(New throughout, updates prices and market activity to close, adds further analyst comment)
By Mark Weinraub
CHICAGO, Aug 15 (Reuters) - U.S. soybean future surged 2.8 percent on Monday to their highest in more than three weeks, supported by strong export demand and a rally in the soyoil market, traders said.
The gains in soybeans pulled corn higher, but wheat closed lower as traders locked in profits from early gains amid ample global stockpiles.
Soybeans notched biggest daily gain in percentage terms since July 12.
"There was a lot of talk of Chinese pricing today and more cargos getting booked, and there just was not much selling in the market," Charlie Sernatinger, global head of grain futures at ED&F Man Capital, said in a note to clients. "As a result, beans moved relentlessly higher during the session."
Soyoil futures rallied 3.4 percent to their highest since April 27 after a monthly National Oilseed Processors Association report showed that supplies were tighter than expected.
The spillover strength, coupled with export hopes allowed the soybean market to shrug off expectations of a record large harvest this fall.
"Despite a record bean yield forecast from U.S. Agriculture Department on Friday, record demand has given us a support area on the charts," CHS Hedging said in a note to clients.
Chicago Board of Trade November soybean futures closed up 27-1/2 cents at $10.09-1/4 a bushel. Prices for the most-active contract hit their highest since July 22.
USDA on Friday boosted its forecast for U.S. soybean exports in the 2015/16 marketing year by 85 million bushels. It also raised its soy export outlook for 2016/17 by 30 million bushels.
The market also was digesting Friday's sale of 258,000 tonnes of new-crop U.S. soybeans to China, the 12th largest soybean sale to be confirmed by the USDA in 13 business days.
CBOT December corn futures were up 4 cents at $3.37 a bushel. The most-active contract hit its highest since July 29.
Technical buying added to the gains in corn. Traders said corn's recovery from a seven-year low on Friday and its higher close to end the week was a bullish signal, indicating that the market had fully accounted for the government's forecast for a record large U.S. crop in the autumn.
CBOT September soft red winter wheat fell 1/2 cent to close at $4.22 a bushel. Technical support for the contract was noted at its 30-day moving average. (Additional reporting by Michael Hogan in Hamburg and Manolo Serapio Jr. in Manila,; Editing by Marguerita Choy and David Gregorio)