Soilless Substrates Research Articles

Effect of Substrate, Growth Condition and Nutrient Application Methods in Morphological and Commercial Attributes of Hybrid Rose (Rosa indica L.) Cv. Kardinal

Rose is an important plant around the world. The largest trader of rose cut-flower and hybrid varieties is Netherland. Countless varieties are introduced in agriculture business for commercial production. While countless soil and soilless substrates are also utilized for commercial production of rose around the globe. Due to that it is important to standardize and see the best soil or soilless substrate for better production of commercial cut-flowers in Rose. Various soil substrates and growing environment (Under partial shade, 70% sunlight and open sun light) was observed for better commercial yield in Rose. The balance fertilizer was applied in both A: Foliar spray (300:300:300 ppm of NPK) along with the various soil substrates of GS: PR: CCD (1:1:1), GS: LC (1:1), GS: PR (100%) and FYM: SL: CL (1:1:1). The liquid substrate was distilled water for foliar application. The foliar application was done after each day. The other nutrient application process was B: soil application of macro nutrient (2g/L of 17:17:17-NPK) along with GS: PR: CCD (1:1:1), GS: LC (1:1), GS: PR (100%) and FYM: SL: CL (1:1:1). Each plant was saturated with 2 days interval. The fertigation was carried by mixing above mentioned fertilizer with the canal water having EC: 0.4 dSm-1 and pH: 6.9 pH. The performance of plants was observed by observing the attributes such as Plant survival (%), Number of flowers per plant, Plowers stem length (cm), Plant health (Number of leaves, leaf size (cm), Flower diameter (mm), Flower stem size (mm) and Flower stem diameter (mm). Completely randomized experimental design (CRD) was used for calculating means of various treatments. The best treatment was FYM: SL: CL for both under partial shade (70%) and open sun light for the significant growth and development of plant morphological and commercial attributes. The same treatment with soil application of 2g/L of NPK (17:17:17) after each day is recommended to the commercial growers of Rose throughout the flowering season.

Technological and Organoleptic Properties of Tomato (Lycopersicum esculentum) Produced on Soilless Substrates in Daloa (Haut Sassandra Region, Côte d'Ivoire)

The present study was carried out to characterise tomatoes produced on soilless substrates (cocoa, sawdust, cashew and rice husk) and to evaluate their impact on the technological and organoleptic characteristics of the tomato. A tomato crop was grown on these different substrates for three months. The tomato fruits from each substrate were subjected to chemical, technological and sensory analysis. The tomatoes of the different substrates have a high water content (94.83- 96.37%). Regarding the technological properties, the results recorded are for saccharin index (1.15%), saccharin coefficient (121.5%) and acidity coefficient (8.29%). The sensory study of the tomatoes reveals that the tasters perceived sensory differences between the tomatoes. Their overall perception of the tomatoes confirms their good acceptability. Also taste, colour, shape and consistency are important criteria of fresh tomatoes. At the end of this study, it was found that the C100 substrate presented the best physicomorphological parameters. Technologically, tomatoes from the RB5050 and B100 substrates can be recommended for industrial processing.

The Effect of Propagation Substrate on Pythium Root Rot Severity and the Efficacy of Biopesticides

Modern greenhouse crop production utilizes soilless substrates that range from inorganic substrates (Oasis foam and rockwool) to blends of organic substrates (sphagnum peat moss, coconut fiber, bark mulch, wood chips, and wood products). Additionally, greenhouse growers utilize beneficial microorganisms in the form of commercial biopesticides to reduce disease. Few research studies have examined the effect of propagation substrate on the efficacy of commercial biopesticides under greenhouse production conditions. The objective of this study was to evaluate the effect of propagation substrates on commercially available microbial biopesticides (Rootshield WP, Cease, and Regalia) applied during propagation and at transplant for management of Pythium root rot. In this study, cucumber and calibrachoa were used as model crops. Over both cropping systems, plants propagated in Oasis foam had lower root rot compared with plants propagated in coconut coir. Across all biopesticide treatments, cucumber plants propagated in Oasis foam had 52% less root rot compared with plants propagated in coconut coir. In both infested and noninfested calibrachoa plants, plants propagated in Oasis foam had 45 to 67% less disease, and plants propagated in peat had 25 to 40% less disease compared with plants propagated in coconut coir. There was no effect of biopesticide on Pythium root rot severity, except for a reduction seen in calibrachoa plants propagated in coconut coir and treated with Rootshield WP. This research suggests that propagation substrate is important for root disease management.

