Effect of gibberellic acid on postharvest of sunflower and its potassium fertilization in alkaline soil

Abstract

Sunflower is a crop that is used as ornamental, oleaginous, forage, and currently as a bioremediation plant, of hard water affected soils. For this reason, the main objective of this investigation was to study the effect of potassium fertilization on yield under field conditions, and the effect of gibberellic acid (GA₃), at postharvest of inflorescences. Two experiments were established, under field and laboratory conditions. In the field experiment, four levels of potassium, 0, 50, 100 and 150 kg/ha were evaluated, under a randomized complete block design and four replicates (4×4) = 16 experimental units. The variables evaluated were agronomic and biological yields, harvest index, leaf area index and intercepted radiation. The variables in the laboratory were: diameter of the stem, basal diameter of the stem, weight of tubular flowers, vase life and days at opening of the capitulum. Treatments consisted of six levels of GA₃ and five replicates (6×5) = 30 experimental units, evaluated under a completely randomized design. The results indicated, that the maximum values for agronomic and biological yields were obtained with the application of 150 kg/ha of potassium. The maximum intercepted radiation was reached at 90 days after sowing on all treatments. In the laboratory, the longer vase life was obtained with the application of 20 and 40 mg/L of GA₃ including the control. As for the opening of capitulum, the control opened in less time, while the concentrations of 40 and 60 mg/L of GA₃ delayed the opening of the capitulum. From this work it is concluded, that the sunflower responds positively to potassium fertilization under soil alkalinity conditions. The application of GA₃, in post-harvest conditions affected the inflorescences of the species, delaying the opening of the capitulum.