The regional Corn Nitrogen Rate Calculator website, which has been helping farmers in Iowa and other northern Corn Belt states determine profitable nitrogen rates since 2005, now has a new URL (cnrc.agron.iastate.edu) and a revised nitrogen response trial database, and is more user friendly for mobile devices.

NO NEED FOR N CREDIT: Maximum return to nitrogen (MRTN) and the most profitable N rates to apply for corn are determined from the newly updated online calculator and are directly the total N fertilization amounts to apply for each crop rotation. No need to further adjust application rate based on previous crop—corn or beans.

The largest changes to the website are the updated individual state nitrogen rate response trial database and, for Iowa, the addition of the southeast Iowa region. Nitrogen response trial sites for Iowa are grouped by two geographic regions, which now matches guidelines in the publication “Nitrogen Use in Iowa Corn Production” (CROP 3073). The publication can be downloaded for free at the online Extension Store.

“The site revisions allow users to have access to the latest nitrogen rate research, and it offers more tailored application rate guidelines in Iowa,” says John Sawyer, professor of agronomy and Extension soil fertility and nutrient management specialist at Iowa State University.

Calculation process of the online tool remains the same

While suggested nitrogen rates may have changed somewhat due to the update, the concept and calculation process of the online tool remains the same. The method continues to be based on a regional approach, providing nitrogen rate guidelines in six states across the Corn Belt: Iowa, Illinois, Michigan, Minnesota, Ohio and Wisconsin.

“The corn nitrogen rate calculator benefits farmers so they can understand needed nitrogen application rates, adjust for different crop rotations, and provide guidance and flexibility in choice of application rate,” says Sawyer. “More importantly, it allows adjustment in your nitrogen application rate for changing nitrogen and corn prices.”

Using the Maximum Return to Nitrogen concept within the CNRC also helps farmers implement the most economical nitrogen rate inputs, which helps moderate water quality issues. For more information about the CNRC, visit cnrc.agron.iastate.edu.

Resources for making N application rate decisions

The Corn Nitrogen Rate Calculator web tool is located at cnrc.agron.iastate.edu/.

Publication CROP 3073, “Nitrogen Use in Iowa Corn Production”, can be ordered through any ISU county Extension and outreach office, downloaded from the ISU Extension Online Store at store.extension.iastate.edu/, or by calling 515-294-5247.

The regional publication “Regional Nitrogen Rate Guidelines for Corn” (PM 2015) can be ordered through any ISU county Extension and outreach office, downloaded from the ISU Extension Online Store at store.extension.iastate.edu/, downloaded from the CNRC website, downloaded from the ISU Agronomy Extension Soil Fertility website, or by calling 515-294-5247.

The ISU Agronomy Extension Soil Fertility website is at agronext.iastate.edu/soilfertility/.