Effect of calcium peroxide assisted microwave irradiation pretreatment on humus formation and microbial community in straw and dairy manure composting

In this study, the effects of four pretreatment methods on the crystallinity of maize straw were compared, and the CaO2 assisted microwave pretreatment was selected for straw and dairy manure composting. The humification and microbial community were investigated. Results showed that the pretreatment increased the initial water-soluble carbon, which favored the microbial activity, and the CO2 release increased by 15.71%. Pretreatment promoted the lignocellulose degradation, with total degradation ratio of 37.06%. The final humic acid content was 11.39 g/kg higher than the control. Spearman correlation analysis indicated that polyphenols and amino acids were significantly related to humus formation. In addition, pretreatment rendered the Firmicutes the most dominant phylum, and increased the metabolic intensity of reducing sugar metabolism, aromatic amino acid biosynthesis and carbon fixation pathways. Redundancy analysis revealed that the dominant genus of Firmicutes was significantly positively correlated with humus, while that of Actinobacteriota was correlated with CO2 release.