Evaluating the Impact of Traditional and Biodegradable Mulch Film Residues on Heavy Metal Dynamics and Maize Productivity: Insights from Arbuscular Mycorrhizal Fungi Community Analysis

Microplastics and heavy metals (HMs) in soil pose significant environmental and health risks, yet the interactions between mulch film residues and HMs, and their effects on maize productivity, remain poorly understood. This study examined the impacts of long-term traditional polyethylene mulch film (TMF) and biodegradable mulch film (BMF) residues on soil properties, maize root accumulation of HMs, the arbuscular mycorrhizal fungi (AMF) community, and maize productivity under open field conditions. TMF residues significantly increased the soil total carbon (TC), C/N ratio, and bioaccumulation coefficients (BACs) of arsenic (As) and cadmium (Cd) while lowering soil pH and water content. These changes altered AMF colonization and enriched the Paraglomus genus, leading to enhanced maize leaf antioxidant activity and reduced chlorophyll content, although maize growth was not statistically affected. In contrast, they improved soil nutrient availability (e.g., nitrogen and phosphorus), increased TC and the C/N ratio, and reduced soil pH. Notably, BMF residues decreased the BACs of As and Cd, reduced AMF spore density without altering community structure, and ultimately enhanced maize biomass. These effects were associated with BMF’s ability to lower pH and chelate HMs, thereby mitigating their bioavailability and promoting plant growth. Furthermore, the enriched abundance of AMF species, particularly from the Claroideoglomus genus, facilitated heavy metal chelation and reduced HM accumulation in plants. The findings underscore the potential of BMF and AMF for co-remediation of microplastics and HMs, highlighting the importance of mulching strategies for sustainable agriculture.