Effects of Tetracyclines on Enzymatic Activity and Soil Nutrient Availability

The objective of this study was to evaluate the influence of tetracyclines associated with swine wastewater on the enzymatic activity of soil over time, in relation to the biogeochemical cycle of the nutrients during two seasons of the year. The experiment was carried out in soil-containing pots that received two successive applications of swine wastewater treatments, in the summer and autumn seasons, corresponding to two experimental periods. The swine wastewater was applied in doses of 0.2 and 0.3 L, with or without tetracycline, chlortetracycline, and doxycycline. Soil samples were collected at 2, 4, 8, 15, 30, 45, and 75 days after treatment application to determine the activities of the enzymes dehydrogenase, beta-glucosidase, acid phosphatase, and urease. During both experimental periods, there was an increase in the activities of all enzymes in the presence of swine wastewater. However, these activities decreased in the presence of the applied antibiotics. The observation of enzyme activity over time facilitated construction of longitudinal predictive models, which described the activity of enzymes over time. Our findings indicate that swine wastewater treatments led to a reduction in the bioavailability of nutrients, thereby reducing soil quality and fertility.