氮是维持动、植物生命最重的元素,它在农业生产中起着极其重要的作用,往往成为世界各国粮食生产的限制因子。目前,全世界每年生产的化学氮肥约为0.5亿吨,仍不能满足农业生产的需要。而全世界通过生物固氮的氮素竟达1.5亿吨,它为化学固氮的3倍。这应当归功于土壤中小小的微生物。迄今所知,固氮微生物有细菌、放线菌和蓝绿藻。 Nitrogen is the most important element in maintaining animals and plants. It plays an extremely important role in agricultural production and often becomes a limiting factor for food production in various countries in the world. At present, about 50 million tons of chemical nitrogen fertilizer is produced each year in the world and it still can not meet the needs of agricultural production. The world nitrogen biological nitrogen fixation reached 150 million tons, which is three times the chemical nitrogen fixation. This should be attributed to the tiny microorganisms in the soil. To date, nitrogen-fixing microorganisms have bacteria, actinomycetes and blue-green algae.