Dynamics of different soil nitrogen pools after appIying different types of nitrogen fertilizers
不同氮肥施用后土壤各氮库的动态研究

The dynamics of different soil nitrogen pools after applying different types of nitrogen fertilizers were studied by pot experiment. The results show that the wheat biomass and nitrogen uptake have no significant difference by mixed application of Urea, NH_4HCO_3, (NH_4)_2SO_4, and Ca(NO_3)_2 with the same rate of nitrogen applied. Nitrifications of ammonia and urea type nitrogen fertilizers were completed in 14 days. The soil microbiomass N decreases with crop growth under Urea, NH_4HCO_3, and (NH_4)_2SO_4 treatments, which may be caused by crop uptake. The utilization of old fixed NH_4 by crop is weak. Soil fixed NH_4 is increased after the application of nitrogen fertilizers, and this kind of fixed NH_4 can be uptaken by crop in growing period. The apparent nitrogen recovery rate, loss rate and fixed rate have no significant difference among four nitrogen fertilizer types.