Two field experiments were conducted at Agricultural Research Farm of the Faculty of Agriculture, Benha University, Egypt, during two growing seasons of 2018 and 2019 to study the effect of sowing dates (May 5, May 20 and June 3), three gibberellin concentrations (0, 50 and 100 ppm) and their interaction on growth attributes of soybean (Giza 111 cultivar). The outcome of this study indicated that early planting date (May 5) improved plant height and No. of pods (at 70 and 90 days after planting) and improved the absolute growth rate (AGR) and net assimilation rate (NAR) relatively to the other treatments (p < 0.05). Furthermore, applying GA3 (100 ppm) recorded the maximal values of the growth parameters, except RGR and chlorophyll content which were at 0 and 50 ppm. At 90 DAP, the tallest plants (120.54 cm), No. of leaves/plant (34.11), No. of pods/plant (55.09), and dry weight of stem (21.67 g), pods (23.55 g) and plant (68.75 g) were obtained following the combined effect of May, 5 planting date and GA3 at 100 ppm.Whereas the interaction between the early planting date and GA3 at 50 ppm produced the maximum values of the AGR (1.074 g/day), RGR (0.019 g/day) and NAR (1.074 g/day). |
