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

30 Soil Survey
Range in Characteristics
Soil temperature: 42 to 47 degrees F
Moisture control section: Between 8 inches and the
lithic contact
Depth to bedrock: 10 to 20 inches
A horizon
Hue: 10YR or 2.5Y
Value: 5 to 7 dry; 3 to 5 moist
Chroma: 2 or 3
Texture (less than 2 mm): Sandy loam
Clay content: 5 to 15 percent
Content of rock fragments: 15 to 60 percent—0 to
5 percent cobbles; 15 to 55 percent gravel
Reaction: pH 6.1 to 7.3
C horizon
Hue: 10YR or 2.5Y
Value: 5 to 7 dry; 4 or 5 moist;
Chroma: 2 or 3
Texture (less than 2 mm): Sandy loam or loam
Clay content: 5 to 25 percent
Content of rock fragments: 50 to 80 percent—0 to
15 percent cobbles; 50 to 65 percent gravel
Reaction: pH 5.6 to 7.3
Attewan Series
Depth class: Very deep (greater than 60 inches)
Drainage class: Well drained
Permeability: In the upper 0 to 21 inches = moderate
(0.6 to 2.0 inches/hour); below this depth = rapid
(6 to 20 inches/hour)
Landform: Stream terrace and terrace
Parent material: Loamy over sandy and gravelly
alluvium
Slope range: 0 to 4 percent
Elevation range: 3,750 to 5,200 feet
Mean annual precipitation: 10 to 14 inches
Mean annual air temperature: 38 to 45 degrees F
Frost-free period: 95 to 125 days
Taxonomic Class: Fine-loamy over sandy or sandyskeletal,
mixed, superactive, frigid Aridic
Argiustolls
Typical Pedon
Attewan loam, in an area of Attewan loam, 0 to
4 percent slopes, in an area of rangeland, 2,150 feet
north and 1,450 feet east of the southwest corner of
sec. 36, T. 1 N., R. 15 E.; USGS Greycliff topographic
quadrangle (lat. 45 o 47'29" N.; long. 109 o 48'31" W.)
A—0 to 4 inches; dark grayish brown (10YR 4/2)
loam, very dark brown (10YR 2/2) moist; weak
fine subangular blocky structure parting to
moderate fine granular; soft, very friable, slightly
sticky, nonplastic; few fine and common very fine
roots; common very fine and fine pores; slightly
alkaline (pH 7.6); abrupt smooth boundary.
Bt—4 to 12 inches; dark grayish brown (10YR 4/2)
clay loam, very dark grayish brown (10YR 3/2)
moist; weak fine and moderate very fine
subangular blocky structure; very hard, friable,
moderately sticky, moderately plastic; common
very fine roots; common fine pores; common
distinct discontinuous very dark brown (10YR
2/2), moist; clay films on faces of peds; slightly
alkaline (pH 7.8); clear smooth boundary.
Bk—12 to 21 inches; light brownish gray (2.5Y 6/2)
loam, dark grayish brown (2.5Y 4/2) moist;
moderate very fine prismatic structure parting to
weak fine and medium subangular blocky;
moderately hard, friable, slightly sticky, slightly
plastic; few very fine roots; common fine pores;
disseminated lime; few fine and medium soft
masses of lime; 5 percent gravel; strongly
effervescent; moderately alkaline (pH 8.0);
gradual smooth boundary.
2BCk—21 to 60 inches; grayish brown (2.5Y 5/2)
very gravelly loamy sand, dark grayish brown
(2.5Y 4/2) moist; single grain; loose, nonsticky,
nonplastic; few very fine roots; many medium
and coarse pores; common discontinuous
carbonate coats on rock fragments; 40 percent
gravel; 10 percent cobbles; strongly effervescent;
moderately alkaline (pH 8.0).
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 12 inches
Depth to the Bk horizon: 10 to 21 inches
Depth to the 2BCk horizon: 20 to 40 inches
Note: Some pedons have a Bk2 horizon.
A horizon
Hue: 10YR or 2.5Y
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture (less than 2 mm): Loam
Clay content: 10 to 20 percent
Content of rock fragments: 0 to 50 percent—0 to
20 percent stones and cobbles; 0 to 30 percent
gravel
Reaction: pH 6.1 to 7.8
Bt horizon
Hue: 10YR or 2.5Y
Value: 4 to 6 dry; 3 or 4 moist