Soilless Production Research Articles

Impacts of Bacillus amyloliquefaciens and Trichoderma spp. on Pac Choi (Brassica rapa var. chinensis) grown in different hydroponic systems.

Soilless production systems (i.e hydroponics, aeroponics, aquaponics) have become commonplace in urban settings and controlled environments. They are efficient nutrient recyclers, space savers, and water conservers. However, they lack high levels of biological richness in the root microbiome when compared to soil production systems, which may affect plant health and nutrient uptake. To address this issue and incorporate more sustainable practices, beneficial microorganisms (i.e. Trichoderma spp., Bacillus sp.) can be added in the form of biofertilizers. However, many factors affect impacts of microorganisms and their interactions with plants. In this experiment, Black Summer Pac Choi (Brassica rapa var. Chinensis) was grown for two trials in a Deep-Water system (DWS) or a Nutrient Film Technique system (NFT) with commercial biofertilizers containing Trichoderma spp., Bacillus amyloliquefaciens, a combination of both, and a control. Plant physiology, nutrient composition, and nutrient uptake efficiency (NUE) were generally negatively affected by Trichoderma spp. both growing systems, indicating that Trichoderma may not be recommended for hydroponic production. However, Bacillus amyloliquefaciens showed promise as an effective biofertilizer in the NFT systems and had a positive influence on NUE in DWS.

Soilless Production of Lettuce (Lactuca sativa) in the Atacama Desert Using Fog Water: Water Quality and Produce Mineral Composition

Soilless vegetable production in the Atacama Desert of Northern Chile is spreading since it is perceived as an alternative that requires much less water than open field soil production. However, strong competition between mining and urban use for human population consumption exists, forcing growers to use alternative water sources. Fog is commonly present in the coastal areas of Northern Chile; however, little information exists with regards to its chemical composition and the effect on nutrient quality of the produce. To address this knowledge gap, a set of experiments was carried out in Chañaral, a small town located in the Atacama Desert of Northern Chile. There, a 200 m2 greenhouse equipped with twenty deep flow pools was used in two consecutive growing cycles. Water for the mixing of the nutrient solution was collected from the fog using fog-catchers and later stored in 2000-L tanks. Fog water quality (electrical conductivity, pH and mineral content) was monitored directly from the storage tanks. Two types of lettuce, green butterhead and red oak leaf, were compared on their yield and accumulation of nutrients and heavy metals. The results indicate that fog water is of good quality for soilless production, with an electrical conductivity value of 0.65 ± 0.18 and low content of heavy metals. Plants’ heavy metal accumulation is below the recommendation of Food and Agriculture Organization and World Health Organization. Fog water presents as a viable water source for soilless production in Northern Chile.

Application of soil amendments to reduce the transfer of trace metal elements from contaminated soils of Lubumbashi (Democratic Republic of the Congo) to vegetables

The extraction of copper and cobalt from mines has led to the contamination of agricultural soils by trace metal elements (TMEs) (e.g. Cu: 204 to 1355 mg/kg). The mining industry is one of the sources of metal discharges into the environment, contributing to water, soil, and air contamination and causing metabolic disorders in the inhabitants of the city of Lubumbashi (R.D. Congo). This study assessed the effectiveness of organocalcareous soil improvers applied to TME-contaminated soils to reduce their transfer to plants. Following a factorial design, increasing doses of organic soil improvers (chicken droppings and sawdust) and agricultural lime were applied to the soils of three market gardens (high, medium, and low Cu contamination). The experiment was monitored for 60 days. Soil physicochemical properties (pH, TOC, and total and available copper, cobalt, lead, cadmium, and zinc (mg/kg)) were determined for the three gardens and in the vegetable biomass. The daily consumption index of the vegetables was determined based on total TME content. The results show that organocalcareous soil improvers did not promote plant growth and survival on soils with high and medium levels of copper contamination. However, on soils with low copper content, organocalcareous soil improvers improved germination and plant survival and reduced the transfer of metals from the soil to the plants. The best germination and plant survival rates were obtained with the lightly contaminated market garden. In addition, the organo-limestone amendments applied to the soils slightly increased the soil pH from acidic to slightly acidic, with pH values ranging from (5.43 ± 0.07 to 7.26 ± 0.33). The daily vegetable consumption index obtained for cobalt in the low-contaminated garden ranged from (0.029 to 0.465 mg/60 kg/day), i.e. from 0.5 to 8.45 times higher than the FAO/WHO limit, unlike the other trace metals (Cd, Cu and Pb) for which the daily consumption index found was lower than the FAO/WHO limit. Organocalcareous soil improvers can only be applied to soils with low levels of TME contamination, but for soils with medium to high levels of metal contamination, new soilless production techniques such as hydroponics or bioponics are needed.

