Investigating lignocellulose degradation and humic substance during cotton straw and cow manure co-composting

Aerobic composting of cattle manure and cotton stalks and improvement of their lignocellulose degradation rate and humification conversion efficiency are hot topics of interest. In this study, the effects of cotton stalks with different particle sizes on the indicators of cellulose, hemicellulose, humus, porosity, greenhouse gas production and emission, and bacterial/fungal diversity of the composting process of cattle manure were investigated by means of Micro-CT and microbial diversity coupling. The results showed that:(1) In this study, the addition of fungicides could effectively change the microbial community structure, improve the diversity and metabolic capacity of microorganisms, and increase the cellulose degradation rate by 14.54% and the humification degree by 21.72%. (2) In addition, the effect of cotton straw particle size less than 2 mm on lignocellulose degradation was significantly higher than that of the 2-10 mm and 10-20 mm particle size groups, while the degree of humification of 10-20 mm was significantly lower than that of the other two groups. However, it is still worth paying attention to the promotion of methane and carbon dioxide emission by the particle size less than 2 mm, which is a result of the combination of the pore structure caused by the different particle sizes and the metabolic function of microorganisms. These findings provide data support for optimizing the efficiency and quality improvement of the cotton straw-cattle manure aerobic composting process.