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Michael R. Evans and David L. Hensley

A biodegradable container made from processed waste poultry feathers was developed, and plant growth was evaluated in plastic, peat, and feather containers. Under uniform irrigation and fertilization, dry shoot weights of `Janie Bright Yellow' marigold (Tagetes patula L.), `Cooler Blush' vinca [Catharanthus roseus (L.) G. Don.] and `Orbit Cardinal' geranium (Pelargonium ×hortorum L.H. Bailey) plants grown in feather containers were higher than for those grown in peat containers, but lower than those grown in plastic containers. Container type did not significantly affect dry shoot weights of `Dazzler Rose Star' impatiens (Impatiens walleriana Hook.f.). `Better Boy' tomato (Lycopersicum esculentum L.) dry shoot weights were similar when grown in peat and feather containers. Feather containers were initially hydrophobic, and several irrigation cycles were required before the feather container walls absorbed water. If allowed to dry, feather containers again became hydrophobic and required several irrigations to reabsorb water from the substrate. Peat containers readily absorbed water from the substrate. Substrate in peat containers dried more rapidly than the substrate in feather containers. Plants grown in peat containers often reached the point of incipient wilting between irrigations, whereas plants grown in feather containers did not. This may have been a factor that resulted in higher dry shoot weights of plants grown in feather containers than in peat containers. Tomato plants grown in feather containers had higher tissue N content than those grown in plastic or peat containers. The availability of additional N from the feather container may also have been a factor that resulted in higher dry shoot weights of plants grown in feather containers than in peat ones. Under non-uniform irrigation and fertilization, dry shoot weights of impatiens and vinca grown in feather containers were significantly higher than those of plants grown in plastic or peat containers. When grown under simulated field conditions, geranium dry shoot weights were significantly higher for plants initially grown in feather containers than for those initially grown in peat containers. Container type did not significantly affect dry shoot weights of vinca when grown under simulated field conditions. As roots readily penetrated the walls of both feather and peat containers, dry root weights of vinca and geranium were not significantly affected by container type when grown under simulated field conditions.

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Timothy A. Prince and Maria S. Cunningham

Lining of shipping cases with low-density polyethylene (PE) greatly reduced moisture loss from packing media and bulbs of Lilium longjlorum Thunb. `Nellie White' during shipping, handling, and case vernalization (CV). Three years of studies showed that use of PE liners accelerated floral sprout emergence above the growing medium, floral bud initiation, and flowering date. Effects of case lining became more pronounced as the initial water content of the spagnum peat packing was lowered. Case lining sometimes increased apical meristem diameters measured immediately after vernalization, or 2 or 4 weeks after bulb planting, but flower bud number was never significantly increased. Root growth during the first 4 weeks after planting was not affected by case lining. Bulb scale and basal plate water contents at planting were greater in lined than nonlined cases and when packed in peat of relatively high moisture content. Handling and vernalization of bulbs in PE-lined cases without a packing medium resulted in similar bulb forcing characteristics as in bulbs held in PE-lined cases packed with sphagnum peat.

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F. Ponton, Y. Piché, S. Parent and M. Caron

The horticultural Boston fern [Nephrolepis exaltata (L.) Schott cv. Verona] was micropropagated in vitro using commercial techniques. Rooted plantlets were transferred into pots containing one of three test substrates made of peat and vermiculite and subsequently inoculated with one of two species of Glomus. Survival of uninoculated control plants growing on a black peat-based mix was less than that on a brown peat-based mix. Vesicular-arbuscular mycorrhizal (VAM) inoculation significantly increased survival on the former, but not the latter, substrate. The growth of roots was enhanced in brown peatmoss, but VAM colonization was faster with black peatmoss. Compared to uninoculated controls growing under the same fertilization regime, inoculated plants had significantly higher frond P and N concentration and also showed better frond and root growth. On a growth-increment basis, our results suggested that the brown peat-based mixed was more suitable for fungal activity and fern growth.

