United States

Department of Agriculture

Keys to

Soil Taxonomy

Eleventh Edition, 2010

Keys to Soil Taxonomy

By Soil Survey Staff

United States Department of Agriculture

Natural Resources Conservation Service

Eleventh Edition, 2010
ii	

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs

and activities on the basis of race, color, national origin, age, disability, and where applicable,

sex, marital status, familial status, parental status, religion, sexual orientation, genetic

information, political beliefs, reprisal, or because all or a part of an individual’s income is

derived from any public assistance program. (Not all prohibited bases apply to all programs.)

Persons with disabilities who require alternative means for communication of program

information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center

at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA,

Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-

9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity

provider and employer.

Cover: Profile of a Lamellic Quartzipsamment. Because of coatings of iron oxide, the part of the profile 

directly below the surface horizon is reddish. Lamellae of loamy sand, mostly less than 0.5 centimeter thick, 

are common in the lower part of the profile. The scale is in 15-centimeter increments. Photo by John Kelley, 

Soil Scientist (retired), Raleigh, North Carolina.
iii

Table of Contents

Foreword .....................................................................................................................................v

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.....................5

Chapter 4: Identification of the Taxonomic Class of a Soil ..................................................31

Chapter 5: Alfisols ................................................................................................................35

Chapter 6: Andisols...............................................................................................................77

Chapter 7: Aridisols..............................................................................................................97

Chapter 8: Entisols..............................................................................................................123

Chapter 9: Gelisols..............................................................................................................145

Chapter 10: Histosols............................................................................................................155

Chapter 11: Inceptisols..........................................................................................................161

Chapter 12: Mollisols............................................................................................................197

Chapter 13: Oxisols...............................................................................................................241

Chapter 14: Spodosols ..........................................................................................................257

Chapter 15: Ultisols ..............................................................................................................267

Chapter 16: Vertisols.............................................................................................................287

Chapter 17: Family and Series Differentiae and Names.......................................................299

Chapter 18: Designations for Horizons and Layers..............................................................315

Appendix ................................................................................................................................323

Index ......................................................................................................................................331
 
v

Foreword

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

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

also acquaints users of the taxonomic system with recent changes in the system. The eleventh 

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

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

Interpreting Soil Surveys (1999). One of the most significant changes in the eleventh edition 

is the addition of the suborders Wassents and Wassists for subaqueous Entisols and Histosols. 

We plan to continue issuing updated editions of the Keys to Soil Taxonomy as changes warrant 

new editions.

Since it was first published 35 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 the 

taxonomic system. The authors encourage the continued use of soil taxonomy internationally 

and look forward to future collaborations with the international soil science community so we 

can continue to make improvements. Through continued communication and collaboration, 

we hope that our efforts will eventually result in a truly universal soil classification system. 

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.

Micheal L. Golden

Director, Soil Survey Division

Natural Resources Conservation Service

1

S

O

I

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. 

This definition is expanded from the 1975 version of Soil 

Taxonomy to include soils in areas of Antarctica where 

pedogenesis occurs but where the climate is too harsh to support 

the higher plant forms. 

The upper limit of soil is the boundary between soil and 

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

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

the surface is permanently covered by water too deep (typically 

more than 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 purposes of classification, the lower boundary of soil 

is arbitrarily set at 200 cm. In soils where either biological 

activity or current pedogenic processes extend to depths greater 

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

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

cemented bedrocks (paralithic materials, defined later) have 

been described and used to differentiate soil series (series 

control section, defined later), even though the paralithic 

materials below a paralithic contact are not considered soil in 

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

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

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

management goals, layers deeper than the lower boundary of 

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

they affect the content and movement of water and air or other 

interpretative concerns.

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

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

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

gleyed soil material may begin a few centimeters below the 

surface and, in some areas, continue down for several meters 

apparently unchanged with increasing depth. The latter 

condition can arise through the gradual filling of a wet basin 

in which the A horizon is gradually added to the surface and 

becomes gleyed beneath. Finally, the A horizon rests on a thick 

mass of gleyed material that may be relatively uniform. In both 

of these situations, there is no alternative but to set the lower 

limit of soil at the arbitrary limit of 200 cm. 

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

horizons, although the presence or absence of horizons and their 

nature are of extreme importance in soil classification. Plants 

can be grown under glass in pots filled with earthy materials, 

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

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

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

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

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

nonsoil. 

Soil has many properties that fluctuate with the seasons. It 

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

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

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

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

The Soils That We Classify

CHAPTER 1
2 

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

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

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

perspective.

Buried Soils

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

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

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

thickness of the named diagnostic horizons that are preserved 

in the buried soil. A surface mantle of new material that does 

not have the required thickness for buried soils can be used to 

establish a phase of the mantled soil or even another soil series 

if the mantle affects the use of the soil.

Any horizons or layers underlying a plaggen epipedon are 

considered to be buried.

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

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

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

has no other diagnostic subsurface horizons, all defined later. 

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

the requirements for all diagnostic horizons, as defined later, 

overlying a horizon sequence that can be clearly identified as 

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

recognition of a surface mantle should not be based only on 

studies of associated soils.
3

D

I

F

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 short-rangeorder 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 surface of 

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

CHAPTER 2

Differentiae for Mineral Soils1 and Organic Soils

1Mineral soils include all soils except the suborder Histels and the order Histosols.
4 

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

Thus, any O horizon at the surface is considered an organic 

horizon if it meets the requirements of organic soil material 

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

organic horizons to determine the total thickness of organic 

soil materials. Plant materials at the soil surface must be at 

least slightly decomposed if they are to be considered part of 

an O horizon. Undecomposed plant litter is excluded from the 

concept of O horizons.

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 voids2 that are filled with 10 percent or less 

organic materials and directly below these materials have 

either a densic, lithic, or paralithic contact; or

b. When added with underlying cindery, fragmental, or 

pumiceous materials, total more than 10 cm between the soil 

surface and a depth of 50 cm; or

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

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

thickness of more than 10 cm; or

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

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

organic materials with an upper boundary within 40 cm of 

the soil surface, have a total thickness of either:

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

volume consists of moss fibers or if their bulk density, 

moist, is less than 0.1 g/cm3; or

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

hemic materials, or of fibric materials with less than 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 interstices2 and directly below these materials 

have a densic, lithic, or paralithic contact; or

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

pumiceous materials, total 40 cm or more between the soil 

surface and a depth of 50 cm; or

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

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

no mineral horizons or have mineral horizons with a total 

thickness of 10 cm or less; or

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

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

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

thickness of either:

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

volume consists of moss fibers or if their bulk density, 

moist, is less than 0.1 g/cm3; or

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

hemic materials, or of fibric materials with less than threefourths (by volume) moss fibers and a bulk density, moist, 

of 0.1 g/cm3 or more; or

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

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

paralithic contact, whichever is shallowest.

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

(Histosol 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.

2Materials 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.
5

D

I

A

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.

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

Required Characteristics

The anthropic epipedon consists of mineral soil material that 

shows some evidence of disturbance by human activity. 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, the anthropic epipedon 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 colors with a value of 3 or less, moist, and 

of 5 or less, dry; and

CHAPTER 3

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

(2) Dominant colors 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 value and 

chroma of 3 or less, moist; or

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

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

5 or less; and

4. An organic-carbon content of:

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

moist, of 4 or 5; or

b. 0.6 percent more (absolute) 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 4-a or 4-b above; and

5. 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.

6. One or both of the following:

a. Has a phosphate content of 1,500 or more milligrams per 

kilogram by citric-acid extraction; and

(1) The phosphorus content decreases regularly with 

increasing depth below the epipedon; and

(2) Phosphorus is not in the form of nodules; or 

b. All parts of the epipedon are moist for less than 90 days 

(cumulative) in normal years during times when the soil 

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

is not irrigated; and

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

Folistic Epipedon

Required Characteristics

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

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

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

1. Consists of organic soil material that:

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

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

moist, of less than 0.1; or

b. Is 15 cm or more thick; or

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

an organic-carbon content (by weight) of:

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

percent or more clay; or

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

clay; or

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

the mineral fraction contains less than 60 percent clay.

Most folistic epipedons consist of organic soil material 

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

that is an Ap horizon consisting of mineral soil material.

Histic Epipedon

Required Characteristics

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

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

and reduction for some time during normal years (or is 

artificially drained) and either:

1. Consists of organic soil material that:

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

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

moist, of less than 0.1; or

b. Is 20 to 40 cm thick; or
Horizons and Characteristics Diagnostic for the Higher Categories 7

D

I

A

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

an organic-carbon content (by weight) of:

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

percent or more clay; or

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

clay; or

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

the mineral fraction contains less than 60 percent clay.

Most histic epipedons consist of organic soil material 

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

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

epipedon consisting of mineral soil material can also be part of 

a mollic or umbric epipedon.

Melanic Epipedon

Required Characteristics

The melanic epipedon has both of the following:

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

mineral soil surface or the upper boundary of an organic 

layer with andic soil properties (defined below), whichever is 

shallower; and

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

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

a. Andic soil properties throughout; and

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

and a melanic index of 1.70 or less throughout; and

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

and 4 percent or more organic carbon in all layers.

Mollic Epipedon

Required Characteristics

The mollic epipedon consists of mineral soil materials and, 

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 colors with a value of 3 or less, moist, and 

of 5 or less, dry; and

(2) Dominant colors 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, moist, of 

5 or less; and

4. A base saturation (by NH4OAc) 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, 

moist, of 4 or 5; 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
8 Keys to Soil Taxonomy

(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. Phosphate:

a. Content less than 1,500 milligrams per kilogram by 

citric-acid extraction; or

b. Content decreasing irregularly with increasing depth 

below the epipedon; or

c. Nodules are within the epipedon; and

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

(cumulative) in normal years during times when the soil 

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

not irrigated; and

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

Ochric Epipedon

The ochric epipedon fails to meet the definitions for any of 

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

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

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

massive and hard or harder when dry. Many ochric epipedons 

have either a color value of 4 or more, moist, and 6 or more, dry, 

or chroma of 4 or more, or they include an A or Ap horizon that 

has both low color values and low chroma but is too thin to be 

recognized as a mollic or umbric epipedon (and has less than 15 

percent calcium carbonate equivalent in the fine-earth fraction). 

Ochric epipedons also include horizons of organic materials 

that are too thin to meet the requirements for a histic or folistic 

epipedon.

The ochric epipedon includes eluvial horizons that are at 

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

diagnostic illuvial horizon (defined below as an argillic, 

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

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

horizon) and there is no surface horizon that is appreciably 

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

lower boundary of the plow layer or an equivalent depth (18 cm) 

in a soil that has not been plowed. Actually, the same horizon 

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

of the cambic horizon; the ochric epipedon and the subsurface 

diagnostic horizons are not all mutually exclusive. The ochric 

epipedon does not have rock structure and does not include 

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

directly overlying such deposits.

Plaggen Epipedon

The plaggen epipedon is a human-made surface layer 50 

cm or more thick that has been produced by long-continued 

manuring.

A plaggen epipedon can be identified by several means. 

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

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

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

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

spade marks throughout its depth and also remnants of thin 

stratified beds of sand that were probably produced on the soil 

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

map unit delineation of soils with plaggen epipedons would tend 

to have straight-sided rectangular bodies that are higher than the 

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

plaggen epipedon.

Required Characteristics

The plaggen epipedon consists of mineral soil materials and 

has the following:

1. Locally raised land surfaces; and one or both of the 

following:

a. Artifacts; or

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

2. Colors with a value of 4 or less, moist, 5 or less, dry, and 

chroma of 2 or less; and

3. An organic-carbon content of 0.6 percent or more; and

4. A thickness of 50 cm or more; and

5. Some part of the epipedon that is moist for 90 days or 

more (cumulative) in normal years during times when the soil 

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

not irrigated.

Umbric Epipedon

Required Characteristics

The umbric epipedon consists of mineral soil materials 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 colors with a value of 3 or less, moist, and of 

5 or less, dry; and

b. Dominant colors with chroma of 3 or less, moist; and
Horizons and Characteristics Diagnostic for the Higher Categories 9

D

I

A

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

(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. Phosphate:

a. Content less than 1,500 milligrams per kilogram by 

citric-acid extraction; or

b. Content decreasing irregularly with increasing depth 

below the epipedon; or

c. Nodules are within the epipedon; and

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

(cumulative) in normal years during times when the soil 

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

not irrigated; and

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

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

marks, and raised surfaces that are characteristic of the plaggen 

epipedon.

Diagnostic Subsurface Horizons

The horizons described in this section form below the 

surface of the soil, although in some areas they form directly 

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

by truncation of the soil. Some of these horizons are generally 

regarded as B horizons, some are considered B horizons by 

many but not all pedologists, and others are generally regarded 

as parts of the A horizon.

Agric Horizon

The agric horizon is an illuvial horizon that has formed 

under cultivation and contains significant amounts of illuvial 

silt, clay, and humus. 

Required Characteristics

The agric horizon is directly below an Ap horizon and has 

the following properties:

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

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

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

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

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

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

less and chroma of 2 or less.

Albic Horizon

The albic horizon is an eluvial horizon, 1.0 cm or more 

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

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

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

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

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.
10 Keys to Soil Taxonomy

Argillic Horizon

An argillic horizon is normally a subsurface horizon with a 

significantly higher percentage of phyllosilicate clay than the 

overlying soil material. It shows evidence of clay illuviation. 

The argillic horizon forms below the soil surface, but it may be 

exposed at the surface later by erosion.

Required Characteristics

1. All argillic horizons must meet both of the following 

requirements:

a. One of the following:

(1) If the argillic horizon 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) CaCO3 equivalent (see 

below), and its CaCO3 equivalent is 5 percent or more 

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

b. 15 percent or more (by weight) CaCO3 equivalent 

and 5 percent or more (by volume) identifiable secondary 

carbonates; or

c. 5 percent or more (by weight) 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; and

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

secondary carbonates or a calcium carbonate equivalent 

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

than that of an underlying horizon; 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.
Horizons and Characteristics Diagnostic for the Higher Categories 11

D

I

A

Required Characteristics

The cambic horizon is an altered horizon 15 cm or more 

thick. If it is composed of lamellae, the combined thickness of 

the lamellae must be 15 cm or more. In addition, the cambic 

horizon must meet all of the following:

1. Has a texture 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 chroma of 0; or

(b) Value of 4 or more and chroma of 1 or less; or

(c) Any value, chroma of 2 or less, and redox 

concentrations; or

b. Does not have the combination of aquic conditions 

within 50 cm of the soil surface or artificial drainage and 

colors, moist, as defined in item 2-a-(3) above, and has soil 

structure or the absence of rock structure, 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, or spodic horizon; 

and

4. Is not part of an Ap horizon and does not have a brittle 

manner of failure in more than 60 percent of the matrix.

Duripan

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

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

which clay and free iron oxides are removed. 

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).
12 Keys to Soil Taxonomy

Gypsic Horizon

The gypsic horizon is a horizon in which gypsum has 

accumulated or been transformed to a significant extent. It 

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, increasing with depth within a vertical distance of 

15 cm or less, is either:

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

surface horizon if that horizon has less than 20 percent 

total clay in the fine-earth fraction; or

(2) 20 percent or more (relative) higher than that in the 

surface horizon if that horizon has 20 to 40 percent total 

clay in the fine-earth fraction; or

(3) 8 percent or more (absolute) higher than that in the 

surface horizon if that horizon has more than 40 percent 

total clay in the fine-earth fraction; and

b. At a depth:

(1) Between 100 cm and 200 cm from the mineral soil 

surface if the upper 100 cm meets the criteria for a sandy 

or sandy-skeletal particle-size class throughout; or

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

the clay content in the fine-earth fraction of the surface 

horizon is 20 percent or more; or

(3) Within 125 cm from the mineral soil surface for all 

other soils; and

3. Has a thickness of either:

a. 30 cm or more; or

b. 15 cm or more if there is a densic, lithic, paralithic, or 

petroferric contact within 50 cm of the mineral soil surface 

and the kandic horizon constitutes 60 percent or more of the 

vertical distance between a depth of 18 cm and the contact; 

and

4. Has a texture 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 one-
Horizons and Characteristics Diagnostic for the Higher Categories 13

D

I

A

tenth 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

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 exchange acidity (at pH 8.2) in one or more 

horizons within 40 cm of its upper boundary if the ESP is 15 

or more (or the SAR is 13 or more) in one or more horizons 

within 200 cm of the mineral soil surface.

Ortstein

Required Characteristics

Ortstein has all of the following:

1. Consists of spodic materials; and

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

3. Is 25 mm or more thick.

Oxic Horizon

Required Characteristics

The oxic horizon is a subsurface horizon that does not 

have andic soil properties (defined below) and has all of the 

following characteristics:

1. A thickness of 30 cm or more; and

2. A texture class of sandy loam or finer in the fine-earth 

fraction; and

3. Less than 10 percent weatherable minerals in the 50- to 

200-micron fraction; and

4. Rock structure in less than 5 percent of its volume, unless 

the lithorelicts with weatherable minerals are coated with 

sesquioxides; and

5. A diffuse upper boundary, i.e., within a vertical distance

of 15 cm, a clay increase with increasing depth of:

a. Less than 4 percent (absolute) in its fine-earth fraction 

if the fine-earth fraction of the surface horizon contains less 

than 20 percent clay; or

b. Less than 20 percent (relative) in its fine-earth fraction if 

the fine-earth fraction of the surface horizon contains 20 to 

40 percent clay; or

c. Less than 8 percent (absolute) in its fine-earth fraction 

if the fine-earth fraction of the surface horizon contains 40 

percent or more clay); and

6. An apparent CEC of 16 cmol(+) or less per kg clay (by 1N 

NH4OAc pH 7) and an apparent ECEC of 12 cmol(+) or less per 

kg clay (sum of bases extracted with 1N NH4OAc pH 7 plus 1N 

KCl-extractable Al). (The percentage of clay is either measured 

by the pipette method or estimated to be 3 times [percent water 

retained at 1500 kPa tension minus percent organic carbon], 

whichever value is higher, but no more than 100.)
14 Keys to Soil Taxonomy

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 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 horizon (Gr. base of plax, flat stone; meaning a 

thin cemented pan) is a thin, black to dark reddish pan that is 

cemented by iron (or iron and manganese) and organic matter. 

Required Characteristics

A placic horizon must meet the following requirements:

1. The horizon is cemented or indurated with iron or iron and 

manganese and organic matter, with or without other cementing 

agents; and

2. Because of lateral continuity, roots can penetrate only along 

vertical fractures with a horizontal spacing of 10 cm or more; 

and

3. The horizon has a minimum thickness of 1 mm and, where 

associated with spodic materials, is less than 25 mm thick.

Salic Horizon

A salic horizon is a horizon of accumulation of salts that are 

more soluble than gypsum in cold water. 

Required Characteristics

A salic horizon is 15 cm or more thick and has, for 90 

consecutive days or more in normal years:

1. An electrical conductivity (EC) equal to or greater than 30 

dS/m in the water extracted from a saturated paste; and

2. A product of the EC, in dS/m, and thickness, in cm, equal to 

900 or more.

Sombric Horizon

A sombric horizon (F. sombre, dark) is a subsurface horizon 

in mineral soils that has formed under free drainage. It contains 

illuvial humus that is neither associated with aluminum, as is 

the humus in the spodic horizon, nor dispersed by sodium, as 

is common in the natric horizon. Consequently, the sombric 

horizon does not have the high cation-exchange capacity in its 

clay that characterizes a spodic horizon and does not have the 

high base saturation of a natric horizon. It does not underlie an 

albic horizon.

Sombric horizons are thought to be restricted to the cool, 

moist soils of high plateaus and mountains in tropical or 

subtropical regions. Because of strong leaching, their base 

saturation is low (less than 50 percent by NH4OAc).

The sombric horizon has a lower color value or chroma, 

or both, than the overlying horizon and commonly contains 

more organic matter. It may have formed in an argillic, cambic, 

or oxic horizon. If peds are present, the dark colors are most 

pronounced on surfaces of peds.

In the field a sombric horizon is easily mistaken for a buried 

A horizon. It can be distinguished from some buried epipedons 

by lateral tracing. In thin sections the organic matter of a 

sombric horizon appears more concentrated on peds and in 

pores than uniformly dispersed throughout the matrix.

Spodic Horizon

A spodic horizon is an illuvial layer with 85 percent or more 

spodic materials (defined below).
Horizons and Characteristics Diagnostic for the Higher Categories 15

D

I

A

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 ochric epipedon or an albic horizon 

and an argillic horizon. It is characterized by a considerable 

increase in clay content within a very short vertical distance in 

the zone of contact. If the clay content in the fine-earth fraction 

of the ochric epipedon or albic horizon is less than 20 percent, 

it doubles within a vertical distance of 7.5 cm or less. If the 

clay content in the fine-earth fraction of the ochric epipedon or 

the albic horizon is 20 percent or more, there is an increase of 

20 percent or more (absolute) within a vertical distance of 7.5 

cm or less (e.g., an increase from 22 to 42 percent) and the clay 

content in some part of the argillic horizon is 2 times or more 

the amount contained in the overlying horizon.

Normally, there is no transitional horizon between an 

ochric epipedon or an albic horizon and an argillic horizon, 

or the transitional horizon is too thin to be sampled. Some 

soils, however, have a glossic horizon or interfingering of 

albic materials (defined below) in parts of the argillic horizon. 

The upper boundary of such a horizon is irregular or even 

discontinuous. Sampling this mixture as a single horizon might 

create the impression of a relatively thick transitional horizon, 

whereas the thickness of the actual transition at the contact may 

be no more than 1 mm.

Albic Materials

Albic (L. albus, white) materials are soil materials with a 

color that is largely determined by the color of primary sand 

and silt particles rather than by the color of their coatings. 

This definition implies that clay and/or free iron oxides have 

been removed from the materials or that the oxides have been 

segregated to such an extent that the color of the materials is 

largely determined by the color of the primary particles.

Required Characteristics

Albic materials have one of the following colors:

1. Chroma of 2 or less; and either

a. A color value, moist, of 3 and a color value, dry, of 6 or 

more; or

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

of 5 or more; or

2. Chroma of 3 or less; and either

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

b. A color value, dry, of 7 or more; or

3. Chroma that is controlled by the color of uncoated grains of 

silt or sand, hue of 5YR or redder, and the color values listed in 

item 1-a or 1-b above.

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 

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 
16 Keys to Soil Taxonomy

(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 + 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 + 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 + 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 conditions (Gr. anydros, waterless) 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 oC 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-cemented 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 oC; or

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.

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 17

D

I

A

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 

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.
18 Keys to Soil Taxonomy

Required Characteristics

Interfingering of albic materials is recognized if albic 

materials:

1. Penetrate 5 cm or more into an underlying argillic or natric 

horizon; and

2. Are 2 mm or more thick between vertical faces of abutting 

peds; and

3. Constitute less than 15 percent (by volume) of the layer that 

they penetrate.

Lamellae

A lamella is an illuvial horizon less than 7.5 cm thick. Each 

lamella contains an accumulation of oriented silicate clay on 

or bridging sand and silt grains (and rock fragments if any are 

present). A lamella has more silicate clay than the overlying 

eluvial horizon.

Required Characteristics

A lamella is an illuvial horizon less than 7.5 cm thick formed 

in unconsolidated regolith more than 50 cm thick. Each lamella 

contains an accumulation of oriented silicate clay on or bridging 

the sand and silt grains (and 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.

Lithologic Discontinuities

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

lithology within a soil. A lithologic discontinuity can also 

denote an age difference. For information on using horizon 

designations for lithologic discontinuities, see the Soil Survey 

Manual (USDA, SCS, 1993).

Not everyone agrees on the degree of change required for 

a lithologic discontinuity. No attempt is made to quantify 

lithologic discontinuities. The discussion below is meant to 

serve as a guideline.

Several lines of field evidence can be used to evaluate 

lithologic discontinuities. In addition to mineralogical and 

textural differences that may require laboratory studies, certain 

observations can be made in the field. These include but are not 

limited to the following:

1. Abrupt textural contacts.—An abrupt change in 

particle-size distribution, which is not solely a change in clay 

content resulting from pedogenesis, can often be observed.

2. Contrasting sand sizes.—Significant changes in sand 

size can be detected. For 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 

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.
Horizons and Characteristics Diagnostic for the Higher Categories 19

D

I

A

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 Fe2O3). 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.

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 
20 Keys to Soil Taxonomy

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 hydroxy-aluminum 

interlayered 2:1 minerals (Burt, 2004).

Slickensides

Slickensides are polished and grooved surfaces and generally 

have dimensions exceeding 5 cm. They are produced when 

one soil mass slides past another. Some slickensides occur 

at the lower boundary of a slip surface where a mass of soil 

moves downward on a relatively steep slope. Slickensides result 

directly from the swelling of clay minerals and shear failure. 

They are very common in swelling clays that undergo marked 

changes in moisture content.

Spodic Materials

Spodic materials form in an illuvial horizon that normally 

underlies a histic, ochric, or umbric epipedon or an albic 

horizon. In most undisturbed areas, spodic materials underlie an 

albic horizon. They may occur within an umbric epipedon or an 

Ap horizon.

A horizon consisting of spodic materials normally has an 

optical-density-of-oxalate-extract (ODOE) value of 0.25 or 

more, and that value is commonly at least 2 times as high as the 

ODOE value in an overlying eluvial horizon. This increase in 

ODOE value indicates an accumulation of translocated organic 

materials in an illuvial horizon. Soils with spodic materials 

show evidence that organic materials and aluminum, with or 

without iron, have been moved from an eluvial horizon to an 

illuvial horizon.

Definition of Spodic Materials

Spodic materials are mineral soil materials that do not 

have all of the properties of an argillic or kandic horizon; are 

dominated by active amorphous materials that are illuvial and 

are composed of organic matter and aluminum, with or without 

iron; and have both of the following:

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

2. One or both of the following:

a. An overlying albic horizon that extends horizontally 

through 50 percent or more of each pedon and, directly 

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

sample), as follows:

(1) Hue of 5YR or redder; or

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

of 4 or less; or

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

chroma of 2 or less; or

(4) A color of 10YR 3/1; or
Horizons and Characteristics Diagnostic for the Higher Categories 21

D

I

A

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

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

chroma of 5 or 6 (crushed and smoothed sample), and one or 

more of the following morphological or chemical properties:

(1) Cementation by organic matter and aluminum, with 

or without iron, in 50 percent or more of each pedon 

and a very firm or firmer rupture-resistance class in the 

cemented part; or

(2) 10 percent or more cracked coatings on sand grains; 

or

(3) Al + 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 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, gypsum, and halite are not considered weatherable 

minerals because they are mobile in the soil. They 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

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

which they are derived; and

3. Either are 2 cm or less in their smallest dimension or 

are decomposed enough to be crushed and shredded with the 

fingers.

Pieces of wood that are larger than 2 cm in cross section and 

are so undecomposed that they cannot be crushed and shredded 

with the fingers, such as large branches, logs, and stumps, 

are not considered fibers but are considered coarse fragments 

(comparable to gravel, stones, and boulders in mineral soils).

Fibric Soil Materials

Fibric soil materials are organic soil materials that either:

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

rubbing, excluding coarse fragments; or

2. Contain two-fifths or more (by volume) fibers after rubbing, 

excluding coarse fragments, and yield color values and chromas 
22 Keys to Soil Taxonomy

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 soil materials (Gr. hemi, half; implying intermediate 

decomposition) are intermediate in their degree of 

decomposition between the less decomposed fibric and more 

decomposed sapric materials. Their morphological features give 

intermediate values for fiber content, bulk density, and water 

content. Hemic soil materials are partly altered both physically 

and biochemically. 

Sapric Soil Materials

Sapric soil materials (Gr. sapros, rotten) are the most highly 

decomposed of the three kinds of organic soil materials. They 

have the smallest amount of plant fiber, the highest bulk density, 

and the lowest water content on a dry-weight basis at saturation. 

Sapric soil materials are commonly very dark gray to black. 

They are relatively stable; i.e., they change very little physically 

and chemically with time in comparison to other organic soil 

materials. 

Sapric materials have the following characteristics:

1. The fiber content, after rubbing, is less than one-sixth (by 

volume), excluding coarse fragments; and

2. The color of the sodium-pyrophosphate extract on white 

chromatographic or filter paper is below or to the right of a 

line drawn to exclude blocks 5/1, 6/2, and 7/3 (fig. 2). If few 

or no fibers can be detected and the color of the pyrophosphate 

extract is to the left of or above this line, the possibility that the 

material is limnic must be considered.

Humilluvic Material

Humilluvic material, i.e., illuvial humus, accumulates in the 

lower parts of some organic soils that are acid and have been 

drained and cultivated. The humilluvic material has a C14 age 

that is not older than the overlying organic materials. It has very 

high solubility in sodium pyrophosphate and rewets very slowly 

after drying. Most commonly, it accumulates near a contact with 

a sandy mineral horizon.

To be recognized as a differentia in classification, the 

humilluvic material must constitute one-half or more (by 

volume) of a layer 2 cm or more thick.

Limnic Materials

The presence or absence of limnic deposits is taken into 

account in the higher categories of Histosols but not Histels. 

The nature of such deposits is considered in the lower categories 

of Histosols. Limnic materials include both organic and 

inorganic materials that were either (1) deposited in water 

by precipitation or through the action of aquatic organisms, 

such as algae or diatoms, or (2) derived from underwater and 

floating aquatic plants and subsequently modified by aquatic 

animals. They include coprogenous earth (sedimentary peat), 

diatomaceous earth, and marl.

Coprogenous Earth

A layer of coprogenous earth (sedimentary peat) is a limnic 

layer that:

1. Contains many fecal pellets with diameters between a few 

hundredths and a few tenths of a millimeter; and

2. Has a color value, moist, of 4 or less; and

3. Either forms a slightly viscous water suspension and is 

nonplastic or slightly plastic but not sticky, or shrinks upon 

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 

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

sapric materials.
Horizons and Characteristics Diagnostic for the Higher Categories 23

D

I

A

on white chromatographic or filter paper that has a color value 

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

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

Diatomaceous Earth

A layer of diatomaceous earth is a limnic layer that:

1. If not previously dried, has a matrix color value of 3, 4, 

or 5, which changes irreversibly on drying as a result of the 

irreversible shrinkage of organic-matter coatings on diatoms 

(identifiable by microscopic, 440 X, examination of dry 

samples); and

2. Either yields a saturated sodium-pyrophosphate extract 

on white chromatographic or filter paper that has a color value 

of 8 or more and chroma of 2 or less or has a cation-exchange 

capacity of less than 240 cmol(+) per kg organic matter 

(measured by loss on ignition), or both.

Marl

A layer of marl is a limnic layer that:

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

2. Reacts with dilute HCl to evolve CO2.

The color of marl usually does not change irreversibly on 

drying because a layer of marl contains too little organic matter, 

even before it has been shrunk by drying, to coat the carbonate 

particles. 

Thickness of Organic Soil Materials 

(Control Section of Histosols and 

Histels)

The thickness of organic materials over limnic materials, 

mineral materials, water, or permafrost is used to define the 

Histosols and Histels.

For practical reasons, an arbitrary control section has been 

established for the classification of Histosols and Histels. 

Depending on the kinds of soil material in the surface 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. Layers of water, which may be 

between a few centimeters and many meters thick in these 

soils, are considered to be the lower boundary of the control 

section only if the water extends below a depth of 130 or 

160 cm, respectively. A densic, lithic, or paralithic contact, if 

shallower than 130 or 160 cm, constitutes the lower boundary of 

the control section. In some soils the lower boundary is 25 cm 

below the upper limit of permafrost. An unconsolidated mineral 

substratum shallower than those limits does not change the 

lower boundary of the control section.

The control section of Histosols and Histels is divided 

somewhat arbitrarily into three tiers—surface, subsurface, and 

bottom tiers.

Surface Tier

The surface tier of a Histosol or Histel extends from the soil 

surface to a depth of 60 cm if either (1) the materials within that 

depth are fibric and three-fourths or more of the fiber volume 

is derived from Sphagnum or other mosses or (2) the materials 

have a bulk density of less than 0.1. Otherwise, the surface tier 

extends from the soil surface to a depth of 30 cm.

Some organic soils have a mineral surface layer less than 40 

cm thick as a result of flooding, volcanic eruptions, additions of 

mineral materials to increase soil strength or reduce the hazard 

of frost, or other causes. If such a mineral layer is less than 30 

cm thick, it constitutes the upper part of the surface tier; if it is 

30 to 40 cm thick, it constitutes the whole surface tier and part 

of the subsurface tier.

Subsurface Tier

The subsurface tier is normally 60 cm thick. If the control 

section ends at a shallower depth (at a densic, lithic, or 

paralithic contact or a water layer or in permafrost), however, 

the subsurface tier extends from the lower boundary of the 

surface tier to the lower boundary of the control section. It 

includes any unconsolidated mineral layers that may be present 

within those depths.

Bottom Tier

The bottom tier is 40 cm thick unless the control section has 

its lower boundary at a shallower depth (at a densic, lithic, or 

paralithic contact or a water layer or in permafrost).

Thus, if the organic materials are thick, there are two 

possible thicknesses of the control section, depending on the 

presence or absence and the thickness of a surface mantle of 

fibric moss or other organic material that has a low bulk density 

(less than 0.1). If the fibric moss extends to a depth of 60 cm 

and is the dominant material within this depth (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.
24 Keys to Soil Taxonomy

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 well 

sealed piezometers or tensiometers is therefore recommended 

for measuring saturation. Problems may still occur, however, 

if water runs into piezometer slits near the bottom of the 

piezometer hole or if tensiometers with slowly reacting 

manometers are used. The first problem can be overcome by 

using piezometers with smaller slits and the second by using 

transducer tensiometry, which reacts faster than manometers. 

Soils are considered wet if they have pressure heads greater 

than -1 kPa. Only macropores, such as cracks between peds 

or channels, are then filled with air, while the soil matrix is 

usually still saturated. Obviously, exact measurements of the wet 

state can be obtained only with tensiometers. For operational 

purposes, the use of piezometers is recommended as a standard 

method.

The duration of saturation required for creating aquic 

conditions varies, depending on the soil environment, and is not 

specified.

Three types of saturation are defined:

a. Endosaturation.—The soil is saturated with water in all 

layers from the upper boundary of saturation to a depth of 

200 cm or more from the mineral soil surface.

b. Episaturation.—The soil is saturated with water in one 

or more layers within 200 cm of the mineral soil surface 

and also has one or more unsaturated layers, with an upper 

boundary above a depth of 200 cm, below the saturated layer. 

The zone of saturation, i.e., the water table, is perched on top 

of a relatively impermeable layer.

c. Anthric saturation.—This term refers to a special kind 

of aquic conditions that 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, moist, of 4 

or more and chroma of 2 or less in macropores; or

(b) Redox concentrations of iron; or

(c) 2 times or more the amount of iron (by dithionite 

citrate) contained in the tilled surface layer.

