Hydroponic Units Research Articles

Evaluation of productivity and efficiency of a large-scale coupled or decoupled aquaponic system

Aquaponics, a sustainable agricultural method, is gaining attention for its closed-loop system's potential to address diverse environmental and economic challenges in traditional agriculture. The aim of this study was to fill knowledge gaps in scaling up lab-scale systems to larger-scale decoupled aquaponics, offering a comprehensive understanding of the system's productivity and water and fertiliser use efficiency. In coupled aquaponics (CAP), the aquaculture, and the hydroponic units are arranged in a single loop, and water flows continuously from the fish tanks to the plant unit and vice-versa. In decoupled aquaponics (DCAP), the aquaculture and hydroponics units are arranged in a multi-loop setup as separate functional units that can be controlled independently. This work compared coupled aquaponics, decoupled aquaponics and hydroponics (HP, in perlite slabs) under the same climatic conditions with a substrate grown crop in a pilot scale greenhouse. The evaluation of growth parameters, yield, water, and fertiliser use for basil, cucumber, parsley, and tomato cultivations co-cultivated with the tilapia recirculating aquaculture system (RAS) are presented. The highest yields were achieved by DCAP plants in all experiments (15% higher than HP and 19% than CAP for basil, 38% than CAP in cucumber, 17% and 72% than HP and CAP in parsley, and 8% and 55% for HP and CAP in tomato experiments). The CAP treatment that did not receive any fertilisers presented the highest water use efficiency compared to both HP and DCAP treatments. Also, compared to HP, the DCAP treatment presented higher water and fertilisers use efficiency. Consequently, the adoption of decoupled aquaponic systems is the key to aquaponic evolution in the future.

Production of Flathead Grey Mullet (Mugil cephalus) and Lettuce (Lactuca sativa) in a Coupled Aquaponic System under Suboptimal Water Temperatures

The combined production of three varieties of lettuce (romaine, iceberg, and red leaf) with flathead grey mullet (Mugil cephalus) was tested in triplicate in three independent coupled aquaponic units with no thermal control. For this purpose, a total of 114 fish (2.5 kg/m3) were stocked in each fish tank (2 m3), and 92 lettuces were planted in the hydroponic unit (6 m2). As no thermal control was included in the design of the aquaponic system, water temperatures declined from maximum values of 20.4 °C to minimum values of 5.0 °C, which directly affected fish growth. However, the conditions imposed by the aquaponic system were suitable for promoting lettuce’s growth and external appearance, as no pests or leaf discoloration were noticed. Lettuce survival was similar among the three tested varieties (98.5 ± 1.7%). The yields for the romaine and iceberg varieties were 384 ± 100 g/lettuce and 316 ± 70 g/lettuce, respectively, and that for the red leaf variety was lower, at 176 ± 75 g/lettuce. Yield values ranged between 3.6 and 4.4 kg/m2 depending on the replicate considered (4.0 ± 0.4 kg/m2). According to present results, each aquaponic unit required ca. 2.6–2.7 L of water per unit of lettuce produced.

Microbiome study of a coupled aquaponic system: unveiling the independency of bacterial communities and their beneficial influences among different compartments

To understand the microbiome composition and interplay among bacterial communities in different compartments of a coupled freshwater aquaponics system growing flathead grey mullet (Mugil cephalus) and lettuces (Lactuca sativa), 16S rRNA gene amplicon sequencing of the V3–V4 region was analysed from each compartment (fish intestine, water from the sedimentation tank, bioballs from the biological filter, water and biofilm from the hydroponic unit, and lettuce roots). The bacterial communities of each sample group showed a stable diversity during all the trial, except for the fish gut microbiota, which displayed lower alpha diversity values. Regarding beta diversity, the structure of bacterial communities belonging to the biofilm adhering to the hydroponic tank walls, bioballs, and lettuce roots resembled each other (weighted and unweighted UniFrac distances), while bacteria from water samples also clustered together. However, both of the above-mentioned bacterial communities did not resemble those of fish gut. We found a low or almost null number of shared Amplicon Sequence Variants (ASVs) among sampled groups which indicated that each compartment worked as an independent microbiome. Regarding fish health and food safety, the microbiome profile did not reveal neither fish pathogens nor bacterial species potentially pathogenic for food health, highlighting the safety of this sustainable food production system.

