Impact of Microplastics on Fagopyrum esculentum: Altered Soil and Plant Responses

Microplastics (MPs) are increasingly accumulating in agricultural soils, posing risks to soil health and plant development. This study evaluated the short-term effects of two common secondary MPs, polypropylene (PP) and polyethylene (PE), introduced via mulch films at four concentrations (0.05%, 0.1%, 0.3%, and 0.5%), on soil properties and the growth of Fagopyrum esculentum (buckwheat). Buckwheat was grown for 50 days under controlled conditions in soil amended with PP or PE MP, and plant growth parameters, soil nutrients, and microbial biomass carbon were measured. Low PP concentrations, particularly 0.1%, stimulated shoot and root elongation, whereas higher concentrations reduced leaf number and biomass. In contrast, PE predominantly showed negative effects, significantly reducing root length and leaf number at 0.3% and above. Neither MP type caused statistically significant changes in soil element contents but affected buckwheat nutrient accumulation. Notably, soil microbial biomass carbon at the early growth stage (Day 29) decreased from ~240 mg C kg−1 in the control to 70–198 mg C kg−1 (17–71% reduction) under PE and several PP treatments. These findings demonstrate that even short-term exposure to MPs can alter key soil parameters and plant physiological responses, with effects strongly dependent on plastic type and concentration, highlighting concerns about continued plastic use in agriculture.