Does drought stress eliminate the benefit of elevated CO2 on soybean yield? Using an improved model to link crop and soil water relations

Authors: SUN, WENGUANG - University Of Nebraska; Fleisher, David; Timlin, Dennis; RAY, CHITTARANJAN - University Of Nebraska; WANG, ZHUANGJI - University Of Maryland; BEEGUM, SAHILA - University Of Nebraska; Reddy, Vangimalla

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2023
Publication Date: 10/23/2023
Citation: Sun, W., Fleisher, D.H., Timlin, D.J., Ray, C., Wang, Z., Beegum, S., Reddy, V. 2023. Does drought stress eliminate the benefit of elevated CO2 on soybean yield? Using an improved model to link crop and soil water relations. Agricultural and Forest Meteorology. 343(2023). Article e109747. https://doi.org/10.1016/j.agrformet.2023.109747.
DOI: https://doi.org/10.1016/j.agrformet.2023.109747

Interpretive Summary: Different types of climate extremes such as heat waves and droughts are projected to become more frequent. Adverse climate conditions can lead to harvest failures and threaten food security. For example, a 2012 US drought and co-occurring heat wave reduced soybean production in the US Midwest by 3% compared to the previous year. Understanding how these climate variables influence soybean growth and development is very important so that scientists can accurately predict potential climate change impacts on soybean production. Many scientific tools are used to simulate these impacts, but the quality of these predictions needs to be improved. The current research focused on improving an existing model for soybean by incorporating a two-dimensional root module. Published experimental data was used to test and evaluate the improvements to this model. Statistical metrics were used to determine how well these changes increased the model accuracy. These showed the new model was able to simulate observed data well including canopy temperature, photosynthesis rate, seasonal LAI, and biomass. We used this improved model to quantify current and future climate change effects on soybean yields in the US Midwest. We found that carbon dioxide fertilization effects on yield were highest in northern counties and declined in southern and the western counties by the end of 21st century. This variation was associated with changes in temperature as well as higher drought periods associated with declining rainfall amounts. This study provided a multiscale modelling framework that linked field experiment sites with broader spatial scales to assess the interactive of drought and carbon dioxide effects on soybean yields.

Technical Abstract: Rising atmospheric carbon dioxide concentration [CO2] is known to stimulate the ground biomass and yield of C3 crops and may ameliorate negative impacts of water deficit on future crop production. Crop simulation models are indispensable tools that facilitate studies for assess climate impacts and adaptation responses, but are limited in terms of predicting water stress responses under high [CO2]. The soybean model, GLYCIM, was previously modified to more mechanistically account for the linkages between photosynthesis and water stress via integration of a coupled leaf-level gas exchange - energy balance model. GLYCIM was newly integrated with a two-dimensional convective-diffusive root growth module which linked soil and leaf water potentials with the regulation of stomatal conductance. Published experimental data from a Free-Air CO2 Enrichment (FACE) site called SoyFACE was used to evaluate the improved soybean model. Result showed that the model accurately matched SoyFACE observed data including canopy temperature, photosynthesis rate, seasonal LAI, biomass and soil water contents and root growth. GLYCIM also reproduced the declining response of CO2 fertilization on yield with increasing drought. We further used this improved model to quantify current and future CO2 effects on soybean yields in the US Midwest. Using an ensemble of five climate model projections, GLYCIM showed that the CO2 fertilization effect on yield was highest in northern counties while it declined in southern and the western counties by the end of 21st century due to increased drought characterized by higher daily maximum temperature and decreased rainfall. This study highlights the potential need to develop adaptive strategies to capitalize the benefits from elevated [CO2] to better counteract increasing drought.