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When to check out N inhibitors

Someone from a different part of the country recently asked what the 2011 season was like, especially in the central to eastern Corn Belt. The best answer from the audience was “inconsistent.” Variation from area to area and even field to field was the norm, not the exception.

A wet spring followed by a quick turn toward dry hot conditions in most areas, mixed with varying degrees of soil compaction and even ponding in some areas, made for an interesting spring.

Key Points

Nitrogen is vulnerable to denitrification in the nitrate form.

Stabilizer helps keep N in the ammonium form longer.

Nitrogen in manure hangs around longer if inhibitor is included.


One of the variables that affected yield last season turned out to be nitrogen. How much rain came after it was applied?

Amir Faghih, product manager for Instinct nitrogen stabilizer for Dow AgroSciences, makes it his job to know how to prevent nitrogen losses to the greatest degree possible.

With green corn behind him where nitrogen had been applied with Instinct, Faghih used field-day opportunities in 2011 to explain where the product fits and how it works.

Best fit

The longtime stabilizer used for anhydrous ammonia applications is N-Serve. For years there was not an effective stabilizer for liquid UAN solutions. That’s one place Instinct fits, the product manager says. He also sees it fitting well in situations where livestock producers apply liquid manure. It can be applied with manure in either the fall or the spring. Depending upon the situation, the label allows higher rates of Instinct with manure in the fall.

Jeff Vetsch and John Lamb from the University of Minnesota Extension note that based on 2010 trials, adding Instinct to swine manure increased yields about 10 to 12 bushels per acre.

In the same study, the researchers found that anhydrous ammonia applied with N-Serve yielded the same as manure applied with Instinct, when both applications were made at the same time in late fall. Incidentally, delaying application 30 days into November increased corn yields about 11 bushels per acre. In a much larger set of field trials in Iowa, Instinct increased corn yields about 5 bushels per acre, compared to N applied without Instinct.

How it works

The goal is to keep nitrogen in the ammonium form as long as possible, no matter when applications are made, Faghih notes. Once the ammonium form converts to nitrate, it is more easily lost by leaching, or by denitrification into the atmosphere. In fact, denitrification can’t occur unless N is in the nitrate form.

Saturated soils tend to have less oxygen. When there’s less oxygen in the soil, the rate of denitrification tends to increase, meaning greater N losses if it is in the nitrate form. Soil temperature also plays a role. If other conditions are met, such as saturated soils, then warmer temperatures favor the bacteria and also increase the rate of denitrification.

What any inhibitor does, Faghih says, is slow the conversion process, keeping N in the ammonium form longer.

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Explain the process: Amir Faghih uses the depiction of N applied to the soil and green corn behind him to explain how N inhibitors help decrease N losses and improve yields.

This article published in the March, 2012 edition of INDIANA PRAIRIE FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.