Wheat futures fell sharply Thursday as investors worried about a slowdown in purchases and new supplies coming on the market from Argentina.The actively traded May contract for wheat fell 16.25 cents, or 3 percent, to $5.8925 a bushel.Wheat had been rising over the past several weeks as traders anticipated that transportation problems in Canada would hinder that country's crop from coming to market.Todd Hultman of DTN in Omaha, Neb. said there were signs that purchases from commercial buyers were slowing down as the price of U.S. wheat increased.Traders also worried that a large purchase of wheat from Egypt announced Thursday didn't include any from the U.S., Hultman said. That caused concerns that prices for U.S. wheat had risen too high, making the crop less competitive on world markets.There were also worries about supplies of wheat increasing in global markets after Argentina announced that it would release another 500,000 metric tons of the grain. Hultman said the size of the release was in line with what the market was expecting, however the timing had been uncertain.Other agricultural futures also declined, but not as much. May corn fell 6.5 cents, or 1 percent, to $4.545 a bushel and May soybeans edged down 7 cents, or 0.5 percent, to $13.90 a bushel.Energy futures closed slightly lower.Crude oil for April delivery fell 19 cents to $102.40 a barrel in New York. Natural gas fell 3 cents to $4.51 per 1,000 cubic feet. Weather forecasts suggested that U.S. households won't have to raise the thermostats so much in the second half of March as the cold winter weather eases.Wholesale gasoline slipped 4 cents to $2.76 per gallon and heating oil shed 4 cents to $3.09 per gallon.Metals futures were mostly higher.Gold for April delivery edged up $3.80 to $1,331.80 an ounce and March silver rose 6 cents to $21.31 an ounce. April platinum increased $24.30 to $1,453.40 an ounce and March palladium rose $10.75 to $742.25 an ounce.