Cultivo de couve-flor em sistema hidropônico NFT utilizando águas salobras

Abstract

The need for utilization and rationalization of brackish water management in hydroponic crops constitute ways of expanding and managing the water supply in semiarid zone due water scarcity. Our aim was to evaluate the use of brackish water and flow rates of nutrient solution in growth, mineral composition and gas exchange in two cauliflower cultivars (Brassica oleracea var. Botrytis L. ) in hydroponic system NFT (laminar flow technique of nutrients) in greenhouse. Two strategic situations of brackish water use were used: In the first experiment the nutritive solutions were prepared with brackish water with EC of 0.2; 1.5; 2.5; 3.5; 4.5 and 5.5 dS m-1, and used to replace the evapotranspiration slide with two flow rates of nutrient solution (1.5 and 2.5 L min-1); In the second experiment the waters used in the preparation of the nutrient solution were produced with the addition of salts in proportions similar to the physico-chemical composition of the brackish water of the underground wells of the Pernambuco semiarid region with EC of (0.2, 1.67, 3.30, 4,71, 5,88 13,84) one more treatment using only local water supply (0.2 dS m-1) with the same evapotranspiration blade replacement and flow rates of nutrient solution described in the first experiment with the purpose of studying the technical feasibility of the use of these waters in the NFT system. The experiments were conducted at the Experimental Station of Irrigated Agriculture Prof. Ronaldo Freire de Moura in the Agricultural Engineering Department (DEAGRI) of UFRPE Recife / PE, using a completely randomized experimental design in a factorial scheme (6 x 2) with six treatments and four replications, totalizing 48 experimental plots. The data were submitted to analysis of variance by the F test and when significant effects were verified to the regression analysis and the Tukey test at 5% of probability. It was observed in both experiments greater reduction in the growth of the plants due to a lower nutrient absorption and photosynthetic activity in the flow of 2.5 L min-1. For macronutrient concentrations, antagonistic interactions were observed, mainly between Na+ and K+, which was more evident in the diagnostic leaf at 49 and 60 DAT in the first and second experiments, respectively.