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Seasonal Variation in Measured H2O and CO2 Flux of Irrigated Rice in the Mid-South

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASABE. 59(1): 199-206. (doi: 10.13031/trans.59.11201) @2016
Authors:   Michele L. Reba, Paul A. Counce
Keywords:   Eddy covariance, Evaporation, Evapotranspiration, Growth stage, Oryza sativa, Rice.

Abstract. Rice () production in the lower Mississippi River basin constitutes over 75% of U.S. 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 carbon dioxide (CO2) fluxes allow for integrated field measurement of the interaction between the landscape and the atmosphere. Measurements of these fluxes using eddy covariance were made in 2012 in a 60 ha rice (CL XL 745) field with typical production practices of the region. One hundred plants were monitored to track plant growth stage. Variability in measured fluxes was related to plant growth and production practices. Peak fluxes were measured during late vegetative stages. Corrected for energy balance closure, the maximum water flux was 6.05 mm d-1 and occurred during later vegetative stages. Average water fluxes during late vegetative and early reproductive stages were approximately 4.45 mm d-1. Diurnal variability in H2O and CO2 flux peaked in early afternoon. Net CO2 influx to the plant dominated the production season; hence, rice was a CO2 sink. These findings begin to address the increased interest in understanding agricultural impact on net greenhouse gas (GHG) production and consumption. 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 net GHG flux.

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