Native populations in the Brazilian Amazon produce manioc as a staple crop for sustenance and sale through slash-and-burn agriculture. Farmers are reducing fallows from 15-25 to 5-7 years, which is not enough time to accumulate the nutrients necessary to sustain the cropping phase of the cycle. In Par, Brazil, a one hectare 7-year-old secondary forest was cleared using a mulching tractor. Four experimental treatments (N=4) were established in four blocks utilizing manioc and native tree species in a mixed culture with and without P and K fertilizer with and without N-fixers. Fertilization increased growth of tree species and biomass production of manioc. In the presence of I. edulis, there were trends of increased growth and survival among all tree species, except P. multijuga, as well as increased biomass of manioc. Fertilization increased biomass of competition, although, the presence of I. edulis reduced competing biomass in the fertilized treatment.