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

112 Soil Survey
A2—7 to 13 inches; brown (10YR 4/3) very gravelly
loam, dark brown (10YR 3/3) moist; moderate
medium subangular blocky structure; slightly
hard, very friable, slightly sticky, slightly plastic;
many very fine and fine roots; many very fine
pores; 10 percent angular cobbles; 45 percent
rounded gravel; neutral (pH 6.8); clear wavy
boundary.
Bw1—13 to 28 inches; brown (10YR 5/3) very
gravelly loam, brown (10YR 4/3) moist; moderate
fine and medium subangular blocky structure;
slightly hard, very friable, slightly sticky, slightly
plastic; many very fine and fine roots; common
very fine pores; 15 percent angular cobbles;
35 percent angular gravel; neutral (pH 7.0);
gradual wavy boundary.
Bw2—28 to 44 inches; pale brown (10YR 6/3) very
gravelly sandy loam, brown (10YR 4/3) moist;
weak fine subangular blocky structure; slightly
hard, very friable, nonsticky, nonplastic; common
very fine and fine roots; common very fine pores;
15 percent angular cobbles; 40 percent angular
gravel; slightly alkaline (pH 7.4); gradual wavy
boundary.
BC—44 to 60 inches; very pale brown (10YR 7/3)
extremely gravelly sandy loam, grayish brown
(10YR 5/2) moist; massive; slightly hard, very
friable, nonsticky, nonplastic; few very fine roots;
20 percent angular cobbles; 50 percent angular
gravel; common faint carbonate coats on
undersides of rock fragments; slightly alkaline
(pH 7.4).
Range in Characteristics
Soil temperature: 38 to 42 degrees F
Moisture control section: Between 8 and 24 inches
Thickness of the mollic epipedon: 10 to 15 inches
A horizons
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Clay content: 7 to 27 percent
Content of rock fragments: 15 to 60 percent—0 to
30 percent stones and cobbles; 10 to
50 percent gravel
Reaction: pH 6.1 to 7.3
Surface stones or boulders: .01 to 3 percent
Bw horizons
Hue: 10YR or 7.5YR
Value: 4 to 6 dry; 3 to 5 moist
Chroma: 2 to 4
Texture (less than 2 mm): Loam or sandy loam
Clay content: 7 to 20 percent
Content of rock fragments: 35 to 85 percent—0 to
50 percent stones and cobbles; 25 to
65 percent gravel
Reaction: pH 6.6 to 7.8
BC horizon
Hue: 10YR or 7.5YR
Value: 4 to 7 dry; 3 to 5 moist
Chroma: 2 to 4
Texture (less than 2 mm): Loam, loamy sand, or
sandy loam
Clay content: 0 to 15 percent
Content of rock fragments: 60 to 85 percent—
10 to 25 percent stones and cobbles; 50 to
60 percent gravel
Reaction: pH 6.6 to 7.8
Pianohill Series
Depth class: Moderately deep (20 to 40 inches)
Drainage class: Well drained
Permeability: Moderate (0.6 to 2.0 inches/hour)
Landform: Hill and structural bench
Parent material: Residuum weathered from tuff
breccia
Slope range: 4 to 35 percent
Elevation range: 4,200 to 6,200 feet
Mean annual precipitation: 15 to 20 inches
Mean annual air temperature: 39 to 45 degrees F
Frost-free period: 70 to 115 days
Taxonomic Class: Fine-loamy, mixed, superactive,
frigid Typic Argiustolls
Typical Pedon
Pianohill loam, in an area of Whitlash-Pianohill
complex, 4 to 15 percent slopes, in an area of
rangeland, 800 feet north and 2,100 feet east of
the southwest corner of sec. 23, T. 2 S., R. 15 E.;
USGS Packsaddle Butte topographic quadrangle
(lat. 45 o 38'27" N.; long. 109 o 50'28" W.)
A1—0 to 6 inches; grayish brown (10YR 5/2) loam,
very dark grayish brown (10YR 3/2) moist; weak
fine granular structure; soft, very friable, slightly
sticky, slightly plastic; many very fine and fine
roots; many very fine and fine pores; 5 percent
cobbles; slightly acid (pH 6.4); abrupt smooth
boundary.
A2—6 to 10 inches; brown (10YR 5/3) loam, dark
brown (10YR 3/3) moist; weak medium
subangular blocky structure parting to weak fine
and medium granular; soft, very friable, slightly
sticky, slightly plastic; many very fine and fine