Chicago Board of Trade (CBOT) grains futures closed lower on Monday as funds increased short positions in corn, wheat and soybeans.

The most active corn contract for December delivery fell 2.5 cents, or 0.71 percent, to 3.51 dollars per bushel. December wheat delivery slid 7.25 cents, or 1.67 percent to 4.28 dollars per bushel. November soybeans went down 3.25 cents,or 0.34 percent, to 9.4125 dollars per bushel.

CBOT brokers reported that funds sold 4,500 contracts of corn, 3,600 contracts of wheat, and 2,300 contracts of soybeans.

Russian wheat yields continue to be impressive, with some traders now expecting a crop of 90 million metric tons this year. With already redundant supplies at world wheat market, the Russian factor put further pressure on the wheat futures.

The massive flooding across southeastern Texas has pushed up the prices of unleaded gasoline and diesel as key US refineries are expected to be shuttered for weeks.

Reduced U.S. refining capacity will impact ethanol demand, but the degree is uncertain. Traders are now following the situation closely, which they think will influence the prices of corn futures.