Hydroponic Production Systems Research Articles

Development of Small Scale Indoor Hydroponic Fodder Production System

Field experiment was conducted to develop a small scale indoor hydroponic fodder production system (May- June 2021). Green fodder supply to the domestic animals is most important factor to improve their health, body weight, milk yield and thus obtaining maximum economic return. Land degradation and urbanisation reduced the area available for the green fodder production. India has 10.7% of world livestock population but only having 2.29% of its land mass and this is putting a huge pressure on land and water resource. Vertical growing of crop and minimising the usage of water is the best solution to solve this problem. Hydroponic technology helps to achieve very high yield and also provides better control over the crop production. Indoor cultivation eliminates the problem of weeds and pests and the use of pesticides and herbicides. Artificial lighting overcomes the disadvantage of seasonal variation of solar radiation and provides continuous source of energy supply. The study shows that green fodder can be efficiently grown at indoor condition. Hydroponic technique helped to achieve yield of 7.535 kg per day with a water requirement of only 4.78 litres per kg. The combination of red and blue LED lights supplied continuous energy for 12 hours a day for the better growth of crop. Results clearly show that the indoor hydroponic fodder production system with artificial supply of light can be recommended for the farmers to meet their fodder requirement.

Potential of hydroponic barley in rabbit diets: effect on productive performance, nutrient digestibility, microbiological and physiological responses

Application of agriculture hydroponic technology with a view to reduce the gap between the animal nutritional requirements and availability of feed ingredients create an important role in animal and rabbit production. Hydroponic fodder production such as barley is an alternative technology to cultivate fodder which provide the growing nutrients requirement for livestock feed with suitable prices, high quantity, a short growth period, a small land for production, a clean environment, water efficiently and reduces cultivate fodder resources. This study was investigated with view to give an overview on the possible role of hydroponic barley (HB) as a feed replacement in rabbit ration. Various scientific published research articles were used HB as a feed replacement in rabbit ration. The most observed and analyzed productive and reproductive performance, nutrient digestibility and physiological responses. Positive effect of feeding HB was observed on serum metabolic profile and microbial count of caecum of rabbits. However, the economics and nutritive values of hydroponic production system should be carefully estimated. This review provides an overview of and illustrates the positive effects of HB as a feed replacement in rabbit diets and their potential effects on productive performance, economic return, nutrient digestibility, microbiology and gut health.

Photosynthesis, Biomass Production, Nutritional Quality, and Flavor-Related Phytochemical Properties of Hydroponic-Grown Arugula (Eruca sativa Mill.) ‘Standard’ under Different Electrical Conductivities of Nutrient Solution

Arugula (Eruca sativa) is cultivated using hydroponic techniques in greenhouses to fulfill high year-round demand, but its nutrient management in hydroponic production has not yet been standardized, potentially leading to limited quality and productivity. Aiming to address this issue, we investigated the effect of electrical conductivity (EC) on yield, nutritional and phytochemical properties of arugula. The model cultivar arugula ‘Standard’ was grown at four different EC levels (1.2, 1.5, 1.8, and 2.1 dS·m−1). Our results indicated photosynthetic properties, SPAD, leaf area, yield and dry weight increased with increasing EC from 1.2 to 1.8 dS·m−1. Foliar nutrient content increased with higher EC, but nutrient solution with 2.1 dS·m−1 showed a significant decline in N, Ca and most of the micronutrients including Fe, Zn, Mo, Cu, B and Mn. Total glucosinolates, total chlorophyll and total carotenoids concentrations increased with increasing EC. In addition, total anthocyanin content was highest in plants grown in EC 1.2 and 2.1 dS·m−1, demonstrating a stress response when grown in extreme EC levels. Our results further indicated a rapid accumulation of nitrate with higher EC, potentially detrimental to human health. This research demonstrated the optimal EC range would be 1.5 to 1.8 dS·m−1 for arugula in hydroponic production systems based on yield, quality criteria and human health considerations.