2. The degree of reduction in a soil can be characterized by the 

direct measurement of redox potentials. Direct measurements 

should take into account chemical equilibria as expressed by 

stability diagrams in standard soil textbooks. Reduction and 

oxidation processes are also a function of soil pH. Obtaining 

accurate measurements of the degree of reduction in a soil is 

difficult. In the context of this taxonomy, however, only a degree 

of reduction that results in reduced iron is considered, because it 

produces the visible redoximorphic features that are identified in 

the keys. A simple field test is available to determine if reduced 

iron ions are present. A freshly broken surface of a field-wet 

soil sample is treated with alpha,alpha-dipyridyl in neutral, 

1N ammonium-acetate solution. The appearance of a strong 

red color on the freshly broken surface indicates the presence 

of reduced iron ions. A positive reaction to the alpha,alphadipyridyl field test for ferrous iron (Childs, 1981) may be 

used to confirm the existence of reducing conditions and is 

especially useful in situations where, despite saturation, normal 

morphological indicators of such conditions are either absent 

or obscured (as by the dark colors characteristic of melanic 

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

reducing conditions are always absent. It may only mean that the 

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

test or that the soil is in an oxidized phase at the time of testing. 

Use of alpha,alpha-dipyridyl in a 10 percent acetic-acid solution 

is not recommended because the acid is likely to change soil 

conditions, for example, by dissolving CaCO3.

The duration of reduction required for creating aquic 

conditions is not specified.

3. Redoximorphic features associated with wetness result 

from alternating periods of reduction and oxidation of iron and 

manganese compounds in the soil. Reduction occurs during 

saturation with water, and oxidation occurs when the soil is not 
Horizons and Characteristics Diagnostic for the Higher Categories 25

D

I

A

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 contact (L. densus, thick) is a contact between soil 

and densic materials (defined below). It has no cracks, or the 

spacing of cracks that roots can enter is 10 cm or more.

Densic Materials

Densic materials are relatively unaltered materials (do 

not meet the requirements for any other named diagnostic 

horizons or any other diagnostic soil characteristic) that have 

a noncemented rupture-resistance class. The bulk density 

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

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

mudflows, and some mechanically compacted materials, for 

example, mine spoils. Some noncemented rocks can be densic 

materials if they are dense or resistant enough to keep roots 

from entering, except in cracks.

Densic materials are noncemented and thus differ from 

paralithic materials and the material below a lithic contact, both 

of which are cemented.

Densic materials have, at their upper boundary, a densic 

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

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

to differentiate soil series if the materials are within the series 

control section. 

Gelic Materials

Gelic materials are mineral or organic soil materials that 

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

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

upper part of the permafrost. Cryoturbation is manifested by 

irregular and broken horizons, involutions, accumulation of 

organic matter on top of and within the permafrost, oriented 

rock fragments, and silt-enriched layers. The characteristic 

structures associated with gelic materials include platy, blocky, 
26 Keys to Soil Taxonomy

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 cemented by ice 

or, in the case of insufficient interstitial water, may be dry. The 

frozen layer has a variety of ice lenses, vein ice, segregated ice 

crystals, and ice wedges. The permafrost table is in dynamic 

equilibrium with the environment.

Soil Moisture Regimes

The term “soil moisture regime” refers to the presence or 

absence either of ground water or of water held at a tension 

of less than 1500 kPa in the soil or in specific horizons during 

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

more is not available to keep most mesophytic plants alive. The 

availability of water is also affected by dissolved salts. If a soil 

is saturated with water that is too salty to be available to most 

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

horizon is considered dry when the moisture tension is 1500 

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

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

be continuously moist in some or all horizons either throughout 

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

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

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 
Horizons and Characteristics Diagnostic for the Higher Categories 27

D

I

A

were used in the 1975 edition of Soil Taxonomy (USDA, SCS, 

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 oC); 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 oC in 

this taxonomy. In some of the very cold regions of the world, 

however, biological activity occurs at temperatures below 5 oC.

Very commonly, the level of ground water fluctuates with 

the seasons; it is highest in the rainy season or in fall, winter, or 

spring if cold weather virtually stops evapotranspiration. There 

are soils, however, in which the ground water is always at or 

very close to the surface. Examples are soils in tidal marshes 

or in closed, landlocked depressions fed by perennial streams. 

Such soils are considered to have a peraquic 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).
28 Keys to Soil Taxonomy

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 oC.

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 oC or higher or if 

the mean summer and winter soil temperatures differ by less 

than 6 oC at a depth of 50 cm below the soil surface, the soil 

moisture control section in areas of the ustic 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 

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; meaning 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
Horizons and Characteristics Diagnostic for the Higher Categories 29

D

I

A

(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 oC; 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 could 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 low categories. 

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 oC 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 oC 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. 

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 
30

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 horizon (L. sulfur) 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 Sbearing 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).

Literature Cited

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

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

Burt, R., ed. 2004. Soil Survey Laboratory Methods Manual. 

Soil Survey Investigations Report 42, Version 4.0. United States 

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.

Pons, L.J., and I.S. Zonneveld. 1965. Soil Ripening and Soil 

Classification. Initial Soil Formation in Alluvial Deposits and a 

Classification of the Resulting Soils. Int. Inst. Land Reclam. and 

Impr. Pub. 13. Wageningen, The Netherlands.

United States Department of Agriculture, Soil Conservation 

Service. 1975. Soil Taxonomy: A Basic System of Soil 

Classification for Making and Interpreting Soil Surveys. Soil 

Surv. Staff. U.S. Dep. Agric. Handb. 436. 

United States Department of Agriculture, Soil Conservation 

Service. 1993. Soil Survey Manual. Soil Surv. Div. Staff. U.S. 

Dep. Agric. Handb. 18.
31

I

D

E

The taxonomic class of a specific soil can be determined 

by using the keys that follow in this and other chapters. It 

is assumed that the reader is familiar with the definitions of 

diagnostic horizons and properties that are given in chapters 

2 and 3 of this publication and with the meanings of the terms 

used for describing soils given in the Soil Survey Manual. The 

Index at the back of this publication indicates the pages on 

which definitions of terms are given.

Standard rounding conventions should be used to determine 

numerical values.

Soil colors (hue, value, and chroma) are used in many of the 

criteria that follow. Soil colors typically change value and some 

change hue and chroma, depending on the water state. In many 

of the criteria of the keys, the water state is specified. If no water 

state is specified, the soil is considered to meet the criterion if it 

does so when moist or dry or both moist and dry.

All of the keys in this taxonomy are designed in such a way 

that the user can determine the correct classification of a soil 

by going through the keys systematically. The user must start 

at the beginning of the “Key to Soil Orders” and eliminate, one 

by one, all classes that include criteria that do not fit the soil in 

question. The soil belongs to the first class listed for which it 

meets all the required criteria.

In classifying a specific soil, the user of soil taxonomy begins 

by checking through the “Key to Soil Orders” to determine 

the name of the first order that, according to the criteria listed, 

includes the soil in question. The next step is to go to the page 

indicated to find the “Key to Suborders” of that particular order. 

Then the user systematically goes through the key to identify 

the suborder that includes the soil, i.e., the first in the list for 

which it meets all the required criteria. The same procedure is 

used to find the great group class of the soil in the “Key to Great 

Groups” of the identified suborder. Likewise, going through the 

“Key to Subgroups” of that great group, the user selects as the 

correct subgroup name the name of the first taxon for which the 

soil meets all of the required criteria.

The family level is determined, in a similar manner, after 

the subgroup has been determined. Chapter 17 can be used, 

as one would use other keys in this taxonomy, to determine 

which components are part of the family. The family, however, 

typically has more than one component, and therefore the entire 

chapter must be used. The keys to control sections for classes 

used as components of a family must be used to determine the 

control section before use of the keys to classes.

The descriptions and definitions of individual soil series are 

not included in this text. Definitions of the series and of the 

control section are given in chapter 17. 

In the “Key to Soil Orders” and the other keys that follow, 

the diagnostic horizons and the properties mentioned do not 

include those below any densic, lithic, paralithic, or petroferric 

contact. The properties of buried soils and the properties of a 

surface mantle are considered on the basis of whether or not 

the soil meets the meaning of the term “buried soil” given in 

chapter 1.

If a soil has a surface mantle and is not a buried soil, the top 

of the original surface layer is considered the “soil surface” for 

determining depth to and thickness of diagnostic horizons and 

most other diagnostic soil characteristics. The only properties 

of the surface mantle that are considered are soil temperature, 

soil moisture (including aquic conditions), 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 ThaptoHistic subgroups. Most other diagnostic soil characteristics 

of the buried soil are not considered, but organic carbon if of 

Holocene age, andic soil properties, base saturation, and all 

properties used to determine family and series placement are 

considered.

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. 145

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 

CHAPTER 4

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

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

shallower; and

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

following:

a. Overlie cindery, fragmental, or pumiceous materials 

and/or fill their interstices1 and directly below these 

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

b. When added with the underlying cindery, fragmental, 

or pumiceous materials, total 40 cm or more between the 

soil surface and a depth of 50 cm; or

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

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

no mineral horizons or have mineral horizons with a total 

thickness of 10 cm or less; or

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

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

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

total thickness of either:

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

volume consists of moss fibers or if their bulk density, 

moist, is less than 0.1 g/cm3; or

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

or hemic materials, or of fibric materials with less 

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

density, moist, of 0.1 g/cm3 or more.

Histosols, p. 155

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 particle-size class that meets the criteria for 

coarse-loamy, loamy-skeletal, or finer 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 meets the sandy 

particle-size class criteria in at least some part between 

the mineral soil surface and the spodic horizon; and

c. A lower boundary as follows:

(1) Either at a depth of 25 cm or more below the 

mineral soil surface or at the top of a duripan or 

fragipan or at a densic, lithic, paralithic, or petroferric 

contact, whichever is shallowest; or

(2) At any depth,

(a) If the spodic horizon meets the criteria for a 

coarse-loamy, loamy-skeletal, or finer particle-size 

class and the soil has a frigid temperature regime; or

(b) If the soil has a cryic 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. 257

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 

1Materials that meet the definition of cindery, fragmental, or pumiceous but have more 

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

to be organic soil materials.
Identification of the Taxonomic Class of a Soil 33

I

D

E

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

duripan, or a petrocalcic horizon.

Andisols, p. 77

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. 241

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. Cracks2 that open and close periodically.

Vertisols, p. 287

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; a calcic, gypsic, petrocalcic, petrogypsic, or salic 

horizon; or a duripan; or

d. An argillic or natric horizon; or

2. Have a salic horizon; and

a. Saturation with water in one or more layers within 

100 cm of the soil surface for 1 month or more during a 

normal year; and

b. A moisture control section that is dry in some or all 

parts at some time during normal years; and

c. No sulfuric horizon within 150 cm of the mineral soil 

surface.

Aridisols, p. 97

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 meets sandy or sandy-skeletal 

particle-size class criteria 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. 267

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, 

2A 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.
34

organic-carbon content, base saturation, and structure 

requirements of a mollic epipedon but is separated from 

the surface horizon by an albic horizon; and

2. A base saturation of 50 percent or more (by NH4OAc) 

in all horizons either between the upper boundary of any 

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

below that boundary, or between the mineral soil surface 

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

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

shallowest.

Mollisols, p. 197

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. 35

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 both of the following:

(1) A salic horizon or a histic, mollic, plaggen, or 

umbric epipedon; or

(2) In 50 percent or more of the layers between 

the mineral soil surface and a depth of 50 cm, an 

exchangeable sodium percentage of 15 or more (or 

a sodium adsorption ratio of 13 or more), which 

decreases with increasing depth below 50 cm, and also 

ground water within 100 cm of the mineral soil surface 

at some time during the year when the soil is not frozen 

in any part.

Inceptisols, p. 161

L. Other soils.

Entisols, p. 123
35

A

L

F

Key to Suborders

JA. Alfisols that have, in one or more horizons within 50 

cm of the mineral soil surface, aquic conditions (other than 

anthraquic conditions) for some time in normal years (or 

artificial drainage) and have one or both of the following:

1. Redoximorphic features in all layers between either the 

lower boundary of an Ap horizon or a depth of 25 cm below 

the mineral soil surface, whichever is deeper, and a depth of 

40 cm; and one of the following within the upper 12.5 cm of 

the argillic, natric, glossic, or kandic horizon:

a. 50 percent or more redox depletions with chroma of 

2 or less on faces of peds and redox concentrations within 

peds; or

b. Redox concentrations and 50 percent or more redox 

depletions with chroma of 2 or less in the matrix; or

c. 50 percent or more redox depletions with chroma of 1 

or less on faces of peds or in the matrix, or both; or

2. In the horizons that have aquic conditions, enough 

active ferrous iron to give a positive reaction to alpha,alphadipyridyl at a time when the soil is not being irrigated.

Aqualfs, p. 35

JB. Other Alfisols that have a cryic or isofrigid soil 

temperature regime.

Cryalfs, p. 44

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

Ustalfs, p. 59

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

Xeralfs, p. 71

JE. Other Alfisols.

Udalfs, p. 47

Aqualfs

Key to Great Groups

JAA. Aqualfs that have a cryic soil temperature regime.

Cryaqualfs, p. 37

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. 43

JAC. Other Aqualfs that have a duripan.

Duraqualfs, p. 37

JAD. Other Aqualfs that have a natric horizon.

Natraqualfs, p. 43

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

mineral soil surface.

Fragiaqualfs, p. 41

JAF. Other Aqualfs that have a kandic horizon.

Kandiaqualfs, p. 42

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. 43

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 or slower (moderately low or lower Ksat class) in the 

argillic horizon.

Albaqualfs, p. 36

JAI. Other Aqualfs that have a glossic horizon.

Glossaqualfs, p. 41

JAJ. Other Aqualfs that have episaturation.

Epiaqualfs, p. 39

JAK. Other Aqualfs.

Endoaqualfs, p. 37

CHAPTER 5

Alfisols
36 Keys to Soil Taxonomy

Albaqualfs

Key to Subgroups

JAHA. Albaqualfs that meet sandy or sandy-skeletal particlesize class criteria 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Albaqualfs

JAHH. Other Albaqualfs that have a mollic epipedon, 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 37

A

L

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Endoaqualfs

JAKB. Other Endoaqualfs that have both of the following:

1. One or both:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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:
38 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 meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria 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
Alfisols 39

A

L

F

JAKL. Other Endoaqualfs 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 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
40 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Epiaqualfs

JAJF. Other Epiaqualfs that have 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 meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria 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

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

moist and dry); or

b. Hue of 10YR or yellower and either:
Alfisols	 41

A

L

F

(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

JAIB. Other Glossaqualfs that meet sandy or sandy-skeletal

particle-size class criteria 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
42 Keys to Soil Taxonomy

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria 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:

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
Alfisols 43

A

L

F

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

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
44 Keys to Soil Taxonomy

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. 47

JBB. Other Cryalfs that have a glossic horizon.

Glossocryalfs, p. 44

JBC. Other Cryalfs.

Haplocryalfs, p. 45

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Glossocryalfs

JBBE. Other Glossocryalfs that have, in one or more 

subhorizons within the upper 25 cm of the argillic, kandic, or 

natric horizon, redox depletions with chroma of 2 or less and 

also aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Glossocryalfs

JBBF. Other Glossocryalfs that are saturated with water in 

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

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Glossocryalfs

JBBG. Other Glossocryalfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or 

more thick that has its upper boundary within 100 cm of the 

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or 

more thick.

Fragic Glossocryalfs

JBBH. Other Glossocryalfs that have 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
Alfisols 45

A

L

F

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

JBCD. Other Haplocryalfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and
46 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 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

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
Alfisols 47

A

L

F

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Palecryalfs

JBAC. Other Palecryalfs that have, in one or more horizons 

within 100 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Palecryalfs

JBAD. Other Palecryalfs that are saturated with water in one 

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

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Palecryalfs

JBAE. Other Palecryalfs that have a xeric 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 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 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

Udalfs

Key to Great Groups

JEA. Udalfs that have a natric horizon.

Natrudalfs, p. 56

JEB. Other Udalfs that have both:

1. A glossic horizon; and
48 Keys to Soil Taxonomy

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. 49

JEC. Other Udalfs that have both:

1. A glossic horizon; and

2. A fragipan within 100 cm of the mineral soil surface.

Fraglossudalfs, p. 49

JED. Other Udalfs that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiudalfs, p. 49

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. 55

JEF. Other Udalfs that have a kandic horizon.

Kanhapludalfs, p. 56

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. 57

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. 59

JEI. Other Udalfs that have a glossic horizon.

Glossudalfs, p. 49

JEJ. Other Udalfs.

Hapludalfs, p. 51
Alfisols 49

A

L

F

Ferrudalfs

Key to Subgroups

JEBA. Ferrudalfs that have, in one or more horizons within 

60 cm of the mineral soil surface, redox depletions with chroma 

of 2 or less and also aquic conditions for some time in normal 

years (or artificial drainage).

Aquic Ferrudalfs

JEBB. Other Ferrudalfs.

Typic Ferrudalfs

Fragiudalfs

Key to Subgroups

JEDA. Fragiudalfs that have, throughout one or more horizons 

with a total thickness of 18 cm or more within 75 cm of the 

mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Fragiudalfs

JEDB. Other Fragiudalfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Fragiudalfs

JEDC. Other Fragiudalfs that have, in one or more horizons 

within 40 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Fragiudalfs

JEDD. Other Fragiudalfs that are saturated with water in one 

or more layers above the fragipan in normal years for either or 

both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Fragiudalfs

JEDE. Other Fragiudalfs.

Typic Fragiudalfs

Fraglossudalfs

Key to Subgroups

JECA. Fraglossudalfs that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Fraglossudalfs

JECB. Other Fraglossudalfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Fraglossudalfs

JECC. Other Fraglossudalfs that have, in one or more 

subhorizons within the upper 25 cm of the argillic or kandic 

horizon, redox depletions with chroma of 2 or less and also 

aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Fraglossudalfs

JECD. Other Fraglossudalfs that are saturated with water in 

one or more layers above the fragipan in normal years for either 

or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Fraglossudalfs

JECE. Other Fraglossudalfs.

Typic Fraglossudalfs

Glossudalfs

Key to Subgroups

JEIA. Glossudalfs that have both:
50 Keys to Soil Taxonomy

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Glossudalfs

JEIE. Other Glossudalfs that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Glossudalfs

JEIF. Other Glossudalfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and
Alfisols 51

A

L

F

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. Meet sandy or sandy-skeletal particle-size class criteria 

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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:

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
52 Keys to Soil Taxonomy

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 

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 
Alfisols 53

A

L

F

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Hapludalfs

JEJH. Other Hapludalfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Hapludalfs

JEJI. Other Hapludalfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm 

or more thick that has its upper boundary within 100 cm 

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm 

or more thick; and

2. Redox depletions with chroma of 2 or less in layers 

that also have aquic conditions in normal years (or artificial 

drainage) either:

a. Within the upper 25 cm of the argillic horizon if 

its upper boundary is within 50 cm of the mineral soil 

surface; or

b. Within 75 cm of the mineral soil surface if the upper 

boundary of the argillic horizon is 50 cm or more below 

the mineral soil surface.

Fragiaquic Hapludalfs

JEJJ. Other Hapludalfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm 

or more thick that has its upper boundary within 100 cm 

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm 

or more thick; and

2. Saturation with water in one or more layers within 100 

cm of the mineral soil surface in normal years for either or 

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Fragic Oxyaquic Hapludalfs

JEJK. Other Hapludalfs that:

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. Meet sandy or sandy-skeletal particle-size class criteria

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. Meet sandy or sandy-skeletal particle-size class criteria 

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:

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:
54 Keys to Soil Taxonomy

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:

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
Alfisols 55

A

L

F

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 meet sandy or sandy-skeletal 

particle-size class criteria 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. Meet sandy or sandy-skeletal particle-size class criteria 

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 Kandiudalfs

JEEE. Other Kandiudalfs that:

1. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

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

mineral soil surface to the top of a kandic horizon at a depth of 

50 to 100 cm.

Arenic Kandiudalfs

JEEG. Other Kandiudalfs that meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 

mineral soil surface to the top of a kandic horizon at a depth of 

100 cm or more.

Grossarenic Kandiudalfs

JEEH. Other Kandiudalfs that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Kandiudalfs

JEEI. Other Kandiudalfs that have, in all subhorizons in the 

upper 100 cm of the kandic horizon or throughout the entire 

kandic horizon if less than 100 cm thick, more than 50 percent 

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

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

value.

Rhodic Kandiudalfs

JEEJ. Other Kandiudalfs that have a mollic epipedon, 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 100 cm of the kandic horizon or throughout the entire 

kandic horizon if less than 100 cm thick, more than 50 percent 

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

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

value.

Rhodic Kanhapludalfs

JEFE. Other Kanhapludalfs.

Typic Kanhapludalfs

Natrudalfs

Key to Subgroups

JEAA. Natrudalfs that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that are 

5 mm or more wide through a thickness of 30 cm or more 

for some time in normal years and slickensides or 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 Natrudalfs

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 
Alfisols 57

A

L

F

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Paleudalfs

JEGD. Other Paleudalfs that have 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 

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 
58 Keys to Soil Taxonomy

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. Meet sandy or sandy-skeletal particle-size class criteria 

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 

mineral soil surface to the top of an argillic horizon at a depth of 

100 cm or more.

Grossarenic Paleudalfs

JEGR. Other Paleudalfs that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Paleudalfs

JEGS. Other Paleudalfs that have either:

1. A glossic horizon; or

2. In the upper part of the argillic horizon, one or more 

subhorizons that have 5 percent or more (by volume) 

skeletans with chroma of 2 or less; or

3. 5 percent or more (by volume) albic materials in some 

subhorizon of the argillic horizon.

Glossic Paleudalfs

JEGT. Other Paleudalfs that have, in all subhorizons in the 

upper 100 cm of the argillic horizon or throughout the entire 

argillic horizon if less than 100 cm thick, more than 50 percent 

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

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

value.

Rhodic Paleudalfs

JEGU. Other Paleudalfs that have a mollic epipedon, or the 

upper 18 cm of the mineral soil meets the color requirements for 

a mollic epipedon after mixing.

Mollic Paleudalfs
Alfisols 59

A

L

F

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. 59

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. 70

JCC. Other Ustalfs that have a natric horizon.

Natrustalfs, p. 65

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. 63

JCE. Other Ustalfs that have a kandic horizon.

Kanhaplustalfs, p. 64

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 both:

a. 35 percent or more noncarbonate clay throughout one 

or more subhorizons in its upper part; and

b. At its upper boundary, a clay increase (in the fineearth fraction) of either 20 percent or more (absolute) 

within a vertical distance of 7.5 cm or of 15 percent or 

more (absolute) within a vertical distance of 2.5 cm. 

Paleustalfs, p. 67

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. 70

JCH. Other Ustalfs.

Haplustalfs, p. 60

Durustalfs

Key to Subgroups

JCAA. All Durustalfs (provisionally).

Typic Durustalfs
60 Keys to Soil Taxonomy

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 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; 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 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.

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 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 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 
Alfisols 61

A

L

F

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. Meet sandy or sandy-skeletal particle-size class criteria 

throughout a layer extending from the mineral soil surface to 

the top of an argillic horizon at a depth of 50 to 100 cm.

Aquic Arenic Haplustalfs

JCHH. Other Haplustalfs that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. An argillic horizon that has a base saturation (by sum of 

cations) of less than 75 percent throughout.

Aquultic Haplustalfs

JCHI. Other Haplustalfs that have, in one or more horizons 

within 75 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Haplustalfs

JCHJ. Other Haplustalfs that are saturated with water in one or 

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

years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplustalfs

JCHK. Other Haplustalfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Haplustalfs

JCHL. Other Haplustalfs that have an argillic horizon that 

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. Meet sandy or sandy-skeletal particle-size class criteria 

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:
62 Keys to Soil Taxonomy

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 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 meet sandy or sandy-skeletal 

particle-size class criteria 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 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.

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 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:

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:
Alfisols 63

A

L

F

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 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 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 oC.

Calcic Udic Haplustalfs

JCHU. Other Haplustalfs that have an argillic horizon with 

a base saturation (by sum of cations) of less than 75 percent 

throughout.

Ultic Haplustalfs

JCHV. Other Haplustalfs that have a calcic horizon 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 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 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 meet sandy or sandy-skeletal 

particle-size class criteria 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 

and also aquic conditions for some time in normal years (or 

artificial drainage); and

2. Meet sandy or sandy-skeletal particle-size class criteria 

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. Meet sandy or sandy-skeletal particle-size class criteria 

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
64 Keys to Soil Taxonomy

(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 meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 

mineral soil surface to the top of a kandic horizon at a depth of 

50 to 100 cm.

Arenic Kandiustalfs

JCDG. Other Kandiustalfs that, when neither irrigated nor 

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in some 

part for six-tenths or more of the cumulative days per year 

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

surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

a. Is moist in some or all parts for less than 90 

consecutive days per year when the 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 oC.

Udic Kandiustalfs

JCDI. Other Kandiustalfs that have, in all subhorizons in the 

upper 100 cm of the kandic horizon or throughout the entire 

kandic horizon if less than 100 cm thick, more than 50 percent 

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

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

value.

Rhodic Kandiustalfs

JCDJ. Other Kandiustalfs.

Typic Kandiustalfs

Kanhaplustalfs

Key to Subgroups

JCEA. Kanhaplustalfs that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Kanhaplustalfs

JCEB. Other Kanhaplustalfs that have, in one or more 

horizons within 75 cm of the mineral soil surface, redox 

depletions with chroma of 2 or less and also aquic conditions 

for some time in normal years (or artificial drainage).

Aquic Kanhaplustalfs

JCEC. Other Kanhaplustalfs that, when neither irrigated nor 

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in some 

part for six-tenths or more of the cumulative days per year 

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

surface is higher than 5 oC; or

2. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

a. Is moist in some or all parts for less than 90 

consecutive days per year when the 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 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 
Alfisols 65

A

L

F

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 100 cm of the kandic horizon or throughout the entire 

kandic horizon if less than 100 cm thick, more than 50 percent 

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

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

value.

Rhodic Kanhaplustalfs

JCEF. Other Kanhaplustalfs.

Typic Kanhaplustalfs

Natrustalfs

Key to Subgroups

JCCA. Natrustalfs that have a salic horizon within 75 cm of 

the mineral soil surface.

Salidic Natrustalfs

JCCB. Other Natrustalfs that have all of the following:

1. Visible crystals of gypsum or other salts more soluble 

than gypsum, or both, within 40 cm of the soil surface; and

2. When neither irrigated nor fallowed to store moisture, 

one of the following:

a. A frigid 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; 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 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 oC; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for six-tenths or more of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for less than 90 

consecutive days per year when the temperature at a 

depth of 50 cm below the soil surface is higher than 

8 oC; and

(2) Is dry in some part for six-tenths or more of the 

cumulative days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

5 oC; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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 
66 Keys to Soil Taxonomy

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 other salts more soluble 

than gypsum, or both, within 40 cm of the mineral soil 

surface; and

2. When neither irrigated nor fallowed to store moisture, 

one of the following:

a. A frigid 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 

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 other salts more soluble than gypsum, or both, within 40 cm 

of the mineral soil surface.

Leptic Natrustalfs

JCCL. Other Natrustalfs that have both of the following:

1. An exchangeable sodium percentage of less than 15 (or 

a sodium adsorption ratio of less than 13) in 50 percent or 

more of the natric horizon; and

2. When neither irrigated nor fallowed to store moisture, 

one of the following:
Alfisols 67

A

L

F

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 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 6 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

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 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:

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 
68 Keys to Soil Taxonomy

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 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 Paleustalfs

JCFD. Other Paleustalfs that have one or both of the 

following:

1. Cracks within 125 cm of the mineral soil surface that are 

5 mm or more wide through a thickness of 30 cm or more 

for some time in normal years and slickensides or 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. Meet sandy or sandy-skeletal particle-size class criteria 

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
Alfisols 69

A

L

F

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 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 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 oC.

Arenic Aridic Paleustalfs

JCFK. Other Paleustalfs that meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria 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 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 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 oC; and

2. A calcic horizon either within 100 cm of the mineral 

soil surface if the weighted average particle-size class of 

the upper 50 cm of the argillic horizon is sandy, or within 

60 cm if it is loamy, or within 50 cm if it is clayey, and free 

carbonates in all horizons above the calcic horizon.

Calcidic Paleustalfs
70 Keys to Soil Taxonomy

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 100 cm of the argillic horizon or throughout the entire 

argillic horizon if less than 100 cm thick, more than 50 percent 

colors that have all of the following:

1. Hue of 2.5YR or redder; and

2. Value, moist, of 3 or less; and

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

value.

Rhodic Paleustalfs

JCFS. Other Paleustalfs that have an argillic horizon with 

a base saturation (by sum of cations) of less than 75 percent 

throughout.

Ultic Paleustalfs

JCFT. Other Paleustalfs that, when neither irrigated nor 

fallowed to store moisture, have either:

1. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in some 

part for four-tenths or less of the time (cumulative) per year 

when the 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 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 oC.

Udic Rhodustalfs

JCGD. Other Rhodustalfs.

Typic Rhodustalfs
Alfisols 71

A

L

F

Xeralfs

Key to Great Groups

JDA. Xeralfs that have a duripan within 100 cm of the mineral 

soil surface.

Durixeralfs, p. 71

JDB. Other Xeralfs that have a natric horizon.

Natrixeralfs, p. 74

JDC. Other Xeralfs that have a fragipan within 100 cm of the 

mineral soil surface.

Fragixeralfs, p. 72

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. 76

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. 76

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 within 15 cm of its upper boundary both:

a. 35 percent or more noncarbonate clay; and

b. A clay increase, in the fine-earth fraction, of either

20 percent or more (absolute) within a vertical distance 

of 7.5 cm or of 15 percent or more (absolute) within a 

vertical distance of 2.5 cm.

Palexeralfs, p. 74

JDG. Other Xeralfs.

Haploxeralfs, p. 72

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 both:

a. A clayey particle-size class throughout some 

subhorizon 7.5 cm or more thick; and

b. At its upper boundary or within some part, a clay 

increase either of 20 percent or more (absolute) within 

a vertical distance of 7.5 cm or of 15 percent or more 

(absolute) within a vertical distance of 2.5 cm, in the fineearth fraction; and

2. A duripan that is strongly cemented or less cemented in 

all subhorizons.

Abruptic Haplic Durixeralfs

JDAE. Other Durixeralfs that have an argillic horizon that has 

both:
72 Keys to Soil Taxonomy

1. A clayey particle-size class throughout some subhorizon 

7.5 cm or more thick; and

2. At its upper boundary or within some part, a clay 

increase either of 20 percent or more (absolute) within 

a vertical distance of 7.5 cm or of 15 percent or more 

(absolute) within a vertical distance of 2.5 cm, in the fineearth fraction.

Abruptic Durixeralfs

JDAF. Other Durixeralfs that have a duripan that is strongly 

cemented or less cemented in all subhorizons.

Haplic Durixeralfs

JDAG. Other Durixeralfs.

Typic Durixeralfs

Fragixeralfs

Key to Subgroups

JDCA. Fragixeralfs that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Fragixeralfs

JDCB. Other Fragixeralfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Fragixeralfs

JDCC. Other Fragixeralfs that have 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

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 
Alfisols 73

A

L

F

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Haploxeralfs

JDGF. Other Haploxeralfs that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Haploxeralfs

JDGG. Other Haploxeralfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Haploxeralfs

JDGH. Other Haploxeralfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm 

or more thick that has its upper boundary within 100 cm 

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm 

or more thick; and

2. Redox depletions with chroma of 2 or less in layers 

that also have aquic conditions in normal years (or artificial 

drainage) either:

a. Within the upper 25 cm of the argillic or kandic 

horizon if its upper boundary is within 50 cm of the 

mineral soil surface; or

b. Within 75 cm of the mineral soil surface if the upper 

boundary of the argillic or kandic horizon is 50 cm or 

more below the mineral soil surface.

Fragiaquic Haploxeralfs

JDGI. Other Haploxeralfs that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. An argillic or kandic horizon that has a base saturation 

(by sum of cations) of less than 75 percent in one or more 

subhorizons within its upper 75 cm or above a densic, lithic, 

or paralithic contact, whichever is shallower.

Aquultic Haploxeralfs

JDGJ. Other Haploxeralfs that have, in one or more horizons 

within 75 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Haploxeralfs

JDGK. Other Haploxeralfs that have an exchangeable sodium 

percentage of 15 or more (or a sodium adsorption ratio of 13 

or more) in one or more subhorizons of the argillic or kandic 

horizon.

Natric Haploxeralfs

JDGL. Other Haploxeralfs that have fragic soil properties:

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
74 Keys to Soil Taxonomy

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

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) fragments coarser 
Alfisols 75

A

L

F

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Palexeralfs

JDFC. Other Palexeralfs that have, throughout one or more 

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

of the mineral soil surface, a fine-earth fraction with both a bulk 

density of 1.0 g/cm3 or less, measured at 33 kPa water retention, 

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0.

Andic Palexeralfs

JDFD. Other Palexeralfs that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Palexeralfs

JDFE. Other Palexeralfs that have both:

1. Fragic soil properties:

a. In 30 percent or more of the volume of a layer 15 cm 

or more thick that has its upper boundary within 100 cm 

of the mineral soil surface; or

b. In 60 percent or more of the volume of a layer 15 cm 

or more thick; and

2. Redox depletions with chroma of 2 or less in layers 

that also have aquic conditions in normal years (or artificial 

drainage) either:

a. Within the upper 25 cm of the argillic or kandic 

horizon if its upper boundary is within 50 cm of the 

mineral soil surface; or

b. Within 75 cm of the mineral soil surface if the upper 

boundary of the argillic or kandic horizon is 50 cm or 

more below the mineral soil surface.

Fragiaquic Palexeralfs

JDFF. Other Palexeralfs that have, in one or more horizons 

within 75 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Palexeralfs

JDFG. Other Palexeralfs that have a petrocalcic horizon 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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
76

JDFL. Other Palexeralfs that have fragic soil properties:

1. In 30 percent or more of the volume of a layer 15 cm or 

more thick that has its upper boundary within 100 cm of the 

mineral soil surface; or

2. In 60 percent or more of the volume of a layer 15 cm or 

more thick.

Fragic Palexeralfs

JDFM. Other Palexeralfs that have a calcic horizon within 150 

cm of the mineral soil surface.

Calcic Palexeralfs

JDFN. Other Palexeralfs that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Palexeralfs

JDFO. Other Palexeralfs that have an argillic or kandic 

horizon that has a base saturation (by sum of cations) of less 

than 75 percent throughout.

Ultic Palexeralfs

JDFP. Other Palexeralfs with an argillic or kandic horizon that 

has, in the fine-earth fraction, either or both:

1. Less than 35 percent clay throughout all subhorizons 

within 15 cm of its upper boundary; or

2. At its upper boundary, a clay increase of less than 20 

percent (absolute) within a vertical distance of 7.5 cm and of 

less than 15 percent (absolute) within a vertical distance of 

2.5 cm.

