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.

牛粪与棉秆的好氧堆肥及其木质纤维素（lignocellulose）降解率、腐殖化转化效率的提升，是当前广受关注的研究热点。本研究通过显微计算机断层扫描（Micro-CT）与微生物多样性联用技术，探究了不同粒径棉秆对牛粪堆肥过程中纤维素、半纤维素（hemicellulose）、腐殖质（humus）、孔隙度、温室气体产生与排放特征，以及细菌/真菌群落多样性的影响。研究结果表明：(1) 本研究中，杀菌剂的添加可有效改变微生物群落结构，提升微生物多样性与代谢能力，使纤维素降解率提升14.54%，腐殖化程度提高21.72%。(2) 此外，粒径小于2mm的棉秆对木质纤维素降解的促进效果显著优于2~10mm与10~20mm粒径组，而10~20mm组的腐殖化程度则显著低于另外两组。但值得注意的是，粒径小于2mm的体系会显著促进甲烷与二氧化碳的排放，该现象是不同粒径所形成的孔隙结构与微生物代谢功能共同作用的结果。本研究结果可为优化棉秆-牛粪好氧堆肥过程的效率与品质提升提供数据支撑。