Oxidation‐Reduction Studies on the Mechanism of B Horizon Formation in Podzols

Abstract Oxidation‐reduction potentials in situ have been measured in a hydro‐sequence of soils in the Podzol region of Michigan with variations in time and space. The soils were well‐drained Kalkaska sand, imperfectly drained Saugatuck sand and poorly drained Roscommon sand. The distribution of citrate‐oxidizing organisms and iron‐oxidizing organisms in horizons of Kalkaska and Saugatuck sands was also studied. Redox potentials were observed to vary with moisture, temperature and soil horizons. The population of citrate‐oxidizing organisms decreased with depth and iron‐oxidizing organisms were isolated from the B ir horizons of both Kalkaska and Saugatuck sands. The results indicate that certain mechanisms of Podzol formation may be active in the soils studied.