1. Universidade de São Paulo Escola Superior de Agricultura “Luiz de Queiroz” Caixa; Postal 09 Piracicaba SP 13418-900 Brazil
2. Department of Soil and Water Science and Department of Agricultural and Biological Engineering at Tropical Research and Education Center; University of Florida; 18905 SW 280 St. Homestead FL 33031
3. Department of Statistics; Institute of Food and Agricultural Sciences; Statistical Consulting Unit; University of Florida; Gainesville FL 32611-0339