United States Department of Agriculture

Natural Resources Conservation Service

Keys to

Soil Taxonomy

Eighth Edition, 1998

Keys to Soil Taxonomy

By Soil Survey Staff

United States Department of Agriculture

Natural Resources Conservation Service

Eighth Edition, 1998
The United States Department of Agriculture (USDA) prohibits discrimination in all its

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disability, political beliefs, sexual orientation, and marital or family status. (Not all

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To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room

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9410 or call 202-720-5964 (voice and TDD). USDA is an equal opportunity provider and

employer.

Cover: Map compiled by the World Soil Resources Staff, Natural Resources Conservation

Service, Washington, D.C.
5

Table of Contents

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

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

Chapter 2: Differentiae for Mineral Soils and Organic Soils ............................................. 11

Chapter 3: Horizons and Characteristics Diagnostic for the Higher Categories ................ 13

Chapter 4: Identification of the Taxonomic Class of a Soil ................................................ 37

Chapter 5: Alfisols ............................................................................................................... 41

Chapter 6: Andisols ............................................................................................................. 83

Chapter 7: Aridisols ........................................................................................................... 103

Chapter 8: Entisols ............................................................................................................ 129

Chapter 9: Gelisols ............................................................................................................ 149

Chapter 10: Histosols ........................................................................................................... 159

Chapter 11: Inceptisols ........................................................................................................ 165

Chapter 12: Mollisols .......................................................................................................... 191

Chapter 13: Oxisols ............................................................................................................. 233

Chapter 14: Spodosols ......................................................................................................... 249

Chapter 15: Ultisols ............................................................................................................. 259

Chapter 16: Vertisols ........................................................................................................... 281

Chapter 17: Family and Series Differentiae and Names ..................................................... 295

Chapter 18: Designations for Horizons and Layers ............................................................ 311

Appendix ............................................................................................................................... 317

Index ...................................................................................................................................... 319

7

Foreword

The publication Keys to Soil Taxonomy serves two purposes. It provides the taxonomic

keys necessary for the classification of soils in a form that can be used easily in the field. It

also acquaints users of the taxonomic system with recent changes in the classification of

soils. This volume includes all revisions of the keys that so far have been approved,

replacing the original keys in Soil Taxonomy: A Basic System of Soil Classification for

Making and Interpreting Soil Surveys (1975), the work on which this and other abridged

versions, the first of which was published in 1983, are based. We plan to continue issuing

updated editions of the Keys to Soil Taxonomy as changes warrant new editions. Plans are

under way to publish an updated version of Soil Taxonomy in its entirety in 1999.

This publication incorporates all amendments approved to date and published in the

National Soil Taxonomy Handbook (NSTH) Issues 1-18. It includes the recommendations of

the International Committee on Low Activity Clays (NSTH Issue 8), the International

Committee on Oxisols (NSTH Issue 11), the International Committee on Andisols (NSTH

Issue 13), the International Committee on Vertisols (NSTH Issue 16), the International

Committee on Aquic Moisture Regime (NSTH Issue 16), the International Committee on

Spodosols (NSTH Issue 16), the International Committee on Aridisols (NSTH Issue 17), and

the International Committee on Families (NSTH Issue 18). Editorial changes have been

made throughout the Keys to Soil Taxonomy to correct grammatical errors and clarify the

intent of the criteria.

The keys reproduced here were extracted from a computerized copy of Soil Taxonomy,

which is maintained in complete, up-to-date form.

The authors of the Keys to Soil Taxonomy are identified as the “Soil Survey Staff.” This

term is meant to include all of the soil classifiers in the National Cooperative Soil Survey

program and in the international community who have made significant contributions to the

improvement of the taxonomic system.

Horace Smith

Director, Soil Survey Division

Natural Resources Conservation Service

1998

9

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The word “soil,” like many common words, has several

meanings. 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.

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 1975

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 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

The Soils That We Classify

CHAPTER 1
10

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.
11

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Soil taxonomy differentiates between mineral soils and

organic 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 3.

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

the thickness of horizons is measured from the surface of the

CHAPTER 2

Differentiae for Mineral Soils1 and Organic Soils

1 Mineral soils include all soils except the suborder Histels and the order Histosols.
12

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.
13

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This chapter defines the horizons and characteristics of

both 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 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.

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.

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

Required Characteristics

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 P2O5 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

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

CHAPTER 3

Horizons and Characteristics Diagnostic for the Higher Categories
14 Keys to Soil Taxonomy

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 2). Item 2 provides for a folistic epipedon

that is an Ap horizon consisting of mineral soil material.

Histic Epipedon

Required Characteristics

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

characterized by saturation (for 30 days or more, cumulative)

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 2). 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

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

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
Horizons and Characteristics Diagnostic for the Higher Categories 15

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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 . 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 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.

Plaggen Epipedon

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

or more thick that has been produced by long-continued

manuring.

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

Required Characteristics

The umbric epipedon consists of mineral soil materials and

has the following properties:
16 Keys to Soil Taxonomy

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. 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 NH4OAc) 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 o

C 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.

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 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
Horizons and Characteristics Diagnostic for the Higher Categories 17

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A

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.

Argillic Horizon

An argillic horizon is normally a subsurface horizon with a

significantly higher percentage of phyllosilicate clay than the

overlying soil material. 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.

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; (deleted text) 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.

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
18 Keys to Soil Taxonomy

(by weight) that is 5 percent or more (absolute) higher

than that of an underlying horizon.

Cambic Horizon

A cambic horizon is the result of physical alterations,

chemical transformations, or removals or of a combination of

two or more of these processes.

Required Characteristics

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

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

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

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.
Horizons and Characteristics Diagnostic for the Higher Categories 19

D

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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.

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

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 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 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

Required Characteristics

The natric horizon has, in addition to the properties of the

argillic horizon:

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.
20 Keys to Soil Taxonomy

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

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

Required Characteristics

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

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). (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.

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.

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
Horizons and Characteristics Diagnostic for the Higher Categories 21

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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.

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.

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 NH4

OAc).

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).

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 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.
22 Keys to Soil Taxonomy

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.

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. These materials,

originally termed “amorphous” (but understood to contain

allophane) in the 1975 edition of Soil Taxonomy (USDA, SCS,

1975), 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.

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 figure 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.
Horizons and Characteristics Diagnostic for the Higher Categories 23

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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

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.

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

Figure 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.
24 Keys to Soil Taxonomy

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

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. 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.

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

particle-size 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 example, 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
Horizons and Characteristics Diagnostic for the Higher Categories 25

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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

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).

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).

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.
26 Keys to Soil Taxonomy

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

Fe2

O3. 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. 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.

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 tham in water with a dispersing agent.

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. They are produced

when one soil mass slides past another. Some slickensides

occur at the lower boundary of a slip surface where 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
Horizons and Characteristics Diagnostic for the Higher Categories 27

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(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.

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).

Fibric Soil Materials

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 (fig. 2) on white

chromatographic or filter paper that is inserted into a paste

made of the soil materials in a saturated sodium-pyrophosphate

solution.
28 Keys to Soil Taxonomy

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.

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 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, fig. 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.

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.

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

Figure 2.—Value and chroma of pyrophosphate solution of

fibric and sapric materials.
Horizons and Characteristics Diagnostic for the Higher Categories 29

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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

white chromatographic or filter paper that has a color value of

7 or more and chroma of 2 or less (fig. 2) or has a cationexchange capacity of less than 240 cmol(+) per kg organic

matter (measured by loss on ignition), or both.

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.

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.

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,

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.
30 Keys to Soil Taxonomy

Horizons and Characteristics

Diagnostic for Both Mineral and

Organic Soils

Following are descriptions of the horizons and

characteristics that are 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.

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

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 31

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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,alpha-dipyridyl 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.

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 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.

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
32 Keys to Soil Taxonomy

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. 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. 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.

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.

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

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
Horizons and Characteristics Diagnostic for the Higher Categories 33

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Hemisphere, summer refers to June, July, and August and

winter refers to December, January, and February.

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 1975 edition of Soil Taxonomy (USDA, SCS,

1975).

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)

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.

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 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.

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

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.

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 o

C.

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
34 Keys to Soil Taxonomy

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.

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 threephase system, solid-liquid-gas, in part or all of the soil

moisture control section when the soil temperature is above

5 oC.

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 is

used. The water moves through the soil in all months when 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.

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 o

C 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

if the mean summer and winter soil temperatures differ by 6 oC

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.

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

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.

Soil Temperature Regimes

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 o

C but do not have permafrost.

1. In mineral soils the mean summer soil temperature (June,

July, and August in the Northern Hemisphere and December,
Horizons and Characteristics Diagnostic for the Higher Categories 35

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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

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 oC 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

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 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.
36

Literature Cited

Brewer, R. 1976. Fabric and Mineral Analysis of Soils.

Second edition. John Wiley and Sons, Inc. New York, New

York.

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.

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.

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.
37

I

D

E

The taxonomic class of a specific soil can be determined

by 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 2

and 3 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 17 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 are given in chapter 17.

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.

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. 149

B. Other soils that:

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

CHAPTER 4

Identification of the Taxonomic Class of a Soil
38 Keys to Soil Taxonomy

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. 159

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 particlesize 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

paralithic contact, a duripan, or a petrocalcic

horizon.

Spodosols, p. 249

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

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 39

I

D

E

shallower, and a densic, lithic, or paralithic contact, a

duripan, or a petrocalcic horizon.

Andisols, p. 83

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. 233

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. 281

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. 103

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:

(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. 259

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

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.
40

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 NH4OAc)

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. 191

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. 41

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. 165

L. Other soils.

Entisols, p. 129
41

A

L

F

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:

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. 41

JB. Other Alfisols that have a cryic or isofrigid temperature

regime.

Cryalfs, p. 50

JC. Other Alfisols that have an ustic moisture regime.

Ustalfs, p. 65

JD. Other Alfisols that have a xeric moisture regime.

Xeralfs, p. 76

JE. Other Alfisols.

Udalfs, p. 54

Aqualfs

Key to Great Groups

JAA. Aqualfs that have a cryic temperature regime.

Cryaqualfs, p. 43

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. 50

JAC. Other Aqualfs that have a duripan.

Duraqualfs, p. 43

JAD. Other Aqualfs that have a natric horizon.

Natraqualfs, p. 49

JAE. Other Aqualfs that have a fragipan with an

upper boundary within 100 cm of the mineral soil

surface.

Fragiaqualfs, p. 47

JAF. Other Aqualfs that have a kandic horizon.

Kandiaqualfs, p. 48

JAG. Other 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.

Vermaqualfs, p. 50

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. 42

CHAPTER 5

Alfisols
42 Keys to Soil Taxonomy

JAI. Other Aqualfs that have a glossic horizon.

Glossaqualfs, p. 48

JAJ. Other Aqualfs that have episaturation.

Epiaqualfs, p. 45

JAK. Other Aqualfs.

Endoaqualfs, p. 43

Albaqualfs

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

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
Alfisols 43

A

L

F

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

Cryaqualfs

Key to Subgroups

JAAA. All Cryaqualfs (provisionally).

Typic Cryaqualfs

Duraqualfs

Key to Subgroups

JACA. All Duraqualfs (provisionally).

Typic Duraqualfs

Endoaqualfs

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
44 Keys to Soil Taxonomy

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 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
Alfisols 45

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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

Epiaqualfs

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
46 Keys to Soil Taxonomy

(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
Alfisols 47

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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

Fragiaqualfs

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
48 Keys to Soil Taxonomy

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

Glossaqualfs

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:

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

Kandiaqualfs

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
Alfisols 49

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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

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

Natraqualfs

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

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
50 Keys to Soil Taxonomy

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

Plinthaqualfs

Key to Subgroups

JABA. All Plinthaqualfs (provisionally).

Typic Plinthaqualfs

Vermaqualfs

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

JAGB. Other Vermaqualfs.

Typic Vermaqualfs

Cryalfs

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. 53

JBB. Other Cryalfs that have a glossic horizon.

Glossocryalfs, p. 50

JBC. Other Cryalfs.

Haplocryalfs, p. 52

Glossocryalfs

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
Alfisols 51

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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 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.

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

3. 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.

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
52 Keys to Soil Taxonomy

Haplocryalfs

Key to Subgroups

JBCA. Haplocryalfs that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplocryalfs

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
Alfisols 53

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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

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

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.

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

Palecryalfs

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
54 Keys to Soil Taxonomy

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

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 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

Udalfs

Key to Great Groups

JEA. Udalfs that have a natric horizon.

Natrudalfs, p. 62

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. 55

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. 55

JED. Other Udalfs that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragiudalfs, p. 55

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. 61

JEF. Other Udalfs that have a kandic horizon.

Kanhapludalfs, p. 62

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
Alfisols 55

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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. 63

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. 65

JEI. Other Udalfs that have a glossic horizon.

Glossudalfs, p. 56

JEJ. Other Udalfs.

Hapludalfs, p. 58

Ferrudalfs

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

Fragiudalfs

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

JEDE. Other Fragiudalfs.

Typic Fragiudalfs

Fraglossudalfs

Key to Subgroups

JECA. 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, a fine-earth fraction with both a

bulk density of 1.0 g/cm3 or less, measured at 33 kPa water
56 Keys to Soil Taxonomy

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

Glossudalfs

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
Alfisols 57

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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 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
58 Keys to Soil Taxonomy

Hapludalfs

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

surface and a depth of 18 cm that, after mixing, have one or

more of the following:
Alfisols 59

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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

boundary of the argillic horizon is 50 cm or more below

the mineral soil surface; and
60 Keys to Soil Taxonomy

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
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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

Kandiudalfs

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

JEEF. Other Kandiudalfs that have a sandy or sandy-skeletal

particle-size class throughout a layer extending from the
62 Keys to Soil Taxonomy

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

Kanhapludalfs

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

Natrudalfs

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:
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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

Paleudalfs

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

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
64 Keys to Soil Taxonomy

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

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
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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

Rhodudalfs

Key to Subgroups

JEHA. All Rhodudalfs (provisionally).

