Inducing nitrogen deficiency at early growth stages of wheat favors high yield and nitrogen recovery efficiency

Application of a dose of fertilizer nitrogen (N) at sowing of wheat is a widely adopted management strategy in Egypt and several wheat growing regions in the world. The objective of this investigation was to study the effect of delaying the application of this dose on yield and N use efficiency. The treatments in the field experiment conducted in 2018/19 consisted of applying 150, 200, 250 and 300 kg N ha(-1) in three equal split doses. In the second experiment conducted in 2019/20, 200 and 250 kg N ha(-1) were applied in three unequal split doses. In both the experiments, the first split dose was applied at 0, 10 or 20 days after sowing (DAS) while second and third split doses were applied at 30 and 50 DAS, respectively. The data indicated that applying the first dose of N at 0 DAS resulted in highest N uptake levels at 20 DAS. However, N uptake at later stages dramatically changed to reach highest when applying the first dose at 20 or 10 DAS. This was significantly reflected on grain yield and N use efficiency. For example, when a total of 250 kg N ha(-1) was applied in the second season, postponing the first dose from 0 to 20 DAS resulted in an increase of 10.5% in grain yield and 10% in N recovery efficiency. Thus, this study reveals that delaying application of the first dose of fertilizer N up to 20 DAS of wheat can result in increased fertilizer use efficiency.