LOCATION PROPOSAL MTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Oxyaquic Haplocryolls
TYPICAL PEDON: Proposal silt loam, in irrigated grass hay (colors are for dry soil unless otherwise noted).
Oi--0 to 2 inches; undecomposed and partially decomposed matted roots; abrupt smooth boundary. (1 to 4 inches thick)
A1--2 to 8 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; few fine faint brownish yellow (10YR 6/6) moist redox concentrations (due to prolonged saturation from flood irrigation); weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many fine and very fine dendritic tubular pores; neutral (pH 6.8); clear smooth boundary.
A2--8 to 16 inches; grayish brown (10YR 5/2) silt loam, dark brown (10YR 3/3) moist; few fine faint brownish yellow (10YR 6/6) moist redox concentrations (due to prolonged saturation from flood irrigation); moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many fine and very fine dendritic tubular pores; neutral (pH 7.0); clear wavy boundary. (combined thickness of A horizons is 10 to 15 inches)
Bw1--16 to 28 inches; pale brown (10YR 6/3) silt loam, dark yellowish brown (10YR 4/4) moist; common fine faint yellowish brown (10YR 5/6) moist redox concentrations (due to prolonged saturation from flood irrigation); moderate coarse subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; common very fine and few fine dendritic tubular pores; 5 percent gravel; slightly alkaline (pH 7.4); clear wavy boundary.
Bw2--28 to 45 inches; light brownish gray (10YR 6/2) silt loam, brown (10YR 4/3) moist; few fine faint yellowish brown (10YR 5/6) moist redox concentrations (due to prolonged saturation from flood irrigation); moderate coarse subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; common very fine and few fine dendritic tubular pores; 5 percent gravel; slightly alkaline (pH 7.6); clear wavy boundary. (combined thickness of Bw horizons is 15 to 35 inches).
Bk--45 to 60 inches; light gray (10YR 7/2) loam, pale brown (10YR 6/3) moist; moderate medium subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; few very fine roots; 10 percent gravel; disseminated lime and many medium and fine patchy soft masses and threads of lime; strongly effervescent; moderately alkaline (pH 8.2); clear wavy boundary.
TYPE LOCATION: Beaverhead County, Montana; approximately 700 feet south and 500 feet west of the NE corner of sec. 28, T 3 S., R 15 W. Wisdom topographic quadrangle, 12T, 308720e, 5047096n, NAD 83
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 35 to 40 degrees F., Cryic temperature regime.
Soil moisture control section - between 4 and 12 inches; dry in some or all parts for 90 or more cumulative days in normal years; not dry in all parts for more than half of the cumulative days. Ustic moisture regime.
Mollic epipedon thickness - 10 to 15 inches.
Depth to Bk horizon - 25 to 46 inches.
A horizons - Value: 4 or 5 dry; 2 or 3 moist
Chroma: 1, 2 or 3
Clay content: 18 to 27 percent
Rock fragments: 0 to 15 percent gravel
Reaction: pH 6.5 to 7.3
Bw horizons - Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: loam or silt loam
Clay content: 18 to 27 percent
Rock fragments: 0 to 15 gravel
Reaction: pH 6.6 to 7.8
Bk horizon - Value: 7 or 8 dry; 6 or 7 moist
Chroma: 2, 3, or 4
Texture: loam, silt loam or sandy loam
Clay content: 12 to 20 percent
Rock Fragments: 0 to 35 percent--0 to 5 percent cobbles; 0 to 30 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - Stream terraces and outwash plains
Elevation - 5,900 to 6,500 feet.
Slope - 0 to 2 percent.
Parent material - Mixed alluvium
Climate - long, cold winters; cool, moist springs; short, cool summers.
Mean annual precipitation - 14 to 19 inches.
Mean annual air temperature - 34 to 39 degrees F.
Frost-free period - 30 to 50 days
GEOGRAPHICALLY ASSOCIATED SOILS:
These are the Cowcamp and Bighole soils. The Cowcamp soils are loamy skeletal and are in concave positions; the Bighole soils have an argillic horizon and are on similar landform positions.
DRAINAGE AND PERMEABILITY: Well drained, moderate permeability.
USE AND VEGETATION: Proposal soils are used for irrigated grass hay and irrigated pasture. The vegetation is mainly Garrison creeping foxtail, meadow foxtail, timothy, tufted hairgrass, and other miscellaneous sedges, rushes and forbs.
DISTRIBUTION AND EXTENT: Proposal soils are not extensive in the intermountain valleys of southwestern Montana. MLRA 44
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Beaverhead County, Montana, Big Hole Valley Area, 2005.
REMARKS: Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from 2 to 16 inches (A horizons); a cambic horizon from 16 to 45 inches (Bw horizons); horizons with redox concentrations at 2 to 45 inches (A and Bw horizons); horizon of secondary carbonate accumulation from 45 to 60 inches (Bk horizon); a particle-size control section from 10 to 40 inches (A2, Bw1, and Bw2 horizons). Proposal soils have a cryic temperature regime and an ustic moisture regime.