Black soldier fly larvae vermicompost alters soil biochemistry and bacterial community composition.

Black soldier fly larvae (Hermetia illucens L. BSFL) bioconversion is a promising biotechnology for food waste recycling, yet little is known about how BSFL vermicompost affects soil health in terms of element availability and related microbial response. In this work, a field soil experiment for luffa (Luffa cylindrica (L.) Roem.) growth was conducted to examine the impacts of BSFL vermicompost (BV, 9750 kg ha-1, equal to total N input rate of chemically treated soil (CK)) on soil biochemistry and bacterial communities. Relative to CK, application of BV significantly increased total soil carbon by 149% and enhanced catalase and urease activity by 59.2% and 16.2%, respectively. BV increased the degree of aromaticity and humification in dissolved organic matter (DOM) in soil by 28.6% and 27.3%, respectively, compared to CK treatment. Among bacterial communities in soil, Bacteroidetes, Firmicutes, Proteobacteria, and Actinobacteria were the phyla that showed the most substantial alteration in response to BV. Redundancy analysis further revealed that the bacterial community structure was affected by DOM and total phosphorus. Functional analyses indicated that BV enhanced xylanolysis (55.4%) and nitrogen fixation (46.3%), but inhibited nitrification (59.8%). BSFL vermicompost input might effectively prevent the harm of soil borne pathogens (e.g., wilt). Moreover, these function groups strongly correlated with Clostridiales, Actinomycetales, and Nitrospirales. Our study reveals that BSFL vermicompost promoted soil nutrient availability, microbial community succession, and biochemical function optimization, which is conducive to the popularization and application of BSFL vermicompost in the field of soil health. KEY POINTS: • Vermicompost enhanced catalase and urease levels while increased DOM aromaticity. • Vermicompost enriched Bacteroidetes and Firmicutes and improved soil health.