Like many farmers, Dennis Brinkman’s nitrogen management practices have evolved over the years as technology and science have improved.
"We used to put it on one time in the fall, and that was it," said Brinkman, who farms near Charles City. "Now we try to split it up in three different applications."
He uses a nitrogen (N) stabilizer to prevent N applied before planting from leaching, a practice he started many years ago.
But working with AgVantage FS in Charles City showed Brinkman he could achieve additional environmental benefits and reduce his overall nitrogen use by splitting up his applications into smaller, more timely increments.
"It seems like that’s a more common sense way," said Brinkman. "There’s a better chance of having that nitrogen there when the plant needs it. Ideally, you would be able to put it on right when the plant needs it, but you’re kind of at the mercy of the weather."
Applying less nitrogen before corn plants are growing reduces the risk of leaching from spring rainfall, said AgVantage FS certified crop specialist Jay Matthews. A post-emergence sidedress application also allows growers to adjust rates depending on crop needs, he added.
Mike Link is also changing his nitrogen management strategies on his farm near Ionia, moving entirely away from fall nitrogen applications after working with Matthews and AgVantage FS.
This year, Link said he plans to apply about one-half of his nitrogen in the form of anhydrous ammonia before planting and have the rest applied as urea with a high-clearance machine before tasseling.
He did several years of side-by-side replicated field trials to make sure it was the best economic as well as environmental decision for his farm. The split applications cost more because urea is more expensive than anhydrous ammonia and there is an additional cost for the extra application, but Link said his trials show yields have increased at lower nitrogen rates.
"Our field trials show that by applying half before planting and half as urea, it more than pays for itself," he said.
Putting in the work for field trials helps assure growers they’re using the right nitrogen rate without sacrificing yields, Matthews said.
"At the end of the year, we can tell them what the right rate was," he said. "The idea is that if we can get enough data points, we can make a recommendation for next year. That’s always hard, because the weather plays such a role in nitrogen management."
A significant number of growers have moved away from single fertilizer applications during the past three years after seeing how split applications perform on their farms, Matthews reported.
"They can see the benefit from a cost and yield standpoint, and from an environmental standpoint," he said. "They see how it benefits everybody."
FS approaches fertilizer management as a flexible system that can adjust to real-world challenges, Matthews said. Agronomists like Matthews use the acronym "MOM" to describe a fertilizer management strategy involving three components:
• Minimizing environmental impact.
• Optimizing yield.
• Maximizing input utilization.
Strategies may change from farm to farm, or even field to field, to achieve a farmer’s yield and environmental goals, Matthews explained.
"It’s about doing what’s best for the crop, the environment and the farmer in that system," he said. "For one farmer, it might be one application in the fall; for the next farmer, it might be three applications.
"We know each farmer is in a unique situation, so you can’t have one plan. You have to have a plan that can adapt and change for those different farmers."
Brinkman and Link also both participate in the N-Watch program sponsored by the Growmark FS system of regional cooperatives, including AgVantage FS.
The program attempts to quantify the form of available, soil-applied nitrogen, where it is located and what happens to the concentration of available N over time in the upper 24 inches of the soil profile.
After harvest, agronomists take composite samples every two to four weeks until the soil freezes. They return to pull more samples after the soil thaws in the spring to see if the residual nitrogen is still there.
"We use the N-watch program to track the nitrogen, so we can better see what’s happening in the field," said Brinkman.
Matthews also encourages farmers to use grid sampling and variable rate applications to apply nitrogen and other nutrients in the proper amounts and locations. The whole system approach to nutrient management fits nicely with other components of Iowa’s Nutrient Reduction Strategy, he said.
"I think something that’s been lost in the conversation is that farming is a business. If you over-apply nutrients, that’s not good for the business part," he said.