The effect of water management and ratoon rice cropping on methane emissions and yield in Arkansas

Authors: LEAVITT, MARGUERITA - University Of Arkansas; MORENO-GARCIA, BEATRIZ - University Of Arkansas; REAVIS, COLBY - Oak Ridge Institute For Science And Education (ORISE); Reba, Michele; RUNKLE, BENJAMIN - University Of Arkansas

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2023
Publication Date: 6/29/2023
Citation: Leavitt, M., Moreno-Garcia, B., Reavis, C., Reba, M.L., Runkle, B. 2023. The effect of water management and ratoon rice cropping on methane emissions and yield in Arkansas. Agriculture, Ecosystems and Environment. 356(108652):1-11. https://doi.org/10.1016/j.agee.2023.108652.
DOI: https://doi.org/10.1016/j.agee.2023.108652

Interpretive Summary: Rice is a staple crop, but rice production is also a major source of anthropogenic CH4 which is a potent greenhouse gas. We studied rice under different irrigation and seeding management practices with the objective of determining the effect this would have on yield and emissions. We also studied a ratoon crop from the harvested stubble of the first crop to determine if ratoon cropping could be a viable method of sustainable intensification. We found that rice managed under an alternate wetting and drying regime produced 79.5% less CH4 than rice managed with delayed flooding without a reduction in yield, and that the ratoon crop produced up to 3.6 times the yield-scaled CH4 of the main crop. These results may be beneficial to farmers interested in improving the environmental sustainability of their crop and agricultural scientists interested in understanding the driving factors behind the generation of CH4 from rice fields.

Technical Abstract: Sustainable intensification of rice farming is crucial to meeting human food needs while reducing environmental impacts. Rice production represents 8% of all anthropogenic emissions of CH4, a potent greenhouse gas. Cultivation practices that minimize the number of days the rice fields are flooded, such as dry seeding instead of water seeding and irrigation using the alternate wetting and drying (AWD) technique instead of delayed, continuous flooding (DF) can potentially reduce CH4 emissions. Ratoon cropping, wherein a second crop of rice is grown from the harvested stubble of the first crop, can produce additional yield with minimal labor, but may generate more CH4 than single cropping. The objective of this study was to test different seeding methods and water management regimes for their impact on yield and CH4 emissions, as well as to determine if ratoon cropping was a viable method of sustainable intensification for rice in Arkansas. Two adjacent fields in Lonoke County, Arkansas were compared under different seeding and irrigation treatments from 2015 through 2020; the 2020 season also included a ratoon crop. Field-scale CH4 emissions were measured using the eddy covariance method at each field. AWD reduced CH4 emissions by 79.5% on average in comparison to DF for the main seasons. Across the field-seasons, the emissions from the main crop ranged from 77.2 to 132.5 kg CH4-C ha-1 under DF and from 7.1 to 40.7 kg CH4-C ha-1 under AWD. The ratoon crop generated emissions from 39.7 to 50.7 kg CH4-C ha-1, up to a 3.6-fold increase from the main crop of the same year. CH4 emissions from the ratoon crop in this study were much lower than those found in previous ratoon studies, suggesting that ratoon cropping combined with AWD might be a viable option for sustainable intensification if the ratoon yield could be improved. The ratoon crop yield was 13% that of the main crop yield on average but there was no significant difference in yield between irrigation treatments for the main seasons. Seeding method had no discernable impact on CH4 emissions or yield.