* Government says farmers planted far less wheat this season * Corn area seen edging down to 4.97 million hectares By Hugh Bronstein BUENOS AIRES, Oct 18 (Reuters) - Argentina's upcoming wheat harvest is expected to shrink 17 percent from last season, the Agriculture Ministry said on Thursday, as farmers skirt government export curbs by shifting to other crops. The forecast drop to 11.5 million tonnes is bad news for consumer nations looking to Argentina to help make up for thin supplies caused by droughts in bread basket producers such as the United States, Russia and Australia. In its monthly crop report, the Argentine ministry stuck by its view that 3.7 million hectares were sown with wheat in the current crop year, down 20 percent from the 2011/12 season. Farmers have shied away from wheat to avoid export limits that do not apply to Argentina's main agricultural export, soy, which will start being planted this month and could be headed for a record year. The country's 2012/13 corn area is seen at 4.97 million hectares, down a touch from 5.00 million hectares in the previous season. The government first revealed its area estimate in a weekly crop report earlier this month. Low global stocks have pushed benchmark Chicago wheat prices 33.4 percent higher this year while soybeans have jumped 28.2 percent and corn 16.6 percent. Argentina is a top world supplier of all three crops at a time of rising global food demand. The flow of grains from Argentina is also 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. The Buenos Aires Grains Exchange forecasts 2012/13 wheat production at 10.12 million tonnes, down 28 percent from last season. The U.S. Department of Agriculture estimates Argentine wheat output of 11.50 million tonnes this crop year. Nearly a third of Argentina's 2012/13 corn area has been planted so far, the monthly report said. "Growing conditions are excellent except for areas with excess moisture, where the lack of firm topsoil has slowed planting," it added. Also on Thursday the grains exchange said 2012/13 corn sowing lags the previous season's tempo by 11 percentage points, although progress of 6.9 percentage points was made over the last week, the report said. But the storms that bogged down sowing earlier this week gave way by Thursday to sunshine that is expected to last for several days, helping farmers drain soaked fields and prepare for soy plantings in the weeks ahead. The grains exchange expects 3.4 million hectares of commercial-use corn to be planted this season, more than one million hectares of which is already in the ground. Some early-planted corn fields in low-lying parts of Entre Rios and Buenos Aires province have been flooded, increasing the risk of poor yields, the exchange report added. Argentina's 2012/13 wheat, which was planted earlier this year and has started to be gathered in some regions, has largely benefited from the wet weather, according to the exchange. "La Pampa and Cordoba provinces have enjoyed optimal moisture conditions, raising the possibility of high yields," it said, warning farmers to beware of moisture-related crop damage that could be caused if the heavy showers continue. "Despite this risk, southeastern and southwestern Buenos Aires province, where 40 percent of Argentina's wheat is planted, have been spared any significant flood damage so far," the exchange said.