LOCATION JOCKO MTEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed, frigid Calcic Haploxerolls
TYPICAL PEDON: Jocko gravelly loam, in cropland (colors are for dry soil unless otherwise noted).
Ap--0 to 6 inches; very dark grayish brown (10YR 3/2) gravelly loam, black (10YR 2/1) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; few very fine tubular pores; 15 percent pebbles and 5 percent cobbles; neutral (pH 6.8); clear smooth boundary.
A--6 to 13 inches; dark grayish brown (10YR 4/2) gravelly loam, very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots, common fine tubular pores; 15 percent pebbles and 5 percent cobbles; neutral (pH 7.0); clear smooth boundary. (Combined thickness of A horizons is 8 to 14 inches.)
Bw1--13 to 19 inches; brown (10YR 4/3) very gravelly loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; common very fine tubular pores; 30 percent pebbles and 15 percent cobbles; neutral (pH 7.0); clear wavy boundary.
Bw2--19 to 25 inches; brown (10YR 5/3) very gravelly loamy sand, brown (10YR 4/3) moist; loose, nonsticky and nonplastic; common very fine and fine roots; 40 percent pebbles and 15 percent cobbles; slightly alkaline (pH 7.6); clear wavy boundary. (Combined thickness of Bw horizons is 6 to 14 inches.)
Bk--25 to 60 inches; light brownish gray (10YR 6/2) extremely gravelly coarse sand, grayish brown (10YR 5/2) moist; single grain; loose, nonsticky and nonplastic; few fine roots; 50 percent pebbles and 20 percent cobbles; few faint soft lime coatings on undersides of pebbles, and few prominent hard lime casts on undersides of pebbles; slightly effervescent; slightly alkaline (pH 7.6).
TYPE LOCATION: Lake County, Montana; 650 feet south and 1,300 feet west of the NE corner of sec. 18, T. 16N., R. 19 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 43 to 47 degrees F.
Moisture control section - between 12 and 35 inches.
Mollic epipedon thickness - 11 to 20 inches.
Control section - 5 to 15 percent clay.
Depth to Bk horizon - 15 to 30 inches.
Depth to sand and gravel - 18 to 24 inches.
Ap horizon - Value: 3 or 4 dry; 2 or 3 moist
Chroma: 1 or 2
Texture: loam or sandy loam
Clay content: 10 to 25 percent
Rock fragments: 5 to 35 percent--0 to 20 percent cobbles or stones, 5 to 25 percent pebbles
Reaction: pH 6.1 to 7.3
A horizon - Value: 3, 4, or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture: loam or sandy loam
Clay content: 10 to 25 percent
Rock fragments: 5 to 35 percent--0 to 20 percent cobbles or stones, 5 to 25 percent pebbles
Reaction: pH 6.1 to 7.3
Bw1 horizon - Value: 3, 4, or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture: loam or sandy loam
Clay content: 5 to 20 percent
Rock fragments: 35 to 60 percent--0 to 25 percent cobbles or stones, 25 to 45 percent pebbles
Reaction: pH 6.6 to 7.8
Bw2 horizon - Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: sandy loam or loamy sand
Clay content: 0 to 5 percent
Rock fragments: 35 to 60 percent--10 to 25 percent cobbles or stones, 25 to 40 percent pebbles
Reaction: pH 6.6 to 7.8
Bk horizon - Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: loamy coarse sand, coarse sand, or sand
Clay content: 0 to 5 percent
Rock fragments: 60 to 85 percent--0 to 30 percent cobbles or stones, 45 to 70 percent pebbles
Calcium carbonate equivalent: 3 to 15 percent
Reaction: pH 6.6 to 7.8
COMPETING SERIES:
Bunting (ID) - has 2Bkq horizon.
Moiese (MT) - has lithologic discontinuity at 12 to 19 inches.
GEOGRAPHIC SETTING:
Landform - stream terraces and dissected alluvial fans.
Elevation - 2,500 to 3,500 feet.
Slope- 0 to 15 percent.
Parent material - glacial outwash and alluvium.
Climate - long, cold winters; moist falls and springs; warm, dry summers.
Mean annual precipitation - 15 to 19 inches and is mainly rain in early spring and late fall.
Mean annual temperature - 41 to 45 degrees F.
Frost-free period - 90 to 120 days.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; rapid permeability.
USE AND VEGETATION: Jocko soils are used for irrigated and dryland crops, pastureland, and rangeland. Potential native vegetation is mainly rough fescue, Idaho fescue, bluebunch wheatgrass, prairie junegrass, threadleaf sedge, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Jocko soils are of moderate extent in intermountain valleys of western Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Lake County, Montana, 1991; proposed in Lake County, Montana, 1970.
REMARKS: Soil interpretation record: MT0421. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 19 inches (Ap, A, Bw1 horizons); a cambic horizon from 19 to 25 inches (Bw2 horizon); a calcareous horizon from 25 to 60 inches (Bk horizon). Jocko soils have a frigid temperature regime and a xeric moisture regime.