Much of China's agricultural soil is contaminated by pollutants, including arsenic and heavy metals, that pose a threat to the country's food production, experts warn.

Zhou Jianmin, director of the China Soil Association, estimates that 1-10th of China's farmland is contaminated, The Guardian reports. But some estimates range as high as 40 percent and a government assessment isn't likely at least for several years.

"The country, the government and the public should realize how serious the soil pollution is," Zhou said. "More areas are being affected, the degree of contamination is intensifying and the range of toxins is increasing."

Shan Yanhong, a researcher with the Nanjing Institute of Environmental Sciences under the Ministry of Environmental Protection, estimates that about half of the farm land in South China is polluted by heavy metals such as cadmium, arsenic and mercury and also petroleum organic compounds, China Daily newspaper reports.

Huang Hongxiang, a researcher from the Institute of Agricultural Resources and Regional Planning says China needs to focus on more than just production volumes for feeding its population of 1.34 billion people.

"If we don't improve the quality of farmland, but only depend on increasing investment and improving technology, then -- regardless of whatever super rice, super wheat and other super quality crops we come up with -- it will be difficult to guarantee the sustainable development of our nation's agriculture."

Citing an incident in Liuyang in central China's Hunan Province in 2009, in which the land within 1,640-4,000 feet of a chemical plant was polluted by cadmium-containing substances, Pan Genxing a Nanjing Agricultural University professor said that pollutants can stay in the soil for hundreds of years if not properly treated. "Sometimes the damage is irreversible."

Chen Tongbin of the Chinese Academy of Sciences says China's worst soil contamination is caused by arsenic released during the mining of copper and other metals.

"This is the most dangerous chemical. The country's 280,000 mines are most responsible," he told The Guardian.

As part of his research, Chen is studying the use of a Chinese fern -- Pteris vittata --that has a strong capacity to extract arsenic from the soil, to clean polluted farm land in the Guangxi Zhuang autonomous region, state-run news agency Xinhua reports.

Chen's team is also cultivating a dozen more pollution-extracting plants, called "hyper-accumulators," which he says can ensure "soil recovery with lower costs and lower risks of secondary pollution."

China's Ministry of Land and Resources, announced in April that it would invest $9.52 billion to treat 27 million hectares of polluted and less productive farm land by 2015.