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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Adaptive Cropping Systems Laboratory » Research » Publications at this Location » Publication #315803

Title: Responses of soybeans and wheat to elevated CO2 in free-air and open top chamber systems

item Bunce, James

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2015
Publication Date: 1/1/2016
Citation: Bunce, J.A. 2016. Responses of soybeans and wheat to elevated CO2 in free-air and open top chamber systems. Field Crops Research. 186:78-85.

Interpretive Summary: There are two common field experimental systems for assessing crop yields at future carbon dioxide concentrations, free-air enrichment systems, and open top chamber systems, but crop responses in the two systems have not been directly compared. This experiment indicated that yield increases at elevated carbon dioxide were larger in both wheat and soybean crops when using open top chambers than when using free-air carbon dioxide enrichment. This work will be of interest to those evaluating crop yield responses to climate change.

Technical Abstract: With increasing demand for agricultural products, more confidence is needed concerning impacts of rising atmospheric CO2 on crop yields. Despite debate about the merits of free-air CO2 enrichment (FACE) and open top chamber (OTC) systems, there has been only one reported experiment directly comparing these systems. In this study soybeans and winter wheat were grown for two years in FACE and OTC systems operated at the same time and location. The elevated CO2 treatment was applied 24 h per day, and was ambient plus 200 ppm. In one year, one cultivar of each species was grown in both systems, and in the second year two cultivars of each species were grown. Leaf area index, and midday leaf gas exchange rates were measured periodically, and total above ground biomass and seed yield were determined at maturity. In soybean, seed yield was increased by elevated CO2 in both FACE and OTC in both cultivars and years. However, the ratio of seed yield at elevated CO2 to that at ambient CO2 averaged significantly higher in OTC (1.49) than in FACE (1.27). In wheat, grain yield was increased by 15 to 30% by elevated CO2 for both cultivars and years in the OTC, but was not increased in either cultivar or year in the FACE system. No differences in midday photosynthetic rates occurred between OTC and FACE in either species at either CO2, but stomatal conductance was more reduced by elevated CO2 in OTC than in FACE.