'American Society of Agricultural and Biological Engineers (ASABE)'
Abstract
Surface irrigation systems that reuse water may deliver bacteria to produce destined for fresh consumption. Four irrigation systems delivered (1) well water free of Escherichia coli via subsurface drip irrigation, (2) canal water with moderate levels of E. coli via subsurface drip irrigation, (3) canal water with moderate levels of E. coli via furrow irrigation, and (4) canal water with enhanced levels of E. coli via furrow irrigation. The four irrigation systems (replicated five times) applied water to onion on silt loam. Water was sampled hourly for E. coli, and the lateral movement of E. coli in the soil solution was tracked by soil samples following irrigations. Onion bulbs were sampled for E. coli contamination. The most probable numbers of E. coli in water and soil water were determined using IDEXX Colilert® and Colisure®, respectively, and Quanti-Tray/2000®. Under both furrow and subsurface drip irrigation, a fraction of the E. coli was delivered to the soil immediately adjacent to the onion bulbs. The silt loam retained most of the E. coli content away from the onion bulbs and close to where the water entered the soil. No E. coli was detected inside of the onion bulbs from any irrigation treatment. Current subsurface drip or furrow (flood) irrigation practices do not appear to pose a significant risk for bacterial contamination of dry bulb onion grown on silt loam
