Suitable moisture and soil nutrient improve degradation of sulfadimidine in soils

Abstract: Widely application of antibiotics in medicine and animal breeding had resulted in its pollution in soil environment. Antibiotic resistance is an increasing challenge for health care services worldwide. Antibiotics of both human and veterinary origins have been widely detected in various environmental matrices including surface water, groundwater, soils, and sediments. Within a relatively short period of time after the first antimicrobial drugs were introduced, bacteria began exhibiting varying degrees of resistance. The excessive use (and abuse) of antibiotics in agriculture, and in both human and veterinary medicine, has played a critical causative role in the development of antibiotic resistance. Sulfadimidine and its epimers/isomers were most frequently detected, and it enters soils by the use of animal excrements as fertilizers. In order to understand the degradation characteristics of antibiotics in agricultural soils, two soils with different nutrient levels were selected to carry out several pot soil culture experiments for studying the effect of fertilizers (organic manure, NPK, N, PK), tillage intensity (tillage, no tillage), water conditions (drought, udic, drought-udic alternation, wetness) and crop plantation (vegetables, not vegetables) on degradation of sulfadimidine in the soils. The results showed that the application of organic manure, NPK, and N fertilizers could promote the degradation of sulfadimidine in the soils, as compared with no fertilizer treatment. The effect of organic manure application on the degradation of sulfadimidine was the most obvious. However, the effect of PK fertilizer application on the degradation of sulfadimidine was not obvious. Tillage also could promote the degradation of sulfadimidine in the soils. Both udic moisture regimes and drought-udic moisture alternation were more favorable for the degradation of sulfadimidine in the soils than drought and wetness. Plantation of vegetable crop could improve the degradation of sulfadimidine in the soils. The degradation proportion of the antibiotics in the rhizosphere soil was higher than the whole soil. While the degradation proportion of the antibiotics in soil with high nutrient level was generally higher than soil with low soil nutrient level. It was thought that effects of fertilization, soil fertility, crop plantation on the degradation of sulfadimidine in the soils were related to alteration in soil microbial activity caused by those factors. Tillage can promote the degradation of antibiotics in the soils by increasing its photolysis.