Effect of nitrogen rates on yield, yield components and essential oil content of several fennel (Foeniculum vulgare Mill.) populatios

This investigation was carried out to study the effect of different nitrogen rates on yield, yield components and essential oil of several fennel (Foeniculum vulgare Mill.) populations. The experiment design was split plot with three replications conducted during 2008 at Research Farm of Isfahan University of Technology. Nitrogen levels were 0, 40, 80, 120 and 160 N kg/ha as the main plot and four populations of fennel (Isfahan, Tehran, Yazd and 11486) located in subplot. Seed yield, essential oil percentage, 1000-seed weight, biomass, harvest index, number of seeds per umbel, number of umbels per plant, seed length, and plant height were measured. Results showed significant differences for seed yield, 1000-seed weight, harvest index, number of seed per umbel, number of umbels per plant, seed length, plant height and percentage of essential oil among fennel populations. Also, seed yield per ha, 1000-seed weight, number of seed per umbel, seed length, number of umbels per plant and percentage of essential oil significantly differed in different nitrogen levels. There was an interaction effect between N rates and populations for 1000-seed weight, harvest index, number of seed per umbel, seed length, number of umbels per plant and plant height. The highest seed yield per hectare among the populations belonged to Isfahan population, obtained on control and 40 and 160 kg/ha nitrogen fertilization. The highest essential oil percentage was obtained on population of 11486 at 40 kg/ha nitrogen fertilization.