cryaquepts are used mainly as

wildlife habitat.

Histic Cryaquepts.—These soils have a histic epipedon but

otherwise are like Typic Cryaquepts. They tend to have ground

water at a higher level than in the soils of the Typic subgroup,

and shallow water stands for some time above the soil surface.

Histic Cryaquepts are considered intergrades to Histosols. They

are of small extent in the United States and occur mostly in

southern Alaska and in the high mountains of the

Northwestern States. Most of the Histic Cryaquepts support

native vegetation. They support forest vegetation or watertolerant shrubs and grasses. Histic Cryaquepts are used mainly

as forest and wildlife habitat.

Histic Lithic Cryaquepts.—These soils have a histic

epipedon, and they have a lithic contact within 50 cm of the

mineral soil surface. They tend to have ground water at a

higher level than in the soils of the Typic subgroup, and very

shallow water stands for some time above the mineral soil

surface. Histic Lithic Cryaquepts are of very small extent in the

United States and are known to occur only in southern Alaska.

They support native vegetation, which consists of watertolerant trees, shrubs, and grasses. These soils are used mainly

as wildlife habitat.

Humic Cryaquepts.—These soils have an umbric or mollic

epipedon but otherwise are like Typic Cryaquepts. They are

considered intergrades to Humaquepts. Humic Cryaquepts are

of small extent in the United States and occur mostly in

southern Alaska and in Idaho. Most of these soils support

native vegetation, which consists of trees or water-tolerant

shrubs and grasses. The soils are used mainly as forest and

wildlife habitat.

Lithic Cryaquepts.—These soils have a lithic contact within

50 cm of the mineral soil surface. They are not known to occur in

the United States. This subgroup is established for use in other

parts of the world.

Sulfic Cryaquepts.—These soils have a sulfuric horizon or

a horizon approaching a sulfuric horizon but otherwise are like

Typic Cryaquepts. They are considered intergrades to

Sulfaquepts. They are rare in the United States.

Vertic Cryaquepts.—These soils are like Typic Cryaquepts,

but they are high in expanding clays and have cracks 5 mm or

more wide, slickensides, wedge-shaped aggregates, or a linear

extensibility of 6.0 cm or more between the mineral soil surface

and either a depth of 100 cm or a densic, lithic, or paralithic

contact, whichever is shallower. These soils are considered to

be transitional to Vertisols. This subgroup is not known to

occur in the United States. It is established for use in other

parts of the world.

Endoaquepts

Endoaquepts are the Aquepts that have endosaturation. The

ground water commonly fluctuates from a level near the soil

surface to below a depth of 50 cm. These soils have a frigid or

warmer soil temperature regime and do not have any sulfuric,

placic, or salic horizon or a fragipan near the soil surface. They

do not have high exchangeable sodium near the soil surface

that becomes less with increasing depth below 50 cm. They

have no horizon within 100 cm of the mineral soil surface in

which plinthite or any other cemented or indurated diagnostic

horizon either forms a continuous phase or constitutes one-half

or more of the volume. Recognizable bioturbation, such as

filled animal burrows, wormholes, or casts, is less than 50

percent (by volume) in all layers that are 25 cm or more thick

(cumulative) within 100 cm of the mineral soil surface. Before

they were cultivated, most Endoaquepts supported forest

vegetation. Generally, Endoaquepts are nearly level, and their

parent materials are typically late-Pleistocene or younger

sediments.

Definition

Endoaquepts are the Aquepts that:

1. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the mineral soil surface;

2. Do not have, within 100 cm of the mineral soil surface,

one or more horizons in which plinthite or a cemented or

indurated diagnostic horizon forms either a continuous phase

or constitutes one-half or more of the volume;

3. Have an exchangeable sodium percentage (ESP) of less

than 15 (or a sodium adsorption ratio [SAR] of less than 13) in

half or more of the soil volume within 50 cm of the mineral

soil surface or an ESP (or SAR) below 50 cm that remains

constant or increases with increasing depth;
Inceptisols 499

4. Have neither a salic horizon nor a fragipan with its upper

boundary within 100 cm of the mineral soil surface;

5. Do not have a cryic soil temperature regime;

6. Do not have, in one or more layers at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, 25

percent or more (by volume) recognizable bioturbation, such as

filled animal burrows, wormholes, or casts;

7. Do not have any histic, melanic, mollic, or umbric

epipedon; and

8. Have endosaturation.

Key to Subgroups

KAIA. Endoaquepts that have, within 150 cm of the mineral

soil surface, one or more of the following:

1. A sulfuric horizon; or

2. A horizon 15 cm or more thick that has all of the

characteristics of a sulfuric horizon, except that it has a pH

between 3.5 and 4.0; or

3. Sulfidic materials.

Sulfic Endoaquepts

KAIB. Other Endoaquepts that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Endoaquepts

KAIC. Other Endoaquepts that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Endoaquepts

KAID. Other Endoaquepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Endoaquepts

KAIE. Other Endoaquepts that have a slope of less than 25

percent; and

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluvaquentic Endoaquepts

KAIF. Other Endoaquepts that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Endoaquepts

KAIG. Other Endoaquepts that have, in one or more

horizons between the A or Ap horizon and a depth of 75 cm

below the mineral soil surface, one of the following colors:

1. Hue of 7.5YR or redder in 50 percent or more of the

matrix; and

a. If peds are present, either chroma of 2 or more on 50

percent or more of ped exteriors or no redox depletions

with chroma of 2 or less in ped interiors; or

b. If peds are absent, chroma of 2 or more in 50 percent

or more of the matrix; or

2. In 50 percent or more of the matrix, hue of 10YR or

yellower and either:

a. Both a color value, moist, and chroma of 3 or more;

or

b. Chroma of 2 or more if there are no redox

concentrations.

Aeric Endoaquepts

KAIH. Other Endoaquepts that have:
500 Soil Taxonomy

1. A color value, moist, of 3 or less and a color value, dry, of

5 or less (crushed and smoothed) in the Ap horizon or in the

upper 15 cm after mixing; and

2. A base saturation (by NH4

OAc) of less than 50 percent in

some part within 100 cm of the mineral soil surface.

Humic Endoaquepts

KAII. Other Endoaquepts that have a color value, moist, of 3

or less and a color value, dry, of 5 or less (crushed and

smoothed) either in the Ap horizon or in the upper 15 cm after

mixing.

Mollic Endoaquepts

KAIJ. Other Endoaquepts.

Typic Endoaquepts

Definition of Typic Endoaquepts

Typic Endoaquepts are the Endoaquepts that:

1. Do not have, within 150 cm of the mineral soil surface,

any sulfuric horizon, a horizon 15 cm or more thick that has

all of the characteristics of a sulfuric horizon, except that it has

a pH between 3.5 and 4.0, or sulfidic materials;

2. Do not have a lithic contact within 50 cm of the mineral

soil surface;

3. Do not have either:

a. Both cracks within 125 cm of the mineral soil surface

that are 5 mm or more wide through a thickness of 30 cm or

more for some time in most years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of less than 6.0 cm between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

5. Either have less than 0.2 percent organic carbon (Holocene

age) at a depth of 125 cm below the mineral soil surface and a

regular decrease in organic-carbon content (Holocene age)

between a depth of 25 cm and either a depth of 125 cm below

the mineral soil surface or a densic, lithic, or paralithic contact,

whichever is shallower, or have a slope of 25 percent or more;

6. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick;

7. Do not have, in one or more horizons between the A or Ap

horizon and a depth of 75 cm below the mineral soil surface,

one of the following colors:

a. Hue of 7.5YR or redder in 50 percent or more of the

matrix; and

(1) If peds are present, either chroma of 2 or more

on 50 percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. In 50 percent or more of the matrix, hue of 10YR or

yellower and either:

(1) Both a color value, moist, and chroma of 3 or more;

or

(2) Chroma of 2 or more if there are no redox

concentrations; and

8. Have a color value, moist, of 4 or more or a color value,

dry, of 6 or more (crushed and smoothed) in the Ap horizon or

in the upper 15 cm after mixing.

Description of Subgroups

Typic Endoaquepts.—The central concept or Typic

subgroup of Endoaquepts is fixed on dominantly gray soils

with endosaturation. High chroma in some subhorizon is the

basis for definition of the Aeric subgroup. Soils that have

layers with some andic soil properties are excluded from the

Typic subgroup because such layers indicate an intergrade to

Aquands. Typic Endoaquepts have both less than 0.2 percent

organic carbon (Holocene age) at a depth of 125 cm below the

mineral soil surface and a regular decrease in organic-carbon

content (Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a densic,

lithic, or paralithic contact, whichever is shallower, unless they
Inceptisols 501

have a slope of 25 percent or more. Soils that have fragic soil

properties in a layer 15 cm or more thick are considered

intergrades to Fragiaquepts. A lithic contact within a depth of

50 cm is the basis for definition of the Lithic subgroup. A high

shrink-swell potential or deep, wide cracks in expanding clays

indicate intergrades to Vertisols. Jarosite mottles, if associated

with a low pH value, indicate intergrades to Sulfaquepts. A

dark colored Ap horizon or a moderately thick, dark colored A

horizon is the basis for defining intergrades to Humaquepts or

to Aquolls, depending on the base status.

Typic Endoaquepts are extensive in the United States and

occur in all parts of the country, except for the coldest and the

driest parts. The native vegetation consists mostly of watertolerant trees, shrubs, and grasses. Many of these soils have

been cleared and artificially drained and are used as cropland

or pasture. Some support their native vegetation.

Aeric Endoaquepts.—These soils have a horizon within

the upper 75 cm that has a chroma too high for Typic

Endoaquepts. The higher chroma is thought to indicate either a

shorter period of saturation of the whole soil with water or

somewhat deeper ground water than that in the soils of the

Typic subgroup. The correlation of color with soil drainage

classes is imperfect. A dark plow layer or a relatively thick,

dark A horizon is permitted, but neither is required. These

soils are extensive in the Eastern United States and occur in all

parts of the United States, except for the coldest and the driest

parts. The native vegetation consists mostly of water-tolerant

trees and shrubs. Many of these soils have been cleared and

artificially drained and are used as cropland or pasture. Some

support their native vegetation.

Aquandic Endoaquepts.—These soils have some andic soil

properties in a layer in the upper 75 cm that is 18 cm or more

thick. The clays in this layer normally do not disperse well and

have a high pH-dependent charge. Typically, this layer is at or

very close to the soil surface. These soils are of small extent in

the United States and are known to occur in California and

Idaho. Most supported water-tolerant grasses, and some

support forest vegetation. Most of the soils are artificially

drained and are used as cropland or hayland. Some are used as

rangeland and some as wildlife habitat.

Fluvaquentic Endoaquepts.—These soils have either 0.2

percent or more organic carbon (Holocene age) at a depth of

125 cm below the mineral soil surface or an irregular decrease

in organic-carbon content (Holocene age) between a depth of

25 cm and either a depth of 125 cm below the mineral soil

surface or a densic, lithic, or paralithic contact, whichever is

shallower. They also have slopes of less than 25 percent. These

soils are extensive in the United States. They are on flood

plains in all parts of the country, except for the coldest and the

driest parts. The native vegetation is mostly water-tolerant

trees and grasses. Some of these soils are used as forest, and

some have been cleared and artificially drained and are used as

cropland or pasture.

Fragic Endoaquepts.—These soils have a significant

volume of fragic soil properties, but they do not have a fragipan

unless the upper boundary is at a depth of more than 100 cm

below the mineral soil surface. The soils are rare in the United

States.

Humic Endoaquepts.—These soils have a darker surface

horizon than that in Typic Endoaquepts and have relatively low

base saturation. They are considered to be intermediate

between Typic Endoaquepts and Humaquepts. Humic

Endoaquepts are of small extent in the United States. They

occur mostly in the Eastern States. The native vegetation

consists mostly of water-tolerant trees and shrubs. Many of

these soils have been cleared and artificially drained and are

used as cropland or pasture. Some support native vegetation.

Lithic Endoaquepts.—These soils have a lithic contact

within 50 cm of the soil surface but otherwise are like Typic

Endoaquepts. Lithic Endoaquepts are of small extent in the

United States. They occur mostly in Florida and New York.

The native vegetation consists mostly of water-tolerant trees,

shrubs, and grasses. Some of these soils are used as forest, and

some have been cleared and artificially drained and are used as

cropland or pasture.

Mollic Endoaquepts.—These soils have a darker surface

horizon than that in Typic Endoaquepts and have relatively

high base saturation. They are considered to be intermediate

between Typic Endoaquepts and Endoaquolls. Mollic

Endoaquepts are moderately extensive in the United States.

They are mostly in the Eastern States. The native vegetation

consists mostly of water-tolerant trees, grasses, and shrubs.

Many of these soils have been cleared and artificially drained

and are used as cropland or pasture. Some support their native

vegetation.

Sulfic Endoaquepts.—These soils are mainly in drained

coastal marshes. Either they have jarosite mottles and a pH

(1:1 water, air-dried slowly in shade) between 3.5 and 4.0 in

some part within a depth of 50 cm, or they have jarosite

mottles and a pH of less than 4.0 (1:1 water, air-dried slowly in

shade) in some part at a depth between 50 and 150 cm from the

surface. The soils are considered intergrades to Sulfaquepts.

Sulfic Endoaquepts are mostly on tidal flats. Many of these

soils have been cleared and artificially drained. Because of the

acidity, however, they now support native vegetation. They

support sparse vegetation of water- and acid-tolerant shrubs

and grasses. They are used mainly as wildlife habitat.

Vertic Endoaquepts.—These soils are fine textured, and they

shrink and swell appreciably when their moisture content

changes. Most of the soils have a high content of smectite, and

some have a dry season in which potential evapotranspiration

exceeds precipitation. The soils are of moderate extent in the

United States and occur in all parts of the country, except for

the coldest and the driest parts. The native vegetation consists

mostly of water-tolerant trees, shrubs, and grasses. Many of

these soils have been cleared and artificially drained and are

used as cropland or pasture. Some support their native

vegetation.
502 Soil Taxonomy

Epiaquepts

Epiaquepts are the Aquepts that have episaturation. The

ground water commonly fluctuates from a level near the soil

surface to below a depth of 200 cm. These soils have a frigid or

warmer soil temperature regime and do not have any sulfuric,

placic, or salic horizon or a fragipan near the soil surface. They

do not have high exchangeable sodium near the soil surface

that becomes less with increasing depth below 50 cm. They

have no horizon within 100 cm of the mineral soil surface in

which plinthite or any other cemented or indurated diagnostic

horizon either forms a continuous phase or constitutes one-half

or more of the volume. Recognizable bioturbation, such as

filled animal burrows, wormholes, or casts, is less than 50

percent (by volume) in all layers at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface. Before

cultivation, most Epiaquepts supported forest vegetation.

Generally, Epiaquepts are nearly level or gently sloping, and

their parent materials are typically late-Pleistocene or younger

sediments.

Definition

Epiaquepts are the Aquepts that:

1. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the mineral soil surface;

2. Do not have, within 100 cm of the mineral soil surface,

one or more horizons in which plinthite or a cemented or

indurated diagnostic horizon either forms a continuous phase

or constitutes one-half or more of the volume;

3. Have an exchangeable sodium percentage (ESP) of less

than 15 (or a sodium adsorption ratio [SAR] of less than 13) in

half or more of the soil volume within 50 cm of the mineral

soil surface or an ESP (or SAR) below 50 cm that remains

constant or increases with increasing depth;

4. Have neither a salic horizon nor a fragipan with its upper

boundary within 100 cm of the mineral soil surface;

5. Do not have a cryic soil temperature regime;

6. Do not have, in one or more layers at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, 25

percent or more (by volume) recognizable bioturbation, such as

filled animal burrows, wormholes, or casts;

7. Do not have a histic, melanic, mollic, or umbric epipedon;

and

8. Have episaturation.

Key to Subgroups

KAHA. Epiaquepts that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Epiaquepts

KAHB. Other Epiaquepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Epiaquepts

KAHC. Other Epiaquepts that have a slope of less than 25

percent; and

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluvaquentic Epiaquepts

KAHD. Other Epiaquepts that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Epiaquepts

KAHE. Other Epiaquepts that have, in one or more horizons
Inceptisols 503

between the A or Ap horizon and a depth of 75 cm below the

mineral soil surface, one of the following colors:

1. Hue of 7.5YR or redder in 50 percent or more of the

matrix; and

a. If peds are present, either chroma of 2 or more on 50

percent or more of ped exteriors or no redox depletions

with chroma of 2 or less in ped interiors; or

b. If peds are absent, chroma of 2 or more in 50 percent

or more of the matrix; or

2. In 50 percent or more of the matrix, hue of 10YR or

yellower and either:

a. Both a color value, moist, and chroma of 3 or more;

or

b. Chroma of 2 or more if there are no redox

concentrations.

Aeric Epiaquepts

KAHF. Other Epiaquepts that have both:

1. A color value, moist, of 3 or less and a color value, dry,

of 5 or less (crushed and smoothed) in the Ap horizon or in

the upper 15 cm after mixing; and

2. A base saturation (by NH4

OAc) of less than 50 percent

in some part within 100 cm of the mineral soil surface.

Humic Epiaquepts

KAHG. Other Epiaquepts that have a color value, moist, of 3

or less and a color value, dry, of 5 or less (crushed and

smoothed) either in the Ap horizon or in the upper 15 cm after

mixing.

Mollic Epiaquepts

KAHH. Other Epiaquepts.

Typic Epiaquepts

Definition of Typic Epiaquepts

Typic Epiaquepts are the Epiaquepts that:

1. Do not have both cracks within 125 cm of the mineral soil

surface that are 5 mm or more wide through a thickness of 30

cm or more for some time in most years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the mineral soil

surface;

2. Have a linear extensibility of less than 6.0 cm between the

mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower;

3. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

4. Either have less than 0.2 percent organic carbon (Holocene

age) at a depth of 125 cm below the mineral soil surface and a

regular decrease in organic-carbon content (Holocene age)

between a depth of 25 cm and either a depth of 125 cm below

the mineral soil surface or a densic, lithic, or paralithic

contact, whichever is shallower, or have a slope of 25 percent

or more;

5. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick;

6. Do not have, in one or more horizons between the A or Ap

horizon and a depth of 75 cm below the mineral soil surface,

one of the following colors:

a. Hue of 7.5YR or redder in 50 percent or more of the

matrix; and

(1) If peds are present, either chroma of 2 or more

on 50 percent or more of ped exteriors or no redox

depletions with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50

percent or more of the matrix; or

b. In 50 percent or more of the matrix, hue of 10YR or

yellower and either:

(1) Both a color value, moist, and chroma of 3 or more;

or

(2) Chroma of 2 or more if there are no redox

concentrations; and

7. Have a color value, moist, of 4 or more or a color value,

dry, of 6 or more (crushed and smoothed) in the Ap horizon or

in the upper 15 cm after mixing.
504 Soil Taxonomy

Description of Subgroups

Typic Epiaquepts.—The central concept or Typic subgroup of

Epiaquepts is fixed on dominantly gray soils with episaturation.

High chroma in some subhorizon is the basis for definition of the

Aeric subgroup. Soils that have some andic soil properties in

layers that are near the surface are excluded from the Typic

subgroup because such layers indicate an intergrade to

Aquands. Typic Epiaquepts have both less than 0.2 percent

organic carbon (Holocene age) at a depth of 125 cm below the

mineral soil surface and a regular decrease in organic-carbon

content (Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower, unless they have a

slope of 25 percent or more. Soils that have fragic soil properties

in a layer 15 cm or more thick are considered intergrades to

Fragiaquepts. Deep, wide cracks in expanding clays indicate

intergrades to Vertisols. A dark colored Ap horizon or a

moderately thick, dark colored A horizon is the basis for defining

intergrades to Humaquepts or to Aquolls, depending on the

base status.

Typic Epiaquepts are of small extent in the United States.

They are widely distributed and occur in all parts of the

country, except for the coldest and the driest parts. The native

vegetation consists mostly of water-tolerant trees, shrubs, and

grasses. Many of these soils have been cleared and artificially

drained and are used as cropland or pasture. Some support

native vegetation.

Aeric Epiaquepts.—These soils have a horizon within the

upper 75 cm that has a chroma too high for Typic Epiaquepts.

The higher chroma is thought to indicate either a shorter

period of saturation of the whole soil with water or somewhat

deeper ground water than that in the soils of the Typic

subgroup. The correlation of color with soil drainage classes is

imperfect. A dark plow layer or a relatively thick, dark A

horizon is permitted, but neither is required. Aeric Epiaquepts

are extensive in the Eastern United States. They occur in all

parts of the United States, except for the coldest and the driest

parts. The native vegetation consists mostly of water-tolerant

trees and shrubs. Many of these soils have been cleared and

artificially drained and are used as cropland or pasture. Some

support native vegetation.

Aquandic Epiaquepts.—These soils have some andic soil

properties in a layer in the upper 75 cm that is 18 cm or more

thick. The clays in this layer normally do not disperse well and

have a high pH-dependent charge. These soils are not known to

occur in the United States. The subgroup is provided for use

elsewhere.

Fluvaquentic Epiaquepts.—These soils have either 0.2

percent or more organic carbon (Holocene age) at a depth of

125 cm below the mineral soil surface or an irregular decrease

in organic-carbon content (Holocene age) between a depth of

25 cm and either a depth of 125 cm below the mineral soil

surface or a densic, lithic, or paralithic contact, whichever is

shallower. They also have slopes of less than 25 percent. They

are moderately extensive in the United States. They are on flood

plains in all parts of the country, except for the coldest and the

driest parts. The native vegetation is mostly water-tolerant trees

and grasses. Some of these soils are used as forest, and some

have been cleared and artificially drained and are used as

cropland or pasture.

Fragic Epiaquepts.—These soils have a significant volume

of fragic soil properties, but they do not have a fragipan unless

it has its upper boundary at a depth of more than 100 cm below

the mineral soil surface. The soils are of small extent in the

United States.

Humic Epiaquepts.—These soils have a darker surface

horizon than that in Typic Epiaquepts and have relatively low

base saturation. They are considered to be intermediate

between Typic Epiaquepts and Humaquepts. Humic Epiaquepts

are rare in the United States. The native vegetation consists

mostly of water-tolerant trees and shrubs.

Mollic Epiaquepts.—These soils have a darker surface

horizon than that in Typic Epiaquepts and have relatively high

base saturation. They are considered to be intermediate

between Typic Epiaquepts and Epiaquolls. Mollic Epiaquepts

are of small extent in the United States. They occur mostly in

the Northern and Eastern States. The native vegetation consists

mostly of water-tolerant trees, grasses, and shrubs. Many of

these soils have been cleared and artificially drained and are

used as cropland or pasture. Some support native vegetation.

Vertic Epiaquepts.—These soils are fine textured, and they

shrink and swell appreciably when their moisture content

changes. Most of them have a high content of smectite, and

some have a dry season in which potential evapotranspiration

exceeds precipitation. These soils are of moderate extent in the

United States. They occur in all parts of the country, except for

the coldest and the driest parts. The native vegetation consists

mostly of water-tolerant trees, shrubs, and grasses. Many of

these soils have been cleared and artificially drained and are

used as cropland or pasture. Some support native vegetation.

Fragiaquepts

These are the Aquepts that have a fragipan within 100 cm of

the mineral soil surface, commonly at a depth of 30 to 50 cm.

Typically, the soils have episaturation and the water table is

perched on the fragipan. The horizons above the pan are grayish

and are saturated with water during some periods in normal

years. Most of these soils have a forest vegetation, but a few

areas have been cleared. The trees have a shallow root system

and are particularly subject to windthrow. A distinct microrelief

of 50 to 60 cm or more is very common above the pan. The upper

surface of the pan generally is smooth. In many areas of these

soils, the horizons above the fragipan appear to have been mixed

by the uplift of the roots of falling trees. In some areas the

horizons above the pan consist of an O horizon, an ochric

epipedon, and an intermittent cambic horizon below the mounds.

In other areas the cambic horizon is continuous.
Inceptisols 505

The Fragiaquepts in the United States have mostly a frigid or

mesic soil temperature regime. They are moderately extensive in

parts of the Northeastern States, and a few of the soils occur in

Oregon and Washington. Fragiaquepts that have a temperature

regime marginal to cryic have been reported in other countries,

but no unique subgroups are provided for these soils. Most

Fragiaquepts are nearly level or gently sloping and developed in

Pleistocene-age sediments.

Definition

Fragiaquepts are the Aquepts that:

1. Have a fragipan with its upper boundary within 100 cm of

the mineral soil surface;

2. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the mineral soil surface;

3. Do not have, within 100 cm of the mineral soil surface,

one or more horizons in which plinthite or a cemented or

indurated diagnostic horizon either forms a continuous phase

or constitutes one-half or more of the volume;

4. Have an SAR of less than 13 (or less than 15 percent

saturation with sodium) in half or more of the upper 50 cm or

have an SAR (or saturation with sodium) that is constant or

increases with increasing depth below 50 cm; and

5. Do not have a salic horizon.

Key to Subgroups

KADA. Fragiaquepts that have, in 50 percent or more of the

matrix of one or more horizons either between the plow layer

and a depth of 75 cm below the mineral soil surface or, if there

is no plow layer, between depths of 15 and 75 cm, chroma of

either:

1. 3 or more; or

2. 2 or more if there are no redox concentrations.

Aeric Fragiaquepts

KADB. Other Fragiaquepts that have a histic, mollic, or

umbric epipedon.

Humic Fragiaquepts

KADC. Other Fragiaquepts.

Typic Fragiaquepts

Definition of Typic Fragiaquepts

Typic Fragiaquepts are the Fragiaquepts that:

1. Do not have a histic, mollic, or umbric epipedon;

and

2. Have, in more than 50 percent of the matrix of one or

more horizons either between the plow layer and 75 cm below

the mineral soil surface or, if there is no plow layer, between

depths of 15 and 75 cm, chroma of either:

a. 2 or less if redox concentrations are present; or

b. 1 or less.

Description of Subgroups

Typic Fragiaquepts.—The central concept or Typic subgroup

of Fragiaquepts is fixed on soils that have an ochric epipedon.

These soils have dominant chroma, in the matrix of all

subhorizons between the Ap horizon or a depth of 15 cm and a

depth of 75 cm below the mineral soil surface, of 2 or less if there

are redox concentrations or of 1 or less if there are no redox

concentrations. Chroma higher than these limits is considered

evidence of somewhat better aeration and is the basis for

defining the Aeric subgroup. An umbric or mollic epipedon is

the basis for defining the Humic subgroup.

Typic Fragiaquepts are of small extent in the United States.

They occur mostly in the Northern and Eastern States. The

native vegetation consists mostly of water-tolerant trees and

shrubs. Many of these soils support native vegetation, but some

have been cleared and artificially drained and are used as

cropland or pasture.

Aeric Fragiaquepts.—These soils have one or more

horizons that have chroma too high for the Typic subgroup but

are otherwise like Typic Fragiaquepts. Aeric Fragiaquepts are

of moderate extent in the United States. They occur mostly in

the Northern and Eastern States. The native vegetation consists

mostly of water-tolerant trees and shrubs. Many of these soils

have been cleared and artificially drained and are used as

cropland or pasture. Some support native vegetation.

Humic Fragiaquepts.—These soils have an umbric

epipedon or, rarely, a mollic epipedon that has been produced

by liming an umbric epipedon. The soils are otherwise like

Typic Fragiaquepts. Humic Fragiaquepts are rare in the United

States.

Halaquepts

These are saline or sodic soils that have both a seasonal high

water table and a season in which capillary rise and

evapotranspiration bring sodium or other salts to or near the

soil surface. Salt efflorescence on the soil surface is common in

dry seasons.

Halaquepts typically have grayish colors, and some have

redox concentrations from near the soil surface downward.

Nearly all are level and formed in Holocene alluvium. The

native vegetation is mostly sedges and salt-tolerant grasses and

shrubs, but some of the soils have been artificially drained and

are used as irrigated cropland. Halaquepts are not extensive in

the United States.

Definition

Halaquepts are the Aquepts that:

1. Have:

a. An SAR of 13 or more (or sodium saturation that is 15
506 Soil Taxonomy

percent or more), in half or more of the upper 50 cm, that

decreases with increasing depth below 50 cm and saturation

with water at some period within a depth of 100 cm; or

b. A salic horizon;

2. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the mineral soil surface; and

3. Do not have, within 100 cm of the mineral soil surface,

one or more horizons in which plinthite or a cemented or

indurated diagnostic horizon either forms a continuous phase

or constitutes one-half or more of the volume.

Key to Subgroups

KACA. Halaquepts that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Halaquepts

KACB. Other Halaquepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Halaquepts

KACC. Other Halaquepts that have a horizon 15 cm or more

thick that has 20 percent or more (by volume) cemented or

indurated soil material and has its upper boundary within 100

cm either of the mineral soil surface or of the top of an organic

layer with andic soil properties, whichever is shallower.

Duric Halaquepts

KACD. Other Halaquepts that have chroma of 3 or more

in 40 percent or more of the matrix of one or more horizons

at a depth between 15 and 75 cm from the mineral soil

surface.

Aeric Halaquepts

KACE. Other Halaquepts.

Typic Halaquepts

Definition of Typic Halaquepts

Typic Halaquepts are the Halaquepts that:

1. Have chroma of 2 or less in 60 percent or more of

the matrix in all subhorizons between depths of 15 and

75 cm;

2. Do not have a horizon 15 cm or more thick that has 20

percent or more (by volume) cemented or indurated soil

material and has its upper boundary within 100 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower;

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.
Inceptisols 507

Description of Subgroups

Typic Halaquepts.—The central concept or Typic subgroup

of Halaquepts is fixed on soils that have chroma of 2 or less in

all subhorizons between depths of 15 and 75 cm. These soils

have less than 20 percent cemented soil material in the upper

100 cm. Some of the soils have a salic horizon. Salinity

commonly varies with seasons in these soils, even under

irrigation. Most of the soils, however, have electrical

conductivity in excess of 2 dS/m in some horizon at some time

of the year. Commonly, the conductivity exceeds 15 dS/m.

Chroma of more than 2 in more than 40 percent of the matrix

of some subhorizon between depths of 15 and 75 cm is the

basis for definition of the Aeric subgroup.

Typic Halaquepts are of moderate extent in the Western

United States. The native vegetation consists mostly of waterand salt-tolerant shrubs and grasses. Most of these soils

support native vegetation and are used as rangeland. Some

have been cleared and artificially drained and are used as

irrigated cropland or pasture.

Aeric Halaquepts.—These soils have chroma too high for

the Typic subgroup in some subhorizon between depths of 15

and 75 cm below the soil surface. The higher chroma is

thought to indicate a lower level of ground water and

somewhat better aeration. These soils are of moderate extent in

the Western United States. The native vegetation is mostly

water- and salt-tolerant shrubs and grasses. Most of these soils

are used as rangeland. Some have been cleared and artificially

drained and are used as irrigated cropland or pasture.

Aquandic Halaquepts.—These soils have some andic soil

properties in a layer in the upper 75 cm that is 18 cm or more

thick. The clays in this layer normally do not disperse well and

have a high pH-dependent charge. These soils are not known to

occur in the United States. The subgroup is provided for use

elsewhere.

Duric Halaquepts.—These soils have 20 percent or more

cemented or indurated soil material in a horizon 15 cm or more

thick that is in the upper 100 cm. The soils are of moderate

extent in the Western United States. They occur in the

semiarid, high valleys east of the Cascade Range in southern

Oregon. The native vegetation consists mostly of water- and

salt-tolerant shrubs and grasses. Most of these soils are used as

rangeland. Some have been cleared and artificially drained and

are used as irrigated cropland or pasture.

Vertic Halaquepts.—These soils are high in expanding

clays and have cracks 5 mm or more wide, slickensides,

wedge-shaped aggregates, or a linear extensibility of 6.0 cm or

more between the mineral soil surface and either a depth of

100 cm or a densic, lithic, or paralithic contact, whichever is

shallower. The soils are considered to be transitional to

Vertisols. Vertic Halaquepts are of small extent and occur in

the Western United States and in Puerto Rico.

Humaquepts

Humaquepts are the Aquepts that have a histic, melanic,

mollic, or umbric epipedon. The ground water commonly

fluctuates from a level near the soil surface to below a depth of

50 cm. These soils have a frigid or warmer soil temperature

regime and do not have any sulfuric, placic, or salic horizon or

a fragipan near the soil surface. They do not have high

exchangeable sodium near the soil surface that becomes less

with increasing depth below 50 cm. They have no horizon

within 100 cm of the mineral soil surface in which plinthite or

any other cemented or indurated diagnostic horizon either

forms a continuous phase or constitutes one-half or more of the

volume. Recognizable bioturbation, such as filled animal

burrows, wormholes, or casts, is less than 50 percent (by

volume) in all layers at least 25 cm thick (cumulative) within

100 cm of the mineral soil surface. Before they were cultivated,

most Humaquepts supported forest vegetation. Generally,

Humaquepts are nearly level, and their parent materials are

typically late-Pleistocene or younger sediments. These soils are

of small extent in the United States.

Definition

Humaquepts are the Aquepts that:

1. Have an umbric, mollic, melanic, or histic epipedon;

2. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the mineral soil surface;

3. Do not have, within 100 cm of the mineral soil surface,

one or more horizons in which plinthite or a cemented or

indurated diagnostic horizon either forms a continuous phase

or constitutes one-half or more of the volume;

4. Have an exchangeable sodium percentage (ESP) of less

than 15 (or a sodium adsorption ratio [SAR] of less than 13) in

half or more of the soil volume within 50 cm of the mineral

soil surface or an ESP (or SAR) below 50 cm that remains

constant or increases with increasing depth;

5. Have neither a salic horizon nor a fragipan with its upper

boundary within 100 cm of the mineral soil surface;

6. Do not have a cryic soil temperature regime; and

7. Do not have, in one or more layers at least 25 cm thick

(cumulative) within 100 cm of the mineral soil surface, 25

percent or more (by volume) recognizable bioturbation, such as

filled animal burrows, wormholes, or casts.

Key to Subgroups

KAGA. Humaquepts that have an n value of either:

1. More than 0.7 (and less than 8 percent clay) in one or
508 Soil Taxonomy

more layers at a depth between 20 and 50 cm from the mineral

soil surface; or

2. More than 0.9 in one or more layers at a depth

between 50 and 100 cm.

Hydraquentic Humaquepts

KAGB. Other Humaquepts that have a histic epipedon.

Histic Humaquepts

KAGC. Other Humaquepts that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Humaquepts

KAGD. Other Humaquepts that have a slope of less than 25

percent; and

1. An umbric or mollic epipedon 60 cm or more thick; and

either

2. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

3. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Cumulic Humaquepts

KAGE. Other Humaquepts that have a slope of less than 25

percent; and

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluvaquentic Humaquepts

KAGF. Other Humaquepts that have hue of 5Y or redder and

chroma of 3 or more in more than 40 percent of the matrix of

one or more subhorizons at a depth between 15 and 75 cm

from the mineral soil surface.

Aeric Humaquepts

KAGG. Other Humaquepts.

Typic Humaquepts

Definition of Typic Humaquepts

Typic Humaquepts are the Humaquepts that:

1. Have chroma of 2 or less, moist, or hue less red than 5Y

in 60 percent or more of the matrix in all subhorizons between

depths of 15 and 75 cm;

2. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

3. Have a content of organic carbon (Holocene age) that

decreases regularly with increasing depth and, unless a densic,

lithic, or paralithic contact occurs at a shallower depth, reaches

a level of 0.2 percent or less within 125 cm of the soil surface;

4. Do not have a histic epipedon; and

5. Have an n value of less than 0.9 between depths of 50

and 100 cm and of 0.7 or less in all layers between depths of

20 and 50 cm.

Description of Subgroups

Typic Humaquepts.—The central concept or Typic

subgroup of Humaquepts is fixed on very poorly drained soils
Inceptisols 509

that have an umbric epipedon that is between 25 and 60 cm

thick, have a low n value, have a regular decrease in organiccarbon content (Holocene age) with increasing depth, and do

not have a significant amount of materials that have some

andic soil properties. A few of these soils have a mollic

epipedon.

An overthickened epipedon indicates addition of materials

at the surface and is the basis for definition of the Cumulic

subgroup. A histic epipedon indicates a transition to Histosols.

A high n value is characteristic of Hydraquents and causes

soils to be excluded from the Typic subgroup. An irregular

decrease in organic-carbon content (Holocene age) with

increasing depth indicates buried horizons and is the basis for

defining the Fluvaquentic subgroup.

Typic Humaquepts are of moderate extent in the United

States. They are widely distributed and commonly occur in the

most moist parts of the country. The native vegetation consists

mostly of water-tolerant trees, shrubs, and grasses. Many of

these soils have been cleared and artificially drained and are

used as cropland or pasture. Some support native vegetation.

Aeric Humaquepts.—These soils have a horizon within the

upper 75 cm that has a hue too red and a chroma too high for

Typic Humaquepts. The higher chroma is thought to indicate

either a shorter period of saturation of the whole soil with

water or somewhat deeper ground water than that in the soils

of the Typic subgroup. Aeric Humaquepts are not known to

occur in the United States.

Aquandic Humaquepts.—These soils have some andic soil

properties in a layer in the upper 75 cm that is 18 cm or more

thick. The clays in this layer normally do not disperse well and

have a high pH-dependent charge. Typically, this layer is at or

very close to the soil surface. An umbric epipedon is common

but is not required. These soils are of small extent in the

United States and are known to occur in Washington, Oregon,

and Idaho. Most of the soils supported water-tolerant forest

vegetation, and some supported water-tolerant grasses and

shrubs. Many of the soils are artificially drained and are used

as cropland or hayland, and many are used as forest. Some are

used as pasture and some as wildlife habitat.

Cumulic Humaquepts.—These soils have an irregular

decrease in organic-carbon content (Holocene age) with

increasing depth or have a relatively high amount of organic

carbon (Holocene age) in the deep layers. In addition, they

have a thick epipedon. These soils commonly are on flood

plains or at the margins of closed depressions where there has

been very slow deposition of new materials. The deposition has

been slow enough for new materials to have become part of the

epipedon. These soils are of moderate extent in the United

States. They are widely distributed and occur mostly in the

most moist parts of the country. The native vegetation consists

mostly of water-tolerant trees, shrubs, and grasses. Most of

these soils support native vegetation. Some have been cleared

and artificially drained and are used as cropland or pasture.

Fluvaquentic Humaquepts.—These soils have an irregular

decrease in organic-carbon content (Holocene age) with

increasing depth or have a relatively high amount of organic

carbon (Holocene age) in the deep layers. They are subject to

flooding by muddy water and have some of the properties of

Fluvents. Fluvaquentic Humaquepts are of small extent in the

United States. They are widely distributed and occur mostly in

the most moist parts of the country. The native vegetation

consists mostly of water-tolerant trees, shrubs, and grasses.

Most of these soils support their native vegetation. Some have

been cleared and artificially drained and are used as cropland

or pasture.

Histic Humaquepts.—These soils have a histic epipedon.

They are the wettest of the Humaquepts and are intergrades to

Histosols. The organic-carbon content (Holocene age) may be

relatively high in the deep layers. Histic Humaquepts are of

moderate extent in the United States and are widely distributed

mostly in the northern and eastern parts of the country. The

native vegetation consists mostly of water-tolerant trees,

shrubs, and grasses. Most of these soils support native

vegetation. A few of the soils have been cleared and artificially

drained and are used as cropland or pasture.

Hydraquentic Humaquepts.—These soils have an n value

of either more than 0.7 in one or more layers at a depth

between 20 and 50 cm from the mineral soil surface or of more

than 0.9 in one or more layers at a depth between 50 and 100

cm from the mineral soil surface. The soils are rare in the

United States. They are on tidal flats. The native vegetation

consists mostly of water-tolerant grasses, sedges, rushes, and

shrubs.

Petraquepts

These are the Aquepts that have one or more horizons,

within 100 cm of the mineral soil surface, in which plinthite or

a cemented or indurated diagnostic horizon either forms a

continuous phase or constitutes one-half or more of the volume.

A layer of plinthite and the placic horizon are the only

horizons known to occur in the Petraquepts in the United

States. A Typic subgroup is provided for Petraquepts with a

duripan or petrocalcic horizon. Petraquepts are soils in which

the ground water table fluctuates considerably during the year,

between a level at or near the soil surface during the rainy

season and a much lower level during less wet seasons. A

histic or umbric epipedon and a cambic horizon may be

present. In some of the soils, the placic horizon is so close to

the soil surface that there is no cambic horizon above it.

Petraquepts are in areas of very high rainfall. The

vegetation may be a rain forest, Sphagnum, or other waterloving plants. The temperature regime is frigid to

isohyperthermic. Slopes generally are such that water does not

pond on the surface, but high rainfall keeps some of the soils

continuously wet. Petraquepts are rare in the world.
510 Soil Taxonomy

Definition

1. Petraquepts are the Aquepts that have, within 100 cm of the

mineral soil surface, one or more horizons in which plinthite or a

cemented or indurated diagnostic horizon either forms a

continuous phase or constitutes one-half or more of the volume;

and

2. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the mineral soil surface.

Key to Subgroups

KABA. Petraquepts that have both:

1. A histic epipedon; and

2. A placic horizon.

Histic Placic Petraquepts

KABB. Other Petraquepts that have a placic horizon.

Placic Petraquepts

KABC. Other Petraquepts that have one or more horizons

within 125 cm of the mineral soil surface in which plinthite

either forms a continuous phase or constitutes one-half or more

of the volume.

Plinthic Petraquepts

KABD. Other Petraquepts.

Typic Petraquepts

Definition of Typic Petraquepts

Typic Petraquepts are the Petraquepts that:

1. Do not have a placic horizon; and

2. Do not have one or more horizons within 125 cm of the

mineral soil surface in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume.

Description of Subgroups

Typic Petraquepts.—The central concept or Typic

subgroup of Petraquepts is fixed on soils that have a duripan or

a petrocalcic horizon within 100 cm of the mineral soil surface.

These soils do not have a horizon within 125 cm of the mineral

soil surface in which plinthite either forms a continuous phase

or constitutes one-half or more of the volume and do not have a

placic horizon. They can have a histic epipedon if there is no

placic horizon. Typic Petraquepts are not the most common

Petraquepts and are not known to occur in the United States.

Histic Placic Petraquepts.—These soils have both a histic

epipedon and a placic horizon. They are like Typic Petraquepts

in other defined properties. Histic Placic Petraquepts are of

very small extent and occur only in Hawaii in the United

States. They are used as wildlife habitat and as water

catchments.

Placic Petraquepts.—These soils have a placic horizon but

do not have a histic epipedon. Normally, the placic horizon lies

within 25 to 50 cm of the mineral soil surface. These soils are

of very small extent and occur only in Hawaii in the United

States. They are used as wildlife habitat and as water

catchments.

Plinthic Petraquepts.—These soils have one or more

horizons within 125 cm of the mineral soil surface in which

plinthite either forms a continuous phase or constitutes onehalf or more of the volume. These soils are not known to occur

in the United States. The subgroup has been established for use

in other countries.

Sulfaquepts

These are the acid sulfate soils (cat clays) that have been

drained and oxidized at some time. They are extremely acid

and toxic to most plants. They are mostly dark gray and have

straw-colored mottles of iron sulfate (jarosite) within 50 cm of

the soil surface. These soils are mainly in drained coastal

marshes near the mouths of rivers that carry sediments that are

free of carbonates or have a low content of carbonates. They

can have any texture, but most are loamy or clayey. The soils

contain an appreciable amount of organic carbon (Holocene

age). They are rare in the United States but occur elsewhere in

a few areas that have been used mainly for the production of

rice.

Definition

Sulfaquepts are the Aquepts that have a sulfuric horizon

that has its upper boundary within 50 cm of the soil surface.

Key to Subgroups

KAAA. Sulfaquepts that have a salic horizon within 75 cm of

the mineral soil surface.

Salidic Sulfaquepts

KAAB. Other Sulfaquepts that have an n value of either:

1. More than 0.7 (and less than 8 percent clay) in one or

more layers at a depth between 20 and 50 cm from the

mineral soil surface; or

2. More than 0.9 in one or more layers at a depth

between 50 and 100 cm from the mineral soil surface.

Hydraquentic Sulfaquepts

KAAC. Other Sulfaquepts.

Typic Sulfaquepts

Definition of Typic Sulfaquepts

Typic Sulfaquepts are the Sulfaquepts that:

1. Do not have a salic horizon within 75 cm of the mineral

soil surface; and

2. Have an n value both:
Inceptisols 511

a. Of 0.7 or less in all layers at a depth between 20 and 50

cm from the mineral soil surface; and

b. Of less than 0.9 in all layers at a depth between 50 and

100 cm from the mineral soil surface.

Description of Subgroups

Typic Sulfaquepts.—The central concept or Typic subgroup

of Sulfaquepts is fixed on very poorly drained soils that do not

have a salic horizon and have an n value of 0.7 or less in all

layers at a depth between 20 and 50 cm from the mineral soil

surface and of 0.9 or less in all layers at a depth between 50

and 100 cm from the mineral soil surface.

These soils are rare in the United States. They are on tidal

flats. The native vegetation is sparse and consists mostly of

water-tolerant grasses, sedges, rushes, and shrubs.

Hydraquentic Sulfaquepts.—These soils have an n value

of either more than 0.7 in one or more layers at a depth

between 20 and 50 cm from the mineral soil surface or of more

than 0.9 in one or more layers at a depth between 50 and 100

cm from the mineral soil surface. The soils are rare in the

United States. They are on tidal flats. The native vegetation is

sparse and consists of water-tolerant grasses, sedges, rushes,

and shrubs.

Salidic Sulfaquepts.—These soils have a salic horizon

within 75 cm of the mineral soil surface. They are rare in the

United States. They are on tidal flats. The native vegetation

consists of very sparse water- and salt-tolerant grasses, sedges,

rushes, and shrubs.

Vermaquepts

Vermaquepts are the Aquepts that have recognizable

bioturbation, such as filled animal burrows, wormholes, or

casts. It has been shown that because krotovinas are dense,

massive, compact, and stratified, they restrict water movement.

Significant amounts of krotovinas in a soil affect soil

morphology, soil hydrology, and soil behavior. These soils are

known to occur along the coastal plain of Texas as well as

other Southeastern States.

Definition

Vermaquepts are the Aquepts that:

1. Have, in one or more layers at least 25 cm thick

(cumulative) within 100 cm of the soil surface, 50 percent or

more (by volume) recognizable bioturbation, such as filled

animal burrows, wormholes, or casts;

2. Do not have a sulfuric horizon that has its upper boundary

within 50 cm of the soil surface;

3. Do not have, within 100 cm of the mineral soil surface,

one or more horizons in which plinthite or a cemented or

indurated diagnostic horizon either forms a continuous phase or

constitutes one-half or more of the volume;

4. Do not have, in one or more horizons with a total

thickness of 25 cm or more within 50 cm of the mineral soil

surface, an exchangeable sodium percentage (ESP) of 15 or

more (or a sodium adsorption ratio [SAR] of 13 or more) and a

decrease in ESP (or SAR) values with increasing depth below

50 cm;

5. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface;

6. Have a soil temperature regime warmer than cryic; and

7. Do not have a salic horizon.

Key to Subgroups

KAFA. Vermaquepts that have an exchangeable sodium

percentage of 7 or more (or a sodium adsorption ratio [SAR] of

6 or more) in one or more subhorizons within 100 cm of the

mineral soil surface.

Sodic Vermaquepts

KAFB. Other Vermaquepts.

Typic Vermaquepts

Definition of Typic Vermaquepts

Typic Vermaquepts are the Vermaquepts that do not have an

exchangeable sodium percentage of 7 or more (or a sodium

adsorption ratio [SAR] of 6 or more) in one or more

subhorizons within 100 cm of the mineral soil surface.

Description of Subgroups

Typic Vermaquepts.—The central concept or Typic

subgroup of Vermaquepts is fixed on poorly drained soils that

have an exchangeable sodium percentage of less than 7 (or a

sodium adsorption ratio [SAR] of less than 6) in all

subhorizons within 100 cm of the mineral soil surface. The

recognizable bioturbation in the soils is caused mainly by

crayfish. These soils are of small extent in the United States.

They occur mostly on the coastal plain in Texas. The native

vegetation consists mostly of water-tolerant trees and shrubs.

Most of these soils have been cleared and are used as cropland.

Rice is among the commonly grown crops. Crayfish are

sometimes raised on the crop residue.

Sodic Vermaquepts.—These soils have an exchangeable

sodium percentage of 7 or more (or a sodium adsorption ratio

[SAR] of 6 or more) in one or more subhorizons within 100 cm

of the mineral soil surface. The recognizable bioturbation in

the soils is caused mainly by crayfish. These soils are of small

extent in the United States. They occur mostly on the coastal

plain in Texas. The native vegetation consists mostly of watertolerant trees and shrubs. Most of these soils have been cleared
512 Soil Taxonomy

and are used as cropland. Rice is among the commonly grown

crops. Crayfish are sometimes raised on the crop residue.

Cryepts

Cryepts are the cold Inceptisols of high mountains or high

latitudes. They cannot have permafrost within 100 cm of the

soil surface. The vegetation is mostly conifers or mixed

conifers and hardwoods. Few of the soils are cultivated.

Cryepts formed in loess, drift, or alluvium or in solifluction

deposits, mostly late Pleistocene or Holocene in age. The soils

commonly have a thin, dark brownish ochric epipedon and a

brownish cambic horizon. Some have bedrock within 100 cm

of the surface. Cryepts are moderately extensive in the United

States. They occur in the high mountains of the West and in

southern Alaska as well as in other mountainous areas of the

world.

Definition

Cryepts are the Inceptisols that:

1. Have a cryic temperature regime;

2. Do not have both aquic conditions and a histic epipedon,

the colors defined for Aquepts, or enough active ferrous iron to

give a positive reaction to alpha,alpha-dipyridyl at a time when

the soil is not being irrigated;

3. Do not have an exchangeable sodium percentage (ESP)

of 15 or more (or a sodium adsorption ratio [SAR] of 13 or

more) in half or more of the soil volume within 50 cm of the

mineral soil surface, an ESP (or SAR) below 50 cm that

decreases with increasing depth, and ground water within 100

cm of the mineral soil surface during some time of the year;

and

4. Have neither a plaggen nor an anthropic epipedon.

Key to Great Groups

KCA. Cryepts that have one or both of the following:

1. Free carbonates within the soils; or

2. A base saturation (by NH4OAc) of 60 percent or more

in one or more horizons at a depth between 25 and 75 cm

from the mineral soil surface.

Eutrocryepts, p. 514

KCB. Other Cryepts.

Dystrocryepts, p. 512

Dystrocryepts

These are the Cryepts that do not have free carbonates and

have a base saturation (by NH4OAc) of less than 60 percent in

all horizons at a depth between 25 and 75 cm from the mineral

soil surface. The vegetation is mostly conifers or mixed

conifers and hardwoods. Few of the soils are cultivated.

Dystrocryepts may have formed in loess, drift, or alluvium or

in solifluction deposits, mostly late Pleistocene or Holocene in

age. The soils commonly have a thin, dark brownish ochric

epipedon and a brownish cambic horizon. Some have an

umbric epipedon, and some have bedrock within 100 cm of the

surface. In the United States, Dystrocryepts are moderately

extensive in the high mountains of the West and in southern

Alaska. They also occur in other mountainous areas of the

world.

Definition

Dystrocryepts are the Cryepts that:

1. Do not have free carbonates within the soils; and

2. Have a base saturation (by NH4

OAc) of less than 60

percent in all horizons at a depth between 25 and 75 cm from

the mineral soil surface.

Key to Subgroups

KCBA. Dystrocryepts that have both:

1. An umbric or mollic epipedon; and

2. A lithic contact within 50 cm of the mineral soil

surface.

Humic Lithic Dystrocryepts

KCBB. Other Dystrocryepts that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Dystrocryepts

KCBC. Other Dystrocryepts that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Dystrocryepts

KCBD. Other Dystrocryepts that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium
Inceptisols 513

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more.

Vitrandic Dystrocryepts

KCBE. Other Dystrocryepts that have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Dystrocryepts

KCBF. Other Dystrocryepts that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Dystrocryepts

KCBG. Other Dystrocryepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Dystrocryepts

KCBH. Other Dystrocryepts that have a horizon 5 cm or

more thick that has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

2. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Dystrocryepts

KCBI. Other Dystrocryepts that have a xeric moisture

regime.

Xeric Dystrocryepts

KCBJ. Other Dystrocryepts that are dry in some part of the

moisture control section for 45 or more days (cumulative) in

normal years.

Ustic Dystrocryepts

KCBK. Other Dystrocryepts that have an umbric or mollic

epipedon.

Humic Dystrocryepts

KCBL. Other Dystrocryepts.

Typic Dystrocryepts

Definition of Typic Dystrocryepts

Typic Dystrocryepts are the Dystrocryepts that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also aquic

conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

5. Have neither an umbric nor a mollic epipedon;

6. Do not have lamellae (two or more) within 200 cm of the

mineral soil surface;

7. Do not have a horizon 5 cm or more thick that has one or

more of the following:

a. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

b. Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

c. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon;

8. Do not have a xeric moisture regime; and

9. Are dry in some part of the moisture control section for

less than 45 days (cumulative) in normal years.

Description of Subgroups

Typic Dystrocryepts.—The central concept or the Typic

subgroup of Dystrocryepts is fixed on deep, more or less freely
514 Soil Taxonomy

drained soils that have an ochric epipedon and that do not have

lamellae.

Soils that have lamellae in which silicate clay has

accumulated are excluded from the Typic subgroup because

they are considered to be intergrades to Alfisols. Shallow hard

rock is used to define the Lithic subgroup. Soils that have a

thin mantle or layer of materials that have some andic soil

properties are excluded from the Typic subgroup because they

are considered to be an intergrade to Andisols. A shallow water

table and redox depletions with low chroma indicate

intergrades to Aquepts. An umbric or mollic epipedon is not

considered typical and is used to define Humic and

combination Humic subgroups.

Typic Dystrocryepts are of large extent in the United States.

They are mostly in the mountains of the Western States and in

Alaska. The vegetation is mostly coniferous forest. The soils

are used mainly for timber production and wildlife habitat.

Andic and Vitrandic Dystrocryepts.—These soils have, in

the upper 75 cm, a layer that is 18 cm or more thick and that

has some andic soil properties or that consists of fine

pyroclastic materials. This layer is most commonly at the

mineral soil surface. Most of these soils have an ochric or

umbric epipedon and a cambic horizon. Andic and Vitrandic

Dystrocryepts are of large extent in the United States. They are

mostly in the mountains of the Western States. The vegetation

is mostly coniferous forest. The soils are used mainly for

timber production and wildlife habitat.

Aquic Dystrocryepts.—These soils have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). In

addition, some of the soils have an umbric or mollic epipedon.

Aquic Dystrocryepts are of small extent in the United States.

They are mostly in Alaska, but a few are in the mountains of

other Western States. The vegetation is mostly coniferous

forest. The soils are used mainly for timber production and

wildlife habitat.

Humic Dystrocryepts.—These soils are like Typic

Dystrocryepts, but they have an umbric or mollic epipedon.

Many of the soils are in areas of higher precipitation than the

soils of the Typic subgroup. Humic Dystrocryepts are of

moderate extent in the United States. They are mostly in the

mountains of the Western States. The vegetation is mostly

coniferous forest. The soils are used mainly for timber

production and wildlife habitat.

Humic Lithic Dystrocryepts.—These soils have an umbric

or mollic epipedon and a lithic contact within 50 cm of the soil

surface. They are of moderate extent in the United States. They

are mostly in the mountains of the Western States. The

vegetation is mostly coniferous forest. The soils are used

mainly for timber production and wildlife habitat.

Lamellic Dystrocryepts.—These soils have two or more

lamellae. The top of the uppermost lamella is within 75 cm of

the soil surface, but others may be deeper. Most of these soils

have a coarse-loamy, coarse-silty, or loamy-skeletal particle-size

class. Lamellic Dystrocryepts are of small extent in the United

States. They are mostly in the mountains of the Western States.

The vegetation is mostly coniferous forest. The soils are used

mainly for timber production and wildlife habitat.

Lithic Dystrocryepts.—These soils have an ochric

epipedon and a lithic contact within 50 cm of the soil surface.

They are of moderate extent in the United States. They are

mostly in the mountains of the Western States. The vegetation

is mostly coniferous forest. The soils are used mainly for

timber production and wildlife habitat.

Oxyaquic Dystrocryepts.—These soils are saturated with

water in one or more layers within 100 cm of the mineral soil

surface for 20 consecutive days or 30 cumulative days in

normal years. The soils are of small extent in the United States.

They are mostly in Alaska and in the mountains of the Western

States. The vegetation is mostly coniferous forest. The soils are

used mainly for timber production and wildlife habitat.

Spodic Dystrocryepts.—These soils have a weak

accumulation of amorphous materials. They are presumed to be

developing toward Spodosols, mainly Cryods, but are too

weakly developed to be classified as Spodosols. Spodic

Dystrocryepts are of small extent in the United States. They are

in the mountains of the Western States.

Ustic Dystrocryepts.—These soils are like Typic

Dystrocryepts, but they are dry in some part of the moisture

control section for 45 or more days (cumulative) in normal

years. They are considered to be transitional to Ustepts. Ustic

Dystrocryepts commonly support a sparse coniferous forest

with widely spaced trees or are used as rangeland. They are not

extensive in the United States.

Xeric Dystrocryepts.—These soils are like Typic

Dystrocryepts, but they have a xeric moisture regime. They are

considered to be transitional to Xerepts. Xeric Dystrocryepts

commonly support coniferous forest vegetation. Some of the

forests have widely spaced trees. Some of the soils are used as

rangeland. Xeric Dystrocryepts are not extensive in the United

States.

Eutrocryepts

These are the Cryepts that have free carbonates or have a

base saturation (by NH4OAc) of 60 percent or more in some

horizon at a depth between 25 and 75 cm from the mineral soil

surface. The vegetation is mostly mixed conifers and

hardwoods or shrubs, grass, and widely spaced trees. Few of

the soils are used as cropland. Eutrocryepts formed mostly in

drift, alluvium, or colluvium or in solifluction deposits, mostly

late Pleistocene or Holocene in age. The soils commonly have a

thin, dark brownish ochric epipedon and a brownish cambic

horizon. Some have an umbric epipedon, and some have

bedrock within 100 cm of the surface. In the United States,
Inceptisols 515

these soils are of small extent in the high mountains of the West.

They also occur in other parts of the world, mostly in

mountainous areas.

Definition

Eutrocryepts are the Cryepts that:

1. Have free carbonates within the soils; or

2. Have a base saturation (by NH4

OAc) of 60 percent or more

in one or more horizons at a depth between 25 and 75 cm from

the mineral soil surface.

Key to Subgroups

KCAA. Eutrocryepts that have both:

1. An umbric or mollic epipedon; and

2. A lithic contact within 50 cm of the mineral soil

surface.

Humic Lithic Eutrocryepts

KCAB. Other Eutrocryepts that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Eutrocryepts

KCAC. Other Eutrocryepts that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3

 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Eutrocryepts

KCAD. Other Eutrocryepts that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Eutrocryepts

KCAE. Other Eutrocryepts that have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Eutrocryepts

KCAF. Other Eutrocryepts that in normal years are saturated

with water in one or more layers within 100 cm of the mineral soil

surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Eutrocryepts

KCAG. Other Eutrocryepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Eutrocryepts

KCAH. Other Eutrocryepts that have a xeric moisture

regime.

Xeric Eutrocryepts

KCAI. Other Eutrocryepts that are dry in some part of the

moisture control section for 45 or more days (cumulative) in

normal years.

Ustic Eutrocryepts

KCAJ. Other Eutrocryepts that have an umbric or mollic

epipedon.

Humic Eutrocryepts

KCAK. Other Eutrocryepts.

Typic Eutrocryepts

Definition of Typic Eutrocryepts

Typic Eutrocryepts are the Eutrocryepts that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and
516 Soil Taxonomy

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

5. Do not have lamellae (two or more) within 200 cm of the

mineral soil surface;

6. Have neither an umbric nor a mollic epipedon;

7. Do not have a xeric moisture regime; and

8. Are dry in some part of the moisture control section for

less than 45 days (cumulative) in normal years.

Description of Subgroups

Typic Eutrocryepts.—The central concept or Typic

subgroup of Eutrocryepts is fixed on deep, more or less freely

drained soils that have an ochric epipedon and that do not have

lamellae.

Soils that have lamellae in which silicate clay has

accumulated are excluded from the Typic subgroup because

they are considered to be intergrades to Alfisols. Shallow hard

rock is used to define the Lithic subgroup. Soils that have a

thin mantle or layer of materials that have some andic soil

properties are excluded from the Typic subgroup because they

are considered to be an intergrade to Andisols. A shallow water

table and redox depletions with low chroma indicate

intergrades to Aquepts. An umbric or mollic epipedon is not

considered typical and is used to define Humic and

combination Humic subgroups.

Typic Eutrocryepts are of large extent in the United States

and occur mostly in the mountains of the Western States and in

southern Alaska. The vegetation is mostly coniferous forest.

The soils are used mainly for timber production and wildlife

habitat.

Andic and Vitrandic Eutrocryepts.—These soils have, in

the upper 75 cm, a layer 18 cm or more thick that has some

andic soil properties or consists of fine pyroclastic materials.

This layer is most commonly at the mineral soil surface. Most

of these soils have an ochric or umbric epipedon and a cambic

horizon. Andic and Vitrandic Eutrocryepts are of very small

extent in the United States. They are mostly in the mountains

of the Western States. The vegetation is mostly coniferous

forest. The soils are used mainly for timber production and

wildlife habitat.

Aquic Eutrocryepts.—These soils have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). In

addition, some of the soils have an umbric or mollic epipedon.

Aquic Eutrocryepts are of small extent in the United States.

They are mostly in Alaska, but a few are in the mountains of

the Western States. The vegetation is mostly coniferous forest.

The soils are used mainly for timber production and wildlife

habitat.

Humic Eutrocryepts.—These soils have an umbric or

mollic epipedon. They are of very small extent in the United

States. They are mostly in the mountains of the Western States.

The vegetation is mostly coniferous forest. The soils are used

mainly for timber production and wildlife habitat.

Humic Lithic Eutrocryepts.—These soils have an umbric

or mollic epipedon and a lithic contact within 50 cm of the soil

surface. They are of very small extent in the United States.

They are mostly in the mountains of the Western States. The

vegetation is mostly coniferous forest. The soils are used

mainly for timber production and wildlife habitat.

Lamellic Eutrocryepts.—These soils have two or more

lamellae. The upper boundary of the uppermost lamella is

within 75 cm of the soil surface, but others may be deeper.

Most of these soils have a coarse-loamy, coarse-silty, or loamyskeletal particle-size class. Lamellic Eutrocryepts are of small

extent in the mountains of the Western United States. The

vegetation is mostly coniferous forest. The soils are used

mainly for timber production and wildlife habitat.

Lithic Eutrocryepts.—These soils have an ochric epipedon

and a lithic contact within 50 cm of the soil surface. They are

of moderate extent in the United States. They are mostly in the

mountains of the Western States. The vegetation is mostly

coniferous forest. The soils are used mainly for timber

production and wildlife habitat.

Oxyaquic Eutrocryepts.—These soils are saturated with

water in one or more layers within 100 cm of the mineral soil

surface for 20 consecutive days or 30 cumulative days in

normal years. The soils are of small extent in the United States.

They are mostly in Alaska and in the mountains of the Western

States. The vegetation is mostly coniferous forest. The soils are

used mainly for timber production and wildlife habitat.

Ustic Eutrocryepts.—These soils are like Typic

Eutrocryepts, but they are dry in some part of the moisture

control section for 45 or more days (cumulative) in normal

years. They are considered to be transitional to Ustepts. Ustic

Eutrocryepts commonly support a sparse coniferous forest with

widely spaced trees or are used as pasture. They are not

extensive in the United States.

Xeric Eutrocryepts.—These soils are like Typic

Eutrocryepts, but they have a xeric moisture regime. They are

considered to be transitional to Xerepts. Xeric Eutrocryepts

commonly support coniferous forest. Some of the forests have

widely spaced trees. Some of the soils are used as pasture.

Xeric Eutrocryepts are not extensive in the United States.

Udepts

Udepts are mainly the more or less freely drained Inceptisols

that have a udic or perudic moisture regime. They formed on

nearly level to steep surfaces, mostly of late-Pleistocene or

Holocene age. Some of the soils, in areas where the soil
Inceptisols 517

moisture regime is perudic, formed in older deposits. Most of the

soils had or now have a forest vegetation, but some support

shrubs or grasses. A few formed from Mollisols by truncation

of the mollic epipedon, mostly under cultivation. Most of the

soils have an ochric or umbric epipedon and a cambic horizon.

Some also have a sulfuric horizon, a fragipan, or a duripan.

The Udepts in the United States are most extensive in the

Appalachian Mountains, on the Allegheny Plateau, and on the

west coast.

Definition

Udepts are the Inceptisols that:

1. Have a udic moisture regime;

2. Do not have both aquic conditions and a histic epipedon,

the colors defined for Aquepts, or enough active ferrous iron to

give a positive reaction to alpha,alpha-dipyridyl at a time when

the soil is not being irrigated;

3. Do not have an exchangeable sodium percentage (ESP)

of 15 or more (or a sodium adsorption ratio [SAR] of 13 or

more) in half or more of the soil volume within 50 cm of the

mineral soil surface, an ESP (or SAR) below 50 cm that

decreases with increasing depth, and ground water within 100

cm of the mineral soil surface during some time of the year;

4. Have neither a plaggen nor an anthropic epipedon; and

5. Have a soil temperature regime warmer than cryic.

Key to Great Groups

KFA. Udepts that have a sulfuric horizon within 50 cm of the

mineral soil surface.

Sulfudepts, p. 530

KFB. Other Udepts that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Durudepts, p. 517

KFC. Other Udepts that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragiudepts, p. 529

KFD. Other Udepts that have one or both of the following:

1. Free carbonates within the soils; or

2. A base saturation (by NH4OAc) of 60 percent or more

in one or more horizons at a depth between 25 and 75 cm

from the mineral soil surface.

Eutrudepts, p. 524

KFE. Other Udepts.

Dystrudepts, p. 518

Durudepts

These are the Udepts that have a duripan that has its upper

boundary within 100 cm of the soil surface. Most of the Udepts

in the United States occur in areas that have a Mediterranean

climate but that have high precipitation. Commonly, the soils

have a perched water table above the duripan for part of winter

or early spring. The vegetation commonly is coniferous forest.

These soils are of very small extent in the United States.

Definition

Durudepts are the Udepts that:

1. Have a duripan that has its upper boundary within 100 cm

of the soil surface; and

2. Do not have a sulfuric horizon within 50 cm of the mineral

soil surface.

Key to Subgroups

KFBA. Durudepts that have both:

1. In one or more horizons above the duripan and

within 60 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions

for some time in normal years (or artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more, above the duripan and within 75 cm of

the mineral soil surface, one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Durudepts

KFBB. Other Durudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more, above the

duripan and within 75 cm of the mineral soil surface, a fineearth fraction with both a bulk density of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0.

Andic Durudepts
518 Soil Taxonomy

KFBC. Other Durudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more, above the

duripan and within 75 cm of the mineral soil surface, one or

both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Durudepts

KFBD. Other Durudepts that have, in one or more horizons

above the duripan and within 30 cm of the mineral soil surface,

distinct or prominent redox concentrations and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Durudepts

KFBE. Other Durudepts.

Typic Durudepts

Definition of Typic Durudepts

Typic Durudepts are the Durudepts that:

1. Do not have, in any horizon above the duripan and

within 30 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions;

and

2. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Durudepts.—These are the Durudepts that are free of

redoximorphic features and that do not have a layer near the

surface that has many of the properties of Andisols. Typic

Durudepts are of very small extent in the United States. The

native vegetation is mostly coniferous forest. The soils are used

mainly as forest, cropland, or homesites.

Andic and Vitrandic Durudepts.—These soils have a layer

near the surface that is 18 cm or more thick and that has many

of the properties of Andisols. Andic and Vitrandic Durudepts

are of very small extent in the United States and are mostly in

western Washington. The native vegetation is mostly

coniferous forest. These soils are used mainly as forest,

cropland, pasture, or homesites.

Aquandic Durudepts.—These soils have a layer near the

surface that is 18 cm or more thick and that has many of the

properties of Andisols. Aquandic Durudepts also have redox

concentrations and aquic conditions and are wetter than Typic

Durudepts. They are rare in the United States.

Aquic Durudepts.—These soils have redox concentrations

and aquic conditions and are wetter than Typic Durudepts.

Commonly, they also have gentler slopes. Aquic Durudepts are

rare in the United States.

Dystrudepts

These are the acid Udepts of humid and perhumid regions.

They developed mostly in late-Pleistocene or Holocene

deposits. Some developed on older, steeply sloping surfaces.

The parent materials generally are acid, moderately or weakly

consolidated sedimentary or metamorphic rocks or acid

sediments. A few of the soils formed in saprolite derived from

igneous rocks. The vegetation was mostly deciduous trees.

Most of the Dystrudepts that formed in alluvium are now

cultivated, and many of the other Dystrudepts are used as

pasture.

The normal horizon sequence in Dystrudepts is an ochric

epipedon over a cambic horizon. Some of the steeper

Dystrudepts have a shallow densic, lithic, or paralithic contact.

Dystrudepts are extensive in the United States. They are mostly

in the Eastern and Southern States.

Definition

Dystrudepts are the Udepts that:

1. Do not have free carbonates within the soils;

2. Have a base saturation of less than 60 percent (by

NH4

OAc) in all subhorizons between depths of 25 and 75 cm

below the soil surface;

3. Do not have a fragipan or duripan that has an upper

boundary within 100 cm of the mineral soil surface; and

4. Do not have a sulfuric horizon within 50 cm of the mineral

soil surface.
Inceptisols 519

Key to Subgroups

KFEA. Dystrudepts that have both:

1. A lithic contact within 50 cm of the mineral soil surface;

and

2. An umbric or mollic epipedon.

Humic Lithic Dystrudepts

KFEB. Other Dystrudepts that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Dystrudepts

KFEC. Other Dystrudepts that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is

shallower.

Vertic Dystrudepts

KFED. Other Dystrudepts that have both:

1. In one or more horizons within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Dystrudepts

KFEE. Other Dystrudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Dystrudepts

KFEF. Other Dystrudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Dystrudepts

KFEG. Other Dystrudepts that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. In one or more horizons within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions in normal years (or artificial

drainage).

Fragiaquic Dystrudepts

KFEH. Other Dystrudepts that have a slope of less than 25

percent; and

1. In one or more horizons within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. Either:

a. At a depth of 125 cm below the mineral soil surface,

an organic-carbon content (Holocene age) of 0.2 percent

or more and no densic, lithic, or paralithic contact within

that depth; or

b. An irregular decrease in organic-carbon content
520 Soil Taxonomy

(Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a

densic, lithic, or paralithic contact, whichever is

shallower.

Fluvaquentic Dystrudepts

KFEI. Other Dystrudepts that have both:

1. An umbric or mollic epipedon; and

2. In one or more horizons within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Humic Dystrudepts

KFEJ. Other Dystrudepts that have, in one or more horizons

within 60 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Dystrudepts

KFEK. Other Dystrudepts that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Dystrudepts

KFEL. Other Dystrudepts that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Dystrudepts

KFEM. Other Dystrudepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Dystrudepts

KFEN. Other Dystrudepts that have both:

1. An umbric or mollic epipedon; and

2. A sandy particle-size class throughout the particle-size

control section.

Humic Psammentic Dystrudepts

KFEO. Other Dystrudepts that have a slope of less than 25

percent; and

1. An umbric or mollic epipedon; and

2. Either:

a. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

b. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a

densic, lithic, or paralithic contact, whichever is

shallower.

Fluventic Humic Dystrudepts

KFEP. Other Dystrudepts that have a slope of less than 25

percent; and either

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluventic Dystrudepts

KEEQ. Other Dystrudepts that have a horizon 5 cm or more

thick that has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

2. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Dystrudepts

KFER. Other Dystrudepts that have in 50 percent or more of

the soil volume between a depth of 25 cm from the mineral soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact if shallower:

1. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+)

per kg clay; or

2. Both a ratio of measured clay in the fine-earth fraction

to percent water retained at 1500 kPa tension of 0.6 or more

and the following: the CEC (by 1N NH4OAc pH 7) divided

by the product of three times [percent water retained at 1500

kPa tension minus percent organic carbon (but no more than

1.00)] is less than 24.

Oxic Dystrudepts
Inceptisols 521

KFES. Other Dystrudepts that have an umbric or mollic

epipedon that is 50 cm or more thick.

Humic Pachic Dystrudepts

KFET. Other Dystrudepts that have an umbric or mollic

epipedon.

Humic Dystrudepts

KFEU. Other Dystrudepts that have both:

1. In each pedon a cambic horizon that includes 10 to 50

percent (by volume) illuvial parts that otherwise meet the

requirements for an argillic, kandic, or natric horizon; and

2. A base saturation (by sum of cations) of 35 percent or

more either at a depth of 125 cm from the top of the cambic

horizon or directly above a densic, lithic, or paralithic

contact if shallower.

Ruptic-Alfic Dystrudepts

KFEV. Other Dystrudepts that have in each pedon a cambic

horizon that includes 10 to 50 percent (by volume) illuvial

parts that otherwise meet the requirements for an argillic,

kandic, or natric horizon.

Ruptic-Ultic Dystrudepts

KFEW. Other Dystrudepts.

Typic Dystrudepts

Definition of Typic Dystrudepts

Typic Dystrudepts are the Dystrudepts that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years;

4. Have a slope of 25 percent or more; or

a. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of less than 0.2

percent or a densic, lithic, or paralithic contact within that

depth; or

b. A regular decrease in organic-carbon content (Holocene

age) between a depth of 25 cm and either a depth of 125 cm

below the mineral soil surface or a densic, lithic, or

paralithic contact, whichever is shallower;

5. Do not have a lithic contact within 50 cm of the mineral

soil surface;

6. Do not have a cambic horizon that includes 10 to 50

percent (by volume) illuvial parts that otherwise meet the

requirements for an argillic, kandic, or natric horizon;

7. Do not have an umbric or mollic epipedon;

8. Do not have lamellae (two or more) within 200 cm of the

soil surface;

9. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick;

10. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

11. Do not have, in 50 percent or more of the soil volume

between a depth of 25 cm from the mineral soil surface and

either a depth of 100 cm or a densic, lithic, or paralithic

contact if shallower, either:

a. A CEC (by 1N NH4

OAc pH 7) of less than 24 cmol(+)

per kg clay; or
522 Soil Taxonomy

b. Both a ratio of measured clay in the fine-earth fraction to

percent water retained at 1500 kPa tension of 0.6 or more and

the following: the CEC (by 1N NH4

OAc pH 7) divided by the

product of three times [percent water retained at 1500 kPa

tension minus percent organic carbon (but no more than

1.00)] is less than 24.

Description of Subgroups

Typic Dystrudepts.—The central concept or Typic

subgroup of Dystrudepts is fixed on soils that are moderately

deep or deep to hard rock, are freely drained and acid, have an

ochric epipedon, and do not have any intermittent argillic,

natric, or kandic horizon. In addition, the percentage of

organic carbon of Holocene age decreases regularly with

increasing depth and is very low at a depth of 125 cm.

Soils that have slickensides, wedge-shaped aggregates, a

high linear extensibility, or wide cracks are assigned to the

Vertic subgroup because these properties are shared with

Vertisols. If the percentage of carbon is relatively high at a

depth of 125 cm or if the percentage decreases irregularly with

increasing depth and slopes are gentle, the parent material

normally is recent Holocene alluvium. The soils that formed in

this alluvium are considered intergrades to Fluvents or to

Fluvaquents if the soils are also wet. A shallow water table and

redox depletions with low chroma indicate intergrades to

Aquepts. An intermittent argillic, natric, or kandic horizon is

considered evidence that the soil is developing toward Alfisols

or Ultisols, depending on the base saturation. A lithic contact

within a depth of 50 cm is the basis for defining the Lithic

subgroup. The presence of an umbric or mollic epipedon is

used to define Humic and combination Humic subgroups. Soils

that have a thin mantle or layer that has some andic soil

properties are excluded from the Typic subgroup because they

are considered to be an intergrade to Andisols. Soils with a low

CEC in the clay fraction are considered intergrades to Oxisols.

Typic Dystrudepts are extensive in the United States. They

are widely distributed. The largest concentration is in the

Northeastern States. The native vegetation consists mostly of

mixed forest. Most of these soils are used as forest. Many of the

less sloping soils have been cleared and are used as cropland or

pasture.

Andic and Vitrandic Dystrudepts.—These soils have some

andic soil properties in a layer in the upper part that is 18 cm

or more thick. Some of the soils contain a significant amount

of volcanic ash. Some have an umbric epipedon. Andic and

Vitrandic Dystrudepts are moderately extensive in the

Northwestern United States. The native vegetation consists

mostly of coniferous forest. Most of these soils support their

native vegetation and are used as forest. A few of the less

sloping soils have been cleared and are used as cropland or

pasture.

Aquandic Dystrudepts.—These soils have aquic conditions

and redox depletions with low chroma in the upper part of the

subsoil. They also have some andic soil properties in a layer in

the upper part that is 18 cm or more thick. Some of these soils

contain a significant amount of volcanic ash, and some have an

umbric epipedon. Ground water commonly is present in the

soils only during winter. These soils have gentle slopes. They

are of small extent in the United States and are mostly in the

State of Washington. The native vegetation consists mostly of

coniferous forest. Most of these soils support native vegetation

and are used as forest. Some have been cleared and are used as

pasture or cropland.

Aquic Dystrudepts.—These soils have redox depletions

with low chroma in a brownish or reddish matrix in the

subsoil. Most of the soils also have redox concentrations with

high chroma. Ground water commonly is present only during

wet periods. Most of the Aquic Dystrudepts in the United

States formed in late-Pleistocene sediments and have gentle

slopes. Some of the soils have an umbric epipedon. Aquic

Dystrudepts are moderately extensive in the United States.

They are widely distributed. The largest concentration is in the

Northeastern States. The native vegetation consists mostly of

mixed forest. Many of these soils have been cleared and are

used as cropland or pasture, and many are used as forest.

Aquic Humic Dystrudepts.—These soils have redox

depletions with low chroma in a brownish or reddish matrix in

the subsoil and have an umbric or mollic epipedon. Most also

have redox concentrations with high chroma. Most of the

Aquic Humic Dystrudepts in the United States formed in latePleistocene sediments and have gentle slopes. Ground water

commonly is present only during wet periods unless the soils

are artificially drained. The native vegetation consists mostly

of mixed forest. Many of these soils are used as forest, and

many have been cleared and are used as cropland or pasture.

Fluvaquentic Dystrudepts.—These soils have redox

depletions with low chroma in a brownish matrix. They formed

in Holocene or recent alluvium. They are on flood plains along

rivers draining regions that have acid soils. During wet periods

ground water is present in the redox-depleted zone unless the

soils have been drained. Most of these soils are subject to

occasional flooding, but they receive little fresh sediment.

Some of the soils have an umbric epipedon. Fluvaquentic

Dystrudepts are moderately extensive in the United States.

They are widely distributed. The largest concentration is in the

Northeastern States. The native vegetation consists mostly of

mixed forest. Many of these soils have been cleared and are

used as cropland or pasture, and some are used as forest.

Fluventic Dystrudepts.—These soils are on flood plains

along rivers draining regions that have acid soils. They formed

in Holocene or recent alluvium. They are subject to occasional

flooding but receive little fresh alluvium. Fluventic Dystrudepts

are moderately extensive in the United States. They are widely

distributed. The largest concentration is in the Northeastern

States. The native vegetation consists mostly of mixed forest.

Most of these soils have been cleared and are used as cropland.

Some are used as pasture and some as forest.

Fluventic Humic Dystrudepts.—These soils are on flood
Inceptisols 523

plains along rivers draining regions that have acid soils. They

have an umbric or mollic epipedon and formed in Holocene or

recent alluvium. These soils are subject to occasional flooding

but receive little fresh alluvium. Fluventic Humic Dystrudepts

are of small extent in the United States. They are in Oregon

and the Nashville Basin and Appalachian valleys in the United

States. The native vegetation consists mostly of mixed forest.

Most of these soils have been cleared and are used as

intensively cultivated cropland. Some are used as pasture and

some as forest.

Fragiaquic Dystrudepts.—These soils are like Typic

Dystrudepts, but they have, at a shallow depth, redox

depletions with low chroma and also aquic conditions for some

time in normal years. In addition, they have fragic soil

properties in 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm of the

mineral soil surface or in 60 percent or more of the volume of a

layer 15 cm or more thick anywhere in the soils. These soils

are permitted to have a mollic or umbric epipedon. They are

considered intergrades to Fraqiaquepts. They are not extensive

in the United States.

Fragic Dystrudepts.—These soils have fragic soil

properties in 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm of the

mineral soil surface or in 60 percent or more of the volume of a

layer 15 cm or more thick anywhere in the soils. These soils

are considered intergrades to Fragiudepts. They are not

extensive in the United States.

Humic Dystrudepts.—These soils have an umbric or mollic

epipedon that is less than 50 cm thick. They are otherwise like

the soils of the Typic subgroup. Humic Dystrudepts are

moderately extensive in the United States. They are widely

distributed but are concentrated in the mountains of the

Eastern and Northwestern States. The native vegetation

consists mostly of mixed forest. Most of these soils are used as

forest. Many of the less sloping soils have been cleared and are

used as cropland or pasture.

Humic Lithic Dystrudepts.—These soils have a lithic

contact at a shallow depth and have an umbric or mollic

epipedon. They formed mostly in acid sedimentary or

metamorphic rocks. Most of the soils have moderate to steep

slopes. Humic Lithic Dystrudepts are moderately extensive in

the United States. They are widely distributed. The largest

concentration is in the Northwestern States. The native

vegetation consists mostly of coniferous forest. Most of these

soils are used as forest. Some of the less sloping soils have been

cleared and are used as pasture.

Humic Pachic Dystrudepts.—These soils have an umbric

or mollic epipedon 50 cm or more thick. They are otherwise

like the soils of the Typic subgroup. Humic Pachic Dystrudepts

are of small extent in the United States. They are widely

distributed but are concentrated in the mountains of the

Eastern and Northwestern States. The native vegetation

consists mostly of mixed forest. Most of these soils are used as

forest. Many of the less sloping soils have been cleared and are

used as cropland or pasture.

Humic Psammentic Dystrudepts.—These soils have an

umbric or mollic epipedon and a sandy particle-size class

throughout all layers at a depth between 25 and 100 cm below

the mineral soil surface. The soils are of small extent in the

United States. The native vegetation consists mostly of forest.

Most of these soils are used as forest. Some of the less sloping

soils have been cleared and are used as cropland or pasture.

Lamellic Dystrudepts.—These soils are like Typic

Dystrudepts, but they have two or more lamellae. They are not

extensive in the United States.

Lithic Dystrudepts.—These soils are like Typic

Dystrudepts, but they have a lithic contact at a shallow depth.

They formed mostly in acid sedimentary or metamorphic rocks.

Most of the soils have moderate to steep slopes. Lithic

Dystrudepts are extensive in the United States. They are widely

distributed. The largest concentration is in the Northeastern

States. The native vegetation consists mostly of mixed forest.

Most of these soils are used as forest. Some of the less sloping

soils have been cleared and are used as pasture.

Oxic Dystrudepts.—These soils have clays with a low

cation-exchange capacity dominant in the particle-size control

section. They are considered intergrades to Oxisols. Oxic

Dystrudepts are not extensive in the United States.

Oxyaquic Dystrudepts.—These soils are saturated with

water within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. The soils are moderately extensive in the United States.

They are considered intergrades to Aquepts. Slopes are gentle.

Many Oxyaquic Dystrudepts have been cleared and are used as

cropland or pasture. Some are used as forest.

Ruptic-Alfic Dystrudepts.—These soils have a cambic

horizon that includes 10 to 50 percent (by volume) illuvial

parts that otherwise meet the requirements for an argillic,

natric, or kandic horizon, and they have a base saturation of 35

percent or more at a depth of 125 cm below the top of the

argillic horizon or directly above a densic, lithic, or paralithic

contact if one is shallower than that depth. Most of these soils

are strongly sloping to steeply sloping, and in most of them the

depth to rock is less than 125 cm. The soils are of very small

extent in the United States.

Ruptic-Ultic Dystrudepts.—These soils have a cambic

horizon that includes 10 to 50 percent (by volume) illuvial

parts that otherwise meet the requirements for an argillic,

natric, or kandic horizon. Most of the soils are shallow over

weakly consolidated sedimentary rock. Generally, the illuvial

part of the cambic horizon is where the rock is deepest. The

base saturation is less than 35 percent. The native vegetation is

mostly hardwood forest. These soils generally are steeply

sloping, and they are used as forest or pasture. They are of

small extent in the United States.

Spodic Dystrudepts.—These soils have a weak

accumulation of amorphous materials. They are presumed to be
524 Soil Taxonomy

developing toward Spodosols, mainly Orthods, but are too

weakly developed to be classified as Spodosols. Spodic

Dystrudepts are of moderate extent in the United States. They

are mainly in the Northeastern States.

Vertic Dystrudepts.—These soils are high in expanding clays

and have cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower. The soils are

considered to be transitional to Vertisols. They are of very small

extent in the United States.

Eutrudepts

These are the base-rich Udepts of humid regions. Many

developed in Holocene or late-Pleistocene deposits. Some of the

soils that have steep slopes formed in older deposits. The

parent materials commonly are calcareous sediments or basic

sedimentary rocks. The vegetation was mostly deciduous

hardwoods, but the gently sloping soils are now cultivated and

many of the steeply sloping soils are used as pasture.

Eutrudepts are not extensive in the United States.

Definition

Eutrudepts are the Udepts that:

1. Have one or both of the following:

a. Free carbonates within the soils; or

b. A base saturation of 60 percent or more (by NH4OAc) in

some subhorizon that is between depths of 25 and 75 cm

below the mineral soil surface;

2. Do not have a fragipan or duripan with its upper boundary

within 100 cm of the mineral soil surface; and

3. Do not have a sulfuric horizon with its upper boundary

within 50 cm of the mineral soil surface.

Key to Subgroups

KFDA. Eutrudepts that have both:

1. An umbric or mollic epipedon; and

2. A lithic contact within 50 cm of the mineral soil

surface.

Humic Lithic Eutrudepts

KFDB. Other Eutrudepts that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Eutrudepts

KFDC. Other Eutrudepts that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. In one or more horizons within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage).

Aquertic Eutrudepts

KFDD. Other Eutrudepts that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Eutrudepts

KFDE. Other Eutrudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Eutrudepts

KFDF. Other Eutrudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Eutrudepts
Inceptisols 525

KFDG. Other Eutrudepts that have anthraquic conditions.

Anthraquic Eutrudepts

KFDH. Other Eutrudepts that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. In one or more horizons within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions in normal years (or artificial

drainage).

Fragiaquic Eutrudepts

KFDI. Other Eutrudepts that have a slope of less than 25

percent; and

1. In one or more horizons within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. Either:

a. At a depth of 125 cm below the mineral soil surface,

an organic-carbon content (Holocene age) of 0.2 percent

or more and no densic, lithic, or paralithic contact within

that depth; or

b. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a

densic, lithic, or paralithic contact, whichever is

shallower.

Fluvaquentic Eutrudepts

KFDJ. Other Eutrudepts that:

1. Have, in one or more horizons within 60 cm of the

mineral soil surface, redox depletions with chroma of 2 or

less and also aquic conditions for some time in normal years

(or artificial drainage); and

2. Do not have free carbonates throughout any horizon

within 100 cm of the mineral soil surface.

Aquic Dystric Eutrudepts

KFDK. Other Eutrudepts that have, in one or more horizons

within 60 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Eutrudepts

KFDL. Other Eutrudepts that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Eutrudepts

KFDM. Other Eutrudepts that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Eutrudepts

KFDN. Other Eutrudepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Eutrudepts

KFDO. Other Eutrudepts that have a slope of less than 25

percent; and

1. Do not have free carbonates throughout any horizon

within 100 cm of the mineral soil surface; and either

2. Have, at a depth of 125 cm below the mineral soil

surface, an organic-carbon content (Holocene age) of 0.2

percent or more and no densic, lithic, or paralithic contact

within that depth; or

3. Have an irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Dystric Fluventic Eutrudepts

KFDP. Other Eutrudepts that have a slope of less than 25

percent; and either

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene Age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluventic Eutrudepts

KFDQ. Other Eutrudepts that have a sandy or sandy-skeletal

particle-size class in all horizons within 50 cm of the mineral

soil surface.

Arenic Eutrudepts
526 Soil Taxonomy

KFDR. Other Eutrudepts that do not have free carbonates

throughout any horizon within 100 cm of the mineral soil

surface.

Dystric Eutrudepts

KFDS. Other Eutrudepts that have 40 percent or more free

carbonates, including coarse fragments as much as 75 mm in

diameter, in all horizons between the top of the cambic horizon

and either a depth of 100 cm from the mineral soil surface or a

densic, lithic, or paralithic contact if shallower.

Rendollic Eutrudepts

KFDT. Other Eutrudepts that have an umbric or mollic

epipedon.

Humic Eutrudepts

KFDU. Other Eutrudepts that have a cambic horizon that

includes 10 to 50 percent (by volume) illuvial parts that

otherwise meet the requirements for an argillic, kandic, or

natric horizon.

Ruptic-Alfic Eutrudepts

KFDV. Other Eutrudepts.

Typic Eutrudepts

Definition of Typic Eutrudepts

Typic Eutrudepts are the Eutrudepts that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 60 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Do not have anthraquic conditions;

4. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30 or

more cumulative days in normal years;

5. Have a texture of very fine sand or finer within 50 cm of the

soil surface;

6. Have free carbonates within 100 cm of the mineral soil

surface in some part of each pedon;

7. Have a slope of 25 percent or more or one or both of the

following:

a. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of less then 0.2

percent and no densic, lithic, or paralithic contact within

that depth; or

b. A regular decrease in organic-carbon content (Holocene

age) between a depth of 25 cm and either a depth of 125 cm

below the mineral soil surface or a densic, lithic, or

paralithic contact, whichever is shallower;

8. Do not have a lithic contact within 50 cm of the soil

surface;

9. Do not have a cambic horizon that includes 10 to 50

percent (by volume) illuvial parts that otherwise meet the

requirements for an argillic, kandic, or natric horizon;

10. Have neither an umbric nor a mollic epipedon;

11. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or

a densic, lithic, or paralithic contact, whichever is

shallower;

12. Have less than 40 percent free carbonates, including

coarse fragments as much as 75 mm in diameter, in and below

the cambic horizon but above a densic, lithic, or paralithic

contact and above a depth of 100 cm from the mineral soil

surface;

13. Do not have lamellae (two or more) within 200 cm of the

soil surface; and

14. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.
Inceptisols 527

Description of Subgroups

Typic Eutrudepts.—The central concept or Typic subgroup

of Eutrudepts is fixed on deep, more or less freely drained,

loamy or clayey soils that have an ochric epipedon and some

free carbonates, but not a large amount, within 100 cm of the

soil surface.

Soils that have a thin mantle or layer that has some andic

soil properties are excluded from the Typic subgroup because

they are considered to be an intergrade to Andisols. Soils that

have redox depletions with low chroma accompanied by

ground water at some time of the year or by artificial drainage

are excluded because they are intergrades to Aquepts. A surface

mantle of sand or loamy sand more than 50 cm thick is the

basis for defining the Arenic extragrade, a convention used in

many other taxa. Typic Eutrudepts have free carbonates above

a depth of 100 cm from the mineral soil surface. The absence

of free carbonates is used to define intergrades to Dystrudepts,

and the presence of 40 percent or more free carbonates

indicates a transition to Haprendolls. An irregular decrease in

content of organic carbon (Holocene age) with increasing depth

or a relatively high percentage in the deep layers is the basis

for defining intergrades to Fluvents or, if the soils are

periodically saturated with water, to Fluvaquents. A lithic

contact shallower than 50 cm defines the Lithic subgroup, a

convention used throughout this taxonomy. A cambic horizon

that includes 10 to 50 percent illuvial parts that otherwise meet

the requirements for an argillic, kandic, or natric horizon

indicates development toward Alfisols and defines the RupticAlfic subgroup. A high content of swelling clays accompanied

by deep cracks indicates intergrades to Vertisols. An umbric or

mollic epipedon is not considered typical and is used to define

Humic and combination Humic subgroups.

Typic Eutrudepts are of moderate extent in the United

States. They are widely distributed. The native vegetation

consists mostly of hardwood or mixed forest. Most of the

strongly sloping soils are used as forest. Many of the less

sloping soils have been cleared and are used as cropland or

pasture.

Andic and Vitrandic Eutrudepts.—These soils have some

andic soil properties in a layer 18 cm or more thick in the

upper part. In some of the soils, this layer was derived at least

in part from pyroclastic materials. Andic and Vitrandic

Eutrudepts are of small extent in the United States. They are

known to occur only in western Montana. The native

vegetation consists of coniferous forest. Most of these soils are

used as forest.

Anthraquic Eutrudepts.—These soils have been irrigated

for the production of paddy rice for many years and have

developed anthraquic conditions. They are permitted, but not

required, to have redox depletions with chroma of 2 or less in

layers that in normal years also have aquic conditions within

75 cm of the mineral soil surface. These soils have level or

nearly level slopes. They are not extensive and are not known to

occur in the United States.

Aquertic Eutrudepts.—These soils have redox depletions

with low chroma within 60 cm of the soil surface and either are

artificially drained or are saturated with water within the

redox-depleted zone at some time of the year. They have a high

COLE and do not have a densic, lithic, or paralithic contact

within 50 cm of the soil surface. These soils are not known to

occur in the United States.

Aquic Dystric Eutrudepts.—These soils have redox

depletions with low chroma above a depth of 60 cm and either

are artificially drained or are saturated with water in the redoxdepleted zone at some time of the year, usually in winter or

spring. In addition, they have no free carbonates to a depth of

100 cm below the mineral soil surface. These soils are of

moderate extent in the United States. Most formed in latePleistocene or Holocene sediments and are in the north-central

and northeastern parts of the United States. The native

vegetation consisted of forest. Most of these soils are nearly

level and have been cleared and are used as cropland or

pasture.

Aquic Eutrudepts.—These soils have redox depletions with

low chroma within 60 cm of the soil surface and either are

artificially drained or are saturated with water within the

redox-depleted zone at some time of the year, usually in winter

or spring. The soils are of small extent in the United States.

Most formed in late-Pleistocene sediments and are in the

Northeastern United States. The native vegetation consisted of

forest. Most of these soils are nearly level and have been

cleared and are used as cropland or pasture.

Arenic Eutrudepts.—These soils have a surface mantle of

sand or loamy sand that is more than 50 cm thick and is

underlain by a cambic horizon. In the United States, they

formed in late-Pleistocene sediments and have gentle or

moderate slopes. These soils are of very small extent in the

United States and are known to occur only in Michigan. The

native vegetation consists of mixed forest. Most of these soils

are used as forest.

Dystric Eutrudepts.—These soils have no free carbonates

above a depth of 100 cm from the mineral soil surface. In the

United States, they formed mostly in late-Pleistocene or

Holocene sediments. Some of the soils that have steep slopes

formed in older deposits. Dystric Eutrudepts are moderately

extensive in the United States. They are widely distributed. The

largest concentration is in the Northeastern States. The native

vegetation consists mostly of mixed forest. Most of these soils

are used as forest. Most of the less sloping soils have been

cleared and are used as cropland or pasture.

Dystric Fluventic Eutrudepts.—These soils formed in

alluvium on flood plains along streams and rivers. They do not

have free carbonates above a depth of 100 cm from the mineral

soil surface. They are subject to occasional overflow but receive

little fresh sediment. These soils are of moderate extent in the
528 Soil Taxonomy

Eastern United States. The native vegetation consists mostly of

forest. Most of these soils have been cleared and are used as

cropland. Some are used as pasture and some as forest.

Fluvaquentic Eutrudepts.—These soils formed mostly in

Holocene alluvium along streams. They have redox depletions

with low chroma within the upper 60 cm, and they either are

artificially drained or are saturated with water at some time of

the year, mostly when the streams are at flood stage. The soils

are subject to occasional overflow but receive little fresh

sediment. They are of moderate extent in the Eastern United

States. The native vegetation consisted mostly of forest. Nearly

all of the Fluvaquentic Eutrudepts in the United States have

been cleared and are used as cropland.

Fluventic Eutrudepts.—These soils formed in alluvium on

flood plains along streams and rivers. The content of organic

carbon (Holocene age) decreases irregularly with increasing

depth or is relatively high at a depth of 125 cm. The soils have

some free carbonates above a depth of 100 cm from the mineral

soil surface. Most are nearly level. These soils are of small

extent in the Eastern United States. The native vegetation

consisted mostly of forest. Nearly all of the Fluventic

Eutrudepts in the United States have been cleared and are used

as cropland.

Fragiaquic Eutrudepts.—These soils have, at a shallow

depth, redox depletions with low chroma and also aquic

conditions for some time in normal years. In addition, they

have fragic soil properties in 30 percent or more of the volume

of a layer 15 cm or more thick that has its upper boundary

within 100 cm of the mineral soil surface or in 60 percent or

more of the volume of a layer 15 cm or more thick anywhere in

the soils. These soils are considered intergrades to

Fraqiaquepts. They are not extensive in the United States.

Fragic Eutrudepts.—These soils have fragic soil properties

in 30 percent or more of the volume of a layer 15 cm or more

thick that has its upper boundary within 100 cm of the mineral

soil surface or in 60 percent or more of the volume of a layer

15 cm or more thick anywhere in the soils. The soils are

considered intergrades to Fraqiudepts. They are not extensive

in the United States.

Humic Eutrudepts.—These soils have an umbric or mollic

epipedon but are otherwise like Typic Eutrudepts. Humic

Eutrudepts are of moderate extent in the United States. They

are widely distributed. The largest concentration is in the

Northwestern States. The native vegetation consists mostly of

coniferous forest. Most of these soils are used as forest. A few

of the less sloping soils have been cleared and are used as

cropland or pasture.

Humic Lithic Eutrudepts.—These soils have an umbric or

mollic epipedon and a lithic contact within 50 cm of the

mineral soil surface. They are of small extent in the United

States. They are widely distributed. The largest concentration

is in the Eastern States. The native vegetation consists mostly

of mixed forest. Most of these soils are used as forest. A few of

the less sloping soils have been cleared and are used as pasture.

Lamellic Eutrudepts.—These soils have two or more lamellae

within 200 cm of the mineral soil surface. They are not extensive

in the United States.

Lithic Eutrudepts.—These soils have an ochric epipedon

and a lithic contact within 50 cm of the mineral soil surface.

They are of small extent in the United States. They are widely

distributed. The largest concentration is in the Northeastern

States. The native vegetation consists mostly of mixed forest.

Most of these soils are used as forest. A few of the less sloping

soils have been cleared and are used as pasture.

Oxyaquic Eutrudepts.—These soils are saturated with

water within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. They are of small extent in the United States. They are

considered intergrades to Aquepts. Slopes are gentle. Many

Oxyaquic Eutrudepts have been cleared and are used as

cropland or pasture. Some are used as forest.

Rendollic Eutrudepts.—These soils formed in marl, chalk,

shattered limestone, or shattered dolomite. They have more

than 40 percent calcium carbonate equivalent in some part

above 100 cm from the mineral soil surface. Fragments more

than 75 mm in diameter and solid limestone are excluded when

the content of carbonates is determined. These soils are

considered to be intergrades to Rendolls, and some of them

have developed from Haprendolls. Rendollic Eutrudepts are of

small extent in the United States. The native vegetation

consisted mostly of trees and grasses. Most the Rendollic

Eutrudepts in the United States have been cleared and are used

as hayland or pasture. Some of the soils, mostly the steeper

ones, are used as forest.

Ruptic-Alfic Eutrudepts.—These soils have a cambic

horizon that includes 10 to 50 percent illuvial parts that

otherwise meet the requirements for an argillic, kandic, or

natric horizon. The soils are moderately sloping or strongly

sloping and are shallow over calcareous, weakly consolidated

sedimentary rock or fractured limestone. The illuvial parts of

the cambic horizon are generally in the parts of the pedon

where the depth to rock is greatest. These soils are of small

extent in the United States. The native vegetation consisted

mostly of hardwood forest. Most of the Ruptic-Alfic Eutrudepts

in the United States have been cleared and are used as hayland

or pasture. Some of the soils, mostly the steeper ones, are used

as forest.

Vertic Eutrudepts.—These soils have a high COLE and do

not have a densic, lithic, or paralithic contact within 50 cm of

the soil surface. Most of the soils have gentle or moderate

slopes. Vertic Eutrudepts are of small extent in the United

States. The native vegetation consisted mostly of forest. Most

of the Vertic Eutrudepts in the United States have been cleared

and are used as cropland or pasture. Some are used as forest.
Inceptisols 529

Fragiudepts

These are the Udepts that have a fragipan within 100 cm of

the mineral soil surface. They do not have a sulfuric horizon

within 50 cm of the mineral soil surface. Commonly, they have

a brownish cambic horizon that is underlain, at a depth of

about 50 cm, by a fragipan. Most Fragiudepts have perched

water above the pan at some time of the year, and few roots

penetrate the pan. Consequently, plants tend to have shallow

root systems. Many Fragiudepts formed in late-Pleistocene or

Holocene deposits on gentle or moderate slopes. Some are

strongly sloping. The parent materials of most Fragiudepts are

loamy and either are acid or have only a small amount of free

carbonates. A few of the materials are sandy and have an

appreciable amount of fine sand and very fine sand. Most of

the Fragiudepts in the United States are in the Northeastern

States and the States bordering the Mississippi and Ohio

Rivers. A few are in the northern Lake States, and some are in

the humid parts of the Northwestern States. These soils are

extensive.

Definition

Fragiudepts are the Udepts that:

1. Have a fragipan within 100 cm of the mineral soil surface;

2. Do not have a sulfuric horizon within 50 cm of the mineral

soil surface; and

3. Do not have a duripan within 100 cm of the mineral soil

surface.

Key to Subgroups

KFCA. Fragiudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Fragiudepts

KFCB. Other Fragiudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more.

Vitrandic Fragiudepts

KFCC. Other Fragiudepts that have, in one or more horizons

within 30 cm of the mineral soil surface, distinct or prominent

redox concentrations and also aquic conditions for some time

in normal years (or artificial drainage).

Aquic Fragiudepts

KFCD. Other Fragiudepts that have an umbric or mollic

epipedon.

Humic Fragiudepts

KFCE. Other Fragiudepts.

Typic Fragiudepts

Definition of Typic Fragiudepts

Typic Fragiudepts are the Fragiudepts that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 30 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions; and

3. Do not have an umbric or mollic epipedon.

Description of Subgroups

Typic Fragiudepts.—The central concept or Typic

subgroup of Fragiudepts is fixed on soils that are free of

distinct or prominent redox concentrations in the upper 30 cm,

that have an ochric epipedon, and that do not have some andic

soil properties in a layer near the surface that is as thick as 18

cm.
530 Soil Taxonomy

A mantle of materials with andic soil properties between 18

and 35 cm thick indicates an intergrade to Andisols. Most

Typic Fragiudepts have perched ground water above the pan at

some time of the year. Shallow redox concentrations indicate

intergrades to Fragiaquepts and is the basis for defining the

Aquic subgroup.

Typic Fragiudepts are moderately extensive in the United

States. They occur mostly in the Northeastern States. The

native vegetation consists of mixed forest. Most of the less

sloping soils have been cleared and are used as cropland or

pasture. Some of the soils, mostly the steeper ones, are used as

forest.

Andic and Vitrandic Fragiudepts.—These soils have some

andic soil properties in a layer near the surface that is 18 cm or

more thick. This layer has many of the properties of Andisols.

Andic and Vitrandic Fragiudepts are not extensive and are not

known to occur in the United States.

Aquic Fragiudepts.—These soils have, at a shallow depth,

redox concentrations of medium or high contrast and are

somewhat wetter than Typic Fragiudepts. Commonly, they also

have gentler slopes. Aquic Fragiudepts are of small extent in

the United States. Most formed in late-Pleistocene sediments

and are in the Northeastern States. The native vegetation

consisted of forest. Most of these soils are nearly level and have

been cleared and are used as cropland or pasture.

Humic Fragiudepts.—These soils are like Typic Fragiudepts,

but they have a mollic or umbric epipedon. They are not

extensive and are rare in the United States.

Sulfudepts

These are extremely acid soils that formed in sulfidic materials

that have been exposed to aerobic conditions, mainly as a result

of surface mining, road construction, dredging, or other earthmoving operations. These soils are of small extent in the United

States.

Definition

Sulfudepts are the Udepts that have a sulfuric horizon within

50 cm of the mineral soil surface.

Key to Subgroups

KFAA. All Sulfudepts (provisionally).

Typic Sulfudepts

Ustepts

Ustepts are mainly the more or less freely drained

Inceptisols that have an ustic moisture regime. They receive

dominantly summer precipitation, or they have an isomesic,

hyperthermic, or warmer temperature regime. They formed

mostly in Pleistocene or Holocene deposits. Some of the soils

that have steep slopes formed in older deposits. Some Ustepts

formed from Mollisols by truncation of the mollic epipedon,

mostly under cultivation. Most Ustepts have an ochric epipedon

and a cambic horizon. Many are calcareous at a shallow depth

and have a Bk or calcic horizon. A few have a duripan or an

umbric epipedon. The native vegetation commonly was grass,

but some of the soils supported trees. Most of the soils are used

as cropland or pasture. Ustepts are of moderate extent in the

United States. They are most common on the Great Plains,

mostly in Montana, Texas, and Oklahoma.

Definition

Ustepts are the Inceptisols that:

1. Have an ustic moisture regime;

2. Do not have, in a layer above a densic, lithic, or paralithic

contact or in a layer at a depth between 40 and 50 cm from the

mineral soil surface, whichever is shallower, aquic conditions

for some time in normal years and one or more of the

following:

a. A histic epipedon; or

b. A sulfuric horizon that has its upper boundary within

50 cm of the mineral soil surface; or

c. A layer directly under the epipedon, or within 50 cm of

the mineral soil surface, that has, on faces of peds or in the

matrix if peds are absent, 50 percent or more chroma of

either:

(1) 2 or less if there are redox concentrations; or

(2) 1 or less; or

d. Within 50 cm of the mineral soil surface, enough active

ferrous iron to give a positive reaction to alpha,alphadipyridyl at a time when the soil is not being irrigated;

3. Do not have an exchangeable sodium percentage (ESP)

of 15 or more (or a sodium adsorption ratio [SAR] of 13 or

more) in half or more of the soil volume within 50 cm of the

mineral soil surface, a decrease in ESP (or SAR) values with

increasing depth below 50 cm, and ground water within 100

cm of the mineral soil surface for some time during the year;

4. Have neither a plaggen nor an anthropic epipedon; and

5. Have a soil temperature regime warmer than cryic.

Key to Great Groups

KDA. Ustepts that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Durustepts, p. 533

KDB. Other Ustepts that both:

1. Have a calcic horizon with its upper boundary

within 100 cm of the mineral soil surface or a petrocalcic
Inceptisols 531

horizon that has its upper boundary within 150 cm of the

mineral soil surface; and

2. Are either calcareous or have a texture of loamy fine sand

or coarser in all parts above the calcic or petrocalcic horizon,

after the soil between the mineral soil surface and a depth of

18 cm has been mixed.

Calciustepts, p. 531

KDC. Other Ustepts that have both of the following:

1. No free carbonates within 200 cm of the mineral soil

surface; and

2. A base saturation (by NH4OAc) of less than 60 percent

in all horizons at a depth between 25 and 75 cm from the

mineral soil surface.

Dystrustepts, p. 534

KDD. Other Ustepts.

Haplustepts, p. 536

Calciustepts

These are the Ustepts that have a calcic or petrocalcic

horizon and that are calcareous or have a sandy particle-size

class in all overlying horizons. The soils do not have a duripan.

The precipitation has been insufficient to remove the

carbonates from the upper horizons, or there is a continuing

external source of carbonates in dust or water.

Calciustepts formed mostly in Pleistocene or older

materials. On the Calciustepts in the United States, the

vegetation was dominantly grass before the soils were

cultivated. The soils are most extensive on the Great Plains in

the United States, but some are in the intermountain valleys of

the Western States.

Definition

Calciustepts are the Ustepts that:

1. Have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface or a petrocalcic

horizon that has its upper boundary within 150 cm of the

mineral soil surface and are calcareous in all parts of all

horizons above the calcic or petrocalcic horizon, after the

upper part of the soil to a depth of 18 cm has been mixed,

unless the texture is coarser than loamy very fine sand or very

fine sand; and

2. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Key to Subgroups

KDBA. Calciustepts that have a petrocalcic horizon and a

lithic contact within 50 cm of the mineral soil surface.

Lithic Petrocalcic Calciustepts

KDBB. Other Calciustepts that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Calciustepts

KDBC. Other Calciustepts that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the temperature

at a depth of 50 cm below the soil surface is higher

than 5 oC.

Torrertic Calciustepts

KDBD. Other Calciustepts that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or
532 Soil Taxonomy

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Calciustepts

KDBE. Other Calciustepts that have a petrocalcic horizon

that has its upper boundary within 100 cm of the mineral soil

surface.

Petrocalcic Calciustepts

KDBF. Other Calciustepts that have a gypsic horizon that has

its upper boundary within 100 cm of the mineral soil surface.

Gypsic Calciustepts

KDBG. Other Calciustepts that have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Calciustepts

KDBH. Other Calciustepts that have, when neither irrigated

nor fallowed to store moisture, one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for six-tenths or more of the cumulative days per

year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some or all parts for six-tenths or more of

the cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Calciustepts

KDBI. Other Calciustepts that have, when neither irrigated

nor fallowed to store moisture, either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for four-tenths or less of the consecutive days per

year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil temperature

regime and a moisture control section that in normal years is

dry in some or all parts for fewer than 120 cumulative days

per year when the temperature at a depth of 50 cm below the

soil surface is higher than 8 o

C.

Udic Calciustepts

KDBJ. Other Calciustepts.

Typic Calciustepts

Definition of Typic Calciustepts

Typic Calciustepts are the Calciustepts that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface;

3. Do not have a gypsic horizon that has its upper boundary

within 100 cm of the mineral soil surface;

4. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

5. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less than

four-tenths of the cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for more than four-tenths but less than six-tenths

of the cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is moist in some or all parts for 90 or more

consecutive days per year or is dry for less than six-tenths of

the cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC

and is dry for more than 120 cumulative days per year when

the temperature at a depth of 50 cm below the soil surface is

higher than 8 oC; and

6. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or
Inceptisols 533

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Calciustepts.—The central concept or Typic

subgroup of Calciustepts is fixed on more or less freely drained

soils that have a calcic rather than a petrocalcic horizon and

that do not have slickensides, wedge-shaped aggregates, a high

linear extensibility, or wide cracks in normal years.

Redox concentrations and a ground water table that

fluctuates within 75 cm of the mineral soil surface are

properties shared with Aquolls and define the Aquic subgroup.

A shallow lithic contact defines the Lithic subgroup, a

convention used throughout this taxonomy. A petrocalcic

horizon indicates development more intensive than normal and

defines the Petrocalcic subgroup. Slickensides, wedge-shaped

aggregates, a high linear extensibility, and wide cracks that are

evident in normal years are characteristics of Vertisols and are

used to define the Vertic subgroup.

Typic Calciustepts are of small extent in the United States.

They are mostly on the northern Great Plains, in Montana and

South Dakota. Many of these soils supported grasses and

shrubs. Most of the soils on plains are now used as cropland.

Aquic Calciustepts.—These soils have redox depletions

with low chroma and either have shallow ground water at some

time of the year or are artificially drained. Color value and

chroma of these soils commonly are lower than those of Typic

Calciustepts. Aquic Calciustepts developed mostly in nearly

level upland areas that commonly are concave. They are of very

small extent in the United States.

Aridic Calciustepts.—These soils are drier than Typic

Calciustepts. They generally receive less precipitation than the

soils of the Typic subgroup, or they lose more water through

runoff. Aridic Calciustepts are of moderately large extent and

are widely distributed in the Western United States. The largest

extent is in the western part of the Great Plains. Slopes range

from nearly level to steep. In the United States, many of the

soils that have suitable slopes are used as cropland. If the

temperature regime is frigid or mesic, many are fallowed in

alternate years to store moisture. Some are irrigated, and most

of the more sloping soils are used as pasture.

Gypsic Calciustepts.—These soils have a gypsic horizon in

addition to the calcic horizon. In most of these soils, the gypsic

horizon is in the lower part of or below the calcic horizon.

These soils are of very small extent in the United States. They

are mostly on the southern Great Plains.

Lithic Calciustepts.—These soils have a shallow lithic

contact. They are of small extent in the United States. They are

mostly in the Western States. They have moderate to very steep

slopes. The vegetation is mostly grass and shrubs, but a few of

the soils support forest vegetation. Lithic Calciustepts are used

mainly as pasture or forest.

Lithic Petrocalcic Calciustepts.—These soils have a

petrocalcic horizon overlying hard bedrock within a depth of

50 cm. Typically, the fractures in the underlying bedrock are

filled with cemented secondary carbonates. Most of these soils

are drier than Typic Calciustepts. Slopes are gentle. Lithic

Petrocalcic Calciustepts formed on surfaces older than the

Pleistocene. They occur locally in Texas. They are used mainly

as pasture.

Petrocalcic Calciustepts.—These soils have a petrocalcic

horizon. In some of the soils, depth to the petrocalcic horizon

is less than 50 cm. Some of the soils that have a petrocalcic

horizon below a depth of 50 cm are underlain by hard bedrock.

Petrocalcic Calciustepts are of small extent on the southern

Great Plains of the United States. The largest extent is in

Texas. Most of the soils are used as pasture.

Torrertic Calciustepts.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. Also, the soils are drier than

Vertic Calciustepts. Torrertic Calciustepts are of very small

extent in the United States.

Udic Calciustepts.—These soils are more moist than Typic

Calciustepts and in most areas receive more precipitation. Udic

Calciustepts are of small extent and are known to occur only in

Texas. The native vegetation is mostly grasses and shrubs.

Slopes generally are gentle. Most of these soils are used as

cropland.

Vertic Calciustepts.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They formed mostly in

material weathered from smectite-rich shale or from limestone.

They are of small extent. The native vegetation was mostly

grasses.

Durustepts

These are the Ustepts that have a duripan with its upper

boundary within 100 cm of the soil surface. Commonly, these

soils formed in the vicinity of volcanic cinders and ash falls.

The parent materials are mainly volcanic tuffs, ash, cinders,

and volcanic rocks. In the United States, the native vegetation

is mostly grasses, shrubs, and trees. These soils are of small

extent. They formed mainly in areas of Pleistocene deposits.

They may be also on the leeward sides of some volcanic

islands.

Definition

Durustepts are the Ustepts that have a duripan that

has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

KDAA. All Durustepts (provisionally).

Typic Durustepts
534 Soil Taxonomy

Dystrustepts

These are the acid Ustepts. They developed mostly in

Pleistocene or Holocene deposits. Some of the soils that have

steep slopes formed in older deposits. The parent materials

generally are acid, moderately or weakly consolidated

sedimentary or metamorphic rocks or acid sediments. The

vegetation was mostly forest. Most of these soils have a thermic

or warmer temperature regime.

A common horizon sequence in Dystrustepts is an ochric or

umbric epipedon over a cambic horizon. Some of the steeper

soils have a shallow densic, lithic, or paralithic contact.

Dystrustepts are of very small extent in the United States.

Definition

Dystrustepts are the Ustepts that:

1. Do not have free carbonates within the soils;

2. Have a base saturation of less than 60 percent (by

NH4OAc) in all subhorizons between depths of 25 and 75 cm

below the soil surface;

3. Do not have a duripan that has an upper boundary

within 100 cm of the mineral soil surface; and

4. Do not meet both of the following:

a. Have a calcic horizon with its upper boundary within

100 cm of the mineral soil surface or a petrocalcic horizon

with its upper boundary within 150 cm of the mineral soil

surface; and

b. Either have a texture of loamy fine sand or coarser in

all parts above the calcic or petrocalcic horizon or are

calcareous after the soil between the mineral soil surface

and a depth of 18 cm has been mixed.

Key to Subgroups

KDCA. Dystrustepts that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Dystrustepts

KDCB. Other Dystrustepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Dystrustepts

KDCC. Other Dystrustepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Dystrustepts

KDCD. Other Dystrustepts that have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Dystrustepts

KDCE. Other Dystrustepts that have a slope of less than 25

percent; and either

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluventic Dystrustepts

KDCF. Other Dystrustepts that have in 50 percent or more of

the soil volume between a depth of 25 cm from the mineral soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact if shallower:

1. A CEC (by 1N NH4

OAc pH 7) of less than 24 cmol(+)

per kg clay; or

2. Both a ratio of measured clay in the fine-earth fraction

to percent water retained at 1500 kPa tension of 0.6 or more

and the following: the CEC (by 1N NH4OAc pH 7) divided

by the product of three times [percent water retained at 1500

kPa tension minus percent organic carbon (but no more than

1.00)] is less than 24.

Oxic Dystrustepts

KDCG. Other Dystrustepts that have an umbric or mollic

epipedon.

Humic Dystrustepts

KDCH. Other Dystrustepts.

Typic Dystrustepts
Inceptisols 535

Definition of Typic Dystrustepts

Typic Dystrustepts are the Dystrustepts that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size, of

1.0 g/cm3

 or less, measured at 33 kPa water retention, and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Have a slope of 25 percent or more; or

a. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of less than 0.2

percent or a densic, lithic, or paralithic contact within that

depth; or

b. A regular decrease in organic-carbon content (Holocene

age) between a depth of 25 cm and either a depth of 125 cm

below the mineral soil surface or a densic, lithic, or

paralithic contact, whichever is shallower;

4. Do not have a lithic contact within 50 cm of the mineral

soil surface;

5. Do not have an umbric or mollic epipedon; and

6. Do not have, in 50 percent or more of the soil volume

between a depth of 25 cm from the mineral soil surface and

either a depth of 100 cm or a densic, lithic, or paralithic

contact if shallower, either:

a. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+)

per kg clay; or

b. Both a ratio of measured clay in the fine-earth fraction

to percent water retained at 1500 kPa tension of 0.6 or more

and the following: the CEC (by 1N NH4OAc pH 7) divided

by the product of three times [percent water retained at 1500

kPa tension minus percent organic carbon (but no more than

1.00)] is less than 24.

Description of Subgroups

Typic Dystrustepts.—The central concept or Typic subgroup

of Dystrustepts is fixed on soils that are moderately deep or

deep to hard rock, are freely drained, are acid, and have an

ochric epipedon. In addition, the percentage of organic carbon

of Holocene age decreases regularly with increasing depth and

is very low at a depth of 125 cm.

If the percentage of organic carbon is relatively high at a

depth of 125 cm or if the percentage decreases irregularly with

increasing depth and slopes are gentle, the parent material

normally is recent Holocene alluvium. The soils that formed in

this alluvium are considered intergrades to Fluvents. A shallow

water table and redox depletions with low chroma indicate

intergrades to Aquepts. A lithic contact within a depth of 50

cm is the basis for defining the Lithic subgroup. The presence

of an umbric or mollic epipedon is used to define the Humic

subgroup. Soils that have a thin mantle or layer that has some

andic soil properties are excluded from the Typic subgroup

because they are considered to be an intergrade to Andisols.

Soils with a low CEC in the clay fraction are considered

intergrades to Oxisols.

Typic Dystrustepts are of very small extent in the United

States and are known to occur only on tropical islands.

Andic and Vitrandic Dystrustepts.—These soils have

some andic soil properties in a layer 18 cm or more thick in the

upper part. Some of the soils contain a significant amount of

volcanic ash, and some have an umbric epipedon. Andic and

Vitrandic Dystrustepts are not known to occur in the United

States.

Aquic Dystrustepts.—These soils have redox depletions

with low chroma in a brownish or reddish matrix in the

subsoil. Most of the soils also have concentrations with high

chroma. Ground water is present during wet periods unless the

soils are artificially drained. Some of these soils have an

umbric epipedon. Aquic Dystrustepts are not known to occur in

the United States.

Fluventic Dystrustepts.—These soils are on flood plains

along rivers draining regions that have acid soils. They formed

in Holocene or recent alluvium. They are subject to occasional

flooding but receive little fresh alluvium. These soils are rare

in the United States.

Humic Dystrustepts.—These soils have an umbric or

mollic epipedon but are otherwise like the soils of the Typic

subgroup. Humic Dystrustepts are known to occur only on

tropical islands in the United States.

Lithic Dystrustepts.—These soils have a lithic contact at a

shallow depth. They formed mostly in material weathered from

acid rocks. Most of the soils have moderate to steep slopes.

Lithic Dystrustepts are not known to occur in the United

States.
536 Soil Taxonomy

Oxic Dystrustepts.—These soils have clays with a low

cation-exchange capacity dominant in the particle-size control

section. They are considered intergrades to Oxisols. Oxic

Dystrustepts are not extensive in the United States.

Haplustepts

These are the more or less freely drained Ustepts that are

calcareous at some depth or have a high base status. Some of

the soils have a Bk or calcic horizon, but they do not have both

a calcic or petrocalcic horizon and a sandy particle-size class or

carbonates in all horizons above the calcic or petrocalcic

horizon. The native vegetation commonly was grass, but some

of the soils supported trees. Haplustepts are not extensive in the

United States, except locally on the Great Plains.

Definition

Haplustepts are the Ustepts that:

1. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface;

2. Do not have both:

a. A calcic horizon with its upper boundary within 100 cm

of the mineral soil surface or a petrocalcic horizon with its

upper boundary within 150 cm of the mineral soil surface;

and

b. Either free carbonates or a texture of loamy fine sand or

coarser in all parts above the calcic or petrocalcic horizon,

after the soil between the mineral soil surface and a depth of

18 cm has been mixed; and

3. Have:

a. Free carbonates within 200 cm of the mineral soil

surface; or

b. A base saturation (by NH4OAc) of 60 percent or more in

some horizon at a depth between 25 and 75 cm from the

mineral soil surface.

Key to Subgroups

KDDA. Haplustepts that have:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. When neither irrigated nor fallowed to store moisture,

either:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days per

year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

5 oC.

Aridic Lithic Haplustepts

KDDB. Other Haplustepts that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Haplustepts

KDDC. Other Haplustepts that have both:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid soil temperature regime and a moisture

control section that in normal years is dry in some or all

parts for fewer than 105 cumulative days per year when

the temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for less than four-tenths of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a
Inceptisols 537

densic, lithic, or paralithic contact, whichever is

shallower.

Udertic Haplustepts

KDDD. Other Haplustepts that have both:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid soil temperature regime and a moisture

control section that in normal years is dry in all parts for

four-tenths or more of the cumulative days per year when

the temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

5 oC; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Torrertic Haplustepts

KDDE. Other Haplustepts that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haplustepts

KDDF. Other Haplustepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Haplustepts

KDDG. Other Haplustepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Haplustepts

KDDH. Other Haplustepts that have anthraquic conditions.

Anthraquic Haplustepts

KDDI. Other Haplustepts that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Haplustepts

KDDJ. Other Haplustepts that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplustepts

KDDK. Other Haplustepts that have in 50 percent or more of

the soil volume between a depth of 25 cm from the mineral soil

surface and either a depth of 100 cm or a densic, lithic, or

paralithic contact if shallower:

1. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+)

per kg clay; or
538 Soil Taxonomy

2. Both a ratio of measured clay in the fine-earth fraction to

percent water retained at 1500 kPa tension of 0.6 or more and

the following: the CEC (by 1N NH4

OAc pH 7) divided by the

product of three times [percent water retained at 1500 kPa

tension minus percent organic carbon (but no more than

1.00)] is less than 24.

Oxic Haplustepts

KDDL. Other Haplustepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Haplustepts

KDDM. Other Haplustepts that have a slope of less than 25

percent; and

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid soil temperature regime and a moisture

control section that in normal years is dry in all parts for

four-tenths or more of the cumulative days per year when

the temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

5 oC; and

2. Either:

a. At a depth of 125 cm below the mineral soil surface,

an organic-carbon content (Holocene age) of 0.2 percent

or more and no densic, lithic, or paralithic contact within

that depth; or

b. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a

densic, lithic, or paralithic contact, whichever is

shallower.

Torrifluventic Haplustepts

KDDN. Other Haplustepts that have a slope of less than 25

percent; and

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid soil temperature regime and a moisture control

section that in normal years is dry in some or all parts for

fewer than 105 cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for less than four-tenths of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

2. Either:

a. At a depth of 125 cm below the mineral soil surface,

an organic-carbon content (Holocene age) of 0.2 percent

or more and no densic, lithic, or paralithic contact within

that depth; or

b. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a

densic, lithic, or paralithic contact, whichever is

shallower.

Udifluventic Haplustepts

KDDO. Other Haplustepts that have a slope of less than 25

percent; and either

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluventic Haplustepts

KDDP. Other Haplustepts that have a gypsic horizon that

has its upper boundary within 100 cm of the mineral soil

surface.

Gypsic Haplustepts
Inceptisols 539

KDDQ. Other Haplustepts that have both:

1. A calcic horizon that has its upper boundary within 100

cm of the mineral soil surface; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid soil temperature regime and a moisture

control section that in normal years is dry in all parts for

four-tenths or more of the cumulative days per year when

the temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than

5 oC.

Haplocalcidic Haplustepts

KDDR. Other Haplustepts that have both:

1. A calcic horizon that has its upper boundary within 100

cm of the mineral soil surface; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid soil temperature regime and a moisture

control section that in normal years is dry in some or all

parts for fewer than 105 cumulative days per year when

the temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for less than four-tenths of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC.

Calcic Udic Haplustepts

KDDS. Other Haplustepts that have a calcic horizon that has

its upper boundary within 100 cm of the mineral soil surface.

Calcic Haplustepts

KDDT. Other Haplustepts that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the cumulative days per year

when the temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some part for six-tenths or more of the

cumulative days per year when the temperature at a depth

of 50 cm below the soil surface is higher than 5 oC.

Aridic Haplustepts

KDDU. Other Haplustepts that have a base saturation (by

sum of cations) of less than 60 percent in some horizon

between either an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and either a depth of

75 cm below the mineral soil surface or a densic, lithic, or

paralithic contact, whichever is shallower.

Dystric Haplustepts

KDDV. Other Haplustepts that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime and a moisture control

section that in normal years is dry in some or all parts for

fewer than 105 cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a moisture

control section that in normal years is dry in some part for
540 Soil Taxonomy

less than four-tenths of the cumulative days per year when

the temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

3. A hyperthermic, isomesic, or warmer iso soil temperature

regime and a moisture control section that in normal years is

dry in some or all parts for fewer than 120 cumulative days

per year when the temperature at a depth of 50 cm below the

soil surface is higher than 8 oC.

Udic Haplustepts

KDDW. Other Haplustepts.

Typic Haplustepts

Definition of Typic Haplustepts

Typic Haplustepts are the Haplustepts that:

1. Either have a content of organic carbon (Holocene age)

that decreases regularly with increasing depth and, unless a

densic, lithic, or paralithic contact occurs at a shallower depth,

reaches a level of 0.2 percent or less within 125 cm of the soil

surface or have a slope of more than 25 percent;

2. Do not have a lithic contact within 50 cm of the surface;

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

4. Do not have anthraquic conditions;

5. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

6. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid soil temperature regime and a moisture control

section that in normal years is dry in some or all parts for

105 or more cumulative days per year but is not dry in all

parts for four-tenths or more of the cumulative days per year

when the temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for four-tenths to six-tenths of the cumulative days per

year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for 90 or more

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

(2) Is dry in some part for a period between 120

cumulative days and six-tenths of the cumulative days

per year when the temperature at a depth of 50 cm below

the soil surface is higher than 5 oC;

7. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

8. Have a base saturation (by sum of cations) of more than 60

percent in all horizons between either an Ap horizon or a depth

of 25 cm from the mineral soil surface, whichever is deeper,

and either a depth of 75 cm or a densic, lithic, or paralithic

contact, whichever is shallower;

9. Do not have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface;

10. Do not have a gypsic horizon that has its upper boundary

within 100 cm of the mineral soil surface;

11. Do not have lamellae (two or more) within 200 cm of the

soil surface;

12. Have in less than 50 percent of the soil volume between a

depth of 25 cm from the mineral soil surface and either a depth

of 100 cm or a densic, lithic, or paralithic contact if shallower:

a. A CEC (by 1N NH4OAc pH 7) of less than 24 cmol(+)

per kg clay; or

b. Both a ratio of measured clay in the fine-earth fraction
Inceptisols 541

to percent water retained at 1500 kPa tension of 0.6 or more

and the following: the CEC (by 1N NH4

OAc pH 7) divided by

the product of three times [percent water retained at 1500 kPa

tension minus percent organic carbon (but no more than

1.00)] is less than 24; and

13. Are not saturated with water in one or more layers

within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years.

Description of Subgroups

Typic Haplustepts.—The central concept or Typic

subgroup of Haplustepts is fixed on thick soils that have a high

base saturation throughout layers below the surface layer but do

not have a calcic horizon. The soils are dry for moderate

periods in normal years.

Gently sloping and nearly level Haplustepts are excluded

from the Typic subgroup if the content of organic carbon

(Holocene age) decreases irregularly with increasing depth or

remains relatively high in the deep layers. These soils have

some of the properties of Fluvents. Soils that have a lithic

contact shallower than 50 cm are excluded from the Typic

subgroup, a convention used throughout this taxonomy. Clayey

soils that have expanding clays and deep cracks are excluded

because they have some properties of Vertisols.

Typic Haplustepts are of large extent on the plains of the

Western United States. They are widely distributed from

Montana to Texas. Most of the soils are gently sloping to

strongly sloping. The native vegetation consists mostly of

grass, shrubs, and trees. Most of the strongly sloping soils are

used as rangeland or forest. Most of the less sloping soils have

been cleared and are used as cropland or pasture.

Andic and Vitrandic Haplustepts.—These soils have some

andic soil properties in a layer 18 cm or more thick in the

upper part and have many of the properties of Andisols. In

some of these soils, this layer was derived at least in part from

pyroclastic materials. Andic and Vitrandic Haplustepts are of

small extent in the United States. They are known to occur

only in western Montana. The native vegetation consists of

coniferous forest. Most of these soils are used as forest.

Anthraquic Haplustepts.—These soils have been irrigated

for the production of paddy rice for many years and have

developed redoximorphic features in the upper part. They are

permitted, but not required, to have redox depletions with

chroma of 2 or less in layers that also have aquic conditions in

normal years within 75 cm of the mineral soil surface. These

soils are not extensive and are not known to occur in the

United States. They have level or nearly level slopes.

Aquic Haplustepts.—These soils have redox depletions

with low chroma commonly in a brownish or reddish matrix in

the subsoil. Redox concentrations with high chroma also are

common. Most of the Aquic Haplustepts in the United States

have nearly level or gentle slopes. Ground water is present

during wet periods unless the soils are artificially drained. These

soils are of small extent in the United States and are widely

distributed on the Great Plains from Montana to Texas. The

native vegetation consists mostly of trees or widely spaced

trees and grass. Most of these soils have been cleared and are

used as pasture.

Aridic Haplustepts.—These soils receive less moisture

than the soils of the Typic subgroup but otherwise are like them

in defined properties. In general, the depth to carbonates is less

than that in the soils of the Typic subgroup. Aridic Haplustepts

are extensive in the western part of the Great Plains in the

United States. Slopes range from gentle to steep. Most of these

soils are used as rangeland. Where slopes are suitable, many of

the soils are used as cropland.

Aridic Lithic Haplustepts.—These soils have a lithic

contact within 50 cm of the soil surface and receive less

moisture than the soils of the Typic subgroup. The vegetation is

mostly grass and shrubs. Slopes are gentle to steep. Aridic

Lithic Haplustepts are used as rangeland or wildlife habitat.

Calcic Haplustepts.—These soils have a calcic horizon but

otherwise are like Typic Haplustepts in defined properties.

Calcic Haplustepts are of small extent on the Great Plains of

the United States. The native vegetation consists mostly of

grass and shrubs but in some areas is coniferous forest. Most of

these soils are used as rangeland or forest. Where slopes are

suitable, some of the soils are used as cropland or pasture.

Calcic Udic Haplustepts.—These soils receive more

moisture than the soils of the Typic subgroup and have a calcic

horizon. Calcic Udic Haplustepts are of small extent in the

southern part of the Great Plains in the United States. The

native vegetation consists mostly of grass, shrubs, and widely

spaced trees. Slopes generally are gentle. Most of these soils

are used as rangeland or pasture.

Dystric Haplustepts.—These soils have a base saturation of

less than 60 percent in some horizon between either an Ap

horizon or a depth of 25 cm from the mineral soil surface,

whichever is deeper, and a depth of 75 cm or a densic, lithic, or

paralithic contact, whichever is shallower. Some of the soils

have free carbonates at some depth within 200 cm of the soil

surface. Dystric Haplustepts are known to occur only on

tropical islands in the United States. They are of very small

extent.

Fluventic Haplustepts.—These soils formed in alluvium.

Slopes are gentle, and coarse stratification is common. These

soils are of small extent in the southern part of the Great Plains

in the United States. The native vegetation consisted mostly of

grass and widely spaced trees. Most of these soils are used as

cropland, rangeland, or pasture.

Gypsic Haplustepts.—These soils have a gypsic horizon

within 100 cm of the mineral soil surface. They are of very

small extent in the United States.

Haplocalcidic Haplustepts.—These soils receive less

moisture than the soils of the Typic subgroup and have a calcic

horizon. They are extensive in the western part of the Great
542 Soil Taxonomy

Plains and on foothills of the Rocky Mountains in the United

States. The native vegetation consists mostly of grass and

shrubs, but it includes pinyon pine and juniper trees in Arizona.

Slopes range from gentle to steep. Most of these soils are used

as rangeland or grazed forest. Where slopes are suitable, some

of the soils are used as cropland.

Lamellic Haplustepts.—These soils are like Typic

Haplustepts, but they have two or more lamellae. They are not

extensive in the United States.

Lithic Haplustepts.—These soils have a lithic contact

within 50 cm of the soil surface. Slopes are gentle to very

steep. These soils are of moderate extent on the plains and

foothills of the Western United States. They are widely

distributed from Montana to Texas. The native vegetation

consists mostly of grass, shrubs, and trees. Most of these soils

are used as rangeland or grazed forest. A few of the less

sloping soils have been cleared and are used as cropland or

pasture.

Oxic Haplustepts.—These soils have a cambic horizon that

approaches the properties of an oxic horizon but are otherwise

like Typic Haplustepts in defined properties. Oxic Haplustepts

are of very small extent in the United States. They occur mostly

on tropical or semitropical islands. The native vegetation

consists mostly of trees and shrubs. Most of these soils are used

as forest. Where slopes are suitable, some of the soils have been

cleared and are used as cropland or pasture.

Oxyaquic Haplustepts.—These soils are saturated with

water within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. The soils are of very small extent in the United States.

They are considered intergrades to Aquepts.

Torrertic Haplustepts.—These soils receive less moisture

than the soils of the Typic subgroup. They are clayey and have

deep cracks at some season in most years, a property that is

shared with Torrerts. Torrertic Haplustepts generally are nearly

level or gently sloping. They are of small extent in the United

States and occur on the Great Plains from Montana to

Oklahoma. The native vegetation consists of grass and shrubs.

Most of these soils are used as rangeland, but some are used as

cropland, some of which is irrigated.

Torrifluventic Haplustepts.—These soils formed in

alluvium and receive less moisture than the soils of the

Fluventic and Typic subgroups. In general, the depth to free

carbonates is less than that in the soils in these subgroups.

Torrifluventic Haplustepts are of very small extent in the

United States. They are mostly in the western part of the Great

Plains.

Udertic Haplustepts.—These soils receive more moisture

than the soils of the Typic subgroup. They are clayey and have

deep cracks at some season in most years, a property that is

shared with Usterts. Udertic Haplustepts generally are nearly

level to sloping. They are of small extent and are known to

occur only in Texas in the United States. The native vegetation

consists of hardwood forest or grass and widely spaced trees.

Most of these soils are used as rangeland or hayland.

Udic Haplustepts.—These soils receive more moisture than

the soils of the Typic subgroup. They are otherwise like Typic

Haplustepts. Udic Haplustepts are of small extent in the United

States. They occur mostly on the southern Great Plains. Where

slopes are suitable, the soils are used mainly as cropland.

Udifluventic Haplustepts.—These soils formed in alluvium

and receive more moisture than the soils of the Typic subgroup.

Udifluventic Haplustepts are of small extent in the southern

part of the Great Plains in the United States. The native

vegetation consists of hardwood forest or grass and widely

spaced trees. Most of these soils are used as cropland or

rangeland or for pecan orchards.

Vertic Haplustepts.—These soils are clayey and have deep

cracks at some season in normal years, a property that is shared

with Usterts. Vertic Haplustepts generally are nearly level to

sloping. They are of moderate extent and occur on the Great

Plains from South Dakota to Texas in the United States. The

native vegetation consists mostly of grass and some shrubs and

widely spaced trees. Most of these soils are used as rangeland

or cropland.

Xerepts

Xerepts are mainly the more or less freely drained Inceptisols

that have a xeric moisture regime. They have a frigid, mesic, or

thermic temperature regime. They formed mostly in Pleistocene

or Holocene deposits. Some of the soils, mostly the ones that

have steep slopes, formed in older deposits. Most of the soils

have an ochric epipedon and a cambic horizon. Some have an

umbric epipedon or a duripan, and a few have a fragipan. Some

are calcareous at a shallow depth and have a Bk or calcic

horizon. The native vegetation commonly is coniferous forest on

the soils that have a frigid or mesic temperature regime and

shrubs, grass, and widely spaced trees on the soils that have a

thermic temperature regime.

Xerepts are of moderate extent in the United States. They

are most common in the States of California, Oregon,

Washington, Idaho, and Utah.

Definition

Xerepts are the Inceptisols that:

1. Have a xeric moisture regime;

2. Do not have, in a layer above a densic, lithic, or paralithic

contact or in a layer at a depth between 40 and 50 cm from the

mineral soil surface, whichever is shallower, aquic conditions

for some time in normal years and one or more of the

following:

a. A histic epipedon; or
Inceptisols 543

b. A sulfuric horizon that has its upper boundary within 50

cm of the mineral soil surface; or

c. A layer directly under the epipedon, or within 50 cm of

the mineral soil surface, that has, on faces of peds or in the

matrix if peds are absent, 50 percent or more chroma of

either:

(1) 2 or less if there are redox concentrations; or

(2) 1 or less; or

d. Within 50 cm of the mineral soil surface, enough active

ferrous iron to give a positive reaction to alpha,alphadipyridyl at a time when the soil is not being irrigated;

3. Do not have an exchangeable sodium percentage (ESP)

of 15 or more (or a sodium adsorption ratio [SAR] of 13 or

more) in half or more of the soil volume within 50 cm of the

mineral soil surface, a decrease in ESP (or SAR) values with

increasing depth below 50 cm, and ground water within 100

cm of the mineral soil surface for some time during the year;

4. Have neither a plaggen nor an anthropic epipedon; and

5. Have a mesic, frigid, or thermic soil temperature regime.

Key to Great Groups

KEA. Xerepts that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Durixerepts, p. 545

KEB. Other Xerepts that both:

1. Have a calcic horizon with its upper boundary

within 100 cm of the mineral soil surface or a petrocalcic

horizon with its upper boundary within 150 cm of the

mineral soil surface; and

2. Are calcareous in all parts above the calcic or

petrocalcic horizon, after the soil between the mineral soil

surface and a depth of 18 cm has been mixed.

Calcixerepts, p. 543

KEC. Other Xerepts that have a fragipan that has its upper

boundary within 100 cm of the mineral soil surface.

Fragixerepts, p. 549

KED. Other Xerepts that have both of the following:

1. No free carbonates within 200 cm of the mineral soil

surface; and

2. A base saturation (by NH4OAc) of less than 60 percent

in all horizons at a depth between 25 and 75 cm from the

mineral soil surface.

Dystroxerepts, p. 546

KEE. Other Xerepts.

Haploxerepts, p. 551

Calcixerepts

These are the Xerepts that do not have a duripan or a

fragipan but have a calcic or petrocalcic horizon and that are

calcareous in all overlying horizons. Either the parent

materials had more carbonates than the rainfall could remove

from the upper horizons, or there is a continuing external

source of carbonates in dust or water.

Calcixerepts formed mostly in Pleistocene sediments or

younger materials on surfaces of comparable age. In the United

States, the vegetation was dominantly grass and shrubs before

the soils were cultivated. These soils are most extensive in

California, Idaho, and Utah.

Definition

Calcixerepts are the Xerepts that:

1. Have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface or a petrocalcic

horizon that has its upper boundary within 150 cm of the

mineral soil surface and are calcareous in all parts of all

horizons above the calcic or petrocalcic horizon; and

2. Do not have a duripan or fragipan that has its upper

boundary within 100 cm of the mineral soil surface.

Key to Subgroups

KEBA. Calcixerepts that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Calcixerepts

KEBB. Other Calcixerepts that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Calcixerepts

KEBC. Other Calcixerepts that have a petrocalcic horizon

that has its upper boundary within 100 cm of the mineral soil

surface.

Petrocalcic Calcixerepts

KEBD. Other Calcixerepts that have an exchangeable
544 Soil Taxonomy

sodium percentage of 15 or more (or a sodium adsorption ratio

[SAR] of 13 or more) in one or more subhorizons within 100 cm

of the mineral soil surface.

Sodic Calcixerepts

KEBE. Other Calcixerepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Calcixerepts

KEBF. Other Calcixerepts that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Calcixerepts

KEBG. Other Calcixerepts.

Typic Calcixerepts

Definition of Typic Calcixerepts

Typic Calcixerepts are the Calcixerepts that:

1. Do not have a lithic contact within 50 cm of the soil

surface;

2. Do not have a petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface;

3. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more;

5. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

6. Have an exchangeable sodium percentage of less than 15

(or a sodium adsorption ratio [SAR] of less than 13) in all

subhorizons within 100 cm of the mineral soil surface.

Description of Subgroups

Typic Calcixerepts.—The central concept or Typic

subgroup of Calcixerepts is fixed on more or less freely drained

soils that have a calcic rather than a petrocalcic horizon. These

soils do not have slickensides, wedge-shaped aggregates, a

high linear extensibility, or wide cracks in normal years.

Soils that have a thin mantle or layer of materials that have

some andic soil properties are excluded from the Typic

subgroup because they are considered to be an intergrade to

Andisols. Redox concentrations and a ground water table that

fluctuates within 75 cm of the mineral soil surface are

properties shared with Aquolls and define the Aquic subgroup.

A shallow lithic contact defines the Lithic subgroup, a

convention used throughout this taxonomy. A petrocalcic

horizon indicates development more intensive than normal and

is used to define the Petrocalcic subgroup. Slickensides, wedgeshaped aggregates, a high linear extensibility, and wide cracks

that are evident in normal years are characteristics of Vertisols

and are used to define the Vertic subgroup.

Typic Calcixerepts are of small extent in the United States.

They are mostly in California, Utah, and Idaho. Many of these

soils supported grasses and shrubs and widely spaced trees.

Most are used as rangeland or irrigated cropland.

Aquic Calcixerepts.—These soils have redox depletions

with low chroma and either have shallow ground water at some

time of the year or are artificially drained. The soils are not

known to occur in the United States.

Lithic Calcixerepts.—These soils have a shallow lithic

contact. They are of very small extent in the Western United

States.

Petrocalcic Calcixerepts.—These soils have a petrocalcic

horizon. They are not known to occur in the United States.

Sodic Calcixerepts.—These soils have a high content of
Inceptisols 545

sodium in the upper part. They are of very small extent in the

United States.

Vertic Calcixerepts.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They are of very small extent in the

United States.

Vitrandic Calcixerepts.—These soils have some andic soil

properties in a layer 18 cm or more thick in the upper part and

have many of the properties of Andisols. In some areas this

layer was derived at least in part from pyroclastic materials.

Vitrandic Calcixerepts are of very small extent in the United

States.

Durixerepts

These are the Xerepts that have a duripan that has its upper

boundary within 100 cm of the soil surface. These soils have a

Mediterranean climate and receive a large part of their annual

precipitation in winter. Commonly, water is perched above the

duripan for part of winter or early spring. The vegetation was

commonly a coniferous forest or a mixture of grasses and

scattered trees. Durixerepts are not extensive in the United

States as a whole but are extensive locally.

Definition

Durixerepts are the Xerepts that have a duripan that has its

upper boundary within 100 cm of the soil surface.

Key to Subgroups

KEAA. Durixerepts that have both:

1. In one or more horizons above the duripan and

within 30 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions

for some time in normal years (or artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more, above the duripan and within 75 cm of

the mineral soil surface, one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Durixerepts

KEAB. Other Durixerepts that have, throughout one or more

horizons with a total thickness of 18 cm or more, above the

duripan and within 75 cm of the mineral soil surface, a fineearth fraction with both a bulk density of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0.

Andic Durixerepts

KEAC. Other Durixerepts that have, throughout one or more

horizons with a total thickness of 18 cm or more, above the

duripan and within 75 cm of the mineral soil surface, one or

both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Durixerepts

KEAD. Other Durixerepts that have, in one or more horizons

above the duripan and within 30 cm of the mineral soil surface,

distinct or prominent redox concentrations and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Durixerepts

KEAE. Other Durixerepts that have a duripan that is strongly

cemented or less cemented in all subhorizons.

Entic Durixerepts

KEAF. Other Durixerepts.

Typic Durixerepts

Definition of Typic Durixerepts

Typic Durixerepts are the Durixerepts that:

1. Have a duripan that is very strongly cemented or is

indurated;

2. Do not have, in any horizon above the duripan and

within 30 cm of the mineral soil surface, distinct or prominent

redox concentrations and also aquic conditions; and
546 Soil Taxonomy

3. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Durixerepts.—The central concept or Typic

subgroup of Durixerepts is fixed on soils that are free of

redoximorphic features and have a very strongly cemented or

indurated duripan. These soils do not have a layer near the

surface that has many of the properties of Andisols. The pan

generally has very coarse polyhedrons that are 100 cm or more

across. It commonly is within 50 cm of the mineral soil

surface. Soils that have a less strongly cemented duripan are

considered to be intergrades to Entisols.

Typic Durixerepts are of small extent in the United States.

The native vegetation is mostly shrubs and grass. These soils

are used mainly as rangeland or irrigated cropland. Some are

used as homesites.

Andic and Vitrandic Durixerepts.—These soils have many

of the properties of Andisols in a layer near the surface that is

18 cm or more thick. Andic and Vitrandic Durixerepts are of

small extent in the United States. They occur mostly in the

western part of Washington State. The native vegetation is

mostly coniferous forest, but in some areas it is shrubs and

grass. These soils are used mainly as forest. Some have been

cleared and are used as cropland, pasture, or homesites.

Aquandic Durixerepts.—These soils have many of the

properties of Andisols in a layer near the surface that is 18 cm

or more thick. Aquandic Durixerepts also have redox

concentrations and aquic conditions and are wetter than Typic

Durixerepts. They are rare in the United States.

Aquic Durixerepts.—These soils have redox concentrations

and aquic conditions and are wetter than Typic Durixerepts.

Commonly, they also have gentler slopes. Aquic Durixerepts

are rare in the United States.

Entic Durixerepts.—These soils have a duripan that is

cemented but is not very strongly cemented or indurated.

Because the pan is not very strongly cemented or indurated,

these soils are considered intergrades to Entisols. Entic

Durixerepts are of small extent in the United States. The

vegetation is mostly annual grasses and scattered trees on the

thermic soils and forest on the cooler soils.

Dystroxerepts

These are the acid Xerepts. They developed mostly in

Pleistocene or Holocene deposits. Some of the soils that have

steep slopes formed in older deposits. The normal horizon

sequence in Dystroxerepts is an ochric epipedon over a cambic

horizon. Some of the steep Dystroxerepts have a shallow

densic, lithic, or paralithic contact. The parent materials

generally are acid, moderately or weakly consolidated

sedimentary or metamorphic rocks or acid sediments,

commonly with additions of volcanic ash near the surface. A

few of the soils formed in saprolite derived from igneous rocks.

The vegetation was mostly coniferous trees. Most

Dystroxerepts are used as forest or pasture. Some of the soils,

mostly the least sloping ones, are used as cropland.

Dystroxerepts are extensive soils in the States of California,

Washington, and Oregon.

Definition

Dystroxerepts are the Xerepts that:

1. Do not have free carbonates within the soils;

2. Have a base saturation of less than 60 percent (by

NH4

OAc) in all subhorizons between depths of 25 and 75 cm

below the soil surface; and

3. Do not have a fragipan or duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Key to Subgroups

KEDA. Dystroxerepts that have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. An umbric or mollic epipedon.

Humic Lithic Dystroxerepts

KEDB. Other Dystroxerepts that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Dystroxerepts

KEDC. Other Dystroxerepts that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or more of the following:
Inceptisols 547

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Dystroxerepts

KEDD. Other Dystroxerepts that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Dystroxerepts

KEDE. Other Dystroxerepts that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Dystroxerepts

KEDF. Other Dystroxerepts that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions in normal years (or artificial

drainage).

Fragiaquic Dystroxerepts

KEDG. Other Dystroxerepts that have a slope of less than 25

percent; and

1. In one or more horizons within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage); and

2. Either:

a. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

b. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a

densic, lithic, or paralithic contact, whichever is

shallower.

Fluvaquentic Dystroxerepts

KEDH. Other Dystroxerepts that have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Dystroxerepts

KEDI. Other Dystroxerepts that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Dystroxerepts

KEDJ. Other Dystroxerepts that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Dystroxerepts

KEDK. Other Dystroxerepts that have a slope of less than 25

percent; and

1. An umbric or mollic epipedon; and

2. Either:

a. At a depth of 125 cm below the mineral soil surface,

an organic-carbon content (Holocene age) of 0.2 percent
548 Soil Taxonomy

or more and no densic, lithic, or paralithic contact within

that depth; or

b. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a

depth of 125 cm below the mineral soil surface or a

densic, lithic, or paralithic contact, whichever is

shallower.

Fluventic Humic Dystroxerepts

KEDL. Other Dystroxerepts that have a slope of less than 25

percent; and either

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluventic Dystroxerepts

KEDM. Other Dystroxerepts that have an umbric or mollic

epipedon.

Humic Dystroxerepts

KEDN. Other Dystroxerepts.

Typic Dystroxerepts

Definition of Typic Dystroxerepts

Typic Dystroxerepts are the Dystroxerepts that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years;

4. Have a slope of 25 percent or more; or

a. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of less than 0.2

percent or a densic, lithic, or paralithic contact within that

depth; or

b. A regular decrease in organic-carbon content (Holocene

age) between a depth of 25 cm and either a depth of 125 cm

below the mineral soil surface or a densic, lithic, or

paralithic contact, whichever is shallower;

5. Do not have a lithic contact within 50 cm of the mineral

soil surface;

6. Do not have an umbric or mollic epipedon; and

7. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Dystroxerepts.—The central concept or Typic

subgroup of Dystroxerepts is fixed on soils that are moderately

deep or deeper to hard rock, are freely drained, are acid, and

have an ochric epipedon. In addition, the content of organic

carbon of Holocene age decreases regularly with increasing

depth and is very low at a depth of 125 cm.

If content of organic carbon is relatively high at a depth of

125 cm or if it decreases irregularly with increasing depth and

slopes are gentle, the parent material normally is recent

Holocene alluvium. The soils that formed in this alluvium are

considered intergrades to Fluvents or, if the soils have aquic

conditions near the surface, to Fluvaquents. A shallow water

table and redox depletions with low chroma indicate

intergrades to Aquepts. A lithic contact within a depth of 50

cm is the basis for defining the Lithic subgroup. The presence

of an umbric or mollic epipedon is used to define Humic and

combination Humic subgroups. Soils that have a thin mantle or

layer that has some andic soil properties are excluded from the

Typic subgroup because they are considered to be an intergrade

to Andisols.

Typic Dystroxerepts are of moderate extent in the United

States. They are mostly in the Northwestern States. The native

vegetation consists mostly of coniferous forest. Most of these

soils are used as forest. Some of the less sloping soils have been

cleared and are used as cropland or pasture.
Inceptisols 549

Andic and Vitrandic Dystroxerepts.—These soils have some

andic soil properties in a layer in the upper part that is 18 cm or

more thick. Some of the soils contain a significant amount of

volcanic ash. Some have an umbric epipedon. Andic and

Vitrandic Dystroxerepts are moderately extensive in the

Northwestern United States. The native vegetation consists

mostly of coniferous forest. Most of these soils support native

vegetation and are used as forest. A few of the less sloping soils

have been cleared and are used as cropland or pasture.

Aquandic Dystroxerepts.—These soils have aquic

conditions in the upper part of the subsoil and have some andic

soil properties in a layer in the upper part that is 18 cm or

more thick. Some of the soils contain a significant amount of

volcanic ash, and some have an umbric epipedon. Ground

water commonly is present only during winter unless the soils

are artificially drained. These soils have gentle slopes. They are

of small extent in the United States. They occur mostly in

Washington State. The native vegetation consists mostly of

coniferous forest. Most of these soils support native vegetation

and are used as forest. Some have been cleared and are used as

pasture or cropland.

