FACTORS AFFECTING EARLY FIELD GROWTH OF FLUE-CURED TOBACCO TRANSPLANTS PRODUCED IN THE FLOAT SYSTEM

Abstract

Observations by growers and county extension agents indicate that early-season field growth of flue-cured tobacco transplants produced in float greenhouses is sometimes slower than that of transplants produced in outside plantbeds (seedbeds). Experiments were conducted in 1995 and 1996 to evaluate possible differences in early field growth of shoots and roots of flue-cured tobacco transplants produced by each method. Treatments included seeding two weeks early, addition of N and/or P to the float water 10 days before transplanting, replacement of the fertilized water with tap water 10 days before transplanting, and severe clipping (0.5 cm above the buds) one day before transplanting. Normally-produced transplants of both transplant sources also received a high P, water-soluble fertilizer in the transplant water. The control treatment consisted of normal recommended practices for greenhouse and field transplants. High weather-related transplant mortality occurred with greenhouse transplants at one location in 1995 and with plantbed transplants that received the transplant water fertilizer at one location in 1996. Root mass of plantbed control plants was greater than that of greenhouse control plants at each sampling date (2, 4 and 6 weeks after transplanting) in 1995 and at the first sampling date in 1996. Shoot mass of plantbed control plants generally was greater than that of greenhouse control plants at the second and third sampling dates in three of four experiments. The seeding date and nutritional treatments imposed on seedlings in the greenhouse did not consistently or substantially influence early growth of roots or shoots in the field, but severe clipping one day before transplanting generally reduced shoot growth and delayed flowering of greenhouse transplants. Root and shoot weights, stem length, and flowering date of both transplants sources were sometimes improved by the transplant water fertilizer, but the effects generally were more consistent for transplants produced in the float greenhouse than for those produced in conventional plantbeds. Cured leaf yields of greenhouse transplants generally were lower than those of plantbed plants under the dry, windy conditions in 1995, and the effect was more pronounced for severely clipped transplants. Reducing sugar and total alkaloid concentrations in cured leaves were not significantly affected by plant source or any treatment imposed on greenhouse seedlings. Overall, early season growth of greenhouse seedlings was slower than that of plantbed seedlings and management treatments imposed in the greenhouse or field had little consistent effect on seedling growth of plantbed or greenhouse seedlings.