Corn Nitrogen Rate Calculator Update

August 17, 2010

By John Sawyer, Department of Agronomy

Nitrogen (N) Response Trials Added
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. Being able to easily update the database with recent data is one of the many advantages to this dynamic database approach for corn N rate guidelines. Having new response trial data allows rapid updating with changing hybrid genetics, 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 (MRTN) 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 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


John Sawyer is professor with research and extension responsibilities in soil fertility and nutrient management.

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