The effect of a supplemental air distribution system was evaluated in a greenhouse producing tomatoes (Lycopersicon esculentum Mill cv. Trust). The system used centrifugal fans to force warmer air from above the canopy through a perforated duct extending longitudinally through each double-canopy row, with the goal of improving yield and decreasing energy use. The experiment employed two commercial-size greenhouses, one as the treatment greenhouse with the air distribution system and one as the control using conventional air handling. The experiment duration was two growing seasons (spring and fall crop). The system significantly reduced vertical temperature and relative humidity gradients while the heater was on during the spring. The treatment greenhouse consumed 9% less fuel and exhibited 14% greater yield than the control house. The net benefit from the treatment greenhouse was estimated as slightly less than $1000 for the spring season, and the benefit/cost ratio of the system was four to one. However, the benefits observed during the spring did not repeat for the fall season. There were no appreciable environmental differences between the greenhouses, and the yields were essentially the same. Because of capital and operating costs, the treatment greenhouse experienced a net economic loss of near $300 in the fall. The difference between fall and spring results is explained by the different relationship between plant size and climate during those seasons; the combination of small plants and cold weather in the spring can benefit the most from this type of air circulation system. The results from a single spring/fall trial suggest that the system could be valuable to producers, but only in the spring.
- Air circulation,
- Environmental control,
- Tomato production
Available at: http://works.bepress.com/raj_raman/28/