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<br /> 12/31/2001 MON 13:39 FAX 2099466036 USDA STOCK-PON SERC CPR 002
<br /> an Joaquin County, California 155
<br /> quire diversions, dikes, or levees to remove and dared Capability Giassifiostion
<br /> control floodwater. Land capability classification shows, in a general
<br /> 'r Reduction of the content of toxic salts is needed in
<br /> areas where salts rise to the surface and accumulate in xray, the suitability of soils for most kinds of field crops
<br /> * a . Gro s that require il ectal management are
<br /> the root zone over a pehod of several years. The ( p q p g
<br /> content of soluble salts can be reduced by leaching. excluded. The soils are grouped according to their
<br /> Kingiie and Rindge are examples of soils in the Delta limitations for field crops, the risk of damage if they are
<br /> area that can be affected by salinity if water in the used for crops, and the way they respond to
<br /> adjacent rivers and sloughs is of poor quality. management. The criteria used in grouping the soils do
<br /> A soil that has a large amount of sodium is not include major and generally expensive landforming
<br /> considered to be sodic. Applying a proper amount of that would
<br /> change '
<br /> of the soils, nor do they Includenge slope, depth, apossible but unlikely other characteristics
<br /> soil amendments, returning crop residue to the sail, and major reclamation projects. Capability classification is
<br /> leaching reduce the sodicify. The Willows and not a substitute for interpretations designed to show
<br /> Pescadero soils in the Tracy area are examples of soils suitability and limitations of groups of soils for rangeland
<br /> 1 that are affected by both salinity and sodicity. Intensive and for engineering purposes.
<br /> management is required to reduce the salinity and
<br /> sodicity of these soils. Carefully applying irrigation water In the capability system, soils are generally grouped
<br /> helps to prevent the buildup of a high water table.'A at three levels: capability class, subclass, and unit.
<br /> drainage system may be needed. These levels are defined in the following paragraphs.
<br /> Capability classes, the broadest groups, are
<br /> Yields Per Acre designated by Roman numerals I through Vlll. The
<br /> The average yields per acre that can be expected of numerals indicate progressively greater limitations and
<br /> the principal crops under a high level of management narrower choices for practical use. The classes are
<br /> re shown in table 7. In any given year, yields may be
<br /> defined as follows:
<br /> gher or lower than those indicated in the table Class I soils have few limitations that restrict their
<br /> ;cause of variations in rainfall and other climatic use.
<br /> j actors and in management_ Class II soils have moderate limitations that reduce
<br /> The yields are based mainly on the experience and the choice of plants or that require moderate
<br /> records of farmers, conservationists, and extension conservation practices.
<br /> agents. Available yield data from nearby counties and Class Ill soils have severe limitations that reduce the
<br /> F results of field.trials.and demonstrations are also choice of plants or that require special conservation
<br /> considered. practices, or both.
<br /> The management needed to obtain the indicated Class IV soils have very severe limitations that .
<br /> F. yields of the various crops depends on the kind of soil reduce the choice of plants or that require very careful
<br /> ,
<br /> and ihe crop. Management can include drainage, management, or both.
<br /> erosion control, and protection from flooding;the proper Class V soils are not likely to erode but have other
<br /> planting and seeding rates; suitable high-yielding crop limitations, impractical to remove, that limit their use.
<br /> 1 varieties; appropriate and timely tillage; control of Class Vi sails have severe limitations that make them
<br /> weeds, plant diseases, and harmful insects; favorable generally unsuitable for cultivation.
<br /> soil reaction and optimum !ovals of nitrogen, Class Vil soils have very severe limitations that make
<br /> phosphorus, potassium, and trace elements for each them unsuitable for cultivation.
<br /> crop; effective use of crop residue, barnyard manure, Class Vill soils and miscellaneous areas have
<br /> and green manure crops; and harvesting that ensures limitations that nearly preclude their use for commercial
<br /> the smallest possible loss. crop production.
<br /> The estimated yields reflect the productive capacity Capability subclasses are soil groups within one
<br /> `t of each soil for each of the principal crops. Yields are class. They are designated by adding a small letter, e,
<br /> liksty to increase as new production technology is w, s, or c, to the Class numeral, for exarnple, lie. The
<br /> developed. The productivity of a given soil compared letter a shows that the main hazard is the risk of
<br /> with that of other soils, however, is not likely to change. erosion unless cfose-growing plant cover is maintained;
<br /> j Crops other than those shown in table 7 are grown in wshows that water!n or on the soil interferes with plant
<br /> survey area. The local office of the Soil growth or cuitivation (in some soils the wetness can be
<br /> iservation Service or of the Cooperative Extension partly corrected by artificial drainage); s shoves that the
<br /> rvice can provide information about the managemont soil is limited mainly because it is shallow, droughty, or
<br /> ind productivity of the sails for those crops. stony; and c, used in only some parts of the United
<br /> Ff
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