Evaluating the impact of future climate change on irrigated maize production in Kansas

Abstract

The United States southern and central High Plains including western Kansas are experiencing declining ground water supplies from the Ogallala as a result of withdrawals for irrigation exceeding annual recharge, this situation will be exacerbated by future climate change. The purpose of this simulation based study was to 1) assess the impact of future climate change on maize (Zea mays L.) yield in western Kansas; and 2) evaluate and understand the possible impacts of climate change on maize irrigation water productivity, transpiration, evapotranspiration and days to maturity. The Crop Estimation through Resource and Environment Synthesis (CERES-Maize) crop model within the Decision Support System for Agrotechnology Transfer Cropping Systems Model (DSSAT-CSM) was used in combination with multiple Global Climate Models under two Representative Concentration Pathways (RCPs), and two irrigation scenarios [full (450mm) and deficit (300)] under three planting dates [early (20th April), normal (5th May) and late (15th May)]. Results showed that maize yield during the mid-21st century will decline relative to the present on average by 18–33% under RCP4.5 and 37–46% under RCP8.5. The yield decline might be caused mainly by shortening of the growing period (9–18% decline in days to maturity), attributed to elevated temperatures. The reduction in transpiration relative to the baseline reached 15% for RCP8.5 under deficit irrigation whereas the reduction was minimal (1–7%) under full irrigation. Indicating that significant yield reductions might occur due to combined effects of deficit irrigation and shortening of the maturity period. Yield increase due to elevated CO2 concentration [CO2] might be masked by the increased temperatures. The current study showed large disparity in simulated yield among the various GCMs. Planting date did not substantially improve yield but there was less simulation variability among GCMs with early planting compared to normal and late planting. There was no substantial difference among the planting dates for water productivity, however, there was a slight tendency of improvement in irrigation water productivity for deficit irrigation under early planting compared to normal and late planting. Under all planting dates and RCPs, the irrigation water productivity of maize under deficit irrigation was slightly higher than that under full irrigation. The difference in irrigation water productivity of maize between the deficit and full irrigation was larger for early compared to normal and late planting. These differences justify that early planting may be suitable under future climate compared to late planting even though the simulated yield with early planting under similar RCPs and irrigation levels are not significantly different from late planting.