ST. LOUIS — U.S. food prices may ease later this year now that farmers have planted the second-largest corn crop in nearly seven decades.

The size of this year’s corn crop will be 92.3 million acres, the U.S. Agriculture Department said today. That’s 9 percent larger than the average annual corn crop over the past decade.

The only crop bigger in the past 67 years was planted in 2007.

Many analysts had worried that wet weather this spring would cut the number of corn acres. But record-high prices are encouraging farmers to use more acres for corn, and fewer for soybeans and wheat.

A greater crop estimate drove corn futures down 30 cents in morning trading, to $6.21 per bushel. That’s the maximum price change allowed by futures exchanges. Corn rose to a record high of $7.99 per bushel earlier this month.

More expensive grain has led to food price increases this year. That could ultimately make everything from beef to cereal to soft drinks more expensive.

For 2011, the USDA predicts food prices will rise 3 percent to 4 percent.

A huge harvest in August could ultimately slow food inflation. It typically takes six months for changes in commodity prices to affect retail food prices.