Biochar and quicklime mitigate Cd, As, and Cu accumulation while preserving medicinal quality in understory Panax notoginseng

Understory cultivation of Panax notoginseng is an ecologically sustainable production system but is increasingly threatened by combined contamination with cadmium (Cd), arsenic (As), and copper (Cu). Reducing Cd, As, and Cu accumulation while maintaining medicinal quality is essential for safe and sustainable production. A two-year field experiment was conducted to evaluate the effects of biochar (BC; 1500 kg ha − 1 ) and quicklime (QL; 2000 kg ha − 1 ) on Cd, As, and Cu accumulation and total saponins production in P. notoginseng . Soil physicochemical properties, microbial community composition, and root transcriptomic responses were simultaneously analyzed to characterize amendment-associated soil, microbial, and plant responses. Both amendments significantly reduced Cd, As, and Cu content in taproots while maintaining total saponins content and yield. Both amendments increased soil pH and reduced the availability of Cd, As, and Cu in soil, while transcriptomic analyses revealed changes in genes associated with metal transport, cell wall-related processes, and detoxification. BC was associated with changes in fungal community composition and increased the availability of selected soil nutrients, whereas QL altered the expression of genes associated with saponin biosynthesis ( SS , SE , CYP716A47 , and PnUGT3 ). The study provides insights into amendment-based strategies for reducing Cd, As, and Cu accumulation in understory-cultivated medicinal plants in contaminated ecosystems.