Demand for growing media is projected to grow rapidly due to the increased production of ornamental and food crops in soilless growing systems. In 2018, Wageningen University and Research conducted a study on “Growing media for food and quality of life in the period 2020-2050” (Blok et al., 2021), where the global need for growing media in 2050 and the availability of its constituents were modelled. Since then, many ground-breaking events have occurred including the COVID crisis, the Russian invasion of Ukraine, the drought in Southern Europe, possible peat bans, changes in licensing, China development, etc. In this new study, the demand for growing media in 2050 will be updated, considering recent developments in the changes in market situation, consumer behavior, used technologies, and climatic conditions. The study aims to address two research questions (1) What is the expected geographical consumption for growing media in 2050 and (2) What raw materials in what quantities will be available in 2050?

The significance of peat as a soilless substrate in agriculture cannot be overstated, particularly due to its exceptional water retention capacity. However, escalating environmental concerns surrounding peat usage have prompted stricter regulations regarding its future application in the United States. Moreover, a limited supply of peat, largely attributed to high reliance on imports from other countries, has created an urgent demand for viable alternatives. This situation has spurred the development of sustainable soilless substrates—environmentally, socially, and economically viable options for growers. The success of these initiatives hinges entirely on their acceptance by growers. Therefore, the primary aim of this research was to gather empirical evidence on the factors influencing growers’ adoption of soilless substrates utilizing both social cognitive theory and technology (innovation) characteristics concepts as research frameworks. A qualitative approach was utilized to thoroughly investigate the factors influencing growers’ decisions regarding the adoption of innovative soilless substrates. Qualitative approaches are particularly effective for exploring complex behaviors, motivations, and social contexts. Focus groups were used as the primary method of data collection because they create an interactive setting where participants can discuss their experiences, perceptions, and attitudes in a social setting. This environment encourages participants to build on one another's responses, allowing for a comprehensive exploration of the factors influencing adoption decisions. A systematic, inductive thematic analysis was conducted to identify the main enablers and barriers to adoption emerging from the data. Based on innovation characteristics, growers were more inclined to adopt innovative substrates if they perceived them to have a relative advantage over existing materials and perceived them to be consistent with existing peat substrates. Additionally, through the social cognitive model, we identified expectations, barriers, and descriptive norms that significantly influenced adoption behaviors. These insights will assist scientists, substrate developers, and policymakers in utilizing the factors that affect growers' decisions regarding the adoption of new soilless substrates when creating new substrates, systems and policy associated with peat reduction.

Introduction
The replacement of peat with more sustainable alternatives is important for climate protection, since peatlands are the most valuable natural carbon sink. On that account, the German government aims to eliminate the use of peat in hobby-gardening on a voluntary basis by 2026.
Approach and methods
To successfully work towards this target, it is important to understand consumer behavior and decision-making at the point of sale. To that end, we conducted a mixed-method study to investigate the purchasing behavior of 309 participants in a simulated purchasing environment in Germany. We captured consumer behavior at the simulated point of sale, using eye-tracking followed by a qualitative exit interview and a quantitative survey using a questionnaire. Theoretically, our study is based on an approach that combines visual attention theory and cue utilization theory.
Results and outlook
Our findings indicate that consumers pass through different behavioral stages when evaluating potting soils at the point of sale. In a phase of orientation, they gain an initial quick overview of the products and the surrounding environment, whereby the eyes follow the habitual reading direction from left to right. Subsequently, the eye-tracking analysis revealed a phase of discovering the individual products and their information in detail. Although our findings indicate a correlation between consumers' stated importance of individual attributes and their perception of those attributes on the selected product package, we also observe a discrepancy between consumers' stated importance and perception of certain product attributes on the one hand and their actual visual inspection behavior with respect to packaging information on the other hand. While participants may consider certain product attributes, such as application instructions, to be important, this may not always translate into action, like turning the packaging over or scanning QR codes. Variances in viewing frequency and intensity are also evident based on different cue types, such as price cues or verbal cues versus graphical cues. However, we also see clear differences in the gaze behavior of our participants within a cue type, as the information on absolute prices received more visual attention than the information on prices per liter. This is noteworthy in light of the prevailing assumption that consumers make decisions in a logical and rational manner.
Our study provides valuable insights for marketers and policy makers on consumers' decision-making behavior regarding substrates at the point of sale. We show that not only the information content, such as peat-related details, but also the presentation on the packaging plays a decisive role in attracting consumers' attention and influencing their purchase decisions.

