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

## TL;DR

This study shows that rotating tobacco with rice improves soil health and microbial activity more effectively than other planting methods.

## Contribution

The research identifies tobacco–rice rotation as the most effective strategy for enhancing soil C/N cycling and microbial balance.

## Key findings

- Tobacco–rice rotation increased soil pH, organic matter, and urease activity by 6.6%, 22.1%, and 12.5%, respectively.
- Tobacco–rice rotation enriched beneficial microbes and upregulated C-cycle and N-assimilation genes while suppressing denitrification.
- Tobacco–sweet potato intercropping increased pathogenic fungi and suppressed key C/N metabolic genes.

## Abstract

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.

Cropping patterns reshape soil fertility and microbial communities. Pattern-specific differentiation in carbon and nitrogen metabolic functions among cropping patterns.Infographic comparing four crop rotation strategies for tobacco: monoculture, tobacco-rice, tobacco-maize, and tobacco-sweet potato. Tobacco-rice rotation shows greatest improvements: increased soil pH, organic matter, urease, C/N cycling, microbial network complexity, and beneficial bacteria. Schematic highlights the optimal mechanism—rice straw input drives improved soil and microbial dynamics, resulting in higher soil fertility and enriched microbiota. Key genes and metabolic functions are enhanced, and soil carbon and nitrogen cycling are optimized.

Cropping patterns reshape soil fertility and microbial communities. Pattern-specific differentiation in carbon and nitrogen metabolic functions among cropping patterns.