In the old days you would have said this was a summer when the sheets stuck to you in bed at night. If you've got air-conditioning, that likely wasn't a problem this summer. But it wasn't for a lack of warm, muggy nights.
Several agronomists, including Dave Nanda, crops consultant Indianapolis, believe high nighttime temperatures across the Corn Belt may play a role in how the final size of the U.S. corn crop turns out. Along with some market analysts, he isn't surprised that the current trend based on two USDA reports is that perhaps there isn't as much corn out there as prognosticators first thought.
When temperatures are high at night, corn continues to respire, using up carbohydrate that otherwise could be added to the grain during grain fill, Nanda notes. Two things happen. The maturity of the crop usually speeds up. That definitely happened this year. Number two, yields may not be quite as good as expected. Field by field, we're still waiting to see how that turns out.
Normally in these types of years, even irrigators have trouble reaching super-high yields. Topping 200 bushels per acre may still be possible, but winning the Beck's 300-bushel yield challenge with a yield of 300 bushels or more may be a little tough.
To see what actually may have affected corn development, Indiana Prairie Farmer asked Ken Scheeringa of the Indiana State Climate office to run numbers for nighttime average lows for the entire state, lumped as a whole, from June 1 through Aug 31, typically considered as the three-month growing season.
Scheeringa found that the normal nighttime low averages 59.2 in June, 63.2 in July and 60.9 degrees F in August. That factors out to a summer-long normal average of 61.1 degrees.
But this summer the three-month average is 65.1 degrees- a full four degrees above normal. In terms of weather over such a long period of time a four degree shift is usually significant.
An independent study of the past 40 years of weather data in Illinois and Iowa done this summer indicates that 64 degrees for the nighttime low is the breaking point. Below averages of 64 for the summer, corn yields above trend line. Above 64 degrees, it yields below trend line.
What all this means is that it may be interesting to follow crop reports all the way to the final yield estimate.