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Juha Heiskanen

Two commercially produced growth media made of light, low humified sphagnum peat, were used to determine how filling into containers affects the particle size distribution and water retention characteristics of peat. It was shown that the filling procedure used broke up the peat particles, resulting in a significant increase in the proportion of particles < 1 mm (g·g-1). Due to the increased proportion of fine particles, the water retention of the peat media increased under wet conditions (-0.1 kPa matric potential), while the air-filled porosity decreased to nearly 0. Also, at matric potentials lower than -0.1 kPa, the reduction in air-filled porosity may restrict aeration and availability of oxygen to roots, thus reducing growth of plants.

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Michael R. Evans, James N. Smith and Raymond A. Cloyd

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.

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F. M. Jeneidi and C. J. Starbuck

The physical characteristics of a container growing medium containing 2 oak sawdust composted with poultry manure: 1 vermiculite: 1 perlite were compared with those of a similar medium containing sphagnum peat rather than compost. Both media were amended with inorganic nutrients based on laboratory analysis to make them nutritionally comparable and with AquaGro wetting agent at 800 g·m–3. Moisture release characteristics of the media were evaluated using tension cups in which desorption at 5, 10, 20, 40, 80, 100, and 160 cm of water was measured. While bulk density of the peat mix (0.129 g·cm–3) was, significantly lower than that of the compost mix (0.157 g·cm–3), total porosity of the peat mix (84%) was significantly greater than that of the compost mix (79%). Air-filled and water-filled porosities of the peat and compost mixes were 18.2% 16.2% and 75.2% 70.5% of container volume, respectively. While the peat mix held more water at tensions between 5 and 20 cm, there was no significant difference between the volumetric water contents of the two media between 20 and 160 cm. Fresh and dry weights of corn plants grown for 3 weeks in compost- and peat-based media were not significantly different.

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Michael Compton and Timothy Zauche

Anaerobic digestion-derived biosolids (ADB) has the potential to become a complete or partial substitute for sphagnum peat in the greenhouse and nursery industry. Bedding plant production being one of the largest segments of the floriculture industry may possess the greatest application for this new organic addendum to soilless media. An experiment was conducted in which geraniums (Pelargonium ×hortorum `Red Elite') were grown in potting mixes formulated with vermiculite and perlite plus various concentrations and combination of anaerobic digestion-derived biosolids (ADB) and sphagnum peat to determine if ADB could be used as a partial or complete replacement for sphagnum peat in soilless horticultural growing media. Plants were grown during June and July 2003–05 in the greenhouse at 75 ± 5 °F and normal light and photoperiod. Plant growth was assessed by measuring the dry weight of stem tissue. Plants were harvested when at least 50% of the total number of plants produced at least one inflorescence. Floriferousness was measured by counting the number of visible inflorescences per plant. Dry weight of plants grown in media containing ADB was greater than those grown in media containing sphagnum peat as the sole organic addendum. Plants grown in media containing ADB were also more floriferous. This study demonstrates that ADB has great potential for use as an organic addendum to horticultural growing media as a partial or complete replacement for sphagnum peat. Use of anaerobic digester-derived biosolids in horticultural growing media is a protected intellectual property and available for license through the WiSys Technology Foundation.

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Nektarios Panayiotis, Tsiotsiopoulou Panayiota and Chronopoulos Ioannis

