United States

Department of

Agriculture

Natural Resources 

Conservation 

Service

In cooperation with 

the National Technical 

Committee for Hydric Soils

Field Indicators of 

Hydric Soils in the 

United States

A Guide for Identifying and Delineating 

Hydric Soils, Version 8.1, 2017

Field Indicators of Hydric Soils 

in the United States

A Guide for Identifying and Delineating Hydric Soils,

Version 8.1, 2017

(Including corrections to version 8.0, 2016, 

on pages 21, 25, and 34)

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 J.F. Berkowitz, Soil Scientist, 

USACE, Vicksburg, MS
ii

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etc.) should contact the responsible Agency or USDA’s TARGET Center at (202) 

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To file a program discrimination complaint, complete the USDA Program 

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USDA and provide in the letter all of the information requested in the form. To 

request a copy of the complaint form, call (866) 632-9992. Submit your completed 

form or letter to USDA by: (1) mail: U.S. Department of Agriculture, Office of the 

Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW, Washington, 

D.C. 20250-9410; (2) fax: (202) 690-7442; or (3) email: program.intake@usda.gov. 

USDA is an equal opportunity provider, employer, and lender.

Copies of this publication can be obtained from:

NRCS Distribution Center 

1-888-526-3227

nrcsdistributioncenter@ia.usda.gov

 Information contained in this publication and additional information concerning 

hydric soils are maintained on the website at http://www.nrcs.usda.gov/wps/portal/

nrcs/main/soils/use/hydric/.

Citation: United States Department of Agriculture, Natural Resources 

Conservation Service. 2016. Field Indicators of Hydric Soils in the United States,

Version 8.0. L.M. Vasilas, G.W. Hurt, and J.F. Berkowitz (eds.). USDA, NRCS, in 

cooperation with the National Technical Committee for Hydric Soils.

Cover: A typical landscape and profile of a hydric soil meeting the requirements 

of indicator F3, Depleted Matrix. Note the close-up of a ped showing a gray matrix 

with redox concentrations characteristic of soils meeting this field indicator. The 

Depleted Matrix indicator is the most commonly used indicator in the United States.
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

Index to Indicators ...................................................................................................... vi

Field Indicators of Hydric Soils in the United States,Version 8.0, 2016 .................1

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

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

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

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

To Comment on the Indicators ..................................................................................6

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

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

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

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

Test Indicators of Hydric Soils .................................................................................29

All Soils ...................................................................................................................29

Sandy Soils .............................................................................................................30

Loamy and Clayey Soils ..........................................................................................30

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 Regions (MLRAs) ..........................................................44

Appendix 3: Indicators That Have Been Deleted or Are No Longer Approved 

for Use ..............................................................................................................45
vi

Index to Indicators

Field Indicators

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 .......................................18

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

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

S9.—Thin Dark Surface ..................................20

S11.—High Chroma Sands..............................20

S12.—Barrier Islands 1 cm Much ....................20

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

F1.—Loamy Mucky Mineral ............................21

F2.—Loamy Gleyed Matrix .............................21

F3.—Depleted Matrix ......................................21

F6.—Redox Dark Surface ...............................22

F7.—Depleted Dark Surface ...........................23

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

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

F11.—Depleted Ochric ...................................24

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

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

F16.—High Plains Depressions ......................24

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

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

F19.—Piedmont Flood Plain Soils ..................25

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

F21.—Red Parent Material ..............................26

F22.—Very Shallow Dark Surface ..................27

Test Indicators

All Soils ..............................................................29

TA4.—Alaska Color Change ...........................29

TA5.—Alaska Alpine Swales ...........................29

TA6.—Mesic Spodic ........................................29

Sandy Soils ........................................................30

TS7.—Barrier Islands Low Chroma Matrix .....30

Loamy and Clayey Soils ...................................30
1

Field Indicators of Hydric Soils in the

United States,Version 8.0, 2016

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). Field indicators (indicators) are 

not intended to replace or modify the requirements 

contained in the definition of a hydric soil. Proper 

use of the indicators requires a basic knowledge 

of soil-landscape relationships and soil survey 

procedures. 

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 layer thick enough to meet the requirements of indicator S7 and does not meet the 

requirements of any other indicator.

The National Technical Committee for Hydric 

Soils (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 
2 Field Indicators of

depletion of oxygen. Prolonged anaerobic conditions 

promote 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 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 indicators are designed to be regionally 

specific. The description of each indicator identifies 

the land resource regions (LRRs) and/or major land 

resource areas (MLRAs) in which the indicator can be 

applied. The geographic extent of LRRs and MLRAs is 

defined in U.S. Department of Agriculture Handbook 

296 (USDA, NRCS, 2006b). See the map or LRRs 

(fig. 6, page 7) and the list of LRR-specific indicators 

(Appendices 1 and 2). 

The list of indicators is dynamic; changes and 

additions are anticipated with new research and field 

testing. 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 NTCHS. The current version of the indicators is 

available on the NRCS hydric soils website (http://

www.nrcs.usda.gov/wps/portal/nrcs/main/soils/use/

hydric/).

