Effect of plant spacing and nitrogen levels on growth and yield of sunflower (Helianthus Annus L.)

To study the effect of plant density and N fertilizer levels on seed yield and its components of sunflower, a field experiment was conducted in Al-Hassa, Saudi Arabia during 2003 and 2004. The treatments comprised five rates of nitrogen (0, 50, 100, 150 and 200 kg N ha-1) and four plant spacing (20, 25, 30 and 35 cm between hills). Plant height, stem diameter, head diameter, number of seeds head-1, 100-seed weight, seed yield ha-1, seed oil percentage and oil yield ha-1 were estimated. Plant spacing significantly affected all estimated characters, except seed oil percentage. Twenty-five cm was observed as a suitable plant spacing, whereas higher or lower plant spacing had a negative effect on seed and oil yields ha-1. Nitrogen application markedly enhanced growth and yield, but resulted in sharp decrease in seed oil percentage. Two-hundred kg N ha-1 produced the highest seed yield ha-1, whereas the highest oil yield ha1 was obtained with the addition of 150 kg N ha1. Considering the superiority of 25 cm plant spacing and 150-200 kg N ha1 for seed and oil yields, it appears that they could be recommended for producing desirable yield under Al-Hassa area conditions