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' San Joaquin County, California 111 irrigated, and IVw-2 (MLRA-16), nonirrigated. It is in material to a depth of 60 inches is olive gray, mottled vegetative soil group E. clay. In some areas the surface layer is silty clay loam or silty clay. 233—Ryde-Peltier complex, partially drained, 0 to Permeability is slow in the Peltier soil. Available ' 2 percent slopes. These nearly level soils are on flood water capacity is high or very high. The shrink-swell plains and deltas. Levees, drainage ditches, and potential is high. The effective rooting depth of the pumping of the water table alter the drainage of these crops commonly grown in the county is limited by an soils. Elevation is 15 feet below sea level to 5 feet apparent water table that is regulated at a depth of 3 to above. The average annual precipitation is about 14 4 feet by pumping. This soil is subject to subsidence. inches, the average annual air temperature is about 60 Runoff is very slow, and the hazard of water erosion is degrees F, and the average frost-free period is about slight. The rate of water intake in irrigated areas is 1.0 270 days. inch per hour. The hazard of soil blowing is moderate. This unit is 50 percent Ryde clay loam and 35 The soil is subject to rare flooding, which occurs during percent Peltier mucky clay loam. The components of years of abnormally high precipitation. this unit occur as areas so intricately intermingled that it Most areas are used for irrigated crops. This unit was not practical to map them separately at the scale may provide wetland functions and values. These used. should be considered in plans for enhancement of Included in this unit are small areas of Scribner soils wildlife habitat or land use conversion. on the slightly higher parts of the landscape and Rindge This unit is suited to irrigated row and field crops. and Venice soils on the slightly lower parts. Also The main limitations are subsidence, the high water included, in landscape positions similar to those of the table, and the slow permeability in the Peltier soil. ' Ryde and Peltier soils, are small areas of Valdez soils General management considerations include the hazard and small areas of moderately fine textured or fine of soil blowing. Because these soils are subject to textured soils that have an organic or coarse textured differential subsidence, frequent leveling of the fields is substratum below a depth of 40 inches. Included areas needed to improve the efficiency of irrigation. Areas ' make up about 15 percent of the total acreage. adjacent to levees are subject to lateral seepage in wet The Ryde soil is very deep and very poorly drained. years when the water level is high. Careful applications It formed in alluvium derived from mixed rock sources of irrigation water are needed to prevent the buildup of ' and in hydrophytic plant remains. Typically, the surface a high water table. Large ditches and small spud layer is grayish brown and dark gray, mottled clay loam ditches provide subirrigation and improve drainage. about 24 inches thick. The underlying material to a Because of the slow permeability in the Peltier soil, depth of 63 inches is very dark gray and dark grayish water applications should be regulated so that the water ' brown, mottled mucky clay loam and silty clay loam. In does not stand on the surface and damage the crops. some areas the surface layer is mucky clay loam or silty Subirrigation, furrow, border, and sprinkler systems are clay loam. suitable. Where a subirrigation system is used, the ' Permeability is moderately slow in the Ryde soil. water table is raised to a depth of 1 foot at planting time Available water capacity is very high. The effective and then is slowly lowered during the growing season rooting depth of the crops commonly grown in the until it is at a depth of about 5 feet at harvest time. county is limited by an apparent water table that is When the wind velocity is high in spring, the hazard of regulated at a depth of 3 to 4 feet by pumping. This soil soil blowing can be reduced by properly managing all is subject to subsidence. Runoff is very slow, and the crop residue and by minimizing tillage. Levees should hazard of water erosion is slight. The rate of water be checked periodically, and a proper maintenance intake in irrigated areas is 0.5 inch per hour. The program should be developed. hazard of soil blowing is moderate. The soil is subject This map unit is in capability units Illw-2 (MLRA-16), to rare flooding, which occurs during years of irrigated, and IVw-2 (MLRA-16), nonirrigated. It is in abnormally high precipitation. vegetative soil group E. The Peltier soil is very deep and poorly drained. It formed in hydrophytic plant remains derived from reeds 234--Sailboat silt loam, drained,0 to 2 percent and tules and in alluvium derived from mixed rock slopes. This very deep, somewhat poorly drained, ' sources. Typically, the upper 22 inches of the surface nearly level soil is on flood plains. It formed in alluvium layer is gray and dark gray mucky clay loam. The lower derived from mixed rock sources. Mottles in the profile 2 inches is brown and very dark gray silty clay. The indicate a somewhat poorly drained soil-, however, subsoil is very dark gray and grayish brown, mottled drainage has been improved by levees and reclamation mucky clay loam about 21 inches thick. The underlying projects. Elevation is 5 to 10 feet. The average annual