United States

Department of

Agriculture

Field Indicators of 

Hydric Soils in the 

United States

A Guide for Identifying and Delineating 

Hydric Soils, Version 7.0, 2010

In cooperation with 

the National Technical 

Committee for Hydric Soils

Natural Resources 

Conservation 

Service

Field Indicators of Hydric Soils 

in the United States

A Guide for Identifying and Delineating Hydric Soils,

Version 7.0, 2010

United States Department of Agriculture,

Natural Resources Conservation Service,

in cooperation with 

the National Technical Committee for Hydric Soils

Edited by L.M. Vasilas, Soil Scientist, NRCS, Washington, DC; G.W. Hurt, Soil 

Scientist, University of Florida, Gainesville, FL; and C.V. Noble, Soil Scientist, 

USACE, Vicksburg, MS
ii

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Copies of this publication can be obtained from:

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1-888-LANDCARE (888-526-3227)

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 Information contained in this publication and additional information concerning 

hydric soils are maintained on the Web site at http://soils.usda.gov/use/hydric/.

Citation: United States Department of Agriculture, Natural Resources 

Conservation Service. 2010. Field Indicators of Hydric Soils in the United States, 

Version 7.0. L.M. Vasilas, G.W. Hurt, and C.V. Noble (eds.). USDA, NRCS, in 

cooperation with the National Technical Committee for Hydric Soils.

Cover: All of the soils on the cover are hydric soils. The soil in the top left meets 

requirements of the indicator S7, Dark Surface; the one in the top right meets the 

requirements of A11, Depleted Below Dark Surface; the one in the bottom left meets 

the requirements of F3, Depleted Matrix; and the one in the bottom right meets the 

requirements of F19, Piedmont Flood Plain Soils.
iii

Foreword

Field Indicators of Hydric Soils in the United States has been developed by soil 

scientists of the Natural Resources Conservation Service (NRCS) in cooperation with 

the U.S. Fish and Wildlife Service (FWS); the U.S. Army Corps of Engineers (COE); the 

Environmental Protection Agency (EPA); various regional, state, and local agencies; 

universities; and the private sector. The editors recognize that this guide could not have 

been developed without the efforts of many individuals. Included in this publication are 

the hydric soil indicators approved by the NRCS and the National Technical Committee 

for Hydric Soils (NTCHS) for use in identifying, delineating, and verifying hydric soils 

in the field. Also included are indicators designated as test indicators, which are not 

approved for use but are to be tested so that their utility can be determined.

v

Contents

Foreword ..................................................................................................................... iii

Location of Indicators by Page ..................................................................................... vi

Introduction ....................................................................................................................1

Concept .........................................................................................................................2

Cautions ........................................................................................................................3

Procedure ......................................................................................................................3

General Guidance for Using the Indicators.....................................................................5

To Comment on the Indicators .......................................................................................5

Field Indicators of Hydric Soils ..................................................................................9

 All Soils ..................................................................................................................9

 Sandy Soils ..........................................................................................................16

 Loamy and Clayey Soils .......................................................................................20

Test Indicators of Hydric Soils .................................................................................27

 All Soils ................................................................................................................27

 Sandy Soils ..........................................................................................................28

 Loamy and Clayey Soils .......................................................................................28

References .................................................................................................................31

Glossary .....................................................................................................................33

Appendices ................................................................................................................43

 Appendix 1: Use Indicators by Land Resource Regions (LRRs) and Certain 

Major Land Resource Areas (MLRAs) ..............................................................43

 Appendix 2: Test Indicators by Land Resource Regions (LRRs) and Certain 

Major Land Resource Areas (MLRAs) ..............................................................44
vi

Location of Indicators by Page

All Soils ....................................................................9

A1 Histosol or Histel .................................................9

A2 Histic Epipedon ...................................................9

A3 Black Histic ..........................................................9

A4 Hydrogen Sulfide ...............................................10

A5 Stratified Layers .................................................10

A6 Organic Bodies ..................................................11

A7 5 cm Mucky Mineral ..........................................11

A8 Muck Presence ..................................................12 

A9 1 cm Muck .........................................................12

A10 2 cm Muck .......................................................12

A11 Depleted Below Dark Surface .........................13

A12 Thick Dark Surface ..........................................14

A13 Alaska Gleyed .................................................15

A14 Alaska Redox ..................................................15

A15 Alaska Gleyed Pores .......................................15

A16 Coast Prairie Redox ........................................16

Sandy Soils ............................................................16

S1 Sandy Mucky Mineral .........................................16

S2 2.5 cm Mucky Peat or Peat.................................17

S3 5 cm Mucky Peat or Peat....................................17 

S4 Sandy Gleyed Matrix ..........................................17

S5 Sandy Redox......................................................17

S6 Stripped Matrix ...................................................17

S7 Dark Surface ......................................................18

S8 Polyvalue Below Surface....................................19

S9 Thin Dark Surface...............................................19

Loamy and Clayey Soils ........................................20

F1 Loamy Mucky Mineral.........................................20

F2 Loamy Gleyed Matrix..........................................20

F3 Depleted Matrix ..................................................20

F6 Redox Dark Surface ...........................................21

F7 Depleted Dark Surface .......................................22

F8 Redox Depressions ............................................23

F9 Vernal Pools........................................................23

F10 Marl ..................................................................23

F11 Depleted Ochric................................................23

F12 Iron-Manganese Masses..................................24

F13 Umbric Surface.................................................24

F16 High Plains Depressions ..................................25

F17 Delta Ochric......................................................25

F18 Reduced Vertic .................................................25

F19 Piedmont Flood Plain Soils...............................26

F20 Anomalous Bright Loamy Soils.........................26

Test Indicators

All Soils ..................................................................27

TA4 Alaska Color Change........................................27

TA5 Alaska Alpine Swales .......................................27

TA6 Mesic Spodic ....................................................27

Loamy and Clayey Soils ........................................28

TF2 Red Parent Material........................................28

TF12 Very Shallow Dark Surface.............................29
1

Field Indicators of Hydric Soils in the

United States,Version 7.0, 2010

Figure 1.—The soil on the right is hydric. It meets the requirements of indicator S7 (Dark Surface). From the surface and to a depth 

of 10 cm, value is 3 or less and chroma is 1 or less. Below 10 cm, the matrix has chroma of 2 or less. The soil on the left is not 

hydric. It does not have a dark surface horizon thick enough to meet the requirements of indicator S7 and does not meet the 

requirements of any other indicator.

Introduction

Field Indicators of Hydric Soils in the United 

States is a guide to help identify and delineate hydric 

soils in the field (fig. 1). Indicators are not intended 

to replace or modify the requirements contained in 

the definition of a hydric soil. The list of indicators is 

considered to be dynamic; changes and additions are 

likely to be made annually. The section “To Comment 

on the Indicators” provides guidance on how to 

recommend deletions, additions, and other changes. 

Any modifications to the indicators must be approved 

by NRCS and the National Technical Committee for 

Hydric Soils (NTCHS). Proper use of the indicators 

requires a basic knowledge of soil-landscape 

relationships and soil survey procedures. 

The indicators are designed to be regionally 

specific. The description of each indicator identifies 

the land resource regions (LRRs) or major land 

resource areas (MLRAs) in which the indicator can be 
 Field Indicators of

used. The geographic extent of LRRs and MLRAs is 

defined in U.S. Department of Agriculture Handbook 

296 (USDA, NRCS, 2006b). See map (figure 6, 

page 7) and LRR-specific indicators (Appendices 1 

and 2). The indicators are used to identify the hydric 

soil component of wetlands; however, there are 

some hydric soils that lack any of the currently listed 

indicators. Therefore, the lack of any listed indicator 

does not prevent classification of the soil as hydric. 

Such soils should be studied and their characteristic 

morphologies identified for inclusion in this guide.

The NTCHS defines a hydric soil as a soil that 

formed under conditions of saturation, flooding, or 

ponding long enough during the growing season 

to develop anaerobic conditions in the upper part 

(Federal Register, 1994). Most hydric soils exhibit 

characteristic morphologies that result from repeated 

periods of saturation or inundation that last more than 

a few days. Saturation or inundation, when combined 

with microbial activity in the soil, causes the depletion 

of oxygen. This anaerobiosis promotes certain 

biogeochemical processes, such as the accumulation 

of organic matter and the reduction, translocation, or 

accumulation of iron and other reducible elements. 

These processes result in distinctive characteristics 

that persist in the soil during both wet and dry periods, 

making them particularly useful for identifying hydric 

soils in the field.

The list of indicators is dynamic; changes and 

additions are anticipated with new research and 

field testing. The current version of the indicators is 

available on the NRCS hydric soils Web site 

(http://soils.usda.gov/use/hydric). 

Concept

Hydric soil indicators are formed predominantly by 

the accumulation or loss of iron, manganese, sulfur, 

or carbon compounds in a saturated and anaerobic 

environment. These processes and the features that 

develop are described in the following paragraphs.

Iron and Manganese Reduction, 

Translocation, and Accumulation

In an anaerobic environment, soil microbes reduce 

iron from the ferric (Fe3+) to the ferrous (Fe2+) form 

and manganese from the manganic (Mn4+) to the 

manganous (Mn2+) form. Of the two, evidence of 

iron reduction is more commonly observed in soils. 

Areas in the soil where iron is reduced often develop 

characteristic bluish gray or greenish gray colors 

known as gley (colors with value of 4 or more on the 

gley pages in the Munsell color book). Ferric iron 

is insoluble, but ferrous iron easily enters the soil 

solution and may be moved or translocated to other 

areas of the soil. Areas that have lost iron typically 

develop characteristic gray or reddish gray colors and 

are known as redox depletions. If a soil reverts to an 

aerobic state, iron that is in solution will oxidize and 

become concentrated in patches as soft masses and 

along root channels and other pores. These areas of 

oxidized iron are called redox concentrations. Since 

water movement in these saturated or inundated 

soils can be multidirectional, redox depletions and 

concentrations can occur anywhere in the soil and 

have irregular shapes and sizes. Soils that are 

saturated and contain ferrous iron at the time of 

sampling may change color upon exposure to the air, 

as ferrous iron is rapidly converted to ferric iron in the 

presence of oxygen. Such soils are said to have a 

reduced matrix (Vepraskas, 1994).

While indicators related to iron or manganese 

depletion or concentration are most common in hydric 

soils, they cannot form in soils with parent materials 

that are low in content of Fe or Mn. Soils that formed 

in such materials may have low-chroma colors that 

are not related to saturation and reduction. Such soils 

may have morphological features that formed through 

accumulation of organic matter.

Sulfate Reduction

Sulfur is one of the last elements to be reduced by 

microbes in an anaerobic environment. The microbes 

convert SO4

2− to H2

S, or hydrogen sulfide gas. This 

conversion results in a very pronounced “rotten egg” 

odor in some soils that are inundated or saturated 

for very long periods. In soils that are not saturated 

or inundated, sulfate is not reduced and there is no 

rotten egg odor. The presence of hydrogen sulfide is 

a strong indicator of a hydric soil, but this indicator 

occurs only on the wettest sites, in soils that contain 

sulfur-bearing compounds.

Organic-Matter Accumulation

Soil microbes use carbon compounds that occur 

in organic matter as an energy source. The rate at 

which soil microbes use organic carbon, however, 

is considerably lower in a saturated and anaerobic 

environment than under aerobic conditions. Therefore, 

in saturated soils, partially decomposed organic 

matter may accumulate. The result in wetlands is often 

the development of thick organic surface horizons, 

such as peat or muck, or dark organic-rich mineral 

surface layers.
Hydric Soils 3

Determining the Texture of Soil Materials 

High in Organic Carbon

Material high in organic carbon could fall into three 

categories: organic, mucky mineral, and mineral. 

In lieu of laboratory data, the following estimation 

method can be used for soil material that is wet 

or nearly saturated with water. This method may 

be inconclusive with loamy or clayey mineral soils. 

Gently rub the wet soil material between forefinger 

and thumb. If upon the first or second rub the 

material feels gritty, it is mineral soil material. If after 

the second rub the material feels greasy, it is either 

mucky mineral or organic soil material. Gently rub 

the material two or three more times. If after these 

additional rubs it feels gritty or plastic, it is mucky 

mineral soil material; if it still feels greasy, it is organic 

soil material. 

If the material is organic soil material, a further 

division should be made. Organic soil materials are 

classified as sapric, hemic, or fibric. Differentiating 

criteria are based on the percentage of visible fibers 

observable with a hand lens in an undisturbed state 

and after rubbing between thumb and fingers 10 

times. Sapric, hemic, and fibric correspond to the 

textures muck, mucky peat, and peat. If there is a 

conflict between unrubbed and rubbed fiber content, 

rubbed content is used. Live roots are not considered.

Cautions

A soil that is drained or protected (for instance, by 

dikes or levees) will meet the definition of a hydric soil 

if the upper part formed under anaerobic conditions 

in an unaltered state. To be identified as hydric, 

the soil should generally have one or more of the 

indicators. Not all areas that have hydric soils qualify 

as wetlands, however, if they no longer have wetland 

hydrology or support hydrophytic vegetation.

There are hydric soils with morphologies that are 

difficult to interpret. These include soils with black, 

gray, or red parent material; soils with high pH; soils 

high or low in content of organic matter; recently 

developed hydric soils; and soils high in iron inputs. 

