Soil organic carbon plays a key role in plant biomass production. On smallholder farms, crop and livestock are traditionally integrated and support each other. However, due to changes in socio-economic factors, this relationship is lost as resources are mismanaged. The present study was conducted in the Central Ethiopian highlands that represent about 90% of the country’s smallholder farmers. The objective of this study was to quantify soil organic carbon in different agricultural management systems and to document the contribution of livestock to carbon storage. The study included a socio-economic survey and soil laboratory analysis. Results showed that different land uses and conservation measures had various impacts on soil carbon addition and depletion. The comparison between different land uses showed that the highest soil organic carbon was found in grazing land (27%), followed by fenced-off land (2.59%) at 0 to 15 cm soil depth. It also showed that animal waste and farmyard manure added to soil had the highest amount of organic carbon (3.90 and 1.85%, respectively) at 0-15 cm soil depth. It was concluded that livestock waste, farmyard manure, and crop residues improved soil fertility and soil organic carbon in the top soil indicating that livestock and by-products made a significant contribution to carbon storage.
Key words: Farmyard manure, land uses, organic carbon inputs, socio-economic survey, soil management practices.