LOCATION SUMATRA MTEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, nonacid, frigid Aridic Ustorthents
TYPICAL PEDON: Sumatra silty clay loam, in grassland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; light brownish gray (2.5Y 6/2) silty clay loam, grayish brown (2.5Y 5/2) moist; moderate fine granular structure; soft, firm, sticky and plastic; common fine roots; strongly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (2 to 4 inches thick)
By--2 to 9 inches; light brownish gray (2.5Y 6/2) silty clay loam, grayish brown (2.5Y 5/2) moist; massive with some vertical cleavage; very hard, firm, sticky and plastic; few fine roots; few fine tubular pores; common fine soft masses of gypsum; strongly effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (5 to 8 inches thick)
BC--9 to 29 inches; light brownish gray (2.5Y 6/2) silty clay loam, light grayish brown (2.5Y 5/2) moist; massive; very hard, firm, sticky and plastic; few fine roots; few fine tubular pores; moderately alkaline (pH 8.2); gradual smooth boundary. (7 to 50 inches thick)
C2--29 to 60 inches; variegated light gray (2.5Y 7/2) and pale yellow (2.5Y 7/4) silty clay loam, light grayish brown (2.5Y 6/2) and light yellowish brown (2.5Y 6/4) moist; massive; very hard, firm, sticky and plastic; few fine roots; few fine tubular pores; moderately alkaline (pH 8.2).
TYPE LOCATION: Rosebud County, Montana; 1,600 feet south and 2,000 feet east of the NW corner of sec. 29, T. 9 N., R. 39 E.
RANGE IN CHARACTERISTICS:
Soil temperature:41 to 47 degrees F. Particle size control section: Texture, F2 mm:silty clay loam or clay loam Clay content:27 to 35 percent Sand fraction:F15 percent coarser than very fine sand
A horizon: Hue:2.5Y Value, dry:5 or 6 Value, moist:4 or 5 Chroma:2 Texture, F2 mm:loam, silt loam, silty clay loam, or clay loam Clay content:22 to 35 percent Reaction:pH 7.9 to 8.4
By horizon: Hue:2.5Y Value, dry:5 or 6 Value, moist:4 or 5 Chroma:2 or 4 Texture, F2 mm:silty clay loam or clay loam Clay content:27 to 35 percent EC:4 to 16 mmhos/cm SAR:10 to 25 Reaction:pH 7.9 to 8.4
C horizons: These horizons are commonly variegated. Very thin weathered sandstone laminations are common. Hue:10YR through 5Y Value, dry:5 through 7 Value, moist:4 through 6 Chroma:1 through 4 Texture, F2 mm:silty clay loam or clay loam Clay content:27 to 35 percent EC:16 to 30 mmhos/cm SAR:25 to 45 Reaction:pH 7.9 to 8.4 NOTE: The C horizons remain moist in some part during the growing season.
COMPETING SERIES: There are no competing series in this family.
GEOGRAPHIC SETTING: Sumatra soils are on sedimentary uplands. Elevations are 2,700 to 3,000 feet. Slopes are 2 to 35 percent. These soils formed in material derived from shale. The climate is cool with long, cold, dry winters; moist springs; and hot, dry summers. Mean annual precipitation is 10 to 14 inches. Mean annual temperature is 39 to 45 degrees F. The frost-free season is 115 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff on 2 to 8 percent slopes and rapid runoff on slopes greater than 8 percent; moderately slow permeability.
USE AND VEGETATION: Sumatra soils are used as rangeland. The potential native vegetation is alkali sacaton, western wheatgrass, inland saltgrass, black greasewood, and Nuttall saltbush.
DISTRIBUTION AND EXTENT: The Sumatra series is moderately extensive in northern Rosebud County.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Rosebud County, Montana, 1990. The name is that of a town in northern Rosebud County.