الفهرس 
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Abstract
Two filed experiment were conducted at Sakha agricultural Research station farm, during 2020 and 2021 seasons to study the effect of plant densities and Nitrogen levels on growth, yield and yield components of some yellow maize hybrid. A split-split plot design with three replications was used in the two experiment. The main plots involved three plant population densities i.e, (20000,25000,30000 plants/fed.) which were obtained from planting at (23,20,17.5 cm) between hills, respectively on ridges 80 cm apart. The sub plots included the three Nitrogen levels (100,124 and 148 kg/fed). The sub sub plots included the three of maize cultivars, i.e. s.c.178, s.c.180 and twc369 (yellow hybrids). The following growth attributes were recorded: 1-Number of days to 50% Silking, Number of days to 50% tassel. 2-Silking – Anthesis interval days, plant height, Ear height. 3-Number of green leaves per plant at 85 DAS, Leaf area, Leaf a At harvest, the following characters were recorded: Prolific plants, Ear length /(cm), Ear diameter, Number of rows per ear, Number of kernels per row, Weight of 100-kernel, Grain yield (ardab/fed). The obtained results could be summarized as following: A. Growth characters: A .1. Number of days to 50% silking: Number of days to 50% silking was not significantly affected by plant density in both seasons and their combined Number of days to 50%silking was significantly decreased with increasing nitrogen rates in both seasons and their combined. The interaction between cultivars and nitrogen Levels significantly affected number of days to 50%silking in 2020 Season. Highly Significant differences between maize hybrids were detected for number of days to 50% Silking in both seasons and Their Combined. AIL order interaction were not Significant for days to50% silking in both seasons and Combined. . A.2. Number of days to 50% tassel: Number of days to50% tassel was not significantly affected by plant density in both seasons and their combined number of days to 50% tassel was not significantly affected by Nitrogen Levels in both seasons and combined The interaction between cultivars and nitrogen Levels Significant affected number of days to 50% tassel in 2020 season Highly significant differences between maize hybrids were detected for number of days to50%tassel in both seasons and Their combined. All order interaction were not significant For days to 50% tassel in both seasons and combined. A.3. Silking –Anthesis interval days. Silking-Anthesis interval days was not significantly affected by Plant density in both seasons and their combined. Silking anthesis interval days was significantly decreased with increasing nitrogen rates in both seasons and combined the interaction between cultivars and nitrogen Levels significantly affected silking anthesis interval days in 2021 season. Highly significant differences between maize hybrids were detected for silking Anthesis interval days in both seasons and their combined All order interaction were not significant for silking Anthesis Interval days in both seasons and their combined. A.4. Plant height (cm): Plant density had no effect on Plant height in both seasons and their combined. Highly significant differences were detected between maize hybrids for plant height SC180 recorded the highest plants, while new TWC 369 gave the Lowest plant height in 2020 and their Combined. Plant height highly significantly affected by nitrogen Levels in both seasons and combined. All other order interactions were not significant in both seasons and their combined. A.5. Ear height (cm): Plant density had no significant effect on ear height in (cm) in both seasons and their Combined. Ear height highly significantly affected by Nitrogen Levels in both seasons and Combined. Data Show that significant differences between maize hybrids in ear height in both seasons and Combined SC180 recorded the highest values of ear height while new 178 had the lowest values of ear height in both seasons and their combined. All other order interactions were not significant in both seasons and their combined. A.6. Number of green leaves / plant at 85 DAS: Number of green Leaves Per plant were significantly decreased by increasing plant densities at 85 days from Sowing in both seasons and their combined was not significantly affected by nitrogen Levels in both seasons and Combined Highly significant differences were found for number of green Levels/plant between maize hybrids in both seasons and Combined SC180 recorded the highest Values in number of green Levels. All order interactions were not significant for number of green leaves/ Plant in both seasons and combined. A.7. Leaf area (dm2/plant): Leaf area Per Plant was decreased