High-dose sheep manure improves black cumin oil composition in field trial

A two-season field experiment in Türkiye found that sheep manure applied at 6,000 kilograms per hectare produced the strongest measured changes in the fatty acid and essential oil composition of black cumin, or Nigella sativa L. The treatment significantly increased the contents of linoleic and oleic acids while enhancing the concentration of thymoquinone, the major component of the crop’s essential oil. Researchers tested the response of the Çameli cultivar at the Gaziosmanpaşa University field site in Tokat. The trial was designed to compare both the type and dose of organic fertilizer under semi-arid field conditions.

It used a split-plot arrangement within a randomized complete block design, with three replications, and covered the 2022 and 2023 growing seasons. The main plots received one of five organic fertilizers: leonardite, vermicompost, solid humus, chicken manure or sheep manure. The subplots received 0, 1,500, 3,000 or 6,000 kilograms per hectare of the assigned fertilizer.

This was an agronomic field study of chemical composition, not a clinical investigation of black cumin oil or its effects on people. Linoleic acid was the predominant fatty acid in all treatments, accounting for 56.64% to 58.23% of the measured profile. Palmitic, oleic and stearic acids were also present, with linoleic acid retaining the leading position throughout the experiment.

Among the fertilizer treatments, sheep manure at 6,000 kilograms per hectare produced the most favorable reported response, significantly increasing the contents of both linoleic and oleic acids. The essential oil showed a consistent major constituent as well. Thymoquinone ranged from 36.82% to 41.75% of the essential-oil profile and was the most abundant component under the experimental conditions.

The highest-rate sheep-manure treatment also enhanced thymoquinone concentration. The reported response therefore linked the sheep-manure treatment with higher measured concentrations of two individual fatty acids and the oil’s leading essential-oil constituent. No further analytical method is specified in the supplied abstract, and the findings do not demonstrate that the chemical changes produce measurable human health benefits.

Within the boundaries of the experiment, sheep manure at 6,000 kilograms per hectare was the most favorable fertilizer-and-dose combination tested for improving the selected components of black cumin seed and essential oil. The study examined one cultivar at one site in Türkiye over two growing seasons, using three replications, so the result cannot automatically be generalized to other cultivars, soils, climates or fertilizer-management systems. The work provides a bounded field observation: under the tested semi-arid conditions, the highest tested sheep-manure rate significantly increased linoleic acid, oleic acid and thymoquinone relative to the study’s comparison treatments, while leaving linoleic acid as the dominant fatty acid and thymoquinone as the principal essential-oil component.

Subject of Research: Organic fertilizer effects on the fatty acid and essential oil composition of the black cumin cultivar Çameli

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

Article References: Acar, A., & Karan, Y. B. (2026). Effects of organic fertilization on fatty acid composition and essential oil profile of Nigella sativa L.. BMC Plant Biology. https://doi.org/10.1186/s12870-026-09828-5

Image Credits: AI Generated

DOI: 10.1186/s12870-026-09828-5

Keywords: black cumin, Nigella sativa, sheep manure, organic fertilization, linoleic acid, oleic acid, thymoquinone, essential oils, field experiment, Türkiye, Effects, organic