Intercropping with Morus alba L. affects Cd accumulation in maize via rhizosphere regulation: Contrasting effects of two Morus alba L. cultivars

To elucidate the mechanisms underlying Cd accumulation in maize under Morus alba L.–maize intercropping in Cd-contaminated tropical farmland, this study established monoculture and intercropping systems using two M. alba cultivars (G62 and G12). Plant and rhizosphere characteristics were assessed, the root bioconcentration factor (BCF R ) and root–to–stem transfer factor (TF RS ) were reduced by 91.09% and 90.63%, respectively. G62 demonstrated competitive dominance, increasing soil pH, organic matter (OM), available phosphorus (AP), and available potassium (AK) to promote Cd stabilization. It reshaped soil physicochemical properties and released metabolites (e.g., ginkgolide B and PC (22:1(13Z)/14:0)) for Cd immobilization, and maize reduced Cd uptake through rhizosphere metabolite regulation (e.g., apocyna blue and astilbin). PLS-SEM identified AP and AK as core regulators. Conversely, G12–maize intercropping enhanced maize Cd accumulation by 77.32% (leaves) and 83.48% (stems), with DTPA–Cd and TCd increased by 34.20% and 34.19%, respectively, due to metabolite–induced Cd mobilization and decreased Fe/Mg. N and P are the key factors in CM2. Specifically, G62–maize intercropping reduced maize Cd uptake through rhizosphere environment remodeling and metabolite synergism, providing a potential phytoremediation model that combines phytostabilizing plants with low Cd-accumulating crops.