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Erin James and Marc van Iersel

The negative effects of nutrient runoff on the environment has come more to the forefront of greenhouse issues in the past few years. Alternative irrigation systems that reduce or eliminate runoff that are widely used in Europe have not yet gained much popularity in the southeastern United States, in part due to a lack of available information on their use. One such system is ebb-and-fl ow, which is a completely closed recirculating system, having no runoff whatsoever. In order to learn more about optimum growing practices using the ebb-and-fl ow system for bedding plants, marigolds and sunflowers were grown under a variety of conditions. After a 6-week period, pH of growing media of both marigolds and sunflowers decreased by 1, while EC increased by ≈1 dS/m. There were also significant differences in EC due to the different media types. The soilless medium with the highest percentage of vermiculite and lowest percentage of pine bark had the highest EC. Different types of fertilizer and fertilizer rates will be discussed, as well as interactions between fertilizer and media.

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Jeffrey M. Hamilton and Jorge M. Fonseca

salinity ( Shannon and Grieve, 1999 ). A demonstration that vegetable nutrition can be maintained in an ebb and flow irrigation (EFI) water recycling system within a controlled environment would suggest the value of recycling irrigation water. In addition

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Matthew W. Kent and David Wm. Reed

Greenhouse cultural methods must minimize runoff to keep pace with environmental regulation aimed at protecting water resources. Two experiments were designed to investigate the effect of N fertilization rate on New Guinea impatiens (Impatiens ×hawkeri) and peace lily (Spathiphyllum Schott) in an ebb-and-flow subirrigation system. Maximum growth response for impatiens was centered around 8 mm N levels as measured by root and shoot fresh and dry weight, height, leaf number, leaf area, and chlorophyll concentration. For peace lily, growth peaked at about 10 mm N. Growing medium was divided into three equal layers: top, middle, and bottom. Root distribution favored the middle and bottom layers, and the relative distribution of roots was consistent as N level increased. EC remained low in middle and bottom layers at N concentrations below 10 mm, but increased significantly for all layers at levels above 10 mm. The EC for the top layer was 2 to 5 times higher than in the middle or bottom layers at all N levels. Increased nitrate concentration paralleled increased EC, while pH decreased as N concentration increased for impatiens and peace lily.

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Trisha Blessington Haley and David Wm. Reed

Two experiments were conducted to investigate the effect of K fertilizer rates on growth of New Guinea impatiens (Impatiens Hawkeri Bull.), vinca (Catharanthus roseus (L.) G. Don) and petunia (Petunia ×hybrida Hort. Vilm.-Andr.) in a recirculating subirrigation system. Based on a variety of growth parameters, a broad range of K concentrations allowed maximum growth, notably 1 to 6 mM for New Guinea impatiens `Ovation Salmon Pink Swirl', 2 mm for New Guinea impatiens `Cameo' and `Illusion', 2 to 8 mm for vinca `Pacifica Apricot', and 2 to 16 mm for petunia `Trailing Wave Misty Lilac'. Thus, the lowest concentration that allowed maximum growth was 1 to 2 mm K. A third experiment compared the optimum K concentration and K balance of vinca grown with recirculating subirrigation versus top-watering. Based on a variety of growth parameters of vinca `Pacifica Red', the lowest concentration that allowed maximum growth was 2 mm K with recirculating subirrigation and 4 mm K with top-watering. The K balance demonstrated that subirrigated plants were twice as efficient in K use compared to the top-watered plants. Leachate loss was the major contributor to inefficiency in top-watered plants. Electrical conductivity (EC) of the growing medium remained below the recommended level of 1.2 dS·m-1 in both irrigation methods at K concentrations of 16 mm and below in the bottom layer and 8 mm and below in the middle layer. In the top layer of the growing medium, EC was above the recommended level at all K concentrations tested in subirrigation at all concentrations, and in top-watering at 16 mm and above.

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Marsha Ann Bower, David H. Trinklein, and John M. Brown

Recent trends in greenhouse container production suggest using ebb and flow irrigation for water conservation and pollution control. A major problem in this system is management of soil borne pathogens. Some species of Trichoderma, a beneficial fungi, are known to control Pythium and Phytopthora in container production. This study investigates the potential of applying a Trichoderma conidial spore suspension in an ebb and flow irrigation system. Trichoderma conidia were collected from culture and placed in 101 l stock solution tanks at 10-2 and 10-4 colony forming units (CFU) per ml. Six inch container grown Dendranthema grandiflora `Delano', were irrigated as needed. To determine Trichoderma density in the root environment, soil samples were acquired from the container at 7 day intervals. Results showed that initial population densities of 10-4 CFU/ml were required to achieve adequate container populations to control disease after one irrigation. This study successfully demonstrated that Trichoderma could be dispersed through irrigation water into container plants in an ebb and flow system.

