The Effect of Application of Mostly Applied Antibiotics in Agriculture on Soil Bacteria and Fungi ‎Count in Rhizosphere Soil, Growth Indices, and Nodule Number of Chickpea Roots

The present study evaluates the effect of various application methods of mostly applied antibiotics in agriculture (gentamicin, oxytetracycline, penicillin) at different concentrations on root and shoot growth indices and number of rhizobial nodules of chickpea plant and the count of total bacteria, fungi, and coliforms in the soil around the plant root after a growth period of 60 days in greenhouse as a split-plot design. Application of antibiotics, even gentamicin, raises plant shoot dry weight, compared to the control, with the lowest weight of 0.98 g/pot observed in the control (without antibiotic). Root dry weight in penicillin-applied treatments, especially at higher concentrations has been the highest (1.1 g/pot), and the lowest in gentamicin-applied treatments, especially when applied as seed coating (0.48 g/pot). In total, antibiotic application decreases the root to shoot ratio compared to the control. Application of all antibiotics increase soil bacterial count in the pots after 60 days in comparison with the control. Also, increasing the concentration of gentamicin and penicillin, decreases plant root nodule number by 78.8% and 59.7%, respectively. Overall, the effect of antibiotics on soil microbial count and plant growth depends on antibiotic type and application method.