Submitted to: The Allium Improvement Newsletter
Publication Type: Government Publication
Publication Acceptance Date: February 10, 2007
Publication Date: December 15, 2007
Citation: Russo, V.M. 2006. Development of greenhouse grown onion transplants and effect of plant density and fertilizer rate on marketable yield. The Allium Improvement Newsletter. 16:13-17. Interpretive Summary: Onion (Allium cepa L.) Can be established in the field from bare root transplants or as transplants produced in a greenhouse. The latter benefit from having intact roots and tops at the time of transplanting. Information is needed to determine how greenhouse grown transplants perform in production systems. Greenhouse grown seedlings of onion cultivars ‘Texas Grano 1015Y' and ‘Candy' were established in the field at 3 densities (70,560, 139,200 and 211,680 plants/ha) and 2 nitrogen fertilizer rates, recommended and 4-times the recommended. At transplanting ‘Candy' seedlings were heavier than ‘Texas Grano 1015Y' seedlings. The amount of N-fertilizer used did not affect yield. As numbers of plants doubled, but not when they tripled, yield increased. Use of the highest planting density is probably not recommended, nor is use of nitrogen fertilizer rate above the recommended. Seedling transplant weight of ‘Candy' was related to the yield that was measured from plants that developed from seedlings. As seedling weight increased subsequent yield decreased. The reason for this is not clear and needs additional research.
Technical Abstract: Greenhouse grown onion (Allium cepa L.) transplants may have potential for use in production systems, but how they respond to cultural practices needs clarification. Seedlings of ‘Candy' and ‘Texas Grano 1015Y' were raised in a greenhouse. ‘Candy' seedlings were heavier than ‘Texas Grano 1015Y' seedlings. Transplants were established in the field at densities of 70,560, 139,200 and 211,680 plants/ha. Plants received two levels of nitrogen (urea). ‘Candy' had a higher marketable yield than ‘Texas Grano 1015Y.' Marketable numbers of bulbs increased with increasing density; yield from the lowest density was least, and the other densities had similar yields. Rate of N-fertilizer had no effect on yield. Transplant fresh and dry weights of ‘Candy' were negatively correlated with numbers of marketable bulbs produced and/or marketable yield. Additional investigation is required to determine why this occurred.