Color Change of Alluvial Gley Slightly Ferruginous Soil during Drying

Resumo

Color change during the drying of samples of medium-loamy slightly ferruginous gley taken from a pit of alluvial swampy mucky-gley soil in the Moscow region was studied using a portable spectrophotometer in the field and at a laboratory. Despite the absence of visual differences, instrumental examination revealed particular changes in the lightness and yellowness of soil samples. Two types of dependencies were determined: at short-term field study and at long-term gley drying at the laboratory. The latter dependence of lightness or yellowness on the duration of the drying period is logistic: there are two steady states of the parameters and a transition area between them, where their values sharply increase. The slow yellowing of the studied gley puts the presence of green rust mineral into question, which is typical for higher ferruginous gley soils. Drying exerts different effects on the rate of color change in the top and deep parts of the visually uniform gley horizon. This is clearly related to its chemical (and mineralogical) differentiation.