Edge-of-field prairie strips and manure management reduce AMR indicators in runoff, researcher says

Dr. Michelle Soupir (Iowa State University) described how unmetabolized antibiotics in animal manure can persist through storage and then be applied to cropland, creating pathways (surface runoff, tile drainage) for movement into surface waters. She presented rainfall-simulator experiments showing manure-amended plots produced runoff containing higher levels of AMR indicator genes, while prairie strips placed at field edges reduced those indicators in runoff and suspended sediments compared with no-strip controls.

Soupir said most indicators were retained in soil columns and only about 10 percent were recovered in leachate in her column experiments, indicating soil retention but noting that high-flow events can overwhelm strip efficacy. She also reported prior studies showing anaerobic digestion, liming and staged storage reduce AMR gene concentrations in manure but do not yield completely 'safe' manure: "we don't... really get to a point where we see, I would say, safe manure or manure where we're not detecting the presence of antimicrobial resistance." Soupir recommended prioritizing mitigation prior to land application and noted economic and scale constraints for some treatments.

Her takeaways emphasized practical design limits (flow intensity, root depth) and opportunities for incentives and further research into scalable farm-level mitigation.