**Acknowledgements**

We would like to thank Norman Madarasz and John G. O'Donnell for their valuable suggestions as well as the German Academic Exchange Service (DAAD). This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nivel Superior—Brasil (CAPES)—Finance Code 001 and CNPq for funding research on *Terra Preta*.
