الفهرس 
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Abstract
The study was aimed at irrigation scheduling effects on the productivity of irrigated wheat and water in relation to mineral organic nitrogen fertilization, including testing of the DSSAT v4.7.0.0 model. The experimental parts of this study were conducted during the two successive growing winter seasons of 2016/17 and 2017/18 at El-Mattaena Agricultural Research Station, Luxor Governorate, Upper Egypt. The farm is located at a 25 18 latitude, 32 34 longitude and its altitude is about 82. m above mean sea level. The experiments were laid out in a split plot design with three replicates. The main plots represented three irrigation regimes ( (I1) 1.2, (I2) 1.0 and (I3) 0.8 pan evaporation coefficient), the spilt plots represented five fertilization regimes (75 kg N fed-1 as compost (F1), 75% N as compost + 25% N as mineral (F2), 50% N as compost + 50% N as mineral (F3), 25% N as compost + 75% N as mineral (F4) and 75 kg N fed-1 as urea (F5)).
The obtained results can be summarized as follows:
1) Wheat Growth characteristics:
Increasing available water during the different growth stages resulted in a promoting effect on wheat growth rate. The tallest plant height of both seasons was obtained through irrigation scheduling at I2. On the contrary, the shortest plants in both seasons were obtained through irrigation at I3, increasing in plant height was insignificant in 2016/17 and significant in the second season.
The 25% N as compost + 75% N as mineral (F4) treatment led to a significant increase in plant height in 2016/17 season, while mineral treatment resulted insignificant effect increase in the second season.
Increasing available water and mineral nitrogen fertilization led to insignificant increase in the tillers number/m2 in both seasons.
The LAI values increased significantly through increasing available water during the two studied seasons, irrigation scheduling at 1.2 PEC led to the highest increase, while the lowest LAI values obtained through irrigation scheduling at 0.8 PEC in the two studied seasons.
Combined organic- mineral fertilization enhanced LAI; the 25% N as compost + 75% N as mineral (F4) treatment had insignificant increase of LAI in 2016/17 season. While 50% N as compost + 50% N as mineral (F3) treatment increased LAI values significantly in the 2017/18.
Irrigation scheduling at 1.2 PEC led to insignificant increase on the days to 50% anthesis in both seasons.
Organic fertilization increased days to 50% anthesis; the use of 100% compost or 75% N as compost + 25% N as mineral treatments led to a significant delaying in this characteristic at both seasons.
In the same trend, irrigated according to 1.2 PEC increased the days to 50% maturity significantly in 2016/17 and insignificant increase in the second season.
Also, Organic fertilization enhanced days to 50% maturity; the use of 100% compost or (75% N as compost + 25% N as mineral) treatments led to a significant delaying in days to 50% maturity in both seasons.
2) Wheat yield and yield components:
2.1) Yield component
Increasing irrigation frequency increased the grains number/spike significantly in both seasons. The highest grains number /spike obtained through irrigation scheduling at 1.2 and 1.0 PEC.
Application of organic and inorganic amendments exerted insignificant variation in wheat grains number /spike during both the seasons, the mineral treatment led to increase grains number /spike in 2016/17 season. While 50% N as compost + 50% N as mineral (F3) treatment increased the grains number /spike in the second season.
The maximum 1000-grains weight (g) through both was obtained through irrigation scheduling at 1.2 PEC with insignificant effect in the first season and significant effect in the second season.
The use of organic and inorganic amendments together exerted variation in 1000-grains (g), application of 25% N as compost + 75% N as mineral (F4) led to a significant increase in this characteristic in 2016/17 season. While 50% N as compost + 50% N as mineral (F3) increased non significantly the number of 1000-grains (g) in the second season
2.2) The Wheat yield
The highest grain yields (3.12 ton/fed.) of 2016/17 were obtained through irrigation scheduling 1.0 PEC, while 1.2 PEC produced the highest grain yields (2.33 ton/fed.) in 2017/18 with significant increase in both seasons. On the contrary, the lowest grain yields (2.13 ton/fed.) of both seasons were obtained through irrigation at 0.8 PEC.
The integrated fertilization clearly enhanced wheat grain yield (ton fed-1), the 25% N as compost + 75% N as mineral (F4) treatment led to a significant increase in grain yield (3.44 ton/fed.) in both seasons, while the lowest grain yields (1.86 ton/fed.) of both seasons were obtained by compost treatment.
