EVALUATION AND ANALYSIS OF SOIL QUALITY CHANGES IN DIFFERENT TIME PERIODS AT SMALL REGIONAL LEVEL IN RED SOIL HILLY REGIONS
Wang Xiaoju Gong Zitong (Institute of Soil Science, Academia Sinica, Nanjing 210008)
Soil quality is one of the most important factors for sustaining the global biosphere and the basis for sustainable agriculture development. A method for evaluating soil quality changes in time and space at small regional level was developed and used to evaluate the changes of soil quality in Qian Yan Zhou Experimental Station (QYZES) located in subtropical zone in China after 11 year reclamation. The characteristics of soil quality changes in crop land, citrus orchards, pasture, sparse grass land, artificial forests, natural forests, bare land and other land use patterns were analyzed and discussed. Supported with the software of ARC/INFO and FOXBASE, the Qian Yan Zhou Soil Quality Information System (QYZSQIS) was developed. By introducing a concept of relative soil quality index (RSQI), soil quality and its changes were evaluated at the small regional level of QYZES from 1983 to 1994. The study proved that the development of QYZSQIS combining with database of soil changes in various periods was an effective method for evaluating changes of soil quality in time and space at small regional levels, which may be suitable to regional levels, RSQI could serve as uniform criteria making quality levels of regional soils comparative, and ΔRSQI, the changed value of RSQI, was a good standard for the evaluation of soil quality changes. After 11 year reclamation, soils with both very low quality and very high quality were decreased in area, and soil with medium quality obviously increased. As to the land use patterns, soil quality in paddy fields, vegetable fields, and citrus orchards was dominantly improved, however, in fuel woods, sparse grass land, and bare land was mainly degraded. Herb plays an important role in conservation and improvement of soil quality in subtropicalzone in China. The study also shows that soils with higher fertility were degraded more easily. It has the same significance both for improving low quality soils and conserving higher quality soils.