Adaptation strategies to increase water productivity of wheat under changing climate

Bangladesh, specifically the northwestern region, faces twin challenges, namely, food and water security, which are pressing now and likely to increase in the future mainly due to climate change. More crops per drop of water, namely crop water productivity (WP), could be a key strategy to address both challenges. This study assessed future wheat (Triticum aestivum L.) WP under changing climate along with adaptation strategies in northwestern Bangladesh. AquaCrop 5.0 model prior to calibration and validation was used coupled with Global Climate Models (GCMs) projections to simulate the yield and WP of wheat for the historical baseline (2000–2019), near future (2020–2039), mid-future (2040–2059), and far future (2080–2099) under Representative Concentration Pathway (RCP) 8.5 scenarios. We have tested adaptation strategies such as shifting sowing dates and introducing virtual heat-tolerant varieties to compensate for the adverse effect of future climate change in yield and WP of wheat. The simulated wheat yields using the observed baseline period (2000–2019) climate data are found as 3.73 t ha−1 for the Dinajpur region. This study observed the wheat yield reduction by 11.5%, 21.7%, and 40.5% in the near-future, mid-future, and 2080 s far-future, respectively. Both future maximum temperature (Tmax) and minimum temperatures (Tmin) are projected to increase significantly during the development and flowering stages of wheat production, which could reduce the yield significantly. The actual evapotranspiration (ETa) of wheat during the baseline period is simulated as 271 mm. This ETa could be reduced by 3.7%, 5.9%, and 3.0% for wheat in future time slices, respectively. The WP of wheat during the base period is simulated as 1.37 kg m−3. Results show that wheat WP could be reduced by 6.6%, 21.2%, and 33.6% in the future time slices, respectively. Shifting sowing date (15 November) as an adaptation measure revealed that 10-day backward shifting of the sowing date from the current optimum (25 November) date, the losses of WP could be replenished for all cases, even be increased 3.5% in the 2030s if compared with the current WP observed. Similarly, the loss of WP could be replenished and even increased up to 10.2% and 11.1% for the 2050s and 2030s, respectively, in the case of the 20-day backward shifting sowing date (5 November). In a 10-day forward shifting (5 December), both the yield and WP could be decreased significantly further for all future time slices. Early sowing of seeds could benefit from escaping the critical periods during the flowering stage and could increase the yields and WPs. Introducing virtual heat-tolerant variety as another adaptation measure, we find both the yield and WP of wheat could be increased significantly if compared to the benchmark wheat varieties. These results suggest that adjusting sowing dates and introducing heat-tolerant variety might be a powerful means to mitigate the effect of climate change.