High temperatures and lack of rain have caused many corn fields to roll in afternoon. Water is transpiring through leaves and the roots are not able to take up enough moisture. Leaf rolling only in the afternoon hours is probably not significant enough to reduce ear size. However, leaf rolling that occurs from shortly after sunup to after dusk will signal severe drought and impact yield.
As far as growth stages, corn is entering critical stages of growth where dry weather and heat can impact yield. The potential ear size is from V-5 through V-16. Early season, the number of rows of ear are being determined and later, potential number of ovules that can be fertilized are determined within the kernel row.
Drought stress two weeks before and after tassel can significantly impact corn yield. During pollination, the potential number of ovules fertilized will impact yield. Heat and drought can reduce fertilized kernels. If stress continues, drought stress may cause the ears to abort kernel tips. The actual number of kernels surviving can be determined following kernel set, which is a couple of weeks after pollination.
The next few weeks will be very important in determining the impact that dry weather will have on corn yield. Hope we receive a nice gentle rain soon.
For more information, contact Wayne Flanary at 660-446-3724 or Kurt Nagel at 816-776-6961, Extension Agronomists, University of Missouri Extension.
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