| The laboratory experiment was conducted to investigate the impacts of biochar incorporation on soil nitrogen mineralization and the accumulation of inorganic nitrogen in loessal soil. The results illustrated that application of chemical nitrogen fertilizer significantly increased the accumulation of inorganic nitrogen in the soil and reduced nitrogen mineralization rates after the peak of inorganic nitrogen release. Compared with nitrate nitrogen fertilizer, amide nitrogen fertilizer and ammonium nitrogen fertilizer obviously reduced the nitrogen mineralization rate. Biochar additions reduced the ammonification, nitrification, net nitrogen mineralization rates by 64.9%，44.6%, and 47.7% after the peak of inorganic nitrogen release, repectively. Moreover, the inhibition effect of biochar on rates of nitrogen mineralization was high at low soil moisture content. However, there was no significant differences in nitrate fertilizer and ammonium fertilizers treatments. The biochar additions reduced cumulative inorganic nitrogen in either amide fertilizer or ammonium fertilizer treatment, especially under low soil moisture content. In summary, application of amide nitrogen fertilizer and ammonium nitrogen fertilizer combined with biochar reduced the accumulation of inorganic nitrogen efficiently, thereby reducing the risks of nitrogen losses. |