Effect of Soil Organic Matter Content on Uptake of Four Veterinary Antibiotics by Pepper

Abstract

The objectives of this study were to investigate the effect of soil organic matter content on the accumulation of veterinary antibiotics in pepper (Capsicum annuum L.) and the effect of antibiotic concentrations on culturable soil-borne bacteria. Soils containing 0%, 5%, or 10% (vol/vol) organic matter content were prepared using coir dust. Four veterinary antibiotics: sulfamethoxazole, sulfamethazine (sulfonamide series), oxytetracycline, and chlortetracycline (tetracycline series), commonly used in Korea were selected for this study. Antibiotic mixtures of equal amount of each antibiotic were used to spike the soil to achieve concentrations of 0, 1, 5, and 10 mg kg−1, respectively. Pepper cultivated for 2 weeks after sowing was transplanted into pots filled with soil treated with organic matter and antibiotics. After 8 weeks, pepper roots, leaves, and fruits were harvested, and antibiotic concentrations in the soil and pepper plants were analyzed. Concentrations of the tetracycline series in soil were higher than those of the sulfonamide series. The amount of sulfonamide series antibiotics transferred to pepper roots increased with increasing organic matter content in the soil, whereas no significant difference was observed in oxytetracycline and chlortetracycline concentrations in roots. Under all organic matter treatments, the microbial activity in soil decreased when antibiotic concentrations increased. For a given antibiotic concentration, the number of culturable soil-borne bacteria increased as the organic matter content increased.