Field Indicators of Hydric Soils in the United States - ITC

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Field Indicators of Hydric Soilswater through the landscape. Significant changes inparent material or lithologic discontinuities in thesoil can affect the hydrologic properties of the soil.After exploratory observations have been madesufficient to understand the soil-hydrologic relationshipsat the site, subsequent excavations may thenbe shallower if identification of appropriate indicatorsallows.To Comment on the IndicatorsThe Indicators are revised and updated as field dataare collected to improve our understanding of hydricsoil processes (fig. 4). Revisions, additions, and othercomments regarding field observations of hydric soilconditions that cannot be documented using thepresently recognized Indicators are welcome; however,any modifications and additions must be approvedby NRCS and NTCHS. Guidelines for requestingchanges to field indicators are as follows:1. Adding indicators or changing existing indicators—Minimally,the following should accompanyall requests for additions and changes to existinghydric soil indicators in Field Indicators of HydricSoils in the United States:(a) Detailed pedon descriptions of at least threepedons that document the addition or changeand detailed pedon descriptions of threeneighboring nonhydric pedons.(b) Detailed vegetative data collected to representthe vegetation of the six pedons.(c) Saturation/inundation data and redox potential(Eh) data for a duration that captures thesaturation cycle (dry-wet-dry) of at least oneof the hydric pedons and one of the nonhydricpedons. Precipitation and in situ soil-water pHdata from the same sites should also be provided.Monitoring instrumentation should beinstalled according to the Hydric Soil TechnicalStandard in Technical Note 11 (http://soils.usda.gov/soil_use/hydric/hstn.htm).2. Adding a test indicator—Minimally, the followingshould accompany all requests for adding atest indicator to Field Indicators of Hydric Soilsin the United States:(a) Detailed pedon descriptions of at least threepedons that document the test indicator anddetailed pedon descriptions of three neighboringnonhydric pedons.(b) Detailed vegetative data collected to representthe vegetation of the six pedons.Figure 4.Proper installation of the right kinds ofmonitoring devices is important to obtainapproval of changes and additions to the hydricsoil indicators.3. All requests involving 1 and 2 above additionallyrequire a short written plan that(a) Identifies the problem,(b) Explains the rationale for the request, and(c) Provides the following:– person responsible and point of contact(e–mail and mail addresses and phonenumber)– timeline for supporting data and final reportto be delivered to NTCHS– timeline needed for final NTCHS decision– partners involved in projectRequests and data should be sent to:Wade Hurt, ChairNTCHS Field Indicator SubcommitteeP.O. Box 110290University of FloridaGainesville, FL 32611-0290e-mail: Wade_Hurt@mail.ifas.ufl.edu4 (430, FIHS, Ver. 5.01, March 2003)
Field Indicators of Hydric SoilsField Indicators of Hydric Soils in the UnitedStates is structured as follows:1. Alpha-numeric listing2. Short name3. Applicable Land Resource Regions (LRRs)4. Description of the field indicator5. User notesFor example, A1 indicates the first indicator for allsoils; Histosol or Histel is the short name; the indicatoris for use in all LRRs; classifies as a Histosolexcept Folists is the field indicator description; andhelpful user notes are added.All soilsAll soils refers to soils that have any USDA soiltexture. Unless otherwise indicated, all minerallayers above any of the Indicators have dominantchroma 2 or less, or the layer(s) with dominantchroma of more than 2 is less than 15 cm (6 in) thick.Also, unless otherwise indicated, nodules and concretionsare not considered to be redox concentrations.Use the following Indicators regardless of texture.Histic Epipedon User Notes: Most histic epipedonsare surface horizons 20 cm (8 in) or more thick oforganic soil material. Aquic conditions or artificialdrainage are required. See Soil Taxonomy, (USDA,NRCS, Soil Survey Staff 1999). Slightly lower organiccarbon contents are allowed in plowed soils (ibid.).See glossary for definitions. See figure 37 (organicsoil material) in the glossary for organic carbonrequirements.A3. Black Histic. For use in all LRRs except W, X,and Y; for testing in LRRs W, X, and Y. A layer ofpeat, mucky peat, or muck 20 cm (8 in) or morethick starting within the upper 15 cm (6 in) ofthe soil surface having hue 10YR or yel-lower,value 3 or less, and chroma 1 or less (fig. 6).Black Histic User Notes: Unlike indicator A2 thisindicator does not require proof of aquic conditionsor artificial drainage. See glossary for definitions ofpeat, mucky peat, and muck. See figure 37 (organicsoil material) in the glossary for organic carbonrequirements.A1. Histosol (for use in all LRRs) or Histel (foruse in LRRs with permafrost). Classifies as aHistosol (except Folist) or as a Histel (exceptFolistel).Histosol User Notes: A Histosol has 40 cm (16 in)or more of the upper 80 cm (32 in) as organic soilmaterial (fig. 5). Organic soil material has an organiccarbon content (by weight) of 12 to 18 percent ormore, depending on the clay content of the soil. Thematerial includes muck (sapric soil material), muckypeat (hemic soil material), or peat (fibric soil material).See glossary for definition of muck, muckypeat, peat, and organic soil material. See figure 37(organic soil material) in the glossary for organiccarbon requirements. Histels are similar to Histosolsexcept they are underlain by permafrost.A2. Histic Epipedon. For use in all LRRs except W,X, and Y; for testing in LRRs W, X, and Y. A histicepipedon.Figure 5.Indicator A1 Histosols. Muck (sapric soilmaterial) is more than 80 cm thick. Scale isfeet (R) and m (L).(430, FIHS, Ver. 5.01, March 2003) 5
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