Increasing Sustainability of Growing Media Constituents and Stand-Alone Substrates in Soilless Culture Systems

Suitability of coconut bran and biochar as a composite substrate for lettuce cultivation in aquaponic systems

Growth substrates are essential for aquaponic systems and play an important role in vegetable growth and water quality. In this study, we explored an innovative combination of coconut bran and coconut shell biochar (CSB) as a composite growth substrate for lettuce cultivation in aquaponic systems. The study included the control (100 % coconut bran as the growth substrate) and treatment groups (T1-T5; containing 10 %, 20 %, 30 %, 40 %, and 50 % CSB as the growth substrate, respectively). The substrate properties; lettuce growth performance; and soil enzyme activity, nitrogen content, and abundance of microbial communities in the substrate were analyzed to determine the optimal substrate. Our findings indicated that CSB incorporation significantly altered the properties of the substrate, resulting in increased dry and bulk densities, pH, and water-holding capacity, and decreased electrical conductivity, water-absorption capacity, and porosity. Furthermore, the fresh weight of lettuce was notably increased in the treatment groups. The activities of fluorescein diacetate hydrolase, urease, nitrate reductase, and hydroxylamine reductase initially increased and further decreased, reaching the maximum in the T3 group. Conversely, the activity of nitrite reductase and contents of available nitrogen, nitrate-nitrogen, and ammonium-nitrogen in the substrates initially decreased and further increased, with the minimum values observed in the T3 group. The microbial sequencing results indicated that CSB incorporation significantly increased the microbial diversity and relative abundance of microorganisms associated with nitrogen transformation. Moreover, 30 % CSB incorporation exhibited the greatest effect on lettuce growth, with a 34.5 % and 31.6 % increase in fresh weight compared to the control during the growth and harvest periods, respectively. This study indicated the enormous potential of biochar in the research and development of green technologies for substrate amendment in aquaponic systems.

Above- and below-ground morpho-physiological traits indicate that biochar is a potential peat substitute for grapevine cuttings nursery production

The growing demand for grapevine planting materials, due to growing global viticulture, is promoting research studies to improve vineyard sustainability. In greenhouse nurseries, peat is the most common growing medium component used although is an expensive and non-renewable material. Indeed, the reduction of peat exploitation is receiving great attention, and currently, several materials are being investigated as peat substitutes for composing the cultivation substrates. Biochar, a carbon-rich, recalcitrant charred organic co-product of the pyrolysis or gasification process, has emerged as a potentially promising replacement for soilless substrates in nursery plant material propagation. Although several studies carried out at greenhouse nurseries have shown that biochar, can improve plant growth, only a few studies have focused on the production of grapevine plant material. To fulfil this knowledge gap and push forward the sustainability of the nursery sector, we evaluated above and below-ground morpho-physiological traits of one-year-old potted grapevine cuttings growing with 30% volume of four different biochar types (i.e., from pyrolysis and gasification) mixed with commercial peat. The present study shows that biochar can be used in growing media mixes without adverse effects on roots, improves soil water retention and leaf water potential, and improves the effects on soil microbiology.

Environmental Impact of Outdoor Cannabis Production

Environmental impacts of cannabis production are of increasing concern because it is a newly legal and growing industry. Although a handful of studies have quantified the impacts of indoor production, very little is known about the impact of outdoor cannabis agriculture. Outdoor production typically uses little direct energy but can require significant fertilizer and other inputs due to dissipative losses via runoff and mineralization. Conversely, fertilizer high in nitrogen can be counterproductive, as it produces flowers with decreased cannabinoid content. This study has two aims: (1) To identify reduced-fertilizer regimes that provide optimal cannabis flower yields with reduced inputs and (2) to quantify how this shifts greenhouse gas emissions, resource depletion (fossil and metal), terrestrial acidification, and the eutrophication potential of outdoor cannabis production. Primary data from a fertilizer response trial are incorporated into a life-cycle assessment model. Results show that outdoor cannabis agriculture can be 50 times less carbon-emitting than indoor production. Dissemination of this knowledge is of utmost importance for producers, consumers, and government officials in nations that have either legalized or will legalize cannabis production.

Utilization of organic-residues as potting media: Physico-chemical characteristics and their influence on vegetable production

Soilless agriculture is acknowledged worldwide because it uses organic leftovers as a means of supporting intensive and efficient plant production. However, the quality of potting media deteriorates because of lower nutrient content and excessive shrinkage of most organic materials. A current study was undertaken to identify the optimal blend of locally available organic materials with desirable qualities for use as potting media. Therefore, different ingredients, viz., Pinus roxburghii needles, sugarcane bagasse, and farmyard manure were used alone or in combination as potting media to test their suitability by growing spinach as a test crop. Results showed that an increase in Pinus roxburghii needles and sugarcane bagasse decreased medium pH and electrical conductivity. Higher pH and electrical conductivity were recorded for the treatments having a higher farmyard manure ratio (≥50%) in combination. Except for pine needles 100%, pH and electrical conductivity were in the recommended range. The growth attributes include, leaves plant-1, shoot length, fresh- and dry shoot weight along with plant macronutrients (nitrogen, phosphorous, and potassium) and micronutrients (iron, copper, manganese, and zinc) content were higher in treatment pine needles 50%+farmyard manure 50% followed by pine needles 25%+farmyard manure 50%+sugarcane bagasse 25%. Moreover, the particular treatment of pine needles 50%+farmyard manure 50% exhibited the highest concentrations of macro- (nitrogen, phosphorus, and potassium) as well as micronutrients (iron, copper, manganese, and zinc) in the potting media following the harvest. This study highlights the potential of utilizing agro-industrial litter/waste as a soilless growing medium for spinach production under greenhouse conditions. When employed in appropriate proportions, this approach not only addresses disposal concerns but also proves effective for sustainable cultivation. Further research is needed to investigate the use of these wastes as potting media by mixing various particle-size ingredients.

Chemical Profile and Bioactivity of Rubus idaeus L. Fruits Grown in Conventional and Aeroponic Systems

Raspberry (Rubus idaeus L.) is a fruit of great interest due to its aroma, nutritional properties, and the presence of many bioactive compounds. However, differences among cultivation systems can affect its composition and, consequently, its potential bioactivity. Herein, for the first time, raspberries grown in an aeroponic system were investigated for their chemical profile and antioxidant and anti-inflammatory activity, as well as their enzyme (α-glucosidase and pancreatic lipase) inhibitory properties in comparison to wild and conventionally cultivated fruits. High-performance liquid chromatography coupled with diode array detection (HPLC-DAD) analyses revealed the presence of gallic acid, caffeic acid, chlorogenic acid, p-coumaric acid, ferulic acid, rutin, and catechin in all the samples. The extracts exhibited in vitro anti-inflammatory activity (inhibition of nitric oxide production) regardless of the cultivation method. Of particular interest is the ability of raspberries to inhibit pancreatic lipase. With the exception of the β-carotene bleaching test, the raspberries grown in conventional and aeroponic systems were more active in terms of antioxidants than wild fruits, as evidenced by the ABTS (IC50 in the range 1.6-3.4 μg/mL), DPPH (IC50 in the range 8.9-28.3 μg/mL), and FRAP tests (24.6-44.9 μM Fe(II)/g). The raspberries from aeroponic cultivation were generally able to exert the same bioactivity as those obtained from both conventionally cultivated and wild fruits, supporting the consideration that in the future, this technology could reshape agriculture by mitigating resource constraints, fostering sustainable practices and increasing yields.