Semi-Transparent Organic Photovoltaics Applied as Greenhouse Shade for Spring and Summer Tomato Production in Arid Climate

Recognizing the growing interest in the application of organic photovoltaics (OPVs) with greenhouse crop production systems, in this study we used flexible, roll-to-roll printed, semi-transparent OPV arrays as a roof shade for a greenhouse hydroponic tomato production system during a spring and summer production season in the arid southwestern U.S. The wavelength-selective OPV arrays were installed in a contiguous area on a section of the greenhouse roof, decreasing the transmittance of all solar radiation wavelengths and photosynthetically active radiation (PAR) wavelengths (400–700 nm) to the OPV-shaded area by approximately 40% and 37%, respectively. Microclimate conditions and tomato crop growth and yield parameters were measured in both the OPV-shaded (‘OPV’) and non-OPV-shaded (‘Control’) sections of the greenhouse. The OPV shade stabilized the canopy temperature during midday periods with the highest solar radiation intensities, performing the function of a conventional shading method. Although delayed fruit development and ripening in the OPV section resulted in lower total yields compared to the Control section (24.6 kg m−2 and 27.7 kg m−2, respectively), after the fourth (of 10 total) harvests, the average weekly yield, fruit number, and fruit mass were not significantly different between the treatment (OPV-shaded) and control group. Light use efficiency (LUE), defined as the ratio of total fruit yield to accumulated PAR received by the plant canopy, was nearly twice as high as the Control section, with 21.4 g of fruit per mole of PAR for plants in the OPV-covered section compared to 10.1 g in the Control section. Overall, this study demonstrated that the use of semi-transparent OPVs as a seasonal shade element for greenhouse production in a high-light region is feasible. However, a higher transmission of PAR and greater OPV device efficiency and durability could make OPV shades more economically viable, providing a desirable solution for co-located greenhouse crop production and renewable energy generation in hot and high-light intensity regions.

First report of root mat disease in a hydroponic tomato production system caused by rhizogenic Agrobacterium biovar 1 in South Korea.

In June 2019, root mat disease was observed in hydroponically cultivated tomatoes in Jinju, South Korea, which occurred in at least 30% of the plants in the greenhouse. To isolate the causal bacteria, 10 g of infested tomato root mat sample was ground with 50 mL of sterile water. A 100-µL aliquot of the homogenate was serially diluted and spread on Mannitol-Glutamate (MG) medium amended with 0.1% yeast extract (MGY) and incubated at 28°C for 48 hours. Fifteen dominant colonies that formed on the MGY medium were purified and subjected to diagnostic polymerase chain reaction (PCR) based on the virD2-ipt gene loci. Because Ti-plasmid harbors both virD2 and ipt genes, Ri-plasmid-borne Agrobacterium species with only virD2 can be differentiated using virD2-ipt PCR. To amplify virD2, the primers 5'-ATG CCC GAT CGA GCT CAA GT-3' and 5'-TCG TCT GGC TGA CTT TCG TCA TAA-3' were used; for ipt amplification, the primers 5'-GAT CG(G/C) GTC CAA TG(C/T) TGT-3' and 5'-GAT ATC CAT CGA TC(T/C) CTT-3' were used. Amplification involved an initial 94°C for 1 min and then 40 cycles at 94°C, 50°C, and 72°C for 1 min at each temperature, with a final 5-min extension at 72°C. For three strains (GNIY2, J10, and J11), virD2 PCR products, but no ipt PCR products, were identified, indicating that three strains are Ri-plasmid-borne Agrobacterium species. A pathogenicity test was performed on 2-week-old tomato plants. Bacteria isolates (GNIY2, J10, and J11) cultured overnight in LB were made into a bacterial suspension (107 cfu/mL) in 50 mM phosphate buffer. Five tomato seedling roots were cut with sterilized scissors and soaked in each bacterial suspension for 1 hour. Phosphate buffer was used as a negative control. The inoculated tomato seedlings were transplanted in new pots and placed in a greenhouse with 25°C day and 20°C night temperature set points in natural light. After 9 weeks, all inoculated tomato plants produced overgrown roots, while the negative control plants had no symptoms. To satisfy Koch's postulates, re-isolation was performed from the diseased tomato and was the re-isolated bacteria were subject to partial 16S rDNA sequencing. Biovar tests performed as previously described revealed that all three isolates were biovar 1. A representative strain (GNIY2) was deposited in the Korean Agricultural Culture Collection (KACC 21759). To confirm the identity, four housekeeping genes of KACC 21759 were sequenced (16S rRNA, trpE, rpoB, and recA) and deposited in GenBank (accession nos. MT071560, MT444428, MT444429, and MT444430). Multilocus sequence analysis performed as previously described showed that the KACC 21759 strain was grouped in Agrobacterium genomospecies 4. This is the first report on mat root disease caused by Agrobacterium biovar 1 in hydroponic tomatoes in South Korea.