Typic Rhodudalfs

Ustalfs

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. 66

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. 76

JCC. Other Ustalfs that have a natric horizon.

Natrustalfs, p. 71

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. 69

JCE. Other Ustalfs that have a kandic horizon.

Kanhaplustalfs, p. 70

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)

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. 73

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
66 Keys to Soil Taxonomy

3. Dry value no more than 1 unit higher than the moist

value.

Rhodustalfs, p. 76

JCH. Other Ustalfs.

Haplustalfs, p. 66

Durustalfs

Key to Subgroups

JCAA. All Durustalfs (provisionally).

Typic Durustalfs

Haplustalfs

Key to Subgroups

JCHA. Haplustalfs that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplustalfs

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
Alfisols 67

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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

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 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
68 Keys to Soil Taxonomy

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 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.

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 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 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
Alfisols 69

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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

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 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 less 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 Haplustalfs

JCHX. Other Haplustalfs.

Typic Haplustalfs

Kandiustalfs

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

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
70 Keys to Soil Taxonomy

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 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 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

Kanhaplustalfs

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 o

C.

Aridic Kanhaplustalfs
Alfisols 71

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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

Natrustalfs

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 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

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 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 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; and
72 Keys to Soil Taxonomy

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

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 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 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.

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
Alfisols 73

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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 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.

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 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 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

Paleustalfs

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:
74 Keys to 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. 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 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 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
Alfisols 75

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throughout the entire argillic horizon if it is less than 75 cm

thick.

Psammentic Paleustalfs

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 o

C; or
76 Keys to Soil Taxonomy

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 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 o

C.

Udic Paleustalfs

JCFU. Other Paleustalfs.

Typic Paleustalfs

Plinthustalfs

Key to Subgroups

JCBA. All Plinthustalfs (provisionally).

Typic Plinthustalfs

Rhodustalfs

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 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 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 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 Rhodustalfs

JCGD. Other Rhodustalfs.

Typic Rhodustalfs

Xeralfs

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. 77

JDB. Other Xeralfs that have a natric horizon.

Natrixeralfs, p. 80

JDC. Other Xeralfs that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragixeralfs, p. 78
Alfisols 77

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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. 82

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. 82

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 mre; 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. 80

JDG. Other Xeralfs.

Haploxeralfs, p. 78

Durixeralfs

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

croma 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 particle-size 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 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
78 Keys to Soil Taxonomy

JDAG. Other Durixeralfs.

Typic Durixeralfs

Fragixeralfs

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

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

ess (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

Haploxeralfs

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

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
Alfisols 79

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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:

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
80 Keys to Soil Taxonomy

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

Natrixeralfs

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

Palexeralfs

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
Alfisols 81

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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

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
82

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

Plinthoxeralfs

Key to Subgroups

JDDA. All Plinthoxeralfs (provisionally).

Typic Plinthoxeralfs

Rhodoxeralfs

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

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
83

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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. 83

DB. Other Andisols that have a cryic soil temperature

regime.

Cryands, p. 86

DC. Other Andisols that have an aridic moisture regime.

Torrands, p. 89

DD. Other Andisols that have a xeric moisture regime.

Xerands, p. 100

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. 99

DF. Other Andisols that have an ustic moisture regime.

Ustands, p. 97

DG. Other Andisols.

Udands, p. 90

Aquands

Key to Great Groups

DAA. Aquands that have a cryic soil temperature

regime.

Cryaquands, p. 84

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. 86

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

CHAPTER 6

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.
84 Keys to Soil Taxonomy

an organic layer with andic soil properties, whichever is

shallower.

Duraquands, p. 84

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. 86

DAE. Other Aquands that have a melanic epipedon.

Melanaquands, p. 85

DAF. Other Aquands that have episaturation.

Epiaquands, p. 85

DAG. Other Aquands.

Endoaquands, p. 84

Cryaquands

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

Duraquands

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

Endoaquands

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
Andisols 85

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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

Epiaquands

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

Melanaquands

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

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 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
86 Keys to Soil Taxonomy

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

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

Placaquands

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

Vitraquands

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

Cryands

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. 87
Andisols 87

A

N

D

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. 88

DBC. Other Cryands that have a melanic epipedon.

Melanocryands, p. 89

DBD. Other Cryands that have a layer that meets the depth,

thickness, and organic-carbon requirements for a melanic

epipedon.

Fulvicryands, p. 87

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. 89

DBF. Other Cryands.

Haplocryands, p. 87

Duricryands

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

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

Fulvicryands

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:

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

Haplocryands

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
88 Keys to Soil Taxonomy

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

Hydrocryands

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
Andisols 89

A

N

D

Melanocryands

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

Vitricryands

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:

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

Torrands

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. 90
90 Keys to Soil Taxonomy

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. 90

DCC. Other Torrands.

Haplotorrands, p. 90

Duritorrands

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

Haplotorrands

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

Vitritorrands

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

Udands

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. 97
Andisols 91

A

N

D

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. 91

DGC. Other Udands that have a melanic epipedon.

Melanudands, p. 95

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. 94

DGE. Other Udands that have a layer that meets the depth,

thickness, and organic-carbon requirements for a melanic

epipedon.

Fulvudands, p. 91

DGF. Other Udands.

Hapludands, p. 92

Durudands

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

alpha,alpha-dipyridyl at a time when the soil is not being

irrigated.

Aquic Durudands

DGBB. Other Durudands 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

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

Fulvudands

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
92 Keys to 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

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

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 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

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

Hapludands

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:
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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

DGFG. 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. 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 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 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
94 Keys to Soil Taxonomy

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

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

Hydrudands

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
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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 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 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

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

Melanudands

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

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
96 Keys to Soil Taxonomy

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 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. 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

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
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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

Placudands

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

Ustands

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. 97

DFB. Other Ustands.

Haplustands, p. 98

Durustands

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
98 Keys to Soil Taxonomy

Haplustands

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 NH4OAc) 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

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
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DFBM. Other Haplustands.

Typic Haplustands

Vitrands

Key to Great Groups

DEA. Vitrands that have an ustic moisture regime.

Ustivitrands, p. 99

DEB. Other Vitrands.

Udivitrands, p. 99

Udivitrands

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

DEBG. Other Udivitrands.

Typic Udivitrands

Ustivitrands

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
100 Keys to Soil Taxonomy

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

Xerands

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. 101

DDB. Other Xerands that have a melanic epipedon.

Melanoxerands, p. 101

DDC. Other Xerands.

Haploxerands, p. 100

Haploxerands

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
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DDCH. Other Haploxerands that have a mollic or umbric

epipedon.

Humic Haploxerands

DDCI. Other Haploxerands.

Typic Haploxerands

Melanoxerands

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

Vitrixerands

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

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

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Key to Suborders

GA. Aridisols that have a cryic soil temperature regime.

Cryids, p. 118

GB. Other Aridisols that have a salic horizon that has its

upper boundary within 100 cm of the soil surface.

Salids, p. 128

GC. Other Aridisols that have a duripan that has its upper

boundary within 100 cm of the soil surface.

Durids, p. 121

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. 124

GE. Other Aridisols that have an argillic or natric

horizon (deleted text) and do not have a petrocalcic 

horizon that has an upper boundary within 100 cm of 

the soil surface.

Argids, p. 103

GF. Other Aridisols that have a calcic or petrocalcic horizon

that has its upper boundary within 100 cm of the soil surface.

Calcids, p. 111

GG. Other Aridisols.

Cambids, p. 114

Argids

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. 111

GEB. Other Argids that have a natric horizon.

Natrargids, p. 108

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. 109

GED. Other Argids that have a gypsic horizon that has its

upper boundary within 150 cm of the soil surface.

Gypsiargids, p. 105

GEE. Other Argids that have a calcic horizon that has its

upper boundary within 150 cm of the soil surface.

Calciargids, p. 104

GEF. Other Argids.

Haplargids, p. 106

CHAPTER 7

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 and J. Nichols.
104 Keys to Soil Taxonomy

Calciargids

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

soil temperature is 5 oC 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 o

C 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 o

C 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
Aridisols 105

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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,

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 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 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 Calciargid

Gypsiargids

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 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
106 Keys to 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, 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

Haplargids

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 oC 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 oC 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
Aridisols 107

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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 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

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 oC 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 oC 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
108 Keys to 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 Haplargids

GEFQ. 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 at a depth of 50 cm is

5 oC 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

Natrargids

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

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
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soil temperature is 5 oC 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 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 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

Paleargids

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
110 Keys to 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 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 oC 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:

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 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
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(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

Petroargids

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 oC 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 oC 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

Calcids

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. 113

GFB. Other Calcids.

Haplocalcids, p. 111

Haplocalcids

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:
112 Keys to Soil Taxonomy

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,

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 o

C 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
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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 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

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 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 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

Petrocalcids

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

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 oC 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
114 Keys to Soil Taxonomy

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 oC 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

Cambids

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. 114

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. 117

GGC. Other Cambids that have an anthropic epipedon.

Anthracambids, p. 114

GGD. Other Cambids.

Haplocambids, p. 115

Anthracambids

Key to Subgroups

GGCA. All Anthracambids.

Typic Anthracambids

Aquicambids

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 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 oC 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
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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

Haplocambids

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 oC 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 o

C 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 o

C 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 o

C 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
116 Keys to Soil Taxonomy

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 oC 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

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 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 oC 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 oC 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:
Aridisols 117

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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 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 oC 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 o

C 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

Petrocambids

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 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 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 o

C or higher and have a soil moisture regime that borders on

xeric.

Xeric Petrocambids
118 Keys to Soil Taxonomy

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

GGBF. Other Petrocambids.

Typic Petrocambids

Cryids

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. 121

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. 120

GAC. Other Cryids that have a gypsic horizon that has its

upper boundary within 100 cm of the soil surface.

Gypsicryids, p. 119

GAD. Other Cryids that have an argillic or natric horizon.

Argicryids, p. 118

GAE. Other Cryids that have a calcic horizon that has its

upper boundary within 100 cm of the soil surface.

Calcicryids, p. 119

GAF. Other Cryids.

Haplocryids, p. 120

Argicryids

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
Aridisols 119

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depth of 50 cm and have a soil moisture regime that borders on

ustic.

Ustic Argicryids

GADH. Other Argicryids.

Typic Argicryids

Calcicryids

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

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

Gypsicryids

Key to Subgroups

GACA. Gypsicryids that have a calcic horizon.

Calcic Gypsicryids

GACB. Other Gypsicryids 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 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
120 Keys to Soil Taxonomy

Haplocryids

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

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

Petrocryids

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
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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

Salicryids

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

Durids

Key to Great Groups

GCA. Durids that have a natric horizon above the

duripan.

Natridurids, p. 123

GCB. Other Durids that have an argillic horizon above the

duripan.

Argidurids, p. 121

GCC. Other Durids.

Haplodurids, p. 122

Argidurids

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

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 o

C or higher at a depth of 50 cm and a

soil moisture regime that borders on xeric.

Haploxeralfic Argidurids
122 Keys to Soil Taxonomy

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

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

Haplodurids

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 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.

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
Aridisols 123

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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 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

Natridurids

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
124 Keys to Soil Taxonomy

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

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

Gypsids

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. 127

GDB. Other Gypsids that have a natric horizon that has its

upper boundary within 100 cm of the soil surface.

Natrigypsids, p. 126

GDC. Other Gypsids that have an argillic horizon that has its

upper boundary within 100 cm of the soil surface.

Argigypsids, p. 124

GDD. Other Gypsids that have a calcic horizon that has its

upper boundary within 100 cm of the soil surface.

Calcigypsids, p. 125

GDE. Other Gypsids.

Haplogypsids, p. 125

Argigypsids

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

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:
Aridisols 125

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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

Calcigypsids

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 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 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

Haplogypsids

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
126 Keys to Soil Taxonomy

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

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 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 o

C 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 o

C or higher and have a soil moisture regime that

borders on ustic.

Ustic Haplogypsids

GDEI. Other Haplogypsids.

Typic Haplogypsids

Natrigypsids

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
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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

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

Petrogypsids

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
128

GDAG. Other Petrogypsids.

Typic Petrogypsids

Salids

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. 128

GBB. Other Salids.

Haplosalids, p. 128

Aquisalids

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

horizon that has an upper boundary within 100 cm of the soil

surface.

Calcic Aquisalids

GBAC. Other Aquisalids.

Typic Aquisalids

Haplosalids

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
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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. 130

LB. Other Entisols that 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 are not arranged in any discernible order.

Arents, p. 133

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. 144

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

CHAPTER 8

Entisols
130 Keys to Soil Taxonomy

15 percent volcanic glass in the 0.02 to 2.0 mm fraction

in some part of the particle-size control section.

Fluvents, p. 134

LE. Other Entisols.

Orthents, p. 139

Aquents

Key to Great Groups

LAA. Aquents that have sulfidic materials within 50 cm of the

mineral soil surface.

Sulfaquents, p. 133

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. 132

LAC. Other Aquents that have a cryic soil temperature

regime.

Cryaquents, p. 130

LAD. Other Aquents 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.

Psammaquents, p. 132

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. 131

LAF. Other Aquents that have episaturation.

Epiaquents, p. 131

LAG. Other Aquents.

Endoaquents, p. 130

Cryaquents

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

Endoaquents

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
Entisols 131

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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 NH4OAc) 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

Epiaquents

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

Fluvaquents

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
132 Keys to Soil Taxonomy

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

Psammaquents

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

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 NH4

OAc) 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,

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

Hydraquents

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
Entisols 133

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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

Sulfaquents

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

Arents

Key to Great Groups

LBA. Arents that have an ustic moisture regime.

