Adjusting Nitrogen Rates with Split Applications: Modelled Effects on N Losses and Profits Across Weather Scenarios

The frequency and timing of nitrogen (N) application on corn strongly influences environmental N losses and yield, particularly in different weather. Split N application is a 4R (Right Source, Right Rate, Right Time, Right Place) nutrient management practice that ensures sufficient N supply when the crop needs it most, minimizing N losses to the environment, while allowing N rate adaptations as the season evolves. The purpose of this study is to investigate the agronomic, environmental, and economic performance of split N application on corn compared to traditional pre-plant broadcast methods under alternative timings, weather scenarios and N rates at Elora, Ontario, using biophysical and economic simulation models. The modelled results show that split N application with rate adjustments may increase profit between 14.6% and 19.5% in dry conditions and between 1.4% and 15.7% in wet conditions, while lowering environmental NO3- leaching, N2O emissions and NH3 volatilization losses in most weather. However, only in dry weather does the profit maximizing split N application strategy maximize environmental benefits, giving rise to the potential for government policy to address this trade-off between economic pursuits and environmental goals.