Biodegradable plastic films as eco-sustainable alternative to polyethylene films: Effects on soil multifunctionality

The use of plastic films is among the major sources of pollution in agricultural soils and can impact soil properties and ecological functions. This study aimed to assess the short-term effects of polyethylene (PE) and biodegradable (BIO) plastic films on soil quality and multifunctionality by comparing them with an untreated control (CNT). A comprehensive set of abiotic (texture, bulk density, pH, water content, organic and total carbon, and total nitrogen) and biotic (enzymatic activities, DNA yield, eubacterial and fungal biomass) soil properties was assessed 6 months after treatment application, both in mesocosm and field experiments. These parameters were used to: (1) calculate ecological indices (IBR, integrated biomarker response index; MAI, metabolic activity index; SQI, soil quality index) to assess soil quality; (2) derive soil functions (N and C storage and decomposition), then integrated into a soil multifunctionality index (SMF) and analyzed using a random forest approach to identify the most influential variables contributing to soil multifunctionality. In the field experiment, both BIO and PE plastic films increased soil water content compared to CNT, while BIO led to a 2-fold increase in β-glucosidase activity relative to PE and CNT. In the mesocosm experiment, PE increased total soil carbon by approximately 1.2-fold compared to BIO and CNT treatments. PE enhanced carbon storage capacity in mesocosm conditions, aligning with the results from the random forest analysis, which identified carbon storage as a key driver of soil multifunctionality. Despite these specific effects, no significant short-term changes in overall soil multifunctionality were observed for both plastic films. Among the indices tested, MAI highlighting differences between treatments emerged as the better integrative tool to monitor early functional changes in soil ecosystems.