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

Abstract

<h4>Introduction</h4>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.<h4>Methods</h4>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.<h4>Results</h4>TR significantly improved soil health: pH (+6.6%), organic matter (+22.1%), and urease activity (+12.5%). It enriched beneficial microbes (<i>Pseudomonadota</i> +16.4%, <i>Mucoromycota</i> +327%) and upregulated C-cycle (<i>korA</i> +42.3%) and N-assimilation genes (<i>amoC</i> +460%), while suppressing denitrification (<i>nirK</i>). TM increased available P/K but enriched oligotrophic taxa and reduced sucrase activity. TP triggered pathogenic fungi (<i>Olpidium</i> +160%), depleted beneficial microbes, and broadly suppressed C/N metabolic genes (<i>cbbL</i> -94.5%, <i>nirS</i> -21.8%).<h4>Discussion</h4>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.