Plant-Soil Feedback Combined with Straw Incorporation Under Maize/Soybean Intercropping Increases Heavy Metals Migration in Soil-Plant System and Soil HMRG Abundance Under Livestock Wastewater Irrigation

Plant–soil feedback (PSF) and straw incorporation improve soil health and enhance plant growth. However, these systems underlying methods and ideas have separately evolved to a larger extent. The purpose of this study was to analyze the impacts of PSF combined with straw incorporation and intercropping on heavy metal (HM) migration in soil-plant systems, heavy metal resistance genes (HMRGs) abundance, and soil bacterial community composition under livestock wastewater irrigation. A two-phase experiment integrating PSF and straw returning was carried out using monocropped and intercropped maize/soybean irrigated with groundwater and treated wastewater. The results indicate that PSF combined with straw incorporation increases HM mobility with more pronounced effects under intercropping system. No potential health risk was recorded considering HM movement in soil-plant system with its content in soil and grains under permissible limits. This study showed that PSF increases soil bacterial composition and the HMRGs’ relative abundance while decreasing the relative abundance of antibiotic resistance genes (ARGs) under straw incorporation. In summary, PSF combined with straw incorporation under maize/soybean intercropping system is a suitable method to achieve safe production while reducing HM accumulation in soil and plant in treated livestock wastewater irrigation.