Nitrogen Mass Flow in China's Animal Production System and Environmental Implications

• Published in: Journal of environmental quality 2010-09, Vol.39 (5), p.1537-1544
• Main Authors: Wang, Fanghao, Dou, Zhengxia, Ma, Lin, Ma, Wenqi, Sims, J.T, Zhang, Fusuo
• Format: Article
• Language: English
• Subjects: Agricultural land; Animal Husbandry; Animal manures; Animal production; Animal products; animal-based foods; Animals; Beneficial use; Bones; byproducts; Cattle; China; Contamination; Crop residues; Crops; Dairy cattle; dairy farms; Demand; Ecological footprint; Economics; Efficiency; Environment; Environmental impact; excreta; feeds; food-production; geographical variation; groundwater; Groundwater pollution; Industrialized nations; Industry analysis; Magnesium; Manure; Manures; Mass flow; Natural resources; Nitrogen; nonfood animal products; Nutrients; oilseed cakes; small grains; Surface water; Sustainable development; Water pollution; Water quality; Wheat
• ISSN: 0047-2425; 1537-2537; 1537-2537
• DOI: 10.2134/jeq2010.0090

China's economic boom in recent decades has stimulated consumer demand for animal products and consequently, a vast expansion in animal production. From 1978 to 2006, the number of animals increased by 322% for pigs, 209% for poultry, and 2770% for dairy cattle. The objective of the present study was to quantify nitrogen mass flow in China's animal production system at the national scale and to elucidate potential environmental implications. A comprehensive analysis was performed combining statistical records with data from the scientific literature and supplemental survey information. Results indicate that approximately 18 Mt of N flowed through the Chinese animal production system in 2006. Nitrogen input to the system was from various feed materials, including 6.8 Mt (38% of total) from roughage, 4.4 Mt (24%) from byproducts, 2.3 Mt (13%) from cereal grains, and 1.6 Mt (9%) each from crop residues and oilseed cakes, with the remaining N (16%) obtained from other feedstuffs. Nitrogen outputs from the system included edible animal products (2.4 Mt, 13% of total), nonedible animal parts (e.g., bones, skins) (3.8 Mt, 21%), and excreta (12 Mt, 66%). At the national level, the excreta would average 28 Mg (as excreted) and 90 kg N ha-1 of cropland. However, at the provincial level, it varied from 1 Mg ha-1 (5 kg N ha-1) in Qinghai to 97 Mg ha-1 (243 kg N ha-1) in Sichuan. In regions with excreta in the intermediate rate (e.g., Hebei Province, 115 kg N ha-1) or high rate (e.g., Sichuan Province, 243 kg N ha-1), animal manure contributes significantly to nutrients polluting groundwater and/or surface waters. It is crucial for China to develop and implement proper management practices to maximum the beneficial use of the 12 Mt excreta N while minimizing its environmental footprint.