Aquic Dystroxerepts.—These soils have redox depletions

with low chroma in a brownish or reddish matrix in the

subsoil. Many of the soils also have redox concentrations with

high chroma. Most of the Aquic Dystroxerepts in the United

States formed in late-Pleistocene sediments and have gentle

slopes. Ground water commonly is present only during wet

periods unless the soils are artificially drained. Some of these

soils have an umbric epipedon. Aquic Dystroxerepts are of

small extent in the United States. They occur mostly in

Washington State. The native vegetation consists mostly of

coniferous forest. Most of these soils are used as forest, but

some have been cleared and are used as cropland or pasture.

Fluvaquentic Dystroxerepts.—These soils have redox

depletions with low chroma in a brownish matrix and formed

in Holocene or recent alluvium. They are on flood plains.

During wet periods ground water is present in the redoxdepleted zone unless the soils have been drained. Most of these

soils are subject to occasional flooding, but they receive little

fresh sediment. Some of the soils have an umbric epipedon.

Fluvaquentic Dystroxerepts are of very small extent in the

United States.

Fluventic Dystroxerepts.—These soils are on flood plains

along rivers and streams. They formed in Holocene or recent

alluvium. They are subject to occasional flooding but receive

little fresh alluvium. These soils are of very small extent in the

United States.

Fluventic Humic Dystroxerepts.—These soils are on flood

plains along rivers and streams. They have an umbric or mollic

epipedon. They formed in Holocene or recent alluvium. They

are subject to occasional flooding but receive little fresh

alluvium. These soils are of very small extent in the United

States.

Fragiaquic Dystroxerepts.—These soils have fragic soil

properties in 30 percent or more of a layer 15 cm or more thick

that has its upper boundary within 100 cm of the mineral soil

surface or in 60 percent or more of a layer 15 cm or more thick

anywhere in the soils. In addition, they have redox depletions

with low chroma in a brownish or reddish matrix in the

subsoil. Commonly, there are also redox concentrations with

high chroma. Ground water commonly is present in these soils

during winter. The soils are considered intergrades to

Fragiaquepts. They are not extensive in the United States.

Fragic Dystroxerepts.—These soils have fragic soil

properties in 30 percent or more of a layer 15 cm or more thick

that has its upper boundary within 100 cm of the mineral soil

surface or in 60 percent or more of a layer 15 cm or more thick

anywhere in the soils. These soils are considered intergrades to

Fragixerepts. They are not extensive in the United States.

Humic Dystroxerepts.—These soils have an umbric or

mollic epipedon but are otherwise like the soils of the Typic

subgroup. Humic Dystroxerepts are moderately extensive in the

United States. They are mostly in California and in the

Northwestern States. The native vegetation consists mostly of

coniferous forest. Most of these soils are used as forest. Many

of the less sloping soils have been cleared and are used as

cropland or pasture.

Humic Lithic Dystroxerepts.—These soils have a lithic

contact within 50 cm of the mineral soil surface and have a

mollic or umbric epipedon. An umbric epipedon is more

common than a mollic epipedon. These soils are of small

extent in the Northwestern United States.

Lithic Dystroxerepts.—These soils have a lithic contact at

a shallow depth. They formed mostly in acid sedimentary or

metamorphic rocks. Most of the soils have moderate to steep

slopes. Lithic Dystroxerepts are of small extent in the United

States. They are mostly in California and Oregon. The native

vegetation consists mostly of coniferous forest. Most of these

soils are used as forest.

Oxyaquic Dystroxerepts.—These soils are saturated with

water within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. The soils are of small extent in the United States. They

are considered intergrades to Aquepts. Most Oxyaquic

Dystroxerepts are used as forest. Some have been cleared and

are used as cropland or pasture.

Fragixerepts

These are the Xerepts that have a fragipan within 100 cm of

the mineral soil surface. Commonly, these soils have a

brownish cambic horizon that is underlain by a fragipan at a

depth of about 70 cm. Most Fragixerepts have perched water

above the pan in winter, and few roots penetrate the pan.

Consequently, plants tend to have shallow root systems. Many

Fragixerepts formed in late-Pleistocene deposits. They have

mostly gentle or moderate slopes, but some are steep. Most of

these soils are loamy and have been leached of any free
550 Soil Taxonomy

carbonates. The Fragixerepts in the United States are mostly in

the States of Idaho and Oregon. They are of small extent.

Definition

Fragixerepts are the Xerepts that:

1. Have a fragipan within 100 cm of the mineral soil surface;

2. Do not have a duripan within 100 cm of the mineral soil

surface; and

3. Do not have both:

a. A calcic horizon with its upper boundary within 100 cm

of the mineral soil surface or a petrocalcic horizon with its

upper boundary within 150 cm of the mineral soil surface;

and

b. Calcareous materials in all parts above the calcic or

petrocalcic horizon, after the soil between the mineral soil

surface and a depth of 18 cm has been mixed.

Key to Subgroups

KECA. Fragixerepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Fragixerepts

KECB. Other Fragixerepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Fragixerepts

KECC. Other Fragixerepts that have, in one or more

horizons within 30 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time in normal years (or artificial drainage).

Aquic Fragixerepts

KECD. Other Fragixerepts that have an umbric or mollic

epipedon.

Humic Fragixerepts

KECE. Other Fragixerepts.

Typic Fragixerepts

Definition of Typic Fragixerepts

Typic Fragixerepts are the Fragixerepts that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have, in any horizon within 30 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions; and

3. Do not have an umbric or mollic epipedon.

Description of Subgroups

Typic Fragixerepts.—The central concept or Typic

subgroup of Fragixerepts is fixed on soils that are free of

distinct or prominent redox concentrations in the upper 30 cm,

have an ochric epipedon, and do not have some andic soil

properties in a layer near the surface that is as thick as 18 cm.

A mantle of materials with andic soil properties between 18

and 35 cm thick indicates an intergrade to Andisols. Most

Typic Fragixerepts have a perched water table above the pan at

times during the winter. Shallow redox concentrations indicate

intergrades to Fragiaquepts and are the basis for defining the

Aquic subgroup.

Typic Fragixerepts are of small extent in the United States.

They occur mostly in the Northwestern States. The native

vegetation consists of mixed forest. Many of the less sloping
Inceptisols 551

soils have been cleared and are used as cropland or pasture.

Some of the soils, mostly the steeper ones, are used as forest.

Andic and Vitrandic Fragixerepts.—These soils have a

layer near the surface that is 18 cm or more thick and that

contains volcanic glass or has some andic soil properties. In

some soils this layer has many of the properties of Andisols.

Andic and Vitrandic Fragixerepts are not extensive and are not

known to occur in the United States.

Aquic Fragixerepts.—These soils have, at a shallow depth,

redox concentrations of medium or high contrast and are

somewhat wetter than Typic Fragixerepts. Commonly, they also

have gentler slopes. Aquic Fragixerepts are of very small

extent in the Northwestern United States. The native

vegetation consisted of forest. Most of these soils are nearly

level or gently sloping and have been cleared and are used as

cropland or pasture.

Humic Fragixerepts.—These soils are like Typic

Fragixerepts, but they have an umbric or mollic epipedon.

They are rare in the United States.

Haploxerepts

These are the more or less freely drained Xerepts that are

calcareous at some depth or have a high base status. Some of

the soils have a Bk or calcic horizon, but they do not have both

a calcic or petrocalcic horizon and free carbonates in all

horizons above the calcic or petrocalcic horizon. Haploxerepts

are moist in winter and into the spring but are thoroughly dry

for much of the summer. They have a frigid, mesic, or thermic

temperature regime. Slopes are gentle to very steep, and the

soils are shallow to very deep. The most common vegetation on

the Haploxerepts in the United States was coniferous forest on

the frigid and mesic soils and grass and widely spaced trees on

the thermic soils. Haploxerepts are in the Western United

States. They are moderately extensive.

Definition

Haploxerepts are the Xerepts that:

1. Have:

a. Free carbonates in some part within 200 cm of the

mineral soil surface; or

b. A base saturation (by NH4

OAc) of 60 percent or more in

some horizon at a depth between 25 and 75 cm from the

mineral soil surface;

2. Have neither a duripan nor a fragipan that has its upper

boundary within 100 cm of the mineral soil surface; and

3. Do not have both:

a. A calcic horizon with its upper boundary within 100 cm

of the mineral soil surface or a petrocalcic horizon with its

upper boundary within 150 cm of the mineral soil surface;

and

b. Free carbonates in all parts above the calcic or

petrocalcic horizon, after the soil between the mineral soil

surface and a depth of 18 cm has been mixed.

Key to Subgroups

KEEA. Haploxerepts that have both:

1. A lithic contact within 50 cm of the mineral soil surface;

and

2. An umbric or mollic epipedon.

Humic Lithic Haploxerepts

KEEB. Other Haploxerepts that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Haploxerepts

KEEC. Other Haploxerepts that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haploxerepts

KEED. Other Haploxerepts that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium
552 Soil Taxonomy

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Haploxerepts

KEEE. Other Haploxerepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm of

the mineral soil surface, a fine-earth fraction with both a bulk

density of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0.

Andic Haploxerepts

KEEF. Other Haploxerepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Haploxerepts

KEEG. Other Haploxerepts that have a gypsic horizon within

100 cm of the mineral soil surface.

Gypsic Haploxerepts

KEEH. Other Haploxerepts that have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage).

Aquic Haploxerepts

KEEI. Other Haploxerepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Haploxerepts

KEEJ. Other Haploxerepts that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Haploxerepts

KEEK. Other Haploxerepts that have a slope of less than 25

percent; and either

1. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of 0.2 percent or

more and no densic, lithic, or paralithic contact within that

depth; or

2. An irregular decrease in organic-carbon content

(Holocene age) between a depth of 25 cm and either a depth

of 125 cm below the mineral soil surface or a densic, lithic,

or paralithic contact, whichever is shallower.

Fluventic Haploxerepts

KEEL. Other Haploxerepts that have a calcic horizon or

identifiable secondary carbonates within one of the following

particle-size class and depth combinations:

1. A sandy or sandy-skeletal particle-size class and

within 150 cm of the mineral soil surface; or

2. A clayey, clayey-skeletal, fine, or very-fine particle-size

class and within 90 cm of the mineral soil surface; or

3. Any other particle-size class and within 110 cm of the

mineral soil surface.

Calcic Haploxerepts

KEEM. Other Haploxerepts that have an umbric or mollic

epipedon.

Humic Haploxerepts

KEEN. Other Haploxerepts.

Typic Haploxerepts

Definition of Typic Haploxerepts

Typic Haploxerepts are the Haploxerepts that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Do not have an umbric or mollic epipedon;

3. Have a slope of 25 percent or more; or

a. At a depth of 125 cm below the mineral soil surface, an

organic-carbon content (Holocene age) of less than 0.2

percent or a densic, lithic, or paralithic contact within that

depth; or

b. A regular decrease in organic-carbon content (Holocene

age) between a depth of 25 cm and either a depth of 125 cm

below the mineral soil surface or a densic, lithic, or

paralithic contact, whichever is shallower;

4. Do not have a lithic contact within 50 cm of the soil

surface in 10 percent or more of each pedon;

5. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or
Inceptisols 553

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the mineral soil

surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower;

6. Do not have a calcic horizon or identifiable secondary

carbonates within the following particle-size class and depth

combinations:

a. A sandy or sandy-skeletal particle-size class and within

150 cm of the mineral soil surface; or

b. A clayey, clayey-skeletal, fine, or very-fine particle-size

class and within 90 cm of the mineral soil surface; or

c. Any other particle-size class and within 110 cm of the

mineral soil surface;

7. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

8. Do not have a gypsic horizon within 100 cm of the soil

surface;

9. Do not have lamellae (two or more) within 200 cm of the

soil surface; and

10. Do not have fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Description of Subgroups

Typic Haploxerepts.—The central concept or Typic subgroup

of Haploxerepts is fixed on moderately deep or deeper, relatively

well drained soils that have an ochric epipedon. These soils do

not have a Bk or calcic horizon, unless it is deep, and do not

have a surface mantle that has some andic soil properties or a

high content of volcanic glass.

Soils that have shallow redox depletions with low chroma

and ground water in the depleted zone or artificial drainage are

excluded from the Typic subgroup because these properties

indicate intergrades to Aquepts and are the basis for

recognition of the Aquic subgroup. A layer or a surface mantle,

18 cm or more thick, that has some andic properties or a high

content of volcanic glass is excluded from the Typic subgroup

because it indicates a transition to Andisols and is used to

define Andic and Vitrandic subgroups. A shallow lithic contact

is the basis for recognition of the Lithic subgroup. Soils that

have a clayey texture accompanied by deep cracks are excluded

from the Typic subgroup because these characteristics indicate

intergrades to Vertisols and define the Vertic subgroup. Soils

that have an umbric or mollic epipedon are not considered

typical and are assigned to Humic and combination Humic

subgroups. Soils that have an organic-carbon content

(Holocene age) that decreases irregularly with increasing depth

or that remains relatively high in the deep layers are excluded

from the Typic subgroup and are considered intergrades to

Fluvents and Fluvaquents. Soils that have a shallow Bk or

calcic horizon are also excluded and are considered intergrades

to Calcixerepts.

Typic Haploxerepts are of moderate extent. They are in the

Western United States. Slopes are gentle to steep. The native

vegetation consists mostly of grass and shrubs. Most of the less

sloping soils are used as cropland. Some of the soils,

commonly the most sloping ones, support their native

vegetation and are used as rangeland.

Andic and Vitrandic Haploxerepts.—These soils have a

layer or a surface mantle, 18 cm or more thick, that has some

andic soil properties and that has many of the properties of

Andisols. In addition, some Andic and Vitrandic Haploxerepts

have an umbric epipedon. Andic and Vitrandic Haploxerepts

are of small extent. Slopes are gentle to very steep. The native

vegetation consists mostly of coniferous forest. Many of these

soils support their native vegetation and are used as forest.

Many of the less sloping soils have been cleared and are used

as cropland or pasture.

Aquandic Haploxerepts.—These soils have redox depletions

with low chroma (less than 2) within 75 cm of the soil surface

and either are artificially drained or are saturated with water in

the redox-depleted horizons at some time of the year, usually in

winter or early spring. The soils also have a layer or a surface

mantle, 18 cm or more thick, that has many of the properties of

Andisols. In addition, Aquandic Haploxerepts commonly have
554

an umbric epipedon. These soils are of very small extent in the

United States. They occur mostly in the State of Washington.

Slopes are gentle. The native vegetation consists mostly of

coniferous forest. Some of these soils have been cleared and are

used as cropland or pasture. Some support their native

vegetation and are used as forest.

Aquic Haploxerepts.—These soils have redox depletions

with low chroma (less than 2) within 75 cm of the soil surface

and either are artificially drained or are saturated with water in

the redox-depleted horizons at some time of the year, usually in

winter or spring. These soils are of small extent in the Western

United States. Slopes are gentle. The native vegetation consists

mostly of coniferous forest. Many of these soils have been

cleared and are used as cropland or pasture. Some support their

native vegetation and are used as forest.

Calcic Haploxerepts.—These soils have, in the upper part,

a calcic or Bk horizon that contains identifiable secondary

carbonates. These soils are of small extent in the United States.

They occur in the Western States. Slopes are gentle to very

steep. The native vegetation consists mostly of grass and

shrubs, but some of the soils support widely spaced trees. Most

Calcic Haploxerepts support their native vegetation and are

used as rangeland. Some of the less sloping soils are used as

cropland.

Fluventic Haploxerepts.—These soils formed in stratified

alluvium on gentle slopes. The soils are of small extent in the

Western United States. The native vegetation consists mostly of

grass and shrubs, but in some areas it is coniferous forest. Most

of these soils have been cleared and are used as cropland or

pasture. Some support their native vegetation and are used as

rangeland or forest.

Fragic Haploxerepts.—These soils have fragic soil

properties in 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm of the

mineral soil surface or in 60 percent or more of the volume of a

layer 15 cm or more thick anywhere in the soils. These soils

are considered intergrades to Fragixerepts. They are not

extensive in the United States.

Gypsic Haploxerepts.—These soils have a gypsic horizon

within 100 cm of the mineral soil surface. They are of very

small extent and are known to occur only in California in the

United States.

Humic Haploxerepts.—These soils have an umbric or

mollic epipedon. They are otherwise like the soils of the Typic

subgroup. The Humic Haploxerepts in the United States

formed mostly in materials weathered from rocks or in other

materials that have few or no free carbonates. Many of the soils

receive a relatively high amount of precipitation. Humic

Haploxerepts are of moderate extent in the Western United

States. Slopes are gentle to very steep. The native vegetation

consists mostly of coniferous forest. Many of these soils

support their native vegetation and are used as forest. Some are

cleared and are used as cropland or pasture.

Humic Lithic Haploxerepts.—These soils have an

umbric or mollic epipedon and have a shallow lithic contact. In

the United States, they formed mostly in materials that

weathered from rocks and have few or no free carbonates.

Many of the soils receive a relatively high amount of

precipitation. Humic Lithic Haploxerepts are of small extent in

the Western United States. Slopes are gentle to very steep. The

native vegetation consists mostly of coniferous forest. Many of

these soils support their native vegetation and are used as

forest.

Lamellic Haploxerepts.—These soils are like Typic

Haploxerepts, but they have two or more lamellae in the

subsoil. They are not extensive in the United States.

Lithic Haploxerepts.—These soils have a shallow lithic

contact. They are of moderate extent in the Western United

States. Slopes are gentle to very steep. The native vegetation

consists mostly of sparse coniferous forest. Many of these soils

support their native vegetation and are used as forest or

rangeland.

Vertic Haploxerepts.—These soils have a clayey texture

and have deep cracks in summer if they are not irrigated.

Vertic Haploxerepts are of small extent in the Western United

States. Slopes are gentle to moderately steep. The native

vegetation consists mostly of grass and shrubs. Most of the less

sloping soils are used as cropland. Some of the soils,

commonly the most sloping ones, support their native

vegetation and are used as rangeland.
555

Mollisols commonly are the very dark colored,base-rich, mineral soils of the steppes. Nearly all of

these soils have a mollic epipedon. Many also have an argillic,

natric, or calcic horizon. A few have an albic horizon. Some

also have a duripan or a petrocalcic horizon.

Mollisols are extensive in subhumid to semiarid areas on

the plains of North America, Europe, Asia, and South

America. They lie generally between the Aridisols of arid

climates and the Spodosols or Alfisols of humid climates. They

are most extensive at mid latitudes, but they also occur at high

latitudes and high altitudes and in tropical regions.

Many of these soils developed under grass at some time,

although many apparently were forested at an earlier time.

Some of the soils that are in the mountains or that were derived

from highly calcareous parent material apparently formed

under forest vegetation. Mollisols may have any of the defined

temperature regimes but do not have permafrost. Soils with

mollic epipedons and permafrost are Gelisols. Mollisols can

have any moisture regime, but enough available moisture to

support perennial grasses seems to be essential.

Most Mollisols at high latitudes formed in late-Pleistocene

or Holocene deposits. Beyond the limits of glaciation, Mollisols

may be in areas of older deposits or on older surfaces dating

back perhaps to the mid Pleistocene or earlier, and these

commonly have an argillic horizon with a reddish hue.

In frigid or warmer areas where slopes are not too steep,

Mollisols are used mainly for small grain in the drier regions

and maize (corn) or soybeans in the warmer, humid regions.

Definition of Mollisols and Limits Between

Mollisols and Soils of Other Orders

Mollisols are mineral soils that either have a mollic

epipedon or have a surface horizon that, after mixing to a

depth of 18 cm, meets all of the requirements for a mollic

epipedon except thickness. They also have an upper subhorizon

that is more than 7.5 cm thick in an argillic or natric horizon

that meets the color, organic-carbon content, base saturation,

and structure requirements for a mollic epipedon but is

separated from the surface horizon by an albic horizon (the

combined thickness must meet the thickness requirements for a

mollic epipedon), and they meet all of the following:

1. Unlike Gelisols, Mollisols do not have either of the

following:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface;

2. Unlike Histosols, Mollisols do not have organic soil

materials that meet one or more of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 6 months or more in

normal years (or are artificially drained), have an upper

boundary within 40 cm of the soil surface, and have a total

thickness of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3

; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more;

3. Unlike Spodosols, Mollisols do not have a spodic

horizon or an Ap horizon containing 85 percent or more

spodic materials and do not have one or more of the

following:

a. An albic horizon in 50 percent or more of each pedon

and a cryic soil temperature regime; or

b. A spodic horizon with all of the following

characteristics:

(1) One or more of the following:

(a) A thickness of 10 cm or more; or

(b) An overlying Ap horizon; or

CHAPTER 16

Mollisols
556 Soil Taxonomy

(c) Cementation in 50 percent or more of each

pedon; or

(d) A coarse-loamy, loamy-skeletal, or finer particlesize class and a frigid temperature soil regime; or

(e) A cryic temperature soil regime; and

(2) An upper boundary within the following depths

from the mineral soil surface: either

(a) Less than 50 cm; or

(b) Less than 200 cm if the soil has a sandy particlesize class between the mineral soil surface and the

spodic horizon; and

(3) A lower boundary as follows:

(a) Either at a depth of 25 cm or more below the

mineral soil surface, at the top of a duripan or

fragipan, or at a densic, lithic, paralithic, or

petroferric contact, whichever is shallowest; or

(b) At any depth if the spodic horizon has a coarseloamy, loamy-skeletal, or finer particle-size class and

the soil has a frigid temperature regime or if the soil

has a cryic temperature regime;

4. Unlike Andisols, Mollisols must not have andic soil

properties in 60 percent or more of the thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and either a

depth of 60 cm from the shallower of the above or a densic,

lithic, or paralithic contact, a duripan, or a petrocalcic horizon

if shallower than 60 cm;

5. Unlike Oxisols, Mollisols must not have:

a. An oxic horizon within 150 cm of the soil surface; or

b. Both:

(1) 40 percent or more clay in the surface 18 cm of the

mineral soil after mixing; and

(2) A kandic horizon with less than 10 percent

weatherable minerals within 150 cm of the soil surface;

6. Unlike Vertisols, Mollisols must not have all of the

following:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

aggregates that have their long axes tilted 10 to 60 degrees

from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact,

duripan, or petrocalcic horizon if shallower; and

c. Cracks that open and close periodically;

7. Unlike Aridisols, Mollisols must:

a. Have a mollic epipedon; and

b. Not have a salic horizon if they also have all of the

following:

(1) Saturation with water in one or more layers

within 100 cm of the soil surface for 1 month or more

in normal years; and

(2) A moisture control section that is, in at least some

part, dry in normal years; and

(3) No sulfuric horizon that has its upper boundary

within 150 cm of the mineral soil surface;

8. Unlike Alfisols and Ultisols, Mollisols must have:

a. Either:

(1) A mollic epipedon; or

(2) Both a surface horizon that meets all of the

requirements for a mollic epipedon except thickness after

the soil has been mixed to a depth of 18 cm and a

subhorizon more than 7.5 cm thick, within the upper part

of an argillic, kandic, or natric horizon, that meets the

color, organic-carbon content, base saturation, and

structure requirements for a mollic epipedon but is

separated from the surface horizon by an albic horizon;

and

b. An argillic, kandic, or natric horizon that has a base

saturation of 50 percent or more (by NH4

OAc) in the upper

125 cm or in all subhorizons if the argillic horizon is less

than 125 cm thick; and

9. Unlike Inceptisols and Entisols, Mollisols have both a

mollic epipedon and a base saturation of 50 percent or more

(by NH4OAc) in all subhorizons to a depth of 180 cm below the

mineral soil surface.

Representative Pedon and Data

Following is a description of a representative Mollisol. Data

for the pedon identified in this description are given in the

table “Characterization Data for a Mollisol.”

Classification: Fine-silty, mixed, superactive, mesic Pachic

Argiustoll

Site identification number: 79P0146

Location: Gosper County, Nebraska; 135 m east and 750 m

north of the southwest corner of sec. 7, T. 7 N., R. 22 W.
Mollisols 557

Landscape: Plains

Soil moisture regime: Ustic

Depth to water table: More than 150 cm

Permeability class: Moderate

Land use: Cropland

Parent material: Loess

Diagnostic horizons: A mollic epipedon from a depth of 0

to 71 cm and an argillic horizon from a depth of 30 to

91 cm

Described by: M. Dixon and S. Scheinost

In the following pedon description, colors are for dry soil

unless otherwise indicated.

Ap—0 to 18 cm; dark grayish brown (10YR 4/2) silt loam,

very dark grayish brown (10YR 3/2) moist; weak fine

granular structure; slightly hard, very friable, nonsticky;

common fine roots; abrupt smooth boundary.

A—18 to 30 cm; dark grayish brown (10YR 4/2) silt loam,

very dark grayish brown (10YR 3/2) moist; weak fine and

medium subangular blocky structure; slightly hard, very

friable, slightly sticky; common fine roots; clear smooth

boundary.

Bt1—30 to 49 cm; dark gray (10YR 4/1) silty clay loam, very

dark gray (10YR 3/1) moist; weak coarse prismatic

structure parting to moderate medium subangular blocky;

hard, friable, slightly sticky; common fine roots; common

faint clay films on faces of peds; clear smooth boundary.

Bt2—49 to 71 cm; dark grayish brown (10YR 4/2) silty clay

loam, very dark grayish brown (10YR 3/2) moist; weak

coarse prismatic structure parting to moderate medium

subangular blocky; slightly hard, friable, slightly sticky;

few fine roots; few fine tubular pores; common faint clay

films on faces of peds; clear wavy boundary.

Bt3—71 to 91 cm; dark grayish brown (10YR 4/2) silty clay

loam, dark grayish brown (10YR 4/2) moist; weak coarse

prismatic structure parting to moderate medium

subangular blocky; few clay films on faces of prisms; few

fine roots; gradual wavy boundary.

BC—91 to 117 cm; light brownish gray (10YR 6/2) silt loam,

grayish brown (10YR 5/2) moist; weak medium prismatic

structure parting to weak fine subangular blocky; slightly

hard, very friable, nonsticky; few fine tubular pores; few

old root channels; gradual wavy boundary.

BCk1—117 to 142 cm; pale brown (10YR 6/3) silt loam,

brown (10YR 5/3) moist; massive; slightly hard, very

friable, nonsticky; few very fine tubular pores; common

fine and medium concretions of lime; common old root

channels; slightly effervescent; diffuse wavy boundary.

BCk2—142 to 165 cm; pale brown (10YR 6/3) silt loam,

brown (10YR 5/3) moist; weak coarse prismatic structure;

slightly hard, very friable, nonsticky; coatings of lime or

carbonate on faces of peds and in pores; common fine and

medium soft masses of lime; slightly effervescent.

Key to Suborders

IA. Mollisols that have:

1. An argillic or natric horizon; and

2. An albic horizon that has chroma of 2 or less and is 2.5

cm or more thick, has its lower boundary 18 cm or more

below the mineral soil surface, and either lies directly below

the mollic epipedon or separates horizons that together meet

all of the requirements for a mollic epipedon; and

3. In one or more subhorizons of the albic horizon and/or

of the argillic or natric horizon and within 100 cm of the

mineral soil surface, redox concentrations in the form of

masses or concretions, or both, and also aquic conditions for

some time in normal years (or artificial drainage).

Albolls, p. 560

IB. Other Mollisols that have, in a layer above a densic,

lithic, or paralithic contact or in a layer at a depth between 40

and 50 cm from the mineral soil surface, whichever is

shallower, aquic conditions for some time in normal years (or

artificial drainage) and one or more of the following:

1. A histic epipedon overlying the mollic epipedon; or

2. An exchangeable sodium percentage (ESP) of 15 or

more (or a sodium adsorption ratio [SAR] of 13 or more) in

the upper part of the mollic epipedon and a decrease in ESP

(or SAR) values with increasing depth below 50 cm from

the mineral soil surface; or

3. A calcic or petrocalcic horizon that has its upper

boundary within 40 cm of the mineral soil surface; or

4. A mollic epipedon, with chroma of 1 or less, that

extends to a lithic contact within 30 cm of the mineral soil

surface; or

5. One of the following colors:

a. Chroma of 1 or less in the lower part of the mollic

epipedon;1 and either

(1) Distinct or prominent redox concentrations in

the lower part of the mollic epipedon; or

(2) Either directly below the mollic epipedon or

within 75 cm of the mineral soil surface if a calcic

horizon intervenes, a color value, moist, of 4 or more

and one of the following:

(a) 50 percent or more chroma of 1 on faces of

peds or in the matrix, hue of 10YR or redder, and

redox concentrations; or

1 If the mollic epipedon extends to a lithic contact within 30 cm of the mineral soil surface,

the requirement for redoximorphic features is waived.
558 Soil Taxonomy

Characterization Data for a Mollisol

 SITE IDENTIFICATION NO.: 79P0146

 CLASSIFICATION: FINE-SILTY, MIXED, SUPERACTIVE, MESIC PACHIC ARGIUSTOLL

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 79P 720 0- 18 Ap 21.1 61.0 17.9 14.8 21.6 39.4 16.9 0.4 0.3 0.1 0.2 -- -- -- 1 --

 79P 721 18- 30 A 21.4 61.0 17.6 16.4 21.0 40.0 16.6 0.6 0.2 0.1 0.1 -- -- -- 1 --

 79P 722 30- 49 Bt1 27.5 58.5 14.0 21.2 20.8 37.7 12.7 0.6 0.4 0.2 0.1 -- -- -- 1 --

 79P 723 49- 71 Bt2 28.5 53.9 17.6 22.3 20.6 33.3 16.7 0.4 0.3 0.1 0.1 -- -- -- 1 --

 79P 724 71- 91 Bt3 25.9 55.5 18.6 18.8 20.9 34.6 18.0 0.3 0.2 0.1 TR -- -- -- 1 --

 79P 725 91-117 BC 21.7 56.5 21.8 13.0 20.9 35.6 20.9 0.6 0.2 0.1 TR -- -- -- 1 --

 79P 726 117-142 BCk1 19.6 59.4 21.0 8.5 0.3 23.0 36.4 20.3 0.4 0.2 0.1 TR -- -- -- 1 --

 79P 727 142-165 BCk2 18.4 56.3 25.3 7.3 22.2 34.1 24.6 0.4 0.2 0.1 TR -- -- -- 1 --

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B1b 6S1a 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 18 1.52 0.149 0.4 0.1 TR 0.96 0.53 33 10 1.31 1.43 0.030 34.6 27.2 11.1 0.21

 18- 30 1.14 0.122 0.4 0.1 TR 0.93 0.52 34 12 1.34 1.45 0.027 32.3 25.7 11.2 0.19

 30- 49 0.99 0.097 0.5 0.1 TR 0.90 0.52 42 22 1.32 1.48 0.039 30.5 27.2 14.3 0.17

 49- 71 0.61 0.067 0.5 0.1 TR 0.88 0.54 44 23 1.46 1.62 0.035 27.5 25.1 15.4 0.14

 71- 91 0.40 0.049 0.5 0.1 TR 0.90 0.53 42 21 1.47 1.58 0.024 26.6 23.4 13.6 0.14

 91-117 0.26 0.039 0.4 0.1 TR 1.00 0.53 34 13 1.41 1.49 0.019 28.4 22.7 11.6 0.16

 117-142 0.18 0.027 0.4 0.1 TR 1.09 0.57 32 11 1.36 1.43 0.017 33.0 25.2 11.2 0.19

 142-165 0.15 0.022 0.4 0.1 TR 1.13 0.57 32 9 1.32 1.38 0.015 37.1 23.8 10.4 0.18

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- (- -CEC- -) EXCH SAR BASE CO3 AS RES. CaSO4 AS (- - - -PH - - -)

 Ca Mg Na K SUM ITY SUM NH4- Na SATURATION CaCO3 ohms GYPSUM SAT CaCl2 H2O

 DEPTH 5B4a 5B4a 5B4a 5B4a BASES CATS OAc SUM NH4OAc <2mm /cm <2mm <20mm PASTE .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H2b 5A3a 5A6a 5D2 5E 5C3 5C1 6E1b 8E1 6F1c 6F1c 8C1b 8C1e 8C1a

 <- - - - - - - - - -meq / 100 g - - - - - - - - - -> Pct <- -Pct- > Pct <- -Pct -> 1:2 1:1

 0- 18 12.0 3.0 TR 2.6 17.6 6.0 23.6 20.3 TR 75 87 5.7 6.3

 18- 30 14.6 3.7 0.1 1.4 19.8 7.6 27.4 19.8 TR 72 100 TR 5.6 6.1

 30- 49 18.1 5.7 0.1 1.0 24.9 4.1 29.0 24.7 TR 86 100 TR 6.4 7.0

 49- 71 17.3 6.2 0.2 1.4 25.1 3.8 28.9 25.0 1 87 100 TR 6.5 7.1

 71- 91 16.2 5.6 0.2 1.5 23.5 2.7 26.2 23.3 1 90 100 TR 6.9 7.4

 91-117 18.3 5.6 0.2 1.8 25.9 1.7 27.6 21.8 1 TR 94 100 TR 2200 7.4 7.4 8.0

 117-142 6.9 0.2 2.2 21.4 1 100 100 2 7.8 8.5

 142-165 7.6 0.3 2.4 20.8 1 100 100 3 7.9 8.6

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - - - - - - - - - -WATER EXTRACTED FROM SATURATED PASTE- - - - - - - - - - - - - )PRED.

 TOTAL ELEC. ELEC.

 Ca Mg Na K CO3 HCO3 F Cl SO4 NO2 NO3 H2O SALTS COND. COND.

 DEPTH EST. 8A1a 8I

 (cm) 6N1b 6O1b 6P1b 6Q1b 6I1b 6J1b 6U1a 6K1c 6L1c 6W1a 6M1c 8A 8D5 mmhos mmhos

 < - - - - - - - - - - - - - -meq / liter - - - - - - - - - - - -> <- -Pct- -> /cm /cm

 91-117 2.0 1.0 0.4 0.7 -- 3.4 -- 0.1 0.2 -- -- 74.0 TR 0.42

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA-

 < - - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION

 NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->

 79P 720 TCLY MI 3 KK 2 MT 2 QZ 1 6.0 2.5

 79P 721 TCLY MI 3 KK 2 MT 2 QZ 1 6.3 2.4

 79P 722 TCLY MT 4 MI 3 KK 2 QZ 1 KK15 6.7 2.2

 79P 723 TCLY MT 3 MI 2 KK 2 QZ 1 6.1 2.0

 79P 724 TCLY MT 3 MI 3 KK 2 QZ 1 6.9 2.2

 79P 725 TCLY MT 3 MI 2 KK 2 QZ 1 6.3 2.3

 79P 726 TCLY MT 3 MI 2 KK 2 QZ 1 6.1 2.2

 79P 727 TCLY MT 2 MI 1 KK 1 QZ 1 6.3 2.2

 -----------------------------------------------------------------------------------------------------------------------------------
Mollisols 559

(b) 50 percent or more chroma of 2 or less on faces

of peds or in the matrix, hue of 2.5Y, and redox

concentrations; or

(c) 50 percent or more chroma of 1 on faces of

peds or in the matrix and hue of 2.5Y or yellower;

or

(d) 50 percent or more chroma of 3 or less on

faces of peds or in the matrix, hue of 5Y, and redox

concentrations; or

(e) 50 percent or more chroma of 0 on faces of

peds or in the matrix; or

(f) Hue of 5GY, 5G, 5BG, or 5B; or

(g) Any color if it results from uncoated sand

grains; or

b. Chroma of 2 in the lower part of the mollic

epipedon; and either

(1) Distinct or prominent redox concentrations in

the lower part of the mollic epipedon; or

(2) Directly below the mollic epipedon, one of the

following matrix colors:

(a) A color value, moist, of 4, chroma of 2, and

some redox depletions with a color value, moist, of

4 or more and chroma of 1 or less; or

(b) A color value, moist, of 5 or more, chroma of 2

or less, and redox concentrations; or

(c) A color value, moist, of 4 and chroma of 1 or

less; or

6. At a depth between 40 and 50 cm from the mineral soil

surface, enough active ferrous iron to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquolls, p. 563

IC. Other Mollisols that:

1. Have a mollic epipedon less than 50 cm thick; and

2. Do not have an argillic or calcic horizon; and

3. Have, either within or directly below the mollic

epipedon, mineral soil materials less than 7.5 cm in

diameter that have a CaCO3 equivalent of 40 percent or

more; and

4. Have either or both a udic moisture regime or a cryic

soil temperature regime.

Rendolls, p. 584

ID. Other Mollisols that have a cryic soil temperature

regime.

Cryolls, p. 575

Characterization Data for a Mollisol--Continued

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA-

 < - - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION

 NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->

 79P 722 CSi 61 QZ52 FK19 FP 7 GS 6 CD 4 PO 3

 79P 722 CSi GA 2 HN 1 AR 1 FE 1 OP 1 MS 1

 79P 722 CSi PR 1 BTtr BYtr STtr ZRtr RUtr

 79P 722 CSi EPtr GNtr TMtr TEtr APtr

 79P 723 CSi 60 QZ51 FK25 FP 7 CD 4 PO 3 GS 2

 79P 723 CSi HN 2 AR 2 OP 1 MS 1 GA 1 TM 1

 79P 723 CSi FEtr BTtr PRtr STtr ZEtr GNtr

 79P 723 CSi CTtr APtr ZRtr BYtr TEtr

 79P 724 CSi 61 QZ54 FK22 FP 7 CD 4 GS 3 AR 3

 79P 724 CSi HN 2 MS 2 OP 2 PR 1 FE 1 POtr

 79P 724 CSi BTtr ZRtr ZEtr FZtr CTtr GNtr

 79P 724 CSi APtr BYtr RUtr TMtr

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.

 Fraction interpretation: TCLY, total clay, <0.002 mm; CSi, coarse silt, 0.02-0.05 mm.

 Mineral interpretation: MI, mica; KK, kaolinite; MT, montmorillonite; QZ, quartz; FK, potassium feldspar; FP, plagioclase feldspar;

 GS, glass; CD, chalcedony; PO, plant opal; GA, glass aggregate; HN, hornblende; AR, weathered aggregate; FE, iron oxides; OP,

 opaques; MS, muscovite; PR, pyroxene; BT, biotite; BY, beryl; ST, stilbite; ZR, zircon; RU, rutile; EP, epidote; GN, garnet;

 TM, tourmaline; TE, tremolite; AP, apatite; ZE, zeolite; CT, cassiterite; FZ, feldspathoid.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
560 Soil Taxonomy

IE. Other Mollisols that have either a xeric moisture regime or

an aridic moisture regime that borders on xeric.

Xerolls, p. 630

IF. Other Mollisols that have either an ustic moisture regime or

an aridic moisture regime that borders on ustic.

Ustolls, p. 601

IG. Other Mollisols.

Udolls, p. 586

Albolls

Albolls are the Mollisols that have an albic horizon and

fluctuating ground water. Most of these soils are saturated with

water to or near the soil surface at some time during winter or

spring in normal years. In summer ground water commonly is

not within a depth of 200 cm. Below the albic horizon, there is

either an argillic or, less commonly, a natric horizon. These

soils developed mostly on broad, nearly level to sloping ridges,

on back slopes, or in closed depressions. Most have

episaturation. In the United States, most Albolls are in areas of

late-Pleistocene deposits. Most Albolls developed under grass

or grass and shrub vegetation. In early stages of development,

some are thought to have had forest vegetation that was

replaced by grass. Because slopes are gentle, most of the

Albolls in the United States are now cultivated.

Definition

Albolls are the Mollisols that have all of the following:

1. An argillic or natric horizon; and

2. An albic horizon that has chroma of 2 or less and that

is 2.5 cm or more thick, has its lower boundary 18 cm or more

below the mineral soil surface, and either lies directly below

the mollic epipedon or separates horizons that together meet all

of the requirements for a mollic epipedon; and

3. In one or more subhorizons of the albic horizon and/or of

the argillic or natric horizon and within 100 cm of the mineral

soil surface, redox concentrations in the form of masses or

concretions, or both, and also aquic conditions for some time in

normal years (or artificial drainage).

Key to Great Groups

IAA. Albolls that have a natric horizon.

Natralbolls, p. 562

IAB. Other Albolls.

Argialbolls, p. 560

Argialbolls

These are the Albolls that have an argillic horizon but do not

have a natric horizon. Most of the soils have very dark gray to

black coatings of humus and clay on the peds in the upper part

of the argillic horizon. In the United States, these soils are most

extensive in the loess-covered areas of the Midwestern States

where temperature regimes are mesic. A very few of the soils

have a frigid or thermic temperature regime. A distinct moisture

deficit in summer and a moisture surplus in winter and spring

seem to be essential to the genesis of these soils. Argialbolls are

associated on the landscape with soils of all other suborders of

Mollisols, except possibly for Rendolls. Because they have

gentle slopes, most of the Argialbolls in the United States are

cultivated.

Definition

Argialbolls are the Albolls that have an argillic horizon but do

not have a natric horizon.

Key to Subgroups

IABA. Argialbolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. If not irrigated, a moisture control section that in

normal years is dry in all parts for 45 or more consecutive

days during the 120 days following the summer solstice.

Xerertic Argialbolls

IABB. Other Argialbolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm
Mollisols 561

or a densic, lithic, or paralithic contact, whichever is

shallower.

Vertic Argialbolls

IABC. Other Argialbolls that:

1. Do not have an abrupt textural change from the albic to

the argillic horizon; and

2. If not irrigated, have a moisture control section that in

normal years is dry in all parts for 45 or more consecutive

days during the 120 days following the summer solstice.

Argiaquic Xeric Argialbolls

IABD. Other Argialbolls that do not have an abrupt textural

change from the albic to the argillic horizon.

Argiaquic Argialbolls

IABE. Other Argialbolls that, if not irrigated, have a

moisture control section that in normal years is dry in all parts

for 45 or more consecutive days during the 120 days following

the summer solstice.

Xeric Argialbolls

IABF. Other Argialbolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Argialbolls

IABG. Other Argialbolls.

Typic Argialbolls

Definition of Typic Argialbolls

Typic Argialbolls are the Argialbolls that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention, and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Have an abrupt textural change from the albic to the

argillic horizon;

3. When not irrigated, have a moisture control section that in

normal years is not dry in all parts for as long as 45

consecutive days during the 120 days following the summer

solstice; and

4. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is

shallower.

Description of Subgroups

Typic Argialbolls.—The central concept or Typic subgroup

of Argialbolls is fixed on soils that are saturated with water at

some season long enough to have a low chroma dominant in

the albic horizon and that receive enough summer rainfall for

the moisture control section to be moistened, at least in some

part, at frequent intervals in normal years. In addition, the

argillic horizon has an abrupt upper boundary, has a markedly

greater percentage of clay than the albic horizon, and has the

accessory property of low or very low hydraulic conductivity

when the water content is at or above field capacity.

Prolonged dryness of the moisture control section occurs in

Mediterranean climates. It is a property of the Xeric suborder

of Mollisols and is the basis for defining the Xeric subgroups

of Argialbolls. A gradual upper boundary of the argillic

horizon or a small difference in the percentage of clay between

the albic and argillic horizons indicates an intergrade to

Argiaquolls. A surface mantle that shows the influence of
562 Soil Taxonomy

pyroclastic materials has many of the properties of Andisols and

is the basis for defining the Aquandic subgroup.

Typic Argialbolls are of moderate extent in the United

States and are mostly on the Great Plains. Most of these soils

supported water-tolerant grasses, sedges, and shrubs. Most are

used as cropland or hayland, and many are artificially drained.

Some are used as grazing land and some as wildlife habitat.

Aquandic Argialbolls.—These soils are like Typic

Argialbolls, but they have a layer in the upper 75 cm that is 18

cm or more thick and has some andic soil properties. The clays

in this layer normally do not disperse well and have a high pHdependent charge. Typically, this layer is at or very close to the

soil surface. Aquandic Argialbolls are of very small extent in

the United States and are known to occur only in California

and Oregon.

Argiaquic Argialbolls.—These soils are like Typic

Argialbolls, but they do not have the abrupt textural change

required of Typic Argialbolls. They are considered to be

intergrades to Argiaquolls. The hydraulic conductivity in the

argillic horizon of soils in the Argiaquic subgroup normally is

greater than that of Typic Argialbolls. Most Argiaquic

Argialbolls supported water-tolerant grasses. Many have been

artificially drained and are used as cropland or hayland. Some

are used as grazing land and some as wildlife habitat.

Argiaquic Xeric Argialbolls.—These soils consistently

have long periods in summer when the moisture control section

is dry, and they do not have the abrupt textural change that

marks the Typic subgroup. In these properties they resemble

Xerolls and Argiaquolls. Argiaquic Xeric Argialbolls are of

small extent in the United States and are known to occur only

in Oregon, Idaho, and Montana. Some of these soils supported

trees, and some supported mostly water-tolerant grasses and

shrubs. Most of the soils are used as cropland, hayland, or

pasture. Some are used as rangeland.

Vertic Argialbolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They are of small extent in the United

States. They occur throughout the Great Plains. These soils

supported mostly water-tolerant grasses. Most are used as

cropland or hayland. Some have been artificially drained.

Some are used as grazing land and some as wildlife habitat.

Xerertic Argialbolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They consistently have long

periods in summer when the moisture control section is dry.

These soils are of small extent in the United States and are

known to occur only in Oregon and Idaho. Some of the soils

supported coniferous forest vegetation, and some supported

mostly water-tolerant grasses. Most of the soils are used as

cropland or hayland. Some are used as forest and some as

grazing land.

Xeric Argialbolls.—These soils consistently have long

periods in summer when the moisture control section is dry.

They are of moderate extent in the United States and occur

mostly in the Northwestern States. Most of these soils

supported water-tolerant grasses, and some supported

coniferous forest vegetation. Most are used as cropland or

hayland. Some are used as grazing land and some as forest.

Natralbolls

These are the Albolls that have a natric horizon. The natric

horizon normally lies very close to the surface. These soils

commonly have a thin epipedon overlying an albic horizon.

The color of the upper part of the soils, after mixing to a depth

of 18 cm, however, is dark enough for a mollic epipedon

because the epipedon and the natric horizon are dark colored.

Ground water is shallow during part of the year, and capillary

rise in many Natralbolls has concentrated salts, including

sodium salts, in the upper 50 cm of the soils.

Natralbolls are known to occur only in subhumid and humid

regions. They are in areas of late-Pleistocene till plains and

lacustrine deposits or Holocene deposits. The vegetation

consists of grasses and sedges. The soils are used as cropland

or rangeland, or the grasses are cut for hay.

Definition

Natralbolls are the Albolls that have a natric horizon.

Key to Subgroups

IAAA. Natralbolls that have visible crystals of gypsum

and/or more soluble salts within 40 cm of the mineral soil

surface.

Leptic Natralbolls

IAAB. Other Natralbolls.

Typic Natralbolls

Definition of Typic Natralbolls

Typic Natralbolls are the Natralbolls that do not have visible

crystals of gypsum and/or more soluble salts within 40 cm of

the mineral soil surface.

Description of Subgroups

Typic Natralbolls.—The central concept or Typic subgroup

of Natralbolls is fixed on soils that do not have visible crystals

of gypsum and/or more soluble salts within 40 cm of the

mineral soil surface. The salts adversely affect the use of these

soils and are the basis for defining the Leptic subgroup. These

soils are of very small extent in the United States. They are

mostly on the northern Great Plains. They supported mostly

salt-tolerant grasses and sedges. Slopes generally are gentle,

and many of these soils are cultivated. Some of the soils are

used as rangeland or hayland.

Leptic Natralbolls.—These soils have visible evidence of

salts at least as soluble as gypsum within 40 cm of the soil

surface. They have thinner sola than those of the Typic

subgroup, and the close proximity of the soluble salts to the
Mollisols 563

surface restricts plant growth. Leptic Natralbolls are

moderately extensive on the northern Great Plains of the

United States. They are on gentle slopes and are used

primarily as rangeland.

Aquolls

Aquolls are the Mollisols that are wet and that have

dominant low chroma, commonly in olive hues, and have highcontrast redox depletions in or below the epipedon. These soils

commonly develop in low areas where water collects and

stands, but some are on broad flats or on seepy hillsides. Most

of the soils have had a vegetation of grasses, sedges, and forbs,

but a few also have had forest vegetation. In the United States,

Aquolls are most extensive in glaciated areas of the

Midwestern States where the drift or loess was calcareous. In a

layer above a densic, lithic, or paralithic contact or in a layer at

a depth between 40 and 50 cm from the mineral soil surface,

whichever is shallower, Aquolls have aquic conditions or are

artificially drained. They can have any temperature regime

from cryic to isohyperthermic.

Definition

Aquolls are the Mollisols that have, in a layer above a

densic, lithic, or paralithic contact or in a layer at a depth

between 40 and 50 cm from the mineral soil surface, whichever

is shallower, aquic conditions for some time in normal years

(or artificial drainage) and meet one or more of the following:

1. Have a histic epipedon overlying the mollic epipedon; or

2. Have an exchangeable sodium percentage (ESP) of 15 or

more (or a sodium adsorption ratio [SAR] of 13 or more) in the

upper part of the mollic epipedon and a decrease in ESP (or

SAR) values with increasing depth below 50 cm from the

mineral soil surface; or

3. Have a calcic or petrocalcic horizon that has its upper

boundary within 40 cm of the mineral soil surface; or

4. Have a mollic epipedon, with chroma of 1 or less, that

extends to a lithic contact within 30 cm of the mineral soil

surface; or

5. Have one of the following colors:

a. Chroma of 1 or less in the lower part of the mollic

epipedon; and either

(1) Distinct or prominent redox concentrations in the

lower part of the mollic epipedon; or

(2) Either directly below the mollic epipedon or

within 75 cm of the mineral soil surface if a calcic

horizon intervenes, a color value, moist, of 4 or more and

one of the following:

(a) 50 percent or more chroma of 1 on faces of peds

or in the matrix, hue of 10YR or redder, and redox

concentrations; or

(b) 50 percent or more chroma of 2 or less on faces of

peds or in the matrix, hue of 2.5Y, and redox

concentrations; or

(c) 50 percent or more chroma of 1 on faces of

peds or in the matrix and hue of 2.5Y or yellower;

or

(d) 50 percent or more chroma of 3 or less on faces

of peds or in the matrix, hue of 5Y, and redox

concentrations; or

(e) 50 percent or more chroma of 0 on faces of peds

or in the matrix; or

(f) Hue of 5GY, 5G, 5BG, or 5B; or

(g) Any color if it results from uncoated sand grains;

or

b. Chroma of 2 in the lower part of the mollic epipedon;

and either

(1) Distinct or prominent redox concentrations in the

lower part of the mollic epipedon; or

(2) Matrix colors directly below the mollic epipedon as

follows: either

(a) A color value, moist, of 4, chroma of 2, and some

redox depletions with a color value, moist, of 4 or

more and chroma of 1 or less; or

(b) A color value, moist, of 5 or more, chroma of 2

or less, and redox concentrations; or

(c) A color value, moist, of 4 and chroma of 1 or

less; or

6. At a depth between 40 and 50 cm from the mineral soil

surface, have enough active ferrous iron to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is not

being irrigated; and

7. Do not have both an albic horizon and, within 100 cm of

the mineral soil surface, any subhorizon of the albic horizon

and/or of the argillic or natric horizon that has redox

concentrations in the form of masses or concretions, or both,

and also aquic conditions.

Key to Great Groups

IBA. Aquolls that have a cryic soil temperature regime.

Cryaquolls, p. 566

IBB. Other Aquolls that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Duraquolls, p. 568
564 Soil Taxonomy

IBC. Other Aquolls that have a natric horizon.

Natraquolls, p. 574

IBD. Other Aquolls that have a calcic or gypsic horizon that

has its upper boundary within 40 cm of the mineral soil surface

but do not have an argillic horizon unless it is a buried

horizon.

Calciaquolls, p. 565

IBE. Other Aquolls that have an argillic horizon.

Argiaquolls, p. 564

IBF. Other Aquolls that have episaturation.

Epiaquolls, p. 571

IBG. Other Aquolls.

Endoaquolls, p. 569

Argiaquolls

These are the Aquolls that have both an argillic horizon and a

temperature regime warmer than cryic. In these soils the depth to

ground water fluctuates appreciably and commonly is shallow in

winter and spring but deep in summer. Most of the Argiaquolls

in the United States have been drained and are used as

cropland. They are extensive and are widely distributed

throughout the Midwest and the western parts of the country.

Definition

Argiaquolls are the Aquolls that:

1. Have an argillic horizon but do not have a natric horizon;

and

2. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface; and

3. Have a soil temperature regime that is warmer than cryic.

Key to Subgroups

IBEA. Argiaquolls that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm.

Arenic Argiaquolls

IBEB. Other Argiaquolls that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more.

Grossarenic Argiaquolls

IBEC. Other Argiaquolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Argiaquolls

IBED. Other Argiaquolls that have an argillic horizon that,

with increasing depth, has a clay increase of 20 percent or

more (absolute, in the fine-earth fraction) within its upper 7.5

cm.

Abruptic Argiaquolls

IBEE. Other Argiaquolls.

Typic Argiaquolls

Definition of Typic Argiaquolls

Typic Argiaquolls are the Argiaquolls that:

1. Do not have an argillic horizon that has an increase in clay

content of 20 percent (absolute) or more within a vertical

distance of 7.5 cm below the upper boundary;

2. Have a texture finer than loamy fine sand in some

subhorizon within 50 cm of the mineral soil surface; and

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Argiaquolls.—The central concept or Typic subgroup

of Argiaquolls is fixed on soils that have a gradual textural

change at the top of the argillic horizon, have a loamy or

clayey particle-size class close to the surface, but do not have

slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks. An abrupt textural change is the

basis for defining Abruptic extragrades of Argiaquolls. A sandy

surface layer more than 50 cm thick is the basis for defining

Arenic and Grossarenic extragrades. Deep cracks, slickensides,

wedge-shaped aggregates, and a high linear extensibility are

characteristics shared with Vertisols and are the basis for

defining the Vertic subgroup.

Typic Argiaquolls are extensive in the United States. They
Mollisols 565

are widely distributed, but the largest extent is in the Midwest

and on the Great Plains. These soils supported mostly watertolerant grasses, sedges, and shrubs. Most have been artificially

drained and are used as cropland. Some are used as grazing

land or hayland and some as wildlife habitat.

Abruptic Argiaquolls.—These soils have an abrupt textural

change at the top of the argillic horizon. They become dry in

the moisture control section in normal years. They may be

intergrades to Argialbolls, but they show no clear evidence of

the development of an albic horizon. These soils are of small

extent in the United States and occur mostly on the Great

Plains. They supported mostly water-tolerant grasses, sedges,

and shrubs. Slopes are gentle, and most of the soils have been

artificially drained and are used as cropland or hayland. Some

of the soils are used as grazing land and some as wildlife

habitat.

Arenic Argiaquolls.—These soils have a sandy or sandyskeletal particle-size class to a depth between 50 and 100 cm.

These soils are of very small extent in the United States and are

known to occur only in Florida.

Grossarenic Argiaquolls.—These soils have a sandy or

sandy-skeletal particle-size class to a depth of more than 100

cm. They are of very small extent in the United States and are

known to occur only in Florida.

Vertic Argiaquolls.—These soils are like Typic Argiaquolls,

but they are high in content of expanding clays and have cracks,

slickensides, wedge-shaped aggregates, or a high linear

extensibility. Most of the soils in this subgroup have a clayey

particle-size class in a significant part. These soils are of

moderate extent in the United States and occur mostly on the

Great Plains. They supported mostly water-tolerant grasses,

sedges, and shrubs. Most of the soils have been artificially

drained and are used as cropland or hayland. Some are used as

grazing land and some as wildlife habitat.

Calciaquolls

These are the Aquolls that have a shallow calcic or gypsic

horizon. They have a temperature regime warmer than cryic,

do not have a natric or argillic horizon, and do not have a

duripan that has its upper boundary within 100 cm of the

mineral soil surface. Capillary rise of calcium-rich water and

then evapotranspiration have been important processes in the

genesis of these soils. In the humid parts of the United States,

the soils commonly formed around the margins of shallow,

intermittent ponds in closed depressions left by glaciers. In

semiarid and arid areas, the soils are mainly on flood plains,

low terraces, and the margins of Pleistocene lakes where

ground water is shallow. A calcic horizon normally is at or

very close to the surface of the soils. Carbonates in high

concentrations act as a white pigment, and not all Calciaquolls

have a surface horizon that is dark colored when dry. Aquolls

with a gypsic horizon are included with Calciaquolls, but no

Calciaquolls with a gypsic horizon have been recognized in the

United States.

Calciaquolls are moderately extensive in the United States.

Most are calcareous from the surface downward, and problems

with plant chlorosis are common. In humid regions potassium

deficiency in plants can be severe. In arid regions salinity may

be a problem.

Definition

Calciaquolls are the Aquolls that:

1. Have a calcic or gypsic horizon that has its upper boundary

within 40 cm of the mineral soil surface;

2. Have a soil temperature regime warmer than cryic;

3. Do not have a natric or argillic horizon; and

4. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Key to Subgroups

IBDA. Calciaquolls that have a petrocalcic horizon that has

its upper boundary within 100 cm of the mineral soil surface.

Petrocalcic Calciaquolls

IBDB. Other Calciaquolls that have 50 percent or more

chroma of 3 or more on faces of peds or in the matrix of one or

more horizons within 75 cm of the mineral soil surface or that

have the following colors directly below the mollic epipedon:

1. Hue of 2.5Y or yellower and chroma of 3 or more; or

2. Hue of 10YR or redder and chroma of 2 or more; or

3. Hue of 2.5Y or yellower and chroma of 2 or more if

there are no distinct or prominent redox concentrations.

Aeric Calciaquolls

IBDC. Other Calciaquolls.

Typic Calciaquolls

Definition of Typic Calciaquolls

Typic Calciaquolls are the Calciaquolls that:

1. Have more than 50 percent chroma of 2 or less on faces of

peds or in the matrix in all horizons within 75 cm of the

mineral soil surface or have the following colors directly below

the mollic epipedon:

a. Hue of 2.5Y or yellower, chroma of 2 or less, and

distinct or prominent redox concentrations; or

b. Hue of 2.5Y or yellower and chroma of 1; or

c. Hue of 10YR or redder and chroma of 1; or

d. Chroma of 0; and
566 Soil Taxonomy

2. Do not have a petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface.

Description of Subgroups

Typic Calciaquolls.—The central concept or Typic

subgroup of Calciaquolls is fixed on soils that have redox

concentrations with high chroma or have low chroma at a

shallow depth and that do not have a petrocalcic horizon

above a depth of 100 cm.

The absence of redox concentrations that have high chroma

and chroma in the matrix higher than that of the Typic

subgroup are evidence of somewhat better natural drainage

than that of the Typic subgroup, and these properties are the

basis for defining the Aeric subgroup. A shallow petrocalcic

horizon is known to occur only in arid climates and is not

considered normal. It is the basis for defining the Petrocalcic

subgroup. Calciaquolls that have a gypsic horizon are included

in the Typic subgroup, but none are known to occur in the

United States.

Typic Calciaquolls are moderately extensive in the United

States. They are widely distributed, but the largest extent is in

the Midwest and on the Great Plains. These soils supported

mostly water-tolerant grasses, sedges, and shrubs. Most are

used as grazing land or hayland. Some are used as cropland

and some as wildlife habitat.

Aeric Calciaquolls.—These soils have chroma higher than

that of Typic Calciaquolls and are deeper to redox

concentrations. Ground water is normally deeper than in soils

of the Typic subgroup. Aeric Calciaquolls are of moderate

extent in the United States, mostly on the Great Plains. They

supported mostly water-tolerant grasses and shrubs. Most of

the soils are used as cropland, grazing land, or hayland, but

some are used as wildlife habitat.

Petrocalcic Calciaquolls.—These soils have a petrocalcic

horizon within 100 cm of the mineral soil surface and

commonly within 50 cm. They are mostly on the margins of

Pleistocene lakes in arid regions. The processes that produced

the petrocalcic horizon are not understood. These soils are of

very small extent in the United States and are known to occur

only in Utah.

Cryaquolls

Cryaquolls are the cold Aquolls of high elevations or

high latitudes. Because they are both wet and cold, most

of these soils are not cultivated. The presence or absence

of horizons used to define the great groups of warmer soils

has less significance to the use of these soils, although the

processes that produced the horizons appear to be similar.

Cryaquolls may have an argillic or cambic horizon or a

shallow calcic horizon. In the United States, these soils are

mostly in high mountain valleys in the West, but they are not

extensive. They are used mostly for grazing, or the grasses are

cut for hay.

Definition

Cryaquolls are the Aquolls that have a cryic temperature

regime.

Key to Subgroups

IBAA. Cryaquolls that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Cryaquolls

IBAB. Other Cryaquolls that have a histic epipedon.

Histic Cryaquolls

IBAC. Other Cryaquolls that have a buried layer of organic

soil materials, 20 cm or more thick, that has its upper

boundary within 100 cm of the mineral soil surface.

Thapto-Histic Cryaquolls

IBAD. Other Cryaquolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Cryaquolls

IBAE. Other Cryaquolls that have an argillic horizon.

Argic Cryaquolls

IBAF. Other Cryaquolls that have a calcic horizon either

within or directly below the mollic epipedon.

Calcic Cryaquolls
Mollisols 567

IBAG. Other Cryaquolls that have a mollic epipedon 50 cm or

more thick.

Cumulic Cryaquolls

IBAH. Other Cryaquolls.

Typic Cryaquolls

Definition of Typic Cryaquolls

Typic Cryaquolls are the Cryaquolls that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

2. Do not have an argillic horizon;

3. Do not have a calcic horizon within or directly below the

mollic epipedon;

4. Have a mollic epipedon that is less than 50 cm thick;

5. Do not have a histic epipedon;

6. Do not have a buried layer of organic soil materials, 20 cm

or more thick, that has its upper boundary within a depth of

100 cm; and

7. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Cryaquolls.—The central concept or Typic subgroup

of Cryaquolls is fixed on soils that have a mollic epipedon less

than 50 cm thick and that do not have a histic epipedon or an

argillic or calcic horizon. These soils do not have slickensides,

wedge-shaped aggregates, a high linear extensibility, or wide

cracks. They do not have a buried Histosol or a surface mantle

or layer in the upper 75 cm that has both a low bulk density

and a high content of weakly crystalline minerals or that

consists of slightly or moderately weathered pyroclastic

materials because these properties are shared with Andisols.

An argillic horizon in or below the mollic epipedon is rare

and is the basis for defining intergrades to Argiaquolls. A

calcic horizon in or directly below the epipedon is rare and is

the basis for defining intergrades to Calciaquolls. The

thickness of the mollic epipedon is normally less than 50 cm,

but in some Cryaquolls the thickness is quite variable within

distances of a few centimeters because of frost action. Tongues

of the mollic epipedon a few centimeters across may penetrate

the cambic horizon for a distance of more than 25 cm. If such

tongues are present, the average penetration is used to

determine the thickness of the epipedon. An overthickened

epipedon is the basis for defining the Cumulic extragrade.

The wettest Cryaquolls may have a histic epipedon, and they

are regarded as a transition to Histosols. A buried Histosol at a

depth of less than 100 cm is the basis for defining the ThaptoHistic subgroup.

Typic Cryaquolls are of moderate extent in the United

States. They are mostly in mountain valleys in the Western

States. These soils supported mostly water-tolerant grasses,

sedges, and shrubs. Most of the soils are used as grazing land

or wildlife habitat.

Aquandic Cryaquolls.—These soils are like Typic

Cryaquolls, but they have a surface mantle or layer in the upper

75 cm that has both a low bulk density and a high content of

weakly crystalline minerals or that consists of slightly or

moderately weathered pyroclastic materials. These soils are of

small extent in the United States. They are in mountain valleys

in the Northwestern States. They supported mostly watertolerant grasses, sedges, and shrubs. Most of the soils are used

as grazing land or wildlife habitat.

Argic Cryaquolls.—These soils have an argillic horizon

and are considered intergrades to Argiaquolls. They are of

small extent in the United States. They are mostly in mountain

valleys in the Western States. They supported mostly watertolerant grasses, sedges, and shrubs. Most of the soils are used

as grazing land or wildlife habitat.

Calcic Cryaquolls.—These soils have a calcic horizon in or

directly below the mollic epipedon and are considered

intergrades to Calciaquolls. The water table usually is high

during the short summer, and the water results in enrichment

of the surface layer with carbonates by capillary rise and
568 Soil Taxonomy

evapotranspiration. These soils are of small extent in the United

States. They are mostly in mountain valleys in the Western

States. They supported mostly water-tolerant grasses, sedges,

and shrubs. Most of the soils are used as grazing land or wildlife

habitat.

Cumulic Cryaquolls.—These soils have an overthickened

mollic epipedon as a result of slow accumulation of material

washed from higher areas. They are subject to occasional

flooding when streams are high. These soils are of small extent

in the United States. They are mostly in narrow mountain

valleys in the Western States. They supported mostly watertolerant grasses, sedges, shrubs, and trees. Most of the soils are

used as grazing land or wildlife habitat.

Histic Cryaquolls.—These soils have a histic epipedon and

are considered intergrades to Histosols. They are the wettest of

the Cryaquolls, and the level of ground water in them

fluctuates the least. Histic Cryaquolls are rare in the United

States. They are known to occur only in Colorado.

Thapto-Histic Cryaquolls.—These soils formed in mineral

deposits over a Histosol. The epipedon may extend to the

buried Histosol, which has its upper boundary within 100 cm

of the mineral soil surface. These soils are not known to occur

in the United States.

Vertic Cryaquolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They are dry periodically in at least the

upper part during normal years. They are not known to occur

in the United States.

Duraquolls

These are the Aquolls that have a duripan and a soil

temperature regime warmer than cryic. In the United States,

these soils are restricted to areas that have a Mediterranean

climate or to arid regions. All Duraquolls are near enough to

volcanoes to have received ash falls. They are wet in winter,

but most are quite dry in summer. The upper boundary of the

duripan most commonly lies about 50 to 75 cm below the soil

surface. These soils range from slightly acid to strongly

alkaline. They are of small extent.

Definition

Duraquolls are the Aquolls that:

1. Have a duripan that has its upper boundary within 100 cm

of the mineral soil surface; and

2. Have a soil temperature regime that is warmer than cryic.

Key to Subgroups

IBBA. Duraquolls that have a natric horizon.

Natric Duraquolls

IBBB. Other Duraquolls that have, above the duripan, one or

both of the following:

1. Cracks that are 5 mm or more wide through a thickness of

30 cm or more for some time in normal years, and slickensides

or wedge-shaped aggregates in a layer 15 cm or more thick;

or

2. A linear extensibility of 6.0 cm or more.

Vertic Duraquolls

IBBC. Other Duraquolls that have an argillic horizon.

Argic Duraquolls

IBBD. Other Duraquolls.

Typic Duraquolls

Definition of Typic Duraquolls

Typic Duraquolls are the Duraquolls that:

1. Do not have an argillic or natric horizon; and

2. Do not have either:

a. Cracks that for some time in normal years are 5 mm or

more wide throughout a layer 30 cm or more thick either

within 125 cm of the mineral soil surface or above a duripan

if shallower, and slickensides or wedge-shaped aggregates

in a layer 15 cm or more thick that has its upper boundary

within 125 cm of the mineral soil surface or above a duripan

if shallower; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact or a duripan, whichever

is shallower.

Description of Subgroups

Typic Duraquolls.—The central concept or Typic subgroup

of Duraquolls is fixed on soils that do not have an argillic

horizon and do not have a natric horizon. These soils do not

have deep cracks, slickensides, wedge-shaped aggregates, or a

high linear extensibility. The presence of an argillic or natric

horizon is the basis for defining intergrades to Argiaquolls and

Natraquolls, respectively. Typic Duraquolls are of small extent

in the United States. They are only in the Western States. They

supported mostly water-tolerant grasses, sedges, and shrubs.

Most of the soils are used as irrigated cropland, hayland, or

rangeland.

Argic Duraquolls.—These soils are like Typic Duraquolls,

but they have an argillic horizon. They are of very small extent

in the United States. They are known to occur only in

California and Oregon, where they are used mostly as

rangeland.

Natric Duraquolls.—These soils are like Typic Duraquolls,

but they have a natric horizon above the duripan. They are of

small extent in the United States. They are only in the Western

States. They supported mostly water-tolerant grasses, sedges,

and shrubs. Most of the soils are used as irrigated cropland,

hayland, or rangeland.
Mollisols 569

Vertic Duraquolls.—These soils are like Typic Duraquolls,

but they have a clayey particle-size class in a significant part,

have expanding clays, and in normal years have deep cracks.

They are of very small extent in the United States. They

supported mostly water-tolerant grasses.

Endoaquolls

These are the Aquolls that have both endosaturation and a

temperature regime warmer than cryic. They do not have an

argillic, natric, calcic, or gypsic horizon. The depth to ground

water fluctuates appreciably in these soils. Commonly, the

ground water is at or near the soil surface in winter and spring

but is deep in summer. Most of the Endoaquolls in the United

States have been artificially drained and are used as cropland.

They are extensive and are widely distributed throughout the

Midwest and the western parts of the country.

Definition

Endoaquolls are the Aquolls that:

1. Have endosaturation;

2. Have a soil temperature regime that is warmer than

cryic;

3. Do not have an argillic or natric horizon;

4. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface; and

5. Do not have a calcic or gypsic horizon that has its upper

boundary within 40 cm of the mineral soil surface.

Key to Subgroups

IBGA. Endoaquolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Endoaquolls

IBGB. Other Endoaquolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. A mollic epipedon 60 cm or more thick.

Cumulic Vertic Endoaquolls

IBGC. Other Endoaquolls that have both of the following:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. A slope of less than 25 percent; and either

a. An organic-carbon content of 0.3 percent or more in

all horizons within 125 cm of the mineral soil surface; or

b. An irregular decrease in organic-carbon content

from a depth of 25 cm to a depth of 125 cm or to a

densic, lithic, or paralithic contact if shallower.

Fluvaquentic Vertic Endoaquolls

IBGD. Other Endoaquolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Endoaquolls

IBGE. Other Endoaquolls that have a histic epipedon.

Histic Endoaquolls

IBGF. Other Endoaquolls that have a buried layer of organic

soil materials, 20 cm or more thick, that has its upper boundary

within 100 cm of the mineral soil surface.

Thapto-Histic Endoaquolls

IBGG. Other Endoaquolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or
570 Soil Taxonomy

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Endoaquolls

IBGH. Other Endoaquolls that have a horizon, 15 cm or

more thick within 100 cm of the mineral soil surface, that

either has 20 percent or more (by volume) durinodes or is

brittle and has a firm rupture-resistance class when moist.

Duric Endoaquolls

IBGI. Other Endoaquolls that have a mollic epipedon 60 cm

or more thick.

Cumulic Endoaquolls

IBGJ. Other Endoaquolls that have a slope of less than 25

percent; and either

1. An organic-carbon content of 0.3 percent or more in all

horizons within 125 cm of the mineral soil surface; or

2. An irregular decrease in organic-carbon content from a

depth of 25 cm to a depth of 125 cm or to a densic, lithic, or

paralithic contact if shallower.

Fluvaquentic Endoaquolls

IBGK. Other Endoaquolls.

Typic Endoaquolls

Definition of Typic Endoaquolls

Typic Endoaquolls are the Endoaquolls that:

1. Do not have a histic epipedon;

2. Do not have a buried layer of organic soil materials, 20 cm

or more thick, that has its upper boundary within 100 cm of the

mineral soil surface;

3. Do not have a horizon, 15 cm or more thick within 100 cm

of the mineral soil surface, that has 20 percent or more (by

volume) durinodes or is brittle and has a firm ruptureresistance class when moist;

4. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

6. Do not have a lithic contact within 50 cm of the mineral

soil surface;

7. Have a mollic epipedon that is less than 60 cm thick; and

8. Either have less than 0.3 percent organic carbon at a depth

of 125 cm below the mineral soil surface and a regular

decrease in organic-carbon content from a depth of 25 cm to a

depth of 125 cm or to a densic, lithic, or paralithic contact if

shallower or have a slope of 25 percent or more.

Description of Subgroups

Typic Endoaquolls.—The Typic subgroup of Endoaquolls is

fixed on deep soils that do not have slickensides, wedge-shaped

aggregates, a high linear extensibility, or wide cracks. These

soils have a mollic epipedon less than 60 cm thick and have

both a regular decrease in organic-carbon content with

increasing depth and an organic-carbon content of less than 0.3

percent in some horizon within 125 cm of the mineral soil

surface. They do not have a horizon within 100 cm of the

mineral soil surface that has 20 percent or more durinodes or is

brittle and has a firm rupture-resistance class when moist.

These soils do not have a lithic contact, a histic epipedon, or a

buried organic layer.

Soils that have slickensides, wedge-shaped aggregates, a

high linear extensibility, or wide cracks are assigned to Vertic

or combination Vertic subgroups because these properties are

shared with Vertisols. Typic Endoaquolls do not have a surface

mantle or layer in the upper 75 cm that has both a low bulk

density and a high content of weakly crystalline minerals or

that consists of slightly or moderately weathered pyroclastic

materials because these properties are shared with Andisols.
Mollisols 571

Typic Endoaquolls are extensive and occur throughout a

large part of the United States. They are most extensive in the

Midwestern States. They are nearly level. Most of the soils

have been artificially drained and are used as cropland, but

some are used as pasture or forest.

Aquandic Endoaquolls.—These soils have a surface mantle

or layer in the upper 75 cm that has both a low bulk density

and a high content of weakly crystalline minerals or that

consists of slightly or moderately weathered pyroclastic

materials. These soils are of small extent in the United States

and occur only in the Western States. They are used mostly as

pasture or have been artificially drained and are used as

cropland.

Cumulic Endoaquolls.—These soils have a mollic epipedon

60 cm or more thick. They commonly have an irregular

decrease in organic-carbon content with increasing depth. They

formed mostly in recent alluvium on flood plains or in closed

depressions. These soils are extensive and occur throughout a

large part of the United States. They are most extensive in the

Midwestern and Western States. Many of the soils have been

artificially drained and are used as cropland. Some are used as

pasture and some as woodland or wildlife habitat.

Cumulic Vertic Endoaquolls.—These soils are high in

content of expanding clays and have cracks 5 mm or more

wide, slickensides, wedge-shaped aggregates, or a high linear

extensibility. They also have a mollic epipedon 60 cm or more

thick. They formed mostly in recent alluvium on flood plains

or in closed depressions. These soils are of small extent and

occur mostly in the Midwestern States of the United States.

Many of the soils have been artificially drained and are used as

cropland. Some are used as pasture and some as woodland or

wildlife habitat.

Duric Endoaquolls.—These soils have a horizon, 15 cm or

more thick within 100 cm of the mineral soil surface, that has

20 percent or more (by volume) durinodes or is brittle and has

a firm rupture-resistance class when moist. These soils are rare

in the United States.

Fluvaquentic Endoaquolls.—These soils are like Typic

Endoaquolls, but they have an irregular decrease in organiccarbon content with increasing depth or have an organiccarbon content of 0.3 percent or more in all horizons within

125 cm of the mineral soil surface. The soils formed mostly in

recent alluvium on flood plains. They are extensive and occur

throughout a large part of the United States. Many of the soils

have been artificially drained and are used as cropland. Some

are used as pasture and some as woodland or wildlife habitat.

Fluvaquentic Vertic Endoaquolls.—These soils are high in

content of expanding clays and have cracks 5 mm or more

wide, slickensides, wedge-shaped aggregates, or a high linear

extensibility. They also have an irregular decrease in organiccarbon content with increasing depth or have an organiccarbon content of 0.3 percent or more in all horizons within

125 cm of the mineral soil surface. These soils formed mostly

in recent alluvium on flood plains. They are of small extent in

the United States. Many of the soils have been artificially

drained and are used as cropland. Some are used as pasture and

some as woodland or wildlife habitat.

Histic Endoaquolls.—These soils are like Typic

Endoaquolls, but they have a histic epipedon. They are more

poorly drained than Typic Endoaquolls. Histic Endoaquolls are

rare in the United States.

Lithic Endoaquolls.—These soils are like Typic

Endoaquolls, but they have a lithic contact within 50 cm of the

mineral soil surface. They are rare in the United States.

Thapto-Histic Endoaquolls.—These soils are like Typic

Endoaquolls, but they have a buried Histosol with its upper

boundary within 100 cm of the mineral soil surface. They are

not known to occur in the United States.

Vertic Endoaquolls.—These soils are like Typic Endoaquolls,

but they are high in content of expanding clays and have cracks,

slickensides, wedge-shaped aggregates, or a high linear

extensibility. They formed mostly in late-Pleistocene or Holocene

deposits. Vertic Endoaquolls are of moderate extent in the United

States, mostly in the Midwest and on the Great Plains. Many of

the soils have been artificially drained and are used as cropland.

Some are used as pasture and some as woodland, rangeland, or

wildlife habitat.

Epiaquolls

These are the Aquolls that have both episaturation and a

temperature regime warmer than cryic. They do not have an

argillic or natric horizon. The depth to ground water fluctuates

appreciably in these soils. A perched water table is at or near

the soil surface during wet periods, mostly in winter and early

spring, but commonly does not occur during dry periods in

summer. Most of the Epiaquolls in the United States have

some artificial drainage, mostly surface drainage, and are

used as cropland. The soils are extensive and are widely

distributed throughout the Midwest and the western parts of

the country.

Definition

Epiaquolls are the Aquolls that:

1. Have episaturation;

2. Have a soil temperature regime that is warmer than cryic;

3. Do not have an argillic or natric horizon;

4. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface; and

5. Do not have a calcic horizon that has its upper boundary

within 40 cm of the mineral soil surface.

Key to Subgroups

IBFA. Epiaquolls that have both of the following:

1. One or both of the following:
572 Soil Taxonomy

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. A mollic epipedon 60 cm or more thick.

Cumulic Vertic Epiaquolls

IBFB. Other Epiaquolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. A slope of less than 25 percent; and either

a. An organic-carbon content of 0.3 percent or more in

all horizons within 125 cm of the mineral soil surface; or

b. An irregular decrease in organic-carbon content

from a depth of 25 cm to a depth of 125 cm or to a

densic, lithic, or paralithic contact if shallower.

Fluvaquentic Vertic Epiaquolls

IBFC. Other Epiaquolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Epiaquolls

IBFD. Other Epiaquolls that have a histic epipedon.

Histic Epiaquolls

IBFE. Other Epiaquolls that have a buried layer of organic soil

materials, 20 cm or more thick, that has its upper boundary

within 100 cm of the mineral soil surface.

Thapto-Histic Epiaquolls

IBFF. Other Epiaquolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Epiaquolls

IBFG. Other Epiaquolls that have a horizon, 15 cm or more

thick within 100 cm of the mineral soil surface, that either has

20 percent or more (by volume) durinodes or is brittle and has

a firm rupture-resistance class when moist.

Duric Epiaquolls

IBFH. Other Epiaquolls that have a mollic epipedon 60 cm or

more thick.

Cumulic Epiaquolls

IBFI. Other Epiaquolls that have a slope of less than 25

percent; and either

1. An organic-carbon content of 0.3 percent or more in all

horizons within 125 cm of the mineral soil surface; or

2. An irregular decrease in organic-carbon content from a

depth of 25 cm to a depth of 125 cm or to a densic, lithic, or

paralithic contact if shallower.

Fluvaquentic Epiaquolls

IBFJ. Other Epiaquolls.

Typic Epiaquolls

Definition of Typic Epiaquolls

Typic Epiaquolls are the Epiaquolls that:

1. Do not have a histic epipedon;
Mollisols 573

2. Do not have a buried layer of organic soil materials, 20 cm or

more thick, that has its upper boundary within 100 cm of the

mineral soil surface;

3. Do not have a horizon, 15 cm or more thick within 100 cm

of the mineral soil surface, that has 20 percent or more (by

volume) durinodes or is brittle and has a firm ruptureresistance class when moist;

4. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

5. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

6. Have a mollic epipedon less than 60 cm thick; and

7. Either have less than 0.3 percent organic carbon at a depth

of 125 cm below the mineral soil surface and a regular

decrease in organic-carbon content from a depth of 25 cm to a

depth of 125 cm or to a densic, lithic, or paralithic contact if

shallower or have a slope of 25 percent or more.

Description of Subgroups

Typic Epiaquolls.—The Typic subgroup of Epiaquolls is

centered on deep soils that do not have slickensides, wedgeshaped aggregates, a high linear extensibility, or wide cracks.

These soils have a mollic epipedon that is less than 60 cm

thick and have both a regular decrease in organic-carbon

content with increasing depth and an organic-carbon content of

less than 0.3 percent in some horizon within 125 cm of the

mineral soil surface. They do not have a horizon within 100

cm of the mineral soil surface that has 20 percent or more

durinodes or is brittle and has a firm rupture-resistance class

when moist.

Soils that have slickensides, wedge-shaped aggregates, a

high linear extensibility, or wide cracks are assigned to Vertic

and combination Vertic subgroups because these properties are

shared with Vertisols. Typic Epiaquolls do not have a surface

mantle or layer in the upper 75 cm that has both a low bulk

density and a high content of weakly crystalline minerals or

that consists of slightly or moderately weathered pyroclastic

materials because these properties are shared with Andisols.

Typic Epiaquolls are moderately extensive in the United

States and are mostly in the Midwestern States. These soils are

nearly level. Most have been artificially drained and are used

as cropland. Some are used as pasture and some as forest.

Aquandic Epiaquolls.—These soils are like Typic

Epiaquolls, but they have a surface mantle or layer in the upper

75 cm that has both a low bulk density and a high content of

weakly crystalline minerals or that consists of slightly or

moderately weathered pyroclastic materials. Aquandic

Epiaquolls are not known to occur in the United States.

Cumulic Epiaquolls.—These soils are like Typic

Epiaquolls, but they have a mollic epipedon 60 cm or more

thick. They commonly have an irregular decrease in organiccarbon content with increasing depth. They formed mostly in

recent alluvium on flood plains or in closed depressions.

Cumulic Epiaquolls are of very small extent.

Cumulic Vertic Epiaquolls.—These soils are like Typic

Epiaquolls, but they are high in content of expanding clays and

have cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a high linear extensibility. They also have a

mollic epipedon 60 cm or more thick. These soils formed

mostly in recent alluvium on flood plains or in closed

depressions. They are of small extent in the United States.

They are nearly level. Most of the soils have been artificially

drained and are used as cropland. Some are used as pasture and

some as forest.

Duric Epiaquolls.—These soils have a horizon, 15 cm or

more thick within 100 cm of the mineral soil surface, that has

20 percent or more (by volume) durinodes or is brittle and has

a firm rupture-resistance class when moist. They are otherwise

like Typic Epiaquolls in their defined properties and in most

other properties. Duric Epiaquolls are not known to occur in

the United States.

Fluvaquentic Epiaquolls.—These soils are like Typic

Epiaquolls, but they have an irregular decrease in organiccarbon content with increasing depth or have an organiccarbon content of 0.3 percent or more in all horizons within
574 Soil Taxonomy

125 cm of the mineral soil surface. These soils formed mostly in

recent alluvium on flood plains. They are not known to occur in

the United States.

Fluvaquentic Vertic Epiaquolls.—These soils are like

Typic Epiaquolls, but they are high in content of expanding

clays and have cracks 5 mm or more wide, slickensides,

wedge-shaped aggregates, or a high linear extensibility. They

also have an irregular decrease in organic-carbon content with

increasing depth or have an organic-carbon content of 0.3

percent or more in all horizons within 125 cm of the mineral

soil surface. These soils formed mostly in recent alluvium on

flood plains. They are not known to occur in the United States.

Histic Epiaquolls.—These soils are like Typic Epiaquolls,

but they have a histic epipedon. They are more poorly drained

than Typic Epiaquolls. Histic Epiaquolls are rare in the United

States.

Thapto-Histic Epiaquolls.—These soils are like Typic

Epiaquolls, but they have a buried Histosol with its upper

boundary within 100 cm of the mineral soil surface. These soils

are not known to occur in the United States.

Vertic Epiaquolls.—These soils are like Typic Epiaquolls, but

they are high in content of expanding clays and have cracks 5

mm or more wide, slickensides, wedge-shaped aggregates, or a

high linear extensibility. These soils formed mostly in latePleistocene or Holocene deposits. They are of moderate extent

in the United States, mostly in the Midwest and on the Great

Plains. Many of the soils have been artificially drained and are

used as cropland. Some are used as pasture and some as

woodland, rangeland, or wildlife habitat.

Natraquolls

These are the Aquolls that have a temperature regime warmer

than cryic and have a natric horizon. They do not have a duripan

within 100 cm of the mineral soil surface. The natric horizon

normally lies very close to the surface. The thin overlying

horizon commonly has a dry color that is too light for a mollic

epipedon. The color of the upper part of the soils, after mixing to

a depth of 18 cm, however, is dark enough for a mollic epipedon

because the natric horizon is nearly black. Ground water is

shallow during most of the year, and capillary rise in many

Natraquolls has concentrated salts, including sodium salts, in

the upper 50 cm of the soils.

Natraquolls are known to occur only in subhumid to arid

regions. They are on flood plains and on the margins of lakes.

They formed in late-Pleistocene or Holocene deposits. The

vegetation consists of grasses, sedges, and shrubs. The soils are

used as rangeland, or the grasses are cut for hay. The soils are

rarely cultivated. They are rare in the United States.

Definition

Natraquolls are the Aquolls that:

1. Have a natric horizon;

2. Have a soil temperature regime that is warmer than cryic;

and

3. Do not have a duripan that has its upper boundary

within 100 cm of the soil surface.

Key to Subgroups

IBCA. Natraquolls that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Natraquolls

IBCB. Other Natraquolls.

Typic Natraquolls

Definition of Typic Natraquolls

Typic Natraquolls are the Natraquolls that do not have

either:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or more

for some time in normal years, and slickensides or wedgeshaped aggregates in a layer 15 cm or more thick that has its

upper boundary within 125 cm of the mineral soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Natraquolls.—The central concept or Typic subgroup

of Natraquolls is fixed on soils that do not have slickensides,

wedge-shaped aggregates, a high linear extensibility, or wide

cracks. Deep cracks, slickensides, wedge-shaped aggregates,

and a high linear extensibility are characteristics shared with

Vertisols and are the basis for defining the Vertic subgroup.

Typic Natraquolls are of small extent in the United States.

They are widely distributed throughout the Western United

States. These soils supported mostly salt-tolerant grasses,

sedges, and shrubs. Some of the soils have been artificially

drained and are used as cropland. Some are used as grazing

land or hayland and some as wildlife habitat.

Vertic Natraquolls.—These soils are like Typic

Natraquolls, but they have a clayey particle-size class in a

significant part, have expanding clays, and in normal years

have deep cracks. They are of small extent in the United States.

They are recognized only in South Dakota. These soils
Mollisols 575

supported mostly salt-tolerant grasses, sedges, and shrubs.

Most are used as hayland or grazing land.

Cryolls

Cryolls are the cool or cold, more or less freely drained

Mollisols. They are moderately extensive in the high

mountains of the Western United States. They also are

extensive on the plains and mountains of Eastern Europe and

in Asia. On the plains they are mainly in areas of latePleistocene or Holocene deposits. In the mountains of the

Western States, some of the soils may be on older surfaces, but

the geomorphology of these areas has had little study.

Cryolls have a cryic temperature regime and a udic, ustic, or

xeric moisture regime.

The vegetation on the Cryolls on the plains was mostly

grasses. The Cryolls in the mountains have either forest or

grass vegetation. On the Cryolls in Alaska, spruce, birch, and

aspen trees are common.

Definition

Cryolls are the Mollisols that:

1. Have a cryic soil temperature regime;

2. Do not have all of the following:

a. An argillic or natric horizon; and

b. An albic horizon that has chroma of 2 or less, that has

its lower boundary 18 cm or more below the mineral soil

surface, and either lies directly below the mollic epipedon or

separates horizons that together meet all of the requirements

for a mollic epipedon; and

c. In one or more subhorizons of the albic horizon and/or

of the argillic or natric horizon and within 100 cm of the

mineral soil surface, redox concentrations in the form of

masses or concretions, or both, and also aquic conditions for

some time in normal years (or artificial drainage);

3. Do not have the characteristics defined for Aquolls; and

4. Have one or more of the following:

a. Either within or directly below the mollic epipedon,

mineral soil materials less than 7.5 cm in diameter that

have a CaCO3 equivalent of less than 40 percent; or

b. A mollic epipedon 50 cm or more thick; or

c. An argillic or calcic horizon.

Key to Great Groups

IDA. Cryolls that have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Duricryolls, p. 579

IDB. Other Cryolls that have a natric horizon.

Natricryolls, p. 582

IDC. Other Cryolls that have both:

1. An argillic horizon that has its upper boundary 60 cm or

more below the mineral soil surface; and

2. A texture finer than loamy fine sand in all horizons above

the argillic horizon.

Palecryolls, p. 583

IDD. Other Cryolls that have an argillic horizon.

Argicryolls, p. 575

IDE. Other Cryolls that:

1. Have a calcic or petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface; and

2. In all parts above the calcic or petrocalcic horizon, after

the materials between the soil surface and a depth of 18 cm

have been mixed, either are calcareous or have a texture of

loamy fine sand or coarser.

Calcicryolls, p. 578

IDF. Other Cryolls.

Haplocryolls, p. 579

Argicryolls

These are the Cryolls that have an argillic horizon close to the

surface. Commonly, the upper part of the argillic horizon is in the

mollic epipedon. Some of these soils have a Bk horizon below

the argillic horizon. Argicryolls do not have a natric horizon or a

duripan.

Argicryolls formed mainly in Pleistocene or Holocene

deposits or are on surfaces of equivalent ages. They have cool

or short summers.

Most Argicryolls in the United States are in the mountains

of the Western States. A few are in Alaska. In other countries

at high latitudes, Argicryolls also developed on plains. In the

United States, the vegetation at the time of settlement was

either forest or grass. Many of the soils had grasses and

scattered conifer trees. Most of the soils are used as rangeland

or forest. Some are cultivated and used for small grain or for

hay.

Definition

Argicryolls are the Cryolls that:

1. Have an argillic horizon that has its upper boundary less

than 60 cm below the mineral soil surface or have a texture of

loamy fine sand or coarser in all horizons above the argillic

horizon;

2. Do not have a natric horizon; and
576 Soil Taxonomy

3. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Key to Subgroups

IDDA. Argicryolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Argicryolls

IDDB. Other Argicryolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Argicryolls

IDDC. Other Argicryolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Argicryolls

IDDD. Other Argicryolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Argicryolls

IDDE. Other Argicryolls that have an argillic horizon that,

with increasing depth, has a clay increase of 20 percent or

more (absolute, in the fine-earth fraction) within its upper

7.5 cm.

Abruptic Argicryolls

IDDF. Other Argicryolls that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Argicryolls

IDDG. Other Argicryolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Argicryolls

IDDH. Other Argicryolls that have a mollic epipedon that is

40 cm or more thick and has a texture finer than loamy fine

sand.

Pachic Argicryolls

IDDI. Other Argicryolls that have either:

1. Above the argillic horizon, an albic horizon or a

horizon that has color values too high for a mollic epipedon

and chroma too high for an albic horizon; or

2. A glossic horizon, or interfingering of albic materials

into the upper part of the argillic horizon, or skeletans of

clean silt and sand covering 50 percent or more of the faces

of peds in the upper 5 cm of the argillic horizon.

Alfic Argicryolls

IDDJ. Other Argicryolls that have an ustic moisture regime.

Ustic Argicryolls

IDDK. Other Argicryolls that have a xeric moisture regime.

Xeric Argicryolls

IDDL. Other Argicryolls.

Typic Argicryolls

Definition of Typic Argicryolls

Typic Argicryolls are the Argicryolls that:

1. Do not have an argillic horizon that has an increase in clay

content of 20 percent (absolute) or more within a vertical

distance of 7.5 cm below the upper boundary;

2. Do not have either:

a. An albic horizon or another horizon above the argillic

horizon that has a color value too high for a mollic epipedon

and chroma too high for an albic horizon; or

b. A glossic horizon, or interfingering of albic materials in

the upper part of the argillic horizon, or skeletans of clean

silt and sand covering 50 percent or more of the faces of

peds in the upper 5 cm or more of the argillic horizon;

3. Do not have, throughout a cumulative thickness of 18 cm
Mollisols 577

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

4. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

5. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

6. Do not have a lithic contact within 50 cm of the mineral

soil surface;

7. Have a udic moisture regime;

8. Have a mollic epipedon that is less than 40 cm thick or has

a texture of loamy fine sand or coarser; and

9. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Argicryolls.—The central concept or Typic subgroup

of Argicryolls is fixed on freely drained soils that have a udic

moisture regime and have a mollic epipedon less than 40 cm

thick. These soils do not have an albic horizon or an abrupt

boundary to the argillic horizon and do not have a surface

mantle or layer in the upper 75 cm that has both a low bulk

density and a high content of weakly crystalline minerals or

that consists of slightly or moderately weathered pyroclastic

materials.

An albic horizon indicates that the soils had forest

vegetation and is the basis for defining intergrades to Alfisols.

Redox concentrations and shallow ground water are properties

of Aquolls and are the basis for defining the Aquic subgroup.

A thick mollic epipedon is the basis for defining the Pachic

subgroup. The vegetation on the Argicryolls on broad plains

was mostly grasses. The Argicryolls in the mountains have

either forest or grass vegetation. Most Argicryolls are used as

rangeland, forest, or wildlife habitat.

Abruptic Argicryolls.—These soils have an abrupt textural

change at the top of the argillic horizon, and most also have an

albic horizon. In the Abruptic Argicryolls in the United States,

the argillic horizon commonly has columnar structure but does

not have the sodium or magnesium necessary for a natric

horizon. The vegetation is mostly grass and shrubs. Slopes are

gentle to moderately steep. Most of the soils are used as

rangeland, pasture, or wildlife habitat.

Alfic Argicryolls.—These soils have an albic horizon or a

horizon that has color values too high for a mollic epipedon

and chroma too high for an albic horizon above the argillic

horizon, or they have a glossic horizon in the upper part of the

argillic horizon. They either have a gradual transition between

those horizons or have only a moderate contrast between the

percentages of clay in the two horizons. These soils are of

moderate extent in the mountains of the Western United States.

Slopes range from gentle to steep. Some of these soils currently

have forest vegetation, but others support mostly grass. Alfic

Argicryolls are used mostly as forest or rangeland, but a few

are used as hayland.

Andic and Vitrandic Argicryolls.—These soils have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals

or that consists of slightly or moderately weathered pyroclastic

materials. These soils are of very small extent in the mountains

of the Western United States. The vegetation is mostly forest or

grass and widely spaced trees. Most of the soils are used as

forest, rangeland, or wildlife habitat.

Aquic Argicryolls.—Ground water fluctuates at some depth

in these soils, and redox concentrations are in the horizons that

are saturated part of the time. These soils are of small extent in

the mountains of the Western United States. The vegetation is

mostly forest or grass and widely spaced trees. Most of the soils

are used as forest, rangeland, or wildlife habitat.

Lithic Argicryolls.—These soils have a lithic contact

within 50 cm of the mineral soil surface. Slopes are gentle to

steep. The vegetation on these soils is mostly grass and shrubs,

but some of the soils support forest vegetation. Most of the soils

are used as rangeland.

Oxyaquic Argicryolls.—These soils are saturated with water

within 100 cm of the mineral soil surface for 20 or more
578 Soil Taxonomy

consecutive days or 30 or more cumulative days in normal

years. They are not known to occur in the United States.

Pachic Argicryolls.—These soils have a thick mollic

epipedon. The argillic horizon generally is in the lower part of

the mollic epipedon. Slopes of the Pachic Argicryolls in the

United States range from gentle to steep. The soils are

extensive in the high mountains of the Western States. Most of

the soils are used for summer grazing, but some are used as

forest.

Ustic Argicryolls.—These soils have an ustic moisture

regime. They are considered to be transitional to Ustolls. They

commonly are used as rangeland or are in sparse forests with

widely spaced trees. They are of small extent in the United

States.

Vertic Argicryolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. The thickness of the mollic epipedon,

the distribution of organic carbon in the epipedon, and the

presence of redoximorphic features or other evidence of

wetness are not definitive of this subgroup. These soils are of

small extent in the mountains of the Western United States.

Xeric Argicryolls.—These soils have a xeric moisture

regime. They are considered to be transitional to Xerolls. They

commonly are in forests with widely spaced trees. They are of

small extent in the United States.

Calcicryolls

These are the Cryolls that have a calcic or petrocalcic

horizon that has its upper boundary within 100 cm of the

mineral soil surface. They are calcareous, or would be

calcareous if plowed, in all parts of the pedon above the calcic

horizon, or they have a texture of loamy fine sand or coarser in

all parts above the calcic or petrocalcic horizon. The mollic

epipedon commonly includes part of the calcic horizon. These

soils formed in materials that have a moderate to high

percentage of carbonates. Many of the soils are in areas of

deposits that originated from limestone.

Calcicryolls occur in areas of cool or short summers. In the

United States, the vegetation at the time of settlement was

either grass or forest. The soils are of moderate extent in the

mountains of the Western United States. Most of the soils are

used as rangeland, forest, or wildlife habitat. A few areas are

cultivated and used for small grain or hay.

Definition

Calcicryolls are the Cryolls that:

1. Have a calcic or petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface;

2. Either are calcareous or have a texture of loamy fine sand

or coarser in all parts above the calcic or petrocalcic horizon

after the materials between the soil surface and a depth of 18

cm have been mixed;

3. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface; and

4. Do not have a natric or argillic horizon.

Key to Subgroups

IDEA. Calcicryolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Calcicryolls

IDEB. Other Calcicryolls that have a petrocalcic horizon that

has its upper boundary within 100 cm of the mineral soil

surface.

Petrocalcic Calcicryolls

IDEC. Other Calcicryolls that have a mollic epipedon that is

40 cm or more thick and has a texture finer than loamy fine

sand.

Pachic Calcicryolls

IDED. Other Calcicryolls that have an ustic moisture regime.

Ustic Calcicryolls

IDEE. Other Calcicryolls that have a xeric moisture regime.

Xeric Calcicryolls

IDEF. Other Calcicryolls.

Typic Calcicryolls

Definition of Typic Calcicryolls

Typic Calcicryolls are the Calcicryolls that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Have a mollic epipedon that is less than 40 cm thick or has

a texture of loamy fine sand or coarser;

3. Have a udic moisture regime; and

4. Do not have a petrocalcic horizon with its upper boundary

within 100 cm of the mineral soil surface.

Description of Subgroups

Typic Calcicryolls.—The central concept or Typic

subgroup of Calcicryolls is fixed on soils that have a udic

moisture regime and have a mollic epipedon less than 40 cm

thick. These soils do not have a lithic contact within 50 cm of

the mineral soil surface. A thick mollic epipedon is the basis

for defining the Pachic subgroup. The vegetation on the Typic

Calcicryolls on broad plains was mostly grasses and shrubs.

The Typic Calcicryolls in the mountains have either grass or

forest vegetation. Most Typic Calcicryolls are used as

rangeland or forest, but a few are used as cropland.

Lithic Calcicryolls.—These soils have a lithic contact

within 50 cm of the mineral soil surface. They are of small

extent in the mountains of the Western United States. Their
Mollisols 579

slopes are gentle to steep. The vegetation on these soils is

mostly grass and shrubs, but some of the soils support widely

spaced trees. Most of the soils are used as rangeland.

Pachic Calcicryolls.—These soils have a thick, calcareous

mollic epipedon that extends into the calcic horizon or is

directly underlain by the calcic horizon. They formed mainly in

calcareous sediments. The vegetation in broad areas is mostly

grasses and shrubs. The more sloping soils in the mountains

have either grass or forest vegetation. Most of the soils are used

as rangeland, but a few are used as forest or cropland.

Petrocalcic Calcicryolls.—These soils have a petrocalcic

horizon with its upper boundary within 100 cm of the mineral

soil surface. They do not have a lithic contact within 50 cm of

the mineral soil surface. They are of limited extent in the

Western United States. They are used for grazing by livestock.

Ustic Calcicryolls.—These soils are like Typic Calcicryolls,

but they have an ustic moisture regime. They are considered to

be transitional to Calciustolls. Ustic Calcicryolls commonly are

used as rangeland or are in forests with widely spaced trees.

They are of small extent in the United States.

Xeric Calcicryolls.—These soils are like Typic Calcicryolls,

but they have a xeric moisture regime. They are considered to be

transitional to Calcixerolls. Xeric Calcicryolls commonly are in

forests with widely spaced trees. They are of small extent in the

United States.

Duricryolls

These are the Cryolls that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface. They are

of small extent in mountain valleys of the Western United

States. Many had grasses and widely spaced conifer trees. Most

of the soils are used as rangeland or forest.

Definition

Duricryolls are the Cryolls that have a duripan that has its

upper boundary within 100 cm of the mineral soil surface.

Key to Subgroups

IDAA. Duricryolls that have an argillic horizon.

Argic Duricryolls

IDAB. Other Duricryolls.

Typic Duricryolls

Definition of Typic Duricryolls

Typic Duricryolls are the Duricryolls that do not have an

argillic horizon.

Description of Subgroups

Typic Duricryolls.—The central concept or Typic subgroup

of Duricryolls is fixed on soils that do not have an argillic

horizon above the duripan. These soils are of small extent.

They are at high elevations in the Western United States. The

natural vegetation is either grass and shrubs or trees. The soils

are used as rangeland or forest.

Argic Duricryolls.—These soils are like the Typic subgroup

of Duricryolls, but they have an argillic horizon above the

duripan. Argic Duricryolls are of small extent. They are at high

elevations in the Western United States. The natural vegetation

is either grass and shrubs or trees. These soils are used as

rangeland or forest.

Haplocryolls

These are the Cryolls that do not have an argillic or natric

horizon. Most Haplocryolls have a cambic horizon. Some have

a calcic horizon. Haplocryolls do not have a duripan that has

its upper boundary within 100 cm of the mineral soil surface.

They do not have a calcic or petrocalcic horizon that has its

upper boundary within 100 cm of the mineral soil surface

unless some part of the soil above the calcic or petrocalcic

horizon, after the materials between the soil surface and a

depth of 18 cm have been mixed, either is not calcareous or has

a texture finer than loamy fine sand.

Haplocryolls formed mainly in Pleistocene or Holocene

deposits or on surfaces of equivalent ages. They have cool or

short summers. They are extensive in the United States. The

vegetation at the time of settlement was either forest or grass.

Many of the soils had grasses and scattered conifer trees. Most

of the soils are used as rangeland or forest. Some are cultivated

and used for small grain or hay.

Definition

Haplocryolls are the Cryolls that:

1. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface;

2. Do not have a natric or argillic horizon; and

3. Do not meet both of the following:

a. Have a calcic or petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface; and

b. In all parts above the calcic or petrocalcic horizon, after

the materials between the soil surface and a depth of 18 cm

have been mixed, either are calcareous or have a texture of

loamy fine sand or coarser.

Key to Subgroups

IDFA. Haplocryolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplocryolls

IDFB. Other Haplocryolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or
580 Soil Taxonomy

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haplocryolls

IDFC. Other Haplocryolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Haplocryolls

IDFD. Other Haplocryolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Haplocryolls

IDFE. Other Haplocryolls that have:

1. A mollic epipedon that is 40 cm or more thick and has

a texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content from a

depth of 25 cm below the mineral soil surface to a depth of

125 cm or to a densic, lithic, or paralithic contact if

shallower; and

3. A slope of less than 25 percent; and

4. In one or more horizons within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Cumulic Haplocryolls

IDFF. Other Haplocryolls that have:

1. A mollic epipedon that is 40 cm or more thick and has

a texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content from a

depth of 25 cm below the mineral soil surface to a depth of

125 cm or to a densic, lithic, or paralithic contact if

shallower; and

3. A slope of less than 25 percent.

Cumulic Haplocryolls

IDFG. Other Haplocryolls that have both:

1. A slope of less than 25 percent; and either

a. An organic-carbon content of 0.3 percent or more

at a depth of 125 cm below the mineral soil surface;

or

b. An irregular decrease in organic-carbon content

from a depth of 25 cm to a depth of 125 cm or to a

densic, lithic, or paralithic contact if shallower; and

2. In one or more horizons within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions for some time in normal years (or

artificial drainage).

Fluvaquentic Haplocryolls

IDFH. Other Haplocryolls that have, in one or more horizons

within 100 cm of the mineral soil surface, distinct or

prominent redox concentrations and also aquic conditions for

some time in normal years (or artificial drainage).

Aquic Haplocryolls

IDFI. Other Haplocryolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplocryolls

IDFJ. Other Haplocryolls that have both:

1. A mollic epipedon that is 40 cm or more thick and has

a texture finer than loamy fine sand; and

2. A calcic horizon either within or directly below the

mollic epipedon, but no argillic horizon in the lower part of

the mollic epipedon.

Calcic Pachic Haplocryolls

IDFK. Other Haplocryolls that have a mollic epipedon that is

40 cm or more thick and has a texture finer than loamy fine

sand.

Pachic Haplocryolls

IDFL. Other Haplocryolls that have a slope of less than 25

percent; and either
Mollisols 581

1. An organic-carbon content of 0.3 percent or more at a

depth of 125 cm below the mineral soil surface; or

2. An irregular decrease in organic-carbon content from a

depth of 25 cm to a depth of 125 cm or to a densic, lithic, or

paralithic contact if shallower.

Fluventic Haplocryolls

IDFM. Other Haplocryolls that have a calcic horizon within

100 cm of the mineral soil surface.

Calcic Haplocryolls

IDFN. Other Haplocryolls that have an ustic moisture

regime.

Ustic Haplocryolls

IDFO. Other Haplocryolls that have a xeric moisture regime.

Xeric Haplocryolls

IDFP. Other Haplocryolls.

Typic Haplocryolls

Definition of Typic Haplocryolls

Typic Haplocryolls are the Haplocryolls that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

3. Do not have, in any horizon within 100 cm of the mineral

soil surface, distinct or prominent redox concentrations and

also aquic conditions;

4. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

5. Do not have a calcic horizon within 100 cm of the mineral

soil surface;

6. Have a mollic epipedon that is less than 40 cm thick or

that has a texture of loamy fine sand or coarser;

7. Have a udic soil moisture regime;

8. Either have a regular decrease in organic-carbon content

with increasing depth and, unless a densic, lithic, or paralithic

contact is at some depth between 50 and 125 cm below the soil

surface, have an organic-carbon content of 0.3 percent or less

at a depth within 125 cm of the mineral soil surface or have a

slope of 25 percent or more; and

9. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Haplocryolls.—The central concept or Typic

subgroup of Haplocryolls is fixed on freely drained soils that

have a udic soil moisture regime and that do not have a calcic

horizon within 100 cm or hard rock within 50 cm of the soil

surface. The horizon sequence is normally a noncalcareous

mollic epipedon of moderate thickness over a cambic horizon.

These soils do not have a surface mantle or layer in the

upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals or that consists of

slightly or moderately weathered pyroclastic materials. In

addition, they do not have a high shrink-swell potential, a

thick mollic epipedon, or an irregular decrease in organiccarbon content.

Redox concentrations and shallow ground water are

properties of Aquolls and are the basis for defining Aquic and

combination Aquic subgroups. A calcic horizon within a depth

of 100 cm is characteristic of Calcicryolls and is the basis for

defining Calcic and combination Calcic subgroups. A thick

mollic epipedon is the basis for defining Pachic and

combination Pachic subgroups.

The vegetation on the Typic Haplocryolls on broad plains

was mostly grasses. The Typic Haplocryolls in the mountains

have either forest or grass vegetation. Most Typic Haplocryolls

are used as rangeland, forest, or wildlife habitat.

Andic and Vitrandic Haplocryolls.—These soils have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals
582 Soil Taxonomy

or that consists of slightly or moderately weathered pyroclastic

materials. These soils are of very small extent in the mountains

of the Western United States. The vegetation is mostly forest or

grass and widely spaced trees. Most of these soils are used as

forest, rangeland, or wildlife habitat.

Aquic Cumulic Haplocryolls.—Ground water fluctuates at

some depth in these soils, and redox concentrations are in the

horizons that are saturated part of the time. The soils have a

thick mollic epipedon, and their content of organic carbon

decreases irregularly with increasing depth. The soils are of

small extent in mountain valleys of the Western United States.

The vegetation is mostly grass, shrubs, and widely spaced

trees. Most of these soils are used as rangeland, pasture, or

cropland, but some are used as forest or wildlife habitat.

Aquic Haplocryolls.—Ground water fluctuates at some

depth in these soils, and redox concentrations are in the

horizons that are saturated part of the time. These soils are of

small extent in mountain valleys of the Western United States.

The vegetation is mostly forest or grass and widely spaced

trees. Most of the soils are used as forest, rangeland, or wildlife

habitat.

Calcic Haplocryolls.—These soils have a calcic horizon

within 100 cm of the mineral soil surface, but they are

otherwise like Typic Haplocryolls. Calcic Haplocryolls are of

small extent. The vegetation is mostly forest or grass and

widely spaced trees. Most of these soils are used as forest,

rangeland, or wildlife habitat, but a few are used as cropland.

Calcic Pachic Haplocryolls.—These soils have a thick

mollic epipedon and a calcic horizon within 100 cm of the

mineral soil surface. They are of small extent. The vegetation

is mostly forest or grass and widely spaced trees. Most of these

soils are used as forest, rangeland, or wildlife habitat, but a few

are used as cropland.

Cumulic Haplocryolls.—These soils have a thick mollic

epipedon, and their content of organic carbon decreases

irregularly with increasing depth. The soils formed in positions

where they receive fresh sediments at a rate slow enough for

this material to become incorporated in the mollic epipedon.

These soils are on flood plains or have concave slopes. They

are of small extent in Alaska and in mountain valleys of the

Western United States. The vegetation is mostly grass, shrubs,

and widely spaced trees. Most of these soils are used as

rangeland, pasture, or cropland, but some are used as forest or

wildlife habitat.

Fluvaquentic Haplocryolls.—These soils are like Typic

Haplocryolls, but ground water fluctuates at some depth in the

soils and redox concentrations are in the horizons that are

saturated part of the time. Fluvaquentic Haplocryolls have an

irregular decrease in organic-carbon content with increasing

depth or have an organic-carbon content of 0.3 percent or more

in all horizons within 125 cm of the mineral soil surface.

These soils formed mostly in recent alluvium on flood plains.

They are of small extent in mountain valleys of the Western

United States. The vegetation is mostly grass, shrubs, and

widely spaced trees. Most of the soils are used as rangeland or

pasture, but some are used as wildlife habitat.

Fluventic Haplocryolls.—These soils are like Typic

Haplocryolls, but they have an irregular decrease in organiccarbon content with increasing depth or have an organiccarbon content of 0.3 percent or more in all horizons within

125 cm of the mineral soil surface. These soils are not known

to occur in the United States.

Lithic Haplocryolls.—These soils have a shallow lithic

contact. They are of moderate extent in the mountains of the

Western United States. Their slopes are gentle to steep. The

vegetation is mostly grass and shrubs, but some of the soils

support forest vegetation. Lithic Haplocryolls are used mostly

as rangeland or forest.

Oxyaquic Haplocryolls.—These soils are like Typic

Haplocryolls, but they are saturated with water within 100 cm

of the mineral soil surface for 20 or more consecutive days or

30 or more cumulative days in normal years. These soils are

not known to occur in the United States.

Pachic Haplocryolls.—These soils are like Typic

Haplocryolls, but they have a thick mollic epipedon. Slopes of

the Pachic Haplocryolls in the United States range from gentle

to steep. The soils commonly are used as rangeland or support

forest vegetation. Some support grass and widely spaced trees.

The soils are extensive in the high mountains of the Western

States. They are used mostly as rangeland or forest. A few of

the soils are used as cropland or hayland.

Ustic Haplocryolls.—These soils are like Typic

Haplocryolls, but they have an ustic moisture regime. They are

considered to be transitional to Ustolls. Ustic Haplocryolls

commonly are used as rangeland or are in forests with widely

spaced trees. They are of small extent in the United States.

Vertic Haplocryolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. The thickness of the mollic

epipedon, the distribution of organic carbon in the epipedon,

and the presence of redoximorphic features or other evidence of

wetness are not definitive of this subgroup. These soils are of

very small extent in the mountains of the Western United

States.

Xeric Haplocryolls.—These soils are like Typic Haplocryolls,

but they have a xeric moisture regime. They are considered to be

transitional to Xerolls. Xeric Haplocryolls commonly are in

forests with widely spaced trees. They are of small extent in the

United States.

Natricryolls

These are the Cryolls that have a natric horizon but do not

have a duripan. The soils are rare in the United States and

probably elsewhere. Few series have been established in the

United States for this group, and subgroups have not been
Mollisols 583

developed. Because these soils are of such limited extent and

have a small range of properties, few subgroups seem to be

needed.

Definition

Natricryolls are the Cryolls that have a natric horizon but do

not have a duripan with an upper boundary within 100 cm of

the mineral soil surface.

Key to Subgroups

IDBA. All Natricryolls.

Typic Natricryolls

Palecryolls

These are the Cryolls that have an argillic horizon with an

upper boundary more than 60 cm below the surface. Most of

the Palecryolls in the United States are in the mountains of the

Western States. In other countries at high latitudes, Palecryolls

also developed on plains.

Palecryolls have cool or short summers. In the United

States, the vegetation at the time of settlement was either forest

or grass. Many of the soils had grasses and scattered conifer

trees. Most of the soils are used as rangeland or forest. Some

are cultivated and used for small grain or hay.

Definition

Palecryolls are the Cryolls that:

1. Have an argillic horizon that has its upper boundary 60 cm

or more below the mineral soil surface and have a texture of

loamy very fine sand or finer in some horizon above the argillic

horizon;

2. Do not have a natric horizon; and

3. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Key to Subgroups

IDCA. Palecryolls that have, in one or more horizons within

100 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Palecryolls

IDCB. Other Palecryolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Palecryolls

IDCC. Other Palecryolls that have an argillic horizon that,

with increasing depth, has a clay increase of 20 percent or

more (absolute, in the fine-earth fraction) within its upper

7.5 cm.

Abruptic Palecryolls

IDCD. Other Palecryolls that have a mollic epipedon that is

40 cm or more thick and has a texture finer than loamy fine

sand.

Pachic Palecryolls

IDCE. Other Palecryolls that have an ustic moisture regime.

Ustic Palecryolls

IDCF. Other Palecryolls that have a xeric moisture regime.

Xeric Palecryolls

IDCG. Other Palecryolls.

Typic Palecryolls

Definition of Typic Palecryolls

Typic Palecryolls are the Palecryolls that:

1. Do not have an argillic horizon that has an increase in clay

content of 20 percent (absolute) or more within a vertical

distance of 7.5 cm below its upper boundary;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

4. Have a mollic epipedon that is less than 40 cm thick; and

5. Have a udic moisture regime.

Description of Subgroups

Typic Palecryolls.—The central concept or Typic subgroup

of Palecryolls is fixed on freely drained soils that have a udic

moisture regime and have a mollic epipedon less than 40 cm

thick. These soils do not have an abrupt boundary to the

argillic horizon.

Redox concentrations and shallow ground water are

properties of Aquolls and are the basis for defining the Aquic

subgroup. A thick mollic epipedon is the basis for defining the

Pachic subgroup. The vegetation on Typic Palecryolls is either

forest or grass and shrubs. Most of these soils are used as

forest, grazing land, or wildlife habitat.

Abruptic Palecryolls.—These soils have an abrupt textural

change at the top of the argillic horizon, and most also have an

albic horizon. The vegetation is either forest or grass and

shrubs. Most of these soils are used as forest, grazing land, or

wildlife habitat.

Aquic Palecryolls.—Ground water fluctuates at some depth
584 Soil Taxonomy

in these soils, and redox concentrations are in the horizons that

are saturated part of the time. These soils are not known to

occur in the United States.

Oxyaquic Palecryolls.—These soils are like Typic

Palecryolls, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. These soils are not

known to occur in the United States.

Pachic Palecryolls.—These soils are like Typic Palecryolls,

but they have a thick mollic epipedon. The argillic horizon

generally is in the lower part of the mollic epipedon. Slopes of

the Pachic Palecryolls in the United States range from gentle to

steep. The soils are moderately extensive in the mountains of

the Western States. The vegetation is either forest or grass and

shrubs. Most of these soils are used as forest, grazing land, or

wildlife habitat.

Ustic Palecryolls.—These soils are like Typic Palecryolls,

but they have an ustic moisture regime. They are considered to

be transitional to Ustolls. Ustic Palecryolls are not known to

occur in the United States.

Xeric Palecryolls.—These soils are like Typic Palecryolls,

but they have a xeric moisture regime. They are considered to

be transitional to Xerolls. Xeric Palecryolls are not known to

occur in the United States.

Rendolls

These are the Mollisols that are of humid regions and that

formed in highly calcareous parent materials, such as

limestone, chalk, drift composed mainly of limestone, or shell

bars. These soils have a mollic epipedon that rests on the

calcareous parent materials or on a cambic horizon that is rich

in carbonates. A few of the soils are so rich in finely divided

lime that the mollic epipedon has a color lighter than normal

but is nevertheless rich in dark colored humus and is within

the limits of a mollic epipedon. Rendolls have a cryic soil

temperature regime or a udic moisture regime, or both.

These soils are not extensive in the United States, but they

are extensive in some parts of the world. They formed under

forest vegetation or under grass and shrubs.

Definition

Rendolls are the Mollisols that:

1. Have a mollic epipedon that is less than 50 cm thick;

2. Have a CaCO3 equivalent of 40 percent or more on the

basis of the whole soil, including coarse fragments as much as

7.5 cm in size in or directly below the mollic epipedon;

3. Do not have an argillic or calcic horizon;

4. Have a udic moisture regime or a cryic temperature regime,

or both; and

5. Do not have both aquic conditions and the colors defined

for Aquolls.

Key to Great Groups

ICA. Rendolls that have a cryic soil temperature regime.

Cryrendolls, p. 584

ICB. Other Rendolls.

Haprendolls, p. 585

Cryrendolls

These are the Rendolls that have a cryic soil temperature

regime. The Cryrendolls in the United States are rare and

occur only in the mountains of the Western States. The

vegetation is mostly grass and shrubs. Some of the soils have

widely spaced coniferous trees.

Definition

Cryrendolls are the Rendolls that have a cryic soil

temperature regime.

Key to Subgroups

ICAA. Cryrendolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Cryrendolls

ICAB. Other Cryrendolls.

Typic Cryrendolls

Definition of Typic Cryrendolls

Typic Cryrendolls are the Rendolls that do not have a lithic

contact within 50 cm of the mineral soil surface.

Description of Subgroups

Typic Cryrendolls.—These soils are more than 50 cm deep

to any lithic contact. Most of the soils have a high content of

small limestone fragments. Typic Cryrendolls are of small

extent. They are in the mountains of Nevada and Wyoming.

The vegetation is mostly grass and shrubs. Some of the soils

have widely spaced coniferous trees. Most of the soils are used

as rangeland or wildlife habitat.

Lithic Cryrendolls.—These soils have a shallow lithic

contact, but they are otherwise like Typic Cryrendolls. The

lithic contact is with limestone. Most Lithic Cryrendolls have a

high content of small limestone fragments. They are of small

extent and are in the mountains of the Western United States.

The vegetation is mostly grass and shrubs. Some of the soils
Mollisols 585

have widely spaced coniferous trees. Most of the soils are used

as rangeland or wildlife habitat.

Haprendolls

These are the Rendolls that have a udic moisture regime and

a soil temperature regime warmer than cryic. Haprendolls are

rare in the United States.

Definition

Haprendolls are the Rendolls that have a udic moisture

regime and a soil temperature regime warmer than cryic.

Key to Subgroups

ICBA. Haprendolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haprendolls

ICBB. Other Haprendolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haprendolls

ICBC. Other Haprendolls that have a cambic horizon.

Inceptic Haprendolls

ICBD. Other Haprendolls that have a color value, dry, of 6 or

more either in the upper 18 cm of the mollic epipedon, after

mixing, or in an Ap horizon 18 cm or more thick.

Entic Haprendolls

ICBE. Other Haprendolls.

Typic Haprendolls

Definition of Typic Haprendolls

Typic Haprendolls are the Rendolls that:

1. Do not have a cambic horizon;

2. Do not have a lithic contact within 50 cm of the mineral

soil surface;

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that are 5

mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

4. Have a dry color value of 5 or less in the upper 18 cm,

after mixing, or in any Ap horizon that is thicker than 18 cm.

Description of Subgroups

Typic Haprendolls.—The central concept or Typic

subgroup of Haprendolls in fixed on freely drained soils that

have a dark mollic epipedon when dry, do not have a cambic

horizon, and do not have a lithic contact within a depth of 50

cm.

A cambic horizon in all or part of each pedon is an extra

horizon that indicates development toward Inceptisols. A high

dry color value in the mollic epipedon suggests weak

development of that horizon and is the basis for defining the

Entic subgroup. A shallow lithic contact is the basis for

defining the Lithic subgroup. Slickensides, wedge-shaped

aggregates, a high linear extensibility, and wide cracks are

properties of Vertisols and are the basis for defining the

intergrades toward soils of that order.

Typic Haprendolls are of small extent. They are in the

humid parts of the United States. They occur from Puerto Rico

to Michigan. The native vegetation is mostly trees and shrubs.

Some of the soils support shrubs and widely spaced trees. Most

of the soils are used as forest, pasture, or wildlife habitat.

Entic Haprendolls.—These soils formed in chalk or marl

and have a color value, dry, of 6 or more, mainly because finely

divided lime is abundant and acts as a white pigment. The soils

do not have a high shrink-swell potential, a cambic horizon, or

a lithic contact within 50 cm of the mineral soil surface. They

are not known to occur in the United States, but they are

extensive in some parts of the world.

Inceptic Haprendolls.—These soils have a cambic horizon

in at least some part of each pedon and generally in the major

part or all of the pedon. The soils are of small extent in the

humid parts of the United States. They occur from Puerto Rico

to Michigan. The native vegetation is mostly trees and shrubs.

Some of the soils support shrubs and widely spaced trees. Most

of the soils are used as cropland, forest, pasture, or wildlife

habitat.

Lithic Haprendolls.—These soils have a shallow lithic

contact but are otherwise like Typic Haprendolls. The

underlying rock is limestone, and there are many small

fragments of the limestone in most of these soils. Lithic
586 Soil Taxonomy

Haprendolls are in the humid parts of the United States. They

occur from Florida to Michigan. The native vegetation is mostly

trees and shrubs. Some of the soils support shrubs and widely

spaced trees. Most of the soils are used as forest, pasture, or

wildlife habitat or for urban development.

Vertic Haprendolls.—These soils have slickensides, wedgeshaped aggregates, a high linear extensibility, or wide cracks.

They are not known to occur in the United States. The subgroup

is provided for use if needed elsewhere.

Udolls

Udolls are the more or less freely drained Mollisols of humid

climates. In addition to the mollic epipedon, these soils may

have a cambic, calcic, natric, or argillic horizon. They formed

mainly in late-Pleistocene or Holocene deposits or on surfaces

of comparable ages. In the United States, their vegetation at the

time of settlement was dominantly a tall grass prairie, but some

of the soils on Pleistocene surfaces appear to have supported at

some time a boreal forest that was supplanted by grasses

several thousand years ago.

Udolls formed in sediments and on surfaces of varying ages

from Holocene to mid Pleistocene or earlier. The Udolls that

have a thermic or warmer temperature regime, in particular,

may have formed during two or more glacial and interglacial

stages.

Most of the Udolls are in the eastern part of the Great Plains

or are east of the Great Plains. The soils are most extensive in

Illinois, Iowa, and adjacent states. Their temperature regime is

frigid or warmer, and their moisture regime is udic. Where

slopes are not too steep, nearly all of these soils are cultivated.

Maize (corn) and soybeans are the major crops.

Definition

Udolls are the Mollisols that:

1. Have a udic moisture regime;

2. Do not have both an albic horizon and, within 100 cm of

the mineral soil surface, any subhorizon of the albic horizon

and/or of the argillic or natric horizon that has redox

concentrations in the form of masses or concretions, or both,

and also aquic conditions;

3. Do not have both aquic conditions and the colors defined

for Aquolls;

4. Do not have a calcareous horizon that lies directly under

the mollic epipedon at a depth of less than 50 cm and that has

a CaCO3 equivalent of more than 40 percent, including coarse

fragments smaller than 7.5 cm, unless the soil also has an

argillic or calcic horizon or a mollic epipedon 50 cm or more

thick; and

5. Do not have a cryic soil temperature regime.

Key to Great Groups

IGA. Udolls that have a natric horizon.

Natrudolls, p. 597

IGB. Other Udolls that:

1. Have a calcic or petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface; and

2. Do not have an argillic horizon above the calcic or

petrocalcic horizon; and

3. In all parts above the calcic or petrocalcic horizon, after

the materials between the soil surface and a depth of 18 cm

have been mixed, either are calcareous or have a texture of

loamy fine sand or coarser.

Calciudolls, p. 592

IGC. Other Udolls that have one or more of the following:

1. A petrocalcic horizon that has its upper boundary

within 150 cm of the mineral soil surface; or

2. All of the following:

a. No densic, lithic, or paralithic contact within 150 cm

of the mineral soil surface; and

b. Within 150 cm of the mineral soil surface, a clay

decrease, with increasing depth, of less than 20 percent

(relative) from the maximum clay content (noncarbonate

clay); and

c. An argillic horizon with one or more of the

following:

(1) In 50 percent or more of the matrix of one or

more subhorizons in its lower half, hue of 7.5YR or

redder and chroma of 5 or more; or

(2) In 50 percent or more of the matrix of horizons

that total more than one-half the total thickness, hue

of 2.5YR or redder, a value, moist, of 3 or less, and a

value, dry, of 4 or less; or

(3) Many redox concentrations with hue of 5YR or

redder or chroma of 6 or more, or both, in one or more

subhorizons; or

3. A frigid temperature regime; and both

a. An argillic horizon that has its upper boundary 60

cm or more below the mineral soil surface; and

b. A texture finer than loamy fine sand in all horizons

above the argillic horizon.

Paleudolls, p. 599

IGD. Other Udolls that have an argillic horizon.

Argiudolls, p. 587
Mollisols 587

IGE. Other Udolls that have a mollic epipedon that:

1. Either below an Ap horizon or below a depth of 18 cm

from the mineral soil surface, contains 50 percent or more

(by volume) wormholes, wormcasts, or filled animal

burrows; and

2. Either rests on a lithic contact or has a transition zone

to the underlying horizon in which 25 percent or more of

the soil volume consists of discrete wormholes, wormcasts,

or animal burrows filled with material from the mollic

epipedon and from the underlying horizon.

Vermudolls, p. 601

IGF. Other Udolls.

Hapludolls, p. 593

Argiudolls

These are the Udolls that have a relatively thin argillic

horizon or one in which the percentage of clay decreases

rapidly with increasing depth. The mollic epipedon commonly

is black to very dark brown, and the argillic horizon is mostly

brownish. Many of these soils are noncalcareous to a

considerable depth below the argillic horizon. Some of the soils

have a Bk horizon in which secondary carbonates are

concentrated.

Argiudolls formed mostly in late-Wisconsinan deposits or

on surfaces of that age. Many or most of these soils during the

Pleistocene supported boreal forests that were replaced by tall

grass prairies during the Holocene. Argiudolls are extensive

soils in Iowa, Illinois, and adjacent states.

Definition

Argiudolls are the Udolls that:

1. Do not have a natric horizon;

2. Do not have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface unless there is an

argillic horizon above the calcic horizon;

3. Do not have a petrocalcic horizon with its upper boundary

within 150 cm of the mineral soil surface; and

4. Have an argillic horizon and a clay distribution in which

the clay content decreases by 20 percent or more from the

maximum clay content within 150 cm of the surface if:

a. Hue is redder than 10YR and chroma of more than 4 is

dominant in the matrix in at least the lower part of the

argillic horizon; or

b. There are many coarse redox concentrations that have

hue redder than 7.5YR or chroma of more than 5.

Key to Subgroups

IGDA. Argiudolls that have a lithic contact within 50 cm of the

mineral soil surface.

Lithic Argiudolls

IGDB. Other Argiudolls that have both:

1. Aquic conditions for some time in normal years (or

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

b. Directly below the mollic epipedon, in one or more

horizons with a total thickness of 15 cm or more that

have one or more of the following:

(1) A color value, moist, of 4 or more and redox

depletions with chroma of 2 or less; or

(2) Hue of 10YR or redder and chroma of 2 or less;

or

(3) Hue of 2.5Y or yellower and chroma of 3 or less;

and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Aquertic Argiudolls

IGDC. Other Argiudolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. In normal years saturation with water in one or more
588 Soil Taxonomy

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Oxyaquic Vertic Argiudolls

IGDD. Other Argiudolls that have:

1. A texture finer than loamy fine sand and either:

a. A frigid temperature regime and a mollic epipedon

40 cm or more thick; or

b. A mollic epipedon 50 cm or more thick; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Pachic Vertic Argiudolls

IGDE. Other Argiudolls that have:

1. Above the argillic horizon, an albic horizon or a

horizon that has color values too high for a mollic epipedon

and chroma too high for an albic horizon; or

2. A glossic horizon, or interfingering of albic materials

into the upper part of the argillic horizon, or skeletans of

clean silt and sand covering 50 percent or more of the faces

of peds in the upper 5 cm of the argillic horizon; and

3. Either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Alfic Vertic Argiudolls

IGDF. Other Argiudolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Argiudolls

IGDG. Other Argiudolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Argiudolls

IGDH. Other Argiudolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Argiudolls

IGDI. Other Argiudolls that have aquic conditions for some

time in normal years (or artificial drainage) either:

1. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

2. Directly below the mollic epipedon, in one or more

horizons with a total thickness of 15 cm or more that have

one or more of the following:

a. A color value, moist, of 4 or more and redox

depletions with chroma of 2 or less; or

b. Hue of 10YR or redder and chroma of 2 or less; or

c. Hue of 2.5Y or yellower and chroma of 3 or less.

Aquic Argiudolls

IGDJ. Other Argiudolls that have a texture finer than loamy

fine sand and either:
Mollisols 589

1. A frigid temperature regime and a mollic epipedon 40 cm

or more thick; or

2. A mollic epipedon 50 cm or more thick.

Pachic Argiudolls

IGDK. Other Argiudolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Argiudolls

IGDL. Other Argiudolls that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more

than 20 cm thick, each with an overlying eluvial horizon,

and above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Argiudolls

IGDM. Other Argiudolls that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Argiudolls

IGDN. Other Argiudolls that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more.

Arenic Argiudolls

IGDO. Other Argiudolls that have an argillic horizon that,

with increasing depth, has a clay increase of 20 percent or

more (absolute, in the fine-earth fraction) within its upper

7.5 cm.

Abruptic Argiudolls

IGDP. Other Argiudolls that have:

1. Above the argillic horizon, an albic horizon or a

horizon that has color values too high for a mollic epipedon

and chroma too high for an albic horizon; or

2. A glossic horizon, or interfingering of albic materials into

the upper part of the argillic horizon, or skeletans of clean silt

and sand covering 50 percent or more of the faces of peds in

the upper 5 cm of the argillic horizon.

Alfic Argiudolls

IGDQ. Other Argiudolls that have an apparent CEC of less

than 24 cmol(+)/kg clay (by 1N NH4

OAc pH 7) in 50 percent

or more either of the argillic horizon if less than 100 cm thick

or of its upper 100 cm.

Oxic Argiudolls

IGDR. Other Argiudolls that have a calcic horizon within

100 cm of the mineral soil surface.

Calcic Argiudolls

IGDS. Other Argiudolls.

Typic Argiudolls

Definition of Typic Argiudolls

Typic Argiudolls are the Argiudolls that:

1. Do not have aquic conditions for some time in normal

years either:

a. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

b. Directly below the mollic epipedon, in horizons with a

total thickness of 15 cm or more that have one or more of

the following:

(1) A color value, moist, of 4 or more and redox

depletions with chroma of 2 or less; or

(2) Hue of 10YR or redder and chroma of 2 or less; or

(3) Hue of 2.5Y or yellower and chroma of 3 or less;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have a lithic contact within 50 cm of the mineral

soil surface;

4. Have an argillic horizon that is finer than the sandy

particle-size class in some part of the upper 75 cm if the

argillic horizon is more than 75 cm thick or in any part if the

argillic horizon is less than 75 cm thick;

5. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that
590 Soil Taxonomy

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

6. Have an apparent CEC (by 1N NH4

OAc pH 7) of 24 or

more in 50 percent or more of the argillic horizon or in 50

percent or more of the upper 100 cm of the argillic horizon if

the argillic horizon is thicker than 100 cm;

7. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

8. Do not have a calcic horizon within 100 cm of the soil

surface;

9. Do not have a texture finer than loamy fine sand and

either:

a. A mollic epipedon 50 cm or more thick; or

b. A mollic epipedon 40 cm or more thick and a frigid

temperature regime;

10. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness

of 5 cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon;

11. Do not have an argillic horizon that, with increasing

depth, has a clay increase of 20 percent or more (absolute, in

the fine-earth fraction) within its upper 7.5 cm;

12. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more; and

13. Do not have:

a. Above the argillic horizon, an albic horizon or a

horizon that has color values too high for a mollic epipedon

and chroma too high for an albic horizon; and

b. A glossic horizon, or interfingering of albic materials

into the upper part of the argillic horizon, or skeletans of

clean silt and sand covering 50 percent or more of the faces

of peds in the upper 5 cm of the argillic horizon.

Description of Subgroups

Typic Argiudolls.—The central concept or Typic subgroup

of Argiudolls is fixed on soils that show little evidence of

wetness within a depth of 40 cm or more, that do not have a

shallow lithic contact, that have a loamy or clayey particle-size

class in at least the argillic horizon, and that do not have

slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks in normal years.

Shallow ground water and redoximorphic features are

properties of Aquolls and are the basis for defining the Aquic

and Oxyaquic subgroups. A shallow lithic contact is the basis

for defining the Lithic subgroup. An argillic horizon that has a

sandy particle-size class or consists either entirely or partly of

thin lamellae is weakly developed and is the basis for defining

Psammentic and Lamellic subgroups. Slickensides, wedgeshaped aggregates, a high linear extensibility, and wide cracks

that are evident in normal years are characteristics of Vertisols

and are the basis for defining the Vertic subgroup. An albic or

glossic horizon or another horizon that has color values too

high for a mollic epipedon and chroma too high for an albic

horizon above the argillic horizon, interfingering of albic

materials into the upper part of the argillic horizon, and

skeletans of clean silt and sand covering 50 percent or more of

the faces of peds in the upper 5 cm of the argillic horizon are

considered characteristics of Alfisols and are the basis for

defining the Alfic subgroup.

Typic Argiudolls are of large extent in the United States.

They are mostly on the eastern Great Plains but occur

throughout much of the country. Most of these soils supported

tall grasses, and most are now used as cropland.
Mollisols 591

Abruptic Argiudolls.—These soils have an abrupt textural

change at the top of the argillic horizon. They show no

evidence of the development of an albic horizon. They are of

very small extent in the United States and occur mostly in

Minnesota. These soils supported chiefly tall grasses. They

commonly are used as cropland.

Alfic Argiudolls.—These soils have an albic or glossic

horizon or another horizon that has color values too high for a

mollic epipedon and chroma too high for an albic horizon

above the argillic horizon, have interfingering of albic

materials into the upper part of the argillic horizon, or have

skeletans of clean silt and sand covering 50 percent or more of

the faces of peds in the upper 5 cm of the argillic horizon.

These soils are of very small extent in the United States and

occur mostly in Minnesota. They supported mostly tall grasses.

They commonly are used as cropland.

Alfic Vertic Argiudolls.—These soils have a clayey

particle-size class in a significant part, have expanding clays,

and in some years have deep cracks. They also have an albic or

glossic horizon or another horizon that has color values too

high for a mollic epipedon and chroma too high for an albic

horizon above the argillic horizon, have interfingering of albic

materials into the upper part of the argillic horizon, or have

skeletans of clean silt and sand covering 50 percent or more of

the faces of peds in the upper 5 cm of the argillic horizon.

These soils are of very small extent in the United States and

occur mostly in North Dakota. They supported mostly tall

grasses. They commonly are used as cropland.

Andic and Vitrandic Argiudolls.—These soils have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals

or that consists of slightly or moderately weathered pyroclastic

materials. These soils are not known to occur in the United

States.

Aquertic Argiudolls.—These soils have lower chroma than

Typic Argiudolls and commonly have faint redoximorphic

features and either shallow ground water at some time during

the year or artificial drainage. They also have a clayey particlesize class in a significant part, have expanding clays, and in

some years have deep cracks. These soils are of moderate

extent in the United States and occur mostly on the northern

Great Plains. They supported mostly tall grasses and commonly

are used as cropland.

Aquic Argiudolls.—These soils have lower chroma than

Typic Argiudolls and commonly have faint redoximorphic

features and either shallow ground water at some time during

the year or artificial drainage. They are extensive soils in the

glaciated regions of the northern Great Plains of the United

States. They commonly occur in areas between Aquolls and

Typic Argiudolls. Slopes generally are nearly level. Most Aquic

Argiudolls have been artificially drained. They supported

chiefly tall grasses and commonly are used as cropland.

Arenic Argiudolls.—These soils have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of the argillic horizon at a

depth of 50 cm or more. The argillic horizon most commonly is at

a depth of 75 to 100 cm. These soils formed in Pleistocene

deposits. They are of very small extent in the United States and

occur mostly in North Dakota and Minnesota. They supported

chiefly tall grasses and commonly are used as cropland.

Calcic Argiudolls.—These soils have a calcic horizon

within 100 cm of the soil surface. They are not known to occur

in the United States. They were established for use in

Argentina.

Lamellic Argiudolls.—These soils are like Typic

Argiudolls in defined properties, but they have an argillic

horizon that consists entirely or partially of lamellae. Most

Lamellic Argiudolls have a sandy particle-size class, and the

upper boundary of the argillic horizon or the upper lamella

may be below a depth of 60 cm. The upper several lamellae are

commonly broken or discontinuous horizontally. These soils

are not known to occur in the United States.

Lithic Argiudolls.—These soils have a shallow lithic

contact but are otherwise like Typic Argiudolls. Slopes are

commonly moderate to steep. Lithic Argiudolls are of small

extent in the United States. They are mostly on the eastern

Great Plains. Most of the soils supported tall grasses and some

widely spaced trees. Most are now used as cropland or pasture.

Oxic Argiudolls.—These soils have a low cation-exchange

capacity in half or more of the argillic horizon (if this horizon

is less than 100 cm thick) or of its upper 100 cm. They are

mostly in areas of warm and humid climates and are not

known to occur in the United States.

Oxyaquic Argiudolls.—These soils are like Typic

Argiudolls, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. They are moderately

extensive soils in the glaciated regions of the northern Great

Plains of the United States. They commonly are in areas

between the Aquic and Typic subgroups of Argiudolls. Slopes

generally are gentle. Oxyaquic Argiudolls supported mostly tall

grasses and commonly are used as cropland.

Oxyaquic Vertic Argiudolls.—These soils have a clayey

particle-size class in a significant part, have expanding clays,

and in some years have deep cracks. They are saturated with

water within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. They are of small extent on the Great Plains of the

United States. Slopes generally are gentle. These soils

supported mostly tall grasses and commonly are used as

cropland.

Pachic Argiudolls.—These soils are like Typic Argiudolls,

but they have a thick mollic epipedon. The argillic horizon

generally starts in the lower part of the mollic epipedon. Slopes

of the Pachic Argiudolls in the United States range from gentle

to steep. The soils are of small extent on the Great Plains of the

United States. Most of the soils are used as cropland.

Pachic Vertic Argiudolls.—These soils have a clayey
592 Soil Taxonomy

particle-size class in a significant part, have expanding clays,

and in some years have deep cracks. They also have a thick

mollic epipedon. The argillic horizon generally starts in the lower

part of the mollic epipedon. These soils are of very small extent

in the United States and occur mostly in North Dakota. They

supported chiefly tall grasses and commonly are used as

cropland.

Psammentic Argiudolls.—These soils formed mostly in

sandy Pleistocene deposits, either dunes or glacial outwash.

The argillic horizon most commonly is 75 to 100 cm below the

soil surface. These soils are of very small extent in the United

States. They supported mostly tall grasses and commonly are

used as cropland.

Vertic Argiudolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in some

years have deep cracks. They are of small extent in the United

States. They occur throughout the Great Plains. They supported

mostly tall grasses and commonly are used as cropland.

Calciudolls

These are the Udolls with a calcic or petrocalcic horizon that

has its upper boundary within 100 cm of the soil surface.

Calciudolls do not have an argillic horizon above the calcic or

petrocalcic horizon. They are calcareous in all subhorizons

overlying the calcic horizon after the upper 18 cm has been

mixed, unless the texture is coarser than loamy very fine sand

or very fine sand. These soils are of small extent on the

northern Great Plains of the United States. They are important

in Argentina.

Definition

Calciudolls are the Udolls that:

1. Have a calcic or petrocalcic horizon that has its upper

boundary within 100 cm of the soil surface;

2. Are calcareous in all parts of all horizons above the calcic

horizon after the upper 18 cm has been mixed, unless the

texture is coarser than loamy very fine sand or very fine sand;

3. Do not have an argillic horizon above the calcic or

petrocalcic horizon; and

4. Do not have a natric horizon.

Key to Subgroups

IGBA. Calciudolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Calciudolls

IGBB. Other Calciudolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Calciudolls

IGBC. Other Calciudolls that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Calciudolls

IGBD. Other Calciudolls that have a slope of less than 25

percent; and either:

1. An organic-carbon content of 0.3 percent or more at a

depth of 125 cm below the mineral soil surface; or

2. An irregular decrease in organic-carbon content from a

depth of 25 cm to a depth of 125 cm or to a lithic or paralithic

contact if shallower.

Fluventic Calciudolls

IGBE. Other Calciudolls.

Typic Calciudolls

Definition of Typic Calciudolls

Typic Calciudolls are the Udolls that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface; and

2. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

3. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions; and

4. Do not have a slope of less than 25 percent and either of

the following:

a. An organic-carbon content of 0.3 percent or more at a

depth of 125 cm below the mineral soil surface; or

b. An irregular decrease in organic-carbon content from a
Mollisols 593

depth of 25 cm to a depth of 125 cm or to a lithic or paralithic

contact if shallower.

Description of Subgroups

Typic Calciudolls.—The central concept or Typic subgroup

of Calciudolls is fixed on deep soils that show little evidence of

wetness within a depth of 40 cm or more and are calcareous

throughout.

Shallow ground water and redoximorphic features are

properties of Aquolls and are the basis for defining the Aquic

subgroup. A shallow lithic contact is the basis for defining the

Lithic subgroup. Slickensides, wedge-shaped aggregates, a

high linear extensibility, and wide cracks that are evident in

normal years are characteristics of Vertisols and are the basis

for defining the Vertic subgroup.

Typic Calciudolls are of small extent on the northern Great

Plains of the United States. Most of these soils supported tall

grasses and are used as cropland.

Aquic Calciudolls.—These soils have ground water at a

moderate depth in the calcic horizon at some time during the

year, and they have redox depletions with low chroma. The

epipedon also commonly has low chroma. These soils are of

small extent on the northern Great Plains of the United States.

They generally are nearly level and formed in late-Wisconsinan

drift. Nearly all of these soils supported tall grasses and are

used as cropland.

Fluventic Calciudolls.—These soils are freely drained and

formed in alluvium deposited recently enough for the content

of organic carbon to decrease irregularly with increasing depth

or to remain relatively high in the deep layers. The soils are

subject to overflow, primarily when snow melts. Most of these

soils are cultivated if they occur in areas suitable in size and

shape. Fluventic Calciudolls are of very small extent in the

United States. Most are used as cropland.

Lithic Calciudolls.—These soils have a lithic contact

within 50 cm of the mineral soil surface. They are otherwise

similar to Typic Calciudolls. Lithic Calciudolls are not known

to occur in the United States.

Vertic Calciudolls.—These soils are like Typic Calciudolls,

but they have a clayey particle-size class in a significant part,

have expanding clays, and in normal years have deep cracks.

Vertic Calciudolls are not known to occur in the United States.

Hapludolls

These are the Udolls that generally have a cambic horizon

below a mollic epipedon. There may be a Bk horizon below the

cambic horizon, and a few of the soils have enough secondary

carbonates for a calcic horizon.

Hapludolls formed mostly in Holocene or late-Pleistocene

deposits or on surfaces of that age. Slopes generally are gentle,

and most of the soils are cultivated. Hapludolls are extensive

soils in Iowa, Minnesota, and adjacent states.

Definition

Hapludolls are the Udolls that:

1. Do not have an argillic or natric horizon;

2. Do not have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface if all parts above the

calcic horizon, after the materials between the soil surface and

a depth of 18 cm have been mixed, either are calcareous or

have a texture of loamy fine sand or coarser; and

3. Have less than 50 percent (by volume) wormholes,

wormcasts, and filled animal burrows in the mollic epipedon

below any plow layer if the epipedon rests on a densic, lithic,

or paralithic contact or have a transition between the mollic

epipedon and the underlying horizon in which less than 25

percent (by volume) consists of wormholes, wormcasts, and

filled animal burrows.

Key to Subgroups

IGFA. Hapludolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Hapludolls

IGFB. Other Hapludolls that have both:

1. Aquic conditions for some time in normal years (or

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

b. Directly below the mollic epipedon, in one or more

horizons with a total thickness of 15 cm or more that

have one or more of the following:

(1) A color value, moist, of 4 or more and redox

depletions with chroma of 2 or less; or

(2) Hue of 10YR or redder and chroma of 2 or less;

or

(3) Hue of 2.5Y or yellower and chroma of 3 or less;

and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Aquertic Hapludolls
594 Soil Taxonomy

IGFC. Other Hapludolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Hapludolls

IGFD. Other Hapludolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and aluminum plus 1/2 iron percentages (by

ammonium oxalate) totaling more than 1.0.

Andic Hapludolls

IGFE. Other Hapludolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Hapludolls

IGFF. Other Hapludolls that have:

1. Either:

a. A frigid soil temperature regime and a mollic

epipedon 40 cm or more thick, of which less than 50

percent has a sandy or sandy-skeletal particle-size class,

and there is no densic or paralithic contact and no sandy

or sandy-skeletal particle-size class at a depth between 40

and 50 cm from the mineral soil surface; or

b. A mollic epipedon 60 cm or more thick, of which 50

percent or more of the thickness has a texture finer than

loamy fine sand; and

2. Either 0.3 percent or more organic carbon at a depth

of 125 cm below the mineral soil surface or an irregular

decrease in organic-carbon content from a depth of 25 cm to a

depth of 125 cm or to a densic, lithic, or paralithic contact if

shallower; and

3. A slope of 25 percent or less; and

4. In one or more horizons within 100 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage).

Aquic Cumulic Hapludolls

IGFG. Other Hapludolls that have:

1. Either:

a. A frigid soil temperature regime and a mollic

epipedon 40 cm or more thick, of which less than 50

percent has a sandy or sandy-skeletal particle-size class,

and there is no densic or paralithic contact and no sandy

or sandy-skeletal particle-size class at a depth between 40

and 50 cm from the mineral soil surface; or

b. A mollic epipedon 60 cm or more thick, of which 50

percent or more of the thickness has a texture finer than

loamy fine sand; and

2. Either 0.3 percent or more organic carbon at a depth

of 125 cm below the mineral soil surface or an irregular

decrease in organic-carbon content from a depth of 25 cm to

a depth of 125 cm or to a densic, lithic, or paralithic contact

if shallower; and

3. A slope of 25 percent or less.

Cumulic Hapludolls

IGFH. Other Hapludolls that have both:

1. Aquic conditions for some time in normal years (or

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

b. Directly below the mollic epipedon, in one or more

horizons with a total thickness of 15 cm or more that

have one or more of the following:

(1) A color value, moist, of 4 or more and redox

depletions with chroma of 2 or less; or

(2) Hue of 10YR or redder and chroma of 2 or less;

or

(3) Hue of 2.5Y or yellower and chroma of 3 or less;

and

2. A slope of less than 25 percent; and either

a. An organic-carbon content of 0.3 percent or more at

a depth of 125 cm below the mineral soil surface; or
Mollisols 595

b. An irregular decrease in organic-carbon content from

a depth of 25 cm to a depth of 125 cm or to a densic, lithic,

or paralithic contact if shallower.

Fluvaquentic Hapludolls

IGFI. Other Hapludolls that have aquic conditions for some

time in normal years (or artificial drainage) either:

1. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

2. Directly below the mollic epipedon, in one or more

horizons with a total thickness of 15 cm or more that have

one or more of the following:

a. A color value, moist, of 4 or more and redox

depletions with chroma of 2 or less; or

b. Hue of 10YR or redder and chroma of 2 or less; or

c. Hue of 2.5Y or yellower and chroma of 3 or less.

Aquic Hapludolls

IGFJ. Other Hapludolls that have a texture finer than loamy

fine sand and either:

1. A frigid temperature regime and a mollic epipedon 40

cm or more thick; or

2. A mollic epipedon 50 cm or more thick.

Pachic Hapludolls

IGFK. Other Hapludolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Hapludolls

IGFL. Other Hapludolls that have a slope of less than 25

percent; and either

1. An organic-carbon content of 0.3 percent or more at a

depth of 125 cm below the mineral soil surface; or

2. An irregular decrease in organic-carbon content from a

depth of 25 cm to a depth of 125 cm or to a densic, lithic, or

paralithic contact if shallower.

Fluventic Hapludolls

IGFM. Other Hapludolls that have both:

1. A mollic epipedon 60 cm or more thick that has a

texture finer than loamy fine sand and contains 50 percent

or more (by volume) wormholes, wormcasts, or filled

animal burrows either below an Ap horizon or below a

depth of 18 cm from the mineral soil surface; and

2. Either do not have a cambic horizon and do not, in the

lower part of the mollic epipedon, meet all of the requirements

for a cambic horizon, except for the color requirements, or

have carbonates throughout either the cambic horizon or the

lower part of the mollic epipedon.

Vermic Hapludolls

IGFN. Other Hapludolls that have a calcic horizon within

100 cm of the mineral soil surface.

Calcic Hapludolls

IGFO. Other Hapludolls that either:

1. Do not have a cambic horizon and do not, in any part of

the mollic epipedon below 25 cm from the mineral soil

surface, meet all of the requirements for a cambic horizon,

except for the color requirements; or

2. Have free carbonates throughout the cambic horizon or

in all parts of the mollic epipedon below a depth of 25 cm

from the mineral soil surface.

Entic Hapludolls

IGFP. Other Hapludolls.

Typic Hapludolls

Definition of Typic Hapludolls

Typic Hapludolls are the Hapludolls that:

1. Do not have aquic conditions for some time in normal

years either:

a. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

b. Directly below the mollic epipedon, in horizons with a

total thickness of 15 cm or more that have one or more of

the following:

(1) A color value, moist, of 4 or more and redox

depletions with chroma of 2 or less; or

(2) Hue of 10YR or redder and chroma of 2 or less; or

(3) Hue of 2.5Y or yellower and chroma of 3 or less;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Have a mollic epipedon that is less than 60 cm thick or has

a texture of loamy fine sand or coarser if it is 60 cm or more

thick;

4. Have a cambic horizon or, in the lower part of the mollic

epipedon, meet all of the requirements for a cambic horizon,

except for the color requirments, and either the cambic horizon

or the lower part of the epipedon is free of carbonates in some

part;
596 Soil Taxonomy

5. Either have a regular decrease in organic-carbon content

with increasing depth and, unless a densic, lithic, or paralithic

contact is at some depth between 50 and 125 cm below the soil

surface, have an organic-carbon content of 0.3 percent or less

at a depth within 125 cm of the surface or have a slope of 25

percent or more;

6. Do not have a lithic contact within 50 cm of the mineral

soil surface;

7. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

8. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

9. Do not have a calcic horizon within 100 cm of the soil

surface; and

10. Do not have a texture finer than loamy fine sand and

either:

a. A mollic epipedon 50 cm or more thick; or

b. A mollic epipedon 40 cm or more thick and a frigid

temperature regime.

Description of Subgroups

Typic Hapludolls.—The central concept or Typic subgroup

of Hapludolls is fixed on soils in which there is little evidence

of wetness within a depth of 40 cm or more, in which there is a

thin or moderately thick mollic epipedon, and in which a

cambic horizon is free of carbonates in some part or the lower

part of the mollic epipedon is free of carbonates and resembles

a cambic horizon. These soils do not have a shallow lithic

contact; do not have slickensides, wedge-shaped aggregates, a

high linear extensibility, or wide cracks in normal years; and

show evidence of only a small amount of animal activity.

Low chroma and redoximorphic features are properties of

Aquolls and are the basis for defining Aquic and combination

Aquic subgroups of Hapludolls. An irregular decrease in

organic-carbon content with increasing depth and a relatively

high organic-carbon content in the deep layers indicate recent

alluvium and are the basis for defining the Fluventic subgroup

or, if the soils also are saturated with water at some period, the

Fluvaquentic subgroup. An overthickened epipedon and a

relatively high content of organic carbon in the deep layers

indicate slow accumulation of materials at the surface and, in

part, are the basis for defining the Cumulic subgroup. The

absence of a cambic horizon or the presence of carbonates

throughout the cambic horizon suggests weak weathering and

is the basis for defining the Entic subgroup. A shallow lithic

contact is the basis for defining the Lithic subgroup. Intensive

animal activity is a property of Vermudolls and is the basis for

defining the Vermic subgroup. Slickensides, wedge-shaped

aggregates, a high linear extensibility, and wide cracks that are

evident in normal years are characteristics of Vertisols and are

the basis for defining the Vertic subgroup.

