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San Joaquin County, California 123 rooting depth of the crops commonly grown in the thick. The next 5 inches is light brownish gray and county is limited by an apparent water table that is grayish brown clay loam. Below this to a depth of 60 _ regulated at a depth of 3 to 4 feet by pumping. This soil inches is a variegated dark grayish brown and brown, is subject to subsidence. Runoff is very slow, and the weakly cemented to strongly cemented hardpan. In hazard of water erosion is slight. The rate of water some areas the surface layer is silty clay loam or loam. intake in irrigated areas is 4.0 inches per hour. The Included in this unit are small areas of Archerdale hazard of soil blowing is severe. The soil is subject to and Cogna soils on the slightly higher parts of the rare flooding, which occurs during years of abnormally landscape and Hollenbeck soils in landscape positions high precipitation. similar to those of the Stockton soil. Also included are Most areas are used for irrigated crops. This unit small areas of Stockton soils that are fine textured may provide wetland functions and values. These throughout. Included areas make up about 15 percent should be considered in plans for enhancement of of the total acreage. _ wildlife habitat or land use conversion. Permeability is slow in the Stockton soil. Available This unit is suited to irrigated row and field crops. water capacity is high. The shrink-swell potential also is The main limitations are subsidence and the high water high. The effective rooting depth is limited by the table. General management considerations include the hardpan at a depth of 40 to 60 inches. Depth to the severe hazard of soil blowing. Because this soil is water table is more than 5 feet, but water may be briefly subject to differential subsidence, frequent leveling of perched above the hardpan after periods of heavy the fields is needed to improve the efficiency of rainfall or irrigation. Runoff is slow, and the hazard of - irrigation. Areas adjacent to levees are subject to lateral water erosion is slight. The rate of water intake in seepage in wet years when the water level is high. irrigated areas is 1.5 inches per hour. The soil is Careful applications of irrigation water are needed to subject to rare flooding, which occurs during years of prevent the buildup of a high water table. Large ditches abnormally high precipitation. and small spud ditches provide subirrigation and Most areas of this unit are used for irrigated crops or improve drainage. Subirrigation, furrow, border, and orchards. A few areas are used for homesite sprinkler systems are suitable. Where a subirrigation development. - system is used, the water table is raised to a depth of 1 This unit is suited to irrigated row, field, and orchard foot at planting time and then is slowly lowered during crops. The main limitations are the slow permeability the growing season until it is at a depth of about 5 feet and depth to the hardpan. Because of the restricted _ at harvest time. When the wind velocity is high in permeability, water applications should be regulated so spring, the hazard of soil blowing can be reduced by that the water does not stand on the surface and properly managing all crop residue and by minimizing damage the crops. The hardpan limits the suitability for tillage. Levees should be checked periodically, and a deep-rooted crops. Where feasible, deep ripping of this proper maintenance program should be developed. restrictive layer can help to overcome this limitation. This map unit is in capability units Illw-10 (MLRA-16), Furrow, border, and sprinkler irrigation systems are irrigated, and IVw-10 (MLRA-16), nonirrigated. It is in suitable. Maintaining crop residue on or near the vegetative soil group E. surface helps to prevent excessive runoff and helps to maintain the rate of water intake and the organic matter 24$—Stockton fine sandy loam, 0 to 2 percent content. Slopes, overwashed. This somewhat poorly drained, If this unit is used for homesite development, the nearly level soil is in basins. It is deep to a hardpan. It main limitations are the high shrink-swell potential, the formed in alluvium derived from mixed rock sources. slow permeability, depth to the hardpan, and low Mottles in the profile indicate a somewhat poorly strength. The rare flooding is a hazard. Properly drained soil; however, drainage has been improved by designing foundations and footings and diverting runoff levees and reclamation projects. A few areas are away from buildings help to prevent the structural dissected by intermittent sloughs that have been filled damage caused by shrinking and swelling. On sites for tha result of land leveling. Elevation is 20 to 70 feet. septic tank absorption fields, the slow permeability can e average annual precipitation is about 14 inches, be overcome by increasing the size of the absorption Fe average annual air temperature is about 60 degrees field, backfilling the trench with sandy material, and and the average frost-free period is about 270 days. installing long absorption lines. Ripping the hardpan TyPically, the surface layer is grayish brown fine improves permeability and thus also improves the S. loam about 16 inches thick. It is underlain by a suitability of the soil for septic tank absorption fields. boned surface layer of dark gray clay about 37 inches Properly designing buildings and roads can offset the ri