Effect of Plant Density and Nitrogen Fertilizer on Different Populations of Cannabis sativa L.

The increasing demand for raw materials in the paper and fermentation industries has intensified pressure on forest resources, highlighting the urgent need for sustainable alternatives. Hemp (Cannabis sativa L.), a fast-growing, non-woody fiber crop with additional medicinal and nutritional benefits, has emerged as a promising candidate. This two-year field study, conducted using a split-split plot design with three replications, evaluated the effects of four planting densities (3.6, 5.5, 9.5, and 20 plants m-2) and four nitrogen levels (0.150, 300, and 450 kg ha-1) on three hemp genotypes: Futura 75 (Germany), Isfahan, and Yazd, in the Alborz region of Iran. Significant effects were observed for all main factors and their interactions on key morphological and yield-related traits. The highest dry matter yield (22.559 kg ha-1) was obtained from the Isfahan genotype under 300 kg ha-1 nitrogen and a plant density of 20 plants m-2.The Futura 75 genotype recorded the greatest stem diameter (5.31 cm) and number of lateral stems (70 per plant) under low density (3.6 or 9.5 plants m-2) and high nitrogen input (450 kg ha-1). Leaf dry weight peaked at 103.66 g plant-1 in the Isfahan genotype with high nitrogen and low density. Yield components were generally higher in the first growing season, suggesting a notable influence of favorable environmental conditions. These findings emphasize the importance of optimizing planting density and nitrogen application according to genotype and environmental conditions. The Isfahan genotype, combined with high plant density and 300 kg ha-1nitrogen, is particularly recommended for enhancing biomass yield in semi-arid regions.