Haplic Palexeralfs

JDFQ. Other Palexeralfs that have a color value, moist, of 3 or 

less and 0.7 percent or more organic carbon either throughout 

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

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 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 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
77

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. 77

DB. Other Andisols that have a gelic soil temperature regime.

Gelands, p. 84

DC. Other Andisols that have a cryic soil temperature regime.

Cryands, p. 80

DD. Other Andisols that have an aridic soil moisture regime.

Torrands, p. 84

DE. Other Andisols that have a xeric soil moisture regime.

Xerands, p. 94

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. 93

DG. Other Andisols that have an ustic soil moisture regime.

Ustands, p. 92

DH. Other Andisols.

Udands, p. 85

Aquands

Key to Great Groups

DAA. Aquands that have a gelic soil temperature regime. 

Gelaquands, p. 79

DAB. Other Aquands that have a cryic soil temperature 

regime.

Cryaquands, p. 78

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. 80

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. 78

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 

CHAPTER 6

Andisols
78 Keys to Soil Taxonomy

layer with andic soil properties, whichever is shallower, and a 

densic, lithic, or paralithic contact.

Vitraquands, p. 80

DAF. Other Aquands that have a melanic epipedon.

Melanaquands, p. 79

DAG. Other Aquands that have episaturation.

Epiaquands, p. 79

DAH. Other Aquands.

Endoaquands, p. 78

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 
Andisols 79

A

N

D

throughout, underlying one or more horizons with a total 

thickness of 10 cm or more that have a color value, moist, 1 unit 

or more higher and an organic-carbon content 1 percent or more 

(absolute) lower.

Thaptic Endoaquands

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 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower.

Hydric Melanaquands
80 Keys to Soil Taxonomy

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. 81

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 
Andisols 81

A

N

D

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. 83

DCC. Other Cryands that have a melanic epipedon.

Melanocryands, p. 83

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

thickness, and organic-carbon requirements for a melanic 

epipedon.

Fulvicryands, p. 81

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. 83

DCF. Other Cryands.

Haplocryands, p. 82

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:

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 
82 Keys to Soil Taxonomy

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 

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 
Andisols 83

A

N

D

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 

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
84 Keys to Soil Taxonomy

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. 84

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. 84

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. 85

DDC. Other Torrands.

Haplotorrands, p. 85

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 
Andisols 85

A

N

D

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. 91

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. 86

DHC. Other Udands that have a melanic epipedon.

Melanudands, p. 90

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 

soil properties, whichever is shallower, and a densic, lithic, or 

paralithic contact, a duripan, or a petrocalcic horizon.

Hydrudands, p. 89

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

thickness, and organic-carbon requirements for a melanic 

epipedon.

Fulvudands, p. 86
86 Keys to Soil Taxonomy

DHF. Other Udands.

Hapludands, p. 87

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 

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 
Andisols 87

A

N

D

(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 

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 
88 Keys to Soil Taxonomy

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 

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 
Andisols 89

A

N

D

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 

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 NH4

OAc) 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 
90 Keys to Soil Taxonomy

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 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 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 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 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 
Andisols 91

A

N

D

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 

fine-earth fraction throughout one or more horizons with a 

total thickness of 15 cm or more at a depth between 25 and 75 

cm either from the mineral soil surface or from the top of an 

organic layer with andic soil properties, whichever is shallower.

Eutric Melanudands

DHCO. Other Melanudands.

Typic Melanudands

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 
92 Keys to Soil Taxonomy

more chroma of 2 or less either in redox depletions on faces 

of peds or in the matrix if peds are absent; or

3. Enough active ferrous iron to give a positive reaction 

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

irrigated.

Aquic 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. 92

DGB. Other Ustands.

Haplustands, p. 92

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 

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 NH4

OAc) plus 1N KClextractable Al3+ totaling less than 15.0 cmol(+)/kg in the 

fine-earth fraction throughout one or more horizons with a 

total thickness of 60 cm or more within 75 cm of the mineral 

soil surface or of the top of an organic layer with andic soil 

properties, whichever is shallower; and
Andisols 93

A

N

D

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. 94

DFB. Other Vitrands.

Udivitrands, p. 93

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
94 Keys to Soil Taxonomy

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 

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. 95
Andisols 95

A

N

D

DEB. Other Xerands that have a melanic epipedon.

Melanoxerands, p. 95

DEC. Other Xerands.

Haploxerands, p. 95

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

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
96

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
97

A

R

I

Key to Suborders

GA. Aridisols that have a cryic soil temperature regime.

Cryids, p. 112

GB. Other Aridisols that have a salic horizon within 100 cm of 

the soil surface.

Salids, p. 122

GC. Other Aridisols that have a duripan within 100 cm of the 

soil surface.

Durids, p. 115

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. 118

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. 97

GF. Other Aridisols that have a calcic or petrocalcic horizon 

within 100 cm of the soil surface.

Calcids, p. 105

GG. Other Aridisols.

Cambids, p. 108

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. 105

GEB. Other Argids that have a natric horizon.

Natrargids, p. 102

GEC. Other Argids that do not have a densic, lithic, or 

paralithic contact within 50 cm of the soil surface and have 

either:

1. A clay increase of 15 percent or more (absolute) within 

a vertical distance of 2.5 cm either within the argillic horizon 

or at its upper boundary; or

2. An argillic horizon that extends to 150 cm or more from 

the soil surface, that does not have a clay decrease with 

increasing depth of 20 percent or more (relative) from the 

maximum clay content, and that has, in 50 percent or more of 

the matrix in some part between 100 and 150 cm, either:

a. Hue of 7.5YR or redder and chroma of 5 or more; or

b. Hue of 7.5YR or redder and value, moist, of 3 or less 

and value, dry, of 4 or less.

Paleargids, p. 104

GED. Other Argids that have a gypsic horizon within 150 cm 

of the soil surface.

Gypsiargids, p. 99

GEE. Other Argids that have a calcic horizon within 150 cm 

of the soil surface.

Calciargids, p. 97

GEF. Other Argids.

Haplargids, p. 100

Calciargids

Key to Subgroups

GEEA. Calciargids that have a lithic contact within 50 cm of 

the soil surface.

Lithic Calciargids

GEEB. Other Calciargids that have both:

1. One or both of the following:

a. Cracks within 125 cm of the soil surface that are 5 

mm or more wide through a thickness of 30 cm or more 

for some time in normal years and slickensides or 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 

CHAPTER 7

Aridisols
98 Keys to Soil Taxonomy

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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

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 
Aridisols 99

A

R

I

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Calciargids

GEEN. Other Calciargids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Calciargids

GEEO. Other Calciargids that, 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Gypsiargids

GEDD. Other Gypsiargids that have, throughout one or more 

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

of the soil surface, one or both of the following:
100 Keys to Soil Taxonomy

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, 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 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 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
Aridisols 101

A

R

I

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplargids

GEFP. Other Haplargids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Haplargids

GEFQ. Other Haplargids that, in normal years, are dry in all 

parts of the moisture control section for less than three-fourths 
102	 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 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

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
Aridisols 103

A

R

I

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 oC 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Natrargids

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Natrargids

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 
104 Keys to Soil Taxonomy

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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

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:
Aridisols 105

A

R

I

a. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Paleargids

GECK. Other Paleargids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Paleargids

GECL. Other Paleargids that, 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

Calcids

Key to Great Groups

GFA. Calcids that have a petrocalcic horizon within 100 cm of 

the soil surface.

Petrocalcids, p. 107

GFB. Other Calcids.

Haplocalcids, p. 105

Haplocalcids

Key to Subgroups

GFBA. Haplocalcids that have both:

1. A lithic contact within 50 cm of the soil surface; and
106 Keys to Soil Taxonomy

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 oC 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 

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
Aridisols 107

A

R

I

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplocalcids

GFBR. Other Haplocalcids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Haplocalcids

GFBS. Other Haplocalcids that, 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 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 
108 Keys to Soil Taxonomy

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 oC 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. 108

GGB. Other Cambids that have a duripan or a petrocalcic or 

petrogypsic horizon within 150 cm of the soil surface.

Petrocambids, p. 112

GGC. Other Cambids that have an anthropic epipedon.

Anthracambids, p. 108

GGD. Other Cambids.

Haplocambids, p. 109

Anthracambids

Key to Subgroups

GGCA. All Anthracambids.

Typic Anthracambids

Aquicambids

Key to Subgroups

GGAA. Aquicambids that have, in a horizon at least 25 cm 

thick within 100 cm of the soil surface, an exchangeable sodium 

percentage of 15 or more (or an SAR of 13 or more) during at 

least 1 month in normal years.

Sodic Aquicambids

GGAB. Other Aquicambids that 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 
Aridisols 109

A

R

I

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Aquicambids

GGAF. Other Aquicambids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Aquicambids

GGAG. Other Aquicambids that have an irregular decrease in 

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 oC or higher and have a soil 

moisture regime that borders on ustic.

Ustic Aquicambids

GGAJ. Other Aquicambids.

Typic Aquicambids

Haplocambids

Key to Subgroups

GGDA. Haplocambids that have 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 Haplocambids

GGDB. 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

GGDC. Other Haplocambids that have a lithic contact within 

50 cm of the soil surface.

Lithic Haplocambids

GGDD. Other Haplocambids that have both:

1. One or both of the following:
110 Keys to Soil Taxonomy

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

GGDE. 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 ustic.

Ustertic Haplocambids

GGDF. 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

GGDG. 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

GGDH. Other Haplocambids that have one or more horizons, 

within 100 cm of the soil surface and with a combined thickness 

of 15 cm or more, that contain 20 percent or more (by volume) 

durinodes or are brittle and have at least a firm ruptureresistance class when moist.

Durinodic Haplocambids

GGDI. 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

GGDJ. 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 ustic.

Petronodic Ustic Haplocambids

GGDK. Other Haplocambids that have one or more horizons, 

within 100 cm of the soil surface and with a combined thickness 

of 15 cm or more, that contain 20 percent or more (by volume) 

nodules or concretions.

Petronodic Haplocambids

GGDL. Other Haplocambids that have both:

1. A horizon at least 25 cm thick within 100 cm of the soil 

surface that has an exchangeable sodium percentage of 15 or 

more (or an SAR of 13 or more) during at least 1 month in 

normal years; and

2. A moisture control section that, in normal years, is dry in 

all parts for less than three-fourths of the time (cumulative) 
Aridisols	 111

A

R

I

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

GGDM. 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 ustic.

Sodic Ustic Haplocambids

GGDN. Other Haplocambids that have, in a horizon at least

25 cm thick within 100 cm of the soil surface, an exchangeable

sodium percentage of 15 or more (or an SAR of 13 or more)

during at least 1 month in normal years.

Sodic Haplocambids

GGDO. Other Haplocambids that have both:

1. A moisture control section that, 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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent

or more is volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplocambids

GGDP. Other Haplocambids that have, throughout one or

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

cm of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted

by ammonium oxalate) times 60] plus the volcanic glass

(percent) is 30 or more.

Vitrandic Haplocambids

GGDQ. Other Haplocambids that:

1. 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 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

GGDR. Other Haplocambids 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 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.

Ustifluventic Haplocambids

GGDS. Other Haplocambids that 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

GGDT. 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

GGDU. 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 o

C or higher and have

a soil moisture regime that borders on ustic.

Ustic Haplocambids

GGDV. Other Haplocambids.

Typic Haplocambids
112 Keys to Soil Taxonomy

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Petrocambids

GGBC. Other Petrocambids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Petrocambids

GGBD. Other Petrocambids that, 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. 115

GAB. Other Cryids that have a duripan or a petrocalcic or 

petrogypsic horizon within 100 cm of the soil surface.

Petrocryids, p. 115

GAC. Other Cryids that have a gypsic horizon within 100 cm 

of the soil surface.

Gypsicryids, p. 114

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

Argicryids, p. 112

GAE. Other Cryids that have a calcic horizon within 100 cm 

of the soil surface.

Calcicryids, p. 113

GAF. Other Cryids.

Haplocryids, p. 114

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
Aridisols 113

A

R

I

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Argicryids

GADE. Other Argicryids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Argicryids

GADF. Other Argicryids that, 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Calcicryids

GAEC. Other Calcicryids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Calcicryids

GAED. Other Calcicryids that, 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
114 Keys to Soil Taxonomy

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Gypsicryids

GACC. Other Gypsicryids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Gypsicryids

GACD. Other Gypsicryids.

Typic Gypsicryids

Haplocryids

Key to Subgroups

GAFA. Haplocryids that have a lithic contact within 50 cm of 

the soil surface.

Lithic Haplocryids

GAFB. Other Haplocryids that have one or both of the 

following:

1. Cracks within 125 cm of the soil surface that are 5 

mm or more wide throughout a thickness of 30 cm or more 

for some time in normal years and slickensides or wedgeshaped 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

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplocryids

GAFD. Other Haplocryids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Haplocryids

GAFE. Other Haplocryids that, 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 Haplocryids
Aridisols	 115

A

R

I

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 o

C 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 oC 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 o

C or higher and have a soil

moisture regime that borders on ustic.

Ustic Petrocryids

GABG. Other Petrocryids.

Typic Petrocryids

Salicryids

Key to Subgroups

GAAA. Salicryids that are saturated with water in one or more

layers within 100 cm of the soil surface for 1 month or more in

normal years.

Aquic Salicryids

GAAB. Other Salicryids.

Typic Salicryids

Durids

Key to Great Groups

GCA. Durids that have a natric horizon above the duripan.

Natridurids, p. 117

GCB. Other Durids that have an argillic horizon above the

duripan.

Argidurids, p. 115

GCC. Other Durids.

Haplodurids, p. 116

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
116 Keys to Soil Taxonomy

2. Saturated with water in one or more layers within 100 

cm of the soil surface for 1 month or more in normal years.

Aquic Argidurids

GCBC. Other Argidurids that have both:

1. An argillic horizon that has 35 percent or more clay in 

the fine-earth fraction of some part; and either

a. A clay increase of 15 percent or more (absolute) 

within a vertical distance of 2.5 cm either within the 

argillic horizon or at its upper boundary; or

b. If there is an Ap horizon directly above the argillic 

horizon, a clay increase of 10 percent or more (absolute) 

at the upper boundary of the argillic horizon; and

2. A moisture control section that, 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.

Abruptic Xeric Argidurids

GCBD. Other Argidurids that have an argillic horizon that has 

35 percent or more clay in the fine-earth fraction of some part; 

and either

1. A clay increase of 15 percent or more (absolute) within a 

vertical distance of 2.5 cm within the argillic horizon or at its 

upper boundary; or

2. If there is an Ap horizon directly above the argillic 

horizon, a clay increase of 10 percent or more (absolute) at 

the upper boundary of the argillic horizon.

Abruptic Argidurids

GCBE. Other Argidurids that have 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 

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Argidurids

GCBH. Other Argidurids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Argidurids

GCBI. Other Argidurids that, 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 oC 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:
Aridisols 117

A

R

I

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 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplodurids

GCCF. Other Haplodurids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Haplodurids

GCCG. Other Haplodurids that have a mean annual soil 

temperature lower than 22 oC, a difference of 5 oC or more 

between mean summer and mean winter soil temperatures at 

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

xeric.

Xeric Haplodurids

GCCH. Other Haplodurids that, 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
118 Keys to Soil Taxonomy

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Natridurids

GCAG. Other Natridurids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Natridurids

GCAH. Other Natridurids that, 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. 121

GDB. Other Gypsids that have a natric horizon within 100 cm 

of the soil surface.

Natrigypsids, p. 121

GDC. Other Gypsids that have an argillic horizon within 100 

cm of the soil surface.

Argigypsids, p. 118

GDD. Other Gypsids that have a calcic horizon within 100 cm 

of the soil surface.

Calcigypsids, p. 119

GDE. Other Gypsids.

Haplogypsids, p. 120

Argigypsids

Key to Subgroups

GDCA. Argigypsids that have a lithic contact within 50 cm of 

the soil surface.

Lithic Argigypsids
Aridisols 119

A

R

I

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Argigypsids

GDCF. Other Argigypsids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 percent or more.

Vitrandic Argigypsids

GDCG. Other Argigypsids that, 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Calcigypsids
120 Keys to Soil Taxonomy

GDDD. Other Calcigypsids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Calcigypsids

GDDE. Other Calcigypsids that, 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

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Haplogypsids

GDEF. Other Haplogypsids that have, throughout one or more 

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

0f the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Haplogypsids

GDEG. Other Haplogypsids that, 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 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
Aridisols 121

A

R

I

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Natrigypsids

GDBE. Other Natrigypsids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent 

or more is volcanic glass, and [(Al plus 1/2 Fe, percent 
122

extracted by ammonium oxalate) times 60] plus the 

volcanic glass (percent) is 30 or more.

Vitrixerandic Petrogypsids

GDAD. Other Petrogypsids that have, throughout one or more 

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is 30 or more.

Vitrandic Petrogypsids

GDAE. Other Petrogypsids that, 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. 122

GBB. Other Salids.

Haplosalids, p. 122

Aquisalids

Key to Subgroups

GBAA. Aquisalids that have a gypsic or petrogypsic horizon 

within 100 cm of the soil surface.

Gypsic Aquisalids

GBAB. Other Aquisalids that have a calcic or petrocalcic 

horizon within 100 cm of the soil surface.

Calcic Aquisalids

GBAC. 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 a gypsic horizon within 

100 cm of the soil surface.

Gypsic Haplosalids

GBBD. Other Haplosalids that have a calcic horizon within 

100 cm of the soil surface.

Calcic Haplosalids

GBBE. Other Haplosalids.

Typic Haplosalids
123

E

N

T

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. 142

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) Chroma of 0; or

(2) Chroma of 1 or less and a color value, moist, of 4 

or more; or

(3) Chroma of 2 or less and redox concentrations; or

b. A texture class of loamy fine sand or coarser and, 

in 50 percent or more of the matrix, one or more of the 

following:

(1) Chroma of 0; or

(2) Hue of 10YR or redder, a color value, moist, of 4 

or more, and chroma of 1; or

(3) Hue of 10YR or redder, chroma of 2 or less, and 

redox concentrations; or

(4) Hue of 2.5Y or yellower, chroma of 3 or less, and 

distinct or prominent redox concentrations; or

(5) Hue of 2.5Y or yellower and chroma of 1; or

(6) Hue of 5GY, 5G, 5BG, or 5B; or

(7) Any color if it results from uncoated sand grains; 

or

c. Enough active ferrous iron to give a positive reaction 

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

being irrigated.

Aquents, p. 124

LC. Other Entisols that have, in one or more layers at a depth 

between 25 and 100 cm below the mineral soil surface, 3 

percent or more (by volume) fragments of diagnostic horizons 

that are not arranged in any discernible order.

Arents, p. 127

LD. 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. 138

LE. Other Entisols that do not have a densic, lithic, or 

paralithic contact within 25 cm of the mineral soil surface and 

have:

1. A slope of less than 25 percent; and

2. 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

3. A soil temperature regime:

a. That is warmer than cryic; or

b. That is 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. 128

CHAPTER 8

Entisols
124 Keys to Soil Taxonomy

LF. Other Entisols.

Orthents, p. 133

Aquents

Key to Great Groups

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

mineral soil surface.

Sulfaquents, p. 127

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. 126

LBC. Other Aquents that have a gelic soil temperature regime. 

Gelaquents, p. 126 

LBD. Other Aquents that have a cryic soil temperature regime.

Cryaquents, p. 124

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. 126

LBF. Other Aquents that have both:

1. A slope of less than 25 percent; and

2. 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. 125

LBG. Other Aquents that have episaturation.

Epiaquents, p. 125

LBH. Other Aquents.

Endoaquents, p. 124

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Cryaquents

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

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
Entisols 125

E

N

T

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:

1. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling more 

than 1.0; or

2. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and
126 Keys to Soil Taxonomy

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:

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, 

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 NH4OAc) 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:
Entisols 127

E

N

T

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

Arents

Key to Great Groups

LCA. Arents that have an ustic soil moisture regime.

Ustarents, p. 127

LCB. Other Arents that have a xeric soil moisture regime.

Xerarents, p. 127

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

regime.

Torriarents, p. 127

LCD. Other Arents.

Udarents, p. 127

Torriarents

Key to Subgroups

LCCA. Torriarents that have, in one or more horizons within 

100 cm of the mineral soil surface, 3 percent or more fragments 

of a natric horizon.

Sodic Torriarents

LCCB. Other Torriarents that have, within 100 cm of the 

mineral soil surface, 3 percent or more fragments of a duripan 

or a petrocalcic horizon.

Duric Torriarents

LCCC. Other Torriarents.

Haplic Torriarents

Udarents

Key to Subgroups

LCDA. Udarents that have 3 percent or more fragments of an 

argillic horizon in some horizon within 100 cm of the mineral 

soil surface and have a base saturation (by sum of cations) of 35 

percent or more in all parts within 100 cm of the mineral soil 

surface.

Alfic Udarents

LCDB. Other Udarents that have 3 percent or more fragments 

of an argillic horizon in some horizon within 100 cm of the 

mineral soil surface.

Ultic Udarents

LCDC. Other Udarents that have 3 percent or more fragments 

of a mollic epipedon in some horizon within 100 cm of the 

mineral soil surface and have a base saturation (by sum of 

cations) of 35 percent or more in all parts within 100 cm of the 

mineral soil surface.

Mollic Udarents

LCDD. Other Udarents.

Haplic Udarents

Ustarents

Key to Subgroups

LCAA. All Ustarents.

Haplic Ustarents

Xerarents

Key to Subgroups

LCBA. Xerarents that have, in one or more horizons within

100 cm of the mineral soil surface, 3 percent or more fragments 

of a natric horizon.

Sodic Xerarents
128 Keys to Soil Taxonomy

LCBB. Other Xerarents that have, within 100 cm of the 

mineral soil surface, 3 percent or more fragments of a duripan 

or a petrocalcic horizon.

Duric Xerarents

LCBC. Other Xerarents that have fragments of an argillic 

horizon with a base saturation (by sum of cations) of 35 percent 

or more within 100 cm of the mineral soil surface.

Alfic Xerarents

LCBD. Other Xerarents.

Haplic Xerarents

Fluvents

Key to Great Groups

LEA. Fluvents that that have a gelic soil temperature regime.

Gelifluvents, p. 128

LEB. Other Fluvents that have a cryic soil temperature 

regime.

Cryofluvents, p. 128

LEC. Other Fluvents that have a xeric soil moisture regime.

Xerofluvents, p. 132

LED. Other Fluvents that have an ustic soil moisture regime.

Ustifluvents, p. 131

LEE. Other Fluvents that have an aridic (or torric) soil 

moisture regime.

Torrifluvents, p. 128

LEF. Other Fluvents.

Udifluvents, p. 130

Cryofluvents

Key to Subgroups

LEBA. 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

LEBB. Other Cryofluvents that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Cryofluvents

LEBC. Other Cryofluvents that have, in one or more horizons 

within 50 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Cryofluvents

LEBD. 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

LEBE. 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

LEBF. Other Cryofluvents.

Typic Cryofluvents

Gelifluvents

Key to Subgroups

LEAA. 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

LEAB. Other Gelifluvents.

Typic Gelifluvents

Torrifluvents

Key to Subgroups

LEEA. 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 
Entisols	 129

E

N

T

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

LEEB. 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

LEEC. 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 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; and

3. Throughout one or more horizons with a total thickness

of 18 cm or more within 75 cm of the mineral soil surface,

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

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

equal to 30 or more.

Vitrixerandic Torrifluvents

LEED. Other Torrifluvents that have, throughout one or more

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Torrifluvents

LEEE. 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

LEEF. 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

LEEG. 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

LEEH. 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

LEEI. Other Torrifluvents that have both:
130 Keys to Soil Taxonomy

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

ustic.

Ustic Torrifluvents

LEEJ. 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

LEEK. Other Torrifluvents that have an anthropic epipedon.

Anthropic Torrifluvents

LEEL. Other Torrifluvents.

Typic Torrifluvents

Udifluvents

Key to Subgroups

LEFA. 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 chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and 

also aquic conditions for some time in normal years (or 

artificial drainage).

Aquertic Udifluvents

LEFB. 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 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 Udifluvents

LEFC. 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

LEFD. Other Udifluvents that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Udifluvents

LEFE. Other Udifluvents that have either:

1. In one or more horizons within 50 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); or

2. In one or more horizons within 100 cm of the mineral 

soil surface, a color value, moist, of 4 or more and either 

chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic 

conditions for some time in normal years (or artificial 

drainage).

Aquic Udifluvents

LEFF. 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:
Entisols 131

E

N

T

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Udifluvents

LEFG. 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

LEFH. Other Udifluvents.

Typic Udifluvents

Ustifluvents

Key to Subgroups

LEDA. 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 chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and 

also aquic conditions for some time in normal years (or 

artificial drainage).

Aquertic Ustifluvents

LEDB. 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 oC; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that, in normal years, is dry in 

some part for six-tenths or more of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that, 

in normal years, remains moist in some or all parts for 

less than 90 consecutive days per year when the 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

LEDC. 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 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 Ustifluvents

LEDD. Other Ustifluvents that have anthraquic conditions.

Anthraquic Ustifluvents

LEDE. Other Ustifluvents that have either:

1. In one or more horizons within 50 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); or

2. In one or more horizons within 150 cm of the mineral 

soil surface, a color value, moist, of 4 or more and either 

chroma of 0 or hue of 5GY, 5G, 5BG, or 5B and also aquic 

conditions for some time in normal years (or artificial 

drainage).

Aquic Ustifluvents
132 Keys to Soil Taxonomy

LEDF. 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

LEDG. 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

LEDH. 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 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 Ustifluvents

LEDI. 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

LEDJ. Other Ustifluvents.

Typic Ustifluvents

Xerofluvents

Key to Subgroups

LECA. 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

LECB. Other Xerofluvents that have:

1. In one or more horizons within 50 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); or

2. In one or more horizons within 150 cm of the mineral 

soil surface, a color value, moist, of 4 or more and either 

chroma of 0 or hue bluer than 10Y and also aquic conditions 

for some time in normal years (or artificial drainage); and

3. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Aquandic Xerofluvents
Entisols 133

E

N

T

LECC. 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

LECD. Other Xerofluvents that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Xerofluvents

LECE. Other Xerofluvents that have either:

1. In one or more horizons within 50 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); or

2. In one or more horizons within 150 cm of the mineral 

soil surface, a color value, moist, of 4 or more and either 

chroma of 0 or hue of 5GY, 5G, 5BG, or 5B or aquic 

conditions for some time in normal years.

Aquic Xerofluvents

LECF. 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

LECG. 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

LECH. 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 

mineral soil (unmixed) or between the mineral soil surface and a 

depth of 15 cm after mixing.

Mollic Xerofluvents

LECI. Other Xerofluvents.

Typic Xerofluvents

Orthents

Key to Great Groups

LFA. Orthents that have a gelic soil temperature regime.

Gelorthents, p. 134 

LFB. Other Orthents that have a cryic soil temperature regime.

Cryorthents, p. 133

LFC. Other Orthents that have an aridic (or torric) soil 

moisture regime.

Torriorthents, p. 134

LFD. Other Orthents that have a xeric soil moisture regime.

Xerorthents, p. 138

LFE. Other Orthents that have an ustic soil moisture regime.

Ustorthents, p. 136

LFF. Other Orthents.

Udorthents, p. 135

Cryorthents

Key to Subgroups

LFBA. Cryorthents that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Cryorthents

LFBB. Other Cryorthents that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Cryorthents

LFBC. Other Cryorthents that have, in one or more horizons 
134 Keys to Soil Taxonomy

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

LFBD. 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

LFBE. Other Cryorthents that have lamellae within 200 cm of 

the mineral soil surface.

Lamellic Cryorthents

LFBF. Other Cryorthents.

Typic Cryorthents

Gelorthents

Key to Subgroups

LFAA. 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

LFAB. 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

LFAC. Other Gelorthents.

Typic Gelorthents

Torriorthents

Key to Subgroups

LFCA. 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 hypertheric, thermic, mesic, frigid, or iso soil 

temperature regime and an aridic (or torric) soil moisture 

regime that borders on ustic.

Lithic Ustic Torriorthents

LFCB. 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

LFCC. Other Torriorthents that have a lithic contact within 50 

cm of the soil surface.

Lithic Torriorthents

LFCD. 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. A thermic, mesic, or frigid soil temperature regime and 

an aridic (or torric) soil moisture regime that borders on 

xeric.

Xerertic Torriorthents

LFCE. 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
Entisols	 135

E

N

T

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

ustic.

Ustertic Torriorthents

LFCF. 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

LFCG. Other Torriorthents that have, throughout one or more

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Torriorthents

LFCH. 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

LFCI. 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

LFCJ. 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

LFCK. 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 o

C 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

LFCL. 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

LFCM. Other Torriorthents.

Typic Torriorthents

Udorthents

Key to Subgroups

LFFA. Udorthents that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Udorthents

LFFB. Other Udorthents that have, throughout one or more

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Udorthents

LFFC. 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

LFFD. Other Udorthents that are saturated with water in one
136	 Keys to Soil Taxonomy

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

LFFE. 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

LFFF. Other Udorthents.

Typic Udorthents

Ustorthents

Key to Subgroups

LFEA. Ustorthents that have both:

1. A lithic contact within 50 cm of the mineral soil surface;

and

2. When neither irrigated nor fallowed to store moisture,

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, remains 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

LFEB. Other Ustorthents that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Ustorthents

LFEC. 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, remains 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

LFED. 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 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 Ustorthents

LFEE. Other Ustorthents that have anthraquic conditions.

Anthraquic Ustorthents

LFEF. 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

LFEG. Other Ustorthents that are saturated with water in
Entisols	 137

E

N

T

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

LFEH. 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

LFEI. Other Ustorthents 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, remains 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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

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

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

equal to 30 or more.

Vitritorrandic Ustorthents

LFEJ. Other Ustorthents that have, throughout one or more

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

of the soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Ustorthents

LFEK. 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 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 Ustorthents

LFEL. 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 o

C.

Udic Ustorthents
138	 Keys to Soil Taxonomy

LFEM. 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

LFEN. Other Ustorthents.

Typic Ustorthents

Xerorthents

Key to Subgroups

LFDA. Xerorthents that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Xerorthents

LFDB. Other Xerorthents that have, throughout one or more

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Xerorthents

LFDC. 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

LFDD. 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

LFDE. 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

LFDF. 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 that is at a shallower

depth.

Dystric Xerorthents

LFDG. Other Xerorthents.

Typic Xerorthents

Psamments

Key to Great Groups

LDA. Psamments that have a cryic soil temperature regime.

Cryopsamments, p. 138

LDB. Other Psamments that have an aridic (or torric) soil

moisture regime.

Torripsamments, p. 140

LDC. 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. 139

LDD. Other Psamments that have an ustic soil moisture

regime.

Ustipsamments, p. 141

LDE. Other Psamments that have a xeric soil moisture regime.

Xeropsamments, p. 141

LDF. Other Psamments.

Udipsamments, p. 140

Cryopsamments

Key to Subgroups

LDAA. Cryopsamments that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Cryopsamments

LDAB. 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

LDAC. 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
Entisols	 139

E

N

T

2. 30 or more cumulative days.

Oxyaquic Cryopsamments

LDAD. Other Cryopsamments that have, throughout one or

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

cm of the mineral soil surface, a fine-earth fraction containing

5 percent or more volcanic glass, and [(Al plus 1/2 Fe, percent

extracted by ammonium oxalate) times 60] plus the volcanic

glass (percent) is 30 or more.

Vitrandic Cryopsamments

LDAE. 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

LDAF. Other Cryopsamments that have lamellae within 200

cm of the mineral soil surface.

Lamellic Cryopsamments

LDAG. Other Cryopsamments.

Typic Cryopsamments

Quartzipsamments

Key to Subgroups

LDCA. Quartzipsamments that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Quartzipsamments

LDCB. 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

LDCC. 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

LDCD. 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

LDCE. 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

LDCF. 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

LDCG. 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

LDCH. 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

LDCI. Other Quartzipsamments that have lamellae within 200

cm of the mineral soil surface.

Lamellic Quartzipsamments
140	 Keys to Soil Taxonomy

LDCJ. Other Quartzipsamments that have an ustic soil

moisture regime.

Ustic Quartzipsamments

LDCK. Other Quartzipsamments that have a xeric soil

moisture regime.

Xeric Quartzipsamments

LDCL. 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

LDCM. Other Quartzipsamments.

Typic Quartzipsamments

Torripsamments

Key to Subgroups

LDBA. Torripsamments that have a lithic contact within 50

cm of the soil surface.

Lithic Torripsamments

LDBB. 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

LDBC. 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

LDBD. 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

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

ustic.

Ustic Torripsamments

LDBF. 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

LDBG. 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

LDBH. Other Torripsamments.

Typic Torripsamments

Udipsamments

Key to Subgroups

LDFA. Udipsamments that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Udipsamments

LDFB. 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

LDFC. 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
Entisols	 141

E

N

T

LDFD. Other Udipsamments that have a horizon, 5 cm or

more thick, either below an Ap horizon or at a depth of 18 cm

or more from the mineral soil surface, whichever is deeper, that

has one or more of the following:

1. In 25 percent or more of each pedon, cementation by

organic matter and aluminum, with or without iron; or

2. Al plus 1/2 Fe percentages (by ammonium oxalate)

totaling 0.25 or more, and half that amount or less in an

overlying horizon; or

3. An ODOE value of 0.12 or more, and a value half as

high or lower in an overlying horizon.

Spodic Udipsamments

LDFE. Other Udipsamments that have lamellae within 200 cm

of the mineral soil surface.

Lamellic Udipsamments

LDFF. Other Udipsamments that have a surface horizon

between 25 and 50 cm thick that meets all of the requirements

for a plaggen epipedon except thickness.

Plagganthreptic Udipsamments

LDFG. Other Udipsamments.

Typic Udipsamments

Ustipsamments

Key to Subgroups

LDDA. Ustipsamments that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Ustipsamments

LDDB. 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

LDDC. 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

LDDD. 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

LDDE. Other Ustipsamments that have lamellae within 200

cm of the mineral soil surface.

Lamellic Ustipsamments

LDDF. 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

LDDG. Other Ustipsamments.

Typic Ustipsamments

Xeropsamments

Key to Subgroups

LDEA. Xeropsamments that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Xeropsamments

LDEB. 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

LDEC. 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
142	

LDED. Other Xeropsamments that are saturated with water in

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

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Xeropsamments

LDEE. 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

LDEF. 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

LDEG. Other Xeropsamments that have lamellae within 200

cm of the mineral soil surface.

Lamellic Xeropsamments

LDEH. 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 that is at a shallower

depth.

Dystric Xeropsamments

LDEI. 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 5:1, by volume, mixture (not extract) of water and

soil.

Frasiwassents, p. 142

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. 143

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. 144

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. 143

LAE. Other Wassents that have 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. 142

LAF. Other Wassents.

Haplowassents, p. 143

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 a 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

n value of more than 0.7 and 8 percent or more clay in the fineearth fraction.

