Vermicompost-Based Media to Enhance Organic Vegetable Seedling Vigor, Yield, Crop Quality and Grower Profitability

Non-Technical Summary: There is strong need for renewable, locally-sourced materials to replace peat-based media for sustainable production of organic vegetable seedlings, especially in the Tropics. Properly produced vermicompost has several advantages as a seedling medium: it is relatively high in nitrate, which can enhance seedling germination and stimulate seedling growth; it has high microbial activity that may protect against some pests; and it has little or no phytotoxicity. However, there is no on-farm research to evaluate the relationship of seedling quality with pest resistance, yield and post harvest crop quality under certified organic conditions. Also, vermicompost is relatively expensive to produce and there is strong need to evaluate economic benefits associated with the costs of partial or complete replacement of peat with vermicompost. The 3-year project proposed herein will engage farmers, researchers, and industry professionals to address these deficiencies through a series of on-farm trials and educational activities to achieve the following objectives: 1. Evaluate quality, field performance and post-harvest quality of produce from seedlings grown in vermicompost-based media in organic production systems. 2. Quantify the impact of vermicompost as an organic seedling medium on vegetable transplant health and pest tolerance. 3. Enhance the efficiency and profitability of Hawaii's approximately 150 organic growers through increased vegetable yield and plant health on their farms using vermicompost. Outcomes of this work will directly address OREI goals through innovative use of local resources to enhance production stability and profitability of organic growers, particularly in the Tropics. <P> Approach: Locally produced vermicomposts will be obtained from commercial producers on the island on O'ahu. Compost will evaluated for chemical, biological, and physical characteristics including pathogen load, total microbial biomass, mineral nutrient content, and water holding capacity. Locally adapted tomato and lettuce varieties will be greenhouse grown on two commercial organic farms and at the long-term organic plots at the University of Hawaii. The methodology for seedling production will be the same across location. Seedlings will be grown for 4-6 weeks in a peat-based media amended with locally produced vermicompost of known qualities at rates of 0, 25, 50, 75, and 100% (v/v) with no additional fertilizer amendments. Control treatments will include 100% organic peat-based mix (OMRI registered peat + perlite) with no supplemental fertilizer and 100% organic peat-based mix with organic liquid fertilizer applied weekly. Seedlings will be grown in standard seedling trays, and trays will be blocked for location within the greenhouse. When seedlings are ready for transplanting, a total of at least 100 seedlings (25 from each of 4 replications) will be evaluated for quality using height, weight, dry matter and mineral content as primary indices. The remainder of the seedlings at each site will be planted to the field. The six treatments (0, 25, 50, 75, 100% vermicompost without supplemental fertilizer, and 0% compost with supplemental fertilizer) will be arranged in a randomized complete block design (RCBD). Plots will be managed in compliance with the National Organic Program according to the standard practice of each farm. The crop will be harvested at market maturity. For tomato, physical measures to be taken include total weight, marketable yield, fruit number per plant, fruit size, and moisture content. Lettuce physical measures to be taken include total weight, marketable yield, leaf number per plant, plant size, and moisture content. Lettuce microbial load and tomato eating quality will be evaluated Pest and disease incidence in the field is unpredictable because of the complex set of interactions governing plant response to pest pressure. A series of trials will be conducted under controlled conditions by the co-PDs to accurately quantify any potential pest tolerance conferred to the seedlings from the use of vermicompost. The work will be conducted over the course of years 1 and 2 of the project. For all greenhouse and on-farm activities, comparisons will be made between standard on-farm practice and control treatments with regard to organic seedling media on marketable yield and cost of production. Economic analysis will include the calculation of gross production costs, total variable costs, gross margins and other key economic parameters. Net benefit of alternative analysis will include all potential economic impacts throughout the production chain including seedling production time, crop yield and post harvest quality.