United States

Department of Agriculture

Keys to

Soil Taxonomy

Twelfth Edition, 2014

Keys to Soil Taxonomy

By Soil Survey Staff

United States Department of Agriculture

Natural Resources Conservation Service

Twelfth Edition, 2014
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ii
Cover Images (clockwise from top left)

A soil profile from the Laguardia series located in Soundview Park, Bronx, New York 

City, USA. The soil formed in a thick deposit of human-transported material that contains a 

high content of cohesive, persistent artifacts such as brick, concrete, and metal. It has an 

anthropic epipedon and an artifactic human-altered and human-transported material family 

class, and classifies as an Anthropic Udorthent. This profile was shown on the field tour for 

the 2009 SUITMA Conference, New York City. (SUITMA, or Soils of Urban, Industrial, 

Transportation, and Mining Areas, is a working group of the International Union of Soil 

Sciences, or IUSS.) Photo by Richard K. Shaw, Soil Scientist, Natural Resources 

Conservation Service, Somerset, New Jersey.

Seasonally flooded cropland of rice and vegetable paddies located in Dhulikhel, Nepal. The 

soils on these paddies have anthric saturation and will qualify in Anthraquic subroups. The 

paddies display anthropogenic microfeatures, namely, the hillslope terraces which were 

contoured to the slope of the land. Deposits of human-transported material are thicker on the 

front portion of each terrace and thinner on the back portions. Photo by John M. Galbraith, 

Associate Professor of Soil Science, Virginia Polytechnic Institute and State University, 

Blacksburg, Virginia, USA.

A soil profile of an Anthroportic Udorthent in a dredgic human-altered and humantransported material family class, located near Stony Creek, Virginia, USA. This soil has an 

irregular decrease in carbon with depth which is unrelated to natural processes such as alluvial 

deposition. It has two distinct deposits of human-transported material. The upper deposit was 

moved by bulldozers and contains mechanically detached and re-oriented pieces of diagnostic 

horizons. Separating the two deposits is a dark-colored horizon with a high content of wood 

ash and charcoal. The lower deposit consists of dredged spoil material with a high content of 

sand and large red bodies of clay. Photo by W. Lee Daniels, Professor of Environmental 

Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA.

A soil profile of an Anthroportic Udorthent in a dredgic human-altered and humantransported material family class, near Stony Creek, Virginia, USA. This soil formed in two 

deposits of human-transported material. The upper deposit was moved by machinery and 

contains mechanically detached and re-oriented pieces of diagnostic horizons in humantransported material; the lower deposit was hydraulically dredged. Photo by John M. 

Galbraith, Associate Professor of Soil Science, Virginia Polytechnic Institute and State 

University, Blacksburg, Virginia, USA.

A soil profile of an Anhydritic Aquisalid from the United Arab Emirates (UAE). This soil 

formed in alluvium on a coastal sabkha. Capillary rise of ground water, which has a high 

content of soluble salts and contains calcium sulfate, aids the accumulation of mobile minerals 

in the soil. An anhydritic horizon and a salic horizon occur together in the zone between the 

soil surface and a depth of about 60 centimeters. Photo by Shabbir A. Shahid, Soil Correlator/

Lead Soil Taxonomist, International Center for Biosaline Agriculture, Dubai, UAE.

A soil profile of an Anthrodensic Udorthent in a spolic human-altered and humantransported material family class, near Stony Creek, Virginia, USA. This soil formed in 

deposits of human-transported material which were compacted by machinery. A densic 

contact occurs at a depth of 8 cm along with an irregular decrease in organic matter 

content with mechanically detached and re-oriented pieces of diagnostic horizons. Photo by 

John M. Galbraith, Associate Professor of Soil Science, Virginia Polytechnic Institute and 

State University, Blacksburg, Virginia, USA.

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v

Table of Contents

Foreword...................................................................................................................................vii

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

Chapter 2: Differentiae for Mineral Soils and Organic Soils..................................................3

Chapter 3: Horizons and Characteristics Diagnostic for the Higher Categories.....................7

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

Chapter 5: Alfisols ................................................................................................................43

Chapter 6: Andisols...............................................................................................................87

Chapter 7: Aridisols............................................................................................................107

Chapter 8: Entisols..............................................................................................................135

Chapter 9: Gelisols..............................................................................................................157

Chapter 10: Histosols............................................................................................................167

Chapter 11: Inceptisols..........................................................................................................173

Chapter 12: Mollisols............................................................................................................211

Chapter 13: Oxisols...............................................................................................................257

Chapter 14: Spodosols ..........................................................................................................273

Chapter 15: Ultisols ..............................................................................................................283

Chapter 16: Vertisols.............................................................................................................305

Chapter 17: Family and Series Differentiae and Names.......................................................317

Chapter 18: Designations for Horizons and Layers..............................................................335

Appendix.................................................................................................................................343

Index .......................................................................................................................................353
 
vii

Foreword

This publication, Keys to Soil Taxonomy, Twelfth Edition, 2014, coincides with the 20th

World Congress of Soil Science, to be held on Jeju Island, Korea in June 2014. The 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 

soil taxonomy with recent changes in the classification system. The twelfth edition of the 

Keys to Soil Taxonomy incorporates all changes approved since the publication in 1999 of 

the second edition of Soil Taxonomy: A Basic System of Soil Classification for Making and 

Interpreting Soil Surveys. 

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. The authors plan to continue issuing updated editions 

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

One change in this edition is recognizing the occurrence of anhydrite (CaSO4 ) in soils 

with the addition of a new diagnostic horizon, a new mineralogy class, and new Anhydritic 

subgroups for use in soil survey. These are significant improvements to soil taxonomy 

which resulted from international collaboration with soil scientists of the United Arab 

Emirates, where the soils with anhydrite were discovered. Pedologists in Argentina have 

also contributed to this edition with amendments to improve classification of the Mollisols 

of the Pampean region and to recognize the abrupt textural change in more soils having this 

important genetic characteristic.

Another major change is the incorporation of many of the final recommendations of 

the International Committee on Anthropogenic Soils (ICOMANTH). This international 

committee began in 1995 under the chairmanship of Dr. Ray Bryant and has continued 

under Dr. John Galbraith of Virginia Polytechnic Institute and State University. Some of 

the recommendations of ICOMANTH broadly expand the use of geomorphic positions as 

taxonomic criteria for soils which occur on artificial (i.e., anthropogenic) landforms and 

microfeatures. One of the attributes of soil taxonomy states that the differentiae selected 

for classification are soil properties. Characteristics of a site, such as geomorphic position, 

are not used as criteria for classifying natural, undisturbed soils. Geomorphic position had 

previously been used only in the required characteristics of the plaggen epipedon; now, 

its appropriateness for classifying other human-altered and human-transported soils is 

being tested. In addition, the definition of the anthropic epipedon has been expanded and 

simplified, two major materials have been defined, higher taxa have been consolidated at 

the subgroup category under seven defined extragrades, and a new family category class has 

been introduced to convey information on the safety and origin of human-altered and humantransported material. Dr. Galbraith’s diligent efforts chairing ICOMANTH have yielded 

amendments which have improved the morphologic description and taxonomic classification 

of human-altered and human-transported soils as well as the recognition of anthropogenic 

earth-surface features.

Since it was first published 39 years ago, Soil Taxonomy: A Basic System of Soil 

Classification for Making and Interpreting Soil Surveys has been used to support soil survey 

efforts in many countries around the world. It has been translated into several languages. 

Soil scientists from many nations have contributed significantly to the development of soil 

taxonomy. The Natural Resources Conservation Service (NRCS) Soil Science Division
viii

encourages the further use of soil taxonomy internationally and anticipates future 

collaborations with the international soil science community in order to continually improve 

this classification system. I hope that continuing communication and collaboration will result 

in a truly universal soil classification system. 

David W. Smith

Soil Science Division Director

Natural Resources Conservation Service
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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, in deep water, or on the barren 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 

(Soil Survey Staff, 1999). This definition is expanded from the 

previous version of Soil Taxonomy (Soil Survey Staff, 1975) 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 

either 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 about 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 

the practicality of soil survey, 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) and noncemented 

bedrocks (some densic materials, defined later) have been 

described below the lower boundary of soil and used to 

differentiate soil series (series control section, defined in chapter 

17). This is permissible even though the paralithic materials 

below a paralithic contact are not considered soil in the true 

sense. In areas where soil has thin, pedogenically 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 

genetic horizons, although the presence or absence of genetic 

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 

or in cracks of exposed bedrock (i.e., rock outcrop), but trees 

and rock outcrop are regarded as nonsoil. 

Soil has many temporal properties that fluctuate hourly, 

daily, and seasonally. It may be alternately cold, warm, dry, 

or moist. Biological activity is slowed or stopped if the soil 

becomes too cold or too dry. The soil receives additions of 

fresh, undecomposed organic matter when leaves fall or grasses 

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

matter and carbon-nitrogen ratio, numbers of microorganisms, 

The Soils That We Classify

CHAPTER 1
2

soil fauna, temperature, and moisture status 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 a sequence of genetic horizons in a pedon 

that is covered with a surface mantle of new soil material 

(defined below) that is 50 cm or more thick, a plaggen epipedon 

(defined in chapter 3), or a layer of human-transported material 

(defined in chapter 3) that is 50 cm or more thick. The rules for 

the taxonomic classification of pedons that include a buried soil 

are given in chapter 4.

Surface Mantle of New Soil Material

A surface mantle of new soil material is a layer of naturally 

deposited mineral material that 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 in chapter 3. 

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

fails the requirements for all diagnostic horizons, as defined 

later, overlying a genetic horizon sequence that can be clearly 

identified as 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. A surface mantle of new soil material 

that does not have the required thickness specified for buried 

soils can be used to establish a phase of a soil series, or even 

another soil series, if the mantle affects use and management of 

the soil.

Literature Cited

Soil Survey Staff. 1975. Soil Taxonomy: A Basic System of 

Soil Classification for Making and Interpreting Soil Surveys. 

Soil Conservation Service. U.S. Department of Agriculture 

Handbook 436.

Soil Survey Staff. 1999. Soil Taxonomy: A Basic System of 

Soil Classification for Making and Interpreting Soil Surveys. 

2nd edition. Natural Resources Conservation Service. U.S. 

Department of Agriculture Handbook 436.
3

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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 fineearth 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 shortrange-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 and Histels.

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 soil surface 

(defined below) whether that is a horizon composed of mineral * Mineral soils include all soils except the suborder Histels and the order Histosols.

Differentiae for Mineral Soils* and Organic Soils

CHAPTER 2
4 Keys to Soil Taxonomy

soil material or one composed of organic soil material. This 

determination is different for buried soils as defined in chapter 

1. Thus, any horizon at the surface, designated with capital letter 

O, is considered an organic horizon if it meets the requirements 

of organic soil material, and its thickness is added to that of 

any other organic horizons to determine the total thickness of 

organic soil material. Plant materials at the soil surface must 

be at least slightly decomposed to be considered part of an 

O horizon. Undecomposed plant litter is excluded from the 

concept of O horizons.

Soil Surface

The term “soil surface” is based on the upper limit of soil. 

The upper limit of soil is the boundary between soil and either 

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

begun to decompose. The soil surface is a horizon composed of 

either mineral soil material or organic soil material.

Mineral Soil Surface

The term “mineral soil surface” is the datum or horizontal 

plane used for measurements of depth or thickness in mineral 

soils (defined below). The mineral soil surface has two forms. 

It is either a soil surface composed of mineral soil material 

or it is the boundary between a horizon composed of organic 

soil material and a horizon composed of mineral soil material. 

The upper boundary of the first horizon, encountered at 

or below the soil surface that is composed of mineral soil 

material, is considered the mineral soil surface. For example, 

a upland mineral soil with an 5-cm-thick Oi horizon within a 

horizon sequence of Oi-A-E-Bt-C has two surfaces for depth 

measurements. There is a soil surface at the boundary between 

either air or undecomposed plant material and the Oi horizon 

(at a depth of 0 cm). There is also a mineral soil surface at the 

boundary between the Oi and A horizons (at a depth of 5 cm).

Definition of Mineral Soils

Mineral soils are soils that have either:

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

following:

a. Overlie cindery, fragmental, or pumiceous materials

and/or have voids† 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 threefourths (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 interstices† and directly below these materials 

have a densic, lithic, or paralithic contact; or

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

pumiceous materials, total 40 cm or more between the soil 

surface and a depth of 50 cm; or

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

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

no mineral horizons or have mineral horizons with a total 

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more 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-

† Materials that meet the definition of the cindery, fragmental, or pumiceous substitute 

for particle-size class but have more than 10 percent, by volume, voids that are filled with 

organic soil materials are considered to be organic soil materials.
Differentiae for Mineral Soils and Organic Soils 5

D

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

of 0.1 g/cm3 or more; or

e. Are 80 percent or more of the 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 or Histel) 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.

7

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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. The “required characteristics” for horizons or 

features, however, are arranged as a key. 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. The exclusions are stated in the 

horizon definitions.

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 (5 mm or less thick) 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 commonly 

forms in deposits of tephra and can receive fresh deposits of 

volcanic 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 fine 

stratifications (5 mm or less thick) or an Ap horizon directly 

underlain by such stratified material is not included in the 

concept of the epipedon because time has not been sufficient 

for soil-forming processes to erase these transient marks of 

deposition and for diagnostic and accessory properties to 

develop.

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

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

matter extends from the soil surface into or through the B 

horizon.

Anthropic Epipedon

The anthropic epipedon forms in human-altered or humantransported material (defined below). These epipedons 

form in soils which occur on anthropogenic landforms and 

microfeatures or which are higher than the adjacent soils by as 

much as or more than the thickness of the anthropic epipedon. 

They may also occur in excavated areas. Most anthropic 

epipedons contain artifacts other than those associated with 

agricultural practices (e.g., quicklime) and litter discarded by 

humans (e.g., aluminum cans). Anthropic epipedons may have 

an elevated phosphorus content from human additions of food 

debris (e.g., bones), compost, or manure, although a precise 

value is not required. Although anthropic epipedons formed 

at the soil surface, they may now be buried. Most anthropic 

epipedons occur in soils of gardens, middens (Hester et al., 

1975), and urban areas, and most also meet the definition of 

another diagnostic mineral epipedon or subsurface horizon.

Required Characteristics

The anthropic epipedon consists of mineral soil material that 

shows evidence of the purposeful alteration of soil properties or 

of earth-surface features by human activity. The field evidence 

Horizons and Characteristics Diagnostic for the Higher Categories

CHAPTER 3
8 Keys to Soil Taxonomy

of alteration is significant and excludes agricultural practices 

such as shallow plowing or addition of amendments, such as 

lime or fertilizer. 

The anthropic epipedon includes eluvial horizons that are at 

or near the soil surface, and it extends to the base of horizons 

that meet all the criteria shown below or it extends to the top of 

the first underlying diagnostic illuvial horizon (defined below 

as an argillic, kandic, natric, or spodic horizon). The anthropic 

epipedon meets all of the following:

1. When dry, has structural units with a diameter of 30 cm or 

less; and

2. Has rock structure, including fine stratifications (5 mm or 

less thick), in less than one-half of the volume of all parts; and

3. Formed in human-altered or human-transported material 

(defined below) on an anthropogenic landform or microfeature 

(defined below); and either:

a. Directly overlies mine or dredged spoil material which 

has rock structure, a root-limiting layer, or a lithologic 

discontinuity with horizons that are not derived from humanaltered or human-transported material (defined below); or

b. Has one or more of the following throughout:

(1) Artifacts, other than agricultural amendments 

(e.g., quicklime) and litter discarded by humans (e.g., 

aluminum cans); or

(2) Midden material (i.e., eating and cooking waste and 

associated charred products); or

(3) Anthraquic conditions; and

4. Has a minimum thickness that is either:

a. The entire thickness of the soil above a root-limiting 

layer (defined in chapter 17) if one occurs within 25 cm of 

the soil surface; or

b. 25 cm; and

5. Has an n value (defined below) of less than 0.7.

Folistic Epipedon

Required Characteristics

The folistic epipedon is 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 g/cm3

; or

b. Is 15 cm or more thick; or

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

an organic-carbon content (by weight) of:

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

percent or more clay; or

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

clay; or

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

the mineral fraction contains less than 60 percent clay.

Most folistic epipedons consist of organic soil material 

(defined in chapter 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 g/cm3; 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
Horizons and Characteristics Diagnostic for the Higher Categories 9

D

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A

* The concept of dominant color is defined in the Soil Survey Manual (Soil Survey 

Division Staff, 1993).

b. A color value of 2.5 or less, moist, and chroma of 2 or 

less throughout; and

c. A melanic index (defined in the appendix) of 1.70 or less 

throughout; and

d. 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 material and, 

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, a petrocalcic horizon, or a duripan (all defined below) 

is less than 18 cm, 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 stratifications (5 mm or less 

thick), in less than one-half of the volume of all parts; and

3. One of the following:

a. Both of the following:

(1) Dominant color* with a value of 3 or less, moist, 

and of 5 or less, dry; and

(2) Dominant color with chroma of 3 or less, moist; 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 of 5 or 

less, moist; and

4. A base saturation (by NH4

OAc) of 50 percent or more 

throughout; and

5. An organic-carbon content of:

a. 2.5 percent or more if the epipedon has a color value of 4 

or 5, moist; or

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

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

1 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 the epipedon does not meet the 

qualifications in 5-a or 5-b above; and

6. The minimum thickness of the epipedon is as follows:

a. 25 cm if:

(1) The texture class of the epipedon is loamy fine sand 

or coarser throughout; or

(2) There are no underlying diagnostic horizons 

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

underlying materials decreases irregularly with increasing 

depth; or

(3) Any of the following, if present, are 75 cm or more 

below the mineral soil surface: 

(a) The upper boundary of the shallowest of any 

identifiable secondary carbonates or a calcic horizon, 

petrocalcic horizon, duripan, or fragipan (defined 

below); and/or

(b) The lower boundary of the deepest of an argillic, 

cambic, natric, oxic, or spodic horizon; or

b. 10 cm if the epipedon has a texture class finer than 

loamy fine sand (when mixed) and it is directly above a 

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

duripan; or

c. 18 to 25 cm and the thickness is one-third or more of the 

total thickness between the mineral soil surface and:

(1) The upper boundary of the shallowest of any 

identifiable secondary carbonates or a calcic horizon, 

petrocalcic horizon, duripan, or fragipan; and/or

(2) The lower boundary of the deepest of an argillic, 

cambic, natric, oxic, or spodic horizon; or

d. 18 cm if none of the above conditions apply; 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 below the soil surface is 5 oC or 

higher, if the soil is not irrigated; and

8. 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 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 
10 Keys to Soil Taxonomy

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 thick, human-made mineral 

surface layer that has been produced by long-continued 

manuring. A plaggen epipedon can be identified by several 

means. Commonly, it contains artifacts, such as brick and 

potsherds, throughout its thickness. There may be earthy 

fragments (i.e., clods) 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 at least in its 

lower part. It may also contain remnants of thin stratified beds 

of sand that were probably produced on the soil surface by 

beating rains and were later buried. A map unit delineation of 

soils with plaggen epipedons would tend to occur on straightsided anthropogenic landforms that are higher than adjacent 

land surfaces by as much as or more than the thickness of the 

plaggen epipedon.

Required Characteristics

The plaggen epipedon consists of mineral soil material and 

meets all of the following:

1. It occurs in soils on locally raised landforms and contains 

one or both of the following:

a. Artifacts, other than agricultural amendments (e.g., 

quicklime) and litter discarded by humans (e.g., aluminum 

cans); or

b. Spade marks below a depth of 30 cm; and

2. It has colors with a value of 4 or less, moist, 5 or less, dry, 

and chroma of 2 or less; and

3. It has an organic-carbon content of 0.6 percent or more; and

4. It has a thickness of 50 cm or more of human-transported 

material (defined below); and

5. 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 below the soil surface is 5 o

C or 

higher, if the soil is not irrigated.

Umbric Epipedon

Required Characteristics

The umbric epipedon consists of mineral soil material and, 

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, a petrocalcic horizon, or a duripan (all defined below) 

is less than 18 cm, 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 stratifications (5 mm or less 

thick), in less than one-half of the volume of all parts; and

3. Both of the following:

a. Dominant color* with a value of 3 or less, moist, and of 

5 or less, dry; and

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

4. A base saturation (by NH4OAc) of less than 50 percent in 

some or all parts; and

5. An organic-carbon content of:

a. 0.6 percent (absolute) more than that of the C horizon 

(if one occurs) if the umbric epipedon has a color value less 

than 1 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 the epipedon does not meet the 

qualifications in 5-a above; and

6. The minimum thickness of the epipedon is as follows:

a. 25 cm if:

(1) The texture class of the epipedon is loamy fine sand 

or coarser throughout; or

(2) There are no underlying diagnostic horizons 

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

underlying materials decreases irregularly with increasing 

depth; or

(3) Any of the following, if present, are 75 cm or more 

below the mineral soil surface: 

(a) The upper boundary of the shallowest of any 

identifiable secondary carbonates or a calcic horizon, 

petrocalcic horizon, duripan, or fragipan (defined 

below); and/or
Horizons and Characteristics Diagnostic for the Higher Categories 11

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(b) The lower boundary of the deepest of an argillic, 

cambic, natric, oxic, or spodic horizon; or

b. 10 cm if the epipedon has a texture class finer than 

loamy fine sand (when mixed) and it is directly above a 

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

duripan; or

c. 18 to 25 cm and the thickness is one-third or more of the 

total thickness between the mineral soil surface and:

(1) The upper boundary of the shallowest of any 

identifiable secondary carbonates or a calcic horizon, 

petrocalcic horizon, duripan, or fragipan; and/or

(2) The lower boundary of the deepest of an argillic, 

cambic, natric, oxic, or spodic horizon; or

d. 18 cm if none of the above conditions apply; 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 below the soil surface is 5 oC or 

higher, if the soil is not irrigated; and

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

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

marks, and locally raised landforms that are characteristics 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 are composed of mineral soil material. 

They may be exposed at the surface by truncation of the soil. 

Some of these horizons are designated as B horizons by many, 

but not all, pedologists and others are generally designated as 

parts of A or E horizons.

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 a

thickness of 10 cm or more, and either:

1. 5 percent or more (by volume) wormholes, including 

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

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

2. 5 percent or more (by volume) lamellae that have a 

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

moist, and chroma of 2 or less.

Albic Horizon

The albic horizon is an eluvial horizon, 1 cm or more 

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

(defined below). It generally occurs below an A horizon but 

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

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

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

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

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

a fragipan. It may lie between a mollic epipedon and an argillic 

or natric horizon or between a cambic horizon and an argillic, 

kandic, or natric horizon or a fragipan. The albic horizon may 

separate horizons that, if they were together, would meet the 

requirements for a mollic epipedon. It may separate lamellae 

that together meet the requirements for an argillic horizon. 

These lamellae are not considered to be part of the albic 

horizon.

Anhydritic Horizon

The anhydritic horizon is a horizon in which anhydrite 

has accumulated through neoformation or transformation to a 

significant extent. It typically occurs as a subsurface horizon. It 

commonly occurs in conjunction with a salic horizon (defined 

below).

Required Characteristics

The anhydritic horizon meets all of the following 

requirements:

1. Is 15 cm or more thick; and

2. Is 5 percent or more (by weight) anhydrite; and

3. Has hue of 5Y, chroma (moist and dry) of 1 or 2, and value 

of 7 or 8; and

4. Has a product of thickness, in cm, multiplied by the 

anhydrite content (percent by weight) of 150 or more (thus, a 

horizon 30 cm thick that is 5 percent anhydrite qualifies as an 

anhydritic horizon); and

5. Has anhydrite as the predominant calcium sulfate mineral 

with gypsum either absent or present only in minor amounts.

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:
12 Keys to Soil Taxonomy

† Particle-size classes are used in this required characteristic as a convenient proxy for 

many possible combinations of USDA texture class and texture modifier and do not imply 

that the soil meeting this option for the diagnostic horizon also meets the particle-size class 

criteria in the family classification.

a. One of the following:

(1) If the argillic horizon meets the particle-size class 

criteria for coarse-loamy, fine-loamy, coarse-silty, finesilty, 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; or

(2) If the argillic horizon meets the sandy or sandyskeletal particle-size criteria, 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:

1. Is 15 cm or more thick; and

2. Has one or more of the following:

a. 15 percent or more (by weight, fine-earth fraction) 

CaCO3

 equivalent, and its CaCO3 equivalent is 5 percent or 

more (absolute) higher than that of an underlying horizon; or

b. 15 percent or more (by weight, fine-earth fraction) 

CaCO3 equivalent and 5 percent or more (by volume) 

identifiable secondary carbonates; or

c. 5 percent or more (by weight, fine-earth fraction) 

calcium carbonate equivalent and:

(1) Has less than 18 percent clay in the fine-earth 

fraction; and

(2) Meets the criteria for a sandy, sandy-skeletal, coarseloamy, or loamy-skeletal particle-size class†

 (defined in 

chapter 17); and

(3) Has 5 percent or more (by volume) identifiable 

secondary carbonates or a calcium carbonate equivalent 

(by weight, fine-earth fraction) that is 5 percent or more 

(absolute) higher than that of an underlying horizon; and

3. Is not cemented or indurated in any part by carbonates, with 

or without other cementing agents, or is cemented in some part 

and the cemented part satisfies one of the following:

a. It is characterized by so much lateral discontinuity that 

roots can penetrate through noncemented zones or along 

vertical fractures with a horizontal spacing of less than 10 

cm; or

b. The cemented layer is less than 1 cm thick and consists 

of a laminar cap underlain by a lithic or paralithic contact; or

c. The cemented layer is less than 10 cm thick.

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:
Horizons and Characteristics Diagnostic for the Higher Categories 13

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1. Has a texture class 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, 

including fine stratifications (5 mm or less thick), 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 neutral colors with no 

hue (N) and zero chroma; 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, including fine 

stratifications (5 mm or less thick), in more than one-half 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, salic, spodic, or 

sulfuric 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

A duripan is a silica-cemented subsurface horizon with or 

without auxiliary cementing agents. It can occur in conjunction 

with a petrocalcic horizon.

Required Characteristics

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 layer 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; and

6. The layer is not effervescent (in dilute HCl).

Glossic Horizon

The glossic (Gr. glossa, tongue) horizon develops as a result 

of the degradation of an argillic, kandic, or natric horizon from 

which clay and free iron oxides are removed. 

Required Characteristics

The glossic horizon is 5 cm or more thick and consists of:

1. An eluvial part (albic materials, defined below), which 

constitutes 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 a horizon in which gypsum has 

accumulated or been transformed to a significant extent. It 
14 Keys to Soil Taxonomy

typically occurs as a subsurface horizon, but it may occur at the 

surface in some soils.

Required Characteristics

A gypsic horizon meets all of the following requirements:

1. Is 15 cm or more thick; and

2. Is not cemented by gypsum, with or without other 

cementing agents; is cemented and the cemented parts are 

less than 5 mm thick; or is cemented but, because of lateral 

discontinuity, roots can penetrate along vertical fractures with a 

horizontal spacing of less than 10 cm; and

3. Is 5 percent or more (by weight) gypsum and has 1 percent 

or more (by volume) visible secondary gypsum that has either 

accumulated or been transformed; and

4. Has a product of thickness, in cm, multiplied by the 

gypsum content (percent by weight) 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 any cementation is as described in 2 above. 

Kandic Horizon

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 is increasing with depth within a vertical distance of 

15 cm and is either:

(1) 4 percent or more (absolute) higher than that in the 

overlying 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 

overlying 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 

overlying 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 upper 100 cm has a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand throughout; or

(2) Within 100 cm from the mineral soil surface if the 

clay content in the fine-earth fraction of the overlying 

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 class 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

A natric horizon is an illuvial horizon that is normally 

present in the subsurface and has a significantly higher 

percentage of silicate clay than the overlying horizons. It shows 

evidence of clay illuviation that has been accelerated by the 

dispersive properties of sodium.

Required Characteristics

The natric horizon:

1. Meets one of the following thickness requirements:

a. If the horizon meets the particle-size class criteria 

for 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 onetenth as thick as the sum of the thickness of all overlying 

horizons, whichever is greater; or

b. If the horizon meets sandy or sandy-skeletal particle-size 

class criteria, it must be at least 15 cm thick; or
Horizons and Characteristics Diagnostic for the Higher Categories 15

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c. If the 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

2. Has evidence of clay illuviation in at least one of the 

following forms:

a. Oriented clay bridging the sand grains; or

b. Clay films lining pores; or

c. Clay films on both vertical and horizontal surfaces of 

peds; or

d. Thin sections with oriented clay bodies that are more 

than 1 percent of the section; or

e. 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

3. 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 horizon, 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 illuvial 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 illuvial 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 illuvial horizon must contain 

at least 8 percent (absolute) more clay (42 percent versus 50 

percent, for example); and

4. Has either:

a. Columnar or prismatic structure in some part (generally 

the upper part), which may part to blocky structure; 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

5. Has 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 extractable acidity (at pH 8.2) in one or more 

horizons within 40 cm of its upper boundary and 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 (defined below); and

2. Is in a layer that is 50 percent or more cemented; and

3. Is 25 mm or more thick.

Continuous ortstein is 90 percent or more cemented and has 

lateral continuity. Because of this continuity, roots can penetrate 

only along vertical fractures with a horizontal spacing of 10 cm 

or more.

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 class of sandy loam or finer in the fine-earth 

fraction; and

3. Less than 10 percent weatherable minerals in the 0.05 to 0.2 

mm 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. Within a vertical distance of 15 cm or more from the upper 

boundary (i.e, diffuse), 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 overlying 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 overlying 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 overlying 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 
16 Keys to Soil Taxonomy

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 a horizon in which visible 

secondary gypsum has accumulated or has been transformed. 

The horizon is cemented (i.e., extremely weakly cemented 

through indurated cementation classes), and the cementation is 

both laterally continuous and root limiting, even when the soil is 

moist. The horizon typically occurs as a subsurface horizon, but 

it may occur at the surface in some soils.

Required Characteristics

A petrogypsic horizon meets all of the following 

requirements:

1. Is cemented or indurated by gypsum, with or without other 

cementing agents; and

2. Because of lateral continuity, can be penetrated by roots 

only along vertical fractures with a horizontal spacing of 10 cm 

or more; and

3. Is 5 mm or more thick; and

4. Is 40 percent or more (by weight) gypsum.

Placic Horizon

The placic (Gr. base of plax, flat stone; meaning a thin 

cemented pan) horizon 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 (defined below), 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 (F. sombre, dark) horizon 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 
Horizons and Characteristics Diagnostic for the Higher Categories 17

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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.

Diagnostic Soil Characteristics for Mineral 

Soils

Diagnostic soil characteristics are features of the soil that 

are used in various places in the keys or in the definitions of 

diagnostic horizons.

Abrupt Textural Change

An abrupt textural change is a specific kind of change 

that may occur between an epipedon composed of mineral 

soil material or an eluvial horizon and an underlying argillic, 

glossic, kandic, or natric horizon. It is characterized by a 

considerable increase in clay content within a very short vertical 

distance in the zone of contact.

In soils that have an abrupt textural change, there normally 

is no transitional horizon between a mineral epipedon or 

an eluvial horizon and an argillic, glossic, kandic, or natric 

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) into parts of an argillic, 

kandic, or natric 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.

Required Characteristics

An abrupt textural change meets both of the following 

requirements:

1. The noncarbonate clay content in the fine-earth fraction of 

the argillic, glossic, kandic, or natric horizon is at least 8 percent 

(by weight); and

2. The noncarbonate clay content in the fine-earth fraction of 

the argillic, glossic, kandic, or natric horizon must either:

a. Double within a vertical distance of 7.5 cm or less if 

the clay content, in the fine-earth fraction of the epipedon 

composed of mineral soil material or the eluvial horizon, is 

less than 20 percent (e.g., an increase from 4 to 8 percent); or

b. Increase by 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 

horizon is 2 times or more the amount contained in the 

overlying epipedon composed of mineral soil material or the 

eluvial horizon.

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 of 3, moist, and 6 or more, dry; or

b. A color value of 4 or more, moist, and 5 or more, dry; or

2. Chroma of 3 or less; and either

a. A color value of 6 or more, moist; or

b. A color value of 7 or more, dry; 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 commonly form during weathering of 

tephra or other parent materials containing a significant content 

of volcanic glass. Soils that are in cool, humid climates and 

have abundant organic carbon, however, may develop andic soil 

properties without the influence of volcanic glass. A suite of 
18 Keys to Soil Taxonomy

glass and glass-coated minerals rich in silica is termed volcanic 

glass in this taxonomy. These minerals are relatively soluble 

and undergo fairly rapid transformation when the soils are 

moist. Andic soil properties represent a stage in transition where 

weathering and transformation of primary alumino-silicates 

(e.g., volcanic glass) have proceeded only to the point of the 

formation of short-range-order materials, such as allophane, 

imogolite, and ferrihydrite, or of metal-humus complexes. The 

concept of andic soil properties includes moderately weathered 

soil material, rich in short-range-order materials or metalhumus complexes, or both, with or without volcanic glass 

(required characteristic 2) and weakly weathered soil, less rich 

in short-range-order materials with volcanic glass (required 

characteristic 3). 

Relative amounts of allophane, imogolite, ferrihydrite, or 

metal-humus complexes in the colloidal fraction are inferred 

from laboratory analyses of aluminum, iron, and silica extracted 

by ammonium oxalate, and from phosphate retention. Soil 

scientists may use smeariness or pH in 1N sodium fluoride 

(NaF) as field indicators of andic soil properties. Volcanic 

glass content is the percent volcanic glass (by grain count) in 

the coarse silt and sand (0.02 to 2.0 mm) fraction. Most soil 

materials with andic soil properties consist of mineral soil 

materials, but some are organic soil materials with less than 25 

percent organic carbon.

Required Characteristics

Soil materials with andic soil properties must have a fineearth fraction that meets the following requirements:

1. Less than 25 percent organic carbon (by weight) and one or 

both of the following: 

2. All of the following:

a. Bulk density, measured at 33 kPa water retention, of 

0.90 g/cm3 or less; and

b. Phosphate retention of 85 percent or more; and

c. Al plus 1⁄2 Fe content (by ammonium oxalate) equal to 

2.0 percent or more; or

3. All of the following:

a. 30 percent or more of the fine-earth fraction is 0.02 to 

2.0 mm in size; and 

b. Phosphate retention of 25 percent or more; and

c. Al plus 1⁄2 Fe content (by ammonium oxalate) equal to 

0.4 percent or more; and

d. Volcanic glass content of 5 percent or more; and 

e. [(Al plus 1⁄2 Fe content, percent) times (15.625)] + 

[volcanic glass content, percent] = 36.25 or more.

The shaded area in figure 1 illustrates criteria 3c, 3d, and 3e.

Anhydrous Conditions

Anhydrous (Gr. anydros, waterless) conditions refer to 

the moisture condition of soils in very cold deserts and other 

areas with permafrost (often dry permafrost). These soils 

typically have low precipitation (usually less than 50 mm 

water equivalent per year) and a moisture content of less than 3 

percent by weight. Anhydrous soil conditions are similar to the 

aridic (torric) soil moisture regimes (defined below), except that 

the soil temperature at 50 cm is less than 5 o

C throughout the 

year in the soil layers with these conditions.

Required Characteristics

Soils with anhydrous conditions have a mean annual soil 

temperature of 0 oC or colder. The layer from 10 to 70 cm 

below the soil surface has a soil temperature of less than 5 oC 

throughout the year and this layer:

1. Includes no ice-impregnated permafrost; and

2. Is dry (water held at 1500 kPa or more) in one-half or more 

of the soil for one-half or more of the time the layer has a soil 

temperature above 0 o

C; or

Figure 1.—Soils that are plotted in the shaded area meet the andic 

soil properties criteria c, d, and e under item 3 of the required 

characteristics. To qualify as soils with andic properties, the soils 

must also meet the listed requirements for organic-carbon content, 

phosphate retention, and particle-size distribution.
Horizons and Characteristics Diagnostic for the Higher Categories 19

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3. Has a rupture-resistance class of loose to slightly hard 

throughout when the soil temperature is 0 oC or colder, except 

where a cemented pedogenic horizon occurs.

Coefficient of Linear Extensibility (COLE)

The coefficient of linear extensibility (COLE) is the ratio 

of the difference between the moist length and dry length of a 

clod to its dry length. It is (Lm - Ld)/Ld, where Lm is the length 

at 33 kPa tension and Ld is the length when dry. COLE can be 

calculated from the differences in bulk density of the clod when 

moist and when dry. An estimate of COLE can be calculated in 

the field by measuring the distance between two pins in a clod 

of undisturbed soil at field capacity and again after the clod has 

dried. COLE does not apply if the shrinkage is irreversible.

Durinodes

Durinodes (L. durus, hard, and nodus, knot) are weakly 

cemented to indurated nodules or concretions 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. Some 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.

Free Carbonates

The term “free carbonates” is used in the definitions of a 

number of taxa, is used as a criterion for the isotic mineralogy 

class, and is mentioned in the discussion of chemical analyses 

in the appendix. It refers to soil carbonates that are uncoated 

or unbound and that effervesce visibly or audibly when treated 

with cold, dilute HCl. The term “free carbonates” is nearly 

synonymous with the term “calcareous.” Soils that have free 

carbonates generally have calcium carbonate as a common 

mineral, although sodium and magnesium carbonates are also 

included in this concept. Soils or horizons with free carbonates 

may have inherited the carbonate compounds from parent 

materials without any translocation or transformation processes 

acting on them. There is no implication of pedogenesis in the 

concept of free carbonates, as there is in identifiable secondary 

carbonates (defined below), although most forms of secondary 

carbonates are freely effervescent.

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 calcareous loess or limestone residuum.

Identifiable secondary carbonates either may disrupt the soil 

structure or fabric, forming masses, nodules, concretions, or 

spheroidal aggregates (white eyes) that are soft and powdery 

when dry, or may be present as coatings in pores, on structural 

faces, or on the undersides of rock or pararock fragments. If 

present as coatings, the secondary carbonates cover a significant 

part of the surfaces. Commonly, they coat all of the surfaces 

to a thickness of 1 mm or more. If little calcium carbonate is 

present in the soil, however, the surfaces may be only partially 

coated. The coatings must be thick enough to be visible when 

moist. Some horizons are entirely engulfed by carbonates. The 

color of these horizons is largely determined by the carbonates. 

The carbonates in these horizons are within the concept of 

identifiable secondary carbonates.

The filaments commonly seen in a dry calcareous horizon are 

within the meaning of identifiable secondary carbonates if the 

filaments are thick enough to be visible when the soil is moist. 

Filaments commonly branch on structural faces.

Interfingering of Albic Materials

The term “interfingering of albic materials” refers to albic 

materials that penetrate 5 cm or more into an underlying 
20 Keys to Soil Taxonomy

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, kandic, 

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

Lamellae (lamella, if singular) are illuvial horizons 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 rock 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 class 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 fine-earth 

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 fineearth 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. Linear extensibility is a criterion for most 

Vertic subgroups in this taxonomy and is calculated as summed 

products from the mineral soil surface to a depth of 100 cm or 

to a root-limiting layer (defined in chapter 17).

Lithologic Discontinuities

Lithologic discontinuities are significant changes in particlesize distribution or mineralogy that represent differences in 

lithology within a soil. A lithologic discontinuity can also 

denote an age difference. For information on using horizon 

designations for lithologic discontinuities, see the Soil Survey 

Manual (Soil Survey Division Staff, 1993) and chapter 18 of 

this document.

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 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 
Horizons and Characteristics Diagnostic for the Higher Categories 21

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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 palm of a 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); and if no soil 

material flows through the fingers during full compression, 

the sample has an n value less than 0.7 (nonfluid 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.

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 level-bedded or 

tilted, and may contain only a small percentage of Fe2O3. In the 

Tropics, the ironstone is generally more or less vesicular.
22 Keys to Soil Taxonomy

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.

Plinthite may occur as a constituent of a number of horizons, 

such as an epipedon, a cambic horizon, an argillic horizon, an 

oxic horizon, or a C horizon. It is one form of the material that 

has been called laterite. It normally forms in a horizon below 

the surface, but it may form at the surface in a seep area at the 

base of a slope.

From a genetic viewpoint, plinthite forms by segregation 

of iron. In many places iron probably has been added from 

other horizons or from the higher adjacent soils. Generally, 

plinthite forms in a horizon that is saturated with water for 

some time during the year. Initially, iron is normally segregated 

in the form of soft, more or less clayey, red or dark red redox 

concentrations. These concentrations are not considered 

plinthite unless there has been enough segregation of iron to 

permit their irreversible hardening on exposure to repeated 

wetting and drying. 

Plinthite is firm or very firm when the soil moisture content 

is near field capacity and hard when the moisture content is 

below the wilting point. Plinthite occurs as discrete bodies 

larger than 2 mm that can be separated from the matrix. A moist 

aggregate of plinthite will withstand moderate rolling between 

thumb and forefinger and is less than strongly cemented. Moist 

or air-dried plinthite will not slake when submerged in water 

even with gentle agitation. Plinthite does not harden irreversibly 

as a result of a single cycle of drying and rewetting. After a 

single drying, it will remoisten and then can be dispersed in 

large part if one shakes it in water with a dispersing agent. 

In a moist soil, plinthite is soft enough to be cut with a spade. 

After irreversible hardening, it is no longer considered plinthite 

but is called ironstone. Indurated ironstone materials can be 

broken or shattered with a spade but cannot be dispersed if one 

shakes them in water with a dispersing agent.

A small amount of plinthite in the soil does not form a 

continuous phase; that is, the individual redox concentrations 

or aggregates are not connected with each other. If a large 

amount of plinthite is present, it may form a continuous phase. 

Individual aggregates of plinthite in a continuous phase are 

interconnected, and the spacing of cracks or zones that roots can 

enter is 10 cm or more.

If a continuous layer becomes indurated, it is a massive 

ironstone layer that has irregular, somewhat tubular inclusions 

of yellowish, grayish, or white, clayey material. If the layer 

is exposed, these inclusions may be washed out, leaving an 

ironstone that has many coarse, tubular pores.

Much that has been called laterite is included in the 

meaning of plinthite. Doughy and concretionary laterite that 

has not hardened is an example. Hardened laterite, whether 

it is vesicular or pisolitic, is not included in the definition of 

plinthite.

Resistant Minerals

Several references are made to resistant minerals in this 

taxonomy. Obviously, the stability of a mineral in the soil is 

a partial function of the soil moisture regime. Where resistant 

minerals are referred to in the definitions of diagnostic horizons 

and of various taxa, a humid climate, past or present, is always 

assumed.

Resistant minerals are durable minerals in the 0.02 to 

2.0 mm fraction. Examples are quartz, zircon, tourmaline, 

beryl, anatase, rutile, iron oxides and oxyhydroxides, 1:1 

dioctahedral phyllosilicates (kandites), gibbsite, and hydroxyaluminum interlayered 2:1 minerals (Burt and Soil Survey 

Staff, 2014).

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:
Horizons and Characteristics Diagnostic for the Higher Categories 23

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1. A pH value in water (1:1) of 5.9 or less and an organiccarbon content of 0.6 percent or more; and

2. One or both of the following:

a. An overlying albic horizon that extends horizontally 

through 50 percent or more of each pedon and, directly 

under the albic horizon, colors, moist (crushed and smoothed 

sample), as follows:

(1) Hue of 5YR or redder; or

(2) Hue of 7.5YR, color value of 5 or less, and chroma 

of 4 or less; or

(3) Hue of 10YR or neutral and a color value and 

chroma of 2 or less; or

(4) A color of 10YR 3/1; or

b. With or without an albic horizon and one of the colors 

listed above or hue of 7.5YR, color value, moist, of 5 or less, 

and 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) Al plus 1/2 Fe 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.

Volcanic Glass

Volcanic glass is defined herein as optically isotropic 

translucent glass or pumice of any color. It includes glass, 

pumice, glass-coated crystalline minerals, glass aggregates, and 

glassy materials. 

Volcanic glass is typically a dominant component in 

relatively unweathered tephra. Weathering and mineral 

transformation of volcanic glass can produce short-range-order 

minerals, such as allophane, imogolite, and ferrihydrite. 

Volcanic glass content is the percent (by grain count) of 

glass, glass-coated mineral grains, glass aggregates, and glassy 

materials in the 0.02 to 2.0 mm fraction. Typically, the content 

is determined for one particle-size fraction (i.e., coarse silt, very 

fine sand, or fine sand) and used as an estimate of glass content 

in the 0.02 to 2.0 mm fraction.

Volcanic glass content is a criterion in classification of andic 

soil properties, subgroups with the formative element “vitr(i),” 

families with “ashy” substitutes for particle-size class, and the 

glassy mineralogy class. 

Weatherable Minerals

Several references are made to weatherable minerals in 

this taxonomy. Obviously, the stability (i.e., ability to remain 

unaltered) 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. Examples of the minerals that are included in 

the meaning of weatherable minerals are all 2:1 phyllosilicates, 

chlorite, sepiolite, palygorskite, allophane, 1:1 trioctahedral 

phyllosilicates (serpentines), feldspars, feldspathoids, 

ferromagnesian minerals, volcanic glass, zeolites, dolomite, and 

apatite in the 0.02 to 2.0 mm fraction.

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. Calcite, carbonate 

aggregates, anhydrite, gypsum, and halite are not considered 

weatherable minerals because they are mobile in the soil. 

Mobile minerals appear to be recharged in some otherwise 

strongly weathered soils. 

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
24 Keys to Soil Taxonomy

Figure 2.—Value and chroma of pyrophosphate solution of fibric and 

sapric soil materials.

2. Show evidence of the cellular structure of the plants from 

which they are derived; and

3. Either are 20 mm 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 20 mm 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 

wood fragments (comparable to rock fragments in mineral 

soils). Wood fragments may be in the soil or on the soil 

surface.

Fibric Soil Materials

Fibric soil materials are organic soil materials that either:

1. Contain three-fourths or more (by volume) fibers after 

rubbing, excluding wood fragments (defined above); 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.

Hemic Soil Materials

Hemic (Gr. hemi, half; implying intermediate decomposition) 

soil materials 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 (Gr. sapros, rotten) soil materials 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 wood fragments (defined above); 

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 (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.

Kinds of Limnic Materials

The presence or absence of limnic deposits is taken into 

account in the higher categories of Histosols but not Histels. 
Horizons and Characteristics Diagnostic for the Higher Categories 25

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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 of 4 or less, moist; and

3. Either forms a slightly viscous water suspension and is 

nonplastic or slightly plastic but not sticky, or shrinks upon 

drying, forming clods that are difficult to rewet and often tend 

to crack along horizontal planes; and

4. Either yields a saturated sodium-pyrophosphate extract 

on 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 cation-exchange 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 

(measured by loss on ignition), or both.

Marl

A layer of marl is a limnic layer that:

1. Has a color value of 5 or more, moist; 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 

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 layers, 

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 layers 

to a depth of 60 cm either contain three-fourths or more fibers 

derived from Sphagnum, Hypnum, or other mosses or have 

a bulk density of less than 0.1 g/cm3. 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 g/cm3. 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.
26 Keys to Soil Taxonomy

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 g/cm3). If the fibric moss extends to a depth of 60 

cm and is the dominant material within this depth (three-fourths 

or more of the volume), the control section is 160 cm thick. If 

the fibric moss is thin or absent, the control section extends to a 

depth of 130 cm.

Horizons and Characteristics 

Diagnostic for Both Mineral and 

Organic Soils

Following are descriptions of the horizons and characteristics 

that are diagnostic for both mineral and organic soils.

Aquic Conditions

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 or the prevention 

of surface or ground water from reaching the soils by dams, 

levees, surface pumps, or other means. In these soils water 

table levels and/or their duration are changed significantly in 

connection with specific types of land use. Upon removal of the 

drainage practices, aquic conditions would return. 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 wellsealed 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 condition that occurs 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 of 4 or more, 

moist, and chroma of 2 or less in macropores; or

(b) Redox concentrations of iron and/or manganese; 

or

(c) 2 times or more the amount of iron (extractable 

by dithionite-citrate) than is 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 
Horizons and Characteristics Diagnostic for the Higher Categories 27

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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, 1N ammonium acetate 

solution. The appearance of a strong red color on the freshly 

broken surface indicates the presence of reduced iron ions 

(i.e., Fe2+). A positive reaction to the alpha,alpha-dipyridyl 

field test for ferrous iron (Childs, 1981) may be used to 

confirm the existence of reducing conditions and is especially 

useful in situations where, despite saturation, normal 

morphological indicators of such conditions are either absent 

or obscured (as by the dark colors characteristic of melanic 

great groups). A negative reaction, however, does not imply 

that reducing conditions are always absent. It may only mean 

that the level of free iron in the soil is below the sensitivity 

limit of the test or that the soil is in an oxidized phase at the 

time of testing. For soils with very low levels of iron, the use 

of a field test such as Indicator of Reduction in Soils (IRIS) 

tubes painted with ferric iron may be warranted in order to 

document reducing conditions. Use of alpha,alpha-dipyridyl in 

a 10 percent solution of aceticacid 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 FeMn 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 (L. densus, thick) contact 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.
28 Keys to Soil Taxonomy

Densic Materials

Densic materials are relatively unaltered materials (do 

not meet the requirements for any other named diagnostic 

horizons or any other diagnostic soil characteristic) that have 

a noncemented rupture-resistance class. The bulk density 

or the organization is such that roots cannot enter, except in 

cracks. These are mostly earthy materials, such as till, volcanic 

mudflows, and some mechanically compacted materials, for 

example, mine spoils. Some noncemented rocks can be densic 

materials if they are dense or resistant enough to keep roots 

from entering, except in cracks.

Densic materials are noncemented and thus differ from 

paralithic materials and the material below a lithic contact, both 

of which are cemented.

Densic materials have, at their upper boundary, a densic 

contact if they have no cracks or if the spacing of cracks that 

roots can enter is 10 cm or more. These materials can be used 

to differentiate soil series if the materials are within the series 

control section. 

Gelic Materials

Gelic materials are mineral or organic soil materials that 

show evidence of cryoturbation (frost churning) and/or ice 

segregation in the active layer (seasonal thaw layer) and/or the 

upper part of the permafrost. Cryoturbation is manifested by 

irregular and broken horizons, involutions, accumulation of 

organic matter on top of and within the permafrost, oriented 

rock fragments, and silt-enriched layers. The characteristic 

structures associated with gelic materials include platy, blocky, 

or granular macrostructures; the structural results of sorting; 

and orbiculic, conglomeric, banded, or vesicular microfabrics. 

Ice segregation is manifested by ice lenses, vein ice, segregated 

ice crystals, and ice wedges. Cryopedogenic processes that lead 

to gelic materials are driven by the physical volume change of 

water to ice, moisture migration along a thermal gradient in the 

frozen system, or thermal contraction of the frozen material by 

continued rapid cooling.

Glacic Layer

A glacic layer is massive ice or ground ice in the form of ice 

lenses or wedges. 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 

Gelisols composed mainly of organic soil materials, the lithic 

contact is diagnostic at the subgroup level if it is within 50 

cm of the soil surface in Folistels or within 100 cm of the soil 

surface in Fibristels, Hemistels, and Sapristels. In Histosols 

the lithic contact must be at the lower boundary of the control 

section to be recognized at the subgroup level.

Paralithic Contact

A paralithic (lithic-like) 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 ruptureresistance 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 impregnated 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 
Horizons and Characteristics Diagnostic for the Higher Categories 29

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periods of the year. Water held at a tension of 1500 kPa or 

more is not available to keep most mesophytic plants alive. 

The availability of water is also affected by dissolved salts. If 

a soil is saturated with water that is too salty to be available to 

most plants, it is considered salty rather than dry. Consequently, 

a horizon is considered dry when the moisture tension is 

1500 kPa or more and is considered moist if water is held at a 

tension of less than 1500 kPa but more than zero. A soil may 

be continuously moist in some or all horizons either throughout 

the year or for some part of the year. It may be either moist 

in winter and dry in summer or the reverse. In the Northern 

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

refers to December, January, and February.

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:

1. Annual precipitation that is plus or minus one standard 

deviation of the long-term (30 years or more) mean annual 

precipitation; and

2. Mean monthly precipitation that is plus or minus one 

standard deviation of the long-term monthly precipitation for 8 

of the 12 months. 

For the most part, normal years can be calculated from the 

mean annual precipitation; however, when catastrophic events 

occur during a year, the standard deviations of the monthly 

means should also be calculated. The term “normal years” 

replaces the terms “most years” and “6 out of 10 years,” which 

were used in the previous edition of Soil Taxonomy (Soil 

Survey Staff, 1975). When precipitation data are evaluated to 

determine if the criterion for the presence of aquic conditions, 

or number of days that the moisture control section is moist, or 

number of days that some part of the soil is saturated has been 

met, it is permissible to include data from periods with below 

normal rainfall. Similarly, when precipitation data are evaluated 

to determine if the criterion for the number of days that the 

moisture control section is dry has been met, it is permissible 

to include data from periods with above normal rainfall. It is 

assumed that if the criteria are met during these periods, they 

will also be met during normal years.

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 of 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 soil moisture regime.—The aquic (L. aqua, water) 

soil 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 soil 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 o

C 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 
30 Keys to Soil Taxonomy

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 soil moisture 

regime. 

Aridic and torric (L. aridus, dry, and L. torridus, hot 

and dry) soil moisture regimes.—These terms are used for 

the same moisture regime but in different categories of the 

taxonomy.

In the aridic (torric) soil 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 below 

the soil surface is above 5 oC; and

2. Moist in some or all parts for less than 90 consecutive days 

when the soil temperature at a depth of 50 cm below the soil 

surface is above 8 oC.

Soils that have an aridic (torric) soil moisture regime 

normally occur in areas of arid climates. A few are in areas of 

semiarid climates and either have physical properties that keep 

them dry, such as a crusty surface that virtually precludes the 

infiltration of water, or are on steep slopes where runoff is high. 

There is little or no leaching in this soil moisture regime, and 

soluble salts accumulate in the soils if there is a source.

The limits set for soil temperature exclude from these soil 

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 soil moisture regime.—The udic (L. udus, humid) 

soil 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 below 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 

soil 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 o

C.

The udic soil 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 soil 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 soil moisture regime.—The ustic (L. ustus, burnt; 

implying dryness) soil 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 soil 

moisture regime is not applied to soils that have permafrost 

(defined above).

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 soil 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 below the soil surface, the 

soil moisture control section in areas of the ustic soil 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 soil 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 soil moisture regime.—The xeric (Gr. xeros, dry) 

soil 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 soil 

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 
Horizons and Characteristics Diagnostic for the Higher Categories 31

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cumulative days per year when the soil temperature at a depth 

of 50 cm below the soil surface is higher than 5 oC 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 

below 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 categorical levels in this 

taxonomy.

Gelic (L. gelare, to freeze).— Soils in this temperature 

regime have a mean annual soil temperature at or below 0 oC 

(in Gelic suborders and Gelic great groups) or 1 oC or lower (in 

Gelisols) either at a depth of 50 cm below the soil surface or at 

a densic, lithic, or paralithic contact, whichever is shallower.

Cryic (Gr. kryos, coldness; indicating very cold 

soils).—Soils in this temperature regime have a mean annual 

temperature between 0 and 8 oC but do not have permafrost.

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

July, and August in the Northern Hemisphere and December, 

January, and February in the Southern Hemisphere) either at a 

depth of 50 cm below 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: between 0 and 15 oC; or

(2) If there is an O horizon: between 0 and 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: between 0 and 13 o

C; or

(2) If there is an O horizon or a histic epipedon: 

between 0 and 6 oC.

2. In organic soils the mean annual soil temperature is 

between 0 and 6 oC.

Cryic soils that have an aquic soil moisture regime 

commonly are churned by frost.

Isofrigid soils can also have a cryic soil 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 lower 

categories of soil taxonomy (i.e., family and soil series). 

Frigid.—A soil with a frigid soil temperature regime is 

warmer in summer than a soil with a cryic regime, but its mean 

annual temperature is between 0 and 8 o

C and the difference 

between mean summer (June, July, and August) and mean 

winter (December, January, and February) soil temperatures is 

6 oC or more either at a depth of 50 cm below 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 6 oC or more either at a 

depth of 50 cm below 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 6 oC or more 

either at a depth of 50 cm below 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 6 oC or more either at a depth of 50 

cm below 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 o

C or higher.

Sulfidic Materials

Sulfidic materials contain oxidizable sulfur compounds 

(elemental S or most commonly sulfide minerals, such as 

pyrite or iron monosulfides). They are mineral or organic soil 

materials that have a pH value of more than 3.5 and that become 

significantly more acid when oxidized. 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 hydroxysulfate mineral 

jarosite may segregate, forming the yellow redoximorphic 

concentrations that commonly characterize a sulfuric horizon. 
32 Keys to Soil Taxonomy

The transition from sulfidic materials to a sulfuric horizon 

normally requires only a few months 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.

Required Characteristics

Sulfidic materials have one or both of the following:

1. A pH value (1:1 in water) of more than 3.5, and, when the 

materials are incubated at room temperature as a layer 1 cm 

thick under moist aerobic conditions (repeatedly moistened 

and dried on a weekly basis), the pH decreases by 0.5 or more 

units to a value of 4.0 or less (1:1 by weight in water or in a 

minimum of water to permit measurement) within 16 weeks or 

longer until the pH reaches a nearly constant value if the pH is 

still dropping after 16 weeks; or

2. A pH value (1:1 in water) of more than 3.5 and 0.75 percent 

or more S (dry mass), mostly in the form of sulfides, and less 

than three times as much calcium carbonate equivalent as S.

