Contextual Microplastic Impacts on Croplands From Field Trials and Global Synthesis

Microplastic accumulation is an increasingly widespread anthropogenic disturbance in agricultural soils, yet ecological risk assessments remain dominated by simplified laboratory assays that may not capture context-dependent responses under field conditions. Here, we combined a five-year experiment across four semi-arid cropland sites with a global synthesis restricted exclusively to outdoor field observations to quantify microplastic effects on crop yield, soil quality, and ecosystem multifunctionality. Under a high microplastic loading (0.2% w/w), we detected no consistent negative functional responses across crops, sites, and growing years. The field-only synthesis revealed weak average effects but substantial cross-study heterogeneity. Plant presence was associated with weaker effects, with vegetated systems showing milder changes in soil quality and ecosystem multifunctionality than plant-free soils. Biodegradable polymers did not show a consistent ecological advantage over conventional polymers across field settings. Our findings indicate that effects inferred primarily from laboratory studies cannot be directly extrapolated to the field scale. Importantly, weak functional responses do not address crop internal microplastic uptake, dietary exposure, or toxicological risk, which require separate assessment. These results provide a more realistic basis for assessing the consequences of microplastic pollution for agricultural ecosystem functioning and resilience under global change.