Response of Some Sunflower Hybrids (Helianthus annuus l.) to Different Nitrogen Fertilizer Rates and Plant Densities

In order to improve sunflower productivity, this investigation aimed to study the performance of some genotypes to different doses of nitrogen and plant population density on seed yield and yield components. Two field Experiments carried out on the Experimental Farm of the Sakha Agriculture Research Station during 2015 and 2016 seasons. The objective of this study aimed to investigate the performance of some sunflower hybrids to different nitrogen fertilizer rates and plant population densities to growth, yield components, seed yield and its quality.The results indicated that tallest plants, highest leaves number/plant, number of achenes/head and highest values of head diameter were obtained from MS.sirena F1 genotype. Biest Brima genotype recorded the highest values of leaf area. The highest weight of 1000 seed and seed yield/ha were recorded from Nsovak genotype.The increases in nitrogen fertilizer rates to 168 Kg N/ha produced tallest plants,thick stems (cm), the highest leaves number/plant, leaf area (cm2), number of achenes/head, head diameter (cm), 1000 achene weight (gm) and achene yield (Kg/ha) in both seasons. It could observed that increasing nitrogen fertilizer from 72 to 168 Kg N/ha significantly increased seed yield by 12.0 and 11.6 % in the first and second seasons, respectively. Increasing hill spacing from 15, 20 and 25 cm produced thickness stem, highest number of leaves/plant, highest values of leaf area, maximum number of achenes/head, head diameter and weight of 1000 achene. The tallest plants and highest and achene yield were produced from 20cm hill spacing. It could concluded that increasing nitrogen fertilizer from 72 to 168 Kg N/ha and sown Nsovak genotype at dense hill spacing of 15 cm between plants maximized seed yield per unite area.

