LOCATION TERRAD MTEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, frigid Typic Argiustolls
TYPICAL PEDON: Terrad silty clay, cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--O to 6 inches, dark reddish gray (5YR 4/2) silty clay, dark reddish brown (5YR 3/3) moist; moderate fine and very fine granular structure; hard, friable, moderately sticky and moderately plastic; common fine and very fine roots; neutral (pH 6.8); abrupt wavy boundary.
Bt--6 to 15 inches, weak red (2.5YR 4/2) clay, dark reddish brown (2.5YR 3/4) moist; moderate medium prismatic structure parting to strong fine and very fine blocky; very hard, firm, moderately sticky and very plastic; common fine and very fine roots; many fine and very fine pores; faint continuous clay films on faces of peds; neutral (pH 6.8); clear irregular boundary.
Bk1--15 to 26 inches, reddish brown (2.5YR 5/4) clay, reddish brown (2.5YR 4/4) moist; moderate medium prismatic structure parting to moderate fine and very fine subangular blocky; very hard, firm, moderately sticky and moderately plastic; few fine and very fine roots; few fine and very fine pores; common medium and coarse soft masses of segregated lime; strongly effervescent; moderately alkaline (pH 8.0); gradual wavy boundary.
Bk2--26 to 45 inches, reddish brown (2.5YR 5/4) silty clay, reddish brown (2.5YR 4/4) moist; weak fine and very fine subangular blocky structure; extremely hard, firm, moderately sticky and moderately plastic; few very fine roots; common fine and very fine pores; common shale fragments; strongly effervescent; moderately alkaline (pH 8.0); gradual wavy boundary.
Cr--45 to 60 inches, weak red (2.5YR 4/2) interbedded shale and mudstone; slightly effervescent moderately alkaline (pH 8.0).
TYPE LOCATION: Cascade County, Montana; 1,600 feet east and 2220 feet north of the southwest corner of sec. 13, T.19N., R.6E.
RANGE IN CHARACTERISTICS:
Depth to the paralithic contact - 40 to 60 inches
Ap horizon
Hue: 5YR to 10R
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3.
Texture: clay loam, clay or silty clay
Clay content: 35 to 50 percent
Reaction: pH 6.6 to 7.8
Bt horizon
Hue: 5YR to 10R
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 3 or 4
Texture: silty clay or clay
Clay content: 45 to 60 percent
Reaction: pH 6.6 to 7.8
Bk horizons
Hue: 5YR to 10R
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: silty clay or clay
Clay content: 40 to 55 percent
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 9.0
Some pedons have 5 to 25 percent shale fragments
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - uplands
Elevation - 2,800 to 4,800 feet
Slope - 0 to 15 percent
Parent material - alluvium over shale or residuum over shale
Mean annual temperature - 40 to 45 degrees F.
Mean annual precipitation - 15 to 19 inches
Frost-free period - 100 to 135 days
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: uSed mainly for dryland cropland and irrigated cropland, but some areas are used for range. Native grasses are primarily rough fescue, bluebunch wheatgrass, green needlegrass, and forbs and shrubs.
DISTRIBUTION AND EXTENT: Terrad soils occur primarily in central Montana and east of the mountains. They are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Judith Basin County, Montana, 1963.
REMARKS: Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the surface to 7 inches mixed (Ap horizon); an argillic horizon which is the particle-size control section from 6 to 15 inches (Bt horizon); horizons of secondary carbonate accumulation from 15 to 45 inches (Bk1 and Bk2 horizons); a paralithic contact at 45 inches (Cr horizon). Terrad soils have an ustic moisture regime and a frigid temperature regime.