الفهرس 
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Abstract
The present investigation was carried out in the Experimental Station of the Medicinal and Aromatic Plants, Fac. Agric., Mansoura Univ., during the two seasons of 2009/10 and 2010/11 to study the effect of planting spaces and biofertilizers as well as their interactions on the vegetative growth, yield, essential oil productivity and chemical compositions of lemon balm. The current research was included 24 treatments which were arranged in split plot design with three replicates. Lemon-balm plants were grown at distance of (40, 50 and 60 cm between plants) in the main plots, while the sub plots were the fertilizers treatments.
The obtained results could be summarized as follow:
A) Effect of planting distances:
1) Cultivation at narrow space 40cm between plants resulted in the tallest plants, the highest production of dry herb and leaves per faddan and the highest essential oil yield per feddan.
2) Cultivation at wider space 60cm between plants increased the number of branches, fresh and dry weights of herb and leaves, the essential oil content per plant, the N, P, K and total carbohydrates percentages as well as total chlorophyll content.
B) Effect of bio-fertilizers:-
1) A mixture of biofertilizers (Nitrobein+Phosphorein) and foliar Potasein-p plus half RD of NPK mineral fertilizers had a positive effect on the vegetative growth expressed as plant height, fresh, dry weights of herb and leaves, the number of branches, herb and leaves yield as well as N, P, K, total carbohydrates percentages and total chlorophyll content and produced the highest essential oil percentage, content and yield compared with the control treatment received only the full recommended dose of NPK.
2) The best results were of plants received half recommended dose of NPK mineral fertilizers and inoculated with Nitrobein and Phosphorein plus foliar Potasein-p followed by inoculated plants with Nitrobein and Phosphorein compared with other biofertilizers treatments and control.
C) Effect of the interaction between planting distances and biofertilizers:
1) The interaction between planting distance 40cm and the combined treatment of biofertilizers )Nitrobein and Phosphorein(, foliar Potasein-p with half RD of NPK mineral fertilizers gave the tallest plants, the highest yield / fed of herb, leaves and essential oil and the highest values of main components citral (neral 30.06 % and geranial 35.65 %).
2) The interaction between planting distance 60cm and the combined treatment of biofertilizers (Nitrobein and Phosphorein), foliar Potasein-p with half RD of NPK mineral fertilizers increased the number of branches, fresh and dry weights of herb and leaves per plant, essential oil percentage and content as well as N, P, K, total carbohydrates percentages and total chlorophyll content.
Finally, combined strains as nitrobein, phosphorein and foliar potasein-p plus half dose of recommended NPK at 40cm planting space gives the greatest plant growth, leaves yield and essential oil content, saves half of the quantity of mineral fertilizers, decreases the production cost and the environmental pollution.