K temperature Question

[Squawkbert]

Go ahead and search out some 96W 10,000K bulbs - I think you'll find some very different spectrums (among the few vendors that post spectral information) as some of these are made for planted tanks and some are for corals.

I'd post links, but it has been a year or two since I did it...

The coral friendly bulbs look very blue, because something like 90% of their output is at wavelengths <400nm, and their CRI is <60. The plant friendly versions have a big spike at a much lower wavelength (700nm area) to complement the blue spike (also centered at a slightly lower wavelength than the coral bulb's blue spike). The result is a much whiter appearing bulb (also blue, but a "washed out" looking blue), that also happens to have a 10,000K rating.

Ideally, bulb manufacturers would include PAR, CRI and a picture of the spectrum on the side of every tube's package along with a K rating.

 

[Spewn]

Plenty of manufacturers publish the information, there's no need to experiment.

Edit; I don't generally deal with bulbs in that range, so I guess that's why I didn't think of them. Of the information available on the more commonly used for growing(for growing production, that is) color temps, the bulbs are all very similar. Generally speaking, an HPS lamp rated at 2100k is going to have nearly the same spectrum as any other HPS lamp. Some bulbs specifically change their output, however, and this may be why some of the 10,000k bulbs(and up) appear so different. If they aren't labeled as to being specifically modified, they should be. For example, look up the SonAgro HPS bulb. The bulb has been modified from a standard HPS design to produce more blue output, but it is still rated at 2100k.

 

[jmhart]

Plenty of manufacturers publish the information, there's no need to experiment.

Yes, but can you point to me any information about how it effects plant growth? It's one thing to say "yeah, color temp(edit: or spectrum) effects plant growth" but another thing to prove that it's anything more than conventional wisdom.

Edit: The question is if, and if so how, Bulb A with X spectrum effects plant growth compared to Bulb B with Y spectrum.

 

[Spewn]

Plenty of resources online to find out for yourself. Just google SonAgro, Hortilux Blue, Agrosun Gold, and go from there.

There's a reason why people don't fruit under "daylight" bulbs, but rather use low-kelvin HPS bulbs instead for best results. It works.

Here's what(so far) 10 seconds on google has yielded;

http://ag.arizona.edu/pubs/garden/mg/botany/environmental.html

"Light quality refers to the color or wavelength reaching the plant surface. Sunlight can be broken up by a prism into respective colors of red, orange, yellow, green, blue, indigo, and violet. On a rainy day, raindrops act as tiny prisms and break the sunlight into these colors producing a rainbow. Red and blue light have the greatest effect on plant growth. Green light is least effective to plants as most plants reflect green light and absorb very little. It is this reflected light that makes them appear green. Blue light is primarily responsible for vegetative growth or leaf growth. Red light when combined with blue light, encourages flowering in plants. Fluorescent or cool-white light is high in the blue range of light quality and is used to encourage leafy growth. These lights are excellent for starting seedlings. Incandescent light is high in the red or orange range but generally produces too much heat to be a valuable light source. Fluorescent "grow" lights have a mixture of red and blue colors that attempts to imitate sunlight as closely as possible. They are costly and generally not of any greater value than regular fluorescent lights."

So, at least I can prove I didn't pull it out of my rear-end. More to come, I have a few hours before work

Oh, and the search phrase was: "how does color temp affect plant growth?". Why must google be so complex and cryptic? Lousy search engines lol

 

[Spewn]

Yet more:


http://succulent-plant.com/light.html
"Red light is very important to plant reproduction. Phytochrome pigments absorb the red and far red portions of the light spectrum and regulate seed germination, root development, tuber and bulb formation, dormancy, flowering and fruit production. Therefore, red light is essential for stimulation of flowering and fruiting.

Blue light stimulates chlorophyll production more than any other colour, encouraging thick leaves, strong stems and compact vegetative growth. Carotenoids, the yellow-orange pigment in plants, absorb blue light and control leaf fall and fruit ripening. Riboflavin, containing another pigment, absorbs violet light and influences "phototropism", the movement of plant foliage in response to light. "

 

[jmhart]

So, that answers the question that spectrum does effect growth, and it answers how spectrum effects the growth terrestrial plants. I have to wonder if aquatic plants respond to different light. I know that corals growing at deeper depths respond to different light than corals at shallower depths due to the distortion of light through the water.

But on a practical standpoint, this only says that we should look for bulbs with strong peaks in the red and blue spectra.

Oh, and the search phrase was: "how does color temp affect plant growth?". Why must google be so complex and cryptic? Lousy search engines lol

That's funny. I always tell my wife "just ask google" and the other day she laughed at me because I really did "just ask google" about something. She thought it was funny that I phrased it as a question in the search, instead search say, "color temp plant growth"

 

[Spewn]

Sure it's funny, but believe it or not, it works. I'm getting plenty of results just modifying my question slightly

http://www.hydrofarm.com/articles/garden_for_all_seasons.php

"Halide bulbs yield wavelengths balanced across the entire range of the spectrum necessary for optimum plant growth. This light is suitable for year-round vegetative growth. Halide lights emit more color spectrum but less light intensity, whereas sodium lights emit a more narrow band of the color spectrum but more light intensity. Sodium bulbs give off more light in the red end of the spectrum, enhancing flowering."

 

[phanmc]

In order to say k rating is useless, you're going to have to demonstrate that spectral output amongst identically-rated(temperature) bulbs is wildly different. I've never seen such a demonstration, not amongst bulbs of the same type.

I can show you the PAR output is different between two identically rated bulbs by the same manufacturer.

http://www.aquabotanic.com/lightcompare.htm

Compare the Philips Advantage fluorescent, 5000K F32T8/ADV850 and the Philips TL950 5000K fluorescent very high CRI (98) F32T8/TL950. Both are 5000K, one has the highest PAR efficiency for standard fluorescent and the other is one of the lowest.

I have tried many kinds of bulbs that range from 3000k to 18000k and even mixed some actinic in, I have yet to see a demonstrative difference in growth patterns from the different lighting.

 

[Mindcrime121]

Bottom line: Red and blue light = good (unless they are in your rear-view mirror)!!

 

[Spewn]

I can show you the PAR output is different between two identically rated bulbs by the same manufacturer.

http://www.aquabotanic.com/lightcompare.htm

Compare the Philips Advantage fluorescent, 5000K F32T8/ADV850 and the Philips TL950 5000K fluorescent very high CRI (98) F32T8/TL950. Both are 5000K, one has the highest PAR efficiency for standard fluorescent and the other is one of the lowest.

I have tried many kinds of bulbs that range from 3000k to 18000k and even mixed some actinic in, I have yet to see a demonstrative difference in growth patterns from the different lighting.

The authors conclusion for that test was:

"The most important conclusion in my opinion is that the efficiency of converting electrical energy into PAR light energy is not that different for the several bulbs and technologies included in the sample. The majority of bulbs in the sample deliver approximately (within a 20% range) the same amount of uE/s/Watt in the 400-700 nm range, about 1 uE/s/Watt. High intensity discharge lamps and high-end fluorescents tend to be more efficient, but not by a large factor. "

You pointed out an anomaly, not the general trend. The author seems to think that the differences even across the various technologies are minimal. The differences across bulbs rated the exact same is yet smaller.

As for not noticing yourself; What can I say except that a whole lot of people(see my links) do indeed notice, and that these people tend to have a vested interest in knowing the difference(growing crops under artificial light).