Changes in Seed and Shoot Essential Oil Yield of Fennel (Foeniculum vulgare Mill.) in Response to Practices of Integrated Nitrogen Management

Abstract

Effects of different nitrogen nutritional systems (biologic, organic, and chemical fertilizers) on fennel were investigated in two cropping years (2013-2014 and 2014-2015) in a completely randomized blocks design. Treatments consisted of control or uniformly spreading 50% urea at planting time, and 50% at stem elongation (N1), uniformly spreading 50% of urea at planting time and spraying the other 50% of urea fertilizer at stem elongation on fennel foliage (N2), cow manure (N3), inoculation of fennel seeds with Azotobacter and Azospirillum (N4), N5 or Integrated-1 (N3 + uniformly spreading urea at stem elongation), N6 or Integrated-2 (N3 + N4). Findings showed that N2 has led to 13.4% and 14.3% more seed yield production than N1 for the first and second years, respectively. Also, the results indicated that N2 could produce 14.3% and 13.6% more essential oil yield than N1 for the first and second years of study, respectively. The main essential oil constituents were anethole, methyl chavicol, α-pinene, limonene, and fenchone. The results of this study showed that there was no positive effect of biofertilizers (Azotobacter and Azospirillum) application on fennel.