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Spring Nitrogen Management: Form and Timing

Most corn producers have planned their spring nitrogen program for 2015, and many have already started to implement their program. Such plans might include fall ammonia application, early spring application of ammonia or another form of nitrogen, or plans to apply all of the nitrogen at or after planting, said a University of Illinois crop scientist.

“In recent years, there has been a trend toward more applications per crop, and it’s not unusual today to have nitrogen applied three or four times on the same field,” said Emerson Nafziger.

In 2014 Nafziger and his team began a study, funded by the Illinois fertilizer checkoff program and administered by the Nutrient Research and Education Council (NREC) board, with the goal of comparing yields from different nitrogen programs. These included a comparison of 15 ways to apply the same rate of nitrogen (150 lb per acre) in the spring at three U of I research centers.

June rainfall at the three sites where trials ran in 2014 ranged from 8 to 10 inches, or more than twice the normal amounts. “This might have meant above-normal nitrogen loss potential, though we did not have water standing on these plots,” Nafziger said. “Even so, most of the nitrogen forms and application times we compared produced similar yields when averaged across sites.”

Across the three sites, the highest-yielding treatment (urea plus Agrotain broadcast at planting) yielded statistically more than the five other treatments, but the second-best treatment (all of the nitrogen as UAN sidedressed at V5) yielded more than only the two lowest-yielding treatments.

“Having so few distinct differences was due to the fact that treatments changed rank so much from one site to another,” Nafziger said. “That lowered the predictive ability of the experiment because we have no way to predict how a treatment that did well at one site but not another will perform at either site (or across sites) in 2015 or 2016, or in a field this year or in future years.”

The 2014 results do raise the possibility that few if any of these nitrogen form and timing treatments may, in the end, stand out as being consistently better or worse than another. Nafziger said that this isn’t alarming, but it does provide a hint that the list of “acceptable” ways to apply nitrogen might turn out to be a little longer than was first thought.

“While we need to be cautious about any predictions, this also hints that some of the treatments that we reason should produce higher nitrogen use efficiency—such as sidedress or split nitrogen applications—might not always do so consistently,” he said. “What we saw it do well in 2014 can’t be considered the ‘best new’ way to apply nitrogen.

Nafziger added that it’s dangerous to speculate about why a treatment might have done well at one site but not another based on weather differences between the two sites. “In part that’s because the weather among sites was reasonably consistent – and excellent – in 2014. It’s likely that the weather in 2015 will be different than in 2014, and that may well change how the different treatments perform,” he said.

Nafziger said most growers can take comfort in the fact that just about any method they choose for putting nitrogen on the corn crop is likely to work reasonably well, though no method is entirely safe from unusual weather or crop conditions. “We only need to look back to 2012 to find a year when no method of applying nitrogen worked very well. When lack of water becomes the main limitation for a crop, things like nitrogen management may make little difference,” he said.

“A sound nitrogen management program should take costs into account, though, and not just the costs of trips across the fields and of the fertilizer material, but also the indirect costs that include such things as the chance for yield loss or of more expensive forms or application methods we might need to use if we can’t get nitrogen on when we expected to,” Nafziger said.

“Most changes we are inclined to make in how we manage nitrogen today involve increasing the complexity, and this often comes at a cost in time, expense, or uncertainty. Such costs have to be covered by consistent improvement in yields,” he said.

Source: Emerson Nafziger, University of Illinois

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