LOCATION LONGMONT COEstablished Series
TAXONOMIC CLASS: Fine, smectitic, calcareous, mesic Aeric Halaquepts
TYPICAL PEDON: Longmont clay - grassland. (Colors are for dry soil unless otherwise noted.)
A11--0 to 5 inches; light brownish gray (2.5Y 6/2) clay, dark grayish brown (2.5Y 4/2) moist; weak fine subangular blocky structure that parts to moderate fine granules; hard, firm, very sticky, very plastic; calcareous; strongly alkaline (pH 9.0); clear smooth boundary. (4 to 8 inches thick)
A12--5 to 21 inches; light olive brown (2.5Y 5/3) clay, olive brown (2.5Y 4/3) moist; weak coarse subangular blocky structure; extremely hard, very firm, very sticky, very plastic; calcareous; very strongly alkaline (pH 9.2); gradual wavy boundary. (10 to 20 inches thick)
C1cscag--21 to 31 inches; light olive brown (2.5Y 5/3) clay, olive brown (2.5Y 4/3) moist; massive; extremely hard, very firm, very sticky, very plastic; many medium distinct mottles of yellowish brown (10YR 5/4) moist; some accumulation of calcium sulfate as crystals and calcium carbonate as concretions; calcareous; strongly alkaline (pH 8.6); gradual wavy boundary. (8 to 32 inches thick)
C2cscag--31 to 60 inches; pale olive (5Y 6/3) clay, olive (5Y 5/3) moist; massive; extremely hard, very firm, very sticky, very plastic; common medium distinct mottles of olive (5Y 4/3) moist; some accumulation of calcium sulfate and calcium carbonate occurring as crystals and small concretions; calcareous; moderately alkaline (pH 8.4).
TYPE LOCATION: Boulder County, Colorado; 100 feet west and 500 feet north of S1/4 corner of Sec. 13, T. 2 N., R. 70 W.
RANGE IN CHARACTERISTICS: Organic carbon in the surface horizon ranges from .7 to 2 percent and decreases uniformly with increasing depth. Accumulation of salt more soluble than gypsum is common in the surface horizons but does not exceed 4 percent in any horizon as much as 6 inches thick above a depth of 40 inches. Exchangeable sodium percentage exceeds 15 percent in 1/2 or more of the upper 20 inches and decreases with increasing depth below 20 inches. These soils are usually moist due to fluctuating water tables and are saturated in some season of most every year. Weighted average clay content of the upper 40 inches is 35 to 60 percent. Rock fragments range from 0 to 15 percent but are typically less than 5 percent. Mean annual soil temperature ranges from 47 to 58 degrees F. and mean summer soil temperature ranges from 59 to 72 degrees F.
The A1 horizon has hue of 5Y through 10YR, value of 5 or 6 dry, 3 through 5 moist, and chroma of 1 through 3. It has weak subangular blocky or fine granular structure depending on concentration of soluble salts. This horizon is soft or slightly hard. It is strongly or very strongly alkaline (pH 8.6 to 9.5) and has more than 15 percent exchangeable sodium in some part.
The Ccscag horizon has hue of 5Y through 10YR and chroma greater than 2. It is moderately or strongly alkaline (pH 8.0 to 8.8) and becomes less alkaline with increasing depth. It typically has less than 10 percent exchangeable sodium throughout most of the horizon and the percentage decreases with increasing depth. This horizon has 4 to 12 percent calcium carbonate equivalent and common calcium sulfate crystals.
COMPETING SERIES: These are the Apishipa and La Sauses series. Apishipa soils have less than 15 percent exchangeable sodium in the control section. La Sauses soils have a mean annual soil temperature colder than 47 degrees F.
GEOGRAPHIC SETTING: The Longmont soils are on nearly level to slightly concave or depressed areas of flood plains or very gently sloping alluvial fans and terraces. Slope gradients typically range from 0 to 6 percent. The soils formed in fine textured calcareous alluvial parent materials derived principally from sedimentary rock. At the type location the average annual precipitation is about 18 inches, but the soils have a fluctuating water table above a depth of 40 inches most of the year that keeps some part of the control section usually moist, and the soil is saturated at some seasons.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Limon and Loveland soils. Limon soils are well drained and have less than 15 percent exchangeable sodium. Loveland soils have mollic epipedons and have less than 15 percent exchangeable sodium and overlie sand and gravel.
DRAINAGE AND PERMEABILITY: Poor to somewhat poorly drained; slow runoff; slow permeability.
USE AND VEGETATION: Used as native pastureland or native hay meadow. Principal native vegetation is alkali sacation and saltgrass.
DISTRIBUTION AND EXTENT: Central Colorado. The series has moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Boulder Area, Colorado, 1971.
REMARKS: Last updated by the state 4/73.