Utilizing Anaerobic Digestates as Nutrient Solutions in Hydroponic Production Systems

Moving food production into the urban and peri-urban areas is one way of facilitating a closed-loop approach, integrating waste handling with food production in order to recirculate nutrients and at the same time reduce the use of mined and fossil resources in the production. Using anaerobic digestion as a way of converting urban wastes to an energy source (methane) and a nutrient-rich biodigestate with subsequent use as fertilizer for food production seems like a feasible approach. However, utilizing urban wastes in plant production systems implies some challenges, such as high salinity of the waste, imbalanced composition of nutrients, and abundance of less favorable forms of nitrogen. In a series of experiments, these problems were addressed. Vegetables (Pak Choi) were cultivated hydroponically in a controlled climate. Experiments included increased salinity, elevated levels of nitrite, and different concentrations of the biogas digestate-based nutrient solution, with mineral based solutions as controls. In general, the mineral controls yielded around 50% higher fresh biomass than the organic solutions. However, the quality of the produce with respect to content of secondary metabolites such as vitamins was enhanced when the plants were cultivated with organic nutrient solutions. Increasing the concentration of NaCl to 241 mg Cl L−1 did not negatively affect plant performance. Increasing the concentration of nitrite negatively affected plant growth, with reductions in biomass production by up to 50%. Given this well-functioning nitrification process that did not result in high nitrite concentrations, the use of anaerobic digestates seems feasible for hydroponic production of vegetables.

Parámetros genéticos de una cruza interespecífica de S. lycopersicum L. y S. habrochaites Knapp & Spooner

The main collection of allelic variants for breeding tomato (Solanum Lycopersicum L.) is represented by its wild relatives, which evolved independently. It is important to study different sources of variation that are useful in breeding; therefore, the aim of this study was to evaluate S. habrochaites Knapp & Spooner as a source of different alleles by estimating the average degree of dominance, heterosis with respect to the mid-parent, and narrow-sense heritability of an interspecific cross with S. lycopersicum L. An S8 line derived from the LOR95 collection, the LA1223 accession of S. habrochaites Knapp & Spooner and the F1 generation from crossing the two materials were used. Genotypes were evaluated in a randomized complete block design during two greenhouse cycles in a hydroponic production system. Of 14 evaluated traits, total soluble solids concentration, stem diameter, total number of fruits and plant height showed an overdominance of LA1223, as well as heterosis of 17.2, 32.3, 55 and 49.2 % each, and heritability of 35, 93, 72 and 66 %, respectively. F1 generation had an increase of 2 mm in stem diameter, 30 cm in plant height, 4 fruits and 1.1 °Brix, with respect to the best parent for each variable; this suggests that it would be possible to use LA1223 to broaden the genetic base in the improvement of this vegetable.