Ustarents, p. 133

LBB. Other Arents that have a xeric moisture regime.

Xerarents, p. 133

LBC. Other Arents that have an aridic (or torric) moisture

regime.

Torriarents, p. 133

LBD. Other Arents.

Udarents, p. 133

Torriarents

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

Udarents

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

Ustarents

Key to Subgroups

LBAA. All Ustarents.

Haplic Ustarents

Xerarents

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
134 Keys to Soil Taxonomy

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

Fluvents

Key to Great Groups

LDA. Fluvents that have a cryic soil temperature regime.

Cryofluvents, p. 134

LDB. Other Fluvents that have a xeric moisture regime.

Xerofluvents, p. 138

LDC. Other Fluvents that have an ustic moisture regime.

Ustifluvents, p. 137

LDD. Other Fluvents that have an aridic (or torric) moisture

regime.

Torrifluvents, p. 134

LDE. Other Fluvents.

Udifluvents, p. 136

Cryofluvents

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 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

Torrifluvents

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 oC or higher; and

3. An aridic (or torric) moisture regime that borders on

ustic.

Ustertic Torrifluvents
Entisols 135

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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

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 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 oC 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 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.

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 oC 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 o

C or higher; and
136 Keys to Soil Taxonomy

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

Udifluvents

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
Entisols 137

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Ustifluvents

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 o

C; 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

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 four-
138 Keys to Soil Taxonomy

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, 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 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

Xerofluvents

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

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
Entisols 139

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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

Orthents

Key to Great Groups

LEA. Orthents that have a cryic soil temperature regime.

Cryorthents, p. 139

LEB. Other Orthents that have an aridic (or torric) moisture

regime.

Torriorthents, p. 140

LEC. Other Orthents that have a xeric moisture regime.

Xerorthents, p. 143

LED. Other Orthents that have an ustic moisture regime.

Ustorthents, p. 141

LEE. Other Orthents.

Udorthents, p. 141

Cryorthents

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

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
140 Keys to Soil Taxonomy

LEAE. Other Cryorthents that have lamellae within 200 cm

of the mineral soil surface.

Lamellic Cryorthents

LEAF. Other Cryorthents.

Typic Cryorthents

Torriorthents

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 oC 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 frigid 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 oC 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
Entisols 141

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oxalate) times 60] plus the volcanic glass (percent) is

equal to 30 or more.

Vitrandic Torriorthents

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 oC 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 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 Torriorthents

LEBM. Other Torriorthents.

Typic Torriorthents

Udorthents

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

Ustorthents

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
142 Keys to Soil Taxonomy

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

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.

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
Entisols 143

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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. 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.

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 oC.

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 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 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

Xerorthents

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:
144 Keys to 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; 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

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

NH4OAc) 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

Psamments

Key to Great Groups

LCA. Psamments that have a cryic soil temperature

regime.

Cryopsamments, p. 144

LCB. Other Psamments that have an aridic (or torric)

moisture regime.

Torripsamments, p. 146

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. 145

LCD. Other Psamments that have an ustic moisture regime.

Ustipsamments, p. 147

LCE. Other Psamments that have a xeric moisture regime.

Xeropsamments, p. 147

LCF. Other Psamments.

Udipsamments, p. 146

Cryopsamments

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
Entisols 145

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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

Quartzipsamments

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

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 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.

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)
146 Keys to Soil Taxonomy

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

Torripsamments

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 oC or higher; and

2. An aridic (or torric) moisture regime that borders on

ustic.

Ustic Torripsamments

LCBE. 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 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 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

Udipsamments

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
Entisols 147

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LCFG. Other Udipsamments.

Typic Udipsamments

Ustipsamments

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

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 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 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

Xeropsamments

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

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
148

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
149

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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. 149

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. 154

AC. Other Gelisols.

Orthels, p. 150

Histels

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. 150

.

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. 150

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. 149

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. 150

AAE. Other Histels.

Sapristels, p. 150

Fibristels

Key to Subgroups

AACA. Fibristels that have a lithic contact within 100 cm of

the soil surface.

Lithic Fibristels

CHAPTER 9

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.
150 Keys to Soil Taxonomy

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

Folistels

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

Glacistels

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

Hemistels

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

or more layers of any thickness within 100 cm of the soil

surface.

Fluvaquentic Hemistels

AADD. Other Hemistels.

Typic Hemistels

Sapristels

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

Orthels

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. 152

ACB. Other Orthels that have, within 50 cm of the mineral
Gelisols 151

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soil surface, redox depletions with chroma of 2 or less and also

aquic conditions during normal years (or artificial drainage).

Aquorthels, p. 151

ACC. Other Orthels that have anhydrous conditions.

Anhyorthels, p. 151

ACD. Other Orthels that have a mollic epipedon.

Mollorthels, p. 152

ACE. Other Orthels that have an umbric epipedon.

Umbrorthels, p. 153

ACF. Other Orthels that have an argillic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

Argiorthels, p. 152

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. 153

ACH. Other Orthels.

Haplorthels, p. 152

Anhyorthels

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

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

Aquorthels

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
152 Keys to Soil Taxonomy

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

Argiorthels

Key to Subgroups

ACFA. Argiorthels that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Argiorthels

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

Haplorthels

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

Historthels

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

Mollorthels

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
Gelisols 153

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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

Psammorthels

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

Umbrorthels

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

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
154 Keys to Soil Taxonomy

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

Turbels

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. 155

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. 154

ABC. Other Turbels that have anhydrous conditions.

Anhyturbels, p. 154

ABD. Other Turbels that have a mollic epipedon.

Molliturbels, p. 155

ABE. Other Turbels that have an umbric epipedon.

Umbriturbels, p. 156

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. 156

ABG. Other Turbels.

Haploturbels, p. 155

Anhyturbels

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

Aquiturbels

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
Gelisols 155

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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

Haploturbels

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

Histoturbels

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

Molliturbels

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
156 Keys to 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 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

Psammoturbels

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

Umbriturbels

Key to Subgroups

ABEA. Umbriturbels that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Umbriturbels

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
Gelisols 157

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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

159

H

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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. 160

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. 159

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. 162

BD. Other Histosols.

Hemists, p. 161

Fibrists

Key to Great Groups

BBA. Fibrists that have a cryic soil temperature

regime.

Cryofibrists, p. 159

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,

fragmental materials, or other mineral soil materials if at a

depth of less than 90 cm.

Sphagnofibrists, p. 160

BBC. Other Fibrists.

Haplofibrists, p. 160

Cryofibrists

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

CHAPTER 10

Histosols
160 Keys to Soil Taxonomy

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

Haplofibrists

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

Sphagnofibrists

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

Folists

Key to Great Groups

BAA. Folists that have a cryic soil temperature regime.

Cryofolists, p. 161

BAB. Other Folists that have an aridic (or torric) soil

moisture regime.

Torrifolists, p. 161

BAC. Other Folists that have an ustic or xeric soil moisture

regime.

Ustifolists, p. 161

BAD. Other Folists.

Udifolists, p. 161
Histosols 161

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Cryofolists

Key to Subgroups

BAAA. Cryofolists that have a lithic contact within 50 cm of

the soil surface.

Lithic Cryofolists

BAAB. Other Cryofolists.

Typic Cryofolists

Torrifolists

Key to Subgroups

BABA. Torrifolists that have a lithic contact within 50 cm of

the soil surface.

Lithic Torrifolists

BABB. Other Torrifolists.

Typic Torrifolists

Udifolists

Key to Subgroups

BADA. Udifolists that have a lithic contact within 50 cm of

the soil surface.

Lithic Udifolists

BADB. Other Udifolists.

Typic Udifolists

Ustifolists

Key to Subgroups

BACA. Ustifolists that have a lithic contact within 50 cm of

the soil surface.

Lithic Ustifolists

BACB. Other Ustifolists.

Typic Ustifolists

Hemists

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. 162

BDB. Other Hemists that have sulfidic materials within 100

cm of the soil surface.

Sulfihemists, p. 162

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. 162

BDD. Other Hemists that have a cryic temperature

regime.

Cryohemists, p. 161

BDE. Other Hemists.

Haplohemists, p. 161

Cryohemists

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

Haplohemists

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
162 Keys to Soil Taxonomy

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

Luvihemists

Key to Subgroups

BDCA. All Luvihemists (provisionally).

Typic Luvihemists

Sulfihemists

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

Sulfohemists

Key to Subgroups

BDAA. All Sulfohemists (provisionally).

Typic Sulfohemists

Saprists

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. 163

BCB. Other Saprists that have sulfidic materials within 100

cm of the soil surface.

Sulfisaprists, p. 163

BCC. Other Saprists that have a cryic temperature

regime.

Cryosaprists, p. 162

BCD. Other Saprists.

Haplosaprists, p. 162

Cryosaprists

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

Haplosaprists

Key to Subgroups

BCDA. Haplosaprists that have a lithic contact within the

control section.

Lithic Haplosaprists
Histosols 163

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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

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

Sulfisaprists

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

BCBB. Other Sulfisaprists.

Typic Sulfisaprists

Sulfosaprists

Key to Subgroups

BCAA. All Sulfosaprists (provisionally).

Typic Sulfosaprists

165

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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. 166

KB. Other Inceptisols that have a plaggen or anthropic

epipedon.

Anthrepts, p. 165

KC. Other Inceptisols that have a cryic soil temperature

regime.

Cryepts, p. 171

KD. Other Inceptisols that have an ustic soil moisture

regime.

Ustepts, p. 178

KE. Other Inceptisols that have a xeric soil moisture

regime.

Xerepts, p. 184

KF. Other Inceptisols that have a udic soil moisture

regime.

Udepts, p. 172

Anthrepts

Key to Great Groups

KBA. Anthrepts that have a plaggen epipedon.

Plagganthrepts, p. 165

KBB. Other Anthrepts.

Haplanthrepts, p. 165

Haplanthrepts

Key to Subgroups

KBBA. All Haplanthrepts (provisionally).

Typic Haplanthrepts

Plagganthrepts

Key to Subgroups

KBAA. All Plagganthrepts (provisionally).

Typic Plagganthrepts

CHAPTER 11

Inceptisols
166 Keys to Soil Taxonomy

Aquepts

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. 170

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. 170

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. 169

KAD. Other Aquepts that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragiaquepts, p. 169

KAE. Other Aquepts that have a cryic soil temperature

regime.

Cryaquepts, p. 166

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. 171

KAG. Other Aquepts that have a histic, melanic, mollic, or

umbric epipedon.

Humaquepts, p. 170

KAH. Other Aquepts that have episaturation.

Epiaquepts, p. 168

KAI. Other Aquepts.

Endoaquepts, p. 167

Cryaquepts

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
Inceptisols 167

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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

Endoaquepts

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
168 Keys to Soil Taxonomy

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:

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 NH4OAc) 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

Epiaquepts

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

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
Inceptisols 169

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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 NH4OAc) 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

Fragiaquepts

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

Halaquepts

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
170 Keys to Soil Taxonomy

KACE. Other Halaquepts.

Typic Halaquepts

Humaquepts

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

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

Petraquepts

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

Sulfaquepts

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
Inceptisols 171

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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

Vermaquepts

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

Cryepts

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. 172

KCB. Other Cryepts.

Dystrocryepts, p. 171

Dystrocryepts

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

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
172 Keys to Soil Taxonomy

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

Eutrocryepts

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

Udepts

Key to Great Groups

KFA. Udepts that have a sulfuric horizon within 50 cm of the

mineral soil surface.

Sulfudepts, p. 178

KFB. Other Udepts that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Durudepts, p. 173

KFC. Other Udepts that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragiudepts, p. 177

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
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in one or more horizons at a depth between 25 and 75 cm

from the mineral soil surface.

Eutrudepts, p. 176

KFE. Other Udepts.

Dystrudepts, p. 173

Durudepts

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

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

Dystrudepts

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
174 Keys to Soil Taxonomy

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

(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
Inceptisols 175

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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

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
176 Keys to Soil Taxonomy

Eutrudepts

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

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
Inceptisols 177

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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

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

Fragiudepts

Key to Subgroups

KFCA. Fragiudepts that have, throughout one or more

horizons with a total thickness of 18 cm or more within 75 cm
178 Keys to 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 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

Sulfudepts

Key to Subgroups

KFAA. All Sulfudepts (provisionally).

Typic Sulfudepts

Ustepts

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. 179

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

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. 178

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. 179

KDD. Other Ustepts.

Haplustepts, p. 180

Calciustepts

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
Inceptisols 179

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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

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 oC.

Udic Calciustepts

KDBJ. Other Calciustepts.

Typic Calciustepts

Durustepts

Key to Subgroups

KDAA. All Durustepts (provisionally).

Typic Durustepts

Dystrustepts

Key to Subgroups

KDCA. Dystrustepts that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Dystrustepts
180 Keys to Soil Taxonomy

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

Haplustepts

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 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 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:
Inceptisols 181

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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

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 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 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 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 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
182 Keys to 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 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

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 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 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 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 o

C;

and

2. Either:

a. At a depth of 125 cm below the mineral soil surface,
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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

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 o

C; 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 o

C.

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 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.

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 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 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
184 Keys to Soil Taxonomy

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 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 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

Xerepts

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. 185

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. 184

KEC. Other Xerepts that have a fragipan that has its upper

boundary within 100 cm of the mineral soil surface.

Fragixerepts, p. 187

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. 185

KEE. Other Xerepts.

Haploxerepts, p. 187

Calcixerepts

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

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
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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

Durixerepts

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

Dystroxerepts

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
186 Keys to Soil Taxonomy

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:

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 pumicelik 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
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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

or more and no densc, 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

Fragixerepts

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

Haploxerepts

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
188 Keys to 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

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

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
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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

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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. 192

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

(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:

CHAPTER 12

Mollisols

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.
192 Keys to Soil Taxonomy

(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. 193

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. 200

ID. Other Mollisols that have a cryic soil temperature

regime.