In some cases we do not currently have indicators 

to assist in the identification of hydric soils in these 

situations. As long as the soil meets the definition of a 

hydric soil, the lack of an indicator does not preclude 

the soil from being hydric.

The indicators were developed mostly to identify 

the boundary of hydric soil areas and generally 

work best on the margins. Not all of the obviously 

wetter hydric soils will be identified by the indicators. 

Redoximorphic features are most likely to occur in 

soils that cycle between anaerobic (reduced) and 

aerobic (oxidized) conditions.

Morphological features of hydric soils indicate that 

saturation and anaerobic conditions have existed 

under either contemporary or former hydrologic 

regimes. Where soil morphology seems inconsistent 

with the landscape, vegetation, or observable 

hydrology, it may be necessary to obtain the 

assistance of an experienced soil or wetland scientist 

to determine whether the soil is hydric.

Procedure

Observe and Document the Site

Before making any decision about the presence 

or absence of hydric soils, the overall site and how it 

interacts with the soil should be considered. The steps 

below, while not required to identify a hydric soil, can 

help to explain why one is or is not present. Always 

look at the landscape features of the immediate site 

and compare them to the surrounding areas. Try to 

contrast the features of wet and dry sites that are in 

close proximity. When observing slope features, look 

first at the area immediately around the sampling 

point. For example, a nearly level bench or depression 

at the sampling point may be more important to the 

wetness of the site than the overall landform on which 

the bench or depression occurs. Understanding 

how water moves across the site helps to clarify the 

reasons for the presence or absence of hydric soil 

indicators.

Observe and Document the Soil

To observe and document a hydric soil, first remove 

from the soil surface any woody material larger than 

2 cm in cross section that cannot be crushed or 

shredded when rubbed. Do not remove the organic 

surface layers of the soil, which generally consist of 

plant remains in various stages of decomposition. Dig 

a hole and describe the soil profile. In general, the 

hole should be dug to the depth needed to document 

an indicator or to confirm the absence of indicators. 

For most soils, the recommended excavation depth is 

approximately 20 inches (50 cm) from the soil surface, 

although a shallower soil pit may suffice for some 

indicators (e.g., A2, Histic Epipedon). Digging may be 

difficult in some areas because of rocks or hardpans. 

Use the completed profile description to determine 

which hydric soil indicators have been met (USDA, 

NRCS, 2006a).
 Field Indicators of

For soils with thick, dark surface layers, deeper 

examination may be required when field indicators 

are not easily seen within 20 inches (50 cm) of the 

surface. The accumulation of organic matter in these 

soils may mask redoximorphic features in the surface 

layers. Examination to a depth of 40 inches (1 m) or 

more may be needed to determine whether the soils 

meet the requirements of indicator A12 (Thick Dark 

Surface). A soil auger or probe may be useful for 

sampling soil materials below a depth of 20 inches.

Whenever possible, excavate the soil deep enough 

to determine if there are layers or materials present 

that might restrict soil drainage. This determination will 

help to indicate why the soil may or may not be hydric. 

After a sufficient number of exploratory excavations 

have been made to determine the soil hydrologic 

relationships at the site, subsequent excavations can 

be limited to the depth needed to identify hydric soil 

indicators. Consider taking photographs of both the 

soil and the overall site, including a clearly marked 

measurement scale in pictures of soil profiles.

In LRRs R, W, X, and Y, we begin our observations 

at the top of the mineral surface (underneath any and 

all fibric, hemic, and/or sapric material), except for 

areas of indicators A1, A2, and A3, where we begin 

at the actual soil surface. In LRRs F, G, H, and M, we 

begin our observations at the actual soil surface if the 

soil is sandy and in areas of indicators A1, A2, and A3 

and at the muck or mineral surface for the remaining 

field indicators. In the remaining LRRs, we begin our 

observations at the top of the muck or mineral surface 

(underneath any fibric and/or hemic material), except 

for areas of indicators A1, A2, and A3, where we 

begin at the actual soil surface (fig. 2).

All colors noted in this guide refer to moist 

Munsell® colors (Gretag-Macbeth, 2000). Dry 

soils should be moistened until the color no longer 

changes, and wet soils should be allowed to dry until 

they no longer glisten (fig. 3). Care should be taken to 

avoid over-moistening dry soil. Soil chromas specified 

in the indicators do not have decimal points; however, 

intermediate colors do occur between Munsell chips. 

Rounding should not be used to make chroma meet 

the requirements of an indicator. A soil matrix with 

chroma between 2 and 3 should be described as 

having chroma of 2+. It does not have chroma of 2 

and would not meet the requirements of any indicator 

that requires chroma of 2 or less. Always examine soil 

matrix colors in the field immediately after sampling. 

Ferrous iron in the soil can oxidize rapidly and create 

colors of higher chroma or redder hue.

Soils that are saturated at the time of sampling may 

contain reduced iron and/or manganese that cannot 

Figure 2.—To determine if a hydric soil Indicator occurs in 

this soil profile, begin measurements at 8 cm on the left 

measuring tape, excluding the organic horizons of mucky 

peat or peat.

be detected by the eye. Under saturated conditions, 

redox concentrations may be absent or difficult to see, 

particularly in dark colored soils. It may be necessary 

to let the soil dry to a moist state (for 5 to 30 minutes 

or more) for the iron or manganese to oxidize and the 

redoximorphic features to become visible.

Particular attention should be paid to changes in 

microtopography over short distances. Small changes 

in elevation may result in repetitive sequences 

of hydric/nonhydric soils, making the delineation 

of individual areas of hydric and nonhydric soils 

difficult. Commonly, the dominant condition (hydric 

or nonhydric) is the only reliable interpretation. The 

shape of the local landform can greatly affect the 

movement of water through the landscape. Significant 

changes in parent material or lithologic discontinuities 

in the soil can also affect the hydrologic properties of 

the soil.
Hydric Soils 5

General Guidance for Using the 

Indicators

Many of the hydric soil indicators were developed 

specifically for purposes of wetland delineation. 

During the development of these indicators, soils in 

the interiors of wetlands were not always examined; 

therefore, there are wetlands that lack any of the 

approved hydric soil indicators in the wettest interior 

portions. Wetland delineators and other users of 

the hydric soil indicators should concentrate their 

sampling efforts near the wetland edge and, if these 

soils are hydric, assume that soils in the wetter, 

interior portions of the wetland also are hydric, even if 

they lack an indicator.

All mineral layers above any layers meeting the 

requirements of any indicator(s), except for indicators 

A16, S6, F8, F12, F19, and F20, have a dominant 

chroma of 2 or less, or the thickness of the layer(s) 

with a dominant chroma of more than 2 is less than 15 

cm (6 inches). See figure 4.

Soil Texture and the indicators

Hydric soil indicators occur in three groups. 

Indicators for “All Soils” are used for any soil 

regardless of texture (A indicators). Indicators for 

“Sandy Soils” are used for soil layers with USDA 

textures of loamy fine sand or coarser (S indicators). 

Indicators for “Loamy and Clayey Soils” are used 

for soil layers of loamy very fine sand and finer (F 

indicators). Both Sandy and Loamy or Clayey layers 

can occur in the same soil profile. Therefore, a soil 

that has a loamy surface layer over sand is hydric if it 

meets all of the requirements of matrix color, amount, 

and contrast of redox concentrations, depth, and 

thickness for any single indicator or combination of 

indicators. 

It is permissible to combine certain hydric soil 

indicators if all requirements of the indicators are met 

except for thickness. The most restrictive requirements 

for thickness of layers in any indicators used must 

be met. Not all indicators are possible candidates 

for combination. For example, indicator F2 (Loamy 

Gleyed Matrix) has no thickness requirement and is 

not a candidate for combination. 

To Comment on the Indicators

The indicators are revised and updated as field 

data are collected to improve our understanding of 

hydric soil processes. Revisions, additions, and other 

comments regarding field observations of hydric 

soil conditions that cannot be documented using 

the presently recognized hydric soil indicators are 

welcome. Any additions or other modifications must 

be approved by the NTCHS. Guidelines for requesting 

changes to field indicators are as follows:

Figure 3.—The left shows moist soil colors, and the right 

shows dry soil colors. Moist soil colors are to be used 

when hydric soils are identified. The moist soil colors in 

this picture would meet the requirements for indicator F6 

(Redox Dark Surface), but the dry colors would not meet 

these requirements.

Figure 4.—This soil profile could meet the requirements 

of indicator F3 (Depleted Matrix); however, above the 

indicator, chroma is higher than 2 in a layer more than 15 

cm thick. Only 15 cm of a chroma higher than 2 is allowed 

above an indicator.
6 Field Indicators of

1. Adding indicators or changing existing 

indicators: Minimally, the following should 

accompany all requests for additions and changes 

to existing hydric soil indicators in Field Indicators of 

Hydric Soils in the United States:

a) Detailed descriptions of at least three pedons 

that document the addition or change and 

detailed descriptions of the neighboring 

nonhydric pedons.

b) Detailed vegetative data collected to 

represent the vegetation of the six pedons.

c) Saturation/inundation data and Eh data for 

a duration that captures the saturation cycle 

(dry-wet-dry) of at least one of the hydric 

pedons and one of the nonhydric pedons. 

Precipitation and in-situ soil-water pH data 

from the same sites should also be provided 

(fig. 5). Data are to be collected according 

to “The Hydric Soil Technical Standard” 

described in Hydric Soils Technical Note 11 

(http://www.soils.usda.gov/use/hydric/).

2. Adding or deleting a test indicator: Minimally, 

the following should accompany all requests for 

adding or deleting a test indicator in Field Indicators of 

Hydric Soils in the United States:

a) Detailed descriptions of at least three pedons 

that document the test indicator and detailed 

descriptions of three neighboring nonhydric 

pedons.

 b) Detailed vegetative data collected to 

represent the vegetation of the six pedons.

3. All requests involving 1 and 2 above require 

a short written plan that: a) identifies the problem, 

b) explains the rationale for the request, and c) 

provides the following—person responsible and point 

of contact (e-mail and postal addresses and phone 

Figure 5.­—Properly installed monitoring equipment (as 

described in the Hydric Soil Technical Standard) is 

important if one is to obtain approval of additions, 

deletions, or other changes to the hydric soil indicators.

number), timeline for supporting data and final report 

to be delivered to NTCHS, timeline needed for final 

NTCHS decision, and partners involved in the project. 

Requests, plans, and data should be sent to:

Lenore Vasilas, Chair

NTCHS Field Indicator Subcommittee 

USDA Natural Resources Conservation Service

P.O. Box 2890, Rm. 4836-S

Washington, DC 20013

E-mail: Lenore.Vasilas@wdc.usda.gov
Hydric Soils 7

Figure 6.—Map of USDA land resource regions.

9

Field Indicators of Hydric Soils

The descriptions in this section are structured as 

follows:

1. Alpha-numeric listing (A, S, or F indicators)

2. Short name

3. Applicable land resource regions (LRRs)

4. Description of the field indicator

5. User notes

For example, A2 is the second indicator for “all 

soils”; the short name is Histic Epipedon; the indicator 

is for use in all LRRs; the description is a histic 

epipedon underlain by mineral soil material with 

chroma of 2 or less; helpful user notes are added.

All Soils

“All soils” refers to soils with any USDA soil texture. 

All mineral layers above any of the layers meeting the 

requirements of any A indicator(s), except for indicator 

A16, have a dominant chroma of 2 or less, or the 

thickness of the layer(s) with a dominant chroma of 

more than 2 is less than 15 cm (6 inches). In addition, 

nodules and concretions are not considered to be 

redox concentrations. Use the following indicators 

regardless of texture.

A1. Histosol (for use in all LRRs) or Histel (for 

use in LRRs with permafrost). Classifies as a Histosol 

(except Folist) or as a Histel (except Folistel).

User Notes: In a Histosol, typically 40 cm (16 

inches) or more of the upper 80 cm (32 inches) is 

organic soil material (fig. 7). Organic soil materials 

have organic-carbon contents (by weight) of 12 to 

18 percent or more, depending on the clay content 

of the soil. These materials include muck (sapric soil 

material), mucky peat (hemic soil material), and peat 

(fibric soil material). See Keys to Soil Taxonomy (Soil 

Survey Staff, 2010) for a complete definition.

A2. Histic Epipedon. For use in all LRRs. A histic 

epipedon underlain by mineral soil material with 

chroma of 2 or less.

User Notes: Most histic epipedons are surface 

horizons 20 cm (8 inches) or more thick of organic soil 

material (fig. 8). Aquic conditions or artificial drainage 

is required. See Keys to Soil Taxonomy (Soil Survey 

Staff, 2010) for a complete definition.

A3. Black Histic. For use in all LRRs. A layer of 

peat, mucky peat, or muck 20 cm (8 inches) or more 

thick that starts within the upper 15 cm (6 inches) of 

the soil surface; has hue of 10YR or yellower, value of 

3 or less, and chroma of 1 or less; and is underlain by 

mineral soil material with chroma of 2 or less.

Figure 7.—Indicator A1 (Histosol or Histel). This soil has more 

than 30 inches of organic material, starting at the surface.
10 Field Indicators of

Figure 8.—Indicators A2 (Histic Epipedon) and A3 (Black 

Histic). This soil meets the depth criterion of A2 and 

the color and depth criteria of A3. The black color, a 

requirement of A3, results from the accumulation of 

organic matter when the soil is saturated and anaerobic.

