The Effect of Sowing Date and Nitrogen fertilizer on Growth, Essential Oil and Essential Oil Compounds of Fennel (Foeniculum vulgare) under Shoushtar Condition

Nowadays, the phytochemical constituents of medicinal plants have received much attention due to their potential use in nutraceuticals and drug industries. Spices and herbs are part of daily food intake across many regions of the world. They have been used as natural sources of flavorings and preservatives. Recently the use of medicinal plants and their derived products in the pharmaceutical and healthcare industry has seen rapid development in recent years. As the other crops, the increase in seed and active ingredient yield of medicinal herbs is influenced by genetic and environmental parameters. Although genetic factors play a significant role in the development of the essential oil of medicinal plants, should also be aware of the role of climatic factors and crops in the field. Therefore, medicinal plants dry matter production and its essential oils are controlled by environmental factors, conditions, sowing date, planting? fertilizing and harvesting time. Researches indicated stated that nitrogenous fertilization and sowing time increased yield by increasing hydrocarbon production owing to the development of shoots and the expansion of carbon-absorbing surface. Therefore to determine the effective N-fertilization level and plant sowing date for Fennel (Foeniculum vulgare) an experiment was carried out to increase the yield of anthodium flowers and content of essential oil.
Field experiment was carried out at the research farm of Islamic Azad University, Shoushtar branch (Shoushtar located in the north of Khouzestan), in Iran during 2010-2011. The experiment was conducted on a split plot design based on randomized completely block design with three replications. The plant sowing date (November, 6 and 22) and UreaTM fertilizer (%46) (100, 125 and 150 kg ha-1) allocated to main plot and sub plot, respectively. For identification of components, Agilent gas chromatography model 6890 N, equipped with MSD model 5973 N and fused silica capillary column (HP-5MS, 30m- 0.25mm) were used for qualitative and quantitative analysis of oils. The GC oven temperature was held at 50 °C for 5 min, then programmed from 50 °C to 240 °C at a rate of 3 °C min-1 and from 240 °C to 290 °C at a rate of 5 °C min-1, held for 2 min at 290 °C, using the gas as the carrier (1.0 ml min-1). The temperature of injector and detector were 240 °C and 280 °C, respectively. The percentage composition of the essential oils was computed from GC peak areas without using any correction factors. Qualitative analysis was based on comparison of retention times and indices on both columns and mass spectra using computer mass spectra libraries model Agilent Technologies 5973 Network and corresponding data available in the literature.
Growth and essential oil yield of Fennel seed and shoot significantly influenced by sowing date and N fertilizer. Results of interaction the effect of sowing date and nitrogen fertilizer showed 6 November sowing date and 125 and 150 Urea fertilizer increase shoot dry weight (442.5 and 438.9 g m-2), seed essential oil percentage (2.9 and 2.8%), shoot essential oil percentage (3.14 and 3.12%), seed essential oil yield (2.2 g m-2) and shoot essential oil yield (13.9 and 13.6 g m-2). Anatole had the highest percentage of essential oil components. Highest percentage of seed and shoot of anatole obtained from samples from plants sowing on November 6th and fertilized with Urea 125kg per hectare under the influence of urea fertilizer by more than 39 percent of (seed) and 45% (shoots), respectively. The highest percentage of seed estragole obtained from plants sowing on 22November and under 125and150 Urea kg per hectare, respectively. Fennel shoot estragole percentages were not affected by various treatments. Highest of seed and shoot De-fench one percentages were observed.in planting of 6 November and125 and 150kg per hectare under the influence of urea.
The results of these experiment revealed that the sowing date and nitrogen content affected the constituents of the essential oil of fennel. Results showed that delaying sowing date under the North of Khuzestan weather conditions leading to reduced growth and yield of essential oil. According to the results, the most suitable sowing date and N fertilizer for Fennel under north of Khuzestan province condition are 6 November and 125 kg ha-1 Urea™ fertilizer.