Integrated Nutrient Management of Fruits, Vegetables, and Crops through the Use of Biostimulants, Soilless Cultivation, and Traditional and Modern Approaches—A Mini Review

The increasing population, its requirements for food, and the environmental impact of the excessive use of inputs make crop production a pressing challenge. Integrated nutrient management (INM) has emerged as a critical solution by maximizing nutrient availability and utilization for crops and vegetables. This review paper highlights the potential benefits of INM for various vegetables and field crops and explores the conceptual strategies, components, and principles underlying this approach. Studies have shown that a wide range of vegetables and field crops benefit from INM, in terms of increased yield and improvements in yield attributes, nutrient contents and uptake, growth parameters, and various physiological and biochemical characteristics. This paper discusses biostimulants, their categories, and their impact on plant propagation, growth, photosynthesis, seed germination, fruit set, and quality. Additionally, this review explores modern sustainable soilless production techniques such as hydroponics, aeroponics, and aquaponics. These cultivation methods highlight the advancements of controlled-environment agriculture (CEA) and its contribution to nutrient management, food security and minimizing the environmental footprint. The review concludes by proposing methods and fostering discussions on INM’s future development, while acknowledging the challenges associated with its adoption. Finally, this review emphasizes the substantial evidence supporting INM as a novel and ecologically sound strategy for achieving sustainable agricultural production worldwide.

The role of biofertilizer on the growing efficiency of Callisia fragrans cultivated under open-air hydroponic conditions of the Ararat Valley

Background: Invention of biofertilizers (BFs) is considered to be one of the most important achievements of modern agriculture. Although these microbial bioproducts have not found widespread usage in soilless production, there is an increasing trend of research studies on BFs in hydroponics. Objective: In consideration of the high potential of biofertilizers (BFs) in hydroponics, this study examines the impact of BF on the growth efficiency of the medicinal plant Callisia fragrans (Lindl.) Woodson (C. fragrans) under open-air hydroponic conditions in the Ararat Valley for the first time. Methods: The plants were grown in a mixture of gravel and volcanic red slag. During the vegetation period, chemical fertilizer (CF), BF, as well as their different combinations were supplied to the plants. Plant’s growth and development regularities were studied via biometrical measurements, which were done periodically during the growing process. Physiological (chlorophyll a, b, carotenoids), bio- and pharmacochemical (extractive substances, total amount of flavonoids, anthocyanins) analyses were done in the medicinal raw material. The obtained data were subjected to the statistical evaluation. Results: At the end of the experimental period, the plants nourished with a combination of CF and BF, where the BF was supplied via foliar feeding (FF), as well as the plants given only CF through root application (RA), exhibited 2.9-3.5 times higher fresh overground biomass compared to the plants given BF (FF) alone. The application of BF (FF) with the combination in CF significantly increased the content of chlorophyll b and carotenoids in the leaves of plants compared to the BF (FF) variant. The maximum accumulation of anthocyanins and flavonoids of plants were mostly observed in the plants given the combination of CF and BF through the roots, as well as the ones given BF (FF) alone. Significant difference on the biosynthesis of extractive substances in the medicinal raw material between the variants has not been observed. Conclusion: Summarizing the preliminary results of the experiments, it is becoming obvious, that the application of BFs has great potential in hydroponics in order to enhance growing efficiency of C. fragrans. Keywords: C. fragrans, biofertilizer, chemical fertilizer, bioactive compounds, hydroponics, medicinal raw material

Life cycle assessment of citrus tree nurseries in Uruguay: Are their environmental impacts relevant?

