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Nitrogen management is simple, says Bob Hoeft, a University of Illinois fertility specialist. “All you have to do is put it on at exactly the right rate, at exactly the right time and use exactly the right application technique for the material of choice.”
Okay, maybe it’s not so simple, he concedes. But he offers no-tillers an overview to help them understand the various factors in nitrogen management and put together a successful program.
An assessment of nitrogen needs should begin with an accounting of what’s already in the field, Hoeft says. “Organic matter in the soil is a large source of nitrogen,” he says. “It contributes a great deal through a process called mineralization, the conversion to inorganic nitrogen.
“We get the inorganic nitrogen either as ammonium or when it converts through the nitrification process to nitrate; those are the two forms the plants use,” he notes.
No-tillers should estimate the amount of organic nitrogen in their soils, despite uncertainties. “The rough rule of thumb is, you get 20 pounds of nitrogen per acre for every 1 percent organic matter in the soil,” Hoeft says. “That’s figured into most recommendation systems. But it can depend on the weather’s effect on mineralization.
“Unfortunately, we can’t predict for sure what kind of season we’re going to have when we’re deciding how much nitrogen we’re going to use that spring,” he says. “Another thing is, if we have a long-term history of excessive nitrogen applications, we might get 170…