Article 2-1 Technique For Effective Lighting

Planning Light -Use in Grow Rooms:

1. Determine Area to be Lit:
Number of plants x space required per plant = total growing area needed.

2. Determine Type of Lamp Required:
Propagation (seedlings and cuttings) - Fluorescent or small (to 400 watt) metal halide lamp, color-corrected mercury vapor lamp (175 watt, self-ballasted).
Green Growth (vegetative growth) - Clear metal halide lamp, 'Optimark' color corrected high pressure sodium lamp (only 400 watt size 'Optimark' available).
Flowering and crop production (long-day crop plants): Use the same lighting products as 'Green Growth' plants.
Flowering and crop production (short-day crop plants): High pressure sodium lamps, phosphor-coated metal halide lamps, "compatible" sodium lamps ( Iwasaki 940 or 360 watt lamps).

3. Determine Hood Use:
Tall crops (over one meter tall) - use "broadside" lighting Use a vertical lamp with no reflector. The lamp is positioned hanging straight down between the plants.

BROADSIDE LIGHTING . For tall crops . hang lamp so bottom of lamp is at half-way point of green zone.

Adjust the distance between the lamp and the top of the plants to supply even light to all the plants. Raise the lamp higher for new transplants, or crops with pest or disease problems- Increase light levels as crops become established and healthy. As plants grow, be sure to maintain minimum distance (or greater) to avoid heat damage to crop.

Minimum lamp distance refers to the closest distance possible between crop and light source. This distance is determined by temperature, since closer lamp positioning would create heat stress and slow plant growth.

Short Crops (to one meter tall). Use top lighting above the plants using a reflector.

Top Lighting . for short plants (to 3 feet)

4. Determine Type of Reflector (for top-lighting)
5. Determine Distance of Lamp from Crops
To find minimum distance between lamp and crop:
Mount small thermometer near top of plants (in the light). Gradually move lamp closer to crops until thermometer reads 30C (steady reading).
This is the closest lamp position recommended.
Note the distance between lamp and top of plants.