The U.S. Agriculture Department raised its already record-high forecast for U.S. corn and soybean harvests on Wednesday, with gains keyed by increased yield estimates in major production states such as Iowa, Minnesota and Ohio.

The bumper harvest will leave a larger-than-expected stockpile of both commodities even with increased usage forecasts, the government said in its monthly supply and demand and production reports.

"This tells us that the corn and soybean markets are not going to run out of supplies any time soon," said Brian Hoops, analyst at Midwest Marketing Solutions. "I don't think we should expect any sustained, meaningful rallies."

Corn and soybean futures fell to session lows after the report was released, with corn hitting its lowest since Oct. 13.

USDA pegged U.S. corn production for the 2016/17 marketing year at 15.226 billion bushels, based on an average yield of 175.3 bushels per acre, up from its October outlook of a 15.057 billion bushel harvest and an average yield of 173.4 bushels per acre.

Analysts had been expecting corn production of 15.041 billion bushels and a yield of 173.2 bushels per acre, based on the average of forecasts in a Reuters survey. The USDA's yield and production view matched the high end of the range of analysts' forecasts.

For soybeans, USDA said the crop would be 4.361 billion bushels, 92 million higher than its October outlook. The government's soy yield view was raised to 52.5 bushels per acre from 51.4.

In Iowa, the top corn production state and the second biggest for soybeans, USDA raised the average soybean yield to 59.0 bushels per acre from 58.0. The Iowa corn yield view also was raised by 1 bushel per acre to 199.0

USDA unexpectedly raised its 2016/17 corn ending stocks outlook to 2.403 billion bushels, which would be the fifth biggest ever, from 2.320 billion.

USDA raised its soybean ending stocks forecast to 480 million bushels, 60 million bushels higher than the average of analysts' estimates and up from its October estimate of 395 million bushels. If realized, soybean ending stocks would be the third biggest on record.

On the demand front, USDA raised its soy usage outlook by just 7 million bushels, with a 20 million bushel cut to crushings largely mitigating 25 million bushels of increased exports.

The government also boosted its wheat ending stocks outlook by 5 million bushels to 1.143 billion, in line with market forecasts.