Abstract: 【Objective】This research was conducted to determine the effects of nitrogen fertilizer rate and ratio of base and topdressing on fertilizer-N use efficiency (N fertilizer accumulation in plant/N supplied, FNUE), wheat(Triticum aestivum L.) grain yield, and fertilizer N residue in 0~200cm soil layers under high-yield condition, so to choose appropriate nitrogen rate and ratio of base and topdressing, considering profitable yield, efficient N fertilizer utilization, and reduction of possible environmental effects.【Method】15N isotope tracing experiment was conducted in PVC cylinders (2.05m length, Ф0.2m, without bottom). The 15N isotope tracing experiment had seven treatments: without applying N fertilizer (N0); N application rate of 168 kg N per ha (0.527g/pot), ratios of base and topdressing N fertilizer were 1/2:1/2, 1/3:2/3 and 0:1, which denoted N1, N2, and N3; N application rate of 240 kg N per ha (0.753g/pot), ratios of base and topdressing N fertilizer were 1/2:1/2, 1/3:2/3 and 0:1, which denoted N4, N5, and N6. 【Result】The results showed that on high-yield condition this study concerned, applying N fertilizer significantly increased grain yield and protein content, and treatment N2 and treatment N5, N6 gain higher grain yield and grain protein content; Treatment N2 enhanced FNUE significantly and decreased fertilizer-N residue rate and losses rate. 15N tracer experiment showed that increasing in basal or topdressing fertilizer-N amount increased fertilizer N residual amount in the soil of 0~200cm, and increased fertilizer N movement depth. At jointing, basal fertilizer N residual amount proportion in 0~40cm, 40~100cm, and 100~200cm to total basal fertilizer N residual amount were 58.8%~76.1%、23.9%~38.2% and 0%~11.8%, and basal fertilizer N residue of treatment N1, N5 were found in 120~140cm, and that of treatment N4 was in 140~160cm. At anthesis, basal fertilizer N residual amount proportion in 0~40cm to total basal fertilizer N residual amount decreased and that in 40~200cm increased, and basal fertilizer N of treatment N4 was moved to 160~180cm. Topdressing fertilizer N residual amount proportion in 0~40cm to total topdressing fertilizer N residual amount was 70.3%~91.2%, and did not find topdressing fertilizer N in 100~200cm. At maturity, basal fertilizer N residual amount proportion in 0~40cm, 40~100cm, and 100~200cm to total basal fertilizer N residual amount were38.3~48.7%、39.7%~51.3%和0%~22%; Topdressing fertilizer N of treatment N3, N6 were moved to 160~180cm and 180~200cm respectively, and treatment N4, N5 were to 140~160cm. Basal and topdressing nitrogen of treatment N2 were not inspected in 100~200cn soil layers in whole growth stage. 【Conclusion】 as far as grain yield, FNUE, fertilizer N residue in 0~200cm soil layers, and fertilizer N loss be concerned, the most appropriate nitrogen fertilizer applying regime recommended is treatment N2, its nitrogen fertilizer rate is 168 kg•ha-1 and ratio of base and topdressing is 1/3:2/3.

Key words: Nitrogen fertilizer rate, Ratio of base and topdressing, 15N, Wheat, Yield, Fertilizer nitrogen fate