University of Tehran Press Iranian Journal of Soil and Water Research 2008-479X 55 11 2025 01 20 Optimizing rainfed barley production by using nitrogen fertilizer and growth regulators in Khorram Abad and Poldokhtar agro-ecosystems Optimizing rainfed barley production by using nitrogen fertilizer and growth regulators in Khorram Abad and Poldokhtar agro-ecosystems 2091 2107 100668 10.22059/ijswr.2024.380069.669768 FA Saeideh Foladvand Department of Agronomy and Crop Breeding, Faculty of Agriculture, Ilam University, Ilam,I. R. Iran. Nosratolah Abbasi Assis. Prof., Dept. of Agronomy, Faculty of Agriculture, Ilam University, Ilam, Iran Fereshteh Darabi Department of Agronomy and Crop Breeding, Faculty of Agriculture, Ilam University, Ilam,I. R. Iran. Behroz Mir PhD in Agronomy, Lorestan Province Agricultural Jihad Organization,I. R. Iran. Journal Article 2024 07 29 The simultaneous application of nitrogen fertilizer and growth regulators in rainfed conditions improves plant growth and development parameters. For this reason, research was conducted in two regions in the crop years of 2022-2023 in Poldokhtar and Khorram Abad cities. The experiment was carried out as a factorial design in the form of a basic randomized complete block design with three replications. The first factor includes four levels of nitrogen chemical fertilizers, including 0, 50, 100 and 150 kg.h-1 urea, and the second factor was foliar application of blank (spraying solution with distilled water), paclobutrazol (120 mg/liter), spermidine (1 mM), and chlormequat chloride (three grams per liter). The highest seed yield was observed in the treatment of 100 kg.h-1nitrogen fertilizer and paclobutrazol foliar spraying at the rate of 2686.4 kg/ha, and the lowest rate was obtained in the absence of nitrogen fertilizer and no foliar spraying at the rate of 1284.8 kg/ha. The highest protein yield was observed in the treatment of 100 kg.h-1 nitrogen fertilizer and paclobutrazol foliar spraying at the rate of 313.25 kg.h-1. The highest total chlorophyll was observed in the treatment of 100 kg.h-1 nitrogen fertilizer and paclobutrazol foliar spraying at the rate of 10.38 mg/g of fresh weight. According to the results of this study, the use of nitrogen fertilizer and foliar application of growth regulators can significantly improve the growth, yield and photosynthetic pigments of barley in rainy conditions. The simultaneous application of nitrogen fertilizer and growth regulators in rainfed conditions improves plant growth and development parameters. For this reason, research was conducted in two regions in the crop years of 2022-2023 in Poldokhtar and Khorram Abad cities. The experiment was carried out as a factorial design in the form of a basic randomized complete block design with three replications. The first factor includes four levels of nitrogen chemical fertilizers, including 0, 50, 100 and 150 kg.h-1 urea, and the second factor was foliar application of blank (spraying solution with distilled water), paclobutrazol (120 mg/liter), spermidine (1 mM), and chlormequat chloride (three grams per liter). The highest seed yield was observed in the treatment of 100 kg.h-1nitrogen fertilizer and paclobutrazol foliar spraying at the rate of 2686.4 kg/ha, and the lowest rate was obtained in the absence of nitrogen fertilizer and no foliar spraying at the rate of 1284.8 kg/ha. The highest protein yield was observed in the treatment of 100 kg.h-1 nitrogen fertilizer and paclobutrazol foliar spraying at the rate of 313.25 kg.h-1. The highest total chlorophyll was observed in the treatment of 100 kg.h-1 nitrogen fertilizer and paclobutrazol foliar spraying at the rate of 10.38 mg/g of fresh weight. According to the results of this study, the use of nitrogen fertilizer and foliar application of growth regulators can significantly improve the growth, yield and photosynthetic pigments of barley in rainy conditions. https://ijswr.ut.ac.ir/article_100668_60e4297c668751ce1b2276576decca4b.pdf