LOCATION ATTEWAN MT+SD WYEstablished Series
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid Aridic Argiustolls
TYPICAL PEDON: Attewan loam, cultivated. (Colors are for dry soil unless otherwise noted)
Ap--0 to 6 inches; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine roots; 5 percent pebbles; neutral (pH 6.6); clear wavy boundary. (4 to 6 inches thick)
Bt--6 to 15 inches; brown (10YR 5/3) clay loam, dark grayish brown (10YR 4/2) moist; moderate fine and medium prismatic structure parting to fine and medium blocky; hard, friable, moderately sticky and moderately plastic; many fine roots; common fine and very fine pores; very dark grayish brown (10YR 3/2) many faint clay films on faces of peds; 5 percent pebbles; slightly alkaline; clear wavy boundary. (5 to 15 inches thick)
Bk1--15 to 20 inches; grayish brown (2.5Y 5/2) clay loam, dark grayish brown (2.5Y 4/2) moist; moderate medium prismatic structure parting to weak medium blocky; hard, very friable, slightly sticky and moderately plastic; common fine roots; many fine and very fine pores; 5 percent fine pebbles; common fine masses and threads of lime; common faint lime coatings on underside of rock; violently effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (3 to 8 inches thick)
Bk2--20 to 25 inches; light brownish gray (2.5Y 6/2) clay loam, grayish brown (2.5Y 5/2) moist; weak medium and coarse prismatic structure; hard, very friable, slightly sticky and moderately plastic; common fine roots; common fine pores; 10 percent pebbles; many medium masses of lime; continuous distinct lime coatings on pebbles; violently effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (Combined Bk horizons 10 to 20 inches thick)
2C--25 to 60 inches; grayish brown (2.5Y 5/2) very gravelly loamy sand; dark grayish brown (2.5Y 4/2) moist; single grain; loose; nonsticky and nonplastic; about 60 percent pebbles; lime crusts on undersides of pebbles in upper part; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Blaine County, Montana; 2,000 feet south and 900 feet west of the northeast corner of sec. 29, T. 37 N., R. 26 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 40 to 47 degrees F.
Moisture control section - between 4 and 12 inches; dry in some part six-tenths or more of the cumulative days per year when the soil temperature at a depth of 20 inches is 41 degrees F or higher.
Mollic epipedon thickness - 7 to 12 inches and may include part or all of the argillic horizon.
Depth to Bk horizon - 10 to 21 inches.
Depth to 2C horizon - 20 to 40 inches.
2Bk and 2Ck horizons are allowed.
Soil phases - stony and wet.
Ap horizon - Hue: 10YR or 2.5Y
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture: loam, clay loam, sandy loam or fine sandy loam
Clay content: 10 to 35 percent
Rock fragments: 0 to 50 percent--0 to 20 percent greater than 3 inch stones and cobbles; 0 to 30 percent less than 3 inch pebbles
Reaction: pH 6.1 to 8.4
Bt horizon - Hue: 10YR or 2.5Y
Value: 4, 5, or 6 dry; 3 or 4 moist
Chroma: 2 or 3; chroma of 4 allowed in the lower part.
Texture: clay loam, sandy clay loam, or loam
Clay content: 20 to 35 percent
Rock fragments: 0 to 25 percent--0 to 5 percent greater than 3 inch stones and cobbles; 0 to 20 percent less than 3 inch pebbles
Reaction: pH 6.6 to 8.4
Bk horizons - Hue: 10YR or 2.5Y
Value: 5, 6, 7, or 8 dry; 4, 5, or 6 moist
Chroma: 2, 3, 4, or 6
Texture: loam, clay loam, silt loam, sandy clay loam, or sandy loam
Clay content: 15 to 30 percent
Rock fragments: 0 to 30 percent--0 to 5 percent stones and cobbles; 0 to 25 percent pebbles
Calcium carbonate equivalent: 1 to 15 percent
Reaction: pH 7.4 to 9.0
2C horizon - Hue: 2.5Y or 10YR
Value: 4, 5, 6 or 7 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: loamy sand, sand, loamy coarse sand, or coarse sand
Clay content: 0 to 10 percent
Rock fragments: 35 to 75 percent--0 to 15 percent stones and cobbles; 35 to 60 percent pebbles
Calcium carbonate equivalent: 1 to 15 percent
Reaction: pH 7.4 to 9.0
COMPETING SERIES:
Beaverflat (MT) - does not have a horizon of secondary calcium carbonate accumulation; is not sandy-skeletal below a depth of 20 to 40 inches.
Degrand (MT) - is not sandy-skeletal below depths of 20 to 40 inches.
GEOGRAPHIC SETTING:
Landform - outwash terraces; stream terraces; eskers; alluvial fans.
Elevations - 2,200 to 6,500 feet.
Slopes- 0 to 8 percent.
Parent materials - alluvium or glacial outwash deposited over sand or loamy sand having more than 35 percent rock fragments.
Climate - long, cold winters; moist springs; hot, dry summers.
Precipitation - 10 to 14 inches.
Mean annual air temperature - 38 to 45 degrees F.
Frost-free period - 90 to 135 day; Frost-free period down to 70 days is allowed in MLRA 44.
GEOGRAPHICALLY ASSOCIATED SOILS:
These are the
Beaverell,
Evanston, and
Tinsley soils. The Beaverell and Tinsley soils are above and the Evanston soils are below the Attawan soils on the landscape. Beaverell and Tinsley soils are less than 20 inches to sand and gravel and Evanston soils are deeper than 40 inches to sand and gravel.
DRAINAGE AND PERMEABILITY: Well drained. Moderate permeability above the 2C horizon and rapid in the 2C horizon. Runoff is negligible to medium depending on slope.
USE AND VEGETATION: These soils are used mainly for irrigated and nonirrigated cropland and as rangeland. The potential native vegetation is mainly bluebunch wheatgrass, needleandthread, western wheatgrass, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Attewan soils are extensive throughout eastern Montana, some dry intermountain valleys, and in the states of Colorado and Utah.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Cascade County, Montana, 1969.
REMARKS: Soil interpretations records: MT0170, MT0468, MT0580, MT0868, and MT0179.
Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface or the soil to a depth of 7 inches (after mixing) (A and part of Bt horizon); argillic horizon - the zone from 6 to 15 inches (Bt horizon); horizon of secondary carbonate accumulation - the zone from 15 to 25 inches (Bk1 and Bk2 horizons); discontinuity of sandy-skeletal material the zone from 25 to 60 inches (2C horizon); particle-size control section the zone from 6 to 40 inches (Bt, Bk1, Bk2 and 2C horizons).