Biochar improves the yield and quality of Erigeron breviscapus in heavily cadmium-polluted soil

Simultaneously utilizing and remediating soil contaminated with cadmium (Cd) is propitious and economically beneficial. In this study, Erigeron breviscapus, a raw medicinal material used to extract scutellarin, was utilized to conduct a pot experiment including five treatments. Under a control without Cd and biochar addition (CK), soil exogenously added with high concentration of Cd (0.01%) were used to investigate the effects of different biochar doses (0%, 5%, 10%, and 15%, denoted as CdB0, CdB5, CdB10, and CdB15, respectively) on the yield (shoot biomass) and quality (represented by scutellarin content) of E. breviscapus as well as soil remediation. The results showed that soil with addition of high Cd decreased the shoot biomass and scutellarin content of E. breviscapus by 33.6% and 70.8%, respectively. Compared with CdB0, the shoot biomass and scutellarin content of CdB15 increased by 24.7% and 312.0%, respectively. Biochar application (CdB5, CdB10, and CdB15) changed the soil Cd speciation and reduced the soil available Cd and plant Cd concentrations by 17.4%–121.8% and 26.4%–42.6%, respectively, compared with CdB0. However, the chlorophyll content, catalase activity, and acquisition of N, Fe, and Cu of E. breviscapus were increased in CdB5, CdB10, and CdB15 compared with CdB0. In addition, the Cd toxicity mitigation effect enhanced with increasing biochar application, and the application of 15% biochar resulted in the highest shoot biomass and scutellarin content of E. breviscapus. The results of this study highlight the importance of biochar for improving the Cd adaptability of E. breviscapus and provide a reference for the simultaneous utilization and remediation of heavily Cd-contaminated soil.