Electrical Conductivity Of Nutrient Solution Research Articles

Reduced fertigation input sustains yield and physiological performance for improved economic returns and cleaner production of greenhouse eggplant

Greenhouse horticulture, a sustainable alternative to conventional horticulture, maximises resource use and return for vegetable production. This study evaluated the impact of varying nutrient solution electrical conductivity (EC) levels (EC 1.8, 2.8, and 3.8) on eggplant cultivars (Solanum melongena L. cv. Lydia, and Tracey) performance and economic viability in high-tech glasshouses. We found that morphological traits such as plant height and leaf number were consistent across EC levels, while fruit weight, length, and width are significantly higher at the lowest EC (1.8). Photosynthetic rates increased significantly with rising EC levels, while other gas exchange parameters such as stomatal conductance, intrinsic water use efficiency, and vapour pressure deficit were similar for all EC levels tested. Yield analysis revealed a negative correlation between eggplant yield and increasing EC levels, with optimal yields in both eggplant varieties (0.81 and 1.14 kg m−2 week−1 in Lydia and Tracey, respectively) achieved at the lowest EC. Economic analysis highlighted that lower EC levels lead to lower operational costs and higher net profit values (NPV). Sensitivity analysis underscored the importance of wholesale price and crop yield in determining NPV, with lower EC levels offering a shorter payback period of approximately 6 years in Australia and China and higher economic returns. The study highlights the significance of optimizing EC levels for achieving more resource-sustainable and profitable eggplant production in greenhouses.

Electrical conductivity of nutrient solutions affects the growth, nutrient levels, and content and composition of essential oils of Acmella oleracea (L.) R. K. Jansen from southeastern Brazil

Jambu, a plant native to the Amazon, is rich in essential oils, particularly spilanthols and phytols. Although hydroponic cultivation of this vegetable is practiced, the process remains relatively understudied. In this context, this study aimed to assess the influence of electrical conductivity of nutrient solutions on jambu production. Greenhouse experiments were conducted at Universidade Estadual do Norte Fluminense (UENF), Brazil, employing a randomized block design encompassing six blocks comprising six Hoagland and Arnon nutrient solutions with electrical conductivities of 0.5, 1.0, 2.0, 2.5, 3.0, and 4.0 mS cm−1. Harvesting occurred 72 d after sowing, and the plants exhibited improved growth at electrical conductivity close to 3.5 mS cm−1. The levels of N, P, K, B, Zn, Mn, and essential oils of jambu plants increased linearly with increasing electrical conductivity. Twenty-three compounds were detected among the investigated essential oils, with spilanthol, phytol, and acmellonate present in the highest amounts. Increase in electrical conductivity led to increases in the percentage areas of several compounds, such as (Z,Z)-1,8,11-heptadecatriene, caryophyllene, 6-pentadecen-1-ol, 1-pentadecene, spilanthol isomer 1, (E)-β-ionone, kessane, and caryophyllene oxide. Furthermore, higher electrical conductivity resulted in decreasing percentages of compounds such as spilanthol, phytol, and Compound 2. Notably, a 609.74 % increase in caryophyllene and a 25.65 % reduction in spilanthol were observed with increasing electrical conductivity. These results suggest that the productivity of jambu plants is improved, including the production of essential oils, with cultivation in solutions with electrical conductivities above 2.5 mS cm−1. However, this condition may negatively affect most cultivated vegetables. The mechanisms underlying the increased tolerance of jambu to higher electrical conductivities require further investigation.

Condutividades elétricas de solução nutritiva completa em comparação com solução nutritiva usada comercialmente na produção de mudas

ABSTRACT: Fertigation is widely used in seedling production for different crops, including passion fruit. There is no consensus on the ideal nutrient solution, and as such, nurseries have used fertigation empirically. This study assessed the electrical conductivity of nutrient solution containing macro and micronutrients in passion fruit seedling production and compared it with commercially used fertigation. A completely randomized design was used, with five treatments and six repetitions. Four electrical conductivities (0.5, 1.0, 2.0 and 4.0 dS m-1) of a complete nutrient solution and an additional treatment (commercial nutrient solution) were analyzed. Daily fertigation with a complete nutrient solution (macro and micronutrients) at electrical conductivities between 2.6 and 3.3 dS m-1 followed by two daily irrigations are efficient at producing FB 300 “Araguari” passion fruit seedlings in coconut fiber substrate, with benefits such as greater biomass and better Dickson quality index when compared to commercial nutrient solution.

