Influence of Leonardite Incorporation on Nitrification and Nitrate Ammonification

Nitrogen turnover is one of the dynamic process in soil which NO-3, NO-2 and NH4+ may be converted to each other by nitrification or nitrate ammonification in a relatively short time. In certain cases farmers want to break the nitrification process to prevent nitrogen losses mainly by denitrification. Alternatively, in some cases farmers want to stimulate nitrate occurrence from ammonium based fertilizers due to the official limitations of nitrate usage. This incubation experiment was conducted to determine whether leonardite could be used for this purpose. To evaluate nitrification or nitrate ammonification rate as a function of leonardite application, either KNO3 or (NH4)2SO4 applied to the soil at 300 mg N kg-1 with different leonardite doses as 0, 10, 20 and 40 metric ton ha-1. Preliminary results revealed that effectiveness of leonardite on nitrogen cycle is rather minor; therefore, it should not be considered for interrupting agent for nitrogen cycle