I've been asked to post on my LED-based Horticulture "hobby" and have decided to share a bit of research into the reason for doing it to begin with.
See the attached brief for an introduction into the amazing effects of selected wavelengths on plants.
Photosynthetically-active light, generally considered to be 400-700nm, is part of the story, but light from deep UV into inftrared affects plants too, including controlling traits that will surprise you!
LEDs Improving Nutritional Content and Taste?
As the cost of distributing produce rises and the "locavore" movement takes hold, "plant factories" are being proposed as new uses for abandoned office and factory space. However, if the customary artificial light sources are used, the costs could be prohibitive.
Combining solar light with artificial light to extend the growing day in classic greenhouses, and even these new concepts is not especially novel. But using LED light instead of wasting energy on unused, reflected spectrum, and the heat produced by metal halide and HPS lamps, has real potential. Add to that, the potential for improving both nutritional content and taste, and now you have an operation using less eneergy to grow superior produce in less time. I believe I have experienced some of these effects in my own personal LED grow-station in my home.
In the interest of sharing information on the potential influence of LEDs on different crops, I obtained permission to share the below two documents from Kevin M. Folta PhD of the University of Florida and an associate of his, Jeffery Bucove of LEC.
Dr. Folta first presented his work on nutritional manipulation at the 2011 ASHS meeting.
The second download is the slide set for his presentation on this same subject material, which would really benefit from a voice-over explaining the images. However, if you first read the "LEDs can affect nutrition" paper, you will see that the slide set provides supporting charts, graphs and spectral information.
I'd really like to hear from anyone interested in this and other papers I have located on LED Horticulture, which I could post in the future.
Hmm- Thought I replied to your post but I guess it didn't stick!
Glad to hear you like it-
Others, PLEASE, let me know what you would like here. I will attempt to tune this to your needs.
I have purchased a professional "PAR" sensor to measure the radiation in the spectrum the industry has defined as "Photosynthetically Active Radiation". This spans precisely 400-700nm, and does clip out some wavelengths known to have photomorphogenetic activity. But because that is "the standard"- I will use it to quantify the plant-useful radiation from several sources including some I have built. It will be interesting to see what the differences are between older, more wasteful technologies and LEDs chosen to put ALL their radiation at wavelengths used by the plant.
Thanks for starting this excellent discussion. I am trying to understand the rated wattage of an LED compared to an HPS for the same growing application. Can you decrease that LEDs wattage decrease further if the light spectrum is appropriately tuned for that plant and its stage of development? Given that LEDs can be placed closer to the plant due to cooler operating temperatures, does that allow for a decrease in wattage as well?
Thanks for opening this interesting topic. I really appreciate that you discuss horticulture connected with LEDs, I thought is a great idea. LED light as an environmental production contribute a lot to the environment protection. It is low power consumption, super bright, recyclable, and long life span. It's not only economical, but also artistic. It can beautify your garden, and highlight your plants. Such as the LED landscape courtesy and flood light, it is really a cool item to beautify home, hotel, marketplace, garden, landscape. Create a Bright, Beautiful and Romantic lighting effect. Plants can have photosynthesis-active under the sunshine, in the same way it can have photosynthesis-active under the lighting, so lighting is very important for plants. It allows plants have photosynthesis-active at night, and our world will become more and more beautiful for light and plants.
Hi Don and thanks for the information.
I have tested myself some LED Grow Light with Stevia Plant.
Stevia has tiny seeds really hard to germinate. I get 1 plant out of 20 seeds. I keep it under LED grow Light and use it for all my cutting. With low heat and low energy use, this is a great way to do it.
I guess the light must be a good quality as the leaf are a really nice green. Each bulb use 7 Watts.
Hi Richard and friends
Sorry for the late reply, I am moving, and right now trying to find a house for a much bigger setup than my temporary apartment allows.
I believe the answer is yes, you can use reduced input power in LED lighting than other grow light technogies because plants can't use much of the radiated spectrum from those other sources, and with LEDs, we are targeting EXACTLY the absorption bands of photosynthesis (and other effects within the plant). But the ratio will vary according to the light sources you compare and the specific plant. I am personally working on experimental hardware that produces 6 or 7 wavelengths and has the ability to program the mix at any given time. This is so I can discover the implications of specific wavelengths. Philips sells (to commercial growers only, I believe) LED lighting for greenhouses already "tuned to the crop" based on years of research with their own scientific staff. Their LEDs are sold as a sole or supplimental light source (likely more common, as in the addition of far red LEDs specifically to increase the flowering in strawberries).
Also yes, the reduced heat (and absence of plant-cooking deep IR) from LEDs has an advantage allowing closer placement to the plants, with a reduction in wasted light and greatly increased local intensity.
I have personally experimented in this area for many years, but recently LEDs for "the interesting wavengths" have become more powerful and affordable. It is still a major pain to build your own as I have chosen to do, but well worth the effort (if you're a plant/electronics geek like me).
Commercial growers will do well to consult with Philips or their reps in various countries (such as Hort Americas, here in the USA and Latin America) to find the correct LEDs, adapted to their applications. They have screw-in lamps for overhead apps, LED light bars for between plant rows and others and have UL approval-pretty important where mist-heads are used.
I hope to post more soon, as I take photon flux measurements from a couple of different large LEDs sources I have built. The Li-COR sensor I will use limits to the wavelengths considered "the photosynthetic absorption range" used by plants, 400-700nm. I personally am not in complete agreement on this methodology for quantifying what a plant uses (a lot of green is reflected, for instance) but it has been used in horticulture for some time. More to come...
Once again, I apologize for not staying in touch- the good news- I have found a house and am working on the plans for my indoor "greenhouse". Because of all the difficulties I have had with plants drying out when I am away- I am going hydroponic. But lots of bad publicity about PVC- the easiest to work and obtain plastic, leaching chemicals into the water and then the plants, has me worried.
I will share my thoughts on the lighting for different crops as my garden comes together, but hope in-turn, some of you can contribute too. I have seen many hydroponic setups and it's a great area for commercial or DIY research. Any thoughts on better, available and innexpensive materials for constructing the waterways would be greatly appreciated.
LED gardening tip for the day-
I can't be sure this works for all species, in fact it likely doesn't, however in rooting "Brown Turkey" fig cuttings using rooting hormone, applying really intense 447nm for 16 hours a day caused AMAZING results. Roots climbing out of a 10" pot in 3 weeks. I covered the 8" cuttings in their pots with polyethylene bags to keep in moisture and they shot roots like I have never seen before. They are what would be called soft wood cuttings.
I tried the same with ginko- no luck, but they were late-season cuttings, a bad plan from the start. I have started ginko trees for 2 other people in the past, outdoors in the shade so maybe it was just too much radiation for them?