by: UNITED STATES DEPARTMENT OF AGRICULTURE, NATURAL RESOURCES CONSERVATION SERVICE, WETLAND SCIENCE INSTITUTE and SOILS DIVISION
in cooperation with:
NATIONAL TECHNICAL COMMITTEE for HYDRIC SOILS
edited by: G.W. Hurt, P.M. Whited, and R.F. Pringle 1
Copies of this publication can be obtained from:
Russell F. Pringle
NRCS Wetland Science Institute
Louisiana State University
104 M. B. Sturgis Hall
Baton Rouge, LA 70303-2110
Topic
Forward
Introduction
Concept
Cautions
Procedure
To Comment on the Indicators
References
Field Indicators of Hydric Soils in the United States
All Soils
Sandy Soils
Loamy and Clayey Soils
Test Indicators of Hydric Soils
All Soils
Sandy Soils
Loamy and Clayey Soils
Glossary
Table 1: List of Field Indicators by Land Resource
region
Table 2: Indicator Correlation
List of Field Indicators
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 US Fish and Wildlife Service (FWS), the US Army Corps of Engineers (COE), the Environmental Protection Agency (EPA), various regional, state, and local agencies, universities, and the private sector. The editors recognize the efforts of the many individuals without which this guide could not have been developed. Included herein are the official hydric soil indicators approved for use by the NRCS when identifying and verifying the presence of hydric soils in the field. In 1995, the National Technical Committee for Hydric Soils (NTCHS) recommended that this document be distributed to all interested government agencies, universities, groups, and individuals involved in wetland delineation for use, testing, and research on wet soils.
1 USDA, NRCS Soil Scientists with Soils Division, Gainesville, FL, Wetland Science Institute, Lincoln, NE, and Wetland Science Institute, Baton Rouge, LA respectively.
FIELD INDICATORS OF HYDRIC SOILS IN THE UNITED STATES
VER. 3.3, DECEMBER, 1996
Field Indicators of Hydric Soils in the United States (hereafter referred to as Indicators) is a guide to help identify and delineate hydric soils in the field. Indicators are not intended to replace or relieve the requirements contained in the definition of a hydric soil. The list of Indicators is considered to be dynamic; changes and additions are anticipated annually. The section To Comment on the Indicators provides guidance to recommend changes, deletions, and additions. Any modifications to the Indicators must be approved by the Interagency Field Indicator Committee. In order to properly use the Indicators, a basic knowledge of soil landscape relationships and soil survey procedures is necessary. The Indicators are designed to be regionally specific. Each indicator states the Land Resource Regions (LRRs) or the Major Land Resource Areas (MLRAs) in which it can be used. The geographic extent of LRRs and MLRAs is defined in USDA Ag. Handbook 296 (US Department of Agriculture, Soil Conservation Service, 1981). The Indicators are used to identify the hydric soil component of wetlands; however, there are some hydric soils that lack one of the currently listed indicators. Therefore, the lack of an indicator does not exclude the soil from being classed as hydric. Such soils should be studied and their characteristic morphologies identified for inclusion in this guide.
Hydric soils are defined as soils 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, July 13, 1994).
Nearly all hydric soils exhibit characteristic morphologies that result from repeated periods of saturation and/or inundation for more than a few days. Saturation or inundation when combined with anaerobic microbiological activity in the soil causes a depletion of oxygen. This anaerobiosis promotes biogeochemical processes such as the accumulation of organic matter and the reduction, translocation, and/or accumulation of iron and other reducible elements. These processes result in characteristic morphologies which persist in the soil during both wet and dry periods, making them particularly useful for identifying hydric soils.
Hydric soil indicators are formed predominantly by the accumulation or loss of iron, manganese, sulfur, or carbon compounds. The presence of hydrogen sulfide gas (rotten egg odor) is a strong indicator of a hydric soil, but this indicator is found in only the wettest sites containing sulfur. While indicators related to Fe/Mn depletions or concentrations are the most common, they cannot form in soils whose parent materials contain low amounts of Fe/Mn. Soil formed in such materials may have low chroma colors that are not related to saturation and reduction. For such soils, features related to accumulations of organic carbon should be used. These features are identified in this guide, in part to handle soils whose parent materials may have had low amounts of Fe/Mn and where hydrogen sulfide gas is not detected. Many of these carbon accumulation features such as Indicators A1 (Histosols), A2 (Histic Epipedon), and A3 (Black Histic) are often used to identify hydric soils but, because they are maximum expressions of anaerobiosis, they are rarely used for delineation purposes.
There are hydric soils whose morphologies are difficult to interpret or seem inconsistent with the landscape, vegetation, or hydrology. Such soils include those formed in grayish or reddish colored parent materials; soils with high pH or low organic matter content; Mollisols and Vertisols; soils with relict redoximorphic features; and disturbed soils such as cultivated soils and filled areas.
Soils that are artificially drained or protected (for instance, by levees) are hydric if the soil in its undisturbed state would meet the definition of a hydric soil. These soils should also have at least one of the Indicators.
Morphological features of hydric soils indicate that saturation and anaerobic conditions have existed under either contemporary or former (recent) hydrologic regimes. Features that do not reflect contemporary or recent hydrologic conditions of saturation and anaerobiosis are relict features. Typically, contemporary and recent hydric soil morphologies have diffuse boundaries; relict hydric soil features have abrupt boundaries. When 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.
To document a hydric soil first remove all loose leaf matter, needles, bark, and other easily identified plant parts (often called duff layer) to expose the surface. Dig a hole and describe the soil profile to a depth of at least 50 cm (20 inches {in.}). Using the completed soil description specify which Indicators have been matched.
Deeper examination of soil may be required where field Indicators are not easily seen within 50 cm (20 in.) of the surface. It is always recommended that soils be excavated and described as deep as necessary to make reliable interpretations. For example, examination to less than 50 cm (20 in.) may suffice in soils with surface horizons of organic material or mucky mineral material because these shallow organic accumulations only occur in hydric soils. Conversely, depth of excavation will often be greater than 50 cm (20 in.) in Mollisols because the upper horizons of these soils, due to the masking effect of organic material, often contain no visible redoximorphic features. In many sites it is necessary to make exploratory observations to a meter or more. These observations should be made with the intent of documenting and understanding the variability in soil properties and hydrologic relationships on the site.
Depths used in the Indicators are measured from the muck or mineral soil surface unless otherwise indicated. All colors refer to moist Munsell colors. Soil colors specified in the Indicators do not have decimal points listed; however, colors do occur between Munsell chips. Soil colors should not be rounded to qualify as meeting an indicator. For example: a soil matrix with a chroma between 2 and 3 should be listed as having a chroma of 2+. This soil material does not have a chroma 2 and would not meet any indicator that requires a chroma 2 or less.
Particular attention should be paid to changes in microtopography over short distances. Small changes in elevation may result in repetitive sequences of hydric/non-hydric soils and the delineation of individual areas of hydric and non- hydric soils may be difficult. Often the dominant condition (hydric/non-hydric) 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 affect the hydrologic properties of the soil. After exploratory observations have been made sufficient to understand the soil-hydrologic relationships at the site, subsequent excavations may then be shallower if identification of appropriate indicators allows.
The Indicators will be revised and updated as field data are collected to improve our understanding of hydric soil processes.
If you know an area where the plant community and hydrologic data strongly suggest that an area is a wetland and there is no indicator that identifies that soil condition, please write to Russell F. Pringle at the address below. To be most helpful, please provide supporting documentation and suggestions for modifications you feel are needed. Supporting documentation should include data to support the definition and criteria of a hydric soil; this includes water table data, saturation data, redox potential measurements, à, à dipyridyl test results, soil pedon descriptions, and vegetative data. The documentation should be submitted to:
Russell F. Pringle
NRCS Wetland Science Institute
Louisiana State University
104 Madison B. Sturgis Hall
Baton Rouge, LA 70803-2110
The following individuals were instrumental in the development of the Indicators:
Natural Resources Conservation Service
G. Wade Hurt, Gainesville, FL
Russell F. Pringle, Baton Rouge, LA
H. Chris Smith, Somerset, NJ
Arlene Tugel, Corvallis, OR
P. Michael Whited, Lincoln, NE
DeWayne Williams, Fort Worth, TX
US Army Corps of Engineers
Dr. Steven W. Sprecher, Vicksburg, MS
USDI, Fish & Wildlife Service
National Wetlands Inventory
Porter B. Reed, Jr., St. Petersburg, FL
North Carolina State University
Dr. Michael J. Vepraskas, Raleigh, NC
Private Consultant
W. Blake Parker, Verona, MS
Unless otherwise noted the following references contain definitions of terms used throughout this document. They also contain additional information concerning the terms in the glossary at the back of this document.
