Soybean prices stayed aloft, bolstered by the second round of U.S. soybean sales to China this week. But corn and wheat prices fell slightly. January soybeans closed up 1 ¼ cents at $10.49. December corn edged down ½ cent at $3.50 ½, while CBOT December wheat slid 3 1/5 cents to $3.86 1/5.