LOCATION RASMUSSEN ID
Tentative Series
Proposed CBR-NHK-RJS
01/2017
RASMUSSEN SERIES
The Rasmussen series consists of very deep, well drained soils that formed in loess or loess influenced slope alluvium from basalt. Rasmussen soils are on valley floors and hills. Slopes range from 1 to 12 percent. Mean annual precipitation is about 650 millimeters, and mean annual air temperature is about 1.7 degrees C.
TAXONOMIC CLASS: Fine-silty, mixed, superactive Xeric Argicryolls
TYPICAL PEDON: Rasmussen silt loam, on a northwest facing, 4 percent slope in sagebrush at an elevation of 1,988 meters. When described on October 27, 2015, the soil was moist in the upper part and dry in the lower part. (Colors are for dry soil unless otherwise noted.)
A1--0 to 10 cm; grayish brown (10YR 5/2) silt loam, very dark brown (10YR 2/2) moist; moderate fine granular structure; slightly hard, very friable, nonsticky and nonplastic; many very fine and medium, and common fine roots; many very fine irregular pores; slightly acid (pH 6.4); clear smooth boundary.
A2--10 to 25 cm; grayish brown (10YR 5/2) silt loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; slightly hard, very friable, nonsticky and slightly plastic; many very fine, and common fine and medium roots; many very fine irregular pores; slightly acid (pH 6.2); clear wavy boundary.
Bt1--25 to 36 cm; brown (10YR 5/3) silt loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; common very fine and fine tubular and irregular pores; 10 percent faint clay films on all faces of peds; moderately acid (pH 6.0); clear wavy boundary.
Bt2--36 to 76 cm; grayish brown (10YR 5/2) silt loam, brown (10YR 4/3) moist; moderate medium angular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; common very fine, fine, and medium tubular and irregular pores; 20 percent distinct clay films on all faces of peds; 10 percent silt coats on all faces of peds; moderately acid (pH 6.0); gradual wavy boundary.
Bt3--76 to 113 cm; light yellowish brown (10YR 6/4) silt loam, brown (10YR 4/3) moist; weak medium prismatic structure parting to strong medium angular blocky; very hard, friable, moderately sticky and moderately plastic; few very fine roots; common very fine, fine, and medium tubular and irregular pores; 30 percent distinct clay films on surfaces along pores and on all faces of peds; 80 percent silt coats on all faces of peds; slightly acid (pH 6.2); gradual wavy boundary.
Bt4--113 to 138 cm; light yellowish brown (10YR 6/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate coarse prismatic structure parting to moderate medium prismatic; very hard, firm, very sticky and very plastic; common very fine and fine tubular pores; 50 percent prominent clay films on surfaces along pores and on all faces of peds; 65 percent silt coats on all faces of peds; slightly acid (pH 6.2); gradual wavy boundary.
Bt5--138 to 150 cm; light yellowish brown (10YR 6/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate coarse subangular blocky structure; very hard, firm, very sticky and very plastic; common very fine, fine, and medium tubular pores; 60 percent prominent clay films on surfaces along pores and on all faces of peds; 3 percent silt coats on all faces of peds; slightly acid (pH 6.4).
TYPE LOCATION: Caribou County, Idaho; about 17 kilometers south of Wayan, ID; located about 200 meters east and 970 meters south of the northwest corner of sec. 9, T. 7 S., R. 44 E.; Wayan East USGS quad; 42 degrees, 49 minutes, 39.4 seconds north latitude and 111 degrees, 19 minutes, 40.2 seconds west longitude, WGS 84.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature -- 1.7 to 3.9 degrees C
Thickness of the mollic epipedon -- 25 to 39 cm
Depth to argillic horizon -- 25 to 35 cm
Particle-size control section (weighted averages)*
*clay content -- 18 to 30 percent
*rock fragments -- 0 to 1 percent
A1, A2 horizons
Hue: 7.5YR or 10YR dry or moist
Value: 2 or 3 moist
Chroma: 2 or 3 moist
Clay content: 10 to 18 percent
Reaction: pH 5.6 to 6.5
Thickness: 25 to 35 cm (combined thickness of A1, A2 horizons)
Bt1, Bt2 horizons
Hue: 7.5YR or 10YR dry or moist
Value: 5 or 6 dry, 3 or 4 moist
Chroma: 2 or 3 dry, 3 or 4 moist
Texture: silt loam or silty clay loam
Clay content: 18 to 30 percent
Reaction: pH 5.8 to 6.5
Rock fragment content: 0 to 1 percent gravel
Thickness: 50 to 75 cm (combined thickness of Bt1, Bt2 horizons)
Bt3, Bt4, or Bt5 horizon(s)
Hue: 7.5YR or 10YR dry or moist
Chroma: 3 or 4 moist
Texture: silt loam or silty clay loam
Clay content: 25 to 38 percent
Reaction: pH 5.8 to 6.5
Rock fragment content: 0 to 5 percent gravel
Thickness: greater than 60 cm (combined thickness of Bt3, Bt4, Bt5 horizons)
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform -- valley floors and hills
Elevation -- 1,975 to 2,150 meters
Slopes -- 1 to 12 percent
Parent material -- loess or loess influenced slope alluvium from basalt
Mean annual air temperature -- 0.6 to 2.8 degrees C
Mean annual precipitation -- 600 to 725 millimeters
Frost-free period -- 30 to 65 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained and 1.0 to 10 um/sec.
USE AND VEGETATION: The major uses are wildlife habitat, pasture and livestock grazing. The native plant community is mainly mountain big sagebrush, mountain brome, and Idaho fescue.
DISTRIBUTION AND EXTENT: Rasmussen soils are of small extent in southeastern Idaho; MLRA 43B.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Caribou County, Idaho, Caribou County Area, Idaho Soil Survey, 2017. The name Rasmussen is from a nearby valley.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: 0 to 36 cm (A1, A2, Bt1 horizons)
Argillic horizon: 25 to greater than 150 cm (Bt1, Bt2, Bt3, Bt4, Bt5 horizons)
Particle-size control section: 25 to 75 cm (Bt1, part of Bt2 horizons).
Rasmussen soils have a cryic temperature regime and a xeric moisture regime bordering on udic.
National Cooperative Soil Survey
U.S.A.