Hydroponics: Exploring innovative sustainable technologies and applications across crop production, with Emphasis on potato mini-tuber cultivation

There is an urgent need to explore climate-resilient alternative agriculture production systems that focus on resilience, resource efficiency, and disease management. Hydroponics, a soilless cultivation system, gaining interest as it reduces the dependency on agricultural land, and pesticides, and can be implemented in areas with poor soil quality, thus mitigating the negative effects of extreme weather events. Potato is an essential dietary staple crop grown throughout the world and is a major source of food security in underdeveloped countries. However, due to the climatic changes, it is predicted that a significant loss in the suitability of land for potato production would occur, thus leading to potato yield loss. Recently, many case studies have emerged to highlight the advancement of agricultural hydroponic systems that provide a promising solution to the massive production of potato mini tuber at high efficiency. This review paper evaluates popular hydroponic methods and demonstrates how hydroponic has emerged as the go-to, long-term, sustainable answer to the perennial problem of insufficient access to high-quality potato seed stock. The paper discusses the research and innovation possibilities (such as artificial intelligence, nanoparticles, and plant growth-promoting rhizobacteria) that potentially increase tuber production per plant under optimal hydroponic growth circumstances. These approaches are examined considering new scientific discoveries and practical applications. Furthermore, it emphasizes that by enduring significant reforms in soilless food production systems (particularly for potatoes), the food supply of a rapidly growing population can be addressed. Since hydroponics systems are productive and easily automated without soil and optimal environmental conditions, future hydroponics farming is promising. In conclusion, the hydroponics system provides better yield and crop productivity by saving water, energy, and space. Henceforth, it can be the alternate choice for modern sustainable agriculture.

Trichoderma atroviride Enhances Impatiens walleriana Hook. f Growth and Flowering in Different Growing Media

Trichoderma spp. are widely reported to regulate plant growth by improving nutrient uptake, photosynthesis, and abiotic stress tolerance. However, their possible application for bedding plants is little explored, especially when comparing different growing media. Considering that coconut coir dust is finding broader application in the ornamental plants sector as a peat substitute, this work was aimed to test the combination of Trichoderma atroviride AT10 and coconut coir dust on Impatiens walleriana plants. Four treatments were tested as a mix of: (i) two growing media (70:30), peat:perlite or coconut coir dust:perlite; and (ii) the absence or presence of a T. atroviride treatment. At the end of the production cycle, the biomass and ornamental parameters, leaf pigments, nutrient content of the plant tissues, and Trichoderma abundance were assessed. The results revealed that T. atroviride can readily colonize coir, and the same positive effects of inoculum were found in plants grown on both substrates. The biostimulant effect of T. atroviride was observed as an increase in the aboveground biomass, number and weight of flowers, pigments and nutrient concentration, thereby improving the commercial quality of I. walleriana. Thus, T. atroviride has shown its potential in making bedding plant cultivation more sustainable and improving the yield and aesthetic parameters of plants grown on peat and coconut coir dust substrates.

Bacterially enhanced plant-growing media for controlled environment agriculture

Microbe-plant interactions in the root zone not only shape crop performance in soil but also in hydroponic cultivation systems. The biological and physicochemical properties of the plant-growing medium determine the root-associated microbial community and influence bacterial inoculation effectiveness, which affects plant growth. This study investigated the combined impact of plant-growing media composition and bacterial community inoculation on the root-associated bacterial community of hydroponically grown lettuce (Lactuca sativa L.). Ten plant-growing media were composed of varying raw materials, including black peat, white peat, coir pith, wood fibre, composted bark, green waste compost, perlite and sand. In addition, five different bacterial community inocula (BCI S1-5) were collected from the roots of lettuce obtained at different farms. After inoculation and cultivation inside a vertical farm, lettuce root-associated bacterial community structures, diversity and compositions were determined by evaluating 16S rRNA gene sequences. The study revealed distinct bacterial community structures among experimental replicates, highlighting the influence of raw material variations on root-associated bacterial communities, even at the batch level. However, bacterial community inoculation allowed modulation of the root-associated bacterial communities independently from the plant-growing medium composition. Bacterial diversity was identified as a key determinant of plant growth performance with green waste compost introducing Bacilli and Actinobacteria, and bacterial community inoculum S3 introducing Pseudomonas, which positively correlated with plant growth. These findings challenge the prevailing notion of hydroponic cultivation systems as sterile environments and highlight the significance of proper plant-growing media raw material selection and bacterial community inoculation in shaping root-associated microbiomes that provide stability through microbial diversity. This study supports the concept of creating bacterially enhanced plant-growing media to promote plant growth in controlled environment agriculture.

Utilizing the power of plant growth promoting rhizobacteria on reducing mineral fertilizer, improved yield, and nutritional quality of Batavia lettuce in a floating culture

In soilless cultivation, plants are grown with nutrient solutions prepared with mineral nutrients. Beneficial microorganisms are very important in plant nutrition. However, they are not present in soilless culture systems. In this study we investigated the impact of introducing Plant Growth Promoting Rhizobacteria (PGPR) as an alternative to traditional mineral fertilizer in hydroponic floating lettuce cultivation. By reducing mineral fertilizers at various ratios (20%, 40%, 60%, and 80%), and replacing them with PGPR, we observed remarkable improvements in multiple growth parameters. Applying PGPR led to significant enhancements in plant weight, leaf number, leaf area, leaf dry matter, chlorophyll content, yield, and nutrient uptake in soilles grown lettuce. Combining 80% mineral fertilizers with PGPR demonstrated a lettuce yield that did not significantly differ from the control treatment with 100% mineral fertilizers. Moreover, PGPR application improved the essential mineral concentrations and enhanced human nutritional quality, including higher levels of phenols, flavonoids, vitamin C, and total soluble solids. PGPR has potential as a sustainable substitute for synthetic mineral fertilizers in hydroponic floating lettuce cultivation, leading to environmentally friendly and nutritionally enriched farming.

Reuse of coir, peat, and wood fiber in strawberry production

Introduction

Production of strawberries in greenhouses and polytunnels is gaining popularity worldwide. This study investigated the effect of reuse of coir and peat, two substrates commonly adapted to soilless strawberry production, as well as stand-alone wood fiber from Norway spruce, a promising substrate candidate.

Methods

The experiment was performed in a polytunnel at NIBIO Apelsvoll, Norway, and evaluated both virgin substrates, as well as spent materials that were used in one or two years. Yield, berry quality and plant architecture of the strawberry cultivar 'Malling Centenary' were registered. In addition, chemical and physical properties of virgin and reused substrates were investigated.

Results

While plants grown in peat and wood fiber had highest yield in the first year of production, the berry yield was slightly reduced when these substrates were utilized for the second and third time. However, yield was comparable to the yield level attained in new and reused coir. Interestingly, berries grown in wood fiber had a tendency to a higher sugar accumulation. This substrate also produced the highest plants. Stand-alone wood fiber was the substrate with the highest accumulation of nitrogen during the three consecutive production cycles. All three investigated materials revealed a trend for decreased potassium accumulation. Wood fiber is characterized by the highest percentage of cellulose, however after three years of production the cellulose content was reducedto the same levels as for coir and peat.

Discussion

Implementation of wood fiber as a growing medium, as well as general practice of substrate reuse can be therefore an achievable strategy for more sustainable berry production.

Greenhouse gas emissions from bio-based growing media: A life-cycle assessment

In this study, using an LCA approach we explored how bio-based peat alternatives (wood fiber, compost, and hydrochar based on willow and degassed fiber from agricultural waste) and their mixtures (75 % peat with 25 % peat alternative) as growing media (GM) for plant production in Denmark may provide benefits for reducing greenhouse gas emissions compared to peat. To perform this, foreground data (collected via personal communication and literature) was used together with background data from Ecoinvent V3.8. The chosen functional unit was 1 m3 of GM and the system boundary was from cradle to use as GM. The global warming potential of all the peat alternatives showed significant reduction, varying between 89 and 109 % compared to peat. When incorporating 25 % of each alternative with peat, the climate footprint was reduced by 16 to 33 % compared to pure peat. Thus, there are large climate prospects in replacing peat with bio-based alternatives, and the results underlines the relevance of being able to increase the proportion of the bio-based components in their mixtures with peat beyond the 25 % and towards 100 % replacement. The effectiveness of peat substitutes in term of reducing the CO2 emissions is affected by choice of the feedstock, their processing method and emissions of their end-use.

