Determination of Optimum N Rates for Corn: Models Versus Reality

Prediction of the optimum N-rate for corn is complex as it involves weather, genetics, soils and management factors. Many crop-based and/or soil-based tools exist to provide N rate predictions that range from empirical (easy to use and understand) to mechanistic (complex to use and understand). Although there is no consensus on which tool is the best, there is a clear consensus that we need to further improve the accuracy of the tools. Mechanistic simulation models have the potential to provide scenarios in addition to N-rate predictions but these models are currently viewed as “black boxes”. In this presentation, I will open the “black box” and I will describe the science behind it and provide examples of pre-plant and in-season predictions of optimum N rates. Prediction accuracy, pros and cons of using modeling, and needs for improved predictions will be discussed. Finally, a new approach to predict N-rates for corn that is based on statistical modeling will be presented.