Effect of drought stress and nitrogen levels on growth, fruit and essential oil yield of fennel (Foenicolum vulgare Mill.)

In order to study the effect of drought stress at different growth reproductive stages and N fertilizer rates on some morphological and quantitative traits and water use efficiency (WUE) of fennel (Foenicolum vulgare Mill.)، an experiment was conducted as a split-plot based on a Randomized Complete Block Design with three replications، at Research Field of Islamic Azad University of Birjand Branch in 2010. The main plot included irrigation at three levels (irrigation stop at start of flowering، and seed-filling stages، and optimum irrigation) and the sub-plot was N fertilizer at four rates (0، 60، 120 and 180 kg N/ha). Results showed that irrigation stop at start of flowering and seed-filling stages decreased plant height by 16. 2 and 5. 2%، fruit yield by 69. 7 and 52. 6%، essential oil yield by 72. 9 and 31. 4%، and WUE for essential oil production by 69. 1 and 4. 5%، respectively as compared to optimum irrigation treatment. Moreover، the increase in rate of nitrogen application from 0 to 120 kg N/ha significantly increased plant height، stem diameter، branch number of main stem and fruit yield، 5. 8، 12، 15. 5 and 24. 3%، respectively. However، the highest yield and WUE for essential oil production was observed in 60 kg N/ha application treatment. In general، according to the results of current study، optimum irrigation with 60 kg N/ha application treatment can be recommended to achieve high essential oil yield of fennel in Birjand، Iran.