Salinity and flow rates of nutrient solution on cauliflower biometrics in NFT hydroponic system

ABSTRACT The use of brackish water in hydroponic crops represents an alternative for vegetable production. In this context, two experiments were conducted to evaluate the effect of using brackish water to prepare the nutrient solution and replace the evapotranspired depth, applied at different flow rates, on cauliflower biometrics in NFT (nutrient film technique) hydroponic system. In both experiments, the experimental design was completely randomized with four repetitions, in a 6 x 2 factorial scheme: six levels of water electrical conductivity (ECw) in interaction with two flow rates of nutrient solution application in the hydroponic channels (1.5 and 2.5 L min-1). In Experiment I, brackish waters with different EC (1.5, 2.5, 3.5, 4.5 and 5.5 dS m-1), obtained by the addition of NaCl in public-supply water (0.2 dS m-1), were used. In Experiment II, the chemical characteristics of brackish waters collected in the semiarid region of Pernambuco were simulated, with EC of 1.67, 3.30, 4.71, 5.88 and 13.84 dS m-1, plus the control (0.2 dS m-1). Increasing salinity reduced cauliflower growth. Flow rate of 1.5 L min-1 promoted the best results of shoot fresh and dry masses, leaf area, number of leaves, plant height and shoot diameter. The best water for cauliflower production was public-supply water and, among the well waters, the best was the calcium sulfate-rich water with EC of 1.67 dS m-1. RESUMO O uso de águas salobras em cultivos hidropônicos representa uma alternativa para a produção de hortaliças. Assim, foram conduzidos dois experimentos objetivando avaliar o uso de águas salobras, no preparo da solução nutritiva e reposição da lâmina evapotranspirada aplicadas em diferentes vazões na biometria de plantas de couve-flor em sistema hidropônico NFT (técnica do fluxo laminar de nutrientes). Nos dois experimentos, o delineamento experimental utilizado foi o inteiramente casualizado com quatro repetições, em esquema fatorial 6 x 2: seis níveis de condutividade elétrica da água (CEa) em interação com duas vazões de aplicação da solução nutritiva nos canais hidropônicos (1,5 e 2,5 L min-1). No Experimento I utilizaram-se águas salobras com diferentes CE (1,5; 2,5; 3,5; 4,5 e 5,5 dS m-1), obtidos a partir da adição de NaCl na água de abastecimento (0,2 dS m-1). No Experimento II foram simuladas as características químicas das águas salobras coletadas na região semiárida de Pernambuco, com CE de 1,67; 3,30; 4,71; 5,88 e 13,84 dS m-1, além do controle (0,2 dS m-1)