Field Indicators of Hydric Soils in the United States - ITC

Field Indicators of Hydric SoilsA9. 1 cm Muck. For use in LRRs D, F, G, H, P,and T; for testing in LRRs I, J, and O. A layer ofmuck 1 cm (0.5 in) or more thick with value 3or less and chroma 1 or less starting within 15cm (6 in) of the soil surface.1 cm Muck User Notes: Unlike Indicator A8 MuckPresence, there is a minimum thickness requirementof 1 cm. Normally this expression of anaerobiosis isat the soil surface; however, it may occur at anydepth within 15 cm (6 in). Muck is sapric soil materialwith at least 12 to 18 percent organic carbon.Organic soil material is called muck (sapric soilmaterial) if virtually all of the material has undergonesufficient decomposition to limit recognition ofthe plant parts. Hemic (mucky peat) and fibric (peat)soil materials do not qualify. To determine if muck ispresent, first remove loose leaves, needles, bark, andother easily identified plant remains. This is sometimescalled a leaf/root mat. Then examine for decomposedorganic soil material. Generally, muck isblack and has a greasy feel; sand grains should not beevident. Hydric soil indicator determinations aremade below the leaf or root mat; however, root matsthat meet the definition of hemic or fibric soil materialare included in the decisionmaking process forMucky Peat, Peat, Organic Bodies, or Histic Indicators.See the glossary for the definition of muck. Seefigure 37 (organic soil material) in the glossary fororganic carbon requirements.A10. 2 cm Muck. For use in LRRs M and N; fortesting in LRRs A, B, C, E, K, L, S, W, X, Y, and Z. Alayer of muck 2 cm (0.75 in) or more thick withvalue 3 or less and chroma 1 or less startingwithin 15 cm (6 in) of the soil surface.2 cm Muck User Notes: This Indicator requires aminimum muck thickness of 2 cm. Normally thisexpression 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 to18 percent organic carbon. Organic soil material iscalled muck (sapric soil material) if virtually all ofthe material has undergone sufficient decompositionto limit recognition of the plant parts. Hemic (muckypeat) and fibric (peat) soil materials do not qualify.To determine if muck is present, first remove looseleaves, needles, bark, and other easily identifiedplant remains. This is sometimes called a leaf/rootmat. Then examine for decomposed organic soilmaterial. Generally, muck is black and has a greasyfeel; sand grains should not be evident. Hydric soilindicator determinations are made below the leaf orroot mat; however, root mats that meet the definitionof hemic or fibric soil material are included in thedecisionmaking process for Mucky Peat, Peat, OrganicBodies, or Histic Indicators. See the glossaryfor the definition of muck. See figure 37 (organic soilmaterial) in the glossary for organic carbon requirements.Sandy soilsSandy soils refers to those soils that have a USDAtexture of loamy fine sand and coarser. Unless otherwiseindicated, all mineral layers above any of theIndicators have dominant chroma 2 or less, or thelayer(s) with dominant chroma of more than 2 is lessthan 15 cm (6 in) thick. In addition, unless otherwiseindicated, nodules and concretions are not consideredto be redox concentrations. Use the following sandyIndicators for sandy mineral soil materials:S1. Sandy Mucky Mineral. For use in all LRRsexcept W, X, and Y. A mucky modified sandy minerallayer 5 cm (2 in) or more thick startingwithin 15 cm (6 in) of the soil surface.Sandy Mucky Mineral User Notes: Mucky is aUSDA texture modifier for mineral soils. The organiccarbon content is at least 5 percent and ranges to ashigh as 14 percent for sandy soils. The percent-agerequirement is dependent upon the clay content ofthe soil; the higher the clay content, the higher theorganic carbon requirement. An example is muckyfine sand that has at least 5 percent organic carbon,but not more than about 12 percent organic carbon.See the glossary for the definition of mucky modifiedmineral texture. See figure 37 (organic soilmaterial) in the glossary for organic carbon requirements.S2. 2.5 cm Mucky Peat or Peat. For use in LRRs Gand H. A layer of mucky peat or peat 2.5 cm (1in) or more thick with value 4 or less andchroma 3 or less starting within 15 cm (6 in) ofthe soil surface underlain by sandy soil material.2.5 cm Mucky Peat and Peat User Notes: Muckypeat (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 ofthe plant remains are sufficiently intact to permitidentification of plant remains. Mucky peat is an(430, FIHS, Ver. 5.01, March 2003) 9