Nitrogen Application Rate
Matching N application rates with the Corn Nitrogen Rate Calculator, a university-developed online tool, has potential to reduce nitrate-N loss. The tool is used in Iowa to determine the Maximum Return To Nitrogen (MRTN) for continuous corn and corn rotated with soybean, which provides the optimal N rate based on the fertilizer and corn prices. The calculator also provides a profitable range around the MRTN that is within $1 per acre net return of the MRTN.
The MRTN and the most profitable range provide an estimated statewide N fertilization rate needed for Iowa corn production. Implementing the nitrogen rate reduction to the MRTN on all corn-soybean and continuous corn acres is estimated to have the potential to reduce nitrate-N loading about 9% statewide.