Faruque Ahmed, A.H.M. Motiur Rahman Talukder, Imrul Mosaddek Ahmed , Md. Shakawat Hossain, Apurbo Kumar Chaki , Taslima Zahan, Sheikh Istiaque , Sohela Akhter, Jatish C. Biswas, M. Mizanur Rahman

The Agricultural Production Systems Simulator (APSIM) model was calibrated and validated and used to optimize the sowing window for mungbean (var. BARI Mung-6) at Gazipur, the South-central climatic zone of Bangladesh. Simulation was also done with elevated temperatures (1, 2 and 3 ºC) to find out the adaptation option against future temperature stress situations. The model was run for eight sowing dates viz., February 20, March 05, March 10, March 15, March 20, March 25, March 30 and April 10 using long-term (41 years) historical weather data. A field experiment was carried out with BARI Mung-6 under four sowing dates (March 10, March 20, March 30, and April 10) during 2021 for model evaluation. The APSIM model was calibrated with the data from March 10 sowing, while validation was done with other sowing dates along with long-term (1981 to 2021) weather data. The evaluations with the experimental data showed that the model performance was satisfactory to predict crop phenology, total biomass and grain yields for BARI Mung-6. Simulated yields during March 10 to March 25 sowing was very similar to attainable seed yields while, very early or late sowing gave comparatively lower seed yields with higher variability over the years. The best planting window was from March 15 to March 25 which simulated the highest mean seed yield with less variability over the years. Climate change scenario analyses at 1, 2 and 3 ºC rises in temperature revealed that 1°C increase in temperature has no significant influence on seed yields across the sowing dates but significant yield reductions were observed with the rise of temperatures by 2 and 3 °C on March 20, March 30 and April 10 sowings. Elevated temperatures showed positive impact on seed yield of March 10 sowing only. Results revealed that optimum sowing window for mungbean is from March 15 to March 25 under existing weather conditions but in future, sowing mungbean seeds in March 10 would be the option to combat temperature rise stress situations for sustained productivity.