Integrating ryegrass-maize intercropping systems for mitigating Cd-Pb contamination: enhancing ecosystem services and habitat sustainability

In agricultural lands, cadmium (Cd) and lead (Pb) co-contamination poses a significant threat to soil health and crop safety. This study evaluates the ryegrass-maize intercropping system as a sustainable approach to mitigate these environmental challenges. A 120-day pot experiment was conducted, revealing that the intercropping system significantly reduced soil Cd and Pb, achieving residual levels below national risk thresholds. Maize grains were confirmed safe, while ryegrass acted as an efficient bioaccumulator. The system enhanced soil ecosystem services, evidenced by a significant increase in key soil enzyme activities and nutrient cycling indicators. Specifically, the intercropping system boosted the activities of catalase, alkaline protease, and urease, which are crucial for redox regulation and nitrogen cycling. Notably, the activity of alkaline protease, responsible for organic nitrogen decomposition, increased by approximately 18.5 times in the intercropping group. Furthermore, the system increased soil organic matter by 5.89%, a core indicator of soil fertility and carbon sequestration, a key supporting service. Habitat sustainability was substantiated through the analysis of microbial community structure and diversity. Although Cd-Pb contamination initially reduced microbial diversity, the intercropping system (C2) mitigated this decline more effectively than monoculture (C1). More importantly, the intercropping system enriched metal-tolerant and functionally critical microbial taxa, such as Actinobacteriota, whose relative abundance reached 43.99% in the C2 group after the experiment. Despite observed phosphorus depletion, which suggests the need for targeted fertilization, the findings support ryegrass-maize intercropping as a viable, nature-based solution for soil remediation. This scalable strategy not only addresses contamination but also supports sustainable land management, contributing to the resilience and restoration of degraded farmlands.