Nitrogen supply is considered a major constraint for plant production when using organic fertilizers in high-producing production systems such as greenhouses. Especially for organic systems where the availability to nitrogen is dependent on biological processes and in turn factors such as temperature and soil moisture. Latent nitrogen deficiency is suggested to be a main factor explaining the relatively low productivity often associated with organic production systems in greenhouses. To investigate this and to find ways to mitigate the problem, an experiment with nitrogen supply partly via leaf sprays was performed. Capsicum annuum was grown with organic fertilizers and urea leaf sprays was supplied weekly. Also a treatment with reduced nitrogen supply to the roots but with urea leaf spray was included in the study. Plant fertilized with mineral fertilizers were used as control treatment. The photosynthesis capacity as well as the yield of photosystem II was positively affected by urea leaf sprays. However, biomass production and leaf area was not significantly affected by the urea spray. The nitrogen use efficiency was reduced by the leaf sprays. It was concluded that growth was not restricted by nitrogen deficiency in the treatments included in the study.

Soilless substrates that are utilized in greenhouse crop production have limited plant-available silicon (Si) compared to mineral soils. The inclusion of supplemental silicon in greenhouse crop production has proven beneficial for several floriculture species. The goal of this study was to evaluate the incorporation of Si substrate amendments on plant growth and micronutrient uptake on zinnia (Zinnia elegans ‘Profusion Double Red’). Plants were grown in a 70:30 peat: perlite substrate with one of two calcium silicate substrate amendments of Si0X and Si1X (0.0 or 2.07 kg/m CaSiO₃), and one of four micronutrient fertility treatments of 1X [0.49 boron (B), 0.19 copper (Cu), 4.02 iron (Fe), 0.99 manganese (Mn), 0.01 molybdenum (Mo), and 0.20 zinc (Zn) mg/L], 2X, 4X, or 6X using a modified Hoagland’s solution, creating a 2 × 4 factorial. Additionally, zinnia plants that received Si1X exhibited significantly lower Mn, B, and Zn concentrations in the lower foliage of the plant when compared to Si0X plants. This research suggests that utilizing a Si substrate amendment in a greenhouse production system can limit excessive uptake and accumulation of micronutrients in the foliage and roots without negative impacts on plant growth.

Strawberry cultivation in substrate systems faces persistent challenges from a range of insect and fungal pathogens. Despite advances in plant genetic resistance, chemical control remains essential for disease management. However, concerns regarding the long-term impact of chemical residues on human health are growing among consumers and agricultural professionals. This study investigates the potential of organic nitrogen fertilizers as an alternative to synthetic nitrogen in substrate-based strawberry production systems.

A variety of commercially available granular and water-soluble organic fertilizers from abattoir and plant waste streams were evaluated in both production and nursery environments. Additionally, the effects of varying nitrogen rate alone or in combination with synthetic nitrogen or enhanced soil biology was assessed.

The results confirm the benefits of substituting synthetic nitrogen with organic forms in order to enhance disease resistance, reduce insect attack and optimize nutrient management and subsequent crop growth in substrate culture. We propose that replacing synthetic nitrogen completely with 100% organic nitrogen is an essential first step in reducing the need for synthetic pesticides in commercial substrate strawberry production in the future.

Climate change has exacerbated rising temperatures, severe droughts, increased plant transpiration, and water shortages. Additionally, excessive and improper fertilizer use has degraded agricultural land, leading to reduced crop yield and quality, which fails to meet the growing global population's needs. Innovative technologies like nanotechnology are playing a crucial role in enhancing food production. To address these challenges, nano-fertilizers combined with drip irrigation systems are being utilized. This approach helps solve problems and boosts agricultural productivity. In this study, the effect of different amounts of nano-nitrogen liquid fertilizer (Lily Nano Liquid Fertilizer) of Lily Pharma Company Limited at 5 different levels, consisting of 10.66, 16.00, 32.00, 80.00, and 160 kilograms/rai, was compared with the granular fertilizer formula 21-0-0 (ammonium sulfate) 160 kilograms/rai by using the drip irrigation system. This research found that 28 days after transplanting, all five levels of nano-nitrogen fertilizer significantly increased the fresh and dry weights of plants and roots, growth rate, and leaf count in Red Oak lettuce compared to granular 21-0-0 (ammonium sulfate) fertilizer. Notably, even the lowest rate of nano-nitrogen fertilizer outperformed the granular fertilizer. Nano-nitrogen fertilizer also reduces the amount of nitrogen needed, improves nitrogen retention in the soil, and significantly minimizes nitrogen loss to the environment.

