Saturation, Aeration, and Color Patterns in a Toposequence of Soils in North‐central Indiana

Abstract

AbstractThe purposes of this study were to determine how geomorphology and stratigraphy influence soil water and O2 regimes, how water and O2 regimes are reflected in soil color patterns, and how soil color patterns can be used to predict soil behavior and suitability for various uses. We measured water table depths, soil‐water O2 levels, and saturated hydraulic conductivity (Ksat), and described soil color patterns in soils formed in silty loess and loam glacial till in two forested toposequences. In both sequences, Aqualfs and Aquolls are on the swells and swales, respectively, of the till plain summit, and Udalfs occupy hillslope shoulder and backslope positions along drainageways cutting back into the till plain. Compact glacial till C horizons had very low Ksat values, which forced subsurface water to flow laterally, through more permeable B horizons, to lower landscape positions. In this manner, stratigraphy and shape of the land surface controlled water movement in the landscape. Udalfs had deeper water tables, shorter saturation periods, higher soil‐water O2 levels, and higher chroma colors than Aqualfs and Aquolls. Udalfs, however, were periodically saturated above a depth of 1 m. Soils with dominant chroma of 2 or less in B horizons had water‐oxygen regimes of saturation and reduction consistent with the aquic moisture regime. Soils with no chromas ≤2 but with some three or four chroma colors had water‐oxygen regimes of saturation and oxidation. Such chromas should be recognized as indicators of soils that are occasionally saturated but not reduced. These saturated‐oxidized soils are not properly recognized in soil interpretation records and published soil surveys. They can be farmed without artificial drainage but they have definite limitations for many nonagricultural uses such as on‐site waste disposal.