Soil erosion is a main factor of soil degradation of purple soil sloping field in the Three Gorges reservoir area,and therefore it leads to impoverishment of soil nutrient.

At present,there are kinds of different impoverishment to farmland soil in Fujian whose organic matter is not high especially the orchard soil,nitrogen and potassium is most serious,phosphorus and available phosphorus is apparently impoverished in some low Fertilizer soil such as the new fruit soil,while available potassium sees no impoverishment.

Putting soil micro algae which were native to fertile soil into sterile soil, and then culturing them under dark and light conditions separately, the results showed: under dark condition, soil micro algae almost come into dormant state or dead in 30days; under light condition, micro algae increase at some degree in 30 days, and then breed rapidly.

The paper fristly compared the fertile soil with the incinerated sterile soil on the number of micro-algae , soil pH value , soil organic matter soil available phosphorus and soil nitrogen.

Study of Soil Nutrient Depletion of Chongqing Based on GIS;

Soil nutrients depletion trend under 4 commercial forests (Cunninghamia lanceilata, Phyllostachy pubescens, Camellia sinensis  and fruit forest) were measured by comparison with broad leaved forest.