Stimulation of C3 crop yield by rising concentrations of atmospheric carbon dioxide ([CO2]) is widely expected to counteract crop losses that are due to greater drought this century. But these expectations come from sparse field trials that have been biased towards mesic growth conditions. This eight-year study used precipitation manipulation and year-to-year variation in weather conditions at a unique open-air field facility to show that the stimulation of soybean yield by elevated [CO2] diminished to zero as drought intensified. Contrary to the prevalent expectation in the literature, rising [CO2] did not counteract the effect of strong drought on photosynthesis and yield because elevated [CO2] interacted with drought to modify stomatal function and canopy energy balance. This new insight from field experimentation under hot and dry conditions, which will become increasingly prevalent in the coming decades, highlights the likelihood of negative impacts from interacting global change factors on a key global commodity crop in its primary region of production.

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SoyFACE operations and this research were supported by the USDA ARS, Illinois Council for Food and Agricultural Research (CFAR); Department of Energy's Office of Science (BER) Midwestern Regional Center of the National Institute for Climatic Change Research at Michigan Technological University, under Award Number DEFC02-06ER64158; and the National Research Initiative of Agriculture and Food Research Initiative Competitive Grants Program Grant No. 2010-65114-20343 from the USDA National Institute of Food and Agriculture. S.B.G. was supported by Department of Energy's Global Change Education Program, a generous gift to the Institute for Genomic Biology from D. Sigman, and the National Science Foundation's Postdoctoral Research Fellowship in Biology. We gratefully acknowledge the following people for their assistance in sample collection, field measurements and maintenance of the SoyFACE field site: A. Betzelberger, C. Black, G. Boise, R. Boyd, M. Boyer, P. Brandyberry, C. Burke, A. Cahill, S. Campbell, B. Castellani, J. Chiang, E. Connelly, N. Couch, R. Darner, F. Dohleman, K. Dommer, D. Drag, K. Gillespie, K. Grennan, K. Gronkewiecz, P. Hall, A. Hargus, G. Johnson, S. Kammlade, D. Klier, B. Koester, C. Leisner, V. Lor, J. McGrath, C. Markelz, M. Masters, T. Mies, C. Mitsdarfer, C. Montes, M. Nantie, O. Niziolek, D. Oh, S. Oikawa, E. Ort, K. Puthuval, R. Ramirez, C. Ramig, K. Richter, L. Rios Acosta, B. Slattery, M. Suguitan, J. Sullivan, J. Sun, B. Usdrowski, C. Yendrek, B. Zehr, M. Zeri and A. Zimbelman.

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Author notes

    • Sharon B. Gray
    • , Stephanie P. Klein
    • , Anna M. Locke
    • , David M. Rosenthal
    •  & Matthew H. Siebers

    Present addresses: Department of Plant Biology, University of California, Davis, California 95616, USA (S.B.G.). CSIRO Plant Industry, Urrbrae, South Australia 5064, Australia (M.H.S.). United States Department of Agriculture, Agricultural Research Service, Raleigh, North Carolina 27695, USA (A.M.L.). Department of Environmental and Plant Biology, Ohio University, Athens, Ohio 45701, USA (D.M.R.). Department of Plant Science, Penn State University, State College, Pennsylvania 16802, USA (S.P.K.).


  1. Department of Plant Biology and Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801, USA

    • Sharon B. Gray
    • , Orla Dermody
    • , Stephanie P. Klein
    • , Anna M. Locke
    • , Justin M. McGrath
    • , Rachel E. Paul
    • , David M. Rosenthal
    • , Ursula M. Ruiz-Vera
    • , Matthew H. Siebers
    • , Reid Strellner
    • , Elizabeth A. Ainsworth
    • , Carl J. Bernacchi
    • , Stephen P. Long
    • , Donald R. Ort
    •  & Andrew D. B. Leakey
  2. United States Department of Agriculture, Agricultural Research Service, Urbana, Illinois 61801, USA

    • Elizabeth A. Ainsworth
    • , Carl J. Bernacchi
    •  & Donald R. Ort


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S.B.G., E.A.A., C.J.B., S.P.L., D.R.O., D.M.R. and A.D.B.L. designed the research. S.B.G., O.D., S.P.K., A.M.L., J.M.M., R.E.P., D.M.R., U.M.R-V., M.H.S., R.S., E.A.A., C.J.B. and A.D.B.L. carried out field instrumentation, data collection and sample collection. S.B.G. carried out leaf and xylem biochemical/hormone analyses. S.P.K., R.E.P. and R.S. carried out root length measurements from minirhizotron images. S.B.G., D.M.R., U.M.R-V., E.A.A. and A.D.B.L. analysed data. S.B.G. and A.D.B.L. wrote the manuscript. All authors discussed the results and commented on the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Andrew D. B. Leakey.

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