Ample supplies of corn and soybeans in hand and bills coming due for farmers, future price rallies also are likely to be followed by an uptick in selling. March corn dropped 5 3/4 cents, or 1.5%, to $3.83 3/4 a bushel. March soybean futures sank 12 cents, or 1.2%, to $9.95 3/4 a bushel.