The remediation of polycyclic aromatic hydrocarbon and lead co-contaminated soils in karst regions remains challenging because of strong soil buffering capacity, complex metal speciation, and the distinct transformation mechanisms of organic pollutants and heavy metals. Although urea and biochar are widely used as soil amendments, their interactive effects on plant-assisted remediation and the associated rhizosphere microbial and metabolic mechanisms remain unclear. In this study, urea and bioch