The sector of ornamental plant production, especially of container-grown plants, needs to increase the sustainability of its cultivation systems due to market and legislative exigencies. Nursery growers are nowadays called to change some well-established practices such as the use of peat-based growing media. Peat extraction and availability are in fact reducing. The new markets in China and European countries are more and more oriented towards peat-less potted plant productions. In this scenario, the materials available as effective alternatives, to peat-based professional growing media, are cocopeat, green compost and stabilized wood fiber. All these products have already been used and studied for many years, but, with some exceptions, they still pose challenges in the correct management due to their physicochemical characteristics compared to peat. In this context, the EDEN Project “Efficientamento, ammodernamento e innovazione nel vivaismo nazionale” (funded by the Italian Ministry of Agriculture, Food Sovereignty and Forests) aims to find and implement valuable and ready-to-use techniques and technologies to support this agricultural sector in Italy. The activities includes: i) increasing the knowledge on new available materials for professional growing media; ii) facing some criticisms like water and nutrient management, especially for those materials that are characterized by low water holding capacity and high nitrogen immobilization; iii) boosting the application of organic fertilizers; and v) evaluating opportunities derived by the application of bioactive compounds and microorganisms to improve growing media performances with particular attention paid on rooting promotion, nutrient uptake and soil-borne disease suppression. The experimental activities are implemented in a site pilot for leaving labs to share information and knowledge with the operational word.      

Germany’s national peat reduction strategy (2023) sets the goals to reduce and replace peat in professional and private uses. Sustainable and renewable alternatives are urgently needed to replace peat in growing media especially for professional horticulture.

The joint project «ToPGa – Development and evaluation of peat-reduced horticultural production systems» (2021-2024) studies unknown relationships in peat-reduced horticultural production systems to elucidate and evaluate the potential use of peat alternatives.

Regionally available candidates for peat alternatives were investigated and examined for their suitability as growing media components by characterizing their basic biological, chemical and physical properties and additional other parameters. Research areas within ToPGa focused on microbiological aspects, useful and harmful organisms, development and testing of new regionally available resources, nitrogen immobilisation and mobilisation in peat-reduced growing media, development and adaption of the cultivation processes, as well as economic aspects and carbon footprints of peat-reduced and peat-free horticultural production systems. Thanks to the common approach within the joint project, correlations were established, which are essential for the development and production of peat-reduced and peat-free horticultural growing media.

With its findings, the ToPGa joint project is helping to reduce the drainage of peatlands and their harvest for horticultural growing media, as well as to develop alternative horticultural growing media for professional and private uses.

ToPGa is funded by the German Federal Ministry of Food and Agriculture (BMEL) via the Agency for Renewable Resources (FNR).

This study evaluates the effectiveness of various peat-free and peat-reduced growing media on the growth and yield of tomatoes and carrots, with the aim to develop sustainable alternatives to traditional peat-based substrates in horticulture. Thirty different growing media mixtures were tested, incorporating materials such as wood fiber, compost, biochar, bio-ash, and struvite, with the goal of identifying viable alternatives to peat. The experiments were conducted in greenhouse conditions, and the performance of these mixtures was assessed based on yield and overall vitality of tomato and carrot plants.

The results revealed that fully peat-free mixtures generally underperformed compared to peat-based references. However, some peat-reduced mixtures with 30% peat in combination with wood fiber, compost, struvite or bio-ash demonstrated promising results. Bio-ash and struvite were evaluated as phosphorus sources, with findings suggesting that both materials can enhance substrate fertility when combined with appropriate nitrogen fertilizers. The effect of biochar was not very pronounced in general. Moreover, the addition of biochar was associated with a disappearance of plant-available nitrogen from the growing media, which likely contributed to its limited effectiveness in improving crop performance.

The study underscores the continual challenge of completely phasing out peat in growing media for horticulture but highlights the potential of reducing it greatly and integrating more sustainable materials such as wood fiber and recycled materials such as compost, bio-ash and struvite. The results suggest that with further refinement, specific combinations of these materials could be developed into optimized substrate mixtures for sustainable horticultural practices without compromising productivity.

