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

70 Soil Survey
slightly plastic; many very fine and fine roots;
few very fine pores; 15 percent rounded cobbles;
15 percent rounded gravel; neutral (pH 7.2);
gradual irregular boundary.
Cg3—45 to 60 inches; yellowish brown (10YR 5/4)
very gravelly sandy clay loam, dark yellowish
brown (10YR 4/4) moist; many distinct yellowish
red (5YR 5/6) redox concentrations; few faint very
dark gray (5Y 3/1) redox depletions; massive;
slightly hard, friable, moderately sticky, slightly
plastic; common very fine and fine roots; few
very fine pores; 10 percent rounded cobbles;
35 percent rounded gravel; neutral (pH 7.2).
Range in Characteristics
Soil temperature: 36 to 42 degrees F
Moisture control section: Between 4 and 12 inches
Thickness of the mollic epipedon: 10 to 19 inches
Depth to the seasonal high water table: Ponded to
12 inches
Surface stones: 0.0 to 0.1 percent
A horizons
Hue: 10YR, 2.5Y, or 5Y
Value: 2, 2.5, or 3 dry
Chroma: 1 or 2
Texture (less than 2 mm): Loam, mucky loam,
mucky silt loam, or sandy loam
Clay content: 10 to 20 percent
Content of rock fragments: 5 to 25 percent—0 to
5 percent cobbles; 5 to 20 percent gravel
Reaction: pH 6.1 to 7.3
Bw horizon
Hue: 10YR, 2.5Y, or 5Y
Texture (less than 2 mm): Sandy clay loam, loam,
or sandy loam
Clay content: 18 to 30 percent
Content of rock fragments: 10 to 35 percent—0 to
10 percent cobbles; 10 to 25 percent gravel
Reaction: pH 6.1 to 7.3
Cg horizons
Hue: 10YR, 2.5Y, or 5Y
Value: 4 or 5 moist; 5 to dry
Texture (less than 2 mm): Loam, sandy clay loam,
or sandy loam
Clay content: 18 to 27 percent
Content of rock fragments: 0 to 50 percent—0 to
15 percent cobbles; 0 to 35 percent gravel
Reaction: pH 5.6 to 7.3
Frenchcreek Series
Depth class: Very deep (greater than 60 inches)
Drainage class: Well drained
Permeability: Moderately rapid (2 to 6 inches/hour)
Landform: Stream terrace
Parent material: Gravelly alluvium
Slope range: 2 to 4 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 Aridic Haplustolls
Typical Pedon
Frenchcreek very gravelly loam, 2,000 feet north
and 800 feet east of the southwest corner of sec. 29,
T. 13 N., R. 3 W.; Lewis and Clark County, Montana.
A—0 to 5 inches; grayish brown (10YR 5/2) very
gravelly loam, very dark grayish brown (10YR
3/3) moist; moderate very thin platy structure
parting to moderate very fine granular; slightly
hard, very friable, slightly sticky, slightly plastic;
many very fine roots; 55 percent angular gravel;
slightly acid (pH 6.1); clear smooth boundary.
Bw1—5 to 12 inches; brown (10YR 5/3) very gravelly
loam, dark brown (10YR 4/3) moist; weak fine
and medium subangular blocky structure; hard,
friable, slightly sticky, slightly plastic; common
very fine roots; many very fine tubular and
interstitial pores; 60 percent angular gravel;
slightly acid (pH 6.2); gradual smooth boundary.
Bw2—12 to 26 inches; pale brown (10YR 6/3)
extremely gravelly sandy loam, dark brown
(10YR 4/3) moist; weak very fine granular
structure; soft, very friable, slightly sticky,
nonplastic; common very fine roots; 70 percent
angular gravel; slightly acid (pH 6.4); gradual
smooth boundary.
C1—26 to 36 inches; pale brown (10YR 6/3)
extremely gravelly loamy sand, dark brown (10YR
4/3) moist; single grain; loose, slightly sticky;
nonplastic; few very fine roots; 70 percent angular
gravel; neutral (pH 6.6); gradual smooth
boundary.
C2—36 to 60 inches; very pale brown (10YR 7/4)
extremely gravelly loam, yellowish brown (10YR
5/4) moist; massive; slightly hard, friable,
moderately sticky and slightly plastic; 70 percent
angular gravel; neutral (pH 6.8).
Range in Characteristics
Soil temperature: 42 to 47 degrees F
Moisture control section: Between 8 and 24 inches
Thickness of the mollic epipedon: 7 to 15 inches; may
or may not include part of the Bw horizon