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IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIItIII 1111111111111111 12/31/2001 MON 13:39 FAX 2099466036 USDA STOCKTON SERC CTP 002 an Joaquin County, California 155 quire diversions, dikes, or levees to remove and Land Capability Classification control floodwater. Reduction of the content of toxic salts is needed in Land capability classification shows, in a general areas where salts rise to the surface and accumulate in way, the suitability of soils for most kinds of field crops the root zone over a period of several years. The (35). Crops that require special management are excluded. The soils are grouped according to their content of soluble salts can be reduced by leaching. Kingile and Rindge are examples of sails in the Delta limitations for field crops, the risk of damage if they are area that can be affected by salinity if water in the used for crops, and the way they respond to adjacent rivers and sloughs is poor quality. management. The criteria used in grouping the soils do A soil that has a large amount of sodium is not include major and generally expensive landforming considered to be sodic. Applying a proper amount of that would change slope, depth, or other characteristics soil amendments, returning crop residue to the soil, and of the soils, nor do they include possible but unlikely major reclamation projects. Capability classification is leaching reduce the sodicity. The Willows and not a substitute for interpretations designed to show Pescadero soils in the Tracy area are examples of soils suitability and limitations of groups of soils for rangeland that are affected by both salinity and sodicity. Intensive and for engineering purposes. management is required to reduce the salinity and sodicity of these soils. Carefully applying irrigation water to the capability system, soils are generally grouped helps to prevent the buildup of a high water table. A at three levels: capability class, subclass, and unit. drainage system may be needed. These levels are defined in the following paragraphs. Capability Gasses, the broadest groups, are Yields Per Acre designated by Roman numerals I through VIII. The The average yields per acre that can be expected of numerals indicate progressively greater limitations and the principal crops under a high level of management narrower choices for practical use. The classes are re shown in table 7. In any given year, yields may be defined as follows: gher or lower than those indicated in the table Class I soils have few limitations that restrict their :cause of variations in rainfall and other climatic use. actors and in management. Class If soils have moderate limitations that reduce The yields are based mainly on the experience and the choice of plants or that require moderate records of farmers, conservationists, and extension conservation practices. agents. Available yield data from nearby counties and Class III soils have severe limitations that reduce the results of field trials and demonstrations are also choice of plants or that require special conservation considered. practices, or both. The management needed to obtain the indicated Class IV soils have very severe limitations that yields of the various crops depends on the kind of soil reduce the choice of plants or that require very careful and the crop. Management can include drainage, management, or both. erosion control, and protection from flooding;the proper Class V soils are not likely to erode but have other planting and seeding rates; suitable high-yielding crop limitations, impractical to remove, that limit their use. varieties; appropriate and timely tillage; control of Class VI soils have severe limitations that make them weeds, plant diseases, and harmful insects; favorable generally unsuitable for cultivation. soil reaction and optimum levels of nitrogen, Class VII soils have very severe limitations that make phosphorus, potassium, and trace elements for each them unsuitable for cultivation. crop; effective use of crop residue, barnyard manure, Class VIII soils and miscellaneous areas have and green manure crops; and harvesting that ensures limitations that nearly preclude their use for commercial the smallest possible loss. crop production. The estimated yields reflect the productive capacity Capability subclasses are soil groups within one of each soil for each of the principal crops. Yields are class. They are designated by adding a small letter, e, likely to increase as new production technology is w, s, or c,to the class numeral, for example, Ile. The developed. The productivity of a given soil compared letter a shows that the main hazard is the risk of with that of other soils, however, is not likely to change. erosion unless close-growing plant cover is maintained; Crops other-than those shown in table 7 are grown in w shows that water in or on the soil interferes with plant survey area. The local office of the Soil growth or cultivation (in some soils the wetness can be tservation Service or of the Cooperative Extension partly corrected by artificial drainage); s shows that the rvice can provide information about the management soil is limited mainly because it is shallow, droughty, or snd productivity of the soils for those crops. stony; and c, used in only some parts of the United FROM 2099466036 T O 12/31/( Land Capability Classification