UPDATE 2-Argentine grain sales strike may slow much-needed corn exports
* Grains truck inflow to Argentine ports falls dramatically
* Government hungry for revenue ahead of October elections
* Farmers threaten more strikes if demands not addressed
(Adds quote from farm group leader)
BUENOS AIRES, June 17 (Reuters) - The number of grain trucks entering Argentina's main shipping hub of Rosario dropped sharply on Monday as farmers protested government policies by refusing to sell recently harvested corn and soybeans.
Argentina is the world's No. 3 exporter of both crops at a time of high demand. Growers began a five-day sales ban on Saturday over high taxes and export curbs that they say hurt profits while 25 percent inflation jacks up production costs.
The protest threatened to slow the loading of cargo ships waiting along the Parana and La Plata rivers for corn needed to replenish global reserves left thin by last year's poor U.S. harvest. With grain markets closed on weekends, Monday was the first day that the strike was felt.
The Rosario grains exchange said 553 trucks entered port by mid-morning on Monday, compared with 3,561 during the same time frame a week earlier.
The strike will continue until Wednesday at midnight. But growers said more and longer protests might be needed to pressure the government into negotiating policy changes. Farm sector leaders are set to meet June 25 to decide what is next.
"We have embarked on a strategy of protest and struggle," said Ruben Ferrero, head of the Argentine Rural Confederation, known by its Spanish initials CRA. "If we don't get any response, that strategy will surely continue."
Global importers' reliance on South American corn and soybeans has increased in 2013 because U.S. stocks of both commodities are the tightest in years due to late planting.
Argentina's port-side corn stocks are also thin after farmers interrupted that harvest to bring in soy, the country's main agricultural export. Before the protest was called, growers had planned to harvest and sell a good amount of corn this week.
So far, farmers have brought in 80 percent of their 2012/13 corn and 99 percent of their soybeans.
The agriculture ministry expects the country to harvest 25.7 million tonnes corn and 50.6 million of soybeans this season.
Argentina's four main farm groups called the strike. The sector has long been at odds with President Cristina Fernandez, who was re-elected in 2011 on promises of increasing the state's role in the economy.
Agriculture Minister Norberto Yauhar accused the leaders of the four growers' organizations of misrepresenting their base. He said they were trying to "generate distress" ahead of October midterm elections that will determine Fernandez's clout in Congress during the last two years of her second term.
Her government puts a 35 percent tax on soybean exports and curbs overseas shipments of corn and wheat to ensure ample domestic food supplies. Growers say the curbs reduce profits by cutting competition among the exporters who bid for the crops.
"We have a government that is deaf and that regards the farm sector as its enemy," Alfredo de Angel, a congressional candidate and a leader of the Argentine Agrarian Federation for Entre Rios province, told local radio on Monday.
Argentina has been locked out of the international capital markets since its 2002 sovereign debt default, and confidence has been further damaged by trade and foreign exchange controls.
With investment falling and state spending rising ahead of the October elections, the government needs farm tax revenue.
Central bank reserves, which the government uses to pay its debts, have fallen 10 percent so far this year to $38.6 billion.
(Additinoal reporting by Nicolas Misculin; Editing by Lisa Von Ahn)