Sulfuric Horizon

Brackish water sediments frequently contain pyrite or other 

iron sulfide minerals (or, rarely, elemental sulfur), which form 

sulfuric acid upon the oxidation of the sulfur forms they contain 

and/or upon the oxidation and hydrolysis of the iron in the 

iron sulfides. Pyrite is an iron sulfide mineral that forms as a 

result of the microbial decomposition of organic matter under 

anaerobic conditions. Pyrite forms after iron oxide and sulfate 

from sea water (or other sources) become reduced to ferrous 

iron and sulfide, respectively, and then combine to form a very 

insoluble compound (see description of the sulfidization process 

given by Fanning and Fanning, 1989, or Fanning et al., 2002). 

Characteristically, the pyrite crystals occur as nests or framboids 

composed of bipyramidal crystals of pyrite. In an oxidizing 

environment, pyrite oxidizes and the products of oxidation (and 

the hydrolysis of the ferric iron produced) are iron oxides (and 

under sufficiently acidic and oxidizing conditions, jarosite 

and/or schwertmannite) and sulfuric acid. The jarosite has 

a straw-yellow color and frequently lines pores in the soil. 

Jarosite concentrations are among the indicators of a sulfuric 

horizon, but jarosite is not present in all sulfuric horizons. 

The low pH and high amount of soluble sulfates, and/or 

underlying sulfidic materials, are other indicators of a sulfuric 

horizon. A quick test of sulfidic materials is a rapid fall in pH 

on drying or after treatment with an oxidizing agent, such as 

hydrogen peroxide.

A sulfuric (L. sulfur) horizon forms as a result of drainage 

(most commonly artificial drainage) and oxidation of sulfiderich mineral or organic soil materials. It can form in areas where 

sulfidic materials have been exposed as a result of surface 

mining, dredging, or other earth-moving operations. A sulfuric 

horizon is detrimental to most plants and, if sufficiently acid at 

the soil surface, may prevent plant growth or limit it to certain 

plant species, such as Phragmites australis, that can tolerate the 

acidity under certain conditions.

Required Characteristics

The sulfuric horizon is 15 cm or more thick and is composed 

of either mineral or organic soil material that has a pH value 

(1:1 by weight in water or in a minimum of water to permit 

measurement) of 3.5 or less or less than 4.0 if sulfide or other 

S-bearing minerals that produce sulfuric acid upon their 

oxidation are present. The horizon shows evidence that the low 

pH value is caused by sulfuric acid. 

The evidence is one or both of the following:

1. The horizon has:

a. Concentrations of jarosite, schwertmannite, or other iron 

and/or aluminum sulfates or hydroxysulfate minerals; or

b. 0.05 percent or more water-soluble sulfate; or 

2. The layer directly underlying the horizon consists of 

sulfidic materials (defined above).

Characteristics Diagnostic for Human-Altered and HumanTransported Soils

Following are descriptions of the characteristics that are 

diagnostic for human-altered and human-transported soils. The 

diagnostic surface and subsurface horizons that may be present 

in these soils are defined above.

Anthropogenic Landforms and 

 Microfeatures

Anthropogenic Landforms

Anthropogenic landforms are discrete, artificial landforms 

that are mappable at common survey scales, such as 1:10,000 

to 1:24,000. For more information on these terms, see Part 629 

of the National Soil Survey Handbook (U.S. Department of 

Agriculture).

Constructional Anthropogenic Landforms

Constructional anthropogenic landforms include the 

following:

1. Artificial islands

2. Artificial levees

3. Burial mounds

4. Dumps

5. Dredge-deposit shoals

6. Dredge spoil banks

7. Filled marshland

8. Earthworks

9. Fill

10. Filled pits
Horizons and Characteristics Diagnostic for the Higher Categories 33

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11. Filled enclosures

12. Irrigationally raised land

13. Raised land

14. Landfills

15. Locally raised landforms

16. Middens

17. Mounds

18. Railroad beds

19. Reclaimed land

20. Rice paddies

21. Road beds

22. Sanitary landfills

23. Spoil banks

24. Spoil piles

Destructional Anthropogenic Landforms

Destructional anthropogenic landforms include the 

following:

1. Beveled cuts

2. Borrow pits

3. Canals

4. Cuts (i.e., road or railroad)

5. Cutbanks

6. Dredged channels

7. Earthworks

8. Floodways

9. Gravel pits

10. Leveled land

11. Log landings

12. Openpit mines

13. Quarries

14. Rice paddies

15. Sand pits

16. Scalped area

17. Sewage lagoons

18. Surface mines

Anthropogenic Microfeatures

Anthropogenic microfeatures are discrete, artificial features 

formed on or near the earth’s surface (and which may now 

be buried) typically too small to delineate at common survey 

scales, such as larger than 1:10,000. For more information on 

these terms, see Part 629 of the National Soil Survey Handbook

(U.S. Department of Agriculture).

Constructional Anthropogenic Microfeatures

Constructional anthropogenic microfeatures include the 

following:

1. Breakwater (i.e., groins or jetties)

2. Burial mounds

3. Conservation terraces

4. Dikes

5. Double-bedding mounds

6. Dumps

7. Embankments

8. Fills

9. Hillslope terraces

10. Interfurrows

11. Middens

12. Revetments (i.e., seawalls)

13. Rice paddies

14. Spoil banks

15. Spoil piles

Destructional Anthropogenic Microfeatures

Destructional anthropogenic microfeatures include the 

following:

1. Cutbanks

2. Ditches

3. Furrows

4. Hillslope terraces

5. Impact craters

6. Skid trails

7. Scalped areas

Artifacts

Artifacts (L. arte, by skill, and factum, to do or make) are 

materials created, modified, or transported from their source 

by humans usually for a practical purpose in habitation, 

manufacturing, excavation, agriculture, or construction 

activities. Examples of discrete (> 2mm) artifacts are bitumen 

(asphalt), brick, cardboard, carpet, cloth, coal combustion 

by-products, concrete, glass, metal, paper, plastic, rubber, 

and both treated and untreated wood products. Mechanically 

abraded rocks (e.g., rocks with metal scrape marks or gouges), 

rocks worn smooth or shaped by physical action (e.g., grinding 

stones), or physically broken and shaped rocks and debitage 

are artifacts (e.g., stone tool flakes). Examples of nonpersistent 

artifacts repeatedly added to soil to improve agricultural 

production include biosolids, aglime, quicklime, and synthetic 

inorganic fertilizers. Humans have also added midden 

material to the soil to increase agricultural productivity, but 

these additions (e.g., bones, shells, and cooking waste and 

associated charred by-products) have persisted to produce 

long-term (hundreds to thousands of years) changes in soil 

properties (e.g., Terra Preta de Indio soils). Artifacts also 

include litter discarded by humans (e.g., aluminum cans) that 

appears to serve no apparent purpose or function for alteration 

of soil.

Human-Altered Material

Human-altered material is parent material for soil that 

has undergone anthroturbation (soil mixing or disturbance) 

by humans. It occurs in soils that have either been used for 

gardening, been deeply mixed in place, excavated and replaced, 

or compacted in place for the artificial ponding of water. 
34 Keys to Soil Taxonomy

‡ Surfaces that formed by shearing intersect irregularly in diverging and converging 

directions.

Human-altered material may be composed of either organic or 

mineral soil material. It may contain artifacts (e.g., shells or 

bones) used as agricultural amendments, but the majority of the 

material has no evidence that it was transported from outside of 

the pedon.

Human-altered material occurs in soils which are disturbed 

for various reasons. For example, human-altered material 

occurs in agricultural soils which are deeply-plowed or ripped 

to disrupt a root-limiting layer (defined in chapter 17) or other 

physical restriction. Gravesites in cemeteries contain humanaltered material as well as artifacts. Densic contacts form at the 

top of wet, slowly permeable (i.e., puddled) layers when they 

are compacted by humans and destroy structure and impede 

water percolation. Subsequent artificial ponding in such humanaltered material results in anthric saturation (defined above) for 

the purpose of growing crops like rice in paddy soils.

Diagnostic horizons formed by significant illuviation (e.g., 

argillic or petrocalcic horizons) have not been documented 

as occurring in human-altered material. However, laterally 

tracing an illuvial horizon or diagnostic characteristic to find 

a discontinuity where the horizon or characteristic is abruptly 

absent can be used to identify human-altered material. The 

lateral discontinuity typically extends along linear boundaries. 

When the lateral discontinuity occurs at the edge of an 

anthropogenic landform or microfeature (defined above), it 

confirms the destructional origin of the landform or feature 

and identifies the human-altered material produced through 

excavation. It is often the preponderance of evidence (best 

professional judgment) along with published or historical 

evidence and onsite observations that allows the most consistent 

identification of excavated human-altered material.

Required Characteristics

Human-altered material meets both of the following:

1. It occurs in one of the following:

a. A field tilled with a subsoiler to a depth of 50 cm or 

more to break up an impermeable or root-restrictive layer; or

b. A destructional (excavated) anthropogenic landform or 

microfeature (e.g., borrow pit); or

c. A field ponded for agriculture (e.g., rice paddy); and

2. It does not meet the requirements of human-transported 

material (defined below) and has evidence of purposeful 

alteration by humans which results in one of the following:

a. 3 percent or more (by volume) mechanically detached 

and re-oriented pieces of diagnostic horizons or 

characteristics in a horizon or layer 7.5 cm or more thick; or

b. 50 percent or more (by volume) divergent-shaped 

structures (from L. divergent, to veer)‡ in a horizon or layer 

7.5 cm or more thick formed from traffic or mechanical 

pressure exceeding the shear strength of moist loamy or 

clayey soil material; or

c. Excavated and replaced soil material overlying either 

bones or artifacts arranged in ceremonial position or human 

body parts prepared to prevent decay; or

d. Mechanically-abraded rock fragments; or

e. Excavated and replaced soil material unconformably 

overlying features (e.g., scrape marks) that indicate 

excavation by mechanical tools in some part of the pedon; or

f. An abrupt lateral discontinuity of subsurface horizons 

and characteristics at the edge of a refilled or unfilled 

destructional (excavated) anthropogenic landform or 

microfeature; or

g. Anthraquic conditions in a horizon or layer 7.5 cm or 

more thick; or

h. A densic contact or thick platy structure in at least 50 

percent of a pedon accompanied by additional evidence 

(e.g., scrape marks) that it was formed by human-induced 

mechanical compaction.

Human-Transported Material

Human-transported material is parent material for soil that 

has been moved horizontally onto a pedon from a source area 

outside of that pedon by purposeful human activity, usually with 

the aid of machinery or hand tools. This material often contains 

a lithologic discontinuity or a buried horizon just below an 

individual deposit. In some cases it is not possible to distinguish 

between human-transported material and parent material from 

mass movement processes (e.g., landslides) without intensive 

onsite examination and analysis. 

Human-transported material may be composed of either 

organic or mineral soil material and may contain detached 

pieces of diagnostic horizons which are derived from excavated 

soils. It may also contain artifacts (e.g., asphalt) that are 

not used as agricultural amendments (e.g., biosolids) or are 

litter discarded by humans (e.g., aluminum cans). Humantransported material has evidence that it did not originate 

from the same pedon which it overlies. In some soils, 

irregular distribution with depth or in proximity away from an 

anthropogenic landform, feature, or constructed object (e.g., a 

road or building) of modern products (e.g., radioactive fallout, 

deicers, or lead-based paint) may mark separate depositions 

of human-transported materials or mark the boundary with 

in situ soil material below or beside the human-transported 

material. In other soils, a discontinuity exists between the 

human-transported material and the parent material (e.g., a 

2C horizon) or root-limiting layer (e.g., a 2R layer) beneath it. 

Multiple forms of evidence may be required to identify humantransported material where combinations of human actions and 

natural processes interact. Examples of these combinations 

include human-transported material deposited by dredging 
Horizons and Characteristics Diagnostic for the Higher Categories 35

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§ A void created when soil materials with a high content of rock fragments are 

transported and deposited without packing or sorting. The result is a trio of rock fragments 

stacked in a manner than prevents fine earth from filling the void.

adjacent to active beaches, human- or water-deposited litter 

on flood plains and beneath water bodies, and deposits from 

natural geologic events (e.g., airfall volcanic ash) mantling 

anthropogenic landforms and microfeatures. Therefore, it is 

often the preponderance of evidence, including published 

or historical evidence and onsite observations, that allows 

identification of human-transported material.

Required Characteristics

Human-transported material meets both of the following:

1. It occurs either:

a. On a constructional anthropogenic landform or 

microfeature (e.g., artificial levees); or

b. Within the boundaries of a destructional (excavated) 

anthropogenic landform or microfeature (e.g., borrow pit); 

and

2. It has evidence of purposeful transportation by humans and 

an origin outside of the pedon by at least one of the following:

a. A layer of soil material 7.5 cm or more thick which 

unconformably overlies material that has no evidence of 

originating outside of the pedon (e.g., an in situ, laterally 

continuous kandic horizon); or

b. Artifacts other than agricultural amendments (e.g., 

quicklime) and litter discarded by humans (e.g., aluminum 

cans); or

c. Mechanically detached pieces of diagnostic horizons 

or characteristics or saprolite (isovolumetric, weathered, 

uncemented pseudomorphs of weathered bedrock) that do 

not correspond with the underlying material. The pieces 

often have random orientation relative to each other and the 

soil surface and contrast abruptly in texture, mineralogy, or 

color with the surrounding material; or

d. Soil material that contains mechanically abraded rock or 

pararock fragments; or

e. Mechanically fractured rock or pararock fragments with 

splintered or sharp edges that do not correspond with the 

fragments in the underlying soil material (i.e., fractures that 

cut through rather than between individual minerals); or

f. Mechanical scrape marks at some part of the boundary 

between materials that do not correspond with each other; or

g. Soil material 7.5 cm or more thick that overlies a 

manufactured layer contact; or

h. Bridging voids§ between rock fragments in a horizon 

or layer 7.5 cm or more thick in mine spoil with at least 35 

percent (by volume) rock fragments; or

i. An irregular distribution pattern of modern anthropogenic 

particulate artifacts (e.g., radioactive fallout or immobile 

pollutants) or discrete artifacts that are unrelated to the 

deposition or transportation processes of natural parent 

materials such as eolian material, alluvium, or colluvium. 

The irregular distribution occurs above or across the contact 

between soil materials that do not correspond with each 

other or laterally with distance away from a source (e.g., 

the amount of lead-based paint decreases away from a 

building).

Manufactured Layer

A manufactured layer is an artificial, root-limiting layer 

beneath the soil surface consisting of nearly continuous, humanmanufactured materials whose purpose is to form an impervious 

barrier. The materials used to make the layer impervious include 

geotextile liners, asphalt, concrete, rubber, and plastic. The 

presence of manufactured layers can be used to differentiate soil 

series.

Manufactured Layer Contact

A manufactured (L. humanus, of or belonging to man, and 

L. factum, to do or make) layer contact is an abrupt contact 

between soil and a manufactured layer (defined above). It has 

no cracks, or the spacing of cracks that roots can enter is 10 cm 

or more.

Subgroups for Human-Altered and Human- 

 Transported Soils

The following subgroup adjectives recognize distinct groups 

of human-altered and human-transported soils. Soils using 

these adjectives are considered extragrades since they do not 

represent an intergrade to any other named taxon (Soil Survey 

Staff, 1999). They are listed in order of interpretive significance 

as a guide, but the significance and order may change slightly 

depending on the great group in which they are recognized. 

They are not used in combination with each other even though 

some soils may have properties of several subgroups. These 

adjectives may be combined alphabetically with adjectives 

connoting other soil properties, such as high organic matter 

content (e.g., Anthropic Humic) or the presence of sulfidic 

materials (e.g., Anthroportic Sulfic), to form the names for 

additional extragrade subgroups. Additional adjectives for 

other properties will generally increase the importance of 

the subgroup and result in higher placement within a key to 

subgroups.

1. Anthraquic (modified from Gr. anthropos, human, and L. 

aqua, water). Soils that have anthraquic conditions (i.e., anthric 

saturation). These soils are extensive in flooded rice paddies.
36

2. Anthrodensic (modified from Gr. anthropos, human, and 

L. densus, marked by compactness). Soils that have a densic 

contact due to mechanical compaction (e.g., a compacted mine 

spoil) in more than 90 percent of the pedon (measured laterally) 

within 100 cm of the mineral soil surface.

3. Anthropic (modified from Gr. anthropos, human). Soils 

that have an anthropic epipedon based on the presence of 

artifacts or midden material.

4. Plaggic (modified from Ger. plaggen, sod). Soils that have 

a plaggen epipedon.

5. Haploplaggic (Gr. haplous, simple, and Ger. plaggen, sod). 

Soils that have a surface horizon 25 cm to less than 50 cm thick 

that meets all of the requirements for a plaggen epipedon except 

thickness.

6. Anthroportic (modified from Gr. anthropos, human, and L. 

portāre, to carry). Soils that formed in 50 cm or more of humantransported material. This adjective is used primarily for soils 

that formed in human-transported material of dredged or mine 

spoil areas as well as for soils of urban areas and transportation 

corridors.

7. Anthraltic (modified from Gr. anthropos, human, and L. 

alterāre, to change). Soils that formed in 50 cm or more of 

human-altered material. This adjective is used primarily for 

human-altered material where ripping or deep plowing has 

fractured and displaced diagnostic subsurface horizons that 

were root-limiting (e.g., duripans) and in excavated areas (e.g., 

borrow pits).

Literature Cited

Brewer, R. 1976. Fabric and Mineral Analysis of Soils. 2nd 

edition. John Wiley and Sons, New York.

Burt, R. and Soil Survey Staff. 2014. Soil Survey Laboratory 

Methods Manual. Soil Survey Investigations Report 42, 

Version 5.0. U.S. Department of Agriculture, Natural Resources 

Conservation Service, National Soil Survey Center.

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.

Fanning, D.S., and M.C.B. Fanning. 1989. Soil: Morphology, 

Genesis, and Classification. John Wiley and Sons, New York.

Fanning, D.S., M.C. Rabenhorst, S.N. Burch, K.R. Islam, 

and S.A. Tangren. 2002. Sulfides and Sulfates. In J.B. Dixon 

and D.G. Schulze (eds.), Soil Mineralogy with Environmental 

Applications, pp. 229-260. Soil Sci. Soc. Am., Madison, WI.

Hester, T.R., R.F. Heizer, and J.A. Graham. 1975. Field 

Methods in Archaeology. Mayfield Publishing, Palo Alto, CA.

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.

Soil Survey Division Staff. 1993. Soil Survey Manual. 

Soil Conservation Service. U.S. Department of Agriculture 

Handbook 18.

Soil Survey Staff. 1975. Soil Taxonomy: A Basic System of 

Soil Classification for Making and Interpreting Soil Surveys. 

Soil Conservation Service. U.S. Department of Agriculture 

Handbook 436.

Soil Survey Staff. 1999. Soil Taxonomy: A Basic System of 

Soil Classification for Making and Interpreting Soil Surveys. 

Soil Conservation Service. 2nd edition. Natural Resources 

Conservation Service. U.S. Department of Agriculture 

Handbook 436.

U.S. Department of Agriculture, Natural Resources 

Conservation Service. National Soil Survey Handbook, title 

430-VI. Part 629: Glossary of Landform and Geologic Terms. 

(Available online.)
37

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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 user is familiar with the definitions of soil 

and buried soils (defined in chapter 1), mineral and organic 

soil material (defined in chapter 2), and the diagnostic horizons 

and characteristics (defined in chapter 3). Users should also be 

familiar with the meanings of the terms used for describing soils 

given in the Soil Survey Manual (Soil Survey Division Staff, 

1993) and the Field Book for Describing and Sampling Soils

(Schoeneberger et al., 2012). Chapter 18 of this publication 

is an excerpt from the Soil Survey Manual that contains the 

symbolic designations for genetic soil horizons and layers. 

Although not a part of soil taxonomy, the designations are 

reproduced in this publication for convenience. The appendix of 

this publication contains general descriptions of the laboratory 

methods for physical, chemical, organic, and mineralogical 

properties and where they are used as criteria in soil taxonomy. 

The index at the back of this publication indicates the pages on 

which definitions of terms are given.

Conventional rules should be used to round numerical 

values. Numerical values are rounded to the same number 

of digits as used in the taxonomic criteria. For example, soil 

taxonomy requires using percentages for clay content in whole 

numbers (integers) when applying taxonomic criteria such as 

the required characteristics of the argillic horizon and the key to 

particle-size classes (defined in chapter 17). However, primary 

characterization data supplied from soil laboratories often report 

clay content, by weight, in tenths of a percent (one decimal 

place). When measured data are applied in classifying the soil, 

one must first note the level of precision used as a class limit 

and then round the measured data to the same level of precision. 

The conventional rules for rounding numbers in soil taxonomy 

are as follows:

• If the digit immediately to the right of the last significant 

figure is more than 5, round up to the next higher digit. For 

example, 34.8 rounds to 35 (round up because the digit to be 

dropped is more than halfway between 34 and 35).

• If the digit immediately to the right of the last significant 

figure is less than 5, round down to the next lower digit. For 

example, 34.4 rounds to 34 (round down because the digit to 

be dropped is less than halfway between 34 and 35).

• If the digit immediately to the right of the last significant 

figure is equal to 5, round to the adjacent even number, either 

up or down. Some examples are 17.5 rounds to 18 (round up 

because the result is an even number) and 34.5 rounds to 34 

(round down because the result is an even number).

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 using 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 

Identification of the Taxonomic Class of a Soil

CHAPTER 4
38 Keys to Soil Taxonomy

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), and 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. Although most other diagnostic 

soil characteristics of the buried soil are not considered, organic 

carbon if of Holocene age, andic soil properties, base saturation, 

and all properties used to determine family and series placement 

are considered.

If diagnostic horizons or characteristics are criteria that must 

be “within” a specified depth measured from the soil surface, 

then the upper boundary of the first subhorizon meeting the 

requirements for the diagnostic horizon or characteristic must 

be within the specified depth.

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. 157

B. Other soils that:

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

of the thickness between the soil surface and either a depth 

of 60 cm or a densic, lithic, or paralithic contact or duripan if 

shallower; and

2. Have organic soil materials that meet one or more of the 

following:

a. Overlie cindery, fragmental, or pumiceous materials 

and/or fill their interstices* and directly below these 

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

b. When added with the underlying cindery, fragmental, 

or pumiceous materials, total 40 cm or more between the 

soil surface and a depth of 50 cm; or

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

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

no mineral horizons or have mineral horizons with a total 

thickness of 10 cm or less; or

d. Are saturated with water for 30 days or more 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. 167

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 or gelic 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 texture class that is finer than coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or 

loamy fine sand in the fine-earth fraction and a frigid 

temperature regime in the soil; or

(5) A cryic or gelic 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 texture class of 

coarse sand, sand, fine sand, loamy coarse sand, loamy 

sand, or loamy fine sand, in the fine-earth fraction, in 

some horizon between the mineral soil surface and the 

spodic horizon; and

* Materials that meet the definition of the cindery, fragmental, or pumiceous substitute 

for particle-size class 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

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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 texture class that is 

finer than coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand in the fineearth fraction and the soil has a frigid temperature 

regime; or

(b) If the soil has a cryic or gelic 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. 273

D. Other soils that have andic soil properties in 60 percent or 

more of the thickness either:

1. Within 60 cm either of the mineral soil surface or of the 

top of an organic layer with andic soil properties, whichever 

is shallower, if there is no densic, lithic, or paralithic contact, 

duripan, or petrocalcic horizon within that depth; or

2. Between either the mineral soil surface or the top of 

an organic layer with andic soil properties, whichever 

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

duripan, or a petrocalcic horizon.

Andisols, p. 87

E. Other soils that have either:

1. An oxic horizon within 150 cm of the mineral soil 

surface and no kandic horizon 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. 257

F. Other soils that have:

1. A layer 25 cm or more thick, within 100 cm of the 

mineral soil surface, that has either slickensides or wedgeshaped 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. Cracks†

 that open and close periodically.

Vertisols, p. 305

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 within 100 cm of the 

soil surface: a cambic horizon with a lower depth of 

25 cm or more; a cryic soil temperature regime and a 

cambic horizon; an anhydritic, 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 within 150 cm of the mineral soil 

surface.

Aridisols, p. 107

† 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 Keys to Soil Taxonomy

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 texture class of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand in the fine-earth fraction 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. 283

I. Other soils that have both of the following:

1. Either:

a. A mollic epipedon; or

b. Both a surface horizon that meets all the requirements 

for a mollic epipedon except thickness after the soil 

has been mixed to a depth of 18 cm and a subhorizon 

more than 7.5 cm thick, within the upper part of an 

argillic, kandic, or natric horizon, that meets the color, 

organic-carbon content, base saturation, and structure 

requirements of a mollic epipedon but is separated from 

the surface horizon by an albic horizon; and

2. A base saturation of 50 percent or more (by NH4

OAc) 

in all horizons either between the upper boundary of any 

argillic, kandic, or natric horizon and a depth of 125 cm 

below that boundary, or between the mineral soil surface 

and a depth of 180 cm, or between the mineral soil surface 

and a densic, lithic, or paralithic contact, whichever depth is 

shallowest.

Mollisols, p. 211

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. 43

K. Other soils that have either:

1. One or more of the following:

a. A cambic horizon that is within 100 cm of the mineral 

soil surface and has a 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 within a depth of 100 cm of the 

mineral soil surface; or

c. A fragipan or an oxic, sombric, or spodic horizon 

within 200 cm of the mineral soil surface; or

d. A sulfuric horizon within 150 cm of the mineral soil 

surface; or

e. A cryic or gelic soil 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 more of the following:

(1) A folistic, histic, mollic, plaggen, or umbric 

epipedon; or

(2) A salic horizon; or

(3) 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
Identification of the Taxonomic Class of a Soil 41

I

D

E

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. 173

L. Other soils.

Entisols, p. 135

Literature Cited

Schoeneberger, P.J., D.A. Wysocki, E.C. Benham, and Soil 

Survey Staff. 2012. Field Book for Describing and Sampling 

Soils, Version 3.0. Natural Resources Conservation Service, 

National Soil Survey Center.

Soil Survey Division Staff. 1993. Soil Survey Manual. 

Soil Conservation Service. U.S. Department of Agriculture 

Handbook 18.

43

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 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. 43

JB. Other Alfisols that have a cryic or isofrigid soil 

temperature regime.

Cryalfs, p. 52

JC. Other Alfisols that have an ustic soil moisture regime.

Ustalfs, p. 67

JD. Other Alfisols that have a xeric soil moisture regime.

Xeralfs, p. 79

JE. Other Alfisols.

Udalfs, p. 56

Aqualfs

Key to Great Groups

JAA. Aqualfs that have a cryic soil temperature regime.

Cryaqualfs, p. 45

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. 51

JAC. Other Aqualfs that have a duripan.

Duraqualfs, p. 45

JAD. Other Aqualfs that have a natric horizon.

Natraqualfs, p. 51

JAE. Other Aqualfs that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiaqualfs, p. 49

JAF. Other Aqualfs that have a kandic horizon.

Kandiaqualfs, p. 50

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. 52

JAH. Other Aqualfs that have an abrupt textural change 

between the ochric epipedon or albic horizon and the argillic 

horizon and have a saturated hydraulic conductivity of 0.4 

cm/hr (1.0 μm/sec) or slower (moderately low or lower Ksat

class) in the argillic horizon.

Albaqualfs, p. 44

JAI. Other Aqualfs that have a glossic horizon.

Glossaqualfs, p. 49

JAJ. Other Aqualfs that have episaturation.

Epiaqualfs, p. 47

JAK. Other Aqualfs.

Endoaqualfs, p. 45

Alfisols

CHAPTER 5
44 Keys to Soil Taxonomy

Albaqualfs

Key to Subgroups

JAHA. Albaqualfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 peds 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 peds 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 wedgeshaped peds 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, or the upper 18 cm of the mineral 

soil meets all of the requirements for a mollic epipedon, 

except for thickness, 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Aquandic Albaqualfs

JAHH. Other Albaqualfs that have a mollic epipedon, or the 

upper 18 cm of the mineral soil meets all of the requirements 

for a mollic epipedon, except for thickness, after mixing.

Mollic Albaqualfs
Alfisols 45

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F

JAHI. Other Albaqualfs that have an umbric epipedon, or the 

upper 18 cm of the mineral soil meets all of the requirements 

for an umbric epipedon, except for thickness, 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) particles 2.0 mm or 

larger in diameter, 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 peds 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 wedgeshaped peds 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 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 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:
46 Keys to Soil Taxonomy

(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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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, or the upper 18 cm of the mineral 

soil meets all of the requirements for a mollic epipedon, 

except for thickness, 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, or the upper 18 cm of the mineral 

soil meets all of the requirements for an umbric epipedon, 

except for thickness, after mixing; and

2. In one or more horizons between the A or Ap horizon 

and a depth of 75 cm below the mineral soil surface, one or a 

combination of the following colors:

a. Hue of 7.5YR or redder in 50 percent or more of the 

matrix; and

(1) If peds are present, chroma of 2 or more on 50 

percent or more of ped exteriors or no redox depletions 

with chroma of 2 or less in ped interiors; or

(2) If peds are absent, chroma of 2 or more in 50 

percent or more of the matrix; or

b. In 50 percent or more of the matrix, hue of 10YR or 

yellower and either:

(1) Both a color value of 3 or more (moist) and 

chroma of 3 or more; or

(2) Chroma of 2 or more if there are no redox 

concentrations.

Aeric Umbric Endoaqualfs

JAKJ. Other Endoaqualfs that have, in one or more horizons 

between the A or Ap horizon and a depth of 75 cm below the 

mineral soil surface, in 50 percent or more of the matrix, one or 

a combination of the following colors:

1. Hue of 7.5YR or redder; and

a. If peds are present, chroma of 2 or more (both moist 

and dry) on 50 percent or more of ped exteriors or no 

redox depletions with chroma of 2 or less (both moist and 

dry) in ped interiors; or

b. If peds are absent, chroma of 2 or more (both moist 

and dry); or

2. Hue of 10YR or yellower and either:

a. Both a color value of 3 or more (moist) and chroma 

of 3 or more (moist and dry); or

b. Chroma of 2 or more (both moist and dry) and no 

redox concentrations.

Aeric Endoaqualfs

JAKK. Other Endoaqualfs that have a mollic epipedon, or the 

upper 18 cm of the mineral soil meets all of the requirements 

for a mollic epipedon, except for thickness, after mixing.

Mollic Endoaqualfs

JAKL. Other Endoaqualfs that have an umbric epipedon, 

or the upper 18 cm of the mineral soil meets all of the 
Alfisols 47

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F

requirements for an umbric epipedon, except for thickness, 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 peds 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 peds 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.

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 peds 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
48 Keys to Soil Taxonomy

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 wedgeshaped peds 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) particles 2.0 mm or 

larger in diameter, 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 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 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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

JAJI. Other Epiaqualfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 both:

1. An umbric epipedon, or the upper 18 cm of the mineral 

soil meets all of the requirements for an umbric epipedon, 

except for thickness, 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
Alfisols 49

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(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, or the upper 18 cm of the mineral 

soil meets all of the requirements for a mollic epipedon, 

except for thickness, 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, or the 

upper 18 cm of the mineral soil meets all of the requirements 

for a mollic epipedon, except for thickness, after mixing.

Mollic Epiaqualfs

JAJN. Other Epiaqualfs that have an umbric epipedon, or the 

upper 18 cm of the mineral soil meets all of the requirements 

for an umbric epipedon, except for thickness, 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 

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 a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Humic Fragiaqualfs

JAEE. Other Fragiaqualfs.

Typic Fragiaqualfs

Glossaqualfs

Key to Subgroups

JAIA. Glossaqualfs that have a histic epipedon.

Histic Glossaqualfs
50 Keys to Soil Taxonomy

JAIB. Other Glossaqualfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 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 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, or the 

upper 18 cm of the mineral soil meets the requirements for a 

mollic epipedon after mixing.

Mollic Glossaqualfs

JAIG. Other Glossaqualfs.

Typic Glossaqualfs

Kandiaqualfs

Key to Subgroups

JAFA. Kandiaqualfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand throughout a layer extending 

from the mineral soil surface to the top of a kandic horizon at a 

depth of 50 to 100 cm below the mineral soil surface.

Arenic Kandiaqualfs

JAFB. Other Kandiaqualfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm 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:
Alfisols 51

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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, 

or the upper 18 cm of the mineral soil meets the color 

requirements for an umbric epipedon 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 wedgeshaped peds 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

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, or the 

upper 18 cm of the mineral soil meets the color requirements for 

a mollic epipedon after mixing.

Mollic Natraqualfs

JADG. Other Natraqualfs.

Typic Natraqualfs

Plinthaqualfs

Key to Subgroups

JABA. All Plinthaqualfs (provisionally).

Typic Plinthaqualfs
52 Keys to Soil Taxonomy

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 class 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. 55

JBB. Other Cryalfs that have a glossic horizon.

Glossocryalfs, p. 52

JBC. Other Cryalfs.

Haplocryalfs, p. 53

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 wedgeshaped peds 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Glossocryalfs

JBBE. Other Glossocryalfs that have, in one or more 

subhorizons within the upper 25 cm of the argillic, kandic, or 

natric horizon, redox depletions with chroma of 2 or less and 

also aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Glossocryalfs

JBBF. Other Glossocryalfs that are saturated with water in 

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

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Glossocryalfs

JBBG. Other Glossocryalfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or 

more thick that has its upper boundary within 100 cm of the 

mineral soil surface; or
Alfisols 53

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2. In 60 percent or more of the volume of a layer 15 cm or 

more thick.

Fragic Glossocryalfs

JBBH. Other Glossocryalfs that have all of the following:

1. A xeric soil moisture regime; and

2. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing; and

3. A base saturation (by NH4OAc) of 50 percent or more 

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 both:

1. A xeric soil moisture regime; and

2. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing.

Umbric Xeric Glossocryalfs

JBBJ. Other Glossocryalfs that meet all of the following:

1. Are dry in some part of the moisture control section for 

45 or more days (cumulative) in normal years; and

2. Have a color value, moist, of 3 or less and a color value, 

dry, of 5 or less (crushed and smoothed sample) either 

throughout the upper 18 cm of the mineral soil (unmixed) or 

between the mineral soil surface and a depth of 18 cm after 

mixing; and

3. Have a base saturation (by NH4OAc) of 50 percent or 

more 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 soil 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 have both:

1. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between 

the mineral soil surface and a depth of 18 cm after mixing; 

and

2. A base saturation (by NH4OAc) of 50 percent or more 

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 a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Umbric Glossocryalfs

JBBO. Other Glossocryalfs that have a base saturation (by 

NH4OAc) of 50 percent or more 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

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 wedgeshaped peds 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
54 Keys to Soil Taxonomy

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) particles 2.0 mm or 

larger in diameter, 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 

meets one of the following:

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:

1. Have an argillic, kandic, or natric horizon that is 35 cm 

or less thick; and

2. Do not have a densic, lithic, or paralithic contact within 

100 cm of the mineral soil surface.

Inceptic Haplocryalfs

JBCJ. Other Haplocryalfs that have all of the following:

1. A xeric soil moisture regime; and

2. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing; and

3. A base saturation (by NH4OAc) of 50 percent ormore 

in all parts from the mineral soil surface to a depth of 180 

cm or to a densic, lithic, or paralithic contact, whichever is 

shallower.

Xerollic Haplocryalfs

JBCK. Other Haplocryalfs that have both:

1. A xeric soil moisture regime; and

2. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing.

Umbric Xeric Haplocryalfs

JBCL. Other Haplocryalfs that meet all of the following:

1. Are dry in some part of the moisture control section for 

45 or more days (cumulative) in normal years; and

2. Have a color value, moist, of 3 or less and a color value, 

dry, of 5 or less (crushed and smoothed sample) either 

throughout the upper 18 cm of the mineral soil (unmixed) or 

between the mineral soil surface and a depth of 18 cm after 

mixing; and

3. Have a base saturation (by NH4OAc) of 50 percent or

more 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 soil moisture 

regime.

Xeric Haplocryalfs
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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 have both:

1. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing; and

2. A base saturation (by NH4OAc) of 50 percent ormore 

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 a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Umbric Haplocryalfs

JBCQ. Other Haplocryalfs that have a base saturation (by 

NH4OAc) of 50 percent ormore 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) particles 2.0 mm or 

larger in diameter, 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 soil moisture 

regime.

Xeric Palecryalfs

JBAF. Other Palecryalfs that are dry in some part of the 

moisture control section for 45 or more days (cumulative) in 

normal years.

Ustic Palecryalfs

JBAG. Other Palecryalfs that have both:

1. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing; and

2. A base saturation (by NH4

OAc) of 50 percent ormore 

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 a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Umbric Palecryalfs

JBAI. Other Palecryalfs.

Typic Palecryalfs
56 Keys to Soil Taxonomy

Udalfs

Key to Great Groups

JEA. Udalfs that have a natric horizon.

Natrudalfs, p. 64

JEB. Other Udalfs that have both:

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. 57

JEC. Other Udalfs that have both:

1. A glossic horizon; and

2. A fragipan within 100 cm of the mineral soil surface.

Fraglossudalfs, p. 57

JED. Other Udalfs that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiudalfs, p. 57

JEE. Other Udalfs that meet all of the following:

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 is 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. 63

JEF. Other Udalfs that have a kandic horizon.

Kanhapludalfs, p. 64

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 is based 

on the following formula: Clay % = 2.5(% water retained 

at 1500 kPa tension - % organic carbon), whichever value 

is greater, but no more than 100]; or

b. Have 5 percent or more (by volume) skeletans on 

faces of peds in the layer that has a 20 percent lower clay 

content and, below that layer, a clay increase of 3 percent 

or more (absolute) in the fine-earth fraction; and

3. Have an argillic horizon with one or more of the 

following:

a. In 50 percent or more of the matrix of one or more 

subhorizons in its lower one-half, hue of 7.5YR or redder 

and chroma of 5 or more; or

b. In 50 percent or more of the matrix of horizons that 

total more than one-half the total thickness, hue of 2.5YR 

or redder, value, moist, of 3 or less, and value, dry, of 4 or 

less; or

c. Many coarse redox concentrations with hue of 5YR 

or redder or chroma of 6 or more, or both, in one or more 

subhorizons; or

4. Have a frigid soil 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 class 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. 65

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. 67
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JEI. Other Udalfs that have a glossic horizon.

Glossudalfs, p. 58

JEJ. Other Udalfs.

Hapludalfs, p. 59

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) particles 2.0 mm or 

larger in diameter, 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 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) particles 2.0 mm or 

larger in diameter, 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
58 Keys to Soil Taxonomy

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 peds 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 peds 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 wedgeshaped peds in a layer 15 cm or more thick that has its upper 

boundary within 125 cm of the mineral soil surface; or

2. A linear extensibility of 6.0 cm or more between the 

mineral soil surface and either a depth of 100 cm or a densic, 

lithic, or paralithic contact, whichever is shallower. 

Vertic Glossudalfs

JEID. Other Glossudalfs that have both:

1. In one or more subhorizons within the upper 25 cm of 

the argillic horizon, redox depletions with chroma of 2 or 

less and also aquic conditions for some time in normal years 

(or artificial drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 
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larger in diameter, 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:

1. In one or more subhorizons within 75 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); and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand throughout a layer extending from the mineral soil 

surface to the top of the argillic horizon at a depth of 50 cm 

or more below the mineral soil surface.

Aquic Arenic Glossudalfs

JEII. 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

JEIJ. Other Glossudalfs 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 a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand throughout a layer extending from the mineral soil 

surface to the top of the argillic horizon at a depth of 50 cm 

or more below the mineral soil surface.

Arenic Oxyaquic Glossudalfs

JEIK. 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

JEIL. 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

JEIM. Other Glossudalfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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

JEIN. Other Glossudalfs that have a glossic horizon less than 

50 cm in total thickness.

Haplic Glossudalfs

JEIO. Other Glossudalfs.

Typic Glossudalfs

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:
60 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 peds 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 peds 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 peds 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 peds 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 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 
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for some time in normal years and slickensides or wedgeshaped peds 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) particles 2.0 mm or 

larger in diameter, 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:

1. In one or more horizons within 75 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); and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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: 

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 a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand throughout a layer extending from the mineral soil 

surface to the top of the argillic horizon at a depth of 50 cm 

or more below the mineral soil surface.

Arenic Oxyaquic Hapludalfs

JEJM. Other Hapludalfs that have anthraquic conditions.

Anthraquic Hapludalfs

JEJN. Other Hapludalfs that have all of the following:

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:
62 Keys to Soil Taxonomy

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. 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

JEJO. 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

JEJP. 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

JEJQ. 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

JEJR. Other Hapludalfs that have both:

1. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm 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

JEJS. 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

JEJT. Other Hapludalfs that have both:

1. A mollic epipedon, or the upper 18 cm of the mineral 

soil meets the color requirements for a mollic epipedon after 

mixing; and

2. Saturation with water in 1 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.

Mollic Oxyaquic Hapludalfs

JEJU. 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:
Alfisols 63

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1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Hapludalfs

JEJV. 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

JEJW. Other Hapludalfs that have an argillic horizon that 

meets one of the following:

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

JEJX. 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

JEJY. Other Hapludalfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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

JEJZ. Other Hapludalfs that have interfingering of albic 

materials in one or more subhorizons of the argillic horizon.

Glossic Hapludalfs

JEJZa. Other Hapludalfs that:

1. Have an argillic horizon that is 35 cm or less thick; and

2. Do not have a densic, lithic, or paralithic contact within 

100 cm of the mineral soil surface.

Inceptic Hapludalfs

JEJZb. 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

JEJZc. Other Hapludalfs that have a mollic epipedon, or the 

upper 18 cm of the mineral soil meets all the color requirements 

for a mollic epipedon after mixing.

Mollic Hapludalfs

JEJZd. 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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
64 Keys to Soil Taxonomy

2. Have 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand throughout a layer extending 

from the mineral soil surface to the top of a kandic horizon at a 

depth of 50 to 100 cm.

Arenic Kandiudalfs

JEEG. Other Kandiudalfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 75 cm of the kandic horizon or throughout the entire 

kandic horizon if 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. 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, or the 

upper 18 cm of the mineral soil meets the color requirements for 

a mollic epipedon 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 50 cm of the kandic horizon or throughout the entire 

kandic horizon if 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. 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 peds 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
Alfisols 65

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JEAB. Other Natrudalfs that have both:

1. Either a glossic horizon or interfingering of albic 

materials into the natric horizon; and

2. Redox depletions with chroma of 2 or less in layers 

that also have aquic conditions in normal years (or artificial 

drainage) either:

a. Within the upper 25 cm of the natric horizon if 

its upper boundary is within 50 cm of the mineral soil 

surface; or

b. Within 75 cm of the mineral soil surface if the upper 

boundary of the natric horizon is 50 cm or more below the 

mineral soil surface.

Glossaquic Natrudalfs

JEAC. Other Natrudalfs that have redox depletions with 

chroma of 2 or less in layers that also have aquic conditions in 

normal years (or artificial drainage) either:

1. Within the upper 25 cm of the natric horizon if its upper 

boundary is within 50 cm of the mineral soil surface; or

2. Within 75 cm of the mineral soil surface if the upper 

boundary of the natric horizon is 50 cm or more below the 

mineral soil surface.

Aquic Natrudalfs

JEAD. Other Natrudalfs.

Typic Natrudalfs

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 wedgeshaped peds 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) particles 2.0 mm or 

larger in diameter, 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 anthraquic conditions.

Anthraquic Paleudalfs

JEGE. 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

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. 5 percent or more (by volume) plinthite in one or more 

horizons within 150 cm of the mineral soil surface.

Plinthaquic 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 
66 Keys to Soil Taxonomy

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

JEGH. 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

JEGI. Other Paleudalfs that have, in one or more horizons 

within 75 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Paleudalfs

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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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 

meets one of the following:

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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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
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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 75 cm of the argillic horizon or throughout the entire 

argillic horizon if 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. Value, moist, of 3 or less; and

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

value.

Rhodic Paleudalfs

JEGU. Other Paleudalfs that have a mollic epipedon, or the 

upper 18 cm of the mineral soil meets the color requirements for 

a mollic epipedon 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 within 100 cm of the mineral 

soil surface.

Durustalfs, p. 68

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. 79

JCC. Other Ustalfs that have a natric horizon.

Natrustalfs, p. 73

JCD. Other Ustalfs that meet all of the following:

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 is 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. 71

JCE. Other Ustalfs that have a kandic horizon.

Kanhaplustalfs, p. 73

JCF. Other Ustalfs that have one or more of the following:

1. A petrocalcic horizon 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 is 

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 

35 percent or more noncarbonate clay throughout one or 
68 Keys to Soil Taxonomy

more subhorizons in its upper part, and one or both of the 

following:

a. At its upper boundary, a clay increase of 20 percent or 

more (absolute, in the fine-earth fraction) within a vertical 

distance of 7.5 cm or of 15 percent or more (absolute, in 

the fine-earth fraction) within a vertical distance of 2.5 

cm; or

b. An abrupt textural change between the eluvial 

horizon and the upper boundary of the argillic horizon.

Paleustalfs, p. 76

JCG. Other Ustalfs that have, in all subhorizons in the upper 

100 cm of the argillic horizon or throughout the entire argillic 

horizon if less than 100 cm thick, more than 50 percent colors 

that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

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

value.

Rhodustalfs, p. 79

JCH. Other Ustalfs.

Haplustalfs, p. 68

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 peds 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 peds 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 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 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 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 
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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 soil surface that are 

5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped peds in a layer 15 cm or more thick that 

has its upper boundary within 125 cm of the soil surface; 

or

b. A linear extensibility of 6.0 cm or more between 

the soil surface and either a depth of 100 cm or a densic, 

lithic, or paralithic contact, whichever is shallower.

Torrertic Haplustalfs

JCHE. Other Haplustalfs that have both:

1. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for four-tenths or less of the cumulative days 

per year when the 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 less than 120 

cumulative days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC; 

and

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 peds 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 wedgeshaped peds 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:

1. In one or more horizons within 75 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); and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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) particles 2.0 mm or 

larger in diameter, 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 
70 Keys to Soil Taxonomy

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 

meets one of the following:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or 

more subhorizons with a thickness of 7.5 to 20 cm, each 

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than 

20 cm thick, each with an overlying eluvial horizon, and 

above these horizons there are either:

a. Two or more lamellae with a combined thickness of 

5 cm or more (that may or may not be part of the argillic 

horizon); or

b. A combination of lamellae (that may or may not be 

part of the argillic horizon) and one or more parts of the 

argillic horizon 7.5 to 20 cm thick, each with an overlying 

eluvial horizon.

Lamellic Haplustalfs

JCHM. Other Haplustalfs that have a sandy particle-size class 

throughout the upper 75 cm of the argillic horizon or throughout 

the entire argillic horizon if it is less than 75 cm thick.

Psammentic Haplustalfs

JCHN. Other Haplustalfs that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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, 

have one of the following:

a. A frigid soil temperature regime and a moisture 

control section that in normal years is dry in all parts for 

four-tenths or more of the cumulative days per year when 

the soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for 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 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.

Arenic Aridic Haplustalfs

JCHO. Other Haplustalfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 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 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 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 soil 
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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 soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC; 

and

b. Is dry in some part for six-tenths or more of the 

cumulative days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Haplustalfs

JCHR. Other Haplustalfs that have a CEC of less than 24 

cmol(+)/kg clay (by 1N NH4OAc pH 7) in 50 percent or more 

either of the argillic horizon if less than 100 cm thick or of its 

upper 100 cm.

Kanhaplic Haplustalfs

JCHS. Other Haplustalfs that:

1. Have an argillic horizon that is 35 cm or less thick; and

2. Do not have a 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 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 less than 105 cumulative days per year when the 

soil temperature at a depth of 50 cm below the soil surface 

is higher than 5 o

C; or

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 soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that 

in normal years is dry in some or all parts for less than 

120 cumulative days per year when the soil temperature 

at a depth of 50 cm below the soil surface is higher than 

8 o

C.

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 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 soil temperature regime and a moisture control 

section that in normal years is dry in some or all parts for 

less than 105 cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface is 

higher than 5 o

C; or

2. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in some 

part for 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

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 soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC.

Udic Haplustalfs

JCHX. Other Haplustalfs.

Typic Haplustalfs

Kandiustalfs

Key to Subgroups

JCDA. Kandiustalfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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:

1. In one or more horizons within 75 cm of the mineral 

soil surface, have redox depletions with chroma of 2 or less 
72 Keys to Soil Taxonomy

and also aquic conditions for some time in normal years (or 

artificial drainage); and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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, 

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 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

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 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.

Arenic Aridic Kandiustalfs

JCDF. Other Kandiustalfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 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 soil 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 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 less than 120 

cumulative days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 o

C.

Udic Kandiustalfs

JCDI. Other Kandiustalfs that have, in all subhorizons in 

the upper 75 cm of the kandic horizon or throughout the entire 

kandic horizon if 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. 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
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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 soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC; 

and

b. Is dry in some part for six-tenths or more of the 

cumulative days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 5 oC.

Aridic Kanhaplustalfs

JCED. Other Kanhaplustalfs that, when neither irrigated nor 

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in some 

part for 135 cumulative days or less per year when the soil 

temperature at a depth of 50 cm below the soil surface is 

higher than 5 o

C; or

2. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years is dry in some or all parts for less 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 Kanhaplustalfs

JCEE. Other Kanhaplustalfs that have, in all subhorizons in 

the upper 50 cm of the kandic horizon or throughout the entire 

kandic horizon if 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. 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 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 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 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 soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for six-tenths or more of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for less than 90 

consecutive days per year when the temperature at a 

depth of 50 cm below the soil surface is higher than 

8 oC; and

(2) Is dry in some part for six-tenths or more of the 

cumulative days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

5 oC; and

3. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped peds in a layer 15 cm or more thick that 
74 Keys to Soil Taxonomy

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 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 soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for six-tenths or more of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for less than 90 

consecutive days per year when the temperature at a 

depth of 50 cm below the soil surface is higher than 

8 oC; and

(2) Is dry in some part for six-tenths or more of the 

cumulative days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

5 oC; and

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 peds 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 peds 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 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 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 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.

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 
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for some time in normal years and slickensides or wedgeshaped peds 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:

1. In one or more horizons within 75 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); and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand throughout a layer extending 

from the mineral soil surface to the top of an argillic horizon at 

a depth of 50 cm or more.

Arenic Natrustalfs

JCCJ. Other Natrustalfs that have a petrocalcic horizon within 

150 cm of the mineral soil surface.

Petrocalcic Natrustalfs

JCCK. Other Natrustalfs that have visible crystals of gypsum 

or 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 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 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 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.

Haplargidic Natrustalfs

JCCM. Other Natrustalfs 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 soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 °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 °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 soil temperature at 

a depth of 50 cm below the soil surface is higher than 

8 °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 °C; and

2. A glossic horizon or interfingering of albic materials into 

the natric horizon.

Aridic Glossic Natrustalfs
76 Keys to Soil Taxonomy

JCCN. Other Natrustalfs 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 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 soil 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

JCCO. Other Natrustalfs that have a mollic epipedon, or the 

upper 18 cm of the mineral soil meets the color requirements for 

a mollic epipedon after mixing.

Mollic Natrustalfs

JCCP. 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 peds in a layer 15 cm or more thick that 

has its upper boundary within 125 cm of the mineral soil 

surface; or

b. A linear extensibility of 6.0 cm or more between 

the mineral soil surface and either a depth of 100 cm 

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

shallower; and

2. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage).

Aquertic Paleustalfs

JCFB. Other Paleustalfs that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped peds 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 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 less than 120 

cumulative days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 o

C; 

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 peds 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
Alfisols 77

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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 wedgeshaped peds 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:

1. In one or more horizons within 75 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); and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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 

meets one of the following:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or 

more subhorizons with a thickness of 7.5 to 20 cm, each 

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than 

20 cm thick, each with an overlying eluvial horizon, and 

above these horizons there are either:

a. Two or more lamellae with a combined thickness of 

5 cm or more (that may or may not be part of the argillic 

horizon); or

b. A combination of lamellae (that may or may not be 

part of the argillic horizon) and one or more parts of the 

argillic horizon 7.5 to 20 cm thick, each with an overlying 

eluvial horizon.

Lamellic Paleustalfs

JCFI. Other Paleustalfs that have a sandy particle-size class 

throughout the upper 75 cm of the argillic horizon or throughout 

the entire argillic horizon if it is less than 75 cm thick.

Psammentic Paleustalfs

JCFJ. Other Paleustalfs that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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, 

have one of the following:

a. A frigid soil temperature regime and a moisture 

control section that in normal years is dry in all parts for 

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 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 soil 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.

Arenic Aridic Paleustalfs

JCFK. Other Paleustalfs that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 
78 Keys to Soil Taxonomy

loamy sand, or loamy fine sand 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 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 soil 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 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 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 o

C; 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 free 

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 soil temperature regime and a moisture control 

section that in normal years is dry in all parts for four-tenths 

or more of the time (cumulative) per year when the soil 

temperature at a depth of 50 cm below the soil surface is 

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in some 

part for six-tenths or more of the time (cumulative) per year 

when the soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

a. Is moist in some or all parts for less than 90 

consecutive days per year when the soil 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 75 cm of the argillic horizon or throughout the entire 

argillic horizon if 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. 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 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 
Alfisols 79

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F

normal years is dry in some or all parts for less 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 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 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 less than 120 

cumulative days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 o

C.

Udic Rhodustalfs

JCGD. Other Rhodustalfs.

Typic Rhodustalfs

Xeralfs

Key to Great Groups

JDA. Xeralfs that have a duripan within 100 cm of the mineral 

soil surface.

Durixeralfs, p. 80

JDB. Other Xeralfs that have a natric horizon.

Natrixeralfs, p. 83

JDC. Other Xeralfs that have a fragipan within 100 cm of the 

mineral soil surface.

Fragixeralfs, p. 80

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. 84

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. 85

JDF. Other Xeralfs that have one or more of the following:

1. A petrocalcic horizon 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 is 

based on the following formula: Clay % = 2.5(% water 

retained at 1500 kPa tension - % organic carbon), 

whichever value is greater, but no more than 100]; or

(2) 5 percent or more (by volume) skeletans on 

faces of peds in the layer that has a 20 percent lower 

clay content and, below that layer, a clay increase of 

3 percent or more (absolute) in the fine-earth fraction; 

and

b. A base at a depth of 150 cm or more; or

3. No densic, lithic, or paralithic contact within 50 cm of 

the mineral soil surface and an argillic or kandic horizon that 

has 35 percent or more noncarbonate clay throughout one or 

more subhorizons in its upper part, and one or both of the 

following:

a. A clay increase of 20 percent or more (absolute, in the 

fine-earth fraction) within a vertical distance of 7.5 cm or

of 15 percent or more (absolute, in the fine-earth fraction) 
80 Keys to Soil Taxonomy

within a vertical distance of 2.5 cm, either within the 

argillic or kandic horizon or at its upper boundary; or

b. An abrupt textural change between the eluvial 

horizon and the upper boundary of the argillic or kandic 

horizon.

Palexeralfs, p. 83

JDG. Other Xeralfs.

Haploxeralfs, p. 81

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 peds in a layer 15 cm or more 

thick; or

2. A linear extensibility of 6.0 cm or more.

Vertic Durixeralfs

JDAC. Other Durixeralfs that have, in one or more 

subhorizons within the argillic horizon, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Durixeralfs

JDAD. Other Durixeralfs that have both:

1. An argillic horizon that has 35 percent or more 

noncarbonate clay throughout one or more subhorizons 

totaling 7.5 cm or more thick, and one or both of the 

following:

a. A clay increase of 20 percent or more (absolute, in the 

fine-earth fraction) within a vertical distance of 7.5 cm or

of 15 percent or more (absolute, in the fine-earth fraction) 

within a vertical distance of 2.5 cm, either within the 

argillic horizon or at its upper boundary; or

b. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon; 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 

35 percent or more noncarbonate clay throughout one or more 

subhorizons totaling 7.5 cm or more thick, and one or both of 

the following:

1. A clay increase of 20 percent or more (absolute, in the 

fine-earth fraction) within a vertical distance of 7.5 cm or

of 15 percent or more (absolute, in the fine-earth fraction) 

within a vertical distance of 2.5 cm, either within the argillic 

horizon or at its upper boundary; or

2. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon.

Abruptic Durixeralfs

JDAF. Other Durixeralfs that have a duripan that is strongly 

cemented or less cemented in all subhorizons.

Haplic Durixeralfs

JDAG. Other Durixeralfs.

Typic Durixeralfs

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) particles 2.0 mm or 

larger in diameter, 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 a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Mollic Fragixeralfs
Alfisols 81

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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 wedgeshaped peds in a layer 15 cm or more thick that has its upper 

boundary within 125 cm of the mineral soil surface; or

2. A linear extensibility of 6.0 cm or more between the 

mineral soil surface and either a depth of 100 cm or a densic, 

lithic, or paralithic contact, whichever is shallower.

Vertic Haploxeralfs

JDGE. Other Haploxeralfs that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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 
82 Keys to Soil Taxonomy

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 

meets one of the following:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or 

more subhorizons with a thickness of 7.5 to 20 cm, each 

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than 

20 cm thick, each with an overlying eluvial horizon, and 

above these horizons there are either:

a. Two or more lamellae with a combined thickness of 

5 cm or more (that may or may not be part of the argillic 

horizon); or

b. A combination of lamellae (that may or may not be 

part of the argillic horizon) and one or more parts of the 

argillic horizon 7.5 to 20 cm thick, each with an overlying 

eluvial horizon.

Lamellic Haploxeralfs

JDGN. Other Haploxeralfs that have a sandy particle-size 

class throughout the upper 75 cm of the argillic horizon or 

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

thick.

Psammentic Haploxeralfs

JDGO. Other Haploxeralfs that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Haploxeralfs

JDGP. Other Haploxeralfs that have a calcic horizon within 

100 cm of the mineral soil surface.

