COMMERCIAL SEEDLING PRODUCTION IN THE UNITED KINGDOM USING FLUORESCENT LAMPS

During the last 15 years, large numbers of seedlings have been raised by commercial growers in the United Kingdom using fluorescent lamps as the only source of light, using methods summarised in Anon. (1980). Initially, relatively small rooms were built based on the design of those already in existence at the Electrical Development Association Station, Shinfield (now part of the University of Reading), but incorporating sub-irrigation to ensure adequate water supply and 2.4 m rather than 1.5 m fluorescent lamps.

For ornamental seedling production, the light and temperature conditions that are used were determined by growing seedlings at the University of Manchester and under a grower's own lamps using continous illumination with different amounts of light, measured by a non-cosine corrected selenium photocell. The commercial seedling producer then decided which seedlings he considered were robust and easiest to transplant. The most suitable compromise was 5 500 lux from Philips TL29, an air temperature of 25°C, the length of growing period being determined by species, but usually no more than 14 days. This grower now produces each year hundreds of thousands of seedlings of a wide range of species. It is possible that production costs could be reduced by using CO₂ enrichment, or by different lighting treatments, for example of the type known to be beneficial for lettuce and tomato seedling production.

The conditions used for the production of seedling tomatoes is based on the observation that the minimum possible time from seedling emergence to initiation of the

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