Concept

Hydric soil indicators are formed predominantly by 

the accumulation or loss of iron, manganese, sulfur, 

or carbon compounds under saturated and anaerobic 

conditions. The processes and the soil features that 

develop under these conditions 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 enters the soil solution, 

where it 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 or 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). Redox 

concentrations, depletions, and reduced matrixes are 

collectively referred to as redoximorphic features.

While indicators related to iron or manganese 

depletions and/or concentrations are most common 

in hydric soils, they cannot form in soils with parent 

materials that are low in Fe or Mn content. Soils that 

formed in such materials may have low-chroma colors 

that are not related to saturation and reduction. Such 

soils may have hydric soil 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 sulfate (SO4

2-) to hydrogen 

sulfide gas (H2S). This conversion results in a very 

pronounced “rotten egg” odor in some soils that are 

inundated or saturated for 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 in very wet portions of 

the landsscape, 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, 
Hydric Soils 3

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.

Determining the Texture of Soil Materials 

High in Organic Carbon

Soil materials fall into three categories based 

upon the organic carbon content: organic soil, mucky 

mineral soil, and mineral soil. In lieu of laboratory 

data, the following field estimation method can be 

used to categorize 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 muck, mucky peat, or peat. 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. Muck, mucky peat, and peat correspond to the 

textures sapric, hemic, and fibric. 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) meets the definition of a hydric soil if 

the upper part formed under anaerobic conditions in 

an unaltered state. Drained or protected hydric soils 

generally have one or more of the indicators. Not 

all areas that have hydric soils qualify as wetlands. 

For example, a soil that formed under anaerobic 

conditions but no longer has wetland hydrology 

or supports hydrophytic vegetation still meets the 

definition of a hydric soil. However, the area will not 

meet the requirements of a wetland determined by 

the three factor approach (presence of hydric soils, 

wetland hydrology, and 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. For example, redoximorphic 

features are most likely to occur in soils that cycle 

between anaerobic (reduced) and aerobic (oxidized) 

conditions. In some cases, portions of an area under 

near-constant saturation will not display an indicator. 

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 a hydric soil 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 
4 Field Indicators of

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).

For soils with thick, dark surface layers, deeper 

examination may be required when field indicators are 

not observed at a depth of ≤20 inches (50 cm) from 

the soil 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, start observations at the 

actual surface for indicators A1, A2, and A3; start 

observations at the muck or mineral surface for A11 

and A12 and for testing indicators that allow muck; 

and start observations at the mineral surface for 

all other indicators. In LRRs F, G, H, and M, start 

observations at the actual soil surface if the soil is 

sandy or when applying indicators A1, A2, and A3 

and at the muck or mineral surface for the remaining 

field indicators. In the remaining LRRs, start 

observations at the top of the muck or mineral surface 

(underneath any peat and/or mucky peat material), 

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

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

All colors noted in this guide refer to moist 

Munsell colors (X-Rite, 2009). 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 overmoistening dry soil. 

Figure 2.— The soil profile above consists of an 8 cm (3.14 

inches) layer of peat and/or mucky peat underlain by 

a 1 cm (0.4 inches) layer of muck. The remaining soil 

layers are sandy soil material. In LRRs R, W, X, and 

Y, observations would begin below the peat, mucky 

peat, and muck layers (9 cm). In LRRs, F, G, H, and M, 

observations would start at the actual soil surface. In all 

remaining LRRs, observations would begin at the muck 

surface (8 cm).

Soil chromas specified in the indicators do not 

have decimal points; however, intermediate colors 

do occur. Colors should not be rounded to make the 

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. 

Value should be rounded to the nearest color chip 

when using the indicators. For example, a color in 

between a value of 3 and 4 should be rounded and 

not excluded from meeting either F3 Depleted Matrix 

or F6 Redox Dark Surface because the color occurs 
Hydric Soils 5

between color chips. If the value is closer to 3, then 

F6 or some other dark surface indicator should be 

considered. If it is closer to 4, then F3 or some other 

depleted matrix indicator should be considered. 

Always examine soil matrix colors in the field 

immediately after sampling. Ferrous iron in the soil 

can oxidize rapidly, resulting in the development of 

colors with higher chroma or redder hue. Soils that are 

saturated at the time of sampling may contain reduced 

iron and/or manganese that cannot 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 

(for 5 to 30 minutes or more) to a moist state before 

the iron or manganese oxidize and the redoximorphic 

features become visible.

Pay particular attention to changes in 

microtopography over short distances. Small changes 

in elevation may result in repetitive sequences of 

hydric/nonhydric soil mosaics, 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.

Figure 3.—The left portion of this ped shows moist soil colors, 

and the right portion shows dry soil colors. Moist colors 

are to be used when hydric soils are identified. The moist 

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.—The lower portion of this soil profile meets the 

color and depth requirements of indicator F3 (Depleted 

Matrix); however, the upper portion of the profile contains 

a layer with chroma of 2 or more that is more than 15 cm 

(6 inches) thick. As a result, indicator F3 (Depleted Matrix) 

is not met.

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, S11, F8, F12, F19, F20, and F21, 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 
6 Field Indicators of

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

indicators). Both Sandy layers 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:

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 oxidationreduction potential (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 soilwater 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.nrcs.usda.gov/wps/portal/

nrcs/main/soils/use/hydric/).