Rejected brine recycling in hydroponic and thermo-solar evaporation systems for leisure and tourist facilities. Changing waste into raw material

For >50years the Canary Islands have been using seawater desalinization facilities in order to satisfy the freshwater demand of their main economic activity –tourism, which continues to contribute to the economic and social progress of the archipelago. However, this desalinization process involves the production of a “waste” product known as rejected brine, which is discharged from coastal regions and islands, whether it originates from public or private facilities. Rejected brines are potentially a serious threat to marine ecosystems. However, here we demonstrate that this “waste” can be processed and reused as a nutrient mineral solution for a hydroponic production system and also a source of freshwater. The efficiency of this management process in terms of fresh-water production and water recycling economy is also discussed. The aim of this paper is to change the attitude towards rejected brines, which should be treated as potential raw material to permit high savings in the running costs of leisure and tourist facilities around the archipelago. In addition, this will also have a positive effect on the environment, making desalinization more sustainable and environmentally friendly, which is nowadays an added value in customer and user satisfaction.

Indoor Gardening with Hydroponics: A Reddit Community Analysis to Identify Knowledge Gaps

Social media platforms such as Reddit, centered on user-generated, anonymous discussions, can facilitate the exchange of information and resources across niche online communities known as “subreddits.” Using data mining tools and content analysis methods, our objectives were to identify recurring questions and characterize comment (“response”) accuracy from four subreddits focused on hydroponic indoor gardening (r/hydro, r/Hydroponics, r/UrbanFarming, and r/Aerogarden). A total of 1617 original posts (OPs) were classified into one of ten topics and 4891 primary responses were analyzed for accuracy. The three topics with the most OPs (production systems, plant lighting, and root-zone environment), which accounted for 50% of the total OPs, were subcategorized and inductively analyzed. Most posts in the analyzed subreddits related to confusion regarding the design and implementation of appropriate hydroponic production systems. In addition, misinformation about plant lighting is a major part of discussions about growing plants indoors. There are also knowledge gaps regarding nutrient solution management, particularly about fertilizer formulation, pH balance, and on the impact that solution temperature has on plant growth and development. In general, there were no differences among response accuracy for all topics included in our analysis. However, regardless of topic, responses for most OPs had less than 50% accuracy, which demonstrates that misinformation can be disseminated in social media platforms such as Reddit. As suggested by the results of this study, targeted, open access research and outreach efforts offer an opportunity to address knowledge gaps among consumers interested in indoor gardening.

Recirculating water and nutrients in urban agriculture: An opportunity towards environmental sustainability and water use efficiency?

Urban agriculture systems, such as rooftop greenhouses, are attractive alternatives for mitigating the impacts of the extensive food supply chains that currently feed cities. In this study, we study the opportunity that nutrient recirculation offers to improve the environmental performance of agricultural systems. In particular, we analyze the environmental burdens of a hydroponic closed-loop production system that recovers nutrients and reduces water demand by recirculating the irrigation water leaching from the substrate bags along with nutrients that have not been assimilated by the plant. The closed-loop system is compared to a linear system in which there is no nutrient or water recovery. Based on two green bean crop cycles in a Mediterranean rooftop greenhouse, we analyze the yield, climatic variables and water and nutrient balances, and apply life cycle assessment (LCA) to study the environmental impacts.The results of this study indicate that closed-loop systems save daily 40% of irrigation water and between 35 and 54% of nutrients. Moreover, leachate reuse leads to reduced eutrophication impacts, but it can entail nutrient deficiencies. However, implementing a closed-loop system requires additional infrastructure causing larger impacts than linear systems in terms of global warming and fossil resource scarcity. The results of the LCA were highly sensitive to the yield, the crop production period and the meteorological conditions. Based on these results, we design improved scenarios, providing recommendations for reducing the impacts of closed-loop systems for more sustainable cities.