Biochar is a horticulturally interesting by-product of energy generated from biomass burned in a pyrolytic process. It can be added to soil directly as a means of capturing carbon from plant material or used first as all or part of a growing media mix; the starting bio-material is important for the usability of the end product in such a mix. Ions present in the dried bio-material that are not lost to combustion remain present and new materials must be tested for potential crop toxicity. Lab testing and cultivation testing of Marinice tomatoes has been performed in 2022 and 2024 using exclusively biochar derived from pistachio shells as a growing media. Challenges related to physical and chemical characteristics were identified in the lab and then addressed in the cultivation trials. The primary difficulties involved in growing in pistachio biochar come from a high EC and pH, the pH buffering capacity, and the cation-exchange capacity of the material. Some benefits of biochar as a substrate are good water holding capacity with large pore space remaining for air in the roots ( > 30% volumetric water content) and a stable physical structure. Making a suitable growing recipe from for the starting cultivation phase is complicated by the ions contributing to the high material EC – primarily chlorine and potassium. The bagged biochar was flush with rain water prior to cultivation to lower the EC, the fertigation recipe was modified to include lower pH and higher concentrations of calcium and ammonium, and the drain EC, pH, and elemental concentrations were closely monitored in the starting weeks of cultivation. Biochar was successfully used in tomato cultivation when compared with a 100% coir growing media.

Rosemary (Salvia rosemarinus ‘Tuscan Blue’) and Petunia (Petunia hybrida ‘Dreams Pink’ and ‘Dreams Midnight’) were grown with one of six continual liquid fertilizer concentrations (37.5, 75, 112.5, 150, 225, 300, 450, and 600 mg L-1 N) using a 17N -2.18P-14.11K fertilizer. After eight weeks of growth, plant height (measured from the pot rim to the uppermost part of the plant), plant diameter (measured at the widest dimension, turned 90°, and averaged), and shoot dry weight were recorded and tissue samples were collected and analyzed for the concentration of 13 elemental nutrients. Based on the evaluation, optimal fertility levels for maximum growth of 75 to 225 mg L^-1 N for rosemary and up to 450 mg L^-1 N for petunia. 

Two experiments were conducted in a polythene tunnel to evaluate the effects of silicon supplementation in the nutrient solution on powdery mildew incidence, albinism, and yield. Albinism is characterized by  irregular mottled fruit colouring.  The trials included nine everbearing and five June-bearing strawberry cultivars. From planting until the end of harvest, all plants were fertigated with a complete nutrient solution. One group (+ Si) received 1 mmol L^-1  silicon in the form of potassium silicate, while the control group (0 Si) received additional potassium to maintain nutrient balance.

Powdery mildew was completely suppressed by silicon amendment in the nutrient solution in June-bearers ‘Elsanta’, ‘Malling Centenary’ and ‘Sonsation’. Silicon supplementation reduced powdery mildew on leaves and fruit by up to 8% and on inflorescences by up to 12% in everbearing ‘Malling Ace’. In ‘Soprano’ powdery mildew on leaves was reduced with 23 % and on inflorescences by up to 39%. However, high rates of albinism (approximately 20%) were observed in everbearing cultivars ‘Lady Emma’, ‘Karima’, ‘Florice’, and ‘Hademar’. In contrast, no albino fruits were detected in ‘Monterey’, ‘Albion’, or ‘San Andreas’. Among the June-bearing cultivars, ‘Elsanta’ and ‘Limalexia’ showed high susceptibility to silicon-induced albinism (45% and 36%, respectively), whereas ‘Sonsation’, ‘Parlando’, and ‘Malling Centenary’ were unaffected.