Cryolls, p. 197

IE. Other Mollisols that have either a xeric moisture regime

or an aridic moisture regime that borders on xeric.

Xerolls, p. 222

IF. Other Mollisols that have either an ustic moisture regime

or an aridic moisture regime that borders on ustic.

Ustolls, p. 207

IG. Other Mollisols.

Udolls, p. 201

Albolls

Key to Great Groups

IAA. Albolls that have a natric horizon.

Natralbolls, p. 193

IAB. Other Albolls.

Argialbolls, p. 192

Argialbolls

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

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
Mollisols 193

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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

Natralbolls

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

Aquolls

Key to Great Groups

IBA. Aquolls that have a cryic soil temperature regime.

Cryaquolls, p. 194

IBB. Other Aquolls that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Duraquolls, p. 194

IBC. Other Aquolls that have a natric horizon.

Natraquolls, p. 197

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. 194

IBE. Other Aquolls that have an argillic horizon.

Argiaquolls, p. 193

IBF. Other Aquolls that have episaturation.

Epiaquolls, p. 196

IBG. Other Aquolls.

Endoaquolls, p. 195

Argiaquolls

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
194 Keys to Soil Taxonomy

Calciaquolls

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

Cryaquolls

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

IBAG. Other Cryaquolls that have a mollic epipedon 50 cm

or more thick.

Cumulic Cryaquolls

IBAH. Other Cryaquolls.

Typic Cryaquolls

Duraquolls

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
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Endoaquolls

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

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
196 Keys to Soil Taxonomy

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

Epiaquolls

Key to Subgroups

IBFA. Epiaquolls 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 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
Mollisols 197

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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

Natraquolls

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

Cryolls

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. 198

IDB. Other Cryolls that have a natric horizon.

Natricryolls, p. 200

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. 200

IDD. Other Cryolls that have an argillic horizon.

Argicryolls, p. 197

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. 198

IDF. Other Cryolls.

Haplocryolls, p. 198

Argicryolls

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
198 Keys to Soil Taxonomy

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

Calcicryolls

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

Duricryolls

Key to Subgroups

IDAA. Duricryolls that have an argillic horizon.

Argic Duricryolls

IDAB. Other Duricryolls.

Typic Duricryolls

Haplocryolls

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

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
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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

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
200 Keys to Soil Taxonomy

IDFO. Other Haplocryolls that have a xeric moisture

regime.

Xeric Haplocryolls

IDFP. Other Haplocryolls.

Typic Haplocryolls

Natricryolls

Key to Subgroups

IDBA. All Natricryolls.

Typic Natricryolls

Palecryolls

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

Rendolls

Key to Great Groups

ICA. Rendolls that have a cryic soil temperature regime.

Cryrendolls, p. 200

ICB. Other Rendolls.

Haprendolls, p. 200

Cryrendolls

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

Haprendolls

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
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Udolls

Key to Great Groups

IGA. Udolls that have a natric horizon.

Natrudolls, p. 206

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. 203

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. 207

IGD. Other Udolls that have an argillic horizon.

Argiudolls, p. 201

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. 207

IGF. Other Udolls.

Hapludolls, p. 204

Argiudolls

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
202 Keys to Soil Taxonomy

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

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
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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:

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

Calciudolls

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
204 Keys to 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

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

Hapludolls

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

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:
Mollisols 205

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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

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
206 Keys to Soil Taxonomy

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

Natrudolls

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
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Paleudolls

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

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

Vermudolls

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

Ustolls

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. 212

IFB. Other Ustolls that have a natric horizon.

Natrustolls, p. 217

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. 211

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
208 Keys to Soil Taxonomy

(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. 220

IFE. Other Ustolls that have an argillic horizon.

Argiustolls, p. 208

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. 222

IFG. Other Ustolls.

Haplustolls, p. 213

Argiustolls

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 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.

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
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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 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
210 Keys to 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.

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

consecutive days per year when the soil temperature at a
Mollisols 211

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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 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

Calciustolls

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 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 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
212 Keys to Soil Taxonomy

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

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

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

Durustolls

Key to Subgroups

IFAA. Durustolls that have a natric horizon above the

duripan.

Natric Durustolls
Mollisols 213

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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

Haplustolls

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

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 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
214 Keys to Soil Taxonomy

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.

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:

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
Mollisols 215

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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 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 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

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
216 Keys to Soil Taxonomy

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

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. 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
Mollisols 217

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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 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 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

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; 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

Natrustolls

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
218 Keys to Soil Taxonomy

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 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.

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 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.

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
Mollisols 219

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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 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.

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

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 o

C.

Aridic Natrustolls
220 Keys to Soil Taxonomy

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

Paleustolls

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 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 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 o

C.

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

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 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
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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 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 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 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 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
222 Keys to Soil Taxonomy

IFDL. Other Paleustolls.

Typic Paleustolls

Vermustolls

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

Xerolls

Key to Great Groups

IEA. Xerolls that have a duripan within 100 cm of the

mineral soil surface.

Durixerolls, p. 225

IEB. Other Xerolls that have a natric horizon.

Natrixerolls, p. 230

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. 230

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. 224

IEE. Other Xerolls that have an argillic horizon.

Argixerolls, p. 222

IEF. Other Xerolls.

Haploxerolls, p. 226

Argixerolls

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
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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

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:
224 Keys to Soil Taxonomy

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

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

Calcixerolls

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
Mollisols 225

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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:

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

Durixerolls

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

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
226 Keys to Soil Taxonomy

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

Haploxerolls

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
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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

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
228 Keys to Soil Taxonomy

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

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
Mollisols 229

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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

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
230 Keys to Soil Taxonomy

IEFZf. Other Haploxerolls.

Typic Haploxerolls

Natrixerolls

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

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

Palexerolls

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
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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

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

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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. 233

EB. Other Oxisols that have an aridic moisture regime.

Torrox, p. 238

EC. Other Oxisols that have an ustic or xeric moisture

regime.

Ustox, p. 243

ED. Other Oxisols that have a perudic moisture regime.

Perox, p. 234

EE. Other Oxisols.

Udox, p. 239

Aquox

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. 233

EAB. Other Aquox that have plinthite forming a continuous

phase within 125 cm of the mineral soil surface.

Plinthaquox, p. 234

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. 234

EAD. Other Aquox.

Haplaquox, p. 234

Acraquox

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

CHAPTER 13

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.
234 Keys to Soil Taxonomy

Eutraquox

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

Haplaquox

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

Plinthaquox

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

Perox

Key to Great Groups

EDA. Perox that have a sombric horizon within 150 cm of

the mineral soil surface.

Sombriperox, p. 238

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. 234

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. 235

EDD. Other Perox that have a kandic horizon that

has its upper boundary within 150 cm of the mineral

soil surface.

Kandiperox, p. 237

EDE. Other Perox.

Haploperox, p. 236

Acroperox

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
Oxisols 235

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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

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

Eutroperox

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
236 Keys to Soil Taxonomy

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 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

Haploperox

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

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
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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

Kandiperox

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
238 Keys to Soil Taxonomy

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

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

Sombriperox

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

Torrox

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. 238

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. 239

EBC. Other Torrox.

Haplotorrox, p. 239

Acrotorrox

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
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Eutrotorrox

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

Haplotorrox

Key to Subgroups

EBCA. Haplotorrox that have a petroferric contact within

125 cm of the mineral soil surface.

Petroferric Haplotorrox

EBCB. Other Haplotorrox that have a lithic contact within

125 cm of the mineral soil surface.

Lithic Haplotorrox

EBCC. Other Haplotorrox.

Typic Haplotorrox

Udox

Key to Great Groups

EEA. Udox that have a sombric horizon within 150 cm of the

mineral soil surface.

Sombriudox, p. 243

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. 239

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. 240

EED. Other Udox that have a kandic horizon that has its

upper boundary within 150 cm of the mineral soil surface.

Kandiudox, p. 242

EEE. Other Udox.

Hapludox, p. 241

Acrudox

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

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
240 Keys to Soil Taxonomy

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

Eutrudox

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
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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

Hapludox

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
242 Keys to Soil Taxonomy

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:

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

Kandiudox

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

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
Oxisols 243

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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

Sombriudox

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

Ustox

Key to Great Groups

ECA. Ustox that have a sombric horizon within 150 cm of

the mineral soil surface.

Sombriustox, p. 247

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. 243

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. 244

ECD. Other Ustox that have a kandic horizon that

has its upper boundary within 150 cm of the mineral

soil surface.

Kandiustox, p. 246

ECE. Other Ustox.

Haplustox, p. 245

Acrustox

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
244 Keys to Soil Taxonomy

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:

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

Eutrustox

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
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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

Haplustox

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
246 Keys to Soil Taxonomy

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

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

Kandiustox

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
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ECDC. Other Kandiustox 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 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

Sombriustox

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

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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. 249

CB. Other Spodosols that have a cryic soil temperature

regime.

Cryods, p. 251

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. 253

CD. Other Spodosols.

Orthods, p. 254

Aquods

Key to Great Groups

CAA. Aquods that have a cryic soil temperature regime.

Cryaquods, p. 250

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. 249

CAC. Other Aquods that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragiaquods, p. 251

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. 251

CAE. Other Aquods that have, in 90 percent or more of each

pedon, a cemented soil layer that has its upper boundary within

100 cm of the mineral soil surface.

Duraquods, p. 250

CAF. Other Aquods that have episaturation.

Epiaquods, p. 251

CAG. Other Aquods.

Endoaquods, p. 251

Alaquods

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:

CHAPTER 14

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).
250 Keys to Soil Taxonomy

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

Cryaquods

Key to Subgroups

CAAA. Cryaquods that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Cryaquods

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

Duraquods

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

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
Spodosols 251

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Endoaquods

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

Epiaquods

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

Fragiaquods

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

Placaquods

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

Cryods

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. 253

CBB. Other Cryods that have, in 90 percent or more of each

pedon, a cemented soil layer that does not slake in water after
252 Keys to Soil Taxonomy

air drying and has its upper boundary within 100 cm of the

mineral soil surface.

Duricryods, p. 252

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. 252

CBD. Other Cryods.

Haplocryods, p. 252

Duricryods

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

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

Haplocryods

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

Humicryods

Key to Subgroups

CBCA. Humicryods that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Humicryods
Spodosols 253

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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

Placocryods

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

Humods

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. 254

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. 253

CCC. Other Humods that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragihumods, p. 253

CCD. Other Humods.

Haplohumods, p. 253

Durihumods

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

Fragihumods

Key to Subgroups

CCCA. All Fragihumods (provisionally).

Typic Fragihumods

Haplohumods

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
254 Keys to Soil Taxonomy

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

Placohumods

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

Orthods

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. 257

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. 255

CDC. Other Orthods that have a fragipan with its upper

boundary within 100 cm of the mineral soil surface.

Fragiorthods, p. 255

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. 254

CDE. Other Orthods.

Haplorthods, p. 255

Alorthods

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

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
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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

Durorthods

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

Fragiorthods

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

Haplorthods

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

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
256 Keys to Soil Taxonomy

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 or more layers within 100 cm of the mineral soil surface in

normal years for either or both:
Spodosols 257

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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

Placorthods

Key to Subgroups

CDAA. All Placorthods (provisionally).

Typic Placorthods

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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. 259

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. 263

HC. Other Ultisols that have a udic moisture regime.

Udults, p. 266

HD. Other Ultisols that have an ustic moisture regime.

Ustults, p. 274

HE. Other Ultisols.

Xerults, p. 278

Aquults

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

a continuous phase or constitutes one-half or more of the

volume.

Plinthaquults, p. 263

HAB. Other Aquults that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragiaquults, p. 261

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. 260

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

CHAPTER 15

Ultisols
260 Keys to Soil Taxonomy

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. 261

HAE. Other Aquults that have a kandic horizon.

Kanhaplaquults, p. 262

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. 262

HAG. Other Aquults that have an umbric or mollic epipedon.

Umbraquults, p. 263

HAH. Other Aquults that have episaturation.

Epiaquults, p. 260

HAI. Other Aquults.

Endoaquults, p. 260

Albaquults

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

HACD. Other Albaquults.

Typic Albaquults

Endoaquults

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

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

Epiaquults

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 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
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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

Fragiaquults

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

Kandiaquults

Key to Subgroups

HADA. Kandiaquults 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.

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

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
262 Keys to Soil Taxonomy

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

Kanhaplaquults

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

Paleaquults

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
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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

Plinthaquults

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

Umbraquults

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

Humults

Key to Great Groups

HBA. Humults that have a sombric horizon within 100 cm of

the mineral soil surface.

Sombrihumults, p. 266

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. 266

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. 264

HBD. Other Humults that have a kandic horizon.

Kanhaplohumults, p. 265

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. 265

HBF. Other Humults.

Haplohumults, p. 263

Haplohumults

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
264 Keys to Soil Taxonomy

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 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

Kandihumults

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

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
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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

Kanhaplohumults

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

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

Palehumults

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
266 Keys to Soil Taxonomy

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

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

Plinthohumults

Key to Subgroups

HBBA. All Plinthohumults.

Typic Plinthohumults

Sombrihumults

Key to Subgroups

HBAA. All Sombrihumults.

Typic Sombrihumults

Udults

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. 274

HCB. Other Udults that have a fragipan with an upper

boundary within 100 cm of the mineral soil surface.

Fragiudults, p. 267

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. 269

HCD. Other Udults that have a kandic horizon.

Kanhapludults, p. 271

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. 272
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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. 274

HCG. Other Udults.

Hapludults, p. 267

Fragiudults

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

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

Hapludults

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
268 Keys to Soil Taxonomy

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

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
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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

Kandiudults

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:

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
270 Keys to Soil Taxonomy

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:

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
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HCCS. Other Kandiudults.

