Catechol addition reshapes microbial metabolic networks to enhance humification and regulate nitrogen transformation in co-composting of chicken manure and corn straw

Catechol was confirmed to promote the formation of humus (HS) by serving as a carbon skeleton during the co-composting of chicken manure and rice straw. However, how exogenous catechol influences the biological pathways underlying humification and nitrogen transformation remains poorly understood. Here, this study investigated how catechol regulates HS formation by reshaping microbial communities and affects nitrogen transformation during the co-composting of chicken manure with corn straw. Catechol addition increased the contents of HS and humic acid (HA) by 122.7% and 100.1%, respectively. Mechanistic analyses indicated that catechol did not simply act as a carbon skeleton for HS synthesis; rather, it strategically altered humification pathways by restructuring key microbial functional guilds. Notably, catechol shifted polyphenols and inorganic nitrogen from limiting factors to primary drivers of humification, thereby accelerating HS synthesis, improving HA polymerization, and enhancing product stabilization. Overall, these findings provide new mechanistic insights and practical strategies to improve humification and nitrogen management of agricultural wastes through targeted modulation of microbial metabolic pathways.