A new publication is available through Iowa State University Extension that explores a recently developed regional Corn Belt approach to nitrogen rate guidelines.
Concepts and Rationale for Regional Nitrogen Rate Guidelines for Corn was developed jointly by soil fertility specialists from University of Illinois, Iowa State University (ISU), University of Minnesota,The Ohio State University, Purdue University, and University of Wisconsin.
Using recent nitrogen (N) rate trial data from multiple states, this publication illustrates a suggested approach for developing corn N rate guidelines. The approach uses an economic evaluation of N application rates, called the maximum return to N (MRTN). The goal of the regional effort was not to develop one N rate recommendation for the region, but rather to explain the science behind corn N use and fertilization requirements, and develop an approach to N guidelines that could provide more consistency between states.
"This publication is targeted for agronomists, crop consultants, and agency personnel, but producers should also find it interesting," said John Sawyer,ISU Extension soil fertility specialist and co-authorof the publication.
"The timing of this publication is importantbecause of the uncertainty in appropriate rates due to historically high N prices. While economic return to N application has been a part of N rate recommendations, this publication brings a timely focus back to that question," said Sawyer.
The publication primarily deals with N use in rain-fed conditions, with corn following soybean and continuous corn. The publication also addresses the question of determining N rates with ever-increasing corn yields. Instead of relying on yield goal, this publication outlines an approach that uses yield increase to N application and determines maximum economic return. Nitrogen application rate is critical because it improves corn yield dramatically but also is one of the largest corn production expenses.
Another outcome of the regional effort is a Web-based tool called the Corn Nitrogen Rate Calculator . Producers in Illinois, Iowa, Minnesota, and Wisconsin can use this tool to calculate the MRTN rate, profitable N rate range, net return, percentage of maximum yield, and other information directly from N response trial databases for each respective state..
Copies of the publication may be ordered through any Iowa State University county extension office, on the Web through the Iowa State University Extension Distribution Center  or by calling (515) 294-5247. An electronic copy of this publication  is available.
This article originally appeared on pages 218-219 of the IC-496(22) -- July 31, 2006 issue.