LOCATION SPANG MTEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Aridic Haplustepts
TYPICAL PEDON: Spang sandy loam, mixed grassland and woodland (colors are for dry soil unless otherwise noted).
A--0 to 6 inches; reddish brown (5YR 5/4) sandy loam, dark reddish brown (5YR 3/4) moist; moderate fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine roots; neutral (pH 6.8); abrupt smooth boundary. (4 to 6 inches)
Bw1--6 to 17 inches; reddish brown (5YR 5/4) sandy loam, reddish brown (5YR 4/4) moist; weak coarse subangular blocky structure parting to weak fine granular; soft, very friable, nonsticky and nonplastic; many very fine roots; many very fine tubular pores; neutral (pH 7.0); clear smooth boundary. (8 to 12 inches thick)
Bw2--17 to 38 inches; red (2.5YR 5/6) sandy loam, red (2.5YR 4/6) moist; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine roots; many very fine tubular pores; neutral (pH 7.0); clear smooth boundary. (16 to 24 inches thick)
C--38 to 61 inches; reddish brown (2.5YR 5/4) sandy loam, reddish brown (2.5YR 4/4) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; neutral (pH 7.0).
TYPE LOCATION: Rosebud County, Montana; 1,880 feet east and 2,50 feet north of the southwest corner of sec. 30, T. 6 S., R 41 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 8 and 24 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 41 degrees or higher.
A moist value of 3 is allowed only with chroma of 4.
A horizon - Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 3 or 4 moist
Chroma: 3 or 4
Texture: sandy loam or fine sandy loam
Clay content: 10 to 20 percent
Rock fragments: 0 to 5 percent angular pebbles of baked sandstone
Reaction: pH 6.1 to 7.3
Bw1 horizon - Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 or 4
Texture: sandy loam or fine sandy loam
Clay content: 10 to 20 percent
Rock fragments: 0 to 5 percent angular pebbles of baked sandstone
Reaction: pH 6.6 to 7.3
Bw2 horizon - Hue: 2.5YR, 5YR, 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3, 4, 5, or 6
Texture: sandy loam or fine sandy loam
Clay content: 8 to 18 percent
Rock fragments: 0 to 15 percent angular pebbles of baked sandstone
Reaction: pH 6.6 to 8.4
C horizon - Hue: 2.5YR, 5YR, or 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3, 4, 5, or 6
Texture: sandy loam, fine sandy loam, or loamy sand
Clay content: 5 to 15 percent
Rock fragments: 0 to 15 percent angular pebbles of baked sandstone
Reaction: pH 6.6 to 8.4
COMPETING SERIES:
Busby (MT) - has horizons of secondary calcium carbonate accumulation; does not have hue redder than 10YR throughout.
Toby (ND) - does not have hue redder than 10YR throughout. (Currently this soil is classified as a Borollic Camborthids.)
Twilight (SD) - has a paralithic contact of sandstone at depths of 20 to 40 inches.
GEOGRAPHIC SETTING:
Landform - alluvial fans; hills; sedimentary plains.
Elevations - 2,200 to 4,500 feet.
Slopes- 2 to 25 percent.
Parent material - alluvium or colluvium derived from scorio.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 12 to 16 inches.
Mean annual temperature - 40 to 45 degrees.
Frost-free season - 100 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability.
USE AND VEGETATION: Spang soils are used mainly for rangeland. Potential native vegetation is mainly bluebunch wheatgrass, western wheatgrass, needleandthread, prairie sandreed, forbs, and shrubs. Some areas have a low density overstory of ponderosa pine.
DISTRIBUTION AND EXTENT: Spang soils are of small extent in southeastern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Rosebud County, Montana, 1985.
REMARKS: Soil interpretations record: MT0169. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the soil surface to 7 inches (mixed) (A, Bw1 horizons); a cambic horizon from 6 to 38 inches (Bw1, Bw2 horizons); a particle-size control section from 10 to 40 inches (Bw1, Bw2, C horizons). Spang soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.