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struwwelpeter

How to Easily Supplement Fluorescent with Incandescent Light

struwwelpeter
9 years ago


Those sockets are available for for $2.75 here and those 35 watt, 600 lumen bulbs are available for $2.50 here.

I was inspired to do some experiments by Comparison of Gro-Lux and Cool White Fluorescent Lamps With and Without Incandescent as Light Sources Used In Plant Growth Rooms for Growth and and Development of Tomato Plants.

Comments (47)

  • organic_oddity

    It's hard to be swayed by research done in 1964. Can you show current results? Why wouldn't I use a CFL to get the same (if not more) lumens for 1/3 the watts?

  • struwwelpeter

    It's hard to be swayed by research done in 1964.

    Many people here, who should know better, confuse experiment with practice. The only "swayed" here is swayed to perform an experiment.

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  • yucatan

    @organic: You wouldn't use a CFL because incandescents supplement more far-red light, which is beneficial for flowering and fruiting. According to that link provided, plants grown primarily under CFL's and Fluorescents benefit from supplemental incandescent light. The benefit is not because of their efficiency, but because they represent a broader spectrum of far-red light than fluorescent bulbs used alone.

    @struwwelpeter: Though your setup is more convenient and aesthetically pleasing, are there any advantages to doing it this way as opposed to positioning a few incandescents between the plants to supplement side growth (with the fluorescents directly above the plants)? I would think that strapping incandescent fixtures directly to the middle fluoro bulb would limit some of the light emitted by that bulb in addition to interefering with the reflective aluminum coating behind all of the bulbs.

  • struwwelpeter

    Though your setup is more convenient and aesthetically pleasing, are there any advantages to doing it this way as opposed to positioning a few incandescents between the plants to supplement side growth (with the fluorescents directly above the plants)?

    The first thing to do is try to duplicate the experiment of that paper as closely as possible. That includes light bulb positions. Much later (like on the bottom of my list of things to try) I may try incandescents between the plants.

    I would think that strapping incandescent fixtures directly to the middle fluoro bulb would limit some of the light emitted by that bulb in addition to interefering with the reflective aluminum coating behind all of the bulbs.

    Since I am only looking for outstanding effects, I can afford to be a little sloppy. Also, note that the bulb filament is perpendicular to the ground and most of its light will be cast to the sides. The sides of the growing area will be covered with aluminized mylar sheet which will reflect the incandescent light back to the tops of the plants from various angles. The reflector in the picture is white enameled steel.

  • yucatan

    Let us know how it goes. I thought about positioning the lights in the middle of my plants to boost growth below the canopy line since I don't think that providing additional incandescent light above the plants will effectively penetrate to the lower parts.

  • struwwelpeter

    Let us know how it goes.

    I will start up my lean-to greenhouse today (turn on the gas and light the pilot on the gas heater). I will place the light fixture at the back of the lean-to where it is otherwise too dark to grow. In the next week, I will plant my seeds and after the tomatoes germinate, I will move some under that fixture. I will put a mylar partition at the middle of the fixture and remove a bulb from one side of that partition. The plants on that side will be the controls. I will also compare the artificial light grown tomatoes with the natural light grown ones.

    I thought about positioning the lights in the middle of my plants to boost growth below the canopy line since I don't think that providing additional incandescent light above the plants will effectively penetrate to the lower parts.

    Theoretically, you want to want a large proportion of other wavelengths of light to be mixed with the far red. Alone, far red produces negligible photosynthesis, but, combined with other wavelengths, it produces substantial photosynthesis through what is called the "Emerson Enhancement Effect." From Emerson Enhancement Effect in Chloroplast Reactions look at this graph:

    The curve labeled "without supplementary light" represents the photosynthesis rate for monochromatic far red light. The curve labeled "with supplementary light" represents the increment in photosynthesis rate produced by adding white light to monochromatic far red light (the photosynthesis produced by white light alone is already subtracted from that curve). Note that

    1. Red between 680 and 695 nm produced the highest rate of photosynthesis when combined with white light. One might reasonably conclude that Emerson Enhancemnt also applies to some wavelengths shorter than 680 nm.

    2. With white light, the incremental photosynthesis produced by far red levels off above 720 nm. Nobody knows how far into the infra red region that curve would continue to be level because that experimenter stopped at 740 nm. Incandescent has a lot of far red above 740 nm and is efficient in that respect.

