The most active wheat contract for December delivery was down 7.25 cents, or 1.45 percent, to settle at 4.93 U.S. dollars per bushel. December corn declined 14 cents, or 3.55 percent, to 3.8025 dollars per bushel. November soybeans fell 0.25 cent, or 0.03 percent, to 9.235 dollars per bushel.
The U.S. Department of Agriculture (USDA), in its monthly supply and demand report released on Thursday, pegged the U.S. corn yield at 168.4 bushels per acre, compared with 168.2 bushels in September. Analysts were expecting a cut to 167.5 bushels.
Poor export demand and investors' profit taking also pressured the corn market.
The USDA said Thursday that corn export sales totaled 284,400 metric tons for the week ending Oct. 3, below the low end of forecasts that ranged from 500,000 metric tons to 800,000 metric tons.
The losses of corn dragged down soybean futures, which earlier approached a three-month high on lower-than-expected U.S. yield in the report.
The USDA reduced its soybean yield estimate to 46.9 bushels per acre from 47.9 bushels last month. Analysts were expecting 47.3 bushels.