Effects of shift in growing season due to climate change on rice yield and crop water requirements

According to recent climate projections for South Korea, increases in temperature and precipitation will affect water use and crop production associated with paddy rice cultivation. Impacts are expected on crop growing season, crop varieties, and farming methods, all of which are highly vulnerable to disruption in weather conditions. Previous studies have estimated the effects on agricultural water resources according to climate change scenario, but most do not consider the growing season. In this study, changes in paddy rice yield and agricultural water requirement are estimated based on the impact of shift in growing season using a crop growth model. Future weather trends for four selected study areas in central and southern regions of South Korea were constructed using the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios developed by the UN Intergovernmental Panel on Climate Change, and the paddy rice yields were simulated using the Crop Environment Resource Synthesis-Rice growth simulation model. Weather, soil, crop data, cultivars, and experimental data were used as model inputs. The results show a delay in the optimal transplanting date in 2100, with the date in the RCP 8.5 scenario delayed rapidly compared with the delay in RCP 4.5. In addition, paddy rice yield and growing period decrease. Consumptive water use and irrigation requirements decrease in the RCP 4.5 scenario due to increased rainfall. However, in RCP 8.5, less precipitation falls during the growing period, leading to an increase in irrigation requirements in some regions. These results are expected to be useful for paddy water management and growing season adjustment and to help establish long-term food security policies.