引言世界上有许多地方氮素往往是粮食生产中的限制因子。大多数亚洲国家化学肥料供应不足而仰赖从他国进口,他们和发达国家相比施肥量很低。其粮食生产中的氮源主要依靠土壤的天然肥力。这些国家要获得粮食高产必须提高肥效。最近的能源危机以及随之而来的肥料不足更有强调经济施肥的必要。某些发展中国家由于关切到环境污染问题,因 Introduction Nitrogen in many parts of the world is often a limiting factor in food production. Most Asian countries rely on insufficient supply of chemical fertilizers to import from other countries, and they have a very low level of fertilizer application compared to developed countries. The nitrogen source in food production relies mainly on the natural fertility of the soil. In order for these countries to obtain high yields of grain, they must improve their efficiency. The recent energy crisis and the ensuing lack of fertilizer underscore the need for economic fertilization. Some developing countries are concerned about environmental pollution due to