Climatic shifts, the occurrence of dry and low-precipitation spells, and inappropriate fertilizer management in semi-arid areas are the main reasons for low safflower yield. Current experiment aimed to evaluate the different irrigation regimes (I1: rainfed or no-irrigated condition, I2: one-time irrigation after seeds planting, I3: supplementary irrigation in the flowering stage, I4: supplementary irrigation in the flowering and seed set stages, I5: well-irrigated conditions) and the use of different fertilizers (C: control or non-use of fertilizers, NPK: chemical nitrogen, phosphorus, and potassium, FYM: 20 t ha-1 animal manure) in the high and semi-arid region of Hashtroud. The results showed that the highest amounts of chlorophyll a (39.33 mg ml-1) and chlorophyll b (18.3 mg ml-1) were recorded under I5+ NPK conditions and the lowest was related to plants grown under I1+ C conditions. The highest xanthophylls was recorded for plants grown under I2+FYM (0.79 mg ml-1), and I3+NPK (0.72 mg ml-1) conditions, and the lowest amount was related to I5+NPK conditions (0.17 mg ml-1). The tallest plants (160.78 cm), the largest canopy span (68.66 cm), the largest head diameter (33 mm), and the largest number of heads per plant (26.2) were recorded under I5+ NPK conditions. The highest 1000-seeds were observed under I3+C conditions (27.66 g) and the lightest seeds (25.16 g) were obtained from plants grown under I4+NPK conditions. The use of one supplementary irrigation during seed planting and flowering, and twice irrigation during flowering and seed set stage increased the yield by 3%, 14%, and 48%, respectively, compared to rainfed conditions. Taken together, the results indicated that to achieve a reasonable economic performance in the studied area, at least two supplementary irrigations are needed in safflower production systems.
