By STEVE ROTHWELLNEW YORK (AP) â¿¿ Soybean prices rose sharply after Argentina didn't get rains that had been forecast over the weekend, just as the crop there is nearing harvest. March soybeans rose 45.75 cents to $14.7025 a bushel as markets reopened after the Presidents Day holiday Monday. The gain of 3.2 percent was the biggest in more than a month. Soybeans are rebounding after slumping for the past two weeks on forecasts for a strong harvest in South America. "It's getting toward the finishing stages of the crop and it really needs a good drink of water and it just didn't happen," Darin Newsom, a commodities analyst at DTN, said referring to the Argentinian crop. In other commodities trading, wheat and corn both fell on forecasts that winter storms would bring snow to the Plains region, giving soil there much-needed moisture and improving the outlook for this year's crops. Wheat for March delivery fell 10 cents, or 1.3 percent, to $7.3225 a bushel. March corn dropped 3.5 cents, or 0.5 percent, to $6.9525 a bushel. Trading in metals was mixed. Gold, silver and copper fell while platinum and palladium rose. Copper dropped 2.3 percent, its biggest decline in four months. The March contract lost 8.75 cents to $3.6495 a pound. Analysts attributed the fall to speculation that the Chinese may move to cool the nation's real estate market, curbing demand for the metal. China is one of the world's largest consumers of copper. Gold edged lower, falling $5.30, or 0.3 percent, to $1,604.20 an ounce. March silver fell 42.7 cents, to $29.422. Palladium for March delivery rose $11, or 1.5 percent, to $764.15 an ounce. April platinum rose $19.80, or 1.2 percent, to $1,697. The price of oil rose slightly Tuesday, following stocks and continuing a run-up that began two months ago.