Corn prices fell from a 2-year high on speculation that drier conditions in the U.S. Midwest will speed up harvesting of the country’s biggest crop. Soybeans were little changed after rising to a 15-month peak.

Dry weather the next two weeks will firm muddy soils for heavy farm machinery, T-Storm Weather LLC said today in a report. As of September 19, both the corn and soybean harvests already were running ahead of the average for the previous five years, according to the USDA.

“Harvest weather looks nearly perfect for the next two weeks and that means a lot of corn and soybeans will be reaching the market,” said Gary Rhea, the president of Risk Management Partners in Des Moines, Iowa. “The market expects to see better yields,” after earlier results in the southern and eastern Midwest were below farmer expectations, Rhea said.

Corn futures for December delivery fell 7.25 cents, or 1.4%, to $5.145 a bushel at 10:46 a.m. on the Chicago Board of Trade. The price earlier touched $5.2875, the highest level since September 2008. On Sept. 24, the most-active contract rose 4.5%, the most since June 30 when the government said U.S. farmers planted less than they planned.

Soybean futures for November delivery rose 0.5 cent to $11.265 a bushel the CBOT. Earlier, the commodity climbed to $11.44, the highest price since June 2009. The oilseed, used to make animal feed and cooking oil, advanced 5.3% last week, the biggest gain in 10 months.

Harvest Progress

An estimated 18% of the corn crop was harvested as of Sept. 19, up from the previous five-year average of 10%, the government said last week. About 8% of the soybean crop was in the bin, compared with the average for the prior five years of 6%.

Corn rose to a record $7.9925 on June 27, 2008, and soybeans reached an all-time high of $16.3675 on July 3, 2008.

Recent surges in wheat and corn prices were caused by crop failures, government policy and speculation, the United Nations’ Food and Agriculture Organization said last week. There are no signs of a world food crisis, the agency said.

Corn is the biggest U.S. crop, valued at $48.6 billion in 2009, followed by soybeans at $31.8 billion, government figures show.

To contact the reporter on this story: Jeff Wilson in Chicago at jwilson29@bloomberg.net

To contact the editor responsible for this story: Steve Stroth at sstroth@bloomberg.net.