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In search of better N efficiency

Next-generation nitrification stabilizers are another step in plant health, with a boost to the environment too

There was a time when farming was simple: plow the ground, plant the seed and harvest the crop.

Now, farmers need to make decisions on tillage practices, crop rotations, pest management, fertility, precision ag technology, soil health, genetics and a changing climate. And just to make it that much more challenging, each decision overlaps and alters the others in one form or another, almost always with an impact on the primary yardstick — yield.

Increasingly, growers are aware of those overlaps, with the realization that adding more nitrogen or phosphorus in one field could affect other nutrients, crop rotations or, unfortunately, pollution in nearby watercourses. One action can have many different effects.

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The use of nutrient inhibitors and stabilizers is not new, as the presence of Agrotain and SuperU illustrates. But their mode of action is different from that of a product like Centuro, dubbed a “next-generation” nitrification inhibitor for the use of ammonia and urea ammonium nitrate (UAN) fertilizers.

Centuro slows the nitrification process, increasing as much as threefold the time it takes for the conversion to ammonium and from there to nitrite and then nitrate. That enables growers to apply it two to three weeks earlier in the fall, protecting applied nitrogen in its ammonium form three times longer than without an inhibitor, thus optimizing the nutrients available for plant uptake. Because it reduces the potential for denitrification and the release of nitrous oxide, it also effectively lengthens the planting/seeding season.

The breakdown of urea or anhydrous to nitrite and then nitrate involves many biochemical reactions, most of them understood by growers, says Dr. Rigas Karamanos, senior agronomist with Koch Agronomic Services (Canada). But growers don’t need to grasp the complexity of those reactions, mediated by the ammonium monooxygenase (AMO) enzyme or that there are competitive and non-competitive reactions. It’s enough to know that Centuro works to boost nitrogen-use efficiency (NUE) while minimizing environmental impact.

“It blocks ammonium monooxygenase from nitrifying ammonium and, as result, slows down the reaction,” says Karamanos, who’s well known as an authority on soil health interactions across Canada and particularly in the West. “It’s also the non-competitive inhibition in Centuro that temporarily inactivates the AMO. It’s a dual mechanism but the bottom line is that it slows down the nitrification reaction.”

That reduces below-ground nitrogen loss through denitrification or through the soil as leaching.

Centuro’s active ingredient is pronitridine, and multi-site research indicates nitrogen-use efficiency to be 25 per cent higher (based on 12 replicated third-party studies conducted in four U.S. states). Such enhancements enable lower nitrogen fertilizer rates while maintaining the highest yields possible.

The product is now available in Canada and should prove to be a useful addition to growers’ cropping plans and fertility programs, regardless of where they farm. According to Karamanos, the benefit from Centuro is crop-independent, and major western Canadian crops like wheat, barley and canola will be the obvious choices for growers to add Centuro to their fertility programs.

“And in Manitoba, for example, with the expanding corn acres, it’ll be an excellent addition to the anhydrous ammonia in the fall or side-dressing in season,” says Karamanos.

There’s also an anticipated benefit for potato growers in Western Canada, where Centuro is seen as an excellent candidate for crops under irrigation, particularly for those growers looking to explore fertigation as an option. Top-dressing the product is also a possibility.

Reducing leaching

Stabilizing fall-applied N will be a big benefit, yet there are scenarios where stabilizing with spring applications will pay off and it’s a more responsible thing to do. One way of approaching it is to differentiate from situations where a urease inhibitor would be more beneficial. So a product like Agrotain is going to be more beneficial in situations where a grower is surface-applying a urea-containing product in conditions that are conducive to volatilization losses.

From an Ontario perspective, Jake Munroe likes what he sees from Centuro and believes there is a potential to adjust its use to a spring application.

“Corn receives the highest rates of nitrogen and nitrogen represents one of the highest variable costs in corn production,” says Munroe, soil management specialist for field crops with Ontario’s Ministry of Agriculture, Food and Rural Affairs (OMAFRA). “It’s worth growers looking at any potential tool that they can use to maximize their return on investment from their nitrogen.”

The risk of volatilization increases when conditions are warmer, drier or with residue on the surface and Munroe says those are the scenarios where urease inhibitors have really proven themselves. Nitrification inhibitors are targeted, so they’re delaying the conversion of ammonium nitrogen, which is not subject to loss by leaching or denitrification. Stabilizing fall-applied N will be a big benefit, yet there are scenarios where stabilizing with spring applications will pay off and is a more responsible thing to do. One way of approaching it is to differentiate from situations where a urease inhibitor would be more beneficial. So a product like Agrotain is going to be more beneficial in situations where a grower is surface-applying a urea-containing product in conditions that are conducive to volatilization losses.

The risk of volatilization increases when conditions are warmer, drier or with residue on the surface, and Munroe says those are the scenarios where urease inhibitors have proven themselves. Nitrification inhibitors are targeted, so they’re delaying the conversion of ammonium nitrogen, which is not subject to loss by leaching or denitrification.

The two scenarios where Munroe believes a nitrification inhibitor might benefit would be on sandy soils that are prone to leaching — particularly if the grower is applying all of the nitrogen up front. In that instance, having that nitrogen stabilized by a product that inhibits nitrification can be beneficial, especially under wet weather where there’s an increased risk of leaching. The other scenario would be in heavier-textured soils and a scenario where corn is planted, all of the nitrogen goes on up front and the weather turns wet in June as temperatures start to climb.

“We can have significant losses from denitrification and lose the nitrate-nitrogen — as both nitrogen gas and nitrous oxide — which is a greenhouse gas,” explains Munroe.

Eye on the environment

The potential environmental benefits of products such as Centuro (as well as Agrotain, SuperU and Tribune) are garnering a lot of attention.

“What it really comes down to is that water quality targets are only going to be met by combining different tools and approaches,” says Munroe. “There is some research to indicate that nitrification inhibitors have been shown to reduce nitrous oxide emissions.

For Karamanos, the environmental benefits are every bit as important as those to nutrient efficiency, soil health and ultimately yield.

“We want to make sure that people understand that whatever we offer them is research-based,” he says. “When you have enhanced efficiency and you increase the plant uptake of nitrogen, you decrease the losses to the environment, so it’s an important component of these nitrogen stabilizers in maintaining environmental integrity.”

For more information on Centuro, go to kochagronomicservices.com.

About the author

CG Production Editor

Ralph Pearce

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