Abstract: 【Objective】Nitrogen is essential to human life, environment quality and ecosystem sustainability; Chemical fertilizer is becoming a dominant source of human’s nitrogen supply, therefore, its role and development strategy are core issues for China’s sustainability. 【Method】This study analyzed the sources of nitrogen in ecosystem, its contribution to crop production and protein production, and nitrogen balance through food chain model. Finally, This study drafted a strategy for nitrogen fertilizer development from fertilizer production to field consumption. 【Result】After half a century development, China’s nitrogen fertilizer production and consumption have both ranked the first in the world since 1991, and in the past two decades (1990-2009) 61% of the world’s increase of nitrogen production and 52% of the world’s increase of nitrogen consumption occurred in China. Results of this study show that 72% of nitrogen in terrestrial ecosystem, and about 56% of human protein consumption come from nitrogen fertilizer. According to its role in crop yield improvement, a kilogram of nitrogen fertilizer is equivalent to 0.016 hm2 cultivated land, and per capita cultivated land area increased by 6.5-fold through technologies innovation including N fertilizer between 1960 and 2009. This is why China survived 20% of world’s population by using 10% of world’s land and 21% of world’s irrigated area. Currently, China’s nitrogen fertilizer production exceeds its consumption, and nitrogen fertilizer application rate exceeds crop demand for maximum yield. The nitrogen surplus in agro-ecosystem is more than 175 kg•hm-2, which has been a main factor of environmental pollution. 【Conclusion】Therefore, nitrogen fertilizer management has to be transformed from solely high yield to both high yield and high resources use efficiency. The strategy is to balance nitrogen input and output in crop land, to update fertilizer products, to improve energy use efficiency in fertilizer production.

Key words: nitrogen , contribution , challenge