Understanding nitrogen to improve retention and ROI

Nitrogen is one of the most important nutrients in corn production; it can also be one of the more difficult inputs to manage. Once applied, nitrogen responds to weather, interacts with the soil and can move out of the root zone long before the crop needs it. For growers who apply nitrogen in the fall, the goal is straightforward: Keep as much of the nutrient available for next season’s corn crop as possible.

Ron Geis, Technical Field Agronomist, Corteva Agriscience, explains fall nitrogen application and stabilization. Geis has been with the company for 42 years and helps growers and retailers in Iowa and Nebraska. He understands the challenges nitrogen application and retention can bring to growers and helps explain the science and guide decisions regarding the management of this crucial nutrient.

Nitrogen’s changing forms

Nitrogen is applied in the ammonium form, which has a positive electrical charge. Soil has a negative charge. After application, bacteria convert the ammonium into a negative charge, which the soil will repel. So, the longer growers can keep nitrogen in the ammonium (positive charge) form, the longer nitrogen will be stable and stay in the soil, not move off or out of the field.

“The positive and the negative side of a magnet will stick together, and if you have two negative sides of a magnet, they’ll push away from each other,” Geis said. “Just like when negative nitrogen is pushed away from the negatively charged soil. The soil is not going to be pushed down; it’s the nitrogen that will be pushed into the groundwater or up in the air as a gas.”

Causes of nitrogen loss

Leaching occurs when nitrate nitrogen moves down through the soil with water. Because nitrate carries a negative charge, it is not held by soil particles and can move freely with moisture through the soil. Nitrate can then be carried below the crop’s root zone, making it unavailable to the corn crop.

Denitrification happens when saturated soils become oxygen-deficient. Under these conditions, soil microorganisms use nitrate instead of oxygen during respiration, converting plant-available nitrate into gaseous forms of nitrogen that are released into the atmosphere.

“Nitrogen is a very leaky system,” Geis said. “When nitrogen converts to a leachable or greenhouse denitrification gas, then it can all be lost with a heavy rainfall event. Knowing that you have a system that has a leak in it, plugging the leak makes good economic sense. If you have a pasture with a hole in your fence, your cows get out. Does it make more sense to keep buying more cows? Or does it make more sense to fix the hole in your fence? With underground nitrogen, you’ve got the exact same situation taking place.”

Stabilization matters

Nitrogen stabilizers buy time for growers by extending nitrogen availability and ensuring its accessibility to corn during critical growth stages. Corteva Agriscience offers two options for nitrogen stabilization. N-Serve® nitrogen stabilizer is applied with anhydrous ammonia. Instinct NXTGEN® nitrogen stabilizer is applied with urea, UAN or liquid manure. Both products help protect nitrogen fertilizer below ground, where up to 70% of nitrogen loss occurs.

N-Serve nitrogen stabilizer has been a trusted brand in the market for 50 years. One of the most effective active ingredients available — Optinyte® technology (nitrapyrin) — in N-Serve also powers Instinct NXTGEN nitrogen stabilizer.

“N-Serve and Instinct NXTGEN sedate the bacteria that is making the nitrogen convert to the negatively charged form,” Geis said. “With a stabilizer, we can hold that bacteria at bay. So if we suppress the bacteria for a week or two in the fall, and then another eight weeks in the spring after the soil temperatures have risen, we’ve effectively protected that nitrogen from the losses that can occur if it’s in the negative form. When we get heavier moisture events in April and May, having stabilized nitrogen with N-Serve or Instinct NXTGEN will protect us when we are most prone to nitrogen losses.”

Fall application timing is vital

In the fall, growers can take advantage of more available application timing windows and lower nitrogen costs. Geis notes that medium-to fine-textured soils where the soil temperatures routinely stay below 40 F and trend down for the winter are the most ideal conditions for fall anhydrous ammonia applications. Ideal soil moisture, not too wet or not too dry, is also important for keeping nitrogen where the plant will need it most.

Particularly with unstabilized nitrogen, a premature application when the conditions aren’t right will lead to nitrogen converting into a leachable form. This puts growers at risk to have a large loss of nitrogen before the plant is ready for it.

Common misconceptions

Misconceptions around nitrogen stabilization products hinder growers from getting the most out of fall nitrogen applications. Geis clears up two of the most common misunderstandings:

• Misconception — By keeping ammonium in the positive form, it cannot go into the corn plant. Truth — Corn will pull nitrogen from the soil in either the positive or negative form. If it’s in the positive form, the corn utilizes it instantly. If it’s in the negative form, the corn converts it back to the positive form to use it. So, the plant unnecessarily expends energy to reconvert back to the positive form that could be going toward beneficial growth./li>
• Misconception — Using a nitrogen stabilizer has a negative effect on beneficial soil bacteria. Truth — The Nitrosomonas bacteria, which converts the ammonium form to the nitrate form, are particularly sensitive to N-Serve nitrogen stabilizer and Instinct NXTGEN nitrogen stabilizer, so rates affecting this bacteria do not harm most other soil bacteria. The recommended stabilizer rates only suppress the Nitrosomonas bacteria; they don’t kill the bacteria.

Economics and stewardship

Good economics and good stewardship aren’t competing goals. Not only financially but also environmentally, it’s a good practice to keep nitrogen in the field and out of the groundwater.

“A nitrogen stabilizer ensures that the hefty nitrogen investment, which is many times more than $100 an acre, has done everything possible to keep nitrogen in the field where it belongs,” Geis said. “Financially, it makes sense, and it also helps farmers continue to be the good stewards of the land that they really are by nature.”

Analyzing results

Evaluating results helps growers refine nitrogen programs and build field-specific strategies for the coming seasons.

“The biggest report card is the yield at the end of the year, but tactics like spring stalk nitrate tests will give you a decent indication about how much nitrogen those corn plants have early in the season,” Geis said. “Then fall stalk nitrate tests can be a good report card at the end of the season as to whether your crop finished with enough nitrogen in the system to maximize the yield potential. Another in-season report card is to soil-sample the fields and compare how much nitrogen is in the ammonium form on the stabilized acres versus the unstabilized acres.”

Fall nitrogen application is, ultimately, a risk management exercise. Understanding how nitrogen changes in the soil, recognizing potential loss pathways, applying nitrogen with stabilization products at the right time and evaluating results can help growers retain vital nitrogen for the next corn crop while improving both profitability and nutrient stewardship.

To learn more about nitrogen stabilization solutions from Corteva Agriscience, visit NitrogenStabilizers.com.