Irrigation and nitrogen application affect Greek oregano (Origanum vulgare ssp. hirtum) dry biomass, essential oil yield and composition

Abstract

Oregano is a perennial crop native to the mountains, which has been extensively cultivated in the last decade. Due to the growing interest in oregano cultivation, the aim of this study was to investigate the effect of irrigation and nitrogen fertilization on the yield of Greek oregano and the production of essential oil in order to increase the harvested yield without reducing the quality of the product. For the purposes of the study, field experiments were established in 2016 and 2017 using a factorial split-plot experimental design with main factor irrigation (I1: rainfed, I2: 100 % ETo) and sub factor nitrogen fertilization (N1: 0, N2: 150, and N3: 300 kg ha−1) under four replicates. Total yield measured by final samplings where plants were cut at 5–8 cm above ground. Essential oil content was determined, using a Clevenger-type distillation apparatus. Irrigation had not a significant effect on yield, with irrigated treatments producing almost the same yield with the rainfed treatments (3650 and 3250 kg ha-1, respectively), probably due to the satisfactory precipitation during the growing period. In addition, nitrogen fertilization had a significant effect on yield and on essential oil. The higher yield and essential oil production were found for the irrigated and fertilized with the higher nitrogen testing amount (I2N3) treatment (4750 and 275 kg ha-1 dry leaves and flower biomass and essential oil, respectively). Therefore, Greek oregano seems to be a promising cultivation in areas characterized by a typical Mediterranean climate with satisfactory precipitation (>250 mm) during growth period, characterized by satisfactory yields.