Three varieties (Aura, Magie, and Indra) of soybean (Glycine max [L.] Merr.) were grown in a small-plot experiment on a calcic chernozem with the application of two types of nitrogen fertilizers: ammonium nitrate (N_an) or carbamide (N_c). These fertilizers at the rate of 20 kg N/ha were applied before sowing together with potassium phosphate (60 kg P₂O₅/ha). The microbial nitrification capacity and the activity of enzymes related to the nitrogen cycle (urease and nitrate reductase) were measured in the rhizosphere (0–20 cm) at the stage of soybean flowering. It was determined that the biological (enzyme) activity of the calcic chernozem in the soybean rhizosphere was more intense on the plots with the N_an fertilizer than on the plots with the N_c fertilizer. The urease activity depended on the type of nitrogen fertilizer (N_an or N_c) under the conditions of soil water deficiency. In the soil under the Aura variety, the urease activity was significantly lower in the treatments with N_c application, and this was accompanied by a decrease in the crop yield. The nitrification capacity of the calcic chernozem was generally low; in the case of the N_c fertilizer, it was significantly lower than in the case of the N_an fertilizer. The nitrate reductase activity of the soil was also lower in the case of the N_c fertilizer. Each of the three soybean varieties had its own response to changes in the nitrogen nutrition aimed at improving the soybean tolerance to fluctuations in the soil water content during the growing season.