Nitrogen Application May Depend on Weather, Growth Rates

Nitrogen Application May Depend on Weather, Growth Rates

U of Illinois professor says weather conditions are affecting how much nitrogen remains in soils

Some growers may wonder about nitrogen supplies in light of strange weather this spring. According to University of Illinois crop sciences professor Emerson Nafziger, if weather dries out nitrogen supply will improve – but if wet weather sticks around, some supplemental nitrogen might be a consideration.

Emerson said so far, samples have shown that wet conditions have caused nitrogen to move down in the soil, and it will continue its descent if soils stay wet. But, Nafziger said, nitrogen can be captured if roots go deeper and soils dry out.

U of Illinois professor says weather conditions are affecting how much nitrogen remains in soils

Luckily, Nafziger said the chances are fairly small that nitrogen deficiency will appear early in corn planted into warm soils, so there may be time for application.

"Nitrogen uptake is slow in small corn plants, and as soils warm up the mineralization process—the production of plant-available nitrogen from soil organic matter—kicks in. This process can provide as much as half the nitrogen needed by the crop in a season, especially in soils with high amounts of organic matter," he added.

But as corn growth speeds up, more attention will again return to nitrogen. To make sure crops get the appropriate amount, Nafziger said application will be necessary but it makes little difference in what form it is applied.

"Placing urea or UAN solution on the soil surface brings some risk of loss, but only if it stays dry for a week or so after application. Injecting UAN or using a urease inhibitor with either of these forms helps to protect the nitrogen from loss," he said.

Nafziger explained that later-applied nitrogen has little time in which to be lost before plant uptake begins.

"This means lower overall loss potential and so less need to apply insurance amounts of nitrogen. As an example, a plan to split-apply nitrogen—right after planting and again at sidedress—might now be modified to apply less total nitrogen in a single application if the first application couldn't be made before the crop emerged," he said.

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