Production of dinitrogen and nitrous oxide in soil suspensions as affected by redox potential

The effect of soil redox potential on N₂O and N₂ emission from soil suspensions was studied under laboratory conditions. Crowley silt loam soil suspensions were equilibrated under controlled (?200, ?100, 0, +100, +200, +300, and +400 mV) redox levels, and the amounts of N₂ and N₂O evolved quantified. At higher redox levels (+300, and +400 mV) nitrification was the dominant soil biological process controlling N chemistry. A small amount of N₂O evolved during nitrification. A redox value between +300 and +200 mV was found critical for denitrification to occur. Both N₂ and N₂O were produced during denitrification. The maximum amount of N₂O evolved at a redox value of 0 mV. Dinitrogen emission increased at lower redox levels. The highest N₂/N₂O evolution ratio was observed at ?200 mV and the ratio decreased with increasing redox. A lack of N-balance during denitrification at redox levels of +100, and +200 mV is also reported.