LOCATION HARTBENCH MT
Established Series
Rev. EMR/JMS/RJS
07/2013
HARTBENCH SERIES
The Hartbench series consists of very deep, well drained soils that formed in outwash derived from granitic rocks. These soils are on outwash fans and fan remnants. Slopes are 2 to 15 percent. Mean annual precipitation is about 370 millimeters and mean annual air temperature is about 6 degrees C.
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid Typic Argiustolls
TYPICAL PEDON: Hartbench loam, in rangeland on a 4 percent slope at 1,002 meters elevation (colors are for dry soil unless otherwise indicated).
A--0 to 20 cm; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; moderate medium granular structure; friable, slightly hard, slightly sticky and nonplastic; many fine and medium roots; many very fine and fine irregular and tubular pores; 5 percent gravel; moderately acid (pH 6.0); clear smooth boundary. (18 to 30 cm thick)
Bt1--20 to 41 cm; light yellowish brown (10YR 6/4) clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure; friable, hard, slightly sticky and moderately plastic; common fine and medium roots; many very fine irregular and tubular pores; common faint dark grayish brown (10YR 4/2) moist clay films on ped faces; 5 percent gravel; moderately acid (pH 6.0); gradual wavy boundary. (10 to 33 cm thick)
Bt2--41 to 56 cm; light yellowish brown (10YR 6/4) clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure; firm, hard, moderately sticky and moderately plastic; few fine and medium roots; common very fine irregular and tubular pores; common distinct dark grayish brown (10YR 4/2) moist clay films on ped faces and along pore linings; 5 percent gravel; moderately acid (pH 6.0); abrupt smooth boundary. (0 to 20 cm thick)
BC--56 to 66 cm; pale brown (10YR 6/3) gravelly sandy loam, brown (10YR 4/3) moist; weak fine subangular blocky structure; very friable, slightly hard, nonsticky and slightly plastic; few fine roots; common very fine irregular and interstitial pores; 15 percent gravel; moderately acid (pH 5.8); abrupt smooth boundary. (0 to 10 cm thick)
C--66 to 152 cm; light yellowish brown (2.5Y 6/3) extremely gravelly coarse sand, light olive brown (2.5Y 5/3) moist; single grained; loose, nonsticky and nonplastic; few fine roots; common very fine interstitial pores; 60 percent gravel, 5 percent cobbles; moderately acid (pH 5.6).
TYPE LOCATION: Stevensville topographic quadrangle, Ravalli County, Montana; 370 meters south and 675 meters east of the NW corner of section 10, T. 9N., R. 20W. UTM Zone 11: 722262e, 5159887n, NAD 83.
RANGE IN CHARACTERISTICS:
Soil temperature - 5 to 8 degrees C
Moisture control section - 10 to 30 cm
Mollic epipedon thickness - 18 to 30 cm
A horizon
Value: 4 or 5 dry; 2 to 3 moist
Chroma: 2 or 3; dry or moist
Texture: loam or sandy loam
Clay content: 15 to 27 percent
Rock fragments: 0 to 25 percent--0 to 20 percent gravel, 0 to 10 percent cobbles, 0 to 5 percent stones
Reaction: pH 5.2 to 6.4
Bt1 horizon
Value: 4 to 6; dry
Chroma: 4 or 5; dry or moist
Texture: sandy clay loam, clay loam, loam or sandy loam
Clay content: 18 to 28 percent
Rock fragments: 0 to 20 percent--0 to 10 percent gravel, 0 to 10 percent cobbles
Reaction: pH 5.6 to 6.4
Bt2 horizon
Value: 3 or 4; moist
Texture: sandy clay loam or clay loam
Clay content: 24 to 34 percent
Rock fragments: 0 to 20 percent--0 to 15 percent gravel, 0 to 10 percent cobbles
Reaction: pH 5.6 to 6.5
BC horizon
Chroma: 3 to 5; dry or moist
Texture: sandy loam or coarse sandy loam
Clay content: 10 to 18 percent
Rock fragments: 0 to 20 percent--0 to 20 percent gravel, 0 to 5 percent cobbles
Reaction: pH 5.6 to 6.4
C horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 or 7 dry; 4 or 5 moist
Chroma: 3 to 5; dry or moist
Texture: loamy coarse sand, loamy sand, coarse sand or sand
Clay content: 0 to 12 percent
Rock fragments: 35 to 70 percent--25 to 65 percent gravel, 0 to 15 percent cobbles, 0 to 5 percent stones
Reaction: pH 5.2 to 6.2
COMPETING SERIES:
Buckcamp (UT) - deep to a lithic contact
Hedstrom (MT) - have horizons of secondary carbonate accumulation
Sourdough (MT) - have pH values greater than 6.5 in the Bt horizons
Turner (MT) - have horizons of secondary carbonate accumulation
GEOGRAPHIC SETTING:
Landform - outwash fans and fan remnants
Elevation - 1,000 to 1,400 meters
Slope - 2 to 15 percent
Parent material - outwash derived from granitic rocks
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 330 to 460 millimeters, much of which falls as snow and as spring rain
Mean annual air temperature - 4 to 7 degrees C
Frost-free period - 70 to 105 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability to a depth of 56 cm and moderate to moderately rapid below.
USE AND VEGETATION: Hartbench soils are primarily used for dry-land pasture; vegetation is chiefly mixed grasses.
DISTRIBUTION AND EXTENT: Hartbench soils are of small extent in the valleys of western Montana. MLRA - 44A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Bitterroot Valley Area, Montana, 2013; proposed in Ravalli County, Montana, 2006.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 20 cm (A horizon)
Argillic horizon - 20 to 56 cm (Bt1 & Bt2 horizons)
Particle-size control section - 20 to 100 cm (Bt1 & Bt2, BC and part of the C horizon)
Hartbench soils have a frigid temperature regime and an ustic moisture regime.
National Cooperative Soil Survey
U.S.A.