Typic Hapludolls are of large extent in the United States.

They are mostly in Iowa, in Minnesota, and throughout the

eastern Great Plains. Some Typic Hapludolls occur throughout

much of the country. Most supported tall grasses, and most are

now used as cropland.

Andic and Vitrandic Hapludolls.—These soils have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals

or that consists of slightly or moderately weathered pyroclastic

materials. These soils are of very small extent in Oregon in the

United States.

Aquertic Hapludolls.—These soils have lower chroma than

Typic Hapludolls and commonly have faint redoximorphic

features and either shallow ground water at some time during

the year or artificial drainage. They also have a clayey particlesize class in a significant part, have expanding clays, and in

some years have deep cracks. These soils are of small extent in

the United States and occur mostly in Minnesota and Iowa.

They supported mostly tall grasses and commonly are used as

cropland.

Aquic Hapludolls.—These soils have lower chroma than

Typic Hapludolls, commonly have faint redoximorphic

features, and either have shallow ground water at some time

during the year or have been artificially drained. These are

extensive soils in the glaciated regions of the northern Great

Plains of the United States. They commonly are in areas
Mollisols 597

between Aquolls and Typic Hapludolls. Slopes generally are

nearly level, and most of the soils have been artificially

drained. Aquic Hapludolls supported mostly tall grasses and

commonly are used as cropland.

Aquic Cumulic Hapludolls.—These soils have an

overthickened mollic epipedon. They also have lower chroma

than Typic Hapludolls, commonly have faint redoximorphic

features, and either have shallow ground water at some time

during the year or have been artificially drained. They are at

the base of slopes or on flood plains, where they receive fresh

sediments at a rate slow enough for the material to become

incorporated into the mollic epipedon. Some of the soils are

calcareous throughout their thickness. Aquic Cumulic

Hapludolls are of small extent and are mostly in Iowa. Slopes

are gentle and are mostly plane or concave. These soils

supported mostly tall grasses and commonly are used as

cropland.

Calcic Hapludolls.—These soils are similar to Typic

Hapludolls but have a calcic horizon within 100 cm of the soil

surface. They are of small extent, mostly in Minnesota, in the

United States. They supported mostly tall grasses and

commonly are used as cropland.

Cumulic Hapludolls.—These soils have an overthickened

mollic epipedon. They are at the base of slopes or on flood

plains, where they receive fresh sediments at a rate slow

enough for the material to become incorporated into the mollic

epipedon. These soils are permitted, but not required, to have a

cambic horizon. They may be calcareous throughout their

thickness. Slopes are gentle and are mostly plane or concave.

These soils are of large extent and are widely distributed in the

United States. Many of the soils supported tall grasses, but

some supported trees and shrubs. Most are used as cropland.

Entic Hapludolls.—These soils either do not have a cambic

horizon or are calcareous in the lower part of the mollic

epipedon or throughout any cambic horizon. Most of the soils

are sandy and show relatively weak horizon development.

Slopes are moderate to strong and are convex. These soils are

of small extent, mostly in Iowa and Minnesota, in the United

States. They supported mostly tall grasses and commonly are

used as cropland.

Fluvaquentic Hapludolls.—These soils have lower chroma

than Typic Hapludolls, have faint redoximorphic features, and

either have shallow ground water at some time during the year

or have been artificially drained. They are on flood plains and

formed in recent alluvium in which there are buried A horizons

or in which the content of organic carbon is relatively high in

deep layers. These soils are of moderate extent and are widely

distributed in the United States. Slopes are gentle and are

mostly plane or concave. Many of the soils supported tall

grasses, but some supported trees and shrubs. Most are used as

cropland.

Fluventic Hapludolls.—These soils are freely drained and

are on flood plains. They formed in recent alluvium in which

there are buried A horizons or in which the content of organic

carbon is relatively high in deep layers. Many of the soils do not

have a cambic horizon. The soils are otherwise like Typic

Hapludolls. Fluventic Hapludolls are of moderate extent and

are widely distributed in the United States. Slopes are gentle

and are mostly plane or concave. Many of the soils supported

tall grasses, but some supported trees and shrubs. Most are

used as cropland.

Lithic Hapludolls.—These soils have a shallow lithic

contact. The mollic epipedon commonly extends to the rock.

Some of the soils have impeded drainage because of shallow,

impermeable rock. Lithic Hapludolls are of moderate extent

and are widely distributed in the United States. Slopes are

gentle to very steep. Many of the soils supported grasses, but

some supported trees and shrubs. Most are used as rangeland

or wildlife habitat.

Oxyaquic Hapludolls.—These soils are like Typic

Hapludolls, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. They are of small

extent but are widely distributed in the United States. They

commonly are in areas between the Aquic and Typic subgroups

of Hapludolls. Slopes generally are gentle. Oxyaquic

Hapludolls supported mostly tall grasses and commonly are

used as cropland.

Pachic Hapludolls.—These soils are like Typic Hapludolls,

but they have a thick mollic epipedon. Slopes range from

gentle to moderately steep. Pachic Hapludolls are of small

extent, mostly on the northern Great Plains of the United

States. They supported mostly tall grasses and commonly are

used as cropland.

Vermic Hapludolls.—These soils show strong evidence of

intensive animal activity, mainly of earthworms and their

predators. The soils are thought to be developing toward

Vermudolls. They do not occur in significant areas in the

United States.

Vertic Hapludolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in some

years have deep cracks. They are of small extent in the United

States and are widely distributed. They supported mostly tall

grasses and commonly are used as cropland.

Natrudolls

These are the Udolls that have a natric horizon. Below

the natric horizon, there is normally one horizon or more

in which carbonates, sulfates, or other soluble salts have

accumulated. Most Natrudolls are in small areas. The soils

are most common in Argentina and on the northern Great

Plains of the United States, where many of the parent

materials contain salts. Most areas of these soils are small

and are nearly level or concave.

Definition

Natrudolls are the Udolls that have a natric horizon.
598 Soil Taxonomy

Key to Subgroups

IGAA. Natrudolls that have a petrocalcic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

Petrocalcic Natrudolls

IGAB. Other Natrudolls that have both:

1. Visible crystals of gypsum and/or more soluble salts

within 40 cm of the mineral soil surface; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Leptic Vertic Natrudolls

IGAC. Other Natrudolls that have:

1. A glossic horizon or interfingering of albic materials

into the natric horizon; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Glossic Vertic Natrudolls

IGAD. Other Natrudolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Natrudolls

IGAE. Other Natrudolls that have visible crystals of gypsum

and/or more soluble salts within 40 cm of the mineral soil

surface.

Leptic Natrudolls

IGAF. Other Natrudolls that have a glossic horizon or

interfingering of albic materials into the natric horizon.

Glossic Natrudolls

IGAG. Other Natrudolls that have a calcic horizon within

100 cm of the mineral soil surface.

Calcic Natrudolls

IGAH. Other Natrudolls.

Typic Natrudolls

Definition of Typic Natrudolls

Typic Natrudolls are the Natrudolls that:

1. Do not have a calcic or petrocalcic horizon that has its

upper boundary within 100 cm of the mineral soil surface;

2. Do not have visible crystals or nests of gypsum or more

soluble salts within 40 cm of the mineral soil surface;

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

4. Do not have a glossic horizon or interfingering of albic

materials into the natric horizon.

Description of Subgroups

Typic Natrudolls.—The central concept or Typic subgroup

of Natrudolls is fixed on soils that do not have a calcic or

petrocalcic horizon that has its upper boundary within 100 cm

of the mineral soil surface. These soils do not have a glossic

horizon or an albic horizon that interfingers into the natric

horizon. An albic horizon commonly is above the natric

horizon. If there is no albic horizon, there generally are some

skeletans and the color of the lower part of the mollic epipedon

approaches that of an albic horizon.

Visible crystals of gypsum and/or more soluble salts within

40 cm of the mineral soil surface adversely affect the use of

these soils and are the basis for defining the Leptic subgroup.

An albic horizon that has an irregular lower boundary or thick

skeletans on the peds in the upper part of the natric horizon are
Mollisols 599

considered evidence of partial destruction of the natric horizon

and are the basis for defining Glossic and combination Glossic

subgroups.

Typic Natrudolls are of small extent in the United States.

They are mostly on the northern Great Plains of the United

States. They supported mostly salt-tolerant grasses and shrubs.

Slopes are commonly gentle, and many of the soils are

cultivated. Some of the soils are used as rangeland or hayland.

Calcic Natrudolls.—These soils are similar to Typic

Natrudolls but have a calcic horizon within 100 cm of the soil

surface. They are of small extent in the United States and are

important in Argentina. They supported mostly grasses and are

used mostly as cropland.

Glossic Natrudolls.—These soils show evidence of

destruction of the natric horizon. Commonly, they have more

exchangeable magnesium and less sodium than Typic

Natrudolls, at least in the upper part of the natric horizon.

Some Glossic Natrudolls receive more moisture, either as

precipitation or as runoff, than the soils of the Typic subgroup.

Glossic Natrudolls are mostly on the northern Great Plains of

the United States. Most of the Glossic Natrudolls in the United

States are nearly level and are used as cropland.

Glossic Vertic Natrudolls.—These soils have both a high

shrink-swell potential and a glossic horizon or interfingering

of albic materials into the natric horizon. The soils do not have

a petrocalcic horizon within 100 cm or soluble salts, including

gypsum, within 40 cm of the soil surface. These soils occur in

the Dakotas and are used for small grain or alfalfa.

Leptic Natrudolls.—These soils have visible evidence of

salts at least as soluble as gypsum within 40 cm of the soil

surface. They have thinner sola than those of the Typic

subgroup, and the close proximity of the soluble salts to the

surface restricts plant growth. Leptic Natrudolls are moderately

extensive on the northern Great Plains of the United States.

They are on gentle slopes and are used primarily as rangeland.

Leptic Vertic Natrudolls.—These soils have a clayey

particle-size class in a significant part, have expanding clays,

and in normal years have deep cracks. They also have visible

evidence of salts at least as soluble as gypsum within 40 cm of

the soil surface. They have thinner sola than those of the Vertic

subgroup, and the close proximity of the soluble salts to the

surface restricts plant growth. Leptic Vertic Natrudolls are of

small extent in the United States. They are recognized only in

South Dakota. They supported mostly grasses and shrubs. Most

of the soils are used as rangeland.

Petrocalcic Natrudolls.—These soils are similar to Typic

Natrudolls but have a petrocalcic horizon within 100 cm of the

soil surface. They are not known to occur in the United States

but are important in Argentina. They supported mostly grasses

and are used mostly as cropland.

Vertic Natrudolls.—These soils are like Typic Natrudolls,

but they have a clayey particle-size class in a significant part,

have expanding clays, and in normal years have deep cracks.

They are of small extent in the United States. They are

recognized only in South Dakota. They supported mostly

grasses and shrubs. Most of the soils are used as cropland or

rangeland.

Paleudolls

These are the Udolls that have a thick or deep argillic horizon.

Most of the soils have a reddish hue and a content of clay that

decreases slowly with increasing depth. Paleudolls are mainly on

surfaces older than Wisconsinan and are thought to have

formed during at least one glacial stage and one interglacial

stage. These soils are mostly on the southern Great Plains and in

the mountains of the Western United States. They are extensive

only locally. Slopes are gentle to steep.

Definition

Paleudolls are the Udolls that:

1. Do not have a natric horizon; and

2. Have a petrocalcic horizon and do not have an argillic

horizon above the petrocalcic horizon; and

a. In all parts above the petrocalcic horizon, after the

materials between the soil surface and a depth of 18 cm

have been mixed, either are calcareous; or

b. Have a texture of loamy fine sand or coarser; or

3. Have an argillic horizon and a clay distribution in

which the clay content does not decrease by as much as 20

percent from the maximum clay content within 150 cm of

the soil surface, do not have a densic, lithic, or paralithic

contact within that depth, and also have one or both of the

following:

a. Hue of 7.5YR or redder and chroma of 5 or more

dominant in the matrix in some part of the lower half of the

argillic horizon; or

b. Many coarse redox concentrations that have hue redder

than 7.5YR or chroma higher than 5; or

4. Have a frigid temperature regime and both an argillic

horizon that has its upper boundary 60 cm or more below the

mineral soil surface and a texture finer than loamy fine sand in

all horizons above the argillic horizon.

Key to Subgroups

IGCA. Paleudolls that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the
600 Soil Taxonomy

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Paleudolls

IGCB. Other Paleudolls that have a petrocalcic horizon

within 150 cm of the mineral soil surface.

Petrocalcic Paleudolls

IGCC. Other Paleudolls that have, in one or more

subhorizons within the upper 50 cm of the argillic horizon,

redox depletions with chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Paleudolls

IGCD. Other Paleudolls that have a texture finer than loamy

fine sand and a mollic epipedon 50 cm or more thick.

Pachic Paleudolls

IGCE. Other Paleudolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Paleudolls

IGCF. Other Paleudolls that:

1. Have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface; and

2. In all parts above the calcic horizon, after the materials

between the soil surface and a depth of 18 cm have been

mixed, either are calcareous or have a texture of loamy fine

sand or coarser.

Calcic Paleudolls

IGCG. Other Paleudolls.

Typic Paleudolls

Definition of Typic Paleudolls

Typic Paleudolls are the Paleudolls that:

1. Do not have, in any subhorizon within the upper 50 cm of

the argillic horizon, redox depletions with chroma of 2 or less

and also aquic conditions;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that are 5

mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

4. Do not have a petrocalcic horizon within 150 cm of the

mineral soil surface;

5. Do not have a calcic horizon within 100 cm of the soil

surface; and

6. Do not have a texture finer than loamy fine sand and a

mollic epipedon 50 cm or more thick.

Description of Subgroups

Typic Paleudolls.—The central concept or Typic subgroup

of Paleudolls is fixed on soils that show little evidence of

wetness within a depth of 100 cm, that have a mollic epipedon

less than 50 cm thick, and that do not have slickensides,

wedge-shaped aggregates, a high linear extensibility, or wide

cracks in normal years. These soils do not have a petrocalcic

horizon or a shallow calcic horizon.

Shallow ground water and redoximorphic features are

properties of Aquolls and are the basis for defining the Aquic

and Oxyaquic subgroups. Slickensides, wedge-shaped

aggregates, a high linear extensibility, and wide cracks that are

evident in normal years are characteristics of Vertisols and are

the basis for defining the Vertic subgroup.

Typic Paleudolls are of small extent in the United States.

They are mostly on the southern Great Plains but also are in

the mountains in the western part of the United States. Most of

these soils supported tall grasses. Many of the soils on plains

are now used as cropland. The soils in the mountains are used

mostly as rangeland or wildlife habitat.

Aquic Paleudolls.—These soils have redox depletions with

low chroma in the upper part of the argillic horizon (within the

upper 50 cm), and, at some time during the year, ground water

stands in the redox-depleted horizon unless the soils have been

artificially drained. The soils are otherwise like Typic

Paleudolls. Aquic Paleudolls are of small extent in the United

States. They occur on the southern Great Plains of the United

States. Most of these soils supported tall grasses. Many have

gentle slopes and are used as cropland.

Calcic Paleudolls.—These soils are like Typic Paleudolls,

but they have a calcic horizon within 100 cm of the soil

surface. They are not known to occur in the United States.

They were established for use in other countries.

Oxyaquic Paleudolls.—These soils are like Typic

Paleudolls, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. Oxyaquic Paleudolls
Mollisols 601

are not known to occur in the United States. They were

established for use in other countries.

Pachic Paleudolls.—These soils are like Typic Paleudolls,

but they have a thick mollic epipedon. The argillic horizon

generally starts in the lower part of the mollic epipedon. Slopes

of the Pachic Paleudolls in the United States range from gentle

to steep. The soils are of small extent, mostly in the mountains

of the Western United States. Many of the soils supported

grasses and shrubs, but some supported trees. Most are used as

rangeland, but some are used as grazeable woodland.

Petrocalcic Paleudolls.—These soils have a petrocalcic

horizon within 150 cm, commonly within 100 cm, of the

mineral soil surface. They are not known to occur in the United

States. They were established for use in other countries.

Vertic Paleudolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in some

years have deep cracks. They are of very small extent in the

United States. They supported mostly tall grasses and

commonly are used as cropland.

Vermudolls

Vermudolls are the Udolls that have been intensively mixed

by earthworms or other burrowing animals and their predators.

The most common horizon sequence is the mollic epipedon

consisting of many wormcasts overlying soil material

containing many worm channels filled with dark material from

the mollic epipedon. These soils are not known to occur in

significant areas of the United States, but they are important in

other countries.

Definition

Vermudolls are the Udolls that:

1. Have a mollic epipedon below any Ap horizon, or below a

depth of 18 cm from the mineral soil surface, that has 50

percent or more (by volume) wormholes, wormcasts, or filled

animal burrows and that either rests on a densic, lithic, or

paralithic contact or has a transition to the underlying horizon

in which 25 percent or more of the material consists of discrete

wormholes, wormcasts, or animal burrows filled with material

from the mollic epipedon and the underlying horizon;

2. Do not have an argillic or natric horizon; and

3. Do not have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface if all parts above the

calcic horizon, after the materials between the soil surface and

a depth of 18 cm have been mixed, either are calcareous or

have a texture of loamy fine sand or coarser.

Key to Subgroups

IGEA. Vermudolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Vermudolls

IGEB. Other Vermudolls that have a mollic epipedon less than

75 cm thick.

Haplic Vermudolls

IGEC. Other Vermudolls.

Typic Vermudolls

Definition of Typic Vermudolls

Typic Vermudolls are the Vermudolls that:

1. Have a mollic epipedon that is 75 cm or more thick;

2. Do not have a lithic contact within 50 cm of the mineral soil

surface.

Description of Subgroups

Typic Vermudolls.—The central concept or Typic subgroup

of Vermudolls is fixed on soils that are deep to a lithic contact

and have a mollic epipedon 75 cm or more thick. These soils

are not known to occur in the United States.

Haplic Vermudolls.—These soils have a mollic epipedon

less than 75 cm thick. They are otherwise like Typic

Vermudolls. Haplic Vermudolls are of very small extent in the

United States. They are known to occur only in South Dakota

and Minnesota. These soils supported tall grasses. Most of the

soils are now used as cropland.

Lithic Vermudolls.—These soils have a lithic contact at a

depth of 50 cm or less from the mineral soil surface. They are

not known to occur in the United States.

Ustolls

Ustolls are the more or less freely drained Mollisols of

subhumid to semiarid climates. Rainfall occurs mainly during

a growing season, often in heavy showers, but is erratic.

Drought is frequent and may be severe. During a drought, soil

blowing becomes a problem. Without irrigation, the low supply

of moisture usually limits crop yields. Ustolls are extensive

soils on the western Great Plains in the United States.

In addition to the mollic epipedon, most Ustolls have a Bk

horizon that has identifiable secondary carbonates or have a

calcic horizon, but a few of the soils that formed in

noncalcareous materials do not have secondary lime. Ustolls

may also have a cambic, argillic, kandic, petrocalcic, or natric

horizon. If there is a natric horizon, there may be an albic

horizon overlying it, or if there is a cambic or argillic horizon,

there may be a duripan below it. The presence or absence of

these horizons is used, in part, as the basis for defining the

great groups of Ustolls.

Most of the Ustolls on the Great Plains in the United States

had a grass vegetation when the country was settled. Some of

the Ustolls in the mountains of the Western States supported

forest vegetation. The Aridic subgroups supported mostly short

grasses, and the others supported mixtures of short and tall

grasses.
602 Soil Taxonomy

Ustolls formed in sediments and on surfaces of varying ages

from Holocene to mid Pleistocene or earlier. Those that have a

thermic or warmer temperature regime, in particular, may have

formed during two or more glacial and interglacial stages.

The temperature regimes of Ustolls are warmer than cryic.

The moisture regimes are dominantly ustic, but a few of the

soils that are marginal to Aridisols have an aridic (torric)

regime.

Definition

Ustolls are the Mollisols that:

1. Have an ustic moisture regime or an aridic moisture regime

that borders on ustic;

2. Have a temperature regime warmer than cryic;

3. Do not have both an albic horizon and, within 100 cm of the

mineral soil surface, any subhorizon of the albic horizon and/or

of the argillic or natric horizon that has redox concentrations in

the form of masses or concretions, or both, and also aquic

conditions; and

4. Do not have both aquic conditions and the colors defined

for Aquolls.

Key to Great Groups

IFA. Ustolls that have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Durustolls, p. 612

IFB. Other Ustolls that have a natric horizon.

Natrustolls, p. 622

IFC. Other Ustolls that:

1. Have either a calcic or gypsic horizon that has its upper

boundary within 100 cm of the mineral soil surface or a

petrocalcic horizon that has its upper boundary within 150

cm of the mineral soil surface; and

2. Do not have an argillic horizon above the calcic, gypsic,

or petrocalcic horizon; and

3. In all parts above the calcic, gypsic, or petrocalcic

horizon, after the materials between the soil surface and a

depth of 18 cm have been mixed, either are calcareous or

have a texture of loamy fine sand or coarser.

Calciustolls, p. 608

IFD. Other Ustolls that have either:

1. A petrocalcic horizon that has its upper boundary

within 150 cm of the mineral soil surface; or

2. An argillic horizon that has one or both of the

following:

a. With increasing depth, no clay decrease of 20 percent

or more (relative) from the maximum clay content

(noncarbonate clay) within 150 cm of the mineral soil

surface (and there is no densic, lithic, or paralithic contact

within that depth); and either

(1) Hue of 7.5YR or redder and chroma of 5 or more in

the matrix; or

(2) Common redox concentrations with hue

of 7.5YR or redder or chroma of 6 or more, or

both; or

b. 35 percent or more clay in its upper part and a clay

increase either of 20 percent or more (absolute) within a

vertical distance of 7.5 cm or of 15 percent or more

(absolute) within a vertical distance of 2.5 cm, in the

fine-earth fraction (and there is no densic, lithic, or

paralithic contact within 50 cm of the mineral soil

surface).

Paleustolls, p. 625

IFE. Other Ustolls that have an argillic horizon.

Argiustolls, p. 602

IFF. Other Ustolls that have a mollic epipedon that:

1. Either below an Ap horizon or below a depth of 18 cm

from the mineral soil surface, contains 50 percent or more

(by volume) wormholes, wormcasts, or filled animal

burrows; and

2. Either rests on a lithic contact or has a transition zone

to the underlying horizon in which 25 percent or more of

the soil volume consists of discrete wormholes, wormcasts,

or animal burrows filled with material from the mollic

epipedon and from the underlying horizon.

Vermustolls, p. 629

IFG. Other Ustolls.

Haplustolls, p. 613

Argiustolls

These are the Ustolls that have an argillic horizon in or

below the mollic epipedon. They do not have a natric or

petrocalcic horizon that has its upper boundary within 150 cm

of the mineral soil surface or a duripan that has its upper

boundary within 100 cm of the mineral soil surface. Most of

these soils have an argillic horizon that, with increasing depth,

has a clay decrease of 20 percent or more (relative) from the

maximum clay content within 150 cm of the mineral soil surface.

Some of the soils have a densic, lithic, or paralithic contact

within 150 cm, and some have no hues of 7.5YR or redder or

have chroma of 4 or less.

Most Argiustolls have a Bk or calcic horizon below the

argillic horizon, and some have a Bz or By horizon below the
Mollisols 603

Bk horizon. Argiustolls formed mostly in late-Pleistocene

deposits or on surfaces of comparable age. They occur in

relatively stable positions. Slopes generally are moderate to

nearly level, and most of the soils are cultivated. Argiustolls

are extensive soils on the western Great Plains and also occur

in the mountains and valleys of the Western United States.

Definition

Argiustolls are the Ustolls that:

1. Have an argillic horizon that has both:

a. A vertical clay distribution in which the clay content

decreases by more than 20 percent from the maximum clay

content (noncarbonate clay) within a depth of less than 150

cm from the soil surface if:

(1) Hue in the matrix is redder than 10YR, and chroma

is higher than 4; or

(2) There are common redox concentrations that have

hue of 7.5YR or redder or chroma higher than 5; and

b. Less than 35 percent clay in the upper part or an

increase of less than 20 percent clay (absolute) within a

vertical distance of 7.5 cm or an increase of less than 15

percent clay (absolute) within a vertical distance of 2.5 cm

at the upper boundary, or there is a densic, lithic, or

paralithic contact within 50 cm of the mineral soil surface;

2. Do not have a duripan that has its upper boundary

within 100 cm of the soil surface;

3. Do not have a petrocalcic horizon that has its upper

boundary within 150 cm of the mineral soil surface;

4. Do not have a natric horizon; and

5. Do not have calcic or gypsic horizon that has its upper

boundary within 100 cm of the soil surface unless there is an

argillic horizon above the calcic or gypsic horizon or some part

of the soil above the calcic or gypsic horizon either is

noncalcareous or has a texture finer than loamy fine sand after

the materials between the soil surface and a depth of 18 cm

have been mixed.

Key to Subgroups

IFEA. Argiustolls that have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC.

Aridic Lithic Argiustolls

IFEB. Other Argiustolls that have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. Above the argillic horizon, either an albic horizon or a

horizon that has color values too high for a mollic epipedon

and chroma too high for an albic horizon.

Alfic Lithic Argiustolls

IFEC. Other Argiustolls that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Argiustolls

IFED. Other Argiustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or
604 Soil Taxonomy

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC.

Torrertic Argiustolls

IFEE. Other Argiustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the soil temperature

at a depth of 50 cm below the soil surface is higher than

8 oC.

Udertic Argiustolls

IFEF. Other Argiustolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick that

has its upper boundary within 125 cm of the mineral soil

surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Argiustolls

IFEG. Other Argiustolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Argiustolls

IFEH. Other Argiustolls that have both:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and
Mollisols 605

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitritorrandic Argiustolls

IFEI. Other Argiustolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Argiustolls

IFEJ. Other Argiustolls that have a texture finer than loamy

fine sand and either:

1. A frigid temperature regime and a mollic epipedon 40

cm or more thick; or

2. A mollic epipedon 50 cm or more thick.

Pachic Argiustolls

IFEK. Other Argiustolls that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Argiustolls

IFEL. Other Argiustolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Argiustolls

IFEM. Other Argiustolls that have either:

1. Above the argillic horizon, an albic horizon or a

horizon that has color values too high for a mollic epipedon

and chroma too high for an albic horizon; or

2. A glossic horizon, or interfingering of albic materials

into the upper part of the argillic horizon, or skeletans of

clean silt and sand covering 50 percent or more of the faces

of peds in the upper 5 cm of the argillic horizon.

Alfic Argiustolls

IFEN. Other Argiustolls that have both:

1. A calcic horizon with its upper boundary within 100 cm

of the mineral soil surface; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Calcidic Argiustolls

IFEO. Other Argiustolls that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for six-tenths or more of the cumulative days per

year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 5 o

C; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90
606 Soil Taxonomy

consecutive days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 o

C;

and

b. Is dry in some or all parts for six-tenths or more of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than

5 oC.

Aridic Argiustolls

IFEP. Other Argiustolls that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for four-tenths or less of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than 120

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC.

Udic Argiustolls

IFEQ. Other Argiustolls that have a brittle horizon that is

within 100 cm of the mineral soil surface, is 15 cm or more

thick, and has either some opal coatings or 20 percent or more

(by volume) durinodes.

Duric Argiustolls

IFER. Other Argiustolls.

Typic Argiustolls

Definition of Typic Argiustolls

Typic Argiustolls are the Argiustolls that:

1. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have a brittle horizon that is 15 cm or more thick,

is within 100 cm of the soil surface, and has some opal

coatings or 20 percent or more (by volume) durinodes;

4. Do not have a lithic contact within 50 cm of the mineral

soil surface;

5. Do not have either:

a. An albic horizon or another horizon above the argillic

horizon that has a color value too high for a mollic epipedon

and chroma too high for an albic horizon; or

b. A glossic horizon, or interfingering of albic materials in

the upper part of the argillic horizon, or skeletans of clean

silt and sand covering more than half the faces of peds in

the upper 5 cm or more of the argillic horizon;

6. Do not have a texture finer than loamy fine sand and

either:

a. A mollic epipedon 50 cm or more thick; or

b. A mollic epipedon 40 cm or more thick and a frigid

temperature regime;

7. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less than

four-tenths of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for more than four-tenths but less than six-tenths

of the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than 5 oC;

or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is moist in some or all parts for 90 or more

consecutive days per year or is dry for less than six-tenths of

the cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC

and is dry for more than 120 cumulative days per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 8 oC;

8. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

9. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,
Mollisols 607

of 1.0 g/cm3

 or less, measured at 33 kPa water retention, and

acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than 35

percent of the whole soil and cinders, pumice, and pumicelike

fragments making up more than 66 percent of these

fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more; and

10. Do not have a calcic horizon with its upper boundary

within 100 cm of the soil surface.

Description of Subgroups

Typic Argiustolls.—The central concept or Typic subgroup

of Argiustolls is fixed on deep, freely drained soils that have

some available moisture during most of the growing season

and do not have a calcic horizon, an albic horizon, a glossic

horizon, interfingering of albic materials, or a horizon that has

color values too high for a mollic epipedon above the argillic

horizon. These soils do not have slickensides, wedge-shaped

aggregates, a high linear extensibility, or wide cracks in

normal years.

Shallow ground water or artificial drainage and redox

depletions with low chroma are properties shared with Aquolls

and are the basis for defining Aquic and Oxyaquic subgroups.

A shallow lithic contact is the basis for defining Lithic and

combination Lithic subgroups. An albic horizon above the

argillic horizon is characteristic of Alfisols and is the basis for

defining the Alfic subgroup. A thick mollic epipedon is the

basis for defining the Pachic subgroup. Argiustolls that are

moist for longer periods of time than is described for the Typic

subgroup are assigned to the Udic subgroup, and those that are

dry for longer periods are assigned to the Aridic subgroup.

Slickensides, wedge-shaped aggregates, a high linear

extensibility, and wide cracks that are evident in normal years

are characteristics of Vertisols and are the basis for defining the

Vertic subgroup.

Typic Argiustolls are of large extent in the United States.

They are mostly on the Great Plains but also are in the

mountains in the western part of the United States. Most of

these soils supported grasses and shrubs. Some of the soils,

mostly those in the mountains, supported trees or grass and

widely spaced trees. Many of the soils on plains are now used

as cropland. The soils in the mountains are used mostly as

rangeland or wildlife habitat.

Alfic Argiustolls.—These soils have an albic horizon or an

eluvial horizon that is too light in color for a mollic epipedon

above the argillic horizon, or they have a glossic horizon,

interfingering of albic materials, or skeletans of clean silt and

sand covering more than half the faces of peds in the upper 5

cm or more of the argillic horizon. The vegetation on these

soils commonly is grass and scattered conifer trees. The soils

are of small extent, mostly in the mountains of Colorado. They

are used mostly as rangeland or wildlife habitat.

Alfic Lithic Argiustolls.—These soils have a lithic contact

within 50 cm of the soil surface and have an albic horizon or

an eluvial horizon that is too light in color for a mollic

epipedon above the argillic horizon, or they have a glossic

horizon, interfingering of albic materials, or skeletans of clean

silt and sand covering more than half the faces of peds in the

upper 5 cm or more of the argillic horizon.

These soils are of very small extent and are known to occur

only in Texas in the United States. They are used as rangeland.

Andic and Vitrandic Argiustolls.—These soils have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals

or that consists of slightly or moderately weathered pyroclastic

materials. These soils are of very small extent in the mountains

of the Western United States. The vegetation is mostly forest or

grass and widely spaced trees. Most of these soils are used as

forest, rangeland, or wildlife habitat.

Aquic Argiustolls.—These soils have redox depletions with

low chroma and either have shallow ground water at some time

of the year or are artificially drained. The color value and

chroma of these soils commonly are lower than those of Typic

Argiustolls. Aquic Argiustolls developed mostly in nearly level

upland areas that commonly are concave. They are of small

extent in the United States. Most of the soils are used as

cropland.

Aridic Argiustolls.—These soils are drier than Typic

Argiustolls, and they do not have a calcic horizon. It is

common but is not required that the color value and chroma

are higher and the depth to carbonates is less than in Typic

Argiustolls. A Bz horizon and a Bk horizon are more common

than in soils of the Typic subgroup. Aridic Argiustolls

generally receive less precipitation than the soils of the Typic

subgroup, or they lose more water through runoff. A few Aridic

Argiustolls that are associated with Aridisols may receive

runoff from other soils.

Aridic Argiustolls are extensive and widely distributed in

the Western United States. The largest extent is on the western

part of the Great Plains. Slopes range from nearly level to

steep. In the United States, many Aridic Argiustolls that have

suitable slopes are used as cropland. Winter wheat and grain

sorghum are common crops. If the temperature regime is frigid

or mesic, many of the soils are fallowed in alternate years to

store moisture. Some of the soils are irrigated, and many of the

more sloping soils are used as rangeland.

Aridic Lithic Argiustolls.—These soils have a lithic

contact within 50 cm of the mineral soil surface and a soil
608 Soil Taxonomy

moisture regime that borders on aridic. They occur on the

western Great Plains of the United States and are used mainly

as rangeland.

Calcidic Argiustolls.—These soils are drier than Typic

Argiustolls and have a calcic horizon with its upper boundary

within 100 cm of the soil surface. Calcidic Argiustolls do not

have a high shrink-swell potential or a lithic contact within 50

cm of the soil surface. They also do not have an albic horizon

above the argillic horizon, a mollic epipedon 50 cm or more

thick, saturation within 100 cm of the soil surface, or a

significant amount of volcanic glass. These soils occur in the

southwestern part of the United States and are used mostly for

grazing by livestock.

Duric Argiustolls.—These soils have a brittle horizon that

is within 100 cm of the mineral soil surface, is 15 cm or more

thick, and has either some opal coatings or 20 percent or more

durinodes. They are otherwise like Typic Argiustolls in their

defined properties and in most other properties. Duric

Argiustolls are not known to occur in the United States.

Lithic Argiustolls.—These soils have a shallow lithic

contact. They may have identifiable secondary carbonates

above the rock, but this feature is not common in the United

States. These soils are of large extent, mostly in the mountains

of the Western United States. They have moderate to very steep

slopes. The vegetation commonly is grass and shrubs, but some

of the soils support forest vegetation. Lithic Argiustolls are

used mostly as rangeland or forest.

Oxyaquic Argiustolls.—These soils are like Typic

Argiustolls, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. They are of very

small extent in the United States.

Pachic Argiustolls.—These soils have a thick mollic

epipedon that commonly includes at least part of the argillic

horizon. Some of these soils receive extra water as runoff from

other soils. Pachic Argiustolls are extensive in the United

States. They are widely distributed on the Great Plains and in

the mountains of the Western United States. Slopes are nearly

level to steep. Many of these soils supported grasses and

shrubs, but some supported trees. Most of the soils on plains

are used as cropland. Most of the soils in the mountains are

used as rangeland, but some are used as grazeable woodland.

Torrertic Argiustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They are drier than Vertic

Argiustolls. Torrertic Argiustolls are of small extent in the

United States and occur on the western Great Plains. The

natural vegetation was mostly grasses and shrubs. Slopes

generally are gentle, and many are concave. Most of these soils

are used as cropland, but some are used as rangeland.

Udertic Argiustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

many years have deep cracks. They are more moist than Vertic

Argiustolls because they either receive more precipitation or

receive runoff from other soils. Udertic Argiustolls are of small

extent in the United States and occur on the southern Great

Plains. The natural vegetation was mostly grasses. Slopes

generally are gentle, and many are concave. Most of these soils

are used as cropland, but some are used as rangeland.

Udic Argiustolls.—These soils are more moist than Typic

Argiustolls because they either receive more precipitation or

receive runoff from other soils. Most of the Udic Argiustolls in

the United States are in areas between Typic Argiustolls and

Udolls. Udic Argiustolls are extensive soils in the southeastern

part of the Great Plains. The natural vegetation was mostly

grasses and shrubs. Slopes generally are gentle. Most of these

soils are used as cropland.

Vertic Argiustolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They formed mostly in material

weathered from smectite-rich shale or in material weathered

from limestone. They are associated on the landscape with

Usterts and with other Ustolls. Vertic Argiustolls occur

throughout the Great Plains in the United States and are

moderately extensive soils. The natural vegetation was mostly

grasses. Slopes generally are gentle, and most of these soils are

used as cropland.

Vitritorrandic Argiustolls.—These soils have significant

amounts of cinders, pumice, and pumicelike fragments or glass

and have a soil moisture regime that borders on aridic. They do

not have a lithic contact within 50 cm of the soil surface or a

high shrink-swell potential. These soils are not known to occur

in the United States.

Calciustolls

These are the Ustolls that have a gypsic, calcic, or petrocalcic

horizon and that are calcareous in all overlying horizons. These

soils do not have a duripan or an argillic or natric horizon above

the calcic, gypsic, or petrocalcic horizon. Either the parent

materials had more carbonates than the limited rainfall could

remove from the upper horizons, or there is a continuing external

source of carbonates in dust or water.

Calciustolls formed mostly in Pleistocene sediments or in

older materials on surfaces of comparable age. In the United

States, their vegetation was dominantly grass before the soils

were cultivated. Calciustolls are most extensive on the Great

Plains in the United States, but some are in the intermountain

valleys of the Western States.

Definition

Calciustolls are the Ustolls that:

1. Have a calcic or gypsic horizon that has its upper boundary

within 100 cm of the soil surface or a petrocalcic horizon that

has its upper boundary within 150 cm of the soil surface and

are calcareous in all parts of all horizons above the calcic,

petrocalcic, or gypsic horizon after the upper 18 cm has been
Mollisols 609

mixed, unless the texture is coarser than loamy very fine sand or

very fine sand;

2. Do not have an argillic horizon above the calcic, gypsic, or

petrocalcic horizon;

3. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface; and

4. Do not have a natric horizon.

Key to Subgroups

IFCA. Calciustolls that have a salic horizon that has its upper

boundary within 75 cm of the mineral soil surface.

Salidic Calciustolls

IFCB. Other Calciustolls that have a petrocalcic horizon and

a lithic contact within 50 cm of the mineral soil surface.

Lithic Petrocalcic Calciustolls

IFCC. Other Calciustolls that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Calciustolls

IFCD. Other Calciustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 o

C; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC.

Torrertic Calciustolls

IFCE. Other Calciustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the soil temperature

at a depth of 50 cm below the soil surface is higher than

8 oC.

Udertic Calciustolls

IFCF. Other Calciustolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Calciustolls

IFCG. Other Calciustolls that have a petrocalcic horizon that
610 Soil Taxonomy

has its upper boundary within 100 cm of the mineral soil

surface.

Petrocalcic Calciustolls

IFCH. Other Calciustolls that have a gypsic horizon with its

upper boundary within 100 cm of the mineral soil surface.

Gypsic Calciustolls

IFCI. Other Calciustolls that have a texture finer than loamy

fine sand and either:

1. A frigid temperature regime and a mollic epipedon 40

cm or more thick; or

2. A mollic epipedon 50 cm or more thick.

Pachic Calciustolls

IFCJ. Other Calciustolls that have, in one or more horizons

within 75 cm of the mineral soil surface, redox concentrations

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Calciustolls

IFCK. Other Calciustolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Calciustolls

IFCL. Other Calciustolls that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for six-tenths or more of the cumulative days per

year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some or all parts for six-tenths or more of

the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Aridic Calciustolls

IFCM. Other Calciustolls that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for four-tenths or less of the consecutive days per

year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than 120

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC.

Udic Calciustolls

IFCN. Other Calciustolls.

Typic Calciustolls

Definition of Typic Calciustolls

Typic Calciustolls are the Calciustolls that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox concentrations and also aquic conditions;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have a lithic contact within 50 cm of the soil

surface;

4. Do not have a texture finer than loamy fine sand and

either:

a. A mollic epipedon 50 cm or more thick; or

b. A mollic epipedon 40 cm or more thick and a frigid

temperature regime;

5. Do not have a petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface;

6. Do not have a salic horizon that has its upper boundary

within 75 cm of the mineral soil surface;

7. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less than
Mollisols 611

four-tenths of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for more than four-tenths but less than six-tenths

of the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than 5 oC;

or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is moist in some or all parts for 90 or more

consecutive days per year or is dry for less than six-tenths of

the cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC

and is dry for more than 120 cumulative days per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 8 oC;

8. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

9. Do not have a gypsic horizon with its upper boundary

within 100 cm of the mineral soil surface.

Description of Subgroups

Typic Calciustolls.—The central concept or Typic subgroup

of Calciustolls is fixed on soils that do not have a fluctuating

ground water table in their deep layers accompanied by

redoximorphic features, that have an ustic moisture regime,

that have a mollic epipedon of moderate thickness, that have a

calcic horizon rather than a petrocalcic horizon, and that do

not have slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks in normal years.

Redox concentrations and a ground water table that

fluctuates within 100 cm of the mineral soil surface are

properties shared with Aquolls and are the basis for defining

Aquic and Oxyaquic subgroups. A shallow lithic contact is the

basis for defining Lithic and combination Lithic subgroups. A

thick mollic epipedon is the basis for defining the Pachic

subgroup. A petrocalcic horizon indicates development that is

more intensive than normal and is the basis for defining the

Petrocalcic subgroup. Slickensides, wedge-shaped aggregates, a

high linear extensibility, and wide cracks that are evident in

normal years are characteristics of Vertisols and are the basis for

defining the Vertic subgroup.

Typic Calciustolls are of moderately large extent in the United

States. They are widely distributed. The largest extent is on the

Great Plains from Montana to Texas. The soils also are on

tropical islands and in some valleys in the mountains of the

Western United States. Most Typic Calciustolls supported

grasses and shrubs. Most of the soils on plains are now used as

cropland. The soils in the mountains are used mostly as

rangeland or wildlife habitat.

Aquic Calciustolls.—These soils have redox depletions

with low chroma and either have shallow ground water at some

time of the year or are artificially drained. The color value and

chroma of these soils commonly are lower than those of Typic

Calciustolls. Aquic Calciustolls developed mostly in nearly

level upland areas that commonly are concave. These soils are

of small extent in the United States. Most are used as cropland.

Aridic Calciustolls.—These soils are drier than Typic

Calciustolls. They generally receive less precipitation than the

soils in the Typic subgroup, or they lose more water through

runoff. A few of the soils that are associated with Aridisols

may receive runoff from other soils. Aridic Calciustolls are

moderately extensive and widely distributed in the Western

United States. The largest extent is on the western part of the

Great Plains. Slopes range from nearly level to steep. In the

United States, many of the soils that have suitable slopes are

used as cropland. If the temperature regime is frigid or mesic,

many of the soils are fallowed in alternate years to store

moisture. Some of the soils are irrigated, and most of the more

sloping soils are used as rangeland.

Gypsic Calciustolls.—These soils have a gypsic horizon.

They do not have a high shrink-swell potential, a salic or

petrocalcic horizon, or a lithic contact within 50 cm of the

mineral soil surface. These soils are not extensive but occur in

southeastern New Mexico and western Texas. They are used as

rangeland.

Lithic Calciustolls.—These soils have a shallow lithic

contact but are otherwise like Typic Calciustolls in defined

characteristics. Lithic Calciustolls soils are of small extent,

mostly in the Western United States. They have moderate to

very steep slopes. The vegetation is mostly grass and shrubs,

but a few of the soils support forest vegetation. The soils are

used mostly as rangeland or forest.

Lithic Petrocalcic Calciustolls.—These soils have a

petrocalcic horizon overlying hard bedrock within a depth of

50 cm. Typically, the fractures in the underlying bedrock are

filled with cemented secondary carbonates. Most of these soils

are drier than Typic Calciustolls. Slopes are gentle. Lithic

Petrocalcic Calciustolls formed on surfaces older than the

Pleistocene. These soils are extensive locally in Texas. They

are used almost exclusively as rangeland.

Oxyaquic Calciustolls.—These soils are like Typic

Calciustolls, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30
612 Soil Taxonomy

or more cumulative days in normal years. These soils are of very

small extent in the United States.

Pachic Calciustolls.—These soils have a thick mollic

epipedon. Most of the soils are nearly level or concave. Many

are on terraces or very broad, flat upland ridges. Pachic

Calciustolls are of small extent on the Great Plains in the

United States. Nearly all of them are used as cropland and are

summer fallowed.

Petrocalcic Calciustolls.—These soils have a petrocalcic

horizon but are otherwise like Typic Calciustolls in defined

properties. In most Petrocalcic Calciustolls, depth to the

petrocalcic horizon is less than 50 cm. Some of the soils that

have a petrocalcic horizon below a depth of 50 cm are

underlain by hard bedrock. Petrocalcic Calciustolls are

extensive on the Great Plains of the United States. The largest

extent is in Texas. Most of the soils are used as rangeland.

Salidic Calciustolls.—These soils have a salic horizon in

the upper part of the profile. They are not known to occur in

the United States.

Torrertic Calciustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They are drier than Vertic

Calciustolls. Torrertic Calciustolls are of very small extent in

the United States.

Udertic Calciustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They are more moist than

Vertic Calciustolls because they generally receive more

precipitation. Udertic Calciustolls are of very small extent.

Udic Calciustolls.—These soils are more moist than Typic

Calciustolls because they generally receive more precipitation.

The Udic Calciustolls in the United States are in areas between

Typic Calciustolls and Udolls. Udic Calciustolls are of small

extent and are extensive only in Texas. The natural vegetation

is mostly grasses and shrubs. Slopes generally are gentle. Most

of these soils are used as cropland.

Vertic Calciustolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They formed mostly in material

weathered from smectite-rich shale or in material weathered

from limestone. They are associated on the landscape with

Usterts and with other Ustolls. Vertic Calciustolls occur mostly

in Texas on the Great Plains and are of small extent. The

natural vegetation was mostly grasses. Slopes are mainly

gentle, and most of the soils are used as cropland.

Durustolls

These are Ustolls that have a duripan with its upper

boundary within 100 cm of the soil surface. These soils formed

in the vicinity of cinders and ash falls. Their parent materials

are mainly siliceous tuffs, volcanic ash, cinders, and basic

volcanic rocks. In the United States, the natural vegetation is

mostly grasses and shrubs. These soils are of small extent.

They formed in late-Pleistocene deposits. They are on alluvial

fans and terraces, on nearly level to rolling cinder fans and

plains, and on hilly to very steep cinder cones. They may be

common on the leeward sides of volcanic islands in the Lesser

Antilles.

Definition

Durustolls are the Ustolls that have a duripan that has an

upper boundary within 100 cm of the mineral soil surface.

Key to Subgroups

IFAA. Durustolls that have a natric horizon above the

duripan.

Natric Durustolls

IFAB. Other Durustolls that:

1. Do not have an argillic horizon above the duripan; and

2. Have an aridic moisture regime that borders on ustic.

Haploduridic Durustolls

IFAC. Other Durustolls that have an aridic moisture regime

that borders on ustic.

Argiduridic Durustolls

IFAD. Other Durustolls that do not have an argillic horizon

above the duripan.

Entic Durustolls

IFAE. Other Durustolls that have a duripan that is strongly

cemented or less cemented in all subhorizons.

Haplic Durustolls

IFAF. Other Durustolls.

Typic Durustolls

Definition of Typic Durustolls

Typic Durustolls are the Durustolls that:

1. Have an argillic horizon above the duripan;

2. Have a duripan that is massive and platy and that has half

or more of its upper boundary coated or indurated with opal

and silica, with or without sesquioxides, or that is indurated in

some subhorizon below its upper boundary;

3. Do not have a natric horizon above the duripan; and

4. Do not have an aridic moisture regime.

Description of Subgroups

Typic Durustolls.—The central concept or Typic subgroup

of Durustolls is fixed on soils that have an argillic horizon

above a strongly developed duripan and that have an ustic

moisture regime. An aridic moisture regime is drier than that

of the Typic subgroup and, if the soils also have an argillic
Mollisols 613

horizon, is the basis for defining intergrades to Argids. Soils

that do not have an argillic horizon and that have a moisture

regime drier than that of the Typic subgroup are assigned to the

Haploduridic subgroup.

The Typic subgroup is not the most extensive subgroup, but

it furnishes the best basis for the definition of subgroups. Typic

Durustolls are not known to occur in the United States.

Argiduridic Durustolls.—These soils have an aridic

moisture regime that borders on ustic, but they are otherwise

like Typic Durustolls in their defined properties. The

Argiduridic Durustolls in the United States generally are nearly

level to strongly sloping. They are not extensive in the United

States, but they are moderately extensive locally in Arizona.

The natural vegetation is mostly grasses and shrubs. Most of

the soils are used as rangeland. Some used as wildlife habitat

or recreational areas.

Entic Durustolls.—These soils do not have an argillic

horizon and have an ustic moisture regime. They are not

known to occur in the United States.

Haplic Durustolls.—These soils have an ustic moisture

regime and have a duripan that is strongly cemented or less

cemented in all subhorizons. They do not have an argillic

horizon. These soils are not known to occur in the United

States.

Haploduridic Durustolls.—These soils have an aridic

moisture regime that borders on ustic and do not have an

argillic horizon. In the United States, they are nearly level to

moderately sloping. These soils are of small extent in the

United States, but they are important locally in Arizona. The

natural vegetation is mostly grasses and shrubs, and most of

the soils are used as rangeland.

Natric Durustolls.—These soils have a natric horizon.

They occur on the western Great Plains and are used as

rangeland.

Haplustolls

Most of these soils have a cambic horizon below the mollic

epipedon, and most have a horizon in which carbonates or

soluble salts have accumulated. A few have a calcic horizon. A

few that formed in noncalcareous sediments do not have a

horizon of carbonate accumulation. These are the Ustolls that

do not have a duripan or a natric, petrocalcic, or argillic

horizon. They do not have a calcic or gypsic horizon unless

part of the soil above the calcic or gypsic horizon either is

noncalcareous or has a texture coarser than loamy fine sand

after the materials between the soil surface and a depth of 18

cm have been mixed.

Haplustolls formed mainly in late-Pleistocene or Holocene

deposits or on surfaces of comparable age. Their vegetation has

been dominantly grasses and forbs. They are extensive soils on

the Great Plains of North America, in Eastern Europe, and on

the Pampas in South America. Where slopes are suitable, most

of the soils are used for grain and feed crops.

Definition

Haplustolls are the Ustolls that:

1. Do not have an argillic or natric horizon;

2. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface;

3. Do not have a calcic or gypsic horizon that has its upper

boundary within 100 cm of the mineral soil surface unless

some part of some horizon overlying the calcic or gypsic

horizon is free of carbonates after the surface soil to a depth of

18 cm has been mixed or the texture to this depth is loamy very

fine sand or finer;

4. Have a transition layer between the mollic epipedon and

the underlying horizon that is less than 25 percent (by volume)

wormholes, wormcasts, or filled animal burrows; and

5. Do not have a petrocalcic horizon that has its upper

boundary within 150 cm of the soil surface.

Key to Subgroups

IFGA. Haplustolls that have a salic horizon that has its upper

boundary within 75 cm of the mineral soil surface.

Salidic Haplustolls

IFGB. Other Haplustolls that have, in part of each pedon, a

lithic contact within 50 cm of the mineral soil surface.

Ruptic-Lithic Haplustolls

IFGC. Other Haplustolls that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Haplustolls

IFGD. Other Haplustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or
614 Soil Taxonomy

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC.

Torrertic Haplustolls

IFGE. Other Haplustolls that have all of the following:

1. A mollic epipedon 50 cm or more thick with a texture 

finer than loamy fine sand; and 

a and b. (Deleted text)

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

3. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the soil temperature

at a depth of 50 cm below the soil surface is higher than 8

o

C.

Pachic Udertic Haplustolls

IFGF. Other Haplustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the soil temperature

at a depth of 50 cm below the soil surface is higher than

8 oC.

Udertic Haplustolls

IFGG. Other Haplustolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haplustolls

IFGH. Other Haplustolls that have both:

1. When neither irrigated nor fallowed to store moisture,

one of the following:
Mollisols 615

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years remains moist in some or all parts for fewer

than 90 consecutive days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 8 oC; and

2. An apparent CEC (by 1N NH4OAc pH 7) of less

than 24 cmol(+)/kg clay in 50 percent or more of the

soil volume between a depth of 25 cm from the mineral

soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact if shallower. (If the ratio of

[percent water retained at 1500 kPa tension minus percent

organic carbon] to the percentage of measured clay is 0.6 or

more, then the percentage of clay is considered to equal

either the measured percentage of clay or three times

[percent water retained at 1500 kPa tension minus percent

organic carbon], whichever value is higher, but no more

than 100.)

Torroxic Haplustolls

IFGI. Other Haplustolls that have an apparent CEC (by

1N NH4OAc pH 7) of less than 24 cmol(+)/kg clay in 50

percent or more of the soil volume between a depth of 25

cm from the mineral soil surface and either a depth of 100

cm or a densic, lithic, or paralithic contact if shallower. (If

the ratio of [percent water retained at 1500 kPa tension

minus percent organic carbon] to the percentage of measured

clay is 0.6 or more, then the percentage of clay is considered

to equal either the measured percentage of clay or three times

[percent water retained at 1500 kPa tension minus percent

organic carbon], whichever value is higher, but no more than

100.)

Oxic Haplustolls

IFGJ. Other Haplustolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Haplustolls

IFGK. Other Haplustolls that have both:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitritorrandic Haplustolls

IFGL. Other Haplustolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and
616 Soil Taxonomy

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Haplustolls

IFGM. Other Haplustolls that have:

1. Either:

a. A frigid soil temperature regime and a mollic

epipedon 40 cm or more thick, of which less than 50

percent has a sandy or sandy-skeletal particle-size class,

and there is no densic or paralithic contact and no sandy

or sandy-skeletal particle-size class at a depth between 40

and 50 cm from the mineral soil surface; or

b. A mollic epipedon that is 50 cm or more thick and

has a texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content from a

depth of 25 cm below the mineral soil surface to a depth of

125 cm or to a densic, lithic, or paralithic contact if

shallower; and

3. A slope of less than 25 percent; and

4. In one or more horizons within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Cumulic Haplustolls

IFGN. Other Haplustolls that have:

1. Either:

a. A frigid soil temperature regime and a mollic

epipedon 40 cm or more thick, of which less than 50

percent has a sandy or sandy-skeletal particle-size class,

and there is no densic or paralithic contact and no sandy

or sandy-skeletal particle-size class at a depth between 40

and 50 cm from the mineral soil surface; or

b. A mollic epipedon that is 50 cm or more thick and

has a texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content from a

depth of 25 cm below the mineral soil surface to a depth of

125 cm or to a densic, lithic, or paralithic contact if

shallower; and

3. A slope of less than 25 percent.

Cumulic Haplustolls

IFGO. Other Haplustolls that have anthraquic conditions.

Anthraquic Haplustolls

IFGP. Other Haplustolls that have both:

1. In one or more horizons within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A slope of less than 25 percent; and either

a. An organic-carbon content of 0.3 percent or more at

a depth of 125 cm below the mineral soil surface; or

b. An irregular decrease in organic-carbon content

from a depth of 25 cm to a depth of 125 cm or to a

densic, lithic, or paralithic contact if shallower.

Fluvaquentic Haplustolls

IFGQ. Other Haplustolls that have a texture finer than loamy

fine sand and either:

1. A frigid temperature regime and a mollic epipedon 40

cm or more thick; or

2. A mollic epipedon 50 cm or more thick.

Pachic Haplustolls

IFGR. Other Haplustolls that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in most years (or artificial drainage).

Aquic Haplustolls

IFGS. Other Haplustolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplustolls

IFGT. Other Haplustolls that have both:

1. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90
Mollisols 617

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 o

C; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC; and

2. A slope of less than 25 percent; and either

a. An organic-carbon content of 0.3 percent or more at

a depth of 125 cm below the mineral soil surface; or

b. An irregular decrease in organic-carbon content

from a depth of 25 cm to a depth of 125 cm or to a

densic, lithic, or paralithic contact if shallower.

Torrifluventic Haplustolls

IFGU. Other Haplustolls that:

1. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC; and

2. Either:

a. Do not have a cambic horizon and do not, in any part

of the mollic epipedon below 25 cm from the mineral soil

surface, meet all of the requirements for a cambic

horizon except color; or

b. Have free carbonates throughout the cambic horizon

or in all parts of the mollic epipedon below a depth of 25

cm from the mineral soil surface.

Torriorthentic Haplustolls

IFGV. Other Haplustolls that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some or all parts for six-tenths or more of

the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Aridic Haplustolls

IFGW. Other Haplustolls that have a slope of less than 25

percent; and either

1. An organic-carbon content of 0.3 percent or more at a

depth of 125 cm below the mineral soil surface; or

2. An irregular decrease in organic-carbon content from a

depth of 25 cm to a depth of 125 cm or to a densic, lithic, or

paralithic contact if shallower.

Fluventic Haplustolls

IFGX. Other Haplustolls that have a brittle horizon that is

within 100 cm of the mineral soil surface, is 15 cm or more

thick, and has either some opal coatings or 20 percent or more

(by volume) durinodes.

Duric Haplustolls

IFGY. Other Haplustolls that:

1. When neither irrigated nor fallowed to store moisture,

have either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil
618 Soil Taxonomy

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 days per year when the soil temperature at a depth of

50 cm below the soil surface is higher than 8 o

C; and

2. Either do not have a cambic horizon and do not, in the

lower part of the mollic epipedon, meet the requirements for

a cambic horizon, except for the color requirements, or have

carbonates throughout either the cambic horizon or the

lower part of the mollic epipedon.

Udorthentic Haplustolls

IFGZ. Other Haplustolls that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for four-tenths or less of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than 120

days per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 8 oC.

Udic Haplustolls

IFGZa. Other Haplustolls that either:

1. Do not have a cambic horizon and do not, in any part of

the mollic epipedon below 25 cm from the mineral soil

surface, meet all of the requirements for a cambic horizon

except color; or

2. Have free carbonates throughout the cambic horizon or

in all parts of the mollic epipedon below a depth of 25 cm

from the mineral soil surface.

Entic Haplustolls

IFGZb. Other Haplustolls.

Typic Haplustolls

Definition of Typic Haplustolls

Typic Haplustolls are the Haplustolls that:

1. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have anthraquic conditions;

4. Do not have a texture finer than loamy fine sand and

either:

a. A mollic epipedon 50 cm or more thick; or

b. A mollic epipedon 40 cm or more thick and a frigid

temperature regime;

5. Do not have a brittle horizon that is 15 cm or more thick,

is within 100 cm of the mineral soil surface, and has some opal

coatings or some durinodes (less than 20 percent, by volume);

6. Have a cambic horizon or in the lower part of the mollic

epipedon, meet the requirements for a cambic horizon, except

for the color and organic-carbon content requirements, and

either the cambic horizon or the lower part of the mollic

epipedon is free of carbonates in some part;

7. Have a regular decrease in organic-carbon content with

increasing depth to a level of 0.3 percent or less within 125 cm

of the mineral soil surface unless a densic, lithic, or paralithic

contact occurs at a shallower depth or the slope is 25 percent or

more;

8. Do not have a lithic contact within 50 cm of the mineral

soil surface in any part of each pedon;

9. Do not have a salic horizon that has its upper boundary

within 75 cm of the mineral soil surface;

10. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in most years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

11. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less than

four-tenths of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for more than four-tenths but less than six-tenths

of the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than 5 o

C;

or

c. A hyperthermic, isomesic, or warmer iso soil
Mollisols 619

temperature regime and a moisture control section that in

normal years is moist in some or all parts for 90 or more

consecutive days per year or is dry for less than six-tenths of

the cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 o

C

and is dry for more than 120 cumulative days per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 8 oC;

12. Have an apparent CEC (by 1N NH4OAc pH 7) of 24 or

more cmol(+)/kg clay in the major part of the soil below a

depth of 25 cm but above 100 cm or a densic, lithic, or

paralithic contact if one is shallower than 100 cm; and

13. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Haplustolls.—The central concept or Typic subgroup

of Haplustolls is fixed on moderately deep or deeper, freely

drained soils that have a mollic epipedon less than 50 cm thick

and either have a cambic horizon or resemble a cambic horizon

in the lower part of the epipedon. These soils do not have

slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks in most years. They generally are

on uplands.

Ground water in the deep layers, redox depletions with low

chroma, and a salic horizon are the basis for defining Aquic

and Salidic subgroups. A thick mollic epipedon in soils that

receive little sediment is the basis for defining the Pachic

subgroup. A moisture regime that borders on udic characterizes

the Udic subgroup. If a cambic horizon is absent and the lower

part of the epipedon does not resemble a cambic horizon, that

feature is considered evidence of weak horizon development

and is the basis for defining the Entic subgroup. A thick

epipedon that shows evidence of accumulation of materials on

the surface is the basis for defining Cumulic and combination

Cumulic subgroups. An irregular decrease in organic-carbon

content with increasing depth or a relatively high content of

organic carbon in the deep layers is a property of Fluvents and

is the basis for defining the Fluventic subgroup or, if ground

water is present and there are redox depletions with low

chroma, the Fluvaquentic subgroup. A clayey texture,

slickensides, wedge-shaped aggregates, a high linear

extensibility, and cracks in normal years are properties shared

with Vertisols and are the basis for defining the Vertic

subgroup.

Typic Haplustolls are of large extent in the United States.

They are mostly on the Great Plains but also are in the

mountains in the western part of the United States and on some

tropical islands. Most of these soils supported grasses and

shrubs. Some of the soils, mostly those in the mountains or on

islands, supported trees or grass and widely spaced trees. Most

of the soils on plains are now used as cropland. The soils in the

mountains are used mostly as rangeland or wildlife habitat.

Andic and Vitrandic Haplustolls.—These soils have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals

or that consists of slightly or moderately weathered pyroclastic

materials. These soils are of very small extent in the mountains

of the Western United States. The vegetation is mostly forest or

grass and widely spaced trees. Most of these soils are used as

forest, rangeland, or wildlife habitat.

Anthraquic Haplustolls.—These soils are like Typic

Haplustolls, but they have been irrigated for the production of

paddy rice for many years and have developed anthraquic

conditions. They are permitted, but not required, to have redox

depletions with chroma of 2 or less in layers that also have

aquic conditions in normal years. They are not extensive and

are not known to occur in the United States. They have level or

nearly level slopes.

Aquic Cumulic Haplustolls.—These soils have a thick

mollic epipedon. They are on flood plains or in concave areas

where fresh sediments have accumulated slowly enough to

have become incorporated in the mollic epipedon. The soils

have ground water and redox depletions with low chroma in

their deep layers. They have ground water when streams are at

high water levels or when they overflow. These soils are of very

small extent in the United States. The natural vegetation is

mostly grass, and some of the soils support widely spaced trees.

Most of the soils are used as cropland or hayland, except for

areas that are very small, that have an irregular shape, or that

are subject to frequent flooding.

Aquic Haplustolls.—These soils have ground water and

redox depletions with low chroma in their deep layers. Most of

the soils are in positions where they receive runoff in addition

to the water that falls on the surface. Slopes are gentle or

concave. The epipedon commonly has a low color value or

chroma, or both. The depth to secondary carbonates may be

greater than normal, and the soils are not required to have a
620 Soil Taxonomy

cambic horizon if the particle-size class is sandy. Some of the

soils are salty. Aquic Haplustolls are mainly in depressions or on

flood plains. They are of small extent in the United States. The

vegetation is mostly grass, and some of the soils support widely

spaced trees. Most of the soils are used as cropland, hayland,

rangeland, or wildlife habitat.

Aridic Haplustolls.—These soils receive less moisture or

lose more water through runoff than Typic Haplustolls, but they

are otherwise like the Typic Haplustolls in defined properties.

A few Aridic Haplustolls that are associated with Aridisols

receive runoff from other soils. Other things being equal, the

depth to carbonates and the organic-carbon content are less in

these soils than in soils of the Typic subgroup. Aridic

Haplustolls are extensive and widely distributed in the Western

United States. The largest extent is in the western part of the

Great Plains. Slopes range from nearly level to steep. In the

United States, many of the soils that have suitable slopes are

used as cropland. Winter wheat and grain sorghum are

common crops. If the temperature regime is frigid or mesic,

many of the soils are fallowed in alternate years to store

moisture. Some of the soils are irrigated, and many of the more

sloping soils are used as rangeland.

Cumulic Haplustolls.—These soils have a thick mollic

epipedon and are on flood plains and alluvial fans where fresh

sediments have accumulated slowly enough to have become

incorporated in the mollic epipedon. The mollic epipedon may

be very thick, or there may be a series of thin buried epipedons.

Consequently, there may not be either a cambic horizon or an

accumulation of secondary carbonates in the soils. These soils

are moderately extensive on the Great Plains and in the

intermountain areas of the southwestern part of the United

States. The natural vegetation is mostly grass and widely

spaced trees. Some of these soils are used as cropland or

hayland, except for areas that are very small, that have an

irregular shape, or are subject to frequent flooding. Other areas

are used for grazing by livestock.

Duric Haplustolls.—These soils have a brittle horizon that

is within 100 cm of the mineral soil surface, is 15 cm or more

thick, and has either some opal coatings or 20 percent or more

durinodes. They are otherwise like Typic Haplustolls in their

defined properties and in most other properties. Duric

Haplustolls are inextensive on the western Great Plains of the

United States.

Entic Haplustolls.—These soils do not have a cambic

horizon, and either the epipedon is mostly calcareous or the

lower part of the epipedon has a coarser texture than is

required for a cambic horizon. Many of the soils have an

epipedon that is calcareous throughout its thickness. Others

have a shallow densic or paralithic contact, and the epipedon

extends to the contact. Entic Haplustolls formed mostly in lateHolocene sediments or are on surfaces of similar age. These

soils are moderately extensive on the Great Plains of the United

States. Slopes are gentle to very steep. The natural vegetation is

mostly grass, and some of the soils support widely spaced trees.

Most of the soils are used as rangeland. If slopes are suitable,

some of the soils are used as cropland.

Fluvaquentic Haplustolls.—These soils formed in relatively

recent sediments and have ground water and redox depletions

with low chroma. Either the organic-carbon content decreases

irregularly with increasing depth, or it is relatively high in the

deep layers. Most of these soils are in low positions on flood

plains. They have ground water when streams are at high water

levels or when they overflow. These soils are of small extent in

the United States. The natural vegetation is mostly grass, and

some of the soils support widely spaced trees. Most of the soils

are used as cropland or hayland, except for areas that are very

small, that have an irregular shape, or that are subject to

frequent flooding.

Fluventic Haplustolls.—These soils formed mostly in

recent alluvium. The epipedon is between 25 and 50 cm thick,

and either the content of organic carbon decreases irregularly

with increasing depth or it is high in the deep layers. These

soils commonly are calcareous throughout their depth, and they

have few or no identifiable secondary carbonates or do not have

a cambic horizon. The natural vegetation is mostly grass, and

some of the soils support widely spaced trees. Slopes of the

Fluventic Haplustolls in the United States are gentle. Most of

the soils are used as cropland or hayland, except for areas that

are very small, that have an irregular shape, or that are subject

to frequent flooding.

Lithic Haplustolls.—These soils have a shallow lithic

contact. Commonly, the mollic epipedon extends to the rock,

and the soils have neither a cambic horizon nor a horizon that

contains identifiable secondary carbonates. These soils are of

large extent, mostly in the mountains of the Western United

States. They have moderate to very steep slopes. The vegetation

is mostly grass and shrubs, but some of the soils support forest

vegetation. The soils are used mostly as rangeland or forest.

Oxic Haplustolls.—These soils have a CEC that is too low

and epipedons that may be too thick or an organic-carbon

content that is too high at a depth of 125 cm to qualify as Typic

Haplustolls. Slopes range from gentle to steep. Oxic

Haplustolls are of moderate extent at the lower elevations in

Hawaii. Sugarcane is the dominant crop.

Oxyaquic Haplustolls.—These soils are like Typic

Haplustolls, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. The soils are of

small extent, mostly on the northern Great Plains in the United

States. The natural vegetation is mostly grass and some shrubs.

Most of the soils are used as cropland or hayland.

Pachic Haplustolls.—These soils have a thick mollic

epipedon. Some of the soils receive runoff but little sediment

from the higher adjacent soils. Pachic Haplustolls are extensive

in the United States. They are widely distributed on the Great

Plains and in the mountains of the Western United States.

Slopes are nearly level to steep. Many of these soils supported

grasses and shrubs, but some supported trees. Most of the soils
Mollisols 621

on plains are used as cropland. Most of the soils in the

mountains are used as rangeland, but some are used as

grazeable woodland.

Pachic Udertic Haplustolls.—These soils have a thick

mollic epipedon, a moisture regime that borders on udic, and a

high shrink-swell potential. They receive runoff and are used

for corn, oats, soybeans, or alfalfa. These soils occur in South

Dakota and Iowa.

Ruptic-Lithic Haplustolls.—These soils have a lithic

contact within 50 cm of the surface in part of each pedon, but

the lithic contact is deeper than 50 cm in the rest of the pedon.

In the deeper parts, there is a cambic horizon and the soils

have the other defined properties of Typic Haplustolls. RupticLithic Haplustolls are of very small extent, mostly in the

mountains of the Western United States. They have moderate

to very steep slopes. The vegetation is mostly grass and shrubs,

but some of the soils support forest vegetation.

Salidic Haplustolls.—These soils have a shallow salic

horizon. Depth to the ground water fluctuates. In the United

States, the soils are known to occur only on flood plains in arid

parts of the intermountain valleys of the Western States. These

soils are used as rangeland.

Torrertic Haplustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They are drier than Vertic

Haplustolls. Torrertic Haplustolls are of small extent in the

United States and occur mostly on the western Great Plains.

Slopes of the Torrertic Haplustolls in the United States are

gentle or moderate. The natural vegetation was mostly grasses

and shrubs. Most of the soils are used as cropland, but some

are used as rangeland.

Torrifluventic Haplustolls.—These soils are drier than

Typic Haplustolls and formed in alluvium recent enough for

the content of organic carbon to decrease irregularly with

increasing depth or to remain high in the deep layers. The

mollic epipedon is between 25 and 50 cm thick. These soils are

on flood plains or low terraces. Most of them receive some

additional water from flooding. Many are calcareous

throughout and are associated on the landscape with

Torrifluvents. Torrifluventic Haplustolls are of small extent,

mostly on the western Great Plains of the United States. Slopes

generally are nearly level. The natural vegetation is mostly

grass, and some of the soils support widely spaced trees. Most

of the soils are used as cropland or hayland, except for areas

that are very small, that have an irregular shape, or that are

subject to frequent flooding. Some of the soils are used as

rangeland.

Torriorthentic Haplustolls.—These soils are drier than

Typic Haplustolls, and the epipedon is mostly calcareous or the

lower part of the epipedon has a coarser texture than is

required for a cambic horizon. Many of the soils have an

epipedon that is calcareous throughout its thickness. Others

have a shallow densic or paralithic contact, and the epipedon

extends to the contact. Torriorthentic Haplustolls formed mostly

in late-Holocene sediments or are on surfaces of similar age.

These soils are moderately extensive in the United States. They

are mostly on the western Great Plains, but some are in the

mountains of the Western United States. Slopes are gentle to

very steep. The natural vegetation is mostly grass, and some of

the soils support widely spaced trees. Most of the soils are used

as rangeland. If slopes are suitable, some of the soils are used as

cropland.

Torroxic Haplustolls.—These soils have a CEC that is too

low to qualify as Typic Haplustolls and are drier than Typic

Haplustolls. In addition, they may have epipedons too thick or

an organic-carbon content too high at a depth of 125 cm, and

they basically have few or no carbonates. Slopes are gentle or

moderate. The soils are of moderate extent at the lower

elevations in Hawaii. They are used mostly as cropland.

Pineapple and irrigated sugarcane are the principal crops.

Many areas are used as grazing land.

Udertic Haplustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

many years have deep cracks. They are more moist than Vertic

Haplustolls because they either receive more precipitation or

receive runoff from other soils. Most of the Udertic Haplustolls

in the United States are on the Great Plains. The natural

vegetation was mostly grasses. Slopes generally are gentle, and

many are concave. Most of the soils are used as cropland, but

some are used as rangeland.

Udic Haplustolls.—These soils are more moist than Typic

Haplustolls because they either receive more precipitation or

receive runoff from other soils. Most of the Udic Haplustolls in

the United States are in areas between Typic Haplustolls and

Udolls. Udic Haplustolls are moderately extensive soils, mostly

in the southeastern part of the Great Plains. The natural

vegetation was mostly grasses and shrubs. Slopes generally are

gentle. Most of the soils are used as cropland.

Udorthentic Haplustolls.—These soils are more moist than

Typic Haplustolls because they either receive more

precipitation or receive runoff from other soils. They do not

have a cambic horizon, and either the epipedon is mostly

calcareous or the lower part of the epipedon has a coarser

texture than is required for a cambic horizon. Some of the soils

have a shallow densic or paralithic contact, and the epipedon

extends to the contact. Udorthentic Haplustolls formed mostly

in late-Holocene sediments or are on surfaces of similar age.

These soils are of small extent on the Great Plains of the

United States. Slopes are gentle to very steep. The natural

vegetation is mostly grass. Most of the soils are used as

rangeland. If slopes are suitable, some of the soils are used as

cropland.

Vertic Haplustolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in many

years have deep cracks. They are otherwise similar to Typic

Haplustolls. Most of the Vertic Haplustolls in the United States
622 Soil Taxonomy

are on the Great Plains. The natural vegetation was mostly

grasses. Slopes generally are gentle. Most of the soils are used

as cropland, but some are used as rangeland.

Vitritorrandic Haplustolls.—These soils have significant

amounts of cinders, pumice, and pumicelike fragments or glass

and have a soil moisture regime that borders on aridic. They do

not have a salic horizon within 75 cm of the soil surface, a

lithic contact within 50 cm of the soil surface, a low CEC, or a

high shrink-swell potential. These soils are not known to occur

in the United States.

Natrustolls

These are the Ustolls that have a natric horizon. The most

common horizon sequence is either a natric horizon in the

lower part of the mollic epipedon or a thin albic horizon over a

columnar natric horizon in which there may or may not be

skeletans on the upper few centimeters of the columns. Below

the natric horizon, there generally is a Bk or Bz horizon. Most

of the areas of these soils are small and are nearly level or

concave. The soils formed mostly in late-Pleistocene sediments.

Definition

Natrustolls are the Ustolls that:

1. Have a natric horizon; and

2. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Key to Subgroups

IFBA. Natrustolls that have all of the following:

1. Visible crystals of gypsum and/or more soluble salts

within 40 cm of the mineral soil surface; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower;

3. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC.

Leptic Torrertic Natrustolls

IFBB. Other Natrustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 o

C; and
Mollisols 623

(2) Is dry in some or all parts for six-tenths or more of

the cumulative days per year when the soil temperature

at a depth of 50 cm below the soil surface is higher than

5 o

C.

Torrertic Natrustolls

IFBC. Other Natrustolls that have both of the following:

1. Visible crystals of gypsum and/or more soluble salts

within 40 cm of the mineral soil surface; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Leptic Vertic Natrustolls

IFBD. Other Natrustolls that have both:

1. A glossic horizon or interfingering of albic materials

into a natric horizon; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Glossic Vertic Natrustolls

IFBE. Other Natrustolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower.

Vertic Natrustolls

IFBF. Other Natrustolls that have both:

1. Visible crystals of gypsum or of more soluble salts, or

both, within 40 cm of the mineral soil surface; and

2. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for fourtenths or more of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC.

Aridic Leptic Natrustolls

IFBG. Other Natrustolls that have visible crystals of gypsum

or of more soluble salts, or both, within 40 cm of the mineral

soil surface.

Leptic Natrustolls

IFBH. Other Natrustolls that have, in one or more horizons at

a depth between 50 and 100 cm from the mineral soil surface,

aquic conditions for some time in normal years (or artificial

drainage) and one of the following:

1. 50 percent or more chroma of 1 or less and hue of 2.5Y

or yellower; or

2. 50 percent or more chroma of 2 or less and redox

concentrations; or

3. 50 percent or more chroma of 2 or less and also a

higher exchangeable sodium percentage (or sodium
624 Soil Taxonomy

adsorption ratio) between the mineral soil surface and a depth

of 25 cm than in the underlying horizon.

Aquic Natrustolls

IFBI. Other Natrustolls that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for four-tenths

or more of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some or all parts for six-tenths or more of

the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Aridic Natrustolls

IFBJ. Other Natrustolls that have a horizon, 15 cm or more

thick within 100 cm of the mineral soil surface, that either has

20 percent or more (by volume) durinodes or is brittle and has

a firm rupture-resistance class when moist.

Duric Natrustolls

IFBK. Other Natrustolls that have a glossic horizon or

interfingering of albic materials into a natric horizon.

Glossic Natrustolls

IFBL. Other Natrustolls.

Typic Natrustolls

Definition of Typic Natrustolls

Typic Natrustolls are the Natrustolls that:

1. Do not have, in any horizon at a depth between 50 and 100

cm from the mineral soil surface, aquic conditions and any of

the following:

a. 50 percent or more chroma of 1 or less throughout and

hue of 2.5Y or yellower in some part; or

b. 50 percent or more chroma of 2 or less and redox

concentrations; or

c. 50 percent or more chroma of 2 or less and also a higher

exchangeable sodium percentage (or sodium adsorption ratio)

between the mineral soil surface and a depth of 25 cm than in

the underlying horizon;

2. Do not have a horizon, 15 cm or more thick within 100 cm of

the mineral soil surface, that either has 20 percent or more (by

volume) durinodes or is brittle and has a firm rupture-resistance

class when moist;

3. Do not have a glossic horizon or interfingering of albic

materials into a natric horizon;

4. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less than

four-tenths of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for more than four-tenths but less than six-tenths

of the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than 5 oC;

or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is moist in some or all parts for 90 or more

consecutive days per year or is dry for less than six-tenths of

the cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC

and is dry for more than 120 cumulative days per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 8 oC;

5. Do not have visible crystals of gypsum or of more soluble

salts, or both, within 40 cm of the mineral soil surface; and

6. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm

or a densic, lithic, or paralithic contact, whichever is

shallower.
Mollisols 625

Description of Subgroups

Typic Natrustolls.—The central concept or Typic subgroup

of Natrustolls is fixed on soils that do not have slickensides,

wedge-shaped aggregates, a high linear extensibility, or wide

cracks in normal years. These soils do not have low chroma

and do not have redox concentrations accompanied by ground

water within 100 cm of the surface. They show little or no

evidence of destruction of the natric horizon and have no

visible crystals of gypsum or of more soluble salts, or both,

within 40 cm of the mineral soil surface. Some of these soils

are saturated with water above the natric horizon.

A glossic horizon and interfingering of albic materials in

the upper part of the natric horizon are considered evidence of

destruction of the natric horizon and are the basis for defining

the Glossic subgroup.

Typic Natrustolls are of small extent in the United States.

They are mostly on the northern Great Plains of the United

States. They supported mostly salt-tolerant grasses and shrubs.

Slopes generally are gentle, and many of these soils are

cultivated. Some of the soils are used as rangeland or hayland.

Aquic Natrustolls.—These soils have redox depletions with

low chroma in the upper part of the natric horizon and, at some

time during the year, have ground water in the redox-depleted

horizon unless the soils are artificially drained. The soils are of

very small extent on the Great Plains of the United States.

Most of the soils supported grasses. The soils have gentle

slopes and are used mostly as cropland.

Aridic Leptic Natrustolls.—These soils are drier than

those in the Typic subgroup because they receive less

precipitation or lose more water through runoff. They do not

have a glossic horizon or interfingering of albic materials into

the natric horizon and do not have a high shrink-swell

potential. They are of small extent on the Great Plains of the

United States. Many of the soils supported grasses. The soils

have gentle slopes and are used mostly as rangeland.

Aridic Natrustolls.—These soils are drier than those in the

Typic subgroup because they receive less precipitation or lose

more water through runoff. They are otherwise like Typic

Natrustolls in defined properties. Aridic Natrustolls do not

have gypsum or more soluble salts close to the surface. They

are of small extent on the Great Plains of the United States.

Many of the soils supported grasses. The soils have gentle

slopes and are used mostly as cropland or rangeland.

Duric Natrustolls.—These soils have a horizon, 15 cm or

more thick within 100 cm of the mineral soil surface, that has

20 percent or more (by volume) durinodes or is brittle and has

a firm rupture-resistance class when moist. They are otherwise

like Typic Natrustolls in their defined properties. Duric

Natrustolls are not known to occur in the United States.

Glossic Natrustolls.—These soils show evidence of

destruction of the natric horizon in the form of a glossic

horizon or interfingering of albic materials into the natric

horizon. Commonly, they have more exchangeable magnesium

and less sodium than Typic Natrustolls, at least in the upper

part of the natric horizon. Some Glossic Natrustolls receive more

moisture, either as precipitation or as runoff, than the soils of the

Typic subgroup. Glossic Natrustolls are mostly on the northern

Great Plains of the United States and supported grasses. In the

United States, most of the soils are nearly level and are used as

cropland.

Glossic Vertic Natrustolls.—These soils have a high

shrink-swell potential and either a glossic horizon or

interfingering of albic materials into a natric horizon. These

soils occur in the Dakotas and are used for small grain.

Leptic Natrustolls.—These soils have visible crystals of

gypsum or salts at least as soluble as gypsum within 40 cm of

the soil surface, and their moisture regime does not border on

aridic. Otherwise, these soils are similar to those of the Typic

subgroup. They are of small extent on the northern Great

Plains of the United States. They supported mostly grasses. In

the United States, most of the soils are nearly level and are

used as rangeland.

Leptic Torrertic Natrustolls.—These soils have gypsum or

soluble salts close to the surface, a high shrink-swell potential,

and a soil moisture regime that borders on aridic. They are

inextensive on the western Great Plains and are used as

rangeland.

Leptic Vertic Natrustolls.—These soils have a clayey

particle-size class in a significant part, have expanding clays,

and in normal years have deep cracks. They also have visible

evidence of salts at least as soluble as gypsum within 40 cm of

the soil surface. They have thinner sola than those of the Vertic

subgroup, and the close proximity of the soluble salts to the

surface restricts plant growth. Leptic Vertic Natrustolls are of

very small extent in the United States. They are recognized

only in North Dakota. They supported mostly grasses and

shrubs. Most of the soils are used as rangeland.

Torrertic Natrustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They are drier than the soils in

the Vertic subgroup because they receive less precipitation or

lose more water through runoff. Torrertic Natrustolls are of

very small extent in the United States. They are recognized

only in North Dakota. They supported mostly grasses and

shrubs. Most of the soils are used as cropland or rangeland.

Vertic Natrustolls.—These soils are like Typic Natrustolls,

but they have a clayey particle-size class in a significant part,

have expanding clays, and in normal years have deep cracks.

They are of small extent on the Great Plains of the United

States. They supported mostly grasses and shrubs. Most of the

soils are used as cropland or rangeland.

Paleustolls

These are the Ustolls on old stable surfaces. They may

commonly have a thick, reddish argillic horizon, or, more

commonly, a clayey argillic horizon that has an abrupt upper

boundary, or they may have a petrocalcic horizon. They
626 Soil Taxonomy

commonly have been partly or completely calcified during the

Holocene, and a Bk or calcic horizon is common in the argillic

horizon. The Paleustolls in the United States are mainly in the

central and southern parts of the Great Plains. At the time of

settlement, they had mostly grass vegetation. Their history

during the Pleistocene has had little study. The petrocalcic

horizon, where it occurs, may be complex, suggesting a

number of alternating cycles of humidity and aridity and slow

accretion of dust and sediment from the arid regions to the

west.

Definition

Paleustolls are the Ustolls that:

1. Have a petrocalcic horizon that has its upper boundary

within 150 cm of the soil surface and either have an argillic

horizon or are noncalcareous in some subhorizon above the

petrocalcic horizon after the surface soil to a depth of 18 cm

has been mixed or have an argillic horizon that has either or

both:

a. A vertical clay distribution in which the clay content

does not decrease by as much as 20 percent from the

maximum clay content (noncarbonate clay) within 150 cm

of the soil surface (and there is no densic, lithic, or

paralithic contact within that depth); and one or both of the

following:

(1) Hue redder than 10YR and chroma greater than 4

in the matrix of at least the lower part; or

(2) Common redox concentrations that have hue

of 7.5YR or redder or chroma greater than 5; or

b. 35 percent or more clay in the upper part and an

increase of at least 20 percent clay (absolute) within a

vertical distance of 7.5 cm or of 15 percent clay (absolute)

within 2.5 cm at the upper boundary and no densic, lithic,

or paralithic contact within 50 cm of the mineral soil

surface;

2. Do not have a duripan that has its upper boundary

within 100 cm of the soil surface; and

3. Do not have a natric horizon.

Key to Subgroups

IFDA. Paleustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less

than four-tenths of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some or all parts for six-tenths or more of the cumulative

days per year when the soil temperature at a depth of 50

cm below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC.

Torrertic Paleustolls

IFDB. Other Paleustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower; and

2. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for four-tenths or less of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil
Mollisols 627

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the soil temperature

at a depth of 50 cm below the soil surface is higher than

8 o

C.

Udertic Paleustolls

IFDC. Other Paleustolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Vertic Paleustolls

IFDD. Other Paleustolls that have a texture finer than loamy

fine sand and a mollic epipedon 50 cm or more thick.

Pachic Paleustolls

IFDE. Other Paleustolls that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Paleustolls

IFDF. Other Paleustolls that have a petrocalcic horizon

within 150 cm of the mineral soil surface.

Petrocalcic Paleustolls

IFDG. Other Paleustolls that:

1. Have a calcic horizon within one of the following

particle-size class (by weighted average in the particle-size

control section) and depth combinations:

a. Sandy or sandy-skeletal and within 100 cm of the

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within

50 cm of the mineral soil surface; or

c. Any other class and within 60 cm of the mineral soil

surface; and

2. When neither irrigated nor fallowed to store moisture,

have one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less

than four-tenths of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil surface

is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for six-tenths or more of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or more

of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface

is higher than 5 oC.

Calcidic Paleustolls

IFDH. Other Paleustolls that, when neither irrigated nor

fallowed to store moisture, have one of the following:

1. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less than

four-tenths of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for six-tenths or more of the cumulative days per year

when the soil temperature at a depth of 50 cm below the soil

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90

consecutive days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some or all parts for six-tenths or more of

the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than

5 oC.

Aridic Paleustolls

IFDI. Other Paleustolls that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a moisture

control section that in normal years is dry in some part for
628 Soil Taxonomy

four-tenths or less of the cumulative days per year when the

soil temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

2. A hyperthermic, isomesic, or warmer iso soil temperature

regime and a moisture control section that in normal years is

dry in some or all parts for fewer than 120 cumulative days

per year when the soil temperature at a depth of 50 cm below

the soil surface is higher than 8 oC.

Udic Paleustolls

IFDJ. Other Paleustolls have a calcic horizon within one of

the following particle-size class (by weighted average in the

particle-size control section) and depth combinations:

1. Sandy or sandy-skeletal and within 100 cm of the

mineral soil surface; or

2. Clayey, clayey-skeletal, fine, or very-fine and within 50

cm of the mineral soil surface; or

3. Any other class and within 60 cm of the mineral soil

surface.

Calcic Paleustolls

IFDK. Other Paleustolls that are calcareous throughout after

the surface soil has been mixed to a depth of 18 cm.

Entic Paleustolls

IFDL. Other Paleustolls.

Typic Paleustolls

Definition of Typic Paleustolls

Typic Paleustolls are the Paleustolls that:

1. Are not calcareous throughout after the surface soil has

been mixed to a depth of 18 cm;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Do not have a texture finer than loamy fine sand and a

mollic epipedon 50 cm or more thick;

4. Do not have a petrocalcic horizon within 150 cm of the

mineral soil surface;

5. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

6. When neither irrigated nor fallowed to store moisture, have

one of the following:

a. A frigid temperature regime and a moisture control

section that in normal years is dry in all parts for less than

four-tenths of the cumulative days per year when the soil

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

or all parts for more than four-tenths but less than six-tenths

of the cumulative days per year when the soil temperature at

a depth of 50 cm below the soil surface is higher than 5 oC;

or

c. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is moist in some or all parts for 90 or more

consecutive days per year or is dry for less than six-tenths of

the cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 8 oC

and is dry for more than 120 cumulative days per year when

the soil temperature at a depth of 50 cm below the soil

surface is higher than 8 oC; and

7. Do not have a calcic horizon with its upper boundary

within 100 cm of the soil surface.

Description of Subgroups

Typic Paleustolls.—The central concept or Typic subgroup

of Paleustolls is fixed on deep, freely drained soils that are

noncalcareous in some part, have a mollic epipedon less than

50 cm thick, and do not have slickensides, wedge-shaped

aggregates, a high linear extensibility, or wide cracks. These

soils do not have a petrocalcic horizon and commonly have an

abrupt increase in content of clay near the top of the argillic

horizon.

A calcic horizon is a property of Calcic great groups and is

the basis for defining intergrades to Calcids and Calciustolls.

Redox depletions with low chroma and ground water are

properties of Aquolls and are the basis for defining the Aquic

subgroup. A thick mollic epipedon is the basis for defining the

Pachic subgroup. A petrocalcic horizon is considered evidence

of more than normal development. Its presence in a soil that

has an ustic moisture regime is the basis for defining the

Petrocalcic subgroup.

A moisture regime that borders on udic is the basis for

defining the Udic subgroup. A clayey texture, slickensides,

wedge-shaped aggregates, a high linear extensibility, and

cracks in normal years are properties shared with Vertisols and

are the basis for defining the Vertic subgroup. An ustic

moisture regime that approaches aridic or a moisture regime

that is aridic is the basis for defining the Aridic subgroup.

Typic Paleustolls are of small extent in the United States.

They are on the Great Plains and in mountain valleys in the
Mollisols 629

western part of the United States. Most of these soils supported

grasses and shrubs and are used as cropland or rangeland.

Aquic Paleustolls.—These soils have ground water within

100 cm of the surface for extended periods and have redox

depletions with low chroma in the saturated zone. Slopes are

gentle. These soils are of very small extent in the United

States.

Aridic Paleustolls.—These soils are drier than those in the

Typic subgroup but are otherwise like Typic Paleustolls in

defined properties. As a group, however, they have less organic

carbon than the soils of the Typic subgroup. Aridic Paleustolls

are moderately extensive in the southwestern part of the Great

Plains in the United States. Slopes are gentle. Most of the soils

supported grasses and shrubs. Many are used as cropland and

commonly are irrigated.

Calcic Paleustolls.—These soils have a calcic horizon in

the argillic horizon. Nearly all are reddish and have a thick,

calcified argillic horizon. They are developing toward

Calciustolls, but the argillic horizon can still be identified.

Calcic Paleustolls are of very small extent in the United States.

Calcidic Paleustolls.—These soils have a calcic horizon in

or below the argillic horizon and are drier than Typic

Paleustolls. Nearly all Calcidic Paleustolls are reddish and

have a thick, calcified argillic horizon. They occur only on the

southern Great Plains and in intermountain areas in the

Western United States, where they are moderately extensive.

Most of these soils supported grasses and shrubs. Many are

used as cropland, but some are used as rangeland.

Entic Paleustolls.—These soils are calcareous throughout

after the surface soil to a depth of 18 cm has been mixed and

do not have a calcic horizon. They are not known to occur in

the United States.

Pachic Paleustolls.—These soils are like Typic Paleustolls,

but they have a thick mollic epipedon. The argillic horizon

generally starts in the lower part of the mollic epipedon. Slopes

of the Pachic Paleustolls in the United States are mostly gentle.

The soils are of small extent, mostly in Texas on the southern

Great Plains of the United States. Most of the soils supported

grasses and shrubs and are used as cropland.

Petrocalcic Paleustolls.—These soils are like Typic

Paleustolls, but they have a petrocalcic horizon within 150 cm

of the surface. They may be calcareous throughout. In the

United States, they are moderately extensive on the southern

Great Plains and in the Southwestern States. These soils

supported grasses and shrubs. Slopes are gentle. Most of the

soils are used for grazing. Some are used as irrigated cropland

if water is available.

Torrertic Paleustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They are drier than Vertic

Paleustolls. Torrertic Paleustolls are of small extent in the

United States and occur mostly on the southwestern Great

Plains. Slopes of the Torrertic Paleustolls in the United States

are gentle or moderate. The natural vegetation was mostly

grasses and shrubs. Most of the soils are used as cropland,

mostly irrigated, but some are used as rangeland.

Udertic Paleustolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They are more moist than

Vertic Paleustolls. They have more precipitation than Typic

Paleustolls. Udertic Paleustolls are moderately extensive soils

in the eastern part of the southern Great Plains. The natural

vegetation was mostly grasses and shrubs. Slopes are gentle,

and nearly all of the soils are used as cropland.

Udic Paleustolls.—These soils are more moist than Typic

Paleustolls and generally have carbonates at a greater depth.

Slopes of the Udic Paleustolls in the United States are mostly

gentle. The soils are of moderate extent, mostly on the southern

Great Plains of the United States. Most of the soils supported

grasses and shrubs and are used as cropland.

Vertic Paleustolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They may have a mollic epipedon that

is more than 50 cm thick. These soils are of small extent in the

United States and commonly occur on gentle slopes on the

Great Plains. The natural vegetation was mostly grasses and

shrubs. Most of the soils are used as cropland, but some are

used as rangeland.

Vermustolls

These are the Ustolls that have been intensively and

repeatedly mixed by animals, mainly by earthworms and their

predators. The most common horizon sequence is a mollic

epipedon that consists mostly of wormcasts and rests on parent

materials that contain many worm channels filled with dark

materials from the epipedon. There may be a horizon in which

carbonates have precipitated, but mixing by animals may have

destroyed such a horizon or prevented its formation. These

soils are not known to occur in North America, but they are

extensive in Eastern Europe.

Definition

Vermustolls are the Ustolls that:

1. Have a mollic epipedon that:

a. Either below an Ap horizon or below a depth of 18 cm

from the mineral soil surface, contains 50 percent or more

(by volume) wormholes, wormcasts, or filled animal

burrows; and

b. Either rests on a lithic contact or has a transition zone

to the underlying horizon in which 25 percent or more of

the soil volume consists of discrete wormholes, wormcasts,

or animal burrows filled with material from the mollic

epipedon and from the underlying horizon;

2. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface;
630 Soil Taxonomy

3. Do not have an argillic or natric horizon; and

4. Do not meet both of the following:

a. Have a calcic or gypsic horizon that has its upper

boundary within 100 cm of the soil surface or a petrocalcic

horizon that has its upper boundary within 150 cm of the

mineral soil surface; and

b. In all parts above the calcic, gypsic, or petrocalcic

horizon, after the materials between the soil surface and a

depth of 18 cm have been mixed, either are calcareous or

have a texture of loamy fine sand or coarser.

Key to Subgroups

IFFA. Vermustolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Vermustolls

IFFB. Other Vermustolls that have, in one or more horizons

within 100 cm of the mineral soil surface, redox depletions

with chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Vermustolls

IFFC. Other Vermustolls that have a mollic epipedon 75 cm

or more thick.

Pachic Vermustolls

IFFD. Other Vermustolls that have a mollic epipedon less

than 50 cm thick.

Entic Vermustolls

IFFE. Other Vermustolls.

Typic Vermustolls

Definition of Typic Vermustolls

Typic Vermustolls are the Vermustolls that:

1. Have a mollic epipedon that is 50 cm to 75 cm thick;

2. Do not have a lithic contact within 50 cm of the mineral

soil surface; and

3. Do not have, in any horizon within 100 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions.

Description of Subgroups

Typic Vermustolls.—The central concept or Typic subgroup

of Vermustolls is fixed on soils that are deep to a lithic contact

and have a mollic epipedon 50 to 75 cm or more thick. These

soils are not known to occur in the United States.

Aquic Vermustolls.—These soils have aquic conditions and

redox depletions with chroma of 2 or less within 100 cm of the

soil surface. They do not have a lithic contact within 50 cm of

the soil surface. They are rare and are not known to occur in the

United States.

Entic Vermustolls.—These soils have a mollic epipedon

less than 50 cm thick. They are otherwise like Typic

Vermustolls. Entic Vermustolls are not known to occur in the

United States.

Lithic Vermustolls.—These soils have a lithic contact at a

depth of 50 cm or less from the mineral soil surface. They are

not known to occur in the United States.

Pachic Vermustolls.—These soils have a mollic epipedon

more than 75 cm thick. They are otherwise like Typic

Vermustolls. Pachic Vermustolls are not known to occur in the

United States.

Xerolls

These soils are Mollisols of regions that have Mediterranean

climates. As their name implies, they generally have a xeric

moisture regime. Some Xerolls that are marginal to Aridisols,

however, have an aridic moisture regime. Xerolls are dry for

extended periods in summer, but moisture moves through most

of the soils in winter and is stored throughout the part of the

soils above the deep layers or above bedrock in normal years.

Soft, white winter wheat is the most common crop on the

Xerolls in the United States where there is no irrigation and

the temperature regime is mesic. Where the temperature

regime is frigid, the soils are used for spring wheat or for

grazing. With irrigation, many crops are grown, especially

where the temperature regime is thermic or mesic. The soils

that have steep slopes mainly support natural vegetation of

native annual or perennial grasses and of shrubs or trees. These

soils are used mainly for grazing in spring or late in fall. The

native perennial grasses remain dormant during the dry

summers, and the annual grasses grow mainly in spring but

sometimes also in fall if rains occur before the temperature

drops too low.

Characteristically, Xerolls have a relatively thick mollic

epipedon, a cambic or argillic horizon, and an accumulation of

carbonates in the lower part of the B horizon and are neutral in

most horizons.

The Xerolls in the United States formed mainly in latePleistocene loess that varies in thickness and that overlies

bedrock on nearly level to steep older surfaces. Tertiary lake

sediments, older crystalline rocks, and alluvium are common

parent materials in some areas. The vegetation at the time of

settlement in the areas that have a mesic or frigid temperature

regime was dominantly bunchgrass and shrubs with

wheatgrass (Agropyron), fescue (Festuca), and bluegrass (Poa)

species in association with sagebrush (Artemisia), bitterbrush

(Purshia), and rabbitbrush (Chrysothamnus) species and some

scattered juniper (Juniperus) and pine (Pinus) species. In the

Willamette Valley of Oregon, the vegetation was a savanna of

perennial grasses, oaks, and Douglas-fir. In the areas in
Mollisols 631

California that have thermic temperature regimes, the vegetation

was a savanna of annual grasses and oak species.

Xerolls are not extensive soils in the world, but they are

extensive in parts of Turkey and of northern Africa near the

Mediterranean Sea, in some of the southern republics of the

former USSR, and in Washington, Oregon, Idaho, Utah,

Nevada, and California in the United States. The temperature

regimes are mostly mesic or frigid, but some are thermic.

Definition

Xerolls are the Mollisols that:

1. Have a mean annual soil temperature lower than 22 oC and

mean summer and mean winter soil temperatures at a depth of

50 cm that differ by 5 oC or more;

2. Do not have both an albic horizon and, within 100 cm of

the mineral soil surface, any subhorizon of the albic horizon

and/or of the argillic or natric horizon that has redox

concentrations in the form of masses or concretions, or both,

and also aquic conditions;

3. Do not have both aquic conditions and the colors defined

for Aquolls;

4. Have a xeric moisture regime or have a moisture regime

that is aridic bordering on xeric; and

5. Do not have a cryic temperature regime.

Key to Great Groups

IEA. Xerolls that have a duripan within 100 cm of the

mineral soil surface.

Durixerolls, p. 639

IEB. Other Xerolls that have a natric horizon.

Natrixerolls, p. 650

IEC. Other Xerolls that have either:

1. A petrocalcic horizon that has its upper boundary

within 150 cm of the mineral soil surface; or

2. An argillic horizon that has one or both of the

following:

a. With increasing depth, no clay decrease of 20

percent or more (relative) from the maximum clay

content (noncarbonate clay) within 150 cm of the mineral

soil surface (and there is no densic, lithic, or paralithic

contact within that depth); and either

(1) Hue of 7.5YR or redder and chroma of 5 or more

in the matrix; or

(2) Common redox concentrations with hue

of 7.5YR or redder or chroma of 6 or more, or both;

or

b. A clayey or clayey-skeletal particle-size class in its

upper part and, at its upper boundary, a clay increase

either of 20 percent or more (absolute) within a vertical

distance of 7.5 cm or of 15 percent or more (absolute)

within a vertical distance of 2.5 cm, in the fine-earth

fraction (and there is no densic, lithic, or paralithic

contact within 50 cm of the mineral soil surface).

Palexerolls, p. 652

IED. Other Xerolls that:

1. Have a calcic or gypsic horizon that has its upper

boundary within 150 cm of the mineral soil surface; and

2. In all parts above the calcic or gypsic horizon, after the

surface soil has been mixed to a depth of 18 cm, either are

calcareous or have a texture of loamy fine sand or coarser.

Calcixerolls, p. 637

IEE. Other Xerolls that have an argillic horizon.

Argixerolls, p. 631

IEF. Other Xerolls.

Haploxerolls, p. 642

Argixerolls

These are the Xerolls that have a relatively thin argillic

horizon or one in which the percentage of clay decreases

rapidly with increasing depth. Generally, the mollic epipedon

is very dark brown and the argillic horizon is dark brown. Most

of these soils have a Bk or calcic horizon below or in the lower

part of the argillic horizon. Argixerolls formed mostly in midPleistocene or earlier deposits or on surfaces of Tertiary age.

Slopes range from nearly level to very steep. The natural

vegetation is mostly grasses and shrubs, but some of the soils

support coniferous forest vegetation with a grass and shrub

understory and some have an open forest or savanna.

Definition

Argixerolls are the Xerolls that:

1. Do not have a natric horizon;

2. Have an argillic horizon that has:

a. A vertical clay distribution in which the content of clay

decreases by more than 20 percent from the maximum clay

content (noncarbonate clay) within a depth of less than 150

cm from the soil surface if:

(1) Hue is redder than 10YR and chroma is greater

than 4 in the matrix; or
632 Soil Taxonomy

(2) There are common redox concentrations that have

hue of 7.5YR or redder or chroma greater than 5; and

b. Less than 35 percent clay in the upper part or an increase

of less than 20 percent clay (absolute) within a vertical

distance of 7.5 cm or of 15 percent clay (absolute) within 2.5

cm at the upper boundary, or there is a densic, lithic, or

paralithic contact within 50 cm of the soil surface;

3. Do not have a duripan that has its upper boundary

within 100 cm of the soil surface;

4. Do not have a petrocalcic horizon that has its upper

boundary within 150 cm of the soil surface; and

5. Do not have a calcic or gypsic horizon that has its upper

boundary within 150 cm of the mineral soil surface unless

some part of some horizon overlying the calcic or gypsic

horizon is free of carbonates or has a texture that is coarser

than loamy very fine sand after the upper 18 cm has been

mixed.

Key to Subgroups

IEEA. Argixerolls that have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. A base saturation (by sum of cations) of 75 percent or

less in one or more horizons between either the mineral soil

surface or an Ap horizon, whichever is deeper, and the lithic

contact.

Lithic Ultic Argixerolls

IEEB. Other Argixerolls that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Argixerolls

IEEC. Other Argixerolls that have both:

1. An aridic moisture regime; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Torrertic Argixerolls

IEED. Other Argixerolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Argixerolls

IEEE. Other Argixerolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Argixerolls

IEEF. Other Argixerolls that have both:

1. An aridic moisture regime; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitritorrandic Argixerolls

IEEG. Other Argixerolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and
Mollisols 633

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is equal

to 30 or more.

Vitrandic Argixerolls

IEEH. Other Argixerolls that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A base saturation (by sum of cations) of 75 percent

or less in one or more horizons between either an Ap

horizon or a depth of 25 cm from the mineral soil

surface, whichever is deeper, and either a depth of 75

cm or a densic, lithic, or paralithic contact, whichever

is shallower.

Aquultic Argixerolls

IEEI. Other Argixerolls that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Argixerolls

IEEJ. Other Argixerolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Argixerolls

IEEK. Other Argixerolls that have either:

1. Above the argillic horizon, an albic horizon or a

horizon that has color values too high for a mollic epipedon

and chroma too high for an albic horizon; or

2. A glossic horizon, or interfingering of albic materials

into the upper part of the argillic horizon, or skeletans of

clean silt and sand covering 50 percent or more of the faces

of peds in the upper 5 cm of the argillic horizon.

Alfic Argixerolls

IEEL. Other Argixerolls that have both:

1. A calcic horizon or identifiable secondary carbonates

within one of the following particle-size class (by weighted

average in the particle-size control section) and depth

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 90

cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil

surface; and

2. A mollic epipedon that is 50 cm or more thick and has a

texture finer than loamy fine sand.

Calcic Pachic Argixerolls

IEEM. Other Argixerolls that have both:

1. A mollic epipedon that is 50 cm or more thick and has

a texture finer than loamy fine sand; and

2. A base saturation (by sum of cations) of 75 percent or

less in one or more horizons between either an Ap horizon

or a depth of 25 cm from the mineral soil surface, whichever

is deeper, and either a depth of 75 cm or a densic, lithic, or

paralithic contact, whichever is shallower.

Pachic Ultic Argixerolls

IEEN. Other Argixerolls that have a mollic epipedon that is

50 cm or more thick and has a texture finer than loamy fine

sand.

Pachic Argixerolls

IEEO. Other Argixerolls that have both:

1. An aridic moisture regime; and

2. A horizon within 100 cm of the mineral soil surface

that is 15 cm or more thick and either has 20 percent or

more (by volume) durinodes or is brittle and has a firm

rupture-resistance class when moist.

Argiduridic Argixerolls

IEEP. Other Argixerolls that have a horizon within 100 cm of

the mineral soil surface that is 15 cm or more thick and either

has 20 percent or more (by volume) durinodes or is brittle and

has a firm rupture-resistance class when moist.

Duric Argixerolls

IEEQ. Other Argixerolls that have both:

1. An aridic moisture regime; and

2. A calcic horizon or identifiable secondary carbonates

within one of the following particle-size class (by weighted

average in the particle-size control section) and depth

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the

mineral soil surface; or
634 Soil Taxonomy

b. Clayey, clayey-skeletal, fine, or very-fine and within 90

cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil

surface.

Calciargidic Argixerolls

IEER. Other Argixerolls that have an aridic moisture

regime.

Aridic Argixerolls

IEES. Other Argixerolls that have a calcic horizon or

identifiable secondary carbonates within one of the following

particle-size class (by weighted average in the particle-size

control section) and depth combinations:

1. Sandy or sandy-skeletal and within 150 cm of the

mineral soil surface; or

2. Clayey, clayey-skeletal, fine, or very-fine and within 90

cm of the mineral soil surface; or

3. Any other class and within 110 cm of the mineral soil

surface.

Calcic Argixerolls

IEET. Other Argixerolls that have a base saturation (by sum

of cations) of 75 percent or less in one or more horizons

between either an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and either a depth of

75 cm or a densic, lithic, or paralithic contact, whichever is

shallower.

Ultic Argixerolls

IEEU. Other Argixerolls.

Typic Argixerolls

Definition of Typic Argixerolls

Typic Argixerolls are the Argixerolls that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have either:

a. An albic horizon or another horizon above the argillic

horizon that has a color value too high for a mollic epipedon

and chroma too high for an albic horizon; or

b. A glossic horizon, or interfingering of albic materials in

the upper part of the argillic horizon, or skeletans of clean

silt and sand covering more than half the faces of peds in the

upper 5 cm or more of the argillic horizon;

4. Do not have a calcic horizon or identifiable secondary

carbonates within one of the following particle-size class (by

weighted average in the particle-size control section) and depth

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 90

cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil

surface;

5. Do not have a horizon within 100 cm of the mineral soil

surface that is more than 15 cm thick and that either has at

least 20 percent durinodes or is brittle and has a firm ruptureresistance class when moist;

6. Do not have a lithic contact within 50 cm of the soil

surface;

7. Have a xeric moisture regime;

8. Have a mollic epipedon that is less than 50 cm thick or has

a texture of loamy fine sand or coarser if it is 50 cm or more

thick;

9. Have a base saturation (by sum of cations) of more than 75

percent in all horizons between either an Ap horizon or a depth

of 25 cm from the mineral soil surface, whichever is deeper,

and either a depth of 75 cm or a densic, lithic, or paralithic

contact, whichever is shallower;

10. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

11. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. A bulk density, in the fraction less than 2.0 mm in size,

of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and acid-oxalate-extractable aluminum plus 1/2 acid-oxalateextractable iron of more than 1.0 percent; or

b. Fragments coarser than 2.0 mm constituting more than
Mollisols 635

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Argixerolls.—The central concept or Typic subgroup

of Argixerolls is fixed on deep soils that have a mollic

epipedon less than 50 cm thick and do not have redox

depletions and aquic conditions within 75 cm of the mineral

soil surface. These soils do not have an albic horizon above the

argillic horizon, nor do they have a glossic horizon or

interfingering of albic materials into the upper part of the

argillic horizon. They are deep to secondary carbonates, but

they have a high base saturation. They do not have

slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks in normal years. These soils do not

have, within a depth of 100 cm, a horizon that is more than 15

cm thick and that has 20 percent or more durinodes or is brittle

and has a firm rupture-resistance class when moist. They are

dry in summer, but they receive and store enough water in

winter and early spring to provide moisture for spring and

early summer crops.

Shallow ground water or artificial drainage and redox

depletions with low chroma are properties of Aquolls and are

the basis for defining the Aquic subgroup. An albic horizon

above the argillic horizon is characteristic of Alfisols and is the

basis for defining the Alfic subgroup. A calcic horizon or

identifiable secondary carbonates at a moderate depth indicate

an intergrade to Calcixerolls and Calcids and are the basis for

defining Calcic and combination Calcic subgroups. A brittle

horizon and the presence of durinodes indicate an intergrade to

Durixerolls and Durids and are the basis for defining the Duric

subgroup. A shallow lithic contact is the basis for defining

Lithic and combination Lithic subgroups. An aridic moisture

regime is a property of Aridisols and is the basis for defining

the Aridic subgroup. A thick mollic epipedon is the basis for

defining Pachic and combination Pachic subgroups. Low base

saturation is a property of Ultisols and is the basis for defining

Ultic and combination Ultic subgroups. Slickensides, wedgeshaped aggregates, a high linear extensibility, and cracks that

are evident in normal years are properties of Vertisols and are

the basis for defining the Vertic subgroup.

The Typic subgroup is the most extensive subgroup of

Argixerolls and is extensive in parts of the Western United

States. The natural vegetation is mostly grasses and shrubs, but

some of the soils support trees. The soils that have gentle

slopes commonly are used as cropland, some of which is

irrigated. The soils that have moderate slopes are used for dryfarmed crops. The steep soils are used as rangeland or grazeable

forest.

Alfic Argixerolls.—These soils have an albic or glossic

horizon or another horizon that has color values too high for a

mollic epipedon and chroma too high for an albic horizon

above the argillic horizon, have interfingering of albic

materials into the upper part of the argillic horizon, or have

skeletans of clean silt and sand covering 50 percent or more of

the faces of peds in the upper 5 cm of the argillic horizon.

These soils are of small extent in the United States and occur

mostly in Idaho and Utah. Some supported grasses and shrubs,

and some supported forest vegetation. Slopes range from nearly

level to very steep. The soils that have gentle to moderately

steep slopes are used mostly as cropland. Other soils, mostly

those that have very steep slopes, are used as forest or

rangeland.

Andic and Vitrandic Argixerolls.—These soils have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals

or that consists of slightly or moderately weathered pyroclastic

materials. These soils are of large extent, mostly in the

mountains of Washington, Oregon, and Idaho in the Western

United States. The vegetation either is mostly grass and shrubs

and some widely spaced trees or is coniferous forest. Slopes

range from nearly level to very steep. Many of the less sloping

soils are used as cropland. Most of the other soils are used as

rangeland, forest, or wildlife habitat.

Aquic Argixerolls.—These soils have redox depletions with

low chroma and either have moderately deep ground water at

some time of the year or have artificial drainage. They are

gently sloping or nearly level. They are of small extent in the

United States. The natural vegetation is mostly grass and

shrubs. Most of the soils are used as cropland, but some are

used as rangeland or pasture.

Aquultic Argixerolls.—These soils have redox depletions

with low chroma and either have moderately deep ground

water at some time of the year or have artificial drainage, and

they have a lower base saturation than that in the soils of the

Typic subgroup. Aquultic Argixerolls are rare in the United

States. They are on gently sloping or nearly level, broad valley

terraces. Most of the soils are used as cropland. Truck crops

and orchard crops are commonly grown under irrigation.

Argiduridic Argixerolls.—These soils have an aridic

moisture regime that borders on xeric, and they have a

subhorizon within 100 cm of the surface that does not meet the

requirements for a duripan but is more than 15 cm thick and

either has 20 percent or more (by volume) durinodes or is

brittle when wet and has a firm rupture-resistance class when

moist. These soils are of small extent in the United States. The
636 Soil Taxonomy

natural vegetation is mostly grass and shrubs. The soils

generally have gentle or moderate slopes and are used mostly as

rangeland. Some of the less sloping soils are used as cropland.

Some of the cropland is irrigated.

Aridic Argixerolls.—These soils have an aridic moisture

regime but are otherwise like Typic Argixerolls in their defined

properties. It is common but not required that the color value of

these soils is higher and the content of organic carbon is less

than in soils of the Typic subgroup. Slopes of the Aridic

Argixerolls in the United States are nearly level to very steep.

The soils generally receive less precipitation or lose more water

through runoff and evapotranspiration than the soils of the

Typic subgroup. Aridic Argixerolls are extensive in parts of the

Western United States. The natural vegetation is mostly grass

and shrubs. Most of the soils are used as rangeland or pasture.

Some of the less sloping soils are used as cropland. Some of the

cropland is irrigated.

Calciargidic Argixerolls.—These soils have an aridic

moisture regime that borders on xeric and have a calcic

horizon or identifiable secondary carbonates at a moderate

depth. The Calciargidic Argixerolls in the United States have

nearly level to steep slopes. They are extensive in parts of the

Western United States. The natural vegetation is mostly grass

and shrubs. Most of the soils are used as rangeland or pasture.

Some of the less sloping soils are used as cropland. Some of the

cropland is irrigated.

Calcic Argixerolls.—These soils have a calcic horizon or

identifiable secondary carbonates at a moderate depth but are

otherwise like Typic Argixerolls in their defined properties.

Slopes are nearly level to very steep. Calcic Argixerolls are

extensive in parts of the Western United States. The natural

vegetation is mostly grass and shrubs. Most of the soils are

used as rangeland or pasture. Many of the less sloping soils are

used as cropland. A small amount of the cropland is irrigated.

Calcic Pachic Argixerolls.—These soils have a calcic

horizon or identifiable secondary carbonates at a moderate

depth and have a mollic epipedon that is thicker than the one

in the Typic subgroup. Slopes are nearly level to steep. The

natural vegetation is mostly grass and shrubs. Most of the soils

are used as rangeland or pasture. Many of the less sloping soils

are used as cropland. A small amount of the cropland is

irrigated.

Duric Argixerolls.—These soils have a subhorizon within

100 cm of the surface that does not meet the requirements for a

duripan but is more than 15 cm thick and either has 20 percent

or more (by volume) durinodes or is brittle and has a firm

rupture-resistance class when moist. The soils are rare in the

United States. They are nearly level or sloping and are used as

irrigated cropland or as rangeland.

Lithic Argixerolls.—These soils have a shallow lithic

contact and are permitted, but not required, to have a calcic

horizon or free carbonates beneath the surface layer. They are

extensive in the Western United States. Slopes range from

nearly level to very steep. The natural vegetation is mostly

grass and shrubs. Most of the soils are used as rangeland, as

watersheds, or as habitat for wildlife.

Lithic Ultic Argixerolls.—These soils have a shallow lithic

contact and have less than 75 percent base saturation above the

lithic contact. They are of small extent in the Western United

States. Slopes range from gentle to very steep. The natural

vegetation is mostly a coniferous forest with widely spaced

trees and a grass and shrub understory. Some of the soils

support mostly grasses and shrubs. Most of the soils are used as

grazeable woodland or as rangeland, but some are used as

watersheds or as wildlife habitat.

Oxyaquic Argixerolls.—These soils are like Typic

Argixerolls, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. Oxyaquic

Argixerolls are of very small extent in the United States.

Pachic Argixerolls.—These soils have a thick mollic

epipedon that commonly includes part of the argillic horizon.

They are extensive soils in parts of the Western United States.

Slopes are nearly level to very steep. The natural vegetation is

mostly grass and shrubs. Some of the soils supported forest

vegetation or oak savanna. Many of the less sloping soils are

used as cropland. The rest of the soils are used mostly as

rangeland or pasture.

Pachic Ultic Argixerolls.—These soils have a thick mollic

epipedon that commonly includes part of the argillic horizon.

They have a base saturation of 75 percent or less in one or

more horizons between either an Ap horizon or a depth of 25

cm from the mineral soil surface, whichever is deeper, and a

depth of 75 cm. These soils are extensive in parts of the

Western United States. Slopes are nearly level to very steep.

The natural vegetation either is mostly a coniferous forest with

a grass and shrub understory or is mostly grasses and shrubs.

Some of the soils supported an open forest or savanna. Many of

the less sloping soils are used as cropland. The rest of the soils

are used mostly as rangeland, pasture, or grazeable forest.

Torrertic Argixerolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. They are drier than Vertic

Argixerolls. Torrertic Argixerolls are of small extent in the

United States and occur mostly in Idaho.

Ultic Argixerolls.—These soils have a base saturation of 75

percent or less in one or more horizons between either an Ap

horizon or a depth of 25 cm from the mineral soil surface,

whichever is deeper, and a depth of 75 cm, but they otherwise

are like Typic Argixerolls in their defined properties. Ultic

Argixerolls are extensive in parts of the Western United States.

Slopes range from nearly level to very steep. The natural

vegetation either is mostly a coniferous forest with a grass and

shrub understory or is mostly grasses and shrubs. Some of the

soils supported an open forest or savanna. Many of the less

sloping soils are used as cropland. The rest of the soils are used

mostly as rangeland, pasture, or grazeable forest.

Vertic Argixerolls.—These soils have a clayey particle-size
Mollisols 637

class in a significant part, have expanding clays, and in normal

years have deep cracks. They are of small extent in the United

States. They formed mostly in fine textured lake sediments.

They are associated on the landscape with Xererts and other

Xerolls. The natural vegetation is mostly grass and shrubs.

Most Vertic Argixerolls are nearly level or gently sloping. They

are used mostly as cropland. Some of the cropland is irrigated.

Vitritorrandic Argixerolls.—These soils have an aridic

moisture regime that borders on xeric and have a surface

mantle or layer in the upper 75 cm that consists of slightly or

moderately weathered pyroclastic materials. They are of small

extent, mostly in Nevada and Washington in the Western

United States. The vegetation is mostly grass and shrubs.

Slopes range from nearly level to steep. Most of the soils are

used as rangeland or wildlife habitat. Many of the less sloping

soils are used as cropland.

Calcixerolls

These are the Xerolls that have a calcic or gypsic horizon and

that are calcareous in all overlying horizons. Either the parent

materials had more carbonates than the water from the rainfall

could remove from the upper horizons, or there is a continuing

external source of carbonates in dust or water.

Calcixerolls formed mostly in late-Pleistocene sediments or

older materials on surfaces of comparable age. In the United

States, their native vegetation was mostly grass and shrubs.

These soils are most extensive in the Great Basin of the

Western United States. Slopes range from nearly level to very

steep.

Definition

Calcixerolls are the Xerolls that:

1. Have a calcic or gypsic horizon that has its upper boundary

within 150 cm of the soil surface;

2. Are calcareous in all parts of all horizons above the calcic

or gypsic horizon after the upper 18 cm has been mixed, unless

the texture is coarser than loamy very fine sand or very fine

sand;

3. Do not have a natric horizon;

4. Do not have a duripan within 100 cm of the mineral soil

surface;

5. Do not have a petrocalcic horizon that has its upper

boundary within 150 cm of the soil surface; and

6. Do not have argillic horizon that has one or both of the

following:

a. With increasing depth, no clay decrease of 20 percent or

more (relative) from the maximum clay content

(noncarbonate clay) within 150 cm of the mineral soil

surface (and there is no densic, lithic, or paralithic contact

within that depth); and either

(1) Hue of 7.5YR or redder and chroma of 5 or more in the

matrix; or

(2) Common redox concentrations with hue of 7.5YR or

redder or chroma of 6 or more, or both; or

b. A clayey or clayey-skeletal particle-size class in its upper

part and, at its upper boundary, a clay increase either of 20

percent or more (absolute) within a vertical distance of 7.5 cm

or of 15 percent or more (absolute) within a vertical distance

of 2.5 cm, in the fine-earth fraction (and there is no densic,

lithic, or paralithic contact within 50 cm of the mineral soil

surface).

Key to Subgroups

IEDA. Calcixerolls that have a lithic contact within 50 cm of the

mineral soil surface.

Lithic Calcixerolls

IEDB. Other Calcixerolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Calcixerolls

IEDC. Other Calcixerolls that have, in one or more horizons

within 75 cm of the mineral soil surface, redox concentrations

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Calcixerolls

IEDD. Other Calcixerolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Calcixerolls

IEDE. Other Calcixerolls that have a mollic epipedon that is

50 cm or more thick and has a texture finer than loamy fine

sand.

Pachic Calcixerolls

IEDF. Other Calcixerolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:
638 Soil Taxonomy

1. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is equal to 30 or more.

Vitrandic Calcixerolls

IEDG. Other Calcixerolls that have an aridic moisture

regime.

Aridic Calcixerolls

IEDH. Other Calcixerolls that have a mollic epipedon that

has, below any Ap horizon, 50 percent or more (by volume)

wormholes, wormcasts, or filled animal burrows.

Vermic Calcixerolls

IEDI. Other Calcixerolls.

Typic Calcixerolls

Definition of Typic Calcixerolls

Typic Calcixerolls are the Calcixerolls that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox concentrations and also aquic conditions;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Have a mollic epipedon that is less than 50 cm thick or has

a texture of loamy fine sand or coarser if it is 50 cm or more

thick;

4. Have a xeric moisture regime;

5. Do not have a lithic contact within 50 cm of the soil

surface;

6. Do not have a mollic epipedon that, below any Ap horizon,

has 50 percent or more (by volume) wormholes, wormcasts, or

filled animal burrows;

7. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

8. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is equal to 30 or more.

Description of Subgroups

Typic Calcixerolls.—The central concept or Typic subgroup

of Calcixerolls is fixed on deep soils that have a moderately

thick mollic epipedon and have a xeric moisture regime. These

soils do not have a fluctuating ground water table accompanied

by redox concentrations. They do not have slickensides, wedgeshaped aggregates, a high linear extensibility, or wide cracks in

normal years. They are dry in summer, but they receive and

store enough water in winter and early spring to provide some

moisture for spring and early summer crops.

Redox concentrations and a ground water table that

fluctuates within 75 cm of the mineral soil surface are

properties shared with Aquolls and are the basis for defining

the Aquic subgroup. An aridic moisture regime is drier than

that of Typic Calcixerolls and is the basis for defining the

Aridic subgroup. A shallow lithic contact is the basis for

defining the Lithic subgroup. A thick mollic epipedon is the

basis for defining the Pachic subgroup. Soils that have been

intensively and repeatedly mixed by animals, mainly by

earthworms and their predators, are classified in the Vermic

subgroup. Slickensides, wedge-shaped aggregates, a high

linear extensibility, and cracks that are evident in normal years

are properties of Vertisols and are the basis for defining the

Vertic subgroup.

The Typic subgroup is the most extensive subgroup of

Calcixerolls. Typic Calcixerolls are moderately extensive in the

Western United States. They are nearly level to very steep. The

natural vegetation is mostly grass and shrubs, but some of the

soils support widely spaced juniper and pine species. Many of

the nearly level and gently sloping soils are used as cropland,

much of which is irrigated. Most of the steeper soils are used as

rangeland.

Aquic Calcixerolls.—These soils have moderately deep

ground water at times or artificial drainage and have redox

concentrations. They are of small extent in the Western United

States. The natural vegetation is mostly grass and shrubs. The

soils generally are nearly level and are used mostly as

cropland, hayland, or pasture, much of which is irrigated.

Some of the soils are used as rangeland.
Mollisols 639

Aridic Calcixerolls.—These soils have an aridic moisture

regime that borders on xeric but otherwise are like Typic

Calcixerolls in their defined properties. Commonly, the calcic

horizon is closer to the surface than that in the soils of the

Typic subgroup and the mollic epipedon has less organic

carbon. Aridic Calcixerolls are nearly as extensive as the soils

of the Typic subgroup and are moderately extensive in the

Western United States. Slopes are nearly level to very steep.

The natural vegetation is mostly grass and shrubs, but some of

the soils support widely spaced juniper species. Many of the

nearly level and gently sloping soils are used as cropland, most

of which is irrigated. Most of the steeper soils are used as

rangeland.

Lithic Calcixerolls.—These soils have a lithic contact within

50 cm of the surface and have a xeric moisture regime or one that

is aridic but borders on xeric. They are of small extent in parts of

Nevada, Utah, and southern Idaho in the United States. The

natural vegetation is mostly grass and shrubs, but some of the

soils support widely spaced juniper species. Lithic Calcixerolls

have nearly level to very steep slopes. They are used mostly as

rangeland.

Oxyaquic Calcixerolls.—These soils have ground water

within 100 cm of the mineral soil surface at times during the

year. They are of very small extent in the Western United

States. The natural vegetation is mostly grass and shrubs. The

soils generally are nearly level and are used mostly as

cropland, hayland, or pasture, much of which is irrigated.

Some of the soils are used as rangeland.

Pachic Calcixerolls.—These soils have a mollic epipedon

that is 50 cm or more thick. Otherwise, they are similar to the

soils of the Typic subgroup. Pachic Calcixerolls are of small

extent in the Western United States. The natural vegetation is

mostly grass and shrubs. Many of these soils have nearly level

or gentle slopes, but some range to very steep. The nearly level

and gently sloping soils are used mostly as cropland, hayland,

or pasture, much of which is irrigated. The more sloping soils

are used mostly as rangeland.

Vermic Calcixerolls.—These soils have been intensively

and repeatedly mixed by animals, mainly earthworms and their

predators. The most common horizon sequence is a mollic

epipedon overlying parent material that has many worm

channels filled with dark material from the epipedon. These

soils are not known to occur in the United States. The subgroup

is provided for use elsewhere.

Vertic Calcixerolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They are of very small extent in the

United States. The natural vegetation is mostly grass and

shrubs. These soils generally are nearly level or gently sloping.

They are used as cropland or rangeland. Some of the cropland

is irrigated.

Vitrandic Calcixerolls.—These soils have significant

amounts of cinders, pumice, and pumicelike fragments or

glass. They do not have a lithic contact within 50 cm of the soil

surface, a high shrink-swell potential, or saturation within 100

cm of the soil surface. These soils are not known to occur in the

United States.

Durixerolls

These are the Xerolls that have a duripan that has its upper

boundary within 100 cm of the soil surface. They formed

mainly in Pleistocene sediments. Some of the materials near

the surface of many of these soils are younger than the duripan.

The parent materials commonly were derived, at least partially,

from basic volcanic rocks, siliceous tuffs, pumice, or volcanic

ash. The natural vegetation on the Durixerolls in the United

States was grass and shrubs. These soils occur in the Western

United States, but they are not extensive. They generally are

gently sloping or moderately sloping.

Definition

Durixerolls are the Xerolls that have a duripan within 100

cm of the mineral soil surface.

Key to Subgroups

IEAA. Durixerolls that have, above the duripan, one or both

of the following:

1. Cracks that are 5 mm or more wide through a thickness

of 30 cm or more for some time in normal years, and

slickensides or wedge-shaped aggregates in a layer 15 cm or

more thick; or

2. A linear extensibility of 6.0 cm or more.

Vertic Durixerolls

IEAB. Other Durixerolls that have both:

1. An aridic moisture regime; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitritorrandic Durixerolls
640 Soil Taxonomy

IEAC. Other Durixerolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm of

the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Durixerolls

IEAD. Other Durixerolls that have, in one or more horizons

above the duripan, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Durixerolls

IEAE. Other Durixerolls that have:

1. An aridic moisture regime; and

2. An argillic horizon that, with increasing depth, has a

clay increase either of 20 percent or more (absolute) within

a vertical distance of 7.5 cm or of 15 percent or more

(absolute) within a vertical distance of 2.5 cm; and

3. A duripan that is neither very strongly cemented nor

indurated in any subhorizon.

Paleargidic Durixerolls

IEAF. Other Durixerolls that have both:

1. An aridic moisture regime; and

2. An argillic horizon that, with increasing depth, has a

clay increase either of 20 percent or more (absolute) within

a vertical distance of 7.5 cm or of 15 percent or more

(absolute) within a vertical distance of 2.5 cm.

Abruptic Argiduridic Durixerolls

IEAG. Other Durixerolls that:

1. Have an aridic moisture regime; and

2. Do not have an argillic horizon above the duripan; and

3. Have a duripan that is neither very strongly cemented

nor indurated in any subhorizon.

Cambidic Durixerolls

IEAH. Other Durixerolls that:

1. Have an aridic moisture regime; and

2. Do not have an argillic horizon above the duripan.

Haploduridic Durixerolls

IEAI. Other Durixerolls that have:

1. An aridic moisture regime; and

2. A duripan that is neither very strongly cemented nor

indurated in any subhorizon.

Argidic Durixerolls

IEAJ. Other Durixerolls that have an aridic moisture regime.

Argiduridic Durixerolls

IEAK. Other Durixerolls that have both:

1. An argillic horizon that, with increasing depth, has a

clay increase either of 20 percent or more (absolute) within

a vertical distance of 7.5 cm or of 15 percent or more

(absolute) within a vertical distance of 2.5 cm; and

2. A duripan that is neither very strongly cemented nor

indurated in any subhorizon.

Haplic Palexerollic Durixerolls

IEAL. Other Durixerolls that have an argillic horizon that,

with increasing depth, has a clay increase either of 20 percent

or more (absolute) within a vertical distance of 7.5 cm or of 15

percent or more (absolute) within a vertical distance of 2.5 cm.

Palexerollic Durixerolls

IEAM. Other Durixerolls that:

1. Have a duripan that is neither very strongly cemented

nor indurated in any subhorizon; and

2. Do not have an argillic horizon above the duripan.

Haplic Haploxerollic Durixerolls

IEAN. Other Durixerolls that do not have an argillic horizon

above the duripan.

Haploxerollic Durixerolls

IEAO. Other Durixerolls that have a duripan that is neither

very strongly cemented nor indurated in any subhorizon.

Haplic Durixerolls

IEAP. Other Durixerolls.

Typic Durixerolls

Definition of Typic Durixerolls

Typic Durixerolls are the Durixerolls that:

1. Have an argillic horizon above the duripan, but the argillic

horizon does not have, with increasing depth, a clay increase

either of 20 percent or more (absolute) within a vertical

distance of 7.5 cm or of 15 percent or more (absolute) within a

vertical distance of 2.5 cm;
Mollisols 641

2. Have a duripan that is either very strongly cemented or

indurated in some subhorizon;

3. Have a xeric moisture regime;

4. Do not have, in any horizon above the duripan, redox

depletions with chroma of 2 or less and also aquic conditions;

5. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1

/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is equal to 30 or more; and

6. Do not have either:

a. Cracks that are 5 mm or more wide, throughout a layer

30 cm or more thick either within 125 cm of the mineral

soil surface or above a duripan if shallower, for some time in

normal years, and slickensides or wedge-shaped aggregates

in a layer 15 cm or more thick that has its upper boundary

within 125 cm of the mineral soil surface or above a duripan

if shallower; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact or a duripan, whichever

is shallower.

Description of Subgroups

Typic Durixerolls.—The central concept or Typic subgroup

of Durixerolls is fixed on freely drained soils that have an

argillic horizon above a very strongly cemented or indurated

duripan. These soils have a relatively gradual increase in

content of clay at the upper boundary of the argillic horizon

and have a xeric moisture regime.

An abrupt increase in content of clay at the upper boundary

of the argillic horizon is a characteristic of soils in which an

argillic horizon has apparently formed after the duripan

developed. This feature is the basis for defining Palexerollic

and combination Palexerollic subgroups and, if the soil also

has an aridic moisture regime, the Abruptic Argiduridic and

Paleargidic subgroups. A weakly developed duripan is

considered less-than-normal development, and its presence is

the basis for defining the intergrades to classes of soils that do

not have a duripan. An aridic moisture regime is drier than

that of the Typic subgroup and is the basis for defining

intergrades to Aridisols. Soils that do not have an argillic

horizon and that have only weak development of the duripan

are classified in Haplic and combination Haplic subgroups.

Soils that do not have an argillic horizon above a strongly

developed duripan are classified in the Haploxerollic subgroup.

Typic Durixerolls are moderately extensive in the Western

United States. These soils generally are nearly level to

moderately sloping. The natural vegetation is mostly grass and

shrubs, but some of the soils support widely spaced juniper and

pine species. Many of the nearly level and gently sloping soils

are used as cropland, some of which is irrigated. Most of the

steeper soils are used as rangeland.

Abruptic Argiduridic Durixerolls.—These soils have an

argillic horizon in which the increase in content of clay is 20

percent (absolute) or more within a vertical distance of 7.5 cm

or is 15 percent (absolute) or more within a vertical distance of

2.5 cm at the upper boundary, have an aridic moisture regime

that borders on xeric, but are otherwise like Typic Durixerolls

in their defined properties. Abruptic Argiduridic Durixerolls

are of small extent in the Western United States. They

generally are nearly level or gently sloping. The natural

vegetation is mostly grass and shrubs, but some of the soils

support widely spaced juniper species. Many of the nearly level

and gently sloping soils are used as cropland, most of which is

irrigated. Most of the steeper soils are used as rangeland or

wildlife habitat.

Aquic Durixerolls.—These soils have redox depletions with

low chroma and either have moderately deep ground water at

some time of the year or have artificial drainage. They are not

known to occur in the United States.

Argidic Durixerolls.—These soils have an argillic horizon

in which the increase in content of clay is less than 20 percent

(absolute) within a vertical distance of 7.5 cm or is less than 15

percent (absolute) within a vertical distance of 2.5 cm at the

upper boundary, have an aridic moisture regime that borders on

xeric, but are otherwise like Typic Durixerolls in their defined

properties. Argidic Durixerolls are of small extent in the

United States. The natural vegetation is mostly grass and

shrubs, but some of the soils support widely spaced juniper and

pine species. Many of the nearly level and gently sloping soils

are used as cropland, most of which is irrigated. Most of the

steeper soils are used as rangeland or wildlife habitat.

Argiduridic Durixerolls.—These soils have an argillic

horizon in which the increase in content of clay is less than 20

percent (absolute) within a vertical distance of 7.5 cm or is less

than 15 percent (absolute) within a vertical distance of 2.5 cm

at the upper boundary. The soils also have an aridic moisture

regime that borders on xeric. These soils are of moderately

small extent in the United States. The natural vegetation is

mostly grass and shrubs, but some of the soils support widely

spaced juniper species. Many of the nearly level and gently

sloping soils are used as cropland, most of which is irrigated.

Most of the steeper soils are used as rangeland or wildlife

habitat.

Cambidic Durixerolls.—These soils have an aridic

moisture regime that borders on xeric and have a duripan that

is less developed than that in the Typic subgroup. The soils
642 Soil Taxonomy

commonly have a cambic horizon but do not have an argillic

horizon above the duripan. They are rare in the United States.

They are nearly level to very steep. The natural vegetation is

mostly grass and shrubs. Many of the nearly level and gently

sloping soils are used as cropland, most of which is irrigated.

Most of the steeper soils are used as rangeland or wildlife

habitat.

Haplic Durixerolls.—These soils have an argillic horizon,

but their duripan is weakly developed. The duripan is less

developed than that of the Typic subgroup. These soils are of

small extent in the United States. They generally are nearly

level to moderately steep. The natural vegetation is mostly

grass and shrubs. Many of the nearly level and gently sloping

soils are used as cropland, some of which is irrigated. Most of

the steeper soils are used as rangeland or wildlife habitat.

Haplic Haploxerollic Durixerolls.—These soils do not

have an argillic horizon and have a weakly developed duripan.

They commonly have a cambic horizon above the duripan.

These soils are rare in the United States. They are nearly level

to very steep. The natural vegetation is mostly grass and

shrubs. Many of the nearly level and gently sloping soils are

used as cropland. Most of the steeper soils are used as

rangeland or wildlife habitat.

Haplic Palexerollic Durixerolls.—These soils have an

argillic horizon in which the increase in content of clay is 20

percent (absolute) or more within a vertical distance of 7.5 cm

or is 15 percent (absolute) or more within a vertical distance of

2.5 cm at the upper boundary. The soils also have a weakly

developed duripan. They are not known to occur in the United

States.

Haploduridic Durixerolls.—These soils do not have an

argillic horizon and have an aridic moisture regime that

borders on xeric, but they are otherwise like Typic Durixerolls

in their defined properties. Haploduridic Durixerolls commonly

have a cambic horizon above the duripan. They are of small

extent in the United States. They are nearly level to steep. The

natural vegetation is mostly grass and shrubs. Many of the

nearly level and gently sloping soils are used as cropland, most

of which is irrigated. Most of the steeper soils are used as

rangeland or wildlife habitat.

Haploxerollic Durixerolls.—These soils do not have an

argillic horizon above the duripan. They commonly have a

cambic horizon above the duripan. They are of small extent in

the United States. They are nearly level to very steep. The

natural vegetation is mostly grass and shrubs, but some of the

soils support widely spaced juniper and pine species. Some of

the nearly level and gently sloping soils are used as cropland.

Most of the steeper soils are used as rangeland or wildlife

habitat.

Paleargidic Durixerolls.—These soils have an argillic

horizon in which the increase in content of clay is 20 percent

(absolute) or more within a vertical distance of 7.5 cm or is 15

percent (absolute) or more within a vertical distance of 2.5 cm

at the upper boundary. The soils also have an aridic moisture

regime that borders on xeric and have a weakly developed

duripan. They are of small extent in the Western United States.

They generally are nearly level or gently sloping. The natural

vegetation is mostly grass and shrubs, but some of the soils

support widely spaced pine and juniper species. Most of the

soils are used as rangeland or wildlife habitat.

Palexerollic Durixerolls.—These soils have an argillic

horizon in which the increase in content of clay is 20 percent

(absolute) or more within a vertical distance of 7.5 cm or is 15

percent (absolute) or more within a vertical distance of 2.5 cm

at the upper boundary. The soils also have a weakly developed

duripan. They are of small extent in the Western United States.

They generally are nearly level or gently sloping. The natural

vegetation is mostly grass and shrubs. Many of the nearly level

and gently sloping soils are used as cropland, some of which is

irrigated. Most of the steeper soils are used as rangeland or

wildlife habitat.

Vertic Durixerolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They are of very small extent in the

Western United States. The natural vegetation is mostly grass

and shrubs. These soils generally are nearly level or gently

sloping. They are used mostly as rangeland.

Vitrandic Durixerolls.—These soils have a surface mantle

or layer in the upper 75 cm that consists of slightly or

moderately weathered pyroclastic materials. They are of small

extent, mostly in Washington and Idaho in the Western United

States. The vegetation is mostly grass and shrubs, but some of

the soils support widely spaced coniferous trees. Slopes range

from nearly level to steep. Most of the less sloping soils are

used as dry cropland. Most of the steep soils are used as

rangeland or wildlife habitat.

Vitritorrandic Durixerolls.—These soils have a surface

mantle or layer in the upper 75 cm that consists of slightly or

moderately weathered pyroclastic materials. They also have an

aridic soil moisture regime that borders on xeric. These soils

are of moderate extent, mostly in Washington and Oregon in

the Western United States. The vegetation is mostly grass and

shrubs, and some of the soils in Oregon have widely spaced

juniper trees. Slopes range from nearly level to moderately

steep. Most of the soils are used as cropland, but some are used

as rangeland or wildlife habitat.

Haploxerolls

These are the more or less freely drained Xerolls that are

characterized by little development in the subsoil. Commonly,

they have a cambic horizon below the mollic epipedon. Some

have only unaltered recent parent materials below the mollic

epipedon. Many have horizons in which secondary carbonates

have accumulated. A few have a calcic horizon, but at least

parts of the surface horizons are free of carbonates.
Mollisols 643

Haploxerolls formed mainly in late-Pleistocene deposits or on

surfaces of comparable age, but some formed on older surfaces.

Parent materials of late-Wisconsinan loess mixed with some

volcanic ash, glacial outwash or till, and alluvium from mixed

sources are common. The natural vegetation is mostly grasses

and shrubs, but some of the soils support a coniferous forest

with a grass and shrub understory and some support an open

forest or savanna. Slopes range from nearly level to very steep.

Definition

Haploxerolls are the Xerolls that:

1. Do not have a duripan that has its upper boundary

within 100 cm of the mineral soil surface;

2. Do not have a petrocalcic horizon that has its upper

boundary within 150 cm of the mineral soil surface;

3. Do not have a calcic or gypsic horizon that has its upper

boundary within 150 cm of the mineral soil surface unless

some part of some horizon overlying the calcic or gypsic

horizon is free of carbonates after the surface soil to a depth of

18 cm has been mixed and the texture is loamy very fine sand,

very fine sand, or finer; and

4. Do not have an argillic or natric horizon.

Key to Subgroups

IEFA. Haploxerolls that have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. A base saturation (by sum of cations) of 75 percent or

less in one or more horizons between either the mineral soil

surface or an Ap horizon, whichever is deeper, and the lithic

contact.

Lithic Ultic Haploxerolls

IEFB. Other Haploxerolls that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Haploxerolls

IEFC. Other Haploxerolls that have both:

1. An aridic moisture regime; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is

shallower.

Torrertic Haploxerolls

IEFD. Other Haploxerolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that are 5

mm or more wide through a thickness of 30 cm or more for

some time in normal years, and slickensides or wedge-shaped

aggregates in a layer 15 cm or more thick that has its upper

boundary within 125 cm of the mineral soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Haploxerolls

IEFE. Other Haploxerolls that have both:

1. An aridic moisture regime; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitritorrandic Haploxerolls

IEFF. Other Haploxerolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Haploxerolls
644 Soil Taxonomy

IEFG. Other Haploxerolls that have:

1. A mollic epipedon that is 50 cm or more thick and has a

texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content from a

depth of 25 cm below the mineral soil surface to a depth of

125 cm or to a densic, lithic, or paralithic contact if shallower;

and

3. A slope of less than 25 percent; and

4. In one or more horizons within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage).

Aquic Cumulic Haploxerolls

IEFH. Other Haploxerolls that have:

1. A mollic epipedon that is 50 cm or more thick and has

a texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content from a

depth of 25 cm below the mineral soil surface to a depth of

125 cm or to a densic, lithic, or paralithic contact if

shallower; and

3. A slope of less than 25 percent; and

4. A base saturation (by sum of cations) of 75 percent or

less in one or more horizons between either an Ap horizon

or a depth of 25 cm from the mineral soil surface, whichever

is deeper, and either a depth of 75 cm or a densic, lithic, or

paralithic contact, whichever is shallower.

Cumulic Ultic Haploxerolls

IEFI. Other Haploxerolls that have:

1. A mollic epipedon that is 50 cm or more thick and has

a texture finer than loamy fine sand; and

2. An irregular decrease in organic-carbon content from a

depth of 25 cm below the mineral soil surface to a depth of

125 cm or to a densic, lithic, or paralithic contact if

shallower; and

3. A slope of less than 25 percent.

Cumulic Haploxerolls

IEFJ. Other Haploxerolls that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A slope of less than 25 percent; and either

a. An organic-carbon content of 0.3 percent or more in

all horizons within 125 cm of the mineral soil surface; or

b. An irregular decrease in organic-carbon content from

a depth of 25 cm to a depth of 125 cm or to a densic, lithic,

or paralithic contact if shallower.

Fluvaquentic Haploxerolls

IEFK. Other Haploxerolls that have both:

1. In one or more horizons within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage); and

2. A horizon, 15 cm or more thick within 100 cm of the

mineral soil surface, that either has 20 percent or more (by

volume) durinodes or is brittle and has a firm ruptureresistance class when moist.

Aquic Duric Haploxerolls

IEFL. Other Haploxerolls that have both:

1. In one or more horizons within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and

also aquic conditions for some time in normal years (or

artificial drainage); and

2. A base saturation (by sum of cations) of 75 percent or

less in one or more horizons between either an Ap horizon

or a depth of 25 cm from the mineral soil surface, whichever

is deeper, and either a depth of 75 cm or a densic, lithic, or

paralithic contact, whichever is shallower.

Aquultic Haploxerolls

IEFM. Other Haploxerolls that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Haploxerolls

IEFN. Other Haploxerolls that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haploxerolls

IEFO. Other Haploxerolls that have both:

1. A mollic epipedon that is 50 cm or more thick and has

a texture finer than loamy fine sand; and

2. A calcic horizon or identifiable secondary carbonates

within one of the following particle-size class (by weighted

average in the particle-size control section) and depth

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the

mineral soil surface; or
Mollisols 645

b. Clayey, clayey-skeletal, fine, or very-fine and within 90

cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil

surface.

Calcic Pachic Haploxerolls

IEFP. Other Haploxerolls that have both:

1. A mollic epipedon that is 50 cm or more thick and has

a texture finer than loamy fine sand; and

2. A base saturation (by sum of cations) of 75 percent or

less in one or more horizons between either an Ap horizon

or a depth of 25 cm from the mineral soil surface, whichever

is deeper, and either a depth of 75 cm or a densic, lithic, or

paralithic contact, whichever is shallower.

Pachic Ultic Haploxerolls

IEFQ. Other Haploxerolls that have a mollic epipedon that is

50 cm or more thick and has a texture finer than loamy fine

sand.

Pachic Haploxerolls

IEFR. Other Haploxerolls that have:

1. An aridic moisture regime; and

2. A slope of less than 25 percent; and either

a. An organic-carbon content of 0.3 percent or more in

all horizons within 125 cm of the mineral soil surface; or

b. An irregular decrease in organic-carbon content

from a depth of 25 cm to a depth of 125 cm or to a

densic, lithic, or paralithic contact if shallower.

Torrifluventic Haploxerolls

IEFS. Other Haploxerolls that have both:

1. An aridic moisture regime; and

2. A horizon within 100 cm of the mineral soil surface

that is 15 cm or more thick and either has 20 percent or

more (by volume) durinodes or is brittle and has a firm

rupture-resistance class when moist.

Duridic Haploxerolls

IEFT. Other Haploxerolls that have both:

1. An aridic moisture regime; and

2. A calcic horizon or identifiable secondary carbonates

within one of the following particle-size class (by weighted

average in the particle-size control section) and depth

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 90

cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil

surface.

Calcidic Haploxerolls

IEFU. Other Haploxerolls that have both:

1. An aridic moisture regime; and

2. A sandy particle-size class in all horizons within 100

cm of the mineral soil surface.

Torripsammentic Haploxerolls

IEFV. Other Haploxerolls that:

1. Have an aridic moisture regime; and

2. Either:

a. Do not have a cambic horizon and do not, in any part

of the mollic epipedon below 25 cm from the mineral soil

surface, meet all of the requirements for a cambic

horizon except color; or

b. Have free carbonates throughout the cambic horizon

or in all parts of the mollic epipedon below a depth of 25

cm from the mineral soil surface.

Torriorthentic Haploxerolls

IEFW. Other Haploxerolls that have an aridic moisture

regime.

Aridic Haploxerolls

IEFX. Other Haploxerolls that have a horizon within 100 cm

of the mineral soil surface that is 15 cm or more thick and

either has 20 percent or more (by volume) durinodes or is

brittle and has a firm rupture-resistance class when moist.

Duric Haploxerolls

IEFY. Other Haploxerolls that have a sandy particle-size

class in all horizons within 100 cm of the mineral soil surface.

Psammentic Haploxerolls

IEFZ. Other Haploxerolls that have a slope of less than 25

percent; and either

1. An organic-carbon content of 0.3 percent or more in all

horizons within 125 cm of the mineral soil surface; or

2. An irregular decrease in organic-carbon content from a

depth of 25 cm to a depth of 125 cm or to a densic, lithic, or

paralithic contact if shallower.

Fluventic Haploxerolls

IEFZa. Other Haploxerolls that have a mollic epipedon that has

granular structure and that has, below any Ap horizon, 50
646 Soil Taxonomy

percent or more (by volume) wormholes, wormcasts, or filled

animal burrows.

Vermic Haploxerolls

IEFZb. Other Haploxerolls that have a calcic horizon or

identifiable secondary carbonates within one of the following

particle-size class (by weighted average in the particle-size

control section) and depth combinations:

1. Sandy or sandy-skeletal and within 150 cm of the

mineral soil surface; or

2. Clayey, clayey-skeletal, fine, or very-fine and within 90

cm of the mineral soil surface; or

3. Any other class and within 110 cm of the mineral soil

surface.

Calcic Haploxerolls

IEFZc. Other Haploxerolls that:

1. Do not have a cambic horizon and do not, in the lower

part of the mollic epipedon, meet all of the requirements for

a cambic horizon except color; and

2. Have a base saturation (by sum of cations) of 75 percent

or less in one or more horizons between either an Ap

horizon or a depth of 25 cm from the mineral soil surface,

whichever is deeper, and either a depth of 75 cm or a densic,

lithic, or paralithic contact, whichever is shallower.

Entic Ultic Haploxerolls

IEFZd. Other Haploxerolls that have a base saturation (by

sum of cations) of 75 percent or less in one or more horizons

between either an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and either a depth of

75 cm or a densic, lithic, or paralithic contact, whichever is

shallower.

Ultic Haploxerolls

IEFZe. Other Haploxerolls that either:

1. Do not have a cambic horizon and do not, in any part of

the mollic epipedon below 25 cm from the mineral soil

surface, meet all of the requirements for a cambic horizon

except color; or

2. Have free carbonates throughout the cambic horizon or

in all parts of the mollic epipedon below a depth of 25 cm

from the mineral soil surface.

Entic Haploxerolls

IEFZf. Other Haploxerolls.

Typic Haploxerolls

Definition of Typic Haploxerolls

Typic Haploxerolls are the Haploxerolls that:

1. Do not have, in any horizon within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also aquic

conditions;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have a calcic horizon or identifiable secondary

carbonates within one of the following particle-size class (by

weighted average in the particle-size control section) and depth

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 90

cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil

surface;

4. Have a mollic epipedon that is less than 50 cm thick or has

a texture of loamy fine sand or coarser if it is 50 cm or more

thick;

5. Do not have a horizon within 100 cm of the mineral soil

surface that is more than 15 cm thick and that either has at

least 20 percent durinodes or is brittle and has a firm ruptureresistance class when moist;

6. Have a cambic horizon or, in the lower part of the

epipedon, meet all of the requirements for a cambic horizon,

except for the color requirments, and either the cambic horizon

or the lower part of the epipedon is free of carbonates in some

part;

7. Either have a regular decrease in organic-carbon content

with increasing depth and, unless a densic, lithic, or paralithic

contact is at some depth between 50 cm and 125 cm below the

soil surface, have an organic-carbon content of 0.3 percent or

less at a depth within 125 cm of the mineral soil surface or

have a slope of 25 percent or more;

8. Do not have a lithic contact within 50 cm of the soil

surface;

9. Have a base saturation (by sum of cations) of more than 75

percent in all horizons between either an Ap horizon or a depth

of 25 cm from the mineral soil surface, whichever is deeper,

and either a depth of 75 cm or a densic, lithic, or paralithic

contact, whichever is shallower;

10. Do not have a mollic epipedon that has granular structure

and that, below any Ap horizon, has 50 percent or more (by

volume) wormholes, wormcasts, or filled animal burrows;

11. Do not have either:
Mollisols 647

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

12. Have a xeric moisture regime;

13. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, one or more of the

following:

a. Fragments coarser than 2.0 mm constituting more than

35 percent of the whole soil and cinders, pumice, and

pumicelike fragments making up more than 66 percent of

these fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more; and

14. Do not have a sandy particle-size class throughout all

horizons within 100 cm of the mineral soil surface.

Description of Subgroups

Typic Haploxerolls.—The central concept or Typic

subgroup of Haploxerolls is fixed on freely drained soils that

have a xeric moisture regime and do not have aquic conditions

within 75 cm of the mineral soil surface. These soils have a

high base saturation, a moderately thick mollic epipedon, and a

regular decrease in organic-carbon content with increasing

depth. They do not have an accumulation of carbonates at a

shallow depth, and they do not show evidence of cementation

in the upper meter. They do not have slickensides, wedgeshaped aggregates, a high linear extensibility, or wide cracks in

normal years. Their cambic horizon is not calcareous in some

part, or the lower part of the mollic epipedon meets the

requirements for a cambic horizon and is not calcareous in

some part.

Shallow ground water or artificial drainage and redox

depletions with low chroma are properties of Aquolls and are

the basis for defining the Aquic and Oxyaquic subgroups. A

calcic horizon or identifiable secondary carbonates at a shallow

depth indicate an intergrade to Calcixerolls and are the basis

for defining Calcic and combination Calcic subgroups. A thick

mollic epipedon is the basis for defining Cumulic and Pachic

subgroups. The absence of both a cambic horizon and, in the

lower part of the epipedon, the properties of a cambic horizon,

except for color, or the presence of free carbonates throughout

these horizons is considered evidence of weak horizon

development and is the basis for defining Entic and

combination Entic subgroups. An irregular decrease in organiccarbon content with increasing depth and a relatively high

content of organic carbon in the deep layers are properties of

Fluvents and, in part, are the basis for defining the Fluventic

subgroup or, if the soil is saturated with water at some period,

the Fluvaquentic subgroup. A shallow lithic contact is the basis

for defining Lithic and combination Lithic subgroups. Low

base saturation is a property of Ultisols and is the basis for

defining the Ultic subgroup. Soils that have been intensively

and repeatedly mixed by animals, mainly by earthworms and

their predators, are classified in the Vermic subgroup. A clayey

texture, slickensides, wedge-shaped aggregates, a high linear

extensibility, and cracks are properties of Vertisols and are the

basis for defining the Vertic subgroup. An aridic moisture

regime is the basis for defining Aridic and Torric subgroups.

