I think you have just answered my question in this post regarding intensity and wattage. How much is too little and when does one go overboard and reach a point of diminishing returns? http://forum.grasscity.com/indoor-medical-marijuana-growing/1347034-your-thoughts-light-intensity-vs-wattage.html You said the magic words... Daily Light Integral. This is what I have been trying to find out. The garden is in the process of being streamlined in order to lower operating costs. After borrowing a PPFD meter, I found rather interesting data. This is an 864w T5/HO fixture in a 5x5 tent used for vegging on a 18/6 schedule. According to the DLI you mentioned above, it is below the suggested rate. What I found most disturbing (and disappointing) is how much actual light I was getting per watt. And look how close they need to be to get the PPFD. The plants grew and they were healthy but the growth rates were less than spectacular. This is the flowering tent with 2x600w (MH&HPS) set on two timers so that the total wattage used in a 12hr period equals that of a 1000w HPS. I am relieved to learn that it is within the specified DLI requirement. These plants were vegged under LEDs. and at the time, they were only under 2x150w panels before they were moved into the HID flowering tent. I recently added a 3rd 150 panel to flower the rest of these plants. Very pleased with my new LEDs and relieved to find that it is with in the recommended DLI requirement. By the time the plants are done stretching, the PPFD will be towards the upper DLI requirement. By the way, these High Intensity LEDs have blown away the T5s and will be replacing them immediately. (The LEDs surpassed them using only 300w on a 24hr schedule) Up until now (and I mean up until I learned about the DLI) I have been using wattage to gauge the amount of light that was needed in the garden. Boy was I ever wrong about that. Is there an upper limit to the DLI before energy is wasted? Thank you Mr. Icemud. Your words are about to save me a bunch of $$. Great INFO man! -PG
Wow...beautiful writeup of your testing of your lights in regards to DLI... Its really hard to say as far as what is the limit of light or "light saturation point" where the intensity actually decreases photosynthesis and coming by cannabis specific information is even harder. Most of my plants during flowering sit between 600umol and 1100umol, but some times the buds get closer to the lights and seem to cause bleaching of the buds around 1500-1600umol... Now I don't know if this is because of the photon count (ppfd) or some other factor such as radient heat or some other unknown, so I try to keep the plants just under the 1500umol, but without sacrificing coverage, which usually sets me around 600-1100umol. I suspect that there is more going on with the bleaching at 1500umol because the sun on a bright day at noon typically puts out around 2000 umol at ground level, so I think it may be some other factor causeing the bleaching... Now the other part of this, which is highly debated in the science community is how particular light wavelengths drive photosynthesis... I believe DLI is based off greenhouse lighting methods which is considering the suns spectrum, and with the McCree curve (photosynthetic action spectrum) we know that reds are more efficiently used by plants than other colors (which is also heavily debated). So I suspect with LEDs, since they are red heavy and tuned to the most used colors, that the DLI may change due to the fact it is not sunlight and a custom spectrum requiring less PPFD than sunlight. Being that the sun emits a ton of green light, and a majority of this is reflected, its really hard to say how the PPFD of LEDs would compare to the PPFD of sunlight... Since photosynthesis rate is primarily affected by 3 components, Light intensity, temperature and available CO2, all 3 of these things must be in "optimal" levels for the plants photosynthesis to increase. The unfortunate part is I have hardly been able to find this information for cannabis, let alone for other plants so I think we kind of have to just figure it out on our own to a point until more lab research is done on the cannabis plant. So to answer your question...im not sure.. but from what I have read in speaking on LED, it seems that anywhere from the DLI of 22 which would be 510umol up to around 1400umol is good for flowering cannabis, but I would probably guess and say anything over around 1000umol or more would probably also require elevated CO2 levels and optimal temps. I also wish I knew at what point the buds become "airy" vs dense... as defintiely light intensity seems to have a direct correlation with this.. some things I noticed were that buds around the edges of my grow tent are always smaller than the ones in direct lighting from the LEDs... so it seems to be cannabis can flower under lower umol than the DLI suggests, but what I don't know is at what point that buds become less weight and airy... I swear I wish I had a big warehouse and a ton of meters, cause I would love to conduct tests on this...
