FAO AquaCrop model ver. 6.1 was calibrated and validated by means of an independent data sets during the harvesting seasons of 2016/2017 and 2017/2018, at El Noubaria site in western north of Egypt. To assess the impact of the increase in temperature and CO2 concentration on potato biomass and tuber yield simulations, experiments were carried out with four downscaled and bias-corrected of General Circulation Models (GCMs) data sets based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5) scenarios under demonstrative Concentration Trails (RCPs) 4.5 and 8.5, selected for 2021–2040 and 2041–2060. The study showed that the model could satisfactorily simulate potato canopy cover, biomass, harvest and soil water content under various irrigation treatments. The biomass and yield decreased for all GCMs in both future series 2030s and 2050s. Biomass reduction varied between 5.60 and 9.95%, while the reduction of the simulated yield varied between 3.53 and 7.96% for 2030. The lowest values of biomass and yield were achieved by HadGEM2-ES under RCP 8.5 with 27.213 and 20.409 Mg∙ha–1, respectively corresponding to –9.95 and –7.96% reduction. The lowest reductions were 5.60 and 3.53% for biomass and yield, respectively, obtained with MIROC5 under RCP 8.5 for 2030. Reductions in biomass and yield in 2050 were higher than in 2030. The results are showing that higher temperatures shortened the growing period based on calculated growing degree days (GDD). Therefore, it is very important to study changing sowing dates to alleviate the impact of climate change by using field trials, simulation and deep learning models.

The inequality between available water supplies and growing water demand from diverse sectors, as well as the predicted climate changes are putting significant pressures on Egypt’s food security. There is a nation-wide demand for new scientifically proven on-farm practices to boost water productivity of major food crops. The objective of this study was to explore the use of various deficit irrigation schemes to improve water productivity ( WP) of tomato cultivated in Egypt under distinct climate change scenarios, RCP4.5 and RCP8.5, in three time-steps of the reference period (2006– 2016), 2030s, and 2050s. The AquaCrop model was used to simulate the influence of climate change on the tomato crop, as well as two deficit irrigation application schemes for the full growing season and the regulated application for the initial and maturity crop stages. With the same irrigation method, the predicted WP increased in a general pattern across all climate change scenarios. The combination of irrigation schedule with the 80% deficit irrigation can enhance WP near the optimum level (approximately 2.2 kg∙m^–3), especially during early and mature stages of the crop, saving up to 16% of water. The results showed that the expected temperature rise by 2050s would reduce the crop growth cycle by 3– 11 days for all irrigation treatments, resulting in a 1–6% decrease in crop evapotranspiration ( ET_c) and affecting the dry tomato yield with different patterns of increase and decrease due to climate change.