Evaluating the feasibility of human excreta-derived material for the production of hydroponically grown tomato plants - Part I: Photosynthetic efficiency, leaf gas exchange and tissue mineral content

There is increasing interest and wide recognition of the potential use of human-excreta derived materials (HEDM) as fertilizer to supply essential nutrients needed for crop production. However, most work on HEDM has focussed on yield responses using soils and very little done on soil-less media using hydroponics. Further, physiological responses of plants to different HEDM in a hydroponic production system is currently not well-understood. This study investigated the effect of Decentralized Waste-water Treatment System (DEWATS) effluents and Nitrified Urine Concentrate (NUC) on leaf gas exchange, photosynthetic efficiency and mineral content of hydroponically-grown tomato. The experiment was conducted in a polyethylene tunnel using a complete randomised design comprising of three treatments namely: DEWATS effluent, NUC and commercial hydroponic fertilizer mix (CHFM). Sampling conducted both before and after flowering showed significant differences (P < 0.05) among different nutrient sources for all physiological parameters (leaf gas exchange and chlorophyll fluorescence) and mineral content. Leaf N and P were significantly (P < 0.05) higher in NUC treatment whereas Ca and K were high in the CHFM treatment. The current study demonstrated that HEDM such as NUC and DEWATS effluent could be an effective source of nutrients of agricultural crops in hydroponic systems with results comparable to commercial fertilizer mix.

The Occurrence of Shiga Toxin-Producing E. coli in Aquaponic and Hydroponic Systems

Food safety concerns have been raised over vegetables and herbs grown in aquaponics and hydroponics due to the reuse of wastewater and spent nutrient solutions. This study was conducted to determine the occurrence of foodborne pathogens in greenhouse-based aquaponic and hydroponic systems. Fish feces, recirculating water, roots, and the edible portions of lettuce, basil, and tomato were collected at harvest, and microbiological analyses were conducted for the bacterial pathogens Shiga toxin-producing Escherichia coli (STEC), Listeria monocytogenes, and Salmonella spp. Enrichments and selective media were used for the isolation, and presumptive positive colonies were confirmed by PCR. STEC was found in fish feces, in the water of both systems, and on the surface of the roots of lettuce, basil, and tomato regardless of the system. However, contaminated water did not lead to the internalization of STEC into the roots, leaves, and/or fruit of the plants. Meanwhile, L. monocytogenes and Salmonella spp. were not present in any samples examined. Our results demonstrated that there are potential food safety hazards for fresh produce grown in aquaponic and hydroponic production systems.

Liquid Nutrient Formulations for Red Rapid Lettuce (Lactuca sativa L.) Production under Aggregate Hydroponic System

This study was conducted to investigate the effects of liquid nutrient formulations on the horticultural characteristics, yield, pigment composition, and free radical scavenging activity of lettuce under aggregate hydroponic production system. The efficacy of three nutrient solutions derived from golden snail, madre de agua, and tilapia fish effluent were evaluated using lettuce (Red Rapid) as test plant in completely randomized design. The aggregates were composed of river sand and coconut coir in a ratio of 3:1 by volume. The pigment composition and free radical scavenging activity were done through an ultraviolet-visible spectrophotometer. Results showed that lettuce grown on fermented golden snail (FGS)have comparable plant height and number of leaves with the plants grown on commercial inorganic nutrient solution. However, lettuce grown on FGS exhibited greater leaf size and yield significantly (p&lt;0.05). Plants grown on tilapia fish effluent showed the highest chlorophyll A and total carotenoid contents followed by the plants grown on FGS which is comparable with the control. Moreover, lettuce grown on FGS gave the highest chlorophyll B content and free radical scavenging activity. The application of FGS enhanced the horticultural characteristics, yield and free radical scavenging activity of lettuce while tilapia fish effluent improved the pigment composition of the test plant. These results indicate the potential of FGS and tilapia fish effluent as valuable sources of organic fertilizer material for lettuce production under an aggregate hydroponic system which can be helpful in community resilience programs.