Cultivation of arugula microgreens: seed densities and electrical conductivity of nutrient solution in two growing seasons

Cultivation of arugula microgreens: seed densities and electrical conductivity of nutrient solution in two growing seasons

The Electrical Conductivity of Nutrient Solution Influenced the Growth, Centellosides Content and Gene Expression of Centella asiatica in a Hydroponic System

Centella asiatica is a herbaceous plant containing medicinal and cosmetic properties: anti-bacterial, anti-aging, memory enhancing and wound healing. The lack of information impedes the development of suitable growth conditions for C. asiatica in the hydroponic system. Maintaining proper electrical conductivity (EC) of a nutrient solution is considered crucial for plant growth and the accumulation of bioactive compounds in a plant grown in hydroponics. This study aimed to investigate an optimal EC that enhances the growth of C. asiatica and its centellosides content. Seedlings were grown in commercial nutrient solution and treated with four different strengths of EC (0.6, 1.2, 1.8 and 2.4 indicated T1, T2, T3 and T4, respectively) under controlled environment conditions. Our results demonstrate that the number of leaves, leaf area, number of runners, shoot fresh weight and shoot dry weight were significantly increased in T2 among the treatments. However, these growth parameters were lowest in T4. Furthermore, the content of asiaticoside, madecassoside, asiatic acid and madecassic acid was the highest in plants that were treated with T2. The expression of centelloside biosynthesis-related genes is also affected by the strength of the nutrient solution. A positive correlation was observed between the number of leaves, leaf area and centellosides content. This study provides valuable background on optimal EC content in the nutrient solution in a hydroponic system with enhanced centellosides content to leverage the C. asiatica production.

Cultivo do almeirão sob soluções nutritivas preparadas em águas salobras e aplicadas em diferentes temperaturas

ABSTRACT 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).

Nutrient Solution Electrical Conductivity Affects Yield and Growth of Sub-Irrigated Tomatoes

Sub-irrigation of greenhouse crops has the potential to increase water and nutrient use efficiency; however, fertilizer salts that are not absorbed by the plants tend to accumulate in the substrate and eventually raise the substrate’s electrical conductivity (EC). The objective of this study was to determine the optimum EC of the nutrient solution in sub-irrigated tomatoes to allow maximum yield. Total fruit yield was higher in sub-irrigated plants with solutions at 2.0 dS m−1 (5105 g per plant), and it was comparable to that obtained for drip-irrigated plants (4903 g per plant); however, the yield of fruits from the second truss was 37% higher in sub-irrigated than in drip-irrigated plants when the EC was 2.0 dS m−1. In contrast, at the end of the growing season, the yield of plants sub-irrigated with nutrient solutions of 2.0 dS m−1 was the lowest, being surpassed by 37% by that of plants treated with 1.4 dS m−1. The dry weight of vegetative plant parts was reduced in sub-irrigated plants, suggesting a shift in dry mass partitioning. Our results show that with sub-irrigation, the growing season should be started using nutrient solutions with higher EC, but eventually, this EC should be decreased to maintain proper substrate EC and high yield.

A Graminaceae-derived protein hydrolysate and its fractions provide differential growth and modulate qualitative traits of lettuce grown under non-saline and mild salinity conditions

