中文摘要：

【目的】评价不同施氮量下不同肥力土壤在小麦孕穗期的土壤活性氮组分（土壤矿质氮、可溶性有机氮和微生物量氮）的转化与氮肥利用率的变化。【方法】以长期（37年）定位试验下不同施肥处理土壤（贫瘠土壤-NF：长期不施肥;低肥力土壤-LF：长期施用化肥;中肥力土壤-MF：长期施用低量有机肥配施无机肥;高肥力土壤-HF：长期施用高量有机肥配施无机肥）为研究对象,通过盆栽试验,利用~（15）N示踪法,研究添加外源硫酸铵氮肥（N0：0 kg·hm^-2、N1：135 kg·hm^-2、N2：180 kg·hm^-2）之后,小麦生长旺盛时期（孕穗期）土壤活性氮组分在不同肥力土壤中的变化以及与土壤供氮效应之间的联系。【结果】随施氮量增加,不同肥力土壤的可溶性氮均呈先增加后降低的趋势,在N1处理最高,而各处理的土壤微生物量氮在N2达到最大,N1最低;不同肥力土壤可溶性氮变化均为高肥力土壤〉中肥力土壤〉低肥力土壤〉贫瘠土壤,而微生物量氮变化均为高肥力土壤〉中肥力土壤〉贫瘠土壤〉低肥力土壤（P〈0.05）;施氮对不同肥力土壤可溶性氮和微生物量氮的影响在低肥力土壤最大,而在高肥力土壤增幅最小。不同肥力土壤供氮量、氮肥利用率以及吸氮总量和吸~（15）N量的变化均为高肥力土壤〉中肥力土壤〉低肥力土壤〉贫瘠土壤（P〈0.05）,其中,吸收~（15）N量所占小麦吸收总氮的百分比大小变化为低肥力土壤〉中肥力土壤〉高肥力土壤〉贫瘠土壤（P〈0.05）。相同肥力不同处理下,土壤供氮量、氮肥利用率以及小麦吸氮量和吸~（15）N肥料的量随施氮量的增加呈先增加后降低的趋势,均以N1处理显著高于其他处理（P〈0.05）,总体上施氮处理下小麦吸肥料氮所占吸收总氮的百分比的平均值为44%;各肥力土壤中肥料损失量均为贫瘠土壤〉低肥力土壤〉中肥力土壤〉高肥力土

英文摘要：

[Objective] The objective of this study is to research the effect of different nitrogen （N） application rates on soil labile N pools transformations （soil mineral N-SMN; soil soluble N-SSON; soil microbial biomass N-SMBN） and N use efficiency in soils after application of N fertilizer at wheat （Triticum aestivum L.） booting stage. [Method] A pot experiment with 15N isotopic tracer technique was conducted to study the soil labile N pools and the effect of supply N in different fertilization managements for 37 years （poor soil-NF： no application of fertilizer; low fertility soil-LF： inorganic fertilizer; moderate fertility soil-MF： low rate of organic fertilizer with inorganic fertilizer; high fertility soil-HF： high rate of organic fertilizer with inorganic fertilizer） after application of three different application rates of N （NO： 0 kg·hm-2, NI： 135 kg.hm2, N2：180 kg·hm2） in soil and their relationships. [Result] SMN and SSON were the highest in the N1 treatment and then decreased with the application rate of N, but SMBN performed opposite tendency with the application rate of N, they were firstly decreased and then increased, and the highest in the N2 treatment. In the same application rate of N, SMN and SSON generally decreased in the order： high fertility soil〉moderate fertility soil〉low fertility soil〉poor soil, while SMBN generally decreased in the order： high fertility soil〉moderate fertility soil〉poor soil〉low fertility soil （P〈0.05）. The increased amplitude of SMN, SSON and SMBN after addition of N into soils with different fertilities were the highest in the low fertility soil treatments, and were the lowest in the high fertility soil treatments. The soil N supply, NUE, N uptake by wheat and assimilated 15N-labeled fertilizer generally decreased in the order： high fertility soil 〉 moderate fertility soil〉low fertility soil〉poor soil （P〈0.05）, respectively. The percentage of N from ammonium sulfate fertilizer by wheat to total N upt