Large-scale livestock and poultry farms have become China's largest pollution source among all agricultural pollutants, according to a report published on Wednesday.

The report, from the Rural Development Institute of the Chinese Academy for Social Sciences, said in 2011 large-scale livestock and poultry farms accounted for 45 percent of the nation's chemical oxygen demand, and 25 percent of the nation's ammonia nitrogen production.

Large-scale livestock and poultry farms were identified as key monitoring spots for China's environmental bureaus, along with power stations, cement plants and paper mills.

The report added that in 2011, 570.4 million metric tons of fertilizer had been used in agriculture, up 1.42 million tons compared with 2010. A total of 469 kilograms of fertilizer was used per hectare of farmland, an increase of 12 kilograms compared with 2010.