Effect of seaweed fertilizer foliar application on growth parameters, yield, and essential oil content and composition of hyssop (Hyssopus officinalis L.)

Ensuring the healthy and sustainable production of agricultural products, esp. medicinal plants, while preserving the environment, is an important issue that is becoming increasingly important every day. To investigate the effect of seaweed fertilizer foliar application on growth characteristics and quantitative and qualitative yield of hyssop (Hyssopus officinalis L.), an experiment was conducted in a randomized complete block design with four treatments of seaweed fertilizer (0, 2.5, 5 and 10 ml.l-1) and three replications in the research farm of faculty of agriculture, Tarbiat Modares University, Tehran province, Iran in 2017. Measured traits included plant height, leaf area, stem diameter, top flowering branch length, fresh and dry weight of the plant, chlorophyll content index, yield, essential oil content, and composition. The results showed that seaweed fertilizer had a significant effect on all studied traits except top flowering branch length and stem diameter, and the highest plant height (49.66 cm), fresh and dry weight of the plant (103.22 and 22.89 g, respectively), leaf area (0.77 cm2) and chlorophyll content (61.83) were obtained in 10 ml.l-1 seaweed fertilizer treatment without significant difference from 5 ml.l-1 treatment. Also, the 10 ml.l-1 treatment caused the highest percentage and yield of essential oil (0.58% and 2.12 g.m-2). Essential oil analysis showed that β-pinene, trans-pinocamphone, and cis-pinocamphone were the main compounds of essential oil in all treatments. The highest content of β-pinene (32.8%), cis-pinocamphone (42.5%), and trans-pinocamphone (19.6%) was observed in 5, 2.5 and 10 ml.l-1 seaweed fertilizer treatments, respectively, without significant difference from control treatment. Based on the results of this study, the application of seaweed fertilizer can improve the growth characteristics and quantitative and qualitative yield of hyssop.