1. Institute of Soil, Water and Environmental Sciences; Agricultural Research Organization, Volcani Center; P.O. Box 6 Bet Dagan 50250 Israel
2. Dep. of Soil and Water Sciences, Robert H. Smith Faculty of Agriculture, Food and Environment; Hebrew Univ. of Jerusalem; Rehovot Israel
3. Dep. of Soil, Water and Climate; University of Minnesota; St. Paul MN 55108