Special Issue "Optimising Soilless Culture Systems and Alternative Growing Media to Current Used Materials"

A special issue of Horticulturae (ISSN 2311-7524). This special issue belongs to the section "Protected Culture".

Deadline for manuscript submissions: 31 December 2021.

Special Issue Editors

Prof. Dr. Nazim Gruda
E-Mail Website1 Website2
Guest Editor
Division of Horticultural Sciences, Institute of Crop Science and Resource Conservation, University of Bonn, Auf dem Hügel 6, 53121 Bonn, Germany
Interests: controlled environment agriculture; grafting; growing media; mycorrhiza; product quality of fruit and vegetables; protected cultivation; soilless culture; stress physiology; sustainable horticulture; vegetables
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Juan A. Fernández
E-Mail Website
Guest Editor

Special Issue Information

Dear Colleagues,

Soilless culture systems have been gaining in popularity worldwide in the last few decades, making them one of the fastest-growing sectors in agriculture. There is an increased interest in producing seedlings and transplants, and growing pot ornamentals and small/soft fruit crops, greens, herbs, and medicinal and aromatic plants, including cannabis, in soilless container systems. Besides, there is an expansion of urban growing systems, such as green-roof and vertical farming, that utilise soilless culture technologies, with an increase in the demand for new and improved products. Within soilless systems, growing media, i.e., crop cultivation in solid, inorganic or organic materials, are relevant for efficient and intensive plant production. However, new strategies and technologies should be continually developed to solve specific cultivation limitations, optimise the existing systems and reduce any related environmental impacts. Remarkably, the problems related to the search for alternative materials to peat and rockwool, due to the despoiling of ecologically important peat bog areas and a pervasive waste problem, are in the focus of the horticultural sciences today.

This Special Issue will focus on optimising soilless culture systems and recent advances in the characterisation and utilisation of novel soilless substrate materials used in plant-production systems.

We welcome high-quality research publications and reviews, covering all related topics in soilless culture and substrate science. These include new promising substrate components; substrate characterisation and analytical techniques; the hydrology and physical properties of growing media; chemical and biological properties; substrate formulation and growth-medium engineering; reducing water and nutrient runoff; biological additives and microbial influences; plant-physiology specifics in such systems; root-medium properties; plant propagation; plant nutrition and chemistry; the advancement of technologies such as green roofs, vertical farming, and modern automated systems for nutrient and water supply, such as Artificial Intelligence and the Internet of Things; and other closely related research areas within soilless substrates and growing media. For more topics, see the keywords below.

Prof. Dr. Nazim Gruda
Prof. Dr. Juan A. Fernández
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 papers will be 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. Horticulturae 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 1400 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

  • Abiotic and biotic stress management
  • Additives and biostimulants for soilless substrates
  • Advances in biochar production and utilisation in substrates
  • Advances in compost utilisation in substrates
  • Advances in plant propagation in growing media
  • Advances in urban gardening, green roof technology, and vertical farming
  • The availability and use of substrates in the future, and novel inorganic and organic materials
  • Biofortification and added-value plant metabolites
  • Cannabis production in soilless systems
  • Carbon footprints, life-cycle analysis, climate change, and sustainable agriculture
  • Hydroponics and aquaponics
  • Increasing plant metabolites
  • Nutrient solutions and fertigation
  • Organic waste management and circular horticulture
  • Peat and mineral-wool alternatives
  • Root-medium properties, architecture, and plant nutrition
  • The stability and biodegradation of growing media
  • Substrate analysis and characterisation
  • Substrate formulation and growing-medium engineering
  • Water-/nutrient-use efficiency, automation, artificial intelligence, and Internet of Things

Published Papers (8 papers)

