New research finds the pathogen E. coli O157:H7 lives about 30 days in soils from California’s Salinas Valley — 10 days more than in the state’s Imperial Valley or Yuma, Ariz.

Lower salinity in Salinas irrigation water is the main cause of the difference, said Mark Ibekwe, a microbiologist with the U.S. Department of Agriculture’s Agricultural Research Service in Riverside, Calif.

Mike Hornick of The Packer reports Ibekwe and three colleagues published their findings, “Persistence of Escherichia coli O157:H7 in Major Leafy Green Producing Soils,” in the journal Environmental Science & Technology in October.

The results were based on laboratory-tested soil samples. Field studies of E. coli are typically limited to nonpathogenic varieties.

Increasing salinity in Salinas water would not be realistic or beneficial for leafy greens growers there, Ibekwe said. Nevertheless, the research underscores the importance of keeping new pathogens from entering the fields.

“You don’t want to introduce another variable into the farming environment that will ultimately cause adverse effects on the crops and result in lower yield,” Ibekwe said. “Because of how salinity will react with other factors there, we are not suggesting that.

“What we’re saying is that because we know there’s a longer survival in the Salinas area, we should be very, very careful in introducing pathogens from manure, poorly composted materials or any source at all into the farming environment,” he said.