Year-round production of tomatoes in the north requires artificial lighting in the greenhouse during the winter months. This West Virginia greenhouse grower wanted to determine if using a traveling light system could save on capital expenditures and electricity consumption while increasing tomato production.
In the traveling system, the lamps are attached to a moveable fixture that travels suspended from a track over the plants, thereby covering twice as many plants than would be illuminated by a stationary lamp. He compared tomato yields and costs for plants exposed to stationary lamps, traveling lamps, and no artificial light. All plants were seeded in July and all treatments were grown in the same greenhouse, using the same cultivar and the same fertility and watering regime.
There was no replication of treatments. The cost of lamps in the fixed system was $3,000 and electricity consumed over the season was $720. Half as many lamps were used in the traveling system, and the traveling mechanism cost $200.
Yields under stationary lamps were 0.75 pounds/plant/week and 0.55 pounds/plant/week under the traveling lamps. Yield with no artificial light was 0.35 pounds/plant/week. Grower calculations, when depreciating the lamps over a two-year period, are that stationary lighting costs $0.12 per pound of yield and the traveling lighting costs $0.09 per pound of yield. Considering only the costs of lights and electricity, the grower judges the traveling system to provide a lower cost of production than the fixed system.