Straw additive enhances manure compost quality by promoting diverse aerobic bacteria and unitary thermophilic fungi

Shortening the initial activation time and extending the duration of the thermophilic phase are key to improving compost product quality in cold-climate regions. This study set up three treatments that cattle manure (CM), manure with rice straw (MR), and manure with maize straw (MM) in the field with ambient temperature ranging from –6–7 ℃. Compared with traditional manure composting, composting with straw performed more effectively, and the effect of the addition of maize straw surpassed that of the addition of rice straw. Straw additives markedly increased the compost pile temperature and extended the thermophilic phase duration. In addition, straw addition improved compost product maturity, as indicated by the humic-like substance content, absorbance ratio, and germination index. To further illustrate this result, the microbial community structure during the composting process was studied. During the thermophilic phase, straw additives, especially maize straw, improved the formation of a diverse aerobic bacterial community and a unitary thermophilic fungal community, and promoted a stronger relationship between the bacterial and fungal communities, as revealed by co-inertia analysis. The abundance of functional genes indicated that straw addition increased the activities of organic carbon degradation and transformation. This study demonstrated the necessity of enhancing the interaction between thermophilic–aerobic bacteria and thermophilic fungi to improve compost product quality.