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—San Joaquin County, California 29
<br /> rooting depth is limited by the bedrock at a depth of 10 in the slightly lower landscape positions. Also included
<br /> to 20 inches. Runoff is slow or medium, and the hazard are small areas of Cogna, Finrod, and Hollenbeck soils
<br /> of water erosion is slight or moderate. in landscape positions similar to those of the Archerdale
<br /> The Lithic Xerorthents are ver/ shallow and are soil. Included areas make up about 15 percent of the
<br /> moderately well drained and well drained. They formed total acreage.
<br /> in material weathered from hard, rhyolitic, tuffaceous Permeability is slow in the Archerdale soil. Available
<br /> sandstone. Typically, 1 to 3 percent of the surface is water capacity is high. The shrink-swell potential also is
<br /> _covered with cobbles. The surface layer is light high. The effective rooting depth is 60 inches or more.
<br /> brownish gray gravelly loam about 3 inches thick. Runoff is slow, and the hazard of water erosion is
<br /> White, rhyolitic, tuffaceous sandstone bedrock is at a slight. The rate of water intake in irrigated areas is 1.0
<br /> depth of 3 inches. In some areas the surface layer is inch per hour. The hazard of soil blowing is moderate.
<br /> —gravelly sandy loam or loam. The soil is subject to rare flooding, which occurs during
<br /> Permeability is moderate in the Lithic Xerorthents. years of abnormally high precipitation.
<br /> Available water capacity is very low. The effective Most areas are used for irrigated crops or orchards.
<br /> ,rooting depth is limited by the bedrock at a depth of 1 to A few areas are used for homesite development. This
<br /> 4 inches. Runoff is rapid, and the hazard of water unit may provide wetland functions and values. These
<br /> erosion is moderate. should be considered in plans for enhancement of
<br /> Most areas of this unit are used for livestock grazing. wildlife habitat or land use conversion.
<br /> General management considerations include the very This unit is suited to irrigated row, field, and orchard
<br /> low available water capacity, the limited depth, and the crops. The main limitation is the slow permeability
<br /> hazard of erosion. The characteristic plant community below the overwash layer. General management
<br /> —on the Amador soil is soft chess, ripgut brome, foxtail considerations include the hazard of soil blowing.
<br /> fescue, and filaree. The Lithic Xerorthents support only Because of the restricted permeability, water
<br /> a sparse stand of plants that are suitable for grazing. applications should be regulated so that the water does
<br /> These plants are soft chess, toad rush, and hairgrass. not stand on the surface and damage the crops.
<br /> The very low available water capacity limits the Furrow, border, and sprinkler irrigation systems are
<br /> production of desirable forage plants. Fencing is difficult suitable. When the wind velocity is high in spring, the
<br /> because of the limited depth to bedrock. Grazing should hazard of soil blowing can be reduced by properly
<br /> -be controlled so that desirable vegetation, such as soft managing all crop residue and by minimizing tillage.
<br /> chess, is maintained and enough vegetation is left If this unit is used for homesite development, the
<br /> standing to protect the soils from erosion. Loss of the main limitations are the high shrink-swell potential, low
<br /> surface layer results in a severe decrease in strength, and the slow permeability below the overwash.
<br /> productivity and in the potential of the unit to produce The rare flooding is a hazard. Properly designing
<br /> plants suitable for grazing. foundations and footings and diverting runoff away from
<br /> This map unit is in capability subclass Vlle buildings help to prevent the structural damage caused
<br /> —(MLRA-18), nonirrigated. It is in vegetative soil group G. by shrinking and swelling. Properly designing buildings
<br /> and roads can offset the limited ability of the soil to
<br /> 106—Archerdale very fine sandy loam, 0 to 2 support a load. On sites for septic tank absorption
<br /> .percent slopes, overwashed. This very deep, well fields, the slow permeability can be overcome by
<br /> drained, nearly level soil is on alluvial fans. It formed in increasing the size of the absorption field. Houses,
<br /> alluvium derived from mixed rock sources. A few areas roads, and streets should be constructed above
<br /> are dissected by intermittent sloughs that have been expected flood levels.
<br /> -filled as a result of land leveling. Elevation is 60 to 90 This map unit is in capability units IIs-3 (MLRA-17).
<br /> feet. The average annual precipitation is about 14 irrigated, and IVs-3 (MLRA-17), nonirrigated. It is in
<br /> inches, the average annual air temperature is about 60 vegetative soil group A.
<br /> ,.degrees F, and the average frost-free period is about
<br /> 270 days. 107—Archerdale clay loam, 0 to 2 percent slopes.
<br /> Typically, the surface layer is brown very fine sandy This very deep, well drained, nearly level soil is on low
<br /> loam about 18 inches thick. Below this is a buried fan terraces. It formed in alluvium derived from mixed
<br /> 'surface layer of dark grayish brown clay loam about 20 rock sources. A few areas are dissected by intermittent
<br /> inches thick. The subsoil to a depth of 60 inches is sloughs that have been filled as a result of land
<br /> brown clay. In some areas the surface layer is fine leveling. Elevation is 40 to 130 feet. The average
<br /> ,—Sandy loam, silt loam, or clay loam.
<br /> annual Included in this unit are small areas of Columbia soils annual airtemperaturepe atu e is about 60 degrees F and the
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