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The use of saline water (low-quality water) in irrigation is a reality in many regions, especially in areas where fresh water is scarce, like semi-arid regions. However, it is important to adopt strategies to minimize the damage caused by salt stress to plants. The use of soil conditioners can help improve soil structure and water retention capacity, reducing salinity effects. The objective was to analyze the potential of a soil conditioner (hydrogel) as a mitigator of salty stress by irrigation with saline water in ornamental sunflower. Two sunflower cycles were carried out in a protected environment with a factorial 4 × 4 consisting of four doses of hydrogel polymer (0.0, 0.5, 1.0, and 1.5 g kg−1) and four different levels of irrigation with saline water (0.5, 2.0, 3.5, and 5.0 dS m−1). Plant biomass and physiological parameters, such as chlorophyll fluorescence measurements and gas exchange parameters, stomatal conductance, transpiration, and photosynthesis, were evaluated. Ornamental sunflower showed better performance with a saline water of 0.5 dS m−1 without the use of hydrogel. At higher salinity levels, with a hydrogel dose of 1.5 g kg−1, the sunflower achieved favorable performance, promoting gains in some gas exchange variables in plants irrigated with saline water at 3.5 dS m−1 and in fluorescence-related variables within the range of 2.0 to 3.5 dS m−1. This positive effect of hydrogel indicates its potential as a mitigating strategy against the adverse effects of salinity, contributing to the maintenance of plant vigor and physiological functionality in saline environments.

High levels of dissolved salts in irrigation water sources limit melon cultivation in northeastern Brazil. In this context, nitrogen fertilization has been employed as one strategy to alleviate the effects of salt stress on plants. This study aimed to evaluate the effect of different nitrogen sources on cantaloupe melon cultivation under fertigation and irrigation with water of the same salinity and different cationic concentrations (Na+ and Ca+). The research consisted of two experiments, each following a randomized complete block design in a 4 × 2 factorial arrangement with four replicates. The treatments included four levels of electrical conductivity of the nutrient solution (2.0; 3.0; 4.0; and 5.0 dS m−1) and two nitrogen sources of different origins: NO3− [Ca(NO3) and KNO3] and NH4+ [CH4N2O and NH4H2PO4]. The following factors were chlorophyll pigments, chlorophyll a fluorescence, and fruit weight. Nitrogen fertilization with NH4+ mitigated salt stress by increasing the synthesis of chlorophyll a and carotenoids in plants irrigated with NaCl-based saline water. Furthermore, there was no influence of nitrogen sources on chlorophyll a fluorescence. Finally, NO3− fertilization reduced the effects of salt stress on the leaf mass ratio, specific leaf area under Ca2+ fertigation, and relative growth rate of leaf area in melons under cationic prevalences of Na+ or Ca2+ (associated with Cl−).

Rationalization of brackish water management in hydroponic crops is one of the ways to expand and manage water supply in shortage areas. Thus, this work was carried out to evaluate the water and physiological relationships of Iceberg lettuce (cv. Tainá) in plants exposed to strategies of replacement of the evapotranspired volume of saline nutrient solutions. Two experiments were conducted in NFT hydroponic system, in which increasing levels of water salinity (0.2, 1.2, 2.2, 3.2, 4.2 and 5.2 dS m-1) were used to prepare the nutrient solutions. In the first experiment, the evapotranspired volume was replaced with the respective brackish water and, in the second one, with public-supply water (0.2 dS m-1). Both experiments were set up in a randomized block design, with six treatments and four replicates, totaling 24 experimental plots. It was concluded that using brackish water to prepare the nutrient solution, regardless of whether the evapotranspired volume was replaced with brackish or public-supply water, affected lettuce water and physiological relationships. However, although it caused a reduction in size, the use of brackish water did not cause visual damages that would compromise the commercial appeal of the plants. It was also found that, when water of up to 5.2 dS m-1 was used to prepare the solution, the replacement of the evapotranspired volume with public-supply water increased water use efficiency by up to five times.

