Quantification techniques of soil organic carbon: an appraisal

This review provides an overview of the analytical methods utilized across laboratory, field, landscape, and regional scales for assessing soil organic carbon (SOC) in agricultural soils. The significance of soil depth in SOC estimation underscores the importance of selecting appropriate sampling designs, soil depths, analytical methods, and baseline selection methods for accurate soil carbon stock estimation. Traditional methods such as wet digestion and dry combustion (DC) remain prevalent in routine laboratory analysis, with DC considered the standard reference method, surpassing wet digestion in accuracy and reliability. Recent advancements in spectroscopic techniques enable SOC measurement both in laboratory settings and in situ, even at greater depths. Aerial spectroscopy, which employs multispectral and hyperspectral sensors, unmanned aerial vehicles (UAVs), or satellites, facilitates surface SOC measurement. While the current precision levels of these techniques may be limited, forthcoming hyperspectral sensors with enhanced signal‒to‒noise ratios are expected to significantly increase the prediction accuracy. Furthermore, at the global level, satellite remote sensing techniques have considerable potential for SOC estimation. Regardless of whether traditional or novel approaches are utilized, the selection of SOC determination depends on available resources and research requirements, each of which plays a distinct role in soil carbon and climate research. This paper provides an overview of various scale-dependent techniques for measuring SOC in agricultural soil, along with its potential limitations.