Abstract
In order to determine the rate of initiative amount of ammonium sulfate fertilizer (0,20,25,50,100) Kg N/ha. The experiment was conducted using phenomena of biological nitrogen fixation, two cultivars of broad bean( vicia faba) were used "Egyption and Moroccian" In this study ,the response of the two cultivars were variable when locally isolated Rhizobium bacteria F2K22 was added as an inoculum in combination with different ammonium sulfate fertilizer rates. The results obtained showed remarkable homogeneity in the studied parameters [ percent of nitrogen in plant, Wight of root nodules, number of root nodules and root Wight ] ,which was agreed with previous studies either inoculated and noninoculated plants with the significant difference at 0.01 in an inoculated plants with Rhizobium inoculum locally isolated F2k22. Finally the result obtained from the two season experiments showed that the addition of 25 kg N/ha in combination with Rhizobium inoculum was the proper promotive rate, this indicates that the known rate 20 kg N/ha is not the proper rate under local conditions to fix nitrogen biologically