BUENOS AIRES - Argentina's embattled President Cristina Fernandez replaced her powerful cabinet chief on Wednesday after suffering a crushing defeat last week over farm policy.

The shake-up did not satisfy opposition leaders, who called for Fernandez to signal a relaxation of interventionist economic policies by firing hard-liners loyal to her husband and predecessor, ex-President Nestor Kirchner.

"We need the president to govern, not the shadow of her husband," said Gerardo Morales, head of the Radical Civic Union, historically Argentina's main opposition party.

Fernandez has been in office only seven months but her popularity has fallen steeply as she fought with farmers who opposed her decision to increase export taxes on soy, the country's main crop.

The battle grew into Argentina's biggest crisis since an economic meltdown early this decade and Fernandez was under pressure to make changes in her center-left government after a Senate defeat forced her to ditch the tax hikes last week.

The new cabinet chief, Sergio Massa, 36, is mayor of a Buenos Aires suburb and served for four years at the head of the social security administration under Kirchner.

He replaces veteran operator Alberto Fernandez, who wielded enormous influence as cabinet chief for both Kirchner and Fernandez and formed part of their inner circle of key advisors where decisions are concentrated.

"Massa is a modern politician, more of a negotiator, more rational, but we'll have to see (how he manages) because Alberto Fernandez brought together a lot of sectors (of the ruling party)," said political analyst Ricardo Rouvier.

The reshuffle failed to cheer investors and Argentina's stock market ended lower.

CALL FOR MORE CHANGES

Critics said the president should purge Domestic Commerce Secretary Guillermo Moreno and Planning Minister Julio De Vido, who have tried to tame roaring inflation with price controls, export curbs, utility rate freezes and fuel subsidies.

"It wouldn't be a good signal as long as it's the only change at the top level of government," said Leopoldo Olivari, a trader at Bacque brokerage.

However, a close presidential aide ruled out a wider cabinet shake-up and played down the cabinet chief's exit.

"There aren't going to be more changes or reshuffles. There's no reason for there to be," Oscar Parrilli, general secretary to the president, told reporters. "Everything's fine and we're happy because there was consensus over the resignation."

With the economy booming for five straight years, the government has increased state control over parts of the economy while maintaining a budget surplus.

During the long battle with farmers, President Fernandez stood firm in what was seen as a continuation of her husband's uncompromising leadership style.

She spoke passionately at big rallies of bussed-in supporters and attacked the media for siding with farmers, who she said were out to topple her government.

But her strategy failed as farmers, fed up with export curbs and price controls, mobilized hundreds of thousands of anti-government protesters against the tax.

Argentina is one of the world's biggest agriculture producers and half of its exports come from farms. But the country is split on how to distribute windfall profits from high-priced products such as soy.

When she took office, Fernandez could count on the support of 48 of 72 senators but a dozen rebelled against her on the grains and oilseed exports tax that she said would generate funds to fight poverty.

Farmers said the tax would hurt growers, and they caused food shortages and interrupted exports by blocking highways at the height of the crisis.

Agriculture Secretary Javier De Urquiza was the first high-level official to lose his job after the Senate vote.