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L LSan Joaquin County, California and minimize the risk of erosion. All tillage should be on " the contour or across the slope. If the soils are plowed in fall, runoff and erosion can be controlled by applying fertilizer and seeding a cover crop. Returning crop r residue to the soil or regularly adding other organic material improves fertility, minimizes crusting, and increases the rate of water intake. This unit is suited to irrigated pasture. The main `limitation is the low available water capacity. General management considerations include the hazard of erosion. Because the soil is droughty, applications of brirrigation water should be light and frequent. The water can be applied by sprinkler and border methods. Seedbed preparation should be on the contour or across the slope where practical. Proper stocking rates, pasture rotation, and restricted grazing during wet periods help to keep the pasture in good condition and protect the soil from erosion. Where this unit is used for dryland grain crops, the main limitation is low rainfall during the growing season. General management considerations include the hazard ..of erosion. Because the amount of precipitation is not sufficient for annual cropping, the best suited cropping system is one that includes small grain and summer fallow. All tillage should be on the contour or across the slope. Leaving crop residue on or near the surface helps to conserve moisture, maintain tilth, and control erosion. This map unit is in capability unit IVe-3 (MLRA-17), irrigated and nonirrigated. It is in vegetative soil group D. 240—San Joaquin loam, thick surface, 0 to 2 Percent slopes. This moderately well drained, nearly level soil is on low terraces. It is moderately deep to a hardpan. It formed in alluvium derived from granitic rock sources. The native vegetation is mainly annual grasses, (orbs, and scattered California white oak. A —few areas are dissected by intermittent sloughs that have been filled as a result of land leveling. Meandering drainageways and closed depressions fill with water to Corm vernal pools during the winter in many areas. Elevation is 20 to 110 feet. The average annual Precipitation is about 16 inches, the average annual air temperature is about 61 degrees F, and the average —frost -free period is about 275 days. Typically, the surface layer is pinkish gray loam about 12 inches thick. The upper 14 inches of the subsoil is brown sandy clay loam. The next 9 inches is a claypan of brown clay. The lower part to a depth of 60 riches is a brown and light brown, indurated hardpan. In some areas the surface layer is fine sandy loam or sandy loam. Included in this unit are small areas of Bruetla and ►. 117 Exeter soils on terraces. Also included are small areas of San Joaquin soils that have slopes of 2 to 8 percent. Included areas make up about 15 percent of the total acreage. Permeability is very slow in the San Joaquin soil. Available water capacity is moderate. The shrink -swell potential is high. The effective rooting depth is limited by the hardpan at a depth of 20 to 40 inches. Roots are restricted to cracks and the faces of peds in the claypan, which is at a depth of 20 to 30 inches. Water is briefly perched above the claypan and hardpan after periods of heavy rainfall or irrigation. Runoff is ponded in the small vernal pools, is very slow or ponded in the leveled areas, and is slow on the convex slopes. The hazard of water erosion is slight. The rate of water intake in irrigated areas is 1.0 inch per hour. Most areas are used for livestock grazing or for irrigated pasture, irrigated crops, or vineyards. A few areas are used for dryland grain crops or for homesite development. This unit may provide wetland functions and values. These should be considered in plans for enhancement of wildlife habitat or land use conversion. Where this unit is used for livestock grazing, general management considerations include saturated soil conditions in concave areas following rainy periods. The characteristic plant community is mainly soft chess, ripgut brome, (oxtail fescue, and filaree. Grazing should be delayed until the soil is firm enough to withstand trampling by livestock and the more desirable forage plants have had an opportunity to set seed. This unit is suited to irrigated pasture. The main limitation is the complex slopes. Leveling helps to ensure a uniform application of water. The water can be applied by sprinkler and border methods. Proper stocking rates, pasture rotation, and restricted grazing during wet periods help to keep the pasture in good condition and protect the soil from compaction. This unit is suited to irrigated row, field, and vineyard crops. The main limitations are the complex slopes and depth to the very slowly permeable claypan and hardpan. Leveling helps to ensure a uniform application of water. Because of the restricted permeability, the applications should be regulated so that the water does not stand on the surface and damage the crops. The hardpan limits the suitability for deep-rooted crops. Where feasible, deep ripping of this restrictive layer can help to overcome this limitation. A tillage pan forms easily if the soil is tilled when wet. Chiseling or subsoiling breaks up the pan. Furrow, border, and sprinkler irrigation systems are suitable. Returning crop residue to the soil or regularly adding other organic material improves fertility, minimizes crusting, and increases the rate of water intake. Where this unit is used for dryland grain crops, the