| dc.description.abstract | In recent years, the government of our country has been actively promoting the utilization of anaerobic digestion processes to convert livestock and poultry waste into biogas slurry and residue, which is subsequently used as a nutrient-rich fertilizer for agricultural land. This approach aims to improve soil quality and increase crop yields through the recycling of organic waste resources. However, with the shift towards intensive livestock farming practices, antibiotics are often administered to animals to promote rapid growth, potentially leading to the emergence of antibiotic resistance in the resulting animal waste. Poor management of these new-generation fertilizers, if derived from antibiotic-exposed livestock, can contribute to increased levels of antibiotic resistance (AR), allowing antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) to enter the environment via the ＂fertilization＂ pathway, indirectly elevating the risk of AR in local soils. Despite the importance of understanding the impact of returning biogas slurry and residue to local soils on AR, there is currently limited research on this topic. This study addresses this gap by conducting soil sampling and testing in agricultural fields where different fertilizers, including biogas slurry and residue, chicken manure compost, chemical fertilizers, and sesame meal powder, were applied. Furthermore, based on laboratory results from previous soil microcosm experiments, the study investigates the long-term accumulation of ARGs in soil following fertilizer application, hypothesizing that the order of ARG accumulation will be biogas slurry and residue > chicken manure compost > chemical fertilizers ~ sesame meal powder.
Soil samples were collected from rice fields where biogas slurry and residue, chemical fertilizers, and sesame meal powder were applied, as well as from vegetable fields treated with chicken manure compost. Four predominant ARGs (tetM, tetO, sul1, blaTEM, ermB) and a specific mobile genetic element (intI1) were selected for analysis and comparison. The research findings indicate that fertilizer application increases the abundance of ARGs in local soils, with biogas slurry and residue soil showing significantly higher relative ARG abundance compared to chemical fertilizer soil (p < 0.05). In contrast, only a few ARGs in chicken manure compost-treated soil were lower than in chemical fertilizer soil. The study also explores the relationship between environmental factors and ARGs and quantifies the decay rates of ARGs in local soils using two different decay models. Results indicate that, among the parameters studied, pH and total nitrogen are the most influential environmental factors affecting ARG abundance. However, the decay rates of ARGs in soil amended with biogas slurry and residue are not statistically different from those in soil amended with other fertilizers. The study observed that ＂the abundance of ARGs in soil amended with biogas slurry and residue remained consistently higher than in soils treated with other fertilizers throughout the sampling period.＂ This highlights the potential risk associated with the use of anaerobic digestate-derived fertilizers in promoting environmental AR. To ensure that this phenomenon is not limited to the scope of this short-term investigation, continuous monitoring and further research are essential to substantiate the substantial risks associated with the promotion of AR in the general environment and public health through the application of anaerobic digestate. | en_US |