| To investigate the effects of tobacco plant health status on rhizosphere soil microecology under different continuous-cropping durations, this study analyzed rhizosphere soils from healthy and diseased tobacco plants collected from 2-year and 5-year continuous-cropping fields in tobacco-growing areas of Henan Province. Changes in soil physicochemical properties, microbial biomass, enzyme activities, and fungal community structure were systematically examined. The results showed that, compared with soils under 2 years of continuous cropping, rhizosphere soils under 5 years of continuous cropping exhibited increases of 9.71% and 34.08% in organic matter and alkali-hydrolyzable nitrogen contents, respectively, whereas soil pH, available phosphorus, and available potassium contents decreased by 8.28%, 26.94%, and 13.61%, respectively. With increasing continuous-cropping duration, soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) decreased significantly. Specifically, in 5-year continuous-cropping fields, MBC and MBN in diseased soils declined by 59.62% and 65.39%, respectively, compared with healthy soils. Soil enzyme activity analysis indicated that urease, dehydrogenase, sucrase, and acid phosphatase activities in rhizosphere soils under 5 years of continuous cropping decreased by 38.63%~52.74%, 46.88%~66.67%, 27.36%~35.36%, and 15.49%~59.61%, respectively, relative to the corresponding values under 2 years of continuous cropping, and enzyme activities in diseased soils were significantly lower than those in healthy soils (P< 0.05). Fungal community composition analysis revealed that Ascomycota, Basidiomycota, and Zygomycota were the dominant phyla. The Chao and Shannon indices of fungal communities in 5-year diseased soils decreased by 12.7% and 26.6%, respectively, compared with healthy soils, indicating a significant reduction in fungal diversity. In summary, long-term continuous cropping of flue-cured tobacco alters soil physicochemical properties, suppresses microbial activity, and disrupts fungal community stability, while the occurrence of soil-borne diseases further exacerbates rhizosphere microecological imbalance |
