1. Department of Soil Chemistry and Plant Nutrition; Institute of Soil, Water and Environmental Sciences, the Volcani Center, Agricultural Research Organization; P.O.B. 6 Bet Dagan 50250 Israel
2. Agricultural Research Organization; Gilat Research Center; D.N. Negev 85280 Israel
3. Shaham, Ministry of Agriculture and Rural Development; Bet Dagan 50250 P.O.B. 6 Israel