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

Sweet Grass County Area, Montana—Part I 85
Taxonomic Class: Loamy-skeletal, carbonatic, frigid
Lithic Calciustolls
Typical Pedon
Lap channery loam, in an area of Lap-Winspect-Rock
outcrop complex, 8 to 35 percent slopes, in an area
of rangeland, 300 feet north and 600 feet west of
the southeast corner of sec. 23, T. 3 S., R. 12 E.;
USGS McLeod Basin topographic quadrangle (lat.
45 o 33'12" N.; long. 110 o 11'58" W.)
A1—0 to 4 inches; dark grayish brown (10YR 4/2)
channery loam, very dark brown (10YR 2/2)
moist; weak fine granular structure; soft, very
friable, slightly sticky, nonplastic; many very fine
and fine roots; many very fine and fine pores;
20 percent angular channers; strongly
effervescent; moderately alkaline (pH 8.4); clear
smooth boundary.
A2—4 to 8 inches; brown (10YR 4/3) very channery
loam, very dark grayish brown (10YR 3/2) moist;
weak medium subangular blocky structure; soft,
very friable, slightly sticky, nonplastic; many very
fine and fine roots; many very fine and fine pores;
35 percent channers; 5 percent cobbles; strongly
effervescent; moderately alkaline (pH 8.4); abrupt
smooth boundary.
Bk—8 to 14 inches; light brownish gray (10YR 6/2)
very channery loam, grayish brown (10YR 5/2)
moist; weak fine and medium granular structure;
slightly hard, friable, slightly sticky, slightly plastic;
common very fine and fine roots; many very fine
and fine pores; 40 percent channers; 15 percent
cobbles; lime casts on undersides of channers
and cobbles; violently effervescent; strongly
alkaline (pH 8.6); abrupt smooth boundary.
R—14 inches; hard limestone bedrock with some
cracks.
Range in Characteristics
Soil temperature: 38 to 47 degrees F
Moisture control section: Between 4 and 12 inches
Thickness of the mollic epipedon: 7 to 12 inches
Depth to bedrock: 10 to 20 inches
A horizons
Hue: 10YR or 2.5Y
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 1 to 3
Texture (less than 2 mm): Loam
Clay content: 15 to 25 percent
Content of rock fragments: 10 to 60 percent—0 to
20 percent stones, flagstones, or cobbles;
10 to 40 percent gravel or channers
Calcium carbonate equivalent: 0 to 15 percent in
the less than 2-mm particle size class and
more than 40 percent in the less than 20-mm
particle size class
Reaction: pH 6.6 to 7.8
Bk horizon
Hue: 7.5YR, 10YR, or 2.5Y
Value: 5 to 8 dry; 4 to 6 moist
Chroma: 2 or 3
Texture (less than 2 mm): Loam or clay loam
Clay content: 20 to 30 percent
Content of rock fragments: 35 to 70 percent—0 to
30 percent stones, flagstones, or cobbles;
35 to 55 percent gravel or channers
Calcium carbonate equivalent: 40 to 60 percent in
the less than 2-mm particle size class and
more than 40 percent in the less than 20-mm
particle size class.
Reaction: pH 7.9 to 8.4
Larry Series
Depth class: Very deep (greater than 60 inches)
Drainage class: Poorly drained
Permeability: Moderately slow (0.2 to 0.6 inch/hour)
Landform: Flood plain and flood-plain step
Parent material: Loamy alluvium
Slope range: 0 to 4 percent
Elevation range: 3,750 to 6,200 feet
Mean annual precipitation: 10 to 20 inches
Mean annual air temperature: 39 to 46 degrees F
Frost-free period: 70 to 130 days
Taxonomic Class: Fine-loamy, mixed, superactive,
frigid Typic Endoaquolls
Typical Pedon
Larry clay loam, in an area of Larry clay loam, 0 to
2 percent slopes, in an area of tame pasture, 700 feet
north and 1,800 feet east of the southwest corner of
sec. 29, T. 2 N., R. 14 E.; USGS Grosfield Ranch
topographic quadrangle (lat. 45 o 53'19" N.; long.
110 o 00'50" W.)
A—0 to 7 inches; gray (5Y 5/1) clay loam, very dark
gray (5Y 3/1) moist; moderate very fine granular
structure; extremely hard, friable, moderately
sticky, moderately plastic; few medium and
coarse and many very fine and fine roots;
common very fine and fine pores; slightly alkaline
(pH 7.4); clear wavy boundary.
Bg—7 to 15 inches; gray (5Y 6/1) clay loam, gray
(5Y 5/1) moist; few fine prominent yellowish