EFFECT OF DEFICIT IRRIGATION IN DIFFERENT PHENOLOGICAL PERIODS ON YIELD AND YIELD PARAMETERS OF SUNFLOWER (HELIANTHUS ANNUUS L.)

This study was carried out to investigate the effects of deficit irrigation in different phenological periods on some yield and agronomic characteristics of sunflower (Helianthus Annuus L.) grown under semi-arid climate conditions during 2018 and 2019 growing seasons. Irrigation treatments were full irrigation (control, I-100), 30% water deficit (I-70) and 65% water deficit (I-35). The results indicated that sunflower yield significantly varied with the phenological periods and the water deficit treatments (p <= 0.01). For the highest water deficit (I-3(5)) condition; the highest yield (2463.33 kg ha(-1)), the lowest CWSI (0.53) and the highest chlorophyll content (CC) (34.33 spad) in the 2018 were recorded in vegetative period (VP), while the lowest yield (2290.00 kg ha(-1)), the highest CWSI (0.59) and the lowest CC (32.00 spad) were obtained in the flowering period (FP). For the full irrigation condition (I-100), the highest yield (3873.33 kg ha(-1)), the lowest CWSI (0.18) and the highest CC (43.33 spad) were recorded in flowering and pollination period (FPP), while the lowest yield (3796.66 kg ha'), the highest CWSI (0.22) and the lowest CC (41.66 spad) were obtained in VP. In the second year, the highest yield (2350.00 kg ha(-1)), the lowest CSWI (0.52) and the highest CC (36.00 spad) for the 1 35 treatment were determined in VP, while the lowest yield (2350.00 kg ha(-1)), the highest CWSI (0.58) and the lowest CC (33.00 spad) were obtained in FPP period. For the I-100 treatment, the highest yield (3946.66 kg ha(-1)), the lowest CWSI (0.17) and the lowest CC (44,33 spad) were recorded in FPP period, while the lowest yield (3856.63 and 3886.65 kg ha(-1)) was obtained in VP and SMP period. The results revealed a significant effect of water deficit and phenological period interaction on seed yield of sunflower. The effects of deficit irrigation in different phenological periods of sunflower on yield and yield parameters were significant. Restricted irrigation during flowering and pollination period should be avoided for an economical and profitable sunflower cultivation. The irrigation can be restricted in the vegetative period, if water deficit is a necessity. Briefly, the results proved that sunflower production is suitable for a sustainable, profitable and disease-free cultivation in semi-arid ecological conditions.