Abstract
Water management impacts both methane (CH4) and nitrous oxide (N2O) emissions from rice paddy fields. Although controlled irrigation is one of the most important tools for reducing CH4emission in rice production systems it can also increase N2O emissions and reduce crop yields. Over three years, CH4 and N2O emissions were measured in a rice field in Uruguay under two different irrigation management systems, using static closed chambers: conventional water management (continuous flooding after 30 days of emergence, CF30); and an alternative system (controlled deficit irrigation allowing for wetting and drying, AWDI). AWDI showed mean cumulative CH4 emission values of 98.4 kg CH4 ha−1, 55 % lower compared to CF30, while no differences in nitrous oxide emissions were observed between treatments ( p > 0.05). No yield differences between irrigation systems were observed in two of the rice seasons ( p > 0.05) while AWDI promoted yield reduction in one of the seasons ( p< 0.05). When rice yield and greenhouse gases (GHG) emissions were considered together, the AWDI irrigation system allowed for lower yield-scaled total global warming potential (GWP). Higher irrigation water productivity was achieved under AWDI in two of the three rice seasons. These findings suggest that AWDI could be an option for reducing GHG emissions and increasing irrigation water productivity. However, AWDI may compromise grain yield in certain years, reflecting the importance of the need for fine tuning of this irrigation strategy and an assessment of the overall tradeoff between relationships in order to promote its adoption by farmers.
Highlights
Methane (CH4) is the dominant greenhouse gas (GHG) produced in irrigated paddy rice fields, contributing approximately 15-20 % to annual global CH4 emissions (Jacobson, 2005; Hadi et al, 2010)
CH4 and N2O emissions were measured in a rice field in Uruguay under two different irrigation management systems, using static closed chambers: conventional water management; and an alternative system
These findings suggest that AWDI could be an option for reducing greenhouse gases (GHG) emissions and increasing irrigation water productivity
Summary
Methane (CH4) is the dominant greenhouse gas (GHG) produced in irrigated paddy rice fields, contributing approximately 15-20 % to annual global CH4 emissions (Jacobson, 2005; Hadi et al, 2010). Water management is one of the most important tools for achieving high levels of production as well as a promising option for the mitigation of CH4. Changes in water management such as intermittent irrigation and mid-season drainage are effective options for the mitigation of CH4 in rice fields (Hadi et al, 2010; Itoh et al, 2011; Jain et al, 2013; Minamikawa and Sakai, 2006; Tyagi et al, 2010; Yagi et al, 1997). These practices of alternate anaerobic and aerobic cycling can stimulate the emission of another GHG, nitrous oxide (N2O), via denitrification and nitrification, respectively. Drainage systems are important for conserving water and improving rice yields (Xu et al, 2007)
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