Antibiotic Ciprofloxacin in Irrigation Water: Its Effect on Medicago sativa (Alfalfa), Including Carbon Fixation and Root Growth

The presence of antibiotics in irrigation water is an emerging problem. This study aimed to evaluate the effect of irrigation using water-containing ciprofloxacin on alfalfa (Medicago sativa) nitrogen and carbon fixation, number of root nodules, root and stem length, and root and stem weight. A surface layer of soil from Piracicaba, Brazil, was used in controlled conditions. The soil pH was adjusted to neutral levels, and alfalfa (M. sativa) was grown. Seeds inoculated with Rhizobium sp. were distributed in 12 pots comprising three treatments employing three repetitions and three controls. The experiment was conducted in a plant growth chamber, where six irrigations were carried out with contaminated water with ciprofloxacin at 0, 1, 10, and 100 mu g L-1 for 40 days. The presence of ciprofloxacin in irrigation water decreased carbon fixation in alfalfa leaves by up to 8.9%, reducing the number of root nodules by 96% at 100 mu g L-1 and leading to their elongation. However, it had no significant effect on soil nitrogen and carbon, similarly in stem length and, finally, in root and stem biomass. This indicates the tolerance capacity of alfalfa to the tested concentrations.