nvestigating the Impact of Climate Change on Irrigated Wheat Production under Torbat-e Jam Region for the Near Future

Wheat production is an important component for national food security. Studying the impact of future climate change on crop production is crucial to manage crop productivity. Improving our understanding of potential responses of the wheat plant to these changes while taking into consideration agricultural management is required for identifying best adaptation strategies. In Khorasan Razavi province, over 12% of the total cultivated wheat area is belong to Torbat-e Jam region. The current study aimed to quantify the potential impacts of climate change on irrigated wheat yield in the next 30 years for this region. In this study, information on regional cropping systems and meteorological data to study the effects of climate change were collected and finally, the impact of climate change on irrigated wheat yield was studied using simulation approaches under different climatic scenarios. Long-term daily weather data for future was generated using MarkSim weather generator software and the past meteorological data was gathered from regional weather station. Daily weather data generated by four scenarios RCP2.6, RCP4.5, RCP6, and RCP8.5 for a 30-year period. The generated and measured daily weather data was used for running CERES-Wheat model. Finally, crop model outputs were used to interpret climate change impacts on wheat growth and production. The average air temperature during the wheat growth period showed that temperature increased about 1.6% in the last five years compared to the first five years of the baseline 30-years period. Furthermore, the average annual precipitation for the last 5 years was 51 mm less than the first 5 years of the baseline period. The air temperature will increase about 1.1, 1.6, 1.2 and 1.8 °C during the wheat growth period for the near future (30 years) under the RCP2.6, RCP4.5, RCP6, and RCP8.5 scenarios, respectively. The precipitation over the wheat growth period will reduce by 9 and 8% under RCP4.5 and RCP8.5 scenarios, respectively. Furthermore, the precipitation over the growth period would increase by 11 and 17% under RCP2.6 and RCP6 scenarios, respectively. The simulated wheat yield by the CEREC-Wheat model showed that the grain yield increased by 5% in the first 5 years compared to the last 5 years of the baseline period (1998-2017). The biomass production and harvest index (HI) also increased by 2.3 and 1%, respectively. The increased dry matter production and HI can be due to temperature increase during the cold seasons, and more amount of precipitation during the reproductive growth. The simulated wheat growth during the near future period (2018-2047) showed that wheat growth cycle will reduce from 5 to 7 days under different emission scenarios. In the different soil textures, wheat yield under RCP2.6, RCP4.5, RCP6, and RCP8.5 scenarios will increase by 24.4, 19.9, 24.9 and 25.2%, respectively. Furthermore, the highest and the lowest yield were obtained from clay and sandy clay loam soils, respectively. Under the different emission scenarios, the mean incident light and light use efficiency during the growth period would be increased by 20.8-24.6% and 5.5-8.3%, respectively, in projected climate change as compare to baseline period. Reducing irrigation water as amount of 300 m3 ha-1 and simultaneous increase in irrigation water use efficiency are possible incident scenarios for the near future. Based on these scenarios, simulations showed that grain yield increased 26.3, 19.6, 27.2 and 25.6 % under RCP2.6, RCP4.5, RCP6, and RCP8.5 emission scenarios, respectively.  The increased temperature and atmospheric CO2 concentration during the next 30 years will decrease wheat growth cycle, but increase the potential biomass and grain wheat yield under the different emission scenarios. The results showed that the increased yield production will occur under climate change conditions, even if the available irrigation water would decrease by 300 m3 ha-1.