  • struwwelpeter

    The curve labeled "with supplementary light" represents the increment in photosynthesis rate produced by adding white light to monochromatic far red light (the photosynthesis produced by white light alone is already subtracted from that curve).

    That should be:

    The curve labeled "with supplementary light" represents the increment in photosynthesis rate produced by adding far red light to white light (the photosynthesis produced by white light alone is already subtracted from that curve).

  • penfold2

    That study did show the benefit of far red light for certain applications, but I wonder if incandescents are really a practical solution. The wattage was increased by 34% when adding the incandescents. But would similar results have been achieved simply by adding 34% more fluorescent tubes? I'm just not sure that the growth enhancement due to far-red light in incandescents outweighs all the wasteful infrared they produce. It would have been nice if they had added one more variable for fluorescent supplementation equivalent in wattage to the incandescent supplementation.

  • struwwelpeter

    But would similar results have been achieved simply by adding 34% more fluorescent tubes?

    Unlikely, because 34% more Gro-Lux light would be expected to produce no more than a 34% increase in dry weight of leaves and stems, whereas adding 34% incandescent wattage produced a 100%*(153-82)/82 = 87% increase.

    Incidentally, although I couldn't find the spectral density chart for Gro-Lux, here is a similar curve for a GE imitation:


    I think these were later renamed "Sho and Gro." As you can see, it has plenty of near red light. Alone, Gro-Lux and Gro and Sho are lousy plant growth lights.

  • wordwiz

    struw,

    Most people don't eat stems and leaves!

    Mike

  • penfold2

    Mike,

    I am in complete agreement that excessive far red light is a bad thing, but sunlight has a red:far red ratio of around 1.2, and these experiments were all conducted at even higher ratios. So it would seem that we're talking about relatively low levels of far red light. It did increase flowering and fruit production, as well as stems and leaves.

    If I were growing tomatoes under fluorescents, I'd probably do my own side by side comparison.

  • wordwiz

    All the studies I read say that sunlight has a Red/Far-red ratio of 1/1 except at sunset when the ratio is higher for far red. Then during the night, it is converting back to red. Providing a higher ratio during the day will means stem elongation and thinner leaves

    I looked at the study and perhaps missed it, but I didn't see any references to the number or weight of fruit.

    My CFL and HPS bulbs both provide some FR light and I cannot see any reason to use more electricity to provide energy that doesn't help. Plus, if I'm growing indoors, whether to sell the seedlings or transplant later, I want short, stocky plants with thick leaves and large roots. Ditto if I want to grow them to maturity indoors.

    YMMV,

    Mike

  • penfold2

    Providing a higher ratio during the day will means stem elongation and thinner leaves.

    A high red:far red ratio means more red and/or less far red. You'd see stem elongation and thinner leaves with a low ratio, not high.

    I looked at the study and perhaps missed it, but I didn't see any references to the number or weight of fruit.

    I take it back. After reading more carefully, it said that Grow-lux + incandescent increased fruit production compared to cool white + incandescent. That says nothing about the addition of incandescent.

    I find this all interesting, but I guess I see no evidence yet for increased fruit production.

  • wordwiz

    My bad, I didn't word it correctly. Providing a higher Far red/Red ratio will do as I said.

    I still maintain that the bottom line is pound of fruit production per watt of energy. If ICD lights was efficient, growers would be using them.

    YMMV,

    Mike

  • struwwelpeter

    Most people don't eat stems and leaves!

    I still maintain that the bottom line is pound of fruit production per watt of energy.

    Maybe, I should also use basil as test plants?

    The tomato plants in my test will be transplanted outdoors at around 18" height, but, if fruit develop before then, I will take a picture before cutting them off.

  • wordwiz

    At least people do eat basil leaves and growers sell part of the stems. If all I want is leggy seedlings I can move them further from the light.

    Mike

  • organic_oddity

    Struw - I'd really like to see you go through a complete fruiting process with this setup. Given what I've read, red lighting (~640-720) is definitely beneficial, but more so in the flowering/fruiting stage. Taking the plants outside is cheating in my opinion.

  • taz6122

    Yeah what's the point if you're not taking it all the way. What would it hurt taking a couple plants through the fruiting stage for the sake of the experiment? You could become yucatans idol. lol

  • yucatan

    @taz: It's obvious that you have no life, or brain for that matter. Your contributions are pointless. Please stop posting.

