Denitrification in underground saturated soil in a rice paddy region

During the rice- and wheat-growing seasons we studied denitrification in the underground saturated soil within a rice paddy region. High concentrations of N2O were observed in the samples taken from observation wells of different depth, with a maximum of 225.4±12.3 μg N-N2O l−1 (n=6) for the rice season and 110.0±35.7 μg N-N2O l−1 (n=6) for wheat at 2.5 m depth, respectively. High δ15N values of NO3− were also observed in the samples collected from observation wells from 2.0 to 5.0 m in depth during the rice and wheat seasons, ranging from 38.0±3.32 (n=3) to 78.8±14.5 (n=3) and from 35.42±6.38 (n=3) to 77.18±2.66 (n=3), respectively. We also found that water from wells for domestic use, sampled at around 5 m in depth had high concentrations of N2O and high δ15NO3− values. In regions with high N input, denitrification in the underground saturated soil, on the one hand, mitigates NO3− load in the groundwater, and contributes N2O to atmosphere on the other.