Irrigation water salinity effects on oregano (Origanum onites L.) water use, yield and quality parameters

Abstract

Irrigation water salinity effects on oregano growth, water use, yield and quality parameters were investigated. For this aim, eight irrigation water salinity levels including 0.54 (control), 1.2, 1.8, 2.5, 3.5, 5.0, 7.0 and 10 dS/m were utilized. The plants in all of 7 and 10 dS/m and two out of five replications of 5 dS/m treatment could not survive until the end of the experiment. The mean soil salinity and seasonal averaged drainage water salinity values increased with increasing salinities of applied irrigation water. Compared to control 27, 33, 44 and 74% reductions in total dry yields, and 27, 38, 49, and 77% decreases in dry leaf yields were calculated for 1.8, 2.5, 3.5 and 5 dS/m treatments, respectively. In general, increased irrigation water salinity caused increases in total phenolic content, total flavonoid content, extract yield which shows the amount of water extractable matter from the plants and antioxidant activity whereas significant decreases in total oil content. Among the essential oil components, carvacrol, β-cymene and γ-terpinene contents decreased with increasing water salinities up to 2.5 dS/m and after this level sharply increased but linalool content showed a reversed pattern. A threshold value of 0.50 dS/m was calculated for total fresh yield of oregano but it was not possible to determine a threshold salinity value for total dry yield, dry leaf yield and total oil content. Based on these results, oregano is a very sensitive plant to salinity.