• 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 continuous cropping obstacle, and the synergistic effects of iron-modified biochar (Fe@BC) combined with urea peroxide (UHP) on alleviating BA-induced toxicity were investigated. The results showed that Fe@BC/UHP treatment significantly promoted Brassica napus seedling growth compared with BA stress alone, with plant height, root length, fresh weight, and dry weight increasing by 47.21%, 46.13%, 18.59%, and 61.76%, respectively. Meanwhile, photosynthetic pigment contents were markedly enhanced, with chlorophyll a and chlorophyll b increasing by 74.57% and 74.90%, respectively. Fe@BC/UHP treatment also effectively alleviated oxidative stress, as indicated by significant reductions in hydrogen peroxide (H 2 O 2 ), superoxide anion (O 2 − ·), hydroxyl radicals (·OH), and malondialdehyde (MDA) contents by 57.12%, 32.7%, 26.01%, and 37.17%, respectively. In contrast, the activities and gene expression levels of antioxidant enzymes were significantly improved, with superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities increasing by 27.98%, 36.34%, and 71.78%, respectively. Furthermore, the ascorbate-glutathione (AsA-GSH) cycle was significantly enhanced, as evidenced by increased ascorbic acid (AsA) and glutathione (GSH) contents, elevated AsA/DHA and GSH/GSSG ratios, and upregulated activities of key cycle enzymes. These results demonstrate that Fe@BC/UHP alleviates BA-induced autotoxic stress through dual mechanisms of soil detoxification and antioxidant system regulation, providing a potential strategy for mitigating continuous cropping obstacles in Brassica napus production.
Zhang et al. (Sun,) studied this question.