The xenobiotic doxycycline affects nitrogen transformations in soil and impacts earthworms and cultivated plants.

The effects of doxycycline (DOX) on microbial biomass C and nitrates production in soil, on earthworms and cultivated plants were examined. The concentrations for the various tests were selected after preliminary experiments, to present impact and be close to the environmentally relevant. The results revealed impacts of the antibiotic on microbial biomass C and NO production at the concentration level of 7.2 mg/kg soil dry weight (d.w.), but these parameters recovered to normal values since the antibiotic was applied once as a pulse. Moreover, the drug had negative effects on earthworm juveniles' total number at the concentration level of 30 mg/kg soil d.w. In addition, the toxicity tests on plant seedling growth revealed negative effects of the antibiotic for tomato at the concentration level of 45.44 mg/kg soil d.w. However, DOX showed positive effects for corn seedling growth, showing that the results of such experiments are valuable for sustainable animal wastes management. Non-significant effects were observed for seedling growth of pea, pumpkin and bean plants. The results of the study are valuable for the impact assessment of the antibiotic in the terrestrial environment and the management of contaminated animal waste.