effect of density and time of urea foliar application on oil yield and essences percentage of black cumin (nigella sativa l.)

in order to study the effect of density and time of urea foliar application on oil yield and essences percentage of black cumin (nigella sativa l.) a field experiment was conducted at research station of faculty of agriculture, azad university of birjand in 1387 growing season. three urea foliar application times [1-control 2-at 8-10 leaves stage 3-at 10% flowering 4-100% flowering ] and three plant densities (100, 200, 300 plant m-²) were compared in split plot based on complete randomized block design with three replications. studied components were seed yield, oil yield, essences yield, oil percentage, essences percentage. results showed that urea foliar application times had significant effects on essences percentage and essences yield. density had significant effects on oil and essences percentage, essences yield and seed yield. between all densities 200 plant m-² and urea application at 8-10 leaves stage had the highest seed yield (593/33 kg/ha) and 100 plant m-² and foliar application at 8-10 leaves stage had the lowest (243/33 kg/ha) seed yield. 300 plant m-² and urea application at 100% flowering stage had the highest essences yield (2/72 kg/ha). 200 plant m-² and urea application at 10% flowering stage had the highest (0/56%) essences percentage. 300 plant m-² and urea application at 100% flowering stage had the highest essences yield (173/15 kg/ha). between all densities 100 plant m-² and urea application at 8-10 leaves stage had the highest (173/15 kg/ha) oil percentage. it seems that 300 plants m-² and urea application at 100% flowering is the best treatment for black cumin yield and it's quality in birjand.