Optimizing nitrogen supply promotes biomass, physiological characteristics and yield components of soybean ( L. .).

Avoidable or inappropriate nitrogen (N) fertilizer rates harmfully affect the yield production and ecological value. Therefore, the aims of this study were to optimize the rate and timings of N fertilizer to maximize yield components and photosynthetic parameter of soybean. This field experiment consists of five fertilizer N rates: 0, 75, 150, 225 and 300 kg N ha arranged in main plots and four N fertilization timings: V (trifoliate leaf), R (full flowering stage) and R (full poding stage), and R (full seeding stage) growth stages organized as subplots. Results revealed that 225 kg N ha significantly enhanced grain yield components, total chlorophyll (Chl), photosynthetic rate ( ), and total dry biomass and N accumulation by 20%, 16%, 28%, 7% and 12% at R stage of soybean. However, stomatal conductance ( , leaf area index (LAI), intercellular CO concentration (i) and transpiration rate () were increased by 12%, 88%, 10%, 18% at R stage under 225 kg N ha. Grain yield was significantly associated with photosynthetic characteristics of soybean. In conclusion, the amount of nitrogen 225 kg ha at R and R stages effectively promoted the yield components and photosynthetic characteristics of soybean.