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Marc van Iersel

Ebb- and-flow irrigation is an economically attractive subirrigation method that reduces labor costs and eliminates runoff from greenhouses. The effects of fertilizer concentration on growth of subirrigated pansy (Viola ×wittrockiana Gam.) and the leachate electrical conductivity (EC) and pH were quantified, using two growing media. Leachate EC increased as the EC of the fertilizer solution increased from 0.6 to 3.6 dS·m–1 (70 to 530 mg·L–1 N). The leachate EC was fairly constant over time when the EC of the fertilizer solution was 0.6 dS·m–1, while it increased throughout the experiment at higher fertilizer concentrations. MetroMix 300 leachate consistently had a higher EC than did MetroMix 500. Leachate pH of both growing media was similar throughout the growing season. The pH decreased over time and was lower with higher fertilizer concentrations. Optimal plant growth occurred with a fertilizer EC of 1.2 or 1.8 dS·m–1, and a leachate EC between 1.5 and 4 dS·m–1. Increasing the concentration of the fertilizer solution resulted in increased shoot tissue levels of P and Mn and decreased tissue levels of K, Mg, and Na. The results of this study indicate that pansy is not very sensitive to the EC of the growing medium and can be grown successfully in a closed subirrigation system.

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Richard G. Snyder

Successful greenhouse tomato businesses are able to keep production and quality high while maintaining reasonable cost controls. One way of controlling costs is to use growing media that are locally available in good supply, and therefore of low cost. In Mississippi. as in other states in the southeast, pine bark is an available byproduct resource from the forestry industry; fines (<=95mm diameter) can be used as a growing medium following composting. Rice hulls are a readily available waste product from rice mills, especially in the Mississippi Delta region; these are suitable after being crushed and composted.

In comparison to plants grown in rock wool, yield from plants in pine bark fines, rice hulls, or sand were higher, while quality was not significantly different in the l-crop/year system. In a spring crop, yield and quality were higher from plants in pine bark, rice hulls, and rock wool than from those grown in sand. On a per plant basis, cost for the rock wool system, perlite system (pre-bagged), perlite (bulk), peat moss, sand, composted rice hulls, and pine bark lines are $1.50, $1.00, $0.35, $0.60, $0.24, $0.22 and $0.17, respectively. Pine bark and rice hulls are good choices for growing media for greenhouse tomatoes in areas where they are available.

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Karen L. Panter, Amy M. Briggs, Michael J. Roll, and Steven E. Newman

The objective of this study was to determine which combination of three types of irrigation systems, three fertilization method, and four growing media produced optimum growth of flowering vinca, Catharanthus roseus. Irrigation systems used included ebb-and-fl ood, drip, and pulse; fertilization methods included slow release, prepackaged, and custom mixed; and the four growing media were peatmoss:perlite:vermiculite (1:1:1, by volume), peatmoss:rockwool (1:1, by volume), and 0.6-cm diameter shredded rubber or fabric from waste tires: vermiculite:peatmoss (1:1:2, by volume). Four replications of five plants each were used in each of the 36 treatment combinations. Plants were potted 29 and 30 May 1996 in 10-cm containers, grown for 10 weeks, and harvested 6 Aug. 1996. The drip-irrigated benches were irrigated once per day for 15 s. Pulse-irrigated benches were watered twice per day for 6 s. This resulted in the drip- and pulse-irrigated plants receiving a similar volume of water daily. Ebb-and-fl ood benches were filled once per day with drainage occurring 15 min after filling. Ending plant heights and dry weights indicated that those plants in the prepackaged fertilizer/drip or ebb-and-fl ood irrigation/shredded tire fiber growing medium were comparable to plants grown in the peatmoss:rockwool medium with the same fertilizer and irrigation methods.

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Elsa S. Du Toit, Ilona Von Maltzahn, and Puffy Soundy

Hypoxis hemerocallidea (African potato) is in high demand as a medicinal plant and therefore it is becoming scarce in its natural habitat. Thus, the objective of this study was to investigate the effect of cultivation practices on the active ingredients of the corm over a 12-month period. Different TLC (Thin Layer Chromatography) methods were also investigated when separating the different compounds. Plants were grown under a tunnel in plastic bags containing bark or sand growing media. The planted corms were treated with different fertigation frequencies and harvesting took place during four seasons. The harvested material was sliced, freeze-dried, and ground into a fine powder. Different solvents, namely methanol, acetone, and chloroform (chosen for their polarity) were used to extract the compounds from the ground material. The extracted residues were redissolved and spotted as thin streaks onto TLC plates. The TLC plates were then developed in different solvents and sprayed with different chemicals to bring out the different compounds found in the plant extract. Results on the TLC plates indicated that the amount of residue extracted with different solvents were significantly different. Therefore, TLC methods need to be considered when separating the different compounds. The growing media affected the amount of compounds produced from the corms during the 12-month period. The harvest season also played a role in the amount of active ingredients produced during the year. Therefore, cultivation practices influence the occurrence of active ingredients of H. hemerocallidea.

