Skip to main content
ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #343280
Title: Increasing drought will diminish the benefits of elevated carbon dioxide for soybean yields across the US Midwest

Author
item JIN, ZHENONG - Stanford University
item Ainsworth, Elizabeth - Lisa
item LEAKEY, ANDREW D B - University Of Illinois
item LOBELL, DAVID - Stanford University

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2017
Publication Date: 11/7/2017
Citation: Jin, Z., Ainsworth, E.A., Leakey, A., Lobell, D.B. 2017. Increasing drought will diminish the benefits of elevated carbon dioxide for soybean yields across the US Midwest. Global Change Biology. 24(2):e522-e533. doi.org/10.1111/gcb.13946.
DOI: https://doi.org/10.1111/gcb.13946

Interpretive Summary: Increase atmospheric carbon dioxide concentrations are expected to improve yields of C3 crops such as soybean by increasing rates of photosynthesis and by reducing leaf and canopy transpiration. The reduction in water use at elevated carbon dioxide concentration is widely believed to lead to greater benefits in dry conditions. In this study we used a crop model to investigate the interaction of rising atmospheric carbon dioxide concentration and drought stress, using data from a long-term field experiment to parameterize and validate the model. We found that the yield response of soybean to elevated carbon dioxide concentration declined with increasing drought stress, opposite to previous expectation. As model projections show increased frequency of drought in the future, the results suggest that the benefits of elevated carbon dioxide concentration on soybean yield will be limited over the U.S. Midwest.

Technical Abstract: Elevated atmospheric CO2 concentrations ([CO2]) are expected to benefit the production of C3 crops through the CO2 fertilization effect (CFE) by stimulating photosynthesis and by reducing stomatal conductance and transpiration. The latter effect is also widely believed to lead to greater benefits in dry rather than wet conditions, although some recent experimental evidence has challenged this view. Here we use a process-based crop model, the Agricultural Production Systems sIMulator (APSIM), to quantify the contemporary and future CFE on soybean, the most important source of vegetable protein and oil globally, in its primary production area of the US Midwest. Results demonstrate that APSIM accurately reproduced experimental data from the Soybean Free-Air Carbon dioxide Enrichment (SoyFACE) site showing that the CFE declined with increasing drought stress. This effect was caused by increases in radiation use efficiency that outpaced gains in transpiration efficiency. Using a suite of eight climate model projections, we find that drought frequency in the US Midwest is projected to increase from once every five years currently to once every other year by 2050, thereby considerably limiting the potential benefit from rising [CO2] at the regional scale. This study highlights that increased drought frequency and severity pose a formidable challenge to maintaining soybean yield progress, in part by diminishing the potential benefits of elevated [CO2].