Properties of Poultry-Manure-Derived Biochar for Peat Substitution in Growing Media

Peat is considered a contentious input in horticulture. Therefore, there is a search for suitable alternatives with similar properties that can be used for partial or complete peat substitution in growing media. Poultry-manure-derived biochar (PMB) is considered such an alternative. This study aimed at determining the properties of PMBs obtained through pyrolysis at selected temperatures and assessing their potentials to substitute peat in growing media based on the selected properties. The scope included the laboratory-scale pyrolysis of poultry manure at the temperatures of 425-725 °C; the determination of selected physico-chemical and physical properties of the obtained biochars, including the contaminants; and the assessment of the potentials of produced biochars to be used as peat substitutes. PMBs contained less than 36% of total organic carbon (TOC). The contents of P and K were about 2.03-3.91% and 2.74-5.13%, respectively. PMBs did not retain N. They can be safely used as the concentrations of heavy metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinatd biphenyls (PCBs), dioxins, and furans are within the permissible values (except for Cr). Due to high pH (9.24-12.35), they can have a liming effect. High water holding capacity (WHC) in the range of 158-232% w/w could allow for the maintenance of moisture in the growing media. PMBs obtained at 525 °C, 625 °C, and 725 °C showed required stability (H/Corg < 0.7).

Compensation of adverse growing media effects on plant growth and morphology by supplemental LED lighting

There is an increasing interest in alternatives to peat in growing media due to environmental constraints. However, plants grown in peat substitutes often show impaired growth compared to plants grown in peat-based media. Hence, it would be interesting to know whether these deficiencies can be compensated by supplementing other growth factors, e.g. light. The present study aims to investigate the interactive nature between growing media and supplemental lighting on plant growth and morphology, and to examine whether supplemental light emitting diode (LED) lighting may compensate adverse growing media effects. Basil (Ocimum basilicum L.) and Chinese cabbage (Brassica rapa subsp. pekinensis) were grown in different growing media consisting of peat, green compost, coconut pulp, wood fibre, perlite and sphagnum moss under blue, red and far-red supplemental LED lighting. We found significant interactions between growing media and supplemental photosynthetically active radiation (PAR) on plant growth, morphology and development. At low light intensities, peat-based and substituted growing media performed similarly, whereas with increasing light intensities the peat-based growing media significantly outperformed their alternatives. The substrate choice determines the required amount of supplemental light to compensate for adverse growing media effects and the amount varies depending on plant species and season. Thereby, it was indicated that red light alleviates adverse growing media effects best. We also found that far-red light is not effective when background PAR is low and becomes more effective under high background PAR. The implications and prospects of the results are discussed.

Influence of tomato waste composts on dry matter and heavy metals content in cucumber and summer squash seedlings

Huge quantities of agricultural waste are available annually in Saudi Arabia, which are not well exploited, leading to large environmental pollution and health problems. The use of different proportions of tomato waste compost (TWC) mixed with commercial peat-moss as a natural, economical, cheap and environmentally friendly fertilizer for fertilizing vegetables is very important, therefore, this study is concerned with investigating and evaluating the dry matter content (DM) and the accumulated heavy metal contents (HMs) in the root and leaf seedlings tissues of cucumber and summer squash plants as a result of using this fertilizer. Five ratios of mixtures (vermiculite: peat moss: TWC by weight) used in the experiment, and the TWC in the mixture represents 0, 5, 10, 15 and 20% (by wieght). The results indicated that, the DM contents in the root and leaf tissues were relatively close between cucumber and summer squash seedlings. However, they were higher in the root than in leaf tissues, particularly under 20% TWC. A TWC application ratio of 20% reduced concentrations of the most HMs in the two vegetable species seedlings due to high EC and pH levels. The amounts of HMs in vegetable species were not high, which proves the that transfer of HMs from the TWC substrate to the seedlings is determined chiefly by metal bioavailability and by a vegetable species. DM, mineral and nutritional quality of vegetable seedlings showed that substrates containing 5% and 10% TWC appeared to be the most suitable growing medium for economic vegetable seedlings; and it is recommended for use in the nursery production. Implications: The idea of this research revolves around the use of different proportions of tomato waste compost in fertilizing cucumber and summer squash seedlings and investigate the effect of this compost on dry matter (DM) and heavy metal (HMs) contents in the root and leaf tissues of the seedlings, and fruit quality of cucumber and summer squash plants.

Make a choice: A rapid strategy for minimizing peat in horticultural press pots substrates using a constrained mixture design and surface response approach

Peat is the most common used substrate in horticultural seedling production. To reduce peat in horticultural potted plant cultivation systems in general is an obstacle, even within the highly specialized horticultural industry. Next to soil-less cultivation systems as e.g. hydroponics, the horticultural industry is eagerly looking for suitable peat substitutes. The demands on these compounds are high, basically mimicking the physical properties of peat. A 100% replacement of peat for press-pots used in seedling production has not yet been found, and only mixes of peat and substrates exist. Several suitable peat substitutes with different properties are known, that usually are used as a share of a mixed peat-substitute substrate. A constrained mixture design was used to test substrates containing 50% v/v and 25% v/v peat and four peat substitutes (two composts and two wood fibers) for vegetable seedling production. By limiting the maximum quantities of each material to be added, there was no negative effect on the growth of Chinese cabbage (Brassica rapa subsp. pekinensis). This means a reduction in of peat to 25% v/v is possible without a change in substrate quality. The mixture design allowed a quick decision to be made regarding the most suitable peat-reduced mixtures. The surface response approach enabled the experimental results to be easily transferred to horticultural practices, additionally. This flexible and efficient method also allows the predictions to be used to meet specific crop management needs.

Organic waste compost and spent mushroom compost as potential growing media components for the sustainable production of microgreens

Microgreens are emerging specialty crops becoming increasingly popular for their rich nutrient profile and variety of colors, flavors, and textures. The growing medium is a significant key factor in microgreen yield, quality, and sustainability. The widespread use of peat-based media raises questions regarding the environmental sustainability of microgreens production, and new substrates that are more sustainable are required. To this purpose, a study was designed with the objective of comparing eight alternative growing media evaluating their physicochemical properties and effect on yield, mineral profile, and nutritional quality of peas and radish microgreens. Tested substrates included a standard peat and perlite mixture (PP), coconut coir (CC), spent mushroom compost (SMC), organic waste compost (CMP), and 50:50 (v:v) mixes of PP and SMC, PP and CMP, CC and SMC, and CC and CMP. The physicochemical properties widely differed among the alternative substrates tested. SMC had high electrical conductivity and salt concentration, which resulted in poor seed germination. Growing media tested significantly influenced the production and nutritional quality of both microgreen species and variations were modulated by the species. With a 39.8% fresh yield increase or a small yield decrease (-14.9%) in radish and peas, respectively, PP+CMP (50:50, v/v) mix provided microgreens of similar or higher nutritional quality than PP, suggesting the potential of substituting at least in part peat with CMP. Using locally available CMP in mix with PP could reduce the microgreens industry reliance on peat while reducing costs and improving the sustainability of the production of microgreens. Further research is needed to evaluate also the potential economic and environmental benefits of using locally available organic materials like CMP as alternative growing media and peat-substitute to produce microgreens.