Calcic Haploxeralfs

JDGQ. Other Haploxeralfs that:

1. Have an argillic or kandic horizon that is 35 cm or less 

thick; and

2. Do not have a 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 

the upper 10 cm of the mineral soil (unmixed) or throughout the 

upper 18 cm of the mineral soil after mixing.

Mollic Haploxeralfs

JDGT. Other Haploxeralfs.

Typic Haploxeralfs
Alfisols 83

A

L

F

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 wedgeshaped peds 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 wedgeshaped peds 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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
84 Keys to Soil Taxonomy

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 

within 150 cm of the mineral soil surface.

Petrocalcic Palexeralfs

JDFH. Other Palexeralfs that have an argillic horizon that 

meets one of the following:

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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand throughout a layer extending 

from the mineral soil surface to the top of an argillic or kandic 

horizon at a depth of 50 cm or more.

Arenic Palexeralfs

JDFK. Other Palexeralfs that have an exchangeable sodium 

percentage of 15 or more (or a sodium adsorption ratio of 13 or 

more) in one or more horizons within 100 cm of the mineral soil 

surface.

Natric Palexeralfs

JDFL. Other Palexeralfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or 

more thick that has its upper boundary within 100 cm of the 

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or 

more thick.

Fragic Palexeralfs

JDFM. Other Palexeralfs that have a calcic horizon within 150 

cm of the mineral soil surface.

Calcic Palexeralfs

JDFN. Other Palexeralfs that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Palexeralfs

JDFO. Other Palexeralfs that have an argillic or kandic 

horizon that has a base saturation (by sum of cations) of less 

than 75 percent throughout.

Ultic Palexeralfs

JDFP. Other Palexeralfs with an argillic or kandic horizon that 

has, 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, in the fine-earth fraction) within a 

vertical distance of 7.5 cm and of less than 15 percent 

(absolute, in the fine-earth fraction) 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 

the upper 10 cm of the mineral soil (unmixed) or throughout the 

upper 18 cm of the mineral soil after mixing.

Mollic Palexeralfs

JDFR. Other Palexeralfs.

Typic Palexeralfs

Plinthoxeralfs

Key to Subgroups

JDDA. All Plinthoxeralfs (provisionally).

Typic Plinthoxeralfs
Alfisols 85

A

L

F

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 peds 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 

within 150 cm of the mineral soil surface.

Petrocalcic Rhodoxeralfs

JDED. Other Rhodoxeralfs that have a calcic horizon 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 35 cm thick or is discontinuous 

horizontally in each pedon.

Inceptic Rhodoxeralfs

JDEF. Other Rhodoxeralfs.

Typic Rhodoxeralfs

87

A

N

D

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. 87

DB. Other Andisols that have a gelic soil temperature regime.

Gelands, p. 94

DC. Other Andisols that have a cryic soil temperature regime.

Cryands, p. 90

DD. Other Andisols that have an aridic soil moisture regime.

Torrands, p. 94

DE. Other Andisols that have a xeric soil moisture regime.

Xerands, p. 105

DF. 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 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 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. 103

DG. Other Andisols that have an ustic soil moisture regime.

Ustands, p. 102

DH. Other Andisols.

Udands, p. 95

Aquands

Key to Great Groups

DAA. Aquands that have a gelic soil temperature regime. 

Gelaquands, p. 89

DAB. Other Aquands that have a cryic soil temperature 

regime.

Cryaquands, p. 88

DAC. Other Aquands that have, in half or more of each 

pedon, a placic horizon within 100 cm of the mineral soil 

surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Placaquands, p. 90

DAD. Other Aquands that have, in 75 percent or more of 

each pedon, a cemented horizon within 100 cm of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Duraquands, p. 88

DAE. 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 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 the mineral soil surface or the top of an organic 

Andisols

CHAPTER 6
88 Keys to Soil Taxonomy

layer with andic soil properties, whichever is shallower, and 

a densic, lithic, or paralithic contact.

Vitraquands, p. 90

DAF. Other Aquands that have a melanic epipedon.

Melanaquands, p. 89

DAG. Other Aquands that have episaturation.

Epiaquands, p. 89

DAH. Other Aquands.

Endoaquands, p. 88

Cryaquands

Key to Subgroups

DABA. Cryaquands 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 Cryaquands

DABB. Other Cryaquands that have a histic epipedon.

Histic Cryaquands

DABC. 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

DABD. Other Cryaquands.

Typic Cryaquands

Duraquands

Key to Subgroups

DADA. Duraquands that have a histic epipedon.

Histic Duraquands

DADB. Other Duraquands that have a sum of 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

DADC. 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

DADD. Other Duraquands.

Typic Duraquands

Endoaquands

Key to Subgroups

DAHA. Endoaquands 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 Endoaquands

DAHB. Other Endoaquands that have a horizon 15 cm or 

more thick that has 20 percent or more (by volume) cemented 

soil material within 100 cm of the mineral soil surface or of the 

top of an organic layer with andic soil properties, whichever is 

shallower.

Duric Endoaquands

DAHC. Other Endoaquands that have a histic epipedon.

Histic Endoaquands

DAHD. Other Endoaquands that have more than 2.0 

cmol(+)/kg Al3+ (by 1N KCl) in the fine-earth fraction of one 

or more horizons with a total thickness of 10 cm or more at a 

depth between 25 and 50 cm either from the mineral soil surface 

or from the top of an organic layer with andic soil properties, 

whichever is shallower.

Alic Endoaquands

DAHE. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Hydric Endoaquands

DAHF. 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 
Andisols 89

A

N

D

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

DAHG. Other Endoaquands.

Typic Endoaquands

Epiaquands

Key to Subgroups

DAGA. Epiaquands that have a horizon 15 cm or more thick 

that has 20 percent or more (by volume) cemented soil material 

within 100 cm of the mineral soil surface or of the top of an 

organic layer with andic soil properties, whichever is shallower.

Duric Epiaquands

DAGB. Other Epiaquands that have a histic epipedon.

Histic Epiaquands

DAGC. 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

DAGD. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Hydric Epiaquands

DAGE. 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

DAGF. Other Epiaquands.

Typic Epiaquands

Gelaquands

Key to Subgroups

DAAA. Gelaquands that have a histic epipedon.

Histic Gelaquands

DAAB. Other Gelaquands that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Gelaquands

DAAC. Other Gelaquands 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 Gelaquands

DAAD. Other Gelaquands.

Typic Gelaquands

Melanaquands

Key to Subgroups

DAFA. Melanaquands 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 Melanaquands

DAFB. Other Melanaquands that have a sum of 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

DAFC. 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 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 of the mineral soil surface or of the top of 

an organic layer with andic soil properties, whichever is 

shallower.

Hydric Pachic Melanaquands

DAFD. 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 of the mineral 
90 Keys to Soil Taxonomy

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Hydric Melanaquands

DAFE. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Pachic Melanaquands

DAFF. 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

DAFG. Other Melanaquands.

Typic Melanaquands

Placaquands

Key to Subgroups

DACA. Placaquands 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 Placaquands

DACB. 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 within 100 cm of 

the mineral soil surface or of the top of an organic layer with 

andic soil properties, whichever is shallower.

Duric Histic Placaquands

DACC. Other Placaquands that have a horizon 15 cm or more 

thick that has 20 percent or more (by volume) cemented soil 

material within 100 cm of the mineral soil surface or of the 

top of an organic layer with andic soil properties, whichever is 

shallower.

Duric Placaquands

DACD. Other Placaquands that have a histic epipedon.

Histic Placaquands

DACE. 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

DACF. Other Placaquands.

Typic Placaquands

Vitraquands

Key to Subgroups

DAEA. Vitraquands 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 Vitraquands

DAEB. Other Vitraquands that have a horizon 15 cm or more 

thick that has 20 percent or more (by volume) cemented soil 

material within 100 cm of the mineral soil surface or of the 

top of an organic layer with andic soil properties, whichever is 

shallower.

Duric Vitraquands

DAEC. Other Vitraquands that have a histic epipedon.

Histic Vitraquands

DAED. 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

DAEE. Other Vitraquands.

Typic Vitraquands

Cryands

Key to Great Groups

DCA. Cryands that have, in 75 percent or more of each pedon, 

a cemented horizon within 100 cm of the mineral soil surface 

or of the top of an organic layer with andic soil properties, 

whichever is shallower.

Duricryands, p. 91
Andisols 91

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DCB. 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 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. 93

DCC. Other Cryands that have a melanic epipedon.

Melanocryands, p. 93

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

thickness, and organic-carbon requirements for a melanic 

epipedon.

Fulvicryands, p. 91

DCE. 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 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 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. 93

DCF. Other Cryands.

Haplocryands, p. 92

Duricryands

Key to Subgroups

DCAA. 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

DCAB. Other Duricryands 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 properties, whichever is shallower; and

2. Saturation with water in one or more layers above the 

cemented horizon in normal years for either or both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Eutric Oxyaquic Duricryands

DCAC. Other Duricryands that are saturated with water in one 

or more layers above the cemented horizon in normal years for 

either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Duricryands

DCAD. Other Duricryands 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 properties, whichever is 

shallower.

Eutric Duricryands

DCAE. Other Duricryands.

Typic Duricryands

Fulvicryands

Key to Subgroups

DCDA. Fulvicryands 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 Fulvicryands

DCDB. Fulvicryands that have a folistic epipedon.

Folistic Fulvicryands

DCDC. Other Fulvicryands that have both:
92 Keys to Soil Taxonomy

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 properties, whichever is shallower; and

2. Throughout a layer 50 cm or more thick within 60 cm of 

the mineral soil surface or of the top of an organic layer with 

andic 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 Fulvicryands

DCDD. Other Fulvicryands 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 properties, whichever is 

shallower.

Eutric Fulvicryands

DCDE. Other Fulvicryands that have, throughout a layer 50 

cm or more thick within 60 cm 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

DCDF. 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 of the mineral soil surface or of 

the top of an organic layer with andic soil properties, whichever 

is shallower.

Vitric Fulvicryands

DCDG. Other Fulvicryands.

Typic Fulvicryands

Haplocryands

Key to Subgroups

DCFA. Haplocryands 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 Haplocryands

DCFB. Other Haplocryands that have a folistic epipedon.

Folistic Haplocryands

DCFC. 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

DCFD. Other Haplocryands that are saturated with water 

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 Haplocryands

DCFE. 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

DCFF. Other Haplocryands that have an albic horizon 

overlying a cambic horizon in 50 percent or more of each pedon 

or have a spodic horizon in 50 percent or more of each pedon.

Spodic Haplocryands

DCFG. Other Haplocryands that have a sum of 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

DCFH. 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 
Andisols 93

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of 25 cm or more within 100 cm of the mineral soil surface or of 

the top of an organic layer with andic soil properties, whichever 

is shallower.

Vitric Haplocryands

DCFI. 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

DCFJ. Other Haplocryands that have a xeric soil moisture 

regime.

Xeric Haplocryands

DCFK. Other Haplocryands.

Typic Haplocryands

Hydrocryands

Key to Subgroups

DCBA. Hydrocryands 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 Hydrocryands

DCBB. Other Hydrocryands that have a placic horizon 

within 100 cm of the mineral soil surface or of the top of an 

organic layer with andic soil properties, whichever is shallower.

Placic Hydrocryands

DCBC. 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

DCBD. 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

DCBE. Other Hydrocryands.

Typic Hydrocryands

Melanocryands

Key to Subgroups

DCCA. Melanocryands that have a lithic contact within 50 cm 

of the mineral soil surface or of the top of an organic layer that 

has andic soil properties, whichever is shallower.

Lithic Melanocryands

DCCB. 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 of the mineral soil surface or of 

the top of an organic layer with andic soil properties, whichever 

is shallower.

Vitric Melanocryands

DCCC. Other Melanocryands.

Typic Melanocryands

Vitricryands

Key to Subgroups

DCEA. Vitricryands that have a lithic contact within 50 cm of 

the mineral soil surface or of the top of an organic layer that has 

andic soil properties, whichever is shallower.

Lithic Vitricryands

DCEB. Other Vitricryands that have a folistic epipedon.

Folistic Vitricryands

DCEC. 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 
94 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 Vitricryands

DCED. 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

DCEE. Other Vitricryands that have an albic horizon 

overlying a cambic horizon in 50 percent or more of each pedon 

or have a spodic horizon in 50 percent or more of each pedon.

Spodic Vitricryands

DCEF. 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

DCEG. Other Vitricryands that have a xeric soil moisture 

regime and a mollic or umbric epipedon.

Humic Xeric Vitricryands

DCEH. Other Vitricryands that have a xeric soil moisture 

regime.

Xeric Vitricryands

DCEI. Other Vitricryands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm or throughout the entire 

argillic or kandic horizon if it is less than 50 cm thick.

Ultic Vitricryands

DCEJ. Other Vitricryands that have an argillic or kandic 

horizon within 125 cm of the mineral soil surface or of the top 

of an organic layer with andic soil properties, whichever is 

shallower.

Alfic Vitricryands

DCEK. Other Vitricryands that have a mollic or umbric 

epipedon.

Humic Vitricryands

DCEL. Other Vitricryands.

Typic Vitricryands

Gelands

Key to Great Groups

DBA. All Gelands are considered Vitrigelands.

Vitrigelands, p. 94

Key to Subgroups

DBAA. Vitrigelands that have a mollic or umbric epipedon.

Humic Vitrigelands

DBAB. Other Vitrigelands that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Vitrigelands

DBAC. Other Vitrigelands.

Typic Vitrigelands

Torrands

Key to Great Groups

DDA. Torrands that have, in 75 percent or more of each 

pedon, a cemented horizon within 100 cm of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Duritorrands, p. 95

DDB. 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 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 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. 95

DDC. Other Torrands.

Haplotorrands, p. 95
Andisols 95

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Duritorrands

Key to Subgroups

DDAA. Duritorrands that have a petrocalcic horizon within 

100 cm of the mineral soil surface.

Petrocalcic Duritorrands

DDAB. 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 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 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

DDAC. Other Duritorrands.

Typic Duritorrands

Haplotorrands

Key to Subgroups

DDCA. Haplotorrands that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Haplotorrands

DDCB. Other Haplotorrands that have a horizon 15 cm or 

more thick that has 20 percent or more (by volume) cemented 

soil material within 100 cm of the mineral soil surface.

Duric Haplotorrands

DDCC. Other Haplotorrands that have a calcic horizon within 

125 cm of the mineral soil surface.

Calcic Haplotorrands

DDCD. Other Haplotorrands.

Typic Haplotorrands

Vitritorrands

Key to Subgroups

DDBA. Vitritorrands that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Vitritorrands

DDBB. Other Vitritorrands that have a horizon 15 cm or more 

thick that has 20 percent or more (by volume) cemented soil 

material within 100 cm of the mineral soil surface.

Duric Vitritorrands

DDBC. 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

DDBD. Other Vitritorrands that have a calcic horizon within 

125 cm of the mineral soil surface.

Calcic Vitritorrands

DDBE. Other Vitritorrands.

Typic Vitritorrands

Udands

Key to Great Groups

DHA. Udands that have, in half or more of each pedon, a 

placic horizon within 100 cm of the mineral soil surface or of 

the top of an organic layer with andic soil properties, whichever 

is shallower.

Placudands, p. 102

DHB. Other Udands that have, in 75 percent or more of 

each pedon, a cemented horizon within 100 cm of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Durudands, p. 96

DHC. Other Udands that have a melanic epipedon.

Melanudands, p. 100

DHD. 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 the 

mineral soil surface or the top of an organic layer with andic 
96 Keys to Soil Taxonomy

soil properties, whichever is shallower, and a densic, lithic, 

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

Hydrudands, p. 99

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

thickness, and organic-carbon requirements for a melanic 

epipedon.

Fulvudands, p. 96

DHF. Other Udands.

Hapludands, p. 97

Durudands

Key to Subgroups

DHBA. 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

DHBB. Other Durudands 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 properties, whichever is 

shallower.

Eutric Durudands

DHBC. Other Durudands that have a sum of 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

DHBD. 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

DHBE. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Pachic Durudands

DHBF. Other Durudands.

Typic Durudands

Fulvudands

Key to Subgroups

DHEA. Fulvudands that have both:

1. 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; 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

DHEB. Other Fulvudands 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 Fulvudands

DHEC. Other Fulvudands that have, in one or more horizons 

at a depth between 50 and 100 cm either from the mineral 

soil surface or from the top of an organic layer with andic soil 

properties, whichever is shallower, aquic conditions for some 

time in normal years (or artificial drainage) and one or more of 

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or 

more chroma of 2 or less either in redox depletions on faces 

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction 

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

irrigated.

Aquic Fulvudands

DHED. Other Fulvudands that are saturated with water 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 Fulvudands

DHEE. Other Fulvudands that have, on undried samples, a 

1500 kPa water retention of 70 percent or more throughout 
Andisols 97

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a layer 35 cm or more thick within 100 cm of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Hydric Fulvudands

DHEF. Other Fulvudands that have a sum of 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

DHEG. Other Fulvudands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic 

horizon.

Ultic Fulvudands

DHEH. 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 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

DHEI. 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

DHEJ. Other Fulvudands that have, throughout a layer 50 cm 

or more thick within 60 cm 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

DHEK. 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

DHEL. Other Fulvudands.

Typic Fulvudands

Hapludands

Key to Subgroups

DHFA. Hapludands 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 Hapludands

DHFB. Other Hapludands that have anthraquic conditions.

Anthraquic Hapludands

DHFC. Other Hapludands that have both:

1. A horizon 15 cm or more thick that has 20 percent or 

more (by volume) cemented soil material within 100 cm of 

the mineral soil surface or of the top of an organic layer with 

andic soil properties, whichever is shallower; and

2. In one or more horizons at a depth between 50 and 100 

cm either from the mineral soil surface or from the top of 

an organic layer with andic soil properties, whichever is 

shallower, aquic conditions for some time in normal years 

(or artificial drainage) and one or more of the following:

a. 2 percent or more redox concentrations; or

b. A color value, moist, of 4 or more and 50 percent or 

more chroma of 2 or less either in redox depletions on 

faces of peds or in the matrix if peds are absent; or

c. Enough active ferrous iron to give a positive reaction 

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

being irrigated.

Aquic Duric Hapludands

DHFD. Other Hapludands that have a horizon 15 cm or more 
98 Keys to Soil Taxonomy

thick that has 20 percent or more (by volume) cemented soil 

material within 100 cm of the mineral soil surface or of the 

top of an organic layer with andic soil properties, whichever is 

shallower.

Duric Hapludands

DHFE. 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

DHFF. Other Hapludands that are saturated with water 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 Hapludands

DHFG. 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

DHFH. Other Hapludands that have both:

1. A sum of extractable bases (by NH4OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness 

of 30 cm or more at a depth between 25 and 100 cm either 

from the mineral soil surface or from the top of an organic 

layer with andic soil properties, whichever is shallower; 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 of the mineral soil surface or of the top of 

an organic layer with andic soil properties, whichever is 

shallower.

Acrudoxic Hydric Hapludands

DHFI. 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. A sum of extractable bases (by NH4OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness 

of 30 cm or more; 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

DHFJ. Other Hapludands that have both:

1. A sum of extractable bases (by NH4OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness 

of 30 cm or more at a depth between 25 and 100 cm either 

from the mineral soil surface or from the top of an organic 

layer with andic soil properties, whichever is shallower; and

2. An argillic or kandic horizon that has both:

a. 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

b. A base saturation (by sum of cations) of less than 35 

percent throughout its upper 50 cm.

Acrudoxic Ultic Hapludands

DHFK. Other Hapludands that have a sum of 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 Hapludands

DHFL. 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 of the mineral soil surface or of 

the top of an organic layer with andic soil properties, whichever 

is shallower.

Vitric Hapludands

DHFM. 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 
Andisols 99

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within 100 cm 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

DHFN. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Hydric Hapludands

DHFO. Other Hapludands that have both:

1. A sum of extractable bases (by NH4OAc) 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

DHFP. 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

DHFQ. Other Hapludands that have a sum of extractable 

bases (by NH4OAc) 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

DHFR. Other Hapludands that have an oxic horizon within 

125 cm of the mineral soil surface or of the top of an organic 

layer with andic soil properties, whichever is shallower.

Oxic Hapludands

DHFS. Other Hapludands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic 

horizon.

Ultic Hapludands

DHFT. Other Hapludands that have an argillic or kandic 

horizon within 125 cm of the mineral soil surface or of the top 

of an organic layer with andic soil properties, whichever is 

shallower.

Alfic Hapludands

DHFU. Other Hapludands.

Typic Hapludands

Hydrudands

Key to Subgroups

DHDA. Hydrudands 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 Hydrudands

DHDB. Other Hydrudands that have, in one or more horizons 

at a depth between 50 and 100 cm either from the mineral 

soil surface or from the top of an organic layer with andic soil 

properties, whichever is shallower, aquic conditions for some 

time in normal years (or artificial drainage) and one or more of 

the following:

1. 2 percent or more redox concentrations; or

2. A color value, moist, of 4 or more and 50 percent or 

more chroma of 2 or less either in redox depletions on faces 

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction 

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

irrigated.

Aquic Hydrudands

DHDC. Other Hydrudands that have, at a depth between 25 
100 Keys to Soil Taxonomy

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. A sum of extractable bases (by NH4OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness 

of 30 cm or more; 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

DHDD. Other Hydrudands that have a sum of 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

DHDE. 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

DHDF. Other Hydrudands that have a sum of extractable 

bases (by NH4

OAc) 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

DHDG. Other Hydrudands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic 

horizon.

Ultic Hydrudands

DHDH. Other Hydrudands.

Typic Hydrudands

Melanudands

Key to Subgroups

DHCA. Melanudands that have a lithic contact within 50 cm 

of the mineral soil surface or of the top of an organic layer that 

has andic soil properties, whichever is shallower.

Lithic Melanudands

DHCB. Other Melanudands that have anthraquic conditions.

Anthraquic Melanudands

DHCC. 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

DHCD. Other Melanudands that have both:

1. A sum of extractable bases (by NH4OAc) plus 1N KClextractable Al3+ totaling less than 2.0 cmol(+)/kg in the fineearth fraction of one or more horizons with a total thickness 

of 30 cm or more at a depth between 25 and 100 cm either 

from the mineral soil surface or from the top of an organic 

layer with andic soil properties, whichever is shallower; 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 of the mineral soil surface or of the top of an organic 

layer with andic soil properties, whichever is shallower.

Acrudoxic Vitric Melanudands

DHCE. Other Melanudands that have both:

1. A sum of 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 
Andisols 101

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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 of the mineral soil surface or of the top of 

an organic layer with andic soil properties, whichever is 

shallower.

Acrudoxic Hydric Melanudands

DHCF. Other Melanudands that have a sum of 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

DHCG. 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 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 of the mineral soil surface or of the top of 

an organic layer with andic soil properties, whichever is 

shallower.

Pachic Vitric Melanudands

DHCH. 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 of the mineral soil surface or of 

the top of an organic layer with andic soil properties, whichever 

is shallower.

Vitric Melanudands

DHCI. 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 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 of the mineral soil surface or of the top of 

an organic layer with andic soil properties, whichever is 

shallower.

Hydric Pachic Melanudands

DHCJ. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Pachic Melanudands

DHCK. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Hydric Melanudands

DHCL. 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

DHCM. Other Melanudands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic 

horizon.

Ultic Melanudands

DHCN. Other Melanudands that have a sum of extractable 

bases (by NH4OAc) of more than 25.0 cmol(+)/kg in the fineearth fraction throughout one or more horizons with a total 

thickness of 15 cm or more at a depth between 25 and 

75 cm either from the mineral soil surface or from the top of 

an organic layer with andic soil properties, whichever is 

shallower.

Eutric Melanudands

DHCO. Other Melanudands.

Typic Melanudands
102 Keys to Soil Taxonomy

Placudands

Key to Subgroups

DHAA. Placudands that have a lithic contact within 50 cm of 

the mineral soil surface or of the top of an organic layer that has 

andic soil properties, whichever is shallower.

Lithic Placudands

DHAB. 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

DHAC. Other Placudands that have a sum of 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 placic horizon.

Acrudoxic Placudands

DHAD. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Hydric Placudands

DHAE. Other Placudands.

Typic Placudands

Ustands

Key to Great Groups

DGA. Ustands that have, in 75 percent or more of each 

pedon, a cemented horizon within 100 cm of the mineral

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Durustands, p. 102

DGB. Other Ustands.

Haplustands, p. 102

Durustands

Key to Subgroups

DGAA. 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

DGAB. 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

DGAC. Other Durustands that have a melanic, mollic, or 

umbric epipedon.

Humic Durustands

DGAD. Other Durustands.

Typic Durustands

Haplustands

Key to Subgroups

DGBA. Haplustands 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 Haplustands

DGBB. 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 
Andisols 103

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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

DGBC. Other Haplustands that have both:

1. A sum of 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 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 of the mineral soil surface or of the top of 

an organic layer with andic soil properties, whichever is 

shallower.

Dystric Vitric Haplustands

DGBD. 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 of the mineral soil surface or of 

the top of an organic layer with andic soil properties, whichever 

is shallower.

Vitric Haplustands

DGBE. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Pachic Haplustands

DGBF. 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

DGBG. Other Haplustands that have a calcic horizon within 

125 cm of the mineral soil surface or of the top of an organic 

layer with andic soil properties, whichever is shallower.

Calcic Haplustands

DGBH. Other Haplustands that have a sum of extractable 

bases (by NH4OAc) 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

DGBI. Other Haplustands that have an oxic horizon within 

125 cm of the mineral soil surface or of the top of an organic 

layer with andic soil properties, whichever is shallower.

Oxic Haplustands

DGBJ. Other Haplustands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm or throughout the entire 

argillic or kandic horizon if it is less than 50 cm thick.

Ultic Haplustands

DGBK. Other Haplustands that have an argillic or kandic 

horizon within 125 cm of the mineral soil surface or of the top 

of an organic layer with andic soil properties, whichever is 

shallower.

Alfic Haplustands

DGBL. Other Haplustands that have a melanic, mollic, or 

umbric epipedon.

Humic Haplustands

DGBM. Other Haplustands.

Typic Haplustands

Vitrands

Key to Great Groups

DFA. Vitrands that have an ustic soil moisture regime.

Ustivitrands, p. 104
104 Keys to Soil Taxonomy

DFB. Other Vitrands.

Udivitrands, p. 104

Udivitrands

Key to Subgroups

DFBA. Udivitrands 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 Udivitrands

DFBB. 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

DFBC. Other Udivitrands that are saturated with water 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 Udivitrands

DFBD. 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

DFBE. Other Udivitrands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic 

horizon.

Ultic Udivitrands

DFBF. Other Udivitrands that have an argillic or kandic 

horizon within 125 cm of the mineral soil surface or of the top 

of an organic layer with andic soil properties, whichever is 

shallower.

Alfic Udivitrands

DFBG. Other Udivitrands that have a melanic, mollic, or 

umbric epipedon.

Humic Udivitrands

DFBH. Other Udivitrands.

Typic Udivitrands

Ustivitrands

Key to Subgroups

DFAA. Ustivitrands 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 Ustivitrands

DFAB. 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

DFAC. Other Ustivitrands that have, at a depth between 25 

and 100 cm either from the mineral soil surface or from the 

top of an organic layer with andic soil properties, whichever 

is shallower, a layer 10 cm or more thick with more than 3.0 

percent organic carbon and the colors of a mollic epipedon 

throughout, underlying one or more horizons with a total 

thickness of 10 cm or more that have a color value, moist, 1 unit 

or more higher and an organic-carbon content 1 percent or more 

(absolute) lower.

Thaptic Ustivitrands

DFAD. Other Ustivitrands that have a calcic horizon within 
Andisols 105

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125 cm of the soil surface or of the top of an organic layer with 

andic soil properties, whichever is shallower.

Calcic Ustivitrands

DFAE. Other Ustivitrands that have a melanic, mollic, or 

umbric epipedon.

Humic Ustivitrands

DFAF. Other Ustivitrands.

Typic Ustivitrands

Xerands

Key to Great Groups

DEA. 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 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 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. 106

DEB. Other Xerands that have a melanic epipedon.

Melanoxerands, p. 106

DEC. Other Xerands.

Haploxerands, p. 105

Haploxerands

Key to Subgroups

DECA. 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

DECB. 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

DECC. 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

DECD. Other Haploxerands that have a calcic horizon within 

125 cm of the mineral soil surface.

Calcic Haploxerands

DECE. Other Haploxerands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm of the argillic or kandic 

horizon.

Ultic Haploxerands

DECF. Other Haploxerands that have both:

1. A mollic or umbric epipedon; and

2. An argillic or kandic horizon 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

DECG. Other Haploxerands that have an argillic or kandic 

horizon 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

DECH. Other Haploxerands that have a mollic or umbric 

epipedon.

Humic Haploxerands

DECI. Other Haploxerands.

Typic Haploxerands
106

Melanoxerands

Key to Subgroups

DEBA. 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 of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Pachic Melanoxerands

DEBB. Other Melanoxerands.

Typic Melanoxerands

Vitrixerands

Key to Subgroups

DEAA. 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

DEAB. 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

DEAC. 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

DEAD. Other Vitrixerands that have both:

1. A melanic, mollic, or umbric epipedon; and

2. An argillic or kandic horizon 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

DEAE. Other Vitrixerands that have both:

1. An argillic or kandic horizon 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 the upper 50 cm or throughout the entire 

argillic or kandic horizon if it is less than 50 cm thick.

Ultic Vitrixerands

DEAF. Other Vitrixerands that have an argillic or kandic 

horizon 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

DEAG. Other Vitrixerands that have a melanic, mollic, or 

umbric epipedon.

Humic Vitrixerands

DEAH. Other Vitrixerands.

Typic Vitrixerands
107

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Key to Suborders

GA. Aridisols that have a cryic soil temperature regime.

Cryids, p. 122

GB. Other Aridisols that have a salic horizon within 100 cm 

of the soil surface.

Salids, p. 132

GC. Other Aridisols that have a duripan within 100 cm of the 

soil surface.

Durids, p. 126

GD. Other Aridisols that have a gypsic or petrogypsic

horizon within 100 cm of the soil surface and do not have a 

petrocalcic horizon overlying these horizons.

Gypsids, p. 129

GE. Other Aridisols that have an argillic or natric horizon 

and do not have a petrocalcic horizon within 100 cm of the soil 

surface.

Argids, p. 107

GF. Other Aridisols that have a calcic or petrocalcic horizon 

within 100 cm of the soil surface.

Calcids, p. 116

GG. Other Aridisols.

Cambids, p. 118

Argids

Key to Great Groups

GEA. Argids that have a duripan or a petrocalcic or 

petrogypsic horizon within 150 cm of the soil surface.

Petroargids, p. 115

GEB. Other Argids that have a natric horizon.

Natrargids, p. 112

GEC. Other Argids that do not have a densic, lithic, or 

paralithic contact within 50 cm of the soil surface and have 

either:

1. An argillic horizon that has 35 percent or more 

noncarbonate clay throughout one or more subhorizons in its 

upper part, and one or both of the following:

a. A clay increase of 15 percent or more (absolute, in 

the fine-earth fraction) within a vertical distance of 2.5 cm 

either within the argillic horizon or at its upper boundary; 

or

b. An abrupt textural change between the eluvial 

horizon and the upper boundary of the argillic horizon; 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. 114

GED. Other Argids that have a gypsic horizon within 150 cm 

of the soil surface.

Gypsiargids, p. 109

GEE. Other Argids that have a calcic horizon within 150 cm 

of the soil surface.

Calciargids, p. 107

GEF. Other Argids.

Haplargids, p. 110

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 

Aridisols

CHAPTER 7
108 Keys to Soil Taxonomy

for some time in normal years and slickensides or wedgeshaped peds 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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 wedgeshaped peds 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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 peds 

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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have a moisture control section that, in normal years, 

is dry in all parts for less than three-fourths of the time 

(cumulative) when the soil temperature at a depth of 50 cm 

below the soil surface is 5 oC or higher and a soil moisture 

regime that borders on ustic.

Arenic Ustic Calciargids

GEEG. Other Calciargids that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and 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 ruptureresistance class when moist.

Durinodic Calciargids

GEEJ. Other Calciargids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Petronodic Xeric Calciargids
Aridisols 109

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GEEK. Other Calciargids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on ustic.

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Calciargids

GEEP. Other Calciargids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic.

Ustic Calciargids

GEEQ. Other Calciargids.

Typic Calciargids

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 ruptureresistance class when moist.

Durinodic Gypsiargids

GEDC. Other Gypsiargids that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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 
110 Keys to Soil Taxonomy

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Gypsiargids

GEDF. Other Gypsiargids that, in normal years, 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 below the soil surface is 5 oC or higher 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 both:

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 both:

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 parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Lithic Xeric Haplargids

GEFC. Other Haplargids that have both:

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 parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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 wedgeshaped peds 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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 peds 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 
Aridisols 111

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soil surface is 5 oC or higher 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 peds 

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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have a moisture control section that, in normal years, 

is dry in all parts for less than three-fourths of the time 

(cumulative) when the soil temperature at a depth of 50 cm 

below the soil surface is 5 oC or higher and a soil moisture 

regime that borders on ustic.

Arenic Ustic Haplargids

GEFJ. Other Haplargids that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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 ruptureresistance class when moist.

Durinodic Haplargids

GEFM. Other Haplargids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface 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) particles 2.0 mm 

or larger in diameter, 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
112 Keys to Soil Taxonomy

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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Haplargids

GEFR. Other Haplargids that, in normal years, 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 below the soil surface is 5 oC or higher 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:

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 parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Lithic Xeric Natrargids

GEBB. Other Natrargids that have both:

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 parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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:

1. In normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric; and

2. Have 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 most years and slickensides or wedgeshaped peds 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.

Xerertic Natrargids

GEBE. Other Natrargids that:

1. In normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic; and

2. Have 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 most years and slickensides or wedgeshaped peds 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.

Ustertic Natrargids

GEBF. 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 peds 

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
Aridisols 113

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GEBG. 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

GEBH. Other Natrargids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Durinodic Xeric Natrargids

GEBI. 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 ruptureresistance class when moist.

Durinodic Natrargids

GEBJ. 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

GEBK. Other Natrargids that have both:

1. Skeletans covering 10 percent or more of the surfaces of 

peds at a depth of 2.5 cm or more below the upper boundary 

of the natric horizon; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on ustic.

Glossic Ustic Natrargids

GEBL. Other Natrargids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher and a soil moisture regime that 

borders on ustic.

Haplic Ustic Natrargids

GEBM. Other Natrargids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Haploxeralfic Natrargids

GEBN. 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

GEBO. Other Natrargids that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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

GEBP. 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) particles 2.0 mm or 

larger in diameter, 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 
114 Keys to Soil Taxonomy

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Natrargids

GEBQ. Other Natrargids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Natrargids

GEBR. Other Natrargids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic.

Ustic Natrargids

GEBS. Other Natrargids that have skeletans covering 10 

percent or more of the surfaces of peds at a depth of 2.5 cm or 

more below the upper boundary of the natric horizon.

Glossic Natrargids

GEBT. 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 peds 

in a layer 15 cm or more thick that has its upper boundary 

within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the soil 

surface and either a depth of 100 cm or a densic, lithic, or 

paralithic contact, whichever is shallower.

Vertic Paleargids

GECB. Other Paleargids that are either:

1. Irrigated and have aquic conditions for some time in 

normal years in one or more layers within 100 cm of the soil 

surface; or

2. Saturated with water in one or more layers within 100 

cm of the soil surface for 1 month or more in normal years.

Aquic Paleargids

GECC. Other Paleargids that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand throughout a layer extending from the mineral soil 

surface to the top of an argillic horizon at a depth of 50 cm or 

more; and

2. Have a moisture control section that, in normal years, 

is dry in all parts for less than three-fourths of the time 

(cumulative) when the soil temperature at a depth of 50 cm 

below the soil surface is 5 oC or higher and a soil moisture 

regime that borders on ustic.

Arenic Ustic Paleargids

GECD. Other Paleargids that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 within 150 

cm of the soil surface.

Calcic Paleargids

GECF. Other Paleargids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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 ruptureresistance class when moist.

Durinodic Paleargids

GECH. Other Paleargids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on ustic.

Petronodic Ustic Paleargids
Aridisols 115

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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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Paleargids

GECM. Other Paleargids that, in normal years, 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 below the surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic.

Ustic Paleargids

GECN. Other Paleargids.

Typic Paleargids

Petroargids

Key to Subgroups

GEAA. Petroargids that have both:

1. A petrogypsic horizon within 150 cm of the soil surface; 

and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

surface is 5 oC or higher and a soil moisture regime that 

borders on ustic.

Petrogypsic Ustic Petroargids

GEAB. Other Petroargids that have a petrogypsic horizon 

within 150 cm of the soil surface.

Petrogypsic Petroargids

GEAC. Other Petroargids that have both:

1. A duripan within 150 cm of the soil surface; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Duric Xeric Petroargids

GEAD. Other Petroargids that have a duripan within 150 cm 

of the soil surface.

Duric Petroargids

GEAE. Other Petroargids that have a natric horizon.

Natric Petroargids

GEAF. Other Petroargids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Petroargids

GEAG. Other Petroargids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic.

Ustic Petroargids

GEAH. Other Petroargids.

Typic Petroargids
116 Keys to Soil Taxonomy

Calcids

Key to Great Groups

GFA. Calcids that have a petrocalcic horizon within 100 cm of 

the soil surface.

Petrocalcids, p. 118

GFB. Other Calcids.

Haplocalcids, p. 116

Haplocalcids

Key to Subgroups

GFBA. Haplocalcids that have both:

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 parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Lithic Xeric Haplocalcids

GFBB. Other Haplocalcids that have both:

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 parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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 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 peds 

in a layer 15 cm or more thick that has its upper boundary 

within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the soil 

surface and either a depth of 100 cm or a densic, lithic, or 

paralithic contact, whichever is shallower.

Vertic Haplocalcids

GFBE. Other Haplocalcids that:

1. Are either:

a. Irrigated and have aquic conditions for some time in 

normal years in one or more layers within 100 cm of the 

soil surface; or

b. Saturated with water in one or more layers within 

100 cm of the soil surface for 1 month or more in normal 

years; and

2. Have one or more horizons, within 100 cm of the soil 

surface and with a combined thickness of 15 cm or more, 

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 both:

1. A duripan within 150 cm of the soil surface; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher and a soil moisture regime that 

borders on xeric.

Duric Xeric Haplocalcids

GFBH. Other Haplocalcids that have a duripan within 150 cm 

of the soil surface.

Duric Haplocalcids

GFBI. Other Haplocalcids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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 
Aridisols 117

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of 15 cm or more, that contain 20 percent or more (by volume) 

durinodes or are brittle and have at least a firm ruptureresistance class when moist.

Durinodic Haplocalcids

GFBK. Other Haplocalcids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Petronodic Xeric Haplocalcids

GFBL. Other Haplocalcids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Sodic Xeric Haplocalcids

GFBO. 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, are dry in all 

parts of the moisture control section for less than three-fourths 
118 Keys to Soil Taxonomy

of the time (cumulative) when the soil temperature at a depth of 

50 cm below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Haplocalcids

GFBT. Other Haplocalcids that, in normal years, 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 below the soil surface is 5 oC or higher 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:

1. An argillic horizon within 100 cm of the soil surface; 

and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher and a soil moisture regime that 

borders on xeric.

Xeralfic Petrocalcids

GFAD. Other Petrocalcids that have both:

1. An argillic horizon within 100 cm of the soil surface; 

and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on ustic.

Ustalfic Petrocalcids

GFAE. Other Petrocalcids that have an argillic horizon within 

100 cm of the soil surface.

Argic Petrocalcids

GFAF. Other Petrocalcids that have both:

1. A calcic horizon overlying the petrocalcic horizon; and

2. A lithic contact within 50 cm of the soil surface.

Calcic Lithic Petrocalcids

GFAG. Other Petrocalcids that have a calcic horizon 

overlying the petrocalcic horizon.

Calcic Petrocalcids

GFAH. Other Petrocalcids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Petrocalcids

GFAI. Other Petrocalcids that, in normal years, 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 below the soil surface is 5 oC or higher 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. 119

GGB. Other Cambids that have a duripan or a petrocalcic or 

petrogypsic horizon within 150 cm of the soil surface.

Petrocambids, p. 122

GGC. Other Cambids.

Haplocambids, p. 119
Aridisols 119

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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 have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and 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 ruptureresistance 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, of which more than 66 percent is 

cinders, pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1

/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Aquicambids

GGAF. Other Aquicambids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) particles 2.0 mm or 

larger in diameter, 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 meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. 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.

Fluventic Aquicambids

GGAH. Other Aquicambids that, in normal years, are dry 

in all parts of the moisture control section for less than threefourths of the time (cumulative) when the soil temperature at a 

depth of 50 cm below the soil surface is 5 oC or higher and have 

a soil moisture regime that borders on xeric.

Xeric Aquicambids

GGAI. Other Aquicambids that, in normal years, 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 below the soil surface is 5 o

C or higher and have a soil 

moisture regime that borders on ustic.

Ustic Aquicambids

GGAJ. Other Aquicambids.

Typic Aquicambids

Haplocambids

Key to Subgroups

GGCA. Haplocambids that have both:

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 parts for less than three-fourths of the time (cumulative) 
120 Keys to Soil Taxonomy

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Lithic Xeric Haplocambids

GGCB. Other Haplocambids that have both:

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 parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on ustic.

Lithic Ustic Haplocambids

GGCC. Other Haplocambids that have a lithic contact within 

50 cm of the soil surface.

Lithic Haplocambids

GGCD. Other Haplocambids 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 wedgeshaped peds 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Xerertic Haplocambids

GGCE. Other Haplocambids 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 wedgeshaped peds 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher and a soil moisture regime that 

borders on ustic.

Ustertic Haplocambids

GGCF. Other Haplocambids 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 peds 

in a layer 15 cm or more thick that has its upper boundary 

within 125 cm of the soil surface; or

2. A linear extensibility of 6.0 cm or more between the soil 

surface and either a depth of 100 cm or a densic, lithic, or 

paralithic contact, whichever is shallower.

Vertic Haplocambids

GGCG. Other Haplocambids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Durinodic Xeric Haplocambids

GGCH. 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 ruptureresistance class when moist.

Durinodic Haplocambids

GGCI. Other Haplocambids that have both:

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Petronodic Xeric Haplocambids

GGCJ. Other Haplocambids that have both:

1. One or more horizons, within 100 cm of the soil 

surface and with a combined thickness of 15 cm or more, 
Aridisols 121

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that contain 20 percent or more (by volume) nodules or 

concretions; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on ustic.

Petronodic Ustic Haplocambids

GGCK. 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

GGCL. 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Sodic Xeric Haplocambids

GGCM. 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher and a soil moisture regime that 

borders on ustic.

Sodic Ustic Haplocambids

GGCN. 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

GGCO. Other Haplocambids that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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

GGCP. Other Haplocambids that have, throughout one or 

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

cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) particles 2.0 mm or 

larger in diameter, 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

GGCQ. Other Haplocambids that meet all of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. In normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric; and

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.

Xerofluventic Haplocambids

GGCR. Other Haplocambids that meet all of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. In normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic; and

3. Have an irregular decrease in organic-carbon content 
122 Keys to Soil Taxonomy

(Holocene age) between a depth of 25 cm and either a depth 

of 125 cm below the mineral soil surface or a densic, lithic, 

or paralithic contact, whichever is shallower.

Ustifluventic Haplocambids

GGCS. Other Haplocambids that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. 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.

Fluventic Haplocambids

GGCT. Other Haplocambids that have an anthropic epipedon.

Anthropic Haplocambids

GGCU. Other Haplocambids that, in normal years, are dry 

in all parts of the moisture control section for less than threefourths of the time (cumulative) when the soil temperature at a 

depth of 50 cm below the soil surface is 5 oC or higher and have 

a soil moisture regime that borders on xeric.

Xeric Haplocambids

GGCV. Other Haplocambids that, in normal years, are dry 

in all parts of the moisture control section for less than threefourths of the time (cumulative) when the soil temperature at a 

depth of 50 cm below the soil surface is 5 oC or higher and have 

a soil moisture regime that borders on ustic.

Ustic Haplocambids

GGCW. 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, are dry 

in all parts of the moisture control section for less than threefourths of the time (cumulative) when the soil temperature at a 

depth of 50 cm below the soil surface is 5 oC or higher and have 

a soil moisture regime that borders on xeric.

Xeric Petrocambids

GGBE. Other Petrocambids that, in normal years, are dry 

in all parts of the moisture control section for less than threefourths of the time (cumulative) when the soil temperature at a 

depth of 50 cm below the soil surface 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 within 100 cm of the 

soil surface.

Salicryids, p. 126

GAB. Other Cryids that have a duripan, petrocalcic horizon, 

or petrogypsic horizon within 100 cm of the soil surface.

Petrocryids, p. 125
Aridisols 123

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GAC. Other Cryids that have a gypsic horizon within 100 cm 

of the soil surface.

Gypsicryids, p. 124

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

Argicryids, p. 123

GAE. Other Cryids that have a calcic horizon within 100 cm 

of the soil surface.

Calcicryids, p. 123

GAF. Other Cryids.

Haplocryids, p. 124

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 peds 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 within 100 

cm of the soil surface.

Natric Argicryids

GADD. Other Argicryids that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Argicryids

GADG. Other Argicryids that, in normal years, 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 below the soil surface is 5 oC or higher 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 
124 Keys to Soil Taxonomy

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Calcicryids

GAEE. Other Calcicryids that, in normal years, 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 below the soil surface is 5 oC or higher 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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

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 

wedge-shaped peds 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
Aridisols 125

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GAFC. Other Haplocryids that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 o

C or higher and have a soil 

moisture regime that borders on xeric.

Xeric Haplocryids

GAFF. Other Haplocryids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic.

Ustic Haplocryids

GAFG. Other Haplocryids.

Typic Haplocryids

Petrocryids

Key to Subgroups

GABA. Petrocryids that have both:

1. A duripan that is strongly cemented or less cemented 

in all subhorizons within 100 cm of the soil surface; 

and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Xereptic Petrocryids

GABB. Other Petrocryids that have both:

1. A duripan within 100 cm of the soil surface; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Duric Xeric Petrocryids

GABC. Other Petrocryids that have a duripan within 100 cm 

of the soil surface.

Duric Petrocryids

GABD. Other Petrocryids that have a petrogypsic horizon 

within 100 cm of the soil surface.

Petrogypsic Petrocryids

GABE. Other Petrocryids that, in normal years, 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 below the soil surface is 5 o

C or higher and have a soil 

moisture regime that borders on xeric.

Xeric Petrocryids

GABF. Other Petrocryids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic.

Ustic Petrocryids

GABG. Other Petrocryids.

Typic Petrocryids
126 Keys to Soil Taxonomy

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. 128

GCB. Other Durids that have an argillic horizon above the 

duripan.

Argidurids, p. 126

GCC. Other Durids.

Haplodurids, p. 127

Argidurids

Key to Subgroups

GCBA. Argidurids that have 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 peds in a layer 15 cm or more 

thick that is 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 both:

1. An argillic horizon that has 35 percent or more 

noncarbonate clay throughout one or more subhorizons and

one or more of the following:

a. A clay increase of 15 percent or more (absolute, in 

the fine-earth fraction) 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, 

in the fine-earth fraction) at the upper boundary of the 

argillic horizon; or

c. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher 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 noncarbonate clay throughout one or more 

subhorizons and one or more of the following:

1. A clay increase of 15 percent or more (absolute, in the 

fine-earth fraction) within a vertical distance of 2.5 cm either 

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, in 

the fine-earth fraction) at the upper boundary of the argillic 

horizon; or

3. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon.

Abruptic Argidurids

GCBE. Other Argidurids that have both:

1. A duripan that is strongly cemented or less cemented in 

all subhorizons; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher and a soil moisture regime that 

borders on xeric.

Haploxeralfic Argidurids

GCBF. Other Argidurids that have a duripan that is strongly 

cemented or less cemented in all subhorizons.

Argidic Argidurids

GCBG. Other Argidurids that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 
Aridisols 127

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soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Argidurids

GCBJ. Other Argidurids that, in normal years, 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 below the soil surface 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 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.

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 both:

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 both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface 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) particles 2.0 mm 

or larger in diameter, 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 Haplodurids
128 Keys to Soil Taxonomy

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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface 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 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 peds in a layer 15 cm or more 

thick that is 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 both:

1. A duripan that is strongly cemented or less cemented in 

all subhorizons; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, of which more than 66 percent is 

cinders, pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1

/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Natridurids

GCAG. Other Natridurids that have, throughout one or more 

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

of the soil surface, one or both of the following:
Aridisols 129

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1. More than 35 percent (by volume) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher 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 

within 100 cm of the soil surface.

Petrogypsids, p. 132

GDB. Other Gypsids that have a natric horizon within 100 cm 

of the soil surface.

Natrigypsids, p. 131

GDC. Other Gypsids that have an argillic horizon within 100 

cm of the soil surface.

Argigypsids, p. 129

GDD. Other Gypsids that have a calcic horizon within 100 cm 

of the soil surface.

Calcigypsids, p. 130

GDE. Other Gypsids.

Haplogypsids, p. 130

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 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 peds 

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, of which more than 66 percent is 

cinders, pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Argigypsids

GDCF. Other Argigypsids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) particles 2.0 mm or 

larger in diameter, 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
130 Keys to Soil Taxonomy

GDCG. Other Argigypsids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Argigypsids

GDCH. Other Argigypsids that, in normal years, 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 below the soil surface 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Calcigypsids

GDDF. Other Calcigypsids that, in normal years, 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 below the soil surface 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 within 

18 cm of the soil surface.

Leptic Haplogypsids

GDEC. Other Haplogypsids that have, in a horizon at least 

25 cm thick within 100 cm of the mineral soil surface, an 

exchangeable sodium percentage of 15 or more (or an SAR of 

13 or more) during at least 1 month in normal years.

Sodic Haplogypsids

GDED. Other Haplogypsids that have one or more horizons, 

within 100 cm of the soil surface and with a combined thickness 

of 15 cm or more, that contain 20 percent or more (by volume) 

durinodes, nodules, or concretions.

Petronodic Haplogypsids
Aridisols 131

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GDEE. Other Haplogypsids that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, are dry 

in all parts of the moisture control section for less than threefourths of the time (cumulative) when the soil temperature at a 

depth of 50 cm below the soil surface is 5 o

C or higher and have 

a soil moisture regime that borders on xeric.

Xeric Haplogypsids

GDEH. Other Haplogypsids that, in normal years, are dry 

in all parts of the moisture control section for less than threefourths of the time (cumulative) when the soil temperature at a 

depth of 50 cm below the soil surface is 5 oC 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 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 peds 

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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, of which more than 66 percent is 

cinders, pumice, and pumicelike fragments; or

b. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1

/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Natrigypsids

GDBE. Other Natrigypsids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) particles 2.0 mm or 
132 Keys to Soil Taxonomy

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Natrigypsids

GDBG. Other Natrigypsids that, in normal years, 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 below the soil surface 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 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, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 

when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC 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) particles 2.0 mm 

or larger in diameter, 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) particles 2.0 mm or 

larger in diameter, 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, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on xeric.

Xeric Petrogypsids

GDAF. Other Petrogypsids that, in normal years, 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 below the soil surface is 5 oC or higher and have a soil 

moisture regime that borders on ustic.

Ustic Petrogypsids

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. 132

GBB. Other Salids.

Haplosalids, p. 133

Aquisalids

Key to Subgroups

GBAA. Aquisalids that have an anhydritic horizon within 100 

cm of the soil surface.

Anhydritic Aquisalids
Aridisols 133

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GBAB. Other Aquisalids that have a gypsic or petrogypsic 

horizon within 100 cm of the soil surface.

Gypsic Aquisalids

GBAC. Other Aquisalids that have a calcic or petrocalcic 

horizon within 100 cm of the soil surface.

Calcic Aquisalids

GBAD. Other Aquisalids.

Typic Aquisalids

Haplosalids

Key to Subgroups

GBBA. Haplosalids that have a duripan within 100 cm of the 

soil surface.

Duric Haplosalids

GBBB. Other Haplosalids that have a petrogypsic horizon 

within 100 cm of the soil surface.

Petrogypsic Haplosalids

GBBC. Other Haplosalids that have an anhydritic horizon 

within 100 cm of the soil surface.

Anhydritic Haplosalids

GBBD. Other Haplosalids that have a gypsic horizon within 

100 cm of the soil surface.

Gypsic Haplosalids

GBBE. Other Haplosalids that have a calcic horizon within 

100 cm of the soil surface.

Calcic Haplosalids

GBBF. Other Haplosalids.

Typic Haplosalids

135

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Key to Suborders

LA. Entisols that have a positive water potential at the soil 

surface for more than 21 hours of each day in all years.

Wassents, p. 154

LB. Other 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 class finer than loamy fine sand and, in 

50 percent or more of the matrix, one or more of the 

following:

(1) Neutral colors with no hue (N) and zero chroma; 

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 class of loamy fine sand or coarser and, 

in 50 percent or more of the matrix, one or more of the 

following:

(1) Neutral colors with no hue (N) and zero chroma; 

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. 136

LC. Other Entisols that have less than 35 percent (by volume) 

rock fragments and a texture class of loamy fine sand or coarser 

in all layers (sandy loam lamellae are permitted) within the 

particle-size control section.

Psamments, p. 150

LD. Other Entisols that do not have a densic, lithic, or 

paralithic contact within 25 cm of the mineral soil surface, a 

total thickness of 50 cm or more of human-transported material 

in the surface horizons, or a surface mantle of new soil material 

50 cm or more thick that is not derived from alluvial deposition, 

and they:

1. Do not occur on an anthropogenic landform or 

microfeature; and

2. Have a slope of less than 25 percent; and

3. Have one or both of the following:

a. An organic-carbon content (Holocene age) of 0.2 

percent or more at a depth of 125 cm below the mineral 

soil surface; 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; and

4. Have a soil temperature regime:

a. That is warmer than cryic; or

b. That is gelic or cryic and the soil has:

(1) No gelic materials; and

(2) Either a slope of less than 5 percent or less 

than 15 percent volcanic glass in the 0.02 to 2.0 

mm fraction in some part of the particle-size control 

section. 

Fluvents, p. 139

Entisols

CHAPTER 8
136 Keys to Soil Taxonomy

LE. Other Entisols.

Orthents, p. 145

Aquents

Key to Great Groups

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

mineral soil surface.

Sulfaquents, p. 139

LBB. 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. 138

LBC. Other Aquents that have a gelic soil temperature regime. 

Gelaquents, p. 138

LBD. Other Aquents that have a cryic soil temperature 

regime.

Cryaquents, p. 136

LBE. Other Aquents that have less than 35 percent (by 

volume) rock fragments and a texture class of loamy fine sand 

or coarser in all layers (sandy loam lamellae are permitted) 

within the particle-size control section.

Psammaquents, p. 138

LBF. Other Aquents that do not have a total thickness of 

50 cm or more of human-transported material in the surface 

horizons or a surface mantle of new soil material 50 cm or more 

thick that is not derived from alluvial deposition, and they:

1 Do not occur on an anthropogenic landform or 

microfeature; and

2. Have a slope of less than 25 percent; and

3. Have one or both of the following:

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

an organic-carbon content (Holocene age) of 0.2 percent 

or more; 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.

Fluvaquents, p. 137

LBG. Other Aquents that have episaturation.

Epiaquents, p. 137

LBH. Other Aquents.

Endoaquents, p. 136

Cryaquents

Key to Subgroups

LBDA. 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) particles 2.0 mm or 

larger in diameter, 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

LBDB. Other Cryaquents.

Typic Cryaquents

Endoaquents

Key to Subgroups

LBHA. 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 and does not have sulfide or other 

sulfur-bearing minerals.

Sulfic Endoaquents

LBHB. Other Endoaquents that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Endoaquents

LBHC. 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
Entisols 137

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LBHD. Other Endoaquents that have, in one or more horizons 

between either the Ap horizon or a depth of 25 cm from the 

mineral soil surface, whichever is deeper, and a depth of 75 cm, 

colors in 50 percent or more of the matrix as follows:

1. Hue of 2.5Y or redder, a color value, moist, of 6 or 

more, and chroma of 3 or more; or

2. Hue of 2.5Y or redder, a color value, moist, of 5 or less, 

and chroma of 2 or more; or

3. Hue of 5Y and chroma of 3 or more; or

4. Hue of 5Y or redder and chroma of 2 or more if there are 

no redox concentrations.

Aeric Endoaquents

LBHE. Other Endoaquents that have both:

1. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 15 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 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.

Humaqueptic Endoaquents

LBHF. Other Endoaquents that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Endoaquents

LBHG. Other Endoaquents.

Typic Endoaquents

Epiaquents

Key to Subgroups

LBGA. 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

LBGB. Other Epiaquents that have both:

1. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 15 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 15 cm after mixing; and

2. A base saturation (by NH4

OAc) of less than 50 percent 

in some part within 100 cm of the mineral soil surface.

Humaqueptic Epiaquents

LBGC. Other Epiaquents that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Epiaquents

LBGD. Other Epiaquents.

Typic Epiaquents

Fluvaquents

Key to Subgroups

LBFA. 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 and does not have sulfide or other 

sulfur-bearing minerals.

Sulfic Fluvaquents

LBFB. 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 wedgeshaped peds 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

LBFC. Other Fluvaquents that have a buried layer of organic 

soil materials, 20 cm or more thick, within 100 cm of the 

mineral soil surface.

Thapto-Histic Fluvaquents

LBFD. 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:
138 Keys to Soil Taxonomy

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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

3. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Aquandic Fluvaquents

LBFE. 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

LBFF. Other Fluvaquents that have both:

1. A color value, moist, of 3 or less and a color value, 

dry, of 5 or less (crushed and smoothed sample) either 

throughout the upper 15 cm of the mineral soil (unmixed) or 

between the mineral soil surface and a depth of 15 cm after 

mixing; and

2. A base saturation (by NH4

OAc) of less than 50 percent 

in some part within 100 cm of the mineral soil surface.

