ALTERNATE PHOTOSYNTHETIC LIGHTING WITH COMPLEMENTARY 1000 W SOURCES IN GREENHOUSES

Field-crops grown under glasshouse conditions often demand not only higher light intensities but also a more specific light spectrum than conventional greenhouse crops.

Essentially this is the case when the natural behaviour during the whole cycle; vegetative growth, flowering, fruit-set and fruit-ripening is the criterium of research.

The use of mixed fluorescent light tubes with different spectra is not possible in greenhouses because of its strong shadowing effect and the distance of more than 2m between the light sources and the cultivated surface.

Preliminary trials in the phytotron showed that light sources with different spectra must not be used simultaneously for complitions of the spectrum.
An alternation in intervals of several hours resulted in the same plant-reaction and quality.
By these long intervals the lifetime of the lamps is not changed remarkably.

Thus in greenhouses with the same basic equipment such as self, condenser, reflector, cables etc., a 1000 W Na-high pressure candle can be alternated with any high pressure halogeen 1000 W lamp, each at a high intensity between 12’000 and 16’000 lux, at a distance of 2–3m from the cultivated surface.

This means a reduction in installation costs, in shadowing effect and in the cable sections despite the high light intensity of each lamp.

The proportion of the different light sources can be chosen corresponding to the need of different field-crops or to different growth-stages.

II International Symposium on Artificial Light in Horticulture

E. Fankhauser

https://doi.org/10.17660/ActaHortic.1982.128.12