Effect of Organic Amendments on Some Quantitative and Qualitative Characteristics of Fennel (Foeniculum vulgar L (.as Affected by Different Irrigation Levels

In order to study the effect of salicylic acid, spermidine and methanol on yield, yield components, proline content, and essential oil quantity and quality of fennel in different levels of irrigation, an experiment was conducted as a split-plot based on randomized complete block design with three replications at Farm Research Station of the College of Agriculture in Bardsir in 2016. The experimental treatments were deficit irrigation levels (90%, 50% and 25% of the field capacity) assigned to main plot and foliar application of salicylic acid (1 mM), spermidine (0.2 mM) and methanol (30% vol) as subplots. The results showed that increased levels of drought stress resulted in significant increase of essential oil percentage and proline content, and significant decrease of other studied traits. The highest percentage of essential oil (2.86) was assigned to irrigation at 25% of the field capacity and the lowest (1.84) in 90% of the field capacity. All the studied traits were affected by foliar application (P≤0.01), except for essential oil percentage. The interaction effect of the treatments on number of branches, number of umbel per plant, number of seeds per umbel, 1000-seed weight, biological yield, seed yield, essential oil yield and proline content were significant. In irrigation at 90% of the field capacity, the highest seed yield (1081 kg.ha-1), biological yield (5413 kg.ha-1), essential oil yield (20.65 kg. ha-1) and proline (32.87 μmol) was related to methanol foliar application. However, at levels of 50 and 25% of the field capacity irrigation, the highest amount of these traits was found in salicylic acid foliar application. In all the traits, no significant difference was observed between spermidine foliar application and control treatment at all the irrigation levels. In general, the results confirmed that methanol foliar application was beneficial for non stress conditions, and the salicylic acid foliar application could satisfactory mitigate the negative effects of drought stress on fennel.