1. Institute of Soil, Water and Environmental Sciences, the Volcani Center Agricultural, Research Organization POB 15159 Rishon LeZion 750510 Israel
2. Dep. of Soil and Water Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment the Hebrew Univ. of Jerusalem Israel
3. Dep. of Earth and Planetary Sciences Weizmann Institute of Science Rehovot 7610001 Israel