Nutrients Use Efficiency in Coupled and Decoupled Aquaponic Systems

Aquaponics is currently undergoing a transformation into an intensive food production system. The initially applied systems focused on small-scale, fish-centric coupled (CAP, the aquaculture, and the hydroponic units are arranged in a single loop, and the water flows continuously from the fish tanks to the plant unit and back) aquaponics. More recently, the primary area of research interest has shifted toward larger-scale, plant-centric decoupled (aquaculture and hydroponics units are arranged in a multi-loop setup as separate functional units that can be controlled independently) systems, aiming to achieve greater economic benefits and employ more environmentally friendly practices. The objective of this study was to address gaps in the expansion of decoupled larger-scale aquaponics and to provide a comprehensive understanding of the water and nutrient flow in the system. For this purpose, experiments were performed in a greenhouse on CAP and DCAP systems, while this study also included measurements in a pure hydroponic system (HP). This study presents an assessment of the water and nutrient flow in four different crops: basil; cucumber; parsley; and tomato, all co-cultivated with a tilapia aquaculture system. Significant nutrient deficiencies and imbalances were identified in the CAP solution, leading to pronounced impacts on nutrient assimilation, particularly for fruiting vegetables. However, the average nutrient use efficiency (NUE) for nitrogen, phosphorous, potassium, and calcium was found to be 42% higher in the CAP treatment compared to HP and DCAP treatments. The nutrient solution in the DCAP treatment did not exhibit differences in water quality parameters and nutrient efficiency when compared to HP, resulting in similar effects on nutrient assimilation. Nonetheless, it was observed that DCAP plants exhibited superior NUE compared to HP plants.

Advance an Automated Indoor Hydroponic Unit for Plant Growth Detection with Compatible for Two Different Plant Varieties

The study aimed to design and fabricate an automated indoor hydroponic plant growth chamber, by comparing the manual system to determine plant growth and development and the sub-objective was to send data to the IoT platform. The sensor-based automated system incorporated pH, TDS, temperature, and humidity sensors, controlled by solenoid valves using Arduino. Tomato and lettuce plants were grown in both systems and growth parameters were measured. The results showed that the automated system maintained consistent temperature, humidity, pH, and EC levels similar to the outdoor system (vary in 30-32, 52-79, 5.5-6.5, and 1.5-2.5 dS/m ranges respectively). Furthermore, the automated indoor system significantly enhanced the plant growth of tomato and lettuce plants compared to the manual system. Significantly higher plant heights of 27.9±1.9 cm and 27.4±4.9 cm, the leaf lengths of 3.2±0.1 cm and 3.9±0.1 cm were observed for the tomatoes and the lettuces respectively in the automated indoor system. A significant difference was observed between the SPAD reading of the automated indoor tomato of 30±0.9 and the outdoor tomato of 26±0.4. Similarly, SPAD readings for the automated indoor lettuce of 23±0.3 and outdoor lettuce of 17±0.5 were significantly different (Pr=<0.0001, Pr≤0.05). These findings highlight the effectiveness of the automated hydroponic system in accommodating plant preferences and its potential for improving agricultural practices. By integrating IoT platforms for data analysis, this technology can optimize plant growth, enhance yields, and facilitate informed decision-making in hydroponic farming.

Monitoring and Controlling Hydroponic Units using IoT

The use of hydroponic systems for growing crops is becoming increasingly popular due to its efficiency and sustainability. However, monitoring and controlling these systems can be challenging and time-consuming. This is where the Internet of Things (IoT) comes into play, as it allows for the real-time monitoring and control of hydroponic systems from anywhere at any time. In this paper, we explore the use of IoT for monitoring and controlling hydroponic units, including sensors for measuring various parameters such as pH, temperature, and nutrient levels, and actuators for controlling water and nutrient supply. We also discuss the advantages of using IoT for hydroponic farming, such as increased yield and reduced resource usage, as well as potential challenges and future research directions. Overall, this paper provides a comprehensive overview of the use of IoT in hydroponics and its potential to revolutionize modern agriculture.

