Effect of Gibberellic Acid Spraying and Different Planting Dates on Vegetative Growth Traits, Yield, and Its Components in Sweet Corn Hybrids

Abstract This experiment was conducted at the Horticulture and Landscape Engineering Department’s Research Station/Open Field, College of Agriculture, Tikrit University, during the spring agricultural season of 2024. The experiment aimed to study the effect of spraying gibberellic acid (GA3) at different planting dates on the growth traits and yield of sweet corn hybrids. The objective was to ascertain the ideal concentration of gibberellic acid, the most advantageous planting date, and the superior hybrid. The experiment included three factors: the first factor, gibberellic acid (GA3) sprayed with water only, 50 and 100 mg L −1 ; the second factor, two planting dates, 15/3 and 1/4; and the third factor, hybrids: Sweet Spirit, 007R, SS3006, and 6800R. The experiment was executed utilizing a split plot approach within a randomized complete block design (RCBD) featuring three replicates. Gibberellic acid was placed on the main plots, while planting dates occupied subplots, and the hybrid was taken as the most important in the sub-secondary plots. Statistical analysis of the experimental data was conducted using the SAS software package, and mean comparisons were performed using Duncan’s multiple range test at a significance level of 0.05. The results showed that spraying with a concentration of 100 mg L −1 of gibberellic acid was superior in most of the growth characteristics and yield and its components studied (plant height, number of leaves, leaf area, chlorophyll concentration in leaves, cob length, cob diameter, fresh cob yield with sheaths, and percentage of total sugars in grains), amounting to 125.1 cm plant −1 , 9.700 leaves plant −1 , 3434.9 cm 2 plant −1 , 1.126 mg g −1 fresh weight, 19.46 cm cob −1 , 45.67 mm cob −1 , 13.04 tons ha −1 , and 8.269%, respectively. As for planting dates, the results showed that the planting date of 1/4 excelled in most growth characteristics, and the yield reached 123.1 cm plant −1 , 9.278 leaves plant −1 , 3283.9 cm 2 plant −1 , 0.9155 mg g −1 fresh weight, 19.00 cm cob −1 , 44.45 mm cob −1 , 12.96 tons ha −1 , and 7.752%, respectively. Regarding the effect of hybrid treatments, the results of the experiment showed that the hybrid SS3006 outperformed the other hybrids in most growth and yield traits, as the number of leaves reached 9,322 leaves per plant, the leaf area reached 3,378.9 cm 2 per plant, the chlorophyll concentration in the leaves reached 1.136 mg g −1 fresh weight, the cob length reached 19.36 cm per cob, the cob diameter reached 46.50 mm per cob, the yield of fresh cob with sheaths reached 13.46 tons per hectare, and the percentage of total sugars in grains reached 8.226%, while the hybrid 6800R outperformed in the plant height trait, recording 128.2 cm per plant. Regarding bi-interactions between gibberellic acid and hybrid, these interactions resulted in substantial differences. The interaction treatment was superior when spraying at a level of 100 mg L −1 of gibberellic acid and planting on 4/1. As for bi-interaction between gibberellic acid and hybrid, the interaction treatment when spraying at a level of 100 mg L −1 , and the hybrid SS3006 was superior in most of the studied traits. As for the interaction between planting dates and sweet corn hybrids, the interaction treatment between the sowing date of 1/4 and the hybrid SS3006 was superior in most growth traits, yield, and its components. Regarding the interaction of the three study factors—gibberellin acid, planting dates, and hybrid—the triple interaction treatment of spraying 100 mg L −1 of gibberellin acid, planting on 1/4 of the spring season, and hybrid SS3006 achieved significant excellence in most growth traits, yield, and its components compared to the other interactions.