Corn Nitrogen Fertilization Rate Tools Compared over Eight Midwest States.

Publicly-available nitrogen (N) rate recommendation tools are utilized to help maximize yield in corn production. These tools often fail when N is over-applied and results in excess N being lost to the environment, or when N is under-applied and results in decreased yield and economic returns. Performance of a tool is often based on the specific soil and weather conditions of a growing season. Research is needed to determine which tools are the most effective at recommending economical optimal N rates (EONR) under varying soil and weather conditions.  Research on N response plots is ongoing to evaluate publically-available recommendation tools across eight Midwest states. This presentation will summarize 2014 and 2015 research. Two sites from each state, resulting in a range of historically productive sites, were used to evaluate differences in soil and weather environments. Performance of publicly-available tools for making N fertilizer recommendations are contrasted in this presentation. Tools to be compared include pre-plant soil nitrate test, pre-sidedress soil nitrate test, maximum return to N (MRTN), and the Maize-N crop model. Analysis will include tool performance by site-specific soil and weather environments to understand the universality of each tool.