LOCATION BRIDGER MT+WY
Established Series
Rev. JB-KTS-RJS
03/2012
BRIDGER SERIES
The Bridger series consists of very deep, well drained soils that formed in alluvium, outwash, colluvium, till or slide deposits derived from mixed rock sources. These soils are on alluvial fans, outwash fans, fan remnants, stream terraces, drainageways, moraines, hills, mountain slopes, ridges and landslides. Slopes are 0 to 45 percent. Mean annual precipitation is about 20 inches, and mean annual air temperature is about 45 degrees F.
TAXONOMIC CLASS: Fine, mixed, superactive Ustic Argicryolls
TYPICAL PEDON: Bridger loam, cultivated (colors are for dry soil unless otherwise noted).
A--0 to 9 inches, very dark gray (10YR 3/1) loam, black (10YR 2/1) moist; moderate fine granular structure; soft, friable, slightly sticky and slightly plastic; many fine and very fine roots; many very fine and fine pores; 5 percent gravel, 1 percent stones below surface; neutral (pH 7.0); clear boundary. (7 to 16 inches thick)
Bt--9 to 24 inches; brown (10YR 5/3) clay, brown (10YR 4/3) moist; moderate medium prismatic structure parting to strong coarse medium and fine blocky structure; very hard, firm, moderately sticky and moderately plastic; common very fine roots; many very fine pores; distinct continuous very dark grayish brown (10YR 3/2) moist; clay films on faces of peds; 5 percent gravel, 1 percent stones; neutral (pH 7.0); clear wavy boundary. (10 to 30 inches thick)
Bk1--24 to 36 inches; brown (10YR 5/3) gravelly clay loam, brown (10YR 4/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; few fine pores; 15 percent gravel, 5 percent cobbles; few large masses of lime; continuous distinct lime casts on underside of rock fragments; strongly effervescent; moderately alkaline (pH 8.0); gradual boundary. (4 to 15 inches thick)
Bk2--36 to 60 inches, light yellowish brown (2.5Y 6/3) gravelly loam, light olive brown (2.5Y 5/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; few fine pores; 20 percent gravel; 5 percent cobbles; common distinct lime casts on undersides of rock fragments mainly in the upper part of the horizon; disseminated lime; strongly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Gallatin County, Montana; 600 feet east and 300 feet south of the N 1/4 corner of sec. 27, T. 3 N., R. 5 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 36 to 47 degrees F.
Mollic epipedon thickness - 7 to 16 inches
Depth to secondary calcium carbonate accumulation - 17 to 40 inches
Note: Some pedons may have a Btk or BC horizon.
A horizon
Hue: 7.5YR, 10YR or 2.5Y; dry or moist
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 1 or 2; dry or moist
Texture: loam or clay loam
Clay content: 18 to 35 percent
Rock fragments: 5 to 35 percent--5 to 25 percent gravel, 0 to 15 percent cobbles and stones
Reaction: pH 6.1 to 7.8
Bt horizon
Hue: 7.5YR, 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 3 to 5 moist
Chroma: 2 to 4; dry or moist
Texture: clay loam, silty clay or clay
Clay content: 35 to 50 percent
Rock fragments: 5 to 35 percent--5 to 25 percent gravel, 0 to 10 percent cobbles and stones
Reaction: pH 6.1 to 7.8
Btk horizon (where present)
Hue: 7.5YR, 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 3 to 5 moist
Chroma: 2 to 4; dry or moist
Texture: clay loam, silty clay or clay
Clay content: 27 to 45 percent
Rock fragments: 5 to 35 percent--5 to 25 percent gravel, 0 to 10 percent cobbles and stones
Reaction: pH 7.5 to 8.0
Bk horizons
Hue: 7.5YR, 10YR or 2.5Y
Value: 6 to 8 dry; 5 to 7 moist
Chroma: 2 to 4; dry or moist
Texture: clay loam, sandy clay loam or loam
Clay content: 20 to 40 percent
Rock fragments: 5 to 40 percent--5 to 40 percent gravel, 0 to 20 percent cobbles and stones
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 9.0
COMPETING SERIES:
Bangtail (MT) - have a paralithic contact at 20 to 40 inches
Duckcreek (MT) - have a paralithic contact at 20 to 40 inches
Echard (UT) - have volcanic ash in the soil profile
Melville (MT) - have a lithologic discontinuity
Mollet (MT) - does not have a secondary calcium carbonate accumulation
Rattler (MT) - have a lithologic discontinuity
Sevier (UT) - have a paralithic contact at 20 to 40 inches
GEOGRAPHIC SETTING:
Landform - alluvial fans, outwash fans, fan remnants, stream terraces, drainageways, moraines, hills, mountain slopes, ridges and landslides
Elevation - 4,500 to 8,500 feet
Slope - 0 to 45 percent
Parent material - alluvium, outwash, colluvium, till or slide deposits derived from mixed rock sources
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 15 to 30 inches
Mean annual air temperature - 34 to 45 degrees F.
Frost-free period - 50 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: Bridger soils are used mainly for native range and for dryland and irrigated production of hay. Potential native vegetation is mainly bluebunch wheatgrass, Idaho fescue, rough fescue, prairie junegrass, bluegrass, lupine, and silver sage.
DISTRIBUTION AND EXTENT: Bridger soils are extensive in valleys of northern Rocky Mountain region in Montana. MLRAs - 43B, 44B and 49.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Gallatin Valley Area, Montana, 1905.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 9 inches (A horizon)
Argillic horizon - from 9 to 24 inches (Bt horizon)
Horizons of calcium carbonate accumulation - from 24 to 60 inches (Bk1, Bk2 horizons)
Particle-size control section - from 9 to 24 inches (Bt horizon)
Bridger soils have a cryic temperature regime and an ustic moisture regime.
ADDITIONAL DATA: Soil interpretations records - MT0056, MT7055, MT1067, MT0368, MT0902.
National Cooperative Soil Survey
U.S.A.