EVALUACIÓN DE SOLUCIONES DE MICROALGAS (SCENEDESMUS SP) COMO BIOESTIMULANTE NATURAL EN EL CULTIVO HIDROPÓNICO DE LECHUGA (LACTUCA SATIVA)

In order to make a first contribution in the use of nutrients coming from unicellular algae, a test was realized, its main purpose consisted on evaluate the nutritional contribution of live unicellular algae. (Scenedesmus sp) in a nutritive solution that is commonly used in hydroponic. Three doses of microalgae solution were evaluated as a natural bio stimulant in the lettuce production. (Lactuca sativa): in a low concentration of algae (40 x 104 cel. ml-1); medium concentration (80 x 104 cel. ml-1); and high (120 x 104 cel. ml-1); the witness was a nutritive solution without microalgae addition. There were used microalgae from the laboratory of Agricultural and Environmental Sciences School where the microalgae were produced to add them to the hydroponic production system later. A completely randomized block design was used in four treatments and three repetitions. The blocks were placed perpendicularly to the luminosity considered as a non-controllable factor. The hydroponic nutritive solution was evaluated daily, the pH was constant 6 to 7,3 and the electrical conductivity was 1,7 a dSm-1. At the end of the development cycle, the roots and leaves were weight. The variance analysis detected significant differences for the treatments (p<0.05). At the end of the essay, the aerial weight average per plant was 34.3 g. for the witness (without microalgae solution addition), while for the high microalgae solution (120 x 104 cel ml-1) was 46.32 g. Therefore, the use of live microalgae solutions during the hydroponic lettuce development cycle provokes a lettuce production increase without affecting the hydroponic solution or the plant.

Exploratory Testing for the Internet of Things in Smart Fertilizer Hydroponic System using Hydropo

Internet of things “Hydropo” was designed for automatic fertilizing in a hydroponic system. It is not only for making sure of working both hardware and software but also the implementation of such products. Therefore, testing is needed for proofing that “Hydropo” can be implemented. Exploratory Testing has already done in order to test the usability and validity of the smart tool in producing vegetable in the hydroponic production system. The result of the research was the Internet of Things “Hydropo” may not still be implemented yet for an outdoor environment. Redesigning “Hydropo” for outdoor implementation is needed including made it more adaptive to temperature and air controlling.

Effects of Fertilization on Growth of Zinnia elegans L. Seedlings Grown in Floating System

The floating system is a promising alternative type of hydroponic seedling production system, which has not been much studied and disseminated in the flower industry. This study aimed to produce seedlings of Zinnia elegans in a floating system and to evaluate the influence of two organic (Codaphos &amp; Codasting and Fish-Fert) and one inorganic nutrient solution formulations on the seedling growth parameters. Z. elegans seeds germinated at a high rate (76.6-82.1%) in all fertilization treatments with a T50 ranging from 9.54 to 10.50 days. Application of Codaphos and Codasting (organic fertilizer containing N- Codasting and P+K- Codaphos) in floating system resulted in better development of the aboveground parts and roots of seedlings comparing with the other organic and the inorganic fertilization. As a conclusion, the present study showed that organic fertilization, especially with Codaphos and Codasting, could successfully be used for the production of Z. elegans seedlings in a floating system; however, further studies must be carried out on this aspect.

Effects of Hydroponic Fodder Feeding on Milk Yield and Composition of Dairy Cow: Review

The aim of this paper was to review the effects of hydroponic fodder feeding on milk yield and composition of the dairy cow. Hydroponic fodder is an effective solution for fodder scarcity and is very promising for sustainable livestock production in different regions of the world. Hydroponics fodder production involves growing of plants without soil for a short duration (5-10 day). In hydroponic fodder production system, it can be possible to grow 5-10kg of green fodder from 1kg seeds. The nutritional increase in crude protein, fibre, ether extract, vitamins and minerals were constantly observed in hydroponic fodder. However, there was a loss of 10-25% dry matter content depending on grain type and duration. The hydroponics fodder feeding improves milk yield and composition of a dairy cow through increased intake and digestibility of nutrients. However, more information is needed to confirm the benefit of hydroponic fodder feeding as part of ration for dairy cow. Keywords: hydroponic fodder, nutrient composition, dairy cow, milk yield, milk composition DOI : 10.7176/JNSR/9-8-01 Publication date : April 30 th 2019

