LOCATION LA POSTA CAEstablished Series
TAXONOMIC CLASS: Sandy, mixed, mesic Entic Haploxerolls
TYPICAL PEDON: La Posta loamy coarse sand - chaparral and annual grasses. (Colors are for dry soil unless otherwise noted.)
A1--0 to 2 inches; grayish brown (10YR 5/2) loamy coarse sand, very dark grayish brown (10YR 3/2) moist; weak very fine granular structure; soft, very friable, nonsticky, nonplastic; many very fine roots; many very fine interstitial pores; micaceous; slightly acid (pH 6.5); clear smooth boundary. (2 to 4 inches thick)
A2--2 to 7 inches; grayish brown (10YR 5/2) loamy coarse sand, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, friable, nonsticky, nonplastic; many fine roots; many very fine interstitial pores; micaceous; neutral (pH 7.2); clear wavy boundary with tongues of this horizon penetrating the underlying horizon. (5 to 9 inches thick)
A3--7 to 10 inches; brown (10YR 5/3) loamy coarse sand, dark brown (10YR 3/3) moist; massive; slightly hard, friable, nonsticky, nonplastic; common fine and medium roots; many very fine interstitial pores; micaceous; neutral (pH 7.2); clear wavy boundary. (3 to 6 inches thick)
C1--10 to 29 inches; brown (10YR 5/3) loamy coarse sand, dark brown (10YR 4/3) moist; massive; hard, friable, nonsticky, nonplastic; few medium and coarse roots; common fine tubular pores; few thin clay films lining pores and on mineral grains; micaceous; arrangement of mineral grains suggests rock structure; slightly acid (pH 6.5); diffuse smooth boundary. (15 to 22 inches thick)
C2--29 to 37 inches; brown (10YR 5/3) weathered granodiorite; dark brown (10YR 4/3) moist; massive; hard, friable, nonsticky, nonplastic; few thin clay films on mineral grains; micaceous; medium acid (pH 6.0); clear smooth boundary.
TYPE LOCATION: San Diego County, California; southeast of Montezuma Honor Camp; approximately 4,650 feet south, 450 feet west of NE corner sec. 23, T.11S., R.4E.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact of weathered rock is 20 to 40 inches. The mean annual soil temperature at a depth of 20 inches is about 58 degrees F. and is above 47 degrees F. from early February until late December. Soil below depth of 12 inches is usually moist in some part from about December 1 until June 1 and is continuously dry the rest of the time. Gravel size rock fragments are 3 to 20 percent and larger rock fragments make up an additional 5 percent of the profile. Texture throughout is loamy sand or loamy coarse sand and the soil is neutral to medium acid. Base saturation is more than 75 percent. The A horizon is brown or grayish brown in 10YR hue. Organic matter is 1 to 3 percent to a depth of 10 to 19 inches. This horizon is massive or has granular structure and is soft or slightly hard. The lower horizon is weathered granodiorite.
COMPETING SERIES: These are the Crafton, Francis, Mottsville, Neptune, Shaver, Sheephead, Sheridan, Tollhouse, and Wasatch series. Crafton soils have coarse-loamy control sections. Francis, Neptune, and Wasatch soils lack a paralithic contact within a depth of 40 inches. Mottsville soils have an aridic moisture regime. Shaver and Sheridan soils have mollic epipedons thicker than 20 inches. Also, Shaver soils are coarse-loamy and Sheridan soils have mean annual temperature above 59 degrees F. Sheephead soils have fractured micaceous schist at depths of less than 20 inches. Tollhouse soils have a paralithic contact at depths of less than 20 inches.
SETTING: The La Posta soils are moderately sloping to very steep and are in hilly mountainous areas at elevations of 2,000 to 4,500 feet. The soils formed in residuum weathered from granitic rocks. The climate is subhumid mesothermal with warm dry summers and cool moist winters. The mean annual precipitation is 15 to 20 inches and comes in the winter. Average January temperature is about 45 degrees F., average July temperature is about 70 degrees F., and mean annual temperature is about 56 degrees F. The freeze-free season is 170 to 225 days.
PRINCIPAL ASSOCIATED SOILS: These are the competing Sheephead and Tollhouse soils and the Kitchen Creek soils. Kitchen Creek soils have coarse-loamy argillic horizons.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; medium or rapid runoff; rapid permeability.
USE AND VEGETATION: Used mainly for range, watershed, and recreation. Vegetation is annual grasses and forbs, chamise, red shank, manzanita, scrub oak, and a few scattered oak trees along drainageways.
DISTRIBUTION AND EXTENT: Coastal Range in southern California. The soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Diego County, California, 1973.
REMARKS: La Posta soils were formerly classified as regosolic Brunizems.
OSED scanned by SSQA. Last revised by state on 10/73.
ADDITIONAL DATA: NSSL pedon S60CA-073-003 that is a Psamment taxadjunct.