Hydric Frasiwassents
Entisols 143

E

N

T

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 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 a 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 a 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 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 Psammowassents

LABD. Other Psammowassents that have a chroma of 3 

or more in 40 percent or more of the matrix of one or more 
144

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 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 a 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
145

G

E

L

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. 145

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. 150

AC. Other Gelisols.

Orthels, p. 146

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. 145

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. 146

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. 145

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. 146

AAE. Other Histels.

Sapristels, p. 146

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 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 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

Folistels

Key to Subgroups

AAAA. Folistels that have a lithic contact within 50 cm of the 

soil surface.

Lithic Folistels

CHAPTER 9

Gelisols
146 Keys to Soil Taxonomy

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 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 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, in 30 percent or more of the pedon, 

more than 40 percent, by volume, organic soil materials from 

the soil surface to a depth of 50 cm.

Historthels, p. 148

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. 147

ACC. Other Orthels that have anhydrous conditions.

Anhyorthels, p. 146

ACD. Other Orthels that have a mollic epipedon.

Mollorthels, p. 149

ACE. Other Orthels that have an umbric epipedon.

Umbrorthels, p. 150

ACF. Other Orthels that have an argillic horizon within 100 

cm of the mineral soil surface.

Argiorthels, p. 147

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. 149

ACH. Other Orthels.

Haplorthels, p. 148

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
Gelisols 147

G

E

L

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 a horizon 15 cm or more 

thick that contains 12 cmol(-)/L nitrate in a 1:5 soil:water 

extract and in which the product of its thickness (in cm) and its 

nitrate concentration is 3,500 or more.

Nitric 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Aquorthels

ACBG. Other Aquorthels that have a salic horizon 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 a slope of less than 25 

percent 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.

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
148	 Keys to Soil Taxonomy

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 a slope of less than 25

percent; and

1. In one or more horizons within 75 cm of the mineral soil

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

aquic conditions for some time in normal years (or artificial

drainage); and

2. 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 a slope of less than 25

percent 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 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

ACAC. Other Historthels that have a slope of less than 25

percent; and

1. In one or more horizons within 75 cm of the mineral soil

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

aquic conditions for some time in normal years (or artificial

drainage); and

2. 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 a slope of less than 25

percent 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 Historthels
Gelisols	 149

G

E

L

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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Mollorthels

ACDF. Other Mollorthels that have 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

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
150	 Keys to Soil Taxonomy

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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Umbrorthels

ACEF. Other Umbrorthels that have 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

the soil surface to a depth of 50 cm.

Histoturbels, p. 151

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. 151

ABC. Other Turbels that have anhydrous conditions.

Anhyturbels, p. 150

ABD. Other Turbels that have a mollic epipedon.

Molliturbels, p. 152

ABE. Other Turbels that have an umbric epipedon.

Umbriturbels, p. 152

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. 152

ABG. Other Turbels.

Haploturbels, p. 151

Anhyturbels

Key to Subgroups

ABCA. Anhyturbels that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Anhyturbels
Gelisols	 151

G

E

L

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 a horizon 15 cm or

more thick that contains 12 cmol(-)/L nitrate in a 1:5 soil:water

extract and in which the product of its thickness (in cm) and its

nitrate concentration is 3,500 or more.

Nitric Anhyturbels

ABCF. Other Anhyturbels that have a salic horizon 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

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
152	 Keys to Soil Taxonomy

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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Molliturbels

ABDF. Other Molliturbels that have 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

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:
Gelisols	 153

G

E

L

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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium

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

equal to 30 or more.

Vitrandic Umbriturbels

ABEF. Other Umbriturbels that have 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
 
155

H

I

S

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. 156

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. 159

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. 155

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. 158

BE. Other Histosols.

Hemists, p. 157

Fibrists

Key to Great Groups

BCA. Fibrists that have a cryic soil temperature regime.

Cryofibrists, p. 155

BCB. Other Fibrists in which fibric Sphagnum constitutes 

three-fourths or more of the volume to either a depth of 90 cm 

from the soil surface or to a densic, lithic, or paralithic contact, 

fragmental materials, or other mineral soil materials if at a depth 

of less than 90 cm.

Sphagnofibrists, p. 156

BCC. Other Fibrists.

Haplofibrists, p. 156

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 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 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

CHAPTER 10

Histosols
156 Keys to Soil Taxonomy

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 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 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. 156

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

regime.

Torrifolists, p. 156

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

regime.

Ustifolists, p. 157

BAD. Other Folists.

Udifolists, p. 157

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
Histosols 157

H

I

S

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. 158

BEB. Other Hemists that have sulfidic materials within 100 

cm of the soil surface.

Sulfihemists, p. 158

BEC. Other Hemists that have a horizon 2 cm or more thick 

in which humilluvic materials constitute one-half or more of the 

volume.

Luvihemists, p. 158

BED. Other Hemists that have a cryic soil temperature regime.

Cryohemists, p. 157

BEE. Other Hemists.

Haplohemists, p. 157

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 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

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 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
158 Keys to Soil Taxonomy

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. 159

BDB. Other Saprists that have sulfidic materials within 100 

cm of the soil surface.

Sulfisaprists, p. 159

BDC. Other Saprists that have a cryic soil temperature regime.

Cryosaprists, p. 158

BDD. Other Saprists.

Haplosaprists, p. 158

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 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

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 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 
Histosols 159

H

I

S

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 

5:1, by volume, mixture (not extract) of water and soil.

Frasiwassists, p. 159

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. 160

BBC. Other Wassists.

Haplowassists, p. 159

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

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 
160

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
161

I

N

C

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. 161

KB. Other Inceptisols that have a plaggen or anthropic 

epipedon.

Anthrepts, p. 161

KC. Other Inceptisols that have a gelic soil temperature regime. 

Gelepts, p. 173

KD. Other Inceptisols that have a cryic soil temperature 

regime.

Cryepts, p. 167

KE. Other Inceptisols that have an ustic soil moisture regime.

Ustepts, p. 182

KF. Other Inceptisols that have a xeric soil moisture regime.

Xerepts, p. 189

KG. Other Inceptisols.

Udepts, p. 174

Anthrepts

Key to Great Groups

KBA. Anthrepts that have a plaggen epipedon.

Plagganthrepts, p. 161

KBB. Other Anthrepts.

Haplanthrepts, p. 161

Haplanthrepts

Key to Subgroups

KBBA. All Haplanthrepts (provisionally).

Typic Haplanthrepts

Plagganthrepts

Key to Subgroups

KBAA. All Plagganthrepts (provisionally).

Typic Plagganthrepts

Aquepts

Key to Great Groups

KAA. Aquepts that have a sulfuric horizon within 50 cm of 

the mineral soil surface.

Sulfaquepts, p. 167

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. 167

KAC. Other Aquepts that have either:

1. A salic horizon; or

CHAPTER 11

Inceptisols
162 Keys to Soil Taxonomy

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. 166

KAD. Other Aquepts that have a fragipan within 100 cm of 

the mineral soil surface.

Fragiaquepts, p. 165

KAE. Other Aquepts that have a gelic soil temperature regime.

Gelaquepts, p. 165

KAF. Other Aquepts that have a cryic soil temperature regime.

Cryaquepts, p. 162

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. 167

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

umbric epipedon.

Humaquepts, p. 166

KAI. Other Aquepts that have episaturation.

Epiaquepts, p. 164

KAJ. Other Aquepts.

Endoaquepts, p. 163

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Cryaquepts

KAFG. Other Cryaquepts that have a slope of less than 25 

percent 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.

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
Inceptisols 163

I

N

C

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

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Endoaquepts

KAJE. 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, a 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; and

3. A slope of less than 25 percent and 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 a slope of less than 25 

percent 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 
164 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.

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 NH4OAc) 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Epiaquepts

KAIC. Other Epiaquepts that have a slope of less than 25 

percent 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.

Fluvaquentic Epiaquepts

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
Inceptisols 165

I

N

C

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 NH4OAc) 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Gelaquepts

KAED. Other Gelaquepts that have a slope of less than 25 

percent 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.

Fluvaquentic Gelaquepts
166 Keys to Soil Taxonomy

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Halaquepts

KACC. Other Halaquepts that have 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Humaquepts

KAHD. Other Humaquepts that have a slope of less than 25 

percent; and

1. An umbric or mollic epipedon that is 60 cm or more 

thick; and 

2. 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 
Inceptisols 167

I

N

C

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 a slope of less than 25 

percent 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.

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

KAGB. Other Vermaquepts.

Typic Vermaquepts

Cryepts

Key to Great Groups

KDA. Cryepts that have an umbric or mollic epipedon.

Humicryepts, p. 171

KDB. Other Cryepts that have a calcic or petrocalcic horizon 

within 100 cm of the mineral soil surface.

Calcicryepts, p. 168

KDC. 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, 
168 Keys to Soil Taxonomy

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. 168

KDD. Other Cryepts.

Haplocryepts, p. 169

Calcicryepts

Key to Subgroups

KDBA. Calcicryepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Calcicryepts

KDBB. 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

KDBC. Other Calcicryepts that have a xeric soil moisture 

regime.

Xeric Calcicryepts

KDBD. Other Calcicryepts that are dry in some part of the 

moisture control section for 45 or more days (cumulative) in 

normal years.

Ustic Calcicryepts

KDBE. Other Calcicryepts.

Typic Calcicryepts

Dystrocryepts

Key to Subgroups

KDCA. Dystrocryepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Dystrocryepts

KDCB. 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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1⁄2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Aquandic Dystrocryepts

KDCC. 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

KDCD. 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, 

one or both of the following:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1⁄2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrixerandic Dystrocryepts

KDCE. 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
Inceptisols 169

I

N

C

KDCF. Other Dystrocryepts that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Dystrocryepts

KDCG. Other Dystrocryepts that have a slope of less than 25 

percent; and

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and 

2. 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

KDCH. Other Dystrocryepts that have a folistic epipedon.

Folistic Dystrocryepts

KDCI. 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

KDCJ. 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

KDCK. Other Dystrocryepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Dystrocryepts

KDCL. Other Dystrocryepts that have a slope of less than 25 

percent 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 Dystrocryepts

KDCM. Other Dystrocryepts that have a horizon 5 cm or 

more thick that has one or more of the following:

1. In 25 percent or more of each pedon, cementation by 

organic matter and aluminum, with or without iron; or

2. Al plus 1⁄2 Fe (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

KDCN. Other Dystrocryepts that have a xeric soil moisture 

regime.

Xeric Dystrocryepts

KDCO. Other Dystrocryepts that are dry in some part of the 

moisture control section for 45 or more days (cumulative) in 

normal years.

Ustic Dystrocryepts

KDCP. 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

KDCQ. Other Dystrocryepts.

Typic Dystrocryepts

Haplocryepts

Key to Subgroups

KDDA. Haplocryepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Haplocryepts

KDDB. Other Haplocryepts that have both:
170 Keys to Soil Taxonomy

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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1⁄2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Aquandic Haplocryepts

KDDC. 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

KDDD. 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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1⁄2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrixerandic Haplocryepts

KDDE. 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

KDDF. 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:

a. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1⁄2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Ustivitrandic Haplocryepts

KDDG. 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

KDDH. 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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and
Inceptisols 171

I

N

C

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

KDDI. Other Haplocryepts that have a slope of less than 25 

percent; and

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. 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

KDDJ. 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

KDDK. 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

KDDL. Other Haplocryepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Haplocryepts

KDDM. Other Haplocryepts that have a slope of less than 25 

percent 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 Haplocryepts

KDDN. Other Haplocryepts that have identifiable secondary 

carbonates within 100 cm of the mineral soil surface.

Calcic Haplocryepts

KDDO. Other Haplocryepts that have a xeric soil moisture 

regime.

Xeric Haplocryepts

KDDP. Other Haplocryepts that are dry in some part of the 

moisture control section for 45 or more days (cumulative) in 

normal years.

Ustic Haplocryepts

KDDQ. Other Haplocryepts.

Typic Haplocryepts

Humicryepts

Key to Subgroups

KDAA. Humicryepts that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Humicryepts

KDAB. 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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1⁄2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Aquandic Humicryepts
172 Keys to Soil Taxonomy

KDAC. 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

KDAD. 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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1⁄2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrixerandic Humicryepts

KDAE. 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

KDAF. 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) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Humicryepts

KDAG. Other Humicryepts that have a slope of less than 25 

percent; and

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. 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 Humicryepts

KDAH. 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

KDAI. 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

KDAJ. Other Humicryepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Humicryepts

KDAK. Other Humicryepts that have a slope of less than 25 

percent 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 Humicryepts

KDAL. Other Humicryepts that have a horizon 5 cm or more 

thick that has one or more of the following:
Inceptisols	 173

I

N

C

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

KDAM. Other Humicryepts that have a xeric soil moisture

regime.

Xeric Humicryepts

KDAN. 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

KDAO. Other Humicryepts.

Typic Humicryepts

Gelepts

Key to Great Groups

KCA. Gelepts that have an umbric or mollic epipedon.

Humigelepts, p. 174

KCB. 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. 173

KCC. Other Gelepts.

Haplogelepts, p. 173

Dystrogelepts

Key to Subgroups

KCBA. Dystrogelepts that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Dystrogelepts

KCBB. Other Dystrogelepts 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 Dystrogelepts

KCBC. 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

KCBD. Other Dystrogelepts that have a slope of less than 25

percent, do not have irregular or broken horizon boundaries, and

have 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 Dystrogelepts

KCBE. Other Dystrogelepts that have gelic materials within

200 cm of the mineral soil surface.

Turbic Dystrogelepts

KCBF. Other Dystrogelepts.

Typic Dystrogelepts

Haplogelepts

Key to Subgroups

KCCA. Haplogelepts that have a lithic contact within 50 cm

of the mineral soil surface.

Lithic Haplogelepts

KCCB. 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

KCCC. Other Haplogelepts that have, in one or more horizons

within 75 cm of the mineral soil surface, redox depletions with
174 Keys to Soil Taxonomy

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Haplogelepts

KCCD. Other Haplogelepts that have a slope of less than 25 

percent, do not have irregular or broken horizon boundaries, and 

have 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 Haplogelepts

KCCE. Other Haplogelepts that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Haplogelepts

KCCF. Other Haplogelepts.

Typic Haplogelepts

Humigelepts

Key to Subgroups

KCAA. Humigelepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humigelepts

KCAB. 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

KCAC. 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

KCAD. 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

KCAE. Other Humigelepts that have a slope of less than 25 

percent, do not have irregular or broken horizon boundaries, and 

have 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 Humigelepts

KCAF. Other Humigelepts that have gelic materials within 

200 cm of the mineral soil surface.

Turbic Humigelepts

KCAG. 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

KCAH. Other Humigelepts.

Typic Humigelepts

Udepts

Key to Great Groups

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

mineral soil surface.

Sulfudepts, p. 182

KGB. Other Udepts that have a duripan or another cemented 

horizon within 100 cm of the mineral soil surface.

Durudepts, p. 175

KGC. Other Udepts that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiudepts, p. 180

KGD. Other Udepts that have an umbric or mollic epipedon.

Humudepts, p. 180

KGE. Other Udepts that have one or both of the following:

1. Free carbonates within the soils; or

2. A base saturation (by NH4OAc) of 60 percent or more in 
Inceptisols 175

I

N

C

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

the mineral soil surface or directly above a root-limiting layer 

if at a shallower depth.

Eutrudepts, p. 178

KGF. Other Udepts.

Dystrudepts, p. 175

Durudepts

Key to Subgroups

KGBA. Durudepts that have both:

1. In one or more horizons above the duripan and within 60 

cm of the mineral soil surface, distinct or prominent redox 

concentrations and also aquic conditions for some time in 

normal years (or artificial drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more, above the duripan and within 75 cm of the 

mineral soil surface, one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Durudepts

KGBB. 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

KGBC. Other Durudepts that have, throughout one or more 

horizons with a total thickness of 18 cm or more, above the 

duripan and within 75 cm of the mineral soil surface, one or 

both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Durudepts

KGBD. 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

KGBE. Other Durudepts.

Typic Durudepts

Dystrudepts

Key to Subgroups

KGFA. 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

KGFB. Other Dystrudepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Dystrudepts

KGFC. 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

KGFD. 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
176	 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 more of the following:

a. A fine-earth fraction with both a bulk density of 1.0

g/cm3 or less, measured at 33 kPa water retention, and Al

plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more

volcanic glass; and

(2) [(Al plus 1

/2 Fe, percent extracted by ammonium

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

equal to 30 or more.

Aquandic Dystrudepts

KGFE. 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

KGFF. Other Dystrudepts that have, throughout one or more

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

of the mineral soil surface, a fine-earth fraction with both a bulk

density of 1.0 g/cm3 or less, measured at 33 kPa water retention,

and Al plus 1/2 Fe percentages (by ammonium oxalate) totaling

more than 1.0.

Andic Dystrudepts

KGFG. Other Dystrudepts that have, throughout one or more

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Dystrudepts

KGFH. 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

KGFI. Other Dystrudepts that have a slope of less than 25

percent; and

1. In one or more horizons within 60 cm of the mineral soil

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

aquic conditions for some time in normal years (or artificial

drainage); and

2. 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

KGFJ. 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

KGFK. Other Dystrudepts that have, in one or more horizons

within 60 cm of the mineral soil surface, redox depletions with
Inceptisols	 177

I

N

C

chroma of 2 or less and also aquic conditions for some time in

normal years (or artificial drainage).

Aquic Dystrudepts

KGFL. 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

KGFM. 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

KGFN. Other Dystrudepts that have lamellae (two or more)

within 200 cm of the mineral soil surface.

Lamellic Dystrudepts

KGFO. 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. A sandy particle-size class in all subhorizons throughout

the particle-size control section.

Humic Psammentic Dystrudepts

KGFP. Other Dystrudepts that have a slope of less than 25

percent; and

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. 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

KGFQ. Other Dystrudepts that have a slope of less than 25

percent 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 Dystrudepts

KGFR. 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

KGFS. 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

KGFT. 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

KGFU. Other Dystrudepts that have in each pedon a cambic

horizon that includes 10 to 50 percent (by volume) illuvial parts
178	 Keys to Soil Taxonomy

that otherwise meet the requirements for an argillic, kandic, or

natric horizon.

Ruptic-Ultic Dystrudepts

KGFV. 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

KGFW. Other Dystrudepts.

Typic Dystrudepts

Eutrudepts

Key to Subgroups

KGEA. 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

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

KGEB. Other Eutrudepts that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Eutrudepts

KGEC. 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

KGED. 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 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 Eutrudepts

KGEE. 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

KGEF. Other Eutrudepts that have, throughout one or more

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Eutrudepts

KGEG. Other Eutrudepts that have anthraquic conditions.

Anthraquic Eutrudepts

KGEH. 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

KGEI. Other Eutrudepts that have a slope of less than 25

percent; and

1. In one or more horizons within 60 cm of the mineral soil

surface, redox depletions with chroma of 2 or less and also
Inceptisols 179

I

N

C

aquic conditions for some time in normal years (or artificial 

drainage); and

2. 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

KGEJ. 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

KGEK. 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

KGEL. 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

KGEM. 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

KGEN. Other Eutrudepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Eutrudepts

KGEO. Other Eutrudepts that have a slope of less than 25 

percent; and

1. Do not have free carbonates throughout any horizon 

within 100 cm of the mineral soil surface; and

2. 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 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

KGEP. Other Eutrudepts that have a slope of less than 25 

percent 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 Eutrudepts

KGEQ. Other Eutrudepts that meet sandy or sandy-skeletal 

particle-size class criteria in all horizons within 50 cm of the 

mineral soil surface.

Arenic Eutrudepts

KGER. Other Eutrudepts that do not have free carbonates 

throughout any horizon within 100 cm of the mineral soil 

surface.

Dystric Eutrudepts

KGES. 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

KGET. 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

KGEU. 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 
180 Keys to Soil Taxonomy

mineral soil (unmixed) or between the mineral soil surface and a 

depth of 18 cm after mixing.

Humic Eutrudepts

KGEV. Other Eutrudepts.

Typic Eutrudepts

Fragiudepts

Key to Subgroups

KGCA. 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

KGCB. Other Fragiudepts that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Fragiudepts

KGCC. 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

KGCD. 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

KGCE. Other Fragiudepts.

Typic Fragiudepts

Humudepts

Key to Subgroups

KGDA. Humudepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humudepts

KGDB. 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

KGDC. 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Humudepts

KGDD. 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 
Inceptisols 181

I

N

C

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 Humudepts

KGDE. 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

KGDF. 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Humudepts

KGDG. Other Humudepts that have a slope of less than 25 

percent; and

1. In one or more horizons within 60 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. 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

KGDH. 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

KGDI. 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

KGDJ. Other Humudepts that have a sandy particle-size class 

in all subhorizons throughout the particle-size control section.

Psammentic Humudepts

KGDK. 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

KGDL. Other Humudepts that have a slope of less than 25 

percent; and

1. An umbric or mollic epipedon that is 50 cm or more 

thick; and

2. 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 Humudepts

KGDM. Other Humudepts that have a slope of less than 25 

percent and one or both of the following:
182 Keys to Soil Taxonomy

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 Humudepts

KGDN. Other Humudepts that have an umbric or mollic 

epipedon that is 50 cm or more thick.

Pachic Humudepts

KGDO. 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

KGDP. 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

KGDQ. Other Humudepts.

Typic Humudepts

Sulfudepts

Key to Subgroups

KGAA. All Sulfudepts (provisionally).

Typic Sulfudepts

Ustepts

Key to Great Groups

KEA. Ustepts that have a duripan within 100 cm of the 

mineral soil surface.

Durustepts, p. 183

KEB. 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. 182

KEC. Other Ustepts that have an umbric or mollic epipedon.

Humustepts, p. 189 

KED. 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. 183

KEF. Other Ustepts.

Haplustepts, p. 185

Calciustepts

Key to Subgroups

KEBA. Calciustepts that have a petrocalcic horizon and a 

lithic contact within 50 cm of the mineral soil surface.

Lithic Petrocalcic Calciustepts

KEBB. Other Calciustepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Calciustepts

KEBC. 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

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 
Inceptisols 183

I

N

C

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

KEBD. 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 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 Calciustepts

KEBE. Other Calciustepts that have a petrocalcic horizon 

within 100 cm of the mineral soil surface.

Petrocalcic Calciustepts

KEBF. Other Calciustepts that have a gypsic horizon within 

100 cm of the mineral soil surface.

Gypsic Calciustepts

KEBG. 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

KEBH. 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 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 

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

KEBI. 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 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 Calciustepts

KEBJ. Other Calciustepts.

Typic Calciustepts

Durustepts

Key to Subgroups

KEAA. All Durustepts (provisionally).

Typic Durustepts

Dystrustepts

Key to Subgroups

KEDA. Dystrustepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Dystrustepts

KEDB. 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 
184 Keys to Soil Taxonomy

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 6 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 Dystrustepts

KEDC. 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

KEDD. 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

KEDE. Other Dystrustepts that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Dystrustepts

KEDF. 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

KEDG. Other Dystrustepts that have a slope of less than 25 

percent 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 Dystrustepts

KEDH. 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 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 

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 
Inceptisols 185

I

N

C

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

KEDI. 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 NH4OAc pH 7) divided 

by the product of three times [percent water retained at 1500 

kPa tension minus percent organic carbon (but no more than 

1.00)] is less than 24.

Oxic Dystrustepts

KEDJ. 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

KEDK. Other Dystrustepts.

Typic Dystrustepts

Haplustepts

Key to Subgroups

KEEA. 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 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 Lithic Haplustepts

KEEB. Other Haplustepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Haplustepts

KEEC. Other Haplustepts that have both:

1. When neither irrigated nor fallowed to store moisture, 

one of the following:

a. A frigid soil temperature regime and a moisture 

control section that in normal years is dry in some or all 

parts for fewer than 105 cumulative days per year when 

the 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

KEED. Other Haplustepts that have both:
186 Keys to Soil Taxonomy

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 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

KEEE. 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

KEEF. 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

KEEG. Other Haplustepts that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Haplustepts

KEEH. Other Haplustepts that have anthraquic conditions.

Anthraquic Haplustepts

KEEI. 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

KEEJ. 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

KEEK. 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
Inceptisols 187

I

N

C

KEEL. Other Haplustepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Haplustepts

KEEM. Other Haplustepts that have a slope of less than 25 

percent; and

1. When neither irrigated nor fallowed to store moisture, 

one of the following:

a. A frigid soil temperature regime and a moisture 

control section that in normal years is dry in all parts for 

four-tenths or more of the cumulative days per year when 

the 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 oC; and

2. 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

KEEN. Other Haplustepts that have a slope of less than 25 

percent; and

1. When neither irrigated nor fallowed to store moisture, 

one of the following:

a. A frigid soil temperature regime and a moisture 

control section that in normal years is dry in some or all 

parts for fewer than 105 cumulative days per year when 

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

an organic-carbon content (Holocene age) of 0.2 percent 

or more and no densic, lithic, or paralithic contact within 

that depth; or

b. An irregular decrease in organic-carbon content 

(Holocene age) between a depth of 25 cm and either 

a depth of 125 cm below the mineral soil surface or a 

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

Udifluventic Haplustepts

KEEO. Other Haplustepts that have a slope of less than 25 

percent 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 Haplustepts

KEEP. Other Haplustepts that have a gypsic horizon within 

100 cm of the mineral soil surface.

Gypsic Haplustepts

KEEQ. 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 oC; or

b. A mesic or thermic soil temperature regime and a 
188 Keys to Soil Taxonomy

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

KEER. 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

KEES. Other Haplustepts that have a calcic horizon within 

100 cm of the mineral soil surface.

Calcic Haplustepts

KEET. 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 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:

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

KEEU. 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

KEEV. 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

KEEW. Other Haplustepts.

Typic Haplustepts
Inceptisols 189

I

N

C

Humustepts

Key to Subgroups

KECA. Humustepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humustepts

KECB. 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

KECC. 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Humustepts

KECD. 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

KECE. 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 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 Humustepts

KECF. 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 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:

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

KECG. Other Humustepts.

Typic Humustepts

Xerepts

Key to Great Groups

KFA. Xerepts that have a duripan within 100 cm of the 

mineral soil surface.

Durixerepts, p. 190

KFB. Other Xerepts that have a fragipan within 100 cm of the 

mineral soil surface.

Fragixerepts, p. 192

KFC. Other Xerepts that have an umbric or mollic epipedon.

Humixerepts, p. 194

KFD. 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. 190
190 Keys to Soil Taxonomy

KFE. 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. 191

KFF. Other Xerepts.

Haploxerepts, p. 193

Calcixerepts

Key to Subgroups

KFDA. Calcixerepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Calcixerepts

KFDB. 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

KFDC. Other Calcixerepts that have a petrocalcic horizon 

within 100 cm of the mineral soil surface.

Petrocalcic Calcixerepts

KFDD. 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

KFDE. Other Calcixerepts that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Calcixerepts

KFDF. Other Calcixerepts that have, in one or more horizons 

within 75 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Calcixerepts

KFDG. Other Calcixerepts.

Typic Calcixerepts

Durixerepts

Key to Subgroups

KFAA. Durixerepts that have both:

1. In one or more horizons above the duripan and within 30 

cm of the mineral soil surface, distinct or prominent redox 

concentrations and also aquic conditions for some time in 

normal years (or artificial drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more, above the duripan and within 75 cm of the 

mineral soil surface, one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Durixerepts

KFAB. 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

KFAC. Other Durixerepts that have, throughout one or more 
Inceptisols 191

I

N

C

horizons with a total thickness of 18 cm or more, above the 

duripan and within 75 cm of the mineral soil surface, one or 

both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Durixerepts

KFAD. 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

KFAE. Other Durixerepts that have a duripan that is strongly 

cemented or less cemented in all subhorizons.

Entic Durixerepts

KFAF. Other Durixerepts.

Typic Durixerepts

Dystroxerepts

Key to Subgroups

KFEA. 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

KFEB. Other Dystroxerepts that have a lithic contact within 

50 cm of the mineral soil surface.

Lithic Dystroxerepts

KFEC. Other Dystroxerepts that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Dystroxerepts

KFED. 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

KFEE. Other Dystroxerepts that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Dystroxerepts

KFEF. 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
192 Keys to Soil Taxonomy

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

KFEG. Other Dystroxerepts that have a slope of less than 25 

percent; and

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. 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

KFEH. 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

KFEI. 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

KFEJ. 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

KFEK. Other Dystroxerepts that have a slope of less than 25 

percent; and

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. 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 Dystroxerepts

KFEL. Other Dystroxerepts that have a slope of less than 25 

percent 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 Dystroxerepts

KFEM. 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

KFEN. Other Dystroxerepts.

Typic Dystroxerepts

Fragixerepts

Key to Subgroups

KFBA. 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

KFBB. Other Fragixerepts that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and
Inceptisols 193

I

N

C

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

KFBC. 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

KFBD. 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

KFBE. Other Fragixerepts.

Typic Fragixerepts

Haploxerepts

Key to Subgroups

KFFA. 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

KFFB. Other Haploxerepts that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Haploxerepts

KFFC. Other Haploxerepts that have one or both of the 

following:

1. Cracks within 125 cm of the mineral soil surface that are 

5 mm or more wide through a thickness of 30 cm or more 

for some time in normal years and slickensides or 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

KFFD. Other Haploxerepts that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Haploxerepts

KFFE. 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

KFFF. 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

KFFG. Other Haploxerepts that have both:

1. Saturation with water within 100 cm of the mineral soil 

surface in normal years for either or both:
194 Keys to Soil Taxonomy

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Oxyaquic Vitrandic Haploxerepts

KFFH. Other Haploxerepts that have, throughout one or more 

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

of the mineral soil surface, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Haploxerepts

KFFI. Other Haploxerepts that have a gypsic horizon within 

100 cm of the mineral soil surface.

Gypsic Haploxerepts

KFFJ. 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

KFFK. Other Haploxerepts that have lamellae (two or more) 

within 200 cm of the mineral soil surface.

Lamellic Haploxerepts

KFFL. 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

KFFM. Other Haploxerepts that have a slope of less than 25 

percent 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 Haploxerepts

KFFN. 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

KFFO. 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

KFFP. Other Haploxerepts.

Typic Haploxerepts

Humixerepts

Key to Subgroups

KFCA. Humixerepts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Humixerepts

KFCB. Other Humixerepts that have both:

1. In one or more horizons within 75 cm of the mineral soil 
Inceptisols 195

I

N

C

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or more of the following:

a. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling 

more than 1.0; or

b. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Humixerepts

KFCC. 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

KFCD. 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Humixerepts

KFCE. 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

KFCF. 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

KFCG. Other Humixerepts that have a slope of less than 25 

percent; and

1. An umbric or mollic epipedon that is 50 cm or more 

thick; and

2. 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

KFCH. Other Humixerepts that have a slope of less than 25 

percent 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 Humixerepts

KFCI. Other Humixerepts that have an umbric or mollic 

epipedon that is 50 cm or more thick.

Pachic Humixerepts

KFCJ. 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

KFCK. Other Humixerepts.

Typic Humixerepts

197

M

O

L

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. 198

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;1 and either

(1) Distinct or prominent redox concentrations in the 

lower part of the mollic epipedon; or

(2) Either directly below the mollic epipedon or 

within 75 cm of the mineral soil surface if a calcic 

horizon intervenes, a color value, moist, of 4 or more 

and one of the following:

(a) 50 percent or more chroma of 1 on faces of 

peds or in the matrix, hue of 10YR or redder, and 

redox concentrations; or

(b) 50 percent or more chroma of 2 or less on 

faces of peds or in the matrix, hue of 2.5Y, and 

redox concentrations; or

(c) 50 percent or more chroma of 1 on faces of 

peds or in the matrix and hue of 2.5Y or yellower; 

or

(d) 50 percent or more chroma of 3 or less on 

faces of peds or in the matrix, hue of 5Y, and redox 

concentrations; or

(e) 50 percent or more chroma of 0 on faces of 

peds or in the matrix; or

(f) Hue of 5GY, 5G, 5BG, or 5B; or

(g) Any color if it results from uncoated sand 

grains; or

b. Chroma of 2 in the lower part of the mollic epipedon; 

and either

(1) Distinct or prominent redox concentrations in the 

lower part of the mollic epipedon; or

(2) Directly below the mollic epipedon, one of the 

following matrix colors:

(a) A color value, moist, of 4, chroma of 2, and 

some redox depletions with a color value, moist, of 

4 or more and chroma of 1 or less; or

(b) A color value, moist, of 5 or more, chroma of 

2 or less, and redox concentrations; or

(c) A color value, moist, of 4 and chroma of 1 or 

less; or

6. At a depth between 40 and 50 cm from the mineral soil 

surface, enough active ferrous iron to give a positive reaction 

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

irrigated.

Aquolls, p. 199

CHAPTER 12

Mollisols

1If the mollic epipedon extends to a lithic contact within 30 cm of the mineral soil 

surface, the requirement for redoximorphic features is waived.
198 Keys to Soil Taxonomy

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. 207

ID. Other Mollisols that have a gelic soil temperature regime. 

Gelolls, p. 206

IE. Other Mollisols that have a cryic soil temperature regime.

Cryolls, p. 203

IF. Other Mollisols that have either a xeric soil moisture 

regime or an aridic soil moisture regime that borders on xeric.

Xerolls, p. 230

IG. Other Mollisols that have either an ustic soil moisture 

regime or an aridic soil moisture regime that borders on ustic.

Ustolls, p. 215

IH. Other Mollisols.

Udolls, p. 207

Albolls

Key to Great Groups

IAA. Albolls that have a natric horizon.

Natralbolls, p. 199

IAB. Other Albolls.

Argialbolls, p. 198

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	 199

M

O

L

2. More than 35 percent (by volume) fragments coarser

than 2.0 mm, of which more than 66 percent is cinders,

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Argialbolls

IABG. Other Argialbolls.

Typic Argialbolls

Natralbolls

Key to Subgroups

IAAA. Natralbolls that have visible crystals of gypsum and/or

more soluble salts within 40 cm of the mineral soil surface.

Leptic Natralbolls

IAAB. Other Natralbolls.

Typic Natralbolls

Aquolls

Key to Great Groups

IBA. Aquolls that have a cryic soil temperature regime.

Cryaquolls, p. 200

IBB. Other Aquolls that have a duripan within 100 cm of the

mineral soil surface.

Duraquolls, p. 200

IBC. Other Aquolls that have a natric horizon.

Natraquolls, p. 202

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. 199

IBE. Other Aquolls that have an argillic horizon.

Argiaquolls, p. 199

IBF.	 		Other Aquolls that have episaturation.

Epiaquolls, p. 201

IBG. Other Aquolls.

Endoaquolls, p. 200

Argiaquolls

Key to Subgroups

IBEA. Argiaquolls that meet sandy or sandy-skeletal particlesize class criteria 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 meet sandy or sandy-skeletal

particle-size class criteria 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 an argillic horizon that,

with increasing depth, has a clay increase of 20 percent or more

(absolute, in the fine-earth fraction) within its upper 7.5 cm.

Abruptic Argiaquolls

IBEE. Other Argiaquolls.

