Effect of foliar application of silicon on improving the qualitative and quantitative traits of two variety of sugar beet (Beta vulgaris L.) grown in Torbat Heydarieh

Abstract Silicon is the second element in the earth's crust, which can play an important role in reducing the effects of biotic and abiotic stresses on plants. This element increases plant resistance to pests, diseases and lodging, increases the absorption of nutrients (especially N and P) and reduces water losses. Application of silicon as a fertilizer is a modern idea in Agriculture. According to researchers, the use of silicon has increased root yield, Gross sugar percent and white sugar yield in sugar beet. The approaches to increase sugar beet production in Iran are based more on the use of chemical fertilizers, which has a large side effect on the environment and humans. Therefore, this experiment was conducted with the aim of investigating the effect of different concentrations of silicon fertilizer on quantitative and qualitative traits of two sugar beet varieties. The research was carried out in Torbat Heydarieh city, Khorasan Razavi in 2017. The study was done as factorial experiment based on randomized block design with three replications. The experimental factors were two sugar beet varieties (Isabella and Efesos) and silicon concentrations as 0, 0.3, 0.5, 0.7, 1.0, 1.2 and 1.5 lit/ha. Foliar application was carried out at stage of 6 leaves and repeated 5 times every 2 weeks. The results showed that the main effects of silicon and variety were significant (P≤0.01) for all measured traits except for sugar yield efficiency. However, the interaction of silicon and variety was not significant for any trait. Efesos variety had a significant superiority to Isabella variety in terms of root yield, gross sugar percent; molasses sugar percent, white sugar content and white sugar yield. Also, in terms of impurities, this variety had lower Na and higher K and N content compared with Isabella variety (P≤0.05). With increasing of silicon concentration, root yield, gross sugar percent, white Sugar content and white sugar yield increased, and the amount of harmful Na, K and N decreased in the root pulp (P≤0.05). The root yield and white sugar yield were increased in treatment of 1.5 lit/ha silicon by 22.6 and 39.22 percent, respectively. In this treatment, root yield and white sugar yield was 89.45 and 17.5 ton/ha in Efesos variety and 77.65 and 14.5 ton/ha in Isabella variety, respectively. The importance of white sugar yield is because the profit of the factories is ultimately calculated on the basis of this parameter. It seems that application of 1.5 lit/ha silicon (CROPSIL) after five stages of foliar spraying (from 6-leaf stage, once every two weeks), was the best treatment for improvement the qualitative and quantitative traits of sugar beet, in the present research conditions. Keywords: silicon, white sugar yield, root yield, harmful nitrogen, foliar application.