Regulating humus formation via improved conversion of microbial necromass and plant lignin during vegetable straw...

This study evaluated the effects of inoculation with agent on the conversion of plant and microbial necromass and humus formation during compost. Results showed that inoculation reduced the contribution of vanillyl-and syringyl-type phenols to total organic carbon (C) but increased the contribution of cinnamyl-type phenol. Furthermore, inoculation significantly increased the ratio of bacterial to fungal necromass C (8.7 %) and promoted the accumulation of humic substance C (23.6 %) by regulating the precursors production, such as polysaccharides. The transformation of plant and microbial necromass was closely related to microbial metabolism mediated by environmental factors. Inoculation enriched functional microbes (Paenibacillus, Sphingomonas, and Penicillium). Mechanism analysis showed that inoculation strengthened the humus formation through influencing composting factors, microbial communities, and precursor substances, among which the microbial necromass C, C/N, and C-acquiring enzymes were identified as the key driving factors. These findings emphasise the often-overlooked role of microbial necromass C in stabilizing C during compost.