Eddy covariance measurements of carbon dioxide and water fluxes in mid-south U.S. cotton production

Authors: FONG, BRYANT - Orise Fellow; Reba, Michele; TEAGUE, TINA - Arkansas State University; RUNKLE, BENJAMIN - University Of Arkansas; SUVOCAREV, KOSANA - University Of Arkansas

Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2019
Publication Date: 4/15/2020
Citation: Fong, B.N., Reba, M.L., Teague, T.G., Runkle, B.R., Suvocarev, K. 2020. Eddy covariance measurements of carbon dioxide and water fluxes in mid-south U.S. cotton production. Agriculture Ecosystems and the Environment. https://doi.org/10.1016/j.agee.2019.106813.
DOI: https://doi.org/10.1016/j.agee.2019.106813

Interpretive Summary: Eddy covariance (EC) is a micro-meteorological technique used to quantify land-atmosphere interaction of CO2 and H2O fluxes. It is the most direct and defensible method to measure field-scale fluxes. In this study, EC was used to measure CO2 and H2O fluxes over a production sized cotton field under typical management for the 2016 and 2017 production season. Measured values of H2O flux were lower than those measured in the arid cotton growing regions but aligned with lysimeter measurements in the humid Mid-South. Measurements from this study will contribute to research efforts to refine inventories of agricultural GHG emissions and may influence management, specifically irrigation, in the humid mid-south.

Technical Abstract: To better understand growing season carbon and water flux dynamics, an eddy covariance (EC) system was used over a cotton field. Historically, here have been limited EC measurements in the US mid-south, likewise US mid-south cotton. Cotton in this region may have different NEE and ET trends and values due to different growing conditions namely higher humidity and greater range of incoming solar radiation. Local measurements are needed to better time crop management decisions or support the current differences in management strategies. Measurements were made in a production-sized field in Northeast Arkansas in the 2016 and 2017 growing seasons (May-October) following typical growing practices of the region. Average NEE during the growing season was -0.40±0.29 g C m-2 d-1 ranging between -12.7 to 10.0 g C m-2 d-1 during 2016 and -0.98±0.29 g C m-2 d-1 ranging between -12.7 to 6.0 g C m-2 d-1 during 2017 and was driven largely by gross primary production (GPP). The average GPP during the growing season was 8.80±0.54 g C m-2 d-1 during 2016 and 8.23±0.45 g C m-2 d-1 during 2017. GPP and ET were found to be related to incoming solar radiation, soil temperature, crop developmental stages, and management events. GPP was lowest during emergence and post-harvest and highest from the first week of flowering (FF) stage to about 3 weeks after cutout. Measured ET was lowest early and late in the season, and highest from FF until cutout. Average ET was 3.3±0.1 mm d-1 during 2016 and 3.6±0.1 mm d-1 during 2017 growing seasons and peak water use was 7.6 mm d-1 during both growing seasons. Measured ET values were similar to results from lysimeter studies conducted in humid southeastern US climates, but lower than those observed in studies in arid regions. The findings suggest that US mid-south cotton production should continue to be separated and managed differently than other more arid US cotton production regions.