the majority of green light is actually absorbed by C3 plants, only around 15-20% less verses blue or red to be less than precise. and there are several other process carried out by plants besides just photosynthesis I.E. phototropism, photomorphogenesis etc and higher plants rely on these wavelengths to complete many functions . so it's easy to see how many can become lost in the light jargon and sales pitches. yellow light on the other hand has been found to more than likely be the culprit of the original green light discussions of past. also note plants do not care whether you run red in flower and blue in veg or the opposite, they control what they absorb and when, you changing the lights offers little to them other than having to compensate for lack of other photons missing, which isn't a good thing. now you can change growth patterns by manipulating wavelengths, but i would venture a guess that you have no way of knowing what that outcome may be to genetics, terpene profile etc.. and that is just a stab in the dark. if i could give anyone advise it would be to keep an acceptable amount of PPFD across the entire 300-750 nm range and if you could, just limit the 560-580 range as this seems to be the wavelength most unused and detrimental to plant physiology, but again much as yet to learn.
How much of a temp change could you expect with a 400 watt light in about 130 cubic feet container? The air can be cycled out every minute with the carbon filter at about 70%. Sent from my iPhone using Grasscity Forum
. Thank you, this has helped me a lot. But if I go with a different brand like https://www.1000bulbs.com/product/137465/TCP-68923B2-SP.html with a CRI of 83 granted its 23w is that still a good bulb? In other words Does the CRI deplete over time and if I get a cheaper brand will it just burn out and be at 60 CRI in a week? Instead of maintaining 83 the whole grow maybe I'm over thinking it or missed something. I am pretty high. Haha or would it be better to go with https://www.1000bulbs.com/product/153587/PLT-10102.html even tho its only 80 CRI and 32w. Either way I'd have the same numbered of watts total should I go with the higher CRI? Sorry for such a long post.
From my testing since this write up I have found that a DLI of 10 for seedling sprouts, 20 for young veg, 30 towards the end of veg and I finish at a DLI of 40 for the last couple weeks of flower to be very productive for cannabis. Any variation to these numbers +/- has caused a decline in growth potential for Indica and Sativa cultivars. This is without c02 supplementation. VPD at 75-77degrees F, 60%-65% humidity. Full spectrum MH and HPS bulbs in operation for the testing. Bulbs used were Hortilux Blue which I like but they don't last very long, Solis Tek 6k 400 watt, far longer life verses the Hortilux and also I use the Ushio Red bulbs mixed with the Solis Tek 6 k bulbs for the last three weeks of flower. I no longer have canopy mass, stem thickness, dry bud weight nor any other data from my testing as I lost it on a drive but kept the outcome written on paper thankfully. The higher DLI during flowering can be used due to canopy thickness and subsequent shading of much of the lower canopy as long as Vapor Pressure Deficits are kept in check. Heat would be your nemesis mainly due to the intensity required to maintain a DLI of 40 with a lighting schedule of 12 hours per day. This is why an even canopy spacing of light is vital. Think bright spots and shade spots from uneven hoods or diodes.
This thread is a bit old but the more recent posts about PAR readings and how they compare to the DLI is the kind of info I think makes more sense of what my light is doing instead of comparing wattage ratings which means nothing when factoring in how much more efficient each generation of LED is over the previous. Wattage is only useful in power consumption. Now Im really curious what kind of readings I can get from my light. I also keep wondering why more PAR data for each manufactures lights isn't available along with DLI ratings as well. And why more members here that spend a lot of money on lights yet never buy a PAR meter to get some real data on what they have light wise. IF anyone can point to more information like this that actually analyzes what the plants like and how its proven besides advertising and claims of wattage, efficiency and wavelength, coverage area etc. Im a small micro grow in a closet. I have however ordered a Apogee MQ-200 meter to get some real info on my single little MH Cree light. After I gather the data I want I will decide if I need more or better light and probably sell the meter on ebay.