Integrated Physiological and Metabolomic Analyses Reveal the Differences in the Fruit Quality of the Blueberry Cultivated in Three Soilless Substrates.

With improving living standards, traditional blueberry planting modes cannot meet commercial demands, and blueberry cultivation with soilless substrate has become a popular solution in the blueberry industry. In this study, different soilless substrate treatments were found to markedly influence fruit appearance and intrinsic quality. The fruit in the 50:50 peat/pine bark (v/v) (FPB) treatment group had the maximum single fruit weight, largest vertical diameter, and brightest color, as well as the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) value, solid-acid ratio and anthocyanin content. The fruit in the 50:50 pine bark/rice husk (v/v) (FBR) treatment group had the highest total phenol and flavonoid levels, largest drip loss value, and lowest total pectin content and firmness value. Metabolomic analysis showed that flavonoid, carbohydrate, and carbohydrate conjugate, and amino acid, peptide, and analog levels were significantly different between groups. Fruit in the FPB group had the highest sucrose, D-fructose 1,6-bisphosphate, salidroside, tectorigenin, naringenin chalcone, trifolirhizin, and galangin contents. The increase in the relative expression of phenylalanine (Phe) promoted the synthesis of fruit polyphenols in the FBR group. Our results provide new insights into the effects of different substrates on the quality of blueberries and a reference for the soilless substrate cultivation of blueberries.

The Effect of Peat Moss Amended with Three Engineered Wood Substrate Components on Suppression of Damping-Off Caused by Rhizoctonia solani

The use of wood-derived materials in soilless substrates for horticultural crop production is increasing; however, there is little information about the effects of wood on the incidence and severity of soilborne diseases of container-grown plants. The objectives of this research were to compare three differently processed wood substrate components blended with sphagnum peat and to investigate the effect of the peat:wood blend ratio on damping-off disease caused by Rhizoctonia solani using radish as a model system. In objective one, raw sphagnum peat was blended with three types of processed pine wood, screw-extruded, twin disc-refined, and hammer-milled, at a volumetric ratio of 70:30 and compared to a 70:30 peat:perlite mix. Radish plants grown in the hammer-milled wood and disc-refined wood had significantly lower damping-off disease severity compared to plants grown in the peat–perlite control. In objective two, sphagnum peat was blended with the three types of processed wood at a volumetric ratio of 90:10, 80:20, and 70:30 and compared to a 70:30 peat–perlite mix. The effect of the blend ratio varied by wood processing type. Higher percentages of Forest Gold and pine tree substrate resulted in lower disease severity. In both objectives, radish plants grown in any of the substrate treatments containing wood infested with R. solani tended to have lower disease severity compared to plants in the control. Results of this study indicate that the blending of processed pine wood-derived components into peat may enhance the natural suppression of damping-off disease of radish. Further research is needed to elucidate the mode of action of wood-derived materials on disease suppression in container-grown crops and to study the effects for other plant pathogens and crop species.

