Lack of crop rotation slowly turns Argentine Pampas into 'sand'

(Reuters) - Argentina's key resource, its agricultural soils, are being depleted by lack of crop rotation as soy farming encroaches on areas once used for corn, wheat and cattle grazing, according to local experts and a government source.

The loss of fertility is a slow-burning threat to crop yields at a time when importers are counting on the world's No. 3 corn and soybean supplier to increase output to help meet the boom in demand expected over the decades ahead.

The geopolitical stakes are high after Arab Spring and other uprisings were sparked in part by high food prices brought on by crop crises over recent years. Argentina is the top exporter of livestock feed to China, where an increasingly demanding middle class has come to expect a high protein diet of beef and pork.

On the Pampas farm belt, the trend toward soy at the expense of corn could rob Argentina of its natural advantage as an agricultural powerhouse in the decades ahead.

The country's farm sector has long feuded with President Cristina Fernandez, who was re-elected in 2011 on promises of increasing state control of Latin America's No. 3 economy.