Typic Kandiudults

Kanhapludults

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

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
272 Keys to Soil Taxonomy

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

Paleudults

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

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
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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

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
274 Keys to Soil Taxonomy

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

Plinthudults

Key to Subgroups

HCAA. All Plinthudults.

Typic Plinthudults

Rhodudults

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

Ustults

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. 277

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. 275

HDC. Other Ustults that have a kandic horizon.

Kanhaplustults, p. 276

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. 277

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. 278

HDF. Other Ustults.

Haplustults, p. 274

Haplustults

Key to Subgroups

HDFA. Haplustults that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haplustults
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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

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

Kandiustults

Key to Subgroups

HDBA. Kandiustults 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.

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:

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 oC; 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
276 Keys to Soil Taxonomy

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 oC.

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

Kanhaplustults

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

NH4OAc 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 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil
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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 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

Paleustults

Key to Subgroups

HDDA. All Paleustults.

Typic Paleustults

Plinthustults

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
278 Keys to Soil Taxonomy

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

Rhodustults

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

Xerults

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. 279

HEB. Other Xerults.

Haploxerults, p. 278

Haploxerults

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:

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,

andabove 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 of 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
Ultisols 279

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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

Palexerults

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

retention, and Al plus 1/2 Fe percentages (by ammonium

oxalate) totaling more than 1.0.

Andic Palexerults

HEAD. Other Palexerults.

Typic Palexerults

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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. 281

FB. Other Vertisols that have a cryic soil temperature regime.

Cryerts, p. 285

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

b. Closed for 60 or more consecutive days during the 90

days following the winter solstice.

Xererts, p. 291

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. 285

FE. Other Vertisols that, if not irrigated during the year,

have cracks in normal years that are 5 mm or more wide,

CHAPTER 16

Vertisols1

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. 288

FF. Other Vertisols.

Uderts, p. 286

Aquerts

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. 284

FAB. Other Aquerts that have a duripan that has its upper

boundary within 100 cm of the mineral soil surface.

Duraquerts, p. 282

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. 284

FAD. Other Aquerts that have a calcic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

Calciaquerts, p. 282

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:

1This chapter was rewritten in 1992 following the recommendations of the International

Committee on the Classification of Vertisols (ICOMERT), chaired by Dr. Juan Comerma.
282 Keys to Soil Taxonomy

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. 282

FAF. Other Aquerts that have episaturation.

Epiaquerts, p. 284

FAG. Other Aquerts.

Endoaquerts, p. 283

Calciaquerts

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

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

Duraquerts

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

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

Dystraquerts

Key to Subgroups

FAEA. Dystraquerts that have, in one or more horizons

within 100 cm of the mineral soil surface, jarosite

concentrations and a pH value of 4.0 or less (1:1 water, airdried 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
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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

Endoaquerts

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

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
284 Keys to 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 Endoaquerts

FAGJ. Other Endoaquerts.

Typic Endoaquerts

Epiaquerts

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

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

Natraquerts

Key to Subgroups

FACA. All Natraquerts.

Typic Natraquerts

Salaquerts

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
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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

Cryerts

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. 285

FBB. Other Cryerts.

Haplocryerts, p. 285

Haplocryerts

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

Humicryerts

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

Torrerts

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. 286

FDB. Other Torrerts that have a gypsic horizon that has its

upper boundary within 100 cm of the soil surface.

Gypsitorrerts, p. 286

FDC. Other Torrerts that have a calcic or petrocalcic horizon

that has its upper boundary within 100 cm of the soil surface.

Calcitorrerts, p. 285

FDD. Other Torrerts.

Haplotorrerts, p. 286

Calcitorrerts

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
286 Keys to Soil Taxonomy

2. A color value, dry, of 6 or more; or

3. Chroma of 3 or more.

Chromic Calcitorrerts

FDCE. Other Calcitorrerts.

Typic Calcitorrerts

Gypsitorrerts

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

Haplotorrerts

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

Salitorrerts

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

Uderts

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:
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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. 287

FFB. Other Uderts.

Hapluderts, p. 287

Dystruderts

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

Hapluderts

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
288 Keys to Soil Taxonomy

Usterts

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. 288

FEB. Other Usterts that have a salic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

Salusterts, p. 291

FEC. Other Usterts that have a gypsic horizon that has its

upper boundary within 100 cm of the mineral soil surface.

Gypsiusterts, p. 289

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. 288

FEE. Other Usterts.

Haplusterts, p. 289

Calciusterts

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

Dystrusterts

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

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
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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

Gypsiusterts

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

Haplusterts

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
290 Keys to Soil Taxonomy

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

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
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Salusterts

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

Xererts

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. 292

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. 291

FCC. Other Xererts.

Haploxererts, p. 292

Calcixererts

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
292 Keys to Soil Taxonomy

FCBG. Other Calcixererts.

Typic Calcixererts

Durixererts

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

Haploxererts

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
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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

295

F

A

M

Families and series serve purposes that are largely

pragmatic, the series name is abstract, and the technical family

name is descriptive. In this chapter 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.

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 17

Family and Series Differentiae and Names
296 Keys to 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 297

F

A

M

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 particle-size 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 2.0

1Pumicelike—vesicular pyroclastic materials other than pumice that have an apparent

specific gravity (including vesicles) of less than 1.0 g/cm3

.
298 Keys to Soil Taxonomy

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 299

F

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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
300 Keys to 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 301

F

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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
302 Keys to 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 fineearth 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 303

F

A

M

4. Have more than one-half (by weight) illite (hydrous

mica) and commonly more than 4 percent K2O.

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, 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 particlesize 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
304 Keys to 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

NH4OAc 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 root-limiting 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 a
Family and Series Differentiae and Names 305

F

A

M

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 oC 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.
306 Keys to 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

3), 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 307

F

A

M

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 3. 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 3) 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
308 Keys to 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 309

F

A

M

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

311

H

O

R

This chapter describes soil layers and genetic soil horizons.

The genetic horizons are not the equivalent of the diagnostic

horizons of Soil Taxonomy. While designations of genetic

horizons express a qualitative judgment about the kinds of

changes that are believed to have taken place in a soil,

diagnostic horizons are quantitatively defined features that are

used to differentiate between taxa. A diagnostic horizon may

encompass several genetic horizons, and the changes implied

by genetic horizon designations may not be large enough to

justify recognition of different diagnostic horizons.

Master Horizons and Layers

The capital letters O, A, E, B, C, R, and W represent the

master horizons and layers of soils. These letters are the base

symbols to which other characters are added to complete the

designations. Most horizons and layers are given a single

capital-letter symbol; some require two.

O horizons or layers: Layers dominated by organic

material. Some are saturated with water for long periods or

were once saturated but are now artificially drained; others

have never been saturated.

Some O layers consist of undecomposed or partially

decomposed litter (such as leaves, needles, twigs, moss, and

lichens) that has been deposited on the surface. They may be

on top of either mineral or organic soils. Other O layers consist

of organic material that was deposited under saturated

conditions and has decomposed to varying stages. The mineral

fraction of such material constitutes only a small percentage of

the volume of the material and generally much less than half of

its weight. Some soils consist entirely of materials designated

as O horizons or layers.

An O layer may be on the surface of a mineral soil, or it

may be at any depth below the surface if it is buried. A horizon

formed by the illuviation of organic material into a mineral

subsoil is not an O horizon, although some horizons that have

formed in this manner contain considerable amounts of organic

matter.

A horizons: Mineral horizons that have formed at the

surface or below an O horizon. They exhibit obliteration of all

or much of the original rock structure1

 and show one or both of

the following: (1) an accumulation of humified organic matter

closely mixed with the mineral fraction and not dominated by

properties characteristic of E or B horizons (defined below) or

(2) properties resulting from cultivation, pasturing, or similar

kinds of disturbance.

If a surface horizon has properties of both A and E horizons

but the feature emphasized is an accumulation of humified

organic matter, it is designated as an A horizon. In some areas,

such as areas of warm, arid climates, the undisturbed surface

horizon is less dark than the adjacent underlying horizon and

contains only small amounts of organic matter. It has a

morphology distinct from the C layer, although the mineral

fraction is unaltered or only slightly altered by weathering.

Such a horizon is designated as an A horizon because it is at

the surface. Recent alluvial or eolian deposits that retain fine

stratification are not considered to be A horizons unless

cultivated.

E horizons: Mineral horizons in which the main feature is

the loss of silicate clay, iron, aluminum, or some combination

of these, leaving a concentration of sand and silt particles.

These horizons exhibit obliteration of all or much of the

original rock structure.

An E horizon is most commonly differentiated from an

underlying B horizon in the same sequum by a color of higher

value or lower chroma, or both, by coarser texture, or by a

combination of these properties. In some soils the color of the

E horizon is that of the sand and silt particles, but in many

soils coatings of iron oxides or other compounds mask the

color of the primary particles. An E horizon is most commonly

differentiated from an overlying A horizon by its lighter color.

It generally contains less organic matter than the A horizon.

An E horizon is commonly near the surface, below an O or A

horizon and above a B horizon, but eluvial horizons that are

within or between parts of the B horizon or extend to depths

greater than those of normal observation can be assigned the

letter E if they are pedogenic.

B horizons: Horizons that have formed below an A, E, or O

horizon. They are dominated by the obliteration of all or much

of the original rock structure and show one or more of the

following:

1. Illuvial concentration of silicate clay, iron, aluminum,

humus, carbonates, gypsum, or silica, alone or in

combination;

2. Evidence of the removal or addition of carbonates;

CHAPTER 18

Designations for Horizons and Layers

1Rock structure includes fine stratification in unconsolidated soil materials as well as

pseudomorphs of weathered minerals that retain their positions relative to each other and to

unweathered minerals in saprolite.
312 Keys to Soil Taxonomy

3. Residual concentration of oxides;

4. Coatings of sesquioxides that make the horizon

conspicuously lower in color value, higher in chroma, or

redder in hue, without apparent illuviation of iron;

5. Alteration that forms silicate clay or liberates oxides, or

both, and that forms a granular, blocky, or prismatic

structure if volume changes accompany changes in moisture

content;

6. Brittleness; or

7. Strong gleying.

All of the different kinds of B horizons are, or were

originally, subsurface horizons. Included as B horizons, where

contiguous to other genetic horizons, are layers of illuvial

concentration of carbonates, gypsum, or silica that are the

result of pedogenic processes (and may or may not be

cemented) and brittle layers that show other evidence of

alteration, such as prismatic structure or illuvial accumulation

of clay.

Examples of layers that are not B horizons are layers in

which clay films either coat rock fragments or cover finely

stratified unconsolidated sediments, regardless of whether the

films were formed in place or by illuviation; layers into which

carbonates have been illuviated but that are not contiguous to

an overlying genetic horizon; and layers with gleying but no

other pedogenic changes.

C horizons or layers: Horizons or layers, excluding

strongly cemented and harder bedrock, that are little affected

by pedogenic processes and lack the properties of O, A, E, or

B horizons. Most are mineral layers. The material of C layers

may be either like or unlike the material from which the solum

has presumably formed. The C horizon may have been

modified, even if there is no evidence of pedogenesis.

Included as C layers are sediment, saprolite, bedrock, and

other geologic materials that are moderately cemented or less

cemented. The excavation difficulty in these materials

commonly is low or moderate. Some soils form in material that

is already highly weathered, and if such material does not meet

the requirements for A, E, or B horizons, it is designated by the

letter C. Changes that are not considered pedogenic are those

not related to the overlying horizons. Some layers that have

accumulations of silica, carbonates, gypsum, or more soluble

salts are included in C horizons, even if cemented. If a

cemented layer formed through pedogenic processes, however,

it is considered a B horizon.

R layers: Strongly cemented to indurated bedrock.

Granite, basalt, quartzite, limestone, and sandstone are

examples of bedrock designated by the letter R. The excavation

difficulty commonly exceeds high. The R layer is sufficiently

coherent when moist to make hand-digging with a spade

impractical, although the layer may be chipped or scraped.

Some R layers can be ripped with heavy power equipment. The

bedrock may have cracks, but these are generally too few and

too small to allow root penetration. The cracks may be coated

or filled with clay or other material.

W layers: Water

This symbol indicates water layers within or beneath the

soil. The water layer is designated as Wf if it is permanently

frozen and as W if it is not permanently frozen. The W (or Wf)

designation is not used for shallow water, ice, or snow above

the soil surface.

Transitional and Combination Horizons

Horizons dominated by properties of one master horizon but

having subordinate properties of another.—Two capital-letter

symbols are used for such transitional horizons, e.g., AB, EB,

BE, or BC. The first of these symbols indicates that the

properties of the horizon so designated dominate the

transitional horizon. An AB horizon, for example, has

characteristics of both an overlying A horizon and an

underlying B horizon, but it is more like the A horizon than

the B horizon.

In some cases a horizon can be designated as transitional

even if one of the master horizons to which it presumably

forms a transition is not present. A BE horizon may be

recognized in a truncated soil if its properties are similar to

those of a BE horizon in a soil from which the overlying E

horizon has not been removed by erosion. A BC horizon may

be recognized even if no underlying C horizon is present; it is

transitional to assumed parent materials.

Horizons with two distinct parts that have recognizable

properties of the two kinds of master horizons indicated by the

capital letters.—The two capital letters designating such

combination horizons are separated by a virgule (/), e.g., E/B,

B/E, or B/C. Most of the individual parts of one horizon

component are surrounded by the other. The designation may

be used even when horizons similar to one or both of the

components are not present, provided that the separate

components can be recognized in the combination horizon. The

first symbol is that of the horizon with the greater volume.

