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 definitions 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 (download percent2texture.dbf data file). 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]

Note that the brackets are required in ARCVIEW.

The texture2percent.dbf file can be used to estimate percentages of sand, silt, and clay from texture class information ( download texture2percent.dbf data file).

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