Addition Pinus massoniana fallen wood improved the growth of Plagiomnium acutum in a substrate cultivation

Soilless culture has been widely used in horticultural plant production, but little research has been done on bryophyte. In this study, we selected a cultivation substrate mixed and proportioned with garden soil, granular soil, grass charcoal soil, general-purpose nutrient soil, and decomposed grade II, III, and IV fallen wood of Pinus massoniana as the raw materials of soilless substrate to investigate its effects on the growth and physiology of Plagiomnium acutum. The results showed that the total porosity, water-holding porosity, and water-holding capacity of the mixed substrate containing fallen wood of P. massoniana were significantly higher than those of other cultivated substrates. The average cover of the P. acutum was significantly and positively correlated with the substrate’s total porosity and water-holding porosity. Chlorophyll content was highly significantly and positively correlated with the water holding capacity and total nitrogen content of the substrate. Among them, VIII decomposition grade Pinus massoniana fallen log:Vgrass charcoal soil = 1:1 (SW8) substrate had the highest overall evaluation index and the best overall growth condition of P. acutum. In summary, VIII decomposition grade Pinus massoniana fallen log:Vgrass charcoal soil = 1:1 (SW8) substrate can be the best substrate for cultivation of P. acutum. The addition of P. massoniana fallen wood to the soil substrate increased the total porosity, water-holding porosity, and water-holding capacity of the substrate, which was conducive to the growth of P. acutum and the increase of chlorophyll content.

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 δ15NSP 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.

Southern highbush blueberry responses to humic acid application in soilless substrates

Humic acids are a biostimulant that has captured the interest of blueberry growers, but information about humic acid use in blueberry is scarce. Blueberry plants suffer water deficit stress during transplant and photosynthetic limitations during fruit development. We hypothesized that humic acid applications improve transplant success and increase fruit yield and quality in southern highbush blueberry (SHB, Vaccinium corymbosum interspecific hybrids) grown in soilless substrates. We tested these hypotheses in two greenhouse experiments. First, we grew ‘Sweetcrisp’ SHB in rhizoboxes. Humic acids were applied via drench at concentrations of 0 mL⋅L−1, 7 mL⋅L−1, 13 mL⋅L−1, and 24 mL⋅L−1 for 10 weeks. Humic acid application increased substrate respiration rates, pH, and electrical conductivity, but they did not increase root growth or improved transplant success. In a separate experiment, one year-old plants of ‘Avanti’, FL 09-311, and FL 06-19 SHB plants in 1.7 L pots were treated with 0 mL⋅L−1, 13 mL⋅L−1, and 24 mL⋅L−1 humic acids during the fruit development period. Humic acid application did not increase yields and occasionally reduced fruit quality. While plant responses were genotype specific, these results suggest that humic acid applications are not beneficial during the transplant or fruit development periods in substrate-grown blueberry.

Substrate composition affects growth and physiological parameters of blueberry

There is currently a growing interest in soilless substrates for blueberry cultivation. Identifying optimal substrate for the growth and development of the crop, and understanding the physiological response of blueberries is not only essential to determine the appropriate growing conditions, but also to improve the quality of the fruit. In this study, we evaluated the development and physiological response, and quality of blueberry plant fruits grown on two types of substrate. For this, the “Legacy” variety blueberry plants (Vaccinium. corymbosum, L) were grown in substrate composed of coconut fiber and peat (3:1) (substrate 1) and in substrate only composed of coconut fiber (substrate 2). The plants were kept in a greenhouse with controlled humidity and temperature conditions, and were drip-irrigated with modified Steiner solution. The blueberry plants grown in substrate 2, had a higher growth and yield compared to substrate 1. The analysis of nutrients in the substrate showed a higher concentration of nutrients in substrate 1, but in a post-transplant percolate analysis, substrate 2 was found to have a higher nutrient retention. Also, the stomatal density and the stomatal conductance show significant and differences and opposite response with the treatments, finding the highest number of stomata per mm2 in the plants grown with substrate 2, and a higher stomatal conductance with substrate 1. The plants with substrate 2 showed a better fruiting potential and reached a larger fruit diameter. The results indicate a higher suitability of substrate 2 for growing blueberry, but not only due to the values obtained, but for the potential better response against any environmental change that could alter water relations.

