Corn is falling on the prospects of a bumper crop.
Farmers planted the most corn in 80 years this year, and favorable weather, compared to last year's drought, has boosted the chances of a good harvest.
Corn fell 4.5 cents, or 1 percent, to $4.49 a bushel. That's the lowest settlement price since Aug. 13.
Wheat and soybean contracts edged higher.
In other commodities trading, most metals fell as traders worried about the outlook for demand from China and the strength of the U.S. economy.
Copper dropped the most. Gold, silver and platinum also declined. Only palladium bucked the trend and rose.
The price of oil slipped below $103 a barrel, as relations between Iran and the U.S. appeared to improve, easing fears of a potential disruption in oil supplies.