The initial report on expected Indiana corn yield, below the national trend, isn't surprising, considering the near-record wet spring and record-setting heat and drought that developed after it in much of Indiana. And 150 bushels per acre compared to 157 bushels per acre as the 2010 yield doesn't sound so discouraging.

Ah, but there's a fly in the ointment. Nobody is trying to mislead, but it's important to note that the 157 bushels per acre was the final yield for the 2010 Indiana corn crop, released by USDA in January of this year. Greg Preston, the state statistician in Indiana, acknowledges that the August estimate a year ago was much higher.

"It was about 166 bushels per acre," he says. "We were expecting Indiana's first billion bushel corn crop when we held the state fair pres conference following the release of the August crop report a year ago. Obviously that didn't happen."

Indeed, it was nearly a record drop, or put differently, one of the most inaccurate August predictions USDA has ever made, both in Indiana and nationally. Yield fell up to 10 bushels in some of the reports from the August report to the final report.

The two years are very different, but there is one similarity. Both featured hot, dry streaks during key pollination and grain fill times, at least in Indiana. The same is not true this year in all other states. That's why the national corn crop is expected to be slightly above last year's actual crop, while Indiana's August forecast is for a smaller crop with a lower average yield per acre.

Since the 23 consecutive days of 90 degree F or higher heat in Indiana is a record and unprecedented, breaking the record set in one of the hottest summers ever, 1936, just as hybrid corn was getting off the ground, it's somewhat difficult to know exactly what effect such continued heat might have on pollination and grain fill. Anecdotal reports range from good fill in some of the better areas that have received rain to erratic pollination and excessive abortion near ear tips in other areas.

There's also the issue of high nighttime temperatures. During part of that stretch, the temperature was never below 80 degrees during the entire 24-hour period. High nighttime temperatures were fingered as a possible cause of inaccuracy in corn yield estimates in August a year ago. Preston says that although they made recommendations which may have caused national officials to drop Indiana's yield a bushel or two, basically the same methods that were used to prepare the report in 2010 were used in 2011. There were no specific adjustments made for the high nighttime temperature effect, for example, in the national formula, as far as he knows.

All that points to a possible lowering of the estimate in Indiana as the season progresses. The next estimate may shed light on that, since enumerators will visit some 300 actual plots, and for the first time will have ears to look at. It will give them a better feel for grain fill.