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Research

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Article
Basil as Secondary Crop in Cascade Hydroponics: Exploring Salinity Tolerance Limits in Terms of Growth, Amino Acid Profile, and Nutrient Composition
Horticulturae 2021, 7(8), 203; https://doi.org/10.3390/horticulturae7080203 - 21 Jul 2021
Cited by 1 | Viewed by 777
Abstract
In a cascade hydroponic system, the used nutrient solution drained from a primary crop is directed to a secondary crop, enhancing resource-use efficiency while minimizing waste. Nevertheless, the inevitably increased EC of the drainage solution requires salinity-tolerant crops. The present study explored the [...] Read more.
In a cascade hydroponic system, the used nutrient solution drained from a primary crop is directed to a secondary crop, enhancing resource-use efficiency while minimizing waste. Nevertheless, the inevitably increased EC of the drainage solution requires salinity-tolerant crops. The present study explored the salinity-tolerance thresholds of basil to evaluate its potential use as a secondary crop in a cascade system. Two distinct but complemented approaches were used; the first experiment examined basil response to increased levels of salinity (5, 10 and 15 dS m−1, compared with 2 dS m−1 of control) to identify the limits, and the second experiment employed a cascade system with cucumber as a primary crop to monitor basil responses to the drainage solution of 3.2 dS m−1. Growth, ascorbate content, nutrient concentration, and total amino acid concentration and profile were determined in both experiments. Various aspects of basil growth and biochemical performance collectively indicated the 5 dS m−1 salinity level as the upper limit/threshold of tolerance to stress. Higher salinity levels considerably suppressed fresh weight production, though the total concentration of amino acids showed a sevenfold increase under 15 dS m−1 and 4.5-fold under 5 and 10 dS m−1 compared to the control. The performance of basil in the cascade system was subject to a compromise between a reduction of fresh produce and an increase of total amino acids and ascorbate content. This outcome indicated that basil performed well under the conditions and the system employed in the present study, and might be a good candidate for use as a secondary crop in cascade-hydroponics systems. Full article
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Article
First Steps toward a Test Procedure to Identify Peat Substitutes for Growing Media by Means of Chemical, Physical, and Biological Material Characteristics
Horticulturae 2021, 7(7), 164; https://doi.org/10.3390/horticulturae7070164 - 28 Jun 2021
Cited by 1 | Viewed by 486
Abstract
Due to the major environmental impact of peat-based growing media production and the need of lowering greenhouse gas emissions in all sectors, a wider application of peat substitutes in growing media is requested. All peat substitutes under use have constraints associated with their [...] Read more.
Due to the major environmental impact of peat-based growing media production and the need of lowering greenhouse gas emissions in all sectors, a wider application of peat substitutes in growing media is requested. All peat substitutes under use have constraints associated with their properties. Therefore, a preliminary test procedure for identifying new raw materials as peat substitutes in growing media was developed and validated. By applying the preliminary test procedure, the potential limitations of cultivation of potential peat substitutes are indicated, and measures for cultivation regulation are recommended. For the development of the new preliminary test procedure, four raw materials were investigated: composted heather, alder, cattail, and reed. The preliminary test procedure comprises several material and technological criteria as well as aspects of plant cultivation, enabling the evaluation of the raw materials and the processed components for growing media. Results derived from the preliminary test procedure were checked and confirmed by experiments with horticultural crops in different sections of commercial horticulture. Within two years, the identification of new peat substitutes was possible by the application of the preliminary test procedure and its test criteria, which provide a structure for the systematic investigation of potential new peat substitutes starting with the raw material. Full article
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Article
Performance of Greenhouse-Grown Beit Alpha Cucumber in Pine Bark and Perlite Substrates Fertigated with Biofloc Aquaculture Effluent
Horticulturae 2021, 7(6), 144; https://doi.org/10.3390/horticulturae7060144 - 09 Jun 2021
Cited by 1 | Viewed by 931
Abstract
Using aquaculture effluent (AE) to fertigate plants is gaining popularity worldwide. However, in substrate-based systems, the choice of substrate is essential due to their effects on crop productivity. Differences in the retention of nutrients by substrates makes it necessary to assess suitability for [...] Read more.
Using aquaculture effluent (AE) to fertigate plants is gaining popularity worldwide. However, in substrate-based systems, the choice of substrate is essential due to their effects on crop productivity. Differences in the retention of nutrients by substrates makes it necessary to assess suitability for use in AE. This study was conducted from January to July in 2016 and September to October in 2019 to evaluate greenhouse-grown Beit Alpha cucumber (Cucumis sativus L. ‘Socrates’) performance fertigated with AE in pine bark or perlite substrates, grown either as one plant or two plants per pot. A 2 × 2 factorial arrangement in a randomized complete block design with four replications for each season was used. The substrate effect on yield in 2016 depended on the density and season. The pooled yield over seasons in 2016 showed pine bark had a significantly higher yield than perlite by 11% in one plant per pot but lowered by the same amount in two plants per pot. In 2019, pine bark significantly reduced the leachate pH in both plant densities and reduced the leachate EC by about 15% in two plants per pot. The foliar boron was occasionally below sufficiency whilst manganese was above sufficiency in pine bark due to its inherently low pH. We conclude that the effect of the substrates on cucumber yield fertigated with AE is dependent on the season and the number of plants per pot. Therefore, due to the local availability of pine bark, it could be a potential substitute for perlite especially when using one plant per pot for AE. In addition, pine bark could be used as an intermediate substrate to reduce the pH in AE for downstream use. Full article
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Article
Coir, an Alternative to Peat—Effects on Plant Growth, Phytochemical Accumulation, and Antioxidant Power of Spinach
Horticulturae 2021, 7(6), 127; https://doi.org/10.3390/horticulturae7060127 - 28 May 2021
Cited by 2 | Viewed by 948
Abstract
The effects of four commercial substrates, a peat-based substrate, and three coir types (coir pith, coir chips, and coir pith + fibers) on yield, phytochemical accumulation, and antioxidant activity were evaluated in Spinacia oleracea L. cv. ‘Manatee’. Soil-blocked spinach seedlings were transplanted into [...] Read more.