The modulation of plant secondary metabolism by the manipulation of nutrient solution (NS) electrical conductivity and biostimulant application has the potential to increase crop growth and the content of bioactive compounds, thus ameliorating the qualitative attributes of vegetables. A Graminaceae-derived protein hydrolysate (pH) and its molecular fractions PH1 (>10 kDa), PH2 (1 < x <10 kDa) and PH3 (<1 kDa) were applied on lettuce grown in a soilless system and irrigated with two levels of NaCl in the NS (0 and 30 mM). The different pH fractions provided distinct responses, with PH2 in saline conditions increasing lettuce fresh weight by 10.48%, and decreased Na, Cl, malate and citrate concentrations in the leaves by 37.24%, 15.45%,31.4% and 33.73% compared to control. Similar results were achieved by the fraction PH3. However, pH and its fractions PH2 and PH3 increased total flavonoids in salinity conditions, while pH and its fraction PH3 increased total phenolic acids in both saline and non-saline conditions. At the same time, all the 3 fractions of pH increased lutein in both conditions. Therefore, pH fractions should be casted, under tailored conditions, to achieve the desired growth and modulation of qualitative attributes. Nonetheless, omic approaches should be further recommended to support and clarify the mechanisms of these fractions.

Effects of LED Red and Blue Spectra Irradiance Levels and Nutrient Solution EC on the Growth, Yield, and Phenolic Content of Lemon Basil (Ocimum citriodurum Vis.)

This research was conducted to study the effects of LED red and blue spectra irradiance levels and nutrient solution (electrical conductivity) and their interaction on the plant growth, yield, and phytochemical contents of lemon basil (Ocimum citriodorum Vis.) in a controlled environment. The controlled environment was equipped with red and blue spectra at a 4:1 ratio with irradiance levels of 80 and 160 µmol m−2 s−1 and irrigated with four different nutrient solution ECs at 1.0, 1.8, 2.6, and 3.4 mS cm−1, cultivated on a vertical structure. The temperature and relative humidity of the controlled environment and the pH of the nutrient solution were maintained at 26 and 18 °C day and night, 65 ± 5%, and pH 6, respectively. It was observed that plant height, canopy diameter, and the number of leaves of lemon basil had significantly increased under the irradiance levels of 160 µmol m−2 s−1 in combination with a nutrient solution EC of 2.6 mS cm−1. In addition, there was an interaction observed between the LED irradiance levels and the nutrient solution EC on the fresh weight of the stem and the dry weight of all the plant parts (leaves, stem, and roots). Lemon basil cultivated at 160 µmol m−2 s−1 and irrigated with 2.6 mS cm−1 was significantly higher in fresh stem weight and dry leaf, stem, and root weight at 17.36, 1.79, 1.82, and 0.22 g, respectively. The ascorbic acid of lemon basil was significantly higher under a treatment of 160 µmol m−2 s−1 irradiance level and an EC of 2.6 mS cm−1, and no interaction was observed. At the same time, there was an interaction observed between the LED irradiance level and the nutrient solution EC on the total phenolic content (TPC), total flavonoid content (TFC), and caftaric acid concentration of lemon basil. Lemon basil cultivated at 160 µmol m−2 s−1 and irrigated with 2.6 mS cm−1 was significantly higher in TPC, TFC, and caftaric acid concentration, with 1440.62 mg gallic acid equivalent to 100 g−1 DW, 1148.79 mg quercetin equivalent to 100 g−1 DW, and 2812.50 mg 100 g−1 DW, respectively. This result indicates that the irradiance levels of red and blue LED spectra at 160 µmol m−2 s−1 and irrigated with a nutrient solution EC of 2.6 mS cm−1 enhances the growth, yield production, and phenolic content of lemon basil in a controlled environment facility.

Application of PSO-BPNN-PID Controller in Nutrient Solution EC Precise Control System: Applied Research.

