More than 10% of China's farm land is polluted, posing a "severe threat" to the nation's food production, state media reports.
Farmers' livelihoods are on the line
Arable land shrank by nearly 307,000 hectares (760,000 acres) in the first 10 months of 2006, government officials were quoted as saying.
Excessive fertiliser use, polluted water, heavy metals and solid wastes are to blame, the reports said.
Rapid economic growth has had a damaging impact on China's environment.
Its cities, countryside, waterways and coastlines are among the most polluted in the world.
The Ministry of Land and Resources said agricultural land in China fell to 121.8 million hectares (300 million acres) by the end of October 2006 - a loss of 306,800 hectares since the start of the year.
Heavy metals alone contaminate 12m tonnes of grain each year, causing annual losses of 20bn yuan ($2.6bn), China's Xinhua news agency quoted the ministry as saying.
Land and Resources Minister Sun Wensheng said agricultural land in China must not be allowed to fall below 120 million hectares.
"This is not only related to social and economic development, but is also vital to the long-term interests of the country," he was quoted as saying.
China's government has promised to spend heavily to clean up the country's heavily polluted environment.
But clean-up efforts are often thwarted by lax enforcement of laws and administrative activity at a local level, correspondents say.