الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
This study was carried out at Sakha Agricultural Research Station, Egypt. The objectives of this study were: 1. Calibrating and validating CERES-Wheat and N-Wheat for wheat and CERESMaize and IXIM-maize models for maize under different irrigation regimes and cultivars 2. Assessment the simulated water use and water use efficiency of wheat and maize under different irrigation regimes using the calibrated models 3. Estimating the impact of climate change on growth, yield, water use and water use efficiency of wheat and maize using calibrated and validated models under different GCMs in three time series (2030, 2050 and 2080). 4. Exploring the most suitable planting dates for wheat and maize achieving higher yield under climate change scenarios. This study included wheat and maize experiments and conducted in in large (12.0 m3) volumetric lysimeters (1.5 × 2.5 m, height 3.0 m) filled with non-saline clay soil since 1994. The lysimeters were placed in an open field and surrounded with wheat in winter and maize in summer to decrease the edge-effects produced by the lysimeters. The experiment was conducted in a large lysimeter during two successive seasons of , 2016/2017 and 2017/2018 for wheat and 2017 and 2018 for maize in a split-plot design, with three replicates. To ensure genetic variability under current conditions, the main plots were assigned to two wheat and maize cultivars. Gemiza9 is sensitive to higher temperatures and drought, while Misr1 is more resistant to both higher temperatures and drought for wheat. Meanwhile, maize cultivars are single cross 10 (SC10) and tri hybrid 24 (TWC24), representing tolerant and sensitive varieties respectively. The sub plots were devoted to three irrigation treatments. These were 35, 55 and 75% soil moisture depletion (SMD). The 55 % SMD was taken as the control. This value is representative of traditional farmer irrigation. The wheat (Triticum aestivum, L) variety Gemiza9 and Misr1 were sown on 20 November in both seasons and harvested on 05 May and 25 April in first and second growing seasons respectively. While, maize (Zea mays L) varieties single cross10 and tri hybrid24 were sown on 15 May and harvested on 05 September and 28 August for first and second seasons respectively. The results of this study can be summarized as follow: Soil properties • Particle size distribution showed that the clay content ranged from 47-51 %, silt content ranged from 32-38 %, and sand content ranged from 15-20 % creating texture of clay loam. • Soil bulk density increased with soil depth, but hydraulic conductivity decreased with depth. • Soil wilting point and field capacity values ranged 21-22 % and 42-44 % respectively. Thus, available soil moisture content ranged from 21 - 22 % in the soil profile (0-120 cm). • Values of soil root growth factor (SRGF) started with 0.7 and decreased slowly with depth up to 0.5. Temperature changes under climate change scenarios • The annual mean maximum and minimum temperatures for the baseline are 27.6 and 15.4°C, respectively, with overall mean of 21.5°C. • According to the three GCMs (GFDL-ES2M, CSIRO-MK3-6-0, and HadGEM2-ES), the overall minimum temperature is expected to increase by 0.7, 1.0 and 1.6°C in 2030; 2.0, 2.5 and 3.1°C in 2050; and by 3.0, 4.5 and 4.9°C in 2080, respectively. • The increase in maximum temperature predicted by the three respective GCMs is 0.7, 0.9 and 1.7°C in the near decades (2030); 2.0, 2.3 and 3.0°C in the mid- Century; and 3.1, 4.1 and 4.7°C in the late Century (2080). • The annual mean temperature is expected to increase by 0.7, 0.9 and 1.6oC in 2030; 2.0, 2.4 and 3.0°C in 2050; and higher increases in 2080 of 3.0, 4.3 and 4.8°C for the three respective GCMs under RCP8.5 Wheat crop: • The calibrations of CERES-Wheat and N-Wheat models proved successful, attaining accurate predictions of wheat yield, phenology and yield components. • Wheat grain yield, biomass and phenology of both cultivars were suitably simulated by the DSSAT models, achieving lower RMSD and higher R2 and WI values • Irrigation at 55 % depletion from AW showed the highest values of both plant height and LAI, followed by 35 and 75 % respectively • The simulated and observed values of plant height and LAI, data showed a robust simulation and good agreement through achieving high values of R2 and WI with lower values of RMSD. • Irrigation at 55 % ASMD gave the highest values of grain yield, biomass, number of grains/m2, and grain weight followed by irrigation at 35 and 75 %. Meanwhile, nitrogen concentration in grains increased with increasing ASMD, recording the highest concentration under treatment of 75 % ASMD. • Misr1 cultivar showed the superiority for all features under all irrigation regimes than Gemiza9, proving the importance of sowing Misr1 in arid and semi-arid regions under water stress. • Values of irrigation water applied was 432, 396 and 374 mm/season for Misr1, while it was 427, 391, and 369 mm/ season for Gemiza9 respectively. • Seasonal irrigation water applied decreased with increasing the ASMD. Also, seasonal irrigation water applied for Gemiza9 was slightly lesser than that with Misr1. • The highest values of seasonal were recorded under irrigation treatment 35 % ASMD, whereas, the lowest ones were detected under irrigation treatment of 75 % ASMD. • There is an acceptable agreement between simulated and observed values of water applied, confirming the robust of model calibrations for irrigation management studies. • Seasonal water consumptive use of wheat decreased as the ASMD increased in the root zone area. Also, water use for Misr1 cultivar was slightly higher than that of Gemiza9. • Plants irrigated at 55% ASMD regime gave the highest water use efficiency followed by 75% ASMD regime without significant differences with a good agreement with simulated data. • Crop yield decreased under all climate scenarios relative to baseline yield. This reduction was calculated as 2.7, 8.5 and 14.9% in 2030; 8.4, 9.5 and 16.2% in 2050; decreasing markedly by 11.0, 11.7 and 17.0% in 2080 for GFDL-ES2M, CSIRO-MK3-6-0 and HADGEM2-ES, respectively. • The crop yield of the Misr1 cultivar decreased less under future scenarios compared with Gemiza9. Where, the relative mean wheat yield decreases for Misr1 under the three-time series of 2030, 2050 and 2080 was 8.3, 10.7 and 11.0%, respectively. Meanwhile, for Gemiza9, the decrease was greater, as 9.0, 11.7 and 15.7%, respectively, as a mean of the three GCMs. • The mean reduction of grain yields due to climate change for both cultivars was 8.7, 11.4 and 13.2% in 2030, 2050 and 2080, respectively, relative to the baseline yield. • The future growing periods for wheat under the climate scenarios were shorter than those in the baseline scenario and this decrease was in the following descending order: GCM3<GCM2<GCM1. Also, the shortest growth period was predicted for 2080, followed by 2050 and then 2030. • Uncertainties in estimating yield impacts were relatively small for GCMs compared with CMs • The predicted water use (ETc) decreased under future climate scenarios, but water use efficiency increased. • Delaying the planting date decreased the yield reduction gap under future climate scenarios, and thus could be considered a potential adaptation option for climate change impacts. • An assumed planting of 25 November partially decreased the predicted mean yield reduction of both cultivars caused by climate change to 4.8, 7.9 and 10.5% in 2030s (2010-2040), 2050s (2040-2069) and 2080s (2070-2099), respectively, meanwhile changing planting date to 30 November was better in decreasing further reduction of yield particularly in 2050 and 2080, thus yield reduction decreased to 5.2, 6.8 and 8.5% in 2030s (2010-2040), 2050s (2040-2069) and 2080s (2070-2099), respectively. • The Misr1 cultivar achieved higher resistance to temperature than Gemiza9 with and without adaptations.