Redox Reactions in Soils Sequence of Redox Reactions in a Waterlogged Soil

An apparatus is described which under laboratory conditions permits sampling of water and gases from a waterlogged soil throughout the experimental period. A cultivated soil supplied with 6% straw is waterlogged during 97 days and the sequence of some redox reactions is shown. After one day of waterlogging the redox potential declines and reaches negative values after six days. pH declines from 7.5 to 6.5 after 17 days of waterlogging and then slowly increases to about neutral again. NO₃₋⁻ is the first compound to be reduced and within two days all NO₃⁻ has disappeared. NO₂⁻ is only detected during the first two days. After NO₃⁻ has been reduced Mn²⁺ increases, followed by a large increase of Fe²⁺. S0₄²⁻- has totally disappeared within the first three weeks of waterlogging. CO₂ is produced during the whole experimental period. A large production of CH₄ begins after three weeks of waterlogging. N₂O was not detected.