الفهرس 
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Abstract
Two field experiments were conducted at the Experimental Farm of the Agriculture Faculty (Saba Basha), Alexandria University, Alexandria, Egypt during the two successive growing summer seasons 2007 and 2008 to study the effect of nitrogenous sources and plant population densities on sunflower (Helianthus annus, L) productivity.
The experiment design in the two seasons was a split plot design with three replicates and the treatments were arranged at random as follows:
Main plots (plant population densities):
(1) 20000 plants/fed. (35 cm between hills).
(2) 25000 plants/fed. (28 cm between hills).
(3) 30000 plants/fed. (23.33 cm between hills).
Sub plots (nitrogen fertilizer):
(1) Unfertilized (control).
(2) 40 kg mineral nitrogen fertilizer/fed. (M).
(3) 20 m3 organic fertilizer/fed. (O).
(4) 1 kg bio-fertilizer/fed. (B).
(5) 30 kg M+ 20 m3 O /fed. (M+O).
(6) 30 kg M+1kg B/fed. (M+B).
(7) 20 m3 O+1kg B/fed. (O+B).
(8) 30 kg M+ 20 m3 O +1kg B/fed. (M+O+B).
All cultural practices for growing sunflower were applied uniformly as recommended.
The studied characteristics of this investigation were divided into three categories as follows:
5. 1. Growth characters and growth attributes:
1- Plant height (cm).
2- Stem diameter (cm).
3- Leaves number per plant.
4- Plant dry weight (g/plant).
5- Leaf area (LA)/plant (dm2).
6- Leaf area index (LAI).
7- Specific leaf weight (SLW) (mg/cm2).
8- Crop growth rate (CGR) (g/m2/week).
9- Relative growth rate (RGR) (g/g/week).
5. 2. Yield and yield components:
1- Plant height (cm).
2- Stem diameter (cm).
3- Head diameter (cm).
4- Head weight (g).
5- Seed yield (g/plant).
6- 100-seed weight (g) (seed index).
7- Seed yield (t/fed.).
8- Straw yield (t/fed.).
9- Biological yield (t/fed.).
10- Harvest index.
5. 3. Seed quality and oil yield per fed.:
1- Seed husk percentage (%)
2- Seed oil content (%)
3- Oil yield (kg/fed.).
4- Seed protein content (%)
The obtained results could be summarized as follows:
I- Growth characters and growth attributes:
I- 1- Plant density effects:
1- Plant density had no significant effect on plant height at all growth stages in both seasons.
2- Stem diameter was significantly affected by plant density at all growth stages in both seasons except at the 1st growth stage in 2007 season. Thicker stem was obtained by plant density 20000 plants/fed.
3- Significant effect on leaves number was induced by plant density only at plant age of 50 DAS in the second season, in favour of lower plant density.
4- Significant differences was observed among planting densities on plant dry weight at all growth stages in the two seasons except at age of 50 and 65 days in the second season. The results indicated that the plant dry weight decreased by increasing planting density up to 30000 plants/fed.
5- Plant density affected significantly on leaf area/plant at age of 65 and 80 DAS in the first season and at age of 50 DAS in the second season where increasing planting density up to 30000 plants/fed. led to decrease in the leaf area/plant.
6- Results showed that leaf area index (LAI) was not significantly affected by planting density at all sampling dates in both seasons with tendency to increase by increasing planting density.
7- No significant effect on specific leaf weight and crop growth rate at all growth stages or periods in both seasons was observed due to plant density.
8- Relative growth rate was significantly affected by plant density only at growth period of 65- 80 DAS in 2008 season where the values of RGR decreased with increasing planting density.
I-2- Nitrogen fertilizer effect:
1- Regarding nitrogen fertilizer, there was no significant effect on plant height at all growth stages in the two growing seasons.
2- Significant effect on stem diameter was found due to nitrogen fertilizer at all growth stages in the two seasons. The treatment of 30 kg mineral nitrogen +20 m3 organic manure + 1 kg bio-fertilizer as nitrobein (M+O+B) was concomitant, generally, with the highest mean values of stem diameter over the control treatment.
3- Nitrogen fertilizer significantly increased leaves number/plant, after 50 and 65 days from planting in the first season, and after 50 and 80 days from planting in the second season. While the differences between M+O+B, M+O and M were not significant.
4- Plant dry weight significantly affected by nitrogen fertilizer application at all growth stages in the two seasons. The highest mean values of plant dry weight were recorded by application of 30 kg mineral nitrogen + 20 m3 organic fertilizer + 1 kg bio-fertilizer/fed. (M+O+B), followed by 40 kg mineral nitrogen /fed. (M) or 30 kg mineral nitrogen + 20 m3 organic fertilizer/fed.(M+O) in both seasons.
5- Significant effect was detected for nitrogen fertilizer on leaf area per plant and leaf area index at all growth stages in both seasons. The highest mean values of LA/plant and LAI were obtained by application of M+O+B, M and M+O in both seasons.
6- No significant effect was obtained due to application of nitrogen fertilizer on specific leaf weight and relative growth rate at all growth stages and intervals in both seasons.
7- Crop growth rate increased significantly by application of nitrogenous fertilization treatments at the 1st growth period (50-65 days after sowing) in the two growing seasons in comparison with control treatment.
I-3- Interaction effect:
There was no significant interaction between plant density and nitrogen fertilizer for all growth characters and growth attributes at all growth stages and intervals in both seasons.
II-Yield and yield components:
II-1- Plant density effect:
1- Plant height at harvest tended to increase by increasing plant density in the two successive seasons, but the differences did not reach the 5% level of significant.
2- Increasing plant density from 20000 to 30000 plants/fed. decreased significantly stem diameter at harvest, head diameter, head dry weight, 100-seed weight, and seed yield/plant in the two growing seasons.
3- Plant density had no significant effect on seed; straw and biological yield/fed. as well as harvest index in both seasons.
II-2- Nitrogen fertilizer effects:
1- Nitrogen fertilizer treatments did not affected significantly plant height at harvest and harvest index in both growing seasons.
2- Application of nitrogen fertilizer significantly influenced stem diameter at harvest, head diameter, head dry weight, 100-seed weight, seed yield per plant and per feddan. Similar trend was observed with respect to straw and biological yield per feddan in the two seasons. The highest mean values for all mentioned characters were obtained with M+O+B followed by M or M+O.
II-3- Interaction effect:
There was no significant interaction between plant density and nitrogen fertilizer except for head diameter in the second season and 100-seed weight in both seasons. where plant density 20000 plants/fed and application of 30 kg mineral nitrogen+20 m3 organic fertilizer+1kg bio-fertilizer/fed. gave the highest head diameter and 100-seed weight.
III- Seed quality and oil yield/fed.
III-1- Plant density effects:
Plant density had no significant effect on seed husk percentage, seed oil and protein content as well as oil yield/fed. in both seasons.
III-2- Nitrogen fertilizer effects:
1- Seed husk percentage, seed oil and protein content did not affected significantly by nitrogen fertilizer application in the two seasons.
2- Fertilization treatments increased significantly oil yield/fed. in the two growing seasons. Application of 30 kg mineral nitrogen +20 m3 organic fertilizer+ 1kg bio- fertilizer/fed. (M+O+B) produced the highest oil yield/fed.
III-3- Interaction effects:
The interaction between plant density and nitrogen fertilizer for seed husk percentage, oil and protein content as well as oil yield/fed. were not significant in both seasons.