Antibiotics commonly applied in animal farming can alter soil biotic effects on plant functioning and responses to drought stress

BackgroundAntibiotic pollution, caused by extensive antibiotic applications in industrial farming, threatens human and animal health, but may also affect plant functioning. However, it remains unknown whether antibiotics affect plant performance directly, or indirectly via effects on soil biota. Potential soil-community-mediated antibiotic effects may be most pronounced under abiotic stress, as plant-stress alleviation by soil biota may be compromised.MethodsWe conducted a greenhouse experiment to examine how two commonly applied antibiotics (tetracycline and amoxicillin) alter the performance of six grassland plant species in the presence and absence of soil biota. We also assessed whether antibiotic effects on plant performance are stronger under drought stress.ResultsAntibiotic presence did not affect plant biomass, but high tetracycline concentrations reduced positive soil microbial-community effects on biomass allocation to roots. Furthermore, high amoxicillin concentrations enhanced the positive soil-community effect on chlorophyll A fluorescence kinetics (a performance index), while limiting the soil biotic drought stress-alleviating effect on leaf chlorophyll concentration. Nevertheless, most antibiotic effects were antibiotic type- and dose-dependent, differed among species and depended on soil-community presence.ConclusionOur study shows that antibiotics at realistic environmental concentrations can alter plant-soil interactions in plant-species-specific ways and therefore may eventually affect natural plant community composition.