1. XIV. MODIFYING LIGHT INTENSITY

2. A. Supplementary Artificial Light 1. Light Intensity and Quality Quality –400-800 nanometers Intensity –100-300 mmols/sec/m 2 –500-2000 ft. cds. Distance vs. Intensity –decrease the greater the distance

3. 2.Types of Lamps a. Incandescent primarily red light point source short life b. Fluorescent deficient in red? 2', 4', 8' lengths greater uniformity shadows

4. c. Combination: -fluorescent lamps -incandescent lamps complete spectrum shadows suitable for growth room

5. d. High intensity discharge (HID) Mercury vapor –not used today Metal halide –good spectrum –lower eff. than HPS & LPS

6. High Pressure Sodium –high light intensity –400-1000 watt –eff. conversion of energy Low Pressure Sodium –narrow band of light –efficient conversion

7. New Lights for Greenhouses Sulfur and microwaveDiode

9. 3. Commercial Application a. Crops Roses, chrysanthemums, seedlings, lettuce, tomatoes b. Benefits timing quality less prod. time; lower cost less fuel costs increasing branching increased keeping quality roses; fewer blind shoots

10. 3.Commercial Application (contu.) c. Where used northern latitudes growth rooms d. Installation/operating costs fixture + ballast $150+ fixture + installation $2.25/sq. ft. operation: $1.50/sq.ft./yr depreciation interest on money borrowed

11. 3.Commercial Application (contu.) e. Management Greenhouse –HPS 400watt; spaced 10 x 10: 10 ft above plant 30-60 umols/sec/m 2 ; 280-460 ft.cd. Oct to Apr night & cloudy days

12. High pressure sodium light arrangement

15. Growth room

16. 20 sq. ft. 2 ft. above plants –106 umols/sec/m2: 750 ft.cd. 7 tubes: @ 40 watts –200 umols/sec/m2: 1400 ft.cd. 13 tubes: @ 40 watts

17. 3. Commercial Application (contu.) f. Accumulated light 200 umol/sec/m 2 for 18 hrs. –equals 23 mol/day/m 2 Summer - natural light –48 mol/day/m 2 Winter - natural light –19 mol/day/m 2

19. A. Reducing light intensity - Why - External shading compounds –Latex paint: 1 part to 8-10 parts H 2 O –Saran cloth –Internal permanent Saran cloth Aluminum strips –Internal movable

20. B. Increasing light intensity –Clean covering –White or reflective surface –Reduce shade producing items