User Notes: Unlike indicator A2, this indicator 

does not require proof of aquic conditions or artificial 

drainage (fig. 8).

A4. Hydrogen Sulfide. For use in all LRRs. A 

hydrogen sulfide odor within 30 cm (12 inches) of the 

soil surface.

User Notes: This “rotten egg smell” indicates that 

sulfate-sulfur has been reduced and therefore the 

soil is anaerobic. In most hydric soils, the sulfidic 

odor occurs only when the soils are saturated and 

anaerobic (fig. 9).

A5. Stratified Layers. For use in LRRs C, F, K, L, 

M, N, O, P, R, S, T, and U; for testing in LRRs V and 

Z. Several stratified layers starting within the upper 15 

cm (6 inches) of the soil surface. At least one of the 

layers has value of 3 or less and chroma of 1 or less, 

or it is muck, mucky peat, peat, or a mucky modified 

mineral texture. The remaining layers have chroma of 

2 or less. For any sandy material that constitutes the 

layer with value of 3 or less and chroma of 1 or less, 

at least 70 percent of the visible soil particles must be 

masked with organic material, viewed through a 10x 

or 15x hand lens. Observed without a hand lens, the 

particles appear to be close to 100 percent masked.

User Notes: Use of this indicator may require 

assistance from a trained soil scientist with local 

experience. The minimum organic-carbon content of 

at least one layer of this indicator is slightly less than 

is required for indicator A7 (5 cm Mucky Mineral). An 

undisturbed sample must be observed. Individual 

strata are dominantly less than 2.5 cm (1 inch) 

Figure 9.­—Indicator A4 (Hydrogen Sulfide) is most likely to occur in salt marshes and other very wet ecosystems.
Hydric Soils 11

thick. A hand lens is an excellent tool to aid in the 

identification of this indicator. Many alluvial soils have 

stratified layers at greater depths; these soils do not 

meet the requirements of this indicator. Many alluvial 

soils have stratified layers at the required depths but 

do not have chroma of 2 or less; these do not meet 

the requirements of this indicator. The stratified layers 

occur in any soil texture (fig. 10).

A6. Organic Bodies. For use in LRRs P (except 

for MLRA 136), T, U, and Z. Presence of 2 percent 

or more organic bodies of muck or a mucky modified 

mineral texture starting within 15 cm (6 inches) of the 

soil surface. 

User Notes: Organic bodies typically occur at 

the tips of fine roots. The content of organic carbon 

in organic bodies is the same as that in the Muck 

or Mucky indicators. The Organic Bodies indicator 

includes the indicator previously named “accretions” 

Figure 10.—Indicator A5 (Stratified Layers) in sandy material. 

The soil also meets the requirements of indicator A6 

(Organic Bodies). 

(Florida Soil Survey Staff, 1992). The size of the 

organic body is not critical, but the content of organic 

carbon is critical. The bodies are commonly 1 to 3 

cm (0.5 to 1 inch) in diameter (figs. 11 and 12), and 

the organic-carbon requirement in the organic bodies 

must meet those of muck or mucky modified textures. 

Many organic bodies do not have the required content 

of organic carbon and are not examples of this 

indicator. Organic bodies of hemic material (mucky 

peat) and/or fibric material (peat) do not meet the 

requirements of this indicator, nor does material 

consisting of partially decomposed root tissue.

Figure 11.­—Indicator A6 (Organic Bodies). An individual 

organic body generally is about 1 to 3 cm in size.

Figure 12.­—Indicator A6 (Organic Bodies). Some organic 

bodies are smaller than 1 cm.

A7. 5 cm Mucky Mineral. For use in LRRs P 

(except for MLRA 136), T, U, and Z. A layer of mucky 

modified mineral soil material 5 cm (2 inches) or 
12 Field Indicators of

more thick, starting within 15 cm (6 inches) of the soil 

surface (fig. 13).

User Notes: “Mucky” is a USDA texture modifier 

for mineral soils. The content of organic carbon is at 

least 5 percent and ranges to as high as 18 percent. 

The percentage required depends on the clay content 

of the soil; the higher the clay content, the higher the 

content of organic carbon required. An example is 

mucky fine sand, which has at least 5 percent organic 

carbon but not more than about 12 percent. Another 

example is mucky sandy loam, which has at least 7 

percent organic carbon but not more than about 14 

percent.

A8. Muck Presence. For use in LRRs U, V and Z. 

A layer of muck with value of 3 or less and chroma of 

1 or less, starting within 15 cm (6 inches) of the soil 

surface.

Figure 13.—Indicator A7 (5 cm Mucky Mineral). This soil has 

more than 5 cm of mucky sand, starting at the surface.

User Notes: The presence of muck of any 

thickness within a depth of 15 cm (6 inches) is 

the only requirement. Normally, this expression of 

anaerobiosis is at the soil surface; however, it may 

occur at any depth within 15 cm (6 inches). Muck is 

sapric soil material with a minimum content of organic 

carbon that ranges from12 to18 percent, depending 

on the content of clay. Organic soil material is called 

muck if virtually all of the material has undergone 

sufficient decomposition to prevent the identification of 

plant parts. Hemic soil material (mucky peat) and fibric 

soil material (peat) do not qualify. Generally, muck is 

black and has a “greasy” feel; sand grains should not 

be evident.

A9. 1 cm Muck. For use in LRRs D, F, G, H, P 

(except for MLRA 136), and T; for testing in LRRs C, I, 

J, and O. A layer of muck 1 cm (0.5 inch) or more thick 

with value of 3 or less and chroma of 1 or less and 

starting within 15 cm (6 inches) of the soil surface.

User Notes: Unlike indicator A8 (Muck Presence), 

this indicator has a minimum thickness requirement 

of 1 cm (fig. 14). Normally, this expression of 

anaerobiosis is at the soil surface; however, it may 

occur at any depth within 15 cm (6 inches). Muck is 

sapric soil material with a minimum content of organic 

carbon that ranges from12 to18 percent, depending 

on the content of clay. Organic soil material is called 

muck if virtually all of the material has undergone 

sufficient decomposition to limit the recognition of 

plant parts. Hemic soil material (mucky peat) and fibric 

soil material (peat) do not qualify. Generally, muck is 

black and has a “greasy” feel; sand grains should not 

be evident

A10. 2 cm Muck. For use in LRR M and N; for 

testing in LRRs A, B, E, K, L, S (except for MLRA 148), 

W, X, and Y. A layer of muck 2 cm (0.75 inch) or more 

thick with value of 3 or less and chroma of 1 or less, 

starting within 15 cm (6 inches) of the soil surface.

User Notes: This indicator requires a minimum 

muck thickness of 2 cm. Normally, this expression of 

anaerobiosis is at the soil surface; however, it may 

occur at any depth within 15 cm (6 inches). Muck is 

sapric soil material with a minimum content of organic 

carbon that ranges from12 to18 percent, depending 

on the content of clay. Organic soil material is called 

muck if virtually all of the material has undergone 

sufficient decomposition to limit the recognition of 

plant parts. Hemic soil material (mucky peat) and fibric 

soil material (peat) do not qualify. Generally, muck is 
Hydric Soils 13

black and has a “greasy” feel; sand grains should not 

be evident. 

A11. Depleted Below Dark Surface. For use in all 

LRRs, except for W, X, and Y; for testing in LRRs W, 

X, and Y. A layer with a depleted or gleyed matrix that 

has 60 percent or more chroma of 2 or less, starting 

within 30 cm (12 inches) of the soil surface, and 

having a minimum thickness of either:

a. 15 cm (6 inches), or 

b. 5 cm (2 inches) if the 5 cm consists of 

fragmental soil material.

Loamy or clayey layer(s) above the depleted 

or gleyed matrix must have value of 3 or less and 

chroma of 2 or less. Any sandy material above the 

depleted or gleyed matrix must have value of 3 or less 

and chroma of 1 or less, and, viewed through a10x 

or 15x hand lens, at least 70 percent of the visible 

soil particles must be masked with organic material. 

Observed without a hand lens, the particles appear to 

be close to 100 percent masked.

User Notes: This indicator often occurs in Mollisols 

but also applies to soils with umbric epipedons and 

dark colored ochric epipedons (figs. 15 and 16). For 

soils with dark colored epipedons more than 30 cm 

(12 inches) thick, use indicator A12. A depleted matrix 

requires value of 4 or more and chroma of 2 or less. 

Redox concentrations, including soft iron-manganese 

masses and/or pore linings, are required in soils 

with matrix colors of 4/1, 4/2, or 5/2. A, E, and calcic 

horizons may have low chromas and high values 

and may therefore be mistaken for a depleted matrix; 

however, they are excluded from the concept of 

depleted matrix unless the soil has common or many 

Figure 14.—Indicator A9 (1 cm Muck). This soil has more than 

1 cm of muck, starting at 8 cm on the left measuring 

tape. Different LRRs may use the presence of muck or 2 

cm of muck as an indicator of a hydric soil.

Figure 15.—Indicator A11 (Depleted Below Dark Surface). 

This soil has a thin dark surface horizon that meets 

the requirements of indicator A11. Because a depleted 

matrix below the surface horizon starts within a depth of 

15 cm and is at least 5 cm thick, the soil also meets the 

requirements of indicator F3 (Depleted Matrix).
14 Field Indicators of

distinct or prominent redox concentrations occurring 

as soft masses or pore linings.

A12. Thick Dark Surface. For use in all LRRs. A 

layer at least 15 cm (6 inches) thick with a depleted 

or gleyed matrix that has 60 percent or more chroma 

of 2 or less starting below 30 cm (12 inches) of the 

surface. The layer(s) above the depleted or gleyed 

matrix must have value of 2.5 or less and chroma 

of 1 or less to a depth of at least 30 cm (12 inches) 

and value of 3 or less and chroma of 1 or less in any 

remaining layers above the depleted or gleyed matrix. 

In any sandy material above the depleted or gleyed 

matrix, at least 70 percent of the visible soil particles 

must be masked with organic material, viewed 

through a 10x or 15x hand lens. Observed without 

a hand lens, the particles appear to be close to 100 

percent masked.

User Notes: This indicator applies to soils that 

have a black layer 30 cm (12 inches) or more thick 

and have value of 3 or less and chroma of 1 or less 

in any remaining layers directly above a depleted or 

gleyed matrix (fig. 17). This indicator is most often 

associated with overthickened soils in concave 

landscape positions. A depleted matrix requires 

value of 4 or more and chroma of 2 or less. Redox 

concentrations, including soft iron-manganese 

masses and/or pore linings, are required in soils 

with matrix colors of 4/1, 4/2, or 5/2. A, E, and calcic 

horizons may have low chromas and high values 

and may therefore be mistaken for a depleted matrix; 

however, they are excluded from the concept of 

depleted matrix unless the soil has common or many 

distinct or prominent redox concentrations occurring 

as soft masses or pore linings.

Figure 16.—Indicator A11 (Depleted Below Dark Surface). 

This soil has a thick dark surface horizon that meets the 

requirements of indicator A11. Unlike the matrix in figure 

15, the depleted matrix below the dark surface horizon 

in this soil starts at a depth of about 29 cm, which is too 

deep to meet the requirements of indicator F3 (Depleted 

Matrix). Indicator 11 allows a deeper depleted matrix than 

does indicator F3.

Figure 17.—Indicator A12 (Thick Dark Surface). Deep 

observation is needed to determine whether a soil meets 

the requirements of this indicator. In this soil, depth to the 

depleted matrix is about 55 cm.
Hydric Soils 15

A13. Alaska Gleyed. For use in LRRs W, X, and Y.

A mineral layer with a dominant hue of N, 10Y, 5GY, 

10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB and 

with value of 4 or more in more than 50 percent of the 

matrix. The layer starts within 30 cm (12 inches) of 

the mineral surface and is underlain within 1.5 m (60 

inches) by soil material with hue of 5Y or redder in the 

same type of parent material.

User Notes: This indicator can be used for all 

mineral soils, not just sandy soils. The indicator has 

two requirements (fig. 18). First, one or more of the 

specified gley colors occurs within 30 cm (12 inches) 

of the soil surface. These must be the colors on the 

pages of the Munsell color book (Gretag-Macbeth, 

2000) that show gley colors, not simply gray colors. 

Second, below these gley colors, the color of similar 

soil material is 5Y or redder (2.5Y, 10YR, 7.5YR, etc.). 

The presence of the truly gley colors indicates that the 

soil has undergone reduction. The requirement for 5Y 

or redder colors lower in the profile ensures that the 

gley colors are not simply the basic color of the parent 

material. Tidal sediments, lacustrine sediments, loess, 

and some glacial tills have base colors that appear as 

gley. On closer examination, their colors will normally 

match any of the colors on the pages of the color 

book that show gley colors. This indicator proves 

that the near-surface gley colors are not natural soil 

material colors and that they are the result of reduced 

conditions. When comparing the near-surface and 

underlying colors, make sure that you are looking at 

the same type of soil material. Many soils in Alaska 

consist of two or more types of material (e.g., silty 

loess overlying gravelly glacial till or sand and gravel 

river deposits).

A14. Alaska Redox. For use in LRRs W, X, and 

Y. A mineral layer that has dominant hue of 5Y 

with chroma of 3 or less, or a gleyed matrix, with 

10 percent or more distinct or prominent redox 

concentrations occurring as pore linings with value 

and chroma of 4 or more. The layer occurs within 30 

cm (12 inches) of the soil surface.

