Impact of Manure-Derived Fertilizers on Bacterial Community and Antibiotic Resistance Genes in Washington Red Raspberry Fields: Final Report

This final report examined how composted dairy manure and raw lagoon manure affected soil bacterial communities and antibiotic resistance genes in a commercial Whatcom County raspberry field. Researchers compared the two manure-derived fertilizers with standard fertilizer using DNA sequencing and PCR analysis. Composted manure increased the richness and evenness of soil bacterial communities and increased several bacterial groups associated with beneficial soil functions. Raw lagoon manure increased bacteria from groups that include potential human and animal pathogens. Researchers detected 45 types of antibiotic resistance genes in soils treated with either compost or raw lagoon manure, compared with 28 under standard fertilization. Some resistance genes occurred only in manure-treated soils, although many were present regardless of fertilizer. The findings demonstrate that manure-derived fertilizers can produce both potential soil-health benefits and microbiological risks.