Effect of Different Levels of Nitrogen on Growth and Yield of Flax under Kabul Agro-Ecological Conditions

Flax is among the most significant industrial oilseed crops in the world, as well as in Afghanistan.  It is high in health-promoting fatty acids. However, its yield and quality are low owing to poor nitrogen fertilizer use and lack of improved cultivars in Afghanistan. Hence, a field trial was conducted at the Research Farm of the Agriculture Faculty of Kabul University during the main cropping season of 2025 to evaluate four nitrogen rates (0, 50, 100, and 150 kg/ha). The study was conducted using a randomized complete block design (RCBD) arrangement with four replications. The size of each experimental unit was 2 m × 2 m (4 m²), with six rows. Distances of 30 cm and 40 cm were left between plots and blocks, respectively. The spacing between rows was 30 cm, and the spacing between plants was 15 cm. Significant differences were observed in the different levels of nitrogen on plant height, number of capsules per plant, number of branches per plant, number of seeds per capsule, 1000-seed weight, length of roots, biological yield, grain yield, and straw yield. However, the results showed that the 100 kg N/ha fertilization level significantly outperformed in number of seeds per capsule, number of capsules per plant, 1000-seed weight, and seed yield. Meanwhile, the 150 kg N/ ha fertilization level excelled in plant height and number of branches per plant, biological yield, and straw yield.