The effect of nitrogen doses on morpho-physiological traits of safflower at different levels of deficit irrigation

This experiment aimed to evaluate the effects of different levels of irrigation based on potential evapotranspiration (100%, 60%, and 40% PET) and doses of nitrogenous fertilizers (0, 40, and 80 kg ha-1) on the performance of safflower in Qazvin, Iran. Three fractions of potential evapotranspiration: 100%, 60%, and 40% PET are considered as full irrigation (FI), mild deficit irrigation (MDI) and severe deficit irrigation (SDI), respectively. The mutual effects of nitrogen and deficit irrigation levels were significant on some growth characteristics such as longitudinal growth, number of secondary branches, canopy width, leaf chlorophyll content, number of capitula, and thousand seed weight. Results revealed that the effectiveness of nitrogen fertilizers was discernable under FI and MDI conditions, however, under SDI, the application of nitrogen fertilizers did not have any improvement effects on evaluated traits. The highest seed yield was recorded in FI+N80 and the seed yield of MDI+N80 was in the second place with a difference of 80 kg ha-1. However, the best seed quality in terms of protein percentage was related to plants grown under SDI+N80, which was 43% higher than FI+N0. The plants grown under FI+N80 and SDI+80 conditions showed the highest seed oil content with 28% and 27.1%, respectively.