Coir-based Substrates Research Articles

Effects of reusing coir-based substrates with municipal compost and biochar on growth and phytochemical accumulation in lettuce

Effects of reusing coir-based substrates with municipal compost and biochar on growth and phytochemical accumulation in lettuce

Reusing Coir-Based Substrates for Lettuce Growth: Nutrient Content and Phytonutrients Accumulation

This research aimed to assess the influence of reusing coir-based substrates on growth, nutrient content, and phytonutrients accumulation in lettuce. The experiment included a new coir pith and four coir-based mixes (1) coir, biochar, and perlite; (2) coir, compost, and perlite; (3) coir, biochar, and pine bark; and (4) coir, compost, and pine bark. All mixes had been previously utilized to grow transplanted spinach and possessed identical ratios of 78:12:10% (v/v) among their components. Lettuce (Lactuca sativa L. cv. ‘Godzilla’) seedlings were transplanted into Styrofoam plant boxes. Each day, the planting boxes received a nutrient solution via drip irrigation. Plants grown in reused mixes had similar macronutrient concentrations as those grown in coir for the first time, except for N and K in the third mix. Plants grown in reused mixtures had similar yields as those in new coir. Lettuce heads yielded 4.6–4.9 kg/m2, while plants grown in reused mixtures had equal or higher total phenols than those in new coir. Ascorbic acid content was higher in plants cultivated in reused mixes. Coir-based growing media can be reused for another short-cycle crop, like lettuce, without yield loss or phytonutrients decrease.

Effects of Coir-Based Growing Medium with Municipal Solid Waste Compost or Biochar on Plant Growth, Mineral Nutrition, and Accumulation of Phytochemicals in Spinach.

The use of municipal solid waste compost (MSW) and biochar, two renewable resources with a low carbon footprint as components of substrates, may be an alternative to reducing peat and coir usage. The aim of this study was to assess the suitability of selectively collected MSW and biochar as components of the coir-based substrate to spinach grown. An experiment was carried out to evaluate five substrates, coir and four coir-based blends (coir + biochar + perlite, coir + municipal waste compost + perlite, coir + biochar + pine bark, and coir + biochar + pine bark) with 12% (v/v) MSW or biochar and 10% (v/v) perlite or pine bark. Spinach seedlings were transplanted into Styrofoam planting boxes filled with the substrate. Each planting box was irrigated daily by drip with a complete nutrient solution. Plants grown with MSW had a higher content of calcium. Shoot Mn increased in the biochar-containing mixes. The shoot dry weight of the plants grown in the different blends was higher than those grown in coir. Fresh yield was higher in mixes with MSW and perlite (3 kg/m2) or pine bark (2.87 kg/m2). Total phenols and DPPH antioxidant activity were not affected by the substrates. However, shoot ascorbate (AsA) content was higher or equal to those plants grown in coir. MSW and biochar are alternatives to reduce the use of coir and peat.

Effect of Different Substrates on Growth Parameters of Zinnia spp.

A study was carried out to assess the effectiveness of various substrates in promoting vegetative and reproductive growth of zinnia elegans. The experiment was designed in CRD with three replications and eight treatments: control, peat, coco coir, and conventional substrate (soil + silt + leaf mould, 1:1:1, v/v/v) alone or in varied combinations. The addition of coco coir to peat or peat alone enhanced plant height, leaf area, stem length, and fresh and dry weight of the stem. Plant height and stem length were considerably greater in coco coir-based substrates (P-0.0001 and P-0.0001, respectively). In peat-based and peat + coco coir-based substrates, growth and floral parameters were much higher. The findings demonstrated that coco coir, either alone or in combination with peat, had a beneficial influence on the productivity and quality of speciality cut flower zinnia crops.

