Farmers who are unprepared to make in-season nitrogen (N) applications to corn are putting their yield and profit at risk, says Peter Scharf, University of Missouri Extension soil scientist.

“N loss in cornfields has been widespread across much of the Midwest due to wet soil conditions for four straight springs — from 2008 to 2011,” Scharf says. “So when thinking about spring fertilizer strategies, number one is to make sure your crop will have enough N when it needs it.”

Yield boosts from rescue N applications averaged 34 bu./acre across six University of Missouri field trials during 2010, and nearly as much in previous years, Scharf says. However, in 2011, rescue N treatments may have provided a lower yield benefit, because many areas that experienced N loss from wet conditions during spring were later hit by drought, making water the limiting factor to yield instead of N, he says.

Due to unpredictable weather patterns, Midwestern farmers need to keep in mind that neither fall nor spring preplant N applications are bulletproof, Scharf notes. “When applying fall N, farmers should calculate an 8-bu./acre yield penalty under normal spring weather conditions and a much higher yield penalty if conditions turn wetter than average,” he says. “Fall N applications make great logistical sense, but you won’t come out ahead if you give up 20 or 30 bu. [due to N loss] when conditions turn wet. You need to be ready to add more N later.”

Preplant spring anhydrous applications have the lowest risk for N loss among all preplant N programs, but even they will lose significant amounts of N if conditions are wet enough, Scharf adds. As a result, he recommends farmers make arrangements now to be able to apply in-season N to cornfields where and if needed during 2012.