By STEVE ROTHWELLPrecious metals prices are falling as demand for alternative investments decreases. Silver prices fell the most, declining for a fifth straight day. May silver fell 69.60 cents, or 2.5 percent, to $27.248 an ounce Tuesday. The price of the metal has fallen more than 7 percent since the start of the year as U.S. stocks have rallied, pushing the Standard & Poor's 500 index 10.1 percent higher this year. Gold, palladium and platinum also fell Tuesday. Only copper bucked the trend and edged higher. "We are seeing a notable decoupling between commodities and stocks," said Edward Meir an analyst at INTL FCStone. "People are all piling into stocks." Gold for June fell $24.90, or 1.6 percent, to $1,575.90. Platinum for July fell $24.60, or 1.5 percent, to $1,571.80. Palladium for June fell $14.55, or 1.9 percent, to $769.40. In other commodities trading, corn fell for a third day. Corn prices have slumped 13 percent in the three trading days since a U.S. Department of Agriculture report showed that corn inventories were higher than analysts had forecast. The government agency also said the same day that farmers intended to plant the most corn since 1936. "It was a big shock to the market and the market reacted accordingly," said Dan Cekander, a director of grain market analysis at Newedge USA. In other agricultural futures trading, wheat rose and soybeans edged higher. Wheat for May delivery fell 6.75 cents to $6.7075. Soybeans for the same month rose 3.25 cents to $13.94. The price of oil rose slightly Tuesday, as traders waited for the latest data on U.S. supplies. Benchmark oil for May delivery gained 12 cents for finish at $97.19 per barrel on the New York Mercantile Exchange. In other energy trading, wholesale gasoline fell 1 cent to $3.1054. Heating oil rose 1.87 cent to $3.0874 a gallon. Natural gas fell 4.6 cents to $3.969 per 1,000 cubic feet.