These findings highlight significant variability in the susceptibility of strawberry cultivars to silicon fertilization, suggesting that cultivar-specific responses should be carefully considered when implementing silicon in nutrient management programs.

The typical symptomology associated with a phosphorus (P) deficiency is the development of a purple coloration on the lower foliage. This symptom of limited P uptake occurs during greenhouse production when temperatures are low or the substrate is consistently saturated.  Purple pigmentation is typically associated with increased anthocyanin production.  Another symptom that is not normally described in the literature is lower leaf yellowing with olive-green leaf spots. This symptom tends to occur with warmer growing temperatures. The objective of our research was to characterize this symptomology and determine critical leaf tissue values. We conducted extensive trials of inducing P deficiencies with our automated irrigation system in silica sand culture and utilizing technical grade fertilizer salts in which P was withheld and then compared with plants grown with a complete fertilizer treatment.  With 26 species, the P deficient plant developed an overall dull green coloration and had stunted growth. This was followed by lower leaf yellowing and olive-green leaf spots.  The leaves quickly abscised. Over time the symptomology progressed up the plant.  Leaf tissue was sampled and analyzed for P concentration.  In general, levels were ~78% lower (range 50.7 to 93.5%) than those found in plants grown with adequate P.  This research provides insights into the varying symptomology possible with a P deficiency. Plant health advisors must be aware that both lower leaf purpling and lower leaf yellowing with olive-green leaf spots can occur. Tissue testing will aid in confirming their diagnosis of the visual symptomology.

To produce Boston ferns (Nephrolepis exaltata), greenhouse growers must be equipped with cultural information including the ability to recognize and characterize nutrient disorders. Plants were grown in silica-sand culture to induce, describe, and photograph symptoms of nutritional disorders. Plants received a complete modified Hoagland's all-nitrate solution of (macronutrient concentrations in millimoles) 15 nitrate-nitrogen (N), 1.0 phosphorus (P), 6.0 potassium (K), 5.0 calcium (Ca), 2.0 magnesium (Mg), and 2.0 sulfur (S) plus (micronutrient concentrations in micromoles) 72 iron (Fe), 18 manganese (Mn), 3 copper (Cu), 3 zinc (Zn), 45 boron (B), and 0.1 molybdenum (Mo). Nutrient-deficient treatments were induced with a complete nutrient formula minus one of the nutrients. The B-toxicity treatment was induced by increasing the element 10-fold higher than the complete nutrient formula. Reagent-grade chemicals and deionized water of 18 million ohms per centimeter purity were used to formulate treatment solutions. We monitored plants daily to document and photograph sequential series of symptoms as they developed. Typical symptomology of nutrient disorders and corresponding tissue concentrations were determined. Symptoms of N, P, K, and Fe manifested early; therefore, these disorders may be more likely problems encountered by growers. Use of tissue concentrations and other diagnostic criteria about location on the plant and progression of the disorder can aid growers in diagnosing nutrient disorders of Boston ferns.

Vertical farms as food production systems may reduce their environmental impact by integrating a circular economy approach in the management of growing media. However, few studies have quantified plant performances with reused substrates in indoor agriculture, especially in vertical farm facilities, even if reusing growing media may reduce the overall resource use of indoor agriculture. The goal of this study was to compare newly sourced and reused coconut fiber growing media by inspecting the growth and secondary metabolites content of hydroponically-grown microgreens, namely kale (Brassica napus cv. Ciro) and mustard (Brassica juncea cv. Senape Pistol), grown on both substrates under the same lighting and environmental conditions. The plants were grown under two different light intensities, both with a red and blue spectrum with a ratio of 1 (RB1-200 with a light intensity of 200 μmol m⁻² s⁻¹ and RB1-250 at 250 μmol m⁻² s⁻¹). The two lighting treatments were performed on either newly sourced or reused substrates for each microgreen species. Morphological, physiological, and biochemical parameters were measured to evaluate plants' performance. This research investigated the potential of the reused substrate and its related environmental benefits as a part of the circular economy strategy for vertical farming, contributing to understanding waste circularity management and resource use reduction to optimize the environmental impact of indoor agriculture.

