Metals, agricultural products and energy prices fell broadly on Monday.
Wheat fell the most among crop futures. The September contract fell 15.25 cents to settle at $6.4525 a bushel.
December corn gave up 3.25 cents to $4.6050 a bushel.
Jason Ward, a commodity analyst at Northstar Commodity in Minneapolis, said corn prices have been slumping after weather conditions turned out to be "near-ideal" in July, a sharp contrast to the severe drought conditions last year.
November soybeans fell 1.75 cents to $11.8325 a bushel.
Metals prices also fell. Silver fell more than other metals.
Gold for December delivery fell $8.10 to $1,302.40 an ounce. September silver fell 19.20 cents to $19.72 an ounce.
Copper, platinum and palladium also fell.
September copper fell 0.45 cents to $3.168 a pound, October platinum fell $3.40 to $1,448.10 an ounce and September palladium fell $5.50 to $735.20 an ounce.
Energy prices ended lower.
Crude oil for September delivery fell 38 cents to close at $106.56 on the New York Mercantile Exchange.
In other energy trading, heating oil fell 2 cents to $3.05 a gallon, natural gas fell 3 cents to $3.32 per 1,000 cubic feet and wholesale gasoline fell 4 cents to $2.95 a gallon.