The impact of the salinity of the nutrient solution on water efficiency can be changed by the application flow. The aim of this work was to analyze the water efficiency and production components of coriander plants, cultivar Verdão, exposed to nutrient solutions (1.7, 3.0, 4.5, and 6.0 dS m⁻¹) applied with different flow rates (1.0, 2.0, 3,0, and 4.0 L min⁻¹) in an NFT hydroponic system. Two experiments were carried out in a greenhouse with two sources of salts to prepare the electrical conductivity. In the first experiment, NaCl was used, and CaCl₂·2H₂O was used in the second. Variables were analyzed related to the production components and the consumption of water use efficiency. It was found that the water efficiency and production components of coriander plants were more affected by increases in electrical conductivity in the nutrient solution. CaCl₂·2H₂O better promotes the lower production of dry mass, plant height, water consumption, and the instantaneous and intrinsic efficiency of water use than NaCl. The coriander’s water relations were inhibited by increases in the concentration of salts in nutrient solution, while increases in the flow rate of the nutrient solution negatively affected the productive parameters of the coriander plants.

The cooling of nutrient solutions prepared in brackish water can have several implications for plants grown in hydroponics. In this context, the present study aimed to evaluate the effects of temperature and salinity stresses in the root zone on the growth, water status, production, and leaf characteristics of chicory cultivar Folha Larga, exposed to four values of electrical conductivity of nutrient solution - ECns (1.7, 3.2, 4.7, and 6.2 dS m^-1), applied at two temperatures (ambient temperature and controlled in the range between 25-30 °C). The randomized block design arranged in a 4 × 2 factorial scheme with four replications was used. Cooling nutrient solution mitigated effects of salinity on stem height and diameter, number of leaves, and leaf area of chicory; provided greater production and water consumption, stability into root-shoot relationships, and membrane integrity within the saline range studied (1.7 to 6.2 dS m^-1).

Although the NFT (nutrient film technique) solution application rate for cilantro is known for fresh water, the application rate is still debatable when using brackish water. The application rate alone influences flow velocity dynamics, which, when associated with nutrient solution salinity, can impact plant development when saline water is used. Knowledge of how to best combine solution salinity and application rates will help decide if brackish water can be used to produce cilantro under hydroponic conditions. Thus, two trials were conducted in sequence from November 2019 to February 2020 under a protected environment. Cilantro cv. Verdão was submitted to four levels of electrical conductivity of nutrient solutions (ECns of 1.7, 3.0, 4.5, and 6.0 dS m⁻¹) combined with four flow rates (1.0, 2.0, 3.0, and 4.0 L min⁻¹). Because Na⁺ and Ca²⁺ are predominant ions in brackish waters in the crystalline and sedimentary regions in the Brazilian Semiarid region, the first study used brackish waters dominated by NaCl and the second study used waters dominated by CaCl₂. We measured gas exchange and other photosynthetic parameters in plants cultivated with nutrient solutions high in Cl⁻ and prevalent in Na⁺ or Ca²⁺, each combined with different application rates. We concluded that the increment in salinity decreased the gas exchange of cilantro plants, especially when the brackish waters were dominant in Ca²⁺ and Cl⁻. Up to an ECns of 4.5 dS m⁻¹, plants maintained their leaf chlorophyll concentrations, although with reduced gas exchange. Salt stress compromised chlorophyll a fluorescence, affecting important parameters such as initial, maximum, and variable fluorescence. Besides the effects of salinity on chlorophyll a and b concentrations, the quantum and maximum yields of photosystem II remained stable, indicating that photosystem II may have adapted to the saline conditions applied in this study. The variation in application rates was unable to attenuate the deleterious effects of salinity, regardless of the ionic prevalence. We conclude that cilantro plants can be cultivated under hydroponic conditions, using currently accepted flow rates, with nutrient solutions of up to 3.0 dS m⁻¹ without severe damage to plant photosynthetic parameters.

The use of brackish water for preparation of nutrient solutions has several impacts on crop performance, depending on the water concentration and cation prevalence. Therefore, this study was conducted to evaluate production and water relations of coriander grown on nutrient solutions prepared with brackish waters with different cationic natures under hydroponic conditions. A randomized block experimental design with four replicates was used, in a 4 × 3 factorial arrangement. The treatments consisted of four electrical conductivities of the nutrient solution (1.6, 3.2, 4.8, and 6.4 dS m^-1) which were prepared in waters with different salts (NaCl, CaCl₂.2H₂O, and MgCl₂.6H₂O). Salinity negatively affected the production and water relations of coriander grown in hydroponic system; plants grown on nutritive solutions with predominance of Na⁺ had higher total dry weight and shoot dry weights, as well as higher stomatal conductance. The largest leaf area was found when using the nutrient solution with predominance of Mg²⁺.

Flow rates for applying nutrient solutions in hydroponic systems are empirically known, yet uncertainties remain regarding whether brackish water affects the optimal flow rate and, consequently, biomass production and allocation. This study evaluated whether variations in application flow rate affect coriander biomass when brackish water is used to prepare the nutrient solution. Two consecutive greenhouse cycles were conducted: In the first, salinity was adjusted using NaCl, and in the second, CaCl ₂ ·2H ₂ O. A completely randomised design (4 × 4) was adopted, comprising four electrical conductivities (1.7, 3.0, 4.5 and 6.0 dS m ⁻¹ ) and four flow rates (1.0, 2.0, 3.0 and 4.0 L min ⁻¹ ), totalling 64 experimental units per cycle. Fresh and dry mass partitioning and dry mass allocation were analysed. Lower flow rates (> 1 and ≤ 2 L min ⁻¹ ) increased shoot fresh mass even under elevated salinity, whereas higher flow rates (> 2 L min ⁻¹ ) favoured root biomass. Increasing salinity reduced the shoot dry mass ratio but raised the overall percentage of dry matter, irrespective of the predominant cation (Na ⁺ or Ca ²⁺ ). A flow rate between 1 and 2 L min ⁻¹ is recommended, even when using brackish water to prepare the nutrient solution, as this range promotes greater shoot biomass in coriander plants.