Soil Spectral Library

In this paper, we present a case-study of utilizing vis-NIR spectroscopy to estimate the content of Soil Organic Carbon (SOC) remotely in Northern Greece. In this agricultural area, SOC plays a pivotal role in the physical, chemical, and biological function of the soils and hence requires rapid and in situ analysis. 474 Entisol soil samples were collected from the two top soil horizons. The wet analytical evaluation of SOC using the Walkley-Black method yielded an average of 0.6599%, with a standard deviation of 0.3908%. The reflectance spectra of these soils were acquired across the vis-NIR region (350-2500 nm) in the laboratory using a standardization protocol. For the chemometric analysis, three pre-processing methods were considered, namely the absorbance transformation, the continuum removal, and the first-derivative. We used two state-of-the-art machine learnings algorithms (Partial Least Squares Regression and Cubist), to estimate the SOC from the spectra. The best results were achieved using the first derivative, by the Cubist algorithm, where an RMSE of 0.1174% was achieved. These results indicate that precise mapping of SOC can be achieved with vis-NIR spectroscopy, facilitating the regular updating of SOC maps for sustainable agriculture, in line with the Sustainable Development Goals 2.4 and 15.3.

Authors: Nikolaos L. Tsakiridis, Nikolaos Tziolas, George Galanis, Eyal Ben-Dor, George C. Zalidis

Keywords: soil spectral library, soil spectroscopy, soil organic carbon, precision agriculture, vis-NIR spectroscopy, reduced input agriculture

Spectral Evolution is a leading manufacturer of field-portable UV-Vis-NIR remote sensing spectroradiometers and spectrometers for applications including geological remote sensing, ground-truthing, spectral remote sensing, environmental and climate research, crop and soil research, vegetative studies, forestry and canopy studies, radiometric calibration transfer, upwelling and downwelling measurement and more. Our UV-Vis-NIR spectrometers and spectroradiometers provide the best combination of high resolution and high sensitivity resulting in the most precise field portable instruments available on the market.

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