Response of Vegetative Growth Traits of Several Soybean Cultivars to Spraying with the Growth Regulator Triacontanol (TRIA)

Abstract

A field experiment was carried out in the fields of a farmer in the (Al-Boouda) area of Al-Karmah district - Al-Anbar Governorate during the summer season of 2022, to study the effect of spraying with several concentrations of the growth regulator (triacontanol) on the vegetative growth characters of soybean cultivars. The experiment was carried out in split plots arrangement, according to the RCBD design, with three replications. Four concentrations of growth regulator TRIA (0, 40, 50, 60) mg L−1 were allocated to the main plots, while three cultivars of soybean (Lee, Shama, Se-220) were allocated to the sub-plots. The result indicates that the Lee cultivar outperformed in most of the vegetative growth characters over the rest of the other cultivars such as the number of branches (6.91 branches Plant−1), plant height (98.08 cm), leaf area (38.62 cm2 Plant−1) and leaf area index (2.05). While the cultivar Shama was earlier to reached the stage of beginning flowering, and it took the least number of 57.00 days, compared to other cultivars. Whereas the cultivar Se-220 outperformed with highest mean of chlorophyll index in the leaves, reaching 37.43 spad. The results showed that the treatments sprayed with a growth regulator at a high concentration (60 mg L−1) were superior in most of the studied growth characteristics, and their average number of branches was (7.40 branches Plant−1), plant height (110.0 cm), and leaf area and leaf area index (44.87 cm2 Plant−1 and 2.38) respectively, and it needed the least number of days to reach the stage of the beginning of flowering at 58.33 days compared to the other concentrations. The results also indicated that the interaction between the study factors had a significant effect on most of the vegetative growth characters, where the Lee cultivar plant sprayed with a concentration of (60 mg L−1) of the growth regulator achieved the highest averages for several characters, including number of branches, plant height, and leaf area, while the two-way interaction did not affect significantly the number of days from planting to the beginning of flowering and the leaf area index.