Available nitrogen in the surface mineral layer of Serbian forest soils

Abstract

Based on a greenhouse experiment, we evaluated nitrogen availability in the surface mineral layer of soil under various deciduous forest stands by analysing the following soil characteristics: total organic C, total N, initial content of easily available N inorganic forms, mineralized N content obtained by aerobic and anaerobic incubations and A-value. The experiment was performed on a test plant and through the application of urea enriched with 5.4% 15N. The studied forest soils are characterized by high mineralization intensity and high N availability indices. Aerobic incubation appears to be the most appropriate method for evaluating the available N content. The amounts of mineralized and nitrified N, obtained by aerobic incubation, with subtraction of the initial content of available mineral N forms are in correlation (P ≤ 0.05) with total organic C content (r = 0.916) and total soil N (r = 0.903) while the correlation with the C/N ratio is poor (r = 0.645).