COMPARISON OF CABBAGE SEEDLING GROWTH IN 4 TRANSPLANT PRODUCTION SYSTEMS

''Float-bed'' (FB) is a simple hydroponic system used by the tobacco i ndustry for transplant production, ''Ebb-and-flood'' (EF is a modified FB system with periodic draining of the bed to limit water availabili ty and control plant growth. Field-bed cabbage (Brassica oleracea L. g p. Capitata) transplant production was compared with FB, EF, and overh ead-irrigated plug-tray greenhouse systems. Plants were produced in Ma y and June and transplanted in a field near Blacksburg, Va., in June a nd July of 1994 and 1995, respectively. Beds for FB and EF production consisted of galvanized metal troughs (3.3 x 0.8 x 0.3 m) lined with a double layer of 0.075-mm-thick black plastic film. In 1994, both EF a nd FB seedlings were not hardened before transplanting, were severely stressed after transplanting, and had higher seedling mortality compar ed with plants from other systems. Plug-tray transplants showed the gr eatest increase in leaf area following transplanting and matured earli er than seedlings produced in other systems. In 1995, EF- and FB-grown cabbage plants were hardened by withholding water before transplantin g, and seedlings had greater fresh mass and leaf area than plug-tray o r field-bed seedlings 3.5 weeks after transplanting. Less succulent ca bbage 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 gr owth, and increased oxygen concentration in the root zone. Both EF and FB systems are suitable for cabbage transplant production.