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J.W. Buxton and Wenwei Jia

The controlled water-table irrigation (CWT) system was evaluated for vegetable seed germination and transplant growth. The system is a modification of capillary mat irrigation except that the mat along one side extends over the edge of the bench into a narrow trough running along the side of the bench. The nutrient solution level in the trough is controlled by a liquid level controller, so it is at a fixed distance below the bench surface. The nutrient solution is drawn by capillarity from the trough upward to the bench surface and then moves by capillarity to the opposite side of the bench. The system automatically maintains a constant air: water ratio in the growing media. Seeds of broccoli, tomato, and pepper were germinated in a 96-cell plug tray and grown to transplanting stage with the CWT system. A factorial experiment consisted of two growing media combined with CWT treatments of 2 and 4 cm. Excellent germination and high-quality seedlings were produced with all treatments. No differences were observed in growth of seedlings at 2 vs. 4 cm or between the two growing media. The CWT system is capable of maintaining a constant uniform water: air ratio in all plug cells on a commercial growing bench. Nutrient solution does not run off the bench. The CWT potentially is an excellent system for the irrigation of vegetable transplants.

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Brian R. Poel and Erik S. Runkle

Supplemental radiation (SR), traditionally provided by high-pressure sodium (HPS) lamps, is recommended for greenhouse production of seedlings during radiation-limiting conditions. Light-emitting diodes (LEDs) have emerged as an appealing alternative to HPS lamps primarily because they can provide SR at improved energy efficiencies, they have longer fixture lifetimes, and the radiation spectrum can be tailored to potentially manipulate plant morphology by targeting radiation absorption of specific photoreceptors. We grew seedlings of three annual bedding plants and two vegetable transplants in greenhouses at 20 °C under a 16-h photoperiod under six SR treatments: five that delivered a photosynthetic photon flux density (PPFD) of 90 μmol·m−2·s–1 from HPS lamps (HPS90) or LEDs [four treatments composed of blue (B; 400–500 nm), red (R; 600–700 nm), far red (FR; 700–800 nm), and/or white LEDs] and one that delivered 10 μmol·m−2·s–1 from HPS (HPS10) lamps as a control with matching photoperiod. The LED treatments, defined by the percentages of B, green (G; 500–600 nm), and R radiation, were B10R90, B45R55, B10G5R85, and B12G20R68 + FR (FR at 12 μmol·m−2·s–1). At transplant, leaf area and seedling height were similar among 90 μmol·m−2·s–1 treatments in all species except snapdragon (Antirrhinum majus), in which seedlings grown under B12G20R68 + FR had 62% greater leaf area than those grown under B45R55 and were 47%, 18%, 38%, and 62% taller than those grown under HPS90, B10R90, B10G5R85, and B45R55, respectively. After transplant and finishing under the same SR treatments, snapdragon flowered on average 7 days earlier under the B12G20R68 + FR treatment than the other LED treatments, whereas geranium (Pelargonium ×hortorum) grown under B45R55 and B12G20R68 + FR flowered 7 to 9 days earlier than those under the B10G5R85 and B10R90 treatments. Seedlings of each species grown under the HPS10 treatment accumulated less dry weight and took longer to flower compared with seedlings under the other SR treatments. We conclude that radiation quality of SR has relatively little effect on seedling growth and subsequent flowering although in some crops, flowering may be earlier when SR includes FR radiation.

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Charles S. Vavrina, N. Kokalis Burrell and J. Kloepper

Bell pepper (Capsicum annuum) seedlings treated with various biological preparations exhibited increased root and shoot growth both in the greenhouse and during subsequent field establishment. Early fruit set and pod development showed signs of possible yield improvement by the treatments, but treatment differences were not apparent at first harvest. Data from subsequent harvests did show yield increases with some preparations. Treatment organisms appeared to activate or induce systemic resistance to bacterial spot (Xanthomonas campestris) infestation though not to the level shown by Actigard (Novartis). Crop/treatment response under soil solarization, fumigation, and compost amended conditions will be discussed.

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John T. Erwin

Seedling stem elongation increased as the difference (DIF) between day (DT) and night (NT) temperatures increased from 10 to 26C (DIF=DT-NT). Stem elongation was primarily dependent on DIF on all crops studied except spring bulb crops. Internode lengths decreased in tomato (68%), watermelon (80%), squash (32%), sweet corn (68%) and snap bean (26%) as the difference between day and night temperatures decreased 12 degrees (C). Cucumber internode length decreased by 84% as DIF decreased 16 degrees (C). The ratio of male to female cucumber flowers decreased from 14 to 1, as DIF decreased 12 degrees (C) from 23 DT/17 NT to 17 DT/26 NT. Stem elongation was very sensitive to cool temperatures during the first 3 hours of the morning. Stem elongation was almost the same if the seedlings were cooled for the first 3 hours of the day versus cooling the plants all day. The interactions between temperature on stem elongation and light quantity and quality, and photoperiod will be discussed. Application of DIF in both northern and southern greenhouses will also be discussed.

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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.

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Wenwei Jia, L.A. Weston and J. Buxton

Tomato and pepper seedlings were grown in six controlled environmental chambers with three different temperature levels (high:24/16°C, medium:20/12°C, and low:16/8°C) and two CO2 levels (1500 ppm and ambient) after cotyledons had unfolded. After 4 weeks, seedlings were planted into 15 cm pots. After 4 weeks, another set were transplanted to the field on 5/13 and arranged with 4 replications in a randomized complete block design. Only temperature treatment had a significant influence on the number of flowers developed in greenhouse experiments. However, for field transplanted seedlings, CO2 enrichment had a significant effect on flower formation and increased total flower numbers and fruit numbers in the early growth stages in field. Temperature also influenced seedling height. In other experiments, cold treatments were given to tomato and pepper seedlings. Seedlings were treated with 13°C temperatures for 0, 1 or 2 weeks after cotyledons unfolded. Results indicate that tomato seedlings with either 1 or 2 weeks of cold treatment had greater dry weight and leaf numbers and larger and more mature flower buds than those given no cold treatment. Pepper seedlings receiving 2 weeks of cold treatment showed similar increases compared to those receiving 0 or 1 weeks of cold treatment. The earliest flower initials were observed microscopically when tomato had only one visible leaf and pepper had 8 or 9 visible leaves. These results indicate that cold treatments should be started as soon as the cotyledons have unfolded to hasten flower formation.

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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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James R. Dunlap, Yin Tung Wang and James L. Carson

Seedling transplants produced for early fall and spring establishment of commercial vegetable crops in the Texas Lower Rio Grande Valley rapidly develop excessive shoot growth if field plantings are delayed. Therefore, several varieties of pepper, watermelon, muskmelon, and tomato transplants were treated at the 2-3 leaf stage by foliar spray with 0, 4, 8, or 12 ppm of the triazole growth retardant, uniconazole. The seedlings were field transplanted 3 weeks later. Total heights taken at the time of transplanting indicated significant varietal differences in responses to the treatments. After 60 days in the field, one of the 5 pepper varieties continued to express retarded growth. However, the uniconazole treatment stimulated early fruiting in 2 of the varieties. Tomato seedlings appeared to overcome the stunting within the first 60 days after transplanting while muskmelon and watermelon remained slightly dwarfed. Additional data on total growth and yield in response to the growth retarding treatments will be presented for each of the vegetable varieties.