How to Dial in a Nitrogen Rate for the Upcoming Corn Crop

The current economic conditions for corn producers require making wise decisions when it comes to crop inputs. One of the higher costs associated with a corn crop is nitrogen (N) fertilizer. Knowing exactly how much you need to purchase can help lock in better prices with early purchase options before the prices are likely to go up as the growing season approaches. Here is a list of things to consider when determining an appropriate N application rate.

Potential Yield – Determine a realistic yield for your operation. This is probably not the year to aim for record yields. Use the average of the last 5 to 10 years of actual yield averages, not just the average you hope for. Consult your seed company agronomist to see how different varieties have yielded in local plot trials.

Nitrogen Use Efficiency – This is the amount of N it takes to produce 1 bushel of corn. Every bushel of corn contains approximately 0.67 pounds of N. However, a corn crop takes up approximately 1.0 pounds of N for every bushel produced. If N can only be applied before planting, generally 1.2 to 1.4 pounds of N per bushel should be applied to account for the greater risk of loss. In a typical system with starter N and sidedress, aim for 1.0 to 1.1 pounds per bushel. If you have the option for late season applications (VT and later), it is possible to reduce rates to 0.7 to 0.9 pounds per bushel.

Maximum Return to Nitrogen (MRTN) – This is a model developed by multiple universities using N response data to calculate the economic optimum N rate for your situation. You begin by selecting your region then entering your expected price per bushel and your cost per pound of N. This model is accessible at https://www.cornnratecalc.org/.

Estimated Nitrogen Release (ENR) – You can use the organic matter from your routine soil tests to help reduce your N application rate. For every 1% organic matter, you can estimate that approximately 20-40 pounds of N will be mineralized or naturally released by the microbes in the soil. However, this is heavily dependent on the weather. So, it is advisable to stay on the lower end of the range.

Presidedress Soil Nitrate Test (PSNT) – Collect a soil test prior to a sidedress application to see how much nitrate has been mineralized by the organic matter. For sampling instructions and data interpretations please see our fact sheet, PSNT for Corn.