LOCATION BRUSHTON MTEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Aridic Argiustolls
TYPICAL PEDON: Brushton silt loam, nonirrigated cropland (colors are for dry soil unless otherwise noted).
Ap--0 to 6 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure parting to moderate medium and coarse granular; soft, friable, sticky and slightly plastic; many fine and very fine roots; slightly alkaline (pH 7.6); clear smooth boundary. (5 to 7 inches thick)
Bt1--6 to 12 inches; brown (10YR 4/3) silty clay loam, dark brown (10YR 3/3) moist; moderate coarse prismatic structure parting to strong fine and medium angular blocky; hard, firm, sticky and plastic; many fine and very fine roots; common fine and very fine pores; very few faint clay films on faces of peds; slightly alkaline (pH 7.6); clear wavy boundary.
Bt2--12 to 18 inches; brown (10YR 5/3) silty clay loam, brown (10YR 4/3) moist; moderate coarse prismatic structure parting to strong medium angular blocky; very hard, firm, sticky and plastic; many fine and very fine roots; many fine and very fine roots; common very few faint clay films on faces of peds; slightly alkaline (pH 7.6); gradual wavy boundary. (The combined thickness of the Bt horizons is 6 to 12 inches.)
Bk1--18 to 28 inches; pale brown (10YR 6/3) silty clay loam, brown (10YR 5/3) moist; moderate coarse prismatic structure parting to moderate coarse subangular blocky; hard, firm, sticky and plastic; common very fine roots; common very fine pores; common fine and medium rounded masses of lime; violently effervescent; moderately alkaline (pH 8.0); clear wavy boundary. (5 to 25 inches thick)
Bk2--28 to 36 inches; pale brown (10YR 6/3) silt loam, grayish brown (10YR 5/2) moist; moderate coarse prismatic structure; hard, firm, slightly sticky and slightly plastic; common very fine roots; common fine and very fine pores; common fine irregular masses of lime; violently effervescent; moderately alkaline (pH 8.0); gradual wavy boundary. (0 to 15 inches thick)
BC--36 to 60 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; moderate coarse prismatic structure; soft, friable, slightly sticky and slightly plastic; strongly effervescent; moderately alkaline (pH 8.2).
TYPE LOCATION: Custer County, Montana; 1,500 feet north and 1,900 feet west of the SE corner of sec. 12, T. 8 N., R. 52 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Mositure control section - between 4 and 12 inches, dry in some part for six tenths or more of the cumulative days per year when the soil temperature at a depth of 20 inches is higher than 41 degrees F.
Mollic epipedon thickness - 7 to 15 inches; in some pedons it includes all or only the upper part of the Bt horizon.
Depth to Bk horizon - 10 to 24 inches.
Ap horizons - Hue: 2.5Y or 10YR
Chroma: 2 or 3
Clay content: 15 to 27 percent
Reaction: pH 6.6 to 7.8
Bt horizons - Hue: 2.5Y or 10YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 or 3
Clay content: 27 to 35 percent
Reaction: pH 6.6 to 7.8
Bk horizons - Hue: 2.5Y or 10YR
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: silt loam or loam
Clay content: 15 to 27 percent
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 8.4
BC horizon - Hue: 2.5Y or 10YR
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: silt loam, loam, or very fine sandy loam
Clay content: 15 to 25 percent
Reaction: pH 7.9 to 9.0
COMPETING SERIES:
Brussett (CO) - has argillic horizons thicker than 19 inches; has bleached sand grains on faces of peds; receives 17 to 21 inches of precipitation.
Norkool (WY) - has secondary calcium carbonate accumulation in the lower part of the argillic horizon; has argillic horizons more than 16 inches thick; receives 15 to 19 inches of precipitation.
Ralph (SD) - has a paralithic contact at depths between 20 and 40 inches.
Vassett (WY) - has argillic horizons more than 12 inches thick; has hues of 7.5YR and redder throughout the soil; receives 15 to 19 inches of precipitation;
Waas (UT) - has hue of 7.5YR and redder throughout the soil; has an argillic horizon that is thicker than 18 inches; receives 15 to 16 inches of precipitation; is at elevations over 7,200 feet;
GEOGRAPHIC SETTING:
Landform - alluvial fans; stream terraces; sedimentary plains.
Elevation - 2,000 to 2,900 feet.
Slope- 0 to 8 percent.
Parent material - alluvium.
Climate - long cold winters; moist spring; warm summers.
Mean annual air temperature - 42 to 45 degrees F.
Mean annual precipitation - 11 to 14 inches.
Frost-free period - 90 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: Brushton soils are used mainly for nonirrigated cropland and rangeland. Potential native vegetation is mainly green needlegrass, western wheatgrass, needleandthread, blue grama, and prairie junegrass.
DISTRIBUTION AND EXTENT: Brushton soils are of small extent. They are on the sedimentary plains of eastern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Custer County, Montana; 1995.
REMARKS: Soil interpretation record: MT1472. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 12 inches, mixed (Ap, Bt1 horizons); an argillic horizon from 6 to 18 inches (Bt1, Bt2 horizons); a particle-size control section from 6 to 18 inches (Bt1, Bt2 horizons); horizons of secondary calcium carbonate accumulation from 18 to 36 inches (Bk1, Bk2 horizons). Brushton soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.