IRRIGATION WITH RECLAIMED WATER AND RISK OF MICROBIAL CROP CONTAMINATION Christopher Y. Choi Dept. of Agricultural and Biosystems Engr., The Univ. of Arizona, Tucson, Arizona, USA Charles P. Gerba Dept. of Soil, Water, and Environmental Sciences, The Univ. of Arizona, Tucson, Arizona, USA Inhong Song Dept. of Agricultural and Biosystems Engr., The Univ. of Arizona, Tucson, Arizona, USA Scott W. Stine Dept. of Soil, Water, and Environmental Sciences, The Univ. of Arizona, Tucson, Arizona, USA Abstract This study aimed to compare as well as evaluate microbial survival under dry and humid conditions using reclaimed irrigation water by two irrigation methods. Three indicator microorganisms, Escherichia coli ATCC 25922, Clostridium perfringens, and coliphage PRD1, were applied through reclaimed irrigation water to sixteen plots growing cantaloupe, lettuce, and bell pepper in a greenhouse. Eight of these plots were subsurface drip irrigated (SDI), while the remaining plots were furrow irrigated (FI). Relative humidity varied from 15 to 65 % in dry condition experiments, whereas relative humidity fluctuated between 55 to 80 % in humid condition experiments. Temperature was maintained at 15 to 33 °C. Six sampling events over the two-week period followed the injection of indicator organisms in the irrigation water. Samples of the edible parts of produce, the surface soil, and the subsurface soil at a depth of 10 cm were collected and assayed. The levels of crop contamination were ranked from the highest to the lowest: cantaloupe, lettuce, and bell pepper, respectively. Greater initial contamination took place on furrow-irrigated crops under both humid and dry conditions as compared to subsurface drip irrigated plots. Overall, E. coli and PRD1 microorganisms survived for longer periods of time in dry conditions than in humid conditions. Careful irrigation and harvest scheduling based on the microbial survival data may reduce health risks by ensuring viral die-off under various field conditions.