Preplant Fertilization Increases Substrate Microbial Respiration But Does Not Affect Southern Highbush Blueberry Establishment in a Coconut Coir-based Substrate

Coconut coir is widely used as a substrate component for southern highbush blueberry [(SHB) Vaccinium corymbosum L. interspecific hybrids] cultivation in containers. Coconut coir-based substrates can exhibit high potassium (K), sodium (Na), and chlorine (Cl) concentrations. Sodium in the substrate is particularly problematic because it can cause salinity stress and nutritional imbalances in young blueberry plants. Thus, Na removal is important to ensure transplant success. We hypothesized that preplant fertilization with large volumes of nutrient solution can reduce substrate salinity, replace Na with nutritional cations, and enhance blueberry establishment. We tested this hypothesis in a greenhouse experiment with ‘Snowchaser’ SHB grown in rhizoboxes filled with a 7:3 mix of coconut coir and perlite. Four different treatments were delivered every 24 hours starting 72 hours before transplant. Treatments included 1.75 g⋅L–1 calcium nitrate (CN), 2.38 g⋅L–1 monoammonium phosphate (MAP), deionized water, and well water. One rooted cutting was transplanted to each rhizobox. Rhizoboxes were fertigated during the 7-week cultivation period. We found that preplant fertilization increased nitrogen (N), phosphorus (P), and calcium (Ca) concentrations in the substrate without replacing Na. Thus, preplant fertilization increased substrate salinity. Preplant fertilization also promoted microbial respiration in the substrate at the start of the experiment. Treatments did not affect SHB root architecture, leaf area index, leaf greenness, or biomass accumulation, likely because nutrients delivered by the fertigation solution provided the plants with homogeneous optimal conditions. These findings suggest that preplant fertilization with large volumes of nutrient solution does not enhance blueberry establishment in coconut coir-based substrates.

Hydrological Behavior of Peat- and Coir-Based Substrates and Their Effect on Begonia Growth

The physical–hydraulic properties of eight substrate mixtures based on sphagnum peat and coir were determined and their effect on the growth of Begonia xelatior was studied. The particle size distribution, water retention curve, saturated hydraulic conductivity, and pore size distribution of the substrates were determined. All substrates exhibited high total porosity, satisfactory water retention capacity, and high saturated hydraulic conductivity. Increasing the percentage of perlite in the mixtures contributed to the reduction of water retention capacity and the increase of large pores. Unsaturated hydraulic conductivity estimated by the Mualem–van Genuchten model showed a sharp decrease within a range of water pressure heads (0 to −50 cm) observed between two successive irrigations. To assess aeration and water retention capacity, total porosity; airspace; and easily, and nonavailable water, as well as the bulk density of the substrates, were determined and concomitantly compared with the “ideal substrates” determined by De Boodt and Verdonck. The comparative results showed that substrate porosity alone is not efficient to create ideal plant growth conditions, but dynamic parameters are also needed. Plants grown in a substrate classified as “nonideal” showed significantly greater growth than the plants grown in most of the other substrates studied.

Preparation and Properties of Coir-Based Substrate Bonded by Modified Urea Formaldehyde Resins for Seedlings

In order to form a firm root plug for the mechanical transplantation, modified urea formaldehyde (UF) resins were applied to bond coir based substrate and form substrate blocks. The physical and chemical structure, thermal stability, and crystallinity of the substrate blocks before and after nursery seedlings were characterized. The results showed that the -NH2 and -OH in the substrate reacted with the modified UF resins to form macromolecular structures. There was almost no difference between the XRD spectra of substrate blocks before and after the growth of seedlings. The modified resins in the substrate block were cured in the form of colloidal particles. The substrate block contained 53.8 At% carbon, 15.0 At% nitrogen, and 23.5 At% oxygen. When compared with the original substrate, the height, stem diameter, root length, and leaf area of tomato seedlings grown in substrate block were improved by 56.1%, 43.3%, 1.3%, and 63.3%, respectively. The qualification percentage of the substrate block was 94.3%, which was well above that of the original substrate (83.4%) according to JB/T 10291 (2013) standards. The substrate block bonded by the modified UF resins was suitable for tomato seedlings growth.

