LOCATION ROY MTEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, frigid Typic Argiustolls
TYPICAL PEDON: Roy stony loam, grassland (colors are for dry soil unless otherwise noted).
A--0 to 6 inches; dark grayish brown (10YR 4/2) stony loam, very dark grayish brown (10YR 3/2) moist; weak very fine granular structure; slightly hard, very friable, nonsticky and nonplastic; many very fine and fine roots; many very fine and fine pores; 10 percent stones, 5 percent pebbles; neutral (pH 6.8); clear wavy boundary. (4 to 10 inches thick)
Bt1--6 to 14 inches; dark grayish brown (10YR 4/2) very stony clay loam, brown (10YR 4/3) moist; strong very fine angular blocky structure; hard, friable, moderately sticky and moderately plastic; many very fine roots; many very fine pores; continuous distinct very dark grayish brown (10YR 3/2) moist clay film on faces of peds; 20 percent stones, 15 percent cobbles, 10 percent pebbles; neutral (pH 7.0); diffuse wavy boundary. (6 to 12 inches thick)
Bt2--14 to 32 inches; brown (7.5YR 5/4) very stony clay loam, brown (7.5YR 4/4) moist; strong very fine angular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine roots; many very fine pores; common distinct brown (7.5YR 4/4) clay films on faces of peds; 25 percent stones, 15 percent cobbles, 10 percent pebbles; neutral (pH 7.0); clear wavy boundary. (6 to 18 inches thick)
Bk--32 to 60 inches; light yellowish brown (10YR 6/4) very stony sandy clay loam, yellowish brown (10YR 5/4) moist; fine subangular blocky structure; hard, friable, moderately sticky and slightly plastic; 25 percent stones, 15 percent cobbles, 10 percent pebbles; disseminated lime; slightly effervescent; slightly alkaline (pH 7.8).
TYPE LOCATION: Cascade County, Montana; 1,050 feet south and 1,320 feet east of the NW corner of sec. 19, T. 18 N., R. 6 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 40 to 47 degrees F.
Moisture control section - between 4 and 12 inches.
Mollic epipedon thickness - 10 to 16 inches.
Depth to Bk horizon - 20 to 40 inches.
A Btk horizon is allowed.
A horizon - Hue: 7.5YR or 10YR
Value: 3, 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture: loam or clay loam
Clay content: 15 to 40 percent
Rock fragments: 5 to 65 percent--5 to 30 percent stones and cobbles, 0 to 35 percent pebbles
Reaction: pH 6.1 to 7.8
Bt1 horizon - Hue: 7.5YR or 10YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2, 3, or 4
Texture: clay loam or clay
Clay content: 35 to 50 percent
Rock fragments: 35 to 80 percent--15 to 50 percent stones and cobbles, 15 to 50 percent pebbles
Reaction: pH 6.6 to 7.8
Bt2 horizon - Hue: 7.5YR or 10YR
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2, 3, 4, or 6
Texture: clay loam or clay
Clay content: 35 to 50 percent
Rock fragments: 35 to 80 percent--15 to 50 percent stones and cobbles, 15 to 50 percent pebbles
Reaction: pH 6.6 to 7.8
Bk horizon - Hue: 7.5YR through 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, 4, 5, or 6
Texture: clay loam or sandy clay loam
Clay content: 27 to 40 percent
Rock fragments: 35 to 80 percent--10 to 50 percent stones and cobbles, 15 to 50 percent pebbles
Calcium carbonate equivalent: 2 to 15 percent
Reaction: pH 7.4 to 9.0
COMPETING SERIES:
Borky (MT) - has a paralithic contact at depths of 20 to 40 inches.
Cebolleta (NM) - has a lithic contact at depths of 20 to 40 inches.
Rionutria (NM) - has a lithic contact at 20 to 40 inches.
Shanley (MT) - does not have horizon of secondary carbonate accumulation.
Storyhill (MT) has a calcic horizon.
GEOGRAPHIC SETTING:
Landform - alluvial fans; stream terraces; escarpments; mountains; hills.
Elevation - 3,000 to 6,800 feet.
Slopes - 0 to 70 percent.
Parent material - alluvium or colluvium derived mainly from sandstone and igneous rocks.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 14 to 20 inches.
Mean annual air temperature - 38 to 45 degrees F.
Frost-free period - 70 to 125 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Blaine, Hilger, Rencot, and Rentsac soils. Blaine soils are moderately deep to a lithic contact. Hilger soils are loamy-skeletal. Rencot and Rentsac soils are shallow to a lithic contact and do not have mollic epipedons.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: Roy soils are mainly used as rangeland with some areas in cropland. Potential native vegetation is mainly bluebunch wheatgrass, Idaho fescue, western wheatgrass, blue grasses, and forbs. In places there are low density stands of ponderosa pine.
DISTRIBUTION AND EXTENT: Roy soils are extensive in central and southwestern Montana; possibly in parts of Wyoming and Colorado.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Reconnaissance Soil Survey of Central Montana, 1946.
REMARKS: Soil interpretations records: MT0123, MT0702, MT0362. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 14 inches (A, Bt1 horizons); an argillic horizon from 6 to 32 inches (Bt1, Bt2 horizons); an accumulation of lime from 32 to 60 inches (Bk horizon); and a particle-size control section from 6 to 20 inches (Bt1, Bt2 horizons). Roy soils have a frigid temperature regime and an ustic moisture regime.