1. Inst. of Soils, Water and Environ. Sci., Agric. Res. Organ., the Volcani CenterP.O. Box 6Bet Dagan50250Israel
2. Dep. of Soil and Water Sci., Faculty of Agric., Food, and Environ. Quality Sci.the Hebrew Univ. of JerusalemP.O. Box 12Rehovot76100Israel