The influence of organic matter on soil color using the regression equations of optical parameters in the system CIE-L*a*b*

Presenting soil color as a colors sum of two phases: mineral matrix and an organic material, in soil sample we can determine color indicators of mineral phase from univariate regression equations: Corg = f (L *), Corg = f (a *) and Corg = f (b *) provided Corg = 0. Influence of organic matter is not limited by neutralization of a lightness of white pigments, for example, on quartz and carbonates, organic matter cover by film the particles of red, yellow and green pigments, it also neutralizes the effect of these pigments in the soil color. From univariate regression equations Corg = f (L *) we calculated the value of pigmentic ability of organic matter in relation to the white pigments. To determine more accurately the organic matter content on soil color we should use three indicators instead of one variable in the regression equation: each of the color parameters in CIE-Lab system separately. Three-factor regression equations allowed to calculate more precisely the Corg--content in the soils of two of the three Cis-Urals Catenas and Kolyma cryosols