Simulation of Phonological Stages of Irrigated Wheat Cv. Mehregan under Drought Stress in Climate Change Condition

It is necessary to evaluation of the occurrence of climate change, Inadequate distribution and Stop of rainfall in the final stages of wheat growth in Varamin.

From the output of HadGEM under RCP4.5 and RCP8.5, to simulate the future climate using AgMIP model with long-term baseline data (1980-2009), in the periods of 2025, 2055 and 2085 were used. SSM model was used to simulate the phonological stages of wheat and in order to calibrate and validate the model, an experiment in the form of a randomized complete block design with five treatments including; [No stress, booting stage, Flowering, Milking, and Doughing], with 3 replications, was carried out during the 2020-2019 growth season in Varamin.

The SSM model simulated the occurrence of phonological stages with high accuracy. In 2085 period under RCP8.5, the highest increase of Tmax and Tmin was observed with 6.9 °C and 5.6 °C compared to the baseline period, respectively. While the amount of precipitation decreased in 2025 and 2055 under RCP8.5, but it increased in RCP4.5. The smallest difference between day to Flowering, BSG, TSG and day to was related to the period 2025 under RCP4.5 with 3, 9, 12 and 11 days, respectively. The highest differences were observed in the period 2085 under the RCP8.5 with 90, 77, 47 and 43 days, respectively.

Increasing the temperature and decreasing rainfall have neutralized the beneficial effects of increasing CO2 concentration and these factors have shortened the duration of phonological stages.