Effects of compost containing oxytetracycline on enzyme activities and microbial communities in maize rhizosphere soil

Abstract

Veterinary antibiotics can enter agricultural fields via the application of livestock manure containing antibiotics. However, the response of soil microorganisms to compost containing antibiotics is not well understood. A 120-day pot experiment was conducted to investigate the impact of compost containing oxytetracycline (OTC) on the enzyme activities and microbial communities in maize rhizosphere soil. Swine manure was artificially spiked with OTC at four concentrations, 35, 70, 105, and 140 mg kg⁻¹, and combined with straw to produce compost. The compost products were applied to soil planted with maize. Rhizosphere soil samples were collected on days 1, 15, 30, 60, and 120. The results indicated that the urease activities first increased and then declined, while in contrast, the alkaline phosphatase activities first decreased and then increased slightly. Catalase exhibited dose-related activation during the maize growth period. At the end of the experiment, the soil enzyme activities were similar to their initial values, indicating that the soil enzymes showed a level of recovery. The carbon metabolic activity levels were higher in the soils with high OTC concentrations than in the control, whereas the Shannon diversity index was higher in the control soil. The results of principal component analysis (PCA) indicated that the application of compost containing OTC shifted the structure of the soil microbial community and negatively affected its stability. These results suggest that the compost containing OTC exerted selective pressure on enzyme activities and microbial communities in maize rhizosphere soil and decreased their resilience to antibiotic pollution.