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Substrates and Fertilizers for Organic Vegetable Transplant Production

Organically produced vegetable and herb transplants represent an important commodity both for direct retail sales to consumers as well as for starter plants for organically grown field crops. Many organic growers plant seeds for transplants or plugs that grow for at least six weeks indoors. This allows field growers to start the growing season early and have more control over planting dates. Plants grown from transplants or plugs allow growers to have an earlier start on the growing season compared to broadcast seeded crops.

Fertility management of transplants differs from that of field-grown crops. Transplants are often grown in small containers and in substrates with low nutrient holding capacity. The reservoir of nutrients is much smaller than it would be in the field, and available nutrients are easily lost due to due to typical irrigation practices. Many transplants are grown for only six to eight weeks, but organic fertilizers typically have slow release rates. This is particularly true in cool greenhouses where microbial activity in substrates may be minimal. For these reasons, growers have found managing organic fertility to be one of the greatest challenges in organic greenhouse production.

With growing interest in organic and sustainable production methods we are seeing interest and increased questions about the use of organic substrates and fertilizers in greenhouse container production. Vermicompost is one the materials that has received a lot of public attention. Vermicompost is the end product of the process whereby worms feed on slowly decomposing materials in a controlled environment to produce a nutrient-rich soil amendment. The worms facilitate an enhanced decomposition process by physically degrading the feedstock and stimulating microbial activity. Worms secrete mucus which enriches the moisture and carbon content of the feedstock enriching the associated microbe community. As worms digest the feedstock physical degradation of particles from gut their gut muscles as well as their associated microbes facilitate decomposition. This improves the structure and the nutrient availability of the final product. Due to the fact that vermicompost is a further processed form of the feedstock than traditional compost, nutrient levels are higher and the plant availability is greater. However, information is lacking on the use of vermicompost as fertilizer/substrate component for commercial production of vegetable transplants.

The objective of this project, funded by a Natural Resources Conservation Service – Conservation Innovation Grant is to use a series of on-campus based research trials and work with commercial producers to develop strategies for successful organic transplant production with a focus on use of vermicompost and other organic fertilizer and substrate amendments. Further, we seek to determine if organic- and vermicompost-based fertility programs are effective at reducing nutrient runoff and determining factors necessary for success with vermicompost. Below are resources developed as part of this project.

Organic Fertilizers and Substrates

Vermicompost

Funding for this project was provided by a Natural Resources Conservation Service – Conservation Innovation Grant

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