The Typic subgroup is one of the most extensive of the

subgroups of Haploxerolls and is extensive in parts of the

Western United States. Typic Haploxerolls are nearly level to

very steep. The native vegetation is dominantly grasses and

shrubs, but some of the soils support widely spaced trees,

mostly pine, oak, and juniper trees. Most of the soils that have

nearly level to moderate slopes are used as cropland, and some

of the nearly level and gently sloping cropland is irrigated.

Some of the soils, mostly those on the steeper slopes, are used

as rangeland.

Aquic Cumulic Haploxerolls.—These soils have redox

depletions with low chroma and either have moderately deep

ground water at some time of the year or are artificially

drained. They also have a thick mollic epipedon. These soils

developed in nearly level areas where they receive more

moisture than the amount that falls on the surface. The native

vegetation is dominantly grasses and shrubs, but some of the

soils support trees, mostly willow and cottonwood. The soils

are of very small extent in the Western United States. They are

used mostly as hayland or pasture, some of which is irrigated.

Aquic Duric Haploxerolls.—These soils have redox

depletions with low chroma and either have shallow ground

water at some time of the year or are artificially drained. Also,

they have a subhorizon within 100 cm of the mineral soil

surface that does not meet the requirements for a duripan but is

more than 15 cm thick and either has 20 percent or more (by

volume) durinodes in a matrix that is not brittle when wet or is

brittle when wet and has a firm rupture-resistance class when

moist. The native vegetation is dominantly grasses and shrubs.

These soils are rare in the United States.

Aquic Haploxerolls.—These soils have redox depletions

with low chroma and either have moderately deep ground

water at some time of the year or are artificially drained. They

are not required to have a cambic horizon, and secondary

carbonates, if present, may be shallower than those in the Typic
648 Soil Taxonomy

subgroup. Aquic Haploxerolls developed in nearly level areas

where they receive more moisture than the amount that falls on

the surface. The native vegetation is dominantly grasses and

shrubs, but some of the soils support trees, mostly pine, willow,

and cottonwood. The soils are of small extent in the Western

United States. They are used mostly as cropland or pasture,

some of which is irrigated.

Aquultic Haploxerolls.—These soils have redox depletions

with low chroma and either have shallow ground water at some

time of the year or are artificially drained. Also, they have a

base saturation of 75 percent or less in one or more horizons

between an Ap horizon or a depth of 25 cm from the mineral

soil surface, whichever is deeper, and a depth of 75 cm. They

are not required to have a cambic horizon. They are nearly

level or gently sloping. The native vegetation is mostly trees.

These soils are of small extent in the Western United States.

The steeper soils are used mainly as forest, and most of the

gently sloping soils have been cleared and are used as

cropland.

Aridic Haploxerolls.—These soils receive less moisture

than Typic Haploxerolls and have an aridic moisture regime.

Aridic Haploxerolls are extensive in the Western United States.

Slopes are nearly level to very steep. The native vegetation is

dominantly grasses and shrubs, and a few of the soils support

widely spaced trees, mostly juniper species. Most of the soils

that have nearly level or gentle slopes are used as cropland,

most of which is irrigated. Some of the soils, mostly the steeper

ones and those with many rock fragments, are used as

rangeland.

Calcic Haploxerolls.—These soils have a calcic horizon or

identifiable secondary carbonates at a moderate depth but are

otherwise like Typic Haploxerolls in their defined properties.

Calcic Haploxerolls are extensive in the Western United States.

Slopes range from nearly level to very steep. The native

vegetation is dominantly grasses and shrubs. Many of the

gently sloping soils are used as cropland, some of which is

irrigated. The steeper soils and the soils with many rock

fragments are used as rangeland.

Calcic Pachic Haploxerolls.—These soils have a calcic

horizon or identifiable secondary carbonates at a moderate

depth and have a mollic epipedon thicker than that of Typic

Haploxerolls. Calcic Pachic Haploxerolls are of moderate

extent in the Western United States. The native vegetation is

dominantly grasses and shrubs, and a few of the soils support

widely spaced trees, mostly oak, juniper, and pine species. The

soils have nearly level to very steep slopes. Many of the nearly

level to moderately sloping soils are used as cropland, some of

which is irrigated. The soils on the steeper slopes are used as

rangeland.

Calcidic Haploxerolls.—These soils have an aridic

moisture regime that borders on xeric. They also have a calcic

horizon or identifiable secondary carbonates at a shallow or

moderate depth. They are permitted, but not required, to have a

cambic horizon. These soils are extensive in parts of the

Western United States. The native vegetation is dominantly

grasses and shrubs, but some of the soils support trees, mostly

juniper and pine species. The soils have nearly level to very

steep slopes. Many of the less sloping soils are used as

cropland, much of which is irrigated. The soils on the steeper

slopes and those with many rock fragments are used as

rangeland or wildlife habitat.

Cumulic Haploxerolls.—These soils have a thick mollic

epipedon. They are on flood plains or in low areas on stream

terraces, or they are in concave areas where fresh sediments

accumulate slowly enough to become part of the mollic

epipedon. The organic-carbon content decreases irregularly

with increasing depth. These soils are permitted, but not

required, to have a cambic horizon or accumulations of

secondary carbonates at a shallow depth. They are moderately

extensive in parts of the Western United States. The native

vegetation is dominantly grasses and shrubs, but some of the

soils support trees, mostly willow and cottonwood. Most of the

soils are nearly level or gently sloping. Many of the larger

areas are used as cropland, much of which is irrigated. The

smaller areas and those dissected by stream channels are used

as rangeland, forest, or wildlife habitat.

Cumulic Ultic Haploxerolls.—These soils have a thick

mollic epipedon and have a base saturation of 75 percent or

less in one or more horizons between either an Ap horizon or a

depth of 25 cm from the mineral soil surface, whichever is

deeper, and a depth of 75 cm. The organic-carbon content

decreases irregularly with increasing depth. These soils are

permitted, but not required, to have a cambic horizon. They are

of small extent in the United States. The native vegetation is

mostly mixed forest. These soils are nearly level or gently

sloping. Most of the larger areas are used as cropland. The

smaller areas and those dissected by stream channels are used

as pasture, forest, or wildlife habitat.

Duric Haploxerolls.—These soils have a subhorizon within

100 cm of the mineral soil surface that does not meet the

requirements for a duripan but is more than 15 cm thick and

either has 20 percent or more (by volume) durinodes or is

brittle when wet and has a firm or very firm rupture-resistance

class when moist. The soils are otherwise like Typic

Haploxerolls. Duric Haploxerolls are not known to occur in the

United States.

Duridic Haploxerolls.—These soils have an aridic moisture

regime that borders on xeric and have a subhorizon within 100

cm of the mineral soil surface that does not meet the

requirements for a duripan but is more than 15 cm thick and

either has 20 percent or more (by volume) durinodes or is

brittle when wet and has a firm or very firm rupture-resistance

class when moist. These soils are not known to occur in the

United States.

Entic Haploxerolls.—These soils do not have a cambic

horizon, and either the epipedon is calcareous or the lower part

of the epipedon is too sandy to be a cambic horizon. Some of

these soils are very shallow to a paralithic or densic contact
Mollisols 649

and have only thin soil horizons. Entic Haploxerolls are of small

extent in the Western United States. The native vegetation is

dominantly grasses and shrubs, and a few of the soils support

widely spaced trees, mostly oak, juniper, or pine species. Slopes

range from nearly level to very steep. The soils are used mostly

as rangeland or wildlife habitat, but some of the soils with nearly

level to moderate slopes are used as cropland, most of which is

irrigated.

Entic Ultic Haploxerolls.—These soils do not have a

cambic horizon, and their base saturation is 75 percent or less

in one or more horizons between an Ap horizon or a depth of

25 cm from the mineral soil surface, whichever is deeper, and a

depth of 75 cm. These soils are of small extent in the United

States. The native vegetation is forest on some of the soils and

grasses and shrubs on others. Slopes range from nearly level to

very steep. The soils are used mostly as forest, rangeland, or

wildlife habitat. Some of the soils with nearly level to moderate

slopes are used as cropland, most of which is irrigated.

Fluvaquentic Haploxerolls.—These soils have redox

depletions with low chroma and either have shallow ground

water at some time of the year or are artificially drained. Their

organic-carbon content either decreases irregularly with

increasing depth or remains relatively high as depth increases.

The soils are not required to have a cambic horizon. They

developed on nearly level flood plains where they receive more

moisture than the amount that falls on the surface. The native

vegetation is dominantly grasses and shrubs, but some of the

soils support trees, mostly willow and cottonwood.

Fluvaquentic Haploxerolls are of small extent in the Western

United States. They are used mostly as cropland, hayland, or

pasture, some of which is irrigated. Some small areas and areas

that are dissected by stream channels or are subject to frequent

flooding are used as pasture, rangeland, or wildlife habitat.

Fluventic Haploxerolls.—These soils have an organiccarbon content that decreases irregularly with increasing depth

or remains high as depth increases. They are permitted, but not

required, to have a cambic horizon or to have secondary

carbonates at a depth shallower than in soils of the Typic

subgroup. Fluventic Haploxerolls are on nearly level flood

plains, formed mainly in loamy alluvium, and commonly are

stratified as a result of frequent flooding. They are of small

extent in the Western United States. They generally are nearly

level. The native vegetation is dominantly grasses and shrubs,

but some of the soils support trees, mostly pine, oak, and

cottonwood. The soils are used mostly as cropland, hayland, or

pasture, much of which is irrigated. Some small areas and

areas that are dissected by stream channels or are subject to

frequent flooding are used as pasture, rangeland, or wildlife

habitat.

Lithic Haploxerolls.—These soils have a shallow lithic

contact. The mollic epipedon commonly extends to bedrock. In

some of the soils, a cambic horizon intervenes. Lithic

Haploxerolls are extensive in the Western United States. The

native vegetation is dominantly grasses and shrubs, and some

of the soils support widely spaced trees, mostly pine, juniper,

and oak. Slopes are nearly level to very steep. Most of the soils

are used as rangeland or grazeable forest.

Lithic Ultic Haploxerolls.—These soils have a shallow lithic

contact, and their base saturation is 75 percent or less in some

part of the soils above the lithic contact. These soils are

moderately extensive in the United States. The native

vegetation is forest on some of the soils and grasses and shrubs

on others. Slopes range from nearly level to very steep. Most of

the soils are used as grazeable forest or rangeland.

Oxyaquic Haploxerolls.—These soils are like Typic

Haploxerolls, but they are saturated with water within 100 cm

of the mineral soil surface for 20 or more consecutive days or

30 or more cumulative days in normal years. These soils are of

small extent in the United States. Slopes are nearly level or

gently sloping. The native vegetation is dominantly grasses and

shrubs, but some of the soils support trees, mostly willow and

cottonwood. The soils are used mostly as cropland, hayland, or

pasture, much of which is irrigated. Some of the soils are used

as pasture, rangeland, or wildlife habitat.

Pachic Haploxerolls.—These soils are similar to Typic

Haploxerolls, but they have a thicker mollic epipedon. They are

extensive in parts of the Western United States. Slopes are

nearly level to very steep. The native vegetation is dominantly

grasses and shrubs, but some of the soils support widely spaced

trees, mostly oak or juniper. Many of the less sloping soils are

used as cropland, some of which is irrigated. The steeper soils

and those with many rock fragments are used as rangeland or

wildlife habitat.

Pachic Ultic Haploxerolls.—These soils have a mollic

epipedon that is thicker than that in soils of the Typic

subgroup, and they have a base saturation of 75 percent or less

in one or more horizons between an Ap horizon or a depth of

25 cm from the mineral soil surface, whichever is deeper, and a

depth of 75 cm. Pachic Ultic Haploxerolls are moderately

extensive in the Western United States. They range from nearly

level to very steep. The native vegetation is grasses and shrubs

on some of the soils and forest on others. Many of the less

sloping soils are used as cropland, some of which is irrigated.

The steeper soils and those with many rock fragments are used

mainly as rangeland, forest, or wildlife habitat.

Psammentic Haploxerolls.—These soils have a sandy

particle-size class. Because they are sandy, they do not have a

cambic horizon. They are of small extent in the United States.

The native vegetation is dominantly grasses and shrubs, and a

few of the soils support widely spaced trees, mostly oak,

juniper, and pine species. Slopes generally are moderate or

gentle, and most of the soils are used as rangeland. Some

nearly level or gently sloping soils are used as irrigated

cropland, hayland, or pasture.

Torrertic Haploxerolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in
650 Soil Taxonomy

normal years have deep cracks. They also have an aridic

moisture regime that borders on xeric. They are not known to

occur in the United States.

Torrifluventic Haploxerolls.—These soils have an aridic

moisture regime that borders on xeric and formed in alluvium that

is recent enough for the content of organic carbon to decrease

irregularly with increasing depth or to remain high as depth

increases. These soils are of small extent in the Western United

States. The native vegetation is dominantly grasses and shrubs,

but some of the soils support widely spaced trees. Most of the

larger areas are used as irrigated cropland or pasture. Some of

the smaller areas and those dissected by stream channels are

used as rangeland or wildlife habitat.

Torriorthentic Haploxerolls.—These soils have an aridic

moisture regime that borders on xeric and do not have a

cambic horizon. They are of small extent in the Western United

States. The native vegetation is dominantly grasses and shrubs,

and a few of the soils support widely spaced trees, mostly

juniper and pine species. Slopes are nearly level to very steep.

Most of the soils are used as rangeland or grazeable forest.

Torripsammentic Haploxerolls.—These soils have a sandy

particle-size class and have an aridic moisture regime that

borders on xeric. Because they are sandy, they do not have a

cambic horizon. They are of small extent in the Western United

States. The native vegetation is dominantly grasses and shrubs,

but some of the soils support trees, mostly juniper and pine

species. Slopes are nearly level to very steep. Most of the soils

are used as rangeland or grazeable forest. Some that are nearly

level or gently sloping are used as irrigated cropland.

Ultic Haploxerolls.—These soils have a lower degree of

base saturation than Typic Haploxerolls. Many Ultic

Haploxerolls receive more precipitation than the Typic

Haploxerolls. The native vegetation is grasses and shrubs on

some of the soils and forest on others. Some of the soils support

widely spaced trees, mostly oak or juniper. Ultic Haploxerolls

are extensive in the Western United States. Many of the less

sloping soils are used as cropland. The steeper soils and those

with many rock fragments are used mainly as rangeland,

forest, or wildlife habitat.

Vermic Haploxerolls.—These soils have a mollic epipedon

that has granular structure. The most common horizon

sequence is a mollic epipedon consisting of many wormcasts

overlying a horizon containing many worm channels filled

with dark soil from the mollic epipedon. These soils have not

been identified in the United States. The subgroup is provided

for use elsewhere.

Vertic Haploxerolls.—These soils have a clayey particlesize class in a significant part, have expanding clays, and in

normal years have deep cracks. The native vegetation is mostly

grasses and forbs on most of the soils but is forest or widely

spaced trees on others. Vertic Haploxerolls are of small extent

in the Western United States. Many of the less sloping soils are

used as cropland, some of which is irrigated. The steeper soils

are used mostly as rangeland, forest, or wildlife habitat.

Vitrandic Haploxerolls.—These soils have a surface

mantle or layer in the upper 75 cm that consists of slightly or

moderately weathered pyroclastic materials. They are of large

extent, mostly in Washington, Oregon, and Idaho in the

Western United States. The vegetation is either mostly grass

and shrubs or coniferous forest. Some of the soils support

widely spaced trees. Slopes range from nearly level to very

steep. Many of the less sloping soils are used as cropland.

Most of the others are used as rangeland, forest, or wildlife

habitat.

Vitritorrandic Haploxerolls.—These soils have an aridic

moisture regime that borders on xeric and have a surface

mantle or layer in the upper 75 cm that consists of slightly or

moderately weathered pyroclastic materials. These soils are

moderately extensive, mostly in Oregon, Nevada, and

Washington in the Western United States. The vegetation is

mostly grass and shrubs, but some of the soils support trees,

mostly juniper species. Slopes range from nearly level to very

steep. Many of the less sloping soils are used as cropland,

much of which is irrigated. The steeper soils and those with

many rock fragments are used mainly as rangeland or wildlife

habitat.

Natrixerolls

These are the Xerolls that have a natric horizon and do not

have a duripan. The natric horizon commonly has either

prismatic or columnar structure, and there is a Bk horizon in

or below the natric horizon. Some of the soils have a thin albic

horizon above the natric horizon. The areas of Natrixerolls are

mostly small. These soils formed mostly in mixed sediments of

late-Pleistocene age, commonly in depressions, in basins, or on

low terraces.

Definition

Natrixerolls are the Xerolls that:

1. Have a natric horizon; and

2. Do not have a duripan that has its upper boundary within

100 cm of the mineral soil surface.

Key to Subgroups

IEBA. Natrixerolls that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Natrixerolls
Mollisols 651

IEBB. Other Natrixerolls that have both:

1. In one or more horizons within 75 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage); and

2. A horizon, 15 cm or more thick within 100 cm of the

mineral soil surface, that either has 20 percent or more (by

volume) durinodes or is brittle and has a firm ruptureresistance class when moist.

Aquic Duric Natrixerolls

IEBC. Other Natrixerolls that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Natrixerolls

IEBD. Other Natrixerolls that have an aridic moisture

regime.

Aridic Natrixerolls

IEBE. Other Natrixerolls that have a horizon within 100 cm

of the mineral soil surface that is 15 cm or more thick and

either has 20 percent or more (by volume) durinodes or is

brittle and has a firm rupture-resistance class when moist.

Duric Natrixerolls

IEBF. Other Natrixerolls.

Typic Natrixerolls

Definition of Typic Natrixerolls

Typic Natrixerolls are the Natrixerolls that:

1. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

2. Do not have a horizon within 100 cm of the mineral soil

surface that is more than 15 cm thick and that either has at

least 20 percent durinodes or is brittle and has a firm ruptureresistance class when moist;

3. Have a xeric moisture regime; and

4. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Natrixerolls.—The central concept or Typic

subgroup of Natrixerolls is fixed on soils that have a xeric

moisture regime, that do not have redox depletions with low

chroma in the upper 75 cm accompanied by ground water at a

shallow depth, and do not have slickensides, wedge-shaped

aggregates, a high linear extensibility, and wide cracks in

normal years.

Shallow ground water or artificial drainage and redox

depletions with low chroma are properties of Aquolls and are

the basis for defining the Aquic subgroup. A brittle horizon

and the presence of durinodes indicate an intergrade to

Durixerolls and are the basis for defining Duric and

combination Duric subgroups. An aridic moisture regime is

used, in part, as the basis for defining the Aridic subgroup. A

clayey texture, slickensides, wedge-shaped aggregates, a high

linear extensibility, and cracks are properties of Vertisols and

are the basis for defining the Vertic subgroup.

The Typic subgroup is the most extensive subgroup of

Natrixerolls, but it is of small extent in the Western United

States. The native vegetation is mostly grasses and shrubs.

Slopes generally are gentle but range from nearly level to steep.

Most of the less sloping soils are used as irrigated cropland or

pasture, and the other soils are used mainly as rangeland or

wildlife habitat.

Aquic Duric Natrixerolls.—These soils have redox

depletions with low chroma and either are saturated with water

at some time of the year or have artificial drainage. In addition,

they have a subhorizon within 100 cm of the surface that does

not meet the requirements for a duripan but is more than 15 cm

thick and either has 20 percent or more (by volume) durinodes

or is brittle when wet and has a firm rupture-resistance class

when moist. These soils are not known to occur in the United

States.

Aquic Natrixerolls.—These soils have redox depletions

with low chroma and either are saturated with water at some

time of the year or have artificial drainage. They developed

mostly on nearly level valley or marine terraces. They are of

very small extent in the Western United States. The native

vegetation is mostly grasses and shrubs. Most of the soils are

used as irrigated cropland or pasture, and the others are used

mainly as rangeland or wildlife habitat.

Aridic Natrixerolls.—These soils are like Typic

Natrixerolls, but they receive less moisture. They are not

known to occur in the United States.

Duric Natrixerolls.—These soils have a subhorizon within

100 cm of the surface that does not meet the requirements for a

duripan but is more than 15 cm thick and either has 20 percent

or more (by volume) durinodes or is brittle when wet and has a

firm rupture-resistance class when moist. These soils are not

known to occur in the United States.

Vertic Natrixerolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. They occur in California
652 Soil Taxonomy

and in other Western States. They commonly are used as

rangeland.

Palexerolls

These are the Xerolls that formed on old surfaces, commonly

on basalt plains of Miocene or Pliocene age that later, during or

after the late Pleistocene, received a thin covering of loess or of

mixed loess and ash. Slopes range

from nearly level to very steep. The soils commonly have a

thick, dark brown or reddish brown, clayey argillic horizon

that has an abrupt upper boundary, or they have a petrocalcic

horizon. A calcic or Bk horizon is common in the lower part

of the argillic horizon or below it. The native vegetation was

mainly bunchgrasses and some shrubs. Some of the soils

supported a coniferous forest with an understory of grasses and

shrubs or supported an open forest or savanna. Palexerolls

occur in parts of the Western United States, but they are not

extensive.

Definition

Palexerolls are the Xerolls that:

1. Have a petrocalcic horizon that has its upper boundary

within 150 cm of the soil surface or have an argillic horizon

that has one or both of the following characteristics:

a. A vertical clay distribution in which the clay content

does not decrease by as much as 20 percent from the

maximum clay content within a vertical distance of 150 cm

below the soil surface and one or more of the following:

(1) Hue redder than 10YR and chroma greater than 4

dominant in the matrix of at least the lower part of the

argillic horizon; or

(2) Common redox concentrations that have hue

of 7.5YR or redder or chroma greater than 5, or both;

or

b. 35 percent or more clay and an increase of at least 20

percent clay (absolute) within a vertical distance of 7.5 cm

or of 15 percent clay (absolute) within a distance of 2.5 cm

at the upper boundary (and there is no densic, lithic, or

paralithic contact within 50 cm of the mineral soil surface);

2. Do not have a natric horizon; and

3. Do not have a duripan that has its upper boundary

within 100 cm of the soil surface.

Key to Subgroups

IECA. Palexerolls that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Palexerolls

IECB. Other Palexerolls that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Palexerolls

IECC. Other Palexerolls that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Palexerolls

IECD. Other Palexerolls that have a mollic epipedon that is

50 cm or more thick and has a texture finer than loamy fine

sand.

Pachic Palexerolls

IECE. Other Palexerolls that have both:

1. An aridic moisture regime; and

2. A petrocalcic horizon that has its upper boundary

within 150 cm of the mineral soil surface.

Petrocalcidic Palexerolls

IECF. Other Palexerolls that have a horizon, 15 cm or more

thick within 100 cm of the mineral soil surface, that either has

20 percent or more (by volume) durinodes or is brittle and has

a firm rupture-resistance class when moist.

Duric Palexerolls

IECG. Other Palexerolls that have an aridic moisture regime.

Aridic Palexerolls
Mollisols 653

IECH. Other Palexerolls that have a petrocalcic horizon that

has its upper boundary within 150 cm of the mineral soil

surface.

Petrocalcic Palexerolls

IECI. Other Palexerolls that have a base saturation of 75

percent or less in one or more subhorizons either within the

argillic horizon if more than 50 cm thick or within its upper 50

cm.

Ultic Palexerolls

IECJ. Other Palexerolls that have an argillic horizon that has

either:

1. Less than 35 percent clay in the upper part; or

2. At its upper boundary, a clay increase that is both less

than 20 percent (absolute) within a vertical distance of 7.5

cm and less than 15 percent (absolute) within a vertical

distance of 2.5 cm, in the fine-earth fraction.

Haplic Palexerolls

IECK. Other Palexerolls.

Typic Palexerolls

Definition of Typic Palexerolls

Typic Palexerolls are the Palexerolls that:

1. Have an argillic horizon that has 35 percent or more clay

in the upper part and an increase in clay content of 20 percent

(absolute) or more within a vertical distance of 7.5 cm or of 15

percent (absolute) or more within a distance of 2.5 cm at the

upper boundary;

2. Do not have, in any horizon within 75 cm of the mineral

soil surface, redox depletions with chroma of 2 or less and also

aquic conditions;

3. Do not have a petrocalcic horizon that has its upper

boundary within 150 cm of the soil surface;

4. Have a mollic epipedon that is less than 50 cm thick or has

a texture of loamy fine sand or coarser if it is more than 50 cm

thick;

5. Have a base saturation of more than 75 percent throughout

the argillic horizon or in the upper 50 cm of the argillic

horizon, whichever is thinner;

6. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower;

7. Do not have a horizon, 15 cm or more thick within 100 cm of

the mineral soil surface, that either has 20 percent or more (by

volume) durinodes or is brittle and has a firm rupture-resistance

class when moist;

8. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more; and

9. Have a xeric moisture regime.

Description of Subgroups

Typic Palexerolls.—The central concept or Typic subgroup

of Palexerolls is fixed on deep, freely drained soils that have a

clayey argillic horizon that has an abrupt upper boundary.

These soils have a moderately thick mollic epipedon, a high

base saturation, and a xeric moisture regime. They do not have

a petrocalcic horizon that has its upper boundary within 150

cm of the soil surface.

A petrocalcic horizon is the basis for defining the

Petrocalcic subgroup. A thick mollic epipedon is the basis for

defining the Pachic subgroup. A base saturation that is less

than normal is the basis for defining the Ultic subgroup.

The Typic subgroup is the most extensive subgroup of

Palexerolls. It is moderately extensive in parts of the Western

United States. The native vegetation is dominantly grasses and

shrubs. Some of the soils support widely spaced trees, mostly

oak and juniper species. Most of the soils are used as

rangeland. Some that have nearly level to moderate slopes are

used as cropland, and some of the nearly level and gently

sloping cropland is irrigated. Most of the soils on the steeper

slopes are used as rangeland.

Aquic Palexerolls.—These soils have redox depletions with

low chroma and either have shallow ground water at some time

of the year or are artificially drained. They developed in nearly

level or gently sloping areas where they receive more moisture

than the amount that falls on the surface. The native vegetation

is dominantly grasses and shrubs, but some of the soils support

trees, mostly oak species. The soils are of very small extent in

the Western United States. They are used mostly as cropland or

pasture, some of which is irrigated.
654

Aridic Palexerolls.—These soils have an aridic moisture

regime that borders on xeric, but they otherwise are like Typic

Palexerolls in their defined properties. They are of small extent

in the Western United States. Slopes are nearly level to very

steep. The native vegetation is dominantly grasses and shrubs,

and a few of the soils support widely spaced trees, mostly

juniper species. Most of the soils are used as rangeland. A few

that have nearly level or gentle slopes are used as irrigated

cropland or pasture.

Duric Palexerolls.—These soils have a horizon, 15 cm or

more thick within 100 cm of the mineral soil surface, that

either has 20 percent or more (by volume) durinodes or is

brittle and has a firm rupture-resistance class when moist. The

soils do not have a high shrink-swell potential; significant

amounts of volcanic ash, cinders, or glass near the surface; a

thick mollic epipedon; a petrocalcic horizon; or aquic

conditions within 75 cm of the mineral soil surface. These soils

occur in Oregon and are used for grazing by livestock.

Haplic Palexerolls.—These soils are similar to Typic

Palexerolls, but they do not have a clayey argillic horizon that

has an abrupt upper boundary. They are not known to occur in

the United States.

Pachic Palexerolls.—These soils have a thick mollic

epipedon. They are of small extent in the Western United

States. Slopes range from nearly level to very steep. The native

vegetation is grasses and shrubs on most of the soils, but some

of the soils support coniferous forest or savanna with widely

spaced trees, mostly juniper. Most of the soils are used as

rangeland. Some are used as grazeable woodland, and a few

that have nearly level or gentle slopes are used as cropland or

pasture, some of which is irrigated.

Petrocalcic Palexerolls.—These soils have a petrocalcic

horizon that generally has its upper boundary within 150 cm of

the soil surface. The argillic horizon that overlies the calcic

horizon commonly is calcareous in the lower part. These soils

are of small extent in the Western United States. The native

vegetation is dominantly a sparse forest of juniper and pine

trees interspersed with grasses and shrubs. Slopes are nearly

level to steep. Most of the soils are used as rangeland. Some are

used as grazeable woodland, and a few that have nearly level or

gentle slopes are used as irrigated cropland or pasture.

Petrocalcidic Palexerolls.—These soils have an aridic

moisture regime that borders on xeric and have a petrocalcic

horizon. The petrocalcic horizon commonly is shallower than

75 cm and, in some of the soils, it is less than 50 cm below the

surface. Petrocalcidic Palexerolls are of small extent in the

Western United States. The native vegetation is dominantly a

sparse forest of juniper and pine trees interspersed with grasses

and shrubs. Slopes are nearly level to steep. Most of the soils

are used as rangeland. Some are used as grazeable woodland,

and a few that have nearly level or gentle slopes are used as

irrigated cropland or pasture.

Ultic Palexerolls.—These soils have a lower degree of base

saturation than Typic Palexerolls. Many Ultic Palexerolls

receive more precipitation than the Typic Palexerolls. The

native vegetation is forest on some Ultic Palexerolls and

grasses and shrubs on others. Some of the soils support widely

spaced trees, mostly oak or juniper. The soils are of small

extent in the Western United States. Slopes are nearly level to

very steep. Some of the soils in the less sloping areas are used

as cropland. The steeper soils and those with many rock

fragments are used mainly as forest, rangeland, or wildlife

habitat.

Vertic Palexerolls.—These soils have a clayey particle-size

class in a significant part, have expanding clays, and in normal

years have deep cracks. The native vegetation is mostly

grasses, shrubs, and forbs. These soils are of small extent in the

Western United States. Most of the soils are used as rangeland.

Some of the less sloping soils are used as cropland or pasture,

some of which is irrigated.

Vitrandic Palexerolls.—These soils have significant

amounts of vocanic ash, cinders, or glass in one or more layers

18 cm or more thick within 75 cm of the mineral soil surface.

They do not have a high shrink-swell potential. These soils

occur in Oregon. They are used for timber production or for

grazing by livestock.
655

Oxisols are weathered soils that are low in fertility. Theyare most common on the gentle slopes of geologically

old surfaces in tropical and subtropical regions. Their profiles

are distinctive because of a lack of obvious horizons. Their

surface horizons are normally somewhat darker than the

subsoil, but the transition of subsoil features is gradual.

Oxisols consist mainly of quartz, kaolinite, oxides, and

organic matter. Both the structure and “feel” of Oxisols are

deceptive. Upon first examination, they appear structureless

and have the feel of a loamy texture. While some are loamy or

even coarser textured, many have a fine or very-fine particlesize class, but the clay is aggregated in a strong grade of fine

and very fine granular structure. To obtain a true “feel” of the

texture, a wet sample must be worked for several minutes in

the hands to break down the aggregates. The strong granular

structure apparently causes most Oxisols to have a much more

rapid permeability than would be predicted, given the particlesize class. Although compaction and reduction in permeability

can be caused by cultivation, the soils are extremely resistant to

compaction and are so free draining that cultivation can take

place soon after rain without puddling.

Oxisols occur in every soil moisture regime from aridic to

perudic and aquic. The natural vegetation ranges from tropical

rain forests to desert savannas. The lack of a unifying climatic

factor throughout their geographic distribution indicates that

climatic changes have taken place since these soils formed or

that highly weathered parent material has been transported to

areas with a dry climate. As part of the definition, the soils are

limited to a very low cation-exchange capacity and very few

weatherable minerals. They occur over many kinds of geologic

bedrock. Close examination, commonly to a great depth,

however, shows evidence that the material in which the soils

formed has been transported. Where the material clearly is not

transported, formation is most common in mafic rock.

Although many Oxisols are extremely infertile, some have

small but adequate supplies of nutrients and are immediately

productive when cultivated. The reserves of plant nutrients

even in the most fertile Oxisols are not great, and, to sustain

high yields, fertilizer and lime are needed after only a few

years of cultivation. In most of the Oxisols, fertilizers are

needed for the first crop unless the soils are fertile enough for

one or two crops because of the ash derived from burning the

natural vegetation. Phosphorus generally is the most restricted

plant nutrient, mainly because of the tendency of the clay- and

oxide-rich surface horizon to fix large amounts of fertilizer

phosphorus in an unavailable form. Once this tendency to fix

the phosphate has been overcome by an initial application,

however, there is no further fixation problem and annual

fertilizer rates are no higher than those for other soils. Because

of the initial expense of fertilization, Oxisols are cultivated

extensively only where modern agronomic techniques are

sustainable by an infrastructure of agribusiness. Under

primitive, shifting cultivation, the soils are used only if they

naturally support a large biomass, which can yield a large

volume of ash upon burning.

Road building and other engineering practices are relatively

easy in most Oxisols because of the physical stability of the

clay. There is little silt in most Oxisols; thus, the soils hold

little water that is available to plants. The content of organic

matter is commonly much higher than is indicated by the soil

color, which may result from red staining of the associated iron

oxides. The organic matter is very stable, infertile humus and

is slow to decompose in many of these soils.

The most extensive areas of Oxisols are on the interior

plateaus of South America, the lower portion of the Amazon

basin, significant portions of the central African basin, and

important areas in Asia, Australia, and several tropical and

subtropical islands. Oxisols are of small extent in the United

States, and many of the taxa are not known to occur in the

country. Because many of the taxa occur only outside the

United States, less is known about the vegetation, extent, and

use of these taxa. The descriptions of many of the subgroups in

this chapter are necessarily brief.

Definition of Oxisols and Limits Between

Oxisols and Soils of Other Orders

Oxisols are mineral soils that:

1. Meet one of these two requirements:

a. Have, within 150 cm of the mineral soil surface, the

upper boundary of an oxic horizon and no kandic horizon;

or

b. Have 40 percent or more (by weight) clay in the fineCHAPTER 17

Oxisols1

1 This chapter was rewritten in 1987 following recommendations of the International

Committee on the Classification of Oxisols (ICOMOX), chaired by Hari Eswaran from 1978 to

1981 and then by S.W. Buol until completion of the task in 1987.
656 Soil Taxonomy

earth fraction between the mineral soil surface and a depth

of 18 cm, after mixing, and a kandic horizon that meets the

weatherable mineral requirements of an oxic horizon and

that has its upper boundary within 150 cm of the mineral

soil surface; and

2. Do not have either of the following:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface; and

3. Do not have, above the oxic or kandic horizon, one or

more of the following:

a. A spodic horizon and an albic horizon in 50 percent or

more of each pedon and a cryic or pergelic soil temperature

regime; or

b. An Ap horizon containing 85 percent or more spodic

materials; or

c. A spodic horizon with all of the following

characteristics:

(1) One or more of the following:

(a) A thickness of 10 cm or more; or

(b) An overlying Ap horizon; or

(c) Cementation in 50 percent or more of each

pedon; or

(d) A coarse-loamy, loamy-skeletal, or finer particlesize class and a frigid temperature regime; or

(e) A cryic or pergelic temperature regime; and

(2) An upper boundary within the following depths

from the mineral soil surface: either

(a) Less than 50 cm; or

(b) Any depth above the kandic or oxic horizon if

the soil has a sandy particle-size class in at least some

part between the mineral soil surface and the spodic

horizon; and

(3) A lower boundary as follows:

(a) Either at a depth of 25 cm or more below the

mineral soil surface, or at the top of a duripan or

fragipan, or at a densic, lithic, paralithic, or

petroferric contact, whichever is shallowest; or

(b) At any depth,

1) If the spodic horizon has a coarse-loamy,

loamy-skeletal, or finer particle-size class and the

soil has a frigid temperature regime; or

2) If the soil has a cryic or pergelic temperature

regime; and

4. Do not have andic soil properties in 60 percent or more of

the thickness between either the mineral soil surface or the top

of an organic layer with andic soil properties, whichever is

shallower, and either a depth of 60 cm from the shallower of

the above or a densic, lithic, or paralithic contact, a duripan, or

a petrocalcic horizon if shallower than 60 cm.

Limits Between Oxisols and the Other Soil Orders

The definition of Oxisols must provide criteria that separate

Oxisols from soils of all other orders. The aggregate of these

criteria defines the limits of Oxisols in relation to all other

known kinds of soil.

1. Unlike Alfisols, Aridisols, Entisols, Inceptisols, Mollisols,

Ultisols, and Vertisols, Oxisols must have one of the following

characteristics:

a. An oxic horizon and no kandic horizon within 150 cm

of the mineral soil surface; or

b. A kandic horizon that meets the weatherable mineral

requirements of an oxic horizon that has its upper boundary

within 150 cm of the mineral soil surface; and 40 percent or

more (by weight) clay in the fine-earth fraction between the

mineral soil surface and a depth of 18 cm after mixing.

2. Unlike Andisols, Oxisols must not have andic soil

properties in 60 percent or more of the thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and either a

depth of 60 cm from the shallower of the above or a densic,

lithic, or paralithic contact, a duripan, or a petrocalcic horizon

if shallower than 60 cm.

3. Unlike Gelisols, Oxisols do not have:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface.

4. Unlike Histosols, Oxisols do not have organic soil

materials that meet one or more of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices and directly below these

materials have a densic, lithic, or paralithic contact; or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more in normal

years (or are artificially drained), have an upper boundary
Oxisols 657

within 40 cm of the soil surface, and have a total thickness

of either:

(1) 60 cm or more if three-fourths or more of their volume

consists of moss fibers or if their bulk density, moist, is

less than 0.1 g/cm3

; or

(2) 40 cm or more if they consist either of sapric or hemic

materials, or of fibric materials with less than three-fourths

(by volume) moss fibers and a bulk density, moist, of 0.1 g/

cm3 or more.

5. Unlike Spodosols, Oxisols must not have an Ap horizon

consisting of spodic materials or a spodic horizon above a

kandic horizon and must not have one or more of the

following:

a. An albic horizon in 50 percent or more of each pedon

and a cryic soil temperature regime; or

b. A spodic horizon with all of the following

characteristics:

(1) One or more of the following:

(a) A thickness of 10 cm or more; or

(b) An overlying Ap horizon; or

(c) Cementation in 50 percent or more of each

pedon; or

(d) A coarse-loamy, loamy-skeletal, or finer particlesize class and a frigid temperature regime; or

(e) A cryic temperature regime; and

(2) An upper boundary within the following depths

from the mineral soil surface: either

(a) Less than 50 cm; or

(b) Less than 200 cm if the soil has a sandy particlesize class between the mineral soil surface and the

spodic horizon; and

(3) A lower boundary as follows:

(a) Either at a depth of 25 cm or more below the

mineral soil surface, or at the top of a duripan or

fragipan, or at a densic, lithic, paralithic, or

petroferric contact, whichever is shallowest; or

(b) At any depth if the spodic horizon has a coarseloamy, loamy-skeletal, or finer particle-size class and

the soil has a frigid temperature regime, or if the soil

has a cryic temperature regime.

Representative Pedon and Data

Following is a description of a representative Oxisol. Data

for the pedon identified in this description are given in the

table “Characterization Data for an Oxisol.”

Classification: Fine, kaolinitic, isohyperthermic Aeric Haplaquox

Site identification number: 85P0741

Location: Brazil; main road to CPAC/EMBRAPA, 3 km from

Br-41 (1.4 km after headquarters), approximately 300 m to

the right

Latitude: 15 degrees 35 minutes 30 seconds S.

Longitude: 47 degrees 43 minutes 10 seconds W.

Slope: 5 percent

Elevation: 950 m above m.s.l.

Soil moisture regime: Aquic

Drainage class: Poorly drained

Diagnostic horizons: An ochric epipedon from a depth of

0 to 30 cm and an oxic horizon from a depth of 30 to

180 cm

In the following pedon description, colors are for moist soil

unless otherwise indicated.

Ap—0 to 18 cm; dark gray (10YR 4/1) clay, dark gray (10YR

4/1) dry; common fine redox concentrations; moderate fine

and medium granular structure; hard, firm, sticky and

plastic; common fine roots; many very fine and fine

tubular pores; yellowish red (5YR 5/8) oxides along roots;

clear smooth boundary.

A—18 to 30 cm; dark gray (10YR 4/1) clay, gray (10YR 5/1)

dry; common fine prominent redox concentrations; weak

fine granular structure parting to weak fine subangular

blocky; very hard, very firm, sticky and plastic; common

fine roots; common very fine and fine tubular pores; abrupt

wavy boundary.

BAg—30 to 38 cm; pale yellow (5Y 8/3) clay, light gray

(10YR 7/1) dry; common fine prominent redox

concentrations; weak fine and medium subangular blocky

structure; slightly hard, firm, sticky and plastic; few roots;

clear wavy boundary.

Bg1—38 to 70 cm; pale yellow (5Y 8/3) clay, white (10YR

8/1) dry; common fine prominent redox concentrations;

weak fine and medium subangular blocky structure;

slightly hard, friable, sticky and plastic; few roots; gradual

wavy boundary.

Bg2—70 to 110 cm; white (5Y 8/2) clay, white (10YR 8/1)

dry; few fine and medium prominent redox concentrations;

weak fine and medium subangular blocky structure; hard,

firm, sticky and plastic; clear wavy boundary.

BCg—110 to 180 cm; pinkish white (5YR 8/2) clay, white

(10YR 8/2) dry; common medium and coarse prominent

redox concentrations; moderate medium and thick platy

structure parting to weak fine and medium angular and

subangular blocky; hard, firm, sticky and plastic; gradual

wavy boundary.

Cg—180 to 220 cm; pale yellow (5Y 7/4 and 2.5Y 7/4) clay;

white (5Y 8/1) to reddish yellow (7.5YR 6/8) redox

depletions and concentrations; wet soil compacted by

auger.
658 Soil Taxonomy

Characterization Data for an Oxisol

 SITE IDENTIFICATION NO.: 85P0741

 CLASSIFICATION: FINE, KAOLINITIC, ISOHYPERTHERMIC AERIC HAPLAQUOX

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 85P3892 0- 18 Ap 53.9 21.1 25.0 40.5 10.1 11.0 6.9 11.3 6.3 0.4 0.1 -- -- -- 18 --

 85P3893 18- 30 A 53.8 20.4 25.8 40.9 9.4 11.0 6.3 12.2 6.9 0.4 -- -- -- -- 19 --

 85P3894 30- 38 BAg 56.9 19.6 23.5 43.0 9.6 10.0 6.4 10.8 5.8 0.5 -- -- -- -- 17 --

 85P3895 38- 70 Bg1 60.0 20.3 19.7 45.0 9.5 10.8 5.7 8.9 4.5 0.3 0.3 -- -- -- 14 --

 85P3896 70-110 Bg2 59.7 20.6 19.7 42.0 10.5 10.1 5.7 9.2 4.5 0.3 -- TR -- -- 14 --

 85P3897 110-180 BCg 60.7 20.4 18.9 40.6 10.3 10.1 5.5 8.8 4.3 0.3 -- TR TR -- 13 --

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 18 2.12 0.139 0.7 0.3 -- 0.19 0.39 41 18 1.28 1.35 0.018 27.4 25.1 18.2 0.05

 18- 30 1.59 0.098 0.3 0.2 -- 0.17 0.40 41 19 1.25 1.41 0.041 32.8 30.2 17.8 0.11

 30- 38 1.00 0.084 0.1 0.2 -- 0.12 0.38 41 19 1.23 1.35 0.032 31.4 28.4 18.3 0.08

 38- 70 0.48 0.028 0.1 0.1 -- 0.11 0.39 45 20 1.09 1.20 0.033 33.9 29.7 19.7 0.07

 70-110 0.26 0.027 0.2 0.1 -- 0.11 0.43 47 21 1.16 1.26 0.028 33.2 29.5 21.0 0.04

 110-180 0.18 0.013 0.4 0.1 -- 0.09 0.43 48 18 1.24 1.32 0.021 30.1 28.2 22.1 0.03

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. (- - - - - PH - - - - -)

 Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms KC1 NaF CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm IN .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9a 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8C1g 8C1d 8C1f 8C1f

 <- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1

 0- 18 0.2 0.4 TR -- 0.6 14.5 2.3 15.1 10.4 2.9 79 4 6 3.7 9.1 3.9 4.1

 18- 30 -- 0.1 TR -- 0.1 12.8 2.9 12.9 9.1 3.0 97 1 1 3.7 9.4 3.9 4.3

 30- 38 -- TR TR -- TR 10.6 2.8 10.6 7.1 2.8 100 TR TR 3.8 4.0 4.4

 38- 70 -- -- TR -- TR 9.2 1.8 9.2 6.3 1.8 100 TR TR 3.9 9.9 4.2 5.0

 70-110 -- -- TR -- TR 8.1 1.9 8.1 6.5 1.9 100 TR TR 4.0 4.2 5.1

 110-180 -- -- TR -- TR 7.1 1.6 7.1 5.4 1.6 100 TR TR 4.0 9.8 4.3 5.3

 -----------------------------------------------------------------------------------------------------------------------------------

 ACID OXALATE EXTRACTION PHOSPHOUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT

 OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL

 DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm

 SAMPLE HZ 8J 6C9a 6V2 6G12 6S4 6S5 6D3 6A2d 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1

 NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>

 85P3892 1 0.13 0.42 0.02 0.38 1.94 21.0

 85P3893 2 0.08 0.19 0.01 0.38 1.45 21.7

 85P3894 3 0.05 0.11 0.39 0.87 21.5

 85P3895 4 0.04 0.05 0.08 0.39 0.46 23.2

 85P3896 5 0.02 0.02 0.08 0.32 0.24 25.8

 85P3897 6 0.02 0.03 0.09 0.28 0.16 25.8

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - ->

 FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA-

 < - - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION

 NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->

 85P3892 TCLY KK 5 GI 2 VR 2 KK70 GI 4 2.3 0.1

 85P3896 TCLY KK 5 GI 2 VR 2 KK80 GI 5 1.1

 85P3897 TCLY KK 5 GI 2 VR 2 GE 1 KK76 GI 5 1.3

 -----------------------------------------------------------------------------------------------------------------------------------

 SAND - SILT MINERALOGY (2.0-0.002mm)

 SAMPLE FRACTION OPTICAL GRAIN COUNT PERCENT

 NUMBER < - - - - - - - -- - - - - - - - - TOTAL RESISTANT - - 7B1a - - - - - - - - ->

 85P3896 VFS 100 QZ88 PO12 OPtr MItr

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.

 Fraction interpretation: TCLY, total clay, <0.002 mm; VFS, very fine sand, 0.05-0.10 mm.

 Mineral interpretation: KK, kaolinite; GI, gibbsite; VR, vermiculite; QZ, quartz; PO, plant opal; OP, opaques; MI, mica;

 GE, goethite.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.

 Pedon mineralogy based on clay: Kaolinitic.

 Family mineralogy: Kaolinitic.
Oxisols 659

Key to Suborders

EA. Oxisols that have aquic conditions for some time in normal

years (or artificial drainage) in one or more horizons within 50 cm

of the mineral soil surface and have one or more of the

following:

1. A histic epipedon; or

2. An epipedon with a color value, moist, of 3 or less

and, directly below it, a horizon with chroma of 2 or less;

or

3. Distinct or prominent redox concentrations within 50

cm of the mineral soil surface, an epipedon, and, directly

below it, a horizon with one or both of the following:

a. 50 percent or more hue of 2.5Y or yellower; or

b. Chroma of 3 or less; or

4. Within 50 cm of the mineral soil surface, enough active

ferrous iron to give a positive reaction to alpha,alphadipyridyl at a time when the soil is not being irrigated.

Aquox, p. 659

EB. Other Oxisols that have an aridic moisture regime.

Torrox, p. 671

EC. Other Oxisols that have an ustic or xeric moisture

regime.

Ustox, p. 683

ED. Other Oxisols that have a perudic moisture regime.

Perox, p. 662

EE. Other Oxisols.

Udox, p. 673

Aquox

These are wet Oxisols in shallow depressions and in

seepage areas at the base of slopes. Because the water table

may fluctuate seasonally in the soils, there is a tendency to

accumulate iron in the form of secondary nodules, concretions,

and plinthite. Most areas of these soils are small.

Definition

Aquox are the Oxisols that have aquic conditions for some

time in normal years (or artificial drainage) in one or more

horizons within 50 cm of the mineral soil surface and have one

or more of the following:

1. A histic epipedon; or

2. An epipedon directly above a horizon with 50 percent or

more hue of 2.5Y or yellower or chroma of 3 or less and

distinct or prominent redox concentrations within 50 cm of the

mineral soil surface; or

3. An epipedon with a color value, moist, of 3 or less directly

above a horizon with chroma of 2 or less; or

4. Within 50 cm of the mineral soil surface, enough active

ferrous iron to give a positive reaction to alpha,alpha-dipyridyl

at a time when the soil is not being irrigated.

Key to Great Groups

EAA. Aquox that have, in one or more subhorizons of an

oxic or kandic horizon within 150 cm of the mineral soil

surface, an apparent ECEC of less than 1.50 cmol(+) per kg

clay and a pH value (in 1N KCl) of 5.0 or more.

Acraquox, p. 659

EAB. Other Aquox that have plinthite forming a continuous

phase within 125 cm of the mineral soil surface.

Plinthaquox, p. 661

EAC. Other Aquox that have a base saturation (by NH4OAc)

of 35 percent or more in all horizons within 125 cm of the

mineral soil surface.

Eutraquox, p. 660

EAD. Other Aquox.

Haplaquox, p. 661

Acraquox

This great group is provided for those Aquox with extremely

low cation-exchange capacities. Few examples have been made

available for study.

Definition

Acraquox are the Aquox that have an apparent ECEC of less

than 1.50 cmol(+) per kg clay and a pH value (1N KCl) of 5.0 or

more in some part of an oxic or kandic horizon within 150 cm of

the mineral soil surface.

Key to Subgroups

EAAA. Acraquox that have 5 percent or more (by volume)

plinthite in one or more horizons within 125 cm of the mineral

soil surface.

Plinthic Acraquox

EAAB. Other Acraquox that have, directly below an

epipedon, a horizon 10 cm or more thick that has 50 percent or

more chroma of 3 or more.

Aeric Acraquox

EAAC. Other Acraquox.

Typic Acraquox
660 Soil Taxonomy

Definition of Typic Acraquox

Typic Acraquox are the Acraquox that:

1. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

and

2. Do not have, directly below an epipedon, a horizon 10

cm or more thick that has 50 percent or more chroma of 3 or

more.

Description of Subgroups

Typic Acraquox.—The central concept or Typic subgroup

of Acraquox is fixed on soils that have dominantly low chroma

in a layer 10 cm or more thick that is directly below an

epipedon. These soils also have less than 5 percent plinthite in

all horizons within a depth of 125 cm. They are not known to

occur in the United States.

Aeric Acraquox.—These soils are like Typic Acraquox, but

they have chroma dominantly of 3 or more in a layer 10 cm or

more thick that is directly below an epipedon. Aeric Acraquox

are considered intergrades between Acraquox and Acrudox or

Acroperox. They are not known to occur in the United States.

Plinthic Acraquox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. The soils are not known to occur in

the United States.

Eutraquox

These Aquox have a base saturation (pH 7) of more than 35

percent in all horizons to a depth of 125 cm. They do not have

plinthite that forms a continuous phase within 125 cm of the

mineral soil surface and do not have both a very low apparent

ECEC and a pH value (1N KCl) of 5.0 or more in some part of

the oxic or kandic horizon.

Definition

Eutraquox are the Aquox that:

1. Have more than 35 percent base saturation (by NH4OAc)

in all parts within 125 cm of the mineral soil surface;

2. Do not have plinthite that forms a continuous phase

within 125 cm of the mineral soil surface; and

3. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of an oxic or kandic horizon within 150 cm of the mineral

soil surface.

Key to Subgroups

EACA. Eutraquox that have a histic epipedon.

Histic Eutraquox

EACB. Other Eutraquox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Eutraquox

EACC. Other Eutraquox that have, directly below an

epipedon, a horizon 10 cm or more thick that has 50 percent or

more chroma of 3 or more.

Aeric Eutraquox

EACD. Other Eutraquox that have 16 kg/m2

 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Eutraquox

EACE. Other Eutraquox.

Typic Eutraquox

Definition of Typic Eutraquox

Typic Eutraquox are the Eutraquox that:

1. Do not have a histic epipedon;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, directly below an epipedon, a horizon 10 cm

or more thick that has 50 percent or more chroma of 3 or more;

and

4. Have less than 16 kg of organic carbon per m2 to a depth

of 100 cm, exclusive of surface litter.

Description of Subgroups

Typic Eutraquox.—The central concept or Typic subgroup

of Acraquox is fixed on soils that do not have a histic epipedon

and have dominantly low chroma in a layer 10 cm or more

thick that is directly below an epipedon. These soils also have

less than 16 kg/m2 organic carbon to a depth of 100 cm and

less than 5 percent plinthite in all horizons within a depth of

125 cm. They are not known to occur in the United States.

Aeric Eutraquox.—These soils have chroma dominantly of

3 or more in a layer 10 cm or more thick that is directly below

an epipedon. Aeric Eutraquox are considered intergrades

between Eutraquox and Eutrudox or Eutroperox. They are not

known to occur in the United States.

Histic Eutraquox.—These soils have a histic epipedon.

They commonly are wet much of the year and are among the

wettest of the soils in this great group. Histic Eutraquox are not

known to occur in the United States.

Humic Eutraquox.—These soils are like Typic Eutraquox,

but they have 16 kg or more organic carbon per m2

 within 100

cm of the mineral soil surface. These soils are not known to

occur in the United States.

Plinthic Eutraquox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. They are not known to occur in the

United States.
Oxisols 661

Haplaquox

These are the Aquox that have low base status in one or

more subhorizons of the oxic or kandic horizon. They do not

have plinthite that forms a continuous phase within 125 cm of

the mineral soil surface and do not have both a very low

apparent ECEC and a pH value (1N KCl) of 5.0 or more in

some part of the oxic or kandic horizon.

Definition

Haplaquox are the Aquox that:

1. Have 35 percent or less base saturation (by NH4OAc) in

some or all parts within 125 cm of the mineral soil surface;

2. Do not have plinthite that forms a continuous phase

within 125 cm of the mineral soil surface; and

3. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of an oxic or kandic horizon within 150 cm of the mineral

soil surface.

Key to Subgroups

EADA. Haplaquox that have a histic epipedon.

Histic Haplaquox

EADB. Other Haplaquox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Haplaquox

EADC. Other Haplaquox that have, directly below an

epipedon, a horizon 10 cm or more thick that has 50 percent or

more chroma of 3 or more.

Aeric Haplaquox

EADD. Other Haplaquox that have 16 kg/m2

 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Haplaquox

EADE. Other Haplaquox.

Typic Haplaquox

Definition of Typic Haplaquox

Typic Haplaquox are the Haplaquox that:

1. Do not have a histic epipedon;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, directly below an epipedon, a horizon 10 cm

or more thick that has 50 percent or more chroma of 3 or more;

and

4. Have less than 16 kg of organic carbon per m2

 to a depth

of 1 m, exclusive of surface litter.

Description of Subgroups

Typic Haplaquox.—The central concept or Typic subgroup of

Haplaquox is fixed on soils that do not have a histic epipedon

and have dominantly low chroma in a layer 10 cm or more thick

that is directly below an epipedon. These soils also have less

than 16 kg/m2

 organic carbon to a depth of 100 cm and less than

5 percent plinthite in all horizons within a depth of 125 cm. They

are not known to occur in the United States.

Aeric Haplaquox.—These soils have chroma dominantly of

3 or more in a layer 10 cm or more thick that is directly below

an epipedon. Aeric Haplaquox are considered intergrades

between Haplaquox and Hapludox or Haploperox. They are not

known to occur in the United States.

Histic Haplaquox.—These soils have a histic epipedon.

They commonly are wet much of the year and are among the

wettest of the soils in this great group. Histic Haplaquox are

not known to occur in the United States.

Humic Haplaquox.—These soils are like Typic Haplaquox,

but they have 16 kg or more organic carbon per m2 within 100

cm of the mineral soil surface. They are of very small extent in

Puerto Rico and generally are forested.

Plinthic Haplaquox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. They are not known to occur in the

United States.

Plinthaquox

This great group is provided for pedons of Aquox that have

continuous plinthite within 125 cm of the mineral soil surface

and an apparent ECEC of more than 1.50 cmol(+) per kg clay

or a pH value (1N KCl) of 5.0 or more in some part of an oxic

or kandic horizon within 150 cm of the mineral soil surface.

Only small areas of Plinthaquox have been observed, and no

data have been made available for study.

Definition

Plinthaquox are the Aquox that:

1. Have plinthite that forms a continuous phase within 125

cm of the mineral soil surface; and

2. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of an oxic or kandic horizon within 150 cm of the mineral

soil surface.

Key to Subgroups

EABA. Plintaquox that have, directly below an epipedon, a

horizon 10 cm or more thick that has 50 percent or more

chroma of 3 or more.

Aeric Plinthaquox

EABB. Other Plinthaquox.

Typic Plinthaquox
662 Soil Taxonomy

Definition of Typic Plinthaquox

Typic Plinthaquox are the Plinthaquox that, directly below an

epipedon, do not have a horizon 10 cm or more thick that has 50

percent or more chroma of 3 or more.

Description of Subgroups

Typic Plinthaquox.—The central concept or Typic

subgroup of Haplaquox is fixed on soils that have dominantly

low chroma in a layer 10 cm or more thick that is directly below

an epipedon. These soils are not known to occur in the United

States.

Aeric Plinthaquox.—These soils have chroma dominantly

of 3 or more in a layer 10 cm or more thick that is directly

below an epipedon. They are not known to occur in the United

States.

Perox

Perox are well drained Oxisols with a perudic soil moisture

regime. Clearing and burning are difficult because of

atmospheric wetness. Curing many seed crops and storing

produce also are difficult. There are no large areas of the

perudic soil moisture regime, but areas of this regime appear

distinctive enough to show and identify on some small-scale

soil maps.

Definition

Perox are the Oxisols that have a perudic soil moisture

regime.

Key to Great Groups

EDA. Perox that have a sombric horizon within 150 cm of

the mineral soil surface.

Sombriperox, p. 671

EDB. Other Perox that have, in one or more subhorizons of

an oxic or kandic horizon within 150 cm of the mineral soil

surface, an apparent ECEC of less than 1.50 cmol(+) per kg

clay and a pH value (1N KCl) of 5.0 or more.

Acroperox, p. 662

EDC. Other Perox that have a base saturation (by NH4OAc)

of 35 percent or more in all horizons within 125 cm of the

mineral soil surface.

Eutroperox, p. 664

EDD. Other Perox that have a kandic horizon that has its

upper boundary within 150 cm of the mineral soil surface.

Kandiperox, p. 668

EDE. Other Perox.

Haploperox, p. 666

Acroperox

These are the Perox that do not have a sombric horizon within

150 cm of the mineral soil surface and have, in all subhorizons of

an oxic or kandic horizon within 150 cm of the mineral soil

surface, a very low effective cation-exchange value and a pH

value (1N KCl) of 5.0 or more.

Definition

Acroperox are the Perox that:

1. Have an apparent ECEC of less than 1.50 cmol(+) per kg

clay and a pH value (1N KCl) of 5.0 or more in some part of an

oxic or kandic horizon within 150 cm of the mineral soil surface;

and

2. Do not have a sombric horizon within 150 cm of the mineral

soil surface.

Key to Subgroups

EDBA. Acroperox that have, within 125 cm of the mineral soil

surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Acroperox

EDBB. Other Acroperox that have a petroferric contact

within 125 cm of the mineral soil surface.

Petroferric Acroperox

EDBC. Other Acroperox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Acroperox

EDBD. Other Acroperox that have a lithic contact within 125

cm of the mineral soil surface.

Lithic Acroperox

EDBE. Other Acroperox that have a delta pH (KCl pH minus

1:1 water pH) with a 0 or net positive charge in a layer 18 cm

or more thick within 125 cm of the mineral soil surface.

Anionic Acroperox

EDBF. Other Acroperox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Acroperox
Oxisols 663

EDBG. Other Acroperox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage).

Aquic Acroperox

EDBH. Other Acroperox that have both:

1. 16 kg/m2

 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Acroperox

EDBI. Other Acroperox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Acroperox

EDBJ. Other Acroperox that have 16 kg/m2 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Acroperox

EDBK. Other Acroperox that have, in all horizons at a depth

between 25 and 125 cm from the mineral soil surface, more

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Acroperox

EDBL. Other Acroperox that have 50 percent or more hue of

7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Acroperox

EDBM. Other Acroperox.

Typic Acroperox

Definition of Typic Acroperox

Typic Acroperox are the Acroperox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Have a delta pH (KCl pH minus 1:1 water pH) with a net

negative charge in all parts within 125 cm of the mineral soil

surface;

3. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

4. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

5. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter; and

6. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Acroperox.—The central concept or Typic subgroup

of Acroperox is fixed on soils that do not have a petroferric

contact, a lithic contact, or redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less within 125 cm of

the mineral soil surface and also do not have aquic conditions

for some time in normal years. These soils have less than 16

kg/m2

 organic carbon to a depth of 100 cm and less than 5

percent plinthite in all horizons within a depth of 125 cm.

Their colors are reddish, but the soils do not have very dark

reddish colors throughout the layers between depths of 25 and

125 cm. These soils are not known to occur in the United

States.

Anionic Acroperox.—These soils have a delta pH (KCl pH

minus 1:1 water pH) with a 0 or net positive charge in a layer

18 cm or more thick within 125 cm of the mineral soil surface.

The soils are of very small extent and are known to occur only

in Hawaii in the United States.

Aquic Acroperox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Acroperox are considered

intergrades between Acroperox and Acraquox. They are not

known to occur in the United States.

Aquic Lithic Acroperox.—These soils have, within 125 cm

of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Acroperox.—These soils have, within 125

cm of the mineral soil surface, both a petroferric contact and

redox depletions with a color value, moist, of 4 or more and
664 Soil Taxonomy

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage). The soils are not known to

occur in the United States.

Humic Acroperox.—These soils are like Typic Acroperox,

but they have 16 kg or more organic carbon per m2

 within 100

cm of the mineral soil surface. They are not known to occur in

the United States.

Humic Rhodic Acroperox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Acroperox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

7.5YR or yellower and value, moist, of 6 or more. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Lithic Acroperox.—These soils have a lithic contact within

125 cm of the mineral soil surface. They are not known to

occur in the United States.

Petroferric Acroperox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthic Acroperox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. They are not known to occur in the

United States.

Rhodic Acroperox.—These soils are like Typic Acroperox,

but they have, in all horizons at a depth between 25 and 125

cm from the mineral soil surface, more than 50 percent colors

that have hue of 2.5YR or redder and a value, moist, of 3 or

less. The soils are not known to occur in the United States.

Xanthic Acroperox.—These soils are like Typic Acroperox,

but they have hue of 7.5YR or yellower and a color value,

moist, of 6 or more in all horizons at a depth between 25 and

125 cm from the mineral soil surface. The soils are not known

to occur in the United States.

Eutroperox

These are the Perox that have a base saturation (by NH4OAc)

of 35 percent or more in all horizons within 125 cm of the mineral

soil surface. They do not have a sombric horizon within 150 cm

of the mineral soil surface and have, in all subhorizons of an oxic

or kandic horizon within 150 cm of the mineral soil surface, an

apparent ECEC of 1.50 or more cmol(+) per kg clay or a pH value

(1N KCl) of less than 5.0.

Definition

Eutroperox are the Perox that:

1. Have more than 35 percent base saturation (by NH4OAc) in

all parts within 125 cm of the mineral soil surface;

2. Do not have a sombric horizon within 150 cm of the mineral

soil surface; and

3. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some part

of an oxic or kandic horizon within 150 cm of the mineral soil

surface.

Key to Subgroups

EDCA. Eutroperox that have, within 125 cm of the mineral soil

surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Eutroperox

EDCB. Other Eutroperox that have a petroferric contact

within 125 cm of the mineral soil surface.

Petroferric Eutroperox

EDCC. Other Eutroperox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Eutroperox

EDCD. Other Eutroperox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Eutroperox

EDCE. Other Eutroperox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Eutroperox

EDCF. Other Eutroperox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Eutroperox

EDCG. Other Eutroperox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less
Oxisols 665

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Eutroperox

EDCH. Other Eutroperox that have a kandic horizon that has

its upper boundary within 150 cm of the mineral soil surface.

Kandiudalfic Eutroperox

EDCI. Other Eutroperox that have both:

1. 16 kg/m2

 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. An oxic horizon that has its lower boundary within 125

cm of the mineral soil surface.

Humic Inceptic Eutroperox

EDCJ. Other Eutroperox that have an oxic horizon that has

its lower boundary within 125 cm of the mineral soil surface.

Inceptic Eutroperox

EDCK. Other Eutroperox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Eutroperox

EDCL. Other Eutroperox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Eutroperox

EDCM. Other Eutroperox that have 16 kg/m2 or more

organic carbon between the mineral soil surface and a depth of

100 cm.

Humic Eutroperox

EDCN. Other Eutroperox that have, in all horizons at a

depth between 25 and 125 cm from the mineral soil surface,

more than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Eutroperox

EDCO. Other Eutroperox that have 50 percent or more hue of

7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Eutroperox

EDCP. Other Eutroperox.

Typic Eutroperox

Definition of Typic Eutroperox

Typic Eutroperox are the Eutroperox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

4. Do not have a kandic horizon with its upper boundary

within 150 cm of the mineral soil surface;

5. Have an oxic horizon with a lower boundary 125 cm or

more from the mineral soil surface;

6. Have less than 16 kg of organic carbon per m2

 to a depth

of 1 m, exclusive of surface litter; and

7. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Eutroperox.—The central concept or Typic subgroup

of Eutroperox is fixed on soils that have a thick oxic horizon.

These soils do not have a petroferric contact, a lithic contact, or

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less within 125 cm of the mineral soil surface

and also do not have aquic conditions for some time in normal

years. The soils have less than 16 kg/m2

 organic carbon to a

depth of 100 cm and less than 5 percent plinthite in all

horizons within a depth of 125 cm. Their colors are reddish,

but the soils do not have very dark reddish colors throughout

the layers between depths of 25 and 125 cm. These soils are not

known to occur in the United States.

Aquic Eutroperox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal
666 Soil Taxonomy

years (or artificial drainage). Aquic Eutroperox are considered

intergrades between Eutroperox and Eutraquox. They are not

known to occur in the United States.

Aquic Lithic Eutroperox.—These soils have, within 125

cm of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Eutroperox.—These soils have, within

125 cm of the mineral soil surface, both a petroferric contact

and redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage). The soils are not

known to occur in the United States.

Humic Eutroperox.—These soils are like Typic

Eutroperox, but they have 16 kg or more organic carbon per m2

within 100 cm of the mineral soil surface. They are not known

to occur in the United States.

Humic Inceptic Eutroperox.—These soils have an oxic

horizon that has its lower boundary within 125 cm of the

mineral soil surface. They also have 16 kg or more organic

carbon per m2 within 100 cm of the mineral soil surface. These

soils are not known to occur in the United States.

Humic Rhodic Eutroperox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Eutroperox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, colors that have hue of 7.5YR or yellower and

value, moist, of 6 or more. They also have 16 kg or more

organic carbon per m2 within 100 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Inceptic Eutroperox.—These soils have an oxic horizon

that has its lower boundary within 125 cm of the mineral soil

surface. They are not known to occur in the United States.

Kandiudalfic Eutroperox.—These soils have a kandic

horizon that has its upper boundary within 125 cm of the

mineral soil surface. They are not known to occur in the United

States.

Lithic Eutroperox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Eutroperox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Eutroperox.—These soils have, within 125 cm of

the mineral soil surface, redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial

drainage). They have 5 percent or more (by volume) plinthite

in one or more horizons within 125 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Plinthic Eutroperox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. They are not known to occur in the

United States.

Rhodic Eutroperox.—These soils are like Typic

Eutroperox, but they have, in all horizons at a depth between

25 and 125 cm from the mineral soil surface, more than 50

percent colors that have hue of 2.5YR or redder and a value,

moist, of 3 or less. These soils are not known to occur in the

United States.

Xanthic Eutroperox.—These soils are like Typic Eutroperox,

but they have hue of 7.5YR or yellower and a color value, moist,

of 6 or more in all horizons at a depth between 25 and 125 cm

from the mineral soil surface. The soils are not known to occur in

the United States.

Haploperox

These are the Perox that have, in all subhorizons of an oxic

horizon within 150 cm of the mineral soil surface, an apparent

ECEC of 1.50 or more cmol(+) per kg clay or a pH value (1N

KCl) of less than 5.0. They also have a base saturation (by

NH4OAc) of less than 35 percent in some horizon within 125

cm of the mineral soil surface and do not have a kandic or

sombric horizon that has its upper boundary within 150 cm of

the mineral soil surface. The subsoil has granular structure,

and the epipedons may be either dark or light colored.

Definition

Haploperox are the Perox that:

1. Have 35 percent or less base saturation (by NH4OAc) in

some or all parts within 125 cm of the mineral soil surface;

2. Do not have a sombric horizon within 150 cm of the

mineral soil surface;

3. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of an oxic horizon within 150 cm of the mineral soil

surface; and

4. Do not have a kandic horizon that has its upper boundary

within 150 cm of the mineral soil surface.

Key to Subgroups

EDEA. Haploperox that have, within 125 cm of the mineral

soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more
Oxisols 667

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Haploperox

EDEB. Other Haploperox that have a petroferric contact

within 125 cm of the mineral soil surface.

Petroferric Haploperox

EDEC. Other Haploperox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Haploperox

EDED. Other Haploperox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Haploperox

EDEE. Other Haploperox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Haploperox

EDEF. Other Haploperox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Haploperox

EDEG. Other Haploperox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Haploperox

EDEH. Other Haploperox that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Haploperox

EDEI. Other Haploperox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from the

mineral soil surface, more than 50 percent colors that have

both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Haploperox

EDEJ. Other Haploperox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Haploperox

EDEK. Other Haploperox that have 16 kg/m2 or more

organic carbon between the mineral soil surface and a depth of

100 cm.

Humic Haploperox

EDEL. Other Haploperox that have, in all horizons at a

depth between 25 and 125 cm from the mineral soil surface,

more than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Haploperox

EDEM. Other Haploperox that have 50 percent or more hue

of 7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Haploperox

EDEN. Other Haploperox.

Typic Haploperox

Definition of Typic Haploperox

Typic Haploperox are the Haploperox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3 or less,

measured at 33 kPa water retention, and acid-oxalate-
668 Soil Taxonomy

extractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

5. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter; and

6. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Haploperox.—The central concept or Typic subgroup

of Haploperox is fixed on soils that do not have a petroferric

contact, a lithic contact, or redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less within 125 cm of

the mineral soil surface and also do not have aquic conditions

for some time in normal years. These soils have less than 16

kg/m2

 organic carbon to a depth of 100 cm and have less than 5

percent plinthite in all horizons within a depth of 125 cm.

Their colors are reddish, but the soils do not have very dark

reddish colors throughout the layers between depths of 25 and

125 cm. They do not have a surface mantle or layer in the

upper 75 cm with both a low bulk density and a high content of

weakly crystalline minerals. These soils are not known to occur

in the United States.

Andic Haploperox.—These soils have a surface mantle or

layer in the upper 75 cm with both a low bulk density and a

high content of weakly crystalline minerals. The soils are not

known to occur in the United States.

Aquic Haploperox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Haploperox are considered

intergrades between Haploperox and Haplaquox. They are not

known to occur in the United States.

Aquic Lithic Haploperox.—These soils have, within 125

cm of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Haploperox.—These soils have, within

125 cm of the mineral soil surface, both a petroferric contact

and redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage). These soils are not

known to occur in the United States.

Humic Haploperox.—These soils are like Typic

Haploperox, but they have 16 kg or more organic carbon per m2

within 100 cm of the mineral soil surface. They are not known to

occur in the United States.

Humic Rhodic Haploperox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also have

16 kg or more organic carbon per m2 within 100 cm of the mineral

soil surface. These soils are not known to occur in the United

States.

Humic Xanthic Haploperox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, colors that have hue of 7.5YR or yellower and

value, moist, of 6 or more. They also have 16 kg or more

organic carbon per m2 within 100 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Lithic Haploperox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Haploperox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Haploperox.—These soils have, in one or

more horizons within 125 cm of the mineral soil surface, 5

percent or more (by volume) plinthite, redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less, and

aquic conditions for some time in normal years (or artificial

drainage). The soils are not known to occur in the United

States.

Plinthic Haploperox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. They are not known to occur in the

United States.

Rhodic Haploperox.—These soils are like Typic

Haploperox, but they have, in all horizons at a depth between

25 and 125 cm from the mineral soil surface, more than 50

percent colors that have hue of 2.5YR or redder and a value,

moist, of 3 or less. The soils are not known to occur in the

United States.

Xanthic Haploperox.—These soils are like Typic Haploperox,

but they have hue of 7.5YR or yellower and a color value, moist,

of 6 or more in all horizons at a depth between 25 and 125 cm

from the mineral soil surface. These soils are not known to occur

in the United States.

Kandiperox

These are the clayey Perox that have a kandic horizon that

has its upper boundary within 150 cm of the mineral soil

surface. They do not have a sombric horizon within 150 cm of

the mineral soil surface, but they have, in all subhorizons of a

kandic horizon within 150 cm of the mineral soil surface, an
Oxisols 669

apparent ECEC of 1.50 or more cmol(+) per kg clay or a pH

value (1N KCl) of less than 5.0. They also have a base

saturation (by NH4

OAc) of less than 35 percent in some

horizon within 125 cm of the mineral soil surface. The subsoil

has granular structure, and the epipedons may be either dark

or light colored.

Definition

Kandiperox are the Perox that:

1. Have the upper boundary of a kandic horizon within 150 cm

of the mineral soil surface;

2. Have 35 percent or less base saturation (by NH4OAc) in

some or all parts within 125 cm of the mineral soil surface;

3. Do not have a sombric horizon within 150 cm of the

mineral soil surface; and

4. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of a kandic horizon within 150 cm of the mineral soil

surface.

Key to Subgroups

EDDA. Kandiperox that have, within 125 cm of the mineral

soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Kandiperox

EDDB. Other Kandiperox that have a petroferric contact

within 125 cm of the mineral soil surface.

Petroferric Kandiperox

EDDC. Other Kandiperox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Kandiperox

EDDD. Other Kandiperox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Kandiperox

EDDE. Other Kandiperox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Kandiperox

EDDF. Other Kandiperox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Kandiperox

EDDG. Other Kandiperox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Kandiperox

EDDH. Other Kandiperox that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Kandiperox

EDDI. Other Kandiperox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Kandiperox

EDDJ. Other Kandiperox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Kandiperox

EDDK. Other Kandiperox that have 16 kg/m2 or more

organic carbon between the mineral soil surface and a depth of

100 cm.

Humic Kandiperox

EDDL. Other Kandiperox that have, in all horizons at a

depth between 25 and 125 cm from the mineral soil surface,

more than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and
670 Soil Taxonomy

2. A value, moist, of 3 or less.

Rhodic Kandiperox

EDDM. Other Kandiperox that have 50 percent or more hue of

7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Kandiperox

EDDN. Other Kandiperox.

Typic Kandiperox

Definition of Typic Kandiperox

Typic Kandiperox are the Kandiperox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

5. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter; and

6. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Kandiperox.—The central concept or Typic

subgroup of Kandiperox is fixed on soils that do not have a

petroferric contact, a lithic contact, or redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less within

125 cm of the mineral soil surface and also do not have aquic

conditions for some time in normal years. These soils have less

than 16 kg/m2

 organic carbon to a depth of 100 cm and less

than 5 percent plinthite in all horizons within a depth of 125

cm. Their colors are reddish, but the soils do not have very

dark reddish colors throughout the layers between depths of 25

and 125 cm. They do not have a surface mantle or layer in the

upper 75 cm with both a low bulk density and a high content of

weakly crystalline minerals. These soils are not known to occur

in the United States.

Andic Kandiperox.—These soils have a surface mantle or

layer in the upper 75 cm with both a low bulk density and a

high content of weakly crystalline minerals. The soils are not

known to occur in the United States.

Aquic Kandiperox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Kandiperox are considered

intergrades between Kandiperox and Aquox. They are not

known to occur in the United States.

Aquic Lithic Kandiperox.—These soils have, within 125

cm of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Kandiperox.—These soils have, within

125 cm of the mineral soil surface, both a petroferric contact

and redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage). The soils are not

known to occur in the United States.

Humic Kandiperox.—These soils are like Typic

Kandiperox, but they have 16 kg or more organic carbon per

m2

 within 100 cm of the mineral soil surface. They are not

known to occur in the United States.

Humic Rhodic Kandiperox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Kandiperox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, colors that have hue of 7.5YR or yellower and

value, moist, of 6 or more. They also have 16 kg or more

organic carbon per m2 within 100 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Lithic Kandiperox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Kandiperox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Kandiperox.—These soils have, in one or

more horizons within 125 cm of the mineral soil surface, 5

percent or more (by volume) plinthite, redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less, and
Oxisols 671

aquic conditions for some time in normal years (or artificial

drainage). The soils are not known to occur in the United

States.

Plinthic Kandiperox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. They are not known to occur in the

United States.

Rhodic Kandiperox.—These soils are like Typic

Kandiperox, but they have, in all horizons at a depth between

25 and 125 cm from the mineral soil surface, more than 50

percent colors that have hue of 2.5YR or redder and a value,

moist, of 3 or less. The soils are not known to occur in the

United States.

Xanthic Kandiperox.—These soils are like Typic Kandiperox,

but they have hue of 7.5YR or yellower and a color value, moist,

of 6 or more in all horizons at a depth between 25 and 125 cm

from the mineral soil surface. The soils are not known to occur in

the United States.

Sombriperox

These are the Perox that have a sombric horizon. They are not

known to occur in the United States at this time but are expected

to occur in other parts of the world.

Definition

Sombriperox are the Perox that have a sombric horizon within

150 cm of the mineral soil surface.

Key to Subgroups

EDAA. Sombriperox that have a petroferric contact within 125

cm of the mineral soil surface.

Petroferric Sombriperox

EDAB. Other Sombriperox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Sombriperox

EDAC. Other Sombriperox that have 16 kg/m2

 or more

organic carbon between the mineral soil surface and a depth of

100 cm.

Humic Sombriperox

EDAD. Other Sombriperox.

Typic Sombriperox

Definition of Typic Sombriperox

Typic Sombriperox are the Sombriperox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface; and

2. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter.

Description of Subgroups

Typic Sombriperox.—The central concept or Typic

subgroup of Sombriperox is fixed on soils that do not have

a petroferric or lithic contact within 125 cm of the mineral

soil surface. These soils also have less than 16 kg/m2

 organic

carbon to a depth of 100 cm. They are not known to occur in

the United States.

Humic Sombriperox.—These soils are like Typic

Sombriperox, but they have 16 kg or more organic carbon per

m2 within 100 cm of the mineral soil surface. They are not

known to occur in the United States.

Lithic Sombriperox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Sombriperox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Torrox

These are Oxisols of arid regions. They have an aridic

moisture regime, and many of them have a higher base

saturation than other Oxisols. Torrox are excellent soils for a

variety of crops if irrigation water and fertilizer are applied.

These soils are known to occur only Hawaii in the United

States and perhaps in some areas in Australia.

Definition

Torrox are the Oxisols that have an aridic (torric) moisture

regime.

Key to Great Groups

EBA. Torrox that have, in one or more subhorizons of an

oxic or kandic horizon within 150 cm of the mineral soil

surface, an apparent ECEC of less than 1.50 cmol(+) per kg

clay and a pH value (1N KCl) of 5.0 or more.

Acrotorrox, p. 671

EBB. Other Torrox that have a base saturation (by NH4OAc)

of 35 percent or more in all horizons within 125 cm of the

mineral soil surface.

Eutrotorrox, p. 672

EBC. Other Torrox.

Haplotorrox, p. 672

Acrotorrox

These are the Torrox that have, in all subhorizons of an oxic

or kandic horizon within 150 cm of the mineral soil surface, a

very low effective cation-exchange value and a pH value (1N

KCl) of 5.0 or more.
672 Soil Taxonomy

Definition

Acrotorrox are the Torrox that have an apparent ECEC of less

than 1.50 cmol(+) per kg clay and a pH value (1N KCl) of 5.0 or

more in some part of an oxic or kandic horizon within 150 cm of

the mineral soil surface.

Key to Subgroups

EBAA. Acrotorrox that have a petroferric contact within 125

cm of the mineral soil surface.

Petroferric Acrotorrox

EBAB. Other Acrotorrox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Acrotorrox

EBAC. Other Acrotorrox.

Typic Acrotorrox

Definition of Typic Acrotorrox

Typic Acrotorrox are the Acrotorrox that have neither a

petroferric nor a lithic contact within 125 cm of the mineral

soil surface.

Description of Subgroups

Typic Acrotorrox.—The central concept or Typic subgroup

of Acrotorrox is fixed on soils that do not have a petroferric or

lithic contact within 125 cm of the mineral soil surface. These

soils are not known to occur in the United States.

Lithic Acrotorrox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Acrotorrox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Eutrotorrox

These are the Torrox that have more than 35 percent base

saturation (by NH4OAc) in all parts within 125 cm of the

mineral soil surface. They also have, in some subhorizon of an

oxic or kandic horizon within 150 cm of the mineral soil

surface, an effective cation-exchange value higher than very

low or a pH value (1N KCl) of less than 5.0. These soils occur

mainly in Hawaii, where they are used for irrigated crops.

Definition

Eutrotorrox are the Torrox that:

1. Have more than 35 percent base saturation (by NH4

OAc)

in all parts within 125 cm of the mineral soil surface; and

2. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of an oxic or kandic horizon within 150 cm of the mineral

soil surface.

Key to Subgroups

EBBA. Eutrotorrox that have a petroferric contact within 125

cm of the mineral soil surface.

Petroferric Eutrotorrox

EBBB. Other Eutrotorrox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Eutrotorrox

EBBC. Other Eutrotorrox.

Typic Eutrotorrox

Definition of Typic Eutrotorrox

Typic Eutrotorrox are the Eutrotorrox that have neither a

petroferric nor a lithic contact within 125 cm of the mineral

soil surface.

Description of Subgroups

Typic Eutrotorrox.—The central concept or Typic

subgroup of Eutrotorrox is fixed on soils that do not have a

petroferric or lithic contact within 125 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Lithic Eutrotorrox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Eutrotorrox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Haplotorrox

These are the Torrox that have 35 percent or less base

saturation (by NH4OAc) in some part within 125 cm of the

mineral soil surface. They also have, in some subhorizon of an

oxic or kandic horizon within 150 cm of the mineral soil

surface, an effective cation-exchange value higher than very

low or a pH value (1N KCl) of less than 5.0.

Definition

Haplotorrox are the Torrox that:

1. Have 35 percent or less base saturation (by NH4OAc) in

some or all parts within 125 cm of the mineral soil surface;

and

2. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of an oxic or kandic horizon within 150 cm of the mineral

soil surface.

Key to Subgroups

EBCA. Haplotorrox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Haplotorrox
Oxisols 673

EBCB. Other Haplotorrox that have a lithic contact within 125

cm of the mineral soil surface.

Lithic Haplotorrox

EBCC. Other Haplotorrox.

Typic Haplotorrox

Definition of Typic Haplotorrox

Typic Haplotorrox are the Haplotorrox that have neither a

petroferric nor a lithic contact within 125 cm of the mineral

soil surface.

Description of Subgroups

Typic Haplotorrox.—The central concept or Typic

subgroup of Haplotorrox is fixed on soils that do not have a

petroferric or lithic contact within 125 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Lithic Haplotorrox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Haplotorrox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Udox

Udox are well drained Oxisols with a udic soil moisture

regime. They are moist because of natural rainfall in normal

years and are dry in some parts for less than 90 days, a period

that is short enough for rain-fed crops to be grown

continuously in normal years. There are fewer than 90 days

during which crops are not planted. In local terms there are 1

to 3 months that considered “dry” in normal years. Udox are an

extensive suborder, occurring mostly in South America and in

parts of Africa and Asia.

Definition

Udox are the Oxisols that have a udic moisture regime.

Key to Great Groups

EEA. Udox that have a sombric horizon within 150 cm of the

mineral soil surface.

Sombriudox, p. 682

EEB. Other Udox that have, in one or more subhorizons of

an oxic or kandic horizon within 150 cm of the mineral soil

surface, an apparent ECEC of less than 1.50 cmol(+) per kg

clay and a pH value (1N KCl) of 5.0 or more.

Acrudox, p. 673

EEC. Other Udox that have a base saturation (by NH4OAc) of

35 percent or more in all horizons within 125 cm of the mineral

soil surface.

Eutrudox, p. 675

EED. Other Udox that have a kandic horizon that has its upper

boundary within 150 cm of the mineral soil surface.

Kandiudox, p. 680

EEE. Other Udox.

Hapludox, p. 678

Acrudox

These are Udox that have very low CEC values in the

subsoil and that do not have a sombric horizon within 150 cm of

the mineral soil surface. Frequent but small applications of

fertilizer and lime are required. Because the CEC is low, the

amount of exchangeable aluminum in the subsoil is low. This

deficiency can be corrected by leaching basic cations from lime

and fertilizer.

Definition

Acrudox are the Udox that:

1. Have an apparent ECEC of less than 1.50 cmol(+) per kg

clay and a pH value (1N KCl) of 5.0 or more in some part of an

oxic or kandic horizon within 150 cm of the mineral soil surface;

and

2. Do not have a sombric horizon within 150 cm of the mineral

soil surface.

Key to Subgroups

EEBA. Acrudox that have, within 125 cm of the mineral soil

surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Acrudox

EEBB. Other Acrudox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Acrudox

EEBC. Other Acrudox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Acrudox
674 Soil Taxonomy

EEBD. Other Acrudox that have a lithic contact within 125 cm

of the mineral soil surface.

Lithic Acrudox

EEBE. Other Acrudox that have, within 125 cm of the

mineral soil surface, both:

1. A delta pH (KCl pH minus 1:1 water pH) with a 0 or

net positive charge in a layer 18 cm or more thick; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Anionic Aquic Acrudox

EEBF. Other Acrudox that have a delta pH (KCl pH minus

1:1 water pH) with a 0 or net positive charge in a layer 18 cm

or more thick within 125 cm of the mineral soil surface.

Anionic Acrudox

EEBG. Other Acrudox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Acrudox

EEBH. Other Acrudox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Acrudox

EEBI. Other Acrudox that have a base saturation (by

NH4OAc) of 35 percent or more in all horizons within 125 cm

of the mineral soil surface.

Eutric Acrudox

EEBJ. Other Acrudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Acrudox

EEBK. Other Acrudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and 125

cm from the mineral soil surface.

Humic Xanthic Acrudox

EEBL. Other Acrudox that have 16 kg/m2 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Acrudox

EEBM. Other Acrudox that have, in all horizons at a depth

between 25 and 125 cm from the mineral soil surface, more

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Acrudox

EEBN. Other Acrudox that have 50 percent or more hue

of 7.5YR or yellower and a color value, moist, of 6 or more

at a depth between 25 and 125 cm from the mineral soil

surface.

Xanthic Acrudox

EEBO. Other Acrudox.

Typic Acrudox

Definition of Typic Acrudox

Typic Acrudox are the Acrudox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Have a delta pH (KCl pH minus 1:1 water pH) with a net

negative charge in all parts within 125 cm of the mineral soil

surface;

3. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

4. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

5. Have 35 percent or less base saturation (by NH4OAc) in

some subhorizon within 125 cm of the mineral soil surface;

6. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter; and

7. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.
Oxisols 675

Description of Subgroups

Typic Acrudox.—The central concept or Typic subgroup of

Acrudox is fixed on soils that do not have a petroferric contact,

a lithic contact, or redox depletions with a color value, moist, of 4

or more and chroma of 2 or less within 125 cm of the mineral soil

surface and also do not have aquic conditions for some time in

normal years. These soils have less than 16 kg/m2

 organic

carbon to a depth of 100 cm and have less than 5 percent

plinthite in all horizons within a depth of 125 cm. Their colors are

reddish, but the soils do not have very dark reddish colors

throughout the layers between depths of 25 and 125 cm. These

soils are of small extent in Hawaii.

Anionic Acrudox.—These soils have a delta pH (KCl pH

minus 1:1 water pH) with a 0 or net positive charge in a layer

18 cm or more thick within 125 cm of the mineral soil surface.

They are of small extent and are known to occur only in

Hawaii and Puerto Rico in the United States.

Anionic Aquic Acrudox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). They have a delta pH (KCl pH

minus 1:1 water pH) with a 0 or net positive charge in a layer

18 cm or more thick within 125 cm of the mineral soil surface.

These soils are not known to occur in the United States.

Aquic Acrudox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Acrudox are considered

intergrades between Acrudox and Acraquox. They are not

known to occur in the United States.

Aquic Lithic Acrudox.—These soils have, within 125 cm

of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Acrudox.—These soils have, within 125

cm of the mineral soil surface, both a petroferric contact and

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage). The soils are not known

to occur in the United States.

Eutric Acrudox.—These soils have a base saturation (by

NH4

OAc) of 35 percent or more in all horizons within 125 cm

of the mineral soil surface. The soils are not known to occur in

the United States.

Humic Acrudox.—These soils are like Typic Acrudox, but

they have 16 kg or more organic carbon per m2 within 100 cm

of the mineral soil surface. They are not known to occur in the

United States.

Humic Rhodic Acrudox.—These soils have, in all horizons at

a depth between 25 and 125 cm from the mineral soil surface,

more than 50 percent colors that have hue of 2.5YR or redder

and a value, moist, of 3 or less. They also have 16 kg or more

organic carbon per m2

 within 100 cm of the mineral soil surface.

These soils are not known to occur in the United

States.

Humic Xanthic Acrudox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, colors that have hue of 7.5YR or yellower and

value, moist, of 6 or more. They also have 16 kg or more

organic carbon per m2 within 100 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Lithic Acrudox.—These soils have a lithic contact within 125

cm of the mineral soil surface. They are not known to occur in

the United States.

Petroferric Acrudox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthic Acrudox.—These soils have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface. They are of small extent in Hawaii.

Rhodic Acrudox.—These soils are like Typic Acrudox, but

they have, in all horizons at a depth between 25 and 125 cm

from the mineral soil surface, more than 50 percent colors that

have hue of 2.5YR or redder and a value, moist, of 3 or less.

The soils are not known to occur in the United States.

Xanthic Acrudox.—These soils are like Typic Acrudox, but

they have hue of 7.5YR or yellower and a color value, moist, of

6 or more in all horizons at a depth between 25 and 125 cm

from the mineral soil surface. The soils are not known to occur

in the United States.

Eutrudox

These are the Udox with high base saturation throughout the

profile. They do not have a sombric horizon within 150 cm of the

mineral soil surface. They have, in all subhorizons of an oxic or

kandic horizon within 150 cm of the mineral soil surface, an

apparent ECEC of 1.50 cmol(+) per kg clay or more or a pH value

(1N KCl) of less than 5.0. These soils are highly valued by

shifting cultivators and are most common in areas near basic

geologic rock.

Definition

Eutrudox are the Udox that:

1. Have more than 35 percent base saturation (by NH4OAc) in

all parts within 125 cm of the mineral soil surface;

2. Do not have a sombric horizon within 150 cm of the mineral

soil surface; and

3. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some part

of an oxic or kandic horizon within 150 cm of the mineral soil

surface.
676 Soil Taxonomy

Key to Subgroups

EECA. Eutrudox that have, within 125 cm of the mineral soil

surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Eutrudox

EECB. Other Eutrudox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Eutrudox

EECC. Other Eutrudox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Eutrudox

EECD. Other Eutrudox that have a lithic contact within 125

cm of the mineral soil surface.

Lithic Eutrudox

EECE. Other Eutrudox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Eutrudox

EECF. Other Eutrudox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Eutrudox

EECG. Other Eutrudox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Eutrudox

EECH. Other Eutrudox that have a kandic horizon that has

its upper boundary within 150 cm of the mineral soil surface.

Kandiudalfic Eutrudox

EECI. Other Eutrudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral soil

surface and a depth of 100 cm; and

2. An oxic horizon that has its lower boundary within 125

cm of the mineral soil surface.

Humic Inceptic Eutrudox

EECJ. Other Eutrudox that have an oxic horizon that has its

lower boundary within 125 cm of the mineral soil surface.

Inceptic Eutrudox

EECK. Other Eutrudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Eutrudox

EECL. Other Eutrudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Eutrudox

EECM. Other Eutrudox that have 16 kg/m2 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Eutrudox

EECN. Other Eutrudox that have, in all horizons at a depth

between 25 and 125 cm from the mineral soil surface, more

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Eutrudox

EECO. Other Eutrudox that have 50 percent or more hue of

7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Eutrudox

EECP. Other Eutrudox.

Typic Eutrudox

Definition of Typic Eutrudox

Typic Eutrudox are the Eutrudox that:
Oxisols 677

1. Have neither a petroferric nor a lithic contact within 125 cm

of the mineral soil surface;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, in any horizon within 125 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions;

4. Do not have a kandic horizon with its upper boundary

within 150 cm of the mineral soil surface;

5. Have an oxic horizon with a lower boundary 125 cm or

more from the mineral soil surface;

6. Have less than 16 kg of organic carbon per m2

 to a depth

of 1 m, exclusive of surface litter; and

7. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Eutrudox.—The central concept or Typic subgroup

of Eutrudox is fixed on soils that have a thick oxic horizon.

These soils do not have a petroferric contact, a lithic contact, or

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less within 125 cm of the mineral soil surface

and also do not have aquic conditions for some time in normal

years. They have less than 16 kg/m2

 organic carbon to a depth

of 100 cm and have less than 5 percent plinthite in all horizons

within a depth of 125 cm. Their colors are reddish, but the

soils do not have very dark reddish colors throughout the layers

between depths of 25 and 125 cm. These soils are of small

extent in Hawaii.

Aquic Eutrudox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Eutrudox are considered

intergrades between Eutrudox and Eutraquox. They are not

known to occur in the United States.

Aquic Lithic Eutrudox.—These soils have, within 125 cm

of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Eutrudox.—These soils have, within

125 cm of the mineral soil surface, both a petroferric contact

and redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some time

in normal years (or artificial drainage). The soils are not known

to occur in the United States.

Humic Eutrudox.—These soils are like Typic Eutrudox, but

they have 16 kg or more organic carbon per m2

 within 100 cm

of the mineral soil surface. They are not known to occur in the

United States.

Humic Inceptic Eutrudox.—These soils have an oxic

horizon that has its lower boundary within 125 cm of the

mineral soil surface. They also have 16 kg or more organic

carbon per m2 within 100 cm of the mineral soil surface. These

soils are not known to occur in the United States.

Humic Rhodic Eutrudox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Eutrudox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, colors that have hue of 7.5YR or yellower and

value, moist, of 6 or more. They also have 16 kg or more

organic carbon per m2 within 100 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Inceptic Eutrudox.—These soils have an oxic horizon that

has its lower boundary within 125 cm of the mineral soil

surface. They are of small extent in Hawaii.

Kandiudalfic Eutrudox.—These soils have a kandic

horizon that has its upper boundary within 125 cm of the

mineral soil surface. They are not known to occur in the United

States.

Lithic Eutrudox.—These soils have a lithic contact within

125 cm of the mineral soil surface. They are of very small

extent, mostly in Puerto Rico.

Petroferric Eutrudox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Eutrudox.—These soils have, within 125 cm

of the mineral soil surface, redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial

drainage). They have 5 percent or more (by volume) plinthite

in one or more horizons within 125 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Plinthic Eutrudox.—These soils have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface. The soils are not known to occur in the

United States.

Rhodic Eutrudox.—These soils are like Typic Eutrudox, but

they have, in all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that have
678 Soil Taxonomy

hue of 2.5YR or redder and a value, moist, of 3 or less. The soils

are not known to occur in the United States.

Xanthic Eutrudox.—These soils are like Typic Eutrudox, but

they have hue of 7.5YR or yellower and a color value, moist, of 6

or more in all horizons at a depth between 25 and 125 cm from

the mineral soil surface. The soils are not known to occur in the

United States.

Hapludox

These are the Udox that do not have a sombric horizon

within 150 cm of the mineral soil surface and have, in all

subhorizons of an oxic horizon within 150 cm of the mineral

soil surface, an apparent ECEC of 1.50 or more cmol(+) per kg

clay or a pH value (1N KCl) of less than 5.0. They also have a

base saturation (by NH4OAc) of less than 35 percent in some

horizon within 125 cm of the mineral soil surface and do not

have a kandic horizon that has its upper boundary within 150

cm of the mineral soil surface. The subsoil has granular

structure, and the epipedons may be either dark or light

colored. Hapludox commonly are acid, and the subsoil ranges

from dark red to pale yellow. These soils are common in the

uplands of Africa, the central part of Indonesia, and many

other areas.

Definition

Hapludox are the Udox that:

1. Have 35 percent or less base saturation (by NH4OAc) in

some or all parts within 125 cm of the mineral soil surface;

2. Do not have a sombric horizon within 150 cm of the

mineral soil surface;

3. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of an oxic horizon within 150 cm of the mineral soil

surface; and

4. Do not have the upper boundary of a kandic horizon

within 150 cm of the mineral soil surface.

Key to Subgroups

EEEA. Hapludox that have, within 125 cm of the mineral

soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Hapludox

EEEB. Other Hapludox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Hapludox

EEEC. Other Hapludox that have, within 125 cm of the mineral

soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Hapludox

EEED. Other Hapludox that have a lithic contact within 125

cm of the mineral soil surface.

Lithic Hapludox

EEEE. Other Hapludox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Hapludox

EEEF. Other Hapludox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Hapludox

EEEG. Other Hapludox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Hapludox

EEEH. Other Hapludox that have an oxic horizon that has its

lower boundary within 125 cm of the mineral soil surface.

Inceptic Hapludox

EEEI. Other Hapludox that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Hapludox

EEEJ. Other Hapludox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:
Oxisols 679

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Hapludox

EEEK. Other Hapludox that have both:

1. 16 kg/m2

 or more organic carbon between the mineral soil

surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a color

value, moist, of 6 or more at a depth between 25 and 125 cm

from the mineral soil surface.

Humic Xanthic Hapludox

EEEL. Other Hapludox that have 16 kg/m2 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Hapludox

EEEM. Other Hapludox that have, in all horizons at a depth

between 25 and 125 cm from the mineral soil surface, more

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Hapludox

EEEN. Other Hapludox that have 50 percent or more hue of

7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Hapludox

EEEO. Other Hapludox.

Typic Hapludox

Definition of Typic Hapludox

Typic Hapludox are the Hapludox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

3. Have an oxic horizon with a lower boundary 125 cm or

more from the mineral soil surface;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

5. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter; and

6. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, less than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6 or

more.

Description of Subgroups

Typic Hapludox.—The central concept or Typic subgroup of

Hapludox is fixed on soils that do not have a petroferric contact,

a lithic contact, or redox depletions with a color value, moist, of 4

or more and chroma of 2 or less within 125 cm of the mineral soil

surface and also do not have aquic conditions for some time in

normal years. These soils have less than 16 kg/m2

 organic

carbon to a depth of 100 cm and have less than 5 percent

plinthite in all horizons within a depth of 125 cm. Their colors are

reddish, but the soils do not have very dark reddish colors

throughout the layers between depths of 25 and 125 cm. They

do not have a surface mantle or layer in the upper 75 cm with

both a low bulk density and a high content of weakly crystalline

minerals. These soils are of small extent, mostly in Puerto Rico

and Hawaii.

Andic Hapludox.—These soils have a surface mantle or

layer in the upper 75 cm with both a low bulk density and a

high content of weakly crystalline minerals. The soils are not

known to occur in the United States.

Aquic Hapludox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Hapludox are considered

intergrades between Hapludox and Haplaquox. They are not

known to occur in the United States.

Aquic Lithic Hapludox.—These soils have, within 125 cm

of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Hapludox.—These soils have, within

125 cm of the mineral soil surface, both a petroferric contact

and redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage). The soils are not

known to occur in the United States.

Humic Hapludox.—These soils are like Typic Hapludox,

but they have 16 kg or more organic carbon per m2

 within 100

cm of the mineral soil surface. They are of very small extent,

mostly in Puerto Rico.

Humic Rhodic Hapludox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also
680 Soil Taxonomy

have 16 kg or more organic carbon per m2

 within 100 cm of the

mineral soil surface. They are not known to occur in the United

States.

Humic Xanthic Hapludox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

7.5YR or yellower and value, moist, of 6 or more. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Inceptic Hapludox.—These soils have an oxic horizon that

has its lower boundary within 125 cm of the mineral soil

surface. They are of small extent, mostly in Puerto Rico and

Hawaii.

Lithic Hapludox.—These soils have a lithic contact within

125 cm of the mineral soil surface. They are of very small

extent, mostly in Puerto Rico.

Petroferric Hapludox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Hapludox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, 5 percent

or more (by volume) plinthite, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less, and aquic

conditions for some time in normal years (or artificial

drainage). The soils are not known to occur in the United

States.

Plinthic Hapludox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. The soils are not known to occur in

the United States.

Rhodic Hapludox.—These soils are like Typic Hapludox,

but they have, in all horizons at a depth between 25 and 125

cm from the mineral soil surface, more than 50 percent colors

that have hue of 2.5YR or redder and a value, moist, of 3 or

less. The soils are of very small extent, mostly in Puerto Rico.

Xanthic Hapludox.—These soils are like Typic Hapludox, but

they have hue of 7.5YR or yellower and a color value, moist, of 6

or more in all horizons at a depth between 25 and 125 cm from

the mineral soil surface. The soils are not known to occur in the

United States.

Kandiudox

These are the clayey Udox that have a kandic horizon that

has its upper boundary within 150 cm of the mineral soil

surface. They do not have a sombric horizon within 150 cm of

the mineral soil surface, but they have, in all subhorizons of a

kandic horizon within 150 cm of the mineral soil surface, an

apparent ECEC of 1.50 or more cmol(+) per kg clay or a pH

value (1N KCl) of less than 5.0. They also have a base

saturation (by NH4OAc) of less than 35 percent in some

horizon within 125 cm of the mineral soil surface. The subsoil

has a moderate grade of blocky structure in most pedons. The

epipedons are either dark or light colored.

Definition

Kandiudox are the Udox that:

1. Have the upper boundary of a kandic horizon within 150 cm

of the mineral soil surface;

2. Have 35 percent or less base saturation (by NH4OAc) in

some or all parts within 125 cm of the mineral soil surface;

3. Do not have a sombric horizon within 150 cm of the

mineral soil surface; and

4. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of a kandic horizon within 150 cm of the mineral soil

surface.

Key to Subgroups

EEDA. Kandiudox that have, within 125 cm of the mineral

soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Kandiudox

EEDB. Other Kandiudox that have a petroferric contact

within 125 cm of the mineral soil surface.

Petroferric Kandiudox

EEDC. Other Kandiudox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Kandiudox

EEDD. Other Kandiudox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Kandiudox

EEDE. Other Kandiudox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Kandiudox
Oxisols 681

EEDF. Other Kandiudox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Kandiudox

EEDG. Other Kandiudox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Kandiudox

EEDH. Other Kandiudox that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3

 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Kandiudox

EEDI. Other Kandiudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral soil

surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from the

mineral soil surface, more than 50 percent colors that have

both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Kandiudox

EEDJ. Other Kandiudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Kandiudox

EEDK. Other Kandiudox that have 16 kg/m2 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Kandiudox

EEDL. Other Kandiudox that have, in all horizons at a depth

between 25 and 125 cm from the mineral soil surface, more

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Kandiudox

EEDM. Other Kandiudox that have 50 percent or more hue

of 7.5YR or yellower and a color value, moist, of 6 or more

at a depth between 25 and 125 cm from the mineral soil

surface.

Xanthic Kandiudox

EEDN. Other Kandiudox.

Typic Kandiudox

Definition of Typic Kandiudox

Typic Kandiudox are the Kandiudox that:

1. Have neither a petroferric nor a lithic contact within 125 cm

of the mineral soil surface;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

5. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter; and

6. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, less than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Kandiudox.—The central concept or Typic subgroup

of Kandiudox is fixed on soils that do not have a petroferric

contact, a lithic contact, or redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less within 125 cm of

the mineral soil surface and also do not have aquic conditions

for some time in normal years. These soils have less than 16

kg/m2

 organic carbon to a depth of 100 cm and have less than 5

percent plinthite in all horizons within a depth of 125 cm.

Their colors are reddish, but the soils do not have very dark

reddish colors throughout the layers between depths of 25 and

125 cm. They do not have a surface mantle or layer in the

upper 75 cm with both a low bulk density and a high content of

weakly crystalline minerals. These soils are of small extent,

mostly in Puerto Rico.

Andic Kandiudox.—These soils have a surface mantle or

layer in the upper 75 cm with both a low bulk density and a
682 Soil Taxonomy

high content of weakly crystalline minerals. The soils are not

known to occur in the United States.

Aquic Kandiudox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma of

2 or less and also aquic conditions for some time in normal years

(or artificial drainage). Aquic Kandiudox are considered

intergrades between Kandiudox and Aquox. They are not known

to occur in the United States.

Aquic Lithic Kandiudox.—These soils have, within 125

cm of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Kandiudox.—These soils have, within

125 cm of the mineral soil surface, both a petroferric contact

and redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage). The soils are not

known to occur in the United States.

Humic Kandiudox.—These soils are like Typic Kandiudox,

but they have 16 kg or more organic carbon per m2

 within 100

cm of the mineral soil surface. They are not known to occur in

the United States.

Humic Rhodic Kandiudox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Kandiudox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

7.5YR or yellower and value, moist, of 6 or more. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Lithic Kandiudox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Kandiudox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Kandiudox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, 5 percent

or more (by volume) plinthite, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less, and aquic

conditions for some time in normal years (or artificial

drainage). The soils are not known to occur in the United

States.

Plinthic Kandiudox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. The soils are not known to occur in the

United States.

Rhodic Kandiudox.—These soils are like Typic

Kandiudox, but they have, in all horizons at a depth between

25 and 125 cm from the mineral soil surface, more than 50

percent colors that have hue of 2.5YR or redder and a value,

moist, of 3 or less. The soils are not known to occur in the

United States.

Xanthic Kandiudox.—These soils are like Typic Kandiudox,

but they have hue of 7.5YR or yellower and a color value, moist,

of 6 or more in all horizons at a depth between 25 and 125 cm

from the mineral soil surface. The soils are not known to occur in

the United States.

Sombriudox

These are the Udox that have a sombric horizon. These soils

are poorly understood. They have an increase in content of

organic carbon in the subsoil. The only known pedons are near

the Rift Valley in Africa.

Definition

Sombriudox are the Udox that have a sombric horizon

within 150 cm of the mineral soil surface.

Key to Subgroups

EEAA. Sombriudox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Sombriudox

EEAB. Other Sombriudox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Sombriudox

EEAC. Other Sombriudox that have 16 kg/m2 or more

organic carbon between the mineral soil surface and a depth of

100 cm.

Humic Sombriudox

EEAD. Other Sombriudox.

Typic Sombriudox

Definition of Typic Sombriudox

Typic Sombriudox are the Sombriudox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface; and

2. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter.

Description of Subgroups

Typic Sombriudox.—The central concept or Typic

subgroup of Sombriudox is fixed on soils that do not have a

petroferric or lithic contact within 125 cm of the mineral soil
Oxisols 683

surface. These soils have less than 16 kg/m2

 organic carbon to a

depth of 100 cm. They are not known to occur in the United

States.

Humic Sombriudox.—These soils are like Typic

Sombriudox, but they have 16 kg or more organic carbon per

m2 within 100 cm of the mineral soil surface. They are not known

to occur in the United States.

Lithic Sombriudox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Sombriudox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Ustox

These are the Oxisols that have an ustic moisture regime.

Because of natural rainfall, they are moist in normal years for

at least 90 days (a period that usually is long enough for one

rain-fed crop) but not for more than 270 days. Crops are not

grown continuously because there is inadequate moisture for at

least 90 days in normal years. Ustox may be the most extensive

suborder, occurring over a large portion of the interior of South

America and in extensive areas of Africa. A few Ustox are in

areas of the xeric soil moisture regime, for example, in

Australia. The range of natural rainfall within the Ustox

provides that two crops can be grown on some Ustox but only

one crop can be grown on others unless supplemental irrigation

is available.

Definition

Ustox are the Oxisols that have an ustic moisture regime.

Key to Great Groups

ECA. Ustox that have a sombric horizon within 150 cm of

the mineral soil surface.

Sombriustox, p. 692

ECB. Other Ustox that have, in one or more subhorizons of

an oxic or kandic horizon within 150 cm of the mineral soil

surface, an apparent ECEC of less than 1.50 cmol(+) per kg

clay and a pH value (1N KCl) of 5.0 or more.

Acrustox, p. 683

ECC. Other Ustox that have a base saturation (by NH4OAc)

of 35 percent or more in all horizons within 125 cm of the

mineral soil surface.

Eutrustox, p. 685

ECD. Other Ustox that have a kandic horizon that has its

upper boundary within 150 cm of the mineral soil surface.

Kandiustox, p. 690

ECE. Other Ustox.

Haplustox, p. 688

Acrustox

These are the Ustox with very low cation-exchange values.

They do not have a sombric horizon within 150 cm of the

mineral soil surface. They can easily have their chemical

environment altered by applications of fertilizer and lime.

Because of a low buffering capacity, small but frequent

applications of fertilizer and lime are desirable. A low content

of exchangeable aluminum in the subsoil can be corrected by

leaching basic cations from lime and fertilizer.

Definition

Acrustox are the Ustox that:

1. Have an apparent ECEC of less than 1.50 cmol(+) per kg

clay and a pH value (1N KCl) of 5.0 or more in some part of an

oxic or kandic horizon within 150 cm of the mineral soil

surface; and

2. Do not have a sombric horizon within 150 cm of the

mineral soil surface.

Key to Subgroups

ECBA. Acrustox that have, within 125 cm of the mineral soil

surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Acrustox

ECBB. Other Acrustox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Acrustox

ECBC. Other Acrustox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Acrustox

ECBD. Other Acrustox that have a lithic contact within 125

cm of the mineral soil surface.

Lithic Acrustox

ECBE. Other Acrustox that have, within 125 cm of the

mineral soil surface, both:
684 Soil Taxonomy

1. A delta pH (KCl pH minus 1:1 water pH) with a 0 or net

positive charge in a layer 18 cm or more thick; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Anionic Aquic Acrustox

ECBF. Other Acrustox that have a delta pH (KCl pH minus

1:1 water pH) with a 0 or net positive charge in a layer 18 cm

or more thick within 125 cm of the mineral soil surface.

Anionic Acrustox

ECBG. Other Acrustox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Acrustox

ECBH. Other Acrustox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Acrustox

ECBI. Other Acrustox that have a base saturation (by

NH4

OAc) of 35 percent or more in all horizons within 125 cm

of the mineral soil surface.

Eutric Acrustox

ECBJ. Other Acrustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Acrustox

ECBK. Other Acrustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Acrustox

ECBL. Other Acrustox that have 16 kg/m2 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Acrustox

ECBM. Other Acrustox that have, in all horizons at a depth

between 25 and 125 cm from the mineral soil surface, more

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Acrustox

ECBN. Other Acrustox that have 50 percent or more hue of

7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Acrustox

ECBO. Other Acrustox.

Typic Acrustox

Definition of Typic Acrustox

Typic Acrustox are the Acrustox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Have a delta pH (KCl pH minus 1:1 water pH) with a net

negative charge in all parts within 125 cm of the mineral soil

surface;

3. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

4. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

5. Have 35 percent or less base saturation (by NH4

OAc) in

some subhorizon within 125 cm of the mineral soil surface;

6. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter; and

7. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Acrustox.—The central concept or Typic subgroup of

Acrustox is fixed on soils that do not have a petroferric contact,

a lithic contact, or redox depletions with a color value, moist,

of 4 or more and chroma of 2 or less within 125 cm of the

mineral soil surface and also do not have aquic conditions for

some time in normal years. These soils have less than 16 kg/m2

organic carbon to a depth of 100 cm and have less than 5

percent plinthite in all horizons within a depth of 125 cm.
Oxisols 685

Their colors are reddish, but the soils do not have very dark

reddish colors throughout the layers between depths of 25 and

125 cm. These soils are not known to occur in the United

States.

Anionic Acrustox.—These soils have a delta pH (KCl pH

minus 1:1 water pH) with a 0 or net positive charge in a layer

18 cm or more thick within 125 cm of the mineral soil surface.

They are of very small extent and are known to occur only in

Hawaii in the United States.

Anionic Aquic Acrustox.—These soils have, in one or

more horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). They have a delta pH (KCl pH

minus 1:1 water pH) with a 0 or net positive charge in a layer

18 cm or more thick within 125 cm of the mineral soil surface.

These soils are not known to occur in the United States.

Aquic Acrustox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Acrustox are considered

intergrades between Acrustox and Acraquox. They are not

known to occur in the United States.

Aquic Lithic Acrustox.—These soils have, within 125 cm

of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Acrustox.—These soils have, within 125

cm of the mineral soil surface, both a petroferric contact and

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage). The soils are not known

to occur in the United States.

Eutric Acrustox.—These soils have a base saturation (by

NH4

OAc) of 35 percent or more in all horizons within 125 cm

of the mineral soil surface. The soils are not known to occur in

the United States

Humic Acrustox.—These soils are like Typic Acrustox, but

they have 16 kg or more organic carbon per m2 within 100 cm

of the mineral soil surface. They are not known to occur in the

United States.

Humic Rhodic Acrustox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Acrustox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

7.5YR or yellower and value, moist, of 6 or more. They also have

16 kg or more organic carbon per m2 within 100 cm of the mineral

soil surface. These soils are not known to occur in the United

States.

Lithic Acrustox.—These soils have a lithic contact within

125 cm of the mineral soil surface. They are not known to

occur in the United States.

Petroferric Acrustox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthic Acrustox.—These soils have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface. The soils are not known to occur in the

United States.

Rhodic Acrustox.—These soils are like Typic Acrustox, but

they have, in all horizons at a depth between 25 and 125 cm

from the mineral soil surface, more than 50 percent colors that

have hue of 2.5YR or redder and a value, moist, of 3 or less.

The soils are not known to occur in the United States.

Xanthic Acrustox.—These soils are like Typic Acrustox, but

they have hue of 7.5YR or yellower and a color value, moist, of 6

or more in all horizons at a depth between 25 and 125 cm from

the mineral soil surface. The soils are not known to occur in the

United States.

Eutrustox

These are the Ustox with high base saturation throughout the

profile. They do not have a sombric horizon within 150 cm of the

mineral soil surface. They have, in all subhorizons of an oxic or

kandic horizon within 150 cm of the mineral soil surface, an

apparent ECEC of 1.50 cmol(+) per kg clay or more or a pH value

(1N KCl) of less than 5.0. These soils are well known by local

farmers because of their relatively high natural fertility.

Commonly, they supported natural forests while the surrounding

areas of like rainfall but low base status supported savannas.

Currently, forest vegetation is rare because the forests have

been completely cut by native farmers. Why these Ustox have

high saturation throughout their profile is not known, but they

tend to occur over or near basic rocks, such as limestone and

basalt.

Definition

Eutrustox are the Ustox that:

1. Have more than 35 percent base saturation (by NH4

OAc) in

all parts within 125 cm of the mineral soil surface;

2. Do not have a sombric horizon within 150 cm of the mineral

soil surface; and

3. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some part

of an oxic or kandic horizon within 150 cm of the mineral soil

surface.
686 Soil Taxonomy

Key to Subgroups

ECCA. Eutrustox that have, within 125 cm of the mineral soil

surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Eutrustox

ECCB. Other Eutrustox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Eutrustox

ECCC. Other Eutrustox that have, within 125 cm of the

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Eutrustox

ECCD. Other Eutrustox that have a lithic contact within 125

cm of the mineral soil surface.

Lithic Eutrustox

ECCE. Other Eutrustox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Eutrustox

ECCF. Other Eutrustox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Eutrustox

ECCG. Other Eutrustox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Eutrustox

ECCH. Other Eutrustox that have a kandic horizon that has

its upper boundary within 150 cm of the mineral soil surface.

Kandiustalfic Eutrustox

ECCI. Other Eutrustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral soil

surface and a depth of 100 cm; and

2. An oxic horizon that has its lower boundary within 125

cm of the mineral soil surface.

Humic Inceptic Eutrustox

ECCJ. Other Eutrustox that have an oxic horizon that has its

lower boundary within 125 cm of the mineral soil surface.

Inceptic Eutrustox

ECCK. Other Eutrustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Eutrustox

ECCL. Other Eutrustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Eutrustox

ECCM. Other Eutrustox that have 16 kg/m2 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Eutrustox

ECCN. Other Eutrustox that have, in all horizons at a depth

between 25 and 125 cm from the mineral soil surface, more

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Eutrustox

ECCO. Other Eutrustox that have 50 percent or more hue of

7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Eutrustox

ECCP. Other Eutrustox.

Typic Eutrustox

Definition of Typic Eutrustox

Typic Eutrustox are the Eutrustox that:
Oxisols 687

1. Have neither a petroferric nor a lithic contact within 125 cm

of the mineral soil surface;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

4. Do not have a kandic horizon with its upper boundary

within 150 cm of the mineral soil surface;

5. Have an oxic horizon with a lower boundary 125 cm or

more from the mineral soil surface;

6. Have less than 16 kg of organic carbon per m2

 to a depth

of 1 m, exclusive of surface litter; and

7. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Eutrustox.—The central concept or Typic subgroup

of Eutrustox is fixed on soils that have a thick oxic horizon.

These soils do not have a petroferric contact, a lithic contact, or

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less within 125 cm of the mineral soil surface

and also do not have aquic conditions for some time in normal

years. The soils have less than 16 kg/m2

 organic carbon to a

depth of 100 cm and have less than 5 percent plinthite in all

horizons within a depth of 125 cm. Their colors are reddish,

but the soils do not have very dark reddish colors throughout

the layers between depths of 25 and 125 cm. These soils are not

known to occur in the United States.

Aquic Eutrustox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Eutrustox are considered

intergrades between Eutrustox and Eutraquox. They are not

known to occur in the United States.

Aquic Lithic Eutrustox.—These soils have, within 125 cm

of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Eutrustox.—These soils have, within

125 cm of the mineral soil surface, both a petroferric contact

and redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some time

in normal years (or artificial drainage). The soils are not known

to occur in the United States.

Humic Eutrustox.—These soils are like Typic Eutrustox,

but they have 16 kg or more organic carbon per m2

 within 100

cm of the mineral soil surface. They are not known to occur in

the United States.

Humic Inceptic Eutrustox.—These soils have an oxic

horizon that has its lower boundary within 125 cm of the

mineral soil surface. They also have 16 kg or more organic

carbon per m2 within 100 cm of the mineral soil surface. These

soils are not known to occur in the United States.

Humic Rhodic Eutrustox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Eutrustox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, colors that have hue of 7.5YR or yellower and

value, moist, of 6 or more. They also have 16 kg or more

organic carbon per m2 within 100 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Inceptic Eutrustox.—These soils have an oxic horizon that

has its lower boundary within 125 cm of the mineral soil

surface. They are of very small extent, mostly in Hawaii and

Guam.

Kandiustalfic Eutrustox.—These soils have a kandic

horizon that has its upper boundary within 125 cm of the

mineral soil surface. They are not known to occur in the United

States.

Lithic Eutrustox.—These soils have a lithic contact within

125 cm of the mineral soil surface. They are of small extent,

mostly in Puerto Rico and Hawaii.

Petroferric Eutrustox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Eutrustox.—These soils have, within 125 cm

of the mineral soil surface, redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less and also aquic

conditions for some time in normal years (or artificial

drainage). They have 5 percent or more (by volume) plinthite

in one or more horizons within 125 cm of the mineral soil

surface. These soils are not known to occur in the United

States.

Plinthic Eutrustox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. The soils are not known to occur in

the United States.

Rhodic Eutrustox.—These soils are like Typic Eutrustox,

but they have, in all horizons at a depth between 25 and 125
688 Soil Taxonomy

cm from the mineral soil surface, more than 50 percent colors

that have hue of 2.5YR or redder and a value, moist, of 3 or

less. The soils are of small extent, mostly in Hawaii.

Xanthic Eutrustox.—These soils are like Typic Eutrustox, but

they have hue of 7.5YR or yellower and a color value, moist, of 6

or more in all horizons at a depth between 25 and 125 cm from

the mineral soil surface. The soils are not known to occur in the

United States.

Haplustox

These are the Ustox that do not have a sombric horizon

within 150 cm of the mineral soil surface but that have, in all

subhorizons of an oxic horizon within 150 cm of the mineral

soil surface, an apparent ECEC of 1.50 or more cmol(+) per kg

clay or a pH value (1N KCl) of less than 5.0. They have a base

saturation (by NH4OAc) of less than 35 percent in some

horizon within 125 cm of the mineral soil surface and do not

have a kandic horizon that has its upper boundary within 150

cm of the mineral soil surface. The subsoil has granular

structure, and the epipedons may be either dark or light

colored. Haplustox are dark red to yellow and all intervening

colors in the subsoil. They occur in vast areas in central South

America and Africa.

Definition

Haplustox are the Ustox that:

1. Have 35 percent or less base saturation (by NH4OAc) in

some or all parts within 125 cm of the mineral soil surface;

2. Do not have a sombric horizon within 150 cm of the

mineral soil surface;

3. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of an oxic horizon within 150 cm of the mineral soil

surface; and

4. Do not have the upper boundary of an oxic horizon

within 150 cm of the mineral soil surface.

Key to Subgroups

ECEA. Haplustox that have, within 125 cm of the mineral

soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Haplustox

ECEB. Other Haplustox that have a petroferric contact

within 125 cm of the mineral soil surface.

Petroferric Haplustox

ECEC. Other Haplustox that have, within 125 cm of the mineral

soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Haplustox

ECED. Other Haplustox that have a lithic contact within 125

cm of the mineral soil surface.

Lithic Haplustox

ECEE. Other Haplustox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Haplustox

ECEF. Other Haplustox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Haplustox

ECEG. Other Haplustox that have, within 125 cm of the

mineral soil surface, both:

1. The lower boundary of the oxic horizon; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aqueptic Haplustox

ECEH. Other Haplustox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Haplustox

ECEI. Other Haplustox that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplustox

ECEJ. Other Haplustox that have an oxic horizon that has its

lower boundary within 125 cm of the mineral soil surface.

Inceptic Haplustox
Oxisols 689

ECEK. Other Haplustox that have both:

1. 16 kg/m2

 or more organic carbon between the mineral soil

surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from the

mineral soil surface, more than 50 percent colors that have

both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Haplustox

ECEL. Other Haplustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Haplustox

ECEM. Other Haplustox that have 16 kg/m2 or more organic

carbon between the mineral soil surface and a depth of 100 cm.

Humic Haplustox

ECEN. Other Haplustox that have, in all horizons at a depth

between 25 and 125 cm from the mineral soil surface, more

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Haplustox

ECEO. Other Haplustox that have 50 percent or more hue of

7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Haplustox

ECEP. Other Haplustox.

Typic Haplustox

Definition of Typic Haplustox

Typic Haplustox are the Haplustox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

4. Are not saturated with water in any layer within 100 cm of

the mineral soil surface in normal years for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

5. Have an oxic horizon with a lower boundary 125 cm or more

from the mineral soil surface;

6. Do not have mottles with a color value, moist, of 4 or more

and chroma of 2 or less within 25 cm of the mineral soil

surface; and

7. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Haplustox.—The central concept or Typic subgroup

of Haplustox is fixed on soils that do not have a petroferric

contact, a lithic contact, or redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less within 125 cm of

the mineral soil surface and also do not have aquic conditions

for some time in normal years. These soils have less than 16

kg/m2

 organic carbon to a depth of 100 cm and have less than 5

percent plinthite in all horizons within a depth of 125 cm.

Their colors are reddish, but the soils do not have very dark

reddish colors throughout the layers between depths of 25 and

125 cm. These soils are not known to occur in the United

States.

Aqueptic Haplustox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). They have an oxic horizon that

has its lower boundary within 125 cm of the mineral soil

surface. Aqueptic Haplustox are considered intergrades

between Haplustox and Aquepts. They are not known to occur

in the United States.

Aquic Haplustox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Haplustox are considered

intergrades between Haplustox and Haplaquox. They are not

known to occur in the United States.

Aquic Lithic Haplustox.—These soils have, within 125 cm

of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Haplustox.—These soils have, within
690 Soil Taxonomy

125 cm of the mineral soil surface, both a petroferric contact and

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage). The soils are not known to

occur in the United States.

Humic Haplustox.—These soils are like Typic Haplustox,

but they have 16 kg or more organic carbon per m2

 within 100

cm of the mineral soil surface. They are not known to occur in

the United States.

Humic Rhodic Haplustox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Haplustox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

7.5YR or yellower and value, moist, of 6 or more. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Inceptic Haplustox.—These soils have an oxic horizon that

has its lower boundary within 125 cm of the mineral soil

surface. They are not known to occur in the United States.

Lithic Haplustox.—These soils have a lithic contact within

125 cm of the mineral soil surface. They are not known to

occur in the United States.

Oxyaquic Haplustox.—These soils are saturated with water

within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. They are not known to occur in the United States.

Petroferric Haplustox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Haplustox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, 5 percent

or more (by volume) plinthite, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less, and aquic

conditions for some time in normal years (or artificial

drainage). The soils are not known to occur in the United

States.

Plinthic Haplustox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. The soils are not known to occur in

the United States.

Rhodic Haplustox.—These soils are like Typic Haplustox,

but they have, in all horizons at a depth between 25 and 125

cm from the mineral soil surface, more than 50 percent colors

that have hue of 2.5YR or redder and a value, moist, of 3 or

less. The soils are of very small extent, mostly in Puerto Rico.

Xanthic Haplustox.—These soils are like Typic Haplustox,

but they have hue of 7.5YR or yellower and a color value,

moist, of 6 or more in all horizons at a depth between 25 and 125

cm from the mineral soil surface. The soils are not known to

occur in the United States.

Kandiustox

These are the clayey Ustox that have a kandic horizon that

has its upper boundary within 150 cm of the mineral soil

surface. They do not have a sombric horizon within 150 cm of

the mineral soil surface, but they have, in all subhorizons of a

kandic horizon within 150 cm of the mineral soil surface, an

apparent ECEC of 1.50 or more cmol(+) per kg clay or a pH

value (1N KCl) of less than 5.0. They also have a base

saturation (by NH4OAc) of less than 35 percent in some

horizon within 125 cm of the mineral soil surface. The subsoil

has a moderate grade of blocky structure in most pedons. The

epipedons are either dark or light colored. The subsoil shows

evidence of translocated clay only in a few areas. In some

pedons it tends to have a weak or moderate grade of blocky

structure. In most of the soils, however, there is a strong

secondary structure that is fine granular.

Definition

Kandiustox are the Ustox that:

1. Have the upper boundary of a kandic horizon within 150

cm of the mineral soil surface;

2. Have 35 percent or less base saturation (by NH4OAc)

in some or all parts within 125 cm of the mineral soil

surface;

3. Do not have a sombric horizon within 150 cm of the

mineral soil surface; and

4. Do not have an apparent ECEC of less than 1.50 cmol(+)

per kg clay and a pH value (1N KCl) of 5.0 or more in some

part of a kandic horizon within 150 cm of the mineral soil

surface.

Key to Subgroups

ECDA. Kandiustox that have, within 125 cm of the mineral

soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Petroferric Kandiustox

ECDB. Other Kandiustox that have a petroferric contact

within 125 cm of the mineral soil surface.

Petroferric Kandiustox

ECDC. Other Kandiustox that have, within 125 cm of the

mineral soil surface, both:
Oxisols 691

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Aquic Lithic Kandiustox

ECDD. Other Kandiustox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Kandiustox

ECDE. Other Kandiustox that have, in one or more horizons

within 125 cm of the mineral soil surface, both:

1. 5 percent or more (by volume) plinthite; and

2. Redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage).

Plinthaquic Kandiustox

ECDF. Other Kandiustox that have 5 percent or more (by

volume) plinthite in one or more horizons within 125 cm of the

mineral soil surface.

Plinthic Kandiustox

ECDG. Other Kandiustox that have, in one or more horizons

within 125 cm of the mineral soil surface, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Kandiustox

ECDH. Other Kandiustox that have both:

1. 16 kg/m2

 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from

the mineral soil surface, more than 50 percent colors that

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Kandiustox

ECDI. Other Kandiustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a

color value, moist, of 6 or more at a depth between 25 and

125 cm from the mineral soil surface.

Humic Xanthic Kandiustox

ECDJ. Other Kandiustox that have 16 kg/m2 or more

organic carbon between the mineral soil surface and a depth of

100 cm.

Humic Kandiustox

ECDK. Other Kandiustox that have, in all horizons at a

depth between 25 and 125 cm from the mineral soil surface,

more than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Kandiustox

ECDL. Other Kandiustox that have 50 percent or more hue

of 7.5YR or yellower and a color value, moist, of 6 or more at a

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Kandiustox

ECDM. Other Kandiustox.

Typic Kandiustox

Definition of Typic Kandiustox

Typic Kandiustox are the Kandiustox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface;

2. Do not have, within 125 cm of the mineral soil surface, a

horizon that has more than 5 percent plinthite (by volume);

3. Do not have, in any horizon within 125 cm of the mineral

soil surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less and also aquic conditions;

4. Have less than 16 kg of organic carbon per m2

 to a depth

of 1 m, exclusive of surface litter; and

5. Have, in some horizon at a depth between 25 and 125 cm

from the mineral soil surface, 50 percent or less colors that

have both of the following:

a. Hue of 2.5YR or redder and a color value, moist, of 3 or

less; and

b. Hue of 7.5YR or yellower and a color value, moist, of 6

or more.

Description of Subgroups

Typic Kandiustox.—The central concept or Typic subgroup

of Kandiustox is fixed on soils that do not have a petroferric

contact, a lithic contact, or redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less within 125 cm of

the mineral soil surface and also do not have aquic conditions

for some time in normal years. These soils have less than 16

kg/m2

 organic carbon to a depth of 100 cm and have less than 5

percent plinthite in all horizons within a depth of 125 cm.

Their colors are reddish, but the soils do not have very dark

reddish colors throughout the layers between depths of 25 and
692 Soil Taxonomy

125 cm. These soils are not known to occur in the United

States.

Aquic Kandiustox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). Aquic Kandiustox are considered

intergrades between Kandiustox and Aquox. They are not

known to occur in the United States.

Aquic Lithic Kandiustox.—These soils have, within 125

cm of the mineral soil surface, both a lithic contact and redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less and also aquic conditions for some time in normal

years (or artificial drainage). The soils are not known to occur

in the United States.

Aquic Petroferric Kandiustox.—These soils have, within

125 cm of the mineral soil surface, both a petroferric contact

and redox depletions with a color value, moist, of 4 or more

and chroma of 2 or less and also aquic conditions for some

time in normal years (or artificial drainage). The soils are not

known to occur in the United States.

Humic Kandiustox.—These soils are like Typic

Kandiustox, but they have 16 kg or more organic carbon per m2

within 100 cm of the mineral soil surface. They are not known

to occur in the United States.

Humic Rhodic Kandiustox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

2.5YR or redder and a value, moist, of 3 or less. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Humic Xanthic Kandiustox.—These soils have, in all

horizons at a depth between 25 and 125 cm from the mineral

soil surface, more than 50 percent colors that have hue of

7.5YR or yellower and value, moist, of 6 or more. They also

have 16 kg or more organic carbon per m2 within 100 cm of the

mineral soil surface. These soils are not known to occur in the

United States.

Lithic Kandiustox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known

to occur in the United States.

Petroferric Kandiustox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

Plinthaquic Kandiustox.—These soils have, in one or more

horizons within 125 cm of the mineral soil surface, 5 percent

or more (by volume) plinthite, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less, and aquic

conditions for some time in normal years (or artificial

drainage). The soils are not known to occur in the United

States.

Plinthic Kandiustox.—These soils have 5 percent or more

(by volume) plinthite in one or more horizons within 125 cm of

the mineral soil surface. The soils are not known to occur in the

United States.

Rhodic Kandiustox.—These soils are like Typic

Kandiustox, but they have, in all horizons at a depth between

25 and 125 cm from the mineral soil surface, more than 50

percent colors that have hue of 2.5YR or redder and a value,

moist, of 3 or less. The soils are not known to occur in the

United States.

Xanthic Kandiustox.—These soils are like Typic Kandiustox,

but they have hue of 7.5YR or yellower and a color value, moist,

of 6 or more in all horizons at a depth between 25 and 125 cm

from the mineral soil surface. The soils are not known to occur in

the United States.

Sombriustox

These are the Ustox that have a sombric horizon. They are

poorly understood. They have an increase in content of organic

carbon in the subsoil. Commonly, this layer has andic soil

properties or some properties of spodic materials. The only

known pedons are near the Rift Valley in Africa.

Definition

Sombriustox are the Ustox that have a sombric horizon

within 150 cm of the mineral soil surface.

Key to Subgroups

ECAA. Sombriustox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Sombriustox

ECAB. Other Sombriustox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Sombriustox

ECAC. Other Sombriustox that have 16 kg/m2

 or more

organic carbon between the mineral soil surface and a depth of

100 cm.

Humic Sombriustox

ECAD. Other Sombriustox.

Typic Sombriustox

Definition of Typic Sombriustox

Typic Sombriustox are the Sombriustox that:

1. Have neither a petroferric nor a lithic contact within 125

cm of the mineral soil surface; and

2. Have less than 16 kg of organic carbon per m2 to a depth

of 1 m, exclusive of surface litter.
Oxisols 693

Description of Subgroups

Typic Sombriustox.—The central concept or Typic

subgroup of Sombriustox is fixed on soils that do not have a

petroferric or lithic contact within 125 cm of the mineral soil

surface. These soils have less than 16 kg/m2

 organic carbon to a

depth of 100 cm. They are not known to occur in the United

States.

Humic Sombriustox.—These soils are like Typic

Sombriustox, but they have 16 kg or more organic carbon per m2

within 100 cm of the mineral soil surface. They are not known to

occur in the United States.

Lithic Sombriustox.—These soils have a lithic contact

within 125 cm of the mineral soil surface. They are not known to

occur in the United States.

Petroferric Sombriustox.—These soils have a petroferric

contact within 125 cm of the mineral soil surface. They are not

known to occur in the United States.

695

The feature that is common to most Spodosols is thepresence of a spodic horizon, in which amorphous

mixtures of organic matter and aluminum, with or without

iron, have accumulated. The spodic horizon may be destroyed

by cultivation, yet spodic materials may still be present. In

undisturbed soils there commonly is an overlying eluvial

horizon, generally with a gray or light gray color similar to

that of uncoated quartz. In some Spodosols this horizon is too

thin to be preserved after cultivation, while in others it is very

thick. Below the spodic horizon, there may be a fragipan or

another sequum that has an argillic horizon. A few Spodosols

have a placic horizon either on or within a spodic horizon or

on a fragipan. Some Spodosols have layers thicker than a

placic horizon that are cemented by spodic materials and

organic matter (ortstein).

Most Spodosols have few clay-sized phyllosilicates. The

particle-size class is mostly sandy, sandy-skeletal, coarseloamy, loamy-skeletal, or coarse-silty. In a few of the soils, it is

fine-loamy.

Spodosols are most extensive in areas of cool, humid or

perhumid climates. They also formed, however, in hot, humid

tropical regions and in warm, humid regions, where they occur

mostly in areas of quartz-rich sands that have a fluctuating

level of ground water. In many of the latter soils, the silt and

sand fractions contain very few weatherable minerals and the

albic horizons tend to be thick. Soils with an albic horizon 200

cm or more thick, however, are excluded from Spodosols and

are grouped with Entisols. Some of the very deep spodic

horizons may be buried, but it seems likely that others have

formed at great depths because the overlying soil materials

have very little iron and aluminum that could precipitate the

organic carbon. In some areas the source of aluminum may be

the ground water. Exclusion of a soil from Spodosols if the

albic horizon is very thick is largely pragmatic. The chemical

and physical properties of many Spodosols and Andisols are

very similar. The definition of spodic materials, however, is

based on the concept of organic matter and aluminum, with or

without iron, accumulating by illuviation.

The Spodosols in the United States occur mainly in areas of

late-Pleistocene or Holocene deposits. They are common in

Alaska, in the higher mountains of the West, in the Great

Lakes States, in the Northeast, and along the Atlantic coast of

both the United States and Canada. They also occur in

Northern Europe and northwestern Asia as well as New

Zealand and southern Australia. Most are covered with

coniferous or, less commonly, hardwood forests if they are not

cultivated or grazed. In tropical areas the vegetation may be

rain forest, palms, or a savanna that probably is anthropic.

The moisture regime of Spodosols is mostly udic, but a few

of the soils have a xeric regime. Some have aquic conditions.

Spodosols may have any soil temperature regime.

Spodosols are naturally infertile, but they can be highly

responsive to good management. Under cultivation, the spodic

horizon may be biologically destroyed, particularly if lime and

nitrogen are applied.

Definition of Spososols and Limits Between

Spodosols and Soils of Other Orders

Spodosols are mineral soils that do not have a plaggen

epipedon or an argillic or kandic horizon above a spodic

horizon and have one or more of the following:

1. A spodic horizon, an albic horizon in 50 percent or more

of each pedon, and a cryic soil temperature regime; or

2. An Ap horizon containing 85 percent or more spodic

materials; or

3. A spodic horizon that has all of the following properties:

a. One or more of the following:

(1) A thickness of 10 cm or more; or

(2) An overlying Ap horizon; or

(3) Cementation in 50 percent or more of each pedon;

or

(4) A coarse-loamy, loamy-skeletal, or finer particlesize class and a frigid temperature regime; or

(5) A cryic temperature regime; and

b. An upper boundary within the following depths from

the mineral soil surface: either

(1) Less than 50 cm; or

(2) Less than 200 cm if the soil has a sandy or sandyCHAPTER 18

Spodosols1

1 This chapter was rewritten in 1992 following recommendations of the International

Committee on the Classification of Spodosols (ICOMOD), chaired initially by F. Ted Miller,

then by Robert V. Rourke (since 1986).
696 Soil Taxonomy

skeletal particle-size class between the mineral soil

surface and the spodic horizon; and

c. A lower boundary as follows:

(1) Either at a depth of 25 cm or more below the

mineral soil surface, at the top of a duripan or fragipan,

or at a densic, lithic, paralithic, or petroferric contact,

whichever is shallowest; or

(2) At any depth,

(a) If the spodic horizon has a coarse-loamy, loamyskeletal, or finer particle-size class and the soil has a

frigid temperature regime; or

(b) If the soil has a cryic temperature regime; and

d. Either:

(1) A directly overlying albic horizon in 50 percent or

more of each pedon; or

(2) No andic soil properties in 60 percent or more of

the thickness either:

(a) Within 60 cm either of the mineral soil surface

or of the top of an organic layer with andic soil

properties, whichever is shallower, if there is no

densic, lithic, or paralithic contact, duripan, or

petrocalcic horizon within that depth; or

(b) Between either the mineral soil surface

or the top of an organic layer with andic soil

properties, whichever is shallower, and a densic,

lithic, or paralithic contact, a duripan, or a petrocalcic

horizon.

Limits Between Spodosols and the Other Soil

Orders

The definition of Spodosols must provide criteria that

separate Spodosols from all other soil orders. These criteria

define the limits of Spodosols in relation to all other known

kinds of soil.

1. Unlike Alfisols and Ultisols, Spodosols do not have an

argillic or kandic horizon above a spodic horizon.

2. Unlike Andisols, Aridisols, Entisols, Inceptisols,

Oxisols, Mollisols, and Vertisols, Spodosols have a spodic

horizon or an Ap horizon with 85 percent or more spodic

materials.

4. Unlike Gelisols, Spodosols do not have permafrost

within 100 cm of the soil surface or both permafrost within

200 cm of the soil surface and gelic materials within 100

cm of the soil surface.

5. Unlike Histosols, Spodosols must meet the definition of

mineral soils.

Representative Pedon and Data

Following is a description of a representative Spodosol. Data

for the pedon identified in this description are given in the table

“Characterization Data for a Spodosol.”

Classification: Coarse-loamy, isotic Typic Haplocryod

Site identification number: 95P0037

Location: Kuopio County, Finland; about 20 m east-southeast

of a gravel road; close to the village of Haapapuro

Finnish coordinates: X—6974.300 & Y—3522.920

Quadrangle name: Finnish Quad 4 Kainuu, Yleiskartta

Generalkarta

Latitude: 62 degrees 52 minutes 17 seconds N.

Longitude: 27 degrees 27 minutes 1 seconds E.

Slope: 7 percent

Aspect: 100 degrees

Horizontal shape: Plane

Vertical shape: Plane

Microrelief: Kind—mound; elevation—40 cm; pattern—

reticulate (net)

Elevation: 120 m

Landscape: Plateaus

Landform: Till plain

Parent material: Basal till

Annual precipitation: 510 mm

Average annual air temperature: 3 o

C

Average annual soil temperature: 5 oC

Weather station name: Kuopio, Finland

Boulders and stones: Covering 2 percent of the surface

Natural drainage class: Well drained

Permeability class: Moderate

Land use: Mixed coniferous and hardwood forest (not grazed)

Plant association: Taiga forest

Soil moisture regime: Udic

Soil temperature regime: Cryic

Particle-size control section: 33 to 108 cm

Diagnostic horizons: An albic horizon from a depth of 8 to 25

cm and a spodic horizon at a depth of 25 to 48 cm

Described by: D.L. Newton, S.E. Lee, Dr. M. Raisanen, and

H.R. Mount

In the following pedon description, colors are for moist soil

unless otherwise indicated.

Oi—0 to 3 cm; dark reddish brown (5YR 3/2) fibric material;

weak very fine granular structure; very friable, nonsticky

and nonplastic; many fine and medium roots throughout;

many fine to coarse interstitial pores; 80 percent fiber

unrubbed, 75 percent rubbed; 5 percent subangular gravel;

extremely acid; abrupt smooth boundary.

Oe—3 to 8 cm; black (5YR 2/1) extremely cobbly hemic material;

weak very fine granular structure; very friable, nonsticky

and nonplastic; many fine and medium roots throughout;

many fine and medium interstitial pores; 60 percent fiber

unrubbed, 20 percent rubbed; 10 percent subangular gravel,
Spodosols 697

Characterization Data for a Spodosol

 SITE IDENTIFICATION NO.: 95P0037

 CLASSIFICATION: COARSE-LOAMY, ISOTIC TYPIC HAPLOCRYOD

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 95P 312 0- 3 Oi -- -- -- --

 95P 313 3- 8 Oe -- -- -- 81

 95P 314 8- 25 E 1.8 19.9 78.3 10.3 9.6 12.7 25.1 23.0 13.1 4.4 4 8 2 70 83

 95P 315 25- 48 Bs 3.3 24.5 72.2 14.2 10.3 12.8 20.6 17.1 13.5 8.2 9 16 4 71 45

 95P 316 48- 64 BC 1.9 34.7 63.4 21.6 13.1 11.5 18.1 16.6 11.4 5.8 8 14 5 65 27

 95P 317 64-100 C 1.9 32.6 65.5 20.4 12.2 12.7 20.5 15.6 10.3 6.4 6 15 1 63 22

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B4a 6S3b 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A5 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 3 52.5 1.679 82.8

 3- 8 50.9 1.279 83.3

 8- 25 0.76 0.073 0.1 TR -- 2.56 1.33 2.4

 25- 48 2.32 0.204 1.6 0.9 -- 4.39 4.48 8.6

 48- 64 0.33 0.031 0.5 0.2 -- 1.58 2.53 2.5

 64-100 0.12 0.015 0.3 0.1 -- 0.95 1.21 1.3

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)

 Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos NaF CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9d 5A3a 5A8c 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1d 8C1f 8C1f

 <- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1

 0- 3 25.4 7.7 0.3 5.2 38.6 73.7 112.3 84.4 34 46 6.1 3.8 4.3

 3- 8 5.9 4.7 0.3 2.5 13.4 99.3 112.7 101.2 12 13 6.0 2.7 3.3

 8- 25 0.2 0.2 0.1 0.1 0.6 3.8 1.5 4.4 4.6 2.1 71 14 13 7.1 3.4 3.9

 25- 48 0.5 0.2 0.1 0.1 0.9 20.9 1.6 21.8 14.5 2.5 64 4 6 10.9 4.4 4.5

 48- 64 0.1 0.1 TR -- 0.2 4.0 0.1 4.2 3.0 0.3 33 5 7 10.3 5.0 4.9

 64-100 0.1 0.1 TR TR 0.2 2.0 TR 2.2 1.8 9 11 9.9 4.9 5.3

 -----------------------------------------------------------------------------------------------------------------------------------

 ACID OXALATE EXTRACTION PHOSPHORUS KCl TOTAL (- -WATER CONTENT- - )(- - - - WATER DISPERSIBLE - - - - ) MIN AGGRT

 OPT Fe Si Al CIT- Mn C 0.06 1- 2- 15 <- - PIPETTE - - >< - HYDROMETER - > SOIL STABL

 DEN RET ACID BAR BAR BAR BAR CLAY SILT SAND CLAY SILT SAND CONT <5mm

 SAMPLE HZ 8J 6C9a 6V2b 6G12b 6S4b 6S5 6D3b 6A2e 4B1c 4B1a 4B1a 4B2b <- - - 3A1c - - -><- - - SML - - -> 8F1 4G1

 NO. NO <- P c t o f < 2 m m -><- p p m ->< - - - - - - - - - - P e r c e n t o f < 2 m m - - - - - - - - - - >< Pct>

 95P 312 1 47.75 152.8 13

 95P 313 2 0.06 0.13 0.02 0.11 45.15 84.6 13

 95P 314 3 0.05 0.11 0.01 0.04 TR 1.40 4.3 2.4

 95P 315 4 0.34 0.93 0.42 1.51 TR 3.77 13.9 14.8

 95P 316 5 0.03 0.29 0.18 0.53 -- 0.43 5.7 4.8

 95P 317 6 0.02 0.17 0.07 0.21 -- 0.16 4.1 2.3

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm) - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - ->< - - - THERMAL - - - ->< - - - - - - - OPTICAL - - - - - - - - >< >INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - ->TOT RE< - - - - - GRAIN COUNT - - - - - ->< >PRETA-

 < - - - - 7A2i - - - - >< - 7A3c - >< - 7A4c - >< - - - - - - - - 7B1a - - - - - - - - ->< > TION

 NUMBER < - ->< - - - Peak Size - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - - - - - - - ->< - ->

 95P 314 FS 46 QZ45 FP23 FK18 BT 4 HN 4 PR 3

 95P 314 FS MS 3 GN 1 OPtr TMtr CAtr

 95P 315 FS 56 QZ51 BT17 FK12 PR 7 FP 5 FE 3

 95P 315 FS HN 2 GN 1 MS 1 OP 1 RAtr MZtr

 95P 315 FS TMtr

 95P 316 FS 54 QZ49 FK24 BT12 FP 6 PR 4 CD 3

 95P 316 FS HN 1 OP 1 FE 1 MStr TMtr GNtr

 95P 317 FS 62 QZ57 FK23 BT 8 PR 4 FP 3 HN 2

 95P 317 FS CD 2 TM 1 OP 1 GN 1 MStr

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.

 Fraction interpretation: FS, fine sand, 0.1-0.25 mm.

 Mineral interpretation: QZ, quartz; FP, plagioclase feldspar; FK, potassium feldspar; BT, biotite; HN, hornblende; PR, pyroxene;

 MS, muscovite; GN, garnet; OP, opaques; TM, tourmaline; CA, calcite; FE, iron oxides; RA, resistant aggregate; MZ, monazite;

 CD, chalcedony.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.
698 Soil Taxonomy

60 percent subangular cobbles, and 10 percent subangular

stones; extremely acid; abrupt smooth boundary.

E—8 to 25 cm; gray (10YR 5/1) extremely cobbly loamy sand,

light gray (10YR 7/1) dry; weak fine granular structure;

very friable, nonsticky and nonplastic; common fine and

medium roots throughout; many fine to coarse interstitial

pores; estimated bulk density of 1.5 g cm-3; 10 percent

subangular gravel, 60 percent subangular cobbles, and 10

percent subangular stones; very strongly acid; abrupt

smooth boundary.

Bs—25 to 48 cm; dark brown (7.5YR 3/4) very cobbly fine

sandy loam; weak fine granular structure; very friable,

moderately smeary, nonsticky and nonplastic; common

fine and medium roots throughout; many fine interstitial

pores; estimated bulk density of 1.2 g cm-3; 20 percent

subangular gravel and 15 percent subangular cobbles;

strongly acid; gradual smooth boundary.

BC—48 to 64 cm; light olive brown (2.5Y 5/4) gravelly fine

sandy loam; weak fine granular structure; very friable,

nonsticky and nonplastic; few fine roots throughout; many

fine interstitial pores; estimated bulk density of 1.5 g cm-3;

15 percent subangular gravel; moderately acid; gradual

smooth boundary.

C—64 to 100 cm; 60 percent olive (5Y 5/3) and 40 percent

olive gray (5Y 5/2) gravelly sandy loam; friable, nonsticky

and nonplastic; few very fine interstitial pores; estimated

bulk density of 1.5 g cm-3; 15 percent subangular gravel;

slightly acid.

Key to Suborders

CA. Spodosols that have aquic conditions for some time in

normal years (or artificial drainage) in one or more horizons

within 50 cm of the mineral soil surface and have one or both

of the following:

1. A histic epipedon; or

2. Within 50 cm of the mineral soil surface,

redoximorphic features in an albic or a spodic horizon.

Aquods, p. 698

CB. Other Spodosols that have a cryic soil temperature

regime.

Cryods, p. 705

CC. Other Spodosols that have 6.0 percent or more organic

carbon in a layer 10 cm or more thick within the spodic

horizon.

Humods, p. 709

CD. Other Spodosols.

Orthods, p. 712

Aquods

Aquods are the Spodosols of wet regions. They are

characterized either by a shallow fluctuating water table or an

extremely humid climate. If the soil temperature regime is

mesic, isomesic, or warmer, most of the soils have a nearly

white albic horizon thick enough to persist under cultivation

or, in the wettest Aquods, a black surface horizon resting on a

dark reddish brown spodic horizon that is virtually free of iron.

Other Aquods have a placic horizon or a duripan or are

cemented by an amorphous mixture of sesquioxides and

organic matter.

The Aquods that do not have a placic horizon normally

have a transitional horizon between the albic horizon and the

spodic horizon, a feature virtually unique to these soils.

Aquods formed mainly in sandy materials of Pleistocene

age. They may have any temperature regime. Water-loving

plants of a very wide variety, ranging from sphagnum in cold

areas to palms in the tropics, grow on these soils. In the United

States, relatively few Aquods are cultivated, except in New

Jersey and Florida.

Definition

Aquods are the Spodosols that have aquic conditions for

some time in normal years (or artificial drainage) in one or

more horizons within 50 cm of the mineral soil surface and

have one or both of the following:

1. A histic epipedon; or

2. Within 50 cm of the mineral soil surface, redoximorphic

features in an albic or spodic horizon.

Key to Great Groups

CAA. Aquods that have a cryic soil temperature regime.

Cryaquods, p. 700

CAB. Other Aquods that have less than 0.10 percent iron (by

ammonium oxalate) in 75 percent or more of the spodic

horizon.

Alaquods, p. 699

CAC. Other Aquods that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragiaquods, p. 704

CAD. Other Aquods that have a placic horizon within 100

cm of the mineral soil surface in 50 percent or more of each

pedon.

Placaquods, p. 704

CAE. Other Aquods that have, in 90 percent or more of each
Spodosols 699

pedon, a cemented soil layer that has its upper boundary within

100 cm of the mineral soil surface.

Duraquods, p. 701

CAF. Other Aquods that have episaturation.

Epiaquods, p. 703

CAG. Other Aquods.

Endoaquods, p. 702

Alaquods

These soils occur primarily in the southeastern part of the

United States. Their water table generally fluctuates and in the

process reduces iron and moves it out of the soils. The spodic

horizon consists mostly of an accumulation of organic matter

and aluminum and commonly has few or no redoximorphic

features. The albic horizon in the drier Alaquods is normally

thick. The wettest Alaquods have no albic horizon but

generally have uncoated sand grains above the spodic horizon.

Alaquods normally have a sandy particle-size class. Because of

their high humus content, however, some of them feel and

behave like loamy soils.

Definition

Alaquods are the Aquods that:

1. Have less than 0.10 percent iron (by ammonium oxalate)

in 75 percent or more of the spodic horizon; and

2. Do not have a cryic soil temperature regime.

Key to Subgroups

CABA. Alaquods that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Alaquods

CABB. Other Alaquods that have, in 90 percent or more of

each pedon, a cemented soil layer that does not slake in water

after air drying and has its upper boundary within 100 cm of

the mineral soil surface.

Duric Alaquods

CABC. Other Alaquods that have a histic epipedon.

Histic Alaquods

CABD. Other Alaquods that have both:

1. Within 200 cm of the mineral soil surface, an argillic or

kandic horizon that has a base saturation of 35 percent or

more (by sum of cations) in some part; and

2. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a spodic horizon at a depth of 75 to 125 cm.

