University of Birjand Journal of Horticulture and Postharvest Research 2588-4883 9 Issue 2 2026 06 01 Evaluation of nutrient management strategies on chicory (Cichorium intybus L.) growth and physiological traits in Arak’s climate 255 278 3892 10.22077/jhpr.2026.8276.1435 EN Abolfazl Mohammadi Khorzani Department of Agronomy, College of Agriculture, Shahed University, Tehran, Iran Heshmat Omidi Department of Agronomy, College of Agriculture, Shahed University, Tehran, Iran Mohammad Hosein Bijeh Keshavarzi Department of Agronomy, College of Agriculture, Shahed University, Tehran, Iran Journal Article 2024 10 13 <strong>Purpose:</strong> This study investigated the effects of phosphorus, potassium, and humic acid fertilizers on growth, yield, and physiological traits of chicory under Arak’s climatic conditions using a factorial experiment. <strong>Research Method:</strong> The experiment was conducted in a randomized complete block design with three replications. Experimental factors included levels of phosphorus fertilizer (0, 8 and 12 kgha^-1), potassium fertilizer (0, 10 and 15 kgha^-1), and humic acid (0, 0.5 and 2 kgha^-1). <strong>Findings</strong> The results showed that the highest Leaf Area Index was observed in the treatment of 12kg/ha phosphorus+10 kg/ha potassium sulfate+2 kg/ha humic acid, with a mean of 2.9. The highest number of flowers and the highest total chlorophyll content were obtained in 12 kg/ha phosphorus + 10 kg/ha potassium sulfate + 0.5 kg/ha humic acid treatment with averages of 49.11 per plant and 39.5µg/g FW respectively. The highest flower yield was in 10 kg/ha potassium sulfate treatment with an average of 330.6 kgha^-1. The highest content of free proline was obtained in 8 kg/ha phosphorus+15kg/ha potassium sulfate+2 kg/ha humic acid treatment with 0.97μmol/g FW. Combined phosphorus, potassium, and humic acid application significantly improved chicory growth, yield, and physiology, increasing leaf area index, flower number/yield, shoot yield, biomass, and chlorophyll content, while decreasing free proline. <strong>Research limitations:</strong> No significant limitations were identified in this study. <strong>Originality/Value:</strong> To maximize chicory growth and yield in the specific climatic conditions of this study, a balanced fertilizer application is crucial, as excessive fertilization can be harmful. This study suggests a combination of 8 kg/ha of superphosphate, 10kg/ha of potassium sulfate, and 0.5 kg/ha of humic acid powder. Future research should focus on understanding how these nutrients affect chicory at a mechanistic level and on evaluating the long-term consequences of various fertilization programs for soil fertility and environmental health. https://jhpr.birjand.ac.ir/article_3892_cf5a5c58e55e32c30e631676b15563e7.pdf