Chicago Board of Trade corn futures ended lower Friday, succumbing to general weakness in the commodity sector.

December corn ended down 7 cents to $3.33 1/2 per bushel and March corn ended down 6 3/4 cents to $3.46 1/2.

Corn was led lower by soybeans, which fell sharply, traders said. Crude oil also weighed, and wheat posted losses as well.

"We've got a definite flow out of all commodities at this point," says Arlan Suderman, analyst for Farm Futures.

But bears say that given the market's poor supply fundamentals, they are surprised that corn has not fallen harder. One trader said that he expects a large crop in the field will eventually prevail over the market and push it another leg lower.

The December contract lost 1/2 cent on the week,

"The inability to go up or down is the hallmark of the corn market the last couple weeks," said Dave Marshall, an independent broker/advisor from Nashville, Ill.

While some are concerned about wet weather delaying the harvest, others are focused on the size of the crop, which many expect to top 13 billion bushels.

That was underscored by estimates released by private analytical firm Informa Economics Friday afternoon, traders said. Informa projected the USDA will peg this year's corn crop at 13.127 billion bushels, with a yield of 164.7 bushels per acre, when it releases new estimates Oct. 9. Both numbers would be up from September estimates.

The market did not react to the numbers, however, which to Suderman indicated a large crop is priced in.

"Traders have been fearing a much bigger crop," Suderman said. "So the Informa numbers just kind of fit right in there."

Suderman added that a break in soybeans prompted technical selling and spilled over into corn, which also hit some sell stops.

The trade continues to watch the weather, but many say that at this point, a cold snap and a frost would not have a significant impact on the crop.

Funds sold an estimated 3,000 contracts Friday.

CBOT oats futures ended lower. December oats ended down 3 1/2 cents to $2.20 1/2 per bushel and March oats ended down 3 1/2 cents to $2.34.

Ethanol futures were higher. October ethanol ended up $0.045 to $1.876 per gallon and November ethanol climbed $0.040 to $1.748.

-By Ian Berry, Dow Jones Newswires; 312-341-5778; ian.berry@dowjones.com