Abstract
Sugar beet (Beta vulgaris L.) is the second most abundant sugar crop after sugarcane. Two field experiments were conducted at the research farm of the Faculty of Agriculture, Saba Basha, Alexandria, Egypt, to study the effects of foliar application treatments and boron (B) fertilizer applications on monogerm sugar beet plants (cultivar classic) during the 2017/2018 and 2018/2019 seasons. The treatments were replicated three times in a split-plot design. Four foliar applications [fulvic acid (FvA), NPK nanoparticles (NPK NPs), FvA + NPK NPs, and a control (water)] were randomly allocated to the main plots. Different numbers of foliar spray applications of B [one application at 120 days after sowing or two applications at 120 and 150 days after sowing, as well as a control (water)] were assigned within the subplots. FvA + NPK NPs significantly increased the root length, root diameter, root weight, and root/shoot ratio of the sugar beet plants; the greatest values were obtained by spraying FvA + NPK NPs during both seasons. B significantly increased the root yield, shoot yield, and biological yield, and two applications of B resulted in the greatest values of root yield, shoot yield, biological yield, and quality of sugar beet. The interaction between FvA or NPK NPs and B significantly affected the yield and quality parameters of the sugar beet plants. However, the greatest mean values of these traits resulted from foliar applications of FvA + NPK NPs in conjunction with applications of B under the conditions at Alexandria, Egypt.