1. Department of Crop and Soil Science Oregon State University Corvallis OR USA
2. Department of Geography University of Oregon Eugene OR USA
3. Geography Department Western Paraná State University, Marechal Cândido Rondon PR Brazil
4. Center of Isotopic Energy in Agriculture University of São Paulo Piracicaba SP Brazil
5. Soil Science Department Luiz de Queiroz Agriculture College, University of São Paulo Piracicaba SP Brazil