Effect of temporary water logging on red ox potential, pH and available Fe and Mn as well as their changes after drainage was studied in three calcareous soils of Isfahan region. Soil samples were waterlogged in plastic containers for 0, 1, 2, 4 & 6 months. Red ox potential, pH and available Fe and Mn were measured both during the water logging period and after drainage in three time intervals. Red ox (pe + pH) and oxidation-reduction potential (Eh) changed non-linearly in three stages during the water logging period. A sharp decrease in the first stage, a slow decrease in second stage followed by no change in the third stage. Oxidation-reduction potential decreased 370 mV during these three stages. The pH decreased, the decrease being sharp initially (0.6 unit in 2 weeks) and then slowly up to 4 or 5 weeks after water logging. Available Fe content in three soils increased with different slops for 8 weeks, and then decreased slowly. Available Mn, increased sharply at the initial stage of water logging and then remained almost unchanged with minor fluctuations. After the soils were drained, available Fe remained significantly higher as compared to the control however, its magnitude was related to the duration of water logging and type of soil, but was independent of the incubation period. Furthermore, available Mn was higher in all three soils as compared to the control but decreased substantially during the first 2 months after drainage. Water logging resulted in a decrease in redox potential and pH and simultaneous increase in available Fe and Mn. Drainage of waterlogged soils sharply decreased available Mn, but available Fe declined very slowly.
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