Effects of PHH and DCD on ammonia-oxidizing bacteria and archaea in Andosols

The effects of the two nitrification inhibitors, Dicyandiamide (DCD) and Phenylhydrazine hydrochloride (PHH), on soil nitrification, and the abundance of AOA and AOB, as well as their community structure, were investigated in a soil microcosm using quantitative PCR and pyrosequencing. The net nitrification rates were markedly increased by the addition of ammonium sulfate but were inhibited by both inhibitors. The inhibitory effect of PHH was greater than that of DCD. The results showed that the growth of AOA and AOB were inhibited more by PHH than by DCD. Moreover, community shift of AOB occurred in the DCD- and PHH-treated samples whereas that of AOA only occurred in the DCD-treated samples.