Humaqueptic Fluvaquents

LBFG. Other Fluvaquents that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Fluvaquents

LBFH. Other Fluvaquents.

Typic Fluvaquents

Gelaquents

Key to Subgroups

LBCA. All Gelaquents.

Typic Gelaquents

Hydraquents

Key to Subgroups

LBBA. 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 and does not have sulfide or other 

sulfur-bearing minerals.

Sulfic Hydraquents

LBBB. Other Hydraquents that have, in one or more horizons 

within 100 cm of the mineral soil surface, an exchangeable 

sodium percentage of 15 or more (or a sodium adsorption ratio 

of 13 or more) for 6 or more months in normal years.

Sodic Hydraquents

LBBC. Other Hydraquents that have a buried layer of organic 

soil materials, 20 cm or more thick, within 100 cm of the 

mineral soil surface.

Thapto-Histic Hydraquents

LBBD. Other Hydraquents.

Typic Hydraquents

Psammaquents

Key to Subgroups

LBEA. Psammaquents that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Psammaquents

LBEB. 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

LBEC. 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:
Entisols 139

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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

LBED. Other Psammaquents that have both:

1. A color value, moist, of 3 or less and a color value, 

dry, of 5 or less (crushed and smoothed sample) either 

throughout the upper 15 cm of the mineral soil (unmixed) or 

between the mineral soil surface and a depth of 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.

Humaqueptic Psammaquents

LBEE. Other Psammaquents that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Psammaquents

LBEF. Other Psammaquents.

Typic Psammaquents

Sulfaquents

Key to Subgroups

LBAA. 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

LBAB. Other Sulfaquents that have a histic epipedon.

Histic Sulfaquents

LBAC. Other Sulfaquents that have a buried layer of organic 

soil materials, 20 cm or more thick, within 100 cm of the 

mineral soil surface.

Thapto-Histic Sulfaquents

LBAD. Other Sulfaquents.

Typic Sulfaquents

Fluvents

Key to Great Groups

LDA. Fluvents that that have a gelic soil temperature regime.

Gelifluvents, p. 140

LDB. Other Fluvents that have a cryic soil temperature 

regime.

Cryofluvents, p. 139

LDC. Other Fluvents that have a xeric soil moisture regime.

Xerofluvents, p. 144

LDD. Other Fluvents that have an ustic soil moisture regime.

Ustifluvents, p. 142

LDE. Other Fluvents that have an aridic (or torric) soil 

moisture regime.

Torrifluvents, p. 140

LDF. Other Fluvents.

Udifluvents, p. 141

Cryofluvents

Key to Subgroups

LDBA. 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

LDBB. 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) particles 2.0 mm or 

larger in diameter, 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

LDBC. Other Cryofluvents that have, in one or more horizons 

within 50 cm of the mineral soil surface, redox depletions with 
140 Keys to Soil Taxonomy

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Cryofluvents

LDBD. 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

LDBE. Other Cryofluvents that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Cryofluvents

LDBF. Other Cryofluvents.

Typic Cryofluvents

Gelifluvents

Key to Subgroups

LDAA. Gelifluvents that have, in one or more horizons within 

100 cm of the mineral soil surface, both redox depletions with 

chroma of 2 or less and aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Gelifluvents

LDAB. Other Gelifluvents.

Typic Gelifluvents

Torrifluvents

Key to Subgroups

LDEA. 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 peds 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 parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher; and

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

ustic.

Ustertic Torrifluvents

LDEB. Other Torrifluvents that have one or both of the 

following:

1. Cracks within 125 cm of the soil surface that are 5 mm 

or more wide through a thickness of 30 cm or more for 

some time in most normal years and slickensides or wedgeshaped peds 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

LDEC. Other Torrifluvents that have:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher; and

2. A thermic, mesic, or frigid soil temperature regime and 

an aridic (or torric) soil 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) particles 2.0 mm 

or larger in diameter, 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

LDED. 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) particles 2.0 mm or 

larger in diameter, 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
Entisols 141

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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

LDEE. 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

LDEF. 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

LDEG. 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 at least a firm 

rupture-resistance class when moist; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher; and

3. A thermic, mesic, or frigid soil temperature regime and 

an aridic (or torric) soil moisture regime that borders on 

xeric.

Duric Xeric Torrifluvents

LDEH. 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 at least a firm rupture-resistance class when 

moist.

Duric Torrifluvents

LDEI. Other Torrifluvents that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher; and

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

ustic.

Ustic Torrifluvents

LDEJ. Other Torrifluvents that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher; and

2. A thermic, mesic, or frigid soil temperature regime and 

an aridic (or torric) soil moisture regime that borders on 

xeric.

Xeric Torrifluvents

LDEK. Other Torrifluvents that have an anthropic epipedon.

Anthropic Torrifluvents

LDEL. Other Torrifluvents.

Typic Torrifluvents

Udifluvents

Key to Subgroups

LDFA. 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 peds 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:

(1) Neutral colors with no hue (N) and zero chroma; 

or

(2) Hue of 5GY, 5G, 5BG, or 5B and also aquic 

conditions for some time in normal years (or artificial 

drainage).

Aquertic Udifluvents

LDFB. 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-
142 Keys to Soil Taxonomy

shaped peds 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

LDFC. 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

LDFD. 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) particles 2.0 mm or 

larger in diameter, 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

LDFE. 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:

a. Neutral colors with no hue (N) and zero chroma; or

b. Hue of 5GY, 5G, 5BG, or 5B and also aquic 

conditions for some time in normal years (or artificial 

drainage).

Aquic Udifluvents

LDFF. 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

LDFG. Other Udifluvents that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Udifluvents

LDFH. Other Udifluvents.

Typic Udifluvents

Ustifluvents

Key to Subgroups

LDDA. 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 peds 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:

(1) Neutral colors with no hue (N) and zero chroma; 

or

(2) Hue of 5GY, 5G, 5BG, or 5B and also aquic 

conditions for some time in normal years (or artificial 

drainage).

Aquertic Ustifluvents

LDDB. Other Ustifluvents that have both of the following:

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 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 
Entisols 143

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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, is moist in some or all parts for less 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. 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 peds 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

LDDC. 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 peds 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

LDDD. Other Ustifluvents that have anthraquic conditions.

Anthraquic Ustifluvents

LDDE. 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:

a. Neutral colors with no hue (N) and zero chroma; or

b. Hue of 5GY, 5G, 5BG, or 5B and also aquic 

conditions for some time in normal years (or artificial 

drainage).

Aquic Ustifluvents

LDDF. 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

LDDG. Other Ustifluvents that, when neither irrigated nor 

fallowed to store moisture, have one of the following:

1. A frigid soil temperature regime and a moisture control 

section that, in normal years, is dry in all parts for fourtenths or more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface is 

higher than 5 oC; or

2. A mesic or thermic soil temperature regime and a 

moisture control section that, in normal years, is dry in some 

part for six-tenths or more of the cumulative days per year 

when the soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 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 soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC.

Aridic Ustifluvents

LDDH. 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 soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

3. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that, in 

normal years, is dry in some or all parts for less than 120 

cumulative days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 o

C.

Udic Ustifluvents

LDDI. Other Ustifluvents that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Ustifluvents
144 Keys to Soil Taxonomy

LDDJ. Other Ustifluvents.

Typic Ustifluvents

Xerofluvents

Key to Subgroups

LDCA. 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 wedgeshaped peds 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

LDCB. 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:

a. Neutral colors with no hue (N) and zero chroma; or

b. 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) particles 2.0 mm 

or larger in diameter, 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

LDCC. 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

LDCD. 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) particles 2.0 mm or 

larger in diameter, 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

LDCE. 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:

a. Neutral colors with no hue (N) and zero chroma; or

b. Hue of 5GY, 5G, 5BG, or 5B; or

c. Aquic conditions for some time in normal years.

Aquic Xerofluvents

LDCF. 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

LDCG. 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

LDCH. Other Xerofluvents that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 
Entisols 145

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mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Xerofluvents

LDCI. Other Xerofluvents.

Typic Xerofluvents

Orthents

Key to Great Groups

LEA. Orthents that have a gelic soil temperature regime.

Gelorthents, p. 145

LEB. Other Orthents that have a cryic soil temperature 

regime.

Cryorthents, p. 145

LEC. Other Orthents that have an aridic (or torric) soil 

moisture regime.

Torriorthents, p. 145

LED. Other Orthents that have a xeric soil moisture regime.

Xerorthents, p. 149

LEE. Other Orthents that have an ustic soil moisture regime.

Ustorthents, p. 147

LEF. Other Orthents.

Udorthents, p. 147

Cryorthents

Key to Subgroups

LEBA. Cryorthents that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Cryorthents

LEBB. 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) particles 2.0 mm or 

larger in diameter, 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

LEBC. 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

LEBD. 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

LEBE. Other Cryorthents that have lamellae within 200 cm of 

the mineral soil surface.

Lamellic Cryorthents

LEBF. Other Cryorthents.

Typic Cryorthents

Gelorthents

Key to Subgroups

LEAA. Gelorthents that have, in one or more horizons within 

100 cm of the mineral soil surface, both redox depletions with 

chroma of 2 or less and aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Gelorthents

LEAB. Other Gelorthents 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 Gelorthents

LEAC. Other Gelorthents.

Typic Gelorthents

Torriorthents

Key to Subgroups

LECA. Torriorthents that have all of the following:

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 parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher; and

3. A hyperthermic, thermic, mesic, frigid, or iso soil 
146 Keys to Soil Taxonomy

temperature regime and an aridic (or torric) soil moisture 

regime that borders on ustic.

Lithic Ustic Torriorthents

LECB. Other Torriorthents that have all of the following:

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 parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher; and

3. A thermic, mesic, or frigid soil temperature regime and 

an aridic (or torric) soil moisture regime that borders on 

xeric.

Lithic Xeric Torriorthents

LECC. Other Torriorthents that have a lithic contact within 50 

cm of the soil surface.

Lithic Torriorthents

LECD. 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 wedgeshaped peds 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 parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher; and

3. A thermic, mesic, or frigid soil temperature regime and 

an aridic (or torric) soil moisture regime that borders on 

xeric.

Xerertic Torriorthents

LECE. 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 wedgeshaped peds 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 parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher; and

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

ustic.

Ustertic Torriorthents

LECF. 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 peds 

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

LECG. Other Torriorthents that have 50 cm or more of 

human-altered material. 

Anthraltic Torriorthents

LECH. 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Torriorthents

LECI. 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

LECJ. 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
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LECK. 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 

at least a firm rupture-resistance class when moist.

Duric Torriorthents

LECL. Other Torriorthents that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below 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) soil moisture 

regime that borders on ustic.

Ustic Torriorthents

LECM. Other Torriorthents that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher; and

2. A thermic, mesic, or frigid soil temperature regime and 

an aridic (or torric) soil moisture regime that borders on 

xeric.

Xeric Torriorthents

LECN. Other Torriorthents.

Typic Torriorthents

Udorthents

Key to Subgroups

LEFA. Udorthents that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Udorthents

LEFB. Other Udorthents that have both of the following:

1. A densic contact due to mechanical compaction in more 

than 90 percent of the pedon (measured laterally) within 100 

cm of the soil surface; and

2. An exchangeable sodium percentage of 15 or more (or a 

sodium adsorption ratio of 13 or more) in a horizon at least 

25 cm thick within 100 cm of the soil surface.

Anthrodensic Sodic Udorthents

LEFC. Other Udorthents that have a densic contact due to 

mechanical compaction in more than 90 percent of the pedon 

(measured laterally) within 100 cm of the soil surface.

Anthrodensic Udorthents

LEFD. Other Udorthents that have 50 cm or more of humantransported material.

Anthroportic Udorthents

LEFE. 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) particles 2.0 mm or 

larger in diameter, 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

LEFF. 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

LEFG. 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

LEFH. 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

LEFI. Other Udorthents.

Typic Udorthents

Ustorthents

Key to Subgroups

LEEA. Ustorthents that have both:

1. A lithic contact within 50 cm of the mineral soil surface; 

and
148 Keys to Soil Taxonomy

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 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, is moist in some or all parts for less 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.

Aridic Lithic Ustorthents

LEEB. Other Ustorthents that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Ustorthents

LEEC. 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 peds 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 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 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, is moist in some or all parts for less 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.

Torrertic Ustorthents

LEED. 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 peds 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

LEEE. Other Ustorthents that have anthraquic conditions.

Anthraquic Ustorthents

LEEF. Other Ustorthents that have a densic contact due to 

mechanical compaction in more than 90 percent of the pedon 

(measured laterally) within 100 cm of the soil surface.

Anthrodensic Ustorthents

LEEG. Other Ustorthents that have 50 cm or more of humantransported material.

Anthroportic Ustorthents

LEEH. 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

LEEI. 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

LEEJ. 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 at least a firm rupture-resistance class when moist.

Durinodic Ustorthents

LEEK. Other Ustorthents that have both:

1. When neither irrigated nor fallowed to store moisture, 

one of the following:
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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 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, is moist in some or all parts for less 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. 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) particles 2.0 mm 

or larger in diameter, 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

LEEL. 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) particles 2.0 mm or 

larger in diameter, 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

LEEM. 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 90 

consecutive days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC.

Aridic Ustorthents

LEEN. 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 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 dry in some or all parts for less 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 Ustorthents

LEEO. 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

LEEP. Other Ustorthents.

Typic Ustorthents

Xerorthents

Key to Subgroups

LEDA. Xerorthents that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Xerorthents
150 Keys to Soil Taxonomy

LEDB. Other Xerorthents that have both of the following:

1. 50 cm or more of human-altered material; and

2. An exchangeable sodium percentage of 15 or more (or a 

sodium adsorption ratio of 13 or more) in a horizon at least 

25 cm thick within 100 cm of the soil surface.

Anthraltic Sodic Xerorthents

LEDC. Other Xerorthents that have 50 cm or more of humanaltered material.

Anthraltic Xerorthents

LEDD. Other Xerorthents that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) particles 2.0 mm or 

larger in diameter, 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

LEDE. 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

LEDF. 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

LEDG. 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 at least a firm rupture-resistance class when moist.

Durinodic Xerorthents

LEDH. 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 or in the 

horizon directly above a root-limiting layer (defined in chapter 

17) that is at a shallower depth.

Dystric Xerorthents

LEDI. Other Xerorthents.

Typic Xerorthents

Psamments

Key to Great Groups

LCA. Psamments that have a cryic soil temperature regime.

Cryopsamments, p. 150

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

moisture regime.

Torripsamments, p. 152

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. 151

LCD. Other Psamments that have an ustic soil moisture 

regime.

Ustipsamments, p. 153

LCE. Other Psamments that have a xeric soil moisture regime.

Xeropsamments, p. 153

LCF. Other Psamments.

Udipsamments, p. 152

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 
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5 percent or more volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the volcanic 

glass (percent) is 30 or more.

Vitrandic Cryopsamments

LCAE. Other Cryopsamments that have a horizon 5 cm or 

more thick that has one or more of the following:

1. In 25 percent or more of each pedon, cementation by 

organic matter and aluminum, with or without iron; or

2. Al plus 1/2 Fe percentages (by ammonium oxalate) 

totaling 0.25 or more, and half that amount or less in an 

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as 

high or lower in an overlying horizon.

Spodic Cryopsamments

LCAF. Other Cryopsamments that have lamellae within 200 

cm of the mineral soil surface.

Lamellic Cryopsamments

LCAG. Other Cryopsamments.

Typic Cryopsamments

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 soil moisture regime; and

2. Have a clay fraction with a CEC of 16 cmol(+) or less 

per kg clay (by 1N 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 soil moisture regime; and

2. Have a clay fraction with a CEC of 16 cmol(+) or less 

per kg clay (by 1N 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 soil 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 soil 

moisture regime.

Ustic Quartzipsamments

LCCK. Other Quartzipsamments that have a xeric soil 

moisture regime.

Xeric Quartzipsamments
152 Keys to Soil Taxonomy

LCCL. Other Quartzipsamments that have a horizon, 5 cm or 

more thick, either below an Ap horizon or at a depth of 18 cm 

or more from the mineral soil surface, whichever is deeper, that 

has one or more of the following:

1. In 25 percent or more of each pedon, cementation by 

organic matter and aluminum, with or without iron; or

2. Al plus 1/2 Fe percentages (by ammonium oxalate) 

totaling 0.25 or more, and half that amount or less in an 

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as 

high or lower in an overlying horizon.

Spodic Quartzipsamments

LCCM. Other Quartzipsamments.

Typic Quartzipsamments

Torripsamments

Key to Subgroups

LCBA. Torripsamments that have a lithic contact within 50 

cm of the soil surface.

Lithic Torripsamments

LCBB. Other Torripsamments 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 Torripsamments

LCBC. 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

LCBD. 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 at least a firm rupture-resistance class when moist.

Haploduridic Torripsamments

LCBE. Other Torripsamments that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 o

C or higher; and

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

ustic.

Ustic Torripsamments

LCBF. Other Torripsamments that have both:

1. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is 5 oC or higher; and

2. A thermic, mesic, or frigid soil temperature regime and 

an aridic (or torric) soil moisture regime that borders on 

xeric.

Xeric Torripsamments

LCBG. 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

LCBH. 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:
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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.

Haploplaggic Udipsamments

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 o

C; or

2. A mesic or thermic soil temperature regime and a 

moisture control section that, in normal years, is dry in some 

part for six-tenths or more of the cumulative days per year 

when the soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that, in 

normal years, is moist in some or all parts for less than 180 

cumulative days per year when the soil 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 that 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 at least 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 
154 Keys to Soil Taxonomy

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 and 

that either has 20 percent or more (by volume) durinodes or is 

brittle and has at least 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 or in the 

horizon directly above a root-limiting layer (defined in chapter 

17) that is at a shallower depth.

Dystric Xeropsamments

LCEI. Other Xeropsamments.

Typic Xeropsamments

Wassents

Key to Great Groups

LAA. Wassents that have, in all horizons within 100 cm of the 

mineral soil surface, an electrical conductivity of less than 0.2 

dS/m in a 1:5 (soil:water), by volume, supernatant (not extract). 

Frasiwassents, p. 154

LAB. Other Wassents that have less than 35 percent (by 

volume) rock fragments and a texture class of loamy fine sand 

or coarser in all layers within the particle-size control section. 

Psammowassents, p. 155

LAC. Other Wassents that have a horizon or horizons with 

a combined thickness of at least 15 cm within 50 cm of the 

mineral soil surface that contain sulfidic materials. 

Sulfiwassents, p. 156

LAD. Other Wassents 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. 

Hydrowassents, p. 155

LAE. Other Wassents that have a total thickness of less than 

50 cm of human-transported material in the surface horizons 

and one or both of the following:

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. 

Fluviwassents, p. 154

LAF. Other Wassents.

Haplowassents, p. 155

Fluviwassents

Key to Subgroups

LAEA. Fluviwassents that have a horizon or horizons with 

a combined thickness of at least 15 cm within 100 cm of the 

mineral soil surface that contain sulfidic materials. 

Sulfic Fluviwassents

LAEB. Other Fluviwassents that have a lithic contact within 

100 cm of the mineral soil surface. 

Lithic Fluviwassents

LAEC. Other Fluviwassents that have a buried layer of 

organic soil materials, 20 cm or more thick, within 100 cm of 

the mineral soil surface. 

Thapto-Histic Fluviwassents

LAED. Other Fluviwassents that have chroma of 3 or more 

in 40 percent or more of the matrix of one or more horizons 

between a depth of 15 and 100 cm from the soil surface. 

Aeric Fluviwassents

LAEE. Other Fluviwassents. 

Typic Fluviwassents

Frasiwassents

Key to Subgroups

LAAA. Frasiwassents that have, in all horizons at a depth 

between 20 and 50 cm below the mineral soil surface, both an 
Entisols 155

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n value of more than 0.7 and 8 percent or more clay in the fineearth fraction. 

Hydric Frasiwassents

LAAB. Other Frasiwassents that have a lithic contact within 

100 cm of the mineral soil surface. 

Lithic Frasiwassents

LAAC. Other Frasiwassents that have less than 35 percent (by 

volume) rock fragments and a texture class of loamy fine sand 

or coarser in all layers within the particle-size control section. 

Psammentic Frasiwassents

LAAD. Other Frasiwassents that have a buried layer of 

organic soil materials, 20 cm or more thick, within 100 cm of 

the mineral soil surface. 

Thapto-Histic Frasiwassents

LAAE. Other Frasiwassents that have a total thickness of 

less than 50 cm of human-transported material in the surface 

horizons and one or both of the following:

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 Frasiwassents

LAAF. Other Frasiwassents that have chroma of 3 or more 

in 40 percent or more of the matrix of one or more horizons 

between a depth of 15 and 100 cm from the soil surface. 

Aeric Frasiwassents

LAAG. Other Frasiwassents. 

Typic Frasiwassents

Haplowassents 

Key to Subgroups 

LAFA. Haplowassents that have a horizon or horizons with 

a combined thickness of at least 15 cm within 100 cm of the 

mineral soil surface that contain sulfidic materials. 

Sulfic Haplowassents

LAFB. Other Haplowassents that have a lithic contact within 

100 cm of the mineral soil surface. 

Lithic Haplowassents

LAFC. Other Haplowassents that have chroma of 3 or 

more in 40 percent or more of the matrix of one or more 

horizons between a depth of 15 and 100 cm from the soil 

surface. 

Aeric Haplowassents

LAFD. Other Haplowassents. 

Typic Haplowassents

Hydrowassents 

Key to Subgroups 

LADA. Hydrowassents that have a horizon or horizons with 

a combined thickness of at least 15 cm within 100 cm of the 

mineral soil surface that contain sulfidic materials. 

Sulfic Hydrowassents

LADB. Other Hydrowassents that have, in all horizons at a 

depth between 20 and 100 cm below the mineral soil surface, 

both an n value of more than 0.7 and 8 percent or more clay in 

the fine-earth fraction. 

Grossic Hydrowassents

LADC. Other Hydrowassents that have a lithic contact within 

100 cm of the mineral soil surface. 

Lithic Hydrowassents

LADD. Other Hydrowassents that have a buried layer of 

organic soil materials, 20 cm or more thick, within 100 cm of 

the mineral soil surface. 

Thapto-Histic Hydrowassents

LADE. Other Hydrowassents. 

Typic Hydrowassents

Psammowassents 

Key to Subgroups 

LABA. Psammowassents that have a horizon or horizons with 

a combined thickness of at least 15 cm within 100 cm of the 

mineral soil surface that contain sulfidic materials. 

Sulfic Psammowassents

LABB. Other Psammowassents that have a lithic contact 

within 100 cm of the mineral soil surface.

Lithic Psammowassents

LABC. Other Psammowassents that have a total thickness of 

less than 50 cm of human-transported material in the surface 

horizons and one or both of the following:

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

an organic-carbon content (Holocene age) of 0.2 percent or 
156

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 Psammowassents

LABD. Other Psammowassents that have chroma of 3 or 

more in 40 percent or more of the matrix of one or more 

horizons between a depth of 15 and 100 cm from the soil 

surface. 

Aeric Psammowassents

LABE. Other Psammowassents. 

Typic Psammowassents

Sulfiwassents 

Key to Subgroups 

LACA. Sulfiwassents that have a lithic contact within 100 cm 

of the mineral soil surface. 

Lithic Sulfiwassents

LACB. Other Sulfiwassents 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 Sulfiwassents

LACC. Other Sulfiwassents that have a buried layer of 

organic soil materials, 20 cm or more thick, within 100 cm of 

the mineral soil surface. 

Thapto-Histic Sulfiwassents

LACD. Other Sulfiwassents that have a total thickness of 

less than 50 cm of human-transported material in the surface 

horizons and one or both of the following:

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 Sulfiwassents

LACE. Other Sulfiwassents that have chroma of 3 or more 

in 40 percent or more of the matrix of one or more horizons 

between a depth of 15 and 100 cm from the soil surface. 

Aeric Sulfiwassents

LACF. Other Sulfiwassents. 

Typic Sulfiwassents
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Gelisols

CHAPTER 9

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. Comprise 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 shallower.

Histels, p. 157

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. 162

AC. Other Gelisols.

Orthels, p. 158

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. 158

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 within 100 cm of the soil surface; and

2. Less than three-fourths (by volume) Sphagnum fibers in 

the organic soil material to a depth of 50 cm or to a densic, 

lithic, or paralithic contact, whichever is shallower.

Glacistels, p. 158

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 

shallower.

Fibristels, p. 157

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 

shallower.

Hemistels, p. 158

AAE. Other Histels.

Sapristels, p. 158

Fibristels

Key to Subgroups

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

the soil surface.

Lithic Fibristels

AACB. Other Fibristels that have a layer of mineral soil 

material 30 cm or more thick within 100 cm of the soil surface.

Terric Fibristels

AACC. Other Fibristels that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 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 (by 

volume) of the fibric soil materials are derived from Sphagnum

to a depth of 50 cm or to a densic, lithic, or paralithic contact, 

whichever is shallower.

Sphagnic Fibristels

AACE. Other Fibristels.

Typic Fibristels
158 Keys to Soil Taxonomy

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 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 soil 

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 

soil 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 layer of mineral soil 

material 30 cm or more thick within 100 cm of the soil surface.

Terric Hemistels

AADC. Other Hemistels that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 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 layer of mineral soil 

material 30 cm or more thick within 100 cm of the soil surface.

Terric Sapristels

AAEC. Other Sapristels that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 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 a histic epipedon.

Historthels, p. 160

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

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

aquic conditions during normal years (or artificial drainage).

Aquorthels, p. 159

ACC. Other Orthels that have anhydrous conditions.

Anhyorthels, p. 159

ACD. Other Orthels that have a mollic epipedon.

Mollorthels, p. 161

ACE. Other Orthels that have an umbric epipedon.

Umbrorthels, p. 162

ACF. Other Orthels that have an argillic horizon within 100 

cm of the mineral soil surface.

Argiorthels, p. 160

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 a texture class of loamy fine sand 

or coarser in all layers within the particle-size control section.

Psammorthels, p. 162
Gelisols 159

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ACH. Other Orthels.

Haplorthels, p. 160

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 within 100 

cm of the mineral soil surface.

Glacic Anhyorthels

ACCC. Other Anhyorthels that have a petrogypsic horizon 

within 100 cm of the mineral soil surface.

Petrogypsic Anhyorthels

ACCD. Other Anhyorthels that have a gypsic horizon within 

100 cm of the mineral soil surface.

Gypsic Anhyorthels

ACCE. Other Anhyorthels that have both of the following:

1. A horizon 15 cm or more thick that has a nitrate 

concentration of 118 mmol(-)/L or more in a 1:5 soil:water 

extract; and

2. The product of horizon thickness (in cm) times nitrate 

concentration [in mmol(-)/L] is 3,500 or more.

Nitric Anhyorthels

ACCF. Other Anhyorthels that have a salic horizon within 100 

cm of the mineral soil surface.

Salic Anhyorthels

ACCG. Other Anhyorthels that have a calcic horizon 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 within 100 

cm of the mineral soil surface.

Glacic Aquorthels

ACBC. Other Aquorthels that have a sulfuric horizon or 

sulfidic materials 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Aquorthels

ACBG. Other Aquorthels that have a salic horizon 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 class of loamy fine sand 

or coarser in all layers within the particle-size control section.

Psammentic Aquorthels

ACBI. Other Aquorthels that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

 a. At a depth of 125 cm below the mineral soil surface, 
160 Keys to Soil Taxonomy

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 Aquorthels

ACBJ. 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 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 within 100 

cm of the mineral soil surface.

Glacic Haplorthels

ACHC. Other Haplorthels that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Haplorthels

ACHD. Other Haplorthels that have a folistic epipedon.

Folistic Haplorthels

ACHE. 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

ACHF. Other Haplorthels that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Haplorthels

ACHG. 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 within 100 

cm of the soil surface.

Glacic Historthels
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ACAC. Other Historthels that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Historthels

ACAD. Other Historthels that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Historthels

ACAE. 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

ACAF. 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 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 wedgeshaped peds 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 Mollorthels

ACDD. Other Mollorthels that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Mollorthels

ACDE. Other Mollorthels that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) particles 2.0 mm or 

larger in diameter, 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 a folistic epipedon.

Folistic Mollorthels

ACDG. Other Mollorthels that have both:

1. A mollic epipedon that is 40 cm or more thick with a 

texture class finer than loamy fine sand; and

2. A slope of less than 25 percent.

Cumulic Mollorthels

ACDH. Other Mollorthels that have, in one or more horizons 

within 100 cm of the mineral soil surface, distinct or prominent 
162 Keys to Soil Taxonomy

redox concentrations and also aquic conditions for some time 

during normal years (or artificial drainage).

Aquic Mollorthels

ACDI. 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 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 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 wedgeshaped peds 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 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Umbrorthels

ACEF. Other Umbrorthels that have a folistic epipedon.

Folistic Umbrorthels

ACEG. Other Umbrorthels that have both:

1. An umbric epipedon that is 40 cm or more thick with a 

texture class finer than loamy fine sand; and

2. A slope of less than 25 percent.

Cumulic Umbrorthels

ACEH. 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

ACEI. 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 soil materials from 
Gelisols 163

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the soil surface to a depth of 50 cm which meet the saturation 

requirement for a histic epipedon.

Histoturbels, p. 164

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. 163

ABC. Other Turbels that have anhydrous conditions.

Anhyturbels, p. 163

ABD. Other Turbels that have a mollic epipedon.

Molliturbels, p. 164

ABE. Other Turbels that have an umbric epipedon.

Umbriturbels, p. 165

ABF. Other Turbels that have less than 35 percent (by 

volume) rock fragments and a texture class of loamy fine sand 

or coarser in all layers within the particle-size control section.

Psammoturbels, p. 164

ABG. Other Turbels.

Haploturbels, p. 163

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 within 100 

cm of the mineral soil surface.

Glacic Anhyturbels

ABCC. Other Anhyturbels that have a petrogypsic horizon 

within 100 cm of the mineral soil surface.

Petrogypsic Anhyturbels

ABCD. Other Anhyturbels that have a gypsic horizon within 

100 cm of the mineral soil surface.

Gypsic Anhyturbels

ABCE. Other Anhyturbels that have both of the following:

1. A horizon 15 cm or more thick that has a nitrate 

concentration of 118 mmol(-)/L or more in a 1:5 soil:water 

extract; and

2. The product of horizon thickness (in cm) times nitrate 

concentration [in mmol(-)/L] is 3,500 or more.

Nitric Anhyturbels

ABCF. Other Anhyturbels that have a salic horizon within 100 

cm of the mineral soil surface.

Salic Anhyturbels

ABCG. Other Anhyturbels that have a calcic horizon 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 within 100 

cm of the mineral soil surface.

Glacic Aquiturbels

ABBC. Other Aquiturbels that have a sulfuric horizon or 

sulfidic materials within 100 cm of the mineral soil surface.

Sulfuric Aquiturbels

ABBD. Other Aquiturbels 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 Aquiturbels

ABBE. Other Aquiturbels that have less than 35 percent (by 

volume) rock fragments and a texture class 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 within 100 

cm of the mineral soil surface.

Glacic Haploturbels
164 Keys to Soil Taxonomy

ABGC. Other Haploturbels that have a folistic epipedon.

Folistic Haploturbels

ABGD. 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

ABGE. 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 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 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 wedgeshaped peds 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 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Molliturbels

ABDF. Other Molliturbels that have a folistic epipedon.

Folistic Molliturbels

ABDG. Other Molliturbels that have both:

1. A mollic epipedon that is 40 cm or more thick with a 

texture class finer than loamy fine sand; and

2. A slope of less than 25 percent.

Cumulic Molliturbels

ABDH. 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

ABDI. 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 within 

100 cm of the mineral soil surface.

Glacic Psammoturbels
Gelisols 165

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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 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 wedgeshaped peds 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 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Umbriturbels

ABEF. Other Umbriturbels that have a folistic epipedon.

Folistic Umbriturbels

ABEG. Other Umbriturbels that have both:

1. An umbric epipedon that is 40 cm or more thick with a 

texture class finer than loamy fine sand; and

2. A slope of less than 25 percent.

Cumulic Umbriturbels

ABEH. 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

ABEI. Other Umbriturbels.

Typic Umbriturbels

167

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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. 168

BB. Other Histosols that have a positive water potential at the 

soil surface for more than 21 hours of each day in all years.

Wassists, p. 171

BC. Other Histosols that:

1. Have more thickness of fibric soil materials than any 

other kind of organic soil materials either:

a. In the organic parts of the subsurface tier if there is no 

continuous layer of mineral soil material 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 and there is a continuous 

layer of mineral soil material 40 cm or more thick that has 

its upper boundary within the subsurface tier; and

2. Do not have a sulfuric horizon within 50 cm of the soil 

surface; and

3. Do not have sulfidic materials within 100 cm of the soil 

surface.

Fibrists, p. 167

BD. 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 layer of mineral soil material 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 and there is a continuous layer 

of mineral soil material 40 cm or more thick that has its 

upper boundary within the subsurface tier.

Saprists, p. 170

BE. Other Histosols.

Hemists, p. 169

Fibrists

Key to Great Groups

BCA. Fibrists that have a cryic soil temperature regime.

Cryofibrists, p. 167

BCB. Other Fibrists in which Sphagnum fibers constitute 

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. 168

BCC. Other Fibrists.

Haplofibrists, p. 168

Cryofibrists

Key to Subgroups

BCAA. Cryofibrists that have a layer of water within the 

control section, below the surface tier.

Hydric Cryofibrists

BCAB. Other Cryofibrists that have a lithic contact at the 

lower boundary of the control section.

Lithic Cryofibrists

BCAC. Other Cryofibrists that have a layer of mineral soil 

material 30 cm or more thick that has its upper boundary within 

the control section, below the surface tier.

Terric Cryofibrists

BCAD. Other Cryofibrists that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 5 cm or more thick or two or more 

Histosols

CHAPTER 10
168 Keys to Soil Taxonomy

layers of mineral soil material of any thickness in the control 

section, below the surface tier.

Fluvaquentic Cryofibrists

BCAE. Other Cryofibrists in which three-fourths or more 

of the fiber volume in the surface tier is derived from 

Sphagnum.

Sphagnic Cryofibrists

BCAF. Other Cryofibrists.

Typic Cryofibrists

Haplofibrists

Key to Subgroups

BCCA. Haplofibrists that have a layer of water within the 

control section, below the surface tier.

Hydric Haplofibrists

BCCB. Other Haplofibrists that have a lithic contact at the 

lower boundary of the control section.

Lithic Haplofibrists

BCCC. Other Haplofibrists that have one or more limnic 

layers with a total thickness of 5 cm or more within the control 

section.

Limnic Haplofibrists

BCCD. Other Haplofibrists that have a layer of mineral soil 

material 30 cm or more thick that has its upper boundary within 

the control section, below the surface tier.

Terric Haplofibrists

BCCE. Other Haplofibrists that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 5 cm or more thick or two or more 

layers of mineral soil material of any thickness in the control 

section, below the surface tier.

Fluvaquentic Haplofibrists

BCCF. 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

BCCG. Other Haplofibrists.

Typic Haplofibrists

Sphagnofibrists

Key to Subgroups

BCBA. Sphagnofibrists that have a layer of water within the 

control section, below the surface tier.

Hydric Sphagnofibrists

BCBB. Other Sphagnofibrists that have a lithic contact at the 

lower boundary of the control section.

Lithic Sphagnofibrists

BCBC. Other Sphagnofibrists that have one or more limnic 

layers with a total thickness of 5 cm or more within the control 

section.

Limnic Sphagnofibrists

BCBD. Other Sphagnofibrists that have a layer of mineral soil 

material 30 cm or more thick that has its upper boundary within 

the control section, below the surface tier.

Terric Sphagnofibrists

BCBE. Other Sphagnofibrists that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 5 cm or more thick or two or more 

layers of mineral soil material of any thickness in the control 

section, below the surface tier.

Fluvaquentic Sphagnofibrists

BCBF. 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

BCBG. Other Sphagnofibrists.

Typic Sphagnofibrists

Folists

Key to Great Groups

BAA. Folists that have a cryic soil temperature regime.

Cryofolists, p. 169

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

regime.

Torrifolists, p. 169

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

regime.

Ustifolists, p. 169
Histosols 169

H

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BAD. Other Folists.

Udifolists, p. 169

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

BEA. Hemists that have a sulfuric horizon within 50 cm of the 

soil surface.

Sulfohemists, p. 170

BEB. Other Hemists that have sulfidic materials within 100 

cm of the soil surface.

Sulfihemists, p. 170

BEC. Other Hemists that have a horizon 2 cm or more thick 

in which humilluvic material constitutes one-half or more of the 

volume.

Luvihemists, p. 170

BED. Other Hemists that have a cryic soil temperature 

regime.

Cryohemists, p. 169

BEE. Other Hemists.

Haplohemists, p. 169

Cryohemists

Key to Subgroups

BEDA. Cryohemists that have a layer of water within the 

control section, below the surface tier.

Hydric Cryohemists

BEDB. Other Cryohemists that have a lithic contact at the 

lower boundary of the control section.

Lithic Cryohemists

BEDC. Other Cryohemists that have a layer of mineral soil 

material 30 cm or more thick that has its upper boundary within 

the control section, below the surface tier.

Terric Cryohemists

BEDD. Other Cryohemists that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 5 cm or more thick or two or more 

layers of mineral soil material of any thickness in the control 

section, below the surface tier.

Fluvaquentic Cryohemists

BEDE. Other Cryohemists.

Typic Cryohemists

Haplohemists

Key to Subgroups

BEEA. Haplohemists that have a layer of water within the 

control section, below the surface tier.

Hydric Haplohemists
170 Keys to Soil Taxonomy

BEEB. Other Haplohemists that have a lithic contact at the 

lower boundary of the control section.

Lithic Haplohemists

BEEC. Other Haplohemists that have one or more limnic 

layers with a total thickness of 5 cm or more within the control 

section.

Limnic Haplohemists

BEED. Other Haplohemists that have a layer of mineral soil 

material 30 cm or more thick that has its upper boundary within 

the control section, below the surface tier.

Terric Haplohemists

BEEE. Other Haplohemists that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 5 cm or more thick or two or more 

layers of mineral soil material of any thickness in the control 

section, below the surface tier.

Fluvaquentic Haplohemists

BEEF. 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

BEEG. 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

BEEH. Other Haplohemists.

Typic Haplohemists

Luvihemists

Key to Subgroups

BECA. All Luvihemists (provisionally).

Typic Luvihemists

Sulfihemists

Key to Subgroups

BEBA. Sulfihemists that have a layer of mineral soil material 

30 cm or more thick that has its upper boundary within the 

control section, below the surface tier.

Terric Sulfihemists

BEBB. Other Sulfihemists.

Typic Sulfihemists

Sulfohemists

Key to Subgroups

BEAA. All Sulfohemists (provisionally).

Typic Sulfohemists

Saprists

Key to Great Groups

BDA. Saprists that have a sulfuric horizon within 50 cm of the 

soil surface.

Sulfosaprists, p. 171

BDB. Other Saprists that have sulfidic materials within 100 

cm of the soil surface.

Sulfisaprists, p. 171

BDC. Other Saprists that have a cryic soil temperature regime.

Cryosaprists, p. 170

BDD. Other Saprists.

Haplosaprists, p. 171

Cryosaprists

Key to Subgroups

BDCA. Cryosaprists that have a lithic contact at the lower 

boundary of the control section.

Lithic Cryosaprists

BDCB. Other Cryosaprists that have one or more limnic 

layers with a total thickness of 5 cm or more within the control 

section.

Limnic Cryosaprists

BDCC. Other Cryosaprists that have a layer of mineral soil 

material 30 cm or more thick that has its upper boundary within 

the control section, below the surface tier.

Terric Cryosaprists

BDCD. Other Cryosaprists that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 5 cm or more thick or two or more 

layers of mineral soil material of any thickness in the control 

section, below the surface tier.

Fluvaquentic Cryosaprists

BDCE. Other Cryosaprists.

Typic Cryosaprists
Histosols 171

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Haplosaprists

Key to Subgroups

BDDA. Haplosaprists that have a lithic contact at the lower 

boundary of the control section.

Lithic Haplosaprists

BDDB. Other Haplosaprists that have one or more limnic 

layers with a total thickness of 5 cm or more within the control 

section.

Limnic Haplosaprists

BDDC. 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 layer of mineral soil material 30 cm or more thick that 

has its upper boundary within the control section, below the 

surface tier.

Halic Terric Haplosaprists

BDDD. Other Haplosaprists that have, throughout a layer 

30 cm or more 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.

Halic Haplosaprists

BDDE. Other Haplosaprists that have a layer of mineral soil 

material 30 cm or more thick that has its upper boundary within 

the control section, below the surface tier.

Terric Haplosaprists

BDDF. Other Haplosaprists that meet both of the following:

1. Have a total thickness of less than 50 cm of humantransported material in the surface horizons; and

2. Have, within the organic soil materials, either one layer 

of mineral soil material 5 cm or more thick or two or more 

layers of mineral soil material of any thickness in the control 

section, below the surface tier.

Fluvaquentic Haplosaprists

BDDG. 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

BDDH. Other Haplosaprists.

Typic Haplosaprists

Sulfisaprists

Key to Subgroups

BDBA. Sulfisaprists that have a layer of mineral soil material 

30 cm or more thick that has its upper boundary within the 

control section, below the surface tier.

Terric Sulfisaprists

BDBB. Other Sulfisaprists.

Typic Sulfisaprists

Sulfosaprists

Key to Subgroups

BDAA. All Sulfosaprists (provisionally).

Typic Sulfosaprists

Wassists

Key to Great Groups

BBA. Wassists that have, in all horizons within 100 cm of the 

soil surface, an electrical conductivity of less than 0.2 dS/m in a 

1:5 (soil:water), by volume, supernatant (not extract).

Frasiwassists, p. 171

BBB. Other Wassists that have a horizon or horizons, with a 

combined thickness of at least 15 cm within 50 cm of the soil 

surface, that contain sulfidic materials.

Sulfiwassists, p. 172

BBC. Other Wassists.

Haplowassists, p. 172

Frasiwassists 

Key to Subgroups

BBAA. Frasiwassists that:

1. Have more thickness of fibric soil materials than any 

other kind of organic soil materials either:

a. In the organic parts of the subsurface tier if there is no 

continuous layer of mineral soil material 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 and there is a 

continuous layer of mineral soil material 40 cm or more 

thick that has its upper boundary within the subsurface 

tier; and
172

2. Do not have sulfidic materials within 100 cm of the soil 

surface.

Fibric Frasiwassists

BBAB. Other Frasiwassists 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 layer of mineral soil material 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 and there is a continuous layer 

of mineral soil material 40 cm or more thick that has its 

upper boundary within the subsurface tier.

Sapric Frasiwassists

BBAC. Other Frasiwassists.

Typic Frasiwassists

Haplowassists

Key to Subgroups

BBCA. Haplowassists that have a horizon or horizons, with a 

combined thickness of 15 cm within 100 cm of the soil surface, 

that contain sulfidic materials.

Sulfic Haplowassists

BBCB. Other Haplowassists that have more thickness of 

fibric 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 layer of mineral soil material 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 and there is a continuous layer 

of mineral soil material 40 cm or more thick that has its 

upper boundary within the subsurface tier.

Fibric Haplowassists

BBCC. Other Haplowassists 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 layer of mineral soil material 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 and there is a continuous layer 

of mineral soil material 40 cm or more thick that has its 

upper boundary within the subsurface tier.

Sapric Haplowassists

BBCD. Other Haplowassists.

Typic Haplowassists

Sulfiwassists

Key to Subgroups

BBBA. Sulfiwassists that have more thickness of fibric 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 layer of mineral soil material 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 and there is a continuous layer 

of mineral soil material 40 cm or more thick that has its 

upper boundary within the subsurface tier.

Fibric Sulfiwassists

BBBB. Other Sulfiwassists 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 layer of mineral soil material 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 and there is a continuous layer 

of mineral soil material 40 cm or more thick that has its 

upper boundary within the subsurface tier.

Sapric Sulfiwassists

BBBC. Other Sulfiwassists.

Typic Sulfiwassists
173

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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 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. 173

KB. Other Inceptisols that have a gelic soil temperature regime.

Gelepts, p. 185

KC. Other Inceptisols that have a cryic soil temperature 

regime.

Cryepts, p. 180

KD. Other Inceptisols that have an ustic soil moisture regime.

Ustepts, p. 195

KE. Other Inceptisols that have a xeric soil moisture regime.

Xerepts, p. 203

KF. Other Inceptisols.

Udepts, p. 187

Aquepts

Key to Great Groups

KAA. Aquepts that have a sulfuric horizon within 50 cm of 

the mineral soil surface.

Sulfaquepts, p. 179

KAB. Other Aquepts that have, within 100 cm of the mineral 

soil surface, one or more horizons in which plinthite or a 

cemented diagnostic horizon either forms a continuous phase or 

constitutes one-half or more of the volume.

Petraquepts, p. 179

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. 178

KAD. Other Aquepts that have a fragipan within 100 cm of 

the mineral soil surface.

Fragiaquepts, p. 177

KAE. Other Aquepts that have a gelic soil temperature 

regime.

Gelaquepts, p. 177

KAF. Other Aquepts that have a cryic soil temperature regime.

Cryaquepts, p. 174

KAG. 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. 179

Inceptisols

CHAPTER 11
174 Keys to Soil Taxonomy

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

umbric epipedon.

Humaquepts, p. 178

KAI. Other Aquepts that have episaturation.

Epiaquepts, p. 176

KAJ. Other Aquepts.

Endoaquepts, p. 175

Cryaquepts

Key to Subgroups

KAFA. 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 

value between 3.5 and 4.0 and does not have sulfide or other 

sulfur-bearing minerals; or

3. Sulfidic materials.

Sulfic Cryaquepts

KAFB. Other Cryaquepts that have both a histic epipedon and 

a lithic contact within 50 cm of the mineral soil surface.

Histic Lithic Cryaquepts

KAFC. Other Cryaquepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Cryaquepts

KAFD. 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 wedgeshaped peds 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

KAFE. Other Cryaquepts that have a histic epipedon.

Histic Cryaquepts

KAFF. 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) particles 2.0 mm or 

larger in diameter, 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

KAFG. Other Cryaquepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Cryaquepts

KAFH. 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

KAFI. 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

KAFJ. Other Cryaquepts that have a mollic or umbric 

epipedon.

Humic Cryaquepts

KAFK. Other Cryaquepts.

Typic Cryaquepts
Inceptisols 175

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Endoaquepts

Key to Subgroups

KAJA. 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 

value between 3.5 and 4.0 and does not have sulfide or other 

sulfur-bearing minerals; or

3. Sulfidic materials.

Sulfic Endoaquepts

KAJB. Other Endoaquepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Endoaquepts

KAJC. 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 wedgeshaped peds 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

KAJD. 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) particles 2.0 mm or 

larger in diameter, 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

KAJE. Other Endoaquepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. In one or more horizons between the A or Ap horizon 

and a depth of 75 cm below the mineral soil surface, one of 

the following colors:

a. Hue of 7.5YR or redder in 50 percent or more of the 

matrix; and

(1) If peds are present, either chroma of 2 or more 

on 50 percent or more of ped exteriors or no redox 

depletions with chroma of 2 or less in ped interiors; 

or

(2) If peds are absent, chroma of 2 or more in 50 

percent or more of the matrix; or

b. In 50 percent or more of the matrix, hue of 10YR or 

yellower; and either

(1) Both a color value, moist, and chroma of 3 or 

more; or

(2) Chroma of 2 or more if there are no redox 

concentrations; and

4. One or both of the following: 

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

an organic-carbon content (Holocene age) of 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 Endoaquepts

KAJF. Other Endoaquepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 
176 Keys to Soil Taxonomy

a densic, lithic, or paralithic contact, whichever is 

shallower.

Fluvaquentic Endoaquepts

KAJG. 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

KAJH. 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

KAJI. Other Endoaquepts that have both:

1. A color value, moist, of 3 or less and a color value, 

dry, of 5 or less (crushed and smoothed sample) either 

throughout the upper 15 cm of the mineral soil (unmixed) or 

between the mineral soil surface and a depth of 15 cm after 

mixing; and

2. A base saturation (by NH4

OAc) of less than 50 percent 

in some part within 100 cm of the mineral soil surface.

Humic Endoaquepts

KAJJ. Other Endoaquepts that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Endoaquepts

KAJK. Other Endoaquepts.

Typic Endoaquepts

Epiaquepts

Key to Subgroups

KAIA. 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 wedgeshaped peds 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

KAIB. 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) particles 2.0 mm or 

larger in diameter, 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

KAIC. Other Epiaquepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Epiaquepts
Inceptisols 177

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KAID. Other Epiaquepts that have fragic soil properties 

either:

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

KAIE. 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

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

KAIF. 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 sample) either throughout 

the upper 15 cm of the mineral soil (unmixed) or between 

the mineral soil surface and a depth of 15 cm after mixing; 

and

2. A base saturation (by NH4

OAc) of less than 50 percent 

in some part within 100 cm of the mineral soil surface.

Humic Epiaquepts

KAIG. Other Epiaquepts that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 15 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 15 cm after mixing.

Mollic Epiaquepts

KAIH. 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

Gelaquepts

Key to Subgroups

KAEA. Gelaquepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Gelaquepts

KAEB. Other Gelaquepts that have a histic epipedon.

Histic Gelaquepts

KAEC. Other Gelaquepts 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) particles 2.0 mm or 

larger in diameter, 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 Gelaquepts
178 Keys to Soil Taxonomy

KAED. Other Gelaquepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Gelaquepts

KAEE. Other Gelaquepts that have a mollic or umbric 

epipedon.

Humic Gelaquepts

KAEF. Other Gelaquepts that have gelic materials within 200 

cm of the mineral soil surface.

Turbic Gelaquepts

KAEG. Other Gelaquepts.

Typic Gelaquepts

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 wedgeshaped peds 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) particles 2.0 mm or 

larger in diameter, 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 one or more horizons, 

with a combined thickness of 15 cm or more, that contain 20 

percent or more (by volume) cemented soil material and are 

within 100 cm of the mineral soil surface or of the top of an 

organic layer with andic soil properties, whichever is shallower.

Duric Halaquepts

KACD. Other Halaquepts that have chroma of 3 or more in 40 

percent or more of the matrix of one or more horizons at a depth 

between 15 and 75 cm from the mineral soil surface.

Aeric Halaquepts

KACE. Other Halaquepts.

Typic Halaquepts

Humaquepts

Key to Subgroups

KAHA. 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

KAHB. Other Humaquepts that have a histic epipedon.

Histic Humaquepts

KAHC. 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or
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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

KAHD. Other Humaquepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. An umbric or mollic epipedon that is 60 cm or more 

thick; and

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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.

Cumulic Humaquepts

KAHE. Other Humaquepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Humaquepts

KAHF. 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

KAHG. 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 8 or more percent clay) in one or 

more layers at a depth between 20 and 50 cm from the 

mineral soil surface; or

2. More than 0.9 in one or more layers at a depth between 

50 and 100 cm from the mineral soil surface.

Hydraquentic Sulfaquepts

KAAC. Other Sulfaquepts.

Typic Sulfaquepts

Vermaquepts

Key to Subgroups

KAGA. 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
180 Keys to Soil Taxonomy

KAGB. Other Vermaquepts.

Typic Vermaquepts

Cryepts

Key to Great Groups

KCA. Cryepts that have an umbric or mollic epipedon.

Humicryepts, p. 184

KCB. Other Cryepts that have a calcic or petrocalcic horizon 

within 100 cm of the mineral soil surface.

Calcicryepts, p. 180

KCC. Other Cryepts that meet both of the following:

1. Do not have free carbonates within 200 cm of the 

mineral soil surface; and

2. Have a base saturation (by NH4OAc) of less than 50 

percent, either:

a. In one-half or more of the thickness between 25 

and 75 cm below the mineral soil surface and there is 

no placic horizon, duripan, fragipan, or densic, lithic, or 

paralithic contact within 50 cm of the mineral soil surface; 

or

b. In a layer, 10 cm or more thick, directly above a 

placic horizon, duripan, fragipan, or densic, lithic, or 

paralithic contact within 50 cm of the mineral soil surface.

Dystrocryepts, p. 180

KCD. Other Cryepts.

Haplocryepts, p. 182

Calcicryepts

Key to Subgroups

KCBA. Calcicryepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Calcicryepts

KCBB. Other Calcicryepts 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 Calcicryepts

KCBC. Other Calcicryepts that have a xeric soil moisture 

regime.

Xeric Calcicryepts

KCBD. Other Calcicryepts that are dry in some part of the 

moisture control section for 45 or more days (cumulative) in 

normal years.

Ustic Calcicryepts

KCBE. Other Calcicryepts.

Typic Calcicryepts

Dystrocryepts

Key to Subgroups

KCCA. Dystrocryepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Dystrocryepts

KCCB. Other Dystrocryepts 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 (by ammonium oxalate) of 1.0 percent or more; 

or

b. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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 Dystrocryepts

KCCC. Other Dystrocryepts that have both:

1. A xeric soil 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 

(by ammonium oxalate) of 1.0 percent or more.

Haploxerandic Dystrocryepts

KCCD. Other Dystrocryepts that have both:

1. A xeric soil moisture regime; and
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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) particles 2.0 mm 

or larger in diameter, 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 Dystrocryepts

KCCE. 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 (by ammonium oxalate) of 1.0 

percent or more.

Andic Dystrocryepts

KCCF. 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) particles 2.0 mm or 

larger in diameter, 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

KCCG. Other Dystrocryepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Dystrocryepts

KCCH. Other Dystrocryepts that have a folistic epipedon.

Folistic Dystrocryepts

KCCI. 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

KCCJ. 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

KCCK. Other Dystrocryepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Dystrocryepts

KCCL. Other Dystrocryepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Dystrocryepts

KCCM. 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
182 Keys to Soil Taxonomy

2. Al plus 1⁄2 Fe (by ammonium oxalate) of 0.25 percent 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

KCCN. Other Dystrocryepts that have a xeric soil moisture 

regime.

Xeric Dystrocryepts

KCCO. Other Dystrocryepts that are dry in some part of the 

moisture control section for 45 or more days (cumulative) in 

normal years.

Ustic Dystrocryepts

KCCP. Other Dystrocryepts that have a base saturation 

(by NH4OAc) of 50 percent or more in one or more horizons 

between 25 and 50 cm from the mineral soil surface.

Eutric Dystrocryepts

KCCQ. Other Dystrocryepts.

Typic Dystrocryepts

Haplocryepts

Key to Subgroups

KCDA. Haplocryepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Haplocryepts

KCDB. Other Haplocryepts 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 (by ammonium oxalate) of 1.0 percent or more; 

or

b. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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 Haplocryepts

KCDC. Other Haplocryepts that have both:

1. A xeric soil 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 

(by ammonium oxalate) of 1.0 percent or more.

Haploxerandic Haplocryepts

KCDD. Other Haplocryepts that have both:

1. A xeric soil 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) particles 2.0 mm 

or larger in diameter, 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 Haplocryepts

KCDE. Other Haplocryepts that have both:

1. A moisture control section that is dry in some part for 45 

or more days (cumulative) in normal years; 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 

(by ammonium oxalate) of 1.0 percent or more.

Haplustandic Haplocryepts

KCDF. Other Haplocryepts that have both:

1. A moisture control section that is dry in some part for 45 

or more days (cumulative) in normal years; 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:
Inceptisols 183

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a. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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.

Ustivitrandic Haplocryepts

KCDG. Other Haplocryepts 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 (by ammonium oxalate) of 1.0 percent or 

more.

Andic Haplocryepts

KCDH. Other Haplocryepts 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) particles 2.0 mm or 

larger in diameter, 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 Haplocryepts

KCDI. Other Haplocryepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Haplocryepts

KCDJ. Other Haplocryepts 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 Haplocryepts

KCDK. Other Haplocryepts 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 Haplocryepts

KCDL. Other Haplocryepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Haplocryepts

KCDM. Other Haplocryepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Haplocryepts

KCDN. Other Haplocryepts that have identifiable secondary 

carbonates within 100 cm of the mineral soil surface.

Calcic Haplocryepts

KCDO. Other Haplocryepts that have a xeric soil moisture 

regime.

Xeric Haplocryepts

KCDP. Other Haplocryepts that are dry in some part of the 
184 Keys to Soil Taxonomy

moisture control section for 45 or more days (cumulative) in 

normal years.

Ustic Haplocryepts

KCDQ. Other Haplocryepts.

Typic Haplocryepts

Humicryepts

Key to Subgroups

KCAA. Humicryepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Humicryepts

KCAB. Other Humicryepts 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 (by ammonium oxalate) of 1.0 percent or more; 

or

b. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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 Humicryepts

KCAC. Other Humicryepts that have both:

1. A xeric soil 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 

(by ammonium oxalate) of 1.0 percent or more.

Haploxerandic Humicryepts

KCAD. Other Humicryepts that have both:

1. A xeric soil 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) particles 2.0 mm 

or larger in diameter, 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 Humicryepts

KCAE. Other Humicryepts 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 (by ammonium oxalate) of 1.0 percent or 

more.

Andic Humicryepts

KCAF. Other Humicryepts 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) particles 2.0 mm or 

larger in diameter, 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 Humicryepts

KCAG. Other Humicryepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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.

Fluvaquentic Humicryepts

KCAH. Other Humicryepts 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 Humicryepts

KCAI. Other Humicryepts 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 Humicryepts

KCAJ. Other Humicryepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Humicryepts

KCAK. Other Humicryepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Humicryepts

KCAL. Other Humicryepts 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 (by ammonium oxalate) of 0.25 percent 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 Humicryepts

KCAM. Other Humicryepts that have a xeric soil moisture 

regime.