Optimal Rate of Organic Fertilizer during the Flowering Stage for Cannabis Grown in Two Coir-based Substrates

In the expanding North American medical cannabis industry, growers lack reliable and systematically investigated information on the horticultural management of their crops, especially with regard to nutrient management and growing substrates. To evaluate organic substrates and their optimal nutrient management, five rates that supplied 57, 113, 170, 226, and 283 mg N/L of a liquid organic fertilizer (2.00N–0.87P–3.32K) were applied to container-grown plants [Cannabis sativa L. ‘WP:Med (Wappa)’] in two coir-based organic substrates. The trial was conducted in a walk-in growth chamber and the two substrates used were ABcann UNIMIX 2-HP (U2-HP) with lower container capacity (CC) and ABcann UNIMIX 2 (U2) with higher CC. U2-HP produced 11% higher floral dry weight (yield), 13% higher growth index (GI), 20% higher ∆9-tetrahydrocannabinol (THC) concentration, 57% higher THC yield (per plant), 22% higher Δ9-tetrahydrocannabidiolic acid (THCA) yield, and 20% higher cannabigerolic acid (CBGA) yield than U2. Increasing fertilizer rate led to increased growth and yield but also to a dilution of THC, THCA, and CBGA. In U2-HP, to maximize both yield and cannabinoid yield, the optimal organic fertilizer rates were those which supplied 212–261 mg N/L. For U2, the highest applied rate, that supplied 283 mg N/L, maximized yield; although lower rates delivered higher cannabinoid concentrations in dry floral material. The results on these substrates and recommended fertilizer rates can serve as a guide when using other organic fertilizers and substrates; although results may differ with cannabis variety.

Optimal Rate of Organic Fertilizer during the Vegetative-stage for Cannabis Grown in Two Coir-based Substrates

Cannabis producers, especially those with organic operations, lack reliable information on the fertilization requirements for their crops. To determine the optimal organic fertilizer rate for vegetative-stage cannabis (Cannabis sativa L.), five rates that supplied 117, 234, 351, 468, and 585 mg N/L of a liquid organic fertilizer (4.0N–1.3P–1.7K) were applied to container-grown plants with one of two coir-based organic substrates. The trial was conducted in a walk-in growth chamber and the two substrates used were ABcann UNIMIX 1-HP with lower water-holding capacity (WHC) and ABcann UNIMIX 1 with higher WHC. No differences in growth or floral dry weight (yield) were found between the two substrates. Pooled data from both substrates showed that the highest yield was achieved at a rate that supplied 389 mg N/L (interpolated from yield-fertilizer responses) which was 1.8 times higher than that of the lowest fertilizer rate. The concentration of ∆9-tetrahydrocannabinol (THC) in dry floral material was maximized at a rate that supplied 418 mg N/L, and no fertilizer rate effects were observed on Δ9-tetrahydrocannabidiolic acid (THCA) or cannabinol (CBN). The highest yield, cannabinoid content, and plant growth were achieved around an organic fertilizer rate that supplied 389 mg N/L during the vegetative growth stage when using the two coir-based organic substrates.

Recipientes e substratos na produção de mudas e no cultivo hidropônico de tomilho (Thymus vulgaris L.)

Bandejas com diferente número de células (128, 200 e 288) e dois substratos (fibra de casca de coco e casca de pinus) foram avaliados para a produção de mudas de tomilho e sobre o desempenho das plantas em sistema hidropônico. Para ambos os experimentos, o delineamento foi em blocos ao acaso. As mudas provenientes de estaquia foram avaliadas aos 30 dias quanto ao comprimento e massa seca de raízes. Aos 40 dias após o transplante das mudas, as plantas cultivadas em sistema hidropônico foram avaliadas quanto à massa fresca da parte aérea, massa seca da parte aérea e massa seca das raízes. A maior massa seca de raízes foi obtida para as mudas cultivadas em substrato à base de casca de fibra de coco. As mudas com maior comprimento de raízes foram obtidas nas bandejas com 128 e 200 células. As plantas de tomilho provenientes de mudas produzidas em bandejas de 128 células apresentaram maior massa fresca da parte aérea, massa seca da parte aérea e massa seca das raízes.

