Short-term hydrothermal fermentation amendments enhance labile organic carbon in deep soil: Synergistic effects of organic carbon, enzymes, and microbes

Organic conditioners, like food waste derived from short-time hydrothermal fermentation (SHF), enhance soil fertility by providing accessible organic carbon for microbial growth. However, the effects of SHF on labile organic carbon (LOC) in deep soils and its linkage with microbial indicators remain poorly understood. This study examined how SHF affects bacterial community structure, enzyme activities, and active carbon in various soil layers. After a three-year field application, SHF significantly increased dissolved organic carbon (DOC), microbial biomass carbon (MBC) and LOC, especially a 244.4 % LOC increase in the 30–40 cm layer. SHF also significantly boosted α-galactosidase, β-glucosidase, and urease activities in the plow layer. Indicator species such as Ktedonobacter and Sphaerobacter, which aid in cellulose degradation and nitrogen fixation, thrived with SHF. Compared to chemical fertilizer, SHF enhanced microbial function and deep-soil fertility. Adding phosphorus and nitrogen or enhancing microbial biomass carbon and LOC could further boost these beneficial species and soil nutrients. Accordingly, SHF shows great potential as a sustainable soil conditioner for deep-rooted crops, facilitating the dual benefits of effective food waste recycling and enhanced soil quality.