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Specialists: Take a hard look at split N for corn

Missouri Correspondent

COLUMBIA, Mo. — Last month, while many were bundling up to arrive or take time off for the holidays, Corn Belt extension specialists sent a reminder to corn growers: Start thinking about your spring nitrogen (N) applications.
That came from specialists in Indiana, Illinois and Iowa – as well as Missouri and Kansas – who highlighted a free online tool to manage fertilization for corn acres in those states. The “Corn Split N” decision tool combines weather data and field considerations to determine the bottom line from two nitrogen applications.
“Research has shown that will ultimately lead to better results because less fertilizer will be needed overall, and not as much will be lost in runoff,” said Ray Massey, University of Missouri extension economist.
The tool was developed as part of a USDA-funded research and extension project that helps Corn Belt farms take into account weather variability. Corn Split N, and other resources, are available on the project website at
The Corn Split N tool will be also available in four new states for 2015, including Ohio and Michigan.
Most corn growers favor single N applications in either fall or spring. A detailed survey of corn fertilizer practices in 2010, for example, showed only 4 percent of corn acres in Minnesota receiving split application. According to the USDA Agricultural Resource Management Survey, last conducted in 2010, 60 percent of corn acres receiving only commercial fertilizer did not meet NRCS nitrogen management criteria.
Nitrogen prices are often a deciding factor for how and when N is applied, according to a 2012 USDA research summary. Some producers avoid splitting nitrogen applications because of a perception that a second field pass adds too much cost.
But the dollars saved by applying less total N may offset fuel, equipment and labor costs from a second application, said Chad Hart, Corn Split N local project coordinator and crop markets specialist at Iowa State University. He said the Corn Split N tool calculates three scenarios for N application, including the costs and benefits from a second field pass.
Corn producers are looking for every chance to improve efficiency this season. Gary Schnitkey, University of Illinois economist, projects non-land costs for Illinois corn will be about the same in 2015 as in 2014. But lower corn prices will result in lower returns per acre.
“At this point, net incomes for 2015 are projected below 2014 average net incomes,” he said.
Weather, soil conditions key

Splitting nitrogen application is not as simple as making a second field pass. The second sidedressing application must be done during the proper plant growth stage and soil conditions. Saturated soils, from high spring rainfall, can result in leaching and denitrification.
That could be why corn growers have usually relied on single N applications – especially when nitrogen is less costly. A survey of U.S. corn production practices from 2001-10, analyzed by USDA economists, showed application rates declined as fertilizer prices increased.
But 66 percent of corn acres did not meet application standards for N; that increased to 92 percent on land receiving manure fertilizer, according to the USDA Economic Research Service summary.
Southern areas, where higher spring temperatures are more likely to cause more rapid corn growth after spring rainfall, may especially benefit from split nitrogen.
Corn uses most of its nitrogen during the vegetative growth spurt.
According to Purdue University guidelines: “The most effective N application method and timing for minimizing N loss is to inject N prior to the beginning of rapid crop N uptake at roughly growth stage V6 (six leaves with visible leaf collars, approximately 18 inches tall).”
Researchers hope the Corn Split N tool, which includes historical climate data and days suitable for fieldwork, will make the practice of splitting nitrogen more timely and cost-effective for producers. That can have a broader, environmental impact said Ben Gramig, Purdue associate professor of agricultural economics and Corn Split N project team member.
“This timing of fertilizer application requires less fertilizer, can improve yields and limit fertilizer losses due to leaching and runoff,” he explained.