Mechanism of Nitrification Inhibition on N2O Emissions Reduction.

Moso bamboo (Phyllostachys pubescens) is one of the important bamboo species in subtropical China with total area of 4.43 million ha by year 2013. Fertilization area was increasing in recent decade to obtain more economic benefits. However, N fertilization may increase in N₂O emissions. To disclose the mechanism of nitrification inhibition to reduce N₂O emissions, an experiment was conducted in situ. It was composed of 5 treatments: CK, urea, urea with respective dicyandiamide (DCD) and dimethyl-phenyl-piperazinium (DMPP), and commercial slow-release fertilizer with nitrification inhibitor included, N rate was 207 kg N ha^-1 for all treatments except for CK (free fertilizer). The flux of N₂O emissions at 10, 20, and 30 days after fertilization, and content of soil nitrate and ammonium, and the community and functional gene abundance of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were measured at 20 days after fertilization.

A higher (P<0.05) N₂O emission flux were observed in treatments of urea and slow-release fertilizer compared with those of CK and urea with DCD and DMPP during 30 days, and accompany with higher abundance of soil nitrate. Some of AOB species were stimulated by urea only, and most of species were restricted by DMPP and DCD, and AOB with DMPP and DCD presented different community from other treatments. However, AOA communities received less affect by DMPP and DCD. The abundance of AOB functional gene (amoA) was observed highest in urea treatment, and followed by slow-release fertilizer, and urea with DMPP among the lowest but little higher than that of CK. The above evidence implied that nitrification mainly responded N₂O emissions in bamboo forest soil, and DMPP and DCD can inhibit the process of nitrification via restricting the activity of AOB rather than AOA.