Hydroponic production of ornamental sunflower with cooling of the nutrient solution and planting density

Abstract The temperature of the nutrient solution is one of the main obstacles of hydroponic production in hot climates and can affect the nutrient absorption of plants. Additionally, the hydroponic cultivation of cut flowers is rarely done, and hence, there is a lack of studies on this topic. The objective of this experiment was to determine the ideal temperature of the nutrient solution as well as the influence of the plant density factor for hydroponic cultivation in NFT (Nutrient Film Technique) of the cultivar Girassol de Jardim Amarelo Alto, ISLA ® . The experiment was installed in a greenhouse, with 50% shading. The experiment adopted a completely randomized design in a factorial scheme with plots subdivided in space, with the main plots composed of two densities (15 and 30 plants m-2) and the subplots of four temperatures of the nutrient solution (20, 25, 30 °C and uncontrolled temperature) with three replications each. The variables analyzed were plant height, stem diameter, internal and external diameter of the flower, number of leaves, number of buds and flowers, dry and fresh root mass, dry and fresh shoot mass, and cultivation cycle. The data were submitted to an analysis of variance using the statistical software SISVAR. The density of 15 plants m-2 proved to be more efficient, presenting plants of commercialization standard. Cooling the nutrient solution did not improve the production and quality of sunflower flowers.