(Updates with markets closing, quotes, details)

By Lucas Bergman

GUALEGUAYCHU, Argentina, May 8 (Reuters) - Thousands of farmers lined Argentina's highways on Thursday in fresh protests to disrupt key grains exports and pressure the government to cut agricultural taxes.

Farmers launched the eight-day strike after breaking off weeks of talks with the government, complaining that President Cristina Fernandez had refused to modify a new system of export taxes that triggered a three-week strike in March.

"They wanted to trample all over us, but they couldn't do it," said Alfredo De Angeli, a farm leader in Entre Rios province who became well-known for his fiery speeches during the first strike.

The Entre Rios town of Gualeguaychu, some 125 miles (200 km) from Buenos Aires, has become the focus of farm protests. Argentina is one of the world's top suppliers of corn, wheat and soy, and the protests have pushed up soy prices on world markets.

Argentina's peso currency <ARSB=> slipped as investors concerned over a prolonged conflict sought refuge in dollars, and the local currency is now languishing close to a five-year low. Bonds and stocks were also jittery.

Traders at Argentina's main grains market in Rosario said they had no orders. Farmers plan to hold back products from soy crushers and exporters through May 15.

But they have ruled out a repeat of the roadblocks that caused food shortages during March's strike, when the government accused them of trying to hurt ordinary Argentines.