(Recasts, updates with closing prices)
By Mark Weinraub
CHICAGO, April 28 (Reuters) - U.S. corn futures rose 1.9 percent on Thursday, with concerns about crops in South America spurring export demand for U.S. supplies, traders said.
Soybean futures closed lower despite strong exports, with traders locking in profits after prices rallied to their highest since August.
Wheat futures were mixed, with benchmark soft red winter wheat contracts eking out a modest gain while hard red winter wheat and MGEX spring wheat easing on good growing conditions across the U.S. Plains.
Corn rallied for the third time in the fourth session, with the market recovering from overnight weakness on the U.S. Agriculture Department's bullish export report. USDA said that weekly corn export sales topped 2.6 million tonnes, the highest combined old-crop and new-crop total in four years.
"The exports were a big wake-up call," said Mark Schultz, chief analyst at Northstar Commodity Investment Co.
Net soybean sales for the combined marketing years were the largest in more than three months and combined wheat sales were the biggest since last July.
Chicago Board of Trade May corn futures settled up 6-1/4 cents at $3.87 a bushel.
Dry weather in Brazil may reduce the country's winter corn crop by 5 million to 10 million tonnes, Bunge Chief Executive Soren Schroder said.
CBOT May wheat rose 1-1/4 cents to $4.75-1/2 a bushel. K.C. hard red winter wheat futures for May delivery shed 3 cents to $4.61 a bushel while MGEX May spring wheat futures dropped 3-1/2 cents to $5.30 a bushel
CBOT May soybean futures closed down 1 cent at $10.18 a bushel. The front-month contract topped out at $10.36-3/4, its highest since Aug. 11.
A third of Argentina's soy farms remain swamped after early April storms. Analysts estimated crop losses at 5 million tonnes as harvesting starts in areas dry enough to support the 30-tonne combines used to bring in the beans.
"This is increasing demand for U.S. products," said Kaname Gokon at brokerage Okato Shoji in Tokyo. (Additional reporting by Naveen Thukral in Singapore and Nigel Hunt in London; Editing by Susan Fenton, James Dalgleish and Marguerita Choy)