LOCATION LITTLE HORN MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic Ustic Argicryolls
TYPICAL PEDON: Little Horn stony loam, in native grassland (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; very dark grayish brown (10YR 3/2) stony loam, very dark brown (10YR 2/2) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine roots; many very fine and fine interstitial pores; 10 percent stones; 10 percent gravel; slightly alkaline (pH 7.6); gradual wavy boundary. (3 to 6 inches thick)
Bt1--4 to 7 inches; brown (10YR 4/3) loam, dark brown (10YR 3/3) moist; coatings of very dark brown (10YR 2/2) moist; moderate medium prismatic structure parting to weak fine and medium subangular blocky; soft, very friable, slightly sticky and slightly plastic; many very fine roots; many fine tubular pores; continuous faint clay films on faces of peds; 10 percent stones; 10 percent gravel; slightly alkaline (pH 7.8); clear smooth boundary. (2 to 4 inches thick)
Bt2--7 to 12 inches; brown (7.5YR 4/3) clay loam, dark brown (7.5YR 3/3) moist; dark brown (10YR 3/3) coats on prisms; moderate medium prismatic structure parting to moderate fine and medium subangular blocky; hard, friable, moderately sticky, moderately plastic; many very fine roots; many very fine and fine tubular pores; continuous faint clay films on all surfaces of peds; slightly alkaline (pH 7.8); gradual wavy boundary. (5 to 10 inches thick)
Bk1--12 to 18 inches; light brown (7.5YR 6/3) clay loam, brown (7.5YR 5/3) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky, moderately plastic; common very fine roots; many very fine and fine tubular pores; patches of clay films on surfaces of peds and on gravel in upper part of horizon; strong effervescence with lime disseminated and as lime flour coats on gravel; moderately alkaline (pH 8.3); clear smooth boundary.
Bk2--18 to 30 inches; very pale brown (10YR 7/3) clay loam, brown (10YR 5/3) moist; common medium prominent reddish brown mottles in lower part; massive; hard, friable; few roots; strong effervescence with accumulated lime disseminated; strongly alkaline (pH 8.6); clear irregular boundary. (Combined thickness of the Bk horizons is 10 to 20 inches thick.)
C--30 to 35 inches; light brown (7.5YR 6/4) clay loam, brown (7.5YR 5/4) and reddish brown (2.5YR 4/4) moist; massive; hard, friable, slightly sticky, moderately plastic; strong effervescence; moderately alkaline (pH 8.4); abrupt wavy boundary. (0 to 10 inches thick)
R--35 inches; hard limestone bedrock.
TYPE LOCATION: Judith Basin County, Montana; 30 feet west and 15 feet south of the center of sec. 26, T. 13 N., R. 12 E.
RANGE IN CHARACTERISTICS:
Soil temperature: 40 to 46 degrees F
Thickness of the mollic epipedon: 7 to 15 inches
Depth to segregated lime and calcareous soil: 10 to 20 inches
Depth to bedrock: 20 to 40 inches
A horizon
Hue: l0YR or 7.5YR
Value: 1 or 2 moist
Chroma: 1 or 2
Texture: Loam or silt loam
Clay content: 18 to 27 percent
Content of rock fragments: 0 to 25 percent--0 to 10 percent stones; 0 to 10 percent cobbles; 0 to 15 percent gravel
Reaction: pH 6.6 to 7.8
Bt1 horizon
Hue: l0YR or 7.5YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 3 or 4
Texture: Loam or silt loam
Clay content: 18 to 27 percent
Content of rock fragments: 0 to 25 percent--0 to 10 percent stones; 0 to 10 percent cobbles; 0 to 15 percent gravel
Reaction: pH 6.6 to 7.8
Bt2 horizon
Hue: l0YR or 7.5YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 3 or 4
Texture: Clay loam or silty clay
Clay content: 35 to 45 percent
Content of rock fragments: 0 to 25 percent--0 to 5 percent stones; 0 to 10 percent cobbles; 0 to 15 percent gravel
Reaction: pH 6.6 to 7.8
Bk and C horizons
Hue: l0YR or 7.5YR
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 3 or 4
Texture: Clay loam or silty clay loam
Clay content: 27 to 40 percent
Content of rock fragments: 0 to 25 percent--0 to 10 percent stones; 0 to 10 percent cobbles; 0 to 20 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.9 to 9.0
COMPETING SERIES:
Florissant (CO) has a paralithic contact at 20 to 40 inches.
Goth (CO) is very deep.
Gothic (CO+UT) is very deep.
Jerry (CO) is very deep.
Judy (CO+SD) has average annual soil temperature of less than 40 degrees F.
Mayoworth (WY+CO MT) has a paralithic contact at 20 to 40 inches.
Owen Creek (WY+MT) has a paralithic contact at 20 to 40 inches.
Parlin (CO+WY) is very deep.
Piltz (CO) has a paralithic contact at 20 to 40 inches.
Sneffels (WY) does not have horizon of lime accumulation.
Tobincreek (MT) has a paralithic contact at 20 to 40 inches.
GEOGRAPHIC SETTING:
Landform: Mountains and foothills
Elevation: 4,500 to 6,500 feet
Slope: 2 to 15 percent
Parent material: Calcareous residuum overlying limestone, quartzite, or sandstone
Climate: Cool subhumid
Mean annual precipitation: 17 to 25 inches
Mean annual temperature: 40 to 45 degrees F
Mean summer temperature: 54 to 60 degrees F
Mean winter temperature: 20 to 25 degrees F
GEOGRAPHICALLY ASSOCIATED SOILS:
Sheege (ID+MT NV UT WY) is on summits; is shallow to a lithic contact.
Skaggs (MT) is on similar landforms; has a calcic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability
USE AND VEGETATION: Little Horn soils are used mainly for range with some used for production of hay and oats. The potential native vegetation is mainly grasses, including bluebunch wheatgrass, Idaho fescue, rough fescue, and fringed sagewort.
DISTRIBUTION AND EXTENT: Little Horn soils are not extensive in the eastern slopes of the northern Rocky Mountains; MLRA 43B and 46.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
Series Established: Sheridan County, Wyoming, 1932
Remarks:
Diagnostic horizons and features recognized in this pedon:
- a mollic epipedon from the surface to 12 inches (A, Bt horizons)
- an argillic horizon which is the particle-size control section from 4 to 12 inches (Bt horizons)
- horizons of secondary calcium carbonate accumulation from 12 to 30 inches (Bk horizons)
- a lithic contact at 35 inches (R horizon)
Little Horn soils have an ustic moisture regime and a cryic temperature regime.
The Little Horn OSD does not list a range of frost-free days. NASIS ranges are from 50 to 125. Frost-free season needs to be investigated.