Tomato Plant Microbiota under Conventional and Organic Fertilization Regimes in a Soilless Culture System

Tomato is the main vegetable cultivated under soilless culture systems (SCSs); production of organic tomato under SCSs has increased due to consumer demands for healthier and environmentally friendly vegetables. However, organic tomato production under SCSs has been associated with low crop performance and fruit quality defects. These agricultural deficiencies could be linked to alterations in tomato plant microbiota; nonetheless, this issue has not been sufficiently addressed. Thus, the main goal of the present study was to characterize the rhizosphere and phyllosphere of tomato plants cultivated under conventional and organic SCSs. To accomplish this goal, tomato plants grown in commercial greenhouses under conventional or organic SCSs were tested at 8, 26, and 44 weeks after seedling transplantation. Substrate (n = 24), root (n = 24), and fruit (n = 24) composite samples were subjected to DNA extraction and high-throughput 16S rRNA gene sequencing. The present study revealed that the tomato core microbiota was predominantly constituted by Proteobacteria, Actinobacteria, and Firmicutes. Remarkably, six bacterial families, Bacillaceae, Microbacteriaceae, Nocardioidaceae, Pseudomonadaceae, Rhodobacteraceae, and Sphingomonadaceae, were shared among all substrate, rhizosphere, and fruit samples. Importantly, it was shown that plants under organic SCSs undergo a dysbiosis characterized by significant changes in the relative abundance of Bradyrhizobiaceae, Caulobacteraceae, Chitinophagaceae, Enterobacteriaceae, Erythrobacteraceae, Flavobacteriaceae, Nocardioidaceae, Rhodobacteraceae, and Streptomycetaceae. These results suggest that microbial alterations in substrates, roots, and fruits could be potential factors in contributing to the crop performance and fruit quality deficiencies observed in organic SCSs.

Hydroponic potato production in wood fiber for food security

The resilience of global food security is a critical concern. Facing limited access to land and potential disruption of the food markets, alternative, scalable, and efficient production systems are needed as a complementary buffer for maintenance of food production integrity. The purpose of this study was to introduce an alternative hydroponic potato growing system where potatoes are grown in bare wood fiber as a growing medium. A system utilizing drip irrigation and plastic bags as containers was tested for three different types of wood fiber, two cultivars and two fertigation strategies. Implementation of the system resulted in ~300% higher tuber production when compared to the local conventional farming. Mineral composition of the tubers obtained from hydroponic system was similar to the composition of tubers grown in the field and revealed potential for biofortification. In addition, a fertigation strategy where the two application points were separated across the root zone resulted in tubers with dry matter content comparable to the potatoes grown in soil. The recyclability, reusability, and simplicity of this solution may encourage its application for improving security of food production in selected areas of the world as well as its utilization in urban agriculture.

Oxygen uptake rate versus CO2 based respiration rate for assessment of the biological stability of peat, plant fibers and woody materials with high C:N ratio versus composts

The biological stability of organic materials predicts their performance when used as either a soil improver or as an ingredient in growing media. CO₂ release in a static measurement and O₂ consumption rate (OUR) were compared for seven groups of growing media components. The ratio between CO₂ release and OUR was matrix-specific. This ratio was highest for plant fibers high in C:N and with a high risk of N immobilization, intermediate for wood fiber and woody composts, and lowest for peat and other compost types. The effect of variable test conditions in the OUR setup was assessed for plant fibers, where addition of mineral N and/or nitrification inhibitor had no effect on the OUR measurements. Testing at 30 °C instead of 20 °C resulted in higher OUR values as expected, but did not change the effect of mineral N dose. A strong increase in the CO₂ flux was measured when plant fibers were mixed with mineral fertilizer; in contrast, addition of mineral N or fertilizer before or during the OUR test had no effect. The present experimental setup did not allow for differentiation between a higher CO₂ release as a result of increased microbial respiration after adding mineral N versus an underestimation of stability due to N limitation in the dynamic OUR setup. Results indicate that type of material, C:N ratio and risk of N immobilization all appear to affect the OUR results. The OUR criteria may therefore require clear differentiation based on the different materials used in horticultural substrates.

Application of Seaweed Generates Changes in the Substrate and Stimulates the Growth of Tomato Plants

Ulva ohnoi is a cosmopolitan green seaweed with commercial potential given the biomass that may be generated. We evaluated the effects of substrate changes induced by U. ohnoi application on the vegetative response of tomato plants under greenhouse conditions. First, the decomposition dynamics and N release of the dry seaweed biomass were studied using the litterbag method. Subsequently, we evaluated the effect of seaweed powder (SP) or seaweed extract (SE) applications on substrate and plant growth. Additionally, the growth parameters responses evaluated were related to the changes in substrate properties associated with each treatment. The results showed that the dry seaweed biomass has a rapid rate of degradation (k = 0.07 day^-1) and N release (k = 0.024 day^-1). The SP application improved the physicochemical and biological characteristics of the substrate by increasing the availability of minerals, the fungi:bacteria ratio, and the growth morphophysiological parameters (length, area, dry and fresh weight), chlorophyll and mineral content. In contrast, SE treatment showed a positive effect on the root, mineral content, and soil microbes. This study highlights the agricultural potential of U. ohnoi powder as an alternative supplement that supports nutrition and promotes the vegetative growth of plants cultivated in soilless horticultural systems.

Closed-loop agriculture systems meta-research using text mining

The growing global population and climate change threaten the availability of many critical resources, and have been directly impacting the food and agriculture sector. Therefore, new cultivation technologies must be rapidly developed and implemented to secure the world's future food needs. Closed-loop greenhouse agriculture systems provide an opportunity to decrease resource reliance and increase crop yield. Greenhouses provide versatility in what can be grown and the resources required to function. Greenhouses can become highly efficient and resilient through the application of a closed-loop systems approach that prioritizes repurposing, reusing, and recirculating resources. Here, we employ a text mining approach to research the available research (meta-research) and publications within the area of closed-loop systems in greenhouses. This meta-research provides a clearer definition of the term “closed-loop system” within the context of greenhouses, as the term was previously vaguely defined. Using this meta-research approach, we identify six major existing research topic areas in closed-loop agriculture systems, which include: models and controls; food waste; nutrient systems; growing media; heating; and energy. Furthermore, we identify four areas that require further urgent work, which include the establishment of better connection between academic research to industry applications; clearer criteria surrounding growing media selection; critical operational requirements of a closed-loop system; and the functionality and synergy between the many modules that comprise a closed-loop greenhouse systems.

Optimizing Alternative Substrate for Tomato Production in Arid Zone: Lesson from Growth, Water Relations, Chlorophyll Fluorescence, and Photosynthesis

Soilless culture is considered the mostpromising, intensive, and sustainable approach with various advantages for plant production in terms of saving water and nutrients. It can provide consumers with sufficient and high-quality food. However, the commonly used growing substrate for soilless cultivation, coconut fiber (CF), is usually imported and expensive or even unavailable. The objectives of this study were to investigate the impact of local organic farm resources substrates on tomato (Solanum lycopersicum L.) plant growth, water relations, photosynthesis, chlorophyll fluorescence, and phytochemical analysis of fruits in a hydroponics culture system. Two growth substrates were evaluated: date-palm waste composted with animal manure (7:3 w/w) (DPAM) and date-palm trunk compost (DPT). CF and local soil were utilized as positive and negative controls, respectively, in randomized blocks. The results revealed that DPAM substrate enhanced plant growth and physiology: shoot development, leaves tissues hydration, and photosynthetic parameters, as well as chlorophyll fluorescence. However, DPT and CF improved fruit quality: water, mineral, sugar, and protein content. The antioxidant activity of the fruit extract was the greater in DPAM, reaching 13.8 mg GAEg^-1 DW. This value wasdecreased in soil by 40%. Photosynthesis activity was the most important in DPAM with 12 µmol CO₂ m^-2 s^-1, and only 6.4 µmol CO₂ m^-2 s^-1 in the soil condition. However, regarding the non-photochemical quenching, the dissipated light energy was greater in soil (0.096 ± 0.02) than in DPAM (0.025 ± 0.04). Date-palm waste-based substrates improved tomato vegetative growth and fruit quality as compared to soil-based culture. Date-palm waste-based substrates supplemented with manure appear to be promising and less expensive alternatives to the coconut fiber substrate extensively used in soilless crops in North Africa.