Influence of different hydroponic units on fish and plant performance and water quality in a snakehead fish-mint aquaponics system

This study was done to assess the effect of two hydroponics cultivation (media bed (MB) and floating raft (FR)) on the performance of striped snakehead fish (SSF) (Channa striata Bloch, 1793) and mint (Mentha arvensis Linnaeus, 1953), and water quality parameters in the aquaponic system. Fish were cultured at a density of 500 fingerlings per m3 for 130 days. Mints were planted at densities of 40 and 34 lettuce m−2 in the MB and FR treatments, respectively, and had two cutting harvests. During the experimental period, levels of most water quality parameters analysed in the two treatments were in the optimal range for SSF and mint. After 130 days, all the growth performances and survival rates of fish in the FR treatment were higher than those in the MB treatment, but these differences were not statistically significant (P > 0.05). Fish growth performance was similar to those reported in other RAS and aquaponics studies, whereas FCR was lower. For mint, the plant height and diameter in the MB were significantly higher than those in the FR, but the fresh biomass in the FR was significantly greater than that in the MB (P < 0.05). In general, these results implied that the FR unit is more effective than the MB for culturing SSF (C. striata) with mint (M. arvensis) in aquaponics.

A multi-criteria linear model on carbon footprint in vertical farms and its relation to energy demand and operational costs

Operational research is the scientific discipline - widespread in sciences like engineering, economics, sociology, politics - that applies advanced analytical methods to assist in decision-making. The aim of this study was to demonstrate the value of such methods to the research of the carbon footprint produced by vertical farms, in specific its decrease in regard to the pre- and post-operational energy consumption and cost that occurs throughout their lifecycle. A logistic structure was designed, dependent on specific parameters, such as the space, location, and fuel of the hydroponic unit that change during the research. This way, multiple possible scenarios could be studied. The results of each scenario were analysed and compared via a linear multi-criteria model. The results demonstrated strong dependencies (and softer links) between particular parameters, such as the choice of space and the food miles required for the product.

System design and production practices of aquaponic stakeholders.

Aquaponics is an agricultural practice incorporating aquaculture and hydroponic principles. This study assesses the current system design and production practices of the aquaponic industry, compares these metrics by stakeholder group, identifies trends, and provides recommendations for future development. An electronic survey of aquaponic stakeholders was conducted from December 2019 to June 2020 targeting hobbyists, producers, and educators from various aquaponic-focused professional associations, email and social media groups. Of 378 total responses, 84% came from the United States and were clustered in plant hardiness zones five to nine. Aquaponic systems were commonly homemade/do-it-yourself (DIY), many of which incorporated commercially available (turn-key) technology. Most growers used coupled systems that integrated recirculating aquaculture systems and either deep-water culture (DWC) or media bed hydroponic units. Common plant lighting sources were sunlight and light emitting diode (LED). Water sources were typically municipal or wells. Personal labor input was typically less than 20 hrs/wk. Funding sources were primarily personal funds, followed by government grants, and private investor funds. System sizes varied greatly, but the median area was 50 to 500 ft2 for hobbyists and educators and 500 to 3,000 ft2 for producers. Respondents commonly sold vegetable produce, training and education, food fish, and microgreens. Tilapia and ornamental fish were commonly grown, with 16 other species reported. Common crops were lettuce, leafy greens, basil, tomatoes, peppers, and herbs with many additional lesser-grown crops reported, including cannabis. Overall, the industry still growing, with a large portion of stakeholders having less than two years of experience. However, veteran growers have remained in operation, particularly in the producer and educator groups. The survey results suggest a shift away from outdoor systems, media beds, tomatoes, ornamental fish, and perch production, and a shift toward decoupled systems, DWC, drip irrigation, and wicking beds, larger system area, leafy greens, and trout/salmon production compared to previous industry surveys. The reduced diversity of plant species grown suggest some level of crop standardization. Commercial producers tended to sell more types of products than other stakeholders, suggesting that diversification of offerings may be key to profitability. The combined production area specified by respondents indicates the industry has grown substantially in recent years. Finally, the presence of bank loan-funded operations suggests increased knowledge and comfort with aquaponics among lenders.

