Some farmers and agronomists have noticed signs of nitrogen deficiency in corn fields, especially in the past two weeks. Coupled with diseases, it has shut some fields down. The photosynthetic factory is closed. Fortunately, many fields were already heading toward the finish line, and the crop will likely still be good in many fields.
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Dave Nanda, consultant for genetics and technology for Seed Consultants, Inc. says drenching rains that followed even split-application of nitrogen by some farmers during the growing season likely caused nitrogen to leach downward. Some of those fields later showed signs of firing even though N was applied late in the growing season.
Nanda says it is worth taking notes for the future. If you run into a situation in a future year when you have 3 to 6 inches of rain following an in-season application, one alternative is reapplying up to half your N fertilizer. It may be even more necessary if you have ponding that lasts three days or more.
In another suggestion, he recommends considering urea or ammonium sulfate instead of nitrogen that is already in the nitrate form when applying when these types of rains are possible. Nitrate is more easily leached from the soil than the other forms.
Nitrogen stabilizers will help reduce leaching, which may be enough to cause you to reconsider if you should use them even at sidedressing. Conventional wisdom in the past was they weren't needed for in-season applications. It adds cost but it's cheaper than losing nitrogen which leads directly to lower yield, Nanda says.
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If you have the opportunity, using manure to supplement nitrogen application would be a good future plan, he adds. It's valuable because it also helps build organic matter content in soils besides just adding nutrients.
Using crop rotation and also growing cover corps are other ways to help put soils in a better situation to have enough N to get through the season. In many areas it's still not too late to plant cover crops. Cereal rye can be planted up until Nov. 1 or even later in the central Corn Belt.