UPDATE 1-Argentine storms could cut projected corn crop 20 pct

* Corn belt hit by a year's worth of rain since September

* Pampas headed for week of sunshine but worries remain

* Expert puts corn harvest 20 pct below USDA estimate

BUENOS AIRES, Oct 30 (Reuters) - Argentina could lose 20 percent of its projected corn crop and 10 percent of its soy this season as violent storms lash the Pampas, turning prime farmland into unplantable mush, a local expert said on Tuesday. Heavy rains since August have swamped Argentina, the world's No. 3 soybean exporter and No. 2 corn supplier. Topsoils have been flooded in the farm belt, which has just barely recovered from a December-January drought that decimated 2011/12 crops. ``Given all the hail, rain, waterlogging and flooding we've seen, some corn fields will be lost. Others can still be replanted, but with uncertain results,'' said Buenos Aires-based economist and agricultural consultant Manuel Alvarado Ledesma. ``You can expect a drop in corn production of about 20 percent, to 22.4 million tonnes,'' he said. ``There has also been a delay in planting soy, which at this point looks like it will reduce the harvest by 10 percent to 50 million tonnes.'' Consumer nations hope South American breadbaskets Argentina and Brazil will produce enough grain to make up for some of the shortfall in Russia and the United States, where droughts decimated crops and pushed prices sky-high. The U.S. Department of Agriculture expects Argentina to harvest 55 million tonnes of soy and 28 million tonnes of corn in the 2012/13 crop year. Martin Fraguio, who heads local corn industry chamber Maizar, said up to 15 percent of Argentina's corn area might be lost to the rains this year. Still, he said, 2012/13 output will be above the 21 million tonnes produced last season. ``Most of the corn belt has received, from September until today, from 50 percent to 100 percent of the rain they would get in a normal year,'' Fraguio said. ``We should have planted 50 to 70 percent by this point in the season but we are only at 35 to 40 percent,'' he added. ``But I think it is still reasonable to expect 24 to 26 million tonnes of production, or even more.'' The flow of grains from Argentina is important to exporters such as Cargill, Bunge Ltd and Noble Group Ltd , which operate grains terminals along the Parana River, leading to the shipping lanes of the South Atlantic.

Thin global food stocks have pushed Chicago soy futures 28 percent higher this year while corn has risen 14 percent. The most recent wave of excessive rains - lasting from Sunday afternoon to Monday night - was concentrated in key growing areas such as central and northern Buenos Aires province, southern Cordoba and Santa Fe. ``Over the next week, until about Nov. 6, most of the farm belt will get sunshine,'' said Ezequiel Marcuzzi, meteorologist at consultancy Clima Campo. ``A large part of the Pampas is in a very complicated situation due to excess moisture,'' he said. ``If weather conditions don't get back to normal over the months ahead, the window will close and there will probably be crop losses.'' The Rosario grains exchange said 2012/13 soy plantings should rise 3.7 percent compared with last year as widespread rains allow growers to seed in areas that are usually too dry. But, it warned, everything depends on the Pampas getting enough sun over the weeks ahead to allow sowing to advance. ``If there were a dry spell in the coming weeks, that would allow plantings to pick up the pace,'' the exchange said in a report. ``But unfortunately this does not seem to be the most likely scenario in the short term.''

SOARING WHEAT PRICES The flooding has also allowed fungus-based diseases to attack wheat crops already hobbled by scant planting. The Agriculture Ministry says it expects Argentina's upcoming wheat harvest to shrink by 17 percent from last season, as farmers skirt export curbs by shifting to other crops. Chicago wheat prices have soared 31 percent since January. Argentine President Cristina Fernandez has riled farmers by increasing the state's role in Latin America's third-biggest economy, clamping down on access to U.S. dollars and slapping export quotas on wheat and corn. The country, robbed of competitiveness by one of the world's highest inflation rates, has been shut out of the international capital markets since its mammoth 2002 sovereign debt default. But with the United Nations projecting food demand will double by 2050 as the global population heads toward 9 billion, Argentina's farm sector is unlikely to fall off the map of international investment funds looking for growth areas.