Cycle length and crop coefficient curves The effect of temperature increase (and relative GDD accumulation) on current and projected crop cycle length and corresponding crop coefficient curves is represented in the following graphs, and the following observations have to be highlighted: ‐ if varietal adaptation is not considered, an important reduction of the total growing cycle is predicted for all planting dates, because of the faster accumulation of the required GGD sum under “future” climate conditions (2050) (fig. 33‐34); ‐ on the contrary, if a late maturing variety will be used, the total crop cycle length (2050 late_var) is projected to remain relatively the same as for the current variety under “present” climate conditions (2000) (fig.34); Growing Degree Days (°C) Growing Degree Days (°C) ‐ with respect to the four crop coefficient stages, a relative reduction is predicted in proportion to the corresponding increase in the cumulative GDD (lower during winter, higher during spring‐summer months), both in the case of early (November) and late (February) sowing dates (fig. 33). 3000 2500 2000 1500 1000 November2050 500 November2000 0 1 21 41 61 81 101 121 141 161 181 201 DAS 1,4 0,6 0,4 November2050 0,2 November2000 0 1 21 41 61 81 101 121 141 161 181 201 DAS 3000 2500 2000 1500 1000 February2050 February2000 500 0 1 21 41 61 81 101 121 141 161 181 DAS 1,4 1 0,4 0,2 February2050 February2000 0 1 21 41 61 81 101 121 141 161 181 DAS Crop coefficient (Kc) Crop coefficient (Kc) Fig. 33 – Predicted cumulative GDD and corresponding Kc curves for wheat in Merguellil catchment (Tunisia) as affected by different planting dates and climate scenarios. February Jaunuary 2050 late_var 2050 2000 December November October 0 50 100 150 200 250 Cycle length (days) Planting date Fig. 34 – Length of total growing cycle of wheat in Merguellil catchment (Tunisia) as affected by planting date, variety selection and climate variations.
Cycle length and crop coefficient curves The effect of temperature increase (and relative GDD accumulation) on current and projected crop cycle length and corresponding crop coefficient curves is represented in the following graphs, and the following observations have to be highlighted: ‐ if varietal adaptation is not considered, an important reduction of the total growing cycle is predicted for all planting dates, because of the faster accumulation of the required GGD sum under “future” climate conditions (2050) (fig. 21‐22); ‐ if a late maturing variety will be used, the total crop cycle length (2050 late_var) is projected to remain relatively the same as for the current variety under “present” climate conditions (2000), especially for late planting dates (fig. 22); 2000 1500 1000 500 October_2050 October_2000 0 1 21 41 61 81 101 121 141 161 181 201 DAS 2000 1500 1000 February2050 500 February2000 0 1 21 41 61 81 101 121 141 161 181 DAS Growing Degree Days (°C) Growing Degree Days (°C) ‐ with respect to the four crop coefficient stages, a relative reduction is predicted in proportion to the corresponding increase in the cumulative GDD (lower during winter, higher during spring‐summer months), but with a greater effect in the case of early (October) rather than late (February) planting dates (fig. 21).
Cycle length and crop coefficient curves The effect of temperature increase (and relative GDD accumulation) on current and projected crop cycle of olive has not been evaluated, because of the lack of sufficient information and data to model the relative length of the stages. Thus, a fixed length of the stages and of total growing period has been considered (270 days), as suggested by FAO (2012). The crop coefficient curves have been modelled by computing the average monthly Kc values according to Orgaz et al. (2006) and FAO (2012) under the different conditions of selected climate scenarios, as affected by the changing of monthly ETo and rainfall pattern and especially of their relative effect on the evaporative Kc components (from soil and canopy). In table 37, a comparison of the main Kc components is reported, showing the relative reduction of the canopy direct evaporative component (Kpd) and of the soil evaporation component (Ks,e) during the autumn to winter months, due to the projected relative decrease in rainfall pattern and increase in reference evapotranspiration. In the figure 27, the monthly trends of crop coefficients under different climate scenarios are reported, as computed according to Xxxxx et. (2006) for a “new” and an “old” type of olive crop plantation, and in comparison to the fixed Kc coefficient suggested by FAO (2012) for an arid environment; the following observations are reported: ‐ there is a clear effect of the type of plantation on Kc values, being higher for “new” types of cropping systems under all climate scenarios; ‐ as yet mentioned, the Kc values for autumn‐winter months progressively reduce because of the reduction in projected ETo and rainfall patterns; ‐ only slight variations are observed during the spring‐summer months, where the Kpd and Ks,e components reduce close to zero and no variations are observed between scenarios. Tab. 37 ‐ Comparison of monthly Kc values and main components for olive in Jordan river basin (Jordan) under “present”, “future” and “extreme weather” climate conditions. Month Kc Xx.xx Kpd Ks.e 2000 2050 2050+1 Avg 2000 2050 2050+1 2000 2050 2050+1 1 0.80 0.65 0.59 0.26 0.09 0.05 0.04 0.39 0.28 0.24 2 0.61 0.61 0.56 0.27 0.04 0.04 0.03 0.23 0.23 0.19 3 0.51 0.52 0.49 0.29 0.02 0.03 0.02 0.14 0.14 0.12 4 0.50 0.47 0.45 0.33 0.02 0.01 0.01 0.09 0.07 0.05 5 0.45 0.45 0.45 0.38 0.01 0.00 0.00 0.00 0.00 0.00 6 0.52 0.52 0.52 0.46 0.00 0.00 0.00 0.00 0.00 0.00 7 0.52 0.52 0.52 0.46 0.00 0.00 0.00 0.00 0.00 0.00 8 0.50 0.51 ...