Environmental Laboratory. 1987. Corps of Engineers Wetland Delineation Manual - Technical Report Y-87-1. US Army Engineers Waterways Experiment Station, Vicksburg, MS.
Federal Register. July 13, 1994. Changes in Hydric Soils of the United States. Washington, DC. (Hydric Soil Definition)
Federal Register. Feb. 24, 1995. Hydric Soils of the United States. Washington, DC.
(Hydric Soil Criteria)
Florida Soil Survey Staff. 1992. Soil and Water Relationships of Florida's Ecological Communities. G. W. Hurt (ed.). USDA, Soil Conservation Service, Gainesville, FL.
Kollmorgen Instruments Corporation. 1994. Munsell Soil Color Charts. Munsell Color, Baltimore, MD.
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.
Soil Science Society of America. 1987. Glossary of Soil Science Terms. Soil Science Society of America, Madison, WI.
Soil Science Society of America. 1993. Special Publication #31. Proceedings of the Symposium on Soil Color. October 21-26, 1990. San Antonio, TX. J. M. Bigham and E. J. Ciolkosz (eds.). Soil Science Society of America, Madison, WI.
US Department of Agriculture, Soil Conservation Service. 1981. Land Resource Regions and Major Land Resource Areas of the United States. USDA-SCS Agricultural Handbook 296. US Govt. Printing Off., Washington, DC.
US Department of Agriculture, Soil Conservation Service. 1991. Hydric Soils of the United States. Soil Conservation Service. In Cooperation with the National Technical Committee for Hydric Soils, Washington, DC.
US Department of Agriculture, Soil Survey Staff. 1951. Soil Survey Manual. USDA Agricultural Handbook 18. US Govt. Printing Off., Washington, DC.
US Department of Agriculture, Soil Survey Staff. 1975. Soil Taxonomy: A basic system of soil classification for making and interpreting soil surveys. USDA Agricultural Handbook 436. US Govt. Printing Off., Washington, DC.
US Department of Agriculture, Soil Survey Staff. 1993. National Soil Survey Handbook. USDA, Soil Conservation Service, US Govt. Printing Off., Washington, DC.
US Department of Agriculture, Soil Survey Division Staff. 1993. Soil Survey Manual. USDA Agricultural Handbook 18. US Govt. Printing Off., Washington, DC.
US Department of Agriculture, Soil Survey Staff. 1994. Keys to Soil Taxonomy, Sixth Edition. US Govt. Printing Off., Washington, DC.
Vepraskas, M. J. 1992. Redoximorphic Features for Identifying Aquic Conditions. Tech. Bulletin 301. North Carolina Ag. Research Service, North Carolina State Univ., Raleigh, North Carolina.
Field Indicators of Hydric Soils in the United States is structured as follows:
For example, A1 indicates the first indicator for all soils; Histosol is the short name; the indicator is for use in all LRRs; classifies as a Histosol, except Folists is the indicator description; helpful User Notes are added.
All soils refers to soils with any USDA soil texture. Unless otherwise indicated, all mineral layers above any of the Indicators have dominant chroma 2 or less, or the layer(s) with dominant chroma of more than 2 is less than 15 cm (6 in.) thick. Also, unless otherwise indicated, nodules and concretions are not considered to be redox concentrations. Use the following Indicators regardless of texture.
A1. Histosol. For use in all LRRs. Classifies as a Histosol, except Folists.
Histosol User Notes: A Histosol has 40 cm (16 in.) or more of the upper 80 cm (32 in.) as organic soil material. Organic soil material has an organic carbon content (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), or peat (fibric soil material). See glossary for definition of muck, mucky peat, peat, and organic soil material.
A2. Histic Epipedon. For use in all LRRs except W, X, and Y; for testing in LRRs W, X, and Y. A histic epipedon.
Histic Epipedon User Notes: Most histic epipedons are surface horizons 20 cm (8 in.) or more thick of organic soil material. Aquic conditions or artificial drainage are required. See Keys to Soil Taxonomy, page 3 (US Department of Agriculture, Soil Survey Staff, 1994). Slightly lower organic carbon contents are allowed in plowed soils (ibid., page 4). See glossary for definitions.
A3. Black Histic. For use in all LRRs except W, X, and Y; for testing in LRRs W, X, and Y. A layer of peat, mucky peat, or muck 20 cm (8 in.) or more thick starting within the upper 15 cm (6 in.) of the soil surface having hue 10YR or yellower, value 3 or less, and chroma 1 or less.
Black Histic User Notes: Unlike indicator A2 this indicator does not require proof of aquic conditions or artificial drainage. See glossary for definitions of peat, mucky peat, and muck.
A4. Hydrogen Sulfide. For use in all LRRs. A hydrogen sulfide odor within 30 cm (12 in.) of the soil surface.
Hydrogen Sulfide User Notes: This "rotten egg smell" indicates that sulfate-sulfur has been reduced and therefore the soil is anaerobic. In most hydric soils, the sulfidic odor is only present when the soil is saturated and anaerobic.
A5. Stratified Layers. For use in LRRs F, K, L, M, N, O, P, R, S, T, and U; for testing in LRRs V and Z . Several stratified layers starting within the upper 15 cm (6 in.) of the soil surface. One or more of the layers has value 3 or less with chroma 1 or less and/or it is muck, mucky peat, peat, or mucky modified mineral texture. The remaining layers have value 4 or more and chroma 2 or less.
Stratified Layers User Notes: Use of this indicator may require assistance from a trained soil scientist with local experience. The minimum organic carbon content of at least one layer of this indicator is slightly less than required for indicator A7 (Mucky Modified Mineral Texture); at least 70 percent of soil material is covered, coated, or similarly masked with organic matter. An undisturbed sample must be observed. Individual strata are dominantly less than 2.5 cm (1 in.) thick. A hand lens is an excellent tool to aid in the identification of this indicator. Stratified layers in soils that fail NTCHS hydric soil criteria and fail anaerobic conditions are not indicative of hydric soils. Many alluvial soils have stratified layers at greater depths; these are not hydric soils. Many alluvial soils have stratified layers at the required depths but lack chroma 2 or less; these do not fit this indicator. Stratified Layers occur in any type soil material.
A6. Organic Bodies. For use in LRRs P, T, U, and Z. Presence of 2% or more organic bodies of muck or a mucky modified mineral texture, approximately 1 to 3 cm (0.5 to 1 in.) in diameter, starting within 15 cm (6 in.) of the soil surface.
Organic Bodies User Notes: The percent organic carbon in organic bodies is the same as in the Muck or Mucky Texture Indicators. This indicator includes the indicator previously named accretions (Florida Soil Survey Staff, 1992). Many organic bodies lack the required amount of organic carbon and are not indicative of hydric soils. The content of organic carbon should be known before this indicator is used. Organic bodies of hemic (mucky peat) and/or fibric (peat) soil materials qualify as this indicator. Material consisting of partially decomposed root tissue does not qualify as the indicator.
A7. 5 cm Mucky Mineral. For use in LRRs P, T, U, and Z. A mucky modified mineral surface layer 5 cm (2 in.) or more thick starting within 15 cm (6 in.) of the soil surface.
5 cm Mucky Mineral User Notes: "Mucky" is a USDA texture modifier for mineral soils. The organic carbon content is at least 5 and ranges to as high as 18 percent. The percentage requirement is dependent upon the clay content of the soil; the higher the clay content, the higher the organic carbon requirement. An example is mucky fine sand, which has at least 5 percent organic carbon but not more than about 12 percent organic carbon. Another example is mucky sandy loam, which has at least 7 percent organic carbon but not more than about 14 percent organic carbon. See the glossary for the definition of mucky modified mineral texture.
A8. Muck Presence. For use in LRRs U, V and Z. A layer of muck with value 3 or less and chroma 1 or less within 15 cm (6 in.) of the soil surface.
Muck Presence User Notes: The presence of muck of any thickness within 15 cm (6 in.) is the only requirement. Normally this expression of anaerobiosis is at the soil surface; however, it may occur at any depth within 15 cm (6 in.). Muck is sapric soil material with at least 12 to 18 percent organic carbon. Organic soil material is called muck (sapric soil material) if virtually all of the material has undergone sufficient decomposition such that plant parts can not be identified. Hemic (mucky peat) and fibric (peat) soil materials do not qualify. To determine if muck is present, first remove loose leaves, needles, bark, and other easily identified plant remains. This is sometimes called a leaf/root mat. Then examine for decomposed organic soil material. Generally muck is black and has a greasy feel; sand grains should not be evident. Hydric soil indicator determinations are made below the leaf or root mat; however, root mats that meet the definition of hemic or fibric soil material are included in the decision making process for Mucky Peat, Peat, Organic Bodies, or Histic Indicators. See the glossary for the definition of muck.
