ENHANCING THE GROWTH AND PRODUCTION OF BLACK CUMIN (NIGELLA SATIVA L.) BY APPLICATION OF HUMIC ACID AND BIOFERTILIZERS

Abstract

The safe production (chemical-free) of medicinal and aromatic plants has been the focus of interest of various researchers worldwide. Therefore, the aim of this experiment was to study the effect of humic acid (HA) and some bio-fertilizers on growth, seed yield and oil content of black cumin (Nigella sativa L.). Plants were foliar sprayed with HA at 100, 200 and 400 mg/L while control plants were sprayed with tap water. The bio-fertilizers used in this study were nitrogen fixing bacteria (Bio 1) that consists of Azotobacter chroococcum + Azospirillum brasilense, phosphate solubilizing bacteria (Bio 2) which consists of Bacillus megatherium var. phosphaticum + Bacillus polymyxa and the mixture of (Bio 1 + Bio 2) as a combination treatment. Plants were not received any bio-fertilizers were set as a control. The growth characters (plant height, branch number and fresh and dry weight per plant), seed yield components (capsule number, seed yield per plant and fed.) were significantly enhanced due to HA and/or biofertilizers treatments relative to the control. In all investigated parameters, the combined treatment of two biofertilizers (Bio 1 + Bio 2) was superior to solely application. Applying HA at 400 mg/L had no impact on growth and yield compared with 200 mg/L. The highest seed yield was recorded by the combined treatment of HA at 200 mg/L and the mixture of Bio 1 + Bio 2. The volatile oil percentage and yield were also improved by applying HA and/or biofertilizers treatments and the same trend was observed for fixed oil as well. Moreover, the GC-MS analysis of volatile oil indicated that the main constituents were also affected by HA and/or biofertilizers applications. Generally, the combination between HA and the mixture of biofertilizers increased the percentages of the main components compared to untreated plants. Furthermore, the N, P, K, total chlorophyll and carbohydrates were significantly increased due to HA and/or biofertilizer treatments relative to the control. To reduce the use of chemical fertilizers, minimize the production cost, improve soil structure, increase the quality of black cumin seeds and oils, the combined treatment of HA at 200 mg/L and the mixture of Bio 1 + Bio2 was recommended.