author(s)
Dugasa Gerenfes, Abraha G Giorgis and Gobena Negasa

abstract
Soil organic carbon (SOC) is an important property in regard to soil and environmental quality. There are many methods to determine SOC. In this study, Walkley Black and Loss on Ignition methods were chosen and sixty sub-samples representing were collected from three different parts of Arsi zone areas of Ethiopia, and then nine a composite samples were used for SOC determination methods. The variables were equipment, accuracy, efficiency, complexity, cost and environmental effect. Walkley–Black and loss on ignition (LOI) were determined on whole soils mesh size of 2 mm. From the two selected methods Loss on Ignition was the accurate and simple method for determining soil organic carbon that do not involve the use of chemicals that damage the environment are required. Walkley-Black method is a wet oxidation procedure which is relatively accurate and popular method for the determination of soil organic matter but it is time-consuming, costly and also has a high potential to cause environmental pollution because of disposal of chromium and strong acids. Therefore, loss-on-ignition procedure is a simple and cheap method for SOM estimation, which also avoids chromic acid wastes, deserves more attention. The aims of this research were to study the statistical relationships between SOC determined with the LOI and WB methods to compare the spatial variability of SOC in the selected study area. One way ANOVA was used for the significance test between the two methods and there was a significant difference between the values determined by the Walkley Black and Loss on Ignition methods, at a confidence level of 95%.