Relay cropping different families crops influenced the growth of tobacco plants by the differential shaping of rhizosphere soil microecology

This study elucidates the mechanistic impacts of relay cropping tobacco with Gramineous or leguminous crops on rhizosphere soil properties and tobacco growth through a consecutive two year pot experiment. Five treatments were established: tobacco monoculture, and relay cropping with silage corn, waxy corn, soybean, or broad bean. Results indicated that relay cropping with Gramineous crops exerted no significant effect on tobacco plant biomass but decreased potassium accumulation in tobacco plants, whereas relay cropping with leguminous crops significantly reduced tobacco plant biomass and the accumulation of nitrogen, phosphorus, and potassium. Compared with CK, all relay cropping models enhanced soil available nitrogen content and sucrase activity, while decreasing available phosphorus content and acid phosphatase activity with Gramineous crops further significantly increasing available phosphorus content, as well as urease and sucrase activities. Relay cropping improved rhizosphere bacterial diversity, reduced fungal diversity, and enriched beneficial microbial taxa, which were positively correlated with amino acid derivatives, phenolic acids, flavonoids, and alkaloids. Metabolomic analysis revealed that relay cropping with gramineous crops elevated amino acid derivatives, while leguminous crops enriched lipid-associated metabolites. Collectively, relay cropping modulated rhizosphere microbial metabolite interactions during the late growth stage of tobacco, improved soil biochemical conditions, and promoted the growth of both tobacco and relay crops. Among all treatments, relay cropping with silage corn was the most effective in activating key soil enzymes and enriching beneficial microorganisms, furnishing a scientific foundation for optimizing crop growth and enhancing food production.