Effects of Drought Stress, Nitrogen Amounts and Plant Densities on Grain Yield, Rapidity and Period of Grain Filing in Sunflower

In order to evaluate the effects of drought stress, nitrogen application, and plant density on grain yield, oil and grain filling of sunflower (Hybrid Iroflor) a field experiment was carried out in the Agricultural and Natural Resources Research Center of West Azarbaijan province, Urmia, Iran during 2010-2011 growth seasons. A split-split-plot experiment was conducted based on Complete Blocks Design (RCBD) with three replications. The main factor was consisted of irrigation treatments, including optimum irrigation, moderate stress and severe stress where irrigation was done after depleting of 50%, 70% and 90% of available soil water, respectively. Three nitrogen levels consisting of 100, 160 and 220 kg N ha-1 were considered as sub plots and sub – sub plots were three plant densities of 55500, 66600 and 83300 plants ha-1. Combined data analysis of variance showed that the effect of drought stress, nitrogen and plant densities on measured traits were statistical significant differences (P≤0.01). Intense of drought stress reduced 60% of grain yield than optimum conditions. By increasing nitrogen application grain yield was increased. There were positive response of grain yield at plant densities. By increasing intensity of drought stress, oil percent, grain yield and nitrogen percent were decreased, but grain nitrogen percent and rapidity of grain filling increased. Interaction between irrigation and nitrogen levels on most traits was significant and with theirs increasing grain nitrogen percent and oil yield increased. By increasing plant densities, oil grain percent was increased but nitrogen grain percent decreased. Interaction of treatments on rapidity and period of grain filing were not significant.