LOCATION SUDWORTH MTEstablished Series
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid Cumulic Haplustolls
TYPICAL PEDON: Sudworth loam, native grassland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 7 inches; dark grayish brown (10YR 4/2) loam, very dark grayish brown (10YR 3/2) moist; the surface 2 inches has moderate fine granular structure, and the lower 5 inches has weak medium and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine and very fine roots; 5 percent angular pebbles; strongly effervescent; slightly alkaline (pH 7.4); gradual wavy boundary. (5 to 8 inches thick)
A2--7 to 19 inches; dark grayish brown (10YR 4/2) loam, very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to weak medium and fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; many fine and very fine roots; many fine and very fine pores; 5 percent angular pebbles; strongly effervescent; slightly alkaline (pH 7.6); gradual wavy boundary. (8 to 13 inches thick)
A3--19 to 28 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak medium and fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many fine and very fine pores; 5 percent angular pebbles; strongly effervescent; moderately alkaline (pH 8.0); clear wavy boundary. (4 to 10 inches thick)
2C--28 to 67 inches; grayish brown (10YR 5/2) extremely gravelly loamy sand, dark grayish brown (10YR 4/2) moist; single grain; common fine and very fine roots; 70 percent angular pebbles; strongly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Fergus County, Montana; 1220 feet east and 920 feet north of the SW corner of sec. 4, T. 15 N., R. 18 E.
RANGE IN CHARACTERISTICS:
Soil temperature: 41 to 47 degrees F.
Moisture control section: between 4 and 12 inches; not dry in all parts for 45 consecutive days.
Depth to 2C horizon: 16 to 36 inches.
A horizons - Hue: 10YR or 2.5Y
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 1 to 3
Texture: silt loam, loam, clay loam or silty clay loam
Clay content: 18 to 35 percent
Rock fragments: 0 to 15 percent--0 to 5 percent cobbles; 0 to 10 percent angular pebbles
Calcium carbonate equivalent: 0 to 10 percent
Reaction: pH 7.4 to 8.4
2C horizon - Hue: 10YR or 2.5Y
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 1 to 4
Texture: loamy sand or sand
Clay content: 2 to 7 percent
Rock fragments: 35 to 80 percent--0 to 30 percent cobbles and stones; 35 to 70 percent angular pebbles
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
NOTE: Some pedons have stratification of sandy loam, or loam.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - flood plains and low stream terraces.
Elevation - 2510 to 5200 feet.
Slope - 0 to 4 percent.
Parent material - alluvium underlain by very gravelly or extremely gravelly loamy sand or sand.
Climate - cool, with long cold winters; warm moist springs; dry summers.
Mean annual precipitation - 15 to 19 inches.
Mean annual temperature - 39 to 45 degrees F.
Frost-free period - 90 to 125 days.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability above the 2C horizon and rapid in the 2C horizon.
USE AND VEGETATION: Some areas of Sudworth soils remain as rangeland or are forested with plains cottonwood. Other areas are used for pasture and, to a lesser extent, for cropland. The potential native vegetation on rangeland areas is basin wildrye, western wheatgrass, needleandthread, bluebunch wheatgrass, green needlegrass, forbs, and shrubs. On forest areas the primary native understory vegetation is basin wildrye, western wheatgrass, western snowberry, common chokecherry, and redosier dogwood.
DISTRIBUTION AND EXTENT: These soils are not extensive, but have wide distribution in valleys of central and southern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Fergus County, Montana, 1979.
REMARKS: Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 28 inches (A horizons); a lithologic discontinuity at 28 inches (2C horizon); a particle-size control section from 10 to 40 inches (part of A2, A3 and part of 2C horizon). Sudworth soils have a frigid temperature regime and an ustic moisture regime.