Demand's in the driver's seat for Thursday's grain trade, and at mid-day, it's driving corn and soybean futures lower.

At mid-day, March corn was 8 1/4 cents lower at $5.93 per bushel, while January soybeans were 13 cents lower at $11.18 1/4. March wheat was the lone grain on the positive site, trading 3 cents higher at $5.98 3/4, according to Barchart.com.

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Lower-than-anticipated export sales released by USDA Thursday morning more than offset bullish sentiment spilling over from the last 2 days of higher trading, traders say. Add to that a favorable crop progress picture in South America, the largest competitor for U.S. soybeans on the world market, and it amounts to a lot of pressure on the grains.

• Read more: Lagging export demand pressures grains