Field Indicators of Hydric Soils in the United States - ITC

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Field Indicators of Hydric Soilscolors of 4/1, 4/2, and 5/2. A, E, and calcic horizonsmay have low chromas and high values and may,therefore, be mistaken for a depleted matrix; however,they are excluded from the concept of depletedmartix unless common or many, distinct or prominentredox concentrations as soft masses or pore liningsare present.F10. Marl. For use in LRR U. A layer of marl thathas a value 5 or more starting within 10 cm (4in) of the soil surface (fig. 30).Marl User Notes: Marl is a limnic material depositedin water by precipitation of CaCO 3 by algae asdefined in Soil Taxonomy (USDA, NRCS, Soil SurveyStaff. 1999). It has a Munsell value 5 or more andreacts with dilute HCl to evolve CO 2 . Marl is not thecarbonatic substrate material associated with limestonebedrock. Some soils have materials with all theproperties of marl except they lack the requiredMunsell value. These soils are hydric if the requiredvalue is present within 10 cm (4 in) of the soil surface.Normally this indicator occurs at the soil surface.Figure 29. Indicator F8 Redox Depressions. This soil hasmainly iron redox concentrations in the upperpart and iron/manganese in the lower part.Scale is cm (L) and inches (R).F11. Depleted Ochric. For use in MLRA 151 ofLRR T. A layer(s) 10 cm (4 in) or more thickthat has 60 percent or more of the matrix withvalue 4 or more and chroma 1 or less. The layeris entirely within the upper 25 cm (10 in) of thesoil surface.Depleted Ochric User Notes: This indicator is applicableon accreting deltaic areas of the MississippiRiver.F12. Iron/Manganese Masses. For use in LRRs N,O, P, and T; for testing in LRR M. On flood plains,a layer 10 cm (4 in) or more thick with 40 percentor more chroma 2 or less, and 2 percent ormore distinct or prominent redox concentrationsas soft iron/manganese masses and diffuseboundaries. The layer occurs entirely within 30cm (12 in) of the soil surface. Iron/manganesemasses have value 3 or less and chroma 3 or less;most commonly they are black (fig. 31). Thethickness requirement is waived if the layer isthe mineral surface layer.Iron/Manganese Masses User Notes: These iron/manganese masses are usually small (2 to 5 mm) andhave a value and chroma 3 or less. They can be black.Figure 30. Indicator F10 Marl. This indicator is known tooccur only in south Florida. Scale is feet.18 (430, FIHS, Ver. 5.01, March 2003)
Field Indicators of Hydric SoilsThe low matrix chroma is because of wetness and isnot a relict or parent material feature. Iron/manganesemasses should not be confused with the largerand redder iron nodules associated with plinthite(USDA, NRCS, 2002) or with concretions that havesharp 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. Indepressions and other concave landforms, alayer 25 cm (10 in) or more thick starting within15 cm (6 in) of the soil surface in which theupper 15 cm (6 in) must have value 3 or less andchroma 1 or less, and the lower 10 cm (4 in) ofthe layer must have the same colors as above orany other color that has a chroma 2 or less (fig.32).Umbric Surface User Notes: Thickness requirementsmay be slightly less than those required for anumbric epipedon. Microlows are not considered to beconcave landforms. Umbric surfaces on higherlandscape positions, such as side slopes dominatedby Humic Dystrudepts, are excluded.F14. Alaska Redox Gleyed. For use in LRRs W, X,and Y. A layer that has dominant matrix hue 5Ywith chroma 3 or less, or hue N, 10Y, 5GY, 10GY,5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB, with 10percent or more redox concentrations as porelinings with value and chroma 4 or more. Thelayer occurs within 30 cm (12 in) of the soilsurface.Alaska Redox Gleyed User Notes: Presence of 10percent redox concentrations as pore linings in adominantly gleyed matrix (hue N, 10Y, 5GY, 10GY, 5G,10G, 5BG, 10BG, 5B, 10B, or 5PB with value 4 ormore); 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 percent hue N, 10Y, 5GY,10GY, 5G, 10G, 5BG, 10BG, 5B, 10B, or 5PB withvalue 4 or more in the matrix or along channelscontaining dead roots or no roots within 30 cm(12 in) of the soil surface. The matrix has dominantchroma 2 or less.Alaska Gleyed Pores User Notes: Presence of 10percent gleyed root channels within a low chromamatrix is required.Figure 32. Indicator F13 Umbric Surface. This umbricsurface is about 20 cm thick. Scale is inches.Figure 31. Indicator F12 Iron/Manganese Masses in a 40percent depleted matrix. Scale is inches.(430, FIHS, Ver. 5.01, March 2003) 19
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Field Indicators of Hydric Soils in the United States - ITC

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