Focus on Floriculture Vol 5 #3
Energy conservation in Northern Europe's potted plant greenhouse ranges is improved by soil warming. Hot water systems are used almost exclusively with distribution throughout the greenhouse by radiation lines. One method of soil warming has PVC tubes extended from the major wall lines and looped the length of benches (Figure 1), but there are other methods (Figure 2). Manual valves regulate the amount of hot water entering the bench tubes and thus the amount of soil heating. Energy saving comes from the cooler air temperatures required for optimum growth. E. Moes from the Government Greenhouse Research Station, Virum, Denmark, recently reported on optimum air temperatures for interior foliage plants with or without soil heating (Table 1). Note that except for Dieffenbachia, bottom-heated plants grew at maximum with either cooler day or cooler night air temperatures. A cooler night temperature is of particular interest. For producers with steam lines below benches, good investments for water would be bench skirts to capture heat, and thermometers in pots to check for overheating.
Keywords: soil warming Hot water systems Night air temperatures steam lines PVC tubes