This study was conducted with the aim of developing an economical potting soil for container cultivation of garden tree seedlings by mixing horticultural soil, crushed granite (masato), and oak bark in various ratios to evaluate the feasibility of using oak bark as a soil substrate material. The garden tree used in this study was ‘Chamaecyparis obtusa’. The potting soil was prepared with 100% horticultural soil as the control group, and six treatment groups were established by mixing horticultural soil, crushed granite, and oak bark in specific ratios. In terms of physical properties, the higher the proportion of oak bark, the higher the particle density and porosity, while available water and buffered water tended to decrease slightly. Notably, as the proportion of oak bark increased, there was a significant increase in the air-filled porosity and a decrease in volumetric water content, even under low water tension conditions. From a chemical perspective, the higher the proportion of oak bark, the more stable the pH within the optimal range for plant growth (5.5-5.7), while the electrical conductivity (EC) showed a negative correlation with the proportion of oak bark. As the proportion of oak bark increased, the organic matter content tended to be higher, whereas the available phosphate content showed the opposite trend. Additionally, with increasing proportions of oak bark, the content of exchangeable cations, except for calcium ions, was lower, and the cation exchange capacity (CEC) followed the same trend. Regarding the growth of ‘Chamaecyparis obtusa’ based on the mixing ratio of oak bark, no significant difference was observed in height and basal diameter growth compared to the use of horticultural soil when the oak bark mixing ratio was 40% or less. However, when the ratio exceeded 40%, the higher the proportion of oak bark, the more the height and basal diameter growth tended to decrease. Particularly, in treatments where the proportion of oak bark was 60% or more, there was a noticeable decline in growth compared to the other treatments. Considering the physical and chemical properties of the potting soil and the growth characteristics of ‘Chamaecyparis obtusa’ comprehensively, it is believed that a potting soil with an oak bark mixing ratio of 40% or less would be advantageous not only for the growth of ‘Chamaecyparis obtusa’ but also in terms of economics and environmental improvement.

*This study was supported by Rural Development Administration(RDA) research project(PJ016184).

Peat is well suited as a growing media (GM) due to its excellent physicochemical profile, abundant supply, and low-cost. However, environmental concerns surrounding peat extraction are driving a transition to peat-free alternatives, with uncertain consequences for crop quality, particularly post-transplant. We investigated whether peat-free GM impacts the yield and accumulation of health-sensory compounds in kale (Brassica oleracea var. acephala) genotypes; specifically focusing on glucosinolates and volatile hydrolysis products. 10 commercially available cultivars and 70 gene bank accessions were raised in four peat-free GMs. GM selection had a large effect on biomass accumulation. Shoot and root dry weights (DW) of the kale were 53% and 26% higher when grown in Sylvamix® (respectively), and 50% and 33% lower in Levington® (respectively), compared with peat. Three independent field trials revealed no evidence that differences in DW (p < 0.05) persist at ~100 days after transplant. In contrast, glucosinolate accumulation in mature crops showed significant differences (p < 0.05) between GM treatments at harvest maturity. Total GSL contents were 90% lower in Levington® compared with a sphagnum moss-based GM in field grown kale cv. Black Magic (p < 0.05 Bonferroni adjusted). In the same trial, kale cv. Reflex F1 raised in Levington® contained increased contents of glucoraphanin (44%), neoglucobrassicin (43%), progoitrin (124%) and sinigrin (41.6%). Moreover, principal component analysis (PCA) of volatile compounds detected by GCxGC-TOF-MS showed clustering according to GM treatment. These results indicate that crop productivity can be maintained with the adoption of peat-free alternative GM, however, the sensory and nutritional properties of plants are affected, and the phytochemical consequences of a peat-free transition should be considered.

