The role of organic manure and some antioxidants in enhancing the growth, yield and oil production of black cumin (Nigella sativa) plants

This field experiment was conducted during the two consecutive seasons of 2021/2022  and 2022/2023 to elucidate the influence of compost as organic manure and some antioxidants ,as well as, their interactions on the growth aspects (branch number /plant and herb dry weight /plant), yield attributes ( capsule number /plant, seed yield /plant and per feddan) (feddan = 4200 m² = 0.420 hectares = 1.037 acres), essential oil production (essential oil % and yield /feddan), fixed oil production (fixed oil % and yield /feddan) and the elements of N, P and K % of black cumin (Nigella sativa) plants. Compost was added at 0, 9, 18 and 27 m³ /feddan and the two examined antioxidants were foliar sprayed as follows: Control (no sprayed plants, citric acid (CA) at 200 and 300 ppm, ascorbic acid (AA) at 200 and 300 ppm, CA at 200 ppm + AA at 200 ppm and CA at 300 ppm + AA at 300 ppm. The obtained results exhibited that supplying the plants with compost at all levels led to a significant augment in all tested traits, except for compost at the low one (9 m³ /feddan), in most cases. It is obvious that the use of compost at the high level (27 m³ /feddan) proved to be more effective in elevating all studied parameters. As for antioxidant treatments, foliar spray with these materials, either individual or in combination at all concentrations resulted a significant increase in all studied traits, except for citric acid at the low concentration (200 ppm), mostly. In this concern, the most effective treatment in augmenting these examined aspects was obtained due to the utilization of the combined treatment (300 ppm CA + 300 ppm AA). Clearly, the most studied parameters were significantly affected by the interaction between the two factors. In general, the addition of compost at the high level (27 m³ /feddan) + foliar spray with the combined treatment (300 ppm CA + 300 ppm AA) achieved the most effective treatment in increasing the growth, seed yield, essential and fixed oils production and the elements of N, P and K %.