Abstract: The spring wheat variety Jichun 34 was used to carry out the three-stage sowing experiment (S1, sowing on December 16, 2016; S2, sowing on January 13, 2017; S3, sowing on February 19, 2017) at Nanjing from 2016 to 2017. The nitrogen content, nitrogen accumulation, nitrogen vertical gradients in leaves and stem-sheaths of spring wheat in different spatial layers of canopy after anthesis, as well as the translocation amount of plant nitrogen, grain protein content and yield were studied in order to clarify the characteristics of nitrogen accumulation, distribution and translocation in plant canopy of spring wheat, and to determine the optimal sowing date in Jiangsu Province. The results showed that the vertical distribution characteristics of canopy nitrogen content were obvious in spring wheat. After anthesis, the plant nitrogen content of spring wheat decreased with the decrease of canopy height. Sowing date significantly affected the accumulation, distribution and translocation of canopy nitrogen. Compared with early sowing date (S1), the nitrogen content and accumulation in the 40−80cm layer of canopy of late sown spring wheat (S2 and S3) were significantly reduced; the peak time of vertical gradients of nitrogen in leaves and stem-sheaths was advanced to the anthesis and filling stage; and the peak spatial position was reduced to the middle and lower canopy; and the amount of nitrogen translocation was significantly reduced by 6.61%−29.12%. The middle and upper vegetative organs of early sown spring wheat canopies could maintain a larger vertical gradients of nitrogen in the late growth period, and promote the transfer of nitrogen. At the same time, during the growth period of late sowing spring wheat, the amount of total solar radiation and precipitation received decreased, the daily average temperature increased, the heat stress increased after anthesis, the duration of growth period decreased, and the absorption and translocation of nitrogen by plants decreased. The grain protein content of late sown spring wheat was 8.46%−9.82% lower than that of early sowing spring wheat, and the protein yield was 40.78−71.47g·m−2 lower. According to the characteristics of nitrogen distribution and translocation in spring wheat canopy, sowing date of S1 (16 December) is the best for spring wheat in Jiangsu Province.

Key words: Jiangsu province, Spring wheat, Sowing date, Nitrogen content, Nitrogen transportation