Wheat School: How early warm weather impacts the nitrogen strategy


When the weather is warm early in the season, everyone starts talking winter wheat.

This spring in Ontario, the winter wheat crop is awake and no one is more excited than RealAgriculture agronomist Peter Johnson.

On this episode of the Wheat School, Johnson is walking a wheat field near Georgetown, Ont. The crop is greening up and new white roots are actively growing, but is the first week of March too early to boost the crop with a shot of nitrogen? Those new roots are actively taking up nitrogen, but the plant has little demand for nitrogen and sulphur as it comes out of dormancy. Johnson says growers will be tempted to apply nitrogen but there are risks, including the possibility of denitrification.

Johnson recalls similar conditions in 2012 when a warm spring prompted many growers to put all their nitrogen on early. It’s a cautionary tale: “Late April, it turned warm and wet, and we lost a whack of that nitrogen. And if you didn’t reapply, you gave up significant yield,” he says, noting that growers who split-applied nitrogen that year faired much better.

What’s Johnson’s advice for growers who are tempted to roll out the fertilizer applicator and head to the field? “If you are a single-application grower, it’s simply too early, the demand is low,” he stresses. “As we get these warmer winters we are going to have to reassess our nitrogen management, but a single shot of your entire nitrogen amount? No way we’re going to do that.”

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But that doesn’t mean growers have to sit on their hands. Johnson says keen wheat growers who want to give their crop a boost should follow the split-application strategy. That first application (by mid March) could include all, or a large portion, of the wheat’s sulphur needs, along with a small shot of nitrogen.

Growers then need to be back in the field around April 20 to stage the crop. “When we see that growing point getting ready to move that’s when we’re going to come back in and put that big nitrogen shot on. We’re not going to wait until mid May, particularly in a warm spring like this.”

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