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The Tripartite of Soilless Systems, Growing Media, and Plants through...
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The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme

A special issue of Agronomy (ISSN 2073-4395). This special issue belongs to the section "Innovative Cropping Systems".

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 49139

Special Issue Editors

Dr. Nikos Tzortzakis

E-Mail Website
Guest Editor
Department of Agricultural Sciences, Biotechnology and Food Science, Cyprus University of Technology, Limassol, Cyprus
Interests: horticulture; vegetable science; aromatic/medicinal plants; greenhouse crops and hydroponics; substrate/growing media evaluation; soil; fresh produce preservation
Special Issues, Collections and Topics in MDPI journals
Dr. Daniele Massa

E-Mail Website
Guest Editor
CREA Research Centre for Vegetable and Ornamental Crops, Council for Agricultural Research and Economics, Pescia, PT, Italy
Interests: DM carries out research activity on plant modelling; crop abiotic stress; crop fertilization; irrigation management; protected cultivation; soilless; plant physiology with special attention to vegetable and ornamental species
Dr. Bart Vandecasteele

E-Mail Website
Guest Editor
Plant Sciences Unit, Flanders Research Institute for Agriculture, Fisheries and Food (ILVO), Burg. van Gansberghelaan 109, 9820 Merelbeke, Belgium
Interests: compost, biochar and plant fibres in sustainable growing media; compost quality; recycling of agricultural organic waste; C sequestration and reduction of N and P losses from horticultural soils

Special Issue Information

Dear Colleagues,

The demands for vegetables, herbs, and fruits have increased along with the increased human population. Ornamental and medicinal/aromatic plants have become important components in our lives, due to their aesthetics and industrial and pharmaceutical uses. Production technology affects not only plant growth and yield but also overall plant quality, thus improving, in turn, the cumulative benefits of plants. Soilless cultivation—including hydroponics, cultures on growing media, and rooftop cultivation—is a modern and sustainable method for crop production and has rapidly expanded throughout the world, especially in cultivation areas affected by shortages of water and quality soil. Therefore, the increased interest in the commercial application of soilless cultivation has encouraged intensive research activity.

Soilless cultivation includes all plant growth systems either on porous substrates or on pure nutrient solution (NS) instead of the natural soil. The major advantage of soilless cultivation is the uncoupling of the plant growth from problems associated with the soil, such as soil-borne diseases, non-arable soil, soil salinity, poor physical properties, low temperature, the use of agrochemicals etc.

The rising interest in growing small/soft fruit crops, vegetables, herbs, and cannabis in soilless container systems has further increased crop production in controlled environment systems worldwide. These systems are used to grow hydroponic and pot ornamentals, seedlings, and transplants, and to increase plant metabolites in medicinal and aromatic plants. Moreover, soilless cultivation has recently gained great interest in urban agriculture and green infrastructure with vertical gardening, green roofs, and rooftop farming.

Successful and smart crop management should be based on a holistic approach taking into consideration cultivation technologies, growing media, and plant physiology. The recycling and the control of excess NS is associated with a considerable reduction in nitrate and phosphate leaching to the water resources and the maintenance of product quality/safety. Modern automated systems for nutrient and water supply constitute a prerequisite for reducing costs and increasing profitability in modern soilless cultivation systems.

The purpose of this Special Issue is to publish high-quality research articles addressing recent developments in growing plants in soilless culture, i.e., hydroponics and growing media, with special attention to horticultural sciences, plant physiology, root media, plant propagation, plant nutrition and chemistry, substrate properties, compost and waste management, engineering, and all other research fields related to soilless culture and growing media.

Dr. Nikos Tzortzakis
Dr. Daniele Massa
Dr. Bart Vandecasteele
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Agronomy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • sustainable growing media
  • urban farming, green roof technology, and vertical farming
  • container crops
  • biofortification and added-value plant metabolites
  • LCA, climate change, and sustainable agriculture
  • novel inorganic and organic materials as soilless media
  • soilless culture, hydroponics, and aquaponics
  • nutrient solution/fertigation
  • organic waste management and circular horticulture
  • peat and mineral wool replacement
  • abiotic and biotic stress management
  • substrate analysis technologies
  • water and nutrient use efficiency

Published Papers (15 papers)

