Abstract:

The study aims to investigate the impacts of continuous cropping obstacles on allelochemicals, soil enzyme activities, and microbial communities in soil, providing a theoretical basis for overcoming tobacco continuous cropping obstacles. We selected three types of tobacco fields: healthy (H-type), continuous cropping obstacle (CCO-type), and disease inhibition (DI-type). Their allelochemical content, rhizosphere soil microbial diversity, and community structure were determined. The microbial community structure characteristics of soils with different degrees of continuous cropping obstacles and their relationships with allelochemicals and enzyme activities were explored. The results showed that the change trend of allelochemicals was CCO-type>DI-type>H-type. The soil enzyme activities of CCO-type and DI-type were significantly lower than those of H-type. The activities of sucrase (SUC) and phosphatase (PHO) were significantly different among the three types of tobacco fields. The diversity and richness of microorganisms in healthy soil were the highest, and the diversity and richness of microorganisms in continuous cropping obstacle soil were the lowest. The relative abundance of Sordariomycetes in Ascomycota and Zygomycota in Mortierellomycota in continuous cropping obstacle soil was lower than that in healthy soil, while the relative abundance of Dothideomycetes in Ascomycota in continuous cropping obstacle soil was higher than that in healthy soil. Redundancy analysis showed that pH, SOC, SUC, PHO, URE, ALA and DEHP might be potential continuous cropping obstacle factors. The results showed that reducing the content of soil allelochemicals, increasing the activities of sucrase and urease and soil microbial diversity were the priority in remediation efforts for overcoming continuous cropping obstacles in tobacco farming.

Key words: continuous cropping obstacle, allelochemicals, soil enzyme activity, microbial community structure, tobacco