1. Instituto de Investigaciones Agropecuarias y ForestalesUniversidad Michoacana de San Nicolás de Hidalgo Tarímbaro Mexico
2. Center for Nuclear Energy in AgricultureUniversity of São Paulo Piracicaba Brazil
3. Instituto Nacional de Investigaciones Nucleares Ocoyoacac Mexico
4. Soil and Water Management & Crop Nutrition SubprogrammeDepartment of Nuclear Sciences and ApplicationsJoint FAO/IAEA Division International Atomic Energy Agency Vienna Austria