Effects of Combined Pollution of Tetracycline and Sulfamethazine on Tomato Growth and Antibiotic Absorption

Antibiotics are widely used in livestock and poultry farming for disease prevention and animal growth promotion. Due to the low absorption rate of antibiotics by animals, antibiotics can remain in livestock and poultry manure as parent or metabolites and enter the farm environment with the application of livestock and poultry manure, which has potential effects on crop growth. This study assessed the effects of single and combined contamination of antibiotics in soil on tomato plants. The accumulation of antibiotics in tomato plants and the impacts on crop growth were investigated. A pot experiment with sandy soil was conducted in a greenhouse, and a 100-day tomato growth experiment was conducted by adding different doses of tetracycline and sulfadiazine (0, 25, and 50 mg/kg). The antibiotic contents in various tissues and organs of the tomato were examined, and the changes in photosynthetic intensity and biomass of the tomato were observed to simulate the effects of exogenous antibiotic addition on the growth and quality of the tomato. The results indicated that tomato plants simultaneously absorbed tetracycline and sulfamethazine from soil. Antibiotics were primarily absorbed by tomato roots and were further delivered to plant leaves, stems, and fruits. Antibiotics exhibited the highest concentration in roots, followed by leaves, stems, and fruits. The contents of tetracycline and sulfamethazine in plant tissues elevated with the increase in soil antibiotics, which were higher in the vegetative growth stage than those in the late growth stage. At concentrations of 25 and 50 mg/kg, tetracycline and sulfamethazine combined pollution significantly reduced leaf photosynthetic rates and plant biomass. Notably, high levels of antibiotics led to decreases in tomato yield and quality. Additionally, high concentrations of antibiotic contamination elevated leaf nitrogen, phosphorus, and potassium, but reduced the leaf carbon/nitrogen ratio, as well as reduced the vitamin C content in the fruits. Overall, since antibiotics can accumulate in vegetables and enter the food chain, the findings are crucial for evaluating the impacts of soil antibiotic contamination on the production and food safety of tomato products, and will also add to our knowledge of antibiotic migration into the food chain.