Soils that are too dry or too wet can result in ammonia loss to the atmosphere from anhydrous ammonia because the application knife tracks may not seal properly. If you use manure or poultry litter, incorporate them into the soil to avoid volatilization.

To determine the economically optimal N rate at various corn and N prices, use the corn nitrogen rate calculator.

"Remember that you don't have to apply the entire amount in the fall," Fernandez says. "If you don't like taking big risks, but a fall application makes sense, it may be better to apply some N in the fall and the rest in spring. Also, research has shown better efficiency of nitrification inhibitors when lower nitrogen rates are used in the fall."

 

Weigh your options

Although N does not have to be applied in the fall, this timing has both economic and logistic advantages, Fernandez says. Unfortunately, because spring weather conditions greatly influence N efficiency, it is impossible to know in any given fall how risky it is to apply N.

"If you decide fall N application is right for you, the guidelines outlined here will help protect your N investment and enhance environmental protection," he says.

 

For more information on fall nitrogen applications, read The Bulletin online.