For use in MLRA 150 of LRR T; for testing in all LRRs with Vertisols and Vertic intergrades.

In Vertisols and Vertic intergrades, a positive reaction to alpha-alpha-dipyridyl that:

1. is the dominant (60 percent or more) condition of a layer 10 cm (4 inches) or more thick starting at a depth of 30 cm (12 inches) or less; or 5 cm (2 inches) or more thick starting at a depth 15 cm (6 inches) or less from the muck or mineral surface,

2. occurs for 7 or more continuous days and 28 cumulative days, and

3. occurs during a normal or drier season and month.

User Notes: The time requirements for this indicator were identified from research in MLRA 150A in LRR T (Gulf Coast Prairies). These requirements or slightly modified time requirements may be used to identify wetland Vertisols and Vertic intergrades in other parts of the Nation. These soils generally have thick, dark surface horizons, but indicators A11, A12, and F6 commonly are not evident, possibly because of masking of redoximorphic features by organic carbon. These soils are a special case of the “Problem Soils with Thick, Dark A Horizons” listed in the “Corps of Engineers Wetlands Delineation Manual“ (Environmental Laboratory, 1987).