Thegrowthand yield data were collected at 18 and 30 days after transplanting (DAT). Two plants of each plot were selected for the evaluation of plant height (cm), measured with a tape measure from the base to the apex, stem diameter (mm) with the aid of a digital caliper andthe number of leaves by direct counting manually. Also destructive evaluations were carried out andthe root length (cm) was measured using a measuring tape, root volume with the aid of a graduated measuring cylinder in mL, the leaf area (cm²) by means of a portable meter (CID Bio- Science, Washington, United State of America, CI-202 model) andthe dry matter mass of the plant organs (g) through a forced ventilation oven at 65 °C for a period of 72 h and thereafter the mass of the dry matter was determined by weighing on a scale.
It is essential to choose the appropriate irrigation system with reuse water to reduce the risk of human and environmental contamination, considering the possible adverse effects of these water systems inthe soil andwater by increasing soil salinityand contaminating water bodies. Wastewater is used in closed systems, including hydroponic systems, to grow medicinal, ornamental, and food plant species because it has an adequate amount of nutrients and reduces the risk of contamination (Santos Júnior et al., 2014; Cuba et al., 2015; Albuquerque Júnior et al., 2016). The increased interest in hydroponics and wastewater underscores the need to further investigate the development and management of crops to establish criteria on plant density and arrangement in each cultivation systemandthe quality of thewater used for preparing the nutrient solution.
& Klapaki, 2000). While attempts to improve the salt tolerance of crops through conventional breeding programs have very limited success (Rozema & Flowers, 2008), most growers still rely on crop management practices to ameliorate salinity problems. Some studies have indicated that the use of saline water requires the improvement of irrigation management in order to maintain salt levels inthe root zone below the threshold values (Oster, 1994; Rubio et al., 2010a). Although a decrease inthe concentration of the NS could help to reduce salt levels inthe root zone. Studies about zucchini squash (Cucurbita pepo) and salvia (Salvia splendens F.) have shown that decreasing the NS concentration reduces fruit yield andgrowth (Rouphael & Colla, 2009; Kang & van Lersel, 2004). Coincidentally, a decrease in nutrient uptake was observed by decreasing the concentration of nutrient inthe irrigation solution. One interesting possibility is the increase of irrigation frequency when the concentration of the NS is reduced in order to synchronize nutrients andwater uptakes by the plant with the supply of nutrients andwater by the irrigation system (Klaring, 2001).
An alternative technique to use underground brackish waters is thehydroponic cultivation system (Santos et al., 2010). This technique consists of substituting soil for an aqueous solution containing only mineral elements defined as essential for plants (Silva et al., 2016). Inhydroponic cultivation system, nutrients supplementation through water, results in reduced losses that normally occur when growing in soil (volatilization, leaching and fixation), besides having advantages of lower use of waterand higher efficiency in its use. Besides, there will be better use of area, higher productivity, reduced vegetative cycle, as well as possibility to control the disposal into environment (Ferreira et al., 2017; Santos et al. 2010). Thus, direct contact of the saline effluent with environment is suppressed, avoiding salinityin adjacent areas.
I n northeastern Brazil, salt-affected soils occupy an area of approximately 9.1 million hectars (Fageria et al., 2010), andthewaterin wells drilled to capture groundwater is generally low flow and present high salt levels. One of the most viable alternatives for the use of saline soils and brackish waters is the use of tolerant plant varieties (Flowers, 2004). The use of hydroponic techniques associated with the tolerant varieties greatly increases the efficiency of water use. Salinity is an abiotic factor that causes stress in plants, limiting their growthand productivity (Munns & Tester, 2008). Environmental stress
For theproduction parameters evaluated, they did not reveal any significant differences after the analysis of variance. Assuming a density of 10,204 plants ha -1 , the commercial productivity of the eggplant, considering only the fruit within the standard commercial size and defect-free, grown on the conventional plot, was 45.84 Mg ha -1 , an equal amount to the conventional system. The total productivity was 47.42 and 47.91 Mg ha -1 respectively inthe NT and CT system, being this production superior to that found by CASTRO et al. (2004). The authors have cultivated eggplant under organic management in different cropping systems (monoculture and intercropped with legumes) getting close to the national average productivity of 25Mg ha -1 inthe conventional cultivation.
