Nitrogen fertilizer use in China - Contributions to food production, impacts on the environment and best management strategies

China is a big country with a huge population and limited farmland area per capita. To produce enough food for feeding the population is of vital importance for the county. A huge achievement in food production since 1949 has been made. The regression analysis in each period of 10 years shows that there is a significant positive linear correlation between the annual food production and annual chemical fertilizer N (CF-N) consumption throughout 1949-1998. However, the regression coefficient, b, in each period of 10 years since 1949 has been declining rapidly. Meanwhile, environmental pollution is becoming a serious issue. In last 20 years, N concentratjons in surface and ground water have been increasing, 'Alga blooms' in lakes and 'red tides' in estuaries occur frequently, and the emissions of N2O and NH3 from farmlands rise. This paper reviews the causes for the declining N efficiency and rising environmental impacts, and the strategies for better fertilizer management.