Four substrates were investigated for their efficacy as roof garden vegetative layers. The substrates comprised a sandy loam soil (S), sandy loam soil amended with urea formaldehyde resin foam (S:F) in a proportion of 60-40 v/v, sandy loam soil amended with peat and perlite (S:P:Per) in a proportion of 50-30-20 v/v and peat amended with urea formaldehyde resin foam (P:F) in a proportion of 60-40 v/v. The substrates were evaluated for their physical and chemical properties and their capacity to sustain growth of Lantana camara L. Physical and chemical evaluation included weight determination at saturation and at field capacity, bulk density determination, water retention, air filled porosity at 40 cm, pH and EC. When compared to the control (S) a weight reduction of 16.8%, 23.9% and 70.3% was obtained at field capacity with S:F, S:P:Per and P:F substrates respectively. Bulk density was reduced by 46%, 43% and 95%, in substrates S:F, S:P:Per and P:F, respectively, compared to the control substrate S. Air-filled porosity at 40 cm was slightly increased for substrate S:F while it was substantially increased for substrate P:F. The pH response between the initiation and the termination of the study was similar for the four substrates. EC decreased in substrates S and S:P:Per but increased in substrates S:F and P:F. Plant growth was monitored as shoot length, shoot number, main shoot diameter and the number of buds and flowers. Substrates S and S:F resulted in similar plant growth, while substrate S:F promoted flowering. Substrate S:P:Per induced slow plant growth during the first 6 months which subsequently increased resulting in a final growth that was satisfactory and comparable to the S and S:F substrates. Substrate P:F did not support sufficient plant growth and its use should be considered only in special cases where reduced weight of the roof garden is imperative.

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Calvin Chong* and Adam Dale

Terminal stem cuttings of seven woody nursery species [boxwood (Buxus sempervirens L. `Green Mountain'), coralberry (Symphoricarpus × chenaultii Rehd. `Hancock'), lilac (Syringa velutina Kom.), Peegee hydrangea (Hydrangea paniculata Siebold. `Grandiflora'), purple-leaf sandcherry (Prunus × cistena N.E. Hansen), Rose-of-Sharon (Hibiscus syriacus L. `Lucy'), and winged spindle-tree (Euonymus alata Thunb.) Siebold. `Compacta')] were rooted under outdoor lath (50% shade) and mist in leached rooting media consisting of 0, 20, 40, 60 and 80% by volume of 2-year-old grape pomace amended in binary mixtures with sphagnum peat, perlite or composted bark. Rooting performance, expressed in terms of percent rooting, mean root number per rooted cutting, and length of the longest root per cutting, was regressed on level of pomace. When there were differences due to amendments, most species rooted better with perlite than with bark and peat, to a lesser degree, due in part to more favourable air-filled porosities with perlite (33% to 42%) than with bark (29% to 37%) or peat (24% to 35%). With boxwood, increasing level of pomace up to ≈60%, especially when mixed with perlite or peat, resulted in substantial increases in rooting percentage, root number and length. All three rooting parameters of winged spindle-tree decreased linearly with increasing level of pomace with perlite or bark. The effect of pomace level on other species varied between these extremes with little or no negative effect on rooting.

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Calvin Chong, R.A. Cline and D.L. Rinker

Four deciduous ornamental shrubs [`Coral Beauty' cotoneaster (Cotoneaster dammeri C.K. Schneid); Tartarian dogwood (Cornus alba L.); `Lynwood' forsythia (Forsythia × intermedia Zab.); `Variegata' weigela (Weigela florida Bunge A.D.C.)] were grown in trickle-fertigated containers. There were eight media consisting of 25% or 50% sphagnum peat or composted pine bark, 25% sand, and the remainder one of two sources of spent mushroom compost; four media with 509″ peat or bark mixed with 50% spent mushroom compost; and a control medium of 10070 pine bark. Initially, higher than desirable salt levels in all compost-amended media were leached quickly (within 2 weeks of planting) and not detrimental to the species tested. Unlike cotoneaster, which showed no difference in growth (shoot dry weight) due to medium, dogwood, forsythia, and weigela grew significantly better in all compost-amended media than in the control. Growth of these three species was 20% greater in peat-based than in bark-based, compost-amended media. Dogwood and forsythia grew slightly more (+8%) with spent mushroom compost based primarily on straw-bedded horse manure than with one based on a blend of straw-bedded horse manure, wheat straw, and hay. The addition of sand (25%) to a mixture of 50% peat or bark and 25 % spent compost produced a medium with minimal compaction.