The effects of four commercial substrates, a peat-based substrate, and three coir types (coir pith, coir chips, and coir pith + fibers) on yield, phytochemical accumulation, and antioxidant activity were evaluated in Spinacia oleracea L. cv. ‘Manatee’. Soil-blocked spinach seedlings were transplanted into Styrofoam planting boxes filled with the substrate. Each planting box was irrigated daily by drip with a complete nutrient solution, and the irrigation scheduling was optimized to the peat. Leaf area and fresh yield in coir pith and coir pith + fiber were similar to those obtained in peat. However, shoot dry weight accumulation and leaf chlorophyll were lower in plants grown in coir. Substrate type did not affect leaf carotenoids. Total flavonoid content was higher in plants grown in the different types of coir. Total phenols and antioxidant activity (DPPH) were higher in plants grown in coir pith. This indicates that the different coir types, mainly coir pith, may provide an alternative to peat since they allowed a high fresh yield to be reached and the total flavonoids to be increased. In contrast, the levels of other phytochemicals and antioxidant activity were usual for spinach. However, further research is necessary to analyze the effects of irrigation scheduling and the nutrient solution adjusted to each growing medium on yield and phytochemical accumulation. Full article
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Article
Effects of Vermicompost Leachate versus Inorganic Fertilizer on Morphology and Microbial Traits in the Early Development Growth Stage in Mint (Mentha spicata L.) And Rosemary (Rosmarinus officinalis L.) Plants under Closed Hydroponic System
Horticulturae 2021, 7(5), 100; https://doi.org/10.3390/horticulturae7050100 - 06 May 2021
Viewed by 595
Abstract
The objective of this study was to compare the morphology of M. spicata and R. officinalis plants, and the relative abundance quantification, colony-forming units, ribotypes, and biofilm former bacteria under an inorganic fertilizer and the use of vermicompost leachate in the rhizosphere under [...] Read more.
The objective of this study was to compare the morphology of M. spicata and R. officinalis plants, and the relative abundance quantification, colony-forming units, ribotypes, and biofilm former bacteria under an inorganic fertilizer and the use of vermicompost leachate in the rhizosphere under a closed hydroponic system. In mint (Mentha spicata) plants treated with the vermicompost leachate, growth increase was determined mainly in root length from an average of 38 cm in plants under inorganic fertilizer to 74 cm under vermicompost leachate. In rosemary (Rosmarinus officinalis), no changes were determined between the two treatments. There were differences in the compositions of microbial communities: For R. officinalis, eight ribotypes were identified, seven for inorganic fertilizer and four for vermicompost leachate. For M. spicata, eight ribotypes were identified, three of them exclusive to vermicompost leachate. However, no changes were observed in microbial communities between the two treatments. Otherwise, some changes were observed in the compositions of these communities over time. In both cases, the main found phylum was Firmicutes, with 60% for R. officinalis and 80% for M. spicata represented by the Bacillus genus. In conclusion, the use of vermicompost leachate under the hydroponic system is a viable alternative to achieve an increase in the production of M. spicata, and for both plants (mint and rosemary), the quality of the product and the microbial communities that inhabited them remained unaltered. Full article
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Article
Calcium Carbonate Can Be Used to Manage Soilless Substrate pH for Blueberry Production
Horticulturae 2021, 7(4), 74; https://doi.org/10.3390/horticulturae7040074 - 07 Apr 2021
Viewed by 821
Abstract
Blueberry (Vacciniumcorymbosum interspecific hybrids) production in soilless substrates is becoming increasingly popular. Soilless substrates have low pH buffering capacity. Blueberry plants preferentially take up ammonium, which acidifies the rhizosphere. Consequently, soilless substrates where blueberry plants are grown exhibit a tendency to [...] Read more.
Blueberry (Vacciniumcorymbosum interspecific hybrids) production in soilless substrates is becoming increasingly popular. Soilless substrates have low pH buffering capacity. Blueberry plants preferentially take up ammonium, which acidifies the rhizosphere. Consequently, soilless substrates where blueberry plants are grown exhibit a tendency to get acidified over time. Agricultural lime (CaCO3) is commonly used to raise soil and substrate pH in other crops, but it is rarely used in blueberry cultivation. We hypothesized that substrate amendment with low rates of agricultural lime increases substrate pH buffering capacity and provides nutritional cations that can benefit blueberry plants. We tested this hypothesis in a greenhouse experiment with ‘Emerald’ southern highbush blueberry plants grown in rhizoboxes filled with a 3:1 mix of coconut coir and perlite. We found that substrate amendment with CaCO3 did not cause high pH stress. This amendment maintained substrate pH between 5.5 and 6.5 and provided Ca and Mg for plant uptake. When blueberry plants were grown in CaCO3-amended substrate and fertigated with low pH nutrient solution (pH 4.5), they exhibited greater biomass accumulation than plants grown in unamended substrates. These results suggest that low rates of CaCO3 could be useful for blueberry cultivation in soilless substrates. Full article
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Article
Composting Spent Mushroom Substrate from Agaricus bisporus and Pleurotus ostreatus Production as a Growing Media Component for Baby Leaf Lettuce Cultivation under Pythium irregulare Biotic Stress
Horticulturae 2021, 7(2), 13; https://doi.org/10.3390/horticulturae7020013 - 25 Jan 2021
Viewed by 737
Abstract
Composts of spent mushrooms substrates can be an alternative for the partial replacement of peat as growing media in horticulture. Three mature composts from Agaricus bisporus (Ag), Pleurotus ostreatus (Pl), and 70% Ag:30% Pl (AgPl) production were used as partial components of peat [...] Read more.
Composts of spent mushrooms substrates can be an alternative for the partial replacement of peat as growing media in horticulture. Three mature composts from Agaricus bisporus (Ag), Pleurotus ostreatus (Pl), and 70% Ag:30% Pl (AgPl) production were used as partial components of peat growing media, used at a 1:4 compost:peat ratio for growing red baby leaf lettuce. They showed higher yields, between 3 and 7 times more than that for peat itself, even under the pressure of the plant pathogen Pythium irregulare. AgPl showed the higher suppressiveness (50%) against Pythium irregulare than Ag- (38%) or Pl- (15%) supplemented media. The combination of these raw materials and a suitable composting process is important for obtaining mature compost for use as a partial component of peat-based growing media. Full article
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Review