Xeric Humicryepts

KCAN. Other Humicryepts that have a base saturation (by 

NH4OAc) of 50 percent or more, either:

1. In one-half or more of the total thickness between 25 

and 75 cm from the mineral soil surface; or

2. In some part of the 10 cm thickness directly above a 

densic, lithic, or paralithic contact that occurs less than 50 

cm below the mineral soil surface.

Eutric Humicryepts

KCAO. Other Humicryepts.

Typic Humicryepts

Gelepts

Key to Great Groups

KBA. Gelepts that have an umbric or mollic epipedon.

Humigelepts, p. 186

KBB. Other Gelepts that have a base saturation (by NH4OAc) 

of less than 50 percent, either:

1. In one or more horizons totaling 25 cm or more in 

thickness within 50 cm below the mineral soil surface and 

there is no placic horizon, duripan, fragipan, or densic, lithic, 

or paralithic contact within 50 cm of the mineral soil surface; 

or

2. In one-half or more of the thickness between the mineral 

soil surface and the top of a placic horizon, duripan, fragipan, 

or densic, lithic, or paralithic contact occurring within 50 cm 

of the mineral soil surface.

Dystrogelepts, p. 185

KBC. Other Gelepts.

Haplogelepts, p. 186

Dystrogelepts

Key to Subgroups

KBBA. Dystrogelepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Dystrogelepts

KBBB. Other Dystrogelepts that have, throughout one or 

more horizons with a total thickness of 18 cm or more within 
186 Keys to Soil Taxonomy

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 Dystrogelepts

KBBC. Other Dystrogelepts 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 Dystrogelepts

KBBD. Other Dystrogelepts that do not have irregular or 

broken horizon boundaries, and have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Dystrogelepts

KBBE. Other Dystrogelepts that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Dystrogelepts

KBBF. Other Dystrogelepts.

Typic Dystrogelepts

Haplogelepts

Key to Subgroups

KBCA. Haplogelepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Haplogelepts

KBCB. Other Haplogelepts 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 Haplogelepts

KBCC. Other Haplogelepts 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 Haplogelepts

KBCD. Other Haplogelepts that do not have irregular or 

broken horizon boundaries, and have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Haplogelepts

KBCE. Other Haplogelepts that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Haplogelepts

KBCF. Other Haplogelepts.

Typic Haplogelepts

Humigelepts

Key to Subgroups

KBAA. Humigelepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Humigelepts

KBAB. Other Humigelepts 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 (by ammonium oxalate) of 1.0 percent or 

more.

Andic Humigelepts

KBAC. Other Humigelepts 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 Humigelepts
Inceptisols 187

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KBAD. Other Humigelepts 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 Humigelepts

KBAE. Other Humigelepts that do not have irregular or 

broken horizon boundaries, and have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Humigelepts

KBAF. Other Humigelepts that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Humigelepts

KBAG. Other Humigelepts that have a base saturation (by 

NH4OAc) of 50 percent or more, either:

1. In one-half or more of the total thickness between 25 

and 75 cm from the mineral soil surface; or

2. In some part of the 10 cm thickness directly above a 

densic, lithic, or paralithic contact that occurs less than 50 

cm below the mineral soil surface.

Eutric Humigelepts

KBAH. Other Humigelepts.

Typic Humigelepts

Udepts

Key to Great Groups

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

mineral soil surface.

Sulfudepts, p. 195

KFB. Other Udepts that have a duripan or another cemented 

horizon within 100 cm of the mineral soil surface.

Durudepts, p. 187

KFC. Other Udepts that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiudepts, p. 193

KFD. Other Udepts that have an umbric or mollic epipedon.

Humudepts, p. 193

KFE. Other Udepts that have one or both of the following:

1. Free carbonates throughout; 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 or directly above a root-limiting 

layer (defined in chapter 17) that is at a shallower depth.

Eutrudepts, p. 190

KFF. Other Udepts.

Dystrudepts, p. 188

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) particles 2.0 mm 

or larger in diameter, 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
188 Keys to Soil Taxonomy

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 

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 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) particles 2.0 mm or 

larger in diameter, 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

KFFA. Dystrudepts 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 a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing.

Humic Lithic Dystrudepts

KFFB. Other Dystrudepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Dystrudepts

KFFC. 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 wedgeshaped peds 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

KFFD. Other Dystrudepts that have both:

1. In one or more horizons within 60 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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

KFFE. Other Dystrudepts that have both:

1. In 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. Saturation with water 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.

Andic Oxyaquic Dystrudepts

KFFF. Other Dystrudepts that have, throughout one or more 

horizons with a total thickness of 18 cm or more within 75 cm 
Inceptisols 189

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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 Dystrudepts

KFFG. 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) particles 2.0 mm or 

larger in diameter, 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

KFFH. Other Dystrudepts that have both:

1. Fragic soil properties either:

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

KFFI. Other Dystrudepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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

KFFJ. Other Dystrudepts that have both:

1. A color value, moist, of 3 or less and a color value, 

dry, of 5 or less (crushed and smoothed sample) either 

throughout the upper 18 cm of the mineral soil (unmixed) or 

between the mineral soil surface and a depth of 18 cm after 

mixing; 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

KFFK. 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

KFFL. 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

KFFM. Other Dystrudepts that have fragic soil properties 

either:

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

KFFN. Other Dystrudepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Dystrudepts

KFFO. Other Dystrudepts that have both:

1. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing; and
190 Keys to Soil Taxonomy

2. A sandy particle-size class in all subhorizons throughout 

the particle-size control section.

Humic Psammentic Dystrudepts

KFFP. Other Dystrudepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing; and

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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

KFFQ. Other Dystrudepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Dystrudepts

KFFR. 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

KFFS. 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

KFFT. 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

KFFU. 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

KFFV. Other Dystrudepts that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Humic Dystrudepts

KFFW. Other Dystrudepts.

Typic Dystrudepts

Eutrudepts

Key to Subgroups

KFEA. Eutrudepts that have both:

1. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 
Inceptisols 191

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the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing; and

2. A lithic contact within 50 cm of the mineral soil surface.

Humic Lithic Eutrudepts

KFEB. Other Eutrudepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Eutrudepts

KFEC. 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 peds 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

KFED. 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 peds 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

KFEE. 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

KFEF. 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) particles 2.0 mm or 

larger in diameter, 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

KFEG. Other Eutrudepts that have anthraquic conditions.

Anthraquic Eutrudepts

KFEH. Other Eutrudepts that have both:

1. Fragic soil properties either:

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

KFEI. Other Eutrudepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 0.2 percent 

or more and no densic, lithic, or paralithic contact within 

that depth; or

b. An irregular decrease in organic-carbon content 

(Holocene age) between a depth of 25 cm and either 

a depth of 125 cm below the mineral soil surface or 

a densic, lithic, or paralithic contact, whichever is 

shallower.

Fluvaquentic Eutrudepts
192 Keys to Soil Taxonomy

KFEJ. Other Eutrudepts that meet both of the following:

1. In one or more horizons within 60 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); and

2. Do not have free carbonates throughout any horizon 

within 100 cm of the mineral soil surface.

Aquic Dystric Eutrudepts

KFEK. 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

KFEL. 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

KFEM. 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

KFEN. Other Eutrudepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Eutrudepts

KFEO. Other Eutrudepts that have do not have free 

carbonates throughout any horizon within 100 cm of the mineral 

soil surface, and have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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.

Dystric Fluventic Eutrudepts

KFEP. Other Eutrudepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Eutrudepts

KFEQ. Other Eutrudepts that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand in all horizons within 50 cm of 

the mineral soil surface.

Arenic Eutrudepts

KFER. Other Eutrudepts that do not have free carbonates 

throughout any horizon within 100 cm of the mineral soil 

surface.

Dystric Eutrudepts

KFES. Other Eutrudepts that have a CaCO3 equivalent of 40 

percent or more, including fragments 2 to 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

KFET. 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

KFEU. Other Eutrudepts that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Humic Eutrudepts
Inceptisols 193

I

N

C

KFEV. 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 

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) particles 2.0 mm or 

larger in diameter, 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 one or both of the 

following:

1. An umbric or mollic epipedon; or

2. A color value, moist, of 3 or less and a color value, 

dry, of 5 or less (crushed and smoothed sample) either 

throughout the upper 18 cm of the mineral soil (unmixed) or 

between the mineral soil surface and a depth of 18 cm after 

mixing.

Humic Fragiudepts

KFCE. Other Fragiudepts.

Typic Fragiudepts

Humudepts

Key to Subgroups

KFDA. Humudepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humudepts

KFDB. Other Humudepts 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 wedgeshaped peds 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 Humudepts

KFDC. Other Humudepts that have both:

1. In one or more horizons within 60 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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 Humudepts

KFDD. Other Humudepts that have both:

1. In 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 
194 Keys to Soil Taxonomy

percentages (by ammonium oxalate) totaling more than 1.0; 

and

2. Saturation with water 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.

Andic Oxyaquic Humudepts

KFDE. Other Humudepts 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 Humudepts

KFDF. Other Humudepts 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) particles 2.0 mm or 

larger in diameter, 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 Humudepts

KFDG. Other Humudepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Humudepts

KFDH. Other Humudepts 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 Humudepts

KFDI. Other Humudepts 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 Humudepts

KFDJ. Other Humudepts that have a sandy particle-size class 

in all subhorizons throughout the particle-size control section.

Psammentic Humudepts

KFDK. Other Humudepts 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 Humudepts

KFDL. Other Humudepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. An umbric or mollic epipedon that is 50 cm or more 

thick; and

4. One or both of the following: 

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

an organic-carbon content (Holocene age) of 0.2 percent 

or more and no densic, lithic, or paralithic contact within 

that depth; or

b. An irregular decrease in organic-carbon content 
Inceptisols 195

I

N

C

(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 Humudepts

KFDM. Other Humudepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Humudepts

KFDN. Other Humudepts that have an umbric or mollic 

epipedon that is 50 cm or more thick.

Pachic Humudepts

KFDO. Other Humudepts that have a base saturation (by 

NH4OAc) of 60 percent or more either:

1. In one-half or more of the total thickness between 25 

and 75 cm from the mineral soil surface; or

2. In some part of the 10 cm thickness directly above a 

densic, lithic, or paralithic contact that occurs less than 50 

cm below the mineral soil surface.

Eutric Humudepts

KFDP. Other Humudepts that do not have a cambic horizon 

and do not, in any part of the umbric or mollic epipedon, meet 

the requirements for a cambic horizon, except for the color 

requirements.

Entic Humudepts

KFDQ. Other Humudepts.

Typic Humudepts

Sulfudepts

Key to Subgroups

KFAA. All Sulfudepts (provisionally).

Typic Sulfudepts

Ustepts

Key to Great Groups

KDA. Ustepts that have a duripan within 100 cm of the 

mineral soil surface.

Durustepts, p. 197

KDB. Other Ustepts that have both:

1. A calcic horizon within 100 cm of the mineral soil 

surface or a petrocalcic horizon within 150 cm of the mineral 

soil surface; and

2. Either free carbonates or a texture class 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. 195

KDC. Other Ustepts that have an umbric or mollic epipedon

Humustepts, p. 202 

KDD. Other Ustepts that meet 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. 197

KDE. Other Ustepts.

Haplustepts, p. 198

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 peds in a layer 15 cm or more thick that 

has its upper boundary within 125 cm of the mineral soil 

surface; or
196 Keys to Soil Taxonomy

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 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 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 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 peds 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 

within 100 cm of the mineral soil surface.

Petrocalcic Calciustepts

KDBF. Other Calciustepts that have a gypsic horizon 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 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 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 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 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 soil temperature at a depth of 50 cm below the 

soil surface is higher than 5 o

C; or

2. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that 

in normal years is dry in some or all parts for fewer than 

120 cumulative days per year when the soil temperature 

at a depth of 50 cm below the soil surface is higher than 

8 oC.

Udic Calciustepts

KDBJ. Other Calciustepts.

Typic Calciustepts
Inceptisols 197

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C

Durustepts

Key to Subgroups

KDAA. All Durustepts (provisionally).

Typic Durustepts

Dystrustepts

Key to Subgroups

KDDA. Dystrustepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Dystrustepts

KDDB. Other Dystrustepts 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 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 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

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 peds 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 Dystrustepts

KDDC. Other Dystrustepts 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 wedgeshaped peds 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 Dystrustepts

KDDD. 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

KDDE. 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) particles 2.0 mm or 

larger in diameter, 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

KDDF. 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

KDDG. Other Dystrustepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and
198 Keys to Soil Taxonomy

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Dystrustepts

KDDH. Other Dystrustepts 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 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 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 Dystrustepts

KDDI. 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 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 NH4

OAc pH 7) divided 

by the product of three times [percent water retained at 1500 

kPa tension minus percent organic carbon (but no more than 

1.00)] is less than 24.

Oxic Dystrustepts

KDDJ. Other Dystrustepts that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Humic Dystrustepts

KDDK. Other Dystrustepts.

Typic Dystrustepts

Haplustepts

Key to Subgroups

KDEA. 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 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 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 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 Lithic Haplustepts

KDEB. Other Haplustepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Haplustepts

KDEC. 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 
Inceptisols 199

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control section that in normal years is dry in some or all 

parts for fewer 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

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 soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years is 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; 

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 peds 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

KDED. 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 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; 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 peds 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

KDEE. 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 wedgeshaped peds 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

KDEF. 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

KDEG. 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Haplustepts
200 Keys to Soil Taxonomy

KDEH. Other Haplustepts that have anthraquic conditions.

Anthraquic Haplustepts

KDEI. 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

KDEJ. 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

KDEK. 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

KDEL. Other Haplustepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Haplustepts

KDEM. Other Haplustepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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 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 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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

KDEN. Other Haplustepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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 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 less than four-tenths of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 o

C; or

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 soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC; 

and

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 0.2 percent 
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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

KDEO. Other Haplustepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Haplustepts

KDEP. Other Haplustepts that have a gypsic horizon within 

100 cm of the mineral soil surface.

Gypsic Haplustepts

KDEQ. Other Haplustepts that have both:

1. A calcic horizon 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 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.

Haplocalcidic Haplustepts

KDER. Other Haplustepts that have both:

1. A calcic horizon 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 soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for less than 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

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 soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC.

Calcic Udic Haplustepts

KDES. Other Haplustepts that have a calcic horizon within 

100 cm of the mineral soil surface.

Calcic Haplustepts

KDET. 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 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:
202 Keys to Soil Taxonomy

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 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 Haplustepts

KDEU. 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

KDEV. 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 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 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 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 Haplustepts

KDEW. Other Haplustepts.

Typic Haplustepts

Humustepts

Key to Subgroups

KDCA. Humustepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humustepts

KDCB. Other Humustepts 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 Humustepts

KDCC. Other Humustepts 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) particles 2.0 mm or 

larger in diameter, 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 Humustepts

KDCD. Other Humustepts 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 Humustepts

KDCE. Other Humustepts 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 NH4

OAc pH 7) divided 

by the product of three times [percent water retained at 1500 

kPa tension minus percent organic carbon (but no more than 

1.00)] is less than 24.

Oxic Humustepts

KDCF. Other Humustepts 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 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 
Inceptisols 203

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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 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 Humustepts

KDCG. Other Humustepts.

Typic Humustepts

Xerepts

Key to Great Groups

KEA. Xerepts that have a duripan within 100 cm of the 

mineral soil surface.

Durixerepts, p. 204

KEB. Other Xerepts that have a fragipan within 100 cm of the 

mineral soil surface.

Fragixerepts, p. 206

KEC. Other Xerepts that have an umbric or mollic epipedon.

Humixerepts, p. 208

KED. Other Xerepts that have both:

1. A calcic horizon within 100 cm of the mineral soil 

surface or a petrocalcic horizon within 150 cm of the mineral 

soil surface; and

2. Free carbonates in all parts above the calcic or 

petrocalcic horizon, after the soil between the mineral soil 

surface and a depth of 18 cm has been mixed.

Calcixerepts, p. 203

KEE. 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. 204

KEF. Other Xerepts.

Haploxerepts, p. 206

Calcixerepts

Key to Subgroups

KEDA. Calcixerepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Calcixerepts

KEDB. 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 wedgeshaped peds 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

KEDC. Other Calcixerepts that have a petrocalcic horizon 

within 100 cm of the mineral soil surface.

Petrocalcic Calcixerepts

KEDD. 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

KEDE. 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) particles 2.0 mm or 

larger in diameter, 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

KEDF. Other Calcixerepts that have, in one or more horizons 

within 75 cm of the mineral soil surface, redox depletions with 
204 Keys to Soil Taxonomy

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Calcixerepts

KEDG. 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) particles 2.0 mm 

or larger in diameter, 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 

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 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) particles 2.0 mm or 

larger in diameter, 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

KEEA. Dystroxerepts 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 a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing.

Humic Lithic Dystroxerepts

KEEB. Other Dystroxerepts that have a lithic contact within 

50 cm of the mineral soil surface.

Lithic Dystroxerepts

KEEC. 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
Inceptisols 205

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b. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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

KEED. 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

KEEE. 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) particles 2.0 mm or 

larger in diameter, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

2. A fine-earth fraction containing 30 percent or more 

particles 0.02 to 2.0 mm in diameter; and

a. In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

b. [(Al plus 1/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Dystroxerepts

KEEF. Other Dystroxerepts that have both:

1. Fragic soil properties either:

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

KEEG. Other Dystroxerepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

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

an organic-carbon content (Holocene age) of 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

KEEH. 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

KEEI. 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

KEEJ. Other Dystroxerepts that have fragic soil properties 

either:

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

KEEK. Other Dystroxerepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing; and

4. One or both of the following:
206 Keys to Soil Taxonomy

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 Dystroxerepts

KEEL. Other Dystroxerepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Dystroxerepts

KEEM. Other Dystroxerepts that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Humic Dystroxerepts

KEEN. Other Dystroxerepts.

Typic Dystroxerepts

Fragixerepts

Key to Subgroups

KEBA. 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

KEBB. 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) particles 2.0 mm or 

larger in diameter, 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

KEBC. 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

KEBD. Other Fragixerepts that have one or both of the 

following:

1. An umbric or mollic epipedon; or

2. A color value, moist, of 3 or less and a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing.

Humic Fragixerepts

KEBE. Other Fragixerepts.

Typic Fragixerepts

Haploxerepts

Key to Subgroups

KEFA. Haploxerepts 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 a color value, dry, 

of 5 or less (crushed and smoothed sample) either throughout 

the upper 18 cm of the mineral soil (unmixed) or between the 

mineral soil surface and a depth of 18 cm after mixing.

Humic Lithic Haploxerepts

KEFB. Other Haploxerepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Haploxerepts

KEFC. 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 
Inceptisols 207

I

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for some time in normal years and slickensides or wedgeshaped peds 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

KEFD. 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) particles 2.0 mm 

or larger in diameter, 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

KEFE. Other Haploxerepts that have both:

1. In 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. Saturation with water 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.

Andic Oxyaquic Haploxerepts

KEFF. 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

KEFG. Other Haploxerepts that have both:

1. Saturation with water 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. 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. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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.

Oxyaquic Vitrandic Haploxerepts

KEFH. 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) particles 2.0 mm or 

larger in diameter, 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

KEFI. Other Haploxerepts that have a gypsic horizon within 

100 cm of the mineral soil surface.

Gypsic Haploxerepts

KEFJ. 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
208 Keys to Soil Taxonomy

KEFK. Other Haploxerepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Haploxerepts

KEFL. Other Haploxerepts that have fragic soil properties 

either:

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

KEFM. Other Haploxerepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Haploxerepts

KEFN. Other Haploxerepts that have a calcic horizon or 

identifiable secondary carbonates within one of the following 

particle-size class and depth combinations:

1. A sandy or sandy-skeletal particle-size class and within 

150 cm of the mineral soil surface; or

2. A clayey, clayey-skeletal, fine, or very-fine particle-size 

class and within 90 cm of the mineral soil surface; or

3. Any other particle-size class and within 110 cm of the 

mineral soil surface.

Calcic Haploxerepts

KEFO. Other Haploxerepts that have a color value, moist, 

of 3 or less and a color value, dry, of 5 or less (crushed and 

smoothed sample) either throughout the upper 18 cm of the 

mineral soil (unmixed) or between the mineral soil surface and 

a depth of 18 cm after mixing.

Humic Haploxerepts

KEFP. Other Haploxerepts.

Typic Haploxerepts

Humixerepts

Key to Subgroups

KECA. Humixerepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humixerepts

KECB. Other Humixerepts 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) particles 2.0 mm 

or larger in diameter, 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 Humixerepts

KECC. Other Humixerepts 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 Humixerepts

KECD. Other Humixerepts 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) particles 2.0 mm or 

larger in diameter, 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
Inceptisols 209

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C

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 Humixerepts

KECE. Other Humixerepts 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 Humixerepts

KECF. Other Humixerepts 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 Humixerepts

KECG. Other Humixerepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. An umbric or mollic epipedon that is 50 cm or more 

thick; and

4. One or both of the following: 

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

an organic-carbon content (Holocene age) of 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.

Cumulic Humixerepts

KECH. Other Humixerepts that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

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

an organic-carbon content (Holocene age) of 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 Humixerepts

KECI. Other Humixerepts that have an umbric or mollic 

epipedon that is 50 cm or more thick.

Pachic Humixerepts

KECJ. Other Humixerepts that do not have a cambic horizon 

and do not, in any part of the umbric or mollic epipedon, meet 

the requirements for a cambic horizon, except for the color 

requirements.

Entic Humixerepts

KECK. Other Humixerepts.

Typic Humixerepts

211

Key to Suborders

IA. Mollisols that have all of the following:

1. An argillic or natric horizon; and

2. An albic horizon that has chroma of 2 or less and 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); and

4. A soil temperature regime that is warmer than cryic.

Albolls, p. 212

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 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;* 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 neutral colors with no 

hue (N) and zero chroma on faces of peds or in the 

matrix; or

(f) Hue of 5GY, 5G, 5BG, or 5B; or

(g) Any color if it results from uncoated sand 

grains; or

b. Chroma of 2 in the lower part of the mollic epipedon; 

and either

(1) Distinct or prominent redox concentrations in the 

lower part of the mollic epipedon; or

(2) Directly below the mollic epipedon, one of the 

following matrix colors:

(a) A color value, moist, of 4, chroma of 2, and 

some redox depletions with a color value, moist, of 

4 or more and chroma of 1 or less; or

(b) A color value, moist, of 5 or more, chroma of 

2 or less, and redox concentrations; or

(c) A color value, moist, of 4 and chroma of 1 or 

less; or

6. At a depth between 40 and 50 cm from the mineral soil 

surface, enough active ferrous iron to give a positive reaction 

* If the mollic epipedon extends to a lithic contact within 30 cm of the mineral soil 

surface, the requirement for redoximorphic features is waived.

M

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Mollisols

CHAPTER 12
212 Keys to Soil Taxonomy

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

irrigated.

Aquolls, p. 213

IC. Other Mollisols that:

1. Have a mollic epipedon that is 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 75 mm in diameter 

that have a CaCO3 equivalent of 40 percent or more; and

4. Have either or both:

a. A udic soil moisture regime; or

b. A cryic soil temperature regime.

Rendolls, p. 221

ID. Other Mollisols that have a gelic soil temperature regime. 

Gelolls, p. 221

IE. Other Mollisols that have a cryic soil temperature regime.

Cryolls, p. 217

IF. Other Mollisols that have either a xeric soil moisture 

regime or an aridic soil moisture regime that borders on xeric.

Xerolls, p. 246

IG. Other Mollisols that have either an ustic soil moisture 

regime or an aridic soil moisture regime that borders on ustic.

Ustolls, p. 230

IH. Other Mollisols.

Udolls, p. 222

Albolls

Key to Great Groups

IAA. Albolls that have a natric horizon.

Natralbolls, p. 213

IAB. Other Albolls.

Argialbolls, p. 212

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 peds 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 wedgeshaped peds 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 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
Mollisols 213

2. More than 35 percent (by volume) particles 2.0 mm or 

larger in diameter, 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. 214

IBB. Other Aquolls that have a duripan within 100 cm of the 

mineral soil surface.

Duraquolls, p. 214

IBC. Other Aquolls that have a natric horizon.

Natraquolls, p. 217

IBD. Other Aquolls that have a calcic or gypsic horizon within 

40 cm of the mineral soil surface but do not have an argillic 

horizon unless it is a buried horizon.

Calciaquolls, p. 213

IBE. Other Aquolls that have an argillic horizon.

Argiaquolls, p. 213

IBF. Other Aquolls that have episaturation.

Epiaquolls, p. 216

IBG. Other Aquolls.

Endoaquolls, p. 214

Argiaquolls

Key to Subgroups

IBEA. Argiaquolls that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 wedgeshaped peds 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 one or both of the 

following:

1. An argillic horizon that has a clay increase of 20 percent 

or more (absolute, in the fine-earth fraction) within a vertical 

distance of 7.5 cm, either within the horizon or at its upper 

boundary; or

2. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon.

Abruptic Argiaquolls

IBEE. Other Argiaquolls.

Typic Argiaquolls

Calciaquolls

Key to Subgroups

IBDA. Calciaquolls that have a petrocalcic horizon within 100 

cm of the mineral soil surface.

Petrocalcic Calciaquolls

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214 Keys to Soil Taxonomy

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 wedgeshaped peds 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) particles 2.0 mm or 

larger in diameter, 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 that is 

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 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 peds in a layer 15 cm or more 

thick that is 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 Duraquolls

IBBC. Other Duraquolls that have an argillic horizon.

Argic Duraquolls

IBBD. Other Duraquolls.

Typic Duraquolls

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 of the following:

1. A mollic epipedon that is 60 cm or more thick; and
Mollisols 215

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 peds 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.

Cumulic Vertic Endoaquolls

IBGC. Other Endoaquolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(Holocene age) between a depth of 25 cm and either 

a depth of 125 cm below the mineral soil surface or 

a densic, lithic, or paralithic contact, whichever is 

shallower; and

4. 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 peds 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.

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 wedgeshaped peds 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) particles 2.0 mm or 

larger in diameter, 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 

at least a firm rupture-resistance class when moist.

Duric Endoaquolls

IBGI. Other Endoaquolls that have a mollic epipedon that is 

60 cm or more thick.

Cumulic Endoaquolls

IBGJ. Other Endoaquolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) of 0.3 

percent or more in all horizons within 125 cm of the 

mineral soil surface; or

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216 Keys to Soil Taxonomy

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 Endoaquolls

IBGK. Other Endoaquolls.

Typic Endoaquolls

Epiaquolls

Key to Subgroups

IBFA. Epiaquolls that have both of the following:

1. A mollic epipedon that is 60 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 peds 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.

Cumulic Vertic Epiaquolls

IBFB. Other Epiaquolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(Holocene age) between a depth of 25 cm and either 

a depth of 125 cm below the mineral soil surface or 

a densic, lithic, or paralithic contact, whichever is 

shallower; and

4. 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 peds 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.

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 wedgeshaped peds 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) particles 2.0 mm or 

larger in diameter, 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 

at least a firm rupture-resistance class when moist.

Duric Epiaquolls
Mollisols 217

IBFH. Other Epiaquolls that have a mollic epipedon that is 60 

cm or more thick.

Cumulic Epiaquolls

IBFI. Other Epiaquolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Epiaquolls

IBFJ. Other Epiaquolls.

Typic Epiaquolls

Natraquolls

Key to Subgroups

IBCA. Natraquolls that have a petrocalcic horizon within 100 

cm of the mineral soil surface.

Petrocalcic Natraquolls

IBCB. Other 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 peds 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

IBCC. Other Natraquolls that have a glossic horizon or 

interfingering of albic materials into the natric horizon.

Glossic Natraquolls

IBCD. Other Natraquolls.

Typic Natraquolls

Cryolls

Key to Great Groups

IEA. Cryolls that have a duripan within 100 cm of the mineral 

soil surface.

Duricryolls, p. 219

IEB. Other Cryolls that have a natric horizon.

Natricryolls, p. 220

IEC. Other Cryolls that have both of the following:

1. An argillic horizon that has its upper boundary 60 cm or 

more below the mineral soil surface; and

2. A texture class finer than loamy fine sand in all horizons 

above the argillic horizon.

Palecryolls, p. 220

IED. Other Cryolls that have an argillic horizon.

Argicryolls, p. 217

IEE. Other Cryolls that have both of the following:

1. A calcic or petrocalcic horizon 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 free carbonates or a texture class of 

loamy fine sand or coarser.

Calcicryolls, p. 218

IEF. Other Cryolls.

Haplocryolls, p. 219

Argicryolls

Key to Subgroups

IEDA. Argicryolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Argicryolls

IEDB. 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 wedgeshaped peds 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

M

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218 Keys to Soil Taxonomy

IEDC. 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

IEDD. 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) particles 2.0 mm or 

larger in diameter, 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

IEDE. Other Argicryolls that have one or both of the 

following:

1. An argillic horizon that has a clay increase of 20 percent 

or more (absolute, in the fine-earth fraction) within a vertical 

distance of 7.5 cm, either within the horizon or at its upper 

boundary; or

2. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon.

Abruptic Argicryolls

IEDF. 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

IEDG. 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

IEDH. Other Argicryolls that have both of the following:

1. A mollic epipedon that is 40 cm or more thick and has a 

texture class finer than loamy fine sand; and

2. A calcic horizon within 100 cm of the mineral soil 

surface.

Calcic Pachic Argicryolls

IEDI. Other Argicryolls that have a mollic epipedon that is 40 

cm or more thick and has a texture class finer than loamy fine 

sand.

Pachic Argicryolls

IEDJ. Other Argicryolls that have a calcic horizon within 100 

cm of the mineral soil surface.

Calcic Argicryolls

IEDK. 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

IEDL. Other Argicryolls that have an ustic soil moisture 

regime.

Ustic Argicryolls

IEDM. Other Argicryolls that have a xeric soil moisture 

regime.

Xeric Argicryolls

IEDN. Other Argicryolls.

Typic Argicryolls

Calcicryolls

Key to Subgroups

IEEA. Calcicryolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Calcicryolls

IEEB. Other Calcicryolls 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) particles 2.0 mm or 

larger in diameter, 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
Mollisols 219

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 Calcicryolls

IEEC. Other Calcicryolls that have a petrocalcic horizon 

within 100 cm of the mineral soil surface.

Petrocalcic Calcicryolls

IEED. Other Calcicryolls that have a mollic epipedon that is 

40 cm or more thick and has a texture class finer than loamy 

fine sand.

Pachic Calcicryolls

IEEE. Other Calcicryolls that have an ustic soil moisture 

regime.

Ustic Calcicryolls

IEEF. Other Calcicryolls that have a xeric soil moisture 

regime.

Xeric Calcicryolls

IEEG. Other Calcicryolls.

Typic Calcicryolls

Duricryolls

Key to Subgroups

IEAA. Duricryolls that have an argillic horizon.

Argic Duricryolls

IEAB. Other Duricryolls that have a calcic horizon above the 

duripan.

Calcic Duricryolls

IEAC. Other Duricryolls.

Typic Duricryolls

Haplocryolls

Key to Subgroups

IEFA. Haplocryolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Haplocryolls

IEFB. 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 wedgeshaped peds 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

IEFC. Other Haplocryolls that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Haplocryolls

IEFD. 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) particles 2.0 mm or 

larger in diameter, 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

IEFE. Other Haplocryolls that have all of the following:

1. A mollic epipedon that is 40 cm or more thick and has a 

texture class finer than loamy fine sand; and

2. A slope of less than 25 percent; and

3. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

4. An irregular decrease in organic-carbon content 

(Holocene age) between a depth of 25 cm and either a depth 

of 125 cm below the mineral soil surface or a densic, lithic, 

or paralithic contact, whichever is shallower; and

5. 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

IEFF. Other Haplocryolls that have all of the following:

1. A mollic epipedon that is 40 cm or more thick and has a 

texture class finer than loamy fine sand; and

2. A slope of less than 25 percent; and

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220 Keys to Soil Taxonomy

3. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

4. 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 Haplocryolls

IEFG. Other Haplocryolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(Holocene age) between a depth of 25 cm and either 

a depth of 125 cm below the mineral soil surface or 

a densic, lithic, or paralithic contact, whichever is 

shallower; and

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).

Fluvaquentic Haplocryolls

IEFH. 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

IEFI. 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

IEFJ. Other Haplocryolls that have both of the following:

1. A mollic epipedon that is 40 cm or more thick and has a 

texture class finer than loamy fine sand; and

2. A calcic horizon within 100 cm of the mineral soil 

surface.

Calcic Pachic Haplocryolls

IEFK. Other Haplocryolls that have a mollic epipedon that 

is 40 cm or more thick and has a texture class finer than loamy 

fine sand.

Pachic Haplocryolls

IEFL. Other Haplocryolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haplocryolls

IEFM. Other Haplocryolls that have a calcic horizon within 

100 cm of the mineral soil surface.

Calcic Haplocryolls

IEFN. Other Haplocryolls that have an ustic soil moisture 

regime.

Ustic Haplocryolls

IEFO. Other Haplocryolls that have a xeric soil moisture 

regime.

Xeric Haplocryolls

IEFP. Other Haplocryolls.

Typic Haplocryolls

Natricryolls

Key to Subgroups

IEBA. All Natricryolls.

Typic Natricryolls

Palecryolls

Key to Subgroups

IECA. 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

IECB. Other Palecryolls that in normal years are saturated 
Mollisols 221

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

IECC. Other Palecryolls that have one or both of the 

following:

1. An argillic horizon that has a clay increase of 20 percent 

or more (absolute, in the fine-earth fraction) within a vertical 

distance of 7.5 cm, either within the horizon or at its upper 

boundary; or

2. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon.

Abruptic Palecryolls

IECD. Other Palecryolls that have a mollic epipedon that is 40 

cm or more thick and has a texture class finer than loamy fine 

sand.

Pachic Palecryolls

IECE. Other Palecryolls that have an ustic soil moisture 

regime.

Ustic Palecryolls

IECF. Other Palecryolls that have a xeric soil moisture 

regime.

Xeric Palecryolls

IECG. Other Palecryolls.

Typic Palecryolls

Gelolls

Key to Great Groups

IDA. All Gelolls.

Haplogelolls, p. 221

Haplogelolls

Key to Subgroups

IDAA. Haplogelolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Haplogelolls

IDAB. Other Haplogelolls 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 Haplogelolls

IDAC. Other Haplogelolls 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 Haplogelolls

IDAD. Other Haplogelolls 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 Haplogelolls

IDAE. Other Haplogelolls that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Haplogelolls

IDAF. Other Haplogelolls that have both of the following:

1. A mollic epipedon that is 40 cm or more thick and has a 

texture class finer than loamy fine sand; and

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.

Cumulic Haplogelolls

IDAG. Other Haplogelolls.

Typic Haplogelolls

Rendolls

Key to Great Groups

ICA. Rendolls that have a cryic soil temperature regime.

Cryrendolls, p. 221

ICB. Other Rendolls.

Haprendolls, p. 222

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

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222 Keys to Soil Taxonomy

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 wedgeshaped peds 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 that is 18 cm or more thick.

Entic Haprendolls

ICBE. Other Haprendolls.

Typic Haprendolls

Udolls

Key to Great Groups

IHA. Udolls that have a natric horizon.

Natrudolls, p. 228

IHB. Other Udolls that:

1. Have a calcic or petrocalcic horizon within 100 cm of 

the mineral soil surface; and

2. Do not have an argillic horizon above the calcic or 

petrocalcic horizon; and

3. Have free carbonates 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.

Calciudolls, p. 225

IHC. Other Udolls that have one or both of the following:

1. 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 noncarbonate clay content; 

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

2. A frigid soil temperature regime and both of the 

following:

a. An argillic horizon that has its upper boundary 60 cm 

or more below the mineral soil surface; and

b. A texture class finer than loamy fine sand in all 

horizons above the argillic horizon.

Paleudolls, p. 229

IHD. Other Udolls that have an argillic horizon.

Argiudolls, p. 222

IHE. 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. 230

IHF. Other Udolls.

Hapludolls, p. 226

Argiudolls

Key to Subgroups

IHDA. Argiudolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Argiudolls
Mollisols 223

IHDB. Other Argiudolls that have a petrocalcic horizon within 

100 cm of the mineral soil surface.

Petrocalcic Argiudolls

IHDC. Other Argiudolls that have both of the following:

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. Within 75 cm of the mineral soil surface, 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 peds in a layer 15 cm or more thick that 

has its upper boundary within 125 cm of the mineral soil 

surface; or

b. A linear extensibility of 6.0 cm or more between 

the mineral soil surface and either a depth of 100 cm 

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

shallower.

Aquertic Argiudolls

IHDD. Other Argiudolls that have both of the following:

1. 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; 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 peds 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 Argiudolls

IHDE. Other Argiudolls that have both of the following:

1. A mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 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 peds 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

IHDF. 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. 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 peds 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

IHDG. 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 

M

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224 Keys to Soil Taxonomy

for some time in normal years and slickensides or wedgeshaped peds 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

IHDH. 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

IHDI. 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) particles 2.0 mm or 

larger in diameter, 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

IHDJ. Other Argiudolls that have both of the following:

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. Within 75 cm of the mineral soil surface, 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 mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 50 cm or more thick.

Aquic Pachic Argiudolls

IHDK. Other Argiudolls that have a mollic epipedon that has a 

texture class finer than loamy fine sand and that is either:

1. 40 cm or more thick in a frigid soil temperature regime; 

or

2. 50 cm or more thick.

Pachic Argiudolls

IHDL. 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. Within 75 cm of the mineral soil surface, 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

IHDM. 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

IHDN. 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 
Mollisols 225

argillic horizon 7.5 to 20 cm thick, each with an overlying 

eluvial horizon.

Lamellic Argiudolls

IHDO. 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

IHDP. Other Argiudolls that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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

IHDQ. Other Argiudolls that have one or both of the 

following:

1. An argillic horizon that has a clay increase of 20 percent 

or more (absolute, in the fine-earth fraction) within a vertical 

distance of 7.5 cm, either within the horizon or at its upper 

boundary; or

2. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon.

Abruptic Argiudolls

IHDR. Other Argiudolls 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 Argiudolls

IHDS. Other Argiudolls that have a 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

IHDT. Other Argiudolls that have a calcic horizon within 100 

cm of the mineral soil surface.

Calcic Argiudolls

IHDU. Other Argiudolls.

Typic Argiudolls

Calciudolls

Key to Subgroups

IHBA. Calciudolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Calciudolls

IHBB. 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 wedgeshaped peds 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

IHBC. Other Calciudolls that have both of the following:

1. An anthropic epipedon; and

2. A petrocalcic horizon that formed in human-transported 

material within 100 cm of the mineral soil surface.

Anthropic Petrocalcic Calciudolls

IHBD. Other Calciudolls 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 Calciudolls

IHBE. Other Calciudolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Calciudolls

IHBF. Other Calciudolls.

Typic Calciudolls

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226 Keys to Soil Taxonomy

Hapludolls

Key to Subgroups

IHFA. Hapludolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Hapludolls

IHFB. Other Hapludolls that have a petrocalcic horizon within 

100 cm of the mineral soil surface.

Petrocalcic Hapludolls

IHFC. Other Hapludolls that have both of the following:

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. Within 75 cm of the mineral soil surface, 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 peds 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

IHFD. Other Hapludolls that have both of the following:

1. A mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 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 peds 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 Hapludolls

IHFE. 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 wedgeshaped peds 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

IHFF. 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 Al + 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Hapludolls

IHFG. 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) particles 2.0 mm or 

larger in diameter, 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

IHFH. Other Hapludolls that have all of the following:

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
Mollisols 227

2. Either:

a. A frigid soil temperature regime and a mollic 

epipedon that is 40 cm or more thick, of which less than 

50 percent meets sandy or sandy-skeletal particle-size 

class criteria, 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 60 cm or more thick, of 

which 50 percent or more of the thickness has a texture 

class finer than loamy fine sand; and

3. A slope of less than 25 percent; and

4. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

5. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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.

Aquic Cumulic Hapludolls

IHFI. Other Hapludolls that have all of the following:

1. Either:

a. A frigid soil temperature regime and a mollic 

epipedon that is 40 cm or more thick, of which less than 

50 percent meets sandy or sandy-skeletal particle-size 

class criteria, 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 60 cm or more thick, of 

which 50 percent or more of the thickness has a texture 

class finer than loamy fine sand; and

2. A slope of less than 25 percent; and

3. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Hapludolls

IHFJ. Other Hapludolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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. Within 75 cm of the mineral soil surface, 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

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Hapludolls

IHFK. Other Hapludolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Hapludolls

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228 Keys to Soil Taxonomy

IHFL. Other Hapludolls that have both of the following:

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. Within 75 cm of the mineral soil surface, 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 mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 50 cm or more thick.

Aquic Pachic Hapludolls

IHFM. Other Hapludolls that have a mollic epipedon that has 

a texture class finer than loamy fine sand and that is either:

1. 40 cm or more thick in a frigid soil temperature regime; 

or

2. 50 cm or more thick.

Pachic Hapludolls

IHFN. 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. Within 75 cm of the mineral soil surface, 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

IHFO. 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

IHFP. Other Hapludolls that have both:

1. A mollic epipedon that is 60 cm or more thick that has 

a texture class 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 the requirements for 

a cambic horizon, except for the color requirements, or have 

free carbonates throughout either the cambic horizon or the 

lower part of the mollic epipedon.

Vermic Hapludolls

IHFQ. Other Hapludolls that have a calcic horizon within 100 

cm of the mineral soil surface.

Calcic Hapludolls

IHFR. 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 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

IHFS. Other Hapludolls.

Typic Hapludolls

Natrudolls

Key to Subgroups

IHAA. Natrudolls that have a petrocalcic horizon within 100 

cm of the mineral soil surface.

Petrocalcic Natrudolls

IHAB. Other Natrudolls 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 peds in a layer 15 cm or more thick that 
Mollisols 229

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

IHAC. Other Natrudolls that have both of the following:

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 peds 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

IHAD. 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 wedgeshaped peds 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

IHAE. Other Natrudolls that have visible crystals of gypsum 

and/or more soluble salts within 40 cm of the mineral soil 

surface.

Leptic Natrudolls

IHAF. Other Natrudolls that have one or both of the 

following:

1. A natric horizon that has a clay increase of 20 percent or 

more (absolute, in the fine-earth fraction) within a vertical 

distance of 7.5 cm, either within the horizon or at its upper 

boundary; or

2. An abrupt textural change between the eluvial horizon 

and the upper boundary of the natric horizon.

Abruptic Natrudolls

IHAG. Other Natrudolls that have a glossic horizon or 

interfingering of albic materials into the natric horizon.

Glossic Natrudolls

IHAH. Other Natrudolls that have a calcic horizon within 100 

cm of the mineral soil surface.

Calcic Natrudolls

IHAI. Other Natrudolls.

Typic Natrudolls

Paleudolls

Key to Subgroups

IHCA. 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 peds 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

IHCB. Other Paleudolls that have both of the following:

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. Within 75 cm of the mineral soil surface, 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 mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 50 cm or more thick.

Aquic Pachic Paleudolls

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230 Keys to Soil Taxonomy

IHCC. Other Paleudolls that have a mollic epipedon that has 

a texture class finer than loamy fine sand and that is 50 cm or 

more thick.

Pachic Paleudolls

IHCD. Other Paleudolls that have, in one or more subhorizons 

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 Paleudolls

IHCE. 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

IHCF. Other Paleudolls that have both of the following:

1. A calcic horizon 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 free carbonates or a texture class of loamy fine 

sand or coarser.

Calcic Paleudolls

IHCG. Other Paleudolls.

Typic Paleudolls

Vermudolls

Key to Subgroups

IHEA. Vermudolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Vermudolls

IHEB. Other Vermudolls that have a mollic epipedon that is 

less than 75 cm thick.

Haplic Vermudolls

IHEC. Other Vermudolls.

Typic Vermudolls

Ustolls

Key to Great Groups

IGA. Ustolls that have a duripan within 100 cm of the mineral 

soil surface.

Durustolls, p. 236

IGB. Other Ustolls that have a natric horizon.

Natrustolls, p. 242

IGC. Other Ustolls that:

1. Have either a calcic or gypsic horizon within 100 cm of 

the mineral soil surface or a petrocalcic horizon 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, have either free carbonates 

or a texture class of loamy fine sand or coarser.

Calciustolls, p. 234

IGD. Other Ustolls that have either:

1. A petrocalcic horizon 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 noncarbonate clay 

content within 150 cm of the mineral soil surface (and 

there is no densic, lithic, or paralithic contact within that 

depth); and either

(1) Hue of 7.5YR or redder and chroma of 5 or more 

in the matrix; or

(2) Common redox concentrations with hue of 7.5YR 

or redder or chroma of 6 or more, or both; or

b. 35 percent or more noncarbonate clay throughout one 

or more subhorizons in its upper part, and one or both of 

the following:

(1) A clay increase of 20 percent or more (absolute, 

in the fine-earth fraction) within a vertical distance 

of 7.5 cm or of 15 percent or more (absolute, in the 

fine-earth fraction) within a vertical distance of 2.5 

cm, either within the argillic horizon or at its upper 

boundary (and there is no densic, lithic, or paralithic 

contact within 50 cm of the mineral soil surface); or

(2) An abrupt textural change between the eluvial 

horizon and the upper boundary of the argillic horizon 

(and there is no densic, lithic, or paralithic contact 

within 50 cm of the mineral soil surface).

Paleustolls, p. 244

IGE. Other Ustolls that have an argillic horizon.

Argiustolls, p. 231

IGF. Other Ustolls that have a mollic epipedon that:
Mollisols 231

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. 246

IGG. Other Ustolls.

Haplustolls, p. 236

Argiustolls

Key to Subgroups

IGEA. Argiustolls that have both of the following:

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 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 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

IGEB. Other Argiustolls that have both of the following:

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

IGEC. Other Argiustolls that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Argiustolls

IGED. Other Argiustolls that have both of the following:

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. 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 peds 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 Argiustolls

IGEE. Other Argiustolls that have both of the following:

1. When neither irrigated nor fallowed to store moisture, 

have one of the following:

a. A frigid soil temperature regime and a moisture 

control section that in normal years is dry in all parts for 

four-tenths or more of the cumulative days per year when 

the soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some 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 

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232 Keys to Soil Taxonomy

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 peds 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 Argiustolls

IGEF. Other Argiustolls that have all of the following:

1. A mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 50 cm or more thick; 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 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; 

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 peds 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 Udertic Argiustolls

IGEG. Other Argiustolls that have both of the following:

1. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for four-tenths or less of the cumulative days 

per year when the 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; 

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 peds 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 Argiustolls

IGEH. Other Argiustolls that have both of the following:

1. A mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 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 peds 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 Argiustolls

IGEI. Other Argiustolls that have one or both of the 

following:

1. Cracks within 125 cm of the mineral soil surface that are 
Mollisols 233

5 mm or more wide through a thickness of 30 cm or more 

for some time in normal years and slickensides or wedgeshaped peds 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

IGEJ. 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

IGEK. Other Argiustolls that have both of the following:

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 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 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) particles 2.0 mm 

or larger in diameter, 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 Argiustolls

IGEL. 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) particles 2.0 mm or 

larger in diameter, 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

IGEM. 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

IGEN. 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

IGEO. Other Argiustolls that have a mollic epipedon that has 

a texture class finer than loamy fine sand and that is either:

1. 40 cm or more thick in a frigid soil temperature regime; 

or

2. 50 cm or more thick.

Pachic Argiustolls

IGEP. 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 

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234 Keys to Soil Taxonomy

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

IGEQ. Other Argiustolls that have both of the following:

1. A calcic horizon 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 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 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

IGER. Other Argiustolls 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 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 Argiustolls

IGES. 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

IGET. Other Argiustolls that have a horizon, 15 cm or more 

thick within 100 cm of the mineral soil surface, that either is 

brittle and has some opal coats or has 20 percent or more (by 

volume) durinodes.

Duric Argiustolls

IGEU. Other Argiustolls.

Typic Argiustolls

Calciustolls

Key to Subgroups

IGCA. Calciustolls that have a salic horizon within 75 cm of 

the mineral soil surface.

Salidic Calciustolls

IGCB. Other Calciustolls that have a petrocalcic horizon and a 

lithic contact within 50 cm of the mineral soil surface.

Lithic Petrocalcic Calciustolls

IGCC. Other Calciustolls that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Calciustolls

IGCD. Other Calciustolls that have both of the following:

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 
Mollisols 235

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 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. 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 peds 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 Calciustolls

IGCE. Other Calciustolls that have both of the following:

1. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for four-tenths or less of the cumulative days 

per year when the 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; 

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 peds 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 Calciustolls

IGCF. 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 peds 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

IGCG. Other Calciustolls that have a petrocalcic horizon 

within 100 cm of the mineral soil surface.

Petrocalcic Calciustolls

IGCH. Other Calciustolls that have a gypsic horizon within 

100 cm of the mineral soil surface.

Gypsic Calciustolls

IGCI. 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

IGCJ. 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

IGCK. Other Calciustolls that have a mollic epipedon that has 

a texture class finer than loamy fine sand and that is either:

1. 40 cm or more thick in a frigid soil temperature regime; 

or

2. 50 cm or more thick.

Pachic Calciustolls

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236 Keys to Soil Taxonomy

IGCL. Other Calciustolls 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 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 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

IGCM. 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 o

C.

Udic Calciustolls

IGCN. Other Calciustolls.

Typic Calciustolls

Durustolls

Key to Subgroups

IGAA. Durustolls that have a natric horizon above the 

duripan.

Natric Durustolls

IGAB. Other Durustolls that:

1. Do not have an argillic horizon above the duripan; and

2. Have an aridic soil moisture regime that borders on 

ustic.

Haploduridic Durustolls

IGAC. Other Durustolls that have an aridic soil moisture 

regime that borders on ustic.

Argiduridic Durustolls

IGAD. Other Durustolls that do not have an argillic horizon 

above the duripan.

Entic Durustolls

IGAE. Other Durustolls that have a duripan that is strongly 

cemented or less cemented in all subhorizons.

Haplic Durustolls

IGAF. Other Durustolls.

Typic Durustolls

Haplustolls

Key to Subgroups

IGGA. Haplustolls that have a salic horizon within 75 cm of 

the mineral soil surface.

Salidic Haplustolls

IGGB. Other Haplustolls that have, in part of each pedon, a 

lithic contact within 50 cm of the mineral soil surface.

Ruptic-Lithic Haplustolls

IGGC. Other Haplustolls that have both of the following:

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 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 
Mollisols 237

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 lithic contact within 50 cm of the mineral soil surface.

Aridic Lithic Haplustolls

IGGD. Other Haplustolls that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Haplustolls

IGGE. Other Haplustolls that have both of the following:

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. 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 peds 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 Haplustolls

IGGF. Other Haplustolls that have both of the following:

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 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; 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 peds 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 Haplustolls

IGGG. Other Haplustolls that have all of the following:

1. A mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 50 cm or more thick; 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 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 o

C; 

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 peds 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 

M

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238 Keys to Soil Taxonomy

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

shallower.

Pachic Udertic Haplustolls

IGGH. Other Haplustolls that have both of the following:

1. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for four-tenths or less of the cumulative days 

per year when the 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; 

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 peds 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 Haplustolls

IGGI. Other Haplustolls that have both of the following:

1. A mollic epipedon that has a texture class finer than 

loamy fine sand and that is either:

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 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 peds 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 Haplustolls

IGGJ. 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 wedgeshaped peds 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

IGGK. Other Haplustolls that have both of the following:

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 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 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, whichever is 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

IGGL. Other Haplustolls that have an apparent CEC (by 1N 

NH4

OAc 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, whichever is 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 
Mollisols 239

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

IGGM. 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

IGGN. Other Haplustolls that have both of the following:

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 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) particles 2.0 mm 

or larger in diameter, 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

IGGO. 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) particles 2.0 mm or 

larger in diameter, 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

IGGP. Other Haplustolls that have all of the following:

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. Either:

a. A frigid soil temperature regime and a mollic 

epipedon that is 40 cm or more thick, of which less than 

50 percent meets sandy or sandy-skeletal particle-size 

class criteria, 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 class finer than loamy fine sand; and

3. A slope of less than 25 percent; and

4. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

5. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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.

Aquic Cumulic Haplustolls

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240 Keys to Soil Taxonomy

IGGQ. Other Haplustolls that have all of the following:

1. Either:

a. A frigid soil temperature regime and a mollic 

epipedon that is 40 cm or more thick, of which less than 

50 percent meets sandy or sandy-skeletal particle-size 

class criteria, 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 class finer than loamy fine sand; and

2. A slope of less than 25 percent; and

3. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haplustolls

IGGR. Other Haplustolls that have anthraquic conditions.

Anthraquic Haplustolls

IGGS. Other Haplustolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haplustolls

IGGT. 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

IGGU. Other Haplustolls that have a mollic epipedon that has 

a texture class finer than loamy fine sand and that is either:

1. 40 cm or more thick in a frigid soil temperature regime; 

or

2. 50 cm or more thick.

Pachic Haplustolls

IGGV. 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

IGGW. Other Haplustolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. 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 soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some or all parts for six-tenths or more of the cumulative 

days per year when the soil temperature at a depth of 50 

cm below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

8 o

C; and

(2) Is dry in some or all parts for six-tenths or 

more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface 

is higher than 5 oC; and
Mollisols 241

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haplustolls

IGGX. Other Haplustolls that:

1. When neither irrigated nor fallowed to store moisture, 

have one of the following:

a. A frigid soil temperature regime and a moisture 

control section that in normal years is dry in all parts for 

four-tenths or more of the cumulative days per year when 

the soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some 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 o

C; 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 the requirements for a cambic horizon, 

except for the color requirements; or

b. Have free carbonates throughout the cambic horizon 

or in all parts of the mollic epipedon below a depth of 25 

cm from the mineral soil surface.

Torriorthentic Haplustolls

IGGY. Other Haplustolls 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 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 Haplustolls

IGGZ. Other Haplustolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haplustolls

IGGZa. Other Haplustolls that have a horizon, 15 cm or more 

thick within 100 cm of the mineral soil surface, that either is 

brittle and has some opal coats or has 20 percent or more (by 

volume) durinodes.

Duric Haplustolls

IGGZb. 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 

M

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242 Keys to Soil Taxonomy

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 

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 

free carbonates throughout either the cambic horizon or the 

lower part of the mollic epipedon.

Udorthentic Haplustolls

IGGZc. 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

IGGZd. 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 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 Haplustolls

IGGZe. Other Haplustolls.

Typic Haplustolls

Natrustolls

Key to Subgroups

IGBA. Natrustolls that have all of the following:

1. Visible crystals of gypsum and/or more soluble salts 

within 40 cm of the mineral soil surface; and

2. 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 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; 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 peds 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 Natrustolls

IGBB. Other Natrustolls that have both of the following:

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 soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some or all parts for six-tenths or more of the cumulative 

days per year when the soil temperature at a depth of 50 

cm below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil 
Mollisols 243

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. 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 peds 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 Natrustolls

IGBC. 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 peds 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

IGBD. Other Natrustolls that have both of the following:

1. A glossic horizon or interfingering of albic materials into 

a natric horizon; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped peds 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

IGBE. 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 wedgeshaped peds 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

IGBF. Other Natrustolls that have both of the following:

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 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; and

2. Visible crystals of gypsum and/or more soluble salts 

within 40 cm of the mineral soil surface.

Aridic Leptic Natrustolls

IGBG. Other Natrustolls that have visible crystals of gypsum 

and/or more soluble salts within 40 cm of the mineral soil 

surface.

Leptic Natrustolls

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244 Keys to Soil Taxonomy

IGBH. 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

IGBI. Other Natrustolls 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 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 o

C.

Aridic Natrustolls

IGBJ. 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 

at least a firm rupture-resistance class when moist.

Duric Natrustolls

IGBK. Other Natrustolls that have a glossic horizon or 

interfingering of albic materials into a natric horizon.

Glossic Natrustolls

IGBL. Other Natrustolls.

Typic Natrustolls

Paleustolls

Key to Subgroups

IGDA. Paleustolls that have both of the following:

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 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. 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 peds 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 Paleustolls

IGDB. Other Paleustolls that have both of the following:

1. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for four-tenths or less of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 o

C; or

b. A hyperthermic, isomesic, or warmer iso soil 
Mollisols 245

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; 

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 peds 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 Paleustolls

IGDC. 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 wedgeshaped peds 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

IGDD. Other Paleustolls that have, in one or more horizons 

within 100 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Paleustolls

IGDE. Other Paleustolls that have a mollic epipedon that has 

a texture class finer than loamy fine sand and that is 50 cm or 

more thick.

Pachic Paleustolls

IGDF. Other Paleustolls that have a petrocalcic horizon within 

150 cm of the mineral soil surface.

Petrocalcic Paleustolls

IGDG. Other Paleustolls that have both of the following:

1. A calcic horizon within one of the following particlesize 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, 

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 soil temperature at a depth of 50 cm below the soil 

surface is higher than 5 o

C; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some or all parts for six-tenths or more of the cumulative 

days per year when the soil temperature at a depth of 50 

cm below the soil surface is higher than 5 o

C; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

8 oC; and

(2) Is dry in some or all parts for six-tenths or 

more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface 

is higher than 5 oC.

Calcidic Paleustolls

IGDH. Other Paleustolls 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 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 

M

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246 Keys to Soil Taxonomy

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

IGDI. 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

IGDJ. Other Paleustolls that 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

IGDK. Other Paleustolls that have free carbonates throughout 

after the surface horizons have been mixed to a depth of 18 cm.

Entic Paleustolls

IGDL. Other Paleustolls.

Typic Paleustolls

Vermustolls

Key to Subgroups

IGFA. Vermustolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Vermustolls

IGFB. 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

IGFC. Other Vermustolls that have a mollic epipedon that is 

75 cm or more thick.

