Responses of nitrification and bacterial community in three size aggregates of paddy soil to both of initial fertility and biochar addition

Abstract

Biochar has been suggested to increase the soil nutrient retention capacity. The interaction of biochar addition and soil initial fertility through modifying soil aggregates on soil bacterial community and nitrogen transformation is still unclear. A 60-day incubation experiment was conducted to investigate the influences of biochar addition on soil nitrification and associated nitrifying microbial community in three size aggregates of different derived soils. The results indicated that potential nitrification rates (PNRs) in three size soil aggregates of biochar addition treatment were significantly (P < 0.05) higher than those of no biochar addition, especially in small size aggregates or in the soils collected from no fertilizer plots. The results of 16S rRNA gene profiling showed that biochar addition significantly (P < 0.05) increased community alpha-diversity. Nitrosomonas was relatively more abundant in microaggregates, whereas Nitrospira was more abundant in macroaggregates. Biochar addition could modify structure of soil microbial communities by changing soil properties, and consequently regulate the nitrification processes as suggested by canonical correlation analysis. Conclusively, biochar addition can promote the nitrification process with the higher community diversity and activity of nitrifying bacteria in soils, more strongly in fertile soils or in the small macroaggregates. The initial soil fertility should be fully considered in practical application of biochar.