LOCATION SHEWAG                  MT

Established Series
Rev: PEM-JJU-RJS
06/2011

SHEWAG SERIES

The Shewag series consists of very deep, well drained soils that formed in mixed alluvium or outwash. These soils are on outwash plains, alluvial fans, fan remnants and stream terraces in valleys. These soils are subject to prolonged saturation from flood irrigation. Slopes are 0 to 4 percent. Mean annual precipitation is about 16 inches, and mean annual air temperature is about 37 degrees F.

TAXONOMIC CLASS: Sandy-skeletal, mixed Oxyaquic Haplocryolls

TYPICAL PEDON: Shewag very gravelly loam, in irrigated grass pasture (colors are for dry soil unless otherwise noted).

Oi--0 to 3 inches; slightly decomposed matted roots; abrupt smooth boundary. (1 to 3 inches thick)

A--3 to 9 inches; dark gray (10YR 4/1) very gravelly loam, black (10YR 2/1) moist; weak very fine and fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; many very fine and few fine roots; many very fine and fine dendritic tubular pores; 35 percent gravel and 5 percent cobbles; neutral (pH 6.8); clear wavy boundary. (4 to 15 inches thick)

Bw--9 to 18 inches; grayish brown (10YR 5/2) extremely gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; few fine prominent yellowish brown (10YR 5/6) moist redox concentrations; 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 common fine dendritic tubular pores; 50 percent gravel and 15 percent cobbles; neutral (pH 7.0); clear wavy boundary. (5 to 10 inches thick)

2C--18 to 60 inches; light brownish gray (10YR 6/2) extremely gravelly sand, grayish brown (10YR 5/2) moist; single grain; loose, nonsticky and nonplastic; 50 percent gravel and 20 percent cobbles; neutral (pH 7.0).

TYPE LOCATION: Beaverhead County, Montana; approximately 200 feet south and 1,250 feet east of the northwest corner of sec. 18, T. 6S, R. 14 W; Butch Hill topographic quadrangle; Latitude 45 degrees 19 minutes 25 seconds N., Longitude 113 degrees 22 minutes 04 seconds W.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 35 to 40 degrees F.
Mollic epipedon thickness - 7 to 15 inches
Redox concentrations - due to prolonged saturation from flood irrigation
Depth to lithologic discontinuity - 10 to 20 inches

Note: Some pedons may have a thin C horizon immediately above the 2C horizon.

A horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 3 or 5 dry; 2 or 3 moist
Chroma: 1 to 3; dry or moist
Texture: sandy loam or loam
Clay content: 10 to 25 percent
Rock fragments: 15 to 60 percent--15 to 40 percent gravel, 0 to 20 percent cobbles
Reaction: pH 6.1 to 7.6

Bw horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 3 or 4 moist
Chroma: 1 to 4; dry or moist
Texture: sandy loam or loam
Clay content: 10 to 20 percent
Rock fragments: 35 to 70 percent--35 to 50 percent gravel, 0 to 30 percent cobbles
Reaction: pH 6.1 to 7.6

2C horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 or 7 dry; 4 to 6 moist
Chroma: 1 to 3; dry or moist
Texture: loamy sand, sand or coarse sand
Clay content: 0 to 10 percent
Rock Fragments: 35 to 80 percent--30 to 50 percent gravel, 10 to 45 percent cobbles
Reaction: pH 6.4 to 7.3

COMPETING SERIES:
Geebarc (OR) - have an udic soil moisture regime

GEOGRAPHIC SETTING:
Landform - outwash plains, alluvial fans, fan remnants and stream terraces
Elevation - 5,900 to 7,400 feet
Slope - 0 to 4 percent
Parent material - mixed alluvium or outwash
Climate - long, cold winters; cool, moist springs; short, cool summers
Mean annual precipitation - 14 to 24 inches
Mean annual air temperature - 34 to 39 degrees F.
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Wisdom and Mooseflat soils. The Wisdom soils are fine-loamy over sandy or sandy-skeletal and are on similar landform positions. The Mooseflat soils are very poorly drained and on flood plains or drainageways.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability above the 2C horizon and very rapid in the 2C horizon.

USE AND VEGETATION: Shewag soils are used for irrigated grass hay and irrigated pasture. The vegetation is mainly Garrison creeping foxtail, meadow foxtail, timothy, tufted hairgrass, and other miscellaneous sedges, rushes and forbs.

DISTRIBUTION AND EXTENT: Shewag soils are not extensive in the intermountain valleys of southwestern Montana. MLRA - 44B.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.

SERIES ESTABLISHED: Beaverhead County, Montana, Big Hole Valley Area, 2005.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 3 to 18 inches (A, Bw horizons)
Redox concentrations - from 9 to 18 inches (Bw horizon)
Lithologic discontinuity - at 18 inches (2C horizon)
Particle-size control section - from 13 to 43 inches (part of Bw, part of 2C horizons)

Shewag soils have a cryic temperature regime, an ustic moisture regime, and an oxyaquic moisture subclass.

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National Cooperative Soil Survey
U.S.A.