LOCATION AMHERST MT+UTEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, frigid Lithic Argiustolls
TYPICAL PEDON: Amherst loam, grassland. (Colors are for dry soil unless otherwise noted)
A--0 to 2 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, very friable, slightly sticky, nonplastic; many very fine roots; many very fine pores; neutral (pH 7.1); abrupt wavy boundary. (2 to 6 inches thick)
Bt1--2 to 5 inches; dark grayish brown (10YR 4/2) channery heavy loam, very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to moderate fine subangular blocky; slightly hard, friable, slightly sticky, slightly plastic; many very fine roots; many very fine tubular pores; many faint clay skins on faces of peds; 20 percent sandstone and shale channers; neutral (pH 7.1); clear wavy boundary. (1 to 8 inches thick)
Bt2--5 to 10 inches; brown (10YR 5/3) channery light clay, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to strong fine subangular blocky; hard, firm, sticky, plastic; common very fine roots; many very fine pores; many prominent brown (10YR 4/3) clay skins on faces of peds; 30 percent shale and sandstone channers; neutral (pH 7.3); clear wavy boundary. (3 to 10 inches thick)
R--10 inches; hard fractured shale and sandstone with thin clay skins between layers and around rock fragments in the upper 6 inches.
TYPE LOCATION: Yellowstone County, Montana; 1,690 feet north and 2,190 feet west of the SE corner of sec. 20, T. 3 N., R. 26 E.
RANGE IN CHARACTERISTICS:
Soil temperature: 42 to 47 degrees F.
Moisture control section: approximately between the depths of 4 and 12 inches Mollic epipedon thickness: 7 to 12 inches (includes A, Bt1, and part or all of Bt2)
Control section: 35 to 50 percent clay and 0 to 5 percent cobbles, 15 to 30 percent channers
Depth to bedrock: 10 to 20 inches
NOTE: Some pedons have a thin BC horizon that has up to 80 percent coarse fragments that have some lime crusts on the undersides.
Phases recognized: cool, moderate temperature, high elevation.
A horizon -
Hue: 7.5YR, 10YR, 2.5Y
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3
Texture, less than 2 mm: loam, clay loam
Clay content: 20 to 35 percent
Rock fragments: 0 to 35 percent - cobbles, 0 to 5 percent; channers, 0 to 30 percent
Reaction: pH 6.6 to 7.8
Bt1 horizon -
Hue: 7.5YR, 10YR, or 2.5Y
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3
Texture, less than 2 mm: loam or clay loam
Clay content: 20 to 35 percent
Rock fragments: 0 to 35 percent - stones and cobbles, 0 to 5 percent; pebbles, 0 to 30 percent
Reaction: pH 6.6 to 7.8
Bt2 horizon -
Hue: 7.5YR, 10YR, or 2.5Y
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: clay loam or clay
Clay content: 35 to 50 percent
Rock fragments: 15 to 35 percent - stones and cobbles, 0 to 5 percent; pebbles, 15 to 30 percent
Reaction: pH 6.6 to 7.8
COMPETING SERIES: This is the Fivepine series. The Fivepine series have precipitation that is evenly distributed throughout the year and have rock fragments dominated by flagstones.
GEOGRAPHIC SETTING: The Amherst soils are on uplands, hills, sedimentary plains and strath terraces. Elevations are 3,200 to 5,000 feet. It ranges up to 6,000 feet in the foothills of the mountains. Slopes are 0 to 35 percent. These soils formed in material derived from hard sandstone and shale. The climate is characterized by long, cold winters; moist springs; and warm summers. Mean annual precipitation is 14 to 19 inches. Mean annual temperature is 40 to 45 degrees F. The frost-free period is 105 to 130 days. It ranges down to 70 days in the foothills of the mountains.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderately slow permeability.
USE AND VEGETATION: Amherst soils are used mainly as rangeland. Potential native vegetation is mainly bluebunch wheatgrass, green needlegrass, and western wheatgrass.
DISTRIBUTION AND EXTENT: Amherst soils are mainly in central Montana, Utah, and Colorado.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Big Horn County (Area), Montana, 1970.
REMARKS: Soil Interpretation Records: MT0180, MT0853. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon after mixing the top 7 inches (A, Bw, and part of Bt horizon); an argillic horizon; a particle-size control section from the surface to 14 inches (A, Bt1, Bt2 horizons) or the argillic horizon if deeper than 14 inches to the lithic contact. Lithic Argiborolls feature: a lithic contact above a depth of 20 inches, an argillic horizon, and a mollic epipedon. Amherst soils have an ustic moisture regime and a frigid temperature regime.