Abstract: A chamber culture experiment was conducted to measure soil nitrogen transformation following application of stabilized ammonium fertilizers in black soil and cinnamon soil. There were three application levels (0.20, 0.50, 1.00 g N·kg^-1 dry soil, respectively) of nitrogen fertilizer. The results showed that nitrification gradually delayed with the increased amount of ammonium application in the cinnamon soil. The treatment of 1.00 g N·kg^-1 significantly inhibited nitrification. Nitrification in the cinnamon soil occurred at day 3 and day 7 with 0.20, 0.50 g N·kg^-1 dry soil respectively. In the black soil, nitrification occurred at day 3 in all treatments, with nitrification potential decreasing with the increases of ammonium application amount. Nitrification maintained three weeks and two weeks under treatment of 0.20 g N·kg^-1 dry soil in cinnamon soil and in black soil, and maintained four weeks and three weeks under treatment of 0.50 g N·kg^-1 dry soil. The application with nitrification inhibitors 3,4-dimethylpyrazole phosphate (DMPP) of 1.0% of total nitrogen and dicyandiamide (DCD) of 4.0% of total nitrogen significantly inhibited nitrification, decreased nitrate concentration and nitrification potential. Our results suggested that nitrification would be inhibited as increased ammonium amount in cinnamon and higher than in black soil. In addition, nitrification was significantly inhibited under the ammonium addition rate of 0.20, 0.50 g N·kg^-1 dry soil with nitrification inhibitor. Therefore, for the nitrification inhibitor culture experi-ment, it is recommended that the amount of ammonium addition does not exceed 1.00 g N·kg^-1 dry soil, and the best concentration is 0.50 g N·kg^-1 dry soil.

Key words: ammonium N, ammonium chloride, nitrate N, nitrification potential, nitrification inhibitor