Corn+Soybean Digest

Nitrogen Recommendations For Eastern Production Areas

There’s still plenty time to apply nitrogen (N) to wheat in the eastern Midwest, says Edwin Lentz, Ohio State University (OSU) agronomist. He says N should be applied between green-up and beginning stem elongation. OSU research has shown that yields are not affected by delayed N until after early stem elongation, generally the end of April.

Studies over the last five years have shown that yields were the same or slightly better when a single application occurred at the first node visible of early stem elongation compared to initial green-up. Yields dropped 10-15% when a single application was delayed to early boot stage.

“At this time, we would recommend producers apply N as soon as field conditions allow application equipment,” says Lentz. “Since we are applying N between initial green-up and early stem elongation, any N source would be appropriate, so selection should be based on cost and availability.”

OSU still recommends the Tri-State Fertility Guide for N rates in wheat. This system relies on yield potential of a field. “As a producer, you can greatly increase or reduce your N rate by changing the value for yield potential,” says Lentz. “Thus, a realistic yield potential is needed to determine the optimum N rate. Once you have selected a
value for yield potential, the recommendation may be based on the following equation for mineral soils, which have 1-5% organic matter and adequate drainage:

N rate = 40 + [1.75 x (yield potential – 50)]
“We do not give any credit for the previous soybean crop, since we do not know if that organic N source will be released soon enough for the wheat crop,” says Lentz, discussing wheat following beans. “Generally, we would recommend that you subtract from the total (spring N) any fall-applied N up to 20 lbs./acre.”

Based on the equation above and deducting 20 lbs. from a fall application, OSU recommends a spring application of 110 lbs. N/acre for a yield potential of 100 bu.; 90 for 90 bu. potential; 70 for a 80-bu. and 40 for a 60-bu potential. Since green-up has started across the region, price should be the main factor in selecting an N source. Volatilization losses should still be minimal for urea-based fertilizers at this time. Potential loss of N from 28% solution may be furthered reduced by applying in a band.

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