Soil management practices shape the abundance, diversity, and spread of antimicrobial resistance

Agricultural soils are critical hotspots of antimicrobial resistance genes (ARGs). Yet, the environmental factors shaping these reservoirs and the hazards they pose to humans and livestock remain poorly understood. Because management practices introduce antibiotics, heavy metals, and nonantibiotic biocides, they can rapidly select for resistance. Most studies have examined components of management practices in isolation, overlooking the multiple stressors of modern industrial agriculture. Here, we used a large-scale field experiment to examine how multiple stressors from soil and crop management interact to shape antimicrobial resistance. We combined shotgun metagenomics, phylogenomics, and risk-score analyses to quantify the diversity of ARGs, mobile genetic elements (MGEs), and the transmission potential of drug-resistant pathogens. Relative to other management systems, intensive, chemically reliant monoculture systems, typical of the US Corn Belt, create strong selective pressures promoting more abundant and diverse ARGs and MGEs. These systems therefore carry greater potential to transmit ARGs, including those with relevance to both livestock and public health such as tetA and bla PAM , likely mediated by integration and excision. In contrast, less-intensive, lower-input systems with diverse crop rotations maintained resistomes with lower abundance, diversity, and transmission potential. Our results suggest that these patterns could arise due to the divergent effects of management practices on overall soil microbial diversity, an ecological barrier that can suppress ARGs. This study highlights the need to understand the combined stressors of agricultural practices, beyond antimicrobial use, to design effective strategies to mitigate antimicrobial resistance.