significantly With increasing Plant densities at 85 days from Sowing in 2021 and their combined were significantly affected by Nitrogen Levels in 2020 and combined Highly Significant differences were found for Leaf area between maize hybrids in both seasons and combined SC180 recorded the highest values in Leaf area. All order interactions were not Significant for leaf area in both seasons and their combined. A.8. Leaf angle: Leaf angle decreased Significantly with increasing leaf angle from 20000 to 30000 plants/ Fed in 2021 seasons was not significantly affected by Nitrogen Levels in both seasons and combined. Highly significant differences were found For leaf angle between maize hybrids in both seasons and Combined SC180 recorded the highest values in leaf angle while, SC178 gave the lowest leaf angle in both seasons and combined All orders of interaction was not significant in both seasons and their combined. B. Yield components: B.1.Number of ears/plant: Number of ears/plant decreased significantly with increasing plant density from 20000 to 30000 plants/fed. In their combined. Number of ears/plant was increased significantly by increasing nitrogen levels from 100 at 124 kgN/fed in the first season. Highly significant differences between maize hybrids were observed in both seasons and their combined. TWC 369 gave the highest number of ears/plant. All older interaction was not significant except the interaction between plant density and maize hybrid in 2021 season and Their Combined. B.2.Ear length(Cm): Ear length (Cm) was Significantly decreased with increasing Plant density from 20000 to 30000 Plants/Fed. In both seasons and their combined. Ear length increased significantly by increasing N-rates in 2020 and their Combined. Significant differences between or among maize hybrids for ear length were observed in both seasons and Combined. SC 178 recorded the highest ear length, while new TWC 369 gave the lowest ear length in both seasons and their combined. All orders of interaction was not significant except the interaction between Pant density and nitrogen levels was significantly in 2020 season and combined, plant density and maize hybrids on ear length in 2020 season; nitrogen levels and maize hybrids on ear length in both seasons and their combined. B.3. Ear diameter: Ear diameter significantly increased with increasing plant density in 2020 and combined. Ear diameter was increased significantly with increasing Nitrogen levels. in 2021 and Combined There were significantly differences between studied hybrids for ear diameter in both seasons and their combined New SC 180 recorded the highest ear diameter anther than Two hybrids. All order interaction was not significant except the interaction between Nitrogen Levels and maize hybrid was significantly in 2020 season only. B.4. Number of rows/ear: number of rows/ear significantly increased with increasing plant density in 2020 and their combined. number of rows/ear was increased Significantly with increasing nitrogen Levels in 2021 and combined There were significantly differences between studied hybrids for number of rows/ear in both seasons and their combined New SC180 recorded the highest number of rows/ear. All order interaction was not significant except the interaction between Plant density and maize hybrid in 2021 season and combined. B.5.Number of kernels/rows: Number of kernels per row was decreased Significantly by plant density in 2020 and combined. Number of kernels per row was increased significantly by increasing nitrogen Levels in2021 and combined number of Kernels per row was significantly affected by cultivars SC180 and SC178 cultivars gave higher number grains per row than twc369 cultivars in both seasons and their Combined. All order interaction was not significant except the interaction between nitrogen Levels and maize hybrid in 2020 season. B.6.Weight of 100-kernle: Weight of 100 kernel was not significantly by affected Plant densities in 2021season. 100 kernel weight was not significantly affected by Nitrogen Levels in both seasons and combined. SC180 and SC 178 cultivars had the heaviest 100-kernel weight. All order interaction was not significant for 100- kernel weight in both seasons and their combined. B.7. Grain yield (ardab/fed): Grain yield was increased significantly with increasing Plant densities from 20000 to 30000 Plants/fed in both and their combined. Grain yield was increased significantly by increasing nitrogen rates to 148 kgN/ fed. There was significantly differences between cultivars for Grain yield. SC 180 gave the higher kernel yield in both seasons and their combined. AIl order interaction were not significant for Grain yield in both seasons and their combined except the interaction between N×H, D×N ×H in their combined.