By gisette
Test 1: Greens, LED triband vs. CFL spotlight
Submitted on Sun, 2010/01/24 - 9:07pm
Last updated on Mon, 2010/02/15 - 9:41pm
Posted in
Test 1: Greens.
Note: This test was pooched by a hardware failure - LED light went bad. Please see Test 3: Greens for the rematch.
Constructed light isolation box for side-by-side growing (all same box, just rearranged):
Lights: 16 hours/day.
- 16W triband LED spotlight, 3rd generation (132 red - 18 blue - 18 full spectrum white LEDs, about 7:1:1)
- 15W 6500 K CFL floodlight, 650 lumens, "daylight" bulb with built-in reflector.
Today I found a CFL flood that was 16W... oh, well, 15W is close enough, I'm not going to buy more bulbs. For comparison, AG Deluxe bulbs are 26W, but unfocused. They also seem yellower to my eye.
The CFL is definitely hotter. Which will probably give the CFL plants a head start.
2009-01-23: Presoaked a couple hours and planted seeds in each of two pots:
- 4 French blush radish (thin to 1 or 2) - harvest time 25 days
- 3 baby leaf spinach (all others thin to 1) - harvest 30-45 days
- 3 tendergreen mustard - harvest 30 days
- 3 little Caesar romaine - harvest 45-60 days
In 9.4" diameter Misco self-watering pots (Walmart plant spa), and fresh Miracle Gro potting mix.
Hypothesis: My best guess :
- There is enough light to grow all 4 species, if somewhat anemically.
- There will be < 10% difference in harvest.
What I want is > 10% difference in harvest - LEDs clearly more grow power for same watts.
Anyone else want to bet? 
Germination:
day 2: Most mustard greens and half the lettuces up. No real difference CFL/LED.
day 3: Three radishes up, both pots. One LED lettuce still MIA. Unfortunately both missing sprouts on the LED side are the ones centerward. All mustard up. No spinach yet.
day 4: Moved 1 outside lettuce into the light on LED side. Only 2 of 3 sprouted. Radishes have same problem - missing the seedling in the light. But I don't think radishes would transplant well.
day 6: Set some spinach seed to germinate in wet paper towels in a baggie. Will use some of those if the ones in pots fail to come up. (Not unusual for spinach.)
day 7: Final radish seeds germinated, one each side. (Not unusual for radish.)
day 11: Still no sign of the original spinaches. Planted 6 more from baggie sproutings, most advanced centerward.
day 14: First spinach emerged, one on each side (baggie sproutings).
day 20&21: Two more spinach emerged (first CFL side with no leaves, 2nd LED side looking good).
Progress:
day 5: Raised only LED light over greens. The spotlight was too concentrated in the center of the pot, with seedlings around the outside visibly stretching toward the light. CFL is not as focused, so raising it would entail a lot less light density at pot surface.
day 7: Lowered the LED back a bit. Maybe 3" higher than CFL now. The LED plants are stretched enough that they can lean into the light circle if they want.
day 8-11: LED side brassicas keeling over. At first just one dark-side radish, but now 2 radishes and a mustard are lying down. Too leggy. The centermost radish (late sprouter in fullest light) is already taller than its CFL counterpart, and behind in leaf development. Best-lit mustard doing OK, but lagging all 3 CFL mustards.
day 14: Thinned. Didn't bother to weigh them. CFL side obviously better by far more than 10% - on the greens experiment.
day 21: Harvested brassicas. It's early, but the radishes were done, and the CFL side mustard was overshadowing everything - there were no questions remaining there. Left the lettuce and spinaches... for the moment.
Thu, 2010/01/28 - 1:58pm
#2
Definite point, Peat, re the vegetative-specialty light of the CFL.
Another problem may be that the CFL is less focused, and that's a good thing in context. I've got both lights down very close to the pots, but with the LED, that means there's a bright circle in the middle of the dirt, and most of the seedlings are beyond its radius. So I'm kinda torn. For a fair trial, should I raise both lights equally? Or say that distance isn't much of an issue with well-focused light, and raise the LED only? Or...? If I raise the CFL much higher, most of its light will go outside the pot.
