EFFECT OF DRIP IRRIGATION METHOD ON GROWTH AND ESSENTIAL OIL COMPOSITION OF FIELD GROWN PEPPERMINT {Mentha piperita L.) AND SPEARMINT (Mentha viridis L.)

摘要

This study was carried out during two successive seasons (2010 and 2011) to assess the effect of two drip irrigation systems (surface and subsurface) on the growth and essential oil of Mentha viridis (spearmint) and Mentha piperita (pepper mint). Forsubsurface drip irrigation, a narrow furrow of about 10 cm depth was made using a pointed hand-hoe, and the irrigation pipe was laid down in the furrow. Each irrigation opening in the pipe was covered with a small clay plate to prevent clogging of the opening by soil, and then the pipe was buried by filling the furrow with soil. The results indicated that the subsurface drip irrigation system had a pronounced effect on the growth characters (plant height, fresh and dry weight of herb) compared with thesurface drip irrigation system. Generally, data revealed that the subsurface drip irrigation system increased significantly essential oil percentage and essential oil yield compared with the surface system. The major components of spearmint essential oilwere found to be carvon, menthyl acetate, a-pinene, 1,8- cineol and limonene. Menthol, menthone, menfhofuran and menthyl acetate were the main components in the essential oil of peppermint.