Elevated atmospheric carbon dioxide effects on dairy crops in the northeast US: A comparison of model predictions and observed data

Authors: CASTANO-SANCHEZ, JOSE - Pennsylvania State University; Rotz, Clarence - Al; KARSTEN, HEATHER - Pennsylvania State University; KEMANIAN, ARMEN - Pennsylvania State University

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2020
Publication Date: 9/15/2020
Citation: Castano-Sanchez, J.P., Rotz, C.A., Karsten, H.D., Kemanian, A.R. 2020. Elevated atmospheric carbon dioxide effects on dairy crops in the northeast US: A comparison of model predictions and observed data. Agricultural and Forest Meteorology. 291:1-10. https://doi.org/10.1016/j.agrformet.2020.108093.
DOI: https://doi.org/10.1016/j.agrformet.2020.108093

Interpretive Summary: Atmospheric carbon dioxide concentration has been increasing since the beginning of the industrial revolution, and this change is known to increase photosynthesis and growth of many plant species. Agroecosystem models, along with projected future climate data, are widely used to predict potential impacts of atmospheric carbon dioxide and related climate change on crop production. We studied the response to carbon dioxide levels for alfalfa and corn forage crops produced in the northeastern U.S. as predicted by three cropping system models and compared those predictions to responses measured through field experiments. We found that the crop models appropriately represented the response in crop yield, but they appear to predict less reduction in plant transpiration than that measured. Further research is needed to better understand and model atmospheric carbon dioxide effects on plant transpiration.

Technical Abstract: In the Northeastern U.S., primary crops on dairy farms include alfalfa (Medicago sativa L.) and maize (Zea mays L.). Projected changes in climate along with increased atmospheric carbon dioxide (CO2) concentration will affect future production of these crops. We evaluated crop yield and evapotranspiration response to CO2 enrichment predicted by three process-based cropping system models (CropSyst, DSSAT and IFSM) in six counties of Pennsylvania and New York, using 25 years of daily weather and two concentrations of atmospheric CO2 (350 and 550 ppm). Positive effects of CO2 enrichment on crop growth have been documented using plants grown under controlled CO2 conditions; of particular relevance are results obtained in fields using free-air CO2 enrichment (FACE) technology. For model evaluation, simulation results were compared among models and to FACE experimental data. The three models simulated similar maize response to increasing CO2 for grain yield, total biomass yield and harvest index, with predicted responses within the ranges reported in FACE experiments. The models may have slightly overestimated the yield response of maize during wet years compared with FACE experiments. The models simulated increased productivity of alfalfa, also within the range of observations in FACE experiments. While DSSAT and IFSM predicted yield increases of about 20%, Cropsyst predicted an increase of 32%, which was in the upper bound of FACE experimental data. For both crops, models simulated less reduction in evapotranspiration under increasing CO2 than that measured in FACE experiments. The greater response in alfalfa yield may either shift rotations towards alfalfa, or allow for a shorter alfalfa phase in a rotation depending on market and other production constraints. While there were uncertainties in the simulation of the evapotranspiration response, which can affect the simulation of soil moisture and regional hydrology, these models appropriately represented crop yield responses to increased atmospheric CO2.