Plant Growth and Lai Estimation Using Quantized Embedded Regression Models for High Through put Phenotyping

Phenotyping involves the quantitative assessment of the anatomical, biochemical, and physiological plant traits. Natural plant growth cycles can be extremely slow, hindering the experimental processes of phenotyping. Deep learning offers a great deal of support for automating and addressing key plant phenotyping research issues. Machine learning-based high- throughput phenotyping is a potential solution to the phenotyping bottleneck, promising to accelerate the experimental cycles within phenomic research. The influence of climate change, and due to its unpredictable nature, majority of agricultural crops have been affected in terms of production and maintenance. Hybrid and cost-effective crops are making their way into the market, but monitoring factors that affect the increase in yield of these crops, and conditions favorable for growth have to be manually monitored and structured to yield high throughput. Farmers are showing transition from traditional means to hydroponic systems for growing annual and perennial crops. These crop arrays possess growth patterns, which depend on environmental growth conditions in the hydroponic units. Semi-autonomous systems, which monitor these growths, may prove to be beneficial, reduce costs and maintenance efforts, and predict future yield beforehand to get an idea on how the crop would perform. These systems are also effective in understanding crop drools and wilt/diseases from visual systems and traits of plants. Forecasting or predicting the crop yield well ahead of its harvest time would assist the strategists and farmers for taking suitable measures for selling and storage. Accurate prediction of crop development stages plays an important role in crop production management. Such predictions will also support the allied industries for strategizing the logistics of their business. Several means and approaches of predicting and demonstrating crop yields have been developed earlier with changing rate of success, as these do not take into considerations the weather and its characteristics and are mostly empirical. Crop yield estimation is also affected by taking into account a few other factors. Plant diseases enormously affect the agricultural crop production and quality with huge economic losses to the farmers and the country. This in turn increases the market price of crops and food, which increase the purchase burden of customers. Therefore, early identification and diagnosis of plant diseases at every stage of plant life cycle is a very critical approach to protect and increase the crop yield. In this article, I propose an Embedded Machine Learning approach to predicting crop yield and biomass estimation of crops using an Image based Regression approach using edge Impulse that runs on Edge system, Sony Spresense, in real time. This utilizes few of the six Cortex M4F cores provided in the Sony Spresense board for Image processing, inferencing and predicting a regression output in real time. This system uses Image processing to analyze the plant in a semi-autonomous environment and predict the numerical serial of the biomass allocated to the plant growth. This numerical serial contains a threshold of biomass, which is then predicted for the plant. The biomass output is then also processed through a linear regression model to analyze efficacy and compared with the ground truth to identify pattern of growth. The image Regression and linear regression model contribute to an algorithm, which is finally used to test and predict biomass for each plant semi-autonomously.

A simplified non-greenhouse hydroponic system for small-scale soilless urban vegetable farming

Majority of under-developed countries continue to face a challenge of food insecurity around urban areas resulting from factors such as; limited access to arable land. This study aimed at developing a simplified low-tech hydroponic system for growing leafy vegetables alongside testing its economic viability. This was intended to support urban vegetable production and henceforth contributing to food security more so in under-developed states dealing with the challenge of increasing urban population vs. reducing arable land around urban/ peri-urban areas. A hydroponic unit for growing 60 leafy vegetables (using lettuce as a study crop) under non-controlled environmental conditions was designed and developed using low-cost and low-tech materials. Kratky hydroponic method which involves growing crops using water as a media without the need for water pumps and electricity was used. A study was also carried out to assess the profitability of the system. The results indicated a: net present values of 16.37$, internal rate of return of 12.57%, profitability index of 1.1 and non-discounted payback period of approximately 8 months (4 cropping seasons).These findings showed that the system has the potential to improve urban food production and availability in especially in developing countries in a profitable manner. Vegetable production using the hydroponic system can also contribute to:•tachievement of sustainable development goals, 2 (zero hunger) and 3 (good health and wellbeing);•improvement in urban agriculture production and income generation among urban farmers;•enhanced adoption of low-cost, low-tech, environmental-friendly and sustainable farming systems.

