Chicago Board of Trade (CBOT) grains futures closed moderately lower on Tuesday as investors awaited a key monthly supply and demand report.

The most active corn contract for December delivery fell 0.25 cent, or 0.07 percent, to 3.4925 dollars per bushel. December wheat delivery went down 0.75 cent, or 0.17 percent, to 4.3525 dollars per bushel. November soybeans lost 0.75 cent, or 0.08 percent, to settle at 9.66 dollars per bushel.

CBOT floor brokers reported that funds bought 2,000 contracts of corn, 1,200 contracts of wheat and 3,100 contracts of soybeans.

The U.S. Department of Agriculture (USDA) is expected to release its monthly supply and demand report on Thursday, so many investors are poised to wait and see before they take on big new positions.

"A lot of traders believe that USDA might go slightly higher with their yield number this month," said Joe Vaclavik with Standard Grain.