The Effect of Potassium (K) and Boron (B) Foliar Application on Quantitative and Qualitative Traits of Sugar Beet (Beta vulgaris L.) under Drought Stress Conditions

In order to study the effects of foliar application of potassium (K) and boron (B) and dificit irrigation treatments on quantitative and qualitative traits of sugar beet (Beta vulgaris L.), a split plot experiment was conducted based on randomized complete block design with three replications in the Research Field of Shahrekord University, Shahrekord, Iran, in 2019. The main plots were allocated to irrigation treatments including: irrigation after 70, 100 and 130 mm (I1, I2 and I3, respectively) cumulative evaporation from class A evaporation pan and the sub plots were allocated to fertilizer treatments in the form of foliar sparying including: control (no fertilizer application), K, B and B + K. The greatest sugar content was obtained from the I2 irrigation treatment and B spraying, which did not have significant difference with I1 irrigation and B+K treatments. Although I2 irrigation treatment increased the sugar content compared to I1 irrigation treatment, however it decreased the white sugar yield probably due to decreased root yield and increased root impurities and consequently drought-associated increase in sugar molasses. The greatest shoot fresh weight, root diameter and single root dry weight were observed in I1 irrigation and B+K treatments. The lowest amount of harmful nitrogen and sugar molasses were obtained under full irrigation conditions and spraying of K and B+K, respectively. Since the highest yield of white sugar was obtained under full irrigation conditions and spraying of B + K, it indicates that drought stress should be avoided during growth and development stages of sugar beet. Given the ever-increasing threat of drought to the sugar beet cropping areas of Iran, foliar application of B and K can be considered as an approach to reduce the effects of drought stress and improve the qualitative and quantitative traits of sugar beet.