Seasonal variation in measured H2O and CO2 flux of irrigated rice in the Mid-South

Authors: Reba, Michele; COUNCE, PAUL - University Of Arkansas

Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2015
Publication Date: 2/17/2016
Publication URL: http://handle.nal.usda.gov/10113/62765
Citation: Reba, M.L., Counce, P. 2016. Seasonal variation in measured H2O and CO2 flux of irrigated rice in the Mid-South. American Society of Agricultural and Biological Engineers. 59(1):199-206.

Interpretive Summary: The Lower Mississippi River Basin produces more than half of US rice, most of which is grown in Arkansas. This paper reports on fluxes of water and CO2 from a production-sized field of drill-seeded hybrid rice grown in 2012. Eddy covariance techniques, which resolve turbulent transport of water and CO2 between the landscape and atmosphere, were used to determine fluxes of water and CO2. The field was a carbon sink during the production season, with steadily increasing photosynthesis rates as the season progressed until the early reproductive phase when rates were reduced. Water flux was largest during the late vegetative stage and slightly increased during the reproductive stage. Peak water flux was 4.31 mm/day. These findings show that plant stage and management impacted measured fluxes. These findings begin to address the increased interest in understanding agricultural impact on greenhouse gas production. Future work might include similar data collection with the addition of methane flux from multiple fields where water management is varied to measure its impact on greenhouse gas production.

Technical Abstract: Rice production in the Lower Mississippi River Basin constitutes over half of US rice production, but little research has been done on water and carbon flux in this region at the field scale. Eddy covariance measurements of water and CO2 flux allow for an integrated field measurement of the interaction between the landscape and the atmosphere. Measurements of these fluxes using eddy covariance were made in 2012 over a 60 ha rice field cultivate in rice under typical production practices of the region. 100 plants were monitored to track plant growth stage following Counce, et al. (2000). Variability in measured fluxes were related to plant growth and production practices. Peak fluxes were measured during late vegetative stages. Maximum water flux was 4.31 mm day-1 during later vegetative stages. Diurnal variability in water and CO2 flux peaked in early afternoon. CO2 flux to the plant dominated the production season. These findings show that plant stage and management impacted measured fluxes. These findings begin to address the increased interest in understanding agricultural impact on greenhouse gas production. Future work might include similar data collection with the addition of methane flux from multiple fields where water management is varied to measure its impact on GHG production.