A9. 1 cm Muck. For use in LRRs D, F, G, H, P, and T; for testing in LRRs I, J, and O. A layer of muck 1 cm (0.5 in.) or more thick with value 3 or less and chroma 1 or less starting within 15 cm (6 in.) of the soil surface.
1 cm Muck User Notes: Unlike Indicator A8 (Muck Presence) there is a minimum thickness requirement of 1 cm. Normally this expression of anaerobiosis is at the soil surface; however, it may occur at any depth within 15 cm (6 in.). Muck is sapric soil material with at least 12 to 18 percent organic carbon. Organic soil material is called muck (sapric soil material) if virtually all of the material has undergone sufficient decomposition to limit recognition of the plant parts. Hemic (mucky peat) and fibric (peat) soil materials do not qualify. To determine if muck is present, first remove loose leaves, needles, bark, and other easily identified plant remains. This is sometimes called a leaf/root mat. Then examine for decomposed organic soil material. Generally muck is black and has a greasy feel; sand grains should not be evident. Hydric soil indicator determinations are made below the leaf or root mat; however, root mats that meet the definition of hemic or fibric soil material are included in the decision making process for Mucky Peat, Peat, Organic Bodies, or Histic Indicators. See the glossary for the definition of muck.
A10. 2 cm Muck. For use in LRR M and N; for testing in LRRs A, B, C, E, K, L, R, S, U, W, X, Y, and Z. A layer of muck 2 cm (0.75 in.) or more thick with value 3 or less and chroma 1 or less starting within 15 cm (6 in.) of the soil surface.
2 cm Muck User Notes: This Indicator requires a minimum muck thickness of 2 cm. Normally this expression of anaerobiosis is at the soil surface; however, it may occur at any depth within 15 cm (6 in.). Muck is sapric soil material with at least 12 to 18 percent organic carbon. Organic soil material is called muck (sapric soil material) if virtually all of the material has undergone sufficient decomposition to limit recognition of the plant parts. Hemic (mucky peat) and fibric (peat) soil materials do not qualify. To determine if muck is present, first remove loose leaves, needles, bark, and other easily identified plant remains. This is sometimes called a leaf/root mat. Then examine for decomposed organic soil material. Generally muck is black and has a greasy feel; sand grains should not be evident. Hydric soil indicator determinations are made below the leaf or root mat; however, root mats that meet the definition of hemic or fibric soil material are included in the decision making process for Mucky Peat, Peat, Organic Bodies, or Histic Indicators. See the glossary for the definition of muck.
Sandy soils refers to those soils with a USDA texture of loamy fine sand and coarser. Unless otherwise indicated, all mineral layers above any of the Indicators have dominant chroma 2 or less, or the layer(s) with dominant chroma of more than 2 is less than 15 cm (6 in.) thick. In addition, unless otherwise indicated, nodules and concretions are not considered to be redox concentrations. Use the following sandy Indicators for sandy mineral soil materials:
S1. Sandy Mucky Mineral. For use in all LRRs except W, X, and Y. A mucky modified mineral layer 5 cm (2 in.) or more thick starting within 15 cm (6 in.) of the soil surface.
Sandy Mucky Mineral User Notes: "Mucky" is a USDA texture modifier for mineral soils. The organic carbon content is at least 5 and ranges to as high as 14 percent for sandy soils. The percentage requirement is dependent upon the clay content of the soil; the higher the clay content, the higher the organic carbon requirement. An example is mucky fine sand, which has at least 5 percent organic carbon but not more than about 12 percent organic carbon. See the glossary for the definition of mucky modified mineral texture.
S2. 3 cm Mucky Peat or Peat. For use in LRRs G and H. A layer of mucky peat or peat 2.5 cm (1 in.) or more thick with value 4 or less and chroma 3 or less starting within 15 cm (6 in.) of the soil surface.
3 cm Mucky Peat and Peat User Notes: Mucky peat (hemic soil material) and peat (fibric soil material) having at least 12 to 18 percent organic carbon. 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 an intermediate stage of decomposition between peat and highly decomposed muck. To determine if mucky peat and/or peat are present, first remove loose leaves, needles, bark, and other easily identified plant remains. This is sometimes called a leaf/root mat. Next examine for undecomposed to partly decomposed organic soil material. See the glossary for the definitions of mucky peat and peat.
S3. 5 cm Mucky Peat or Peat. For use in LRRs F, and M; for testing in LRR R. A layer of mucky peat or peat 5 cm (2 in.) or more thick with value 3 or less and chroma 2 or less starting within 15 cm (6 in.) of the soil surface.
5 cm Mucky Peat and Peat User Notes: Mucky peat (hemic soil material) and peat (fibric soil material) have at least 12 to 18 percent organic carbon. 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 an intermediate stage of decomposition between peat and highly decomposed muck. To determine if mucky peat and/or peat are present, first remove loose leaves, needles, bark, and other easily identified plant remains. This is sometimes called a leaf/root mat. Next examine for undecomposed to partly decomposed organic soil material. See the glossary for the definitions of mucky peat and peat.
S4. Sandy Gleyed Matrix. For use in all LRRs except W, X, and Y. A gleyed matrix which occupies 60% or more of a layer starting within 15 cm (6 in.) of the soil surface.
Sandy Gleyed Matrix User Notes: Gley colors are not synonymous with gray colors. Gley colors are those colors that are found on the gley page (Kollmorgen Instruments Corporation, 1994). They have hue N, 10Y, 5GY, 10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB with value 4 or more. The gleyed matrix only has to be present within 15 cm (6 in.) of the surface. Soils with gleyed matrices are saturated for a significant duration; this is why no thickness of the layer is required. See the glossary for the definition of gleyed matrix.
S5. Sandy Redox. For use in all LRRs except V, W, X, and Y. A layer starting within 15 cm (6 in.) of the soil surface that is at least 10 cm (4 in.) thick, and has a matrix chroma 2 or less with 2% or more distinct or prominent redox concentrations as soft masses and/or pore linings.
Sandy Redox 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 this concept of redox concentrations are iron/manganese bodies as soft masses with diffuse boundaries. The iron/manganese masses are 2 to 5 mm in size and have a value 3 or less and a chroma 3 or less; most commonly they are black. Iron/manganese masses should not be confused with concretions and nodules (US Department of Agriculture, Soil Survey Staff, 1993) associated with plinthitic soils or relict concretions. Common to many redox concentrations (US Department of Agriculture, Soil Survey Division Staff, 1993) are required.
S6. Stripped Matrix. For use in all LRRs except V, W, X, and Y. A layer starting within 15 cm (6 in.) of the soil surface in which iron/manganese oxides and/or organic matter have been stripped from the matrix exposing the primary base color of soil materials. The stripped areas and translocated oxides and/or organic matter form a diffuse splotchy pattern of two or more colors. The stripped zones are 10% or more of the volume; they are rounded and approximately 1 to 3 cm (0.5 to 1 in.) in diameter.
Stripped Matrix User Notes: This indicator includes the indicator previously named polychromatic matrix (Florida Soil Survey Staff, 1992) as well as the term streaking (Environmental Laboratory, 1987). Common to many (US Department of Agriculture, Soil Survey Division Staff, 1993) areas of stripped (uncoated) soil materials 1 to 3 cm (0.5 to 1 in.) in size is a requirement. Commonly the splotches of color have value 5 or more and chroma 1 and/or 2 (stripped) and chroma 3 and/or 4 (unstripped). The matrix may lack the 3 and/or 4 chroma material. The mobilization and translocation of the oxides and/or organic matter is the important process and should result in splotchy coated and uncoated soil areas.
S7. Dark Surface. For use in LRRs N, P, R, S, T, U, V, and Z. A layer 10 cm (4 in.) or more thick starting within the upper 15 cm (6 in.) of the soil surface with a matrix value 3 or less and chroma 1 or less. At least 70% of the visible soil particles must be covered, coated, or similarly masked with organic material. The matrix color of the layer immediately below the dark layer must have value 4 or more and chroma 2 or less.
