Much of Kentucky has turned hot and dry at the worst possible time for corn. About half of the corn crop was silking or complete with silking as of July 5, 2010, according to the USDA Crop and Weather Report. Corn is most sensitive to stress around silking and blister development. In addition, corn uses the most water at silking, as much as 0.35 inches per day.
Pollen shed and pollination is improved when temperatures are mild. The majority of pollen is shed in the morning after the dew has dried. A second release of pollen may occur in the late afternoon or early evening as temperatures cool again. The hot, dry weather we are currently experiencing does not favor good pollination. The hot weather will tend to dry out both the pollen and the silks. Temperatures above 100 F can kill pollen.
The good news is that most corn fields will pollinate for about 14 days and most pollen shed occurs when temperatures are a little cooler. So, even when conditions are hot and dry, the corn plant will attempt to work around those poor conditions. The bad news is that high temperatures seem to quicken pollen shed. Taking the good with the bad: each field still has a chance for successful pollination.
For corn that was through pollination before things turned dry, abortion of kernels is a possibility. The corn plant will recognize that water reserves are low and abort kernels near the tip of the ear, first. Very high plant populations can increase the water stress and increase kernel abortion.
What can you do about it? Unless you have irrigation, not much can be done on the agronomics. If you are marketing the current crop on the futures, you might want to be more cautious with your yield targets. Of course, a good rain in the next couple days will solve most of our problems.
R.L. Nielsen, Tassel Emergence and Pollen Shed, July 2010. Purdue. http://www.agry.purdue.edu/ext/corn/news/timeless/Tassels.html
R. Elmore. Corn Development from R1 to R6. Iowa State. http://www.agronext.iastate.edu/corn/production/management/growth/yield.html
Kentucky Weekly Crop and Weather Update. July 5, 2010.