Effect of Plant Spacing and Harvesting Age on Herbal and Oil Yield Oregano (Origanum vulgare L.) in Ethiopia

Background and Objective: Oregano (Origanum vulgare L.) is important aromatic and medicinal herb used as medicine and spice since ancient. But crop management information is not well investigated in Ethiopia. Therefore, the objective of this study was to evaluate the optimum plant spacing and harvesting age for oregano to maximize herbal and essential oil yield. Materials and Methods: The experiment took place at the Wondo Genet Agricultural Research Center in Southern Ethiopia from 2017 to 2019. The experiment followed a Randomized Complete Block Design (RCBD) with three replications. The treatments involved 5 spacing options (30×30, 30×60, 60×60, 60×90 and 90×90 cm) and three harvesting ages (3, 4 and 5 months after transplanting). Data on plant height, fresh leaf weight per plant, fresh stem weight per plant, fresh above-ground biomass per plant, fresh leaf yield per hectare and essential oil yield (kg/ha) were collected from three replications arranged in randomized complete block design and analyzed using R software. Results: The results showed that spacing had a very significant influence on fresh leaf weight per plant, fresh leaf yield per hectare and essential oil yield per hectare. It also had a highly significant influence on plant height and a non-significant effect on fresh stem weight and fresh above-ground biomass per plant. Additionally, harvesting age had a very highly significant influence on plant height, fresh leaf weight per plant, fresh stem weight per plant and fresh above-ground biomass per plant. It also had a highly significant influence on fresh leaf yield per hectare and essential oil yield per hectare. Thus, the highest essential oil yield (45.51 and 32.49 kg/ha) was obtained from 30×30 cm spacing and 5 months after planting, respectively. Conclusion: The study demonstrated that both the spacing and age at which oregano plants are harvested have a significant impact on their growth and yield of oregano.