NitroDar is a biological preparation intended for use in agriculture. The preparation contains Bradyrhizobium japonicum strain TA-11 Nod+ bacteria with a titer of not less than 3×10^9 per 1 g of the preparation. The biological preparation NitroDar is used to enhance the growth and development of soybean crops by fixing nitrogen from the air. The preparation is supplied in powder form, which ensures ease of storage and application. Use of the biological preparation contributes to increased yields and improved product quality without the use of chemical fertilizers.