Gorgan University of Agricultural Sciences and Natural Resources Environmental Resources Research 2783-4832 13 2 2025 10 01 Effect of irrigation and foliar spraying of salicylic acid and humic acid on yield and water use efficiency of sunflower (Helianthus annuus L.) 393 406 7501 10.22069/ijerr.2025.23496.1496 EN Hamed Javadi Soil and Water Research Department, South Khorassan Agricultural and Natural Resources Research and Education Center,AREEO, Birjand, Iran Samira Arefi Master of Agriculture, Agricultural Jihad Organization of South Khorasan, Iran Journal Article 2025 04 06 In order to investigate the effect of irrigation levels, humic acid and salicylic acid on yield and water use efficiency of sunflower, a split factorial experiment based on randomized complete blocks with three replications was conducted in the farm of Islamic Azad University, Birjand branch. In this research, irrigation at two levels (120 and 240 mm of evaporation from the pan) were considered as the main factor, humic acid at three levels (0, 20 and 40 Lit. ha-1) and salicylic acid at two levels (0 and 0.75 mM) to were considered as secondary factors.The results showed that seed yield (1126.9 kg ha-1), oil percentage (38.7%), oil yield (440 kg ha-1), protein yield (208.5 kg ha-1), water use efficiency for protein production (18.1 kg m-3) and water use efficiency for oil production (38.2 kg m-3) was obtained from the irrigation level of 120 mm evaporation from the pan and the highest percentage of protein (22.8%) was obtained from the irrigation level of 240 mm evaporation from the pan. The application of 20 liters per hectare of humic acid in the irrigation cycle of 120 mm of evaporation from the pan increased the number of seeds in head, while the application of humic acid decreased this trait. Based on the results of this research, in order to achieve the maximum grain yield, protein yield and sunflower oil yield in Birjand region, irrigation treatment can be used after 120 mm cumulative evaporation from the evaporation pan and consumption of 0.75 mM salicylic acid. https://ijerr.gau.ac.ir/article_7501_d6dddf254e264c5464f415b75a2661cd.pdf