LOCATION HEADWATERS MTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Aridic Calciustolls
TYPICAL PEDON: Headwaters loam, cropland (colors are for dry soil unless otherwise noted).
Ap--0 to 5 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; strongly effervescent; slightly alkaline (pH 7.8); clear smooth boundary. (2 to 6 inches thick)
A2--5 to 7 inches; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and plastic; common very fine, fine, and few medium roots; slightly effervescent; neutral (pH 7.0); clear wavy boundary. (2 to 7 inches thick)
Bk--7 to 29 inches; light gray (10YR 7/2) clay loam, pale brown (10YR 6/3) moist; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine roots, few fine and medium roots; violently effervescent; common medium soft masses of segregated lime; moderately alkaline (pH 8.0); clear wavy boundary. (16 to 26 inches thick.)
Cr--29 to 60 inches; pale yellow (2.5Y 7/4) semiconsolidated sedimentary beds that crush to a silty clay loam (interbedded with semiconsolidated sandy materials), light yellowish brown (2.5Y 6/4) moist; moderately alkaline (pH 8.4).
TYPE LOCATION: Gallatin County, Montana; 1,000 feet west and 2,800 feet south of the NE corner of sec. 25, T. 1 N., R. 1 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 43 to 47 degrees F.
Moisture control section - between 4 and 12 inches; dry in all parts for four to five tenths of the cumulative days per year when the soil temperature at a depth of 20 inches is higher than 41 degrees F. Not dry in all parts for forty five consecutive days in the four months following the summer solstice.
Mollic epipedon thickness - 7 to 10 inches.
Control section - 18 to 35 percent clay.
Depth to calcic horizon - 5 to 13 inches.
Depth to paralithic contact - 20 to 40 inches (typically ranges 23 to 37 inches).
Ap horizon - Hue: 10YR or 2.5Y
Chroma: 2 or 3
Clay content: 18 to 27 percent
Rock fragments: 0 to 35 percent--0 to 15 percent pebbles, 0 to 20 percent cobbles
Reaction: pH 7.4 to 8.4
A2 horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 3 or 4 moist
Chroma: 2 or 3
Clay content: 18 to 27 percent
Rock fragments: 0 to 25 percent--0 to 15 percent pebbles, 0 to 15 percent cobbles
Reaction: pH 6.6 to 7.8
Bk horizon - Hue: 10YR, 2.5Y, or 5Y
Value: 6, 7, or 8 dry; 5, 6, or 7 moist
Chroma: 2 or 3
Texture: clay loam, sandy clay loam, loam
Clay content: 20 to 35 percent
Rock fragments: 0 to 15 percent pebbles
Calcium carbonate equivalent: 15 to 35 percent
Reaction: pH 7.9 to 9.0
In some pedons this horizon is stratified silty clay loam and sandy clay loam.
COMPETING SERIES:
Emmons (CO) - are very deep.
Rabbitex (CO) - are deep or very deep.
Rothican (WY) - are very deep.
Rothiemay (MT) - are very deep.
Zinzer (CO) - are very deep.
GEOGRAPHIC SETTING:
Landform - dissected alluvial fans, stream terraces, hills, and sedimentary plains.
Elevation - 4,200 to 4,700 feet.
Slope - 2 to 15 percent.
Parent material - alluvium deposited over semiconsolidated sediments.
Climate - long, cold winter; moist springs; warm summers.
Mean annual precipitation - 10 to 14 inches.
Mean annual temperature - 41 to 45 degrees F.
Frost-free period - 95 to 115 days.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability.
USE AND VEGETATION: Headwaters soils are used mainly for nonirrigated small grain crops and hay. Potential native vegetation is mainly bluebunch wheatgrass, needleandthread, western wheatgrass, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Headwaters soils are of small extent in southwestern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Gallatin County, Montana, 1997.
REMARKS: Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the surface to 7 inches (Ap and A2 horizons); a calcic horizon from 7 to 29 inches (Bk horizon); and a paralithic contact at a depth of 29 inches (Cr horizon). Headwaters soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.