Insights into nitrogen metabolism and humification process in aerobic composting facilitated by microbial inoculation

To enhance the retention of compost nutrients, specifically in nitrogen metabolism and humification, compound microbial agents were added during the aerobic composting of bagasse pith and buffalo manure. The introduction of the microbial agent successfully colonized the mixture, boosted the degradation capacity of organic matter, and facilitated the formation of nitrogenous substances and humic substances (HSs). The incorporation of a composite microbial inoculum led to a substantial rise in total Kjeldahl nitrogen (TKN) by 62.04%, nitrate nitrogen (NO- 3-N) by 291.65%, and amino acid (AA) by 78.77%. Furthermore, this intervention resulted in achieving a humic acid (HA) to fulvic acid (FA) ratio of 1.64. Metagenomic sequencing revealed enhanced synergistic interactions among microorganisms through inoculation, increasing the abundance of functional genes related to nitrification and nitrogen fixation compared to the uninoculated control. Spearman correlation analysis identified unclassified_c__Deltaproteobacteria, unclassified_f__Planctomycetaceae, Chryseosolibacter, unclassified_f__Hyphomicrobiaceae as the principal producers of HA. This research provides insights into the interactions between nitrogen metabolism and humification in composting, aiming to effectively retain compost nutrients and support the long-term sustainability of agriculture.