LOCATION DILLON MT
Established Series
Rev. GFB-KTS-RJS
04/2011
DILLON SERIES
The Dillon series consists of very deep, somewhat poorly drained soils that formed in alluvium. These soils are on flood plains, flood-plain steps and stream terraces. Slopes are 0 to 4 percent. Mean annual precipitation is about 12 inches. Mean annual air temperature is about 39 degrees F.
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid Oxyaquic Haplustepts
TYPICAL PEDON: Dillon silt loam, in cropland (colors are for dry soil unless otherwise noted).
Ap--0 to 4 inches; gray (2.5Y 5/1) silt loam, very dark grayish brown (2.5Y 3/2) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; many very fine and few fine roots; many very fine and few fine interstitial pores; finely disseminated calcium carbonate; strongly effervescent; slightly alkaline (pH 7.7); clear smooth boundary. (4 to 10 inches thick)
Bw--4 to 11 inches; gray (2.5Y 6/1) silt loam, dark gray (2.5Y 4/1) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and slightly plastic; many very fine and few fine roots; many very fine and few fine tubular and interstitial pores; finely disseminated calcium carbonate; strongly effervescent; slightly alkaline (pH 7.8); clear smooth boundary. (6 to 10 inches thick)
BC--11 to 31 inches; light gray (2.5Y 7/1) loam, gray (2.5Y 6/1) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and few fine roots; common very fine and few fine tubular and interstitial pores; finely disseminated calcium carbonate; violently effervescent; moderately alkaline (pH 8.1); clear smooth boundary. (5 to 20 inches thick)
2C1--31 to 36 inches; light gray (5Y 7/1) loamy sand, gray (5Y 6/1) moist; common medium and fine distinct brown (7.5YR 4/4) moist redox concentrations; single grain; loose; nonsticky and nonplastic; finely disseminated calcium carbonate; strongly effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (0 to 10 inches thick)
2C2--36 to 60 inches; light gray (5Y 7/1) very gravelly sand, gray (5Y 6/1) moist; single grain, loose; nonsticky and nonplastic; 40 percent gravel, 10 percent cobbles; slightly effervescent; slightly alkaline (pH 7.6).
TYPE LOCATION: Beaverhead County, Montana; 850 feet south and 2,450 feet west of the NE corner of sec. 24, T. 7 S., R. 9 W. Dillon West topographic quadrangle. Latitude 45 degrees 12 minutes 55 seconds N. and Longitude 112 degrees 39 minutes 00 seconds W.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 42 to 46 degrees F.
Depth to lithologic discontinuity - 20 to 40 inches
Depth to seasonal high water table - 24 to 42 inches
Soil phases - saline
Note: A thin (less than 3 inches) Oe horizon may be present.
A horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 3 to 5 moist
Chroma: 1 to 3; dry or moist
Texture: silt loam, loam, clay loam or silty clay loam
Clay content: 18 to 35 percent
Rock fragments: 0 to 10 percent gravel
Calcium carbonate equivalent: 10 to 30 percent
EC: 0 to 4 mmhos/cc; saline phase 4 to 16
Reaction: pH 7.6 to 8.6; saline phase 7.9 to 9.0
Bw horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 1 to 3; dry or moist
Texture: silt loam, loam, clay loam, sandy clay loam or silty clay loam
Clay content: 18 to 35 percent
Rock fragments: 0 to 10 percent gravel
Calcium carbonate equivalent: 10 to 30 percent
EC: 0 to 4 mmhos/cc; saline phase 4 to 16
Reaction: pH 7.6 to 8.6; saline phase 7.9 to 9.2
BC horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 1 to 3; dry or moist
Texture: loam, sandy loam or sandy clay loam
Clay content: 18 to 30 percent
Rock fragments: 0 to 10 percent gravel
Calcium carbonate equivalent: 10 to 30 percent
EC: 0 to 4 mmhos/cc; saline phase 2 to 25
Reaction: pH 7.6 to 8.6; saline phase 8.5 to 9.0
2C1 horizon
Hue: 2.5Y or 5Y; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 1 to 3; dry or moist
Texture: loamy sand, loamy coarse sand, sand or coarse sand
Clay content: 0 to 10 percent
Rock fragments: 0 to 35 percent gravel
Calcium carbonate equivalent: 5 to 20 percent
EC: 0 to 4 mmhos/cc; saline phase 4 to 16
Reaction: pH 7.4 to 8.4; saline phase 8.5 to 9.0
2C2 horizon
Hue: 5Y, N or 10Y; dry or moist
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 1 to 3; dry or moist
Texture: loamy sand, loamy coarse sand, sand or coarse sand
Clay content: 0 to 10 percent
Rock fragments: 35 to 80 percent--35 to 65 percent gravel, 0 to 30 percent cobbles
Calcium carbonate equivalent: 0 to 10 percent
Reaction: pH 7.4 to 8.4
COMPETING SERIES:
Silverking (MT) - has hues of 10YR in the 2C horizon; does not have a BC horizon
GEOGRAPHIC SETTING:
Landform - flood plains, flood-plain steps and stream terraces
Elevation - 4,500 to 6,500 feet
Slope - 0 to 4 percent
Parent material - alluvium
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 10 to 14 inches
Mean annual air temperature - 36 to 43 degrees F.
Frost-free period - 70 to 105 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; moderate permeability above the 2C horizon and very rapid permeability in the 2C horizon.
USE AND VEGETATION: Dillon soils are used for rangeland and cropland. The potential native vegetation is mainly basin wildrye, sandberg bluegrass, western wheatgrass, thickspike wheatgrass, woods rose, and snowberry.
DISTRIBUTION AND EXTENT: Dillon soils are of small extent in southwestern Montana. MLRA - 44B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Beaverhead County, Montana, 2001.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 7 inches (Ap, and part of Bw horizons)
Cambic horizon - from 4 to 11 inches (Bw horizon)
Horizon with redox features - from 31 to 36 inches (2C1 horizon)
Lithilogic discontinuity - at 31 inches (2C horizon)
Particle size control section - from 10 to 40 inches (part of Bw, BC, 2C1, and part of 2C2 horizons)
Dillon soils have a frigid temperature regime, an ustic moisture regime and an oxyaquic moisture subclass.
National Cooperative Soil Survey
U.S.A.