Effects of Tobacco Stem-Derived Biochar on Soil Properties and Bacterial Community Structure under Continuous Cropping of Bletilla striata

Biochar has been shown to promote the growth of crops under continuous cropping. It has been proposed that biochar could improve soil properties and alter bacterial community structure, which however remains to be validated. This study aims to investigate the effects of tobacco stem-derived biochar on soil properties, bacterial community structure, and the growth of Bletilla striata, a traditional Chinese medicinal herb, under continuous cropping. Tobacco stem-derived biochar was applied at 0.00, 3.00, and 7.50 t center dot ha(-1) to the soil after 8-year continuous cropping of B. striata. Soil pH, nutrient availability, enzyme activity, and the growth of B. striata were investigated after transplanting for 6 months. Further, the bacterial community structure was analyzed within the metagenomic framework through high-throughput DNA sequencing. Soil pH, electrical conductivity, available nitrogen, available phosphorus, and available potassium increased significantly with biochar application (P < 0.05). Besides, the activities of soil phosphatase and sucrase also elevated (P < 0.05). The biochar promoted the growth of B. striata, as indicated by the increased plant height, average leaf width, and the content of chlorophyll (P < 0.05). Metagenomic analysis revealed that biochar treatment increased bacterial richness and promoted phylogenetic clustering in the bacterial community. The application of tobacco stem-derived biochar significantly improved soil properties and altered bacterial community structure, which could be the key mechanism for biochar to promote the growth of B. striata under continuous cropping.