ABSTRACT:

Veterinary antibiotics (VAs) contamination has become a pressing concern for soil health and crop productivity. Therefore, this greenhouse study evaluated the effects of VAs on the rhizosphere soils of Trifolium alexandrinum and Eruca vesicaria. We compared different concentrations of enrofloxacin (ENR), penicillin (PCN) and sulfamethazine (SMZ) applied individually and as a mixture (MIX) at different concentrations: 0 mg kg^-1, 20 mg kg^-1, 50 mg kg^-1, 100 mg kg^-1, 250 mg kg^-1, 500 mg kg^-1 and 1000 mg kg^-1. Results demonstrated clear concentration-dependent effects of VAs on soil physicochemical and biological properties, with the most pronounced effects observed under MIX treatment. High ENR concentrations (>250 mg kg⁻¹) significantly increased soil pH and bulk density, while reducing electrical conductivity and water-holding capacity.  Increasing concentrations of ENR and MIX resulted in marked declines in calcium carbonate (CaCO₃), total organic carbon (TOC), total dissolved carbon (TDC), total nitrogen (TN), total phosphorus (TP), and exchangeable K, Ca, Na, and Ba. . Microbial analyses revealed a significant suppression of both bacterial and fungal populations with increasing antibiotic concentrations. Enzymatic activities showed differential sensitivity, with esterase being the most responsive indicator of antibiotic stress, phosphatase strongly affected by SMZ, and urease exhibiting a comparatively weaker response. Comparative analysis further indicated that E. vesicaria was more sensitive to VAs than T. alexandrinum, as evidenced by greater disruptions in soil physicochemical, biochemical, and microbial functions. Collectively, this study demonstrates the ecological risks of VAs and emphasize the need for regulated antibiotic use and improved manure management to protect soil health and sustain agroecosystem productivity.

Keywords: veterinary antibiotics; soil health; microbial abundance; enzyme activities; rhizosphere.

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