NITROGEN FERTILIZER REQUIREMENTS OF STEVIA REBAUDIANA BERTONI, UNDER EGYPTIAN CONDITIONS

Field trail was carried out during 1998 to 2000 at Giza Experi-mental Station (ARC), to find out the suitable nitrogen rate and cutting time that would insure optimum stevia yields and stevioside content. Three nitrogen rates (10, 20 and 30 Kg N/F) and ten cutting times (from July 1998 at a two month interval up to Feb. 2000). Results showed a gradual and significant increase in fresh and dry leaves, stern, biomass yields, total soluble carbohydrate and stevioside, over and with‌in cuts as nitrogen fertilizer increased up to 30 Kg N/F. Dry leaves yield and stevioside content (represent stevia eco-nomic yield and quality) increased by 64% and 1.99% at 30Kg N/F as compared to 10 Kg N/F. All studied traits showed significant increase in all successive cuts, but they manifested a remarkable increase during the summer cuts and surpassed those during winter cuts. These results give evidence that climate conditions such as tem-perature, length and intensity of photoperiod greatly affected stevia ec-onomic production and quality parameters more than successive cuts . The interaction between nitrogen fertilizer levels and cutting time significantly affected most studied traits. The highest dry leaves yield/F and leaves stevioside content were obtained from summer cuts fertilized with 30 Kg N/F.