LOCATION BRENTWOOD CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Typic Haploxerepts
TYPICAL PEDON: Brentwood clay loam - apricot orchard. (Colors are for dry soil unless otherwise noted).
Ap--0 to 8 inches; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; massive; hard, friable, sticky, plastic; common fine and very fine roots; many fine and very fine tubular and interstitial pores; moderately alkaline (pH 8.0); clear smooth boundary. (6 to 8 inches thick)
A--8 to 18 inches; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) most; dark brown (10YR 3/3) when rubbed, moist; massive; hard, friable, sticky, plastic; few fine and very fine roots; many fine and very fine tubular and interstitial pores; moderately alkaline (pH 8.0); gradual wavy boundary. (8 to 12 inches thick)
Bt1--18 to 33 inches; brown (10YR 4/3) heavy clay loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; hard, friable, sticky, plastic; few fine and very fine roots; many fine and very fine tubular pores; few thin clay films on faces of peds and lining pores; moderately alkaline (pH 8.0); clear wavy boundary. (12 to 18 inches thick)
Bt2--33 to 50 inches; yellowish brown (10YR 5/4) clay loam, dark yellowish brown (10YR 3/4) moist; massive; hard, very friable, sticky plastic; few fine and very fine, and very few medium roots; many fine and very fine tubular pores; few thin clay films in pores; moderately alkaline (pH 8.0); gradual wavy boundary. (14 to 22 inches thick)
C--50 to 60 inches; yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 3/4) moist; massive; hard, very friable, sticky slightly plastic; few very fine roots; many fine and very fine tubular and many fine interstitial pores; strongly effervescent; disseminated lime; moderately alkaline (pH 8.0).
TYPE LOCATION: Contra Costa County, California; one half mile south of Brentwood; 180 feet west of Walnut Boulevard and 150 feet south of irrigation canal in the NE 1/4, NE 1/4, SE 1/4, sec. 24, T. 1 N., R. 2 E.
RANGE IN CHARACTERISTICS: Disseminated or segregated lime is present in some pedons below a depth of 36 inches and is lacking in all parts of other pedons. The 10 to 40 inch section contains 35 to 40 percent clay and a little more than 15 percent material coarser than very fine sand. Clay films may be few or common but there is less than 20 percent more clay in the B horizon than in the A horizon. A small amount of clay-size minerals has been produced by weathering of primary minerals in some pedons. The mean soil temperature at a depth of 20 inches is about 64 degrees F, and the soil temperature remains above 47 degrees F at all times. The soils are usually moist in some or all parts between depths of 4 and 12 inches from early December until May. The soils are dry, unless irrigated all the rest of the time.
The A horizon is brown, grayish brown, dark grayish brown or dark brown. It is clay loam, light silty clay or silt loam. This horizon ranges from slightly acid t moderately alkaline.
The Bt horizon is grayish brown, dark grayish brown, brown, dark yellowish brown or yellowish brown. It is heavy clay loam, heavy silty clay loam or clay. This horizon ranges from slightly acid to moderately alkaline but is usually alkaline.
The lower part of the C horizon is yellowish brown, light yellowish brown, pale brown, dark yellowish brown or brown. Few faint mottles are present below a depth of 35 inches in some pedons and mottles are entirely lacking in other pedons.
COMPETING SERIES: These are the Danville, El Solyo, Landow, Rincon, Salinas, Sorrento, Yolo, and Zamora series. Danville soils have mollic epipedons and argillic horizons. El Solyo soils have dry value of 6 in the A and B horizons. Landlow soils have lime cementation and mottles. Rincon and Zamora soils have argillic horizons. Salinas and Sorrento soils have mollic epipedons and less than 35 percent clay in the control section. Yolo soils have less than 35 percent clay and less than 15 percent fine sand or coarser.
GEOGRAPHIC SETTING: Brentwood soils are on nearly level to gently sloping fans and formed in valley fill from sedimentary rocks. They occur at elevations of 40 to 400 feet. The climate is dry subhumid mesothermal, with hot dry summers, and cool moist winters. Mean annual rainfall is 12 to 20 inches. Mean annual temperature is about 60 to 62 degrees F, average January temperature is about 46 degrees F, and the average July temperature is about 76 degrees F. The average frost-free season is 245 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Altamont and Sycamore soils and the competing Rincon, Sorrento, Yolo, and Zamora soils. Altamont soils are on the uplands and have a paralithic contact. Sycamore soils have mottles above 20 inches.
DRAINAGE AND PERMEABILITY: Well to moderately well drained; very slow to medium runoff; moderately slow permeability.
USE AND VEGETATION: Most areas are irrigated and are used for tree fruit, nut crops, vegetables, and field crops. Vegetation is annual grasses, forbs, and scattered oaks.
DISTRIBUTION AND EXTENT: Valleys of the Coast Range and west side of the Sacramento and San Joaquin Valleys. The soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Contra Costa County, California, 1935.
REMARKS: The soil was formerly classified as a Noncalcic Brown-Prairie soils intergrade.
Last revised by the state on 1/73.
ADDITIONAL DATA: NSSL pedon S78CA-013-000 (79P 88). This data reflects a fine-loamy particle size family.