The effects of nitrogen source and amount on growth, chlorophyll, oil, and essence contents of black cumin (Nigella sativa L.)

The objective of the present study was evaluation of the effects of different nitrogen fertilizer sources (urea, ammonium nitrate, and ammonium sulfate) and levels (0, 50, 100, and 150 kg/ha) on growth parameters, chlorophyll, oil and essence contents of black cumin (Nigella sativa L.). The experiment was conducted based on a complete randomized block design with 3 replications in a farm field near Gorgan. The results indicated that the highest number of flowering branch, plant dry weight, number of capsule per plant, number of seeds per capsule, harvest index, biological yield, seed yield, oil yield and percentage, essence yield and percentage, and chlorophyll a, b and total content were observed in 150 kg/ha urea. The number of flowering branch, chlorophyll a, b and total content and essence and oil percentage achieved to their maximum amount following use of 50 kg/ha urea, however, harvest index, biological yield, seed yield, oil yield and essence yield increased by increment of level of urea fertilizer up to 150 kg/ha. Ammonium nitrate and ammonium sulfate fertilizers increased most of the studied parameters including biological yield, seed yield, oil yield, and essence yield compared with control and ranked 2nd and 3rd after urea, respectively. Application of ammonium nitrate and ammonium sulfate fertilizer beyond 50 kg/ha resulted in no significant effect on these parameters. The data indicated that 150 kg/ha urea could resulted in the highest growth and oil and essence yield. Further experiments in other climates and soil condition are suggested.