2. Adding or deleting a test indicator: Minimally, 

the following should accompany all requests for 

Figure 5.—Proper installation and monitoring of equipment 

as described in the Hydric Soil Technical Standard is 

required to collect data regarding proposed additions, 

deletions, or other changes to the hydric soil indicators.

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 

(email and postal addresses and phone 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 

USDA Natural Resources Conservation Service

5601 Sunnyside Ave.

Room 1-2126, Stop Code 5471

Beltsville, MD 20705-5471

Email: Lenore.Vasilas@wdc.usda.gov
Figure 6.—Map of USDA land resource regions.

9

Field Indicators of Hydric Soils

The indicator 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 alpha numeric listing for 

the second indicator for All Soils; Histic Epipedon is

the short name; “For use in all LRRs” indicates the 

applicable LRRs; and “a histic epipedon underlain by 

mineral soil material with chroma of 2 or less” is the 

description. The helpful user notes follow the indicator. 

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 for the application of the 

indicators. Use the following A-indicators in all soil 

layers, 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, 2014) 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.

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

than 40 cm (16 inches) of organic material, starting at the 

soil surface

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, 2014) 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 at a depth of ≤15 cm (6 inches) from 

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

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

mineral soil material with chroma of 2 or less.

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 starting at a depth ≤30 cm (12 

inches) from the soil surface.

User Notes: This “rotten egg smell” indicates that 

sulfate-sulfur has been reduced to hydrogen sulfide 

gas and therefore the soil is 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 Q, V 

and Z. Several stratified layers starting at a depth ≤15 

cm (6 inches) from 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. A stratified layer is depositional and not 

pedogenic. 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 

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

strata are dominantly less than 2.5 cm (1 inch) 

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).

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

This soil also meets the requirements of indicator A6 

(Organic Bodies).

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 at a depth ≤15 cm (6 inches) 

from the soil surface.

User Notes: Organic bodies typically occur at the 

tips of fine roots. In order to meet the Organic Bodies 

indicator, the organic carbon content in organic 

bodies must meet the requirements of muck or mucky 

modified textures. The size of the organic body is not 

specifically defined, but the bodies are commonly 

1 to 3 cm (0.5 to 1 inch) in diameter (figs. 11 and 

12). Many organic bodies do not have the required 

content of organic carbon and as a result do not meet 

this indicator. For example, organic bodies of mucky 

peat (hemic material) and/or peat (fibric material) 

do not meet the requirements of this indicator, nor 

does material consisting of partially decomposed 

root tissue. The Organic Bodies indicator includes the 

indicator previously named “accretions” (Florida Soil 

Survey Staff, 1992).

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 more 
12 Field Indicators of

thick, starting at a depth ≤15 cm (6 inches) from 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. For example, a 

mucky fine sandy soil contains between 5 and 12 

percent organic carbon. When the amount of clay 

is increased as in a mucky sandy loam, the organic 

carbon content increases to between 7 and 14 

percent.

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

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

A8.—Muck Presence. For use in LRRs Q, U, V, 

and Z. A layer of muck with value of 3 or less and 

chroma of 1 or less, starting at a depth ≤15 cm (6 

inches) from the soil surface.

User Notes: The presence of muck of any 

thickness at 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 ≤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. Mucky peat 

(hemic material) and/or peat (fibric material) 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 at a depth ≤15 cm (6 inches) from 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 ≤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. Mucky peat (hemic material) and/or peat 

(fibric material) 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, and S (except for 

MLRA 148). 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 at a depth ≤15 cm (6 inches) from 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 ≤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. Mucky peat (hemic material) and/or peat 
Hydric Soils 13

(fibric material) do not qualify. Generally, muck is 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 at a depth ≤30 cm (12 inches) from 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.

Organic, loamy, or clayey layer(s) above the 

depleted or gleyed matrix must have value of 3 or 

less and chroma of 2 or less starting at a depth ≤15 

cm (6 inches) from the soil surface and extend to the 

depleted or gleyed matrix. Any sandy material above 

the depleted or gleyed matrix must have value of 3 

or less and chroma of 1 or less starting at a depth 

≤15 cm (6 inches) from the soil surface and extend to 

the depleted or gleyed matrix. Viewed through a 10x 

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

sand particles must be masked with organic material. 

Observed without a hand lens, the sand 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 

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 at a depth of ≤15 cm from 

the soil surface and is at least 5 cm thick, the soil also 

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

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.

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 and starting at a depth ≤15 cm (6 inches) from 

the soil surface 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 

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 A11 allows a deeper depleted matrix 

than 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

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.

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 at a depth ≤30 cm (12 

inches) from the mineral surface and is underlain at a 

depth ≤1.5 m (60 inches) from the soil surface 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 

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.

specified gley colors occurs ≤30 cm (12 inches) from 

the soil surface. These must be the colors on the 

pages of the Munsell color book (X-Rite, 2009) 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. 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 both are 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 at a depth 

≤30 cm (12 inches) from 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, determine if the dominant color(s) of the soil 

layer match the chroma 3 or less or 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 saturation 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 at a depth ≤30 

cm (12 inches) from the soil surface. The matrix has a 

dominant hue of 5Y or redder.
16 Field Indicators of

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.

