A method for preparing a concentrated inoculating composition which contains a universal use culture medium which is sterilized and cooled, then added to Rhizobium Japonicum and then allowed to multiply for 46 hours. This is followed by the addition to the culture medium of powdered maltose, liquid maltose and lactose saccharides as well as the fungicide potassium sorbate. The general use culture medium can comprise previously treated peat as one of its components. The above results in an inoculating composition for use with leguminous plants with or without peat incorporated as part of the general use culture medium.