Plant species used for ecological restoration of urban and degraded areas are usually produced in soilless systems. In the last decades, the worsening of drought events undermines plant capability to overcome the post-transplanting stress, particularly in areas with poor soil and unavailable irrigation. Therefore, ornamental and forestry plant nursery growers must produce high quality products with a great adaptability to stress conditions. This needed must be combined with the demand for peat-less potted plants representing both a challenge and an opportunity for this sector. Peat reduction means increasing the use of organic materials like stabilized wood fibers, coco fibers, and green compost. These materials have physicochemical characteristics that require adaptations in irrigation and fertilization but, on the other hand, the same characteristics can be a resource for improving abiotic stress adaptability. With this aim, plants of Viburnum lantana L. were grown in 4-L pots in standard nursery conditions, comparing three growing media: (i) peat:pumice 70:30 v v-1, used as control (PP); (ii) coconut coir dust:pumice 70:30 v v-1 (CP); (iii) coconut coir dust:green compost 55:45 v v-1 (CGC). After a one-year growing cycle, in late spring, a half of the plants were destroyed for biometric, eco-physiological, and tissue analysis assessment, while 12 plants per treatment were transplanted providing irrigation only once during the trial. Roughly 100 days after transplant, biometric and eco-physiological measures were assessed. Plants grown on CGC appeared the more capable in overcoming transplanting. Indeed, PP and CP treatments showed higher values of leaf necrotic area percentage and a relevant defoliation (only PP), while CGC treatment resulted in higher SPAD Index, as well as had a lower value of stomatal conductance (versus PP only). Therefore, our results highlighted the CGC substrate as a suitable alternative to peat-based substrate, also for post-transplanting in degraded areas.

For years, Swiss organic farming has required that the peat content in growing media for vegetable and herb cultivation be limited to a maximum of 70%. From 2025 this will be further reduced to 60%. The substrate industry, seedling cultivation and vegetable production are prepared for this step. Conventional vegetable growers in Switzerland have also signed a declaration of intent to reduce peat to 40% by 2028. A Federal Office for the Environment (FOEN) research project running from 2022 to 2026 will support this process. Cultivation and application trials on vegetable farms show predominantly positive results for peat-reduced growing media and confirm the feasibility of a reduction to 50% for both organic and conventional farming. In 2024, trials with summer lettuce showed that a reduction to 30 or 40% peat replacement can also work. A slight delay in growth during the growing season was compensated for in the field by harvest. The technical feasibility of pressed soil block pot production was confirmed for substrate with up to 70% peat substitution, as was mechanical planting in the field using semi-automated block tranplanter systems. Depending on the crop, substrate composition and cultivation techniques, the main challenges are water, nutrient management and economic efficiency. Good planting techniques and suitable soil and weather conditions will ensure a gradual reduction in peat use in vegetable production. Mixtures of different substrate components inevitably lead to additional work and costs. It remains to be seen how the substrate market will respond to the increased demand for peat-reduced substrates in the near future.

In Germany, press pots are the most common vegetable seedling system, largely relying on the physico-chemical characteristics of black peat. Alternative systems mostly use reusable multi-cell trays or cells made from biodegradable tissue, which often have smaller cell volumes. While no applicable peat-free press pot substrates are currently available, cell systems offer significant potential for reducing peat use due to both the lower substrate demand of smaller cells and the less stringent requirements regarding physical substrate characteristics. Vegetable crops respond differently to restricted seedling rooting volume, but larger volumes are often associated with better plant growth and higher yields.

To quantify the effect of smaller cell volumes, different seedling production systems were compared, using iceberg lettuce (Lactuca sativa var. capitata) as a model crop. The systems used included press pots with a 3.7 x 3.7 cm base area, the two multi-cell trays systems “Quickpot“ (228 plants tray^-1) and “Speedy“ (216 plants tray^-1), as well as two chain pot systems: “Paper Pot“ (132 plants tray^-1) and “PlantTape“ (810 plants tray^-1). Lettuce was sown twice, resulting in two sets of transplants with an age difference of five days. 

Leaf area and above-ground dry matter of transplants were influenced by plant age and the seedling system itself.  However, yield formation did not depend solely on transplant parameters but was also affected by plant age and seedling system, although differences between systems decreased over time. Press pot transplants reached harvest weight first, while low-volume systems showed extended cultivation times, tending to correspond to the reduction in cell volume. However, low-volume systems allow substrate savings by 50 to 90%, as well as higher amount of plants per area during the nursery phase and transportation.