Effect of Silicon on Growth and Temperature Stress Tolerance of Nephrolepis exaltata ‘Corditas’

Effect of silicon (Si) nutrition on growth and temperature stress tolerance of Nephrolepis exaltata 'Corditas' grown in a soilless substrate was examined. In vitro-grown acclimatized plantlets were transplanted into the pots containing a coir-based substrate. A nutrient solution containing 0, 50, or <TEX>$100mg{\cdot}L^{-1}$</TEX> Si was supplied through a drip-irrigation system. After 5 months of cultiv ation, S i-treated and -untreated p lants were grown at 10, 25, or <TEX>$40{\pm}1^{\circ}C$</TEX> under a 12 h photoperiod with <TEX>$530{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$</TEX> PPFD and 60% RH. After 7 days, chlorophyll content and chlorophyll fluorescence parameters were measured. Silicon nutrition had a negative effect on growth characteristics of N. exaltata 'Corditas'. However, Si-treated plants had more tolerance to temperature stress than the control plants. The Fv/Fm value was not significantly different when the plants were exposed to <TEX>$25^{\circ}C$</TEX>. However, significant difference in Fv/Fm was recorded when plants were exposed to 10 or <TEX>$40^{\circ}C$</TEX>. Thus, Fv/Fm could be used as an indicator of low and high temperature tolerance in ferns. The present study also suggests that application of Si may be used to enhance temperature tolerance of ferns.

Growth of Chrysanthemum Cultivars as Affected by Silicon Source and Application Method

The effect of different silicon (Si) sources and methods of application on the growth of two chrysanthemum cultivars grown in a soilless substrate was investigated. Rooted terminal cuttings of Dendranthema grandiflorum ‘Lemmon Eye’ and ‘Pink Eye’ were transplanted into pots containing a coir-based substrate. A nutrient solution containing 0 or 50 mg?L -1 Si from calcium silicate (CaSiO₃), potassium silicate (K₂SiO₃) or sodium silicate (Na₂SiO₃) was supplied once a day through an ebb-and-flood sub irrigation system. A foliar spray of 0 or 50 mg?L -1 Si was applied twice a week. Cultivar and application method had a significant effect on plant height. Cultivar, application method, and Si source had a significant effect on plant width. Of the three Si sources studied, K₂SiO₃ was found to be the best for the increasing number of flowers, followed by CaSiO₃ and Na2SiO₃. In both the cultivars, sub irrigational supply of Si developed necrotic lesions in the older leaves at the beginning of the flowering stage as compared to the control and foliar spray of Si. Cultivar, application method, Si source, and their interactions had significant influence on leaf tissue concentrations of calcium (Ca), potassium (K), phosphorus (P), magnesium (Mg), sulfur (S), sodium (Na), boron (B), iron (Fe), and zinc (Zn). The addition of Si to the nutrient solution decreased leaf tissue concentrations of Ca, Mg, S, Na, B, Cu, Fe, and Mn in both cultivars. The greatest Si concentration in leaf tissue was found in ‘Lemmon Eye’ (1420 μg?g -1 ) and ‘Pink Eye’ (1683 μg?g-1) when K₂SiO₃ was applied through a sub irrigation system and by foliar spray, respectively.

