الفهرس 
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Abstract
Lemongrass (Cymbopogon citratus), belonging to Fam. Gramineae, is an essential oil crops. It is cultivated in many tropical counties of South America, Africa and Asia. It is turfied perennial grass, with numerous stiff stems and long narrow leaves, propagated by root divisions and flourish in sunny, warm and humid conditions. Essential oil content in the leaves and stem averages 0.25-0.35 % with citral being the main component (80-85 %).
This study aimed to investigate the effect of different compost levels (0, 4, 6 and 8 ton/fed.) and various NPK and/or biofertilization treatments, as well as the interactions between both factors on vegetative growth characters, essential oil parameters and chemical constituents.
The must important results could be summarized as follows :
I- Effect of compost levels :
* All studied vegetative growth characters, including plant height, leaf area, number of tillers/plants and leaves fresh and dry weights per plant and per fed., in both experimental seasons and along the three cuts for each seasons, were gradually augmented parallel to the increase in compost level. However, the differences in all these character between the medium and high compost levels (6 and 8 ton/fed.) were slight (no significant).
* Essential oil percent and essential oil yield per plant and per fed. were increased upward by each increase in compost level with the highest values being obtained due to 6 and 8 ton/fed. of compost. Such two compost level treatments outgrew, considerably, the low (4 ton/fed.) and unfertilized treatments..
* Regarding chemical constituents, i.e. chlorophyll a, chlorophyll b, carotenoids contents and total soluble sugars %, they all followed the same previous trend shown for vegetative growth characters and essential oil parameters. Therefore, chemical constituents were increased due to each increase in compost level with the high level (8 ton/fed.) giving the highest values in both seasons and for the three cuts.
II- Effect of NPK and/or bio-fertilization treatments :
* Obtained results in both seasons and along the three cuts, showed clearly that both treatments of 100 % NPK and 75 % NPK + E.M. + yeast proved to be much more effective than the other two treatments (75 % NPK + E.M. and 75 % NPK + yeast) in producing taller plants, more leaf area, higher number of tillers/plant and heavier leaves fresh and dry weights per plant and per fed. It was clear that both 100 % NPK and 75 % NPK + E.M. + yeast were almost similar in producing different vegetative growth characters. It was noticed also, that combining E.M. with 75 % NPK was more effective than combining yeast with 75 % NPK.
* Concerning essential oil parameters, the combination between 75 % NPK and both E.M. and yeast, as well as the recommended 100 % NPK were superior to those of 75 % NPK plus E.M. or yeast. However, E.M. looked to be always better than yeast when combined with 75 % NPK.
* The three photosynthetic pigments, chlorophyll a and b and carotenoids, as well as, total soluble sugars %, in the leaves of lemongrass plants, were remarkably higher due to either 100 % NPK or 75 % NPK + E.M. + yeast treatments in comparison with those of 75 % NPK plus E.M. or yeast only. But E.M. seems to be more effective than yeast in this concern.
III- Effect of the interaction between compost levels and NPK and/or bio-fertilization treatments :
* Obtained results illustrated that combining 6 ton/fed. of compost with either 100 % NPK or 75 % NPK + both E.M. and yeast was superior to all other possible interactions, in both seasons and during the three cuts, in augmenting different vegetative growth characters, increasing various essential oil parameters and stimulating photosynthetic pigment content and total sugars %.