LOCATION TOSTON MTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Aridic Natrustalfs
TYPICAL PEDON: Toston silty clay loam, rangeland (colors are for moist soil unless otherwise noted).
A--0 to 2 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; moderate thin platy structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine roots and pores; strongly alkaline (pH 8.8); abrupt smooth boundary. (1 to 3 inches thick)
Btny1--2 to 4 inches; very dark gray (10YR 3/1) silty clay, gray (10YR 6/1) dry; moderate medium columnar structure parting to moderate medium platy; very hard, firm, sticky and plastic; few fine roots; many fine tubular pores; common distinct clay films on faces of peds; common fine masses and filaments of gypsum; very strongly alkaline (pH 9.2); clear smooth boundary.
Btny2--4 to 8 inches; very dark grayish brown (2.5Y 3/2) silty clay, gray (10YR 6/1) dry; moderate medium subangular blocky structure; very hard, firm, sticky and plastic; streaks of organic stains on faces of some peds; common distinct clay films on faces of peds; common fine masses of gypsum; slightly effervescent; very strongly alkaline (pH 9.2); clear smooth boundary. (3 to 6 inches thick.)
Bknyz--8 to 16 inches; brown (10YR 5/3) silty clay loam, very pale brown (10YR 7/3) dry; weak medium subangular blocky structure; hard, friable, sticky and plastic; many fine tubular pores; common fine masses and filaments of gypsum and other salts; common fine masses of lime; strongly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (6 to 20 inches thick)
Bnyz--16 to 34 inches; brown (10YR 5/3) silt loam, light gray (10YR 7/2) dry; massive; hard, very friable, slightly sticky and slightly plastic; common fine faint brown (10YR 5/3) dry redox concentrations; disseminated lime; few to common fine masses and seams of gypsum and other salts; strongly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary.
C--34 to 60 inches; grayish brown (2.5Y 5/2) thinly stratified loam, sandy loam and loamy sand, light gray (2.5Y 7/2) dry; massive; hard, very friable, slightly sticky and nonplastic; common fine distinct brown (10YR 5/3) dry redox concentrations; strongly effervescent; moderately alkaline (pH 8.2).
TYPE LOCATION: Broadwater County, Montana; 2,100 feet west of the SW corner of sec. 36, T. 5 N., R. 1 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 40 to 47 degrees F.
Moisture control section - between 4 and 12 inches.
Depth to seasonal water table - 24 to 42 inches.
A horizon - Hue: 10YR or 2.5Y
Value: 4, 5, or 6 dry; 3, 4, or 5 moist
Chroma: 1, 2, or 3
Texture: loam, silt loam, silty clay loam, silty clay, or clay loam
Clay content: 18 to 45 percent
EC: 2 to 8 mmhos/cm
Reaction: pH 7.9 to 9.0
Btny horizons - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 3, 4, or 5 moist
Chroma: 1, 2, or 3
Texture: silty clay, silty clay loam, clay loam
Clay content: 35 to 45 percent with 15 to 35 percent sand coarser than very fine sand
SAR: 13 to 30
EC: 4 to 16 mmhos/cm
Gypsum: 1 to 3 percent
Reaction: pH 8.4 to 9.6
Bknyz horizon - Hue: 10YR or 2.5Y
Value: 5, 6 or 7 dry; 3, 4 or 5 moist
Chroma: 1, 2, or 3
Clay content: 27 to 35 percent with 15 to 35 percent sand coarser than very fine sand
Calcium carbonate equivalent: 5 to 15 percent
SAR: 13 to 30
EC: 8 to 16 mmhos/cm
Gypsum: 1 to 5 percent
Reaction: pH 8.4 to 9.6
Bnyz horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 3, 4, or 5 moist
Chroma: 1, 2, or 3
Texture: silt loam or silty clay loam stratified with silty clay, loam, loamy fine sand, or loamy sand
Clay content: 10 to 30 percent with 15 to 35 percent sand coarser than very fine sand
Redox concentrations: faint to prominent and common to many
Rock fragments: 0 to 10 percent pebbles
Calcium carbonate equivalent: 2 to 15 percent
SAR: 13 to 30
EC: 8 to 16 mmhos/cm
Reaction: pH 7.9 to 9.6
C horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 3, 4, or 5 moist
Chroma: 1, 2, or 3
Texture: stratified silty clay loam through loamy sand
Clay content: 10 to 30 percent
Redox concentrations: faint to prominent and common to many
Rock fragments: 0 to 10 percent pebbles
Calcium carbonate equivalent: 2 to 15 percent
EC: 8 to 16 mmhos/cm
SAR: 13 to 30
Reaction: pH 7.9 to 9.6
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - flood plains and stream terraces.
Elevation - 3,000 to 4,500 feet.
Slope- 0 to 5 percent.
Parent material - calcareous, strongly alkaline alluvium.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 10 to 14 inches.
Mean annual air temperature - 38 to 45 degrees F.
Frost-free period - 70 to 135 days.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow permeability through the Bt horizons and moderate permeability below.
USE AND VEGETATION: Toston soils are used mainly as rangeland. Potential native vegetation is mainly alkali sacaton, greasewood, western wheatgrass, basin wildrye, alkali cordgrass, and inland saltgrass.
DISTRIBUTION AND EXTENT: Toston soils are of limited extent in west-central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Broadwater County area, Montana, 1971.
REMARKS: Soil interpretations record: MT0275.
Diagnostic horizons and features recognized in this pedon are: natric horizon - from 2 to 18 inches (Btny1, Btny2, Bknyz, Bnyz horizons); particle-size control section - from 2 to 40 inches. Toston soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.
ADDITIONAL DATA: Laboratory sample S88MT-007-001.