Wheat (Triticum durum) yields have increased significantly because of the increasing higher irrigationand fertilizer inputs since the last half of 20th century. With varying climate and rising population,increasing focus is being given to enhancing resource use efficiency while increasing yields. Thisstudy utilized the CERES (Crop Estimation through Resource and Environment Synthesis) - Wheatmodel to analyse the impact of irrigation, nitrogen (N) and climate on wheat yield, using 58-year climatedata. Analyses were conducted using four assumed scenarios with step-by-step method. Resultsshowed that the optimum irrigation and nitrogen ranges were not uncertain when taking into accounta single factor. When considering both irrigation and nitrogen, the impact of irrigation on simulated grainyield was greater than that of nitrogen, which was similar to the results obtained from the experiments.The average variation in grain yield was attributed to irrigation (46.8%), nitrogen (5.5%) and climate(2.4%). Besides, relative humidity and maximum temperature were consistently and significantlycorrelated with grain yield under all conditions, while precipitation had a significant correlation withgrain yield when no irrigation or N was applied, or one of them was applied. However, solar radiationwas significantly correlated with grain yield when both irrigation and N were available.
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