User Notes: In a soil layer that has been 

reduced, one of the first areas where oxygen will be 

reintroduced is along pores and the channels of live 

roots (fig. 19). As oxidation occurs in these areas, 

characteristic reddish orange redox concentrations 

(with value and chroma of 4 or more) will be apparent 

along the pores and linings. These will stand out in 

contrast to the matrix color of the overall soil layer. 

First, note the dominant color(s) of the soil layer to 

see if it matches the gley colors indicated. Then break 

open pieces of the soil and look for reddish orange 

redox concentrations along pores and root linings. The 

occurrence of these concentrations indicates that the 

soil has been reduced during periods of wetness and 

is now oxidizing in a drier state. 

A15. Alaska Gleyed Pores. For use in LRRs W, X, 

and Y. A mineral layer that has 10 percent or more hue 

of N, 10Y, 5GY, 10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, 

or 5PB with value of 4 or more along root channels or 

other pores and that starts within 30 cm (12 inches) of 

the soil surface. The matrix has a dominant hue of 5Y 

or redder.

User Notes: In a soil layer that is becoming 

anaerobic, reduced conditions will first occur where 

the soil microbes have an ample supply of organic 

carbon. Colder soils, such as those in Alaska, 

normally have a low content of organic carbon, so 

the microbes will congregate along the channels 

containing dead roots. Gley colors will first appear 

along these channels (fig. 20). In a soil layer that is not 

already dominated by gley colors, break open pieces 

Figure 18.­—Indicator A13 (Alaska Gleyed). The bluish band at 

a depth of about 20 cm indicates the presence of reduced 

soil material. The material below 20 cm reflects both the 

color of the parent material and soil weathering under 

aerobic conditions.
16 Field Indicators of

of the soil and look closely at the root channels. 

Many of these will be very thin or fine. See if you can 

observe thin coatings along the channels that match 

the gley colors listed in the indicator. If they occur, 

they indicate that the soil is becoming anaerobic.

A16. Coast Prairie Redox. For use in MLRA 150A 

of LRR T; for testing in LRR S (except for MLRA 

149B). A layer starting within 15 cm (6 inches) of 

the soil surface that is at least 10 cm (4 inches) thick 

and has a matrix chroma of 3 or less with 2 percent 

or more distinct or prominent redox concentrations 

occurring as soft masses and/or pore linings.

User Notes: These hydric soils occur mainly 

on depressional landforms and portions of the 

intermound landforms on the Lissie Formation. Redox 

concentrations occur mainly as iron-dominated pore 

linings. Common or many redox concentrations are 

required. Chroma-3 matrices are allowed because 

they may be the color of stripped sand grains or 

because few or common sand-sized reddish chert 

particles occur and may prevent obtaining chroma of 

2 or less.

Sandy Soils

Sandy soils have a USDA texture of loamy fine 

sand and coarser. All mineral layers above any of the 

layers meeting the requirements of any S indicator(s), 

except for indicator S6, have a dominant chroma 

of 2 or less, or the thickness of the layer(s) with a 

dominant chroma of more than 2 is less than 15 

cm (6 inches). In addition, nodules and concretions 

are not considered to be redox concentrations. Use 

the following sandy indicators for sandy mineral soil 

materials.

S1. Sandy Mucky Mineral. For use in all LRRs, 

except for W, X, and Y, and those LRRs that use 

indicator A7 (P, T, U, and Z). A layer of mucky modified 

sandy soil material 5 cm (2 inches) or more thick 

starting within 15 cm (6 inches) of the soil surface.

User Notes: “Mucky” is a USDA texture modifier 

for mineral soils. The content of organic carbon is at 

least 5 percent and ranges to as high as 14 percent 

for sandy soils. The percent required depends on the 

clay content of the soil; the higher the clay content, 

the higher the content of organic carbon required. 

An example is mucky fine sand, which has at least 5 

percent but not more than about 12 percent organic 

carbon. 

Figure 19.—Indicator A14 (Alaska Redox). The matrix color 

meets the requirements of a gleyed matrix. Reddish 

orange redox concentrations occur along the pores and 

channels of living roots.

Figure 20.—Indicator A15 (Alaska Gleyed Pores). Gleyed colors 

are along root channels. Reduction occurs first along root 

channels, where organic carbon is concentrated.
Hydric Soils 17

S2. 2.5 cm Mucky Peat or Peat. For use in LRRs 

G and H. A layer of mucky peat or peat 2.5 cm (1 

inch) or more thick with value of 4 or less and chroma 

of 3 or less, starting within 15 cm (6 inches) of the soil 

surface, and underlain by sandy soil material.

User Notes: Mucky peat (hemic soil material) and 

peat (fibric soil material) have a minimum organiccarbon content of 12 to 18 percent, depending on the 

content of clay. Organic soil material is called peat if 

virtually all of the plant remains are sufficiently intact 

to permit identification of plant remains. Mucky peat 

is at an intermediate stage of decomposition between 

peat and highly decomposed muck. To ascertain if 

mucky peat and/or peat are present, determine the 

percentage of rubbed fibers.

S3. 5 cm Mucky Peat or Peat. For use in LRRs 

F and M; for testing in LRRs K, L, and R. A layer of 

mucky peat or peat 5 cm (2 inches) or more thick with 

value of 3 or less and chroma of 2 or less, starting 

within 15 cm (6 inches) of the soil surface, and 

underlain by sandy soil material.

User Notes: Mucky peat (hemic soil material) and 

peat (fibric soil material) have a minimum organiccarbon content of 12 to 18 percent, depending on the 

content of clay. Organic soil material is called peat if 

virtually all of the plant remains are sufficiently intact 

to permit identification of plant remains. Mucky peat 

is at an intermediate stage of decomposition between 

peat and highly decomposed muck. To ascertain if 

mucky peat and/or peat are present, determine the 

percentage of rubbed fibers. 

S4. Sandy Gleyed Matrix. For use in all LRRs, 

except for W, X, and Y. A gleyed matrix that occupies 

60 percent or more of a layer starting within 15 cm (6 

inches) of the soil surface.

User Notes: Gley colors are not synonymous 

with gray colors (fig. 21). They are the colors on the 

gley color pages in the Munsell color book (GretagMacbeth, 2000). They have hue of N, 10Y, 5GY, 10GY, 

5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB and value of 4 

or more. For this indicator, the gleyed matrix only has 

to be present within 15 cm (6 inches) of the surface. 

Soils with gleyed matrices are saturated for periods of 

a significant duration; as a result, there is no thickness 

requirement for the layer. 

S5. Sandy Redox. For use in all LRRs, except 

for V, W, X, and Y. A layer starting within 15 cm (6 

inches) of the soil surface that is at least 10 cm (4 

inches) thick and has a matrix with 60 percent or more 

chroma of 2 or less and 2 percent or more distinct 

or prominent redox concentrations occurring as soft 

masses and/or pore linings.

User Notes: “Distinct” and “prominent” are defined 

in the Glossary. Redox concentrations include iron 

and manganese masses (reddish mottles) and pore 

linings (Vepraskas, 1994). Included within the concept 

of redox concentrations are iron-manganese bodies 

occurring as soft masses with diffuse boundaries. 

Common (2 to less than 20 percent) or many (20 

percent or more) redox concentrations are required 

(USDA, NRCS, 2002). If the soil is saturated at the 

time of sampling, it may be necessary to let it dry to 

a moist condition for redox features to become visible 

(figs. 22 and 23).

This is a very common indicator of hydric soils 

and is often used to identify the hydric/nonhydric soil 

boundary in sandy soils.

S6. Stripped Matrix. For use in all LRRs, except 

for V, W, X, and Y. A layer starting within 15 cm (6 

inches) of the soil surface in which iron-manganese 

oxides and/or organic matter have been stripped 

from the matrix and the primary base color of the 

soil material has been exposed. The stripped areas 

and translocated oxides and/or organic matter form a 

faintly contrasting pattern of two or more colors with 

Figure 21.—Indicator S4 (Sandy Gleyed Matrix). The gleyed 

matrix begins at the surface of the soil.
18 Field Indicators of

diffuse boundaries. The stripped zones are 10 percent 

or more of the volume and are rounded.

User Notes: This indicator includes the indicator 

previously named “polychromatic matrix” as well 

as the term “streaking.” Common or many areas of 

stripped (unmasked) soil materials are required. The 

stripped areas are typically 1 to 3 cm (0.5 to 1 inch) in 

size but may be larger or smaller (fig. 24). Commonly, 

the stripped areas have value of 5 or more and 

chroma of 1 and/or 2, and the unstripped areas have 

chroma of 3 and/or 4. The matrix (predominant color) 

may not have the material with chroma of 3 and/or 4. 

The mobilization and translocation of oxides and/or 

organic matter is the important process and should 

result in splotchy masked and unmasked soil areas. 

This may be a difficult pattern to recognize and is 

more evident when a horizontal slice is observed.

S7. Dark Surface. For use in LRRs N, P, R, S, T, U, 

V, and Z; for testing in LRRs K, L, and M. A layer 10 

cm (4 inches) thick, starting within the upper 15 cm 

(6 inches) of the soil surface, with a matrix value 3 of 

or less and chroma of 1 or less. At least 70 percent of 

the visible soil particles must be masked with organic 

material, viewed through a 10x or 15x hand lens. 

Observed without a hand lens, the particles appear to 

be close to 100 percent masked. The matrix color of 

the layer directly below the dark layer must have the 

same colors as those described above or any color 

that has chroma of 2 or less.

User Notes: For this indicator, the content of 

organic carbon is slightly less than is required for 

“mucky.” An undisturbed sample must be observed 

Figure 22.—Indicator S5 (Sandy Redox). This soil meets the 

requirements of indicator S5, having a matrix chroma 

of 2 or less and at least 2 percent redox concentrations 

starting at a depth of about 10 cm.

Figure 23.—Indicator S5 (Sandy Redox). A close-up of the layer 

in figure 22 that has chroma of 2 or less and at least 2 

percent redox concentrations. 

Figure 24.—Indicator S6 (Stripped Matrix). This indicator 

requires diffuse splotchy patterns with rounded areas 

stripped of organic matter or iron, as exemplified in this 

photo.
Hydric Soils 19

S8. Polyvalue Below Surface. For use in LRRs 

R, S, T, and U; for testing in LRRs K and L. A layer 

with value of 3 or less and chroma of 1 or less 

starting within 15 cm (6 inches) of the soil surface. At 

least 70 percent of the visible soil particles must be 

masked with organic material, viewed through a 10x 

or 15x hand lens. Observed without a hand lens, the 

particles appear to be close to 100 percent masked. 

Directly below this layer, 5 percent or more of the soil 

volume has value of 3 or less and chroma of 1 or less, 

and the remainder of the soil volume has value of 4 or 

(fig. 25). Many wet soils have a ratio of about 50 

percent soil particles that are masked with organic 

matter and about 50 percent unmasked soil particles, 

giving the soils a salt-and-pepper appearance. Where 

the coverage is less than 70 percent, a Dark Surface 

indicator does not occur. 

Figure 25.—Indicator S7 (Dark Surface). This soil has value of 

3 or less and chroma of 1 or less from the surface to a 

depth of 10 cm. Directly below 10 cm, it is the same color, 

meeting the requirement of having chroma of 2 or less.

more and chroma of 1 or less to a depth of 30 cm (12 

inches) or to the spodic horizon, whichever is less.

User Notes: This indicator applies to soils with 

a very dark gray or black surface or near-surface 

layer that is less than 10 cm (4 inches) thick and 

is underlain by a layer in which organic matter has 

been differentially distributed within the soils by water 

movement (fig. 26). The mobilization and translocation 

of organic matter result in splotchy coated and 

uncoated soil. 

S9. Thin Dark Surface. For use in LRRs R, S, 

T, and U; for testing in LRRs K and L. A layer 5 cm 

(2 inches) or more thick, within the upper 15 cm (6 

inches) of the soil, with value of 3 or less and chroma 

of 1 or less. At least 70 percent of the visible soil 

Figure 26.—Indicator S8 (Polyvalue Below Surface). The diffuse 

splotchy pattern of black (value of 3 or less and chroma of 

1 or less) and gray (value of 4 or more and chroma of 1 or 

less) below a black surface horizon is evidence of organic 

matter that has been mobilized and translocated. This 

soil also meets the requirements of indicator S5 (Sandy 

Redox).
20 Field Indicators of

particles must be masked with organic material, 

viewed through a 10x or 15x hand lens. Observed 

without a hand lens, the particles appear to be close 

to 100 percent masked. This layer is underlain by a 

layer or layers with value of 4 or less and chroma of 

1 or less to a depth of 30 cm (12 inches) or to the 

spodic horizon, whichever is less. 

User Notes: This indicator applies to soils with 

a very dark gray or black near-surface layer that is 

at least 5 cm (2 inches) thick and is underlain by 

a layer in which organic matter has been carried 

downward by flowing water (fig. 27). The mobilization 

and translocation of organic matter result in an even 

distribution of organic matter in the eluvial (E) horizon. 

The chroma of 1 or less is critical because it limits 

application of this indicator to only those soils that are 

depleted of iron. This indicator commonly occurs in 

hydric Spodosols, but a spodic horizon is not required. 

S10. Alaska Gleyed. This indicator is now indicator 

A13 (Alaska Gleyed). 

