Common basil (Ocimum basilicum L.) is a cosmopolitan herb and aromatic plant commonly growing in all parts of the world. Basil is a multipurpose plant with great applications in pharmaceutical, food and fragrance industries. Medicinally, this plant and its essential oil have long been used to treat nausea, dysentery, mental fatigue colds and rhinitis. The effects of applications of humic acid 18% (0, 500,1000 and 2000 mg.l-1) on some growth characteristics such as leaf number, height, total plant fresh and dry weight, fresh and dry yield and essential oil yield were investigated under hydroponic production. This experiment was carried out at the research greenhouse of department of Horticultural Sciences, University of Maragheh,during spring-summer of 2016. This study was conducted by completely randomized design. In general, it appears that humic acid had a promising effects on morphological charactristics and essential oil yield. The result showed that the application of humic acid had significant effects on growth characteristics despite of leaf number in compare with control. There was no significant difference between the leaf number of plant which treated by several concertation of humic acid but in other characteristics increased by application of humic acid. The result of this experiment showed that dry and fresh yield was increased by application of humic acid. Furthermore, humic acid could increase the essential oils yield and the 1000 mg.l-1 of humic acid was showed highest essential oil yield between other treatments. According of the result, 1000 mg.l-1 of humic acid had the best result in all factors which measured in this experiments. In summary, it seems that regarding the results of this experiment, basil plant has the production potential under hydroponic condition and humic acid could have positive effects on growth factors and essential oil production.
