PHOSPHORUS CONTENT, SORPTION AND SATURATION OF TOPSOIL IN CHAOHU LAKE WATERSHED, CHINA

摘要

The impact of non-point phosphorus pollution on surface and subsurface water quality is an important environmental concern in China, especially in the watersheds dominated by agriculture. A long term accumulation of phosphorus in agricultural topsoil will lead to phosphorus saturation and increase phosphorus loss risk. Studying spatial variance of phosphorus content, phosphorus fixation capacity and saturation of topsoil, is helpful to evaluate phosphorus loss risk and develop best management practices. A GIS-based geostatistical method was applied to analyze the spatial variance of topsoil total phosphorus in Chaohu Lake watershed. The phosphorus fixation capacity and saturation degree were also analyzed for different soil types and the soil under different landuse. The kriging results showed that total phosphorus had good spatial structure at NE-SW direction on a large scale. Tests for phosphorus sorption index showed general lower phosphorus fixation capacity of topsoil in Chaohu Lake watershed than Taihu and other areas in the world. Over 30% of the samples were phosphorus saturated with the saturation degree overpass 25%. Further studies are essential on a small scale to better explain the distribution of topsoil phosphorus and critical areas should be focused with management practices to control phosphorus loss.