Greenhouse Gases Emission from Rice Paddy under Different Tillage Intensity during Fallow Season

Abstract

Reduced tillage is a useful practice to increase soil organic carbon (SOC) stock and decrease methane (CH4) emission in a rice paddy. However, the impacts of reduced tillage on the global warming potential (GWP) are generally analyzed for CH4 fluxes only during rice cultivation season. This study was conducted to investigate the effects of tillage on greenhouse gas (GHG) emission including both CH4 and nitrous oxide (N2O) and SOC stock changes were evaluated during the fallow season under two different tillage systems (conventional tillage and reduced tillage practice). The emission rate of GHG emissions was monitored using the closed chamber method. The SOC stock changes were estimated by the net ecosystem C budget (NECB), which is defined as the difference between total organic C input and output. Finally, the net global warming potential (net GWP), which was calculated as CO2 equivalents was compared between the different tillage system in rice paddy during fallow season. The net GWP of tillage and reduced tillage treatment were 4.09 and 4.96 Mg CO2 eq. ha-1, respectively during fallow season. However, the net GWP was not significantly different tillage systems. The decrease of SOC stock as CO2 emission was the most influential part on increasing the net GWP. Our study suggest that regardless of tillage conditions, it is necessary to establish a greenhouse gas reduction strategy focusing on increasing SOC accumulation during the fallow season. However, as this study was conducted for only single fallow season, long-term study is required to estimate the cumulative effects of tillage treatment on GHG emissions during fallow seasons in paddy.Net global warming potential (net GWP) under different tillage systems during fallow season in rice paddy (CT, conventional tillage; RT, reduced tillage).