In regions with water scarcity, it is necessary to use well water, often brackish water, in the irrigation of crops, which requires the adoption of management mitigation strategies. This study was carried out in the Fazenda Pedra Preta, Mossoró, Brazil, with the objective of evaluating the use of 10 management strategies of irrigation with two types of water (electrical conductivity ECWP1 = 0.57 dS m−1 and ECWP2 = 4.33 dS m−1). This was based on alternating and/or varied application as a function of the phenological stage during the plant growth phase, on the production, mean weight, and quality of the “Toad Skin” melons (Cucumis melo L., cv Sancho). A randomized complete block design with four replications was used, totaling 40 experimental plots. It was concluded that irrigation with water of electrical conductivity of 0.57 dS m−1 in the flowering and fruiting phases and water of 4.33 dS m−1 in the vegetative growth and maturation phases has produced more commercial fruits with higher mean weight. Through time, water management strategies did not influence the number of fruits per plant, fruit productivity, soluble solids content, and pulp firmness.

In this study, the authors analyzed the consequences of irrigation management strategies as an essential factor to save water and maintain high crop yields. The present research aimed at comparing coriander (Coriandrum sativum L.), cv. Verdão, yields under fertigation via drip irrigation with a continuous application and in pulses, with 40, 60, 80, 100 and 120% of the crop evapotranspiration (ETc) being recovered. These treatments were distributed in randomized blocks in a 2 × 5 factorial scheme, with three replications, in a greenhouse located at the Federal Rural University of Pernambuco, northeast Brazil (08°01′6.50″ S and 34°56′46″ W, average elevation 6.5 m). The continuous irrigation consisted of the application of water depth in a single daily event, while pulsed irrigation comprised the application of the same irrigation depth split up into five events with a 1-hour interval between pulses. Crop evapotranspiration (ETc) was determined via the water balance by lysimetric drainage. The fertilizers were applied in every watering. The biometric and productivity crop pointed that pulsed irrigation to a mean depth of 58% of the ETc corresponds to the results obtained with the application of the depth equivalent to 100% of the ETc by continuous irrigation, consequently with reduced input costs.

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.

Water and nitrogen (N) availability are among the primary limiting factors for the productivity of tomato (Solanum licopersicum L.). This study evaluated the interaction between these factors by assessing the effects of different N concentrations (85.5, 128.3, 171.0, 213.8, and 256.1 ppm N) on the water consumption, growth, and photosynthetic efficiency of hydroponically-grown tomato plants. The variables that were analyzed included the leaf N content, leaf chlorophyll index (LCI), maximum quantum efficiency of photosystem II (the ratio of variable to maximum chlorophyll fluorescence; Fv/Fm), non-photochemical quenching (NPQ), fresh mass (FM), dry mass (DM), cumulative water consumption, and water use efficiency (WUE). Increasing N concentrations led to higher water consumption and FM accumulation. Dry biomass was quadratically related to the N concentration, which peaked between doses of 213.8 and 256.1 ppm N. The LCI and Fv/Fm increased with the N supply, reaching a peak at N concentrations above 171 ppm, and then remained relatively constant. Conversely, the NPQ was reduced at the highest N level (256.1 ppm), which indicated diminished excess energy dissipation capacity. The highest WUE was observed at 213.8 ppm N, which was associated with greater DM and reduced water consumption compared to the highest N treatment. These findings suggest that the N concentration significantly affects the biomass production and water use in hydroponically-grown tomato plants, with 213.8 ppm N being the most efficient for vegetative growth under the studied conditions.

