The experiment reported in this paper was carried out to determine the amount of nitrogen fixed from the air by nodule bacteria associated with soybean roots. The soybean plants were sown in Mitscherlich pots filled with the "terra-roxa-misturada" type of soil that had received the following treatments: 1) check; 2) NPK; 3) NPK 4- limestone; 4) NPK + inoculant; 5) NPK + limestone + + inoculant; 6) PK + limestone + inoculant; and 7) PK + limestone. When the plants started to blossom, both the aerial part, as well as the roots were collected separately, dried, and analysed for their nitrogen content. The soil was also analysed prior to planting and after the plants had been harvested. The results indicated that under the conditions of the experiment the symbiotic association - nodule bacteria plus soybean - did not show, a great capacity for fixing nitrogen from the air.