Abstract: Based on incubation tests under normal soil water condition and waterlogging,this paper discussed the effect of different combinations of urease inhibitor hydroquinone and nitrification inhibitors dicyandiamide and calcium carbide on the hydrolysis of soil urea, the adsorption,oxidation and volatilization of its released ammonia.as well as the emission of produced N₂O.It's indicated that hydroquinone in cooperation with dicyandiamide can both delay the hydrolysis of soil urea and make its released ammonia be conserved in soil witll more amount and longer period,and decrease the accumulation of soil nitrate, the loss of ammonia volatilization and the formation of nitrous oxide, which shows .that there probably exists a definite synergistic effect between urease inhibitor and nitrification inhibitor,and,to make full use of this effect will be beneficial to promote the efficiency of urea application and decrease the damage of its Nloss and environmental pollution.

Key words: Urease inhibitor, Nitrification inhibitor, Synergistic effect, Urea-N transformation, N₂O emission, Hydroquinone, Dicyandiamide, Calcium carbide, improved TOPSIS method, Zhangjiajie, early warning, grey GM (1,1) model, tourism ecological security