A field study on purple basil (Ocimum basilicum L.) was carried out to determine the effect of different
irrigation water levels in 2007 and 2008 in the research field of Ege University, Faculty of Agriculture, in
Turkey. Four irrigation treatments were determined as the irrigation water being needed to raise root
zone soil water to field capacity (I100: 100%, at field capacity) and a percentage of water applied to I100
treatment (I50: 50%, I75: 75% and I125: 125% of field capacity). The effect of different irrigation water levels
on purple basil’s plant height, green herb yield, drug herb yield, and drug leaf yield, the irrigation water
use efficiency, essential oil ratio, and composition of essential oil were evaluated.
According to the results, the highest plant height (38.6 cm), green herb yield (2269.4 kg da−1), drug
herb yield (417.2 kg da−1), drug leaves yield (300.6 kg da−1) were determined in the I125 treatment for
both years. However, the highest essential oil ratio (1.10%) was found in the I50 treatment. The results
revealed that purple basil plant is sensitive to water stress or the amount of irrigation water applied.
Water stress negatively affected the plant height and the yields of purple basil plant. On the contrary,
the essential oil ratio of the plant increased as the applied amount of irrigation water decreased. Water
stress has a positive effect on essential oil composition of the plant. The main components of the essential
oil were linalool, eugenol and methyl chavicol. Since the yields changed in parallel with the amount of
irrigation water applied, the irrigation water use efficiencies were not significantly different according
to the irrigation water levels.