Nitrogen (N) supply and seed rate (SR) are two essential factors that affect the accumulation and partitioning of N and dry matter (DM) and, therefore, grain yield (GY) and N use efficiency (NUE). The objective of this experiment was to optimize N application and SR to regulate wheat growth and increase both GY and NUE. The results revealed that net photosynthetic rate (Pn), stomatal conductance (Gs), chlorophyll content, and activities of metabolic enzymes (NR and GS) significantly increased with increasing of N levels while decreasing SR. Plant tillers, GY, DM before anthesis, and N translocation, N agronomic efficiency (NAE), N recovery efficiency (NRE), and N uptake efficiency (NUPE) were highest in a combined treatment of N235 and SR180. However, N levels beyond 235 kg ha-1 significantly decreased NAE, NRE, and NUPE. By increasing SR from 135 to 180 kg ha-1 an increase of 12.9 % and 9.1% GY and NUPE, respectively, was observed. Based on this result, we estimate that 1 kg N ha-1 might be replaced by an increase of approximately 0.6 kg ha-1 SR. Our study suggested that using a combination of N and SR (N235 + SR180) could attain maximum GY and improve NUE parameters.
Keywords: N use efficiency; high yield; nitrogen application; seed rate; winter wheat.