LOCATION GRAYHORSE MT
Established Series
Rev. EMR/JMS/RJS
07/2013
GRAYHORSE SERIES
The Grayhorse series consists of very deep, somewhat poorly drained soils that formed in alluvium derived from mixed sources. These soils are on stream terraces and inset fans. Slopes range from 0 to 4 percent. The mean annual precipitation is 330 mm, and the mean annual temperature is 6 degrees C.
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid Aquic Cumulic Haplustolls
TYPICAL PEDON: Grayhorse silt loam, in rangeland on a 1 percent slope at 1,033 meters elevation (colors are for dry soil unless otherwise stated).
A1--0 to 30 cm; dark gray (10YR 4/1) silt loam, very dark gray (10YR 3/1) moist; strong medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and medium roots; many very fine and fine irregular and tubular pores; 5 percent cobbles; slightly effervescent; moderately alkaline (pH 8.0); gradual smooth boundary.
A2--30 to 46 cm; gray (10YR 5/1) loam, very dark gray (10YR 3/1) moist; weak fine subangluar blocky structure parting to moderate fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and medium roots; many very fine and fine irregular and tubular pores; 5 percent gravel, 5 percent cobbles; slightly alkaline (pH 7.4); gradual smooth boundary.
A3--46 to 74 cm; grayish brown (10YR 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist, weak fine subangular blocky; soft, very friable, nonsticky and nonplastic; common fine and medium roots; common fine irregular pores; 5 percent medium distinct light olive gray (5Y 6/2) moist redox depletions; 15 percent gravel, 5 percent cobbles; neutral (pH 7.3); gradual smooth boundary. (combined thickness of the A horizons is 50 to 90 cm)
C1--74 to 86 cm; light brownish gray (10YR 6/2) very cobbly fine sandy loam, dark grayish brown (10YR 4/2) moist, massive; soft, very friable, nonsticky and nonplastic; few fine roots; common medium irregular pores; 10 percent medium distinct light olive gray (5Y 6/2) moist redox depletions; 30 percent gravel, 25 percent cobbles; neutral (pH 7.3); gradual smooth boundary. (0 to 12 cm thick)
2C2--86 to 152 cm; light brownish gray (2.5Y 6/2) extremely gravelly loamy sand, dark grayish brown (2.5Y 4/2) moist, single grain; loose, nonsticky and nonplastic; 25 percent medium prominent yellowish brown (10YR 5/8) moist redox concentrations and 20 percent medium distinct light olive gray (5Y 6/2) moist redox depletions; many medium irregular pores; 50 percent gravel, 15 percent cobbles; neutral (pH 7.0).
TYPE LOCATION: Stevensville topographic quadrangle, Ravalli County, Montana; 850 meters north and 115 meters west of the SE corner of section 23, T. 9 N., R. 20 W. UTM Zone 11: 724865e, 5156362n, NAD 83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 5 to 8 degrees C
Moisture control section - 20 to 60 cm
Depth to seasonal high water table - 60 to 100 cm for extended periods during portions of the late spring or early summer
Mollic epipedon thickness - 50 to 90 cm
Depth to sandy-skeletal material - 50 to 90 cm
A1 and A2 horizons
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 1 or 2 dry or moist
Texture: silt loam or loam
Clay content: 18 to 26 percent
Rock fragments: 0 to 15 percent--0 to 10 percent gravel; 0 to 5 percent cobbles and stones
Reaction: pH 6.6 to 8.4
A3 horizon
Value: 4 or 5 dry; 2 or 3 moist
Texture: loam or fine sandy loam
Clay content: 16 to 24 percent
Rock fragments: 0 to 35 percent--0 to 20 percent gravel; 0 to 15 percent cobbles and stones
Reaction: pH 6.6 to 8.2
C1 horizon
Hue: 10YR or 2.5Y
Value: 5, 6, or 7 dry; 4 or 5 moist
Texture: fine sandy loam, sandy loam, or loam
Clay content: 10 to 22 percent
Rock fragments: 35 to 70 percent--35 to 70 percent gravel; 0 to 30 percent cobbles and stones
Reaction: pH 6.6 to 8.2
2C2 horizon
Hue: 10YR or 2.5Y
Value: 5, 6, or 7 dry; 4 or 5 moist
Texture: loamy sand or loamy coarse sand
Clay content: 0 to 15 percent
Rock fragments: 35 to 80 percent--35 to 70 percent gravel; 0 to 30 percent cobbles and stones
Reaction: pH 6.6 to 7.8
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - stream terraces and inset fans
Slopes - 0 to 4 percent
Elevation - 990 to 1,505 meters
Parent material - alluvium derived from mixed sources
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 305 to 380 mm
Mean annual air temperature - 4 to 7 degrees C
Frost-free period - 90 to 115 days
GEOGRAPHICALLY ASSOCIATED SOILS:
DRAINAGE AND PERMEABILITY: somewhat poorly drained; moderate permeability with rapid permeability below 74 cm.
USE AND VEGETATION: These soils are used primarily for pasture, rangeland, and wildlife habitat. Vegetation is chiefly mixed grasses, small grains, and minor acreages of other specialty crops.
DISTRIBUTION AND EXTENT: The Grayhorse series is of small extent in the intermountain valleys of southwestern Montana. MLRA 44A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Bitterroot Valley Area, Montana, 2013; proposed in Ravalli County, Montana, 2006.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 74 cm (A1, A2, and A3 horizons)
Redoximorphic features - from 60 to 152 cm (part of the A3, C1, and 2C2 horizons)
Particle-size control section - from 25 to 100 cm (part of the A1, A2, A3, C1, and part of the 2C2 horizons)
Grayhorse soils have a frigid temperature regime, an ustic moisture regime, and an aquic moisture subclass.
National Cooperative Soil Survey
U.S.A.