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 

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 experiences anaerobic 

conditions.

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

of LRR T; for testing in LRR S (except for MLRA 149B). 

A layer starting at a depth ≤15 cm (6 inches) from the 

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

are along root channels. Reduction occurs first along root 

channels, where organic carbon is concentrated.

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. Matrix colors with chroma 3 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 and S11, 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 S-indicators for sandy mineral soil materials.

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

except for T, U, W, X, Y , and Z and portions of LRR 

P outside of MLRA 136t. A layer of mucky modified 

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

starting at a depth ≤15 cm (6 inches) from the soil 

surface.
Hydric Soils 17

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. For 

example, a mucky fine sandy soil contains between 5 

and 12 percent organic carbon. 

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 at a depth ≤15 cm (6 inches) 

from the soil surface, and underlain by sandy soil 

material.

User Notes: Mucky peat (hemic soil material) and 

peat (fibric soil material) have a minimum organic 

carbon 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 at 

a depth ≤15 cm (6 inches) from the soil surface, and 

underlain by sandy soil material.

User Notes: Mucky peat (hemic soil material) and 

peat (fibric soil material) have a minimum organic 

carbon 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 at a depth ≤15 

cm (6 inches) from 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 (X-Rite, 2009) 

that 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 

at a depth ≤15 cm (6 inches) from 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 

Q, V, W, X, and Y. A layer starting at a depth ≤15 cm (6 

inches) from 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.

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

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

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.

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

for V, W, X, and Y. A layer starting at a depth ≤15 

cm (6 inches) from the soil surface in which ironmanganese 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 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 

2 or less, 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 a splotchy 

pattern of masked and unmasked soil areas. This may 

be a difficult pattern to recognize and is more evident 

when a horizontal slice is observed.

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.

S7.—Dark Surface. For use in LRRs K, L, M, N, P, 

Q, R, S, T, U, V, and Z. A layer 10 cm (4 inches) thick, 

starting at a depth less than or equal to the upper 

15 cm (6 inches) from 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 
Hydric Soils 19

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: An undisturbed sample must be 

observed (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, the Dark Surface indicator does not occur.

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 

at a depth ≤15 cm (6 inches) from the soil surface. At 

least 70 percent of the visible soil particles must be 

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.

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 

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.

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

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, starting at a depth ≤15 cm (6 

inches) from the soil surface, 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. 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. 

S11.—High Chroma Sands. For use along 

shorelines and near shore regions of the Great Lakes 

in LRRs K and L. In coastal zones and dune-andswale complexes, a layer 5 cm (2 inches) or more 

thick starting at a depth ≤10 cm (4 inches) from the 

soil surface with chroma 4 or less and 2% or more 

distinct or prominent redox concentrations.

User Notes: Along the shorelines of the Great 

Lakes within LRRs L and K, some wetlands exhibit 

the presence of high chroma sands (often a chroma 

3 to 4). These high-chroma, sandy soils occur at the 

landward edge of coastal marshes or in interdunal 

landscape positions of dune-and-swale complexes. 

These soils exhibit redox concentrations as pore 

linings and/or soft masses starting at a depth ≤10 cm 

(4 inches) from the soil surface. In adjacent upland 

areas, redox concentrations are absent or are only 

observed below 15 cm (6 inches). It may be helpful 

to involve a soil scientist to identify those soils that 

qualify for this indicator.

S12.—Barrier Islands 1 cm Muck. For use in 

MLRA 153B and 153D of LRR T. In the swale portion 

of dune-and-swale complexes of barrier islands, a 

layer of muck 1 cm (0.5 inch) or more thick with value 

of 3 or less and chroma of 2 or less and starting at a 

depth ≤15 cm (6 inches) from the soil surface.

User Notes: This indicator is similar to A9 but 

allows chroma of greater than 1, but not greater 

than 2. The indicator is limited to dune-and-swale 

complexes on barrier islands.

Loamy and Clayey Soils

“Loamy and Clayey 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, F20, and F21, 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 F-indicators for 

loamy or clayey mineral soil materials.

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

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

except for N, Q, 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 at a depth ≤15 cm (6 

inches) from 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. For example, mucky sandy 

loam requires between 8 and 14 percent organic carbon.

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 at a depth ≤30 

cm (12 inches) from 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 (Xrite, 2006) that 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 at a depth ≤30 cm (12 inches) from 

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 

W, X, and Y; for testing in LRRs 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 starts at a depth ≤10 

cm (4 inches) from the soil surface, or

b. 15 cm (6 inches), starting at a depth ≤25 cm 

(10 inches) from the soil surface.

User Notes: A depleted matrix requires a value 

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

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 more and chroma of 2 or less and redox 

concentrations starting at a depth of 8 cm. Since the 

depleted matrix starts at a depth of ≤15 cm from the soil 

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

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.

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

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

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

at a depth ≤20 cm (8 inches) from the mineral soil 

surface, 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.

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 are commonly 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 

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 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 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

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 surface layer when applying this indicator. 

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

except 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, starting at a depth ≤20 cm (8 inches) from the 

mineral soil surface, 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 

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 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 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 starts at a depth 

≤10 cm (4 inches) from the soil surface.