The straw yield (ton/fed) increased significantly in accordance with decreasing irrigation intervals in both seasons. Irrigation scheduling at 1.2 and 1.0 PEC increased the straw yield (ton/fed) significantly as compared to irrigation scheduling at 0.8 PEC. The maximum straw yield was (8.01 ton/fed), while the lowest one (5.75 ton/fed) was recorded under irrigation scheduling at 0.8 PEC.
Mineral fertilization enhanced wheat straw yield (ton fed-1), the mineral treatment led to a significant increase (8.87 ton/fed) in straw yield in both seasons. On the other hand, the lowest straw yield (5.47 ton/fed) in both seasons was obtained with the compost treatments.
The interaction of (irrigation scheduling (1.2) x fertilization regimes (F5)) was significant in this character in 2016/17. The maximum straw yield was (9.81 ton fed-1).
The irrigation scheduling at 1.2 and 1.0 PEC increased the biological yield (ton/fed) significantly as compared to 0.8 PEC irrigation scheduling. The highest biological yield value was (11.05 ton/fed), while, the lowest biological yield (7.88 ton/fed) in both seasons was obtained with irrigation scheduling at 1.2 and 0.8 PEC treatments, respectively.
The mineral fertilization treatment led to a significant increase in biological yield in 2016/17 season and 25% N as compost + 75% N as mineral (F4) treatment led to a significant increase in the second season. While the lowest biological yields (ton/fed.) in both seasons were obtained with the compost treatments. The highest biological yield value was (12.15 ton/fed), while, the lowest straw yield value (7.34 ton/fed) in both seasons was obtained with the mineral and compost treatments, respectively.
The interaction of (irrigation scheduling (1.2) x fertilization regimes (F5)) was significant in this character in 2016/17. The maximum biological yield was (13.13 ton fed-1).
3) Wheat grains NUE (kg/fed)
The NUE (kg/fed) values of wheat grains increased non significantly under 0.8 PEC irrigation scheduling in the 2016/17, while the significant increase (10.6%) was in the second season.
As for the effect of fertilization regimes. The organic fertilizer (F1) increased significantly wheat grains NUE (kg/fed). and produced the maximum value (11.1%) in both seasons.
4) Total soil residual nitrogen content:
The organic amendments have a positive effect on soil residual N contents. On the contrary, the traditional fertilization exhausts soil fertility. The use of compost led to a significant increase (0.16%) in this characteristic, by contrast, mineral fertilizer led to the least total soil N2value (0.09%) in both seasons.
5) Soil– plant and water relationships
5.1) Irrigation requirements (applied water m3):
The seasonal irrigation requirement for irrigation treatments was higher at irrigation scheduling at 1.2 PEC, while it was lower at irrigation scheduling at 0.8 PEC in both seasons.
The average values of applied water (m3) for irrigation treatments 1.2, 1.0 and 0.8 PEC were 2465.0, 2360.8 and 2281.9 in 2016/17, and 2711.3, 2661.4 and 2534.4 in the second season, respectively.
5.2) Wheat evapotranspiration (ETcrop):
Daily ET began with a little amount and then rose gradually to reach the peak use after 87 till 124 and 75 till 107 days from planting in 2016/17 and 2017/18, respectively.
The seasonal wheat evapotranspiration (ETcrop) for irrigation treatments was the highest at 1.2 PEC (2092.5 m3/fed), while it was the lowest (1710.7 m3/fed) at 0.8 PEC for both seasons.
The organic fertilization increased slightly wheat consumptive use (ETcrop) compared to the values of chemical fertilizers.
5.3) Wheat crop coefficient (Kc):
The obtained Kc values during 2016/17 and 2017/18 at different stages of plant growth stages (ini, dev, mid and late) and under the different irrigation treatments 1.2, 1.0 and 0.8 PEC were (0.62, 0.99, 1.21 and 0.81), (0.62, 0.95, 1.19 and 0.75) and (0.62, 0.93, 1.11 and 0.65) in 2016/17 and (0.62, 1.19, 1.59 and 1.10), by (0.62, 1.17, 1.57 and 1.07) and (0.62, 1.09, 1.52 and 1.03) in 2017/18, respectively
The Kc values were low at the initial stage. As the plant developed, a gradual increase was observed in the crop coefficient. The crop coefficient reaches its peaks in the medium growth stage. Then, the crop coefficient was decreased during the late season of plants
5.4) Water Productivity (WP):
Irrigation scheduling at 1.0 PEC increased significantly values of WP in 2016/17 and Irrigation scheduling at 1.2 PEC increased insignificantly values of WP in 2017/18, compared to irrigated at 0.8 PEC.
