Agronomic and Quality Responses of Durum Wheat (<i>Triticum turgidum</i> L. var. Durum) Varieties to Varying Nitrogen Fertilizer Rates in Bishoftu, Ethiopia

In the 2021 cropping season, an experiment was conducted to enhance productivity and refine the grain quality of durum wheat varieties by identifying the optimal N-fertilizer rate in Ethiopia's central highlands. The treatments included five N fertilizer levels with recommended P<sub>2</sub>O<sub>5</sub> (0, 46, 69, 92, and 115 kg ha<sup>-1</sup>), alongside an absolute control group (no NP fertilizer application), and three durum wheat varieties (Utuba, Et cross -21, and Mangudo). Employing a design featuring randomized complete blocks in triplicate, the analysis of variance indicated that aboveground biomass yield, grain yield and straw yield were harvested significantly influenced by the main effect of nitrogen fertilizer level (P<0.01). The highest aboveground biomass (12975.0 kg/ha<sup>-1</sup>) and straw yield (8312.2 kg/ha<sup>-1</sup>) occurred at the highest nitrogen rate (115 kg ha<sup>-1</sup>), while the maximum grain yield (4786.1 kg ha<sup>-1</sup>) was observed at 69 kg N/ha. Additionally, factors like leaf area index, total tillers, productive tillers, thousand seeds weight, and lodging index were significantly impacted by the combined influence of nitrogen fertilizer application and different durum wheat varieties. The results demonstrated that applying 69 kg N ha<sup>-1</sup> yielded the highest economic benefit of 180782.4 ETB ha<sup>-1</sup> with an acceptable marginal rate of return of 3277.8%. Thus, it is concluded that applying 69 kg N ha<sup>-1</sup> along with the three durum wheat varieties led to economically profitable yield production. However, to provide more conclusive recommendations, the experiment should be repeated across multiple locations and seasons, incorporating balanced nutrient management.