Dark Surface User Notes: The organic carbon content of this indicator is slightly less than required for mucky. An undisturbed sample must be observed. A 10X or 15X hand lens is an excellent tool to help aid this decision. Many wet soils have a ratio of about 50 percent soil particles that are covered or coated with organic matter and about 50 percent uncoated or uncovered soil particles, giving the soil a salt and pepper appearance. When the percent of covered or coated soil particles is less than 70 percent, a Dark Surface indicator is not present.
S8. Polyvalue Below Surface. For use in LRRs R, S, and T; for testing in LRRs K and L. A layer with value 3 or less and chroma 1 or less starting within 15 cm (6 in.) of the soil surface underlain by a layer(s) where translocated organic matter unevenly covers the soil material forming a diffuse splotchy pattern. At least 70% of the visible soil particles in the upper layer must be covered, coated, or masked with organic material. Immediately below this layer, the organic coating occupies 5% or more of the soil volume and has value 3 or less and chroma 1 or less. The remainder of the soil volume has value 4 or more and chroma 1 or less.
Polyvalue Below Surface User Notes: This indicator describes soils with a very dark gray or black surface or near surface layer less than 10 cm (4 in.) thick underlain by a layer where organic matter has been differentially distributed within the soil by water movement. The mobilization and translocation of organic matter results in splotchy coated and uncoated soil areas as described in the Sandy Redox and Stripped Matrix Indicators except that for S8 the whole soil is in shades of black and gray. The chroma 1 or less is critical because it limits application of this indicator to only those soils which are depleted of iron. This indicator includes the indicator previously termed streaking (Environmental Laboratory, 1987).
S9. Thin Dark Surface. For use in LRRs R, S, and T; for testing in LRRs K and L. A layer 5 cm (2 in.) or more thick within the upper 15 cm (6 in.) of the surface, with value 3 or less and chroma 1 or less. At least 70% of the visible soil particles in this layer must be covered, coated, or masked with organic material. This layer is underlain by a layer(s) with value 4 or less and chroma 1 or less to a depth of 30 cm (12 in.) or to the spodic horizon, whichever is less.
Thin Dark Surface User Notes: This indicator describes soils with a very dark gray or black near- surface layer at least 5 cm (2 in.) thick underlain by a layer where organic matter has been carried downward by flowing water. The mobilization and translocation of organic matter results in an even distribution of organic matter in the eluvial (E) horizon. The chroma 1 or less is critical because it limits application of this indicator to only those soils which are depleted of iron. This indicator commonly occurs in hydric Spodosols; however, the identification of a spodic horizon is not required.
S10. Alaska Gleyed. For use in LRRs W, X, and Y. Dominant hue N, 10Y, 5GY, 10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB, with value 4 or more in the matrix, within 30 cm (12 in.) of the mineral surface, and underlain by hue 5Y or redder in the same type of parent material.
Alaska Gleyed User Notes: Gley colors are not synonymous with gray colors. Gley colors are those colors that are found on the gley page (Kollmorgen Instruments Corporation, 1994). They have hue N, 10Y, 5GY, 10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB, with value 4 or more. Color comparison to underlying material must be based on material of the same type or lithology.
Loamy and clayey soils refers to those soils with USDA textures of loamy very fine sand and finer. Unless otherwise indicated, all mineral layers above any of the Indicators have dominant chroma 2 or less, or the layer(s) with dominant chroma of more than 2 is less than 15 cm (6 in.) thick. In addition, unless otherwise indicated, nodules and concretions are not considered to be redox concentrations. Use the following loamy and clayey Indicators for loamy or clayey mineral soil materials:
F1. Loamy Mucky Mineral. For use in all LRRs except V, W, X, and Y. A mucky modified mineral layer 10 cm (4 in.) or more thick starting within 15 cm (6 in.) of the soil surface.
Loamy Mucky Mineral User Notes: "Mucky" is a USDA texture modifier for mineral soils. The organic carbon is at least 8 percent but can range to as high as 18 percent. The percentage requirement is dependent upon the clay content of the soil; the higher the clay content, the higher the organic carbon requirement. An example is mucky sandy loam, which has at least 8 percent organic carbon but not more than about 14 percent organic carbon. See the glossary for the definition of mucky modified mineral texture.
F2. Loamy Gleyed Matrix. For use in all LRRs except W, X, and Y. A gleyed matrix that occupies 60% or more of a layer starting within 30 cm (12 in.) of the soil surface.
Loamy Gleyed Matrix User Notes: Gley colors are not synonymous with gray colors. Gley colors are those colors that are found on the gley pages (Kollmorgen Instruments Corporation, 1994). They have hue N, 10Y, 5GY, 10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB, with value 4 or more. The gleyed matrix only has to be present within 30 cm (12 in.) of the surface. Soils with gleyed matrices are saturated for a significant duration, this is why no thickness of the layer is required. See glossary for the definition of gleyed matrix.
F3. Depleted Matrix. For use in all LRRs except W, X, and Y. A layer at least 15 cm (6 in.) thick with a depleted matrix that has 60% or more chroma 2 or less starting within 25 cm (10 in.) of the surface.
Depleted Matrix User Notes: The depleted matrix must begin within 25 cm (10 in.) and continue for at least 15 cm (6 in.).Redox concentrations including iron and manganese soft masses and/or pore linings are required in soils with matrix colors of 4/1, 4/2, and 5/2. See glossary for the complete definition of depleted matrix. The low chroma matrix must be due to wetness and not a relict or parent material feature.
F4. Depleted Below Dark Surface. For use in all LRRs except LRRs W, X, and Y; for testing in LRRs W, X, and Y. A layer at least 15 cm (6 in.) thick with a depleted matrix that has 60% or more chroma 2 or less starting within 30 cm (12 in.) of the surface. The layer(s) above the depleted matrix have value 3 or less and chroma 2 or less.
Depleted Below Dark Surface User Notes: This indicator often occurs in Mollisols but also applies to soils with umbric epipedons and dark colored ochric epipedons. For soils with dark colored epipedons greater than 30 cm (12 in.) thick, use Indicator F5. See glossary for the definition of depleted matrix.
F5. Thick Dark Surface. For use in all LRRs except LRRs W, X, and, Y; for testing in LRRs W, X, and Y. A layer at least 15 cm (6 in.) thick with a depleted matrix that has 60% or more chroma 2 or less (or a gleyed matrix) starting below 30 cm (12 in.) of the surface. The layer(s) above the depleted or gleyed matrix have hue N and value 3 or less to a depth of 30 cm (12 in.) and value 3 or less and chroma 1 or less in the remainder of the epipedon.
Thick Dark Surface User Notes: The soil has a black or very dark gray surface layer 30 cm (12 in.) or more thick. The dark colored subsoil has value 3 or less, chroma 1 or less. Below the dark colored epipedon is a depleted matrix or gleyed matrix. This indicator is most often associated with overthickened soils in concave landscape positions. See glossary for the definition of depleted matrix.
F6. Redox Dark Surface. For use in all LRRs except LRRs W, X, and Y; for testing in LRRs W, X, and Y. A layer at least 10 cm (4 in.) thick entirely within the upper 30 cm (12 in.) of the mineral soil that has:
a. matrix value 3 or less and chroma 1 or less and 2% or more distinct or prominent redox concentrations as soft masses or pore linings, or
b. matrix value 3 or less and chroma 2 or less and 5% or more distinct or prominent redox concentrations as soft masses or pore linings.
Redox Dark Surface User Notes: Redox concentrations in high organic matter mineral soils with dark surfaces are often difficult to see. The organic matter "masks" some or all of the concentrations that may be present. Careful examination is required in order to see what are often brownish "mottles" in the darkened materials. In some instances, drying of the samples makes the concentrations (if present) easier to see. Dried colors, if used, need to have matrix chromas of 1 or 2 and the redox concentrations need to be distinct or prominent. In soils which are wet due to subsurface saturation, the layer immediately below the dark epipedon should have a depleted or gleyed matrix. Soils which are wet due to ponding or shallow perched layer of saturation may not always have a depleted/gleyed matrix below the dark surface. It is recommended that delineators evaluate the hydrologic source and examine and describe the layer below the dark colored epipedon when applying this indicator.
F7. Depleted Dark Surface. For use in all LRRs except LRRs W, X, and Y; for testing in LRRs W, X, and Y. Redox depletions, with value 5 or more and chroma 2 or less, in a layer at least 10 cm (4 in.) thick entirely within the upper 30 cm (12 in.) of the mineral soil that has:
a. matrix value 3 or less and chroma 1 or less and 10% or more redox depletions,
or
b. matrix value 3 or less and chroma 2 or less and 20% or more redox depletions.
