Harmonizing soil organic carbon estimates in historical and current data

Abstract

Estimation of soil organic carbon (SOC) is indispensable in studies involving soils and global climate change. SOC retention in soil is a function of climate, vegetation and intrinsic soil properties. Historically, SOC estimates are based on wet digestion which gives low carbon recovery. This results in underestimation of its density and stock, however, most of the existing historical and current SOC data sets are based on wet digestion. Hence, we have compared the wet digestion with precise oxidative combustion method for SOC estimation, to develop factors for conversion of historical data into comparable values. It was found that the recovery percentage of SOC is lower than oxidative method and it further decreased with increase in clay content. In case of land use, the recovery percentage is higher in forest soils, followed by agricultural soils and the least in wasteland. A general correction factor of 1.42 and clay content specific correction factors of 1.35, 1.45 and 1.81 are recommended to convert historical data into current reliable SOC estimates.