Single sets of horizon designators do not cover all

situations; therefore, some improvising is needed. For example,

Argic Udipsamments have lamellae that are separated from

each other by eluvial layers. Because it is generally not

practical to describe each lamella and eluvial layer as a

separate horizon, the horizons can be combined but the

components described separately. One horizon then has several

lamellae and eluvial layers and can be designated an “E and

Bt” horizon. The complete horizon sequence for these soils

could be: Ap-Bw-E and Bt1-E and Bt2-C.

Suffix Symbols

Lowercase letters are used as suffixes to designate specific

kinds of master horizons and layers. The term “accumulation”

is used in many of the definitions of such horizons to indicate
Designations for Horizons and Layers 313

H

O

R

that these horizons must contain more of the material in

question than is presumed to have been present in the parent

material. The suffix symbols and their meanings are as follows:

a Highly decomposed organic material

This symbol is used with O to indicate the most highly

decomposed organic materials, which have a fiber

content of less than 17 percent (by volume) after rubbing.

b Buried genetic horizon

This symbol is used in mineral soils to indicate

identifiable buried horizons with major genetic features

that were developed before burial. Genetic horizons may

or may not have formed in the overlying material, which

may be either like or unlike the assumed parent material

of the buried soil. This symbol is not used in organic

soils, nor is it used to separate an organic layer from a

mineral layer.

c Concretions or nodules

This symbol indicates a significant accumulation of

concretions or nodules. Cementation is required. The

cementing agent commonly is iron, aluminum,

manganese, or titanium. It cannot be silica, dolomite,

calcite, or more soluble salts.

d Physical root restriction

This symbol indicates noncemented, root-restricting

layers in naturally occurring or human-made sediments

or materials. Examples are dense basal till, plowpans,

and other mechanically compacted zones.

e Organic material of intermediate decomposition

This symbol is used with O to indicate organic

materials of intermediate decomposition. The fiber

content of these materials is 17 to 40 percent (by volume)

after rubbing.

f Frozen soil or water

This symbol indicates that a horizon or layer contains

permanent ice. The symbol is not used for seasonally

frozen layers or for dry permafrost.

ff Dry permafrost

This symbol indicates a horizon or layer that is

continually colder than 0 oC and does not contain enough

ice to be cemented by ice. This suffix is not used for

horizons or layers that have a temperature warmer than

0 oC at some time of the year.

g Strong gleying

This symbol indicates either that iron has been

reduced and removed during soil formation or that

saturation with stagnant water has preserved it in a

reduced state. Most of the affected layers have chroma of

2 or less, and many have redox concentrations. The low

chroma can represent either the color of reduced iron or

the color of uncoated sand and silt particles from which

iron has been removed. The symbol g is not used for

materials of low chroma that have no history of wetness,

such as some shales or E horizons. If g is used with B,

pedogenic change in addition to gleying is implied. If no

other pedogenic change besides gleying has taken place,

the horizon is designated Cg.

h Illuvial accumulation of organic matter

This symbol is used with B to indicate the

accumulation of illuvial, amorphous, dispersible

complexes of organic matter and sesquioxides if the

sesquioxide component is dominated by aluminum but is

present only in very small quantities. The organosesquioxide material coats sand and silt particles. In

some horizons these coatings have coalesced, filled

pores, and cemented the horizon. The symbol h is also

used in combination with s as “Bhs” if the amount of the

sesquioxide component is significant but the color value

and chroma, moist, of the horizon are 3 or less.

i Slightly decomposed organic material

This symbol is used with O to indicate the least

decomposed of the organic materials. The fiber content of

these materials is 40 percent or more (by volume) after

rubbing.

j Accumulation of jarosite

Jarosite is a potassium or iron sulfate mineral that is

commonly an alteration product of pyrite that has been

exposed to an oxidizing environment. Jarosite has hue of

2.5Y or yellower and normally has chroma of 6 or

more, although chromas as low as 3 or 4 have been

reported.

jj Evidence of cryoturbation

Evidence of cryoturbation includes irregular and

broken horizon boundaries, sorted rock fragments, and

organic soil materials occurring as bodies and broken

layers within and/or between mineral soil layers. The

organic bodies and layers are most commonly at the

contact between the active layer and the permafrost.

k Accumulation of carbonates

This symbol indicates an accumulation of alkalineearth carbonates, commonly calcium carbonate.

m Cementation or induration

This symbol indicates continuous or nearly continuous

cementation. It is used only for horizons that are more

than 90 percent cemented, although they may be
314 Keys to Soil Taxonomy

fractured. The cemented layer is physically rootrestrictive. The predominant cementing agent (or the two

dominant cementing agents) may be indicated by adding

defined letter suffixes, singly or in pairs. The horizon

suffix km indicates cementation by carbonates; qm,

cementation by silica; sm, cementation by iron; ym,

cementation by gypsum; kqm, cementation by lime and

silica; and zm, cementation by salts more soluble than

gypsum.

n Accumulation of sodium

This symbol indicates an accumulation of

exchangeable sodium.

o Residual accumulation of sesquioxides

This symbol indicates a residual accumulation of

sesquioxides.

p Tillage or other disturbance

This symbol indicates a disturbance of the surface

layer by mechanical means, pasturing, or similar uses. A

disturbed organic horizon is designated Op. A disturbed

mineral horizon is designated Ap even though it is

clearly a former E, B, or C horizon.

q Accumulation of silica

This symbol indicates an accumulation of secondary

silica.

r Weathered or soft bedrock

This symbol is used with C to indicate cemented

layers (moderately cemented or less cemented). Examples

are weathered igneous rock and partly consolidated

sandstone, siltstone, or shale. The excavation difficulty is

low to high.

s Illuvial accumulation of sesquioxides and organic

matter

This symbol is used with B to indicate an

accumulation of illuvial, amorphous, dispersible

complexes of organic matter and sesquioxides if both the

organic-matter and sesquioxide components are

significant and if either the color value or chroma, moist,

of the horizon is 4 or more. The symbol is also used in

combination with h as “Bhs” if both the organic-matter

and sesquioxide components are significant and if the

color value and chroma, moist, are 3 or less.

ss Presence of slickensides

This symbol indicates the presence of slickensides.

Slickensides result directly from the swelling of clay

minerals and shear failure, commonly at angles of 20 to

60 degrees above horizontal. They are indicators that

other vertic characteristics, such as wedge-shaped peds

and surface cracks, may be present.

t Accumulation of silicate clay

This symbol indicates an accumulation of silicate clay

that either has formed within a horizon and subsequently

has been translocated within the horizon or has been

moved into the horizon by illuviation, or both. At least

some part of the horizon should show evidence of clay

accumulation either as coatings on surfaces of peds or in

pores, as lamellae, or as bridges between mineral grains.

v Plinthite

This symbol indicates the presence of iron-rich,

humus-poor, reddish material that is firm or very firm

when moist and hardens irreversibly when exposed to the

atmosphere and to repeated wetting and drying.

w Development of color or structure

This symbol is used with B to indicate the

development of color or structure, or both, with little or

no apparent illuvial accumulation of material. It should

not be used to indicate a transitional horizon.

x Fragipan character

This symbol indicates a genetically developed layer

that has a combination of firmness and brittleness and

commonly a higher bulk density than the adjacent layers.

Some part of the layer is physically root-restrictive.

y Accumulation of gypsum

This symbol indicates an accumulation of gypsum.

z Accumulation of salts more soluble than gypsum

This symbol indicates an accumulation of salts that

are more soluble than gypsum.

Conventions for Using Letter Suffixes

Many master horizons and layers that are symbolized by a

single capital letter have one or more lowercase letter suffixes.

The following rules apply:

1. Letter suffixes should directly follow the capital letter.

2. More than three suffixes are rarely used.

3. If more than one suffix is needed, the following letters,

if used, are written first: a, d, e, h, i, r, s, t, and w. Except in

the Bhs or Crt2 horizon designations, none of these letters

are used in combination in a single horizon.

4. If more than one suffix is needed and the horizon is not

2 Indicates weathered bedrock or saprolite in which clay films are present.
Designations for Horizons and Layers 315

H

O

R

buried, the following symbols, if used, are written last: c, f,

g, m, v, and x. Some examples: Btc, Bkm, and Bsv.

5. If a horizon is buried, the suffix b is written last. It is

used only for buried mineral soils.

A B horizon that has a significant accumulation of clay and

also shows evidence of a development of color or structure, or

both, is designated Bt (t has precedence over w, s, and h). A B

horizon that is gleyed or has accumulations of carbonates,

sodium, silica, gypsum, or salts more soluble than gypsum or

residual accumulations of sesquioxides carries the appropriate

symbol: g, k, n, q, y, z, or o. If illuvial clay also is present, t

precedes the other symbol: Bto.

Unless needed for explanatory purposes, the suffixes h, s,

and w are not used with g, k, n, q, y, z, or o.

Vertical Subdivision

Commonly, a horizon or layer identified by a single letter or

a combination of letters has to be subdivided. For this purpose,

Arabic numerals are added to the letters of the horizon

designation. These numerals follow all the letters. Within a C

horizon, for example, successive layers may be designated C1,

C2, C3, etc. If the lower part is gleyed and the upper part is

not gleyed, the layers may be designated C1-C2-Cg1-Cg2 or

C-Cg1-Cg2-R.

These conventions apply whatever the purpose of the

subdivision. In many soils a horizon that could be identified

by a single set of letters is subdivided because of the need to

recognize differences in morphological features, such as

structure, color, or texture. These divisions are numbered

consecutively with Arabic numerals, but the numbering starts

again with 1 wherever in the profile any letter of the horizon

symbol changes, e.g., Bt1-Bt2-Btk1-Btk2 (not Bt1-Bt2-Btk3-

Btk4). The numbering of vertical subdivisions within a

horizon is not interrupted at a discontinuity (indicated by a

numerical prefix) if the same letter combination is used in

both materials, e.g., Bs1-Bs2-2Bs3-2Bs4 (not Bs1-Bs2-2Bs1-

2Bs2).

During sampling for laboratory analyses, thick soil horizons

are sometimes subdivided even though differences in

morphology are not evident in the field. These subdivisions are

identified by Arabic numerals that follow the respective

horizon designations. For example, four layers of a Bt horizon

sampled by 10-cm increments are designated Bt1, Bt2, Bt3,

and Bt4. If the horizon has already been subdivided because of

differences in morphological features, the set of Arabic

numerals that identifies the additional sampling subdivisions

follows the first numeral. For example, three layers of a Bt2

horizon sampled by 10-cm increments are designated Bt21,

Bt22, and Bt23. The descriptions for each of these sampling

subdivisions can be the same, and a statement indicating that

the horizon has been subdivided only for sampling purposes

can be added.

Discontinuities

Arabic numerals are used as prefixes to horizon

designations (preceding the letters A, E, B, C, and R) to

indicate discontinuities in mineral soils. These prefixes are

distinct from the Arabic numerals that are used as suffixes

denoting vertical subdivisions.

A discontinuity that can be identified by a number prefix is

a significant change in particle-size distribution or mineralogy

that indicates a difference in the material from which the

horizons have formed and/or a significant difference in age,

unless that difference in age is indicated by the suffix b.

Symbols that identify discontinuities are used only when they

can contribute substantially to an understanding of the

relationships among horizons. The stratification common to

soils that formed in alluvium is not designated as a

discontinuity, unless particle-size distribution differs markedly

from layer to layer (i.e., particle-size classes are strongly

contrasting), even though genetic horizons may have formed in

the contrasting layers.

Where a soil has formed entirely in one kind of material, the

whole profile is understood to be material 1 and the number

prefix is omitted from the symbol. Similarly, the uppermost

material in a profile consisting of two or more contrasting

materials is understood to be material 1, but the number is

omitted. Numbering starts with the second layer of contrasting

material, which is designated 2. Underlying contrasting layers

are numbered consecutively. Even when the material of a layer

below material 2 is similar to material 1, it is designated 3 in

the sequence; the numbers indicate a change in materials, not

types of material. Where two or more consecutive horizons

have formed in the same kind of material, the same prefix

number is applied to all the designations of horizons in that

material: Ap-E-Bt1-2Bt2-2Bt3-2BC. The suffix numbers

designating subdivisions of the Bt horizon continue in

consecutive order across the discontinuity.

If an R layer is present below a soil that has formed in

residuum and if the material of the R layer is judged to be like

the material from which the soil has developed, the Arabicnumber prefix is not used. The prefix is used, however, if it is

thought that the R layer would produce material unlike that in

the solum, e.g., A-Bt-C-2R or A-Bt-2R. If part of the solum

has formed in residuum, the symbol R is given the appropriate

prefix: Ap-Bt1-2Bt2-2Bt3-2C1-2C2-2R.

A buried horizon (designated by the letter b) presents

special problems. It is obviously not in the same deposit as the

overlying horizons. Some buried horizons, however, have

formed in material that is lithologically like the overlying

deposit. A prefix is not used to distinguish material of such a

buried horizon. If the material in which a horizon of a buried

soil has formed is lithologically unlike the overlying material,

however, the discontinuity is indicated by a number prefix and

the symbol for the buried horizon also is used, e.g., Ap-Bt1-

Bt2-BC-C-2ABb-2Btb1-2Btb2-2C.
316

Discontinuities between different kinds of layers in organic

soils are not identified. In most cases such differences are

identified either by letter-suffix designations if the different

layers are organic or by the master symbol if the different

layers are mineral.

Use of the Prime Symbol

If two or more horizons of the same kind are separated by

one or more horizons of a different kind in a pedon, identical

letter and number symbols can be used for those horizons that

have the same characteristics. For example, the sequence A-EBt-E-Btx-C identifies a soil that has two E horizons. To

emphasize this characteristic, the prime symbol ( ́) is added

after the master-horizon symbol of the lower of the two

horizons that have identical designations, e.g., A-E-Bt-E ́-BtxC. The prime symbol, when appropriate, is applied to the

capital-letter horizon designation, and any lowercase letter

symbols follow it: B ́t. The prime symbol is used only when the

letter designations of the two layers in question are completely

identical. In the rare cases when three layers have identical

letter symbols, double prime symbols can be used for the lowest

of these layers: E ́ ́.

