Effect of Long-term Biogas Slurry Fertilization on Distribution of Tetracycline and Sulfonamide Resistance Genes in Soil

  Objective  Effect of long-term application of pig manure biogas slurry on the abundance and seasonal variations of antibiotic resistance genes (ARGs) presented in the soil was studied.

  Method  Soil specimens at the fields using biogas slurry of pig manure for fertilization for many years were collected in four seasons to compare with those at a nearby location without such practice. The presence and abundance of tetracycline and sulfonamide ARGs in the soils were determined by quantitative PCR.

  Result  There were 11 to 13 classes of ARGs detected in the biogas slurry fertilized soils. The ARG diversity was significantly greater in them than control with a relative abundance of tetG, sul1 and sul2 genes. The increased levels of tetracycline and sulfonamide ARGs also showed significant seasonal variations with the highest relative abundance in spring. Long application of biogas slurry on land resulted in abundant tetG, tetZ, tetM, tetO, tetW, sul1, and sul2 genes, which were the dominant ARGs year-round, in the soil.

  Conclusion  Long-term biogas slurry application could elevate the ARG level in the soil. Therefore, it was highly recommended the waste material utilization be optimized by a fermentation process prior to fertilization for antibiotic contamination mitigation on farmland.