Effects of Urea Fertilizer Levels on Growth and Yield of Safflower (Carthamus tinctorius L.) Under Kabul Climatic Conditions

Abstract

Safflower (Carthamus tinctorius L.) is an important oil-bearing crop with significant economic and medicinal value, well adapted to arid and semi-arid climates. Despite its agronomic potential, systematic research on optimal nitrogen fertilization for safflower under the specific climatic conditions of Kabul, Afghanistan, remains limited. This study evaluated the effects of six urea levels (0, 40, 60, 80, 100, and 120 kg ha⁻¹) on the growth and yield of safflower using a Randomized Complete Block Design (RCBD) with three replications at the Kabul University research farm during the spring season of 2025. Data were analyzed by analysis of variance (ANOVA), and treatment means were compared using the least significant difference (LSD) test at the 5% probability level. Results demonstrated that urea application significantly influenced plant height, number of leaves, number of branches, days to 50% flowering, number of capitula plant⁻¹, number of seeds capitulum⁻¹, thousand-seed weight (TSW), seed yield, and straw yield. The highest seed yield (1,650 kg ha⁻¹) and TSW (41.50 g) were recorded at T5 (100 kg urea ha⁻¹), whereas the highest straw yield (3,300 kg ha⁻¹) was obtained at T6 (120 kg urea ha⁻¹), albeit with a slight decline in seed yield and TSW. These findings indicate that 100 kg urea ha⁻¹ represents the optimal nitrogen application rate for economically viable safflower production under Kabul conditions.