Nitrogen Effects On The Essential Oil And Biomass Production Of Field Grown Greek Oregano (Origanum Vulgare Subsp. Hirtum) Populations

This study investigates the effect of different nitrogen fertilization levels on the agronomic traits of five Greek oregano populations. Nitrogen supply positively affected dry bio-mass production, with the highest accumulation recorded at 80 kg N ha(-1) (N2), which was 59% higher compared to the control plots (no additional nitrogen). In contrast, the essential oil content (mL 100 g(-1) DW) was reduced, with the control treatment showing a 15% higher value compared to the mean value of the nitrogen treatments. However, nitrogen supply positively affected the essential oil yield (L ha(-1)), and the highest value was recorded at 80 kg N ha(-1), (N2), showing a 40% increase compared to the control. A wide phenotypic variation among the five populations was also observed. In the three-year analysis, the population with the highest dry biomass production was Papadates (92% higher), that with the highest essential oil content was Vytina (25% higher), and the highest essential oil yield was observed for Papadates and Litochoro (57% and 51% higher, respectively), compared to the least yielding population. Significant interactions were also found between nitrogen levels and populations, implying that, in all cases, nitrogen levels should be specified for each population in order to optimize oregano productivity in sustainable farming systems.