The nitrogen assimilating bacterium Rhizobium species is naturally existing symbiotic nodule forming bacterium in the roots of Arachis hypogaea. In laboratory the In-vitro conditions it grows in the standard media called Yeast Extract Mannitol media. In this study experiment was set up using saturated solution of Mangnous sulphate (MnSO4). The bacterium Rhizobium species having pink nodulation activity in the plant of Arachis hypogaea (Groundnut) was aseptically inoculated in the presterilised Yeast Extract Mannitol broth and shake incubated for 48 hrs at room temperature.  One ml of this pure culture bacterium was serially diluted to 109 dilution. 0.1 ml of 109 dilution was aseptically spread inoculated on pre-sterilised petriplate containing media called Congo Red Yeast Extract Mannitol Agar (Cr.Y.E.M.A) plate having media thickness of 5mm. The petri plate was kept in fridge at 4OC for 5 minutes for diffusion. Pre-sterilised whatman filter paper - disc grade 1 was dipped in pre-sterile saturated solution of magnous sulphate (MnSO4) and placed in the centre of Cr.Y.E.M.A petri plate previously spread inoculated with pure culture of Rhizobium species. The petri plate was incubated at 32OC, for 72 hours. In vitro experimental observations for of MnSO4 no bacterial growth upto 2mm radial zone was observed from the periphery of the filter paper disc. Here it is necessary to note that compound MnSO4 of commercial grade are generally produced by companies for farmers to use in their farms.