A Center for Produce Safety (CPS) –funded study led by a University of Arizona researcher is underway to determine how irrigation water that is treated to control microbial activity may affect pathogens on crop surfaces or soil. Principal investigator Channah Rock, Ph.D. hopes to capture new data that will provide a better understanding of the potential added benefits of irrigation water treatment, with the end goal of developing a quantitative microbial risk assessment (QMRA) for industry to gauge the reduction in microbial risk from treated water applied to crops preharvest.
For the study, the researchers inoculated plant tissue and soil with known microbial populations, using a nonpathogenic Escherichia coli strain as a surrogate. The researchers then applied irrigation water treated with common sanitizers like peroxyacetic acid (PAA) or calcium hypochlorite to the test crops, sampling plants and soil periodically to determine pathogen die-off over time. The work is being conducted in commercial-scale university fields of spinach and Romaine lettuce.