Medicinal plants are known for their antioxidant, anti-stress, anxiolytic, antimicrobial, and other therapeutic properties, often with no adverse side effects. Despite these benefits, the cultivation of medicinal plants remains limited. The study from the Good-herb project indicates that 90% of the raw materials are sourced from the wild, while only 10% are cultivated outdoors. Overharvesting from wild sources has placed many species at risk of endangerment. Additionally, climate change increases the challenges of outdoor cultivation due to unpredictable events like floods, droughts, hailstorms, and thunderstorms. Hydroponic systems allow plants to be grown soilless or in inert substrates using water-based nutrient solutions, offering a promising alternative. These systems include Nutrient Film Technique (NFT), Ebb & Flow, Deep Water Culture, and Aeroponics. Hydroponics presents a unique opportunity for the sustainable cultivation of root-based medicinal plants, as it reduces the loss of secondary roots during harvesting and minimizes the time and labor spent on cleaning roots in traditional soil-based farming. Furthermore, numerous studies have demonstrated that hydroponic cultivation can result in higher yields of secondary metabolites compared to conventional outdoor methods. Research conducted by our group also showed an increase in secondary metabolite production in plants grown hydroponically, as opposed to those cultivated outdoors in crops like Rhodiola rosea and Valeriana officinalis. Moreover, hydroponic systems are well-suited to high-tech agricultural applications, such as indoor vertical farming. This study explores the potential of different hydroponic systems for the cultivation of root-based medicinal plants, with an emphasis on their accessibility and practicality for farmers based on own research and literature.

The growing significance of Vertical Indoor Farming (VIF) and the increasing global demand for sustainable protein sources necessitates the optimization of cultivation conditions for protein-rich crops. Peas, with their high protein content (20 to 25 %) and versatile food industry applications, present a promising option. However, VIF mainly uses hydroponic irrigation systems with the aim of substrate-free crop cultivation. Little research on peas yield, growth, and protein content has addressed soilless cultivation, especially in a multilayer system and VIF conditions. This study aimed to identify strategies for hydroponically cultivating peas under controlled conditions, focusing on irrigation systems and light management. A two-stage experimental setup investigated the combined effects of deep-water culture and ebb-and-flow irrigation with three different LED light spectra: T1 (blue 12 %, red 88 %), T2 (blue 18 %, green 26 %, red 55 %, far-red 1 %) and T3 (blue 19 %, green 36 %, red 39 %, far-red 6 %). Subsequently, using deep-water cultivation, two light intensities (150 and 300 µmol m-2 s-1) were analyzed under T3 conditions. Growth parameters, yields, plant biomass, protein content and efficiency were calculated. Initial results showed that deep-water achieved a higher Surface Use Efficiency (SUE) across all light treatments, with a dry matter Harvest Index of 0.54-0.58. Light treatment T3 induced the highest SUE, reaching 2.13 kg m-2 a-1 under deep-water conditions. The results will give valuable insights into the integration of legumes for vertical farming systems and their potential regarding resource-efficient, sustainable protein production.

The research was funded by the German Federal Ministry of Education and Research (BMBF). 

Microorganisms in the soil live in close proximity with plants and are subject to control by the plant roots through the release of molecules known as root exudate. Soilless horticulture can benefit from knowledge on root exudates and microbiomes to improve the use of plant growth promoting bacteria, or the defenses against pathogens. However, research on root exudate is mostly focused on sterile environments or natural soil environments. It is barely focused on peat-based potting soil, or other organic or inert growing media. Growing media can affect root exudation, as has been observed in lettuce. Whether other leafy vegetables react similarly is not yet known. We hypothesize that the growing media will mainly affect the phenolics exudation rate, as it did in lettuce. Moreover, exudation rates are usually highest for younger plants. Therefore, we expect growing media will have more impact on root exudation rates when the plants are youngest. Arugula was grown in a gradient from 100% peat-based potting soil to 100% perlite (0.6-3mm). Root exudate samples were taken at 11/12 days, 18/19 days or 25/26 days after transplanting. Root exudate was quantified spectrophotometrically with the following parameters: total C exudation rate, total carbohydrate exudation rate and total phenolics exudation rate. Youngest arugula plants had a higher exudation rate than older plants. Growing medium significantly (p < 0.05) affected the exudation rate of total C of arugula. Exudation rate of total C was lower at 20% potting soil than at 100% potting soil or 0% potting soil. Therefore, leafy vegetables seem to have different responses to growing media in root exudation patterns.

