Understand nitrogen loss, timing and placement to build the foundation for high yields
Managing nitrogen in corn is not a one-day process—for optimum yields, it requires 365 days of attention. Farm Journal Field Agronomist Ken Ferrie encourages farmers to approach their nitrogen program as a complete management system to meet the needs of the crop through black layer.
The key to growing healthy corn is to reduce stress, especially during crucial periods such as pollination. But the healthiest corn receives adequate nitrogen throughout the entire process, so it never stops growing.
“Nitrogen works in corn like gas in a vehicle, fueling the crop from emergence through maturity,” Ferrie notes.
“You receive 5 bu. for every kernel in length. If approximately 10 kernels in length abort that totals a 50 bu. per acre loss,” says Farm Journal Associate Field Agronomist Missy Bauer. “It’s common to see yield losses above 5 bu. per acre because a farmer missed the target on his nitrogen program.”
With up to 50 bu. per acre swings in yield impact, it’s important to effectively manage nitrogen. Appreciating the role of nitrogen starts with understanding the nitrogen cycle, including how the crop uses nitrogen and the risks of nitrogen loss, Bauer says.
Nitrogen is lost through volatilization, denitrification and leaching. There are many tools to monitor loss and identify nitrogen deficiencies in the crop. These include: weather data; soil nitrate and ammonium sampling; tissue sampling; thermal imagery and normalized difference vegetation index (NDVI) mapping; yield maps; and test plots.
“Depending on your soils, determine how much rain it takes to impact nitrogen,” Bauer says. “Farmers should keep tabs on the makeup of their soils and the triggers to better manage nitrogen.”
A good place to start is with the soil itself, Ferrie says. The soil alone serves as an important source of nitrogen for the corn plant.
“Between 3,000 lb. and 6,000 lb. of organic nitrogen can be stored in the soil and used to help the crop,” he says. “If the nitrogen cycle works efficiently, 30% to 70% of nitrogen needed to grow the crop can come from the soil.”
Part of the reason why farmers apply nitrogen is to stimulate the soil microbes to help with the process, Ferrie explains. The soil microbes immobilize nitrogen and then it is mineralized back in the soil.
One way to ensure the nitrogen cycle is able to efficiently work is to maintain proper soil pH because the microbes have a narrow pH window to work in.
Once the basics of the nitrogen cycle are established, the next step to achieve maximum yield is to focus on nitrogen timing and placement. The key is providing nitrogen when the crop demands it. This requires mid-season attention and regular scouting.
Boots on the ground to monitor the crop and weather provide a better idea of how nitrogen affects final yield, Ferrie says. Ground-truthing and pulling nitrate samples is important, as growing environments fluctuate every year.
“Corn that is nitrogen-deficient at the beginning of the growing season gives up yield potential,” Ferrie says. “Nitrogen-deficient corn in the late reproductive stages costs actual yield.”
For optimum results, divide your timings and placements throughout the growing season, Bauer suggests. For example, if a small amount of nitrogen is broadcast applied in the fall or early spring, it can help break down residue, feed microbes and reduce immobilization. A preplant broadcast application might need to be paired with a stabilizer or inhibitor based on the product and environment.
When nitrogen is applied with the planter, it can be put in various placements, but anytime it’s banded, it will be more efficient for plant uptake. The same goes for sidedress applications at V6 or late season.
“I typically suggest applying nitrogen at least four times a year,” Bauer says. “Take the same total amount of nitrogen as you would traditionally apply, but divide it by timing and placement for maximum impact.”
The goal is to stretch your nitrogen dollars as far as possible, especially in a year with tighter margins. Ultimately, if you allocate your fertilizer dollars by applying nitrogen during crucial reproductive stages, you can raise more bushels with the same pounds of nitrogen.
Of course, weather conditions play an integral role in the success of nitrogen timing and placement.
Tips to Balance Your Nitrogen Program
To help plan your nitrogen program in corn, Farm Journal Field Agronomist Ken Ferrie provides these tips:
- Assess the environment for every field. Know your risk of nitrogen loss from leaching, denitrification and volatilization.
- Pick the right nitrogen sources, timings and placements. These three factors have a bigger impact than picking the correct rate.
- Assess the carbon penalty potential based on the amount and type of carbon left from your previous crop. Don’t forget to assess a carbon penalty for grass cover crops.
- Consider split applications and nitrogen inhibitors as part of the balance for your nitrogen plan.
- If corn significantly greens up right after a side- dress application, it is telling you the crop was waiting for the nitrogen and it was giving up yield potential during the process.
- Season-long scouting is the only way to get a handle on nitrogen needs and management. Knowing when you run short is more important than knowing how much you ran short.