LOCATION BULLHOOK MTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, calcareous, frigid Aridic Ustifluvents
TYPICAL PEDON: Bullhook clay loam, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 3 inches; light brownish gray (2.5Y 6/2) clay loam, dark grayish brown (2.5Y 4/2) moist; weak very fine granular structure; hard, firm, sticky and plastic; common very fine roots; common very fine pores; strongly effervescent; strongly alkaline (pH 8.6); clear smooth boundary. (2 to 5 inches thick)
C--3 to 8 inches; grayish brown (2.5Y 5/2) clay loam consisting of clay loam with thin layers of loam, dark grayish brown (2.5Y 4/2) moist; massive; slightly hard, friable, sticky and plastic; common very fine roots; common very fine pores; strongly effervescent; very strongly alkaline (pH 9.6); clear wavy boundary. (3 to 10 inches thick)
Cyz--8 to 60 inches; grayish brown (2.5Y 5/2) clay loam consisting of clay loam with thin layers of loam or fine sandy loam, dark grayish brown (2.5Y 4/2) moist; massive; slightly hard, friable, sticky and plastic; common very fine roots; common very fine pores; common fine small masses and seams of gypsum and other salts; strongly effervescent; very strongly alkaline (pH 9.4).
TYPE LOCATION: Hill County, Montana; 1,300 feet south and 50 feet east of the NW corner of sec. 2, T. 35 N., R. 12 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Soil moisture control section - between 4 and 12 inches; dry in all parts between four-tenths and five-tenths of the cumulative days per year when the soil temperature at 20 inches is 41 degrees F or above.
A horizon - Hue: 10YR or 2.5Y
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay loam, loam, or silty clay loam with or without thin layers of loam, fine sandy loam, clay loam, silty clay loam, or silt loam
Clay content: 15 to 40 percent
Electrical conductivity: 2 to 8 mmhos/cm
Sodium adsorption ratio: 8 to 13
Reaction: pH 7.4 to 9.4
Calcium carbonate equivalent: 0 to 10
C horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay loam, loam, or silty clay loam with or without thin layers of loam, clay, silty clay loam, fine sandy loam, or silt loam
Clay content: 18 to 35 percent
Electrical conductivity: 4 to 16 mmhos/cm
Sodium adsorption ration: 13 to 20
Reaction: pH 7.4 to 9.6
Calcium carbonate equivalent: 5 to 10
Cyz horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay loam, loam, or silty clay loam with or without thin layers of fine sandy loam, loam, clay loam, silty clay loam, or silt loam
Clay content: 18 to 35 percent
Electrical conductivity: 8 to 16 mmhos/cm
Sodium adsorption ratio: 13 to 30
Gypsum: 2 to 5 percent
Reaction: pH 7.4 to 9.6
Calcium carbonate equivalent: 5 to 10
Gypsum and other salts are inherent in the parent material.
COMPETING SERIES:
Havermon (WY) - has a sandy loam surface; has a water table at 4 to 5 feet; differ by 10 to 25 day frost-free period; is at elevations above 6,000 feet and differ by 3,700 to 5,200 feet in elevation.
Havre (MT) - has electrical conductivity of less than 4 mmhos/cm; has a sodium adsorption ratio of less than 8 throughout.
Thibadeau (MT) - somewhat poorly drained; has an electrical conductivity of 8 to 16 mmhos/cm throughout; slowly permeable; has a high water table between 3 and 5 feet.
GEOGRAPHIC SETTING:
Landform - flood plains.
Elevations - 2,000 to 3,500 feet.
Slopes- 0 to 6 percent.
Parent material - alluvium.
Climate - long, cold winters; moist springs; hot, dry summers.
Mean annual precipitation - 10 to 14 inches, most of which falls during spring and early summer.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 100 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Bullhook soils are used mainly as rangeland. Few areas are used for nonirrigated cropland. The potential plant community is western wheatgrass, inland saltgrass, alkali sacaton, greasewood, and gardner saltbush.
DISTRIBUTION AND EXTENT: Bullhook soils are extensive throughout Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Hill County, Montana, 1994; proposed in Hill County, Montana, 1992. Bullhook is the name of a creek draining into the Milk River in Hill County, Montana.
REMARKS: Soil interpretation record: MT1350, MT1351.
Diagnostic horizon and features recognized in this pedon are: ochric epipedon - from 0 to 7 inches, mixed (A, C horizons); particle-size control section - from 10 to 40 inches. Bullhook soils have a frigid temperature regime and an aridic moisture regime that borders on ustic.
ADDITIONAL DATA: Laboratory sample S91MT-041-2.