Pachic Vermustolls

IGFD. Other Vermustolls that have a mollic epipedon that is 

less than 50 cm thick.

Entic Vermustolls

IGFE. Other Vermustolls.

Typic Vermustolls

Xerolls

Key to Great Groups

IFA. Xerolls that have a duripan within 100 cm of the mineral 

soil surface.

Durixerolls, p. 249

IFB. Other Xerolls that have a natric horizon.

Natrixerolls, p. 255

IFC. Other Xerolls that have either:

1. A petrocalcic horizon 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 noncarbonate clay 

content within 150 cm of the mineral soil surface (and 

there is no densic, lithic, or paralithic contact within that 

depth); and either

(1) Hue of 7.5YR or redder and chroma of 5 or more 

in the matrix; or

(2) Common redox concentrations with hue of 7.5YR 

or redder or chroma of 6 or more, or both; or

b. 35 percent or more noncarbonate clay throughout one 

or more subhorizons in its upper part, and one or both of 

the following:

(1) A clay increase of 20 percent or more (absolute, 

in the fine-earth fraction) within a vertical distance 

of 7.5 cm or of 15 percent or more (absolute, in the 

fine-earth fraction) within a vertical distance of 2.5 

cm, either within the argillic horizon or at its upper 

boundary (and there is no densic, lithic, or paralithic 

contact within 50 cm of the mineral soil surface); or

(2) An abrupt textural change between the eluvial 

horizon and the upper boundary of the argillic horizon 

(and there is no densic, lithic, or paralithic contact 

within 50 cm of the mineral soil surface).

Palexerolls, p. 255
Mollisols 247

IFD. Other Xerolls that have both of the following:

1. A calcic or gypsic horizon 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 free 

carbonates or a texture class of loamy fine sand or coarser.

Calcixerolls, p. 249

IFE. Other Xerolls that have an argillic horizon.

Argixerolls, p. 247

IFF. Other Xerolls.

Haploxerolls, p. 251

Argixerolls

Key to Subgroups

IFEA. Argixerolls that have both of the following:

1. An aridic soil moisture regime; and

2. A lithic contact within 50 cm of the mineral soil surface.

Aridic Lithic Argixerolls

IFEB. Other Argixerolls that have both of the following:

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

IFEC. Other Argixerolls that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Argixerolls

IFED. Other Argixerolls that have both of the following:

1. An aridic soil 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 peds in a layer 15 cm or more thick that 

has its upper boundary within 125 cm of the mineral soil 

surface; or

b. A linear extensibility of 6.0 cm or more between 

the mineral soil surface and either a depth of 100 cm 

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

shallower.

Torrertic Argixerolls

IFEE. 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 peds 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

IFEF. 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

IFEG. Other Argixerolls that have both of the following:

1. An aridic soil 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) particles 2.0 mm 

or larger in diameter, 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

IFEH. 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) particles 2.0 mm or 

larger in diameter, 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

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248 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 Argixerolls

IFEI. Other Argixerolls that have both of the following:

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

IFEJ. 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

IFEK. 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

IFEL. 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

IFEM. Other Argixerolls that have both of the following:

1. A calcic horizon or identifiable secondary carbonates 

within one of the following particle-size class (by weighted 

average in the particle-size control section) and depth 

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the 

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 

90 cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil 

surface; and

2. A mollic epipedon that is 50 cm or more thick and has a 

texture class finer than loamy fine sand.

Calcic Pachic Argixerolls

IFEN. Other Argixerolls that have both of the following:

1. A mollic epipedon that is 50 cm or more thick and has a 

texture class 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

IFEO. Other Argixerolls that have a mollic epipedon that is 50 

cm or more thick and has a texture class finer than loamy fine 

sand.

Pachic Argixerolls

IFEP. Other Argixerolls that have both of the following:

1. 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 at least a firm ruptureresistance class when moist; and

2. An aridic soil moisture regime.

Argiduridic Argixerolls

IFEQ. 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 at least a firm rupture-resistance class when moist.

Duric Argixerolls

IFER. Other Argixerolls that have both of the following:

1. A calcic horizon or identifiable secondary carbonates 

within one of the following particle-size class (by weighted 

average in the particle-size control section) and depth 

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the 

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 

90 cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil 

surface; and

2. An aridic soil moisture regime.

Calciargidic Argixerolls
Mollisols 249

IFES. Other Argixerolls that have an aridic soil moisture 

regime.

Aridic Argixerolls

IFET. 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

IFEU. 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

IFEV. Other Argixerolls.

Typic Argixerolls

Calcixerolls

Key to Subgroups

IFDA. Calcixerolls that have both of the following:

1. An aridic soil moisture regime; and

2. A lithic contact within 50 cm of the mineral soil surface.

Aridic Lithic Calcixerolls

IFDB. Other Calcixerolls that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Calcixerolls

IFDC. 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 wedgeshaped peds 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

IFDD. 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

IFDE. 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

IFDF. Other Calcixerolls that have a mollic epipedon that is 

50 cm or more thick and has a texture class finer than loamy 

fine sand.

Pachic Calcixerolls

IFDG. 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) particles 2.0 mm or 

larger in diameter, 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

IFDH. Other Calcixerolls that have an aridic soil moisture 

regime.

Aridic Calcixerolls

IFDI. 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

IFDJ. Other Calcixerolls.

Typic Calcixerolls

Durixerolls

Key to Subgroups

IFAA. Durixerolls that have 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 

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250 Keys to Soil Taxonomy

slickensides or wedge-shaped peds in a layer 15 cm or more 

thick that is 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 Durixerolls

IFAB. Other Durixerolls that have both of the following:

1. An aridic soil 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) particles 2.0 mm 

or larger in diameter, 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

IFAC. 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) particles 2.0 mm or 

larger in diameter, 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

IFAD. 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

IFAE. Other Durixerolls that have all of the following:

1. An aridic soil moisture regime; and

2. One or both of the following:

a. An argillic horizon that has a clay increase of 20 

percent or more (absolute, in the fine-earth fraction) 

within a vertical distance of 7.5 cm or of 15 percent or 

more (absolute, in the fine-earth fraction) within a vertical 

distance of 2.5 cm, either within the horizon or at its 

upper boundary; or

b. An abrupt textural change between the eluvial 

horizon and the upper boundary of the argillic horizon; 

and

3. A duripan that is neither very strongly cemented nor 

indurated in any subhorizon.

Paleargidic Durixerolls

IFAF. Other Durixerolls that have both of the following:

1. An aridic soil moisture regime; and

2. One or both of the following:

a. An argillic horizon that has a clay increase of 20 

percent or more (absolute, in the fine-earth fraction) 

within a vertical distance of 7.5 cm or of 15 percent or 

more (absolute, in the fine-earth fraction) within a vertical 

distance of 2.5 cm, either within the horizon or at its 

upper boundary; or

b. An abrupt textural change between the eluvial 

horizon and the upper boundary of the argillic horizon.

Abruptic Argiduridic Durixerolls

IFAG. Other Durixerolls that:

1. Have an aridic soil 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

IFAH. Other Durixerolls that:

1. Have an aridic soil moisture regime; and

2. Do not have an argillic horizon above the duripan.

Haploduridic Durixerolls

IFAI. Other Durixerolls that have both of the following:

1. An aridic soil moisture regime; and

2. A duripan that is neither very strongly cemented nor 

indurated in any subhorizon.

Argidic Durixerolls

IFAJ. Other Durixerolls that have an aridic soil moisture 

regime.

Argiduridic Durixerolls
Mollisols 251

IFAK. Other Durixerolls that have both of the following:

1. A duripan that is neither very strongly cemented nor 

indurated in any subhorizon; and

2. One or both of the following:

a. An argillic horizon that has a clay increase of 20 

percent or more (absolute, in the fine-earth fraction) 

within a vertical distance of 7.5 cm or of 15 percent or 

more (absolute, in the fine-earth fraction) within a vertical 

distance of 2.5 cm, either within the horizon or at its 

upper boundary; or

b. An abrupt textural change between the eluvial 

horizon and the upper boundary of the argillic horizon.

Haplic Palexerollic Durixerolls

IFAL. Other Durixerolls that have one or both of the 

following:

1. An argillic horizon that has a clay increase of 20 percent 

or more (absolute, in the fine-earth fraction) within a vertical 

distance of 7.5 cm or of 15 percent or more (absolute, in 

the fine-earth fraction) within a vertical distance of 2.5 cm, 

either within the horizon or at its upper boundary; or

2. An abrupt textural change between the eluvial horizon 

and the upper boundary of the argillic horizon.

Palexerollic Durixerolls

IFAM. 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

IFAN. Other Durixerolls that do not have an argillic horizon 

above the duripan.

Haploxerollic Durixerolls

IFAO. Other Durixerolls that have a duripan that is neither 

very strongly cemented nor indurated in any subhorizon.

Haplic Durixerolls

IFAP. Other Durixerolls.

Typic Durixerolls

Haploxerolls

Key to Subgroups

IFFA. Haploxerolls that have both of the following:

1. An aridic soil moisture regime; and

2. A lithic contact within 50 cm of the mineral soil surface.

Aridic Lithic Haploxerolls

IFFB. Other Haploxerolls that have both of the following:

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

IFFC. Other Haploxerolls that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Haploxerolls

IFFD. Other Haploxerolls that have both of the following:

1. An aridic soil 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 peds in a layer 15 cm or more thick that 

has its upper boundary within 125 cm of the mineral soil 

surface; or

b. A linear extensibility of 6.0 cm or more between 

the mineral soil surface and either a depth of 100 cm 

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

shallower.

Torrertic Haploxerolls

IFFE. 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 wedgeshaped peds 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

IFFF. 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, 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 Haploxerolls

IFFG. Other Haploxerolls that have both of the following:

1. An aridic soil moisture regime; and

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252 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, 

one or both of the following:

a. More than 35 percent (by volume) particles 2.0 mm 

or larger in diameter, 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

IFFH. 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) particles 2.0 mm or 

larger in diameter, 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

IFFI. Other Haploxerolls that have all of the following:

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 mollic epipedon that is 50 cm or more thick and has a 

texture class finer than loamy fine sand; and

3. A slope of less than 25 percent; and

4. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

5. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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.

Aquic Cumulic Haploxerolls

IFFJ. Other Haploxerolls that have all of the following:

1. A mollic epipedon that is 50 cm or more thick and has a 

texture class finer than loamy fine sand; and

2. A slope of less than 25 percent; and

3. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(Holocene age) between a depth of 25 cm and either 

a depth of 125 cm below the mineral soil surface or 

a densic, lithic, or paralithic contact, whichever is 

shallower; and

5. 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

IFFK. Other Haploxerolls that have all of the following:

1. A mollic epipedon that is 50 cm or more thick and has a 

texture class finer than loamy fine sand; and

2. A slope of less than 25 percent; and

3. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haploxerolls

IFFL. Other Haploxerolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and
Mollisols 253

3. 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

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haploxerolls

IFFM. Other Haploxerolls that have both of the following:

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 at least a firm ruptureresistance class when moist.

Aquic Duric Haploxerolls

IFFN. Other Haploxerolls that have both of the following:

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

IFFO. 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

IFFP. 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

IFFQ. Other Haploxerolls that have both of the following:

1. A calcic horizon or identifiable secondary carbonates 

within one of the following particle-size class (by weighted 

average in the particle-size control section) and depth 

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the 

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 

90 cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil 

surface; and

2. A mollic epipedon that is 50 cm or more thick and has a 

texture class finer than loamy fine sand.

Calcic Pachic Haploxerolls

IFFR. Other Haploxerolls that have both of the following:

1. A mollic epipedon that is 50 cm or more thick and has a 

texture class 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

IFFS. Other Haploxerolls that have a mollic epipedon that is 

50 cm or more thick and has a texture class finer than loamy 

fine sand.

Pachic Haploxerolls

IFFT. Other Haploxerolls that have all of the following:

1. An aridic soil moisture regime; and

2. A slope of less than 25 percent; and

3. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

4. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haploxerolls

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254 Keys to Soil Taxonomy

IFFU. Other Haploxerolls that have both of the following:

1. An aridic soil 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 at least a firm ruptureresistance class when moist.

Duridic Haploxerolls

IFFV. Other Haploxerolls that have both of the following:

1. An aridic soil moisture regime; and

2. A calcic horizon or identifiable secondary carbonates 

within one of the following particle-size class (by weighted 

average in the particle-size control section) and depth 

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the 

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 

90 cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil 

surface.

Calcidic Haploxerolls

IFFW. Other Haploxerolls that have both of the following:

1. An aridic soil moisture regime; and

2. A sandy particle-size class in all horizons within 100 cm 

of the mineral soil surface.

Torripsammentic Haploxerolls

IFFX. Other Haploxerolls that:

1. Have an aridic soil 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 the requirements for a cambic horizon, 

except for the color requirements; 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

IFFY. Other Haploxerolls that have an aridic soil moisture 

regime.

Aridic Haploxerolls

IFFZ. 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 at least a firm rupture-resistance class when moist.

Duric Haploxerolls

IFFZa. Other Haploxerolls that have a sandy particle-size 

class in all horizons within 100 cm of the mineral soil surface.

Psammentic Haploxerolls

IFFZb. Other Haploxerolls that have all of the following:

1. A slope of less than 25 percent; and

2. A total thickness of less than 50 cm of humantransported material in the surface horizons; and

3. One or both of the following:

a. An organic-carbon content (Holocene age) 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 

(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 Haploxerolls

IFFZc. 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

IFFZd. 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

IFFZe. Other Haploxerolls that:

1. 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; 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 
Mollisols 255

is deeper, and either a depth of 75 cm or a densic, lithic, or 

paralithic contact, whichever is shallower.

Entic Ultic Haploxerolls

IFFZf. 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

IFFZg. 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 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 Haploxerolls

IFFZh. Other Haploxerolls.

Typic Haploxerolls

Natrixerolls

Key to Subgroups

IFBA. 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 peds 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

IFBB. Other Natrixerolls that have both of the following:

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 at least a firm ruptureresistance class when moist.

Aquic Duric Natrixerolls

IFBC. 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

IFBD. Other Natrixerolls that have an aridic soil moisture 

regime.

Aridic Natrixerolls

IFBE. 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 at least a firm rupture-resistance class when moist.

Duric Natrixerolls

IFBF. Other Natrixerolls.

Typic Natrixerolls

Palexerolls

Key to Subgroups

IFCA. 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 peds 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

IFCB. 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) particles 2.0 mm or 

larger in diameter, 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

IFCC. Other Palexerolls that have, in one or more horizons 

within 75 cm of the mineral soil surface, redox depletions with 

M

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chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Palexerolls

IFCD. Other Palexerolls that have a mollic epipedon that is 50 

cm or more thick and has a texture class finer than loamy fine 

sand.

Pachic Palexerolls

IFCE. Other Palexerolls that have both of the following:

1. A petrocalcic horizon within 150 cm of the mineral soil 

surface; and

2. An aridic soil moisture regime.

Petrocalcidic Palexerolls

IFCF. 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 

at least a firm rupture-resistance class when moist.

Duric Palexerolls

IFCG. Other Palexerolls that have an aridic soil moisture 

regime.

Aridic Palexerolls

IFCH. Other Palexerolls that have a petrocalcic horizon within 

150 cm of the mineral soil surface.

Petrocalcic Palexerolls

IFCI. Other Palexerolls that have a base saturation (by sum of 

cations) 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

IFCJ. 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

IFCK. Other Palexerolls.

Typic Palexerolls
257

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Oxisols

CHAPTER 13

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. 257

EB. Other Oxisols that have an aridic soil moisture regime.

Torrox, p. 262

EC. Other Oxisols that have an ustic or xeric soil moisture 

regime.

Ustox, p. 267

ED. Other Oxisols that have a perudic soil moisture regime.

Perox, p. 258

EE. Other Oxisols.

Udox, p. 263

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 (1N KCl) of 5.0 or more.

Acraquox, p. 257

EAB. Other Aquox that have plinthite forming a continuous 

phase within 125 cm of the mineral soil surface.

Plinthaquox, p. 258

EAC. Other Aquox that have a base saturation (by NH4

OAc) 

of 35 percent or more in all horizons within 125 cm of the 

mineral soil surface.

Eutraquox, p. 257

EAD. Other Aquox.

Haplaquox, p. 258

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

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
258 Keys to Soil Taxonomy

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. Plinthaquox 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. 262

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. 258

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. 259

EDD. Other Perox that have a kandic horizon within 150 cm 

of the mineral soil surface.

Kandiperox, p. 261

EDE. Other Perox.

Haploperox, p. 260

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

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 
Oxisols 259

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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 

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 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
260 Keys to Soil Taxonomy

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

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
Oxisols 261

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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

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
262 Keys to Soil Taxonomy

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. 262

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. 262

EBC. Other Torrox.

Haplotorrox, p. 262

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

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
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Udox

Key to Great Groups

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

mineral soil surface.

Sombriudox, p. 267

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. 263

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. 264

EED. Other Udox that have a kandic horizon within 150 cm 

of the mineral soil surface.

Kandiudox, p. 266

EEE. Other Udox.

Hapludox, p. 265

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 and 

also aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Acrudox

EEBI. Other Acrudox 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 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
264 Keys to Soil Taxonomy

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 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
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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

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
266 Keys to Soil Taxonomy

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 hat have 5 percent or more (by 

volume) plinthite in one or more horizons within 125 cm of the 

mineral soil surface.

Plinthic Kandiudox

EEDG. Other Kandiudox that have, in one or more horizons 

within 125 cm of the mineral soil surface, redox depletions with 

a color value, moist, of 4 or more and chroma of 2 or less and 

also aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Kandiudox

EEDH. Other Kandiudox that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Kandiudox

EEDI. Other Kandiudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from 

the mineral soil surface, more than 50 percent colors that 

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Kandiudox

EEDJ. Other Kandiudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a color 

value, moist, of 6 or more at a depth between 25 and 125 cm 

from the mineral soil surface.

Humic Xanthic Kandiudox

EEDK. Other Kandiudox that have 16 kg/m2

 or more organic 

carbon between the mineral soil surface and a depth of 100 cm.

Humic Kandiudox

EEDL. Other Kandiudox that have, in all horizons at a depth 

between 25 and 125 cm from the mineral soil surface, more 

than 50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Kandiudox

EEDM. Other Kandiudox that have 50 percent or more hue 
Oxisols 267

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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. 271

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. 267

ECC. Other Ustox that have a base saturation (by NH4

OAc) of 

35 percent or more in all horizons within 125 cm of the mineral 

soil surface.

Eutrustox, p. 268

ECD. Other Ustox that have a kandic horizon within 150 cm 

of the mineral soil surface.

Kandiustox, p. 270

ECE. Other Ustox.

Haplustox, p. 269

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

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 
268 Keys to Soil Taxonomy

also aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Acrustox

ECBI. Other Acrustox that have a base saturation (by 

NH4OAc) 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 

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 within 

150 cm of the mineral soil surface.

Kandiustalfic Eutrustox
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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 

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 
270 Keys to Soil Taxonomy

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

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 
Oxisols 271

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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. 273

CB. Other Spodosols that have a gelic soil temperature 

regime.

Gelods, p. 277

CC. Other Spodosols that have a cryic soil temperature 

regime.

Cryods, p. 275

CD. 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. 277

CE. Other Spodosols.

Orthods, p. 278

Aquods

Key to Great Groups

CAA. Aquods that have a cryic soil temperature regime.

Cryaquods, p. 274

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. 273

CAC. Other Aquods that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiaquods, p. 275

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. 275

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

pedon, a cemented horizon within 100 cm of the mineral soil 

surface.

Duraquods, p. 274

CAF. Other Aquods that have episaturation.

Epiaquods, p. 275

CAG. Other Aquods.

Endoaquods, p. 274

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 horizon within 100 cm of the mineral 

soil surface.

Duric Alaquods

CABC. Other Alaquods that have a histic epipedon.

Histic Alaquods

CABD. Other Alaquods that:

1. Within 200 cm of the mineral soil surface, have an 

argillic or kandic horizon that has a base saturation (by sum 

of cations) of 35 percent or more in some part; and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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:

1. Have an argillic or kandic horizon within 200 cm of the 

mineral soil surface; and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand throughout a layer extending from the mineral soil 

Spodosols

CHAPTER 14
274 Keys to Soil Taxonomy

surface to the top of a spodic horizon at a depth of 75 to 125 

cm.

Arenic Ultic Alaquods

CABF. Other Alaquods that:

1. Have an umbric epipedon; and

2. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 (by sum of cations) of 35 percent or more 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 horizon 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

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
Spodosols 275

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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 (by sum of cations) of 35 percent or more 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 

between 25 and 50 cm thick that meets all of the requirements 

for a plaggen epipedon except thickness.

Haploplaggic 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

CCA. Cryods that have a placic horizon within 100 cm of the 

mineral soil surface in 50 percent or more of each pedon.

Placocryods, p. 277

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

pedon, a cemented horizon within 100 cm of the mineral soil 

surface.

Duricryods, p. 275

CCC. 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. 276

CCD. Other Cryods.

Haplocryods, p. 276

Duricryods

Key to Subgroups

CCBA. 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
276 Keys to Soil Taxonomy

CCBB. 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

CCBC. 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

CCBD. 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

CCBE. 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

CCBF. Other Duricryods.

Typic Duricryods

Haplocryods

Key to Subgroups

CCDA. Haplocryods that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Haplocryods

CCDB. 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

CCDC. 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

CCDD. Other Haplocryods that have a folistic epipedon.

Folistic Haplocryods

CCDE. 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

CCDF. 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

CCDG. Other Haplocryods that have 1.1 percent or less 

organic carbon in the upper 10 cm of the spodic horizon.

Entic Haplocryods

CCDH. Other Haplocryods.

Typic Haplocryods

Humicryods

Key to Subgroups

CCCA. Humicryods that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humicryods

CCCB. 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

CCCC. 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

CCCD. Other Humicryods that have a folistic epipedon.

Folistic Humicryods

CCCE. Other Humicryods that have redoximorphic features 
Spodosols 277

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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

CCCF. 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

CCCG. Other Humicryods.

Typic Humicryods

Placocryods

Key to Subgroups

CCAA. 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

CCAB. 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

CCAC. Other Placocryods.

Typic Placocryods

Gelods

Key to Great Groups

CBA. Gelods that have 6.0 percent or more organic carbon 

throughout a layer 10 cm or more thick within the spodic 

horizon.

Humigelods, p. 277

CBB. Other Gelods.

Haplogelods, p. 277

Haplogelods

Key to Subgroups

CBBA. Haplogelods that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Haplogelods

CBBB. Other Haplogelods 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 Haplogelods

CBBC. Other Haplogelods 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 Haplogelods

CBBD. Other Haplogelods that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Haplogelods

CBBE. Other Haplogelods.

Typic Haplogelods

Humigelods 

Key to Subgroups

CBAA. Humigelods that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humigelods

CBAB. Other Humigelods 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 Humigelods

CBAC. Other Humigelods 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 Humigelods

CBAD. Other Humigelods that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Humigelods

CBAE. Other Humigelods.

Typic Humigelods

Humods

Key to Great Groups

CDA. Humods that have a placic horizon within 100 cm 

of the mineral soil surface in 50 percent or more of each 

pedon.

Placohumods, p. 278
278 Keys to Soil Taxonomy

CDB. Other Humods that have, in 90 percent or more of each 

pedon, a cemented horizon within 100 cm of the mineral soil 

surface.

Durihumods, p. 278

CDC. Other Humods that have a fragipan within 100 cm of 

the mineral soil surface.

Fragihumods, p. 278

CDD. Other Humods.

Haplohumods, p. 278

Durihumods

Key to Subgroups

CDBA. 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

CDBB. Other Durihumods.

Typic Durihumods

Fragihumods

Key to Subgroups

CDCA. All Fragihumods (provisionally).

Typic Fragihumods

Haplohumods

Key to Subgroups

CDDA. Haplohumods that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Haplohumods

CDDB. Other Haplohumods that have andic soil properties 

throughout horizons that have a total thickness of 25 cm or 

more within 75 cm either of the mineral soil surface or of the 

top of an organic layer with andic soil properties, whichever is 

shallower.

Andic Haplohumods

CDDC. Other Haplohumods that have a surface horizon 

between 25 and 50 cm thick that meets all of the requirements 

for a plaggen epipedon except thickness.

Haploplaggic Haplohumods

CDDD. Other Haplohumods.

Typic Haplohumods

Placohumods

Key to Subgroups

CDAA. 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

CDAB. Other Placohumods.

Typic Placohumods

Orthods

Key to Great Groups

CEA. Orthods that have, in 50 percent or more of each pedon, 

a placic horizon within 100 cm of the mineral soil surface.

Placorthods, p. 281

CEB. Other Orthods that have, in 90 percent or more of each 

pedon, a cemented horizon within 100 cm of the mineral soil 

surface.

Durorthods, p. 279

CEC. Other Orthods that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiorthods, p. 279

CED. Other Orthods that have less than 0.10 percent iron 

(by ammonium oxalate) in 75 percent or more of the spodic 

horizon.

Alorthods, p. 278

CEE. Other Orthods.

Haplorthods, p. 280

Alorthods

Key to Subgroups

CEDA. 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

CEDB. Other Alorthods that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand throughout a layer extending from the mineral soil 
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surface to the top of a spodic horizon at a depth of 75 to 125 

cm; and

2. Have an argillic or kandic horizon below the spodic 

horizon.

Arenic Ultic Alorthods

CEDC. Other Alorthods that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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

CEDD. Other Alorthods that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. 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 Grossarenic Alorthods

CEDE. 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

CEDF. Other Alorthods that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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

CEDG. Other Alorthods that have a surface horizon between 

25 and 50 cm thick that meets all of the requirements for a 

plaggen epipedon except thickness.

Haploplaggic Alorthods

CEDH. Other Alorthods that have, within 200 cm of the 

mineral soil surface, an argillic or kandic horizon that has a base 

saturation (by sum of cations) of 35 percent or more in some 

part.

Alfic Alorthods

CEDI. Other Alorthods that have an argillic or kandic horizon 

within 200 cm of the mineral soil surface.

Ultic Alorthods

CEDJ. Other Alorthods.

Typic Alorthods

Durorthods

Key to Subgroups

CEBA. 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

CEBB. Other Durorthods.

Typic Durorthods

Fragiorthods

Key to Subgroups

CECA. 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

CECB. 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 (by sum 

of cations) of 35 percent or more in some part.

Alfic Oxyaquic Fragiorthods

CECC. 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

CECD. Other Fragiorthods that have a surface horizon 

between 25 and 50 cm thick that meets all of the requirements 

for a plaggen epipedon except thickness.

Haploplaggic Fragiorthods

CECE. Other Fragiorthods that have, within 200 cm of the 

mineral soil surface, an argillic or kandic horizon that has a base 

saturation (by sum of cations) of 35 percent or more in some 

part.

Alfic Fragiorthods
280 Keys to Soil Taxonomy

CECF. Other Fragiorthods that have an argillic or kandic 

horizon within 200 cm of the mineral soil surface.

Ultic Fragiorthods

CECG. Other Fragiorthods that have a spodic horizon that has 

one of the following:

1. A texture class of very fine sand, loamy very fine sand, 

or finer and all of the following:

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 class 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

CECH. Other Fragiorthods.

Typic Fragiorthods

Haplorthods

Key to Subgroups

CEEA. Haplorthods that have a lithic contact within 50 cm of 

the mineral soil surface and either:

1. A spodic horizon with a texture class of very fine sand, 

loamy very fine sand, or finer and all of the following:

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 class 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

CEEB. Other Haplorthods that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Haplorthods

CEEC. 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

CEED. 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 (by sum of cations) 

of 35 percent or more in some part.

Aqualfic Haplorthods

CEEE. 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 class of very fine sand, 

loamy very fine sand, or finer and all of the following:

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 class 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

CEEF. 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

CEEG. Other Haplorthods that have:

1. Within 200 cm of the mineral soil surface, an argillic or 

kandic horizon that has a base saturation (by sum of cations) 

of 35 percent or more 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:
Spodosols 281

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a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Alfic Oxyaquic Haplorthods

CEEH. 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

CEEI. Other Haplorthods that have fragic soil properties 

either:

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

CEEJ. Other Haplorthods that have both:

1. Saturation with water in 1 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. Below the spodic horizon but not below an argillic 

horizon, lamellae (two or more) within 200 cm of the 

mineral soil surface.

Lamellic Oxyaquic Haplorthods

CEEK. 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

CEEL. 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:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplorthods

CEEM. 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

CEEN. Other Haplorthods that have, within 200 cm of the 

mineral soil surface, an argillic or kandic horizon that has a base 

saturation (by sum of cations) of 35 percent or more in some 

part.

Alfic Haplorthods

CEEO. Other Haplorthods that have an argillic or kandic 

horizon within 200 cm of the mineral soil surface.

Ultic Haplorthods

CEEP. Other Haplorthods that have a spodic horizon that has 

one of the following:

1. A texture class of very fine sand, loamy very fine sand, 

or finer and all of the following:

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 class 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

CEEQ. Other Haplorthods.

Typic Haplorthods

Placorthods

Key to Subgroups

CEAA. 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. 283

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. 287

HC. Other Ultisols that have a udic soil moisture regime.

Udults, p. 290

HD. Other Ultisols that have an ustic soil moisture regime.

Ustults, p. 298

HE. Other Ultisols.

Xerults, p. 302

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. 287

HAB. Other Aquults that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiaquults, p. 285

HAC. Other Aquults that have an abrupt textural change 

between the ochric epipedon or albic horizon and the argillic or 

kandic horizon and have a saturated hydraulic conductivity of 

0.4 cm/hr (1.0 μm/sec) or slower (moderately low or lower Ksat

class) in the argillic or kandic horizon.

Albaquults, p. 284

HAD. Other Aquults that:

1. Do not have a densic, lithic, paralithic, or petroferric 

contact within 150 cm of the mineral soil surface; and

2. Have a kandic horizon; and

3. Within 150 cm of the mineral soil surface, either:

a. With increasing depth, do not have a clay decrease 

of 20 percent or more (relative) from the maximum clay 

content; or

b. Have 5 percent or more (by volume) clay depletions 

on faces of peds in the layer that has a 20 percent lower 

clay content and, below that layer, a clay increase of 3 

percent or more (absolute) in the fine-earth fraction.

Kandiaquults, p. 285

HAE. Other Aquults that have a kandic horizon.

Kanhaplaquults, p. 286

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:

Ultisols

CHAPTER 15
284 Keys to Soil Taxonomy

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. 286

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

Umbraquults, p. 287

HAH. Other Aquults that have episaturation.

Epiaquults, p. 284

HAI. Other Aquults.

Endoaquults, p. 284

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 wedgeshaped peds 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 peds 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 both of the following:

1. Fragic soil properties either:

a. In 30 percent or more of the volume of a layer 15 cm 

or more thick that has its upper boundary within 100 cm 

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm 

or more thick; and

2. 50 percent or more chroma of 3 or more in one or more 

horizons between either the A or Ap horizon or a depth of 25 

cm from the mineral soil surface, whichever is deeper, and a 

depth of 75 cm.

Aeric Fragic Epiaquults

HAHC. Other Epiaquults that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 
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loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 

either:

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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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 texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have a mollic or umbric epipedon.

Arenic Umbric Kandiaquults

HADD. Other Kandiaquults that have a texture class (fineearth fraction) of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand 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 texture class (fineearth fraction) of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand 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 
286 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) particles 2.0 mm or 

larger in diameter, 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 have both of the following:

1. 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; and

2. A mollic or umbric epipedon.

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 wedgeshaped peds 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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 texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have a mollic or umbric epipedon.

Arenic Umbric Paleaquults

HAFD. Other Paleaquults that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand throughout a layer extending 
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from the mineral soil surface to the top of an argillic horizon at 

a depth of 100 cm or more.

Grossarenic Paleaquults

HAFF. Other Paleaquults that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Paleaquults

HAFG. Other Paleaquults that have 50 percent or more 

chroma of 3 or more in one or more horizons between either 

the A or Ap horizon or a depth of 25 cm from the mineral soil 

surface, whichever is deeper, and a depth of 75 cm.

Aeric Paleaquults

HAFH. Other Paleaquults that have a mollic or umbric 

epipedon.

Umbric Paleaquults

HAFI. Other Paleaquults.

Typic Paleaquults

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. 290

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. 290

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) 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.

Kandihumults, p. 288

HBD. Other Humults that have a kandic horizon.

Kanhaplohumults, p. 289

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) 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.

Palehumults, p. 289

HBF. Other Humults.

Haplohumults, p. 287

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 of the following:

1. In one or more subhorizons within the upper 25 cm of 

the argillic horizon, redox depletions with a color value, 
288 Keys to Soil Taxonomy

moist, of 4 or more and chroma of 2 or less, accompanied 

by both redox concentrations and 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 both redox concentrations 

and 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 soil moisture 

regime.

Ustic Haplohumults

HBFH. Other Haplohumults that have a xeric soil 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 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, 

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 soil 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 both redox concentrations 

and 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 soil moisture 

regime.

Ustic Kandihumults

HBCH. Other Kandihumults that have a xeric soil 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 of the 

following:

1. An ustic soil 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 both redox concentrations 

and 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 soil 

moisture regime.

Ustic Kanhaplohumults

HBDG. Other Kanhaplohumults that have a xeric soil 

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 of the following:

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 both redox concentrations and aquic conditions for some 

time in normal years (or artificial drainage); and
290 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 both redox concentrations 

and 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 soil moisture 

regime.

Ustic Palehumults

HBEG. Other Palehumults that have a xeric soil 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. 298

HCB. Other Udults that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiudults, p. 291

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) 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.

Kandiudults, p. 293

HCD. Other Udults that have a kandic horizon.

Kanhapludults, p. 295

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) 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.

Paleudults, p. 296
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HCF. Other Udults that have both of the following:

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. 298

HCG. Other Udults.

Hapludults, p. 291

Fragiudults

Key to Subgroups

HCBA. Fragiudults that have a texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 have both:

1. 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 peds; 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, 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 peds; 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
292 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 wedgeshaped peds 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 of the following:

1. Fragic soil properties either:

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 both redox 

concentrations and aquic conditions for some time in normal 

years (or artificial drainage).

Fragiaquic Hapludults

HCGE. Other Hapludults that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. 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 both redox concentrations and 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 both redox concentrations and aquic conditions 

for some time in normal years (or artificial drainage).

Aquic Hapludults

HCGG. Other Hapludults that have fragic soil properties 

either:

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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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:

1. Do not have a densic, lithic, or paralithic contact within 

50 cm of the mineral soil surface; and

2. Have an argillic horizon that is 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 all of the following:

1. A texture class (fine-earth fraction) of coarse sand, sand, 

fine sand, loamy coarse sand, loamy sand, or loamy fine sand 

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 both redox concentrations and aquic conditions for some 

time in normal years (or artificial drainage).

Arenic Plinthaquic Kandiudults

HCCB. Other Kandiudults that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have, 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 both redox concentrations and 

aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Arenic Kandiudults

HCCC. Other Kandiudults that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. 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:

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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand throughout a layer extending 
294 Keys to Soil Taxonomy

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 of the following:

1. 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; and

2. 5 percent or more (by volume) plinthite in one or more 

horizons within 150 cm of the mineral soil surface.

Acrudoxic Plinthic Kandiudults

HCCI. Other Kandiudults that have an ECEC of 1.5 

cmol(+)/kg clay or less (sum of bases extracted with 1N 

NH4OAc pH 7, plus 1N KCl-extractable Al) in one or more 

horizons within 150 cm of the mineral soil surface.

Acrudoxic Kandiudults

HCCJ. Other Kandiudults that have both of the following:

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 both redox 

concentrations and aquic conditions for some time in normal 

years (or artificial drainage).

Plinthaquic Kandiudults

HCCK. Other Kandiudults that have both of the following:

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 both redox 

concentrations and 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) particles 2.0 mm 

or larger in diameter, 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 both redox concentrations and 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 
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kandic horizon if it is less than 75 cm thick, more than 50 

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist 

value.

Rhodic Kandiudults

HCCS. Other Kandiudults.

Typic Kandiudults

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 of the following:

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 both redox 

concentrations and aquic conditions for some time in normal 

years (or artificial drainage).

Plinthaquic Kanhapludults

HCDC. Other Kanhapludults that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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 texture class (fineearth fraction) of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand 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 

NH4OAc 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 of the following:

1. Fragic soil properties either:

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 both redox 

concentrations and 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 both redox concentrations and 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
296 Keys to Soil Taxonomy

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 

either:

1. In 30 percent or more of the volume of a layer 15 cm or 

more thick that has its upper boundary within 100 cm of the 

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or 

more thick.

Fragic Kanhapludults

HCDM. Other Kanhapludults that have, in all subhorizons 

in the upper 50 cm of the kandic horizon or throughout the 

entire kandic horizon if it is less than 50 cm thick, more than 50 

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist 

value.

Rhodic Kanhapludults

HCDN. Other Kanhapludults.

Typic Kanhapludults

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 wedgeshaped peds 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 all of the following:

1. A texture class (fine-earth fraction) of coarse sand, sand, 

fine sand, loamy coarse sand, loamy sand, or loamy fine sand 

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. 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 argillic horizon, redox depletions with a color value, 

moist, of 4 or more and chroma of 2 or less, accompanied 

by both redox concentrations and aquic conditions for some 

time in normal years (or artificial drainage).

Arenic Plinthaquic Paleudults

HCED. Other Paleudults that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have, 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 both redox concentrations and 

aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Arenic Paleudults

HCEE. Other Paleudults that have anthraquic conditions.

Anthraquic Paleudults

HCEF. Other Paleudults that have both of the following:

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 
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by both redox concentrations and aquic conditions for some 

time in normal years (or artificial drainage).

Plinthaquic Paleudults

HCEG. Other Paleudults that have both of the following:

1. Fragic soil properties either:

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 both redox 

concentrations and aquic conditions for some time in normal 

years (or artificial drainage).

Fragiaquic Paleudults

HCEH. 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 both redox concentrations and aquic conditions 

for some time in normal years (or artificial drainage).

Aquic Paleudults

HCEI. Other Paleudults 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. 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:

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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand throughout a layer extending 
298 Keys to Soil Taxonomy

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 texture class (fine-earth 

fraction) of coarse sand, sand, fine sand, loamy coarse sand, 

loamy sand, or loamy fine sand 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 

either:

1. In 30 percent or more of the volume of a layer 15 cm or 

more thick that has its upper boundary within 100 cm of the 

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or 

more thick.

Fragic Paleudults

HCES. Other Paleudults that have, in all subhorizons in the 

upper 75 cm of the argillic horizon or throughout the entire 

argillic horizon if it is less than 75 cm thick, more than 50 

percent colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less; and

3. A dry value no more than 1 unit higher than the moist 

value.

Rhodic Paleudults

HCET. Other Paleudults.

Typic Paleudults

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. 302

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. 299

HDC. Other Ustults that have a kandic horizon.

Kanhaplustults, p. 300

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. 301

HDE. Other Ustults that have both of the following:

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:
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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. 302

HDF. Other Ustults.

Haplustults, p. 299

Haplustults

Key to Subgroups

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

the mineral soil surface.

Lithic Haplustults

HDFB. Other Haplustults that have a petroferric contact 

within 100 cm of the mineral soil surface.

Petroferric Haplustults

HDFC. Other Haplustults that have, in one or more layers 

both within the upper 12.5 cm of the argillic horizon and within 

75 cm of the mineral soil surface, redox depletions with a color 

value, moist, of 4 or more and chroma of 2 or less, accompanied 

by both redox concentrations and aquic conditions for some 

time in normal years (or artificial drainage).

Aquic Haplustults

HDFD. Other Haplustults that have a texture class (fineearth fraction) of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand 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 both redox concentrations and aquic conditions 

for some time in normal years (or artificial drainage).

Aquic Kandiustults

HDBC. Other Kandiustults that:

1. Have a texture class (fine-earth fraction) of coarse sand, 

sand, fine sand, loamy coarse sand, loamy sand, or loamy 

fine sand 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. Have 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 texture class (fineearth fraction) of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand 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 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, 

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
300 Keys to Soil Taxonomy

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 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 

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.

Udandic Kandiustults

HDBF. Other Kandiustults that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Kandiustults

HDBG. Other Kandiustults that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Kandiustults

HDBH. Other Kandiustults that, when neither irrigated nor 

fallowed to store moisture, have either:

1. A thermic, mesic, or colder soil temperature regime and 

a moisture control section that in normal years is dry in some 

part for more than four-tenths of the cumulative days per 

year when the soil temperature at a depth of 50 cm below the 

soil surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

a. Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil 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 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 Kandiustults

HDBJ. Other Kandiustults 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 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 both redox concentrations and aquic conditions 

for some time in normal years (or artificial drainage).

Aquic Kanhaplustults

HDCD. Other Kanhaplustults that have a texture class 

(fine-earth fraction) of coarse sand, sand, fine sand, loamy 

coarse sand, loamy sand, or loamy fine sand 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 of the following:
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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 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.

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 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 soil 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 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 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
302 Keys to Soil Taxonomy

Plinthustults

Key to Subgroups

HDAA. Plinthustults that have either:

1. A densic, lithic, paralithic, or petroferric contact within 

150 cm of the mineral soil surface; or

2. Within 150 cm of the mineral soil surface, both:

a. With increasing depth, a clay decrease of 20 percent 

or more (relative) from the maximum clay content; and

b. Less than 5 percent (by volume) skeletans on faces of 

peds in the layer that has a 20 percent lower clay content 

or, below that layer, a clay increase of less than 3 percent 

(absolute) in the fine-earth fraction.

Haplic Plinthustults

HDAB. Other Plinthustults.

Typic Plinthustults

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. 303

HEB. Other Xerults.

Haploxerults, p. 302

Haploxerults

Key to Subgroups

HEBA. Haploxerults that have both of the following:

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 both redox 

concentrations and 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, and 

above these horizons there are either:

a. Two or more lamellae with a combined thickness of 5 

cm or more (that may or may not be part of the argillic or 

kandic horizon); or

b. A combination of lamellae (that may or may not be 

part of the argillic or kandic horizon) and one or more 

parts of the argillic or kandic horizon 7.5 to 20 cm thick, 

each with an overlying eluvial horizon.

Lamellic Haploxerults
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HEBF. Other Haploxerults that have a sandy particle-size 

class throughout the upper 75 cm of the argillic or kandic 

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

thick.

Psammentic Haploxerults

HEBG. Other Haploxerults that have a texture class (fineearth fraction) of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand 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 texture class (fineearth fraction) of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand 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 of the following:

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 both redox concentrations and 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 both redox 

concentrations and 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 to give a positive reaction 

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

irrigated.

Aquerts, p. 305

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

Cryerts, p. 309

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. 315

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. 309

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

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

thickness of 25 cm or more within 50 cm of the mineral soil 

surface, for 90 or more cumulative days per year.

Usterts, p. 311

FF. Other Vertisols.

Uderts, p. 310

Aquerts

Key to Great Groups

FAA. Aquerts that have within 100 cm of the mineral soil 

surface either:

1. A sulfuric horizon; or

2. Sulfidic materials.

Sulfaquerts, p. 309

FAB. Other Aquerts that have a salic horizon within 100 cm 

of the mineral soil surface.

Salaquerts, p. 308

FAC. Other Aquerts that have a duripan within 100 cm of the 

mineral soil surface.

Duraquerts, p. 306

FAD. Other Aquerts that have a natric horizon within 100 cm 

of the mineral soil surface.

Natraquerts, p. 308

FAE. Other Aquerts that have a calcic horizon within 100 cm 

of the mineral soil surface.

Calciaquerts, p. 306

FAF. Other Aquerts that have, throughout one or more 

horizons with a total thickness of 25 cm or more within 50 cm 

of the mineral soil surface, both:

1. An electrical conductivity in the saturation extract of less 

than 4.0 dS/m at 25 oC; and

2. A pH value of 4.5 or less in 0.01 M CaCl2 (5.0 or less in 

1:1 water).

Dystraquerts, p. 306

FAG. Other Aquerts that have episaturation.

Epiaquerts, p. 307

FAH. Other Aquerts.

Endoaquerts, p. 307

Vertisols

CHAPTER 16
306 Keys to Soil Taxonomy

Calciaquerts

Key to Subgroups

FAEA. 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

FAEB. Other Calciaquerts.

Typic Calciaquerts

Duraquerts

Key to Subgroups

FACA. 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

FACB. 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

FACC. 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

FACD. 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

FACE. 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

FACF. Other Duraquerts.

Typic Duraquerts

Dystraquerts

Key to Subgroups

FAFA. 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, air-dried slowly in shade).

Sulfaqueptic Dystraquerts

FAFB. 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

FAFC. 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

FAFD. 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
Vertisols 307

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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

FAFE. Other Dystraquerts that have a densic, lithic, or 

paralithic contact within 100 cm of the mineral soil surface.

Leptic Dystraquerts

FAFF. Other Dystraquerts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

Entic Dystraquerts

FAFG. 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

FAFH. Other Dystraquerts.

Typic Dystraquerts

Endoaquerts

Key to Subgroups

FAHA. 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

FAHB. 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

FAHC. 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

FAHD. 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

FAHE. 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

FAHF. 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

FAHG. Other Endoaquerts that have a densic, lithic, or 

paralithic contact within 100 cm of the mineral soil surface.

Leptic Endoaquerts

FAHH. Other Endoaquerts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

Entic Endoaquerts

FAHI. Other Endoaquerts that have, in one or more horizons 

within 30 cm of the mineral soil surface, one or both of the 

following in more than half of each pedon:

1. A color value, moist, of 4 or more; or

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

Chromic Endoaquerts

FAHJ. Other Endoaquerts.

Typic Endoaquerts

Epiaquerts

Key to Subgroups

FAGA. Epiaquerts that have, throughout a layer 15 cm 

or more thick within 100 cm of the mineral soil surface, an 
308 Keys to Soil Taxonomy

electrical conductivity of 15 dS/m or more (saturated paste) for 

6 or more months in normal years.

Halic Epiaquerts

FAGB. 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

FAGC. 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

FAGD. 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

FAGE. 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

FAGF. 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

FAGG. Other Epiaquerts that have a densic, lithic, or 

paralithic contact within 100 cm of the mineral soil surface.

Leptic Epiaquerts

FAGH. Other Epiaquerts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

Entic Epiaquerts

FAGI. 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

FAGJ. Other Epiaquerts.

Typic Epiaquerts

Natraquerts

Key to Subgroups

FADA. All Natraquerts.

Typic Natraquerts

Salaquerts

Key to Subgroups

FABA. 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

FABB. 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

FABC. Other Salaquerts that have a densic, lithic, or paralithic 

contact within 100 cm of the mineral soil surface.

Leptic Salaquerts

FABD. Other Salaquerts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

Entic Salaquerts

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

3. Chroma of 3 or more.

Chromic Salaquerts

FABF. Other Salaquerts.

Typic Salaquerts

Sulfaquerts

Key to Subgroups

FAAA. Sulfaquerts that have a salic horizon within 75 cm of 

the mineral soil surface.

Salic Sulfaquerts

FAAB. Other Sulfaquerts that do not have a sulfuric horizon 

within 100 cm of the mineral soil surface.

Sulfic Sulfaquerts

FAAC. Other Sulfaquerts.

Typic Sulfaquerts

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. 309

FBB. Other Cryerts.

Haplocryerts, p. 309

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 within 100 cm of the 

soil surface.

Salitorrerts, p. 310

FDB. Other Torrerts that have a gypsic horizon within 100 cm 

of the soil surface.

Gypsitorrerts, p. 310

FDC. Other Torrerts that have a calcic or petrocalcic horizon 

within 100 cm of the soil surface.

Calcitorrerts, p. 309

FDD. Other Torrerts.

Haplotorrerts, p. 310

Calcitorrerts

Key to Subgroups

FDCA. Calcitorrerts that have a petrocalcic horizon within 

100 cm of the soil surface.

Petrocalcic Calcitorrerts

FDCB. Other Calcitorrerts that have a densic, lithic, or 

paralithic contact or a duripan within 100 cm of the soil surface.

Leptic Calcitorrerts

FDCC. Other Calcitorrerts that have a layer, 25 cm or more 

thick within 100 cm of the soil surface, that contains less than 

27 percent clay in its fine-earth fraction.

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
310 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 a duripan within 100 cm of the soil 

surface.

Leptic Haplotorrerts

FDDD. Other Haplotorrerts that have a layer, 25 cm or more 

thick within 100 cm of the soil surface, that contains less than 

27 percent clay in its fine-earth fraction.

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 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, a duripan, or a petrocalcic horizon within 100 

cm of the soil surface.

Leptic Salitorrerts

FDAC. Other Salitorrerts that have a layer, 25 cm or more 

thick within 100 cm of the soil surface, that contains less than 

27 percent clay in its fine-earth fraction.

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:
Vertisols 311

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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. 311

FFB. Other Uderts.

Hapluderts, p. 311

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 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 within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

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 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 either or both:

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 within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

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

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:
312 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 

saturated paste).

Dystrusterts, p. 312

FEB. Other Usterts that have a salic horizon within 100 cm of 

the mineral soil surface.

Salusterts, p. 314

FEC. Other Usterts that have a gypsic horizon within 100 cm 

of the mineral soil surface.

Gypsiusterts, p. 313

FED. Other Usterts that have a calcic or petrocalcic horizon 

within 100 cm of the mineral soil surface.

Calciusterts, p. 312

FEE. Other Usterts.

Haplusterts, p. 313

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 

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 a duripan within 100 cm of the mineral soil 

surface.

Leptic Calciusterts

FEDH. Other Calciusterts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

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 to give a positive reaction 

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

irrigated.

Aquic Dystrusterts

FEAC. Other Dystrusterts that, if not irrigated during the 

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

through a thickness of 25 cm or more within 50 cm of the 

mineral soil surface, for 210 or more cumulative days per year.

Aridic Dystrusterts

FEAD. Other Dystrusterts that, if not irrigated during the 

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

through a thickness of 25 cm or more within 50 cm of the 

mineral soil surface, for less than 150 cumulative days.

Udic Dystrusterts
Vertisols 313

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FEAE. Other Dystrusterts that have a densic, lithic, or 

paralithic contact or a duripan within 100 cm of the mineral soil 

surface.

Leptic Dystrusterts

FEAF. Other Dystrusterts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

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, a duripan, or a petrocalcic horizon within 100 

cm of the mineral soil surface.

Leptic Gypsiusterts

FECG. Other Gypsiusterts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

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 

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 

within 150 cm of the mineral soil surface.

Petrocalcic Haplusterts

FEEE. Other Haplusterts that have a gypsic horizon within 

150 cm of the mineral soil surface.

Gypsic Haplusterts

FEEF. Other Haplusterts that have a calcic horizon within 150 

cm of the mineral soil surface.

Calcic Haplusterts
314 Keys to Soil Taxonomy

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 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.

Leptic Udic Haplusterts

FEEJ. Other Haplusterts that have both:

1. A layer, 25 cm or more thick within 100 cm of the 

mineral soil surface, that contains less than 27 percent clay in 

its fine-earth fraction; 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 a duripan within 100 cm of the mineral soil 

surface.

Leptic Haplusterts

FEEN. Other Haplusterts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

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

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 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, 
Vertisols 315

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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, a duripan, or a petrocalcic horizon within 100 cm of the 

mineral soil surface.

Leptic Salusterts

FEBF. Other Salusterts that have a layer, 25 cm or more thick 

within 100 cm of the mineral soil surface, that contains less than 

27 percent clay in its fine-earth fraction.

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 within 100 cm of the 

mineral soil surface.

Durixererts, p. 315

FCB. Other Xererts that have a calcic or petrocalcic horizon 

within 100 cm of the mineral soil surface.

Calcixererts, p. 315

FCC. Other Xererts.

Haploxererts, p. 316

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 

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 within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

Entic Calcixererts

FCBF. Other Calcixererts that have, in one or more horizons 

within 30 cm of the mineral soil surface, 50 percent or more 

colors as follows:

1. A color value, moist, of 4 or more; or

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

3. Chroma of 3 or more.

Chromic Calcixererts

FCBG. Other Calcixererts.

Typic Calcixererts

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 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, 
316

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 to give a positive reaction 

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

irrigated.

Aquic Haploxererts

FCCF. Other Haploxererts that, if not irrigated during the 

year, have cracks in normal years that remain 5 mm or more 

wide, through a thickness of 25 cm or more within 50 cm of the 

mineral soil surface, for less than 90 consecutive days.

Udic Haploxererts

FCCG. Other Haploxererts that have a densic, lithic, or 

paralithic contact within 100 cm of the mineral soil surface.

Leptic Haploxererts

FCCH. Other Haploxererts that have a layer, 25 cm or more 

thick within 100 cm of the mineral soil surface, that contains 

less than 27 percent clay in its fine-earth fraction.

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
317

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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 differentiae are used to 

form the family name. The class names are listed and defined in 

the same sequence (shown below) in which they appear in the 

family names.

Particle-size classes and their substitutes

Human-altered and human-transported material classes

Mineralogy classes

Cation-exchange activity classes

Calcareous and reaction classes

Soil temperature classes

Soil depth classes

Rupture-resistance classes

Classes of coatings on sands

Classes of permanent 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, 

cinders, rock fragments, or gypsum.

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 pedological classifications have set it at either 20, 50, or 

63 microns. The USDA and this taxonomy use a diameter of 

50 microns to set the limit between sand and silt. Engineering 

classifications have been based on grain-size percentages, 

by weight, in the soil fraction less than 75 mm (3 inches) in 

diameter, while texture 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 class 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 fraction if the texture class 

(fine-earth fraction) of a soil is fine sand, loamy fine sand, or 

coarser. It is treated as silt, however, if the texture class 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 10 

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 mm in diameter. Rock fragments are particles 2 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 mm or 

more in diameter that are in a rupture-resistance class that is 

less cemented than the strongly cemented class are referred to 

as pararock fragments. Pararock fragments, like rock fragments, 

include all particles between 2 mm and a horizontal dimension 

smaller than the size of a pedon. Most pararock fragments 

Family and Series Differentiae and Names

CHAPTER 17
318 Keys to Soil Taxonomy

are broken into particles less than 2 mm 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 assignment of particle-size classes. 

However, cinders, lapilli, pumice, and pumicelike fragments 

are treated as general fragments in the pumiceous and cindery 

substitute classes (defined below), regardless of their ruptureresistance class. Rock fragments and pararock fragments may 

be of either geologic or pedogenic origin. Artifacts (defined 

in chapter 3) are of human origin. Artifacts 2 mm or larger in 

diameter which are both cohesive and persistent* (e.g., brick) 

are treated as rock fragments for the assignment of particle-size 

classes.

Substitutes for particle-size classes are used for soils 

that have andic soil properties or a high content of volcanic 

glass, pumice, cinders, rock fragments, or gypsum. These 

materials cannot be readily dispersed and have variable results 

of dispersion. The substitute classes dominated by rock and 

pararock fragments have too little fine-earth material for valid 

data, and soil properties are dominated by the fragments. 

Consequently, normal particle-size classes do not adequately 

characterize these soils. Substitutes for particle-size class names 

are used for those parts of soils that have andic soil properties 

or a high content of volcanic glass, pumice, or cinders, as is the 

case with Andisols and many Andic and Vitrandic subgroups 

of other soil orders. The “gypseous” substitutes for particlesize class are used for mineral soils (e.g., Aridisols) that have 

a high content of gypsum. 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 nor a substitute for a particle-size 

class is used for Psamments, Psammaquents, Psammowassents, 

Psammoturbels, Psammorthels, and Psammentic subgroups that 

meet sandy particle-size class criteria. These taxa, by definition, 

meet sandy particle-size class criteria (i.e., have a texture class 

of sand or loamy sand), so the sandy particle-size class is 

considered redundant in the family name. The ashy substitute 

class, however, is used, if appropriate in these taxa (e.g., high 

content of volcanic glass).

Particle-size classes are applied, although with reservations, 

to the control sections of soils with 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 is used for 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 

a modifier 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 particlesize 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 and 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 control 

section for particle-size classes and their substitutes. 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 

* Artifact cohesion is the relative ability of an artifact to remain intact after significant 

disturbance and is based on whether the artifact can be easily broken into <2 mm diameter 

pieces either by hand or with a mortar and pestle. Cohesive artifacts cannot easily be 

broken. Artifact persistence is the relative ability of artifacts to withstand weathering and 

decay over time. Persistent artifacts remain intact for a decade or more. Part 618 of the 

National Soil Survey Handbook (available online) contains more information on the data 

elements used for describing artifacts.
Family and Series Differentiae and Names 319

F

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may coincide with the upper boundary of a root-limiting layer 

(defined below). 

Root-Limiting Layers

The concept of root-limiting layers as used in this taxonomy 

defines the base of the soil horizons considered for most (but 

not all) differentiae at the family level. The properties of soil 

materials above the base and within the control section are 

used for assignment of classes, such as particle-size classes and 

their substitutes. One notable exception to the concept of rootlimiting layers is in assignment of soil depth classes (defined 

below) to soils with fragipans. Unless otherwise indicated, the 

following are considered root-limiting layers in this chapter: 

a duripan; a fragipan; petrocalcic, petrogypsic, and placic 

horizons; continuous ortstein (i.e., 90 percent or more cemented 

and has lateral continuity); and densic, lithic, manufactured 

layer, paralithic, and petroferric contacts. 

Key to the Control Section for Particle-Size Classes and 

Their Substitutes in Mineral Soils

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 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.

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 items 1 through 4 below. For other soils, go to section 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 section 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 either in a Lamellic subgroup or that 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 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 soil 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 
320 Keys to Soil Taxonomy

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 

pumicelike† fragments and, in the fraction 2 mm or larger 

in diameter, 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 2 mm or larger in diameter, 

less than two-thirds (by volume) pumice and/or pumicelike 

fragments.