Insights into production and consumption processes of nitrous oxide emitted from soilless culture systems by dual isotopocule plot and functional genes

Soilless culture systems (SCS) play an increasing role in greenhouse vegetable production. In the SCS, soilless substrates serve as the major substitute for soil, supplying nutrients to plants but releasing greenhouse gases into the atmosphere. Remarkably, there is a serious problem of N₂O emission due to excessive input of N fertilizer. However, the microbial processes of N₂O production and consumption in soilless substrates have been rarely studied resulting in difficultly interpreting for its global warming potential. Therefore, these pathways from two classic soilless substrates under two irrigation patterns were investigated by stable isotope technology combined with qPCR analysis in present study. The results according to the dual isotopocule plot of δ¹⁵N^SP vs. δ¹⁸O showed that the mean contribution of denitrification and the mean extent of N₂O reduction of case i (Reduction-Mixing) were 26.2 and 81.2 % for the treatment of peat based substrate under drip irrigation (PD), 47.7 and 70.3 % for the treatment of coir substrate under drip irrigation (CD), 29.0 and 80.8 % for the treatment of peat based substrate under tidal irrigation (PT), and 50.8 and 47.4 % for the treatment of coir substrate under tidal irrigation (CT). These results were also further confirmed by the abundance of major functional genes including AOA amoA, nirK and nosZ. Altogether, N₂O emission and its microbial processes are determined by substrate types instead of irrigation patterns. For detail, denitrification dominated in the peat based substrate and nitrification dominated in the coir substrate. Compared to the coir substrate, the peat based substrate had higher abundance of functional genes and stronger denitrification and thus generated more N₂O. For the two soilless substrates, moreover, the microbiome replaced the mineral N content as the limiting factor for N₂O emission. In the SCS, in summary, the two soilless substrates play an important role in tomato growth, but might suffer from inorganic nutrient surplus and microbial shortage. More importantly, the combined analysis of N₂O isotopocule deltas and functional genes is a robust tool and provides reliable conclusions for clarifying the microbial processes of N₂O production and consumption, thus it is also recommended for use in environments other than soilless substrates.

Effect of Soil Type and In Vitro Proliferation Conditions on Acclimation and Growth of Willow Shoots Micropropagated in Continuous Immersion Bioreactors

Salix viminalis L. is a species with high capacity for micropropagation and acclimation and could therefore be used to evaluate emergent techniques in the field of plant propagation. The aims of this study were to propagate willow in liquid medium with a continuous immersion system, to explore the application of photoautotrophic conditions and to investigate the adaptation of willow plantlets to different soils that could be used as alternatives to commercial peat. For proliferation, we used 3% sucrose or sugar-free medium, and as substrates, we used commercial peat, a soil from an oak forest with high organic matter content and a crop soil with low organic matter content. The effect of sugar supplementation during proliferation and the soil characteristics during acclimation and growth were evaluated on the basis of aerial and root growth and the hydrolytic and dehydrogenase enzymatic activities of the soils. The results indicate that under photoautotrophic conditions, the supplementation of sucrose during micropropagation did not affect the subsequent growth of the plantlets. All plants acclimated without loss, but the type of soil influenced the height and vigor. Plants produced the highest shoots in peat, whereas the most root development occurred in crop soil. Soil enzyme activities were more influenced by the type of soil than by the presence of plants.

Effect of biofertilizers on leaf yield, nitrate amount, mineral content and antioxidants of basil (Ocimum basilicum L.) in a floating culture

Hydroponics is one of the systems in agriculture which reinforce productivity by controlling environmental and growing conditions. In this study, we evaluated the effect of three bio-fertilizers, namely bacteria, micro-algae, and mycorrhiza, on basil leaf yield and quality (Ocimum basilicum L.) in a floating culture system. Soil has rich amounts of beneficial microorganisms, supporting plant nutrition, producing phytohormones, controlling phytopathogens, and improving soil structure. However, soilless culture usually contains no beneficial microorganisms if we do not include them in the system. This study aims to evaluate the response of three bio-fertilizers where mineral fertilizers are reduced by 50%. Considering the total harvest data, bacteria, mycorrhiza, and micro-algae treatments increased basil yield compared to 50% control by about 18.94%, 13.94%, and 5.72%, respectively. The maximum total yield and leaf area were recorded using bacteria with 2744 g m^-2 and 1528 cm² plant^-1. Plants with mycorrhiza achieved the highest number of leaves and branches, with 94.3 leaves plant^-1 and 24.50 branches plant^-1, respectively. It was observed that this bio-fertilizer increased the formation of lateral branches in the basil plant without thickening its stems. In addition, bacteria and mycorrhiza induced the highest percentage of dry matter and total soluble solids. The effect of bio-fertilizers on basil leaf EC and pH was insignificant for all the treatments at different harvest periods (p < 0.05). Using bio-fertilizers enhanced the intake of nutrients N (nitrogen), P (phosphorus), K (potassium), Ca (calcium), Mg (magnesium), Fe (iron), Mn (manganese), Zn (zinc), and Cu (copper). Using bio-fertilizers represents a promising and environmentally friendly approach to increasing crop yields and ameliorating quality and antioxidant compounds with fewer resources. An application of bio-fertilizers in hydroponic cultivation of basil cv. 'Dino' reduced the need for mineral fertilizers. At the same time, bio-fertilizers affected an increased plant yield and improved product quality. Furthermore, the bacteria had a pronounced enhancing effect on the increase of phenol and flavonoids in the leaves of basil plants.

Genome Editing for Sustainable Crop Improvement and Mitigation of Biotic and Abiotic Stresses

Climate change poses a serious threat to global agricultural activity and food production. Plant genome editing technologies have been widely used to develop crop varieties with superior qualities or can tolerate adverse environmental conditions. Unlike conventional breeding techniques (e.g., selective breeding and mutation breeding), modern genome editing tools offer more targeted and specific alterations of the plant genome and could significantly speed up the progress of developing crops with desired traits, such as higher yield and/or stronger resilience to the changing environment. In this review, we discuss the current development and future applications of genome editing technologies in mitigating the impacts of biotic and abiotic stresses on agriculture. We focus specifically on the CRISPR/Cas system, which has been the center of attention in the last few years as a revolutionary genome-editing tool in various species. We also conducted a bibliographic analysis on CRISPR-related papers published from 2012 to 2021 (10 years) to identify trends and potential in the CRISPR/Cas-related plant research. In addition, this review article outlines the current shortcomings and challenges of employing genome editing technologies in agriculture with notes on future prospective. We believe combining conventional and more innovative technologies in agriculture would be the key to optimizing crop improvement beyond the limitations of traditional agricultural practices.

Characterization of Microbial Communities and Naturally Occurring Radionuclides in Soilless Growth Media Amended with Different Concentrations of Biochar

Biochar, derived from the pyrolysis of plant materials has the potential to enhance plant growth in soilless media. Howevetar, little is known about the impact of biochar amendments to soilless growth media, microbial community composition, and fate of chemical constituents in the media. In this study, different concentrations of biochar were added to soilless media and microbial composition, and chemical constituents were analyzed using metagenomics and gamma spectroscopy techniques, respectively. Across treatments, carboxyl-C, phenolic-C, and aromatic-C were the main carbon sources that influenced microbial community composition. Flavobacterium (39.7%), was the predominantly bacteria genus, followed by Acidibacter (12.2%), Terrimonas (10.1%), Cytophaga (7.5%), Ferruginibacter (6.0%), Lacunisphaera (5.9%), Cellvibrio (5.8%), Opitutus (4.8%), Mucilaginibacter (4.0%) and Bryobacter (4.0%). Negative relationships were found between Cytophaga and 226Ra (r = −0.84, p = 0.0047), 40K (r = −0.82, p = 0.0069) and 137Cs (r = −0.93, p = 0.0002). Similarly, Mucilaginibacter was negatively correlated with 226Ra (r = −0.83, p = 0.0054) and 137Cs (r = −0.87, p = 0.0021). Overall, the data suggest that high % biochar amended samples have high radioactivity concentration levels. Some microorganisms have less presence in high radioactivity concentration levels.

