CHICAGO (Dow Jones)--Chicago Board of Trade corn futures ended mostly flat amid pressure from large crop expectations and short-covering, analysts said.

September corn, which is in delivery, ended up 1 cent at $3.13 1/4 per bushel, and December corn, one of several contracts that settled unchanged, ended at $3.19 1/4. Wednesday was the second straight day the Dec contract ended right at the summer's low close.

Prices had been slightly lower for much of the session, but crawled back to unchanged late. John Kleist, broker/analyst for Allendale, noted that corn's early break stalled even as soybeans continued to make new lows.

He said this may have been a sign of commercial pricing and that it prompted short-covering.

"We may go into consolidation and sideways trade for the next two days because we have a three-day weekend coming up," Kleist added. The market will be closed Monday for Labor Day.

The market is under pressure from expectations of a large crop, which were heightened by a Tuesday estimate from FCStone projecting a corn crop of more than 13 billion bushels. Traders said that weighed on the market Wednesday. Another private firm is expected to release production estimates Thursday.

Jim Riley, analyst for the Linn Group, said in a commentary that there is some talk about yields as high as 165 or 170 bushels per acre, which would shatter the previous record of 160.4 bushels.

The crop would likely need a late frost to reach such heights, analysts said, while bulls are hoping for an early frost that could hurt the late-developing crop.

Although cooler, wet weather is expected after Labor Day in the Midwest, which would keep crop development slow, there's no clear frost threat.

Kleist said that even if a frost does materialize in late September, which could still be considered early, the market's upside potential would be limited.

"It's not like we're on razor-thin supplies," he said.

Traders said volume was low Wednesday. Funds sold an estimated 1,000 contracts. A trader said there has been "continued spec selling on rallies."

CBOT oats futures ended lower Wednesday. September oats ended down 1 3/4 cents at $2.01 1/2 per bushel, and December oats ended down 1 1/2 cents at $2.14.

Ethanol futures were slightly lower. September ethanol ended down $0.005 at $1.600 per gallon, and November ethanol settled down $0.003 at $1.554.

-By Ian Berry, Dow Jones Newswires; 312-341-5778;