1. Dep. of Soil Chemistry and Plant Nutrition; Agricultural Res. Organization, Inst. of Soils and Water; Bet Dagan 50-250 Israel
2. Dep. of Field Crops, Faculty of Agriculture; Hebrew Univ. of Jerusalem; POB 12 Rehovot Israel
3. Dep. of Soil and Environmental Sciences; Univ. of California; Riverside CA 92521