Root Exploration, Initial Moisture Conditions, and Irrigation Scheduling Influence Hydration of Stratified and Non-Stratified Substrates

Soilless substrate stratification (i.e., layering unique substrates within a single container) is an emerging substrate management strategy that may provide opportunities to augment nursery resource use. As such, this research aimed to analyze water movement through containers during hydration events under different initial moisture conditions. The results indicated substrate stratification had minimal influence on water movement compared to non-stratified systems (uniformly filled nursery containers). Cyclic irrigation significantly increased the stratified substrates’ ability to retain water when irrigated at 20% volumetric water content (p < 0.0001) and significantly decreased the total volume leached (p < 0.0001). Moreover, irrigating the substrate profile with shallow and more frequent irrigations facilitated stratified substrates ty reach effective container capacity conditions (p < 0.0001n compared to non-stratified systems. The stratified systems took longer to leach all gravitational pores (p = 0.0266). In dry moisture conditions, non-stratified substrates were more hydrated when cyclic irrigation applications were applied compared to single applications (p = 0.0492). This study demonstrated that cyclic irrigation scheduling enhanced water retention in both non-stratified and stratified profiles under different initial moisture conditions and can be used as an irrigation strategy when dry substrate conditions prevail.

Effect of Irrigation, Fertilizer Rate and Placement, and Two Substrates on Growth of Rose and Hydrangea

Abstract Current best management practices for containerized nursery crops maximize plant growth while minimizing nutrient leaching. This study tested how plant growth was affected by reducing the standard fertilizer rate when grown in two soilless substrates with different physical properties under two irrigation levels. Controlled-release fertilizer (CRF) treatments included 1.0x (45g) applied as topdress (TD), 1.0x (45 g) incorporated throughout (IT), or 0.75x (34 g) incorporated into only the top half (TH) of the container. Rosa ‘BAIneon' Screaming Neon Red™ rose and Hydrangea macrophylla ‘PIIHM-II' Endless Summer® Bloomstruck® hydrangea were potted using Aeration+Potting Mix (AS40) or All-purpose Potting Mix (PM2) substrates. Plants received higher [12.7 mm (0.5 in)] or lower [8.3 mm ( 0.33 in)] irrigation per day for 18 weeks. Final dry weight (DW) was most affected by fertilizer, to a lesser extent substrate, and not at all by irrigation. Regardless of taxa, the largest DWs were produced when plants were grown in PM2 and received nutrients via IT or TD compared to TH. Electrical conductivity was greatest in PM2 substrate with a 1.0x fertilizer rate, regardless if applied IT or TD. Taxa were unsaleable in the TH treatment, thus negating the environmental benefits achieved by reductions in leaching from lower fertilization rates. Species used in this study: ‘Screaming Neon Red™' rose (Rosa ‘BAIneon'); ‘Endless Summer® Bloomstruck®' hydrangea [Hydrangea macrophylla (Thunb.) Ser.]‘PIIHM-II').

Effects of Digested Pig Slurry on Photosynthesis, Carbohydrate Metabolism and Yield of Tomato (Solanum lycopersicum L.)

Soilless cultivation of vegetables is widely used in production. It is also well accepted that digested slurry is frequently applied as a fertilizer in agricultural production. However, the effect of digested pig slurry on yield and quality of tomato soilless cultivation, as well as the yield and quality influenced by plant carbohydrate metabolism, remain unexplored. Here, the dual inputs of fertilizers (digested pig slurry (D) and mineral fertilizer (M)) and soilless substrates (peat substrate (P) and cinder substrate(C)) consisted of four treatments. The dry biomass and fruit yields, photosynthetic parameters, carbohydrate contents and metabolism enzymes in leaves and fruits were recorded during the experimental period. The highest fruit yields were obtained in DP and MP treatments. Although DP treatment significantly increased the fresh weight of single fruits by 18.0% compared to MP treatment, it reduced the number of ripe fruits. The photosynthetic efficiency and carbohydrate contents (sucrose, glucose and fructose) in leaves were generally higher in DP treatment compared to other treatments, as well as the activities of sucrose phosphate synthase and AGPase in leaves. The soluble sugar contents of fruits in DP and DC treatments were enhanced by 12.3% and 37.0%, respectively, compared to MP and MC treatments. Moreover, the current results showed that DP treatment significantly increased the activity of acid invertase in fruit by 36.3%, 31.3%, and 42.2%, respectively, compared to MP, DC, and MC treatments, and decreased the activity of AGPase by 24.2%, 16.0%, and 36.4%, respectively. The current results have demonstrated that DP treatment had better yield and quality, owing to digested pig slurry increasing the photosynthetic efficiency and source strength, and regulated the activities of carbohydrate metabolism enzymes.

