The results of numerous scientific studies indicate that long-term mineral nitrogen fertilization caused soil acidification. Knowledge of impact of individual contributors to the soil acidification is very important in order to maintain soil productive function through sustainable management practice. The aim of this thesis was to determine the influence of soil depth, increasing doses of nitrogen fertilization, soil texture and content of calcium and magnesium ions on the vertical variability of soil reaction in Stagnosols. The study included analysis of soil samples collected up to two meters depth in 2007 and 2008 from long-term experimental field located central part of Croatia with four nitrogen treatments in the range of 0-300 kg N/ha. The results indicate that increasing doses of applied nitrogen significantly influenced on soil acidification up to 50 cm depth in 2007 and 2008. In surface soil layer in 2007, the application of 200 kg N/ha contributed to reduction of soil reaction for 1.5 pH units, and the application of 300 kg N/ha in 2008 reduced the soil reaction for 0.7 pH units. Also, significant influence of soil depth was recorded. Soil reaction increased significantly with increase soil depth due to carbonate leaching in dipper soil layers. The decrement of clay, silt and sand content increase soil reaction which was in the strong and positive correlation with the content of the investigated cations (pH vs Ca2 +, r = 0.661; pH vs Mg2 +, r = 0.691).