LOCATION SOBOBA CAEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed, thermic Typic
Xerofluvents
TYPICAL PEDON: Soboba stony sand, annual grass pasture. (Colors are for dry soil unless otherwise noted.)
A--0 to 11 inches; grayish brown (2.5Y 5/2) stony loamy sand, dark grayish brown (2.5Y 4/2) moist; single grained; loose, very friable; many medium and fine roots; many fine interstitial pores; neutral (pH 7.0); clear smooth boundary. (8 to 14 inches thick)
C--11 to 60 inches; grayish brown (2.5Y 5/2) stratified very gravelly and cobbly sand, sand, and loamy sand, somewhat lighter in color than the surface, dark grayish brown (2.5Y 4/2) moist; single grained; loose, very friable; common medium and fine roots; many fine interstitial pores; neutral (pH 6.8).
TYPE LOCATION: Riverside County, California; about 3 miles east of San Jacinto, California, 3/4 mile southeast of the intersection of Highway 79 and Soboba Road; approximately 1,200 feet east, 200 feet north of the SW corner section 14, T.4S., R.1W.
RANGE IN CHARACTERISTICS: The soils are usually moist in some or all parts between depths of 12 and 35 inches from about December 1 to April 15. The mean annual soil temperature is about 63 to 65 degrees F.
The A horizon is grayish brown, brown, or pale brown, and has hue of 2.5Y or 10YR, value of 5 or 6 dry, 4 or 5 moist and chroma of 2 or 3. It ranges from coarse sand to sandy loam and is gravelly, cobbly or stony in some pedons. This horizon is slightly acid to mildly alkaline.
The C horizon is commonly somewhat lighter in color, coarser in texture, and higher in proportion of coarse fragments than the A horizon. Rock fragments make up 35 to 75 percent of the volume of the 10 to 40 inch control section. Darker colors buried surface soils occur randomly in the C horizon.
COMPETING SERIES: These are the Cajon, Carrizo, Cortin, Delhi, Gorgonio, and Tujunga series. Cajon soils have less than 35 percent rock fragments in the control section and are dry more than 3/4 of the time. Carrizo soils have average soil temperature of about 74 degrees F. Cortina soils have very gravelly sandy loam control sections. Delhi soils have less than 15 percent rock fragments in the control section. Gorgonio soils have dark colored surface horizons, with more than 1 percent organic matter. Tujunga soils have less than 35 percent rock fragments in the control section.
GEOGRAPHIC SETTING: Soboba soils are on alluvial fans and flood plains at elevations of 25 to 3,700 feet. Slopes range from 0 to 30 percent. The soils formed in recent alluvium, mostly from granitic rocks. The climate is one of long dry summers and mild, moist winters with an average annual rainfall of 10 to 20 inches. The average January temperature is 50 degrees F.; the average July temperature is 72 degrees F.; and the average annual temperature is 60 to 62 degrees F. The frost free season is 260 to 330 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Fallbrook, Hanford, Ramona, and Vista soils and the competing Tujunga soils. Fallbrook soils are upland soils with reddish brown argillic horizons. Hanford soils have sandy loam texture, with less than 35 percent coarse fragments in the control section. Ramona soils are terrace soils with reddish brown argillic horizons. Vista soils lack many coarse fragments and have a paralithic contact of weathered granite.
DRAINAGE AND PERMEABILITY: Excessively drained; very slow runoff; very rapid permeability.
USE AND VEGETATION: The soils are used mostly for pasture. The native vegetation is annual grasses and forbs and chaparral shrubs.
DISTRIBUTION AND EXTENT: Interior valleys of southern California. The soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Riverside County, California, 1971.
REMARKS: Soboba soils represent very gravelly, cobbly, or stony soils formerly included in the Tujunga series.