How it looks so far, is that no CFL seedlings are straining for light, but the outside-beam LED seedlings are. I even moved an LED lettuce seedling into radius. Radishes... are less movable, I think.
We'll see how the tomato & pepper do. In the vegetative stage, do we also expect CFL would have an edge?
Thu, 2010/01/28 - 2:18pm
#3
Perhaps you'd better move the LED up a little to give some light to the dark side. 
It's got a little extra watt of power so it's still fair?
As for the tom & pepper, my guess, it's only a guess, is that the CFL may be better to start with before the LED pulls away - I'm intrigued to see how this all works out.
Thu, 2010/01/28 - 2:23pm
#4
Thanks... yeah, I think I'll raise the LED tonight on the greens.
The theory was, that LED would grow better than CFL/T8 in all cases, of course. 
Theory being that it maximized wattage to the photosynthetic wavelengths. In the case of red lettuce, that does seem pretty dubious. Perhaps with greens too, though.
Thu, 2010/01/28 - 2:36pm
#5
Before my cuke bit the dust, it positively thrived in the light from my UFO - I thought the leaves looked in much better condition than my 125 watt CFL, much more 'lush' and stockier.
The theory was proved in my case, but, the conditions were much different in that the LED was in a better grow area.
Thu, 2010/01/28 - 3:07pm
#6
That was 90W LED vs 125W CFL, right?
My cukes seem quite fond of the LED light, too, though I don't have any controls on that (not set up as an experiment).
Well, this was why I wanted to try a variety of plants. It wouldn't be surprising to learn that they don't all respond the same. But - lettuce was the application NASA originally developed LED grow lights for. I was expecting results to fall off as we got farther from lettuce.
Thu, 2010/01/28 - 3:35pm
#7
That's correct with the lights.
The NASA reason is why I also wanted to try the LED technology, plus, lower electricity bills do have some appeal.
Sat, 2010/01/30 - 3:00pm
#8
7 days, still no spinach. Hmph.
Found this discussion on GardenWeb and decided to try it. I need to start some spinach for outdoor transplants in March, anyway. (Finally found an answer to 'what exactly do they mean by as early as the soil can be worked?'. Lettuce & spinach supposed to go out 4-6 weeks before last frost, which is about March 1 here.)
Pre-soaked a bunch of spinach seeds (actually 2 bunches - two varieties) in cold tap water for a couple hours, in the fridge part of the time. Then wrapped them in cold wet paper towels and a plastic baggie, and placed on a chilly dark windowsill. Start checking for germination in a couple days.
Whichever 4-6 sprout first (including the ones already in those pots), get to be in the LED/CFL experiment.
Sun, 2010/01/31 - 6:08pm
#9
One week progress:
Note how much leggier the greens are on the LED side. CFL side has clearly superior seedlings. Though not much difference in development for best-mustard between the two sides.
But - having seen the 'clearly better' dishtub cuke just nosedive, we'll keep going with both sides of this experiment for now.
Edit: Although... if the CFL side had been the one stretching hopelessly, I would have added a bulb to see whether two equalled one of the other. Kinda pointless the other way around, though, since the LED spot is 4x more expensive than the fancy CFL bulb.
Sat, 2010/02/06 - 8:33pm
#10
Two weeks' progress:
Thinned today. Didn't bother to weigh them. CFL side obviously better by far more than 10% - on the greens experiment. On the CFL side, radishes are beginning to form bulbous stems - already split, actually. The brassicas on that side look great. The lettuce on both sides looks pretty poor. Maybe the air's too dry, or the soil too rich?
This experiment is not going at all the way I expected. Lettuce was supposed to be the easy win, plant most likely to succeed. I wasn't sure the CFL side would have enough light for the brassicas. In practice, the brassicas are doing best of all, under CFL, and will certainly have radishes on day 25 as scheduled. The mustard looks fine, too.
And I expected both sides of greens to way outperform either side tomatoes. Not so...
It'll be interesting to see what happens with the spinach. But I'm not expecting much.
