NEW YORK -- Back in January, economists were calling food and energy expensive. They didn't know what expensive was.

The surge in food and energy prices has been a boon to many banks and hedge funds who have used commodities trading to turn a profit during the worst credit crisis in decades. But fortunes made on the trading floors of New York, Chicago and London have meant food riots in Africa, Asia and the West Indies.

On Monday, the last day of the quarter, corn prices retreated from record levels after the government said Midwest farmers planted more corn than expected to make up for crops lost to flooding. Soybean prices, however, pushed further into uncharted terrain after the crop report showed that farmers planted fewer soybeans than the market anticipated.

Corn for December delivery fell 30 cents Monday to finish at $7.57 a bushel on the Chicago Board of Trade, after reaching a record $7.96 in trading on Friday. Soybeans for November delivery gained 14.5 cents to close at $15.74 a bushel, after rising as high as $15.77 during trading. The contract briefly hit a record $15.79 a bushel on Friday.

Prices have been driven higher lately by the weather. Heavy downpours have damaged key growing regions in states such as Iowa, Illinois and Indiana, giving investors reason to pour money into commodities.

The soaring price of commodities is not a pure supply-and-demand story, however.

Due to the weakening U.S. economy and tight credit climate, the Dow Jones industrial average has tumbled to its lowest level since the fall of 2006. Meanwhile, the dollar continues to lose value versus the euro, pound, and other currencies.

As a result, traders have found commodities a lucrative place to invest their money. Commodities are priced in dollars, so they are seen as a hedge against the falling U.S. currency. Meanwhile, investors have been hesitant about fleeing to Treasury bonds -- the more typical safe-haven during a shaky economy -- due to worries about inflation devaluing the government securities over time.

Monday's trading had more to do with the size of this year's crops. The U.S. Department of Agriculture said Monday that farmers expect to harvest 78.9 million acres of corn, down 8.7 percent from last year. But the number of acres planted with corn, 87.3 million, came in higher than the 86 million acres that farmers forecast back in March.

"We've having some losses, but they're losses off of a higher planted area than people expected," said Jerry Norton, a corn analyst for the USDA. He added that the amount of corn in stock, 4.03 billion bushels, was a bit better than anticipated as well.

Still, the USDA report estimated that farmers planted 74.5 million acres with soybeans -- a lower figure than the March forecast. That shortfall sent soybeans higher.

Corn and soybean supplies -- and, in turn, their prices -- are going to depend heavily on the weather, which appears to be getting warmer and drier.

"The crop's in kind of a fragile state," said Jason Ward, an analyst with Northstar Commodity in Minneapolis, referring to both corn and soybeans. "It can't be too hot and too dry, but it can't be wet and cool, either. They have to walk this tightrope to harvest. But today, that looks like the forecast."

Wheat prices sank Monday on the CBOT along with corn. The September wheat contract fell 53.25 cents to $8.5875 a bushel.

Ideal weather could help pull grains prices back down. But there's another factor that will need to improve, too: the U.S. dollar. The dollar remains weak against the euro, after falling about 10 percent against the 15-nation currency in 2007. So far this year, the euro has gained more than 7 percent on the U.S. currency.

The dollar has also been stoking the rise in energy prices.

On the New York Mercantile Exchange Monday, crude oil hit an all-time high above $143 a barrel before pulling back to settle down 21 cents at $140.00 a barrel. On Friday, crude had settled at a record $140.21.

Gasoline ended up 0.03 cent at $3.5015 a gallon; heating oil finished down 0.37 cent at $3.9029 a gallon; and natural gas closed flat at $11.805 per 1,000 cubic feet.

Precious metals declined Monday on the Nymex. Gold for August delivery fell $3.00 to $928.30 an ounce; July silver fell 20 cents to $17.42 an ounce; and July copper rose 0.45 cent to $3.8825 a pound.

But gold has risen about 11 percent from its price at the start of the year; silver has gained nearly 17 percent; and copper has increased about 28 percent.