Typic Argiaquolls

Calciaquolls

Key to Subgroups

IBDA. Calciaquolls that have a petrocalcic horizon within 100

cm of the mineral soil surface.

Petrocalcic Calciaquolls

IBDB. Other Calciaquolls that have 50 percent or more

chroma of 3 or more on faces of peds or in the matrix of one or

more horizons within 75 cm of the mineral soil surface or that

have the following colors directly below the mollic epipedon:

1. Hue of 2.5Y or yellower and chroma of 3 or more; or

2. Hue of 10YR or redder and chroma of 2 or more; or

3. Hue of 2.5Y or yellower and chroma of 2 or more if

there are no distinct or prominent redox concentrations.

Aeric Calciaquolls
200 Keys to Soil Taxonomy

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Cryaquolls

IBAE. Other Cryaquolls that have an argillic horizon.

Argic Cryaquolls

IBAF. Other Cryaquolls that have a calcic horizon either 

within or directly below the mollic epipedon.

Calcic Cryaquolls

IBAG. Other Cryaquolls that have a mollic epipedon 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:

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 mollic epipedon that is 60 cm or more thick.

Cumulic Vertic Endoaquolls
Mollisols 201

M

O

L

IBGC. Other Endoaquolls that have both of the following:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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 slope of less than 25 percent and 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 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Endoaquolls

IBGH. Other Endoaquolls that have a horizon, 15 cm or more 

thick within 100 cm of the mineral soil surface, that either has 

20 percent or more (by volume) durinodes or is brittle and has 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 a slope of less than 25 

percent and one or both of the following:

1. An organic-carbon content (Holocene age) of 0.3 percent 

or more in all horizons within 125 cm of the mineral soil 

surface; or

2. An irregular decrease in organic-carbon content 

(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. 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
202 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. A mollic epipedon that is 60 cm or more thick.

Cumulic Vertic Epiaquolls

IBFB. Other Epiaquolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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 slope of less than 25 percent and 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 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Aquandic Epiaquolls

IBFG. Other Epiaquolls that have a horizon, 15 cm or more 

thick within 100 cm of the mineral soil surface, that either has 

20 percent or more (by volume) durinodes or is brittle and has at 

least a firm rupture-resistance class when moist.

Duric Epiaquolls

IBFH. Other Epiaquolls that have a mollic epipedon that is 60 

cm or more thick.

Cumulic Epiaquolls

IBFI. Other Epiaquolls that have a slope of less than 25 

percent and one or both of the following:

1. An organic-carbon content (Holocene age) of 0.3 percent 

or more in all horizons within 125 cm of the mineral soil 

surface; or

2. An irregular decrease in organic-carbon content 

(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 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-
Mollisols 203

M

O

L

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

IBCB. Other Natraquolls that have a glossic horizon or 

interfingering of albic materials into the natric horizon.

Glossic Natraquolls

IBCC. 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. 204

IEB. Other Cryolls that have a natric horizon.

Natricryolls, p. 206

IEC. Other Cryolls that have both:

1. An argillic horizon that has its upper boundary 60 cm or 

more below the mineral soil surface; and

2. A texture class finer than loamy fine sand in all horizons 

above the argillic horizon.

Palecryolls, p. 206

IED. Other Cryolls that have an argillic horizon.

Argicryolls, p. 203

IEE. Other Cryolls that have both:

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. 204

IEF. Other Cryolls.

Haplocryolls, p. 204

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

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Argicryolls

IEDE. Other Argicryolls that have an argillic horizon that, 

with increasing depth, has a clay increase of 20 percent or more 

(absolute, in the fine-earth fraction) within its upper 7.5 cm.

Abruptic Argicryolls

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
204 Keys to Soil Taxonomy

2. 30 or more cumulative days.

Oxyaquic Argicryolls

IEDH. Other Argicryolls that have both:

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic 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:
Mollisols 205

M

O

L

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Haplocryolls

IEFE. Other Haplocryolls that have:

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; and

3. A slope of less than 25 percent; and

4. In one or more horizons within 100 cm of the mineral 

soil surface, distinct or prominent redox concentrations and 

also aquic conditions for some time in normal years (or 

artificial drainage).

Aquic Cumulic Haplocryolls

IEFF. Other Haplocryolls that have:

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; and

3. A slope of less than 25 percent.

Cumulic Haplocryolls

IEFG. Other Haplocryolls that have both:

1. A slope of less than 25 percent and 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

2. In one or more horizons within 100 cm of the mineral 

soil surface, distinct or prominent redox concentrations and 

also aquic conditions for some time in normal years (or 

artificial drainage).

Fluvaquentic Haplocryolls

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:

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
206 Keys to Soil Taxonomy

IEFL. Other Haplocryolls that have a slope of less than 25 

percent and one or both of the following:

1. An organic-carbon content (Holocene age) of 0.3 percent 

or more at a depth of 125 cm below the mineral soil surface; 

or

2. An irregular decrease in organic-carbon content 

(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 

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 an argillic horizon that, 

with increasing depth, has a clay increase of 20 percent or more 

(absolute, in the fine-earth fraction) within its upper 7.5 cm.

Abruptic Palecryolls

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. 206

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
Mollisols	 207

M

O

L

IDAF. Other Haplogelolls that have both:

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

IDAE. Other Haplogelolls.

Typic Haplogelolls

Rendolls

Key to Great Groups

ICA. Rendolls that have a cryic soil temperature regime.

Cryrendolls, p. 207

ICB. Other Rendolls.

Haprendolls, p. 207

Cryrendolls

Key to Subgroups

ICAA. Cryrendolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Cryrendolls

ICAB. Other Cryrendolls.

Typic Cryrendolls

Haprendolls

Key to Subgroups

ICBA. Haprendolls that have a lithic contact within 50 cm of

the mineral soil surface.

Lithic Haprendolls

ICBB. Other Haprendolls that have one or both of the

following:

1. Cracks within 125 cm of the mineral soil surface that are

5 mm or more wide through a thickness of 30 cm or more

for some time in normal years and slickensides or 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. 213

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. 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, have either free carbonates or a texture

class of loamy fine sand or coarser.

Calciudolls, p. 210

IHC. Other Udolls that have one or more of the following:

1. A petrocalcic horizon within 150 cm of the mineral soil

surface; or

2. All of the following:

a. No densic, lithic, or paralithic contact within 150 cm

of the mineral soil surface; and

b. Within 150 cm of the mineral soil surface, a clay

decrease, with increasing depth, of less than 20 percent

(relative) from the maximum clay content (noncarbonate

clay); and

c. An argillic horizon with one or more of the following:

(1) In 50 percent or more of the matrix of one or

more subhorizons in its lower half, hue of 7.5YR or

redder and chroma of 5 or more; or

(2) In 50 percent or more of the matrix of horizons

that total more than one-half the total thickness, hue

of 2.5YR or redder, a value, moist, of 3 or less, and a

value, dry, of 4 or less; or

(3) Many redox concentrations with hue of 5YR or

redder or chroma of 6 or more, or both, in one or more

subhorizons; or

3. A frigid soil temperature regime; and
208 Keys to Soil Taxonomy

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. 214

IHD. Other Udolls that have an argillic horizon.

Argiudolls, p. 208

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. 215

IHF. Other Udolls.

Hapludolls, p. 211

Argiudolls

Key to Subgroups

IHDA. Argiudolls that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Argiudolls

IHDB. Other Argiudolls that have both:

1. Aquic conditions for some time in normal years (or 

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons 

that also have redoximorphic features; or

b. 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

IHDC. Other Argiudolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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 normal years saturation with water in one or more 

layers within 100 cm of the mineral soil surface for either or 

both:

a. 20 or more consecutive days; or

b. 30 or more cumulative days.

Oxyaquic Vertic Argiudolls

IHDD. Other Argiudolls that have:

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

IHDE. Other Argiudolls that have:

1. Above the argillic horizon, an albic horizon or a horizon 
Mollisols 209

M

O

L

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

IHDF. Other Argiudolls that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that are 

5 mm or more wide through a thickness of 30 cm or more 

for some time in normal years and slickensides or 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

IHDG. 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

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, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Argiudolls

IHDI. Other Argiudolls that have both:

1. Aquic conditions for some time in normal years (or 

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons 

that also have redoximorphic features; or

b. 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

IHDJ. 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

IHDK. 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

IHDL. Other Argiudolls that in normal years are saturated 
210 Keys to Soil Taxonomy

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

IHDM. Other Argiudolls that have an argillic horizon that:

1. Consists entirely of lamellae; or

2. Is a combination of two or more lamellae and one or 

more subhorizons with a thickness of 7.5 to 20 cm, each 

layer with an overlying eluvial horizon; or

3. Consists of one or more subhorizons that are more than 

20 cm thick, each with an overlying eluvial horizon, and 

above these horizons there are either:

a. Two or more lamellae with a combined thickness of 

5 cm or more (that may or may not be part of the argillic 

horizon); or

b. A combination of lamellae (that may or may not be 

part of the argillic horizon) and one or more parts of the 

argillic horizon 7.5 to 20 cm thick, each with an overlying 

eluvial horizon.

Lamellic Argiudolls

IHDN. 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

IHDO. Other Argiudolls that meet sandy or sandy-skeletal 

particle-size class criteria 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

IHDP. Other Argiudolls that have an argillic horizon that, 

with increasing depth, has a clay increase of 20 percent or more 

(absolute, in the fine-earth fraction) within its upper 7.5 cm.

Abruptic Argiudolls

IHDQ. Other Argiudolls that have:

1. Above the argillic horizon, an albic horizon or a horizon 

that has color values too high for a mollic epipedon and 

chroma too high for an albic horizon; or

2. A glossic horizon, or interfingering of albic materials 

into the upper part of the argillic horizon, or skeletans of 

clean silt and sand covering 50 percent or more of the faces 

of peds in the upper 5 cm of the argillic horizon.

Alfic Argiudolls

IHDR. Other Argiudolls 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.

Oxic Argiudolls

IHDS. Other Argiudolls that have a calcic horizon within 100 

cm of the mineral soil surface.

Calcic Argiudolls

IHDT. 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, 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

IHBD. Other Calciudolls that have a slope of less than 25 

percent and one or both of the following:

1. An organic-carbon content (Holocene age) of 0.3 percent 

or more at a depth of 125 cm below the mineral soil surface; 

or

2. An irregular decrease in organic-carbon content 

(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

IHBE. Other Calciudolls.

Typic Calciudolls
Mollisols 211

M

O

L

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 both:

1. Aquic conditions for some time in normal years (or 

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons 

that also have redoximorphic features; or

b. 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

IHFC. Other Hapludolls 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. 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.

Pachic Vertic Hapludolls

IHFD. 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

IHFE. 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

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, one or both of the following:

1. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Hapludolls

IHFG. Other Hapludolls that have:

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
212	 Keys to Soil Taxonomy

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. 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

3. A slope of less than 25 percent; and

4. In one or more horizons within 75 cm of the mineral soil

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

aquic conditions for some time in normal years (or artificial

drainage).

Aquic Cumulic Hapludolls

IHFH. Other Hapludolls that have:

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. 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

3. A slope of less than 25 percent.

Cumulic Hapludolls

IHFI. Other Hapludolls that have both:

1. Aquic conditions for some time in normal years (or

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

b. 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 slope of less than 25 percent and 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

IHFJ. Other Hapludolls that have a slope of less than 25

percent and one or both of the following:

1. An organic-carbon content (Holocene age) of 0.3 percent

or more at a depth of 125 cm below the mineral soil surface;

or

2. An irregular decrease in organic-carbon content

(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

IHFK. Other Hapludolls that have both:

1. Aquic conditions for some time in normal years (or

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons

that also have redoximorphic features; or

b. 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:
Mollisols 213

M

O

L

a. 40 cm or more thick in a frigid soil temperature 

regime; or

b. 50 cm or more thick.

Aquic Pachic Hapludolls

IHFL. 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

IHFM. 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

IHFN. 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

IHFO. 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

IHFP. Other Hapludolls that have a calcic horizon within 100 

cm of the mineral soil surface.

Calcic Hapludolls

IHFQ. 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

IHFR. 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:

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 Natrudolls

IHAC. Other Natrudolls that have:

1. A glossic horizon or interfingering of albic materials into 

the natric horizon; and

2. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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
214 Keys to Soil Taxonomy

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 a glossic horizon or 

interfingering of albic materials into the natric horizon.

Glossic Natrudolls

IHAG. Other Natrudolls that have a calcic horizon within 100 

cm of the mineral soil surface.

Calcic Natrudolls

IHAH. 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 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 Paleudolls

IHCB. Other Paleudolls that have a petrocalcic horizon within 

150 cm of the mineral soil surface.

Petrocalcic Paleudolls

IHCC. Other Paleudolls that have both:

1. Aquic conditions for some time in normal years (or 

artificial drainage) either:

a. Within 40 cm of the mineral soil surface, in horizons 

that also have redoximorphic features; or

b. 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

IHCD. 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

IHCE. 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

IHCF. 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

IHCG. Other Paleudolls that have both:

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, free carbonates or a texture class of loamy fine sand 

or coarser.

Calcic Paleudolls

IHCH. Other Paleudolls.

Typic Paleudolls
Mollisols 215

M

O

L

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. 221

IGB. Other Ustolls that have a natric horizon.

Natrustolls, p. 226

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. 219

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 clay content 

(noncarbonate clay) within 150 cm of the mineral soil 

surface (and there is no densic, lithic, or paralithic contact 

within that depth); and either

(1) Hue of 7.5YR or redder and chroma of 5 or more 

in the matrix; or

(2) Common redox concentrations with hue of 7.5YR 

or redder or chroma of 6 or more, or both; or

b. 35 percent or more noncarbonate clay in its upper 

part and a clay increase either of 20 percent or more 

(absolute) within a vertical distance of 7.5 cm or of 15 

percent or more (absolute) within a vertical distance of 

2.5 cm, in the fine-earth fraction (and there is no densic, 

lithic, or paralithic contact within 50 cm of the mineral 

soil surface).

Paleustolls, p. 228

IGE. Other Ustolls that have an argillic horizon.

Argiustolls, p. 215

IGF. Other Ustolls that have a mollic epipedon that:

1. Either below an Ap horizon or below a depth of 18 

cm from the mineral soil surface, contains 50 percent or 

more (by volume) wormholes, wormcasts, or filled animal 

burrows; and

2. Either rests on a lithic contact or has a transition zone 

to the underlying horizon in which 25 percent or more of the 

soil volume consists of discrete wormholes, wormcasts, or 

animal burrows filled with material from the mollic epipedon 

and from the underlying horizon.

Vermustolls, p. 230

IGG. Other Ustolls.

Haplustolls, p. 221

Argiustolls

Key to Subgroups

IGEA. Argiustolls that have both:

1. A lithic contact within 50 cm of the mineral soil surface; 

and

2. When neither irrigated nor fallowed to store moisture, 

have one of the following:

a. A frigid 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 
216 Keys to Soil Taxonomy

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:

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:

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:

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, 

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.

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. 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

3. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for four-tenths or less of the cumulative days 
Mollisols 217

M

O

L

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.

Pachic Udertic Argiustolls

IGEG. Other Argiustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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, 

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.

Udertic Argiustolls

IGEH. Other Argiustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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 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.

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 

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:

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 
218 Keys to Soil Taxonomy

of 18 cm or more within 75 cm of the mineral soil surface, 

one or both of the following:

a. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Vitritorrandic 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Argiustolls

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 

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:

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 part for six-tenths or more of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some part for six-tenths or more of the 

cumulative days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

5 oC.

Calcidic Argiustolls

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 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 

or all parts for six-tenths or more of the cumulative days per 
Mollisols 219

M

O

L

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:

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 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 Calciustolls

IGCE. Other Calciustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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
220 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 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.

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 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 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

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 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 

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 oC.

Udic Calciustolls

IGCN. Other Calciustolls.

Typic Calciustolls
Mollisols 221

M

O

L

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:

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 6 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. 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:

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:

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:
222 Keys to Soil Taxonomy

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 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. 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

3. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for four-tenths or less of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 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.

Pachic Udertic Haplustolls

IGGH. Other Haplustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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, 

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.

Udertic Haplustolls

IGGI. Other Haplustolls that have both:

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
Mollisols 223

M

O

L

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:

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 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 

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.)

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:

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 or all parts for six-tenths or 

more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface 

is higher than 5 oC; and

2. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

one or both of the following:

a. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and
224 Keys to Soil Taxonomy

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

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

equal to 30 or more.

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

b. [(Al plus 1

/2 Fe, percent extracted by ammonium 

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

equal to 30 or more.

Vitrandic Haplustolls

IGGP. Other Haplustolls that have:

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. 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

3. A slope of less than 25 percent; and

4. In one or more horizons within 100 cm of the mineral 

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

also aquic conditions for some time in normal years (or 

artificial drainage).

Aquic Cumulic Haplustolls

IGGQ. Other Haplustolls that have:

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. 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

3. A slope of less than 25 percent.

Cumulic Haplustolls

IGGR. Other Haplustolls that have anthraquic conditions.

Anthraquic Haplustolls

IGGS. Other Haplustolls that have both:

1. In one or more horizons within 100 cm of the mineral 

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

also aquic conditions for some time in normal years (or 

artificial drainage); and

2. A slope of less than 25 percent and 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
Mollisols 225

M

O

L

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 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 or all parts for six-tenths or 

more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface 

is higher than 5 oC; and

2. A slope of less than 25 percent and 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 oC; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for six-tenths or more of the cumulative days 

per year when the soil temperature at a depth of 50 cm 

below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

8 oC; and

(2) Is dry in some or all parts for six-tenths or 

more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface 

is higher than 5 oC; and

2. 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 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:

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
226 Keys to Soil Taxonomy

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 a slope of less than 25 

percent and one or both of the following:

1. An organic-carbon content (Holocene age) of 0.3 percent 

or more at a depth of 125 cm below the mineral soil surface; 

or

2. An irregular decrease in organic-carbon content 

(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 

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. 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

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 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
Mollisols 227

M

O

L

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than

8 oC; and

(2) Is dry in some or all parts for six-tenths or 

more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface 

is higher than 5 oC.

Leptic Torrertic Natrustolls

IGBB. Other Natrustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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 oC; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some or all parts for six-tenths or more of the cumulative 

days per year when the soil temperature at a depth of 50 

cm below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

8 oC; and

(2) Is dry in some or all parts for six-tenths or 

more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface 

is higher than 5 oC.

Torrertic Natrustolls

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:

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:

1. Visible crystals of gypsum or of more soluble salts, or 

both, within 40 cm of the mineral soil surface; and

2. When neither irrigated nor fallowed to store moisture, 

one of the following:

a. A frigid soil temperature regime and a moisture 
228 Keys to Soil Taxonomy

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 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

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 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:

a. Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC; 

and

b. Is dry in some or all parts for six-tenths or more of 

the cumulative days per year when the soil temperature 

at a depth of 50 cm below the soil surface is higher than 

5 oC.

Aridic Natrustolls

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:

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 

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
Mollisols 229

M

O

L

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some or all parts for six-tenths or more of the cumulative 

days per year when the soil temperature at a depth of 50 

cm below the soil surface is higher than 5 oC; or

c. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

(1) Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at 

a depth of 50 cm below the soil surface is higher than 

8 oC; and

(2) Is dry in some or all parts for six-tenths or 

more of the cumulative days per year when the soil 

temperature at a depth of 50 cm below the soil surface 

is higher than 5 oC.

Torrertic Paleustolls

IGDB. Other Paleustolls that have both:

1. One or both of the following:

a. Cracks within 125 cm of the mineral soil surface that 

are 5 mm or more wide through a thickness of 30 cm or 

more for some time in normal years and slickensides or 

wedge-shaped 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, 

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.

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 

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 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:

1. Have a calcic horizon within one of the following 

particle-size class (by weighted average in the particle-size 

control section) and depth combinations:

a. Sandy or sandy-skeletal and within 100 cm of the 

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 

50 cm of the mineral soil surface; or

c. Any other class and within 60 cm of the mineral soil 

surface; and

2. When neither irrigated nor fallowed to store moisture, 

have one of the following:

a. A frigid soil temperature regime and a moisture 

control section that in normal years is dry in all parts for 

less than four-tenths of the cumulative days per year when 

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

surface is higher than 5 oC; or

b. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for 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 
230 Keys to Soil Taxonomy

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 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

2. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in some 

part for six-tenths or more of the cumulative days per year 

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

surface is higher than 5 oC; or

3. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

a. Is moist in some or all parts for fewer than 90 

consecutive days per year when the soil temperature at a 

depth of 50 cm below the soil surface is higher than 8 oC; 

and

b. Is dry in some or all parts for six-tenths or more of 

the cumulative days per year when the soil temperature 

at a depth of 50 cm below the soil surface is higher than 

5 oC.

Aridic Paleustolls

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 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. 234

IFB. Other Xerolls that have a natric horizon.

Natrixerolls, p. 239

IFC. Other Xerolls that have either:

1. A petrocalcic horizon within 150 cm of the mineral soil 

surface; or
Mollisols 231

M

O

L

2. An argillic horizon that has one or both of the following:

a. With increasing depth, no clay decrease of 20 percent 

or more (relative) from the maximum clay content 

(noncarbonate clay) within 150 cm of the mineral soil 

surface (and there is no densic, lithic, or paralithic contact 

within that depth); and either

(1) Hue of 7.5YR or redder and chroma of 5 or more 

in the matrix; or

(2) Common redox concentrations with hue of 7.5YR 

or redder or chroma of 6 or more, or both; or

b. 35 percent or more noncarbonate clay in its upper 

part and, at its upper boundary, a clay increase either of 

20 percent or more (absolute) within a vertical distance 

of 7.5 cm or of 15 percent or more (absolute) within a 

vertical distance of 2.5 cm, in the fine-earth fraction (and 

there is no densic, lithic, or paralithic contact within 50 

cm of the mineral soil surface).

Palexerolls, p. 239

IFD. Other Xerolls that have both:

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. 233

IFE. Other Xerolls that have an argillic horizon.

Argixerolls, p. 231

IFF. Other Xerolls.

Haploxerolls, p. 235

Argixerolls

Key to Subgroups

IFEA. Argixerolls that have both:

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:

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:

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 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 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:

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and
232 Keys to Soil Taxonomy

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Vitritorrandic 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Argixerolls

IFEI. Other Argixerolls that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. A base saturation (by sum of cations) of 75 percent or 

less in one or more horizons between either an Ap horizon 

or a depth of 25 cm from the mineral soil surface, whichever 

is deeper, and either a depth of 75 cm or a densic, lithic, or 

paralithic contact, whichever is shallower.

Aquultic Argixerolls

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:

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:

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:

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.

Argiduridic Argixerolls

IFEQ. Other Argixerolls that have a horizon within 100 cm of 
Mollisols 233

M

O

L

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:

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.

Calciargidic Argixerolls

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:

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter, of which 5 percent or 

more is volcanic glass, and [(Al plus 1/2 Fe, percent extracted 

by ammonium oxalate) times 60] plus the volcanic glass 

(percent) is equal to 30 or more.

Vitrandic Calcixerolls
234 Keys to Soil Taxonomy

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 

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:

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Vitritorrandic Durixerolls

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Durixerolls

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. An argillic horizon that, with increasing depth, has a 

clay increase either of 20 percent or more (absolute) within 

a vertical distance of 7.5 cm or of 15 percent or more 

(absolute) within a vertical distance of 2.5 cm; and

3. A duripan that is neither very strongly cemented nor 

indurated in any subhorizon.

Paleargidic Durixerolls

IFAF. Other Durixerolls that have both:

1. An aridic soil moisture regime; and

2. An argillic horizon that, with increasing depth, has a 

clay increase either of 20 percent or more (absolute) within 

a vertical distance of 7.5 cm or of 15 percent or more 

(absolute) within a vertical distance of 2.5 cm.

Abruptic Argiduridic Durixerolls

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:

1. An aridic soil moisture regime; and
Mollisols 235

M

O

L

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

IFAK. Other Durixerolls that have both:

1. An argillic horizon that, with increasing depth, has a 

clay increase either of 20 percent or more (absolute) within 

a vertical distance of 7.5 cm or of 15 percent or more 

(absolute) within a vertical distance of 2.5 cm; and

2. A duripan that is neither very strongly cemented nor 

indurated in any subhorizon.

Haplic Palexerollic Durixerolls

IFAL. Other Durixerolls that have an argillic horizon that, 

with increasing depth, has a clay increase either of 20 percent 

or more (absolute) within a vertical distance of 7.5 cm or of 15 

percent or more (absolute) within a vertical distance of 2.5 cm.

Palexerollic Durixerolls

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:

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:

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:

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:

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) fragments coarser 
236 Keys to Soil Taxonomy

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Vitritorrandic Haploxerolls

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Haploxerolls

IFFI. 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. 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

3. A slope of less than 25 percent; and

4. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Cumulic Haploxerolls

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. 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

3. A slope of less than 25 percent; and

4. A base saturation (by sum of cations) of 75 percent or 

less in one or more horizons between either an Ap horizon 

or a depth of 25 cm from the mineral soil surface, whichever 

is deeper, and either a depth of 75 cm or a densic, lithic, or 

paralithic contact, whichever is shallower.

Cumulic Ultic Haploxerolls

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. 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

3. A slope of less than 25 percent.

Cumulic Haploxerolls

IFFL. Other Haploxerolls that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. A slope of less than 25 percent and 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
Mollisols 237

M

O

L

IFFM. Other Haploxerolls that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. A horizon, 15 cm or more thick within 100 cm of the 

mineral soil surface, that either has 20 percent or more (by 

volume) durinodes or is brittle and has at least a firm ruptureresistance class when moist.

Aquic Duric Haploxerolls

IFFN. Other Haploxerolls that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. A base saturation (by sum of cations) of 75 percent or 

less in one or more horizons between either an Ap horizon 

or a depth of 25 cm from the mineral soil surface, whichever 

is deeper, and either a depth of 75 cm or a densic, lithic, or 

paralithic contact, whichever is shallower.

Aquultic Haploxerolls

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:

1. A mollic epipedon that is 50 cm or more thick and has a 

texture class finer than loamy fine sand; and

2. A calcic horizon or identifiable secondary carbonates 

within one of the following particle-size class (by weighted 

average in the particle-size control section) and depth 

combinations:

a. Sandy or sandy-skeletal and within 150 cm of the 

mineral soil surface; or

b. Clayey, clayey-skeletal, fine, or very-fine and within 

90 cm of the mineral soil surface; or

c. Any other class and within 110 cm of the mineral soil 

surface.

Calcic Pachic Haploxerolls

IFFR. Other Haploxerolls that have both:

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. 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

IFFU. Other Haploxerolls that have both:

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:

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
238 Keys to Soil Taxonomy

c. Any other class and within 110 cm of the mineral soil 

surface.

Calcidic Haploxerolls

IFFW. Other Haploxerolls that have both:

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 a slope of less than 25 

percent and one or both of the following:

1. An organic-carbon content (Holocene age) of 0.3 percent 

or more in all horizons within 125 cm of the mineral soil 

surface; or

2. An irregular decrease in organic-carbon content 

(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 

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
Mollisols 239

M

O

L

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 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 Natrixerolls

IFBB. Other Natrixerolls that have both:

1. In one or more horizons within 75 cm of the mineral soil 

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

aquic conditions for some time in normal years (or artificial 

drainage); and

2. A horizon, 15 cm or more thick within 100 cm of the 

mineral soil surface, that either has 20 percent or more (by 

volume) durinodes or is brittle and has 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 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 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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Vitrandic Palexerolls

IFCC. Other Palexerolls that have, in one or more horizons 

within 75 cm of the mineral soil surface, redox depletions with 

chroma of 2 or less and also aquic conditions for some time in 

normal years (or artificial drainage).

Aquic Palexerolls

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:

1. An aridic soil moisture regime; and

2. A petrocalcic horizon within 150 cm of the mineral soil 

surface.

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
240

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
241

O

X

I

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. 241

EB. Other Oxisols that have an aridic soil moisture regime.

Torrox, p. 246

EC. Other Oxisols that have an ustic or xeric soil moisture 

regime.

Ustox, p. 251

ED. Other Oxisols that have a perudic soil moisture regime.

Perox, p. 242

EE. Other Oxisols.

Udox, p. 247

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. 241

EAB. Other Aquox that have plinthite forming a continuous 

phase within 125 cm of the mineral soil surface.

Plinthaquox, p. 242

EAC. Other Aquox that have a base saturation (by NH4OAc) 

of 35 percent or more in all horizons within 125 cm of the 

mineral soil surface.

Eutraquox, p. 241

EAD. Other Aquox.

Haplaquox, p. 242

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

CHAPTER 13

Oxisols
242 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. 246

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. 242

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. 243

EDD. Other Perox that have a kandic horizon within 150 cm 

of the mineral soil surface.

Kandiperox, p. 245

EDE. Other Perox.

Haploperox, p. 244

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 243

O

X

I

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
244 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 245

O

X

I

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
246 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. 246

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. 246

EBC. Other Torrox.

Haplotorrox, p. 246

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
Oxisols 247

O

X

I

Udox

Key to Great Groups

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

mineral soil surface.

Sombriudox, p. 251

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. 247

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. 248

EED. Other Udox that have a kandic horizon within 150 cm of 

the mineral soil surface.

Kandiudox, p. 250

EEE. Other Udox.

Hapludox, p. 249

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 

NH4OAc) of 35 percent or more in all horizons within 125 cm 

of the mineral soil surface.

Eutric Acrudox

EEBJ. Other Acrudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from 

the mineral soil surface, more than 50 percent colors that 

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Acrudox

EEBK. Other Acrudox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a color 

value, moist, of 6 or more at a depth between 25 and 125 cm 

from the mineral soil surface.

Humic Xanthic Acrudox

EEBL. Other Acrudox that have 16 kg/m2 or more organic 
248 Keys to Soil Taxonomy

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
Oxisols 249

O

X

I

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
250 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
Oxisols 251

O

X

I

EEDM. Other Kandiudox that have 50 percent or more hue 

of 7.5YR or yellower and a color value, moist, of 6 or more at a 

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Kandiudox

EEDN. Other Kandiudox.

Typic Kandiudox

Sombriudox

Key to Subgroups

EEAA. Sombriudox that have a petroferric contact within 125 

cm of the mineral soil surface.

Petroferric Sombriudox

EEAB. Other Sombriudox that have a lithic contact within 125 

cm of the mineral soil surface.

Lithic Sombriudox

EEAC. Other Sombriudox that have 16 kg/m2 or more 

organic carbon between the mineral soil surface and a depth of 

100 cm.

Humic Sombriudox

EEAD. Other Sombriudox.

Typic Sombriudox

Ustox

Key to Great Groups

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

mineral soil surface.

Sombriustox, p. 255

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. 251

ECC. Other Ustox that have a base saturation (by NH4OAc) of 

35 percent or more in all horizons within 125 cm of the mineral 

soil surface.

Eutrustox, p. 252

ECD. Other Ustox that have a kandic horizon within 150 cm 

of the mineral soil surface.

Kandiustox, p. 254

ECE. Other Ustox.

Haplustox, p. 253

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 
252 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
Oxisols 253

O

X

I

ECCH. Other Eutrustox that have a kandic horizon within 

150 cm of the mineral soil surface.

Kandiustalfic Eutrustox

ECCI. Other Eutrustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. An oxic horizon that has its lower boundary within 125 

cm of the mineral soil surface.

Humic Inceptic Eutrustox

ECCJ. Other Eutrustox that have an oxic horizon that has its 

lower boundary within 125 cm of the mineral soil surface.

Inceptic Eutrustox

ECCK. Other Eutrustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from 

the mineral soil surface, more than 50 percent colors that 

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Eutrustox

ECCL. Other Eutrustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a color 

value, moist, of 6 or more at a depth between 25 and 125 cm 

from the mineral soil surface.

Humic Xanthic Eutrustox

ECCM. Other Eutrustox that have 16 kg/m2 or more organic 

carbon between the mineral soil surface and a depth of 100 cm.

Humic Eutrustox

ECCN. Other Eutrustox that have, in all horizons at a depth 

between 25 and 125 cm from the mineral soil surface, more than 

50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Eutrustox

ECCO. Other Eutrustox that have 50 percent or more hue of 

7.5YR or yellower and a color value, moist, of 6 or more at a 

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Eutrustox

ECCP. Other Eutrustox.

Typic Eutrustox

Haplustox

Key to Subgroups

ECEA. Haplustox that have, within 125 cm of the mineral soil 

surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more 

and chroma of 2 or less and also aquic conditions for some 

time in normal years (or artificial drainage).

Aquic Petroferric Haplustox

ECEB. Other Haplustox that have a petroferric contact within 

125 cm of the mineral soil surface.

Petroferric Haplustox

ECEC. Other Haplustox that have, within 125 cm of the 

mineral soil surface, both:

1. A lithic contact; and

2. Redox depletions with a color value, moist, of 4 or more 

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
254 Keys to Soil Taxonomy

ECEH. Other Haplustox that have, in one or more horizons 

within 125 cm of the mineral soil surface, redox depletions with 

a color value, moist, of 4 or more and chroma of 2 or less and 

also aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Haplustox

ECEI. Other Haplustox that are saturated with water in one or 

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

years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Haplustox

ECEJ. Other Haplustox that have an oxic horizon that has its 

lower boundary within 125 cm of the mineral soil surface.

Inceptic Haplustox

ECEK. Other Haplustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from 

the mineral soil surface, more than 50 percent colors that 

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Haplustox

ECEL. Other Haplustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a color 

value, moist, of 6 or more at a depth between 25 and 125 cm 

from the mineral soil surface.

Humic Xanthic Haplustox

ECEM. Other Haplustox that have 16 kg/m2 or more organic 

carbon between the mineral soil surface and a depth of 100 cm.

Humic Haplustox

ECEN. Other Haplustox that have, in all horizons at a depth 

between 25 and 125 cm from the mineral soil surface, more than 

50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Haplustox

ECEO. Other Haplustox that have 50 percent or more hue of 

7.5YR or yellower and a color value, moist, of 6 or more at a 

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Haplustox

ECEP. Other Haplustox.

Typic Haplustox

Kandiustox

Key to Subgroups

ECDA. Kandiustox that have, within 125 cm of the mineral 

soil surface, both:

1. A petroferric contact; and

2. Redox depletions with a color value, moist, of 4 or more 

and chroma of 2 or less and also aquic conditions for some 

time in normal years (or artificial drainage).

Aquic Petroferric Kandiustox

ECDB. Other Kandiustox that have a petroferric contact 

within 125 cm of the mineral soil surface.

Petroferric Kandiustox

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 
Oxisols 255

O

X

I

a color value, moist, of 4 or more and chroma of 2 or less and 

also aquic conditions for some time in normal years (or artificial 

drainage).

Aquic Kandiustox

ECDH. Other Kandiustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. In all horizons at a depth between 25 and 125 cm from 

the mineral soil surface, more than 50 percent colors that 

have both of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less.