In this paper, we present a nutrient solution control system, designing a nutrient solution electrical conductivity (EC) sensing system composed of multiple long-range radio (LoRa) slave nodes, narrow-band Internet of Things (NB-IoT) master nodes, and a host computer, building a nutrient solution EC control model and using the particle swarm optimization (PSO) algorithm to optimize the initial weights of a back-propagation neural network (BPNN). In addition, the optimized best weights are put into the BPNN to adjust the proportional–integral–derivative (PID) control parameters Kp, Ki, and Kd so that the system performance index can be optimized. Under the same initial conditions, we input EC = 2 mS/cm and use the particle swarm optimization BP neural network PID (PSO-BPNN-PID) to control the EC target value of the nutrient solution. The optimized scale factors were Kp = 81, Ki = 0.095, and Kd = 0.044; the steady state time was about 43 s, the overshoot was about 0.14%, and the EC value was stable at 1.9997 mS/cm–2.0027 mS/cm. Compared with the BP neural network PID (BPNN-PID) and the traditional PID control approach, the results show that PSO-BPNN-PID had a faster response speed and higher accuracy. Furthermore, we input 1 mS/cm, 1.5 mS/cm, 2 mS/cm, and 2.5 mS/cm, respectively, and simulated and verified the PSO-BPNN-PID system model. The results showed that the fluctuation range of EC was 0.003 mS/cm~0.119 mS/cm, the steady-state time was 40 s~60 s, and the overshoot was 0.3%~0.14%, which can meet the requirements of the rapid and accurate integration of water and fertilizer in agricultural production.

Effects of Nutrient Solution Electrical Conductivity on the Leaf Gas Exchange, Biochemical Stress Markers, Growth, Stigma Yield, and Daughter Corm Yield of Saffron in a Plant Factory

Indoor saffron farming systems under controlled conditions are required to meet the high demand for this valuable crop. The aim of the present study was to determine the flowering, growth, and yield responses of saffron grown using nutrient solutions with different electrical conductivity (EC) levels (0.7, 1.4, and 2.1 dS m−1). Sprouted saffron corms were cultured for 24 weeks under a volcanic rock-based aerated continuous immersion system. Vegetative growth and leaf gas exchange, but not flowering, were affected significantly by EC levels. The optimal EC in a balanced nutrient solution was 0.7 dS m−1, at which level the highest plant height, leaf area, biomass, photosynthetic rate, number of daughter corms, and percentage of corms ≥ 25 mm were recorded. An EC level of 2.1 dS m−1 decreased the photosynthetic rate, stomatal conductance, and transpiration rate of saffron but increased biochemical stress marker levels and elevated various antioxidant defense enzyme levels significantly in saffron leaves, possibly reflecting a defense response to the cellular damage provoked by the higher EC level. In terms of nutrient solution EC, 0.7 dS m−1 was optimal in saffron, whereas 2.1 dS m−1 caused oxidative stress that led to reduced growth and daughter corm production.

Application of Electrical Conductivity (EC) for Some Potato Varieties in the Aeroponically Seed Production with Root Zone Cooling and Evaporative Cooling in Tropical Lowlands

Aeroponic potato seed production in the lowlands has been carried out by root zone cooling and evaporative cooling in order to reduce high temperature stress for the roots and tops of potato plants. However, the effect of nutrient solution EC on several varieties of potato seeds for an aeroponic system with a combination of root zone cooling and evaporative cooling for potato seed production in the lowlands has not been done. This study aims to obtain the response of potato varieties and the application of different ECs on aeroponic seed production with root zone and evaporative cooling in tropical lowlands. The factors analyzed : 1. Variety (V): V1 (MZ), V2 (Granola K), V3 (Granola L), and 2. Nutrient concentration (EC): EC1 (1.5 mS/cm for Week 1- 4, 2 mS/cm for Week 5 until harvest), and EC2 (1.5 mS/cm for Week 1-4, and 3 mS/cm for Week 5 until harvest), while the design used was RAK with 3 replications. The results showed that the Granola K and EC2 varieties are more efficient for potato seed production in the lowlands with the application of root zone and evaporative cooling. This variety produced the highest number of tubers up to 30 tubers/plant. Similarly, the Granola L and MZ varieties showed similar results with a total number of tubers above 10 tubers/plant. Keywords: Cultivation, Greenhouse, Hydroponics, Nutrition, Tubers

Morphological Responses of Viola Accessions to Nutrient Solution Application and Electrical Conductivity

