The Iowa nitrogen (N) response database in the corn nitrogen rate calculator was recently updated, with response trials added from 2009 research. There are now 188 trials for corn following soybean and 89 trials for corn following corn, says John Sawyer, Iowa State University Extension soil fertility specialist.

Being able to easily update the database with recent data is one of the many advantages to this dynamic database approach for providing nitrogen fertilizer application rate guidelines for corn, says the ISU agronomist. Having new response trial data allows rapid updating of the N rate recommendations due to changing hybrid genetics, economics, crop rotations and climatic conditions.

With the updated database, calculated N rates have changed slightly from last year. The table below gives the N rate at the maximum return to N and the profitable N rate range from the updated calculator for several N:corn grain price ratios. You can work with any price of N and corn you wish when running the calculator. Output information includes the N rate at the MRTN, the profitable N rate range, the net return to N application, the percent of maximum yield and the selected N fertilizer product rate and cost.

What is the Corn Nitrogen Rate Calculator?

The Corn Nitrogen Rate Calculator Web tool is located at extension.agron.iastate.edu/soilfertility/nrate.aspx. It is a resource that aids N rate decisions for corn production and is helpful in determining the effect of fertilizer and corn price on application rates. The method for calculating suggested N rates is based on a regional (Corn Belt) approach to N rate guidelines. Details on the approach are provided in the regional publication "Concepts and Rationale for Regional Nitrogen Rate Guidelines for Corn", PM 2015. This approach and the Corn Nitrogen Rate Calculator are now being used by seven states across the Corn Belt: Iowa, Illinois, Indiana, Michigan, Minnesota, Ohio and Wisconsin.

Resources for N Rate Decisions

The Corn Nitrogen Rate Calculator Web tool is located at extension.agron.iastate.edu/soilfertility/nrate.aspx.

The regional publication Regional Nitrogen Rate Guidelines for Corn (PM 2015) can be ordered through any ISU county office, on the Web through the ISU Extension Distribution Center at www.extension.iastate.edu/store, or by calling 515-294-5247. An electronic copy of the publication is available at www.extension.iastate.edu/Publications/2015.pdf.

The ISU Agronomy Extension Soil Fertility Web site is located at extension.agron.iastate.edu/soilfertility/.