Optimizing substrates, composts, and fertilizer additions for organic transplant production

Optimizing substrates, composts, and fertilizer additions for organic transplant production

Summary

Conventional and organic potting mixes were tested to compare effects on seed germination and seedling growth of tomato. Materials tested showed variation in chemical composition with time and batch indicating a need to conduct nutrient analyses on substrates prior to use. Germination was sometimes reduced in media containing higher quantities of organic amendments emphasizing the need to optimize germination conditions through careful watering and the use of vermiculite to cover seeds. While a portion of transplant nutrition can be provided through pre-plant incorporation of organic fertilizers into potting media, all media tested would require additions of soluble fertilizer to provide complete nutrition.

Objectives/Performance Targets

The goal of this study was to provide guidance for growers in terms of efficient and cost-effective combinations of ingredients for an organic growing media and the period of time over which these mixes should be able to support seedling growth without the costly addition of soluble organic fertilizer. Various organic amendments were examined in terms of their effectiveness for seedling production and in terms of the period in which mineral nutrition was provided to the plant by that particular amendment.

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