Composting and vermicomposting residues of açaí and babassu for sustainable agriculture in Amazon

Agroindustrial wastes in southeastern Amazon are abundant and there are policies encouraging proper disposal for such wastes for sustainable agriculture. In this study we compared the chemical parameters of composts resulting from composting and vermicomposting sheep manure added to agroindustrial wastes as a bulking agent. Piles of compost were created using sheep manure, fruit waste, and a bulking agent. The treatments consisted of compost piles of: Tc - sheep manure and fruit pulp; Ta - sheep manure, fruit pulp and triturated açaí seeds; Ts - sheep manure, fruit pulp and sawdust, and Tb - sheep manure, fruit pulp and babassu coconut residue. After 50 days, a fraction of the compost from each pile was transferred to vermireactors to compare processes. At the end of the experiment, samples were taken in triplicate from all treatments in both composting and vermicomposting units for chemical analysis. The assessed variables were daily temperature of compost piles and vermireators, C/N ratio, Volatile solids (VS), total kjeldahl nitrogen (TKN), total phosphorus (TP), total potassium (TK), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), boron (Bo). Sawdust-based and babassu-based compost, from composting process, has the lower time for stabilization (about 40 days), pH closer to neutral and more efficient in reducing the C:N ratio than vermicomposts. Vermicomposting process increased the concentration of almost all nutrients in treatments, except for babassu-based compost.