The Effect of Soil Redox Potential and pH on the Reduction and Production of Nitrous Oxide

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Abstract
Experiments were conducted in controlled redox systems to assess the effects of pH and Eh on N2O reduction and production. Soil/water suspensions (ratio 1:3) were incubated at pH 5, 6, 7 and 8.5, and the redox potential (Eh) was controlled at selected potentials between −200 and +350 mV. Maximum N2O reduction was measured at pH 6 and 7. The critical Eh for N2O reduction and production occurred at +250 mV for pH 6, 7, and 8.5, and +300 mV for pH 5. Although N2O reduction began at a higher potential at pH 5, the rate of reduction was slightly lower under anoxic conditions at this pH. Alkaline conditions did not change the critical redox potential, but the rate of N2O reduction was lower. The data also demonstrate that soil can act as a sink for N2O under anoxic conditions.