Alfic Arenic Alaquods

CABE. Other Alaquods that have both:

1. An argillic or kandic horizon within 200 cm of the mineral

soil surface; and

2. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a spodic horizon at a depth of 75 to 125 cm.

Arenic Ultic Alaquods

CABF. Other Alaquods that have both:

1. An umbric epipedon; and

2. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a spodic horizon at a depth of 75 cm or more.

Arenic Umbric Alaquods

CABG. Other Alaquods that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a spodic horizon at a depth of

75 to 125 cm.

Arenic Alaquods

CABH. Other Alaquods that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a spodic horizon at a depth of

125 cm or more.

Grossarenic Alaquods

CABI. Other Alaquods that have, within 200 cm of the

mineral soil surface, an argillic or kandic horizon that has a

base saturation of 35 percent or more (by sum of cations) in

some part.

Alfic Alaquods

CABJ. Other Alaquods that have an argillic or kandic

horizon within 200 cm of the mineral soil surface.

Ultic Alaquods

CABK. Other Alaquods that have an ochric epipedon.

Aeric Alaquods

CABL. Other Alaquods.

Typic Alaquods

Definition of Typic Alaquods

Typic Alaquods are the Alaquods that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have, in 90 percent or more of each pedon, any

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface;
700 Soil Taxonomy

3. Do not have a histic or ochric epipedon;

4. Do not have an argillic or kandic horizon; and

5. Do not have a sandy particle-size class throughout a layer

extending from the mineral soil surface to the top of a spodic

horizon at a depth of 75 cm or more.

Description of Subgroups

Typic Alaquods.—The Typic subgroup of Alaquods is

centered on soils that have an umbric epipedon but do not have

a lithic contact within 50 cm of the soil surface, an argillic or

kandic horizon within 200 cm, a histic or ochric epipedon, a

cemented layer, or a sandy or sandy-skeletal particle-size class

from the soil surface to the top of a spodic horizon at a depth of

75 cm or more. Typic Alaquods commonly are saturated for

shorter periods than the Histic subgroups and for longer

periods than the Aeric subgroups. They occur in the

southeastern part of the United States as well as along the

Atlantic coast as far north as New Jersey. Typic Alaquods are

used as woodland, as grazing land, or for cultivated crops,

when water is controlled.

Aeric Alaquods.—These are the Alaquods that have an

ochric epipedon. The presence of the ochric epipedon is

indicative of Alaquods that are saturated for shorter periods

than the Typic subgroup. These soils do not have a lithic

contact within 50 cm of the soil surface, an argillic or kandic

horizon within 200 cm, a histic epipedon, a cemented layer, or

a sandy or sandy-skeletal particle-size class from the soil

surface to the top of a spodic horizon at a depth of 75 cm or

more. Commonly, the soils are forested. They occur along the

Atlantic coast from Florida to Virginia.

Alfic Alaquods.—These are the Alaquods that have an

argillic or kandic horizon with a base saturation of 35 percent

or more in some part. These soils do not have a lithic contact

within 50 cm of the soil surface, a histic epipedon, a cemented

soil layer, or a sandy or sandy-skeletal particle-size class from

the surface to the top of a spodic horizon at a depth of 75 cm or

more. The soils are mostly in wooded areas in Florida. Some

have been planted to pine or citrus trees.

Alfic Arenic Alaquods.—These are the Alaquods that have

a thick sandy E horizon above the spodic horizon and an

argillic or kandic horizon with a base saturation of at least 35

percent in at least some part. These soils most commonly occur

in Florida and are used as grazing land or for citrus.

Arenic Alaquods.—These are the Alaquods that have a

sandy E horizon 75 to 125 cm above the spodic horizon. These

soils do not have an argillic or kandic horizon, a lithic contact

within 50 cm of the soil surface, a cemented layer, or a histic

epipedon. They occur in Florida and North Carolina and are

used as woodland, as grazing land, or for citrus production.

Arenic Ultic Alaquods.—These are the Alaquods that have

an argillic or kandic horizon and sandy E horizons 75 to 125

cm thick above the spodic horizon. These soils do not have a

lithic contact within 50 cm of the soil surface, a cemented layer,

or a histic epipedon. They occur in Florida and commonly have

been planted to pine trees.

Arenic Umbric Alaquods.—These soils have an umbric

epipedon and sandy E horizons at least 75 cm thick above the

spodic horizon. These soils do not have a lithic contact within

50 cm of the soil surface, a cemented layer, a histic epipedon,

or an argillic or kandic horizon. They occur in Florida.

Duric Alaquods.—These are the Alaquods that have a

cemented soil layer but do not have a lithic contact within 50

cm of the soil surface. The cemented soil layer commonly is

ortstein, but it could also be cemented by silica. These soils are

rare in the United States.

Grossarenic Alaquods.—These are the Alaquods that have

sandy E horizons 125 cm or more thick above the spodic

horizon. These soils do not have an argillic or kandic horizon,

a histic epipedon, a cemented layer, or a lithic contact within

50 cm of the soil surface. They occur in Florida and the

Carolinas and commonly are used for pulp production.

Histic Alaquods.—These are the Alaquods that have a

histic epipedon. Typically, these soils are saturated close to the

surface. They do not have a lithic contact within 50 cm of the

soil surface or a cemented layer. They occur in Florida and are

used as woodland.

Lithic Alaquods.—These are the Alaquods that have a

lithic contact within 50 cm of the soil surface. These soils are

rare in the world.

Ultic Alaquods.—These are the Alaquods that have an

argillic or kandic horizon that has less than 35 percent base

saturation in all parts. These soils do not have a lithic contact

within 50 cm of the soil surface, a cemented layer, a histic

epipedon, or thick sandy E horizons above the spodic horizon.

They occur in Florida, the Carolinas, and Georgia. Some of

these soils have been planted to pine, and some are used as

grazing land or for the production of truck crops.

Cryaquods

These Aquods occur in areas of cold climates, mainly at high

latitudes. Because they are both cold and wet, Cryaquods have

been given low priority for study. Most are covered with

coniferous forest or tundra vegetation. Aquic conditions persist

during much of the growing season. In the United States, these

soils occur in Alaska.

Definition

Cryaquods are the Aquods that have a cryic soil temperature

regime.

Key to Subgroups

CAAA. Cryaquods that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Cryaquods
Spodosols 701

CAAB. Other Cryaquods that have a placic horizon within 100

cm of the mineral soil surface in 50 percent or more of each

pedon.

Placic Cryaquods

CAAC. Other Cryaquods that have, in 90 percent or more of

each pedon, a cemented soil layer that does not slake in water

after air drying and has its upper boundary within 100 cm of

the mineral soil surface.

Duric Cryaquods

CAAD. Other Cryaquods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Cryaquods

CAAE. Other Cryaquods that have a spodic horizon less than

10 cm thick in 50 percent or more of each pedon.

Entic Cryaquods

CAAF. Other Cryaquods.

Typic Cryaquods

Definition of Typic Cryaquods

Typic Cryaquods are the Cryaquods that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower;

3. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface;

4. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface; and

5. Have a spodic horizon 10 cm or more thick in 50 percent

or more of each pedon.

Description of Subgroups

Typic Cryaquods.—The Typic subgroup of Cryaquods is

centered on soils that have a spodic horizon 10 cm or more

thick. Typic Cryaquods do not have a lithic contact within 50

cm of the soil surface, a placic horizon, a cemented soil layer,

or andic soil properties in a layer 25 cm or more thick within

75 cm of the soil surface.

Andic Cryaquods.—These are the Cryaquods that have

andic soil properties throughout horizons with a total thickness

of 25 cm or more within 75 cm of the soil surface. These soils

do not have a lithic contact within 50 cm of the soil surface, a

placic horizon, or a cemented soil layer.

Duric Cryaquods.—These are the Cryaquods that have a

cemented soil layer. The cemented layer commonly is ortstein,

but in some soils the cementing agents are not well understood.

These soils do not have a lithic contact within 50 cm of the soil

surface or a placic horizon.

Entic Cryaquods.—These are the Cryaquods that have a

spodic horizon that is less than 10 cm thick. These soils do not

have a lithic contact within 50 cm of the soil surface, a placic

horizon, a cemented layer, or andic soil properties in one-third

or more of the upper 75 cm.

Lithic Cryaquods.—These are the Cryaquods that have a

lithic contact within 50 cm of the mineral soil surface. These

soils are relatively rare in the world. They commonly are

forested.

Placic Cryaquods.—These are the Cryaquods that have a

placic horizon. The placic horizon commonly is convoluted.

These soils do not have a lithic contact within 50 cm of the soil

surface.

Duraquods

These Aquods have a cemented soil layer that in many areas

is a combination of iron and/or aluminum and organic matter.

In some of these soils, silica also is a cementing agent.

Duraquods are seasonally saturated above the cemented soil

layer but not necessarily below it. In the United States, these

soils occur mostly in the Northwest and in Michigan. They also

are known to occur in New Zealand, under kauri pine. The

cemented soil layer in Duraquods severely restricts plant

rooting. Currently, few of these soils are recognized.

Definition

Duraquods are the Aquods that:

1. Have, in 90 percent or more of each pedon, a cemented soil

layer that does not slake in water after air drying and has its

upper boundary within 100 cm of the mineral soil surface;

2. Have 0.10 percent or more iron (by ammonium oxalate)

in 75 percent or more of the spodic horizon;

3. Do not have a cryic temperature regime;

4. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface; and

5. Do not have a placic horizon within 100 cm of the mineral

soil surface in 50 percent or more of each pedon.

Key to Subgroups

CAEA. Duraquods that have a histic epipedon.

Histic Duraquods

CAEB. Other Duraquods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or
702 Soil Taxonomy

more within 75 cm either of the mineral soil surface or of the top

of an organic layer with andic soil properties, whichever is

shallower.

Andic Duraquods

CAEC. Other Duraquods.

Typic Duraquods

Definition of Typic Duraquods

Typic Duraquods are the Duraquods that:

1. Do not have a histic epipedon; and

2. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Description of Subgroups

Typic Duraquods.—The Typic subgroup of Duraquods is

centered on soils that do not have a histic epipedon and do not

have andic soil properties in one-third or more of the upper 75

cm. Typic Duraquods are the most common subgroup of

Duraquods and occur on the west coast, in New England, and

in Indiana and Michigan in the United States.

Andic Duraquods.—These soils have a cemented layer that

commonly is ortstein but is not limited to ortstein. These soils

do not have a histic epipedon. They occur in the State of

Washington.

Histic Duraquods.—These soils have a histic epipedon.

They are rare in the world.

Endoaquods

These Aquods do not have a perched water table. They have

a considerable accumulation of iron in addition to aluminum

and organic carbon in the spodic horizon. The spodic horizon

has few to many redoximorphic features and commonly is

brown to dark reddish brown. Most Endoaquods have an albic

horizon. Some of the wettest do not have an albic horizon but

normally have uncoated sand grains above the spodic horizon.

Definition

Endoaquods are the Aquods that:

1. Have endosaturation;

2. Have 0.10 percent or more iron (by ammonium oxalate)

in 75 percent or more of the spodic horizon;

3. Do not have a cryic temperature regime;

4. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface;

5. Do not have a placic horizon within 100 cm of the mineral

soil surface in 50 percent or more of each pedon; and

6. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CAGA. Endoaquods that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Endoaquods

CAGB. Other Endoaquods that have a histic epipedon.

Histic Endoaquods

CAGC. Other Endoaquods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Endoaquods

CAGD. Other Endoaquods that have an argillic or kandic

horizon within 200 cm of the mineral soil surface.

Argic Endoaquods

CAGE. Other Endoaquods that have an umbric epipedon.

Umbric Endoaquods

CAGF. Other Endoaquods.

Typic Endoaquods

Definition of Typic Endoaquods

Typic Endoaquods are the Endoaquods that:

1. Do not have a histic or umbric epipedon;

2. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower;

3. Do not have an argillic or kandic horizon underlying the

spodic horizon; and

4. Do not have a lithic contact within 50 cm of the mineral

soil surface.

Description of Subgroups

Typic Endoaquods.—The Typic subgroup of Endoaquods is

centered on soils that have an ochric epipedon. These soils do

not have a lithic contact within 50 cm of the soil surface, an

argillic or kandic horizon, or andic soil properties in a layer 25

cm or more thick within 75 cm of the soil surface. The soils

occur in both the western and northeastern parts of the United

States and in Michigan, Wisconsin, and Indiana.

Andic Endoaquods.—These are the Endoaquods that have

andic soil properties throughout horizons totaling 25 cm or
Spodosols 703

more thick from the soil surface to a depth of 75 cm. These soils

do not have a histic epipedon or a lithic contact within 50 cm of

the soil surface.

Argic Endoaquods.—These are the Endoaquods that have

an argillic or kandic horizon below the spodic horizon. These

soils do not have a lithic contact within 50 cm of the soil

surface, a histic epipedon, or andic soil properties in a layer 25

cm or more thick from the soil surface to a depth of 75 cm. The

soils occur in Michigan and Wisconsin.

Histic Endoaquods.—These are the Endoaquods that have

a histic epipedon. Commonly, these soils are saturated

throughout most of the year. They do not have a lithic contact

within 50 cm of the soil surface.

Lithic Endoaquods.—These are the Endoaquods that have

a lithic contact within 50 cm of the soil surface. These soils are

rare in the world.

Umbric Endoaquods.—These are the Endoaquods that have

an umbric epipedon. These soils do not have a lithic contact

within 50 cm of the soil surface, a histic epipedon, an argillic or

kandic horizon, or andic soil properties in a layer 25 cm or more

thick from the soil surface to a depth of 75 cm. The soils occur in

North Carolina and Florida.

Epiaquods

These Aquods have a perched water table above one or more

relatively impermeable layers. Epiaquods normally have a

considerable accumulation of iron in addition to aluminum and

organic matter. The relatively impermeable layers commonly

are argillic horizons or dense till.

Definition

Epiaquods are the Aquods that:

1. Have episaturation;

2. Have 0.10 percent or more iron (by ammonium oxalate)

in 75 percent or more of the spodic horizon;

3. Do not have a cryic temperature regime;

4. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface;

5. Do not have a placic horizon within 100 cm of the

mineral soil surface in 50 percent or more of each pedon;

and

6. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CAFA. Epiaquods that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Epiaquods

CAFB. Other Epiaquods that have a histic epipedon.

Histic Epiaquods

CAFC. Other Epiaquods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Epiaquods

CAFD. Other Epiaquods that have, within 200 cm of the

mineral soil surface, an argillic or kandic horizon that has a

base saturation of 35 percent or more (by sum of cations) in

some part.

Alfic Epiaquods

CAFE. Other Epiaquods that have an argillic or kandic

horizon within 200 cm of the mineral soil surface.

Ultic Epiaquods

CAFF. Other Epiaquods that have an umbric epipedon.

Umbric Epiaquods

CAFG. Other Epiaquods.

Typic Epiaquods

Definition of Typic Epiaquods

Typic Epiaquods are the Epiaquods that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a histic or umbric epipedon;

3. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower; and

4. Do not have an argillic or kandic horizon underlying the

spodic horizon.

Description of Subgroups

Typic Epiaquods.—The Typic subgroup of Epiaquods is

centered on soils that have an ochric epipedon. These soils do

not have an argillic or kandic horizon, a lithic contact within

50 cm of the soil surface, or andic soil properties in a layer 25

cm or more thick from the surface to a depth of 75 cm. These

soils occur in the northeastern part of the United States and in

Michigan and Wisconsin.

Alfic Epiaquods.—These soils have an argillic or kandic

horizon that has a base saturation of 35 percent or more in at

least some part. They do not have a lithic contact within 50 cm

of the soil surface or andic soil properties in a layer 25 cm or

more thick within 75 cm of the soil surface. These soils occur

in Michigan, Minnesota, and Wisconsin.
704 Soil Taxonomy

Andic Epiaquods.—These soils have andic soil properties in a

layer 25 cm or more thick within 75 cm of the soil surface. They

do not have a lithic contact within 50 cm of the soil surface or a

histic epipedon.

Histic Epiaquods.—These soils have a histic epipedon.

They tend to be saturated during most of the growing season.

They do not have a lithic contact within 50 cm of the soil

surface. These soils occur in Michigan.

Lithic Epiaquods.—These soils have a lithic contact within

50 cm of the soil surface. They are rare in the world.

Ultic Epiaquods.—These soils have an argillic horizon that

has a base saturation of less than 35 percent in all parts. They

do not have a lithic contact within a depth of 50 cm, a histic

epipedon, or andic soil properties in a layer 25 cm or more

thick within 75 cm of the soil surface. These soils occur in

Michigan, Minnesota, and Wisconsin.

Umbric Epiaquods.—These are the Epiaquods that have an

umbric horizon. These soils do not have a lithic contact within

50 cm of the soil surface, a histic epipedon, an argillic or

kandic horizon, or andic soil properties in a layer 25 cm or

more thick within 75 cm of the soil surface.

Fragiaquods

These are the Aquods that have a fragipan below the spodic

horizon, normally at a depth of 40 to 75 cm below the mineral

soil surface. Plant roots are shallow, and the soil clinging to the

roots of falling trees has in many areas developed a microrelief

of 20 to 50 cm. The soil temperature regime is normally frigid.

These soils are nearly level, but few of them are cultivated,

except for those used for the production of hay. Most of the

soils are forested. Fragiaquods are not extensive in the United

States.

Definition

Fragiaquods are the Aquods that:

1. Have a fragipan with its upper boundary within 100 cm of

the mineral soil surface;

2. Have 0.10 percent or more iron (by ammonium oxalate)

in 75 percent or more of the spodic horizon; and

3. Do not have a cryic temperature regime.

Key to Subgroups

CACA. Fragiaquods that have a histic epipedon.

Histic Fragiaquods

CACB. Other Fragiaquods that have a surface horizon 30 cm

or more thick that meets all of the requirements for a plaggen

epipedon except thickness.

Plagganthreptic Fragiaquods

CACC. Other Fragiaquods that have an argillic or kandic

horizon within 200 cm of the mineral soil surface.

Argic Fragiaquods

CACD. Other Fragiaquods.

Typic Fragiaquods

Definition of Typic Fragiaquods

Typic Fragiaquods are the Fragiaquods that:

1. Do not have a histic epipedon;

2. Do not have a surface horizon more than 30 cm thick that

meets all of the requirements for a plaggen epipedon except

thickness; and

3. Do not have, within 200 cm of the mineral soil surface, an

argillic or kandic horizon that has a base saturation of 35

percent or more (by sum of cations) in any part.

Description of Subgroups

Typic Fragiaquods.—The Typic subgroup of Fragiaquods

is centered on soils that do not have a histic epipedon, an

argillic or kandic horizon, or a surface horizon 30 cm or more

thick that meets all of the requirements for a plaggen epipedon

except thickness. These soils generally support forest

vegetation, but some have been cleared and are used as pasture.

Typic Fragiaquods occur in Michigan, New York, and

Vermont.

Argic Fragiaquods.—These soils have an argillic or kandic

horizon. Commonly, the argillic or kandic horizon is within

the fragipan. These soils do not have a histic epipedon or a

surface horizon 30 cm or more thick that meets all of the

requirements for a plaggen epipedon except thickness. They

are known to occur in Michigan.

Histic Fragiaquods.—These soils have a histic epipedon.

Commonly, they are saturated throughout most of the growing

season. They are rare in the world.

Plagganthreptic Fragiaquods.—These are the Fragiaquods

that have a surface horizon 30 cm or more thick that has all of

the properties of a plaggen epipedon except thickness. These

soils are rare in the world, but they do occur in Europe.

Placaquods

These are the Aquods that have an involute placic horizon.

The horizons above the placic horizon have low-contrast

mottles that are probably caused by organic matter. Placaquods

are known to occur only in areas of perhumid oceanic climates.

Many have, or used to have, sphagnum and heath vegetation.

Definition

Placaquods are the Aquods that:
Spodosols 705

1. Have a placic horizon within 100 cm of the mineral soil

surface in 50 percent or more of each pedon;

2. Have 0.10 percent or more iron (by ammonium oxalate)

in 75 percent or more of the spodic horizon;

3. Do not have a cryic temperature regime; and

4. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface.

Key to Subgroups

CADA. Placaquods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Placaquods

CADB. Other Placaquods.

Typic Placaquods

Definition of Typic Placaquods

Typic Placaquods are the Placaquods that do not have andic

soil properties throughout horizons that have a total thickness

of 25 cm or more within 75 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Description of Subgroups

Typic Placaquods.—The Typic subgroup of Placaquods

is centered on soils that do not have andic soil properties

in a layer 25 cm or more thick within 75 cm of the soil

surface. These soils occur in Great Britain and in Western

Europe.

Andic Placaquods.—These are the Placaquods that have

andic soil properties in a layer 25 cm or more thick within 75

cm of the surface. These soils are rare in the world.

Cryods

Cryods are the Spodosols of high latitudes and/or high

elevations. In the United States, they occur mostly in southeast

Alaska and in the mountains of Washington and Oregon. Some

of these soils are in the mountains of New York and northern

New England. Many Cryods formed in volcanic ash or glacial

drift, and some formed in residuum or colluvium on mountain

slopes. Cryods commonly have an O horizon over a very thin

or intermittent albic horizon, which overlies a well-developed

spodic horizon. Some of the soils have a placic horizon,

ortstein, or another cemented soil layer within 100 cm of the

mineral soil surface. In many Cryods the content of organic

carbon in the upper part of the spodic horizon is relatively

high. The vegetation is mostly a coniferous forest or alpine

tundra.

Definition

Cryods are the Spodosols that:

1. Have a cryic temperature regime; and

2. Do not have both aquic conditions within 50 cm of the

mineral soil surface and either of the following:

a. A histic epipedon; or

b. Within 50 cm of the mineral soil surface,

redoximorphic features in an albic or spodic horizon.

Key to Great Groups

CBA. Cryods that have a placic horizon within 100 cm of the

mineral soil surface in 50 percent or more of each pedon.

Placocryods, p. 709

CBB. Other Cryods that have, in 90 percent or more of each

pedon, a cemented soil layer that does not slake in water after

air drying and has its upper boundary within 100 cm of the

mineral soil surface.

Duricryods, p. 705

CBC. Other Cryods that have 6.0 percent or more organic

carbon throughout a layer 10 cm or more thick within the

spodic horizon.

Humicryods, p. 708

CBD. Other Cryods.

Haplocryods, p. 706

Duricryods

These are the Cryods that have, either within or below the

spodic horizon, a cemented horizon that is considered ortstein

if it is more than 2.5 cm thick and part of the spodic horizon.

In the United States, these soils are known to occur in the State

of Washington. They probably also occur in other cold regions

of the world.

Definition

Duricryods are the Cryods that:

1. Have, in 90 percent or more of each pedon, a cemented soil

layer that does not slake in water after air drying and has its

upper boundary within 100 cm of the mineral soil surface; and

2. Do not have a placic horizon within 100 cm of the mineral

soil surface in 50 percent or more of each pedon.

Key to Subgroups

CBBA. Duricryods that have both:

1. Redoximorphic features in one or more horizons

within 75 cm of the mineral soil surface and also aquic
706 Soil Taxonomy

conditions for some time in normal years (or artificial

drainage); and

2. Andic soil properties throughout horizons that have a

total thickness of 25 cm or more within 75 cm either of the

mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Aquandic Duricryods

CBBB. Other Duricryods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Duricryods

CBBC. Other Duricryods that have redoximorphic features in

one or more horizons within 75 cm of the mineral soil surface

and also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Duricryods

CBBD. Other Duricryods that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Duricryods

CBBE. Other Duricryods that have 6.0 percent or more

organic carbon throughout a layer 10 cm or more thick within

the spodic horizon.

Humic Duricryods

CBBF. Other Duricryods.

Typic Duricryods

Definition of Typic Duricryods

Typic Duricryods are the Duricryods that:

1. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower;

2. Do not have 6.0 percent or more organic carbon

throughout a layer 10 cm or more thick within the spodic

horizon;

3. Do not have redoximorphic features in one or more

horizons within 75 cm of the mineral soil surface and also

aquic conditions for some time in normal years; and

4. Are not saturated with water in any layer within 100 cm of

the mineral soil surface in normal years for either or both 20 or

more consecutive days or 30 or more cumulative days.

Description of Subgroups

Typic Duricryods.—The Typic subgroup of Duricryods is

centered on soils that are not saturated with water within 100

cm of the soil surface and soils that do not have andic soil

properties in a layer 25 cm or more thick within 75 cm of the

soil surface. These soils also do not have thick Bh or Bhs

horizons. They are wooded and occur in Alaska.

Andic Duricryods.—These are the Duricryods that are

intergrades to the Andisols. They have andic soil properties in

a layer 25 cm or more thick within 75 cm of the soil surface.

They do not have aquic conditions and redox features within

75 cm of the soil surface. They are wooded and occur in the

State of Washington.

Aquandic Duricryods.—These are the Duricryods that

have andic soil properties in a layer 25 cm or more thick

within 75 cm of the soil surface and have aquic conditions

accompanied by redoximorphic features within 75 cm of the

soil surface. These soils are rare in the world.

Aquic Duricryods.—These are the Duricryods that have

aquic conditions accompanied by redoximorphic features

within 75 cm of the soil surface. These soils do not have andic

soil properties in a layer 25 cm or more thick within 75 cm of

the soil surface. They are rare in the world.

Humic Duricryods.—These are the Duricryods that have

a thick Bh or Bhs horizon. These soils are not saturated

within 100 cm of the soil surface and do not have andic soil

properties in a layer 25 cm or more thick within 75 cm of the

soil surface.

Oxyaquic Duricryods.—These are the Duricryods that are

saturated within 100 cm of the soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. Commonly, these soils are saturated by snowmelt during

the spring. They do not have either redoximorphic features

within 75 cm of the soil surface or andic soil properties in a

layer 25 cm or more thick within 75 cm of the soil surface.

Haplocryods

These are the Cryods of high latitudes or high elevations that

do not have a fragipan, a placic horizon, or other cemented soil

layers and do not have a very high content of organic matter in

the spodic horizon. The horizons are mostly thin but may be

strongly contrasting. The base of the spodic horizon is generally

less than 50 cm below the mineral soil surface. Some

Haplocryods have permafrost at varying depths below the

spodic horizon. Others have, below the spodic horizon, another

sequum with an argillic or kandic horizon. In the United

States, these soils occur mostly in Alaska and in the higher

mountains of the West and Northeast.

Definition

Haplocryods are the Cryods that:

1. Do not have 6.0 percent or more organic carbon
Spodosols 707

throughout a layer 10 cm or more thick within the spodic

horizon;

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface; and

3. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CBDA. Haplocryods that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Haplocryods

CBDB. Other Haplocryods that have both:

1. Redoximorphic features in one or more horizons

within 75 cm of the mineral soil surface and also aquic

conditions for some time in normal years (or artificial

drainage); and

2. Andic soil properties throughout horizons that have a

total thickness of 25 cm or more within 75 cm either of the

mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Aquandic Haplocryods

CBDC. Other Haplocryods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Haplocryods

CBDD. Other Haplocryods that have redoximorphic features

in one or more horizons within 75 cm of the mineral soil

surface and also aquic conditions for some time in normal

years (or artificial drainage).

Aquic Haplocryods

CBDE. Other Haplocryods that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplocryods

CBDF. Other Haplocryods that have 1.1 percent or less

organic carbon in the upper 10 cm of the spodic horizon.

Entic Haplocryods

CBDG. Other Haplocryods.

Typic Haplocryods

Definition of Typic Haplocryods

Typic Haplocryods are the Haplocryods that:

1. Do not have a lithic contact within 50 cm of the mineral soil

surface;

2. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower;

3. Do not have redoximorphic features in one or more

horizons within 75 cm of the mineral soil surface and also

aquic conditions for some time in normal years;

4. Are not saturated with water in any layer within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years; and

5. Have 1.2 percent or more organic carbon in the upper 10

cm of the spodic horizon.

Description of Subgroups

Typic Haplocryods.—The Typic subgroup of Haplocryods

is centered on soils that have more than 1.1 percent organic

carbon in the upper 10 cm of the spodic horizon. These soils do

not have a lithic contact within 50 cm of the soil surface, andic

soil properties in a layer 25 cm or more thick within 75 cm of

the soil surface, or a saturated layer within 100 cm of the soil

surface. They commonly are forested, and some are used for

timber production. A few have been cleared and are used for

hay. Typic Haplocryods occur in Oregon and Alaska.

Andic Haplocryods.—These are the Haplocryods that have

andic soil properties in a layer 25 cm or more thick within 75

cm of the soil surface. These soils do not have a lithic contact

within 50 cm of the soil surface and do not have aquic

conditions and redoximorphic features within 75 cm of the soil

surface. They occur in Washington and Alaska, where they are

used for timber production and wildlife habitat. A few areas

have been cleared for crop production.

Aquandic Haplocryods.—These are the Haplocryods that

have both andic soil properties in a layer 25 cm or more thick

within 75 cm of the soil surface and aquic conditions and

redoximorphic features within 75 cm of the soil surface. These

soils do not have a lithic contact within 50 cm of the soil

surface. They are rare in the world.

Aquic Haplocryods.—These are the Haplocryods that have

aquic conditions and redoximorphic features within 75 cm of

the soil surface. These soils do not have andic soil properties in

a layer 25 cm or more thick within 75 cm of the soil surface or

a lithic contact within 50 cm of the soil surface. The soils

support forest vegetation and occur in New Hampshire, Maine,

and New York.

Entic Haplocryods.—These are the Haplocryods that have

1.1 percent or less organic carbon in the upper 10 cm of the

spodic horizon. These soils do not have a lithic contact within
708 Soil Taxonomy

50 cm of the soil surface, andic soil properties in a layer 25 cm or

more thick within 75 cm of the soil surface, or a saturated layer

within 100 cm of the soil surface. The soils occur in Alaska and

commonly are forested.

Lithic Haplocryods.—These are the Haplocryods that have

a lithic contact within 50 cm of the soil surface. These soils

occur under forest vegetation in Washington and in an alpine

environment in Alaska.

Oxyaquic Haplocryods.—These are the Haplocryods that are

saturated with water within 100 cm of the soil surface for 20 or

more consecutive days or 30 or more cumulative days

in normal years. These soils do not have redoximorphic

features within 75 cm of the soil surface or andic soil

properties in a layer 25 cm or more thick within 75 cm of

the soil surface.

Humicryods

Humicryods are the Cryods of high latitudes or high

elevations. In the United States, they occur mostly in southeast

Alaska and in the mountains of Washington and Oregon. Some

are in the higher mountains of the Northeast. Humicryods

commonly have a thick O horizon over a very thin or

intermittent albic horizon, which overlies a dark colored spodic

horizon. They have a high content of organic carbon in the

upper part of the spodic horizon. The vegetation commonly is a

coniferous forest or alpine tundra.

Definition

Humicryods are the Cryods that:

1. Have 6.0 percent or more organic carbon throughout a

layer 10 cm or more thick within the spodic horizon;

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface; and

3. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CBCA. Humicryods that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Humicryods

CBCB. Other Humicryods that have both:

1. Redoximorphic features in one or more horizons

within 75 cm of the mineral soil surface and also aquic

conditions for some time in normal years (or artificial

drainage); and

2. Andic soil properties throughout horizons that have a

total thickness of 25 cm or more within 75 cm either of the

mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Aquandic Humicryods

CBCC. Other Humicryods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Humicryods

CBCD. Other Humicryods that have redoximorphic features

in one or more horizons within 75 cm of the mineral soil

surface and also aquic conditions for some time in normal

years (or artificial drainage).

Aquic Humicryods

CBCE. Other Humicryods that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Humicryods

CBCF. Other Humicryods.

Typic Humicryods

Definition of Typic Humicryods

Typic Humicryods are the Humicryods that:

1. Are not saturated with water in any layer within 100 cm of

the mineral soil surface in normal years for either or both 20 or

more consecutive days or 30 or more cumulative days;

2. Do not have redoximorphic features in one or more

horizons within 75 cm of the mineral soil surface and also

aquic conditions for some time in normal years;

3. Do not have a lithic contact within 50 cm of the mineral

soil surface; and

4. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower.

Description of Subgroups

Typic Humicryods.—The Typic subgroup of Humicryods is

centered on soils that do not have a lithic contact within 50 cm

of the soil surface, saturation with water within 100 cm of the

soil surface, or andic soil properties in a layer 25 cm or more

thick within 75 cm of the soil surface. These soils commonly

are forested and are used for timber production and wildlife

habitat. They occur in the northeastern part of the United

States and in Oregon and Alaska.
Spodosols 709

Andic Humicryods.—These are the Humicryods that have

andic soil properties in a layer 25 cm or more thick within 75

cm of the soil surface. These soils do not have a lithic contact

within 50 cm of the soil surface or aquic conditions and

redoximorphic features within 75 cm of the soil surface. They

occur in the States of Alaska and Washington. In Alaska the

soils occur under alpine tundra, and in Washington they are

under forest vegetation.

Aquandic Humicryods.—These are the Humicryods that

have andic soil properties in a layer 25 cm or more thick

within 75 cm of the soil surface and have aquic conditions and

redoximorphic features within 75 cm of the soil surface. These

soils do not have a lithic contact within 50 cm of the soil

surface. They occur in the State of Washington. They are used

for woodland and wildlife habitat.

Aquic Humicryods.—These are the Humicryods that have

aquic conditions and redoximorphic features within 75 cm of

the soil surface. These soils do not have a lithic contact within

50 cm of the soil surface or andic soil properties in a layer 25

cm or more thick within 75 cm of the soil surface. The soils

occur in the Northeastern United States and support forest

vegetation.

Lithic Humicryods.—These are the Humicryods that have

a lithic contact within 50 cm of the soil surface. These soils

occur in Alaska, Maine, Vermont, New Hampshire, and New

York and are used for wildlife habitat and woodland.

Oxyaquic Humicryods.—These are the Humicryods that are

saturated with water for 20 or more consecutive days or 30 or

more cumulative days in normal years. These soils do not have a

lithic contact within 50 cm of the soil surface or andic soil

properties in a layer 25 cm or more thick within 75 cm of the soil

surface. The soils formed under forest vegetation in Maine, New

Hampshire, New York, and Vermont.

Placocryods

These Cryods have a placic horizon, normally within the

spodic horizon. In the United States, they are known to occur

only in Alaska. They are thought to be rare elsewhere in the

world.

Definition

Placocryods are the Cryods that have a placic horizon

within 100 cm of the mineral soil surface in 50 percent or more

of each pedon.

Key to Subgroups

CBAA. Placocryods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Placocryods

CBAB. Other Placocryods that have 6.0 percent or more

organic carbon in a layer 10 cm or more thick within the

spodic horizon.

Humic Placocryods

CBAC. Other Placocryods.

Typic Placocryods

Definition of Typic Placocryods

Typic Placocryods are the Placocryods that:

1. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower; and

2. Do not have 6.0 percent or more organic carbon in a

layer 10 cm or more thick within the spodic horizon.

Description of Subgroups

Typic Placocryods.—The Typic subgroup of Placocryods is

centered on soils that do not have andic soil properties in a

layer 25 cm or more thick within 75 cm of the soil surface or

6.0 percent or more organic carbon in a layer 10 cm or more

thick within the spodic horizon. These soils are rare in the

world.

Andic Placocryods.—These are the Placocryods that

have andic soil properties in a layer 25 cm or more thick

within 75 cm of the soil surface. These soils are rare in the

world.

Humic Placocryods.—These are the Placocryods that have

6.0 percent or more organic carbon in a layer 10 cm or more

thick within the spodic horizon. These soils do not have andic

soil properties in a layer 25 cm or more thick within 75 cm of

the soil surface.

Humods

Humods are the relatively freely drained Spodosols that

have a large accumulation of organic carbon in the spodic

horizon. Undisturbed Humods may have either a thin,

intermittent or a distinct, continuous albic horizon over a

spodic horizon, which in its upper part is nearly black and

has reddish hue. The hue normally becomes yellower with

increasing depth.

Humods formed predominantly in Pleistocene or Holocene

deposits. In the United States, they developed mainly under a

coniferous forest. In Western Europe they are common in areas

of sandy materials where heather (Calluna vulgaris) is, or used

to be, a dominant plant. In tropical regions most Humods have

supported a rain forest.

Humods are not extensive in the United States. They are

known to occur in Maine and in the Pacific Northwest, mostly

in small areas, and may occur in the Southeast.
710 Soil Taxonomy

Definition

Humods are the Spodosols that:

1. Have 6.0 percent or more organic carbon in a layer 10 cm or

more thick within the spodic horizon;

2. Do not have a cryic temperature regime; and

3. Do not have both aquic conditions within 50 cm of the

mineral soil surface and either of the following:

a. A histic epipedon; or

b. Within 50 cm of the mineral soil surface,

redoximorphic features in an albic or spodic horizon.

Key to Great Groups

CCA. Humods that have a placic horizon within 100 cm of

the mineral soil surface in 50 percent or more of each pedon.

Placohumods, p. 711

CCB. Other Humods that have, in 90 percent or more of each

pedon, a cemented soil layer that does not slake in water after

air drying and has its upper boundary within 100 cm of the

mineral soil surface.

Durihumods, p. 710

CCC. Other Humods that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragihumods, p. 710

CCD. Other Humods.

Haplohumods, p. 710

Durihumods

These are the Humods with a layer that is cemented,

commonly with sesquioxides and organic matter but in some

areas also with silica. These soils are not common in the

United States but occur in some areas in the Pacific Northwest

and the Southeast.

Definition

Durihumods are the Humods that:

1. Have, in 90 percent or more of each pedon, a cemented soil

layer that does not slake in water after air drying and has its

upper boundary within 100 cm of the mineral soil surface; and

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface.

Key to Subgroups

CCBA. Durihumods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Durihumods

CCBB. Other Durihumods.

Typic Durihumods

Definition of Typic Durihumods

Typic Durihumods are the Durihumods that do not have

andic soil properties throughout horizons that have a total

thickness of 25 cm or more within 75 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Description of Subgroups

Typic Durihumods.—The Typic subgroup of Durihumods

is centered on soils that do not have andic soil properties in a

layer 25 cm or more thick within 75 cm of the soil surface.

These soils are rare in the world.

Andic Durihumods.—These are the Durihumods that have

andic soil properties in a layer 25 cm or more thick within 75

cm of the soil surface. These soils are rare in the United States.

Fragihumods

These Humods have a fragipan below the spodic horizon and

do not have a placic horizon. They are not known to occur in the

United States, and a classification of subgroups has not been

developed.

Definition

Fragihumods are the Humods that:

1. Have a fragipan with its upper boundary within 100 cm of

the mineral soil surface;

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface; and

3. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CCCA. All Fragihumods (provisionally).

Typic Fragihumods

Haplohumods

Haplohumods are the Humods commonly in cool to warm,

moist coastal regions, although some are in inland areas at

higher elevations. These soils occur in the Northeast and the

Pacific Northwest; in the Southeastern United States,

particularly in areas of sandy deposits; and in Western Europe,

where most of them at some time supported heather (Calluna
Spodosols 711

vulgaris). If undisturbed, these soils generally have an umbric

epipedon and an albic horizon overlying a spodic horizon with

reddish hue and a black upper subhorizon rich in organic

carbon. Some of the soils, however, have an ochric epipedon.

Definition

Haplohumods are the Humods that:

1. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface;

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface; and

3. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CCDA. Haplohumods that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Haplohumods

CCDB. Other Haplohumods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Haplohumods

CCDC. Other Haplohumods that have a surface horizon 30

cm or more thick that meets all of the requirements for a

plaggen epipedon except thickness.

Plagganthreptic Haplohumods

CCDD. Other Haplohumods.

Typic Haplohumods

Definition of Typic Haplohumods

Typic Haplohumods are the Haplohumods that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower; and

3. Do not have a surface horizon more than 30 cm thick that

meets all of the requirements for a plaggen epipedon except

thickness.

Description of Subgroups

Typic Haplohumods.—The Typic subgroup of

Haplohumods is centered on soils that do not have a lithic

contact within 50 cm of the soil surface, andic soil properties in a

layer 25 cm or more thick within 75 cm of the soil surface, or a

surface horizon 30 cm or more thick that meets all of the

requirements for a plaggen epipedon except thickness.

Andic Haplohumods.—These soils have andic soil

properties in a layer 25 cm or more thick within 75 cm of the

soil surface. They do not have a lithic contact within 50 cm of

the soil surface.

Lithic Haplohumods.—These soils have a lithic contact

within 50 cm of the soil surface.

Plagganthreptic Haplohumods.—These soils have a surface

horizon 30 cm or more thick that has all of the attributes of a

plaggen epipedon except thickness. They do not have a lithic

contact within 50 cm of the soil surface or andic soil properties

in a layer 25 cm or more thick within 75 cm of the soil surface.

They occur in Europe.

Placohumods

These are the Humods that have a placic horizon within the

spodic horizon. They are probably rare in the world but are

known to occur in eastern Canada and in parts of Western

Europe, where their vegetation is, or used to be, heather.

Definition

Placohumods are the Humods that have a placic horizon

within 100 cm of the mineral soil surface in 50 percent or more

of each pedon.

Key to Subgroups

CCAA. Placohumods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Placohumods

CCAB. Other Placohumods.

Typic Placohumods

Definition of Typic Placohumods

Typic Placohumods are the Placohumods that do not have

andic soil properties throughout horizons that have a total

thickness of 25 cm or more within 75 cm either of the mineral

soil surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Description of Subgroups

Typic Placohumods.—The Typic subgroup of Placohumods

is centered on soils that do not have andic soil properties in a

layer 25 cm or more thick within 75 cm of the soil surface.

These soils are rare in the world.

Andic Placohumods.—These are the Placohumods that

have andic soil properties in a layer 25 cm or more thick
712 Soil Taxonomy

within 75 cm of the soil surface. These soils are rare in the

world.

Orthods

Orthods are the relatively freely drained Spodosols that have

a horizon of accumulation containing aluminum, or aluminum

and iron, and organic carbon. These are the most common

Spodosols in the northern parts of Europe and in the United

States. They formed predominantly in coarse, acid Pleistocene

or Holocene deposits under a mostly coniferous forest

vegetation. If undisturbed, Orthods normally have an O

horizon, an albic horizon, and a spodic horizon and may have

a fragipan. Some of these soils, however, have been mixed by

the roots of falling trees or by animals and have a very thin

albic horizon or no albic horizon. In cultivated areas the albic

horizon is very commonly mixed with part of the spodic

horizon. In the United States, the moisture regime of Orthods

is predominantly udic, but a few have a xeric regime. The soil

temperature regimes range from frigid to hyperthermic.

Orthods are extensive in the southeastern part of the United

States, the Northeast, the Great Lakes States, and the

mountains of the West.

Definition

Orthods are the Spodosols that:

1. Do not have 6.0 percent or more organic carbon in a

layer 10 cm or more thick within the spodic horizon;

2. Do not have a cryic temperature regime; and

3. Do not have both aquic conditions within 50 cm of the

mineral soil surface and either of the following:

a. A histic epipedon; or

b. Within 50 cm of the mineral soil surface,

redoximorphic features in an albic or spodic horizon.

Key to Great Groups

CDA. Orthods that have, in 50 percent or more of each

pedon, a placic horizon within 100 cm of the mineral soil

surface.

Placorthods, p. 720

CDB. Other Orthods that have, in 90 percent or more of each

pedon, a cemented soil layer that does not slake in water after

air drying and has its upper boundary within 100 cm of the

mineral soil surface.

Durorthods, p. 714

CDC. Other Orthods that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragiorthods, p. 714

CDD. Other Orthods that have less than 0.10 percent iron (by

ammonium oxalate) in 75 percent or more of the spodic

horizon.

Alorthods, p. 712

CDE. Other Orthods.

Haplorthods, p. 716

Alorthods

These are the Orthods that have accumulations of aluminum

that are relatively high compared to the accumulations of iron.

These soils formed predominantly in sandy deposits. The soils

have low accumulations of iron either because of intensive

leaching or because of parent materials that are low in iron.

Alorthods normally have a thick albic horizon and an ochric

epipedon. They are more common in areas of warm climates

than in cool environments. In the United States, they occur

mainly in the Southeast.

Definition

Alorthods are the Orthods that:

1. Have less than 0.10 percent iron (by ammonium oxalate)

in 75 percent or more of the spodic horizon;

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface;

3. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface; and

4. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CDDA. Alorthods that are saturated with water in one or

more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Alorthods

CDDB. Other Alorthods that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a spodic horizon at a depth of 75 to 125 cm; and

2. An argillic or kandic horizon below the spodic horizon.

Arenic Ultic Alorthods

CDDC. Other Alorthods that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the
Spodosols 713

mineral soil surface to the top of a spodic horizon at a depth of

75 to 125 cm.

Arenic Alorthods

CDDD. Other Alorthods that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a spodic horizon at a depth of 125 cm or more; and

2. In 10 percent or more of each pedon, less than 3.0

percent organic carbon in the upper 2 cm of the spodic

horizon.

Entic Grossarenic Alorthods

CDDE. Other Alorthods that have, in 10 percent or more of

each pedon, less than 3.0 percent organic carbon in the upper 2

cm of the spodic horizon.

Entic Alorthods

CDDF. Other Alorthods that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of a spodic horizon at a depth of

125 cm or more.

Grossarenic Alorthods

CDDG. Other Alorthods that have a surface horizon 30 cm

or more thick that meets all of the requirements for a plaggen

epipedon except thickness.

Plagganthreptic Alorthods

CDDH. Other Alorthods that have, within 200 cm of the

mineral soil surface, an argillic or kandic horizon that has a

base saturation of 35 percent or more (by sum of cations) in

some part.

Alfic Alorthods

CDDI. Other Alorthods that have an argillic or kandic

horizon within 200 cm of the mineral soil surface.

Ultic Alorthods

CDDJ. Other Alorthods.

Typic Alorthods

Definition of Typic Alorthods

Typic Alorthods are the Alorthods that:

1. Are not saturated with water in any layer within 100 cm of

the mineral soil surface in normal years for either or both 20 or

more consecutive days or 30 or more cumulative days;

2. Do not have a sandy particle-size class throughout a layer

extending from the mineral soil surface to the top of a spodic

horizon at a depth of 75 cm;

3. Do not have an argillic or kandic horizon;

4. Do not have a surface horizon 30 cm or more thick that

meets all of the requirements for a plaggen epipedon except

thickness;

5. Do not have an argillic or kandic horizon within 200 cm of

the mineral soil surface; and

6. Have, in 10 percent or more of each pedon, 3.0 percent or

more organic carbon in the upper 2 cm of the spodic horizon.

Description of Subgroups

Typic Alorthods.—The Typic subgroup of Alorthods is

centered on soils that are not saturated with water for 20 or

more consecutive days or 30 or more cumulative days in

normal years and do not have an argillic or kandic horizon, a

sandy or sandy-skeletal particle-size class from the mineral soil

surface to the top of a spodic horizon at a depth of 75 to 125

cm, less than 3.0 percent organic carbon in the upper 2 cm of

the spodic horizon, or a surface horizon 30 cm or more thick

that has all of the attributes of a plaggen epipedon except

thickness. These soils have not been recognized in the United

States.

Alfic Alorthods.—These are the Alorthods that have an

argillic or kandic horizon with 35 percent or more base

saturation in at least some part. These soils are not saturated

with water for 20 or more consecutive days or 30 or more

cumulative days in normal years and do not have a sandy or

sandy-skeletal particle-size class from the mineral soil surface

to the top of a spodic horizon at a depth of 75 cm or more, less

than 3.0 percent organic carbon in the upper 2 cm of the spodic

horizon, or a surface horizon 30 cm or more thick that has all

of the attributes of a plaggen epipedon except thickness. Alfic

Alorthods are rare in the world.

Arenic Alorthods.—These are the Alorthods that have a

sandy or sandy-skeletal particle-size class from the mineral soil

surface to the top of a spodic horizon at a depth of 75 to 125

cm. These soils do not have an argillic or kandic horizon and

are not saturated with water for 20 or more consecutive days or

30 or more cumulative days in normal years. They occur in

Florida. They generally support woodland vegetation, but some

have been cleared for community development.

Arenic Ultic Alorthods.—These are the Alorthods that

have a sandy or sandy-skeletal particle-size class from the

mineral soil surface to the top of a spodic horizon at a depth of

75 to 125 cm and have an argillic or kandic horizon. These

soils are not saturated with water for 20 or more consecutive

days or 30 or more cumulative days in normal years. They

occur in Europe.

Entic Alorthods.—These are the Alorthods that have less

than 3.0 percent organic carbon in the upper 2 cm of the spodic

horizon. These soils are not saturated with water for 20 or

more consecutive days or 30 or more cumulative days in

normal years and do not have an argillic or kandic horizon or a

sandy or sandy-skeletal particle-size class from the mineral soil

surface to the top of a spodic horizon at a depth of 75 to 125
714 Soil Taxonomy

cm. The soils occur in Puerto Rico and Florida. Among the

uses of these soils are native pasture and coconut production.

Entic Grossarenic Alorthods.—These are the Alorthods that

have a sandy or sandy-skeletal particle-size class from the

mineral soil surface to the top of a spodic horizon at a depth of

125 cm or more and have less than 3.0 percent organic carbon

in the upper 2 cm of the spodic horizon. These soils are not

saturated with water for 20 or more consecutive days or 30 or

more cumulative days in normal years and do not have an

argillic or kandic horizon. They are common in the

southeastern part of the United States. Most do or did support

hardwood vegetation, but some have been cleared for crop

production.

Grossarenic Alorthods.—These are the Alorthods that

have a sandy or sandy-skeletal particle-size class from the

mineral soil surface to the top of a spodic horizon at a depth of

125 cm or more and have 3.0 percent or more organic carbon

in the upper 2 cm of the spodic horizon. These soils do not

have an argillic or kandic horizon and are not saturated with

water for 20 or more consecutive days or 30 or more

cumulative days in normal years. They are rare in the world.

Oxyaquic Alorthods.—These are the Alorthods that are

saturated with water for 20 or more consecutive days or 30 or

more cumulative days in normal years. These soils occur in

many States in the southeastern part of the United States. They

have a variety of uses, including tame pasture, woodland, and

the production of citrus and other crops.

Plagganthreptic Alorthods.—These are the Alorthods that

have a surface horizon 30 cm or more thick that meets all of

the requirements for a plaggen epipedon except thickness.

These soils are not saturated with water for 20 or more

consecutive days or 30 or more cumulative days in normal

years and do not have an argillic or kandic horizon, a sandy or

sandy-skeletal particle-size class from the mineral soil surface

to the top of a spodic horizon at a depth of 75 cm or more, or

less than 3.0 percent organic carbon in the upper 2 cm of the

spodic horizon. The soils are rare but are known to occur in

Europe.

Ultic Alorthods.—These are the Alorthods that have an

argillic or kandic horizon with a base saturation of less than 35

percent in all parts. These soils are not saturated with water for

20 or more consecutive days or 30 or more cumulative days in

normal years and do not have a sandy or sandy-skeletal

particle-size class from the mineral soil surface to the top of a

spodic horizon at a depth of 75 cm or more or less than 3.0

percent organic carbon in the upper 2 cm of the spodic horizon.

The soils are rare in the United States.

Durorthods

These are the Orthods that have a cemented soil layer.

These soils formed in sandy and loamy deposits. The cemented

soil layer commonly is composed of spodic materials and in

many areas is within 50 cm of the mineral soil surface. The

cementing agents commonly are combinations of iron, aluminum,

and organic matter, but silica may be an important cementing

agent in some of these soils.

Definition

Durorthods are the Orthods that:

1. Have, in 90 percent or more of each pedon, a cemented soil

layer that does not slake in water after air drying and has its

upper boundary within 100 cm of the mineral soil surface; and

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface.

Key to Subgroups

CDBA. Durorthods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Durorthods

CDBB. Other Durorthods.

Typic Durorthods

Definition of Typic Durorthods

Typic Durorthods are the Durorthods that do not have andic

soil properties throughout horizons that have a total thickness

of 25 cm or more within 75 cm either of the mineral soil

surface or of the top of an organic layer with andic soil

properties, whichever is shallower.

Description of Subgroups

Typic Durorthods.—The Typic subgroup of Durorthods is

centered on soils without andic soil properties in a layer 25 cm

or more thick within 75 cm of the soil surface. The cemented

layer in these soils commonly is ortstein. The soils occur in

Michigan and New York. Most are forested, but some areas

have been cleared and are used for hay and pasture.

Andic Durorthods.—These are the Durorthods that have

andic soil properties in a layer 25 cm or more thick in the

upper 75 cm. These soils occur in the State of Washington and

support forest vegetation.

Fragiorthods

Fragiorthods are the Orthods that have a fragipan below the

spodic horizon. They formed mainly in loamy deposits, but

some formed in sandy deposits containing a considerable

amount of fine and very fine sand. The fragipan may be thick,

or it may have formed in the eluvial (E ́) horizon of a lower

sequum that overlies an argillic horizon. Generally, a lighter

colored eluvial horizon has developed above the fragipan,

presumably because of the lateral movement of ground water.

Trees growing on Fragiorthods are normally shallow rooted
Spodosols 715

and are sometimes blown down. When the trees are blown

down, there is a mixing of soil horizons above the fragipan. As

a consequence, many of these soils have a weakly expressed

albic horizon or no albic horizon or have a thin, intermittent

albic horizon below part of the spodic horizon. A distinct

microrelief is a normal feature, unless the soils have been

smoothed by cultivation. In the United States, the soil

temperature regimes of Fragiorthods are mostly frigid, but

some are mesic bordering on frigid.

Definition

Fragiorthods are the Orthods that:

1. Have a fragipan with its upper boundary within 100 cm of

the mineral soil surface;

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface; and

3. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CDCA. Fragiorthods that have redoximorphic features in one

or more horizons within 75 cm of the mineral soil surface and

also aquic conditions for some time in normal years (or

artificial drainage).

Aquic Fragiorthods

CDCB. Other Fragiorthods that:

1. Are saturated with water in one or more layers

within 100 cm of the mineral soil surface in normal

years for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days; and

2. Have, within 200 cm of the mineral soil surface, an

argillic or kandic horizon that has a base saturation of 35

percent or more (by sum of cations) in some part.

Alfic Oxyaquic Fragiorthods

CDCC. Other Fragiorthods that are saturated with water in

one or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Fragiorthods

CDCD. Other Fragiorthods that have a surface horizon 30

cm or more thick that meets all of the requirements for a

plaggen epipedon except thickness.

Plagganthreptic Fragiorthods

CDCE. Other Fragiorthods that have, within 200 cm of the

mineral soil surface, an argillic or kandic horizon that has a

base saturation of 35 percent or more (by sum of cations) in

some part.

Alfic Fragiorthods

CDCF. Other Fragiorthods that have an argillic or kandic

horizon within 200 cm of the mineral soil surface.

Ultic Fragiorthods

CDCG. Other Fragiorthods that have a spodic horizon that

has one of the following:

1. A texture of very fine sand, loamy very fine sand, or

finer; and

a. A thickness of 10 cm or less; and

b. A weighted average of less than 1.2 percent organic

carbon; and

c. Within the upper 7.5 cm, either or both a moist color

value or chroma of 4 or more (crushed and smoothed

sample); or

2. A texture of loamy fine sand, fine sand, or coarser and

either or both a moist color value or chroma of 4 or more

(crushed and smoothed sample) in the upper 2.5 cm.

Entic Fragiorthods

CDCH. Other Fragiorthods.

Typic Fragiorthods

Definition of Typic Fragiorthods

Typic Fragiorthods are the Fragiorthods that:

1. Do not have redoximorphic features in any horizon

within 75 cm of the mineral soil surface and also aquic

conditions;

2. Are not saturated with water in any layer within 100

cm of the mineral soil surface in normal years for either or

both 20 or more consecutive days or 30 or more cumulative

days;

3. Do not have a surface horizon 30 cm or more thick that

meets all of the requirements for a plaggen epipedon except

thickness;

4. Do not have an argillic or kandic horizon within 200 cm of

the mineral soil surface; and

5. Have a spodic horizon with one or more of the following:

a. A texture of very fine sand, loamy very fine sand, or

finer; and

(1) A thickness of more than 10 cm; or

(2) A weighted average of 1.2 percent or more organic

carbon in the upper 10 cm; or
716 Soil Taxonomy

(3) Within the upper 7.5 cm, either or both a moist color

value or chroma of 3 or less (crushed and smoothed

sample); or

b. A texture of loamy fine sand, fine sand, or coarser and a

color value, moist, and chroma of 3 or less (crushed and

smoothed sample) in the upper 2.5 cm.

Description of Subgroups

Typic Fragiorthods.—The Typic subgroup of Fragiorthods

is centered on properties that are not evident. Typic

Fragiorthods are not saturated within 100 cm of the soil surface

and do not have an argillic or kandic horizon, a surface

horizon 30 cm or more thick that has all of the attributes of a

plaggen epipedon except thickness, or a moist value and

chroma of 4 or more. These soils are forested and occur in

Michigan, New York, and Pennsylvania.

Alfic Fragiorthods.—These are the Fragiorthods that have

an argillic horizon that has a base saturation of 35 percent or

more in at least some part. These soils are not saturated for

extended periods within 100 cm of the soil surface. They do

not have a surface layer 30 cm or more thick that has all of the

attributes of a plaggen epipedon except thickness. They are

wooded and occur in Wisconsin and Michigan.

Alfic Oxyaquic Fragiorthods.—These are the Fragiorthods

that have an argillic horizon with a base saturation of 35

percent or more in some part and are saturated with water for

extended periods within 100 cm of the soil surface. These soils

do not have redoximorphic features within 75 cm of the soil

surface. They occur in Michigan and Wisconsin. They

commonly are wooded, but some have been cleared and are

used for small grain or hay.

Aquic Fragiorthods.—These are the Fragiorthods that have

aquic conditions and redoximorphic features within 75 cm of

the soil surface. These soils commonly occur in New York and

Pennsylvania. They generally support forest vegetation, but

some areas have been cleared for crop production.

Entic Fragiorthods.—These are the Fragiorthods that have

a value and chroma, moist, of 4 or more. These soils are not

saturated for extended periods within 100 cm of the surface, do

not have an argillic or kandic horizon, and do not have a

surface horizon 30 cm or more thick that meets all of the

requirements for a plaggen epipedon except thickness. The

soils support forest vegetation and occur in New York, New

Hampshire, and Vermont.

Oxyaquic Fragiorthods.—These are the Fragiorthods that

are saturated for extended periods within 100 cm of the soil

surface. These soils do not have redoximorphic features within

75 cm of the soil surface or an argillic or kandic horizon with a

base saturation of 35 percent or more in at least some part.

Oxyaquic Fragiorthods occur in Wisconsin and Michigan and

support northern hardwoods.

Plagganthreptic Fragiorthods.—These are the

Fragiorthods that have a surface layer 30 cm or more thick that

has all of the properties of a plaggen epipedon except thickness.

These soils do not have an argillic or kandic horizon with a base

saturation of 35 percent or more in at least some part and are not

saturated with water for extended periods within 100 cm of the

soil surface. The soils are rare. They occur in small areas of

Europe.

Ultic Fragiorthods.—These are the Fragiorthods that have

an argillic or kandic horizon with a base saturation of less than

35 percent in all parts. These soils are not saturated with water

for extended periods within 100 cm of the soil surface and do

not have a surface horizon 30 cm or more thick that meets all

of the requirements for a plaggen epipedon except thickness.

The soils are rare in the world.

Haplorthods

These are the relatively freely drained Orthods that either

have an albic horizon and a spodic horizon or, under

cultivation, commonly have only a spodic horizon below an Ap

horizon. The spodic horizon may rest on a lower sequum with

an argillic or kandic horizon, on relatively unaltered

unconsolidated materials, or on rock. The soil temperature

regime is frigid or warmer, and the moisture regime is

predominantly udic. Most Haplorthods have, or used to have,

forest vegetation, mainly conifers but also hardwoods in some

areas. A majority of these soils formed in sandy deposits or in

materials weathered from sandstone or quartzite.

Definition

Haplorthods are the Orthods that:

1. Do not have less than 0.10 percent iron (by ammonium

oxalate) in 75 percent or more of the spodic horizon;

2. Do not have, in 50 percent or more of each pedon, a placic

horizon within 100 cm of the mineral soil surface;

3. Do not have a fragipan with its upper boundary within 100

cm of the mineral soil surface; and

4. Do not have, in 90 percent or more of each pedon, a

cemented soil layer that does not slake in water after air drying

and has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

CDEA. Haplorthods that have a lithic contact within 50 cm

of the mineral soil surface; and either

1. A spodic horizon with a texture of very fine sand,

loamy very fine sand, or finer; and

a. A thickness of 10 cm or less; and
Spodosols 717

b. A weighted average of less than 1.2 percent organic

carbon; and

c. Within the upper 7.5 cm, either or both a moist color

value or chroma of 4 or more (crushed and smoothed

sample); or

2. A spodic horizon with a texture of loamy fine sand, fine

sand, or coarser and either or both a moist color value or

chroma of 4 or more (crushed and smoothed sample) in the

upper 2.5 cm.

Entic Lithic Haplorthods

CDEB. Other Haplorthods that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Haplorthods

CDEC. Other Haplorthods that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. Redoximorphic features in one or more horizons

within 75 cm of the mineral soil surface and also aquic

conditions for some time in normal years (or artificial

drainage).

Fragiaquic Haplorthods

CDED. Other Haplorthods that have both:

1. Redoximorphic features in one or more horizons

within 75 cm of the mineral soil surface and also aquic

conditions for some time in normal years (or artificial

drainage); and

2. Within 200 cm of the mineral soil surface, an argillic or

kandic horizon that has a base saturation of 35 percent or

more (by sum of cations) in some part.

Aqualfic Haplorthods

CDEE. Other Haplorthods that have redoximorphic features

in one or more horizons within 75 cm of the mineral soil

surface and also aquic conditions for some time in normal

years (or artificial drainage); and either

1. A spodic horizon with a texture of very fine sand,

loamy very fine sand, or finer; and

a. A thickness of 10 cm or less; and

b. A weighted average of less than 1.2 percent organic

carbon; and

c. Within the upper 7.5 cm, either or both a moist color

value or chroma of 4 or more (crushed and smoothed

sample); or

2. A spodic horizon with a texture of loamy fine sand, fine

sand, or coarser and either or both a moist color value or

chroma of 4 or more (crushed and smoothed sample) in the

upper 2.5 cm.

Aquentic Haplorthods

CDEF. Other Haplorthods that have redoximorphic features

in one or more horizons within 75 cm of the mineral soil

surface and also aquic conditions for some time in normal

years (or artificial drainage).

Aquic Haplorthods

CDEG. Other Haplorthods that have:

1. Within 200 cm of the mineral soil surface, an argillic or

kandic horizon that has a base saturation of 35 percent or

more (by sum of cations) in some part; and

2. Saturation with water in one or more layers within 100

cm of the mineral soil surface in normal years for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Alfic Oxyaquic Haplorthods

CDEH. Other Haplorthods that have:

1. Within 200 cm of the mineral soil surface, an argillic or

kandic horizon; and

2. Saturation with water in one or more layers within 100

cm of the mineral soil surface in normal years for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Oxyaquic Ultic Haplorthods

CDEI. Other Haplorthods that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Haplorthods

CDEJ. Other Haplorthods that, below the spodic horizon but

not below an argillic horizon, have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Haplorthods

CDEK. Other Haplorthods that are saturated with water in one
718 Soil Taxonomy

or more layers within 100 cm of the mineral soil surface in normal

years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplorthods

CDEL. Other Haplorthods that have andic soil properties

throughout horizons that have a total thickness of 25 cm or

more within 75 cm either of the mineral soil surface or of the

top of an organic layer with andic soil properties, whichever is

shallower.

Andic Haplorthods

CDEM. Other Haplorthods that have, within 200 cm of the

mineral soil surface, an argillic or kandic horizon that has a

base saturation of 35 percent or more (by sum of cations) in

some part.

Alfic Haplorthods

CDEN. Other Haplorthods that have an argillic or kandic

horizon within 200 cm of the mineral soil surface.

Ultic Haplorthods

CDEO. Other Haplorthods that have a spodic horizon that

has one of the following:

1. A texture of very fine sand, loamy very fine sand, or

finer; and

a. A thickness of 10 cm or less; and

b. A weighted average of less than 1.2 percent organic

carbon; and

c. Within the upper 7.5 cm, either or both a moist color

value or chroma of 4 or more (crushed and smoothed

sample); or

2. A texture of loamy fine sand, fine sand, or coarser and

either or both a moist color value or chroma of 4 or more

(crushed and smoothed sample) in the upper 2.5 cm.

Entic Haplorthods

CDEP. Other Haplorthods.

Typic Haplorthods

Definition of Typic Haplorthods

Typic Haplorthods are the Haplorthods that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have redoximorphic features in any horizon

within 75 cm of the mineral soil surface and also aquic

conditions;

3. Are not saturated with water in any layer within 100 cm of

the mineral soil surface in normal years for either or both 20 or

more consecutive days or 30 or more cumulative days;

4. Do not have an argillic or kandic horizon within 200 cm of

the mineral soil surface;

5. Do not have andic soil properties throughout horizons that

have a total thickness of 25 cm or more within 75 cm either of

the mineral soil surface or of the top of an organic layer with

andic soil properties, whichever is shallower;

6. Have a spodic horizon with one or more of the following:

a. A texture of very fine sand, loamy very fine sand, or

finer; and

(1) A thickness of more than 10 cm; or

(2) A weighted average of 1.2 percent or more organic

carbon in the upper 10 cm; or

(3) Within the upper 7.5 cm, either or both a moist

color value or chroma of 3 or less (crushed and smoothed

sample); or

b. A texture of loamy fine sand, fine sand, or coarser and a

color value, moist, and chroma of 3 or less (crushed and

smoothed sample) in the upper 2.5 cm;

7. Do not have lamellae (two or more) within 200 cm of the

soil surface; and

8. Have fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Description of Subgroups

Typic Haplorthods.—The Typic subgroup of Haplorthods

is centered on soils that do not have an argillic or kandic

horizon, a lithic contact within 50 cm of the mineral soil

surface, saturation with water for extended periods within 100

cm of the mineral soil surface, andic soil properties in a layer

25 cm or more thick within 75 cm of the soil surface, fragic

properties, lamellae, or both a chroma and value, moist, of 4 or

more. These soils occur in the northeastern and northwestern

parts of the United States as well as Michigan, Wisconsin,

Minnesota, West Virginia, and Maryland. They generally

support forest vegetation, but some have been cleared for

pasture or crop production. The most common crops are small

grain, corn for silage, and in Maine potatoes.

Alfic Haplorthods.—These are the Haplorthods that have

an argillic or kandic horizon that has a base saturation of 35
Spodosols 719

percent or more in at least some part. These soils do not have a

lithic contact within 50 cm of the soil surface, saturation with

water for extended periods within 100 cm of the mineral soil

surface, fragic properties, lamellae, or andic soil properties in a

layer 25 cm or more thick within 75 cm of the soil surface. The

soils occur in Michigan, Wisconsin, and New York. They

generally are forested, but some of the less sloping areas are

used for small grain or hay.

Alfic Oxyaquic Haplorthods.—These are the Haplorthods

that have an argillic or kandic horizon with a base saturation of

35 percent or more in at least some part and are saturated with

water for extended periods within 100 cm of the mineral soil

surface. These soils do not have aquic conditions and

redoximorphic features within 75 cm of the mineral soil

surface or a lithic contact within 50 cm of the soil surface.

They occur in Wisconsin and Michigan. Most of the soils are

forested, but some have been cleared and are used for small

grain or hay.

Andic Haplorthods.—These are the Haplorthods that have

andic soil properties in a layer 25 cm or more thick within 75

cm of the soil surface. These soils do not have a lithic contact

within 50 cm of the soil surface, fragic soil properties,

saturation with water for extended periods within 100 cm of

the soil surface, or lamellae. They occur in Washington and are

wooded.

Aqualfic Haplorthods.—These are the Haplorthods that

have an argillic or kandic horizon with a base saturation of 35

percent or more in at least some part and aquic conditions and

redoximorphic features within 75 cm of the mineral soil

surface. These soils do not have a lithic contact within 50 cm

of the soil surface or fragic soil properties. They occur in

Washington, Michigan, and Wisconsin. Most of the soils are

forested, but some have been cleared for crop production.

Aquentic Haplorthods.—These are the Haplorthods that

have aquic conditions and redoximorphic features within 75

cm of the soil surface and have a value and chroma, moist, of 4

or more. These soils do not have an argillic or kandic horizon,

fragic soil properties, or a lithic contact within 50 cm of the

mineral soil surface. They occur in Oregon, Washington,

Minnesota, Michigan, Wisconsin, and New York. They formed

under forest vegetation. Some areas have been cleared and are

used for hay or pasture.

Aquic Haplorthods.—These are the Haplorthods that have

aquic conditions and redoximorphic features within 75 cm of

the mineral soil surface. These soils do not have a lithic contact

within 50 cm of the soil surface, an argillic or kandic horizon,

fragic soil properties, or a value and chroma, moist, of 4 or

more. They occur in New England and the Lake States. Most

are forested.

Entic Haplorthods.—These are the Haplorthods that have

both a value and chroma, moist, of 4 or more. These soils do

not have an argillic or kandic horizon, a lithic contact within

50 cm of the mineral soil surface, saturation with water for

extended periods within 100 cm of the mineral soil surface,

andic soil properties in a layer 25 cm or more thick within 75

cm of the soil surface, fragic properties, or lamellae. The soils

occur in the Pacific Northwest, in the Northeast, and in

Michigan, Wisconsin, Virginia, Pennsylvania, Maryland, and

West Virginia. Commonly, these soils are wooded, but some

have been cleared and are used for hay, corn, oats, potatoes, or

fruit crops.

Entic Lithic Haplorthods.—These are the Haplorthods that

have both a value and chroma, moist, of 4 or more and have a

lithic contact within 50 cm of the mineral soil surface. These

soils are wooded and occur in Wisconsin.

Fragiaquic Haplorthods.—These are the Haplorthods that

have aquic conditions and redoximorphic features within 75

cm of the mineral soil surface and have fragic properties or a

fragipan between depths of 100 and 200 cm. These soils do not

have a lithic contact within 50 cm of the mineral soil surface.

They are rare in the world.

Fragic Haplorthods.—These are the Haplorthods that have

fragic properties or a fragipan between depths of 100 and 200

cm. These soils do not have a lithic contact within 50 cm of the

soil surface and are not saturated with water for extended

periods within 100 cm of the mineral soil surface. They are

rare in the world.

Lamellic Haplorthods.—These are the Haplorthods that

have lamellae. These soils do not have a lithic contact within

50 cm of the soil surface, saturation with water for extended

periods within 100 cm of the mineral soil surface, or fragic

properties. They occur in Michigan. In some areas they are

forested. In other areas they have been cleared and are used for

small grain, hay, or potatoes.

Lithic Haplorthods.—These are the Haplorthods that have

a lithic contact within 50 cm of the soil surface but do not have

both a value and chroma, moist, of 4 or more. These soils occur

in the Northeast as well as Michigan. Most support forest

vegetation, but some areas have been cleared and are used for

hay or pasture.

Oxyaquic Haplorthods.—These are the Haplorthods that

are saturated with water within 100 cm of the mineral soil

surface for 20 or more consecutive days or 30 cumulative days

in normal years. These soils do not have a lithic contact within

50 cm of the mineral soil surface, aquic conditions and

redoximorphic features within 75 cm of the mineral soil

surface, fragic properties, or lamellae. The soils occur in

Washington, Michigan, Wisconsin, and the northeastern part

of the United States. In most areas these soils are wooded, but

some areas have been cleared and are used for hay and pasture.

Oxyaquic Ultic Haplorthods.—These are the Haplorthods

that have an argillic or kandic horizon with a base saturation of

less than 35 percent in all parts and in normal years are

saturated with water for 20 or more consecutive days or 30 or
720

more cumulative days within 100 cm of the mineral soil

surface. These soils do not have a lithic contact within 50 cm

of the soil surface or aquic conditions and redoximorphic

features within 75 cm of the mineral soil surface. Oxyaquic

Ultic Haplorthods occur in Wisconsin. They generally are

wooded, but some have been cleared and are used for corn,

hay, or pasture.

Ultic Haplorthods.—These are the Haplorthods that have an

argillic horizon that has a base saturation of less than 35 percent

in all parts. These soils do not have a lithic contact within 50 cm

of the mineral soil surface, fragic soil properties, lamellae, or

andic soil properties in a layer 25 cm or more thick within 75 cm

of the soil surface and are not saturated with water for extended

periods within 100 cm of the mineral soil surface. The soils are

rare in the world.

Placorthods

These are the Orthods that have a placic horizon within 100

cm of the mineral soil surface. These soils are not known to

occur in the continental United States and are thought to be

rare elsewhere in the world.

Definition

Placorthods are the Orthods that have a placic horizon

within 100 cm of the mineral soil surface in 50 percent or more

of each pedon.

Key to Subgroups

CDAA. All Placorthods (provisionally).

Typic Placorthods
721

Ultisols are soils that have an argillic or kandic horizonwith low base saturation. They may have any soil

temperature regime and any soil moisture regime except aridic.

There is more precipitation than evapotranspiration at some

season, and some water moves through the soils and into a

moist or wet substratum. The release of bases by weathering

usually is equal to or less than the removal by leaching, and

most of the bases commonly are held in the vegetation and the

upper few centimeters of the soils. Base saturation in most

Ultisols decreases with increasing depth because the vegetation

has concentrated the bases at a shallow depth. Cultivation,

therefore, is a shifting cultivation unless soil amendments are

applied.

Ultisols are most extensive in warm, humid climates that

have a seasonal deficit of precipitation. They are mainly on

Pleistocene or older surfaces. They formed in a very wide

variety of parent materials, but very few have many primary

minerals that contain bases other than some micas. Some of the

few that have a supply of bases are intensively cultivated.

Kaolin, gibbsite, and aluminum-interlayered clays are common

in the clay fraction. Smectites also may be present if they are in

the parent materials. Extractable aluminum normally is high

except in the Paleudults and other pale-groups. A calciumdeficient argillic horizon is common in the Ultisols in the

United States.

Most of the Ultisols in the United States had a vegetation of

coniferous or hardwood forests at the time of settlement.

Savannas are present in other parts of the world, but they may

be anthropic.

Definition of Ultisols and Limits Between

Ultisols and Soils of Other Orders

Ultisols are the mineral soils that:

1. Have either:

a. An argillic or kandic horizon, but no fragipan, and a

base saturation (by sum of cations) of less than 35 percent at

one of the following depths:

(1) If the epipedon has a sandy or sandy-skeletal

particle-size class throughout, either:

(a) 125 cm below the upper boundary of the argillic

or kandic horizon (but no deeper than 200 cm below

the mineral soil surface) or 180 cm below the mineral

soil surface, whichever is deeper; or

(b) At a densic, lithic, paralithic, or petroferric

contact if shallower; or

(2) The shallowest of the following depths:

(a) 125 cm below the upper boundary of the argillic

or kandic horizon; or

(b) 180 cm below the mineral soil surface; or

(c) At a densic, lithic, paralithic, or petroferric

contact; or

b. A fragipan and both of the following:

(1) Either an argillic or kandic horizon above, within,

or below it or clay films 1 mm or more thick in one or

more of its subhorizons; and

(2) A base saturation (by sum of cations) of less than 35

percent at the shallowest of the following depths:

(a) 75 cm below the upper boundary of the fragipan;

or

(b) 200 cm below the mineral soil surface; or

(c) At a densic, lithic, paralithic, or petroferric

contact;

2. Do not have either of the following:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface;

3. Do not have andic soil properties in 60 percent or more of

the thickness between either the mineral soil surface or the top

of an organic layer with andic soil properties, whichever is

shallower, and either a depth of 60 cm from the shallower of

the above or a densic, lithic, or paralithic contact, a duripan, or

a petrocalcic horizon if shallower than 60 cm;

4. Do not have an Ap horizon containing 85 percent or more

spodic materials;

5. Have an argillic or kandic horizon above any spodic

horizon that has either of the following:

a. An overlying albic horizon in 50 percent or more of

CHAPTER 19

Ultisols
722 Soil Taxonomy

each pedon and a cryic soil temperature regime; or

b. All of the following characteristics:

(1) One or more of the following:

(a) A thickness of 10 cm or more; or

(b) An overlying Ap horizon; or

(c) Cementation in 50 percent or more of each

pedon; or

(d) A coarse-loamy, loamy-skeletal, or finer particlesize class and a frigid soil temperature regime; or

(e) A cryic soil temperature regime; and

(2) An upper boundary within the following depths

from the mineral soil surface: either

(a) Less than 50 cm; or

(b) Less than 200 cm if the soil has a sandy particlesize class in at least some part between the mineral

soil surface and the spodic horizon; and

(3) A lower boundary as follows:

(a) Either at a depth of 25 cm or more below the

mineral soil surface, or at the top of a duripan or

fragipan, or at a densic, lithic, paralithic, or

petroferric contact, whichever is shallowest; or

(b) At any depth,

1) If the spodic horizon has a coarse-loamy,

loamy-skeletal, or finer particle-size class and the

soil has a frigid temperature regime; or

2) If the soil has a cryic temperature regime;

6. Do not have an oxic horizon that has its upper boundary

within 150 cm of the mineral soil surface unless there is a

kandic horizon above the oxic horizon;

7. Have less than 40 percent (by weight) clay in the fine-earth

fraction between the mineral soil surface and a depth of 18 cm

(after mixing) if the kandic horizon has the weatherablemineral properties of an oxic horizon and has its upper

boundary within 150 cm of the mineral soil surface;

8. Do not have all of the following:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

aggregates that have their long axes tilted 10 to 60 degrees

from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon if shallower; and

c. Cracks that open and close periodically;

9. Do not have an aridic moisture regime; and

10. Do not have a salic horizon and meet all of the following

criteria:

a. Are not saturated with water in one or more layers

within 100 cm of the soil surface for 1 month or more in

normal years; and

b. Do not have a moisture control section that is dry in at

least some part in normal years; and

c. Have a sulfuric horizon that has its upper boundary

within 150 cm of the mineral soil surface.

Limits Between Ultisols and the Other Soil Orders

The definition of Ultisols must provide criteria that separate

Ultisols from soils of all other orders. The aggregate of these

criteria defines the limits of Ultisols in relation to all other

known kinds of soil.

1. Unlike Alfisols, Ultisols must have one of the following

characteristics:

a. No fragipan and a base saturation (by sum of cations) of

less than 35 percent at one of the following depths:

(1) If there is an epipedon that has a sandy or sandyskeletal particle-size class throughout, either:

(a) 125 cm below the upper boundary of the argillic

horizon (but no deeper than 200 cm below the mineral

soil surface) or 180 cm below the mineral soil surface,

whichever is deeper; or

(b) At a densic, lithic, paralithic, or petroferric

contact if shallower; or

(2) If the epipedon does not have a sandy or sandyskeletal particle-size class throughout, the shallowest of

the following depths:

(a) 125 cm below the upper boundary of the argillic

or kandic horizon; or

(b) 180 cm below the mineral soil surface; or

(c) At a densic, lithic, paralithic, or petroferric

contact; or

b. A fragipan and a base saturation (by sum of cations) of

less than 35 percent at the shallowest of the following

depths:

(1) 75 cm below the upper boundary of the fragipan; or
Ultisols 723

(2) 200 cm below the mineral soil surface; or

(3) At a densic, lithic, paralithic, or petroferric

contact.

2. Unlike Andisols, Ultisols must not have andic soil

properties in 60 percent or more of the thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and either a

depth of 60 cm from the shallower of the above or a densic,

lithic, or paralithic contact, a duripan, or a petrocalcic horizon

if shallower than 60 cm.

3. Unlike Aridisols, Ultisols must not:

a. Have an aridic soil moisture regime; and

b. Have a salic horizon and meet all of the following

criteria:

(1) Are not saturated with water in one or more layers

within 100 cm of the soil surface for 1 month or more in

normal years; and

(2) Do not have a moisture control section that is dry in

at least some part in normal years; and

(3) Have a sulfuric horizon that has its upper boundary

within 150 cm of the mineral soil surface.

4. Unlike Entisols and Inceptisols, Ultisols must have one of

the following:

a. An argillic or kandic horizon; or

b. A fragipan that meets all of the requirements for an

argillic or kandic horizon or that has clay films more than

1 mm thick in some part.

5. Unlike Gelisols, Ultisols do not have:

a. Permafrost within 100 cm of the soil surface; or

b. Gelic materials within 100 cm of the soil surface and

permafrost within 200 cm of the soil surface.

6. Unlike Histosols, Ultisols do not have organic soil

materials that meet one or more of the following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or fill their interstices1 and directly below these

materials have either a densic, lithic, or paralithic contact;

or

b. When added with the underlying cindery, fragmental, or

pumiceous materials, total 40 cm or more between the soil

surface and a depth of 50 cm; or

c. Constitute two-thirds or more of the total thickness of

the soil to a densic, lithic, or paralithic contact and have no

mineral horizons or have mineral horizons with a total

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more in normal

years (or are artificially drained), have an upper boundary

within 40 cm of the soil surface, and have a total thickness

of either:

(1) 60 cm or more if three-fourths or more of their

volume consists of moss fibers or if their bulk density,

moist, is less than 0.1 g/cm3; or

(2) 40 cm or more if they consist either of sapric or

hemic materials, or of fibric materials with less than

three-fourths (by volume) moss fibers and a bulk density,

moist, of 0.1 g/cm3 or more.

7. Unlike Mollisols, Ultisols must have one of the following:

a. An argillic or kandic horizon, but no fragipan, and a

base saturation (by sum of cations) of less than 35 percent at

one of the following depths:

(1) If there is an epipedon that has a sandy or sandyskeletal particle-size class throughout, either:

(a) 125 cm below the upper boundary of the argillic

horizon (but no deeper than 200 cm below the mineral

soil surface) or 180 cm below the mineral soil surface,

whichever is deeper; or

(b) At a densic, lithic, paralithic, or petroferric

contact if shallower; or

(2) If the epipedon does not have a sandy or sandyskeletal particle-size class throughout, the shallowest of

the following depths:

(a) 125 cm below the upper boundary of the argillic

or kandic horizon; or

(b) 180 cm below the mineral soil surface; or

(c) At a densic, lithic, paralithic, or petroferric

contact; or

b. A fragipan and a base saturation (by sum of cations) of

less than 35 percent at the shallowest of the following

depths:

(1) 75 cm below the upper boundary of the fragipan;

or

(2) 200 cm below the mineral soil surface; or

(3) At a densic, lithic, paralithic, or petroferric contact.

8. Unlike Oxisols, Ultisols must not have either:

a. An oxic horizon that has its upper boundary within 150

cm of the mineral soil surface; or

b. 40 percent or more (by weight) clay in the fine-earth

fraction between the mineral soil surface and a depth of 18

1Materials that meet the definition of cindery, fragmental, or pumiceous but have more

than 10 percent (by volume) voids that are filled with organic soil materials are considered to

be organic soil materials.
724 Soil Taxonomy

cm (after mixing) and a kandic horizon that has less than 10

percent weatherable minerals and has its upper boundary

within 150 cm of the mineral soil surface.

9. Unlike Spodosols, Ultisols must not have an Ap horizon

consisting of spodic materials or a spodic horizon above the

argillic, kandic, or natric horizon and must not have have one

or more of the following:

a. An albic horizon in 50 percent or more of each pedon

and a cryic soil temperature regime; or

b. A spodic horizon with all of the following

characteristics:

(1) One or more of the following:

(a) A thickness of 10 cm or more; or

(b) An overlying Ap horizon; or

(c) Cementation in 50 percent or more of each

pedon; or

(d) A coarse-loamy, loamy-skeletal, or finer particlesize class and a frigid soil temperature regime; or

(e) A cryic soil temperature regime; and

(2) An upper boundary within the following depths

from the mineral soil surface: either

(a) Less than 50 cm; or

(b) Less than 200 cm if the soil has a sandy particlesize class between the mineral soil surface and the

spodic horizon; and

(3) A lower boundary as follows:

(a) Either at a depth of 25 cm or more below the

mineral soil surface, or at the top of a duripan or

fragipan, or at a densic, lithic, paralithic, or

petroferric contact, whichever is shallowest; or

(b) At any depth if the spodic horizon has a coarseloamy, loamy-skeletal, or finer particle-size class and

the soil has a frigid temperature regime or if the soil

has a cryic temperature regime.

10. Unlike Vertisols, Ultisols must not have all of the

following:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

aggregates that have their long axes tilted 10 to 60 degrees

from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon if shallower; and

c. Cracks that open and close periodically.

Representative Pedon and Data

Following is a description of a representative Ultisol. Data for

the pedon identified in this description are given in the table

“Characterization Data for an Ultisol.”

Classification: Fine, kaolinitic, thermic Typic Kandiudult

Site identification number: 82P0398

Location: Autauga County, Alabama; SW1/4SW1/4SW1/4 sec.

33, T. 18 N., R. 16 E.

Latitude: 32 degrees 29 minutes 19 seconds N.

Longitude: 86 degrees 28 minutes 10 seconds W.

Slope: 1 percent

Elevation: 122 m

Landform: Terrace

Parent material: Fluvial or marine sediments

Soil moisture regime: Udic

Permeability class: Moderate

Drainage class: Well drained

Water table: None observed within a depth of 9 m

Land use: Forest land (not grazed)

Vegetation: Native hardwoods and pine

Particle-size control section: 12 to 62 cm

Diagnostic features: An ochric epipedon from a depth of 0 to

12 cm, a kandic from a depth of 12 to more than 200 cm,

and an argillic horizon from a depth of 12 to more than

200 cm

Described by: Brown and Stubbs

In the following pedon description, colors are for moist soil

unless otherwise indicated. Texture terms are for field textures.

Ap—0 to 12 cm; dark yellowish brown (10YR 4/4) fine sandy

loam; weak medium subangular blocky structure; very

friable; many fine and medium roots; common organic

coatings; few wormcasts; abundant active fire ant cavities;

strongly acid; clear smooth boundary.

Bt1—12 to 40 cm; red (2.5YR 4/6) clay loam; moderate

medium subangular blocky structure; friable; common fine

and medium roots; many tubular pores (abandoned root

channels); few distinct clay films on faces of peds;

common active fire ant cavities; very strongly acid; clear

wavy boundary.

Bt2—40 to 86 cm; red (2.5YR 4/6) clay loam; moderate

medium subangular blocky structure; firm; common

distinct clay films on faces of peds; very strongly acid;

clear wavy boundary.

Bt3—86 to 140 cm; red (2.5YR 4/6) clay loam; common

medium prominent yellowish brown (10YR 5/4) redox

depletions; weak medium and coarse prismatic structure
Ultisols 725

Characterization Data for an Ultisol

 SITE IDENTIFICATION NO.: 82P0398

 CLASSIFICATION: FINE, KAOLINITIC, THERMIC TYPIC KANDIUDULT

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 82P2043 0- 12 Ap 12.3 15.3 72.4 9.9 8.6 6.7 12.2 33.6 22.5 3.4 0.7 1 1 -- 61 2

 82P2044 12- 40 Bt1 35.0 18.4 46.6 26.5 13.4 5.0 7.6 21.4 14.8 2.3 0.5 TR TR -- 39 TR

 82P2045 40- 86 Bt2 35.3 17.7 47.0 27.6 12.2 5.5 7.6 21.2 14.8 2.4 1.0 TR TR -- 39 TR

 82P2046 86-140 Bt3 40.9 12.3 46.8 29.6 8.5 3.8 7.0 21.3 15.3 2.4 0.8 TR TR -- 40 TR

 82P2047 140-280 Bt4 44.6 9.3 46.1 28.0 5.3 4.0 6.9 20.7 15.2 2.4 0.9 TR TR -- 39 TR

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 12 1.25 0.057 0.3 0.1 TR 0.34 0.36 1.46 1.50 0.009 9.6 4.4 0.08

 12- 40 0.51 0.037 1.3 0.2 -- 0.16 0.34 1.55 1.60 0.011 15.1 11.8 0.05

 40- 86 0.32 0.019 1.4 0.2 -- 0.15 0.36 1.51 1.58 0.015 18.1 12.7 0.08

 86-140 0.20 1.7 TR -- 0.14 0.34 1.75 1.80 0.009 16.0 14.0 0.04

 140-280 0.19 1.8 0.2 -- 0.12 0.33 1.72 1.75 0.006 17.2 14.8 0.04

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- EXTR (- - - -CEC - - -) Al -BASE SAT- CO3 AS RES. COND.(- - - -PH - - -)

 Ca Mg Na K SUM ITY Al SUM NH4- BASES SAT SUM NH4 CaCO3 ohms mmhos KCl CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc + Al OAc <2mm /cm /cm IN .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 6G9a 5A3a 5A8b 5A3b 5G1 5C3 5C1 6E1g 8E1 8I 8C1g 8C1f 8C1f

 <- - - - - - - - - - - -meq / 100 g - - - - - - - - - - -> <- - - - -Pct - - - -> 1:2 1:1

 0- 12 1.3 0.4 -- 0.1 1.8 4.5 0.4 6.3 4.2 2.2 18 29 43 4.1 4.9 5.1

 12- 40 1.5 0.7 0.2 0.1 2.5 6.1 1.0 8.6 5.7 3.5 29 29 44 3.9 4.7 5.0

 40- 86 0.9 0.8 0.2 0.1 2.0 6.4 1.4 8.4 5.3 3.4 41 24 38 3.8 4.7 5.0

 86-140 0.1 0.3 0.1 0.1 0.6 7.0 2.7 7.6 5.6 3.3 82 8 11 3.7 4.6 5.0

 140-280 0.2 0.3 0.2 0.1 0.8 13.0 2.9 13.8 5.3 3.7 78 6 15 3.7 4.5 4.9

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA-

 < - - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION

 NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->

 82P2044 TCLY KK 4 VR 3 MI 1 GI 1 KK49 GI 4 8.7 0.5

 82P2047 TCLY KK 5 VR 3 GI 1 GE 1 KK61 GI 1 8.6 0.4

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 < - - - - - - - - - - - - - - - - - - SAND - SILT MINERALOGY (2.0-0.002mm)- - - - - >

 < -- - - - - - - - - -- OPTICAL - - - - - - - - - - - - - - - - - - - - - - - - - - >

 SAMPLE FRACTION TOTAL RESISTANT < - - - - - - - - - - -GRAIN COUNT - - - - - -- - - - - - ->

 82P2044 VFS 99 QZ98 OP 1 TMtr ZRtr BTtr FKtr MStr EPtr

 82P2047 VFS 99 QZ96 KK 3 MStr BTtr OPtr HNtr ZRtr TMtr

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 The chemical data are based on the fraction less than 2 mm in size.

parting to moderate medium subangular blocky; very firm;

few tubular pores (abandoned root channels); many

distinct clay films on faces of peds; few highly weathered

quartz pebbles less than 3 cm in diameter; very strongly

acid; gradual wavy boundary.

Bt4—140 to 280 cm; red (2.5YR 4/6) clay; common medium

prominent light brownish gray (10YR 6/2) and common

medium prominent brownish yellow (10YR 6/6) redox

depletions; weak medium and coarse prismatic structure

parting to weak medium subangular blocky; very firm;
726 Soil Taxonomy

common tubular pores (abandoned root channels); common

faint clay films on faces of peds; few black stains on faces

of peds; strongly acid; gradual wavy boundary.

Bt5—280 to 430 cm; yellowish red (5YR 4/6) clay; common

medium prominent gray (10YR 6/1) and common medium

prominent red (2.5YR 4/6) redox depletions and

concentrations; weak medium and coarse prismatic

structure parting to moderate medium subangular blocky;

very firm; few faint clay films on faces of peds; 5 percent

rounded quartzite gravel; very strongly acid; clear wavy

boundary.

2C1—430 to 530 cm; stratified yellow (10YR 8/6), red (2.5YR

5/6), and gray (N 6/0) loamy sand; firm; few mica flakes;

very strongly acid; abrupt wavy boundary.

3C2—530 to 900 cm; stratified red (2.5YR 5/6) and yellowish

brown (10YR 5/6) very gravelly sandy loam; very firm; 60

percent rounded quartzite gravel; few highly weathered,

gray and light gray pebbles; very strongly acid.

Key to Suborders

HA. Ultisols that have aquic conditions for some time in

normal years (or artificial drainage) in one or more horizons

within 50 cm of the mineral soil surface and one or both of the

following:

1. Redoximorphic features in all layers between either the

lower boundary of an Ap horizon or a depth of 25 cm from

the mineral soil surface, whichever is deeper, and a depth of

40 cm and one of the following within the upper 12.5 cm of

the argillic or kandic horizon:

a. Redox concentrations and 50 percent or more redox

depletions with chroma of 2 or less either on faces of

peds or in the matrix; or

b. 50 percent or more redox depletions with chroma of

1 or less either on faces of peds or in the matrix; or

c. Distinct or prominent redox concentrations and 50

percent or more hue of 2.5Y or 5Y in the matrix and also

a thermic, isothermic, or warmer soil temperature

regime; or

2. Within 50 cm of the mineral soil surface, enough active

ferrous iron to give a positive reaction to alpha,alphadipyridyl at a time when the soil is not being irrigated.

Aquults, p. 726

HB. Other Ultisols that have one or both of the following:

1. 0.9 percent (by weighted average) or more organic

carbon in the upper 15 cm of the argillic or kandic horizon;

or

2. 12 kg/m2 or more organic carbon between the mineral

soil surface and a depth of 100 cm.

Humults, p. 738

HC. Other Ultisols that have a udic moisture regime.

Udults, p. 747

HD. Other Ultisols that have an ustic moisture regime.

Ustults, p. 767

HE. Other Ultisols.

Xerults, p. 778

Aquults

These are the Ultisols in wet areas where ground water is

very close to the surface during part of each year, usually in

winter and spring in middle latitudes, and is deep at another

time. These soils are mostly grayish or olive in the subsoil and

formed mainly in alluvium and marine deposits that are of

Pleistocene age or older.

Aquults are extensive on the coastal plains in the United

States, particularly along the Atlantic Ocean and the Gulf of

Mexico. Their slopes are gentle. Most of the soils had and

many still have a forest vegetation.

Aquults have an ochric or umbric epipedon and an argillic

or kandic horizon. Some have a fragipan, and others have

plinthite in or below the argillic or kandic horizon.

Definition

Aquults are the Ultisols that have aquic conditions for some

time in normal years (or artificial drainage) in one or more

horizons within 50 cm of the mineral soil surface and one or

both of the following:

1. Redoximorphic features in all layers between either the

lower boundary of an Ap horizon or a depth of 25 cm below the

mineral soil surface, whichever is deeper, and a depth of 40 cm

or more and one of the following within the upper 12.5 cm of

the argillic or kandic horizon:

a. Redox concentrations and 50 percent or more redox

depletions with chroma of 2 or less either on faces of peds or

in the matrix; or

b. 50 percent or more redox depletions with chroma of 1

or less either on faces of peds or in the matrix; or

c. Distinct or prominent redox concentrations and 50

percent or more hue of 2.5Y or 5Y in the matrix and also a

thermic, isothermic, or warmer soil temperature regime; or

2. Within 50 cm of the mineral soil surface, enough active

ferrous iron to give a positive reaction to alpha,alpha-dipyridyl

at a time when the soil is not being irrigated.

Key to Great Groups

HAA. Aquults that have one or more horizons within 150

cm of the mineral soil surface in which plinthite either forms
Ultisols 727

a continuous phase or constitutes one-half or more of the

volume.

Plinthaquults, p. 737

HAB. Other Aquults that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragiaquults, p. 731

HAC. Other Aquults that have an abrupt textural change

between the ochric epipedon or albic horizon and the argillic or

kandic horizon and have 0.4 cm/hr or slower (moderately low or

lower) saturated hydraulic conductivity in the argillic or kandic

horizon.

Albaquults, p. 727

HAD. Other Aquults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Have a kandic horizon; and

3. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) clay depletions

on faces of peds in the layer that has a 20 percent lower

clay content and, below that layer, a clay increase of 3

percent or more (absolute) in the fine-earth fraction.

Kandiaquults, p. 732

HAE. Other Aquults that have a kandic horizon.

Kanhaplaquults, p. 734

HAF. Other Aquults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) clay depletions

on faces of peds in the layer that has a 20 percent lower

clay content and, below that layer, a clay increase of 3

percent or more (absolute) in the fine-earth fraction.

Paleaquults, p. 735

HAG. Other Aquults that have an umbric or mollic epipedon.

Umbraquults, p. 738

HAH. Other Aquults that have episaturation.

Epiaquults, p. 729

HAI. Other Aquults.

Endoaquults, p. 728

Albaquults

These are the Aquults that have a marked increase in

percentage of clay at an abrupt boundary at the top of the

argillic or kandic horizon. The argillic or kandic horizon

generally is clayey and has moderately low or lower hydraulic

conductivity. In normal years water is perched for a while

above the argillic or kandic horizon when the soils are

rewetting and later saturates the whole soil. Slopes are nearly

level, and draining the soils is difficult. In the Southeastern

United States, these soils formed mostly in acid, latePleistocene sediments and are on low marine or stream

terraces. Most of them have a season when the upper horizons

are dry. Some of the Albaquults in the United States have been

cleared for grazing or cropping, but many are still in forests.

Definition

Albaquults are the Aquults that:

1. Have an abrupt textural change between the ochric

epipedon or the albic horizon and the argillic or kandic horizon

and have saturated hydraulic conductivity in the argillic

horizon of 0.4 cm/hr or slower;

2. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface; and

3. Do not have plinthite that forms a continuous phase or

constitutes half or more of the matrix of any subhorizon within

150 cm of the mineral soil surface.

Key to Subgroups

HACA. Albaquults that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Albaquults

HACB. Other Albaquults that have a kandic horizon.

Kandic Albaquults

HACC. Other Albaquults that have 50 percent or more

chroma of 3 or more in one or more horizons between either

the A or Ap horizon or a depth of 25 cm from the mineral soil

surface, whichever is deeper, and a depth of 75 cm.

Aeric Albaquults
728 Soil Taxonomy

HACD. Other Albaquults.

Typic Albaquults

Definition of Typic Albaquults

Typic Albaquults are the Albaquults that:

1. Have more than 50 percent chroma of 2 or less in all

horizons between either the A or Ap horizon or a depth of 25

cm from the mineral soil surface, whichever is deeper, and a

depth of 75 cm; and

2. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

and

3. Do not have a kandic horizon.

Description of Subgroups

Typic Albaquults.—These are the Albaquults that have 50

percent or more chroma of 2 or less in all horizons between

either the A or Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and a depth of 75

cm. These soils do not have slickensides, wedge-shaped

aggregates, a high linear extensibility, or wide cracks. Soils

that have slickensides, wedge-shaped aggregates, a high linear

extensibility, or wide cracks are assigned to the Vertic subgroup

because these properties are shared with Vertisols.

Typic Albaquults are nearly level and are difficult to drain.

Some are cultivated, but many are used as pasture or are in

forests. The soils occur mostly on the coastal plain of the

Southeastern United States and are of moderately small extent.

Aeric Albaquults.—Chroma in these soils is 3 or more in

more than 50 percent of some horizon between the bottom of

the A or Ap horizon and a depth of 75 cm. The period of

saturation with water in these soils is shorter than the one

characteristic of Typic Albaquults. Aeric Albaquults are of very

small extent in the United States and occur mostly in

California. They generally are either cultivated or used as

pasture.

Kandic Albaquults.—These soils are like Typic

Albaquults, but they have a kandic horizon. Kandic Albaquults

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Vertic Albaquults.—These soils are like Typic Albaquults,

but they are high in expanding clays and have cracks 5 mm or

more wide, slickensides, wedge-shaped aggregates, or a linear

extensibility of 6.0 cm or more between the mineral soil surface

and either a depth of 100 cm or a densic, lithic, or paralithic

contact, whichever is shallower. The soils are considered

intergrades between Albaquults and Aquerts. Vertic Albaquults

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Endoaquults

Endoaquults are the Aquults that have endoaquic saturation

and do not have a mollic or umbric epipedon. The ground

water fluctuates from a level near the soil surface to below the

argillic horizon and is sometimes below a depth of 200 cm.

These soils have an epipedon that rests on an argillic horizon

without an abrupt textural change if the argillic horizon has

moderately low or lower saturated hydraulic conductivity. They

do not have a kandic horizon. They have no fragipan or

horizon in which plinthite either forms a continuous phase or

constitutes one-half or more of the volume within 150 cm of

the mineral soil surface.

Before cultivation, most Endoaquults supported either

deciduous broadleaf or coniferous forest plants. Generally, the

soils are nearly level.

Definition

Endoaquults are the Aquults that:

1. Have endosaturation;

2. Do not have a kandic horizon;

3. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

4. Do not have an abrupt textural change at the upper

boundary of the argillic horizon if the hydraulic conductivity of

that horizon is 0.4 cm/hr or slower;

5. Do not have plinthite that either forms a continuous phase

or constitutes more than half the matrix (by volume) in any

horizon within 150 cm of the mineral soil surface;

6. Do not have a mollic or umbric epipedon; and

7. Have, with increasing depth within 150 cm of the mineral

soil surface, a decrease of 20 percent or more (relative) from

the maximum clay content and either less than 5 percent (by

volume) clay depletions on faces of peds in the layer that has

the 20 percent lower clay content or, below that layer, no clay

increase or an increase of less than 3 percent (absolute).

Key to Subgroups

HAIA. Endoaquults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm.

Arenic Endoaquults

HAIB. Other Endoaquults that have a sandy or sandy-skeletal
Ultisols 729

particle-size class throughout a layer extending from the mineral

soil surface to the top of an argillic horizon at a depth of 100 cm

or more.

Grossarenic Endoaquults

HAIC. Other Endoaquults that have 50 percent or more

chroma of 3 or more in one or more horizons between either

the A or Ap horizon or a depth of 25 cm from the mineral soil

surface, whichever is deeper, and a depth of 75 cm.

Aeric Endoaquults

HAID. Other Endoaquults.

Typic Endoaquults

Definition of Typic Endoaquults

Typic Endoaquults are the Endoaquults that:

1. Do not have a sandy particle-size class throughout a layer

extending from the mineral soil surface to the top of an argillic

horizon at a depth of 50 cm or more; and

2. Have more than 50 percent chroma of 2 or less in all

horizons between either the A or Ap horizon or a depth of 25

cm from the mineral soil surface, whichever is deeper, and a

depth of 75 cm.

Description of Subgroups

Typic Endoaquults.—These are the Endoaquults that have

50 percent or more chroma of 2 or less in all horizons between

either the A or Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and a depth of 75

cm. These soils do not have a sandy particle-size class

throughout a layer extending from the mineral soil surface to

the top of the argillic horizon if the argillic horizon is at a

depth of 50 cm or more. Slopes generally are nearly level. The

natural vegetation consisted of forest plants. Some of the soils

are cultivated, but many are used as pasture or are in forests.

The soils occur mostly on the coastal plain of the Southeastern

United States and are of moderate extent.

Aeric Endoaquults.—Chroma in these soils is 3 or more in

more than 50 percent of some horizon between the bottom of

the A or Ap horizon and a depth of 75 cm. The period of

saturation with water in these soils is shorter than the one

characteristic of Typic Endoaquults. Aeric Endoaquults are of

small extent and occur mostly on the coastal plain of the

Southeastern United States. The natural vegetation consisted of

forest plants. Most of these soils are nearly level. Some have

been cleared and artificially drained and are used as cropland

or pasture, and some are used as forest.

Arenic Endoaquults.—These soils have a sandy layer,

starting at the mineral soil surface, that is between 50 and 100

cm thick. Many of the soils developed in somewhat sandier

materials and have less clay in the argillic horizon than the

Typic Endoaquults. Arenic Endoaquults are mainly on the

coastal plain of the Southeastern United States. They are of

small extent. The natural vegetation consisted of forest plants.

Most of these soils are nearly level. Most are used as forest, but

some have been cleared and artificially drained and are used as

cropland or pasture.

Grossarenic Endoaquults.—These soils have a sandy layer,

starting at the mineral soil surface, that is between 100 and 200

cm thick in the major part of the pedon, but they are otherwise

similar to Typic Endoaquults in defined properties. Grossarenic

Endoaquults are not known to occur in the United States. The

subgroup is provided for use in other parts of the world.

Epiaquults

Epiaquults are the Aquults that have epiaquic saturation and

do not have a mollic or umbric epipedon. Water is perched on a

less permeable layer, commonly an argillic horizon. These soils

have an epipedon that rests on an argillic horizon without an

abrupt textural change if the argillic horizon has moderately

low or lower saturated hydraulic conductivity. They do not

have a kandic horizon. They do not have a fragipan or a

horizon in which plinthite either forms a continuous phase or

constitutes one-half or more of the volume within 150 cm of

the mineral soil surface.

Before cultivation, most Epiaquults supported either

deciduous broadleaf or coniferous forest plants. Slopes

generally are nearly level.

Definition

Epiaquults are the Aquults that:

1. Do not have a kandic horizon;

2. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

3. Do not have an abrupt textural change at the upper

boundary of the argillic horizon if the hydraulic conductivity of

that horizon is low;

4. Do not have plinthite that either forms a continuous phase

or constitutes more than half the matrix (by volume) in any

horizon within 150 cm of the mineral soil surface;

5. Do not have a mollic or umbric epipedon;

6. Have, with increasing depth within 150 cm of the mineral

soil surface, a decrease of 20 percent or more (relative) from

the maximum clay content and either less than 5 percent (by

volume) clay depletions on faces of peds in the layer that has

the 20 percent lower clay content or, below that layer, no clay

increase or an increase of less than 3 percent (absolute); and

7. Have episaturation.

Key to Subgroups

HAHA. Epiaquults that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that are 5
730 Soil Taxonomy

mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Epiaquults

HAHB. Other Epiaquults that have:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. 50 percent or more chroma of 3 or more in one or more

horizons between either the A or Ap horizon or a depth of

25 cm from the mineral soil surface, whichever is deeper,

and a depth of 75 cm.

Aeric Fragic Epiaquults

HAHC. Other Epiaquults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm.

Arenic Epiaquults

HAHD. Other Epiaquults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more.

Grossarenic Epiaquults

HAHE. Other Epiaquults that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Epiaquults

HAHF. Other Epiaquults that have 50 percent or more

chroma of 3 or more in one or more horizons between either

the A or Ap horizon or a depth of 25 cm from the mineral soil

surface, whichever is deeper, and a depth of 75 cm.

Aeric Epiaquults

HAHG. Other Epiaquults.

Typic Epiaquults

Definition of Typic Epiaquults

Typic Epiaquults are the Epiaquults that:

1. Do not have a sandy particle-size class throughout a layer

extending from the mineral soil surface to the top of an argillic

horizon at a depth of 50 cm or more;

2. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

3. Have more than 50 percent chroma of 2 or less in all

horizons between either the A or Ap horizon or a depth of 25

cm from the mineral soil surface, whichever is deeper, and a

depth of 75 cm; and

4. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Epiaquults.—These are the Epiaquults that have 50

percent or more chroma of 2 or less in all horizons between

either the A or Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and a depth of 75

cm. These soils do not have slickensides, wedge-shaped

aggregates, a high linear extensibility, or wide cracks. They do

not have a sandy particle-size class throughout a layer

extending from the mineral soil surface to the top of the

argillic horizon if the argillic horizon is at a depth of 50 cm or

more. Soils that have slickensides, wedge-shaped aggregates, a

high linear extensibility, or wide cracks are assigned to the

Vertic subgroup because these properties are shared with

Vertisols.

Typic Epiaquults generally are nearly level. They occur

mostly in the Eastern United States and are of very small

extent. The natural vegetation consisted of forest plants. The

soils commonly are underlain by slowly permeable materials

and are difficult to drain. Some are used as cropland, but many

are used as pasture or forest.

Aeric Epiaquults.—Chroma in these soils is 3 or more in

more than 50 percent of some horizon between the bottom of

the A or Ap horizon and a depth of 75 cm. The period of

saturation with water in these soils is shorter than the one
Ultisols 731

characteristic of Typic Epiaquults. Aeric Epiaquults range from

nearly level to moderately steep. The natural vegetation

consisted of forest plants. These soils are of small extent in the

Eastern United States. Some are underlain by slowly permeable

materials and are difficult to drain. Some are used as cropland,

but many are used as pasture or forest.

Aeric Fragic Epiaquults.—Chroma in these soils is 3 or

more in more than 50 percent of some horizon between the

bottom of the A or Ap horizon and a depth of 75 cm. These

soils have fragic soil properties in 30 percent or more of the

volume of a layer 15 cm or more thick that has its upper

boundary within 100 cm of the mineral soil surface or in 60

percent or more of the volume of a layer 15 cm or more thick.

The soils are not known to occur in the United States. The

subgroup is provided for use in other parts of the world.

Arenic Epiaquults.—These soils have a sandy layer,

starting at the mineral soil surface, that is between 50 and 100

cm thick. They are otherwise like Typic Epiaquults in most

other defined properties. Arenic Epiaquults are not known to

occur in the United States. The subgroup is provided for use in

other parts of the world.

Fragic Epiaquults.—These soils have fragic soil properties

in 30 percent or more of the volume of a layer 15 cm or more

thick that has its upper boundary within 100 cm of the mineral

soil surface or in 60 percent or more of the volume of a layer

15 cm or more thick. These soils are not known to occur in the

United States. The subgroup is provided for use in other parts

of the world.

Grossarenic Epiaquults.—These soils have a sandy layer,

starting at the mineral soil surface, that is between 100 and 200

cm thick in the major part of the pedon. They are not known to

occur in the United States. The subgroup is provided for use in

other parts of the world.

Vertic Epiaquults.—These soils are similar to Typic

Epiaquults, but they are high in expanding clays and have

cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

The soils are considered intergrades between Epiaquults and

Aquerts. Vertic Epiaquults are of very small extent in the

United States. The subgroup is provided for use in other parts

of the world.

Fragiaquults

These are the Aquults that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface. Plinthite

does not form a continuous phase or constitute one-half or

more of the volume of any layer with an upper boundary within

150 cm of the mineral soil surface. Normally, the fragipan lies

below the argillic or kandic horizon. In a few of the soils,

however, it may be in the lower part of the argillic or kandic

horizon. The fragipan in some Fragiaquults is virtually

identical to the one in Alfisols, Inceptisols, and Spodosols. In

some Fragiaquults, however, there is one aberrant feature—a

small amount of plinthite. At this stage of knowledge, it is not

certain that the fragipan that has plinthite is the same as the

others. The behavior, however, is the same. For pragmatic

reasons, the pan that has plinthite currently is considered to be

a fragipan if its upper boundary is within 100 cm of the

mineral soil surface.

Definition

Fragiaquults are the Aquults that:

1. Have a fragipan with an upper boundary within 100 cm of

the mineral soil surface; and

2. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix of any subhorizon within

150 cm of the mineral soil surface.

Key to Subgroups

HABA. Fragiaquults that have 50 percent or more chroma of

3 or more in one or more horizons between either the A or Ap

horizon or a depth of 25 cm from the mineral soil surface,

whichever is deeper, and the fragipan.

Aeric Fragiaquults

HABB. Other Fragiaquults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Fragiaquults

HABC. Other Fragiaquults that have a mollic or umbric

epipedon.

Umbric Fragiaquults

HABD. Other Fragiaquults.

Typic Fragiaquults

Definition of Typic Fragiaquults

Typic Fragiaquults are the Fragiaquults that:

1. Do not have a mollic or umbric epipedon;

2. Have 50 percent or more chroma of 2 or less in all

horizons between the A or Ap horizon and the fragipan; and

3. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface.

Description of Subgroups

Typic Fragiaquults.—The central concept or Typic

subgroup of Fragiaquults is fixed on soils that have an ochric

epipedon and are gray and mottled in all horizons between the

bottom of the A or Ap horizon and the top of the fragipan.

These soils have little or no plinthite in the fragipan.

The presence of plinthite is considered abnormal and is used

to define the Plinthic subgroup. Chroma of 3 or more in some
732 Soil Taxonomy

subhorizon above the fragipan suggests somewhat better

drainage than that in Typic Fragiaquults and defines the Aeric

subgroup.

Typic Fragiaquults generally are nearly level or gently

sloping. They occur mostly in the Eastern United States and

are of very small extent. The natural vegetation consisted of

forest plants. The fragipan commonly is slowly permeable. As

a result, these soils are difficult to drain. Some of the soils are

used as cropland, but many are used as pasture or forest.

Aeric Fragiaquults.—These soils have dominant chroma of

3 or more in some horizon between the bottom of the A or Ap

horizon and the top of the fragipan. They generally are

somewhat better drained than soils of the Typic subgroup.

Aeric Fragiaquults range from nearly level to moderately

sloping. The natural vegetation consisted of forest plants.

These soils are of very small extent in the Eastern United

States. The fragipan commonly is slowly permeable. As a

result, the soils are difficult to drain. Some of the soils are used

as cropland, but many are used as pasture or forest.

Plinthic Fragiaquults.—These soils have plinthite that

constitutes between 5 and 50 percent of the matrix in the

fragipan. These soils are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Umbric Fragiaquults.—These soils have a mollic or

umbric epipedon. They are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Kandiaquults

Kandiaquults are the Aquults that have a kandic horizon and

a clay distribution in which the percentage of clay does not

decrease from its maximum amount by as much as 20 percent

within a depth of 150 cm from the mineral soil surface, or the

layer in which the clay percentage decreases has at least 5

percent of the volume consisting of clay depletions on faces of

peds and there is at least a 3 percent (absolute) increase in clay

content below this layer. These soils have an epipedon that

rests on a kandic horizon without an abrupt textural change if

the kandic horizon has moderately low or lower saturated

hydraulic conductivity. They do not have a fragipan or a

horizon in which plinthite either forms a continuous phase or

constitutes one-half or more of the volume within 150 cm of

the mineral soil surface. Kandiaquults are not known to occur

in the United States. The great group is provided for use in

other parts of the world.

Definition

Kandiaquults are the Aquults that:

1. Have a kandic horizon;

2. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface;

3. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases by more

than 20 percent has at least 5 percent of the volume consisting

of clay depletions on faces of peds and there is at least a 3

percent (absolute) increase in clay content below this layer;

4. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the mineral soil surface;

5. Do not have a fragipan that has its upper boundary

within 100 cm of the mineral soil surface; and

6. Do not have both an abrupt textural change between the

epipedon or the albic horizon and the kandic horizon and a

saturated hydraulic conductivity of 0.4 cm/hr or slower in the

kandic horizon.

Key to Subgroups

HADA. Kandiaquults that have an ECEC of 1.5 cmol(+)/kg

clay or less (sum of bases extracted with 1N NH4

OAc pH 7,

plus 1N KCl-extractable Al) in one or more horizons within

150 cm of the mineral soil surface.

Acraquoxic Kandiaquults

HADB. Other Kandiaquults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 to 100 cm; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthic Kandiaquults

HADC. Other Kandiaquults that:

1. Have a mollic or umbric epipedon; and

2. Have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface

to the top of a kandic horizon at a depth of 50 to 100 cm.

Arenic Umbric Kandiaquults

HADD. Other Kandiaquults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 50 to 100 cm.

Arenic Kandiaquults

HADE. Other Kandiaquults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 100 cm or more.

Grossarenic Kandiaquults
Ultisols 733

HADF. Other Kandiaquults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kandiaquults

HADG. Other Kandiaquults that have 50 percent or more

chroma of 3 or more in one or more horizons between either

the A or Ap horizon or a depth of 25 cm from the mineral soil

surface, whichever is deeper, and a depth of 75 cm.

Aeric Kandiaquults

HADH. Other Kandiaquults that have a mollic or umbric

epipedon.

Umbric Kandiaquults

HADI. Other Kandiaquults.

Typic Kandiaquults

Definition of Typic Kandiaquults

Typic Kandiaquults are the Kandiaquults that:

1. Do not have a subhorizon that has dominant chroma of 3

or more within 75 cm of the mineral soil surface;

2. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more;

3. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface;

4. Do not have a mollic or umbric epipedon; and

5. Have an ECEC (sum of bases plus 1N KCl-extractable Al)

of more than 1.5 cmol(+)/kg clay in all subhorizons to a depth

of 150 cm below the mineral soil surface.

Description of Subgroups

Typic Kandiaquults.—The central concept or Typic

subgroup of Kandiaquults is fixed on soils that (1) have

dominantly low chroma between the A or Ap horizon and a

depth of 75 cm or more from the mineral soil surface, (2) do

not have a mollic or umbric epipedon, (3) do not have a thick

epipedon with a sandy or sandy-skeletal particle-size class

throughout, (4) have less than 5 percent (by volume) plinthite

in all subhorizons within 150 cm of the mineral soil surface,

and (5) have an ECEC (sum of bases plus 1N KCl-extractable

Al) of more than 1.5 cmol(+)/kg clay in all subhorizons to a

depth of 150 cm below the mineral soil surface.

A chroma higher than that of Typic Kandiaquults is

characteristic of soils that are saturated for shorter periods and

serves to define intergrades to freely drained soils. Color

values, moist, of 2 or 3 in a plow layer indicate a higher-thannormal content of organic matter and form the basis for

defining intergrades to other great groups. A thick layer of

sand or loamy sand, starting at the mineral soil surface, is the

basis for defining the Arenic and Grossarenic subgroups.

Typic Kandiaquults are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Acraquoxic Kandiaquults.—These soils have an ECEC of

1.5 cmol(+)/kg clay or less (sum of bases extracted with 1N

NH4

OAc pH 7, plus 1N KCl-extractable Al) in one or more

horizons within 150 cm of the mineral soil surface. Recycling

of plant nutrients from decaying vegetation is critical for plant

growth on the soils. These soils are not known to occur in the

United States. The subgroup is provided for use in other parts

of the world.

Aeric Kandiaquults.—Below the A or Ap horizon, these

soils have chroma that is too high for the Typic subgroup, but

they are otherwise like Typic Kandiaquults in their defined

properties and in many other properties. Aeric Kandiaquults

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Arenic Kandiaquults.—These soils have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 50 to 100 cm below the mineral soil surface. These

soils are not known to occur in the United States.

Arenic Plinthic Kandiaquults.—These soils have a sandy

or sandy-skeletal particle-size class throughout a layer

extending from the mineral soil surface to the top of a kandic

horizon at a depth of 50 to 100 cm below the mineral soil

surface. They also have 5 percent or more (by volume) plinthite

in one or more horizons within 150 cm of the mineral soil

surface. These soils are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Arenic Umbric Kandiaquults.—These soils have a sandy

or sandy-skeletal particle-size class throughout a layer

extending from the mineral soil surface to the top of a kandic

horizon at a depth of 50 to 100 cm below the mineral soil

surface. They also have an umbric or mollic epipedon. These

soils are not known to occur in the United States. The subgroup

is provided for use in other parts of the world.

Grossarenic Kandiaquults.—These soils have a sandy or

sandy-skeletal particle-size class throughout a layer extending

from the mineral soil surface to the top of a kandic horizon at a

depth of 100 cm or more below the mineral soil surface. They

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Plinthic Kandiaquults.—These soils have 5 percent or

more (by volume) plinthite in one or more horizons within 150

cm of the mineral soil surface. They are not known to occur in

the United States. The subgroup is provided for use in other

parts of the world.

Umbric Kandiaquults.—These soils are like Typic

Kandiaquults, but they have an umbric or mollic epipedon.
734 Soil Taxonomy

They are not known to occur in the United States. The

subgroup is provided for use in other parts of the world.

Kanhaplaquults

Kanhaplaquults are the Aquults that have a kandic horizon

and a clay distribution in which the percentage of clay

decreases from its maximum amount by as much as 20 percent

within a depth of 150 cm from the mineral soil surface, and the

layer in which the clay percentage decreases has less than 5

percent of the volume consisting of clay depletions on faces of

peds or there is an increase in clay content of less than 3

percent (absolute) below this layer. These soils have an

epipedon that rests on a kandic horizon without an abrupt

textural change if the kandic horizon has moderately low or

lower saturated hydraulic conductivity. They do not have a

fragipan or a horizon in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume

within 150 cm of the mineral soil surface. Kanhaplaquults are

not known to occur in the United States. The great group is

provided for use in other parts of the world.

Definition

Kanhaplaquults are the Aquults that:

1. Have a kandic horizon;

2. Have a clay distribution in which the percentage of clay

decreases from its maximum amount by 20 percent or more

within a depth of 150 cm from the mineral soil surface, and the

layer in which the percentage of clay is less than the maximum

has less than 5 percent of the volume consisting of clay

depletions on faces of peds or there is an increase in clay

content of less than 3 percent (absolute) below this layer;

3. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the mineral soil surface;

4. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface; and

5. Do not have both an abrupt textural change between the

epipedon or the albic horizon and the kandic horizon and

saturated hydraulic conductivity of 0.4 cm/hr or slower in the

kandic horizon.

Key to Subgroups

HAEA. Kanhaplaquults that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, one or more of the following:

1. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

2. More than 35 percent (by volume) fragments coarser than

2.0 mm, of which more than 66 percent is cinders, pumice, and

pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Kanhaplaquults

HAEB. Other Kanhaplaquults that have 5 percent or more

(by volume) plinthite in one or more horizons within 150 cm of

the mineral soil surface.

Plinthic Kanhaplaquults

HAEC. Other Kanhaplaquults that:

1. Have a mollic or umbric epipedon; and

2. Have 50 percent or more chroma of 3 or more in one or

more horizons between either the A or Ap horizon or a

depth of 25 cm from the mineral soil surface, whichever is

deeper, and a depth of 75 cm.

Aeric Umbric Kanhaplaquults

HAED. Other Kanhaplaquults that have 50 percent or more

chroma of 3 or more in one or more horizons between either

the A or Ap horizon or a depth of 25 cm from the mineral soil

surface, whichever is deeper, and a depth of 75 cm.

Aeric Kanhaplaquults

HAEE. Other Kanhaplaquults that have a mollic or umbric

epipedon.

Umbric Kanhaplaquults

HAEF. Other Kanhaplaquults.

Typic Kanhaplaquults

Definition of Typic Kanhaplaquults

Typic Kanhaplaquults are the Kanhaplaquults that:

1. Do not have a mollic or umbric epipedon;

2. Do not have a subhorizon that has dominant chroma of 3

or more within 75 cm of the mineral soil surface;

3. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface; and

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0
Ultisols 735

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Description of Subgroups

Typic Kanhaplaquults.—The central concept or Typic

subgroup of Kanhaplaquults is fixed on soils that (1) have

dominantly low chroma between the A or Ap horizon and a

depth of 75 cm or more from the mineral soil surface, (2) do

not have a mollic or umbric epipedon, (3) have less than 5

percent (by volume) plinthite in all subhorizons within 150 cm

of the mineral soil surface, and (4) do not have a surface

mantle or layer in the upper 75 cm that has both a low bulk

density and a high content of weakly crystalline minerals or

that consists of slightly or moderately weathered pyroclastic

materials.

A chroma higher than that of Typic Kanhaplaquults is

characteristic of soils that are saturated for shorter periods and

serves to define intergrades to freely drained soils. A mollic or

umbric epipedon is the basis for defining the Umbric subgroup.

Typic Kanhaplaquults are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Aeric Kanhaplaquults.—Below the A or Ap horizon, these

soils have chroma that is too high for the Typic subgroup, but

they are otherwise like Typic Kanhaplaquults in their defined

properties and in many other properties. Aeric Kanhaplaquults

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Aeric Umbric Kanhaplaquults.—These soils have an

umbric or mollic epipedon. Below the A or Ap horizon, they

have chroma that is too high for the Typic subgroup. They are

otherwise like Typic Kanhaplaquults in their defined properties

and in many other properties. Aeric Umbric Kanhaplaquults

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Aquandic Kanhaplaquults.—These soils are influenced by

volcanic ejecta. When weathered, they have high P-retention,

low bulk density, and high porosity. They are not known to

occur in the United States.

Plinthic Kanhaplaquults.—These soils have 5 to 50

percent (by volume) plinthite in one or more horizons within

150 cm of the mineral soil surface. They are not known to occur

in the United States. The subgroup is provided for use in other

parts of the world.

Umbric Kanhaplaquults.—These soils have an umbric or

mollic epipedon. They are otherwise like Typic Kanhaplaquults

in their defined properties and in most other properties. These

soils are not known to occur in the United States. The subgroup

is provided for use in other parts of the world.

Paleaquults

These are the Aquults that have a clay distribution in which

the percentage of clay does not decrease from its maximum

amount by as much as 20 percent within a depth of 150 cm

from the mineral soil surface, or the layer in which the clay

percentage decreases has at least 5 percent of the volume

consisting of clay depletions on faces of peds and there is at

least a 3 percent increase in clay content below this layer.

These soils have an epipedon that rests on an argillic horizon

without an abrupt textural change if the argillic horizon has

moderately low or lower saturated hydraulic conductivity. They

do not have a fragipan or a horizon in which plinthite either

forms a continuous phase or constitutes one-half or more of the

volume within 150 cm of the mineral soil surface.

Paleaquults formed mostly on mid-Pleistocene or older land

surfaces, on high marine or river terraces or old deltas. They

are of large extent in the Southeastern United States. The

natural vegetation consisted of forest plants, mostly watertolerant conifers or hardwood trees.

Definition

Paleaquults are the Aquults that:

1. Have a clay distribution in which the percentage of clay

does not decrease from its maximum by as much as 20 percent

within a depth of 150 cm from the mineral soil surface, or the

layer in which the clay percentage decreases by more than 20

percent has at least 5 percent of the volume consisting of clay

depletions on faces of peds and there is at least a 3 percent

(absolute) increase in clay content below this layer;

2. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface;

3. Do not have a kandic horizon;

4. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

5. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix in any subhorizon within

150 cm of the mineral soil surface; and

6. Do not have both an abrupt textural change between the

epipedon or the albic horizon and the argillic horizon and

saturated hydraulic conductivity of 0.4 cm/hr or slower in the

argillic horizon.
736 Soil Taxonomy

Key to Subgroups

HAFA. Paleaquults that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Paleaquults

HAFB. Other Paleaquults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 to 100 cm; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthic Paleaquults

HAFC. Other Paleaquults that:

1. Have a mollic or umbric epipedon; and

2. Have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface

to the top of an argillic horizon at a depth of 50 to 100 cm.

Arenic Umbric Paleaquults

HAFD. Other Paleaquults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm.

Arenic Paleaquults

HAFE. Other Paleaquults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more.

Grossarenic Paleaquults

HAFF. Other Paleaquults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Paleaquults

HAFG. Other Paleaquults that have 50 percent or more

chroma of 3 or more in one or more horizons between either

the A or Ap horizon or a depth of 25 cm from the mineral soil

surface, whichever is deeper, and a depth of 75 cm.

Aeric Paleaquults

HAFH. Other Paleaquults that have a mollic or umbric

epipedon.

Umbric Paleaquults

HAFI. Other Paleaquults.

Typic Paleaquults

Definition of Typic Paleaquults

Typic Paleaquults are the Paleaquults that:

1. Do not have, between either the bottom of the A or Ap

horizon or a depth of 25 cm from the mineral soil surface,

whichever is deeper, and a depth of 75 cm from the mineral

soil surface, a horizon that has dominant chroma of 3 or more;

2. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more;

3. Have less than 5 percent (by volume) plinthite in all

horizons within 150 cm of the mineral soil surface;

4. Do not have a mollic or umbric epipedon; and

5. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Description of Subgroups

Typic Paleaquults.—The central concept or Typic subgroup

of Paleaquults is fixed on soils that have grayish colors in the

matrix below the A or Ap horizon, do not have plinthite, have

a texture finer than loamy fine sand within 50 cm of the

mineral soil surface, and have an ochric epipedon.

Chroma in some subhorizon too high for Typic Paleaquults

is a characteristic used to define the Aeric subgroup, an

intergrade to Paleudults. A thick sandy layer, starting at the

mineral soil surface, defines Arenic and Grossarenic

subgroups. A small amount of plinthite suggests intergrades to

Plinthaquults. An umbric or mollic epipedon is used to define

the Umbric subgroup.

Typic Paleaquults generally are nearly level. They occur

mostly on the coastal plain of the Southeastern United States

and are of moderate extent. The natural vegetation consisted of

forest plants. Most of these soils are used as forest, but some

have been cleared and are used as cropland or pasture.

Aeric Paleaquults.—These soils have a subhorizon,

generally near the surface, that has chroma of 3 or more and
Ultisols 737

normally have a seasonal high water table that is deeper than

that in Typic Paleaquults or has more oxygen. Aeric

Paleaquults commonly are nearly level or gently sloping. The

natural vegetation consisted of forest plants. These soils occur

mostly on the coastal plain of the Southeastern United States

and are of moderate extent. Many of the soils have been cleared

and are used as cropland, but some are used as pasture or

forest.

Arenic Paleaquults.—These soils have a sandy layer,

starting at the mineral soil surface, that is between 50 and 100

cm thick and are permitted to have brownish colors in the

matrix below the A or Ap horizon, but they are otherwise like

Typic Paleaquults in defined properties. Most Arenic

Paleaquults developed in somewhat sandier materials and have

less clay in the argillic horizon than the soils in the Typic

subgroup. The natural vegetation consisted of forest plants.

The Arenic Paleaquults in the United States are mainly on the

coastal plains in Georgia, Alabama, and Florida. They are

moderately extensive. Most of these soils are used as forest, but

some have been cleared and are used as cropland or pasture.

Arenic Plinthic Paleaquults.—These soils have a sandy

layer, starting at the mineral soil surface, that is between 50

and 100 cm thick and have 5 to 50 percent plinthite at a depth

of less than 150 cm. The horizons that have plinthite are

mostly firm and less permeable than the overlying horizons.

The Arenic Plinthic Paleaquults in the United States are mostly

in Florida and Georgia. They are of small extent. Most of these

soils are used as forest, but some have been cleared and are

used as cropland or pasture.

Arenic Umbric Paleaquults.—These soils have an umbric

or mollic epipedon, and their particle-size class is sandy or

sandy-skeletal to a depth between 50 and 100 cm, although the

epipedon is not necessarily that thick. These soils formed in

somewhat sandier parent materials and in some areas are

wetter than Typic Paleaquults. Arenic Umbric Paleaquults are

of very small extent in the Southeastern United States. Most of

these soils are used as forest, but some have been cleared and

are used as cropland or pasture.

Grossarenic Paleaquults.—These soils have a sandy layer,

starting at the mineral soil surface, that is between 100 and 200

cm thick in the major part of the pedon and are permitted to

have brownish colors in the matrix below the A or Ap horizon,

but they are otherwise similar to Typic Paleaquults in defined

properties. The parent materials commonly are more sandy

than those of the soils in the Typic subgroup. Grossarenic

Paleaquults are of small extent in the Southeastern United

States. Most of these soils are used as forest, but some have

been cleared and are used as cropland or pasture.

Plinthic Paleaquults.—These soils have 5 to 50 percent (by

volume) plinthite in some horizon within 150 cm of the

mineral soil surface. They are of small extent in the Southern

United States. These soils are used as forest or have been

cleared and are used as cropland or pasture.

Umbric Paleaquults.—These soils have an umbric or

mollic epipedon but are otherwise like Typic Paleaquults in

defined properties. Many Umbric Paleaquults are the wettest of

the Paleaquults and are ponded in winter. Umbric Paleaquults are

of small extent in the Southeastern United States. Most of these

soils are used as forest, but some have been cleared and are

used as cropland or pasture.

Vertic Paleaquults.—These soils are high in expanding clays

and have cracks 5 mm or more wide, slickensides, wedge-shaped

aggregates, or a linear extensibility of 6.0 cm or more between

the mineral soil surface and either a depth of 100 cm or a densic,

lithic, or paralithic contact, whichever is shallower. These soils

are intergrades between Paleaquults and Aquerts. They are not

known to occur in the United States. The subgroup is provided

for use in other parts of the world.

Plinthaquults

These are the Aquults that have plinthite that either forms a

continuous phase or constitutes more than half the matrix of

some subhorizon within 125 cm of the mineral soil surface.

These soils are mostly in intertropical areas. They make up a

small area in Puerto Rico.

Definition

Plinthaquults are the Aquults that have plinthite that forms

a continuous phase or constitutes more than half the matrix of

some subhorizon within 125 cm of the mineral soil surface.

Key to Subgroups

HAAA. Plinthaquults that have a kandic horizon or a CEC

(by 1N NH4OAc pH 7) of less than 24 cmol(+)/kg clay in 50

percent or more (by volume) of the argillic horizon if less than

100 cm thick or of its upper 100 cm.

Kandic Plinthaquults

HAAB. Other Plinthaquults.

Typic Plinthaquults

Definition of Typic Plinthaquults

Typic Plinthaquults are the Plinthaquults that have a CEC

of 24 cmol(+) or more per kg clay (by 1N NH4OAc pH 7) in the

major part of the argillic horizon or the major part of the upper

100 cm of the argillic horizon if it is thicker than 100 cm.

Description of Subgroups

Typic Plinthaquults.—Typic Plinthaquults are the

Plinthaquults that have a CEC of 24 cmol(+) or more per kg

clay (by 1N NH4OAc pH 7) in 50 percent or more of the

argillic horizon or of the upper 100 cm of the argillic horizon if

it is thicker than 100 cm. These soils are not known to occur in

the United States. The subgroup is provided for use in other

parts of the world.

Kandic Plinthaquults.—These are the Plinthaquults that

have a kandic horizon or have a CEC of less than 24 cmol(+)
738 Soil Taxonomy

per kg clay (by 1N NH4

OAc pH 7) in 50 percent or more of the

argillic horizon or of the upper 100 cm of the argillic horizon if it

is thicker than 100 cm. These soils are of very small extent. They

are known to occur only in Puerto Rico.

Umbraquults

These are the Aquults that commonly have an umbric

epipedon. These soils do not have a horizon within 150 cm of

the mineral soil surface in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume.

They do not have a fragipan with an upper boundary within

100 cm of the mineral soil surface or a kandic horizon. They

do not have both an abrupt textural change between an albic

horizon and the argillic horizon and low or very low saturated

hydraulic conductivity in the argillic horizon. They have,

within 150 cm of the mineral soil surface, either a densic,

lithic, paralithic, or petroferric contact, or they have, with

increasing depth, a clay decrease of 20 percent or more

(relative) from the maximum clay content and less than 5

percent (by volume) skeletans on faces of peds in the layer that

has the 20 percent lower clay content or, below that layer, no

clay increase of 3 percent or more (absolute) in the fine-earth

fraction.

Umbraquults are among the wettest of the Aquults, and

their argillic horizon is not so strongly developed as that in

most of the other Aquults. The natural vegetation consisted

mostly of water-tolerant trees and herbs.

Definition

Umbraquults are the Aquults that:

1. Have an umbric or mollic epipedon;

2. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

3. Do not have plinthite that forms a continuous phase or

constitutes more than half of the matrix of any subhorizon

within 150 cm of the mineral soil surface;

4. Have a clay distribution in which the percentage of clay

decreases from its maximum by 20 percent or more within a

depth of 150 cm below the mineral soil surface, and the layer

in which the percentage of clay is less than the maximum has

less than 5 percent of the volume consisting of clay depletions

on faces of peds or there is an increase in clay content of less

than 3 percent (absolute) below this layer;

5. Do not have an abrupt textural change at the upper

boundary of the argillic horizon if the hydraulic conductivity of

that horizon is 0.4 cm/hr or slower; and

6. Do not have a kandic horizon.

Key to Subgroups

HAGA. Umbraquults that have 5 to 50 percent (by volume)

plinthite in one or more horizons within 150 cm of the mineral

soil surface.

Plinthic Umbraquults

HAGB. Other Umbraquults.

Typic Umbraquults

Definition of Typic Umbraquults

Typic Umbraquults are the Umbraquults that have less than

5 percent (by volume) plinthite in all subhorizons within 150

cm of the mineral soil surface.

Description of Subgroups

Typic Umbraquults.—These soils are the Umbraquults that

do not have plinthite that constitutes 5 percent or more of the

matrix of any subhorizon within 150 cm of the soil surface.

They are moderately extensive on the low coastal plains along

the Atlantic Ocean. Some of the soils have been drained and

cleared and are used as cropland or pasture, but many are used

as forest.

Plinthic Umbraquults.—These soils have plinthite that

constitutes 5 percent or more of the matrix of a horizon within

150 cm of the soil surface. This subgroup is not known to occur

in the United States. It is provided for use in other parts of the

world.

Humults

Humults are the more or less freely drained, humus-rich

Ultisols of mid or low latitudes. At mid latitudes they are

mostly dark colored, but at low latitudes the content of humus

is not necessarily reflected by the color. These soils are mainly

in mountainous areas that have high rainfall but also have a

moisture deficit during some season. Most of the Humults in

the United States formed in a basic country rock on surfaces

that are late Pleistocene or older. Slopes commonly are strong.

If the soils are cultivated, the argillic or kandic horizon may be

at the surface. To keep the eroded and uneroded soils together

in the classification, the definition of the suborder is written in

terms of the carbon content of the whole soil or of the argillic

or kandic horizon. The natural vegetation consisted mostly of

coniferous forest plants at mid latitudes and rain forest plants

at low latitudes.

Definition

Humults are the Ultisols that do not have both aquic

conditions and the colors defined for Aquults and that meet

either or both of the following:
Ultisols 739

1. Have 0.9 percent or more organic carbon in the upper 15 cm

of the argillic or kandic horizon; or

2. Have 12 kg or more organic carbon in a unit volume

of 1 m2

 to a depth of 100 cm, exclusive of any O horizon.

Key to Great Groups

HBA. Humults that have a sombric horizon within 100 cm of

the mineral soil surface.

Sombrihumults, p. 747

HBB. Other Humults that have one or more horizons within

150 cm of the mineral soil surface in which plinthite either

forms a continuous phase or constitutes one-half or more of the

volume.

Plinthohumults, p. 747

HBC. Other Humults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Have a kandic horizon; and

3. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) clay depletions

on faces of peds in the layer that has a 20 percent lower

clay content and, below that layer, a clay increase of 3

percent or more (absolute) in the fine-earth fraction.

Kandihumults, p. 741

HBD. Other Humults that have a kandic horizon.

Kanhaplohumults, p. 743

HBE. Other Humults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) clay depletions

on faces of peds in the layer that has a 20 percent lower

clay content and, below that layer, a clay increase of 3

percent or more (absolute) in the fine-earth fraction.

Palehumults, p. 745

HBF. Other Humults.

Haplohumults, p. 739

Haplohumults

These are the Humults that have an argillic horizon and

have one of the following: (1) a densic, lithic, paralithic, or

petroferric contact within 150 cm of the mineral soil surface or

(2) with increasing depth, a clay decrease of 20 percent or

more (relative) from the maximum clay content and less than 5

percent (by volume) clay depletions on faces of peds in any

layer that has a 20 percent lower clay content or, below that

layer, the fine-earth fraction has a clay increase of less than 3

percent. Many of these soils have a thin argillic horizon. The

Haplohumults in the United States are mainly in mountains

close to the Pacific Ocean and have gentle to very steep slopes.

Most of the soils had and still have a coniferous forest

vegetation. Their content of organic carbon, in kilograms per

hectare, commonly is high relative to that of most other kinds

of soil. Some of the soils have an umbric epipedon, but many

have a color value and chroma higher than the value and

chroma of mollic or umbric epipedons.

Definition

Haplohumults are the Humults that:

1. Do not have a fragipan or kandic horizon;

2. Have a clay distribution in which, with increasing depth,

the percentage of clay decreases from its maximum amount

by more than 20 percent within 150 cm of the mineral soil

surface, and the layer in which the percentage of clay is less

than the maximum has less than 5 percent of the volume

consisting of skeletans on faces of peds or there is an increase

in clay content of less than 3 percent (absolute) below this

layer;

3. Do not have a sombric horizon within 100 cm of the mineral

soil surface; and

4. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the mineral soil surface.

Key to Subgroups

HBFA. Haplohumults that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Haplohumults

HBFB. Other Haplohumults that have both:

1. In one or more subhorizons within the upper 25 cm of

the argillic horizon, redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less, accompanied by

redox concentrations, and also aquic conditions for some

time in normal years (or artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface, a

fine-earth fraction with both a bulk density of 1.0 g/cm3

 or
740 Soil Taxonomy

less, measured at 33 kPa water retention, and Al plus 1

/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0.

Aquandic Haplohumults

HBFC. Other Haplohumults that have, in one or more

subhorizons within the upper 25 cm of the argillic horizon,

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less, accompanied by redox concentrations and

by aquic conditions for some time in normal years (or artificial

drainage).

Aquic Haplohumults

HBFD. Other Haplohumults that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Haplohumults

HBFE. Other Haplohumults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Haplohumults

HBFF. Other Haplohumults that in normal years are

saturated with water in one or more layers within 100 cm of

the mineral soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplohumults

HBFG. Other Haplohumults that have an ustic moisture

regime.

Ustic Haplohumults

HBFH. Other Haplohumults that have a xeric moisture

regime.

Xeric Haplohumults

HBFI. Other Haplohumults.

Typic Haplohumults

Definition of Typic Haplohumults

Typic Haplohumults are the Haplohumults that:

1. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

2. Have a udic moisture regime;

3. In normal years are not saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

4. Do not have a lithic contact within 50 cm of the mineral soil

surface; and

5. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface.

Description of Subgroups

Typic Haplohumults.—The central concept or Typic

subgroup of Haplohumults is fixed on relatively freely drained

soils that have a udic moisture regime.

Both the precipitation and the humidity are high. Redox

depletions with low chroma and a fluctuating level of ground

water are properties shared with Aquults and define the Aquic

subgroup. An appreciable amount of plinthite is considered

abnormal and is used to define the Plinthic subgroup. Ustic and

xeric moisture regimes are considered abnormal but are highly

significant to soil-plant relationships and define the Ustic and

Xeric subgroups, respectively. A shallow lithic contact is the

basis for definition of the Lithic subgroup. Soils that have a

thin mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals

are excluded because they are considered to be intergrades to

Andisols.

Typic Haplohumults are gently sloping to very steep. They

are moderately extensive in the Western United States. They

are mostly in western Oregon, Puerto Rico, California, and

Hawaii. Most of the soils are used as forest. Where slopes are

suitable, some of the soils have been cleared and are used as

cropland or pasture.

Andic Haplohumults.—These soils have a surface mantle

that has a low bulk density and a high content of weakly

crystalline minerals in at least some part of the upper 75 cm.

The soils are rare in the United States and occur only in the

western part of the State of Washington. The natural vegetation

consisted of coniferous forest plants. Slopes range from gentle

to very steep. These soils are used as forest.

Aquandic Haplohumults.—These soils have a surface

mantle that has a low bulk density and a high content of

weakly crystalline minerals in at least some part of the upper

75 cm. They have redox depletions with low chroma, and the

level of ground water fluctuates in the horizons with

redoximorphic depletions or the soils are artificially drained.

These soils occur in the Pacific Northwest.

Aquic Haplohumults.—These soils have redox depletions

with low chroma, and the level of ground water fluctuates in

the horizons with redoximorphic depletions or the soils are

artificially drained. These soils developed in sediments derived

largely from basic rocks. They are of small extent, mostly in
Ultisols 741

Oregon, in the United States. The natural vegetation consisted

of coniferous forest plants. Slopes generally are nearly level or

gently sloping. Many of the soils have been cleared and are

used as hayland, pasture, or cropland.

Lithic Haplohumults.—These soils have a shallow lithic

contact and an argillic horizon that commonly is thin. They are

not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Oxyaquic Haplohumults.—These soils are saturated with

water for 20 consecutive days and/or 30 cumulative days within

100 cm of the mineral soil surface during normal years. They

may or may not have redoximorphic features. If they occur, the

redoximorphic features are either weakly expressed or lower in

the profile than is defined for the Aquic subgroup. Oxyaquic

Haplohumults occur in Oregon and are used for timber

production or pasture.

Plinthic Haplohumults.—These soils have a subhorizon

with 5 to 50 percent (by volume) plinthite within 150 cm of the

mineral soil surface. They are rare in the United States and are

known to occur only on marine terraces along the northern

California coast. The natural vegetation consisted of coniferous

forest plants. Slopes generally are nearly level to moderately

steep. Most of these soils are used as forest, but some are used

as sites for homes.

Ustic Haplohumults.—These soils have an ustic soil

moisture regime. They occur in Hawaii and along the coast of

California, where the soil temperature regime is isomesic,

isothermic, or isohyperthermic. The natural vegetation

consisted of forest plants. Slopes generally are nearly level to

moderately steep. Most of these soils are used as pasture, but

some are used as cropland or homesites.

Xeric Haplohumults.—These soils have a xeric moisture

regime but are otherwise like Typic Haplohumults in defined

properties. Most Xeric Haplohumults have an ochric epipedon

despite the high content of organic carbon. The color of the

epipedon is dark, but the chroma is too high for an umbric

epipedon. Xeric Haplohumults are moderately extensive and

occur mostly in California and Oregon. In the United States,

slopes are nearly level to very steep. Most of these soils are

used as forest, but some are used as cropland, pasture, or

homesites.

Kandihumults

Kandihumults are the Humults that have a kandic horizon and

a clay distribution in which the percentage of clay does not

decrease from its maximum amount by as much as 20 percent

within a depth of 150 cm from the mineral soil surface, or the

layer in which the clay percentage decreases has at least 5

percent of the volume consisting of skeletans on faces of peds

and there is at least a 3 percent (absolute) increase in clay

content below this layer. These soils do not have a sombric

horizon. They have no horizon in which plinthite either forms

a continuous phase or constitutes one-half or more of the

volume within 150 cm of the mineral soil surface. Kandihumults

are of small extent in California and Hawaii.

Definition

Kandihumults are the Humults that:

1. Have a kandic horizon;

2. Do not have a densic, lithic, paralithic, or petroferric contact

within 150 cm of the mineral soil surface;

3. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases by more

than 20 percent has at least 5 percent of the volume consisting

of clay depletions on faces of peds and there is at least a 3

percent (absolute) increase in clay content below this layer;

4. Do not have a sombric horizon within 150 cm of the

mineral soil surface; and

5. Do not have plinthite that forms a continuous phase or that

constitutes more than 50 percent of the volume of some

subhorizon within 150 cm of the mineral soil surface.

Key to Subgroups

HBCA. Kandihumults that meet all of the following:

1. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

have a fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; and

2. In one or more horizons within 75 cm of the mineral

soil surface, have redox concentrations, a color value, moist,

of 4 or more, and hue that is 10YR or yellower and becomes

redder with increasing depth within 100 cm of the mineral

soil surface; and

3. In normal years are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Andic Ombroaquic Kandihumults

HBCB. Other Kandihumults that have both:

1. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface, a

fine-earth fraction with both a bulk density of 1.0 g/cm3 or

less, measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0;

and
742 Soil Taxonomy

2. An ustic moisture regime.

Ustandic Kandihumults

HBCC. Other Kandihumults that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3

 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Kandihumults

HBCD. Other Kandihumults that have, in one or more

subhorizons within the upper 25 cm of the kandic horizon,

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less, accompanied by redox concentrations and

by aquic conditions for some time in normal years (or artificial

drainage).

Aquic Kandihumults

HBCE. Other Kandihumults that:

1. Have, in one or more horizons within 75 cm of the

mineral soil surface, redox concentrations, a color value,

moist, of 4 or more, and hue that is 10YR or yellower and

becomes redder with increasing depth within 100 cm of the

mineral soil surface; and

2. In normal years are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Ombroaquic Kandihumults

HBCF. Other Kandihumults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kandihumults

HBCG. Other Kandihumults that have an ustic moisture

regime.

Ustic Kandihumults

HBCH. Other Kandihumults that have a xeric moisture

regime.

Xeric Kandihumults

HBCI. Other Kandihumults that have an anthropic epipedon.

Anthropic Kandihumults

HBCJ. Other Kandihumults.

Typic Kandihumults

Definition of Typic Kandihumults

Typic Kandihumults are the Kandihumults that:

1. Do not have, in any subhorizon within the upper 25 cm of

the kandic horizon, redox depletions with a color value, moist,

of 4 or more and chroma of 2 or less, accompanied by redox

concentrations and by aquic conditions;

2. Have a udic moisture regime;

3. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

4. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface;

5. Do not have, in one or more horizons within 75 cm of the

mineral soil surface, redox concentrations, a color value, moist,

of 4 or more, and hue that is 10YR or yellower and becomes

redder with increasing depth within 100 cm of the mineral soil

surface; and

6. Do not have an anthropic epipedon.

Description of Subgroups

Typic Kandihumults.—The central concept or Typic

subgroup of Kandihumults is fixed on freely drained soils that

do not have an anthropic epipedon and have a udic moisture

regime. These soils also have less than 5 percent plinthite in all

horizons to a depth of 150 cm or more below the mineral soil

surface. Soils that have redox depletions with low chroma near

the surface in one or more horizons that also have aquic

conditions for some time in normal years (or artificial

drainage) are excluded from Typic Kandihumults because these

properties are shared with Aquults.

Soils that have a mantle or layer in the upper 75 cm that has

both a low bulk density and a high content of weakly

crystalline minerals are excluded from the Typic subgroup

because they are considered to be intergrades to Andisols. A

soil moisture regime that is ustic or xeric is considered

abnormal and defines the Ustic and Xeric subgroups,

respectively.

Typic Kandihumults are of small extent in the United States

and are known to occur only in California. The natural

vegetation consisted of coniferous forest plants. Slopes range

from gentle to steep. These soils are used mostly as forest.

Where slopes are suitable, some of the soils have been cleared

and are used as cropland or pasture.

Andic Kandihumults.—These soils have a mantle or layer

in the upper 75 cm that has both a low bulk density and a high
Ultisols 743

content of weakly crystalline minerals. They are not known to

occur in the United States. They are defined for use in other

parts of the world.

Andic Ombroaquic Kandihumults.—These soils have, in

one or more horizons within 75 cm of the mineral soil surface,

redox concentrations, a color value, moist, of 4 or more, and

hue that is 10YR or yellower and becomes redder with

increasing depth within 100 cm of the mineral soil surface.

They also have a mantle or layer in the upper 75 cm that has

both a low bulk density and a high content of weakly

crystalline minerals. These soils are not known to occur in the

United States. They are defined for use in other parts of the

world.

Anthropic Kandihumults.—These soils are similar to

Typic Kandihumults, but they have been used as cropland for

long periods and have an anthropic epipedon. They are not

known to occur in the United States. They are defined for use

in other parts of the world.

Aquic Kandihumults.—These soils are like Typic

Kandihumults, but they have redox depletions with low

chroma within 75 cm of the mineral soil surface. The redox

depletions are caused by periods of wetness. The soils are in

nearly level to sloping areas. They are not known to occur in

the United States. They are defined for use in other parts of

the world.

Ombroaquic Kandihumults.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

concentrations, a color value, moist, of 4 or more, and hue that

is 10YR or yellower and becomes redder with increasing depth

within 100 cm of the mineral soil surface. The soils are not

known to occur in the United States. They are defined for use

in other parts of the world.

Plinthic Kandihumults.—These soils are similar to Typic

Kandihumults, but they have 5 to 50 percent (by volume)

plinthite in one or more horizons within 150 cm of the

mineral soil surface. The soils are not known to occur in the

United States. They are defined for use in other parts of the

world.

Ustandic Kandihumults.—These soils have an ustic

moisture regime and a mantle or layer in the upper 75 cm

that has both a low bulk density and a high content of weakly

crystalline minerals. They are not known to occur in the

United States. They are defined for use in other parts of the

world.

Ustic Kandihumults.—These soils are like Typic

Kandihumults, but they have an ustic moisture regime. They

are intergrades between Kandihumults and Kandiustults. Ustic

Kandihumults are not known to occur in the United States.

They are defined for use in other parts of the world.

Xeric Kandihumults.—These soils are like Typic

Kandihumults, but they have a xeric moisture regime. They are

intergrades between Kandihumults and Xerults. Xeric

Kandihumults are not known to occur in the United States.

They are defined for use in other parts of the world.

Kanhaplohumults

Kanhaplohumults are the Humults that have a kandic horizon

and have a clay distribution in which the percentage of clay

decreases from its maximum amount by as much as 20 percent

within a depth of 150 cm from the mineral soil surface, and the

layer in which the clay percentage decreases has less than 5

percent of the volume consisting of skeletans on faces of peds

or there is an increase in clay content of less than 3 percent

(absolute) below this layer. These soils do not have a sombric

horizon within 100 cm of the mineral soil surface. They have no

horizon in which plinthite either forms a continuous phase or

constitutes one-half or more of the volume within 150 cm of the

mineral soil surface. Kanhaplohumults are of very small extent

and are known to occur only in California and Hawaii in the

United States.

Definition

Kanhaplohumults are the Humults that:

1. Have a kandic horizon;

2. Have a clay distribution in which the percentage of clay

decreases from its maximum amount by 20 percent or more

within a depth of 150 cm from the mineral soil surface, and the

layer in which the percentage of clay is less than the maximum

has less than 5 percent of the volume consisting of skeletans on

faces of peds or there is an increase in clay content of less than

3 percent (absolute) below this layer;

3. Do not have a sombric horizon within 150 cm of the

mineral soil surface; and

4. Do not have plinthite that forms a continuous phase or that

constitutes more than 50 percent of the volume of some

subhorizon within 150 cm of the mineral soil surface.

Key to Subgroups

HBDA. Kanhaplohumults that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Kanhaplohumults

HBDB. Other Kanhaplohumults that have both:

1. An ustic moisture regime; and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface, a

fine-earth fraction with both a bulk density of 1.0 g/cm3 or

less, measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0.

