Agronomists from seven Corn Belt states have developed a new approach to making nitrogen application rate recommendations. The approach was explained at the annual North Central Extension-Industry Soil Fertility Conference, held Nov. 16-17 in Des Moines, Iowa.
The new approach determines the net return on nitrogen application by subtracting the cost of the nitrogen fertilizer from the value of the increased corn yield produced by that nitrogen. The approach is referred to as the Maximum Return to N (MRTN) and it is based on hundreds of nitrogen rate trials conducted in several states.
John Sawyer, Iowa State University extension soil fertility specialist, gave an overview of the new calculator and N recommendation system.
He explains that the Web site provides a process to calculate economic return to N application with different nitrogen and corn prices and to find profitable N rates directly from N rate research data. The method used follows a newly developed regional approach for determining corn N rate guidelines that is being implemented in several Corn Belt states.
To try the MRTN rate calculator for one of your fields, here's what you do. First, go to http://extension.agron.iastate.edu/soilfertility/nrate.aspx
You choose your state. Then you choose the crop rotation you are in such as corn following corn or corn following soybeans. Then you set your corn and nitrogen prices. Say you have a nitrogen price per pound of 22 cents and a corn price per bushel of $2.20. Then you hit the calculate button.
The page also has a button to click if you want "more information" and it has a button to click on "how to use" the calculator.
The MRTN may change from state to state based on environmental conditions (soil, rainfall, latitude, etc.). But the concept behind the approach to determining the N rate is uniform.