  • struwwelpeter

    I intend to use tomato Big Zac as test plants which are too large to fruit under that 4' fixture. Maybe, I will include some cherry tomato plants. In any event, I want to end the test soon so I can use that fixture to test a different combination of bulbs.

    Meanwhile, I am waiting for my tomato seeds, planted on 4/3/10, to sprout. I have some worries about using a new soil mix of 2/3 peat moss plus 1/3 parboiled rice hulls (PBH) because there is some contamination with rice. I can see some rice grains on the soil surface because the grains have white mold growing on them. I hope this doesn't interfere with germination. My marigold and zinnia seeds have already germinated and seem to be OK.

  • taz6122


    "It's obvious that you have no life, or brain for that matter"

    You're right! I have no life. I'm physically disabled. My brain however is fine.

    "Your contributions are pointless"

    To most they are priceless.

    "Please stop posting"

    Maybe....when I have nothing to add.

    Have a nice day !

  • wordwiz

    Rob,

    I don't agree with taz about everything but close. He knows what he is talking about.

    YMMV,

    Mike

  • struwwelpeter

    There is a mylar partition down the middle separating the Gro-Lux only (left) from the Gro-Lux plus incandescent (right). All sides except the top are shrouded in aluminized mylar sheet. The front shroud is lifted to take the picture. This is located in the back of my greenhouse. These shrouds are also intended to keep daylight out of the interior.

    In hopes of keeping plants stocky, I will try to keep the average dark temperature higher than the average light temperature. To do this, the lights are on only from 6 PM to 10 AM. The greenhouse heater is set to go on below 55 deg. F. and the greenhouse ventilator fans and shutter are set to go on at more than 95 deg. F.. I am aiming for 80 deg. F. light temperature and 95 deg. F dark temperature.

    On each side are 6 tomato seedlings in 4" pots. They are Best Boy, Bush Early Girl, Velvet Red, Riesentraube, and 2 Big Zac. The potting mix is 2/3 peat moss plus 1/3 Riceland parboiled rice hulls. They have been fertilized with a fertilizer designed for hydroponic use.

    I would have started yesterday but a ballast burned out. It may have been caused by the extra heat from the 35 watt halogen incandescent bulb. Today, I replaced the ballast and installed small fans to circulate air inside.

  • yucatan

    I learned from a very knowledge horticultural professor that a seedling mixture which is high in peat is not favorable for seedlings. He proved this in powerpoint slides by showing the differences in growth between seedlings grown in a variety of other mixtures, which all outperformed the mixture high in peat. At the current height of your seedlings, I was expecting them to have more leafy growth. I see no convincing differences between the vigor of seedlings on both sides at this stage. Consequently, there may be more at play here than proper lighting, i.e. peaty soil. Additionally, fertilizers for hydroponic use are not recommended for soil-based plants, nor should you need to fertilize them much, if at all, when they are this young.

    I don't understand the whole temperature experiment idea. Tomatoes should perform best with dark temps. between 60-70 and light temps between 75-85 F. You'll also have much better results if you run your lights 20 hours/day.

    Please don't take my advice as criticism. You may dismiss it if you disagree. I am simply trying to help. Take care struw.

  • chefrobert

    I agree with yucatan. This light seems very red to me. You may benefit from a little more blue, which will help you gain more leafy growth.

    Plus, aren't those containers too big for seedlings? You should maybe start out in seed starter trays and progressively transplant into larger containers to promote strong, healthy root systems. A tiny seedling in a big pot also has a harder time absorbing nutrients and water.

  • organic_oddity

    From an experiment point of view, there are too many different factors going on here. Granted, the only real differences between the two sides are the IC lights and the extra heat generated by the IC lights (or extra wind movement due to the fans alleviating heat but changing conditions), and those may not be enough to affect the results of the test.

    I'd be interested to see light meter results as well as a thermometer on the other side.

    But yeah, using the peat, hydroponic fertilizer, messing with the temperatures, etc. all throw a lot of different factors into this test that violate not only best practices of growing tomatoes, but unless the IC side has some serious differences at the end I would doubt the results.

    @struh - thought you were going to grow cherry tomatoes through fruiting stage?

  • struwwelpeter

    1. The seeds were planted on 1/3/10 and germinated on 1/8/10. Between 1/8/10 and moving under those lights on 1/12/10, they were grown under daylight in my greenhouse.

