Oil and seed yields affected by sowing dates and irrigation regimes applied in growth phenological stages of safflower

Research establishing optimal sowing dates and irrigation can help to alleviate the adverse effects of drought on safflower (Carthamus tinctorius L.). The main objective of this study was to assess the effects of sowing date and irrigation quantity on safflower traits. Irrigation treatments were applied based on crop evapotranspiration (ETc) at the vegetative, flowering, and capitulum development stages. Evapotranspiration increased as the number of irrigations increased. Morphological, yield and oil traits, and water use efficiency (WUE) were significantly higher in the early than in late sowing. Grain yield varied from 440 to 1,460 kg ha(-1) in early and from 340 to 1,240 kg ha(-1) in late sowing dates. Oil yield of early sown safflower varied between 188.56 and 338.84 kg ha(-1) and between 24.4 and 308.82 kg ha(-1) in late sowing. The oil yield of one supplemental irrigation in the vegetative stage (I1V treatment) was significantly lower than in treatments with two (I2VF, vegetative and flowering stages) and three supplemental irrigations (I3VFG, vegetative, flowering, and capitulum development stages) in early sowing. In late sowing, the oil yield of I2VF was higher than other irrigation treatments. The range of saving irrigation water in I1 treatments was from 57.0 to 83.0% in early sowing but with a corresponding 30.0 to 66.0% reduction in grain yield compared with full irrigation treatment. For most of the tested traits, irrigation in the vegetative and especially flowering stages improved safflower yield and WUE, and thus can be an alternative irrigation strategy for water conservation in dry regions.