Effects of reduced fertilizer application on environmental quality of paddy field

A paddy field in the Tai Lake region of Yixing County was selected to study the effects of reduced fertilizer application on rice yield, nitrogen and phosphorus concentrations in surface water, leachate through field trial and indoor analyses. The results show that rice yield under optimum fertilization treatment does not significantly differ from conventional fertilization treatment, and that optimum fertilization saves N-fertilizer by 22% and reduces runoff N by 30%～40%, and leaching N by 32.3%. Total Dissolved Nitrogen (TDN) concentration in surface water and leachate increase with N-fertilizer application rate, with peak concentrations occurring 1～2 days after fertilization. A significant difference in TDN is observed between two fertilization treatments within one week after fertilization. Total Dissolved Phosphorus (TDP) concentration in surface water during the rice growing season exceeds critical value of water eutrophication by a merging as high as 15.8 mg·L-1 after fertilization, leading to pollution of surrounding surface water. Paddy field is able to filter P in irrigation water. It is therefore believed to reduce fertilization to appropriate rates and rationally manage fertilizer and water are important measures to control non-point source pollution in agriculture.