Spending two hours in a hot cornfield right now, when it's up to 95 degrees and 110 degrees heat index in parts of the country, is dedication…or stupidity- you decide. Some of those who have done out are bringing reports out of the field that may make others think they're delusional. Past history says they might be quite sane.
Those making yield estimates by the method that involves counting ears in 1/1000th acre, then picking ears at random and averaging rows of kernels and number of kernels per row, before plugging it into a formula, say they've been able to come up with over 200 bushels per acre in some fields planted in mid-April.
Here's the formula, from the Purdue University Corn & Soybean Field Guide. Simply take the number of ears per 1/1000th acre time s the average number of kernel rows times the average number of kernels per row, then divide that number by 90.
For example, if you find 32 ears at 18 rows at 38 kernels, =243.2 bushels per acre.
That's what the formula says. For some, at least, their gut says something different. One farmer recalls a year he scouted a field, which happened to have a special high-value trait, and came up with 198 down to 160 bushels per acre, with most being in the 180's, ye the field only averaged 158 bushels per acre. Other regular commercial corn fields actually yielded more than his formula suggested. So he concluded that the specialty corn didn't pack nutrients into the kernel late in the season.
He and others are suggesting that may happen with regular corn this year. As nitrogen shortage, flat-out fast maturity, hot nights, and disease combine to shorten the growing season, kernels may miss Dave Nanda's fifth factor to big yields- packing lots of starch into kernels late in the growing season. Nanda is a crops consultant based in Indianapolis, Ind.
What's bothering some people is what else they're finding- corn where it's drying up quickly, possibly because during earlier monsoons, roots didn't go very deep, or because soils were compacted coming off a later, wet harvest, or both; corn with leaf disease, nitrogen shortages showing up near the end of grain fill, and last but not least, diplodia ear rot.
Diplodia is favored by heat and humidity. If a hybrid is at all susceptible, this would be the year of the perfect storm for diplodia, depending upon timing in your area. What some are finding are barren stalks, where there was a shoot or husks whose color is indicative of diplodia.
Go ahead and make your pre-season estimates, although your neighbors might think you a bit more same if you wait until it cools down. While you're in the field, look for signs of lodging and stalk rot to decide which fields to put on your harvest order first. Just remember that this may be a year when the early- yield estimate method needs to be backed off 10 to 20%, allowing for less late kernel fill, to get a more realistic expectation.