Nutrient use efficiency in the food chain of China

Key words: Nitrogen, phosphorus, food chain, food pyramid, food system, food security, food cost, environmental impacts, nutrient cycling, nutrient management Nitrogen (N) and phosphorus (P) fertilizer applications have greatly contributed to the increased global food production during the last decades, but have also contributed to decreasing N and P use efficiencies (NUE and PUE) in the food production - consumption chain, and to increased N and P losses to air and water, with major ecological implications. The aim of this thesis is to increase the quantitative understanding of N and P flows and losses in the food production - consumption chain in China at regional level in the past 30 years and to develop strategies to increase NUE and PUE in the food chain. A novel ‘food chain’ approach and the NUFER model were developed to analyse N and P flows in crop production, animal production, food processing and retail, and households. Data were derived from statistical sources, literature and field surveys. Between 1980 and 2005, NUE and PUE decreased in crop production, increased in the animal production and decreased in the whole food chain. Total N losses to water and atmosphere almost tripled between 1980 (14.3 Tg) and 2005 (42.8 Tg), and P losses to water systems increased from 0.5 to 3.0 Tg. There were significant regional differences in NUE, PUE, and N and P losses; regions with high N and P losses were in Beijing and Tianjin metropolitans, Pearl River Delta, and Yangzi River Delta. Urban expansion is a major driving force for change; total N losses increased 2.9 folds, and P losses increased even 37 folds during the development of Beijing metropolitan, between 1978 and 2008. Scenario analyses indicated that implementation of a package of integrated nutrient management measures, combined with diet changes and increased imports of animal food and feed, are the most effective management options for increasing NUE and PUE, and for decreasing N and P losses. Application of the food chain approach and the NUFER model can help policy makers in China to plan food production - consumption chains, and thereby manage N and P flows in this chain at regional level.