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  • Author or Editor: Zhengxing Shen x
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“Float-bed” (FB) is a simple hydroponic system used by the tobacco industry for transplant production. “Ebb-and-flood” (EF) is a modified FB system with periodic draining of the bed to limit water availability and control plant growth. Field-bed cabbage (Brassica oleracea L. gp. Capitata) transplant production was compared with FB, EF, and overhead-irrigated plug-tray greenhouse systems. Plants were produced in May and June and transplanted in a field near Blacksburg, Va., in June and July of 1994 and 1995, respectively. Beds for FB and EF production consisted of galvanized metal troughs (3.3 × 0.8 × 0.3 m) lined with a double layer of 0.075-mm-thick black plastic film. In 1994, both EF and FB seedlings were not hardened before transplanting, were severely stressed after transplanting, and had higher seedling mortality compared with plants from other systems. Plug-tray transplants showed the greatest increase in leaf area following transplanting and matured earlier than seedlings produced in other systems. In 1995, EF- and FB-grown cabbage plants were hardened by withholding water before transplanting, and seedlings had greater fresh mass and leaf area than plug-tray or field-bed seedlings 3.5 weeks after transplanting. Less succulent cabbage transplants were grown in EF and FB systems containing 66 mg·L-1 N (40% by nitrate) and 83 mg·L-1 K. Compared with the FB system, the EF system allowed control of water availability, which slowed plant growth, and increased oxygen concentration in the root zone. Both EF and FB systems are suitable for cabbage transplant production.

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An open-market window has been identified in Virginia for fall broccoli (Brassica oleracea var. italica). Vegetable producers using plasticulture systems can capitalize on this opportunity by growing broccoli as a second crop after summer vegetables. The objective of this project was to evaluate suitability of two broccoli cultivars, Everest and Gypsy, for the fall production of large single-heads (>6 inches in diameter) for the fresh market. Planting density and rate of nitrogen (N) fertilizer (25, 60, and 100 lb/acre N) effects on yield characteristics were evaluated in a plasticulture system during a 3-year study (2003–05) conducted with broccoli transplants at the Virginia Polytechnic Institute and State University Kentland Agricultural Research Farm near Blacksburg, VA. The percentage of large heads was cultivar, plant density, and N rate dependent. The midseason ‘Gypsy’ produced significantly higher total yield and head weight compared with the early-season ‘Everest’. The optimum density to maximize floret production per area was 12,500 plants/acre and a supplemental N rate of 100 lb/acre. This N rate significantly (P < 0.002) improved marketable yield, large head yield, and leaf N accumulation compared with the lower rates. The data indicate that the feasibility of growing fall broccoli using a plasticulture system depends on the number of large heads produced for the fresh market. This in turn will depend on the choice of cultivar, stand establishment, and the requirement for supplemental N fertilizer over the residual level available in the soil after the first crop.

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Sweet corn (Zea mays L.) cultivars containing the shrunken-2 (sh2 ) gene have superior kernel quality but often germinate poorly and display poor seedling vigor. The transplanting of sh2 sweet corn was investigated as a method to improve stand establishment and hasten maturity. Three-week-old plants (sh2 cv. Krispy King) were raised in 200-cell polystyrene trays in either plug-trays (PT), float beds (FB), or ebb-and-flood (EF) production systems and compared with direct-seeded (DS) controls for transplant quality, successful establishment, and early harvest. In 1994, when plants were established in early June, PT plants matured 1 week earlier than DS and FB plants, which had similar mean times to harvest. In 1995, when field planting occurred in July, all plants flowered prematurely when only 60 cm tall. In 1996, the experiment was begun in early May, and survival of all transplants was >85% vs. 54% for DS plants. In 1996, transplants matured 10 to 13 days earlier than DS plants, however, >90% of DS plants produced marketable ears vs. 63%, 49%, and 44% of EF, FB, and PT plants, respectively. The DS plants were also taller with better root development than transplants in all years. Transplants produced smaller, lower-quality ears than did DS plants, thus nullifying the benefits of greater plant populations and earlier maturity. The EF system produced high-quality seedlings because of the greater control of water availability during seedling development. In some areas, the increased value of early sh2 sweet corn may be worth the additional cost of transplanting and greater percentage of unmarketable ears.

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