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Joyce G. Latimer and Ronald D. Oetting

`Sunny' tomato (Lycopersicon esculentum Mill.), `Black Beauty' eggplant (Solanum melongena var. esculentum L. Nees.), or `Sugar Baby' watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] were nontreated, subjected to brushing (20 strokes twice daily) or drought conditioning (2 hours daily wilt), or maintained undisturbed using ebb-and-flow irrigation. One week after brushing or drought conditioning, plants were inoculated with western flower thrips (Frankliniella occidentalis Pergande) or green peach aphid (Myzus persicae Sulzer). Brushing and drought conditioning reduced plant height and shoot dry weight of all crops. Brushing of all three species generally reduced the number of thrips, as indicated by number of feeding scars or percent leaf area damaged. Drought conditioning did not affect thrips populations consistently. Undisturbed plants grown with ebb-and-flow irrigation exhibited the greatest damage from thrips. Brushing reduced the number of aphids on tomato relative to the nontreated controls. Drought did not reduce aphid populations consistently on any crop. Brushing for height control may be advantageous in an integrated pest-management program to control aphids and thrips.

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Charles S. Vavrina and George Hochmuth

`Allstar” tomatoes raised from seed in Todd™ containerized transplant trays were treated with 1/4 strength Hoagland's solution modified to supply 0, 15, 30, 45, 60, or 75 mg·l-1 N daily. Nutrient application was achieved via ebb and flow irrigation. N was supplied as ammonium nitrate. Tissue sample values for elements tested, excluding N, were essentially adequate for all treatments at transplanting (6 weeks after seeding). Visible transplant differences in the plant house did not translate to significant yield differences in the field when rates of 30 mg·l-1 or greater were used in either spring or fall plantings in FL. A similar trial shipped to PA showed that 75 mg·l-1 in the plant house resulted in the greatest early field yields, but 45 mg·l-1 produced the greatest overall yield.

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E. Jay Holcomb, Silvia Gamez, David Beattie, and George C. Elliott

Ebb-and-flow irrigation reduced water and fertilizer use by ≈ 40% when compared to overhead hand-watering by hose in the production of Hedera helix. In contrast, water and fertilizer use were not significantly different between ebb-and-flow and drip irrigation systems in the production of Asiatic hybrid lilies. Adequate growth of Hedera helix `Baltica' was obtained with 50 mg N/liter of 20-10-20 (20N-4.4-16.6K) or 20-19-18 (20N-8.4P-14.9K). Also, good market-quality hybrid lilies were produced with 75 mg N/liter of 20-19-18 (20N-8.4P-14.9K), 16-4-12 (16N-1.8P-10K), 20-0-20 (20N-0P-16.6K), and 20-10-20 (20N-4.4P-16.6K).

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Joyce G. Latimer and Ronald D. Oetting

During greenhouse production in Spring 1995, conditioning treatments were applied to columbine (Aquilegia×hybrida Sims `McKana Giants'), New Guinea impatiens (Impatiens hawkeri Bull. `Antares'), marigold (Tagetes erecta L. `Little Devil Mix') and ageratum (Ageratum houstonianum Mill. `Blue Puffs') plants. Treatments included: mechanical conditioning (brushing 40 strokes twice daily); moisture stress conditioning (MSC) (wilting for ≈2 hours per day); undisturbed ebb-and-flow irrigation; overhead irrigation; high (500 mg·L-1 N) or low (50 mg·L-1 N) 3×/week N fertilizer regimes; daminozide (5000 mg·L-1); or paclobutrazol (30, 45, or 180 mg·L-1). One week after initiation of treatments, individual plants in separate greenhouses were inoculated with two adult green peach aphids (Myzus persicae Sulzer) or five two-spotted spider mites (Tetranychus urticae Koch). A natural infestation of western flower thrips (Frankliniella occidentalis Pergande) in the mite-inoculated greenhouse provided an additional insect treatment. Brushing was the only treatment that consistently reduced thrips and mite populations. Aphid populations were lower on low-N than on high-N plants, but thrips and mite populations were not consistently affected by plant fertilization. Moisture stress conditioning tended to increase aphid populations on New Guinea impatiens and marigold, but had little effect on spider mite or thrips populations. Ebb-and-flow irrigation reduced the mite population on ageratum relative to that on overhead irrigated (control) plants. Plant growth regulators did not consistently affect pest populations. Chemical names used: butane-dioic acid mono(2,2-dimethylhydrazide) (daminozide); β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-1-ethanol (paclobutrazol).

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Puffy Soundy, Daniel J. Cantliffe, George J. Hochmuth, and Peter J. Stoffella

Although floatation irrigation has numerous advantages for vegetable transplant production, including improved seedling health, lettuce (Lactuca sativa L.) transplants grown with floatation (ebb and flow) irrigation can have poor root systems. Floatation fertigation of `South Bay' transplants with K at 15, 30, 45, or 60 mg·L-1 K applied every 2 to 4 days, increased fresh and dry root weight at 28 days. Higher K (24 mg·kg-1) in the medium did not affect root weight. Fresh and dry shoot weight, leaf area, relative shoot ratio (RSR), relative growth rate (RGR), leaf weight ratio (LMR), and root weight ratio (RMR) were unaffected by applied K, regardless of the initial K concentration in the medium. Available K in a vermiculite-containing medium may have supplied all the K required. When 60 was compared with 100 mg·L-1 N at various levels of K, the applied K again did not influence dry root weight; however, at 100 mg·L-1 N, root weight was reduced as compared with 60 mg·L-1 N, regardless of the level of applied K. In a field experiment, pretransplant K had no effect on growth. Transplants grown with no added K in a peat + vermiculite mix with at least 24 mg·L-1 water-extractable K produced yields equivalent to transplants supplied with 15, 30, 45, or 60 mg·L-1 K via floatation irrigation.