Optimizing Nitrogen and Seed Rate Combination for Improving Grain Yield and Nitrogen Uptake Efficiency in Winter Wheat.

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 NU E . 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 (NA E ), N recovery efficiency (NR E ), and N uptake efficiency (NUP E ) were highest in a combined treatment of N 235 and SR 180 . However, N levels beyond 235 kg ha -1 significantly decreased NA E , NR E , and NUP E . 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 (N 235 + SR 180 ) could attain maximum GY and improve NU E parameters.