The Nutrient Research and Education Council continues to fund on-farm nitrogen-rate trials that enhance science-based nitrogen application recommendations for growing corn using the MRTN university system. The University of Illinois develops protocols for these trials and IFCA coordinates implementation. They work closely with participants on the project to recruit farmers and retailers to take part in these studies, facilitate site mapping, and assure accurate collection and reporting of harvest yield.
In 2015, high nitrate-nitrogen loss conditions, as well as damage from standing water, resulted in high optimum nitrate-nitrogen rates. Conversely, in 2016, relatively low rates of nitrate-nitrogen were necessary to maximize yield because the soil provided a significant amount of mineralized nitrogen. Calculations reveal a very high efficiency—two-thirds of a pound of nitrate-nitrogen per bushel of yield, or 1.5 bushels per pound of nitrate-nitrogen used. In 26 trials only five had an optimum nitrate-nitrogen rate higher than the MRTN rate, an\d, on average, only 150 pounds of nitrate-nitrogen were necessary to produce an average yield at the optimum nitrate-nitrogen rate of 225 bushels per acre.
These results help demonstrate that the range of nitrogen rates established through the MRTN system factor in weather variations. The results also provide the best available recommendation for optimum economic return on nitrogen investment and thus mitigate the consequences of over-ap plying or under-applying nitrogen.
The Illinois Fertilizer & Chemical Association and the University of Illinois have shared this information in many outreach and educational sessions. Nitrogen rate results from trials in 2014–2016 are available on the IFCA website at https://ifca.com/4R/Trials. These data illustrate the response to various nitrogen fertilizer rates for corn under different weather, soil type, or crop rotation scenarios.