Perennial fruit production at the commercial scale, such as citrus fruits, begins with seedling production in a nursery. This stage lasts several months and involves different phases and the use of substrates and infrastructure. As the seedling does not produce fruit but does consume inputs, studying the environmental impacts associated with this stage becomes relevant, especially to understand its contribution to the total impact of the crop cycle. Despite the global relevance of fruit tree seedlings production, LCA studies in the literature focus on horticultural crop nurseries, and those on perennial tree nurseries do not consider both substrate and structures in the analysis, which is key for this type of crop since the main production system is soilless production in greenhouses. Thus, the main goal of this study is to quantify the environmental impacts related to the production of citrus fruit tree seedlings using LCA, analyse the main production system applied nowadays, and study its relevance with respect to the crop cycle. To this end, a certified Uruguayan citrus nursery was analysed, from which primary data was obtained. As well, methodological issues concerning water consumption and modelling emissions from input applications in soilless greenhouse systems are tackled. Results show that the main hotspots of the nursery stage are infrastructure production and peat transportation, which highlights the relevance of their inclusion when modelling the system. Extending the lifespan of the galvanised steel structures and decreasing substrate transport distances are shown to be effective measures to reduce environmental impacts. The contribution of the nursery stage to the citrus production cycle is negligible for almost all the impact categories assessed except cancer human toxicity, as it accounts for 0–3.6% of the impacts depending on the impact category. Great differences (from 10 to 400 times higher results on average) are observed when comparing the results with those from commercial databases, as they consider open-field nurseries where seedlings are grown in the soil. The need to develop harmonised methods to model water consumption and fertiliser and pesticide emissions for soilless crops in greenhouses arises. The present study presents a complete quantification of the environmental impacts of the main production system of citrus fruit tree seedlings and provides scientific and quantitative evidence of its contribution to the production cycle, helping decision-makers understand where efforts should be focused to achieve a more sustainable fruticulture.

Sustainable and bioactive substrates to enhance nutrient delivery in soilless production systems

Sustainable and bioactive substrates to enhance nutrient delivery in soilless production systems

Increasing the resource use efficiency of organic soilless production by using natural nitrogen from plasma activated water

Increasing the resource use efficiency of organic soilless production by using natural nitrogen from plasma activated water

Effect of augmented nutrient composition and fertigation system on biomass yield and cannabinoid content of medicinal cannabis (Cannabis sativa L.) cultivation.

Growing evidence underscores the role of nutrients and fertigation systems in soilless production, influencing medicinal cannabis biomass and secondary metabolite content. This study delves into the impact of enhanced nutrient regimes on the 'ionome' and its ramifications for biomass and cannabinoid production in medicinal cannabis, comparing two distinct fertigation systems: recirculation and drain-to-waste. Notably, we assess the optimal harvest time for maximizing profitability. In comparing the experimental variant with elevated levels of phosphorus (P), potassium (K), and iron (Fe) in the nutrient solution to the control variant, we observe distinct patterns in element composition across stems, leaves, and flowers, with significant differences between fertigation systems. Total nitrogen content was determined through the Kjeldahl method. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma optical emission spectrometry (ICP-OES) were employed for elemental analysis. Cannabinoid identification and quantification used high-performance liquid chromatography with a diode-array detector (HPLC/DAD). Followed statistical analyses included ANOVA and Tukey's HSD test. Although the augmented nutrient regimen does not substantially increase plant biomass, interesting differences emerge between the two fertigation systems. The recirculation fertigation system proves more profitable during the recommended harvest period. Nonetheless, the altered nutrient regime does not yield statistically significant differences in final inflorescence harvest mass or cannabinoid concentrations in medicinal cannabis. The choice of fertigation system influences the quantity and quality of harvested inflorescence. To optimize the balance between the dry biomass yield of flowers and cannabinoid concentration, primarily total THC yield (sum of tetrahydrocannabinolic acid, Δ9-tetrahydrocannabinol, and Δ8-tetrahydrocannabinol), we propose the 11th week of cultivation as the suitable harvest time for the recirculation system. Importantly, the recirculation system consistently outperformed the drain-to-waste system, especially after the ninth week, resulting in significantly higher total THC yields. Enriched nutrition, when compared with control, increased THC yield up to 50.7%, with a remarkable 182% surge in the recirculation system when compared with the drain-to-waste system.