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Editorial

Jump to: Research, Review

4 pages, 190 KiB  
Editorial
The Tripartite of Soilless Systems, Growing Media, and Plants through an Intensive Crop Production Scheme
by Nikolaos Tzortzakis, Daniele Massa and Bart Vandecasteele
Agronomy 2022, 12(8), 1896; https://doi.org/10.3390/agronomy12081896 - 12 Aug 2022
Cited by 5 | Viewed by 1285
Abstract
The demands for vegetables, herbs, and fruits have increased, along with the increased human population [...] Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)

Research

Jump to: Editorial, Review

19 pages, 2756 KiB  
Article
Lignite Substrate and EC Modulates Positive Eustress in Cucumber at Hydroponic Cultivation
by Radosław Łaźny, Małgorzata Mirgos, Jarosław L. Przybył, Monika Niedzińska, Janina Gajc-Wolska, Waldemar Kowalczyk, Jacek S. Nowak, Stanisław Kalisz and Katarzyna Kowalczyk
Agronomy 2022, 12(3), 608; https://doi.org/10.3390/agronomy12030608 - 28 Feb 2022
Cited by 7 | Viewed by 2333
Abstract
Hydroponic cultivation using organic, fully biodegradable substrates that provide the right physical properties for plant growth and development is now the future of soilless production. Despite the high productivity and strict control of production conditions in this method, excessive salinity of the substrate [...] Read more.
Hydroponic cultivation using organic, fully biodegradable substrates that provide the right physical properties for plant growth and development is now the future of soilless production. Despite the high productivity and strict control of production conditions in this method, excessive salinity of the substrate often occurs. However, recent research results indicate that salinity at a high enough threshold can improve yield quality, while prolonged exposure to too high EC, or exceeding the safe EC threshold for a given species, leads to reduced quality and reduced or even no yield. The aim of this study was to determine the effect of biodegradable lignite substrate (L) and eustressor in the form of high EC nutrient solution (7.0 dS·m−1) on morphological and physiological parameters, as well as the quality and yield of cucumber (Cucumis sativus L.) in hydroponic cultivation compared to the mineral wool substrate (MW). The MW/high EC combination showed a significant reduction in shoot diameter by nearly 6% compared to the MW/control EC combination. The stomatal conductance (gs) and the transpiration rate (E) were also significantly reduced in this combination. The present study indicates that the effects of eustressor application vary depending on the growing medium used, and more favorable effects in terms of yield quality were obtained using biodegradable lignite substrate. The high EC of nutrient solution combined with lignite substrate (L/high EC) significantly increased in cucumber fruit the content of β-carotene, lutein, chlorophyll a, chlorophyll b and the sum of chlorophyll a + b by 33.3%, 40%, 28.6%, 26.3% and 26.7%, respectively, as compared to MW/high EC combination. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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18 pages, 603 KiB  
Article
Sustainable Growing Media Blends with Woody Green Composts: Optimizing the N Release with Organic Fertilizers and Interaction with Microbial Biomass
by Bart Vandecasteele, Koen Van Loo, Sarah Ommeslag, Siebert Vierendeels, Maxim Rooseleer and Elke Vandaele
Agronomy 2022, 12(2), 422; https://doi.org/10.3390/agronomy12020422 - 08 Feb 2022
Cited by 13 | Viewed by 2652
Abstract
The aim of the current study was to create a high quality growing medium blend that replaces 70 vol% peat with 40 vol% woody green compost and 30 vol% bark compost and organic fertilizers (i.e., blood meal and chitin), all locally sourced. A [...] Read more.
The aim of the current study was to create a high quality growing medium blend that replaces 70 vol% peat with 40 vol% woody green compost and 30 vol% bark compost and organic fertilizers (i.e., blood meal and chitin), all locally sourced. A range of “woody composts”, i.e., green composts based on feedstock selection with mainly woody material from tree prunings, were produced for this purpose at green compost facilities. First, the woody composts were characterized chemically and biologically, including their microbial biomass and net N release. In comparison with regular green composts or vegetable, fruit and garden (VFG) waste composts, woody composts are more suitable for use in growing media due to their lower pH, EC and inorganic C content; however, the woody compost had a low N mineralization rate. Three types of composts supported a higher microbial biomass than wood fiber or bark compost. The additional mineral N release after 100 days for compost mixed with blood meal was tested for different VFG and green composts. A significantly higher additional net N release was measured for composts with higher initial mineral N concentrations (317 mg Nmin/L) as well as VFG composts (417 mg Nmin/L) than for green composts with a lower initial mineral N concentration (148 mg Nmin/L). In a last step, woody compost, bark compost, wood fiber, coir and peat were mixed in different ratios, resulting in six blends ranging from 100% peat-free to 100% peat. Two batches of woody compost were compared, and the blends were mixed with blood meal or chitin. A strong effect of both the