Rhizosphere substances and microbial regulation of Nicotiana tabacum L. growth under preceding crop planting: Insights from soil quality, microbial communities, and metabolic profiling
Description
In a pot experiment intercropping with tobacco, we studied the effects of different early crops on soil Y nutrient enzyme activity and rhizosphere metabolism, as well as their subsequent effects on tobacco growth. The effects of different planting methods on soil physicochemical properties, enzyme activities and rhizosphere metabolites of tobacco were studied. Fallow + tobacco (CK), corn + tobacco (T1), rapeseed + tobacco (T2) and wheat + tobacco (T3) were compared. Compared to fallow (CK), planting different prior crops significantly increased the availability of soil nutrients (P, K, Zn, and B) and soil enzyme activity (urease, acid phosphatase, peroxidase). Planting modes T1 and T2 significantly enhanced tobacco growth. Extensive targeted metabolomics analyses revealed changes in lipids, organic acids, flavonoids, alkaloids, and terpenoids due to differences in previous crops, enriching secondary metabolite synthesis pathways. These metabolites are closely related to soil nutrients and rhizosphere metabolites. Early crops regulate rhizosphere metabolites through root exudation. Overall, the study shows that different prior crops have an improving effect on tobacco soil, providing insights into how various cultivation patterns promote tobacco growth by improving the soil microenvironment. Sample collection: During tobacco ripening, soil samples are collected by removing topsoil to access root-associated soil in the pot. Soil nutrient and microbial samples were randomly mixed in 2 POTS and repeated once per treatment for a total of 5 replicates. Microbial samples In a -80◦C refrigerator, soil nutrient samples are naturally air-dried through a 2 mm screen to remove impurities and store away from light. The roots, stems, and leaves of mature tobacco plants are harvested, weighed (fresh weight), briefly heated (105°C, 15 minutes), and dried (70°C) to achieve constant weight. Collect 3 replicates per processing. Soil Chemical Properties Test：Air-dried soil samples were sieved, and pH was determined using water immersion. Organic matter was quantified using the potassium dichromate titration method. Quick nitrogen was determined by alkali diffusion, available phosphorus by molybdenum antimony colorimetry, quick potassium by flame photometry, available zinc by flame atomic absorption spectroscopy, available boron by curcumin colorimetry, and available molybdenum by potassium thiocyanate colorimetry (Tan et al., 2022). Enzyme activities (sucrase, urease, acid phosphatase, peroxidase) were assessed using their respective assay kits (Suzhou Grace Biotechnology Co., Ltd., China) (Borase et al., 2020). Metabolite extraction from soil samples for targeted metabolomic analysis was conducted by Metware Biotechnology Co.