Uso de condicionadores de substrato no cultivo do girassol ornamental irrigado com águas salobras

Abstract

Use of substrate conditioners in ornamental sunflower cultivation irrigated with brackish waterThe reduction of water offer has encouraged the search for strategies for economy and more efficient use in agricultural production. The use of water of inferior quality that has been used in conjunction with some techniques, such as the use of conditioners in the cultivation, an alternative that allows greater absorption and availability of water for plants. Given the above, the objective was to study irrigation with brackish water using substrate conditioners, analyzing the economic aspects of these conditioners and the physiological aspects of the ornamental sunflower crop, an agronomic species of high commercial movement due to the exuberance of its flowers and rapid economic return. The experiments were carried out between September 2020 and March 2021, in a protected environment on the premises of the "Luiz de Queiroz" College of Agriculture (ESALQ/USP), in the municipality of Piracicaba -SP (22º 42' S, 47º 38' W, 546 m of average altitude), and the treatments were allocated in an experimental design in randomized blocks, in a split-plot scheme with four replications. Two different experiments were carried out, one with 4 doses of hydrogel (0.0, 0.5, 1.0 and 1.5 g kg -1 ) and the other with 4 proportions of coconut fiber (0, 15, 20 and 25% of the substrate volume), both irrigated with 4 levels of electrical water conductivity (0.5, 2.0, 3.5 and 5.0 dS m -1 ), the two experiments obtained two cycles, one performed in spring (from September to December) and another in summer (from January to March). Physiological variables related to gas exchange and photochemical efficiency of the plants were analyzed, as well as the production through the shoot dry matter. These data were submitted to analysis of variance using an F test at 0.05 probability. Also, analyzes of fixed irrigation costs and variables of maintenance, labor, water, pumping and substrate were carried out jointly with analysis of growth through plant height and external diameter of the chapter. Among the main conclusions, it's highlighted that the use of both substrate conditioners in saline environment leads to improvements in the productive, physiological and growth aspects of ornamental sunflower plants, cv. Anão de jardim, not compensating the use of both without salinity. In economic aspects, as the amount of coconut fiber in the substrate increases, costs decrease, however, excess fiber did not improve plant growth and under electrical conductivity of 5.0 dS m -1 the results with fiber were not as expressive, while hydrogel, despite being more expensive, resulted in improvements at all doses for the four electrical conductivities analyzed.