LOCATION HAMILTON MT
Established Series
Rev. JMS/EMR/JCK
05/2012
HAMILTON SERIES
The Hamilton series consists of very deep, well drained soils formed in alluvium derived from mixed sources. These soils are on stream terraces. Slopes are 0 to 4 percent. Mean annual precipitation is about 330 mm and mean annual temperature is about 6 degrees C.
TAXONOMIC CLASS: Coarse-silty, mixed, superactive, frigid Aridic Haplustolls
TYPICAL PEDON: Hamilton loam, in hayland on a 1 percent slope, at 1,060 meters elevation (Colors are for dry soil unless otherwise indicated).
Ap--0 to 16 cm; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, very friable, nonsticky, slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; neutral (pH 7.0); clear smooth boundary.
A--16 to 26 cm; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky parting to moderate fine granular structure; soft, very friable, nonsticky, slightly plastic; common very fine and fine roots; many very fine and fine tubular pores; neutral (pH 7.0); clear smooth boundary. (combined thickness of A horizons 18 to 38 cm)
Bw--26 to 47 cm; pale brown (10YR 6/3) silt loam, dark grayish brown (10YR 4/2) moist; moderate fine subangular blocky structure; soft, friable, nonsticky, nonplastic; common very fine and fine roots; common fine tubular pores; 2 percent gravel; neutral (pH 7.2); gradual smooth boundary. (15 to 21 cm thick)
Bk1--47 to 82 cm; pale brown (10YR 6/3) silt loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; common very fine and fine roots; common fine tubular pores; 2 percent gravel; few fine faint calcium carbonate masses in the matrix; strongly effervescent; moderately alkaline (pH 8.1); gradual smooth boundary.
Bk2--82 to 137 cm; light yellowish brown (10YR 6/4) silt loam, brown (10YR 5/3) moist; moderate medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; common fine tubular pores; 2 percent gravel; common fine distinct calcium carbonate masses in the matrix; strongly effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (combined thickness of Bk horizons 59 to 117 cm)
2C--137 to 152 cm; light yellowish brown (2.5Y 6/3) gravelly loamy fine sand, light olive brown (2.5Y 5/3) moist; single grain; loose, nonsticky and nonplastic; few fine roots; many fine interstitial pores; 20 percent gravel; slightly alkaline (pH 7.4).
TYPE LOCATION: Corvallis topographic quadrangle, Ravalli County, Montana; 125 meters south and 165 meters west of the NE corner of section 8, T 6 N, R 20 W; UTM zone 11, 259980E, 5131779N, NAD 83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 5 to 8 degrees C
Mollic epipedon thickness - 18 to 38 cm
Depth to secondary calcium carbonate accumulation - 33 to 59 cm
Depth to lithologic discontinuity - 118 to 150 cm
A horizon(s)
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 1 to 3 dry or moist
Texture: silt loam or loam
Clay content: 12 to 22 percent
Content of rock fragments: 0 to 5 percent gravel
Reaction: pH 6.4 to 7.4
Bw horizon
Hue: 10YR, 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 4 dry or moist
Texture: silt loam or very fine sandy loam
Clay content: 10 to 18 percent
Content of rock fragments: 0 to 5 percent gravel
Reaction: pH 6.6 to 7.4
Bk horizon(s)
Hue: 10YR, 2.5Y
Value: 4 or 5 moist
Chroma: 3 or 4 dry; 2 or 3 moist
Texture: silt loam or very fine sandy loam
Clay content: 10 to 18 percent
Content of rock fragments: 0 to 10 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.8 to 8.6
2C horizon
Hue: 10YR, 2.5Y
Value: 5 to 8 dry; 4 to 7 moist
Chroma: 3 or 4 dry or moist
Texture: loamy fine sand or loamy sand
Clay content: 2 to 15 percent
Content of rock fragments: 0 to 35 percent--0 to 30 percent gravel, 0 to 10 percent cobbles
Calcium carbonate equivalent: 0 to 5 percent
Reaction: pH 6.6 to 7.8
COMPETING SERIES:
Hingham (MT) - do not have a lithologic discontinuity
Kelstrup (MT) - have a calcic horizon; do not have a lithologic discontinuity
GEOGRAPHIC SETTING:
Landform - stream terraces
Elevation - 975 to 1,370 meters
Slope - 0 to 4 percent
Parent material - alluvium derived from mixed sources
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 305 to 380 mm
Mean annual air temperature - 4 to 7 degrees C
Frost-free period - 90 to 115 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability to 137 cm and rapid permeability below.
USE AND VEGETATION: These soils are used primarily for irrigated pasture and hayland, or for dry-land pasture. Vegetation is chiefly bluebunch wheatgrass, needle and thread, and prairie Junegrass.
DISTRIBUTION AND EXTENT: Hamilton soils are of small extent in the intermountain valleys of southwest Montana. MLRA 44A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Ravalli County (Bitterroot Valley Area), Montana, 1952.
REMARKS: Diagnostic features and horizons recognized in this pedon are:
Particle-size control section - from 25 to 100 cm (part of the A, Bw, Bk1, and part of the Bk2 horizons)
Mollic epipedon - from the soil surface to 26 cm (Ap and A horizons)
Cambic horizon - from 26 to 47 cm (Bw horizon)
Horizon of secondary calcium carbonate accumulation - from 47 to 137 cm (Bk1 and Bk2 horizons)
Hamilton soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.
The type location has been moved and re-described to current description standards.
National Cooperative Soil Survey
U.S.A.