Ustandic Kanhaplohumults

HBDC. Other Kanhaplohumults that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa
744 Soil Taxonomy

water retention, and Al plus 1

/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Kanhaplohumults

HBDD. Other Kanhaplohumults that have, in one or more

subhorizons within the upper 25 cm of the kandic horizon,

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less, accompanied by redox concentrations and

by aquic conditions for some time in normal years (or artificial

drainage).

Aquic Kanhaplohumults

HBDE. Other Kanhaplohumults that:

1. Have, in one or more horizons within 75 cm of the

mineral soil surface, redox concentrations, a color value,

moist, of 4 or more, and hue that is 10YR or yellower and

becomes redder with increasing depth within 100 cm of the

mineral soil surface; and

2. In normal years are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Ombroaquic Kanhaplohumults

HBDF. Other Kanhaplohumults that have an ustic moisture

regime.

Ustic Kanhaplohumults

HBDG. Other Kanhaplohumults that have a xeric moisture

regime.

Xeric Kanhaplohumults

HBDH. Other Kanhaplohumults that have an anthropic

epipedon.

Anthropic Kanhaplohumults

HBDI. Other Kanhaplohumults.

Typic Kanhaplohumults

Definition of Typic Kanhaplohumults

Typic Kanhaplohumults are the Kanhaplohumults that:

1. Do not have, in any subhorizon within the upper 25 cm of

the argillic or kandic horizon, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations and by aquic conditions;

2. Do not have a lithic contact within 50 cm of the mineral

soil surface;

3. Have a udic moisture regime;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

5. Have, within 75 cm of the mineral soil surface, hue

of 7.5YR or redder in all horizons with a color value, moist,

of 4 or more if there are redox concentrations or if the hue

becomes redder with increasing depth within 100 cm of the

mineral soil surface; and

6. Do not have an anthropic epipedon.

Description of Subgroups

Typic Kanhaplohumults.—The central concept or Typic

subgroup of Kanhaplohumults is fixed on moderately deep or

deeper, freely drained soils that do not have an anthropic

epipedon and that have a udic moisture regime. Soils that have

redox depletions with low chroma near the surface in one or

more horizons that also have aquic conditions for some time in

normal years (or artificial drainage) are excluded from the

Typic subgroup because these properties are shared with

Aquults.

Soils that have a mantle or layer in the upper 75 cm that has

both a low bulk density and a high content of weakly

crystalline minerals are excluded from the Typic subgroup

because they are considered to be intergrades to Andisols. A

soil moisture regime that is ustic or xeric is considered

abnormal and defines the Ustic and Xeric subgroups,

respectively.

Typic Kanhaplohumults are of very small extent in the

United States and are known to occur only in California and

Hawaii. The natural vegetation consisted of forest plants.

Slopes range from nearly level to sloping. These soils are used

mostly as forest, cropland, or pasture.

Andic Kanhaplohumults.—These soils have a mantle or

layer in the upper 75 cm that has both a low bulk density and a

high content of weakly crystalline minerals. They are not

known to occur in the United States. They are defined for use

in other parts of the world.

Anthropic Kanhaplohumults.—These soils are similar to

Typic Kanhaplohumults, but they have been used as cropland

for long periods and have an anthropic epipedon. They are not

known to occur in the United States. They are defined for use

in other parts of the world.

Aquic Kanhaplohumults.—These soils are similar to Typic

Kanhaplohumults, but they have redox depletions with low

chroma within 75 cm of the mineral soil surface. The redox

depletions are caused by periods of wetness. The soils are in

nearly level to sloping areas. They are not known to occur in

the United States. They are defined for use in other parts of the

world.

Lithic Kanhaplohumults.—These soils have a lithic

contact within 50 cm of the mineral soil surface. They are not
Ultisols 745

known to occur in the United States. They are defined for use in

other parts of the world.

Ombroaquic Kanhaplohumults.—These soils have, in one

or more horizons within 75 cm of the mineral soil surface,

redox concentrations, a color value, moist, of 4 or more, and

hue that is 10YR or yellower and becomes redder with

increasing depth within 100 cm of the mineral soil surface.

They are not known to occur in the United States. They are

defined for use in other parts of the world.

Ustandic Kanhaplohumults.—These soils have an ustic

moisture regime and a mantle or layer in the upper 75 cm that

has both a low bulk density and a high content of weakly

crystalline minerals. They are not known to occur in the United

States. They are defined for use in other parts of the world.

Ustic Kanhaplohumults.—These soils are like Typic

Kanhaplohumults, but they have an ustic moisture regime.

They are intergrades between Kanhaplohumults and

Kanhaplustults. They are not known to occur in the United

States. The subgroup is defined for use in other parts of the

world.

Xeric Kanhaplohumults.—These soils are like Typic

Kanhaplohumults, but they have a xeric moisture regime. They

are intergrades between Kanhaplohumults and Xerults. Xeric

Kanhaplohumults are not known to occur in the United States.

The subgroup is defined for use in other parts of the world.

Palehumults

These are the Humults that are on old stable surfaces and

that have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases has at least

5 percent of the volume consisting of clay depletions on faces

of peds and there is at least a 3 percent increase in clay content

below this layer. These soils have an argillic horizon. They do

not have plinthite that forms a continuous phase or that

constitutes more than half the volume of any subhorizon within

125 cm of the mineral soil surface. These soils are moderately

extensive. They are mostly in California, western Oregon and

Washington, and Hawaii. Like other Humults in the United

States, they formed mostly in material weathered from basic

rocks or in alluvium derived from basic rocks. Most

Palehumults have had a forest vegetation, and many still have

a forest vegetation.

Definition

Palehumults are the Humults that:

1. Do not have a kandic horizon;

2. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by 20 percent or

more within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases by more

than 20 percent has at least 5 percent of the volume consisting

of clay depletions on faces of peds and there is at least a 3

percent (absolute) increase in clay content below this layer;

3. Do not have a sombric horizon within 100 cm of the

mineral soil surface; and

4. Do not have plinthite that forms a continuous phase or that

constitutes more than half the volume of any subhorizon within

125 cm of the mineral soil surface.

Key to Subgroups

HBEA. Palehumults that have both:

1. In one or more subhorizons within the upper 25 cm of

the argillic horizon, redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less, accompanied by

redox concentrations, and also aquic conditions for some

time in normal years (or artificial drainage); and

2. Throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral

soil surface, a fine-earth fraction with both a bulk density

of 1.0 g/cm3

 or less, measured at 33 kPa water retention,

and Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling more than 1.0.

Aquandic Palehumults

HBEB. Other Palehumults that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Palehumults

HBEC. Other Palehumults that have, in one or more

subhorizons within the upper 25 cm of the argillic horizon,

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less, accompanied by redox concentrations and

by aquic conditions for some time in normal years (or artificial

drainage).

Aquic Palehumults

HBED. Other Palehumults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Palehumults

HBEE. Other Palehumults that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Palehumults
746 Soil Taxonomy

HBEF. Other Palehumults that have an ustic moisture

regime.

Ustic Palehumults

HBEG. Other Palehumults that have a xeric moisture regime.

Xeric Palehumults

HBEH. Other Palehumults.

Typic Palehumults

Definition of Typic Palehumults

Typic Palehumults are the Palehumults that:

1. In normal years are not saturated with water in one or

more layers within 100 cm of the mineral soil surface for either

or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

2. Have a udic moisture regime;

3. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface; and

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent.

Description of Subgroups

Typic Palehumults.—The central concept or Typic

subgroup of Palehumults is fixed on freely drained soils that

have a udic moisture regime. These soils typically have an

ochric epipedon and albic and argillic horizons. Redox

depletions with low chroma and a fluctuating level of ground

water are properties shared with Aquults and define the Aquic

subgroup. An appreciable amount of plinthite is considered

abnormal and is used to define the Plinthic subgroup. Ustic and

xeric moisture regimes are considered abnormal but are highly

significant to soil-plant relationships and define Ustic and

Xeric subgroups, respectively. Soils that have a mantle or layer

in the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals are excluded from the

Typic subgroup because they are considered to be intergrades to

Andisols.

Typic Palehumults are moderately extensive in the United

States. They are mostly in western Oregon and Washington, in

Hawaii, and in Puerto Rico. The natural vegetation consisted

mostly of coniferous forest plants in Oregon and Washington

and tropical broadleaf forest plants in Hawaii and Puerto Rico.

Slopes range from nearly level to very steep. These soils are

used mostly as forest. Where slopes are suitable, some of the

soils have been cleared and are used as pasture, cropland, or

homesites.

Andic Palehumults.—These soils have a surface mantle or

layer in the upper 75 cm that has both a low bulk density and a

high content of weakly crystalline minerals in at least some

part of the upper 75 cm. The soils are of very small extent in

California. The natural vegetation consisted mostly of grasses

and shrubs. Slopes range from nearly level to moderately

sloping. These soils are used mostly as pasture or cropland.

Aquandic Palehumults.—These soils have a surface mantle

or layer in the upper 75 cm that has both a low bulk density

and a high content of weakly crystalline minerals in at least

some part of the upper 75 cm. They have redox depletions with

low chroma, and the level of ground water fluctuates in the

iron-depleted horizons or the soils are artificially drained.

These soils occur in the Pacific Northwest.

Aquic Palehumults.—These soils have redox depletions

with low chroma, and the level of ground water fluctuates in

the redox-depleted horizons or the soils are artificially drained.

In the United States, these soils are of very small extent and

occur in western Oregon. The natural vegetation consisted

mostly of coniferous forest plants. Slopes range from nearly

level to steep. These soils are used mostly as forest. Some of

the less sloping soils have been cleared and are used as pasture.

Oxyaquic Palehumults.—These soils are saturated with

water for 20 or more consecutive days and/or 30 or more

cumulative days during normal years. They may or may not

have redoximorphic features. If present, the redoximorphic

features are either weakly expressed or lower in the profile than

is required for the Aquic subgroup. Oxyaquic Palehumults

occur in the Pacific Northwest and are used as pasture or

woodland.

Plinthic Palehumults.—These soils have 5 to 50 percent

(by volume) plinthite in some horizon within 150 cm of the

mineral soil surface but otherwise are similar to the soils in the

Typic subgroup. Plinthic Palehumults are of very small extent.

They are known to occur in Puerto Rico. The natural

vegetation consisted of tropical trees and shrubs. These soils

are used mostly as pasture or cropland.

Ustic Palehumults.—These soils have an ustic moisture

regime. They are of very small extent in the United States.

They are known to occur in Hawaii. They are used mostly as

pasture or cropland.

Xeric Palehumults.—These soils have a xeric moisture

regime but are otherwise like Typic Palehumults in defined

properties. They are moderately extensive in the United States.

They occur in the Sierra Nevada and Coast Ranges of

California and the Coast Range and western Cascade

Mountains of Oregon and Washington. They also occur in the

Willamette Valley and Puget lowlands of Oregon and

Washington, respectively. The natural vegetation consisted

mostly of coniferous forest plants. Slopes range from nearly

level to very steep. These soils are used mostly as forest. Where
Ultisols 747

slopes are suitable, some of the soils have been cleared and are

used as pasture, cropland, or homesites.

Plinthohumults

Plinthohumults are the Humults that do not have a sombric

horizon within 100 cm of the mineral soil surface and have

plinthite that forms a continuous phase in, or constitutes more

than half the volume of, one or more horizons within 150 cm

of the mineral soil surface. These soils are not known to occur

in the United States. The great group has been provided for use

in other countries.

Key to Subgroups

HBBA. All Plinthohumults.

Typic Plinthohumults

Sombrihumults

These Humults have a sombric horizon that has its upper

boundary within 100 cm of the mineral soil surface. They are

not known to occur in the United States. The great group is

provided for use elsewhere.

Key to Subgroups

HBAA. All Sombrihumults.

Typic Sombrihumults

Udults

These are the more or less freely drained, humus-poor

Ultisols that have a udic moisture regime. They are in humid

climates, and most receive well distributed rainfall. Most have

light colored upper horizons, commonly a grayish horizon that

rests on a yellowish brown to reddish argillic or kandic

horizon. A few that developed from basic rocks have a dark

brown or reddish brown surface horizon that rests on a dark

red or dusky red argillic or kandic horizon. Some have a

fragipan or plinthite, or both, in or below the argillic or kandic

horizon.

Udults developed in sediments and on surfaces that range

from late Pleistocene to Pliocene or possibly older. Many are

cultivated, either with the use of soil amendments or in a

system in which they are cropped for a very few years and then

are returned to forest to allow the trees to regather in their

tissues the small supply of nutrients. Most of these soils have

or had a forest vegetation, but some have a savanna that

probably is anthropic.

Definition

Udults are the Ultisols that:

1. Do not have both aquic conditions and the colors defined

for Aquults;

2. Have less than 0.9 percent, by weighted average, organic

carbon in the upper 15 cm of the argillic or kandic horizon and

have less than 12 kg organic carbon in a unit volume of 1 m2 to

a depth of 100 cm, exclusive of any O horizon; and

3. Have a udic moisture regime.

Key to Great Groups

HCA. Udults that have one or more horizons within 150 cm

of the mineral soil surface in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume.

Plinthudults, p. 766

HCB. Other Udults that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragiudults, p. 748

HCC. Other Udults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Have a kandic horizon; and

3. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) clay depletions

on faces of peds in the layer that has a 20 percent lower

clay content and, below that layer, a clay increase of 3

percent or more (absolute) in the fine-earth fraction.

Kandiudults, p. 754

HCD. Other Udults that have a kandic horizon.

Kanhapludults, p. 758

HCE. Other Udults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) clay depletions

on faces of peds in the layer that has a 20 percent lower

clay content and, below that layer, a clay increase of 3

percent or more (absolute) in the fine-earth fraction.

Paleudults, p. 761
748 Soil Taxonomy

HCF. Other Udults that have both:

1. An epipedon that has a color value, moist, of 3 or less

throughout; and

2. In all subhorizons in the upper 100 cm of the argillic

horizon or throughout the entire argillic horizon if it is less

than 100 cm thick, more than 50 percent colors that have all

of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the

moist value.

Rhodudults, p. 766

HCG. Other Udults.

Hapludults, p. 750

Fragiudults

These are the Udults that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface. They have

no horizon within 150 cm of the mineral soil surface in which

plinthite either forms a continuous phase or constitutes onehalf or more of the volume. These soils formed mainly in

loamy alluvium or in residuum. The fragipan commonly has an

upper boundary about 50 to 75 cm below the mineral soil

surface. Perched ground water is above the pan at some period

during the year, and many of the soils have thick, gray clay

depletions near the top of the fragipan and in vertical seams

between structural units.

The Fragiudults in the United States are principally on

gentle slopes throughout the Southeastern States. The

temperature regime is mesic or thermic. The vegetation on the

Fragiudults in the United States has been a forest either of

conifers or of broadleaf deciduous trees.

Definition

Fragiudults are the Udults that:

1. Have a fragipan with an upper boundary within 100 cm of

the mineral soil surface; and

2. Do not have one or more horizons within 150 cm of the

mineral soil surface in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume.

Key to Subgroups

HCBA. Fragiudults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic or kandic horizon

at a depth of 50 to 100 cm.

Arenic Fragiudults

HCBB. Other Fragiudults that have both of the following:

1. In one or more horizons within 40 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also

aquic conditions for some time in normal years (or artificial

drainage); and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Plinthaquic Fragiudults

HCBC. Other Fragiudults that meet both of the following:

1. Meet one or more of the following:

a. Have a glossic horizon above the fragipan; or

b. Do not have, above the fragipan, an argillic or

kandic horizon that has clay films on both vertical and

horizontal surfaces of any structural aggregates; or

c. Between the argillic or kandic horizon and the

fragipan, have one or more horizons with 50 percent or

more chroma of 3 or less and with a clay content 3

percent or more (absolute, in the fine-earth fraction)

lower than that in both the argillic or kandic horizon and

the fragipan; and

2. In one or more horizons within 40 cm of the mineral

soil surface, have redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage).

Glossaquic Fragiudults

HCBD. Other Fragiudults that have, in one or more

subhorizons above the fragipan and within the upper 25 cm of

the argillic or kandic horizon, redox depletions with chroma of

2 or less and also aquic conditions for some time in normal

years (or artificial drainage).

Aquic Fragiudults

HCBE. Other Fragiudults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Fragiudults

HCBF. Other Fragiudults that meet one or more of the

following:

1. Have a glossic horizon above the fragipan; or

2. Do not have, above the fragipan, an argillic or kandic

horizon that has clay films on both vertical and horizontal

surfaces of any structural aggregates; or

3. Between the argillic or kandic horizon and the fragipan,

have one or more horizons with 50 percent or more chroma

of 3 or less and with a clay content 3 percent or more

(absolute, in the fine-earth fraction) lower than that in both

the argillic or kandic horizon and the fragipan.

Glossic Fragiudults
Ultisols 749

HCBG. Other Fragiudults that have a color value, moist, of 3 or

less and a color value, dry, of 5 or less (crushed and smoothed

sample) in either:

1. An Ap horizon that is 18 cm or more thick; or

2. The surface layer after mixing of the upper 18 cm.

Humic Fragiudults

HCBH. Other Fragiudults.

Typic Fragiudults

Definition of Typic Fragiudults

Typic Fragiudults are the Fragiudults that:

1. Above the fragipan, have an argillic or kandic horizon that

has some clay films on both vertical and horizontal surfaces of

some structural aggregates;

2. Do not have a glossic horizon above the fragipan;

3. Between the argillic or kandic horizon and the fragipan,

do not have an intervening horizon (one or more) that has

dominant chroma of 3 or less and that has as much as 3

percent less clay (absolute) than both the overlying argillic or

kandic horizon and the underlying fragipan;

4. Do not have, in any subhorizon above the fragipan and

within the upper 25 cm of the argillic or kandic horizon, redox

depletions with chroma of 2 or less and also aquic conditions;

5. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic or kandic horizon at a depth of 50 to 100

cm;

6. Have less than 5 percent (by volume) plinthite in all

horizons within 150 cm of the mineral soil surface; and

7. Have a color value, moist, of 4 or more or a value, dry, of 6

or more, when crushed and smoothed, in any Ap horizon 18

cm or more thick and in any surface layer after mixing of the

upper 18 cm.

Description of Subgroups

Typic Fragiudults.—The central concept or Typic subgroup

of Fragiudults is fixed on soils that have an argillic or kandic

horizon that is underlain by a fragipan without an intervening

eluvial horizon. These soils do not have redox depletions with

low chroma in the upper 25 cm of the argillic horizon or above

the fragipan if the part of the argillic or kandic horizon above

the fragipan is less than 25 cm thick. The soils have less than 5

percent plinthite within 150 cm of the mineral soil surface. The

surface layer has a color value of 4 or more, moist, and 6 or

more, dry, after mixing of the upper 18 cm.

Typic Fragiudults are more extensive than the soils of the

other subgroups. Their characteristics provide the best basis for

defining other subgroups. Since no Fragiudult is freely drained,

redox depletions with low chroma and ground water at some time

of the year must be present at a shallower depth in Aquic

Fragiudults than in many other kinds of Aquic subgroups.

A perched water table at the top of the fragipan tends to

reduce and remove free iron oxides and accelerate the

eluviation of clay and thus to produce a glossic horizon or a

second eluvial horizon, an E ́. If the marks of this process are

distinct, the part of the B horizon above the fragipan is a

cambic horizon and the clay films in the fragipan tend to be

thick. This combination of horizons defines the glossic

intergrades. A thick sandy (sand or loamy sand) layer, starting

at the mineral soil surface, is considered abnormal and defines

the Arenic subgroup. Plinthite in Fragiudults suggests

polygenesis and defines the Plinthic subgroup.

Typic Fragiudults are of large extent in the Southeastern

United States. The natural vegetation consisted of forest plants.

Slopes range from nearly level to moderately steep. These soils

are used mostly as forest. Where slopes are suitable, some of

the soils have been cleared and are used as pasture, cropland,

or homesites.

Aquic Fragiudults.—These soils have redox depletions

with low chroma at a shallow depth and have aquic conditions

in the iron-depleted horizon at some time of the year unless the

soils have been artificially drained. The soils are otherwise

similar to Typic Fragiudults in defined properties and also in

most accessory properties. Most Aquic Fragiudults have a

mesic soil temperature regime. Aquic Fragiudults are

moderately extensive in the Eastern United States. They

generally are nearly level to moderately sloping. The natural

vegetation consisted of forest plants. Many of these soils are

used as forest. Some have been cleared and are used as pasture,

cropland, or homesites.

Arenic Fragiudults.—These soils have a sandy layer,

starting at the mineral soil surface, that is between 50 and 100

cm thick. They are not known to occur in the United States.

The subgroup is provided for use in other parts of the world.

Glossaquic Fragiudults.—These soils have redox

depletions with low chroma at a shallow depth and also have

aquic conditions in the iron-depleted horizon at some time of

the year or have been artificially drained. They meet one or

more of the following: (1) have a glossic horizon, (2) do not

have an argillic or kandic horizon above the fragipan, or (3)

have an eluvial horizon at the top of the fragipan. These soils

are of small extent in the Eastern United States. They generally

are nearly level or gently sloping. The natural vegetation

consisted of forest plants. The soils are used mostly as forest.

Some areas have been cleared and are used as cropland or

pasture.

Glossic Fragiudults.—These soils meet one or more of the

following: (1) have a glossic horizon, (2) do not have an

argillic or kandic horizon above the fragipan, or (3) have an

eluvial horizon at the top of the fragipan. The soils are

otherwise like Typic Fragiudults in defined properties and in

other properties. Glossic Fragiudults are moderately extensive
750 Soil Taxonomy

in the areas adjoining the lower Mississippi River Valley. They

generally are nearly level to strongly sloping. The natural

vegetation consisted of forest plants. Many of the soils have

been cleared and are used as cropland, but large areas are used

as forest.

Humic Fragiudults.—These soils have dark colored surface

layers. They are not sandy from the mineral soil surface to a

depth of 50 cm or more and do not have aquic conditions close

to the surface. They do not have plinthite or a glossic horizon.

Most of these soils are forested.

Plinthaquic Fragiudults.—These soils have plinthite in the

fragipan, have redox depletions with low chroma at a shallow

depth, and have either a fluctuating water table in the irondepleted zone or artificial drainage. These soils are not known

to occur in the United States. The subgroup is provided for use

in other parts of the world.

Plinthic Fragiudults.—These soils have 5 to 50 percent

plinthite in some layer within 150 cm of the mineral soil

surface. They are of small extent in the United States and occur

only on coastal plain in the South. They generally are nearly

level or gently sloping. The natural vegetation consisted of

forest plants. Many of the soils have been cleared and are used

as cropland, but large areas are used as forest.

Hapludults

These are the Udults that do not have a fragipan and that

have less than 50 percent plinthite in all horizons within 150

cm of the mineral soil surface. These soils have one of the

following: (1) a densic, lithic, paralithic, or petroferric contact

within 150 cm of the mineral soil surface or (2) with

increasing depth, a clay decrease of 20 percent or more

(relative) from the maximum clay content and less than 5

percent (by volume) clay depletions on faces of peds in any

layer that has a 20 percent lower clay content or, below that

layer, the fine-earth fraction has a clay increase of less than 3

percent. Many of the soils have a thin argillic horizon. The

color of the argillic horizon is not both dark and reddish

throughout the upper 100 cm. Most of the soils formed in areas

of acid rocks or sediments on surfaces that are at least of

Pleistocene age. Where the soils are not cultivated, the

vegetation consists almost exclusively of forest plants, either

hardwood trees or conifers.

Hapludults are extensive in the Southeastern United States,

in the Middle Atlantic States, and on the coastal plain along

the Gulf of Mexico in the Southern States east of the

Mississippi River. Slopes generally are gently sloping to steep,

but a few of the soils on the lowest part of the coastal plain are

nearly level.

Definition

Hapludults are the Udults that:

1. Do not have a kandic horizon;

2. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

3. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix in any subhorizon within

150 cm of the mineral soil surface;

4. Have a color:

a. With hue of 5YR or yellower; or

b. With a value, moist, of 4 or more in some part of the

epipedon or a value of 5 or more, dry, or of 4 or more,

moist, in some subhorizon of an argillic horizon; and

5. Have a clay distribution in which, with increasing depth,

the percentage of clay decreases from its maximum amount by

more than 20 percent within 150 cm of the mineral soil

surface, and the layer in which the percentage of clay is less

than the maximum has less than 5 percent of the volume

consisting of skeletans on faces of peds or there is an increase

in clay content of less than 3 percent (absolute) below this

layer.

Key to Subgroups

HCGA. Hapludults that have either or both:

1. In each pedon, a discontinuous lithic contact within 50

cm of the mineral soil surface; and

2. In each pedon, a discontinuous argillic horizon that is

interrupted by ledges of bedrock.

Lithic-Ruptic-Entic Hapludults

HCGB. Other Hapludults that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Hapludults

HCGC. Other Hapludults that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Hapludults

HCGD. Other Hapludults that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or
Ultisols 751

b. In 60 percent or more of the volume of a layer 15 cm or

more thick; and

2. In one or more layers within 75 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations, and also aquic conditions for some time in

normal years (or artificial drainage).

Fragiaquic Hapludults

HCGE. Other Hapludults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 to 100 cm; and

2. In one or more subhorizons within the upper 60 cm

of the argillic horizon, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations, and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Arenic Hapludults

HCGF. Other Hapludults that have, in one or more

subhorizons within the upper 60 cm of the argillic horizon,

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less, accompanied by redox concentrations and

by aquic conditions for some time in normal years (or artificial

drainage).

Aquic Hapludults

HCGG. Other Hapludults that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Hapludults

HCGH. Other Hapludults that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Hapludults

HCGI. Other Hapludults that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more

than 20 cm thick, each with an overlying eluvial horizon,

and above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Hapludults

HCGJ. Other Hapludults that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Hapludults

HCGK. Other Hapludults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm.

Arenic Hapludults

HCGL. Other Hapludults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more.

Grossarenic Hapludults

HCGM. Other Hapludults that have:

1. No densic, lithic, or paralithic contact within 50 cm of

the mineral soil surface; and

2. An argillic horizon 25 cm or less thick.

Inceptic Hapludults

HCGN. Other Hapludults that have a color value, moist, of 3

or less and a color value, dry, of 5 or less (crushed and

smoothed sample) in either:

1. An Ap horizon that is 18 cm or more thick; or

2. The surface layer after mixing of the upper 18 cm.

Humic Hapludults

HCGO. Other Hapludults.

Typic Hapludults

Definition of Typic Hapludults

Typic Hapludults are the Hapludults that:

1. Do not have, in any subhorizon within the upper 60 cm of

the argillic horizon, redox depletions with a color value, moist,
752 Soil Taxonomy

of 4 or more and chroma of 2 or less, accompanied by redox

concentrations and by aquic conditions;

2. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more;

4. Have an argillic horizon more than 25 cm thick;

5. Have a color value, moist, of 4 or more or a value, dry, of 6

or more, when crushed and smoothed, in any Ap horizon 18

cm or more thick and in any surface layer after mixing of the

upper 18 cm;

6. Do not have a lithic contact within 50 cm of the mineral

soil surface in some or all parts of each pedon;

7. Have an argillic horizon that is finer than the sandy

particle-size class in some part of the upper 75 cm if the

argillic horizon is more than 75 cm thick or in any part if the

argillic horizon is less than 75 cm thick;

8. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

9. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon; and

10. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Hapludults.—The central concept or Typic subgroup

of Hapludults is fixed on freely drained soils that are

moderately deep or deeper to hard rock, have an ochric

epipedon that is not both thick and sandy (not sand or loamy

sand), have a loamy or clayey particle-size class in the argillic

horizon, but do not have deep cracks in normal years. Ground

water at a moderate depth, redox depletions with low chroma

at a shallow depth, and a fluctuating level of ground water in

the iron-depleted zone are properties shared with Aquults and

define the Oxyaquic and Aquic subgroups.

A thick sandy layer, starting at the mineral soil surface,

defines Arenic and Grossarenic subgroups. A shallow lithic

contact defines the Lithic subgroup. A dark colored, relatively

thick ochric epipedon or an umbric epipedon is considered

abnormal and indicates an intergrade to Humults. A very thin

argillic horizon also is considered abnormal and is used to

define the Inceptic subgroup. A sandy particle-size class and

lamellae in the argillic horizon indicate development that is

weaker than normal and define the Psammentic and Lamellic

subgroups. A clayey particle-size class, deep cracks, and a high

COLE are properties shared with Vertisols and define the

Vertic subgroup.

Typic Hapludults are of very large extent in the Eastern and

Southeastern United States. The natural vegetation consisted of

forest plants. Slopes range from nearly level to steep. Where

slopes are suitable, many of these soils are used as cropland.

Many of the soils, particularly those that are steep, are used as

forest. Some are used as pasture or homesites.

Aquic Arenic Hapludults.—These soils have a layer,

starting at the mineral soil surface, that has a sandy or sandyskeletal particle-size class and is 50 to 100 cm thick. They are

artificially drained or have ground water that fluctuates in

depth, and the horizons that are or were saturated have redox

depletions with low chroma. The ground water may be more

than 60 cm below the top of the argillic horizon if artificial

drainage has been provided. Most of these soils are in the

sandy parts of the coastal plain in the Eastern and Southeastern

United States. The natural vegetation consisted of forest plants.

Aquic Arenic Hapludults are of small extent. Many of these

soils are used as cropland or forest. Some are used as pasture or

homesites.

Aquic Hapludults.—These soils are artificially drained or

have ground water that fluctuates in depth, and the horizons

that are or were saturated have redox depletions with low
Ultisols 753

chroma. The ground water may be more than 60 cm below the

top of the argillic horizon if artificial drainage has been

provided. The level of ground water is high in winter and early

spring. These soils are of large extent in the Eastern and

Southeastern United States. The natural vegetation consisted of

forest plants. Slopes are nearly level to moderately sloping.

Many of these soils are used as cropland or forest. Some are

used as pasture or homesites.

Arenic Hapludults.—These soils have a layer, starting at

the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class and is between 50 and 100 cm thick. Most of

these soils are in the sandy parts of the coastal plain in the

Eastern and Southeastern United States. The natural vegetation

consisted of forest plants. Arenic Hapludults are of moderate

extent. Many of these soils are used as cropland, and many are

used as forest. Some are used as pasture or homesites.

Fragiaquic Hapludults.—These soils are similar to Typic

Hapludults, but they have redox depletions with low chroma

and also aquic conditions at a shallow depth for some time in

normal years. They have fragic soil properties in 30 percent or

more of the volume of a layer 15 cm or more thick that has its

upper boundary within 100 cm of the mineral soil surface or in

60 percent or more of the volume of a layer 15 cm or more

thick anywhere in the soils. These soils are not extensive in the

United States.

Fragic Hapludults.—These soils are similar to Typic

Hapludults, but they have fragic soil properties in 30 percent or

more of the volume of a layer 15 cm or more thick that has its

upper boundary within 100 cm of the mineral soil surface or in

60 percent or more of the volume of a layer 15 cm or more

thick anywhere in the soils. These soils are not extensive in the

United States.

Grossarenic Hapludults.—These soils have a layer,

starting at the mineral soil surface, that has a sandy or sandyskeletal particle-size class and is more than 100 cm thick.

These soils are not known to occur in the United States. The

subgroup is provided for use in other parts of the world.

Humic Hapludults.—These soils have a dark colored

surface layer. Some have an umbric epipedon or, if heavily

limed, a mollic epipedon. Humic Hapludults are mainly in the

mountains in the Southeastern United States. They are of

moderate extent. The natural vegetation consisted of forest

plants. Slopes range from nearly level to very steep. Many of

these soils are used as cropland or forest. Some are used as

pasture.

Inceptic Hapludults.—These soils have a thin argillic

horizon. Some of the soils are moderately deep to a lithic,

densic, or paralithic contact. Some have a thin argillic horizon

over sandy materials. In the United States, Inceptic Hapludults

are moderately extensive in the Piedmont and on the coastal

plain of the Middle Atlantic and Southern States. The natural

vegetation consisted of forest plants. Slopes range from nearly

level to very steep. Most of the soils are used as forest,

cropland, or pasture.

Lamellic Hapludults.—These soils are like Typic

Hapludults, but they have an argillic horizon that consists

entirely of lamellae or is a combination of two or more

lamellae and one or more subhorizons with a thickness of 7.5

to 20 cm, each layer with an overlying eluvial horizon. In some

of the soils, the argillic horizon consists of one or more

subhorizons that are more than 20 cm thick, each with an

overlying eluvial horizon, and above these horizons there are

either two or more lamellae with a combined thickness of 5 cm

or more or a combination of lamellae and one or more parts of

the argillic horizon 7.5 to 20 cm thick, each with an overlying

eluvial horizon. These soils are not known to occur in the

United States. The subgroup is provided for use in other parts

of the world.

Lithic Hapludults.—These soils have a continuous shallow

lithic contact and an argillic horizon that is continuous

throughout each pedon. These soils are of small extent, mostly

in the Eastern United States. The natural vegetation consisted

of forest plants. Slopes range from nearly level to very steep.

The soils are used mainly as forest.

Lithic-Ruptic-Entic Hapludults.—These soils have either

a discontinuous argillic horizon in each pedon or a shallow

lithic contact only in part of each pedon, or both. Where the

lithic contact is shallow, the argillic horizon commonly is thin.

Where the lithic contact is very shallow, there is no argillic

horizon. In some of these soils, depth to the lithic contact

varies greatly within a pedon and an argillic horizon is only in

the deepest parts of the pedon. Lithic-Ruptic-Entic Hapludults

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Oxyaquic Hapludults.—These soils are like Typic

Hapludults, but they are saturated with water within 100 cm of

the mineral soil surface for 20 or more consecutive days or 30

or more cumulative days in normal years. In addition, they are

permitted to have a dark colored Ap horizon or a dark colored

A horizon after the upper 18 cm has been mixed. These soils

are of small extent in the United States. Slopes are gentle to

steep. The natural vegetation consisted of forest plants. Most of

these soils are used as forest. Some have been cleared and are

used as cropland or pasture.

Psammentic Hapludults.—These soils have a sandy or

sandy-skeletal particle-size class throughout the upper 75 cm of

the argillic horizon or throughout the entire argillic horizon if

it is less than 75 cm thick. They are of small extent in the

United States. They are considered intergrades between

Udipsamments and Hapludults. Slopes generally are nearly

level to moderately steep. The natural vegetation consisted of

forest plants. About half of these soils have been cleared and

are used as cropland or pasture, and about half are used as

forest.

Vertic Hapludults.—These soils have deep cracks and

appreciable amounts of swelling clays. The swelling clays and

low saturated hydraulic conductivity seem to be the most

important properties of the soils of this subgroup. Most of these
754 Soil Taxonomy

soils formed in clayey parent materials. Vertic Hapludults are of

small extent. The natural vegetation consisted of forest plants.

Slopes are gentle to moderately steep. Most of the soils are used

as forest, but some, mostly the less sloping ones, have been

cleared and are used as cropland or pasture.

Kandiudults

Kandiudults are the Udults that are very deep and have a

kandic horizon and a clay distribution in which the percentage

of clay does not decrease from its maximum amount by as

much as 20 percent within a depth of 150 cm from the mineral

soil surface, or the layer in which the clay percentage decreases

has at least 5 percent of the volume consisting of skeletans on

faces of peds and there is at least a 3 percent (absolute)

increase in clay content below this layer. These soils do not

have a fragipan or a horizon in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume

within 150 cm of the mineral soil surface. Kandiudults are of

moderate extent in the Southeastern United States.

Definition

Kandiudults are the Udults that:

1. Have a kandic horizon;

2. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface;

3. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases by more

than 20 percent has at least 5 percent of the volume consisting

of skeletans on faces of peds and there is at least a 3 percent

(absolute) increase in clay content below this layer;

4. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume in some subhorizon

within 150 cm of the mineral soil surface; and

5. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface.

Key to Subgroups

HCCA. Kandiudults that have:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 to 100 cm; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface; and

3. In one or more layers either within 75 cm of the

mineral soil surface or, if the chroma throughout the upper

75 cm results from uncoated sand grains, within the upper

12.5 cm of the kandic horizon, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations, and also aquic

conditions for some time in normal years (or artificial

drainage).

Arenic Plinthaquic Kandiudults

HCCB. Other Kandiudults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 to 100 cm; and

2. In one or more layers either within 75 cm of the

mineral soil surface or, if the chroma throughout the upper

75 cm results from uncoated sand grains, within the upper

12.5 cm of the kandic horizon, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations, and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Arenic Kandiudults

HCCC. Other Kandiudults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 to 100 cm; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthic Kandiudults

HCCD. Other Kandiudults that have both:

1. A sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface

to the top of a kandic horizon at a depth of 50 to 100 cm;

and

2. In all subhorizons in the upper 75 cm of the kandic

horizon or throughout the entire kandic horizon if it is less

than 75 cm thick, more than 50 percent colors that have all

of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the

moist value.

Arenic Rhodic Kandiudults

HCCE. Other Kandiudults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 50 to 100 cm.

Arenic Kandiudults

HCCF. Other Kandiudults that have both:
Ultisols 755

1. A sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface

to the top of a kandic horizon at a depth of 100 cm or more;

and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Grossarenic Plinthic Kandiudults

HCCG. Other Kandiudults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 100 cm or more.

Grossarenic Kandiudults

HCCH. Other Kandiudults that have both:

1. An ECEC of 1.5 cmol(+)/kg clay or less (sum of bases

extracted with 1N NH4

OAc pH 7, plus 1N KCl-extractable

Al) in one or more horizons within 150 cm of the mineral

soil surface; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Acrudoxic Plinthic Kandiudults

HCCI. Other Kandiudults that have an ECEC of 1.5

cmol(+)/kg clay or less (sum of bases extracted with 1N

NH4OAc pH 7, plus 1N KCl-extractable Al) in one or more

horizons within 150 cm of the mineral soil surface.

Acrudoxic Kandiudults

HCCJ. Other Kandiudults that have both:

1. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface; and

2. In one or more layers within 75 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations, and also aquic conditions for some time in

normal years (or artificial drainage).

Plinthaquic Kandiudults

HCCK. Other Kandiudults that have both:

1. In one or more layers within 75 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations, and also aquic conditions for some time in

normal years (or artificial drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Aquandic Kandiudults

HCCL. Other Kandiudults that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Kandiudults

HCCM. Other Kandiudults that have, in one or more layers

within 75 cm of the mineral soil surface, redox depletions with

a color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations and by aquic conditions

for some time in normal years (or artificial drainage).

Aquic Kandiudults

HCCN. Other Kandiudults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kandiudults

HCCO. Other Kandiudults that:

1. Have, in one or more horizons within 75 cm of the

mineral soil surface, redox concentrations, a color value,

moist, of 4 or more, and hue that is 10YR or yellower and

becomes redder with increasing depth within 100 cm of the

mineral soil surface; and

2. In normal years are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Ombroaquic Kandiudults

HCCP. Other Kandiudults that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:
756 Soil Taxonomy

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Kandiudults

HCCQ. Other Kandiudults that have a sombric horizon

within 150 cm of the mineral soil surface.

Sombric Kandiudults

HCCR. Other Kandiudults that have, in all subhorizons in

the upper 75 cm of the kandic horizon or throughout the entire

kandic horizon if it is less than 75 cm thick, more than 50

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Rhodic Kandiudults

HCCS. Other Kandiudults.

Typic Kandiudults

Definition of Typic Kandiudults

Typic Kandiudults are the Kandiudults that:

1. Do not, in any layer either within 75 cm of the mineral

soil surface or, if the chroma throughout the upper 75 cm

results from uncoated sand grains, within the upper 12.5

cm of the kandic horizon, have redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations and by aquic conditions;

2. In normal years are not saturated with water in any

layer within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of a kandic horizon at a depth of 50 cm or more;

4. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface;

5. In all parts of the upper 75 cm of the kandic horizon,

have 50 percent or less colors that have all of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist

value;

6. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, any of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

c. A fine-earth fraction containing 30 percent or more

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1/2 Fe, percent extracted by ammonium

oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more;

7. Have, within 75 cm of the mineral soil surface, hue

of 7.5YR or redder in all horizons with a color value, moist,

of 4 or more if there are redox concentrations or if the hue

becomes redder with increasing depth within 100 cm of the

mineral soil surface;

8. Have an ECEC (sum of bases plus 1N KCl-extractable Al)

of more than 1.5 cmol(+)/kg clay in all subhorizons to a depth

of 150 cm below the mineral soil surface; and

9. Do not have a sombric horizon within 150 cm of the

mineral soil surface.

Description of Subgroups

Typic Kandiudults.—The central concept or Typic

subgroup of Kandiudults is fixed on freely drained soils that do

not have a sombric horizon and are very deep. The epipedon is

not both thick and sandy (not sand or loamy sand). These soils

have less than 5 percent plinthite and have a low, but not

extremely low, cation-exchange capacity. They do not have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals.

Ground water at a moderate depth, redox depletions with

low chroma at a shallow depth, and a fluctuating level of

ground water in the iron-depleted zone are properties shared

with Aquults and define the Oxyaquic and Aquic subgroups. A

thick sandy layer, starting at the mineral soil surface, defines

Arenic and Grossarenic subgroups.

Typic Kandiudults are of small extent in the Southeastern

United States. The natural vegetation consisted of forest plants.

Slopes range from nearly level to steep. Where slopes are

suitable, many of these soils are used as cropland. Where

slopes are steep, the soils are used as forest. Some of the soils

are used as pasture or homesites.

Acrudoxic Kandiudults.—These soils have an extremely

low cation-exchange capacity. Recycling of plant nutrients

from decaying vegetation is critical for plant growth on these

soils. The soils are not known to occur in the United States.

The subgroup is provided for use in other parts of the world.
Ultisols 757

Acrudoxic Plinthic Kandiudults.—These soils have an

extremely low cation-exchange capacity and have 5 to 50

percent (by volume) plinthite in some subhorizon within 150

cm of the surface. Recycling of plant nutrients from decaying

vegetation is critical for plant growth on these soils. The soils

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Andic Kandiudults.—These soils have a surface mantle or

layer in the upper 75 cm that has both a low bulk density and a

high content of weakly crystalline minerals in at least some

part of the upper 75 cm. The soils are not known to occur in

the United States. The subgroup is provided for use in other

parts of the world.

Aquandic Kandiudults.—These soils have a surface mantle

or layer in the upper 75 cm that has both a low bulk density

and a high content of weakly crystalline minerals in at least

some part of the upper 75 cm. They also have ground water

that fluctuates in depth or are artificially drained, and the

horizons that are or were saturated have redox depletions with

low chroma. These soils are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Aquic Arenic Kandiudults.—These soils have a layer,

starting at the mineral soil surface, that has a sandy or sandyskeletal particle-size class and is 50 to 100 cm thick. They

have ground water that fluctuates in depth or are artificially

drained, and the horizons that are or were saturated have redox

depletions with low chroma. These soils are not known to

occur in the United States. The subgroup is provided for use in

other parts of the world.

Aquic Kandiudults.—These soils have ground water that

fluctuates in depth or are artificially drained, and the horizons

that are or were saturated have redox depletions with low

chroma. These soils are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Arenic Kandiudults.—These soils have a layer, starting at

the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class and is between 50 and 100 cm thick. Most of

the soils are in the sandy parts of the coastal plain in the

Southeastern United States. The natural vegetation consisted of

mixed forest plants. Arenic Kandiudults are of small extent in

the United States. Many of these soils are used as cropland or

forest, but some are used as pasture or homesites.

Arenic Plinthaquic Kandiudults.—These soils have a

layer, starting at the mineral soil surface, that has a sandy or

sandy-skeletal particle-size class and is between 50 and 100 cm

thick. They have, in one or more horizons within 75 cm of the

mineral soil surface, redox depletions with chroma of 2 or less

and also aquic conditions for some time in normal years (or

artificial drainage). In addition, the soils have 5 to 50 percent

(by volume) plinthite in one or more horizons within 150 cm of

the mineral soil surface. These soils are not known to occur in

the United States. The subgroup is provided for use in other

parts of the world.

Arenic Plinthic Kandiudults.—These soils have a layer,

starting at the mineral soil surface, that has a sandy or sandyskeletal particle-size class and is between 50 and 100 cm thick.

They also have 5 to 50 percent (by volume) plinthite in one or

more horizons within 150 cm of the mineral soil surface. These

soils are of very small extent in the United States.

Arenic Rhodic Kandiudults.—These soils have a layer,

starting at the mineral soil surface, that has a sandy or sandyskeletal particle-size class and is between 50 and 100 cm thick.

They also have, in the epipedon and the upper part of the

kandic horizon, hue of 2.5YR or redder, a value, moist, of 3 or

less, and a dry color value no more than 1 unit higher than the

moist value. These soils are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Grossarenic Kandiudults.—These soils have a sandy or

sandy-skeletal particle-size class throughout a layer extending

from the mineral soil surface to the top of a kandic horizon at a

depth of 100 cm or more below the mineral soil surface. These

soils are of small extent in the United States.

Grossarenic Plinthic Kandiudults.—These soils have 5

percent or more plinthite (by volume) in some subhorizon

within 150 cm of the surface. In addition, they have a sandy or

sandy-skeletal particle-size class throughout a layer extending

from the mineral soil surface to the top of a kandic horizon at a

depth of 100 cm or more below the mineral soil surface. These

soils are not known to occur in the United States. The subgroup

is provided for use in other parts of the world.

Ombroaquic Kandiudults.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

concentrations, a color value, moist, of 4 or more, and hue that

is 10YR or yellower and becomes redder with increasing depth

within 100 cm of the mineral soil surface. The soils are not

known to occur in the United States. They are defined for use

in other parts of the world.

Oxyaquic Kandiudults.—These soils are saturated with

water within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. The soils are not known to occur in the United States.

The subgroup is provided for use in other parts of the world.

Plinthaquic Kandiudults.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). They

have 5 to 50 percent (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface. Plinthaquic

Kandiudults are intergrades between Plinthaquults and

Kandiudults. They are not known to occur in the United States.

They are defined for use in other parts of the world.

Plinthic Kandiudults.—These soils have 5 to 50 percent (by

volume) plinthite in some subhorizon within 150 cm of the
758 Soil Taxonomy

surface. They are not known to occur in the United States. They

are defined for use in other parts of the world.

Rhodic Kandiudults.—These soils are like Typic

Kandiudults, but the upper part of their kandic horizon has hue

of 2.5YR or redder, a color value, moist, of 3 or less, and a dry

value no more than 1 unit higher than the moist value. Rhodic

Kandiudults are of small extent in the United States. The

natural vegetation consisted of forest plants. Slopes range from

nearly level to moderately steep. Many of these soils are used

as cropland. Some, particularly the most sloping ones, are used

as forest. Some are used as pasture or homesites.

Sombric Kandiudults.—These soils are like Typic

Kandiudults, but they have a sombric horizon. They are not

known to occur in the United States. They are defined for use

in other parts of the world.

Kanhapludults

Kanhapludults are the Udults that have a kandic horizon.

They do not have a fragipan with an upper boundary within

100 cm of the mineral soil surface or plinthite that forms a

continuous phase or constitutes more than half the volume in

some subhorizon within 150 cm of the soil surface. The soils

are less than 150 cm deep, or the kandic horizon has a clay

distribution in which the content of clay decreases from its

maximum amount by 20 percent or more within a depth of 150

cm from the soil surface, and the layer in which the percentage

of clay is less than the maximum has less than 5 percent of the

volume consisting of skeletans on faces of peds or there is an

increase in clay content of less than 3 percent (absolute) below

this layer. Most of these soils have a thermic or warmer soil

temperature regime. The natural vegetation consisted of forest

plants. Many of the soils have been cleared and are used as

cropland or pasture.

Definition

Kanhapludults are the Udults that:

1. Have a kandic horizon;

2. Have a clay distribution in which the percentage of clay

decreases from its maximum amount by 20 percent or more

within a depth of 150 cm from the soil surface, and the layer in

which the percentage of clay is less than the maximum has less

than 5 percent of the volume consisting of skeletans on faces of

peds or there is an increase in clay content of less than 3

percent (absolute) below this layer;

3. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume in some subhorizon

within 150 cm of the soil surface; and

4. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface.

Key to Subgroups

HCDA. Kanhapludults that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Kanhapludults

HCDB. Other Kanhapludults that have both:

1. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface; and

2. In one or more layers within 75 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations, and also aquic conditions for some time in

normal years (or artificial drainage).

Plinthaquic Kanhapludults

HCDC. Other Kanhapludults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 to 100 cm; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthic Kanhapludults

HCDD. Other Kanhapludults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 50 to 100 cm.

Arenic Kanhapludults

HCDE. Other Kanhapludults that have an ECEC of 1.5

cmol(+)/kg clay or less (sum of bases extracted with 1N

NH4

OAc pH 7, plus 1N KCl-extractable Al) in one or more

horizons within 150 cm of the mineral soil surface.

Acrudoxic Kanhapludults

HCDF. Other Kanhapludults that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. In one or more layers within 75 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations, and also aquic conditions for some time in

normal years (or artificial drainage).

Fragiaquic Kanhapludults
Ultisols 759

HCDG. Other Kanhapludults that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3

 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Kanhapludults

HCDH. Other Kanhapludults that have, in one or more layers

within 75 cm of the mineral soil surface, redox depletions with

a color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations and by aquic conditions

for some time in normal years (or artificial drainage).

Aquic Kanhapludults

HCDI. Other Kanhapludults that:

1. Have, in one or more horizons within 75 cm of the

mineral soil surface, redox concentrations, a color value,

moist, of 4 or more, and hue that is 10YR or yellower and

becomes redder with increasing depth within 100 cm of the

mineral soil surface; and

2. In normal years are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Ombroaquic Kanhapludults

HCDJ. Other Kanhapludults that in normal years are

saturated with water in one or more layers within 100 cm of

the mineral soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Kanhapludults

HCDK. Other Kanhapludults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kanhapludults

HCDL. Other Kanhapludults that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Kanhapludults

HCDM. Other Kanhapludults that have, in all subhorizons in

the upper 50 cm of the kandic horizon or throughout the entire

kandic horizon if it is less than 50 cm thick, more than 50 percent

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Rhodic Kanhapludults

HCDN. Other Kanhapludults.

Typic Kanhapludults

Definition of Typic Kanhapludults

Typic Kanhapludults are the Kanhapludults that:

1. Do not, in any layer either within 75 cm of the mineral soil

surface or, if the chroma throughout the upper 75 cm results

from uncoated sand grains, within the upper 12.5 cm of the

kandic horizon, have redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less, accompanied by

redox concentrations and by aquic conditions;

2. In normal years are not saturated with water in one or

more layers within 100 cm of the mineral soil surface for either

or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days;

3. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of a kandic horizon at a depth of 50 to 100 cm;

4. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the soil surface;

5. Do not have a lithic contact within 50 cm of the soil

surface;

6. Have, within 75 cm of the mineral soil surface, hue

of 7.5YR or redder in all horizons with a color value, moist,

of 4 or more if there are redox concentrations or if the hue

becomes redder with increasing depth within 100 cm of the

mineral soil surface;

7. In all parts of the upper 50 cm of the kandic horizon,

have 50 percent or less colors that have all of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist

value;

8. Do not have, throughout a cumulative thickness of 18

cm or more and within a depth of 75 cm, a bulk density, in

the fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalate-
760 Soil Taxonomy

extractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

9. Have an ECEC (sum of bases plus 1N KCl-extractable Al) of

more than 1.5 cmol(+)/kg clay in all subhorizons to a depth of

150 cm below the soil surface; and

10. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick.

Description of Subgroups

Typic Kanhapludults.—The central concept or Typic

subgroup of Kanhapludults is fixed on freely drained soils that

are more than 50 cm deep to a lithic contact. The epipedon is

not both thick and sandy (not sand or loamy sand). These soils

have less than 5 percent plinthite and have a low, but not

extremely low, cation-exchange capacity. They do not have a

surface mantle or layer in the upper 75 cm that has both a low

bulk density and a high content of weakly crystalline minerals.

Soils that have, in the upper part of the kandic horizon, 50

percent or more colors with hue of 2.5YR or redder, a value,

dry, of 3 or less, and moist and dry color values that differ from

each other by 1 unit or less than 1 unit are excluded from Typic

Kanhapludults because these properties are shared with

Rhodudults. Ground water at a moderate depth, redox

depletions with low chroma at a shallow depth, and a

fluctuating level of ground water in the redox-depleted zone

are properties shared with Aquults and define the Oxyaquic

and Aquic subgroups. A thick sandy layer, starting at the

mineral soil surface, defines the Arenic subgroup.

Typic Kanhapludults are of small extent in the Southeastern

United States. The natural vegetation consisted of forest plants.

Slopes range from nearly level to steep. Where slopes are

suitable, many of the soils are used as cropland. The steeper

soils are used as forest. Some of the soils are used as pasture or

homesites.

Acrudoxic Kanhapludults.—These soils have an extremely

low cation-exchange capacity. Recycling of plant nutrients

from decaying vegetation is critical for plant growth on these

soils. The soils are not known to occur in the United States.

The subgroup is provided for use in other parts of the world.

Andic Kanhapludults.—These soils have a surface mantle

or layer in the upper 75 cm that has both a low bulk density

and a high content of weakly crystalline minerals in at least

some part of the upper 75 cm. The soils are not known to occur

in the United States. The subgroup is provided for use in other

parts of the world.

Aquic Kandhapludults.—These soils have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). The soils

are of very small extent in the United States.

Arenic Kanhapludults.—These soils have a layer, starting

at the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class and is between 50 and 100 cm thick. They

are of very small extent in the United States. They are on the

coastal plain in the Southeastern United States. The natural

vegetation consisted of mixed forest plants. These soils are

used mostly as cropland or forest.

Arenic Plinthic Kanhapludults.—These soils have a layer,

starting at the mineral soil surface, that has a sandy or sandyskeletal particle-size class and is between 50 and 100 cm thick.

They also have 5 to 50 percent (by volume) plinthite in one or

more horizons within 150 cm of the mineral soil surface. These

soils are not known to occur in the United States. The subgroup

is provided for use in other parts of the world.

Fragiaquic Kanhapludults.—These soils have redox

depletions with low chroma and also aquic conditions at a

shallow depth for some time in normal years. They have fragic

soil properties in 30 percent or more of the volume of a layer

15 cm or more thick that has its upper boundary within 100 cm

of the mineral soil surface or in 60 percent or more of the

volume of a layer 15 cm or more thick anywhere in the soils.

These soils are not extensive in the United States.

Fragic Kanhapludults.—These soils have fragic soil

properties in 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm of the

mineral soil surface or in 60 percent or more of the volume of a

layer 15 cm or more thick anywhere in the soils. These soils

are not extensive in the United States.

Lithic Kanhapludults.—These soils have a lithic contact

within 50 cm of the mineral soil surface. In addition, they are

permitted to have any color, saturation, or redox feature

allowed in Kanhapludults. Lithic Kanhapludults are not known

to occur in the United States. The subgroup is provided for use

in other parts of the world.

Ombroaquic Kanhapludults.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

concentrations, a color value, moist, of 4 or more, and hue that

is 10YR or yellower and becomes redder with increasing depth

within 100 cm of the mineral soil surface. The soils are not

known to occur in the United States. They are defined for use

in other parts of the world.

Oxyaquic Kanhapludults.—These soils are saturated with

water within 100 cm of the mineral soil surface for 20 or more

consecutive days or 30 or more cumulative days in normal

years. In addition, the soils are permitted, but not required, to

have a kandic horizon that has 50 percent or more colors with

hue of 2.5YR or redder, a value, dry, of 3 or less, and moist and

dry color values that differ from each other by 1 unit or less

than 1 unit. These soils are considered intergrades to Aquults.

They are of very small extent in the United States.

Plinthaquic Kanhapludults.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox
Ultisols 761

depletions with chroma of 2 or less and also aquic conditions for

some time in normal years (or artificial drainage). They have 5 to

50 percent (by volume) plinthite in one or more horizons within

150 cm of the mineral soil surface. They are intergrades between

Plinthaquults and Kanhapludults. They are not known to occur

in the United States. The subgroup is defined for use in other

parts of the world.

Plinthic Kanhapludults.—These soils have 5 to 50 percent

(by volume) plinthite in some subhorizon within 150 cm of the

surface. They are not known to occur in the United States. The

subgroup is defined for use in other parts of the world.

Rhodic Kanhapludults.—These soils are like Typic

Kanhapludults, but the upper part of their kandic horizon has

hue of 2.5YR or redder, a color value, moist, of 3 or less, and a

dry value no more than 1 unit higher than the moist value.

Rhodic Kanhapludults are of small extent in the United States.

The natural vegetation consisted of forest plants. Slopes range

from nearly level to moderately steep. These soils are used

mostly as cropland or forest, but some are used as pasture or

homesites.

Paleudults

These are the very deep, more or less freely drained Udults

on very old stable land surfaces. These soils do not have a

kandic horizon. Many have a thick argillic horizon. The soils

have a clay distribution in which the percentage of clay does

not decrease from its maximum amount by as much as 20

percent within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases has at least

5 percent of the volume consisting of clay depletions on faces

of peds and there is at least a 3 percent (absolute) increase in

clay content below this layer. These soils do not have a

fragipan or a horizon in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume

within 150 cm of the mineral soil surface.

Paleudults are extensive in the Southeastern United States

and in the Middle Atlantic States. Slopes generally are gently

sloping to steep, but a few of the soils on coastal plains are

nearly level. The natural vegetation consisted of forest plants,

mostly hardwoods or mixed conifers and hardwoods. Many of

these soils have been cleared and are used as cropland or

pasture.

Definition

Paleudults are the Udults that:

1. Do not have a densic, lithic, or paralithic contact

within 150 cm of the soil surface;

2. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by more than 20

percent within 150 cm of the soil surface, or the layer in which

the percentage of clay decreases by more than 20 percent has at

least 5 percent of the volume consisting of skeletans on faces of

peds and there is at least a 3 percent (absolute) increase in clay

content below this layer;

3. Do not have a kandic horizon;

4. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface; and

5. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix in any subhorizon within

150 cm of the soil surface.

Key to Subgroups

HCEA. Paleudults that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

2. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower.

Vertic Paleudults

HCEB. Other Paleudults that have a horizon 5 cm or more

thick, either below an Ap horizon or at a depth of 18 cm or

more from the mineral soil surface, whichever is deeper, that

has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

2. Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Paleudults

HCEC. Other Paleudults that have:

1. In one or more layers either within 75 cm of the

mineral soil surface or, if the chroma throughout the upper

75 cm results from uncoated sand grains, within the upper

12.5 cm of the argillic horizon, redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations, and also aquic

conditions for some time in normal years (or artificial

drainage); and

2. A sandy or sandy-skeletal particle-size class throughout
762 Soil Taxonomy

a layer extending from the mineral soil surface to the top of an

argillic horizon at a depth of 50 cm or more; and

3. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthaquic Paleudults

HCED. Other Paleudults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon that is 50 cm or more below the mineral

soil surface; and

2. In one or more layers either within 75 cm of the

mineral soil surface or, if the chroma throughout the upper

75 cm results from uncoated sand grains, within the upper

12.5 cm of the argillic horizon, redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations, and also aquic

conditions for some time in normal years (or artificial

drainage).

Aquic Arenic Paleudults

HCEE. Other Paleudults that have both:

1. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface; and

2. In one or more layers either within 75 cm of the

mineral soil surface or, if the chroma throughout the upper

75 cm results from uncoated sand grains, within the upper

12.5 cm of the argillic horizon, redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations, and also aquic

conditions for some time in normal years (or artificial

drainage).

Plinthaquic Paleudults

HCEF. Other Paleudults that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm

or more thick that has its upper boundary within 100 cm

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm

or more thick; and

2. In one or more layers within 75 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations, and also aquic conditions for some time in

normal years (or artificial drainage).

Fragiaquic Paleudults

HCEG. Other Paleudults that have, in one or more layers

within 75 cm of the mineral soil surface, redox depletions with a

color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations and by aquic conditions

for some time in normal years (or artificial drainage).

Aquic Paleudults

HCEH. Other Paleudults that have anthraquic conditions.

Anthraquic Paleudults

HCEI. Other Paleludults that in normal years are saturated

with water in one or more layers within 100 cm of the mineral

soil surface for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Paleudults

HCEJ. Other Paleudults that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more

than 20 cm thick, each with an overlying eluvial horizon,

and above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon.

Lamellic Paleudults

HCEK. Other Paleudults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 to 100 cm; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthic Paleudults

HCEL. Other Paleudults that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Paleudults

HCEM. Other Paleudults that have both:

1. A sandy or sandy-skeletal particle-size class throughout
Ultisols 763

a layer extending from the mineral soil surface to the top of an

argillic horizon at a depth of 100 cm or more; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Grossarenic Plinthic Paleudults

HCEN. Other Paleudults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Paleudults

HCEO. Other Paleudults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

an argillic horizon at a depth of 50 to 100 cm; and

2. In all subhorizons in the upper 75 cm of the argillic

horizon or throughout the entire argillic horizon if it is less

than 75 cm thick, more than 50 percent colors that have all

of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the

moist value.

Arenic Rhodic Paleudults

HCEP. Other Paleudults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 to 100 cm.

Arenic Paleudults

HCEQ. Other Paleudults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 100 cm or more.

Grossarenic Paleudults

HCER. Other Paleudults that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or

more thick that has its upper boundary within 100 cm of the

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or

more thick.

Fragic Paleudults

HCES. Other Paleudults that have, in all subhorizons in the

upper 75 cm of the argillic horizon or throughout the entire

argillic horizon if it is less than 75 cm thick, more than 50

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Rhodic Paleudults

HCET. Other Paleudults.

Typic Paleudults

Definition of Typic Paleudults

Typic Paleudults are the Paleudults that:

1. Do not, in any layer either within 75 cm of the mineral soil

surface or, if the chroma throughout the upper 75 cm results

from uncoated sand grains, within the upper 12.5 cm of the

argillic horizon, have redox depletions with a color value,

moist, of 4 or more and chroma of 2 or less, accompanied by

redox concentrations and by aquic conditions;

2. Do not have anthraquic conditions;

3. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 cm or more;

4. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the soil surface;

5. In all parts of the upper 75 cm of the argillic horizon,

have 50 percent or less colors that have all of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist

value;

6. Have an argillic horizon that is finer than the sandy

particle-size class in some part of the upper 75 cm if the

argillic horizon is more than 75 cm thick or in any part if the

argillic horizon is less than 75 cm thick;

7. Do not have a horizon 5 cm or more thick, either below an

Ap horizon or at a depth of 18 cm or more from the mineral

soil surface, whichever is deeper, that has one or more of the

following:

a. In 25 percent or more of each pedon, cementation

by organic matter and aluminum, with or without iron;

or

b. Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

c. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon;

8. Have fragic soil properties:

a. In less than 30 percent of the volume of all layers 15 cm
764 Soil Taxonomy

or more thick that have an upper boundary within 100 cm of

the mineral soil surface; and

b. In less than 60 percent of the volume of all layers 15 cm

or more thick;

9. Do not have either:

a. Cracks within 125 cm of the mineral soil surface that

are 5 mm or more wide through a thickness of 30 cm or

more for some time in normal years, and slickensides or

wedge-shaped aggregates in a layer 15 cm or more thick

that has its upper boundary within 125 cm of the mineral

soil surface; or

b. A linear extensibility of 6.0 cm or more between the

mineral soil surface and either a depth of 100 cm or a

densic, lithic, or paralithic contact, whichever is shallower;

10. Have an argillic horizon that meets none of the following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness

of 5 cm or more (that may or may not be part of the

argillic horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic horizon) and one or more parts of the

argillic horizon 7.5 to 20 cm thick, each with an

overlying eluvial horizon; and

11. In normal years are not saturated with water in any layer

within 100 cm of the mineral soil surface for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Description of Subgroups

Typic Paleudults.—The central concept or Typic subgroup

of Paleudults is fixed on freely drained soils that have an

epipedon that is not both sandy and thick, that have little or no

plinthite, and that have an argillic horizon that is loamy or

clayey and is not composed of thin lamellae.

A fluctuating ground water table at a moderately shallow

depth, with or without redox depletions with low chroma, is a

property shared with Aquults and is used as the basis for

defining Aquic and Oxyaquic subgroups. A thick sandy layer,

starting at the mineral soil surface, is considered abnormal and

is used to define Arenic and Grossarenic subgroups. An

appreciable amount of plinthite also is considered abnormal

and is used to define the Plinthic subgroup. A dark red argillic

horizon is a property shared with Rhodudults and is used to

define the Rhodic subgroup. A sandy argillic horizon is used to

define the Psammentic subgroup. An argillic horizon composed

partly or wholly of lamellae is used to define the Lamellic

subgroup.

Typic Paleudults are of large extent in the Eastern and

Southeastern United States. The natural vegetation consisted of

forest plants. Slopes range from nearly level to steep. Where

slopes are suitable, many of the soils are used as cropland. The

steeper soils are used as forest. Some of the soils are used as

pasture or homesites.

Anthraquic Paleudults.—These soils have anthraquic

conditions. Nearly all of them have been used for rice in

irrigated paddies for long periods of time. Anthraquic

Paleudults are not known to occur in the United States. The

subgroup is provided for use in other parts of the world.

Aquic Arenic Paleudults.—These soils have a layer,

starting at the mineral soil surface, that is 50 cm or more thick

and has a sandy or sandy-skeletal particle-size class

throughout. They also have ground water that fluctuates in

depth or are artificially drained, and the zone in which the

water stands or formerly stood has redox depletions with low

chroma within 75 cm of the soil surface or in the upper 12.5

cm of the argillic horizon. Commonly, the argillic horizon has

more sand and less clay than the argillic horizon in the Typic

subgroup. The Aquic Arenic Paleudults in the United States

are mostly in areas of sandy deposits on the coastal plain in the

Southeastern States. The natural vegetation consisted of forest

plants. The soils are of small extent. They are nearly level or

gently sloping. Most are used as cropland or forest.

Aquic Paleudults.—These soils have, within 75 cm of the

soil surface, ground water that fluctuates in depth or are

artificially drained, and the zone in which water stands or

formerly stood has redox depletions with low chroma. These

soils are extensive on the coastal plains in the Southern United

States. The natural vegetation consisted of forest plants. These

soils generally are nearly level or gently sloping. Many are

used as cropland, and many are used as forest. Some are used

as pasture or homesites.

Arenic Paleudults.—These soils have a layer, starting at

the mineral soil surface, that is between 50 and 100 cm thick

and has a sandy or sandy-skeletal particle-size class, that is, the

texture is sand or loamy sand. The soils are otherwise like

Typic Paleudults in defined properties, but the argillic horizon

tends to have more sand and less clay than the one in the Typic

subgroup. In the United States, Arenic Paleudults occur on the

coastal plain from Maryland to Texas. The natural vegetation

consisted of forest plants. The soils are of moderate extent.

Slopes generally are nearly level to strongly sloping. Most of

the soils are used as cropland or forest, but some are used as

pasture.

Arenic Plinthaquic Paleudults.—These soils have a layer,

starting at the mineral soil surface, that is 50 cm or more thick
Ultisols 765

and has a sandy or sandy-skeletal particle-size class, that is, the

texture of the fine-earth fraction is sand or loamy sand. The

soils also have a small or moderate amount of plinthite in the

argillic horizon, and the ground water fluctuates at some depth

within the epipedon but is sometimes above the argillic

horizon. The subhorizons that have plinthite normally restrict

the movement of water, and the soils may have a perched water

table for short periods. These soils occur on the coastal plains

in the Southern United States. The natural vegetation consisted

of forest plants. These soils are of small extent. They are nearly

level or gently sloping. Most are used as cropland or forest.

Some are used as pasture.

Arenic Plinthic Paleudults.—These soils have some

plinthite in the argillic horizon and have a layer, starting at the

mineral soil surface, that is between 50 and 100 cm thick and

has a sandy or sandy-skeletal particle-size class, that is, the

texture of the fine-earth fraction is sand or loamy sand. The

soils are otherwise like Typic Paleudults in defined properties,

but they differ from the Typic subgroup in several respects. The

argillic horizon commonly has more sand and less clay than

the one in the Typic subgroup, the subhorizons that have

plinthite normally slow the movement of water, and the soils

may have a perched water table for short periods. The natural

vegetation consisted of forest plants. These soils are of small

extent in the United States. They are mostly on the coastal

plains in the Southern States. They are nearly level or gently

sloping. Most are used as cropland or forest. Some are used as

pasture.

Arenic Rhodic Paleudults.—These soils have a low color

value and are mostly dark red throughout the upper part of the

argillic horizon. The epipedon also is normally dark colored,

and there is a layer, starting at the mineral soil surface and

extending to a depth of 50 to 100 cm, that has a sandy or

sandy-skeletal particle-size class. The dark color is caused

chiefly by the large amount of free iron oxides rather than by

organic matter. These soils are not known to occur in the

United States. They are defined for use in other parts of the

world.

Fragiaquic Paleudults.—These soils have, within 75 cm of

the soil surface, ground water that fluctuates in depth or are

artificially drained, and the zone in which water stands or

formerly stood has redox depletions with low chroma. The soils

also have a large amount of soil aggregates with fragic soil

properties in a layer 15 cm or more thick. The amount of

plinthite in any subhorizon within a depth of 150 cm is

restricted to less than 5 percent. These soils are moderately

extensive in the Southern United States. They are nearly level

or gently sloping. Most are used as cropland or forest. Some

are used as pasture.

Fragic Paleudults.—These soils have a large amount of soil

aggregates with fragic soil properties in a layer 15 cm or more

thick. The amount of plinthite in any subhorizon is restricted to

less than 5 percent in any subhorizon within a depth of 150

cm. These soils are of small extent in the Southeastern United

States. Most of the soils are used as forest or cropland. Some

are used as pasture.

Grossarenic Paleudults.—These soils have a layer, starting

at the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class (a texture of sand or loamy sand in the fineearth fraction) and that is between 100 and 200 cm thick. The

argillic horizon tends to have appreciably more sand and less

clay than the one in the soils of the Typic subgroup.

Grossarenic Paleudults are moderately extensive on the coastal

plains in the Southern United States. The natural vegetation

consisted of forest plants. Slopes range from nearly level to

moderately steep. These soils are used mostly as cropland or

forest. Some are used as pasture or homesites.

Grossarenic Plinthic Paleudults.—These soils have a

layer, starting at the mineral soil surface, that has a sandy or

sandy-skeletal particle-size class (a texture of sand or loamy

sand in the fine-earth fraction) and that is between 100 and

200 cm thick. These soils have 5 to 50 percent plinthite in

some horizon within 150 cm of the soil surface. The argillic

horizon has appreciably more sand and less clay than the one

in Typic Paleudults. Grossarenic Plinthic Paleudults are of

small extent in the Southeastern United States. The natural

vegetation consisted of forest plants. These soils generally are

nearly level or gently sloping. They are used mostly as forest or

cropland.

Lamellic Paleudults.—These soils are similar to Typic

Paleudults, but they have an argillic horizon that consists

entirely of lamellae or is a combination of two or more

lamellae and one or more subhorizons with a thickness of 7.5

to 20 cm, each layer with an overlying eluvial horizon. In some

of the soils, the argillic horizon consists of one or more

subhorizons that are more than 20 cm thick, each with an

overlying eluvial horizon, and above these horizons there are

either two or more lamellae with a combined thickness of 5 cm

or more or a combination of lamellae and one or more parts of

the argillic horizon 7.5 to 20 cm thick, each with an overlying

eluvial horizon. These soils are of small extent in the

Southeastern United States. The natural vegetation consisted of

forest plants. These soils generally are nearly level or gently

sloping. They are used mostly as forest or cropland. Some are

used as pasture or homesites.

Oxyaquic Paleudults.—These soils are saturated with

water within 100 cm of the mineral soil surface for 20 or more

consecutive days and/or 30 or more cumulative days during

normal years. The soils are in scattered areas throughout the

Southeastern United States. Many were forested but have been

cleared and are used for crop production.

Plinthaquic Paleudults.—These soils have 5 to 50 percent

plinthite in some horizon within 150 cm of the soil surface.

Ground water in the soils fluctuates in depth, or there is

artificial drainage. The subhorizon in which water stands or

formerly stood has redox depletions with low chroma, or the

soil color is a result of the color of the uncoated sand grains.

The argillic horizon, especially the subhorizons that have
766 Soil Taxonomy

plinthite, tends to slow the movement of water, and there may

be ground water perched above these subhorizons for short

periods. These soils are of very small extent in the Southeastern

United States. The natural vegetation consisted of forest plants.

Slopes generally are nearly level or gently sloping. These soils

are used mostly as forest or cropland.

Plinthic Paleudults.—These soils have 5 to 50 percent

plinthite in some horizon within 150 cm of the soil surface.

The argillic horizon, especially the subhorizons that have

plinthite, tends to slow the movement of water. These soils

formed on the coastal plain in the Southeastern United States.

They are of moderate extent. The natural vegetation consisted

of forest plants. Slopes generally are nearly level to strongly

sloping. Plinthic Paleudults are used mostly as cropland or

forest. Some are used as pasture.

Psammentic Paleudults.—These soils have an argillic

horizon that has a sandy or sandy-skeletal particle-size class

throughout or throughout the upper 75 cm if it is more than 75

cm thick. The sand fraction of the Psammentic Paleudults in

the United States is dominantly quartz. The upper part of the

epipedon commonly is an albic horizon. These soils are of

small extent and occur only on the coastal plains of the

Southern States. The natural vegetation consisted of forest

plants. Slopes generally are nearly level to strongly sloping.

These soils are used mostly as forest or cropland. Some are

used as pasture or homesites.

Rhodic Paleudults.—These soils have a low color value

and are mostly dark red throughout the upper part of the

argillic horizon. The epipedon also is normally dark colored.

The dark color is mainly the result of a large amount of free

iron oxides rather than the content of organic matter, but

organic matter tends to be more abundant in these soils than in

Typic Paleudults. Most Rhodic Paleudults formed in basic

parent materials and tend to have more total phosphorus than

the soils of the Typic subgroup. Rhodic Paleudults are of small

extent in the Southeastern United States. The natural

vegetation consisted of forest plants. Slopes generally are

nearly level to moderately steep. Most of these soils are used as

cropland if slopes are gentle. Some of the soils, mainly the

most sloping ones, are used as forest or pasture.

Spodic Paleudults.—In these soils, the upper part of the B

horizon has a weak accumulation of amorphous materials and

the lower part is an argillic horizon. In the Spodic Paleudults

in the United States, the horizons above the argillic horizon

have a texture of sand or loamy sand. These soils are of very

small extent in the Southeastern United States. The natural

vegetation consisted of forest plants. The soils are nearly level

or gently sloping. They are used mostly as cropland or forest.

Vertic Paleudults.—These soils are high in expanding

clays and have cracks 5 mm or more wide, slickensides,

wedge-shaped aggregates, or a linear extensibility of 6.0 cm or

more between the mineral soil surface and either a depth of 100

cm or a densic, lithic, or paralithic contact, whichever is

shallower. The soils are considered intergrades between

Paleudults and Uderts. They are not known to occur in the

United States. The subgroup is provided for use in other parts

of the world.

Plinthudults

These are the more or less freely drained Udults that have a

large amount of plinthite in the argillic or kandic horizon.

They are mainly in intertropical regions and in some areas are

extensive. They are not known to occur in the United States.

The great group is provided for use in other parts of the world.

Definition

Plinthudults are the Udults that have plinthite that either

forms a continuous phase in, or constitutes more than half the

matrix of, one or more horizons within 150 cm of the mineral

soil surface.

Key to Subgroups

HCAA. All Plinthudults.

Typic Plinthudults

Rhodudults

These are the freely drained Udults that are of mid or low

latitudes and have a dark colored epipedon and an argillic

horizon with dark reddish colors throughout the upper part.

These soils do not have a fragipan, and they have less than 50

percent plinthite in all horizons within 150 cm of the mineral

soil surface. They have one of the following: (1) a densic,

lithic, paralithic, or petroferric contact within 150 cm of the

mineral soil surface or (2) with increasing depth, a clay

decrease of 20 percent or more (relative) from the maximum

clay content and less than 5 percent (by volume) skeletans on

faces of peds in any layer that has a 20 percent lower clay

content or, below that layer, the fine-earth fraction has a clay

increase of less than 3 percent. Many of the soils have a thin

argillic horizon. Rhodudults formed under forest vegetation

and commonly from basic rocks or sediments. As a

consequence, they tend to have more total phosphorus than

most other Udults. They also tend to be less erosive.

Rhodudults range from nearly level to very steep. Most of

these soils formed in sediments or on surfaces of the latter half

of the Pleistocene (Illinoian or Wisconsinan). Where slopes are

suitable, most of the soils are used as cropland. In many of the

soils, the plow layer includes material that was part of the

argillic horizon.

Definition

Rhodudults are the Udults that:

1. Have an epipedon that has a color value, moist, of 3 or less

throughout;

2. In all subhorizons in the upper 100 cm of the argillic
Ultisols 767

horizon or throughout the entire argillic horizon if it is less than

100 cm thick, have more than 50 percent colors with all of the

following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist

value;

3. Do not have a kandic horizon;

4. Do not have a fragipan with an upper boundary within 100

cm of the mineral soil surface;

5. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix in any subhorizon within

150 cm of the mineral soil surface; and

6. Have a clay distribution in which, with increasing depth,

the percentage of clay decreases from its maximum amount by

more than 20 percent within a depth of 150 cm below the soil

surface, and the layer in which the percentage of clay is less

than the maximum has less than 5 percent of the volume

consisting of skeletans on faces of peds or there is an increase

in clay content of less than 3 percent (absolute) below this

layer.

Key to Subgroups

HCFA. Rhodudults that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Rhodudults

HCFB. Other Rhodudults that have a sandy particle-size class

throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Rhodudults

HCFC. Other Rhodudults.

Typic Rhodudults

Definition of Typic Rhodudults

Typic Rhodudults are the Rhodudults that:

1. Have an argillic horizon that is finer than the sandy

particle-size class in some part of the upper 75 cm if the

argillic horizon is more than 75 cm thick or in any part if the

argillic horizon is less than 75 cm thick; and

2. Do not have a lithic contact within 50 cm of the soil

surface.

Description of Subgroups

Typic Rhodudults.—The central concept or Typic subgroup

of Rhodudults is fixed on well drained soils that are moderately

deep to very deep. The only features that cause exclusions from

the Typic subgroup are those that have been used as

conventions throughout this taxonomy. The absence of an

Aquic subgroup probably reflects the nature of the underlying

rock, which seems to preclude the presence of shallow ground

water. These soils formed mostly from basic rocks and

sediments.

Typic Rhodudults are of moderate extent in the Southeastern

United States. The natural vegetation consisted of forest plants.

Slopes are nearly level to very steep. Most of these soils are

used as cropland if slopes are gentle. Some of the soils, mainly

the most sloping ones, are used as forest or pasture.

Lithic Rhodudults.—These soils have a lithic contact

within 50 cm of the mineral soil surface. They are not known

to occur in the United States. The subgroup is provided for use

in other parts of the world.

Psammentic Rhodudults.—These soils have a sandy or

sandy-skeletal particle-size class throughout the argillic

horizon or throughout the upper 75 cm of the argillic horizon if

it is more than 75 cm thick. The soils are not known to occur

in the United States. The subgroup is provided for use in other

parts of the world.

Ustults

These are the more or less freely drained Ultisols that have an

ustic soil moisture regime and a relatively low content of organic

carbon. They occur in regions where rainfall is moderately low to

high but evapotranspiration exceeds precipitation. Some Ustults

have a single dry season each year, as in areas of a monsoon

climate, and others have alternating moist and dry periods

throughout the growing season. Ustults can have any soil

temperature regime but generally have one that is isomesic,

thermic, or warmer.

Most Ustults have an ochric epipedon that rests on an

argillic or kandic horizon, which may or may not contain

plinthite. A petroferric contact is common in some parts of the

world.

The vegetation commonly consists of forest or savanna

plants. These soils are of small extent in the United States.

Definition

Ustults are the Ultisols that:

1. Do not have both aquic conditions and the colors defined

for Aquults;

2. Have an ustic moisture regime;

3. Have less than 0.9 percent (by weighted average) organic

carbon in the upper 15 cm of the argillic or kandic horizon,

exclusive of any Ap horizon; and

4. Have less than 12 kg organic carbon in a unit volume
768 Soil Taxonomy

of 1 m2

 to a depth of 100 cm below the base of any O horizon or

the mineral soil surface.

Key to Great Groups

HDA. Ustults that have one or more horizons within 150 cm of

the mineral soil surface in which plinthite either forms a

continuous phase or constitutes one-half or more of the volume.

Plinthustults, p. 776

HDB. Other Ustults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Have a kandic horizon; and

3. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) skeletans on

faces of peds in the layer that has a 20 percent lower clay

content and, below that layer, a clay increase of 3 percent

or more (absolute) in the fine-earth fraction.

Kandiustults, p. 770

HDC. Other Ustults that have a kandic horizon.

Kanhaplustults, p. 773

HDD. Other Ustults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) skeletans on

faces of peds in the layer that has a 20 percent lower clay

content and, below that layer, a clay increase of 3 percent

or more (absolute) in the fine-earth fraction.

Paleustults, p. 776

HDE. Other Ustults that have both:

1. An epipedon that has a color value, moist, of 3 or less

throughout; and

2. In all subhorizons in the upper 100 cm of the argillic

horizon or throughout the entire argillic horizon if it is less

than 100 cm thick, more than 50 percent colors that have all

of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist

value.

Rhodustults, p. 777

HDF. Other Ustults.

Haplustults, p. 768

Haplustults

These are the Ustults that have a thin or moderately thick

zone of maximum clay content in the argillic horizon and are

very deep to any horizon that is one-half or more plinthite.

They are not both dark colored in the epipedon and dark red

throughout the argillic horizon. Slopes range from gentle to

very steep. Many of these soils are in tropical climates and are

farmed by means of shifting cultivation.

Haplustults are of small extent in the United States. They

are mainly in Texas, California, and Puerto Rico. They are

extensive in some parts of the world.

Definition

Haplustults are the Ustults that:

1. Do not have a kandic horizon;

2. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix in any subhorizon within

150 cm of the mineral soil surface;

3. Have a color value of 4 or more, moist, in some part of the

epipedon or have an argillic horizon that has a color with hue

less red than 2.5YR and a value of 5 or more, dry, or of 4 or

more, moist, in some subhorizon; and

4. Have a clay distribution in which, with increasing depth,

the percentage of clay decreases from its maximum amount by

more than 20 percent within 150 cm of the mineral soil

surface, and the layer in which the percentage of clay is less

than the maximum has less than 5 percent of the volume

consisting of skeletans on faces of peds or there is an increase

in clay content of less than 3 percent (absolute) below this

layer.

Key to Subgroups

HDFA. Haplustults that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplustults

HDFB. Other Haplustults that have a petroferric contact

within 100 cm of the mineral soil surface.

Petroferric Haplustults

HDFC. Other Haplustults that have, in one or more layers

both within the upper 12.5 cm of the argillic horizon and

within 75 cm of the mineral soil surface, redox depletions with
Ultisols 769

a color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations and by aquic conditions

for some time in normal years (or artificial drainage).

Aquic Haplustults

HDFD. Other Haplustults that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth

of 50 cm or more below the mineral soil surface.

Arenic Haplustults

HDFE. Other Haplustults that:

1. Have, in one or more horizons within 75 cm of the

mineral soil surface, redox concentrations, a color value,

moist, of 4 or more, and hue that is 10YR or yellower and

becomes redder with increasing depth within 100 cm of the

mineral soil surface; and

2. In normal years are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Ombroaquic Haplustults

HDFF. Other Haplustults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Haplustults

HDFG. Other Haplustults that have a CEC (by 1N NH4

OAc

pH 7) of less than 24 cmol(+)/kg clay in 50 percent or more of

the entire argillic horizon if less than 100 cm thick or of its

upper 100 cm.

Kanhaplic Haplustults

HDFH. Other Haplustults.

Typic Haplustults

Definition of Typic Haplustults

Typic Haplustults are the Haplustults that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have a petroferric contact within 100 cm of the

mineral soil surface;

3. Do not have, in any layer within the upper 12.5 cm of the

argillic horizon and within 75 cm of the mineral soil surface,

redox depletions with a color value, moist, of 4 or more and

chroma of 2 or less, accompanied by redox concentrations and

by aquic conditions;

4. Have, within 75 cm of the mineral soil surface, hue

of 7.5YR or redder in all horizons with a color value, moist,

of 4 or more if there are redox concentrations or if the hue

becomes redder with increasing depth within 100 cm of the

mineral soil surface;

5. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface;

6. Have a CEC of 24 cmol(+) or more per kg clay (by 1N

NH4

OAc pH 7) in the major part of the argillic horizon or in

the major part of the upper 100 cm of the argillic horizon if

this horizon is thicker than 100 cm; and

7. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic horizon at a depth of 50 to 100 cm.

Description of Subgroups

Typic Haplustults.—The central concept or Typic subgroup

of Haplustults is fixed on freely drained soils that are deep or

moderately deep to hard rock or to a petroferric contact, do not

have a thick epipedon of sand or loamy sand, have little or no

plinthite, and have clay that is at least semiactive.

Redox depletions with low chroma at a moderately shallow

depth accompanied by seasonal ground water in the irondepleted zone are properties shared with Aquults and define

the Aquic subgroup. A yellowish brown or olive brown color in

the upper part of the soils along with reddish redox

concentrations and a redder hue at some depth are associated

with wetness at the surface and define the Ombroaquic

subgroup. A thick sandy layer, starting at the mineral soil

surface, defines the Arenic subgroup. Clay that has low activity

suggests strong weathering, a property of Kanhaplustults, and

defines the Kanhaplic subgroup. Plinthite is considered

abnormal, and its presence is used to define the Plinthic

subgroup. A petroferric contact also is considered abnormal

and defines the Petroferric subgroup.

Typic Haplustults are of small extent in the United States.

They are mostly in Texas, California, Puerto Rico, and the

Virgin Islands. The natural vegetation consisted mostly of

coniferous forest plants in California, broadleaf forest or

savanna plants in Texas, and tropical forest plants in Puerto

Rico and the Virgin Islands. Slopes range from nearly level to

very steep. Some of these soils are used as forest. Where slopes

are suitable, many of the soils have been cleared and are used

as pasture, cropland, or homesites.

Aquic Haplustults.—These soils have ground water in the

upper part of the argillic horizon at some time of the year or

are artificially drained, and they have redox depletions with

low chroma in the horizons that are or were saturated. They are

not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Arenic Haplustults.—These soils have a thick layer of sand

or loamy sand, starting at the mineral soil surfac. The argillic

horizon normally has more sand and less clay than the one in
770 Soil Taxonomy

Typic Haplustults. Arenic Haplustults are rare in the United

States and are known to occur only in Texas.

Kanhaplic Haplustults.—These soils have a strongly

weathered clay fraction that has a moderately low or low CEC.

They are otherwise like Typic Haplustults in defined properties,

but they tend to have less extractable aluminum and a higher

pH. Kanhaplic Haplustults are not known to occur in the

United States or in Puerto Rico. The subgroup is provided for

use in other parts of the world.

Lithic Haplustults.—These soils have a shallow lithic

contact. They are not known to occur in the United States or in

Puerto Rico. The subgroup is provided for use in other parts of

the world.

Ombroaquic Haplustults.—These soils have yellowish

brown or olive brown colors in the upper horizons, commonly

on the faces of peds only, and have redder redox concentrations

inside the peds. The hue becomes redder with increasing depth.

These soils are not known to occur in the United States or in

Puerto Rico. The subgroup is provided for use in other parts of

the world.

Petroferric Haplustults.—These soils have a petroferric

contact within 100 cm of the mineral soil surface but are

otherwise similar to Typic Haplustults in defined properties.

They are not known to occur in the United States or in Puerto

Rico. The subgroup is provided for use in other parts of the

world.

Plinthic Haplustults.—These soils have a moderate or small

amount of plinthite in or below the argillic horizon but are

otherwise like Typic Haplustults in defined properties. They

probably have or have had a fluctuating level of ground water,

which is or was absent or is present for shorter periods in the

soils of the Typic subgroup. Plinthic Haplustults are not known

to occur in the United States. The subgroup is provided for use

in other parts of the world.

Kandiustults

Kandiustults are the Ustults that have a kandic horizon.

These soils have a clay distribution in which the percentage of

clay does not decrease from its maximum amount by as much

as 20 percent within a depth of 150 cm from the mineral soil

surface, or the layer in which the clay percentage decreases by

more than 20 percent has at least 5 percent of the volume

consisting of clay depletions on faces of peds and there is at

least a 3 percent (absolute) increase in clay content below this

layer. The soils do not have plinthite that forms a continuous

phase or constitutes more than half the volume in some

subhorizon within 150 cm of the soil surface. Most of the soils

have a thermic or warmer soil temperature regime. The natural

vegetation consisted of forest or savanna plants. Many of the

soils have been cleared and are used as cropland or pasture.

Definition

Kandiustults are the Ustults that:

1. Have a kandic horizon;

2. Do not have a densic, lithic, paralithic, or petroferric contact

within 150 cm of the mineral soil surface;

3. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases by more

than 20 percent has at least 5 percent of the volume consisting

of clay depletions on faces of peds and there is at least a 3

percent (absolute) increase in clay content below this layer; and

4. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the mineral soil surface.

Key to Subgroups

HDBA. Kandiustults that have an ECEC of 1.5 cmol(+)/kg

clay or less (sum of bases extracted with 1N NH4

OAc pH 7,

plus 1N KCl-extractable Al) in one or more horizons within

150 cm of the mineral soil surface.

Acrustoxic Kandiustults

HDBB. Other Kandiustults that have, in one or more layers

within 75 cm of the mineral soil surface, redox depletions with

a color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations and by aquic conditions

for some time in normal years (or artificial drainage).

Aquic Kandiustults

HDBC. Other Kandiustults that have both:

1. A sandy or sandy-skeletal particle-size class throughout

a layer extending from the mineral soil surface to the top of

a kandic horizon at a depth of 50 cm or more; and

2. 5 percent or more (by volume) plinthite in one or more

horizons within 150 cm of the mineral soil surface.

Arenic Plinthic Kandiustults

HDBD. Other Kandiustults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 50 cm or more.

Arenic Kandiustults

HDBE. Other Kandiustults that have both:

1. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface, a

fine-earth fraction with both a bulk density of 1.0 g/cm3

 or

less, measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0;

and

2. When neither irrigated nor fallowed to store moisture,

either:
Ultisols 771

a. A mesic or thermic soil temperature regime and a

moisture control section that is dry in some part for 135

or fewer of the cumulative days per year when the

temperature at a depth of 50 cm below the soil surface is

higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that is

dry in some or all parts for fewer than 120 cumulative

days per year when the temperature at a depth of 50 cm

below the soil surface is higher than 8 oC.

Udandic Kandiustults

HDBF. Other Kandiustults that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Kandiustults

HDBG. Other Kandiustults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kandiustults

HDBH. Other Kandiustults that, when neither irrigated nor

fallowed to store moisture, have either:

1. A thermic, mesic, or colder soil temperature regime and

a moisture control section that in normal years is dry in

some part for more than four-tenths of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Kandiustults

HDBI. Other Kandiustults that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for 135 or fewer of the cumulative days per year when

the temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil temperature

regime and a moisture control section that in normal years is

dry in some or all parts for fewer than 120 cumulative days

per year when the temperature at a depth of 50 cm below the

soil surface is higher than 8 o

C.

Udic Kandiustults

HDBJ. Other Kandiustults that have, in all subhorizons in

the upper 50 cm of the kandic horizon or throughout the entire

kandic horizon if it is less than 75 cm thick, more than 50

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Rhodic Kandiustults

HDBK. Other Kandiustults.

Typic Kandiustults

Definition of Typic Kandiustults

Typic Kandiustults are the Kandiustults that:

1. Do not have, in any layer within 75 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations and by aquic conditions;

2. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface;

3. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of a kandic horizon at a depth of 50 to 100 cm;

4. In all parts of the upper 75 cm of the kandic horizon,

have 50 percent or less colors that have all of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist

value;

5. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

6. When neither irrigated nor fallowed to store moisture:

a. If the soil temperature regime is thermic, mesic, or colder,

are moist in some part of the moisture control section (not

necessarily the same part) for more than
772 Soil Taxonomy

six-tenths of the time in normal years when the soil

temperature at a depth of 50 cm exceeds 5 o

C; or

b. If the soil temperature regime is hyperthermic,

isomesic, or warmer, have a moisture control section that in

normal years:

(1) Is moist in some or all parts for 90 or more

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

or

(2) Is dry in some part for less than six-tenths of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 5 oC;

7. When neither irrigated nor fallowed to store moisture:

a. If the soil temperature regime is mesic or thermic, are

dry in some part of the moisture control section for more

than 135 cumulative days per year when the soil

temperature at a depth of 50 cm exceeds 5 oC; or

b. If the soil temperature regime is hyperthermic,

isomesic, or warmer, are dry in some or all parts of the

moisture control section for 120 or more cumulative days

per year during a period when the soil temperature at a

depth of 50 cm exceeds 8 oC; and

8. Have an ECEC (sum of bases plus 1N KCl-extractable Al)

of more than 1.5 cmol(+)/kg clay in all subhorizons to a depth

of 150 cm below the mineral soil surface.

Description of Subgroups

Typic Kandiustults.—The central concept or Typic

subgroup of Kandiustults is fixed on freely drained, very deep

soils that have an ustic moisture regime that is approaching

neither the udic nor the aridic regime. The epipedon is not both

thick and sandy (not sand or loamy sand). These soils have less

than 5 percent plinthite and have a low, but not extremely low,

cation-exchange capacity. They do not have a surface mantle or

layer in the upper 75 cm that has both a low bulk density and a

high content of weakly crystalline minerals.

Ground water at a moderate depth, redox depletions with

low chroma at a shallow depth, and a fluctuating level of

ground water in the redox-depleted zone are properties shared

with Aquults and define the Aquic subgroup. A thick sandy

layer, starting at the mineral soil surface, defines the Arenic

subgroup.

Typic Kandiustults are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Acrustoxic Kandiustults.—These soils have an extremely

low cation-exchange capacity. Recycling of plant nutrients

from decaying vegetation is critical for plant growth on these

soils. The soils are not known to occur in the United States.

The subgroup is provided for use in other parts of the world.

Andic Kandiustults.—These soils have a surface mantle or

layer in the upper 75 cm that has both a low bulk density and a

high content of weakly crystalline minerals in at least some

part of the upper 75 cm. The soils are not known to occur in

the United States. The subgroup is provided for use in other

parts of the world.

Aquic Kandiustults.—These soils have ground water that

fluctuates in depth or are artificially drained, and the horizons

that are or were saturated have redox depletions with low

chroma. These soils are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Arenic Kandiustults.—These soils have a layer, starting at

the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class and is 50 cm or more thick. They are not

known to occur in the United States. The subgroup is provided

for use in other parts of the world.

Arenic Plinthic Kandiustults.—These soils have a layer,

starting at the mineral soil surface, that has a sandy or sandyskeletal particle-size class and is between 50 and 100 cm thick.

They also have 5 to 50 percent (by volume) plinthite in one or

more horizons within 150 cm of the mineral soil surface. These

soils are of very small extent in the United States.

Aridic Kandiustults.—These soils are drier than Typic

Kandiustults. They are intergrades between Argids and

Kandiustults. Aridic Kandiustults are not known to occur in

the United States. They are defined for use in other parts of the

world.

Plinthic Kandiustults.—These soils have 5 to 50 percent

(by volume) plinthite in some subhorizon within 150 cm of the

surface. They are not known to occur in the United States.

They are defined for use in other parts of the world.

Rhodic Kandiustults.—These soils are like Typic

Kandiustults, but the upper part of their kandic horizon has

hue of 2.5YR or redder, a color value, moist, of 3 or less, and a

dry value no more than 1 unit higher than the moist value.

Rhodic Kandiustults are not known to occur in the United

States. They are defined for use in other parts of the world.

Udandic Kandiustults.—These soils have a surface mantle

or layer in the upper 75 cm that has both a low bulk density

and a high content of weakly crystalline minerals in at least

some part of the upper 75 cm. They are dry in some part of the

moisture control section for less than four-tenths of the

cumulative days per year when the soil temperature at a depth

of 50 cm exceeds 5 o

C if the soil temperature regime is mesic

or thermic and are dry in some or all parts of the moisture

control section for fewer than 90 days during a period when the

soil temperature at a depth of 50 cm exceeds 8 oC if the soil

temperature regime is hyperthermic, isomesic, or warmer.

These soils are intergrades between Kandiustults and Udands.

They are not known to occur in the United States. They are

defined for use in other parts of the world.

Udic Kandiustults.—These soils are like Typic Kandiustults,

but they are dry in some part of the moisture control section for
Ultisols 773

less than four-tenths of the cumulative days per year when the

soil temperature at a depth of 50 cm exceeds 5 o

C if the soil

temperature regime is mesic or thermic and are dry in some or all

parts of the moisture control section for fewer than 90 days

during a period when the soil temperature at a depth of 50 cm

exceeds 8 oC if the soil temperature regime is hyperthermic,

isomesic, or warmer. These soils are intergrades between

Kandiustults and Kandiudults. They are not known to occur in

the United States. They are defined for use in other parts of the

world.

Kanhaplustults

These are the Ustults that have a kandic horizon and are

very deep to any horizon that is one-half or more plinthite.

They have a clay distribution in which the percentage of clay

decreases from its maximum amount by 20 percent or more

within a depth of 150 cm from the mineral soil surface, and the

layer in which the percentage of clay is less than the maximum

has less than 5 percent of the volume consisting of clay

depletions on faces of peds or there is an increase in clay

content of less than 3 percent (absolute) below this layer. These

soils have a thin or moderately thick zone of maximum clay

content. Slopes range from gentle to very steep. Many of the

soils are in tropical climates and are farmed by means of shifting

cultivation.

Kanhaplustults are not known to occur in the United States.

They are defined for use in other parts of the world.

Definition

Kanhaplustults are the Ustults that:

1. Have a kandic horizon;

2. Have a clay distribution in which the percentage of clay

decreases from its maximum amount by 20 percent or more

within a depth of 150 cm from the mineral soil surface, and the

layer in which the percentage of clay is less than the maximum

has less than 5 percent of the volume consisting of skeletans on

faces of peds or there is an increase in clay content of less than

3 percent (absolute) below this layer; and

3. Do not have plinthite that forms a continuous phase or

constitutes more than half the volume of some subhorizon

within 150 cm of the mineral soil surface.

Key to Subgroups

HDCA. Kanhaplustults that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Kanhaplustults

HDCB. Other Kanhaplustults that have an ECEC of 1.5

cmol(+)/kg clay or less (sum of bases extracted with 1N

NH4

OAc pH 7, plus 1N KCl-extractable Al) in one or more

horizons within 150 cm of the mineral soil surface.

Acrustoxic Kanhaplustults

HDCC. Other Kanhaplustults that have, in one or more

layers within 75 cm of the mineral soil surface, redox

depletions with a color value, moist, of 4 or more and chroma

of 2 or less, accompanied by redox concentrations and by

aquic conditions for some time in normal years (or artificial

drainage).

Aquic Kanhaplustults

HDCD. Other Kanhaplustults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of a kandic horizon at a

depth of 50 to 100 cm.

Arenic Kanhaplustults

HDCE. Other Kanhaplustults that have both:

1. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface, a

fine-earth fraction with both a bulk density of 1.0 g/cm3

 or

less, measured at 33 kPa water retention, and Al plus 1/2 Fe

percentages (by ammonium oxalate) totaling more than 1.0;

and

2. When neither irrigated nor fallowed to store moisture,

either:

a. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in

some part for 135 or fewer of the cumulative days per

year when the temperature at a depth of 50 cm below the

soil surface is higher than 5 oC; or

b. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than

120 cumulative days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC.

Udandic Kanhaplustults

HDCF. Other Kanhaplustults that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Kanhaplustults

HDCG. Other Kanhaplustults that have 5 percent or more (by

volume) plinthite in one or more horizons within 150 cm of the

mineral soil surface.

Plinthic Kanhaplustults

HDCH. Other Kanhaplustults that:

1. Have, in one or more horizons within 75 cm of the mineral

soil surface, redox concentrations, a color value, moist, of 4 or

more, and hue that is 10YR or yellower and becomes redder
774 Soil Taxonomy

with increasing depth within 100 cm of the mineral soil

surface; and

2. In normal years are saturated with water in one or more

layers within 100 cm of the mineral soil surface for either or

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Ombroaquic Kanhaplustults

HDCI. Other Kanhaplustults that, when neither irrigated nor

fallowed to store moisture, have either:

1. A thermic, mesic, or colder soil temperature regime and

a moisture control section that in normal years is dry in

some part for more than four-tenths of the cumulative days

per year when the soil temperature at a depth of 50 cm

below the soil surface is higher than 5 o

C; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years:

a. Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

b. Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature

at a depth of 50 cm below the soil surface is higher than

5 oC.

Aridic Kanhaplustults

HDCJ. Other Kanhaplustults that, when neither irrigated nor

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a

moisture control section that in normal years is dry in some

part for 135 or fewer of the cumulative days per year when

the temperature at a depth of 50 cm below the soil surface is

higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil

temperature regime and a moisture control section that in

normal years is dry in some or all parts for fewer than 120

cumulative days per year when the temperature at a depth of

50 cm below the soil surface is higher than 8 oC.

Udic Kanhaplustults

HDCK. Other Kanhaplustults that have, in all subhorizons in

the upper 50 cm of the kandic horizon or throughout the entire

kandic horizon if it is less than 50 cm thick, more than 50

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist

value.

Rhodic Kanhaplustults

HDCL. Other Kanhaplustults.

Typic Kanhaplustults

Definition of Typic Kanhaplustults

Typic Kanhaplustults are the Kanhaplustults that:

1. Do not have a lithic contact within 50 cm of the mineral

soil surface;

2. Do not have, in any layer within 75 cm of the mineral soil

surface, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations and by aquic conditions;

3. Have, within 75 cm of the mineral soil surface, hue

of 7.5YR or redder in all horizons with a color value, moist,

of 4 or more if there are redox concentrations or if the hue

becomes redder with increasing depth within 100 cm of the

mineral soil surface;

4. Have less than 5 percent (by volume) plinthite in all

subhorizons within 150 cm of the mineral soil surface;

5. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of a kandic horizon at a depth of 50 to 100 cm;

6. In all parts of the upper 50 cm of the kandic horizon,

have 50 percent or less colors that have all of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist

value;

7. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

8. Have an ECEC (sum of bases plus 1N KCl-extractable Al)

of more than 1.5 cmol(+)/kg clay in all subhorizons to a depth

of 150 cm below the mineral soil surface;

9. When neither irrigated nor fallowed to store moisture:

a. If the soil temperature regime is thermic, mesic, or

colder, are moist in some part of the moisture control

section (not necessarily the same part) for more than sixtenths of the time in normal years when the soil temperature

at a depth of 50 cm exceeds 5 oC; or

b. If the soil temperature regime is hyperthermic,
Ultisols 775

isomesic, or warmer, in normal years are moist in some or all

parts of the moisture control section for 180 or more days

during a period when the soil temperature at a depth of 50 cm

exceeds 8 o

C; and

10. When neither irrigated nor fallowed to store moisture:

a. If the soil temperature regime is mesic or thermic, are dry

in some part of the moisture control section for more than 135

cumulative days per year when the soil temperature at a

depth of 50 cm exceeds 5 oC; or

b. If the soil temperature regime is hyperthermic,

isomesic, or warmer, in normal years the moisture control

section:

(1) Is moist in some or all parts for fewer than 90

consecutive days per year when the temperature at a

depth of 50 cm below the soil surface is higher than 8 oC;

and

(2) Is dry in some part for six-tenths or more of the

cumulative days per year when the soil temperature at a

depth of 50 cm below the soil surface is higher than 5 oC.

Description of Subgroups

Typic Kanhaplustults.—The central concept or Typic

subgroup of Kanhaplustults is fixed on freely drained soils that

have an ustic moisture regime that is approaching neither the

udic nor the aridic regime. These soils are more than 50 cm

deep to a lithic contact. The epipedon is not both thick and

sandy (not sand or loamy sand). The soils have less than 5

percent plinthite and have a low, but not extremely low, cationexchange capacity. They do not have a surface mantle or layer

in the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals.

Soils that have, in the upper part of the kandic horizon, 50

percent or more colors with hue of 2.5YR or redder, a value,

dry, of 3 or less, and moist and dry color values that differ from

each other by 1 unit or less than 1 unit are excluded from Typic

Kanhaplustults because these properties are shared with

Rhodustults. Ground water at a moderate depth, redox

depletions with low chroma at a shallow depth, and a

fluctuating level of ground water in the redox-depleted zone

are properties shared with Aquults and define the Oxyaquic

and Aquic subgroups. A thick sandy layer, starting at the

mineral soil surface, defines the Arenic subgroup.

Typic Kanhaplustults are not known to occur in the United

States. They are defined for use in other parts of the world.

Acrudoxic Kanhaplustults.—These soils have an

extremely low cation-exchange capacity. Recycling of plant

nutrients from decaying vegetation is critical for plant growth

on these soils. The soils are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Andic Kanhaplustults.—These soils have a surface mantle

or layer in the upper 75 cm that has both a low bulk density and

a high content of weakly crystalline minerals in at least some

part of the upper 75 cm. The soils are not known to occur in the

United States. The subgroup is provided for use in other parts

of the world.

Aquic Kanhaplustults.—These soils have, in one or more

horizons within 75 cm of the mineral soil surface, redox

depletions with chroma of 2 or less and also aquic conditions

for some time in normal years (or artificial drainage). The soils

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Arenic Kanhaplustults.—These soils have a layer, starting

at the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class and is between 50 and 100 cm thick. They

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Aridic Kanhaplustults.—These soils are drier than Typic

Kanhaplustults. They are intergrades between Argids and

Kanhaplustults. Aridic Kanhaplustults are not known to occur

in the United States. They are defined for use in other parts of

the world.

Lithic Kanhaplustults.—These soils have a lithic contact

within 50 cm of the mineral soil surface. In addition, they are

permitted to have any color, saturation, or redox feature

allowed in Kanhaplustults. Lithic Kanhaplustults are not

known to occur in the United States. The subgroup is provided

for use in other parts of the world.

Ombroaquic Kanhaplustults.—These soils have, in one or

more horizons within 75 cm of the mineral soil surface, redox

concentrations, a color value, moist, of 4 or more, and hue that

is 10YR or yellower and becomes redder with increasing depth

within 100 cm of the mineral soil surface. The soils are not

known to occur in the United States. They are defined for use

in other parts of the world.

Plinthic Kanhaplustults.—These soils have 5 to 50 percent

(by volume) plinthite in some subhorizon within 150 cm of the

surface. They are not known to occur in the United States.

They are defined for use in other parts of the world.

Rhodic Kanhaplustults.—These soils are like Typic

Kanhaplustults, but the upper part of their kandic horizon has

hue of 2.5YR or redder, a color value, moist, of 3 or less, and a

dry value no more than 1 unit higher than the moist value.

Rhodic Kanhaplustults are not known to occur in the United

States. They are defined for use in other parts of the world.

Udandic Kanhaplustults.—These soils have a moisture

regime that borders on udic and have a surface mantle or layer

in the upper 75 cm that has both a low bulk density and a high

content of weakly crystalline minerals in at least some part of

the upper 75 cm. These soils are not known to occur in the

United States. They are defined for use in other parts of the

world.

Udic Kanhaplustults.—These soils are like Typic

Kanhaplustults, but they are dry in some part of the moisture

control section for less than four-tenths of the cumulative days
776 Soil Taxonomy

per year when the soil temperature at a depth of 50 cm exceeds

5 o

C if the soil temperature regime is mesic or thermic and are dry

in some or all parts of the moisture control section for fewer than

90 days during a period when the soil temperature at a depth of

50 cm exceeds 8 oC if the soil temperature regime is hyperthermic,

isomesic, or warmer. The soils are intergrades between

Kanhaplustults and Kanhapludults. Udic Kanhaplustults are not

known to occur in the United States. They are defined for use in

other parts of the world.

Paleustults

These are the more or less freely drained Ustults that have an

argillic horizon. They have a clay distribution in which the

percentage of clay does not decrease from its maximum amount

by as much as 20 percent within a depth of 150 cm from the

mineral soil surface, or the layer in which the clay percentage

decreases has at least 5 percent of the volume consisting of

skeletans on faces of peds and there is at least a 3 percent

(absolute) increase in clay content below this layer. These soils

have no horizon in which plinthite either forms a continuous

phase or constitutes one-half or more of the volume within 150

cm of the mineral soil surface. Many of the soils have a thick

argillic horizon. Commonly, there are small or moderate

amounts of plinthite at some depth in the soils. Paleustults are

on old stable surfaces that have gentle slopes. They are very

rare in the United States and are known to occur only in

California. The great group is provided for use elsewhere.

Definition

Paleustults are the Ustults that:

1. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of 20

percent or more (relative) from the maximum clay content;

or

b. Have 5 percent or more (by volume) skeletans on faces

of peds in the layer that has a 20 percent lower clay content

and, below that layer, a clay increase of 3 percent or more

(absolute) in the fine-earth fraction; and

2. Do not have any horizon within 150 cm of the mineral soil

surface in which plinthite either forms a continuous phase or

constitutes one-half or more of the volume; and

3. Do not have a kandic horizon.

Key to Subgroups

HDDA. All Paleustults.

Typic Paleustults

Plinthustults

These are the more or less freely drained Ustults that have a

large amount of plinthite. Slopes are mostly gentle or

moderate. These soils are not known to occur in the United

States or in Puerto Rico. The great group is provided for use

elsewhere.

Definition

Plinthustults are the Ustults that have one or more horizons

within 150 cm of the mineral soil surface in which plinthite

either forms a continuous phase or constitutes one-half or more

of the volume.

Key to Subgroups

HDAA. Plinthustults that have:

1. A densic, lithic, paralithic, or petroferric contact

within 150 cm of the mineral soil surface; or

2. Within 150 cm of the mineral soil surface, both:

a. With increasing depth, a clay decrease of 20 percent

or more (relative) from the maximum clay content; and

b. Less than 5 percent (by volume) skeletans on faces of

peds in the layer that has a 20 percent lower clay content

or, below that layer, a clay increase of less than 3 percent

(absolute) in the fine-earth fraction.

Haplic Plinthustults

HDAB. Other Plinthustults.

Typic Plinthustults

Definition of Typic Plinthustults

Typic Plinthustults are the Plinthustults that:

1. Do not have a densic, lithic, paralithic, or petroferric

contact within 150 cm of the mineral soil surface; and

2. Have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases by more

than 20 percent has at least 5 percent of the volume consisting

of skeletans on faces of peds and there is at least a 3 percent

(absolute) increase in clay content below this layer.

Description of Subgroups

Typic Plinthustults.—These are the very deep Plinthustults

that have a clay distribution in which the percentage of clay

does not decrease from its maximum amount by as much as 20

percent within a depth of 150 cm from the mineral soil surface,

or the layer in which the clay percentage decreases by more

than 20 percent has at least 5 percent of the volume consisting

of skeletans on faces of peds and there is at least a 3 percent

(absolute) increase in clay content below this layer. These soils

are not known to occur in the United States. They are defined

for use in other parts of the world.

Haplic Plinthustults.—These are the Plinthustults that are

moderately deep or that have a clay distribution in which the
Ultisols 777

percentage of clay decreases from its maximum amount by 20

percent or more within a depth of 150 cm from the mineral soil

surface, and the layer in which the clay percentage decreases

by more than 20 percent has less than 5 percent of the volume

consisting of skeletans on faces of peds or there is an increase

in clay content of less than 3 percent (absolute) below this

layer. These soils are not known to occur in the United States.

They are defined for use in other parts of the world.

Rhodustults

These are the Ustults that have a dark colored epipedon and

a dark red or dusky red argillic horizon. They are moderately

deep or have a clay distribution in which the percentage of clay

decreases from its maximum amount by 20 percent or more

within a depth of 150 cm from the mineral soil surface, and the

layer in which the clay percentage decreases by more than 20

percent has less than 5 percent of the volume consisting of

skeletans on faces of peds or there is an increase in clay content

of less than 3 percent (absolute) below this layer. These soils

formed mainly in material weathered from basic rocks. As a

consequence, they tend to have more total phosphorus than

most other Ustults.

Rhodustults have gentle to steep slopes. Most of the soils

formed in alluvium or on slopes of the later half of the

Pleistocene, either Illinoian or Wisconsinan.

Rhodustults are rare in the United States and are known to

occur only on the Pacific Trust Islands.

Definition

Rhodustults are the Ustults that:

1. Have an epipedon that has a color value, moist, of 3 or less

throughout;

2. In all subhorizons in the upper 100 cm of the argillic

horizon or throughout the entire argillic horizon if it is less

than 100 cm thick, have more than 50 percent colors with all

of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist

value;

3. Do not have plinthite that forms a continuous phase or

constitutes more than half the matrix in any subhorizon in the

upper 150 cm;

4. Have a clay distribution in which, with increasing depth,

the percentage of clay decreases from its maximum amount by

more than 20 percent within 150 cm of the mineral soil

surface, and the layer in which the percentage of clay is less

than the maximum has less than 5 percent of the volume

consisting of skeletans on faces of peds or there is an increase

in clay content of less than 3 percent (absolute) below this layer;

and

5. Do not have a kandic horizon.

Key to Subgroups

HDEA. Rhodustults that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Rhodustults

HDEB. Other Rhodustults that have a sandy particle-size

class throughout the upper 75 cm of the argillic horizon or

throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Rhodustults

HDEC. Other Rhodustults.

Typic Rhodustults

Definition of Typic Rhodustults

Typic Rhodustults are the Rhodustults that:

1. Have an argillic horizon that is finer than the sandy

particle-size class in some part of the upper 75 cm if the

argillic horizon is more than 75 cm thick or in any part if the

argillic horizon is less than 75 cm thick;

2. Do not have a lithic contact within 50 cm of the mineral

soil surface.

Description of Subgroups

Typic Rhodustults.—The central concept or Typic

subgroup of Rhodustults is fixed on well drained soils that are

moderately deep to very deep. These soils do not have a lithic

contact within 50 cm of the mineral soil surface. The argillic

horizon is finer than the sandy or sandy-skeletal particle-size

class. The absence of an Aquic subgroup probably reflects the

nature of the underlying rock, which seems to preclude the

presence of shallow ground water. These soils formed mostly

from basic rocks and sediments.

Typic Rhodustults are of small extent on the Pacific

Trust Islands of the United States. The natural vegetation

consisted of savanna plants. Slopes are nearly level to very

steep. Most of these soils are used as cropland if slopes are

gentle.

Lithic Rhodustults.—These soils have a lithic contact

within 50 cm of the mineral soil surface. They are not known

to occur in the United States. The subgroup is provided for use

in other parts of the world.

Psammentic Rhodustults.—These soils have a sandy or

sandy-skeletal particle-size class throughout the entire argillic

horizon or throughout the upper 75 cm of the argillic horizon if

this horizon is more than 75 cm thick. Psammentic

Rhodustults are not known to occur in the United States. The

subgroup is provided for use in other parts of the world.
778 Soil Taxonomy

Xerults

These are more or less freely drained Ultisols of

Mediterranean climates. These soils have a xeric moisture

regime and a moderate or small amount of organic matter. They

generally have an ochric or umbric epipedon that rests on a

brownish to reddish argillic or kandic horizon. They are not

extensive in the United States, except locally in California and

Oregon. They are gently sloping to very steep. Most of the

Xerults in the United States are in the mountains. The natural

vegetation consisted mostly of coniferous forest plants.

Definition

Xerults are the Ultisols that:

1. Have a xeric soil moisture regime;

2. Have less than 0.9 percent organic carbon in the upper 15

cm of the argillic horizon, exclusive of any Ap horizon;

3. Have less than 12 kg organic carbon in a unit volume

of 1 m2 to a depth of 100 cm below the base of any O horizon

or the mineral soil surface; and

4. Do not have both aquic conditions and the colors defined

for Aquults.

Key to Great Groups

HEA. Xerults that:

1. Do not have a densic, lithic, or paralithic contact

within 150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of

20 percent or more (relative) from the maximum clay

content; or

b. Have 5 percent or more (by volume) skeletans on

faces of peds or 5 percent or more (by volume) plinthite,

or both, in the layer that has a 20 percent lower clay

content and, below that layer, a clay increase of 3 percent

or more (absolute) in the fine-earth fraction.

Palexerults, p. 780

HEB. Other Xerults.

Haploxerults, p. 778

Haploxerults

These are the Xerults that have a clay distribution in which

the percentage of clay decreases from its maximum amount by

as much as 20 percent within a depth of 150 cm from the

mineral soil surface, and the layer in which the clay percentage

decreases has less than 5 percent of the volume consisting of

skeletans on faces of peds or there is an increase in clay content

of less than 3 percent (absolute) below this layer. These soils

typically have an ochric epipedon that rests on a brownish or

reddish argillic or kandic horizon. In the United States, they

occur mostly in the Sierra Nevada and Cascade Mountains and

support coniferous forest plants. The soils are moderately

extensive in those mountains but are rare elsewhere in the

United States.

Definition

Haploxerults are the Xerults that:

1. Have a densic, lithic, or paralithic contact within 150 cm

of the mineral soil surface; or

2. Within 150 cm of the mineral soil surface, have:

a. With increasing depth, a clay decrease of 20 percent or

more (relative) from the maximum clay content; and

b. Less than 5 percent (by volume) skeletans on faces of

peds in the layer that has a 20 percent lower clay content or,

below that layer, no clay increase of 3 percent or more

(absolute) in the fine-earth fraction.

Key to Subgroups

HEBA. Haploxerults that have both:

1. A lithic contact within 50 cm of the mineral soil

surface; and

2. In each pedon, a discontinuous argillic or kandic

horizon that is interrupted by ledges of bedrock.

Lithic Ruptic-Inceptic Haploxerults

HEBB. Other Haploxerults that have a lithic contact within

50 cm of the mineral soil surface.

Lithic Haploxerults

HEBC. Other Haploxerults that have, in one or more

subhorizons within the upper 25 cm of the argillic or kandic

horizon, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations and by aquic conditions for some time in

normal years (or artificial drainage).

Aquic Haploxerults

HEBD. Other Haploxerults that have, throughout one or

more horizons with a total thickness of 18 cm or more within

75 cm of the mineral soil surface, a fine-earth fraction with

both a bulk density of 1.0 g/cm3

 or less, measured at 33 kPa

water retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Haploxerults

HEBE. Other Haploxerults that have an argillic or kandic

horizon that:
Ultisols 779

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or more

subhorizons with a thickness of 7.5 to 20 cm, each layer with

an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more

than 20 cm thick, each with an overlying eluvial horizon,

and above these horizons there are either:

a. Two or more lamellae with a combined thickness of

5 cm or more (that may or may not be part of the argillic

or kandic horizon); or

b. A combination of lamellae (that may or may not be

part of the argillic or kandic horizon) and one or more

parts o the argillic or kandic horizon 7.5 to 20 cm thick,

each with an overlying eluvial horizon.

Lamellic Haploxerults

HEBF. Other Haploxerults that have a sandy particle-size

class throughout the upper 75 cm of the argillic or kandic

horizon or throughout the entire horizon if it is less than 75 cm

thick.

Psammentic Haploxerults

HEBG. Other Haploxerults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of an argillic or kandic

horizon at a depth of 50 to 100 cm.

Arenic Haploxerults

HEBH. Other Haploxerults that have a sandy or sandyskeletal particle-size class throughout a layer extending from

the mineral soil surface to the top of an argillic or kandic

horizon at a depth of 100 cm or more.

Grossarenic Haploxerults

HEBI. Other Haploxerults.

Typic Haploxerults

Definition of Typic Haploxerults

Typic Haploxerults are the Haploxerults that:

1. Do not have, in any subhorizon within the upper 25 cm of

the argillic horizon, redox depletions with a color value, moist,

of 4 or more and chroma of 2 or less, accompanied by redox

concentrations and by aquic conditions;

2. Do not have a lithic contact within 50 cm of the mineral

soil surface;

3. Have an argillic or kandic horizon that is finer than the

sandy particle-size class in some part of the upper 75 cm if the

argillic or kandic horizon is more than 75 cm thick or in any

part if the argillic or kandic horizon is less than 75 cm thick;

4. Do not have, throughout a cumulative thickness of 18 cm

or more and within a depth of 75 cm, a bulk density, in the

fraction less than 2.0 mm in size, of 1.0 g/cm3

 or less,

measured at 33 kPa water retention, and acid-oxalateextractable aluminum plus 1

/2 acid-oxalate-extractable iron of

more than 1.0 percent;

5. Do not have a sandy or sandy-skeletal particle-size class

throughout a layer extending from the mineral soil surface to

the top of an argillic or kandic horizon at a depth of 50 to 100

cm; and

6. Have an argillic or kandic horizon that meets none of the

following:

a. Consists entirely of lamellae; or

b. Is a combination of two or more lamellae and one or

more subhorizons with a thickness of 7.5 to 20 cm, each

layer with an overlying eluvial horizon; or

c. Consists of one or more subhorizons that are more than

20 cm thick, each with an overlying eluvial horizon, and

above these horizons there are either:

(1) Two or more lamellae with a combined thickness

of 5 cm or more (that may or may not be part of the

argillic or kandic horizon); or

(2) A combination of lamellae (that may or may not be

part of the argillic or kandic horizon) and one or more

parts of the argillic or kandic horizon 7.5 to 20 cm thick,

each with an overlying eluvial horizon.

Description of Subgroups

Typic Haploxerults.—The central concept or Typic

subgroup of Haploxerults is fixed on freely drained soils that

are deep or moderately deep to hard rock, have an epipedon

that is not both thick and sandy (not sand or loamy sand), have

a continuous argillic or kandic horizon throughout the pedon,

and do not have a surface mantle that is influenced by

pyroclastic materials. Most of the Haploxerults in the United

States are Typic Haploxerults. Typic Haploxerults occur mostly

in the Sierra Nevada and Cascade Mountains in California and

Oregon. The natural vegetation consists mostly of coniferous

forest plants, but in some areas it consists of savanna plants or

is dominated by shrubs. These soils are of moderate extent.

Most are used as forest. Where slopes are suitable, some of the

soils have been cleared and are used as cropland, pasture, or

homesites.

Andic Haploxerults.—These soils have a surface mantle or

layer in the upper 75 cm that has both a low bulk density and a

high content of weakly crystalline minerals in at least some

part of the upper 75 cm. The soils are not known to occur in

the United States. They are defined for use in other parts of the

world.

Aquic Haploxerults.—These soils have redox depletions

with low chroma and also aquic conditions at a shallow depth

for some time in normal years. The soils are not known to
780 Soil Taxonomy

occur in the United States. They are defined for use in other

parts of the world.

Arenic Haploxerults.—These soils have a layer, starting at

the mineral soil surface, that has a sandy or sandy-skeletal

particle-size class and is between 50 and 100 cm thick. The

soils are not known to occur in the United States. They are

defined for use in other parts of the world.

Grossarenic Haploxerults.—These soils have a layer,

starting at the mineral soil surface and extending to the top of

the argillic or kandic horizon, that has a sandy or sandyskeletal particle-size class and is more than 100 cm thick. The

soils are not known to occur in the United States. The subgroup

is provided for use in other parts of the world.

Lamellic Haploxerults.—These soils have an argillic or

kandic horizon that consists entirely of lamellae or is a

combination of two or more lamellae and one or more

subhorizons with a thickness of 7.5 to 20 cm, each layer with

an overlying eluvial horizon. In some of the soils, the argillic

or kandic horizon consists of one or more subhorizons that are

more than 20 cm thick, each with an overlying eluvial horizon,

and above these horizons there are either two or more lamellae

with a combined thickness of 5 cm or more or a combination of

lamellae and one or more parts of the argillic or kandic horizon

7.5 to 20 cm thick, each with an overlying eluvial horizon.

Lamellic Haploxerults are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Lithic Haploxerults.—These soils are like Typic

Haploxerults, but they have a lithic contact within 50 cm of the

mineral soil surface. They are not known to occur in the United

States. The subgroup is provided for use in other parts of the

world.

Lithic Ruptic-Inceptic Haploxerults.—These soils have a

lithic contact within 50 cm of the mineral soil surface and an

intermittent argillic or kandic horizon. They characteristically

have an irregular or wavy boundary at the lithic contact. The

argillic or kandic horizon typically does not occur in the parts

of the pedon that have a very shallow lithic contact. These soils

are not known to occur in the United States. The subgroup is

provided for use in other parts of the world.

Psammentic Haploxerults.—These soils have an argillic or

kandic horizon that has a sandy or sandy-skeletal particle-size

class throughout or throughout the upper 75 cm if the horizon

is more than 75 cm thick. The soils are not known to occur in

the United States. The subgroup is provided for use in other

parts of the world.

Palexerults

These are the Xerults that have a clay distribution in which

the percentage of clay does not decrease from its maximum

amount by as much as 20 percent within a depth of 150 cm

from the mineral soil surface, or the layer in which the clay

percentage decreases has at least 5 percent of the volume

consisting of skeletans on faces of peds and there is at least a 3

percent increase in clay content below this layer. These soils

are mainly on old stable or metastable surfaces in the Cascade

and coastal mountains of Oregon and California. Slopes are

gentle to very steep. The soils are probably rare in the world,

but they may be extensive locally in areas of humid

Mediterranean climates.

Definition

Palexerults are the Xerults that:

1. Do not have a densic, lithic, or paralithic contact

within 150 cm of the mineral soil surface; and

2. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease of 20

percent or more (relative) from the maximum clay content;

or

b. Have 5 percent or more (by volume) skeletans on faces

of peds in the layer that has a 20 percent lower clay content

and, below that layer, a clay increase of 3 percent or more

(absolute) in the fine-earth fraction.

Key to Subgroups

HEAA. Palexerults that have both:

1. In one or more subhorizons within the upper 25 cm of

the argillic or kandic horizon, redox depletions with a color

value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations, and also aquic

conditions for some time in normal years (or artificial

drainage); and

2. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

a fine-earth fraction with both a bulk density of 1.0 g/cm3

or less, measured at 33 kPa water retention, and Al plus

1

/2 Fe percentages (by ammonium oxalate) totaling more

than 1.0.

Aquandic Palexerults

HEAB. Other Palexerults that have, in one or more

subhorizons within the upper 25 cm of the argillic or kandic

horizon, redox depletions with a color value, moist, of 4 or

more and chroma of 2 or less, accompanied by redox

concentrations and by aquic conditions for some time in

normal years (or artificial drainage).

Aquic Palexerults

HEAC. Other Palexerults that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm

of the mineral soil surface, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water
Ultisols 781

retention, and Al plus 1

/2 Fe percentages (by ammonium oxalate)

totaling more than 1.0.

Andic Palexerults

HEAD. Other Palexerults.

Typic Palexerults

Definition of Typic Palexerults

Typic Palexerults are the Palexerults that:

1. Do not have, in one or more subhorizons within the

upper 25 cm of the argillic or kandic horizon, redox depletions

with a color value, moist, of 4 or more and chroma of 2 or less,

accompanied by redox concentrations and by aquic conditions

for some time in normal years;

2. Do not have, throughout one or more horizons with a total

thickness of 18 cm or more within 75 cm of the mineral soil

surface, a fine-earth fraction with both a bulk density of 1.0

g/cm3

 or less, measured at 33 kPa water retention, and Al plus 1

/2 Fe percentages (by ammonium oxalate) totaling more than

1.0.

Description of Subgroups

Typic Palexerults.—The central concept or Typic subgroup

of Palexerults is fixed on well drained soils that are not

significantly influenced by volcanic ash. These soils are on old

landscapes, and in some areas the clay mineralogy is

influenced by kaolinite. The soils occur in the Pacific

Northwest and are used for timber production.

Andic Palexerults.—These are the well drained Palexerults

that are significantly influenced by volcanic ash. When

weathered, the volcanic ash influences P-retention, porosity,

and other soil properties. These soils occur in the Pacific

Northwest and are used for timber production.

Aquandic Palexerults.—These soils have aquic conditions

in the upper 25 cm of the argillic or kandic horizon and are

significantly influenced by volcanic ash. The soils occur in the

Pacific Northwest and are used for timber production.

Aquic Palexerults.—These soils have aquic conditions in

the upper 25 cm of the argillic or kandic horizon but are not

significantly influenced by volcanic ash. The soils occur in the

Pacific Northwest and are used for timber production.

783

The central concept of Vertisols is that of clayey soils thathave deep, wide cracks for some time during the year

and have slickensides within 100 cm of the mineral soil

surface. They shrink when dry and swell when moistened.

Vertisols make up a relatively homogeneous order because of

the amounts and kinds of clay common to them; however, their

microvariability within a pedon is great. Before the advent of

modern classification systems, these soils were already well

known for their characteristic color, the cracks they produce

during the dry season, and the difficulty of their engineering

properties.

In many countries where Vertisols are extensive, they are

known by local names, such as cracking clays (Australia),

Adobe (Philippines), Shachiang (China), Black Cotton soils

(India), Smolnitza (Bulgaria, Rumania), Tirs (Morocco),

Makande (Malawi), Vleigrond (South Africa), and Sonsosuite

(Nicaragua). In addition, numerous coined terms have been

used to identify the soils. Examples are Margalite soils

(Indonesia), Densinegra soils (Angola), and Grumusols

(United States).

These soils generally are sticky in the wet season and hard

in the dry season, so they require special cultivation practices

regardless of whether modern equipment or traditional

implements, such as a hoe or bullock-drawn plow, are used.

Because their unique properties restrict engineering uses, the

soils are well known among engineers. The movement of these

soils can tilt trees; throw fenceposts, telephone poles, and

power poles out of line; and break pipelines, highway

pavements, and the masonry foundations of buildings.

Vertisols are mapped in many countries. The largest areas

are in Australia (80,000,000 ha), India (73,000,000 ha), the

Sudan (50,000,000 ha), and the United States (18,000,000 ha).

The soil moisture regime is ustic in about 65 percent of the

areas where the Vertisols occur, aridic in 18 percent of the

areas, udic in 13 percent, and xeric in 4 percent. The defined

moisture regimes, however, have little significance in areas of

these soils because, when rainfall occurs, the water commonly

runs into the cracks, so that the soils are remoistened from both

above and below. Because of the difficulty in defining soil

moisture regimes in Vertisols, the duration that cracks open

CHAPTER 20

Vertisols1

and close are used to differentiate the various soil moisture

regimes. Vertisols are known to occur in all soil temperature

regimes that are cryic and warmer.

The shrink-swell phenomenon, which is responsible for the

genesis and behavior of Vertisols, is a complex, dynamic, but

incompletely understood set of processes. Expressions of this

phenomenon are linear and normal gilgai, cyclic horizons,

surface cracking upon desiccation, and the formation of

slickensides. Of these properties, cracks when the soils are dry

and slickensides are the unifying morphogenetic markers in all

Vertisols. Although the process of shrinking and swelling is

important in Vertisols, it does not preclude the formation of

diagnostic horizons and features. For example, Vertisols can

have calcic, gypsic, or salic horizons. Taxa have been

developed to accommodate these diagnostic horizons and

features.

Internal movement affects the thickness of soil horizons,

which can vary widely within a pedon. A black A horizon, for

example, may be only a few centimeters thick or even absent

on microknolls but is more than 100 cm thick in

microdepressions. The organic-matter content and the depth to

carbonates or to a Bk horizon can be equally variable.

Shrink-swell processes in soils are related to the total

content of clay, the content of fine clay, and mineralogy.

Vertisols generally have a high clay content (50 to 70 percent)

and a relatively large proportion of fine clay in the clay

fraction. The clays in Vertisols consist predominantly of 2:1-

and 2:2-layer clay minerals, but some have considerable

amounts of other clay minerals. Apart from the amounts and

types of clay, a number of other factors determine the

morphological features of Vertisols. Prior soil moisture content,

for example, is a very important factor in the shrink-swell

process; vertic features are best expressed where the soil has

undergone maximum change from a wet to a dry state. The

moisture change by itself, however, is insufficient to induce all

the vertic properties. To produce movement along the

slickensides, there must be a confining pressure, which is

provided by the thickness of the soil material above the

slickensides. The shrink-swell potential of the clays may be

reduced by an admixture of organic matter, carbonates, or other

particles. The coefficient of linear extensibility (COLE)

normally ranges from 0.07 to 0.2.

Intergrades to Vertisols are recognized in several of the

1This chapter was rewritten in 1992 following the recommendations of the International

Committee on the Classification of Vertisols (ICOMERT), chaired by Dr. Juan Comerma.
784 Soil Taxonomy

other soil orders. There are basically two kinds of intergrades,

although both are considered in the same subgroup. One

consists of soils that show evidence of swelling and shrinking

as a result of changes from a wet to a dry state but that do not

meet the minimum requirements for Vertisols. The intergrades

of the other kind show little or no evidence of actual soil

movement, but they have potential for soil movement because

of the relatively high COLE. These intergrades, however, do

not become dry enough or moist enough for soil movement to

occur, except in years with unusually low or abnormally high

precipitation.

Vertisols generally have gentle slopes, although a few are

strongly sloping. The natural vegetation is predominantly

grass, savanna, open forest, or desert shrub.

Most Vertisols are well suited to mechanized farming if

there is plenty of rainfall or irrigation water and if suitable

management practices are followed. Large areas of Vertisols in

the world are not farmed, however, because their cultivation

would require too much energy, especially where traditional,

low-input methods are used. This constraint is a major limiting

land-use characteristic of Vertisols.

Irrigation of Usterts, Xererts, and Torrerts presents special

problems because of very slow permeability. Bypass flow

through open cracks is common. Because the permeability of

these soils is so slow, irrigation may result in waterlogging and

a buildup of salinity unless adequate artificial drainage is

provided. A drainage system designed for Alfisols or Ultisols

may be totally inadequate for Vertisols.

Definition of Vertisols and Limits Between

Vertisols and Soils of Other Orders

Vertisols are mineral soils that have all of the following:

1. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

structural units that have their long axes tilted 10 to 60 degrees

from the horizontal; and

2. A weighted average of 30 percent or more clay in the fineearth fraction either between the mineral soil surface and a

depth of 18 cm or in an Ap horizon, whichever is thicker, and

30 percent or more clay in the fine-earth fraction of all

horizons between a depth of 18 cm and either a depth of 50 cm

or a densic, lithic, or paralithic contact, a duripan, or a

petrocalcic horizon if shallower; and

3. Cracks2

 that open and close periodically.

Limits Between Vertisols and Soils of Other

Orders

The definition of Vertisols must provide criteria that separate

Vertisols from all other soil orders. The aggregate of these

criteria defines the limits of Vertisols in relation to the other

known kinds of soil.

1. Unlike Gelisols, Vertisols do not have permafrost

within 100 cm of the soil surface or both permafrost within

200 cm of the soil surface and gelic materials within 100 cm

of the soil surface.

2. Unlike Andisols, Vertisols do not have andic soil

properties in 60 percent or more of the thickness between

either the mineral soil surface or the top of an organic layer

with andic soil properties, whichever is shallower, and a depth

of 60 cm or a densic, lithic, or paralithic contact, a duripan, or

a petrocalcic horizon, whichever is shallowest.

3. Unlike Spodosols, Vertisols do not have a spodic horizon

or an Ap horizon consisting of spodic materials.

4. Unlike Oxisols, Vertisols do not have, within 150 cm of

the mineral soil surface, an oxic horizon or a kandic horizon

that meets the weatherable-mineral requirements for an oxic

horizon and also 40 percent or more clay in the surface 18 cm

after mixing.

5. Unlike Alfisols, Ultisols, Inceptisols, Aridisols, and

Entisols, Vertisols have the following properties:

a. A layer 25 cm or more thick, with an upper boundary

within 100 cm of the mineral soil surface, that has either

slickensides close enough to intersect or wedge-shaped

structural units that have their long axes tilted 10 to 60

degrees from the horizontal; and

b. A weighted average of 30 percent or more clay in the

fine-earth fraction either between the mineral soil surface

and a depth of 18 cm or in an Ap horizon, whichever is

thicker, and 30 percent or more clay in the fine-earth

fraction of all horizons between a depth of 18 cm and either

a depth of 50 cm or a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon if shallower; and

c. Cracks that open and close periodically.

Representative Pedon and Data

Following is a description of a representative Vertisol. Data

for the pedon identified in this description are given in the

table “Characterization Data for a Vertisol.”

Classification: Fine, smectitic, isohyperthermic Typic Haplustert

Site identification number: 90P0616

Location: Icrasat Prod. Agriculture Field #Bw1, India

Latitude: 16 degrees 00 minutes 00 seconds N.

2

A crack is a separation between gross polyhedrons. If the surface horizon is strongly selfmulching, i.e., a mass of loose granules, or if the soil is cultivated while cracks are open, the

cracks may be largely filled with granular materials from the surface, but they are open in the

sense that the polyhedrons are separated. A crack is regarded as open if it controls the

infiltration and percolation of water in a dry, clayey soil.
Vertisols 785

Longitude: 78 degrees 00 minutes 00 seconds E.

Landscape: Plains

Landform: Playa

Microrelief: 20 to 50 cm, linear

Slope: 1 percent, plane, northeast facing

Annual precipitation: 760 mm

Weather station: Icrasat

Soil moisture regime: Ustic

Permeability class: Moderately slow

Drainage class: Well drained

Depth to water table: More than 200 cm

Land use: Cropland

Vegetation: Sorghum, pigeon pea

Hazard of erosion or deposition: Slight

Runoff: None

Parent material: Alluvium derived from igneous material

Described by: R.J. Engel

In the following pedon description, colors are for moist soil

unless otherwise indicated.

Ap—0 to 15 cm; dusky red (2.5YR 3/2), crushed, clay;

moderate medium subangular blocky structure parting to

moderate very fine and fine subangular blocky; very firm,

very sticky and very plastic; many very fine and fine roots

throughout; many very fine and fine vesicular and tubular

pores; neutral (pH 7.2); 5 percent igneous pebbles; abrupt

smooth boundary.

AB—15 to 30 cm; very dark gray (10YR 3/1), crushed, clay;

moderate fine and medium subangular blocky structure;

very firm, very sticky and very plastic; common very fine

and fine roots throughout; many very fine and fine

vesicular and tubular pores; neutral (pH 7.0); 2 percent

igneous pebbles; clear wavy boundary.

Bss1—30 to 53 cm; very dark gray (10YR 3/1), crushed, clay;

strong fine angular blocky structure parting to strong fine

subangular blocky; very firm, very sticky and very plastic;

common very fine and fine roots between peds; common

very fine and fine tubular pores; few discontinuous distinct

intersecting slickensides on horizontal faces of peds;

neutral (pH 7.0); 1 percent igneous pebbles; clear wavy

boundary.

Bss2—53 to 89 cm; very dark gray (10YR 3/1), crushed,

clay; strong fine angular blocky structure; very firm, very

sticky and very plastic; few very fine and fine roots

between peds; common very fine and fine tubular pores;

common continuous distinct intersecting slickensides on

horizontal faces of peds; neutral (pH 7.0); gradual wavy

boundary.

Bss3—89 to 122 cm; very dark grayish brown (2.5Y 3/2),

crushed, clay; strong fine and medium angular blocky

structure; very firm, very sticky and very plastic; few very

fine and fine roots between peds; common very fine and

fine tubular pores; common continuous distinct

intersecting slickensides on horizontal faces of peds;

neutral (pH 7.0); gradual wavy boundary.

Bssck1—122 to 155 cm; dark grayish brown (2.5Y 4/2), crushed,

clay; strong medium and coarse angular blocky structure;

very firm, very sticky and very plastic; few very fine and

fine roots between peds; common continuous distinct

intersecting slickensides on horizontal faces of peds;

common irregular carbonate concretions and common

medium and coarse rounded dark concretions; moderately

alkaline (pH 8.0); gradual wavy boundary.

Bssck2—155 to 193 cm; dark grayish brown (2.5Y 4/2),

crushed, clay; strong medium and coarse angular blocky

structure; very firm, very sticky and very plastic; few very

fine and fine roots between peds; common continuous

distinct intersecting slickensides on horizontal faces of

peds; common irregular carbonate concretions and

common medium and coarse rounded dark concretions;

moderately alkaline (pH 8.0); clear smooth boundary.

Bck—193 to 234 cm; olive brown (2.5Y 4/4), crushed, clay;

moderate medium and coarse angular blocky structure;

very firm, very sticky and very plastic; many irregular

carbonate concretions and common medium and coarse

rounded dark concretions; moderately alkaline (pH 8.2).

Key to Suborders

FA. Vertisols that have, in one or more horizons within 50 cm

of the mineral soil surface, aquic conditions for some time in

normal years (or artificial drainage) and one or both of the

following:

1. In more than half of each pedon, either on faces of peds

or in the matrix if peds are absent, 50 percent or more

chroma of either:

a. 2 or less if redox concentrations are present; or

b. 1 or less; or

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquerts, p. 787

FB. Other Vertisols that have a cryic soil temperature regime.

Cryerts, p. 796

FC. Other Vertisols that in normal years have both:

1. A thermic, mesic, or frigid soil temperature regime; and

2. If not irrigated during the year, cracks that remain both:

a. 5 mm or more wide, through a thickness of 25 cm or

more within 50 cm of the mineral soil surface, for 60 or

more consecutive days during the 90 days following the

summer solstice; and
786 Soil Taxonomy

Characterization Data for a Vertisol

 SITE IDENTIFICATION NO.: 90P0616

 CLASSIFICATION: FINE, SMECTITIC, ISOHYPERTHERMIC TYPIC HAPLUSTERT

 GENERAL METHODS: 1B1A, 2A1, 2B

 -1- -2- -3- -4- -5- -6- -7- -8- -9- -10- -11- -12- -13- -14- -15- -16- -17- -18- -19- -20-

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - -TOTAL - - -)(- -CLAY- -)(- -SILT- -)(- - - - - -SAND- - - - - -)(-COARSE FRACTIONS(mm)-)(>2mm)

 CLAY SILT SAND FINE CO3 FINE COARSE VF F M C VC - - - - WEIGHT - - - - WT

 SAMPLE DEPTH HORIZON LT .002 .05 LT LT .002 .02 .05 .10 .25 .5 1 2 5 20 .1- PCT OF

 NO. (cm) .002 -.05 -2 .0002 .002 -.02 -.05 -.10 -.25 -.50 -1 -2 -5 -20 -75 75 WHOLE

 <- - - - - - - - - - - - Pct of <2mm (3A1) - - - - - - - - - - - - -> <- Pct of <75mm(3B1)-> SOIL

 90P3653 0- 14 Ap 49.0 26.3 24.7 8.0 20.4 5.9 4.8 8.9 5.7 3.1 2.2 6 4 1 29 11

 90P3654 14- 29 AB 51.3 28.3 20.4 8.4 20.7 7.6 2.5 7.4 5.2 2.7 2.6 6 3 -- 25 9

 90P3655 29- 54 Bss1 53.5 25.3 21.2 9.9 20.5 4.8 3.9 5.7 4.2 3.1 4.3 4 3 -- 23 7

 90P3656 54- 89 Bss2 56.6 26.9 16.5 13.8 21.8 5.1 4.0 5.0 3.3 2.4 1.8 3 2 -- 17 5

 90P3657 89-121 Bss3 61.2 25.9 12.9 18.2 21.6 4.3 2.9 3.5 2.3 2.2 2.0 1 2 -- 13 3

 90P3658 121-155 Bssck1 61.0 27.4 11.6 24.1 21.6 5.8 2.5 4.1 2.5 1.4 1.1 2 2 -- 13 4

 90P3659 155-193 Bssck2 60.7 24.5 14.8 27.0 1.3 21.0 3.5 3.1 4.0 2.9 2.4 2.4 5 7 -- 22 12

 90P3660 193-234 Bck 58.3 24.3 17.4 27.0 1.3 21.0 3.3 3.3 4.4 3.1 2.8 3.8 5 24 -- 39 29

 -----------------------------------------------------------------------------------------------------------------------------------

 ORGN TOTAL EXTR TOTAL (- - DITH-CIT - -)(RATIO/CLAY)(ATTERBERG )(- BULK DENSITY -) COLE (- - -WATER CONTENT - -) WRD

 C N P S EXTRACTABLE 15 - LIMITS - FIELD 1/3 OVEN WHOLE FIELD 1/10 1/3 15 WHOLE

 DEPTH Fe Al Mn CEC BAR LL PI MOIST BAR DRY SOIL MOIST BAR BAR BAR SOIL

 (cm) 6A1c 6B3a 6S3 6R3a 6C2b 6G7a 6D2a 8D1 8D1 4F1 4F 4A3a 4A1d 4A1h 4D1 4B4 4B1c 4B1c 4B2a 4C1

 Pct <2mm ppm <- Percent of <2mm --> Pct <0.4mm <- - g/cc - - -> cm/cm <- - -Pct of <2mm - -> cm/cm

 0- 14 0.63 1.10 0.38 1.28 1.66 0.085 31.3 18.7 0.15

 14- 29 0.42 1.06 0.39 1.27 1.68 0.092 32.7 19.9 0.16

 29- 54 0.39 1.04 0.39 1.31 1.79 0.105 33.1 21.1 0.15

 54- 89 0.35 1.02 0.42 1.24 1.91 0.151 38.7 23.5 0.18

 89-121 0.19 0.92 0.42 1.25 1.91 0.149 37.5 25.4 0.15

 121-155 0.11 0.93 0.42 1.19 1.96 0.176 39.7 25.6 0.16

 155-193 0.08 0.89 0.41 1.08 1.85 0.181 48.1 24.9 0.24

 193-234 0.04 0.86 0.42 1.25 1.89 0.118 36.5 24.2 0.13

 -----------------------------------------------------------------------------------------------------------------------------------

 (- NH4OAc EXTRACTABLE BASES -) ACID- (- -CEC- -) EXCH SAR BASE CO3 AS RES. CaSO4 AS (- - - -PH - - -)

 Ca Mg Na K SUM ITY SUM NH4- Na SATURATION CaCO3 ohms GYPSUM SAT CaCl2 H2O

 DEPTH 5B5a 5B5a 5B5a 5B5a BASES CATS OAc SUM NH4OAc <2mm /cm <2mm <20mm PASTE .01M

 (cm) 6N2e 6O2d 6P2b 6Q2b 6H5a 5A3a 5A8b 5D2 5E 5C3 5C1 6E1g 8E1 6F1a 6F4 8C1b 8C1f 8C1f

 <- - - - - - - - - -meq / 100 g - - - - - - - - - -> Pct <- -Pct- > Pct <- -Pct -> 1:2 1:1

 0- 14 9.2 0.1 0.8 0.8 54.0 TR TR 100 1 7.7 7.2 7.6

 14- 29 10.0 -- 0.7 54.6 -- 100 100 4 7.4 8.1

 29- 54 13.1 0.1 0.9 1.0 55.9 TR 100 3 7.5 7.9

 54- 89 18.2 0.4 0.8 57.5 1 100 100 2 7.6 8.3

 89-121 21.2 1.1 0.8 56.4 2 2 100 100 3 1700 7.7 7.7 8.3

 121-155 22.7 2.2 0.8 56.5 4 100 100 3 7.7 8.4

 155-193 22.8 3.3 0.8 54.3 6 100 100 5 7.8 8.3

 193-234 21.6 4.7 0.7 50.4 9 8 100 100 7 8.0 7.8 8.5

 -----------------------------------------------------------------------------------------------------------------------------------

 (- - - - - - - - - - -WATER EXTRACTED FROM SATURATED PASTE- - - - - - - - - - - - - )PRED.

 TOTAL ELEC. ELEC.

 Ca Mg Na K CO3 HCO3 F Cl SO4 NO2 NO3 H2O SALTS COND. COND.

 DEPTH EST. 8A3a 8I

 (cm) 6N1b 6O1b 6P1b 6Q1b 6I1b 6J1b 6U1a 6K1c 6L1c 6W1a 6M1c 8A 8D5 mmhos mmhos

 < - - - - - - - - - - - - - -meq / liter - - - - - - - - - - - -> <- -Pct- -> /cm /cm

 0- 14 4.2 1.1 0.1 0.1 -- 4.5 0.1 0.2 0.7 -- -- 72.9 TR 0.49 0.29

 14- 29 0.19

 29- 54 0.17

 54- 89 0.20

 89-121 1.3 0.8 1.8 TR -- 2.3 0.2 0.1 1.3 0.1 -- 91.3 TR 0.39 0.27

 121-155 0.02

 155-193 0.01

 193-234 0.3 0.2 4.2 TR -- 2.6 0.6 0.2 0.9 0.1 0.4 98.4 TR 0.48 0.44

 -----------------------------------------------------------------------------------------------------------------------------------

 < - - - - - - - - - - - - - - - - - - - - - - - CLAY MINERALOGY (<.002mm) - - - - - - - - - - - - - - - - - - - - - - >

 FRAC- < - - - - - X-RAY - - - - - ->< - - - THERMAL - - - ->< - - - - - - - ELEMENTAL - - - - - - - ->< - -> EGME INTER-

 SAMPLE TION < >< - DTA - ->< - TGA - -> SiO2 Al2O3 Fe2O3 MgO CaO K2O Na2O < > RETN PRETA-

 < - - - - - 7A2i - - - - - ->< - 7A6 - >< - 7A4b - >< - - - - - - - - - 7C3 - - - - - - - - ->< > 7D2 TION

 NUMBER <- - >< - - - - Peak size - - - - ->< - - - Percent - - - ->< - - - - - - - - Percent - - - - - - - ->< - -><mg/g>< - ->

 90P3655 TCLY MT 4 KK 2 MI 2 QZ 1 19.0 9.7 1.0

 90P3657 TCLY MT 4 KK 3 MI 2 QZ 1 20.0 9.9 1.2

 90P3659 TCLY MT 4 KK 2 MI 2 QZ 1 19.0 9.7 1.3

 -----------------------------------------------------------------------------------------------------------------------------------

 The chemical data are based on the fraction less than 2 mm in size.

 Fraction interpretation: TCLY, total clay, <0.002 mm.

 Mineral interpretation: MT, montmorillonite; KK, kaolinite; MI, mica; QZ, quartz.

 Relative peak size: 5, very large; 4, large; 3, medium; 2, small; 1, very small; 6, no peaks.

 Pedon mineralogy based on clay: Smectitic.

 Family mineralogy: Smectitic.
Vertisols 787

b. Closed for 60 or more consecutive days during the 90

days following the winter solstice.

Xererts, p. 813

FD. Other Vertisols that, if not irrigated during the year, have

cracks in normal years that remain closed for less than 60

consecutive days during a period when the soil temperature at a

depth of 50 cm from the soil surface is higher than 8 oC.

Torrerts, p. 797

FE. Other Vertisols that, if not irrigated during the year, have

cracks in normal years that are 5 mm or more wide, through a

thickness of 25 cm or more within 50 cm of the mineral soil

surface, for 90 or more cumulative days per year.

Usterts, p. 804

FF. Other Vertisols.

Uderts, p. 801

Aquerts

Aquerts are the wet Vertisols. They have aquic conditions at

or near the surface for extended periods during the year, but

they also are dry for periods long enough in normal years for

cracks to open. These soils are typically in low areas, such as

glacial lake plains, flood plains, stream terraces, and

depressions. Previously, there were no provisions for wet

Vertisols in soil taxonomy, and these soils were assigned to the

Vertic subgroups of Aquolls, Aqualfs, and Aquepts.

Definition

Aquerts are the Vertisols that have, in one or more horizons

within 50 cm of the mineral soil surface, aquic conditions for

some time in normal years (or artificial drainage) and one or

both of the following:

1. In more than half of each pedon, either on faces of peds or

in the matrix if peds are absent, 50 percent or more chroma of

either:

a. 2 or less if redox concentrations are present; or

b. 1 or less; or

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is not

being irrigated.

Key to Great Groups

FAA. Aquerts that have a salic horizon that has its upper

boundary within 100 cm of the mineral soil surface.

Salaquerts, p. 795

FAB. Other Aquerts that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Duraquerts, p. 788

FAC. Other Aquerts that have a natric horizon or have an

exchangeable sodium percentage of 15 percent or more (or a

sodium adsorption ratio of 13 or more) within 100 cm of the

mineral soil surface.

Natraquerts, p. 795

FAD. Other Aquerts that have a calcic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

Calciaquerts, p. 787

FAE. Other Aquerts that have, throughout one or more

horizons with a total thickness of 25 cm or more within 50 cm

of the mineral soil surface, both:

1. An electrical conductivity in the saturation extract of less

than 4.0 dS/m at 25 oC; and

2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in 1:1

water).

Dystraquerts, p. 789

FAF. Other Aquerts that have episaturation.

Epiaquerts, p. 793

FAG. Other Aquerts.

Endoaquerts, p. 791

Calciaquerts

Calciaquerts are the Aquerts that have a calcic horizon. In

addition, they commonly have a mollic epipedon. In the United

States, these soils occur on the northern Great Plains. They are

used mostly for crops. Before 1992, most of these soils were

classified as Calciaquolls.

Definition of Subgroups

Calciaquerts are the Aquerts that:

1. Have a calcic horizon that has its upper boundary

within 100 cm of the mineral soil surface;

2. Do not have a salic horizon or a duripan that has its upper

boundary within 100 cm of the mineral soil surface; and

3. Do not have a natric horizon or an exchangeable sodium

percentage of 15 percent or more (or a sodium adsorption ratio

of 13 or more) within 100 cm of the mineral soil surface.

