The effect of organic carbon, temperature, time, and redox conditions on soil color
1990
Dobos, Robert R. | Ciolkosz, E. J. | Waltman, W. J.
This study was undertaken to observe the effects of organic carbon content (3.2, 9.6, and 15.4 g kg), organic carbon quality (26 and 107 g kg nonstructural carbohydrates), temperature (5, 15, and 25°C), and time (7, 14, 21, and 35 wk) on color changes in soil material (originally 7.5YR 5/6) under alternating oxidizing and reducing conditions in the laboratory. Hues of the mottle and matrix colors were strongly influenced by organic carbon content and ranged from 7.5 YR to 2.5Y as organic carbon was added. Temperature and time influenced matrix color and mottle hues to a lesser extent. Mottle and matrix color values were altered but did not exhibit any trends with organic carbon, temperature, or time. The chromas of the mottle and matrix colors were strongly influenced by organic carbon content. Mottle chromas were strongly influenced by organic carbon content. Mottle chromas ranged from 8 to 1 whereas matrix chromas ranged from 6 to 3. Temperature and time influenced mottle and matrix chromas to a lesser extent. The areal extent of color changes increased with organic carbon content, temperature, and time. The increased yellow (10YR and 2.5Y) components, higher values, and lower chroma of the colors was attributed to hematite dissolution, which allowed goethite and non-iron oxide minerals to influence the observed colors more strongly. A decrease in color values was attributed to new precipitates on existing oxide or silicate mineral surfaces.
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