Depleted Dark Surface User Notes: Care should be taken not to mistake mixing of an E or calcic horizon into the surface layer as 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 which are wet due to subsurface saturation, the layer immediately below the dark surface should have a depleted or gleyed matrix. Redox depletions should have associated microsites redox concentrations 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 LRRs W, X, and Y; for testing in LRRs W, X, and Y. In closed depressions subject to ponding, 5% or more distinct or prominent redox concentrations as soft masses or pore linings in a layer 5 cm (2 in.) or more thick entirely within the upper 15 cm (6 in.) of the soil surface.
Redox Depressions User Notes: This indicator occurs on landforms such as: vernal pools, playa lakes, rainwater basins, Grady ponds, and potholes: not micro-depressions on convex or plane landscapes.
F9. Vernal Pools. For use in LRRs C and D. In closed depressions subject to ponding, presence of a depleted matrix in a layer 5 cm (2 in.) thick entirely within the upper 15 cm (6 in.) of the soil surface.
Vernal Pools User Notes: Most often soils pond water for two reasons: they occur on landscape positions that collect water and they have a restrictive layer(s) that prevents water from moving downward through the soil. Normally this indicator occurs at the soil surface.
F10. Marl. For use in LRR U. A layer of marl with a value 5 or more starting within 10 cm (4 in.) of the soil surface.
Marl User Notes: Marl is a limnic material deposited in water by precipitation of CaCO3 by algae as defined in Soil Taxonomy (US Department of Agriculture Soil Survey Staff. 1975 and 1994). It has a Munsell value 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 the properties of marl except they lack the required Munsell value. These soils are hydric if the required value is present within 10 cm (4 in) of the soil surface. Normally this indicator occurs at the soil surface.
F11. Depleted Ochric. For use in LRR O. A layer(s) 10 cm (4 in.) or more thick that has 60% or more of the matrix with value 4 or more and chroma 1 or less. The layer is entirely within the upper 25 cm (10 in.) of the soil surface.
Depleted Ochric User Notes: This indicator is most applicable on backswamps, meander troughs, and oxbows of the Mississippi River Delta.
F12. Iron/Manganese Masses. For use in LRRs N, O, P, and T; for testing in LRR M. On floodplains, a layer 10 cm (4 in.) or more thick with 40% or more chroma 2 or less, and 2% or more distinct or prominent redox concentrations as soft iron/manganese masses with diffuse boundaries. The layer occurs entirely within 30 cm (12 in.) of the soil surface. Iron/manganese masses have value 3 or less and chroma 3 or less; most commonly they are black. The thickness requirement is waived if the layer is the mineral surface layer.
Iron/Manganese Masses User Notes: These iron/manganese masses are usually small (2 to 5 mm in size) and have a value and chroma 3 or less. They can be black. The low matrix chroma must be due to wetness and not be a relict or parent material feature. Iron/manganese masses should not be confused with the larger and redder iron nodules (US Department of Agriculture, Soil Survey Staff, 1993) associated with plinthitic soils or with concretions that have abrupt boundaries. This indicator occurs on floodplains of rivers such as the Apalachicola, Congaree, Mobile, Savannah, and Tennessee Rivers.
F13. Umbric Surface. For use in LRRs P and T. On concave positions of interstream divides and in depressions, a layer 15 cm (6 in.) or more thick starting within the upper 15 cm (6 in.) of the soil surface with value 3 or less and chroma 1 or less immediately underlain by a layer 10 cm (4 in.) or more thick with chroma 2 or less.
Umbric Surface User Notes: Thickness requirements are slightly less that those required for an umbric epipedon. Umbric surfaces on higher landscape positions, such as Umbrepts, are excluded.
F14. Alaska Redox Gleyed. For use in LRRs W, X, and Y. A layer that has dominant matrix hue 5Y with chroma 3 or less, or hue N, 10Y, 5GY, 10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB, with 10% or more redox concentrations as pore linings with value and chroma 4 or more. The layer occurs within 30 cm (12 in.) of the soil surface.
Alaska Redox Gleyed User Notes: Presence of 10 percent redox concentrations as pore linings in a dominantly gleyed matrix (hue N, 10Y, 5GY, 10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB with value 4 or more); or hue 5Y with chroma 3 or less is required. Pore linings must have value and chroma 4 or more.
F15. Alaska Gleyed Pores. For use in LRRs W, X, and Y. Presence of 10% hue N, 10Y, 5GY, 10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB with value 4 or more in the matrix or along channels containing dead roots or no roots within 30 cm (12 in.) of the soil surface. The matrix has dominant chroma 2 or less.
Alaska Gleyed Pores User Notes: Presence of 10 percent gleyed root channels within a low chroma matrix is required.
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 subject to ponding, the presence of a layer at least 10 cm (4 in.) thick within the upper 35 cm (13.5 in.) of the mineral soil that has chroma 1 or less and:
a. 1% or more redox concentrations as nodules or concretions, or
b. redox concentrations as nodules or concretions with distinct or prominent corona.
High Plains Depressions User Notes: This indicator is for closed depressions (FSA playas ) in western Kansas, southwestern Nebraska, eastern Colorado, and southeastern Wyoming. It occurs in soils such as the Ness and Pleasant series. The matrix color of the 10 cm (4 in.) layer must be a chroma 1 or less; chroma 2 matrix colors are excluded; value is usually 3. The nodules/concretions are rounded, hard to very hard, range in size from < 1 mm to 3 mm, and most commonly are black or reddish black. The corona usually are reddish brown, strong brown, or yellowish brown. The nodules/concretions can be removed from the soil and the corona (halos) 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.
The Indicators listed above should be tested for use in LRRs other than those listed. Other Indicators for testing are listed below. This list of Test Indicators is not extensive. Users of the Indicators are encouraged to submit descriptions of other soil morphologies they think indicative of hydric soils along with supporting data for inclusion in subsequent editions of Field Indicators of Hydric Soils in the United States.
TA1. Playa Rim Stratified Layers. For testing in LRR D. Stratified layers starting within the upper 15 cm (6 in.) of the soil surface. At least one layer has value 3 or less and chroma 1 or it has value 2 or more and chroma 2 or less with 2% or more distinct or prominent redox concentrations as soft masses or pore linings. The upper 15 cm (6 in.) has dominant chroma 2 or less.
Playa Rim Stratified Layers User Notes. This indicator is for the sparsely vegetated playas of the western United States. Unlike the national Stratified Layer Indicator (A5), this indicator does not require continuous chroma 2 or less. Thin layers of chroma 3 or higher may occur as long as the upper 15 cm (6 in.) is dominantly chroma 2 or less. A minimum amount of organic carbon is not required. A layer with redox concentrations is substitutional for the dark layer. As inferred, this indicator occurs on sparsely vegetated playas and playa rims adjacent to the non-vegetated playas.
TS1. Iron Staining. For testing in LRRs W, X, and Y. A continuous zone, 3 cm (1 in.) or more thick, of iron staining with value 4 or more and chroma 6 or more within 15 cm (6 in.) of the soil surface. The zone is immediately below a horizon in which iron/manganese oxides have been removed from the matrix and exposed the primary base color of the silt and sand grains.
TS2. Thick Sandy Dark Surface. For testing in LRR F. A layer at least 15 cm (6 in.) thick with a depleted matrix that has 60% or more chroma 2 or less or a gleyed matrix starting below 30 cm (12 in.) of the soil surface. The layer(s) above the depleted or gleyed matrix have hue N and value 3 or less; or hue 10YR or yellower with value 2 or less and chroma 1 to a depth of 30 cm (12 in.) and chroma 1 or less in the remainder of the epipedon.
TS3. Dark Surface 2. For testing in LRR G. A layer 10 cm (4 in.) or more thick starting within 15 cm (6 in.) of the soil surface with matrix value 2 or less and chroma 1 or less. At least 70% of the soil materials are covered, coated, or masked with organic material. The matrix color of the layer immediately below the dark surface must have value 4 or more and chroma 2 or less.
TS4. Sandy Neutral Surface. For testing in LRR M. A layer at least 10 cm (4 in.) thick with a depleted matrix that has 60% or more chroma 2 or less or a gleyed matrix starting within 30 cm (12 in.) of the soil surface. The layer(s) above the depleted or gleyed matrix have hue N and value 3 or less.
TS5. Chroma 3 Sandy Redox . For testing in LRRs F, G, H, K, L, and M. A layer starting within 15 cm (6 in.) of the soil surface that is at least 10 cm (4 in.) thick and has a matrix chroma 3 or less with 2% or more distinct or prominent redox concentrations as soft masses and/or pore linings.
