Study of the Effect of Drought Stress on Yield, Yield Components and Harvest Index of Sunflower Hybrid Iroflor at Different Levels of Nitrogen and Plant Population
AbstractThis work was carried out to study the effects of water deficiency stress, different levels of nitrogen application, and plant populationon Water Uptake Efficiency and Nitrogen consumption of oily sunflower. It was conducted at West-Azarbaijanâ€™s Research Center forAgriculture during 2008 and 2009. The study consisted of split-split-plot experiments using Randomized Complete Block Design withthree replications. The main factor was considered to be irrigation treatments including optimum irrigation, moderate stress and severestress in which irrigation was done after depletion of 50%, 70% and 90% of field capacity, respectively. Three nitrogen levels of 100, 160and 220 Kg N ha-1 were considered as sub plots with sub â€“ sub plots consisting of three plant population of 5.55, 6.66 and 8.33 plant m-2.The combined variance analyses indicated that water deficiency stress, nitrogen and plant population have a considerable impact on grainand biological yields, seeds per head, head diameter, kernel percentage to seed, 1000-grain weight, plant grain yield and harvest index. Themaximum grain yield (4200 kg/ha) was attributed to optimum irrigation treatment. Severe drought stress reduced the grain yield by 44%compared to the optimum irrigation condition. Grain yield increased at higher nitrogen application rates. The response of grain yieldto increase in plant population was positive. All yield components were affected by the changes in plant population. The harvest indexdecreased with increasing severe drought stress and plant population. According to the results obtained in this research, application of 220kg N ha-1 and larger plant population in optimum conditions and moderate drought stress is recommended for suitable yield, although anincrease in nitrogen consumption and plant population has a little impact on grain yield in severe drought stress conditions.
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