Inferential control of the phosphate concentration in hydroponic systems via measurement of the nutrient solution's pH-buffering capacity

Urban hydroponics is expanding on a global scale. This provides environmentalists with an ideal opportunity to couple sustainability principles to the development of the sector. A primary concern in hydroponics is the generation of large amounts of nutrient laden wastewater. Unlike conventional agriculture, the water effluent typically exits the urban farm via a dedicated outlet, where water quality can be monitored and regulated. It is therefore imperative to develop processes in which the quality of the exit water is part of the design objective. Minimisation of nitrogen and phosphorous in the effluent is key in this regard. This study presents an affordable technique to control phosphate levels in a hydroponic unit. The technique relies solely on continuous pH measurement from which the pH-buffering capacity of the nutrient solution is calculated. The pH-buffering capacity is then used as an inferential measurement to control the phosphate concentration in solution. This concentration can then be controlled at significantly lower levels and thereby reduce phosphate spillage proportionally. Experiments were performed in which the phosphate concentration was controlled at 1 ±0.08 mM (representing standard protocol), 0.2 ±0.03 mM and 0.1 ±0.03 mM. No significant variation in plant growth rate or leaf mass fraction was observed in the runs with lower phosphate concentrations, suggesting that optimal growth is possible at phosphate levels ten times lower than conventional practice. Since the phosphate concentration in the hydroponic outlet is directly proportional to the load of phosphate spillage, the results are encouraging from a nutrient pollution perspective.

A Combined Vermifiltration-Hydroponic System for Swine Wastewater Treatment

Intensive swine farming causes strong local environmental impacts by generating effluents rich in solids, organic matter, nitrogen, phosphorus, and pathogenic bacteria. Insufficient treatment of hog farm effluents has been reported for common technologies, and vermifiltration is considered a promising treatment alternative that, however, requires additional processes to remove nitrate and phosphorus. This work aimed to study the use of vermifiltration with a downstream hydroponic culture to treat hog farm effluents. A treatment system comprising a vermifilter and a downstream deep-water culture hydroponic unit was built. The treated effluent was reused to dilute raw wastewater. Electrical conductivity, pH, and changes in BOD5, ammonia, nitrite, nitrate, phosphorus, and coliform bacteria were assessed. Plants were monitored throughout the experiment. Electrical conductivity increased due to vermifiltration; pH stayed within a neutral to mild alkaline range. Vermifiltration removed 83% of BOD5, 99% of ammonia and nitrite, and increased nitrate by 11%. Hydroponic treatment removed BOD5 (63%), ammonia (100%), nitrite (66%), nitrate (27%), and phosphorus (47% total and 44% dissolved) from vermifiltered water. Coliforms were reduced by vermifiltration but recovered in the hydroponic unit. Plants showed the ability to grow on vermifiltered wastewater, although requiring nutrient supplementation. Vermifiltration combined with hydroponics is a promising treatment for swine wastewater, although optimization will be needed for a sustainable real-scale implementation.

ЭЛЕМЕНТЫ АГРОТЕХНИКИ ЗВЕРОБОЯ ПРОДЫРЯВЛЕННОГО (HYPERICUM PERFORATUM) В УСЛОВИЯХ СВЕТОКУЛЬТУРЫ

This paper discusses the productivity evaluation results (shoot length, shoot number, leaf size, and yields) of hy-droponically grown perforate St. John’s wort (Hypericum perforatum L.). Hydroponic technique enables year-round growing of this medicinal plant preserving natural plant population in the Khanty-Mansiysk Autonomous District -Yugra; perforate St. John’s wortis listed in the District’s Red Book as the species that should be closely monitored in its natural habitat. A vertical ebb-and-flow hydroponic unit was used for growing. The research target was the Optimist variety of perforate St. John’s wort. Generally ac-cepted research methods were applied. Phytopathological evaluation of the perforate St. John’s wort plantation re-vealed low level of infestation with fusarium disease (less than 5%). The experiment showed that the plants reached the best values of all growth indices when grown under white lights of luminous flux of 8000 lm, color temperature of 4000 K, and РРF of 165 μmol s m2. Moreover, lighting with white LEDs stimulates transition of growing plants to flowering stage on the 97th day after planting and increas-es yield to 3.12 kg m2. The variety Optimist variety of perfo-rate St. John’s wort in hydroponic environment forms creeping, aggressively branching shoots that should be considered during growing.