organic fertilizer and the blend composition on the mineral N release was observed, with a clear link between the microbial biomass and the net N release. There was a significant negative correlation between the net change in microbial biomass and the net N release (R = −0.85), which implies that a larger increase in microbial biomass during incubation with the organic fertilizer resulted in less N mineralization. The blends containing woody compost scored better for nitrification activity, as the NH4-N concentrations were lower in these than for the blends without woody compost. For the peat blends, no effect on the microbial biomass was observed after addition of organic fertilizers; mineral N did increase, however. Woody composts have the potential to be used in high vol% in growing media blends, but the blends still need further optimization when supplemented with organic fertilizers. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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27 pages, 4050 KiB  
Article
Primary Mechanical Modification to Improve Performance of Miscanthus as Stand-Alone Growing Substrates
by Van T. H. Nguyen, Thorsten Kraska, Winona Winkler, Sercan Aydinlik, Brian E. Jackson and Ralf Pude
Agronomy 2022, 12(2), 420; https://doi.org/10.3390/agronomy12020420 - 08 Feb 2022
Cited by 13 | Viewed by 2091
Abstract
Selecting proper mechanical processing can improve performance of miscanthus substrates. We studied the effects of mechanical processing methods on substrate morphology, hydrological properties, pH, and nitrogen immobilization. Miscanthus × giganteus biomass was processed into field chips (FC, forage harvester), shreds (S5, mechanical fraying [...] Read more.
Selecting proper mechanical processing can improve performance of miscanthus substrates. We studied the effects of mechanical processing methods on substrate morphology, hydrological properties, pH, and nitrogen immobilization. Miscanthus × giganteus biomass was processed into field chips (FC, forage harvester), shreds (S5, mechanical fraying machine through a 5-mm screen) and chips (C15, C10, C5 and C3, hammermill with screen size of 15, 10, 5, or 3 mm). Processed miscanthus materials were also tested as propagation substrates for Chinese cabbage seedlings. Results showed that particle size distribution of miscanthus substrates formed four groups in ascending order of particle size: C3 < C5 < (C10, C15, S5) < FC. The finer miscanthus substrates had higher water holding capacity following the same groupings in particle size. The hydrophobicity of processed miscanthus was low and reversible, with the increasing order of risk as C3 < C5 < C10, C15 < S5, FC. All miscanthus substrates had similar and low pH buffering capacity. Nitrogen immobilization was similar among miscanthus substrates. The seedlings in miscanthus substrates had similar germination rates but a lower biomass compared to those grown in peat and coir. Primary mechanical modification of miscanthus offers opportunities for different sizes of substrate materials with few changes to the physical or chemical properties tested in this work. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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22 pages, 2781 KiB  
Article
Ammonium to Total Nitrogen Ratio Interactive Effects with Salinity Application on Solanum lycopersicum Growth, Physiology, and Fruit Storage in a Closed Hydroponic System
by Nikolaos Tzortzakis, Georgia Pitsikoulaki, Aristeidis Stamatakis and Antonios Chrysargyris
Agronomy 2022, 12(2), 386; https://doi.org/10.3390/agronomy12020386 - 03 Feb 2022
Cited by 15 | Viewed by 2399
Abstract
Using high-salinity water for plant fertigation may have negative consequences for plant growth, overall yield and crop quality. In the present study, the effects of NaCl-salinity in conjunction with three different ammonium to nitrate ratios (Nr) on tomato (Solanum lycopersicum Mill.) plant [...] Read more.
Using high-salinity water for plant fertigation may have negative consequences for plant growth, overall yield and crop quality. In the present study, the effects of NaCl-salinity in conjunction with three different ammonium to nitrate ratios (Nr) on tomato (Solanum lycopersicum Mill.) plant growth, nutritional status, yield, fruit quality and postharvest storage were examined. The electrical conductivity (EC) was increased by adding NaCl into the nutrient solution and three different Nr ratios were applied, Nr0.05, Nr0.10 and Nr0.15, while the other macronutrient and micronutrient concentrations were constant in all treatments. The EC of the nutrient solution supplied to the plants was 2.2 mS cm−1 at the low salinity treatments and 7.5 mS cm−1 at the high salinity treatments. Increased salinity resulted in decreased plant growth factors and fruit yield, despite the Nr. An increased Nr reduced the pH value of the nutrient solution, while the fruits of the plants cultivated under high salinity obtained reduced Ca, K, Mg, P and N content. Reduced Ca content can lead to blossom end rot disorder and this was evidenced on tomato cultivation under high salinity. However, in the present study, this disorder appeared at the very late stages and did not affect the marketability of the fruits. On the other hand, both salinity and Nr0.15 increased fruit firmness at harvest or following storage, while citric acid, total soluble solid and vitamin C contents were also increased by salinity. Total phenols were increased by salinity at harvest, and lycopene and β-carotene content were increased by salinity at harvest and/or following storage at 12 °C or 25 °C. Salinity enhances fruit quality and improves the organoleptic characteristics of the crop, while an appropriate Nr ratio may restrict the detrimental effects of salinity on the nutritional status of plants by regulating the pH in hydroponic systems. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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10 pages, 1418 KiB  
