Mineral nutrition and plant ontogeny influence both the physiological balance between nutrients in a plant and determine the proper nutritional status of a plant, which is necessary to realize the yielding potential of a cultivated species. The aim of the present study was to assess the effect of nitrogen doses (0, 4, 8, 12, 16 g N·m−2) and plant development phases (the beginning and full flowering) on the content of macroelements and changes in ionic ratios occurring in the herb of the summer savory cv. ‘Saturn’. The two-factor experiment was carried out in a random-block design with five replications. The mineral nitrogen nutrition applied increased the concentration of total nitrogen and its mineral forms in the plants. There was a change in ion homeostasis in the individual stages of the ontogenesis process, i.e., a higher content of P, K, Ca, and S in the initial flowering phase as well as Mg and Cl in the full flowering phase. The increase in the availability of mineral nitrogen in the soil solution caused a decrease in total sorption capacity, reducing the potential of the soil for saturation with alkaline cations.