LOCATION STOCKTON CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Xeric Epiaquerts
TYPICAL PEDON: Stockton clay - on a nearly level slope of less than 1 percent in a fallow corn field at an elevation of 43 feet. (Colors are for dry soil unless otherwise stated. When described on September 30, 1982, the soil was moist throughout).
Ap--0 to 7 inches; dark gray (10YR 4/1) clay, very dark gray (10YR 3/1) moist; moderate medium angular blocky structure; very hard, firm, very sticky and plastic; few fine roots; many very fine interstitial and few very fine tubular pores; mildly alkaline (pH 7.8); clear smooth boundary. (6 to 12 inches thick)
A--7 to 15 inches; dark gray (10YR 4/1) clay, very dark gray (10YR 3/1) moist; weak fine and medium subangular blocky structure; very hard, firm, very sticky and plastic; few very fine roots; many very fine tubular pores and common very fine interstitial pores; few fine black (10YR 2/1) manganese concretions; moderately alkaline (pH 8.0); gradual wavy boundary. (6 to 12 inches thick)
Bss1--15 to 22 inches; dark gray (10YR 4/1) clay, very dark gray (10YR 3/1) moist; massive; very hard, firm, very sticky and plastic; few very fine roots; many very fine tubular pores and common very fine interstitial pores; few fine black (10YR 2/1) manganese concretions; many intersecting slickensides; moderately alkaline (pH 8.0); gradual wavy boundary. (6 to 15 inches thick)
Bss2--22 to 29 inches; dark gray (10YR 4/1) clay; very dark gray (10YR 3/1) moist; massive; very hard, firm, very sticky and plastic; few very fine roots; common very fine tubular and interstitial pores; few fine black (10YR 2/1) manganese concretions; many intersecting slickensides; moderately alkaline (pH 8.0); gradual wavy boundary. (0 to 12 inches thick)
Bssk1--29 to 37 inches; dark gray (10YR 4/1) clay, dark gray clay (10YR 4/1) moist; massive; very hard, firm, very sticky and plastic; few very fine roots; common very fine tubular and interstitial pores; few fine black (10YR 2/1) manganese concretions; intersecting slickensides; strongly effervescent with disseminated lime and segregations of accumulated lime in few fine soft masses; moderately alkaline (pH 8.0); gradual wavy boundary. (6 to 13 inches thick)
Bssk2--37 to 42 inches; mixed grayish brown (10YR 5/2) and light brownish gray (10YR 6/2) clay loam, dark grayish brown (10YR 4/2) and grayish brown (10YR 5/2) moist; massive parting to weak fine subangular blocky structure; hard, firm, sticky and plastic; many very fine tubular and interstitial pores; few fine black (10YR 2/1) manganese concretions; intersecting slickensides; violently effervescent with disseminated lime and segregations of accumulated lime in common fine to medium soft masses; moderately alkaline (pH 8.0); gradual wavy boundary. (5 to 16 inches thick)
Bqkm1--42 to 45 inches; variegated dark grayish brown (10YR 4/2) and brown (10YR 4/3) weakly cemented duripan, dark grayish brown (10YR 4/2) moist, massive; brittle; strongly cemented laminar capping; 50 to 75 percent silica cementation within the matrix; violently effervescent with segregations of accumulated lime in few fine seams; moderately alkaline (pH 8.0); gradual smooth boundary. (3 to 5 inches thick)
Bqkm2--45 to 60 inches; variegated dark grayish brown (10YR 4/2) and brown (10YR 4/3) strongly cemented duripan, dark brown (10YR 4/3) moist; massive; brittle; 70 to 85 percent silica cementation within the matrix; violently effervescent with segregations of accumulated lime in few fine seams; moderately alkaline (ph 8.0).
TYPE LOCATION: San Joaquin County, California; approximately 2 miles southeast of Stockton; 37 degrees 56' 33" north Lat., 121 degrees 11' 17" west Long. (in an unsectioned area) Stockton East quadrangle:
RANGE IN CHARACTERISTICS: The thickness of the mollic epipedon is 20 to 36 inches. Combined thickness of the A and Bss horizons and depth to a duripan ranges from 40 to 60 inches. The mean annual soil temperature is 62 degrees to 63 degrees F. On drying, large cracks extend as deep as 48 inches or to the duripan and form large prisms. The cracks open and close at least once each year and are open by June or July and are closed by October or November. Common to many slickensides are at depths of about 12 to 48 inches. These soils have a calcium to magnesium ratio of more than 2.0.
