1. Departamento de Ciências do Solo, Federal University of Lavras, Lavras, Minas Gerais, Brazil
2. Department of Research and Development, Brazilian Agricultural Research Corporation (Embrapa Meio-Norte), Teresina, Piauí, Brazil
3. Department of Agronomia, Federal University of Piauí, Teresina, Piauí, Brazil
4. Departamento de Fitotecnia, Federal University of Ceará, Fortaleza, Ceará, Brazil