May call this experiment complete at 30 days.
Edit: I had a better picture of the CFL side radishes from yesterday:
Sat, 2010/02/13 - 2:59pm
#11
Three weeks' progress:
Harvested brassicas. It's early, but the radishes were done, and the CFL side mustard was overshadowing everything - there were no questions remaining there.
I don't have a very good scale, and I broke off half the leaves on the smaller radish yesterday by dropping the camera. 
But remaining biomass was ~ 1.5 oz. CFL side, maybe .25 oz. LED size. So with missing radish leaves, maybe 7x (700%) better growth on CFL side. More if you count only harvest and don't like radish leaves. The LED side radishes would never have developed a bulb.
Left the lettuce and spinaches... for the moment. But in my experience it's 3-4 weeks from this point to harvest size on these plants.
Although I'm still a little curious about the spinach, continuing this doesn't seem worth the electricity. Question answered. Any other opinions?
Sun, 2010/02/14 - 9:12am
#12
Now that's a huge difference!
I was surprised to see the LED beaten so comprehensively, I have read that different plants need different light spectrums, but, the LED is a complete non-starter in this test.
In contrast, have a look here. Someone else has done a CFL vs LED experiment with much different results... We don't know if he used a reflector for the CFL or what sort of setup he had - no pictures of the grow!
Sun, 2010/02/14 - 1:45pm
#13
Huh. That test was odd. His LED side got 20 hours light a day, CFL only 16, and non-comparable conditions. (CFL with heat mat (not something lettuce would appreciate) and moisture dome (moisture good for lettuce, but steam bath risk under so much heat/light), and he used a mega-powerful hot CFL, instead of equivalent wattage.) And his CFL seedlings don't look ill, just slightly smaller than the LED seedlings.
And his plants are just seedlings - any growth differential compounds over time.
My CFL bulb was 1/4 the price of the LED, unlike his. And cost the same electricity to operate.
My results so far are brassicas, not lettuce, though the writing is on the wall for the lettuce. Brassicas and spinach grow differently than lettuce, for sure.
< shrug> I could try it again with another of my LED lamps, since that was my only reservation - if maybe just that one lamp was bad. But I don't have any reason to believe that, other than that the LED tomato did much better. Or, I could try again with 2 lights on each side, so everybody hopefully has more than enough light. But what more would that tell me.
Edit: Gisette struck that last...
Sun, 2010/02/14 - 2:26pm
#14
Aw, hell! 
I thunk, "Eh, it wouldn't hurt to replace the LED lamp for the rest of the test. I have another."
The original LED lamp was one third dead LEDs. When did that happen... 
Soaking more lettuce and radish seeds. 
Guess we'll try this again...
Sun, 2010/02/14 - 5:22pm
#15
Sorry about the LED, that didn't last very long!
Hopefully you will now get comparable results to Test 2.
Sun, 2010/02/14 - 5:31pm
#16
Yeah, I need to have a discussion with HTGSupply. I've heard good things about that company - I hope for a replacement.
Seeds are soaking, Test 3 greens about to begin... Need to stop being mad at myself for not noticing sooner. 
Sun, 2010/02/14 - 6:07pm
#17
The dead LED lamp.
I went back over my pictures (taken every day, just didn't post them here), and I can't tell when the lamp went bad.
Did learn a few things here, though:
- The 15W daylight CFL was bright enough to grow radish and mustard really well. I wasn't sure of that - the dimmest AG uses a 26W CFL.
- 15W CFL probably also bright enough for lettuce and spinach - those plants had other little issues.
- The surviving ~10W LED was not bright enough to grow well. However, the plants didn't die for lack of light. So... the experiment is in the right ballpark wattage-wise.
The revamped experiment will be same radishes and lettuce, but replace mustard with toy choi, and spinach with swiss chard.
Nice little trial Gisette, interesting to see which one has the edge...
Tricky call this one, I'm wondering if the CFL may be better on these greens purely because it's in the dedicated vegetative spectrum. The LED is a sort of 'jack-of-all-trades' so I'm unsure who will win/draw?
Personal preference is for the LED to dominate.