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Q
Hi ,
How many T5 lights do I need to grow lettuce in an aquaponic raft system measuring 4X4 feet ?
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A Hello ,
Thank you for your question . T5 fluorescent lighting is an excellent choice for growing lettuce or other leafy green crops . One advantage of using T5s for growing lettuce is thay they automatically distribute the light more evenly than other types of lighting systems . This more even light distribution can be attributed to the length of the bulbs themselves and how fluorescent bulbs operate . Light energy emitted from a T5 fluorescent is distributed consistently down the entire length of the bulb . This means plants directly under the bulbs will receive the same light energy , no matter if they are located near the center or closer to the ends of the lighting fixture . For lettuce crops , this means even growth and more consistent results . Conversely , plants grown under HID lighting systems will receive different amounts of light energy depending on where they are positioned under the fixture . That is because HID lights emit all their light energy from a small focal point in the center of the fixture . So , plants located under the center of a HID lighting fixture will receive more light energy than the plants sitting farther from the center . This leads to uneven growth . To avoid this , growers need to move the plants or the lighting system itself to help even out the distribution of light energy . In addition to their even light distribution , T5 bulbs can be purchased in different Kelvin ( K ) ratings . That means growers can purchase T5 bulbs that emit either more red or more blue light , depending on their crops ’ particular needs . When growing lettuce , it would be most advantageous to use blue spectrum — or 6,400 K — T5 bulbs as they will emit a spectrum that lettuce plants tend to respond to best .
Measuring the amount of light energy needed for any type of indoor garden can get tricky because there are many different methods used to measure light and many different lighting technologies to consider . However , it is still safe to use the watts-per-square-foot formula for T5 fluorescents , assuming regular bulb changes will be implemented . For lettuce and other leafy green crops , 20-30W per square foot of T5 lighting will be sufficient . In a 16-square-foot ( 4x4-foot ) space , you would need 320-480W of T5 lighting to grow lettuce efficiently . A four-foot-long , eightbulb T5 lighting system would provide 432W and give you 27W per square foot . I believe an eight-bulb T5 lighting system equipped with 6,400 K bulbs would be the best fit for your lettuce garden . I hope this answers your question .
Keep on Growing , Eric Hopper
Eric Hopper ’ s past experiences within the indoor gardening industry include being a hydroponic retail store manager and owner . Currently , he works as a writer , consultant and product tester for various indoor horticulture companies . His inquisitive nature keeps him busy seeking new technologies and methods that could help maximize a garden ’ s performance .
KELVIN RATINGS
Kelvin ( K ) is a unit of measurement for temperature . The Kelvin scale was invented by Lord Kelvin in the 1800s , when he saw the need for a scale that began at absolute zero . For comparison , 0 K is equal to -273 ℃.
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