Chisel tillage and moderate nitrogen fertilization enhance maize straw decomposition through microbial and enzymatic synergy in wheat–maize system

Background and aims

In the wheat–maize cropping system, the return of substantial maize straw to the field can hinder winter wheat germination and growth. This study aims to clarify the mechanisms that accelerate maize straw decomposition, thereby mitigating these effects.

Methods

This study evaluated three tillage methods: zero tillage, chisel tillage, and plow tillage, and three nitrogen fertilization rates (180, 240, and 300 kg·N ha⁻¹). It examined the relationships between straw decomposition rates and factors such as straw chemical composition, soil properties, enzyme activities, and microbial community.

Results

In this study, chisel tillage and 240 kg·N ha⁻¹ significantly improved soil properties and biological activity and promoted straw decomposition. The combination of chisel tillage and 240 kg N ha⁻¹ resulted in the highest rate of straw degradation of 52%. Chisel tillage significantly reduced easily degradable functional groups (methoxyl C and carbonyl C) and enhanced the activities of β-glucosidase, N-acetyl glucosaminidase, peroxidase, and polyphenol oxidase, as well as fungal diversity (P < 0.05). Nitrogen fertilization further increased enzyme activity and the fungal Shannon index (P < 0.05). Proteobacteria and Ascomycota were dominant phyla during the decomposition process, with microbial dominant order shifts linked to decomposition stages, straw chemical structure, and soil conditions. Proteobacteria contributed primarily to hydrolase activity, while Mortierellomycota were closely related to oxidative enzymes.

Conclusions

The finding reveals the principal drivers of maize straw decomposition and provide guidance for optimizing nitrogen fertilization strategies in conservation tillage systems to accelerate straw breakdown.