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

Sweet Grass County Area, Montana—Part I 111
subangular blocky; very hard, firm, very sticky,
very plastic; common fine roots; common very
fine and fine pores; common pressure faces and
cracks 1 /4- to 1 /2-inch wide; many distinct
continuous grayish brown (10YR 5/2) moist; clay
films on faces of peds and lining pores; 5 percent
gravel; slightly alkaline (pH 7.4); clear smooth
boundary.
2Bk1—27 to 42 inches; brown (10YR 5/3) very
gravelly sandy clay loam, dark brown (10YR 4/3)
moist; weak coarse prismatic structure; slightly
hard, very friable, slightly sticky, slightly plastic;
few very fine and fine roots; common fine and
medium pores; many distinct carbonate coats on
undersides of rock fragments; 35 percent gravel;
15 percent cobbles; 5 percent stones; strongly
effervescent; moderately alkaline (pH 8.4);
gradual smooth boundary.
3Bk2—42 to 60 inches; pale brown (10YR 6/3) very
gravelly coarse sand, brown (10YR 5/3) moist;
single grain; loose, nonsticky, nonplastic; few faint
carbonate coats on undersides of rock fragments;
35 percent gravel; 15 percent cobbles; 5 percent
stones; strongly effervescent; moderately alkaline
(pH 8.4).
Range in Characteristics
Soil temperature: 42 to 47 degrees F
Moisture control section: Between 4 and 12 inches
Thickness of the mollic epipedon: 7 to 15 inches
Depth to the 2Bk horizon: 20 to 36 inches
Depth to the 3Bk horizon: 40 to over 60 inches
A horizon
Hue: 7.5YR or 10YR
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture (less than 2 mm): Clay loam
Clay content: 27 to 40 percent
Content of rock fragments: 0 to 25 percent—0 to
5 percent cobbles; 0 to 20 percent gravel
Reaction: pH 6.6 to 7.8
Bt horizons
Hue: 7.5YR or 10YR
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 4
Texture (less than 2 mm): Clay or silty clay
Clay content: 40 to 60 percent
Content of rock fragments: 0 to 15 percent—0 to
5 percent cobbles; 0 to 10 percent gravel
Reaction: pH 6.6 to 7.8
2Bk1 horizon
Hue: 7.5YR or 10YR
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 4
Texture (less than 2 mm): Sandy clay loam, clay
loam, loam, or sandy loam
Clay content: 15 to 35 percent
Content of rock fragments: 35 to 70 percent—0 to
5 percent stones; 5 to 20 percent cobbles;
30 to 45 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
3Bk2 horizon
Hue: 7.5YR, 10YR, or 2.5Y
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 to 4
Texture (less than 2 mm): Coarse sand, sand,
loamy sand, or loamy coarse sand
Clay content: 1 to 10 percent
Content of rock fragments: 35 to 80 percent—0 to
10 percent stones; 5 to 25 percent cobbles;
30 to 45 percent gravel
Calcium carbonate equivalent: 1 to 10 percent
Reaction: pH 7.4 to 8.4
Perma Series
Depth class: Very deep (greater than 60 inches)
Drainage class: Somewhat excessively drained
Permeability: Moderate (0.6 to 2.0 inches/hour)
Landform: Fan, hill, landslide, stream terrace, and fan
on escarpment
Parent material: Gravelly alluvium or colluvium
Slope range: 0 to 60 percent
Elevation range: 3,900 to 6,200 feet
Annual precipitation: 15 to 20 inches
Mean annual air temperature: 43 to 45 degrees F
Frost-free period: 70 to 115 days
Taxonomic Class: Loamy-skeletal, mixed,
superactive, frigid Typic Haplustolls
Typical Pedon
Perma cobbly loam, in an area of Perma, stony-
Whitlash, very stony complex, 15 to 35 percent
slopes, in an area of rangeland, 1,520 feet north and
2,590 feet east of the southwest corner of sec. 28,
T. 7 N., R. 4 W.; Jefferson County, Montana.
A1—0 to 7 inches; dark grayish brown (10YR 4/2)
cobbly loam, very dark grayish brown (10YR 3/2)
moist; moderate fine granular structure; soft, very
friable, slightly sticky, slightly plastic; many very
fine and fine roots; 15 percent angular cobbles;
15 percent angular gravel; neutral (pH 6.6); clear
wavy boundary.