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.

F10.—Marl. For use in LRR K, L, and U. A layer 

of marl with value of 5 or more and chroma 2 or less 

starting at a depth ≤10 cm (4 inches) from the soil 

surface (fig. 35).

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.

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.

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 at a depth ≤10 

cm (4 inches) from the soil surface. Normally, this 

indicator occurs at the soil surface.
24 Field Indicators of

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 

or more and chroma of 1 or less. The layer starts at a 

depth ≤15 cm (6 inches) from the soil surface.

User Notes: This indicator is applicable in deltaic 

accreting areas along the Mississippi River.

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 starts at a 

depth ≤20 cm (8 inches) from the soil surface. Ironmanganese 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. 36). 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 35.—Indicator F10 (Marl). In this profile, marl begins at a 

depth ≤10 cm of the soil surface. The scale is in cm.

Figure 36.—Indicator F12 (Iron-Manganese Masses). Although 

this indicator requires only 40 percent value of 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 at a depth ≤15 cm (6 inches) from 

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 

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. 37). 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. 

F16.—High Plains Depressions. For use in 

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

MLRAs of 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 starting 

at a depth ≤25 cm (10 inches) from the mineral soil 

surface that has either: 

a. One 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 (Food Security Act “playas”) in western 

Kansas, southwestern Nebraska, eastern Colorado, 
Hydric Soils 25

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 (fig. 37). 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 

Figure 37.—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).

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

concentrations. This layer starts at a depth less than 

or equal to the upper 20 cm (8 inches) from the soil 

surface.

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 10 cm (4 inches) thick starting 

at a depth ≤30 cm (12 inches); or at least 5 cm 

(2 inches) thick staring at a depth of 15 cm (6 

inches) from 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 

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 (Environmental Laboratory, 1987). Follow the 

procedures and note the considerations in Hydric 

Soils Technical Note 8, Use of alpha-alpha-Dipyridyl,

available online at http://www.nrcs.usda.gov/wps/

portal/nrcs/main/soils/use/hydric/.

F19.—Piedmont Flood Plain Soils. For use in 

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

plains subject to Piedmont deposition throughout 

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

least 15 cm (6 inches) thick, starting at a depth ≤25 

cm (10 inches) from 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 flood plains in the Mid-Atlantic and Southern 

Piedmont Provinces and areas where sediments 

derived from the Piedmont are being deposited 
26 Field Indicators of

on flood plains on the Coastal Plain (fig. 38). This 

indicator does not apply to stream terraces, which 

are associated with a historic stream level and are 

representative of an abandoned flood plain. While 

these soils are found on flood plains, flooding may be 

rare and groundwater is often the source of hydrology.

Figure 38.—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.

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) from estuarine marshes or water 

and at a depth ≤1 m (3.28 feet) of mean high water, a 

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

at a depth ≤20 cm (8 inches) from 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. 39).

F21.—Red Parent Material. For use in MLRA 

127 of LRR N; MLRA 145 of LRR R; and MLRAs 147 

and 148 of LRR S; for testing in all soils derived from 

red parent materials. A layer derived from red parent 

materials (see Glossary) that is at least 10 cm (4 

inches) thick, starting at a depth ≤25 cm (10 Inches) 

from the soil surface with a hue of 7.5YR or redder. 

The matrix has a value and chroma greater than 2 

and less than or equal to 4. The layer must contain 

10 percent or more depletions and/or distinct or 

Figure 39.—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.

prominent concentrations occurring as soft masses or 

pore linings. Redox depletions should differ in color by 

having:

a. A minimum difference of one value higher and 

one chroma lower than the matrix, or

b. Value of 4 or more and chroma of 2 or less 

(fig. 40).

User Notes: This indicator was developed for use 

in areas of red parent material, such as residuum 

in the Piedmont Province Triassic lowlands section 

or the Paleozoic “red beds” of the Appalachian 

Mountains, and in alluvium or colluvium derived from 

these materials. This indicator may occur along the 

Red River (Arkansas and Louisiana). In glaciated 

areas, the indicator may form in glacial till, outwash, 

deltaic sediments, or glaciolacustrine sediments 

derived from similar parent materials in the area. 

Soils potentially derived from red parent materials 
Hydric Soils 27

Figure 40.—Indicator F21 (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.

should be evaluated to determine the Color Change 

Propensity Index (CPPI) and be shown to have CCPI 

values below 30 (Rabenhorst and Parikh, 2000). In 

landscapes where mixing or stratification of parent 

materials occur, it cannot be assumed that sediment 

overlying red parent material is derived solely from 

that parent material. The total percentage of all redox 

concentrations and redox depletions must add up 

to at least 10 percent to meet the threshold for this 

indicator.

This indicator is typically found at the boundary 

between hydric and non-hydric soils. Other, more 

common indicators may be found on the interior (fig. 

41). It may be helpful to involve a soil scientist familiar 

with these soils to identify those soils that qualify for 

this indicator.