Cost Benefit Analysis of Growing Cucumbers in Greenhouse at Different Cooling of Nutrient Solution Temperatures in Closed Hydroponic System in Oman

Oman is a country that is mostly dry and hot, with daily maximum temperatures easily reaching 40&amp;deg;C or more during summer. The Oman weather therefore renders conventional open field agriculture almost impossible. The sustainable future of agriculture in Oman and other similar desert countries will therefore depend very much on the adoption of land and water saving technologies such as greenhouses and soilless culture or hydroponics. Soilless culture (Hydroponics) is the technique of growing plants without soil with their roots immersed in nutrient solution. Among factors affecting hydroponic production systems, is the nutrient solution temperature which is considered to be one of the most important determining factors of crop yield and quality. The aim of this research is therefore to investigate the economic effect of cooling nutrient solutions temperature technique on cucumber output. Four nutrient solutions temperatures are investigated and a Cost Benefit Analysis is undertaken. Results indicate that all the four cooling nutrient temperature yields positive returns (benefits) above variable and total costs for the two years of this experiment. Cooling nutrient temperature (22&amp;ordm;C) yields higher returns than the other treatments followed by treatment (25&amp;ordm;C), (28&amp;ordm;C) and then the CONTROL treatment. Returns for the second year are higher than the first year. Therefore treatment (22&amp;ordm;C) was observed to be the best overall producing the highest return above variable and total costs. It is therefore considered the best alternative for cucumber growers.

Electrical conductivity of nutrient solution influenced photosynthesis, quality, and antioxidant enzyme activity of pakchoi (Brassica campestris L. ssp. Chinensis) in a hydroponic system.

To find an electrical conductivity (EC) in the nutrient solution used for pakchoi (Brassica campestris L. ssp. Chinensis) cultivation that optimizes the plant’s physiology, growth, and quality, we conducted an experiment with eight EC treatments (from EC0 to EC9.6) in a hydroponic production system (i.e. soilless culture) under greenhouse condition in Shanghai, China. Plants biomass production, leaf photosynthesis, vegetable quality variables, tissue nitrate and nitrite contents, and antioxidant enzyme activities were measured. The results showed that very high (EC9.6) or low EC (EC0-0.6) treatments clearly decreased plants fresh weight (FW) and dry weight (DW), leaf size, leaf water content, leaf net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and taste score. Nitrite content, and antioxidant enzyme activities were low in medium EC treatments (EC1.8 and EC2.4), but high in very high or low EC treatments. Leaf relative chlorophyll, ascorbic acid, and nitrate contents increased gradually from low EC to high EC treatments, while crude fiber and soluble sugar contents decreased. Based on growth and quality criteria, the optimal EC treatment would be EC1.8 or EC2.4 for pakchoi in the hydroponic production system. Too high or too low EC would induce nutrient stress, enhance plant antioxidant enzyme activities, and suppress pakchoi growth and quality.

Utility of Arbuscular Mycorrhizal Fungi for Improved Production and Disease Mitigation in Organic and Hydroponic Greenhouse Crops

Arbuscular mycorrhizal (AM) fungi are considered to be enormously important in contemporary agriculture and horticulture for their ability to improve crop disease and fertility management in commercial field and greenhouse crop production. Recently, commercial greenhouse producers have begun using AM inoculum to increase yields and provide sustainable growing conditions in organic and hydroponic production systems. However, strong evidence in support of their effectiveness in hydroponic production is still lacking. Future research is expected to address benefits of the use of AM fungi in hydroponic greenhouse crops, such as defense against pathogen, herbivore attack and the effective management of photo-assimilates by plants, which are essential for fruit production. In order to increase our understanding of the usefulness of AM fungi in hydroponic greenhouses, large-scale trial and a cost-benefit evaluation of the process are needed. This article discusses the use of AM fungi for improving organic and hydroponic greenhouse crop production and disease control, considering that AM fungi inoculations in soil-based greenhouses and fields have proven to be very effective.