Eddy covariance assessment of alternate wetting and drying floodwater management on rice methane emissions

Authors: Anapalli, Saseendran; PINNAMANENI, SRINIVASA - Oak Ridge Institute For Science And Education (ORISE); Reddy, Krishna; Wagle, Pradeep; Ashworth, Amanda

Submitted to: Heliyon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/15/2023
Publication Date: 3/27/2023
Citation: Anapalli, S.S., Pinnamaneni, S.R., Reddy, K.N., Wagle, P., Ashworth, A.J. 2023. Eddy covariance assessment of alternate wetting and drying floodwater management on rice methane emissions. Heliyon. 9(4):e14696. https://doi.org/10.1016/j.heliyon.2023.e14696.
DOI: https://doi.org/10.1016/j.heliyon.2023.e14696

Interpretive Summary: Reducing the amount of water pumped out of the Mississippi Valley Alluvial Aquifer for crop irrigations, especially in supporting flooded rice systems, is key to sustainable irrigated agriculture in the Mississippi Delta. Equally critical is reducing methane, a greenhouse gas emitted from flooded soils with about thirty-fold more global warming potential than carbon dioxide, emissions from flooded rice fields. We investigated possible reductions in irrigation water use and methane emissions from practicing intermittent flooding (also known as alternate wetting and drying) method of floodwater management over conventional continuous flooded rice cultivation system in farmer’s fields in the MS Delta. The eddy covariance, a cutting-edge science-based method, was used to monitor methane and water vapor emitted from rice cropping systems. The study revealed that water pumped out of the aquifers for floodwater management could be reduced by about 24% and methane emissions by about 54% without compromising rice yield by practicing the intermittent flooding systems over continuous flooding systems in rice cultivation in the MS Delta region. The investigation carried out in large-scale fields gives better confidence in recommending the intermittent flooding practice to farmers for adaptation in rice production systems for saving water and reducing greenhouse gas emissions.

Technical Abstract: Reducing methane emissions and water use is critical for combating climate change and declining aquifers on food production. Reductions in irrigation water use and methane emissions are known benefits of practicing alternate wetting and drying (AWD) over continuous flooding (CF) water management in lowland rice (Oryza sativa L.) production systems. In a two-year (2020 and 2021) study, methane emissions from large farm-scale (~50 ha) rice fields managed under CF and AWD in soils dominated by Sharkey clay (Sharkey clay, clay over loamy, montmorillonitic non-acid, thermic Vertic halauepet) (Table 1). An open-path laser gas analyzer was used to monitor air methane gas density in the constant flux layer of the atmosphere over the rice-crop canopies. Total water pumped into the field for floodwater management was higher in CF compared to AWD by 24 and 14% in 2020 and 2021, respectively. Considerable variations between seasons in the amount of methane emitted from the CF and AWD treatments were observed: CF emitted 29 and 75 kg ha-1 and AWD emitted 14 and 34 kg ha-1 methane in 2020 and 2021, respectively. Notwithstanding, the extent of reduction in methane emissions due to AWD over CF was similar each crop seasons (52% in 2020 and 55% in 2021). Rice grain yield harvested differed by only ± 2% between AWD and CF. This investigation of large-scale system-level evaluation confirmed that by practicing AWD floodwater management in rice, water pumped from aquifers and methane emissions from rice fields could be cut down by about half without affecting grain yields thereby promoting sustainable water management and greenhouse gas emission reduction during rice production in the Lower Mississippi Delta.