Oxygen Regulates Nitrous Oxide Production Directly in Agricultural Soils

Oxygen (O-2) plays a critical and yet poorly understood role in regulating nitrous oxide (N2O) production in well-structured agricultural soils. We investigated the effects of in situ O-2 dynamics on N2O production in a typical intensively managed Chinese cropping system under a range of environmental conditions (temperature, moisture, ammonium, nitrate, dissolved organic carbon, and so forth). Climate and management (fertilization, irrigation, precipitation, and temperature), and their interactions significantly affected soil O-2 and N2O concentrations (P < 0.05). Soil O-2 concentration was the most significant factor correlating with soil N2O concentration (r = -0.71) when compared with temperature, water-filled pore space, and ammonium concentration (r = 0.30, 0.25, and 0.26, respectively). Soil N2O concentration increased exponentially with decreasing soil O-2 concentrations. The exponential model of N treatments and fertilization with irrigation/precipitation events predicted 74-90% and 58% of the variance in soil N2O concentrations, respectively. Our results highlight that the soil O-2 status is the proximal, direct, and the most decisive environmental trigger for N2O production, outweighing the effects of other factors and could be a key variable integrating the aggregated effects of various complex interacting variables. This study offers new opportunities for developing more sensitive approaches to predicting and through appropriate management interventions mitigating N2O emissions from agricultural soils.