Effects of Nitrogen Management on the Yield of WinterWheat in Cold Area of Northeastern China

A plot experiment including four treatments, CK (N 105 kg ha-1 as urea, including a basal N application of 35 kg ha-1 and a topdressing N 70 kg ha-1 at turned green stage) and optimized N management (OPT1, OPT2 and OPT3, applied two-thirds, one-third and two-fifths N at jointing stage, respectively, total N 60 kg ha-1), was conducted to evaluate the effects of nitrogen management on growth and N uptake of winter wheat (Triticum aestivum), Dongnong 1, which is the first highly cold tolerant winter wheat in China. Index of population quality, N uptake and yield were determined. The ear-bearing tiller rate was increased by above 12%, and the leaf area index, biomass and N uptake were significantly decreased (P<0.05) at jointing stage. OPT treatments increased the grain to leaf area ratio at heading stage, the dry matter weight and N uptake after heading by 14.3-27.9%, 11.6-28.7% and 118.1-161.8 %, respectively. The yield of the OPT treatments was increased by 14.2-37.5% compared with CK, and there was a significant difference (P<0.05) between CK and OPT1 treatments. Harvest index and N partial factor productivity (PFP, kg grain yield per kg N applied) was clearly enhanced from 0.4 and 35.6 kg, respectively for CK to an average of 0.48 (P<0.05) and 77.6 kg (P<0.05) in the OPT treatments. These results indicated that the optimized N management increased the harvest index, yield and N use efficiency by decreasing the N application rate and postponing N application time, improved wheat population quality, controlled excessive growth in the vegetative stages and increased dry matter and N accumulation rates after heading.