Assessing the methane mitigation potential of innovative management in US rice production

Authors: REAVIS, COLBY - Oak Ridge Institute For Science And Education (ORISE); Reba, Michele; SHULTS, DANIEL - Arkansas State University; RUNKLE, BENJAMIN - University Of Arkansas

Submitted to: Environmental Research Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2023
Publication Date: 11/13/2023
Citation: Reavis, C., Reba, M.L., Shults, D., Runkle, B.R. 2023. Assessing the methane mitigation potential of innovative management in US rice production. Environmental Research Letters. 18(12):1-12. https://doi.org/10.1088/1748-9326/ad0925.
DOI: https://doi.org/10.1088/1748-9326/ad0925

Interpretive Summary: In the US, rice production is concentrated in the Mid-South and California. Given the challenge of climate change and its impact on the future of agriculture, rice production is of interest as a source of methane. Sustainable growing practices are able to mitigate the amount of methane being released without reducing yields. However, understanding the broad impacts of applying these practices is difficult given differences in production systems between the Mid-South and California. In this work, we apply a relatively simple method to estimate emissions in both regions using region-specific details on management to inform our emissions estimates. Furthermore, we examine how altering floodwater and post-harvest residue management can be used to mitigate methane emissions in both regions. With this approach, we can estimate how much methane is being released and which areas would have the most reduction under sustainable management. The outcomes of this paper can be used to target where sustainable growing practices may be most effectively applied across regions. We can also use the method to generate annual emissions estimates, which can be further incorporated into state and national methane budgets used for emissions and reduction targets.

Technical Abstract: Rice is a globally relevant crop while also being a source of anthropogenic methane emissions. To support rice production in the future, more information is needed on the impacts of different sustainable practices used to grow rice while reducing emissions. Recent support for the impacts of different growing practices in the US has prompted the application of a Tier 2 methodology to estimate methane emissions. The Tier 2 approach estimates rice methane emissions from the US Mid-South and California using region-specific scaling factors applied to a region-specific baseline flux. In our study, we leverage landcover data and soil clay content to estimate methane emissions while also examining how changes in common production practices can affect overall emissions in the US. Using the Tier 2 approach, US rice produced between 0.27 and 0.42 Tg CH4 annually, which were approximately 25% and 53% lower on average compared to FAO and EPA inventories, respectively. The Tier 2 estimates were 28% greater on average compared to Tier 1 estimates over the same production area. Introducing aeration events into irrigation resulted in the greatest methane reductions across both regions. When accounting for differences between baseline and reduction scenarios, the US Mid-South typically had higher reduction potential compared to California. The differences in reduction potential were likely driven by lower production area clay content as well as the lower number of years in rice for the US Mid-South compared to California. However, the added spatial representation of reduction potential is useful in surveying how impactful methane-reducing practices might be within and across regions.