Greenhouse Gas Emissions Under Different Drainage and Flooding Regimes of Cultivated Peatlands

Globally, approximately 10-20% of peatlands have been drained for agricultural purposes. A strategy to protect peatlands and mitigate carbon dioxide (CO2) emissions, while continuing agricultural production, is the use of intermittent flooding and drainage. A potential drawback of this strategy could be increases in methane (CH4) and nitrous oxide (N2O) emissions. The objective of this study was to compare greenhouse gas (GHG) emissions from peatlands under various flooding-drainage cycles. A laboratory study was performed using intact soil cores subjected to different durations of flooding and drainage for 6months. Average daily emissions of CO2 and N2O were significantly higher (P<0.001) under drained (66737mgCO(2)-Cm(-2)d(-1) and 13519gN(2)O-Nm(-2)d(-1)) than flooded conditions (866mgCO(2)-Cm(-2)d(-1) and 482gN(2)O-Nm(-2)d(-1)). Methane emissions were not influenced by drained/flooded conditions, with an average rate of 116 +/- 11gCH(4)-Cm(-2)d(-1). Peaks of CH4 and N2O emissions were observed after flooding events and lasted less than 24h. The peak emissions were approximately 8 and 19 times higher than the mean CH4 and N2O emissions, respectively. Carbon dioxide was the dominant component of GHGs, irrespective of hydrologic regime, accounting for more than 92% of overall global warming potential. Global warming potential was inversely proportional to the flooding period, indicating that prolonging the flooding period of peatlands would help mitigate soil oxidation and GHG emissions and enhance sustainability of these agricultural peatlands.