ECONOMIC AND ENVIRONMENTAL FEASIBILITY OF VARIABLE RATE NITROGEN FERTILIZER APPLICATION WITH CARRY-OVER EFFECTS

This study evaluates the long-term profitability and environmental impacts of variable rate versus uniform nitrogen application in seed potato production with nitrogen carry-over effects included. Seed potato yields were simulated for four different areas of a field using the EPIC crop growth model. A dynamic optimization model was used to determine optimal steady-state nitrogen levels for each area and the entire field. Average nitrogen losses and economic returns were evaluated for both uniform and variable rate nitrogen fertilizer. Variable rate nitrogen application was found to be unprofitable for the field when compared to uniform nitrogen application. Nitrogen losses for the field were about the same under both strategies. The results indicate greater economic and environmental benefits may be achieved by splitting nitrogen applications, especially for areas of the field exhibiting low yield productivity.