# Effects of Different Crop Rotations on Microbial Diversity and Enzyme Activities in Brassica napus Rhizosphere Soil

## TL;DR

Rotating crops with wheat improves soil health and microbial diversity in rapeseed fields more than other rotations.

## Contribution

Identifies wheat as the optimal preceding crop for enhancing microbial diversity and enzyme activity in Brassica napus rhizosphere soil.

## Key findings

- Wheat rotation (TaBn) showed the highest soil enzyme activities and microbial diversity indices.
- Wheat and beet rotations (TaBn, BvBn) significantly altered microbial community structure compared to continuous Brassica napus.
- Wheat rotation enriched beneficial bacterial phyla like Pseudomonadota and Actinomycetota.

## Abstract

Continuous cropping of Brassica napus impairs sustainable production via soil nutrient imbalance and microecological degradation. We evaluated rhizosphere soil properties and microbial communities under rotations crops (Triticum aestivum [TaBn], Beta vulgaris [BvBn], Glycine max [GmBn], Sorghum bicolor [SbBn], Hordeum vulgare [HvBn], and Brassica napus [BnBn]). BvBn had the highest total nitrogen, total potassium, available potassium, and organic matter contents. TaBn exhibited the highest soil enzyme activities, and its bacterial/fungal Chao1/Simpson indices and unique operational taxonomic units (OTUs; bacteria: 333, fungi: 37) exceeded other patterns. Principal coordinate analysis showed distinct microbial community separation in BvBn/TaBn versus BnBn. TaBn enriched dominant bacterial phyla Pseudomonadota and Actinomycetota; all preceding crops increased fungal phylum Ascomycota while reducing Mucoromycota. Comprehensive assessment confirmed all preceding crops, except oilseed rape altered rhizosphere microbial structure, with TaBn as the optimal preceding crops.