Article
Quality and Yield of Lettuce in an Open-Air Rooftop Hydroponic System
by Maha Ezziddine and Helge Liltved
Agronomy 2021, 11(12), 2586; https://doi.org/10.3390/agronomy11122586 - 19 Dec 2021
Cited by 4 | Viewed by 4229
Abstract
In this study, the yield and growth performance of lettuce in an open-air rooftop hydroponic system were investigated. Lettuce was grown in a closed recirculating nutrient film technique (NFT) unit using a standard nutrient solution (NS). Yield, fresh weight, and nutrient content in [...] Read more.
In this study, the yield and growth performance of lettuce in an open-air rooftop hydroponic system were investigated. Lettuce was grown in a closed recirculating nutrient film technique (NFT) unit using a standard nutrient solution (NS). Yield, fresh weight, and nutrient content in the leaf tissue of the harvested lettuce were measured. The results were compared with the results obtained in indoor hydroponic lettuce growth with artificial lightning. Despite strong winds during the growth period, 25% of the total lettuce heads weighed twice the marketable weight; however, 25% of the total lettuce heads were below the marketable weight. A more efficient nutrient uptake was indicated by the lettuces in the rooftop system compared with the uptake in the indoor system. Foliar analysis revealed a higher content of all nutrients in the leaves of rooftop hydroponic lettuce compared with indoor hydroponic lettuce. This study suggests that hydroponic rooftop-grown lettuce can be competitive with their indoor counterparts if the rooftop hydroponic system is protected from extreme weather conditions. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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21 pages, 1844 KiB  
Article
Sensor-Based Irrigation Reduces Water Consumption without Compromising Yield and Postharvest Quality of Soilless Green Bean
by Michela Palumbo, Massimiliano D’Imperio, Vincenzo Tucci, Maria Cefola, Bernardo Pace, Pietro Santamaria, Angelo Parente and Francesco Fabiano Montesano
Agronomy 2021, 11(12), 2485; https://doi.org/10.3390/agronomy11122485 - 07 Dec 2021
Cited by 11 | Viewed by 2654
Abstract
Real-time monitoring of substrate parameters in the root-zone through dielectric sensors is considered a promising and feasible approach for precision irrigation and fertilization management of greenhouse soilless vegetable crops. This research investigates the effects of timer-based (TIMER) compared with dielectric sensor-based irrigation management [...] Read more.
Real-time monitoring of substrate parameters in the root-zone through dielectric sensors is considered a promising and feasible approach for precision irrigation and fertilization management of greenhouse soilless vegetable crops. This research investigates the effects of timer-based (TIMER) compared with dielectric sensor-based irrigation management with different irrigation set-points [SENSOR_0.35, SENSOR_0.30 and SENSOR_0.25, corresponding to substrate volumetric water contents (VWC) of 0.35, 0.30 and 0.25 m3 m−3, respectively] on water use, crop performance, plant growth and physiology, product quality and post-harvest parameters of soilless green bean (Phaseolus vulgaris L., cv Maestrale). In SENSOR treatments, an automatic system managed irrigation in order to maintain substrate moisture constantly close to the specific irrigation set-point. The highest water amount was used in TIMER treatment, with a water saving of roughly 36%, 41% and 47% in SENSOR_0.35, SENSOR_0.30 and SENSOR_0.25, respectively. In TIMER, the leaching rate was ≈31% of the total water consumption, while little leaching (<10%) was observed in SENSOR treatments. TIMER and SENSOR_0.35 resulted in similar plant growth and yield, while irrigation set-points corresponding to lower VWC values (SENSOR_0.30 and SENSOR_0.25) resulted in inadequate water availability conditions and impaired the crop performance. The study confirms that rational sensor-based irrigation allows to save water without compromising anyhow the product quality. In SENSOR irrigation management, in fact, especially in the case of optimal water availability conditions, it was possible to obtain high quality pods, with fully satisfactory characteristics during storage at 7 °C for 15 days. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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11 pages, 2301 KiB  
Article
Allelopathic Efficiency of Plant Extracts to Control Cyanobacteria in Hydroponic Culture
by Chan Saem Gil, Shucheng Duan, Ji Hye Kim and Seok Hyun Eom
Agronomy 2021, 11(11), 2350; https://doi.org/10.3390/agronomy11112350 - 19 Nov 2021
Cited by 8 | Viewed by 3123
Abstract
