Redox Development in Soil Materials as Influenced by Time, Temperature, and Carbon Level – Part A: Morphological and Physical Changes.
Douglas Malo1, Rebecca Blue2, Thomas Schumacher3, James Doolittle4, and Jennifer Lund2. (1) Box 2140C SNP 247C, Plant Science Dept, SDSU, Brookings, SD 57007-2141, (2) South Dakota State Univ, Npb 247, Brookings, SD 57007, (3) NPB 247A, Box 2140C, South Dakota State Univ, Brookings, SD 57007, (4) Plant Science Dept , SDSU, NB247D Box 214OC, Brookings, SD 57007-2141
Land management and restrictions are impacted by our understanding of hydric soils, emphasizing the importance of understanding the factors that affect the formation of hydric soils and redoximorphic conditions. Currently, hydric soils are defined as soil that forms under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part. All soils are subjected to the same criteria, however, additional factors impact the formation of these conditions. The objective of this study was to observe and quantify the morphological and physical changes that occur in saturated till soil as a function of time, temperature, and carbon level. The soil used in the experiment was collected from the Bw horizon of a Vienna series (Calcic Hapludoll), representing a typical till parent material from eastern South Dakota. The treatment combinations applied included eight time periods (ranging from 1-48 weeks), four temperatures (5º, 10º, 20º, and 40ºC) and three carbon levels (low, moderate, and high). Samples were analyzed at each time interval to observe treatment effects. Carbon and temperature levels affected the rate of redox concentrations, with the highest carbon and temperature levels producing iron concentrations in the shortest time. Increased carbon and temperature levels sped the development of color changes, however, all treatments experienced similar changes throughout the study. Colors shifted from 10YR 3/2 toward a yellower hue (5Y), despite differing redox states between the treatments. Results of this study demonstrate that temperature and carbon level influence the rate of change of soil color and the development of redox features. However, with time, color changes became harder to interpret based on treatment combinations. Therefore, the results verify the need for a more precise definition of hydric soils that incorporates additional soil factors (such as carbon level and temperature) that impact hydric soil formation.