Chicago agricultural commodities closed lower Tuesday on harvest and weather report.

The most active corn contract for December delivery fell 5.75 cents, or 1.53 percent, to close at 3.71 U.S. dollars per bushel. Soybean contract for November delivery dropped 12.75 cents, or 1. 15 percent, to close at 10.95 dollars per bushel. The most active wheat contract for September delivery shed 14.75 cents, or 2.76 percent, to close at 5.2 dollars per bushel.

Corn and soybean futures have given back most of Monday's gains as traders followed closely rain forecast. All of the major weather models present better chances for rain in a week to 10-day period with cool temperatures throughout early August. Some producers report that the recent cool temperatures and sunshine has really helped soybean plant growth.

Analysts noted that two or three good rains are needed to finish off the U.S. corn and soybean crops, although soybeans have the highest risk to go down.

Another round of lofty Russian production estimates and weaker Black Sea prices have pushed down U.S. wheat futures to a seasonal low.

The Black Sea free on board (fob) August wheat offered at 236 dollars to 237 dollars per metric ton, down another 1 to 2 dollars per metric ton as supplies continue to flow to port and farmers report much better than expected yields.