LOCATION PHILIPSBURG MTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Calcic Argicryolls
TYPICAL PEDON: Philipsburg silt loam, in rangeland (colors are for dry soil unless otherwise noted).
A1--0 to 5 inches; dark grayish brown (10YR 4/2) silt loam, black (10YR 2/1) moist; weak medium and fine subangular blocky structure parting to weak fine and very fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine and few fine roots; many fine and very fine dendritic tubular pores; 10 percent gravel; neutral (pH 6.8); clear wavy boundary.
A2--5 to 14 inches; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium prismatic structure parting to moderate medium and fine granular; slightly hard, friable, slightly sticky and slightly plastic; many very fine and few fine roots; many fine and very fine dendritic tubular pores; 10 percent gravel; neutral (pH 6.7); clear wavy boundary.
Bt1--14 to 20 inches; brown (10YR 5/3), silty clay loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium and fine subangular blocky; slightly hard, friable, moderately sticky and moderately plastic; common very fine and few fine roots; common very fine and few fine dendritic tubular pores; many distinct patchy clay films on faces of peds; 10 percent gravel; neutral (pH 7.0); clear wavy boundary.
Bt2--20 to 32 inches; yellowish brown (10YR 5/4) clay loam, dark yellowish brown (10YR 4/4) moist; strong medium subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; common very fine and few fine roots; common very fine and few fine dendritic tubular pores; common distinct patchy clay films on faces of peds; 10 percent gravel; neutral (pH 6.8); gradual wavy boundary.
Bk1--32 to 43 inches; very pale brown (10YR 8/4), gravelly loam, very pale brown (10YR 7/4) moist; weak medium and fine subangular blocky structure parting to weak fine and very fine granular; soft, very friable, slightly sticky and slightly plastic; few very fine roots; common very fine irregular pores; 25 percent gravel; disseminated lime; common medium and fine soft masses of lime; many distinct continuous lime coatings on rock fragments; violently effervescent; moderately alkaline (pH 8.2); clear wavy boundary.
Bk2--43 to 60 inches; very pale brown (10YR 8/3), very gravelly sandy loam, very pale brown (10YR 7/3) moist; weak very fine and fine granular structure; soft, very friable, slightly sticky and non-plastic; few very fine roots; common very fine irregular pores; 35 percent gravel, 15 percent cobbles; disseminated lime; common medium and fine soft masses of lime; many distinct continuous lime coatings on rock fragments; violently effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Beaverhead County, Montana; approximately 950 feet west and 1550 feet south of the NE corner of sec. 28, T. 4 S., R. 15 W., Fox Gulch topographic quadrangle, UTM 12T, 308264e, 5036779n. NAD 83.
RANGE IN CHARACTERISTICS:
Soil temperature - 35 to 42 degrees F.
Moisture control section - between 4 and 12 inches.
Mollic epipedon thickness - 7 to 15 inches.
Depth to argillic horizon - 6 to 15 inches.
Depth to the Bk horizon - 20 to 39 inches.
A horizons - Hue: 7.5YR or 10YR
Value: 2, 3, 4, or 5 dry; 2 or 3 moist
Chroma: 1, 2, or 3
Texture: loam, silt loam, or clay loam
Clay content: 18 to 30 percent
Rock fragments: 0 to 30 percent--0 to 5 percent cobbles; 0 to 25 percent gravel
Reaction: pH 6.1 to 7.3
Bt horizons - Hue: 7.5YR or 10YR
Value: 4, 5 or 6 dry; 3, 4, or 5 moist
Chroma: 2, 3, or 4
Texture: loam, clay loam, or silty clay loam
Clay content: 25 to 35 percent, less than 40 percent sand
Rock fragments: 0 to 35 percent--0 to 10 percent cobbles; 0 to 35 percent gravel
Reaction: pH 6.6 to 7.8
Bk horizons - Hue: 10YR or 2.5Y
Value: 6, 7 or 8 dry; 5, 6 or 7 moist
Chroma: 2, 3, or 4
Texture: sandy loam, loam or clay loam
Clay content: 12 to 35 percent
Rock fragments: 10 to 50 percent--0 to 15 percent cobbles, 10 to 35 percent gravel
Calcium carbonate equivalent: 15 to 25 percent
Reaction: pH 7.9 to 8.4
COMPETING SERIES:
Accola (MT) has an O horizon.
Michelson (MT) - has a buried argillic horizon below a depth of 40 inches.
Oro Fino (MT) - is sandy-skeletal at depths of 40 to 60 inches.
GEOGRAPHIC SETTING:
Landform - alluvial fans; stream terraces; hills.
Elevation - 5,500 to 8,000 feet.
Slope - 0 to 60 percent.
Parent material - alluvium derived from mixed rock sources.
Climate - long, cold winters; cold, moist springs; short, cool summers.
Mean annual precipitation - 14 to 24 inches.
Mean annual air temperature - 34 to 40 degrees F.
Frost-free period - 30 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Adel, Bridger, Maciver and Tiban series. Adel soils have mollic epipedon more than 40 mm thick and lack argillic horizons. Bridger soils have more than 35 percent clay in the argillic horizons and lack a calcic horizon. Maciver soils have loamy-skeletal argillic horizons. Tiban soils have a loamy skeletal control section, and lack both argillic and calcic horizons.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: Philipsburg soils are primarily used for rangeland and wildlife habitat. The potential native vegetation is mainly rough fescue, Idaho fescue, bluebunch wheatgrass, prairie junegrass, mountain brome, parry danthonia, sticky geranium, sedum (stoneseed), Western yarrow, milkvetch, shrubby cinquefoil, and mountain big sagebrush.
DISTRIBUTION AND EXTENT: Philipsburg soils are of moderate extent in southwestern Montana.
MLRA OFFICE RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Granite County, Montana, 1972. Type location moved to Jefferson County, Montana, 1993. Type location moved to Beaverhead County, Montana, 2005.
REMARKS: Soil interpretation record: MT0525. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the surface to 14 inches (A horizons); an argillic horizon from 14 to 32 inches (Bt1, Bt2 horizons); a particle-size control section from 10 to 30 inches (Bt1, Bt2 horizons); a calcic horizon from 32 to 60 inches (Bk1, Bk2 horizons). Philipsburg soils have a cryic temperature regime and an ustic moisture regime.