[Objective] To study changes in microbiological characteristics of Albic soil by regulating nitrogen application levels during the critical periods of maize growth .[Method] Different levels of nitro-gen (0, 150, 200 and 250 kg· hm -2) were applied to the maize field.The dynamic changes in the microbial biomass carbon , microbial biomass nitrogen and the activities of urease , alkaline phosphatase , protease and catalase from typical Albic soil in mid-temperate zone of eastern China under different nitro-gen levels during the maize production process were studied .[Result]Urea application increased urease activity in Albic soil at seedling stage by activating microorganisms related with urease release .Higher nitrogen level increased alkaline phosphatase activity at seedling stage .With the growth of maize , phos-phatase activity clearly decreased under different nitrogen levels , however , phosphatase activity increased with no nitrogen added .Urea addition at the initial stage was not beneficial for the improvement of cata-lase activity , but with the growth of maize , catalase activity increased under different nitrogen levels .At seedling stage , protease activity increased with the increase of nitrogen level , but decreased when the nitrogen level reached 250 kg· hm-2 .When the maize was mature , no nitrogen or low amount of nitro-gen application was more beneficial for the improvement of protease activity .Urea as a base fertilizer reduced microbial biomass carbon ( MBC ) content at seedling stage , while with the growth of maize , nitrogen application helped the preservation and stability of MBC .No nitrogen or excessive nitrogen appli-cation increased microbial biomass nitrogen (MBN) content, while appropriate amount of nitrogen promo-ted MBN to turnover and convert into available nutrients for plants .[Conclusion]The concentrated and excessive application of urea is not helpful to the preservation of soil biological fertility .Considering maize yield and soil fertility improvement , the appropriate amount of nitrogen application level in Albic soil is 200 kg· hm -2 .%【目的】结合玉米生育的关键时期，通过施氮水平的调控探究白浆土微生物学特性的规律变化。【方法】以玉米试验田为研究对象，通过不同施氮水平（0、150、200和250 kg· hm－2）的设置，研究中温带典型白浆土微生物生物量碳、氮以及脲酶、碱性磷酸酶、蛋白酶和过氧化氢酶活性对当季玉米生产过程不同施氮水平的动态响应。【结果】尿素的施入能够在玉米苗期激活释放脲酶相关的微生物，使脲酶活性增强，其作为底物，较低用量更易获得玉米拔节期较高的脲酶活性；在玉米苗期，施氮量增加有利于碱性磷酸酶活性的提升；随玉米的生长，施氮使碱性磷酸酶活性明显下降，不施氮反而会使该酶活性有所提升；尿素添加在起初阶段并不利于过氧化氢酶活性的改善，但随玉米的生长，不同施氮水平下过氧化氢酶活性均呈增加趋势；在玉米苗期，随施氮水平增加，蛋白酶活性也增加，但当施氮量增至250 kg· hm－2时，蛋白酶活性有所降低；当玉米成熟后，不施氮和低量施氮更有利于蛋白酶活性的提升。尿素基施能够在玉米苗期降低微生物生物量碳（ MBC）的水平，但随玉米的生长，施氮有利于MBC的保蓄和稳定；不施氮或过量施氮均有助于白浆土微生物生物量氮（ MBN）的提升，而适量供氮则更利于其周转，向植物可利用的方向转化。【结论】集中过量施用尿素不利于土壤生物肥力的保蓄，综合考虑玉米产量及培肥效应，白浆土适宜的氮素用量应为200 kg· hm－2。
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