'The temperature is 82 degrees F, and we'll have another hot one tomorrow,” the radio commentator says. That was during the third week of July, and it was the temperature for midnight, not noon. During the streak of 23 days where it reached at least 90 degrees F every day, nighttime temperatures were unseasonably high. It wasn't uncommon for them to stay in the mid-to-high 70s, if not the lower 80s.
Corn likes nighttime lows under 65 degrees F. Arlan Suderman, Farm Progress market analyst, who writes Market Outlook in the magazine each month and whom also provides reports on line, believe that the effect of nighttime temperatures staying high on corn yield was ignored for way too long. One year ago when the same situation occurred he worked with two different research groups, who used data going back 40 years to uncover the trend. As if to bear it out, the USDA estimate was off by nearly a record level last year. The only other time it was off that much was in another year when nighttime temperature were very high.
There were likely other factors involved in USDA's constant reduction of the yield estimate one year ago, but some researchers and analysts like Suderman believe it was a key factor. It affects yield because plants burn up energy that they could otherwise put into kernels just to keep plant functions going, including respiration. After the fact, some believe it's why plant kernels weren't as full and often not as heavy last fall as they are in some other years.
The nighttime effect is being ignored again in USDA's estimate, Suderman has noted. In fact, at the national level at least, it doesn't appear that USDA made any changes to how they prepare estimates for the August report. As a result, some people, Suderman included, believe that there could be a repeat to some degree this year. Depending on stage of growth and conditions and temperatures when plants were trying to fill kernels,. Yields may once again be affected by those high yields.
Irrigators typically don't get full potential in year's like these. One farmer has evaluated his commercial corn under irrigation at about 200 bushel per acre. However, the same field made about 220 in a dry year in '07. It just wasn't as hot that summer.