Cyanobacteria rapidly form harmful algal blooms (HABs) that cause serious nutritional imbalances in crop production via hydroponics. Allelopathic extracts from plants can be applied as a solution for ecologically sustainable control of algal blooms. In this study, the effects of 11 aqueous extracts [...] Read more.
Cyanobacteria rapidly form harmful algal blooms (HABs) that cause serious nutritional imbalances in crop production via hydroponics. Allelopathic extracts from plants can be applied as a solution for ecologically sustainable control of algal blooms. In this study, the effects of 11 aqueous extracts of 10 allelopathic plants in controlling Microcystis aeruginosa were evaluated. Among the extracts, walnut husk and rose leaf extracts exhibited high inhibitory levels for efficient control of algae. High inhibitory levels were achieved owing to large amounts of water-soluble tannins, especially tannic acid. The effective extracts were applied to a hydroponic system cultivated on leafy perilla vegetables. Although the severe doses (IC90) did not guarantee complete algal control due to partial algal regrowth, walnut husk and rose leaf extracts only exerted strong persistent effects on algae control. Persistent algae inhibition contributed to the increase in perilla growth and leaf quality. Rose leaf was potentially a more useful resource for controlling algae in a hydroponic system because the application of rose leaf extract efficiently controlled the algae and was less toxic to perilla growth. In contrast, the treatment of walnut husk extract also controlled algae but inhibited perilla growth with pale green leaves. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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16 pages, 556 KiB  
Article
Regulated Salinity Eustress in a Floating Hydroponic Module of Sequentially Harvested Lettuce Modulates Phytochemical Constitution, Plant Resilience, and Post-Harvest Nutraceutical Quality
by Petronia Carillo, Georgios A. Soteriou, Marios C. Kyriacou, Maria Giordano, Giampaolo Raimondi, Francesco Napolitano, Emilio Di Stasio, Ida Di Mola, Mauro Mori and Youssef Rouphael
Agronomy 2021, 11(6), 1040; https://doi.org/10.3390/agronomy11061040 - 22 May 2021
Cited by 16 | Viewed by 2598
Abstract
A mild salinity stress (eustress) may modulate the induction of the plant defense system in horticultural crops and the synthesis of phytochemical components able to enhance plant resilience, post-harvest performance, and the nutraceutical quality of produce. However, the choice of the correct eustress [...] Read more.
A mild salinity stress (eustress) may modulate the induction of the plant defense system in horticultural crops and the synthesis of phytochemical components able to enhance plant resilience, post-harvest performance, and the nutraceutical quality of produce. However, the choice of the correct eustress type and dose to induce the synthesis of these protective phytochemicals is pivotal to avoid potential interference with plant growth and productivity. In order to study how green and red lettuce (Lactuca sativa L.) plants equilibrate the nutritional and nutraceutical components of quality with yield components, we applied iso-osmotic concentrations of three different salts (20 mM NaCl, 20 mM KCl, and 13.3 mM CaCl2, with a final total ionic concentration of 40 mM) in combination with two successive harvests in a floating raft system. The biometric parameters, mineral composition, bioactive compounds, and antioxidant activity of both cultivars were analyzed. The green cultivar had a superior response concerning biometric traits and productivity compared to the red one during the first cut but lower phytochemical content (e.g., ascorbic acid). The effect of cut order, independently of cultivar and salinity treatments, demonstrated that at the first harvest plants could redirect metabolism by increasing the lipophilic antioxidant content (LAA) at the expense of plant yield, therefore increasing plant resilience and post-harvest nutraceutical quality; whereas, at the second harvest, plants reverted principally to tissue expansion. The treatments with iso-osmotic salt concentrations did not affect K and Mg ion contents but further increased LAA and resulted only in a moderate decrease of fresh yield. The lettuce nitrate content was reduced during the second cut only when lettuce plants were treated with NaCl and especially CaCl2. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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21 pages, 2621 KiB  
Article
Effect of Bacillus spp. on Lettuce Growth and Root Associated Bacterial Community in a Small-Scale Aquaponics System
by Nasser Kasozi, Horst Kaiser and Brendan Wilhelmi
Agronomy 2021, 11(5), 947; https://doi.org/10.3390/agronomy11050947 - 11 May 2021
Cited by 23 | Viewed by 5509
Abstract
The integration of probiotics in aquaponics systems is a strategy for mitigating environmental impacts and for promoting sustainable agriculture. In order to understand the role of probiotics, we investigated the effect of a commercial probiotic mixture of Bacillus subtilis and B. licheniformis on [...] Read more.
