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San Joaquin County, California 113
<br /> Proper stocking rates, pasture rotation, and restricted by the hardpan at a depth of 20 to 40 inches. Roots are
<br /> grazing during wet periods help to keep the pasture in restricted to cracks and the faces of peds in the
<br /> good condition and protect the soil from compaction. claypan, which is at a depth of 10 to 20 inches. Water
<br /> It this unit is used for homesite development, the is briefly perched above the claypan and hardpan after
<br /> main limitations are the moderately slow permeability periods of heavy rainfall or irrigation. Runoff is ponded
<br /> and low strength. The occasional flooding is a hazard. in the small vernal pools, is very slow or ponded in
<br /> On sites for septic tank absorption fields, the leveled areas, and is slow on the convex slopes. The
<br /> moderately slow permeability can be overcome by hazard of water erosion is slight. The rate of water
<br /> increasing the size of the absorption field. Properly intake in irrigated areas is 1.5 inches per hour.
<br /> designing buildings and roads can offset the limited Most areas are used for livestock grazing or for
<br /> ability of the soil to support a load. Dikes and channels irrigated pasture, irrigated crops, or vineyards. A few
<br /> that have outlets for floodwater can protect buildings areas are used for dryland grain crops or homesite
<br /> and onsite sewage disposal systems from flooding. development. This unit may provide wetland functions
<br /> This map unit is in capability units Ilw-2 (MLRA-17), and values. These should be considered in plans for
<br /> irrigated, and IVw-2 (MLRA-17), nonirrigated. It is in enhancement of wildlife habitat or land use conversion.
<br /> vegetative soil group A. Where this unit is used for livestock grazing, general
<br /> management considerations include saturated soil
<br /> 236—San Joaquin sandy loam, 0 to 2 percent conditions in concave areas following rainy periods. The
<br /> slopes. This moderately well drained, nearly level soil is characteristic plant community is mainly soft chess,
<br /> on terraces. It is moderately deep to a hardpan. It ripgut brome, foxtail fescue, and filaree. Grazing should
<br /> formed in alluvium derived from granitic rock sources. be delayed until the soil is firm.enough to withstand
<br /> The native vegetation is mainly annual grasses, (orbs, trampling by livestock and the more desirable forage
<br /> and scattered California white oak. Slopes are complex, plants have had an opportunity to set seed.
<br /> and the landscape is characterized by hummocky This unit is suited to irrigated pasture. The main
<br /> microrelief, depressions, minor drainageways, and limitations are the complex slopes and the very low
<br /> areas that have been leveled. Meandering available water capacity. Leveling helps to ensure a
<br /> drainageways and closed depressions fill with water to uniform application of water. Because the soil is
<br /> form vernal pools during the winter in many areas_ droughty, the applications should be light and frequent.
<br /> Elevation is 20 to 150 feet. Tne average annual The water can be applied by sprinkler and border
<br /> precipitation is about 14 inches, the average annual air methods. Proper stocking rates, pasture rotation, and
<br /> temperature is about 61 degrees F, and the average restricted grazing during wet periods help to keep the
<br /> frost-free period is about 275 days. pasture in good condition and protect the soil from
<br /> Typically, the surface layer is brown sandy loam compaction.
<br /> about 13 inches thick. The upper part of the subsoil is a This unit is suited to irrigated row, field, and vineyard
<br /> claypan of brown clay about 7 inches thick. The lower crops. The main limitations are the complex slopes,
<br /> part to a depth of 60 inches is a brown and light brown, depth to the very slowly permeable claypan and
<br /> indurated hardpan. in some areas the surface layer is hardpan, and the very low available water capacity.
<br /> fine sandy loam, loam, or gravelly sandy loam. Leveling helps to ensure a uniform application of water.
<br /> Included in this unit are small areas of Bruella and Because of the restricted permeability, the applications
<br /> Rocklin soils on the slightly higher terraces, Jahant soils should be regulated so that the water does not stand on
<br /> in landscape positions similar to those of the San the surface and damage the crops. The hardpan limits
<br /> Joaquin soil, and Madera soils on the slightly higher the suitability for deep-rooted crops. Where feasible,
<br /> parts of the landscape. Also included are small areas of deep ripping of this restrictive layer can help to
<br /> San Joaquin soils that have slopes of 2 to 5 percent overcome this limitation. A tillage pan forms easily if the
<br /> and are on the slightly higher parts of the landscape, soil is tilled when wet. Chiseling or subsoiling breaks up
<br /> areas that have as much as 20 inches of overburden, the pan. Because the soil is droughty, applications of
<br /> and areas where most of the soil horizons have been irrigation water should be light and frequent. Furrow,
<br /> -emoved or altered or fragments of hardpan and border, and sprinkler irrigation systems are suitable.
<br /> :laypan materials are within 10 inches of the surface as Returning crop residue to the soil or regularly adding
<br /> 3 result of land leveling. Included areas make up about other organic material improves fertility, minimizes
<br /> 15 percent of the total acreage. crusting, and maintains the rate of water intake.
<br /> Permeability is very slow in the San Joaquin soil. Where this unit is used for dryland grain crops, the
<br /> 4vailable water capacity is very low. The shrink-swell main limitation is low rainfall during the growing season.
<br /> )otential is high. The effective rooting depth is limited Because the amount of precipitation is not sufficient for
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