Evaluation effects of alternative substrates for soilless cultivation of strawberry (Fragaria x ananassa)

Strawberry is one of the major cultivations in Mexico, nonetheless, low development of planting techniques reduces fruit quality. The present research aimed to evaluate alternative substrates for soilless cultivation of strawberry, variety festival (Fragaria x annanasa). Four substrates were evaluated to achieve the goal: T1 coconut fiber substrate, T2 volcanic rock “tezontle”, T3 coconut fiber 50 % volcanic rock “tezontle” 50 %, and T4 soil as control. To compare the substrates, some properties that people chose in the fruit were selected: number of fruits per plant, fruit weight, fruit size, and Brix degrees (° Brix). The ° Brix did not show differences among the treatments; however, under T2 and T3 the best results were observed in terms of the number of fruits per plant, fruit weight and fruit size, which are considered remarkable market fruit qualities. In all the cases, T4 showed the lowest values in comparison to the other substrates. In conclusion, due to its low-cost volcanic rock alone or combined with coconut fiber could be used as a promising substrate for the production of strawberries; however, further work is needed to optimize other factors such as fertilization regimes and irrigation to reduce the production cost in a soilless production system.

Soilless cultivation systems to produce tailored microgreens for specific nutritional needs.

The awareness of the importance of following dietary recommendations that meet specific biological requirements related to an individual's health status has significantly increased interest in personalized nutrition. The aim of this research was to test agronomic protocols based on soilless cultivation for providing consumers with new dietary sources of iodine (I), as well as alternative vegetable products to limit dietary potassium (K) intake; proposed cultivation techniques were evaluated according to their suitability to obtain such products without compromising agronomic performance. Two independent experiments, focused on I and K respectively, were conducted in a commercial greenhouse specializing in soilless production. Four different species were cultivated using three distinct concentrations of I (0, 1.5 and 3 mg L-1 ) and K (0, 60 and 120 mg L-1 ). Microgreens grown in I-rich nutrient solution accumulate more I, and the increase is dose-dependent. Compared to unbiofortified microgreens, the treatments with 1.5 and 3 mg L-1 of I resulted in 4.5 and 14 times higher I levels, respectively. Swiss chard has the highest levels of K (14 096 mg kg-1 of FW), followed by rocket, pea and radish. In radish, rocket and Swiss chard, a total reduction of K content in the nutrient solution (0 mg L-1 ) resulted in an average reduction of 45% in K content. It is possible to produce I-biofortified microgreens to address I deficiency, and K-reduced microgreens for chronic kidney disease-affected people. Species selection is crucial to customize nutritional profiles according to specific dietary requirements due to substantial mineral content variations across different species. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Using Date Palm Waste as an Alternative for Rockwool: Sweet Pepper Performance under Both Soilless Culture Substrates.