The same principle applies in designating layers of organic

soils. The prime symbol is used only to distinguish two or more

horizons that have identical symbols, e.g., Oi-C-O ́i-C ́ (when

the soil has two identical Oi layers) or Oi-C-Oe-C ́ (when the

two C layers are of the same kind).
317

Appendix

Pressure:

15-bar water = 1500 kPa water retention

1

/3-bar water = 33 kPa water retention

Percentages of clay (less than 0.002 mm), silt (0.002 to 0.05 mm),

and sand (0.05 to 2.0 mm) in the basic soil textural classes

CEC and ECEC: 1 meq/100 g soil = 1 cmol(+)/kg soil

Conductivity: 1 mmho/cm = 1 dS/m

SI unit conversion table

319

Index

A

A horizons. See Horizons and layers.

Abrupt textural change............................................................ 21

Acraquox ............................................................................... 233

Acroperox .............................................................................. 234

Acrotorrox ............................................................................. 238

Acrudox ................................................................................. 239

Acrustox ................................................................................ 243

Agric horizon .......................................................................... 16

Alaquods ................................................................................ 249

Albaqualfs................................................................................ 42

Albaquults ............................................................................. 260

Albic horizon ........................................................................... 16

Albic materials ........................................................................ 22

Albolls ................................................................................... 192

Alfisols .................................................................................... 41

Alorthods ............................................................................... 254

Andic soil properties ............................................................... 22

Andisols ................................................................................... 83

Anhydrous conditions ............................................................. 22

Anhyorthels ........................................................................... 151

Anhyturbels ........................................................................... 154

Aniso class ............................................................................. 296

Anthracambids ...................................................................... 114

Anthrepts ............................................................................... 165

Anthropic epipedon ................................................................. 13

Aqualfs .................................................................................... 41

Aquands ................................................................................... 83

Aquents .................................................................................. 130

Aquepts .................................................................................. 166

Aquerts .................................................................................. 281

Aquic conditions ..................................................................... 30

Aquic moisture regime. See Soil moisture regimes.

Aquicambids .......................................................................... 114

Aquisalids .............................................................................. 128

Aquiturbels ............................................................................ 154

Aquods ................................................................................... 249

Aquolls .................................................................................. 193

Aquorthels ............................................................................. 151

Aquox .................................................................................... 233

Aquults .................................................................................. 259

Arents .................................................................................... 133

Argialbolls ............................................................................. 192

Argiaquolls ............................................................................ 193

Argicryids .............................................................................. 118

Argicryolls ............................................................................. 197

Argids .................................................................................... 103

Argidurids ............................................................................. 121

Argigypsids............................................................................ 124

Argillic horizon ....................................................................... 17

Argiorthels ............................................................................. 152

Argiudolls .............................................................................. 201

Argiustolls ............................................................................. 208

Argixerolls ............................................................................. 222

Aridic moisture regime. See Soil moisture regimes.

Aridisols ................................................................................ 103

B

B horizons. See Horizons and layers.

Bottom tier ............................................................................... 29

Buried soils .............................................................................. 10

C

C horizons or layers. See Horizons and layers.

Calcareous and reaction classes for mineral soils ................ 304

Calciaquerts ........................................................................... 282

Calciaquolls ........................................................................... 194

Calciargids ............................................................................. 104

Calcic horizon ......................................................................... 17

Calcicryids ............................................................................. 119

Calcicryolls ............................................................................ 198

Calcids ....................................................................................111

Calcigypsids .......................................................................... 125

Calcitorrerts ........................................................................... 285

Calciudolls ............................................................................. 203

Calciustepts ........................................................................... 178

Calciusterts ............................................................................ 288

Calciustolls ............................................................................ 211

Calcixerepts ........................................................................... 184

Calcixererts............................................................................ 291

Calcixerolls ............................................................................ 224

Cambic horizon ....................................................................... 18

Cambids ................................................................................. 114

Cation-exchange activity classes for mineral soils ............... 303

Coatings (classes) on sands ................................................... 306

Coefficient of linear extensibility (COLE).............................. 22

Control section of Histosols and Histels ................................. 29
320 Keys to Soil Taxonomy

Coprogenous earth. See Organic soil material.

Cryalfs ..................................................................................... 50

Cryands .................................................................................... 86

Cryaqualfs................................................................................ 43

Cryaquands .............................................................................. 84

Cryaquents ............................................................................. 130

Cryaquepts ............................................................................. 166

Cryaquods .............................................................................. 250

Cryaquolls.............................................................................. 194

Cryepts ................................................................................... 171

Cryerts ................................................................................... 285

Cryic temperature regime. See Soil temperature

regimes.

Cryids .................................................................................... 118

Cryods .................................................................................... 251

Cryofibrists ............................................................................ 159

Cryofluvents .......................................................................... 134

Cryofolists.............................................................................. 161

Cryohemists ........................................................................... 161

Cryolls ................................................................................... 197

Cryopsamments ..................................................................... 144

Cryorthents ............................................................................ 139

Cryosaprists ........................................................................... 162

Cryoturbation........................................................................... 31

Cryrendolls ............................................................................ 200

D

Densic contact ......................................................................... 31

Densic materials ...................................................................... 31

Diagnostic subsurface horizons .............................................. 16

Diagnostic surface horizons .................................................... 13

Diatomaceous earth. See Organic soil material.

Discontinuities identified by horizon designators ................ 315

Duraqualfs ............................................................................... 43

Duraquands ............................................................................. 84

Duraquerts ............................................................................. 282

Duraquods ............................................................................. 250

Duraquolls ............................................................................. 194

Duricryands ............................................................................. 87

Duricryods ............................................................................. 252

Duricryolls ............................................................................. 198

Durids .................................................................................... 121

Durihumods ........................................................................... 253

Durinodes ................................................................................ 23

Duripan .................................................................................... 18

Duritorrands ............................................................................ 90

Durixeralfs ............................................................................... 77

Durixerepts ............................................................................ 185

Durixererts............................................................................. 292

Durixerolls ............................................................................. 225

Durorthods ............................................................................. 255

Durudands ............................................................................... 91

Durudepts .............................................................................. 173

Durustalfs ................................................................................ 66

Durustands............................................................................... 97

Durustepts.............................................................................. 179

Durustolls .............................................................................. 212

Dystraquerts........................................................................... 282

Dystrocryepts ......................................................................... 171

Dystroxerepts ......................................................................... 185

Dystrudepts ............................................................................ 173

Dystruderts ............................................................................ 287

Dystrustepts ........................................................................... 179

Dystrusterts ............................................................................ 288

E

E horizons. See Horizons and layers.

Endoaqualfs ............................................................................. 43

Endoaquands ........................................................................... 84

Endoaquents .......................................................................... 130

Endoaquepts .......................................................................... 167

Endoaquerts ........................................................................... 283

Endoaquods ........................................................................... 251

Endoaquolls ........................................................................... 195

Endoaquults ........................................................................... 260

Entisols .................................................................................. 129

Epiaqualfs ................................................................................ 45

Epiaquands .............................................................................. 85

Epiaquents ............................................................................. 131

Epiaquepts ............................................................................. 168

Epiaquerts .............................................................................. 284

Epiaquods .............................................................................. 251

Epiaquolls .............................................................................. 196

Epiaquults .............................................................................. 260

Epipedon .................................................................................. 13

Eutraquox .............................................................................. 234

Eutrocryepts ........................................................................... 172

Eutroperox ............................................................................. 235

Eutrotorrox ............................................................................ 239

Eutrudepts ............................................................................. 176

Eutrudox ................................................................................ 240

Eutrustox ............................................................................... 244

F

Family differentiae for Histosols and Histels ........................ 306

Family differentiae for mineral soils ..................................... 295

Ferrudalfs ................................................................................ 55

Fibers. See Organic soil material.

Fibric soil materials. See Organic soil material.

Fibristels ................................................................................ 149

Fibrists ................................................................................... 159
Index 321

Fluvaquents ........................................................................... 131

Fluvents ................................................................................. 134

Folistels.................................................................................. 150

Folistic epipedon ..................................................................... 13

Folists .................................................................................... 160

Fragiaqualfs ............................................................................. 47

Fragiaquepts .......................................................................... 169

Fragiaquods ........................................................................... 251

Fragiaquults ........................................................................... 261

Fragic soil properties ............................................................... 23

Fragihumods .......................................................................... 253

Fragiorthods .......................................................................... 255

Fragipan .................................................................................. 18

Fragiudalfs ............................................................................... 55

Fragiudepts ............................................................................ 177

Fragiudults............................................................................. 267

Fragixeralfs.............................................................................. 78

Fragixerepts ........................................................................... 187

Fraglossudalfs .......................................................................... 55

Frigid temperature regime. See Soil temperature regimes.

Fulvicryands ............................................................................ 87

Fulvudands .............................................................................. 91

G

Gelic materials ........................................................................ 32

Gelisols .................................................................................. 149

Glacic layer .............................................................................. 32

Glacistels ............................................................................... 150

Glossaqualfs ............................................................................ 48

Glossic horizon ........................................................................ 18

Glossocryalfs ........................................................................... 50

Glossudalfs .............................................................................. 56

Gypsiargids ............................................................................ 105

Gypsic horizon ........................................................................ 19

Gypsicryids ............................................................................ 119

Gypsids .................................................................................. 124

Gypsitorrerts .......................................................................... 286

Gypsiusterts ........................................................................... 289

H

Halaquepts ............................................................................. 169

Haplanthrepts ........................................................................ 165

Haplaquox.............................................................................. 234

Haplargids ............................................................................. 106

Haplocalcids ...........................................................................111

Haplocambids ........................................................................ 115

Haplocryalfs ............................................................................. 52

Haplocryands ........................................................................... 87

Haplocryerts........................................................................... 285

Haplocryids ............................................................................ 120

Haplocryods ........................................................................... 252

Haplocryolls ........................................................................... 198

Haplodurids ........................................................................... 122

Haplofibrists .......................................................................... 160

Haplogypsids ......................................................................... 125

Haplohemists ......................................................................... 161

Haplohumods ......................................................................... 253

Haplohumults ........................................................................ 263

Haploperox ............................................................................ 236

Haplorthels ............................................................................ 152

Haplorthods ........................................................................... 255

Haplosalids ............................................................................ 128

Haplosaprists ......................................................................... 162

Haplotorrands .......................................................................... 90

Haplotorrerts.......................................................................... 286

Haplotorrox ........................................................................... 239

Haploturbels .......................................................................... 155

Haploxeralfs ............................................................................ 78

Haploxerands ......................................................................... 100

Haploxerepts .......................................................................... 187

Haploxererts .......................................................................... 292

Haploxerolls .......................................................................... 226

Haploxerults .......................................................................... 278

Hapludalfs................................................................................ 58

Hapludands .............................................................................. 92

Hapluderts ............................................................................. 287

Hapludolls ............................................................................. 204

Hapludox ............................................................................... 241

Hapludults ............................................................................. 267

Haplustalfs ............................................................................... 66

Haplustands ............................................................................. 98

Haplustepts ............................................................................ 180

Haplusterts ............................................................................. 289

Haplustolls ............................................................................. 213

Haplustox ............................................................................... 245

Haplustults ............................................................................. 274

Haprendolls ........................................................................... 200

Hemic soil materials. See Organic soil material.

Hemistels ............................................................................... 150

Hemists .................................................................................. 161

Histels .................................................................................... 149

Histic epipedon ........................................................................ 14

Historthels ............................................................................. 152

Histosols ................................................................................ 159

Histoturbels............................................................................ 155

Horizons and layers ............................................................... 311

A horizons ......................................................................... 311

B horizons ......................................................................... 311

C horizons or layers .......................................................... 312

E horizons ......................................................................... 311

O horizons or layers .......................................................... 311

R layers .............................................................................. 312

W layers ............................................................................. 312

Humaquepts ........................................................................... 170
322 Keys to Soil Taxonomy

Humicryerts ........................................................................... 285

Humicryods............................................................................ 252

Humilluvic material. See Organic soil material.

Humods .................................................................................. 253

Humults ................................................................................. 263

Hydraquents ........................................................................... 132

Hydrocryands ........................................................................... 88

Hydrudands ............................................................................. 94

Hyperthermic temperature regime. See Soil temperature

regimes.

I

Identifiable secondary carbonates ........................................... 23

Inceptisols .............................................................................. 165

Interfingering of albic materials ............................................. 24

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 ........................................................................... 48

Kandiaquults ......................................................................... 261

Kandic horizon ........................................................................ 19

Kandihumults ........................................................................ 264

Kandiperox ............................................................................ 237

Kandiudalfs ............................................................................. 61

Kandiudox ............................................................................. 242

Kandiudults ........................................................................... 269

Kandiustalfs ............................................................................. 69

Kandiustox ............................................................................ 246

Kandiustults .......................................................................... 275

Kanhaplaquults ..................................................................... 262

Kanhaplohumults .................................................................. 265

Kanhapludalfs ......................................................................... 62

Kanhapludults ....................................................................... 271

Kanhaplustalfs ......................................................................... 70

Kanhaplustults....................................................................... 276

Key to soil orders..................................................................... 37

L

Lamellae .................................................................................. 24

Limnic materials. See Organic soil material.

Linear extensibility (LE) ......................................................... 24

Lithic contact ........................................................................... 32

Lithologic discontinuities ........................................................ 24

Luvihemists ........................................................................... 162

M

Marl. See Organic soil material.

