LOCATION COPUS CATentative Series
TAXONOMIC CLASS: Fine, smectitic, thermic Xeric Endoaquerts
TYPICAL PEDON: Copus silty clay, in a plowed field, at an elevation of 280 feet. (When described on March 3, 1989, the soil was moist throughout; Colors are for dry soil unless otherwise stated).
Ap1--0 to 9 inches; gray (10YR 5/1) silty clay, very dark gray (5Y 3/1) moist; moderate fine granular structure; hard, friable, very sticky and very plastic; few very fine and fine roots; many very fine and few fine interstitial, and many very fine tubular pores; neutral (pH 7.0); clear smooth boundary. (8 to 12 inches thick).
Ap2--9 to 18 inches; gray (10YR 5/1) clay, very dark gray (5Y 3/1) moist; few fine yellowish brown (10YR 5/8) and light olive brown (2.5Y 5/4) prominent mottles, moist; moderate medium subangular blocky structure parting to moderate fine granular; very hard, firm, very sticky and very plastic; common very fine and few fine roots; many very fine and few fine interstitial, and common very fine tubular pores; neutral (pH 7.0); clear smooth boundary. (8 to 15 inches thick).
Bw--18 to 26 inches; gray (5Y 6/1) silty clay, dark gray (5Y 4/1) moist; few medium and fine yellowish brown (10YR 5/8) prominent mottles, moist; weak coarse subangular blocky structure parting to weak fine granular; very hard, firm, sticky and very plastic; common very fine and few fine roots; common very fine and few fine tubular pores; slightly acid (pH 6.5); clear wavy boundary. (5 to 10 inches thick).
Bssy1--26 to 40 inches; gray (5Y 5/1) clay, dark grayish brown (2.5Y 4/2) moist; few fine black (N2/0) and medium light olive brown (2.5Y 5/4) distinct mottles, moist; weak coarse prismatic structure parting to weak fine and medium subangular blocky; very hard, firm, sticky and very plastic; common very fine and few fine roots; few very fine tubular pores; few fine and medium masses of gypsum crystals; few intersecting slickensides; slightly acid (pH 6.2); clear wavy boundary. (10 to 24 inches thick)
Bssy2--40 to 50 inches; light olive brown (2.5Y 5/4) and olive gray (5Y 5/2) clay, olive brown (2.5Y 4/4) and olive gray (5Y 4/2) moist; common medium very dark gray (5Y 3/1) distinct mottles and common medium yellowish brown (10YR 5/6) prominent mottles, moist; massive; very hard, firm, sticky and very plastic; common very fine and few fine roots; common very fine tubular pores; few fine and medium masses of gypsum crystals; common intersecting slickensides; neutral (pH 7.0); abrupt wavy boundary. (8 to 20 inches thick)
C--50 to 60 inches; light olive gray (5Y 6/2) silty clay loam, olive gray (5Y 5/2) moist; few medium brown (7.5YR 4/2) and common fine brownish yellow (10YR 6/8) prominent mottles, moist; massive; very hard, firm, sticky and very plastic; common very fine and few fine roots; common very fine tubular pores; neutral (pH 7.0).
TYPE LOCATION: Kern County, California; about 22 miles southwest of downtown Bakersfield in the Buena Vista Lake Bed; 2600 feet west and 120 feet north of the southeast corner of Sec. 29, T. 32 S., R. 25 E., MDB&M; Mouth of Kern quadrangle.
RANGE IN CHARACTERISTICS:
Soil temperature - Average annual: 62 to 67 degrees F and the soil temperature is never below 47 degrees F.
Soil moisture - dry throughout from mid June to mid December.
Particle size control section:
Clay content: 35 to 60 percent
Gypsum: averages 2 to 10 percent
Reaction: moderately acid to neutral
Electrical conductivity: 2 to 8 mmhos/cm
Sodium absorption ratio: less than 5
Ap horizons
Hue: 10YR or 5Y, dry and moist
Value: 5 or 6 dry, 2 or 3 moist
Mottles: prominent mottles in lower part with hue of 10YR or 2.5Y, chroma of 5 dry and 4 moist, and value of 4 through 8.
