[Dynamic characteristics of phosphorus in purple paddy soil and its environmental Impact]

The dynamic characteristics of phosphorus (P) in the surface water and runoff of paddy field with different P fertilizing treatments were investigated using the field experiment under the independent irrigation system as well as its environmental impact. The results showed that the concentration of total phosphorus (TP) in the surface water increased as the fertilizing amounts enhanced and reached the peak values after 24 h for all treatments in range of 0.928-3.824 mg/L. And the fluctuation of TP concentration in surface water was drastic during the first 30 days with the average contents of 0.259-1.433 mg/L which exceeded the critic values of eutrophication. Therefore, the field managements such as inter-tillage and drainage should be avoided during the time. After 40 days, the TP concentration declined slowly and then came to stabilization with low values after 60 days. The contents of different P forms in the runoff water increased with the improved amounts of precipitation and fertilizing and above 50% was dissolved phosphorus (DP). The DP was the dominant one in the P loss of the purple paddy soil and the loss load changed between 0.358 and 2.579 kg/hm2. Additionally, the P loss more easily occurred for the treatment of utilizing the cattle manure than that of straw, approximately 40% of loss load higher. Both the loss load and apparent P loss ratio evidently declined with the treatment of fertilizer combined with straw, suggesting that it was the better measure for reducing the P loss in the paddy field.