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Applying nitrogen on soybeans is a controversial topic, because farmers want to do it, but university experts say it doesn’t work.
Agronomists know that soybeans require 4.5-5 pounds of N per bushel produced. A 60-bushel crop will require about 300 pounds, and soybeans fix only enough nitrogen to produce about 50 or 60 bushels — and often, maybe only half of what the plant needs.
So the rest of that nitrogen has to come from the soil.
However, when you apply nitrogen on soybeans — either preplant or after the crop is up — there is usually no response, or maybe a positive response only 20-30% of the time.
Let’s be honest, in most case, soybeans won’t respond to nitrogen based on average yields. If your yield won’t break 70 bushels, there is generally no reason to apply it because something else is limiting yield.
Because of inconsistent results, most university researchers say it doesn’t work and it could be an environmental disaster because you’re adding more nitrogen back to the environment at the same time they’re being encouraged to manage it more wisely on corn.
But there’s a lot of interest on applying nitrogen on soybeans today, and growers who have produced 90- or 100-bushel soybeans and won yield contests say it took supplemental nitrogen.
University of Illinois plant physiologist Fred Below, who runs the “Six Secrets of Soybean Success” project, says the question he’s asked most on soybeans is about applying N.