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

Sweet Grass County Area, Montana—Part I 139
Texture (less than 2 mm): Clay loam, silty clay,
clay, or silty clay loam
Clay content: 35 to 50 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
Bk1 horizon
Hue: 10YR or 2.5Y
Value: 5 to 8 dry; 4 to 6 moist
Chroma: 2 or 3
Texture (less than 2 mm): Clay loam, silty clay, or
silty clay loam
Clay content: 30 to 45 percent
Content of rock fragments: 0 to 25 percent—0 to
5 percent cobbles; 0 to 20 percent gravel
Calcium carbonate equivalent: 20 to 30 percent
Reaction: pH 7.4 to 9.0
2Bk2 horizon
Hue: 10YR or 2.5Y
Value: 6 to 8 dry; 4 to 7 moist
Chroma: 2 to 4
Texture (less than 2 mm): Loam or clay loam
Clay content: 18 to 35 percent
Content of rock fragments: 20 to 45 percent—0 to
10 percent cobbles; 20 to 35 percent gravel
Calcium carbonate equivalent: 25 to 40 percent
Reaction: pH 7.9 to 9.0
2Bk3 horizon
Hue: 10YR or 2.5Y
Value: 6 to 8 dry; 5 to 7 moist
Chroma: 2 to 4
Texture (less than 2 mm): Sandy loam, sandy
clay loam, or loam
Clay content: 8 to 25 percent
Content of rock fragments: 50 to 80 percent—5 to
20 percent cobbles; 35 to 60 percent gravel
Calcium carbonate equivalent: 25 to 40 percent
Reaction: pH 7.9 to 9.0
Tanna Series
Depth class: Moderately deep (20 to 40 inches)
Drainage class: Well drained
Permeability: Slow (0.06 to 0.20 inch/hour)
Landform: Escarpment, fan, hill, strath terrace,
terrace, and swale on plain
Parent material: Clayey residuum weathered from
sandstone and shale
Slope range: 2 to 35 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: Fine, smectitic, frigid Aridic
Argiustolls
Typical Pedon
Tanna clay loam, in an area of Tanna-Hinterland clay
loams, 2 to 8 percent slopes, in an area of rangeland,
2,200 feet north and 2,100 feet west of the southeast
corner of sec. 23, T. 1 N., R. 16 E.; USGS Lone Indian
Butte topographic quadrangle (lat. 45 o 49'07" N.; long.
109 o 41'56" W.)
A—0 to 5 inches; grayish brown (10YR 5/2) clay
loam, very dark grayish brown (10YR 3/2) moist;
weak fine subangular blocky structure parting to
moderate fine granular; slightly hard, friable,
slightly sticky, slightly plastic; common very
fine and fine roots; common fine pores; neutral
(pH 6.8); abrupt smooth boundary.
Bt1—5 to 12 inches; brown (10YR 5/3) clay, dark
brown (10YR 3/3) moist; moderate fine
subangular blocky structure; moderately hard,
firm, moderately sticky, moderately plastic;
common very fine and fine roots; common
fine pores; continuous distinct dark brown (10YR
4/3) moist; clay films on faces of peds; neutral
(pH 7.0); gradual smooth boundary.
Bt2—12 to 19 inches; grayish brown (10YR 5/2) clay
loam, dark grayish brown (10YR 4/2) moist;
moderate medium prismatic structure parting to
moderate fine subangular blocky structure; very
hard, very firm, moderately sticky, moderately
plastic; few fine roots; few fine pores; many
distinct brown (10YR 4/3) moist; clay films on
faces of peds; slightly alkaline (pH 7.4); clear
smooth boundary.
Bk—19 to 27 inches; light brownish gray (10YR 6/2)
clay loam, brown (10YR 5/3) moist; weak coarse
prismatic structure; moderately hard, firm, slightly
sticky, slightly plastic; few fine roots; few very fine
pores; common fine threads of lime; strongly
effervescent; moderately alkaline (pH 8.2); clear
wavy boundary.
Cr—27 to 60 inches; semiconsolidated shale
interbedded with layers of sandstone.
Range in Characteristics
Soil temperature: 40 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 20 inches
Depth to the Cr horizon: 20 to 40 inches