The degradation of soil quality due to environmental conditions and improper management practices has caused a shrinkage in land areas suitable for crop cultivation. This necessitates a transition towards soilless culture systems, which offer desirable conditions for crop growth and development and increase resource use efficiency. One of the growth-limiting factors in soilless culture systems is the type of growing substrate. The use of more sustainable resources and environmentally friendly growing substrates is a challenge that affects the soilless culture industry. This work evaluates the efficacy of date palm waste (DPW) and rockwool as growing substrates for sweet pepper (Capsicum annuum L.) under greenhouse conditions. The plant height, stem diameter, average total leaf area, φPSII, and Fm' of leaf fluorescence show significant increases when plants are grown in rockwool. No differences are found in terms of the total yield or the number of marketable fruits and fruit quality between the two substrates. However, the DPW substrate shows a significant decrease in the number of unmarketable fruits and number of Blossom End Rot (BER) fruits. Plants grown in both growing substrates consume equal water amounts for the optimal fruit production, while the water use efficiency of rockwool is better than that of DPW. Our results highlight DPW's role in soilless production and as a key solution for resource-saving production systems.

Response of gerbera under soil and soil-less production systems

Response of gerbera var. Arka Nesara was studied under different soil-less production systems with the aim to improve quality, productivity and water use efficiency, in completely randomized design with eight treatments viz., deep flow technique (DFT), nutrient film technique (NFT), aggregate wick system (AWS) with pots on NFT bench, AWS with pots on ground, AWS with grow bags on ground, AWS on soil bed, aeroponics and conventional soil-based drip system, which were replicated five times. Results revealed that AWS with pots on ground recorded maximum plant height (31.66 cm), leaf length (21.31 cm), leaf breadth (9.96 cm) and stalk diameter near neck (4.75 mm), minimum stem deviation (1.27 cm) and stem deflection (2.2o), prolonged vase life (9.2 days), greater water use efficiency (92 mL/plant/day) and water saving (83.46%). Hence, cultivation of gerbera var. Arka Nesara under aggregate wick system with pots on ground could be the superior alternative for traditional soil cultivation.

Impact of organic liquid fertilizers on growth and yield performance of Green Bean (<em>Phaseolus vulgaris</em> L.) in non-circulating hydroponic system

Non-circulating hydroponic systems are a type of soilless production system that has been found to be extremely productive, low-cost, water, land efficient, and well-suited to avoid fertilizer leaching and groundwater contamination. The experiment was conducted to study the effect of liquid organic nutrient solutions on Green Bean (Phaseolus vulgaris L.) cultivation in non-circulating hydroponic system. The experiment was laid out in a Completely Randomized Design (CRD) with seven treatments having fifteen replicates. The treatments were recommended inorganic fertilizer application (T1), ½ doses of Albert’s solution with 0.5% vermiwash (T2), 1% vermiwash (T3), 1.5% vermiwash (T4), 0.5% vegetable waste solution (T5), 1% vegetable waste solution (T6), 1.5% vegetable waste solution (T7) was used as media. The results revealed that plant height, number of leaves and branches per plant, leaf area, dry weight of leaves and length of pods were significantly (P<0.05) varied at 6th week after planting and it was high in T5. However, number of pods per plant, girth of pods, fresh and dry weight of pods and yield were high in T2 at 3rd picking while yield at 1st and 2nd picking were high in T5. This result suggests that ½ doses of Albert’s solution with 0.5% vegetable waste solution (T5) and ½ doses of Albert’s solution with 0.5% vermiwash (T2) would be the potential source of plant nutrients for sustainable crop production of bean in Non-circulating Hydroponic system.

Prediction of organic nitrogen mineralization from fertilizers in soilless production

Prediction of organic nitrogen mineralization from fertilizers in soilless production

How the use of companion plants can improve the colonization of tomato crop by Macrolophus pygmaeus, in the context of soilless production?

How the use of companion plants can improve the colonization of tomato crop by <i>Macrolophus pygmaeus</i>, in the context of soilless production?

