[Potential of organic manures nutrient resources and their environmental risk in China]

Based on the data from China Agriculture Yearbook 2006 and other documents, the amounts of crop straws and of the excreta from human, livestock, and poultry in China in 2005 were estimated, with the potential and the environmental risk of their nutrient resources analyzed. In 2005, the total amount of crop straws in this country was 643 million tons, and that of the excreta from human, livestock, and poultry was 4625 million tons. The amounts of N, P2O5, and K2O from the straws and the excreta were 28.24, 12.82, and 29.48 million tons, being 1.08, 0.86, and 4.56 times of the inputs from chemical fertilizers in the same year, respectively. There was a great regional difference in the distribution of the organic manures nutrient resources. The total amount of N, P2O5, and K2O in the excreta was more than 4 million tons in Henan, Shandong, and Sichuan provinces, but less in Beijing, Tianjin, Shanghai, and northwest China, while the total amount of these nutrients in crop straws was more than 1.5 million tons in Henan and Shandong provinces, the main grain production areas, but less in northwest China. The per unit farmland load of N, P2O5, and K2O from the excreta was the highest (787.26 kg x hm(-2)) in Beijing, followed by in Tianjin (515.31 kg x hm(-2)) and Shanghai (505.35 kg x hm(-2)), where the environmental risk could be more serious.