In Situ Measurement of Soil Carbon with Depth using Near Infrared (NIR) Spectroscopy

Abstract

Information on soil carbon (C) content is necessary in order to figure out the amount of C stock in soil, as the emission of CO2 from soil pool can increase CO2 concentration in the atmospheric pool, causing global warming. However, methods to measure this soil property are labour intensive and time-consuming. This study is aimed to investigate the ability of visible near infrared spectroscopy (Vis-NIRS) to in situ measure soil C from 0 to 50 cm depth. Soil cores from a Luvisol in Manawatu Region New Zealand were collected using a metallic cylindrical corer and scanned using a soil probe attached to the spectrometer at 1-cm interval from 0 to 50 cm depth. Reference data were generated by measuring soil C of the sliced soil cores using dry combustion technique. Pre-processed spectral data and the reference data were used to build partial least square regression (PLSR) model. The model was able to predict soil C with depth from surface to subsurface horizons. Thus, the Vis-NIRS-soil coring technique can be rapidly used to measure in situ soil C content with depth that can be used to measure the amount of soil C stock.