Silicon supply through the subirrigation system affects growth of three chrysanthemum cultivars

The effect of silicon (Si) treatment on the growth of three chrysanthemum cultivars grown in a soilless substrate was evaluated. Rooted terminal cuttings of Dendranthema grandiflorum ‘Gaya Pink’, ‘Lemmon Tree’, and ‘White Angel’ were transplanted into pots containing a coir-based substrate. A nutrient solution containing 0, 50, or 100 mg·L−1 Si from potassium silicate was supplied once a day through a subirrigation system. Application of Si significantly increased the plant height, stem diameter, number of branches, and chlorophyll content, as compared to the control. Addition of Si at 50 and 100 mg·L−1 into the nutrient solution significantly enhanced number and size of flowers, respectively. When plants were treated with Si necrotic lesions appeared in the older leaves at the beginning of the flowering stage. Concentrations of phosphorus (P), sulfur (S), calcium (Ca), magnesium (Mg), and zinc (Zn) in the leaves increased, while the concentrations of potassium (K), boron (B), copper (Cu), iron (Fe), and manganese (Mn) decreased with the increasing Si concentration in the nutrient solution. Among the cultivars, ‘Lemmon Tree’ contained the greatest Si concentration (1364 μg·g−1) followed by ‘Gaya Pink’ (1158 μg·g−1) and ‘White Angel’ (586 μg·g−1).

Simultaneous Determination of Water Retention Curve and Unsaturated Hydraulic Conductivity of Substrates Using a Steady-state Laboratory Method

For effective irrigation and fertilization management, the knowledge of substrate hydraulic properties is essential. In this study, a steady-state laboratory method was used to determine simultaneously the water retention curve, θ(h), and unsaturated hydraulic conductivity as a function of volumetric water content, K(θ), and water pressure head, K(h), of five substrates used widely in horticulture. The substrates examined were pure peat, 75/25 peat/perlite, 50/50 peat/perlite, 50/50 coir/perlite, and pure perlite. The experimental retention curve results showed that in the case of peat and its mixtures with perlite, there is a hysteresis between drying and wetting branches of the retention curve. Whereas in the case of coir/perlite and perlite, the phenomenon of hysteresis was less pronounced. The increase of perlite proportion in the peat/perlite mixtures led to a decrease of total porosity and water-holding capacity and an increase of air space. Study of the K(θ) and K(h) experimental data showed that the hysteresis phenomenon of K(θ) was negligible compared with the K(h) data for all substrates examined. Within a narrow range of water pressure head (0 to –70 cm H2O) that occurs between two successive irrigations, a sharp decrease of the unsaturated hydraulic conductivity was observed. The comparison of the K(θ) experimental data between the peat-based substrate mixtures and the coir-based substrate mixture showed that for water contents lower than 0.40 m3·m−3, the hydraulic conductivity of the 50/50 coir/perlite mixture was greater. The comparison between experimental water retention curves and predictions using Brooks-Corey and van Genuchten models showed a high correlation (0.992 ≤ R2 ≤ 1) for both models for all substrates examined. On the other hand, in the case of unsaturated hydraulic conductivity, the comparison showed a relatively good correlation (0.951 ≤ R2 ≤ 0.981) for the van Genuchten-Mualem model for all substrates used except perlite and a significant deviation (0.436 ≤ R2 ≤ 0.872) for the Brooks-Corey model for all substrates used.

Development of the Press Extraction Method for Plug Substrate Analysis: Quantitative Relationships Between Solution Extraction Techniques

Substrate electrical conductivity (EC), pH, and nutrient content should be monitored frequently during seedling plug production. Current testing methods are either complicated, unsuited to plug production, or interpretation standards do not exist. This study compares the press extraction (PE) method developed at North Carolina State Univ. with the saturated media extract (SME) method and the 1 substrate: 2 water suspension method (1:2). These solution extraction methods were applied to plug trays containing peat-based germination mix treated with four levels of fertilizer. Two sample sizes of 20 or 60 plug cells were used to determine if the smaller, less destructive sample size would produce satisfactory results. Resulting pH values varied within 0.3 units among methods, but variability in EC and nutrient content was greater. The PE method resulted in the highest values for EC, NH4+-N, NO3--N, K, Ca, and Mg while sample size had little effect on analyses. The three extraction methods were then compared on peat- and coir-based substrates. Within substrates, pH, EC, and nutrients tested were similar for the PE and the SME. The coir extract had a higher pH and much higher levels of K and Na than did the peat extract but was lower in N, P, Ca, and Mg. Overall, fairly strong correlations among testing methods were found, especially between the SME and PE.

