Impact of soil water stress on Nigellone oil content of black cumin seeds grown in calcareous-gypsifereous soils

• Published in: Agricultural water management 2011-11, Vol.100 (1), p.46-57
• Main Authors: Al-Kayssi, A.W., Shihab, R.M., Mustafa, S.H.
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; Biological and medical sciences; Black cumin seeds; Crop water stress index, Nigellone, Black cumin seeds, Gypsifereous soils, Dithymoquinone; Crops; deficit irrigation; Depletion; essential oils; experimental design; field capacity; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Gypsum; Irrigation; irrigation scheduling; lipid content; nectar secretion; Nigella sativa; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; plant available water; rhizosphere; seed yield; Seeds; Soil (material); Soil science; soil water content; Stresses; traditional medicine; Water and solute dynamics; water holding capacity; water stress
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2011.08.007

► Crop water stress index (CWSI) reflect the water requirement at different crop growth stages of black cumin crop. ► Soil water stress as well as soil gypsum content influence the yield of black cumin crop seed and its constituents, i.e., the pharmacologically active volatile oil dithymoquinone. ► The semi-empirical equations developed for CWSI can be used to determine the crop water stress using observed canopy-air temperature difference and vapor pressure deficits for pre-heading and post-heading stages of the black cumin crop grown in soils with different gypsum contents. Nigellone (dithymoquinone) is the main active constituent of volatile oil of black cumin ( Nigella sativa) seeds. It is presently used in traditional medicines, for culinary as ornamentals, and is also considered for its abundant nectar secretion. While black cumin, investigated recently (for the oil, essential oil, and other biologically active constituents of their seeds) the effects of deficit irrigation on seeds Nigellone content produced on gypsifereous soils are not known. Randomized complete block design experiments were conducted with three replications and four irrigation treatments on soils with five different gypsum contents over two growing seasons (2008–2009 and 2009–2010). These experiments aim to monitor and quantify water stress and Nigellone volatile oil content of black cumin as a function of crop water stress index and soil gypsum content. The soil gypsum content treatments were 60.0 (G 1), 137.6 (G 2), 275.2 (G 3), 314.2 (G 4) and 486.0 (G 5) g kg −1. Three irrigation treatments were based on replenishing the 0.60 m deep root zone to field capacity when the maximum allowable depletion (MAD) of the available soil water holding capacity of 25% (I 1), 50% (I 2) and 75% (I 3) were maintained in the crop experiments. A dryland treatment (fully stressed, I 4) was also included. The lower (non-stressed) and upper (stressed) baselines were measured to calculate crop water stress index. The crop water stress index behaved as expected, dropping to near zero following an irrigation and increasing gradually as black cumin plants depleted soil water reserves. The seasonal mean values of crop water stress index for the irrigation treatments; I 1, I 2, and I 3 were increased from 0.189, 0.287, 0.380 to 0.239, 0.366, 0.467, respectively when the soil gypsum content increased from 60.0 to 486.0 g kg −1. The highest Nigellone volatile oil content of black cumin seeds was obtained fo