Short-term comparative effects of different sources of organic residue on soil organic carbon and aggregate stability

Identifying specific organic amendments that can maximize stable aggregates and increase soil organic carbon (C) recovery is a critical component of soil management. In this study, we investigated comparatively, the short- term effects of poultry droppings (PM), cow dung (CD),swine slurry (SS), rice chaff (RF), boiler ash (BA) and control (no amendment) on significant soil properties such as aggregate stability, organic carbon fractions, pH and soil temperature. The research, which involved incubation of a mixture of each organic residue with soil in the laboratory for 90 days, adopted a completely randomized design (CRD). Results indicated that mean weight diameter – an index of aggregate stability and strength was highest (1.26 mm) in RF treated soil followed by BA, which did not differ significantly from SS. Aggregate stability in CD treated soils did not differ significantly from that of PM. The soil organic carbon was higher in all amended soils and ranked in the order of RF > CD >SS >PM > BA > Control and highest at 30 days sampling. Soil pH was highest (pH 7.0) in CD and PM treated soils and least (5.7) in SS treated soil and generally at 90 days sampling. There were significant (p=0.05) interactions between applied organic waste and incubation time on soil pH and organic carbon content. The organic residues differed in their effect on soil temperature at different sampling dates with PM treated having the highest.