Abstract: Returning livestock manure to the field is a fundamental strategy for addressing the pollution issues associated with livestock and poultry farming. However, antibiotics contained in manure can pose significant risks to soils after being applied to farmland, compromising environmental safety and human health. In recent years, many studies on the potential risks of antibiotic contamination in farmland soil have been conducted under laboratory conditions, typically by adding manure to simulate contamination. However, these studies cannot fully assess the contamination risks of antibiotics under natural fertilization conditions. We evaluated the impacts of chicken manureborne antibiotics on soil health in Changtu County, Tieling City, Liaoning Province. Chicken manure was applied to replace chemical fertilizers at the rates of 0%, 25%, 50%, 75%, and 100%. We examined the concentration changes and ecological risks of three tetracycline antibiotics (TCs) and three sulfonamide antibiotics (SAs) in the soils. The results showed that TCs in chicken manure were 2.54-4.82 mg·kg^-1 and SAs were 30.41-41.23 μg·kg^-1. Applying chicken manure significantly increased the content of antibiotics in the surface soil, especially for TCs. All six antibiotics could migrate downward in the soil. Under the experimental conditions, SAs had greater migration capacity than TCs. After half a year of fertilization, the SAs were mainly concentrated at 40-60 cm soil layer. Ecological risks of antibiotics in soil were assessed by the risk quotient method. SAs might reach a higher ecological risk at low dose concentrations. By a mixed antibiotic risk assessment, the ecological risk of antibiotics is relatively low when replacing chemical fertilizers with 50% or less proportions of organic fertilizers.

Key words: tetracycline, sulfonamide, organic fertilizer, farmland, ecological risk