LOCATION ALAMOSA COEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Typic Argiaquolls
TYPICAL PEDON: Alamosa loam, grassland. (Colors are for dry soil unless otherwise noted.)
A--0 to 8 inches; dark gray (10YR 4/1) loam, black (10YR 2/1) moist; few fine faint yellowish brown (10YR 5/6) mottles; moderate very fine granular structure; soft, very friable, slightly plastic; neutral (pH 7.2); clear smooth boundary. (6 to 10 inches thick)
BA--8 to 12 inches; gray (10YR 5/1) heavy loam, very dark gray (10YR 3/1) moist; few fine faint yellowish brown (10YR 5/6) mottles; moderate medium subangular blocky structure; slightly hard, very friable, slightly plastic; peds are hard; mildly alkaline (pH 7.4); clear smooth boundary. (4 to 6 inches thick)
Btg--12 to 30 inches; gray (10YR 5/1) light clay loam, very dark gray (10YR 3/1) moist; common medium distinct yellowish brown (10YR 5/6) mottles; mottling is most pronounced in the lower part of the horizon; moderate medium subangular blocky structure; slightly hard, friable, slightly plastic; peds are hard; thin glossy and wax-like patches on faces of peds; wax-like coatings in root channels and pores; mildly alkaline (pH 7.6); gradual wavy boundary. (10 to 20 inches thick)
BCkg--30 to 40 inches; brown (10YR 5/3) loam, dark brown (10YR 4/3) moist; massive; common medium distinct dark brown (7.5YR 4/4) and dark gray (5Y 4/1) mottles; massive; hard, very friable, slightly plastic; weakly calcareous; moderately alkaline (pH 8.0).
Cg--40 to 60 inches; brown (10YR 5/3) loam, dark brown (10YR 4/3) moist; massive; common medium distinct dark brown (7.5YR 4/4) and dark gray (5Y 4/1) mottles; massive; hard, very friable, slightly plastic; weakly calcareous; moderately alkaline (pH 8.0).
TYPE LOCATION: Alamosa County, Colorado approximately 150 feet west and 90 feet south of the NE corner of sec. 24, T.38N., R.9E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges 43 degrees to 46 degrees F., and mean summer soil temperature ranges from 60 degrees to 64 degrees F. Depth to the base of the argillic horizon ranges from 20 to 50 inches. Depth to continuous subhorizons of visible
secondary calcium carbonate and/or sulfate accumulation ranges from 15 to 50 inches. Rock fragments range from 0 to 20 percent in the solum and C horizon. The partical size control section contains 10 to 35 percent fine and coarser sand. Hue ranges from 5Y to 7.5YR in most pedons. Some pedons contain thin subhorizons of 5YR hue. Water table may range seasonally to 1 to 2 feet below the surface.
The A horizon has hue of 10YR or 7.5YR value of 3 through 5, 2 or 3 moist and chroma of 1 or 2. Reaction ranges from neutral through moderately alkaline. Mottling in this horizon is faint to prominent.
The Bt horizon has hue of 10YR or 7.5YR value of 4 through 6, 2 through 4 moist, and chroma of 0 through 2. Reaction is neutral to moderately alkaline. Mottling in this horizon is faint to prominent.
The C horizon contain minor stratification and loamy sand with gravelly modifiers is in some pedons below 30 inches.
COMPETING SERIES: This is the Smiley series. Smiley soils are formed in loamy glacial till on glacial plains under a Udic moisture regime.
GEOGRAPHIC SETTING: Alamosa soils are on alluvial flood plains, old lake basins, or alluvial fans. Slope gradients range from 0 to about 6 percent. The soil formed in moderately fine textured mixed alluvium. At the type location, the average annual precipitation is 7 inches, with peak periods of precipitation in the spring and early summer months. The soil, however, is saturated with water due to a fluctuating water table throughout most of the season when not frozen. Mean annual temperature ranges from 39 degrees to 43 degrees F. and mean summer temperature is 59 degrees to 62 degrees F. In areas outside the San Luis Valley in southwest Colorado, mean annual precipitation ranges to 24 inches, however production by subirrigation is similar.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Torsido soils and the Vastine soils. Vastine soils lack argillic horizons.
DRAINAGE AND PERMEABILITY: Poorly to somewhat poorly drained; slow runoff; moderately slow permeability. The water table fluctuates, but is typically within 40 inches of the surface during most of the season when not frozen.
USE AND VEGETATION: These soils are used principally as native pastureland or for native hayland. Principal native plants are water tolerant grasses, sedges, rushes, willows, and iris.
DISTRIBUTION AND EXTENT: San Luis Valley of south-central Colorado. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Alamosa County (Soil Survey of the San Luis Valley Area), Colorado, 1903.
REMARKS:
The superactive cation exchange activity class was added in 03/2003 to the taxonomic classification by the National Soil Survey Center on request of the Reno MLRA office, without review of the soil series property data. The remainder of this document has not been updated.