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i e San Joaquin County, California 117 and minimize the risk of erosion. All tillage should be on Exeter soils on terraces. Also included are small areas the contour or across the slope. If the soils are plowed of San Joaquin soils that have slopes of 2 to 8 percent. in fall, runoff and erosion can be controlled by applying Included areas make up about 15 percent of the total fertilizer and seeding a cover crop. Returning crop acreage. residue to the soil or regularly adding other organic Permeability is very slow in the San Joaquin soil. material improves fertility, minimizes crusting, and Available water capacity is moderate. The shrink-swell increases the rate of water intake. potential is high. The effective rooting depth is limited This unit is suited to irrigated pasture. The main by the hardpan at a depth of 20 to 40 inches. Roots are limitation is the low available water capacity. General restricted to cracks and the faces of peds in the management considerations include the hazard of claypan, which is at a depth of 20 to 30 inches. Water erosion. Because the soil is droughty, applications of is briefly perched above the claypan and hardpan after irrigation water should be light and frequent. The water periods of heavy rainfall or irrigation. Runoff is ponded can be applied by sprinkler and border methods. in the small vernal pools, is very slow or ponded in the Seedbed preparation should be on the contour or leveled areas, and is slow on the convex slopes. The across the slope where practical. Proper stocking rates, hazard of water erasion is slight. The rate of water pasture rotation, and restricted grazing during wet intake in irrigated areas is 1.0 inch per hour. periods help to keep the pasture in good condition and Most areas are used for livestock grazing or for protect the soil from erosion. irrigated pasture, irrigated crops, or vineyards. A few Where this unit is used for dryland grain crops, the areas are used for dryland grain crops or for homesite main limitation is low rainfall during the growing season. development. This unit may provide wetland functions General management considerations include the hazard and values. These should be considered in plans for of erosion. Because the amount of precipitation is not enhancement of wildlife habitat or land use conversion. sufficient for annual cropping, the best suited cropping Where this unit is used for livestock grazing, general system is one that includes small grain and summer management considerations include saturated soil fallow. All tillage should be on the contour or across the conditions in concave areas following rainy periods. The slope. Leaving crop residue on or near the surface characteristic plant community is mainly soft chess, helps to conserve moisture, maintain tilth, and control ripgut brome, (oxtail-fescue,Fand filaree. Grazing should erosion. be delayed until the soil is firm enough to withstand This map unit is in capability unit 1Ve-3 (MLRA-17), trampling by livestock and the more desirable forage irrigated and nonirrigated. It is in vegetative soil group plants have had an opportunity to set seed. 13. This unit is suited to irrigated pasture. The main limitation is the complex slopes. Leveling helps to 240—San Joaquin loam, thick surface, 0 to 2 ensure a uniform application of water. The water can be percent slopes. This moderately well drained, nearly applied by sprinkler and border methods. Proper level soil is on low terraces. It is moderately deep to a stocking rates, pasture rotation, and restricted grazing hardpan. It formed in alluvium derived from granitic rock during wet periods help to keep the pasture in good sources. The native vegetation is mainly annual condition and protect the soil from compaction. grasses, forbs, and scattered California white oak. A This unit is suited to irrigated row, field, and vineyard few areas are dissected by intermittent sloughs that crops. The main limitations are the complex slopes and have been filled as a result of land leveling. Meandering depth to the very slowly permeable claypan and drainageways and closed depressions fill with water to hardpan. Leveling helps to ensure a uniform application form vernal pools during the winter in many areas. of water. Because of the restricted permeability, the Elevation is 20 to 110 feet. The average annual applications should be regulated so that the water does precipitation is about 16 inches, the average annual air not stand on the surface and damage the crops. The temperature is about 61 degrees F, and the average hardpan limits the suitability for deep-rooted crops. frost-free period is about 275 days. Where feasible, deep ripping of this restrictive layer can Typically, the surface layer is pinkish gray loam help to overcome this limitation. A tillage pan forms about 12 inches thick. The upper 14 inches of the easily if the soil is tilled when wet. Chiseling or subsoil is brown sandy clay loam. The next 9 inches is subsoiling breaks up the.pan. Furrow, border, and a claypan of brown clay. The lower part to a depth of 60 sprinkler irrigation systems are suitable. Returning crop inches is a brown and light brown, indurated hardpan. residue to the soil or regularly adding other organic In some areas the surface layer is fine sandy loam or material improves fertility, minimizes crusting, and sandy loam, increases the rate of water intake. Included in this unit are small areas of Bruella and Where this unit is used for dryland grain crops, the �e_