Growing of ornamental flowering plants represents an important sector of horticulture. Viola × wittrockiana (garden pansy) is used in garden beds and borders due to their colorful blooming, which occurs in early spring and late autumn. Nowadays, breeders focus on applying different nutrient solutions to improve the quality, flowering, and ornamental properties of plants, yet electrical conductivity (EC) level is an important fact to know. It is known that higher EC levels can inhibit plants’ growth. In the present study, pansy seedlings were subjected to different EC nutrient solutions 1 (control), 2, 3.5, 5, and 6.5 mS cm−1 EC to assess the positive or negative effects regarding the plant’s growth and development. The results indicated that an appropriate EC level of nutrient solution can have a positive effect on growth parameters, as well as on the flowering of plants. According to the hierarchical clustering, the used EC nutrient solutions significantly influenced the growth, number of shoots and leaves and the inflorescences number. From the present study results, it can be concluded that even though all EC levels increased growth parameters compared with control, the greatest results were obtained in plants under the effect of the 5 mS cm−1 of EC.

Enlarging of Grape Hyacinth Bulb at Different Nutrient Solution Ratios in Soilless Culture

ABSTRACT Grape hyacinth bulbs must be of a certain size in order to bloom. It is commercially important to extend the circumference of grape hyacinth bulbs in a short time. This study was conducted to determine the effects of different nutrient solution rates on the bulb enlargement, the bulblet formation and plant growth characteristics in soilless culture. Grape hyacinth bulbs (Muscari armeniacum Leichtlin ex Baker) with a circumference of 3 cm were grown in perlite bag culture at six different nutrient solution rates (25%, 50%, 75%, 100%, 125% and 150% of the final nutrient solution). According to the variance analysis; the effect of nutrient solution ratios on bulb diameter, bulb weight, bulblet number, adventitious root number, adventitious root length, adventitious root weight, leaf length and leaf weight was found to be insignificant. Bulb diameter enlarged between 14.44% and 29.13%. Bulb diameter varied between 10.95 mm and 12.20 mm, bulb weight 0.74–0.90 g, bulblet number 1.00–1.56 piece, leaf length 23.05–27.33 cm. Electrical conductivity (EC) of drainage waters increased with increasing nutrient solution ratio. A positive correlation was determined between leaf number and bulb diameter, nutrient solution ratio and EC. In addition, a positive correlation was determined between bulb weight, leaf number and EC and bulblet number. All these results showed that grape hyacinth bulbs could maintain their normal development at low nutrient solution doses, thus saving on fertilizers.

Supplementary Light with Increased Blue Fraction Accelerates Emergence and Improves Development of the Inflorescence in Aechmea, Guzmania and Vriesea

In protected cultivation, increasing the light level via supplementary lighting (SL) is critical to improve external quality, especially in periods with low light availability. Despite wide applications, the effect of light quality remains understated. In this study, the effect of SL quality and nutrient solution electrical conductivity (EC) on growth and flowering of three bromeliad species was investigated. Treatments included solar light, and this supplemented with R90B10 [90% red (R) and 10% blue (B)], R80B20 (80% R and 20% B), and R70B30 (70% R and 30% B). These were combined with an EC of 1 and 2 dS m-l. Irrespective of the light treatment, the higher EC promoted growth, inflorescence emergence, and development in Aechmea fasciata (Lindl.) Baker, whereas adverse effects were noted in Guzmania and Vriesea. The higher EC-induced negative effect in Guzmania and Vriesea was slightly alleviated by SL. With few notable exceptions, SL exerted limited effects on photosynthetic functionality. Depending on the species, SL improved external quality traits. In all species, SL increased root and inflorescence weight and stimulated biomass allocation to generative organs. It also accelerated inflorescence emergence and promoted inflorescence development. In this way, the time to commercial development stage was considerably shortened. These effects were more prominent at R80B20 and R70B30. Under those conditions, for instance, inflorescence emergence occurred 3–5 weeks earlier than in the control, depending on the species. In conclusion, SL with increased B proportion leads to shorter production period owing to faster emergence and improved development of the inflorescence and is recommended for commercial use.

