ИСТИНА

The physical characterization of soil horizons based on colour is a key diagnostic method in the description of soil profiles, and has been integrated in to diagnostic keys such as the World Reference Base for Soil Resources [2]. The Munsell colour system has been the primary qualitative or semi-quantitative means to describe soil colour. At the same time, the main quantitative way to describe colour in soil science is through the CIE L*a*b* system. In this colour space system, the colour coordinates (a*, b*) are separated from the lightness (L*) coordinate [3]. Flatbed scanners have been used previously for colorimetric characterization of rocks and sediments [1]. In this study, we explore the feasibility of using flatbed scanners to derive colorimetrically accurate images and data of soil samples, and hence assess the suitability of the method as a diagnostic tool for soil characterization. The basic principle underlying our approach is to characterise and calibrate scanners using a variety of colour charts/targets. We tested the accuracy of these calibrations through analysis of a soil sample set containing 161 spectrophotometrically analysed soils. The efficacy of our approach was tested with 2 low-cost scanners, and included analysis of 2 commercial colour charts, 6 printed colour charts, and 3 editions of the Munsell Soil Colour chart to assess optimum colorimetric calibration methods. For both scanners tested, we found that accurate colour characterization could be achieved for >95% of the studied soil samples (ΔEab* colour errors of <3, equating to a colour difference barely perceptible by the human eye). Of all the studied printed charts, the Munsell soil colour charts gave the best result to characterize scanners colorimetrically. This is an encouraging result given their popular use amongst soil scientists. We find that using a Munsell chart for scanner calibration can provide mean ΔEab* of <2, with ΔEab* <3 for more than 90% of tested samples. These results demonstrate the merit and efficacy of this rapid and low cost approach for soil colour evaluation.