Melanaquands ......................................................................... 85

Melanic epipedon .................................................................... 14

Melanocryands ........................................................................ 89

Melanoxerands ...................................................................... 101

Melanudands ........................................................................... 95

Mesic temperature regime. See Soil temperature

regimes.

Mineral soil material ............................................................... 11

Mineral soils ............................................................................ 12

Mineralogy classes for Histosols and Histels ........................ 307

Mineralogy classes for mineral soils..................................... 301

Mollic epipedon ....................................................................... 14

Mollisols ................................................................................ 191

Molliturbels ........................................................................... 155

Mollorthels ............................................................................ 152

N

n value ..................................................................................... 25

Natralbolls ............................................................................. 193

Natraqualfs .............................................................................. 49

Natraquerts ............................................................................ 284

Natraquolls ............................................................................ 197

Natrargids.............................................................................. 108

Natric horizon ......................................................................... 19

Natricryolls ............................................................................ 200

Natridurids ............................................................................ 123

Natrigypsids........................................................................... 126

Natrixeralfs .............................................................................. 80

Natrixerolls ............................................................................ 230

Natrudalfs ................................................................................ 62

Natrudolls .............................................................................. 206

Natrustalfs ............................................................................... 71

Natrustolls ............................................................................. 217

Normal years ........................................................................... 33

O

O horizons or layers. See Horizons and layers.

Ochric epipedon ...................................................................... 15

Organic soil material ............................................................... 11

Fibers ................................................................................... 27

Fibric soil materials ............................................................. 27

Hemic soil materials ............................................................ 28

Humilluvic material ............................................................ 28

Limnic materials ................................................................. 28

Coprogenous earth .......................................................... 28

Diatomaceous earth ......................................................... 29

Marl ................................................................................. 29

Sapric soil materials ............................................................ 28

Organic soils ............................................................................ 12
Index 323

Orthels ................................................................................... 150

Orthents ................................................................................. 139

Orthods .................................................................................. 254

Ortstein .................................................................................... 20

Oxic horizon ............................................................................ 20

Oxisols ................................................................................... 233

P

Paleaquults ............................................................................ 262

Paleargids .............................................................................. 109

Palecryalfs ............................................................................... 53

Palecryolls ............................................................................. 200

Palehumults ........................................................................... 265

Paleudalfs ................................................................................ 63

Paleudolls .............................................................................. 207

Paleudults .............................................................................. 272

Paleustalfs ................................................................................ 73

Paleustolls .............................................................................. 220

Paleustults.............................................................................. 277

Palexeralfs ............................................................................... 80

Palexerolls ............................................................................. 230

Palexerults ............................................................................. 279

Paralithic contact ..................................................................... 32

Paralithic materials ................................................................. 32

Particle-size classes for Histosols and Histels ...................... 306

Particle-size classes for mineral soils ................................... 295

Permafrost ............................................................................... 32

Permanent cracks (classes) in mineral soils ......................... 306

Perox ...................................................................................... 234

Petraquepts ............................................................................ 170

Petroargids ..............................................................................111

Petrocalcic horizon .................................................................. 20

Petrocalcids............................................................................ 113

Petrocambids ......................................................................... 117

Petrocryids ............................................................................. 120

Petroferric contact ................................................................... 25

Petrogypsic horizon ................................................................. 20

Petrogypsids........................................................................... 127

Placaquands ............................................................................. 86

Placaquods ............................................................................. 251

Placic horizon .......................................................................... 21

Placocryods ............................................................................ 253

Placohumods ......................................................................... 254

Placorthods ............................................................................ 257

Placudands ............................................................................... 97

Plagganthrepts....................................................................... 165

Plaggen epipedon .................................................................... 15

Plinthaqualfs............................................................................ 50

Plinthaquox ........................................................................... 234

Plinthaquults ......................................................................... 263

Plinthite ................................................................................... 26

Plinthohumults ...................................................................... 266

Plinthoxeralfs .......................................................................... 82

Plinthudults ........................................................................... 274

Plinthustalfs ............................................................................. 76

Plinthustults........................................................................... 277

Prime symbol in horizon designators ................................... 316

Psammaquents ....................................................................... 132

Psamments ............................................................................. 144

Psammorthels ........................................................................ 153

Psammoturbels ...................................................................... 156

Q

Quartzipsamments................................................................. 145

R

R layers. See Horizons and layers.

Reaction classes for Histosols and Histels ............................ 308

Rendolls ................................................................................. 200

Resistant minerals ................................................................... 26

Rhodoxeralfs............................................................................ 82

Rhodudalfs ............................................................................... 65

Rhodudults............................................................................. 274

Rhodustalfs .............................................................................. 76

Rhodustults ............................................................................ 278

Rupture-resistance classes for mineral soils ......................... 305

S

Salaquerts .............................................................................. 284

Salic horizon ........................................................................... 21

Salicryids ............................................................................... 121

Salids ..................................................................................... 128

Salitorrerts ............................................................................. 286

Salusterts ............................................................................... 291

Sapric soil materials. See Organic soil material.

Sapristels ............................................................................... 150

Saprists .................................................................................. 162

Series control section ............................................................ 308

Series differentiae within a family ........................................ 308

Slickensides ............................................................................. 26

Soil ............................................................................................. 9

Soil depth classes for Histosols and Histels .......................... 308

Soil depth classes for mineral soils ....................................... 305

Soil moisture regimes .............................................................. 32

Aquic ................................................................................... 33

Aridic and torric .................................................................. 33

Udic ..................................................................................... 34

Ustic ..................................................................................... 34

Xeric .................................................................................... 34

Soil temperature classes for Histosols and Histels................ 308
324 Keys to Soil Taxonomy

Soil temperature classes for mineral soils ............................ 304

Soil temperature regimes ........................................................ 34

Cryic .................................................................................... 34

Frigid ................................................................................... 35

Hyperthermic ....................................................................... 35

Isofrigid ............................................................................... 35

Isohyperthermic ................................................................... 35

Isomesic ............................................................................... 35

Isothermic ............................................................................ 35

Mesic ................................................................................... 35

Thermic ............................................................................... 35

Sombric horizon ...................................................................... 21

Sombrihumults ...................................................................... 266

Sombriperox .......................................................................... 238

Sombriudox ........................................................................... 243

Sombriustox ........................................................................... 247

Sphagnofibrists ...................................................................... 160

Spodic horizon ........................................................................ 21

Spodic materials ...................................................................... 26

Spodosols ............................................................................... 249

Strongly contrasting particle-size classes ............................. 299

Subsurface tier ......................................................................... 29

Suffix symbols in horizon designators .................................. 312

Conventions for using letter suffixes ................................ 314

Vertical subdivision ........................................................... 315

Sulfaquents ............................................................................ 133

Sulfaquepts ............................................................................ 170

Sulfidic materials .................................................................... 35

Sulfihemists ........................................................................... 162

Sulfisaprists ........................................................................... 163

Sulfohemists .......................................................................... 162

Sulfosaprists .......................................................................... 163

Sulfudepts .............................................................................. 178

Sulfuric horizon ....................................................................... 35

Surface tier .............................................................................. 29

T

Thermic temperature regime. See Soil temperature

regimes.

Torrands................................................................................... 89

Torrerts .................................................................................. 285

Torriarents ............................................................................. 133

Torric moisture regime. See Soil moisture regimes.

Torrifluvents .......................................................................... 134

Torrifolists ............................................................................. 161

Torriorthents.......................................................................... 140

Torripsamments ..................................................................... 146

Torrox .................................................................................... 238

Transitional and combination horizons ................................ 312

Turbels ................................................................................... 154

U

Udalfs....................................................................................... 54

Udands ..................................................................................... 90

Udarents ................................................................................ 133

Udepts .................................................................................... 172

Uderts .................................................................................... 286

Udic moisture regime. See Soil moisture regimes.

Udifluvents ............................................................................ 136

Udifolists ............................................................................... 161

Udipsamments ....................................................................... 146

Udivitrands .............................................................................. 99

Udolls..................................................................................... 201

Udorthents ............................................................................. 141

Udox ...................................................................................... 239

Udults .................................................................................... 266

Ultisols ................................................................................... 259

Umbraquults .......................................................................... 263

Umbric epipedon ..................................................................... 15

Umbriturbels .......................................................................... 156

Umbrorthels ........................................................................... 153

Ustalfs ...................................................................................... 65

Ustands .................................................................................... 97

Ustarents ................................................................................ 133

Ustepts ................................................................................... 178

Usterts .................................................................................... 288

Ustic moisture regime. See Soil moisture regimes.

Ustifluvents............................................................................ 137

Ustifolists ............................................................................... 161

Ustipsamments ...................................................................... 147

Ustivitrands ............................................................................. 99

Ustolls .................................................................................... 207

Ustorthents ............................................................................ 141

Ustox ...................................................................................... 243

Ustults .................................................................................... 274

V

Vermaqualfs ............................................................................. 50

Vermaquepts .......................................................................... 171

Vermudolls............................................................................. 207

Vermustolls ............................................................................ 222

Vertisols ................................................................................. 281

Vitrands ................................................................................... 99

Vitraquands ............................................................................. 86

Vitricryands ............................................................................. 89

Vitritorrands ............................................................................ 90

Vitrixerands........................................................................... 101
Index 325

W

W layers. See Horizons and layers.

Weatherable minerals .............................................................. 27

X

Xeralfs ..................................................................................... 76

Xerands.................................................................................. 100

Xerarents ............................................................................... 133

Xerepts ................................................................................... 184

Xererts ................................................................................... 291

Xeric moisture regime. See Soil moisture regimes.

Xerofluvents .......................................................................... 138

Xerolls ................................................................................... 222

Xeropsamments ..................................................................... 147

Xerorthents ............................................................................ 143

Xerults ................................................................................... 278
326

S

O

I

D

I

F

D

I

A

I

I

D

E

The Soils That We Classify

Differentiae for Mineral Soils and Organic Soils

A

L

F

A

N

D

A

R

I

E

N

T

G

E

L

H

I

S

I

N

C

M

O

L

O

X

I

S

P

O

U

L

T

V

E

R

F

A

M

H

O

R

Horizons and Characteristics Diagnostic for the Higher Categories

Andisols

Identification of the Taxonomic Class of a Soil

Designations for Horizons and Layers

Family and Series Differentiae and Names

Vertisols

Ultisols

Spodosols

Oxisols

Mollisols

Inceptisols

Histosols

Gelisols

Entisols

Aridisols

Alfisols
327

The date that changes were posted to the PDF file is indicated at the end of each item on

this list of corrections.

Page 16, column 1, umbric epipedon, item 2b: Add the word “moist” after “3 or less” (2/99).

Page 17, column 1, argillic horizon, item 1a(1): Delete “. For example, if the eluvial and illuvial

horizons together are more than 150 cm thick, then the argillic horizon must be 15 cm or more

thick” (2/99).

Page 18, column 1, cambic horizon, item 4: Delete “, is not appreciably darkened (does not

meet the color requirements for a mollic or umbric epipedon, and is not brittle” and add “and

does not have a brittle manner of failure in more than 60 percent of the matrix” (2/99).

Page 21, column 1, salic horizon, item 1, line 2: Add “the water extracted from” after

“dS/m in” (5/00).

Page 26, column 2, definition of spodic materials, item 2a(2): Change “Hue of 5YR” to “Hue of

7.5YR” (2/99).

Page 28, column 2, 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 28, column 2, lower right of diagram: Change “Sapric soil materials” to “Sapric soil

colors” (8/02).

Page 34, column 1, udic moisture regime, line 7: Change “5 oC” to “6 oC” (2/99).

Page 34, ustic moisture regime, column 2, line 8: Change “6 oC” to “5 oC” (2/99).

Page 37, column 2, third full paragraph, last line: Add “and family criteria” (8/02).

Pages 103-128: Change the first letter of the symbols for all Aridisols from “F” to “G” (5/00).

Page 103, column 1, key to suborders, GE, line 2: Delete “that has its upper boundary within

100 cm of the soil surface” (5/00).

Page 112, column 2, Petronodic Ustic Haplocalcids: Change the symbol FEBL to GFBL

(5/00).

Page 116, column 1, Petronodic Ustic Haplocambids: Change the symbol FEDJ to GGDJ

(5/00).

Page 129, column 2, LC, Psamments, line 3: Add “(sandy loam lamellae are permitted)” after “in

all layers” (8/02).

Page 130, column 1, LAD, Psammaquents, line 3: Add “(sandy loam lamellae are permitted)”

after “in all layers” (8/02).

Page 160, column 1, BBCF, Hemic Haplofibrists, line 3: Change “more below the surface tier”

to “more in the control section, below the surface tier” (2/99).

 Keys to Soil Taxonomy

Eighth Edition, 1998

Errata
328 Keys to Soil Taxonomy

Page 160, column 2, BBBF, Hemic Spagnofibrists, line 3: Change “more below the surface tier”

to “more in the control section, below the surface tier” (2/99).

Page 162, column 1, BDEF, Fibric Haplohemists, lines 2 and 3: Change “more below the surface

tier” to “more in the control section, below the surface tier” (2/99).

Page 163, column 2, BCDG, Hemic Haplosaprists, line 3: Change “more below the surface tier”

to “more in the control section, below the surface tier” (2/99).

Page 185, column 2: Change the heading “Dystrxerepts” to “Dystroxerepts” (2/99).

Page 213, column 2, 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 259, column 2, HAC, Albaquults, line 3: Change “(low or very low)” to “(moderately low

or lower)” (8/02).

Page 268, column 1, HCGE, Aquic Arenic Hapludults, item 2, line 2: Change “concentrations”

to “depletions” (2/99).

Page 301, column 2, and page 302, 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 304, 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).

Page 305, column 1, key to soil temperature classes, item B, line 2: Change “5 oC” to “6 oC”

(2/99).

Page 313, column 2, accumulation of jarosite, line 4: Change “2.5YR” to “2.5Y” (2/99).