LOCATION HORSEGRASS WY
Tentative Series
Rev. TAG-DMM-RJS
05/2011
HORSEGRASS SERIES
The Horsegrass series consists of very deep, very poorly drained soils that formed in alluvium derived from metamorphic and sedimentary rock. These soils are on drainageways, flood plains and stream terraces. Slopes are 0 to 4 percent. Mean annual precipitation is about 430 mm, and mean annual air temperature is about 1 degrees C.
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, calcareous Calcic Cryaquolls
TYPICAL PEDON: Horsegrass clay loam, in irrigated pastureland (colors are for moist soil unless otherwise noted).
Oe--0 to 6 cm; mucky peat; clear smooth boundary. (4 to 10 cm thick)
A--6 to 45 cm; black (10YR 2/1) clay loam, very dark gray (10YR 3/1) dry; moderate fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; many fine roots; many fine interstitial pores; 2 percent distinct manganese masses in matrix and 25 percent faint masses of reduced iron in matrix; slightly effervescent; slightly alkaline (pH 7.6); clear smooth boundary. (25 to 40 cm thick)
Bk--45 to 90 cm; pale brown (10YR 6/3) clay loam, very pale brown (10YR 7/3) dry; moderate fine and medium subangular blocky structure; moderately hard, firm, moderately sticky and moderately plastic; many fine roots; many fine tubular pores; 2 percent distinct manganese masses in matrix and 15 percent faint masses of reduced iron in matrix; 10 percent gravel; 15 percent irregular carbonate masses in matrix; slightly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (30 to 55 cm thick)
BCk1--90 to 120 cm; brown (10YR 5/3) gravelly sandy loam, pale brown (10YR 6/3) dry; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; many fine tubular pores; 20 percent gravel; 5 percent irregular carbonate masses in matrix; strongly effervescent; moderately alkaline (pH 8.0); clear wavy boundary. (20 to 40 cm thick)
BCk2--120 to 200 cm; dark yellowish brown (10YR 4/4) very gravelly coarse sand, yellowish brown (10YR 5/4) dry; single grain; loose, nonsticky and nonplastic; few fine roots; many fine interstitial pores; 35 percent gravel; slightly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Sublette County, Wyoming; located approximately 1100 feet west and 1410 feet south of the northeast corner. of section 36, T. 34N, R. 112W; USGS Onion Springs, Wyoming topographic quadrangle; 42 degrees 52 minutes 16.00 seconds north latitude and 110 degrees 9 minutes 34.00 seconds west longitude.
RANGE IN CHARACTERISTICS:
Soil temperature - 1.5 to 3.5 degrees C.
Mollic epipedon thickness - 25 to 40 cm
Depth to calcic horizon - 30 to 50 cm
Depth to sandy-skeletal material - 100 to 150 cm
Depth to a seasonally high water table - 0 to 30 cm
A horizon
Hue: 2.5Y or 10YR; dry or moist
Value: 2 or 3; dry or moist
Chroma: 1 or 2; dry or moist
Clay content: 27 to 35 percent
Calcium carbonate equivalent: 3 to 8 percent
Reaction: pH 7.6 to 8.0
Bk horizon
Hue: 2.5Y or 10YR; dry or moist
Value: 7 or 8 dry; 6 or 7 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy clay loam, clay loam
Clay content: 25 to 35 percent
Rock fragments: 0 to 15 percent gravel
Calcium carbonate equivalent: 15 to 25 percent
Sodium adsorption ratio: 2 to 10
Reaction: pH 7.9 to 8.4
BCk1 horizon
Hue: 2.5Y or 10YR; dry or moist
Value: 5 or 6; dry or moist
Texture: loam, sandy loam, sandy clay loam
Clay content: 18 to 28 percent
Rock fragments: 10 to 25 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
Sodium adsorption ratio: 2 to 10
Reaction: pH 7.9 to 8.4
BCk2 horizon
Hue: 2.5Y or 10YR; dry or moist
Value: 4 or 5; dry or moist
Chroma: 3 or 4; dry or moist
Texture: loamy sand, coarse sand
Clay content: 2 to 10 percent
Rock fragments: 35 to 55 percent-- 30 to 55 percent gravel, 0 to 10 percent cobbles
Calcium carbonate equivalent: 5 to 15 percent
Sodium adsorption ratio: 2 to 10
Reaction: pH 7.9 to 8.4
COMPETING SERIES:
Bigrant (ID) - do not have a sandy-skeletal horizon within 150 cm
Thosand (ID) - have greater than 40 percent calcium carbonate equivalent in the mollic epipedon
GEOGRAPHIC SETTING:
Landform - drainageways, flood plains, stream terraces
Elevation - 2160 to 2440 meters
Slope - 0 to 4 percent
Parent Material - alluvium derived from metamorphic and sedimentary rock
Climate - long, cold winters; cool, moist springs; short, cool summers
Mean annual precipitation - 380 to 485 mm with peak periods of precipitation occurring during the spring
Mean annual air temperature - 0.5 to 1.5 degrees C.
Frost-free period - 25 to 45 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Very poorly drained; moderate permeability.
USE AND VEGETATION: Horsegrass soils are primarily used for irrigated pasture or hayland. The potential native vegetation is mainly Nebraska sedge, tufted hairgrass, Garrison creeping foxtail, meadow foxtail, and timothy.
DISTRIBUTION AND EXTENT: Horsegrass soils are of small extent in southwestern Wyoming. MLRA - 43B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES PROPOSED: Sublette County, Wyoming, 2011. The series name is coined from a local landmark.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 6 to 45 cm (A horizon)
Calcic horizon - from 45 to 90 cm (Bk horizon)
Redoximorphic features - 6 to 90 cm (A, Bk horizons)
Sandy-skeletal material - at 120 cm (BCk2 horizons)
Particle-size control section - from 31 to 106 cm (part of A, Bk, part of BCk1 horizons)
Horsegrass soils have a cryic temperature regime and an aquic moisture regime.
National Cooperative Soil Survey
U.S.A.