氮是组成生命的基本元素之一,是农作物的主要营养元素。空氮中百分之八十的成分是氮,但因为它呈氮体状态而不能为作物吸收利用。至今利用空氮中氮来为农业生产服务的途径主要有两条:一是通过微生物、低等生物的新陈代谢活动来固氮,二是通过化学反应的手段,在特殊的温度和压力下,来制造化学氮肥。人们在水田里放养绿萍、 Nitrogen is one of the basic elements of life and is a major nutrient of crops. Eighty percent of the nitrogen in the nitrogen is nitrogen, but can not be absorbed by crops because of its nitrogen status. So far, there are mainly two ways to use nitrogen in nitrogenous space to serve agricultural production. One is to fix nitrogen by the metabolic activities of microorganisms and lower organisms, and the other is to make it under special temperature and pressure by means of chemical reaction Chemical nitrogen fertilizer. People stocking green leaves in the paddy field,