Can Corn Get Too Much Nitrogen?

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Corn field too much Nitrogen

This time of year, you’re likely on the lookout for signs of nitrogen deficiency in your corn. However, it’s also important to be aware of the opposite problem: While it’s typically not as common as nitrogen deficiency, too much nitrogen also can be detrimental to your corn-growing operation.

Nitrogen is one of the most expensive inputs on your farm every season, and many fertilizer costs reached record highs this year. The prices have eased somewhat, but as prices remain volatile, the risks of over-applying nitrogen become even higher.

Too Much Nitrogen?

Before we discuss the impact too much nitrogen can have on your corn yield potential, let’s talk about the other impacts that an over-application of the nutrient can have on your operation. Pioneer agronomist Chris Doud says there are two important practical considerations.

“Two of the greater risks of over-applying nitrogen would be the economic loss to the profitability of your cropping input expenses and the environmental risk of losing excess nitrogen beyond what the plant requires for optimum yield into the atmosphere and/or waterways,” Doud says. “With significantly higher nitrogen prices, it’s extremely important to utilize the proper amount of nitrogen to allow the potential for optimum yields and the greatest potential profitability.”

Aside from the poor return on investment of buying more nitrogen than you actually need and the environmental cost of the unnecessary nitrogen, there also is the effect that too much nitrogen can have on your corn yield potential.

“Over-applications of nitrogen can impact a corn plant’s ability to mature properly and extend the plant’s health and staygreen, impacting the corn’s normal drydown,” Doud says.

Too much nitrogen uptake in corn can lead to increased stalk lodging, disease incidence, grain moisture and decreased uptake of other nutrients, all of which can lead to lower yield potential at harvest. 

Doud says you typically need to wait until the end of the season to see for certain whether your corn got too much nitrogen: “Taking a late-season stalk nitrate test one to three weeks after black layer is one method for evaluating nitrogen management and utilization in a corn plant.”

Avoid Over-applying Nitrogen

At this point in the season, there isn’t much you can do to pull back your nitrogen if you’ve already completed applications. However, Doud says that if you are concerned you may have over-applied nitrogen this year — or if over/under-applying has been a struggle in the past — there are steps you can take in the future to ensure you’re applying the right amount of nitrogen and getting the max out of that investment.

“The first step is to accurately estimate the crop’s nitrogen needs based on various factors like yield potential, soil types, drainage, application timing, nutrient form, placement, etc., as well as utilize nitrogen estimation crop modeling to evaluate the crop’s needs throughout the season,” Doud says.

Granular Agronomy offers precision tools, expert advice and custom prescriptions to help farmers pinpoint the correct inputs for their fields. This is a great option to help precisely dial in nitrogen and other nutrient needs based on desired yield.

Doud says another great step is to protect these nitrogen applications: “I suggest that farmers utilize a nitrogen stabilizer to decrease the risk of nitrogen loss and more efficiently manage their nitrogen inputs.”

The Nutrient Maximizers portfolio from Corteva Agriscience offers three stabilization solutions, all of which can be used with fall, spring or sidedress applications

  • N-Serve® nitrogen stabilizer, which provides proven protection of anhydrous ammonia from nitrogen loss below ground caused by leaching and denitrification.
  • Instinct NXTGEN® nitrogen stabilizer, an enhanced formulation, which provides unrivaled protection of urea, UAN and liquid manure from nitrogen loss below ground caused by leaching and denitrification.
  • PinnitMax® TG nitrogen stabilizer, which maximizes nitrogen above ground, preventing volatilization of urea and UAN applications. PinnitMax TG will be widely available in 2023.

It’s true that farmers will sometimes add more nitrogen to their corn as an insurance policy against loss. However, with volatile costs, that can become a very expensive insurance policy. And on top of that, it’s important to remember that applying additional nitrogen in crop doesn’t guarantee it will be there when the corn needs it. No matter how much nitrogen you apply, it will still be vulnerable to loss. 

Using a nitrogen stabilizer will help keep more nitrogen available in the corn’s root zone during key growth stages, leading to better yield potential. And by using a stabilizer as an insurance policy instead of continuing to apply more fertilizer, you also can avoid over-applying nitrogen.

While we spend a lot of time talking about the risks of corn not getting enough nitrogen, the opposite problem is certainly a concern too. Your local ag retailer — and other trusted advisers — can help you choose the tools and solutions to dial in the right nitrogen rates on your farm and get the maximum return on your nitrogen investment.

Instinct NXTGEN® and PinnitMax® TG are not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Do not fall-apply anhydrous ammonia south of Highway 16 in the state of Illinois. Always read and follow label directions.