Investigation of evapotranspiration. yield, yield components and some physiological traits of winter safflower under drought and salinity stresses

Drought and salinity stresses are among the main challenges in the agricultural sector, especially in arid and semi-arid regions. In this study, in order to investigate the interaction effect of salinity and drought stresses on safflower (cv Goldasht), a factorial experiment was conducted in 2020 as a completely randomized design with three replications in the greenhouse of Pistachio Research Station of Ardakan city located in Yazd province. The irrigation treatments were applied as 5 (I1), 10 (I2) and 15 (I3) days of irrigation interval and salinity levels of irrigation water were included 0.7 (S1), 4 (S2), 7 (S3) and 10 (S4) dS/m. At the end of the growth period, safflower traits such as grain yield, 1000-seed weight, shoot dry weight, harvest index, water productivity, leaf area, evapotranspiration, electrolyte leakage and SPAD index were measured. Results showed that the main effect of the salinity levels of the irrigation water and irrigation intervals were significant on all traits. Also, the interaction effects of salinity and irrigation interval were significant on all traits except leaf area and electrolyte leakage at one percent level. By increasing irrigation water salinity and lengthening of irrigation interval, all traits decreased except electrolyte leakage percentage. In the highest salinity level (S4) compared to the control treatment (S1), the average of evapotranspiration during the stress period and grain yield decreased by 32 and 84.7 percent, respectively. Increasing irrigation interval up to 15 days reduced evapotranspiration during the stress period and grain yield by 38 and 86.4 percent compared to 5 days irrigation interval, respectively. The coefficient of readily available water for safflower grain yield was obtained 0.45. The salinity threshold of the soil solution for reducing safflower grain yield was obtained about 3.4 dS/m and the slope for decreasing grain yield was 5.8% per unit increase in salinity.