Chroma 3 Sandy Redox User Notes: Redox concentrations include iron and manganese masses (reddish mottles) and pore linings (Vepraskas, 1994). Included within this concept as redox concentrations are iron/manganese bodies as soft masses with diffuse boundaries. The iron/manganese masses are 2 to 5 mm in size and have a value 3 or less and a chroma 3 or less; most commonly they are black. Iron/manganese masses should not be confused with the larger and redder iron nodules (US Department of Agriculture, Soil Survey Staff, 1993) associated with plinthitic soils or relict concretions. Common to many redox concentrations are required.
TF1. ? cm Mucky Peat or Peat. For testing in LRRs F, G, H, and M. A layer of mucky peat or peat ? cm thick with value 4 or less and chroma 3 or less starting within 15 cm (6 in.) of the soil surface.
? cm Mucky Peat or Peat User Notes: Testing from 1994 indicates that the diagnostic thickness for mucky peat and for peat is 1 to 5 cm. Further testing is needed to find the definitive thickness.
TF2. Red Parent Material. For testing in LRRs with red parent material. In parent materials with a hue of 7.5YR or redder; a layer at least 10 cm (4 in.) thick with a matrix value 4 or more and chroma 3 or less and 2% or more redox depletions and/or redox concentrations as soft masses and/or pore linings. The layer is entirely within 30 cm (12 in.) of the soil surface.
Red Parent Material User Notes: This indicator was developed for use in areas of red parent material such as: Triassic/Jurassic sediments in the Connecticut river valley, Permian "red beds" in Kansas, clayey red till and associated lacustrine deposits around the Great Lakes, and Jurassic sediments associated with "hogbacks" on the eastern edge of the Rocky mountains. This indicator also occurs on "Red River" flood plains such as the Chattachoochee, Congaree, Red, and Tennessee Rivers Redox features most noticeable in red materials include redox depletions and soft manganese masses which are black or dark reddish black.
TF3. Alaska Concretions. For testing in W, X, and Y. Within 30 cm (12 in.) of the soil surface redox concentrations as nodules or concretions greater than 2 mm in diameter that occupy more than approximately 2% of the soil volume in a layer 10 cm (4 in.) or more thick with a matrix chroma 2 or less.
TF4. 2.5Y/5Y Below Dark Surface. For testing in LRRs F, M, N, P, S, and T. A layer at least 15 cm (6 in.) thick with 60% or more hue 2.5 Y or yellower, value 4 or more, and chroma 1; or hue 5Y or yellower, value 4 or more, and chroma 2 or less starting within 30 cm (12 in.) of the soil surface. The layer(s) above the 2.5Y/5Y layer have value 3 or less and chroma 2 or less.
2.5Y/5Y Below Dark Surface User Notes: Further testing is required to investigate whether these colors below a Mollic epipedon are indicative of wetness.
TF5. 2.5Y/5Y Below Thick Dark Surface. For testing in LRRs D, F, and M. A layer at least 15 cm (6 in.) thick with 60% or more hue 2.5Y or yellower, value 4 or more, and chroma 1; or hue 5Y or yellower, value 4 or more, and chroma 2 or less starting below 30 cm (12 in.) of the soil surface. The layer(s) above the 2.5Y/5Y layer have hue N and value 3 or less; or have hue 10YR or yellower with value 2 or less and chroma 1 or less to a depth of 30 cm (12 in.) and value 3 or less and chroma 1 or less in the remaining of the epipedon.
TF6. Calcic Dark Surface. For testing in LRRs F, G, and M. A layer with an accumulation of calcium carbonate (CaCO3), or calcium carbonate equivalent, occurs within 40 cm (16 in.) of the soil surface. It is overlain by a layer(s) with value 3 or less and chroma 1 or less. The layer of CaCO3 accumulation is underlain by a layer within 75 cm (30 in.) of the surface 15 cm (6 in.) or more thick having 60% or more by volume one or more of the following:
a. depleted matrix, or
b. gleyed matrix, or
c. hue 2.5Y or yellower value 4 and chroma 1.
Calcic Dark Surface User Notes: This indicator is the Soil Taxonomy criterion that separates Aeric Calciaquolls from Typic Calciaquolls, with an additional requirement of black or very dark gray surface layers. In the Midwest, the hydric/non- hydric boundary has generally been accepted as the line between Aeric and Typic Calciaquolls. Typic Calciaquolls (Vallers series and others) are documented to occur on upland plant communities on convex slopes (evaporative rims of potholes). Further documentation is needed to determine what soil morphological features can be used to separate hydric Typic Calciaquolls from non-hydric.
TF7. Thick Dark Surface 2/1. For testing in all LRRs except LRRs O, P, T, and U. A layer at least 15 cm (6 in.) thick with a depleted matrix that has 60% or more chroma 2 or less (or a gleyed matrix) starting below 30 cm (12 in.) of the soil surface. The layer(s) above the depleted or gleyed matrix have hue 10YR or yellower, value 2.5 or less to a depth of 30 cm (12 in.) and value 3 or less and chroma 1 or less in the remainder of the epipedon.
Thick Dark Surface 2/1 User Notes: The soil has a black surface layer 30 cm (12 in.) or more thick. The dark colored subsoil has value 3 or less and chroma 1. Below the mollic (umbric) epipedon is a depleted matrix or gleyed matrix. This indicator is most often associated with overthickened soils in concave landscape positions. Further testing is needed to determine if cumulic soils with surface hues of 10YR or yellower are hydric. Testing notes need to indicate on what landscape position this indicator fails . It may be necessary to limit this indicator to concave landscapes.
TF8. Redox Spring Seeps. For testing in LRR D. A layer with value 5 or more and chroma 3 or less with 2 percent or more distinct or prominent redox concentrations as soft masses or pore linings. The layer is at least 5 cm (2 in.) thick and is within the upper 15 cm (6 in.) of the soil surface.
Redox Spring Seeps User Notes: This indicator is similar to Indicator F9 (Vernal Pools). However, in order to more fully correlate hydric soils to wetland vegetation, chroma 3 is included in this indicator as well as the redox concentrations portions of the depleted matrix concept. This indicator is not unique to depressional landscapes; therefore, that requirement is dropped. As inferred, this indicator may occur in seeps and flow-through areas adjacent to springs and up-slope end of drainageways as well as depressional seeps surrounded by uplands.
TF9. Delta Ochric. For testing in LRR O. A layer 10 cm (4 in.) or more thick that has 60% or more of the matrix with value 4 or more and chroma 2 or less with no redox concentrations. This layer occurs entirely within the upper 30 cm (12 in.) of the soil surface.
Delta Ochric User Notes: This indicator is applicable in accreting areas of the Mississippi River Delta.
TF10. Alluvial Depleted Matrix. For testing in LRRs M, N, and S. On frequently flooded flood plains, a layer with a matrix that has 60% or more chroma 3 or less with 2% redox concentrations as soft iron masses, starting within 15 cm (6 in.) of the soil surface and extending to a depth of more than 30 cm (12 in.).
A Horizon - A mineral horizon that formed at the surface or below an O horizon where organic material is accumulating. See Keys to Soil Taxonomy (1994) for complete definition.
*Abrupt Boundary - Used to describe redoximorphic features that grade sharply from one color to another. The color grade is commonly less than 0.5 mm wide. Clear and gradual are used to describe boundary color gradations intermediate between abrupt and diffuse.
Accreting Areas - Landscape positions where soil material accumulates through deposition from higher elevations or upstream positions more rapidly than 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 Keys to Soil Taxonomy (1994) for complete definition.
Calcic Horizon - An illuvial horizon in which carbonates have accumulated to a significant extent. See Keys to Soil Taxonomy (1994) for complete definition.
Calcium Carbonate (CaCO3 ) - Calcium carbonate effervesces when treated with cold hydrochloric acid.
CaCO3 Equivalent - Is the acid neutralizing capacity of a soil expressed as a weight percentage of CaCO3 (molecular weight of CaCO3 equals 100).
Closed Depressions - A low-lying area surrounded by higher ground with no natural outlet for surface drainage.
COE - US Army Corps of Engineers.
Common - When referring to redox concentrations and/or depletions common represents 2 to 20 percent of the observed surface.