    2. I have been planting in a mixture of 2/3 peat moss and 1/3 perlite for decades. The only new thing for me is that I am substituting rice hulls for perlite. Rice hulls are cheaper than either peat moss or perlite.

    3. Also, I have been using Hydro-Gardens 10-8-22, which I modify by adding 20% urea and 20% urea phosphate, for decades. The purpose of using a hydroponic fertilizer is to add substantial amounts of calcium, magnesium and sulfur, which peat moss lacks. Some other people's poor results with peat moss can be attributed to a lack of Ca, Mg and S.

    From an experiment point of view, there are too many different factors going on here.

    I agree, but I can't afford to take time at my age. The negative light to dark temperature differential experiment needs to be done in cold weather. By the next opportunity, next Spring, I might be dead.

  • yucatan

    @struw: You planted them on January 3 and that picture is dated April 12... are they still that small?

    There's nothing wrong with using peat, just a mixture that is HIGH in peat. The pH is too acidic and requires much amending before plants grow well in the medium. Why spend all that time trying to correct pH, when you can add a majority of pine bark fines or partially composted forest products along with a little peat and perlite? I remember you mentioned that your rice hulls were getting moldy too. It just seems like too much of a headache to continue using that decade-old mixture. Calcium promotes a more basic soil while sulphur promotes a more acidic soil, so by adding both, you're not doing much to correct pH.

    See this link for more detail about what I am referencing about pH:

    http://www.plantanswers.com/garden_column/march04/1.htm

    Also, here's some more visual evidence of underperforming seedlings high in peat.

    http://userwebs.batnet.com/rwc-seed/Pepper.growing.tips.html

  • struwwelpeter

    1. The seeds were planted on 4/3/10 and germinated on 4/8/10. Between 4/8/10 and moving under those lights on 4/12/10, they were grown under daylight in my greenhouse.

    See, I'm getting senile.

  • struwwelpeter

    I remember you mentioned that your rice hulls were getting moldy too.

    No, there were a small proportion, maybe less than 1%, of rice grains (the stuff you eat) mixed in with the rice hulls. Normally, you can't find them (like looking for a needle in a hay stack) until fluffy white mold grows on them. So far, there is no problem. Otherwise, these rice grains should turn to compost soon enough.

    pH is too acidic and requires much amending before plants grow well in the medium.

    That is not my experience and, like I said before, I have been doing this for decades. In fact, my fertilizer is also acidic and adding urea phosphate to it makes it more acidic. I determined that urea phosphate improves growth a long time ago.

    Here is a partial analysis of Hydro-Gardens 10-8-22:

    Ca 5%
    Mg 1%
    S 2%
    B 0.05%
    Cu 0.05%
    Fe 0.2%
    Mn 0.1%
    Mo 0.05%
    Zn 0.05%

    Nitrate N 8%
    Ammonia N 2%

    This exact fertilizer is no longer available, but a version without Ca and Mg is available with the intent that calcium nitrate and magnesium sulfate be added later to the solution. High acidity helps keep Ca soluble.

  • struwwelpeter

    No outstanding differences between Gro-Lux and Gro-Lux plus incandescent grown tomatoes, yet. The greenhouse grown ones (not shown) are also very similar.

  • struwwelpeter

    Still, no outstanding differences between Gro-Lux and Gro-Lux plus incandescent grown tomatoes. I suspect that the negative light-dark temperature differential negated phytochrome mediated stem lengthening and Emerson Enhancement of photosynthesis was negligible. The cherry tomato, Riesentraube, is the shortest.

    To my amazement, these tomato plants are shorter but heavier looking than their greenhouse grown counterparts. The weather was mostly sunny, and, my Gro-Lux bulbs are decades old and used. Who would have guessed?

    In several days, I will have to lower the shelf and thin the plants. I will keep two Big Zac and two Riesentraube.

    I upgraded my enclosure on 4/23/10. Note that the fluorescent fixture just lays on top and I can easily replace it with a board with LEDs, small HID bulbs or any combination.


    Note that the aluminized mylar shroud in front leaves a 2" opening at the bottom that serves as an air inlet and the fans at the ends blow out. Those exhaust fans are on the same timer as the lights. There are two other fans at the bottom of the inside of the enclosure that are on continuously and blow upward. The fan pairs are connected in series which causes them to turn slowly.

