A case study of economic and environmental impacts of variable rate nitrogen and water application

摘要

This study evaluated profitability and environmental outcomes associated with variable rate applications of nitrogen and irrigation water in seed potato production. The EPIC (Environmental Policy Integrated Climate) crop growth model was used to simulate seed potato yields and nitrogen losses for four different areas under both uniform and variable rate water application. A dynamic optimization model was used to determine optimal levels of nitrogen under each irrigation scenario. Average nitrogen losses and economic returns were evaluated for all management strategies. Variable rate application of nitrogen was unprofitable and resulted in little to no reduction in nitrogen losses when compared to conventional application. Split application of nitrogen increased economic returns and reduced nitrogen losses relative to preplant application when irrigation water was applied uniformly across the field. Variable rate application of irrigation water produced the greatest economic returns and the greatest reductions in nitrogen loss regardless of the nitrogen management strategy employed. The results indicated that spatially variable water management may be more important than spatially variable nitrogen management for some fields in irrigated agriculture.