INTRODUCTION Sunflower (Helianthus annuus L.) plants the greatest significant oilseeds and occupies the fourth next to the soybean, palm oil and canola as anoil source.The cultivated area in Egypt is limited to old soils of Nile Valley and the Delta because its cultivation in it competes with other important summercrops like rice.Therefore, it could be cultivated on newlyreclaimed soils in the desert area, for minimizing this existing gap between production and import of edible oil; we should grow sunflower crops preferably. For increasing sunflower productivity, oil content and tothe oilyield to this area are the major target ofresearch programs.The hybrid S-278 erected out supreme for head diameters,seed numbers/head, weight of 1000-seed, seed yield. Maximum seed and oil percentageobtained from S-278 hybrid (Ali et al., 2012). The hybrid S-278 gave a higher seed yield/ha than Hysun-33 hybrid (Ali et al., 2014).The great seed yield (2.06 t/ha) produced from sown sunflower hybrid PSH 569, excelling SH 332' by 3.5% and PSFH 118 by 13.8 % (Parvender et al., 2014).The highest seed yield/ha, thousand seed weight and head diameters obtained from Isera cultivar; the highoil content, oil yield/ha and plant height observed from C-70165, Isera and Teknosol cultivars (Gul and Kara, 2015).The highest percentages of seed oil recorded in Hysun-33, SMH-0917 and SMH-0907. Overall Hysun-33, SMH-0917 and SMH-0907 hybrids achieved improved for plant height, head diameters, seed numbers/head and seed yield/ha (Iqrasanet al., 2017). Sunflower Hysun38 hybrids excelled the other two hybrids in seed yield/ha and oil percentage (Nasim et al., 2017). Nitrogen fertilizerconsidered as one of the realelements that supplement the metabolic developmentsfounded on protein, reproducedupsurge on vegetative, generative growth stage and seed production. Different varieties need different plant densities and nitrogen requirements forproducing high seed and oil yields/ha.In this respect, nitrogen fertilizer rates muchexaggerated on seed numbers/head, yield to seed/head, weight of 1000-seeds, seed and oil yields/ha. Maximum seed and oil yields/ha produced from about 60 kg N/ha fertilization (Killi, 2004).Fertilization of nitrogen decidedlyincreased the growth and seed yields, but occasionedreduced seed oil content. Application of 200 kg nitrogen/ha recorded the highest seed yield/ha, becauseapplication of 150 kg nitrogen/ha produced the higher oil yield/ha (Al-Thabet, 2006).Fertilization of nitrogen at levels of 150 kg/ha produced the highestyield/ha of achenewhich followed with nitrogen fertilization at a level of 125 kg N/ha while the lowest seed yield/haobtainedfrom fertilization of nitrogen at the rate of 100 kg N/ha (Jahangir et al., 2006). The greatest seed yield/ha was gottenfrom nitrogen fertilization ata rate of 50 kg N/ha for DW-2 cultivar and nitrogen fertilization at a rate of 80 kg N/ha for DW-2 and Trakya-80 cultivars. (Süzer, 2010).Seed yield and its attributes significantly increased, but decreased oil percentage with increasing nitrogen fertilizer rates(Naseem et al. 2011). Theincreases in rates of nitrogen had a significant effect and recorded the tallest plants, the highest biological and seed yields/haas well as seed oil percentage.Increasing nitrogen fertilizer rates of 225 kg/ha nitrogen were recorded the most of study traits (Mollashahi et al., 2013). Each nitrogen increase improves seed yield and its attributes, science oil percentage were enviably affected (Awais et al., 2015). Plant density is among the factors affecting sunflower yield and seed oil percentages.Maximum yields to achenes obtained from an increasing sunflower population ofa certain level. Optimum population depends on cultural, environmental and field management factors (Weiss, 2000).Sunflower hybrids, plant height reduced retortedimproved to high plant populations than the standard and tall hybrids did (Johnson, 2002).The widerof hill spacing improvesto stem and head diameters, and weight of the seed/head,butthe narrow hill spacing significantly increased plant height, seed and oil yields/fed (Allam et al., 2003).With the increase in plant populations per unit area significantly decreased head diameters, number and seed weight/head and a higher plant density of a boundaryinsignificantly effect of yield of achene/ha (Majiri and Arzani, 2003).The less plant population density produced the more head diameter, the higher seed number/head and seed yield/head as well as the heaviest of 1000-seed weight while, the more plant population densities produced the higher oil percentage, seed and oil yields/ha (Killi, 2004). Hill spacing influenced moststudiedtraits, except oil content. Sown at 25 cm hills spacing was the suitable hill spacing, butthe higher or the lower hill spacing had anundesirableresult of seed and oil yields/ha. Application of nitrogen fertilizerevidentlyimproved both growth and seed yield, neverthelesscaused decreases in the percentage of oil (Al-Thabet, 2006). Maximum yield toachenesyield and itsattributes as well as oil percentageproduced from the optimum with 60 x 20 cm. The lowestseed and oil yields/ha logged with planting decoration of 45 x 10cm summarized that Hysun-38 hybrid maximized seed yield/ha by fertilization of nitrogen at a rate of 180 kg N/ha. Therefore, the purposes of this study evaluating the outcome of plant population density of some sunflower hybrids at different application of nitrogen fertilizer rates on growth, seed yield, yield components, its seed quality, and the interaction effects among population densitiesof some hybrids at different nitrogen fertilization rates on seed yield and seed quality.

Research time and location:
Two field Experiments carried out on the Experimental Farm of the Sakha Agriculture ResearchStation, ARC Egypt during the two consecutive summer seasons (2015 and 2016). A split-split plot of RCBD with four replication used.The main plots assigned to the three sunflower cultivars (Nsovak, MS.Sirena F1, BiestBrima), while the three nitrogen fertilizer rates (72, 120 and 168 Kg N/ha) which arranged in the sub-plot and the three hills spacing (15, 20 and 25 cm apart) were assigned to the sub-sub plot.Each experimental unit contained of five ridges with 3 m in length and 60 cm between hills. The size of each sub-plot was 12m 2 . The middle two rows used for determining seed yield and its components.Seeds of the studied sunflower cultivars obtained from the Field Crops Research Institute, A.R.C. Giza Egypt. The preceding crop was wheat.Analyses of chemical and physical properties of the experimental soil (0 to 30 cm depth) carried out according to the methods reported by Page et al. (1982). The soil was loamy clay in texture, the pH was 7.6, 7.8, organic matter was 4.9, 5.1%, 7.9, 7.6, E.C. dS/m -1 available nitrogen was 15.9 and 16.8 ppm and available phosphorus was 40.6 and 39.8 ppm of both seasons, respectively. After plotting and before the planting, sulfate of potassium (48 % K2O) at a rate of 120 kg/ha and 240 kg/ha as calcium super-phosphate (15.5 % P2O5) supplied to experimental plots. Nitrogen at above rates of the form of ammonium nitrate (33.5 % N) added in two equal portions before the first and third irrigations.

