LOCATION SOMSEN IDEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Xeric Haplocalcids
TYPICAL PEDON: Somsen very stony fine sandy loam, rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 1.5 inches; grayish brown (10YR 5/2) very stony light fine sandy loam, very dark grayish brown (10YR 3/2) moist; massive; soft, very friable, nonsticky and nonplastic; many very fine roots; many very fine interstitial pores; mildly alkaline (pH 7.6); abrupt smooth boundary. (0 to 2 inches thick)
A2--1.5 to 4 inches; light brownish gray (10YR 6/2) fine sandy loam, dark grayish brown (10YR 4/2) moist; weak very thin platy structure that parts to very weak very fine granular structure; slightly hard, very friable, nonsticky and slightly plastic; common very fine roots; many very fine tubular pores; 15 percent basalt stones and angular cobblestones; slightly calcareous; moderately alkaline (pH 8.0); abrupt smooth boundary. (3 to 6 inches thick)
Bw--4 to 9 inches; light brownish gray (10YR 6/2) pale brown (10YR 6/3, crushed) cobbly fine sandy loam, brown (10YR 4/3) moist; very weak coarse subangular blocky structure; slightly hard, very friable, nonsticky and slightly plastic; common very fine and fine roots; many very fine tubular and interstitial pores; 15 percent basalt stones and angular cobblestones; moderately calcareous; moderately alkaline (pH 8.1); clear smooth boundary. (3 to 8 inches thick)
Bk1--9 to 14 inches; light brownish gray (10YR 6/2) cobbly fine sandy loam, brown (10YR 4/3) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; common very fine interstitial and tubular pores; 20 percent basalt stones and angular cobblestones; moderately calcareous, few very fine veins and splotches of lime and common small chunks of highly calcareous material; moderately alkaline (pH 8.2); clear smooth boundary. (5 to 11 inches thick)
Bk2--14 to 24 inches; white (10YR 8.2) cobbly fine sandy loam, pale brown (10YR 6/3) moist; massive; hard, friable, slightly sticky and slightly plastic; common very fine roots; few very fine tubular pores; 25 percent basalt stones and angular cobblestones; common subrounded nodular krotovinas; thin (about 12 inches thick), discontinuous, very weakly cemented material on top of bedrock; strongly calcareous; strongly alkaline (pH 8.6); abrupt wavy boundary. (9 to 12 inches thick)
2R--24 inches; basalt; lime coating on surface and in cracks.
TYPE LOCATION: Blaine County, Idaho; 25 feet north of the southwest corner of sec. 20, T.8S., R.26E.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 47 to 52 degrees F.
Depth to bedrock - 20 to 40 inches
Depth to the calcic horizon - 7 to 16 inches
Particle size control section
Clay content - 8 to 18 percent
Rock fragment content - 15 to 35 average; the upper part may contain less than 15 percent
A horizon
Value - 5 through 7 dry, 3 through 5 moist
Chroma - 2 or 3
Effervescence - none or slightly
Reaction - mildly or moderately alkaline
Bw horizon
Value - 4 or 5 moist
Chroma - 2 or 3
Effervescence - slightly or moderately
Reaction - mildly or moderately alkaline
Bk horizon
Value - 6 through 8 dry, 4 through 7 moist
Chroma - 2 or 3
Texture - FSL, GR-FSL, L, GR-L, SL, GR-SL, CB-FSL, or ST-FSL
Reaction - moderately to strongly alkaline
COMPETING SERIES: These are the Bertelson, Declo, Eccles, Escalante, Holsine, Kecko, Malm, Matheson, Palisade, and Vining series. All of these soils lack bedrock above depth of 40 inches except the Malm and Vining soils. Bertelson soils are loamy sand in the upper 20 inches, are strongly calcareous throughout, and have weakly lime-cemented layers. Declo and Palisade soils are dominantly medium textured in the control section. Eccles soils have strongly calcareous sola and bedrock below depth of 40 inches. Holsine, Malm and Matheson soils have average annual soil temperatures colder than 47 degrees F. Kecko soils are noncalcareous to depths of 20 to 30 inches. Palisade soils have 20 to 40 percent lime in the calcic horizon. Vining soils lack calcic horizons.
GEOGRAPHIC SETTING: Somsen soils are on basalt uplands that have been covered by a layer of mixed eolian materials. Slopes range from 0 to 30 percent. Elevations range from 3,000 to 4,660 feet. The climate is semiarid and has dry summers. Average annual precipitation is 8 to 12 inches, including 1 to 3 feet of snow, and the average frost-free period is 115 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Escalante, Portneuf, Quincy, and Taunton soils and the competing Kecko and Vining soils. All these, except the Vining soils, lack bedrock within 40 inches of the surface. All of the listed soils are on basalt plains. Escalante, Kecko, and Portneuf soils are also on fan terraces.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately rapid permeability.
USE AND VEGETATION: Grazing is the dominant use. Only a minor acreage is cultivated and irrigated and produces hay, barley, wheat, oats, beans, potatoes, and pasture. The natural vegetation is mainly Wyoming big sagebrush, rabbitbrush, needle-and-thread grass, Indian ricegrass, sod wheatgrass, and cheatgrass.
DISTRIBUTION AND EXTENT: South-central Idaho and in central Utah. The series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Blaine County, Idaho, 1973.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 4 inches (A1 and A2 horizons)
Cambic horizon - the zone from 4 to 9 inches (Bw horizon)
Calcic horizon - the zone from 9 to 24 inches (Bk1 and Bk2 horizons)
Lithic contact - the contact with bedrock at 24 inches (R horizon)