LOCATION SCRAVO MT+UT WY
Established Series
Rev. JB-JJU-RJS
03/2012
SCRAVO SERIES
The Scravo series consists of very deep, somewhat excessively drained soils that formed in alluvium, slope alluvium or colluvium. These soils are on stream terraces, alluvial fans, fan remnants, drainageways, basin floors, escarpments and hills. Slopes are 0 to 45 percent. Mean annual precipitation is about 12 inches, and mean annual air temperature is about 42 degrees F.
TAXONOMIC CLASS: Sandy-skeletal, mixed, frigid Aridic Calciustepts
TYPICAL PEDON: Scravo gravelly loam, cultivated (colors are for dry soil unless otherwise noted).
Ap--0 to 6 inches; light brownish gray (10YR 6/2) gravelly loam, dark grayish brown (10YR 4/2) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; 20 percent gravel; finely disseminated calcium carbonate and continuous prominent calcium carbonate casts on underside of rock fragments; strongly effervescent; slightly alkaline (pH 7.6); clear smooth boundary. (3 to 6 inches thick)
Bk--6 to 17 inches; light gray (10YR 7/2) extremely gravelly sandy loam, grayish brown (10YR 5/2) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; common very fine roots; 65 percent gravel; finely disseminated calcium carbonate, many fine masses of calcium carbonate, and continuous prominent calcium carbonate casts on underside of rock fragments; violently effervescent; moderately alkaline (pH 8.0); clear wavy boundary. (6 to 14 inches thick)
2BCk--17 to 60 inches; light brownish gray (10YR 6/2) extremely gravelly loamy sand, dark grayish brown (10YR 4/2) moist; single grain; loose, nonsticky and nonplastic; few very fine roots; 65 percent gravel; finely disseminated calcium carbonate, and common prominent calcium carbonate and silica casts on underside of rock fragments; strongly effervescent; moderately alkaline.
TYPE LOCATION: Lewis and Clark County, Montana; 250 feet north and 50 feet east of the southwest corner of sec. 19, T. 11N, R. 3W.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 40 to 47 degrees F.
Depth to calcic horizon - 3 to 6 inches
Depth to lithologic discontinuity - 9 to 20 inches
A horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 or 3; dry or moist
Texture: loam or sandy loam
Clay content: 10 to 25 percent
Rock fragments: 0 to 60 percent--0 to 40 percent gravel, 0 to 30 percent cobbles
Calcium carbonate equivalent: 1 to 15 percent
Reaction: pH 7.4 to 8.2
Bk horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 to 8 dry; 4 to 6 moist
Chroma: 2 or 3; dry or moist
Texture: sandy loam or loam
Clay content: 5 to 25 percent
Rock fragments: 35 to 70 percent--35 to 55 percent gravel, 0 to 15 percent cobbles
Electrical conductivity: 0 to 2 mmhos/cm
Calcium carbonate equivalent: 15 to 40 percent
Reaction: pH 7.9 to 8.4
2BCk horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 8 dry; 4 to 6 moist
Chroma: 2 or 4; dry or moist
Texture: loamy sand or sand
Clay content: 0 to 10 percent
Rock fragments: 35 to 80 percent--35 to 65 percent gravel, 0 to 15 percent cobbles
Electrical conductivity: 0 to 2 mmhos/cm
Calcium carbonate equivalent: 10 to 30 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES:
Kellycreek (MT) - are moderately deep to a paralithic contact
GEOGRAPHIC SETTING:
Landform - stream terraces, alluvial fans, fan remnants, drainageways, basin floors, escarpments and hills
Elevation - 3,500 to 6,700 feet
Slope - 0 to 45 percent
Parent material - alluvium, slope alluvium or colluvium
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 10 to 14 inches
Mean annual temperature - 38 to 45 degrees F.
Frost-free period - 70 to 120 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; moderately rapid permeability through the Bk horizon and rapid permeability in the sandy-skeletal material.
USE AND VEGETATION: Scravo soils are used mainly as rangeland. Some areas are cropped to irrigated alfalfa, small grain, and pasture. Potential native vegetation is mainly bluebunch wheatgrass, western wheatgrass, needleandthread, and Indian ricegrass.
DISTRIBUTION AND EXTENT: Moderately extensive in Montana and Utah. MLRAs - 43B, 44B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Broadwater County Area, Montana, 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 6 inches (Ap horizon)
Calcic horizon - from 6 to 60 inches (Bk, 2BCk horizons)
Particle-size control section - from 10 to 40 inches (part of Bk, part of 2BCk horizons)
Scravo soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.
ADDITIONAL DATA: Soil interpretation records - MT0509, MT0510.
National Cooperative Soil Survey
U.S.A.