Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2004
Publication Date: 6/15/2005
Citation: Russo, V.M. 2005. Organic vegetable transplant production. HortScience. 40:623-628.
Interpretive Summary: It is not clear if organic practices can be used to produce vigorous vegetable seedlings. A study was conducted where bell pepper, onion and watermelon seedlings were grown using organic and conventional practices. Only watermelon seedlings were ready on time for transplanting. The other crops did not produce vigorous seedlings using organic practices, but did under conventional management. Other combinations of organic production practices were tested using bell pepper and compared to conventional practices. Organic fertilizer level was varied and added to organic fertilizers to support plant development in transplant trays. It was determined that if the rate of 'Sea Tea', an organic fertilizer, was applied at three to four times the label rate to 'Sunshine' organic potting medium then seedlings of bell peppers produced would be as vigorous as those produced by methods using synthetic fertilizers and a conventional potting medium.
Technical Abstract: Bell pepper, onion and watermelon seedlings were produced in 3 organic (Lawn and Garden Soil, Potting Soil, Container Mix), and a conventional (Reddi-Earth), potting media in a greenhouse. Organic media were amended with a 1-fold rate of an organic fertilizer (Sea Tea) and in 'Reddi-Earth' with a 0.5-fold rate of a soluble conventional fertilizer (Peters). Watermelon, bell pepper and onion seedlings were lifted at 3, 6 and 8 weeks, and heights and dry weights determined. Watermelon were ready for transplanting regardless of how produced. Bell pepper and onion had sufficient vigor only if produced with conventional practices. Additional experiments were designed to determine the reason for the weaker seedlings. Six week old bell pepper, or 8-week-old onions, were transferred to 'Reddi-Earth' in pots and supplied with Sea Tea or Peters. Bell pepper treated with Peters were taller and heavier, but onions plants were similar in height and weight regardless of fertilizer used. Other pepper seed were planted in to 'Reddi-Earth' and fertilized with Sea Tea at 0.5-, 1-, 2-, or 4-fold the recommended rate, or at 0.5-fold rate of Peters. There was a linear relationship between seedling height and dry weight for plants treated with an increasing Sea Tea rate. Other pepper seed were planted in to 'Potting Soil', or another organic potting medium (Sunshine), and fertilized with a 2- or 4-fold rate of Sea Tea, or a 1-, 2- or 4-fold rate of another organic fertilizer (Rocket Fuel), or in to 'Reddi-Earth' fertilized with a 0.5-fold rate of Peters. There was a positive linear relationship between Rocket Fuel rate and heights and dry weights of bell pepper seedlings. Plants treated with a 4-fold rate of Sea Tea were similar to those produced using conventional practices. There is a fully organic mixture of potting medium ('Sunshine') and fertilizer (4-fold Sea Tea) that can be used to produce seedlings that are equivalent to those produced using conventional practices.