Increase of CO2 and Climate Change Effects on Iowa Soybean Yield, Simulated Using GLYCIM

Abstract

AbstractIncreases in atmospheric CO2 concentration are likely to have a significant impact on the climate and to affect the growth and development of crops. The effect of climate change on crops has to be assessed for large areas to provide information for global estimates and regional strategy development. In this study, computer simulations were done using the soybean [Glycine max (L.) Merr.] crop model GLYCIM to assess the effects of these changes on soybean yields in the state of Iowa. The ability of the model to accurately predict the effect of changes in atmospheric CO2 concentration was tested by comparing model results with a curve fit of CO2 concentration yield response derived from measured data. To simulate the effects of climate change, we used projected monthly weather variables for ambient and increased CO2 from three general circulation models (GCMs): Goddard Institute for Space Studies (GISS), Geophysical Fluid Dynamics Laboratory (GFDL), and United Kingdom Meteorological Office (UKMO). The monthly weather variables were converted to the daily weather to simulate soybean crop yields in nine crop reporting districts (CRDs) of Iowa, with and without increases in atmospheric CO2. When climate change was simulated with increasing levels of CO2 (baseline 350, 450, 550, and 650 µL L−1), yields increased. Without increases in atmospheric CO2, yields remained essentially constant in the GFDL and GISS scenarios, while decreasing by 2 to 10% in the UKMO scenario. The variability in yields among nine CRDs increased for all scenarios as climate changed and levels of CO2 increased. Overall, projected climate changes did not substantially alter simulated soybean yields. The increase in CO2 concentration in the atmosphere was the primary determinant of yield response.