Alternative techniques for cultivation without soil are widespread; however, studies comparing hydroponic systems still need to be studied, mainly in semi-arid regions. The present study aimed to evaluate the effect of hydroponic systems on the yield and quality of lettuce cultivars subjected to different electrical conductivities of the nutrient solution. The research was conducted in a greenhouse, adopting a completely randomized design in a 2 × 2 × 3 factorial scheme, being two lettuce cultivars (Cinderela and Rubinela), two electrical conductivities (2.90 and 1.6 dS m^-1), and three hydroponics systems (NFT, semi-hydroponic, and floating), with three replications. The number of leaves, leaf succulence, specific leaf area, leaf fresh mass, total dry mass, leaf area, titratable acidity, vitamin C, and soluble solids were evaluated. Cinderela cultivar showed the highest average leaf fresh mass, total dry mass, leaf area, and vitamin C values. The NFT and floating systems provided the highest leaf yield and quality, especially in the solution of 1.60 dS m^-1. The semi-hydroponic system provided greater development of the plants with a more concentrated nutrient solution (2.90 dS m^-1).

Seed germination of species that develop in arid and semi-arid soils can be altered by water deficit and abundance of salts in the soil. Knowledge on tolerance limits is fundamental to understand the adaptive capacity of species under such conditions. The objective of this study was to evaluate the physiological changes (germination and vigor) of Mimosa caesalpiniifolia seeds from different regions and submitted to water and saline stresses. To simulate water stress, the osmotic agent polyethylene glycol (PEG 6000) was adjusted to the potentials of 0, -0.2, -0.4, -0.6 and -0.8 MPa, whereas for the saline stress, NaCl solutions were adjusted to the potentials of 0, -0.1, -0.3, -0.5, -0.7; -0.9 and -1.1 MPa. The experimental design was completely randomized, in a 3 x 5 factorial scheme for water stress and 3 x 7 factorial scheme for saline stress, with four replicates of 25 seeds. The variables analysed were: germination, germination speed index and seedling shoot length, root length, shoot dry matter and root dry matter. M. caesalpiniifolia seeds, coming from different geographic regions, showed similar physiological responses to water stress; with respect to salt stress, their tolerance varies according to the region of harvest, and those from Vazante, MG, Brazil were more tolerant during germination and initial growth of seedlings.

The treatment with low temperatures, for a certain period, stimulates the accumulation of phytohormones in garlic seed cloves, which influence the growth and development of the plants. Thus, this work aimed to evaluate the effects of garlic seed cloves under negative temperatures for different periods on the development and productivity of noble garlic cultivated in the Brazilian semi-arid region. Two experiments were carried out and analyzed separately in the municipalities of Mossoró and São Miguel, RN, Brazil, in which three temperature ranges (−5 to −3 °C, −2 to 0 °C and 1 to 3 °C) and three periods (50, 55, and 60 days) were tested. Low-temperature conditioning of the garlic seed cloves was carried out in a temperature-controlled freezer. Relative humidity during treatment ranged from 60 to 70%. Seed cloves submitted to temperatures below zero provided the differentiation of cloves, even in unfavorable edaphoclimatic conditions for cultivating noble garlic. Seed cloves conditioned with negative temperatures increased the productivity of garlic grown in Mossoró, but with a lower average yield than garlic produced in São Miguel. Garlic seed cloves treated at negative temperatures in São Miguel provided garlic productivity equivalent to the yield of garlic grown in the states of the southern region. In addition, it produced class 6 and 7 bulbs, which have greater commercial value and acceptance by consumers. The results demonstrated the potential of garlic seed cloves treated with temperatures below zero to increase the production of noble garlic in the semi-arid region of the country.

The common climatic characteristics in semi-arid regions can cause abiotic stress and be a limiting factor for crops. Under these conditions, the use of beneficial elements such as selenium (Se) is an alternative to mitigate the harmful effects of abiotic stresses and increase yield. Therefore, this research aimed to evaluate the agronomic performance of onion grown in a semi-arid region under the application of Se. A field experiment was performed in a randomized block design, where five doses of Se (0, 15, 30, 45, and 60 g ha^-1), by foliar application, were tested on two onion hybrids (Andrômeda and Rio das Antas). Growth, nutritional and yield variables were analyzed. Se increased the height and accumulation of dry mass in onion plants, with a maximum at the 60 g ha^-1 dose of Se, the same dose at which the highest commercial (78.15 t ha^-1) and total (86.03 t ha^-1) bulb yields were obtained in Rio das Antas; however, for Andrômeda, there was no effect of Se on yield. Applied Se doses also increased the content of this element in the bulbs. Despite increasing bulb yields only in the Rio das Antas hybrid, 60 g ha^-1 of Se is recommended for onions due to its effects on plant growth and the biofortification of bulbs with Se.

Nutritional management can be an efficient strategy to mitigate the effects of salinity on fruit production and quality. This study aimed to evaluate the production and quality of fruits of mini watermelon crop, Sugar Baby cultivar, grown in a protected environment, under salt stress and K+/Ca2+ ratios. The study was carried out in a greenhouse, using a randomized block design, 1 + 5 scheme, resulting in six treatments and four replications. Six nutrient solutions were employed, one using low-salinity water, with NaCl (0.5 dS m-1) and standard nutrient solution (S1, control treatment), and the others using salinized water at 5.0 dS m-1 (S2) and extra addition of K (S3 = 50% and S4 = 100%) and Ca (S5 = 50% and S6 = 100%). The production (fruit production, longitudinal and transverse diameter of fruit, rind thickness, pulp firmness) and postharvest quality (soluble solids, vitamin C, titratable acidity, and maturation index), in addition to the variables related to the color of the pulp (lightness, chroma index, and Hue angle) were evaluated. The addition of NaCl reduced fruit production, longitudinal, and transverse diameter of fruit, rind thickness, and vitamin C content. Among saline nutrient solutions, extra addition of 50% K (S3) attenuates the deleterious effects of salt stress on the production variables and vitamin C content. Under salt stress, extra addition of 50% K (S3) and 100% Ca (S6) intensifies the red color of the pulp.

The economically profitable production of crops is related, among other factors, to seed quality, the production system, and the water used in irrigation or preparation of nutrient solutions. Therefore, the objective was to evaluate the phenology, production, and vigor of seeds of mini watermelons grown in saline nutrient solution and different substrates. In the fruit and seed production phase, the experiment occurred in a greenhouse with five electrical conductivities of water for nutrient solution preparation, ECw (0.5, 2.4, 4.0, 5.5, and 6.9 dS m⁻¹), and two growing substrates (coconut fiber and sand). We evaluated the physiological quality of seeds previously produced under the five electrical conductivities of water and two substrates. High salinities for the hydroponic cultivation of the mini watermelon cultivar ‘Sugar Baby’ accelerated fruit maturation and crop cycle, decreasing fruit size. However, in both substrates, the seed production of mini watermelons, seed viability, and seed vigor occurred adequately with a reject brine of 6.9 dS m⁻¹ in the hydroponic nutrient solution. The seed production of ‘Sugar Baby’ mini watermelons using reject brine in a hydroponic system with coconut fiber and sand substrates is viable in regions with water limitations.