Humic Rhodic Kandiustox

ECDI. Other Kandiustox that have both:

1. 16 kg/m2 or more organic carbon between the mineral 

soil surface and a depth of 100 cm; and

2. 50 percent or more hue of 7.5YR or yellower and a color 

value, moist, of 6 or more at a depth between 25 and 125 cm 

from the mineral soil surface.

Humic Xanthic Kandiustox

ECDJ. Other Kandiustox that have 16 kg/m2 or more organic 

carbon between the mineral soil surface and a depth of 100 

cm.

Humic Kandiustox

ECDK. Other Kandiustox that have, in all horizons at a depth 

between 25 and 125 cm from the mineral soil surface, more than 

50 percent colors that have both of the following:

1. Hue of 2.5YR or redder; and

2. A value, moist, of 3 or less.

Rhodic Kandiustox

ECDL. Other Kandiustox that have 50 percent or more hue 

of 7.5YR or yellower and a color value, moist, of 6 or more at a 

depth between 25 and 125 cm from the mineral soil surface.

Xanthic Kandiustox

ECDM. Other Kandiustox.

Typic Kandiustox

Sombriustox

Key to Subgroups

ECAA. Sombriustox that have a petroferric contact within 125 

cm of the mineral soil surface.

Petroferric Sombriustox

ECAB. Other Sombriustox that have a lithic contact within 

125 cm of the mineral soil surface.

Lithic Sombriustox

ECAC. Other Sombriustox that have 16 kg/m2 or more organic 

carbon between the mineral soil surface and a depth of 100 cm.

Humic Sombriustox

ECAD. Other Sombriustox.

Typic Sombriustox

257

S

P

O

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. 257

CB. Other Spodosols that have a gelic soil temperature 

regime.

Gelods, p. 261

CC. Other Spodosols that have a cryic soil temperature 

regime.

Cryods, p. 259

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. 261

CE. Other Spodosols.

Orthods, p. 262

Aquods

Key to Great Groups

CAA. Aquods that have a cryic soil temperature regime.

Cryaquods, p. 258

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. 257

CAC. Other Aquods that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiaquods, p. 259

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. 259

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. 258

CAF. Other Aquods that have episaturation.

Epiaquods, p. 259

CAG. Other Aquods.

Endoaquods, p. 258

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. Meet sandy or sandy-skeletal particle-size class criteria 

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. Meet sandy or sandy-skeletal particle-size class criteria 

throughout a layer extending from the mineral soil surface to 

the top of a spodic horizon at a depth of 75 to 125 cm.

Arenic Ultic Alaquods

CHAPTER 14

Spodosols
258 Keys to Soil Taxonomy

CABF. Other Alaquods that:

1. Have an umbric epipedon; and

2. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria 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

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
Spodosols 259

S

P

O

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 30 cm 

or more thick that meets all of the requirements for a plaggen 

epipedon except thickness.

Plagganthreptic Fragiaquods

CACC. Other Fragiaquods that have an argillic or kandic 

horizon within 200 cm of the mineral soil surface. 

Argic Fragiaquods

CACD. Other Fragiaquods.

Typic Fragiaquods

Placaquods

Key to Subgroups

CADA. Placaquods that have andic soil properties 

throughout horizons that have a total thickness of 25 cm or 

more within 75 cm either of the mineral soil surface or of the 

top of an organic layer with andic soil properties, whichever is 

shallower.

Andic Placaquods

CADB. Other Placaquods.

Typic Placaquods

Cryods

Key to Great Groups

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. 261

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. 259

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. 260

CCD. Other Cryods.

Haplocryods, p. 260

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

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
260 Keys to Soil Taxonomy

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 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
Spodosols 261

S

P

O

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. 261

CBB. Other Gelods.

Haplogelods, p. 261

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. 262

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. 262

CDC. Other Humods that have a fragipan within 100 cm of 

the mineral soil surface.

Fragihumods, p. 262

CDD. Other Humods.

Haplohumods, p. 262
262 Keys to Soil Taxonomy

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 

30 cm or more thick that meets all of the requirements for a 

plaggen epipedon except thickness.

Plagganthreptic 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. 265

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. 263

CEC. Other Orthods that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiorthods, p. 263

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. 262

CEE. Other Orthods.

Haplorthods, p. 264

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. Meet sandy or sandy-skeletal particle-size class criteria 

throughout a layer extending from the mineral soil surface to 

the top of a spodic horizon at a depth of 75 to 125 cm; and

2. Have an argillic or kandic horizon below the spodic 

horizon.

Arenic Ultic Alorthods

CEDC. Other Alorthods that meet sandy or sandy-skeletal 

particle-size class criteria 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. Meet sandy or sandy-skeletal particle-size class criteria 
Spodosols 263

S

P

O

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 30 cm 

or more thick that meets all of the requirements for a plaggen 

epipedon except thickness.

Plagganthreptic 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 30 cm 

or more thick that meets all of the requirements for a plaggen 

epipedon except thickness.

Plagganthreptic 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

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

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 
264 Keys to Soil Taxonomy

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

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

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:

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 
Spodosols 265

S

P

O

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

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
 
267

U

L

T

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. 267

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. 271

HC. Other Ultisols that have a udic soil moisture regime.

Udults, p. 274

HD. Other Ultisols that have an ustic soil moisture regime.

Ustults, p. 281

HE. Other Ultisols.

Xerults, p. 285

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. 271

HAB. Other Aquults that have a fragipan within 100 cm of the

mineral soil surface.

Fragiaquults, p. 269

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 or slower (moderately low or lower Ksat class) in the

argillic or kandic horizon.

Albaquults, p. 268

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. 269

HAE. Other Aquults that have a kandic horizon.

Kanhaplaquults, p. 269

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:

CHAPTER 15

Ultisols
268 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. 270

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

Umbraquults, p. 271

HAH. Other Aquults that have episaturation.

Epiaquults, p. 268

HAI. Other Aquults.

Endoaquults, p. 268

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria 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 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 Epiaquults

HAHB. Other Epiaquults that have:

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 
Ultisols 269

U

L

T

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 mollic or umbric epipedon; and

2. Meet sandy or sandy-skeletal particle-size class criteria 

throughout a layer extending from the mineral soil surface to 

the top of a kandic horizon at a depth of 50 to 100 cm.

Arenic Umbric Kandiaquults

HADD. Other Kandiaquults that meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria 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 

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 
270 Keys to Soil Taxonomy

within 75 cm of the mineral soil surface, one or more of the 

following:

1. A fine-earth fraction with both a bulk density of 1.0 

g/cm3 or less, measured at 33 kPa water retention, and Al 

plus 1/2 Fe percentages (by ammonium oxalate) totaling more 

than 1.0; or

2. More than 35 percent (by volume) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

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

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Kanhaplaquults

HAEB. Other Kanhaplaquults that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Kanhaplaquults

HAEC. Other Kanhaplaquults that:

1. Have a mollic or umbric epipedon; and

2. Have 50 percent or more chroma of 3 or more in one or 

more horizons between either the A or Ap horizon or a depth 

of 25 cm from the mineral soil surface, whichever is deeper, 

and a depth of 75 cm.

Aeric Umbric Kanhaplaquults

HAED. Other Kanhaplaquults that have 50 percent or more 

chroma of 3 or more in one or more horizons between either 

the A or Ap horizon or a depth of 25 cm from the mineral soil 

surface, whichever is deeper, and a depth of 75 cm.

Aeric Kanhaplaquults

HAEE. Other Kanhaplaquults that have a mollic or umbric 

epipedon.

Umbric Kanhaplaquults

HAEF. Other Kanhaplaquults.

Typic Kanhaplaquults

Paleaquults

Key to Subgroups

HAFA. Paleaquults that have one or both of the following:

1. Cracks within 125 cm of the mineral soil surface that are 

5 mm or more wide through a thickness of 30 cm or more 

for some time in normal years and slickensides or 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. Meet sandy or sandy-skeletal particle-size class criteria 

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 mollic or umbric epipedon; and

2. Meet sandy or sandy-skeletal particle-size class criteria 

throughout a layer extending from the mineral soil surface to 

the top of an argillic horizon at a depth of 50 to 100 cm.

Arenic Umbric Paleaquults

HAFD. Other Paleaquults that meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 

mineral soil surface to the top of an argillic horizon at a depth of 

100 cm or more.

Grossarenic Paleaquults

HAFF. Other Paleaquults that have 5 percent or more (by 

volume) plinthite in one or more horizons within 150 cm of the 

mineral soil surface.

Plinthic Paleaquults

HAFG. Other Paleaquults that have 50 percent or more 

chroma of 3 or more in one or more horizons between either 

the A or Ap horizon or a depth of 25 cm from the mineral soil 

surface, whichever is deeper, and a depth of 75 cm.

Aeric Paleaquults

HAFH. Other Paleaquults that have a mollic or umbric 

epipedon.

Umbric Paleaquults

HAFI. Other Paleaquults.

Typic Paleaquults
Ultisols 271

U

L

T

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. 274

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. 274

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. 272

HBD. Other Humults that have a kandic horizon.

Kanhaplohumults, p. 273

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. 273

HBF. Other Humults.

Haplohumults, p. 271

Haplohumults

Key to Subgroups

HBFA. Haplohumults that have a lithic contact within 50 cm 

of the mineral soil surface.

Lithic Haplohumults

HBFB. Other Haplohumults that have both:

1. In one or more subhorizons within the upper 25 cm of 

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

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
272 Keys to Soil Taxonomy

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:

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

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
Ultisols 273

U

L

T

Kanhaplohumults

Key to Subgroups

HBDA. Kanhaplohumults that have a lithic contact within 50 

cm of the mineral soil surface.

Lithic Kanhaplohumults

HBDB. Other Kanhaplohumults that have both:

1. An ustic 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:

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

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
274 Keys to Soil Taxonomy

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. 281

HCB. Other Udults that have a fragipan within 100 cm of the 

mineral soil surface.

Fragiudults, p. 274

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. 276

HCD. Other Udults that have a kandic horizon.

Kanhapludults, p. 278

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. 279

HCF. Other Udults that have both:

1. An epipedon that has a color value, moist, of 3 or less 

throughout; and

2. In all subhorizons in the upper 100 cm of the argillic 

horizon or throughout the entire argillic horizon if it is less 

than 100 cm thick, more than 50 percent colors that have all

of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist 

value.

Rhodudults, p. 281

HCG. Other Udults.

Hapludults, p. 275

Fragiudults

Key to Subgroups

HCBA. Fragiudults that meet sandy or sandy-skeletal particlesize class criteria 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:
Ultisols 275

U

L

T

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

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:

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 
276	 Keys to Soil Taxonomy

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 meet sandy or sandy-skeletal

particle-size class criteria 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 meet sandy or sandy-skeletal

particle-size class criteria throughout a layer extending from the

mineral soil surface to the top of an argillic horizon at a depth of

100 cm or more.

Grossarenic Hapludults

HCGM. Other Hapludults that:

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:

1. Meet sandy or sandy-skeletal particle-size class criteria

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; and

3. 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).

Arenic Plinthaquic Kandiudults

HCCB. Other Kandiudults that:

1. Meet sandy or sandy-skeletal particle-size class criteria

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
Ultisols 277

U

L

T

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. Meet sandy or sandy-skeletal particle-size class criteria 

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria 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. Meet sandy or sandy-skeletal particle-size class criteria

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 meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 

mineral soil surface to the top of a kandic horizon at a depth of 

100 cm or more.

Grossarenic Kandiudults

HCCH. Other Kandiudults that have both:

1. An ECEC of 1.5 cmol(+)/kg clay or less (sum of bases 

extracted with 1N 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:

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:

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) fragments coarser 

than 2.0 mm, of which more than 66 percent is cinders, 

pumice, and pumicelike fragments; or

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

particles 0.02 to 2.0 mm in diameter; and

(1) In the 0.02 to 2.0 mm fraction, 5 percent or more 

volcanic glass; and

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

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

equal to 30 or more.

Aquandic Kandiudults
278 Keys to Soil Taxonomy

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 

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:

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandyskeletal particle-size class criteria 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:

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
Ultisols 279

U

L

T

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

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:

1. Have, in one or more layers either within 75 cm of 
280 Keys to Soil Taxonomy

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); and

2. Meet sandy or sandy-skeletal particle-size class criteria 

throughout a layer extending from the mineral soil surface 

to the top of an argillic horizon at a depth of 50 cm or more; 

and

3. Have 5 percent or more (by volume) plinthite in one or 

more horizons within 150 cm of the mineral soil surface.

Arenic Plinthaquic Paleudults

HCED. Other Paleudults that:

1. Meet sandy or sandy-skeletal particle-size class criteria 

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:

1. 5 percent or more (by volume) plinthite in one or more 

horizons within 150 cm of the mineral soil surface; and

2. In one or more layers either within 75 cm of the mineral 

soil surface or, if the chroma throughout the upper 75 cm 

results from uncoated sand grains, within the upper 12.5 cm 

of the argillic horizon, redox depletions with a color value, 

moist, of 4 or more and chroma of 2 or less, accompanied 

by both redox concentrations and aquic conditions for some 

time in normal years (or artificial drainage).

Plinthaquic Paleudults

HCEG. Other Paleudults 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 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. Meet sandy or sandy-skeletal particle-size class criteria 

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 
Ultisols 281

U

L

T

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. Meet sandy or sandy-skeletal particle-size class criteria 

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 

mineral soil surface to the top of an argillic horizon at a depth of 

50 to 100 cm.

Arenic Paleudults

HCEQ. Other Paleudults that meet sandy or sandy-skeletal 

particle-size class criteria 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. 285

HDB. Other Ustults that:

1. Do not have a densic, lithic, paralithic, or petroferric 

contact within 150 cm of the mineral soil surface; and
282 Keys to Soil Taxonomy

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. 282

HDC. Other Ustults that have a kandic horizon.

Kanhaplustults, p. 284

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. 285

HDE. Other Ustults that have both:

1. An epipedon that has a color value, moist, of 3 or less 

throughout; and

2. In all subhorizons in the upper 100 cm of the argillic 

horizon or throughout the entire argillic horizon if it is less 

than 100 cm thick, more than 50 percent colors that have all

of the following:

a. Hue of 2.5YR or redder; and

b. A value, moist, of 3 or less; and

c. A dry value no more than 1 unit higher than the moist 

value.

Rhodustults, p. 285

HDF. Other Ustults.

Haplustults, p. 282

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 NH4OAc 

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 
Ultisols 283

U

L

T

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. Meet sandy or sandy-skeletal particle-size class criteria 

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 meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 

mineral soil surface to the top of a kandic horizon at a depth of 

50 cm or more.

Arenic Kandiustults

HDBE. Other Kandiustults that have both:

1. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

a fine-earth fraction with both a bulk density of 1.0 g/cm3 or 

less, measured at 33 kPa water retention, and Al plus 1/2 Fe 

percentages (by ammonium oxalate) totaling more than 1.0; 

and

2. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that is dry in some part for 135 

or fewer of the cumulative days per year when the 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 o

C; or

2. A hyperthermic, isomesic, or warmer iso soil 

temperature regime and a moisture control section that in 

normal years:

a. Is moist in some or all parts for fewer than 90 

consecutive days per year when the 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 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 Kandiustults

HDBJ. Other Kandiustults that have, in all subhorizons in 

the upper 50 cm of the kandic horizon or throughout the entire 

kandic horizon if it is less than 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
284 Keys to Soil Taxonomy

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 meet sandy or sandyskeletal particle-size class criteria throughout a layer extending 

from the mineral soil surface to the top of a kandic horizon at a 

depth of 50 to 100 cm.

Arenic Kanhaplustults

HDCE. Other Kanhaplustults that have both:

1. Throughout one or more horizons with a total thickness 

of 18 cm or more within 75 cm of the mineral soil surface, 

a fine-earth fraction with both a bulk density of 1.0 g/cm3 or 

less, measured at 33 kPa water retention, and Al plus 1/2 Fe 

percentages (by ammonium oxalate) totaling more than 1.0; 

and

2. When neither irrigated nor fallowed to store moisture, 

either:

a. A mesic or thermic soil temperature regime and a 

moisture control section that in normal years is dry in 

some part for 135 or fewer of the cumulative days per year 

when the 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
Ultisols	 285

U

L

T

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

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. 286

HEB. Other Xerults.

Haploxerults, p. 285

Haploxerults

Key to Subgroups

HEBA. Haploxerults that have both:

1. A lithic contact within 50 cm of the mineral soil surface;

and

2. In each pedon, a discontinuous argillic or kandic horizon

that is interrupted by ledges of bedrock.

Lithic Ruptic-Inceptic Haploxerults

HEBB. Other Haploxerults that have a lithic contact within 50

cm of the mineral soil surface.

Lithic Haploxerults

HEBC. Other Haploxerults that have, in one or more

subhorizons within the upper 25 cm of the argillic or kandic
286

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

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 meet sandy or sandy-skeletal 

particle-size class criteria 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 meet sandy or sandy-skeletal 

particle-size class criteria throughout a layer extending from the 

mineral soil surface to the top of an argillic or kandic horizon at 

a depth of 100 cm or more.

Grossarenic Haploxerults

HEBI. Other Haploxerults.

Typic Haploxerults

Palexerults

Key to Subgroups

HEAA. Palexerults that have both:

1. In one or more subhorizons within the upper 25 cm 

of the argillic or kandic horizon, redox depletions with a 

color value, moist, of 4 or more and chroma of 2 or less, 

accompanied by 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
287

V

E

R

Key to Suborders

FA. Vertisols that have, in one or more horizons within 50 

cm of the mineral soil surface, aquic conditions for some time 

in normal years (or artificial drainage) and one or both of the 

following:

1. In more than half of each pedon, either on faces of 

peds or in the matrix if peds are absent, 50 percent or more 

chroma of either:

a. 2 or less if redox concentrations are present; or

b. 1 or less; or

2. Enough active ferrous iron (Fe2+) to give a positive 

reaction to alpha,alpha-dipyridyl at a time when the soil is 

not being irrigated.

Aquerts, p. 287

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

Cryerts, p. 291

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. 297

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. 291

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. 293

CHAPTER 16

Vertisols

FF. Other Vertisols.

Uderts, p. 292

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. 291

FAB. Other Aquerts that have a salic horizon within 100 cm of 

the mineral soil surface.

Salaquerts, p. 290

FAC. Other Aquerts that have a duripan within 100 cm of the 

mineral soil surface.

Duraquerts, p. 288

FAD. Other Aquerts that have a natric horizon within 100 cm 

of the mineral soil surface.

Natraquerts, p. 290

FAE. Other Aquerts that have a calcic horizon within 100 cm 

of the mineral soil surface.

Calciaquerts, p. 288

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. 288

FAG. Other Aquerts that have episaturation.

Epiaquerts, p. 289

FAH. Other Aquerts.

Endoaquerts, p. 289
288 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

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
Vertisols 289

V

E

R

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 

electrical conductivity of 15 dS/m or more (saturated paste) for 

6 or more months in normal years.

Halic Epiaquerts
290 Keys to Soil Taxonomy

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

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

3. Chroma of 3 or more.

Chromic Salaquerts

FABF. Other Salaquerts.

Typic Salaquerts
Vertisols 291

V

E

R

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. 291

FBB. Other Cryerts.

Haplocryerts, p. 291

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. 292

FDB. Other Torrerts that have a gypsic horizon within 100 cm 

of the soil surface.

Gypsitorrerts, p. 292

FDC. Other Torrerts that have a calcic or petrocalcic horizon 

within 100 cm of the soil surface.

Calcitorrerts, p. 291

FDD. Other Torrerts.

Haplotorrerts, p. 292

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

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

3. Chroma of 3 or more.

Chromic Calcitorrerts

FDCE. Other Calcitorrerts.

Typic Calcitorrerts
292 Keys to Soil Taxonomy

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 (Fe2+) to give a positive 

reaction to alpha,alpha-dipyridyl at a time when the soil is 

not being irrigated.

Aquic Salitorrerts

FDAB. Other Salitorrerts that have a densic, lithic, or 

paralithic contact, 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:

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. 293

FFB. Other Uderts.

Hapluderts, p. 293
Vertisols 293

V

E

R

Dystruderts

Key to Subgroups

FFAA. Dystruderts that have, in one or more horizons within 

100 cm of the mineral soil surface, aquic conditions for some 

time in normal years (or artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron (Fe2+) to give a positive 

reaction to alpha,alpha-dipyridyl at a time when the soil is 

not being irrigated.

Aquic Dystruderts

FFAB. Other Dystruderts that are saturated with water in one 

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

normal years for either or both:

1. 20 or more consecutive days; or

2. 30 or more cumulative days.

Oxyaquic Dystruderts

FFAC. Other Dystruderts that have a densic, lithic, or 

paralithic contact within 100 cm of the mineral soil surface.

Leptic Dystruderts

FFAD. Other Dystruderts that have a layer, 25 cm or more 

thick 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 (Fe2+) to give a positive 

reaction to alpha,alpha-dipyridyl at a time when the soil is 

not being irrigated.

Aquic Hapluderts

FFBC. Other Hapluderts that are saturated with water in one 

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

normal years for 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:

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. 294

FEB. Other Usterts that have a salic horizon within 100 cm of 

the mineral soil surface.

Salusterts, p. 296
294 Keys to Soil Taxonomy

FEC. Other Usterts that have a gypsic horizon within 100 cm 

of the mineral soil surface.

Gypsiusterts, p. 295

FED. Other Usterts that have a calcic or petrocalcic horizon 

within 100 cm of the mineral soil surface.

Calciusterts, p. 294

FEE. Other Usterts.

Haplusterts, p. 295

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 (Fe2+) to give a positive 

reaction to alpha,alpha-dipyridyl at a time when the soil is 

not being irrigated.

Aquic Dystrusterts

FEAC. Other Dystrusterts that, if not irrigated during the 

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

through a thickness of 25 cm or more within 50 cm of the 

mineral soil surface, for 210 or more cumulative days per year.

Aridic Dystrusterts

FEAD. Other Dystrusterts that, if not irrigated during the 

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

through a thickness of 25 cm or more within 50 cm of the 

mineral soil surface, for less than 150 cumulative days.

Udic Dystrusterts

FEAE. Other Dystrusterts that have a densic, lithic, or 

paralithic contact or a duripan within 100 cm of the mineral soil 

surface.

Leptic Dystrusterts
Vertisols 295

V

E

R

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

FEEG. Other Haplusterts that have both:

1. A densic, lithic, or paralithic contact within 100 cm of 

the mineral soil surface; and
296 Keys to Soil Taxonomy

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 (Fe2+) to give a positive 

reaction to alpha,alpha-dipyridyl at a time when the soil is 

not being irrigated.

Aquic Salusterts

FEBD. Other Salusterts that, if not irrigated during the year, 

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

through a thickness of 25 cm or more within 50 cm of the 

mineral soil surface, for 210 or more cumulative days per year.

Aridic Salusterts
Vertisols 297

V

E

R

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. 297

FCB. Other Xererts that have a calcic or petrocalcic horizon 

within 100 cm of the mineral soil surface.

Calcixererts, p. 297

FCC. Other Xererts.

Haploxererts, p. 298

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 (Fe2+) to give a positive 

reaction to alpha,alpha-dipyridyl at a time when the soil is 

not being irrigated.

Aquic Durixererts

FCAD. Other Durixererts that, if not irrigated during the year, 

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

through a thickness of 25 cm or more above the duripan, for 180 

or more consecutive days.

Aridic Durixererts
298

FCAE. Other Durixererts that, if not irrigated during the year, 

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

through a thickness of 25 cm or more above the duripan, for less 

than 90 consecutive days.

Udic Durixererts

FCAF. Other Durixererts that have a duripan that is not 

indurated in any subhorizon.

Haplic Durixererts

FCAG. Other Durixererts that have, in one or more horizons 

within 30 cm of the mineral soil surface, 50 percent or more 

colors as follows:

1. A color value, moist, of 4 or more; or

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

3. Chroma of 3 or more.

Chromic Durixererts

FCAH. Other Durixererts.

Typic Durixererts

Haploxererts

Key to Subgroups

FCCA. Haploxererts that have a lithic contact within 50 cm of 

the mineral soil surface.

Lithic Haploxererts

FCCB. Other Haploxererts that have, throughout a layer 15 

cm or more thick within 100 cm of the mineral soil surface, an 

electrical conductivity of 15 dS/m or more (saturated paste) for 

6 or more months in normal years.

Halic Haploxererts

FCCC. Other Haploxererts that have, in one or more horizons 

within 100 cm of the mineral soil surface, an exchangeable 

sodium percentage of 15 or more (or a sodium adsorption ratio 

of 13 or more) for 6 or more months in normal years.

Sodic Haploxererts

FCCD. Other Haploxererts that, if not irrigated during the 

year, have cracks in normal years that remain 5 mm or more 

wide, through a thickness of 25 cm or more within 50 cm of the 

mineral soil surface, for 180 or more consecutive days.

Aridic Haploxererts

FCCE. Other Haploxererts that have, in one or more horizons 

within 100 cm of the mineral soil surface, aquic conditions for 

some time in normal years (or artificial drainage) and either:

1. Redoximorphic features; or

2. Enough active ferrous iron (Fe2+) to give a positive 

reaction to alpha,alpha-dipyridyl at a time when the soil is 

not being irrigated.

Aquic Haploxererts

FCCF. Other Haploxererts that, if not irrigated during the 

year, have cracks in normal years that remain 5 mm or more 

wide, through a thickness of 25 cm or more within 50 cm of the 

mineral soil surface, for less than 90 consecutive days.

Udic Haploxererts

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
299

F

A

M

Families and series serve purposes that are largely pragmatic; 

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

descriptive. In this chapter the descriptive terms used in the 

names of families are defined, the control sections to which the 

terms apply are given, and the criteria, including the taxa in 

which they are used, are indicated. 

Family Differentiae for Mineral Soils and 

Mineral Layers of Some Organic Soils

The following differentiae are used to distinguish families of 

mineral soils and the mineral layers of some organic soils within 

a subgroup. The class names of these components are used to 

form the family name. The components are listed and defined 

in the same sequence in which the components appear in the 

family names.

Particle-size classes and their substitutes

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 pedologic classifications have set it at either 50 or 20 

microns. Engineering classifications have been based on grainsize percentages, by weight, in the soil fraction less than 74 mm 

in diameter, while 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 if the texture 

class (fine-earth fraction) of a soil is 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 11 

more narrowly defined classes, which permit relatively fine 

distinctions between families of soils for which particle size 

is important, while providing broader groupings for soils in 

which narrowly defined particle-size classes would produce 

undesirable separations. Thus, the term “clayey” is used for 

some soil families to indicate a clay content of 35 percent (30 

percent in Vertisols) or more in specific horizons, while in other 

families the more narrowly defined terms “fine” and “very-fine” 

indicate that these horizons have a clay content either of 35 (30 

percent in Vertisols) to 60 percent or of 60 percent or more in 

their fine-earth fraction. Fine earth refers to particles smaller 

than 2.0 mm in diameter. Rock fragments are particles 2.0 mm 

or more in diameter that are strongly cemented or more resistant 

to rupture and include all particles with horizontal dimensions 

smaller than the size of a pedon. Cemented fragments 2.0 mm 

or more in diameter that are in a 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 2.0 mm and a horizontal dimension 

smaller than the size of a pedon. Most pararock fragments 

are broken into fragments 2.0 mm or less in diameter during 

the preparation of samples for particle-size analysis in the 

laboratory. Therefore, pararock fragments are generally included 

CHAPTER 17

Family and Series Differentiae and Names
300 Keys to Soil Taxonomy

with the fine earth in the particle-size classes, although cinders, 

pumice, and pumicelike fragments are treated as fragments in 

the substitutes for classes, regardless of their rupture-resistance 

class.

Substitutes for particle-size classes are used for soils 

that have andic soil properties or a high content of volcanic 

glass, pumice, 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 component 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 spodic horizons and other horizons that do not have andic 

soil properties but contain significant amounts of allophane, 

imogolite, ferrihydrite, or aluminum-humus complexes. The 

isotic mineralogy class (defined below) is helpful in identifying 

these particle-size classes.

In general, the weighted average particle-size class of the 

whole particle-size control section (defined below) determines 

what particle-size class name is used as a component of the 

family name.

Strongly Contrasting Particle-Size Classes

If the particle-size control section consists of two parts with 

strongly contrasting particle-size or substitute classes (listed 

below), if both parts are 12.5 cm or more thick (including parts 

not in the control section), and if the transition zone between 

them is less than 12.5 cm thick, both class names are used. For 

example, the family particle-size class is sandy over clayey if 

all of the following criteria are met: the soil meets criterion D 

(listed below) under the control section for particle-size classes 

or their substitutes; any Ap horizon is less than 30 cm thick; the 

weighted average particle-size class of the upper 30 cm of the 

soil is sandy; the weighted average of the lower part is clayey; 

and the transition zone is less than 12.5 cm thick. If a substitute 

name applies to one or more parts of the particle-size control 

section and the parts are not strongly contrasting classes, the 

name of the thickest part (cumulative) is used as the soil family 

name.

Aniso Class

If the particle-size control section includes more than one 

pair of the strongly contrasting classes, listed below, then the 

soil is assigned to an aniso class named for the pair of adjacent 

classes that contrast most strongly. The aniso class is considered 

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 

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; and densic, lithic, paralithic, and 

petroferric contacts. 
Family and Series Differentiae and Names 301

F

A

M

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 root-limiting 

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 in a Lamellic subgroup or have an 

argillic, kandic, or natric horizon that has its upper boundary 

at a depth of 100 cm or more from the mineral surface and that 

are not in a Grossarenic or Arenic subgroup: Between the lower 

boundary of an Ap horizon or a depth of 25 cm from the mineral 

soil surface, whichever is deeper, and 100 cm below the mineral 

soil surface or a root-limiting layer, whichever is shallower; or

E. For other soils that have an argillic or natric horizon that 

has its lower boundary at a depth of less than 25 cm from the 

mineral 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 

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:
302	 Keys to Soil Taxonomy

1. Have, in the whole soil, more than 60 percent

(by weight) volcanic ash, cinders, lapilli, pumice, and

pumicelike1 fragments and, in the fraction more than 2.0 mm

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 more than 2.0 mm in diameter,

less than two-thirds (by volume) pumice and/or pumicelike

fragments.

Cindery

or

3. Other mineral soils that have a fine-earth component of

less than 10 percent (including associated medium and finer

pores) of the total volume.

Fragmental

or

B. Other mineral soils that have a fine-earth component of 10

percent or more (including associated medium and finer pores)

of the total volume and meet, in the thickest part of the control

section (if the control section is not in one of the strongly

contrasting particle-size classes listed below), or in a part of the

control section that qualifies as an element in one of the strongly

contrasting particle-size classes listed below, or throughout

the control section, one of the following sets of substitute class

criteria:

1. They:

a. Have andic soil properties and have a water

content at 1500 kPa tension of less than 30 percent

on undried samples and less than 12 percent on dried

samples; or

b. Do not have andic soil properties, have 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. 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. Have a fine-earth fraction that has andic soil properties

and that has a water content at 1500 kPa tension of 100

percent or more on undried samples; and

a. Have a total of 35 percent or more (by volume) rock

and pararock fragments, of which two-thirds or more (by

volume) is pumice or pumicelike fragments.

Hydrous-pumiceous

or

b. Have 35 percent or more (by volume) rock fragments.

Hydrous-skeletal

or

c. Have less than 35 percent (by volume) rock fragments.

Hydrous

or

4. 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 

1Pumicelike—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 303

F

A

M

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).

C. Other mineral soils that, in the thickest part of the control 

section (if part of the control section has a substitute for 

particle-size class and is not in one of the strongly contrasting 

particle-size classes listed below), or in a part of the control 

section that qualifies as an element in one of the strongly 

contrasting particle-size classes listed below, or throughout the 

control section, meet one of the following sets of particle-size 

class criteria:

1. Have 35 percent or more (by volume) rock fragments 

and a fine-earth fraction with a texture class of sand or loamy 

sand, including less than 50 percent (by weight) very fine 

sand.

Sandy-skeletal

or

2. Have 35 percent or more (by volume) rock fragments 

and less than 35 percent (by weight) clay.

Loamy-skeletal

or

3. Have 35 percent or more (by volume) rock fragments.

Clayey-skeletal

or

4. Have a texture class of sand or loamy sand, including 

less than 50 percent (by weight) very fine sand particles 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 an element 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, 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, in 

the fine-earth fraction, 18 to 35 percent (by weight) clay 

(Vertisols are excluded).

Fine-loamy

or

8. Have, in the fraction less than 75 mm in diameter, less 

than 15 percent (by weight) particles with diameters of 0.1 

to 75 mm (fine sand or coarser, including gravel) and, in the 

fine-earth fraction, less than 18 percent (by weight) clay.

Coarse-silty

or

9. Have, in the fraction less than 75 mm in diameter, less 

than 15 percent (by weight) particles with diameters of 0.1 

to 75 mm (fine sand or coarser, including gravel) and, in 

the fine-earth fraction, 18 to 35 percent (by weight) clay 

(Vertisols are excluded).

Fine-silty

or

10. Have 35 percent or more (by weight) clay (more than 

30 percent in Vertisols) and are in a shallow family (defined 

below) or in a Lithic, Arenic, or Grossarenic subgroup, or 

the layer is an element in a strongly contrasting particle-size 

class (listed below).

Clayey

or

11. Have (by weighted average) less than 60 percent (by 

weight) clay in the fine-earth fraction.

Fine

or

12. Have 60 percent or more (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 
304 Keys to Soil Taxonomy

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 of 

25 percent or more between clay percentages of the fineearth 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)
Family and Series Differentiae and Names 305

F

A

M

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)

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), by dithionite citrate, in the fineearth fraction.

Ferritic

or
306 Keys to Soil Taxonomy

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), 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), by dithionite citrate, in the fine-earth 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 in the fraction less than 0.002 mm in size; 

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 in the fraction less than 0.002 mm in size.

Halloysitic

or

8. All other soils in section A.

Mixed

or

B. Other soil layers or horizons, in the mineralogy control 

section, that have a substitute class that replaces the particle-size 

class, other than fragmental, and that:

1. Have 40 percent or more (by weight) gypsum either in 

the fine-earth fraction or in the fraction less than 20 mm in 

size, whichever has a higher percentage of gypsum.

Hypergypsic

or

2. Have 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 8 times the Si is more than 2 times the Fe.

Amorphic

or

3. Other soils that have 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. Other soils that have 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 soil layers or horizons, in the mineralogy 

control section, in all other mineral soil orders and in Terric 

subgroups of Histosols and Histels that have:

1. Any particle-size class and 15 percent or more (by 

weight) gypsum, either in the fine-earth fraction or in the 

fraction less than 20 mm in size, whichever has a higher 

percentage of gypsum.

Gypsic

or

2. Any particle-size class and more than 40 percent (by 

weight) carbonates (expressed as CaCO3) plus gypsum, 

either in the fine-earth fraction or in the fraction less than 20 

mm in size, whichever has a higher percentage of carbonates 

plus gypsum.

Carbonatic

or

3. Any particle-size class, except for fragmental, and more 

than 40 percent (by weight) iron oxide as Fe2O3 (more than 

28 percent Fe) extractable by dithionite citrate, in the fineearth fraction.

