With farmers moving to cities amid fast urbanization, China has 7.6 million hectares of idle land that could be used as farmland and land for construction, a study has found.

"One-fourth to one-third of land in traditional agricultural regions is not in use, being occupied by empty houses and abandoned farmland," said Liu Yansui, author of the report and a researcher with the Institute of Geographic Sciences and Natural Resources Research under the Chinese Academy of Sciences.

The number of rural residents could fall to 280 million by 2020, from 300 million now, according to the report issued on Monday.

Jiang Daguang has been renting out his 10-plus hectares of farmland since he moved to Shenyang in Northeast China's Liaoning province.

He said that is the trend in his village.

"Ninety percent of young and middle-age people in my village have left for more decent lives. Even if we only earn half the money we earned from farming, being a waiter or something like that, we just prefer city life," Jiang said.

Other farmers simply abandon their land.

According to the report, 16.5 million hectares of land have been allocated to farmers as residential land, which can be used by farmers to build houses, but they are not allowed to transfer it to others if they move.

"Most villagers would return the land if they could receive compensation," said Liu Weidong, a researcher from the institute.

In a pilot project being carried out in Chongqing, villagers can trade their residential land after reclamation, Liu said.

Survey results in East China's Shandong province show that about 90 percent of villagers think abandoned residential land is a waste of resources, while nearly 60 percent said they would be willing to return the land if they were adequately compensated.

Reusing the idle land will help boost the amount of arable land, as China has tried to make sure it has at least 120 million hectares of arable land to feed its population of 1.37 billion.

In August, the country had less than 121.7 million hectares of arable land, according to the Ministry of Land and Resources.

However, Li Maosong, director of the Chinese Academy of Agricultural Sciences' agriculture information office, said it is likely that most of the idle land in rural areas will be developed for construction, instead of being used as farmland.

"More farmers now shun agricultural life for more money in the cities. Therefore, it is impossible to develop much of the idle land for agricultural production," he said.

Idle land not far from the cities is good for construction, such as commercial residential housing and shopping centers, he said.

"Meanwhile, government authorities should leave sufficient idle land to local villagers for improving their living conditions, such as beautifying the environment and providing leisure venues," he said.