In the current study, we evaluated the impacts of organic and chemical fertilizers as well as the foliar application of growth regulators on quantitative traits and seed oil content of safflower grown in northwestern Iran. The experiment was done as a split-plot (3 × 5), and the main plot was assigned to different fertilizers, including organic fertilizer (FYM: farmyard manure 20 t ha-1), full chemical fertilizer (FCF) and no fertilization “control” (NF). The sub-plots were allocated to foliar spray treatments, which included control (no-spray application; S0), choline (S1), chitosan (S2) and salicylic acid (S3). The results showed that the application of fertilizers significantly affected the oil and protein content of the seed. However, the effect of FYM was more prominent than FCF on oil qualitative characteristics. A significant positive correlation was observed between oil content, protein content, and some fatty acid composition such as oleic acid, arachidonic acid, stearic acid, and palmitic acid. The highest values of the previously mentioned traits were obtained using FYMS1, FCFS1 and FYMS3. This trend was also clearly obvious in the content of linoleic acid as the main fatty acid in safflower oil. Among the foliar spraying treatments, the most improving effect was obtained with the use of choline. In conclusion, improving soil conditions through the application of FYM and appropriate amounts of chemical fertilizers is one of the most important agronomic management measures to improve the oil quality of safflower seeds.
