Effects of Organic Matter, Flooding Time, and Temperature on the Dissolution of Iron and Manganese from Soil in situ

Abstract

AbstractA field plot study was conducted to determine the effects of added alfalfa, four flooding times, and two temperatures on EH (Oxidation‐reduction potential) and dissolution of iron and manganese from a silty clay soil. With no alfalfa added, flooding caused only a small decrease in EH at either temperature. The addition of alfalfa at the higher temperature resulted in a reduction in EH to −100 millivolts. Flooding time had no significant effect on EH until the third day, when the soils subjected to shorter flooding periods began to dry out. Flooding without organic matter increased the Mn2+ and Fe2+ concentrations in solution to maxima of only 3.7 and 2.1 ppm, respectively; while the combination of flooding, organic matter and high temperature increased the levels to 46 and 30 ppm. Flooding time had no effect on the dissolution of iron and manganese. The results of this study show the importance of temperature and organic matter on dissolution of iron and manganese and the relation between EH and soluble iron and manganese.