Crop evapotranspiration and irrigation requirements. The impact of climate change on maximum and effective crop evapotranspiration as well as on net irrigation requirements, also considering the relative effect of selected adaptation strategies (planting dates, variety selection and deficit irrigation strategies), is summarized in the following tables and graphs. In brief, the following observations are reported: ‐ maximum seasonal crop evapotranspiration is projected to reduce for the current variety under “future” (2050) scenario as a consequence of the expected shortening of the crop growing cycle, on average of about ‐4.6% with respect to current conditions (2000) (fig. 36 and tab. 48); ‐ on the contrary, if a late maturing variety (2050 late_var) is selected, maximum evapotranspiration is projected to increase (+7.6%) for all the planting dates (fig. 36 and tab. 48); ‐ the relative effect of the projected variation of rainfall patterns (‐13.6%) seems to be slightly important the crop water balance, due to their very low values in absolute terms (tab.49); ‐ maximum seasonal crop evapotranspiration is observed always to increase (in absolute terms) for late (February) planting date with respect to earlier (October) ones, because of the shifting of most of the cycle towards the spring‐summer season (fig. 36 and tab. 48); ‐ effective seasonal crop evapotranspiration and net irrigation requirements are both highly dependent on the irrigation strategy, progressively reducing going from full irrigation to rainfed conditions (fig. 36 and tab.50‐51); ‐ as for ETc_max, also the ETc_eff and NIR are projected to decrease in 2050 if the current variety is used, or to increase if a late maturing variety is selected, especially under full irrigated to mild stress conditions (fig. 36 and tab.50‐51); Tab. 48 – Effect of planting date and variety selection on the maximum crop evapotranspiration of wheat in Merguellil catchment (Tunisia) under “present” and “future” climate conditions. Planting date ETc_max 2000 ETc_max 2050 ETc_max 2050 late_var [mm/season] [mm/season] (variation vs 2000) [mm/season] (variation vs 2000) october 521.8 477.5 ‐8.5% 551.8 5.8% november 607.5 566.3 ‐6.8% 647.0 6.5% december 666.5 639.1 ‐4.1% 717.4 7.6% january 685.5 663.3 ‐3.2% 742.8 8.4% february 727.5 716.7 ‐1.5% 794.0 9.1% average 641.8 612.6 ‐4.6% 690.6 7.6% Tab. 49 – Effect of planting date and variety selection on the effective rainfall pattern during crop cycle of wheat in Merguellil catchment (Tunisia) under “present” and “future” cli...
