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JCB- San Joaquin loam, 2 to 8 percent slopes, eroded. This moderately deep to hardpan, moderately well drained soil is on undulating dissected low terraces. It formed in alluvium from granitic rock sources. The native vegetation is mainly annual grasses, forbs and scattered valley oaks. Slopes are a complex of plane and convex side slopes and concave drainages. Elevation is 20 to 100 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 brown loam about 6 inches thick. The upper 10 inches of the subsoil is brown loam. The lower 10 inches is brown clay. The next layer to a depth of 60 inches is a brown and light brown indurated hardpan. Depth to hardpan ranges from 20 to 40 inches. In some areas the surface layer is fine sandy loam. Included in this unit are small areas of Kimball and Bruella soils on adjacent terraces and moderately coarse textured soils with hardpan at a depth of 10 to 20 inches. Also included are small areas of San Joaquin soils on 0 to 2 percent slopes and on 8 to 15 slopes on narrow embankments. Included areas make up about 15 percent of the total acreage. Permeability of the San Joaquin soil is very slow. Available water capacity is low. Shrink-swell potential is high. Effective rooting depth is 20 to 40 inches but roots are restricted to cracks and faces of peds in the claypan which occurs at a depth of 10 to 20 inches. Runoff is slow or medium and the hazard of water erosion is moderate. The water intake family for irrigation is 1.0. Water is perched above the claypan and hardpan for brief periods after heavy rains or irrigations. Most areas of this unit are used for rangeland. A few areas are used for irrigated vineyards, irrigated pastureland and dryland grain. Where this unit is used for livestock grazing, general management considerations include saturated soil conditions in concave areas following rainy periods and the hazard of erosion. The characteristic plant community on this unit is mainly soft chess, ripgut brome, foxtail 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. Grazing should be controlled so that desirable vegetation, such as soft chess, is maintained and enough vegetation is left standing to protect the soil from erosion. Loss of the surface layer results in a severe decrease in productivity and in the potential of the unit to produce plants suitable for grazing. This unit is suited to irrigated vineyard crops. The main limitations are depth to the very slowly permeable claypan and hardpan and low available water capacity. General management considerations include the hazard of erosion. Because of the very slow permeability of this soil, the application of water should be regulated so that water does not stand on the surface and damage the crops. The hardpan reduces the yield of deep rooted crops. Where feasible, deep ripping of this restrictive layer helps to overcome this limitation. A tillage pan forms easily if this soil is tilled when wet. Chiseling or subsoiling breaks up the tillage pan. Because this soil is droughty, applications of irrigation water should be light and frequent. Sprinkler and drip irrigation'systems are suited to this unit. Use of this method permits the even, controlled application of water, reduces runoff and minimizes 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 reduced by fertilizing and seeding to a cover crop. Returning crop residue to the soil or regularly adding other organic matter improves fertility, reduces crusting and increases the water intake rate. This unit is suited to irrigated pasture. The main limitation is low available water capacity. General management considerations include the hazard of erosion. Because this soil is droughty, applications of irrigation water should be light and frequent. Irrigation water can be applied by the sprinkler and border methods. Seedbed preparation should be on the contour or across the slope where practical. Use of proper stocking rates, pasture rotation and restricted grazing during wet periods helps to keep the pasture in good condition and to 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 precipitation is not sufficient for annual cropping, a cropping system that includes small grain and summer fallow is most suitable. All tillage should be on the contour or across the slope. Crop residue left on or near the surface helps to conserve moisture, maintain tilth and control erosion. The map unit is in capability units IVe-3 (MLRA-17), irrigated and IVe-3 (MLRA-17), nonirri3ated. This map unit is vegetative soil group D. Cui nAr4iTkl rrdwiTV Cntl CIIDVCV DOCI TWT�jACIV nG6CT 7/0n cImICr7 Tri NJAu(C