Response of Wheat (Triticum aestivum L.) Genotypes to Different Nitrogen Fertilizer Levels under Desert Farming Conditions

Background: Wheat production in desert environments is constrained by poor soil fertility, particularly limited nitrogen availability. Optimizing nitrogen fertilization and selecting well-adapted genotypes are therefore important for improving wheat productivity under desert farming conditions. This study aimed to evaluate the response of different wheat genotypes to nitrogen fertilization under sandy soil conditions in Basra, Iraq. Methods: A field experiment was conducted during the 2024-2025 winter season in Al-Zubair District, Basra Governorate, Iraq, using a factorial arrangement within a randomized complete block design (RCBD) with three replicates. Four nitrogen fertilizer levels were tested: 0, 75, 150 and 225 kg N ha-1 (N0, N1, N2 and N3, respectively), combined with five wheat genotypes: Srank, Jamran, Mehrkan, Sirwan and Buhouth 22. Growth, yield and yield-component traits were evaluated. Result: Increasing nitrogen application significantly improved flag leaf area and most yield components. The application of 150 kg N ha-1 produced the highest flag leaf area, number of spikes, number of grains spike-1 and grain yield (5.013 Mg ha-1), whereas the control treatment (0 kg N ha-1) recorded the highest 1000-grain weight (39.593 g). The Mehrkan genotype significantly outperformed the other genotypes in flag leaf area, number of spikes, number of grains spike-1, grain yield (5.458 Mg ha-1) and harvest index. The interaction between nitrogen levels and genotypes significantly affected several traits, with Mehrkan combined with 150 kg N ha-1 achieving the highest values for most yield components, while the interaction had no significant effect on harvest index.