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tSan Joaquin County, California 87 during years of abnormally high precipitation. 198—Manteca fine sandy loam, 0 to 2 percent Most areas are used for irrigated pasture or irrigated slopes. This moderately well drained, nearly level soil is ' crops. A few areas are used for homesite development. on low terraces. It is moderately deep to a hardpan. It This unit may provide wetland functions and values. formed in alluvium derived from mixed rock sources. These should be considered in plans for enhancement Elevation is 20 to 110 feet. The average annual of wildlife habitat or land use conversion. precipitation is about 11 inches, the average annual air This unit is suited to irrigated pasture. The main temperature is about 60 degrees F, and the average limitations are the low available water capacity and the frost-free period is about 270 days. high water table. Because these soils are droughty, Typically, the surface layer is grayish brown fine ' applications of irrigation water should be light and sandy loam about 11 inches thick. The upper part of the frequent. A drainage system may be needed. Irrigation subsoil is grayish brown and light brownish gray fine water can be applied by sprinkler and border methods. sandy loam about 13 inches thick. The next part is a Proper stocking rates, pasture rotation, and restricted light gray, indurated hardpan, which extends to a depth ' grazing during wet periods help to keep the pasture in of 35 inches. The lower part is a light gray, weakly good condition and protect the soils from compaction. cemented to strongly cemented hardpan, which extends This unit is suited to irrigated row, field, and vineyard to a depth of 54 inches. The underlying material to a ' crops. The main limitations are depth to the very slowly depth of 74 inches is variegated light gray and white permeable claypan and hardpan, the high water table in sandy loam. In some areas the surface layer is loam or the Alamo soil, and the low available water capacity. clay loam. Because of the restricted permeability, water Included in this unit are small areas of Tinnin and ' applications should be regulated so that the water does Veritas soils on the slightly higher parts of the not stand on the surface and damage the crops. The landscape, small areas of Guard and Trahern soils on hardpan limits the suitability for deep-rooted crops. the slightly lower parts, and a few areas where depth to Where feasible, deep ripping of this restrictive layer can the hardpan is as little as 10 inches, mainly where deep help to overcome this limitation. A drainage system may leveling cuts have been made. Also included are some be needed. Because these soils are droughty, areas of soils that have been subsoiled or deeply ripped ' applications of irrigation water should be light and and have fragments of cemented material on the frequent. Furrow, border, and sprinkler irrigation surface and throughout the profile. Included areas make systems are suitable. Returning crop residue to the up about 15 percent of the total acreage. soils or regularly adding other organic material improves Permeability is moderate in the Manteca soil. ' fertility, minimizes crusting, and maintains the rate of Available water capacity is low. The effective rooting water intake. depth is limited by the hardpan at a depth of 20 to 40 If this unit is used for homesite development, the inches. Depth to the water table is more than 6 feet, but ' main limitations are depth to the very slowly permeable water may be perched above the hardpan after periods claypan and hardpan, the high water table in the Alamo of heavy rainfall or Irrigation. Runoff is slow, and the soil, the high shrink-swell potential, and low strength in hazard of water erosion is slight. The rate of water the clayey subsoil. On sites for septic tank absorption intake in irrigated areas is 1.5 inches per hour. The ' fields, the very slow permeability can be overcome by hazard of soil blowing is moderate. The soil is subject increasing the size of the absorption field. Excavation to rare flooding, which occurs during years of for building sites is limited by the hardpan. The very abnormally high precipitation. ' slow permeability and the high water table increase the Most areas are used for irrigated crops or vineyards, possibility that septic tank absorption fields will not A few areas are used as irrigated pasture or for function properly. A drainage system is needed if roads homesite development. This unit may provide wetland or building foundations are constructed. Properly functions and values. These should be considered in designing foundations and footings and diverting runoff plans for enhancement of wildlife habitat or land use away from buildings help to prevent the structural conversion. damage caused by shrinking and swelling. Properly This unit is suited to irrigated row, field, and vineyard ' designing buildings and roads can offset the limited crops. The main limitations are depth to the hardpan ability of the soils to support a load. and the low available water capacity. General This map unit is in capability unit IVs-3 (MLRA-17), management considerations include the hazard of soil irrigated and nonirrigated. The Madera soil is in blowing. The hardpan limits the suitability for deep- vegetative soil group D, and the Alamo soil is in rooted crops. Where feasible, deep ripping of this vegetative soil group E. restrictive layer can help to overcome this limitation. 1