Evaluating the soil block technique for organic vegetable transplant production

Project Overview

Project Type: Graduate Student
Funds awarded in 2021: $14,926.00
Projected End Date: 09/30/2023
Grant Recipient: Iowa State University
Region: North Central
State: Iowa
Graduate Student:
Faculty Advisor:
Dr. Ajay Nair
Department of Horticulture, Iowa State University


  • Vegetables: cucurbits, peppers


  • Crop Production: greenhouses, transplants
  • Education and Training: demonstration, extension, technical assistance, workshop
  • Production Systems: organic agriculture
  • Soil Management: soil analysis, soil chemistry, soil physics

    Proposal abstract:

    Evaluating the soil block technique for organic vegetable transplant production

    Proper transplant production is an important part of a successful vegetable operation, ensuring better field establishment, increased yields, and higher profitability for farmers. Many organic vegetable farmers in the North Central region employ the soil block method for transplant production, following anecdotal evidence that this alternative technique improves root development of seedlings through air pruning and an increase in root volume, but there is limited scientific research evaluating these claims. Furthermore, much research has been conducted on specific recipes and components of organic media for vegetable transplant production, but less is known about commercially available products which are commonly used by organic farmers. This project aims to address these issues by scientifically evaluating the growth parameters and root system architecture of organic vegetable transplants grown with the soil block technique, in plastic flats, and with five commercially available organic media. The experiment will be conducted at the Iowa State University Horticulture Greenhouse over the course of seven weeks with organic tomato seedlings. On three occasions data will be collected on plant height, stem diameter, and chlorophyll leaf content of seedlings in each treatment. On each occasion four representative seedlings will be destructively sampled to determine root to shoot ratio. Final samples will be analyzed with the WinRhizoTM software for root system architecture characteristics.

    As a result of this project and the output activities farmers will increase knowledge and awareness of the soil block method, successful organic transplant production practices, and regionally available organic media options. Farmers will also build skills in transplant production and with the soil block technique. By employing the new knowledge and skills, farmers will improve their transplant production, improving yields and farm profitability. Farmers will also have scientific knowledge to make decisions when purchasing organic media, including a consideration of regionally produced organic media. A targeted outreach effort focused on beginning farmers will enhance their relationship to extension services, offering guidance for the future and opportunities for research collaboration. These outputs will be evaluated through follow up interviews with workshop participants.

    Publication of extension articles, a journal article, and a thesis chapter will increase scientific understanding of the soil block method and organic media options, spurring more research for organic methods. The success of this will be evaluated by the number of downloads and citations of the articles.

    Project objectives from proposal:

    Demonstration workshops will be held at the Iowa State Horticulture Greenhouses and during on-farm extension visits. The developed curriculum will increase farmer’s knowledge of successful organic vegetable transplant production methods, the availability of good quality organic media, and increase awareness of the soil block technique as an alternative technique. In the workshop farmers will improve their organic transplant production skills, including appropriate fertilization, watering, and compaction of cells. This will lead to the action outcome of farmers adopting more successful production practices for transplants. These learning and action outcomes will be evaluated through follow up interviews with workshop attendees.

    Outreach specifically targeted at beginning farmers will improve extension education for this historically under-served group, allowing for future on-farm problem solving and collaboration. This project will also spur further research on organic transplant production as more questions arise from collaboration with farmers and the results of the experiment. The project results will be printed in extension publications, published as an article in a scientific journal, and be a chapter in the graduate student’s thesis. These publications will lead to citations from other researchers and a continued increase in knowledge, awareness, and skill development of good organic transplant production practices. A recorded video of the soil block technique will also be made available online to increase learning opportunities for those not able to attend the in-person demonstration workshop, again increasing skill building and knowledge of organic growers.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.