Key to Subgroups

FADA. Calciaquerts that have, in one or more horizons

between either an Ap horizon or a depth of 25 cm from the
788 Soil Taxonomy

mineral soil surface, whichever is deeper, and either a depth of 75

cm or the upper boundary of a duripan if shallower, 50 percent or

more colors as follows:

1. Hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and chroma of 3 or

more; or

b. A color value, moist, of 5 or less and chroma of 2 or

more; or

2. Hue of 5Y and chroma of 3 or more; or

3. Chroma of 2 or more and no redox concentrations.

Aeric Calciaquerts

FADB. Other Calciaquerts.

Typic Calciaquerts

Definition of Typic Calciaquerts

Typic Calciaquerts are the Calciaquerts that, in more than

half of each pedon, do not have a horizon, between either an

Ap horizon or a depth of 25 cm from the mineral soil surface,

whichever is deeper, and either a depth of 75 cm or the upper

boundary of a duripan if shallower, that has any of the

following:

1. Hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and chroma of 3 or

more; or

b. A color value, moist, of 5 or less and chroma of 2 or

more; or

2. Hue of 5Y or yellower and chroma of 3 or more; or

3. Chroma of 2 or more and no redox concentrations.

Description of Subgroups

Typic Calciaquerts.—The Typic subgroup of Calciaquerts

is centered on poorly drained or very poorly drained soils that

have dominantly gleyed colors close to the surface. These soils

occur in Minnesota, Montana, South Dakota, and North

Dakota and are used for small grain or sugar beets.

Aeric Calciaquerts.—These are the Calciaquerts with

dominantly bright colored layers toward the soil surface. These

soils do not have aquic conditions that persist for long periods.

They occur in Minnesota and are used for small grain, sugar

beets, or sunflowers.

Duraquerts

Duraquerts are the Aquerts that have a duripan. These soils

commonly are derived from volcanic materials. In the United

States, all of these soils have aquic conditions for part of the

year and either have a xeric moisture regime or border a xeric

moisture regime. Several subgroups are provided for use in other

parts of the world.

Definition

Duraquerts are the Aquerts that:

1. Do not have a salic horizon that has its upper boundary

within 100 cm of the mineral soil surface; and

2. Have a duripan that has its upper boundary within 100 cm

of the mineral soil surface.

Key to Subgroups

FABA. Duraquerts that, if not irrigated during the year, have

cracks in normal years that are 5 mm or more wide, through a

thickness of 25 cm or more within 50 cm of the mineral soil

surface, for 210 or more cumulative days per year.

Aridic Duraquerts

FABB. Other Duraquerts that have a thermic, mesic, or frigid

soil temperature regime and that, if not irrigated during the

year, have cracks in normal years that remain both:

1. 5 mm or more wide, through a thickness of 25 cm or

more within 50 cm of the mineral soil surface, for 60 or

more consecutive days during the 90 days following the

summer solstice; and

2. Closed for 60 or more consecutive days during the 90

days following the winter solstice.

Xeric Duraquerts

FABC. Other Duraquerts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 90 or more cumulative days per year.

Ustic Duraquerts

FABD. Other Duraquerts that have, in one or more horizons

between either an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and either a depth of

75 cm or the upper boundary of the duripan if shallower, 50

percent or more colors as follows:

1. Hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and chroma of 3

or more; or

b. A color value, moist, of 5 or less and chroma of 2 or

more; or

2. Hue of 5Y and chroma of 3 or more; or

3. Chroma of 2 or more and no redox concentrations.

Aeric Duraquerts

FABE. Other Duraquerts that have, in one or more horizons
Vertisols 789

within 30 cm of the mineral soil surface, one or both of the

following in more than half of each pedon:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more.

Chromic Duraquerts

FABF. Other Duraquerts.

Typic Duraquerts

Definition of Typic Duraquerts

Typic Duraquerts are the Duraquerts that:

1. If not irrigated during the year, do not have cracks in

normal years that are 5 mm or more wide, through a thickness

of 25 cm or more within 50 cm of the mineral soil surface, for

90 or more cumulative days per year;

2. Do not have, in more than half of each pedon, a horizon,

between either an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and either a depth of

75 cm or the upper boundary of the duripan if shallower, that

has any of the following:

a. Hue of 2.5Y or redder and either:

(1) A color value, moist, of 6 or more and chroma of 3

or more; or

(2) A color value, moist, of 5 or less and chroma of 2 or

more; or

b. Hue of 5Y or yellower and chroma of 3 or more; or

c. Chroma of 2 or more and no redox concentrations;

3. Have, in all horizons within 30 cm of the mineral soil

surface, one or both of the following in more than half of each

pedon:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; and

4. Do not have both a thermic, mesic, or frigid soil

temperature regime and, if not irrigated during the year, cracks

in normal years that remain both:

a. 5 mm or more wide, through a thickness of 25 cm or

more within 50 cm of the mineral soil surface, for 60 or

more consecutive days during the 90 days following the

summer solstice; and

b. Closed for 60 or more consecutive days during the 90

days following the winter solstice.

Description of Subgroups

Typic Duraquerts.—The Typic subgroup of Duraquerts is

centered on poorly drained or very poorly drained soils with

dark colored surface layers. These soils do not have a moisture

regime that borders on xeric, aridic, or ustic. They are not known

to occur in the United States.

Aeric Duraquerts.—These are the Duraquerts that

commonly are considered to be somewhat poorly drained.

Bright colors toward the surface indicate that aquic conditions

do not persist for long periods. These soils do not have a

moisture regime that borders on aridic, ustic, or xeric.

Aridic Duraquerts.—These are the Duraquerts that have

aquic conditions for short periods during the year and are dry

for most of the year. These soils require cracks to be open 210

cumulative days during normal years.

Chromic Duraquerts.—These are the Duraquerts that have

light colored surface layers. They are dominantly gleyed below

the surface layers and do not have a moisture regime that

borders on aridic, ustic, or xeric.

Ustic Duraquerts.—These are the Duraquerts that have a

moisture regime that borders on ustic. These soils have aquic

conditions for part of the year but have moisture deficits for

much of the growing season.

Xeric Duraquerts.—These are the Duraquerts that have

aquic conditions for at least a part of the winter but are dry

during the summer. These soils occur in California. They are

used for pasture or irrigated crops, including rice.

Dystraquerts

Dystraquerts are the Aquerts that have dominantly low pH

values and low electrical conductivity in the upper 50 cm.

These soils commonly occur in low areas, such as flood plains

and terraces, but a few occur on uplands. The soils are

extensive in the Southern United States. Many of them are

cropped, but some are forested.

Definition

Dystraquerts are the Aquerts that:

1. Have, throughout one or more horizons with a total

thickness of 25 cm or more within 50 cm of the mineral soil

surface, both:

a. An electrical conductivity in the saturation extract of

less than 4.0 dS/m at 25 o

C; and

b. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

1:1 water);

2. Do not have a calcic or salic horizon or a duripan that has

its upper boundary within 100 cm of the mineral soil surface;

and

3. Do not have a natric horizon or an exchangeable sodium

percentage of 15 percent or more (or a sodium adsorption ratio

of 13 or more) within 100 cm of the mineral soil surface.

Key to Subgroups

FAEA. Dystraquerts that have, in one or more horizons

within 100 cm of the mineral soil surface, jarosite concentrations
790 Soil Taxonomy

and a pH value of 4.0 or less (1:1 water, air-dried slowly in

shade).

Sulfaqueptic Dystraquerts

FAEB. Other Dystraquerts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 210 or more cumulative days per year.

Aridic Dystraquerts

FAEC. Other Dystraquerts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 90 or more cumulative days per year.

Ustic Dystraquerts

FAED. Other Dystraquerts that have, in one or more horizons

between either an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and a depth of 75

cm, 50 percent or more colors as follows:

1. Hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and chroma of 3

or more; or

b. A color value, moist, of 5 or less and chroma of 2 or

more; or

2. Hue of 5Y and chroma of 3 or more; or

3. Chroma of 2 or more and no redox concentrations.

Aeric Dystraquerts

FAEE. Other Dystraquerts that have a densic, lithic, or

paralithic contact within 100 cm of the mineral soil surface.

Leptic Dystraquerts

FAEF. Other Dystraquerts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Dystraquerts

FAEG. Other Dystraquerts that have, in one or more horizons

within 30 cm of the mineral soil surface, one or both of the

following in more than half of each pedon:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more.

Chromic Dystraquerts

FAEH. Other Dystraquerts.

Typic Dystraquerts

Definition of Typic Dystraquerts

Typic Dystraquerts are the Dystraquerts that:

1. Do not have, in any horizon within 100 cm of the mineral soil

surface, both jarosite concentrations and a pH value of 4.0 or

less (1:1 water, air-dried slowly in shade);

2. If not irrigated during the year, do not have cracks in normal

years that are 5 mm or more wide, through a thickness of 25 cm

or more within 50 cm of the mineral soil surface, for 90 or more

cumulative days per year;

3. Do not have, in any horizon between either an Ap horizon or

a depth of 25 cm from the mineral soil surface, whichever is

deeper, and a depth of 75 cm, any of the following in more

than half of each pedon:

a. Hue of 2.5Y or redder and either:

(1) A color value, moist, of 6 or more and chroma of 3

or more; or

(2) A color value, moist, of 5 or less and chroma of 2 or

more; or

b. Hue of 5Y or yellower and chroma of 3 or more; or

c. Chroma of 2 or more and no redox concentrations;

4. Do not have a densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface;

5. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface; and

6. Have, in all horizons within 30 cm of the mineral soil

surface, one or both of the following in more than half of each

pedon:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less.

Description of Subgroups

Typic Dystraquerts.—The Typic subgroup of Dystraquerts

is centered on poorly drained or very poorly drained, deep or

very deep, clayey soils with dark colored surface layers. These

soils do not have concentrations of jarosite or a soil moisture

regime that borders on aridic or ustic.

Aeric Dystraquerts.—These are the Dystraquerts that are

not dominated by gleyed colors from a depth of 25 to 75 cm.

Most of these soils are considered somewhat poorly drained.

Aeric Dystraquerts do not have concentrations of jarosite or a

soil moisture regime that borders on ustic or aridic. They occur

in Texas and are used as woodland.

Aridic Dystraquerts.—These are the Dystraquerts that

have aquic conditions for a short period during the year and

are dry the remainder of the year. These soils do not have

concentrations of jarosite.

Chromic Dystraquerts.—These are the deep or very deep,

clayey, poorly drained or very poorly drained Dystraquerts that

have light colored surface layers. These soils do not have
Vertisols 791

concentrations of jarosite or a soil moisture regime that borders

on aridic or ustic. They occur in many of the Southern States of

the United States. Most of these soils have been cleared for

crop production. Some are wooded.

Entic Dystraquerts.—These are the deep or very deep,

poorly drained or very poorly drained Dystraquerts that have

less than 27 percent clay in a layer 25 cm or more thick within

100 cm of the soil surface. These soils do not have

concentrations of jarosite or a soil moisture regime that borders

on aridic or ustic.

Leptic Dystraquerts.—These are the poorly drained or

very poorly drained Dystraquerts that are less than 100 cm to a

lithic, densic, or paralithic contact. These soils do not have

concentrations of jarosite or a soil moisture regime that borders

on ustic or aridic.

Sulfaqueptic Dystraquerts.—These are the Dystraquerts

that have concentrations of jarosite. They commonly occur in

coastal areas. They have not been recognized in the United

States.

Ustic Dystraquerts.—These are the Dystraquerts that have a

soil moisture regime that borders on ustic. These soils do not

have concentrations of jarosite. They occur in Texas and are

wooded.

Endoaquerts

Endoaquerts are the Aquerts that do not have a soil layer

that perches water. These soils commonly are wet from the

bottom to the top. They occur in the Far Western States, on the

northern Great Plains, and in the Southern States. Before 1992,

most were considered Haplaquepts.

Definition

Endoaquerts are the Aquerts that:

1. Do not have a salic or calcic horizon or a duripan that has

its upper boundary within 100 cm of the mineral soil surface;

2. Do not have both of the following:

a. An electrical conductivity in the saturation extract of

less than 4.0 dS/m at 25 oC; and

b. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

1:1 water) in more than 50 percent of the soil volume

between the mineral soil surface and a depth of 50 cm in

each pedon;

3. Have endosaturation; and

4. Do not have a natric horizon or an exchangeable sodium

percentage of 15 percent or more (or a sodium adsorption ratio

of 13 or more) within 100 cm of the mineral soil surface.

Key to Subgroups

FAGA. Endoaquerts that have, throughout a layer 15 cm or

more thick within 100 cm of the mineral soil surface, an

electrical conductivity of 15 dS/m or more (saturated paste) for 6

or more months in normal years.

Halic Endoaquerts

FAGB. Other Endoaquerts that have, in one or more horizons

within 100 cm of the mineral soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio

of 13 or more) for 6 or more months in normal years.

Sodic Endoaquerts

FAGC. Other Endoaquerts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 210 or more cumulative days per year.

Aridic Endoaquerts

FAGD. Other Endoaquerts that have a thermic, mesic, or

frigid soil temperature regime and that, if not irrigated during

the year, have cracks in normal years that remain both:

1. 5 mm or more wide, through a thickness of 25 cm or

more within 50 cm of the mineral soil surface, for 60 or

more consecutive days during the 90 days following the

summer solstice; and

2. Closed for 60 or more consecutive days during the 90

days following the winter solstice.

Xeric Endoaquerts

FAGE. Other Endoaquerts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 90 or more cumulative days per year.

Ustic Endoaquerts

FAGF. Other Endoaquerts that have, in one or more horizons

between either an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and a depth of 75

cm, 50 percent or more colors as follows:

1. Hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and chroma of 3

or more; or

b. A color value, moist, of 5 or less and chroma of 2 or

more; or

2. Hue of 5Y and chroma of 3 or more; or

3. Chroma of 2 or more and no redox concentrations.

Aeric Endoaquerts

FAGG. Other Endoaquerts that have a densic, lithic, or

paralithic contact within 100 cm of the mineral soil surface.

Leptic Endoaquerts

FAGH. Other Endoaquerts that have a layer 25 cm or more
792 Soil Taxonomy

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Endoaquerts

FAGI. Other Endoaquerts that have, in one or more horizons

within 30 cm of the mineral soil surface, one or both of the

following in more than half of each pedon:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more.

Chromic Endoaquerts

FAGJ. Other Endoaquerts.

Typic Endoaquerts

Definition of Typic Endoaquerts

Typic Endoaquerts are the Endoaquerts that:

1. Do not have both a thermic, mesic, or frigid soil

temperature regime and, if not irrigated during the year, cracks

in normal years that remain both:

a. 5 mm or more wide, through a thickness of 25 cm or

more within 50 cm of the mineral soil surface, for 60 or

more consecutive days during the 90 days following the

summer solstice; and

b. Closed for 60 or more consecutive days during the 90

days following the winter solstice;

2. If not irrigated during the year, do not have cracks in

normal years that are 5 mm or more wide, through a thickness

of 25 cm or more within 50 cm of the mineral soil surface, for

90 or more cumulative days per year;

3. Do not have, in any horizon between either an Ap horizon

or a depth of 25 cm from the mineral soil surface, whichever is

deeper, and a depth of 75 cm, any of the following in more

than half of each pedon:

a. Hue of 2.5Y or redder and either:

(1) A color value, moist, of 6 or more and chroma of 3

or more; or

(2) A color value, moist, of 5 or less and chroma of 2 or

more; or

b. Hue of 5Y or yellower and chroma of 3 or more; or

c. Chroma of 2 or more and no redox concentrations;

4. Do not have a densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface;

5. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

6. Have, throughout all layers 15 cm or more thick

within 100 cm of the mineral soil surface, an electrical

conductivity of less than 15 dS/m (saturated paste) for 6 or

more months in normal years;

7. Have, in all horizons within 100 cm of the mineral soil

surface, an exchangeable sodium percentage of less than 15 (or

a sodium adsorption ratio of less than 13) for 6 or more months

in normal years; and

8. Have, in all horizons within 30 cm of the mineral soil

surface, one or both of the following in more than half of each

pedon:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less.

Description of Subgroups

Typic Endoaquerts.—The Typic subgroup of Endoaquerts

is centered on deep or very deep, poorly drained or very poorly

drained, clayey soils with dark colored surface layers. These

soils do not have significant amounts of salts or sodium and do

not have a soil moisture regime that borders on aridic, xeric, or

ustic. They occur in North Dakota, South Dakota, and

Minnesota and are used for hay and pasture or for small grain,

when drained.

Aeric Endoaquerts.—These are the Endoaquerts that are

not dominantly gleyed from a depth of 25 to 75 cm. Most of

these soils are considered somewhat poorly drained. Aeric

Endoaquerts do not have significant amounts of salts or sodium

or a soil moisture regime that borders on aridic, xeric, or ustic.

They occur in Texas and are used mostly as native pasture.

Aridic Endoaquerts.—These are the Endoaquerts that have

aquic conditions for short periods and are dry for most of the

year. These soils do not have significant amounts of salts or

sodium. They occur in California and are used as irrigated

pasture.

Chromic Endoaquerts.—These are the deep or very deep,

poorly drained or very poorly drained, clayey Endoaquerts that

have light colored surface layers. These soils do not have

significant amounts of sodium or salts or a soil moisture

regime that borders on xeric, aridic, or ustic. Chromic

Endoaquerts occur in the Dakotas, Montana, Texas, and

Arkansas. They are used mostly as pasture, but some are used

for hay.

Entic Endoaquerts.—These are the deep or very deep,

poorly drained or very poorly drained Endoaquerts that have a

layer 25 cm or more thick with less than 27 percent clay. These

soils do not have significant amounts of sodium or salts or a

soil moisture regime that borders on ustic, aridic, or xeric.

They are not known to occur in the United States.

Halic Endoaquerts.—These are the Endoaquerts that have

significant amounts of salts. They are not known to occur in

the United States.

Leptic Endoaquerts.—These are the poorly drained or very

poorly drained Endoaquerts that have a lithic, paralithic, or
Vertisols 793

densic contact within 100 cm of the soil surface. These soils do

not have significant amounts of sodium or salts or a moisture

regime that borders on ustic, aridic, or xeric. They are rare in

the world.

Sodic Endoaquerts.—These are the Endoaquerts that have

significant amounts of sodium, but not salts. They occur in

California and are used mostly as irrigated cropland or pasture.

Ustic Endoaquerts.—These are the Endoaquerts that have

a moisture regime that borders on xeric or aridic. They do not

have significant amounts of salts or sodium.

Xeric Endoaquerts.—These are the Endoaquerts that have a

soil moisture regime that borders on xeric. They do not have

significant amounts of sodium or salts. These soils occur in

Oregon, Washington, and California. They are used for

pasture, rangeland, or irrigated crops.

Epiaquerts

Epiaquerts are the Aquerts that have one or more soil layers

that perch water. Commonly, these layers are close to the

surface. These soils occur on a variety of landforms, including

flood plains, glacial lake planes, and depressions. In the United

States, they occur in a number of Western States, on the

northern Great Plains, and in the South. They also occur in

Puerto Rico.

Definition

Epiaquerts are the Aquerts that:

1. Do not have a calcic or salic horizon or a duripan that has

its upper boundary within 100 cm of the mineral soil surface;

2. Do not have both:

a. An electrical conductivity in the saturation extract of

less than 4.0 dS/m at 25 oC; and

b. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste) in more than 50 percent of the soil volume

between the mineral soil surface and a depth of 50 cm in

each pedon;

3. Have episaturation; and

4. Do not have a natric horizon or an exchangeable sodium

percentage of 15 percent or more (or a sodium adsorption ratio

of 13 or more) within 100 cm of the mineral soil surface.

Key to Subgroups

FAFA. Epiaquerts that have, throughout a layer 15 cm or

more thick within 100 cm of the mineral soil surface, an

electrical conductivity of 15 dS/m or more (saturated paste) for

6 or more months in normal years.

Halic Epiaquerts

FAFB. Other Epiaquerts that have, in one or more horizons

within 100 cm of the mineral soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio of

13 or more) for 6 or more months in normal years.

Sodic Epiaquerts

FAFC. Other Epiaquerts that, if not irrigated during the year,

have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 210 or more cumulative days per year.

Aridic Epiaquerts

FAFD. Other Epiaquerts that have a thermic, mesic, or frigid

soil temperature regime and that, if not irrigated during the

year, have cracks in normal years that remain both:

1. 5 mm or more wide, through a thickness of 25 cm or

more within 50 cm of the mineral soil surface, for 60 or

more consecutive days during the 90 days following the

summer solstice; and

2. Closed for 60 or more consecutive days during the 90

days following the winter solstice.

Xeric Epiaquerts

FAFE. Other Epiaquerts that, if not irrigated during the year,

have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 90 or more cumulative days per year.

Ustic Epiaquerts

FAFF. Other Epiaquerts that have, in one or more horizons

between either an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and a depth of 75

cm, 50 percent or more colors as follows:

1. Hue of 2.5Y or redder and either:

a. A color value, moist, of 6 or more and chroma of 3

or more; or

b. A color value, moist, of 5 or less and chroma of 2 or

more; or

2. Hue of 5Y and chroma of 3 or more; or

3. Chroma of 2 or more and no redox concentrations.

Aeric Epiaquerts

FAFG. Other Epiaquerts that have a densic, lithic, or

paralithic contact within 100 cm of the mineral soil surface.

Leptic Epiaquerts

FAFH. Other Epiaquerts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Epiaquerts

FAFI. Other Epiaquerts that have, in one or more horizons
794 Soil Taxonomy

within 30 cm of the mineral soil surface, one or both of the

following in more than half of each pedon:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more.

Chromic Epiaquerts

FAFJ. Other Epiaquerts.

Typic Epiaquerts

Definition of Typic Epiaquerts

Typic Epiaquerts are the Epiaquerts that:

1. Do not have both a thermic, mesic, or frigid soil

temperature regime and, if not irrigated during the year, cracks

in normal years that remain both:

a. 5 mm or more wide, throughout a layer 25 cm or more

thick within 50 cm of the mineral soil surface, for 60 or

more consecutive days during the 90 days following the

summer solstice; and

b. Closed for 60 or more consecutive days during the 90

days following the winter solstice;

2. Do not have, in any horizon between either an Ap horizon

or a depth of 25 cm from the mineral soil surface, whichever is

deeper, and a depth of 75 cm, any of the following in more

than half of each pedon:

a. Hue of 2.5Y or redder and either:

(1) A color value, moist, of 6 or more and chroma of 3

or more; or

(2) A color value, moist, of 5 or less and chroma of 2 or

more; or

b. Hue of 5Y or yellower and chroma of 3 or more; or

c. Chroma of 2 or more and no redox concentrations;

3. Do not have a densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface;

4. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

5. Have, if not irrigated during the year, cracks in normal

years that are 5 mm or more wide, through a thickness of 25

cm or more within 50 cm of the mineral soil surface, for 90 to

210 or more cumulative days per year;

6. Have, throughout all layers 15 cm or more thick

within 100 cm of the mineral soil surface, an electrical

conductivity of less than 15 dS/m (saturated paste) for 6

or more months in normal years;

7. Have, in all horizons within 100 cm of the mineral soil

surface, an exchangeable sodium percentage of less than 15

(or a sodium adsorption ratio of less than 13) for 6 or more

months in normal years; and

8. Have, in all horizons within 30 cm of the mineral soil

surface, one or both of the following in more than half of each

pedon:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less.

Description of Subgroups

Typic Epiaquerts.—The Typic subgroup of Epiaquerts is

centered on deep or very deep, poorly drained or very poorly

drained, clayey soils with dark colored surface layers. These

soils do not have significant amounts of salts or sodium and do

not have a soil moisture regime that borders on aridic, xeric, or

ustic. They occur in North Dakota, South Dakota, Minnesota,

Montana, Missouri, Arkansas, Louisiana, and Mississippi.

They are used for hay and pasture or as cropland, when

drained.

Aeric Epiaquerts.—These are the Epiaquerts that are not

dominantly gleyed from a depth of 25 to 75 cm. Many of these

soils are considered somewhat poorly drained. Aeric

Epiaquerts do not have significant amounts of salts or sodium

or a soil moisture regime that borders on aridic, xeric, or ustic.

They occur in Texas, Louisiana, Oklahoma, Alabama,

Mississippi, and Missouri. These soils are mostly cropped, but

some are wooded.

Aridic Epiaquerts.—These are the Epiaquerts that have

aquic conditions for short periods and are dry for most of the

year. These soils do not have significant amounts of salts or

sodium.

Chromic Epiaquerts.—These are the deep or very deep,

poorly drained or very poorly drained, clayey Epiaquerts that

have light colored surface layers. These soils do not have

significant amounts of sodium or salts or a soil moisture

regime that borders on xeric, aridic, or ustic. They occur in

Arkansas. They are used mostly as pasture, but some are used

for hay or other crops.

Entic Epiaquerts.—These are the deep or very deep, poorly

drained or very poorly drained Epiaquerts that have a layer 25

cm or more thick with less than 27 percent clay. These soils do

not have significant amounts of sodium or salts or a soil

moisture regime that borders on ustic, aridic, or xeric. They are

not known to occur in the United States.

Halic Epiaquerts.—These are the Epiaquerts that have

significant amounts of salts. They are not known to occur in

the United States.

Leptic Epiaquerts.—These are the poorly drained or very

poorly drained Epiaquerts that have a lithic, paralithic, or

densic contact within 100 cm of the soil surface. These soils do

not have significant amounts of sodium or salts or a moisture

regime that borders on ustic, aridic, or xeric.

Sodic Epiaquerts.—These are the Epiaquerts that have

significant amounts of sodium, but not salts. They occur in
Vertisols 795

California, Montana, and Puerto Rico. They are used mostly as

irrigated cropland, as wildlife habitat, or as pasture. In Puerto

Rico they are used for sugarcane.

Ustic Epiaquerts.—These are the Epiaquerts that have a

moisture regime that borders on ustic. These soils do not have

significant amounts of salts or sodium. They occur in Texas

and Oklahoma and are used as rangeland.

Xeric Epiaquerts.—These are the Epiaquerts that have a soil

moisture regime that borders on xeric. These soils do not have

significant amounts of sodium or salts. They occur in Oregon,

Nevada, Idaho, and California. They are used for pasture,

rangeland, or irrigated crops. In some areas they are used for rice

production.

Natraquerts

Natraquerts are the Aquerts with significant amounts of

sodium. In many areas these soils occur on flood plains or

glacial lake plains. The high sodium content limits their use as

cropland. Most of the soils are used as rangeland, pasture, or

hayland. Most Natraquerts in the United States formed in

alluvium or lacustrine deposits derived dominantly from

sedimentary rocks. Natraquerts occur in the Dakotas, Montana,

Iowa, Nebraska, and Texas.

Definition

Natraquerts are the Aquerts that:

1. Do not have a salic horizon or a duripan that has its upper

boundary within 100 cm of the mineral soil surface; and

2. Have a natric horizon or an exchangeable sodium

percentage of 15 percent or more (or a sodium adsorption ratio

of 13 or more) within 100 cm of the mineral soil surface.

Key to Subgroups

FACA. All Natraquerts.

Typic Natraquerts

Salaquerts

Salaquerts are the Aquerts with significant amounts of salts.

These soils are not known to occur in the United States.

Definition

Salaquerts are the Aquerts that have a salic horizon that

has an upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

FAAA. Salaquerts that, if not irrigated during the year, have

cracks in normal years that are 5 mm or more wide, through a

thickness of 25 cm or more within 50 cm of the mineral soil

surface, for 210 or more cumulative days per year.

Aridic Salaquerts

FAAB. Other Salaquerts that, if not irrigated during the year,

have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 90 or more cumulative days per year.

Ustic Salaquerts

FAAC. Other Salaquerts that have a densic, lithic, or

paralithic contact within 100 cm of the mineral soil surface.

Leptic Salaquerts

FAAD. Other Salaquerts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Salaquerts

FAAE. Other Salaquerts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Salaquerts

FAAF. Other Salaquerts.

Typic Salaquerts

Definition of Typic Salaquerts

Typic Salaquerts are the Salaquerts that:

1. If not irrigated during the year, do not have cracks in

normal years that are 5 mm or more wide, through a thickness

of 25 cm or more within 50 cm of the mineral soil surface, for

90 or more cumulative days per year;

2. Do not have a densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface;

3. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface; and

4. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Salaquerts.—The Typic subgroup of Salaquerts is

centered on deep or very deep, clayey soils with dark colored

surface layers. These soils do not have a soil moisture regime

that borders on ustic or aridic.
796 Soil Taxonomy

Aridic Salaquerts.—These are the Salaquerts that have

aquic conditions for short periods during the year and are dry

for most of the year.

Chromic Salaquerts.—These are the deep or very deep,

clayey Salaquerts that have light colored surface layers. These

soils do not a soil moisture regime that borders on aridic or

ustic.

Entic Salaquerts.—These are the deep or very deep

Salaquerts that have a layer 25 cm or more thick with less than

27 percent clay. These soils do not have a moisture regime that

borders on ustic or aridic.

Leptic Salaquerts.—These are the Salaquerts that have a

lithic, paralithic, or densic contact within 100 cm of the soil

surface. These soils do not have a moisture regime that borders

on aridic or ustic.

Ustic Salaquerts.—These are the Salaquerts that have aquic

conditions for part of the year but also are dry for significant

periods during a normal year.

Cryerts

Cryerts are the Vertisols that have a cryic temperature

regime. Previously, the definition of Vertisols limited their

extent to warmer climates. Fine textured soils in cold

temperature regimes periodically shrink and swell, forming the

diagnostic characteristics of Vertisols. Cracks commonly open

once a year, late in the summer. Cryerts occur on the cold

prairies of Canada, where they commonly are derived from

lacustrine deposits. They also occur in the Rocky Mountains

of the United States.

Definition

Cryerts are the Vertisols that:

1. Have a cryic soil temperature regime; and

2. Do not have, in any horizon within 50 cm of the mineral soil

surface, aquic conditions and any of the following:

a. In more than half of each pedon, either on faces of peds

or in the matrix if peds are absent, 50 percent or more

chroma of either:

(1) 2 or less if redox concentrations are present; or

(2) 1 or less if redox concentrations are absent; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Key to Great Groups

FBA. Cryerts that have 10 kg/m2 or more organic carbon

between the mineral soil surface and a depth of 50 cm.

Humicryerts, p. 797

FBB. Other Cryerts.

Haplocryerts, p. 796

Haplocryerts

Haplocryerts are the Cryerts without significant

accumulations of organic carbon. These soils occur in the

Rocky Mountains of the United States. They are of limited

extent.

Definition

Haplocryerts are the Cryerts that have less than 10 kg/m2

organic carbon between the mineral soil surface and a depth of

50 cm.

Key to Subgroups

FBBA. Haplocryerts that have, in one or more horizons

within 100 cm of the mineral soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio

of 13 or more) for 6 or more months in normal years.

Sodic Haplocryerts

FBBB. Other Haplocryerts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Haplocryerts

FBBC. Other Haplocryerts.

Typic Haplocryerts

Definition of Typic Haplocryerts

Typic Haplocryerts are the Haplocryerts that have:

1. In all horizons within 100 cm of the mineral soil surface,

an exchangeable sodium percentage of less than 15 (or a

sodium adsorption ratio of less than 13) for 6 or more months

in normal years; and

2. In all horizons within 30 cm of the mineral soil surface, 50

percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Haplocryerts.—The Typic subgroup of Haplocryerts

is centered on soils that have dark colored surface horizons and

do not have significant amounts of sodium. These soils are rare

in the world.
Vertisols 797

Chromic Haplocryerts.—These are the Haplocryerts that

have light colored surface horizons but do not have significant

amounts of sodium. These soils are rare in the world.

Sodic Haplocryerts.—These are the Haplocryerts that have

significant amounts of sodium. These soils are rare in the

world.

Humicryerts

Humicryerts are the Cryerts that have rather high amounts

of organic carbon. These soils formed under a variety of

vegetative types. They occur in the Rocky Mountains of the

United States.

Definition

Humicryerts are the Cryerts that have 10 kg/m2 or more

organic carbon between the mineral soil surface and a depth of

50 cm.

Key to Subgroups

FBAA. Humicryerts that have, in one or more horizons

within 100 cm of the mineral soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio

of 13 or more) for 6 or more months in normal years.

Sodic Humicryerts

FBAB. Other Humicryerts.

Typic Humicryerts

Definition of Typic Humicryerts

Typic Humicryerts are the Humicryerts that have, in all

horizons within 100 cm of the mineral soil surface, an

exchangeable sodium percentage of less than 15 (or a sodium

adsorption ratio of less than 13) for 6 or more months in

normal years.

Description of Subgroups

Typic Humicryerts.—The Typic subgroup of Humicryerts

is centered on soils that do not have significant amounts of

sodium. These soils occur in Idaho and are used as wildlife

habitat.

Sodic Humicryerts.—These are the Humicryerts that have

significant amounts of sodium. These soils are rare in the

world.

Torrerts

Torrerts are the Vertisols of arid climates. Their cracks

commonly stay open for most of the year but may close for at

least a few days in most years. The cracks are closed for less

than 60 days during the growing season. Many of these soils

dot the landscape in closed depressions that may be ponded

from time to time by runoff from the higher areas. Some

Torrerts are more continuous and commonly are underlain by

parent materials that tend to weather to smectictic clays, such as

basalt.

Torrerts are subdivided by the presence or absence of

accumulations of salts, which are important to the use and

management of the soils. Salitorrerts, Gypsitorrerts, and

Calcitorrerts have a salic, gypsic, and calcic horizon,

respectively. Haplotorrerts do not have significant

accumulations of salts.

The Torrerts in the United States occur mostly in the

Southwest, although a few are in Hawaii. Most commonly, they

are used as rangeland.

Definition

Torrerts are the Vertisols that:

1. If not irrigated during the year, have cracks in normal years

that remain closed for less than 60 consecutive days during a

period when the soil temperature at a depth of 50 cm from the

soil surface is continuously higher than 8 oC;

2. Do not have a cryic soil temperature regime;

3. Do not have, in any horizon within 50 cm of the mineral soil

surface, aquic conditions and any of the following:

a. In more than half of each pedon, either on faces of peds

or in the matrix if peds are absent, 50 percent or more

chroma of either:

(1) 2 or less if redox concentrations are present; or

(2) 1 or less if redox concentrations are absent; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated; and

4. In normal years do not have both:

a. A thermic, mesic, or frigid soil temperature regime; and

b. If not irrigated during the year, cracks that remain both:

(1) 5 mm or more wide, throughout a layer 25 cm or

more thick within 50 cm of the soil surface, for 60 or

more consecutive days during the 90 days following the

summer solstice; and

(2) Closed for 60 or more consecutive days during the

90 days following the winter solstice.

Key to Great Groups

FDA. Torrerts that have a salic horizon that has its upper

boundary within 100 cm of the soil surface.

Salitorrerts, p. 800
798 Soil Taxonomy

FDB. Other Torrerts that have a gypsic horizon that has its

upper boundary within 100 cm of the soil surface.

Gypsitorrerts, p. 798

FDC. Other Torrerts that have a calcic or petrocalcic horizon

that has its upper boundary within 100 cm of the soil surface.

Calcitorrerts, p. 798

FDD. Other Torrerts.

Haplotorrerts, p. 799

Calcitorrerts

Calcitorrerts are the Torrerts that have a calcic or petrocalcic

horizon. These soils are not extensive among the Torrerts. They

are used mostly for grazing by livestock. Some are used for

irrigated alfalfa. Calcitorrerts occur in Arizona and other areas of

the Southwestern United States.

Definition

Calcitorrerts are the Torrerts that:

1. Have a calcic or petrocalcic horizon that has its upper

boundary within 100 cm of the soil surface; and

2. Do not have a gypsic or salic horizon that has its upper

boundary within 100 cm of the soil surface.

Key to Subgroups

FDCA. Calcitorrerts that have a petrocalcic horizon that has

its upper boundary within 100 cm of the soil surface.

Petrocalcic Calcitorrerts

FDCB. Other Calcitorrerts that have a densic, lithic, or

paralithic contact, or the upper boundary of a duripan, within

100 cm of the soil surface.

Leptic Calcitorrerts

FDCC. Other Calcitorrerts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the soil

surface.

Entic Calcitorrerts

FDCD. Other Calcitorrerts that have, in one or more

horizons within 30 cm of the soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Calcitorrerts

FDCE. Other Calcitorrerts.

Typic Calcitorrerts

Definition of Typic Calcitorrerts

Typic Calcitorrerts are the Calcitorrerts that:

1. Do not have a petrocalcic horizon that has its upper

boundary within 100 cm of the soil surface;

2. Do not have a densic, lithic, or paralithic contact, or

the upper boundary of a duripan, within 100 cm of the soil

surface;

3. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface; and

4. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Calcitorrerts.—The Typic subgroup of Calcitorrerts

is centered on deep or very deep soils that have a clay loam or

finer texture in all layers within 100 cm of the soil surface and

that have relatively dark surface layers. These soils do not have

a petrocalcic horizon. They occur in Arizona and are used for

grazing by livestock.

Chromic Calcitorrerts.—These are the deep or very deep

Calcitorrerts that have a color value, moist, of 4 or more; a dry

value of 6 or more; or chroma of 3 or more. These soils have a

clay loam or finer texture in all layers from the soil surface to a

depth of 100 cm and do not have a petrocalcic horizon.

Entic Calcitorrerts.—These are the deep or very deep

Calcitorrerts that have a layer 25 cm or more thick within 100

cm of the soil surface that contains less than 27 percent clay.

These soils do not have a petrocalcic horizon.

Leptic Calcitorrerts.—These are the Calcitorrerts that are

moderately deep or shallower to a densic, paralithic, or lithic

contact or a duripan. These soils do not have a petrocalcic

horizon.

Petrocalcic Calcitorrerts.—These are the Calcitorrerts that

have a petrocalcic horizon. They occur in Arizona and are used

for grazing by livestock.

Gypsitorrerts

Gypsitorrerts are the Torrerts that have a gypsic horizon that

has its upper boundary within 100 cm of the soil surface. These

soils occur in arid areas of the world where the parent

materials are high in content of gypsum. A high shrink-swell

potential and gypsum content in these soils limit many

building activities unless measures that counteract the

shrinking and swelling and the dissolution of gypsum are

applied. These soils occur in the Southwestern United States.
Vertisols 799

Definition

Gypsitorrerts are the Torrerts that:

1. Have a gypsic horizon that has its upper boundary

within 100 cm of the soil surface; and

2. Do not have a salic horizon that has its upper boundary

within 100 cm of the soil surface.

Key to Subgroups

FDBA. Gypsitorrerts that have, in one or more horizons

within 30 cm of the soil surface, 50 percent or more colors as

follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Gypsitorrerts

FDBB. Other Gypsitorrerts.

Typic Gypsitorrerts

Definition of Typic Gypsitorrerts

Typic Gypsitorrerts are the Gypsitorrerts that have, in all

horizons within 30 cm of the soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 3 or less; or

2. A color value, dry, of 5 or less; or

3. Chroma of 2 or less.

Description of Subgroups

Typic Gypsitorrerts.—The Typic subgroup of Gypsitorrerts

is centered on soils that have surface layers with a color value,

moist, of 3 or less; a value, dry, of 5 or less; and chroma of 2 or

less. These soils are relatively rare, but they occur in Arizona.

They are used for grazing by livestock.

Chromic Gypsitorrerts.—These are the Gypsitorrerts that

have a color value, moist, of 4 or more; a color value, dry, of 6

or more; or chroma of 3 or more. These soils occur in New

Mexico and are used for grazing by livestock.

Haplotorrerts

Haplotorrerts are the Torrerts that do not have a salic, gypsic,

or calcic horizon. This is the most extensive great group of

Torrerts. These soils occur in many of the Western States and in

Texas and Hawaii. They are used as urban land, cropland, or

rangeland.

Definition

Haplotorrerts are the Torrerts that do not have a calcic,

gypsic, petrocalcic, or salic horizon that has its upper boundary

within 100 cm of the soil surface.

Key to Subgroups

FDDA. Haplotorrerts that have, throughout a layer 15 cm or

more thick within 100 cm of the soil surface, an electrical

conductivity of 15 dS/m or more (saturated paste) for 6 or more

months in normal years.

Halic Haplotorrerts

FDDB. Other Haplotorrerts that have, in one or more

horizons within 100 cm of the soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio

of 13 or more) for 6 or more months in normal years.

Sodic Haplotorrerts

FDDC. Other Haplotorrerts that have a densic, lithic, or

paralithic contact, or the upper boundary of a duripan, within

100 cm of the soil surface.

Leptic Haplotorrerts

FDDD. Other Haplotorrerts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the soil

surface.

Entic Haplotorrerts

FDDE. Other Haplotorrerts that have, in one or more

horizons within 30 cm of the soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Haplotorrerts

FDDF. Other Haplotorrerts.

Typic Haplotorrerts

Definition of Typic Haplotorrerts

Typic Haplotorrerts are the Haplotorrerts that:

1. Do not have a densic, lithic, or paralithic contact, or the

upper boundary of a duripan, within 100 cm of the soil

surface;

2. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the soil surface;

3. Have, in all layers 15 cm or more thick within 100 cm of

the soil surface, an electrical conductivity of less than 15 dS/m

(saturated paste) for 6 or more months in normal years;

4. Have, in all horizons within 100 cm of the soil surface, an

exchangeable sodium percentage of less than 15 (or a sodium

adsorption ratio of less than 13) for 6 or more months in

normal years; and
800 Soil Taxonomy

5. Have, in all horizons within 30 cm of the soil surface, 50

percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Haplotorrerts.—The Typic subgroup of Haplotorrerts

is centered on soils that are deep or very deep, that have a clay

loam or finer texture in all horizons between the soil surface and

a depth of 100 cm, that have relatively dark colored surface

horizons, and that do not have significant amounts of salts or

sodium. In Texas, New Mexico, and Arizona, these soils are used

for rangeland or irrigated crops. In Hawaii the soils are used for

irrigated sugarcane.

Chromic Haplotorrerts.—These are the deep or very deep

Haplotorrerts that have a color value, moist, of 4 or more; a

color value, dry, of 6 or more; or chroma of 3 or more. These

soils do not have significant amounts of salts or sodium. They

occur in Idaho, California, Colorado, New Mexico, and Texas.

Most commonly, they are used for grazing.

Entic Haplotorrerts.—These are the deep or very deep

Haplotorrerts that have a layer 25 cm or more thick within 100

cm of the soil surface that has 27 percent or less clay. These

soils do not have significant amounts of salts or sodium. They

occur in New Mexico and are used as urban land, rangeland, or

irrigated cropland.

Halic Haplotorrerts.—These are the Haplotorrerts that

have a significant accumulation of salts. They occur in Texas

and New Mexico and are used for grazing by livestock.

Leptic Haplotorrerts.—These are the Haplotorrerts that

have a lithic, paralithic, or densic contact or a duripan within

100 cm of the soil surface. These soils do not have significant

amounts of salts or sodium. They are known to occur in New

Mexico and Hawaii, where they are used as rangeland and

pasture, respectively.

Sodic Haplotorrerts.—These are the Haplotorrerts that

have a significant accumulation of sodium and do not have

significant amounts of salts. These soils occur in Nevada,

California, and Texas. They are used for rangeland or irrigated

crops.

Salitorrerts

Salitorrerts are the Torrerts that have a salic horizon. In some

of these soils, salts accumulate because of a periodic water

table. In others, scant precipitation and the impermeable nature

of the soils facilitate the accumulation of salts. Salitorrerts have

not been recognized in the United States.

Definition

Salitorrerts are the Torrerts that have a salic horizon that has

its upper boundary within 100 cm of the soil surface.

Key to Subgroups

FDAA. Salitorrerts that have, in one or more horizons within

100 cm of the soil surface, aquic conditions for some time in

normal years (or artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquic Salitorrerts

FDAB. Other Salitorrerts that have a densic, lithic, or

paralithic contact, or the upper boundary of a duripan or

petrocalcic horizon, within 100 cm of the soil surface.

Leptic Salitorrerts

FDAC. Other Salitorrerts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the soil

surface.

Entic Salitorrerts

FDAD. Other Salitorrerts that have, in one or more horizons

within 30 cm of the soil surface, 50 percent or more colors as

follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Salitorrerts

FDAE. Other Salitorrerts.

Typic Salitorrerts

Definition of Typic Salitorrerts

Typic Salitorrerts are the Salitorrerts that:

1. Do not have, in any horizon within 100 cm of the soil

surface, aquic conditions and either:

a. Redoximorphic features; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

2. Do not have a densic, lithic, or paralithic contact, or the

upper boundary of a duripan or petrocalcic horizon, within 100

cm of the soil surface;

3. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the soil surface; and

4. Have, in all horizons within 30 cm of the soil surface, 50

percent or more colors as follows:
Vertisols 801

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Salitorrerts.—The Typic subgroup of Salitorrerts is

centered on deep or very deep soils that have a clay loam or

finer texture from the soil surface to a depth of 100 cm. These

soils do not have aquic conditions within 100 cm of the soil

surface, and they have relatively dark colored surface layers.

Aquic Salitorrerts.—These are the Salitorrerts that have

aquic conditions within 100 cm of the soil surface for some

time in normal years. The aquic conditions commonly are of

very short duration.

Chromic Salitorrerts.—These are the deep or very deep

Salitorrerts that have a color value, moist, of 4 or more; a color

value, dry, of 6 or more; or chroma of 3 or more. These soils

have a clay loam or finer texture from the soil surface to a

depth of 100 cm.

Entic Salitorrerts.—These are the deep or very deep

Salitorrerts that have a layer 25 cm or more thick that has 27

percent or less clay within 100 cm of the soil surface. These

soils do not have aquic conditions within 100 cm of the soil

surface.

Leptic Salitorrerts.—These are the Salitorrerts that are

moderately deep or shallower to a lithic, paralithic, or densic

contact or a duripan or petrocalcic horizon. These soils do not

have aquic conditions within 100 cm of the soil surface.

Uderts

Uderts are the Vertisols of humid areas. These soils have

cracks that open and close, depending upon the amount of

precipitation. In some years the cracks may not open

completely.

The Uderts in the United States occur on gentle slopes and

are derived dominantly from marine shales, marls, and

alluvium. At one time many of these soils supported grass,

although some support a hardwood or pine forest.

Definition

Uderts are the Vertisols that:

1. Do not have a cryic soil temperature regime;

2. Do not have, in any horizon within 50 cm of the mineral

soil surface, aquic conditions and any of the following:

a. In more than half of each pedon, either on faces of peds

or in the matrix if peds are absent, 50 percent or more

chroma of either:

(1) 2 or less if redox concentrations are present; or

(2) 1 or less if redox concentrations are absent; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

3. In normal years do not have both:

a. A thermic, mesic, or frigid soil temperature regime;

and

b. If not irrigated during the year, cracks that remain both:

(1) 5 mm or more wide, throughout a layer 25 cm or

more thick within 50 cm of the mineral soil surface, for

60 or more consecutive days during the 90 days following

the summer solstice; and

(2) Closed for 60 or more consecutive days during the

90 days following the winter solstice;

4. If not irrigated during the year, do not have cracks in

normal years that remain closed for less than 60 consecutive

days during a period when the soil temperature at a depth of 50

cm from the soil surface is continuously higher than 8 oC; and

5. If not irrigated during the year, do not have cracks in

normal years that are 5 mm or more wide, through a thickness

of 25 cm or more within 50 cm of the mineral soil surface, for

90 or more cumulative days.

Key to Great Groups

FFA. Uderts that have, throughout one or more horizons with

a total thickness of 25 cm or more within 50 cm of the mineral

soil surface, both:

1. An electrical conductivity in the saturation extract of

less than 4.0 dS/m at 25 oC; and

2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste).

Dystruderts, p. 801

FFB. Other Uderts.

Hapluderts, p. 803

Dystruderts

Dystruderts are the acid Uderts. These soils are derived

dominantly from acid, fine textured materials and occur on

alluvial plains, deltas, interfluves, and side slopes. Commonly,

they are underlain by sediments high in bases. Some of these

soils have diagnostic horizons, including argillic, calcic, and

gypsic horizons.

In the United States, these soils occur in Texas and in the

Southeastern States from Arkansas to Florida. They are used as

cropland, pasture, or woodland.
802 Soil Taxonomy

Definition

Dystruderts are the Uderts that have, throughout one or more

horizons with a total thickness of 25 cm or more within 50 cm of

the mineral soil surface, both:

1. An electrical conductivity in the saturation extract of less

than 4.0 dS/m at 25 o

C; and

2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste).

Key to Subgroups

FFAA. Dystruderts that have, in one or more horizons within

100 cm of the mineral soil surface, aquic conditions for some

time in normal years (or artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquic Dystruderts

FFAB. Other Dystruderts that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Dystruderts

FFAC. Other Dystruderts that have a densic, lithic, or

paralithic contact within 100 cm of the mineral soil surface.

Leptic Dystruderts

FFAD. Other Dystruderts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Dystruderts

FFAE. Other Dystruderts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Dystruderts

FFAF. Other Dystruderts.

Typic Dystruderts

Definition of Typic Dystruderts

Typic Dystruderts are the Dystruderts that:

1. Do not have, in any horizon within 100 cm of the mineral soil

surface, aquic conditions and either:

a. Redoximorphic features; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

2. Do not have a densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface;

3. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

4. Are not saturated with water in any layer within 100 cm of

the mineral soil surface in normal years for:

a. 20 or more consecutive days; or

b. 30 or more cumulative days; and

5. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Dystruderts.—The Typic subgroup of Dystruderts is

centered on deep or very deep, dark colored soils that are not

saturated within 100 cm of the soil surface for extended

periods. These soils do not have a layer as much as 25 cm thick

with less than 27 percent clay from the soil surface to a depth

of 100 cm.

Aquic Dystruderts.—These are the Dystruderts that have

aquic conditions and redoximorphic features within 100 cm of

the mineral soil surface. These soils do not have high amounts

of aluminum. In the United States, they commonly formed in

thick sediments of acid clays over more alkaline clays. These

soils occur in Mississippi, Alabama, Arkansas, and Louisiana

and are used as cropland, pasture, or woodland.

Chromic Dystruderts.—These are the deep or very deep

Dystruderts that have light colored layers within 30 cm of the

mineral soil surface. These soils are not saturated for extended

periods within 100 cm of the mineral soil surface. They do not

have layers with less than 27 percent clay within 100 cm of the

mineral soil surface. The soils are extensive in the

Southeastern United States and commonly are wooded.

Entic Dystruderts.—These are the deep or very deep

Dystruderts that have a layer 25 cm or more thick that contains

less than 27 percent clay and has its upper boundary within

100 cm of the mineral soil surface. These soils are not

saturated within 100 cm of the mineral soil surface for

significant periods.

Leptic Dystruderts.—These are the shallow or moderately
Vertisols 803

deep Dystruderts. They are not saturated within a depth of 100

cm for significant periods. They are not known to occur in the

United States.

Oxyaquic Dystruderts.—These are the Dystruderts that are

saturated for significant periods within 100 cm of the mineral

soil surface but do not have redoximorphic features. These soils

occur in Texas and Louisiana.

Hapluderts

Hapluderts are the Uderts with pH values that are dominantly

above 5.0 in the upper 50 cm. These soils typically have high

base saturation, and some have diagnostic horizons, including

argillic horizons. Hapluderts occur on uplands and in lower

areas. They formed in a variety of fine textured parent material,

including alluvium.

In the United States, these soils commonly occur in the

Southeast but also occur on the northern Great Plains and in

the Pacific Northwest.

Definition

Hapluderts are the Uderts that do not have both:

1. An electrical conductivity in the saturation extract of less

than 4.0 dS/m at 25 oC; and

2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste) in more than 50 percent of the soil volume

between the mineral soil surface and a depth of 50 cm in each

pedon.

Key to Subgroups

FFBA. Hapluderts that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Hapluderts

FFBB. Other Hapluderts that have, in one or more horizons

within 100 cm of the mineral soil surface, aquic conditions

for some time in normal years (or artificial drainage) and

either:

1. Redoximorphic features; or

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquic Hapluderts

FFBC. Other Hapluderts that are saturated with water in one

or more layers within 100 cm of the mineral soil surface in

normal years for:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Hapluderts

FFBD. Other Hapluderts that have a densic, lithic, or paralithic

contact within 100 cm of the mineral soil surface.

Leptic Hapluderts

FFBE. Other Hapluderts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Hapluderts

FFBF. Other Hapluderts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Hapluderts

FFBG. Other Hapluderts.

Typic Hapluderts

Definition of Typic Hapluderts

Typic Hapluderts are the Hapluderts that:

1. Do not have a densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, aquic conditions and either:

a. Redoximorphic features; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

3. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

4. Are not saturated with water in any layer within 100 cm of

the mineral soil surface in normal years for:

a. 20 or more consecutive days; or

b. 30 or more cumulative days; and

5. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Hapluderts.—The Typic subgroup of Hapluderts is

centered on deep or very deep soils that are not saturated for
804 Soil Taxonomy

significant periods within 100 cm of the mineral soil surface.

These soils have rather dark colored surface layers and a clay

loam or finer texture throughout. They occur in Texas,

Alabama, Oklahoma, and Arkansas and on the northern Great

Plains. They are used as cropland, pasture, or rangeland.

Aquic Hapluderts.—These are the Hapluderts that have

aquic conditions and redoximorphic features within 100 cm of

the mineral soil surface. They do not have a lithic contact

within 50 cm of the mineral soil surface. These soils occur in

Alabama, Texas, Oklahoma, Kansas, Louisiana, and Puerto

Rico. They are used as cropland, woodland, or pasture.

Chromic Hapluderts.—These are the deep or very deep

Hapluderts that have light colored surface layers. These soils

are not saturated for extended periods within 100 cm of the

mineral soil surface. They have a clay loam or finer texture

from the mineral soil surface to a depth of 100 cm. These soils

are common in the South, in the Southeast, and on the

northern Great Plains. They are used as cropland, pasture, or

woodland.

Entic Hapluderts.—These are the deep or very deep

Hapluderts that have a layer 25 cm or more thick that contains

less than 27 percent clay within 100 cm of the mineral soil

surface. These soils are not saturated for extended periods

within 100 cm of the mineral soil surface. They are

uncommon. They occur in Texas and are used as pasture or

cropland.

Leptic Hapluderts.—These are the Hapluderts that have a

densic, lithic, or paralithic contact within 100 cm of the

mineral soil surface but do not have a lithic contact within 50

cm of the mineral soil surface. These soils are not saturated for

extended periods within 100 cm of the mineral soil surface.

They occur in Alabama and Louisiana and are used as

cropland, pasture, or hayland.

Lithic Hapluderts.—These are the Hapluderts that have a

lithic contact within 50 cm of the mineral soil surface. They

are not common and have not been recognized in the United

States.

Oxyaquic Hapluderts.—These are the Hapluderts that are

saturated with water for extended periods within 100 cm of the

mineral soil surface but do not have redoximorphic features.

They also do not have a lithic contact within 50 cm of the

mineral soil surface. They are extensive and occur in the

South, the Southeast, and the Pacific Northwest. They are used

mostly as cropland or pasture.

Usterts

These are the Vertisols in temperate areas that do not receive

high amounts of rainfall during the summer, in areas of

monsoonal climate, and in tropical and subtropical areas that

have two rainy and two dry seasons. Cracks open and close

once or twice during the year. Usterts are extensive in Texas,

on the Great Plains, in Australia, in Africa south of the Sahara,

and in India. Many of these soils formed in gently sloping

areas of fine textured marine deposits or alluvium. Some are

derived from basic igneous rocks. If irrigated, Usterts are used

intensively, but large areas are used for grazing because of a

lack of machinery to till the soils.

Definition

Usterts are the Vertisols that:

1. Do not have a cryic soil temperature regime;

2. Do not have, in any horizon within 50 cm of the mineral soil

surface, aquic conditions and any of the following:

a. In more than half of each pedon, either on faces of peds

or in the matrix if peds are absent, 50 percent or more

chroma of either:

(1) 2 or less if redox concentrations are present; or

(2) 1 or less if redox concentrations are absent; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

3. In normal years do not have both:

a. A thermic, mesic, or frigid soil temperature regime; and

b. If not irrigated during the year, cracks that remain both:

(1) 5 mm or more wide, throughout a layer 25 cm or

more thick within 50 cm of the mineral soil surface, for

60 or more consecutive days during the 90 days following

the summer solstice; and

(2) Closed for 60 or more consecutive days during the

90 days following the winter solstice;

4. If not irrigated during the year, do not have cracks in

normal years that remain closed for less than 60 consecutive

days during a period when the soil temperature at a depth of 50

cm from the soil surface is continuously higher than 8 o

C; and

5. If not irrigated during the year, have cracks in normal

years that are 5 mm or more wide, through a thickness of 25

cm or more within 50 cm of the mineral soil surface, for 90 or

more cumulative days per year.

Key to Great Groups

FEA. Usterts that have, throughout one or more horizons

with a total thickness of 25 cm or more within 50 cm of the

mineral soil surface, both:

1. An electrical conductivity in the saturation extract of

less than 4.0 dS/m at 25 oC; and

2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste).

Dystrusterts, p. 806
Vertisols 805

FEB. Other Usterts that have a salic horizon that has its upper

boundary within 100 cm of the mineral soil surface.

Salusterts, p. 811

FEC. Other Usterts that have a gypsic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

Gypsiusterts, p. 808

FED. Other Usterts that have a calcic or petrocalcic horizon

that has its upper boundary within 100 cm of the mineral soil

surface.

Calciusterts, p. 805

FEE. Other Usterts.

Haplusterts, p. 809

Calciusterts

Calciusterts are the Usterts that have a calcic or petrocalcic

horizon. These soils commonly are derived from parent

materials rich in carbonates, such as marine deposits or even

eolian material. Previously, it was thought that diagnostic

horizons could not form in Vertisols because of self-churning.

These earlier concepts were not accurate. Some Calciusterts

have mollic epipedons. Although Calciusterts have limited

acreage in the United States, they are significant in other parts

of the world.

Definition

Calciusterts are the Usterts that:

1. Have a calcic or petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface;

2. Do not have both:

a. An electrical conductivity in the saturation extract of

less than 4.0 dS/m at 25 oC; and

b. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste) in more than 50 percent of the soil volume

between the mineral soil surface and a depth of 50 cm in

each pedon; and

3. Do not have a gypsic or salic horizon that has its upper

boundary within 100 cm of the mineral soil surface.

Key to Subgroups

FEDA. Calciusterts that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Calciusterts

FEDB. Other Calciusterts that have, throughout a layer 15

cm or more thick within 100 cm of the mineral soil surface, an

electrical conductivity of 15 dS/m or more (saturated paste) for

6 or more months in normal years.

Halic Calciusterts

FEDC. Other Calciusterts that have, in one or more horizons

within 100 cm of the mineral soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio

of 13 or more) for 6 or more months in normal years.

Sodic Calciusterts

FEDD. Other Calciusterts that have a petrocalcic horizon

that has its upper boundary within 100 cm of the mineral soil

surface.

Petrocalcic Calciusterts

FEDE. Other Calciusterts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 210 or more cumulative days per year.

Aridic Calciusterts

FEDF. Other Calciusterts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for less than 150 cumulative days per

year.

Udic Calciusterts

FEDG. Other Calciusterts that have a densic, lithic, or

paralithic contact, or the upper boundary of a duripan, within

100 cm of the mineral soil surface.

Leptic Calciusterts

FEDH. Other Calciusterts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Calciusterts

FEDI. Other Calciusterts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Calciusterts

FEDJ. Other Calciusterts.

Typic Calciusterts

Definition of Typic Calciusterts

Typic Calciusterts are the Calciusterts that:

1. Do not have a densic, lithic, or paralithic contact, or the

upper boundary of a duripan or petrocalcic horizon, within 100

cm of the mineral soil surface;

2. Do not have a layer 25 cm or more thick that contains less
806 Soil Taxonomy

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

3. If not irrigated during the year, have cracks in normal

years that are 5 mm or more wide, through a thickness of 25

cm or more within 50 cm of the mineral soil surface, for 150 to

210 cumulative days per year;

4. Have, throughout all layers 15 cm or more thick

within 100 cm of the mineral soil surface, an electrical

conductivity of less than 15 dS/m (saturated paste) for 6

or more months in normal years;

5. Have, in all horizons within 100 cm of the mineral soil

surface, an exchangeable sodium percentage of less than 15 (or

a sodium adsorption ratio of less than 13) for 6 or more months

in normal years; and

6. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Calciusterts.—The Typic subgroup of Calciusterts is

centered on deep or very deep soils that do not have significant

amounts of salts or sodium. In addition, these soils do not have

a petrocalcic horizon, soil moisture regimes that border on

aridic or udic, a layer with less than 27 percent clay, or light

colored surface layers. These soils are rare in the United States

but occur in Puerto Rico, where they are used for pasture or

sugarcane.

Aridic Calciusterts.—These are the Calciusterts that have

a soil moisture regime that borders on aridic. These soils do

not have a lithic contact within 50 cm of the soil surface, a

petrocalcic horizon, or significant amounts of salts or sodium.

They are of small extent in the Southwestern United States and

are used as rangeland.

Chromic Calciusterts.—These are the deep or very deep

Calciusterts that have light colored surface layers but do not

have significant amounts of salts or sodium. These soils do not

have a petrocalcic horizon, soil moisture regimes that border

on aridic or udic, or a layer with less than 27 percent clay. The

soils are rare in the United States.

Entic Calciusterts.—These are the deep or very deep

Calciusterts that have a layer with less than 27 percent clay but

do not have significant amounts of salts or sodium. These soils

do not have a petrocalcic horizon or soil moisture regimes that

border on aridic or udic. The soils are rare in the United States.

Halic Calciusterts.—These are the Calciusterts that have a

significant accumulation of salts. These soils do not have a

lithic contact within 50 cm of the soil surface. They are not

known to occur in the United States.

Leptic Calciusterts.—These are the Calciusterts that have

a lithic, paralithic, or densic contact within 100 cm of the soil

surface but do not have a lithic contact within 50 cm of the soil

surface. These soils do not have significant amounts of salts or

sodium, a moisture regime that borders on udic or aridic, or a

petrocalcic horizon. The soils are rare in the United States.

Lithic Calciusterts.—These are the Calciusterts that have a

lithic contact within 50 cm of the soil surface. They are not

known to occur in the United States.

Petrocalcic Calciusterts.—These are the Calciusterts that

have a petrocalcic horizon. They do not have a lithic contact

within 50 cm of the soil surface or significant amounts of salts

or sodium. These soils occur in Texas and are used as

rangeland or pasture.

Sodic Calciusterts.—These are the Calciusterts that have

significant amounts of sodium, but not salts. They do not have

a lithic contact within 50 cm of the soil surface. These soils are

rare in the United States and are used as rangeland.

Udic Calciusterts.—These are the Calciusterts that have a

soil moisture regime that borders on udic. They do not have a

petrocalcic horizon, a lithic contact within 50 cm of the soil

surface, or significant amounts of salts or sodium. These soils

occur in Texas. They commonly are used as rangeland, but

some are used for cultivated crops.

Dystrusterts

Dystrusterts are the Usterts that have a dominant pH value of

5.0 or less and an electrical conductivity of less than 4.0

dS/m within 50 cm of the soil surface. These soils commonly

formed in acid clays and are underlain by more alkaline parent

materials. They commonly are derived from marine sediments.

They are not known to occur in the United States but were

established to accommodate other countries.

Definition

Dystrusterts are the Usterts that have, throughout one or

more horizons with a total thickness of 25 cm or more within

50 cm of the mineral soil surface, both:

1. An electrical conductivity in the saturation extract of less

than 4.0 dS/m at 25 oC; and

2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste).

Key to Subgroups

FEAA. Dystrusterts that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Dystrusterts

FEAB. Other Dystrusterts that have, in one or more horizons

within 100 cm of the mineral soil surface, aquic conditions

for some time in normal years (or artificial drainage) and

either:

1. Redoximorphic features; or
Vertisols 807

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquic Dystrusterts

FEAC. Other Dystrusterts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 210 or more cumulative days per

year.

Aridic Dystrusterts

FEAD. Other Dystrusterts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for less than 150 cumulative days.

Udic Dystrusterts

FEAE. Other Dystrusterts that have a densic, lithic, or

paralithic contact, or the upper boundary of a duripan, within

100 cm of the mineral soil surface.

Leptic Dystrusterts

FEAF. Other Dystrusterts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Dystrusterts

FEAG. Other Dystrusterts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Dystrusterts

FEAH. Other Dystrusterts.

Typic Dystrusterts

Definition of Typic Dystrusterts

Typic Dystrusterts are the Dystrusterts that:

1. Do not have a densic, lithic, or paralithic contact, or the

upper boundary of a duripan, within 100 cm of the mineral soil

surface;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, aquic conditions and either:

a. Redoximorphic features; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

3. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

4. If not irrigated during the year, have cracks in normal

years that are 5 mm or more wide, through a thickness of 25

cm or more within 50 cm of the mineral soil surface, for 150 to

210 cumulative days per year; and

5. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Dystrusterts.—The Typic subgroup of Dystrusterts is

centered on deep or very deep soils that do not have a soil

moisture regime that borders on udic or aridic. These soils do

not have aquic conditions for significant periods within 100 cm

of the soil surface. In addition, they do not have a layer with

less than 27 percent clay or light colored surface layers.

Aquic Dystrusterts.—These are the Dystrusterts that have

aquic conditions for extended periods within 100 cm of the soil

surface. These soils do not have a lithic contact within 50 cm

of the soil surface.

Aridic Dystrusterts.—These are the Dystrusterts that have

a soil moisture regime that borders on aridic. They do not have

a lithic contact within 50 cm of the soil surface or aquic

conditions for extended periods within 100 cm of the soil

surface.

Chromic Dystrusterts.—These are the deep or very deep

Dystrusterts that have light colored surface layers but do not

have a lithic contact within 50 cm of the soil surface or aquic

conditions for extended periods within 100 cm of the soil

surface. These soils do not have soil moisture regimes that

border on aridic or udic or a layer with less than 27 percent

clay.

Entic Dystrusterts.—These are the deep or very deep

Dystrusterts that have a layer with less than 27 percent clay but

do not have a lithic contact within 50 cm of the soil surface.

These soils do not have soil moisture regimes that border on

aridic or udic or aquic conditions for extended periods within

100 cm of the soil surface.

Leptic Dystrusterts.—These are the Dystrusterts that have

a lithic, paralithic, or densic contact within 100 cm of the soil

surface but do not have a lithic contact within 50 cm of the soil

surface. These soils do not have a moisture regime that borders

on udic or aridic or aquic conditions for extended periods

within 100 cm of the soil surface.

Lithic Dystrusterts.—These are the Dystrusterts that have

a lithic contact within 50 cm of the soil surface.

Udic Dystrusterts.—These are the Dystrusterts that have a

soil moisture regime that borders on udic. They do not have a
808 Soil Taxonomy

lithic contact within 50 cm of the soil surface or aquic

conditions for extended periods within 100 cm of the soil

surface.

Gypsiusterts

These are the Usterts that have a gypsic horizon. They are

derived from parent materials rich in gypsum. Even in areas of

an ustic moisture regime, the gypsum is not leached because of

the very slow permeability associated with these soils. Some of

the soils occur on the edges of depressions where gypsum is

deposited at the capillary fringe. Gypsiusterts are rare in the

United States, but they occur in Texas, where they are used as

rangeland or pasture.

Definition

Gypsiusterts are the Usterts that:

1. Have a gypsic horizon that has its upper boundary

within 100 cm of the mineral soil surface;

2. Do not have both:

a. An electrical conductivity in the saturation extract of

less than 4.0 dS/m at 25 oC; and

b. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste) in more than 50 percent of the soil volume

between the mineral soil surface and a depth of 50 cm in

each pedon; and

3. Do not have a salic horizon that has its upper boundary

within 100 cm of the mineral soil surface.

Key to Subgroups

FECA. Gypsiusterts that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Gypsiusterts

FECB. Other Gypsiusterts that have, throughout a layer 15

cm or more thick within 100 cm of the mineral soil surface, an

electrical conductivity of 15 dS/m or more (saturated paste) for

6 or more months in normal years.

Halic Gypsiusterts

FECC. Other Gypsiusterts that have, in one or more horizons

within 100 cm of the mineral soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio

of 13 or more) for 6 or more months in normal years.

Sodic Gypsiusterts

FECD. Other Gypsiusterts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more

wide, through a thickness of 25 cm or more within 50 cm of

the mineral soil surface, for 210 or more cumulative days per

year.

Aridic Gypsiusterts

FECE. Other Gypsiusterts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for less than 150 cumulative days per

year.

Udic Gypsiusterts

FECF. Other Gypsiusterts that have a densic, lithic, or

paralithic contact, or the upper boundary of a duripan or

petrocalcic horizon, within 100 cm of the mineral soil

surface.

Leptic Gypsiusterts

FECG. Other Gypsiusterts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Gypsiusterts

FECH. Other Gypsiusterts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Gypsiusterts

FECI. Other Gypsiusterts.

Typic Gypsiusterts

Definition of Typic Gypsiusterts

Typic Gypsiusterts are the Gypsiusterts that:

1. Do not have a densic, lithic, or paralithic contact, or the

upper boundary of a duripan or petrocalcic horizon, within 100

cm of the mineral soil surface;

2. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

3. Have, throughout all layers 15 cm or more thick

within 100 cm of the mineral soil surface, an electrical

conductivity of less than 15 dS/m (saturated paste) for 6

or more months in normal years;

4. Have, in all horizons within 100 cm of the mineral soil

surface, an exchangeable sodium percentage of less than 15 (or

a sodium adsorption ratio of less than 13) for 6 or more months

in normal years;

5. If not irrigated during the year, have cracks in normal

years that are 5 mm or more wide, through a thickness of 25

cm or more within 50 cm of the mineral soil surface, for 150 to

210 cumulative days per year; and
Vertisols 809

6. Have, in all horizons within 30 cm of the mineral soil surface,

50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Gypsiusterts.—The Typic subgroup of Gypsiusterts

is centered on deep or very deep soils that do not have

significant amounts of salts or sodium. In addition, these soils

do not have soil moisture regimes that border on aridic or udic, a

layer with less than 27 percent clay, or light colored surface

layers.

Aridic Gypsiusterts.—These are the Gypsiusterts that have

a soil moisture regime that borders on aridic. They do not have

a lithic contact within 50 cm of the soil surface or significant

amounts of salts or sodium.

Chromic Gypsiusterts.—These are the deep or very deep

Gypsiusterts that have light colored surface layers but do not

have significant amounts of salts or sodium. These soils do not

have soil moisture regimes that border on aridic or udic or a

layer with less than 27 percent clay.

Entic Gypsiusterts.—These are the deep or very deep

Gypsiusterts that have a layer with less than 27 percent clay

but do not have significant amounts of salts or sodium. These

soils do not have a soil moisture regime that borders on aridic

or udic.

Halic Gypsiusterts.—These are the Gypsiusterts that have

a significant accumulation of salts. These soils do not have a

lithic contact within 50 cm of the soil surface.

Leptic Gypsiusterts.—These are the Gypsiusterts that have

a lithic, paralithic, or densic contact within 100 cm of the soil

surface but do not have a lithic contact within 50 cm of the soil

surface. These soils do not have significant amounts of salts or

sodium or a moisture regime that borders on udic or aridic.

Lithic Gypsiusterts.—These are the Gypsiusterts that have

a lithic contact within 50 cm of the soil surface.

Sodic Gypsiusterts.—These are the Gypsiusterts that have

significant amounts of sodium, but not salts. These soils do not

have a lithic contact within 50 cm of the soil surface. They

occur in Texas and are used as rangeland or pasture.

Udic Gypsiusterts.—These are the Gypsiusterts that have a

soil moisture regime that borders on udic. They do not have a

lithic contact within 50 cm of the soil surface or significant

amounts of salts or sodium.

Haplusterts

Haplusterts are the most common of the Usterts. They are

derived from a variety of parent materials, including

sedimentary rocks, alluvium, marl, and basic igneous rocks.

Slopes range from nearly level to strongly sloping.

Haplusterts occur in many Western and Southwestern States,

on the northern Great Plains, and in Puerto Rico and

the Virgin Islands. They are used as rangeland, cropland, or

pasture.

Definition

Haplusterts are the Usterts that:

1. Do not have both:

a. An electrical conductivity in the saturation extract of less

than 4.0 dS/m at 25 oC; and

b. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste) in more than 50 percent of the soil volume

between the mineral soil surface and a depth of 50 cm in

each pedon; and

2. Do not have a calcic, gypsic, petrocalcic, or salic horizon

that has its upper boundary within 100 cm of the mineral soil

surface.

Key to Subgroups

FEEA. Haplusterts that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplusterts

FEEB. Other Haplusterts that have, throughout a layer 15 cm

or more thick within 100 cm of the mineral soil surface, an

electrical conductivity of 15 dS/m or more (saturated paste) for

6 or more months in normal years.

Halic Haplusterts

FEEC. Other Haplusterts that have, in one or more horizons

within 100 cm of the mineral soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio

of 13 or more) for 6 or more months in normal years.

Sodic Haplusterts

FEED. Other Haplusterts that have a petrocalcic horizon that

has its upper boundary within 150 cm of the mineral soil

surface.

Petrocalcic Haplusterts

FEEE. Other Haplusterts that have a gypsic horizon that has

its upper boundary within 150 cm of the mineral soil surface.

Gypsic Haplusterts

FEEF. Other Haplusterts that have a calcic horizon that has

its upper boundary within 150 cm of the mineral soil surface.

Calcic Haplusterts

FEEG. Other Haplusterts that have both:

1. A densic, lithic, or paralithic contact within 100 cm of

the mineral soil surface; and

2. If not irrigated during the year, cracks in normal years
810 Soil Taxonomy

that are 5 mm or more wide, through a thickness of 25 cm or

more within 50 cm of the mineral soil surface, for 210 or more

cumulative days per year.

Aridic Leptic Haplusterts

FEEH. Other Haplusterts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for 210 or more cumulative days per year.

Aridic Haplusterts

FEEI. Other Haplusterts that have both:

1. A densic, lithic, or paralithic contact within 100 cm of

the mineral soil surface; and

2. If not irrigated during the year, cracks in 6 or more out

of 10 years that are 5 mm or more wide, through a thickness

of 25 cm or more within 50 cm of the mineral soil surface,

for less than 150 cumulative days per year.

Leptic Udic Haplusterts

FEEJ. Other Haplusterts that have both:

1. A layer 25 cm or more thick that contains less than 27

percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface; and

2. If not irrigated during the year, cracks in normal years

that are 5 mm or more wide, through a thickness of 25 cm

or more within 50 cm of the mineral soil surface, for less

than 150 cumulative days per year.

Entic Udic Haplusterts

FEEK. Other Haplusterts that have both:

1. In one or more horizons within 30 cm of the mineral

soil surface, 50 percent or more colors as follows:

a. A color value, moist, of 4 or more; or

b. A color value, dry, of 6 or more; or

c. Chroma of 3 or more; and

2. If not irrigated during the year, cracks in normal years

that are 5 mm or more wide, through a thickness of 25 cm

or more within 50 cm of the mineral soil surface, for less

than 150 cumulative days per year.

Chromic Udic Haplusterts

FEEL. Other Haplusterts that, if not irrigated during the year,

have cracks in normal years that are 5 mm or more wide,

through a thickness of 25 cm or more within 50 cm of the

mineral soil surface, for less than 150 cumulative days per

year.

Udic Haplusterts

FEEM. Other Haplusterts that have a densic, lithic, or

paralithic contact, or the upper boundary of a duripan, within

100 cm of the mineral soil surface.

Leptic Haplusterts

FEEN. Other Haplusterts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Haplusterts

FEEO. Other Haplusterts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Haplusterts

FEEP. Other Haplusterts.

Typic Haplusterts

Definition of Typic Haplusterts

Typic Haplusterts are the Haplusterts that:

1. Do not have a densic, lithic, or paralithic contact, or the

upper boundary of a duripan or petrocalcic horizon, within 100

cm of the mineral soil surface;

2. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

3. Have, throughout all layers 15 cm or more thick

within 100 cm of the mineral soil surface, an electrical

conductivity of less than 15 dS/m or more (saturated paste)

for 6 or more months in normal years;

4. Have, in all horizons within 100 cm of the mineral soil

surface, an exchangeable sodium percentage of less than 15 (or

a sodium adsorption ratio of less than 13) for 6 or more months

in normal years;

5. If not irrigated during the year, have cracks in normal

years that are 5 mm or more wide, through a thickness of 25

cm or more within 50 cm of the mineral soil surface, for 150 to

210 cumulative days per year;

6. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less; and

7. Do not have a calcic or gypsic horizon with an upper

boundary within 150 cm of the mineral soil surface.
Vertisols 811

Description of Subgroups

Typic Haplusterts.—The Typic subgroup of Haplusterts is

centered on deep or very deep soils that do not have significant

amounts of salts or sodium. In addition, these soils do not have

a petrocalcic horizon, soil moisture regimes that border on

aridic or udic, a calcic or gypsic horizon within a depth of 150

cm, a layer with less than 27 percent clay, or light colored

surface layers. In the United States, these soils occur in Texas,

New Mexico, Oklahoma, South Dakota, Hawaii, and Puerto

Rico. They are used for crop production as well as rangeland.

Aridic Haplusterts.—These are the Haplusterts that have a

soil moisture regime that borders on aridic. They do not have a

lithic contact within 50 cm of the soil surface, a petrocalcic

horizon, or significant amounts of salts or sodium. These soils

occur in South Dakota, Montana, Colorado, Nebraska, Texas,

and Wyoming. They commonly are used as rangeland.

Aridic Leptic Haplusterts.—These are the Haplusterts that

have a soil moisture regime that borders on aridic and that

have a lithic, paralithic, or densic contact within 100 cm of the

soil surface but do not have a lithic contact within 50 cm of the

soil surface. These soils do not have a petrocalcic horizon or

significant amounts of salts or sodium. They occur on the

northern Great Plains and in the Southwestern United States

and commonly are used as rangeland.

Calcic Haplusterts.—These are the Haplusterts that have a

calcic horizon with its upper boundary within 150 cm of the

soil surface. They do not have significant accumulations of

salts or sodium. These soils occur in India and the United

States. Most are used as cropland.

Chromic Haplusterts.—These are the deep or very deep

Haplusterts that have light colored surface layers but do not

have significant amounts of salts or sodium. These soils do not

have a petrocalcic horizon, soil moisture regimes that border

on aridic or udic, or a layer with less than 27 percent clay.

They occur in New Mexico and Texas and are used mostly as

rangeland.

Chromic Udic Haplusterts.—These are the deep or very

deep Haplusterts that have light colored surface layers and a

moisture regime that borders on udic but do not have

significant amounts of salts or sodium. These soils do not have

a petrocalcic horizon or a layer with less than 27 percent clay.

They occur in Colorado, Texas, Montana, North Dakota,

Wyoming, and Oklahoma. They are used as rangeland or

cropland.

Entic Haplusterts.—These are the deep or very deep

Haplusterts that have a layer with less than 27 percent clay but

do not have significant amounts of salts or sodium. These soils

do not have a petrocalcic horizon or soil moisture regimes that

border on aridic or udic. They are rare in the United States.

Entic Udic Haplusterts.—These are the deep or very deep

Haplusterts that have a layer with less than 27 percent clay and

a moisture regime that borders on udic but do not have

significant amounts of salts or sodium. These soils do not have

a petrocalcic horizon. They occur in Texas, where they are used

as rangeland, and in Puerto Rico, where they are used for

sugarcane.

Gypsic Haplusterts.—These are the Haplusterts that have a

gypsic horizon with its upper boundary within 150 cm of the

soil surface. They do not have significant accumulations of

salts or sodium. These soils occur in India and the United

States. Many are used as cropland. Some of the soils in India

are mined for gypsum.

Halic Haplusterts.—These are the Haplusterts that have a

significant accumulation of salts. These soils do not have a

lithic contact within 50 cm of the soil surface. They are not

known to occur in the United States.

Leptic Haplusterts.—These are the Haplusterts that have a

lithic, paralithic, or densic contact within 100 cm of the soil

surface but do not have a lithic contact within 50 cm of the soil

surface. These soils do not have significant amounts of salts or

sodium, a moisture regime that borders on udic or aridic, or a

petrocalcic horizon. They occur in South Dakota and Nebraska

and are used as rangeland or cropland.

Leptic Udic Haplusterts.—These are the Haplusterts that

have a lithic, paralithic, or densic contact within 100 cm of the

soil surface and a moisture regime that borders on udic but do

not have a lithic contact within 50 cm of the soil surface. These

soils do not have significant amounts of salts or sodium or a

petrocalcic horizon. They occur in the Southwestern United

States and on the northern Great Plains. They are used as

cropland, rangeland, or pasture.

Lithic Haplusterts.—These are the Haplusterts that have a

lithic contact within 50 cm of the soil surface. They are rare in

the United States.

Petrocalcic Haplusterts.—These are the Haplusterts that

have a petrocalcic horizon. They do not have a lithic contact

within 50 cm of the soil surface or significant amounts of salts

or sodium. These soils are not known to occur in the United

States.

Sodic Haplusterts.—These are the Haplusterts that have

significant amounts of sodium, but not salts. They do not have

a lithic contact within 50 cm of the soil surface. These soils

occur in Montana, Utah, Puerto Rico, Texas, South Dakota, the

Virgin Islands, and the Channel Islands off the coast of

southern California. Most of the soils are used as rangeland,

but some are used as cropland.

Udic Haplusterts.—These are the Haplusterts that have a soil

moisture regime that borders on udic. They do not have a

petrocalcic horizon, a lithic contact within 50 cm of the soil

surface, or significant amounts of salts or sodium. These soils

occur in the Southwestern United States and on the northern

Great Plains. They commonly are used as rangeland, but some

are used for cultivated crops.

Salusterts

These are the Usterts that have a salic horizon. Many of

these soils are derived from salty marine deposits. Salts are
812 Soil Taxonomy

difficult to leach in Salusterts, and few areas are used as

cropland. These soils are not known to occur in the United

States.

Definition

Salusterts are the Usterts that:

1. Have a salic horizon that has its upper boundary

within 100 cm of the mineral soil surface; and

2. Do not have both:

a. An electrical conductivity in the saturation extract of

less than 4.0 dS/m at 25 o

C; and

b. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in

saturated paste) in more than 50 percent of the soil volume

between the mineral soil surface and a depth of 50 cm in

each pedon.

Key to Subgroups

FEBA. Salusterts that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Salusterts

FEBB. Other Salusterts that have, in one or more horizons

within 100 cm of the mineral soil surface, an exchangeable

sodium percentage of 15 or more (or a sodium adsorption ratio

of 13 or more) for 6 or more months in normal years.

Sodic Salusterts

FEBC. Other Salusterts that have, in one or more horizons

within 100 cm of the mineral soil surface, aquic conditions for

some time in normal years (or artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquic Salusterts

FEBD. Other Salusterts that, if not irrigated during the

year, have cracks in normal years that are 5 mm or more

wide, through a thickness of 25 cm or more within 50 cm of

the mineral soil surface, for 210 or more cumulative days per

year.

Aridic Salusterts

FEBE. Other Salusterts that have a densic, lithic, or

paralithic contact, or the upper boundary of a duripan or

petrocalcic horizon, within 100 cm of the mineral soil surface.

Leptic Salusterts

FEBF. Other Salusterts that have a layer 25 cm or more thick

that contains less than 27 percent clay in its fine-earth fraction

and has its upper boundary within 100 cm of the mineral soil

surface.

Entic Salusterts

FEBG. Other Salusterts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Salusterts

FEBH. Other Salusterts.

Typic Salusterts

Definition of Typic Salusterts

Typic Salusterts are the Salusterts that:

1. Do not have a densic, lithic, or paralithic contact, or the

upper boundary of a duripan or petrocalcic horizon, within 100

cm of the mineral soil surface;

2. Do not have, in any horizon within 100 cm of the mineral

soil surface, aquic conditions and either:

a. Redoximorphic features; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

3. If not irrigated during the year, do not have cracks in

normal years that are 5 mm or more wide, through a thickness

of 25 cm or more within 50 cm of the mineral soil surface, for

210 or more cumulative days per year;

4. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

5. Have, in all horizons within 100 cm of the mineral soil

surface, an exchangeable sodium percentage of less than 15 (or

a sodium adsorption ratio of less than 13) for 6 or more months

in normal years; and

6. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Salusterts.—The Typic subgroup of Salusterts is

centered on deep or very deep soils that do not have significant
Vertisols 813

amounts of sodium. In addition, these soils do not have a soil

moisture regime that borders on aridic, aquic conditions within

100 cm of the soil surface, a layer with less than 27 percent

clay, or light colored surface layers.

Aquic Salusterts.—These are the Salusterts that have aquic

conditions within 100 cm of the soil surface. These soils do not

have a lithic contact within 50 cm of the soil surface or

significant amounts of sodium.

Aridic Salusterts.—These are the Salusterts that have a soil

moisture regime that borders on aridic. They do not have a

lithic contact within 50 cm of the soil surface, aquic conditions

within 100 cm of the soil surface, or significant amounts of

sodium.

Chromic Salusterts.—These are the deep or very deep

Salusterts that have light colored surface layers but do not have

significant amounts of sodium. These soils do not have a soil

moisture regime that borders on aridic, a layer with less than

27 percent clay, or aquic conditions within 100 cm of the soil

surface.

Entic Salusterts.—These are the deep or very deep

Salusterts that have a layer with less than 27 percent clay but

do not have significant amounts of sodium. These soils do not

have a soil moisture regime that borders on aridic or aquic

conditions within 100 cm of the soil surface.

Leptic Salusterts.—These are the Salusterts that have a

lithic, paralithic, or densic contact within 100 cm of the soil

surface but do not have a lithic contact within 50 cm of the soil

surface. These soils do not have significant amounts of sodium,

a moisture regime that borders on aridic, or aquic conditions

within 100 cm of the soil surface.

Lithic Salusterts.—These are the Salusterts that have a

lithic contact within 50 cm of the soil surface.

Sodic Salusterts.—These are the Salusterts that have

significant amounts of sodium. These soils do not have a lithic

contact within 50 cm of the soil surface.

Xererts

Xererts are the Vertisols of Mediterranean climates, which are

typified by cool, wet winters and warm, dry summers. These

soils have cracks that regularly close and open each year.

Because the soils dry every summer and remoisten in the

winter, damage to structures and roads is very significant. If

not irrigated, these soils are used for small grain or grazing. In

the United States, most of the soils supported grasses before

they were cultivated.

Definition

Xererts are the Vertisols that:

1. Do not have a cryic soil temperature regime;

2. Do not have, in any horizon within 50 cm of the mineral soil

surface, aquic conditions and any of the following:

a. In more than half of each pedon, either on faces of peds

or in the matrix if peds are absent, 50 percent or more

chroma of either:

(1) 2 or less if redox concentrations are present; or

(2) 1 or less if redox concentrations are absent; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated; and

3. In normal years, have both:

a. A thermic, mesic, or frigid soil temperature regime; and

b. If not irrigated during the year, cracks that remain both:

(1) 5 mm or more wide, throughout a layer 25 cm or

more thick within 50 cm of the mineral soil surface, for

60 or more consecutive days during the 90 days following

the summer solstice; and

(2) Closed for 60 or more consecutive days during the

90 days following the winter solstice.

Key to Great Groups

FCA. Xererts that have a duripan that has its upper boundary

within 100 cm of the mineral soil surface.

Durixererts, p. 814

FCB. Other Xererts that have a calcic or petrocalcic horizon

that has its upper boundary within 100 cm of the mineral soil

surface.

Calcixererts, p. 813

FCC. Other Xererts.

Haploxererts, p. 816

Calcixererts

Calcixererts are the Xererts that have a calcic or petrocalcic

horizon. Many of these soils formed in fine textured

sedimentary rocks. In the United States, some of the soils are

used for irrigated crops. The others are used as rangeland,

pasture, or nonirrigated cropland.

Definition

Calcixererts are the Xererts that:

1. Have a calcic or petrocalcic horizon with an upper

boundary within 100 cm of the mineral soil surface; and
814 Soil Taxonomy

2. Do not have a duripan with an upper boundary within 100

cm of the mineral soil surface.

Key to Subgroups

FCBA. Calcixererts that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Calcixererts

FCBB. Other Calcixererts that have a petrocalcic horizon

that has its upper boundary within 100 cm of the mineral soil

surface.

Petrocalcic Calcixererts

FCBC. Other Calcixererts that, if not irrigated during the

year, have cracks in normal years that remain 5 mm or more

wide, through a thickness of 25 cm or more within 50 cm of

the mineral soil surface, for 180 or more consecutive days.

Aridic Calcixererts

FCBD. Other Calcixererts that have a densic, lithic, or

paralithic contact within 100 cm of the mineral soil surface.

Leptic Calcixererts

FCBE. Other Calcixererts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Calcixererts

FCBF. Other Calcixererts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Calcixererts

FCBG. Other Calcixererts.

Typic Calcixererts

Definition of Typic Calcixererts

Typic Calcixererts are the Calcixererts that:

1. Do not that have a densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface;

2. If not irrigated during the year, do not have cracks in

normal years that remain 5 mm or more wide, through a

thickness of 25 cm or more within 50 cm of the mineral soil

surface, for 180 or more consecutive days;

3. Do not have a petrocalcic horizon that has its upper

boundary within 100 cm of the mineral soil surface;

4. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its

upper boundary within 100 cm of the mineral soil surface;

and

5. Have, in all horizons within 30 cm of the mineral soil surface,

50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Calcixererts.—The Typic subgroup of the Calcixererts

is centered on deep or very deep soils that do not have a

petrocalcic horizon or a soil moisture regime that borders on

aridic. These soils tend to have dark colored surface layers and a

clay loam or finer texture throughout.

Aridic Calcixererts.—These are the Calcixererts that have

a soil moisture regime that borders on aridic and do not have a

lithic contact within 50 cm of the soil surface. These soils are

used for irrigated crops or rangeland.

Chromic Calcixererts.—These are the deep or very deep

Calcixererts that have light colored surface layers. These soils

do not have a petrocalcic horizon or a soil moisture regime that

borders on aridic. They typically have a clay loam or finer

texture throughout. These soils occur in Idaho and are used as

rangeland or for irrigated or nonirrigated crops.

Entic Calcixererts.—These are the deep or very deep

Calcixererts that have a layer 25 cm or more thick that

contains less than 27 percent clay. These soils do not have a

petrocalcic horizon or a soil moisture regime that borders on

aridic. They occur in California and Idaho and are used as

rangeland or for irrigated or nonirrigated crops.

Leptic Calcixererts.—These are the Calcixererts that have

a densic, lithic, or paralithic contact within 100 cm of the soil

surface but do not have a lithic contact within 50 cm of the soil

surface. They do not have a petrocalcic horizon or a soil

moisture regime that borders on aridic. These soils occur in

California and are used for pasture and hay.

Lithic Calcixererts.—These are the Calcixererts that have

a lithic contact within 50 cm of the soil surface. These soils are

not extensive in the world and are not known to occur in the

United States.

Petrocalcic Calcixererts.—These are the Calcixererts that

have a petrocalcic horizon. They do not have a lithic contact

within 50 cm of the soil surface or a soil moisture regime that

borders on aridic. These soils occur in California and are used

for pasture, rangeland, or irrigated or nonirrigated crops.

Durixererts

Durixererts are the Xererts that have a duripan. Most of

these soils are derived from basic igneous rocks, but some

formed in mixed alluvium. The Durixererts in the United States
Vertisols 815

occur in California and Idaho and are used for crop production

or rangeland.

Definition

Durixererts are the Xererts that have a duripan that has its

upper boundary within 100 cm of the mineral soil surface.

Key to Subgroups

FCAA. Durixererts that have, throughout a layer 15 cm or

more thick above the duripan, an electrical conductivity of 15

dS/m or more (saturated paste) for 6 or more months in normal

years.

Halic Durixererts

FCAB. Other Durixererts that have, in one or more horizons

above the duripan, an exchangeable sodium percentage of 15 or

more (or a sodium adsorption ratio of 13 or more) for 6 or

more months in normal years.

Sodic Durixererts

FCAC. Other Durixererts that have, in one or more horizons

above the duripan, aquic conditions for some time in normal

years (or artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquic Durixererts

FCAD. Other Durixererts that, if not irrigated during the

year, have cracks in normal years that remain 5 mm or more

wide, through a thickness of 25 cm or more above the duripan,

for 180 or more consecutive days.

Aridic Durixererts

FCAE. Other Durixererts that, if not irrigated during the

year, have cracks in normal years that remain 5 mm or more

wide, through a thickness of 25 cm or more above the duripan,

for less than 90 consecutive days.

Udic Durixererts

FCAF. Other Durixererts that have a duripan that is not

indurated in any subhorizon.

Haplic Durixererts

FCAG. Other Durixererts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Durixererts

FCAH. Other Durixererts.

Typic Durixererts

Definition of Typic Durixererts

Typic Durixererts are the Durixererts that:

1. Do not have, in any horizon above the duripan, aquic

conditions and either:

a. Redoximorphic features; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

2. Have, throughout all layers 15 cm or more thick above the

duripan, an electrical conductivity of less than 15 dS/m

(saturated paste) for 6 or more months in normal years;

3. Have, in all horizons above the duripan, an exchangeable

sodium percentage of less than 15 (or a sodium adsorption

ratio of less than 13) for 6 or more months in normal years;

4. If not irrigated during the year, have cracks in normal

years that remain 5 mm or more wide, throughout a layer 25

cm or more thick above the duripan, for 90 to 180 consecutive

days;

5. Have a duripan that is either platy or massive and also is

indurated in some subhorizon; and

6. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Durixererts.—The Typic subgroup of Durixererts is

centered on soils that have dark colored surface layers and a

duripan that is indurated in at least some part. These soils do

not have significant amounts of salts and sodium. In addition,

they do not have aquic conditions within 100 cm of the soil

surface or a soil moisture regime that borders on aridic or udic.

Aquic Durixererts.—These are the Durixererts that have

aquic conditions within 100 cm of the soil surface for extended

periods. These soils do not have significant amounts of salts

and sodium. They occur in California and are used for crop

production, pasture, or rangeland.

Aridic Durixererts.—These are the Durixererts that have a

soil moisture regime that borders on aridic. They do not have

significant amounts of salts or sodium or aquic conditions for

significant periods within 100 cm of the soil surface. These

soils occur in California and are used mostly for irrigated

crops.

Chromic Durixererts.—These are the Durixererts that have

light colored surface layers and a duripan that is indurated in
816 Soil Taxonomy

at least some part. These soils do not have significant amounts

of salts and sodium, a moisture regime that borders on aridic or

udic, or aquic conditions for extended periods within 100 cm of

the soil surface. They occur in Idaho and California and are

used as rangeland.

Halic Durixererts.—These are the Durixererts that have

significant amounts of salts. They are not known to occur in

the United States.

Haplic Durixererts.—These are the Durixererts that have a

duripan that is not indurated in any part. These soils do not

have significant amounts of salts and sodium, a moisture

regime that borders on aridic or udic, or aquic conditions for

significant periods within 100 cm of the soil surface. They

occur in California and are used for crop production or

rangeland.

Sodic Durixererts.—These are the Durixererts that have

significant amounts of sodium, but not salts. These soils are

not known to occur in the United States.

Udic Durixererts.—These are the Durixererts that have

a soil moisture regime that borders on udic. These soils do

not have significant amounts of salts or sodium or aquic

conditions for extended periods within 100 cm of the soil

surface.

Haploxererts

Haploxererts are the Xererts that do not have a calcic or

petrocalcic horizon or a duripan. These are the most common

of the Xererts. They formed in a variety of parent materials,

including volcanic and sedimentary rocks, lacustrine deposits,

and alluvium. In many areas these soils are used for grazing by

livestock. In some areas they are used for citrus, small grain,

truck crops, or rice.

Definition

Haploxererts are the Xererts that do not have a duripan or a

calcic or petrocalcic horizon that has its upper boundary within

100 cm of the mineral soil surface.

Key to Subgroups

FCCA. Haploxererts that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Haploxererts

FCCB. Other Haploxererts that have, throughout a layer 15

cm or more thick within 100 cm of the mineral soil surface, an

electrical conductivity of 15 dS/m or more (saturated paste) for

6 or more months in normal years.

Halic Haploxererts

FCCC. Other Haploxererts that have, in one or more

horizons within 100 cm of the mineral soil surface, an

exchangeable sodium percentage of 15 or more (or a sodium

adsorption ratio of 13 or more) for 6 or more months in normal

years.

Sodic Haploxererts

FCCD. Other Haploxererts that, if not irrigated during the

year, have cracks in normal years that remain 5 mm or more

wide, through a thickness of 25 cm or more within 50 cm of

the mineral soil surface, for 180 or more consecutive days.

Aridic Haploxererts

FCCE. Other Haploxererts that have, in one or more

horizons within 100 cm of the mineral soil surface, aquic

conditions for some time in normal years (or artificial

drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated.

Aquic Haploxererts

FCCF. Other Haploxererts that, if not irrigated during the

year, have cracks in normal years that remain 5 mm or more

wide, through a thickness of 25 cm or more within 50 cm of

the mineral soil surface, for less than 90 consecutive days.

Udic Haploxererts

FCCG. Other Haploxererts that have a densic, lithic, or

paralithic contact within 100 cm of the mineral soil surface.

Leptic Haploxererts

FCCH. Other Haploxererts that have a layer 25 cm or more

thick that contains less than 27 percent clay in its fine-earth

fraction and has its upper boundary within 100 cm of the

mineral soil surface.

Entic Haploxererts

FCCI. Other Haploxererts that have, in one or more horizons

within 30 cm of the mineral soil surface, 50 percent or more

colors as follows:

1. A color value, moist, of 4 or more; or

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Haploxererts

FCCJ. Other Haploxererts.

Typic Haploxererts

Definition of Typic Haploxererts

Typic Haploxererts are the Haploxererts that:

1. Do not have a densic, lithic, or paralithic contact

within 100 cm of the mineral soil surface;
Vertisols 817

2. Do not have, in any horizon within 100 cm of the mineral soil

surface, aquic conditions and either:

a. Redoximorphic features; or

b. Enough active ferrous iron (Fe2+) to give a positive

reaction to alpha,alpha-dipyridyl at a time when the soil is

not being irrigated;

3. Do not have a layer 25 cm or more thick that contains less

than 27 percent clay in its fine-earth fraction and has its upper

boundary within 100 cm of the mineral soil surface;

4. Have, throughout all layers 15 cm or more thick

within 100 cm of the mineral soil surface, an electrical

conductivity of less than 15 dS/m (saturated paste) for 6

or more months in normal years;

5. Have, in all horizons within 100 cm of the mineral soil

surface, an exchangeable sodium percentage of less than 15 (or

a sodium adsorption ratio of less than 13) for 6 or more months

in normal years;

6. If not irrigated during the year, have cracks in normal

years that remain 5 mm or more wide, through a thickness of

25 cm or more within 50 cm of the mineral soil surface, for 90

or more but less than 180 consecutive days; and

7. Have, in all horizons within 30 cm of the mineral soil

surface, 50 percent or more colors as follows:

a. A color value, moist, of 3 or less; or

b. A color value, dry, of 5 or less; or

c. Chroma of 2 or less.

Description of Subgroups

Typic Haploxererts.—The Typic subgroup of Haploxererts

is centered on deep or very deep, clayey soils with dark colored

surface layers. These soils do not have significant amounts of

sodium or salts, a soil moisture regime that borders on aridic or

udic, or aquic conditions within 100 cm of the soil surface for

extended periods. They occur in Oregon, Idaho, and California

and are used for rangeland, pasture, or dryland or irrigated

crops.

Aquic Haploxererts.—These are the Haploxererts that have

aquic conditions within 100 cm of the soil surface for extended

periods. These soils do not have significant amounts of salts or

sodium or a lithic contact within 50 cm of the soil surface.

They occur in Oregon and California and are used for pasture

or irrigated crops, including rice.

Aridic Haploxererts.—These are the Haploxererts that

have a soil moisture regime that borders on aridic. They do not

have a lithic contact within 50 cm of the soil surface or

significant amounts of sodium and salts. These soils occur in

Nevada and California, including the Channel Islands off the

coast of southern California. The soils are used for rangeland

or crop production. In some areas they are irrigated and

planted to citrus.

Chromic Haploxererts.—These are the deep or very deep,

clayey Haploxererts with light colored surface layers. These

soils do not have significant amounts of sodium or salts, a soil

moisture regime that borders on udic or aridic, or aquic

conditions for significant periods within 100 cm of the soil

surface. They occur in California, Idaho, and Oregon. They

generally are used as rangeland, but the more nearly level areas

are used for irrigated or nonirrigated crops.

Entic Haploxererts.—These are the deep or very deep

Haploxererts that have a layer 25 cm or more thick with less

than 27 percent clay. These soils do not have significant

amounts of salts or sodium, a moisture regime that borders on

aridic or udic, or aquic conditions for extended periods within

100 cm of the soil surface. They occur in Oregon and are used

as rangeland.

Halic Haploxererts.—These are the Haploxererts that have

significant amounts of salts. These soils do not have a lithic

contact within 50 cm of the soil surface. They occur in

California, including the Channel Islands off the coast of

southern California. They are used for rangeland or irrigated

crops.

Leptic Haploxererts.—These are the Haploxererts that

have a densic, lithic, or paralithic contact within 100 cm of the

soil surface but do not have a lithic contact within 50 cm of the

soil surface. These soils do not have significant amounts of

sodium or salts, a soil moisture regime that borders on udic or

aridic, or aquic conditions for extended periods within 100 cm

of the soil surface. They occur in Nevada, California, Oregon,

and Idaho. They are used mostly as rangeland, but small areas

are used for irrigated crops.

Lithic Haploxererts.—These are the Haploxererts that

have a lithic contact within 50 cm of the soil surface. They are

not known to occur in the United States.

Sodic Haploxererts.—These are the Haploxererts that have

significant amounts of sodium, but not salts. These soils do not

have a lithic contact within 50 cm of the soil surface. They

occur in California. Some of the soils are used for crops,

including rice.

Udic Haploxererts.—These are the Haploxererts that have

a soil moisture regime that borders on udic. These soils do not

have significant amounts of sodium or salts, a lithic contact

within 50 cm of the soil surface, or aquic conditions for

significant periods within 100 cm of the soil surface. They

occur in Oregon, where they are used for nonirrigated or

irrigated crops, including orchards.

819

As was noted in chapter 6, families and series servepurposes that are largely pragmatic, the series name is

abstract, and the technical family name is descriptive. In the

paragraphs that follow, the descriptive terms used in the names

of families are defined, the control sections to which the terms

apply are given, and the criteria, including the taxa in which

they are used, are indicated. An example of a family is given to

show how the family name is derived, and the differences

between two series in that family are pointed out as examples

of series differentiae.

Family Differentiae for Mineral Soils and

Mineral Layers of Some Organic Soils

The following differentiae are used to distinguish families of

mineral soils and the mineral layers of some organic soils

within a subgroup. The class names of these components are

used to form the family name. The components are listed and

defined in the same sequence in which the components appear

in the family names.

Particle-size classes

Mineralogy classes

Cation-exchange activity classes

Calcareous and reaction classes

Soil temperature classes

Soil depth classes

Rupture-resistance classes

Classes of coatings

Classes of cracks

Particle-Size Classes and Their Substitutes

Definition of Particle-Size Classes and Their Substitutes for

Mineral Soils

The first part of the family name is the name of either a

particle-size class or a substitute for a particle-size class. The

term particle-size class is used to characterize the grain-size

composition of the whole soil, including both the fine earth and

the rock and pararock fragments up to the size of a pedon, but

it excludes organic matter and salts more soluble than gypsum.

Substitutes for particle-size classes are used for soils that have

andic soil properties or a high content of volcanic glass,

pumice, or cinders.

The particle-size classes of this taxonomy represent a

compromise between conventional divisions in pedologic and

engineering classifications. Engineering classifications have

set the limit between sand and silt at a diameter of 74 microns,

while pedologic classifications have set it at either 50 or 20

microns. Engineering classifications have been based on grainsize percentages, by weight, in the soil fraction less than 74

mm in diameter, while textural classes in pedologic

classifications have been based on percentages, by weight, in

the fraction less than 2.0 mm in diameter. In engineering

classifications, the separate very fine sand (diameter between

50 and 100 microns or 0.05 and 0.1 mm) has been subdivided

at 74 microns. In defining the particle-size classes for this

taxonomy, a similar division has been made, but in a different

way. Soil materials that have a texture of fine sand or loamy

fine sand normally have an appreciable amount of very fine

sand, most of which is coarser than 74 microns. A silty

sediment, such as loess, may also contain an appreciable

amount of very fine sand, most of which is finer than 74

microns. Thus, in the design of particle-size classes for this

taxonomy, the very fine sand has been allowed to “float.” It is

included with the sand if the texture (fine-earth fraction) of a

soil is sand, loamy fine sand, or coarser. It is treated as silt,

however, if the texture is very fine sand, loamy very fine sand,

sandy loam, silt loam, or finer.

No single set of particle-size classes seems adequate to serve

as family differentiae for all of the different kinds of soil. Thus,

this taxonomy provides 2 generalized and 11 more narrowly

defined classes, which permit relatively fine distinctions

between families of soils for which particle size is important,

while providing broader groupings for soils in which narrowly

defined particle-size classes would produce undesirable

separations. Thus, the term “clayey” is used for some soil

families to indicate a clay content of 35 percent (30 percent in

Vertisols) or more in specific horizons, while in other families

the more narrowly defined terms “fine” and “very-fine”

indicate that these horizons have a clay content either of 35 (30

percent in Vertisols) to 60 percent or of 60 percent or more in

their fine-earth fraction. Fine earth refers to particles smaller

than 2.0 mm in diameter. Rock fragments are particles 2.0 mm

or more in diameter that are strongly cemented or more

resistant to rupture and include all particles with horizontal

dimensions smaller than the size of a pedon. Cemented

fragments 2.0 mm or more in diameter that are in a ruptureresistance class that is less cemented than the strongly

CHAPTER 21

Family and Series Differentiae and Names
820 Soil Taxonomy

cemented class are referred to as pararock fragments. Pararock

fragments, like rock fragments, include all particles between

2.0 mm and a horizontal dimension smaller than the size of a

pedon. Most pararock fragments are broken into fragments 2.0

mm or less in diameter during the preparation of samples for

particle-size analysis in the laboratory. Therefore, pararock

fragments are generally included with the fine earth in the

particle-size classes, although cinders, pumice, and pumicelike

fragments are treated as fragments in the substitutes for

classes, regardless of their rupture-resistance class.

Substitutes for particle-size classes are used for soils that

have andic soil properties or a high content of volcanic glass,

pumice, or cinders. These materials cannot be readily

dispersed, and the results of dispersion vary. Consequently,

normal particle-size classes do not adequately characterize

these components. Substitutes for particle-size class names are

used for those parts of soils that have andic soil properties or a

high amount of volcanic glass, pumice, or cinders, as is the

case with Andisols and many Andic and Vitrandic subgroups

of other soil orders. Some Spodosols, whether identified in

Andic subgroups or not, have andic soil properties in some

horizons within the particle-size control section, and particlesize substitute class names are used for these horizons.

Neither a particle-size class name nor a substitute for a

particle-size class name is used for Psamments,

Psammaquents, and Psammentic subgroups that are in a sandy

particle-size class. These taxa have, by definition, either a

sandy particle-size class or an ashy substitute class. The sandy

particle-size class is considered redundant in the family name.

The ashy substitute class, however, is named, if appropriate in

these taxa.

Particle-size class names are applied, although with

reservations, to spodic horizons and other horizons that do not

have andic soil properties but contain significant amounts of

allophane, imogolite, ferrihydrite, or aluminum-humus

complexes. The isotic mineralogy class (defined below) is

helpful in identifying these particle-size classes.

In general, the weighted average particle-size class of the

whole particle-size control section (defined below) determines

what particle-size class name is used as a component of the

family name.

Strongly Contrasting Particle-Size Classes

If the particle-size control section consists of two parts with

strongly contrasting particle-size or substitute classes (listed

below), if both parts are 12.5 cm or more thick (including parts

not in the control section), and if the transition zone between

them is less than 12.5 cm thick, both class names are used. For

example, the family particle-size class is sandy over clayey if

all of the following criteria are met: the soil meets criterion D

(listed below) under the control section for particle-size classes

or their substitutes; any Ap horizon is less than 30 cm thick;

the weighted average particle-size class of the upper 30 cm of

the soil is sandy; the weighted average of the lower part is

clayey; and the transition zone is less than 12.5 cm thick. If a

substitute name applies to one or more parts of the particle-size

control section and the parts are not strongly contrasting

classes, the name of the thickest part (cumulative) is used as

the soil family name.

Aniso Class

If the particle-size control section includes more than one

pair of the strongly contrasting classes, listed below, then the

soil is assigned to an aniso class named for the pair of adjacent

classes that contrast most strongly. The aniso class is

considered part of the particle-size class name and is set off by

commas after the particle-size name. An example is a sandy

over clayey, aniso, mixed, active, mesic Aridic Haplustoll.

Generalized Particle-Size Classes

Two generalized particle-size classes, loamy and clayey, are

used for shallow classes (defined below) and for soils in

Arenic, Grossarenic, and Lithic subgroups. The clayey class is

used for all strongly contrasting particle-size classes with more

than 35 percent clay (30 percent in Vertisols). The loamy

particle-size class is used for contrasting classes, where

appropriate, to characterize the lower part of the particle-size

control section. The generalized classes, where appropriate, are

also used for all strongly contrasting particle-size classes that

include a substitute class. For example, loamy over pumiceous

or cindery (not fine-loamy over pumiceous or cindery) is used.

Six generalized classes, defined later in this chapter, are

used for Terric subgroups of Histosols and Histels.

Control Section for Particle-Size Classes or Their

Substitutes in Mineral Soils

The particle-size and substitute class names listed below are

applied to certain horizons, or to the soil materials within

specific depth limits, that have been designated as the particlesize control section. The lower boundary of the control section

may be at a specified depth (in centimeters) below the mineral

soil surface or below the upper boundary of an organic layer

with andic soil properties, or it may be at the upper boundary

of a root-limiting layer. Unless otherwise indicated, the

following are considered root-limiting layers in this chapter: a

duripan; a fragipan; petrocalcic, petrogypsic, and placic

horizons; continuous ortstein; and densic, lithic, paralithic,

and petroferric contacts. The following list of particle-size

control sections for particular kinds of mineral soils is

arranged as a key. This key, like other keys in this taxonomy, is

designed in such a way that the reader makes the correct

classification by going through the key systematically, starting

at the beginning and eliminating one by one all classes that

include criteria that do not fit the soil in question. The soil

belongs to the first class for which it meets all of the criteria

listed. The upper boundary of an argillic, natric, or kandic

horizon is used in the following key. This boundary is not

always obvious. If one of these horizons is present but the
Family and Series Differentiae and Names 821

upper boundary is irregular or broken, as in an A/B or B/A

horizon, the depth at which half or more of the volume has the

fabric of an argillic, natric, or kandic horizon should be

considered the upper boundary.

Key to the Control Section for Particle-Size Classes or Their

Substitutes in Mineral Soils

A. For mineral soils that have a root-limiting layer (listed

above) within 36 cm of the mineral soil surface or below the

upper boundary of organic soil materials with andic soil

properties, whichever is shallower: From the mineral soil

surface or the upper boundary of the organic soil materials with

andic soil properties, whichever is shallower, to the rootlimiting layer; or

B. For Andisols: Between either the mineral soil surface or

the upper boundary of an organic layer with andic soil

properties, whichever is shallower, and the shallower of the

following: (a) a depth 100 cm below the starting point or (b) a

root-limiting layer; or

C. For those Alfisols, Ultisols, and great groups of Aridisols

and Mollisols, excluding soils in Lamellic subgroups, that have

an argillic, kandic, or natric horizon that has its upper

boundary within 100 cm of the mineral soil surface and its

lower boundary at a depth of 25 cm or more below the mineral

soil surface or that are in a Grossarenic or Arenic subgroup,

use 1 through 4 below. For other soils, go to D below.

1. Strongly contrasting particle-size classes (defined and

listed later) within or below the argillic, kandic, or natric

horizon and within 100 cm of the mineral soil surface: The

upper 50 cm of the argillic, kandic, or natric horizon or to a

depth of 100 cm, whichever is deeper, but not below the

upper boundary of a root-limiting layer; or

2. All parts of the argillic, kandic, or natric horizon in or

below a fragipan: Between a depth of 25 cm from the

mineral soil surface and the top of the fragipan; or

3. A fragipan at a depth of less than 50 cm below the top

of the argillic, kandic, or natric horizon: Between the upper

boundary of the argillic, kandic, or natric horizon and the

top the fragipan; or

4. Other soils that meet C above: Either the whole argillic,

kandic, or natric horizon if 50 cm or less thick or the upper

50 cm of the horizon if more than 50 cm thick.

D. For those Alfisols, Ultisols, and great groups of Aridisols

and Mollisols that are in a Lamellic subgroup or have an

argillic, kandic, or natric horizon that has its upper boundary

at a depth of 100 cm or more from the mineral surface and that

are not in a Grossarenic or Arenic subgroup: Between the

lower boundary of an Ap horizon or a depth of 25 cm from the

mineral soil surface, whichever is deeper, and 100 cm below

the mineral soil surface or a root-limiting layer, whichever is

shallower; or

E. For other soils that have an argillic or natric horizon that has

its lower boundary at a depth of less than 25 cm from the mineral

surface: Between the upper boundary of the argillic

or natric horizon and a depth of 100 cm below the mineral

soil surface or a root-limiting layer, whichever is shallower;

or

F. All other mineral soils: Between the lower boundary of an

Ap horizon or a depth of 25 cm below the mineral soil surface,

whichever is deeper, and the shallower of the following: (a) a

depth of 100 cm below the mineral soil surface or (b) a rootlimiting layer.

Key to the Particle-Size and Substitute Classes of Mineral

Soils

This key, like other keys in this taxonomy, is designed in such

a way that the reader makes the correct classification by going

through the key systematically, starting at the beginning and

eliminating one by one all classes that include criteria that do

not fit the soil or layer in question. The class or substitute name

for each layer within the control section must be determined

from the key. If any two layers meet the criteria for strongly

contrasting particle-size classes (listed below), the soil is named

for that strongly contrasting class. If more than one pair meets

the criteria for strongly contrasting classes, the soil is also in an

aniso class named for the pair of adjacent classes that contrast

most strongly. If the soil has none of the strongly contrasting

classes, the weighted average soil materials within the particlesize control section generally determine the class. Exceptions are

soils that are not strongly contrasting and that have a substitute

class name for one or more parts of the control section. In these

soils the class or substitute name of the thickest (cumulative)

part within the control section is used to determine the family

name.

A. Mineral soils that have, in the thickest part of the control

section (if the control section is not in one of the strongly

contrasting particle-size classes listed below), or in a part of the

control section that qualifies as an element in one of the

strongly contrasting particle-size classes listed below, or

throughout the control section, a fine-earth component

(including associated medium and finer pores) of less than 10

percent of the total volume and that meet one of the following

sets of substitute class criteria:

1. Have, in the whole soil, more than 60 percent (by

weight) volcanic ash, cinders, lapilli, pumice, and

pumicelike1

 fragments and, in the fraction coarser than

1Pumicelike—vesicular pyroclastic materials other than pumice that have an apparent

specific gravity (including vesicles) of less than 1.0 g/cm3

.
822 Soil Taxonomy

2.0 mm, two-thirds or more (by volume) pumice and/or

pumicelike fragments.

Pumiceous

or

2. Have, in the whole soil, more than 60 percent (by

weight) volcanic ash, cinders, lapilli, pumice, and

pumicelike fragments and, in the fraction coarser than 2.0

mm, less than two-thirds (by volume) pumice and

pumicelike fragments.

Cindery

or

3. Other mineral soils that have a fine-earth component of

less than 10 percent (including associated medium and finer

pores) of the total volume.

Fragmental

or

B. Other mineral soils that have a fine-earth component of 10

percent or more (including associated medium and finer pores)

of the total volume and meet, in the thickest part of the control

section (if the control section is not in one of the strongly

contrasting particle-size classes listed below), or in a part of

the control section that qualifies as an element in one of the

strongly contrasting particle-size classes listed below, or

throughout the control section, one of the following sets of

substitute class criteria:

1. They:

a. Have andic soil properties and have a water

content at 1500 kPa tension of less than 30 percent on

undried samples and less than 12 percent on dried

samples; or

b. Do not have andic soil properties, have a total of 30

percent or more of the fine-earth fraction in the 0.02 to

2.0 mm fraction, and have (by grain count) 30 percent or

more of that fraction consisting of volcanic glass, glass

aggregates, glass-coated grains, and other vitric

volcaniclastics; and

c. Have one of the following;

(1) A total of 35 percent or more (by volume) rock

and pararock fragments, of which two-thirds or more

(by volume) is pumice or pumicelike fragments.

Ashy-pumiceous

or

(2) 35 percent or more (by volume) rock fragments.

Ashy-skeletal

or

(3) Less than 35 percent (by volume) rock

fragments.

Ashy

or

2. Have a fine-earth fraction that has andic soil properties

and that has a water content at 1500 kPa tension of 12

percent or more on air-dried samples or of 30 to 100 percent

on undried samples; and

a. Have a total of 35 percent or more (by volume) rock

and pararock fragments, of which two-thirds or more (by

volume) is pumice or pumicelike fragments.

Medial-pumiceous

or

b. Have 35 percent or more (by volume) rock

fragments.

Medial-skeletal

or

c. Have less than 35 percent (by volume) rock

fragments.

Medial

or

3. Have a fine-earth fraction that has andic soil properties

and that has a water content at 1500 kPa tension of 100

percent or more on undried samples; and

a. Have a total of 35 percent or more (by volume) rock

and pararock fragments, of which two-thirds or more (by

volume) is pumice or pumicelike fragments.

Hydrous-pumiceous

or

b. Have 35 percent or more (by volume) rock

fragments.

Hydrous-skeletal

or

c. Have less than 35 percent (by volume) rock

fragments.

Hydrous

or

Note: In the following classes, “clay” excludes clay-size

carbonates. Carbonates of clay size are treated as silt. If the

ratio of percent water retained at 1500 kPa tension to the

percentage of measured clay is 0.25 or less or 0.6 or more in

half or more of the particle-size control section or part of the

particle-size control section in strongly contrasting classes,
Family and Series Differentiae and Names 823

then the percentage of clay is estimated by the following

formula: Clay % = 2.5(% water retained at 1500 kPa tension - %

organic carbon).

C. Other mineral soils that, in the thickest part of the control

section (if part of the control section has a substitute for

particle-size class and is not in one of the strongly contrasting

particle-size classes listed below), or in a part of the control

section that qualifies as an element in one of the strongly

contrasting particle-size classes listed below, or throughout the

control section, meet one of the following sets of particle-size

class criteria:

1. Have 35 percent or more (by volume) rock fragments

and a fine-earth fraction with a texture of sand or loamy

sand, including less than 50 percent (by weight) very fine

sand.

Sandy-skeletal

or

2. Have 35 percent or more (by volume) rock fragments

and less than 35 percent (by weight) clay.

Loamy-skeletal

or

3. Have 35 percent or more (by volume) rock fragments.

Clayey-skeletal

or

4. Have a texture of sand or loamy sand, including less

than 50 percent (by weight) very fine sand in the fine-earth

fraction.

Sandy

or

5. Have a texture of loamy very fine sand, very fine sand,

or finer, including less than 35 percent (by weight) clay in

the fine-earth fraction (excluding Vertisols), and are in a

shallow family (defined below) or in a Lithic, Arenic, or

Grossarenic subgroup, or the layer is an element in a

strongly contrasting particle-size class (listed below) and the

layer is the lower element or the other element is a

substitute for particle-size class.

Loamy

or

6. Have, in the fraction less than 75 mm in diameter, 15

percent or more (by weight) particles with diameters of 0.1

to 75 mm (fine sand or coarser, including rock fragments up

to 7.5 cm in diameter) and, in the fine-earth fraction, less

than 18 percent (by weight) clay.

Coarse-loamy

or

7. Have, in the fraction less than 75 mm in diameter, 15

percent or more (by weight) particles with diameters of 0.1 to

75 mm (fine sand or coarser, including rock fragments up to

7.5 cm in diameter) and 18 to 35 percent (by weight) clay

(Vertisols are excluded).

Fine-loamy

or

8. Have, in the fraction less than 75 mm in diameter, less

than 15 percent (by weight) particles with diameters of 0.1

to 75 mm (fine sand or coarser, including rock fragments up

to 7.5 cm in diameter) and, in the fine-earth fraction, less

than 18 percent (by weight) clay.

Coarse-silty

or

9. Have, in the fraction less than 75 mm in diameter, less

than 15 percent (by weight) particles with diameters of 0.1

to 75 mm (fine sand or coarser, including rock fragments up

to 7.5 cm in diameter) and, in the fine-earth fraction, 18 to

35 percent (by weight) clay (Vertisols are excluded).

Fine-silty

or

10. Have 35 percent or more (by weight) clay (more

than 30 percent in Vertisols) and are in a shallow family

(defined below) or in a Lithic, Arenic, or Grossarenic

subgroup, or the layer is an element in a strongly

contrasting particle-size class (listed below).

Clayey

or

11. Have (by weighted average) less than 60 percent (by

weight) clay in the fine-earth fraction.

Fine

or

12. Have 60 percent or more clay.

Very-fine

Strongly Contrasting Particle-Size Classes

The purpose of strongly contrasting particle-size classes is

to identify changes in pore-size distribution or composition that

are not identified in higher soil categories and that seriously

affect the movement and retention of water and/or nutrients.

The following particle-size or substitute classes are

considered strongly contrasting if both parts are 12.5 cm or

more thick (including parts not in the particle-size control

section; however, substitute class names are used only if the

soil materials to which they apply extend 10 cm or more into

the upper part of the particle-size control section) and if the

transition zone between the two parts of the particle-size

control section is less than 12.5 cm thick.

Some classes, such as sandy and sandy-skeletal, have been

combined in the following list. In those cases the combined
824 Soil Taxonomy

name is used as the family class if part of the control section

meets the criteria for either class.

1. Ashy over clayey

2. Ashy over clayey-skeletal

3. Ashy over loamy-skeletal

4. Ashy over loamy

5. Ashy over medial-skeletal

6. Ashy over medial (if the water content at 1500 kPa tension in

dried samples of the fine-earth fraction is 10 percent or less for

the ashy materials and 15 percent or more for the medial

materials)

7. Ashy over pumiceous or cindery

8. Ashy over sandy or sandy-skeletal

9. Ashy-skeletal over fragmental or cindery (if the volume of

the fine-earth fraction is 35 percent or more [absolute] greater

in the ashy-skeletal part than in the fragmental or cindery part)

10. Cindery over loamy

11. Cindery over medial-skeletal

12. Cindery over medial

13. Clayey over fine-silty (if there is an absolute difference of

25 percent or more between clay percentages of the fine-earth

fraction in the two parts of the control section)

14. Clayey over fragmental

15. Clayey over loamy (if there is an absolute difference of 25

percent or more between clay percentages of the fine-earth

fraction in the two parts of the control section)

16. Clayey over loamy-skeletal (if there is an absolute

difference of 25 percent or more between clay percentages of

the fine-earth fraction in the two parts of the control section)

17. Clayey over sandy or sandy-skeletal

18. Clayey-skeletal over sandy or sandy-skeletal

19. Coarse-loamy over clayey

20. Coarse-loamy over fragmental

21. Coarse-loamy over sandy or sandy-skeletal (if the coarseloamy material contains less than 50 percent fine sand or

coarser sand)

22. Coarse-silty over clayey

23. Coarse-silty over sandy or sandy-skeletal

24. Fine-loamy over clayey (if there is an absolute difference

of 25 percent or more between clay percentages of the fineearth fraction in the two parts of the control section)

25. Fine-loamy over fragmental

26. Fine-loamy over sandy or sandy-skeletal

27. Fine-silty over clayey (if there is an absolute difference of

25 percent or more between clay percentages of the fine-earth

fraction in the two parts of the control section)

28. Fine-silty over fragmental

29. Fine-silty over sandy or sandy-skeletal

30. Hydrous over clayey-skeletal

31. Hydrous over clayey

32. Hydrous over fragmental

33. Hydrous over loamy-skeletal

34. Hydrous over loamy

35. Hydrous over sandy or sandy-skeletal

36. Loamy over sandy or sandy-skeletal (if the loamy

material contains less than 50 percent fine sand or coarser

sand)

37. Loamy over pumiceous or cindery

38. Loamy-skeletal over cindery (if the volume of the fineearth fraction is 35 percent or more [absolute] greater in the

loamy-skeletal part than in the cindery part)

39. Loamy-skeletal over clayey (if there is an absolute

difference of 25 percent or more between clay percentages of

the fine-earth fraction in the two parts of the control section)

40. Loamy-skeletal over fragmental (if the volume of the

fine-earth fraction is 35 percent or more [absolute] greater in

the loamy-skeletal part than in the fragmental part)

41. Loamy-skeletal over sandy or sandy-skeletal (if the loamy

material has less than 50 percent fine sand or coarser sand)

42. Medial over ashy (if the water content at 1500 kPa

tension in dried samples of the fine-earth fraction is 15 percent

or more for the medial materials and 10 percent or less for the

ashy materials)

43. Medial over ashy-pumiceous or ashy-skeletal (if the water

content at 1500 kPa tension in dried samples of the fine-earth

fraction is 15 percent or more for the medial materials and 10

percent or less for the ashy part)

44. Medial over clayey-skeletal

45. Medial over clayey

46. Medial over fragmental

47. Medial over hydrous (if the water content at 1500 kPa

tension in undried samples of the fine-earth fraction is 75

percent or less for the medial materials)
Family and Series Differentiae and Names 825

48. Medial over loamy-skeletal

49. Medial over loamy

50. Medial over pumiceous or cindery

51. Medial over sandy or sandy-skeletal

52. Medial-skeletal over fragmental or cindery (if the volume

of the fine-earth fraction is 35 percent or more [absolute]

greater in the medial-skeletal part than the fragmental or cindery

part)

53. Pumiceous or ashy-pumiceous over loamy

54. Pumiceous or ashy-pumiceous over medial-skeletal

55. Pumiceous or ashy-pumiceous over medial

56. Pumiceous or ashy-pumiceous over sandy or sandyskeletal

57. Sandy over clayey

58. Sandy over loamy (if the loamy material contains less

than 50 percent fine sand or coarser sand)

59. Sandy-skeletal over loamy (if the loamy material contains

less than 50 percent fine sand or coarser sand)

Mineralogy Classes

The mineralogy of soils is known to be useful in making

predictions about soil behavior and responses to management.

Some mineralogy classes occur or are important only in certain

taxa or particle-size classes, and others are important in all

particle-size classes. The following key to mineralogy classes is

designed to make those distinctions.

Control Section for Mineralogy Classes

The control section for mineralogy classes is the same as

that defined for the particle-size classes and their substitutes.

Key to Mineralogy Classes

This key, like other keys in this taxonomy, is designed in

such a way that the reader makes the correct classification by

going through the key systematically, starting at the beginning

and eliminating one by one any classes that include criteria

that do not fit the soil in question. The soil belongs to the first

class for which it meets all of the required criteria. The user

should first check the criteria in section A and, if the soil in

question does not meet the criteria listed there, proceed on to

sections B, C, D, and E, until the soil meets the criteria listed.

All criteria are based on a weighted average.

For soils with strongly contrasting particle-size classes, the

mineralogy for both named particle-size classes or substitutes

are given, unless they are the same. Examples are an ashy over

clayey, mixed (if both the ashy and clayey parts are mixed),

superactive, mesic Typic Vitraquand and a clayey over sandy

or sandy-skeletal, smectitic over mixed, thermic Vertic

Haplustept.

A. Oxisols and “kandi” and “kanhap” great groups of

Alfisols and Ultisols that in the mineralogy control section

have:

1. More than 40 percent iron oxide (more than 28 percent

Fe), by dithionite citrate, in the fine-earth fraction.

Ferritic

or

2. More than 40 percent gibbsite in the fine-earth fraction.

Gibbsitic

or

3. Both:

a. 18 to 40 percent iron oxide (12.6 to 28 percent Fe),

by dithionite citrate, in the fine-earth fraction; and

b. 18 to 40 percent gibbsite in the fine-earth fraction.

Sesquic

or

4. 18 to 40 percent iron oxide (12.6 to 28 percent Fe), by

dithionite citrate, in the fine-earth fraction.

Ferruginous

or

5. 18 to 40 percent gibbsite in the fine-earth fraction.

Allitic

or

6. More than 50 percent (by weight) kaolinite plus

halloysite, dickite, nacrite, and other 1:1 and nonexpanding

2:1 layer minerals and gibbsite in the fraction less than

0.002 in size and more kaolinite than halloysite.

Kaolinitic

or

7. More than 50 percent (by weight) halloysite plus

kaolinite and allophane in the fraction less than 0.002 in

size.

Halloysitic

or

8. All other properties.

Mixed

or

B. Other soil layers or horizons, in the mineralogy control
826 Soil Taxonomy

section, that have a substitute class that replaces the particlesize class, other than fragmental, and that:

1. Have a sum of 8 times the Si (percent by weight extracted

by acid oxalate) plus 2 times the Fe (percent by weight

extracted by acid oxalate) of 5 or more, and 8 times the Si is

more than 2 times the Fe.

Amorphic

or

2. Other soils that have a sum of 8 times the Si (percent

by weight extracted by acid oxalate) plus 2 times the Fe

(percent by weight extracted by acid oxalate) of 5 or

more.

Ferrihydritic

or

3. Other soils that have 30 percent or more (by grain

count) volcanic glass in the 0.02 to 2.0 mm fraction.

Glassy

or

4. All other soils that have a substitute class.

Mixed

or

C. Other mineral soil layers or horizons, in the mineralogy

control section, in all other mineral soil orders and in Terric

subgroups of Histosols and Histels that have:

1. Any particle-size class and more than 40 percent (by

weight) carbonates (expressed as CaCO3

) plus gypsum, with

gypsum constituting more than 35 percent of the total

weight of carbonates plus gypsum, either in the fine-earth

fraction or in the fraction less than 20 mm in size,

whichever has a higher percentage of carbonates plus

gypsum.

Gypsic

or

2. Any particle-size class and more than 40 percent (by

weight) carbonates (expressed as CaCO3) plus gypsum,

either in the fine-earth fraction or in the fraction less than

20 mm in size, whichever has a higher percentage of

carbonates plus gypsum.

Carbonatic

or

3. Any particle-size class, except for fragmental, and more

than 40 percent (by weight) iron oxide (extractable by

dithionite citrate), reported as Fe2

O3 (or 28 percent reported

as Fe), in the fine-earth fraction.

Ferritic

or

4. Any particle-size class, except for fragmental, and more

than 40 percent (by weight) hydrated aluminum oxides,

reported as gibbsite and bohemite, in the fine-earth

fraction.

Gibbsitic

or

5. Any particle-size class, except for fragmental, and more

than 40 percent (by weight) magnesium-silicate minerals,

such as the serpentine minerals (antigorite, chrysotile, and

lizardite) plus talc, olivines, Mg-rich pyroxenes, and Mgrich amphiboles, in the fine-earth fraction.

Magnesic

or

6. Any particle-size class, except for fragmental, and a total

iron oxide, by weight (Fe extracted by citrate-dithionite times

1.43 is used to determine the iron oxide), plus percent (by

weight) gibbsite of more than 10 percent in the fine-earth

fraction.

Parasesquic

or

7. Any particle-size class, except for fragmental, and more

than 20 percent (by weight) glauconitic pellets in the fineearth fraction.

Glauconitic

or

D. Other mineral soil layers or horizons, in the mineralogy

control section, of soils in all other mineral orders and in

Terric subgroups of Histosols and Histels, in a clayey, clayeyskeletal, fine or very-fine particle-size class, that in the fraction

less than 0.002 mm in size:

1. Have more than one-half (by weight) halloysite plus

kaolinite and allophane and more halloysite than any other

single mineral.

Halloysitic

or

2. Have more than one-half (by weight) kaolinite plus

halloysite, dickite, and nacrite, and other 1:1 or

nonexpanding 2:1 layer minerals or gibbsite, and less than

10 percent (by weight) smectite.

Kaolinitic

or

3. Have more smectite (montmorillonite, beidellite, and

nontronite), by weight, than any other single kind of clay

mineral.

Smectitic

or
Family and Series Differentiae and Names 827

4. Have more than one-half (by weight) illite (hydrous mica)

and commonly more than 4 percent K2

O.

Illitic

or

5. Have more vermiculite than any other single kind of clay

mineral.

Vermiculitic

or

6. In more than one-half of the thickness, meet all of the

following:

a. Have no free carbonates; and

b. The pH of a suspension of 1 g soil in 50 ml 1 M NaF

is more than 8.4 after 2 minutes; and

c. The ratio of 1500 kPa water to measured clay is 0.6

or more.

Isotic

or

7. All other soils in this category.

Mixed

or

E. All other mineral soil layers or horizons (except for those

in Quartzipsamments), in the mineralogy control section, that

have:

1. More than 40 percent (by weight) (80 percent by grain

count) mica and stable mica pseudomorphs in the 0.02 to

2.0 mm fraction.

Micaceous

or

2. More than 25 percent (by weight) (65 percent by grain

count) mica and stable mica pseudomorphs in the 0.02 to

2.0 mm fraction.

Paramicaceous

or

3. In more than one-half of the thickness, all of the

following:

a. No free carbonates; and

b. The pH of a suspension of 1 g soil in 50 ml 1 M NaF

is more than 8.4 after 2 minutes; and

c. A ratio of 1500 kPa water to measured clay of 0.6 or

more.

Isotic

or

4. More than 90 percent (by weight) silica minerals

(quartz, chalcedony, or opal) and other extremely durable

minerals that are resistant to weathering, in the 0.02 to 2.0 mm

fraction.

Siliceous

or

5. All other properties.

Mixed

Cation-Exchange Activity Classes

The cation-exchange activity classes help in making

interpretations of mineral assemblages and of the nutrientholding capacity of soils in mixed and siliceous mineralogy

classes of clayey, clayey-skeletal, coarse-loamy, coarse-silty,

fine, fine-loamy, fine-silty, loamy, loamy-skeletal, and very-fine

particle-size classes. Cation-exchange activity classes are not

assigned to Histosols and Histels, and they are not assigned to

Oxisols and “kandi” and “kanhap” great groups and

subgroups of Alfisols and Ultisols because assigning such

classes to them would be redundant. Cation-exchange activity

classes are not assigned to the sandy, sandy-skeletal, or

fragmental particle-size class because the low clay content

causes cation-exchange activity classes to be less useful and

less reliable.

The cation-exchange capacity (CEC) is determined by

NH4OAc at pH 7 on the fine-earth fraction. The CEC of the

organic matter, sand, silt, and clay is included in the

determination. The criteria for the classes use ratios of CEC to

the percent, by weight, of silicate clay, both by weighted

average in the control section. In the following classes “clay”

excludes clay-size carbonates. If the ratio of percent water

retained at 1500 kPa tension to the percentage of measured

clay is 0.25 or less or 0.6 or more in half or more of the

particle-size control section (or part in contrasting families),

then the percentage of clay is estimated by the following

formula: Clay % = 2.5(% water retained at 1500 kPa tension -

% organic carbon).

Control Section for Cation-Exchange Activity Classes

The control section for cation-exchange activity classes is

the same as that used to determine the particle-size and

mineralogy classes. For soils with strongly contrasting particlesize classes, where both named parts of the control section use

a cation-exchange activity class, the class associated with the

particle-size class that has the most clay is named. For

example, in a pedon with a classification of loamy over clayey,

mixed, active, calcareous, thermic Typic Udorthent, the cationexchange activity class “active” is associated with the clayey

part of the control section.

Key to Cation-Exchange Activity Classes

A. Soils that are not Histosols, Histels, or Oxisols, that are

not in “kandi” or “kanhap” great groups or subgroups of

Alfisols and Ultisols, that are in either a mixed or siliceous
828 Soil Taxonomy

mineralogy class, that are not in a fragmental, sandy, or sandyskeletal particle-size class or any substitute for a particle-size

class, and that have a ratio of cation-exchange capacity (by

NH4

OAc at pH 7) to clay (percent by weight) of:

1. 0.60 or more.

Superactive

2. 0.40 to 0.60.

Active

3. 0.24 to 0.40.

Semiactive

4. Less than 0.24.

Subactive

or

B. All other soils: No cation-exchange activity classes used.

Calcareous and Reaction Classes of Mineral Soils

The presence or absence of carbonates, soil reaction, and the

presence of high concentrations of aluminum in mineral soils

are treated together because they are so intimately related.

There are four classes—calcareous, acid, nonacid, and allic.

These are defined later in the key to calcareous and reaction

classes. The classes are not used in all taxa, nor is more than

one used in the same taxa.

Use of the Calcareous and Reaction Classes

The calcareous, acid, and nonacid classes are used in the

names of the families of Entisols, Aquands, and Aquepts,

except they are not used in any of the following:

1. Duraquands and Placaquands

2. Sulfaquepts, Fragiaquepts, and Petraquepts

3. Sandy, sandy-skeletal, cindery, pumiceous, or fragmental

families

4. Families with carbonatic or gypsic mineralogy

The calcareous class, in addition to those listed above, is

used in the names of the families of Aquolls, except it is not

used with any of the following:

1. Calciaquolls, Natraquolls, and Argiaquolls

2. Cryaquolls and Duraquolls that have an argillic horizon

3. Families with carbonatic or gypsic mineralogy

The allic class is used only in families of Oxisols.

Control Section for Calcareous and Reaction Classes

The control section for the calcareous class is one of the

following:

1. Soils with a root-limiting layer that is 25 cm or less below the

mineral soil surface: A 2.5-cm-thick layer directly above the rootlimiting layer.

 2. Soils with a root-limiting layer that is 26 to 50 cm below the

mineral soil surface: The layer between a depth of 25 cm below

the mineral soil surface and the root-limiting layer.

3. All other listed soils: Between a depth of 25 and 50 cm below

the mineral soil surface.

The control section for the acid, nonacid, and allic classes is

the same as that for particle-size classes.

Key to Calcareous and Reaction Classes

A. Oxisols that have a layer, 30 cm or more thick within the

control section, that contains more than 2 cmol(+) of KClextractable Al per kg soil in the fine-earth fraction.

Allic

B. Other listed soils that, in the fine-earth fraction, effervesce

(in cold dilute HCl) in all parts of the control section.

Calcareous

C. Other listed soils with a pH of less than 5.0 in 0.01 M

CaCl2 (1:2) (about pH 5.5 in H2O, 1:1) throughout the control

section.

Acid

D. Other listed soils with a pH of 5.0 or more in 0.01 M

CaCl2 (1:2) in some or all layers in the control section.

Nonacid

It should be noted that a soil containing dolomite is

calcareous and that effervescence of dolomite, when treated

with cold dilute HCl, is slow.

The calcareous, acid, nonacid, and allic classes are listed in

the family name, when appropriate, following the mineralogy

and cation-exchange activity classes.

Soil Temperature Classes

Soil temperature classes, as named and defined here, are used

as part of the family name in both mineral and organic soils.

Temperature class names are used as part of the family name

unless the criteria for a higher taxon carry the same limitation.

Thus, frigid is implied in all cryic suborders, great groups, and

subgroups and would be redundant if used in the names of

families within these classes.

The Celsius (centigrade) scale is the standard. It is assumed

that the temperature is that of a soil that is not being irrigated.

Control Section for Soil Temperature

The control section for soil temperature either is at a depth

of 50 cm from the soil surface or is at the upper boundary of
Family and Series Differentiae and Names 829

a root-limiting layer, whichever is shallower. The soil

temperature classes, defined in terms of the mean annual

soil temperature and the difference between mean summer

and mean winter temperatures, are determined by the following

key.

Key to Soil Temperature Classes

A. Gelisols that have a mean annual soil temperature as

follows:

1. -10 o

C or lower.

Hypergelic

or

2. -4 oC to -10 oC.

Pergelic

or

3. +1 oC to -4 oC.

Subgelic

or

B. Other soils that have a difference in soil temperature of

6 oC or more between mean summer (June, July, and August in

the Northern Hemisphere) and mean winter (December,

January, and February in the Northern Hemisphere) and a

mean annual soil temperature of:

1. Lower than 8 oC (47 oF).

Frigid

or

2. 8 oC (47 oF) to 15 oC (59 oF).

Mesic

or

3. 15 oC (59 oF) to 22 oC (72 oF).

Thermic

or

4. 22 oC (72 oF) or higher.

Hyperthermic

or

C. All other soils that have a mean annual soil temperature

as follows:

1. Lower than 8 oC (47 oF).

Isofrigid

or

2. 8 oC (47 oF) to 15 oC (59 oF).

Isomesic

or

3. 15 oC (59 oF) to 22 oC (72 oF).

Isothermic

or

4. 22 oC (72 oF) or higher.

Isohyperthermic

Soil Depth Classes

Soil depth classes are used in all families that have a rootlimiting layer at a specified depth from the mineral soil

surface, except for those families in Lithic subgroups and those

with a fragipan. The root-limiting layers included in soil depth

classes are duripans; petrocalcic, petrogypsic, and placic

horizons; continuous ortstein (90 percent or more); and densic,

lithic, paralithic, and petroferric contacts. Soil depth classes for

Histosols and Histels are given later in this chapter. One soil

depth class name, “shallow,” is used to characterize certain

mineral soil families that have one of the depths indicated in

the following key.

Key to Soil Depth Classes

A. Oxisols that are less than 100 cm deep (from the mineral

soil surface) to a root-limiting layer and are not in a Lithic

subgroup.

Shallow

or

B. Soils in all other mineral soil orders that are less than 50

cm deep (from the mineral soil surface) to a root-limiting layer

and are not in a Lithic subgroup.

Shallow

or

C. All other mineral soils: No soil depth class used.

Rupture-Resistance Classes

In this taxonomy, some partially cemented soil

materials, such as durinodes, serve as differentiae in

categories above the family, while others, such as partially

cemented spodic materials (ortstein), do not. No single

family, however, should include soils both with and without

partially cemented horizons. In Spodosols, a partially

cemented spodic horizon is used as a family differentia.

The following rupture-resistance class is defined for families

of Spodosols:

A. Spodosols that have an ortstein horizon.

Ortstein

or

B. All other soils: No rupture-resistance class used.
830 Soil Taxonomy

Classes of Coatings (on Sands)

Despite the emphasis given to particle-size classes in this

taxonomy, variability remains in the sandy particle-size class,

which includes sands and loamy sands. Some sands are very

clean, i.e., almost completely free of silt and clay, while others

are mixed with appreciable amounts of finer grains. Clay is

more efficient at coating sand than is silt. A weighted average

silt (by weight) plus 2 times the weighted average clay (by

weight) of more than 5 makes a reasonable division of the

sands at the family level. Two classes of Quartzipsamments are

defined in terms of their content of silt plus 2 times their content

of clay.

Control Section for Classes of Coatings

The control section for classes of coatings is the same as that

for particle-size classes or their substitutes and for mineralogy

classes.

Key to Classes of Coatings

A. Quartzipsamments that have a sum of the weighted average

silt (by weight) plus 2 times the weighted average clay of more

than 5.

Coated

or

B. Other Quartzipsamments.

Uncoated

Classes of Permanent Cracks

Some Hydraquents consolidate or shrink after drainage and

become Fluvaquents or Humaquepts. In the process they can

form polyhedrons roughly 12 to 50 cm in diameter, depending

on their n value and texture. These polyhedrons are separated

by cracks that range in width from 2 mm to more than 1 cm.

The polyhedrons may shrink and swell with changes in the

moisture content of the soils, but the cracks are permanent and

can persist for several hundreds of years, even if the soils are

cultivated. The cracks permit rapid movement of water through

the soils, either vertically or laterally. Such soils may have the

same texture, mineralogy, and other family properties as soils

that do not form cracks or that have cracks that open and close

with the seasons. Soils with permanent cracks are very rare in

the United States.

Control Section for Classes of Permanent Cracks

The control section for classes of permanent cracks is from

the base of any plow layer or 25 cm from the soil surface,

whichever is deeper, to 100 cm below the soil surface.

Key to Classes of Permanent Cracks

A. Fluvaquents or Humaquepts that have, throughout a layer

50 cm or more thick, continuous, permanent, lateral and

vertical cracks 2 mm or more wide, spaced at average lateral

intervals of less than 50 cm.

Cracked

or

B. All other Fluvaquents and Humaquepts: No class of

permanent cracks used.

Family Differentiae for Histosols and

Histels

Most of the differentiae that are used to distinguish families

of Histosols and Histels have already been defined, either

because they are used as differentiae in mineral soils as well as

Histosols and Histels or because their definitions are used for

the classification of some Histosols and Histels in categories

higher than the family. In the following descriptions,

differentiae not previously mentioned are defined and the

classes in which they are used are enumerated.

The order in which family classes, if appropriate for a

particular family, are placed in the technical family names of

Histosols and Histels is as follows:

Particle-size classes

Mineralogy classes, including the nature of limnic deposits in

Histosols

Reaction classes

Soil temperature classes

Soil depth classes (used only in Histosols)

Particle-Size Classes

Particle-size classes are used only for the family names of

Terric subgroups of Histosols and Histels. The classes are

determined from the properties of the mineral soil materials in

the control section through use of the key to particle-size

classes. The classes are more generalized than those for soils in

other orders.

Control Section for Particle-Size Classes

The particle-size control section is the upper 30 cm of the

mineral layer or of that part of the mineral layer that is within

the control section for Histosols and Histels (given in chapter

4), whichever is thicker.

Key to Particle-Size Classes of Histosols and Histels

A. Terric subgroups of Histosols and Histels that
Family and Series Differentiae and Names 831

have (by weighted average) in the particle-size control

section:

1. A fine-earth component of less than 10 percent

(including associated medium and finer pores) of the total

volume.

Fragmental

or

2. A texture (of the fine earth) of sand or loamy sand,

including less than 50 percent (by weight) very fine sand in

the fine-earth fraction.

Sandy or sandy-skeletal

or

3. Less than 35 percent clay in the fine-earth fraction and

a content of rock fragments of 35 percent or more of the

total volume.

Loamy-skeletal

or

4. A content of rock fragments of 35 percent or more of

the total volume.

Clayey-skeletal

or

5. A clay content of 35 percent or more in the fine-earth

fraction.

Clayey

or

6. All other Terric subgroups of Histosols and Histels.

Loamy

or

B. All other Histosols and Histels: No particle-size class

used.

Mineralogy Classes

There are three different kinds of mineralogy classes

recognized for families in certain great groups and subgroups

of Histosols. The first kind is the ferrihumic soil material

defined below. The second is three types of limnic materials—

coprogenous earth, diatomaceous earth, and marl, defined in

chapter 4. The third is mineral layers of Terric subgroups. The

key to mineralogy classes for these mineral layers is the same

as that for mineral soils. Terric subgroups of Histels also have

the same mineralogy classes as those for mineral soils.

Ferrihumic Mineralogy Class

Ferrihumic soil material, i.e., bog iron, is an authigenic

(formed in place) deposit consisting of hydrated iron oxide

mixed with organic matter, either dispersed and soft or cemented

into large aggregates, in a mineral or organic layer that has all of

the following characteristics:

1. Saturation with water for more than 6 months per year (or

artificial drainage);

2. 2 percent or more (by weight) iron concretions having lateral

dimensions ranging from less than 5 to more than 100 mm and

containing 10 percent or more (by weight) free iron oxide (7

percent or more Fe) and 1 percent or more (by weight) organic

matter; and

3. A dark reddish or brownish color that changes little on

drying.

The ferrihumic mineralogy class is used for families of

Fibrists, Hemists, and Saprists, but it is not used for

Sphagnofibrists and Sphagnic subgroups of other great groups.

If the ferrihumic class is used in the family name of a Histosol,

no other mineralogy classes are used in that family because the

presence of iron is considered to be by far the most important

mineralogical characteristic.

Mineralogy Classes Applied Only to Limnic Subgroups

Limnic materials (defined in chapter 4) with a thickness of

5 cm or more are mineralogy class criteria if the soil does not

also have ferrihumic mineralogy. The following family classes

are used: coprogenous, diatomaceous, and marly.

Control Section for the Ferrihumic Mineralogy Class and

Mineralogy Classes Applied to Limnic Subgroups

The control section for the ferrihumic mineralogy class and

the classes applied to Limnic subgroups is the same as the

control section for Histosols.

Mineralogy Classes Applied Only to Terric Subgroups

For Histosols and Histels in Terric subgroups, use the same

key to mineralogy classes as that used for mineral soils unless a

Histosol also has ferrihumic mineralogy.

Control Section for Mineralogy Classes Applied Only to

Terric Subgroups

For Terric subgroups of Histosols and Histels, use the same

control section for mineralogy classes as that used for the

particle-size classes.

Key to Mineralogy Classes

A. Histosols (except for Folists), Sphagnofibrists, and

Sphagnic subgroups of other great groups that have ferrihumic

soil material within the control section for Histosols.

Ferrihumic

or

B. Other Histosols that have, within the control section for
832 Soil Taxonomy

Histosols, limnic materials, 5 cm or more thick, that consist of:

1. Coprogenous earth.

Coprogenous

or

2. Diatomaceous earth.

Diatomaceous

or

3. Marl.

Marly

or

C. Histels and other Histosols in Terric subgroups: Use the

key to mineralogy classes for mineral soils.

or

D. All other Histels and Histosols: No mineralogy class used.

Reaction Classes

Reaction classes are used in all families of Histosols and

Histels. The two classes recognized are defined in the

following key:

A. Histosols and Histels that have a pH value, on undried

samples, of 4.5 or more (in 0.01 M CaCl2) in one or more

layers of organic soil materials within the control section for

Histosols.

Euic

or

B. All other Histosols and Histels.

Dysic

Soil Temperature Classes

The soil temperature classes of Histosols are determined

through use of the same key and definitions as those used for

mineral soils. Histels have the same temperature classes as

other Gelisols.

Soil Depth Classes

Soil depth classes refer to the depth to a root-limiting layer, a

fragmental particle-size class, or a cindery or pumiceous

substitute class. The root-limiting layers included in soil depth

classes of Histosols are duripans; petrocalcic, petrogypsic, and

placic horizons; continuous ortstein; and densic, lithic,

paralithic, and petroferric contacts. The following key is used

for families in all subgroups of Histosols. The shallow class is

not used in the suborder Folists.

Key to Soil Depth Classes

A. Histosols that are less than 18 cm deep to a root-limiting

layer, to a fragmental particle-size class, or to a cindery or

pumiceous substitute class.

Micro

or

B. Other Histosols, excluding Folists, that have a rootlimiting layer, a fragmental particle-size class, or a cindery or

pumiceous substitute class at a depth between 18 and 50 cm

from the soil surface.

Shallow

or

C. All other Histosols: No soil depth class used.

Series Differentiae Within a Family

The function of the series is pragmatic, and differences

within a family that affect the use of a soil should be

considered in classifying soil series. The separation of soils at

the series level of this taxonomy can be based on any property

that is used as criteria at higher levels in the system. The

criteria most commonly used include presence of, depth to,

thickness of, and expression of horizons and properties

diagnostic for the higher categories and differences in texture,

mineralogy, soil moisture, soil temperature, and amounts of

organic matter. The limits of the properties used as differentiae

must be more narrowly defined than the limits for the family.

The properties used, however, must be reliably observable or be

inferable from other soil properties or from the setting or

vegetation.

The differentiae used must be within the series control

section. Differences in soil or regolith that are outside the

series control section and that have not been recognized as

series differentiae but are relevant to potential uses of certain

soils are considered as a basis for phase distinctions.

Control Section for the Differentiation of Series

The control section for the soil series is similar to that for

the family, but it differs in a few important respects. The

particle-size and mineralogy control sections for families end

at the upper boundary of a fragipan, duripan, or petrocalcic

horizon because these horizons have few roots. In contrast to

the control section for the series, the thickness of such horizons

is not taken into account in the control sections for the family.

The series control section includes materials starting at the soil

surface and also the first 25 cm below a densic or paralithic

contact if its upper boundary is less than 125 cm below the

mineral soil surface. Properties of horizons and layers below

the particle-size control section, a depth between 100 and 150
Family and Series Differentiae and Names 833

cm (or to 200 cm if in a diagnostic horizon) from the mineral soil

surface, also are considered.

Key to the Control Section for the Differentiation of Series

The part of a soil to be considered in differentiating series

within a family is as follows:

A. Mineral soils that have permafrost within 150 cm of the

soil surface: From the soil surface to the shallowest of the

following:

1. A lithic or petroferric contact; or

2. A depth of 100 cm if the depth to permafrost is less

than 75 cm; or

3. 25 cm below the upper boundary of permafrost if

that boundary is 75 cm or more below the soil surface;

or

4. 25 cm below a densic or paralithic contact; or

5. A depth of 150 cm; or

B. Other mineral soils: From the soil surface to the

shallowest of the following:

1. A lithic or petroferric contact; or

2. A depth of either 25 cm below a densic or paralithic

contact or 150 cm below the soil surface, whichever is

shallower, if there is a densic or paralithic contact within

150 cm; or

3. A depth of 150 cm if the bottom of the deepest

diagnostic horizon is less than 150 cm from the soil surface;

or

4. The lower boundary of the deepest diagnostic horizon

or a depth of 200 cm, whichever is shallower, if the lower

boundary of the deepest diagnostic horizon is 150 cm or

more below the soil surface; or

C. Organic soils (Histosols and Histels): From the soil surface

to the shallowest of the following:

1. A lithic or petroferric contact; or

2. A depth of 25 cm below a densic or paralithic contact;

or

3. A depth of 100 cm if the depth to permafrost is less

than 75 cm; or

4. 25 cm below the upper boundary of permafrost if that

boundary is between a depth of 75 and 125 cm below the

soil surface; or

5. The base of the bottom tier.

Application of Family and Series Differentiae

Application of Family Differentiae

The differentiae of families, like those of the higher

categories, can be more readily understood if they are applied

to real soils. A rather complex family can demonstrate how the

family criteria are determined. The Boistfort and Bunker series

are in the medial over clayey, mixed over parasesquic, mesic

family of Pachic Fulvudands. A pedon (not the typifying

pedon) of the Boistfort series has been sampled and studied in

the laboratory. The discussion that follows shows how the

classes used as components of the family name are selected.

