Evaluation of methods for measuring soil organic carbon in West African soils

Abstract

-1 soil). Various indirect methods have been recommended for estimating soil C which can be readily implemented in a limited resource environment but they require more evaluation in terms of accuracy. This study compares soil carbon results obtained by direct elemental analysis using dry combustion to estimates obtained by indirect methods such as dichromate oxidation, mass loss-on-ignition (LOI), and diffused reflectance infrared spectroscopy that has advantages in being simple, inexpensive, and/or rapid. The results showed that both dichromate oxidation and loss-on-ignition had substantial limitations when used to analyze the low carbon soils within the region. Diffused reflectance spectroscopy using either the near- or mid- infrared spectral regions performed well for predicting soil organic carbon as well as sand, silt and clay content. These results indicate that once calibrated, infrared spectroscopy holds great promise for quantifying soil properties in the Sahel region and that regional laboratories could adopt the technology if instrumentation were made available.