Studied Characters:
Ten guarded plants occupied at harvest time from the 2 nd and 3 th ridges in each sub-plot to estimate plant height (cm),stem diameters (cm), number of leaves/plant, leaf area per plant (cm2), achene diameter (cm), achene weight (g), weight of 1000 seed (g), seed yields/head and per hectare.

Experimental analysis:
The analysis of data collected done, statistically by the analysis of variance technique using the MSTAT-C statistical package programmed as described by a procedure of Gomez and Gomez (1991).Lest significant differences test (LSD) at 5 and 1 % level of probability used to compare between treatment means according toSnedecor and Cochran (1980).

III. RESULTS AND DISCUSSIONS 3.1. Performance of cultivars:
Average of plant height (cm), leaves number/plant and leaf area (cm 2 ), number of achenes/head, head diameter (cm), 1000 achene weight (gm) and achene yield (Kg/ha) significantly differed in studied sunflower cultivars in both seasons as presented in Tables 1 and 2 Whereas, the highest weight of 1000 seed (56.31, 56.40 g) and highest seed yield per hectare (3397.8, 3402.4 kg/ha) were recorded from Nsovak genotype in the first and second seasons, respectively. The results clearly indicated that Biest Brima genotyperecorded the lowest seed yield/ha and MS.sirena F1 genotype the lowest of 1000 achene weight in both seasons. The differences between studying genotypes in seed yields may attributed to the genotype genetics.The highest percentages of seed oil recorded in Hysun-33, SMH-0917 and SMH-0907.

Effect of nitrogen fertilizer rates:
Average of plant height (cm), stem diameter (cm), leaves number/plant, leaf area (cm 2 ), number of achenes/head, head diameter (cm), 1000 achene weight (gm) and achene yield (Kg/ha) as affected by nitrogen fertilizer rates    The shortest plants and lowest achene yield kg/ha was obtained from wide space (25 cm). The increases of these characters may be due to the sufficiency of environmental conditions reflected less competition between plants in wide spacing due to increases in light penetration within sunflower canopies that improved assimilation rate and oil creation. Plant population density significantly differed from plant height, the diameters of the stem and head, the weight of achenes, weight of 100-seed and seed yield ha. The highest of seed yield/ha obtained by plant

.2. Interaction between cultivars and hill spacing:
The interaction between cultivars and hill spacing significantly affected plant height (cm), leaf area (cm 2 ), achene numbers/head, diameter of head (cm), 1000achene weight (g) and achene yield (Kg/ha), except, stem diameter (cm) and leaves number/plant, in both seasons as presented in Tables Fig. 9. However, the lowest values of plant height (cm), leaf area (cm 2 ), achene numbers/head, diameter of head (cm), 1000-achene weight (g) were produced from sown Nsovak genotype at wider hills (25 cm). Results demonstrated in Fig. 10 clearly indicated that maximum achene yield (1558.7, 1520.9 kg/ha) produced from sown Nsovak genotype at dense hills (15 cm) in both seasons, respectively. The less yield obtained from sown Biest Brima genotypeat wider hills (25 cm). In view of the superiority, over 22.5 cm hills spacing for both Hysun-38 hybrid recorded the high productivity. FH-331 hybrid recorded the lowest in seed yield compared to with hysun-38 hybrid (Ali et al., 2011).

Interaction between nitrogen fertilizer rates and hill spacing:
The interaction between nitrogen fertilizer rates and hill spacing significantly affected plant height (cm),leaf area (cm 2 ), achene numbers/head, head diameter (cm), and achene yield (kg/ha), except, and stem diameter (cm), leaves number/plant and 1000 achene weight (g) in both seasons as presented in Tables 1 and 2. The results graphically illustrated in Fig. 11