By John Sawyer
Nitrogen fertilizer used efficiently on corn can improve yields while protecting water quality
A new publication, Nitrogen Use in Iowa Corn Production (CROP 3073) released by Iowa State University Extension and Outreach provides an overview of nitrogen use in regard to the soil system and corn fertilization. Included is use of economical optimum nitrogen rates and how they should be used to increase crop yields, use nitrogen efficiently, and enhance water quality.
“Nitrogen is essential for growth and reproduction of crops and is involved in many important plant biochemical processes,” said John Sawyer, professor of agronomy and Extension soil fertility specialist with Iowa State University and author of the new publication. “Nitrogen management is critical for optimal yields for corn production systems.
"Of great interest to farmers, crop advisers, agricultural businesses and suppliers will be the maximum return rate to nitrogen (MRTN) system; the nitrogen rate approach used across the Midwest Corn Belt. “The publication contains the nitrogen rate guidelines for Iowa called MRTN and are provided in both the publication and the online Corn Nitrogen Rate Calculator,” he said.
Also, new rate guidelines were added for the Southeast Iowa area.
The publication highlights long-term nitrogen rate research conducted in Iowa, where corn yields average 60 bushels per acre for continuous corn and 115 bushels per acre for corn following soybean when corn is not fertilized. However, corn fertilized with proper nitrogen levels can easily yield 200 bushels per acre or more. Such yield increases highlight the importance of nitrogen use in corn production systems.
The publication also provides an overview of corn nitrogen fertilization use in different rotations, nitrogen cycling in soils, economic return to nitrogen application and nitrogen use relative to water quality. Soil is an open system where nitrogen losses occur naturally with the movement of water through the soil or with gaseous loss.
Jamie Benning, water quality program manager with ISU Extension and Outreach explains, “Farmers consider many factors when selecting nitrogen rates and timing of application, they strive for optimum corn yields while trying to minimize nitrogen loss and negative impacts to water quality.”