The Effect of Humic Acid and Nano-Chelate Iron on the Absorption of Some Nutrients, Grain Yield, Oil, and Essential Oil of (Nigella sativa) under Drought Stress

To examine the effect of humic acid and nano-chelate iron on the absorption of some nutrients and oil content and essential oil of (Nigella sativa) under two-year experimental drought stress (2018-and 2019-) in Agricultural and Natural Resources Research Station of Eqlid city, an experiment was conducted as a split factorial design in the form of a randomized complete block design with three replications. The main plots included irrigation at three levels (50, 75, and 100% of available water), sub-factors including humic acid at three levels (0, 250, and 500 mg/l), and nano-chelate iron at three levels (0, 1, and 2 g/l). The results revealed that drought stress decreased nutrient absorption and the amount of essential oil and oil content. Applying humic acid and nano-chelate iron decreased the effects of stress so that the application of humic acid and nano-chelate iron increased the yield by 21 and 27% compared to the control treatment. Interaction of humic acid, nano-chelate iron showed that the highest grain yield (1036) kg/ha) was observed in 500 mg/l of humic acid and 2 g/l of nano-chelate iron with 75% of available water. In general, it can be concluded that the use of humic acid and nano-chelate iron in conditions of water scarcity caused more absorption of nutrients, increased grain yield, and moderated the effects of drought stress compared to the control.