LOCATION OPITZ MTEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive Ustic Argicryolls
TYPICAL PEDON: Opitz coarse sandy loam, bouldery, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 10 inches; very dark grayish brown (10YR 3/2) coarse sandy loam, very dark brown (10YR 2/2) moist; moderate medium granular structure; slightly hard, very friable, nonsticky and nonplastic; many very fine and fine roots; many very fine and fine interstitial pores; 10 percent pebbles; neutral (pH 6.6); clear wavy boundary. (7 to 13 inches thick)
Bt1--10 to 15 inches; brown (10YR 5/3) gravelly sandy clay loam, dark brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine tubular pores; common distinct clay films on faces of peds; 20 percent pebbles; neutral (pH 6.6); clear wavy boundary. (4 to 8 inches thick)
Bt2--15 to 22 inches; pale brown (10YR 6/3) gravelly coarse sandy loam, grayish brown (10YR 5/2) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; slightly hard, very friable, slightly sticky and nonplastic; common very fine and fine roots; many very fine and fine tubular pores; common faint clay films on faces of peds; 30 percent pebbles; neutral (pH 6.8); gradual wavy boundary. (6 to 12 inches thick)
BC--22 to 36 inches; grayish brown (10YR 5/2) very gravelly coarse sandy loam, brown (10YR 4/3) moist; massive; slightly hard, very friable, nonsticky and nonplastic; common very fine and fine roots; common fine and very fine tubular pores; 40 percent pebbles; neutral (pH 6.8); gradual irregular boundary. (6 to 18 inches thick)
Cr--36 to 57 inches; decomposed granite bedrock (grus) that crushes to very gravelly coarse sand. (17 to 30 inches thick)
R--57 inches; hard granite bedrock.
TYPE LOCATION: Jefferson County, Montana; 2,650 feet north and 975 feet west of the SE corner of sec. 6, T. 3 N., R. 3 W.
RANGE IN CHARACTERISTICS:
Soil Temperature - 36 to 42 degrees F
Moisture control section - between 8 and 24 inches
Mollic epipedon thickness - 7 to 13 inches
Depth to Cr horizon - 20 to 40 inches
Depth to R horizon - 40 to 60 inches
Surface stones and boulders - 0 to 0.1 percent
Weighted average clay content of Bt horizons is 18 percent or less
A horizon - Hue: 10YR or 2.5Y
Value: 3 or 4 dry, 2 or 3 moist
Texture: coarse sandy loam or sandy loam
Clay content: 12 to 15 percent
Rock fragments: 5 to 35 percent pebbles (mostly less than 7 mm in diameter)
Reaction: pH 6.1 to 7.3
Bt1 horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2, 3 or 4
Texture: coarse sandy loam, sandy clay loam or sandy loam
Clay content: 15 to 22 percent
Rock fragments: 10 to 35 percent pebbles (mostly less than 7 mm in diameter)
Reaction: pH 6.1 to 7.3
Bt2 horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry, 5 or 6 moist
Chroma: 2, 3 or 4
Texture: coarse sandy loam or sandy loam
Clay content: 15 to 18 percent
Rock fragments: 15 to 35 percent pebbles (mostly less than 7 mm in diameter)
Reaction: pH 6.1 to 7.3
BC horizon - Hue: 10YR or 2.5Y
Value: 5, 6 or 7 dry, 4, 5 or 6 moist
Chroma: 2, 3, or 4
Texture: coarse sandy loam, loamy coarse sand or coarse sand
Clay content: 3 to 15 percent
Rock fragments: 15 to 50 percent pebbles (mostly less than 10 mm in diameter)
Reaction: pH 6.1 to 7.3
COMPETING SERIES:
Bassel (CO) - does not have a lithic contact above 60 inches; has horizons of secondary carbonate accumulation.
Burgess (WY) - has a lithic contact at 20 to 40 inches.
Ethelman (CO) - does not have a lithic contact above 60 inches; has horizon of secondary carbonate accumulation.
Greenman (WY) - has lithic contact at 20 to 40 inches; formed in material weathered from sandstone.
Scriver (ID) - does not have a paralithic contact at 20 to 40 inches; has horizons containing lamaellae.
Spinney (CO) - does not have a lithic contact above 60 inches; has horizon of secondary carbonate accumulation.
Tiagos (CO) - does not have a lithic contact above 60 inches.
Washpass (NM) - does not have a lithic contact above 60 inches; formed in colluvium from basalt and tuff-breccia; depth to base of argillic is 60 inches or more.
GEOGRAPHIC SETTING:
Landform - plateaus, ridges and sideslopes of mountains
Elevation - 5,500 to 7,500 feet
Slope- 2 to 35 percent
Parent material - alluvium, colluvium and residuum from coarse grained igneous rocks and coarse grained metamorphic rocks
Climate - long, cold winters; cool, moist springs; short, cool summers
Mean annual precipitation - 15 to 24 inches
Mean annual air temperature - 36 to 40 degrees F.
Frost-free period - 30 to 70 days
DRAINAGE AND PERMEABILITY: Well drained, moderately rapid permeability.
USE AND VEGETATION: Opitz soils are primarily used for rangeland. The potential native vegetation is mainly Idaho fescue, rough fescue, parry danthonia, bluebunch wheatgrass, Western yarrow, lupine, Rocky Mountain juniper, rubber rabbitbrush and big sagebrush. Some areas have scattered Douglas-fir and Rocky Mountain juniper.
DISTRIBUTION AND EXTENT: Opitz soils are of moderate extent in southwestern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Jefferson County, Montana, 1998.
REMARKS: Soil interpretation record: MT1574, MT3055. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the surface to 10 inches (A horizon); an argillic horizon from 10 to 22 inches (Bt1 and Bt2 horizons); a particle-size control section from 10 to 22 inches (Bt1 and Bt2 horizons); a layer of decomposed granite (grus) from 36 to 57 inches (Cr horizon); hard granite bedrock at 57 inches (R horizon). Opitz soils have a cryic temperature regime and an ustic moisture regime.