The Nitrotrifin preparation is a biological agent containing the Bradyrhizobium japonicum bacterial strain named ZA-Bj 19. The viability of bacterial cells in the preparation is not less than 1×1010 CFU/ml. The preparation is intended for use in agriculture and is applied to soybean crops. The bacteria included in the preparation contribute to the formation of biological nitrogen, which may enhance plant growth and development. The preparation is produced by Znamiansky Agrokhim, located in the city of Kyiv, Ukraine.