Control of Viral and Bacterial Contamination of Lettuce by Subsurface Drip Irrigation

Foodborne outbreaks have been associated with the use of irrigation water contaminated with human and animal wastes. The use of subsurface drip irrigation may reduce the contamination of leafy green produce. The goal of this study was to quantitatively assess the impact of a subsurface irrigation system on the contamination of romaine lettuce contaminated with a fecal bacterium and a virus. Plants were transplanted and grown in bottom watering pots. They were irrigated with contaminated water containing Escherichia coli and MS2 bacterial virus. The HYDRUS 2D/3D program was used to model the water movement in the soil to ensure that the soil surface did not become wet and consequently contaminated. Neither E. coli nor MS2 were detected on the surface or internally on/in romaine lettuce. The results demonstrated that subsurface irrigation may successfully reduce the risk of contamination by bacterial and viral pathogens so long as the contaminated irrigation water does not reach the soil surface and thereby come in direct contact with the aboveground portions of the plant.