China is "very confident" of guaranteeing its bottom line of 120 million hectares of farmland to ensure the nation's food security, Minister of Land and Resources Xu Shaoshi said on Sunday.

"The central government has attached great importance to preserving farmland and local governments have also enhanced their efforts to protect farmland in recent years," Xu said while attending the annual session of the National People's Congress in Beijing.

In 2011, the country restored a total of 300,000 hectares of farmland and developed 4 million hectares of high-quality farmland, according to data from the ministry.

The ministry is optimistic about its plans to develop 27 million hectares of high-quality farmland by the end of 2015, Xu said.

China has achieved increased grain output for eight consecutive years. In 2011, the country's grain output increased 4.5 percent year-on-year to a record of 571 million tons, which already meets the government's 2020 grain output target, according to the National Bureau of Statistics.

But agricultural experts said shrinking natural resources, such as farmland and water, posed severe challenges to maintaining the level of grain output.

Industry data showed that the country's farmland has shrunk by more than 8 million hectares since 1997.

Illegal land use, sanctioned by local governments to construct projects such as golf courses, railways and industrial parks, is an obstacle to the nation's farmland preservation, according to the ministry.

Illegal land use surged 11 percent year-on-year to 16,400 hectares in the first nine months of 2011, the ministry said.

Environmental pollution from the excessive use of agricultural chemicals and the inappropriate disposal of heavy metal has also taken its toll.

Heavy metal pollution has so far damaged approximately 10 percent of the country's farmland and caused the loss of 12 million tons of grain every year, according to research by the Institute of Geographic Sciences and Natural Resources Research at the Chinese Academy of Sciences.

"Efforts to preserve farmland should never be relaxed," said Chen Xiwen, director of the office of the Communist Party of China Central Committee's Leading Group on Rural Work.

China has long insisted that, to ensure national food security, it should produce 90 percent of the grain it consumes. But Ministry of Agriculture data showed that the country imported 10.7 percent of the grain it used in 2011.

"If imports keeps rising, China's national food security will be compromised," Chen said.

The central government this year will allocate 1.2 trillion yuan ($192 billion), an increase of 186.8 billion yuan from last year, to developing the agricultural industry, the country's rural areas and improving farmers' livelihoods, Premier Wen Jiabao said on Monday.

More than 70 percent of China's arable area is low- to middle-yield land. Half of the nation's farmland depends on rain for irrigation, according to the Ministry of Water Resources.

zhousiyu@chinadaily.com.cn