Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 10, 2008
Publication Date: September 17, 2008
Citation: Russo, V.M. 2008. Plant density and N fertilizer rate on yield and nutrient content of onion developed from greenhouse grown transplants. HortScience. 43(6):1759-1764. Interpretive Summary: There are several ways to produce onion (Allium cepa L.) transplants. One way is by greenhouse culture. There is a need to determine the cultural activities that can affect yield of onion plants developed from greenhouse grown transplants. Seedlings of 'Candy,' an intermediate-day plant, and 'Texas Grano 1015 Y,' a short-day plant, were established at densities of 41,000, 82,000 or 124,000 plants/ha**-1 and 100 (recommended) and 400 kg/ha**-1 of nitrogen in mid-March of 2006 and 2007. Yield and nutrient content of bulbs were determined. The recommended level of fertilizer and the highest density appeared to be the best combination to maximize yield. Plant density and fertilizer rate did not affect nutrient content of bulbs. This indicates that additional work is needed to determine the optimal fertilizer requirements for onion developed from greenhouse grown transplants. 'Candy' had higher yields and may be better adapted to the local environmental conditions.
Technical Abstract: Onions (Allium cepa L.) can be established from seed or transplants. The latter planting material can be dormant or actively growing when transplanted to the field. Onion transplants can be produced in a greenhouse, but additional information is needed regarding the cultural requirements for these plants after transplanting. Greenhouse grown transplants of 'Candy', intermediate-day plant, and 'Texas Grano 1015 Y,' short-day plant, were established at densities of 41,000, 82,000 or 124,000 plants/ha**-1 and 100 (recommended) and 400 kg/ha**-1 of nitrogen in mid-March of 2006 and 2007. Nitrogen fertilizer rate did not affect yield; yield increased as density increased, and yield of 'Texas Grano 1015 Y' was higher in 2006 than in 2007. 'Candy' had a higher number of large size bulbs and 'Texas Grano 1015 Y' more small bulbs. Bulb nutrient content was affected only by year with nitrate-N, K, Na and SO4 were higher in 2006 and nitrite-N, Ca, Mg, and PO4 were higher in 2007. Precipitation levels in the two years were different with 2007 being the wetter. This may have contributed to the responses to year and it appears that 'Candy' was better able to respond in a more uniform manner to the changed environmental conditions. For plants developed from greenhouse grown transplants the recommended rate of fertilizer and the highest plant density are beneficial to improved marketable yield.