|
12/31/2001 )ll0fr' 13:39 FrLI 20994EE036 „Us A S,WC1�ION"SERC Ct'Ft
<br /> �y �002, ,.
<br /> an Joaquin County; California 155
<br /> 1
<br /> quire diversions, dikes, or levees to remove and Land CapeWllty Classification
<br /> controlJ !_and capability classification shows, in a general
<br /> Reductionc6on off the content of toxic salts is needed in way, the suitabilitf soils fkinds s
<br /> areas where salts rise to the surface and accumulate in y oor most nds of field crops
<br /> s the root zone over a period of several years. Tho (35) Crops that require spatial management are
<br /> content of soluble salts can be reduced by leaching. excluded, The soils are grouped according to their
<br /> Kingile and Rlndgo are examples of soils in the Delta limitations for field crops, the risk of damage'd 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 change slope, depth, or other characteristics
<br /> soil amendments, returning crop residue to the soil, and of the soils, nor do!they Include possible but unlikely
<br /> leaching reduce the sodlcity, The Willows and major reclamation projects. Capability classification is
<br /> not a substitute for interpretations designed to show
<br /> Pescadero soils in the Tracy area are examples of soils ,
<br /> that are affected by both salinity and sodicity. Intensive suitability and limitations of groups of soils fdr rangeland
<br /> management is required to reduce the salinity and and for engineering purposes.
<br /> sodicity of these sails. 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 Gasses, the broadest groups, are
<br /> Yields Per Acre designated by Roman numerals l through VIII. 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 duffined as foiiows:
<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 /> ' actors and in management. Class II soils have moderate limitations that reduce
<br /> w The yields are basad-mainly on the experience and the choicd 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 III 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 /> yields of the various crops depends on the kind of soil reduce the choice of plants or that require very careful
<br /> and the 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 /> pianting and seeding rates; suitable high-yielding crop limitations, impractical to remove, that limit their use
<br /> varieties; appropriate and timely tillage; control of Class VI soils have severe limitations that make them
<br /> weeds, plant dlseases, and harmful insects; favorable generally unsuitable for cultivation.
<br /> soil reaction and optimum levels of Ntrogen, Class VIl soils have very severe limitations that make
<br /> phosphorus, potassium, and trace elements for each them unsuitable for cultNation.
<br /> crop; effective use of crop residue, barnyard manure, Class Vlil 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 /> of each soil for each of the principal crops. Yields are class. They are deslgnated by adding a small letter, a,
<br /> ¢ likely to increase as new production technology is w, s, or c, to the class numeral, for example, 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 close-growing plant cover is maintained;
<br /> Crops other than those shown in table 7 are grown in w shows that water In or on the soil interferes with plant
<br /> survey area. The local office of the Soil growth or cuitivation on some sails the wetness can be
<br /> iservation Service or of the Cooperative Extension partly corrected by artificial drainage); s shows that the
<br /> rvice can provide Information about the management soil is limited mainly because tt is shallow, droughty, or
<br /> end productivity of the soils for those crops. stony; and c, used in only some parts of the United
<br /> rl
<br /> FROM 2099466036 TO 12/3;1/01 1 : 45 PM page 2
<br /> Land. Capability Classification
<br /> IXD '
<br />
|