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Roy A. Larson

Plastic products have revolutionized commercial floriculture. Even plastic flowers have caused a new marketing consideration because they are quite competitive with the marketing of live material. Plastic pots are used widely because they are lightweight, attractive, and relatively inexpensive. Plastic flats and trays have been readily accepted by the consumer, and were instrumental in the development of plug culture. Major components of automatic watering systems are made of plastic, and much of the plumbing practiced in commercial floriculture is done with plastic pipe and fittings. Plastic foams are used in floral arrangements, growing media, and propagation cubes or strips. Plastic is used to make steam-sterilization covers, shading material for the manipulation of both light intensity and photoperiod, and mulches or ground covers to help control weeds. Very large quantities of plastic are used in commercial floriculture, and recent landfill restrictions have necessitated procedures for recycling. Recycling procedures are known, but logistics and economics of recycling have not been resolved completely.

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Ahmed A. Al-Badawy and El-Sayed H. Hussien

In a randomized complete-block design, two separate experiments were conducted to study the response of lead tree Leucaena leucocephala and Hibiscus rosa sinensis to the application of the organic fertilizer, SoilRich. Seedlings of both species were grown in pots filled with growing media containing sandy soil and SoilRich. SoilRich was added at the rates of 0%, 5%, 10%, or 15% (v/v). The obtained results indicated that the application of SoilRich significantly increased plant height, stem elongation, branch number, shoots fresh and dry weights, and enhanced root growth of both Leucaena leucocephala and Hibiscus rosa sinensis. Total nitrogen, phosphorus, and potassium percentages in the shoots were increased in both species as the applied rate of SoilRich was increased. SoilRich treatments increased the water holding capacity of the soil. Moreover, they increased organic matter, total nitrogen, phosphorus, and potassium percentages in the soil. The application of SoilRich at 15% gave the best results.

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GyeSoon Jeong, John M. Brown, and Byoung Ryong Jeong

Trichoderm a spp. are currently being investigated for biological control of soil-borne pathogens and their potential to enhance plant growth and development. The influence of T. harzianum and T. hamatum on growth of 7 bedding plant species was Investigated. Trichoderm a formulated in peat moss and wheat bran, was mixed into germination and growing media at 1 × 106 cfu per gram of medium. Seeds were germinated in plugs and later grown in cellpacks containing a treated and non-treated medium until market stage. Plants were evaluated by measuring height, fresh and dry weight, and number and timing of flowering. Growth enhancement was found in marigold (14.8% dw), petunia (15.5% dw) and tomato (38.2% dw), however, no significant differences were seen in celosia, impatiens, salvi a and vinca. Results suggest that growth enhancement by Trichoderm a is species dependent and that Trichoderm a applied in the plug mix remains-effective through marketing stage.

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Jim E. Wyatt and Marla C. Akridge

Tomato transplants were grown in plastic foam trays floated in nutrient solutions using a system adapted from tobacco transplant growers. Nutrient solutions were compared which contained equivalent amounts of nitrogen and potassium and either 35 or 70 mg·liter-1 phosphorus (P). Growing media tested were 1) Jiffy-Mix*, 2) Pro-Mix®, 3) horticultural vermiculite, or 4) perlite. The higher P rate caused increases in stem diameter, and in plant fresh and dry weight. Plant height, root dry weight and leaf area were not affected by P rate. Transplants grown in Pro-Mix® had significantly greater plant height and stem diameter than other media. Leaf area, and plant fresh and dry weight did not differ between Pro-Mix* and Jiffy-Mix@. Vermiculite and perlite produced smaller tomato transplants and should not be considered when using this production system.

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J. McConnell

A local ground orchid, Spathoglottis plicata Blume, and coconut, Cocos nucifera L., were used in the classroom to teach seed germination. S. plicata, a common orchid on Guam, was utilized to demonstrate the aseptic culture of seeds under non-sterile conditions. The procedures were done in the classroom without a laminar air-flow cabinet. Nonsterile seeds were sown on growing media which were prepared without autoclaving, but by incorporating sodium hypochlorite into the media. Students had a high rate of success in germinating the orchid seeds without contamination by spraying sodium hypochlorite on the seeds. Different stages of coconut seed development were presented to students by simply cutting coconut in half. Unique features and botanical terms of coconut seed development can be taught throughout the year. Teaching materials on seed germination of the two tropical plants are being developed by print-on-demand methods.

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Arthur S. Greathead

The use of disease-free greenhouse-grown plug transplants for the establishment of field plantings of many vegetable crops in the arid west and southwestern regions of the United States has become a very important part of the agricultural system in these areas. The development of effective disease-control programs for use in the greenhouse involves a broad knowledge of production systems, water management, growing media, cultural techniques, etc., as well as knowledge of the discipline of plant pathology. The consultant in this field also must know the people and organizations with whom he is working. His goal is not simply the passing on of technical information, but also assisting in the incorporation of that information into the total growing program. Good communication skills and the development of an atmosphere of trust between all parties concerned are a vital part of the consultant's work.