LOCATION YORBA CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Typic Haploxeralfs
TYPICAL PEDON: Yorba gravelly sandy loam, native pasture. (Colors are for dry soil unless otherwise noted.)
A1--0 to 3 inches; pinkish-gray (7.5YR 6/2) gravelly sandy loam, brown (7.5YR 4/2) when moist; massive; slightly hard, friable, nonsticky and nonplastic; common fine roots; common fine tubular pores; 15 percent gravel and cobbles (by volume); slightly acid (pH 6.5); clear, smooth boundary. 2 to 6 inches thick.
A2--3 to 11 inches; brown (7.5YR 5/2) gravelly sandy loam brown (7.5YR 4/2) when moist; massive; slightly hard, friable, slightly sticky and nonplastic; common fine roots; many fine tubular pores; 15 percent gravel and cobbles (by volume); slightly acid (pH 6.5); abrupt, smooth boundary. 7 to 12 inches thick.
Bt1--11 to 25 inches; red (2.5YR 5/6) very gravelly sandy clay loam, dark red (2.5YR 3/6) when moist; weak, medium, angular blocky structure; very hard, firm, sticky and very plastic; few fine roots; common fine tubular pores; many moderately thick clay films on faces of peds and as bridges; 40 percent gravel and cobbles (by volume); slightly acid (pH 6.5); diffuse, smooth boundary. 10 to 18 inches thick.
Bt2--25 to 40 inches; red (2.5YR 5/6) very gravelly sandy clay loam, dark red (2.5YR 3/6) when moist; weak, medium, angular blocky structure; very hard, firm, sticky and very plastic; few fine roots; common fine tubular and common fine interstitial pores; many moderately thick clay films on faces of peds and as bridges; 50 percent gravel and cobbles (by volume); slightly acid (pH 6.5); gradual, smooth boundary. 8 to 10 inches thick.
B1--40 to 63 inches, red (2.5YR 5/6) very gravelly sandy loam, dark red (2.5YR 3/6) when moist; massive; hard, friable, sticky and slightly plastic; few fine roots; many fine interstitial pores; common thin clay films as bridges; 60 percent gravel and cobbles (by volume); slightly acid (pH 6.5)
TYPE LOCATION: Orange County, California; Irvine Ranch about 3,500 feet north of entrance to Irvine Park; NE1/4 NE1/4 sec. 18 (sections by a private survey on the geological survey maps), T.4S., R.8W., SBBM.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is about 61 degrees to 63 degrees F. The soil between depths of 8 and 24 inches is usually moist in some part from sometime in November or December until May and is dry all the rest of the year. The A1 horizon is pinkish gray, brown or light brownish gray in 7.5YR or 10YR hue; moist value is 4 or more. This horizon is gravelly or cobbly and has 10 to 25 percent rock fragments by volume. It has weak subangular blocky structure or is massive. It is slightly or medium acid. A thin A2 horizon is present in some pedons and lacking in other pedons.
The Bt horizon is brown, dark brown, yellowish red, red or reddish brown is 2.5YR, 5YR or 7.5 YR hue. If hue is 2.5YR, dry value is more than one unit higher than moist value. This horizon is sandy clay loam or clay loam and has 35 to 65 percent rock fragments by volume. It has angular or subangular blocky structure and is medium acid to moderately alkaline.
COMPETING SERIES: These are the Agua Dulce, Arbuckle, Keefers, Newville, Olivenhain, and Soper series. Agua Dulce and Keefers soils have, throughout the upper 4 inches, moist value of less than 3.5 and more than 0.7 percent organic carbon. Keefers soils also have 35 percent or more clay in the fine earth fraction of the argillic horizon. Arbuckle, Newville, and Soper soils have less than 35 percent rock fragments in the argillic horizon. Also, Newville soils have 35 percent or more clay in the argillic horizon and Soper soils have a mollic epipedon. Olivenhain soils have an argillic horizon that has kaolinitic mineralogy, base saturation less than 75 percent in some part, and 35 percent or more clay in the fine earth fraction.
GEOGRAPHIC SETTING: The Yorba soils are on nearly level to steep terraces at elevations of 100 to 2,500 feet. They formed in gravelly and cobbly alluvium from a variety of rocks. The climate is dry subhumid mesothermal with cool moist winters and somewhat foggy dry summers. The mean annual precipitation is 12 to 20 inches. Mean annual temperature is about 62 degrees F. The average frost-free season is 300 to 350 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Newville and Soper soils and the Modjeska, Soboba, and Solano soils. Modjeska and Soboba soils lack an argillic horizon. Solano soils have a natric horizon and lack rock fragments.
DRAINAGE AND PERMEABILITY: Well-drained; medium and rapid runoff; slow permeability.
USE AND VEGETATION: Used mainly for dryland native pasture or range. Some areas are now being used for urban development. Naturalized vegetation is scattered chamise, flattop buckwheat, sumac, California sage, and annual grasses and forbs.
DISTRIBUTION AND EXTENT: Coastal Plain of southern California. The soils are inextensive in MLRA 19.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Orange and Western Part of Riverside Counties, California, 1974.
REMARKS: The Yorba soils would have been classified as Noncalcic Brown soils.
ADDITIONAL DATA: NSSL pedon S71CA-059-017 (type location)
OSED scanned by SSQA. Last revised by state on 7/74.