A field experiment was carried out during two successive seasons 2014/2015 and 2015/2016 at the Experimental Farm of Faculty of Agriculture, Menoufia University, Shibin El-Kom, Egypt. The objective of this study was to evaluate the effect of different N2-fixing bacterial strains as bio-fertilizers such as Rhizobacterin, Biogein, Microbein and Nitrobein, with different levels of urea fertilizer (46% N) (0, 50, 100 and 150 kg /fed as well as their interactions treatments on the growth characters, herb yield and some chemical constituents of Rosmariuns officinalis L. plants. The grown plants were inoculated three times with 400 m L from each bacterial strain added with irrigation water. The first inoculation was applied one week after transplanting while the second and the third inoculations were applied one week after the first and the second harvesting cut, respectively. Meanwhile; the N-fertilization doses were added in three equal side dressings during the growing period. The first addition was after two weeks from transplanting meanwhile, the second and the third doses were added after two weeks from the first and the second cuts, respectively in both growing seasons. The results of the present investigation revealed that the plant height, mean number of branches / plant, fresh and dry weights of herb /cut were significantly increased as a result of inoculation with the different bacterial biofertilizers separately or in combinations the different urea fertilization rates in comparison with the control in the two cuts in both growing seasons. Furthermore, the application of the different N2-fixing bacteria and the different urea fertilization levels individually or in combinations caused a considerable improvement in the chemical composition of the plant such as NPK percentages in dried herb, photosynthetic pigments and in the fresh leaves, total carbohydrate content in the dried herb when compared with the untreated plants in the two cuts of both experimental seasons. The second investigation was carried out during two successive seasons 2014/2015 and 2015/2016 at the Experimental Farm of Faculty of Agriculture, Menoufia University, Shibin El-Kom, Egypt. The objective of this study was to estimate the effect of different organic manure (cattle, chicken and compost) with recommended doses of urea On Mentha Langfolia L . plants. The first addition was after two weeks from transplanting meanwhile, the second and the third doses were added after two weeks from the first and the second cuts, respectively in both growing seasons. The results of the present investigation revealed that the plant height, mean number of branches / plant, fresh and dry weights of herb /cut was significantly increased. Meanwhile; a considerable improvement in the chemical composition of the plant such as NPK percentages in dried herb, photosynthetic pigments and in the fresh leaves, total carbohydrate content in the dried herb when compared with the untreated plants in the two cuts of both experimental seasons.