F22.—Very Shallow Dark Surface. For use in 

MLRA 138 and West Florida portions of MLRA 152A 

of LRR T and MLRA 154 of LRR U; for testing in all 

other MLRAs and LRRs. In depressions and flood 

plains subject to frequent ponding and/or flooding, 

one of the following must be observed:

a. If bedrock occurs between 15 cm (6 inches) 

and 25 cm (10 inches) of the soil surface, a 

layer at least 15 cm (6 inches) thick starting at 

a depth ≤10 cm (4 inches) from the soil surface 

with value 2.5 or less and chroma 1 or less, 

and the remaining soil to bedrock must have 

the same colors as above or any other color 

that has chroma 2 or less. 

Or,

b. If bedrock occurs at a depth ≤15 cm (6 inches) 

from the soil surface, more than half of the 

soil thickness must have value 2.5 or less and 

chroma 1 or less, and the remaining soil to 

bedrock must have the same color as above or 

any other color that has a chroma 2 or less.

Figure 41.—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.

29

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

TA4.—Alaska Color Change. For testing in LRRs 

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

more thick, starting at a depth ≤30 cm (12 inches) 

from 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 microhighs. Soils should be 

examined in both landscape positions and compared. 

If both positions have a mineral surface layer of the 

same color, but the dark surface 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, 

including 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 at a depth 

≤15 cm (6 inches) from the mineral soil surface, that 

has value of 3 or less and chroma of 2 or less and is 

underlain by either:

a. One or more layers 8 cm (3 inches) or more 

thick occurring at a depth ≤30 cm (12 inches) 

from the mineral soil surface, having value and 

chroma of 3 or less, and showing evidence of 

spodic development; or

b. One or more layers 5 cm (2 inches) or more 

thick occurring at a depth ≤30 cm (12 inches) 

from 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. The layer 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.
30

Sandy Soils

TS7.—Barrier Islands Low Chroma Matrix. For 

testing in MLRA 153B and 153D of LRR T. In the 

swale portion of the swale-and-dune complexes of 

barrier islands, a surface layer 1 cm (0.5 inches) or 

more thick with value 4 or less and chroma 2 or less. 

Below the dark surface, one or more layers 10 cm (4 

inches) or more thick occurs with a dominant hue of 

2.5Y or yellower and value 4 or more and chroma less 

than 2 starting at a depth ≤15 cm (6 inches) from the 

soil surface.

User Notes: The requirement of a dark surface 

layer above the low chroma layer excludes sediments 

from recent depositional events (especially common 

in overwash areas) which are not hydric. Low chroma 

colors in recent deposits are likely due to the nature of 

the parent material and not related to hydrology. There 

is no color requirement for any layer(s) between the 

dark surface and the low chroma matrix. This indicator 

is limited to sandy soils in dune-and-swale complexes 

of barrier islands.

Loamy and Clayey Soils

As of this printing, no test indicators are approved 

for loamy and clayey soils. To propose a new test 

indicator, contact the National Technical Committee 

for Hydric Soils.
31

References

Elless, M.P., and M.C. Rabenhorst. 1994. Hematite in the shales of the Triassic 

Culpeper Basin of Maryland. Soil Science 158:150–154.

Elless, M.P., M.C. Rabenhorst, and B.R. James. 1996. Redoximorphic features in soils 

of the Triassic Culpeper Basin. Soil Science 161:58–69.

Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. 

United States Army Corps of Engineers. Waterways Experiment Station Technical 

Report Y-87-1. 

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

Washington, DC. (Definition of hydric soils.)

Florida Soil Survey Staff. 1992. Soil and water relationships of Florida’s ecological 

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

Mausbach, M.J., and J.l. Richardson. 1994. Biogeochemical processes in hydric soils. 

Current Topics in Wetland Biogeochemistry 1:68–127. Wetlands Biogeochemistry 

Institute, Louisiana State University, Baton Rouge, LA.

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

Academy Press, Washington, DC.

National Technical Committee for Hydric Soils (NTCHS). Use of alpha-alpha-dipyridyl. 

Hydric Soils Technical Note 8. https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/

use/hydric/?cid=nrcs142p2_053983 (accessed 19 September 2016).

National Technical Committee for Hydric Soils (NTCHS). 2015. The hydric soil technical 

standard. Hydric Soils Technical Note 11. https://www.nrcs.usda.gov/Internet/FSE_

DOCUMENTS/nrcs142p2_051608.pdf (accessed 19 September 2016).

Rabenhorst, M.C., and S. Parikh. 2000. Propensity of soils to develop redoximorphic 

color changes. Soil Science Society of America Journal 64:1904–1910.

Schoeneberger, P.J., D.A.Wysocki, E.C Benham, and W.D. Broderson (editors). 

2002. Field book for describing and sampling soils, version 2.0. Natural Resources 

Conservation Service, National Soil Survey Center, Lincoln, NE.

Soil Science Society of America. 1993. Proceedings of the Symposium on Soil Color, 

October 21-26, 1990, San Antonio, TX. J.M. Bigham and E.J. Coilkosz (editors). Soil 

Science Society of America, Madison, WI, Special Publication 31.

Soil Science Society of America. 2001. Glossary of soil science terms. Soil Science 

Society of America, Madison, WI. https://www.soils.org/publications/soils-glossary

(accessed 19 September 2016).

