James B. Wills, Gary Honea, Carl Sams, Allen Straw

Ten varieties of long-shelf-life tomatoes were grown outside the greenhouse in plastic bags filled with perlite and irrigated with spray stakes. Fertilizer was applied by two dosatron injectors controlled by a solar timer and sensor. Tomato fertilizer (4-18-38) mixed with magnesium sulfate was injected by one dosatron and calcium nitrate mixed with potassium nitrate was injected by a second dosatron throughout the growing season. The main intent of the project was to determine the yield potential and quality of tomatoes grown using a hydroponic system outside a greenhouse.

Many tomato production areas are infested with soil nematodes and other soil borne pathogens. Growing tomatoes year after year on the same ground tends to cause a buildup of these pathogens and nematodes that reduces crop yield and quality. If plants were grown on the same land area, but separated from the soil by containers with artificial media, growers could utilize past production areas with greatly reduced risk of soil borne pathogens. This study was conducted to evaluate the yield and fruit quality of ten different varieties of field tomatoes grown under hydroponic conditions outside of the greenhouse.

Ten plants each of ten different varieties of long-shelf-life field tomatoes were grown in three-gallon plastic bags filled with perlite and fed through an irrigation system containing water and soluble plant fertilizers recommended for tomato production. All varieties were planted on May 26, 2003. The amount of fertilizer solution used daily was determined by a solar sensor that activated an irrigation controller based on incident sunlight each day. An optimum amount of fertilizer solution was injected using dosatrons and spray stakes into individual bags daily based on sunlight received by the plants.

The ten varieties of tomatoes evaluated were (1) Emperador (2) HMX 2807 (3) Sebring (4) Celebrity (5) Empire (6) Mountain Fresh (7) Florida 47 (8) RFT 0252 (9) Fabulous (10) RFT 6153. Fertilizers used were 4-18-38 mixed with magnesium sulfate and injected by one dosatron, Calcium nitrate and potassium nitrate were mixed and injected by a second dosatron. Plants were sprayed with Quadris, Thiodan, Asana, and Bravo to control insects and disease. Chemicals were alternated at each spray application to lessen the possibility of resistance to each chemical. Almost daily rainfall during the growing season made it difficult to get good pest control as rainfall removed spray applications from the plants soon after application. Quality and yield from the tomato plants was not good due to excessive flushing of nutrients from the bags and removal of plant protection chemicals by the rainfall. Plant bags were placed on a black woven-plastic ground cover to help control weeds around the bags. No herbicides were used. Tomatoes were harvested as fruit ripened on the vine and were graded with respect to size and quality and weights of each grade were recorded. Plants were harvested a total of six times during the growing season in 2003.

Total weights of marketable tomatoes of all grades for all varieties are listed in the table below along with average weight of yield from each variety (Table 1). Also shown is the total weight of culls and the average weight of culls from each plant. RFT 6153 was the best yielding of the ten varieties and also had a low percentage (4%) of culls as compared to all other varieties with the exception of HMX 2807 (2% culls). Sebring had low yields, but had the highest percentage (44%) of culls.

Table 1. Yield per plant and culls for long-shelf life tomatoes grown in bags outside at the Knoxville Experiment Station in 2003.

Excessive rainfall throughout the growing season contributed to lower than normal yields of all varieties due to leaching of plant nutrients from the bags and removal of pesticides soon after application. Many of the fruit graded as culls would have been graded marketable if not for damage caused by insects and disease where pesticides were removed by excessive rainfall.

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Copyright © 1999 by The University of Tennessee. All rights reserved.

This research represents one season's data and does not constitute recommendations.  After sufficient data is collected over the appropriate number of seasons, final recommendations will be made through research and extension publications.