Site-specific feasibility of alternate wetting and drying as a greenhouse gas mitigation option in irrigated rice fields in Southeast Asia: a synthesis

Abstract

This study comprises a comprehensive assessment, integration, and synthesis of data gathered from a 3-year field experiment conducted at four sites in Southeast Asia, namely Hue, Vietnam; Jakenan, Indonesia; Prachin Buri, Thailand; and Muñoz, Philippines, to assess the site-specific feasibility of alternate wetting and drying (AWD) as a greenhouse gas (GHG) mitigation option in irrigated rice fields. AWD effectively reduced water use compared to continuous flooding (CF) but did not significantly reduce rice grain yield and soil carbon content in all sites. Methane (CH 4) emissions varied significantly among sites and seasons as affected by soil properties and water management. AWD reduced CH 4 emissions relative to CF by 151 (25%), 166 (37%), 9 (31%), and 22 (32%) kg CH 4 ha −1 season −1 in Hue, Jakenan, Prachin Buri, and Muñoz, respectively. In Prachin Buri and Muñoz, AWD reduced CH 4 emissions only during the dry season. Site-specific CH 4 emission factors (EFs) ranged 0.13-4.50 and 0.08-4.88 kg CH 4 ha −1 d −1 under CF and AWD, respectively. The mean AWD scaling factors (SFs) was 0.69 (95% confidence interval: 0.61-0.77), which is slightly higher than the Intergovernmental Panel on Climate Change (IPCC)' SF for multiple aeration of 0.52 (error range: 0.41-0.66). Significant reductions in the global warming potential (GWP) of CH 4 +nitrous oxide (N 2 O) by AWD were observed in Hue and Jakenan (27.8 and 36.1%, respectively), where the contributions of N 2 O to the total GWP were only 0.8 and 3.5%, respectively. In Muñoz, however, CH 4 emission reduction through AWD was offset by the increase in N 2 O emissions. The results indicate that the IPCC's SF for multiple aeration may only be applied to irrigated rice fields where surface water level is controllable for a substantial period. This study underscores the importance of practical feasibility and appropriate timing of water management in successful GHG reductions by AWD.

Nitrous oxide and nitric oxide emissions from lowland rice cultivation with urea deep placement and alternate wetting and drying irrigation

“…In this study, the average (two-year) N losses as N 2 O from UDP and broadcast PU treatments were 0.49% and 0.23% of applied N, respectively, which are higher compared to losses that occurred with continuous flooding irrigation (UDP: 0.11%; broadcast PU: 0.33%) 37 . Despite the small increase in N 2 O emissions, the contribution of N 2 O (196 and 138 kg CO 2 eq ha −1 , respectively) to total GHG emissions (methane [CH 4 ] +N 2 O) from rice fields is fairly small (<5%) because of the higher (>95%) contribution of CH 4 , a major GHG emitted from rice fields (but not measured in this study) 58 . AWD irrigation can drastically reduce CH 4 emissions, which offsets increased N 2 O emissions.…”

“…AWD irrigation can drastically reduce CH 4 emissions, which offsets increased N 2 O emissions. Overall, AWD irrigation reduces GHG (CH 4 and N 2 O) emissions from rice fields by up to 40% 58 . Therefore, efficient N management strategies, such as UDP with AWD irrigation, can contribute to mitigating the negative environmental effects of N fertilizer while permitting savings on fertilizers and increasing crop yields.…”

Potential of Alternate Wetting and Drying Irrigation Practices for the Mitigation of GHG Emissions from Rice Fields: Two Cases in Central Luzon (Philippines)

“…The experimental sites were carefully chosen in order to assess the efficiency of AWD in pump irrigation systems where field management was under the complete control of local farmers. From Table 3 it can be seen that the reduction in CH 4 under AWD as compared to CF in DS (54-83%; average 73%) is at the higher end compared to findings of other studies [26][27][28] and is also higher than the IPCC default reduction factor (48%) for "multiple drainage" [29]. This is irrespective of the emissions under CF.…”

Effect of the long-term application of organic matter on soil carbon accumulation and GHG emissions from a rice paddy field in a cool-temperate region, Japan-II. Effect of different compost applications-

“…Methane (CH 4 ) emissions from paddy fields varies greatly depending on various factors such as organic matter application and water management (Cheng et al 2018;Sander et al 2018;Tirol-Padre et al 2018;Toma et al 2016). The application of organic matter to paddy fields may increase CH 4 emission; however, it has been reported, mainly by short-term application experiments (within several years), that the increase in CH 4 emission by application of compost is smaller than that by application of rice straw, (e.g., rice straw compost: Yagi and Minami 1990; cattle manure compost: Kumagai et al 2010).…”