Corn dropped to the lowest in four years as waning prospects for frost damage this week boosted speculation that yields will be bigger than the government forecast in the U.S., the world’s biggest producer.

Farmers will harvest 14.276 billion bushels this year, more than the U.S. Department of Agriculture’s August forecast for a record 14.032 billion, a Bloomberg survey of analysts and traders showed. The USDA will update its crop estimates Sept. 11. Risk of a damaging freeze later this week is “very low,” Commodity Weather Group said in a report today.

“The old adage is that big crops get bigger,” Matthew Bennett, owner of Windsor, Illinois-based Bennett Consulting, said in a telephone interview. “People are not worried about running out of corn, even though demand is pretty solid.”

Corn futures for December delivery fell 1.1 percent to $3.445 a bushel on the Chicago Board of Trade at 10:36 a.m. Prices dropped to $3.43, the lowest for a most-active contract since June 2010.

There is little chance for a damaging hard freeze from cold expected this weekend in far northern Iowa and the Minnesota- Wisconsin border, and “there are no other major frost risks apparent into early October,” Commodity Weather Group in Bethesda, Maryland, said.

The USDA said yesterday that 74 percent of the crop was rated in good or excellent condition as of Sept. 7, unchanged from a week earlier and up from 54 percent at the same time last year, the USDA said yesterday. Yields may be 170.7 bushels an acre, compared with the USDA’s estimate of 167.4, according to the Bloomberg survey.

Soybeans futures for November delivery declined 1.4 percent to $9.9475 a bushel. Earlier, the price touched $9.9225, the lowest since July 30, 2010.

Production in the U.S., the largest grower, will be 3.894 billion bushels, 2 percent bigger than the government estimated last month, the survey showed.

Wheat futures for delivery in December fell 1.5 percent to $5.255 a bushel in Chicago.