The March contract for soybeans ended at $14.525 a bushel, down 34.25 cents or 2.3 percent.
Higher production estimates for the South American crop, which is just beginning to be harvested, were a main factor behind the decline, said Brandon Marshall, a commodity adviser with Northstar Commodity in Minneapolis.
"They're looking for a pretty sizable crop out of Brazil," Marshall said. "That's a reason we're going to be down, because production is going to be higher than people thought."
With about 10 percent of the crop harvested, yields are coming in higher than previously expected, Marshall said. That's leading traders to anticipate that big consumers of soybeans like China may pick up more beans from South American producers instead of buying beans grown in the U.S.
In metals trading, April gold fell $4.40 to $1,666.90 an ounce. Silver for March delivery rose 3.8 cents to $31.441 an ounce. Platinum for April delivery fell $7.60 to $1,714.70 an ounce. March copper rose 3.25 cents to $3.7595 a pound and March palladium rose $1.05 to $751.50 an ounce.
Benchmark crude for March delivery fell 11 cents to finish at $95.72 per barrel on the New York Mercantile Exchange. It rose as high as $96.57 in the morning.
In other energy trading, wholesale gasoline rose 5.89 cents to finish at $3.0588 a gallon, natural gas fell 1.3 cents to end at $3.272 per 1,000 cubic feet, and heating oil gained 3.89 cents to finish at $3.2384 a gallon.