Abstract
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(-1) arranged in main plots and four N fertilization timings: V-5 (trifoliate leaf), R-2 (full flowering stage) and R-4 (full poding stage), and R-6 (full seeding stage) growth stages organized as subplots. Results revealed that 225 kg N ha(-1) significantly enhanced grain yield components, total chlorophyll (Chl), photosynthetic rate (P-N), and total dry biomass and N accumulation by 20%, 16%, 28%, 7% and 12% at R-4 stage of soybean. However, stomatal conductance (g(s)), leaf area index (LAI), intercellular CO2 concentration (Ci) and transpiration rate (E) were increased by 12%, 88%, 10%, 18% at R-6 stage under 225 kg N ha(-1). Grain yield was significantly associated with photosynthetic characteristics of soybean. In conclusion, the amount of nitrogen 225 kg ha(-1) at R-4 and R-6 stages effectively promoted the yield components and photosynthetic characteristics of soybean. (C) 2021 The Authors. Published by Elsevier B.V. on behalf of King Saud University.