Two field experiments were carried out during 2016 and 2017 consecutive seasons at a Private Farm at Mit-Ghamr Distrect, Dakahlia Governorate, Egypt, to study the effect of humic acid rates (0.0, 325.60, 651.2 and 976.80 g/fad.), NPK fertilization rates [0.0, 25, 50, 75 and 100% of the recommended rate (RR)] and their interactions on growth, leaves and herb yield and some chemical constituents as well as active ingredients of stevia plants. The obtained results referred that the maximum value for each of plant height, branch and leaf number/plant, total dry weight/plant, dry weight of leaves and herb/fad., total N, P, K and total sugar percentages as well as total chlorophyll content (a+b) were detected when plants were applied with the highest rate of humic acid (976.80 g/fad.) and fertilized with 75% RR of NPK, in most cases. The main constituents of Stevia rebaudiana leaves as detected by high performance liquid chromatography-mass spectrometry (LC-MS) were Rebaudioside A, Rebaudioside B, Rebaudioside C, Dulcoside and Steviolbioside which increased with treatment of 100% RR of NPK fertilizers combined with the highest rate of humic acid (976.80 g/fad.) compared to control.

The present work was carried out during the two successive seasons of 2015 and 2016 at the Experimental Farm of El-Quassassin Horticultural Research Station, Ismailia Governorate, Egypt, to study the effect of complete NPK fertilization rates (control, 50, 75 and 100% from the recommended dose), bio and organic fertilizers (control, EM 1 applied as the rate of 100 ml/shrub and active dry yeast with the concentration of 4 g/l as a rate of 2 liters/shrub) and the interaction treatments between them on the growth, (fruits and seeds yields), fixed oil content and its components in seeds of Jatropha (Jatropha curcas) shrubs. The results showed that, the best vegetative growth parameters (increasing percentage of shrub height, number of branches and canopy width/shrub), number and weight of fruits (kg)/shrub, number and weight of seeds (kg)/shrub, the yield of fruits and seeds (ton)/fed, fixed oil percentage, weight of fixed oil (g)/shrub and yield of fixed oil (kg)/fed were recorded from the interaction treatment of 75% complete NPK fertilization + EM 1 . The analysis of fixed oil of Jatropha shrub showed that, the treatment of 50% NPK gave the best palmitic acid percentage and the treatment of 50% NPK + EM 1 recorded maximum percentages of stearic and oleic acids, while the treatment of 100% NPK + EM 1 gave the highest percentage of linoleic acid.

The field work was carried out at the Experimental Farm of Horticultural Research Station in El-Quassassin, Ismailia Governorate, Egypt, during the two successive seasons of 2009-2011 and 2010-2012, to investigate the effect of drip irrigation treatments (1, 2 and 3 times/week, 2 hours every time) and fertilization treatments (ammonium sulphate (20.5 N %) at 300 kg/fed., calcium superphosphate (15.5 P2O5 %) at 300 kg/fed. and potassium sulphate (48 K2O %) at 100 kg/fed., humic acid at 280 g/fed., effective microorganisms (EM1) at 5 liters/fed. and active dry yeast at 6 g/L.) and their interactions on the vegetative growth parameters (plant height, number of branches and fresh weight of herb/plant), yield of herb (fresh herb yield/fed./cut and fresh herb yield/fed./year), essential oil contents (essential oil percentage, content(ml.)/plant, oil yield (L.)/fed./cut and oil yield (L.)/fed./year) and the chemical compositions (N, P, K and carbohydrates %) of Pelargonium graveolens L. plant.The results showed that, the treatment of irrigation 3 times every week gave the highest values of all vegetative growth parameters, essential oil contents and chemical composition (N, P and carbohydrates %) followed by 2 times/week, during 4 cuts in the two seasons. Fertilizing with recommended NPK gave the highest results of all vegetative growth parameters, yield of herb, essential oil contents and chemical composition (N, P and K %), followed by humic acid, throughout the four cuts in both seasons. The combined treatment of irrigation 3 times/week + NPK resulted in the highest values of vegetative growth parameters, yield of herb, essential oil contents and chemical composition (N, P and carbohydrates %) followed by the interaction treatment of irrigation 3 times/week + humic acid fertilizer, during 4 cuts in the two seasons. From the results of this study, we observed that, the highest values of vegetative growth parameters, herb yield, essential oil contents obtained in the third cut followed by the fourth cut in the second year of season, while the least results found in the first and second cuts, in the first year of season, these findings repeated in the two seasons.