Biochar application affects Nitrobacter rather than Nitrospira in plastic greenhouse vegetable soil

Abstract

Nitrite oxidation, driven by nitrite-oxidizing bacteria, is an important step of nitrification and thus plays a vital role in biogeochemical nitrogen cycling in agricultural ecosystems. Although biochar has been widely recognized as a promising material for use in vegetable fields to slowly release nutrients, the current understanding of how nitrite oxidizers respond to the application of biochar in a plastic greenhouse vegetable field is very limited. A soil incubation experiment showed that soil nitrite oxidation was increased by 13.0%, 35.0% and 64.2% (P < 0.05) with the application of 0.5% (C0.5), 1.5% (C1.5), and 4.0% (C4.0) biochar (mass ratio), respectively. Methods including qPCR and Illumina MiSeq sequencing were also used to explore the impact of biochar on functional communities involved in nitrite oxidation. Nitrobacter and Nitrospira were the main genera of the nitrite-oxidizing bacteria and were assumed to be very important in the soil environment. Moreover, the increases in soil nitrite oxidation were positively correlated with the abundance of Nitrobacter-like NOB (P < 0.05) but not the Nitrospira-like NOB gene abundance. Furthermore, biochar application combined with nitrogen fertilizer had a significant effect on the Nitrobacter community composition, with lineages such as Nitrobacter alkalicus and Nitrobacter vulgaris being significantly enriched. Redundancy analysis indicated that the observed variations in the Nitrobacter community structure were associated with changes in soil microbial biomass nitrogen and nitrate nitrogen induced by biochar. These results implied that Nitrobacter rather than Nitrospira was significantly improved by biochar added to the soil for vegetable production.