He singled out Hunan province which, with its booming heavy industries, had repeatedly reported much higher levels of cadmium found in rice than permitted by national standards.

Answering a China Daily question on whether the tainted land is still being farmed, Wang said no further planting will be allowed on it, as food safety is a top concern for governments at various levels.

Each year, the central government will earmark several billion yuan to rehabilitate farmland tainted by heavy metals and threatened by the over-draining of underground water, Wang said, without giving details.

"Only rehabilitated farmland that has passed assessment will be used again," he said.

Wu Xiaoqing, vice-minister of environmental protection, said in early December that the number of enterprises engaged in soil restoration accounted for only 3.7 percent of the 8,000 enterprises in the environmental service industry, far below the ratio of companies dealing with water and air pollution control.

Wang Qi, an expert on solid-waste treatment, said, "This is probably because soil pollution requires higher costs, sometimes hundreds of times more than the cost of solving air and water pollution."

Wang said he does not think there are any efficient and quick solutions to soil pollution, as the popular method of using plants to trap heavy metals in the soil usually takes more than a decade to work.

"One of the most practicable plans may be to replace crops with other plants such as trees," said Wang, head of the Institute of Environmental Engineering Technology at the Chinese Research Academy of Environmental Sciences.

Ren Tianzhi, director of the Agro-Environmental Protection Institute under the Ministry of Agriculture, said that in addition to heavy metals from industry, excessive use of pesticides and feed additives also contaminates farmland.

"Scientists are working to select plant varieties resistant to heavy metal pollution, to ensure food safety," he said.

Lawmakers have already deliberated on revisions to the Environmental Protection Law, to address and remedy the soil pollution problem. The law was enacted in 1989.

In October, they proposed an amendment, requiring the State to set up a system covering soil investigation, pollution monitoring, evaluation and rehabilitation.

In addition, the country will legislate the prevention of soil pollution by the end of 2017, according to a plan released in October by the Standing Committee of the National People’s Congress, the top legislature.

A central rural work conference, presided over by President Xi Jinping last week, vowed to improve food safety and improve the environment where agricultural products are grown.

If farmland or water is seriously polluted, such areas should be taken out of use, a statement issued after the conference said.

Jin Zhu contributed to this story.