The integration of probiotics in aquaponics systems is a strategy for mitigating environmental impacts and for promoting sustainable agriculture. In order to understand the role of probiotics, we investigated the effect of a commercial probiotic mixture of Bacillus subtilis and B. licheniformis on the growth of lettuce (Lactuca sativa L.) under deep-water culture integrated with Mozambique tilapia (Oreochromis mossambicus). We determined plant growth, water quality parameters, and leaf mineral analysis, and assessed the influence of a probiotic mixture on the microbiota. Bacterial communities were analyzed by high-throughput 16S rRNA gene sequencing. Compared to the control systems, the addition of the probiotic Bacillus significantly increased the concentration of nitrate and phosphate in deep water culture solution, which contributed to improved lettuce growth. In both the growth trials, the Fv/Fm, the mean shoot dry weight, and the mean fresh weight of the harvested shoots from the Bacillus treatment were significantly higher than those observed for the control plants. Higher concentrations of phosphorus, potassium, and zinc in the lettuce leaves were found in systems that received the Bacillus. Although differences were observed at the phylum level, Proteobacteria and Bacteroidetes were predominant in both the Bacillus-treatment and the control systems. At the genus level, however, the communities present in the two types of systems were heterogeneous with Bacillus-treated systems, containing significantly higher numbers of Chryseobacterium, Bacillus, Nitrospira, Polynucleobacter, and Thermomonas. The results indicate that Bacillus supplementation can effectively alleviate nutrient deficiencies, improve water quality, and modify the composition of bacterial communities in aquaponics systems. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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12 pages, 1044 KiB  
Article
Managing pH of Organic Matrices and New Commercial Substrates for Ornamental Plant Production: A Methodological Approach
by Sonia Cacini, Sara Di Lonardo, Simone Orsenigo and Daniele Massa
Agronomy 2021, 11(5), 851; https://doi.org/10.3390/agronomy11050851 - 27 Apr 2021
Cited by 6 | Viewed by 1779
Abstract
Professional peat-free substrates for ornamental plant production are increasingly required by nursery growers. Most promising materials are green compost, coconut coir dust, and woody fibre, used alone or in mixtures. One of the major concerns is pH, usually higher than optimal. In this [...] Read more.
Professional peat-free substrates for ornamental plant production are increasingly required by nursery growers. Most promising materials are green compost, coconut coir dust, and woody fibre, used alone or in mixtures. One of the major concerns is pH, usually higher than optimal. In this work, a method based on a three-step procedure was adopted to acidify three organic matrices alone or in mixtures and to individuate the most suitable product, between iron(II) sulphate 7-hydrate and elemental sulphur chips. Firstly, the determination of the buffering capacity by dilution with sulphuric acid was carried out to determine dosages. Afterwards, an incubation trial of 84 (iron(II) sulphate) or 120 days (sulphur chips) was conducted on matrices and substrate mixtures with calculated doses in a climatic chamber maintained at 21 °C. Iron(II) sulphate resulted not suitable because it caused a rapid, but not lasting, pH lowering and an excessive electrical conductivity (EC) increase. Sulphur chips could instead guarantee an adequate and lasting pH lowering. These results were then validated in the open field trial on matrices and substrates. The proposed acidification methodology could be considered in developing new substrates, but the rapidity of pH acidification and EC increase on plant and mineral nutrition should be further investigated. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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19 pages, 17821 KiB  
Article
Effects of Selenium and/or Arbuscular Mycorrhizal Fungal Inoculation on Strawberry Grown in Hydroponic Trial
by Omiros Antoniou, Antonios Chrysargyris, Panayiota Xylia and Nikolaos Tzortzakis
Agronomy 2021, 11(4), 721; https://doi.org/10.3390/agronomy11040721 - 09 Apr 2021
Cited by 9 | Viewed by 2406
Abstract
Strawberry is considered as a fruit of high nutritional value, with appreciated benefits on human health. Arbuscular mycorrhizal fungi (AMF) are commonly used plant symbionts that affect plant growth and its effectiveness is plant species specific. Additionally, selenium (Se) projects a special interest [...] Read more.
Strawberry is considered as a fruit of high nutritional value, with appreciated benefits on human health. Arbuscular mycorrhizal fungi (AMF) are commonly used plant symbionts that affect plant growth and its effectiveness is plant species specific. Additionally, selenium (Se) projects a special interest to humans for its antioxidant specialties, and to plants, because of the potential to make them grow faster when added to the nutrient solution. Nonetheless, the performance of arbuscular mycorrhizal fungi (AMF) in Se biofortification in strawberry is unexplored. The purpose of the present study experiment was to determine whether mycorrhizal inoculation of AMF can have a positive impact on growth and quality of strawberries, and whether Se contributes in this effort or will adversely affect the plants. Four Se concentrations (0, 1, 5 and 10 mg L−1) in the nutrient solution, with or without mycorrhizal inoculation of AMF to the root system, were evaluated. Results demonstrated that Se of 10 mg L−1 negatively affected plant growth, photosynthetic rates, decreased fruit firmness and total soluble solids, induced oxidative stress in fruits and affected nutrient accumulation in different plant organs. Mycorrhizal inoculation of AMF mainly stimulated antioxidative mechanisms of the fruits and increased nutrient accumulation for plants grown at high Se levels. Based on our observations, mycorrhizal inoculation can enhance the nutritional value of strawberry fruits and strawberry plants seem to be a strong candidate for Se biofortification, allowing the rise of Se of the consumers’ intake. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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19 pages, 1467 KiB  