563 Development of the Press Extraction Method for Plug Substrate Analysis: Quantitative Relationships Between Solution Extraction Techniques

Methods for extracting growing substrate root-zone solution include the saturated media extract (SME) and the 2 water: 1 substrate (v/v) suspension, neither of which are particularly suited to bedding plant plug systems. We have developed the press extraction method (PEM) as a simple and quick alternative to these methods. The grower simply collects a representative sample of plug trays and presses the top of the plug, collecting the expelled solution. Solution pH and EC can be measured immediately and the sample then sent to an analytical laboratory for nutrient analysis. Initial experiments demonstrated that differing manual pressures did not affect solution chemical properties. The PEM then was compared to the SME and 2:1 methods over a range of fertilizer levels and with peat- and coir-based substrates. Within substrates, pH, EC, and macronutrients were similar between the PEM and the SME. The level of dilution inherent in the 2:1 method resulted in much lower EC and nutrient levels when compared to the other two methods. Further experiments compared the PEM to the SME and 2:1 on plug flats collected from several commercial greenhouses and also those grown in the research greenhouse. The wide range of bedding plant species and fertility levels tested introduced variation needed to develop regression equations and correlations to create quantitative interpretation ranges for the PEM based on previously published sufficiency ranges for the SME and 2:1.

Paclobutrazol Drench Activity in Coir- and Peat-based Root Substrates

Paclobutrazol drench applications of 0, 2, and 4 mg a.i./pot were applied to `Pacino' potted sunflowers (Helianthus annuus L.) and `Red Pigmy' tuberous rooted dahlias (Dahlia variabilis Willd.) grown in substrates containing 50%, 60%, 70%, or 80% (by volume) sphagnum peat or coir, with the remainder being perlite, to study the efficacy of paclobutrazol (Bonzi). Potted sunflower plant height differed significantly for peat- and coir-based substrates, with greater plant height being observed in coir-based substrates. Plant diameter was significantly greater at higher percentages of peat or coir in the substrate at 2 and 4 mg of paclobutrazol. Inflorescence diameter also was significantly decreased as paclobutrazol concentration increased. When the percent of height control from the untreated plants for potted sunflower was compared between coir and peat-based substrates, the percent height reduction was similar for peat- and coir-based substrates at 2 mg of paclobutrazol and height control was greater at 4 mg of paclobutrazol in coir-based substrates. The differences in plant growth observed in peat- and coir-based substrates can be attributed to differences in physical properties of these substrates. Dahlia plant height, diameter, and number of days until anthesis were not influenced by substrate type or percentage. However, dahlia growth was significantly reduced as paclobutrazol concentration increased. Coir-based substrates did not reduce the activity of paclobutrazol drenches compared to peat-based substrates, although to compensate for the greater amount of plant growth in coir-based substrates, paclobutrazol concentrations may need to be increased slightly to achieve a similar plant height as with peat-based substrates.

Fungus Gnat Population Development in Coconut Coir and Sphagnum peat-based Substrates

