Hydric Soils Technical Note 9
Additional changes to "Field Indicators of Hydric Soils in the United States" (Version 4.0, March 1998).
Send comments to Wade Hurt.
The NTCHS met in Indianapolis, Indiana in August 1999 and made the following changes and corrections.
Change 1: On page 7, A6, column 1, next to last sentence in User Notes should read as follows: Organic bodies of hemic (mucky peat) and/or fibric (peat) soil materials do not qualify as this indicator.
Change 2: On page 15, F4, column 1 definition of Depleted Below Dark Surface. Insert the following sentence between the 2 existing sentences: The minimum thickness requirement of the depleted matrix is 5 cm (2 in.) if it consists of fragmental soil material (see glossary).
Change 3: On page 17, F9, top of column 2 the words "iron/manganese soft masses and/or pore linings are required in soils with matrix colors of 4/1, 4/2, and 5/2" are deleted.
Change 4: On Page 18, F11, The For Use statement in changed to read as: For use in MLRA 151 of LRR T.
Change 5: On page 21, TF4, bottom of column 1 the following is added: value 4 or more and chroma 1; or hue 5Y or yellower,. Therefore, the sentence starting in column 1 and ending in column 2 is: A layer at least 15 cm (6 in.) thick with 60% or more hue 2.5 Y or yellower, value 4 or more, and chroma 1; or hue 5Y or yellower, value 4 or more, and chroma 2 or less starting within 30 cm (12 in.) of the soil surface.
Change 6: On page 22, add the following test indicator:
TF11. Reduced Vertic. For testing in all LRRs with Vertisols and Vertic intergrades. In Vertisols and Vertic intergrades, a positive reaction to alpha-alpha-Dipyridyl that: (a) is the dominant (60% or more) condition of a layer at least 4 inches thick within the upper 12 inches (or at least 2 inches thick within the upper 6 inches) of the mineral or muck soil surface, (b) occurs for at least 7 continuous days and 28 cumulative days, and (c) occurs during a normal (within 16-84% of probable precipitation) or drier season and month. Please follow the procedures and note the considerations in Hydric Soil Tech. Note 8 (use of alpha-alpha-Dipyridyl).
Reduced Vertic User Notes: The time requirements for this indicator were identified from research in MLRA 150A in LRR T (Gulf Coastal Prairies); these or slightly modified time requirements may be found to identify wetland Vertisols and Vertic Intergrades in other parts of the nation. These soils usually have thick dark surface horizons but Indicators F4, F5, and F6 are often lacking; possibly due to 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 1987 Corps of Engineers Wetlands Delineation Manual.
Change 7: On page 24, Glossary, add the following term and definition:
Fragmental Soil Material - Soil material that consists of 90% or more rock fragments. Less than 10% of the volume consists of particles 2 mm or smaller.
Change 8: On page 13, F1, Loamy Mucky Mineral, the first sentence is changed to For use in all LRRs except N, R, S, V, W, X, Y, those using A7, and MLRA 1 of LRR A.
Change 9: On page 29, Table 2 add TF11 (Reduced Vertic) to the list of Indicators that correlate to the 1987 Manual problem soils (soils with thick dark A horizons) following TF7 (Thick Dark Surface 2/1).
Change 10: On page 20, TS2 (Thick Sandy Dark Surface), last sentence; on page 20, TS2 (Dark Surface 2), first sentence; and on page 21, TF5 (2.5Y/5Y Below Thick Dark Surface) change value 2 to value 2.5.