The tolerance of crops to salinity is greater in hydroponic systems due to the low contribution of the matric potential to the total potential of the water. The objective of this study was to evaluate the use of brackish water, to prepare the nutrient solution and replace the evapotranspired volume, and rates of application of this solution on the water stress index, water potential, leaf succulence and water consumption of cauliflower cv. ‘Piracicaba Precoce’. The experimental design was completely randomized in a 6 x 2 factorial scheme, with six salinity levels used to prepare the nutrient solutions (0.2, 1.5, 2.5, 3.5, 4.5 and 5.5 dS m^-1) and two application rates of these solutions (1.5 and 2.5 L min^-1), with four replicates. Water stress index (WSI), water and osmotic leaf potentials, leaf succulence (LS) and water consumption were analyzed. The increase in water salinity reduced LS and increased WSI. Water salinity reduced the water and osmotic leaf potentials and water consumption of the crop; however, the effects were more pronounced at the rate of 2.5 L min^-1. Application rate of 2.5 L min^-1 led to the highest WSI and lowest LS.

The underground water reserves in the semi-arid region present high salinity levels. However, the scarcity of the resource compels the use of this water for several human activities, including agriculture. The aim of this work was to evaluate the use of brackish water for watercress cultivation (Nasturtium officinale) in a hydroponic NFT system (laminar flow of nutrients) and effects on water consumption, growth, yield and nutrient extraction by the plant. We studied six levels of salinity (0.2; 1.2; 2.2; 3.2; 4.2 and 5.2 dS m^-1), in a completely randomized experimental design, with four replicates. Salinity was obtained by the addition of NaCl into the local water supply, being these waters used to prepare the nutrient solution and to replace the evapotranspirated water volume. We noticed a reduction in leaf area, fresh and dry mass of shoot, K content in plant and water consumption of the crop and, increased contents of P, Na, Cl in the plants, with increasing salinity of the solution. The use of brackish water for watercress cultivation in hydroponics is possible as an alternative for producers who have availability of brackish water and restricted possibility of fresh water. A reduction in dry mass of plants was observed with increasing electrical conductivity.

Plantas de alface cv. Elba foram cultivadas em dois sistemas hidropônicos, Floating e NFT, com o objetivo de avaliar três tipos de água: a água salobra natural (2,47 dS m-1) obtida a partir de um poço profundo; água doce (0,11 dS m-1) produzido por dessalinização por osmose inversa, e o rejeito salino (5,15 dS m-1), um efluente do processo de dessalinização. Estas águas foram combinadas em seis tratamentos resultantes da sua utilização alternada para preparar a solução nutritiva (SN) e/ou substituir as perdas por evapotranspiração (ETc). O experimento foi conduzido em casa de vegetação na região semiárida de Pernambuco, utilizando 48 unidades experimentais em blocos casualizados em esquema fatorial 6x2 com quatro repetições. O rendimento da alface (massa de matéria fresca) foi maior nas condições do Floating. O uso exclusivo da água do poço profundo e do rejeito de dessalinizadores diminuiu 22,7 e 39,6% a produção de alface, respectivamente. Para uma melhor combinação de águas doces e salobras, o uso de água salobra para repor a perda por ETc pode aumentar a produção de alface em relação ao uso dessas águas para preparar a SN, estes resultados foram registrados para a água do poço profundo e o rejeito. Plants of lettuce cv. Elba were grown under two hydroponic systems, Floating and NFT, aiming to evaluate three water resources: natural brackish water (2,47 dS m-1) obtained from a deep well; fresh water (0,11 dS m-1) produced by reverse osmosis desalination; and reject brine (5,15 dS m-1), a wastewater from desalination process. These waters were combined in six treatments resulted from their alternated use to prepare nutrient solution (NS) and/or replace the evapotranspiration loss (ETc). The experiment was carried out under a greenhouse condition in the semiarid region of Pernambuco State, Brazil; 48 experimental units were used for both hydroponic systems. The lettuce yield (shoot fresh matter) was higher under Floating conditions. The single use of deep well water and reject brine decreased 22.7 and 39.6% the lettuce yield, respectively. For a better combination of fresh and brackish waters, the use of brackish water to replace ETc loss may increase the lettuce yield in comparison to use these waters to prepare the NS; this result was registered for deep well water and reject

The objective was to evaluate the growth and yield of sugarcane irrigated with brackish water and leaching fractions. A completely randomized experimental design was used, in a 5 x 2 factorial scheme, with four replicates. The treatments consisted of five irrigation water salinity levels (0.5, 2.0, 3.5, 5.0 and 6.5 dS m^-1) and two leaching fractions (0 and 0.17), corresponding to 100 and 120% of the crop evapotranspiration. The irrigation management was performed daily. Irrigation water salinity levels were obtained by adding NaCl and CaCl₂ to the public-supply water, in order to obtain a molar ratio between Na:Ca of 1:1. The following measurements were taken: height and stem diameter; number of tillers; number of leaves and leaf area with monthly frequency between 60 and 300 days after planting (DAP). It was concluded that irrigation water salinity negatively influenced the variables of growth and yield in the sugarcane, and the leaching fraction of 0.17 was capable of reducing the deleterious effects of the salts on the plants.

Groundwater with high salt concentrations is common in the semiarid region of Brazil. It often makes them inappropriate to conventional agricultural production of vegetables. Therefore, the objective of this work was to evaluate watercress and Chinese cabbage crops under a nutrient film technique (NFT) hydroponic system using brackish groundwater. The experiment was carried out in the Poço do Boi region, in Ibimirim, Pernambuco, Brazil (8º32'15"S, 37º41'30"W, and altitude of 431 m). The treatments used were: public water (T1), calcium sulfate water (T2), magnesium chloride water S1 (T3), calcium chloride water (T4), sodium chloride water (T5), and magnesium chloride water S2 (T6). A completely randomized experimental design was used, with six treatments and four replications, totaling 24 plots for each crop. The fresh and dry shoot weights and rates of relative and absolute growths were analyzed. The different waters used affected negatively the growth and yield of the watercress and Chinese cabbage plants. The calcium chloride water was the most suitable for the watercress production. However, none of the groundwaters used could be recommended for production of Chinese cabbage. The lowest growth rates (5.88% to watercress and 0.75% to Chinese cabbage) of the fresh matter were found with the use of magnesium water.