As late as some of Indiana's corn crop was planted, you might think the big concern would be whether it would mature in time. Actually, that looks like less of an issue now than it did when the crop was planted. Bob Nielsen, Purdue University Extension corn specialist, says because of all the heat, corn maturity has moved ahead, and corn planted late is at one-week or less behind corn planted in a more normal time, such as early May. Later-planted corn typically adjusts to require fewer growing degree days anyway, and then the extreme hit has produced many growing degree days, especially from mid-July through the first 10 days of August.
The concern instead is how well did it pollinate? Reports vary from area to area. One farmer who planted earlier, on May 10, is reasonably satisfied with everything but his fuller season, 115 day corn. It's showing considerable tip-back, or aborted kernels near the tip, because it pollinated several days later than the other hybrids planted the same time. Pollination was underway for it closer to the heart of the hot, dry streak.
The question becomes- if his 115 – day corn planted May 10 suffered significant tip-back, then what about corn planed May 20, the first opportunity for many people, at 107 to 110 day maturity. Do the math and it puts it pollinating at about the same time as the 115-day corn planted earlier, which is afflicted with enough tip-back to result in enough lost kernels to significantly drop yield.
And if the hybrids planted May 20 ran into some pollination issues, what about corn planted from then through the first of June? That corn was exposed to the entire 23-day streak of 90 degrees F or higher, in some cases much higher.
Part of the problem is that there isn't a good reference point in history to look for to understand how such a prolonged heat period might affect today's hybrids. The 23-day streak broke the 19-day record, set in 1936, widely remembered as one of the hottest summers ever in Indiana. Hybrid corn was in its' infancy. Obviously today's hybrids would be expected to handle heat better, but they're also planted at much higher populations in much different systems than corn was planted in 1936.
The $64,000 question, give or take, depending upon how many acres you have, is what did that extended streak do to pollination and kernel development? There is no way to tell since it's never happened before. Harvest will bring the answers.