Cindery

or

3. Other 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 portion of 

the control section (if the control section is not in one of the 

strongly contrasting particle-size classes listed below), or in 

a portion of the control section that qualifies as a part 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 30 percent 

or more of the fine-earth fraction in the 0.02 to 2.0 mm 

fraction, and have a volcanic glass content (by grain 

count) of 30 percent or more in the 0.02 to 2.0 mm 

fraction; 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. They have a fine-earth fraction that has andic soil 

properties and that has a water content at 1500 kPa tension 

of less than 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. They 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

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

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

.
Family and Series Differentiae and Names 321

F

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c. Have less than 35 percent (by volume) rock 

fragments.

Hydrous

or

4. They have, in the fraction less than 20 mm in diameter, 

40 percent of more (by weight) gypsum and one of the 

following:

a. A total of 35 percent or more (by volume) rock 

fragments.

Gypseous-skeletal

or

b. Less than 35 percent (by volume) rock fragments and 

50 percent or more (by weight) particles with diameters of 

0.1 to 2.0 mm.

Coarse-gypseous

or

c. Less than 35 percent (by volume) rock fragments.

Fine-gypseous

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, then 

the percentage of clay is estimated by the following formula: 

Clay % = 2.5(% water retained at 1500 kPa tension - % organic 

carbon). See appendix for more information.

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 a total content of rock fragments, plus any 

artifacts 2 mm or larger in diameter which are both cohesive 

and persistent, of 35 percent or more (by volume) and a 

texture class of coarse sand, sand, fine sand, loamy coarse 

sand, loamy sand, or loamy fine sand in the fine-earth 

fraction.

Sandy-skeletal

or

2. Have a total content of rock fragments, plus any 

artifacts 2 mm or larger in diameter which are both cohesive 

and persistent, of 35 percent or more (by volume) and less 

than 35 percent (by weight) clay.

Loamy-skeletal

or

3. Have a total content of rock fragments, plus any artifacts 

2 mm or larger in diameter which are both cohesive and 

persistent, of 35 percent or more (by volume).

Clayey-skeletal

or

4. Have a texture class of coarse sand, sand, fine sand, 

loamy coarse sand, loamy sand, or loamy fine sand in the 

fine-earth fraction.

Sandy

or

5. Have a texture class 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 a part in a strongly 

contrasting particle-size class (listed below).

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 gravel and 

artifacts 2 to 75 mm in diameter which are both cohesive and 

persistent) 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 gravel and 

artifacts 2 to 75 mm in diameter which are both cohesive and 

persistent) and, in the fine-earth fraction, 18 to less than 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 gravel and 

artifacts 2 to 75 mm in diameter which are both cohesive and 

persistent) and, in the fine-earth fraction, less than 18 percent 

(by weight) clay.

Coarse-silty

or
322 Keys to Soil Taxonomy

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 gravel and 

artifacts 2 to 75 mm in diameter which are both cohesive and 

persistent) and, in the fine-earth fraction, 18 to less than 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 a part 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 (by weight) 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 particle-size or substitute classes listed below are 

considered strongly contrasting if both parts are 12.5 cm or 

more thick (including the thickness of these parts not entirely 

within 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 

name is used as the family class if part of the control section 

meets the criteria for either class. The following classes are 

listed alphabetically and are not presented in a key format.

1. Ashy over clayey

2. Ashy over clayey-skeletal

3. Ashy over loamy

4. Ashy over loamy-skeletal

5. 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 part and 15 percent or more for the 

medial part)

6. Ashy over medial-skeletal

7. Ashy over pumiceous or cindery

8. Ashy over sandy or sandy-skeletal

9. Ashy-skeletal over clayey

10. 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)

11. Ashy-skeletal over loamy-skeletal

12. Ashy-skeletal over sandy or sandy-skeletal

13. Cindery over loamy

14. Cindery over medial

15. Cindery over medial-skeletal

16. Clayey over coarse-gypseous

17. Clayey over fine-gypseous (if there is an absolute 

difference of 15 percent or more gypsum between the two 

parts of the control section)

18. Clayey over fragmental

19. Clayey over gypseous-skeletal

20. 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)

21. 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)

22. Clayey over sandy or sandy-skeletal

23. Clayey-skeletal over sandy or sandy-skeletal

24. Coarse-loamy over clayey

25. Coarse-loamy over fragmental

26. Coarse-loamy over sandy or sandy-skeletal (if the coarseloamy material contains less than 50 percent, by weight, 

fine sand or coarser sand)

27. Coarse-silty over clayey

28. Coarse-silty over sandy or sandy-skeletal

29. Fine-loamy 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)

30. Fine-loamy over fragmental

31. Fine-loamy over sandy or sandy-skeletal

32. Fine-silty over clayey (if there is an absolute difference 
Family and Series Differentiae and Names 323

F

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of 25 percent or more between clay percentages of 

the fine-earth fraction in the two parts of the control 

section)

33. Fine-silty over fragmental

34. Fine-silty over sandy or sandy-skeletal

35. Hydrous over clayey

36. Hydrous over clayey-skeletal

37. Hydrous over fragmental

38. Hydrous over loamy

39. Hydrous over loamy-skeletal

40. Hydrous over sandy or sandy-skeletal

41. Loamy over ashy or ashy-pumiceous

42. Loamy over coarse-gypseous (if there is an absolute 

difference of 15 percent or more gypsum between the two 

parts of the control section)

43. Loamy over fine-gypseous (if there is an absolute 

difference of 15 percent or more gypsum between the two 

parts of the control section)

44. Loamy over pumiceous or cindery

45. Loamy over sandy or sandy-skeletal (if the loamy material 

contains less than 50 percent, by weight, fine sand or 

coarser sand)

46. 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)

47. 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)

48. Loamy-skeletal over fragmental (if the volume of the fineearth fraction is 35 percent or more [absolute] greater in 

the loamy-skeletal part than in the fragmental part)

49. Loamy-skeletal over gypseous-skeletal (if there is an 

absolute difference of 15 percent or more gypsum between 

the two parts of the control section)

50. Loamy-skeletal over sandy or sandy-skeletal (if the loamy 

material contains less than 50 percent, by weight, fine 

sand or coarser sand)

51. 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 part and 10 percent or less for the 

ashy part)

52. Medial over ashy-pumiceous or ashy-skeletal (if the water 

content at 1500 kPa tension in dried samples of the fineearth fraction is 15 percent or more for the medial part and 

10 percent or less for the ashy part)

53. Medial over clayey

54. Medial over clayey-skeletal

55. Medial over fragmental

56. 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 part)

57. Medial over loamy

58. Medial over loamy-skeletal

59. Medial over pumiceous or cindery

60. Medial over sandy or sandy-skeletal

61. 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 in the fragmental 

or cindery part)

62. Medial-skeletal over loamy-skeletal

63. Medial-skeletal over sandy or sandy-skeletal

64. Pumiceous or ashy-pumiceous over loamy

65. Pumiceous or ashy-pumiceous over loamy-skeletal

66. Pumiceous or ashy-pumiceous over medial

67. Pumiceous or ashy-pumiceous over medial-skeletal

68. Pumiceous or ashy-pumiceous over sandy or sandyskeletal

69. Sandy over clayey

70. Sandy over loamy (if the loamy material contains less than 

50 percent, by weight, fine sand or coarser sand)

71. Sandy-skeletal over loamy (if the loamy material contains 

less than 50 percent, by weight, fine sand or coarser sand)

Human-Altered and Human-Transported 

 Material Classes

Human-altered and human-transported material classes are 

intended to provide useful information on the behavior and 

interpretations for use of soils which formed in human-altered 

or human-transported material (defined in chapter 3).

Use of Human-Altered and Human-Transported Material 

 Classes

Human-altered and human-transported material classes are 

only used in taxa of mineral soils where one of the following 

occurs: (1) human-altered or human-transported material 

extends from the soil surface to a depth of 50 cm or to a 
324 Keys to Soil Taxonomy

root-limiting layer, whichever is shallower; or (2) the soil 

classifies in an Anthraltic, Anthraquic, Anthrodensic, Anthropic, 

Anthroportic, Haploplaggic, or Plaggic extragrade subgroup 

(defined in chapter 3). In other taxa, the class is omitted from 

the family name and the parent material is identified at the soil 

series level.

Examples of soils that use human-altered and humantransported material classes and formed in human-transported 

material are a fine, methanogenic, mixed, active, nonacid, 

thermic Anthrodensic Ustorthent, which was compacted during 

construction of a sanitary landfill, and a fine-loamy, spolic, 

mixed, active, calcareous, mesic Anthroportic Udorthent, which 

resulted from reclamation of a surface coal mine. An example 

of a soil using a human-altered and human-transported material 

class, which formed in human-altered material as a result of 

mechanical displacement of a preexisting natric horizon, is 

a fine, araric, smectitic, calcareous, thermic Anthraltic Sodic 

Xerorthent.

Key to the Control Section for Human-Altered and HumanTransported Material Classes

The control section for the human-altered and humantransported material classes is from the soil surface to one of the 

following depths, whichever is shallower:

A. 200 cm; or

B. The lower boundary of the deepest horizon formed in 

human-altered or human-transported material; or

C. A lithic or paralithic contact.

Key to Human-Altered and Human-Transported Material 

 Classes

The following key to human-altered and human-transported 

material classes is designed to make important distinctions in 

the order of most importance to human health and safety.

A. Mineral soils that have, in some part of the human-altered 

and human-transported material control section, one of the 

following:

1. The detectible evolution (>1.6 ppb) of methanethiol (i.e., 

methyl mercaptan) odor from the decomposition of nonpersistent artifacts (e.g., garbage, wood-mill pulp, sewage treatment plant by-products) or evidence of the collection and/or 

burning of methane gas.

Methanogenic

or

2. A horizon or layer 7.5 cm or more thick, with more than 

35 percent (by volume) artifacts of asphalt (bitumen) that are 

2 mm in diameter or larger.

Asphaltic

or

3. A horizon or layer 7.5 cm or more thick, with more than 

35 percent (by volume) artifacts of concrete that are 2 mm in 

diameter or larger.

Concretic

or

4. A horizon or layer 7.5 cm or more thick, with more than 

40 percent (by weight) artifacts of synthetic gypsum products 

such as flue gas desulfurization gypsum, phosphogypsum, 

or fluorogypsum (e.g., drywall or plaster) in the fine-earth 

fraction.

Gypsifactic

or

5. A horizon or layer 7.5 cm or more thick, with more than 

35 percent (by volume) artifacts of coal combustion by-products (e.g., bottom ash or coal slag) that are 2 mm in diameter 

or larger.

Combustic

or

6. A horizon or layer 7.5 cm or more thick, with more than 

15 percent (by grain count in the 0.02 to 0.25 mm fraction) 

artifacts of light-weight, coal combustion by-products (e.g., 

fly ash scrubbed from emission stacks).

Ashifactic

or

7. A horizon or layer 7.5 cm or more thick, with more than 

5 percent (by grain count in the 0.02 to 0.25 mm fraction) 

artifacts of pyrolysis (e.g., fuel coke or biochar).

Pyrocarbonic

or

8. A horizon or layer 50 cm or more thick, with 35 percent 

or more (by volume) artifacts which are both cohesive and 

persistent and are 2 mm in diameter or larger.

Artifactic

or

9. A horizon or layer 50 cm or more thick, with 15 percent 

or more (by volume) artifacts which are both cohesive and 

persistent and are 2 mm in diameter or larger.

Pauciartifactic

or

10. A horizon or layer 50 cm or more thick, with finely 

stratified (5 cm or less thick) human-transported material 

that was water-deposited (e.g., sediment from dredging or 

irrigation).

Dredgic

or
Family and Series Differentiae and Names 325

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11. A horizon or layer 50 cm or more thick of humantransported material.

Spolic

or

12. A horizon or layer 7.5 cm or more thick, with 3 percent 

or more (by volume) mechanically detached and re-oriented 

pieces of diagnostic horizons or characteristics.

Araric

or

B. All other soils: No human-altered or human-transported 

material classes are used.

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. A mineralogy class is assigned to all 

mineral soils, except for Quartzipsamments.

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, 

mineralogy classes are used for both of the named parts of 

particle-size classes or substitute classes, unless they are the 

same. The same mineralogy class name cannot be used for 

both parts of the control section (e.g., “mixed over mixed”). 

Examples of soils that require assignment of two different 

mineralogy classes are a clayey over sandy or sandy-skeletal, 

smectitic over mixed, thermic Vertic Haplustept and an ashyskeletal over loamy-skeletal, glassy over mixed (if the ashyskeletal part has 30 percent or more volcanic glass), superactive 

Vitrandic Argicryoll. Examples of soils that are not assigned 

two mineralogy classes are an ashy over clayey, mixed (if both 

the ashy part with andic soil properties and the clayey part 

without andic soil properties are mixed), superactive, mesic 

Typic Vitraquand and a fine-loamy over sandy or sandy-skeletal, 

mixed (if both the fine-loamy and sandy or sandy-skeletal parts 

are mixed), active, frigid Pachic Argiudoll.

A. Oxisols and “kandi” and “kanhap” great groups of Alfisols 

and Ultisols that in the mineralogy control section have:

1. More than 40 percent (by weight) iron oxide as Fe2O3

(more than 28 percent Fe), extractable by dithionite-citrate, 

in the fine-earth fraction.

Ferritic

or

2. More than 40 percent (by weight) gibbsite in the fineearth fraction.

Gibbsitic

or

3. Both:

a. 18 to 40 percent (by weight) iron oxide as Fe2O3 (12.6 

to 28 percent Fe), extractable by dithionite-citrate, in the 

fine-earth fraction; and

b. 18 to 40 percent (by weight) gibbsite in the fine-earth 

fraction.

Sesquic

or

4. 18 to 40 percent (by weight) iron oxide as Fe2O3 (12.6 to 

28 percent Fe), extractable by dithionite-citrate, in the fineearth fraction.

Ferruginous

or

5. 18 to 40 percent (by weight) gibbsite in the fine-earth 

fraction.

Allitic

or

6. More than 50 percent (by weight) kaolinite plus 

halloysite, dickite, nacrite, and other 1:1 or nonexpanding 

2:1 layer minerals and gibbsite and less than 10 percent (by 

weight) smectite minerals (montmorillonite, beidellite, and 

nontronite) in the fraction less than 0.002 mm in diameter, 

and more kaolinite than halloysite.

Kaolinitic

or

7. More than 50 percent (by weight) halloysite plus 

kaolinite and allophane and less than 10 percent (by 

weight) smectite minerals (montmorillonite, beidellite, and 

nontronite) in the fraction less than 0.002 mm in diameter.

Halloysitic

or
326 Keys to Soil Taxonomy

8. All other soils in section A.

Mixed

or

B. Other soils with horizons in the mineralogy control section 

that have a substitute class that replaces the particle-size class, 

other than fragmental, and that have:

1. 40 percent or more (by weight) gypsum either in the 

fine-earth fraction or in the fraction less than 20 mm in 

diameter, whichever has a higher percentage of gypsum.

Hypergypsic

or

2. Both:

a. A sum of 8 times the Si (percent by weight extracted 

by ammonium oxalate from the fine-earth fraction) plus 

2 times the Fe (percent by weight extracted by 

ammonium oxalate from the fine-earth fraction) of 5 or 

more; and

b. The product of 8 times the Si is more than the product 

of 2 times the Fe.

Amorphic

or

3. A sum of 8 times the Si (percent by weight extracted by 

ammonium oxalate from the fine-earth fraction) plus 2 times 

the Fe (percent by weight extracted by ammonium oxalate 

from the fine-earth fraction) of 5 or more.

Ferrihydritic

or

4. 30 percent or more (by grain count) volcanic glass in the 

0.02 to 2.0 mm fraction.

Glassy

or

5. All other soils in section B.

Mixed

or

C. Other mineral soils and soils in Terric subgroups of 

Histosols and Histels that have horizons or layers in the 

mineralogy control section composed of mineral soil material 

that has:

1. Any particle-size class and 15 percent or more (by 

weight) anhydrite, either in the fine-earth fraction or in the 

fraction less than 20 mm in diameter, whichever has a higher 

percentage of anhydrite.

Anhydritic

or

2. Any particle-size class and 15 percent or more (by 

weight) gypsum, either in the fine-earth fraction or in the 

fraction less than 20 mm in diameter, whichever has a higher 

percentage of gypsum.

Gypsic

or

3. 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 diameter, whichever has a higher percentage of 

carbonates plus gypsum.

Carbonatic

or

4. Any particle-size class, except for fragmental, and more 

than 40 percent (by weight) iron oxide as Fe2O3 (more than 

28 percent Fe) extractable by dithionite-citrate, in the fineearth fraction.

Ferritic

or

5. Any particle-size class, except for fragmental, and more 

than 40 percent (by weight) gibbsite and boehmite in the 

fine-earth fraction.

Gibbsitic

or

6. 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 Mg-rich 

amphiboles, in the fine-earth fraction.

Magnesic

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 soils and soils in Terric subgroups of 

Histosols and Histels that have a clayey, clayey-skeletal, fine, 

or very-fine particle-size class and have horizons or layers 

composed of mineral soil material that:

1. In the fine-earth fraction, have a total percent (by 

weight) iron oxide as Fe2O3 (percent Fe extractable by 

dithionite-citrate times 1.43) plus the percent (by weight) 

gibbsite of more than 10.

Parasesquic

or

2. In the fraction less than 0.002 mm in diameter:
Family and Series Differentiae and Names 327

F

A

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a. Have more than 50 percent (by weight) halloysite 

plus kaolinite and allophane and more halloysite than any 

other single kind of clay mineral.

Halloysitic

or

b. Have more than 50 percent (by weight) kaolinite plus 

halloysite, dickite, nacrite, and other 1:1 or nonexpanding 

2:1 layer minerals and gibbsite and less than 10 percent 

(by weight) smectite minerals (montmorillonite, 

beidellite, and nontronite).

Kaolinitic

or

c. Have more smectite minerals (montmorillonite, 

beidellite, and nontronite), by weight, than any other 

single kind of clay mineral.

Smectitic

or

d. Have more than 50 percent (by weight) illite (hydrous 

mica) and commonly more than 4 percent K2O.

Illitic

or

e. Have more vermiculite than any other single kind of 

clay mineral.

Vermiculitic

or

f. In more than one-half of the thickness, have all of the 

following:

(1) No free carbonates; and

(2) A sodium fluoride pH (NaF pH) of 8.4 or more; 

and

(3) A ratio of 1500 kPa water to measured clay of 0.6 

or more.

Isotic

or

g. All other soils in section D.

Mixed

or

E. All other soils (except for Quartzipsamments) that 

have horizons or layers composed of mineral soil material that 

has:

1. More than 45 percent (by grain count) mica and stable 

mica pseudomorphs in the 0.02 to 0.25 mm fraction.

Micaceous

or

2. A total percent (by weight) iron oxide as Fe2O3 (percent 

Fe extractable by dithionite-citrate times 1.43) plus the 

percent (by weight) gibbsite of more than 10 in the fine-earth 

fraction.

Parasesquic

or

3. In more than one-half of the thickness, all of the 

following:

a. No free carbonates; and

b. A sodium fluoride pH (NaF pH) of 8.4 or more; 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 or grain count) silica 

minerals (quartz, chalcedony, or opal) and other resistant 

minerals in the 0.02 to 2.0 mm fraction.

Siliceous

or

5. All other soil properties.

Mixed

Cation-Exchange Activity Classes

The cation-exchange activity classes help in making 

interpretations about the nutrient-holding capacity of soils 

and their suites of colloids. The cation-exchange capacity 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, calculated by weighted 

average in the control section. In the following classes “clay” 

excludes clay-size carbonates. Percent carbonate clay must be 

subtracted from percent total clay before calculating the CEC 

to clay ratio. 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 

in a part of contrasting families), then the percentage of clay 

is estimated by the following formula: Clay % = 2.5(% water 

retained at 1500 kPa tension - % organic carbon). See appendix 

for more information.

Use of the Cation-Exchange Activity Classes

The cation-exchange activity classes are used for soils 

classified in the mixed or 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 nor to Oxisols or “kandi” and “kanhap” 
328 Keys to Soil Taxonomy

great groups and subgroups of Alfisols and Ultisols because 

assigning classes to organic soils or taxa defined by low-activity 

clay would be misleading or redundant information. Cationexchange activity classes are not assigned to Psamments, 

“psamm” great groups of Entisols and Gelisols, Psammentic 

subgroups, or other soils with sandy or sandy-skeletal particlesize classes or the fragmental substitute class because the low 

clay content causes cation-exchange activity classes to be less 

useful and less reliable. Soils with other substitutes for particlesize class (e.g., ashy) or with mineralogy classes such as 

smectitic also are not assigned cation-exchange activity classes, 

since such soils have a high cation-exchange capacity (CEC) 

and/or the clay mineralogy dictates soil properties.

For soils with strongly contrasting particle-size classes, 

where both named parts of the control section use a cationexchange activity class, the class associated with the particlesize class that has the most clay is named. For example, in a 

pedon with a classification of fine-loamy over clayey, mixed, 

active, calcareous, thermic Typic Udorthent, the cationexchange activity class “active” is associated with the clayey, 

lower part of the control section. For other soils with strongly 

contrasting particle-size classes, where one named part of the 

control section uses a cation-exchange activity class and one 

named part does not, the class is associated with the part which 

requires usage. For example, in a pedon with a classification of 

coarse-loamy over sandy or sandy-skeletal, mixed, superactive, 

calcareous, mesic Oxyaquic Ustifluvent, the cation-exchange 

activity class “superactive” is associated with the coarse-loamy, 

upper part of the control section.

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.

Key to Cation-Exchange Activity Classes

A. Soils that are not Histosols, Histels, Oxisols, or 

Psamments, that are not in “psamm” great groups of Entisols 

or Gelisols, that are not in Psammentic subgroups, that are not 

in “kandi” or “kanhap” great groups or subgroups of Alfisols or 

Ultisols, that do not have a sandy or sandy-skeletal particle-size 

class or any substitute for a particle-size class throughout the 

entire control section, and that have:

1. A mixed or siliceous mineralogy class; and

2. A ratio of cation-exchange capacity (by 1N NH4OAc 

pH 7) to percent clay (by weight) of:

a. 0.60 or more.

Superactive

or

b. 0.40 to 0.60.

Active

or

c. 0.24 to 0.40.

Semiactive

or

d. Less than 0.24.

Subactive

or

B. All other soils: No cation-exchange activity classes are 

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 below, 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 taxon.

Use of the Calcareous Class

The calcareous class is used in the names of the families of 

Entisols, Gelisols, Aquands, Aquepts, Aquolls, and all Gelic 

suborders and Gelic great groups, but it is not used for any of 

the following:

1. Calciaquolls, Natraquolls, and Argiaquolls

2. Cryaquolls and Duraquolls that have an argillic or natric 

horizon

3. Duraquands and Placaquands

4. Sulfaquepts, Fragiaquepts, and Petraquepts

5. The Psamments, Psammaquents, Psammowassents, 

Psammoturbels, Psammorthels, and Psammentic subgroups that 

have no particle-size class

6. Sandy, sandy-skeletal, cindery, pumiceous, or fragmental 

families

7. Families with anhydritic, carbonatic, gypsic, or hypergypsic 

mineralogy

8. Histels

Use of the Acid and Nonacid Reaction Classes

The acid and nonacid classes are used in the names of the 

families of Entisols, Gelisols, Aquands, Aquepts, and all Gelic 

suborders and Gelic great groups, but they are not used for any 

of the following:

1. Duraquands and Placaquands

2. Sulfaquepts, Fragiaquepts, and Petraquepts

3. The Psamments, Psammaquents, Psammowassents, 

Psammoturbels, Psammorthels, and Psammentic subgroups that 

have no particle-size class
Family and Series Differentiae and Names 329

F

A

M

4. Sandy, sandy-skeletal, cindery, pumiceous, or fragmental 

families

5. Families with anhydritic, carbonatic, gypsic, or hypergypsic 

mineralogy

6. Histels

Use of the Allic Class

The allic class is used only in the families of Oxisols.

Control Section for Calcareous and Reaction Classes

The control section for the calcareous class is one of the 

following:

1. All Gelisols (except for Histels) and all Gelic suborders 

and Gelic great groups: The layer from the mineral soil surface 

to a depth of 25 cm or to a root-limiting layer, whichever is 

shallower.

2. 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.

3. 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.

4. All other listed soils: Between a depth of 25 and 50 cm 

below the mineral soil surface.

The control section for the acid and nonacid classes is one of 

the following:

1. All Gelisols (except for Histels) and all Gelic suborders 

and Gelic great groups: The layer from the mineral soil surface 

to a depth of 25 cm or to a root-limiting layer, whichever is 

shallower.

2. All other listed soils: The same control section depths as 

those for particle-size classes.

The control section for the allic class 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 is either at a depth 

of 50 cm below the soil surface or at the upper boundary of a 

root-limiting layer, whichever is shallower. The soil temperature 

classes, defined in terms of the mean annual soil temperature 

and the difference between mean summer and mean winter 

temperatures, are determined by the following key.

Key to Soil Temperature Classes

A. Gelisols and Gelic suborders and great groups that have a 

mean annual soil temperature as follows:

1. -10 oC or lower.

Hypergelic

or

2. -4 o

C 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
330 Keys to Soil Taxonomy

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 of mineral soils 

and Histels that have a root-limiting layer at a specified 

depth from the mineral soil surface, except for those families 

in Lithic subgroups (defined below) and those with a fragipan. 

The root-limiting layers included in soil depth classes are 

duripans; petrocalcic, petrogypsic, and placic horizons; 

continuous ortstein (i.e., is 90 percent or more cemented and 

has lateral continuity); and densic, lithic, manufactured 

layer, paralithic, and petroferric contacts. Soil depth classes 

for Histosols are given later in this chapter. One soil depth 

class name, “shallow,” is used to characterize certain soil 

families that have one of the depths indicated in the following 

key. 

Key to Soil Depth Classes for Mineral Soils and Histels

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. Other mineral soils and Folistels 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. Other Histels that are less than 50 cm deep to a rootlimiting layer.

Shallow

or

D. All other Histels and 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.

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 plus 2 times the weighted average clay 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 on Sands

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 on Sands

A. Quartzipsamments that have a sum of the weighted average 

silt (by weight) plus 2 times the weighted average clay (by 

weight) of more than 5.

Coated

or
Family and Series Differentiae and Names 331

F

A

M

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 

depending on the season. 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 Organic Soils

Most of the differentiae that are used to distinguish families 

of organic soils (Histosols and Histels) have already been 

defined, either because they are used as differentiae in mineral 

soils as well as organic soils or because their definitions are 

used for the classification of some Histosols and Histels in 

categories above 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 class names, if appropriate for a 

particular soil, are placed in the 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 six classes defined below are more generalized than 

those used for mineral soils.

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 Organic Soils

A. Terric subgroups of Histosols and Histels that 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 class of coarse sand, sand, fine sand, loamy 

coarse sand, loamy sand, or loamy fine sand in the fine-earth 

fraction.

Sandy or sandy-skeletal

or

3. Less than 35 percent (by weight) clay in the fine-earth 

fraction and a total content of rock fragments plus any 

artifacts 2 mm or larger in diameter which are both cohesive 

and persistent of 35 percent or more (by volume).

Loamy-skeletal

or

4. A total content of rock fragments plus any artifacts 2 mm 

or larger in diameter which are both cohesive and persistent 

of 35 percent or more (by volume).

Clayey-skeletal

or

5. A clay content of 35 percent or more (by weight) in the 

fine-earth fraction.

Clayey

or
332 Keys to Soil Taxonomy

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 Soil Material and 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); and

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) extractable by dithionite-citrate 

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 Folists, 

Sphagnofibrists, or 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 

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
Family and Series Differentiae and Names 333

F

A

M

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 

or to a pumiceous, cindery, or fragmental substitute class. The 

root-limiting layers included in soil depth classes of Histosols 

are duripans; petrocalcic, petrogypsic, and placic horizons; 

continuous ortstein (i.e., is 90 percent or more cemented and 

has lateral continuity); and densic, lithic, manufactured layer, 

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 for Histosols

A. Histosols that are less than 18 cm deep to a root-limiting 

layer or to a pumiceous, cindery, or fragmental substitute class. 

Micro

or

B. Other Histosols, excluding Folists, that have a root-limiting 

layer or a pumiceous, cindery, or fragmental 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 certain diagnostic subsurface 

horizons, such as a duripan, fragipan, or petrocalcic horizon, 

because these horizons have few roots. The thickness of such 

root-limiting horizons is taken into account in differentiating 

concepts of competing soil series, when they occur within 

the series control section. In contrast, the thickness of such 

horizons is not used in the control sections for the family. The 

series control section includes materials starting at the soil 

surface and extends into the first 25 cm of densic materials, 

a manufactured layer, or paralithic materials, if the densic, 

manufactured layer, or paralithic contacts, respectively, are less 

than 125 cm below the mineral soil surface. In contrast, the 

properties of materials below any densic, lithic, manufactured 

layer, paralithic, or petroferric contact are not used for 

classification in the categories above the series (i.e., order 

through family). The properties of horizons and layers below 

the particle-size control section, a depth between 100 and 150 

cm (or to 200 cm if in a diagnostic horizon) from the mineral 

soil surface, also are considered in the series category of this 

taxonomy.

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, manufactured layer, 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, manufactured 

layer, or paralithic contact or 150 cm below the soil surface, 
334

whichever is shallower, if there is a densic, manufactured 

layer, or paralithic contact within 150 cm; or

3. A depth of 150 cm if the base 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, manufactured layer, 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.
335

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, L, A, E, B, C, R, M, 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: Horizons or layers dominated by 

organic soil materials. Some are saturated with water for long 

periods or were once saturated but are now artificially drained; 

others have never been saturated.

Some O horizons or layers consist of slightly decomposed to 

highly decomposed litter, such as leaves, needles, twigs, moss, 

and lichens, that has been deposited on the surface of either 

mineral or organic soils. Other O horizons or layers consist of 

organic materials that were deposited under saturated conditions 

and have 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 horizon or layer may be at the surface of a mineral 

soil, or it may be at any depth below the surface if it is buried. A 

horizon formed by 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. Horizons or layers composed of limnic materials are not 

designated as O horizons.

L horizons or layers: Limnic horizons or layers include 

both organic and mineral limnic materials that were either (1) 

deposited in water by precipitation or through the actions of 

aquatic organisms, such as algae and diatoms, or (2) derived 

from underwater and floating aquatic plants and subsequently 

modified by aquatic animals. 

L horizons or layers include coprogenous earth (sedimentary 

peat), diatomaceous earth, and marl. They are used only 

in Histosols. They have only the following subordinate 

distinctions: co, di, or ma. They do not have the subordinate 

distinctions of the other master horizons and layers.

A horizons: Mineral horizons that have formed at the soil 

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

or much of any original rock structure*

 and show one or more 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); 

2. Properties resulting from cultivation, pasturing, or 

similar kinds of disturbance; or

3. A morphology that is distinct from the underlying E, B, 

or C horizon, resulting from processes related to the surface.

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 regions with 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 horizon, although the 

mineral fraction is unaltered or only slightly altered by the 

weathering of minerals considered to be weatherable (defined in 

chapter 3). Such a horizon is designated as an A horizon because 

it is at the soil surface. Recent alluvial or eolian deposits that 

retain most of the original rock structure are not considered to 

have A horizons unless they are cultivated.

E horizons: Mineral horizons in which the main feature 

is the eluvial 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 

* Rock structure includes fine stratification (5 mm or less thick) 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.

Designations for Horizons and Layers

CHAPTER 18
336 Keys to Soil Taxonomy

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 soil surface, below an O 

or A horizon and above a B horizon. However, the symbol E 

can be used for eluvial horizons that are at the soil surface, that 

are within or between parts of the B horizon, or that extend to 

depths greater than those of normal observation, if the horizons 

have resulted from pedogenic processes.

B horizons: Mineral horizons that have formed below an A, 

E, or O horizon. They exhibit obliteration of all or much of the 

original rock structure and show one or more of the following 

as evidence of pedogenesis:

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

humus, sesquioxides, carbonates, anhydrite, gypsum, salts 

more soluble than gypsum, or silica, alone or in combination;

2. Evidence of the removal, addition, or transformation of 

carbonates, anhydrite, and/or gypsum;

3. Residual concentration of oxides, sesquioxides, and 

silicate clay, alone or in combination;

4. Coatings of sesquioxides that make the horizon color 

conspicuously lower in value, higher in chroma, or redder 

in hue, than overlying and underlying horizons, without 

apparent illuviation of iron; 

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

both, and that forms pedogenic structure if volume changes 

accompany changes in moisture content; 

6. Brittleness; or

7. Strong gleying when accompanied by other evidence of 

pedogenic change.

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

originally, subsurface horizons. Examples of B horizons are 

horizons (which may or may not be cemented) with illuvial 

concentrations of carbonates, gypsum, anhydrite, or silica that 

are the result of pedogenic processes and are contiguous to other 

genetic horizons and brittle horizons 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 strong gleying but no 

other pedogenic changes.

C horizons or layers: Mineral horizons or layers, excluding 

strongly cemented and harder bedrock, that are little affected 

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

L horizons. The material of C horizons or 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 (typically designated Cr) 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. However, if a cemented layer 

formed through pedogenic processes, versus geologic processes 

(e.g., lithification), it is considered a B horizon.

R layers: Strongly cemented to indurated bedrock.

Granite, basalt, quartzite, limestone, and sandstone are 

examples of bedrock that commonly are cemented enough to be 

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 fractures, but 

these are generally too few or too widely spaced to allow root 

penetration. The fractures may be coated or filled with clay or 

other material.

M layers: Root-limiting layers beneath the soil surface 

consisting of nearly continuous, horizontally oriented, humanmanufactured materials.

Examples of materials designated by the letter M include 

geotextile liners, asphalt, concrete, rubber, and plastic, if they 

are present as continuous, horizontal layers.

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 capitalletter 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 
Designations for Horizons and Layers 337

H

O

R

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, Lamellic 

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 are described 

separately. One horizon then has several lamellae and eluvial 

layers and can be designated as 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 

subordinate distinctions within master horizons and layers. The 

term “accumulation” is used in many of the definitions of such 

suffixes to indicate that these horizons must contain more of the 

material in question than is presumed to have been present in 

the parent material. The use of a suffix symbol is not restricted 

only to those horizons that meet certain criteria for diagnostic 

horizons and other criteria as defined in Soil Taxonomy. If 

there is any evidence of accumulation, the appropriate suffix 

(or suffixes) should be assigned. The suffix symbols and their 

meanings are as follows:

a Highly decomposed organic material

This symbol is used with O horizons 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 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 

horizon. This symbol is not used to separate horizons 

composed of organic soil material, that are forming at 

the soil surface, from underlying horizons composed of 

mineral soil material. It may be used for organic soils, but 

only if they are buried by mineral soil materials.

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, gypsum, anhydrite, or soluble salts.

co Coprogenous earth

This symbol, used only with L horizons, indicates a 

limnic layer of coprogenous earth (sedimentary peat).

d Physical root restriction

This symbol indicates noncemented, root-restricting 

layers in naturally occurring or human-made sediments 

or materials. Examples of natural layers are dense till and 

some noncemented shales and siltstones. Examples of 

human-made dense layers are plowpans and mechanically 

compacted zones in human-transported material.

di Diatomaceous earth

This symbol, used only with L horizons, indicates a 

limnic layer of diatomaceous earth.

e Organic material of intermediate decomposition

This symbol is used with O horizons to indicate 

organic materials of intermediate decomposition. The 

fiber content of these materials is 17 to less than 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 
338 Keys to Soil Taxonomy

that have no history of wetness, such as some shales 

or E horizons. If the symbol is used with B horizons, 

pedogenic change (e.g., soil structure) 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 horizons to indicate 

the accumulation of illuvial, amorphous, dispersible 

complexes of organic matter and sesquioxides. The 

sesquioxide component is dominated by aluminum and 

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 (e.g., Bhs) if the amount of the 

sesquioxide component is significant but the value and 

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

i Slightly decomposed organic material

This symbol is used with O horizons 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 (ferric) iron hydroxy sulfate 

mineral, KFe3(SO4)2(OH)6, 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 chroma as 

low as 3 or 4 has been reported. It forms in preference to 

iron (hydr)oxides in active acid sulfate soils at pH of 3.5 

or less and can be stable in post-active acid sulfate soils 

for long periods of time at higher pH.

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 secondary carbonates

This symbol indicates an accumulation of visible 

pedogenic calcium carbonate (less than 50 percent, by 

volume). Carbonate accumulations occur as carbonate 

filaments, coatings, masses, nodules, disseminated 

carbonate, or other forms. 

kk Engulfment of horizon by secondary carbonates

This symbol indicates major accumulations of 

pedogenic calcium carbonate. The suffix kk is used when 

the soil fabric is plugged with fine grained pedogenic 

carbonate (50 percent or more, by volume) that occurs as 

an essentially continuous medium. The suffix corresponds 

to stage III of the carbonate morphogenetic stages (Gile et 

al., 1966) or a higher stage.

m Pedogenic cementation

This symbol indicates continuous or nearly continuous 

pedogenic cementation. It is used only for horizons that 

are 90 percent or more cemented, although they may 

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

dominant ones) may be indicated by adding defined letter 

suffixes, singly or in pairs. The horizon suffix kkm (and 

less commonly km) indicates cementation by carbonates; 

qm, cementation by silica; sm, cementation by iron; yym, 

cementation by gypsum; kqm, cementation by carbonates 

and silica; and zm, cementation by salts more soluble than 

gypsum. The symbol m is not used for permanently frozen 

layers impregnated by ice.

ma Marl

This symbol, used only with L horizons, indicates a 

limnic layer of marl.

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 a horizon 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 layers of 

bedrock that are 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 horizons to indicate 

an accumulation of illuvial, amorphous, dispersible 
Designations for Horizons and Layers 339

H

O

R

complexes of organic matter and sesquioxides if both the 

organic matter and sesquioxide components are significant 

and if either the value or chroma, moist, of the horizon is 

4 or more. The symbol is also used in combination with 

h (e.g., Bhs) if both the organic matter and sesquioxide 

components are significant and if the value and chroma, 

moist, are 3 or less.

se Presence of sulfides

This symbol indicates the presence of sulfides in 

mineral or organic horizons. Horizons with sulfides 

typically have dark colors (e.g., value ≤ 4, chroma ≤ 2). 

These horizons typically form in soils associated with 

coastal environments that are permanently saturated 

or submerged (i.e., tidal marshes or estuaries). Soil 

materials which have sulfidization actively occurring 

emanate hydrogen sulfide gas, which is detectable by its 

odor (Fanning and Fanning, 1989; Fanning et al., 2002). 

Sulfides may also occur in upland environments that 

have a source of sulfur. Soils in such environments are 

often of geologic origin and may not produce a hydrogen 

sulfide odor. Examples include soils formed in parent 

materials derived from coal deposits, such as lignite, or 

soils formed in coastal plain deposits, such as glauconite, 

that have not been oxidized because of thick layers of 

overburden.

ss Presence of slickensides

This symbol indicates the presence of pedogenic 

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.

u Presence of human-manufactured materials (artifacts)

This symbol indicates the presence of objects 

or materials that have been created or modified by 

humans, usually for a practical purpose in habitation, 

manufacturing, excavation, or construction activities. 

Examples of artifacts are bitumen (asphalt), boiler 

slag, bottom ash, brick, cardboard, carpet, cloth, coal 

combustion by-products, concrete (detached pieces), 

debitage (i.e., stone tool flakes), fly ash, glass, metal, 

paper, plasterboard, plastic, potsherd, rubber, treated 

wood, and untreated wood products.

v Plinthite

This symbol indicates the presence of iron-rich, 

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

when moist and is less than strongly cemented. The 

material hardens irreversibly when exposed to the 

atmosphere and to repeated wetting and drying.

w Development of color or structure

This symbol is used only with B horizons 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. 

The suffix y is used when the horizon fabric is dominated 

by soil particles or minerals other than gypsum. Gypsum 

is present in amounts that do not significantly obscure or 

disrupt other features of the horizon. In unique but rare 

soils, this symbol may be used to connote the presence of 

anhydrite.

yy Dominance of horizon by gypsum

This symbol indicates a horizon that is dominated 

by the presence of gypsum. The gypsum content may 

be due to an accumulation of secondary gypsum, the 

transformation of primary gypsum inherited from parent 

material, or other processes. The suffix yy is used when 

the horizon fabric has such an abundance of gypsum 

(generally 50 percent or more, by volume) that pedogenic 

and/or lithologic features are obscured or disrupted 

by growth of gypsum crystals. Colors associated with 

horizons that have suffix yy typically are highly whitened 

(e.g., value of 7 through 9.5 and chroma of 4 or less). In 

unique but rare soils, this symbol may be used to connote 

the presence of anhydrite.

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 directly follow the capital letter of the 

master horizon or layer, or the prime symbol, if used.
340 Keys to Soil Taxonomy

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 horizon or Crt† layer designations, none of these letters 

are used in combination for a single horizon.

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

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

g, m, v, and x. Examples are Bjc and Bkkm. If any of these 

suffixes are used together in the same horizon, symbols 

c and g are written last (e.g., Btvg), with one exception. 

For horizons using symbol f together with any of the other 

symbols in this rule, symbol f (frozen soil or water) is written 

last, e.g., Cdgf.

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

e.g., Oab. 

6. Suffix symbols h, s, and w are not used with g, k, kk, n, 

o, q, y, yy, or z.

7. If the above rules do not apply to certain suffixes, such 

as k, kk, q, y, or yy, the suffixes may be listed together 

in order of assumed dominance or listed alphabetically if 

dominance is not a concern.

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 (suffix symbol t has precedence 

over symbols 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, kk, n, q, y, 

yy, z, or o. If illuvial clay also is present, t precedes the other 

symbol, e.g., Bto.

Vertical Subdivision

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

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

numbers are added to the letters of the horizon designation. 

These numbers follow all the letters. Within a sequence of C 

horizons, for example, successive horizons may be designated 

C1, C2, C3, etc. If the lower horizons are strongly gleyed 

and the upper horizons are not strongly gleyed, they 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, 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 consecutive horizons 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 numbers that follow the respective horizon 

designations. For example, four subdivisions 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 numbers 

that identifies the additional sampling subdivisions follows the 

first number. For example, three subdivisions 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

Numbers are used as prefixes to horizon designations 

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

discontinuities in mineral soils. These prefixes are distinct 

from the numbers 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 parent 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 

indicating the discontinuity is applied to all the designations 

of horizons in that material, e.g., Ap-E-Bt1-2Bt2-2Bt3-2BC. † Indicates weathered bedrock or saprolite in which clay films are present.
Designations for Horizons and Layers 341

H

O

R

The suffix numbers designating vertical subdivisions of the Bt 

horizon continue in consecutive order across the discontinuity. 

However, vertical subdivisions do not continue across lithologic 

discontinuities if the horizons are not consecutive or contiguous 

to each other. If other horizons intervene, another vertical 

numbering sequence begins for the lower horizons, e.g., A-C1-

C2-2Bw1-2Bw2-2C1-2C2.

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 number 

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, e.g., 

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

A buried genetic 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, 

the discontinuity is indicated by a number prefix and the symbol 

for the buried horizon also is used, e.g., Ap-Bt1-Bt2-BC-C2ABb-2Btb1-2Btb2-2C.

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 materials (e.g., Oe vs. Oa) or by the master 

horizon symbol if the different layers are mineral or limnic 

materials (e.g., Oa vs. Ldi).

Use of the Prime Symbol

If two or more horizons with identical number prefixes and 

letter combinations are separated by one or more horizons with 

a different horizon designation in a pedon, identical letter and 

number symbols can be used for those horizons that have the 

same characteristics. For example, the sequence A-E-Bt-EBtx-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 ́-Btx-C. The prime 

symbol, where appropriate, is placed after the capital-letter 

horizon designation and before the lowercase suffix letter 

symbols that follow it, e.g., B ́t. 

The prime symbol is not used unless all letters and number 

prefixes are completely identical. The sequence A-Bt1-Bt2-

2E-2Bt1-2Bt2 is an example. It has two Bt master horizons 

of different lithologies; thus, the Bt horizons are not identical 

and the prime symbol is not needed. The prime symbol is 

used for soils with lithologic discontinuities when horizons 

have identical designations, e.g., A-C-2Bw-2Bc-2B ́w-3Bc. In 

this example, the soil has two identical 2Bw horizons but two 

different Bc horizons (a 2Bc and a 3Bc), so the prime symbol is 

used only with the lower 2Bw horizon (2B ́w). In the rare cases 

where three layers have identical letter symbols, double prime 

symbols can be used for the lowest of these horizons, e.g., E ́ ́.

Vertical subdivisions of horizons or layers (number suffixes) 

are not taken into account when the prime symbol is assigned. 

The sequence A-E-Bt-E ́-B ́t1-B ́t2-B ́t3-C is an example.

These same principles apply 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 and C layers) and Oi-C-Oe-C ́ 

(when the soil has two identical C layers). The prime symbol is 

added to the lower layers to differentiate them from the upper.

Use of the Caret Symbol

The caret symbol (^) is used as a prefix to master horizon 

designations to indicate mineral or organic horizons formed 

in human-transported material. This material has been moved 

horizontally onto a pedon from a source area outside of that 

pedon by purposeful human activity, usually with the aid of 

machinery or hand tools. All horizons and layers formed in 

human-transported material are indicated by a caret prefix (e.g., 

^A-^C-Ab-Btb). When they can contribute substantially to 

an understanding of the relationship of the horizons or layers, 

number prefixes may be used before the caret symbol to indicate 

the presence of discontinuities within the human-transported 

material (e.g., ^Au-^Bwu-^BCu-2^Cu1-2^Cu2) or between the 

human-transported material and underlying horizons formed in 

other parent materials (e.g., ^A-^C1-2^C2-3Bwb).

Sample Horizon and Layer Sequences

The following examples illustrate some common horizon and 

layer sequences of important soils (subgroup taxa) and the use 

of numbers to identify vertical subdivisions and discontinuities. 

Transitional horizons, combination horizons, and the use of the 

prime and caret symbols are also illustrated. The examples were 

selected from soil descriptions on file and modified to reflect 

present conventions.

Mineral soils

Typic Hapludoll: A1-A2-Bw-BC-C 

Typic Haplustoll: Ap-A-Bw-Bk-Bky1-Bky2-C 

Cumulic Haploxeroll: Ap-A-Ab-C-2C-3C 

Typic Argialboll: Ap-A-E-Bt1-Bt2-BC-C 

Typic Argiaquoll: A-AB-BA-Btg-BCg-Cg 

Alfic Udivitrand: Oi-A-Bw1-Bw2-2E/Bt-2Bt/E1-2Bt/E2-

 2Btx1-2Btx2 

Entic Haplorthod: Oi-Oa-E-Bs1-Bs2-BC-C 

Typic Haplorthod: Ap-E-Bhs-Bs-BC-C1-C2 

Typic Fragiudalf: Oi-A-E-BE-Bt1-Bt2-B/E-Btx1-Btx2-C 

Typic Haploxeralf: A1-A2-BAt-2Bt1-2Bt2-2Bt3-2BC-2C 

Glossic Hapludalf: Ap-E-B/E-Bt1-Bt2-C 

Typic Paleudult: A-E-Bt1-Bt2-B/E-B’t1-B’t2-B’t3 

Typic Hapludult: Oi-A1-A2-BA-Bt1-Bt2-BC-C 

Arenic Plinthic Paleudult: Ap-E-Bt-Btc-Btv1-Btv2-BC-C 
342

Xeric Haplodurid: A-Bw-Bkq-2Bkqm 

Vertic Natrigypsid: A-Btn-Btkn-Bky-2By-2BCy-2Cr 

Typic Calciargid: A-Bt-Btk1-Btk2-C 

Typic Dystrudept: Ap-Bw1-Bw2-C-R 

Typic Fragiudept: Ap-Bw-E-Bx1-Bx2-C 

Typic Endoaquept: Ap-AB-Bg1-Bg2-BCg-Cg 

Typic Haplustert: Ap-A-Bss-BCss-C 

Typic Hapludox: Ap-A/B-Bo1-Bo2-Bo3-Bo4-Bo5 

Typic Udifluvent: Ap-C-Ab-C’ 

Anthrodensic Ustorthent: ^Ap-^C/B-^Cd-2C 

Anthroportic Udorthent: ^Ap-^Cu-Ab-Btb-C 

Typic Aquiturbel: Oi-OA-Bjjg-Cjjg-Cjjgf 

Organic soils

Typic Haplosaprist: Oap-Oa1-Oa2-Oa3-C 

Typic Sphagnofibrist: Oi1-Oi2-Oi3-Oe 

Limnic Haplofibrist: Oi-Lco-O’i1-O’i2-L’co-Oe-C 

Lithic Cryofolist: Oi-Oa-R 

Typic Hemistel: Oi-Oe-Oef

Literature Cited

Fanning, D.S., and M.C.B. Fanning. 1989. Soil: Morphology, 

Genesis, and Classification. John Wiley and Sons, New York.

Fanning, D.S., M.C. Rabenhorst, S.N. Burch, K.R. 

Islam, and S.A. Tangren. 2002. Sulfides and Sulfates. In 

J.B. Dixon and D.G. Schulze (eds.), Soil Mineralogy with 

Environmental Applications, pp. 229-260. Soil Sci. Soc. Am., 

Madison, WI.

Gile, L.H., F.F. Peterson, and R.B. Grossman. 1966. 

Morphological and Genetic Sequences of Carbonate 

Accumulation in Desert Soils. Soil Sci. 101:347–360.
343

Laboratory Methods for Soil 

 Taxonomy

The standard laboratory methods upon which the operational 

definitions of the second edition of Soil Taxonomy (Soil 

Survey Staff, 1999) are based are described in the Soil Survey 

Laboratory Methods Manual (Burt and Soil Survey Staff, 

2014). The Charles E. Kellogg Soil Survey Laboratory (KSSL) 

of the National Soil Survey Center in Lincoln, Nebraska 

is where many of the standard methods were developed 

and are routinely performed to support the characterization 

and classification of soils. Laboratory data for the National 

Cooperative Soil Survey (NCSS) program is available from 

KSSL and cooperators’ laboratories in the online NCSS soil 

characterization database.

The Soil Survey Laboratory Methods Manual documents 

methodology and serves as a reference for the laboratory 

analyst. The Soil Survey Laboratory Information Manual (Soil 

Survey Staff, 2011) is a companion manual that provides brief 

summaries of the KSSL methods as well as detailed discussion 

of the use and application of the resulting data. The Soil Survey 

Field and Laboratory Methods Manual (Soil Survey Staff, 

2009) is a how-to reference for the scientist in a soil survey 

office setting.

Pedon characterization data, or any soil survey data, are 

most useful when the operations for collecting the data are well 

understood. The mental pictures and conceptual definitions that 

aid in visualizing properties and processes often differ from 

the information supplied by an analysis. Also, results differ by 

method, even though two methods may carry the same name 

or the same concept. There is uncertainty in comparing one 

bit of data with another without knowledge of how both bits 

were gathered. Operational definitions (definitions tied to a 

specific method) are needed. Soil taxonomy has many class 

limits, at all categorical levels, that are based on chemical 

or physical properties determined in the laboratory. One can 

question the rationale for a given class limit, but that is not the 

purpose of this appendix. This appendix is designed to show 

what procedures are used for measuring given class limits. 

By using specific class limits, everyone will come to the same 

classification if they follow the same procedures.

This taxonomy is based almost entirely on criteria that are 

defined operationally. One example is the definition of “clay” 

as used in the criteria for particle-size classes. There is no 

one definition of clay that works well for all soils. Hence, a 

process for testing the validity of a pipette clay measurement 

and a default operation for those situations where the clay 

measurement is not valid, are defined. The default method is 

based on a gravimetric water content measurement at 1500 kPa 

tension and on percent organic carbon. See the section below 

titled “Other Information Useful in Classifying Soils,” for more 

information.

Data Elements Used in Classifying Soils

Detailed explanations of laboratory methods are given in 

the Soil Survey Laboratory Methods Manual (Burt and Soil 

Survey Staff, 2014). Each method is listed by code on the data 

sheet at the beginning of the chapters describing soil orders 

in the second edition of Soil Taxonomy. On the data sheets 

presented with each order, the method code (e.g., 3A1 for 

Particles <2mm) is shown for each determination made. These 

data sheets should be consulted for reference to the Soil Survey 

Laboratory Methods Manual. This manual specifies method 

codes for pedon sampling, sample handling, site selection, 

sample collection, and sample preparation. 

The units of measurement reported on the data sheets in the 

second edition of Soil Taxonomy and some units used as criteria 

in the Keys to Soil Taxonomy are not SI (international system 

of units) units. The following are conversions to SI units of 

measurement:

1 meq/100 g = 1 cmol(+)/kg

1 meq/liter = 1 mmol (±)/L

1 mmho/cm = 1 dS/m

15 bar = 1500 kPa

1

/3 bar = 33 kPa 1

/10 bar = 10 kPa

1 percent = 10 g kg-1

In this taxonomy the terms (1) particle-size analysis (size 

separates), (2) texture, and (3) particle-size classes are all used. 

Particle-size analysis is needed to determine both texture and 

particle-size classes. Texture class differs from particle-size 

class in that texture includes only the fine-earth fraction (less 

than 2 mm), while particle-size includes both the fraction less 

than 2 mm in diameter and the fraction equal to or more than 2 

mm.

Physical Analyses

Bulk density is obtained typically by equilibration of Sarancoated natural fabric clods at designated pressure differentials. 

Appendix
344 Keys to Soil Taxonomy

Bulk densities are determined at two or more water contents. 

For coarse textured and moderately coarse textured soils, they 

are determined when the sample is at 10 kPa tension and when 

ovendry. For soils of medium and finer texture, the bulk density 

is determined when the sample is at 33 kPa tension and when 

ovendry. Bulk density is used as a criterion in the definitions of 

mineral and organic soils, the required characteristics for folistic 

and histic epipedons, the key to soil orders (i.e., Histosols), 

the required characteristics for andic soil properties, and the 

intergrade subgroups of Andic (except Kandic), Aquandic, and 

Vitrandic (“vitr”). Bulk density measured at 33 kPa tension 

is also used to convert other analytical results to a volumetric 

basis. For example, the Humults suborder has a critical limit 

of 12 kilograms or more of organic carbon per square meter 

(kg/m2) between the mineral soil surface and a depth of 100 cm. 

The calculation is described below in the section titled “Other 

Information Useful in Classifying Soils.”

Coefficient of linear extensibility (COLE) is a derived value. 

It is computed from the difference in bulk density between a 

moist clod and an ovendry clod. It is based on the shrinkage of a 

natural soil clod between a water content of 33 kPa (10 kPa for 

sandier soils) and ovendry. The COLE is used to compute linear 

extensibility (defined below). COLE multiplied by 100 is called 

linear extensibility percent (LEP).

Linear extensibility (LE) of a soil layer is the product of the 

thickness, in centimeters, multiplied by the COLE of the layer 

in question. The LE of a soil is the sum of these products for 

all soil horizons from the mineral soil surface to a depth of 100 

cm or to a root-limiting layer if shallower. Linear extensibility 

is used as an alternate criterion in Vertic (“ertic”) subgroups 

throughout soil taxonomy. 

Particle-size analysis in the laboratory determines the 

proportion of the various size particles (separates) in a soil 

sample. The values for sand, silt, and clay content as well as 

their various size fractions are reported in percent of the <2 mm 

material (fine-earth fraction) on a dry weight basis. Material 

2 mm or larger in diameter (e.g., rock fragments) are visually 

estimated or measured separately (on a volume basis), sieved 

out of the sample, and thus are not considered in the analysis 

of the sample. Of the material smaller than 2 mm in diameter, 

the amount of the five sand fractions is determined by sieving. 

The amount of the silt and clay fractions is determined by 

a differential rate of settling in water. Either the pipette or 

hydrometer method is used for measuring silt and clay contents. 

Organic matter and dissolved mineral matter are removed in 

the pipette procedure but not in the hydrometer procedure. 

The two procedures are generally very similar, but a few 

samples, especially those with high organic matter or high 

soluble salts, exhibit wide discrepancies. Routinely removing 

these substances (and, for some samples, carbonates, iron, and 

silica) helps the dispersion process prior to fractioning the soil 

separates and measuring them. For samples suspected of having 

andic soil properties, the samples are not dried and are analyzed 

in a field-moist state. This protocol avoids the irreversible 

hardening of colloids into microaggregates that occurs during 

drying and which decreases measured clay contents. For 

soils high in gypsum (>40 %), the samples are dispersed 

using sonication and an aqueous ethanol solution to prevent 

dissolution of gypsum prior to particle-size analysis.

Particle-size analysis data is used in the definitions of soil 

texture class (Soil Survey Division Staff, 1993). They are used 

in soil taxonomy for many criteria based on texture class, clay 

content, sand fraction content, and content of coarse silt through 

very coarse sand (0.02 to 2 mm). The ratios discussed below 

in the section titled “Other Information Useful in Classifying 

Soils” are useful internal checks of the validity of particle-size 

analyses.

Water content (retention) is the soil water content at a given 

soil water tension. In KSSL data, it is computed and reported 

as gravimetric water content on a fine-earth (< 2 mm) basis. 

Measurements of water content are commonly made at 33 

kPa (10 kPa for coarse textured and some moderately coarse 

textured soils) and 1500 kPa tension. The water content at 1500 

kPa tension is determined by desorption of crushed and sieved 

fine-earth (<2 mm) soil material which may be undried (i.e., 

field-moist) or air-dried. Water content at 1500 kPa tension is 

used as a criterion in the Vitrands suborder; in the Vitric (“vitr”) 

and Hydric (“hydr”) great groups and subgroups of Andisols; 

for the ashy, medial, and hydrous substitutes for particle-size 

class; and for several strongly contrasting particle-size classes. 

Measurement of 1500 kPa water content on undried samples 

is particularly important for soils suspected of having andic 

soil properties since it is needed for classification in the ashy, 

medial, and hydrous substitutes for particle-size class.

