Fate of Biodegradable and Conventional Mulch Films in Agricultural Soils: Aging-Induced Microplastic Formation, Azoxystrobin Sorption–Desorption Dynamics, and Penicillium expansum Growth on Films

Agricultural mulch films are utilized to optimize crop yields. However, their extensive use is linked to environmental drawbacks, including microplastics (MPs) formation due to aging and pesticide adsorption. This study integrated three connected aspects of mulch aging: (i) MPs’ formation from biodegradable (PBAT/PLA, TPS) and conventional (PE) films under natural/artificial aging, (ii) azoxystrobin (AZO) sorption/desorption dynamics on/from resulting MPs, and (iii) inhibitory effects of films with adsorbed AZO on Penicillium expansum growth and patulin production. MP surfaces were characterized using ATR-FTIR, SEM, and contact angle measurements. The one-year field experiment demonstrated the formation of biodegradable MPs (≥100 μm) from TPS and PBAT/PLA mulch films under the tested field conditions, while particles < 100 μm remained unquantified. Biodegradable MPs rapidly adsorbed over 85% of AZO and showed minimal desorption (<15%), with artificially aged MPs exhibiting the highest partition coefficients. By contrast, PE adsorbed AZO only after natural aging. Aged agricultural films inhibited P. expansum more strongly than pristine ones, with inhibition increasing alongside adsorbed AZO levels.