Abstract
Water-intensive systems of rice cultivation are facing major challenges to increase rice grain yield under conditions of water scarcity while also reducing greenhouse gas (GHG) emissions. The adoption of effective irrigation strategies in the paddy rice system is one of the most promising options for mitigating GHG emissions while maintaining high crop yields. To evaluate the effect of different alternate wetting and drying (AWD) irrigation strategies on GHG emissions from paddy rice in dry and wet seasons, a field experiment was conducted at the Tamil Nadu Rice Research Institute (TRRI), Aduthurai, Tamil Nadu, India. Four irrigation treatments were included: One-AWD (one early drying period), Two-AWD (two early drying periods), Full-AWD (wetting and drying cycles throughout the rice season), and CF (continuous flooding). Different rice varieties were also tested in the experiment. In this study, we emphasized one factor (irrigation effect) that affects the dependent variable. The results show that early AWD treatments reduced methane (CH4) emissions by 35.7 to 51.5% in dry season and 18.5 to 20.1% in wet season, while full-AWD practice reduced CH4 emissions by 52.8 to 61.4% compared with CF. Full-AWD in dry season not only significantly reduced CH4 emission during that season, it also resulted in the decline of the early season emission in the succeeding wet season. Global warming potential (GWP) and yield-scaled GWP were reduced by early or full season AWD in both rice seasons. The GWP value from nitrous oxide (N2O) was relatively low compared to that from CH4 in both rice seasons. Rice yield was not affected by irrigation treatments although varietal differences in grain and straw yields were observed in both rice seasons. This study demonstrated that early season water managements are also effective in reducing CH4 and total GHG emissions without affecting rice yield.
Highlights
Global agriculture in the 21st century is expected to double food production to provide sufficient and healthy food for a growing population under conditions of increasing water scarcity, while minimizing environmental consequences [1,2]
Our results show that Full-AWD irrigation significantly decreased CH4 emissions from paddy rice soil in either rice season
This is the first study showing that only early season AWD practices are an effective option for farmers to mitigate greenhouse gas (GHG) emissions where full-scale practice of AWD is not feasible
Summary
Global agriculture in the 21st century is expected to double food production to provide sufficient and healthy food for a growing population under conditions of increasing water scarcity, while minimizing environmental consequences [1,2]. Irrigated rice accounts for about 80% of the total fresh water resources used for irrigation in Asia [6]. Increases in rice production over the last half-century relied heavily on irrigated rice, which is increasingly constrained by water scarcity [7]. Alternate wetting and drying (AWD) is an irrigation practice in rice paddies and has been shown to reduce irrigation water use. Overall rice yields have been reduced in AWD; the degree of soil drying has a large effect on rice yield [9]. Yang et al [12] and
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