Yellow corn has become a common sight in areas receiving far too much rain in June. Reports of 12 inches in the month by June 16 were common in northern counties of parts of Illinois, Indiana and Ohio.
Rivers were out in many areas, and fields were all or partially flooded in lowland areas.
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Assuming you have fields where corn is surviving, maybe even thriving, for the most part, what do you do about yellow patches? Is it a sign that you need more N and should figure out how to make a rescue application of N with high-clearance equipment?
The answer may be "yes," but it may be "no." Justin Petrosino, an agronomist for Stewart Seeds, Greensburg, Ind., and part of the Agronomy in Motion program, says yellow corn isn't always due to a nitrogen shortage.
"Be sure that N loss is the reason the corn is yellow," he says. He has dug in fields where corn is dark green and found roots grown vigorously in a foot of soil.
In the same field with the same hybrid, he has found plants that are yellow with stunted roots. "Where corn is yellow (in this case) and stunted the roots are struggling to move through the clay layer that is closer to the surface," he says.
"If rainfall has not been too heavy, you may be seeing differences in soils rather than differences in nitrogen availability. Wade out into your fields (where some corn is yellow) and do a little digging, run some simulations, or even pull some soil samples to determine if the corn is in need of extra N, rather than just guessing you need 40 to 50 pounds more nitrogen per acre."
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Computer simulation programs are available. Climate Corporation is one company offering these simulations. You can sign up 250 acres for free and try their service.