LOCATION SUBWELL MT+COEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Typic Haplustolls
TYPICAL PEDON: Subwell loam, in grassland. (Colors are for dry soil unless otherwise noted.)
A--0 to 3 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate very fine and fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; 10 percent pebbles; mildly alkaline (pH 7.6); clear smooth boundary. (3 to 7 inches thick)
Bw1--3 to 8 inches; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure parting to moderate fine subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; 10 percent pebbles; mildly alkaline (pH 7.6); clear smooth boundary. (0 to 5 inches thick)
Bw2--8 to 16 inches; yellowish brown (10YR 5/4) gravelly loam, brown (10YR 4/3) moist; moderate coarse subangular blocky structure parting to moderate medium subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; 20 percent pebbles; mildly alkaline (pH 7.6); clear smooth boundary. (7 to 9 inches thick)
2Ck--16 to 28 inches; light gray (2.5Y 7/2) very gravelly sandy loam, light yellowish brown (2.5Y 6/4) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; 55 percent pebbles; many prominent lime coatings on surface of pebbles; violently effervescent; strongly alkaline (pH 8.6); gradual wavy boundary.
(10 to 18 inches thick)
2C--28 to 60 inches; light brownish gray (2.5Y 6/2) very gravelly sandy loam, light yellowish brown (2.5Y 6/4) moist; single grain; loose, nonsticky and nonplastic; 50 percent pebbles; strongly effervescent; strongly alkaline (pH 8.8).
TYPE LOCATION: Prairie County, Montana; 1,300 feet south and 200 feet west of the NE corner of sec. 9, T. 15 N., R. 48 E.
RANGE IN CHARACTERISTICS:
Soil temperature: 42 to 47 degrees F.
Moisture control section: approximately between the depths of 4 and 12 inches.
Mollic epipedon thickness: 7 to 12 inches (includes the Bw1 horizon). Depth to 2Ck horizon: 10 to 20 inches.
Control section: 15 to 24 percent clay and 40 to 55 percent rock fragments.
A horizon - Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Clay content: 18 to 27 percent
Rock fragments: 0 to 10 percent pebbles
Reaction: pH 7.4 to 7.8
Bw1 horizon - Clay content: 18 to 27 percent
Rock fragments: 5 to 20 percent pebbles
Reaction: pH 7.4 to 8.4
Bw2 horizon - Value: 5 or 6 dry; 4 moist
Chroma: 3 or 4
Clay content: 8 to 27 percent
Rock fragments: 5 to 20 percent pebbles
Reaction: pH 7.4 to 8.4
NOTE: Some pedons have a Bk horizon and a calcium carbonate equivalent that ranges from 20 to 30 percent.
2Ck horizon - Hue: 2.5Y or 10YR
Value: 6 or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: sandy loam or loam
Clay content: 10 to 27 percent
Rock fragments: 35 to 60 percent--0 to 5 percent cobbles; 35 to 55 percent pebbles
EC: less than 4 mmhos/cm
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.9 to 9.0
2C horizon - Hue: 2.5Y or 10YR
Value: 6 or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: sandy loam, loamy sand, or coarse sandy loam Clay content: 5 to 18 percent
Rock fragments: 40 to 60 percent--0 to 5 percent cobbles; 40 to 55 percent pebbles
EC: less than 4 mmhos/cm
Calcium carbonate equivalent: 8 to 15 percent
Reaction: pH 7.9 to 9.0
COMPETING SERIES: These are the Bitton, Datino, Grousecreek (t), Heely (t), Labra, Perma, Peso, Pesowyo (t), Sandia, Slimbutte (t), Veatch, and Wanagan series. The Bitton soils do not have a calcic horizon and do not have a lithological discontinuity at a depth of 10 to 20 inches. The Datino soils have lime at a depth of 7 inches, and the rock fragments are mainly cobbles below a depth of 7 inches and do not have a lithological discontinuity. Grousecreek soils are medium acid to neutral throughout and do not have a calcic or Bk horizon. Heely soils are moderately deep over schist. The Labra soils do not have a lithological discontinuity above a depth of 10 to 20 inches; also, the coarse fragments are channers derived from burnt coal seams. Perma soils do not have a calcic horizon and are noncalcareous throughout. Peso soils are lithic below a depth of 20 to 40 inches. Pesowyo and Veatch soils are moderately deep. Sandia soils do not have a calcic horizon, have more than 50 percent stones and cobbles in the control section and do not have a lithological discontinuity above a depth of 40 inches. Slimbutte soils do not have a lithological discontinuity above a depth of 40 inches and have more than 20 percent rock fragments, mainly cobble size above a depth of 20 inches. Wanagan soils do not have a calcic horizon.
GEOGRAPHIC SETTING: The Subwell soils are on fans and terraces. Elevations are 2,400 to 3,500 feet. Slopes are 0 to 8 percent. These soils formed in gravelly alluvium. The climate is characterized by long, cold winters; moist springs; and warm summers. Mean annual precipitation is 12 to 16 inches, most of which falls during the spring and early summer. Mean annual temperature is 40 to 45 degrees F. The frost-free period is 100 to 125 days.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability through the 2Ck horizon and moderately rapid permeability in the 2C horizon.
USE AND VEGETATION: Subwell soils are used mainly as rangeland and for dryland crops. Potential native vegetation is mainly bluebunch wheatgrass, little bluestem, plains muhly, needleandthread, and western wheatgrass.
DISTRIBUTION AND EXTENT: Subwell soils are of moderate extent in southeastern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES PROPOSED: Prairie County, Montana, 1984. Subwell is a coined name.
REMARKS: Soil Interpretation Records: MT0873. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 8 inches (A, Bw1 horizons); a cambic horizon from 8 to 16 inches (Bw2 horizon); a calcic horizon from 16 to 28 inches
(2Ck horizon); a particle size control section from 10 to 40 inches (Bw2, 2Ck, and 2C horizons). Subwell soils have a frigid temperature regime and an ustic moisture regime.