The Effects of Nitrogen and Boron on the Yield and Biochemical Traits of Sugar Beets (Beta vulgaris L.)

An experiment was performed to reveal how nitrogen and boron fertilizers affect the yield and quality of sugar beets. A split-plot design with random blocks was used, and the experiment was repeated three times in two areas of northwest Iran (Khoy and Naqadeh) from 2019-2020. Nitrogen fertilizer was used in the main plot at four levels: N₁ (300 kg ha-1 of urea with 50% consumption at planting and 50% at the 6-8 leaf stage), N₂ (300 kg ha-1 of urea with 50% consumption at planting and 50% at the 8-12 leaf stage), N₃ (1.5 times that of N1), N₄ (1.5 times that of N2), and boron fertilizer was used as a subagent at four levels: B₁ (no boron, used as a control), B₂ (boron used as boric acid at the rate of 20 kg ha -1), B₃ (foliar spray with Boroplus, a liquid fertilizer with 10% boron, used at the 6-8 leaf and 8-12 leaf stages), and B₄ (foliar spray with Boroplus at the 12-8 and 16-20 leaf stages). The results revealed that as more nitrogen and boron were applied, the leaf dry weight, root yield, sugar content, and pure sugar yield increased. However, the percentage of sugar in the roots decreased as more nitrogen was added. Therefore, the maximum root yield was reached in the N4 treatment, and the maximum percentage of sugar (21.4%) was reached in the B₄ treatment, which represented the minimum level of nitrogen. The maximum pure sugar yield (1228.8 g m-²) was reached in the N₁B₄ treatments. Therefore, nitrogen and boron should be applied following the N₁B₄ treatment for sugar beet planting.