中文摘要：

【目的】大豆结瘤固氮和产量对氮肥的反应不同，实际上是由于大豆共生固氮系统及其根系系统对土壤无机氮浓度的感知不同造成的。通过对不同土壤无机氮浓度下大豆结瘤、固氮及产量影响的研究，探索能提高大豆产量、结瘤和固氮的土壤无机氮浓度，即掌握土壤无机氮浓度与大豆共生固氮和产量的数量关系，为调控氮肥施用量及施用时期、预测氮肥对大豆共生固氮能力和产量的影响提供理论依据。【方法】采用盆栽土培试验方法，分别在第一片复叶充分生长（V2期）、始花期（R1期）、始荚期（R3期）和始粒粒（R5期）一次性施用不同量的氮肥，从而形成不同无机氮浓度的土壤。利用获得的不同无机氮浓度土壤为供试土壤，对各生育时期根瘤数量、干重和固氮酶活性及成熟期产量及其构成因子进行调查，明确大豆根瘤固氮和产量对土壤无机氮浓度的响应，掌握土壤无机氮浓度与氮肥及与大豆固氮和产量的数量关系。【结果】不同时期土壤无机氮浓度处理下的根瘤干重、数量和固氮酶活性均随着大豆生育时期的推进在R4期时达到最大值。R6期时大豆平均根瘤干重、数量和固氮酶活性均表现为：V2期＞R5期＞R3期＞R1期，较CK处理根瘤平均干重分别下降15%、18%、17%和32%；根瘤数量下降13%、18%、19%和20%；固氮酶活性下降19%、22%、23%和32%。不同生育时期土壤无机氮浓度与R6期大豆根瘤干重、数量和固氮酶活性间均具有显著的线性负相关关系，即土壤无机氮浓度越大对根瘤干重、数量和固氮酶活性的抑制作用越大。大豆干物质积累量和产量的变化趋势均表现为：R1期＞R3期＞V2期＞R5期。除R5期不同土壤无机氮浓度处理与CK处理间的生物量和产量差异不显著外，V2、R1和R3期不同土壤无机氮浓度处理，均显著地促进大豆生物量和产量的增加。不?

英文摘要：

[Objective]The response of N2 fixation and yield to N fertilizer, even with same N application rate, gives varyingand contradicting results. The contradicting results depend on the perception of the system of soybean nitrogen fixation and root to the soil inorganic N concentration. The nodulation, fixation and yield of soybean with different soil inorganic N concentrations were studied to find the reasonable soil inorganic N concentration for promoting soybean yield, nodulation and fixation. i.e. to master the quantified relationship between soil inorganic N concentration, nodulation and fixation. Then it will have a significant theory and production meaning for adjusting N application rate, timing, and forecasting the effect of N fertilizer on the fixation and yield. [Method]A pot experiment was conducted to study the effects of different soil inorganic nitrogen concentrations, which derived from total fertilizer N （as urea） applied at vegetative stage （V2）, at early blooming stage （R1）, at early podding stage （R3） and at grain filling stage （R5）, on the ability of N2 fixation and yield, by measuring the nodule number, biomass and nitrogenase activity and yield components. Through the research, the response of soybean nodulation and yield to soil inorganic N concentration cleared, and thus mastering the quantity relationship between soil inorganic N concentration and N application, nodulation and yield, and then providing a theoretical basis for agriculture production and scientific research.[Result]The nodule number, biomass and nitrogenase activity of soybean reached peak at R4 stage, while decreased at R6 stage, and the nodule number, biomass and nitrogenase activity were in order of V2〉R5〉R3〉R1. The nodule biomass decreased by 15%, 18%, 17%and 32%compared to that of CK. The nodule number decreased by 13%, 18%, 19%and 20%. The nitrogenase activity decreased by 19%, 22%, 23% and 32%. Meanwhile, there were significant negative linear correlations between nodule number, biomass and nitr