Concave Landscapes - A landscape whose surface curves downward.
of reduction and translocation to create colors of low chroma and high value. 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 common or many, distinct or prominent redox concentrations as soft masses or pore linings are present. In some places the depleted matrix may change color upon exposure to air (reduced Matrix), this phenomena is included in the concept of depleted matrix. The following combinations of value and chroma identify a depleted matrix:
E Horizon - A mineral horizon in which the main dominant process is loss of silicate clay, iron, and/or aluminum, leaving a concentration of sand and silt particles. See Keys to Soil Taxonomy (1994) for complete definition.
EPA - US Environmental Protection Agency.
Epipedon - A horizon that has developed at the soil surface. See Keys to Soil Taxonomy (1994) for complete definition.
*Faint - Evident only on close examination. In the same hue or 1 hue change (e.g. 10YR to 7.5YR or 10YR to 2.5Y) a change of 1 unit in chroma, or 1 to 2 units in value, or 1 unit of chroma and 1 unit of value.
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 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 complete discussion.
Few - When referring to redox concentrations and/or depletions few represents less than 2 percent of the observed surface.
Fibric - See peat.
Frequently Flooded or Ponded - A frequency class in which flooding or ponding is likely to occur often under usual weather conditions (more than 50 percent chance in any year, or more than 50 times in 100 years).
FWS - US Department of Interior, Fish and Wildlife Service.
Glauconitic - A mineral aggregate that contains micaceous mineral resulting in a characteristic green color, e.g. glauconitic shale or clay.
*Gleyed Matrix - Soils with a gleyed matrix have the following combinations of hue, value, and chroma and the soils are not glauconitic:
In some places the gleyed matrix may change color upon exposure to air (reduced matrix). This phenomena is included in the concept of gleyed matrix.
*Hemic - See Mucky peat.
Histic Epipedon - A thick (20-60 cm {8-24 in.}) organic soil horizon that is saturated with water at some period of the year unless artificially drained and that is at or near the surface of a mineral soil. See Keys to Soil Taxonomy (1994) for complete definition.
Histosols - Organic soils that have organic soil materials in more than half of the upper 80 cm (32 in.), or that are of any thickness if they overly rock or fragmental materials that have interstices filled with organic soil materials. See Keys to Soil Taxonomy (1994) for complete definition.
Horizon - A layer, approximately parallel to the surface of the soil, distinguishable from adjacent layers by a distinctive set of properties produced by soil forming processes. See Keys to Soil Taxonomy (1994) for complete definition.
Hydric Soil Criteria (1995):
a. somewhat poorly drained with a water table equal to 0.0 foot (ft.) from the surface during the growing season, or
b. poorly drained or very poorly drained and have either:
(1) water table equal to 0.0 ft. during the growing season if textures are coarse sand, sand, or fine sand in all layers within 20 inches (in.), or for other soils, or
(2) water table at less than or equal to 0.5 ft. from the surface during the growing season if permeability is equal to or greater than 6.0 in/hour (h.) in. all layers within 20 in., or
(3) water table at less than or equal to 1.0 ft. from the surface during the growing season, if permeability is less than 6.0 in./h. in any layer within 20 in., or
3. Soils that are frequently ponded for long or very long duration during the growing season, or
4. Soils that are frequently flooded for long or very long duration during the growing season.
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 - An odor similar to rotten eggs.
Hydromorphic - Features in the soil caused or formed by water.
Layer(s) - A horizon, subhorizon, or combination of contiguous horizons or subhorizons that share a property(s) 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, climates, water resources, and land use. Each LRR has a different letter of the alphabet (A-Z). LRRs are defined in USDA Ag. Handbook 296.
Many - When referring to redox concentrations and/or depletions many represents more than 20 percent of the observed surface.
Marl - An earthy, unconsolidated deposit consisting chiefly of calcium carbonate mixed with clay in approximately equal proportions; formed primarily under fresh water lacustrine conditions. See Keys to Soil Taxonomy (1994) for complete definition.
Matrix - The dominant soil volume which is continuous in appearance and envelops microsites. When three colors exist, 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 USDA Ag. Handbook 296.
Mollic Epipedon - A mineral surface horizon that is relatively thick, dark colored, humus rich, and has high base saturation. See Keys to Soil Taxonomy (1994) for complete definition.
Mollisols - Mineral soils that have a mollic epipedon. See Keys to Soil Taxonomy (1994) for complete definition.
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 an organic carbon content of: 18 percent or more 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.
*Peat - A fibric organic soil material with virtually all of the organic material allowing for identification of plant forms. Bulk density is normally <0.1. Peat has 3/4 or more fibers after rubbing, or 2/5 or more fibers after rubbing and sodium pyrophosphate solution extract color of 7/1, 7/2, 8/2, or 8/3.
Plinthite - The sesquioxide-rich, humus-poor, highly weathered mixture of clay with quartz and other diluents. See Keys to Soil Taxonomy (1994) for a complete discussion of plinthite.
Ponding - Standing water in a closed depression that is removed only by percolation, evaporation, or transpiration. Duration is greater than seven days.
Pore Linings - Zones of accumulation that may be either coatings on a pore surface or impregnations of the matrix adjacent to the pore. See Vepraskas (1994) for complete discussion.
*Prominent - Contrasts strongly with the color to which they are compared. In the same hue or a 1 hue change (e.g. 10YR to 2.5Y or 10YR to 7.5YR), a change of 4 units in chroma and/or 4 units in value. With a change of 2 hues (e.g. 10YR to 5Y or 10YR to 5YR) a change of 3 or more units of value and/or a change of 3 or more units of chroma is prominent.
Redox Concentrations - Bodies of apparent accumulation of Fe/Mn oxides. 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 complete discussion.
Redox Depletions - Bodies of low chroma (2 or less) having value 4 or more where Fe-Mn oxides have been stripped or where both Fe-Mn oxides and clay have been stripped. Redox deletions contrast distinctly or prominently with the matrix. See Vepraskas (1994) for complete discussion.
Redoximorphic Features - Features formed by the processes of reduction, translocation, and/or oxidation of Fe and Mn oxides. Formerly called mottles and low chroma colors. See Vepraskas (1994) for complete discussion.
Reduced Matrix - Soil matrices that have low chroma and high value, but whose color changes in hue or chroma when exposed to air. See Vepraskas (1994) for complete discussion.
*Reduction - For the purpose of the Indicators, when the redox potential (Eh) is below the ferric/ferrous iron threshold as adjusted for pH. In hydric soils, this is the point when the transformation of ferric iron (Fe+++) to ferrous iron (Fe++) occurs.
Relict Features - Soil morphological features that do not reflect recent hydrologic conditions of saturation and anaerobiosis. See Vepraskas, M. J. (1994) for complete discussion.
*Sapric - See muck.
Saturation - When the soil water pressure is zero or positive. Most all the soil pores are filled with water.
SCS - USDA - Soil Conservation Service (now Natural Resources Conservation Service.)
Soft Masses - Redox concentrations, that are not hard, frequently within the matrix, whose shape is variable. See Vepraskas, M. J. (1994) for complete discussion.
Soil Texture - The weight proportion of the soil separates for particles less than 2 mm.
Spodic Horizon - A mineral soil horizon that is characterized by the illuvial accumulation of amorphous materials composed of aluminum and organic carbon with or without iron. The spodic horizon has certain minimum thickness, and a minimum quantity of oxalate extractable carbon plus aluminum. It also has specific color requirements. See Keys to Soil Taxonomy (1994) for complete definition.
Umbric Epipedon - A thick, dark mineral surface horizon with base saturation of less than 50 percent. See Keys to Soil Taxonomy (1994) for 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 contain slickensides or wedge-shaped peds. See Keys to Soil Taxonomy (1994) for complete definition.
Wetland - An area that has hydrophytic vegetation, hydric soils, and wetland hydrology, per the FSA Manual and the Corps of Engineers 1987 Wetlands Delineation Manual.
LRR Indicators
A A1, A2, A3, A4, A10, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TF2, TF7.
B A1, A2, A3, A4, A10, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TF2, TF7.
C A1, A2, A3, A4, A10, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, F9, TF2, TF7.
D A1, A2, A3, A4, A9, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, F9, TA1, TF2, TF5, TF7, TF8.
E A1, A2, A3, A4, A10, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TF2, TF7.
F A1, A2, A3, A4, A5, A9, S1, S3, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TS2, TS5, TF1, TF2, TF4, TF5, TF6, TF7.
G A1, A2, A3, A4, A9, S1, S2, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TS3, TS5, TF1, TF2, TF6, TF7.
H A1, A2, A3, A4, A9, S1, S2, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, F16, TS5, TF1, TF2, TF7.
I A1, A2, A3, A4, A9, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TF2, TF7.
J A1, A2, A3, A4, A9, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TF2, TF7.
