1. Institute of Soil, Water and Environmental Sciences; The Volcani Center, Agricultural Research Organization; P.O. Box 6 Bet Dagan 50250 Israel
2. Dep. of Hydrology & Microbiology; Zuckerberg Institute for Water Research, Blaustein Institutes for Desert Research, Ben Gurion University of the Negev; Sde Boker Campus Negev 84990 Israel