Testing the hydroponic performance of the edible halophyte Halimione portulacoides, a potential extractive species for coastal Integrated Multi-Trophic Aquaculture

Sea purslane Halimione portulacoides (L.) Aellen is a candidate extractive species for coastal Integrated Multi-Trophic Aquaculture (IMTA) to recycle the dissolved inorganic nitrogen (DIN) and phosphorus (DIP) wasted by excretive species. To test its suitability, saline aquaculture effluents were simulated in the laboratory using a hydroponics approach to cultivate the plants. Nutrient extraction efficiency, growth performance and nutritional profile were assessed under a range of DIN and DIP concentrations representing three different aquaculture intensification regimes and using Hoagland's solution as a control. Over a 10-week period, hydroponic units under non-limited N and P conditions displayed daily extraction rates between 1.5 and 2.8 mg DIN-N L−1 day−1 and 0.1–0.2 mg DIP-P L−1 day−1 and yielded between 63.0 and 73.0 g m−2 day−1 of H. portulacoides biomass. Relatively to biomass produced, H. portulacoides extracted between 2.6 and 4.2 mg DIN-N g−1 and 0.1–0.4 mg DIP-P g−1. The treatment with low-input of DIN and DIP (6.4 mg N L−1 and 0.7 mg P L−1) induced some degree of nutrient limitation, as suggested by the extremely high extraction efficiencies of DIN extraction (99%) in parallel with lower productivity. The nutritional profile of H. portulacoides leaves is comparable to that of other edible halophytes and leafy greens and could be a low-sodium alternative to salt in its lyophilized form. From the present study, we conclude that the edible halophyte H. portulacoides can be highly productive in hydroponics using saline water irrigation with non-limiting concentrations of DIN and DIP and is, therefore, a suitable extractive species for coastal IMTA in brackish waters.

Review on Aquaponics System as A Sustainable Food Production Source

ABSTRACT: The global population is growing day by day, so the food demand is escalating as well. Traditional farming practices cannot cater to increasing fooddemand. Environmental stresses like global warming, mass flooding, insects attack, droughts are some of the key players affecting crop yield. These factors leave the soil barren for cultivation and attaining the highest yield. These changes demand a selection of an alternative method that is not only environment friendly but also sustainable. Aquaponics provides an ideal system for growing plants in soilless conditions. The Aquaponics system is a dual scheme of growing plants and fish at the same time. These systems utilize different approaches for growing plants and fishes simultaneously. This is through by circulating mechanism of an aquaponic system where fish waste in aquaculture provides nutrients to plants for the nourishment of hydroponic units. And plants purify water by utilizing nitrogen to maintain water for fish survival and growth. An aquaponic system is a sustainable methodology that does not affect the environment like conventional farming and is built on the recycling principle. A variety of vegetables like lettuce, cucumber, coriander, spinach, eggplant, basil are popular among domestic aquaponics farmers. Fishes are selected based on features like temperature for growth, nutritional requirements, etc. This review some of the main aquaponics systems and their components. Different requirements for establishing a successful aquaponic system are discussed. Furthermore, thesustainability of the aquaponic system is investigated, as the aquaponics system saves water and delivers nutritious food at smaller and larger scales

Micronutrient supplementation needs for halophytes in saline aquaponics with BFT system water

