1. IAEA–Soil and Water Management and Crop Nutrition Section Wagrammer Strasse 5, P.O. Box 100, 1400 Vienna Austria Vienna 1010
2. Univ. of California Dep. of Land, Air and Water Resources Davis CA 95616
3. USDA‐ARS, Soil and Water Management Research Unit P.O. Drawer 10 Bushland TX 79012
4. FAO Viale delle Terme di Caracalla Rome Italy 00153