K A1, A2, A3, A4, A5, A10, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TS5, TF2, TF7.
L A1, A2, A3, A4, A5, A10, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, TS5, TF2, TF7.
M A1, A2, A3, A4, A5, A10, S1, S3, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, F12, TS4, TS5, TF1, TF2, TF4, TF5, TF6, TF7, TF10.
N A1, A2, A3, A4, A5, A10, S1, S4, S5, S6, S7, F1, F2, F3, F4, F5, F6, F7, F8, F12, TF2, TF7, TF10.
O A1, A2, A3, A4, A5, A9, S1, S4, S5, S6, F1, F2, F3, F4, F5, F6, F7, F8, F11, F12, TF2, TF9.
P A1, A2, A3, A4, A5, A6, A7, A9, S4, S5, S6, S7, F2, F3, F8, F12, F13.
R A1, A2, A3, A4, A5, A10, S1, S3, S4, S5, S6, S7, S8, S9, F1, F2, F3, F4, F5, F6, F7, F8, TF2, TF7.
S A1, A2, A3, A4, A5, A10, S1, S4, S5, S6, S7, S8, S9, F1, F2, F3, F4, F5, F6, F7, F8, TF2, TF4, TF10.
T A1, A2, A3, A4, A5, A6, A7, A9, S4, S5, S6, S7, S8, S9, F2, F3, F8, F12, F13, TF2.
U A1, A2, A3, A4, A5, A6, A7, A8, A10, S1, S4, S5, S6, S7, F1, F2, F3, F4, F5, F6, F7, F10.
V A1, A2, A3, A4, A5, A8, S1, S4, S7, F2, F3, F4, F5, F6, F7, F8, TF2, TF7.
W A1, A2, A3, A4, A10, S10, F4, F5, F6, F7, F8, F14, F15, TS1, TF2, TF3, TF7.
X A1, A2, A3, A4, A10, S10, F4, F5, F6, F7, F8, F14, F15, TS1, TF2, TF3, TF7.
Y A1, A2, A3, A4, A10, S10, F4, F5, F6, F7, F8, F14, F15, TS1, TF2, TF3, TF7.
Z A1, A2, A3, A4, A5, A6, A7, A8, S4, S5, S6, S7, F2, F3, F4, F5, F6, F7, F8, TF2, TF7.
1987 Manual 1996 Indicators
NON-SANDY SOILS:
a. Organic soils (Histosols) A1 (Histosols)
b. Histic Epipedon A2 (Histic Epipedon)
A3 (Black Histic)
c. Sulfidic material A4 (Hydrogen sulfide)
d. Aquic or peraquic moisture regime ----------------------------
e. Reducing soil conditions ----------------------------
f (1). Gleyed soils (gray color) F2 (Loamy Gleyed Matrix)
F14 (Alaska Redox Gleyed
F15 (Alaska Gleyed Pores)
f (2). Soils with bright mottles F3 (Depleted Matrix)
and/or low matrix chroma F8 (Redox Depressions)
F9 (Vernal Pools)
F11 (Depleted Ochric)
F16 (High Plains Depressions)
TF8 (Redox Spring Seeps)
TF9 (Delta Ochric)
TF10 (Alluvial Depleted Matrix)
g. Soil appearing on the hydric soils list ----------------------------
h. Iron and Manganese concretions F12 (Iron/Manganese Masses)
TF3 (Alaska Concretions)
Not listed in the 1987 Manual A5 (Stratified Layers)
A6 (Organic Bodies)
A7 (5 cm Mucky Mineral)
A8 (Muck Presence)
A9 (1 cm Muck)
A10 (2 cm Muck)
F1 (Loamy Mucky Mineral)
F4 (Dep. Below Dark Surface)
F5 (Thick Dark Surface)
F6 (Redox Dark Surface)
F7 (Depleted Dark Surface)
F10 (Marl)
F13 (Umbric Surface)
TA1 (Playa Rim Strat. Layers)
TF1 (? cm Mucky Peat or Peat)
TF2 (Red Parent Material)
TF4 (Y Below Dark Surface.)
TF5 (Y Below Thick Dark Sur.)
TF6 (Calcic Dark Surface)
TF7 (Thick Dark Surface 2/1)
SANDY SOILS
a. Organic soils (Histosols) A1 (Histosols)
b. Histic Epipedon A2 (Histic Epipedon)
A3 (Black Histic)
c. Sulfidic material A4 (Hydrogen sulfide)
d. Aquic or peraquic moisture regime --------------------------
e. Reducing soil conditions --------------------------
f. Iron and Manganese concretions S5 (Sandy Redox)
TS5 (Chroma 3 Sandy Redox
g. High organic matter content in A6 (Organic Bodies)
the surface horizon A7 (5 cm Mucky Mineral)
A8 (Muck Presence)
A9 (1 cm Muck)
A10 (2 cm Muck)
S1 (Sandy Mucky Mineral)
S2 (3 cm Mucky Peat or Peat)
S3 (5 cm Mucky Peat or Peat)
S7 (Dark Surface)
TS2 (Tk. Sandy Dark Surface)
h. Streaking of subsurface horizons
by organic matter S6 (Stripped Matrix)
S8 (Polyvalue Below Surface)
i. Organic pan S9 (Thin Dark Surface)
j. Soils appearing on the hydric soils list--------------------------
Not listed in the 1987 Manual A5 (Stratified Layers)
S4 (Sandy Gleyed Matrix)
S10 (Alaska Gleyed)
TA1 (Playa Rim Strat. Layers)
TS1 (Iron Staining)
TS4 (Sandy Neutral Surface)
PROBLEM SOILS
Recently deposited sandy materials A5 (Stratified Layers)
S6 (Stripped Matrix)
S8 (Polyvalue Below Surface)
TA1 (Playa Rim Strat. layers)
Soils with thick dark A horizons F4 (Dep. Below Dark Surface)
F5 (Thick Dark Surface)
F6 (Redox Dark Surface)
F7 (Depleted Dark Surface)
F13 (Umbric Surface)
F16 (High Plains Depressions)
TF4 (2.5Y/5Y Below Dark Surface)
TF5 (2.5Y/5Y Below Thick. Dark Sur.)
TF6 (Calcic Dark Surface)
TS2 (Tk. Sandy Dark Surface)
TF7 (Thick Dark Surface 2/1)
Soils with red parent material F8 (Redox Depressions)
F9 (Vernal Pools)
TS1 (Iron Staining)
TF2 (Red Parent Material)
TF8 (Redox Spring Seeps)
Soils with low chroma parent material S4 (Sandy Gleyed Matrix)
S10 (Alaska Gleyed)
F10 (Marl)
TS4 (Sandy Neutral Surface)
ALL SOILS LOAMY AND CLAYEY SOILS
A1 Histosols F1 Loamy Mucky Mineral
A2 Histic Epipedon F2 Loamy Gleyed Matrix
A3 Black Histic F3 Depleted Matrix
A4 Hydrogen Sulfide F4 Depleted Below Dark Surface
A5 Stratified Layers F5 Thick Dark Surface
A6 Organic Bodies F6 Redox Dark Surface
A7 5 cm Mucky Mineral F7 Depleted Dark Surface
A8 Muck Presence F8 Redox Depressions
A9 1 cm Muck F9 Vernal Pools
A10 2 cm Muck F10 Marl
TA1 Playa Rim Stratified Layers F11 Depleted Ochric
F12 Iron/Manganese Masses
F13 Umbric Surface
SANDY SOILS F14 Alaska Redox Gleyed
S1 Sandy Mucky Mineral F15 Alaska Gleyed Pores
S2 3 cm Mucky Peat or Peat F16 High Plains Depressions
S3 5 cm Mucky Peat or Peat
S4 Sandy Gleyed Matrix TF1 ? cm Mucky Peat or Peat
S5 Sandy Redox TF2 Red Parent Material
S6 Stripped Matrix TF3 Alaska Concretions
S7 Dark Surface TF4 2.5Y/5Y Below Dark Surface
S8 Polyvalue Below Surface TF5 2.5Y/5Y Below Thick Dark Surface
S9 Thin Dark Surface TF6 Calcic Dark Surface
S10 Alaska Gleyed TF7 Thick Dark Surface 2/1
TS1 Iron Staining TF8 Redox Spring Seeps
TS2 Thick Sandy Dark Surface TF9 Delta Ochric
TS3 Dark Surface 2 TF10 Alluvial Depleted Matrix
TS4 Sandy Neutral Surface
TS5 Chroma 3 Sandy Redox