Established Series


The Las Flores series la a member of the fine, montmorillonitic, thermic family of Natric Palexeralfs. Typically, Las Flores soils have light brownish gray, slightly and medium acid, loamy sand A horizons, grayish brown and light brownish gray, slightly acid and neutral, sandy clay B2t horizons grading to weakly consolidated siliceous marine sandstone.

TAXONOMIC CLASS: Fine, smectitic, thermic Natric Palexeralfs

TYPICAL PEDON: Las Flores loamy sand - native pasture. (Colors are for dry soil unless otherwise noted.)

A11--0 to 3; Light brownish gray (10YR 6/2) loamy sand, dark grayish brown (10YR 4/2) moist; weak fine granular structure; soft, very friable, nonsticky, nonplastic; many very fine roots; many very fine interstitial pores; medium acid (pH 5.8); abrupt smooth boundary. (2 to 4 inches thick)

A12--3 to 14 inches; Light brownish gray (10YR 6/2) loamy sand, dark grayish brown (10YR 4/2) moist; massive; hard, friable, nonsticky, nonplastic; common fine roots; many fine tubular pores; slightly acid ( H 6.2); abrupt wavy boundary. (8 to 12 inches thick)

B21t--14 to 22 inches; Grayish brown (10YR 5/2) sandy clay, dark grayish brown (10YR 4/2) moist; strong medium columnar structure; very hard, firm, very sticky, very plastic; few very fine exped roots; common very fine tubular pores; continuous moderately thick clay films on faces of peds; slightly acid (pH 6.5); gradual smooth boundary. (6 to 10 inches thick)

B22t--22 to 38 inches; Light brownish gray (10YR 6/2) sandy clay, grayish brown (10YR 5/2) moist; strong medium prismatic structure; very hard, firm, very sticky, very plastic; few very fine exped roots; common very fine tubular pores; continuous thick clay films on faces of peds; neutral (pH 6.8); diffuse irregular boundary. (12 to 18 inches thick)

C1--38 to 48 inches; Pale yellow (5Y 8/3) loamy coarse sand, pale yellow (5Y 8/4) moist; weak coarse angular blocky structure; hard, friable, slightly sticky, nonplastic; few fine exped roots; few fine tubular pores; few moderately thick clay films on faces of peds; neutral (pH 7.0); diffuse smooth boundary. (8 to 12 inches thick)

C2--48 to 54 inches; Light gray (5Y 7/1) soft marine sandstone; hard, firm, nonsticky, nonplastic; few fine tubular pores; few moderately thick clay films along fracture planes in the weathered rock; neutral (pH 7.3).

TYPE LOCATION: San Diego County, California; about 5 miles west of Vista, on south side of State Highway 78; approximately 1,600 feet west-southwest of NE corner sec. 33, T.11S., R.4W., (projected).

RANGE IN CHARACTERISTICS: Depth to a paralithic contact of soft sandstone is 42 to 52 inches. Mean annual soil temperature at a depth of 20 inches is 61 degrees to 65 degrees F. The soil between depths of 10 and 18 inches is usually moist in some part from about December 1 until late in May and is continuously dry the rest of the year. The A horizon is pale brown, light brownish gray or grayish brown (10YR 6/3, 6/2, 5/2). It is loamy sand or loamy fine sand. In some pedons the upper 2 or 3 inches have granular structure. Some pedons are massive throughout the A horizon and are hard when dry. It is slightly or medium acid. The B2t horizon is light brownish gray, grayish brown or dark gray (10YR 6/2, 5/2, 4/1). It is sandy clay or clay. The upper boundary is abrupt and the clay increase from the A horizon to the B2t horizon is about 18 to 24 percent. Some pedons have a distinct light gray or gray A2 horizon about 1/4 inch thick. The upper part of the B2t horizon has medium to strong prismatic or columnar structure. The lower part has weak or moderate prismatic or moderate or strong columnar structure. Exchangeable sodium is 5 to 15 percent in the upper 16 inches of the B2t horizon and is 15 to 30 percent in some part below the upper boundary. It is slightly acid or neutral in the upper part and neutral to moderately alkaline in the lower part. A few fine soft lime bodies are present in some pedons in the lower part of the B2t horizon. The C horizon is light gray, pale yellow or white.

COMPETING SERIES: These are the Antioch, Bonsall, Milpitas, Placentia, San Miguel, Sesame, Solano, Stockpen, Tierra, and Waukena series. Antioch, Placentia, San Miguel, Solano, Stockpen, and Waukena soils have natric horizons. Bonsall soils have argillic horizons with chroma of 3 or more. Milpitas and Tierra soils have less than 15 percent exchangeable sodium throughout the argillic horizons. Sesame soils have argillic horizons with 18 to 35 percent clay.

SETTING: Las Flores soils are gently to strongly sloping and are on marine terraces at elevations of less than 700 feet. The climate is dry subhumid mesothermal with warm dry summers and cool moist winters. Mean annual precipitation is about 10 to 13 inches. Average January temperature is 53 degrees F., average July temperature is 71 degrees F., and mean annual temperature is 61 degrees F. The frost-free season is 300 to 340 days.

PRINCIPAL ASSOCIATED SOILS: These are the competing Antioch and Stockpen soils and the Altamont, Diablo, and Shedd soils. Altamont and Diablo soils have fine textured sola with prominent slickensides. Shedd soils are light gray and lack argillic horizons.

DRAINAGE AND PERMEABILITY: Moderately well-drained; medium to rapid runoff; very slow permeability.

USE AND VEGETATION: Used for growing irrigated truck crops, nonirrigated beans, and pasture, and urban use.

DISTRIBUTION AND EXTENT: Coastal plains of southern California. The soils are moderately extensive.


SERIES ESTABLISHED: San Diego County, California, 1915.

REMARKS: The Las Flores soils formerly were classified as (maximal) Noncalcic Brown soils.

OSED scanned by SSQA. Last revised by state on 10/73.

National Cooperative Soil Survey