The 2012 U.S. average corn yield will be one of the dominant factors in determining the level of corn prices over the next year.

Expectations about that yield have started at a pretty high level, but according to a University of Illinois agricultural economist, the critical period for yield determination is just beginning.

“The small percentage of the crop planted late this year suggests that the U.S. average yield will be higher than if a normal percentage had been planted late, but the level of yields is still to be determined,” Darrel Good said.

Good said that a small percentage of the crop planted late this year and the early condition of the crop point to the potential for an above-trend yield in 2012, but the most important part of the season is just beginning.

“The corn market will continue to follow weather developments and crop condition ratings in order to refine yield expectations,” he said.

“At this juncture, two important developments may be required in order to maintain high yield expectations. The first is some convincing evidence that the relatively long period (8 months or so) of above-average temperatures is giving way to normal or below-normal temperatures. The second is for soil moisture deficits in important areas of the central, eastern, and southern Corn Belt to be eliminated.”

A second piece of early information relative to corn yield potential Good reported is the crop condition rating provided in the USDA’s weekly Crop Progress report.

He said there has historically been a positive relationship between the percentage of the crop rated good or excellent at the end of the season and the U.S. average yield relative to trend.

“Early crop condition ratings are suggestive of yield potential, but ratings can, and do, change substantially by the end of the season,” Good said. “The first crop condition rating of the season this year showed that 77 percent of the crop was in good or excellent condition as of May 20.