Biochar reduces colloidal phosphorus in leachate by regulating phoD- and phoC-harboring microbial communities during drying/rewetting cycles

Abstract Drying and rewetting (DRW) events cause the release of colloidal phosphorus (P coll , 1–1000 nm) in leachate, and biochar is considered an effective inhibitor; however, the microbial mechanism remains elusive. In this study, three successive DRW cycles were performed on the soil columns to assess the effect of biochar addition on P coll content and its possible associates, including phosphatase-producing microbial populations ( phoD - and phoC -harboring microbial communities) and alkaline/acid phosphatase (ALP/ACP) activities. Results showed that the biochar addition significantly decreased the P coll by 15.5–32.1% during three DRW cycles. The structural equation model (SEM) confirmed that biochar addition increased phoD- and phoC -harboring microbial communities and ALP/ACP activities, which reduces the release of P coll into leachate. In addition, the manure biochar was more effective than the straw biochar in promoting competition and cooperation in the co-occurrence network (2–5% nodes increased on average), and the key taxa Proteobacteria and Cyanobacteria were identified as the dominant species of potential ALP/ACP activities and P coll content. Our findings provide a novel understanding of biochar reducing P coll loss from the phosphatase perspective by regulating the phoD - and phoC -harboring communities during DRW events. Graphical abstract