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Plants and artificial Light

Prof.Dr.Klaus Peper peper at med-ph.uni-sb.de
Fri Jan 27 09:00:08 EST 1995

What light for what purpose?

Artificial light is used for:
1) Photoperiodic lighting   2) Photosynthesis lighting.
For 1) only little light is necessary and fluorecsent tubes do well.
For 2) only long-life high-efficient metal halide lamps are effective.

I have more than 5 years experience with artificial light. Please
forget everything about fluorescent tubes, flora lamps etc., they
do not output enough light ( except for seedlings, here you can place a 
normal daylight tubes 10 cm above the plants).

Metal halide lamps are available through most companies like 
Osram, Philips, Tungsram, etc. Please contact them for information.
Philips has a very useful leaflet on artificial lighting in agri-
culture. Metal halide lamps (HQI, HPI or similar) are useful in
the following wattage: 70, 150, 250, 400 W.

These lamps are gas discharge bulbs and need a ballast and starter.
There colour temperature is between 4200 and 5600 °K, this is almost
sunlight. Efficiency is about 22%. Unfortunately it is difficult to
obtain complete setups. For indoor use, 150 W setups are very often
used in windows for display, so ask your electrician. A 400 W setup
is available in Germany at Bahrs Technik Fax:02157-90203 at ~550 DM.

Usage: 70 W for decorative lighting indoors, i.e. single plants;
150 W for cabinets, basements, conservatories; 400 W for greenhouses,
this lamp puts out an incredible amount of light, and you get easily 
5000 Lux at 1 m, so lightloving plants will prosper.

I mostly use 150 W, buy them in batches (12 bulbs, 6 ballasts+starter)
and mount them in ordinary 500 W halogen floodlights, which are
cheap and offered in supermarkets. Some mechanical work is needed 
since the sockets have to be widened. Metal halide bulbs should be
protected by the housing, since they might explode, and, further, 
they have heavy UV light, which is filtered by the floodlight-glass.

These setups are expensive, however longlife and worthwhile. Commercial
agriculturers use similar equipment, however, sodium bulbs instead of
metal halide, they are even more effective (25%), but orange.

If anybody knows about a supplier of these most useful lamps, please 
post it in bionet.garden. If you have questions, dont hesitate to
contact me. 

Please forget my title, the server demands it to announce.
Sorry about that.

Klaus Peper FAX: (49) 06841-166655 EMAIL: peper at med-ph.uni-sb.de

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