Saturation and Temperature Effects on the Development of Reducing Conditions in Soils

Abstract

Oxidation‐reduction (redox) reactions regulate many chemical processes that occur in soils. Saturation, C availability, microorganisms, and temperature dictate the rate and type of redox reactions that will occur. The measurement of redox potential enables researchers to predict the stability of redox‐sensitive species, such as Fe oxides. We determine the amount of time Mid‐Atlantic Piedmont floodplain soils must be saturated at a given temperature before becoming reduced with respect to ferrihydrite. Three representative floodplains in Maryland and Delaware were selected for this study. Redox potential, pH, temperature, and depth to water table were measured in six profiles over a 2‐yr period. At lower temperatures, longer periods of saturation were required to induce soil reduction with respect to ferrihydrite ( p < 0.0001). The soils were reduced with respect to ferrihydrite after the soils were saturated for 2 to 20 d depending on the 14‐d average soil temperature ranging from 1 to 21°C. When the soil temperature was between 1 and 3.9°C, saturation was required for 20 d before the onset of reducing conditions. At 4 to 6.9°C, 11 d of saturation were required, while at 7 to 8.9°C, 7 d of saturation were required. When the soil temperature was above 9°C, reduction occurred after approximately 2 d. This investigation reveals the importance of considering soil temperature when relating length of saturation to reduction, specifically pertaining to floodplain soils in the Mid‐Atlantic Piedmont physiographic province.