Effect of crop rotation and crop succession on microorganisms and yield of tobacco rhizosphere soil

Continuous cropping of tobacco can lead to the occurrence of deterioration of soil microbial ecosystems, exacerbation of viral pests, and reduction of quality, whereas corn-tobacco rotation can effectively alleviate the obstacles of continuous cropping. The study objective was to explore the effects of different planting styles on the microbial environment and yield of tobacco. The experiment was carried out in March-October 2023 in a tobacco planting demonstration field in Xianru Township, Dunhua City, Jilin Province. The experiment was conducted on rhizosphere soils of 2 years of corn - 1 year of tobacco, 3 years of corn - 1 year of tobacco, 2 years of continuous tobacco, 3 years of continuous tobacco. Soil nutrients and enzyme activities were determined, and the effects of microbial community structure on tobacco yield were analyzed based on 16 S rDNA and ITS sequences. Crop rotation significantly increased the total nitrogen, quick-acting phosphorus and organic matter contents as well as protease activity of the rhizosphere soil, and significantly decreased the peroxidase activity. Crop rotation increased the diversity and richness of bacteria in tobacco-planting soil, while continuous cropping significantly enhanced the richness of the fungal community, and crop rotation could improve the diversity of the fungal community (P < 0.05). The relative abundance of Gemmatimonas was significantly higher in crop rotation than in continuous cropping, while the relative abundance of Penicillium, Asterostroma and Fusarium in the continuous cropping pattern was significantly higher than that in the rotational cropping. Crop rotation pattern tobacco plant dry weight, stem circumference, maximum leaf length and wide leaf were increased, and the proportion of upper and medium tobacco increased. Gemmatimonas was positively correlated with plant height, stem girth and dry weight; Sphingomonas was positively correlated with medium and top-quality cigarettes; at the level of fungal genera, Asterostroma and Fusarium were negatively correlated with agronomic traits of tobacco. Corn-tobacco rotation can effectively improve soil fertility, enrich bacterial communities, and increase the proportion of indicator beneficial bacteria. Continuous cropping leads to increased abundance of pathogenic bacteria. This study provides theoretical support for the mitigation of tobacco continuous cropping disorder and the detection and remediation of farmland soil.