Distribution and Leaching of Inorganic Phosphorus in Soils of the Lakeshore Buffer Zone and Farmlands Around Lake Dianchi

In order to get to konow how soil phosphorus is distributed in and leached from the soils around Lake Dinachi,soil samples were collected from the lakeshore buffer zone and farmlands around the lake for analysis of physicochemical properties,distribution of soil phosphorus and its relationship with groundwater.Results show that soil organic carbon and total nitrogen was higher in the buffer zone than in the farmland,and so was COD and total phosporus in shallow groundwater.No significant difference was observed between the soils of the lakeshore buffer zone and the farmland in total phosphous concentration in the 0-40 cm soil layer,however,the former was much lower than the latter in Olsen-P concentration.Ca-P was the dominant fraction of inorganic phosphorus in the buffer zone soil,accounting for 63%-69% of the total inorganic phosphorus.The buffer zone soil was also apparently higher than the farmland soil in proportion of O-P to soil total inorganic phosphorous,but much lower in proportion of Al-P and Fe-P.All these indicate that the 3 years of buffer zone construction has led to apparent differentiation of fractionation and distribution of inorganic phosphorous in the soils around the lake.Correlation analysis shows that depth of shallow groundwater table was in extremely significant negative relationship with COD and total phosphorus in the groundwater,and that phosphorus in groundwater was also in siginificant or extremely siginificant negative relationships with Olsen-P,AL-P and Fe-P in the surface soil layer.All the findings indicate that the surface soil layer around the lake is the major source of phosphorous leaching into the lake,and depth of shallow groundwater table the major factor affecting soil phosphorus leaching in the area.