Nutrient Use in Vertical Farming: Optimal Electrical Conductivity of Nutrient Solution for Growth of Lettuce and Basil in Hydroponic Cultivation

During the past few decades, vertical farming has attracted a lot of interest as an alternative food production method. Vertical farms use engineered growth environments and hydroponic cultivation techniques for growing plants indoors. One of the important factors in vertical farming for the cultivation of different plants is the amount of nutrients, which can be measured as electrical conductivity (EC). Studying the optimal EC is important for avoiding nutrient loss and deficiency in vertical farms. In this study, we investigated the effect of five EC levels (2, 1.2, 0.9, 0.7, and 0.5 dS m−1) of Hoagland nutrient solution on the growth and development of basil cultivar ‘Emily’ and lettuce cultivar ‘Batavia-Caipira’. During the study, the environmental parameters were kept fixed using an automatic dosing machine. The experiment was done in automatic vertical farms using the hydroponic ebb–flow cultivation technique with a temperature of 20 ± 1 °C, relative humidity of 50–60%, CO2 concentration of 450 ppm, pH = 6, the PPFD (photosynthetic photon flux density) of 215 ± 5.5 μmol m−2 s−1, and the photoperiod of 16:8 h (day/night). Each treatment was replicated four times. We studied the effects on several growth parameters (including the dry and fresh weight of leaves and roots, number of leaves, and leaf area) as well as the chlorophyll and nitrogen concentration of the leaves. According to the results, the basil and lettuce growth parameters among the five treatments have been significantly higher in the treatment with EC of 1.2 and 0.9 dS m−1. These EC values are lower than the recommended EC value given as the optimum in the previous studies. However, the concentration of chlorophyll and nitrogen show different trends and were higher in full strength of nutrient solution with EC = 2 dS m−1.

Salinity tolerance of tomato fertigated with different K+/Ca2+ proportions in protected environment

ABSTRACT Adequate potassium and calcium nutrition is a strategy to reduce salt stress on tomatoes, as it reduces nutritional imbalance in plants. With the objective of evaluating tomato production using irrigation with saline waters and fertigation with different potassium-calcium proportions, an experiment was carried out in a protected environment in Mossoró, RN, Brazil. The experimental design used was randomized blocks, in a 5 x 4 factorial scheme, with four replicates. The treatments consisted of the combination of four electrical conductivity of nutrient solution (ECns) (1.75; 3.25; 4.75; and 6.25 dS m-1) combined with five ionic proportions (m/m) of potassium and calcium (F1 = 2.43:1; F2 = 2.03:1; F3 = 1.62:1; F4 = 1.30:1 and F5 = 1.08:1). The response variables were: number of fruits, mean fruit weight, fruit production per plant and relative yield. It was possible to identify satisfactory results of production when higher salinity was used. Fertigation with low K+/Ca2+ proportions intensifies the effect of salinity on tomato crop.

Effect of the nutrient solution electrical conductivity (EC) on the growth, development and nutrient content of Viola tricolor var. hortensis grown in perlite

ISHS III International Symposium on Soilless Culture and Hydroponics: Innovation and Advanced Technology for Circular Horticulture Effect of the nutrient solution electrical conductivity (EC) on the growth, development and nutrient content of Viola tricolor var. hortensis grown in perlite

Basil (Ocimum basilicum L.) growth response to wood fiber based growing media in ebb-and-flow system as a function of the electrical conductivity of nutrient solution and pot size

Basil (<i>Ocimum basilicum</i> L.) growth response to wood fiber based growing media in ebb-and-flow system as a function of the electrical conductivity of nutrient solution and pot size

Automatic hydroponic nutrient mixing for hydroponic NFT and fertigation

This paper aims to create hydroponic nutrient mixing system automatically for circulation hydroponic system like NFT (Nutrient Film Technique) and for non-circulation hydroponic system such as drip irrigation system. System continuously sense nutrient concentration and pH level with EC (Electrical Conductivity) sensor and pH sensor. This data will process by ESP32 Wi-Fi microcontroller for monitoring and control dosing pump to maintain nutrient solution EC and pH with the predefined target. In non-circulated hydroponic, nutrition and water will flow into the irrigation system, to control humidity level in plant media, system use soil moisture level sensor. System use IoT cloud Blynk for easy user control and monitoring, user can use application in their smartphone. Test result shows system can increase the EC value from current condition 0.7 to target 3 within ±9 minutes and can maintain the EC value.