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

128 Soil Survey
Clay content: 15 to 27 percent
Content of rock fragments: 15 to 80 percent—0 to
30 percent stones and cobbles; 15 to
50 percent gravel
Reaction: pH 6.6 to 7.3
Bt horizon
Hue: 7.5YR or 10YR
Value: 3 to 5 dry; 2 to 4 moist
Chroma: 2 to 4
Texture (less than 2 mm): Clay loam or sandy
clay loam
Clay content: 20 to 35 percent
Content of rock fragments: 35 to 80 percent—0 to
35 percent stones and cobbles; 30 to
45 percent gravel
Reaction: pH 6.6 to 7.8
Btk horizon:
Hue: 7.5YR or 10YR
Value: 3 to 6 dry; 2 to 5 moist
Chroma: 2 to 4
Texture (less than 2 mm): Clay loam, loam, sandy
clay loam, or sandy loam
Clay content: 18 to 30 percent
Content of rock fragments: 35 to 80 percent—0 to
40 percent stones and cobbles; 30 to
60 percent gravel
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 6.6 to 7.9
Bk1 horizon
Hue: 10YR or 2.5Y
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 4
Texture (less than 2 mm): Loam, sandy loam,
sandy clay loam, or clay loam
Clay content: 18 to 30 percent
Content of rock fragments: 35 to 80 percent—0 to
40 percent stones and cobbles; 30 to
60 percent gravel
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.9 to 8.4
Bk2 horizon
Hue: 10YR or 2.5Y
Value: 5 to 8 dry; 4 to 7 moist
Chroma: 2 to 4
Texture (less than 2 mm): Loam, sandy loam, or
sandy clay loam
Clay content: 5 to 25 percent
Content of rock fragments: 50 to 85 percent—0 to
40 percent stones and cobbles; 45 to
70 percent gravel
Calcium carbonate equivalent: 10 to 25 percent
Reaction: pH 7.9 to 9.0
Sieben Series
Depth class: Very deep (greater than 60 inches)
Drainage class: Well drained
Permeability: Moderate (0.6 to 2.0 inches/hour)
Landform: Fan, stream terrace, and terrace
Parent material: Gravelly alluvium
Slope range: 2 to 15 percent
Elevation range: 3,750 to 5,200 feet
Mean annual precipitation: 10 to 14 inches
Mean annual air temperature: 43 to 46 degrees F
Frost-free period: 95 to 125 days
Taxonomic Class: Loamy-skeletal, mixed,
superactive, frigid Calcidic Argiustolls
Typical Pedon
Sieben gravelly loam, 1,900 feet south and 50 feet
east of the northwest corner of sec. 15, T. 13 N.,
R. 4 W.; Lewis and Clark County, Montana.
A1—0 to 5 inches; grayish brown (10YR 5/2) gravelly
loam, very grayish brown (10YR 3/2) moist;
moderate very thin platy structure parting to
moderate very fine granular; slightly hard, very
friable, slightly sticky, slightly plastic; many very
fine roots; 20 percent angular gravel; slightly acid
(pH 6.2); clear smooth boundary.
A2—5 to 9 inches; grayish brown (10YR 5/2) gravelly
loam, very dark grayish brown (10YR 3/2) moist;
moderate medium prismatic structure parting to
moderate fine and medium subangular blocky;
slightly hard, very friable, slightly sticky, slightly
plastic; many very fine roots; many very fine
tubular and interstitial pores; 20 percent angular
gravel; slightly acid (pH 6.2); clear smooth
boundary.
Bt1—9 to 17 inches; pale brown (10YR 6/3) very
gravelly clay loam, dark brown (10YR 4/3) moist;
moderate medium prismatic structure parting to
moderate fine and medium subangular blocky;
hard, friable, moderately sticky, moderately
plastic; common very fine roots; many very
fine tubular and interstitial pores; many distinct
brown (10YR 5/3) clay films on faces of peds;
45 percent angular gravel; slightly acid (pH 6.4);
gradual smooth boundary.
Bt2—17 to 21 inches; pale brown (10YR 6/3) very
gravelly loam, dark brown (10YR 4/3) moist; weak
fine subangular blocky structure; slightly hard,
very friable, moderately sticky, slightly plastic;
common very fine roots; many very fine tubular
and interstitial pores; few faint clay films on faces
of peds and rock fragments; 55 percent angular