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

Department of Agriculture Handbook 18. http://www.nrcs.usda.gov/wps/portal/nrcs/

detail/soils/ref/?cid=nrcs142p2_054262 (accessed 19 September 2016). 
32

Soil Survey Staff. 1999. Soil Taxonomy: A basic system of soil classification for making 

and interpreting soil surveys. U.S. Department of Agriculture Handbook 436. http://

www.nrcs.usda.gov/wps/portal/nrcs/main/soils/survey/class/taxonomy/ (accessed 19 

September 2016).

Soil Survey Staff. 2014. Keys to soil taxonomy, 12th ed. USDA, Natural Resources 

Conservation Service. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/

class/taxonomy/?cid=nrcs142p2_053580 (accessed 19 September 2016).

United States Department of Agriculture, Natural Resources Conservation Service. 

1996. Field indicators of hydric soils in the United States, version 3.2. G.W. Hurt, 

P.M. Whited, and R.F. Pringle (editors). In cooperation with the National Technical 

Committee for Hydric Soils.

United States Department of Agriculture, Natural Resources Conservation Service. 

1998. Field indicators of hydric soils in the United States, version 4.0. G.W. Hurt, 

P.M. Whited, and R.F. Pringle (editors). In cooperation with the National 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). 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). 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. 2006b. U.S. Department of 

Agriculture Handbook 296. http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/

survey/?cid=nrcs142p2_053624 (accessed 19 September 2016).

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.). In cooperation with the National Technical Committee 

for Hydric Soils.

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://www.nrcs.usda.gov/wps/portal/

nrcs/detail/soils/ref/?cid=nrcs142p2_054242 (accessed 19 September 2016). 

Vepraskas, M.J. 1994. Redoximorphic features for identifying aquic conditions. 

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

State University, Raleigh, NC.

X-Rite. 2009. Munsell® soil color charts: Revised edition. X-Rite. Grand Rapids, MI.
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. 42 and 43). 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.

COE. U.S. Army Corps of Engineers.

Figure 42.—Artificial drainage does not alter the hydric status 

of a soil.

Common. When referring to redox concentrations, 

redox depletions, or both, “common” represents 2 

to 20 percent of the observed surface.

Concave landscapes. Landscapes in which the 

surface curves downward.
34 Field Indicators of

Figure 43.—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.

*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. 44). 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. 45).

Diffuse boundary. Used to describe redoximorphic 

features that grade gradually from one color to 

another (fig. 46). The color grade is commonly 

more than 2 mm wide. “Clear” is used to describe 

boundary color gradations intermediate between 

sharp and diffuse.

Figure 44.—Illustration of values and chromas that 

require 2 percent or more distinct or prominent redox 

concentrations and those that do not, for hue 10YR, to 

meet the definition of a depleted matrix. Due to inaccurate 

color reproduction, do not use this page to determine soil 

colors in the field. Background image from the Munsell 

Soil Color Charts reprinted courtesy of Munsell Color 

Services Lab, a part of X-Rite, Inc. (Xrite 2009).

With or without redox 

concentrations

2% or more distinct 

or prominent redox 

concentrations
Hydric Soils 35

Figure 45.—A depleted matrix with value of 4 or more and 

chroma of 2 or less. Redox concentrations occur as soft 

masses and pore linings.

Figure 46.—Iron concentration with a diffuse boundary 

exhibited by bright colors in the center of the 

concentration and a lighter color away from the center.

Distinct. 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

a) Delta value = 0 and delta chroma >0 to <2, 

or

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

Regardless 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. 47). 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:

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

Figure 47.—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

Any delta hue if both colors have value <3 and 

chroma <2 (fig. 48).

Upper Threshold for Faint

Delta Delta Delta

Hue Value Chroma

0 ≤2 ≤1

1 ≤1 ≤1

2 0 0

Hue Value Chroma

Any ≤3 ≤2

Any feature above the upper threshold for faint 

features would be considered either distinct or 

prominent. If an indicator requires distinct or 

prominent features then those features at or 

below the faint threshold do not count.

Figure 48.—Relationships among the hues of the Munsell 

Color System. Solid lines represent hues contained in the 

Munsell Soil Color Charts (2009). Dotted lines represent 

all other possible 2.5-unit steps. Moving from one hue line 

to the adjacent hue line represents a delta hue of 1 (2.5 

units). Moving from hue N to any other hue the delta hue 

is 1. Adapted from the Soil Survey Manual (Soil Survey 

Staff, 1993).

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, redox 

depletions, or both, “few” represents less than 2 

percent of the observed surface.

Fibric. See Peat.

Flood plain. The nearly level plain that borders a 

stream and is subject to inundation under floodstage conditions unless protected artificially. It is 

usually a constructional landform built of sediment 

deposited during overflow and lateral migration of 

the stream.

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.
Hydric Soils 37

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).

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

inch) organic soil horizon that is saturated with 

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 

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).

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 

ponding long enough during the growing season 

to develop anaerobic conditions in the upper 

part.

Hydrogen sulfide odor. The odor of H2

S. It is similar 

to the smell of rotten eggs.

Hydromorphic features. Features in the soil caused 

or formed by water.
38 Field Indicators of

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.

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 U.S. 

Department of Agriculture Handbook 296 (USDA, 

NRCS, 2006b).