The applied irrigation depths were equal to 135, 165, 191, and 213 mm, respectively, for L1, L2, L3, and L4. Aiming for a greater yield of tomato plants in a protected environment, Santana, Vieira, Barreto, and Cruz (2010) and Macêdo and Alvarenga (2005) applied irrigation depths varying from 372 to 802 mm and from 158.1 to 399.2 mm, respectively. Also in a protected environment and producing tomatoes in pots, Silva et al. (2013) applied irrigation depths ranging from 180 to 828 mm. Inthe present study, the lower values of applied irrigation depth are essentially due to the cultivation systemin pots andin a protected environment and due to the irrigation method, in which water is locally applied, associated with the adequate management of the irrigation system with an automatic device for irrigation. All these factors contributed to the lower waterconsumption during the productive process.
stress was due to an increase of the external osmotic pressure, what adversely affects thewater absorption by seeds. According to Bewley et al. (2013), it is necessary that the seeds reach an adequate level of hydration during the imbibition phase, in order to occur the reactivation of seed metabolic processes andgrowth of the embryonic axis. Seeds exposed to drought or saline stress require more time to adjust the internal osmotic potential in accordance with the external environment (Munns & Tester 2008). A highly negative osmotic pressure may affect the seed water uptake, making germination not possible (Soares et al. 2015). Additionally, the osmotic stress affects the starch synthesis reactions and energy production process (adenosine triphosphate - ATP) through seed respiration (Bewley et al. 2013), resulting in a reduced germination speed index and thus inthe delay of the germination time. The most common responses of plants to the reduction of osmotic potential are a delay inthe initial germination and a reduction inthe germination rate (Mut & Akay 2010, Soares et al. 2015, Steiner et al. 2017).
Climate change andthe increasing human population worldwide challenge sustainable growthand food security. Hence, there is a dire need to save waterand fertilizers and to maintain or increase food production. To satisfy that need, basic and technical questions must be answered, and novel information has to be generated. Thus, this study was carried out in order to determine the use efficiency of waterand fertilizers applied in a closed hydroponicsystemand compare it with an open system during a tomato production cycle.
Irrigation was carried out with deionized water until seed germination, and then with nutrient solution until 30 days after germination, when plants were transplanted. Plants inthehydroponic growing beds were irrigated with the solutions for vegetative growth, and, after 21 days, the solutions were replaced by solutions for fruit setting. At 45 and 60 days after transplanting, the fresh weight, length, diameter, volume and firmness of the fruit were evaluated, and, at 45 days after transplanting, the macronutrient concentrations inthe leaves were determined. The use of different N:K ratios during fruit setting influenced the cucumber production. The ratio of 1.0:1.7 N: K (w/w), with 10% of N inthe form of ammonia, is recommended for the whole cycle.
of 98%. Lima et al. (2011) report that micro-sprinkler irrigation is more suitable for the bean crop, because it reduces losses caused by the Bean Golden Mosaic Virus. Soil water content inthe root zone (W, mm) was obtained by measurements of volumetric soil water content every 30 min by sensors using the time-domain reflectometry (TDR) technique (CS616, Campbell Scientific), connected to a CR1000 data acquisition system. The probes were positioned vertically inthe soil, 0.15 m away from the plants and inside the central rows, in at 0-0.30 m depth, according to the methodology recommended by Rocha et al. (2014).
being used to prepare the nutrient solution and to make up the volume lost through evapotranspiration. The results showed that with the exception of the treatment at the lowest salinity, there was a tendency to increased electrical conductivity of the nutrient solution with the increasing salinity of thewater; that the pH of the nutrient solution remained within the normal range throughout the cycle; that with the increasing salinity of the solution there was a reduction in all growthandproduction variables under analysis, inwaterconsumption, andin leaf N, K, Ca and Mg, and an increase in leaf concentrations of Na and Cl. It is possible to use brackish water for theproduction of Chinese cabbage when grown hydroponically as an alternative for those producers who have an available supply of brackish waterand a restricted supply of fresh water, however with a reduction in productivity. Key words: Brassica pekinensis L.. Nutrient solution. Salinity. Mineral nutrition.
