We tested a new spectroradiometric method of color measurement in soil samples and found that the main advantage of this method is that it determines reliably the color of undisturbed soil fragments. To standardize the process, and to compare the accuracy of the spectroradiometric measurements with the results of visual determinations, we measured color in natural soil aggregates and in ground-homogenized samples and represented the results in the CIE 1976 (L*a*b*) color space. Variability in colors in a given aggregate was evaluated with the parameter <ΔE*ab> and was, on average, 10-fold greater than for ground samples. Grinding and homogenization of soil materials resulted in significant changes in color (18.3 CIELAB units in average), 89% of this color difference being attributable to an increase in lightness. Visual measurements of color with standard soil color charts showed an interobserver variability very similar for disturbed and undisturbed samples. However, color differences between the instrumental measurements of soil samples and the average visual judgments were 4.41 and 10.19 CIELAB units for disturbed and undisturbed samples, respectively, with the greatest errors in the estimation of the L* coordinates in both cases.
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Sánchez‐Marañón et al. (1995) studied this question.