This work was performed during two successive growth seasons (2013 and 2014) at the Experimental Farm, Faculty of Agriculture, Menoufia University, Shebin El – Kom , Egypt to study the individual and combined effects of foliar application of benzyl adenine (BA) at (0, 50 and 100 mg/l) and mixture of some micronutrients (iron, manganese, zinc and boron) as a compound chelated (EDTA form) at different levels on growth, yield and active constituents of lemongrass plant (Cymbopogon citratus L.) grown on a clayey soil. Micronutrients were sprayed at different concentrations, i.e., M0 = irrigation water without any of micronutrients, M1= 100, 50, 50 and 25 mg/l, M2 = 150, 100, 100 and 50 mg/l, M3 = 200, 150, 150 and 75 mg/l for Fe, Mn, Zn and B, respectively. The experiment was carried out in a split plot design with three replicates.
Results indicated that, the combinations between different rates of BA and mixture of micronutrients had a significant improvement effect on growth and yield characters in most cases expressed as plant height (cm), number of tillers/plant, fresh and dry weights of herb (g/plant) and fresh weight of herb (ton/fed) in the 1st and 2nd cuts during the two seasons. Their highest values were obtained in the plants treated with BA at 100 mg/l combined with M2 level of micronutrients in the two cuts through the first and second seasons. The highest oil percentages were obtained by using BA at 50 mg/l + M2 level of micronutrients and BA at 100 mg/l + M1 level of micronutrients for the first and second cuts respectively during the two seasons. Citral a (geranial), citral b (neral) and myrcene were found to be the major compounds in the essential oil of Cymbopogon citrates which reached its maximum values by using BA at 100 mg/l + M1 level of micronutrients, BA at 50 mg/l + M2 level of micronutrients and M1 level of micronutrients without using BA respectively, during the 2nd cut in the first season.