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一般认为浸水田土壤肥力得以保持是由于自养和异养生物固氮的作用。稻田中生物固氮主要有:兰绿藻、与藻类密切结合的细菌、萍藻共生体、根际异养菌等。为了解固氮微生物固氮活性,前人曾探索过许多测定方法,如经典的凯氏定氮法,~(15)N法,这些虽较准确,但自发现固氮酶可使乙炔还原为乙烯用以测定固氮活性以来,此方法快速、灵敏,它比凯氏法与~(15)N法灵敏度高10~6～10~3倍。它是目前测定固氮活性较好方法。其原理是固氮酶能还原氮为氨,也能还原乙炔为乙烯。
Soil fertility in paddy fields is generally believed to be due to the role of autotrophic and heterotrophic nitrogen fixation. Biological nitrogen fixation in paddy fields are: blue-green algae, and bacteria closely linked to algae, Ping algae symbiont, Rhizosphere heterotrophic bacteria. In order to understand the nitrogen fixation activity of nitrogen fixation microorganisms, many determination methods have been explored before, such as classical Kjeldahl method and ~ (15) N method. Although these are more accurate, self-discovered nitrogenase can reduce acetylene to ethylene Since the determination of nitrogen fixation activity, this method is rapid and sensitive. It is 10 ~ 6 ~ 10 ~ 3 times more sensitive than Kjeldahl and ~ (15) N methods. It is the better method to determine the activity of nitrogen fixation. The principle is that nitrogenase can reduce nitrogen to ammonia, but also reduce acetylene to ethylene.