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

50 Soil Survey
flagstones; slightly alkaline (pH 7.8); abrupt
smooth boundary.
R—14 inches; hard sandstone.
Range in Characteristics
Soil temperature: 37 to 47 degrees F
Moisture control section: Between 4 and 12 inches
Thickness of the mollic epipedon: 7 to 16 inches
Depth to the Bk horizon: 7 to 16 inches
Depth to bedrock: 10 to 20 inches
A1 horizon
Hue: 7.5YR, 10YR, or 2.5Y
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 1 or 2
Texture (less than 2 mm): Loam
Clay content: 10 to 27 percent
Content of rock fragments: 0 to 60 percent—0 to
50 percent stones, flagstones or cobbles, and
channers; 0 to 10 percent gravel
Reaction: pH 6.6 to 7.8
A2 horizon
Hue: 7.5YR, 10YR, or 2.5Y
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 1 to 3
Texture (less than 2 mm): Fine sandy loam, loam,
or sandy loam
Clay content: 10 to 27 percent
Content of rock fragments: 35 to 75 percent—0 to
65 percent stones, flagstones or cobbles, and
channers; 10 to 30 percent gravel
Calcium carbonate equivalent: 0 to 5 percent
Reaction: pH 7.4 to 9.0
Bk horizon
Hue: 7.5YR, 10YR, or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 4
Texture (less than 2 mm): Fine sandy loam, loam,
or sandy loam
Clay content: 10 to 27 percent
Content of rock fragments: 35 to 75 percent—0 to
65 percent stones, flagstones or cobbles, and
channers; 20 to 30 percent gravel
Calcium carbonate equivalent: 3 to 10 percent
Reaction: pH 7.4 to 9.0
Chinook Series
Depth class: Very deep (greater than 60 inches)
Drainage class: Well drained
Permeability: Moderately rapid (2 to 6 inches/hour)
Landform: Hill and swale on plain
Parent material: Sandy residuum weathered from
sandstone
Slope range: 4 to 25 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: Coarse-loamy, mixed,
superactive, frigid Aridic Haplustolls
Typical Pedon
Chinook fine sandy loam, in an area of Chinook-
Twilight fine sandy loams, 8 to 25 percent slopes, in
an area of rangeland, 2,500 feet north and 1,000 feet
east of the southwest corner of sec. 8, T. 5 N.,
R. 15 E.; USGS Melville NW topographic quadrangle
(lat. 46 o 11'51" N.; long. 109 o 52'44" W.)
A1—0 to 3 inches; grayish brown (10YR 5/2) fine
sandy loam, very dark brown (10YR 2/2) moist;
moderate very fine and fine granular structure;
soft, very friable, nonsticky, nonplastic; common
medium and coarse and many very fine and fine
roots; many very fine and fine pores; neutral
(pH 6.8); clear wavy boundary.
A2—3 to 10 inches; grayish brown (10YR 5/2) sandy
loam, very dark grayish brown (10YR 3/2) moist;
weak medium subangular blocky structure
parting to moderate very fine and fine granular;
soft, very friable, nonsticky, nonplastic; common
fine and medium and many very fine roots; many
very fine and fine pores; neutral (pH 7.2); gradual
wavy boundary.
Bw1—10 to 20 inches; light olive brown (2.5Y 5/3)
sandy loam, olive brown (2.5Y 4/3) moist; weak
fine subangular blocky structure; soft, very friable,
nonsticky, nonplastic; few very fine and fine roots;
many very fine and fine pores; slightly alkaline
(pH 7.4); gradual wavy boundary.
Bw2—20 to 31 inches; light yellowish brown (2.5Y
6/3) sandy loam, light olive brown (2.5Y 5/3)
moist; weak very fine and fine subangular blocky
structure; soft, very friable, nonsticky, nonplastic;
few very fine roots; many very fine and fine pores;
slightly alkaline (pH 7.4); gradual wavy boundary.
Bk1—31 to 45 inches; light brownish gray (2.5Y 6/2)
sandy loam, light olive brown (2.5Y 5/3) moist;
weak very fine subangular blocky structure; soft,
very friable, nonsticky, nonplastic; few very fine
roots; common very fine and fine pores; common
fine irregular soft masses of lime; strongly
effervescent; moderately alkaline (pH 8.4);
gradual wavy boundary.