Loamy and Clayey Soils

These soils have USDA textures of loamy very fine 

sand and finer. All mineral layers above any of the 

layers meeting the requirements of any F indicator(s), 

except for indicators F8, F12, F19, and F20, have 

a dominant chroma of 2 or less, or the thickness of 

the layer(s) with a dominant chroma of more than 2 

is less than 15 cm (6 inches). (See figure 4.) Also, 

except for indicator F16, nodules and concretions are 

not considered to be redox concentrations. Use the 

following loamy and clayey indicators for loamy or 

clayey mineral soil materials.

F1. Loamy Mucky Mineral. For use in all LRRs, 

except for N, R, S, V, W, X, and Y, those using A7 

(LRRs P, T, U, and Z), and MLRA 1 of LRR A. A layer 

of mucky modified loamy or clayey soil material 10 

cm (4 inches) or more thick starting within 15 cm (6 

inches) of the soil surface. 

User Notes: “Mucky” is a USDA texture modifier for 

mineral soils. The content of organic carbon is at least 

8 percent but can range to as high as 18 percent. 

The percentage required depends on the clay content 

of the soil; the higher the clay content, the higher 

the content of organic carbon required. An example 

is mucky sandy loam, which has at least 8 percent 

organic carbon but not more than about 14 percent.

F2. Loamy Gleyed Matrix. For use in all LRRs, 

except for W, X, and Y. A gleyed matrix that occupies 

60 percent or more of a layer starting within 30 cm (12 

inches) of the soil surface (fig. 28).

User Notes: Gley colors are not synonymous with 

gray colors. They are the colors on the gley color 

pages of the Munsell color book (Gretag-Macbeth, 

2000). They have hue of N, 10Y, 5GY, 10GY, 5G, 10G, 

5BG, 10BG, 5B, 10B, or 5PB and value of 4 or more. 

The gleyed matrix only has to be present within 30 cm 

(12 inches) of the surface. Soils with gleyed matrices 

are saturated for periods of a significant duration; as a 

result, there is no thickness requirement for the layer. 

F3. Depleted Matrix. For use in all LRRs, except 

for W, X, and Y. A layer that has a depleted matrix with 

60 percent or more chroma of 2 or less and that has a 

minimum thickness of either:

a. 5 cm (2 inches) if the 5 cm is entirely within the 

upper 15 cm (6 inches) of the soil, or

Figure 27.—Indicator S9 (Thin Dark Surface). A dark surface 

horizon about 5 cm thick overlies a thin layer with value 

of 4 or less and chroma of 1 or less. Directly below the 

second layer is a spodic horizon, starting at a depth of 

about 7 cm.
Hydric Soils 21

b. 15 cm (6 inches), starting within 25 cm (10 

inches) of the soil surface.

User Notes: A depleted matrix requires a value 

of 4 or more and chroma of 2 or less (fig. 29). Redox 

concentrations, including soft iron-manganese 

masses and/or pore linings, are required in soils 

with matrix colors of 4/1, 4/2, or 5/2. A, E, and calcic 

horizons may have low chromas and high values 

and may therefore be mistaken for a depleted matrix; 

however, they are excluded from the concept of 

depleted matrix unless the soil has common or many 

distinct or prominent redox concentrations occurring 

as soft masses or pore linings. The low-chroma matrix 

must be the result of wetness and not a weathering or 

parent material feature. 

F4. Depleted Below Dark Surface. This indicator 

is now indicator A11 (Depleted Below Dark Surface). 

F5. Thick Dark Surface. This indicator is now 

indicator A12 (Thick Dark Surface). 

F6. Redox Dark Surface. For use in all LRRs, 

except for W, X, and Y; for testing in LRRs W, X, and 

Y. A layer that is at least 10 cm (4 inches) thick, is 

entirely within the upper 30 cm (12 inches) of the 

mineral soil, and has:

a. Matrix value of 3 or less and chroma of 1 

or less and 2 percent or more distinct or 

prominent redox concentrations occurring as 

soft masses or pore linings, or

b. Matrix value of 3 or less and chroma of 2 

or less and 5 percent or more distinct or 

prominent redox concentrations occurring as 

soft masses or pore linings.

Figure 28.—Indicator F2 (Loamy Gleyed Matrix). The gleyed 

matrix begins at the surface and extends to a depth of 

about 14 cm.

Figure 29.—Indicator F3 (Depleted Matrix). This soil has 

value of 4 or less and chroma of 2 or less and redox 

concentrations starting at a depth of 8 cm. Since the 

depleted matrix starts within a depth of 15 cm, the 

minimum thickness requirement is only 5 cm.
22 Field Indicators of

User Notes: This is a very common indicator used 

to delineate wetland soils that have a dark surface 

layer. Redox concentrations in mineral soils with a 

high content of organic matter and a dark surface 

layer commonly are small and difficult to see (figs. 

30, 31, and 32). The organic matter masks some or 

all of the concentrations that may be present. Careful 

examination is required to see what are commonly 

brownish redox concentrations in the darkened 

materials. If the soil is saturated at the time of 

sampling, it may be necessary to let it dry at least to a 

moist condition for redox features to become visible.

Soils that are wet because of ponding or have a 

shallow, perched layer of saturation may have any 

color below the dark surface. It is recommended 

that delineators evaluate the hydrologic source and 

examine and describe the layer below the dark 

colored epipedon when applying this indicator.

F7. Depleted Dark Surface. For use in all LRRs, 

except for W, X, and Y; for testing in LRRs W, X, and Y. 

Redox depletions with value of 5 or more and chroma 

of 2 or less in a layer that is at least 10 cm (4 inches) 

thick, is entirely within the upper 30 cm (12 inches) of 

the mineral soil, and has:

a. Matrix value of 3 or less and chroma of 1 or 

less and 10 percent or more redox depletions, or

b. Matrix value of 3 or less and chroma of 2 or 

less and 20 percent or more redox depletions.

User Notes: Care should be taken not to mistake 

mixing of an E or calcic horizon into the surface 

layer for depletions. The “pieces” of E and calcic 

horizons are not redox depletions. Knowledge of 

Figure 31.—Indicators F6 (Redox Dark Surface) and 

F7 (Depleted Dark Surface). A soil that meets the 

requirements of indicator F7 commonly also meets the 

requirements of indicator F6. If the dark surface layer has 

depletions, it most likely also has concentrations. 

Figure 30.—Indicator F6 (Redox Dark Surface). A soil that 

meets the requirements of indicator F6 must have a dark 

surface layer with value of 3 or less and chroma of 2 or 

less and redox concentrations in the dark layer.

Figure 32.—Indicators F6 (Redox Dark Surface) and F7 

(Depleted Dark Surface). An example of both depletions 

and concentrations in a dark matrix.
Hydric Soils 23

local conditions is required in areas where E and/or 

calcic horizons may be present. In soils that are wet 

because of subsurface saturation, the layer directly 

below the dark surface layer should have a depleted 

or gleyed matrix. Redox depletions should have 

associated microsite redox concentrations (fig. 32) 

that occur as Fe pore linings or masses within the 

depletion(s) or surrounding the depletion(s) .

F8. Redox Depressions. For use in all LRRs, 

except for W, X, and Y; for testing in LRRs W, X, and 

Y. In closed depressions subject to ponding, 5 percent 

or more distinct or prominent redox concentrations 

occurring as soft masses or pore linings in a layer that 

is 5 cm (2 inches) or more thick and is entirely within 

the upper 15 cm (6 inches) of the soil.

User Notes: This indicator occurs on depressional 

landforms, such as vernal pools, playa lakes, 

rainwater basins, “Grady” ponds, and potholes (figs. 

33 and 34). It does not occur in microdepressions 

(approximately 1 m) on convex or plane landscapes.

F9. Vernal Pools. For use in LRRs B, C, and D. 

In closed depressions that are subject to ponding, 

presence of a depleted matrix with 60 percent or more 

chroma of 2 or less in a layer 5 cm (2 inches) thick 

entirely within the upper 15 cm (6 inches) of the soil.

User Notes: Most often, soils are ponded because 

they occur in landscape positions that collect water 

or because they have a restrictive layer(s) that keeps 

water from moving downward through the soils. 

Normally, this indicator occurs at the soil surface 

(fig. 35). A depleted matrix requires a value of 4 or 

more and chroma of 2 or less. Redox concentrations, 

including soft iron-manganese masses and/or pore 

linings, are required in soils with matrix colors of 

4/1, 4/2, or 5/2. A, E, and calcic horizons may have 

low chromas and high values and may therefore be 

mistaken for a depleted matrix; however, they are 

excluded from the concept of depleted matrix unless 

the soil has common or many distinct or prominent 

redox concentrations occurring as soft masses or 

pore linings.

F10. Marl. For use in LRR U. A layer of marl with 

value of 5 or more and starting within 10 cm (4 

inches) of the soil surface (fig. 36).

User Notes: Marl is a limnic material deposited in 

water by precipitation of CaCO3 by algae as defined 

in Soil Taxonomy (Soil Survey Staff, 1999). It has a 

Munsell value of 5 or more and reacts with dilute HCl 

to evolve CO2. Marl is not the carbonatic substrate 

material associated with limestone bedrock. Some 

soils have materials with all of the properties of marl, 

except for the required Munsell value. These soils are 

hydric if the required value is present within 10 cm 

(4 inches) of the soil surface. Normally, this indicator 

occurs at the soil surface. 

F11. Depleted Ochric. For use in MLRA 151 of 

LRR T. A layer(s) 10 cm (4 inches) or more thick in 

which 60 percent or more of the matrix has value of 4 

Figure 34.—Indicator F8 (Redox Depressions). Indicator F8 

requires that the soil be in a closed depression subject to 

ponding. This soil is in a backwater depression on a flood 

plain.

Figure 33.—Indicator F8 (Redox Depressions). Indicator F8 

requires only 5 percent redox concentrations in the upper 

part of the soil. The matrix does not have chroma of 2 or 

less.
24 Field Indicators of

or more and chroma of 1 or less. The layer is entirely 

within the upper 25 cm (10 inches) of the soil.

User Notes: This indicator is applicable in 

accreting deltaic areas along the Mississippi River.

Figure 35.—Incicator F9 (Vernal Pools). A depleted matrix only 

5 cm thick is required.

F12. Iron-Manganese Masses. For use in LRRs 

N, O, P, and T; for testing in LRRs D, K, L, M, and 

R. On flood plains, a layer 10 cm (4 inches) or more 

thick with 40 percent or more chroma of 2 or less 

and 2 percent or more distinct or prominent redox 

concentrations occurring as soft iron-manganese 

masses with diffuse boundaries. The layer occurs 

entirely within 30 cm (12 inches) of the soil surface. 

Iron-manganese masses have value and chroma of 3 

or less. Most commonly, they are black. The thickness 

requirement is waived if the layer is the mineral 

surface layer.

User Notes: These iron-manganese masses 

generally are small (2 to 5 mm in size) and have 

value and chroma of 3 or less (fig. 37). They can be 

dominated by manganese and therefore have a color 

approaching black. The low matrix chroma must be 

the result of wetness and not be a weathering or 

parent material feature. Iron-manganese masses 

should not be confused with the larger and redder iron 

nodules associated with plinthite or with concretions 

that have sharp boundaries. This indicator occurs on 

flood plains along rivers, such as the Apalachicola, 

Congaree, Mobile, Savannah, and Tennessee Rivers. 

Figure 37.—Indicator F12 (Iron-Manganese Masses). While this 

indicator requires only 40 percent value of 4 or more and 

chroma of 2 or less, at least 2 percent iron-manganese 

masses is needed. These masses are indicated by black 

splotches in this photo.

F13. Umbric Surface. For use in LRRs P, T, and 

U and MLRA 122 of LRR N. In depressions and 

other concave landforms, a layer 25 cm (10 inches) 

or more thick, starting within 15 cm (6 inches) of the 

soil surface, in which the upper 15 cm (6 inches) 

has value of 3 or less and chroma of 1 or less and in 

Figure 36.—Indicator F10 (Marl). In this profile, marl begins 

within 10 cm of the soil surface. The scale is in cm.
Hydric Soils 25

which the lower 10 cm (4 inches) has the same colors 

as those described above or any other color that has 

chroma of 2 or less.

User Notes: The thickness requirements may be 

slightly less than those for an umbric epipedon (fig. 

38). Microlows (approximately 1 m) are not considered 

to be concave landforms. Umbric surfaces in the 

higher landscape positions, such as side slopes 

dominated by Humic Dystrudepts, are excluded.

F14. Alaska Redox Gleyed. This indicator is now 

indicator A14 (Alaska Redox).

F15. Alaska Gleyed Pores. This indicator is now 

indicator A15 (Alaska Gleyed Pores).

F16. High Plains Depressions. For use in MLRAs 

72 and 73 of LRR H; for testing in other MLRAs of 

Figure 38.—Indicator F13 (Umbric Surface). This soil has 

an umbric surface horizon about 44 cm thick. It meets 

the requirements not only of indicator F13 but also of 

indicators A7 (5 cm Mucky Mineral) and A12 (Thick Dark 

Surface).

LRR H. In closed depressions that are subject to 

ponding, a mineral soil that has chroma of 1 or less 

to a depth of at least 35 cm (13.5 inches) and a layer 

at least 10 cm (4 inches) thick within the upper 35 cm 

(13.5 inches) of the mineral soil that has either: 

a. 1 percent or more redox concentrations 

occurring as nodules or concretions, or

b. Redox concentrations occurring as nodules or 

concretions with distinct or prominent corona.