Many. When referring to redox concentrations, redox 

depletions, or both, “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. 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) 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 peat (fibric material) 

and that of muck (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 peat (fibric) or muck 

(sapric) soil material.
Hydric Soils 39

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.

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.

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. 

Percent Clay

Percent Organic Carbon

Mineral Soil Material

Mucky Modified Mineral Soil Material

Organic Soil Material

Peat (Fibric)

Mucky Peat (Hemic)

Much (Sapric)

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.

Bulk density is normally <0.1. Peat has threefourths or more fibers after rubbing, or it has twofifths or more fibers after rubbing and has sodium 

pyrophosphate solution extract color of 7/1, 7/2, 

8/2, or 8/3.

Ped. A unit of soil structure such as a block, column, 

granule, plate, or prism, formed by natural 

processes (in contrast with a clod, which is 

formed artificially).

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 
40 Field Indicators of

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

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.

Redox concentrations. Bodies of apparent 

accumulation of Fe-Mn oxides (figs. 54 and 

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 Fe-Mn 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 

oxidation of Fe and Mn oxides (figs. 54 and 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 

Figure 55.—Redox concentrations occurring as soft masses 

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

channel.

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 
Hydric Soils 41

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

eluvial horizon above a reddish brown spodic horizon.

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.

Stream terrace. Flat-topped landforms in a stream 

valley that flank and are parallel to the stream 

channel, originally formed by previous stream 

level, and representing the abandoned flood plain, 

stream bed, or valley floor produced during a past 

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.

state of fluvial erosion or deposition (i.e., currently 

very rarely or never flooded; inactive cut and fill 

and/or scour and fill processes). Stream terraces 

may occur singularly or as a series. Erosional 

surfaces cut into bedrock and thinly mantled 

with stream deposits (alluvium) are called “strath 

terraces.” Remnants of constructional valley floors 

thickly mantled with alluvium are called “alluvial 

terraces.”

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.

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 

(Environmental Laboratory, 1987).

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

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

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

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, S7, S11, F1, F2, F3, F6, F7, F8, F10

L A1, A2, A3, A4, A5, A11, A12, S1, S4, S5, S6, S7, S11, F1, F2, F3, F6, F7, F8, F10

M A1, A2, A3, A4, A5, A10, A11, A12, S1, S3, S4, S5, S6, S7, 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), F21 

(MLRA 127)

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, S1 (MLRA 136), S4, S5, S6, S7, F1 (MLRA 136), F2, F3, F6, F7, F8, F12, F13, F22 (MLRA 

138 and West Florida portion of 152A)

Q A1, A2, A3, A4, A8, A11, A12, S1, S4, S6, S7, F2, F3, F6, F7, F8

R A1, A2, A3, A4, A5, A11, A12, S1, S4, S5, S6, S7, S8, S9, F2, F3, F6, F7, F8, F21 (MLRA 145)

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), F21 (MLRA 147 and 148)

T A1, A2, A3, A4, A5, A6, A7, A9, A11, A12, A16 (MLRA 150A), S4, S5, S6, S7, S8, S9, S12 (MLRA 153B 

and 153D), 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, F22 

(MLRA 154)

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 Field Indicators of

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

Certain Major Land Resource Regions (MLRAs)

LRR Indicators

A A10, F22

B A10, F18, F22

C A9, F18 (MLRA 14), F22

D F12, F22

E A10, F22

F F18 (MLRA 56), F22

G F22

H F16 (except for MLRAs 72 and 73), 

F22

I A9, F22

J A9, F18 (MLRA 86), F22

K A10, S3, S8, S9, F12, F22

L A10, S3, S8, S9, F12, F22

M F12, F22

N F22

O A9, F18 (MLRA 131), F21 (MLRA 

131C), F22

P F18 (MLRA 135), F19, F22 (except 

for MLRA 138 and West Florida 

portion of MLRA 152A

Q A5, F22

R S3, F12, F22, TA6 (MLRAs 144A 

and 145)

S A10 (except for MLRA 148), A16 

(except for MLRA 149B), F19 

(except for MLRAs 148 and 

149A ), TA6 (MLRA 149B), F22

T F19, F20 (MLRA 153B), F22, TS7 

(153B and 153D)

U F22 (except for MLRA 154)

V A5, F22

W A11, F3, F6, F7, F8, F22, TA4, TA5

X A11, F3, F6, F7, F8, F22, TA4, TA5

Y A11, F3, F6, F7, F8, F22, TA4, TA5

Z A5, F22
Hydric Soils 45

Appendix 3: Indicators That Have Been Deleted or Are No Longer 

Approved for Use

S10. Alaska Gleyed.—This indicator is now indicator A13 (Alaska Gleyed). 

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).

F9.—Vernal Pools. This indicator has been deleted and its concepts are included in Field Indicator F3 (Depleted 

Matrix). 

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).

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).

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).

TF1. ? cm Mucky Peat or Peat.—This test indicator has been deleted.

TF2. Red Parent Material.—This test indicator has been deleted. Its concept has been approved for use as 

indicator F21 (Red Parent Material).

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.—This test indicator has been approved for use and is now indicator F22 (Very 

Shallow Dark Surface).

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