Influence of irrigation frequency on greenhouse gases emission from a paddy soil

Water management is known to be a key factor on methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) emissions from paddy soils. A field experiment was conducted to study the effect of continuous irrigation (CI) and intermittent irrigation (II) on these emissions. Methane, CO2, and N2O emissions from a paddy soil were sampled weekly using a semi-static closed chamber and quantified with the photoacoustic technique from May to November 2011 in Amposta (Ebro Delta, NE Spain). Intermittent irrigation of rice paddies significantly stimulated (N2O + N-2)-N emission, whereas no substantial N2O emission was observed when the soil was re-wetted after the dry phase. The cumulative emission of (N2O + N-2)-N was significantly larger from the II plots (0.73 kg N2O-N ha(-1) season(-1), P < 0.05) than from the CI plots (-1.40 kg N2O-N ha(-1) season(-1)). Draining prior to harvesting increased N2O emissions. Draining and flooding cycles controlled CO2 emission. The cumulative CO2 emission from II was 8416.35 kg CO2 ha(-1) season(-1), significantly larger than that from CI (6045.26 kg CO2 ha(-1) season(-1), P < 0.05). Lower CH4 emission due to water drainage increased CO2 emissions. The soil acted as a sink of CH4 for both types of irrigation. Neither N2O-N nor CH4 emissions were affected by soil temperature. Global warming potential was the highest in II (4738.39 kg CO2 ha(-1)) and the lowest in CI (3463.41 kg CO2 ha(-1)). These findings suggest that CI can significantly mitigate the integrative greenhouse effect caused by CH4 and N2O from paddy fields while ensuring the highest rice yield.