User Notes: This indicator is applicable in closed 

depressions (FSA “playas”) in western Kansas, 

southwestern Nebraska, eastern Colorado, and 

southeastern Wyoming. It occurs in such soils as 

those of the Ness and Pleasant series. The matrix 

color of the 35-cm (13.5-inch) layer must have chroma 

of 1 or less; chroma-2 matrix colors are excluded; 

value generally is 3. The nodules and concretions are 

rounded, are hard or very hard, range in size from 

less than 1 mm to 3 mm, and most commonly are 

black or reddish black. The corona (halos) generally 

are reddish brown, strong brown, or yellowish brown. 

The nodules and concretions can be removed from 

the soil, and the corona will occur as coatings on 

the concentration or will remain attached to the soil 

matrix. Use of 10x to 15x magnification aids in the 

identification of these features.

F17. Delta Ochric. For use in MLRA 151 of LRR 

T. A layer 10 cm (4 inches) or more thick in which 

60 percent or more of the matrix has value of 4 or 

more and chroma of 2 or less and there are no redox 

concentrations. This layer occurs entirely within the 

upper 30 cm (12 inches) of the soil.

User Notes: This indicator is applicable in 

accreting areas of the Mississippi River Delta.

F18. Reduced Vertic. For use in MLRA 150 of 

LRR T; for testing in all LRRs with Vertisols and Vertic 

intergrades. In Vertisols and Vertic intergrades, a 

positive reaction to alpha-alpha-dipyridyl that: 

a. Is the dominant (60 percent or more) condition 

of a layer at least 4 inches thick within the 

upper 12 inches (or at least 2 inches thick 

within the upper 6 inches) of the mineral or 

muck soil surface, 

b. Occurs for at least 7 continuous days and 28 

cumulative days, and 

c. Occurs during a normal or drier season and 

month (within 16 to 84 percent of probable 

precipitation). 

User Notes: The time requirements for this 

indicator were identified from research in MLRA 150A 

in LRR T (Gulf Coast Prairies). These requirements 
26

or slightly modified time requirements may be found 

to identify wetland Vertisols and Vertic intergrades in 

other parts of the Nation. These soils generally have 

thick dark surface horizons, but indicators A11, A12, 

and F6 commonly are not evident, possibly because 

of masking of redoximorphic features by organic 

carbon. The soils are a special case of the “Problem 

Soils with Thick, Dark A Horizons” listed in the Corps 

of Engineers Wetlands Delineation Manual (United 

States Army Corps of Engineers, 1987). Follow the 

procedures and note the considerations in Hydric 

Soils Technical Note 8 (“Use of alpha-alpha-Dipyridyl,” 

available online at http://www.soils.usda.gov/use/

hydric/).

F19. Piedmont Flood Plain Soils. For use in 

MLRAs 149A and 148 of LRR S; for testing on flood 

plains subject to Piedmont deposition throughout 

LRRs P, S, and T. On active flood plains, a mineral 

layer at least 15 cm (6 inches) thick, starting within 25 

cm (10 inches) of the soil surface, with a matrix (60 

percent or more of the volume) chroma of less than 

4 and 20 percent or more distinct or prominent redox 

concentrations occurring as soft masses or pore 

linings.

User Notes: This indicator is for use or testing on 

active flood plains in the Mid-Atlantic and Southern 

Piedmont Provinces and areas where sediments 

derived from the Piedmont are being deposited on 

flood plains on the Coastal Plain (fig. 39).

F20. Anomalous Bright Loamy Soils. For use in 

MLRA 149A of LRR S and MLRAs 153C and 153D of 

LRR T; for testing in MLRA 153B of LRR T. Within 200 

meters (656 feet) of estuarine marshes or water and 

within 1 m (3.28 feet) of mean high water, a mineral 

layer at least 10 cm (4 inches) thick, starting within 

20 cm (8 inches) of the soil surface, with a matrix (60 

percent or more of the volume) chroma of less than 

5 and 10 percent or more distinct or prominent redox 

concentrations occurring as soft masses or pore 

linings and/or depletions.

User Notes: These soils are expected to occur 

on linear or convex landforms that are adjacent to 

estuarine marshes or water (fig. 40).

Figure 40.—Indicator F20 (Anomalous Bright Loamy Soils). 

This indicator is restricted to areas near estuarine 

marshes or water. It does not require a matrix color with 

chroma of 2 or less.

Figure 39.—Indicator F19 (Piedmont Flood Plain Soils). This 

indicator is restricted to active flood plains. It does not 

require a matrix color with chroma of 2 or less.
27

Test Indicators of Hydric Soils

The indicators listed under the heading “Field 

Indicators of Hydric Soils” should be tested for use 

in LRRs other than those listed. Other indicators for 

testing are listed below. The test indicators are not to 

be used for the purpose of delineating hydric soils. 

Users of the indicators are encouraged to submit 

descriptions of other soil morphologies that they think 

are indicative of hydric soils along with supporting 

data for inclusion in subsequent editions of Field 

Indicators of Hydric Soils in the United States.

All Soils

TA1. Playa Rim Stratified Layers. This test 

indicator has been deleted.

TA2. Structureless Muck. This test indicator has 

been deleted. 

TA3. Coast Prairie Redox. This test indicator has 

been approved for use and is now A16 (Coast Prairie 

Redox).

TA4. Alaska Color Change. For testing in LRRs 

W, X, and Y. A mineral layer 10 cm (4 inches) or more 

thick, starting within 30 cm (12 inches) of the surface, 

that has a matrix value of 4 or more and chroma of 2 

or less and that within 30 minutes becomes redder by 

one or more Munsell unit in hue and/or chroma when 

exposed to air.

User Notes: The soil should be at or near 

saturation when examined. Care must be taken to 

immediately obtain an accurate color of the soil 

sample upon excavation. The colors should then be 

closely examined again after several minutes. Do not 

allow the sample to begin drying, as drying will result 

in a color change. Care must be taken to closely 

observe the colors. As always, do not obtain colors 

while wearing sunglasses. Colors must be obtained in 

the field under natural lighting and not under artificial 

light. Also, look for the presence of other indicators.

TA5. Alaska Alpine Swales. For testing in LRRs 

W, X, and Y. On concave landforms, the presence of 

a surface mineral layer 10 cm (4 inches) or more thick 

having hue of 10YR or yellower, value of 2.5 or less, 

and chroma of 2 or less. The dark surface layer is at 

least twice as thick as the mineral surface layer of 

soils in the adjacent convex micro-positions.

User Notes: Soils with this indicator occur in 

concave areas where moisture accumulates. In these 

areas the source of the hydrology is meltwater from 

adjacent snowpacks that persist well into the growing 

season. The landscape generally is a complex microtopography of concave depressions and adjacent 

convex “micro-highs.” Soils should be examined in 

both landscape positions and compared. If both 

positions have a mineral surface layer of the same 

color, but the layer is at least twice as thick in the 

concave position, the soil in the concave position is 

considered hydric. Make sure that there is reasonable 

evidence of the hydrology source. This includes either 

direct observation of the melting snowpack or aerial 

imagery that shows snowpack at that location earlier 

in the growing season.

TA6. Mesic Spodic. For testing in MLRAs 144A 

and 145 of LRR R and MLRA 149B of LRR S. A layer 

5 cm (2 inches) or more thick, starting within 15 cm (6 

inches) of the mineral soil surface, that has value of 

3 or less and chroma of 2 or less and is underlain by 

either: 

a. A layer(s) 8 cm (3 inches) or more thick 

occurring within 30 cm (12 inches) of the 

mineral soil surface, having value and chroma 

of 3 or less, and showing evidence of spodic 

development; or

b. A layer(s) 5 cm (2 inches) or more thick 

occurring within 30 cm (12 inches) of the 

mineral soil surface, having value of 4 or more 

and chroma of 2 or less, and directly underlain 

by a layer(s) 8 cm (3 inches) or more thick 

having value and chroma of 3 or less and 

showing evidence of spodic development.

User Notes: This indicator is used to identify wet 

soils that have spodic materials or that meet the 

definition of Spodosols, only in MLRAs 144A and 145 

of LRR R and in MLRA 149B of LRR S. The layer 
28 Field Indicators of

that has value of 4 or more and chroma of 2 or less 

is typically described as an E or Eg horizon (typically 

having a color pattern referred to as stripped or 

partially stripped matrices). The layers with evidence 

of the accumulation of translocated organic matter 

typically are described as Bh, Bhs, Bhsm, Bsm, or 

Bs horizons. These layers typically have several color 

patterns or cementation indicative of translocated iron, 

aluminum, and/or organic matter.

Sandy Soils

TS1. Iron Staining. This test indicator has been 

deleted.

TS2. Thick Sandy Dark Surface. This test 

indicator has been deleted. Its concepts have been 

approved for use and are now included with indicator 

A12 (Thick Dark Surface). 

TS3. Dark Surface 2. This test indicator has been 

deleted. It is now the same as indicator S7 (Dark 

Surface).

TS4. Sandy Neutral Surface. This test indicator 

has been deleted. Most of its concepts have been 

approved for use and are now included in indicator 

A11 (Depleted Below Dark Surface). 

TS5. Chroma 3 Sandy Redox. This test indicator 

has been deleted. It has been approved for use as 

indicator A16 (Coast Prairie Redox). 

Loamy and Clayey Soils

TF1. ? cm Mucky Peat or Peat. This test indicator 

has been deleted. 

TF2. Red Parent Material. For testing in LRRs 

with red parent material. In parent material with hue 

of 7.5YR or redder, a layer at least 10 cm (4 inches) 

thick with a matrix value and chroma of 4 or less and 

2 percent or more redox depletions and/or redox 

concentrations occurring as soft masses and/or 

pore linings. The layer is entirely within 30 cm (12 

inches) of the soil surface. The minimum thickness 

requirement is 5 cm (2 inches) if the layer is the 

mineral surface layer.

User Notes: This indicator was developed 

for use in areas of red parent material, such as 

Triassic-Jurassic sediments in the Connecticut River 

Valley, Permian “red beds” in Kansas, clayey red 

till and associated lacustrine deposits around the 

Great Lakes, and Jurassic sediments associated 

with “hogbacks” on the eastern edge of the Rocky 

Mountains. This indicator also occurs on “Red River” 

flood plains, such as those along the Chattahoochee, 

Congaree, Red, and Tennessee Rivers. The most 

noticeable redox features in red materials are redox 

depletions and soft manganese masses that are black 

or dark reddish black (figs. 41 and 42). 

Figure 41.—Indicator TF2 (Red Parent Material). This indicator 

should be used only in areas of red parent material that 

is resistant to reduction. Not all red soils formed in red 

parent material.

Figure 42.—Indicator F3 (Depleted Matrix) in red parent 

material. If a soil that formed in red parent material stays 

wet and anaerobic long enough, it may develop the 

indicator F3.
Hydric Soils 29

TF3. Alaska Concretions. This test indicator has 

been deleted.

TF4. 2.5Y/5Y Below Dark Surface. This test 

indicator has been deleted.

TF5. 2.5Y/5Y Below Thick Dark Surface. This test 

indicator has been deleted. 

TF6. Calcic Dark Surface. This test indicator has 

been deleted.

TF7. Thick Dark Surface 2/1. This test indicator 

has been deleted. Its concepts have been approved 

for use and are now included in indicator A12 (Thick 

Dark Surface). 

TF8. Redox Spring Seeps. This test indicator has 

been deleted. 

TF9. Delta Ochric. This test indicator has been 

approved for use and is now indicator F17 (Delta 

Ochric).

TF10. Alluvial Depleted Matrix. This test indicator 

has been deleted.

TF11. Reduced Vertic. This test indicator has been 

approved for use and is now indicator F18 (Reduced 

Vertic). 

TF12. Very Shallow Dark Surface. For testing 

in all LRRs. In depressions and other concave 

landforms, one of the following:

a. If bedrock occurs between depths of 15 cm (6 

inches) and 25 cm (10 inches), a layer at least 15 cm 

(6 inches) thick starting within 10 cm (4 inches) of the 

soil surface and having value of 3 or less and chroma 

of 1 or less; the remaining soil to bedrock must have 

the same colors as above or any other color that has 

chroma of 2 or less. 

b. If bedrock occurs within a depth of 15 cm (6 

inches), more than half of the soil thickness must have 

value of 3 or less and chroma of 1 or less and the 

remaining soil to bedrock must have the same colors 

as above or any other color that has chroma of 2 or 

less.

31

References

Unless otherwise noted, the following references include definitions of terms used 

throughout this document. They also provide information concerning the terms in the 

Glossary of this document. The list includes works consulted as well as works cited.

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Federal Register. July 13, 1994. Changes in Hydric Soils of the United States. 

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Florida Soil Survey Staff. 1992. Soil and Water Relationships of Florida’s Ecological 

Communities. G.W. Hurt (editor). USDA, Soil Conservation Service, Gainesville, FL.

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National Research Council. 1995. Wetlands: Characteristics and Boundaries. National 

Academy Press, Washington, DC. 

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Technical Standard. Hydric Soils Technical Note 11 (http://www.soils.usda.gov/use/

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Soil Survey Division Staff. 1993. Soil Survey Manual. Soil Conservation Service. U.S. 

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Technical Committee for Hydric Soils.

