The Effect of Silicon Application on Some Physiological Characteristics, Yield and Yield Components of Sunflower (Helianthus.annus L.) under Different Moisture Levels

Available water is the main limiting factor in crop growth and production in arid lands. In order to investigate the effect of silicon application on yield and yield components of sunflower under different moisture levels, an experiment was conducted in the form of split plots in a randomized complete block design with three replications in Gonabad. The main factor of irrigation with different moisture levels based on water requirement includes 100% water requirement, 80% water requirement, 60% water requirement and 40% water requirement, and the secondary factor of silicon consumption time in four levels No application (control), application in vegetative stage, application in reproductive stage, application in both vegetative and reproductive stage. The experimental results showed that reducing the moisture level from 100% to 40% water requirement reduced head diameter, head dry weight, chlorophyll index, relative water content, number of seed per head, 1000-seed weight, seed yield, biological yield, harvest index, oil percentage, oil yield and seed yield; So that the lowest amount of seed yield (1730.8 kg / ha) and biological yield (10458.21 kg / ha) were obtained in the treatment of moisture level of 40% water requirement. Also, the application of silicon under low irrigation levels based on water requirement improved the effects of reducing moisture levels in all evaluated traits and seed yield. The highest seed yield (7572.96 kg / ha) was obtained in the treatment of 80% water requirement and application silicon in the vegetative and reproductive stages and the lowest seed yield (1193.54 kg / ha) was obtained in the treatment of 40% water requirement and without the use of silicon. The application of silicon in the vegetative and reproductive stages compared to the control treatment increased 2.5, 1.5 and 2.5 times the oil yield at different levels of irrigation, including 80, 60 and 40% water requirement. In general, the results showed that the use of silicon in the vegetative and reproductive stages at a moisture level 80% the water requirement compensated for the adverse effects of reducing the moisture level in the studied traits.