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ARS Home » Southeast Area » Jonesboro, Arkansas » Delta Water Management Research » Research » Publications at this Location » Publication #330942
Title: Methane emission reductions from the alternate wetting and drying of rice fields detected using the eddy covariance method

Author
item RUNKLE, BENJAMIN - University Of Arkansas
item SOVUCAREV, KOSANA - University Of Arkansas
item SMITH, FAYE - University Of Arkansas
item Reba, Michele

Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2018
Publication Date: 12/19/2018
Citation: Runkle, B.R., Sovucarev, K., Smith, F.S., Reba, M.L. 2018. Methane emission reductions from the alternate wetting and drying of rice fields detected using the eddy covariance method. Environmental Science and Technology. 53: 671-681. https://10.1021/acs.est.8b05535.
DOI: https://doi.org/10.1021/acs.est.8b05535

Interpretive Summary: Approximately 11% of the global anthropogenic methane emissions are currently attributed to rice cultivation. In this study, the impact of water irrigation practices on rice field CH4 emissions was evaluated in Arkansas, where more than half of US rice is produced. Typical rice irrigation uses continuous flooding (CF) during the majority of the production season. While conserving water, the Alternate Wetting and Drying (AWD) irrigation practice can also reduce CH4 emissions through the deliberate, periodic introduction of non-flooded conditions. Continuous measurements of methane flux indicated a 79% reduction in season-long emissions from the AWD field relative to the CF field. The seasonal cumulative carbon losses by CH4 emission were 30.3 and 141.9 kg CH4-C ha-1 for the AWD and CF fields, respectively. Considering differences in field conditions and soils, the AWD practice is attributable to a 36-51% reduction in seasonal emissions. The substantial decrease in CH4 emissions by AWD offers strong evidence for the efficacy of AWD in reducing methane emissions in Arkansas rice production. The AWD practice is under consideration for carbon offsets trading and this new market could encourage greater reductions in methane emissions on a larger scale.

Technical Abstract: Rice cultivation contributes 11% of the global 308 Tg CH4 anthropogenic emissions. The alternate wetting and drying (AWD) irrigation practice can conserve water while reducing CH4 emissions through the deliberate, periodic introduction of aerobic soil conditions. This paper is the first to measure the impact of AWD on rice field CH4 emissions using the eddy covariance (EC) method. This method provides continuous, direct observations over a larger footprint than in previous chamber-based approaches. Seasonal CH4 emissions from a pair of adjacent, production-sized rice fields under delayed flood (DF) and AWD irrigation were compared from 2015 to 2017. Across the 2 fields and 3 years, cumulative CH4 emissions in the production season were in the range of 7.1 to 31.7 kg CH4–C ha–1 for the AWD treatment and in the range of 75.7–141.6 kg CH4–C ha–1 for the DF treatments. Correcting for field-to-field differences in CH4 production, the AWD practice reduced seasonal CH4 emissions by 64.5 ± 2.5%. The AWD practice is increasingly implemented for water conservation in the mid-south region of the United States; however, based on this study, it also has great potential for reducing CH4 emissions.