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A semi-commercial project was undertaken for 2 yr to demonstrate the use of reduced night temperatures and rootzone heating as a means of saving energy in the production of greenhouse tomatoes. A commercial greenhouse was divided into a warm and a cold section to arrange for night tempera tures of 18 and 11?C, respectively, while the day temperatures were kept the same. The project involved three types of growing media (Nutrient Film Technique, Rockwool, and Soil), heated and unheated rootzones (NFT, Rockwool), two cultivars (Buffalo and Caruso), and three replicationsfor each treatment in both greenhouse sections. There fore there were 60 separate modules containing about 50 plants each. Energy consumption data indicated that savings of at least 30% are possible for both the spring and fall crops with a reduction in night temperature. Yield data showed that all treatments yielded about twice the commercial average of 7.2 kg/plant, which can be attributed to the use of proper management techniques and appropriate equipment. Rootzone heating was generally not beneficial with the exception of rockwool in the early spring.
L. Otten, P.G. Muller, H. Tiessen, S. Khosla, F. Rey, and H.A. Jackson 1989. ENERGY SAVING HYDROPONIC GREENHOUSE PILOT PROJECT: ENERGY ASPECTS. Canadian Agricultural Engineering 31(2):147-152.
Canadian Society for Bioengineering