Effects of organic fertilization on fatty acid composition and essential oil profile of Nigella sativa L.

Black cumin ( Nigella sativa L.) is a valuable medicinal and aromatic crop whose seed oil quality is strongly influenced by agronomic practices. This study was conducted over two consecutive growing seasons (2022 and 2023) to evaluate the effects of various organic fertilizers and their application doses on the fatty acid composition and essential oil profile of black cumin (cv. Çameli). The field experiments were conducted at Tokat, Gaziosmanpasa University, Turkiye, in a split-plot design arranged in a randomized complete block arrangement with three replications. Five organic fertilizers (leonardite, vermicompost, solid humus, chicken manure and sheep manure) were applied to the main plots at four doses (0, 1500, 3000 and 6000 kg ha −1 ). Linoleic acid was the predominant fatty acid (56.64–58.23%), followed by palmitic, oleic and stearic acids. Thymoquinone was the major essential oil component ranging from 36.82 and 41.75%. Among all treatments, the application of sheep manure at 6000 kg ha −1 produced the most favorable results, significantly increasing linoleic and oleic acid contents while enhancing thymoquinone concentration in the essential oil. These findings demonstrate that optimized organic fertilization, particularly high-dose sheep manure, can effectively improve both the nutritional quality and bioactive value of black cumin seed oil under semi-arid conditions.