LOCATION LASAUSES COEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, nonacid, frigid Aeric Halaquepts
TYPICAL PEDON: LaSauses sandy clay loam - grassland. (Colors are for dry soil unless otherwise noted.)
A1sa1--0 to 5 inches; brown (10YR 5/3) sandy clay loam, dark brown (7.5YR 4/4) moist; weak fine granular structure; slightly hard, friable; salt concentrated on the surface in a white crust; calcareous; strongly alkaline; clear smooth boundary. (3 to 7 inches thick)
A1sa2--5 to 10 inches; brown (10YR 5/3) loam, dark brown (7.5YR 4/4) moist; very weak medium subangular blocky structure parting to weak fine granules; hard, firm; few small salt spots; calcareous; strongly alkaline; clear smooth boundary. (3 to 7 inches thick)
B21g--10 to 17 inches; brown (7.5YR 5/4) heavy clay loam, dark reddish brown (5YR 3/3) moist; common large distinct gray (2.5Y 5/1) moist mottles; weak medium granular structure; hard, firm, slightly sticky, plastic; noncalcareous in matrix with many gypsum crystals and other salts; mildly alkaline; gradual smooth boundary.
(6 to 15 inches thick)
B22g--17 to 60 inches; mottled red, yellow, and gray heavy clay; moderate fine subangular blocky structure; very hard, very firm, sticky, very plastic; many gypsum crystals; medium acid.
TYPE LOCATION: Alamosa County, Colorado; approximately 2,400 feet north of the southeast corner of Sec. 9, T. 36 N., R. 10 E.
RANGE IN CHARACTERISTICS: The LaSauses soils are calcareous and strongly or very strongly alkaline in their uppermost horizon, but are slightly to strongly acid in the lower part of the control section. At least some subhorizon between depths of 10 and 20 inches is noncalcareous. Exchangeable sodium ranges from 15 to 45 percent in the surface horizons and decreases as depth increases. Calcium carbonate, calcium sulfate, and other soluble salts are concentrated in the upper part of the control section but decrease as depth increases. Calcium sulfate may depress pH readings in some pedons. The soil is base saturated in the upper part of the control section but ranges from 60 to 100 percent base saturated in the lower part. The control section is usually heavy clay loam or clay and has 35 to 60 percent clay, 5 to 45 percent silt, and 10 to 60 percent sand. Rock fragments range from 0 to 15 percent by volume in a major part of the control section and usually less than 3 inches in diameter. A major part of the control section above a depth of 60 inches has hue of 7.5YR or yellower. Mottling of redder hue occurs in most pedons but does not predominate. Chroma of 2 or less comprises less than 60 percent of the soil mass between depths of 6 and 30 inches. The mean annual soil temperature is 45 degrees F; and the mean summer soil temperature is 62 degrees F.
The A horizon has hue of 2.5Y through 7.5YR, value of 5 through 8 dry, 3 through 7 moist, and chroma of 1 through 6. It ranges from moderately to very strongly alkaline.
The B2g horizon has hue of 5Y through 7.5YR, value of 5 through 7 dry, 3 through 7 moist, and chroma of 1 through 6. It ranges from mildly alkaline to strongly acid and becomes more acid as depth increases.
COMPETING SERIES: These are the Longmont and Mishak series. Longmont soils are calcareous and moderately alkaline in the lower part of the control section and have montmorillonitic mineralogy. Mishak soils have medium to moderately fine textured control sections with less than 35 percent clay, and are calcareous in the lower part of the control section.
GEOGRAPHIC SETTING: The LaSauses soils are on nearly level to very gently sloping flood plains and alluvial fans. The soils formed in alluvial parent materials. At the type location the average annual precipitation is 7 inches, with peak periods of precipitation in the spring and summer.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arena, Hooper, and LaJara soils. Arena soils have duripans. Hooper soils have natric horizons and overlie sand and gravel substratums. LaJara soils have mollic epipedons and have less than 15 percent sodium.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; slow permeability.
USE AND VEGETATION: These soils are used principally as native pastureland; however some areas are used for irrigated meadows. Native vegetation is mainly greasewood, rabbitbrush, saltgrass, and alkali sacaton.
DISTRIBUTION AND EXTENT: 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: Pronunciation: La sa ses. Last updated by the state 8/74.
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 Lakewood MLRA office, without review of the soil series property data. The remainder of this document has not been updated.