Microgreens are tender young plants grown from vegetable and herb seeds, harvested when the cotyledon leaves are fully extended. They have become a popular culinary trend, particularly in recent years, offering intense flavors, vibrant colors, and appealing textures despite their small size. In their cultivation, the choice of substrate plays a crucial role, not only affecting the quality and yield but also influencing the sustainability of the production process. This study aimed to reduce the use of peat as a substrate, given its environmental unsustainability.

We conducted an experiment comparing three substrates—jute fiber, cellulose pulp, and peat—using two species from the Apulia region (Italy): Cima di rapa (Brassica rapa L. Broccoletto group) and Cima nera (Brassica oleracea L. Italica group). Three replications were conducted for each species and substrate, with each replication consisting of six trays, each with a surface area of 84 cm². The seeding density was 4 seeds/cm², corresponding to 0.879 g per tray for Cima di rapa and 1.217 g per tray for Cima nera. Morphological traits, yield, dry matter, and color traits were analyzed. The harvest was carried out at approximately 2 cm above the substrate.

Our results revealed that the height and first true leaf length were influenced by the interaction between species and substrate, while the yield was species-dependent. In conclusion, the choice of substrate can impact certain biometric parameters, but an essential factor to consider is the eco-sustainability of the substrate. Jute fiber showed good performance comparable to peat, without the associated environmental concerns.

As nutrient salts for use in hydroponics become more expensive, and as awareness of the environmental costs of their production increases, the search for more sustainable alternatives becomes increasingly relevant. At the same time, the growing poultry industry is facing an escalating problem of manure disposal. In particular, incorrectly stored and disposed manure waste can lead to runoff, polluting rivers and lakes and causing ecological damage.

To address these issues, we investigated the use of liquefied, bacterially digested poultry manure as a nutrient solution in a biological hydroponic (bioponic) system growing sweet basil (Ocimum basilicum).

The system designed in this project relies on four 150 L pH- and temperature-controlled bioreactors inoculated with soil bacteria, where dried and pelleted poultry manure is aerobically digested to produce a complete nutrient solution with high nitrate and low ammonium concentrations suitable for basil growth. Previous research using similar methods to produce poultry manure-based nutrient solutions has suggested that pH control during production improves both nitrate yield and production rate.

We will test four different pH levels during solution production, using custom-made, microcontroller-based dosing systems on each bioreactor. These systems allow for accurate and regular dosing to maintain a stable pH, as well as high-frequency data collection.

Quantification of all essential nutrients (including sodium) will be carried out to understand the effect of pH treatments on nutrient production and to enable comparison with a commercial chemical nutrient solution. Further testing of the nutrient solution’s viability will be conducted by growing basil plants in pH-controlled hydroponic systems. These data will be used to complete environmental and economic cost–benefit analyses compared to commercial chemical nutrient solutions.

Highwire crop production in controlled environment agriculture (CEA) has grown recently and provides benefits compared to field production. Dutch buckets, or Bato buckets, and regular plastic containers (RPC) are common methods of vegetable production in substrate-based hydroponic systems. Growers new to the industry may be uncertain of the differences between the systems when deciding how to produce their crops. The objective of this study was to quantify the growth and development of highwire tomatoes (Solanum lycopersicum ‘Favorita’) in Dutch buckets (11L) and RPCs (11.3L) filled with a substrate consisting of Coir and wood fiber (60%:40%). Following propagation, plants were transplanted into five single containers of each of the systems. To evaluate weekly changes, the number of leaves, foliar chlorophyll content, leaf area and leachate data were collected. Fruit yield began approximately one month after transplanting and the number, quality, and weight of the fruit was recorded per plant weekly. At final harvest, width, length, fresh weight, and dry weight of the stem were measured. There was no significant difference in the average total fresh weight of the fruit per plant. In the RPCs, there was an average of 2.13 kg per plant while the Dutch buckets yielded an average of 2.06 kg fruit. Leaf tissue nutrient data taken at early fruiting stage were not significantly different and showed on-target macronutrient percentages according to sufficiency ranges. Fresh weight of vegetative portion (stems and leaves) of the plants grown in Dutch buckets were significantly higher than those of the RPCs with a 9.20% difference. Despite this, the dry weights were not significantly different. In conclusion, these two substrate-based production systems have a similar yield, with marginal differences in overall growth. Therefore, other factors such as resource avaibility, nutrient recycling, and convenience to manage can be key determinants for selection between Dutch buckets and RPCs for tomato production.

