ORGANIC TOMATO TRANSPLANT PRODUCTION IN COMPOST-AMENDED SUBSTRATE

Abstract

There is limited information available about organic fertilization of vegetable transplants. The availability and release of the mineral nutrients from organic fertilizers is not fully understood. The objective of this study was to determine the effect of compost rate and chicken manure on the growth of tomato transplants. Tomato transplants were grown in an organic peat-based substrate (Garden Safe® Organic Potting Mix) amended with six rates of either compost (0% to 50%, by weight) or chicken manure (0% to 40%, by weight). The results showed that plant dry weight was minimally affected by compost rates, suggesting that compost provided only a minimal amount of nutrients to the plants. However, since transplants produced with compost-amended substrate were of similar quality compared to those produced exclusively with the substrate, it suggests that compost may be used to partially replace peat-based substrates used for transplant production. Shoot, root and plant dry weight increased with increasing rates of chicken manure (applied prior to seeding) reaching a maximum at 10%-20% (by weight) and then declined at 40% rate. Thus, chicken manure mixed with the substrate appeared to provide enough nutrients to tomato transplants. INTRODUCTION Organic vegetable growers are increasingly faced with reduced supply and poor quality transplants (plugs). Vegetable transplants produced organically are often of low quality because of poor fertilization management. There is limited information available on fertilization of organic production of vegetable transplants. A major challenge in organic production is the uncertainties in bio-availability of macro and micro nutrients contained in organic fertilizers or amendments. In most instances the essential nutrients are in unavailable forms or need to be chemically modified to be available to plants. Thus, it is usually difficult to determine optimum application rates of organic fertilizers based only on the chemical composition of organic amendments. Chicken manure has a higher mineral nutrient content and higher rates of N mineralization compared to compost (Eklind et al., 2001). The objective of this study was to determine the effect of compost rate and chicken manure rate on growth and development of tomato plugs grown organically. MATERIALS AND METHODS The study was conducted in a greenhouse at the Horticulture Farm, Coastal Plain Experiment Station, Tifton, Ga, during the fall of 2006. Tomato (Solanum lycopersicum L.) ‘Florida-47’ transplants were grown in organic substrate (Garden Safe® Organic Potting Mix) amended with different rates of either compost or chicken manure. The design was a randomized complete block with four replications (replication = one 200cell tray) and six treatments (rates of compost or chicken manure). In the compost trial, the treatments were 0%, 10%, 20%, 30%, 40%, or 50% (by weight). Compost (Longwood Plantation, Newington, Georgia) was prepared from cotton gin waste, chicken litter, and a small amount of peat humus, mixed, and composted for a minimum of 10 weeks. In the Proc. IV IS on Seed, Transplant and Stand Establishment