By Diana Johnson
Lighting is of crucial importance to plant growth and plays a key role in determining plant yields. Hydroponics growing equipment manufacturers have, therefore incorporated a wide range of lighting system designs to meet specific requirements of different plants that are grown in indoor grow rooms.
Lighting requirements vary, depending mainly on the plant type, the area over which the plants are grown and the proximity of the plant to the light source. The most important consideration is the lighting level that a particular plant needs for healthy growth. Some plants like houseplants and ferns do not require as much light as salads and culinary herbs while tomatoes, orchids and flowering plants require the maximum amount of lighting. It has been observed that indoor growers typically tend to under-illuminate their indoor grow rooms as they try to cover too large an area with the available light. They need to understand the importance of adequate lighting bearing in mind that a smaller area that is adequately lighted will produce better results than a larger one with inadequate lighting.
Fluorescent Lighting Fluorescent lamps are ideally suited for small scale salad and herb gardens and for the production of seedlings and cuttings. T-5 Fluorescent lights are suitable for slightly larger plants as the T-5 fluorescent bulbs are about equal in PAR value to a 400 watt Metal Halide light. These lights need to be kept close to the plants on all sides, but will grow fabulous plants with short internode distances as long as the plant are not too large. T-5’s are best suited for vegetative growth.
High Intensity Discharge Lighting Vegetables, flowers and several other plant varieties do best with all the light they can get and the modern HID lights provide just what they need. HID lighting has developed with improvements in lamp and reflector design from a piece of equipment for specific needs to an almost “plug and play” use for the lay person. HID lights come in two designs – with remote ballasts and as integrated ballasts. The remote ballast design has the advantage of only its lightweight reflector unit needing to be suspended from the ceiling; the integrated design requires the full unit including the heavy ballast to be suspended.
HID lighting comes in two basic types- Metal Halide and High Pressure Sodium. Metal Halide HID lighting produces a blue white light, and has been recognized as especially well suited for overall plant growth, while the High Pressure Sodium which produces a red/orange light is better suited to the flowering and fruiting period during which plants can more readily make use of it. Both types of HID lighting are in use with growers either alternating the two according to the plant growth cycle or mixing the two throughout the crop. However, the latest design of Sodium lamps which are now available in the “Agro” or “PLANTA” range can provide the light energy required during the entire cycle of plant growth and are being increasingly used by professional growers.
HID lights are available in wattage from 250 upto 1000 watts and beyond. The lamp which gives the maximum light output, watts used to lumens given is the 600 watt sodium lamp, producing 92,000 lumens.
Reflector While it is important to use the right lamps to generate the right amount and type of light, it is equally important to ensure that the light is directed in a manner that ensures minimal wastage. Reflector design plays and important role in maximizing light utilization; a well designed reflector can be as much as 30 % more effective than a poorly designed reflector in terms of its capacity to minimize light wastage. The most efficient reflectors now in the market feature designs generated using computer aided modeling techniques. These designs maximize light reflection onto the plants and enhance lamp life.
1. Light Movers
In addition to efficient light reflectors, rail systems that enable movement of lamp to ensure light exposure to the most remote plant go a long way in enhancing light utilization. A rail system called the Light Rail 3.5 has proved to be particularly effective in improving light utilization and should be considered by those who have a rectangular growing area. This is a simple device that uses a six foot rail with a precision engineered carrier that moves the light back and forth over the growing area. The Light Rail 3.5 system offers several advantages- it covers a greater area and ensures that all plants receive the same amount of light; it eliminates having the plants moved around for light exposure and it eliminates shadows thus ensuring uniform plant growth. It also affords closer exposure of plants to light without burning the foliage. There are other systems that move the light along a circular path, these are more suited to square grow rooms. Some systems also allow combination lighting with a Metal Halide Lamp on one arm and a High Pressure Sodium on the other, or 4 different ceramic bulbs on 4 separate arms, each giving a different color temperature. These 4 different bulbs combine to make one very full spectrum when mixed via a circular or rotating light mover.
2. Reflected Light
Reflective surfaces around the growing area can make a difference in the amount of light that plants will receive. Poor reflectivity of the surfaces around a plant will diminish the amount of light as the surfaces will absorb most of the incident light. It is not difficult to ensure highly reflecting surfaces around the plants in a grow room. Walls can be easily painted with flat white paint, which is an excellent reflector. If this is not possible the walls can be covered with black/white plastic film which can also be used for the floor. Polystyrene foam sheeting can also be used as it is a good reflecting surface. The most reflective floor covering is brilliant white vinyl. It is tough and hard and makes an ideal reflecting surface. Finally, there is MYLAR, the most reflective material that can reflect 92 % of the light it receives.
3. Timers
Automatic turning on and off of the lighting system requires the use of an efficient timer. Incorporating a timer in the lighting system ensures that the plants in the grow room are exposed to light for the “on” set time after which the lights are switched off for the “off” set time. The continuous uninterrupted repetition of this on/off cycle is essential; a reliable, good quality timer is therefore important. It is best to avoid ordinary non-grounded plug-in timers as these are prone to failures causing disruption of flowering cycles in certain plants and increased power bills.
Power Consumption
Power consumption is one of the factors that need to be considered while working the economics of the project. However, this should not ordinarily deter the beginner as the costs involved are surprisingly small. The beginner should work out the power requirement and its economics at the outset to avoid problems later.
Warning
Grow-rooms can be damp and humid. All electrical equipment, fittings and accessories should be carefully located to avoid any contact with water splashes. It is advisable to seek the help of a licensed electrician while installing the electrical system.
Lighting Considerations in Indoor Hydroponics
5:54 AM
ThanateTan
