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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Plant Physiology and Genetics Research » Research » Publications at this Location » Publication #203654

Title: The Direct Effects of Atmospheric Change on Evapotranspiration from Corn and Soybean Crops

item Kimball, Bruce

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2006
Publication Date: 11/16/2006
Citation: Bernacchi, C.J., Kimball, B.A., Long, S.P., Ort, D.R. 2006. The Direct Effects of Atmospheric Change on Evapotranspiration from Corn and Soybean Crops. Agronomy Abstracts. American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, Madison, WI. {CD-ROM P22428).

Interpretive Summary:

Technical Abstract: Tropospheric concentrations of carbon dioxide ([CO2]) and ozone ([O3]) are increasing as a result of land-use changes and fossil fuel combustion. These changes are hypothesized to have a large effect on water use for crops. While leaf-level responses to elevated [CO2] and [O3] are well documented, few studies have addressed canopy responses to increases in these pollutants. Evapotransporation (ET) for soybean was measured using an energy balance approach. Plots were exposed to a 180 µmol mol-1 increase in [CO2], a 25% increase in ambient [O3], or both. Data for elevated [CO2] and elevated [O3] were collected throughout the 2002-2005 growing seasons and the elevated [CO2]+[O3] treatment was added in 2003. Micrometeorological measurements were recorded in 10-minute intervals throughout the season for each of the treatments. Sensible heat flux was calculated from the wind and temperature measurements. ET was determined as a residual in the energy balance from net radiation, sensible heat flux, and soil heat flux. The results show a general decrease in ET for all three treatments with the largest decrease observed for the plants grown in elevated [O3] during most years. When integrated over the entire growing season for 2002 and 2003, plants grown in elevated [CO2] and elevated [O3] used 10 and 18% less water, respectively. Elevated [CO2] showed a greater decrease in 2004 and 2005 than 2002 or 2003 which is consistent with a larger decrease in leaf level stomatal conductance measured in 2004. During 2004, when ambient [O3] was lower, there was no effect of increases in [O3] on ET. While the effect of these treatments on ET are lower than observed for leaf stomatal conductance, periods with a large treatment- induced decrease in stomatal conductance result in larger decreases in ET, suggesting that stomatal conductance is strongly involved in the observed decreases in ET.