Principles of Nutrient and Water Management for Indoor Agriculture

Mass balance principles are a cornerstone of efficient fertilizer use and can be utilized to optimize plant nutrition without discarding or leaching solution. Here, we describe the maintenance of closed hydroponic and soilless substrate systems based on mass balance. Water removed by transpiration is restored with solution that replaces the nutrients that were taken up with the water. The concentration of nutrients in this refill/irrigation solution is determined by multiplying the optimal concentration of each nutrient in plant tissue by the water-use efficiency (WUE; ratio of dry mass to water transpired). Optimal leaf nutrient concentrations are well established, but WUE in controlled environments varies widely and is less well characterized. Elevated CO2 increases photosynthesis and demand for nutrients, but partially closes stomata and reduces transpiration; so high CO2 dramatically increases WUE. The concentration of the refill/irrigation solution must be adjusted to account for a two-fold range of WUE, from 3 g L−1 in ambient CO2 in lower humidity, to 6 g L−1 in elevated CO2 in higher humidity. WUE and nutrient requirements vary during the vegetative and reproductive stages of growth, and adjustment of the solution over the lifecycle can be beneficial. Measurement of solution electrical conductivity (EC) is helpful, but if the solution is appropriate, low EC usually means healthy plants and active nutrient uptake. The ammonium to nitrate ratio is critical to pH management. We have applied these principles across multiple species and environments to achieve long-term, steady-state nutrient concentrations with no discharge or leaching of solution.

Biochar Enhances Plant Growth, Fruit Yield, and Antioxidant Content of Cherry Tomato (Solanum lycopersicum L.) in a Soilless Substrate

Biochar soil amendment can improve growing medium water and nutrient status and crop productivity. A pot experiment was conducted using Solanum lycopersicum var. cerasiforme plants to investigate the effects of biochar amendment (20% application rate) on a soilless substrate, as well as on plant growth, fruit yield, and quality. During the experiment, substrate characteristics, plant morphological traits, and root and leaf C/N content were analyzed at three sampling points defined as early stage (36 days after germination), vegetative stage (84 days a. g.), and fruit stage (140 days a. g.). Fruit morphological traits, titratable acidity, lycopene, and solid soluble content were measured at the end of the experiment. Biochar ameliorated substrate characteristics (Nav increase of 17% and Ctot increase of 13% at the beginning of the study), resulting in a promotion effect on plant root, shoot, and leaf morphology mainly at the vegetative and fruit stages. Indeed, at these two sampling points, the biochar-treated plants had a greater number of leaves (38 and 68 at the vegetative and fruit stages, respectively) than the untreated plants (32 and 49, respectively). The biochar also increased leaf area with a rise of 26% and 36% compared with the values measured in the untreated plants. Moreover, the amendment increased twofold root length, root surface area, and root, stem, and leaf biomasses in comparison with untreated plants. Regarding plant productivity, although fruit morphology remained unchanged, biochar increased flower and fruit numbers (six times and two times, respectively), acidity (75%), lycopene (28%), and solid soluble content (16%). By unveiling promoting changes in morphological traits, fruit number, and antioxidant content occurring in cherry tomato plants growing in a biochar-treated soilless substrate, it could be possible to highlight the importance of biochar for future applications in the field for enhancing plant production and fruit quality in a sustainable agriculture framework.

