Impact of different tillage on soil health: enhancement of enzymatic activities and functional microbial communities in accelerating maize straw degradation

Straw return to the field is an effective agricultural practice for improving soil fertility and productivity by increasing soil organic matter and enhancing soil structure. However, in wheat-maize rotations, the slow degradation of maize straw severely affects wheat emergence quality and seedling growth, emphasizing the need to understand and regulate key mechanisms driving straw degradation. This study evaluated soil properties, straw chemical structure, extracellular enzyme activity, microbial community composition, and functional genes during the straw degradation process under three tillage practices: zero tillage (ZT), chisel plough tillage (CPT), and plow tillage (PT). The results showed that CPT had the most significant effect on promoting straw degradation, with the lowest straw residue rate of 42.24 % after 220 days of degradation. CPT treatment also has a significant effect on the early degradation of unstable carbon structures, such as O-alkyl C and di-O-alkyl C. The fungal community diversity index increased at 220 days of degradation, with the fungal Shannon index under ZT and CPT significantly increasing by 29.79 % and 10.99 % compared to PT. Actinomycetia was the dominant phylum involved in straw degradation under all three tillage practices, and ZT significantly increased its abundance by 5.55 % compared to PT. In addition, Actinomycetia was also recognized as a dominant phylum for the production of six extracellular enzymes such as β-glucosidase, N-acetyl-glucosaminidase, leucine aminopeptidase, etc. The abundance of functional genes involved in degrading mono- and polysaccharides was higher than that of other functional genes. Hemicellulose and Chitin functional genes abundance was increased by 5.98 % and 5.97 % under CPT compared to PT. Regression analysis revealed a positive correlation between the abundance of the dominant phylum Actinobacteria and alkyl C, but a negative correlation with aryl C and phenolic C. In contrast, Proteobacteria exhibited the opposite pattern. Partial least squares path modeling indicated that enzyme activity showed the largest positive direct effect on straw degradation. CPT reduces tillage intensity to indirectly enhance microbial phylum abundance and enzyme activities, and accelerate the process of straw degradation. This study elucidates the microbial and enzyme-mediated regulatory mechanisms of conservation tillage on maize straw degradation, providing a scientific basis for its broader application in agricultural production.