Impact of Humic Acid and Nano-Fe Chelate on Improving Vegetative Traits, Yield and Essential Oil Content of Black Cumin (Nigella sativa) under Drought Stress

In order to investigate the effects of humic acid and Fe nano-chelate on improvement of vegetative characteristics, seed yield and essential oil content of black cumin (Nigella sativa) under drought stress an experiment was done during two cropping seasons (2018-2019 and 2019-2020) in Agricultural and Natural Resources Research Station of Eghlid. The experiment was conducted as a factorial split plot in a randomized complete block design with three replications. The main plots were irrigation at three levels (50, 75 and 100% of available water), humic acid at three levels (0, 250, and 500 mg/l) and nano-Fe chelate at three levels (0, 1 and 2 g/l). The results showed that drought stress reduced the vegetative and yield traits. The interaction of humic acid, nano-Fe chelate and drought stress showed that the highest yield with 1036.7 kg/ha was observed in plants treated with 500 mg/l humic acid and 2 g/l iron nano chelate with 75% water available use. Also, the highest essential oil, seed oil, and leaf protein content was observed in plants treated with 500 mg/l humic acid and 2 g/l iron nano chelate with 100% usable water. As a conclusion, application of humic acid and nano-Fe chelate leads to the improvement of vegetative and chemical factors of black cumin in under drought stress conditions