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Determining soil texture from sand, silt, and clay content
The following files and ARC/INFO AML instructions calculate soil texture based on the values of sand, silt and clay found in the Soil Layer File (SLF). The calculations are based on the definitons found in the CanSIS manual for describing soils in the field (which are identical to those found in the Glossary? and the American system). Please note the ambiguity for values bordering SiL,L and SiCL,CL. Here, these textures are assigned to the SiL,L classes.ARCVIEW 2.1 instructions
The percent2texture.dbf file can be used to assign texture classes where percent sand, silt, and clay are known. The file is joined to the SLF by creating a texture_key field in the SLF. Calculate the texture_key to equal:([Sand] * 1000000) + ([Silt] * 1000) + [Clay]
The texture2percent.dbf file can be used to estimate percentages of sand, silt, and clay from texture class information.
ARC/INFO 7 instructions
the AML requires that there be a texture field and a temp field.
ITEM NAME WDTH OPUT TYP N.DEC TEXTURE 20 20 C - TEMP 4 4 I -i.e, if your info file is called SLF, then
additem SLF SLF TEXTURE 20 20 C additem SLF SLF TEMP 4 4 I
&data ARC INFO ARC SELECT TEXTURE ASEL RESEL SAND GE 85 CALC TEMP = CLAY * 1.5 + SILT RESEL TEMP LE 15 MOVE 'SAND' TO TEXTURE CALC S = 1 NSEL CALC TEMP = CLAY * 2 + SILT RESEL TEMP LE 30 MOVE 'LOAMY SAND' TO TEXTURE CALC LS = 1 ASEL CALC TEMP = CLAY * 2 + SILT RESEL TEMP GT 30 RESEL CLAY LT 7 RESEL SILT LT 50 MOVE 'SANDY LOAM' TO TEXTURE CALC SL = 1 ASEL CALC TEMP = CLAY * 2 + SILT RESEL TEMP GT 30 RESEL CLAY GE 7 RESEL CLAY LE 20 RESEL SAND GE 52 MOVE 'SANDY LOAM' TO TEXTURE CALC SL = 1 ASEL RESEL CLAY GE 7 RESEL CLAY LE 27 RESEL SILT GE 28 RESEL SILT LT 50 RESEL SAND LT 52 MOVE 'LOAM' TO TEXTURE CALC L = 1 ASEL RESEL SILT GE 50 RESEL CLAY GE 12 RESEL CLAY LE 27 MOVE 'SILT LOAM' TO TEXTURE CALC SIL = 1 ASEL RESEL SILT GE 50 RESEL SILT LT 80 RESEL CLAY LT 12 MOVE 'SILT LOAM' TO TEXTURE CALC SIL = 1 ASEL RESEL SILT GE 80 RESEL CLAY LT 12 MOVE 'SILT' TO TEXTURE CALC SI = 1 ASEL RESEL CLAY GT 20 RESEL CLAY LT 35 RESEL SILT LT 28 RESEL SAND GE 45 MOVE 'SANDY CLAY LOAM' TO TEXTURE CALC SCL = 1 ASEL RESEL CLAY GT 27 RESEL CLAY LT 40 RESEL SAND GT 20 RESEL SAND LT 45 MOVE 'CLAY LOAM' TO TEXTURE CALC CL = 1 ASEL RESEL CLAY GT 27 RESEL CLAY LT 40 RESEL SAND LE 20 MOVE 'SILTY CLAY LOAM' TO TEXTURE CALC SICL = 1 ASEL RESEL CLAY GE 35 RESEL SAND GE 45 MOVE 'SANDY CLAY' TO TEXTURE CALC SC = 1 ASEL RESEL CLAY GE 40 RESEL CLAY LE 60 RESEL SAND LT 45 RESEL SILT LT 40 MOVE 'CLAY' TO TEXTURE CALC C = 1 ASEL RESEL CLAY GE 40 RESEL SILT GE 40 MOVE 'SILTY CLAY' TO TEXTURE CALC SIC = 1 ASEL RESEL CLAY GT 60 MOVE 'HEAVY CLAY' TO TEXTURE CALC HC = 1 QUIT STOP &END
