Field Indicators of Hydric Soils in the United States - ITC

Field Indicators of Hydric SoilsF16. High Plains Depressions. For use in MLRAs72 and 73 of LRR H; for testing in other MLRAs ofLRR H. In closed depressions subject to ponding,a mineral soil that has chroma 1 or less to adepth of at least 35 cm (13.5 in) and a layer atleast 10 cm (4 in) thick within the upper 35 cm(13.5 in) of the mineral soil that has either:a. 1 percent or more redox concentrations asnodules or concretions, orb. redox concentrations as nodules orconcretions with distinct or prominentcorona.High Plains Depressions User Notes: This indicatoris for closed depressions (FSA playas) in westernKansas, southwestern Nebraska, eastern Colorado,and southeastern Wyoming. It occurs in soils such asthe Ness and Pleasant series. The matrix color of the35 cm (13.5 in) layer must be a chroma 1 or less;chroma 2 matrix colors are excluded; value is usually3. The nodules/concretions are rounded, hard to veryhard, range in size from less than 1 mm to 3 mm, andmost commonly are black or reddish black. Thecorona usually are reddish brown, strong brown, oryellowish brown. The nodules/concretions can beremoved from the soil, and the corona (halos) willoccur as coatings on the concentration or will remainattached to the soil matrix. Use of 10X to 15X magnificationaids in the identification of these features.Test Indicators of Hydric SoilsThe Indicators listed before this section should betested for use in LRRs other than those listed. OtherIndicators for testing are listed below. This list oftest indicators is not extensive. Users of the Indicatorsare encouraged to submit descriptions of othersoil morphologies they think indicative of hydricsoils along with supporting data for inclusion insubsequent versions of Field Indicators of HydricSoils in the United States.All soilsTA1. Playa Rim Stratified Layers. For testing inLRR D. Stratified layers starting within the upper15 cm (6 in) of the soil surface. At least onelayer has value 3 or less and chroma 1 or less orit has value 2 or more and chroma 2 or less with2 percent or more distinct or prominent redoxconcentrations as soft masses or pore linings.The upper 15 cm (6 in) has dominant chroma 2or less.Playa Rim Stratified Layers User Notes: Unlikethe Indicator A5 Stratified Layers, this indicator doesnot require continuous chroma 2 or less. Thin layersof chroma 3 or higher may occur as long as the upper15 cm (6 in) is dominantly chroma 2 or less. A minimumamount of organic carbon is not required. Alayer that has redox concentrations is substitutionalfor the dark layer. This indicator occurs on sparselyvegetated playas and playa rims adjacent tononvegetated playas.TA2. Structureless Muck. For testing in MLRAs141, 143, 144b, 145, and 146 of LRR R. Startingwithin 15 cm (6 in) of the soil surface on concavepositions or in depressions, a layer of muck2 cm (0.75 in) or more thick that has no soilstructure.Structureless Muck User Notes: Nonhydric muckhorizons have low moisture content and are usuallyfluffy or have weak to moderate structure. Hydricmuck horizons are usually wet and amorphous or, ifdry, then are hard and difficult to rewet.TA3. Coast Prairie Redox. For use in MLRA 150Aof LRR T. A layer starting within 15 cm (6 in) ofthe soil surface that is at least 10 cm (4 in)thick and has a matrix chroma 3 or less with 2percent or more distinct or prominent redoxconcentrations as soft masses or pore linings, orboth.Coast Prairie Redox User Notes: These hydricsoils occur mainly on depressional landforms andportions of the intermound landforms on the LissieFormation. Redox concentrations occur mainly asiron dominated pore linings (Vepraskas, 1994). Commonto many redox concentrations are required.Chroma 3 matrices are allowed because they may be20 (430, FIHS, Ver. 5.01, March 2003)