The environmental risk of antibiotic resistance genes from manure compost fertilizer gradually diminished during ryegrass planting

Abstract

As one of the emerging pollutants in the environment, antibiotic resistance genes (ARGs) have attracted much attention. Composting is an effective way to reduce ARGs and the compost products were often used as soil amendments. However, the environmental risk of ARGs from compost products to soil and plants has not been well studied. Here, we assessed the environmental risk of ARGs from soil and ryegrass after applying manure composting. This study detected 21 different types of ARGs. Multidrug and tetracycline resistance genes were the most dominant ones, accounting for 39.2%/12.5% and 38.6%/11.6% in soil/ryegrass, respectively. This might be attributed to the decrease of Streptomyces, which is the potential host of multidrug and tetracycline ARGs. The environmental risk value, which was associated with mobile genetic elements (MGEs) and pathogens, increased in the soil and ryegrass, and return to the original level at the end of the growth cycle. The absolute environmental risk values of AH (high additive amount of the swine manure compost) and BH (high additive amount of the sheep manure compost) decreased by 0.0826 and 0.1505, respectively. The outcomes of this study revealed the environmental behavior and risk of ARGs transferring from compost to soil, and then entering into ryegrass, which is important to assess the environmental risk of compost and provide new insights into agricultural food safety.