Effect of water stress and different amounts of sulfur fertilizer on grian yield, grain yield components and osmotic adjustment in Nigella sativa L

In order to study the effects of water stress and different amounts of sulfur fertilizer on the grain yield, grain yield components, two osmotic components (carbohydrate and proline) and essential oil yield in Nigella sativa L. a field experimental split-plot design with three replications was conducted in 2009 at Ghaen city. Treatments included three levels of irrigation as 50, 100 and 150 mm evaporation from class A pan evaporation in main plot and four levels of sulfur fertilizer included 0, 75, 150 and 225 kg ha-1 as Bentonite in sub plot. Results showed that water stress significantly affect the grain yield of Nigella sativa as grain yield decreased up to 22.8% at the level of 150 mm evaporation from the class A evaporation. Except 1000-seed weight, water stress significantly decreased all grain yield components, including biomass production, the number of capsules per plant and seeds per capsule. Maximum reduction at the highest level of water stress related to the number of seed capsules (31.64 percent). Carbohydrate and proline increased under water stress while essential oil yield decreased in Nigella sativa. Sulfur fertilizer improved grain yield as applying 225 kg/ha sulfur fertilizer increased it up to 7.2 percent. Sulfur fertilizer especially at 150 kg/ha had significant positive effects on the grain yield components, osmotic solutes and essential oil yield.