Response of wild Egyptian oregano to nitrogen fertilization in a sandy soil

Abstract

The response of Egyptian oregano (Origanum syriacum L. var. aegyptiacum Tackh) to nitrogen (N) fertilization in sandy soil was studied in pot experiments in two successive seasons. Four N levels (1,2,4, and 8 g ammonium sulfate [(NH₄)₂SO₄] per pot} along with zero level were applied. Nitrogen fertilization significantly affected plant height, and fresh and dry weight in all cuttings of both seasons. Plant biomass responded linearly to N application up to 4 g pot^‐1, while increasing N up to 8 g pot^‐1 resulted in insignificant increments. Nitrogen fertilization up to 2 g pot^‐1 increased oil percent then tended to decrease with increasing applicated N level. Essential oil content (mL plant^‐1) increased with application of N in all cuttings of both seasons. A positive correlation coefficient between N and essential oil contents in herbage was recorded in all cuttings. Gas liquid chromatography (GLC) analysis of essential oil content found thymol and carvacrol as the two main constituents in all treatments. Nitrogen fertilization seemed to increase the biosynthesis of thymol and carvacrol to the disadvantage of a‐terpinene and p‐cymene.