Essential Oil Production, Yield and Water Use Efficiency of Fennel (Foeniculum vulgare Mill.) as Affected by Sowing Date and Plant Density

Abstract In order to study the effect of sowing date and plant density on essential oil, yield and water use efficiency (WUE) of fennel, an experiment was conducted in research field of Islamic Azad University, Birjand branch, Iran as a split-plot experiment based on a randomized complete block design with nine treatments and three replications. The main plot was sowing date at three levels of March 19, April 9 and April 20. The sub-plot was plant density at three levels of 6.7, 10 and 20 plants m-2. According to the results of analysis of variance, seed, biological and essential oil yield and WUE were significantly affected by sowing date, plant density and their interaction at 1% probability level, but the interaction between sowing date and plant density did not significantly affect essential oil percentage. As means comparison showed, delay in sowing from March 19 to April 20 led to 85.6 and 85.6% loss of seed yield and biological yield, respectively. Despite higher essential oil percentage at delayed sowing, the highest oil yield was obtained at sowing date of March 19 with the average amount of 20.96 L ha-1 which was 5.82 times as high as that at the sowing date of April 20. The sowing date of March 19 had higher water use efficiency (WUE) for seed and oil production than the sowing date of April 20 by 5.5 and 3.67%, respectively. However, it increased biological yield and WUE for seed, biomass and essential oil production by 71.8, 64, 44.9 and 74.9%, respectively. The highest seed yield with the average amount of 726.90 kg ha-1 was obtained at the density of 20 plants m-2 which was 16 and 62% higher than that at the densities of 10 and 6.7 plants m-2. Lower densities had lower essential oil yield despite higher oil percentage. In general, it is recommended to use sowing date of March 19 with the density of 20 plants m-2 for the cultivation of fennel because of having the highest seed and essential oil yield and WUE.