الفهرس 
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Abstract
Two field experiments were carried out at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate, Egypt during the two successive seasons of 2014/2015 and 2015/2016. The objectives of this research were: (i) to study the effect of irrigation regime using tow irrigation levels (40% and 60%) of soil moisture depletion on wheat grain yield; (ii) to evaluate the growth, yield and N use efficiency of wheat as affected by different rates of N fertilization. The experimental used design was split split plot design with three replicates. Irrigation regimes I1 (irrigated at 40% depletion) and I2 irrigated at 60% depletion were assigned in the main plots. Three nitrogen rates i.e. zero, 50, and 75 kg N fed-1 in the sub plots namely N0, N50, and N75 and two doses of nitrogen i.e D1 one time and D2 tow times Results showed that irrigation at 40% depletion significantly increased grain yield by 6.03, 5.5% and straw yield by 7.8, 9.1% compared to irrigation at 60% depletion during the tow growing seasons respectively. The highest grain yield value of 3107.43, 2955.50 kg fed-1 was obtained with I1N75D2 treatment, while the lowest one was 2265.05, 2174.05 kg fed-1 with I2N50D1¬ in the 1st and 2nd seasons respectively. Also irrigation at 40% depletion resulted in the higher amount of irrigation water to be 1810, 1920 m3 fed-1 distributed on 5 irrigations while it was 1460, 1600 m3 fed-1 irrigated at 60% depletion distributed on 4 irrigations during the 1st and 2nd seasons respectively. The highest consumptive water use was obtained under irrigation at 40% depletion i.e 38.53, 39.6 cm while the lowest 32.48, 32.58 cm obtained from irrigation at 60% depletion in the 1st and 2nd seasons respectively. Increasing nitrogen rates up to 75 kg N fed-1 (N75) significantly increased grain yield by 234.4%, 119.0% and 218.5%, 111.2 % as compared to control N0; N50 treatments in the 1st and 2nd seasons respectively. Also, increased straw yield by 192.9%, 111.4% and 182.4%, 111.6% as compared to N0; N50 treatments in the 1st and 2nd seasons respectively. Nitrogen use efficiency (NUE) increased with increasing water applied. It was 0, 42.07, 24.23 and 0, 31.74, 17.32 for N0, N50 and N75 on the 1st and 2nd seasons respectively, results showed that increasing the applied N-rate decrease the NUE since the highest value was obtained with N50 and the lowest one obtained with N75. The highest water productivity (WP) of 2.20, 2.4 kg m-3 was obtained with I2N75D2 treatment during 1st and 2nd seasons respectively. Therefore, it could be recommended that irrigate wheat at 60% depletion in north Nile Delta soils to save water of about (1). The experimental design of used treatments was split split plot design with three replicates. Irrigation regimes I1( irrigated at 40% depletion )and I2 (irrigated at 60% depletion) were assigned in the main plots , three nitrogen rates i.e. zero,50, and 75 kg N fed.-1 in the sub plots namely N0, N50, and N75 and tow doses of nitrogen i.e. D1( one time) and D2 two times).