Nitrogen fertilization of soya bean is usually limited to the starter rate. This results from the ability to plant self-supply in atmospheric nitrogen, thanks to symbiosis with nodule bacteria from the genus Bradyrhizobium japonicum. These bacteria do not occur commonly in Polish soils. Therefore it is of great importance to inoculate seed material of soya bean with the bacterial inoculant – Nitragina. In 2011-2013 a strict field experiment was conducted located at the Experimental Station of Varietal Testing in Przecław. The test plant was soya bean of the cultivar Aldana. The following factors were taken into consideration in the one-factorial experiment: the control, Nitragina, the starter rate of nitrogen (25 kg·ha^-1), Nitragina with the starter rate of nitrogen (25 kg·ha^-1). The aim of this study was to estimate the effect of application of Nitragina and nitrogen fertilization on the chemical composition of soya bean seeds. It was found that the used starter rate of nitrogen had a significant effect on increase in the total protein content in seeds as compared with the control. The ash content increased after the application of the bacterial inoculant – Nitragina. Significant differences in the amino acid composition of soya bean seeds were found only after the combined application of nitrogen fertilization and Nitragina. The seeds then contained the most glutamic acid and methionine and less cysteine. Nitrogen fertilization and the inoculant Nitragina did not have an effect on the content of crude fat, fibre, macroelements, zinc and copper in soya bean seeds. The application of Nitragina with the starter rate of nitrogen increased the iron content as compared with the content determined in seeds of plants fertilized with nitrogen. Manganese concentration decreased after the combined application of Nitragina with the starter rate of nitrogen, as compared with seeds harvested from the control.

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