LOCATION BURGRAFF MT+NDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Aridic Calciustolls
TYPICAL PEDON: Burgraff silt loam, in grassland (colors are for dry soil unless otherwise noted).
A1--0 to 3 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; moderate very fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine roots; strongly effervescent; slightly alkaline (pH 7.8); clear smooth boundary.
A2--3 to 6 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium and fine subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; many very fine roots; many very fine tubular and interstitial pores; strongly effervescent; slightly alkaline (pH 7.8); clear smooth boundary. (Combined A horizons 5 to 8 inches thick)
Bk1--6 to 17 inches; pinkish gray (7.5YR 7/2) silt loam, pinkish gray (7.5YR 6/2) moist; moderate medium and fine subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; common very fine roots; many very fine tubular and interstitial pores; 5 percent soft angular pebbles of siltstone; many fine and medium seams of lime; continuous faint coatings of lime on faces of peds; violently effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (10 to 20 inches thick)
Bk2--17 to 27 inches; light gray (10YR 7/2) silt loam, grayish brown (10YR 5/2) moist; weak medium and fine subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; common very fine roots; many very fine tubular and interstitial pores; 20 percent small, soft, angular pebbles of siltstone; common fine and medium seams of lime; continuous faint coatings of lime on faces of peds; violently effervescent; moderately alkaline (pH 8.2); gradual smooth boundary. (Combined Bk horizons 16 and 35 inches thick)
Cr--27 to 60 inches; gray (5Y 6/l) fractured semiconsolidated siltstone; few fine roots in fractures in upper part, strongly effervescent.
TYPE LOCATION: Lewis and Clark County, Montana; 2,500 feet south and 2,400 feet east of the NW corner of sec. 34, T. 20 N., R. 6 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 4 and l2 inches; dry in all parts between four-tenths and five-tenths of the cumulative days per year when the soil temperature at a depth of 20 inches is higher than 41 degrees F.
Control section - 20 to 30 percent clay.
Depth to Cr horizon - 20 to 40 inches.
A horizon - Hue: 7.5YR or 10YR
Chroma: 2 or 3
Clay content: 20 to 25 percent
Rock fragments: 0 to 15 percent soft channers
Reaction: pH 6.6 to 7.8
Bk horizon - Hue: 10YR, 7.5YR, or 2.5Y
Value: 7 or 8 dry, 5 or 6 moist
Chroma: 2 or 3
Texture: silt loam or silty clay loam
Clay content: 20 to 30 percent
Rock fragments: 0 to 25 percent soft channers
Calcium carbonate equivalent: 25 to 35 percent
Reaction: 7.9 to 8.4
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - sedimentary plains.
Elevation - 3,500 to 4,500 feet.
Slope - 0 to 35 percent.
Parent material - silty material weathered from soft sedimentary bedrock.
Climate - long, cold winters; moist springs; and warm summers.
Mean annual precipitation - 12 to 14 inches.
Mean annual temperature - 40 to 45 degrees F.
Frost-free period - 105 to 120 days.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Burgraff soils are used mainly for rangeland and dryland crops. Potential native vegetation is mainly bluebunch wheatgrass, needleandthread, western wheatgrass, prairie junegrass, Sandberg bluegrass, and plains muhly.
DISTRIBUTION AND EXTENT: Burgraff soils are of small extent. They occur mainly in west-central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Lewis and Clark County Area, Montana, 1991; proposed in Lewis and Clark County, Montana, 1987.
REMARKS: Soil Interpretation Record: MT1103. Diagnostic horizons and features recognized in this soil are: a mollic epipedon from the soil surface to 7 inches (A1, A2, and Bk1); a calcic horizon from 6 to 27 inches (Bk1, Bk2 horizons); a paralithic contact at a depth of 27 inches. Burgraff soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.