Chemical Analyses

Ion Exchange and Extractable Cations

Cation-exchange capacity (CEC) as determined with 

ammonium acetate (1N NH4OAc) at pH 7 (CEC-7), by sum of 

cations at pH 8.2 (CEC-8.2), and by bases plus aluminum is 

used for different purposes in soil taxonomy. The CEC depends 

on the method of analysis as well as the nature of the exchange 

complex. CEC by ammonium acetate is measured at pH 7. CEC 

by the sum of cations at pH 8.2 is calculated by adding the sum 

of bases and the extractable acidity (defined below). CEC by 

bases plus aluminum, or effective cation-exchange capacity 

(ECEC), is derived by adding the sum of extractable bases 

and the KCl-extractable Al. Aluminum extracted by 1N KCl 

is negligible if the extractant pH rises toward 5.5. ECEC then 

is equal to extractable bases. CEC and ECEC are reported on 

KSSL data sheets as cmol(+)/kg-1 soil. 

The reported CEC may differ from the CEC of the soil at 

its natural pH. The standard methods allow the comparison 

of one soil with another even though the pH of the extractant 

differs from the pH of the natural soil. Cation-exchange 

capacity by ammonium acetate and by sum of cations applies 
Appendix 345

to all soils. CEC at pH 8.2 is not reported if the soil contains 

free carbonates, gypsum, or significant amounts of soluble 

salts because bases, such as calcium, are extracted from these 

soluble (i.e., mobile) substances. The effective cation-exchange 

capacity (ECEC) is reported only for acid soils. ECEC is 

not reported for soils having soluble salts, although it can be 

calculated by subtracting the soluble components from the 

extractable components. ECEC also may be defined as bases 

plus aluminum plus hydrogen. That is the more common 

definition for agronomic interpretations. This taxonomy 

specifies bases plus aluminum. 

Generally, the ECEC is less than the CEC at pH 7, which 

in turn is less than the CEC at pH 8.2. If the soil is dominated 

by positively charged colloids (e.g., iron oxides), however, the 

trend is reversed. Most soils have negatively charged colloids, 

which cause the CEC to increase with increasing pH. This 

difference in CEC is commonly called the pH-dependent or 

variable charge. The CEC at the soil pH can be estimated by 

plotting the CEC of the soil vs. the pH of the extractant on a 

graph and reading the CEC at the soil pH. CEC measurements 

at pH levels other than those described in the paragraphs 

above and CEC derived by using other extracting cations will 

yield somewhat different results. It is important to know the 

procedure, pH, and extracting cation used before CEC data are 

evaluated or data from different sources are compared.

If the ratio of CEC-7 or ECEC to percent clay is multiplied 

by 100, the product represents the cation-exchange capacity of 

just the clay fraction and is expressed in whole numbers which 

are cmol(+)/kg clay. The CEC-7 and ECEC of the clay fraction 

are used directly in this taxonomy in the required characteristics 

of the kandic and oxic horizons. The CEC-7 of the clay fraction 

is also used as a criterion in Kandic and Kanhaplic subgroups 

of Alfisols and Ultisols, Udoxic and Ustoxic subgroups of 

Quartzipsamments, and Oxic subgroups of Inceptisols and 

Mollisols. The ECEC of the clay fraction is used as criteria 

for Acric (“acr”) great groups of Oxisols and Acric (“acr”) 

subgroups of Ultisols.

Extractable acidity is the acidity released from the soil by 

a barium chloride-triethanolamine solution buffered at pH 

8.2. It includes all the acidity generated by replacement of the 

hydrogen and aluminum from permanent and pH-dependent 

exchange sites. It is reported as cmol(+)/kg-1 soil. Extractable 

acidity data are reported on some data sheets as exchangeable 

acidity and on others as exchangeable H+. Extractable acid is 

used to calculate the cation-exchange capacity by the sum of 

cations method (CEC-8.2) and is also used as an option in the 

required characteristics of the natric horizon.

Extractable aluminum is the amount of aluminum extracted 

by 1N KCl. It is considered exchangeable and a measure 

of the “active” acidity present in soils with a 1:1 water pH 

≤5.5. Extractable aluminum is measured at KSSL by atomic 

absorption. Many laboratories measure the aluminum by 

titration with a base to the phenolphthalein end point. Titration 

measures exchangeable acidity as well as extractable aluminum. 

Soils with a pH below 4.0 or 4.5 are likely to have values 

determined by atomic absorption similar to values determined 

by titration because very little hydrogen is typically on the 

exchange complex. If there is a large percentage of organic 

matter, however, some hydrogen may be present. For some soils 

it is important to know which procedure was used. Extractable 

aluminum is reported as cmol(+)/kg-1 soil. It is used to calculate 

ECEC and in the criteria for Alic and some Eutric subgroups of 

Andisols. 

Sum of extractable bases is the sum of the basic cations 

calcium, magnesium, sodium, and potassium that are extracted 

with ammonium acetate buffered at pH 7. The bases are 

extracted from the cation-exchange complex by displacement 

with ammonium ions. They are equilibrated, filtered in an autoextractor, and measured by atomic absorption. The individual 

cations and the sum of cations are reported as cmol(+)/kg-1 soil. 

The term “extractable bases” is used instead of “exchangeable 

bases” because soluble salts and some bases from carbonates 

can be included in the extract.

Exchangeable magnesium plus sodium and calcium plus 

extractable acidity (at pH 8.2) is used as a criterion for the 

natric horizon and Albic subgroups of Natraqualfs. The 

extractable acidity is measured at pH 8.2, and the magnesium, 

sodium, and calcium are extracted at pH 7.0 with ammonium 

acetate. See the paragraphs above on extractable acidity and 

extractable bases.

Base saturation is reported on the data sheets as the 

percentage of the cation-exchange capacity (CEC) occupied 

by the four basic cations described above. It is reported in 

KSSL data by two methods: sum of cations at pH 8.2 and 

ammonium acetate at pH 7. Base saturation by ammonium 

acetate is equal to the sum of extractable bases, divided by 

the CEC by ammonium acetate (CEC-7), and multiplied by 

100. If calcium carbonate or gypsum are present in a sample, 

then the extractable calcium may contain calcium from these 

minerals and the base saturation is assumed to be 100 percent. 

Base saturation by sum of cations is equal to the sum of bases 

extracted by ammonium acetate, divided by the CEC by sum 

of cations (CEC-8.2), and multiplied by 100. This value is not 

reported if either extractable calcium or extractable acidity is 

omitted. Differences between the two methods of determining 

base saturation reflect the amount of the pH-dependent CEC. 

Class definitions in this taxonomy specify which method is 

used.

The sum of exchangeable cations is considered equal to the 

sum of bases extracted by ammonium acetate unless carbonates, 

gypsum, or other salts are present. When these salts are present, 

the sum of the bases extracted by ammonium acetate typically 

exceeds 100 percent of the CEC. Therefore, a base saturation of 

100 percent is assumed. The amount of calcium from carbonates 

is usually much larger than the amount of magnesium from the 

carbonates. Extractable calcium is shown on KSSL datasheets 

even if carbonates (reported as calcium carbonate) are present. 

The base saturation (by CEC-7) is set to 100 percent if 
346 Keys to Soil Taxonomy

significant amounts of carbonates or gypsum are present. Base 

saturation by ammonium acetate is used in this taxonomy in the 

required characteristics for the mollic and umbric epipedons, 

the key to soil orders (Mollisols), and many great groups (e.g., 

Eutrudepts) and subgroups (e.g., Eutric Haplocryalfs) in several 

orders. Base saturation by sum of cations is used in the key to 

soil orders to identify Ultisols and in several Alfic, Dystric, and 

Ultic subgroups of Alfisols, Andisols, Inceptisols, Mollisols, and 

Spodosols (e.g., Alfic Fragiorthods).

Soil pH

The pH of soil is measured in water and salt solutions by 

several methods. It is measured by a digital pH meter in a 

soil-water solution, soil-salt solution, or saturated paste. The 

extent of the dilution is shown in the heading on the data sheets. 

A ratio of 1:1 means one part dry soil and one part water, by 

weight.

The 1:1 water pH is determined in a solution of one part 

dry soil mixed with one part water. It is used directly in the 

required characteristics for sulfidic materials, Sulfic subgroups 

of Entisols and Inceptisols, and the Sulfaqueptic Dystraquerts 

subgroup. It is also used in a calculation with 1N KCl pH 

(described below).

The 1:2 CaCl2 pH is determined in a solution of one part 

soil to two parts 0.01M calcium chloride (CaCl2 ). It is used in 

mineral soils as a criterion for Dystric (“dystr”) great groups of 

Vertisols and in the key to calcareous and reaction classes. It is 

used in organic soils (i.e., Histosols and Histels) in the key to 

reaction classes.

The 1N KCl pH is measured in a solution of 1N potassium 

chloride (KCl) mixed 1:1 with soil. It is used directly as a 

criterion for the Acric (“acr”) great groups of Oxisols. It is also 

used in a simple calculation with the 1:1 water pH. The “delta 

pH” (a term for 1N KCl pH minus 1:1 water pH) is used as a 

criterion for the Anionic subgroups of Oxisols.

Measurement of pH in a dilute salt solution is common 

because it tends to mask seasonal variations in pH. Readings in 

0.01M CaCl2

 tend to be uniform regardless of the time of year 

and are more popular in regions with less acidic soils. Readings 

in 1N KCl also tend to be uniform and are more popular 

in regions with more acidic soils. If KCl is used to extract 

exchangeable aluminum, the pH reading (in KCl) shows the pH 

at which the aluminum was extracted.

The saturated paste pH is usually compared to the 1:1 water 

pH and the 1:2 CaCl2 pH. The usual pH sequence is as follows: 

1:1 water pH > 1:2 CaCl2 pH > saturated paste pH. If the 

saturated paste pH is > 1:2 CaCl2 pH, the soil is nonsaline. If the 

saturated paste pH is ≥ 1:1 water pH, the soil may be sodium 

saturated and does not have free carbonates. The saturated paste 

pH is used as a criterion for the Dystrusterts and Dystruderts 

great groups.

The oxidized pH is used to determine whether known or 

suspected sulfidic materials are present and whether they will 

oxidize to form a sulfuric horizon. Soil materials that have 

a pH value (1:1 water pH) of more than 3.5 are incubated at 

room temperature in a 1-cm-thick layer under moist, aerobic 

conditions and repeatedly dried and remoistened on a weekly 

basis. Sulfidic materials 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 16 weeks or 

longer, if the pH is still dropping after 16 weeks, until the pH 

reaches a nearly constant value.

The sodium fluoride pH (NaF pH) is measured in a 

suspension of 1 gram of soil in 50 ml 1M NaF after stirring for 

2 minutes. A NaF pH of 9.4 or more is a strong indicator that 

short-range-order minerals dominate the soil exchange complex. 

A NaF pH of 8.4 or more is a criterion for the isotic mineralogy 

class. It indicates a significant influence of short-range-order 

minerals on the exchange complex. Soil materials with free 

carbonates also have high NaF pH values. NaF is poisonous 

with ingestion and eye contact and moderately hazardous with 

skin contact.

Sulfur and Extractable Anions

Nitrate concentration is measured in a 1:5 soil:water extract. 

The nitrate content (NO3

-

) of the extract is measured by a flowinjection analyzer. The results are reported in mmol(-)/L-1 and 

are used in a simple calculation as criteria for Nitric subgroups 

of Gelisols.

Phosphate retention refers to the percent phosphorus retained 

by soil after equilibration with 1,000 mg/kg phosphorus solution 

for 24 hours. This analyte is also referred to as New Zealand 

(NZ) phosphorus retention. Percent phosphate retention is 

used in the required characteristics for andic soil properties. It 

identifies soils in which phosphorus fixation may be a problem 

affecting agronomic uses.

Total sulfur (S) is the content of organic and inorganic forms 

of sulfur. KSSL uses a combustion technique for analysis of 

total S. It is reported as percent of air-dry, fine-earth material. 

Total sulfur is used, along with 1:1 water pH, as a criterion in 

the required characteristics for sulfidic materials.

Water-soluble sulfate is used as a criterion for the sulfuric 

horizon. The sulfate content (SO4

2-)is measured from a 1:500 

soil:water extract using an ion chromatograph. The sulfate 

content is initially measured in mg L-1 and later converted to 

percent in the soil. It is reported as aqueous-extractable sulfate 

to the nearest hundredths of a percent.

Carbonates and Calcium Sulfates

Calcium carbonate equivalent is the amount of carbonates 

in the soil as measured by treating the sample with 3N HCl. 

The evolved carbon dioxide is measured manometrically. The 

amount of carbonate is then calculated as a calcium carbonate 

equivalent regardless of the form of carbonates (dolomite, 

sodium carbonate, magnesium carbonate, etc.) in the sample. 

Calcium carbonate equivalent is reported as a percentage 

of the total dry weight of the sample. It can be reported on 

material that is either less than 2 mm or less than 20 mm in 
Appendix 347

diameter. Calcium carbonate equivalent is used in the required 

characteristics for the mollic epipedon and calcic horizon and 

as criteria for the Rendolls suborder, the Rendollic Eutrudepts 

subgroup, and the carbonatic mineralogy class.

Gypsum content is determined by extraction in water and 

precipitation in acetone. The amount of gypsum (CaSO4 •2H2O) 

is reported as a percentage of the total dry weight of the fraction 

less than 2 mm in diameter and the fraction less than 20 mm 

in diameter. Drying soils to oven-dryness, the standard base 

for reporting the data, removes part of the water of hydration 

from the gypsum. Many measured values, particularly water 

retention values, must be recalculated to compensate for the 

weight of the water of hydration lost during drying. Gypsum 

content is used in the required characteristics for gypsic and 

petrogypsic horizons and as criteria for the gypseous substitute 

classes, several strongly contrasting particle-size classes, and 

the hypergypsic, gypsic, and carbonatic mineralogy classes.

Anhydrite content is quantified by the difference in two 

analytical procedures. Anhydrite (CaSO4) and gypsum are 

both extracted and measured by a procedure using acetone to 

precipitate dissolved calcium sulfate from an aqueous solution. 

The acetone procedure commonly used to quantify gypsum also 

extracts anhydrite, and for soils with both of these minerals, 

the results of the analysis represent the sum of gypsum and 

anhydrite in the soil. Gypsum (but not anhydrite) is quantified 

by thermal gravimetric analysis, a method that measures the 

weight loss of a sample by heating it from 20 to 200oC at a rate 

of 2oC/min. The weight of water loss between 75 and 115oC 

is used to quantify the gypsum based on a theoretical weigh 

loss of 20.9% (Karathanasis and Harris, 1994). Therefore, the 

percent anhydrite in a sample can be derived from the difference 

between the acetone method (Σgypsum+anhydrite) and thermal 

(gypsum) procedure. More details can be found in Wilson et al. 

(2013). Anhydrite content is used in the required characteristics 

for the anhydritic horizon and as a criterion for the anhydritic 

mineralogy class.

Soluble Salts

Electrical conductivity (EC) is the conductivity of electricity 

through the water extracted from saturated soil paste. It is 

reported as dS/m and is used as a criterion for the salic horizon 

and in Halic subgroups of Vertisols. 

Electrical conductivity 1:1 is the electrolytic conductivity 

of a suspension of 1 part soil to 1 part water. The results are 

used to classify some saline organic soils composed of highly 

decomposed organic materials into the Halic subgroups of 

Haplosaprists. The conductivity is reported as dS/m.

Electrical conductivity 1:5 by volume(EC1:5 vol ) is the 

electrolytic conductivity of a diluted, unfiltered supernatant of 1 

part soil to 5 parts distilled water as measured by volume. The 

EC1:5 vol is used to indicate the threshold between different taxa 

for freshwater and brackish subaqueous soils. It is reported as 

dS/m.

Exchangeable sodium percentage (ESP) is reported as a 

percentage of the CEC by ammonium acetate at pH 7. Watersoluble sodium is converted to cmol(+)/kg-1 soil. This value 

is subtracted from extractable sodium, divided by the CEC 

(by ammonium acetate), and multiplied by 100. An ESP of 15 

percent or more is used in this taxonomy as a criterion for the 

natric horizon, the Halaquepts great group, Natric subgroups, 

and most Sodic subgroups.

Sodium adsorption ratio (SAR) was developed as a measure 

of irrigation water quality. This calculated value uses the 

soluble calcium, magnesium, and sodium content (reported in 

mmol(+) L-1) determined in water extracted from a saturated 

paste and measured by atomic absorption spectrophotometry. 

The formula is SAR = Na/[(Ca+Mg)/2]0.5. An SAR of 13 or 

more is used as an alternate criterion to the exchangeable 

sodium percentage criterion for the natric horizon, the 

Halaquepts great group, Natric subgroups, and most Sodic 

subgroups.

Selective Dissolutions

Ammonium oxalate extractable aluminum, iron, and silicon

are determined by a single extraction made in the dark with 

0.2 molar ammonium oxalate at a pH of 3.5. The amount of 

aluminum, iron, and silicon is measured by atomic absorption 

and reported as a percentage of the total dry weight of the 

fine-earth fraction. The procedure extracts iron, aluminum, 

and silicon from organic matter and from amorphous mineral 

material. It is used in conjunction with dithionite-citrate and 

pyrophosphate extractions (described below) to identify the 

sources of iron and aluminum in the soil. Pyrophosphate 

extracts iron and aluminum associated with organic materials. 

Dithionite-citrate extracts iron from iron oxides and 

oxyhydroxides as well as from organic matter. A field test using 

potassium hydroxide (KOH) can be used to estimate the amount 

of aluminum that is extractable by ammonium oxalate (Soil 

Survey Staff, 2009).

The oxalate-extractable aluminum plus one-half iron 

contents are used as criteria for andic soil properties and spodic 

materials (used for classifying soils in the Andisol and Spodosol 

orders) and in the Andic and Spodic subgroups in other orders. 

The relative amounts of oxalate-extractable iron and silicon 

are used to define the amorphic and ferrihydritic mineralogy 

classes.

Optical density of oxalate extract (ODOE) is determined 

with a spectrophotometer using a 430 nm wavelength. An 

increase in the ODOE value in an illuvial horizon, relative 

to an overlying eluvial horizon, indicates an accumulation of 

translocated organic materials. The optical density of oxalate 

extract is used in the definition of spodic materials as well 

as Spodic subgroups of Entisols, Gelisols, Inceptisols, and 

Ultisols.

Dithionite-citrate extractable iron is the percentage of iron as 

Fe2

O3 removed in a single extraction. It is measured by atomic 

absorption and reported as a percentage of the total dry weight. 

The iron is primarily from ferric oxides (e.g., hematite and 
348 Keys to Soil Taxonomy

magnetite) and iron oxyhydroxides (e.g., goethite). Aluminum 

substituted into these minerals is extracted simultaneously. 

The dithionite reduces the ferric iron, and the citrate stabilizes 

the iron by chelation. Iron and aluminum bound in organic 

matter are extracted if the citrate is a stronger chelator than the 

organic molecules. Manganese extracted by this procedure also 

is recorded. The iron extracted is commonly related to the clay 

distribution within a pedon. Percent iron oxide extracted by 

dithionite-citrate is used to define anthric saturation (anthraquic 

conditions), the ferritic, ferruginous, sesquic, and parasesquic 

mineralogy classes, and ferrihumic soil material.

Organic Analyses

Color of sodium-pyrophosphate extract is used as a criterion 

in the identification of different kinds of organic soil materials 

and limnic materials. A saturated solution is made by adding 1 g 

of sodium pyrophosphate to 4 ml of distilled water, and a moist 

organic matter sample is added to the solution. The sample is 

mixed and allowed to stand overnight, chromatographic paper is 

dipped in the solution, and the color of the paper is compared to 

the chips of a Munsell soil-color chart.

Fiber content is determined for horizons of organic soil 

material on the decomposed plant materials that are less than 

20 mm in cross section. The fiber content is reported as percent 

by volume before rubbing and after rubbing between the 

thumb and fingers. Only the fiber content after rubbing is used 

as criteria in soil taxonomy since it partially defines the three 

kinds of organic soil materials (fibric, hemic, and sapric) used 

to classify organic soils (i.e., Histosols and Histels). The rubbed 

fiber content is in the definitions of suffix symbols “a,” “e,” 

and “i” which are used with master symbol “O” to designate 

horizons in both organic and mineral soils (Soil Survey Division 

Staff, 1993).

Melanic index is used in the required characteristics of the 

melanic epipedon. The index is related to the ratio of the humic 

and fulvic acids in the organic fraction of the soil (Honna et al., 

1988). The index is used to distinguish humified organic matter 

thought to result from large amounts of gramineous vegetation 

from humified organic matter formed from forest vegetation. 

The melanic index is calculated as the absorbance of the 

extracting solution at wavelength 450 nm over the absorbance at 

wavelength 520 nm.

Organic carbon data in the NCSS soil characterization 

database have been determined mostly by wet digestion 

(Walkley, 1935). Because of environmental concerns about 

waste products, however, that method is no longer used 

at KSSL. The method that is currently used at KSSL to 

determine organic carbon is a dry combustion procedure that 

determines the percent total carbon. Total carbon is the sum of 

organic and inorganic carbon. In calcareous horizons the content 

of organic carbon is determined by subtracting the amount of 

inorganic carbon contributed by carbonates from 

the total carbon data (percent organic carbon = percent total 

carbon – [% <2 mm CaCO3

 x 0.12]). The content of organic 

carbon determined by this computation is very close to the 

content determined by the wet digestion method. Values for 

organic carbon are multiplied by the Van Bemmelen factor 

of 1.724 to estimate percent organic matter. Organic-carbon 

content is used in many places in soil taxonomy. Some 

examples are the definition of mineral soil material, the required 

characteristics of diagnostic surface horizons (such as a Histic 

epipedon), and criteria for taxa that connote the presence of 

horizons high in organic matter (such as the Humults suborder).

Organic matter is determined by measuring the mineral 

content of a sample using loss on ignition (LOI). The percent 

organic matter is calculated by difference (i.e., 100 – percent 

mineral content). The organic matter content measured by LOI 

is used with CEC data in criteria which define coprogenous 

earth and diatomaceous earth.

Mineral Analyses

Mineralogy of the clay, silt, and sand fractions is needed 

for classification in some taxa. X-ray diffraction (XRD) and 

thermal and petrographic analyses are classically viewed as 

mineralogy techniques, although some mineralogy classes (e.g., 

ferritic, amorphic, gypsic, carbonatic, and isotic) are determined 

by chemical and/or physical analyses.

Halloysite, illite, kaolinite, smectite, vermiculite, and other 

minerals in the clay fraction (less than 0.002 mm) may be 

identified by XRD analysis. Relative peak positions identify 

clay minerals, and peak intensities are the basis for semiquantitative estimates of mineral percent by weight in the clay 

fraction. KSSL reports relative peak intensities of clay minerals 

from XRD in a five-class system that generally corresponds 

to percent by weight of a mineral (class 1 = 0 to 2 percent, 

class 2 = 3 to 9 percent, class 3 = 10 to 29 percent, class 4 = 

30 to 50 percent, and class 5 = more than 50 percent). There 

are multiple potential interferences in the analysis of a clay 

sample (Burt and Soil Survey Staff, 2014). Peak intensities may 

be attenuated by one or more interferences, and the reported 

class may underestimate the actual amount of mineral present. 

Thus, these assigned percentages are given for informational 

use only and should not be used to quantify minerals in a clay 

fraction. Clay minerals are listed in the order of decreasing 

quantity on the data sheet. XRD is used to determine smectitic, 

vermiculitic, illitic, kaolinitic, or halloysitic mineralogy classes 

in Soil Taxonomy. Some family classes require a clay mineral 

to be more than one-half (by weight) of the clay fraction, 

corresponding to XRD class 5. Other mineralogy classes require 

more of the specified mineral than any other single mineral, 

corresponding to the clay mineral being listed in the first ordinal 

position on the KSSL data sheet. 

Kaolinite and gibbsite may be determined by thermal 

analysis. Results from this analysis are reported as percent 

by weight in the clay fraction and are more quantitative than 

the results of XRD for these minerals. Thermal analysis is a 

technique in which the dried sample (typically the clay fraction) 

is heated in a controlled environment. Certain minerals undergo 
Appendix 349

decomposition at specific temperature ranges, and the mineral 

can be quantified when compared to standard clays. Results may 

be used to determine kaolinitic and gibbsitic family mineralogy 

classes, complementary to or in lieu of XRD data. 

Resistant minerals, weatherable minerals, volcanic glass, 

magnesium-silicate minerals, glauconitic pellets, mica, and 

stable mica pseudomorphs may be determined by petrographic 

analysis. Magnesium-silicate minerals (e.g., serpentine 

minerals) and glauconitic pellets are reported as percent by 

weight in the fine-earth fraction (less than 2.0 mm). Resistant 

minerals, weatherable minerals, and volcanic glass are 

determined as percent of total grains counted in the coarse silt 

through very coarse sand (0.02 to 2.0 mm) fractions, while 

mica and stable mica pseudomorphs are determined in the 

0.02 to 0.25 mm fractions (coarse silt, very fine sand, and fine 

sand).

Individual mineral grains in a specific particle-size fraction 

are mounted on a glass slide, identified, and counted (at least 

300 grains) under a polarizing light microscope. Data are 

reported as percent of grains counted for a specific size fraction. 

This percentage is generally regarded as equivalent to weight 

percent for spherical minerals. Alternative techniques are 

available for determining weight percent micas and other platy 

grains in a soil separate. The usual KSSL protocol is to count 

mineral grains in either the coarse silt (0.02-0.05 mm), very 

fine sand (0.05-0.10 mm), or fine sand (0.10-0.25 mm) fraction, 

whichever one has the highest weight percent based on particlesize analysis. Mineral or glass content in the analyzed fraction 

is assumed to be representative of the content in the whole 0.02 

to 2.0 mm or fine-earth fraction. It may be necessary to count 

additional fractions to obtain a reliable estimate of volcanic 

glass content in soil materials with a non-uniform distribution 

of glass in dominant particle-size fractions. If more than 

one fraction is counted, the weighted average of the counted 

fractions may be calculated to represent glass content in the 

0.02 to 2.0 mm fraction. For soils expected to have significant 

amounts of glass in dominant fractions of medium, coarse, or 

very coarse sand, grain counts are needed.

Two general types of petrographic analysis are conducted at 

KSSL: (1) complete mineral grain count, in which all minerals 

in the sample are identified and counted, or (2) a glass count, 

in which glass, glass aggregates, glass-coated minerals, and 

glassy materials are identified and quantified and all other 

minerals are counted as “other.” Other isotropic grains, such as 

plant opal, sponge spicules, and diatoms, also are identified and 

quantified in the glass count grain studies. Glass-coated grains 

are crystalline mineral grains in which more than 50 percent 

of the grain is coated with glass. Grains coated with glass 

are either specifically identified (e.g., glass-coated feldspar) 

or are identified with a general category (e.g., glass-coated 

grain) depending on the level of certainty. “Glassy materials” 

is a general category for grains that have optical properties of 

glass but lack definitive characteristics of glass, glass-coated 

grains, or glass aggregates. Percent of total resistant minerals 

is reported on the KSSL data sheet. (Calcite and more soluble 

minerals are included in determinations of the percentage of 

resistant minerals reported on the laboratory data sheet but 

are not included in the values used in this taxonomy.) Total 

percent volcanic glass, weatherable minerals, or other groups of 

minerals used in classification may be calculated by summing 

the percent of individual minerals included in the group. A 

current, complete list of minerals in each category is in the Soil 

Survey Laboratory Information Manual (Soil Survey Staff, 

2011). 

Other Information Useful in Classifying 

 Soils

Volumetric amounts of organic carbon are used in some 

taxonomic criteria (e.g., Humults suborder). The following 

calculation is used: (Datum [percent] times bulk density [at 33 

or 10 kPa] times thickness [cm]) divided by 10. This calculation 

is normally used for organic carbon, but it can be used for some 

other measurements. Each horizon is calculated separately, and 

the product of the calculations can be summed to any desired 

depth, commonly 100 cm.

Ratios that can be developed from the data are useful in 

making internal checks of the data, in making managementrelated interpretations, and in answering taxonomic questions. 

Some of the ratios are used as criteria in determining argillic, 

kandic, natric, or oxic horizons.

The ratio of water content at 1500 kPa tension to clay content 

is used to indicate the relevancy of a particle-size analysis. 

If the ratio is 0.6 or more and the soil does not have andic 

soil properties, incomplete dispersion of the clay is assumed. 

For most soils, clay is estimated by the following formula: 

Clay % = 2.5(% water retained at 1500 kPa tension - % organic 

carbon). For a typical soil with well dispersed clays, the 1500 

kPa water to clay ratio is 0.4. Some soil-related factors that 

can cause deviation from the 0.4 value are: (1) low-activity 

clays (kaolinites, chlorites, and some micas), which tend to 

have a ratio of 0.35 or below; (2) iron oxides and clay-sized 

carbonates, which tend to decrease the ratio; (3) organic matter, 

which increases the ratio because it increases the water content 

at 1500 kPa; (4) andic and spodic materials and materials with 

an isotic mineralogy class, which increase the ratio because they 

do not disperse well; (5) large amounts of gypsum or anhydrite, 

which decrease the ratio to less than 0.3; and (6) clay minerals 

within grains of sand and silt, which hold water at 1500 kPa and 

thus increase the ratio (which are most common in shale and in 

pseudomorphs of primary minerals in saprolite). 

The ratio of CEC by ammonium acetate at pH 7 (CEC-7) 

to percent total clay can be used to estimate clay mineralogy 

and clay dispersion. The following ratios are typical for the 

following classes of clay mineralogy: less than 0.2, kaolinitic; 

0.2-0.3, kaolinitic or mixed; 0.3-0.5, mixed or illitic; 0.5-

0.7, mixed or smectitic; and more than 0.7, smectitic. These 

ratios are most valid when some detailed mineralogy data are 
350 Keys to Soil Taxonomy

available. As described previously, if the ratio of 1500 kPa 

water to clay is 0.25 or less or 0.6 or more, the measured clay 

content and the calculated ratio of CEC-7 to percent clay is not 

valid. The ratio of CEC-7 to percent clay is used as a criterion in 

applying cation-exchange activity classes for certain loamy and 

clayey soils which have either mixed or siliceous mineralogy. 

It is important to note that the ratio must be recalculated for 

soils which contain clay-sized carbonates since carbonate 

clay is excluded from the concept of “clay” for taxonomic 

classifications. Measured carbonate clay is subtracted from 

measured total clay to arrive at a valid number for the silicate 

(i.e., noncarbonate) clay fraction, and the ratio is recalculated. 

Literature Cited

Burt, R., and Soil Survey Staff. 2014. Soil Survey 

Laboratory Methods Manual. Soil Survey Investigations Report 

42, Version 5.0. U.S. Department of Agriculture, Natural 

Resources Conservation Service, National Soil Survey Center.

Honna, T., S. Yamamoto, and K. Matsui. 1988. A Simple 

Procedure to Determine Melanic Index That Is Useful for 

Differentiating Melanic from Fulvic Andisols. Pedol. 32:69-78.

Karathanasis, A.D., and W.G. Harris. 1994. Quantitative 

Thermal Analysis of Soil Minerals. In J.E. Amonette and L.W. 

Zelany (eds.), Quantitative Methods in Soil Mineralogy. SSSA 

Misc. Pub., pp. 360-411. Soil Sci. Soc. Am., Madison, WI.

Soil Survey Division Staff. 1993. Soil Survey Manual. 

Soil Conservation Service. U.S. Department of Agriculture 

Handbook 18.

Soil Survey Staff. 1999. Soil Taxonomy: A Basic System of 

Soil Classification for Making and Interpreting Soil Surveys. 

2nd edition. Natural Resources Conservation Service. U.S. 

Department of Agriculture Handbook 436.

Soil Survey Staff. 2009. Soil Survey Field and Laboratory 

Methods Manual. Soil Survey Investigations Report No. 51, 

Version 1.0. R. Burt (ed.). U.S. Department of Agriculture, 

Natural Resources Conservation Service.

Soil Survey Staff. 2011. Soil Survey Laboratory Information 

Manual. Soil Survey Investigations Report No. 45, Version 

2.0. R. Burt (ed.). U.S. Department of Agriculture, Natural 

Resources Conservation Service. (Available online.)

Walkley, A. 1935. An Examination of Methods for 

Determining Organic Carbon and Nitrogen in Soils. J. Agr. Sci. 

25:598-609.

Wilson, M.A., S.A. Shahid, M.A. Abdelfattah, J.A. 

Kelley, and J.E. Thomas. 2013. Anhydrite Formation on 

the Coastal Sabkha of Abu Dhabi, United Arab Emirates. 

In Shahid, S.A., F.K. Taha, and M.A. Abdelfattah (eds.), 

Advances in Soil Classification, Land Use Planning and Policy 

Implications—Innovative Thinking of Resource Inventory for 

Sustainable Use and Management of Land Resources, Chapter 

8, pp. 123-140. Springer SBM Publishing, The Netherlands.
Appendix 351

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 texture classes

353

Index

A

A horizons. See Horizons and layers.

Abrupt textural change..............................................................17

Acraquox.................................................................................257

Acroperox ...............................................................................258

Acrotorrox...............................................................................262

Acrudox...................................................................................263

Acrustox..................................................................................267

Agric horizon ............................................................................11

Alaquods.................................................................................273

Albaqualfs.................................................................................44

Albaquults...............................................................................284

Albic horizon ............................................................................11

Albic materials..........................................................................17

Albolls.....................................................................................212

Alfisols......................................................................................43

Alorthods.................................................................................278

Andic soil properties.................................................................17

Andisols....................................................................................87

Anhydritic horizon....................................................................11

Anhydrous conditions...............................................................18

Anhyorthels.............................................................................159

Anhyturbels.............................................................................163

Aniso class..............................................................................318

Anthric saturation. See Aquic conditions.

Anthropic epipedon.....................................................................7

Anthropogenic landforms and microfeatures............................32

Aqualfs......................................................................................43

Aquands ....................................................................................87

Aquents...................................................................................136

Aquepts...................................................................................173

Aquerts....................................................................................305

Aquic conditions.......................................................................26

Redoximorphic features........................................................26

Reduced matrix .................................................................27

Redox concentrations........................................................27

Redox depletions...............................................................27

Reduction ..............................................................................26

Saturation ..............................................................................26

Anthric saturation (anthraquic conditions) .......................26

Endosaturation ..................................................................26

Episaturation .....................................................................26

Aquic moisture regime. See Soil moisture regimes.

Aquicambids...........................................................................119

Aquisalids ...............................................................................132

Aquiturbels..............................................................................163

Aquods....................................................................................273

Aquolls....................................................................................213

Aquorthels...............................................................................159

Aquox......................................................................................257

Aquults....................................................................................283

Argialbolls...............................................................................212

Argiaquolls..............................................................................213

Argicryids................................................................................123

Argicryolls ..............................................................................217

Argids......................................................................................107

Argidurids...............................................................................126

Argigypsids.............................................................................129

Argillic horizon.........................................................................11

Argiorthels ..............................................................................160

Argiudolls................................................................................222

Argiustolls...............................................................................231

Argixerolls ..............................................................................247

Aridic moisture regime. See Soil moisture regimes.

Aridisols..................................................................................107

Artifacts.....................................................................................33

Artificial drainage. See Aquic conditions.

B

B horizons. See Horizons and layers.

Bottom tier................................................................................26

Buried soils.................................................................................2

C

C horizons or layers. See Horizons and layers.

Calcareous and reaction classes of mineral soils....................328

Calciaquerts.............................................................................306

Calciaquolls.............................................................................213

Calciargids ..............................................................................107

Calcic horizon ...........................................................................12

Calcicryepts.............................................................................180

Calcicryids ..............................................................................123

Calcicryolls.............................................................................218

Calcids.....................................................................................116

Calcigypsids............................................................................130

Calcitorrerts.............................................................................309

Calciudolls..............................................................................225

Calciustepts.............................................................................195
354 Keys to Soil Taxonomy

Calciusterts..............................................................................312

Calciustolls..............................................................................234

Calcixerepts.............................................................................203

Calcixererts.............................................................................315

Calcixerolls.............................................................................249

Cambic horizon.........................................................................12

Cambids..................................................................................118

Caret symbol in horizon designations.....................................341

Cation-exchange activity classes for mineral soils.................327

Chemical analyses...................................................................344

Ion exchange and extractable cations .................................344

Soil pH ................................................................................346

Sulfur and extractable anions..............................................346

Carbonates and calcium sulfates.........................................346

Soluble salts........................................................................347

Selective dissolutions..........................................................347

Coatings (classes) on sands.....................................................330

Coefficient of linear extensibility (COLE) ...............................19

Control section of Histosols and Histels...................................25

Coprogenous earth. See Limnic materials.

Cryalfs.......................................................................................52

Cryands.....................................................................................90

Cryaqualfs.................................................................................45

Cryaquands ...............................................................................88

Cryaquents ..............................................................................136

Cryaquepts ..............................................................................174

Cryaquods...............................................................................274

Cryaquolls...............................................................................214

Cryepts....................................................................................180

Cryerts.....................................................................................309

Cryic temperature regime. See Soil temperature regimes.

Cryids......................................................................................122

Cryods.....................................................................................275

Cryofibrists..............................................................................167

Cryofluvents............................................................................139

Cryofolists...............................................................................169

Cryohemists............................................................................169

Cryolls.....................................................................................217

Cryopsamments.......................................................................150

Cryorthents..............................................................................145

Cryosaprists.............................................................................170

Cryoturbation ............................................................................27

Cryrendolls..............................................................................221

D

Densic contact...........................................................................27

Densic materials........................................................................28

Diagnostic subsurface horizons ................................................11

Diagnostic surface horizons........................................................7

Diatomaceous earth. See Limnic materials.

Discontinuities in horizon designations..................................340

Duraqualfs.................................................................................45

Duraquands...............................................................................88

Duraquerts...............................................................................306

Duraquods...............................................................................274

Duraquolls...............................................................................214

Duricryands...............................................................................91

Duricryods...............................................................................275

Duricryolls ..............................................................................219

Durids......................................................................................126

Durihumods.............................................................................278

Durinodes..................................................................................19

Duripan .....................................................................................13

Duritorrands..............................................................................95

Durixeralfs ................................................................................80

Durixerepts..............................................................................204

Durixererts ..............................................................................315

Durixerolls ..............................................................................249

Durorthods ..............................................................................279

Durudands.................................................................................96

Durudepts................................................................................187

Durustalfs..................................................................................68

Durustands ..............................................................................102

Durustepts...............................................................................197

Durustolls................................................................................236

Dystraquerts............................................................................306

Dystrocryepts..........................................................................180

Dystrogelepts ..........................................................................185

Dystroxerepts..........................................................................204

Dystrudepts.............................................................................188

Dystruderts..............................................................................311

Dystrustepts.............................................................................197

Dystrusterts.............................................................................312

E

E horizons. See Horizons and layers.

Endoaqualfs...............................................................................45

Endoaquands.............................................................................88

Endoaquents............................................................................136

Endoaquepts............................................................................175

Endoaquerts.............................................................................307

Endoaquods.............................................................................274

Endoaquolls.............................................................................214

Endoaquults.............................................................................284

Endosaturation. See Aquic conditions.

Entisols....................................................................................135

Epiaqualfs .................................................................................47

Epiaquands................................................................................89

Epiaquents...............................................................................137

Epiaquepts...............................................................................176

Epiaquerts ...............................................................................307

Epiaquods................................................................................275

Epiaquolls ...............................................................................216

Epiaquults ...............................................................................284

Epipedon .....................................................................................7

Episaturation. See Aquic conditions.
Index 355

Eutraquox................................................................................257

Eutroperox...............................................................................259

Eutrotorrox..............................................................................262

Eutrudepts...............................................................................190

Eutrudox..................................................................................264

Eutrustox.................................................................................268

F

Family differentiae for mineral soils.......................................317

Family differentiae for organic soils.......................................331

Ferrihumic soil material..........................................................332

Ferrudalfs..................................................................................57

Fibers. See Organic soil materials.

Fibric soil materials. See Organic soil materials.

Fibristels..................................................................................157

Fibrists.....................................................................................167

Fluvaquents.............................................................................137

Fluvents...................................................................................139

Fluviwassents..........................................................................154

Folistels...................................................................................158

Folistic epipedon.........................................................................8

Folists......................................................................................168

Fragiaqualfs...............................................................................49

Fragiaquepts............................................................................177

Fragiaquods.............................................................................275

Fragiaquults.............................................................................285

Fragic soil properties.................................................................19

Fragihumods ...........................................................................278

Fragiorthods............................................................................279

Fragipan ....................................................................................13

Fragiudalfs ................................................................................57

Fragiudepts..............................................................................193

Fragiudults..............................................................................291

Fragixeralfs...............................................................................80

Fragixerepts.............................................................................206

Fraglossudalfs...........................................................................57

Frasiwassents ..........................................................................154

Frasiwassists ...........................................................................171

Free carbonates .........................................................................19

Frigid temperature regime. See Soil temperature regimes.

Fulvicryands..............................................................................91

Fulvudands................................................................................96

G

Gelands .....................................................................................94

Gelaquands................................................................................89

Gelaquents...............................................................................138

Gelaquepts...............................................................................177

Gelepts ....................................................................................185

Gelic materials..........................................................................28

Gelic temperature regime. See Soil temperature regimes.

Gelifluvents.............................................................................140

Gelisols ...................................................................................157

Gelods.....................................................................................277

Gelolls.....................................................................................221

Gelorthents..............................................................................145

Glacic layer...............................................................................28

Glacistels.................................................................................158

Glossaqualfs..............................................................................49

Glossic horizon .........................................................................13

Glossocryalfs.............................................................................52

Glossudalfs................................................................................58

Gypsiargids.............................................................................109

Gypsic horizon..........................................................................13

Gypsicryids.............................................................................124

Gypsids ...................................................................................129

Gypsitorrerts ...........................................................................310

Gypsiusterts.............................................................................313

H

Halaquepts...............................................................................178

Haplaquox...............................................................................258

Haplargids...............................................................................110

Haplocalcids............................................................................116

Haplocambids .........................................................................119

Haplocryalfs..............................................................................53

Haplocryands ............................................................................92

Haplocryepts...........................................................................182

Haplocryerts............................................................................309

Haplocryids.............................................................................124

Haplocryods............................................................................276

Haplocryolls............................................................................219

Haplodurids.............................................................................127

Haplofibrists............................................................................168

Haplogelepts ...........................................................................186

Haplogelods ............................................................................277

Haplogelolls............................................................................221

Haplogypsids...........................................................................130

Haplohemists...........................................................................169

Haplohumods..........................................................................278

Haplohumults..........................................................................287

Haploperox..............................................................................260

Haplorthels..............................................................................160

Haplorthods.............................................................................280

Haplosalids..............................................................................133

Haplosaprists...........................................................................171

Haplotorrands............................................................................95

Haplotorrerts...........................................................................310

Haplotorrox.............................................................................262

Haploturbels............................................................................163

Haplowassents.........................................................................155

Haplowassists..........................................................................172

Haploxeralfs..............................................................................81

Haploxerands ..........................................................................105

Haploxerepts...........................................................................206

Haploxererts............................................................................316

Haploxerolls............................................................................251

Haploxerults............................................................................302
356 Keys to Soil Taxonomy

Hapludalfs.................................................................................59

Hapludands ...............................................................................97

Hapluderts...............................................................................311

Hapludolls...............................................................................226

Hapludox.................................................................................265

Hapludults...............................................................................291

Haplustalfs ................................................................................68

Haplustands.............................................................................102

Haplustepts..............................................................................198

Haplusterts ..............................................................................313

Haplustolls..............................................................................236

Haplustox ................................................................................269

Haplustults..............................................................................299

Haprendolls.............................................................................222

Hemic soil materials. See Organic soil materials.

Hemistels.................................................................................158

Hemists ...................................................................................169

Histels .....................................................................................157

Histic epipedon ...........................................................................8

Historthels...............................................................................160

Histosols..................................................................................167

Histoturbels.............................................................................164

Horizons and layers.................................................................335

A horizons...........................................................................335

B horizons...........................................................................336

C horizons or layers............................................................336

E horizons ...........................................................................335

L horizons or layers.............................................................335

M layers ..............................................................................336

O horizons or layers............................................................335

R layers ...............................................................................336

W layers..............................................................................336

Human-altered and human-transported material classes

for mineral soils ..................................................................323

Human-altered material ............................................................33

Human-transported material .....................................................34

Humaquepts ............................................................................178

Humicryepts............................................................................184

Humicryerts.............................................................................309

Humicryods.............................................................................276

Humigelepts............................................................................186

Humigelods.............................................................................277

Humilluvic material ..................................................................24

Humixerepts............................................................................208

Humods...................................................................................277

Humudepts..............................................................................193

Humults...................................................................................287

Humustepts .............................................................................202

Hydraquents............................................................................138

Hydrocryands............................................................................93

Hydrowassents........................................................................155

Hydrudands...............................................................................99

Hyperthermic temperature regime. See Soil temperature 

regimes.

I

Identifiable secondary carbonates.............................................19

Inceptisols...............................................................................173

Interfingering of albic materials................................................19

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.............................................................................50

Kandiaquults...........................................................................285

Kandic horizon..........................................................................14

Kandihumults..........................................................................288

Kandiperox..............................................................................261

Kandiudalfs...............................................................................63

Kandiudox...............................................................................266

Kandiudults.............................................................................293

Kandiustalfs ..............................................................................71

Kandiustox ..............................................................................270

Kandiustults............................................................................299

Kanhaplaquults .......................................................................286

Kanhaplohumults....................................................................289

Kanhapludalfs...........................................................................64

Kanhapludults.........................................................................295

Kanhaplustalfs...........................................................................73

Kanhaplustults.........................................................................300

Key to soil orders......................................................................38

L

L horizons or layers. See Horizons and layers.

Laboratory methods for soil taxonomy...................................343

Lamellae....................................................................................20

Limnic materials (kinds)...........................................................24

Coprogenous earth ................................................................25

Diatomaceous earth...............................................................25

Marl.......................................................................................25

Linear extensibility (LE)...........................................................20

Lithic contact ............................................................................28

Lithologic discontinuities..........................................................20

Luvihemists.............................................................................170

M

M layers. See Horizons and layers.

Manufactured layer...................................................................35

Manufactured layer contact.......................................................35

Marl. See Limnic materials.

Melanaquands...........................................................................89

Melanic epipedon........................................................................8

Melanocryands..........................................................................93

Melanoxerands........................................................................106

Melanudands...........................................................................100
Index 357

Mesic temperature regime. See Soil temperature regimes.

Mineral analyses .....................................................................348

Mineral soil material...................................................................3

Mineral soil surface.....................................................................4

Mineral soils................................................................................4

Mineralogy classes for mineral soils.......................................325

Mineralogy classes for organic soils.......................................332

Mollic epipedon ..........................................................................9

Mollisols .................................................................................211

Molliturbels.............................................................................164

Mollorthels..............................................................................161

N

n value.......................................................................................21

Natralbolls...............................................................................213

Natraqualfs................................................................................51

Natraquerts..............................................................................308

Natraquolls..............................................................................217

Natrargids................................................................................112

Natric horizon ...........................................................................14

Natricryolls .............................................................................220

Natridurids ..............................................................................128

Natrigypsids............................................................................131

Natrixeralfs ...............................................................................83

Natrixerolls .............................................................................255

Natrudalfs..................................................................................64

Natrudolls................................................................................228

Natrustalfs.................................................................................73

Natrustolls...............................................................................242

Normal years.............................................................................29

O

O horizons or layers. See Horizons and layers.

Ochric epipedon..........................................................................9

Organic analyses.....................................................................348

Organic soil material...................................................................3

Organic soil materials (kinds) ................................................. 23

Fibers.....................................................................................23

Fibric soil materials...............................................................24

Hemic soil materials .............................................................24

Sapric soil materials..............................................................24

Organic soils ...............................................................................4

Orthels.....................................................................................158

Orthents...................................................................................145

Other information useful in classifying soils..........................349

Orthods....................................................................................278

Ortstein......................................................................................15

Oxic horizon..............................................................................15

Oxisols....................................................................................257

P

Paleaquults..............................................................................286

Paleargids................................................................................114

Palecryalfs.................................................................................55

Palecryolls...............................................................................220

Palehumults.............................................................................289

Paleudalfs..................................................................................65

Paleudolls................................................................................229

Paleudults................................................................................296

Paleustalfs.................................................................................76

Paleustolls...............................................................................244

Paleustults...............................................................................301

Palexeralfs.................................................................................83

Palexerolls...............................................................................255

Palexerults...............................................................................303

Paralithic contact.......................................................................28

Paralithic materials....................................................................28

Pararock fragments .................................................................317

Particle-size classes and their substitutes for mineral soils ....317

Particle-size classes for organic soils......................................331

Permafrost.................................................................................28

Permanent cracks (classes) in mineral soils............................331

Peraquic moisture regime. See Soil moisture regimes.

Perox .......................................................................................258

Perudic moisture regime. See Soil moisture regimes.

Petraquepts..............................................................................179

Petroargids ..............................................................................115

Petrocalcic horizon....................................................................16

Petrocalcids.............................................................................118

Petrocambids...........................................................................122

Petrocryids ..............................................................................125

Petroferric contact.....................................................................21

Petrogypsic horizon ..................................................................16

Petrogypsids............................................................................132

Physical analyses ....................................................................343

Placaquands...............................................................................90

Placaquods ..............................................................................275

Placic horizon............................................................................16

Placocryods.............................................................................277

Placohumods...........................................................................278

Placorthods..............................................................................281

Placudands ..............................................................................102

Plaggen epipedon......................................................................10

Plinthaqualfs .............................................................................51

Plinthaquox .............................................................................258

Plinthaquults ...........................................................................287

Plinthite.....................................................................................22

Plinthohumults........................................................................290

Plinthoxeralfs............................................................................84

Plinthudults.............................................................................298

Plinthustalfs...............................................................................79

Plinthustults.............................................................................302

Prime symbol in horizon designations....................................341

Psammaquents.........................................................................138

Psamments..............................................................................150

Psammorthels..........................................................................162
358 Keys to Soil Taxonomy

Psammoturbels........................................................................164

Psammowassents.....................................................................155

Q

Quartzipsamments...................................................................151

R

R layers. See Horizons and layers.

Ratio, 1500 kPa water to clay .................................................349

Ratio, CEC to clay ..................................................................349

Reaction classes for organic soils...........................................332

Redoximorphic features. See Aquic conditions.

Reduction. See Aquic conditions.

Rendolls..................................................................................221

Resistant minerals.....................................................................22

Rhodoxeralfs.............................................................................85

Rhodudalfs................................................................................67

Rhodudults..............................................................................298

Rhodustalfs ...............................................................................79

Rhodustults .............................................................................302

Rock fragments.......................................................................317

Rock structure .............................................................................7

Root-limiting layers................................................................319

Rounding...................................................................................37

Rupture-resistance classes for mineral soils...........................330

S

Salaquerts................................................................................308

Salic horizon .............................................................................16

Salicryids.................................................................................126

Salids.......................................................................................132

Salitorrerts...............................................................................310

Salusterts.................................................................................314

Sample horizon and layer sequences ......................................341

Sapric soil materials. See Organic soil materials.

Sapristels.................................................................................158

Saprists....................................................................................170

Saturation. See Aquic conditions.

Series control section ..............................................................333

Series differentiae within a family..........................................333

Slickensides...............................................................................22

Soil .............................................................................................1

Soil color, water state criteria ...................................................37

Soil depth classes for Histosols...............................................333

Soil depth classes for mineral soils and Histels......................330

Soil moisture regimes ...............................................................28

Aquic.....................................................................................29

Aridic and torric....................................................................30

Peraquic.................................................................................30

Perudic ..................................................................................30

Udic.......................................................................................30

Ustic ......................................................................................30

Xeric......................................................................................30

Soil surface..................................................................................4

Soil temperature classes for mineral soils...............................329

Soil temperature classes for organic soils...............................333

Soil temperature regimes ..........................................................31

Cryic......................................................................................31

Frigid.....................................................................................31

Gelic......................................................................................31

Hyperthermic ........................................................................31

Isofrigid.................................................................................31

Isohyperthermic ....................................................................31

Isomesic ................................................................................31

Isothermic .............................................................................31

Mesic.....................................................................................31

Thermic .................................................................................31

Sombric horizon........................................................................16

Sombrihumults........................................................................290

Sombriperox............................................................................262

Sombriudox.............................................................................267

Sombriustox ............................................................................271

Sphagnofibrists........................................................................168

Spodic horizon ..........................................................................17

Spodic materials........................................................................22

Spodosols................................................................................273

Strongly contrasting particle-size classes ...............................318

Subgroups for human-altered and human-transported soils .....35

Subsurface tier ..........................................................................25

Suffix symbols in horizon designations..................................337

Conventions for using letter suffixes ..................................339

Sulfaquents..............................................................................139

Sulfaquepts..............................................................................179

Sulfaquerts ..............................................................................309

Sulfidic materials ......................................................................31

Sulfihemists.............................................................................170

Sulfisaprists.............................................................................171

Sulfiwassents...........................................................................156

Sulfiwassists............................................................................172

Sulfohemists............................................................................170

Sulfosaprists............................................................................171

Sulfudepts ...............................................................................195

Sulfuric horizon ........................................................................32

Surface mantle of new soil material............................................2

Surface tier................................................................................25

T

Thermic temperature regime. See Soil temperature regimes.

Torrands ....................................................................................94

Torrerts....................................................................................309

Torric moisture regime. See Soil moisture regimes.

Torrifluvents............................................................................140

Torrifolists...............................................................................169

Torriorthents............................................................................145

Torripsamments.......................................................................152

Torrox......................................................................................262

Transitional and combination horizons...................................336

Turbels ....................................................................................162
Index 359

U

Udalfs........................................................................................56

Udands ......................................................................................95

Udepts.....................................................................................187

Uderts......................................................................................310

Udic moisture regime. See Soil moisture regimes.

Udifluvents..............................................................................141

Udifolists.................................................................................169

Udipsamments.........................................................................152

Udivitrands..............................................................................104

Udolls......................................................................................222

Udorthents...............................................................................147

Udox........................................................................................263

Udults......................................................................................290

Ultisols....................................................................................283

Umbraquults............................................................................287

Umbric epipedon.......................................................................10

Umbriturbels...........................................................................165

Umbrorthels ............................................................................162

Ustalfs.......................................................................................67

Ustands....................................................................................102

Ustepts.....................................................................................195

Usterts.....................................................................................311

Ustic moisture regime. See Soil moisture regimes.

Ustifluvents.............................................................................142

Ustifolists................................................................................169

Ustipsamments........................................................................153

Ustivitrands.............................................................................104

Ustolls.....................................................................................230

Ustorthents..............................................................................147

Ustox.......................................................................................267

Ustults.....................................................................................298

V

Vermaqualfs ..............................................................................52

Vermaquepts............................................................................179

Vermudolls..............................................................................230

Vermustolls .............................................................................246

Vertical subdivision in horizon designations ..........................340

Vertisols...................................................................................305

Vitrands...................................................................................103

Vitraquands...............................................................................90

Vitricryands...............................................................................93

Vitrigelands...............................................................................94

Vitritorrands..............................................................................95

Vitrixerands.............................................................................106

Volcanic glass............................................................................23

W

W layers. See Horizons and layers.

Wassents..................................................................................154

Wassists...................................................................................171

Weatherable minerals................................................................23

X

Xeralfs.......................................................................................79

Xerands...................................................................................105

Xerepts....................................................................................203

Xererts.....................................................................................315

Xeric moisture regime. See Soil moisture regimes.

Xerofluvents............................................................................144

Xerolls.....................................................................................246

Xeropsamments.......................................................................153

Xerorthents..............................................................................149

Xerults.....................................................................................302
360

The Soils That We Classify

Differentiae for Mineral Soils and Organic Soils

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

 S

 O

 I

 D

 I

 F

 D

 I

 A

 I

 D

 E

 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

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 P

 O

 U

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1

Chapter 8, page 147

The subgroup “Anthropic Udorthents” is added with the code 

LEFD. Codes for other subgroups are adjusted accordingly.

Delete: 

LEFD. Other Udorthents that have 50 cm or more of humantransported material.

Anthroportic Udorthents

LEFE. 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) particles 2.0 mm or 

larger in diameter, 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

LEFF. 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

LEFG. 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

LEFH. 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

LEFI. Other Udorthents.

Typic Udorthents

Insert:

LEFD. Other Udorthents that have an anthropic epipedon.

Anthropic Udorthents

LEFE. Other Udorthents that have 50 cm or more of humantransported material.

Anthroportic Udorthents

LEFF. 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) particles 2.0 mm or 

larger in diameter, 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

LEFG. 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

LEFH. 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:

Errata for Keys to Soil Taxonomy, 12th edition
2 Errata for Keys to Soil Taxonomy, 12th edition

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Udorthents

LEFI. 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

LEFJ. Other Udorthents.

Typic Udorthents

Chapter 18, Page 335

The paragraphs describing A horizons are reverted to 

the paragraphs from the 11th edition of the “Keys to Soil 

Taxonomy.”

Delete:

A horizons: Mineral horizons that have formed at the soil 

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

or much of any original rock structure* and show one or more 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);

2. Properties resulting from cultivation, pasturing, or 

similar kinds of disturbance; or

3. A morphology that is distinct from the underlying E, B, 

or C horizon, resulting from processes related to the surface.

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 regions with 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 horizon, although the 

mineral fraction is unaltered or only slightly altered by the 

weathering of minerals considered to be weatherable (defined in

chapter 3). Such a horizon is designated as an A horizon because 

it is at the soil surface. Recent alluvial or eolian deposits that 

retain most of the original rock structure are not considered to 

have A horizons unless they are cultivated.

Insert:

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 structure* 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.

Issued May 15, 2014