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.