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Syn Joaquin County, California 113 Proper stocking rates, pasture rotation, and restricted by the hardpan at a depth of 20 to 40 inches. Roots are grazing during wet periods help to keep the pasture in restricted to cracks and the faces of peds in the good condition and protect the soil from compaction. claypan, which is at a depth of 10 to 20 inches. Water If this unit is used for homesite development, the is briefly perched above the claypan and hardpan after main limitations are the moderately slow permeability periods of heavy rainfall or irrigation. Runoff is ponded and low strength. The occasional flooding is a hazard. in the small vernal pools, is very slow or ponded in On sites for septic tank absorption fields, the leveled areas, and is slow on the convex slopes. The moderately slow permeability can be overcome by hazard of water erosion is slight. The rate of water increasing the size of the absorption field. Properly intake in irrigated areas is 1.5 inches per hour. designing buildings and roads can offset the limited Most areas are used for livestock grazing or for ability of the soil to support a load. Dikes and channels irrigated pasture, irrigated crops, or vineyards. A few that have outlets for floodwater can protect buildings areas are used for dryland grain crops or homesite and onsite sewage disposal systems from flooding. development. This unit may provide wetland functions This map unit is in capability units Ilw-2 (MLRA-17), and values. These should be considered in plans for irrigated, and IVw-2 (MLRA-17), nonirrigated. It is in enhancement of wildlife habitat or land use conversion. vegetative soil group A. Where this unit is used for livestock grazing, general management considerations include saturated soil 236—San Joaquin sandy loam, 0 to 2 percent conditions in concave areas following rainy periods. The slopes. This moderately well drained, nearly level soil is characteristic plant community is mainly soft chess, on terraces. It is moderately deep to a hardpan. It ripgut brome, (oxtail fescue, and filaree. Grazing should formed in alluvium derived from granitic rock sources. be delayed until the soil is firm enough to withstand The native vegetation is mainly annual grasses, (orbs, trampling by livestock and the more desirable forage and scattered California white oak. Slopes are complex, plants have had an opportunity to set seed. and the landscape is characterized by hummocky This unit is suited to irrigated pasture. The main microrelief, depressions. minor drainageways, and limitations are the complex slopes and the very low areas that have been leveled. Meandering available water capacity. Leveling helps to ensure a drainageways and closed depressions fill with water to uniform application of water. Because the soil is form vernal pools during the winter in many areas. droughty, the applications should be light and frequent. Elevation is 20 to 150 feet. The average annual The water can be applied by sprinkler and border precipitation is about 14 inches, the average annual air methods. Proper stocking rates, pasture rotation. and temperature is about 61 degrees F. and the average restricted grazing during wet periods help to keep the frost-free period is about 275 days. pasture in good condition and protect the soil from Typically, the surface layer is brown sandy loam compaction. about 13 inches thick. The upper part of the subsoil is a This unit is suited to irrigated row, field, and vineyard claypan of brown clay about 7 inches thick. The lower crops. The main limitations are the complex slopes, Part to a depth of 60 inches is a brown and light brown, depth to the very slowly permeable claypan and indurated hardpan. In some areas the surface layer is hardpan. and the very low available water capacity. fine sandy loam, loam. or gravelly sandy loam. Leveling helps to ensure a uniform application of water. Included in this unit are small areas of Bruella and Because of the restricted permeability, the applications Rocklin soils on the slightly higher terraces. Jahant soils should be regulated so that the water does not stand on in landscape positions similar to those of the San the surface and damage the crops. The hardpan limits Joaquin soil, and Madera soils on the slightly higher the suitability for deep-rooted crops. Where feasible, Parts of the landscape. Also included are small areas of deep ripping of this restrictive layer can help to San Joaquin soils that have slopes of 2 to 5 percent overcome this limitation. A tillage pan forms easily if the and are on the slightly higher parts of the landscape, soil is tilled when wet. Chiseling or subsoiling breaks up areas that have as much as 20 inches of overburden, the pan. Because the soil is droughty, applications of and areas where most of the soil horizons have been irrigation water should be light and frequent. Furrow, removed or altered or fragments of hardpan and border. and sprinkler irrigation systems are suitable. claypan materials are within 10 inches of the surface as Returning crop residue to the soil or regularly adding a result of land leveling. Included areas make up about other organic material improves fertility, minimizes 15 percent of the total acreage. crusting, and maintains the rate of water intake. Permeability is very slow in the San Joaquin soil. Where this unit is used for dryland grain crops. the Available water capacity is very low. The shrink-swell main limitation is low rainfall during the growing season. Potential is high. The effective rooting depth is limited Because the amount of precipitation is not sufficient for