Article
Parameters of Drainage Waters Collected during Soilless Tomato Cultivation in Mineral and Organic Substrates
by Jacek Dyśko, Magdalena Szczech, Stanisław Kaniszewski and Waldemar Kowalczyk
Agronomy 2020, 10(12), 2009; https://doi.org/10.3390/agronomy10122009 - 20 Dec 2020
Cited by 7 | Viewed by 3013
Abstract
The aim was to determine the suitability of various substrates for application in a closed system of soilless tomato cultivation, based on the potential fitness of drainage waters from these substrates for recirculation. Four substrates were used: rockwool, coir substrate, lignite substrate (Carbomat) [...] Read more.
The aim was to determine the suitability of various substrates for application in a closed system of soilless tomato cultivation, based on the potential fitness of drainage waters from these substrates for recirculation. Four substrates were used: rockwool, coir substrate, lignite substrate (Carbomat) and biodegradable organic substrate (Biopot). Tomato plants grown in these substrates were fertilized with the same amount of nutrient solution, containing the same concentration of nutrients. The characteristics of drainage water from these substrates were analyzed during cultivation. The highest amount of drainage water was collected from the lignite substrate Carbomat. However, these leachates showed good properties for further recirculation: low electro conductivity and turbidity, high nutrient content, moderate microbial load with high population of Trichoderma fungi, and being beneficial for plant growth. Moreover, Carbomat produced the highest tomato yield compared to other substrates. This indicates that this organic substrate is an efficient alternative to rockwool and its drainage water may be reused in a recirculation system. On the contrary, the drainage water from the Biopot substrate showed the worst qualities: high pH and low EC, low concentration of nitrate nitrogen and phosphorus, very high turbidity and a high number of microorganisms. These parameters do not qualify Biopot drainage waters for reuse. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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15 pages, 2715 KiB  
Article
Growth, Yield and Quality of Sweet Pepper Fruits Fertilized with Polyphosphates in Hydroponic Cultivation with LED Lighting
by Anna Sobczak, Katarzyna Kowalczyk, Janina Gajc-Wolska, Waldemar Kowalczyk and Monika Niedzińska
Agronomy 2020, 10(10), 1560; https://doi.org/10.3390/agronomy10101560 - 13 Oct 2020
Cited by 16 | Viewed by 3895
Abstract
The aim of this study was to investigate the effect of phosphorus application in the form of polyphosphates on the yield and quality of sweet pepper fruits grown with LED (light-emitting diodes) assimilation lighting. Phosphorus is absorbed by the root system of plants [...] Read more.
The aim of this study was to investigate the effect of phosphorus application in the form of polyphosphates on the yield and quality of sweet pepper fruits grown with LED (light-emitting diodes) assimilation lighting. Phosphorus is absorbed by the root system of plants mainly in the form of orthophosphates ions. The availability of phosphorus depends, among other things, on the pH of the substrate and the temperature. Two cultivars of sweet pepper with red fruits were tested in hydroponic cultivation on a mineral wool substrate. The plants were fertilized with one of three schedules, each of the same concentration of components, but differing only in the form of the applied phosphorus: polyphosphates (PP) and orthophosphates (OP). In the experiment, stem length extensions and number of leaves, chlorophyll concentration in leaves and fluorescence of the chlorophyll in a leaf were measured. The number and weight of fruits in total as well as marketable and non-commercial fruits with symptoms of dry rot (BER—blossom end rot) were studied. The concentration of dry matter and selected chemical components in fruits were examined and the sensory quality of fruits was evaluated using the QDA (Quantitative Description Analysis) method. The nutrient status of the pepper plants was also examined. Polyphosphates used in the medium increase the activity of photosynthetic apparatus of leaves and have a positive effect on the share of marketable yield of the total yield in the cultivar susceptible to BER. Fertigation in hydroponic cultivation with medium containing 30% phosphorus in the form of polyphosphates increased the uptake of calcium in pepper plants growing with LED lighting. The pepper cultivars tested differ in, among other things, the susceptibility to BER and the quality attributes of the fruit. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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Review

