Assessment of microplastic pollution on soil health and crop responses: Insights from dose-dependent pot experiments

Microplastics (MPs) are increasingly recognized as environmental contaminants with complex impacts on soil health and crop productivity. This study investigates the effects of MP contamination in soil through field investigation and pot experiments. Field analysis revealed the presence of polyethylene terephthalate (PET) and high-density polyethylene in soil and plant roots, with visible pollution concentrated in the upper layers. In controlled pot experiments, Brassica juncea (mustard) and Lycopersicum solanaceae (tomato) plants were exposed to PET, polystyrene (PS) and nylon (NL) at different concentrations. The plants exhibited dose-dependent responses, with the treatments of 5% and 10% MPs showing the most detrimental effects (p < 0.05) on soil properties, particularly pH and available nitrogen levels. Both species displayed significantly different responses to treatments (p<0.05). Specifically, PS at a 5% concentration notably suppressed leaf area index while 10% NL resulted in reduced root length and chlorophyll content. PET posed the most significant hindrance to root growth. Interestingly, 10% NL with a high Potential Hazard Index score and a rating of hazard category IV, emerged as the most hazardous polymer at concentrations of 1% and 10%, while at 5%, PS had the most significant impact on plant properties. NL had an overall detrimental effect on mustard plants, whereas PS was more harmful to tomato plants. PET affected both species similarly. The results add to the growing information on the potential risks of MP pollution in the terrestrial environment which supports soil health and dependent organisms.