LOCATION HAPNEY CO+MT WYEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Aridic Natrustolls
TYPICAL PEDON: Hapney very fine sandy loam - grassland. (Colors are for dry soil unless otherwise noted.)
E--0 to 2 inches; light brownish gray (10YR 6/2) very fine sandy loam, dark grayish brown (10YR 4/2) moist; moderate thin platy structure parting to moderate very fine granular; soft, very friable; moderately alkaline; abrupt smooth boundary. (0 to 3 inches thick)
Btn--2 to 20 inches; light brownish gray (10YR 5/2) clay, very dark grayish brown (10YR 3/2) moist; moderate medium columnar structure parting to moderate medium and fine angular and subangular blocky; slightly hard, friable, sticky, plastic; few fine roots; thin continuous clay films on peds and in root channels and pores; slightly effervescent in the lower few inches; very strongly alkaline; gradual wavy boundary. (10 to 30 inches thick)
BCn--20 to 26 inches; light olive brown (2.5Y 5/4) clay loam, dark olive brown (2.5Y 4/4) moist; moderate medium subangular blocky structure; hard, friable, slightly sticky, slightly plastic; few fine roots; thin patchy clay films on some peds and in some root channels and pores; strongly effervescent; very strongly alkaline; gradual wavy boundary. (5 to 8 inches thick)
C--26 to 60 inches; light yellowish brown (2.5Y 6/4) sandy clay loam, olive brown (2.5Y 4/4) moist; massive; very hard, friable, slightly sticky, slightly plastic; strongly alkaline.
TYPE LOCATION: Alamosa County, Colorado; 695 feet west and 75 feet south of the NE corner of Sec. 27, T. 38 N., R. 11 E.
RANGE IN CHARACTERISTICS: The Hapney soils typically have albic horizons but such horizons are absent in some truncated pedons. Thin A horizons occur in some pedons. Depth to uniformly calcareous material normally ranges from 6 to 20 inches. The C horizons typically are noncalcareous. Buried soil horizons occur below the natric horizon in some pedons. Depth to the base of the argillic horizon ranges from 12 to 40 inches. Continuous subhorizons of visible secondary calcium carbonate and/or sulfate do not occur within the control section although inconsistent accumulation of visible soluble salt occurs in the lower solum in some pedons. E.S.P. ranges from 15 to 40 percent in the solum but decreases with increasing depth in the C horizon. A 2C horizon of loose sand occurs within a depth of 60 inches in some pedons. Rock fragments range from 0 to 35 percent by volume in a major part of the solum and in the C horizon above a depth of 40 inches, but typically are less than 10 percent.
Rock fragments are mainly less than 3 inches in diameter but range from 1/8 to 10 inches in diameter. The mean annual soil temperature ranges from 43 to 46 degrees F, and mean summer soil temperature ranges from 60 to 64 degrees F.
The E horizon has hue of 5Y through 7.5YR, value of 5 through 8, 4 through 7 moist, and chroma of 1 through 4. It ranges from neutral to very strongly alkaline.
The Bt horizon has hue of 5Y through 7.5YR, value of 4 through 7 dry, 3 through 6 moist, and chroma of 1 through 6. It is typically clay loam or clay and has 35 to 50 percent clay, 5 to 45 percent silt and 15 to 55 percent sand with more than 15 percent being fine or coarser sand. This horizon is strongly or very strongly alkaline.
The C horizon has hue of 5Y through 7.5YR. It is loam, clay loam, or sandy clay loam. This horizon ranges from mildly alkaline to very strongly alkaline.
COMPETING SERIES: There are currently no other series in this family. The Sorum and Stumpp series are similar. Sorum soils have medium to moderately fine textured natric horizons of less than 35 percent clay. Stumpp soils have mean summer soil temperature of less than 59 degrees F, and overlie sandy-skeletal substratums.
GEOGRAPHIC SETTING: These soils are on flood plains or alluvial fans. Slope gradients range from 0 to 6 percent. The soils formed in mixed alluvial deposits. The average annual precipitation is 6 to 9 inches, with peak periods of precipitation in the middle and late summer. Average annual temperature is 41 to 44 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the San Luis and Hooper soils, both of which lack mollic epipedons and overlie sand and gravel.
DRAINAGE AND PERMEABILITY: Well to moderately well drained; slow runoff; slow permeability; these soils typically have a fluctuating water table at 4 to 5 feet during some seasons of the year.
USE AND VEGETATION: These soils are used principally as native pastureland; however, they are irrigated in some localities. Principal native vegetation is mainly western wheat, snakeweed, and rabbitbrush.
DISTRIBUTION AND EXTENT: The San Luis Valley area of south-central Colorado. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Alamosa County, Colorado, 1974.
REMARKS: Diagnostic features are a mollic epipedon after mixing and an argillic natric horizon from 2 to 20 inches. Last updated by the state 12/90.