China's promise to allow 600 million farmers to trade land could enable vast numbers to find a better life, but Lu Jinliang's experience shows the challenges of implementing reform, including entrenched local government interests.

Two years ago, he rented out a small patch of fallow land to a neighbour in Gangzhong village to raise pigs, with the 480 yuan ($79) annual income supplementing his salary from working in a sweater factory.

But local authorities invalidated the arrangement for Lu and 25 other families in July, saying pig sties were not allowed on the land even though it was earmarked for "agriculture".

They demolished six pig pens and accused the man who rented the terrain of "illegal use of farmland" -- which carries a potential jail term.

In a groundbreaking reform pledge just announced by China's ruling Communist Party, farmers are to be granted legal basis to transfer and rent land, which is ultimately owned by the state.

Rural residents will be able to buy and sell so-called "land use rights", giving farmers the same rights as urban dwellers.

"Efforts must be made to allow farmers to participate in China's modernisation," the ruling Communist Party said in a document issued on November 15, after a key meeting known as the Third Plenum.

"Farmers will be given more property rights."

But the Gangzhong case shows the challenges in implementing the policy across the vast country and the power of local officials over land.

The man who rented the land, Lu Longfei, is effectively carrying out government policy by building large scale agriculture and helping farmers transform land into a commodity, but implementation of the reform faces opposition from local governments, who reap big gains from the current situation.

At present farmers can "collectively" own land, but local officials have the power to appropriate it with little or no compensation, then sell it to property developers for massive profits.

"The new policy hasn't come to us," said Lu Jinliang. "Zhongnanhai is far from here," he added, referring to the centre of power where Chinese leaders work in Beijing.

The party's Third Plenum meeting also said rural residents will have their rights to social services in the cities improved, another incentive to move.

Analysts said the measures will boost incomes in impoverished rural areas and encourage millions of farmers to leave the land, as China encourages greater urbanisation to raise living standards and tackle a yawning wealth gap.

"This revolutionary change will undermine local governments' monopoly over land markets and boost farmers' income, providing them with the start-up capital to settle in the city," said Yao Wei, China economist for Societe Generale.

But Zhu Qizhen, director of a research institute addressing farmers' issues at the China Agricultural University, warned: "Local governments won't easily give up their own interests."

"It will depend on the authority of the central authorities and whether the measures to carry forward this mechanism are forceful enough," he said.

Gangzhong, in the eastern province of Zhejiang near Shanghai, is dotted with barns for pigs interlaced by yellowing stalks of rice, with farmers using small combines to harvest the grain.

Lu Longfei, who signed 18-year contracts to rent a total of two hectares (five acres), believes he is being unfairly singled out.

"I want justice and I want fairness," said Lu, a third-generation pig farmer.

Gesturing to other barns for raising pigs in the area, he said some were doing the same thing but had avoided scrutiny by authorities.

"They have political connections with the town government," he said, hinting at corruption.

A Communist Party member himself, he returned to the family trade after a four-year stint in the Chinese navy and an unsuccessful career as a small businessman, and thinks farmers should have the freedom to decide how they use their land.

"They all wanted to rent to me," he said. "Elderly people are too tired to farm. Young people are all in the factories."

He vowed to fight the authorities' planned demolition of his remaining six pig pens, with all the determination of a military veteran.

"I'll stand in a pig pen and let them pull it down on me," he said.