LOCATION BONSALL CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Natric Palexeralfs
TYPICAL PEDON: Bonsall sandy loam - annual grass pasture (Colors are for dry soil unless otherwise noted).
A11--0 to 6 inches; brown (10YR 5/3) sandy loam, dark brown (10YR 3/3) moist; moderate fine and medium crumb structure; hard, friable, slightly sticky nonplastic; many very fine, fine and medium roots; many very fine tubular and interstitial pores; slightly acid (pH 6.2); abrupt smooth boundary. (4 to 8 inches thick)
A12--6 to 10 inches; brown (10YR 5/3) sandy loam, dark brown (10YR 3/3) moist; massive; hard, friable, slightly sticky, nonplastic; common very fine, fine, and medium roots; common very fine and fine tubular pores; slightly acid (pH 6.2); abrupt smooth boundary. (4 to 12 inches thick)
B1t--10 to 14 inches; brown (7.5YR 5/4) clay loam, dark brown (7.5YR 4/4) moist; moderate medium subangular blocky structure; very hard, firm, sticky, plastic; common very fine, fine, and medium roots; few fine and medium tubular pores; slightly acid (pH 6.5); clear smooth boundary. (0 to 8 inches thick)
B21t--14 to 27 inches; yellowish brown (10YR 5/4) clay loam, dark yellowish brown (10YR 4/4) moist; strong coarse blocky structure; extremely hard, very firm, sticky, plastic; few very fine, fine and medium roots; few fine and medium tubular pores; many moderately thick clay films on faces of peds; slightly effervescent; mildly alkaline (pH 7.8); clear smooth boundary. (12 to 20 inches thick)
B22tca--27 to 28 inches; light yellowish brown (10YR 6/4) clay loam, yellowish brown (10YR 5/4) moist; strong coarse angular blocky structure; extremely hard, very firm, sticky, plastic; few very fine, fine, and medium roots; few fine and medium tubular pores; many moderately thick clay films on faces of peds; strongly effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (6 to 12 inches thick)
B31t--38 to 48 inches; brown (7.5YR 5/4) and reddish brown (2.5YR 5/4) sandy loam, dark brown (7.5YR 4/4) and reddish brown (2.5YR 4/4) moist; massive; very hard, firm, nonsticky, slightly plastic; few medium roots; few medium tubular pores; mildly alkaline (pH 7.8); clear smooth boundary. (8 to 12 inches thick)
B32t--48 to 60 inches; brown (7.5YR 5/4) sandy loam, dark brown (7.5YR 4/4) moist; massive; very hard, firm, nonsticky, slightly plastic; few medium roots; few medium tubular pores; mildly alkaline (pH 7.8); clear smooth boundary. (8 to 14 inches thick)
C1--60 to 89 inches; light brown (7.5YR 6/4) sandy loam, brown (7.5YR 5/4) moist; massive; very hard, friable, slightly sticky, slightly plastic; few medium roots; few medium tubular pores; mildly alkaline (pH 7.8); clear smooth boundary. (10 to 30 inches thick)
C2--89 to 110 inches; very pale brown (10YR 8/3) light yellowish brown (10YR 6/4) and very dark gray (10YR 3/1) decomposed granodiorite; mildly alkaline (pH 7.5); clear smooth boundary. (10 to 36 inches thick)
C3--110 to 120 inches; pale yellow (2.5Y 7/4 and 8/4) decomposed granodiorite; neutral (pH 7.0).
TYPE LOCATION: San Diego County, California; 2 miles south of Fallbrook, approximately 30 feet north of SE corner of Fallbrook High School Campus; NE 1/3 SW 1/4, Sec. 31, T. 9 S., R. 3 W.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact of weathered rock is about 50 to 90 inches. The mean annual soil temperature at a depth of 220 inches is about 66 degrees F. Soil between the depths of about 5 and 15 inches usually is continuously dry from late April or May until early December and usually is moist in some or all parts all the rest of the year. Rock fragments mostly mineral grains 2 to 5mm in diameter, make up as much as 10 percent of the A and C horizons and up to 5 percent of the Bt horizon.
The A horizon is brown, reddish brown or dark grayish brown. It has on the average less than 1 percent organic matter. This horizon is sandy loam or loam and is medium acid to neutral.
The B2t horizon is yellowish brown, light yellowish brown, brown, strong brown or reddish brown in 10YR, 7.5YR or 5YR hue and with dominant chroma of 4. It is clay loam or clay with about 35 to 50 percent clay in the upper 20 to 40 inches. The upper boundary of the Bt horizon is abrupt and the absolute clay increase from the A horizon is 15 to 30 percent. The upper part of the Bt horizon is slightly acid to mildly alkaline and has less than 15 percent exchangeable sodium in the upper 16 to 30 inches. The lower part of the Bt horizon is sandy clay loam or sandy loam, is mildly to strongly alkaline and has 15 to 30 percent exchangeable sodium. The lower part of the Bt horizon has secondary lime as a few thin coats and veins to numerous distinct seams and rounded masses. In some pedons there is slight to moderate cementation by silica in the C horizon.
COMPETING SERIES: These are the Blasingame, Fallbrook, Las Flores, Placentia, Sesame, and Tivy series. Blasingame, Fallbrook, Sesame, and Tivy soils have less than 35 percent clay and less than 15 percent exchangeable sodium in all parts of the argillic horizon. Las Flores soils have a chroma of 2 or less in 10YR hue in the natric horizon. Placentia soils have antric horizon with an exchangeable sodium percentage of 15 or more to, or nearly to, the upper boundary of the natric horizon.
GEOGRAPHIC SETTING: The Bonsall soils are gently to moderately sloping and are in concave positions at elevations of 200 to 2,500 feet. They formed in residuum weathered from granite or granodiorite. The climate is dry subhumid mesothermal with long dry summers and short most mild winters. Average annual precipitation is 10 to 16 inches. The average January temperature is 45 degrees, average July temperature is 70 degrees F, and the average annual temperature is 60 to 65 degrees F. Freeze-free season is 240 to 340.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Fallbrook soils and Bosanko, Hanford, Ramona, and Vista soils. Bosanko soils are clayey throughout and have prominent slickensides. Hanford soils lack an argillic horizon. Ramona soils have 18 to 27 percent clay in the argillic horizon and less than 15 percent exchangeable sodium. Vista soils have a cambic horizon and lack an argillic horizon.
DRAINAGE AND PERMEABILITY: Moderately well-drained; slow to medium runoff; very slow permeability.
USE AND VEGETATION: The Bonsall soils are used mainly for range or for growing grain or grain hay and to a limited extent irrigated citrus and truck crops. Naturalized vegetation is mainly annual forbs and grasses.
DISTRIBUTION AND EXTENT: Foothills of southern California. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Diego County, California, 1973.
REMARKS: The Bonsall soils were formerly classified as (Maximal) Noncalcic Brown soils.
Last revised by the state on 8/73.
ADDITIONAL DATA: Riverside Laboratory data on typifying pedon, S64CALIF-37-3.