Ferritic

or

4. Any particle-size class, except for fragmental, and more 

than 40 percent (by weight) gibbsite and boehmite in the 

fine-earth fraction.

Gibbsitic

or
Family and Series Differentiae and Names 307

F

A

M

5. Any particle-size class, except for fragmental, and more 

than 40 percent (by weight) magnesium-silicate minerals, 

such as the serpentine minerals (antigorite, chrysotile, and 

lizardite) plus talc, olivines, Mg-rich pyroxenes, and Mg-rich 

amphiboles, in the fine-earth fraction.

Magnesic

or

6. Any particle-size class, except for fragmental, and more 

than 20 percent (by weight) glauconitic pellets in the fineearth fraction.

Glauconitic

or

D. Other mineral soil layers or horizons, in the mineralogy 

control section, of soils in all other mineral orders and in Terric 

subgroups of Histosols and Histels, in a clayey, clayey-skeletal, 

fine, or very-fine particle-size class, that:

1. In the fine-earth fraction, have a total percent (by weight) 

iron oxide as Fe2O3 (percent Fe by dithionate 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 size:

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.

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 50 percent of the thickness, meet all of 

the following:

(1) Have no free carbonates; and

(2) The pH of a suspension of 1 g soil in 50 ml 1 M 

NaF is more than 8.4 after 2 minutes; and

(3) The ratio of 1500 kPa water to measured clay is 

0.6 or more.

Isotic

or

g. All other soils in section D.

Mixed

or

E. All other mineral soil layers or horizons (except for those 

in Quartzipsamments), in the mineralogy control section, that 

have:

1. More than 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 by dithionate 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. 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 soils.

Mixed

Cation-Exchange Activity Classes

The cation-exchange activity classes help in making 

interpretations of mineral assemblages and of the nutrientholding capacity of soils in mixed and siliceous mineralogy 
308	 Keys to Soil Taxonomy

classes of clayey, clayey-skeletal, coarse-loamy, coarse-silty,

fine, fine-loamy, fine-silty, loamy, loamy-skeletal, and very-fine

particle-size classes. Cation-exchange activity classes are not

assigned to Histosols and Histels, and they are not assigned to

Oxisols and “kandi” and “kanhap” great groups and subgroups

of Alfisols and Ultisols because assigning such classes to them

would be redundant. Cation-exchange activity classes are not

assigned to Psamments, “psamm” great groups of Entisols and

Gelisols, Psammentic subgroups, or other soils with sandy or

sandy-skeletal particle-size 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 particle-size class (e.g., ashy) or with such

mineralogy classes as smectitic also are not assigned cationexchange activity classes since cation-exchange capacity

(CEC) is high in such soils or the clay mineralogy dictates soil

properties.

The cation-exchange capacity is determined by NH4

OAc at

pH 7 on the fine-earth fraction. The CEC of the organic matter,

sand, silt, and clay is included in the determination. The criteria

for the classes use ratios of CEC to the percent, by weight, of

silicate clay, both by weighted average in the control section.

In the following classes “clay” excludes clay-size carbonates.

If the ratio of percent water retained at 1500 kPa tension to

the percentage of measured clay is 0.25 or less or 0.6 or more

in half or more of the particle-size control section (or part in

contrasting families), then the percentage of clay is estimated by

the following formula: Clay % = 2.5(% water retained at 1500

kPa tension - % organic carbon).

Control Section for Cation-Exchange Activity Classes

The control section for cation-exchange activity classes is the

same as that used to determine the particle-size and mineralogy

classes. For soils with strongly contrasting 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 loamy over clayey, mixed, active,

calcareous, thermic Typic Udorthent, the cation-exchange

activity class “active” is associated with the clayey part of the

control section.

Key to Cation-Exchange Activity Classes

A. Soils that are not Histosols, Histels, 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 are not in a sandy or sandy-skeletal particlesize class or any substitute for a particle-size class (including

fragmental), and that have:

1. A mixed or siliceous mineralogy class; and

2. A ratio of cation-exchange capacity (by IN NH4

OAc

pH 7) to percent clay (by weight) of:

a. 0.60 or more.

Superactive

b. 0.40 to 0.60.

Active

c. 0.24 to 0.40.

Semiactive

d. Less than 0.24.

Subactive

or

B. All other soils: No cation-exchange activity classes used.

Calcareous and Reaction Classes of Mineral Soils

The presence or absence of carbonates, soil reaction, and the

presence of high concentrations of aluminum in mineral soils

are treated together because they are so intimately related. There

are four classes—calcareous, acid, nonacid, and allic. These are

defined later, in the key to calcareous and reaction classes. The

classes are not used in all taxa, nor is more than one used in the

same taxa.

Use of the Calcareous and Reaction Classes

The calcareous, acid, and nonacid classes are used in the

names of the families of Entisols, Gelisols, Aquands, Aquepts,

and all Gelic suborders and Gelic great groups, except they are

not used in 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

4. Sandy, sandy-skeletal, cindery, pumiceous, or fragmental

families

5. Families with carbonatic, gypsic, or hypergypsic

mineralogy

6. Histels

The calcareous class is used not only in the names of the taxa

listed above but also in the names of the families of Aquolls,

except that it is not used with any of the following:

1. Calciaquolls, Natraquolls, and Argiaquolls

2. Cryaquolls and Duraquolls that have an argillic or natric

horizon

3. Families with carbonatic, gypsic, or hypergypsic

mineralogy

The allic class is used only in families of Oxisols.
Family and Series Differentiae and Names 309

F

A

M

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 in Oxisols 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 oC to -10 oC.

Pergelic

or

3. +1 oC to -4 oC.

Subgelic

or

B. Other soils that have a difference in soil temperature of 

6 oC or more between mean summer (June, July, and August 

in the Northern Hemisphere) and mean winter (December, 

January, and February in the Northern Hemisphere) and a mean 

annual soil temperature of:

1. Lower than 8 oC (47 oF).

Frigid

or

2. 8 o

C (47 oF) to 15 oC (59 oF).

Mesic

or
310 Keys to Soil Taxonomy

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 (90 percent or more); and densic, lithic, 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

B. Other Quartzipsamments.

Uncoated
Family and Series Differentiae and Names 311

F

A

M

Classes of Permanent Cracks

Some Hydraquents consolidate or shrink after drainage and 

become Fluvaquents or Humaquepts. In the process they can 

form polyhedrons roughly 12 to 50 cm in diameter, depending 

on their n value and texture. These polyhedrons are separated by 

cracks that range in width from 2 mm to more than 1 cm. The 

polyhedrons may shrink and swell with changes in the moisture 

content of the soils, but the cracks are permanent and can persist 

for several hundreds of years, even if the soils are cultivated. 

The cracks permit rapid movement of water through the soils, 

either vertically or laterally. Such soils may have the same 

texture, mineralogy, and other family properties as soils that do 

not form cracks or that have cracks that open and close with the 

seasons. Soils with permanent cracks are very rare in the United 

States.

Control Section for Classes of Permanent Cracks

The control section for classes of permanent cracks is from 

the base of any plow layer or 25 cm from the soil surface, 

whichever is deeper, to 100 cm below the soil surface.

Key to Classes of Permanent Cracks

A. Fluvaquents or Humaquepts that have, throughout a layer 

50 cm or more thick, continuous, permanent, lateral and vertical 

cracks 2 mm or more wide, spaced at average lateral intervals of 

less than 50 cm.

Cracked

or

B. All other Fluvaquents and Humaquepts: No class of 

permanent cracks used.

Family Differentiae for Histosols and 

Histels

Most of the differentiae that are used to distinguish families 

of Histosols and Histels have already been defined, either 

because they are used as differentiae in mineral soils as well as 

Histosols and Histels or because their definitions are used for 

the classification of some Histosols and Histels in categories 

higher than the family. In the following descriptions, differentiae 

not previously mentioned are defined and the classes in which 

they are used are enumerated.

The order in which family classes, if appropriate for a 

particular family, are placed in the technical family names of 

Histosols and Histels is as follows:

Particle-size classes

Mineralogy classes, including the nature of limnic deposits 

in Histosols

Reaction classes

Soil temperature classes

Soil depth classes (used only in Histosols)

Particle-Size Classes

Particle-size classes are used only for the family names 

of Terric subgroups of Histosols and Histels. The classes are 

determined from the properties of the mineral soil materials 

in the control section through use of the key to particle-size 

classes. The classes are more generalized than those for soils in 

other orders.

Control Section for Particle-Size Classes

The particle-size control section is the upper 30 cm of the 

mineral layer or of that part of the mineral layer that is within 

the control section for Histosols and Histels (given in chapter 

3), whichever is thicker.

Key to Particle-Size Classes of Histosols and Histels

A. Terric subgroups of Histosols and Histels that 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 the fine-earth material) of sand or 

loamy sand, including less than 50 percent (by weight) very 

fine sand in the fine-earth fraction.

Sandy or sandy-skeletal

or

3. Less than 35 percent (by weight) clay in the fine-earth 

fraction and a content of rock fragments of 35 percent or 

more of the total volume.

Loamy-skeletal

or

4. A content of rock fragments of 35 percent or more of the 

total volume.

Clayey-skeletal

or

5. A clay content of 35 percent or more (by weight) in the 

fine-earth fraction.

Clayey

or

6. All other Terric subgroups of Histosols and Histels.

Loamy

or

B. All other Histosols and Histels: No particle-size class used.
312 Keys to Soil Taxonomy

Mineralogy Classes

There are three different kinds of mineralogy classes 

recognized for families in certain great groups and subgroups 

of Histosols. The first kind is the ferrihumic soil material 

defined below. The second is three types of limnic materials—

coprogenous earth, diatomaceous earth, and marl, defined in 

chapter 3. The third is mineral layers of Terric subgroups. The 

key to mineralogy classes for these mineral layers is the same as 

that for mineral soils. Terric subgroups of Histels also have the 

same mineralogy classes as those for mineral soils.

Ferrihumic Mineralogy Class

Ferrihumic soil material, i.e., bog iron, is an authigenic 

(formed in place) deposit consisting of hydrated iron oxide 

mixed with organic matter, either dispersed and soft or 

cemented into large aggregates, in a mineral or organic layer 

that has all of the following characteristics:

1. Saturation with water for more than 6 months per year (or 

artificial drainage);

2. 2 percent or more (by weight) iron concretions having 

lateral dimensions ranging from less than 5 to more than 100 

mm and containing 10 percent or more (by weight) free iron 

oxide (7 percent or more Fe) and 1 percent or more (by weight) 

organic matter; and

3. A dark reddish or brownish color that changes little on 

drying.

The ferrihumic mineralogy class is used for families of 

Fibrists, Hemists, and Saprists, but it is not used for 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

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.
Family and Series Differentiae and Names 313

F

A

M

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; and densic, lithic, paralithic, and petroferric 

contacts. The following key is used for families in all subgroups 

of Histosols. The shallow class is not used in the suborder 

Folists.

Key to Soil Depth Classes 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 particlesize and mineralogy control sections for families end at the 

upper boundary of a fragipan, duripan, or petrocalcic horizon 

because these horizons have few roots. In contrast to the control 

section for the series, the thickness of such horizons is not taken 

into account in the control sections for the family. The series 

control section includes materials starting at the soil surface 

and also the first 25 cm below a densic or paralithic contact if 

its upper boundary is less than 125 cm below the mineral soil 

surface. Properties of horizons and layers below the particle-size 

control section, a depth between 100 and 150 cm (or to 200 cm 

if in a diagnostic horizon) from the mineral soil surface, also are 

considered.

Key to the Control Section for the Differentiation of Series

The part of a soil to be considered in differentiating series 

within a family is as follows:

A. Mineral soils that have permafrost within 150 cm of the 

soil surface: From the soil surface to the shallowest of the 

following:

1. A lithic or petroferric contact; or

2. A depth of 100 cm if the depth to permafrost is less than 

75 cm; or

3. 25 cm below the upper boundary of permafrost if that 

boundary is 75 cm or more below the soil surface; or

4. 25 cm below a densic or paralithic contact; or

5. A depth of 150 cm; or

B. Other mineral soils: From the soil surface to the shallowest 

of the following:

1. A lithic or petroferric contact; or

2. A depth of either 25 cm below a densic or paralithic 

contact or 150 cm below the soil surface, whichever is 

shallower, if there is a densic or paralithic contact within 150 

cm; or

3. A depth of 150 cm if the bottom of the deepest 

diagnostic horizon is less than 150 cm from the soil surface; 

or

4. The lower boundary of the deepest diagnostic horizon 

or a depth of 200 cm, whichever is shallower, if the lower 

boundary of the deepest diagnostic horizon is 150 cm or 

more below the soil surface; or

C. Organic soils (Histosols and Histels): From the soil surface 

to the shallowest of the following:

1. A lithic or petroferric contact; or

2. A depth of 25 cm below a densic or paralithic contact; or

3. A depth of 100 cm if the depth to permafrost is less than 

75 cm; or

4. 25 cm below the upper boundary of permafrost if that 

boundary is between a depth of 75 and 125 cm below the soil 

surface; or

5. The base of the bottom tier.
 
315

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 layers consist of undecomposed or partially 

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

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

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

organic material that was deposited under saturated conditions 

and has decomposed to varying stages. The mineral fraction 

of such material constitutes only a small percentage of the 

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

weight. Some soils consist entirely of materials designated as O 

horizons or layers.

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

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

formed by the illuviation of organic material into a mineral 

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

formed in this manner contain considerable amounts of organic 

matter.

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 

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

or much of the original rock structure1 and show one or both of 

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

closely mixed with the mineral fraction and not dominated by 

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

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

kinds of disturbance.

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

but the feature emphasized is an accumulation of humified 

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

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

horizon is less dark than the adjacent underlying horizon 

and contains only small amounts of organic matter. It has a 

morphology distinct from the C layer, although the mineral 

fraction is unaltered or only slightly altered by weathering. 

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

at the surface. Recent alluvial or eolian deposits that retain 

fine stratification are not considered to be A horizons unless 

cultivated.

E horizons: Mineral horizons in which the main feature is 

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

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

horizons exhibit obliteration of all or much of the original rock 

structure.

An E horizon is most commonly differentiated from an 

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

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

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

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

soils coatings of iron oxides or other compounds mask the 

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

differentiated from an overlying A horizon by its lighter color. It 

generally contains less organic matter than the A horizon. An E 

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

CHAPTER 18

Designations for Horizons and Layers

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

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

unweathered minerals in saprolite.
316 Keys to Soil Taxonomy

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

between parts of the B horizon or extend to depths greater than 

those of normal observation can be assigned the letter E if they 

are pedogenic.

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

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

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

following:

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

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

combination;

2. Evidence of the removal, addition, or transformation of 

carbonates and/or gypsum;

3. Residual concentration of oxides;

4. Coatings of sesquioxides that make the horizon 

conspicuously lower in color value, higher in chroma, or 

redder in hue, without apparent illuviation of iron; 

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

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

if volume changes accompany changes in moisture content; 

6. Brittleness; or

7. Strong gleying.

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

originally, subsurface horizons. Some examples included as 

B horizons, where contiguous to other genetic horizons, are 

layers of illuvial concentration of carbonates, gypsum, or silica 

that are the result of pedogenic processes (and may or may not 

be cemented) and brittle layers that show other evidence of 

alteration, such as prismatic structure or illuvial accumulation 

of clay.

Examples of layers that are not B horizons are layers in 

which clay films either coat rock fragments or cover finely 

stratified unconsolidated sediments, regardless of whether the 

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

carbonates have been illuviated but that are not contiguous to an 

overlying genetic horizon; and layers with gleying but no other 

pedogenic changes.

C horizons or layers: Horizons or layers, excluding 

strongly cemented and harder bedrock, that are little affected 

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

horizons. Most are mineral layers. The material of C 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. If a cemented layer formed through 

pedogenic processes, however, it is considered a B horizon.

R layers: Strongly cemented to indurated bedrock.

Granite, basalt, quartzite, limestone, and sandstone are 

examples of bedrock designated by the letter R. The excavation 

difficulty commonly exceeds high. The R layer is sufficiently 

coherent when moist to make hand-digging with a spade 

impractical, although the layer may be chipped or scraped. 

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

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

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

filled with clay or other material.

M layers: Root-limiting subsoil layers consisting of nearly 

continuous, horizontally oriented, human-manufactured 

materials.

Examples of materials designated by the letter M are 

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

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 

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 
Designations for Horizons and Layers 317

H

O

R

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 described 

separately. One horizon then has several lamellae and eluvial 

layers and can be designated an “E and Bt” horizon. The 

complete horizon sequence for these soils could be: Ap-Bw-E 

and Bt1-E and Bt2-C.

Suffix Symbols

Lowercase letters are used as suffixes to designate specific 

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

used in many of the definitions of such horizons to indicate that 

these horizons must contain more of the material in question 

than is presumed to have been present in the parent material. 

The suffix symbols and their meanings are as follows:

a Highly decomposed organic material

This symbol is used with O to indicate the most highly 

decomposed organic materials, which have a fiber content 

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

b Buried genetic horizon

This symbol is used in mineral soils to indicate 

identifiable buried horizons with major genetic features 

that were developed before burial. Genetic horizons may 

or may not have formed in the overlying material, which 

may be either like or unlike the assumed parent material 

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

nor is it used to separate an organic layer from a mineral 

layer.

c Concretions or nodules

This symbol indicates a significant accumulation 

of concretions or nodules. Cementation is required. 

The cementing agent commonly is iron, aluminum, 

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

calcite, or more soluble salts.

co Coprogenous earth

This symbol, used only with L, indicates a limnic layer 

of coprogenous earth (or sedimentary peat).

d Physical root restriction

This symbol indicates noncemented, root-restricting 

layers in naturally occurring or human-made sediments 

or materials. Examples are dense basal till, plowpans, and 

other mechanically compacted zones.

di Diatomaceous earth

This symbol, used only with L, indicates a limnic layer 

of diatomaceous earth.

e Organic material of intermediate decomposition

This symbol is used with O to indicate organic 

materials of intermediate decomposition. The fiber 

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

after rubbing.

f Frozen soil or water

This symbol indicates that a horizon or layer contains 

permanent ice. The symbol is not used for seasonally 

frozen layers or for dry permafrost.

ff Dry permafrost

This symbol indicates a horizon or layer that is 

continually colder than 0 oC and does not contain enough 

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

horizons or layers that have a temperature warmer than

0 oC at some time of the year.

g Strong gleying

This symbol indicates either that iron has been reduced 

and removed during soil formation or that saturation with 

stagnant water has preserved it in a reduced state. Most 

of the affected layers have chroma of 2 or less, and many 

have redox concentrations. The low chroma can represent 

either the color of reduced iron or the color of uncoated 

sand and silt particles from which iron has been removed. 

The symbol g is not used for materials of low chroma 

that have no history of wetness, such as some shales 

or E horizons. If g is used with B, pedogenic change 

in addition to gleying is implied. If no other pedogenic 

change besides gleying has taken place, the horizon is 

designated Cg.

h Illuvial accumulation of organic matter

This symbol is used with B to indicate the 

accumulation of illuvial, amorphous, dispersible 

complexes of organic matter and sesquioxides if the 

sesquioxide component is dominated by aluminum but 

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

some horizons these coatings have coalesced, filled 

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

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

sesquioxide component is significant but the color value 

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

i Slightly decomposed organic material

This symbol is used with O to indicate the least 

decomposed of the organic materials. The fiber content 
318 Keys to Soil Taxonomy

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 chromas as 

low as 3 or 4 have 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 the stage III plugged horizon or higher of the carbonate 

morphogenetic stages (Gile et al., 1966).

m Cementation or induration

This symbol indicates continuous or nearly continuous 

cementation. It is used only for horizons that are more 

than 90 percent cemented, although they may be fractured. 

The cemented layer is physically root-restrictive. 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.

ma Marl

This symbol, used only with L, 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 the surface 

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

disturbed organic horizon is designated Op. A disturbed 

mineral horizon is designated Ap even though it is clearly 

a former E, B, or C horizon.

q Accumulation of silica

This symbol indicates an accumulation of secondary 

silica.

r Weathered or soft bedrock

This symbol is used with C to indicate 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 to indicate an accumulation 

of illuvial, amorphous, dispersible complexes of organic 

matter and sesquioxides if both the organic matter and 

sesquioxide components are significant and if either the 

color value or chroma, moist, of the horizon is 4 or more. 

The symbol is also used in combination with h as “Bhs” if 

both the organic matter and sesquioxide components are 

significant and if the color value and chroma, moist, are 3 

or less.

ss Presence of slickensides

This symbol indicates the presence of slickensides. 

Slickensides result directly from the swelling of clay 

minerals and shear failure, commonly at angles of 20 to 

60 degrees above horizontal. They are indicators that other 

vertic characteristics, such as wedge-shaped peds and 

surface cracks, may be present.

t Accumulation of silicate clay

This symbol indicates an accumulation of silicate clay 

that either has formed within a horizon and subsequently 

has been translocated within the horizon or has been 

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

some part of the horizon should show evidence of clay 

accumulation either as coatings on surfaces of peds or in 

pores, as lamellae, or as bridges between mineral grains.
Designations for Horizons and Layers 319

H

O

R

u Presence of human-manufactured materials (artifacts)

This symbol indicates the presence of manufactured 

artifacts that have been created or modified by 

humans, usually for a practical purpose in habitation, 

manufacturing, excavation, or construction activities. 

Examples of artifacts are processed wood products, liquid 

petroleum products, coal combustion by-products, asphalt, 

fibers and fabrics, bricks, cinder blocks, concrete, plastic, 

glass, rubber, paper, cardboard, iron and steel, altered 

metals and minerals, sanitary and medical waste, garbage, 

and landfill waste.

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. It 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.

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. 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 

with value of 7 through 9.5 and chroma of 2 or less.

z Accumulation of salts more soluble than gypsum

This symbol indicates an accumulation of salts that are 

more soluble than gypsum.

Conventions for Using Letter Suffixes

Many master horizons and layers that are symbolized by a 

single capital letter have one or more lowercase letter suffixes. 

The following rules apply:

1. Letter suffixes should directly follow the capital letter.

2. More than three suffixes are rarely used.

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

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

the Bhs or Crt2 horizon designations, none of these letters are 

used in combination in a single horizon.

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

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

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

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

used only for buried mineral soils.

6. If the above rules do not apply to certain suffixes, such 

as k, kk, q, or y, the suffixes may be listed together in order 

of assumed dominance or they are 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 (t has precedence over w, s, and h). A 

B horizon that is gleyed or has accumulations of carbonates, 

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

residual accumulations of sesquioxides carries the appropriate 

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

precedes the other symbol: Bto.

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

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

Vertical Subdivision

Commonly, a horizon or layer identified by a single letter 

or a combination of letters has to be subdivided. For this 

purpose, Arabic numerals are added to the letters of the horizon 

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

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

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

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

C-Cg1-Cg2-R.

These conventions apply whatever the purpose of the 

subdivision. In many soils a horizon that could be identified 

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

to recognize differences in morphological features, such as 

structure, color, or texture. These divisions are numbered 

consecutively with Arabic numerals, but the numbering starts 

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

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

2Indicates weathered bedrock or saprolite in which clay films are present.
320 Keys to Soil Taxonomy

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 Arabic numerals that follow the respective horizon 

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

by 10-cm increments are designated Bt1, Bt2, Bt3, and Bt4. If 

the horizon has already been subdivided because of differences 

in morphological features, the set of Arabic numerals that 

identifies the additional sampling subdivisions follows the first 

numeral. For example, three layers of a Bt2 horizon sampled 

by 10-cm increments are designated Bt21, Bt22, and Bt23. The 

descriptions for each of these sampling subdivisions can be 

the same, and a statement indicating that the horizon has been 

subdivided only for sampling purposes can be added.

Discontinuities

Arabic numerals are used as prefixes to horizon designations 

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

discontinuities in mineral soils. These prefixes are distinct from 

the Arabic numerals that are used as suffixes denoting vertical 

subdivisions.

A discontinuity that can be identified by a number prefix is 

a significant change in particle-size distribution or mineralogy 

that indicates a difference in the material from which the 

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

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

Symbols that identify discontinuities are used only when 

they can contribute substantially to an understanding of the 

relationships among horizons. The stratification common 

to soils that formed in alluvium is not designated as a 

discontinuity, unless particle-size distribution differs markedly 

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

contrasting), even though genetic horizons may have formed in 

the contrasting layers.

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

the whole profile is understood to be material 1 and the number 

prefix is omitted from the symbol. Similarly, the uppermost 

material in a profile consisting of two or more contrasting 

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

omitted. Numbering starts with the second layer of contrasting 

material, which is designated 2. Underlying contrasting layers 

are numbered consecutively. Even when the material of a layer 

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

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

types of material. Where two or more consecutive horizons have 

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

indicating the discontinuity is applied to all the designations 

of horizons in that material: Ap-E-Bt1-2Bt2-2Bt3-2BC. 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: 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 Arabicnumber prefix is not used. The prefix is used, however, if it is 

thought that the R layer would produce material unlike that in 

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

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

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

A buried horizon (designated by the letter b) presents 

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

the overlying horizons. Some buried horizons, however, have 

formed in material that is lithologically like the overlying 

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

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

soil has formed is lithologically unlike the overlying material, 

however, the discontinuity is indicated by a number prefix and 

the symbol for the buried horizon also is used, e.g., Ap-Bt1-Bt2-

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

Discontinuities between different kinds of layers in organic 

soils are not identified. In most cases such differences are 

identified either by letter-suffix designations if the different 

layers are organic or by the master symbol if the different layers 

are mineral.

Use of the Prime Symbol

If two or more horizons with identical Arabic-numeral 

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-E-Btx-C identifies a soil that has two E 

horizons. To emphasize this characteristic, the prime symbol ( ́) 

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

horizons that have identical designations, e.g., A-E-Bt-E ́-BtxC. The prime symbol, where appropriate, is placed after the 

capital-letter horizon designation and before the lowercase 

suffix letter symbols that follow it: B ́t. 

The prime symbol is not used unless all letters and Arabicnumeral 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: A-C-2Bw-2Bc-2B ́w-3Bc. This soil has 

two identical 2Bw horizons but has two different Bc horizons (a 

2Bc and a 3Bc), so the prime symbol is used only with the lower 
Designations for Horizons and Layers 321

H

O

R

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 ́ ́.

Vertical subdivisions of horizons or layers (Arabic-numeral 

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 layers of humantransported material. This material has been moved horizontally 

onto a pedon from a source area outside of that pedon by 

directed human activity, usually with the aid of machinery. 

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, Arabic-numeral prefixes 

may be used before the caret symbol to indicate the presence 

of discontinuities within the human-transported material or 

between the human-transported material and underlying layers 

(e.g., ^A-^C1-2^C2-3Bwb).

Literature Cited

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.

323

Appendix

Laboratory Methods for Soil Taxonomy

The standard laboratory methods upon which the operational

definitions of the second edition of Soil Taxonomy are based

are described in the Soil Survey Laboratory Methods Manual

(Burt, 2004). Copies of standard laboratory data sheets are

included with the typifying pedons in the chapters on soil

orders in the second edition of Soil Taxonomy. For specific

information about an analytical procedure, these data sheets

should be checked and reference should be made to the Soil 

Survey Laboratory Methods Manual. Much of the information

included in this appendix is derived from “Soil Survey

Laboratory Methods for Characterizing Physical and Chemical

Properties and Mineralogy of Soils” (Kimble et al., 1993). Also,

the information is summarized in the Soil Survey Laboratory 

Information Manual (USDA, NRCS, 1995).

Pedon characterization data, or any soil survey data, are

most useful when the operations for collecting the data are well

understood. The mental pictures and conceptual definitions that

aid in visualizing properties and processes often differ from

the information supplied by an analysis. Also, results differ by

method, even though two methods may carry the same name

or the same concept. There is uncertainty in comparing one bit

of data with another without knowledge of how both bits were

gathered. Operational definitions, definitions tied to a specific

method, are needed. This soil taxonomy has many class limits

(at all levels) that are based on chemical or physical properties

determined in the laboratory. One can question a given limit,

but that is not the purpose of this appendix. This appendix is

written to show what procedures are used for given class limits.

By using specific class limits, everyone will come to the same

classification if they follow the same procedures.

This taxonomy is based almost entirely on criteria that are

defined operationally. One example is the definition of particlesize classes. There is no one definition of clay that works well

for all soils. Hence, an operation for testing the validity of a

clay measurement and a default operation for those situations

where the clay measurement is not valid are defined. The default

method is based on a water content at 1500 kPa and on content

of organic carbon.

Data Elements Used in Classifying Soils

Detailed explanations of laboratory methods are given in the

Soil Survey Laboratory Methods Manual (Burt, 2004). 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 measure reported on the data sheets in the

second edition of Soil Taxonomy are not SI units. Following are

SI conversions:

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

In this taxonomy the terms (1) particle-size analysis (size

separates), (2) texture, and (3) particle-size classes are all

used. Particle-size analysis is needed to determine texture and

particle-size classes. Texture differs from particle-size class in

that texture includes only the fine-earth fraction (less than 2

mm), while particle size includes both the fraction less than 2

mm in size and the fraction equal to or more than 2 mm.

Physical Analyses

Atterberg limits are determined on the fraction less than

0.4 mm in size. Plasticity index is the difference in water

content between liquid limit and plastic limit. It is the range

of water content over which a soil paste can be deformed

without breaking, but it does not include flow as a liquid under

operationally defined conditions. Liquid limit is the minimum

water content at which the paste begins to flow as a liquid.

Samples that do not deform without breaking at any water

content are reported as NP, nonplastic. Operational definitions

are in the Annual Book of ASTM Standards (ASTM, 1998).

Bulk density is obtained typically by equilibration of Sarancoated natural fabric clods at designated pressure differentials.

Bulk densities are determined at two or more water contents.

For coarse textured and moderately coarse textured soils,

they are determined when the sample is at 10 kPa suction and

when ovendry. For soils of medium and finer texture, the bulk
324	 Keys to Soil Taxonomy

densities are determined when the sample is at 33 kPa suction

and when ovendry.

Bulk density determined at 33 kPa suction is used to convert

other analytical results to a volumetric basis (for example, kg of

organic carbon per m3).

Coefficient of linear extensibility (COLE) is a derived value.

It is computed from the difference in bulk density between a

moist clod and an ovendry clod. It is based on the shrinkage of a

natural soil clod between a water content of 33 kPa (10 kPa for

sandier soils) and ovendry.

Linear extensibility (LE) of a soil layer is the product of

the thickness, in centimeters, multiplied by the COLE of the

layer in question. The LE of a soil is the sum of these products

for all soil horizons. COLE multiplied by 100 is called linear

extensibility percent (LEP).

Water retention difference (WRD) is computed from

gravimetric water retentions at 33 kPa (10 kPa for sandier

soils) and 1500 kPa suction. It is converted to cm of water per

cm of soil through use of the bulk density. The 33 or 10 kPa

water contents are determined by desorption of the natural

fabric clods, and the 1500 kPa water content is determined by

desorption of crushed and sieved fine-earth (<2 mm) soil.

Chemical Analyses

Aluminum saturation is the amount of KCl-extractable Al

divided by extractable bases (extracted by ammonium acetate)

plus the KCl-extractable Al. It is expressed as percent. A

general rule of thumb is that if there is more than 50 percent

Al saturation, Al problems in the soil are likely. The problems

may not be related to Al toxicity but to a deficiency of calcium

and/or magnesium.

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. These values are used as criteria in

identifying soils in the Andisol and Spodosol orders and in

the andic and spodic subgroups in other orders. They also are

used to determine amorhic and ferrihydric mineralogy classes.

The procedure extracts iron, aluminum, and silicon from

organic matter and from amorphous mineral material. It is

used in conjunction with dithionite-citrate and pyrophosphate

extractions to identify the sources of iron and aluminum in the

soil. Pyrophosphate extracts iron and aluminum from organic

matter. Dithionite-citrate extracts iron from iron oxides and

oxyhydroxides as well as from organic matter. A field test using

potassium hydroxide (KOH) can be used to estimate the amount

of aluminum that is extractable by ammonium oxalate.

Base saturation is reported on the data sheets as percent of

the CEC. It is reported as CEC by sum of cations at pH 8.2 and

by ammonium acetate at pH 7. Base saturation by ammonium

acetate is equal to the sum of the bases extracted by ammonium

acetate, divided by the CEC (by ammonium acetate), and

multiplied by 100. If extractable calcium is not reported on the

data sheet because of free carbonates or salts in the sample, then

the base saturation is assumed to be 100 percent.

Base saturation percentage by sum of cations is equal to the

sum of bases extracted by ammonium acetate, divided by the

CEC (by sum of cations), and multiplied by 100. This value is

not reported if either extractable calcium or extractable acidity

is omitted.

Differences between the two methods of determining base

saturation reflect the amount of the pH-dependent CEC. Class

definitions in this taxonomy specify which method is used.

The sum of exchangeable cations is considered equal to the

sum of bases extracted by ammonium acetate unless carbonates,

gypsum, or other salts are present. When these salts are present,

the sum of the bases extracted by ammonium acetate typically

exceeds 100 percent of the CEC. Therefore, a base saturation of

100 percent is assumed. The amount of calcium from carbonates

is usually much larger than the amount of magnesium from

the carbonates. Extractable calcium is not shown on the data

sheet if more than a trace (more than 0.4 percent) of carbonates

(reported as calcium carbonate) is present or if calculated base

saturation exceeds 110 percent, based on CEC by ammonium

acetate at pH 7.

Calcium carbonate equivalent is the amount of carbonates

in the soil as measured by treating the sample with HCl. The

evolved carbon dioxide is measured manometrically. The

amount of carbonate is then calculated as a calcium carbonate

equivalent regardless of the form of carbonates (dolomite,

sodium carbonate, magnesium carbonate, etc.) in the sample.

Calcium carbonate equivalent is reported as a percentage of the

total dry weight of the sample. It can be reported on material

that is less than 2 mm or less than 20 mm in size.

Calcium sulfate as gypsum is determined by extraction in

water and precipitation in acetone. The amount of gypsum is

reported as a percentage of the total dry weight of the fraction

less than 2 mm in size and the fraction less than 20 mm in size.

Drying soils to oven-dryness, the standard base for reporting the

data, removes part of the water of hydration from the gypsum.

Many measured values, particularly water retention values, must

be recalculated to compensate for the weight of the water of

hydration lost during drying.

Cation-exchange capacity (CEC) by ammonium acetate (1N

NH4OAc pH 7), by sum of cations (at pH 8.2), and by bases

plus aluminum is given on the data sheets in the chapters on

soil orders. The CEC depends on the method of analysis as

well as the nature of the exchange complex. CEC by sum of

cations at pH 8.2 is calculated by adding the sum of bases and

the extractable acidity. CEC by ammonium acetate is measured

at pH 7. CEC by bases plus aluminum, or effective cationexchange capacity (ECEC), is derived by adding the sum of

bases and KCl-extractable Al. Aluminum extracted by 1N KCl
Appendix	 325

is negligible if the extractant pH rises toward 5.5. ECEC then is

equal to extractable bases. CEC and ECEC are reported on the

data sheets as 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 to all

soils. CEC at pH 8.2 is not reported if the soil contains free

carbonates because bases are extracted from the carbonates.

