A REPORT. Ref. W/T7, by C. A. Cameron Brown and E. W. Golding, issued by the British Electrical and Allied Industries Research Association, describes experiments carried out to determine whether a simple method of heating hotbeds electrically can be applied successfully to the intensive production of early salad crops in small frames such as are used by non-professional growers. The method consists essentially in equipping a frame with a soil-heating cable or with a transformer-fed bare iron wire to give a loading of 2-5 watts per sq. ft. Heating is controlled, from a convenient point in the domestic premises from which supply is taken, to give certain regular 'doses' of heat in each 24-hour period. These doses vary from 40 to 45 watt-hours per sq. ft. per day, depending on the district. The two most convenient modes of procedure appear to be either with a loading suitable for all-night running or with a lower loading suitable for continuous running. The method is designed for operation on the domestic two-part tariff and to take advantage of the low running charges available. The experiments have shown that the method is a practical and economical way of producing lettuces of first-class quality from mid-March onwards, with little attention and at a total cost, including overhead charges, well below the current retail prices in shops. While early lettuce is the main crop, other crops can be raised, either simultaneously, such as carrots, or in succession, thus adding to the value obtainable from the hotbed installation.
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Simplified Electrically Heated Hotbeds. Nature 150, 659 (1942). https://doi.org/10.1038/150659a0