LOCATION SAN YSIDRO CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Typic Palexeralfs
TYPICAL PEDON: San Ysidro fine sandy loam, cultivated field. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 7 inches; light brownish gray (10YR 6/2) fine sandy loam, dark brown (10YR 4/3) moist; few fine distinct mottles of brownish yellow (10YR 6/6); massive; hard, friable, nonsticky and slightly plastic; many very fine, common fine and medium roots; common very fine tubular and interstitial pores; slightly acid (pH 6.5); clear smooth boundary. (5 to 10 inches thick)
A--7 to 14 inches; light brownish gray (10YR 6/2) fine sandy loam, dark brown (10YR 3/3) moist; few fine distinct mottles of brownish yellow (10YR 6/6); massive; hard, friable, nonsticky and slightly plastic; many very fine, common fine and medium roots; common very fine tubular pores; medium acid (pH 6.0); abrupt smooth boundary. (7 to 20 inches thick)
Bt1--14 to 28 inches; dark yellowish brown (10YR 4/4) clay, dark brown (7.5YR 4/4) moist; a thin 1/4 inch bleached layer, light gray (10YR 7/2), light brownish gray (10YR 6/2) moist, rests immediately on top of the prisms; strong coarse prismatic structure; extremely hard, very firm, sticky and plastic; few very fine and fine roots along ped faces; common very fine tubular pores; many moderately thick clay films on faces of peds and lining pores; common fine iron and manganese concretions; slightly acid (pH 6.5); gradual smooth boundary. (10 to 15 inches thick)
Bt2--28 to 40 inches; yellowish brown (10YR 5/6) sandy clay loam, dark yellowish brown (10YR 4/4) moist, dark brown (7.5YR 4/4) coatings moist; strong medium prismatic structure; extremely hard, very firm, sticky and plastic; few very fine and fine exped roots; common very fine tubular pores; many moderately thick clay films on faces of peds and lining pores; common fine iron and manganese concretions; neutral (pH 7.0); gradual smooth boundary. (10 to 14 inches thick)
C1--40 to 54 inches; yellowish brown (10YR 5/4) light sandy clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure; extremely hard, very firm, sticky and plastic; few very fine exped roots; common very fine tubular pores; many moderately thick clay films on faces of peds and lining pores; common iron and manganese concretions; neutral (pH 7.0); gradual wavy boundary. (10 to 15 inches thick)
C2--54 to 68 inches; yellowish brown (10YR 6/4) light clay loam, dark yellowish brown (10YR 4/4) moist, brown (7.5YR 4/4) coatings moist; strong medium prismatic structure; hard, firm, sticky and plastic; few very fine exped roots; common very fine tubular pores; continuous moderately thick clay films on faces of peds and lining pores; moderately alkaline (pH 8.0).
TYPE LOCATION: Solano County, California; approximately 3.5 miles west and 1 mile south of the town of Dixon; approximately 300 yards south and 100 yards west of northeast corner of NW 1/4 sec. 29, T.7N., R.1E. 38 degrees North latitude, 25 minutes, 45 seconds, 121 degrees West longitude, 53 minutes, 16 seconds.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is about 60 degrees to 65 degrees F. The soil is usually moist in some or all parts between depths of 5 and 15 inches from late November or early December until May. The soil usually is dry all the rest of the time.
The Ap horizon is light brownish gray or pale brown in 10YR hue. It is sandy loam, fine sandy loam, or loam. This horizon is medium acid to neutral.
The A horizon is up to 6 inches thick and is present in some pedons or there is a thin layer of bleached grains just above the Bt horizon. Fine yellowish or brownish mottles are present in some pedons in part of the Ap horizon and A horizon where present.
The Bt horizon is brown, light brown, very pale brown, yellowish brown, dark yellowish brown, light yellowish brown or brownish yellow in hue 10YR or 7.5YR. It is heavy clay loam or clay and has about 35 to 45 percent clay in at least the upper part and moderate to strong angular blocky structure in the lower part. Some pedons have columnar structure. The Bt horizon is slightly acid to moderately alkaline and increases in alkalinity with increasing depth. Exchangeable sodium is less than 15 percent.
The C horizon is pale brown, light yellowish or yellowish brown. It is somewhat stratified and ranges from sandy loam to silty clay loam. This horizon is mildly or moderately alkaline and has small amounts of segregated lime in some pedons.
COMPETING SERIES: These are the Hillgate series in this family and the Antioch, Cometa, Corning, Millsap, Newville, Positas, and Tierra series in other families. Hillgate soils lack a subsurface A horizon and lack mottles in the Ap horizon. Antioch soils have more than 15 percent exchangeable sodium in all parts of the B2t horizon. Cometa soils have hue of 7.5YR or 5YR in the B2t horizon. Corning soils have hue of 5YR through 2.5YR in the Bt horizon and are strongly acid throughout. Millsap soils have a lithic contact. Newville soils lack A2 horizons, are gravelly throughout with very gravelly C horizons. Positas and Tierra soils have dark A1 horizons with moist value of 2 or 3.
GEOGRAPHIC SETTING: San Ysidro soils are on old low terraces at elevations of less than 1,500 feet. Gradient is 0 to 9 percent. They formed in alluvium from sedimentary rocks. The climate is dry subhumid mesothermic with hot dry summers and cool moist winters. Mean annual precipitation is 12 to 25 inches, average January temperature is about 46 degrees F., and average July temperature is about 76 degrees F., and mean annual temperature is 58 degrees to 60 degrees F. Average frost-free season is 200 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Antioch, Capay, Hillgate, Pescadero, Pleasanton, and solano soils. Capay soils lack argillic horizons and have slickensides. Pescadero soils are on slightly lower terraces and have more than 15 percent ESP. Pleasanton soils have less than 35 percent clay and lack an abrupt A-B horizon boundary. Solano soils have more than 15 percent ESP and have natric horizons.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to medium runoff; very slow permeability.
USE AND VEGETATION: Used for growing dryland grains, dryland pasture, and shallow rooted row crops, and pasture under irrigation. Uncultivated areas have a cover of annual grasses and forbs.
DISTRIBUTION AND EXTENT: Foothills and valleys of the Coast Range of central California. The soils are moderately extensive.
MLRA OFFICE RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Gilroy Area, California, 1923.
OSED scanned by SSQA. Last revised by state on 3/77.
REMARKS: San Ysidro needs to be recompeted with Hillgate during MLRA update. Hillgate is the same as San Ysdiro but is mapped on slopes 0-50%. The 0-9% Hillgate map units should be correlated to San Ysidro and Hillgate set up for the 9-50% slope map units.
ADDITIONAL DATA: NSSL pedon S64CA-095-001 (type location but data shows the pedon to be Mollic Haploxeralf, fine-loamy, mixed, active, thermic)