Impacts of Agricultural Management Practices on the Risk of Nitrogen and Phosphorus Losses at Catchment Scales by Using GIS and Index Models

The unreasonable agricultural management measure is the main cause of the risk of nitrogen and phosphorus losses. The objective of this paper was to evaluate the impacts of agricultural management practices on the risk of nitrogen and phosphorus losses at catchment scales based on GIS and integrated index models. The results showed that 93.1% of the catchment was no risk and low risk area, while 6.9% for medium and high risk of nitrogen and phosphorus losses. Spatial analysis of risk index indicated that different agricultural management practices lead to number and proportion of grids are different. At very high risk area, about 599 of grid number is only for the actual management practice, accounting for 0.22% of the total, while at very low risk area, 165884.00 and 60.51% for river buffer zone respectively. Control effect of different agricultural management practices for risk of nitrogen and phosphorus losses is better, which very low and low risk areas of based fertilizer applied deeply and buffer zone construction accounted for 98% and 95.6%, and the control effect sorted as follows: base fertilizer applied deeply> construction of river buffer zone> reduced nitrogen application> reduced phosphorus application.