The use of peat in horticulture causes environmental damage. In particular, it accelerates climate change and leads to a decline in biodiversity. In Switzerland, peatlands have been protected since 1987 and no more peat may be extracted. However, it is estimated that more than 500,000 m³ of peat are imported annually. Measures to reduce the import and use of peat in Switzerland were called for. On 14 December 2012, the Swiss government approved the peat phase-out plan. The peat phase-out plan consists of two phases: in phase 1, the aim is to phase out the use of peat in Switzerland through voluntary measures. If the goal of the first phase cannot be achieved, the introduction of trade policy measures is to be examined in phase 2. In this context, voluntary measures have been taken with the trade in bagged substrates and the ornamental plants, vegetables and berries sectors.

In cooperation with research, it has been observed that bark (compost, humus), wood fibres and coconut fibres, as well as other alternatives such as sheep's wool (maximum 8%), plant fibres and husks are interesting peat alternatives. In trials with strawberries and raspberries crops on substrate different peat proportions (100, 75, 50, 25 and 0% peat) were tested in combination with a commercial substrate, that gave very good results as a peat alternative. There were no negative effects on the yield and quality of the berries up to a 75% reduction in peat. The processes without peat and with only 25% peat showed a lower yield.

The example with berries showed that it is possible to significantly reduce the amount of peat in substrates for horticultural crops without negative consequences on yield and quality.

More and more strawberries and raspberries are being grown in substrates. Substrate production has many advantages, such as preventing soil-borne diseases and reducing labour, i.e. increasing harvesting speed. Currently, most substrates are made from peat and/or coconut fibre. Peat is considered a non-renewable resource and the exploitation of peatlands contributes to the increase of carbon dioxide concentration in the earth's atmosphere and to the loss of biodiversity. Coconut coir is mainly produced in India and Sri Lanka and therefore requires long distance transport.

The aim of this project was to test substrates for strawberry and raspberry production using renewable, recycled (organic waste from the agri-food and from wood processing) and local materials. An interesting material in this context is bark. Bark is stripped, milled, and screened into various sizes. The production process affects bark quality, and manufacturers often undergo secondary processing, such as composting or aging to meet performance requirements. In order to determine the productivity potential of aged bark material for berry production in substrates, bark was compared with conventional coconut fibre and substrates containing peat.

Our data show that substrates with only bark as a substrate component can be successfully used for strawberry and raspberry production. Bark substrate is produced from local, renewable and recycled organic materials and is therefore very sustainable.

With the objective of assessing locally available substances as growing media for high tunnel tabletop strawberry (Fragaria ×ananassa Duch.) production in urban agriculture, a pilot study was conducted during December 2023 - June 2024 at the University of Florida Plant Science Research and Education Unit (Citra, FL) to compare soilless substrates containing pine bark and different types of composts, with coco coir as the control. Bareroot ‘Albion’ (day neutral) and containerized Sweet Sensation® ‘Florida127’ (short day) strawberry plants were transplanted into the tabletop troughs (6 plants per linear meter) filled with different substrate treatments (two troughs for each substrate per cultivar) in four high tunnels arranged in randomized complete blocks. While the coco coir had the highest water holding capacity, substrates formulated with pine bark and compost products, including yardwaste-based compost, sugarcane bagasse-based compost, and cow manure-based vermicompost, showed greater porosity and permeability which helped reduce the incidence and severity of root diseases. Strawberry fruit harvests started in February and continued through late June. For ‘Albion’, the substrates containing vermicompost or yardwaste-based compost produced the highest marketable and total fruit yields, significantly greater than the coco coir control. In contrast, no significant differences in fruit yield of ‘Florida127’ were found among substrate treatments. At the end of the production season, the substrates with yardwaste-based compost or sugarcane bagasse-based compost had pH values around 5.9 and EC levels around 1.3, significantly higher than the substrate containing vermicompost and the coco coir control (around 5.3 and 0.8 for pH and EC, respectively). Results from this pilot study demonstrated the feasibility of using locally sourced pine bark and composts to develop potential soilless substrates for growing tabletop strawberries in protected culture to serve local and urban food systems. More research is needed to further examine strawberry cultivar adaptation and optimization of substrate formulation.     

