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s <br />4. Class IV soils have severe limitations that reduce the <br />choice of crops or require very careful management, or <br />both. <br />5. Class V soils are not likely to erode but have other <br />limitations, impractical to remove, that limit their use. <br />(None in Orange County) <br />6. Class VI soils have severe limitations that make them <br />generally unsuitable for cultivation. <br />7. Class VII soils have very severe limitations that make <br />them unsuitable for cultivation. <br />8. Class VIII soils have limitations that nearly preclude <br />their use for commercial crop production. (None in orange <br />County) <br />Capability subclasses are soil groups within one class. They <br />are designated by adding a small letter e, w, or s to the class <br />numeral, for example, Ile. The letter a means that the main <br />limitation is risk of erosion unless close- growing plant cover is <br />maintained. W means that water in or on the soil interferes with <br />plant growth or cultivation. S means that the soil is limited <br />mainly because of inherent soil qualities. <br />Soils are placed in agricultural groups according to their <br />land capability class. The lowest land capability class for the <br />soils should occur in agricultural group 1, with subclass <br />designations used to identify different groups; e.g., Ile in group <br />2. IIw in group 3, etc. It is acceptable, however, to have <br />agricultural groups that have more than one capability class or <br />subclass. <br />The land capability classes and subclasses for Orange County <br />soils are shown in Appendix A. In Column 4 of Table 2, soils have <br />been placed in agricultural groups according to land capability <br />classification. <br />Soil Productivity Index <br />Soil':_ptoductivity is the capacity of a soil to produce a <br />specified_ rckp using the most recent soil. -- and crop management <br />practices;- aiid is reflected in the estimated yield /acre that can be <br />expected. Estimated yields are based on the records of farmers, <br />conservationists, and extension agents. It is the differences in <br />yields of a specific crop on different soils that provide a measure <br />of comparison among soils. <br />To derive the productivity index for a given soil or group of <br />soils, an indicator crop, such as corn, is selected which <br />represents the single most cultivated crop. Next, the estimated <br />yields for corn on various soils are obtained from the local soil <br />survey or the local or state Soil Conservation Service office. If <br />the estimated yield exceeds 100 bushels /acre for any soil, it is <br />