Response of black cumin (Nigella sativa L.) to deficit irrigation in a semi-arid region: Growth, yield, quality, and water productivity

Given the growing and urgent need for more effective irrigation strategies in arid and semi-arid regions, a field study was conducted in 2014 and 2015 in eastern Anatolia, Turkey, to evaluate the effects of water deficit treatments on the growth, yield, yield components, quality, and water productivity of black cumin (Nigella saliva L.). Four irrigation treatments (I-1, I-2, I-3, and I-4), based on Class A pan measurements, corresponded to 100, 80, 60 and 40 % cumulative evaporation were studied. The treatments were tested under a randomized, complete block design with three replications. The results indicated that considerable variation in yield and yield components of black cumin occurred, and that yield significantly increased with decreasing water deficit. Maximum seed and oil yields were recorded for the plots grown under the I-1 (full irrigation) treatment. The results showed that under full irrigation (I-3), seed yield was 1413.5 kg ha(-1) and decreased by 13.5 %, 18.9 %, and 30.1 % in I-2, I-3, and I-4 treatments, respectively. Irrigation water use efficiency under the full irrigation treatment was determined to be 6.2 %, 23.0 %, 37.6 % lower than I-2, I-3, and I-4 treatments, although full irrigation provided the highest yield. Water use efficiency increased significantly when the water deficit was more than or equal to 40 %. The study, therefore, suggests that for black cumin grown in areas with sufficient water resources, full irrigation may be the most productive practice while deficit irrigation practices can improve water productivity.