Jump to: Editorial, Research

29 pages, 824 KiB  
Review
The Role of Peat-Free Organic Substrates in the Sustainable Management of Soilless Cultivations
by Giulia Atzori, Catello Pane, Massimo Zaccardelli, Sonia Cacini and Daniele Massa
Agronomy 2021, 11(6), 1236; https://doi.org/10.3390/agronomy11061236 - 18 Jun 2021
Cited by 41 | Viewed by 6747
Abstract
Vegetable and ornamental crops require high input demand to adequately support their standard commercial quality and yield. For these crops, a very high level of agronomic use efficiency of many productive factors can be achieved in soilless culture. For example, the benefits derived [...] Read more.
Vegetable and ornamental crops require high input demand to adequately support their standard commercial quality and yield. For these crops, a very high level of agronomic use efficiency of many productive factors can be achieved in soilless culture. For example, the benefits derived from the adoption of soilless closed loops for the recirculation of the nutrient solution are well known as a benchmark of excellence for nutrient and water use efficiency. The challenges that we now face are as follows: (i) making soilless systems more inclusive of sustainable and eco-friendly growing substrates, possibly available at a local level; (ii) replacing chemicals with more sustainable products (e.g., organic active compounds) as much as possible for plant nutrition and protection. These goals can be addressed by following different approaches, but the adoption of peat-free organic substrates may play a central role. This work investigates four organic materials, i.e., biochar, coir, green compost, and wood fibers, to assess their role in plant nutrition and protection when used as components for the preparation of growing media in the soilless cultivation of containerized crops. In further detail, the work highlights how these materials may support normal agronomic practices. Full article
(This article belongs to the Special Issue The Tripartite of Soilless Systems, Growing Media, and Plants through An Intensive Crop Production Scheme)
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