Abstract

A field experiment was conducted in the fields of the Faculty of Agriculture, Tikrit University for the 2019-2020 agricultural season to study the effect of plant spacings and the level of nitrogen and boron fertilization on growth and yield of broccoli in a gypsiferous soil. The study included three factors, the first factor, plant spacings included four distances (35, 45, 55, and 65 cm) (D1, D2, D3, and D4), respectively. The second factor, the level of nitrogen application, included two levels of nitrogen, which are 70 and 140 (kg N ha-1) (N1 and N2), respectively in the form of urea fertilizer (46% N). The third factor was the level of boron application and it included two levels of boron, which are (without boron addition and 6 kg B. ha-1) (B0 and B1), respectively, in the form of boric acid (17% B). Results showed that nitrogen level N2 gave a clear significant increase compared to the N1 level, as the nitrogen concentration in the vegetative part and the blossom disc in the second level N2 reached (2.79 and 3.02%), respectively, while in the first level N1 it reached (2.53 and 2.53%). The concentration of sulfur in the shoot and the floral heads for the second nitrogen level reached (0.501 and 0.389%), respectively, with a significant increase compared to the first level N1, which gave an average of (0.464 and 0.368%), respectively, and the concentration of boron in the shoot and the floral heads for the second nitrogen level N2 (19.15 and 36.95 mg B; kg-1), respectively and was superior with significant increase compared with  the first level N1, which gave an average of (17.58 and 33.61 mg B kg-1), respectively. Application  of boron fertilizer at a rate of (6 kg B. ha-1) resulted in a significant increase in the content of leaves and floral heads of boron, reaching 22.40 and 38.41 mg kg-1), while the control treatment gave a rate of (14.32 and 32.14 mg kg-1). ) Respectively. Following the distance 65 cm between broccoli plants (D4) led to a significant increase in the concentration of nitrogen, boron, and sulfur in the leaves and the floral heads. The triple interaction between nitrogen (N) and plant spacings (D) and boron (B)  (treatment D4N2B1) gave the highest value for nitrogen, boron, and sulfur concentrations in leaves and the floral heads.