为探明施氮量对四川省同纬度不同海拔地区超级杂交稻产量形成及氮肥利用率的影响，以超级杂交稻泸优727和高产杂交稻内6优107为材料，在四川省汉源县（高海拔）、沐川县（中海拔）和泸县（低海拔）进行大田试验，研究不同施氮量（225、180、150、105、0 kg/hm²，分别记作N₁、N₂、N₃、N₄、N₀）对超级杂交稻产量形成和氮肥利用率的影响。结果表明，同纬度不同海拔地区间超级杂交稻产量差异较大。与泸县点和沐川点相比，汉源点超级杂交稻产量分别增加62.1%和84.1%，其增产优势主要表现在有效穗数、每穗粒数、齐穗前干物质、齐穗后干物质、总干物质和收获指数增加上。超级杂交稻产量对施氮量的响应随海拔高度的变化而改变。汉源点和沐川点4个施氮处理间超级杂交稻产量差异不显著；泸县点N₂处理超级杂交稻产量与N₁处理相当，N₃、N₄处理超级杂交稻产量较N₁处理分别显著降低6.7%和18.0%。超级杂交稻氮肥农学利用率和氮肥偏生产力随着氮肥减施量的增加呈显著增加趋势。与N₁处理相比，N₂、N₃和N₄处理超级杂交稻氮肥农学利用率分别增加6.8%~27.1%、27.9%~70.0%和37.3%~138.6%，氮肥偏生产力分别增加20.9%~25.5%、40.5%~53.6%和81.6%~118.8%。综合考虑超级杂交稻产量和氮肥利用率，汉源点和沐川点氮肥适宜减施量为20.0%~33.3%，泸县点氮肥适宜减施量为20.0%。

Field experiments were conducted at Hanyuan County (high altitude), Muchuan County (medium altitude) and Luxian County (low altitude) in Sichuan Province in 2022 in order to explore the effects of nitrogen (N) application rate on yield formation and N use efficiency (NUE) of super hybrid rice grown under different altitudes with same latitude. Super hybrid rice Luyou 727 and high yield hybrid rice Nei 6 you107 were grown under five N treatments (225、180、150、105、0 kg/hm²，named as N₁、N₂、N₃、N₄、N₀, respectively). Grain yield, yield components, dry matter and NUE were measured for each rice cultivar. The results showed that there were a large difference in grain yield among the three locations. The grain yield of super hybrid rice was 62.1% and 84.1% higher at Hanyuan County than that at Luxian County and Muchuan County, respectively. The higher grain yield observed for Hanyuan County were attributed to higher panicle number, spikelets per panicle, pre- and post-heading biomass production, total biomass and harvest index. The responses of grain yield of super hybrid rice to N application rate varied with the altitudes. There were not significantly differences in grain yield of super hybrid rice among four receiving N treatments in Hanyuan County and Muchuan County. Grain yield of super hybrid rice under N₁ treatment was 6.7% and 18.0% higher than that under N₃ and N₄ treatments, respectively, while the difference in grain yield of super hybrid rice between N₁ and N₂ treatment was relatively small. The agronomic efficiency of applied N (AEN) and partial factor productivity of applied N (PFPN) of super hybrid rice showed a significant increasing trend with the increasement of reduced N application rate. The AEN under N₂, N₃ and N₄ treatments were higher than that under N₁ treatment by 6.8%-27.1%, 27.9%-70.0% and 37.3%-138.6%, respectively; and the N₂, N₃ and N₄ treatments produced higher PFPN than that the N₁ treatment by 20.9%-25.5% and 40.5%-53.6% and 81.6%-118.8%, respectively. Comprehensively taken the grain yield and nitrogen use efficiency of super hybrid rice, the suitable reduction rate of N application is 20.0%-33.3% at Hanyuan County and Muchuan County, whereas the suitable reduction rate of N application is 20.0% at Luxian County.