The research work was done at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, Bangladesh. The experimental site (24°75' N latitude and 90°50' E longitude at an elevation of 18 m above sea level) belongs to the Old Brahmaputra Floodplain Agro-ecological Zone (AEZ-9) having non-calcareous dark gray floodplain soils (UNDP and FAO, 1988). The experimental plot is medium high land having silty-loam texture with pH 6.9, EC (electrical conductivity) 0.4 ds/m, OC (organic carbon) 1.00%, N 0.09%, P 1.60 ppm, K 0.10% meq/100g soil, Ca 8.30 meq/100 g soil, Mg 3.29 meq/100 g soil, S 2.98 ppm, Zn 0.21 ppm, and B 0.23 ppm. The experimental area was under the sub-tropical climate with temperature 12.16°C to 31.69 °C, relative humidity 67.76 % to 83%, and total rainfall 1mm to 66.80 mm during experimentation. The experiment comprised four foliar applications of boron concentrations viz. 0 ppm (B0) 50 ppm (B1), 100 ppm (B2), 150 ppm (B3), and three application times viz. once at 40 days after emergence (T1), twice at 40 and 65 days after emergence (T2), and thrice at 40, 65 and 90 days after emergence (T3). The experiment was laid out in a factorial randomized complete block design with three replications. The size of the unit plot was 5.0 m2 (2.5 m × 2.0 m). The distance between two adjacent plots was 0.5 m and plant to plant distances was 0.2 m. The land was fertilized with urea, triple superphosphate (TSP), muriate of potash (MoP), gypsum, and zinc sulphate @ of 260, 100, 225, 100, and 10 kg ha-1, respectively. One-third of urea, the total amount of triple superphosphate, muriate of potash, gypsum, and zinc sulphate were applied at final land preparation and mixed well with soil. Two-third urea was applied in two equal splits at 40 and 70 days after sowing (DAS). Tropical sugar beet variety ‘KWS Allayana’ was used as a test crop for the study. Seeds were sown on 23 November 2018 (after soaking in water) in rows on the ridge with 50 cm × 20 cm spacing @ two seeds hill-1 for protecting the germination failure two seeds were placed in a hill on the ridge of the experimental plot. Some seeds were broadcasted separately by the side of the experimental field for necessary gap-filling operation. Intercultural operations were done as and when necessary. The special precaution was taken during weeding in the early stage because in the early stage the seedlings were less vigorous, soft, and thin. Four hand weeding were done very carefully with "niri" at 15, 30, 45, and 60 DAS. The optimum plant population was maintained by thinning in each plot as two seeds were placed in hill-1. Thinning and earthing-up were done at 35 and 60 DAS, respectively. Plants were infected by Sclerotium root rot disease at seedling and later stages of growth which was controlled by spraying Amister top 0.5ml L- 1 water + Provax 1g L-1 water at 15 days intervals. At the early stages of growth, seedlings were infested by the caterpillar of cutworm (Agrotis ipsilon) while leaf-eating caterpillar (Spodoptera litura) invaded in later stages. Sevin dust (500 g) was used with 5 kg wheat bran and citagoor 1 kg for cutworm, and Pheromone trap (commercial name: Spodo-Lure, generic name: (Z, E)-9, 11 Tetradecadien-1-yl acetate 97.52% w/w) was used to control the lepidopteran insect (leaf eater). Five plants (excluding border hills) were selected randomly from each plot and marked by bamboo stick to collect data on plant height and leaf number. The height was measured from the base of the plant to the tip of the tallest leaf and the number of leaves was recorded at every 25 days interval beginning at 40 DAS up to 140 DAS. The mean values of 5 plants for each plot were determined. Two plants were uprooted carefully and measured their root length then the leaves and roots were separated and packed in labeled brown paper bags and dried in the oven at 85±5°C for 72 h until a constant weight was reached. The samples were weighed carefully after oven drying to measure the dry weight of shoots and roots. The harvesting was done at full maturity of beets at 165 DAS. After harvesting, ten plants were selected randomly then washed and cleaned by removing dead and dried leaves and soil adhering to beets. The beets were weighed and adapted to average beet weight (kg/beet). Data were analyzed using the analysis of variance (ANOVA) technique with the help of the computer package program MSTAT-C and mean differences were adjudged by Duncan’s Multiple Range Test (Gomez and Gomez, 1984).