The reliance on peat in horticulture, particularly in Belgian strawberry cultivation, stems from its unique agronomic qualities. With growing environmental concerns and legislative pressures surrounding peat use, the industry must proactively explore and develop alternative growing media to maintain both environmental integrity and crop yield stability. Two complementary greenhouse trials with cultivar Elsanta in a double cropping system have been conducted on two locations in Flanders, Belgium. The primary objective was to screen organic materials, including several local waste streams, for their viability as peat substitutes in growing media. Laboratory analyses of key characteristics, including pH, electrical conductivity (EC), oxygen uptake rate (OUR), organic matter (OM), and bulk density, were conducted to identify and select the 25 streams with the highest replacement potential. The tested materials fall into the following categories: wood fiber, bark products, coconut coir products, dried plant fibers, processed grass fibers, woody biochar, and spent growing media.These materials were tested by mixing them at 25%, 50%, and 75% with a standard peat substrate, allowing for a detailed assessment of their impact on plant growth, root development, yield and fruit quality. Weekly measurements of drainage volume and composition were conducted during the trial, and, combined with data from soil sensors, provided insights into the effects of peat substitution on the conditions in the root environment and its implications for future fertigation strategies. While some components or mixing ratios already raised concerns from the very start of cultivation, there were also treatments where the peat substitution was successful, suggesting that reduced peat dependency in Flanders intensive strawberry cultivation is achievable.

Medicinal cannabis has high nutritional and water demands when grown under high light conditions. Therefore irrigation management as well as choice of growing medium are considered to affect growth and product quality. We investigated three peat-free coir-based growing media in a phytotron at two different irrigation strategies (daily drain (‘HIGH’) or intermittent drain (‘LOW’)).  Water Content (WC_pF 1) of the media were between 50 and 60% (v/v) prior to use. In the cultivation trial 10 cm high cylinders were placed in 4,5 litre pots and subsequently filled with media and planted with Cannabis sativa. Non-planted pots with cylinders were used as control. WC and EC as measured weekly using Frequency Domain sensors showed – after a decrease in the exponential growth period – a steady increase during the 7 week short-day period. After harvest WC_pF1 of media in non-rooted pots was increased up to 54-72%, . In rooted pots WC_pF1 was even more increased up to 59-79%, presumably as a result of root production, besides a higher bulk density. Concomitantly, air filled porosity  (AFP) showed a significant decrease after cultivation. ‘HIGH’ and ‘LOW’ irrigation showed on average 42% and 18% daily drain respectively. Plant length and shoot fresh weight were significantly higher under the ‘HIGH’ irrigation, but were not affected by the growing medium. Higher shoot weight was correlated with both a higher WC_FD and nutritional status (EC_FD) under ‘HIGH’ irrigation. Bud weight and THC% were not significantly affected by substrate or irrigation however. The results showed that irrigation management had a greater impact on plant growth and morphology than the used growing media. Besides, the beneficial use of FD sensors as a tool for decision support to irrigation management is discussed.

The use of polypropylene containers in ornamental greenhouse production generates a significant amount of plastic waste, most of which is non-recyclable. These pots are rarely reused due to the difficulty of disinfection and often end up in landfills. This contributes significantly to pollution, as polypropylene can take up to 500 years to degrade. The horticultural sector has expressed a desire to reduce plastic usage by opting for more sustainable solutions, such as biodegradable containers and blocks. However, replacing plastic pots poses a considerable challenge, as their low cost, flexibility, and durability make them a practical and advantageous choice for businesses.

Producers have been slow to adopt biodegradable containers and blocks. Beyond the higher costs, a major obstacle is the limited knowledge about their agronomic performance in commercial greenhouse production. Gaining a better understanding of the agronomic aspects of these containers and blocks could help identify which biodegradable products are most effective at a commercial scale, enabling companies to become more sustainable and produce plants with less plastic while remaining competitive.

The main objective of this study is to determine the impact of biodegradable containers and blocks on the quality of three plants (Basil, New Guinea Impatiens, Rieger Begonia) grown on trough benches and irrigated by subirrigation in a greenhouse. Other objectives are to evaluate (i) the quality of the plants produced (height, width, visual rating); (ii) the ease of handling the containers and blocks (physical integrity); and (iii) consumer response to this type of product (visual appearance of the containers and blocks, and the plants produced).