COLUMBIA, Mo.– No farmer wants to turn down 30 extra bushels of corn per acre at harvest, yet in many fields farmers will be doing just that if they don't apply more nitrogen.

“If you get 30 more bushels per acre and sell that corn for $6 a bushel, that’s $180 an acre,” said Peter Scharf, a University of Missouri Extension nutrient management specialist. “Even if you go over the top and pay someone with an airplane $15 per acre to put on 50 pounds nitrogen per acre, you’re spending at most $45 to make $180.”

Scharf said that most farmers have at least a two-week window now to apply nitrogen to fields where spring applications have leached out of the soil. With an airplane or high-clearance spreader, there’s still the opportunity to boost your corn’s yield.

The biggest gain comes in areas of the field with the worst-looking corn.

“If there’s still a live plant, even if it’s yellow and sorry-looking, that’s where you should put your rescue nitrogen,” Scharf said. “It’s all related to the water. The places where your rain goes and pools will be the wettest and lose the most.”

Losses are due to excessive rainfall this spring.

While Scharf noted that the problem isn’t quite as bad in Missouri as it had been in the past three years, nitrogen levels in some parts of the state have entered a danger zone. Northeast Missouri will benefit most from rescue nitrogen, but most of southern and eastern Missouri up to the Iowa border warrants some fresh applications. Yellowing corn in Clark, Lewis, Scotland, Schuyler and Knox counties in northeast Missouri indicate losses of up to 50 bushels per acre.

Some farmers might be worried about burning back their corn with such a late application of nitrogen, but the yield harm is minimal, Scharf said.

“In tests we’ve put 150 pounds of nitrogen on 4-foot-tall corn, and the average yield we lost was four bushels per acre to leaf burn from urea,” he said. “That’s not much compared to what you’ll gain if your corn needs N. It will make a bit of an ugly burn, but urea is the way to go if you’re broadcasting N on tall corn. It’s much easier on corn than ammonium nitrate, ammonium sulfate or liquid solution.”

Farmers can work with neighbors or a co-op to hire a pilot to fly on nitrogen, and many co-ops have high-clearance machines for late-season application. Machines like the John Deere 4930 offer 50-inch clearance for nearly full-season application.

Using high-clearance sprayers applying liquid N between rows with drop nozzles is another excellent option available at many co-ops and service providers. Drops need to run below ear level and be semi-rigid to avoid burning the corn plants and causing yield loss.

For more information on nitrogen, including the weekly “Nitrogen Watch 2011,” go to