Spatial variability of soil fertility under agroforestry system and native forest in eastern Amazonia, Brazil oleh Cassio Rafael Costa dos Santos, Augusto Takayuki Matsunaga, Luiz Rodolfo Reis Costa, Mario Lima dos Santos, Alberto Bentes Brasil Neto, Richard Pinheiro Rodrigues, Maria de Nazaré Martins Maciel, Vânia Silva de Melo