1. Sequence of chemical compounds being reduced in soil after submergence
Oxidized
Slightly Reduced
Moderately Reduced
Severely Reduced
NO3-
H2O
MnO2 N2
Mn2+
Fe3+
Fe2+
SO4-2
CO2
H2S
CH4
Reaction sequence following submergence
Reaction sequence after draining

2. Chemical Compounds in Aerated Soil
Nitrate
Manganese
(IV)
dioxide
Iron
(III)
Hydroxide
Sulfate
Carbon
dioxide
Submerging soil causes a change from aerobic to anaerobic organisms
Anaerobic bacteria cause a sequence of chemical reductions during respiration
Nitrogen
gas
Manganese
(II) ion
Iron
(II) ion
Hydrogen
Sulfide
Methane
Chemical Compounds in Submerged Soil

4. Oxygen (O2) in the soil is reduced to water (H2O)
Oxygen (O2) in the soil is reduced to water (H2O). It is the first to undergo reduction and O2 levels are undetectable within a day.
Manganese oxide (MnO2) is reduced to Manganese ion (Mn2+)
Redox Potential (mV)
Nitrate (NO3) is the next to be reduced after O2 concentrations are already low. Nitrate reduces to nitrogen gas (N2) in a process called denitrification. O2
Carbon dioxide (CO2) is reduced to methane (CH4)
CO2
NO2
Iron hydroxide (Fe(OH)3 is reduced to iron ions (Fe2+).
Mn2+
NH4
Fe2+
Sulphate (SO42-) is reduced to (H2S)
SO42-
Reaction Sequence in Anaerobic Soils
Reaction Sequence in Reaerated Soils