Lamp Spacing

Light intensity virtually doubles for every six Inches (15 cm) closer an HID is to the canopy of a garden. When light intensity is low, plants stretch for it. Low light intensity

IQQO-watt: LPW -110

140,000 lumens 35,000 lumens 15,555 lumens 9999 lumens

1000-watt HP sodium @ 4 feet = 10,000 lumens 4x4-16 square feet, 1000 waits / 16 square feet • 62.5 watts per square foot, 1000 waits / MJ 100 watts per cm'

1000 watt: LPW 115

4 feet (120 cm) away

115,000 lumens 28,750 lumens 12,777 lumens 8214 lumens

1000-watt metal halide @ 3.25 feet <= 10,000 lumens 3.25 x 3.25 12.25 square feet, 1000 watts / 12.25 = 81.6 watts per square foot. 1000 waits / m* = 10 watts per cm'

4 feet (120 cm) away

90,000 lumens 22,500 lumens 9,999 lumens 6428 lumens

600-walt HP sodium ® 3 feet => 10,000 lumens 3x39 square feet, 600 walls / 9 = 66 watts per square foot 600 walls / nv = 6 watts per cm-'

4 feet (120 cm) away

50,000 lumens 12,500 lumens 5,555 lumens 3571 lumens

400-watl HP sodium @ 2.25 feet = 10,000 lumens 2,25 x 2.25 5 square feet, 400 watts / 5 square feet = 30 watts per square fool. 400 watts / nv' - 4 waits per cm-'

40,000 lumens 10,000 lumens 4,444 lumens 2857 lumens

400-watl metal halide (a' 2 feet j 10,000 lumens 2x2 4 square feet, 400 watts / 4 100 waits per square loot 400 waits / nv = 4 walls per cm-'

This gardener is able to rotate and move plants around within the garden beds. Wheels on the bed make it easy to rotate or remove entire beds.

¡s often caused by the lamp being too far away from plants. Dim light causes sparse foliage and spindly branches that are further apart on the stem.

Increase yield by giving growing area uniform light distribution. Uneven light distribution causes strong branch tips to grow toward the intense light. Foliage in dimly lit areas is shaded when light distribution is uneven.

Reflective hoods ultimately dictate lamp placement-distance between lamps and above the plants. Nearly all stationary lamps have bright (hot) spots that plants grow toward.

Growers prefer high-wattage lamps-400, 600, 1000, or 1100 watts-because they have lumens-per-watt and their PAR rating is higher than smaller bulbs. Plants receive more light when the lamp is closer to the garden. Even though 400-watt lamps produce fewer lumens-per-watt than a 1000-watt bulb, when properly set up, they actually deliver more usable light to plants, The 600-watt bulb has the highest lumen-perwatt conversion (150 LPW) and can be placed closer to the canopy of the garden than 1000 or 1100-watt bulbs. When the 600-watt bulb is closer to plants, they receive more light.

A 1000-watt HID emits a lot of light. It also radiates a lot ol heat. The bulb must be farther away from the plants lo avoid burning them. In many cases it is more effective to use smaller wattage bulbs. For example, two 400-watt bulbs can be placed closer to plants than one 1000-watt bulb, and the 400-watt bulbs emit light from two points. The disadvantage is that two 400-watt systems cost more than one 1000-watt system.

Check out the diagrams that show the difference in usable light in different sized growing areas. Growers who use these drawings fine-tune the area with a hand-held light meter,

Look at the simple mathematical examples below to see how much more efficient 400 and 600-walt lamps are than 1000-watt lamps.

For example, a 1000-watt lamp that produces 100,000 lumens at the source produces the following:

The goal is to give plants 10,000 lumens.

A large bed on casters is easy to maintain.

Light intensity is brightest directly under the bulb. To promote even growth, arrange plants under lamps so they receive the same intensity ol light.

This gardener is able to rotate and move plants around within the garden beds. Wheels on the bed make it easy to rotate or remove entire beds.

If you use three 600-watt HP sodium ¡amps, you get a total of 270,000 lumens at a cost of $0.18 per hour (cost per kWh = SO. 10). If you use two 1000-walt HP sodium lamps, you get a total of 280,000 lumens at a cost of ¡£0,20 per hour.

Use the examples above to see the 1000-watt HP sodium offers more watts per square foot and m2 to achieve the desired lumen output of 10,000 lumens. However, the bulb also produces a hot spot near the center of the illuminated area. Plants lend to grow into the hot spot and shade other plants.

Although 400-watt lamps have a lower lumen-per-watt conversion, when used properly they may be more efficient than higher wattage bulbs. One 1000-watt halide produces 115,000 initial lumens and a 400-watt halide only 40,000. This means each 400-watt lamp must be located closer to the canopy of the garden lo provide a similar amount of light. It also means that several different point sources sustain more even, intense light distribution.

Side Lighting

Side lighting is generally not as efficient as lighting from above, Vertically oriented lamps without reflectors are efficient, but require plants to be oriented around the bulb. To promote growth, light must penetrate the dense foliage of a garden. The lamps are mounted where light intensity is marginal-along the walls-to provide sidelight.

Compact fluorescent lamps are not a good choice for side lighting when using HID lamps. (See Compact Fluorescent Lamps below for more information.)

Rotating Plants

Rotating the plants will help ensure even distribution of light. Rotate plants every day or two by moving them one-quarter to one-half turn. Rotating promotes even growth and fully-developed foliage,

Move plants around under the lamp so they receive the most possible light. Move smaller

Tall lanky buck are easy to grow in small containers.
Some clones grow so fast that the harvest is ready before plants shade one another.
You can really pack plants into a garden when they receive a lot of bright light,

plants toward the center and taller plants toward the outside of the garden. Set small plants on a Stand to even out the garden profile. Arrange plants in a concave shape (stadium method) under the lamp so all plants receive the same amount of light. Containers with wheels are easier to move.

Take advantage of the different levels of light below the HID. Place seedlings and cuttings requiring low light levels on the perimeter and flowering plants needing higher light levels under bright bulbs,

Plant Spacing

When light shines on a garden, the leaves near the top of plants get more intense light than the leaves at the bottom. The top leaves shade the bottom leaves and absorb light energy, making less light energy available to lower leaves. If the lower leaves do not receive enough light, they will yellow and die. Tall six-foot (1.8 m) plants take longer to grow and have higher overall yields than shorter four-foot (1.2 m) plants, but the yield of prtmo tops will be about the same. Due to lack of light, the taller plants have large flowers on the top three to four feel (90-120 cm) and spindly buds nearer the bottom. Tall plants tend to develop heavy flower tops whose weight the stem cannot support. These plants need to he tied up. Short plants better support the weight of the tops and have much more flower weight than leaf weight.

At least 99 two-week-old seedlings or clones can be huddled directly under a single 400-watt HID. The young plants will need more space as they grow. If packed loo closely together, plants sense the shortage of space and do not grow to their maximum potential. Leaves from one plant shade another plant's foliage and slow overall plant growth. It is very important to space young plants just far enough apart so their leaves do not touch or touch very little. This will keep shading to a minimum and growth to a maximum. Check and alter the spacing every few days. Eight to sixteen mature females three to four months old will completely fill the space under one 1000-watt HID,

Plants can absorb light only if it falls on their leaves, Plants must be spaced so their leaves do not overlap too much. Yield increases very little when plants are crowded. Plants also stretch for light, which makes less efficient use of intense light.

Best number of plants per square foot or m-' is often a matter of experimenting to find the magic number for your garden. In general, each 40-inch-square (mJ) space will hold Irom 16 to 32 plants.

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