The A and Bss horizons are N3/0, N4/0, N5/0; 10YR 3/1, 4/1 or 5/1. Moist color is N3/0, N2/0; 10YR 2/1 or 3/1. Iron or manganese concretions are present in all pedons. Reaction is mildly alkaline or moderately alkaline. Texture is clay or silty clay. In areas adjacent to streams or sloughs, there is an overwash of stratified fine sandy loam or silty clay loam. It is 10YR 4/2, 4/3 or 5/2. Moist color is 10YR 3/2, 3/3 or 4/2.
The Bssk horizon is 10YR 4/1, 5/1, 5/2 or 6/2. Moist color is 10YR 4/1, 4/2 or 5/2. Reaction is mildly alkaline or moderately alkaline. Texture is clay or silty clay in the upper part and clay loam or silty clay loam in the lower part. It has segregations of accumulated lime in soft masses and seams.
The Bqkm horizon is 10YR 4/2, 4/3, 4/4, 5/4 or 5/6. Moist color is 10YR 4/2, 4/3, 4/4, 5/2 or 5/4. It is strongly cemented in the laminar capping and weakly to strongly cemented in the underlying material. It has segregations of accumulated lime as soft masses and seams.
COMPETING SERIES: These are the Clear Lake, Copus (T), Hildreth, Jacktone, Maxwell, Subaco and Willows series. Clear Lake soils lack a duripan below 40 inches. Hildreth soils overlie unrelated material and have 7.5YR hues (see remarks). Jacktone soils have a duripan at depths of 20 to 40 inches. Maxwell soils have a Ca/Mg ratio of 2 or less. Subaco soils have a paralithic contact at depths of 20 to 40 inches. Willows soils are strongly alkaline and have more than 15 percent exchangeable sodium in some or all parts.
GEOGRAPHIC SETTING: Stockton soils are in basins and in swales of level drainage ways. Slopes are 0 to 2 percent. Elevations are 0 to 100 feet. The soils formed in fine textured alluvium from mixed igneous and sedimentary rock sources. The soils are in a dry subhumid climate of relatively hot dry summers and cool moist winters. Dense ground fog often occurs in the winter months. Mean annual precipitation ranges from 12 to 18 inches. Mean January temperature is 45 degrees F; the mean July temperature varies from 77 degrees F., and mean annual temperature is 60 to 61 degrees F. The frost-free period is 260 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Jacktone soils and the Galt and Hollenbeck soils on similar positions. Galt soils have a duripan at depths of 20 to 40 inches. Hollenbeck soils have a chroma of 2 or more throughout.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; very slow and slow runoff; slow permeability. Most areas are artificially drained.
USE AND VEGETATION: Used for growing row and field crops such as corn, tomatoes, beans and sugar beets, dry farmed to grain, or irrigated pasture. Also used for urban development. Vegetation is mainly annual grasses and forbs and a few scattered California White Oaks.
DISTRIBUTION AND EXTENT: The Stockton soils occur in the northern San Joaquin Valley and southern Sacramento Valley. The soils are moderately extensive in MLRA-17.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Joaquin County, California, 1990. First mapped in Stockton Area, 1905, San Joaquin County. Modal series locations redescribed in 1961 and later put on inactive list of soil series mapped in California.
REMARKS: The Stockton series was originally established in Stockton Area California Soil Survey Series 1939 issued May 1951. The series was placed on the inactive list in 1963. This reactivates the original series concept. Hildreth soils are currently listed in the same family. As currently described, Hildreth soils would not classify as Vertisols. A part of the Hildreth soils may belong to another series or different subgroup. More study of the Hildreth soils is needed to accurately classify these soils.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the surface to a depth of 29 inches (Ap, A, Bss1, Bss2 horizons)
Duripan - the zone from 42 to 60 inches (Bqkm1, Bqkm2 horizons)