Optimization of applied irrigation water and nitrogen fertilizer for barley in a semi-arid region: a case study in Iran

摘要

This study was conducted to estimate the optimal amounts of water and nitrogen of barley production under water- and land-limited conditions. Two years of field experiments were performed with two treatments using a spilt plot design with three replications. The treatments included four levels of irrigation regimes (0, 50, 75 and 100% of water requirement) as the main plots and four nitrogen fertilizer levels (0, 70, 140 and 210 kg N ha(-1)) as the subplots. Straw yield income was about 35% of total income, indicating the important role of both grain and straw yield in the economic analysis. The optimal amounts of water and nitrogen considering the rainfall and residual amount of nitrogen in the soil were estimated using a generalized reduced gradient nonlinear method as 0.758 m and 236 kg N ha(-1) for maximum income per unit area, while these values were obtained as 0.758 m and 232 kg N ha(-1) for maximum profit under land-limited and 0.56 m and 293 kg N ha(-1) for maximum profit under water-limited conditions, respectively. The results show that the highest profit was obtained under land-limited, maximum income and water-limited criteria, respectively.