The effective CEC (ECEC) is reported only for acid soils.

ECEC is not reported for soils having soluble salts, although it

can be calculated by subtracting the soluble components from

the extractable components. ECEC also may be defined as

bases plus aluminum plus hydrogen. That is the more common

definition for agronomic interpretations. This taxonomy

specifies bases plus aluminum.

Generally, the ECEC is less than the CEC at pH 7, which in

turn is less than the CEC at pH 8.2. If the soil is dominated by

positively charged colloids (e.g., iron oxides), however, the trend

is reversed. Most soils have negatively charged colloids, which

cause the CEC to increase with increasing pH. This difference

in CEC is commonly called the pH-dependent or variable

charge. The CEC at the soil pH can be estimated by plotting

the CEC of the soil vs. the pH of the extractant on a graph and

reading the CEC at the soil pH.

CEC measurements at pH levels other than those described

in the paragraphs above and CEC derived by use of other

cations will yield somewhat different results. It is important to

know the procedure, pH, and extracting cation used before CEC

data are evaluated or data from different sources are compared.

Citric-acid-extractable phosphorus (acid-soluble phosphate)

is used to separate the mollic epipedon (less than 1,500 mg/kg

P2O5) from the anthropic epipedon (equal to or more than 1,500

mg/kg).

Color of sodium-pyrophosphate extract is used as a criterion

in the separation of different types of organic materials.

A saturated solution is made by adding 1 g of sodium

pyrophosphate to 4 ml of distilled water, and a moist organic

matter sample is added to the solution. The sample is mixed and

allowed to stand overnight, chromatographic paper is dipped in

the solution, and the color of the paper is ascertained through

use of a Munsell color chart.

Electrical conductivity (EC) is the conductivity of the water

extracted from saturated paste. The EC is used to determine the

total content of salts. It is reported as dS/m.

Exchangeable magnesium and calcium plus exchangeable 

acidity (at pH 8.2) is used as a criterion for the natric

horizon. The exchangeable acidity is measured at pH 8.2,

and the magnesium and calcium are extracted at pH 7.0 with

ammonium acetate. See the paragraphs about extractable acidity

and exchangeable bases.

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 more

than 15 percent is used in this taxonomy as a criterion for the

natric horizon.

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 aluminum is exchangeable aluminum extracted

by 1N KCl. It is a major constituent only in strongly acid

soils (pH of less than 5.0). Aluminum will precipitate if the

pH rises above 4.5 to 5.0 during analysis. The extractant

KCl usually affects the soil pH 1 unit or less. Extractable

aluminum is measured at the Soil Survey Laboratory (SSL),

National Soil Survey Center, by atomic absorption. Many

laboratories measure the aluminum by titration with a base to

the phenopthalein end point. Titration measures exchangeable

acidity as well as extractable aluminum. Soils with a pH below

4.0 or 4.5 are likely to have values determined by atomic

absorption similar to values determined by titration because

very little hydrogen is typically on the exchange complex. If

there is a large percentage of organic matter, however, some

hydrogen may be present. For some soils it is important to know

which procedure was used. Extractable aluminum is reported as

cmol(+)/kg-1 soil.

Extractable bases (calcium, magnesium, sodium, and 

potassium) are extracted with ammonium acetate buffered

at pH 7. They are equilibrated, filtered in an auto-extractor,

and measured by atomic absorption. They are reported as

cmol(+)/kg-1 soil. The bases are extracted from the cationexchange complex by displacement with ammonium ions.

The term “extractable bases” is used instead of “exchangeable

bases” because soluble salts and some bases from carbonates

can be included in the extract.

Sum of bases is the sum of the calcium, magnesium, sodium,

and potassium described in the previous paragraph.

Iron and aluminum extracted by citrate are removed in a

single extraction. They are measured by atomic absorption

and reported as a percentage of the total dry weight. The iron

is primarily from ferric oxides (hematite, magnetite) and iron

oxyhydroxides (goethite). Aluminum substituted into these

minerals is extracted simultaneously. The dithionite reduces

the ferric iron, and the citrate stabilizes the iron by chelation.

Iron and aluminum bound in organic matter are extracted if

the citrate is a stronger chelator than the organic molecules.

Manganese extracted by this procedure also is recorded. The

iron extracted is commonly related to the clay distribution

within a pedon.

Melanic index is used in the identification of the melanic

epipedon. The index is related to the ratio of the humic and
326	 Keys to Soil Taxonomy

fulvic acids in the organic fraction of the soil (Honna et al.,

1988). About 0.50 gram of air-dried soil material that is

less than 2 mm in size is shaken with 25 ml of 0.5 percent

NaOH solution in a 50-ml centrifuge tube for 1 hour at room

temperature. One drop of a flocculating agent is added, and the

mixture is centrifuged at 4,000 rpm for 10 minutes. The melanic

index is the ratio of the absorbance at 450 nm over that at 520

nm.

Nitrogen in the SSL database is reported as a percentage

of the total dry weight. A soil sample is combusted at high

temperature with oxygen, and atmospheric nitrogen (N2) is

measured by thermal conductivity detection.

Optical density of the ammonium 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.

Organic carbon data in the SSL database have been

determined mostly by wet digestion (Walkley, 1935). Because

of environmental concerns about waste products, however,

that procedure is no longer in use. The only procedure that is

currently used to determine organic carbon is a dry combustion

procedure that determines the percent of total carbon. In

calcareous horizons the content of organic carbon is determined

by subtracting the amount of 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 procedure.

pH is measured in water and in salts. The pH measured in

water is determined in distilled water typically mixed 1:1 with

dry soil. The pH measured in potassium chloride is determined

in 1N KCl solution mixed 1:1 with soil. The pH measured in

calcium chloride is determined in 0.01M CaCl2 solution mixed

2:1 with soil.

The pH is measured by a pH meter in a soil-water or soil-salt

solution. The extent of the dilution is shown in the heading on

the data sheets. A ratio of 1:1 means one part dry soil and one

part water, by weight.

Measurement of pH in a dilute salt solution is common

because it tends to mask seasonal variations in pH. Readings in

0.01M CaCl2 tend to be uniform regardless of the time of year.

Readings in 1N KCl also tend to be uniform. The former are

more popular in regions with less acid soils. The latter are more

popular in regions with more acid soils. If KCl is used to extract

exchangeable aluminum, the pH reading (in KCl) shows the pH

at which the aluminum was extracted.

pH in sodium fluoride (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-rangeorder 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 component of short-range-order minerals

in 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.

Phosphate retention (P ret.) refers to the percent phosphorus

retained by soil after equilibration with 1,000 mg/kg phosphorus

solution for 24 hours. This procedure is used in the detection

of andic soil properties. It identifies soils in which phosphorus

fixation may be a problem affecting agronomic uses.

Sodium adsorption ratio (SAR) was developed as a measure

of irrigation water quality. Water-soluble sodium is divided by

water-soluble calcium and magnesium. The formula is SAR

= Na/[(Ca+Mg)/2]0.5. An SAR of 13 or more is used as an

alternate to the ESP criterion for the natric horizon.

Sodium-pyrophosphate-extractable iron and aluminum are

determined by a single extraction and measured by atomic

absorption. Results are reported as a percentage of the total dry

weight. This procedure has been used widely to extract iron and

aluminum from organic matter. It successfully removes much of

the organo-metal accumulations in spodic horizons but extracts

little of the inorganically bound iron and aluminum.

Total salts is calculated from the electrical conductivity of

the saturation extract. It is reported as a weight percentage of

the total water-soluble salts in the soil.

Water-soluble cations and anions are determined in water

extracted from a saturated paste. The cations include calcium,

magnesium, sodium, and potassium, and the anions include

carbonate, bicarbonate, sulfate, chloride, nitrite, nitrate, fluoride,

phosphate, silicate, and borate. The cations and anions are

reported as mmol(±) L-1.

Water-soluble sulfate is used as a criterion for the sulfuric

horizon. The sulfate is determined in the saturation extract and

is reported as one of the anions.

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 semi-quantitative

estimates of mineral percent by weight in the clay fraction.

The SSL 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, 2004). 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
Appendix	 327

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 first on the SSL 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

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 SSL 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, a request is made to count grains in the larger

fractions.

Two general types of petrographic analysis are conducted

in the SSL: (a) complete mineral grain count, in which all

minerals in the sample are identified and counted, or (b) 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 materials, 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 (e.g., quartz and feldspar)

in which more than 50 percent of the grain is covered in glass.

“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 SSL 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 complete list of minerals in each category is in the Soil 

Survey Laboratory Methods Manual (Burt, 2004).

Other Information Useful in Classifying Soils

Volumetric amounts of organic carbon are used in some

taxonomic criteria. The following calculation is used: (Datum

[percent] times bulk density [at 33 or 10 kPa] times thickness

[cm]) divided by 10. This calculation is normally used for

organic carbon, but it can be used for some other measurements.

Each horizon is calculated separately, and the product of the

calculations can be summed to any desired depth, commonly

100 cm.

Ratios that can be developed from the data are useful in

making internal checks of the data, in making managementrelated interpretations, and in answering taxonomic questions.

Some of the ratios are used as criteria in determining argillic,

kandic, or oxic horizons.

The ratio of 1500 kPa water to clay is used to indicate the

relevancy of the particle-size determination. If the ratio is

0.6 or more and the soil does not have andic soil properties,

incomplete dispersion of the clay is assumed and clay is

estimated by the following formula: Clay % = 2.5(% water

retained at 1500 kPa tension - % organic carbon). For a typical

soil with well dispersed clays, the ratio is 0.4. Some soil-related

factors that can cause deviation from the 0.4 value are: (1) lowactivity clays (kaolinites, chlorites, and some micas), which tend

to have a ratio of 0.35 or below; (2) iron oxides and clay-size

carbonates, which tend to decrease the ratio; (3) organic matter,

which increases the ratio because it increases the water content

at 1500 kPa; (4) andic and spodic materials and materials with

an isotic mineralogy class, which increase the ratio because they

do not disperse well; (5) large amounts of gypsum; and (6) clay

minerals within grains of sand and silt. These clay minerals hold
328	 Keys to Soil Taxonomy

water at 1500 kPa and thus increase the ratio. They are most

common in shale and in pseudomorphs of primary minerals in

saprolite.

The ratio of CEC by ammonium acetate at pH 7 to

percent clay can be used to estimate clay mineralogy and

clay dispersion. If the ratio is multiplied by 100, the product

is cmol(+)/kg clay. The following ratios are typical for the

following classes of clay mineralogy: less than 0.2, kaolinitic;

0.2-0.3, kaolinitic or mixed; 0.3-0.5, mixed or illitic; 0.5-

0.7, mixed or smectitic; and more than 0.7, smectitic. These

ratios are most valid when some detailed mineralogy data are

available. If the ratio of 1500 kPa water to clay is 0.25 or less

or 0.6 or more, the ratio of CEC by ammonium acetate to clay

is not valid. Ratios of 1500 kPa water to clay of 0.6 or more are

typical of poorly dispersed clays, andic and spodic materials,

and materials with an isotic mineralogy class, and ratios of less

than 0.3 are common in some soils that contain large amounts

of gypsum.

A ratio of CEC at pH 8.2 to 1500 kPa water of more than 1.5

and more exchange acidity than the sum of bases plus KClextractable Al imply a soil with a high pH-dependent charge.

Along with bulk density data, they help to distinguish soils that

have andic and spodic materials or soils that have materials

with an isotic mineralogy class from soils with minerals that are

more crystalline.

Literature Cited

American Society for Testing and Materials (ASTM). 1998.

Annual Book of ASTM Standards. Vol. 4.08, D 4318-95a.

Burt, R., ed. 2004. Soil Survey Laboratory Methods Manual.

Soil Survey Investigations Report 42, Version 4.0. United States

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.

Kimble, J.M, E.G. Knox, and C.S. Holzhey. 1993. Soil

Survey Laboratory Methods for Characterizing Physical and

Chemical Properties and Mineralogy of Soils. In Applications

of Agriculture Analysis in Environmental Studies, ASTM Spec.

Pub. 1162, K.B. Hoddinott and T.A. O’Shay, eds.

United States Department of Agriculture, Natural Resources

Conservation Service. 1995. Soil Survey Laboratory

Information Manual. National Soil Survey Center, Soil Survey

Laboratory, Soil Survey Investigations Report 45.

Walkley, A. 1935. An Examination of Methods for

Determining Organic Carbon and Nitrogen in Soils. J. Agr. Sci.

25: 598-609.
Appendix 329

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

331

Index

A

A horizons. See Horizons and layers.

Abrupt textural change..............................................................15

Acraquox.................................................................................241

Acroperox................................................................................242

Acrotorrox...............................................................................246

Acrudox...................................................................................247

Acrustox..................................................................................251

Agric horizon ..............................................................................9

Alaquods.................................................................................257

Albaqualfs.................................................................................36

Albaquults...............................................................................268

Albic horizon ..............................................................................9

Albic materials..........................................................................15

Albolls.....................................................................................198

Alfisols......................................................................................35

Alorthods ................................................................................262

Andic soil properties.................................................................15

Andisols....................................................................................77

Anhydrous conditions...............................................................16

Anhyorthels.............................................................................146

Anhyturbels.............................................................................150

Aniso class..............................................................................300

Anthracambids........................................................................108

Anthrepts.................................................................................161

Anthropic epipedon.....................................................................5

Aqualfs......................................................................................35

Aquands ....................................................................................77

Aquents...................................................................................124

Aquepts...................................................................................161

Aquerts....................................................................................287

Aquic conditions.......................................................................24

Redoximorphic features........................................................24

Reduced matrix .................................................................25

Redox concentrations........................................................25

Redox depletions...............................................................25

Reduction ..............................................................................24

Saturation ..............................................................................24

Anthric saturation (anthraquic conditions) .......................24

Endosaturation ..................................................................24

Episaturation .....................................................................24

Aquic moisture regime. See Soil moisture regimes.

Aquicambids...........................................................................108

Aquisalids ...............................................................................122

Aquiturbels..............................................................................151

Aquods....................................................................................257

Aquolls....................................................................................199

Aquorthels...............................................................................147

Aquox......................................................................................241

Aquults....................................................................................267

Arents......................................................................................127

Argialbolls...............................................................................198

Argiaquolls..............................................................................199

Argicryids ...............................................................................112

Argicryolls ..............................................................................203

Argids........................................................................................97

Argidurids...............................................................................115

Argigypsids.............................................................................118

Argillic horizon.........................................................................10

Argiorthels..............................................................................147

Argiudolls................................................................................208

Argiustolls...............................................................................215

Argixerolls...............................................................................231

Aridic moisture regime. See Soil moisture regimes.

Aridisols....................................................................................97

Artificial drainage. See Aquic conditions.

B

B horizons. See Horizons and layers.

Bottom tier................................................................................23

Buried soils.................................................................................2

C

C horizons or layers. See Horizons and layers.

Calcareous and reaction classes of mineral soils....................308

Calciaquerts ............................................................................288

Calciaquolls.............................................................................199

Calciargids ................................................................................97

Calcic horizon ...........................................................................10

Calcicryepts.............................................................................168

Calcicryids..............................................................................113

Calcicryolls.............................................................................204

Calcids.....................................................................................105

Calcigypsids............................................................................119

Calcitorrerts ............................................................................291

Calciudolls..............................................................................210

Calciustepts.............................................................................182

Calciusterts..............................................................................294
332 Keys to Soil Taxonomy

Calciustolls..............................................................................219

Calcixerepts.............................................................................190

Calcixererts.............................................................................297

Calcixerolls .............................................................................233

Cambic horizon.........................................................................10

Cambids..................................................................................108

Caret symbol in horizon designations.....................................321

Cation-exchange activity classes for mineral soils.................307

Chemical analyses...................................................................324

Coatings (classes) on sands.....................................................310

Coefficient of linear extensibility (COLE) ...............................16

Control section of Histosols and Histels...................................23

Coprogenous earth. See Organic soil materials.

Cryalfs.......................................................................................44

Cryands.....................................................................................80

Cryaqualfs.................................................................................37

Cryaquands ...............................................................................78

Cryaquents..............................................................................124

Cryaquepts..............................................................................162

Cryaquods...............................................................................258

Cryaquolls...............................................................................200

Cryepts....................................................................................167

Cryerts.....................................................................................291

Cryic temperature regime. See Soil temperature regimes.

Cryids......................................................................................112

Cryods.....................................................................................259

Cryofibrists..............................................................................155

Cryofluvents............................................................................128

Cryofolists...............................................................................156

Cryohemists............................................................................157

Cryolls.....................................................................................203

Cryopsamments.......................................................................138

Cryorthents..............................................................................133

Cryosaprists.............................................................................158

Cryoturbation ............................................................................25

Cryrendolls..............................................................................207

D

Densic contact...........................................................................25

Densic materials........................................................................25

Diagnostic subsurface horizons..................................................9

Diagnostic surface horizons........................................................5

Diatomaceous earth. See Organic soil materials.

Discontinuities in horizon designations..................................320

Duraqualfs.................................................................................37

Duraquands...............................................................................78

Duraquerts...............................................................................288

Duraquods...............................................................................258

Duraquolls...............................................................................200

Duricryands...............................................................................81

Duricryods...............................................................................259

Duricryolls ..............................................................................204

Durids......................................................................................115

Durihumods.............................................................................262

Durinodes..................................................................................17

Duripan .....................................................................................11

Duritorrands..............................................................................84

Durixeralfs ................................................................................71

Durixerepts..............................................................................190

Durixererts ..............................................................................297

Durixerolls ..............................................................................234

Durorthods..............................................................................263

Durudands.................................................................................86

Durudepts................................................................................175

Durustalfs..................................................................................59

Durustands................................................................................92

Durustepts...............................................................................183

Durustolls................................................................................221

Dystraquerts............................................................................288

Dystrocryepts..........................................................................168

Dystrogelepts ..........................................................................173

Dystroxerepts..........................................................................191

Dystrudepts.............................................................................175

Dystruderts..............................................................................293

Dystrustepts ............................................................................183

Dystrusterts.............................................................................294

E

E horizons. See Horizons and layers.

Endoaqualfs...............................................................................37

Endoaquands.............................................................................78

Endoaquents............................................................................124

Endoaquepts............................................................................163

Endoaquerts ............................................................................289

Endoaquods.............................................................................258

Endoaquolls.............................................................................200

Endoaquults.............................................................................268

Endosaturation. See Aquic conditions.

Entisols....................................................................................123

Epiaqualfs .................................................................................39

Epiaquands................................................................................79

Epiaquents...............................................................................125

Epiaquepts...............................................................................164

Epiaquerts ...............................................................................289

Epiaquods................................................................................259

Epiaquolls ...............................................................................201

Epiaquults ...............................................................................268

Epipedon .....................................................................................5

Episaturation. See Aquic conditions.

Eutraquox................................................................................241

Eutroperox...............................................................................243

Eutrotorrox..............................................................................246

Eutrudepts...............................................................................178

Eutrudox..................................................................................248

Eutrustox.................................................................................252
Index 333

F

Family differentiae for Histosols and Histels..........................311

Family differentiae for mineral soils.......................................299

Ferrudalfs..................................................................................49

Fibers. See Organic soil materials.

Fibric soil materials. See Organic soil materials.

Fibristels..................................................................................145

Fibrists.....................................................................................155

Fluvaquents.............................................................................125

Fluvents...................................................................................128

Fluviwassents..........................................................................142

Folistels...................................................................................145

Folistic epipedon .........................................................................6

Folists......................................................................................156

Fragiaqualfs...............................................................................41

Fragiaquepts............................................................................165

Fragiaquods.............................................................................259

Fragiaquults.............................................................................269

Fragic soil properties.................................................................17

Fragihumods............................................................................262

Fragiorthods............................................................................263

Fragipan ....................................................................................11

Fragiudalfs ................................................................................49

Fragiudepts..............................................................................180

Fragiudults ..............................................................................274

Fragixeralfs ...............................................................................72

Fragixerepts.............................................................................192

Fraglossudalfs...........................................................................49

Frasiwassents...........................................................................142

Frasiwassists............................................................................159

Free carbonates .........................................................................17

Frigid temperature regime. See Soil temperature regimes.

Fulvicryands..............................................................................81

Fulvudands................................................................................86

G

Gelands .....................................................................................84

Gelaquands................................................................................79

Gelaquents...............................................................................126

Gelaquepts...............................................................................165

Gelepts ....................................................................................173

Gelic materials..........................................................................25

Gelic temperature regime. See Soil temperature regimes.

Gelifluvents.............................................................................128

Gelisols ...................................................................................145

Gelods.....................................................................................261

Gelolls.....................................................................................206

Gelorthents..............................................................................134

Glacic layer ...............................................................................26

Glacistels.................................................................................146

Glossaqualfs..............................................................................41

Glossic horizon .........................................................................11

Glossocryalfs ............................................................................44

Glossudalfs................................................................................49

Gypsiargids...............................................................................99

Gypsic horizon..........................................................................12

Gypsicryids.............................................................................114

Gypsids ...................................................................................118

Gypsitorrerts...........................................................................292

Gypsiusterts ............................................................................295

H

Halaquepts...............................................................................166

Haplanthrepts..........................................................................161

Haplaquox ...............................................................................242

Haplargids...............................................................................100

Haplocalcids............................................................................105

Haplocambids .........................................................................109

Haplocryalfs..............................................................................45

Haplocryands............................................................................82

Haplocryepts...........................................................................169

Haplocryerts............................................................................291

Haplocryids.............................................................................114

Haplocryods............................................................................260

Haplocryolls............................................................................204

Haplodurids.............................................................................116

Haplofibrists............................................................................156

Haplogelepts............................................................................173

Haplogelods ............................................................................261

Haplogelolls............................................................................206

Haplogypsids...........................................................................120

Haplohemists...........................................................................157

Haplohumods..........................................................................262

Haplohumults..........................................................................271

Haploperox..............................................................................244

Haplorthels..............................................................................148

Haplorthods.............................................................................264

Haplosalids..............................................................................122

Haplosaprists...........................................................................158

Haplotorrands............................................................................85

Haplotorrerts...........................................................................292

Haplotorrox.............................................................................246

Haploturbels............................................................................151

Haplowassents.........................................................................143

Haplowassists..........................................................................159

Haploxeralfs..............................................................................72

Haploxerands.............................................................................95

Haploxerepts ...........................................................................193

Haploxererts............................................................................298

Haploxerolls............................................................................235

Haploxerults............................................................................285

Hapludalfs.................................................................................51

Hapludands ...............................................................................87

Hapluderts...............................................................................293

Hapludolls...............................................................................211

Hapludox.................................................................................249

Hapludults...............................................................................275
334 Keys to Soil Taxonomy

Haplustalfs ................................................................................60

Haplustands...............................................................................92

Haplustepts..............................................................................185

Haplusterts..............................................................................295

Haplustolls..............................................................................221

Haplustox ................................................................................253

Haplustults..............................................................................282

Haprendolls.............................................................................207

Hemic soil materials. See Organic soil materials.

Hemistels.................................................................................146

Hemists ...................................................................................157

Histels .....................................................................................145

Histic epipedon ...........................................................................6

Historthels...............................................................................148

Histosols..................................................................................155

Histoturbels.............................................................................151

Horizons and layers.................................................................315

A horizons...........................................................................315

B horizons...........................................................................316

C horizons or layers ............................................................316

E horizons ...........................................................................315

L horizons or layers.............................................................315

M layers...............................................................................316

O horizons or layers............................................................315

R layers................................................................................316

W layers ..............................................................................316

Humaquepts ............................................................................166

Humicryepts............................................................................171

Humicryerts ............................................................................291

Humicryods.............................................................................260

Humigelepts............................................................................174

Humigelods.............................................................................261

Humilluvic material. See Organic soil materials.

Humixerepts............................................................................194

Humods...................................................................................261

Humudepts..............................................................................180

Humults...................................................................................271

Humustepts .............................................................................189

Hydraquents............................................................................126

Hydrocryands............................................................................83

Hydrowassents ........................................................................143

Hydrudands...............................................................................89

Hyperthermic temperature regime. See Soil temperature 

regimes.

I

Identifiable secondary carbonates.............................................17

Inceptisols...............................................................................161

Interfingering of albic materials................................................17

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.............................................................................42

Kandiaquults...........................................................................269

Kandic horizon..........................................................................12

Kandihumults..........................................................................272

Kandiperox..............................................................................245

Kandiudalfs...............................................................................55

Kandiudox...............................................................................250

Kandiudults.............................................................................276

Kandiustalfs ..............................................................................63

Kandiustox ..............................................................................254

Kandiustults............................................................................282

Kanhaplaquults .......................................................................269

Kanhaplohumults....................................................................273

Kanhapludalfs...........................................................................56

Kanhapludults.........................................................................278

Kanhaplustalfs...........................................................................64

Kanhaplustults.........................................................................284

Key to soil orders......................................................................31

L

L horizons or layers. See Horizons and layers.

Lamellae....................................................................................18

Limnic materials. See Organic soil materials.

Linear extensibility (LE)...........................................................18

Lithic contact ............................................................................26

Lithologic discontinuities..........................................................18

Luvihemists.............................................................................158

M

M layers. See Horizons and layers.

Marl. See Organic soil materials.

Melanaquands...........................................................................79

Melanic epipedon........................................................................7

Melanocryands..........................................................................83

Melanoxerands..........................................................................95

Melanudands.............................................................................90

Mesic temperature regime. See Soil temperature regimes.

Mineral analyses .....................................................................326

Mineral soil material...................................................................3

Mineral soils................................................................................4

Mineralogy classes for Histosols and Histels .........................312

Mineralogy classes for mineral soils.......................................305

Mollic epipedon ..........................................................................7

Mollisols .................................................................................197

Molliturbels.............................................................................152

Mollorthels..............................................................................149
Index 335

N

n value.......................................................................................19

Natralbolls...............................................................................199

Natraqualfs................................................................................43

Natraquerts..............................................................................290

Natraquolls..............................................................................202

Natrargids................................................................................102

Natric horizon ...........................................................................12

Natricryolls .............................................................................206

Natridurids ..............................................................................117

Natrigypsids............................................................................121

Natrixeralfs................................................................................74

Natrixerolls..............................................................................239

Natrudalfs..................................................................................56

Natrudolls................................................................................213

Natrustalfs.................................................................................65

Natrustolls...............................................................................226

Normal years.............................................................................26

O

O horizons or layers. See Horizons and layers.

Ochric epipedon..........................................................................8

Organic soil materials.................................................................3

Fibers.....................................................................................21

Fibric soil materials...............................................................21

Hemic soil materials .............................................................22

Humilluvic material ..............................................................22

Limnic materials ...................................................................22

Coprogenous earth ............................................................22

Diatomaceous earth...........................................................23

Marl...................................................................................23

Sapric soil materials..............................................................22

Organic soils ...............................................................................4

Orthels.....................................................................................146

Orthents...................................................................................133

Orthods....................................................................................262

Ortstein......................................................................................13

Oxic horizon..............................................................................13

Oxisols....................................................................................241

P

Paleaquults..............................................................................270

Paleargids................................................................................104

Palecryalfs.................................................................................47

Palecryolls...............................................................................206

Palehumults.............................................................................273

Paleudalfs..................................................................................57

Paleudolls................................................................................214

Paleudults................................................................................279

Paleustalfs.................................................................................67

Paleustolls...............................................................................228

Paleustults...............................................................................285

Palexeralfs.................................................................................74

Palexerolls...............................................................................239

Palexerults...............................................................................286

Paralithic contact.......................................................................26

Paralithic materials....................................................................26

Pararock fragments .................................................................299

Particle-size classes for Histosols and Histels........................311

Particle-size classes and their substitutes for mineral soils ....299

Permafrost.................................................................................26

Permanent cracks (classes) in mineral soils............................311

Perox .......................................................................................242

Perudic moisture regime. See Soil moisture regimes.

Petraquepts..............................................................................167

Petroargids...............................................................................105

Petrocalcic horizon....................................................................14

Petrocalcids.............................................................................107

Petrocambids...........................................................................112

Petrocryids ..............................................................................115

Petroferric contact.....................................................................19

Petrogypsic horizon...................................................................14

Petrogypsids............................................................................121

Physical analyses.....................................................................323

Placaquands...............................................................................80

Placaquods ..............................................................................259

Placic horizon............................................................................14

Placocryods.............................................................................261

Placohumods...........................................................................262

Placorthods..............................................................................265

Placudands ................................................................................91

Plagganthrepts.........................................................................161

Plaggen epipedon........................................................................8

Plinthaqualfs .............................................................................43

Plinthaquox .............................................................................242

Plinthaquults ...........................................................................271

Plinthite.....................................................................................19

Plinthohumults........................................................................274

Plinthoxeralfs............................................................................76

Plinthudults.............................................................................281

Plinthustalfs...............................................................................70

Plinthustults.............................................................................285

Prime symbol in horizon designations....................................320

Psammaquents.........................................................................126

Psamments..............................................................................138

Psammorthels..........................................................................149

Psammoturbels........................................................................152

Psammowassents.....................................................................143

Q

Quartzipsamments ..................................................................139

R

R layers. See Horizons and layers.

Ratio, 1500 kPa water to clay..................................................303

Ratio, CEC to clay ..................................................................308

Reaction classes for Histosols and Histels..............................312
336 Keys to Soil Taxonomy

Redoximorphic features. See Aquic conditions.

Reduction. See Aquic conditions.

Rendolls..................................................................................207

Resistant minerals.....................................................................20

Rhodoxeralfs.............................................................................76

Rhodudalfs................................................................................59

Rhodudults..............................................................................281

Rhodustalfs ...............................................................................70

Rhodustults .............................................................................285

Rock fragments.......................................................................299

Rock structure .............................................................................5

Root-limiting layers ................................................................300

Rounding...................................................................................31

Rupture-resistance classes for mineral soils...........................310

S

Salaquerts................................................................................286

Salic horizon .............................................................................14

Salicryids ................................................................................115

Salids.......................................................................................122

Salitorrerts...............................................................................292

Salusterts.................................................................................296

Sapric soil materials. See Organic soil materials.

Sapristels.................................................................................146

Saprists....................................................................................158

Saturation. See Aquic conditions.

Series control section ..............................................................313

Series differentiae within a family ..........................................313

Slickensides...............................................................................20

Soil .............................................................................................1

Soil color, water state criteria....................................................31

Soil depth classes for Histosols...............................................313

Soil depth classes for mineral soils and Histels......................310

Soil moisture regimes ...............................................................26

Aquic.....................................................................................27

Aridic and torric....................................................................27

Perudic ..................................................................................28

Udic.......................................................................................28

Ustic ......................................................................................28

Xeric......................................................................................28

Soil temperature classes for Histosols and Histels .................312

Soil temperature classes for mineral soils...............................309

Soil temperature regimes ..........................................................28

Cryic......................................................................................28

Frigid.....................................................................................29

Gelic......................................................................................28

Hyperthermic ........................................................................29

Isofrigid.................................................................................29

Isohyperthermic ....................................................................29

Isomesic ................................................................................29

Isothermic .............................................................................29

Mesic.....................................................................................29

Thermic.................................................................................29

Sombric horizon........................................................................14

Sombrihumults........................................................................274

Sombriperox............................................................................246

Sombriudox.............................................................................251

Sombriustox ............................................................................255

Sphagnofibrists........................................................................156

Spodic horizon ..........................................................................14

Spodic materials........................................................................20

Spodosols................................................................................257

Strongly contrasting particle-size classes ...............................303

Subsurface tier ..........................................................................23

Suffix symbols in horizon designations..................................317

Conventions for using letter suffixes...................................319

Sulfaquents..............................................................................127

Sulfaquepts..............................................................................167

Sulfaquerts..............................................................................291

Sulfidic materials ......................................................................29

Sulfihemists.............................................................................158

Sulfisaprists.............................................................................159

Sulfiwassents...........................................................................144

Sulfiwassists............................................................................160

Sulfohemists............................................................................158

Sulfosaprists............................................................................159

Sulfudepts ...............................................................................182

Sulfuric horizon ........................................................................29

Surface tier................................................................................23

T

Thermic temperature regime. See Soil temperature 

regimes.

Torrands....................................................................................84

Torrerts....................................................................................291

Torriarents...............................................................................127

Torric moisture regime. See Soil moisture regimes.

Torrifluvents............................................................................128

Torrifolists...............................................................................156

Torriorthents............................................................................134

Torripsamments.......................................................................140

Torrox......................................................................................246

Transitional and combination horizons...................................316

Turbels.....................................................................................150

U

Udalfs........................................................................................47

Udands ......................................................................................85

Udarents..................................................................................127

Udepts.....................................................................................174

Uderts......................................................................................292

Udic moisture regime. See Soil moisture regimes.

Udifluvents..............................................................................130

Udifolists.................................................................................157

Udipsamments.........................................................................140

Udivitrands................................................................................93

Udolls......................................................................................207
Index 337

Udorthents...............................................................................135

Udox........................................................................................247

Udults......................................................................................274

Ultisols....................................................................................267

Umbraquults............................................................................271

Umbric epipedon.........................................................................8

Umbriturbels...........................................................................152

Umbrorthels............................................................................150

Ustalfs.......................................................................................59

Ustands......................................................................................92

Ustarents .................................................................................127

Ustepts.....................................................................................182

Usterts.....................................................................................293

Ustic moisture regime. See Soil moisture regimes.

Ustifluvents.............................................................................131

Ustifolists................................................................................157

Ustipsamments........................................................................141

Ustivitrands...............................................................................94

Ustolls.....................................................................................215

Ustorthents..............................................................................136

Ustox .......................................................................................251

Ustults.....................................................................................281

V

Vermaqualfs..............................................................................43

Vermaquepts............................................................................167

Vermudolls..............................................................................215

Vermustolls .............................................................................230

Vertical subdivision in horizon designations ..........................319

Vertisols ..................................................................................287

Vitrands.....................................................................................93

Vitraquands...............................................................................80

Vitricryands...............................................................................83

Vitrigelands...............................................................................84

Vitritorrands..............................................................................85

Vitrixerands...............................................................................95

Volcanic glass............................................................................21

W

W layers. See Horizons and layers.

Wassents..................................................................................142

Wassists...................................................................................159

Weatherable minerals................................................................21

X

Xeralfs.......................................................................................71

Xerands.....................................................................................94

Xerarents.................................................................................127

Xerepts....................................................................................189

Xererts.....................................................................................297

Xeric moisture regime. See Soil moisture regimes.

Xerofluvents............................................................................132

Xerolls.....................................................................................230

Xeropsamments.......................................................................141

Xerorthents..............................................................................138

Xerults.....................................................................................285
338

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

H

O

R

F

A

M

V

E

R

U

L

T

S

P

O

O

X

I

M

O

L

I

N

C

H

I

S

G

E

L

E

N

T

A

R

I

A

N

D

A

L

F

I

D

E

D

I

A

D

I

F