Fe@BC/UHP alleviates continuous cropping obstacle by removing benzoic acid in Brassica napus

• First use of Fe@BC/UHP composite alleviates benzoic acid stress in Brassica napus . • Fe@BC adsorbs BA while Fe₃O₄ catalyzes UHP to generate ·OH for degradation. • Fe@BC/UHP enhances both enzymatic and non-enzymatic antioxidant systems. • Provides a material-based strategy for sustainable continuous cropping management. Continuous cropping of Brassica napus is increasingly limited by soil autotoxicity caused by phenolic acid accumulation. In this study, benzoic acid (BA) was used to simulate c