United States Department of Agriculture, Natural Resources Conservation Service. 

2002. Field Indicators of Hydric Soils in the United States, Version 5.0. G.W. Hurt, 

P.M. Whited, and R.F. Pringle (editors). USDA-NRCS, in cooperation with the National 

Technical Committee for Hydric Soils.

United States Department of Agriculture, Natural Resources Conservation Service. 

2006a. Field Indicators of Hydric Soils in the United States, Version 6.0. G.W. Hurt 

and L.M. Vasilas (editors). USDA-NRCS, in cooperation with the National Technical 

Committee for Hydric Soils.

United States Department of Agriculture, Natural Resources Conservation Service. 

2006b. Land Resource Regions and Major Land Resource Areas of the United States, 

the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. 

(http://soils.usda.gov/survey/geography/mlra/index.html) 

United States Department of Agriculture, Natural Resources Conservation Service. 

2008. National Food Security Act Manual. Fourth Edition. M_180_TOC.

United States Department of Agriculture, Natural Resources Conservation Service. 

2010. National Soil Survey Handbook, title 430-VI. (http://soils.usda.gov/technical/

handbook/) 

Vepraskas, M.J. 1994. Redoximorphic Features for Identifying Aquic Conditions. 

Technical Bulletin 301. North Carolina Agricultural Research Service, North Carolina 

State University, Raleigh, NC.
33

Glossary

As defined in this Glossary, terms marked with an asterisk (*) have definitions that 

are slightly different from the definitions in the referenced materials. The definitions in 

the Glossary are intended to assist users of this document and are not intended to add 

to or replace definitions in the referenced materials.

A horizon. A mineral soil horizon that formed at the 

surface or below an O horizon where organic 

material is accumulating. See Soil Taxonomy

(Soil Survey Staff, 1999) for a complete 

definition.

Accreting areas. Landscape positions in which soil 

material accumulates through deposition from 

higher elevations or upstream positions more 

rapidly than the rate at which soil material is 

being lost through erosion.

Anaerobic. A condition in which molecular oxygen is 

virtually absent from the soil.

Anaerobiosis. Microbiological activity under 

anaerobic conditions.

Aquic conditions. Conditions in the soil represented 

by depth of saturation, occurrence of 

reduction, and redoximorphic features. See 

Soil Taxonomy (Soil Survey Staff, 1999) for a 

complete definition.

*Artificial drainage. The use of human efforts and 

devices to remove free water from the soil 

surface or from the soil profile (figs. 43 and 44). 

The hydrology may also be modified by levees 

and dams, which keep water from entering a 

site. 

CaCO3 equivalent. The acid neutralizing capacity 

of a soil expressed as a weight percentage of 

CaCO3 (molecular weight of CaCO3 equals 100).

Calcic horizon. An illuvial horizon in which 

carbonates have accumulated to a significant 

extent. See Soil Taxonomy (Soil Survey Staff, 

1999) for a complete definition.

Calcium carbonate. Calcium carbonate has the 

chemical formula of CaCO3. It effervesces 

when treated with cold hydrochloric acid.

Closed depressions. Low-lying areas that are 

surrounded by higher ground and have no 

natural outlet for surface drainage.

Figure 43.—Artificial drainage does not alter the hydric status 

of a soil.

COE. U.S. Army Corps of Engineers.

Common. When referring to redox concentrations 

and/or depletions, “common” represents 2 to 20 

percent of the observed surface.
34 Field Indicators of

Concave landscapes. Landscapes in which the 

surface curves downward.

*Depleted matrix. For loamy and clayey material (and 

sandy material in areas of indicators A11 and 

A12), a depleted matrix refers to the volume 

of a soil horizon or subhorizon in which the 

processes of reduction and translocation have 

removed or transformed iron, creating colors 

of low chroma and high value (fig. 45). A, E, 

and calcic horizons may have low chromas and 

high values and may therefore be mistaken for 

a depleted matrix; however, they are excluded 

from the concept of depleted matrix unless the 

soil has common or many distinct or prominent 

redox concentrations occurring as soft masses 

or pore linings. In some areas the depleted 

matrix may change color upon exposure to 

air (see Reduced matrix); this phenomenon is 

included in the concept of depleted matrix. The 

following combinations of value and chroma 

identify a depleted matrix:

1. Matrix value of 5 or more and chroma of 1 

or less with or without redox concentrations 

occurring as soft masses and/or pore linings; 

or

2. Matrix value of 6 or more and chroma of 2 

or less with or without redox concentrations 

occurring as soft masses and/or pore linings; 

or

3. Matrix value of 4 or 5 and chroma of 2 

and 2 percent or more distinct or prominent 

redox concentrations occurring as soft 

masses and/or pore linings; or

4. Matrix value of 4 and chroma of 1 and 2 

percent or more distinct or prominent redox 

concentrations occurring as soft masses 

and/or pore linings (fig. 46).

Diffuse boundary. Used to describe redoximorphic 

features that grade gradually from one 

color to another (fig. 47). The color grade is 

commonly more than 2 mm wide. “Clear” is 

used to describe boundary color gradations 

intermediate between sharp and diffuse. 

Figure 45.—Soils with depleted matrices have a matrix value 

of 4 or more (above the bottom horizontal red line) and 

chroma of 2 or less (to the left of the vertical red line). 

Redox concentrations are not required if the color has 

chroma of 2 or less and is above the top red line. For 4/1, 

4/2, and 5/2 colors, two redox concentrations are required.

Figure 44.—The profile on the right is from a drained wetland 

adjacent to a ditch. The profile on the left is from an 

area not affected by the ditch. Both soils meet the 

requirements for indicators F3 (Depleted Matrix) and A11 

(Depleted Below Dark Surface) and thus are hydric soils.
Hydric Soils 35

Figure 46.—A depleted matrix with value of 4 or more and 

chroma of 2 or less and with redox concentrations 

occurring as soft masses and pore linings.

Distinct.1 Readily seen but contrasting only 

moderately with the color to which compared. 

The contrast is distinct if:

1. Delta hue = 0, then

 a) Delta value <2 and delta chroma >1

 to <4, or

 b) Delta value >2 to <4 and delta

 chroma <4.

2. Delta hue = 1, then

 a) Delta value <1 and delta chroma >1

 to <3, or

 b) Delta value >1 to <3 and delta

 chroma <3.

3. Delta hue = 2, then

Figure 47.­—Iron concentration with a diffuse boundary 

exhibited by bright colors in the center of the 

concentration and a lighter color away from the center.

 a) Delta value = 0 and delta chroma >0 to

 <2, or

 b) Delta value >0 to <2 and delta chroma

 <2. 1Regardless of the magnitude of hue difference, 

where both colors have value <3 and chroma <2, the 

contrast is faint.

E horizon. A mineral horizon in which the dominant 

process is loss of silicate clay, iron, and/or 

aluminum, leaving a concentration of sand and 

silt particles (fig. 48). See Soil Taxonomy (Soil 

Survey Staff, 1999) for a complete definition.

EPA. U.S. Environmental Protection Agency.

Epipedon. A horizon that has developed at the soil 

surface. See Soil Taxonomy (Soil Survey Staff, 

1999) for a complete definition.

Faint. Evident only on close examination. The contrast 

is faint if:

Figure 48.—A soil profile with an albic (white) E horizon 

between depths of about 35 and 60 cm. The white color 

results from loss of iron through weathering.
36 Field Indicators of

1. Delta hue = 0, then delta value <2 and 

 delta chroma <1, or 

2. Delta hue = 1, then delta value <1 and 

 delta chroma <1, or

3. Delta hue = 2, then delta value = 0 and 

 delta chroma = 0, or

Any delta hue if both colors have value <3

 and chroma <2.

Fe-Mn concretions. Firm to extremely firm, 

irregularly shaped bodies with sharp to diffuse 

boundaries. When broken in half, concretions 

have concentric layers. See Vepraskas (1994) 

for a complete discussion.

Fe-Mn nodules. Firm to extremely firm, irregularly 

shaped bodies with sharp to diffuse 

boundaries. When broken in half, nodules do 

not have visibly organized internal structure. 

See Vepraskas (1994) for a complete 

discussion.

Few. When referring to redox concentrations and/or 

depletions, “few” represents less than 2 percent 

of the observed surface.

Fibric. See Peat.

Fragmental soil material. Soil material that consists 

of 90 percent or more rock fragments. Less 

than 10 percent of the soil consists of particles 

2 mm or smaller. 

Frequently flooded or ponded. A frequency class 

in which flooding or ponding is likely to occur 

often under usual weather conditions (a chance 

of more than 50 percent in any year, or more 

than 50 times in 100 years).

FWS. U.S. Department of the Interior, Fish and 

Wildlife Service.

*g. A horizon suffix indicating that the horizon is 

gray because of wetness but not necessarily 

that it is gleyed. All gleyed matrices (defined 

below) should have the suffix “g”; however, not 

all horizons with the “g” suffix are gleyed. For 

example, a horizon with the color 10YR 6/2 that 

is at least seasonally wet, with or without other 

redoximorphic features, should have the “g” 

suffix.

Glauconitic. Refers to a mineral aggregate that 

contains a micaceous mineral resulting in a 

characteristic green color, e.g., glauconitic 

shale or clay (fig. 49).

*Gleyed matrix. Soils with a gleyed matrix have the 

following combinations of hue, value, and 

chroma (the soils are not glauconitic):

1. 10Y, 5GY, 10GY, 10G, 5BG, 10BG, 5B, 10B, 

or 5PB with value of 4 or more and chroma 

of 1; or

2. 5G with value of 4 or more and chroma of 1 

or 2; or

3. N with value of 4 or more; or

In some places the gleyed matrix may change 

color upon exposure to air. (See Reduced 

matrix). This phenomenon is included in the 

concept of gleyed matrix (figs. 50 and 51).

*Hemic. See Mucky peat.

Histels. Organic soils that overlie permafrost and 

show evidence of cryoturbation. See Soil 

Taxonomy (Soil Survey Staff, 1999) for a 

complete definition.

Histic epipedon. A thick (20- to 60-cm, or 8- to 24- 

inch) organic soil horizon that is saturated with 

Figure 49.—Glauconitic soils typically have gleyed, green 

or black matrices and can have mottles of weathered 

sulfides that can be mistaken for redox concentrations. 

If the weathered sulfides in this glauconitic soil were 

mistaken for redox concentrations, this nonhydric soil 

would appear to meet the requirements of indicator F6 

(Redox Dark Surface).
Hydric Soils 37

water at some period of the year (unless the 

soil is artificially drained) and that is at or near 

the surface of a mineral soil. 

Histosols. Organic soils that have organic soil 

materials in more than half of the upper 80 cm 

(32 inches) or that have organic materials of 

any thickness if they overlie rock or fragmental 

materials that have interstices filled with 

organic soil materials. See Soil Taxonomy (Soil 

Survey Staff, 1999) for a complete definition.

Horizon. A layer, approximately parallel to the surface 

of the soil, distinguishable from adjacent layers 

by a distinctive set of properties produced by 

soil-forming processes. See Soil Taxonomy

(Soil Survey Staff, 1999) for a complete 

definition.

Hydric soil definition (1994). A soil that formed 

under conditions of saturation, flooding, or 

Figure 50.—A gleyed matrix must have the colors on one of 

the two pages showing gleyed colors in the Munsell Soil 

Color Book. Values are 4 or more (above the red line).

Figure 51.—The gleyed matrix in this soil starts at a depth of 

about 15 cm. The matrix color has value of 4 or more and 

is shown on one of the pages showing gleyed colors in 

the Munsell Soil Color Book.

ponding long enough during the growing 

season to develop anaerobic conditions in the 

upper part.

Hydrogen sulfide odor. The odor of H2S. It is similar 

to the smell of rotten eggs.

Hydromorphic features. Features in the soil caused 

or formed by water.

Layer(s). A horizon, subhorizon, or combination of 

contiguous horizons or subhorizons sharing at 

least one property referred to in the indicators.

Lithologic discontinuity. Occurs in a soil that has 

developed in more than one type of parent 

material. Commonly determined by a significant 

change in particle-size distribution, mineralogy, 

etc. that indicates a difference in material from 

which the horizons formed.

LRR. Land resource region. LRRs are geographic 

areas characterized by a particular pattern 

of soils, climate, water resources, and land 

use. Each LRR is assigned a different letter 

of the alphabet (A-Z). LRRs are defined in 
38 Field Indicators of

U.S. Department of Agriculture Handbook 296 

(USDA, NRCS, 2006b).

Many. When referring to redox concentrations and/or 

depletions, “many” represents more than 20 

percent of the observed surface.

Marl. An earthy, unconsolidated deposit consisting 

chiefly of calcium carbonate mixed with 

clay in approximately equal proportions; 

formed primarily under freshwater lacustrine 

conditions. See Soil Taxonomy (Soil Survey 

Staff, 1999) for a complete definition.

*Masked. Through redoximorphic processes, the 

color of soil particles is hidden by organic 

material, silicate clay, iron, aluminum, or some 

combination of these.

Matrix. The dominant soil volume that is continuous 

in appearance and envelops microsites. When 

three colors occur, such as when a matrix, 

depletions, and concentrations are present, the 

matrix may represent less than 50 percent of 

the total soil volume.

MLRA. Major land resource areas. MLRAs are 

geographically associated divisions of land 

resource regions. MLRAs are defined in U.S. 

