The results of the paper draw attention to the fact that the hyperspectral image of soil surface at micro-relief scale may display variation in the soil spectral shape due to illumination conditions of the surface. The image of an extremely rough cultivated soil surface, very deeply ploughed, was obtained by a hyperspectral camera, in the range of 0.4-1.0 mm with 0.67-0.74 nm spectral resolution. It was found that the soil reflectance spectra of the studied surface, illuminated by the direct sunbeams, are clearly convex with distinct absorption features. Furthermore, the soil normalized reflectance spectra were used to distinguish the subtlety of the analysed shaded soil spectra shape. They show that depressions caused by the absorption features of O2 and H2O, contained in the atmosphere above directly illuminated soil fragments, transform into peaks, if the same soil is deeply shaded.
Bibliographical noteFunding Information:
This work was supported by the ‘Sixth EU Framework Programme – Transnational Access implemented as Specific Support Action – Dryland Research’ (EC contract number: 026064). The authors wish to thank Aleksander Goldberg for his help in the field measurements.