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: V5 (trifoliate leaf), R2 (full flowering stage) and R4 (full poding stage), and R6 (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 R4 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 R6 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 R4 and R6 stages effectively promoted the yield components and photosynthetic characteristics of soybean.
Keywords: Ci, intercellular CO2 concentration; DW, dry weight; E, transpiration rate; GM, grain mass; GNP, grain number per pod; GY, grain yield; Grain yield; J, journal; LAI, leaf area index; Nitrogen rates; PN, photosynthetic rate; PNP, pod number per plant; PPFD, photosynthetic photon flux density; Photosynthetic characteristics; R2, R4 and R6, reproductive stage; TCC, total chlorophyll contents; TN, total nitrogen; Timing; V5, Vegetative stage of five trifoliate leaf; g, grams; gs, stomatal conductance.
© 2021 The Authors.