China has listed food safety and modernising farms as among key priorities this year, its 2015 rural policy outline showed, as it tackles falling agricultural productivity that has raised concerns about its future food supply.

The "number one document", issued every January and released by state news agency Xinhua on Sunday, showed China will also protect farmland and lend more to farmers to narrow a wealth gap between rural and urban areas.

Attempts to clean up land that has been damaged by heavy metal mining and processing will be widened this year, and "permanent farmland" that is off-limit to industrial and urban development will be created, the document said.

Modern farms will be set up, and regulation of the quality of food and other farm products will be enhanced, it said. On land reforms, aimed at allowing farmers to trade their land to alleviate poverty and create bigger and more efficient farms, the document said the focus is on expanding an experiment that registers land usage rights to cover entire provinces.

Chinese farmers typically hold long-term land use contracts allocated by the government, which allow them to farm the land but not sell it.

China has been struggling to squeeze as much food out of its dwindling, contaminated land as possible as demand increases from ever-expanding urban regions.