Optimizing flue-cured tobacco planting patterns: enhanced rhizosphere nutrient availability and microbial community...

Continuous monoculture of flue-cured tobacco causes soil degradation and microbial dysbiosis. While crop rotation can alleviate these obstacles, how different cropping patterns regulate soil carbon (C) and nitrogen (N) metabolic functions remains unclear.

A four-year field experiment compared tobacco monoculture (CK), tobacco-maize rotation (TM), tobacco-rice rotation (TR), and tobacco-sweet potato intercropping (TP). Soil physicochemical properties, enzyme activities, metagenomic sequencing, and microbial network analysis were integrated.

TR significantly improved soil health: pH (+6.6%), organic matter (+22.1%), and urease activity (+12.5%). It enriched beneficial microbes (Pseudomonadota +16.4%, Mucoromycota +327%) and upregulated C-cycle (korA +42.3%) and N-assimilation genes (amoC +460%), while suppressing denitrification (nirK). TM increased available P/K but enriched oligotrophic taxa and reduced sucrase activity. TP triggered pathogenic fungi (Olpidium +160%), depleted beneficial microbes, and broadly suppressed C/N metabolic genes (cbbL -94.5%, nirS -21.8%).

Cropping patterns differentially reshape microbial communities and metabolic functions, determining their efficacy against continuous cropping obstacles. TR establishes efficient C/N cycling with "high assimilation, low denitrification," whereas TP induces pathogenic proliferation and metabolic suppression. This provides a functional framework for designing cropping systems to enhance soil health and tobacco productivity.