LOCATION DAST MT+WYEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Typic Calciustepts
TYPICAL PEDON: Dast fine sandy loam in grassland (colors are for dry soil unless otherwise noted).
A--0 to 3 inches; pale brown (10YR 6/3) fine sandy loam, olive brown (2.5Y 4/4) moist; weak fine granular structure; loose, nonsticky and nonplastic; many fine and very fine roots and few medium roots; disseminated lime; strongly effervescent; slightly alkaline (pH 7.4); clear smooth boundary. (2 to 6 inches thick)
Bw1--3 to 9 inches; pale brown (10YR 6/3) fine sandy loam, olive brown (2.5Y 4/4) moist; weak coarse and very coarse prismatic structure parting to weak fine subangular blocky; soft, very friable, nonsticky and nonplastic; many fine roots and common very fine roots; many fine and very fine pores; disseminated lime; strongly effervescent; moderately alkaline (pH 7.4); gradual smooth boundary.
Bw2--9 to 21 inches; light yellowish brown (2.5Y 6/4) fine sandy loam, light olive brown (2.5Y 5/4) moist; weak medium subangular blocky; soft, very friable, nonsticky and nonplastic; common fine and very fine roots; many and common fine and very fine pores; disseminated lime; strongly effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (The combined thickness of the Bw horizons is 10 to 24 inches.)
Bk--21 to 35 inches; very pale brown (10YR 7/3) fine sandy loam, yellowish brown (10YR 5/4) moist; weak coarse prismatic; soft, very friable, nonsticky and slightly plastic; few fine and very fine roots; few fine and very fine pores; many fine and medium masses of lime; violently effervescent; moderately alkaline (pH 8.4); clear smooth boundary. (7 to 15 inches thick)
Cr--35 to 60 inches; brownish yellow (10YR 6/6) weakly consolidated sedimentary beds that crush to loamy fine sand, yellowish brown (10YR 5/6) moist; strongly effervescent; strongly alkaline (pH 9.0).
TYPE LOCATION: Prairie County, Montana; 1,100 feet north and 1,400 feet west of the SE corner of sec. 1, T. 16 N., R. 47 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 8 and 24 inches.
Depth to Bk horizon - 12 to 24 inches.
Depth to Cr horizon - 20 to 40 inches.
A horizon - Hue: 10YR or 2.5Y
Value: 4, 5, or 6 dry; 3, 4 or 5 moist
Chroma: 2, 3, or 4
Texture: fine sandy loam or sandy loam
Clay content: 2 to 18 percent
Rock fragments: 0 to 15 percent pebbles or channers
Reaction: pH 7 4 to 8.4
Bw1 horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: fine sandy loam, sandy loam, loam
Clay content: 2 to 18 percent
Rock fragments: 0 to 15 percent pebbles or channers
Reaction: pH 7.4 to 8.4
Bw2 horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: fine sandy loam, sandy loam, loam
Clay content: 2 to 18 percent
Rock fragments: 0 to 15 percent pebbles or channers
Reaction: pH 7.4 to 8.4
Bk horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture: fine sandy loam, sandy loam, loam
Clay content: 2 to 18 percent
Rock fragments: 0 to 15 percent pebbles or channers
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
COMPETING SERIES:
Ambrant (MT) - is very deep; has horizon which contains lamellae; has 2C horizon at 28 to 46 inches.
Kellygulch (MT) - has lithic contact at 23 to 40 inches; does not have horizon of secondary carbonate accumulation; formed in colluvium and residuum from granite.
Lisk (MT) - is very deep.
Ramps (UT) - have a lithic contact at a moderate depth; have 15 to 35 percent coarse fragments throughout the profile.
GEOGRAPHIC SETTING:
Landform - sedimentary plains and hills.
Elevation - 2,900 to 5,000 feet.
Slopes- 0 to 70 percent.
Parent material - alluvium, colluvium, and residuum derived from semiconsolidated sandstone.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 12 to 19 inches, of which more than half falls in spring and early summer.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 90 to 135 days. In Wyoming the frost-free period is 80 to 100 days.
DRAINAGE AND PERMEABILITY: Well-drained; moderately rapid permeability.
USE AND VEGETATION: These soils are used for nonirrigated crops and rangeland. The potential native vegetation is mainly prairie sandreed, little bluestem, needleandthread, and thickspike wheatgrass, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Dast soils are in the eastern part of Montana. They are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Big Horn County, Montana, 1970.
REMARKS: Soil interpretation records: MT0006.
Diagnostic horizons and features recognized in this pedon are: ochric epipedon - from the soil surface to 7 inches (A, Bw1 horizons); cambic horizon - from 3 to 21 inches (Bw1, Bw2 horizons); accumulation of lime - from 21 to 35 inches (Bk horizon); particle-size control section - from 10 inches to the paralithic contact (Bw2, Bk horizons). Dast soils have a frigid temperature regime and an ustic moisture regime.