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Customized Lighting for Growers |
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Customized Lighting for Growers New tools and new lighting technologies are allowing greenhouse operators to highly customize their lighting designs to optimize results. Growers have long been faced with limited information as well as limited choices for lighting plants. This trend is changing as lighting manufacturers, researchers and educators are accumulating and offering new information that is giving growers a better opportunity to effectively use lighting. Each of these groups are, of course, using the internet as a vehicle to pool information. Lighting manufacturers can now provide not only product information, but reference material in their web sites (or via links) that can not only educate in general, but provide guidance towards specific types of light and relative intensity levels. Use caution, however, when reviewing older technical papers as they may not take into consideration more current technological innovations which may override old conclusions. One example of this is with metal halide light evolution.
Measuring Light for Plant Growth
The older standard for measuring light is footcandles. Footcandles are a measure of all visible light measured against the human eye. Plants, however, respond primarily to light in the range of 400 – 700 NM (nanometers). Rather than working in footcandles, growers are better off looking at the measure of energy known as PAR (photosynthetically active radiation). This is expressed in uMOLS (micromoles) and can be simply measured using a Quantum meter. Inexpensive Quantum meters (about $150.00) can be purchased from several companies. Using this tool and measurement puts growers in the right framework to understand the information available from researchers and educators.
New High Intensity Lamp Types
High pressure sodium lights have traditionally been the primary choice for greenhouse lighting with metal halides coming in a distant second. Halides were more commonly used in controlled environmental growth chambers where more balanced sun simulation light was required. Sodium lamps provide a high lumen to watt energy efficiency but are less balanced in spectrum. When measured for PAR value, standard sodiums can be matched or exceeded by halides in many cases. There are some newer enhanced sodiums that offer a little more output and a slightly better spectrum which growers are trying now. These could generate better results for some crops. The more natural light that is available and less supplemental light that is needed tends to point toward sodium lamps as a choice. There are some plants, which will respond to sodium light sufficiently to dictate their more extensive use.
Technological evolution in halides has raised their profile as a choice for growers. New lamps are available which offer the balance of standard halides but add more red like sodium lamps. Plus, horizontally engineered halide lamps can provide more light energy closing the lumen gap towards sodiums. PAR testing reveals that enhanced warm color halides can provide PAR values equal to sodium lamps. With the output and spectrum enhancements, halides are a logical choice for many growing situations. Growers needing more balanced light for seed starting, vegetative growth or limited natural light environments can get excellent results using these newer types of halides. Many commercial growers like Degroot Nurseries are now using halides with good success.
New Fixtures for Greenhouses
A good lamp can not do its job unless it has a good reflector. An older reflector design may waste a lot of energy before it gets down to the plant surface. Reflector efficiency can vary greatly. Open ended fixtures or older warehouse-type high bay lights can be as much as 50% less efficient due to lost or poorly delivered light. High bays can focus (not spread) light incorrectly over the planted surface requiring more lights or providing uneven light. Uneven light delivery will result in uneven growth. Different greenhouse structures, plant types, and required light levels may dictate different fixtures. Some fixtures work to provide higher light levels while others may spread light better at relatively lower mounting heights.
In addition to determining a good reflector type, ease of installation should be factored in. Newer remote ballasted options can save on installation costs and provide flexibility for growing crops or changing parameters. Raising, lowering, or maintaining fixtures is far easier with the remote ballast types.
Tools to Help Growers
Lighting layout programs are now offered by lighting manufacturers and greenhouse lighting distributors to help growers determine their needs. The best of these are engineered for greenhouse application, not for lighting offices or warehouses. A good program can provide layouts for a variety of lamp and fixture types and can give the grower light levels and spacing so that various scenarios can be evaluated.
Lighting can be a critical element for growing success. Without lighting, growers are subject to the whims of Mother Nature and could face significant financial impact in poor weather periods. Proper lighting allows growers to positively affect their crop timing, quality and profitability. While the cost of installing a high intensity lighting system can be significant, they typically last for many years and will pay off for the enlightened grower.
Peter Wardenburg is the vice president for Hydrofarm Greenhouse Lighting in Petaluma, CA.
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