Bacterial and Fungal Communities Impact on Degradation of Plastic Mulch Residuals in Soil

Although plastic mulching films can help increase agricultural productivity, their removal poses a significant environmental danger. The use of biodegradable plastic mulches is an appealing eco-sustainable solution to environmental contamination problems for agroecosystems. Because the biodegradation of plastic pieces in soil is strongly dependent on microbial populations, it is critical to investigate whether and how microbial communities affect different types of mulch residuals in the soil. Through the study of the degradation of different mulches residues and of the microbial dynamics for a 6-month incubation of soil trial at three different incubation temperatures (room temperature, 30°C and 45°C) it was possible to evidence that biodegradation of mulch residual depending on of the catabolic activities of specific microbial population and the temperature of incubation. In particular, the increase of temperature up to 45°C determined a reduction of the degradation capacity for all types of mulch considered. Moreover, high-throughput sequencing bacterial alpha diversity was primarily influenced by plastic type and temperature, while fungal populations were mainly affected by temperature. Beta diversity was impacted by all experimental variables. Predicted functional genes crucial for degrading complex substrates, including those encoding hydrolases, cutinases, cellobiosidases, and lipases, were derived from 16S rRNA gene sequencing data. Cluster analysis based on predicted enzyme-encoding gene abundance revealed two clusters, mainly linked to sampling time. Finally, core microbiome analysis identified dominant bacterial and fungal ASVs in various soil-plastic ecosystems during degradation, pinpointing species potentially involved in plastic breakdown.