Stone Wool Substrate Cover Incision Impacts on the Root-Zone Water Content, Temperature, and Yield of Tomato Cultures

Standardized cultivation systems are crucial for establishing reproducible agronomic techniques. Especially stone wool-based cultivation is governed by standardized specifications and provides a controllable root-zone environment. However, the effects of stone wool cover incision on root-zone variability have rarely been studied. Therefore, in this study, we focused on the effect of the stone wool cover incision method on environmental variations and their subsequent effects on tomato plant productivity. Stone wool slab plastic covers represent a core component of this substrate system that can potentially affect the performance of water control techniques. We designed a cover incision method to create four different levels of drainage performances that were tested by cultivating tomato plants (Solanum lycopersicum "Dafnis"). The water content, root-zone temperature, and dissolved oxygen were measured and analyzed relative to the tomato yield. We found that the incision level with the lowest drainage performance showed a lower air-root zone temperature correlation slope than those of slabs with favorable drainage conditions. Furthermore, these slabs had low dissolved oxygen levels (3.2 mg/L); nevertheless, the tomatoes grown in the slabs with incision level showing the lowest drainage performance had greater fruit yield (6,748 g/plant) than those in the slabs with favorable drainage conditions (6,160 g/plant). Furthermore, the normalized yield separation timing between treatments coincided with the hotter air temperature (27°C average) periods. We noted that manipulating the cover incision process consequently entailed variations in the correlation slope between the air temperature and root-zone temperature in the substrate. Our results reveal another trade-off relationship in the conventional perspective on the drainage performance effects and provide insights into further optimization of crop production and water use in the stone wool-based system.

Optimizing Shade Cultivation Method and Irrigation Amount to Improve Photosynthetic Characteristics, Bean Yield, and Quality of Coffee in a Subtropical Monsoon Climate

Reasonable water and light management technology can improve economic benefits, coffee yield, and quality. We used cluster analysis and principal component analysis to evaluate and optimize the water and light management technology with high coffee yield, quality, and economic benefits in a subtropical monsoon climate region of China. The experiment was arranged in a randomized complete block design with two factors (3 irrigation levels × 4 shade cultivation treatments) replicated four times during 2016-2017. The irrigation levels consisted of full irrigation (FI) and two deficit irrigations (DI _L : 75% FI, DI _S : 50% FI). The shade cultivation treatments consisted of no shade cultivation (S₀) and three shade cultivation modes (S _L : intercropping with four lines of coffee and one line of banana; S _M : intercropping with three lines of coffee and one line of banana; S _S : intercropping with two lines of coffee and one line of banana). The results showed that the effects of irrigation level and shade cultivation mode on growth, crop yield, most of the photosynthetic characteristics, and nutritional quality were significant (p < 0.05). Regression analysis showed that the leaf radiation use efficiency (RUE) showed a significant negative exponential relation or logistic-curve variation with photosynthetically active radiation (PAR). The bean yield increased with an increase of the shade degree when water was seriously deficient, whereas it first increased and then decreased with an increase of the shade degree under FI and DI _L . Based on both cluster analysis and principal component analysis, the FIS _S treatment resulted in the highest comprehensive quality of coffee, followed by the FIS _M treatment; the DI _S S₀ treatment obtained the lowest quality. Compared with the FIS₀ treatment, the FIS _M treatment increased the 2-year average bean yield and net income by 15.0 and 28.5%, respectively, whereas the FIS _S treatment decreased these by 17.8 and 8.7%, respectively. To summarize, FIS _S treatment significantly improved the nutritional quality of coffee, and FIS _M treatment significantly increased the dry bean yield and economic benefits of coffee. The results of the study could provide a theoretical basis for water-saving irrigation and shade cultivation management of coffee in a subtropical monsoon climate region of China.

Effect of Selected Physical Parameters of Lignite Substrate on Morphological Attributes, Yield and Quality of Cucumber Fruits Fertigated with High EC Nutrient Solution in Hydroponic Cultivation

Environmentally friendly substrates that are biodegradable may provide an alternative to mineral wool, which is commonly used in hydroponic growing technology. Little is known about the relationship between the physical characteristics of lignite substrate and cucumber yield. The study analyzed the effect of bulk density and water holding capacity of lignite substrate in comparison to mineral wool and EC of nutrient solution on plant morphological parameters, yield and fruit quality of greenhouse cucumber. A positive relation was found between the bulk density of lignite mats and the increase in the number of leaves per week, shoot diameter as well as leaf length and leaf area (calculated as the product of leaf length × width) in cucumbers grown in this medium. Bulk density of lignite growing mats also affected the macro- and micro-nutrient content of cucumber leaves. The physical properties of the substrate and the high EC of the medium had a significant effect on the hardness, color and lutein content of cucumber fruits. The content of biologically active compounds in cucumber fruits depended on the water holding capacity of the medium and the water readily available to plants; these parameters were lower in the lignite medium compared to mineral wool. However, when the lignite substrate was used in hydroponic cucumber cultivation, for a period of 51 days after planting (DAP) there was an increase of more than 23% in the bulk density of the substrate and an increase of nearly 55% in the water readily available compared to the new lignite mats.

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

In the last few decades, soilless culture systems (SCSs) have been gaining worldwide popularity, making them one of the fastest-growing sectors in agriculture [...]

Effects of different fermentation assisted enzyme treatments on the composition, microstructure and physicochemical properties of wheat straw used as a substitute for peat in nursery substrates

To solve the central problems caused by traditional composting treatments, such as long-time consumption and poor regulation effects, this study used three fermentation methods and four enzymes to develop rapid and directional regulation methods to convert wheat straw into a suitable substrate. The results showed that the mixed anaerobic method led to better pH (4.39-5.75) and EC values (1.27-1.89 mS/cm) in the straw substrates, while the aerobic method retained more nutrients and increased lignin and cellulose contents by 5.07-8.04% and 1.52-3.32%. The cellulase mixed with hemicellulase or laccase treatments all increased the crystallinity by 0.45-7.23%. The TG/DTG results showed that all treatments decreased the initial straw glass transition temperature, particularly when using the mixed anaerobic method, with decreases of 10.63-25.48 °C. Overall, mixed anaerobic fermentation and multiple enzymes, including cellulase, have been suggested as alternative biological modification methods for straw substrates.

Comparison of organic substrates in urban rooftop agriculture, towards improving crop production resilience to temporary drought in Mediterranean cities

BACKGROUND

Urban agriculture contributes to meeting the growing food production demand in cities. In the context of low water availability, it is important to consider alternatives that are able to maintain production. Through a circular economy vision, this study aimed to assess the use of substrates made from local materials as an alternative for urban agriculture in periods of low water availability, due to water supply cuts. The substrates used were coir commercial organic substrate, vegetable compost from urban organic waste and perlite commercial standard substrate; a mixture of the urban compost and perlite (1:1) was used for three consecutive crop cycles of lettuce (Lactuca sativa L. var. crispa). The crop cycles were performed in the spring and summer periods of 2018 to observe the performance during warmer periods of the year in an integrated rooftop greenhouse near Barcelona. Each substrate was assessed under conventional irrigation (0-5 kPa) and temporary water restricted conditions (irrigation stopped until the water tension reached -20 kPa perlite).

RESULTS

In terms of yield, our results show that the compost and mixture were similar to those obtained from perlite (11.5% and 3.7% more production under restricted water conditions). Organic substrates increased the crop's resilience to water restriction, in contrast to the perlite. In particular, water loss took longer in coir (one- and two-crop cycle); however, when dryness began, it occurred quickly.

CONCLUSION

The vegetable compost and the substrate mixture presented tolerance to temporary water restriction when water restriction reached -20 kPa. © 2021 Society of Chemical Industry.

Formalin fumigation and steaming of various composts differentially influence the nutrient release, growth and yield of muskmelon (Cucumis melo L.)

