Linda Geist

COLUMBIA, Mo.– Grain producers can track rainfall and risk of nitrogen loss during spring on a website from a University of Missouri plant scientist.

Nitrogen Watch 2013” identifies “danger areas” that are on track to have widespread problems with nitrogen loss.

These areas have not necessarily lost enough nitrogen yet to cause serious nitrogen deficiency in corn, but soon might if rains continue at the same rate, said Peter Scharf, a professor of plant sciences and an MU Extension nutrient management specialist.

“This is a serious production and environmental problem that I estimate cost Midwestern corn producers 2 billion bushels total from 2008 to 2011,” Scharf said.

The map, which will be updated weekly through the end of June, also distinguishes between well-drained and poorly drained soils, which have different critical periods during which rain is likely to cause N loss.

“On New Year’s Day, we likely had a lot of N left by last year’s droughted corn still in our fields in Missouri,” Scharf said. “Most or all of that N is gone now.”

Nitrate loss depends on the weather, the soil and the source and date of nitrogen application. Nitrate is the main form of nitrogen that is vulnerable to loss, and all nitrogen fertilizer eventually will convert to nitrate in the soil.

Urea, ammonium nitrate and urea-ammonium nitrate solution are probably more than half nitrate within two weeks of application, Scharf said, while anhydrous ammonia probably takes six weeks or even longer when soil temperatures are low. That is why anhydrous ammonia is sometimes applied earlier than other forms of nitrogen.

After fertilizer application, time and rain increase the risk that nitrogen won’t be there when the crop needs it, he said.

Many producers have not applied nitrogen fertilizer yet this year. Scharf said that is a good thing, given the year’s rain and weather. “That’s because the nitrogen is safe in the bin or in the tank.” But it’s also bad. “There is going to be a lot to get done in a short time.”

This year, Scharf recommends that producers plant first when conditions are right, then apply nitrogen later. This may require a change in equipment or nitrogen source.

To access the website, go to and click on the “N Watch 2013” link.

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