Microplastics in cropping systems: Evidence of their effects on soil nutrients, trace elements, enzyme activities and microbial function. Proyect ECOS ANID 220007

Presence of microplastics (MPs) in soils is an emerging concern due to their potential interaction with other contaminants and their effects on soil. This study aimed to evaluate the influence of cropping systems on the MPs content, trace elements (TE), chemical and biological properties of the soil, and structure of microbial communities. Soils were sampled from five crops: maize, oat, sugar beet, tomato, and wheat. Concentrations of MPs, chemical parameters, total and bioavailable concentrations of TE, enzyme activities, and microbial composition were determined through 16S and ITS sequencing. MPs content was higher in sugar beet and oat (260 and 200 items kg-1, respectively) and lower in maize (60 items kg-1), with polypropylene as the dominant MPs. Tomatoes showed higher nutrient availability, with Olsen P at 98 mg kg-1 (3-8 times higher), increased urease, phosphatase, and beta-glucosidase activities, and elevated Cd levels. Bacterial communities were dominated by Actinomycetota, with Acidobacteriota present in all cropping systems except wheat, and Bacillota was particularly abundant in tomato, clearly separating this crop from the others. Fungal communities were consistently dominated by Ascomycota, while Basidiomycota appeared in lower proportions, with slightly higher representation in oats and beets. Minor fractions of Mortierellomycota and Mucoromycota were detected. Multivariate analysis revealed associations between MPs, bioavailable TE, and enzyme activities (beta-glucosidase), although the correlations were weak. These results show that crop type, agricultural management, and the presence of contaminants interact and may affect microbial communities without demonstrating the detrimental effects of MPs.