1a.Objectives (from AD-416):
The objective of this cooperative project is to maintain a FACE research site for investigating the effects of global change, including increased levels of atmospheric carbon dioxide and ozone, on soybean and corn.
1b.Approach (from AD-416):
FACE technology is used to elevate and control levels of atmospheric carbon dioxide ozone. Canopy energy balance technologies are used to measure evapotranspiration and canopy temperature, capacitance probes and soil access tubes are used to measure soil moisture profiles, and a fully instrumented weather station monitors all aspects of weather at the research site.
Over the lifetime of this Specific Cooperative Agreement, five growing seasons of a fully replicated (n=4) factorial drought by elevated (carbon dioxide) CO2 interaction experiments were conducted. The interaction between drought and elevated [CO2] was determined not to be additive. The five year experiment revealed that growth at elevated CO2 substantially reduces evapotranspiration in soybean and this is reflected in increased soil moisture reserves but there is considerable interannual variability in the interaction, which is driven by seasonal climatic conditions. Specifically, in years in which precipitation is low, the increase in leaf area driven by the stimulation of photosynthesis by elevated [CO2] can completely offset the conservation of soil moisture due to improved water use efficiency. Nevertheless, over all water usage by soybean crops grown at elevated [CO2] was lower even though the canopy was larger.