    From 10 am to 6pm, I wrap a black plastic sheet around the chamber to keep light from leaking in and to help sunlight raise the inside temperature.

  • struwwelpeter

    Front Row is Daylight Grown in Greenhouse
    Middle Row is Gro-Lux Grown
    Back Row is Gro-Lux Plus Incandescent Grown

    Columns starting with leftmost are Bush Early Girl, Best Boy, Riesentraube, Velvet Red, Big Zac, and Big Zac.


    As I said before, the experiment will continue with Big Zac and Riesentraube.

  • organic_oddity

    Thanks for the update. Also interested to see continued differences in the plants (flowering, yields, etc.) although I think the difference will be between the greenhouse and the enclosure grown plants in general, with the IC not having much effect.

    When taking pictures can you shoot two plants (one enclosure, one non) side by side so we can see the differences close up?

  • struwwelpeter

    Left to right, daylight, Gro-Lux, Gro-Lux Plus Incandescent. You can read the variety on some of the tags. The pots are 4.06 inches diameter at the top outside.



    The biggest difference is with Velvet Red (which some people claim is the best tasting cherry tomato that isn't sweeter than a normal tomato). This is the first time I have grown it. It is supposed to have bluish foliage and fuzzy fruit.

  • taz6122

    You're over watering the 'light' grown plants.

  • struwwelpeter

    You're over watering the 'light' grown plants.

    It is practically impossible to over water my rice hull potting mix because it drains water well while leaving many air pockets so that there is sufficient oxygen to promote healthy root growth and kill anaerobic bacteria.

  • taz6122

    It's obvious to me that the soil in the artificial light grown plants is wetter than that in the natural grown as it's darker and has more cyanobacteria growing on it and the plants have leaf curl. Ignore it if you want but it is obvious.

  • struwwelpeter

    The soil of the plants grown under sunlight dried out at different times and therefore were watered at times other than the plants grown under light bulbs. In the first two pictures, FuorInc3.5.1.jpg and FuorInc3.5.2.jpg, some of the daylight grown tomato plants were beginning to wilt. All of the soil surfaces have algae.

  • organic_oddity

    Thanks for the pictures. Tomato leaves will curl under any condition that isn't "optimal", and given what I know about the test I'd say heat might be more of a problem.

    Aside from that it looks like IC didn't do a whole lot. In comparison, it *might* have hurt the Big Zack (first pic) while helping the Velvet Red. Possibly not surprising as each plant is going to have different growing conditions, but I'm not seeing a big push to add IC to my setup. Your thoughts?

    Useful stuff here. I'm planning to grow some hydro tomatoes and jalapenos indoors this winter and, as I'd mentioned in other threads, lighting is my biggest concern.

  • wordwiz

    oo,

    Check out my Why I like LEDs thread in this section. I'm growing a 7-pod under an LED. I also have a Legend tomato plant (and three broccoli plants) under the same light. But I'm also using a 2.8 watt, 64 bulb white LED that I am using to supplement the tomato. It hangs about 1/2" from the very heart of the mater plant.

    Mike

  • struwwelpeter

    I'm not seeing a big push to add IC to my setup. Your thoughts?

    Like I said before, my experiment suggests that a negative light-dark temperature differential negates phytochrome mediated far red responses. With a positive temperature differential, you would likely see longer stems, maybe bigger plants, with incandescent supplementation.

    However, I am most interested in increasing photosynthesis via the Emerson Enhancement Effect. Since this has nothing to do with temperature differential, I conclude that there was negligible effect under this combination of wavelengths.

    In my next experiment, I am going to look for Emerson like enhancement between near violet and far red wavelengths.

  • struwwelpeter

    Left to right, the plants are Riesentraube, Big Zac, Big Zac and Riesentraube. Only the Big Zac, on the right, under Gro-Lux plus incandescent, has flower buds. I will have to lower the shelf again tomorrow, but, this time I will prop up the Riesentraube.

  • struwwelpeter

    The remaining Big Zacs had to be removed from the growth chamber because they grew too big to fit. Here they are:


    Notice the flower buds.

    The Riesentraube remain in the growth chamber and also have flower buds. I will try to grow Riesentraube fruit in the growth chamber.

  • wordwiz

    Struw,

    Any updates? How do the plants look after five weeks?

    Mike

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