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Don't sleep on nitrogen
A dry spell over much of the Midwest in June caused wet weather earlier this spring to seem like it was in the rear-view mirror. Still, rain over the weekend and earlier this week in areas like southern Minnesota, northeastern South Dakota, and central Iowa has keyed potential for nitrogen losses from cornfields. In addition, large areas of Missouri (and Illinois, Iowa, Kentucky, and Ohio) are in the Danger Zone for N loss. Peter Scharf, University of Missouri Extension fertility specialist, believes farmers are poised to have a large problem with N loss and little time to respond if the last two weeks of June are wet. In this story, he stresses why it’s important to have a plan in place for how to assess N loss and to apply additional fertilizer if needed.
A plan for how to apply additional fertilizer means knowing which machines can do the job, their cost, their availability, and your order of preference. Planes, high-clearance spinners, and high-clearance sprayers with large tanks are all increasing in number in Missouri. If you would hire this work done, reaching out now to the person who controls the machine(s) would be a good idea. By early July, planes will no longer be an option because they will switch to applying fungicide.
Assessing N loss is more difficult. If you’re not in the Danger Zone at the end of June, you don’t have to worry. If you are, aerial/satellite images can let you assess a lot of acres in a hurry. Deep soil samples are an option, but they should probably be 2 feet deep and require lots of cores if N was banded, so they are hard work and slow. Results can be interpreted using MU Guide G9177 probably until corn is hip-high. For farmers signed up for nitrogen models (Adapt-N, Nitrogen Adviser), this is an easy way to assess N loss. If you’re not signed up, it reportedly takes 20 to 40 minutes to enter the information for each field. This is not as slow as soil sampling but is still an obstacle.
We’ve already had some N loss with the tropical storm remnants that swept up through the middle of Missouri in mid-June. Especially in poorly-drained fields that stayed wet for several days, some N was lost due to the warm and wet soil conditions. In well-drained soils, nitrate moved farther down and possibly some moved out of reach of corn roots.
The amount of N lost so far has, for most fields, not been enough to make extra unplanned N applications profitable. But profitable yield responses to extra N on some fields (wetter than average, or more vulnerable due to soils or management) would not be surprising, even if no more N is lost. For farmers who still have a planned N application to do, it makes sense to increase the rate if you’re in the Danger Zone.
Most of all, if we get extra rain and more N loss, the stakes will go up and it will be crucial to be prepared, have a plan, and execute it.