Organic Vegetable Transplant Production

in HortScience
Author: V.M. Russo 1
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  • 1 U.S. Department of Agriculture, Agricultural Research Service, South Central Agricultural Research Laboratory, P.O.B. 159, Lane, OK 74555

The efficacy of using potting media and fertilizers that are alternatives to conventional materials to produce vegetable transplants needs clarification. Bell pepper, onion and watermelon seed were sown in Container Mix, Lawn and Garden Soil, and Potting Soil, which can be used for organic production in greenhouse transplant production. The alternative media were amended with a 1× rate of Sea Tea liquid fertilizer. Comparisons were made to a system using a conventional potting medium, Reddi-Earth, fertilized with a half-strength (0.5×) rate of a soluble synthetic fertilizer (Peters). Watermelon, bell pepper and onion seedlings were lifted at 3, 6, and 8 weeks, respectively, and heights and dry weights determined. Watermelon were sufficiently vigorous for transplanting regardless of which medium and fertilizer was used. Bell pepper and onion at the scheduled lifting were sufficiently vigorous only if produced with conventional materials. Additional experiments were designed to determine the reason(s) for the weaker seedlings when the alternative products were used. Seedlings maintained in transplant trays, in which media amended weekly with Sea Tea were required to be held for up to an additional 34 days before being vigorous enough for transplanting. Six-week-old bell pepper, or 8-week-old onion, seedlings were transferred to Reddi-Earth in pots and supplied with Sea Tea or Peters fertilizer. 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 Reddi-Earth and fertilized weekly with Sea Tea at 0.5×, 1×, 2×, or 4× the recommended rate, or the 0.5× rate of Peters. There was a positive linear relationship between seedling height and dry weight for seedlings treated with increasing rates of Sea Tea. Other pepper seed were planted in to Potting Soil, or an organically certified potting medium (Sunshine), and fertilized with a 2× or 4× rate of Sea Tea or a 1×, 2×, or 4× rate of an organic fertilizer (Rocket Fuel), or in Reddi-Earth fertilized with a 0.5× rate of Peters. There was a positive linear relationship between the rate of Rocket Fuel and heights and dry weights of bell pepper seedlings. However, even at the highest rate seedlings were not equivalent to those produced with conventional practices. Plants treated with the 4× rate of Sea Tea were similar to those produced using conventional materials. Use of Sunshine potting medium and the 4× rate of Sea Tea will produce bell pepper seedlings equivalent in height and dry weight to those produced using conventional materials. The 4× rate of Rocket Fuel used in Sunshine potting medium will produce adequate bell pepper seedlings. The original poor showing of seedlings in the alternative potting media appears to be due to fertilization with Sea Tea at a rate that does not adequately support seedling development.

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