Effect of Drought Tension, Nitrogen Supply Source and Planting Density on Yield and Yield Components of Sunflower (Helianthus annus L.) Haissan Cultivar in the North of Golestan Province

In order to investigate the effect of drought tension, nitrogen supply source and planting density on agronomic and physiological characteristics of sunflower cultivar Haissan in the north of Golestan province, an experiment was conducted in 2015 and 2016. The present research was performed in the form of split- split plots in randomized complete blocks design with three replications and 27 treatments. The main factor included drought treatment with three rainfed levels, one irrigation stage (cultivation stage) and three irrigation stages (cultivation, flowering, grain filling stages). The sub-factor included three levels of nitrogen supply (100 percent urea, 50 percent nitroxin and 100 percent nitroxin) and plant density as a sub-sub-treatment had three levels of 50, 75 and 100 thousand plants per hectare that were randomly placed in main and sub-plots and sub-sub-plots. The results showed that the effect of drought tension, nitrogen supply source and plant density on plant height, seed diameter, number of seeds, one-thousand grain, oil percentage, harvest index, biological yield and economic yield were significant at one percent probability level. The highest plant height, head diameter, number of seeds per head, one-thousand grain weight, oil percentage, harvest index, biological yield and economic yield were obtained in the treatment of three irrigation stages. Application of treatment (50 percent nitroxin and 50 percent urea) as nitrogen supply sources improved all traits. Based on the obtained results of the present research, three stages of irrigation and application of 50 percent nitroxin and 50 percent urea as a source of nitrogen supply and increasing plant density are recommended for proper production and yield.