The days of applying a growing season’s worth of nitrogen either before or at corn planting can now be officially declared history. Yes, a foundation of fall- or spring-applied nitrogen is necessary to meet the nutrient needs for an emerging corn crop.
But research and practical experience have also established that when nitrogen in any form is applied in higher quantities, varying amounts will be lost through leaching, volatilization and denitrification.
It would stand to reason, then, that whatever can be done to closely match nitrogen application to plant uptake would minimize nutrient loss, maximize utilization and improve plant performance and yield.
Experts at The Fertilizer Institute agree. They note, “By postponing a portion of the N treatment until the crop is better able to utilize the nutrient, plants take up the nitrogen more quickly and efficiently. That means growers get more from their fertilizer investment and fertilizer losses that can contribute to environmental concerns are lessened.”1
One answer, supported by decades of research, new technology and, most importantly, bottom-line performance, is the move toward split and late-season nitrogen application—a best management practice for corn production today.
With the increased emphasis on just-in-time nitrogen application has come a discussion of the optimum timing of later-season applications—and how best to apply needed nitrogen.
After two decades of research, researchers at the University of Missouri found that corn yields always improve when nitrogen is applied as late as tasseling. In fact, in investigating rescue nitrogen application the researchers stated that they “…failed to find corn that was so late and so pitiful that rescue N was unprofitable.”2
How late is too late? That question remains to be answered. “Researchers agree that a positive response to nitrogen application is seen when nitrogen is applied around the time of tasseling,” says Erik Tribelhorn, CEO of Agri-Inject,Agri-Inject.com, in Yuma, Colorado. “The corn plant, however, takes up 20% of its total nitrogen after R2.”
Much of that late-season nitrogen is utilized by the corn plant for grain fill. The difficulty in addressing the late-season need most efficiently, Tribelhorn notes, is that most application systems can’t operate much beyond the tasseling stage. For corn growers with pivot irrigation systems, however, nitrogen can be spoon-fed to the corn crop throughout the entire period of nutrient uptake, avoiding the peaks and valleys inherent in other application methods.
“Corn plants don’t eat nitrogen—they drink it,” Tribelhorn points out. “It makes sense to feed the plant at the same time it is taking up water. With today’s injection systems, you can precisely match the level of nitrogen delivered to the needs of the corn plant throughout its entire life cycle.”
The results of one 2015 study conducted by Beck’s Hybrids3 make a particularly strong case for nitrogen fertigation. Two hybrids received 30 pounds of UAN via fertigation at VT stage. Compared to irrigation alone, the summary response to the VT application was an additional 29 bushels of corn, with a return on investment from the nitrogen alone of $98.98 per acre.
Tribelhorn also notes that nitrogen is not the only beneficial plant nutrient that can be spoon- fed to the corn crop through fertigation.
“More than half of a corn plant’s sulfur uptake, for example, occurs after VT/R1,” Tribelhorn says. “As a result, many farmers will apply 28-0-0-5 through their pivots during the critical late stages of grain fill.”
In light of current high input prices, tight margins and concerns about nutrient stewardship, it would appear that spoon-feeding nitrogen with fertigation is a best practice well suited to progressive corn production.
Split Fertilizer Application Helps Optimize Nutrient Management, The Fertilizer Institute,http://www.nutrientstewardship.com/implementation/article/split-fertilizer-application-helps-optimize-nutrient-management
Peter Scharf, Never too late for rescue nitrogen in corn, Dakota Farmer, July 18, 2016, http://farmprogress.com/story-never-too-late-rescue-nitrogen-corn-9-144105
Beck’s Hybrids, Pivot Irrigation Study, 2015 Beck’s Practical Farm Research,
Response of Corn to Late-season Nitrogen Applicationhttps://www.agry.purdue.edu/ext/corn/news/timeless/CornRespLateSeasonN.html
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