As early as 1929, university scientists began the quest to determine the ideal age at which to transplant tomatoes (Lycopersicon esculentum Mill.). Investigations have included seedlings of 2 to 15 weeks of age produced in wood, peat, plastic, or Styrofoam containers. Early researchers often omitted descriptions of soil mixes and nutrient regimes, and used a wide variety of container types. Later investigators were inclined to use commercial soilless mixes, well-defined nutrient regimes, and polystyrene trays. Pioneers of transplant age research tended to use plants of 7 weeks and older, whereas work within the past 30 years has concentrated on younger plants. Many researchers drew conclusions after only 1 year of experimentation, while others found that results varied across years. Prior to the 1980s, virtually all studies were initiated and conducted in areas far from the thriving transplant industry established in the southeastern United States. Southern-grown transplants often were not in cluded for comparison, and few studies were implemented using plants grown under commercial conditions. After more than 60 years of transplant age research, it appears that transplants of 2 to 13 weeks can produce comparable yields, depending on the many factors involved in commercial production.
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