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Corn+Soybean Digest

How To Manage Expensive Nitrogen

Managing your nitrogen (N) properly has never saved you so much money. Bob Hoeft University of Illinois, Urbana-Champaign professor of soil fertility, offers these pointers for squeezing every penny out of your input dollar:

*Application timing makes a difference. Fall application increases your chances of N loss through denitrification and leaching, he says.

*Precipitation makes a huge difference. Rainfall threatens to carry away your N unless you have a plan to anchor it in the soil.

“We can manage to reduce N loss but we cannot overcome what Mother Nature sends our way” Hoeft says.

“Excessively wet years have a lot of expensive N coming out of tile lines. In the dry spring of 2001, we had virtually no N coming out of tile lines no matter how much we applied,” Hoeft says. “Yet on the same plots in 2002, it rained constantly and water flowing out of the tile lines carried a lot of N away.”

Denitrification and leaching are the two major routes of N loss, Hoeft says. “There is very good evidence that N inhibitors reduce this.”

*Cutting N rates may or may not be the answer. “Apply the right rate at the right time, and use the right application technique for the form of N you’ve chosen,” Hoeft says.

“After decades of research, we still don’t know how to set the right rate; in the heart of the Corn Belt, there is no soil test that does that for you,” Hoeft says. “In the western Corn Belt and Dakotas you can use a nitrate test, but that does not work in the Corn Belt.

“The variation in the response rate to applied N is huge from year to year,” he says. “For example, in Monmouth, IL, the optimum N rate is somewhere between 70 and 240 lbs./acre of N. Which rate you pick depends on the year, and we never know in advance which type of year it will be. So we have gone with the maximum return to N approach.”

Anhydrous ammonia will continue to become more scarce, as domestic ammonia plants have been shuttered and imported forms of liquid N solutions and urea replace anhydrous ammonia, Hoeft says.

Phosphorus is another area of concern, but is easier to manage, Hoeft says. “Get it underground,” he says.

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