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Review
Environmental and Cultivation Factors Affect the Morphology, Architecture and Performance of Root Systems in Soilless Grown Plants
Horticulturae 2021, 7(8), 243; https://doi.org/10.3390/horticulturae7080243 - 12 Aug 2021
Cited by 3 | Viewed by 877
Abstract
Soilless culture systems are currently one of the fastest-growing sectors in horticulture. The plant roots are confined into a specific rootzone and are exposed to environmental changes and cultivation factors. The recent scientific evidence regarding the effects of several environmental and cultivation factors [...] Read more.
Soilless culture systems are currently one of the fastest-growing sectors in horticulture. The plant roots are confined into a specific rootzone and are exposed to environmental changes and cultivation factors. The recent scientific evidence regarding the effects of several environmental and cultivation factors on the morphology, architecture, and performance of the root system of plants grown in SCS are the objectives of this study. The effect of root restriction, nutrient solution, irrigation frequency, rootzone temperature, oxygenation, vapour pressure deficit, lighting, rootzone pH, root exudates, CO2, and beneficiary microorganisms on the functionality and performance of the root system are discussed. Overall, the main results of this review demonstrate that researchers have carried out great efforts in innovation to optimize SCS water and nutrients supply, proper temperature, and oxygen levels at the rootzone and effective plant–beneficiary microorganisms, while contributing to plant yields. Finally, this review analyses the new trends based on emerging technologies and various tools that might be exploited in a smart agriculture approach to improve root management in soilless cropping while procuring a deeper understanding of plant root–shoot communication. Full article
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