Clay content: 40 to 60 percent
Organic matter: 2 to 5 percent
Reaction: neutral to moderately alkaline
Bw horizon
Hue: 10YR, 2.5Y or 5Y
Value: 5 or 6 dry, 3 or 4 moist
Chroma: 0, 1 or 2
Mottles: prominent mottles with hue of 10YR or 2.5Y, chroma of 5 dry and 4 moist, and value of 4 through 8.
Texture: clay, silty clay, or silty clay loam with 35 to 60 percent clay.
Reaction: moderately acid to neutral
Bssy horizons
Hue: 10YR, 2.5Y and 5Y
Value: 5 or 6 dry, 3 or 4 moist
Chroma: 1 through 4
Mottles: faint to prominent mottles with hue of 10YR, 2.5Y or 5Y, chroma of 2 through 6 dry and 2 through 5 moist, and value of 0 through 8.
Texture: clay, silty clay, or silty clay loam with 35 to 60 percent clay.
Reaction: moderately acid to neutral
C horizon
Hue: 2.5Y and 5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 through 4
Mottles: faint to prominent mottles with hue of 10YR, 2.5Y or 5Y, chroma of 2 through 6 dry and 2 through 5 moist, and value of 0 through 8.
Texture: clay, silty clay, or silty clay loam with 35 to 60 percent clay.
COMPETING SERIES: These are the Clear Lake, Hildreth, Jacktone, Maxwell, Stockton (T), Subaco, and Willows series. Clear Lake and Hildreth soils are mildly to moderately alkaline in the C horizon. Jacktone soils have a duripan at a depths of 20 to 40 inches. Maxwell soils are moderately alkaline below 40 inches, have segregated lime at a depth of 24 to 56 inches, and do not have segregated gypsum. Stockton soils do not have segregated gypsum. Subaco soils have a paralithic contact at depths of 20 to 40 inches. Willows soils are strongly alkaline and have more than 15 percent exchangeable sodium in some or all parts.
GEOGRAPHIC SETTING: Copus soils are on basin floors. Slopes are 0 to 1 percent. The soils formed in alluvium derived dominantly from mixed rock. Elevations are 275 to 290 feet. The climate is arid with hot dry summers and cool, slightly moist winters. The mean annual precipitation is 5 to 6 inches. The mean annual temperature is 62 to 65 degrees F. Mean July temperature is about 85 degrees F., and mean January temperature is about 47 degrees F. The frost-free season is 250 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Buttonwillow, Fages (T), Lokern, Millux (T), and Zalvidea (T) soils. Buttonwillow soils are on similar landforms, are clayey over loamy, and have an irregular decrease in organic carbon. Fages (T) and Millux (T) soils are on adjacent relic basin floors, are calcareous, have an SAR greater than 13, and do not have intersecting slickensides. Lokern soils are on similar surfaces and do not have intersecting slickensides. Zalvidea (T) soils are on similar landforms, are coarse-loamy, and have a gypsic horizon.
DRAINAGE AND PERMEABILITY: Very poorly drained, very slow runoff or ponded; slow permeability. Copus soils have been artificially drained by dams and levees. The soil now has a water table at a depth of 4 to 6 feet during the summer and at greater than 6 feet during the rest of the year. The soils are still subject to rare flooding. Some areas of this soil are subject to occasional very long periods of flooding between January and July when floodwaters from the Sierra Nevada mountains are diverted to designated basins. During these times much of the basin, in which these Copus soils occur, is used as a temporary reservoir.
USE AND VEGETATION: Used primarily for irrigated crops such as cotton, alfalfa, and wheat.
DISTRIBUTION AND EXTENT: Southern San Joaquin Valley of California. The series is moderately extensive. MLRA is 17.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: Kern County, California, 1989. The name is taken from nearby Copus Road.
REMARKS: The proposed classification under the ICOMERT 5th circular letter would be fine, montmorillonitic, thermic, Xeric Haplaquerts. Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon-- 0 to 18 inches (Ap1, Ap2)
Vertic properties: 35 to 60 percent clay throughout; cracks 1 to 5 cm wide to a depth of 20 inches; few to common intersecting slickensides from a depth of 26 to 50 inches.
Particle size class: 10 to 40 inches
Series reclassified on September, 1994. Competing series not reviewed at that time.