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

摘要

The unreasonable agricultural management measure is the main cause of the risk of nitrogen and phosphoruslosses. The objective of this paper was to evaluate the impacts of agricultural management practices on the risk of nitrogenand 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 ofgrids are different. At very high risk area, about 599 of grid number is only for the actual management practice, accountingfor 0.22% of the total, while at very low risk area, 165884.00 and 60.51% for river buffer zone respectively. Controleffect of different agricultural management practices for risk of nitrogen and phosphorus losses is better, which very lowand low risk areas of based fertilizer applied deeply and buffer zone construction accounted for 98% and 95.6%, and thecontrol effect sorted as follows: base fertilizer applied deeply> construction of river buffer zone> reduced nitrogen application>reduced phosphorus application.