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Researchers Explore Food Safety of Dairy Manure as Fertilizer on Raspberries

Researchers from Washington State University recently published results of a study on the
food safety of using dairy manure as fertilizer on red raspberries. The study evaluated a number of manure-derived fertilizers: anaerobically digested liquid effluent, aerobically composted dairy manure, and more concentrated refined fertilizers, such as ammonium sulfate and phosphorus solids. The study found no Shiga toxin-producing E. coli or Listeria monocytogenes in any soil samples. Though Salmonella was found in some fertilizer samples, it was not present in soil, foliar, or fruit samples taken after two or four months. Based on results of this study, the researchers concluded that application of manure-derived fertilizers to raspberry plots four months prior to harvest under GAP did not introduce microbiological safety risk.