LAND CAPABILITY CLASSIFICATION

land capability map 地力图

The U.S. Department of Agriculture, Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service (SCS), has distinguished eight classes of land capability according to the risk of land damage or the difficulty of land use: (1) Class I: Soils that have few limitations restricting their use; (2) Class II: Soils that have some limitations, reducing the choice of plants or requiring moderate conservation practices; (3) Class III: Soils that have severe limitations that reduce the choice of plants or require special conservation practices, or both; (4) Class IV: Soils that have very severe limitations that restrict the choice of plants, require very careful management, or both; The following classes are generally not considered suitable for cultivation without some form of major treatment: (5) Class V: Soils that have little or no erosion hazard, but that have other limitations, impractical to remove, that limit their use largely to pasture, range, woodland, or wildlife food and cover; (6) Class VI: Soils that have severe limitations that make them generally unsuited for cultivation and limit their use largely to pasture or range, woodland, or wildlife food and cover; (7) Class VII: Soils that have very severe limitations that make them unsuited to cultivation and that restricts their use largely to grazing, woodland, or wildlife; (8) Class VIII: Soils and land forms that preclude their use for commercial plant production and restrict their use to recreation, wildlife, water supply, or aesthetic purposes.

The quality of soil resources for agricultural use is commonly expressed as land capability classes and subclasses, which show, in a general way, the suitability of soils for most kinds of field crops. Soils are grouped according to their limitations when they are used to grow field crops, the risk of damage when they are used, and the way they respond to treatment. Capability classes, the broadest groups, are designated by Roman numerals I through VIII, with I being the best soils and VIII being the poorest.
  

A grouping of kinds of soils in classes and units which describe their capability for intensive agricultural use and the treatments required for sustained use.