A field experiment with split-plot design was laid out to investigate the effect of organic fertilization, foliar spray of yeast and their interaction on productivity and active constituents of three-lobed sage plants under Siwa Oasis conditions. The main plots included two compost manure levels of 10 and 20 m³ per feddan. The sub-plots included foliar spray of active dry yeast concentrations of 0, 5 and 10 g /liter. The interaction effect proved that the highest compost manure level at 20 m³ per feddan combined with foliar spray of the highest yeast concentration at 10 g/liter gave significantly maximum increments in vegetative growth parameters, yields of herb and essential oil as well as a higher 1,8-cineole constituent content in the volatile oil over control treatment, which recorded the lowest parameters.