* Wet weather so far a net benefit despite some flooding * Argentina is world's No. 1 soyoil, soymeal exporter * Some wheat losses seen due to August-September floods By Hugh Bronstein BUENOS AIRES, Oct 9 (Reuters) - Corn and soy planting in the eastern Argentine province of Entre Rios will be helped by light rains this week while the country's key farm area to the south starts getting the sunshine needed to recover from recent flooding, a forecaster said on Tuesday. The wet start to Argentina's spring planting season has raised hopes for big harvests after dry crop weather in the United States, Russia and Australia sapped food stocks and squeezed global grains prices higher. The South American country is a top exporter of corn, soybeans and derivatives such as soyoil, used to make biofuels, and meal, used as cattle feed as far away as China, whose fast-expanding middle class is acquiring a taste for beef steak. "We are going to see a lot of rainfall - coming to 50 millimeters in some areas - in Entre Rios, Corrientes and parts of Chaco and Misiones provinces," said Jose Luis Aiello, head of the Applied Climatology Consultancy in Buenos Aires province. Entre Rios is part of the Pampas grains belt. Just south of the province is the country's key bread basket region of Buenos Aires, where little rain is expected over the next five days. "This is good news because Buenos Aires has had an excess of water," Aiello said, adding moderate rains should fall throughout Argentina next week. Farmers are expected to sow a record 19.7 million hectares (48.7 million acres) with soybeans in the 2012/13 crop year, up 4.5 percent from the 2011/12 season. The U.S. Department of Agriculture forecasts Argentine soy production in the upcoming season at 55 million tonnes, rising from 41 million tonnes in 2011/12. The flow of grains from the country is of interest to exporters such as Bunge Ltd and Noble Group Ltd , which operate gigantic terminals along the Parana River, leading to the shipping lanes of the South Atlantic. Chicago corn futures are up 14 percent so far this year, while wheat has risen 31 percent and soybeans 29 percent. More than 17 percent of Argentina's 2012/13 corn is already in the ground, according to the Buenos Aires Grains Exchange, and farmers start planting soy this month. Grain markets have meanwhile been shaken by the worst U.S. drought in more than 50 years, which has parched crops in the world's biggest corn producer. With global stocks sliding lower, attention is fixed on No. 2 corn exporter Argentina. "The weather has complicated things in central Buenos Aires," said Martin Fraguio, executive director of Argentine corn industry chamber Maizar. "Some farms were flooded and still have a high water table that inhibits planting." DOUBLE WHEAT WHAMMY Argentine wheat has already been planted and farmers are evaluating damage done by recent floods, particularly in Buenos Aires, which accounts for more than half of Argentine output. Low production was already expected as growers shifted toward soy and other more profitable crops to avoid export curbs on wheat and corn. Corn area is seen holding steady at about 5 million hectares this season thanks to corn's higher profitability, while the Agriculture Ministry estimates wheat area fell 20 percent this season to 3.7 million hectares. "On top of that, it rained too much during all of August and part of September," said farm consultant Sergio Conterjnic, a former head of the ArgenTrigo wheat growers chamber. "The flooding affected the heart of the wheat belt. We know there will be losses but we still do not know how severe they will be," Conterjnic said.