Saline aquaponics is a fast-growing research field, although little attention has been paid to micronutrients in water from aquaculture and their nutritional potential to sustain commercial vegetable production. This study evaluated the effects of micronutrient supplementation, direct in the water and by foliar spraying, against a no nutrient addition control, on growth and biomass production of the Brazilian halophytes Salicornia neei Lag., Apium graveolens L. and Paspalum vaginatum Sw., using saline aquaponics with one-year-old BFT system water from breeding stock tanks of the shrimp Litopenaeus vannamei. Plants were established in hydroponic units and clarified saline water from a BFT system was recirculated and replaced weekly over 30 days. Micronutrient addition in the water significantly increased the concentrations of iron, manganese and molybdenum, but water quality parameters and macronutrients were not modified. Micronutrient addition in the water increased P. vaginatum growth (shoot height and leaf number) and biomass production 20–30% compared to non-supplemented plants, showing the high micronutritional requirement of this species, most likely for iron. Salicornia neei plants showed no benefits when grown with the extra supply of micronutrients in the water, but a 73% reduction of shoot biomass occurred using foliar fertilization compared to the control treatment. Due to the poor development of A. graveolens plants, the response of this species to micronutrient additions could not be evaluated. Overall, clarified BFT system water can supply micronutritional requirements for halophytes, but supplementation may be necessary for species that have high demands and/or are more sensitive to the neutral-alkaline condition of marine aquaculture (e.g., impairment of Fe availability), such as P. vaginatum. Foliar spraying was not effective at improving halophyte growth, and caution should be taken when reusing water supplemented with micronutrients after it leaves an aquaponics system, due to the lack of knowledge about the toxicity of these added elements to animals.

Performance evaluation of hydroponic system for co-cultivation of microalgae and tomato plant

Conventional hydroponic units producing disease free plants with 30–40% faster growth rate are regarded as a promising agricultural alternative in case of unfertile/metal contaminated soil. However, most nutrients in hydroponics medium remain unused and are drained off creating environmental pollution. To reduce the nutrient load and eutrophication effects, cocultivation of plant and microalgae in the hydroponic units has attracted the attention of researchers over the past few years. The present study aims to explore the influence of initial inoculum concentration of a native algal consortium over the performance of hydroponic system. Cocultivation of tomato plant with varying initial inoculum algal concentration of 0.2–0.8 mg/ml, showed that 0.8 mg/ml concentration resulted in positive interactions between microalgae and plant, with algal and plant productivity of 0.149 ± 0.024 and 0.328 ± 0.087 g/m2/d respectively after 42 days. Higher chlorophyll accumulation, along with nutritionally rich algal and plant biomass revealed lack of unwanted competition during cocultivation. Increase in dissolved oxygen during cocultivation was corroborated with efficient root respiration. Highly developed roots also provided adequate metabolic energy thus significantly increasing the nutrient uptake and accumulation, thereby reducing the nutrient load during drainage. The supernatant after algal harvesting (recycled media) supported plant growth for 24 days due to limited nutrients. Such system with microalgae symbiotically favouring plant productivity and simultaneous nutrient load reduction would ultimately support in attaining sustainable agriculture.

INTERVARIETAL DIFFERENCES OF BIOMETRIC INDICATORS AND PRODUCTIVITY OF LETTUCE (LACTUCA SATIVA L.) DEPENDING ON DENSITY OF THE PLANT GROWTH IN HYDROPONIC SYSTEMS

The article discusses conditions for growing varieties of lettuce in closed photoculture using hydroponic method. The purpose of the study was an agrobiological assessment and development of individual elements of the technology for growing Dutch lettuce varieties Caipira, Crispinet, Almadraba, Azirka, Cristabel, Ezrilla and Ovired in a hydroponic flooded system. We studied two options for the density of plants on the pallets of a hydroponic unit, which provide different crop production efficiencies.

Multidirectional Relationship between Energy Resources, Climate Changes and Sustainable Development: Technoeconomic Analysis

Global changes in temperature will likely change energy use and electricity production capacity. Considering the relationship between climate change and energy resource use, changes in temperature and the frequency and intensity of extreme events will affect how much energy is produced and consumed. The green economy and green growth are located at the heart of the fight against climate change in creating sustainable development. This paper considers the multidirectional relations between climate change, energy resources, and sustainable development including the perspective of a green economy via a technoeconomic analysis. A link among energy resources, climate changes and sustainable development has been displayed via a technoeconomic analysis in the case study, which was focused on taking into consideration the needs of the hydroponic units, the product selling price, the electricity price of the wind farm (WF), and at the same time the energy demand, under a nexus approach. Via the technoeconomic analysis, it was proven that moving on to smaller investments of 2 MWs is more efficient compared to larger projects e.g. 18 MWs, however, this cannot be considered immediately as the preferred solution since it is always a matter of impact on the local society.