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Tim Hushon, agronomist at The Mill, points to a diagram of test plots Chris Torres
TESTING N RATES: Tim Hushon, agronomist at The Mill, said the company’s test plots are looking at preplant nitrogen rates used in tandem with the Adapt-N modeling program.

Test plots experiment with split-applied nitrogen in corn

Agronomist Tim Hushon discussed the test plots during The Mill’s crop showcase event.

In Chesapeake Bay country, conserving resources such as nitrogen and phosphorus are crucial, especially if you’re following a nutrient management plan.

For the past six years the agronomists at The Mill in Maryland have been recommending split-applied nitrogen applications; the idea being that farmers put up two-thirds of their required nitrogen up front and come back with a topdress later.

“Our acres, and the amount of growers and the belief and the validity behind topdressing and split-applied nitrogen has just grown dramatically. We’ve had huge success with that,” said Tim Hushon, agronomist at The Mill, speaking at the company’s crop showcase in White Hall, Md.

But no two years on the farm are the same, and every farm has different needs. Knowing this, Hushon and other agronomists at The Mill wanted to change things up based on their work with nitrogen modeling programs like Adapt-N.

They started questioning whether the two-thirds upfront rate was the “magic number” for farmers.

“There’s other guys who are doing a little bit higher, a little bit less, so we said, ‘Alright, let’s put it to the test. Let’s see what we can do out here,’” he said.

Six different preplant nitrogen rates — starting with 0 and going up to the full rate of 191 pounds, and another plot of 145 pounds with potash — are being evaluated this year. The Adapt-N tool “operated in the background,” Hushon said, spitting out recommended topdress rates based on the preplant rates and other factors such as soil type. The plots were replicated three times and topdressings were done June 6, right around the time when corn was at the V10 stage. Nitrogen stabilizers were also used in the plots.

Ears of corn from The Mill's test plots varied based on the pre-plant and top-dress ratesDIFFERING RESULTS: Random corn ears were pulled from The Mill’s test plot to show how corn was growing. Results varied based on the preplant and topdress rates, which are listed with each group of corn ears.

The purpose of the plots, he said, is to get farmers thinking about optimal times for nitrogen application and utilizing nitrogen modeling tools to assist.

Targeting nitrogen

Lana St. John, district sales manager for Winfield United, said corn nutrient uptake for 300-bushel yields is generally greatest between V5 and V7, about 40 to 60 days after planting,

“The corn is ready to take off and needs food, so you have to think about it a little bit,” she said.

What was eye-opening for her was pulling ears from the plot and seeing the various ways corn was growing. She went into the plots pulling four ears at random in each plot. Ear sizes varied greatly based on the plots they were grown in.

Nothing is definitive, of course, until the combine goes through. but placing the full nitrogen rate upfront didn’t pay this year, at least from what she saw.

“But it does beg the question thinking through whether or not you need to put out N at preplant and how much,” she said. “So, it just goes to show us that there is a lot of variability that we need to be thinking through season by season.”

Value of stabilizers

Josh Mayfield, regional agronomist with Winfield United, said farmers have a lot of high-tech tools at their fingertips to better manage nitrogen in the field.

These include nitrogen stabilizers, which can prevent the quick loss of nitrogen applied in the field.

Nitrogen can be lost as ammonia gas on Day 1, he said. While you can’t prevent ammonium from turning into ammonia, a stabilizer slows that conversion down, he said.

Nitrogen can also be tilled into the soil or incorporated by Mother Nature’s rain, but nitrogen will stay on the surface in a no-till operation, making the use of a stabilizer even more critical.

“We want to keep it in the ammonium form as long as we can,” Mayfield said.

Hushon said yield results would be released in late October.

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