In irrigated areas around the world, the recommendation for the use of subsurface drainage is also associated with controlling salinity problems. Due to the high implementation cost, the search for solutions that make this requirement more flexible is necessary. Among the options to be investigated is the hypothesis that the height and salinity of the water table in plots located at the highest points of a toposequence are lower and do not compromise plant development, even without underground drainage systems. In this context, the present work was developed to monitor and evaluate the variation in water level or mottling over twelve months, as well as to measure and analyze the electrical conductivity and average pH of the water table during this period and its possible impact on plants. For this purpose, three lots in toposequence were selected in the Senador Nilo Coelho Public Irrigation Project, Petrolina—PE, with previously defined characteristics: soil classification (Plinthic Yellow—Ultisol), crop planted (Mangifera indica L.) and irrigation system used (micro-sprinkler). Precipitation, reference evapotranspiration and volume of water applied via irrigation were monitored by an automatic weather station and hydrometers in each lot. In each plot, nine observation wells were installed, distributed in a grid, with the aim of make monthly measurements of the water table level or mottling. The electrical conductivity and pH of the groundwater were also measured to obtain the average monthly value for each lot. Illustrative 3D maps of the water table level in relation to the ground surface were created using the simple kriging method, in the UTM SIRGAS 2000 24S projection system. The absence and presence of groundwater in the upper and lower hillslope lots, respectively, were favored by the toposequence. The decision to install underground drainage or not can be made on a case-by-case basis; this must take into account, among other aspects, changes in physical characteristics along the soil profile, possible occurrence of mottling, the quality of water for irrigation, the irrigation management adopted and the position of the lot in the toposequence.

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.

ABSTRACT Pulse irrigation may be more advantageous for peanut crops than continuous irrigation, when using brackish water. However, studies on pulse irrigation with brackish water considering the environmental conditions of the Northeast region of Brazil using are incipient. Therefore, the objective of this study was to evaluate the effect of using brackish water for pulse and continuous dripping irrigations on the grain yield and production characteristics of peanut (Arachis hypogaea L.) crops. A completely randomized block design with four repetitions was used, in a 6*2 factorial arrangement consisted of six electrical conductivities of the irrigation water (EC; 0.2, 1.6, 2.8, 4.0, 5.2, and 6.4 dS m-1) set by adding NaCl to the irrigation water, which originally had 0.2 dS m-1, until reaching the respective EC; and two irrigation methods (pulse and continuous). The evaluated variables were fresh and dry weights of shoot, 10 grains, pods, grains, and production; number of pods and grains; and percentages of empty pods (EP%) and perfect grains (PG%). The addition of salt to the irrigation water negatively affected all variables studied, except for EP% and PG%. The lowest EP% were found for the pulse irrigation, which increased the pod and grain yields, regardless of the EC of the irrigation water. Under the conditions of the present study, the use of brackish waters with electrical conductivities of up to 2.98 dS m-1 is viable for peanut production. RESUMO A irrigação por pulsos pode proporcionar maiores rendimentos para a cultura do amendoim em comparação a irrigação contínua com a utilização de águas salobras, contudo, estudos para as condições do Nordeste brasileiro utilizando esta técnica de manejo da irrigação associada ao uso de águas salobras são incipientes. Diante disso, objetivou-se com o trabalho avaliar o efeito do uso de águas salobras e da irrigação por gotejamento pulsado e contínuo sobre a produção de grãos e características produtivas do amendoim (Arachis hypogaea L.). O delineamento experimental utilizado foi o de blocos casualizados, em esquema fatorial de 6 x 2, composto por seis condutividades elétricas da água de irrigação (CEa: 0,2; 1,6; 2,8; 4,0; 5,2 e 6,4 dS m-1), na qual foi adicionada NaCl a água de abastecimento (CEa: 0,2 dS m-1) até atingir as respectivas CEa, e duas formas de aplicação da irrigação por gotejamento (com pulsos e contínua), com quatro repetições. As variáveis analisadas foram: a massa fresca e seca da parte aérea de 10 grãos, das vagens, dos grãos e da produção, além do número de vagens, do número de grãos, da percentagem de vagens chochas (PerVC) e da percentagem de grãos perfeitos (PerGP). A salinidade influenciou negativamente todas as variáveis estudadas, com exceção do PerVC e da PerGP. As menores percentagens de vagens chochas foram obtidas com a irrigação pulsada que por sua vez demonstrou a maior produção de vagens e de grãos independentemente dos níveis de condutividade elétrica da água avaliados. Nas condições desta pesquisa, é viável produzir amendoim utilizando águas salobras com condutividade elétrica de até 2,98 dS m-1.