Coir and peat-based substrates were tested for their effectiveness in inhibiting the development of fungus gnat populations. The first experiment was conducted in July under relatively high temperatures (20 to 35 °C) and a second experiment was conducted in April under relatively low temperatures (20 °C). Euphorbia pulcherrima Willd. ex Klotzch `Freedom' plants were planted into 18-cm-diameter containers filled with substrates containing 80% sphagnum peat or coir, with the remainder being perlite. Half of the containers of each substrate were inoculated with fungus gnat larvae and sealed with either cheesecloth or thrips screen for Expts. 1 and 2, respectively. After 6 and 8 weeks for Expts. 1 and 2, respectively, fungus gnat adult and larval populations were sampled. Adults and larvae were recovered from coir and peat-based substrates in both experiments. In Expt. 1, significantly more adults and larvae were recovered from coir-based than peat-based substrates. In Expt. 2, significantly more adults and larvae were recovered from the peat-based than coir-based substrates. In a third experiment, the peat- and coir-based substrates used in Expts. 1 and 2 were used as well as the Iowa State greenhouse substrate, which contained 40% Sphagnum peat, 40% perlite, and 20% loam (v/v). Helianthus annuus L. `Pacino' seeds were sown into 18-cm-diameter containers filled with the test substrates. Natural infestation was allowed to occur for 6 weeks, after which time potato disks were used to sample the fungus gnat larvae population. Larvae were recovered from all substrates, and there was no significant difference in the number of larvae collected from the three substrates. Based on the results of these experiments, we concluded that coir does not inhibit the development of fungus gnat larvae populations and, when presented with options, fungus gnats will infest coir-based substrates as readily as peat-based substrates.

Growth of Viburnum dentatum and Syringa × prestoniae ‘Donald Wyman’ in Sphagnum Peat and Coir Dust-Based Substrates

Abstract Bare-root viburnum (Viburnum dentatum L.) were grown in 25:0:75, 50:0:50, 75:0:25, 100:0:0, 0:25:75, 0:50:50, 0:75:25, and 0:100:0 peat:coir:sand (by vol) substrates, and Preston lilac (Syringa × prestoniae McKelv. ‘Donald Wyman’) were grown in 25:0:65:10, 50:0:40:10, 75:0:15:10,0:25:65:10, 0:50:40:10, and 0:75:15:10 peat:coir:bark:sand (v/v) substrates over two seasons. After one season of growth, viburnum grown in 25% and 50% coir were taller than plants grown in comparable peat-based substrates, and overall, plants grown in coir-based substrates were taller than plants grown in peat-based substrates. Lilac plants grown in coir-based substrates had similar heights as plants grown in peat-based substrates. After two seasons, viburnum grown in 100% coir had greater plant width than plants grown in 100% peat. No significant difference occurred between plants grown in 25% and 50% peat or coir. No significant difference occurred in shoot fresh mass between viburnum plants grown in coir and peat-based substrates. However, those grown in 50% and 100% coir had greater root fresh mass than those grown in comparable peat-based substrates. Overall, root fresh mass was greater for plants grown in coir-based substrates than peat-based substrates. After two seasons, height and root fresh mass were not significantly different between substrates for lilac. Plant width was greater for plants grown in 25% and 50% coir than for plants grown in 25% or 50% peat. Plants grown in 75% coir had greater shoot fresh mass than plants grown in 75% peat.

Effect of Coir and Sphagnum Peat-based Substrates on Fungus Gnat Populations

Fifteen-centimeter (1700-ml) containers were prepared for this experiment by sealing the drainage holes with insect screen (Hummert International, Earth City, Mo.) that had openings of 0.026 cm × 0.0805 cm. Containers were filled with substrates composed of either a 80% sphagnum peat or 80% coir. The remainder of the substrates was composed of perlite. Rooted cuttings of Euphorbia pulcherrima `Freedom' were planted into the containers and the containers were sealed with the insect screen and plants were allowed to grow and the substrate to age for 2 weeks. Fungus gnat (Bradysia spp.) larvae were collected using potato disks placed on the surface of infested substrates. After 3 days, larvae were collected from the disks, and 10 larvae were added per container. Uninoculated controls were included. After a period of 6 weeks, the adult population was sampled by placing 2.5 × 5.0-cm yellow sticky cards in each container. The larval population was sampled by placing a 4-cm-diameter potato disk on the substrate surface of each container. Fungus gnat larvae and adults were recovered from both sphagnum peat and coir-based substrates. Neither the number of adults nor the number of larvae recovered were significantly different between sphagnum peat and coir-based substrates.