Soil texture governs the influence of different microplastics on soil hydraulic properties

Abstract Adequate water availability in soil is crucial for optimal plant growth. However, even small amounts of microplastics (MPs) can disrupt the soil pore structure, impacting water retention and hydraulic conductivity, and consequently plant‐available water. This study investigated the effects of various MPs on soil water availability and hydraulic properties in three soil types (Luvisol, Albic Luvisol, and Chernozem). Four polymer types—low‐density polyethylene, polypropylene (PP), polystyrene (PS) particles, and polyester (PET) microfibers—were tested at a mass concentration of 0.4 weight‐%. Results showed that the impact of MPs varied with soil texture and saturated water content. In the Luvisol (silt loam), PET microfibers enhanced porosity, creating more air‐filled pore volume, macropores, and increased water retention and saturated hydraulic conductivity. Conversely, PS and PP particles reduced porosity in the Luvisol, enhancing near‐saturated hydraulic conductivity, likely due to decreased tortuosity. In the Albic Luvisol (sand), PET microfibers increased porosity and plant‐available water, but both microfibers and particles negatively affected saturated and near‐saturated hydraulic conductivity, with PS particles and PET microfibers potentially clogging soil pores. In the Chernozem (silt loam), PET microfibers significantly increased air‐filled pore volume without changing overall porosity but negatively impacted water retention and plant‐available water. The increase in saturated conductivity was likely due to preferential flow paths, while under dry conditions near‐saturated hydraulic conductivity decreased, likely due to increased tortuosity.