Use of Emulsion-Templated, Highly Porous Polyelectrolytes for In Vitro Germination of Chickpea Embryos: a New Substrate for Soilless Cultivation

The application of highly porous and 3D interconnected microcellular polyelectrolyte polyHIPE (PE-PH) monoliths based on (3-acrylamidopropyl)-trimethylammonium chloride as soilless cultivation substrates for in vitro embryo culture is discussed. The embryo axes isolated from chickpea seeds are inoculated onto the surface of the monoliths and allowed to germinate. Germination study show that the newly disclosed PE-PH substrate performs much better than the conventionally used agar as the germination percentage, shoot and root length, fresh and dry weight as well as the number of leaves are enhanced. The PE-PHs exhibit a higher absorption capacity of the plant growth medium, that is, 36 g·g–1 compared to agar, that is, 20 g·g–1, and also survive autoclaving conditions without failing. The key advantage over standard agar substrates is that they can be reused several times and also without prior sterilization. These results suggest that PE-PHs with exceptional absorption/retention properties and robustness have great potential as soilless substrates for in vitro plant cultivation.

Economic analysis of tomato (Solanum lycopersicum) cultivar grown in different soilless substrates under protected conditions

Protected cultivation has great potential in northern India, where the extreme temperature, unpredictable heavy rainfall and problematic soil conditions have affected the year around availability of tomato crop in the different agro climatic zones of the region. Therefore, this study was conducted under protected structure at Hi-Tech Vegetable Centre, Bir Charik, Moga, Punjab during two seasons in 2018 and 2019 with an objective to standardize the best economical growing media and tomato cultivars in Punjab. The experiment was conducted with 6 promising tomato cultivars (viz., Heemshikhar, 2853, NS-4266, Punjab Gaurav, Punjab Sartaj, Punjab Swarna) under poly-house structure. Six different media substrate treatments [Soil as control, Cocopeat only, Cocopeat+ Vermicompost in ratio {(2:1, v/v) & (3:1, v/v)}, Cocopeat + Vermiculite + Perlite in ratio (3:1:1, v/v) and (6:1:1, v/v)] were used. The soil is the most economical growing media for growing all the cultivars, but in the case of problematic soils (saline soils/soil borne insect-pest problems), the soilless substrate can be a better option for commercial cultivation of tomato. The maximum B:C ratio (0.80) was recorded in cultivar (P3) which was statistically significant than check cultivar (P1). The maximum B:C ratio (0.93) was recorded under Soil only (M1), followed by (0.74) under media combination (M3) cocopeat + vermicompost (2:1, v/v) which was statistically significant than all other treatments. The economic yield of NS-4266 was (608 q/acre) higher in the soilless growing media (M3) with the combination of Cocopeat + Vermicompost (2:1, v/v) for tomato cultivation in Punjab, whereas the soilless growing media Cocopeat + Vermiculite + Perlite in the ratio (6:1:1, v/v) can be exploited for further research experiments.

Interception Strategies for Managing Exotic Ambrosia Beetles (Coleoptera: Curculionidae) in Nurseries

Interception Strategies for Managing Exotic Ambrosia Beetles (Coleoptera: Curculionidae) in Nurseries

Improving Containerized Nursery Crop Sustainability: Effects of Conservation-driven Adaptations in Soilless Substrate and Water Use on Plant Growth and Soil-borne Disease Development

Containerized crop production faces increasing sustainability challenges with both soilless substrate and water use. To facilitate use of sustainable practices, we evaluated plant health impacts of two substrates, bark and wood fiber, which we contrasted with peat, a substrate that is slower to renew; this was overlaid with an analysis of the effects of water-saving–targeted irrigation reductions, compared with typical well-watered conditions. Health impacts were evaluated in two crops, considering both physiological and disease impacts for tomato with and without Phytophthora capsici, and chrysanthemum with and without Phytopythium helicoides. Substrate type was a strong determinant of plant health, wherein crops grown in a HydraFiber-peat mix (“fiber”) performed worse than those in bark and peat, with up to a 50% and 45% reduction in shoot biomass in tomato and chrysanthemum, respectively (P < 0.001). Tomato decline incidence from P. capsici was 3–6 times higher in fiber than other substrates, and fiber was the only substrate where the effect of P. capsici enhanced decline and rot development compared with noninoculated plants (P < 0.05). In bark, reduced irrigation consistently inhibited tomato and chrysanthemum growth and shoot water content (typically P < 0.001). In peat, whereas tomato growth was inhibited under reduced irrigation (P = 0.012–0.013), chrysanthemum growth was often unaffected. Growth in fiber was uniformly poor regardless of irrigation regime for both crops, and an irrigation treatment effect was not typically apparent. Reduced irrigation enhanced pathogen effects in fiber and peat for tomato and fiber and bark for chrysanthemum (P < 0.05). This is perhaps the first study to evaluate HydraFiber interactions with disease and reduced irrigation and suggests that this product consistently incurs costs to crop productivity. However, the peat-replacing bark substrate has strong potential to optimize plant growth physiologically and via disease suppression and can be used under reduced irrigation without compromising economic productivity of the system.

