Modeling the impacts of climate change on irrigated corn production in the Central Great Plains

Abstract

The changes in temperature and precipitation patterns along with increasing levels of atmospheric carbon dioxide (CO2) may change evapotranspiration (ET) demand, and affect water availability and crop production. An assessment of the potential impact of climate change and elevated CO2 on irrigated corn (Zea mays L.) in the Central Great Plains of Colorado was conducted using the Root Zone Water Quality Model (RZWQM2) model. One hundred and twelve bias corrected and spatially disaggregated (BCSD) climate projections were used to generate four different multi-model ensemble scenarios of climate change: three of the ensembles represented the A1B, A2, and B1 emission scenarios and the fourth comprised of all 112 BCSD projections. Three different levels of irrigation, based on meeting 100, 75, and 50% of the crop ET demand, were used to study the climate change effects on corn yield and water use efficiency (WUE) under full and deficit irrigation. Predicted increases in mean monthly temperature during the crop growing period varied from 1.4 to 1.9, 2.1 to 3.4, and 2.7 to 5.4°C during the 2020s, 2050s, and 2080s, respectively, for the different climate change scenarios. During the same periods, the projected changes in mean monthly precipitation varied in the range of −4.5 to 1.7, −6.6 to 4.0 and −11.5 to 10.2%, respectively. Simulation results showed a decrease in corn yield, because the negative effects of increase in temperature dominated over the positive effects of increasing CO2 levels. The mean overall decrease in yield for the four different climate change scenarios, with full irrigation, ranged from 11.3 to 14.0, 17.1 to 21.0, and 20.7 to 27.7% during the 2020s, 2050s, and 2080s, respectively, even though the CO2 alone increased yield by 3.5 to 12.8% for the scenario representing ensembles of 112 projections (S1). The yield decrease was linearly related to the shortening of the growing period caused by increased temperature. Under deficit irrigation, the yield decreases were smaller due to increased WUE with elevated CO2. Because of the shortened crop growing period and the CO2 effect of decreasing the ET demand, there was a decrease in the required irrigation. Longer duration cultivars tolerant to higher temperatures may be one of the possible adaptation strategies. The amount of irrigation water needed to maintain the current yield for a longer duration corn cultivar, having the same WUE as the current cultivar, is projected to change in the range of −1.7 to 6.4% from the current baseline, under the four different scenarios of climate change evaluated in this research.