Millet, Pennisetum glaucum (L.) R. Br., is an alternative for agricultural diversification and soil protection (Spehar & Trecenti, 2011). It is a traditional crop in Africa and wide adopted in India, with adaptation to locations under abiotic stresses (The world…, 1996). Despite millet’s rusticity, its genetic improvement has provided that under favorable conditions its production increases have favored the expansion of cultivation in Brazil (Pereira Filho, 2009). Jimenez et al. (2008) compared millet and quinoa as cover plants, andthe first one stood out for its root system, even in a simulating treatment of compacted soil. Water stress can affect plants by reducing the plant height, relative growth rate, cell growth, photosynthetic rate, andthe respiration activation (Hýsková et al., 2014). Cultivated plants have several mechanisms of adaptation to water deficit, but the responses are complex and adaptation is attributed to the ability of plants to control water losses by transpiration, which depends on the stomatal
ABSTRACT - Water availability inthe Brazilian semiarid is restricted and often the only water source available has high salt concentrations. Hydroponics allows using these waters for production of various crops, including vegetables, however, thewatersalinity can cause nutritional disorders. Thus, two experiments were conducted in a greenhouse at the Department of Agricultural Engineering of the Federal Rural University of Pernambuco, to evaluate the effects of salinity on the mineral nutrition of crisphead lettuce, cultivar Taina, in a hydroponicsystem (Nutrient Film Technique), using brackish waterinthe nutrient solution, which was prepared by adding NaCl to the local water (0.2 dS m -1 ). A randomized blocks experimental design was used in
ABSTRACT - Irrigation with brackish water is common inthe semiarid region of the Brazilian Northeast, potentiating the process of salinization of the soil in these areas. Thehydroponicsystem stands out as an important strategy for crop management in semiarid regions, since crops show greater tolerance to the salt stress underhydroponic conditions, which minimize the effects of soil salinization. Thus, the objective of this work was to evaluate the effects of salt stress on thegrowth, fruit yield and mineral nutrition of sweet pepper inhydroponicsystem, using brackish waterand coconut fiber substrate. The experiment was conducted in Recife, State of Pernambuco, Brazil (8°3'15''S, 34°52'53''W). A randomized block experimental design in a 5x2 factorial arrangement with five replications was used, consisting of five watersalinity levels of the nutrient solution (2.0; 3.5; 4.5; 5.5 and 6.5 dS m -1 ) and two sweet pepper cultivars (Bruno and Rubia). The increasing
water regimes (with and without water restriction). Plant height, stem diameter, number of leaves, shoot dry matter, root dry matter and total dry matter were measured. For all the studied variables, there was statistical significance for the factors species (A) andsalinity (B), individually. However, water deficit (Factor C) andthe interaction among factors (A x B x C) did not cause any statistical effect. The 50% reduction inwater replacement for the four species studied was not enough to cause significant damage to plant growth, with a mean reduction in dry matter production lower than 10%. It was observed that the tolerance index found varied according to the imposition of the stresses, being caused mainly by salinity. Based on shoot dry matter production, the species Neem behaved as moderately tolerant, while the other species were moderately sensitive to salinity. The applied water deficit was not enough to intensify the effects of the salt stress underthe conditions of the present study.
Protected cultivation has increased over the years. More studies on the benefits of using photoselective agrofilms are necessary. The choice of material to cover the greenhouse is a decisive factor for crop development andproduction. The aim of this study was to evaluate the effect of diffuser and blue-colored agrofilms on theproduction of different tomato cultivars of indeterminate growth habit under NFT hydroponicsystem. A completely randomized design in a 2x3 factorial scheme (two environments and three cultivars) was used: two agrofilm types (blue and diffuser) and 3 cultivars (Monterrey, Arendell and Totalle). Each plot consisted of 30 plants per treatment, with four replicates. Commercial tomato seedlings of indeterminate growth habit grafted on rootstock cultivar (Shincheonggang) were used. During the experiment, the electrical conductivity, intensity of radiation inside the greenhouse, gas exchange, soluble solids, lycopene content, pH and fruit production were evaluated. We concluded that the amount of radiation transmitted through the diffuser favors an increase of about 18% in gas exchange, 12% in lycopene content and 9.4% in tomato crop production.
Table 1. Analysis of variance for plant height (PH), stem diameter (SD), leaf number (LN), total leaf area (TLA) and root length (RL), absolute and relative growth rate of plant height (AGRph and RGRph), stem diameter (AGRsd and GRGsd) and leaf area (AGRla and RGRla), dry matter of root (DMR), stem (DMS), leaf (DML) and total dry matter (TDM) of eggplant under effect of levels of electrical conductivity in irrigation water (ECw) as a function to the application of bovine biofertilizer (B).
as citrus rootstocks [HTR - 069, HTR - 116, HTR - 127, LCR x TR - 001 and TSKC x (LCR x TR) - 040)], with three replications. The hybrids were grown inhydroponicsystem, using Leonard’s pots and Hoagland’s solution. The application of salinized solution was started at 90 days after sowing, when the gas exchange and PSII fluorescence were evaluated at 0, 24 and 48 hours after imposition of treatments, in order to determine the time interval for beginning of salt stress by physiological aspects. The initial fluorescence, stomatal conductance andwater use efficiency were the variables that best described the perception of stress in this study. The hybrid TSKC x (LCR x TR) - 040 proved to be more tolerant to salinity, followed by hybrid HTR - 069. The hybrid LCR x TR - 001 was the most sensitive to salinity, due to damages in its PSII activity.
Differences in NUE as a function of doses of N andwater depths are reported inthe literature. For example, Pandey et al. (2000), in a study with the maize crop, found increasing linear trend of NUE as a function of the irrigation depth. In this case, the higher water availability inthe soil favored better N use by plants, through the increase in N absorption under conditions of total water supply, compared to the 57% reduction inthe irrigation. However, Chilundo et al. (2016) found higher NUE values under conditions of lower water availability in treatments with 25% reduction in drip system; in this case, N losses were associated with the highest irrigation depths, which were larger than the storage capacity.