Brief review of supplemental lighting in the greenhouse.

1. Supplemental
Lighting

2. Why Supplemental Lighting?
 During winter light intensity suboptimal
 Previous methods discussed not enough
 Crop growth slows down
 Blindness increases
 Flower size is smaller
 Stems thinner
 Plants often too tall.

3. Lamp Types
 Incandescent
 Fluorescent
 HID
– High pressure mercury
– Metal-halide
– Low pressure sodium
– High pressure sodium

4. Incandescent Lamps
 Poor light quality
 High heat load
 Low efficiency (7%)
 Too much light in Red
Far red range

6. Fluorescent Lamps
 Commonly used over
small growing areas
(germination)
 Rare for finishing crops
 More efficient (20%)
 Low wattage, so you need
a lot of them (shadow
creation)

8. HID/High Pressure Mercury-Type
 Mostly replaced by Metal Halide lamps
 Similar spectrum to fluorescent lights
 13% efficiency
 Up to 1000 W; can last over 10,000 hours
 Also used to light roadways

10. HID/Metal-halide type
 Up to 2000 W
 20% efficiency
 More expensive than Mercury types, and
have a shorter life

13. HID/ Low Pressure Sodium
 Very narrow band at 589 nm
 Little in the 700-850 nm range
 Low level of blue lights
 Some success in combining
with incandescents
 In Northern areas can affect
leaf morphology
 Large reflectors cause shadows

15. HID/ High Pressure Sodium
 Life expectancy of up to 24,000 hours (2.75
years)
 Cheaper to purchase
 Better spectrum than LPS
 Most common worldwide today
 25% efficiency !!
 For some crops extended light spectrum
results in increased fresh weight, stem
elongation, and early flowering.

16. http://aesop.rutgers.edu/~horteng/images/fhgreenhouse/HPS_lamp_in_GH.jpg

19. Supplemental Lighting
 Already common above 40ºN latitude in U.S. and
50ºN latitude in EU
 Gaining popularity in south
 Especially profitable in winter months
 Cost about $2.90/ft2 of growing space (HPS)
 Chrysanthemum, geranium, begonia, rose, and
plugs
 300 – 600 fc for ornamentals 600-1000 fc for
vegetable crops

20. Other Notes:
 Use only horticultural fixtures – reflectors
important
 Reflectors for different locations in the
greenhouse
 Usually 16-18 photoperiod used
 Higher plant densities are more economic.