This study investigates the impact of microplastics on soil biophysical properties and microbial function. Microplastics, including polyactic fibers, polyamide beads, polyester fibers, and polyethylene fragments, were added to a loamy sand soil at environmentally relevant concentrations (up to 2% of soil weight). The effects on bulk density, water holding capacity, hydraulic conductivity, soil aggregation, and microbial activity were measured. Microplastics significantly altered these properties, with polyester fibers causing the most pronounced changes. The study highlights that microplastics can disrupt the natural relationships between soil particles and biota, potentially leading to long-term anthropogenic stressors and drivers of global change in terrestrial ecosystems. The findings suggest that microplastic contamination levels may be underestimated in current assessments, and further research is needed to fully understand their environmental impacts.This study investigates the impact of microplastics on soil biophysical properties and microbial function. Microplastics, including polyactic fibers, polyamide beads, polyester fibers, and polyethylene fragments, were added to a loamy sand soil at environmentally relevant concentrations (up to 2% of soil weight). The effects on bulk density, water holding capacity, hydraulic conductivity, soil aggregation, and microbial activity were measured. Microplastics significantly altered these properties, with polyester fibers causing the most pronounced changes. The study highlights that microplastics can disrupt the natural relationships between soil particles and biota, potentially leading to long-term anthropogenic stressors and drivers of global change in terrestrial ecosystems. The findings suggest that microplastic contamination levels may be underestimated in current assessments, and further research is needed to fully understand their environmental impacts.