Effect of Foliar Application of Gibberellic Acid at Different Concentrations on Growth, Yield and Quality of Soybean (Glycine max L) under Semi-Arid of Kabul conditions

Abstract : Soybean (Glycine max L.) is one of the most important legume crops cultivated worldwide for its high-quality protein and oil content. Using the Plant Growth Regulators (PGRs), particularly gibberellic acid (GA₃) for foliar application, is considered to have great potential in enhancing the yield of soybeans. This study was conducted to investigate the effect of foliar-applied GA₃ on the growth and yield of soybean under the semi-arid condition prevailing in the Kabul University research farm during the 2025 growing season (May-September). Different concentrations of GA₃, such as 0, 50, 100, and 150 ppm, were used at the V6, pre-flowering, and pod-setting stages. The results showed that GA₃ application significantly influenced the growth performance, yield attributes and, seed quality. The plants treated with 150 ppm produced the tallest plants (64.14 cm). The maximum branch number (6.1) and leaf area (42.4 cm²) were recorded in plants treated with 100 ppm GA₃, and there was no significant difference between 100 and 150 ppm. The maximum number of pods per plant (60.35), seed yield (2967.3 kg ha), harvest index (43.4%), 100-seed weight (15.17 g), and seeds per pod (3.07) were noted in plants treated with 150 ppm. However, for all these parameters, there was no significant difference between 100 ppm and 150 ppm treatments. Protein and oil contents were highest in the 100-ppm treatment (38.03 and 19 %).