The soils of the serozem belt in the Zeravshan Valley are characterized by low nitrogen content, necessitating the application of nitrogen fertilizers to achieve high agricultural productivity. The main challenge in using nitrogen fertilizers on the sloping soils of the region is significant nitrogen losses due to leaching by surface runoff and irrigation water, as well as volatilization. These losses can exceed 50% of the applied amount. One promising approach to minimizing these losses is the combined application of nitrogen fertilizers with nitrification inhibitors. As part of the conducted research, the effect of the nitrification inhibitor 1-carbamoyl-3(5)-methylpyrazole (CMP) on the dynamics of urea losses was studied when applied to various crops cultivated on soils prone to irrigation-induced erosion and nitrification. Microfield experiments were carried out on typical serozems (under tobacco and cotton) and meadow-serozem soil (under corn), with plots located in the upper parts of slopes. Nitrogen fertilizers were applied against a background of phosphorus-potassium nutrition in the form of urea labeled with the stable isotope 15N (25 at.% excess). The use of the nitrification inhibitor in combination with a single application of the full dose of nitrogen fertilizer led to a significant increase in crop yields: tobacco by 17.6%, seed cotton by 31.2%, and corn (green mass) by 25.1%. The inhibitor allowed for a 30% reduction in nitrogen application rates and decreased the frequency of fertilizer applications without compromising yield compared to regional standards. Furthermore, CMP improved nitrogen uptake efficiency by plants, enhanced nitrogen immobilization in the soil, and reduced losses due to leaching and gaseous emissions. It was found that the proportion of fertilizer-derived nitrogen in total plant uptake increased, while the share of soil-derived nitrogen decreased.