A Review and Analysis of Horticultural Substrate Characterization by Sieve Analysis

The physical, hydrological, and physico-chemical properties of horticultural substrates are influenced by particle shape and size. Sieve analysis has been the predominate method used to characterize the particle size distribution of horticultural substrates. However, the literature shows a diversity of techniques and procedures. The effects of agitation time and sample size on particle size distributions of soilless substrates were evaluated for several measures of sieve analysis, including sieve rate (a calculation of the percentage of material passed for each unit time of agitation), distribution median, sd, mass relative span, skewness, and kurtosis. To obtain the standard sieve rate (0.1%/min), pine bark, peat, perlite, and coir required agitation times of 4 minutes and 47 seconds, 7 minutes and 18 seconds, 10 minutes, and 11 minutes, respectively. However, there was concern that unwanted particle breakdown may occur during the particle size analysis of some materials. Therefore, a sieve rate (0.15%/min) for more friable materials was also determined. As a result, the endpoint of sieving was reached sooner for pine bark, peat, perlite, and coir, at 3 minutes and 10 seconds, 4 minutes and 42 seconds, 5 minutes and 14 seconds, and 6 minutes and 24 seconds, respectively. Increasing agitation time resulted in decreased distribution median, sd, and skewness for all materials. Sample sizes half and twice the volume of the recommended initial volume sieved did not change particle size distributions. For more precise characterization of particle size distributions when characterizing substrate components, agitation times and sample sizes should be specified for each material or collectively for all materials to ensure consistency and allow comparisons between results.

Metabolomics combined with physiological and transcriptomic analyses reveal regulatory features associated with blueberry growth in different soilless substrates

The objective of this study was to evaluate the effects of soilless substrate mixtures on blueberry seedling growth under greenhouse conditions and to determine the optimal growth media for soilless blueberry (Vaccinium australe) cultivation. Trials were carried out with two-year-old blueberry seedlings from April to August 2021. Three mixed substrates (PB: peat and bark (1:1, v/v), PR: peat and rice husk (1:1, v/v), and BR: bark and rice husk (1:1, v/v)) were investigated. The results showed that the plant height, stem diameter and chlorophyll content were much higher in PB and PR than in BR. The PB and PR substrates triggered antioxidant system activity and exerted marked positive effects on blueberry seedling growth. The total flavonoid content was greatly increased in the PB group compared with the other two groups. Most element contents were greatly increased with BR compared with PB and PR. Furthermore, metabolomic and transcriptomic analyses revealed the critical responses of metabolic pathways to different substrate treatments in blueberry leaves collected in June. Overall, the metabolomic data revealed 757 metabolites with decreased levels and 1383 metabolites with increased levels. The levels of multiple prenol lipids, flavonoids, organooxygen compounds, carboxylic acids and derivatives were changed. “Flavonoid biosynthesis” was the most significantly enriched pathway and may be closely related to blueberry growth. Integrated transcriptomic and metabolomic data suggested that the expression of 4 DEGs, VcPAL, VcHCT, VcF14G24.3, and VcCHS, was strongly correlated with flavonoid biosynthesis. This work provides insights for elucidating the mechanisms that mediate the growth adaptability of blueberry cv. ‘Zhaixuan 7’ in different substrates.