Overview of developments in recirculation of drainage solution for crops in soilless production systems

Overview of developments in recirculation of drainage solution for crops in soilless production systems

Growing Safer Greens: Exploring Food Safety Practices and Challenges in Indoor, Soilless Production Through Thematic Analysis of Leafy Greens Grower Interviews

Indoor, soilless production—often referred to more broadly as controlled environment agriculture (CEA)—is increasingly used for the cultivation of leafy greens. Minimal information is currently available regarding food safety practices during production and distribution of leafy greens grown within indoor, soilless environments in the United States (U.S.). This study aimed to describe production challenges and implementation of good agricultural practices among CEA growers. Data collection methods included semi-structured interviews (N = 25) and a supplemental online survey completed by growers (N = 12) in the U.S. Out of 18 total responses (i.e., multiple responses allowed per completed survey), survey data indicated that lettuce (n = 5; 27.8%) was the most commonly grown leafy green, followed by culinary herbs (n = 3; 16.7%) and arugula (n = 3; 16.7%). Most growers (n = 7; 58.3%) grew other agricultural products, specifically other crops in addition to leafy greens. Revenue from sales ranged from <US$25 000 to >US$500 000 per year. Meanwhile, nearly half (n = 5; 45.5%) of respondents (N = 11) were uncertain whether their produce was subject to the FSMA Produce Safety Rule. Most survey respondents used vertical farming techniques (5 out of 11; 45.5%) or some variety of greenhouse (4 out of 11; 36.4%). Based on 35 total responses, leafy greens were most commonly sold to “Commercial Restaurants” (n = 7; 20.0%), “Grocery Stores” (n = 7; 20.0%), “Institutional Foodservice Establishments (hospitals, schools, childcare, long-term care)” (n = 6; 17.1%), and “Wholesaler/Distributers” (n = 6; 17.1%). The 11 interview questions elucidated three major themes: contextual, barriers to risk management and regulatory compliance, and research needs. Thirteen subthemes were identified, and an example of a subtheme within each major theme, respectively, includes worker hygiene and training, regulatory and certification environment, and risk assessments of individual issues.

Estimating Nitrogen Release from Organic Fertilizers for Soilless Production by Analysis of C and N Pools

The use of organic fertilizers in soilless pot plant production has sharply increased in recent years. However, there is still a lack of methods for characterizing the N release from organic fertilizers. This bears the risk of an inadequate nutrient supply and, thus, a waste of resources. Therefore, the current research analyzed fourteen commercial organic fertilizers for various C and N pools by extraction in cold and hot water, acid hydrolysis, and thermal fractionation. Furthermore, we conducted an incubation test using a growing medium (80 vol% peat plus 20 vol% green waste compost) and fitted the nitrogen release to different kinetic models. Finally, we calculated the correlations among the best-suited kinetic model parameters and the C and N pools. The C and N pools soluble in water and weak hydrochloride acid varied significantly among the fourteen fertilizers but were closely correlated with each other. The N release from most organic fertilizers could be described very well using the Gompertz function (R² &gt; 0.9), and the parameters of the Gompertz function showed significant correlations with the C and N pools. Hydrolyzable C and N pools provided valuable information about the N release characteristics of organic fertilizers.

Effect of different substrates on in vitro symbiotic seed germination for soilless production of Anacamptis laxiflora orchid

In recent years, the orchid species have become endangered due to overuse and habitat destruction. As with most flowering plants, seed production is the primary strategy for reproduction in orchids. Orchids produce tiny seeds consisting of a seed coat and a rudimentary embryo. However, it lacks the endosperm, which is generally required as the primary energy source during germination. The only way to germinate orchid seeds is to get nutrients from an external source. In nature, this is achieved by mycorrhizal symbiosis. This study used Ceratobasidium sp. inoculation of Anacamptis laxiflora (Lam.) seeds combined with media with various organic substrates to determine their effectiveness on germination and seedling development by in vitro culture. The highest germination rate (35.78%) was obtained in the medium with addition of young hazelnut leaves. Then, soilless ex vitro symbiotic germination was performed on young hazelnut leaves, the most effective organic substrate. Seed germination was determined to be 19.01% in this medium while 14.87% seedlings with developed leaves and roots were formed. For the first time, success was achieved by producing A. laxiflora from seed in ex vitro conditions without soil and adapting it to nature.