Nutrient disorder and presence of disease-causing agents in soilless media negatively influence the growth of muskmelon. To combat these issues, use of environmentally-friendly sanitation techniques is crucial for increased crop productivity. The study was conducted under greenhouse and field conditions to investigate the effect of two different sanitation techniques: steaming and formalin fumigation on various media's characteristics and their impact on muskmelon yield. Media: jantar, guar, wheat straw and rice hull and peat moss of 10% air-filled porosity and sanitized with formalin and steaming. Steaming of guar, jantar, and wheat straw increased the phosphorus (P) and potassium (K) concentrations by 13.80-14.86% and 6.22-8.45% over formalin fumigation. Likewise, P and K concentrations in muskmelon were higher under steaming. Steaming significantly inhibited the survival of Fusarium wilt sp. melonis, root knot nematode sp. meloidogyne and nitrifying bacteria in media than formalin fumigation. In conclusion, steaming decreased the prevalence of nitrifying bacteria and pathogens which thus improved the NO₃^--N:NH₄⁺-N ratios, P and K nutritional balance both in the media and muskmelon transplants. Hence, steaming as an environment-friendly approach is recommended for soilless media. Further, optimization of steaming for various composts with different crops needs to be investigated with steaming teachnique.

Agro-industrial-residues as potting media: physicochemical and biological characters and their influence on plant growth

Nursery cultivation is recognized globally as an intensive production system to support quality seedlings as well as to manage resources efficiently. Apart from other factors, potting media (PM) play a crucial role in determining the success of nursery cultivation. Worldwide, peat is the most commonly used substrate in PM because of its favorable physicochemical properties. However, due to ascending environmental and ecological concerns regarding the use of peat, a variety of new substrates have been used/tested by researchers/practitioners/growers as PM. Bark, coir pith, wood fiber, compost derived from various agro-residues, and vermicompost either alone or in combination are some of the commonly explored substrates and found to have the potential to replace peat to a greater extent. In lieu of availability, abundance, low cost, and no/low processing requirement, the use of agro-industrial residue (AIR) in the PM is the current trend. However, challenges associated with their adoption cannot be ignored. The present review is focused on providing collective information, scientific knowledge and detailed analysis of various AIR used in PM. The critical evidence-based review would help in developing a consistent approach for the identification, selection and characterization of a new renewable substrate. In addition, it would help in developing a rationale understanding of the practical and economic realities involved in the adoption of the same in PM.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13399-021-01998-6.

Occupational exposure to fungi on recyclable paper pots and growing media and associated health effects - A review of the literature

Different types of pots and growing and casing media, including biodegradable materials, are used for plant and mushroom production. The fungus Peziza ostracoderma has gained attention for its visible growth on growing media for plants and casing media for mushrooms. Through a review of the literature we aim to evaluate whether exposure to fungi from recyclable pots and different growing and casing media occurs and causes occupational health effects. Based on the published papers, specific fungal species were not related to a specific medium. Thus P. ostracoderma has been found on paper pots, peat, sterilized soil, vermiculite, and rockwool with plants, and on peat, pumice, and paper casing for mushrooms. It has been found in high concentrations in the air in mushroom farms. Also Acremonium spp., Aspergillus niger, A. fumigatus, Athelia turficola, Aureobasidium pullulans, Chaetomium globosum, Chrysonilia sitophila, Cladosporium spp., Cryptostroma corticale, Lecanicillium aphanocladii, Sporothrix schenckii, Stachybotrys chartarum, and Trichoderma spp. have been found on different types of growing or casing media. Most of the fungi have also been found in the air in greenhouses, but the knowledge about airborne fungal species in mushroom farms is very limited. Eight publications describe cases of health effects associated directly with exposure to fungi from pots or growing or casing media. These include cases of hypersensitivity pneumonitis caused by exposure to: A. fumigatus, A. niger, Au. pullulans, Cr. corticale, P. ostracoderma, and a mixture of fungi growing on different media. Different approaches have been used to avoid growth of saprophytes including: chemical fungicides, the formulation of biodegradable pots and growing media and types of peat. To increase the sustainability of growing media different types of media are tested for their use and with the present study we highlight the importance of also considering the occupational health of the growers who may be exposed to fungi from the media and pots.

The High Cost of the Low-Cost Polybag System: A Review of Nursery Seedling Production Systems

An important strategy for meeting global landscape restoration goals is nursery production of high-quality seedlings. Growing seedlings with attributes that promote post-planting survival and growth can be dramatically influenced by the nursery container system. In many countries, nurseries produce seedlings in polybags filled with excavated soil. These seedlings often develop deformed roots with limited fibrosity which can lead to poor survival and growth after outplanting. Polybags are initially inexpensive but using these single-use plastic containers accrues expenses that are often untracked. Comparisons among nursery production systems must account for factors such as container longevity, labor efficiency, and seedling field performance. A more holistic approach to account for environmental, economic, social, logistic, and cultural elements in the cost–benefit equation that influences nursery production systems is needed. Converting to a modern container system requires concomitant adjustments in nursery scheduling and culturing matched to the new stock type. Doing so provides an opportunity to align nursery production techniques and resulting seedling attributes with anticipated field conditions. This article describes and discusses the advantages and disadvantages of nursery production systems and provides recommendations and case studies to aid nurseries in improving seedling quality toward meeting restoration goals in a cost-effective and timely manner.

Basil as Secondary Crop in Cascade Hydroponics: Exploring Salinity Tolerance Limits in Terms of Growth, Amino Acid Profile, and Nutrient Composition

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.

First Steps toward a Test Procedure to Identify Peat Substitutes for Growing Media by Means of Chemical, Physical, and Biological Material Characteristics

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.

Coir, an Alternative to Peat—Effects on Plant Growth, Phytochemical Accumulation, and Antioxidant Power of Spinach

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.

Theoretical and Experimental Analyses of Nutrient Control in Electrical Conductivity-Based Nutrient Recycling Soilless Culture System

An electrical conductivity (EC)-based closed-loop soilless culture system is practical for in-field deployment. Literature on the closed-loop soilless culture nutrient management premise the limitations in managing recycled nutrients under dynamic changes in individual nutrient uptake concentrations. However, recent systems analysis studies predicting solutions for nutrient fluctuation stabilization in EC-based closed-loop soilless culture systems suggest that the system may have a deterministic side in nutrient variation. This study aims to derive a nutrient control principle in an EC-based nutrient recycling soilless culture system by theoretical and experimental analyses. An integrated model of solutes such as K⁺, Ca²⁺, and Mg²⁺ and water transport in growing media, automated nutrient solution preparation, and nutrient uptake was designed. In the simulation, the intrinsic characteristics of nutrient changes among open-, semi- closed-, and closed-loop soilless cultures were compared, and stochastic simulations for nutrient control were performed in the closed-loop system. Four automated irrigation modules for comparing nutrient changes among the soilless culture systems were constructed in the greenhouse. Sweet pepper plants were used in the experiment. In the experimental analysis, nutrient concentration conversion to the proportion between nutrients revealed distinctive trends of nutrient changes according to the treatment level of drainage recycling. Theoretical and experimental analyses exhibited that nutrient variations in open-, semi- closed-, and closed-loop soilless culture systems can be integrated as a function of nutrient supply to the system's boundary areas. Furthermore, stochastic simulation analysis indicated that the nutrient ratio in the soilless culture system reveals the nutrient uptake parameter-based deterministic patterns. Thus, the nutrient ratio in the closed-loop soilless culture could be controlled by the long-term feedback of this ratio. We expect that these findings provide theoretical frameworks for systemizing nutrient management techniques in EC-based closed-loop soilless culture systems.

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

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.

Non-Thermal Plasma Treatment Influences Shoot Biomass, Flower Production and Nutrition of Gerbera Plants Depending on Substrate Composition and Fertigation Level

Non-thermal plasma (NTP) appears a promising strategy for supporting crop protection, increasing yield and quality, and promoting environmental safety through a decrease in chemical use. However, very few NTP applications on containerized crops are reported under operational growing conditions and in combination with eco-friendly growing media and fertigation management. In this work, NTP technology is applied to the nutrient solution used for the production of gerbera plants grown in peat or green compost, as an alternative substrate to peat, and with standard or low fertilization. NTP treatment promotes fresh leaf and flower biomass production in plants grown in peat and nutrient adsorption in those grown in both substrates, except for Fe, while decreasing dry plant matter. However, it causes a decrease in the leaf and flower biomasses of plants grown in compost, showing a substrate-dependent effect under a low fertilization regime. In general, the limitation in compost was probably caused by the high-substrate alkalinization that commonly interferes with gerbera growth. Under low fertilization, a reduction in the photosynthetic capacity further penalizes plant growth in compost. A lower level of fertilization also decreases gerbera quality, highlighting that Ca, Mg, Mn, and Fe could be reduced with respect to standard fertilization.

