Phosphorus-Enriched Biochar Promotes Brassica napus L. Growth under Cadmium Stress by Immobilizing Cadmium and Sustained Phosphorus Release

• • CBC and MBC treatments reduced DTPA-extractable Cd by 45.73% and 48.92%, respectively, demonstrating high efficacy in immobilizing cadmium in contaminated soils. • • The C5 treatment increased leaf area by 100%, and M7 increased plant height by 26.8%, indicating significant promotion of Brassica napus growth under Cd stress. • • M3 treatment reduced MDA by 72.5% and H2O2 by 61.2%, showing substantial alleviation of oxidative stress in plants. • • Phosphorus-enriched biochar exhibited sustained phosphorus release, improving soil phosphorus availability while minimizing environmental losses, as evidenced by changes in soil solution phosphorus.