Nitrogen accumulation, distribution and utilization characteristics of wheat at yield level of 9000kg/ha in rice-wheat rotation

Nitrogen (N) is one of the essential nutrients for wheat production. It is very important to figure out what are the definite characteristics of N accumulation, distribution and utilization in different yield level populations, which is much theoretical and practical meaning to agricultural production. In this study, these characteristics of wheat population at yield level of 9000 kg/ha (LV. 9000) were studied by agronomic management on the mediumgluten wheat, Yangmai 20 (Triticum aestivum L.), grown in rice-wheat rotation. The field experiments were performed at 32 combinations of two planting densities (150104 and 225104/ha) and different N managements, including N amount (210 and 262.5 kg/ha), the ratio of basis∶tillering∶elongation∶late topdressing of N (3∶1∶3∶3 and 5∶1∶2∶2), and N topdressing stage (flag leaves stage, booting stage, heading stage and anthesis). The results show that the LV. 9000 N accumulation amounts (NAA) at stages from the elongation to the anthesis, at the anthesis and at the maturity are 104-117, 197-205 and 234-251 kg/ha, respectively, which are significantly higher than those of other populations. The NAAs in leaves, stems and spikes at the anthesis and in grain at the maturity are respectively significant linear positive correlation with the grain yield, and are 89-91, 74-83, 32-33 and 177-188 kg/ha under the LV. 9000 The N translocation amount (NTA) from vegetative organ at anthesis to grain is significantly linear positive correlation with grain yield. The LV. 9000 NTAs from leaves, stems, and raches and hulls at the thesis to grain are 65-73, 53-54 and 16-20 kg/ha, separately. For the LV. 9000 in ricewheat rotation, the N amount to produce 100 kg of grain, N use efficiency and N harvest index are 2.9-3.0 kg, 32.9-34.5 kg/kg and 0.73-0.77, respectively.