Legume–cereal intercropping with AMF reduces cadmium bioavailability and enhances land productivity

The combined implementation of intercropping systems and arbuscular mycorrhizal fungi (AMF) inoculation represents a promising phytoremediation strategy for heavy metal-contaminated farmland, providing both ecological and economic benefits. However, additional research is necessary to understand the influence of AMF and intercropping on Cd bioavailability. This study examines the synergistic effects of maize–soybean intercropping and AMF inoculation on crop growth, cadmium (Cd) allocation patterns, and rhizosphere soil dynamics through comprehensive field and pot experiments. Field trials revealed significant yield advantages in maize–soybean intercropping systems, with land equivalent ratios (LERs) of 1.62 (common maize) and 1.64 (sweet maize). Intercropping decreased soybean Cd accumulation across all tissues, notably in grains (42.8% reduction), while maintaining maize grain Cd concentrations below China’s food safety threshold (0.20 mg kg^–1). The metal removal equivalent ratio (MRER) achieved 1.33–1.38 in field conditions, validating intercropping’s dual advantage in productivity and Cd phytoextraction. Pot experiments indicated the AMF-inoculated intercropping system (IN+A) increased maize yield by 16.4% while reducing Cd accumulation in both crops, with grain concentrations meeting safety standards. Rhizosphere analysis demonstrated IN+A treatment substantially improved soil health indicators: 34.5% reduction in bioavailable Cd, elevated pH, decreased redox potential (Eh), and enhanced catalase activity. AMF colonization rates were 2.2–4.3 times higher in inoculated treatments (11.5–14.0%) vs. controls (3.2–5.3%). These results establish that AMF-enhanced legume–cereal intercropping reduces Cd bioavailability through soil alkalinization (pH increase) coupled with redox potential reduction, and metal allocation plasticity redirecting Cd to root tissues. This interaction between microbial symbiosis and plant community design stabilizes Cd in soils while maintaining crop safety (grain Cd<0.20 mg kg^–1), establishing an ecoengineering approach for contaminated farmland remediation.