In Situ Soil Characterization: Should Mohammed Go to the Mountain?.

There has been a flurry of recent interest over in situ soil characterization in order to more rapidly and inexpensively acquire soil data needed for digital soil mapping.  With a focus on soil carbon measurement, we report results from both our own research and others working on Inelastic Neutron Scattering (INS), Visible and Near-Infrared (VisNIR) diffuse reflectance spectroscopy, Mid-Infrared (MIR) diffuse reflectance spectroscopy, and Laser-Induced Breakdown Spectroscopy (LIBS).  Both our experience and a discerning read of the published literature suggest that in situ soil characterization might remain semi-quantitative at best for a substantial period of time.  As such these tools would be best utilized for soil-landscape stratification to guide traditional sampling and analysis.  It is therefore imperative that we find ways to improve the efficiency of soil coring, processing and laboratory analysis, a research agenda that has so far attracted little attention.