THE EFFECT OF CHEMICAL FERTILIZERS ON THE QUANTITATIVE AND QUALITATIVE TRAITS OF OREGANO (Origanum vulgare L) PLANT

This experiment was conducted to investigate the effects of NPK fertilizer on oregano (Origanum vulgare L.) plant for two years (2017 and 2018). Various levels of nitrogen (0, 50 and 100 kg ha-1), potash (0, 40 and 80 kg ha-1), and phosphorus (0 and 30 kg ha-1) fertilizers were applied. The results revealed that the use of NPK fertilizers significantly increased the dry weight of the oregano plant's aerial parts (leaves, inflorescences, and whole aerial parts). In the first year, the dry weight of the whole shoot increased by 82 to 124 g m-2, and in the second year, it increased by 82 to 129 g m-2. Moreover, regarding essential oil concentration, this parameter in inflorescence ranged from 2.38% to 3.66% in the first year, while in the second year, it ranged from 3.02% to 4.14%. Notably, the inflorescence had a higher essential oil concentration compared to the leaves. The study also found that the use of NPK fertilizer at a ratio of 100:20:40 kg ha-1resulted in the highest percentage of essential oil in the aerial. Conversely, the control treatment led to a decrease in essential oil yield. Among the essential oil compounds, Carvacrol and p-Cymene were the predominant components, with concentrations ranging from 49.36% to 60.32% and 2.03% to 4.56%, respectively, in various oregano plant organs. Keywords: Dry weight, Essential oil, Inflorescence, Oregano, Nitrogen.