Department of Agriculture Handbook 296 

(USDA, NRCS, 2006b).

Mollic epipedon. A mineral surface horizon that is 

relatively thick, dark colored, and humus rich 

and has high base saturation (fig. 52). See 

Soil Taxonomy (Soil Survey Staff, 1999) for a 

complete definition.

Mollisols. Mineral soils that have a mollic epipedon. 

See Soil Taxonomy (Soil Survey Staff, 1999) for 

a complete definition.

*Muck. Sapric organic soil material in which virtually 

all of the organic material is so decomposed 

that identification of plant forms is not possible. 

Bulk density is normally 0.2 or more. Muck has 

less than one-sixth fibers after rubbing, and its 

sodium pyrophosphate solution extract color 

has lower value and chroma than 5/1, 6/2, and 

7/3.

*Mucky modified mineral soil material. A USDA 

soil texture modifier, e.g., mucky sand. Mucky 

modified mineral soil material that has 0 

percent clay has between 5 and 12 percent 

organic carbon. Mucky modified mineral soil 

material that has 60 percent clay has between 

12 and 18 percent organic carbon. Soils 

with an intermediate amount of clay have 

intermediate amounts of organic carbon. Where 

the organic component is peat (fibric material) 

Figure 52.—A soil with a mollic epipedon, which is a thick, 

black surface horizon that has high base saturation. Soils 

that have a mollic epipedon are classified as Mollisols.

or mucky peat (hemic material), mucky mineral 

soil material does not occur. 

*Mucky peat. Hemic organic material, which is 

characterized by decomposition that is 

intermediate between that of fibric material and 

that of sapric material. Bulk density is normally 

between 0.1 and 0.2 g/cm3. Mucky peat does 

not meet the fiber content (after rubbing) or 

sodium pyrophosphate solution extract color 

requirements for either fibric or sapric soil 

material.

Nodules. See Fe-Mn nodules.

NRCS. USDA, Natural Resources Conservation 

Service (formerly Soil Conservation Service).

NTCHS. National Technical Committee for Hydric 

Soils.

Organic matter. Plant and animal residue in the soil 

in various stages of decomposition. 
Hydric Soils 39

Organic soil material. Soil material that is saturated 

with water for long periods or artificially drained 

and, excluding live roots, has 18 percent or 

more organic carbon with 60 percent or more 

clay or 12 percent or more organic carbon 

with 0 percent clay. Soils with an intermediate 

amount of clay have an intermediate amount 

of organic carbon. If the soil is never saturated 

for more than a few days, it contains 20 percent 

or more organic carbon. Organic soil material 

includes muck, mucky peat, and peat (fig. 53).

*Peat. Fibric organic soil material. The plant forms 

can be identified in virtually all of the organic 

material. Bulk density is normally <0.1. Peat 

has three-fourths or more fibers after rubbing, 

or it has two-fifths or more fibers after rubbing 

and has sodium pyrophosphate solution extract 

color of 7/1, 7/2, 8/2, or 8/3.

Plinthite. The sesquioxide-rich, humus-poor, highly 

weathered mixture of clay with quartz and other 

diluents. See Soil Taxonomy (Soil Survey Staff, 

1999) for a complete discussion.

Ponding. Standing water in a closed depression that 

is removed only by percolation, evaporation, or 

transpiration. The ponding lasts for more than 

7 days.

Pore linings. Zones of accumulation that may be 

either coatings on a ped or pore surface or 

impregnations of the matrix adjacent to the 

pore or ped (fig. 54). See Vepraskas (1994) for 

a complete discussion.

Prominent. Contrasts strongly in color. Color 

contrasts more contrasting than faint and 

distinct are prominent.

Red parent material. The parent material with a 

natural inherent reddish color attributable to 

the presence of iron oxides, typically hematite 

(Elless and Rabenhorst, 1994; Elless et al., 

1996), occurring as coatings on and occluded 

within mineral grains. Soils that formed in 

red parent material have conditions that 

greatly retard the development and extent 

of the redoximorphic features that normally 

occur under prolonged aquic conditions. They 

typically have a Color Change Propensity 

Index (CCPI) of <30 (Rabenhorst and Parikh, 

2000). Most commonly, the material consists of 

dark red, consolidated Mesozoic or Paleozoic 

sedimentary rocks, such as shale, siltstone, 

and sandstone, or alluvial materials derived 

from such rocks. Assistance from a local soil 

scientist may be needed to determine where 

red parent material occurs.

Figure 53.—Percent organic carbon required for organic 

soil material, mucky modified mineral soil material, and 

mineral soil material as it is related to content of clay.

Figure 54.—A redox concentration occurring as a pore lining.

Redox concentrations. Bodies of apparent 

accumulation of Fe-Mn oxides (fig. 55). 

Redox concentrations include soft masses, 

pore linings, nodules, and concretions. For 

the purposes of the indicators, nodules and 

concretions are excluded from the concept 

of redox concentrations unless otherwise 

specified by specific indicators. See Vepraskas 

(1994) for a complete discussion.

Redox depletions. Bodies of low chroma (2 or 

less) having value of 4 or more where FeMn oxides have been stripped or where both 

Fe-Mn oxides and clay have been stripped 

(fig. 55). Redox depletions contrast distinctly 

or prominently with the matrix. See Vepraskas 

(1994) for a complete discussion.

Redoximorphic features. Features formed by the 

processes of reduction, translocation, and/or 
40 Field Indicators of

Figure 55.—Redox concentrations occurring as soft masses 

and pore linings. Also, a redox depletion along a root 

channel.

oxidation of Fe and Mn oxides (fig. 55); formerly 

called mottles and low-chroma colors. See 

Vepraskas (1994) for a complete discussion.

Reduced matrix. A soil matrix that has low chroma 

and high value, but in which the color changes 

in hue or chroma when the soil is exposed 

to air. See Vepraskas (1994) for a complete 

discussion.

*Reduction. For the purpose of the indicators, 

reduction occurs when the redox potential (Eh) 

is below the ferric-ferrous iron threshold as 

adjusted for pH. In hydric soils, this is the point 

when the transformation of ferric iron (Fe3+) to 

ferrous iron (Fe2+) occurs.

Relict features. Soil morphological features that 

reflect past hydrologic conditions of saturation 

and anaerobiosis. See Vepraskas (1994) for a 

complete discussion. 

*Sapric. See Muck.

Saturation. Wetness characterized by zero or positive 

pressure of the soil water. Almost all of the soil 

pores are filled with water.

Sharp boundary. Used to describe redoximorphic 

features that grade sharply from one color to 

another. The color grade is commonly less than 

0.1 mm wide.

Soft masses. Noncemented redox concentrations, 

frequently within the soil matrix, that are of 

various shapes and cannot be removed as 

discrete units. 

Soil texture. The relative proportions, by weight, of 

sand, silt, and clay particles in the soil material 

less than 2 mm in size.

Spodic horizon. A mineral soil horizon that is 

characterized by the illuvial accumulation of 

amorphous materials consisting of aluminum 

and organic carbon with or without iron (figs. 

56 and 57). The spodic horizon has a minimum 

thickness, a minimum quantity of oxalate 

extractable carbon plus aluminum, and/or 

specific color requirements. 

Umbric epipedon. A thick, dark mineral surface 

horizon with base saturation of less than 50 

percent. See Soil Taxonomy (Soil Survey Staff, 

1999) for a complete definition.

Figure 56.­—A wet Spodosol with a splotchy gray and black 

eluvial horizon above a reddish brown spodic horizon.
Hydric Soils 41

Vertisol. A mineral soil with 30 percent or more clay 

in all layers. These soils expand and shrink, 

depending on moisture content, and have 

slickensides or wedge-shaped peds. See 

Soil Taxonomy (Soil Survey Staff, 1999) for a 

complete definition.

Wetland. An area that has hydrophytic vegetation, 

hydric soils, and wetland hydrology, as per 

the “National Food Security Act Manual” 

and the 1987 Corps of Engineers Wetlands 

Delineation Manual (United States Army Corps 

of Engineers, 1987).

Within. When referring to specific indicator depth 

requirements, “within” means not beyond in 

depth. “Within a depth of 15 cm,” for example, 

indicates that the depth is less than or equal to 

15 cm.

Figure 57.­—Even in wet Spodosols, the spodic horizon may 

be bright colored. If iron occurs in the horizon, redox 

concentrations may be evident in the bright spodic 

material. Some spodic horizons, however, do not have 

iron.

43

Appendices

Appendix 1: Use Indicators by Land Resource Regions (LRRs) and Certain 

Major Land Resource Areas (MLRAs)

LRR	 	 	 	 	 	 Indicators

A	 	 A1, A2, A3, A4, A11, A12, S1, S4, S5, S6, F1 (except for MLRA 1), F2, F3, F6, F7, F8

B	 	 A1, A2, A3, A4, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8, F9

C	 	 A1, A2, A3, A4, A5, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8, F9

D	 	 A1, A2, A3, A4, A9, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8, F9

E	 	 A1, A2, A3, A4, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8

F	 	 A1, A2, A3, A4, A5, A9, A11, A12, S1, S3, S4, S5, S6, F1, F2, F3, F6, F7, F8

G	 	 A1, A2, A3, A4, A9, A11, A12, S1, S2, S4, S5, S6, F1, F2, F3, F6, F7, F8

H	 	 A1, A2, A3, A4, A9, A11, A12, S1, S2, S4, S5, S6, F1, F2, F3, F6, F7, F8, F16 (MLRAs 72 and 73)

I	 	 A1, A2, A3, A4, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8

J	 	 A1, A2, A3, A4, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8

K	 	 A1, A2, A3, A4, A5, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8

L	 	 A1, A2, A3, A4, A5, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8

M	 	 A1, A2, A3, A4, A5, A10, A11, A12, S1, S3, S4, S5, S6, F1, F2, F3, F6, F7, F8

N	 	 A1, A2, A3, A4, A5, A10, A11, A12, S1, S4, S5, S6, S7, F2, F3, F6, F7, F8, F12, F13 (MLRA 122)

O	 	 A1, A2, A3, A4, A5, A11, A12, S1, S4, S5, S6, F1, F2, F3, F6, F7, F8, F12

P	 	 A1, A2, A3, A4, A5, A6 (except for MLRA 136), A7 (except for MLRA 136), A9 (except for MLRA 136),

A11, A12, S4, S5, S6, S7, F2, F3, F6, F7, F8, F12, F13

R	 	 A1, A2, A3, A4, A5, A11, A12, S1, S3, S4, S5, S6, S7, S8, S9, F2, F3, F6, F7, F8

S	 	 A1, A2, A3, A4, A5, A11, A12, S1, S4, S5, S6, S7, S8, S9, F2, F3, F6, F7, F8, F19 (MLRAs 148 and

149A), F20 (MLRA 149A)

T	 	 A1, A2, A3, A4, A5, A6, A7, A9, A11, A12, A16 (MLRA 150A), S4, S5, S6, S7, S8, S9, F2, F3, F6, F7, F8,

F11 (MLRA 151), F12, F13, F17 (MLRA 151), F18 (MLRA 150), F20 (MLRAs 153C and 153D)

U	 	 A1, A2, A3, A4, A5, A6, A7, A8, A11, A12, S4, S5, S6, S7, S8, S9, F2, F3, F6, F7, F8, F10, F13

V	 	 A1, A2, A3, A4, A8, A11, A12, S1, S4, S7, F2, F3, F6, F7, F8

W	 	 A1, A2, A3, A4, A12, A13, A14, A15

X	 	 A1, A2, A3, A4, A12, A13, A14, A15

Y	 	 A1, A2, A3, A4, A12, A13, A14, A15 

Z	 	 A1, A2, A3, A4, A6, A7, A8, A11, A12, S4, S5, S6, S7, F2, F3, F6, F7, F8
44

Appendix 2: Test Indicators by Land Resource Regions (LRRs) and Certain 

Major Land Resource Regions (MLRAs)

LRR	 Indicators

A	 	 A10, TF12

B	 	 A10, F18, TF12

C	 	 A9, F18 (MLRA 14), TF12

D	 	 S1, F12, TF12

E	 	 A10, TF12

F	 	 TF2, F18 (MLRA 56), TF12

G	 	 S7, TF2, TF12

H	 	 TF2, TF12

I	 	 A9, TF12

J	 	 A9, F18 (MLRA 86), TF12

K	 	 A10, S3, S7, S8, S9, F12, TF2,	

TF12

L	 	 A10, S3, S7, S8, S9, F12, TF2,

TF12

M	 	 S7, F12, A16, TF12

N	 	 TF2, TF12

O	 	 A9, F18 (MLRA 131), TF12

P	 	 F18 (MLRA 135), F19, TF2, TF12

R	 	 A10, S3, F12, F19, TF2, TA6

(MLRAs 144A and 145), TF12

S	 	 A10, A16 (except for MLRA 149B),

F19 (except for MLRAs 149A	

and 148),TF2, TA6 (MLRA

149B), TF12

T	 	 F19, F20 (MLRA 153B), TF2, TF12

U	 	 TF12

V	 	 A5, TF2, TF12

W	 	 A10, A11, F6, F7, F8, TA4, TA5,

TF12

X	 	 A10, A11, F6, F7, F8, TA4, TA5,

TF12

Y	 	 A10, A11, F6, F7, F8, TA4, TA5,

TF12

Z	 	 A5, TF2, TF12
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