The particle-size class or substitute class is the first

component in the name of a family. Before the class can be

selected, the control section must be known, and before the

control section can be determined, the diagnostic horizons and

properties must be identified. The epipedon of the Boistfort

soils has andic soil properties. It is not dark colored enough for

a melanic epipedon but is dark enough, is thick enough, and

has enough organic carbon for a mollic or umbric epipedon.

The base saturation is less than 6 percent throughout. Thus, the

epipedon is umbric. The 2Bw horizon in the Boistfort soils

does not have the evidence that organic carbon and aluminum

have been moved from an eluvial to an illuvial horizon

required for spodic materials. The soils have the required

thickness of andic soil properties in the required location (item

D in the “Key to Soil Orders” in chapter 8) for the Andisol

order. The control section for particle-size is determined

through use of the criteria in item B (a). The particle-size control

section is from 5 cm (the mineral soil surface) to 105 cm.

The upper part of the particle-size control section, from 5 to

53 cm, in the type location meets the criteria for medial listed

in item B-2-c in the key to particle-size classes and substitutes

for classes. The lower part, from 53 to 105 cm, in the type

location meets the criteria for clayey, item 10 under C. The soil

materials meet the requirements for strongly contrasting

particle-size classes, and the combination “medial over clayey”

is included as number 45 on the list of classes considered as

strongly contrasting.

The control section for mineralogy classes is the same as

that used for the particle-size classes. The mineralogy classes

are given for both named particle-size classes for families with

strongly contrasting particle-size classes, unless the mineralogy

classes are the same for both parts. The mineralogy classes are

determined through use of the key to mineralogy classes.

“Medial” is a substitute class name that replaces the name of

particle-size classes. This family is part of the Andisol soil

order. Thus, it fails item A and meets item B of the key. Based

on the laboratory data, this part of the control section has
834 Soil Taxonomy

mixed mineralogy. The clayey part fails items A and B. This

layer meets the criteria listed in item C. The parasesquic class,

item 6 under C, is the first class in the key for which this layer

meets all of the criteria. The family mineralogy is mixed over

parasesquic.

Cation-exchange activity classes are used only for layers

with both mixed or siliceous mineralogy and a clayey, clayeyskeletal, coarse-loamy, coarse-silty, fine, fine-loamy, fine-silty,

loamy, loamy-skeletal, or very-fine particle-size class. In this

family, the mixed mineralogy is associated with the medial

substitute for a particle-size class and the parasesquic

mineralogy is associated with the clayey particle-size class.

Therefore, no cation-exchange activity class is used in this

family name.

Calcareous and reaction classes are not used in families of

Udands.

The mean soil temperatures are estimated from climatic data.

The mean winter soil temperature is about 3 oC (38 oF), the mean

summer soil temperature is about 16 oC (60 oF), and the mean

annual soil temperature is about 15 oC (59 oF). These data are

within the class criteria for mesic temperatures, item 2 under B, in

the key to temperature classes.

The Boistfort and Bunker soils have no root-limiting layers

within 100 cm. They therefore fail items A and B in the key to

soil depth classes but meet criterion C. No soil depth class is

used for soils that meet criterion C.

The keys indicate that families of Andisols do not have

rupture-resistance classes, classes of coatings (on sands), or

classes of permanent cracks.

The classes that are components of the family name are

medial over clayey, mixed over parasesquic, and mesic. The

family name is medial over clayey, mixed over parasesquic,

mesic Pachic Fulvudands.

Application of Series Differentiae

Standard descriptions of the Boistfort and Bunker series are

given at the end of this chapter. If we compare the descriptions

of the typifying pedons of these two series, we note that the

particle-size control section of the Bunker soils averages 15 to 35

percent basalt fragments and that of the Boistfort soils averages

less than 10 percent. This difference is relatively small but

reflects differences in setting and parent materials that affect the

use of the soils. The Boistfort soils formed in material weathered

from basalt in the more stable positions on foothills and

mountains, and the Bunker soils formed in colluvium derived

from basalt on metastable slopes. Both of the soils are used for

the production of lumber. The differences in these soils affect

both tree growth and the construction and maintenance of the

roads needed when the trees are harvested.

The Bunker series allows basalt at a depth of 100 to more

than 150 cm from the mineral soil surface. This range in depth

to a lithic contact could be used as a criterion to divide the

Bunker series into two series, as the lithic contact is within the

control section for the series. Because this depth difference is

difficult to separate in mapping and has little effect on the use

of these soils for the production of lumber, the series is allowed

this wide range in soil depth. Many soil series that are in other

climates or that have more intensive uses are separated on the

basis of having or not having a lithic contact between 100 and

150 cm.

This example shows the nature of series differentiae.

Generally, the series within a given family have several small

differences in the nature or arrangement of horizons, in the

absence of horizons, in the nature of the soil materials in the

series control section, or in soil moisture or soil temperature.

These differences commonly reflect differences in setting,

climate, and/or parent materials that have important effects on

the use of the soils. The differences permit, but do not require,

the separation of soil series within a family. The differentiae

are discussed under the category of series in chapter 6.

A full treatment of series differentiae within families is

beyond the scope of this text. Series differentiae vary among

families, subgroups, great groups, and even orders. The

principle, however, remains the same. The series are

distinguished within a family primarily because of the need to

facilitate quantitative interpretations of soil behavior.
Family and Series Differentiae and Names 835

LOCATION BOISTFORT WA

Established Series

Rev. CJM/RFP/RJE/TLA

08/98

BOISTFORT SERIES

The Boistfort series consists of very deep, well drained soils formed in

material weathered from basalt and a component of volcanic ash in the

upper part. Boistfort soils are on foothills and mountains and have slopes

of 0 to 65 percent. The average annual precipitation is about 2,300 mm,

and the average annual temperature is about 10 degrees C.

TAXONOMIC CLASS: Medial over clayey, mixed over parasesquic,

mesic Pachic Fulvudands

TYPICAL PEDON: Boistfort silt loam - forested. (Colors are for moist

soil unless otherwise stated. All textures are apparent field textures.)

Oi—0 to 5 cm (0 to 2 inches); slightly decomposed twigs, needles, and

moss.

Ac—5 to 28 cm (2 to 11 inches); dark brown (7.5YR 3/2) silt loam, dark

grayish brown (10YR 4/2) dry; weak fine granular structure; soft, very

friable, slightly sticky and slightly plastic, and weakly smeary; many

coarse, medium, and fine roots; many medium tubular pores; 25 percent

weakly cemented shotlike concretions; very strongly acid; clear wavy

boundary. (18 to 30 cm thick)

A—28 to 53 cm (11 to 21 inches); dark brown (7.5YR 3/2) silty clay

loam, dark brown (10YR 4/3) dry; moderate very fine subangular blocky

structure; slightly hard, friable, sticky and plastic, and weakly smeary;

many coarse, medium, and fine roots; many medium tubular pores; few

firm shotlike concretions; very strongly acid; clear wavy boundary. (0 to

25 cm thick)

2Bw1—53 to 99 cm (21 to 39 inches); dark brown (7.5YR 4/4) silty clay,

yellowish brown (10YR 5/6) dry; weak fine subangular blocky structure; hard,

friable, sticky and plastic, and weakly smeary; few fine roots; common medium

tubular and interstitial pores; extremely acid; gradual wavy boundary.

2Bw2—99 to 140 cm (39 to 55 inches); strong brown (7.5YR 5/6) silty clay,

strong brown (10YR 5/8) dry; weak very fine subangular blocky structure; very

hard, friable, sticky and plastic, and weakly smeary; few fine tubular and common

medium interstitial pores; extremely acid; clear wavy boundary. (Combined

thickness of the 2Bw horizon: 50 to 100 cm)

2BC—140 to 157 cm (55 to 62 inches); strong brown (7.5YR 5/6) silty clay,

yellowish brown (10YR 5/6) dry; weak very fine subangular blocky structure;

very hard, friable, sticky and plastic, and weakly smeary; few fine tubular and

common medium interstitial pores; extremely acid.

TYPE LOCATION: Thurston County, Washington; Capitol State Forest, about 5

miles northwest of Littlerock, 540 meters west and 180 meters north of the

southeast corner of sec. 24, T. 17 N., R. 4 W.

RANGE IN CHARACTERISTICS: The thickness of the solum ranges from 100

to more than 150 cm, and the depth to basalt is more than 150 cm. The content of

rock fragments averages less than 10 percent in the particle-size control section.

The upper part of the particle-size control section, 5 to 105 cm, has an estimated

moist bulk density of 0.65 to 0.90 g/cc, a volcanic glass content of 0 to 5

percent, acid-oxalate-extractable aluminum plus one-half iron of 2.0 to

3.0 percent, phosphate retention of 85 to 100 percent, and 15-bar water

retention of 15 to 30 percent for air-dried samples. The content of

organic carbon is less than 4 percent in some part between 50 and 75 cm.

Under forest cover, the mean annual soil temperature is about 10 degrees

C (50 degrees F) and ranges from 8 to 11 degrees C.

The A horizon has value and chroma of 2 or 3 when rubbed and moist and

value and chroma of 2, 3, or 4 when dry. This horizon is moderately acid

to very strongly acid.

Some pedons have AB and BA horizons.

The 2Bw horizon has hue of 5YR or 7.5YR and value and chroma of 4

through 6 moist, 5 through 8 dry. The apparent field texture averages clay

loam, silty clay loam, or silty clay, but in some thin subhorizons it is

gravelly or cobbly silty clay loam, gravelly or cobbly clay loam, or

gravelly or cobbly silty clay. This horizon is moderately acid to extremely

acid.

COMPETING SERIES: These are the Bunker soils. Bunker soils

contain 15 to 35 percent rock fragments in the particle-size control

section.

GEOGRAPHIC SETTING: Boistfort soils are in stable positions on

foothills and mountains. Slopes are mostly less than 30 percent, but they

range from 0 to 65 percent. The soils formed in material weathered from

basalt and a component of volcanic ash in the upper part. Elevations

range from 30 to 540 meters. These soils are in a marine climate with

cool, wet winters and cool, dry summers. The average annual precipitation

ranges from 1,800 to 3,000 mm. The average January temperature is

about 3 degrees C, the average July temperature is about 16 degrees C, and

the average annual temperature is about 10 degrees C. The growing season

(-2 degrees C) is 200 to 240 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing

Bunker soils and the Astoria, Elochoman, Katula, Lates, Lytell, Murnen, and

Zenker soils. Astoria soils are in a fine class and are Udepts. Elochoman, Lytell,

and Zenker soils are in a medial class. In addition, Lytell and Zenker soils average

more than 35 percent pararock fragments, consisting of weathered sandstone or

siltstone, in the particle-size control section. Katula soils are in a medial-skeletal

class and have a lithic contact between 50 and 100 cm. Lates and Murnen soils are

in a medial class and a frigid class.

DRAINAGE , RUNOFF, AND PERMEABILITY: Well drained; very low to

medium runoff; moderate permeability.

USE AND VEGETATION: Forested. The vegetation is mainly Douglas-fir,

western redcedar, and red alder with an understory of western swordfern,

Oregongrape, red huckleberry, and vine maple.

DISTRIBUTION AND EXTENT: Southwestern Washington. The series is of

moderate extent.

SERIES ESTABLISHED: Grays Harbor County (Grays Harbor County Area),

Washington, 1970.

REMARKS: The diagnostic horizons and features recognized in this pedon are an

umbric epipedon from the mineral soil surface (at 5 cm) to 53 cm and a cambic

horizon from 53 to 157 cm. The upper 48 cm of the particle-size control section

has andic soil properties.

ADDITIONAL DATA: Characterization data for this series are available;

NSSL pedon numbers 84P0906 and 40A3303.

National Cooperative Soil Survey

U.S.A.
836

LOCATION BUNKER WA

Established Series

Rev. FG/RFP/RJE/TLA

08/98

BUNKER SERIES

The Bunker series consists of deep, well drained soils formed in colluvium

weathered from basalt and a component of volcanic ash in the upper part. These

soils are on foothills and mountains. Slopes are 1 to 90 percent. The average

annual precipitation is about 2,300 mm, and the average annual temperature is

about 10 degrees C.

TAXONOMIC CLASS: Medial over clayey, mixed over parasesquic, mesic

Pachic Fulvudands

TYPICAL PEDON: Bunker loam - forested. (Colors are for moist soil unless

otherwise stated. All textures are apparent field textures.)

Oi—0 to 3 cm (0 to 1 inch); loose, slightly decomposed Douglas-fir needles, twigs,

and moss.

Oa—3 to 5 cm (1 to 2 inches); decomposed litter; dark red with many white

mycelia.

A—5 to 29 cm (2 to 12 inches); dark reddish brown (5YR 3/3) loam, reddish

brown (5YR 4/3) dry; moderate fine granular structure; slightly hard, friable,

slightly sticky and slightly plastic, and weakly smeary; many roots; 15 percent

angular basalt pebbles; moderately acid (pH 5.9); clear wavy boundary. (25 to 36

cm thick)

BA—29 to 47 cm (12 to 19 inches); dark reddish brown (5YR 3/4) gravelly clay

loam, reddish brown (5YR 4/4) dry; moderate medium and fine subangular blocky

structure; hard, friable, sticky and plastic, and weakly smeary; many roots; 30

percent angular basalt pebbles; few medium and fine shotlike concretions;

moderately acid (pH 5.9); clear irregular boundary. (5 to 25 cm thick)

2Bw1—47 to 88 cm (19 to 35 inches); dark reddish brown (5YR 3/4) gravelly

clay loam, reddish brown (5YR 4/4) dry; moderate medium and fine subangular

blocky structure; hard, firm, sticky and plastic, and weakly smeary; common roots;

many fine pores; 30 percent angular basalt pebbles; moderately acid (pH 5.8);

gradual wavy boundary.

2Bw2—88 to 134 cm (35 to 53 inches); reddish brown (5YR 4/4) clay loam,

reddish brown (5YR 5/4) dry; moderate medium subangular blocky structure;

slightly hard, firm, sticky and plastic, and weakly smeary; many roots; many fine

pores; 10 percent angular basalt pebbles; moderately acid (pH 6.0); clear irregular

boundary. (Combined thickness of the 2Bw horizon: 50 to 90 cm)

2BC—134 to 156 cm (53 to 62 inches); dark brown (7.5YR 3/4) clay loam,

reddish brown (5YR 4/4) dry; weak medium subangular blocky structure; slightly

hard, friable, sticky and plastic, and weakly smeary; few roots; 10 percent angular

basalt pebbles; moderately acid (pH 6.0); clear irregular boundary. (10 to 30 cm

thick)

2R—156 cm (62 inches); fractured basalt.

TYPE LOCATION: Lewis County, Washington; on logging road number

5, Weyerhaeuser Company McDonald Tree Farm; approximately 570

meters south and 570 meters west of the northeast corner of sec. 11, T.

12 N., R. 5 W.

RANGE IN CHARACTERISTICS: The mean annual soil temperature

ranges from 8 to 11 degrees C. The depth to fractured bedrock ranges

from 100 to more than 150 cm from the mineral soil surface. The

content of basalt fragments in the particle-size control section averages

15 to 35 percent. The upper part of the particle-size control section (4 to

104 cm) has an estimated moist bulk density of 0.65 to 0.90 g/cc, a

volcanic glass content of 0 to 5 percent, acid-oxalate-extractable

aluminum plus one-half iron of 2.0 to 3.0 percent, phosphate retention of

85 to 100 percent, and 15-bar water retention of 15 to 30 percent for airdried samples. The content of organic carbon is less than 4 percent in

some part of the upper 75 cm of the particle-size control section.

Reaction ranges from very strongly acid to moderately acid.

The A horizon has hue of 5YR or 7.5YR, value of 2 or 3 moist, 4 or 5

dry, and chroma of 1 to 3 moist, 3 or 4 dry. It has 0 to 35 percent

pebbles.

The BA horizon has hue of 5YR or 7.5YR, value of 3 or 4 moist, 4 or 5

dry, and chroma of 2 to 4 moist. It has 0 to 35 percent pebbles.

The 2B horizon has hue of 5YR through l0YR, value of 3 or 4 moist, 4 or

5 dry, and chroma of 3 or 4 moist. It ranges from loam to clay loam, silt

loam, or silty clay loam with 10 to 35 percent rock fragments.

COMPETING SERIES: These are the Boistfort soils. Boistfort soils

average 0 to 10 percent basalt fragments in the particle-size control

section.

GEOGRAPHIC SETTING: Bunker soils are on metastable side slopes and

foot slopes at elevations of 30 to 660 meters. Slopes are mostly 30 to 90

percent but range from 1 to 90 percent. These soils formed in colluvium

weathered from basalt and a component of volcanic ash in the upper part.

Winters are cool and moist, and summers are warm and dry. The average

annual temperature is about 10 degrees C, the average January temperature

is about 3 degrees C, and the average July temperature is about 16 degrees

C. The annual precipitation ranges from 1,800 to 3,000 mm. The growing

season (-2 degrees C) is 200 to 240 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Astoria,

Katula, Lytell, Swem, Murnen, Squally, and Zenker soils and the competing

Boistfort soils. Astoria soils are Udepts and are in a fine class. Katula and

Squally soils are in a medial-skeletal class. Lytell and Zenker soils are in a

medial class and average more than 35 percent sandstone or siltstone

pararock fragments in the particle-size control section. Murnen soils are

in a frigid temperature class. Swem soils are in a medial class and have

grayish iron depletions in the particle-size control section.

DRAINAGE, RUNOFF, AND PERMEABILITY: Well drained; very low

to high runoff; moderate permeability.

USE AND VEGETATION: Forested. Bunker soils are used for timber

production, watershed, wildlife habitat, and recreation. The vegetation is mainly

Douglas-fir and western hemlock with an understory of western swordfern,

Oregongrape, red huckleberry, and vine maple.

DISTRIBUTION AND EXTENT: Southwestern Washington. The series is

extensive.

SERIES ESTABLISHED: Wahkiakum County, Washington, 1976.

REMARKS: The diagnostic horizons and features recognized in this pedon are an

umbric epipedon from the mineral soil surface to 29 cm and a cambic horizon from

29 to 156 cm. The upper 43 cm of the particle-size control section has andic soil

properties.

ADDITIONAL DATA: The classification is based on laboratory data taken on the

Boistfort series. These data are available at the National Soil Survey Laboratory,

Lincoln, Nebraska: Pedon numbers 40A3303 and 84P0906.

National Cooperative Soil Survey

U.S.A.
837

This chapter describes the geographic extent and patternof the 12 soil orders and 64 suborders recognized in the

current taxonomic system as these taxa occur in the United

States. The geography of the orders and suborders, the nature

of the topography on which they occur, the parent materials,

and the principal uses of the soils are specified. More detailed

descriptions of the soil orders and suborders and the lower

categories of the taxonomic system are given in individual

chapters on the soil orders.

The maps of the United States at the end of this publication

show the geographic distribution of the soil orders and

suborders in the United States and the territories,

commonwealths, and island nations served by the United States

Department of Agriculture, Natural Resources Conservation

Service. The dominant order map and the dominant suborder

maps are at scales of approximately 1:15,000,000 and

1:52,000,000, respectively, except in Alaska and the Pacific Basin

islands.

The maps provide an illustration of the dominant soil

orders and suborders derived from the State Soil Geographic

Data Base, or STATSGO (USDA, NRCS, 1994, revised 1998;

USDA, NRCS, 1996). The dominant soil orders and

suborders represent the largest land area of each STATSGO

map unit (summed component percentage) for each order

and suborder category. The soil orders and suborders for

the U.S. Virgin Islands and the Pacific Basin islands served

by the Natural Resources Conservation Service were

determined from published soil survey reports and from local

information.

The soil order and suborder concepts for each STATSGO

map unit were revised according to soil series name (118,568

component records for 10,872 map units) through use of the

Soil Classification File (USDA, NRCS, 1997). These data records

were further correlated to make them consistent with the current

concepts of the taxonomic system.

The maps of the United States include 1 map showing the

dominant orders and 12 maps showing the dominant suborders

within each order. The dominant order map has a legend that

includes 12 dominant order categories, 1 category of

codominant orders, and 2 categories for miscellaneous lands,

plus water. The codominant category is used only in Alaska,

where the STATSGO scale is 1:1,000,000. Given this smaller

scale, there is much greater uncertainty associated with this

portion of the map and a multi-taxa unit was chosen.

During the correlation of the STATSGO component records,

the following were included in the rock outcrop category:

badlands, cinder land, lava flows, rock outcrop, rough

mountainous land, and rubble land. Glacier ice fields in

Alaska and continuously snow-covered areas at high elevations

of the mountains in the Western States were included in the

ice/tundra category. In addition, several miscellaneous land

areas were included with the Entisol and Aridisol orders and

suborders. Psamments included dune land, coastal dunes, and

blown-out land. Salids included playas and salt flats. Orthents

included dumps, pits, gullied land, and scoria land. Fluvents

included riverwash and beaches; however, they excluded areas

of riverwash and beaches with permafrost. Arents included

urban land.

Gelisols did not occur in the Alaska STATSGO and Soil

Classification File (USDA, NRCS, Soil Survey Staff, 1997) and

were approximated through use of the pergelic subgroups for

STATSGO components. Additional study and evaluation are

needed to determine the proper placement and extent of these

map units in Alaska.

The 12 dominant suborder maps each have legends that

identify the possible suborders within a given order. The

dominant suborder for each STATSGO map unit is the most

extensive suborder of the dominant order in the map unit. The

Gelisol suborders were approximated through use of local

information that helped to correlate the Alaska STATSGO

component soil series.

The table “Total Area of Soil Orders and Suborders in the

United States” shows the approximate area, in square kilometers,

and the percentages of the soil orders and suborders in the

United States, based on a total area of 9,147,537 square

kilometers. Some suborders are of very small extent or are not

known to occur in the United States. These suborders are not

shown on the map; however, the extent of all STATSGO map

unit components is accounted for in the table.

Alfisols

Alfisols are extensive in the United States. They make up

about 13.9 percent of the surface area. Typically, they have an

ochric epipedon, an argillic horizon, and moderate or high base

saturation. In normal years water is held at less than 1500 kPa

tension in some or all parts of the moisture control section

more than one-half of the time when the soils are warm enough

CHAPTER 22

Soils of the United States
838 Soil Taxonomy

Alfisols ........................................... 1,269,283 ................ 13.88

Aqualfs ......................................... 215,497 .................. 2.36

Cryalfs............................................. 69,129 .................. 0.76

Udalfs............................................ 622,300 .................. 6.80

Ustalfs ........................................... 281,586 .................. 3.08

Xeralfs............................................. 80,771 .................. 0.88

Andisols .......................................... 155,812 .................. 1.69

Aquands ........................................... 2,299 .................. 0.03

Cryands ........................................... 87,531 .................. 0.95

Torrands ............................................... 134 ..................<.01

Udands............................................ 17,456 .................. 0.19

Ustands............................................. 1,149 .................. 0.01

Vitrands ........................................... 17,319 .................. 0.18

Xerands ........................................... 29,924 .................. 0.33

Aridisols .......................................... 760,122 .................. 8.30

Argids ........................................... 322,921 .................. 3.53

Calcids .......................................... 221,716 .................. 2.42

Cambids ........................................ 103,009 .................. 1.12

Cryids................................................... 562 .................. 0.01

Durids ............................................. 74,371 .................. 0.81

Gypsids ........................................... 14,061 .................. 0.15

Salids............................................... 23,482 .................. 0.26

Entisols .......................................... 1,122,383 ................ 12.27

Aquents ........................................ 124,331 .................. 1.36

Arents ............................................. 21,232 .................. 0.23

Fluvents ........................................ 178,579 .................. 1.95

Orthents ........................................ 549,579 .................. 6.01

Psamments .................................... 248,662 .................. 2.72

Gelisols ............................................. 792,945 .................. 8.68

Histels ............................................. 87,440 .................. 0.96

Orthels .......................................... 124,975 .................. 1.37

Turbels .......................................... 580,530 .................. 6.35

Histosols .......................................... 149,555 .................. 1.63

Fibrists ............................................ 22,058 .................. 0.24

Folists ............................................... 8,795 .................. 0.09

Hemists ........................................... 29,159 .................. 0.32

Saprists ........................................... 89,543 .................. 0.98

Inceptisols ....................................... 889,441 .................. 9.71

Anthrepts................................................ 0 .................. 0

Aquepts ........................................ 123,753 .................. 1.35

Cryepts .......................................... 190,517 .................. 2.08

Udepts .......................................... 348,528 .................. 3.81

Ustepts.......................................... 149,122 .................. 1.62

Xerepts ............................................ 77,521 .................. 0.85

Mollisols ........................................ 1,966,457 ................ 21.49

Albolls ............................................ 15,314 .................. 0.17

Aquolls ......................................... 233,749 .................. 2.55

Cryolls........................................... 136,132 .................. 1.49

Rendolls ............................................ 3,223 .................. 0.03

Udolls............................................ 356,064 .................. 3.89

Ustolls ........................................... 884,688 .................. 9.67

Xerolls........................................... 337,287 .................. 3.69

Oxisols ................................................. 1,666 .................. 0.02

Aquox ..................................................... 0 .................. 0

Perox ......................................................15 ..................<.01

Torrox ...................................................... 0 .................. 0

Udox .................................................. 1,048 .................. 0.01

Ustox .................................................... 603 .................. 0.01

Spodosols ........................................ 317,665 .................. 3.47

Aquods ........................................... 55,269 .................. 0.60

Cryods ............................................ 85,873 .................. 0.94

Humods ............................................. 4,612 .................. 0.05

Orthods ......................................... 171,911 .................. 1.88

Ultisols ............................................. 842,259 .................. 9.20

Aquults ........................................... 75,472 .................. 0.82

Humults........................................... 16,489 .................. 0.18

Udults ........................................... 742,749 .................. 8.12

Ustults ................................................. 823 .................. 0.01

Xerults .............................................. 6,726 .................. 0.07

Vertisols ........................................... 181,482 .................. 1.99

Aquerts ........................................... 55,469 .................. 0.61

Cryerts .................................................... 0 .................. 0

Torrerts............................................ 10,025 .................. 0.11

Uderts ............................................. 30,934 .................. 0.34

Usterts ............................................ 74,120 .................. 0.81

Xererts ............................................ 10,934 .................. 0.12

Water2 ............................................... 118,973 .................. 1.30

Rock and ice ..................................... 577,304 .................. 6.35

Rock .............................................. 269,382 .................. 2.94

Rock and ice .................................. 307,922 .................. 3.41

Ice ..................................................... 1,108 .................. 0.01

Unclassified .......................................... 1,082 .................. 0.01

Total surface area ........................... 9,147,537 .................. 100

1 Percentage of the surface area of the United States and the territories, commonwealths,

and island nations served by the Natural Resources Conservation Service. 2 Water as represented in State Soil Geographic Data Base (USDA, NRCS, 1994 and

1996).

Total Area of Soil Orders and Suborders in the United States

Order/suborder Square kilometers Percent1 Order/suborder Square kilometers Percent1
Soils of the United States 839

for plants to grow. Some Alfisols also have a fragipan, a duripan,

a kandic horizon, a natric horizon, a petrocalcic horizon, plinthite,

or other features.

Alfisols are divided into five suborders based on soil

moisture or soil temperature. These properties tend to limit the

suborders to specific regions of the country.

Aqualfs, which have aquic conditions, are of moderate

extent in the United States. They make up about 2.4 percent of

the surface area. They occur mostly in association with soils

that have a udic moisture regime. The largest extent is in an

area bordering the southern part of the Mississippi River, in

southern Illinois, and in Indiana and Ohio. Most Aqualfs,

except those that have a frigid or cryic temperature regime,

have some artificial drainage or other water control and are

used as cropland. Corn and soybeans are the most common

crops. Rice also is a common crop on Aqualfs that have a

thermic or warmer temperature regime. Before they were

cultivated, some of the soils were under forest vegetation and

others were under grass. Nearly all Aqualfs are believed to

have supported forest vegetation at some time in the past.

Cryalfs, which have a cryic soil temperature regime, are of

small extent in the United States. They make up about 0.8

percent of the surface area. They occur mostly in association

with Inceptisols and Mollisols at high elevations, mainly in the

Rocky Mountains in the Western United States. Most of the

Cryalfs in the United States are used as forest because of their

short, cool growing season.

Udalfs, which have a udic moisture regime, are of large

extent in the United States. They make up about 6.8 percent of

the surface area. They form a belt extending from Minnesota

through Wisconsin, Michigan, Indiana, and Ohio and ending

in New York State. This belt has mostly Spodosols and

Inceptisols to the north, Mollisols to the west, and Ultisols to

the south and east. Another large area of Udalfs begins in

southern Iowa and extends through Missouri, Illinois, and the

States to the south bordering the Mississippi River. Smaller

areas of Udalfs are associated with the Ultisols in the

Southeastern States. The Alfisols in the Southern States formed

mostly in materials that are younger and/or have more bases

than those of the associated Ultisols. All Udalfs are believed to

have supported forest vegetation at some time during

development. Most of the Udalfs with a mesic or warmer

temperature regime currently support or formerly supported

deciduous forest vegetation, and many with a frigid

temperature regime currently support or formerly supported

mixed coniferous and deciduous trees. Many Udalfs have been

cleared of trees and are used intensively as cropland. As a

result of erosion, some have only an argillic or kandic horizon

below an Ap horizon. Others retain most of their eluvial

horizons above the argillic or kandic horizon.

Ustalfs, which have an ustic soil moisture regime, are of

large extent in the United States. They make up about 3.1

percent of the surface area. They tend to occur in association

with Mollisols on the southern Great Plains, mostly in Texas

and Oklahoma. They also occur in association with Aridisols,

Inceptisols, and Mollisols throughout the Rocky Mountain

States from Montana to Arizona and New Mexico and in

association with Entisols in the Black Hills of South Dakota.

The dry season or seasons are pronounced enough for the trees

to be either deciduous or xerophytic. Many Ustalfs currently

support or formerly supported savanna vegetation, and some

supported grassland vegetation. Most are used as cropland or

grazing land. Some are used as irrigated cropland. Wheat and

sorghum are the most common crops. Cotton also is grown on

the Ustalfs with a thermic or warmer temperature regime.

Xeralfs, which have a xeric soil moisture regime, are of small

extent in the United States. They make up about 0.9 percent of

the surface area. They occur mainly in association with

Mollisols, Inceptisols, and Andisols. They are mostly in

California, but small areas are in Oregon, Washington, Idaho,

and Utah. The natural vegetation was a mixture of annual

grasses, forbs, and woody shrubs on the warmest and driest

Xeralfs and coniferous forest on the coolest and most moist

Xeralfs. Xeralfs are used mostly as cropland, forest, or grazing

land. Small grains, mostly winter wheat, are the most common

crops. A wide variety of crops are grown on irrigated Xeralfs.

Andisols

Andisols are of small extent in the United States. They

make up about 1.7 percent of the surface area. The colloidal

fraction of these soils is dominated by short-range-order

minerals or Al-humus complexes. Many Andisols developed in

volcanic ejecta and/or in volcaniclastic materials. Some of the

soils are dominated by short-range-order minerals that

weathered from nonvolcanic primary alumino-silicates. The

dominant process in the formation of Andisols is the

transformation of minerals. Translocation within the soils and

accumulation of the translocated compounds are normally

minimal. The accumulation of organic matter, complexed with

aluminum, however, is characteristic of some Andisols.

Andisols may have any diagnostic epipedon, provided that the

minimum requirements for the order are met in and/or below the

epipedon. These soils commonly have an ochric or umbric

epipedon and a cambic horizon. Some have buried diagnostic

horizons. Andisols can have any soil moisture regime and any

soil temperature regime, but they cannot have permafrost. They

can occupy any position on the landscape and can occur at any

elevation. One of the outstanding features of Andisols is their

generally high natural productivity. The dominance of physical

properties that favor the growth of most plants and the most

common occurrence of the soils in areas of considerable rainfall

have resulted in volcanic soils that generally are regarded as

highly fertile.

Andisols are divided into seven suborders based on soil

moisture and temperature regimes, soil wetness, and the

amount of water held too tightly for plants to use.

Aquands, which have aquic conditions at or near the soil
840 Soil Taxonomy

surface, are of very small extent in the United States. They make

up less than 0.1 percent of the surface area and do not dominate

any areas on the map. They commonly have dark colored

surface horizons that meet the requirements for a histic, umbric,

or mollic epipedon. They occur mostly in western Washington

and Oregon, in the lower landscape positions and under forest

or grass vegetation. Some of the soils have been drained and are

used as cropland or pasture.

Cryands, which have a cryic temperature regime, are of

moderate extent in the United States. They make up about 1.0

percent of the surface area. They dominate some areas in

Alaska and in the mountains of the Pacific Northwest. Most

of the soils formed under coniferous forest vegetation.

Cryands commonly have a thin O horizon, an ochric or

umbric epipedon, and a cambic horizon. They developed

mostly in late-Pleistocene or Holocene deposits. Most are used

as forest.

Torrands, which have an aridic (or torric) moisture regime

and a temperature regime warmer than cryic, are of very small

extent in the United States. They make up less than 0.1 percent

of the surface area. The extent is too small for the soils to be

shown on the map. A very few areas of these soils are in

western Oregon and in Hawaii. Most of the soils formed under

grassy or shrub vegetation. Commonly, Torrands have an

ochric or mollic epipedon and a cambic horizon. Some have a

duripan or a petrocalcic horizon. The Torrands in the United

States generally developed in late-Pleistocene or Holocene

deposits. They are used as rangeland or as irrigated cropland.

Udands, which have a udic moisture regime, a temperature

regime warmer than cryic, and a relatively high content of

water held too tightly for plants to use, are of small extent in

the United States. They make up about 0.2 percent of the

surface area. They dominate in some areas, mostly in western

Washington and Oregon and in Hawaii. Most of the soils

formed under forest vegetation. Characteristically, Udands

have an ochric or umbric epipedon and a cambic horizon.

Some have a cemented pan. Most developed in late-Pleistocene

or Holocene deposits. Udands are used mostly as forest, but

some have been cleared and are used as cropland or pasture.

Ustands, which have an ustic moisture regime, a

temperature regime warmer than cryic, and a relatively high

content of water held too tightly for plants to use, are of very

small extent in the United States. They make up less than 0.1

percent of the surface area. They are mostly in Hawaii. They

formed mostly under forest or savanna vegetation.

Characteristically, Ustands have an ochric, mollic, or umbric

epipedon and a cambic horizon. Most of the Ustands in the

United States developed in late-Pleistocene or Holocene

deposits. Ustands are used mostly as forest, cropland, or

pasture or for urban development.

Vitrands, which are the more or less well drained, coarse

textured Andisols that have a udic or ustic moisture regime, a

temperature regime warmer than cryic, and a low content of

water held too tightly for plants to use, are of small extent in

the United States. They make up about 0.2 percent of the surface

area. They occur mostly in Idaho, Oregon, and Washington.

Most of the soils formed under coniferous forest vegetation, but

some formed under grass and shrubs. Characteristically, Vitrands

have an ochric or mollic epipedon and a cambic horizon. They

are relatively young soils that developed mostly in Holocene

deposits. They are used mostly as forest, but some are used as

rangeland and some have been cleared and are used as cropland

or pasture.

Xerands, which have a xeric moisture regime and a frigid,

mesic, or thermic temperature regime, are of small extent in

the United States. They make up about 0.3 percent of the

surface area. They are mostly in Washington, California,

Oregon, and Idaho. Most of the Xerands that have a frigid or

mesic temperature regime formed under coniferous forest

vegetation. Some Xerands, mostly those with a thermic

temperature regime, formed under grass and shrub vegetation.

Characteristically, Xerands have an ochric or mollic epipedon

and a cambic horizon. They developed mostly in latePleistocene or Holocene deposits. They are used mostly as

forest, but some have been cleared and are used as cropland or

pasture.

Aridisols

Aridisols are moderately extensive in the United States. They

make up about 8.3 percent of the surface area. They are in the

Western States. For long periods, they are too dry for

mesophytic plants to grow. During most of the time when they

are warm enough for plants to grow, the soils are dry or salty,

or both. There are no periods as long as 90 consecutive days

when the soils are warm enough for plants to grow and soil

moisture is continuously available for plant growth. The

concept of Aridisols is based on the limited availability of soil

moisture for sustained plant growth. In areas bordering deserts,

the absolute precipitation may be high. Because of runoff or a

very low storage capacity in the soils, or both, however, the

actual soil moisture regime is aridic.

Soil moisture and, to a lesser extent, soil temperature

regimes control processes in these soils. The soil moisture

regime is used, in conjunction with diagnostic horizons, to

define the Aridisol order. The soil moisture regime is the single

most important limitation affecting the use of the soils.

Because of an extreme imbalance between evapotranspiration

and precipitation, many Aridisols in a sense are incipient

evaporites. The dominant process in Aridisols is one of

accumulation and concentration of weathering products. The

redistribution and accumulation of soluble materials in some

layer of the soils are common. The products of this process not

only give special attributes that distinguish the soils but also

limit the use of the soils. Four of the seven suborders are

defined on the basis of the composition and accumulation of

the soluble fraction. Weathering and clay and silica

translocation also occur in Aridisols.
Soils of the United States 841

Aridisols are divided into seven suborders based on

diagnostic horizons and soil temperature regimes.

Argids are the Aridisols that have an argillic or natric horizon,

but not a duripan or a gypsic, petrocalcic, petrogypsic, or salic

horizon, within 100 cm of the soil surface. They are of large

extent in the United States and are the suborder with the largest

extent on the map. They make up about 3.5 percent of the

surface area. They have a temperature regime warmer than cryic.

The presence of an argillic horizon is often attributed to a more

moist paleoclimate, although there is evidence that clay

illuviation has occurred during the Holocene in arid soils,

especially where the soil moisture regime grades toward ustic

or xeric. Most Argids are used as rangeland or wildlife habitat.

Some are used as irrigated cropland.

Calcids are the Aridisols that have a calcic or petrocalcic

horizon and have calcium carbonate in the layers above. They

are of moderate extent in the United States. They make up

about 2.4 percent of the surface area. They have a temperature

regime warmer than cryic. The parent materials are high in

content of carbonates, or carbonates were added as dust, or

both. Precipitation has been insufficient to remove the

carbonates or even move them to great depths. The upper

boundary of the calcic or petrocalcic horizon is normally

within 50 cm of the soil surface. These soils are in the Western

States. Most are used as rangeland or wildlife habitat. Some

are used as irrigated cropland. If the soils are used as cropland,

micronutrient deficiencies are normal.

Cambids are the Aridisols that have a cambic horizon

within 100 cm of the soil surface. They do not have other

diagnostic horizons, such as petrocalcic, gypsic, or calcic

horizons, unless the upper boundary of such horizons is 100

cm or more below the soil surface. The soils are characterized

by the least degree of soil development. They are of moderate

extent in the United States. They make up about 1.1 percent of

the surface area. They are mostly in Washington State. These

soils have a temperature regime warmer than cryic. Most are

used as rangeland or wildlife habitat. Some are used as

irrigated cropland.

Cryids are the Aridisols of cold areas. They have a cryic

temperature regime. The growing season is short. The short

growing season and arid conditions severely limit the use of

these soils. The soils are of very small extent in the United

States. They make up about 0.01 percent of the surface area.

The extent is too small for the soils to be shown on the map.

The soils are at high elevations in mountain valleys and basins

in Idaho. They can have a duripan or an argillic, calcic,

cambic, gypsic, natric, petrocalcic, petrogypsic, or salic

horizon. Most of these soils are used as rangeland or wildlife

habitat.

Durids are the Aridisols that have a duripan, but not a salic

horizon, that has an upper boundary within 100 cm of the soil

surface. Many duripans are within 50 cm of the soil surface.

These soils have a temperature regime warmer than cryic. They

are of small extent in the United States. They make up about

0.8 percent of the surface area. They are in the Western States.

The largest extent is in Nevada and Idaho. These soils occur

dominantly on gentle slopes. Many formed in sediments that

contain pyroclastics. Most of the soils are used as rangeland or

wildlife habitat. A few are used as irrigated cropland.

Gypsids are the Aridisols that have a gypsic or petrogypsic

horizon, but not a duripan or a salic horizon, within 100 cm of

the soil surface. They have a temperature regime warmer than

cryic. They are of small extent in the United States. They make

up about 0.15 percent of the surface area. They are mostly in

the Southwestern States. They are on many segments of the

landscape. Some of the soils have a calcic horizon or related

horizons, which overlie the gypsic horizon. The gypsic horizon

limits many soil uses. A petrogypsic horizon is an even greater

limitation. Most of these soils are used as rangeland or wildlife

habitat.

Salids are the Aridisols that have a salic horizon that has its

upper boundary within 100 cm of the soil surface. They are

commonly in depressions (playas). They are of small extent in

the United States. They make up about 0.26 percent of the

surface area. They are mostly in Utah and Nevada. In a warm,

arid environment, salts commonly accumulate at or near the

surface if there are both a supply of salts in the soils or in water

and a net upward movement of water in the soils. In some

areas salic horizons formed in salty parent materials without

the presence of ground water. Silica can accumulate and form

duripans if the ground water is sufficiently alkaline. As a rule,

Salids are unsuitable for agricultural uses unless they are

leached of salts. Leaching the salts is an expensive

undertaking, particularly if there is no natural outlet for the

drainage water. Most of these soils are used as rangeland or

wildlife habitat.

Entisols

Entisols are extensive in the United States. They make up

about 12 percent of the surface area. Most of the soils have no

diagnostic horizons other than an ochric epipedon. Some have

a cambic horizon with its base at a depth of less than 25 cm

below the mineral soil surface. A few Entisols that have a

sandy or sandy-skeletal particle-size class have a horizon that

would be a cambic horizon were it not for the particle-size

class exclusion, and a very few have an albic horizon. In

coastal marshes some Entisols that have sulfidic materials

within 50 cm of the mineral soil surface have a histic epipedon.

On many landscapes the soil material is too thin or has not

been in place long enough for pedogenic processes to form

diagnostic horizons. Some Entisols have steep, actively eroding

slopes, and others are on flood plains or glacial outwash plains

that receive new deposits of alluvium at frequent intervals.

Some Entisols are old and deep enough to have formed

diagnostic horizons, but they consist mostly of quartz or other

minerals that are resistant to the weathering needed to form

diagnostic horizons. Buried diagnostic horizons are permitted
842 Soil Taxonomy

in Entisols if they meet the definition of “buried soil” in

chapter 1.

Entisols may have any mineral parent material, vegetation,

age, or moisture regime and any temperature regime, but they

cannot have permafrost at a depth of less than 100 cm below

the soil surface. The only features common to all Entisols are

the virtual absence of diagnostic horizons and the mineral

nature of the soils.

Entisols are divided into five suborders based on wetness

and soil characteristics.

Aquents, or the wet Entisols, are of moderate extent in the

United States. They make up about 1.4 percent of the surface

area. They are widely distributed. They dominate some of the

delineations along the southern Atlantic and gulf coasts and on

the flood plains along the Mississippi River and along other

rivers and streams. Some Aquents are forming, mostly in sandy

deposits, in other parts of the country. Aquents can have any

temperature regime, but they cannot have permafrost within

100 cm of the soil surface. Most of the soils are forming in

recent sediments. They support vegetation that tolerates

permanent or periodic wetness. They are used mostly as

pasture, cropland, forest, or wildlife habitat.

Arents are of small extent in the United States. They make

up about 0.2 percent of the surface area. They do not have

diagnostic horizons because they have been deeply mixed by

plowing, spading, or other methods of moving by humans.

They are important soils for irrigated crop production in

California. Small areas also occur throughout the country.

Some are areas where the soil profile was removed and then

replaced after strip-mining. Others are urban areas and resulted

from cuts and fills made to shape or level the soils for

development. Some were modified for use as irrigated

cropland. Arents retain some fragments that can be identified

as parts of a former spodic or argillic horizon, a duripan, or

other feature, but the fragments do not themselves form

diagnostic horizons, are not arranged in any discernible order,

and are mixed with the materials of other horizons. Some of

the soils are the result of deliberate soil modification intended

to break up or remove a duripan or another root-restrictive

layer. Arents are used mostly as cropland, urban land, or

pasture. Some are used as wildlife habitat.

Fluvents are the more or less freely drained Entisols that

formed in recent water-deposited sediments on flood plains,

fans, and deltas along rivers and small streams throughout

the country. They are of moderate extent in the United

States. They make up about 2.0 percent of the surface area.

Some of the largest areas are on the flood plains along the

Mississippi River. The age of the sediments is commonly a

few years or decades to a few hundred years in humid areas.

It may be somewhat more in arid areas. Most Fluvents are

frequently flooded, unless they are protected by dams or

levees. Stratification of the materials is normal. These soils

can have any kind of vegetation and any temperature regime,

but they cannot have permafrost within 100 cm of the soil

surface. They can have any moisture regime but cannot

meet the criteria for Aquents. Most Fluvents are used as

rangeland, forest, pasture, or wildlife habitat. Some are used

as cropland.

Orthents are extensive in the United States. They make up

about 6.0 percent of the surface area. They are mainly in the

Western States. They are commonly on recent erosional

surfaces. The erosion may be geologic or may have been

induced by cultivation, mining, or other factors, but any soil

that existed has been completely removed or so truncated that

the diagnostic horizons are very thin or do not occur. Some of

the soils, mostly those in the Rocky Mountain States, are less

than 25 cm deep to a lithic or paralithic contact. Some of the

soils, mostly those in the Western States, are deep, have an

aridic moisture regime, and are characterized by little horizon

development. A few Orthents are forming in recent volcanic

deposits, loamy or fine textured eolian deposits, solifluction or

glacial deposits, landslide debris, or mudflows. Orthents can

have any kind of vegetation and any temperature regime, but

they cannot have permafrost within 100 cm of the soil surface.

They cannot have aquic conditions, a high water table, and the

colors defined for Aquents. Orthents are used mostly as

rangeland, pasture, or wildlife habitat.

Psamments are moderately extensive in the United States.

They make up about 2.7 percent of the surface area. They occur

throughout the country. Some of the largest areas are in

Nebraska, California, Minnesota, Wisconsin, Michigan,

Arizona, and Florida. These soils are sandy in all layers within

the particle-size control section. Because Psamments store less

water than other deep soils, they have lower yields than most

other soils in humid climates. Because they lose little

precipitation to runoff and store the moisture deeply, they are

among the most productive rangeland soils in some arid and

semiarid climates. Some Psamments are forming in poorly

graded (well sorted) sands on shifting or stabilized sand dunes,

in cover sands, or in sandy parent materials that were sorted in

an earlier geologic cycle. Some are forming in sands that were

sorted by water and are on outwash plains, lake plains, natural

levees, or beaches. Psamments occur under any climate, but

they cannot have permafrost within 100 cm of the soil surface.

They can have any vegetation and are on surfaces of virtually

any age from recent historic to Pliocene or older. The

Psamments on old stable surfaces commonly consist of quartz

sand, which cannot form diagnostic horizons that involve the

accumulation of clays or sesquioxides. Ground water is

typically deeper than 50 cm and commonly is much deeper.

Some Psamments that are nearly bare are subject to soil

blowing and drifting and provide poor support for wheeled

vehicles. Because very gravelly sands do not have these two

qualities, they are excluded from Psamments and are grouped

with Orthents. Psamments are used mostly as rangeland,

pasture, or wildlife habitat.
Soils of the United States 843

Gelisols

Gelisols are moderately extensive in the United States. They

make up about 8.7 percent of the surface area. They are known

to occur only in Alaska. Most of the soils have a layer of gelic

materials that is underlain by permafrost within 100 cm of the

soil surface. Diagnostic horizons may or may not be present.

Permafrost influences pedogenesis through its effect on the

downward movement of the soil solution and on the soilforming processes. Cryoturbation (frost mixing) is an

important process in many Gelisols and results in irregular or

broken horizons, involutions, organic matter accumulation on

the permafrost table, oriented rock fragments, and silt caps on

rock fragments. Cryoturbation occurs when two freezing fronts,

one from the surface and the other from the permafrost, merge

during freeze-back in autumn. Ice segregation is an important

property of gelic materials and occurs when the soil solution

migrates toward ice, increasing the volume of ice. Volume

changes also occur as the water freezes. In the drier areas

cryoturbation is less pronounced or does not occur, but the soils

still have gelic materials, as manifested by structure that results

from segregated ice. The importance of any diagnostic

horizons is overshadowed by the properties of the gelic

materials and the associated permafrost.

Gelisols are divided into three suborders based on the kind

of soil materials (organic or mineral) and expression of

cryoturbation in the mineral soil materials. The delineation

Gelisols/Inceptisols is a mosaic of Gelisols with a subgelic

temperature class and Cryepts.

Histels are the Gelisols with large amounts of organic

carbon that commonly accumulate under anaerobic conditions,

or the organic matter at least partially fills voids in fragmental,

cindery, or pumiceous materials. Cold temperatures contribute

to the accumulation of organic matter. These soils are of small

extent in the United States. They make up about 0.96 percent

of the surface area. They are in Alaska. The vegetation is

mostly mosses, sedges, and shrubs. The soils are used as

wildlife habitat.

Orthels are the Gelisols that show little or no evidence of

cryoturbation. These soils are of moderate extent in the United

States. They make up about 1.4 percent of the surface area.

They occur throughout the Gelisol area in Alaska. Orthels are

generally drier than Turbels and Histels. The vegetation is

mostly lichens, mosses, sedges, shrubs, black spruce, and white

spruce. The soils are used mostly as wildlife habitat. A small

amount of the acreage is used as cropland or for urban

development.

Turbels are the Gelisols that have one or more horizons

showing cryoturbation in the form of irregular, broken, or

distorted horizon boundaries, involutions, an accumulation of

organic matter on top of the permafrost, ice or sand wedges, or

oriented rock fragments. These soils are of large extent in the

United States. They make up about 6.4 percent of the surface

area. They occur throughout the Gelisol area in Alaska. The

vegetation is mostly mosses, sedges, shrubs, and black spruce.

The soils are used mostly as wildlife habitat. A small amount

of the acreage is used as cropland or for urban development.

The Gelisols in the Gelisols/Inceptisols delineation include

Turbels, Orthels, and Histels in a mosaic with Cryepts. The

Gelisols generally have a subgelic temperature class. The

Cryepts occur on slopes that receive more solar radiation or in

areas where fire or land clearing has changed the thermal

properties of the soils enough to allow the permafrost to thaw

to a depth of 2 meters or more.

Histosols

Histosols are of small extent in the United States. They make

up about 1.6 percent of the surface area. They are forming in

organic soil materials that do not have permafrost within 100 cm

of the soil surface. The general rule is that a soil is classified as a

Histosol if half or more of the upper 80 cm is organic. A soil also

is classified as a Histosol without regard to the thickness of

organic materials if the organic materials rest on rock or fill or

partially fill voids in fragmental, cindery, or pumiceous materials.

If the bulk density is very low (less than 0.1 gram per cubic

centimeter), three-fourths or more of the upper 80 cm must be

organic.

Histosols are divided into four suborders based on soil

wetness and the degree of decomposition of the organic

materials.

Fibrists are the wet, slightly decomposed Histosols. They are

of small extent in the United States. They make up about 0.24

percent of the surface area. The largest extent is in southern

Alaska. More than two-thirds of these soils consists of fiber

that is not destroyed by rubbing between the thumb and

fingers. The botanic origin of much of the materials can be

readily determined. The bulk density generally is less than 0.1

gram per cubic centimeter. These soils commonly are in closed

depressions or on broad flats, such as coastal plains. Many

have ground water near the soil surface nearly all the time. The

level of the ground water fluctuates, but it seldom drops much

below the bottom of the surface tier. Most of the soils support

natural vegetation of widely spaced, small trees, shrubs, forbs,

and grasses and grasslike plants.

Folists are the more or less freely drained Histosols that

consist primarily of O horizons derived from leaf litter, twigs,

and branches resting on bedrock or on fragmental materials in

which the interstices are partly or completely filled with

organic materials. These soils are of very small extent in the

United States. They make up about 0.09 percent of the surface

area. The largest extent is in Hawaii and Alaska. Some Folists

developed in the mountains and the most humid parts of the

conterminous United States. Most of these soils support forest

vegetation. Some of the soils in Hawaii mainly support grass.

A few of the soils in Hawaii are used for specialty crops or for

urban or recreational development.

Hemists are the wet Histosols in which the organic materials
844 Soil Taxonomy

are moderately decomposed. These soils are of small extent in

the United States. They make up about 0.3 percent of the

surface area. The largest extent is in Minnesota and Alaska.

The soils are mainly in closed depressions and on broad flats,

such as coastal plains and outwash plains. The botanic origin

of much of the organic material cannot be readily determined.

The fiber content of the organic material is mostly between

one-sixth and two-thirds after rubbing between the thumb and

fingers. The bulk density commonly is between 0.1 and 0.2

gram per cubic centimeter. Ground water is at or very close to

the surface much of the time unless artificial drainage has been

provided. The level of ground water may fluctuate but seldom

drops much below the bottom of the surface tier. Most Hemists

support natural vegetation and are used as woodland,

rangeland, or wildlife habitat. Some have been cleared and

drained and are used as cropland.

Saprists are the wet Histosols in which the organic materials

are well decomposed. These soils are of moderate extent in the

United States. They make up about 1.0 percent of the surface

area. The largest extent is in Michigan, Florida, Wisconsin,

Minnesota, and Alaska. Small areas are common on the

Atlantic and gulf coasts. The soils are mainly in closed

depressions and on broad flats, such as coastal plains and

outwash plains. The botanic origin of the organic material is

difficult to determine in most of these soils. The fiber content

of the organic material is mostly less than one-sixth after

rubbing between the thumb and fingers. Most of the soils have

a bulk density of more than 0.2 gram per cubic centimeter. The

water table tends to fluctuate within the soils, or the soils were

aerobic during drier periods in the past. Many Saprists support

natural vegetation and are used as woodland, rangeland, or

wildlife habitat. Some of the soils, mostly those with a mesic or

warmer temperature regime, have been cleared and drained

and are used as cropland.

Inceptisols

Inceptisols are soils of cool to very warm, humid and

subhumid regions. They are moderately extensive and widely

distributed in the United States. They make up about 9.7

percent of the surface area. The largest area is one that includes

the southern New England States and the Appalachian

Mountains. Other areas are on the southern Great Plains; in

the Rocky Mountains; in eastern Montana; in the coastal and

Cascade Mountains of California, Oregon, and Washington;

and in northeastern Minnesota.

Inceptisols have many kinds of diagnostic horizons and

epipedons. They cannot have an argillic, kandic, or natric

horizon unless it is buried. Spodic and oxic horizons also are

excluded unless the top of the horizon is deep. Inceptisols can

have an anthropic, histic, mollic, ochric, plaggen, or umbric

epipedon. The most common diagnostic horizons in the

Inceptisols in the United States are an ochric epipedon and a

cambic horizon. An umbric epipedon and a fragipan also are

common. Most Inceptisols do not have sandy texture

throughout. They are largely forming on late- or postPleistocene surfaces if evapotranspiration normally exceeds

precipitation at some time of the year. If precipitation exceeds

potential evapotranspiration in most months, Inceptisols occur

in areas of old as well as young surfaces or deposits. If the soil

temperature regime is frigid or cryic in these humid regions,

Inceptisols form mainly in the more clayey parent materials

and Spodosols form in the materials that have little clay.

Inceptisols range from very poorly drained to excessively

drained. A cambic horizon is not required if there is an umbric,

histic, or plaggen epipedon or if there is a fragipan or duripan

or a placic, calcic, petrocalcic, gypsic, petrogypsic, salic, or

sulfuric horizon.

Inceptisols may have any moisture regime except aridic and

any temperature regime, but they cannot have permafrost at a

depth of less than 100 cm below the soil surface.

Inceptisols are divided into four suborders based on soil

moisture and temperature regimes, soil wetness, and the kind

of epipedon.

Anthrepts are the more or less freely drained Inceptisols that

have either an anthropic or plaggen epipedon. They can have

almost any temperature regime and almost any vegetation.

These soils are not known to occur in the United States.

Aquepts are the wet Inceptisols. They are of moderate extent

and are widely distributed in the United States. They make up

about 1.4 percent of the surface area. Their natural drainage is

poor or very poor, and, if the soils have not been artificially

drained, ground water is at or near the soil surface at some

time during normal years but typically not in all seasons. The

soils generally have a gray to black surface horizon and a gray

subsurface horizon that has redox concentrations and begins at

a depth of less than 50 cm. Most Aquepts formed in latePleistocene or younger deposits in depressions, on nearly level

plains, or on flood plains. They can have almost any particlesize class except fragmental and any temperature regime, but

they cannot have permafrost. Many formed under forest

vegetation, but they can have almost any kind of vegetation.

Most of the soils have a cambic horizon, and some have a

fragipan. Aquepts are used mostly as cropland, pasture, forest,

or wildlife habitat.

Cryepts are the cold Inceptisols of high mountains or high

latitudes. They cannot have permafrost. They are of moderate

extent in the United States. They make up about 2.1 percent of

the surface area. They are mostly in the high mountains of the

West as well as southern Alaska. The vegetation is mostly

conifers or mixed conifers and hardwoods. These soils formed

mostly in loess, drift, or alluvium or in solifluction deposits of

late-Pleistocene or Holocene age. They commonly have a thin

ochric epipedon and a brownish cambic horizon. Some have

bedrock within 100 cm of the surface. Most are used as forest

or wildlife habitat. Some of the soils, mostly those in Alaska,

are used as cropland.

Udepts are mainly the more or less freely drained Inceptisols
Soils of the United States 845

that have a udic or perudic moisture regime. They are of large

extent in the United States. They make up about 3.8 percent of

the surface area. They are most extensive in the Appalachian

Mountains, on the Allegheny Plateau, in northeastern

Minnesota, and in Oregon. They formed on nearly level to

steep surfaces, mostly of late-Pleistocene or Holocene age.

Where the soil moisture regime is perudic, some of the soils

formed in older deposits. Most of the soils currently support or

formerly supported forest vegetation, but some support shrub or

grass vegetation. The vegetation was mostly coniferous forest

in the Northwest and mixed or hardwood forest in the Eastern

States. A few Udepts have been formed from Mollisols through

truncation of the mollic epipedon, mostly under cultivation.

Most Udepts have an ochric or umbric epipedon and a cambic

horizon. Some also have a fragipan, a duripan, or a sulfuric

horizon. Most are used as forest or have been cleared and are

used as cropland or pasture.

Ustepts are the more or less freely drained Inceptisols that

have an ustic moisture regime. They are of moderate extent in

the United States. They make up about 1.6 percent of the

surface area. They are most common on the Great Plains,

mostly in Montana, Texas, and Oklahoma. They receive

dominantly summer precipitation. They formed mostly in

Pleistocene or Holocene deposits or on steep slopes. Many of

these soils are calcareous at a shallow depth and have a Bk or

calcic horizon. A few have formed from Mollisols through

truncation of the mollic epipedon, mostly under cultivation.

Most of the soils have an ochric or umbric epipedon and a

cambic horizon. Some have a duripan. The native vegetation

commonly was grass, but some of the soils supported trees.

Most Ustepts are used as cropland or pasture. Some are used as

rangeland, forest, or wildlife habitat.

Xerepts are mainly the more or less freely drained Inceptisols

that have a xeric moisture regime. They are of small extent in the

United States. They make up about 0.85 percent of the surface

area. They are in the western part of the United States, mostly in

California, Oregon, and Washington. They receive dominantly

winter precipitation and have a frigid, mesic, or thermic

temperature regime. Most Xerepts formed in Pleistocene or

Holocene deposits or on steep slopes. Many are calcareous at a

shallow depth and have a Bk or calcic horizon. Most have an

ochric or umbric epipedon and a cambic horizon. Some have a

duripan, and a few have a fragipan. The native vegetation

commonly was coniferous forest on the soils with a frigid or

mesic temperature regime and shrubs, grasses, and widely

spaced trees on the soils with a thermic temperature regime.

Most Xerepts are used as forest, cropland, or pasture. Some are

used as rangeland or wildlife habitat.

Mollisols

Mollisols are very extensive in the United States. They make

up about 21.5 percent of the surface area. Most are on the

Great Plains and in the Western States. Nearly all Mollisols

have a mollic epipedon. Many also have an argillic or natric

horizon or a calcic horizon. A few have an albic horizon. Some

also have a duripan or a petrocalcic horizon. Most have

supported grass vegetation at some time, although many

apparently have been forested at times. Some of the soils,

mostly those in the mountains, formed in base-rich materials

under forest vegetation. Mollisols may have any of the defined

temperature regimes but do not have permafrost. They can

have any moisture regime, but enough available moisture to

support perennial grasses seems to be essential. Where the

temperature is frigid or warmer and slopes are not too steep,

Mollisols are used mainly as cropland. Generally, grains and

sorghum are grown in the drier regions and maize (corn) and

soybeans in the warmer, humid regions.

Mollisols are divided into seven suborders based on soil

moisture, soil temperature, and diagnostic horizons.

Albolls are the Mollisols that have both an albic horizon

and fluctuating ground water. They are of small extent in the

United States. They make up about 0.2 percent of the surface

area. They are mostly on the Great Plains, in eastern

Washington, and in Oregon and Idaho. Most are saturated with

water at or near the soil surface at some time during winter or

spring in normal years. In summer ground water is commonly

deeper than 200 cm. Below the albic horizon, there is either an

argillic horizon or, less commonly, a natric horizon. Albolls

developed mostly on broad, nearly level to sloping ridges and

back slopes or in closed depressions. Most have a perched

water table. Most formed in late-Pleistocene deposits. Most

supported grass or grass and shrub vegetation. In early stages

of development, some are thought to have supported forest

vegetation that was later succeeded by grass. Most of the soils

have gentle slopes and are used as cropland.

Aquolls are the wet Mollisols that do not have an albic

horizon and that have dominantly low-chroma and highcontrast redox depletions or concentrations in or below the

epipedon. These soils are of moderate extent in the United

States. They make up about 2.6 percent of the surface area.

They occur in all areas where there are Mollisols, but they are

most extensive in glaciated areas of the Midwestern States,

mainly Iowa, Minnesota, North Dakota, and Indiana. They also

occur in Florida. Commonly, they are in low areas where water

collects and stands, but some are on broad flats or on seepy

hillsides. Most have supported a vegetation of grasses, sedges,

and forbs, but some supported forest vegetation. Aquolls can

have any temperature regime, but they cannot have permafrost.

Most have a mesic or frigid temperature regime, have been

artificially drained, and are used as cropland.

Cryolls are the cool or cold, more or less freely drained

Mollisols. They are of moderate extent in the United States.

They make up about 1.5 percent of the surface area. Most are

in the high mountains of the Western States. Some are in

Alaska. Cryolls have a cryic temperature regime and a udic or

xeric moisture regime. They support forest, grass, or grass and

shrub vegetation. In Alaska forests of spruce, birch, and aspen
846 Soil Taxonomy

trees are common. Cryolls are used mostly as rangeland. Some

are used as forest and some as pasture.

Rendolls are the Mollisols that are of humid regions and

formed in highly calcareous parent materials, such as

limestone, chalk, and drift composed mainly of limestone, or

on shell bars. These soils are of very small extent in the United

States. They make up less than 0.1 percent of the surface area.

They are in Florida, on tropical islands, and in a few areas in

the mountains of the Western States. They formed mostly

under forest vegetation or under grass and shrubs. They have a

mollic epipedon that rests on the calcareous parent materials or

on a cambic horizon that is rich in carbonates. A few of the

soils are so rich in finely divided lime that the mollic epipedon

has a color lighter than normal but is nevertheless rich in darkcolored humus and is within the limits of a mollic epipedon.

Rendolls have a cryic soil temperature regime or a udic

moisture regime, or both. Most are used as cropland or pasture,

but some are used as rangeland or forest.

Udolls are the more or less freely drained Mollisols of

humid climates. They are of large extent in the United States.

They make up about 3.9 percent of the surface area. They are

in the eastern part of the Great Plains and east of the Great

Plains. They are most extensive in Minnesota, Illinois, Iowa,

and North Dakota. In addition to the mollic epipedon, most of

the soils have a cambic, calcic, natric, or argillic horizon. The

soils formed mainly in late-Pleistocene or Holocene deposits

or on surfaces of comparable age. The vegetation at the time

of settlement was dominantly tall grass prairie. The

temperature regime is frigid or warmer, and the moisture

regime is udic. Where slopes are not too steep, nearly all of

these soils are used as cropland. Some are used as pasture or

rangeland.

Ustolls are the more or less freely drained Mollisols of

subhumid to semiarid climates. They are of large extent in the

United States. They make up about 9.7 percent of the surface

area. They are mostly on the western Great Plains. They also

are common throughout the Rocky Mountain States. In

addition to the mollic epipedon, most Ustolls have a Bk

horizon that has identifiable secondary carbonates or have a

calcic horizon, but a few that formed in noncalcareous

materials do not have secondary lime. Ustolls may also have a

cambic, argillic, kandic, or natric horizon. Most of the Ustolls

on the Great Plains supported grass vegetation when the

country was settled. Some Ustolls, mostly those in the

mountains of the Western States, supported forest vegetation.

On the Great Plains, the most moist Ustolls supported mostly

tall grasses, the drier ones supported mostly short grasses, and

the others supported mixtures of short and tall grasses. Ustolls

have a frigid or warmer temperature regime. They generally

have an ustic moisture regime, but a few that are marginal to

Aridisols have an aridic moisture regime. Rainfall comes

mainly during a growing season, often in heavy showers, but is

erratic. Drought is frequent and may be severe. Without

irrigation, the low supply of moisture usually limits crop yields.

During a drought, soil blowing can be a problem. Most of these

soils are used as cropland or rangeland.

Xerolls are the more or less freely drained Mollisols of

regions that have Mediterranean climates. These soils are of

large extent in the United States. They make up about 3.7

percent of the surface area. They are in the Pacific Northwest,

California, Idaho, Nevada, and western Utah. They generally

have a xeric moisture regime, but some that are marginal to

Aridisols have an aridic moisture regime. Xerolls are dry for

extended periods in summer, but moisture moves through most

of the soils in winter and is stored above the deep layers or

above bedrock in normal years. Characteristically, Xerolls have

a relatively thick mollic epipedon and a cambic or argillic

horizon. Any accumulation of carbonates is in the lower part of

the B horizon. These soils are neutral in most horizons. The

vegetation at the time of settlement was dominantly bunchgrass

and shrubs or trees in the areas that have a mesic or frigid

temperature regime, a savanna of perennial grasses and oak

and Douglas-fir in the Willamette Valley of Oregon, and a

savanna of annual grasses and oak species on the Xerolls in

California that have a thermic temperature regime. Many

irrigated crops are grown on the Xerolls in the United States,

especially where the temperature regime is thermic or mesic.

Most of the soils that have gentle or moderate slopes are used

as cropland. The very steep soils are used mainly as rangeland,

but some are used as forest.

Oxisols

Oxisols are of very small extent in the United States. They

make up less than 0.1 percent of the surface area. They are

only on tropical and subtropical islands. They are most

common on the gentle slopes of geologically old surfaces on

the tropical and subtropical islands. Their profiles are

distinctive because of a lack of obvious horizons. Both the

structure and “feel” of Oxisols are deceptive. Upon first

examination, they appear structureless and have the feel of a

loamy texture. While some are loamy or even coarser textured,

many are in a fine or very-fine particle-size class, but the clay

is aggregated in a strong grade of fine and very fine granular

structure. Oxisols have a very low cation-exchange capacity

and have very few weatherable minerals. Most are infertile.

The natural vegetation ranges from tropical rain forests to

desert savannas.

Oxisols are divided into five suborders based on the

moisture regime and soil wetness.

Aquox are the wet Oxisols. They are rare in the United

States and are known to occur only in Puerto Rico. They are in

shallow depressions and in seepage areas at the base of slopes.

Most areas of these soils are small.

Perox are the well drained Oxisols with a perudic soil

moisture regime. They are rare in the United States and are

known to occur only in Hawaii. Curing many seed crops and

storage of produce are difficult on these soils.
Soils of the United States 847

Torrox are the Oxisols of arid regions. They have an aridic

moisture regime. Many have a higher base saturation than that

in other Oxisols. Torrox are very rare in the United States.

Udox are well drained Oxisols with a udic soil moisture

regime. They are of very small extent in the United States.

They make up less than 0.1 percent of the surface area. They

are known to occur only in Hawaii, Puerto Rico, and Guam.

They have a year-round growing season. They are moist

because of rainfall in normal years and are dry in some parts

for less than 90 days. The dry period is short enough for rainfed crops to be grown continuously in normal years.

Ustox are the Oxisols that have an ustic moisture regime.

They are of very small extent in the United States. They make

up less than 0.1 percent of the surface area. They are known to

occur only in Hawaii, Puerto Rico, and Guam. Because of

natural rainfall, they are moist for at least 90 but not more than

270 days in normal years, a period that is usually long enough

for one rain-fed crop. Crops are not grown continuously on

these soils because there is inadequate moisture for at least 90

days in normal years.

Spodosols

Spodosols are of small extent in the United States. They make

up about 3.5 percent of the surface area. They have a spodic

horizon or spodic materials, both of which consist of

accumulated amorphous mixtures of organic matter and

aluminum, with or without iron. The moisture regime

generally is udic, but some of the soils have aquic conditions.

Spodosols may have any soil temperature regime, but they

cannot have permafrost. In undisturbed soils there is commonly

an overlying eluvial horizon, generally with a gray or light

gray color similar to that of uncoated quartz. The spodic

horizon may be destroyed by cultivation. Yet, spodic materials

may still be present. Below the spodic horizon, there may be a

fragipan or another sequum that has an argillic horizon. In

some Spodosols spodic materials are cemented by sesquioxides

and organic matter (ortstein) that are thicker than a placic

horizon. Most Spodosols are forming in late-Pleistocene or

Holocene deposits. Most have few clay-sized phyllosilicates

and have a sandy, sandy-skeletal, coarse-loamy, loamy-skeletal,

or coarse-silty particle-size class.

Spodosols are most extensive in areas of cool, humid or

perhumid climates in the Northeastern States, southern Alaska,

the Great Lakes States, and the high mountains of the

Northwestern States. These soils also formed in warm, humid

subtropical and tropical regions, mainly Florida and the

southern Atlantic coast, where they occur mostly in areas of

quartz-rich sands that have a fluctuating level of ground

water. In many of the latter soils, the silt and sand fractions

contain very little iron and very few weatherable minerals and

the albic horizons tend to be thick. The chemical and physical

properties of many Spodosols and Andisols are very similar.

The definition of spodic materials, however, is based on the

concept of organic matter and aluminum, with or without

iron, accumulating through illuviation. Spodosols are

naturally infertile soils, but they can be highly responsive to

good management. Under cultivation, particularly if lime

and nitrogen are applied, the spodic horizon may be

destroyed.

Spodosols are divided into four suborders based on soil

wetness, soil temperature regime, or content of organic matter

in the spodic horizon.

Aquods are the wet Spodosols. They are characterized by a

shallow fluctuating water table. They are of small extent in the

United States. They make up about 0.6 percent of the surface

area. They dominate the Spodosol delineations in Florida and

along the Atlantic coast. They are a component of many of the

delineations in the Northeastern and Great Lakes States.

Aquods formed mainly in materials of Pleistocene age. They

can have any temperature regime, but they cannot have

permafrost. In the warmer areas most of the soils have a nearly

white albic horizon thick enough to persist under cultivation

or, in the wettest Aquods, a black surface horizon resting on a

dark reddish brown spodic horizon that is virtually free of iron.

Some Aquods have ortstein that is cemented by an amorphous

mixture of sesquioxides and organic matter. The vegetation is

water-loving plants, ranging from moss, shrubs, and trees in

cold areas to mixed forests and palms in the warmest areas.

Most Aquods are used as forest or wildlife habitat. Some,

mostly in Florida and New Jersey, have been cleared and are

used as cropland or pasture. Aquods are naturally infertile, but

they can be highly responsive to good management. The spodic

horizon can be destroyed under cultivation, particularly if lime

and nitrogen are applied.

Cryods are the cold Spodosols of high latitudes and/or high

elevations. They are of small extent in the United States. They

make up about 0.9 percent of the surface area. They are mostly

in southern Alaska and in the mountains of Washington and

Oregon. Some are in the high mountains of New York and

northern New England. Most Cryods formed in glacial drift

and some in residuum or colluvium. Those in Alaska,

Washington, and Oregon commonly formed at least partially in

volcanic ash. Cryods commonly have an O horizon over a very

thin or intermittent albic horizon, which overlies a well

developed spodic horizon. Some have ortstein or another

cemented soil layer within 100 cm of the mineral soil surface.

In many Cryods the content of organic carbon in the upper part

of the spodic horizon is relatively high. The vegetation is

mostly coniferous forest. Most Cryods are used as forest or

wildlife habitat.

Humods are the relatively freely drained Spodosols that

have a large accumulation of organic carbon in the spodic

horizon. They are of very small extent in the United States.

They make up less than 0.1 percent of the surface area. They

are mostly in Washington State, but a few are known to occur

on tropical islands and in the Northeastern and Southeastern

States. Humods formed dominantly in Pleistocene or Holocene
848 Soil Taxonomy

sediments. The undisturbed soils may have either a thin,

intermittent or a distinct, continuous albic horizon over a

spodic horizon. The upper part of the spodic horizon

commonly is nearly black and has a reddish hue. The hue

normally becomes less red with increasing depth. Most

Humods formed under coniferous forest vegetation. These

soils are used mainly as forest.

Orthods are the relatively freely drained Spodosols that have

a moderate accumulation of organic carbon in the spodic

horizon. They are of moderate extent in the United States.

They make up about 1.9 percent of the surface area. They occur

in all of the Spodosol delineations, except for those in Alaska.

They are most extensive in the Northeastern United States and

the Great Lakes States. Most Orthods formed in coarse

textured, acid Pleistocene or Holocene deposits under

coniferous forest vegetation. If undisturbed, Orthods normally

have thin O and albic horizons over a spodic horizon. A few

have a fragipan below the spodic horizon. Under cultivation,

the albic horizon is very commonly mixed with part of the

spodic horizon. The Orthods in the United States generally

have a udic moisture regime, but a few have a xeric moisture

regime. The soil temperature regime ranges from frigid to

hyperthermic. Most Orthods are used as forest or have been

cleared and are used as cropland or pasture. Orthods are

naturally infertile, but they can be highly responsive to good

management. The spodic horizon can be destroyed under

cultivation, particularly if lime and nitrogen are applied.

Ultisols

Ultisols are moderately extensive in the United States. They

make up about 9.2 percent of the surface area. Typically, they

have an ochric epipedon and an argillic or kandic horizon that

has few bases and commonly is calcium deficient. The base

saturation in most Ultisols decreases with increasing depth,

probably because the vegetation has added recycled bases at the

surface. Ultisols can have any soil moisture regime except

aridic and any soil temperature regime, but they cannot have

permafrost. Most of the Ultisols in the United States have a

udic moisture regime and a mesic or thermic temperature

regime. Ultisols are extensive in the warm, humid parts of the

country. They formed in a wide variety of parent materials,

mainly on Pleistocene or older surfaces. Most of these soils

supported mixed coniferous and hardwood forest vegetation at

the time of settlement. Some are now used as cropland or

pasture.

Ultisols are divided into five suborders based on the soil

moisture regime, soil wetness, and content of organic carbon in

the upper part of the profile.

Aquults are the Ultisols in wet areas where ground water is

very close to the surface during part of each year, usually in

winter and spring, and is deep at other times. These soils are of

small extent in the United States. They make up about 0.8

percent of the surface area. They are on the coastal plains,

particularly along the Atlantic Ocean and the Gulf of Mexico.

The soils are mostly grayish or olive in the subsoil and formed

mainly in alluvium and marine deposits that are of Pleistocene

age or older. They have an ochric or umbric epipedon and an

argillic or kandic horizon. Some have a fragipan. Slopes are

gentle. Most of the soils formerly supported forest vegetation.

Many still support forest vegetation.

Humults are the more or less freely drained, humus-rich

Ultisols. They are of small extent in the United States. They

make up about 0.2 percent of the surface area. They dominate

most of the Ultisol delineations in Oregon and Washington and

also occur in California and Puerto Rico. They commonly

receive high rainfall but also have a moisture deficit during

some season. Most of the Humults in the United States formed

in material weathered from basic country rock on latePleistocene or older surfaces. Slopes are commonly steep. If the

soils are cultivated, the argillic or kandic horizon may be near

the surface. Humults generally have a dark colored epipedon.

The vegetation was mostly coniferous forest in the Northwest

and rain forest in the tropics. Most of these soils are used as

forest or have been cleared and are used as cropland or pasture.

Udults are the more or less freely drained, relatively humuspoor Ultisols that have a udic moisture regime. They are of

large extent in the United States. They make up about 8.1

percent of the surface area. They dominate most of the Ultisol

delineations in the southern and eastern parts of the country.

Most of these soils receive well distributed rainfall. Most have

light colored upper horizons, commonly including a grayish

horizon that rests on a yellowish brown to reddish argillic or

kandic horizon. A few of the Udults that formed in material

weathered from basic rocks have a dark brown or reddish

brown surface horizon that rests on a dark red or dusky red

argillic or kandic horizon. Some Udults have a fragipan or

plinthite, or both, in or below the argillic or kandic horizon.

Udults developed in sediments and on surfaces that range from

late Pleistocene to Pliocene or possibly older. Most of these

soils currently support or formerly supported mixed forest

vegetation. Many have been cleared and are used as cropland,

mostly with the use of soil amendments.

Ustults are the more or less freely drained Ultisols that have

an ustic soil moisture regime and have a relatively low content

of organic carbon. They are of very small extent in the United

States. They make up less than 0.1 percent of the surface area.

They occur in the extreme western part of the Ultisol

delineation in Texas. Some are in California and on tropical

islands. Ustults formed in regions where rainfall is moderately

low to high but where evapotranspiration exceeds precipitation.

Some Ustults, mostly those in California, have a single dry

season each year, and others have alternating moist and dry

periods throughout the growing season. Most Ustults have a

thermic or warmer temperature regime. The vegetation is

commonly forest or savanna. Some of the soils have been

cleared and are used as cropland or pasture.

Xerults are the more or less freely drained Ultisols of
Soils of the United States 849

Mediterranean climates. They are of moderate extent in the

United States. They make up about 0.1 percent of the surface

area. They dominate some Ultisol delineations in California

and Oregon. They have a xeric moisture regime and a

moderate amount of organic matter. Most Xerults have an

ochric or umbric epipedon and a brownish to reddish argillic

horizon. They are generally on gentle to very steep mountain

slopes. The vegetation formerly was and currently is mostly

coniferous forest. Most of these soils are used as forest, but

some have been cleared and are used as cropland or pasture.

Vertisols

Vertisols are of small extent in the United States. They make

up about 2.0 percent of the surface area. They are clayey soils

that have deep, wide cracks for some time during the year and

have slickensides within 100 cm of the mineral soil surface.

They shrink as they dry and swell as they become moist. They

are a relatively homogeneous order because of the kinds and

amounts of clay common to them, but their microvariability

within a pedon is great. Vertisols can have any soil temperature

regime but cannot have permafrost, and they can have any

moisture regime. Although the process of shrinking and

swelling is important in Vertisols, it does not preclude the

formation of diagnostic horizons and features. For example,

Vertisols commonly have a mollic epipedon and a cambic

horizon and can have a calcic, gypsic, or salic horizon. They

generally have gentle slopes, although a few are strongly

sloping. The natural vegetation is predominantly grass,

savanna, open forest, or desert shrub. Most Vertisols are well

suited to mechanized frming if there is plenty of rainfall or

irrigation water. Vertisols are well known among engineers

because their unique properties limit engineering uses.

Vertisols are divided into six suborders based on soil

wetness, soil temperature, and soil moisture. These properties

tend to limit the suborders to specific regions of the country.

Aquerts are of small extent in the United States. They make

up about 0.6 percent of the surface area. They are the wet

Vertisols. They have aquic conditions at or near the soil surface

for extended periods during the year but also are dry enough in

normal years for cracks to open during some periods. These

soils are mostly in Texas, the lower Mississippi River Valley,

and the valley of the Red River of the North. They typically are

nearly level and are in low areas, such as glacial lake plains,

flood plains, stream terraces, and coastal lowlands. The natural

vegetation is predominantly forest, grass, or savanna. These

soils are used mostly as rangeland, cropland, or forest.

Drainage of cropland presents special problems since the

saturated hydraulic conductivity of these soils is very low.

Because the permeability of these soils is so slow, a surface

drainage system commonly is installed in areas used as

cropland or pasture. Rice is grown on some Aquerts that have a

thermic or warmer temperature regime.

Cryerts are not known to occur in the United States. They

are the Vertisols that have a cryic temperature regime. They are

cold, but they periodically shrink and swell, forming the

diagnostic characteristics of Vertisols. Cracks commonly open

once a year, late in summer.

Torrerts are of small extent in the United States. They make

up about 0.1 percent of the surface area. They are in areas too

small to be shown on the map. They are the Vertisols of arid

climates. They are in western Texas and in Arizona and New

Mexico. The cracks in these soils commonly stay open for most

of the year but close for at least part of the winter in normal

years. Many of the soils are in closed depressions that may be

ponded from time to time. Some areas of Torrerts are more

continuous and are commonly underlain by basalt or other

parent materials that tend to weather to smectitic clays.

Torrerts commonly have an ochric epipedon and a cambic,

salic, gypsic, or calcic horizon. The native vegetation is mostly

grasses and forbs. These soils are used mainly as rangeland.

The use of Torrerts as irrigated cropland presents special

problems since the saturated hydraulic conductivity is very low.

Bypass flow through open cracks is common. Because the

permeability of these soils is so slow, irrigation may result in

water-logging and a buildup of salinity unless an adequate

artificial drainage system can be installed.

Uderts are of small extent in the United States. They make

up about 0.3 percent of the surface area. They are the Vertisols

of humid areas. They have cracks that open and close,

depending on the amount of precipitation. In some years the

cracks may not open completely. These soils are mostly in

Texas, in the lower Mississippi River Valley, in the valley of

the Red River of the North, and in Alabama and Mississippi.

They typically are nearly level or gently sloping and are mostly

on coastal plains, flood plains, stream terraces, and glacial lake

plains. Most Uderts occur on gentle slopes and are derived

from marine shales, marl, and alluvium. At one time many of

these soils supported grass and widely spaced trees, although

some supported hardwood forest vegetation. Uderts are used

mostly as pasture, cropland, or forest. Because the saturated

hydraulic conductivity of these soils is very low, a surface

drainage system is commonly used to remove excess water

from cropland. Rice is grown on some Uderts that have a

thermic or warmer temperature regime.

Usterts are of small extent in the United States. They make

up about 0.8 percent of the surface area. They are mostly in

Texas, South Dakota, and Montana. They receive low amounts

of rainfall during the summer, and cracks open and close once

or twice during normal years. A few of these soils are on

tropical and subtropical islands. Many Usterts formed in nearly

level or gently sloping areas of fine textured marine deposits,

shale, or alluvium. Some formed in material weathered from

basic igneous rocks. The native vegetation is mostly grasses

and forbs. Usterts are used mainly as rangeland or cropland.

The use of Usterts as irrigated cropland presents special

problems since the saturated hydraulic conductivity is very low.

Bypass flow through open cracks is common. Because the
850

permeability of these soils is so slow, irrigation may result in

water-logging and a buildup of salinity unless an adequate

artificial drainage system can be installed.

Xererts are of small extent in the United States. They make

up about 0.1 percent of the surface area. They are the Vertisols

of Mediterranean climates, which are typified by cool, wet

winters and warm, dry summers. Xererts are mostly in California,

Oregon, and Idaho. They have cracks that regularly close and

open each year. Because these soils become dry every summer

and moisten in winter, damage to structures and roads is very

significant. Many Xererts are nearly level to sloping. Most

formed in material weathered from basic igneous rocks or shale

or in alluvium. The native vegetation is mostly grasses and

forbs. Xererts are used mainly as rangeland or cropland.

Irrigated rice is grown on some Xererts that have a thermic

temperature regime. Bypass flow through open cracks is a

concern. The use of Xererts as irrigated cropland presents some

special problems. Because the permeability of these soils is so

slow, irrigation may result in water-logging and a buildup of

salinity unless an adequate artificial drainage system can be

installed.

Literature Cited

United States Department of Agriculture, Natural Resources

Conservation Service. 1994 (revised 1998). State Soil Geographic

Data for U.S. States and Territory of Puerto Rico. Soil Surv. Staff.

(Digital general soil maps and attribute tables)

United States Department of Agriculture, Natural Resources

Conservation Service. 1996. Alaska State Geographic Data

Base. Soil Surv. Staff. (Digital general soil maps and attribute

tables)

United States Department of Agriculture, Natural

Resources Conservation Service. March 1997. Soil

Classification File. Soil Surv. Staff. Iowa State Univ. Stat. Lab.,

Ames, Iowa.
851

CHAPTER 23

World Distribution of Orders and Suborders

The only comprehensive and international effort todevelop an assessment of the soil resources of the world

was undertaken in the 1960’s by the Food and Agriculture

Organization of the United Nations (FAO-UNESCO). After

World War II, many Western countries undertook systematic

soil surveys and similar activities were initiated in developing

countries through bilateral programs. FAO also had ongoing

national assessments in some developing countries and to

enable these assessments developed a legend for the eventual

Soil Map of the World at a scale of 1:5,000,000. The maps of

the different regions of the world were published at different

periods during the 1970’s. No information was available for

many countries or regions within these countries. For these

reasons, there is a high degree of variability in the quality of

information from country to country. Despite this variability,

the maps are the only reference base available on a global

scale. In 1992, the maps were digitized by FAO. The digital

copy was used for the world map in this publication.

Soil Taxonomy has been subject to many changes since its

first edition was published in 1975. Though the translation of

the FAO legend to the most recent version of Soil Taxonomy

presents only minor problems, converting the FAO soil map

results in important errors. The conversion was done by

assigning terms in Soil Taxonomy to FAO terms, taking into

consideration the soil moisture and temperature regimes (SMR

and STR). All polygons with the same FAO class term have an

equivalent term in Soil Taxonomy. The errors introduced by

this process are illustrated by the case of the soils in the

western Amazon Basin. On the FAO map, these are shown as

Orthic Ferralsols, which are equivalent to Typic Hapludox in

Soil Taxonomy. A recent soil map of Brazil depicts these soils

as Acrisols, or Ultisols in Soil Taxonomy. Consequently, though

every effort was made to incorporate recent information, in

some cases the process of manipulating rastorized digital data

made it impossible to make the changes.

The map of the world at the end of this publication shows

the distribution of the major soil orders. The table “World

Distribution of Orders and Suborders” provides estimates of

the area of different orders and suborders on a global basis and

also the area of climatic environments, or major eco-regions.

Only the suborders that are extensive enough to be shown on

the world map are listed. Soil patterns are distinct and show

the role of soil moisture and temperature regimes interacting

with parent materials. In Europe, the soil moisture regimes

show a north-south trend and the consequent effect on soil

formation is illustrated by horizontal patterns of the soils. In

North America and particularly in the United States, the soil

moisture regimes show an east-west trend and the soil patterns

reflect this trend. On the eastern seaboard, the soils are Ultisols,

and as one proceeds westward, they give way to Mollisols,

Alfisols, and Aridisols. Finally, in the Rocky Mountains, the

soils are Inceptisols and some Andisols. Farther north in North

America, the soils are dominantly Inceptisols and Spodosols,

which give way to Histosols and Gelisols in the northern tundra

zone.

Gelisols, the most recent soil order introduced into the

system of soil taxonomy, occupy about 8.6 percent of the icefree land surface. Few detailed soil maps depict these soils, as

previous classification systems did not differentiate the soils

based on permafrost. The lower geographic limit of Gelisols for

this map is defined by a mean annual soil temperature of less

than 0 oC and by a mean summer soil temperature of less than

10 oC. The northern part of the Gelisol zone grades to ice.

Organic soils, or Histosols, occupy about 1.2 percent of the

land surface. This percentage does not include the 0.8 percent

of Histels, which are present in the Gelisol region and which

form the largest contiguous extent of organic soils. The next

largest area of organic soils is adjacent to the tundra soils in

the boreal belt. These organic soils are the “Cryo” great groups

of Fibrists, Hemists, and Saprists. Tropical Histosols are

dominantly in Southeast Asia, mainly in Sumatra and

Kalimantan. Many of the tropical Histosols are on coastal

plains and have very low pH because of the presence of acid

sulfate materials. Unlike the temperate and boreal Histosols,

which formed in areas of moss and grassy vegetation, tropical

Histosols are woody and frequently contain large trunks of

undecomposed trees. These woody materials make cultivation

of such soils difficult.

Spodosols are dominantly in the colder regions of the world

where STR is mesic or colder and SMR is udic or perudic.

These boreal Spodosols occupy about 2.7 percent of the land

surface. Podsolization results from release of large quantities of

organic acids in the organic-rich surface soil horizons.

Characteristically, these soils form in sandy materials or in

materials with only small amounts of weatherable minerals that

have the potential to alter and release bases. In the Tropics,

soils with similar morphology are in areas of coastal beach

deposits. The largest contiguous extent of such soils is on the

coastal plains of the Amazon Basin. The soils are described

and classified as Spodosols but frequently are not the result of
852 Soil Taxonomy

Histels ......... 1.01 0.77 0 0 0 0 0 0 1.011 0.77

Turbels ........ 6.33 4.84 0 0 0 0 0 0 6.316 4.83

Orthels......... 3.91 2.99 0 0 0 0 0 0 3.903 2.98

Gelisols ....................................11.26 8.61 0 0 0 0 0 0 11.230 8.59

Fibrists ........ 0.20 0.15 0 0 0 0 0.194 0.15 0 0

Saprists ....... 0.34 0.26 0.317 0.24 0.022 0.02 0 0 0 0

Hemists ....... 0.99 0.76 0 0 0.099 0.08 0.884 0.68 0 0

Histosols.................................. 1.53 1.17 0.317 0.24 0.121 0.09 1.078 0.82 0 0

Aquods ....... 0.17 0.13 0.013 0.01 0.055 0.04 0.099 0.08 0 0

Cryods......... 2.46 1.88 0 0 0 0 2.455 1.88 0 0

Humods ....... 0.06 0.04 0.029 0.02 0.028 0.02 0.000078 0 0 0

Orthods ....... 0.67 0.51 0.018 0.01 0.508 0.39 0.138 0.11 0 0

Spodosols ................................ 3.35 2.56 0.060 0.05 0.592 0.45 2.693 2.06 0 0

Cryands ....... 0.26 0.2 0 0 0 0 0.254 0.19 0 0

Torrands ...... 0.001 0 0.001 0 0 0 0 0 0 0

Xerands ....... 0.032 0.02 0 0 0.032 0.02 0 0 0 0

Vitrands ....... 0.28 0.21 0.202 0.15 0.077 0.06 0.000605 0 0 0

Ustands....... 0.62 0.05 0.058 0.04 0.003 0 0 0 0 0

Udands........ 0.28 0.21 0.185 0.14 0.089 0.07 0.001 0 0 0

Andisols .................................. 0.91 0.7 0.448 0.34 0.202 0.16 0.256 0.2 0 0

Aquox ......... 0.32 0.24 0.320 0.24 0 0 0 0 0 0

Torrox .......... 0.031 0.02 0.027 0.02 0.004 0 0 0 0 0

Ustox ........... 3.10 2.37 3.086 2.36 0.009 0.01 0 0 0 0

Perox ............ 1.16 0.89 1.010 0.77 0.151 0.12 0 0 0 0

Udox ............ 5.20 3.98 5.166 3.95 0.032 0.02 0 0 0 0

Oxisols ..................................... 9.81 7.5 9.610 7.35 0.197 0.15 0 0 0 0

Order Suborder

World Distribution of Orders and Suborders

Area ice-free land

106 km2 %

Area tropical

106 km2 %

Area temperate

106 km2 %

Area boreal

106 km2 %

Area tundra

106 km2 %
World Distribution of Orders and Suborders 853

Aquerts ....... 0.054 0 0.000763 0 0.004 0 0 0 0 0

Cryerts......... 0.014 0.01 0 0 0 0 0.014 0.01 0 0

Xererts......... 0.098 0.08 0 0 0.098 0.08 0 0 0 0

Torrerts ........ 0.889 0.68 0.238 0.18 0.647 0.5 0 0 0 0

Usterts......... 1.767 1.35 1.169 0.89 0.594 0.45 0.002 0 0 0

Uderts ......... 0.384 0.29 0.086 0.07 0.297 0.23 0 0 0 0

Vertisols ................................... 3.160 2.42 1.494 1.14 1.642 1.26 0.017 0.01 0 0

Cryids .......... 0.943 0.72 0 0 0 0 0.940 0.72 0 0

Salids ........... 0.890 0.68 0.052 0.04 0.632 0.48 0.195 0.15 0.000691 0

Gypsids ....... 0.682 0.52 0.228 0.17 0.429 0.33 0.024 0.02 0 0

Argids ......... 5.407 4.13 0.573 0.44 4.035 3.09 0.782 0.6 0 0

Calcids......... 4.872 3.73 0.451 0.34 4.400 3.36 0.013 0.01 0 0

Cambids ...... 2.931 2.24 0.561 0.43 2.063 1.58 0.302 0.23 0 0

Aridisols ..................................15.728 12.02 1.867 1.43 11.560 8.84 2.258 1.73 0.000691 0

Aquults ....... 1.280 0.98 1.042 0.8 0.235 0.18 0.000058 0 0 0

Humults....... 0.343 0.26 0.277 0.21 0.061 0.05 0.004 0 0 0

Udults ......... 5.539 4.24 2.654 2.03 2.872 2.2 0.009 0.01 0 0

Ustults......... 3.869 2.96 3.630 2.78 0.234 0.18 0.001 0 0 0

Xerults......... 0.018 0.01 0 0 0.0009 0 0.017 0.01 0 0

Ultisols.....................................11.052 8.45 7.605 5.81 3.405 2.6 0.033 0.03 0 0

Albolls......... 0.027 0.02 0 0 0.001 0 0.026 0.02 0 0

Aquolls ....... 0.118 0.09 0.001 0 0.084 0.06 0.031 0.02 0 0

Rendolls ...... 0.265 0.2 0.120 0.09 0.103 0.08 0.040 0.03 0 0

Cryolls ......... 1.163 0.89 0 0 0 0 1.160 0.89 0 0

Xerolls ......... 0.924 0.71 0 0 0.873 0.67 0.050 0.04 0 0

Ustolls ......... 5.244 4.01 0.184 0.14 2.370 1.81 2.682 2.05 0 0

Udolls .......... 1.261 0.96 0.054 0.04 1.058 0.81 0.146 0.11 0 0

Mollisols .................................. 9.005 6.89 0.361 0.28 4.491 3.43 4.139 3.16 0 0

Order Suborder

World Distribution of Orders and Suborders--Continued

Area ice-free land

106 km2 %

Area tropical

106 km2 %

Area temperate

106 km2 %

Area boreal

106 km2 %

Area tundra

106 km2 %
854 Soil Taxonomy

Aqualfs ....... 0.836 0.64 0.407 0.31 0.373 0.29 0.054 0.04 0 0

Cryalfs ......... 2.517 1.92 0 0 0 0 2.509 1.92 0 0

Ustalfs ......... 5.663 4.33 3.773 2.88 1.719 1.31 0.165 0.13 0 0

Xeralfs ......... 0.896 0.69 0 0 0.848 0.65 0.046 0.04 0 0

Udalfs .......... 2.706 2.07 0.616 0.47 1.926 1.47 0.158 0.12 0 0

Alfisols ....................................12.620 9.65 4.797 3.67 4.868 3.72 2.933 2.24 0 0

Aquepts ...... 3.199 2.45 1.498 1.15 1.183 0.9 0.502 0.38 0 0

Cryepts ........ 0.456 0.35 0 0 0 0 0.456 0.35 0 0

Ustepts ........ 4.241 3.24 2.804 2.14 1.372 1.05 0.060 0.05 0 0

Xerepts ........ 0.685 0.52 0 0 0.674 0.52 0.009 0.01 0 0

Udepts......... 4.247 3.25 1.755 1.34 2.153 1.65 0.333 0.26 0 0

Inceptisols ...............................12.829 9.81 6.058 4.63 5.383 4.12 1.362 1.04 0 0

Aquents ...... 0.116 0.09 0.105 0.08 0.010 0.01 0 0 0 0

Psamments .. 4.428 3.39 2.799 2.14 1.625 1.24 0.001 0 0 0

Fluvents ...... 2.860 2.19 1.017 0.78 1.455 1.11 0.368 0.28 0 0

Orthents ......13.733 10.5 2.095 1.6 11.264 8.61 0.363 0.28 0 0

Entisols ....................................21.137 16.16 6.019 4.6 14.355 10.98 0.732 0.56 0 0

Total ..................................130.796 100 39.193 29.97 51.865 39.65 19.327 14.78 20.188 15.43

Ocean ..........364.654

Shifting

sands ......... 5.321 4.07 0.545 0.42 4.680 3.58 0.092 0.07 0 0

Rock ............ 13.076 10 0.007 0.01 0.363 0.28 3.727 2.85 8.956 6.85

Ice................ 14.640

Miscellaneous ..........................397.692

Order Suborder

World Distribution of Orders and Suborders--Continued

Area ice-free land

106 km2 %

Area tropical

106 km2 %

Area temperate

106 km2 %

Area boreal

106 km2 %

Area tundra

106 km2 %
World Distribution of Orders and Suborders 855

the podsolization process that operates in the temperate or

boreal climates. The sandy levee deposits or stranded beach

deposits occur in association with Aquepts and Saprists. The

dissolved organic colloids seep up the sands (capillary effect)

and precipitate at the capillary fringe of the ground water table.

The resulting morphology is that of a spodic horizon.

Andisols dominate the circum-Pacific belt, or the Ring of

Fire. They are frequently associated with current or former

volcanic activity. Depending on the intensity and periodicity of

the volcanic activity, deposits of several ages may characterize

a soil. In the colder and moister parts of the world, Andisols

are characterized by dark mollic-like or umbric-like epipedons.

Buried horizons with similar organic-rich horizons may be

typical. In the Tropics, organic accumulation is not so rapid. In

addition, weathering and mineral alteration lead to the formation

of a clay fraction dominated by halloysite and kaolinite. A

normal toposequence in the Tropics is Andisols on the upper

slopes, in association with Inceptisols, which give way to

Ultisols and Oxisols on the gentler topography. In some

Andisols in which the content of organic matter is low and

short-range-order minerals dominate the colloids, the soils may

have a net positive charge. These Andisols are counterparts of

the suborder Anionic Acrudox in terms of mineral-chemical

composition.

Oxisols are confined to the intertropical regions, which by

definition have an iso STR. Most of the Oxisols occur between

the Tropics of Cancer and Capricorn. The largest extent is in

Brazil, followed by the Congo Basin in Central Africa.

Characteristically, Oxisols formed in preweathered and

transported deposits. Weathering may continue in the

postdepositional phase. Other pedogenic processes are slow

unless there is a fluctuating water table. On the volcanic

islands of the Pacific and in Southeast Asia, basic or ultrabasic

rocks may weather to form Oxisols. Although there is always

the possibility of admixture with alluvial or colluvial products,

these soils are generally thought to have formed directly on the

rocks, unlike the Oxisols of the Amazon or Congo Basins.

Vertisols occupy about 2.4 percent of the land surface and

are about equally distributed in tropical and temperate areas.

They are among the soils in which soil properties are a function

of the mineralogical composition of the clay fraction. For the

smectites to form and persist in the soils, one of the

requirements is that the soil solution have a high pH, which

results in high amounts of bases and soluble silica. Thus, most

of the Vertisols occur in semiarid or arid environments. The

countries with large areas of Vertisols are Sudan, India,

Australia, and the United States. In semiarid southern Africa,

large contiguous areas of Vertisols are in Zambia, Zimbabwe,

and South Africa. In other areas Vertisols occur sporadically in

basins adjoining Andisols.

Although about a third of the land mass of the world is arid,

Aridisols occupy only about 12 percent of the land surface. By

definition, Aridisols must have a diagnostic horizon; the

remaining soils in arid regions are Entisols with associated

unstabilized dunes and rocky land. About 60 percent of the

Aridisols are in the temperate parts of the world. The rest have

tropical and boreal climates. Argids are the most extensive

Aridisols and are frequently in areas where the aridic SMR

borders on the ustic or xeric SMR. Calcids, which occupy about

3.7 percent of the land area, are associated with the Argids.

Translocation and subsurface accumulation of carbonates,

gypsum, and salts require some moisture. Formation of the

horizons diagnostic for these suborders may be a current

process or may have taken place in historic or geologic periods.

Because of the current aridity of the sites where these soils

occur, it is generally assumed that many of the diagnostic

features may have a “paleo” origin.

Ultisols and Alfisols occupy 8.5 and 9.7 percent of the land

surface, respectively. Ultisols are more common in the

intertropical areas, while Alfisols are in the temperate areas.

Also, there is greater proportion of Alfisols than of Ultisols in

the semiarid parts of the world. The dominant feature of both

Ultisols and Alfisols is the presence of an argillic horizon.

Other diagnostic horizons or properties define the subclasses.

A lighter textured surface soil, which makes tillage easy, and a

heavier textured underlying argillic horizon, which enables

greater storage of water and nutrients, favor crop production.

Many of these soils occur on flat to gently undulating

landscapes and have been used by farmers since the beginning

of civilization.

Mollisols, which have a thick, organic-rich surface horizon,

are among the most productive soils in the world. Some of the

world’s record yields have been obtained on these soils.

Mollisols occupy about 6.9 percent of the land mass and are

concentrated in the temperate and boreal regions of the world.

They are important soils in the semiarid parts of the world,

particularly in the regions with a Mediterranean climate. The

cool climate permits a slow accumulation of the humified

organic matter. Because of the excellent quality of the soils and

the very favorable climate, these soils are very productive and

make up the breadbasket of modern times. Large areas of such

soils characterize the Midwest in the United States, the steppes

of the former Soviet Union, the northern part of Argentina, and

part of Uruguay.

Inceptisols and Entisols together occupy about 25 percent of

the land surface. Generally on young surfaces, they occur in

association with rock outcrops and sand dunes. These soils

formed in recent coastal and riverine deposits. They formed in

marine alluvium under brackish water conditions. Entisols are

potential acid sulfate soils, and Inceptisols are actual acid

sulfate soils. When drained, potential acid sulfate soils

(Sulfaquents) are converted to actual acid sulfate soils

(Sulfaquepts). The process results in release of a considerable

amount of sulfuric acid, making these soils and the soils

adjacent to them extremely acid.

Because of different data sets, the map of the world and the

map of the United States in this publication do not always

exactly match.

857

Laboratory Methods for Soil Taxonomy

The standard laboratory methods upon which the

operational definitions of this edition of Soil Taxonomy are

based are described in the Soil Survey Laboratory Methods

Manual (USDA, NRCS, 1996). Copies of standard laboratory

data sheets are included with the typifying pedons in the

chapters on soil orders in this edition of Soil Taxonomy. For

specific information about an analytical procedure, these data

sheets should be checked and reference should be made to the

Soil Survey Laboratory Methods Manual. Much of the

information included in this appendix is derived from “Soil

Survey Laboratory Methods for Characterizing Physical and

Chemical Properties and Mineralology of Soils” (Kimble,

Knox, and Holzhey, 1993). Also, the information is summarized

in the Soil Survey Laboratory Information Manual (USDA,

NRCS, 1995).

Pedon characterization data, or any soil survey data, are most

useful when the operations for collecting the data are well

understood. The mental pictures and conceptual definitions

that aid in visualizing properties and processes often differ

from the information supplied by an analysis. Also, results

differ by method, even though two methods may carry the same

name or the same concept. There is uncertainty in comparing

one bit of data with another without knowledge of how both

bits were gathered. Operational definitions, definitions tied to a

specific method, are needed. This soil taxonomy has many

class limits (at all levels) that are based on chemical or

physical properties determined in the laboratory. One can

question a given limit, but that is not the purpose of this

appendix. This appendix is written to show what procedures

are used for given class limits. By using specific class limits,

everyone will come to the same classification if they follow the

same procedures.

This taxonomy is based almost entirely on criteria that are

defined operationally. One example is the definition of particlesize classes. There is no one definition of clay that works well

for all soils. Hence, an operation for testing the validity of a

clay measurement and a default operation for those situations

where the clay measurement is not valid are defined. The

default method is based on a water content at 1500 kPa and on

content of organic carbon.

Data Elements Used in Classifying Soils

Detailed explanations of laboratory methods are given in the

Soil Survey Laboratory Methods Manual (USDA, NRCS, 1996).

Each method is listed by code on the data sheet at the beginning

of the chapters describing soil orders. On the data sheets

presented with each order, the method code is shown for each

determination made. These data sheets should be consulted for

reference to the Soil Survey Laboratory Methods Manual. This

manual specifies method codes for pedon sampling, sample

handling, site selection, sample collection, and sample

preparation.

The units of measure reported on the data sheets are not SI

units. Following are SI conversions:

1 meq/100 g = 1 cmol(+)/kg

1 mmho/cm = 1 dS/m

15 bar = 1500 kPa

1

/3 bar = 33 kPa

1

/10 bar = 10 kPa

In this taxonomy the terms (1) particle-size analysis (size

separates), (2) texture, and (3) particle-size classes are all used.

Particle-size analysis is needed to determine texture and

particle-size classes. Texture differs from particle-size class in

that texture includes only the fine-earth fraction (less than 2

mm), while particle size includes both the fraction less than 2

mm in size and the fraction equal to or more than 2 mm.

Atterberg limits are determined on the fraction less than 0.4

mm in size. Plasticity index is the difference in water content

between liquid limit and plastic limit. It is the range of water

content over which a soil paste can be deformed without

breaking, but it does not include flow as a liquid under

operationally defined conditions. Liquid limit is the minimum

water content at which the paste begins to flow as a liquid.

Samples that do not deform without breaking at any water

content are reported as NP, nonplastic. Operational definitions

are in the Annual Book of ASTM Standards (ASTM, 1998).

Bulk density is obtained typically by equilibration of Sarancoated natural fabric clods at designated pressure differentials.

Bulk densities are determined at two or more water contents.

For coarse textured and moderately coarse textured soils, they

are determined when the sample is at 10 kPa suction and when

APPENDIX
858 Soil Taxonomy

ovendry. For soils of medium and finer texture, the bulk densities

are determined when the sample is at 33 kPa suction and when

ovendry.

Bulk density determined at 33 kPa suction is used to convert

other analytical results to a volumetric basis (for example, kg

of organic carbon per m3

).

Coefficient of linear extensibility (COLE) is a derived value.

It is computed from the difference in bulk density between a

moist clod and an ovendry clod. It is based on the shrinkage of

a natural soil clod between a water content of 33 kPa (10 kPa

for sandier soils) and ovendry.

Linear extensibility (LE) of a soil layer is the product of the

thickness, in centimeters, multiplied by the COLE of the layer

in question. The LE of a soil is the sum of these products for

all soil horizons. COLE multiplied by 100 is called linear

extensibility percent (LEP).

Water retention difference (WRD) is computed from water

retentions at 33 kPa (10 kPa for sandier soils) and 1500 kPa

suction. It is converted to cm of water per cm of soil through

use of the bulk density. The 33 or 10 kPa water is determined

by desorption of the natural fabric clods, and the 1500 kPa

water is determined by desorption of crushed soil.

Organic carbon data in the National Soil Survey Laboratory

(NSSL) data base have been determined mostly by wet

digestion (Walkley, 1935). Because of environmental concerns

about waste products, however, that procedure is no longer in

use. The only procedure that is currently used to determine

organic carbon is a dry combustion procedure that determines

the percent of total carbon. The content of organic carbon is

determined by subtracting the amount of carbon contributed by

carbonates from total carbon data. The content of organic

carbon determined by this computation is very close to the

content determined by the wet digestion procedure.

Nitrogen in the NSSL data base is reported as a percentage

of the total dry weight. A soil sample is combusted at high

temperature with oxygen to release NOx, and the N2 is

measured by thermal conductivity detection.

Iron and aluminum extracted by citrate dithionite are

removed in a single extraction. They are measured by atomic

absorption and reported as a percentage of the total dry weight.

The iron is primarily from ferric oxides (hematite, magnetite)

and iron oxyhydroxides (goethite). Aluminum substituted into

these minerals is extracted simultaneously. The dithionite

reduces the ferric iron, and the citrate stabilizes the iron by

chelation. Iron and aluminum bound in organic matter are

extracted if the citrate is a stronger chelator than the organic

molecules. Manganese extracted by this procedure also is

recorded. The iron extracted is commonly related to the clay

distribution within a pedon.

Extractable bases (calcium, magnesium, sodium, and

potassium) are extracted with ammonium acetate buffered at

pH 7. They are equilibrated, filtered in an auto-extractor, and

measured by atomic absorption. They are reported as meq/100

g soil. The bases are extracted from the cation-exchange

complex by displacement with ammonium ions. The term

“extractable bases” is used instead of “exchangeable bases”

because soluble salts and some bases from carbonates can be

included in the extract.

Sum of bases is the sum of the calcium, magnesium,

sodium, and potassium described in the previous paragraph.

Extractable acidity is the acidity released from the soil by a

barium chloride-triethanolamine solution buffered at pH 8.2. It

includes all the acidity generated by replacement of the

hydrogen and aluminum from permanent and pH-dependent

exchange sites. It is reported as meq/100 g soil. Extractable

acidity data are reported on some data sheets as exchangeable

acidity and on others as exchangeable H+

.

Extractable aluminum is exchangeable aluminum extracted

by 1N KCl. It is a major constituent only in strongly acid soils

(pH of less than 5.0). Aluminum will precipitate if the pH rises

above 4.5 to 5.0 during analysis. The extractant KCl usually

affects the soil pH 1 unit or less. Extractable aluminum is

measured at the NSSL by atomic absorption. Many laboratories

measure the aluminum by titration with a base to the

phenopthalein end point. Titration measures exchangeable

acidity as well as extractable aluminum. Soils with a pH below

4.0 or 4.5 are likely to have values determined by atomic

absorption similar to values determined by titration because

very little hydrogen is typically on the exchange complex. If

there is a large percentage of organic matter, however, some

hydrogen may be present. For some soils it is important to

know which procedure was used. Extractable aluminum is

reported as meq/100 g soil.

Aluminum saturation is the amount of KCl-extractable Al

divided by extractable bases (extracted by ammonium acetate)

plus the KCl-extractable Al. It is expressed as percent. A

general rule of thumb is that if there is more than 50 percent

Al saturation, Al problems in the soil are likely. The problems

may not be related to Al toxicity but to a deficiency of calcium

and/or magnesium.

Cation-exchange capacity (CEC) by ammonium acetate (at

pH 7), by sum of cations (at pH 8.2), and by bases plus

aluminum is given on the data sheets in the chapters on soil

orders. The CEC depends on the method of analysis as well as

the nature of the exchange complex. CEC by sum of cations at

pH 8.2 is calculated by adding the sum of bases and the

extractable acidity. CEC by ammonium acetate is measured at

pH 7. CEC by bases plus aluminum, or effective cationexchange capacity (ECEC), is derived by adding the sum of

bases and KCl-extractable Al. Aluminum extracted by 1N KCl

is negligible if the extractant pH rises toward 5.5. ECEC then

is equal to extractable bases. CEC and ECEC are reported on

the data sheets as meq/100 g soil.

The reported CEC may differ from the CEC of the soil at its

natural pH. The standard methods allow the comparison of one

soil with another even though the pH of the extractant differs

from the pH of the natural soil. Cation-exchange capacity by

ammonium acetate and by sum of cations applies to all soils.
Appendix 859

CEC at pH 8.2 is not reported if the soil contains free carbonates

because bases are extracted from the carbonates. The effective

CEC (ECEC) is reported only for acid soils. ECEC is not reported

for soils having soluble salts, although it can be calculated by

subtracting the soluble components from the extractable

components. ECEC also may be defined as bases plus aluminum

plus hydrogen. That is the more common definition for

agronomic interpretations. This taxonomy specifies bases plus

aluminum.

Generally, the ECEC is less than the CEC at pH 7, which in

turn is less than the CEC at pH 8.2. If the soil is dominated by

positively charged colloids (e.g., iron oxides), however, the

trend is reversed. Most soils have negatively charged colloids,

which cause the CEC to increase with increasing pH. This

difference in CEC is commonly called the pH-dependent or

variable charge. The CEC at the soil pH can be estimated by

plotting the CEC of the soil vs. the pH of the extractant on a

graph and reading the CEC at the soil pH.

CEC measurements at pH levels other than those described

in the paragraphs above and CEC derived by use of other

cations will yield somewhat different results. It is important to

know the procedure, pH, and cation used before evaluating

CEC data or comparing data from different sources.

Base saturation is reported on the data sheets as percent of

the CEC. It is reported as CEC by sum of cations at pH 8.2 and

by ammonium acetate at pH 7. Base saturation by ammonium

acetate is equal to the sum of the bases extracted by ammonium

acetate, divided by the CEC (by ammonium acetate), and

multiplied by 100. If extractable calcium is not reported on the

data sheet because of free carbonates or salts in the sample,

then the base saturation is assumed to be 100 percent.

Base saturation percentage by sum of cations is equal to the

sum of bases extracted by ammonium acetate, divided by the

CEC (by sum of cations), and multiplied by 100. This value is

not reported if either extractable calcium or extractable acidity

is omitted.

Differences between the two methods of determining base

saturation reflect the amount of the pH-dependent CEC. Class

definitions in this taxonomy specify which method is used.

The sum of exchangeable cations is considered equal to the

sum of bases extracted by ammonium acetate unless

carbonates, gypsum, or other salts are present. When these

salts are present, the sum of the bases extracted by ammonium

acetate typically exceeds 100 percent of the CEC. Therefore, a

base saturation of 100 percent is assumed. The amount of

calcium from carbonates is usually much larger than the

amount of magnesium from the carbonates. Extractable

calcium is not shown on the data sheet if more than a trace

(more than 0.4 percent) of carbonates (reported as calcium

carbonate) is present or if calculated base saturation exceeds

110 percent, based on CEC by ammonium acetate at pH 7.

Calcium carbonate equivalent is the amount of carbonates

in the soil as measured by treating the sample with HCl. The

evolved carbon dioxide is measured manometrically. The

amount of carbonate is then calculated as a calcium carbonate

equivalent regardless of the form of carbonates (dolomite,

sodium carbonate, magnesium carbonate, etc.) in the sample.

Calcium carbonate equivalent is reported as a percentage of the

total dry weight of the sample. It can be reported on material

that is less than 2 mm or less than 20 mm in size.

Calcium sulfate as gypsum is determined by extraction in

water and precipitation in acetone. The amount of gypsum is

reported as a percentage of the total dry weight of the fraction

less than 2 mm in size and the fraction less than 20 mm in

size. Drying soils to oven-dryness, the standard base for

reporting the data, removes part of the water of hydration from

the gypsum. Many measured values, particularly water

retention values, must be recalculated to compensate for the

weight of the water of hydration lost during drying.

pH is measured in water and in salts. The pH measured in

water is determined in distilled water typically mixed 1:1 with

dry soil. The pH measured in potassium chloride is determined

in 1N KCl solution mixed 1:1 with soil. The pH measured in

calcium chloride is determined in 0.01M CaCl2

 solution mixed

2:1 with soil.

The pH is measured by a pH meter in a soil-water or soilsalt solution. The extent of the dilution is shown in the heading

on the data sheets. A ratio of 1:1 means one part dry soil and

one part water, by weight.

Measurement of pH in a dilute salt solution is common

because it tends to mask seasonal variations in pH. Readings in

0.01M CaCl2 tend to be uniform regardless of the time of year.

Readings in 1N KCl also tend to be uniform. The former are

more popular in regions with less acid soils. The latter are

more popular in regions with more acid soils. If KCl is used to

extract exchangeable aluminum, the pH reading (in KCl)

shows the pH at which the aluminum was extracted.

The pH may also be measured in 1N sodium fluoride. This

measurement is usually used to identify soils that are

dominated by short-range-order minerals, such as Andisols and

Spodosols. In soils that have a significant component of poorly

ordered minerals, such as the soils in the isotic mineralogy

class, the pH in NaF will be greater than 8.5. Soils with free

carbonates also have high pH values in NaF. Therefore, care

must be taken in interpreting these data.

Water-soluble cations and anions are determined in water

extracted from a saturated paste. The cations include calcium,

magnesium, sodium, and potassium, and the anions include

carbonate, bicarbonate, sulfate, chloride, nitrate, fluoride,

phosphate, silicate, and borate. The cations and anions can be

reported as cmol(+)/l.

Exchangeable sodium percentage (ESP) is reported as a

percentage of the CEC by ammonium acetate at pH 7. Watersoluble sodium is converted to meq/100 g soil. This value is

subtracted from extractable sodium, divided by the CEC (by

ammonium acetate), and multiplied by 100. An ESP of more

than 15 percent is used in this taxonomy as a criterion for the

natric horizon.
860 Soil Taxonomy

Sodium adsorption ratio (SAR) was developed as a measure

of irrigation water quality. Water-soluble sodium is divided by

water-soluble calcium and magnesium. The formula is SAR =

Na/[(Ca+Mg)/2]0.5. An SAR of 13 or more is used as an

alternate to the ESP criterion for the natric horizon.

Electrical conductivity (EC) is the conductivity of the water

extracted from saturated paste. The EC is used to determine the

total content of salts. It is reported as mmhos/cm, which is

equal to dS/m.

Total salts is calculated from the electrical conductivity of

the saturation extract. It is reported as a weight percentage of

the total water-soluble salts in the soil.

Phosphate retention (P ret.) refers to the percent phosphorus

retained by soil after equilibration with 1,000 mg/kg

phosphorus solution for 24 hours. This procedure is used in the

classification of andic soil materials. It identifies soils in which

phosphorus fixation may be a problem affecting agronomic

uses.

Acid-oxalate-extractable aluminum, iron, and silicon are

determined by a single extraction made in the dark with 0.2

molar ammonium oxalate at a pH of 3.5. The amount of

aluminum, iron, and silicon is measured by atomic absorption

and reported as a percentage of the total dry weight. These

values are used as criteria in identifying soils in the Andisol

and Spodosol orders and in the andic and spodic subgroups in

other orders. The procedure extracts iron, aluminum, and

silicon from organic matter and from amorphous mineral

material. It is used in conjunction with dithionite-citrate and

pyrophosphate extractions to identify the sources of iron and

aluminum in the soil. Pyrophosphate extracts iron and

aluminum from organic matter. Dithionite citrate extracts iron

from iron oxides and oxyhydroxides as well as from organic

matter.

Sodium-pyrophosphate-extractable iron and aluminum are

determined by a single extraction and measured by atomic

absorption. Results are reported as a percentage of the total dry

weight. This procedure has been used widely to extract iron

and aluminum from organic matter. It successfully removes

much of the organo-metal accumulations in spodic horizons

but extracts little of the inorganically bound iron and

aluminum.

Potassium-hydroxide-extractable aluminum is determined

by atomic absorption spectrophotometry. This procedure has

been used in the past but is not used in this taxonomy. The data

can be used in the field to estimate the amount of acid-oxalateextractable aluminum.

Melanic index is used in the identification of the melanic

epipedon. The index is a ratio of the humic and fulvic acids

in the organic fraction of the soil (Honna, Yamamoto, and

Matsui, 1988). About 0.50 gram of air-dried soil material that is

less than 2 mm in size is shaken with 25 ml of 0.5 percent NaOH

solution in a 50-ml centrifuge tube for 1 hour at room

temperature. One drop of a flocculating agent is added, and

the mixture is centrifuged at 4,000 rpm for 10 minutes. The

melanic index is the ratio of the absorbance at 450 nm over that

at 520 nm.

Citric-acid-extractable phosphorus (acid-soluble

phosphate) is used to separate the mollic epipedon (less than

1,500 mg/kg P2

O5) from the anthropic epipedon (equal to or

more than 1,500 mg/kg).

Exchangeable manganese and calcium plus exchangeable

acidity (at pH 8.2) is used as a criterion for the natric horizon.

The exchangeable acidity is measured at pH 8.2, and the

manganese and calcium are extracted at pH 7.0 with

ammonium acetate. See the paragraphs about extractable

acidity and exchangeable bases.

Color of sodium-pyrophosphate extract is used as a criterion

in the separation of different types of organic materials. A

saturated solution is made by adding 1 g of sodium

pyrophosphate to 4 ml of distilled water, and a moist organic

matter sample is added to the solution. The sample is mixed

and allowed to stand overnight, chromatographic paper is

dipped in the solution, and the color of the paper is ascertained

through use of a Munsell color chart.

Water-soluble sulfate is used in the definition of the sulfuric

horizon. The sulfate is determined in the saturation extract and

is reported as one of the anions.

Mineralogy of the clay, silt, and sand fractions is required in

some taxa. The different techniques employed are X-ray

diffraction analysis, thermal analysis, and petrographic

analysis.

X-ray diffraction analysis (XRD) is reported in a five-class

system based mostly on relative peak intensities. It is useful in

determining relative amounts of clay minerals. It is used to

differentiate between the smectitic and vermiculitic mineralogy

classes.

Thermal analysis is reported as weight percent of the clay

fraction. It helps to determine kaolinitic, gibbsitic, and other

mineralogy classes.

Petrographic analysis is reported as percent of grains

counted. Minerals are identified by use of a petrographic

microscope. At least 300 grains of a coarse silt, very fine sand,

or fine sand separate are identified and counted. Weatherable

minerals, resistant minerals, and volcanic glass are identified

by this procedure. A complete list of these is in Appendix XXI

of the Soil Survey Laboratory Methods Manual (USDA, NRCS,

1996).

Other Information Useful in Classifying Soils

Volumetric amounts of organic carbon are used in some

taxonomic criteria. The following calculation is used: (Datum

[percent] times bulk density [at 33 or 10 kPa] times thickness

[cm]) divided by 10. This calculation is normally used for

organic carbon, but it can be used for some other

measurements. Each horizon is calculated separately, and the

product of the calculations can be summed to any desired

depth, commonly 100 cm.
Appendix 861

Ratios that can be developed from the data are useful in

making internal checks of the data, in making managementrelated interpretations, and in answering taxonomic questions.

Some of the ratios are used as criteria in determining argillic,

kandic, or oxic horizons.

The ratio of 1500 kPa water to clay is used to indicate the

relevancy of the particle-size determination. If the ratio is

greater than 0.6 and the soil does not have andic soil

properties, incomplete dispersion of the clay is assumed and

clay is estimated by the following formula: Clay % = 2.5(%

water retained at 1500 kPa tension - % organic carbon). For a

typical soil with well dispersed clays, the ratio is 0.4. Some

soil-related factors that can cause deviation from the 0.4 value

are: (1) low-activity clays (kaolinites, chlorites, and some

micas), which tend to have a ratio of 0.35 or below; (2) iron

oxides and clay-size carbonates, which tend to decrease the

ratio; (3) organic matter, which increases the ratio because it

increases the water content at 1500 kPa; (4) andic and spodic

materials and materials with an isotic mineralogy class, which

increase the ratio because they do not disperse well; (5) large

amounts of gypsum; and (6) clay minerals within grains of

sand and silt. These clay minerals hold water at 1500 kPa and

thus increase the ratio. They are most common in shale and in

pseudomorphs of primary minerals in saprolite.

The ratio of CEC by ammonium acetate at pH 7 to clay can

be used to estimate clay mineralogy and clay dispersion. If the

ratio is multiplied by 100, the product is cmol(+)/kg clay. The

following ratios are typical for the following classes of clay

mineralogy: less than 0.2, kaolinitic; 0.2-0.3, kaolinitic or

mixed; 0.3-0.5, mixed or illitic; 0.5-0.7, mixed or smectitic;

and more than 0.7, smectitic. These ratios are most valid when

some detailed mineralogy data are available. If the ratio of

1500 kPa water to clay is less than 0.3 or more than 0.6, the

ratio of CEC by ammonium acetate to clay is not valid. Ratios

of 1500 kPa water to clay of 0.6 or more are typical of poorly

dispersed clays, andic and spodic materials, and materials with

an isotic mineralogy class, and ratios of less than 0.3 are

common in some soils that contain large amounts of gypsum.

A ratio of CEC at pH 8.2 to 1500 kPa water of more than

1.5 and more exchange acidity than the sum of bases plus KClextractable Al imply a soil with a high pH-dependent charge.

Along with bulk density data, they help to distinguish soils that

have andic and spodic materials or soils that have materials

with an isotic mineralogy class from soils with minerals that

are more crystalline.

Literature Cited

American Society for Testing and Materials. 1998. Annual

Book of ASTM Standards. Vol. 4.08, D 4318-95a.

Honna,T., S. Yamamoto, and K. Matsui. 1988. A Simple

Procedure to Determine Melanic Index That Is Useful for

Differentiating Melanic from Fulvic Andisols. Pedol. 32: 69-

78.

Kimble, J.M, E.G. Knox, and C.S. Holzhey. 1993. Soil

Survey Laboratory Methods for Characterizing Physical and

Chemical Properties and Mineralology of Soils. In

Applications of Agriculture Analysis in Environmental

Studies, ASTM Spec. Pub. 1162, K.B. Hoddinott and T.A.

O’Shay, eds.

United States Department of Agriculture, Natural Resources

Conservation Service. 1995. Soil Survey Laboratory

Information Manual. Natl. Soil Surv. Cent., Soil Surv. Lab.,

SSIR 45.

United States Department of Agriculture, Natural Resources

Conservation Service. 1996. Soil Survey Laboratory Methods

Manual. Natl. Soil Surv. Cent., SSIR 42.

Walkley, A. 1935. An Examination of Methods for

Determining Organic Carbon and Nitrogen in Soils. J. Agr.

Sci. 25: 598-609.

863

Index

A

Abrupt textural change ............................................................. 79

Acraquox ................................................................................ 659

Acroperox ............................................................................... 662

Acrotorrox ............................................................................... 671

Acrudox .................................................................................. 673

Acrustox ................................................................................. 683

Agric horizon ............................................................................ 28

Alaquods ................................................................................ 699

Albaqualfs .............................................................................. 168

Albaquults .............................................................................. 727

Albic horizon ............................................................................ 29

Albic materials .......................................................................... 79

Albolls .................................................................................... 560

Alfisols ................................................................................... 163

Alorthods................................................................................ 712

Andic soil properties ................................................................ 80

Andisols ................................................................................. 271

Anhydrous conditions ............................................................. 80

Anhyorthels............................................................................ 452

Anhyturbels............................................................................ 463

Aniso class ............................................................................. 820

Anthracambids ....................................................................... 357

Anthrepts................................................................................ 494

Anthropic epipedon .................................................................. 22

Aqualfs ................................................................................... 167

Aquands ................................................................................. 275

Aquents .................................................................................. 393

Aquepts .................................................................................. 494

Aquerts ................................................................................... 787

Aquic conditions ...................................................................... 90

Aquic moisture regime. See Soil moisture regimes.

Aquicambids ........................................................................... 357

Aquisalids ............................................................................... 387

Aquiturbels ............................................................................. 464

Aquods ................................................................................... 698

Aquolls ................................................................................... 563

Aquorthels.............................................................................. 453

Aquox ..................................................................................... 659

Aquults ................................................................................... 726

Arents ..................................................................................... 403

Argialbolls .............................................................................. 560

Argiaquolls ............................................................................. 564

Argicryids ............................................................................... 366

Argicryolls .............................................................................. 575

Argids ..................................................................................... 331

Argidurids ............................................................................... 372

Argigypsids ............................................................................ 379

Argillic horizon ......................................................................... 29

Argiorthels .............................................................................. 455

Argiudolls ............................................................................... 587

Argiustolls .............................................................................. 602

Argixerolls............................................................................... 631

Aridic moisture regime. See Soil moisture regimes.

Aridisols ................................................................................. 329

B

Bottom tier ................................................................................ 90

Buried soils ............................................................................... 10

C

Calcareous and reaction classes for mineral soils ................... 828

Calciaquerts ............................................................................ 787

Calciaquolls............................................................................. 565

Calciargids .............................................................................. 333

Calcic horizon............................................................................ 34

Calcicryids .............................................................................. 367

Calcicryolls ............................................................................. 578

Calcids .................................................................................... 351

Calcigypsids ........................................................................... 381

Calcitorrerts............................................................................. 798

Calciudolls .............................................................................. 592

Calciustepts ............................................................................ 531

Calciusterts ............................................................................. 805

Calciustolls ............................................................................. 608

Calcixerepts ............................................................................. 543

Calcixererts.............................................................................. 813

Calcixerolls .............................................................................. 637

Cambic horizon ......................................................................... 35

Cambids .................................................................................. 357

Cation-exchange activity classes for mineral soils .................. 827

Classification ............................................................................ 15

Coatings (classes) on sands ................................................... 830

Coefficient of linear extensibility (COLE) .................................. 80

Control section of Histosols and Histels .................................. 89

Coprogenous earth. See Organic soil material.

Cryalfs..................................................................................... 189
864 Soil Taxonomy

Cryands ................................................................................... 285

Cryaqualfs ............................................................................... 171

Cryaquands............................................................................. 276

Cryaquents ............................................................................. 394

Cryaquepts ............................................................................. 495

Cryaquods .............................................................................. 700

Cryaquolls ............................................................................... 566

Cryepts ................................................................................... 512

Cryerts .................................................................................... 796

Cryic temperature regime. See Soil temperature

regimes.

Cryids...................................................................................... 365

Cryods .................................................................................... 705

Cryofibrists ............................................................................. 475

Cryofluvents ........................................................................... 407

Cryofolists .............................................................................. 478

Cryohemists ............................................................................ 480

Cryolls..................................................................................... 575

Cryopsamments ...................................................................... 432

Cryorthents ............................................................................. 420

Cryosaprists ............................................................................ 484

Cryoturbation............................................................................ 92

Cryrendolls ............................................................................. 584

D

Densic contact .......................................................................... 92

Densic materials ........................................................................ 92

Diagnostic subsurface horizons ............................................... 28

Diagnostic surface horizons ..................................................... 21

Diatomaceous earth. See Organic soil material.

Duraqualfs .............................................................................. 171

Duraquands ............................................................................ 277

Duraquerts .............................................................................. 788

Duraquods .............................................................................. 701

Duraquolls .............................................................................. 568

Duricryands ............................................................................ 285

Duricryods .............................................................................. 705

Duricryolls .............................................................................. 579

Durids ..................................................................................... 372

Durihumods ............................................................................ 710

Durinodes ................................................................................. 80

Duripan ..................................................................................... 38

Duritorrands ............................................................................ 294

Durixeralfs ............................................................................... 254

Durixerepts.............................................................................. 545

Durixererts............................................................................... 814

Durixerolls ............................................................................... 639

Durorthods ............................................................................. 714

Durudands .............................................................................. 298

Durudepts ............................................................................... 517

Durustalfs ............................................................................... 230

Durustands ............................................................................. 316

Durustepts .............................................................................. 533

Durustolls ............................................................................... 612

Dystraquerts ........................................................................... 789

Dystrocryepts ......................................................................... 512

Dystroxerepts.......................................................................... 546

Dystrudepts ............................................................................ 518

Dystruderts ............................................................................. 801

Dystrustepts ........................................................................... 534

Dystrusterts ............................................................................ 806

E

Endoaqualfs ............................................................................ 171

Endoaquands .......................................................................... 278

Endoaquents........................................................................... 395

Endoaquepts........................................................................... 498

Endoaquerts ............................................................................ 791

Endoaquods ............................................................................ 702

Endoaquolls ............................................................................ 569

Endoaquults ............................................................................ 728

Entisols ................................................................................... 389

Epiaqualfs ............................................................................... 175

Epiaquands ............................................................................. 279

Epiaquents .............................................................................. 396

Epiaquepts .............................................................................. 502

Epiaquerts ............................................................................... 793

Epiaquods ............................................................................... 703

Epiaquolls ............................................................................... 571

Epiaquults ............................................................................... 729

Epipedon ................................................................................... 21

Eutraquox ................................................................................ 660

Eutrocryepts ........................................................................... 514

Eutroperox ............................................................................... 664

Eutrotorrox .............................................................................. 672

Eutrudepts .............................................................................. 524

Eutrudox .................................................................................. 675

Eutrustox ................................................................................. 685

Extragrades ............................................................................. 123

F

Families ................................................................................... 123

Family differentiae for Histosols and Histels .......................... 830

Family differentiae for mineral soils ......................................... 819

Ferrudalfs ................................................................................ 201

Fibers. See Organic soil material.

Fibric soil materials. See Organic soil material.

Fibristels ................................................................................. 448

Fibrists .................................................................................... 474

Fluvaquents ............................................................................ 397

Fluvents .................................................................................. 406

Folistels ................................................................................... 449

Folistic epipedon ...................................................................... 22

Folists ..................................................................................... 478

Fragiaqualfs ............................................................................ 181
Index 865

Fragiaquepts ........................................................................... 504

Fragiaquods ............................................................................ 704

Fragiaquults ............................................................................ 731

Fragic soil properties ................................................................ 81

Fragihumods ........................................................................... 710

Fragiorthods ........................................................................... 714

Fragipan .................................................................................... 39

Fragiudalfs .............................................................................. 202

Fragiudepts ............................................................................. 529

Fragiudults .............................................................................. 748

Fragixeralfs.............................................................................. 256

Fragixerepts............................................................................. 549

Fraglossudalfs ........................................................................ 203

Frigid temperature regime. See Soil temperature

regimes.

Fulvicryands ........................................................................... 286

Fulvudands ............................................................................. 300

G

Gelic materials ........................................................................... 92

Gelisols ................................................................................... 445

Glacic layer ................................................................................ 92

Glacistels................................................................................. 450

Glossaqualfs ........................................................................... 182

Glossic horizon ......................................................................... 41

Glossocryalfs .......................................................................... 189

Glossudalfs ............................................................................. 205

Great groups ........................................................................... 122

Gypsiargids ............................................................................. 337

Gypsic horizon .......................................................................... 42

Gypsicryids ............................................................................. 368

Gypsids ................................................................................... 379

Gypsitorrerts ........................................................................... 798

Gypsiusterts ............................................................................ 808

H

Halaquepts .............................................................................. 505

Haplanthrepts ......................................................................... 494

Haplaquox ............................................................................... 661

Haplargids ............................................................................... 339

Haplocalcids ........................................................................... 351

Haplocambids ......................................................................... 359

Haplocryalfs ............................................................................ 193

Haplocryands.......................................................................... 287

Haplocryerts ........................................................................... 796

Haplocryids ............................................................................. 369

Haplocryods ........................................................................... 706

Haplocryolls ............................................................................ 579

Haplodurids ............................................................................ 375

Haplofibrists ........................................................................... 476

Haplogypsids.......................................................................... 382

Haplohemists .......................................................................... 481

Haplohumods.......................................................................... 710

Haplohumults.......................................................................... 739

Haploperox .............................................................................. 666

Haplorthels ............................................................................. 456

Haplorthods ............................................................................ 716

Haplosalids ............................................................................. 388

Haplosaprists .......................................................................... 485

Haplotorrands ......................................................................... 295

Haplotorrerts ........................................................................... 799

Haplotorrox ............................................................................. 672

Haploturbels ........................................................................... 465

Haploxeralfs ............................................................................ 258

Haploxerands .......................................................................... 323

Haploxerepts ........................................................................... 551

Haploxererts ............................................................................ 816

Haploxerolls ............................................................................ 642

Haploxerults ............................................................................ 778

Hapludalfs ............................................................................... 208

Hapludands............................................................................. 303

Hapluderts .............................................................................. 803

Hapludolls ............................................................................... 593

Hapludox ................................................................................. 678

Hapludults .............................................................................. 750

Haplustalfs .............................................................................. 230

Haplustands ............................................................................ 317

Haplustepts............................................................................. 536

Haplusterts ............................................................................. 809

Haplustolls .............................................................................. 613

Haplustox ................................................................................ 688

Haplustults ............................................................................. 768

Haprendolls ............................................................................. 585

Hemic soil materials. See Organic soil material.

Hemistels ................................................................................ 450

Hemists ................................................................................... 480

Histels ..................................................................................... 448

Histic epipedon ......................................................................... 22

Historthels .............................................................................. 457

Histosols................................................................................. 473

Histoturbels ............................................................................ 466

Humaquepts ............................................................................ 507

Humicryerts............................................................................. 797

Humicryods ............................................................................. 708

Humilluvic material. See Organic soil material.

Humods ................................................................................... 709

Humults................................................................................... 738

Hydraquents ........................................................................... 400

Hydrocryands ......................................................................... 289

Hydrudands ............................................................................ 308

Hyperthermic temperature regime. See Soil temperature

regimes.

I

Identifiable secondary carbonates ............................................ 81
866 Soil Taxonomy

Inceptisols .............................................................................. 489

Interfingering of albic materials ................................................. 81

Intergrades .............................................................................. 122

Isofrigid temperature regime. See Soil temperature

regimes.

Isohyperthermic temperature regime. See Soil temperature

regimes.

Isomesic temperature regime. See Soil temperature

regimes.

Isothermic temperature regime. See Soil temperature

regimes.

K

Kandiaqualfs ........................................................................... 184

Kandiaquults .......................................................................... 732

Kandic horizon .......................................................................... 42

Kandihumults.......................................................................... 741

Kandiperox .............................................................................. 668

Kandiudalfs ............................................................................. 217

Kandiudox ............................................................................... 680

Kandiudults ............................................................................ 754

Kandiustalfs ............................................................................ 237

Kandiustox .............................................................................. 690

Kandiustults ........................................................................... 770

Kanhaplaquults ....................................................................... 734

Kanhaplohumults.................................................................... 743

Kanhapludalfs ......................................................................... 219

Kanhapludults ........................................................................ 758

Kanhaplustalfs ........................................................................ 240

Kanhaplustults ....................................................................... 773

Key to soil orders.................................................................... 160

L

Lamellae .................................................................................... 82

Liminc materials. See Organic soil material.

Linear extensibility (LE)............................................................. 83

Lithic contact ............................................................................ 92

Lithologic discontinuities ......................................................... 83

Luvihemists ............................................................................. 483

M

Marl. See Organic soil material.

Melanaquands ........................................................................ 281

Melanic epipedon ..................................................................... 23

Melanocryands ....................................................................... 291

Melanoxerands ....................................................................... 325

Melanudands .......................................................................... 310

Mesic temperature regime. See Soil temperature regimes.

Mineral soil material .................................................................. 19

Mineral soils ............................................................................. 20

Mineralogy classes for Histosols and Histels ........................ 831

Mineralogy classes for mineral soils ....................................... 825

Mollic epipedon ........................................................................ 23

Mollisols ................................................................................. 555

Molliturbels ............................................................................. 466

Mollorthels ............................................................................. 457

N

n value ...................................................................................... 84

Natralbolls ............................................................................... 562

Natraqualfs ............................................................................. 186

Natraquerts ............................................................................. 795

Natraquolls ............................................................................. 574

Natrargids ............................................................................... 343

Natric horizon............................................................................ 44

Natricryolls ............................................................................. 582

Natridurids .............................................................................. 377

Natrigypsids ........................................................................... 384

Natrixeralfs .............................................................................. 263

Natrixerolls .............................................................................. 650

Natrudalfs ............................................................................... 221

Natrudolls ............................................................................... 597

Natrustalfs .............................................................................. 241

Natrustolls .............................................................................. 622

Nomenclature in soil taxonomy ............................................... 125

Names of families ................................................................ 126

Names of great groups ........................................................ 125

Names of orders .................................................................. 125

Names of series ................................................................... 126

Names of subgroups ........................................................... 125

Names of suborders ............................................................ 125

Rules of nomenclature ........................................................ 157

Single formative elements ................................................... 157

Normal years ............................................................................. 94

O

Ochric epipedon ........................................................................ 25

Orders ..................................................................................... 119

Organic soil material .................................................................. 19

Fibers .................................................................................... 87

Fibric soil materials ............................................................... 87

Hemic soil materials............................................................... 87

Humilluvic material ................................................................ 88

Limnic materials..................................................................... 88

Coprogenous earth ........................................................... 88

Diatomaceous earth .......................................................... 89

Marl................................................................................... 89

Sapric soil materials ............................................................... 87

Organic soils ............................................................................. 20

Orthels .................................................................................... 452

Orthents .................................................................................. 420

Orthods ................................................................................... 712

Ortstein ..................................................................................... 45
Index 867

Oxic horizon .............................................................................. 45

Oxisols .................................................................................... 655

P

Paleaquults ............................................................................. 735

Paleargids................................................................................ 346

Palecryalfs ............................................................................... 198

Palecryolls ............................................................................... 583

Palehumults ............................................................................. 745

Paleudalfs................................................................................ 222

Paleudolls................................................................................ 599

Paleudults ............................................................................... 761

Paleustalfs ............................................................................... 246

Paleustolls ............................................................................... 625

Paleustults .............................................................................. 776

Palexeralfs ............................................................................... 264

Palexerolls ............................................................................... 652

Palexerults ............................................................................... 780

Paralithic contact ...................................................................... 92

Paralithic materials .................................................................... 92

Particle-size classes for Histosols and Histels ........................ 830

Particle-size classes for mineral soils ...................................... 819

Pedon ........................................................................................ 10

Permafrost ................................................................................. 93

Permanent cracks (classes) in mineral soils ............................. 830

Perox ....................................................................................... 662

Petraquepts ............................................................................. 509

Petroargids .............................................................................. 350

Petrocalcic horizon .................................................................... 47

Petrocalcids ............................................................................. 355

Petrocambids .......................................................................... 364

Petrocryids .............................................................................. 371

Petroferric contact ..................................................................... 85

Petrogypsic horizon .................................................................. 48

Petrogypsids........................................................................... 386

Placaquands............................................................................ 282

Placaquods ............................................................................. 704

Placic horizon ............................................................................ 48

Placocryods ............................................................................ 709

Placohumods .......................................................................... 711

Placorthods ............................................................................. 720

Placudands ............................................................................. 314

Plagganthrepts ........................................................................ 494

Plaggen epipedon ..................................................................... 26

Plinthaqualfs ........................................................................... 188

Plinthaquox ............................................................................. 661

Plinthaquults ........................................................................... 737

Plinthite ..................................................................................... 85

Plinthohumults ........................................................................ 747

Plinthoxeralfs .......................................................................... 269

Plinthudults ............................................................................. 766

Plinthustalfs ............................................................................ 252

Plinthustults ............................................................................ 776

Psammaquents ........................................................................ 401

Psamments .............................................................................. 432

Psammorthels .......................................................................... 459

Psammoturbels ........................................................................ 468

Q

Quartzipsamments................................................................... 434

R

Reaction classes for Histosols and Histels ............................. 832

Redox concentrations ............................................................... 91

Redox depletions ...................................................................... 91

Redoximorphic features ............................................................. 91

Reduced matrix .......................................................................... 91

Reduction.................................................................................. 90

Rendolls .................................................................................. 584

Resistant minerals ..................................................................... 85

Rhodoxeralfs ........................................................................... 269

Rhodudalfs ............................................................................. 228

Rhodudults ............................................................................. 766

Rhodustalfs ............................................................................. 252

Rhodustults ............................................................................ 777

Rupture-resistance classes for mineral soils ........................... 829

S

Salaquerts ............................................................................... 795

Salic horizon .............................................................................. 49

Salicryids ................................................................................ 372

Salids ...................................................................................... 387

Salitorrerts ............................................................................... 800

Salusterts ................................................................................ 811

Sapric soil materials. See Organic soil material.

Sapristels ................................................................................ 451

Saprists ................................................................................... 484

Saturation.................................................................................. 90

Series ...................................................................................... 123

Series control section.............................................................. 832

Series differentiae within a family............................................ 832

Slickensides .............................................................................. 85

Soil ..............................................................................................9

Soil depth classes for Histosols and Histels ........................... 832

Soil depth classes for mineral soils ......................................... 829

Soil moisture control section .................................................... 94

Soil moisture regimes ................................................................ 93

Aquic .................................................................................... 96

Aridic and torric .................................................................... 96

Udic ....................................................................................... 97

Ustic ...................................................................................... 98

Xeric ...................................................................................... 99

Soil temperature classes for Histosols and Histels ................. 832

Soil temperature classes for mineral soils................................ 828
868 Soil Taxonomy

Soil temperature regimes ......................................................... 100

Cryic .................................................................................... 111

Frigid ................................................................................... 112

Hyperthermic ...................................................................... 112

Isofrigid ............................................................................... 112

Isohyperthermic .................................................................. 112

Isomesic .............................................................................. 112

Isothermic ........................................................................... 112

Mesic .................................................................................. 112

Thermic ............................................................................... 112

Sombric horizon ........................................................................ 49

Sombrihumults ........................................................................ 747

Sombriperox ............................................................................ 671

Sombriudox ............................................................................. 682

Sombriustox ............................................................................ 692

Sphagnofibrists ....................................................................... 477

Spodic horizon .......................................................................... 49

Spodic materials ........................................................................ 86

Spodosols ............................................................................... 695

Strongly contrasting particle-size classes ............................... 820

Subgroups .............................................................................. 122

Suborders................................................................................ 121

Subsurface tier .......................................................................... 89

Sulfaquents ............................................................................. 403

Sulfaquepts ............................................................................. 510

Sulfidic materials ..................................................................... 112

Sulfihemists............................................................................. 483

Sulfisaprists ............................................................................ 486

Sulfohemists ........................................................................... 483

Sulfosaprists ........................................................................... 487

Sulfudepts ............................................................................... 530

Sulfuric horizon ....................................................................... 112

Surface tier ................................................................................ 89

T

Thermic temperature regime. See Soil temperature

regimes.

Torrands .................................................................................. 294

Torrerts ................................................................................... 797

Torriarents ............................................................................... 404

Torric moisture regime. See Soil moisture regimes.

Torrifluvents ........................................................................... 408

Torrifolists ............................................................................... 479

Torriorthents ........................................................................... 421

Torripsamments ....................................................................... 436

Torrox ...................................................................................... 671

Turbels .................................................................................... 462

Typic subgroups ..................................................................... 122

U

Udalfs...................................................................................... 200

Udands ................................................................................... 297

Udarents ................................................................................. 404

Udepts .................................................................................... 516

Uderts ..................................................................................... 801

Udic moisture regime. See Soil moisture regimes.

Udifluvents ............................................................................. 411

Udifolists ................................................................................ 479

Udipsamments ........................................................................ 438

Udivitrands ............................................................................. 320

Udolls...................................................................................... 586

Udorthents.............................................................................. 425

Udox ........................................................................................ 673

Udults ..................................................................................... 747

Ultisols .................................................................................... 721

Umbraquults ........................................................................... 738

Umbric epipedon ....................................................................... 26

Umbriturbels ........................................................................... 469

Umbrorthels ............................................................................ 460

Ustalfs ..................................................................................... 228

Ustands................................................................................... 315

Ustarents ................................................................................ 405

Ustepts ................................................................................... 530

Usterts .................................................................................... 804

Ustic moisture regime. See Soil moisture regimes.

Ustifluvents ............................................................................ 414

Ustifolists................................................................................ 479

Ustipsamments ....................................................................... 439

Ustivitrands ............................................................................ 322

Ustolls ..................................................................................... 601

Ustorthents ............................................................................. 426

Ustox ....................................................................................... 683

Ustults .................................................................................... 767

V

Vermaqualfs............................................................................. 188

Vermaquepts ........................................................................... 511

Vermudolls .............................................................................. 601

Vermustolls ............................................................................. 629

Vertisols .................................................................................. 783

Vitrands ................................................................................... 319

Vitraquands ............................................................................. 283

Vitricryands ............................................................................. 292

Vitritorrands ............................................................................ 296

Vitrixerands ............................................................................. 326

W

Weatherable minerals ................................................................ 86

X

Xeralfs..................................................................................... 253

Xerands ................................................................................... 323

Xerarents ................................................................................ 406
Index 869

Xerepts ................................................................................... 542

Xererts .................................................................................... 813

Xeric moisture regime. See Soil moisture regimes.

Xerofluvents ........................................................................... 417

Xerolls..................................................................................... 630

Xeropsamments ...................................................................... 441

Xerorthents ............................................................................. 430

Xerults .................................................................................... 778
870

The date that changes were posted to the PDF file is indicated at the end of each item on

this list of corrections.

Page 28, column 1, umbric epipedon, required characteristics, item 2b: Add the word “moist”

after “3 or less” (8/02).

Page 49, column 2, salic horizon, required characteristics, item 1, line 2: Add “the water

extracted from” after “dS/m in” (5/00).

Page 57, caption for photo 11: Change “Umbrept” to “Xerept” (5/00).

Page 88, column 1, top of diagram: Change “Fibric soil materials that have a rubbed fiber

content of four-tenths to six-tenths by volume” to “Fibric soil materials that have a fiber

content, after rubbing, of two-fifths to three-fourths by volume” (8/02).

Page 88, column 1, lower right of diagram: Change “Sapric soil materials” to “Sapric soil

colors” (8/02).

Page 126, the table “Formative Elements in Names of Soil Orders,” the column “Derivation of

formative element,” Ultisols: Change ultumus to ultimus (8/02).

Page 127, the table “Formative Elements in Names of Suborders,” the “Derivation” column:

For the element “Fol,” change “leaf” to “leaves,” and for the element “Turb,” change turbidis

to turbidus (8/02).

Page 129, the table “Formative Elements in Names of Great Groups,” the “Derivation” column:

For the element “Verm,” change “worm” to “worms” (8/02).

Page 156, the table “Adjectives in Names of Extragrades and Their Meaning,” the “Derivation”

column: For the adjective “Abruptic,” change abruptum to abruptus (8/02).

Page 159, column 2, third full paragraph, last line: Add “and family criteria” (8/02).

Pages 331-388: Change the first letter of the symbols for all Aridisols from “F” to “G” (5/00).

Page 331, column 2, key to suborders, GE, line 2: Delete “that has its upper boundary within

100 cm of the soil surface” (5/00).

Page 333, column 1, definition of Argids, item 1: Delete “that has its upper boundary within

100 cm of the soil surface” (5/00).

Page 352, column 2, Petronodic Ustic Haplocalcids: Change the symbol FEBL to GFBL

(5/00).

Page 361, column 1, Petronodic Ustic Haplocambids: Change the symbol FEDJ to GGDJ

(5/00).

Page 393, column 1, LC, Psamments, line 3: Add “(sandy loam lamellae are permitted)” after “in

all layers” (8/02).

Page 394, column 1, LAD, Psammaquents, line 3: Add “(sandy loam lamellae are permitted)”

after “in all layers” (8/02).

 Soil Taxonomy

Second Edition, 1999

Errata
Errata 871

Page 399, definition of Typic Fluvaquents, item 1: Change “Have, in one or more horizons” to

“Have, in all horizons” (8/02).

Page 403, description of Thapto-Histic Sulfaquents, sentence 2: Change “These soils do not

have n values above 0.7” to “These soils have both n values of more than 0.7 and 8 or more

percent clay in the fine-earth fraction” (8/02).

Page 406, column 1, LBAA: Change “Utarents” to Ustarents” (8/02).

Page 474, column 2, description Fibrists, paragraph 1, sentence 2: Change “More than twothirds of the soil consists of fibers” to “More than two-fifths or more than three-fourths

(depending on solubility in a sodium-pyrophosphate solution) of the soil consists of fibers”

(8/02).

Page 614, column 1, IFGE , Pachic Udertic Haplustolls, item 1, lines 1 and 2: Change “A mollic

epipedon with a texture finer than loamy fine sand; and either ” to “A mollic epipedon 50 cm or

more thick with a texture finer than loamy fine sand; and ” and delete items a and b (5/00).

Page 727, column 1, HAC, line 2: Change “(low or very low)” to “(moderately low or lower)”

(8/02).

Page 727, column 2, description of Albaquults, sentence 2: Change “low or very low hydraulic

conductivity” to “moderately low or lower hydraulic conductivity” (8/02).

Page 825, column 2, and page 826, column 1, key to mineralogy classes, item B, lines 2 and 3:

Change “that replaces the particle-size class and that” to “that replaces the particle-size class,

other than fragmental, and that” (5/00).

Page 828, column 2, key to calcareous and reaction classes, last sentence: Change “following

the mineralogy class” to “following the mineralogy and cation-exchange activity classes”

(5/00).
Maps

Dominant Soil Orders in the United States

Dominant Suborders

Alfisols

Andisols

Aridisols

Entisols

Gelisols

Histosols

Inceptisols

Mollisols

Oxisols

Spodosols

Ultisols

Vertisols

Global Soil Regions (To print this map on 8.5 x 11 inch paper, select File, Print, Fit to Page.)

Click here to go to Table of Contents.













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30 ̊ 60 ̊ 

AlfisolsAndisolsAridisolsEntisolsGelisols HistosolsInceptisolsMollisolsOxisolsSpodosolsUltisolsVertisolsRocky LandShifting Sands Ice/glacier 

Global Soil Regions U.S. Dept. of Agriculture Natural Resources Conservation Service Soil Survey Division World Soil Resources

Country boundaries are not authoritative.