Color index values to represent wetness and aeration in some Indiana soils

Abstract

The objective of this study was to devise a numerical index of saturation/aeration based on soil morphology, compare it with saturation depth and content of dissolved oxygen in the soil water, and relate it to definitions of soil classes. We periodically measured depth to the water table and soil-water oxygen content for ten soils in north-central Indiana. The soils were formed from loess over compact loam glacial till in a dissected till plain. They included Aquolls in swales, Aqualfs on swells, and Udalfs on hillslope shoulders and backslopes along drainage-ways cutting back into the till plain. All soils were at least periodically saturated, but not all soils had gray (< 2 chroma) colors. Those that lacked gray colors had some horizons with mottles or argillans with 3 or 4 chroma. Several color indexes were defined. One was based on hue and chroma and one on chroma only. They were applied to the upper 0.3 m of the B horizon and to a uniform 0.3–0.6 m depth zone. They were all highly correlated with the duration of saturation, especially when the soil temperature was > 5°C. They were also correlated with the O 2 levels of ground water, especially the duration when O 2 content of soil water was < 5 mg kg −1. The saturation duration and the O 2 content of soil water were also correlated with each other. Soils that are periodically saturated but not reduced should be recognized more specifically in Soil Taxonomy.