Phytotoxicity of hydrochars obtained by hydrothermal carbonization of manure-based digestate

The management of digestate, the main by-product of the anaerobic digestion (AD) process, is one of the most serious environmental issues. Although digestate is used on arable land as a fertilizer, it can have a negative impact on the environment due to nitrate leaching into the groundwater and ammonia volatilization into the atmosphere, with high economic and environmental disposal costs. Therefore, hydrothermal carbonization (HTC), a thermochemical biomass conversion process, could represent a sustainable and efficient alternative for digestate management. Hydrochar, the solid product of the HTC process, has been recently proposed as a plant growing medium in soilless culture systems (SCS). Here, using cow manure digestate as feedstock, we investigated the influence of the HTC process reaction temperature (180, 220 and 250 °C) and residence time (1 and 3 h) on the physical-chemical properties (pH, electrical conductivity, and mineral element concentrations) of the resulting hydrochars. Furthermore, in order to fully valorize hydrochar as a growing medium, their possible phytotoxic effects and those of their water extracts (prepared at two different concentrations and at different pHs) were tested in germination tests with cress seeds (Lepidium sativum L.). Concentrations of nutrients, heavy metals, organic acids, sugars and furan compounds were determined in the water extracts. Characterization analysis of these hydrochars revealed that they can be distinguished from each other by their physical-chemical properties, which were significantly affected by the two process parameters. Specifically, the HTC temperature had a greater effect on the composition of hydrochars than the residence time. Germination tests found hydrochar water extracts to show significantly lower phytotoxicity than the hydrochars themselves. Notably, the phytotoxic effect of the extracts decreased with increasing extraction ratio and decreasing pH. The chromatographic characterization of extracts identified the presence of potential phytotoxins, such as furan compounds (i.e., hydroxymethylfurfural and furfural). However, before using hydrochars as potential and innovative growing media for plants, their phytotoxicity should be limited, for example through their dilution with other substrates. Overall, AD-HTC coupling could represent a valuable eco-sustainable expedient in the field of biomasses, green economy and waste conversion and, therefore, further investigations in this direction are necessary.

A case study on integrating anaerobic digestion into agricultural activities in British Columbia: Environmental, economic and policy analysis

This paper provides an example of the kind of analysis needed to support better targeted policies to reduce the environmental impacts of agricultural activities, using the specific case of Anaerobic Digestion (AD) to treat animal manure and other agricultural and food wastes in British Columbia (BC). Economic and life cycle environmental performance metrics are estimated to compare integrated and stand-alone systems using the resulting biogas and digestate. Using biogas for heating outperforms purifying it for distribution as renewable natural gas (RNG). However, current policy and energy prices in BC perversely support RNG, making biogas-fired heating systems economically unattractive. The performance of biogas-fired heating system can be improved and their dependence on subsidies reduced by integration with local agricultural activities, exploiting CO₂ and digestate as by-products. Biogenic CO₂, from combustion of the biogas and from mushroom cultivation, can displace natural gas use in producing CO₂-enriched atmospheres to enhance growth rates in greenhouse production. Using digestate as growing media in greenhouses and mushroom cultivation can generate significant revenues but the environmental benefits are nugatory. Co-digestion of food waste can further improve performance by increasing biogas yield. With all extra benefits combined, integrated AD systems can increase both GHG mitigation and revenues by at least 80%. The analysis illustrates the general point that, to avoid perverse outcomes, policy measures must support options based on their actual GHG mitigation benefits, rather than targetting any specific technology.

Evaluating the Aqueous Phase From Hydrothermal Carbonization of Cow Manure Digestate as Possible Fertilizer Solution for Plant Growth

Improving the agronomic use of recycled nutrients derived from organic waste is one of the priorities within the measures adopted by the European community to reduce environmental issues but remains an unexplored area of research. This study focused on investigating the possibility of using innovative fertilizer solutions in hydroponic systems for the growth of agricultural plants. To this purpose, a liquid fraction [aqueous hydrothermal carbonization (HTC) liquid (AHL)] derived from HTC of cow manure digestate was chemically characterized (pH, electrical conductivity, mineral elements, and organic compounds such as phytotoxins), diluted with distilled water (1:30, 1:60, and 1:90, v/v) to reduce its potential phytotoxicity, and used to grow hydroponic maize (Zea mays L.) plants instead of the classical full-strength nutrient solution. The results indicated that the dilution ratio 1:30 of the AHL solution maintained a high level of toxicity for the plants (phytotoxic substances, especially Na and alkalinity), inducing the arrest of their growth. Differently, the two other dilution ratios (i.e., 1:60 and 1:90) seemed to considerably limit the levels of toxicity, since they allowed the plants to develop. However, these dilution ratios were poor in nutrient elements, inducing alteration in photosynthesis and an onset of deficiency symptoms such as pronounced leaf chlorosis. In view of an eco-friendly approach, future studies are, therefore, needed to identify the correct species-specific dilution ratio to supply both low levels of phytotoxins and adequate content of essential nutrients for appropriate plant growth and development. Furthermore, in order to lower specific Na phytotoxicity, treatments are of utmost importance before using AHL as a fertilizer solution.

Acidification of composts versus woody management residues: Optimizing biological and chemical characteristics for a better fit in growing media

Previous research has demonstrated that composts (COM) and woody residues from nature management (MR) are potential peat replacers for growing media, but their compositions are highly variable. Our goal is to make growing media more sustainable by optimizing the selection of local and sustainable alternatives for peat. Different batches of COM and MR were incubated to assess the microbial activity based on (1) the N drawdown risk, (2) the C mineralization and (3) the inoculation efficiency of a commercially available biocontrol fungus. The various batches were characterized based on biochemical, chemical (pH, available and total nutrients) and microbiological biomass analysis. COM and MR were scored based on chemical or stability characteristics to assess their suitability to replace peat, lime and fertilizers in growing media. This score allowed for a clear differentiation between the materials; MR received higher scores on average than COM. Five composts were further tested for the effect of storage after blending with an acidic MR, acidification with elemental S, or removal of the finer fraction. One batch of chopped soft rush was acidified with elemental S. Blending and acidification were the most effective treatments as they resulted in a clear increase of the suitability score.

A Cloud-Based IoT Platform for Precision Control of Soilless Greenhouse Cultivation

Food security has become an increasingly important challenge for all countries globally, particularly as the world population continues to grow and arable lands are diminishing due to urbanization. Water scarcity and lack of labor add extra negative influence on traditional agriculture and food production. The problem is getting worse in countries with arid lands and harsh climate, which exacerbates the food gap in these countries. Therefore, smart and practical solutions to promote cultivation and combat food production challenges are highly needed. As a controllable environment, greenhouses are the perfect environment to improve crops’ production and quality in harsh climate regions. Monitoring and controlling greenhouse microclimate is a real problem where growers have to deal with various parameters to ensure the optimal growth of crops. This paper shows our research in which we established a multi-tier cloud-based Internet of Things (IoT) platform to enhance the greenhouse microclimate. As a case study, we applied the IoT platform on cucumber cultivation in a soilless medium inside a commercial-sized greenhouse. The established platform connected all sensors, controllers, and actuators placed in the greenhouse to provide long-distance communication to monitor, control, and manage the greenhouse. The implemented platform increased the cucumber yield and enhanced its quality. Moreover, the platform improved water use efficiency and decreased consumption of electrical energy. Based on the positive impact on water use efficiency and enhancement on cucumber fruit yield and quality, the established platform seems quite suitable for the soilless greenhouse cultivation in arid regions.