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

Highlight

•	Biochar reduced Pcoll by 15.5–32.1% in leachate during DRW cycles.
•	Pcoll decreased with increasing phoD- and phoC-harboring microbial communities.
•	Proteobacteria and Cyanobacteria were the key taxa driving Pcoll content.

Funding

National Natural Science Foundation of China(22076163)

Bingtuan Science and Technology Program(2021DB019)

Science and Technology Program of Zhejiang Province(2023C02016)