Microbes in a neutral-alkaline paddy soil react differentially to intact and acid washed biochar

Purpose The effects of biochar additions on soil nutrients and biotic processes have been studied extensively. However, the impact of intact and acid washed biochar on the microbial community assembly process in a neutral-alkaline paddy soil remains unknown. Materials and methods A microcosm experiment with six treatments (CK: control; CB: CK-added intact biochar; CWB: CK-added acid washed biochar; NPK: N, P, and K fertilizer application; NPKB: NPK-added intact biochar; NPKWB: NPK-added acid washed biochar) was conducted using soil samples from a long-term rice–wheat rotation ecosystem. Soil microbial phospholipid fatty acids (PLFAs) and high-throughput sequencing were utilized to evaluate microbial biomass and community structure. Results and discussion Less than 24% of PLFA biomass dropped in CB and CWB treatments whereas 27% decreased in NPKB and NPKWB treatments. Archaeal diversity in NPK soils was lower than in CK soils but rose in NPKB and NPKWB soils. However, only intact biochar reduced bacterial diversity, whereas acid washed biochar reduced fungal diversity. Acidobacteria , Chloroflexi , Firmicutes , Nitrospirota , and Planctomycetota behaved differentially to both intact and acid washed biochar treatments. Biochar was more responsive to saprophytic than pathotrophic and symbiotrophic fungi. The soil pH and available P content influenced fungi community structure, whereas DOC, DON, NH 4 + -N, and NO 3 − -N influenced bacteria community structure. Archaeal taxa were dominated by ammonia oxidizing and methane cycling species, which were susceptible to biochar treatment. Conclusions Our findings suggest that intact or acid washed biochar has a different effect on soil microbial sublineages (archaea, bacteria, and fungus) community, and then in turn modulated soil carbon and nitrogen cycling in the neutral-alkaline paddy soil.