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2008 yield expectations study

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[July 16, 2008]  URBANA -- A new study by University of Illinois agricultural economists projects that average 2008 corn yields could be reduced by 2.9 bushels per acre in Illinois, 3.5 bushels in Indiana and 6.3 bushels in Iowa due to later-than-normal planting and above-normal precipitation in May. Soybean yields may be down 1.1 bushels, 0.4 bushels and 1.0 bushels per acre, respectively, in those same states for the same reasons.

"The purpose of our study was to evaluate 2008 yield potential for corn and soybeans in Illinois, Indiana and Iowa, using previously developed crop weather models that estimate the impact of technology and state average monthly weather variables on state average yields," explained Scott Irwin, a professor in the U of I Department of Agricultural and Consumer Economics and lead author of the study. Department colleagues Darrel Good and Mike Tannura were co-authors.

The study, "Forming Expectations About 2008 U.S. Corn and Soybean Yields -- Application of Crop Weather Models that Incorporate Planting Progress," is available online from U of I Extension. (See study.)

"In the current environment of strong domestic and export demand, relatively low world stocks, and historically high prices, the expected size of the 2008 U.S. corn and soybean crops takes on added significance," he said.

"The market's expectation about the prospective size of the crops will have a major influence on prices for the next three months."

Typically, acreage expectations are "solidified," he said, with the USDA's June Acreage report.

"That is not the case this year, however, due to widespread flooding and replanting in Illinois, Indiana, Iowa, Minnesota, Missouri and Wisconsin," Irwin said. "A special USDA survey in those areas this month will provide a clearer picture of planted and harvested acreage in the USDA's August Crop Production report."

The magnitude of the expected yield declines due to slow planting progress in 2008 is relatively small due to the fact that May precipitation, while high, was not extremely high. The magnitude of late planting, while above average, was considerably less than highs recorded in previous years.

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"It is important to keep in mind that these estimates do not take into account the impact of replanting due to flooding in some areas of Illinois, Indiana and, especially, Iowa during June," Irwin said.

The various models used by Irwin and his colleagues in projecting 2008 yields resulted in a wide range of forecasts of U.S. average yields for both crops.

"Corn yield forecasts range from 129.3 to 163.8 bushels per acre, and the soybean yield forecasts range from 37.8 to 45.3 bushels," he said.

"Production expectations for both crops, however, remain very uncertain for at least three reasons."

First, he noted, the magnitude of harvested acreage is not yet known. Second, remaining summer weather is an unknown.

"Finally, the crop yield models have relatively large forecast errors," he said.

Irwin said that with the exception of the unfavorable July and August weather forecasts used in the models, these yield and production expectations exceed those of the USDA's World Agricultural Outlook Board.

[Text from file received from the University of Illinois College of Agricultural, Consumer and Environmental Sciences]


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