Nitrogen content and C/N ratio in straw are the key to affect biological nitrogen fixation in a paddy field

Straw amendment can increase nitrogen fixation in paddy field, however, the efficiency of carbon sources with different biochemical properties to enhance N2 and activity is still unclear. A 15N2-labelling system was used field environment determine biological (BNF) under addition three kinds straw. The nifH gene (DNA) RNA (cDNA) soil were amplified by real-time fluorescent quantitative PCR. diversity community composition fixing microorganisms studied high-throughput sequencing. study expected reveal how impact its mechanism system. Results showed that absolute abundance diazotrophs treatment mature stage wheat straw (MWS) 4.88 times as high CK treatment, but jointing (JWS) poplar branch (PB) did not induce any significant changes. had no on cyanobacteria abundance. proportion increased MWS 2.07 times, which much lower than heterotrophic diazotrophs, leading a decrease diazotrophic activity. Mature biologically fixed increasing number bacteria. results indicated system, straws low content C/N ratio recommended.