Soil Survey of Sweet Grass County Area, Montana - Soil Data Mart

150 Soil Survey
2Bk—21 to 60 inches; light brownish gray (10YR 6/2)
very gravelly loam, grayish brown (10YR 5/2)
moist; weak medium prismatic structure; soft,
friable, slightly sticky, slightly plastic; few fine
roots; discontinuous carbonate coats on
undersides of rock fragments; few fine soft
masses of lime; 40 percent gravel; 10 percent
cobbles; strongly effervescent; moderately
alkaline (pH 8.0).
Range in Characteristics
Soil temperature: 43 to 47 degrees F
Moisture control section: Between 4 and 12 inches
Thickness of the mollic epipedon: 7 to 12 inches
Depth to the Bk horizon (where present): 11 to
21 inches
Depth to the 2Bk horizon: 15 to 36 inches
Note: Some pedons have a Bk horizon.
A horizon
Hue: 10YR or 2.5Y
Value: 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture (less than 2 mm): Loam or clay loam
Clay content: 20 to 35 percent
Content of rock fragments: 0 to 15 percent—0 to
5 percent cobbles; 0 to 10 percent gravel or
channers
Reaction: pH 6.1 to 7.3
Bt horizons
Hue: 7.5YR, 10YR, or 2.5Y
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 to 4
Texture (less than 2 mm): Clay loam, silty clay,
clay, or silty clay loam
Clay content: 35 to 55 percent
Content of rock fragments: 0 to 15 percent—0 to
5 percent cobbles; 0 to 15 percent gravel or
channers
Reaction: pH 6.1 to 7.8
2Bk horizon
Hue: 10YR or 2.5Y
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 2 to 4
Texture (less than 2 mm): Loam or sandy loam
Clay content: 5 to 25 percent
Content of rock fragments: 50 to 85 percent—5 to
10 percent cobbles; 40 to 75 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
Vision Series
Depth class: Very deep (greater than 60 inches)
Drainage class: Well drained
Permeability: Moderate (0.6 to 2.0 inches/hour)
Landform: Hill
Parent material: Gravelly colluvium weathered from
tuff breccia
Slope range: 35 to 60 percent
Elevation range: 3,900 to 6,000 feet
Mean annual precipitation: 15 to 19 inches
Mean annual air temperature: 43 to 45 degrees F
Frost-free period: 85 to 115 days
Taxonomic Class: Loamy-skeletal, mixed,
superactive, frigid Typic Haplustalfs
Typical Pedon
Vision gravelly loam, in an area of Vision-Sweetweed-
Whitlash complex, 25 to 60 percent slopes, in an area
of coniferous forest, 2,400 feet south and 250 feet
east of the northwest corner of sec. 19, T. 2 S.,
R. 16 E.; USGS Packsaddle Butte topographic
quadrangle (lat. 45 o 38'46" N.; long. 109 o 48'28" W.)
Oi—0 to 1 inch; slightly decomposed needles, twigs,
and leaves.
A1—1 to 4 inches; dark grayish brown (10YR 4/2)
gravelly loam, very dark brown (10YR 2/2) moist;
weak thin platy structure parting to weak fine
granular; soft, very friable, slightly sticky, slightly
plastic; many very fine and fine roots; many very
fine and fine pores; 13 percent gravel; 5 percent
cobbles; slightly acid (pH 6.4); abrupt smooth
boundary.
A2—4 to 8 inches; dark grayish brown (10YR 4/2)
gravelly loam, very dark brown (10YR 2/2) moist;
weak medium subangular blocky structure; soft,
very friable, slightly sticky, slightly plastic;
common medium and many fine roots; many very
fine and fine pores; 20 percent gravel; 5 percent
cobbles; slightly acid (pH 6.4); clear wavy
boundary.
Bt1—8 to 13 inches; grayish brown (10YR 5/2)
gravelly loam, dark grayish brown (10YR 4/2)
moist; weak medium subangular blocky structure;
slightly hard, friable, slightly sticky, slightly plastic;
common fine and medium roots; many very fine
and fine pores; common faint discontinuous dark
brown (10YR 3/3) moist; clay films on faces