Effects of Water Management Practices On Greenhouse Gas Emissions and Rice Yield.

Rice paddy fields are a major source of methane (CH4) emissions. The mitigation options for CH4 emission from rice paddy fields are shown to be of effective with intermittent irrigation. However, variously saturated soil by intermittent irrigation may emit carbon dioxide (CO2) and nitrous oxide (N2O). In addition, the emission of these gases may be varied with various irrigation intervals. The purpose of this study was to investigate the effects of water management practices on greenhouse gas emissions and rice yield in rice paddy fields. Three treatments for water management practices were: (1) continuous flooding except during the midseason drainage, (2) intermittent irrigation with two-day drainage, and (3) intermittent irrigation with four-day drainage. The longer the drainage period in intermittent irrigation, the less the CH4 was emitted whereas the more the N2O was. Two-day drainage treatment had the smallest cumulative CO2-equivalent fluxes for CH4 and N2O. Decreases in a drainage period resulted in the reduction of the net greenhouse gas emission. A brown rice yield was the highest for the continuous flooding treatment. The yields of two-day and four-day drainage treatments were smaller than that of the continuous flooding treatment by 13% and 18%, respectively. The two-day drainage treatment was achieved the smallest net greenhouse gas emission per brown rice yield, thus mitigated the emission of CH4 and N2O with maintaining yield.