Effect of postponing N application on soil N supply, plant N uptake and utilization in winter wheat

Field experiment was carried out to investigate postponing N application on soil N supply, plant N uptake and utilization in winter wheat. Results obtained showed that, compared with farmers practice (N 300 kg/ha, 1/2 basal and 1/2 topdressing at jointing stage, respectively), postponing N application treatment (N 210 kg/ha, 1/3 basal, 1/3 topdressing at jointing stage and 1/3 topdressing at booting stage, respectively) improved N use efficiency greatly, and minimized apparent N losses without grain yield losses. Excessive N application (N 300 kg/ha) increased NO3--Ncontent below 60 cm soil profile at different growth stage, which would result in high risk of NO3--Nleaching into underground water. Postponing N application increased nitrate accumulation in the soil of 0-20 cm and reduced nitrate accumulation in 20-100 cm soil profile. Therefore it was concluded that postponing N application based on plant N uptake at different growth stage is a feasible N management practice, and nitrogen fertilizer could be saved by 30% as compared with farmerspractice.