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GJ_ Cogna loam, 0 to 2 percent slopes. This very deep, well drained soil is on nearly level low fan terraces. It formel in alluvium from mired rack sources. A few areas are dissected by intermittent sloughs that have been filled because of land-leveling. Elevation is 40 to 130 feet. The average annual precipitation is aQut 16 Inches, the average annual air temperature is about 60 degrees F, and the average frost-free period is about 270 days. Typically, the upper 13 inches of the surface layer is dark grayish brown loam. The lower 12 inches is dare: brown loam. The upper 13 inches of the underlying material is brown clay loam. The lower part to a depth of 64 inches 'is pale brown and brown loam. In some areas the surface layer is clay Islam or silt loam. Included in this unit are small areas of Archerdale and Vignolo soils on similar positions and Columbia � soils on slightly l"Ewer- positions. Also included are small areas of Cogna soils with, hardpan bel=ow 40 inches. In an incised drainage area near Farmington, there K a similar soil that has 15 to 20 percent fine and or coarser throughout the profile. Included areas make up about 15 percent of the total acreage. Permeability of this Cogna soil is moderate. Available water capacity is high. Effective rooting depth is 60 inches or more. ;,Runoff is slow and the hazard of water erosion is slight. The water intake family for irrigation is 1.0. : The soil is subject to rare flooding which reccurs during years of abnormally high, precipitation. i, Most areas of this unit are used for irrigated cropland and orchards. A few areas are used for homesite development. This unit is well suited to irrigated view, field and orchard crops. It has few limitations. Furrow, border, corrugationiand sprinkler- irrigation systems are suited to this soil . Returning crop residue to the soil or regularly adding ether organic matter- improves fertility, reduces crusting and increases the water intake rate. , If this unit is used for homesite development, general management considerations include rare fiooding. 'toads and streets should be located above the expected flood level. -The map unit is in capability units I (MLRA-17), irrigated and IVc-1 SMLRA-17?, nonirrigated. This map -unit is vegetative ski I group A. :1 SAN JOAQUIN COUNTY BOIL SURVEY PRELIMINARY DRAFT 7/90 SUBJECT TO CHANGE I f E 1 �1 II