Nitrogen Rate Prediction Tools

Which Nitrogen Rate Prediction Tool is best for Corn?

The Economically Optimum Corn Nitrogen Rate (EONR) is a moving target, every season is a little or lot different and growers are left at doing an ‘educated guess’ at the most profitable rate. A researcher told me recently in reviewing 40 years of N rate research trials, the locally accepted PSNT recommendation could easily be off by +/- 30 lb N/ac in any one year. An article that appeared in Jan/Feb issue of Agronomy Journal shows that some Nitrogen prediction tools are getting closer to the mark. Researchers evaluated eleven Nitrogen fertilizer recommendation tools over 3 year period & 8 midwest US states for their ability to accurately estimate the EONR. None of the tools were able to recommend N within +/- 27 lbs. N of EONR for more than 50% of sites. Two of the most successful tools were canopy reflectance and PSNT testing. Ontario experience would suggest that PSNT and the Ont Corn Nitrogen Calculator as most reliable. Interestingly the researchers reported the poorest performing tool was the yield goal method, a method most states and all Canadian provinces have since moved away from. What we draw from the study is that available tools are regionally specific, need local validation, but can be expected to reasonably help growers get closer to estimating the EONR, & far better than relying on yield goals. We still have lots to learn. View the summary: or full article: