1. Department of Soil Science, Luiz de Queiroz College of Agriculture (Esalq), University of São Paulo (USP), Av. Pádua Dias, 11, 13418-900 Piracicaba, SP, Brazil
2. Laboratory of Nuclear Instrumentation (LIN), Center for Nuclear Energy in Agriculture (CENA), University of São Paulo (USP), Av. Centenário, 303, 13416000 Piracicaba, SP, Brazil