In this paper investigations were carried out on two soil types (vertisol and brown forest soil) with different doses of applied N-fertilizer: diameter, N₆₀; N₉₀; N₁₂₀ and N₂₅₀. The potential ammonification in soil was obtained by arginine method. The following properties of soil were determined: pH value organic C, available NH₄-N and mobile-Al. The pH value in vertisol was 3.75-4.07; mobile-Al was 0.67-4.90 mg/100g; % organic C 1.38-1.46 and the content of available nitrogen was 4.4-11.2 ppm. The amount of released NH₄-N by arginine ammonification in this soil type was very low [(-0.12)-0.27mg/g^-1h-¹]. Correlation coefficients between released NH₄-N from arginine and soil pH were (-0.96*), mobile Al - (-0.99**), applied fertilizer doses - (-0.95*). In brown forest soil the amount of released NH₄-N by arginine ammonification was greater than in vertisol, ranging from 3.16 to 7.11mg/g-1h^-1. Correlation coefficients between soil properties and released NH₄-N from arginine were not statistically significant.