Introduction: Nutrition is one of the important factors in improving the quantity and quality of crops. Meanwhile, silicon is a useful element for rice and has positive effects on its quantitative and qualitative properties. Silicon (Si) is the 2nd and 8th extensive element on earth surface or soils and in nature, respectively. In soils, Si is mostly insoluble and not available for plants. In plants, Si-accumulation ranges from 0.1 to 10% dry weight. Plants take up Si either actively or passively in form of monosilicic acid (H₄SiO₄), which typically occurs in a range of 0.1–0.6 mM in soil solution. Salicylic acid, which is known as a regulator of plant growth, plays an important role in plant growth and yield, especially in conditions of environmental stress. Salicylic acid (SA) is eminent as signal molecule and phytohormone which can effectively participate in the induction of plant defense mechanisms against abiotic stress. It has the potential to regulate a number of physio-biochemical processes such as photosynthetic traits, nutrients balance, osmotic adjustments, antioxidant defense systems and improves plant protection or tolerance against drought. The external application of SA is believed to improve the adaptation to drought and osmotic stress by the generation of antioxidant enzymes activies.
Materials and Methods: In order to investigate the effect of foliar application of silicon and salicylic acid on the quantitative yield and some quality characteristics of rice (Shiroodi cultivar), an experiment was conducted in the country's rice research farm (Amol). The experiment was performed as a factorial experiment in a randomized complete block design with 3 replications. Experimental treatments included foliar application of silicon from potassium silicate source at three levels of 0, 3 and 6 cc / l as the first factor and salicylic acid at four levels of 0, 0.5, 1 and 1.5 mM / l as the second factor. Sampling was done in two stages of flowering and physiological maturation.
Results and Discussion: The results showed that silicon had no significant effect on grain yield and its use was only significant on grain yield components such as number of tillers and number of grains per panicle and increased them. This increase was up to the level of 3 cc silicon per liter. Meanwhile, the use of salicylic acid up to 0.5 mM caused a significant increased grain yield 17.14%. The interaction between silicon and salicylic acid had on nitrogen percentage and the content of phosphorus in seed and the highest amount of them were obtained in the treatment of 6 cc silicon, 0.5 mM salicylic acid. Leaf chlorophyll content was not affected by silicon and salicylic acid treatment but the content of leaf silicon was increased only to the level of 3 cc silicon per liter.
Conclusion: From the results obtained in this experiment, it can be stated that the use of silicon up to the level of 6 cc of silicon per liter did not have a significant effect on the grain yield of Shiroudi variety and only on some components of grain yield such as the number of tillers per plant and the number of seeds. It had a significant effect on panicle and caused their increase. Chlorophyll, as an effective pigment in leaf photosynthesis, was not affected by silicon and salicylic acid treatment, but the amount of silicon in rice leaves was increased up to the level of 3 cc of silicon per liter. Then from the results obtained in this experiment can be stated that the use of 3 cc of silicon and 0.5 mM salicylic acid had good performance in improving grain yield and some quantitative and qualitative characteristics of rice in Shiroodi cultivar.