Quality evaluation of slaughterhouse waste compost

Abstract

This study evaluated physical and chemical characteristics and the stability and maturity of slaughterhouse waste (SHW) composted with fresh (FYT) or with semicomposted yard trimmings (SCYT). Also evaluated was the agronomic response of the gramineous forage Brachiaria brizantha cv. Mulato to the application of 0 and 400 kg N/ha as SHW compost. The treatments evaluated were composts containing none, single, or double layers of SHW with FYT or with SCYT as bulking agents. Also evaluated were three commercial composts made from vegetable residues, yard trimmings, goat manure and alluvial residues (CC1); these same materials minus alluvial residues (CC2); and sewage sludge and wood chips (CC3). Among treatments, FYT-single layer SHW compost had the highest concentrations (P < 0.05) of organic matter (OM) (687 g/kg) and carbon (C) (382 g/kg); CC1 and CC2 presented very high inorganic matter concentration (779 and 743 g/kg, respectively); C:N ratio was highest for SCYT-single layer SHW (15.61).The mineral profile, cation exchange capacity, particle density, and electrical conductivity of the experimental treatments were within accepted limit values usable for compost. No significant differences were observed for relative germination of seeds exposed to the composts, whereas root elongation and germination index differed (P < 0.05) among treatments but not in a systematic manner. After six weeks of growth of the forage grass fertilized with the composts, chlorophyll concentration, N (%), and biomass (g DM/pot) exhibited low values in all treatments.The composts evaluated were mature and stable and constituted potentially useful soil amendments; however, as indicated by the agronomic performance, compost alone, even when applied at equivalent N rate of 400 kg/ha, cannot provide the optimum quantities of nutrients that cultivar Mulato needs for initial rapid development.