Container plant production is a rapidly expanding sector in Quebec. The substrates used in these systems have low nutrient retention capacity, and root volume is limited, necessitating precise fertilization strategies.

In outdoor container production, controlled-release fertilizers (CRFs) are widely used, with various coating technologies available. In Quebec, the most commonly used CRFs have a release duration of approximately 5–6 months, but alternative formulations with different release durations are also available. However, limited research has been conducted under Quebec’s climatic conditions to evaluate the performance of these fertilizers. With climate change extending and warming the growing season, the optimal CRF release duration may need reassessment. Additionally, the use of coconut fiber disks is becoming increasingly common among container growers, yet few studies have investigated the ideal placement of CRFs in relation to these disks to optimize nutrient availability. 

This study aimed to assess the efficiency of different CRF formulations in container-grown ornamental plant production. The specific objectives were to (i) compare the nutrient release efficiency of various CRF coating technologies, (ii) evaluate the performance of CRFs with nitrogen release durations of 8–9 months versus 5–6 months, and (iii) examine the effect of CRF placement relative to a coconut fiber disk on nutrient release efficiency. 

A two-year experiment was conducted at two nurseries to evaluate the growth and physiological performance of Hydrangea arborescens ‘Annabelle’ and Hydrangea paniculata ‘Phantom’ under different CRF treatments. Measured parameters included vegetative growth (plant height and diameter), quality index, flower number and biomass, senescence index, SPAD index, substrate chemical properties, and foliar nutrient composition.

The increasing frequency and severity of heatwaves worldwide are significantly impacting horticultural production systems. Plants grown in substrates, particularly in commercial nursery settings in the United States, are highly vulnerable to these extreme temperatures. These systems commonly use black plastic containers, which absorb heat more rapidly than field soil, and are often placed above ground on gravel or black plastic fabric. Such substrates are typically less well-buffered against temperature fluctuations compared to natural soils. Additionally, the use of polymer-coated fertilizers, designed to release nutrients based on temperature, further complicates the situation, as these coatings can degrade more quickly under intense heat, rendering the fertilization system fragile and less reliable.

To address these issues, our study investigates the combined effects of container color and heatwaves on controlled-release fertilizer (CRF) performance and plant health. We conducted an experiment across two distinct climatic regions—the Pacific Northwest (Oregon) and the Gulf South (Louisiana)—to assess how varying environmental conditions influence substrate temperature and nutrient release. Our experimental setup involved 3-gallon nursery containers filled with bark-based substrates and treated with commercially available CRF. Containers were differentiated by color (black vs. white) and irrigation regimes (single vs. cyclic applications), with temperature sensors and leachate collection systems used to monitor key parameters.

Preliminary results reveal that black containers, which absorb more heat, experienced significantly higher substrate temperatures compared to white containers. This temperature differential influenced CRF nutrient release rates, with accelerated leaching observed in the hotter Gulf South compared to the cooler Pacific Northwest. These findings highlight the critical need to address temperature sensitivity in CRF systems and suggest that container color can play a role in mitigating heat-related impacts.

This research provides essential evidence on the interaction between heatwaves and CRF efficacy, offering practical insights into container design and substrate management. The results underscore the importance of adapting horticultural practices to better withstand extreme temperatures, and future research will be crucial to further explore these dynamics and develop resilient strategies for sustainable nursery production amidst climate change.