The integrated fertilization caused the highest WP in both seasons, the use of 25% N as compost + 75% N as mineral (F4) led to a significant increase in this characteristic in the 2016/17 season, and the second season.
The highest value of WP of both seasons (2.08 kg m-3) was obtained from I2×F4 in the first season. While the lowest (0.88 kg m-3) was obtained from I1×F1 in the second season.
6) Wheat WP modeling:
• The calibration process of CERES-Wheat model showed a good performance of simulated values of maturity days and grain yields when compared to observed data during 2016/17 season.
• A good validation of the CERES-Wheat model for predicting wheat maturity days as well as grain yield during 2017/18 season under Upper Egypt condition.
• Under CERES-Wheat model simulation, the 2050s climate and rising air temperature under RCP2.6 and RCP8.5 scenarios in 2050s would cause a reduction in growing cycle length of wheat, reduction would be about 5 days less than the simulated 2016/17 season as a baseline under RCP2.6 scenario in 2025s. While the length of the growing cycle would reduce by 7 days under the RCP8.5 scenario in 2050s.
• Traditional or mineral fertilization (F5) would be low resistance towards the bad effect of 2050s climate change. The average grain yield reduction percentage with mineral fertilization in 2050s under RCP2.6 and RCP8.5 would be about 22.6% and 18.9%, compared with the same condition under the baseline, respectively.
The average grain yield value with organic fertilization (F1) in 2050s under RCP2.6 and RCP8.5 would be increased by 13.1 and 18.2%, compared to the same treatments under the baseline.
• The ETo values would increase under 2050s scenarios. The increased percentages would be by 20.8 and by 21.2% under RCP2.6 and RCP8.5 scenarios in 2050s, respectively, compared to baseline.
• Consequently, ETcrop would increase by 21% under RCP2.6 and RCP8.5 scenarios in 2050s, compared to baseline.
• The WP would be reduced under 2050s climate change conditions, compared to its value under recent climate conditions. WP would decrease by 23.8 and 21.4% % under RCP2.6 and RCP8.5 scenarios in 2050s, respectively, compared to baseline.
• Irrigation scheduling at 1.2, 1.0 and 0.8 of accumulated pan evaporation would result in WP with average values of (1.49, 1.14, and 1.18), (1.56, 1.17 and 1.21) and (1.45, 1.13 and 1.15) for baseline, 2050s RCP2.6 and RCP8.5 scenarios, respectively.
• The relationship of organic fertilizer regimes and WP reduction percentage among recent time, 2050s RCP2.6 and RCP8.5 scenarios reflects a strong linear relationship, The maximum reduction percentage of 36 and 33.2% would be recorded with 100% mineral nitrogen fertilizer (F5), while, the minimum of 6.3 and 2.4% would be recorded with 100% organic nitrogen fertilizer (F1) under RCP2.6 and for RCP8.5 scenarios in 2050s respectively. Which highlights the promoting and the buffering effect of adding organic fertilizer to control the bad impact of future climate change.
Recommendations
Irrigation scheduling is an intelligent tool that applies the required amount of water at the appropriate time and at the same time guarantees water saving with suitable productivity. Using evaporation pan _A under the Upper Egypt condition could be a very good tool for saving water and maximizing wheat water productivity.
Integrated nitrogen fertilization has a clear effect on maximizing wheat crop production and improve soil from soil conditions.
The DSSAT-CERES-Wheat model performance was good under different irrigation and nitrogen application management for Upper Egypt conditions. It could be recommended that the model works well for Upper Egypt condition, thus, analysis of the impacts of different management and climate change can be applied.
Using integrated fertilizer (50% N as compost + 50% N as mineral, or 25% N as compost + 75% N as mineral under 1.0 pan evaporation coefficient) could avoid or control the bad impact of future climate change 2050s.
Irrigation scheduling under 1.0 of accumulated pan evaporation will result in greatest WP. The highest reduction in WP under conventional fertilizer in 2050s in both scenarios could be avoided or controlled by using integrated fertilizer.