SYNERGISTIC EFFECTS OF BIOGAS FERTILIZER AND NATURAL EXTRACTS OF GARLIC, AZOLLA, AND YUCCA ON THE VEGETATIVE GROWTH AND ESSENTIAL OIL YIELD OF STEVIA REBAUDIANA L. PLANT UNDER SOUTH SINAI CONDITIONS

Two field experiments were conducted in 2018/2019 and 2019/2020 seasons, at Ras Sidr Experimental Station in south SinaiAffiliated to Desert Research Center, Mataria, Cairo Egypt in cooperation with the Department of Horticulture, Faculty of Agriculture, Benha University, to study the effect of biogas fertilizer and natural extracts on vegetative characteristics and essential oil yield of Stevia rebaudiana L. plant. Results showed that biogas fertilizer along with different natural extracts exerted a significant influence on the growth characteristics and essential oil content of stevia. The highest values in most of the parameters in the first cut were found from T1 (recommended dose of chemical fertilizer) combining with (M4), (M5) or (M2). On the other hand, the second cut took the same line as the first cut but with T3 (50% NPK + biogas slurry at 5000 kg h-1) as (T3×M4) or (T3×M2) as drench addition registered the highest values of parameters mention before in most cases. Conclusively, the use of half (50%) of the recommended dose of chemical fertilizer with the equivalent of the recommended nitrogen content and replaced it with biogas fertilizer led to reducing the problem of the use of chemical fertilizers on the health and economic damages, in addition to the use of both extracts of Azolla and garlic as a drench addition with organic fertilization and half the dose of chemical fertilizer.