LOCATION KOFA AZEstablished Series
TAXONOMIC CLASS: Clayey over sandy or sandy-skeletal, smectitic over mixed, calcareous, hyperthermic Vertic Torrifluvents
TYPICAL PEDON: Kofa clay - idle cropland. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 12 inches; pale brown (10YR 6/3) clay, brown (10YR 4/3) moist; massive; very hard, very firm, moderately sticky and very plastic; many fine roots; few very fine tubular pores; few cracks 1.5 to 2 inches wide extending to lower boundary; strongly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (12 to 18 inches thick)
C1--12 to 28 inches; pale brown (10YR 6/3) clay, brown (10YR 4/3) moist; moderate medium and coarse subangular blocky structure; very hard, very firm, moderately sticky and very plastic; many fine roots; few very fine tubular pores; few cracks .5 to 2 inches wide extending to lower boundary; strongly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (8 to 22 inches thick)
2C2--28 to 60 inches; very pale brown (10YR 7/4) stratified sand, light yellowish brown (10YR 6/4) moist; single grain; loose; many very fine and fine roots; many very fine irregular pores; common thin strata of loamy sand, sandy loam and silt loam; slightly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Yuma County, Arizona; 250 feet east and 2,000 feet south of the northwest corner of section 3, T. 10 S., R. 24 W.
RANGE IN CHARACTERISTICS:
Soil Moisture - Intermittently moist in some part of the soil moisture control section during July - August and December - February. Driest during May and June. Typic aridic soil moisture regime.
Soil Temperature - 72 to 78 degrees F.
Rock fragments - less than 15 percent in the upper part and as much as 65 percent in the sandy lower part
Salinity- Usually has EC of 1 to 8 dS/m, but ranges to as much as 30
Reaction - Slightly alkaline to very strongly alkaline
Sodicity- SAR is usually 1 to 3, but ranges to 60 in some parts of some pedons
Depth to contrasting layer - 20 to 40 inches
Cracking- 1 cm to 2 inches wide to depths of 20 inches or more
Ap and C horizons
Hue: 10YR, 7.5YR, 5YR
Value: 4, 5, 6 or 7 dry, 3 through 6 moist
Chroma: 2, 3 or 4, dry or moist
Texture: Clay, silty clay, with thin strata of silty clay loam or silt textures
Organic matter: Less than 1 percent
2C horizon
Hue: 10YR, 7.5YR, 5YR
Value: 5, 6 or 7 dry, 3 through 6 moist
Chroma: 2, 3 or 4, dry or moist
Texture: sand, fine sand, loamy sand, loamy fine sand
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Kofa soils are on flood plains and have slopes of 0 to 3 percent, but are generally less than 1 percent. They formed in stratified alluvium from mixed rocks. Elevations are 75 to 700 feet. The climate is hot, arid and continental. The mean annual precipitation is 2 to 7 inches; mean January air temperature is 55 degrees F.; mean July air temperature is 95 degrees F.; mean annual air temperature is 70 to 76 degrees F. The frost-free period is 250 to 325 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cibola, Gadsden, Glenbar and Rositas soils. Cibola soils are fine-silty. Gadsden and Glenbar soils do not have contrasting textures. Rositas soils are sandy.
DRAINAGE AND PERMEABILITY: Well drained; low runoff; slow
permeability.
USE AND VEGETATION: These soils are used mainly for irrigated cropland, but some areas are still used for livestock grazing. Crops grown are cotton, sugar beets, small grains, vegetables, bermudagrass for seed, and citrus. Native areas have sparse cover of bursage, paloverde and annuals.
DISTRIBUTION AND EXTENT: Southwestern Arizona and southeastern California. These soils are moderately extensive. Occurs in MLRA 30, 31 and 40.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Yuma County, Arizona; Soil survey of Parts of Yuma County, Arizona and Imperial County, California; 1978.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Entisol feature - The absence of diagnostic subsurface horizons
Classified according to the Keys to Soil Taxonomy, Ninth Edition, 2003.