The effect of moisture on nitrous oxide emissions from soil and the N2O/(N2O+N2) ratio under laboratory conditions

Nitrous oxide (N2O) contributes to greenhouse effect; however, little information on the consequences of different moisture levels on N2O/(N2O+N-2) ratio is available. The aim of this work was to analyze the influence of different soil moisture values and thus of redox conditions on absolute and relative emissions of N2O and N-2 at intact soil cores from a Vertic Argiudoll. For this reason, the effect of water-filled porosity space (WFPS) values of soil cores of 40, 80,100, and 120% (the last one with a 2-cm surface water layer) was investigated. The greatest N2O emission occurred at 80% WFPS treatment where conditions were not reductive enough to allow the complete reduction to N-2. The N2O/(N2O+N-2) ratio was lowest (0-0.051) under 120% WFPS and increased with decreasing soil moisture content. N2O/(N2O+N-2) ratio values significantly correlated with soil Eh; redox conditions seemed to control the proportion of N gases emitted as N2O. N2O emissions did not correlate satisfactorily with N2O/(N2O+N-2) ratio values, whereas they were significantly explained by the amount of total N2O+N-2 emissions.