How reliable is the Walkley-Black method for analyzing carbon-poor, semi-arid soils in Ethiopia?

Abstract

Soil degradation in sub-Saharan Africa necessitates accurate soil carbon quantification using a locally applicable method. We assessed the reliability of the original Walkley-Black method for analyzing soil organic carbon (SOC) in semi-arid soils in northern Ethiopia characterized by low SOC (1.3 ± 0.09%) and lack of carbonates. Eighty samples from entire soil profiles were collected in four prevalent land use systems along an elevation gradient and analyzed using the Walkley-Black method and CN elemental analyzer. The results were compared by linear regression analysis followed by the Bland and Altman analysis, eliminating the possible bias of regression. The analyses demonstrated the universal applicability of the Walkley-Black method using the standard correction factor (1.32) for SOC evaluation in carbon-poor, non-calcareous soils.