Most LED companies are just investors that buy bulk wholesale lights from chinese suppliers, slap a logo on it and rebrand it for a 5x mark up in price. Most of their websites are just copy and pasted information that many times is false, misleading and incorrect and when you talk to the owners they claim everything is "proprietary". The truth is there are very few LED manufactures that know anything about lights, plants, reactions etc. This is why they don't post the info like DLI, PPFD, PPF or any useful info as most have no clue what it means or how to apply it. Also many companies sell inferior products that wouldn't even compare datawise to better quality products so they would actually ruin their sales by being honest. Also, most LED panels that use 3w or 5w chips are very directional and the beams don't spread, so generally a light that is advertised for a 2x4 coverage usually only covers the actual size of the light plus about 1' around that surface area.. which most are about 2'x2' actual coverage. By being honest, most people would laugh at the coverage and not buy their overpriced, rebranded junk.
I've never been motivated to sign up to a forum, But recently I was online and noticed this company offered a zero interest payment plan on grow supplies. I figured I could use a new set of bulbs which I typically buy original Gavita replacement 1000W D/E well this company only sold there own HydroLight Brand 1000W HydroLight D/E which kind of made me worry about the quality of the product, I called the 888.943.3015 number and talked to a guy and when asking him about the bulbs he kept saying " Man these are the best bulbs on the planet my boss spent 12 years developing our bulbs " He told me there lights are so bright that he want to brand them 2Brite. Guy sounded like My Cousin Vinny I totally felt like I was being pitches some bullshit. But a part of me figured Its same as cash no money down and the bulbs were pretty cheap 89.95 Hmmmm should i risk getting swindled for my identity i must of been on a great smoke that day i went ahead and Financed 16 bulbs my payment was like 65.00 a month balance due in 6 months figured id pay when i harvested. TO my Suprise I received the bulbs in like 3 days .. Honestly more than i expected from a company i found on craigslist claiming to finance your growing supplies wholeheartedly thought it was a scam and i was high when i did it. So i installed 8 of the HYDROLIGHT BULBS ran them right next to my OLD gavita bulbs they were certainly much brighter I mean Much Brighter like so bright it was tough to look into that side of the room.. Whoaaa I need to get out of the room these are way too bright , Wait a minute the guy said i wanted to brand these bulbs 2brite ... He's right these suckers are Bright made me feel like heavens gates opened up in my face... So I ran along and replaced the last 8 Wholly Molley are these suckers bright the intensity is outrageous , Push come to shove 3 months later i dropped some gg#4 four per light 7 gallon coco pots i averaged between 10-14 oz a plant i had 64 plants i yielded 48LBs of some rock hard dense nug.. I called back the my cousin Vinny Guy and wanted to KISS him threw the Phone.... He told me your using Klunker Junker Gavita's you'd actually jump on a flight and actually come kiss me if you used my ballast and reflector with my bulb it will reduce the heat by 40% over a gavita.. Guess what since i paid off my first loan i was approved for up to 5000.00 the first time i used only 1500 and paid it off with zero interest, he's like i can approve you for 10,000 this time you ready for new fixtures, they pay for them selves with all the extra yield and reduced heat output.. IM had to do it rarely do you ever find a company thats better and far ahead of the market place and they basically give it to you for free.. its that deal thats always to good to be true hydrolight.com that guy over there I call him My cousin vinny now , He calls me the smartest red neck in the midwest LOL ... Freggin fantastic company and product i urge anyone that needs 1000W MH HPS or D/E to try this product it is actually 2brite.
A poster being presented at this weeks Cannabis West Conference on various tools to measure light regimes.