perhaps but i would have thought that the ones with a lower total range are likely to be more accurate (as a percentage error)
good that they are nice and cheep though, i did find a quantum one but it was about $500 (£300)
Why go 24 hours lights on??
- Thread starter thcrefugee
- Start date
perhaps but i would have thought that the ones with a lower total range are likely to be more accurate (as a percentage error)
good that they are nice and cheep though, i did find a quantum one but it was about $500 (£300)
No, I can't say unless you also know the distance to canopy and age of lamp and type of ballast (magnetic vs. digital) and type of reflector (wide vs. deep and "pebbled" vs. "mirrored") and use of a 'light spreader' for the hot spot under the lamp (or no use of a 'light spreader') and use of glass ex. in an air cooled hood (glass reduces irradiance by 10%+). It's very hard to guess. But, for a 1000w hps running a new lamp with a magnetic ballast and pebbled, wide reflector with a glass insert below the lamp, the PPFD could be around 1,000-1,500 if the lamp is 14-18" inches away. But, that is only a very rough guess, I could be wrong, it's just too hard to say considering all the variables involved.
If a grower uses less than a meter^2 canopy, they could more easily provide higher irradiance, as umoles/foot^2/second, for example. Irradiating a smaller canopy with high irradiance is easier than irradiating a bigger canopy with high irradiance.
I think you misread what I wrote, it's a new topic to most people, so you may want to re-read what I wrote again. 1,500 PPFD fits into my DLI model because I used a natural PPFD bell curve from high irradiance location (Hawaii) that peaked at ~1,800 PPFD around noon; the same PPFD that offers highest rate of photosynthesis for cannabis.
What do you mean "why is there no mention of DLI"? I wrote a lot about DLI. I do not know to what you are referring.
Like I wrote, we shouldn't use 1,500 PPFD all day, either in veg or flowering. That isn't natural for plants, and can/will cause photoinhibition of Pn, etc. The sun has a bell curve of PPFD over a day, it's not a flat PPFD from morning to night. That is why I did the math, using a good example of natural high irradiance PPFD bell curve that has a peak PPFD of ~1,800 around noon.
My model for floweing (12 hour day) puts DLI at 46-48 (mol/meter^2/day); that is achived using ~1,000-1,100 PPFD (specifically ~1,065 to ~1,111 PPFD).
hey spurr i was reading the paper and the conclusion cites it as 120,000 lux too (which is defined (by wiki) as 'brightest sunlight' -
I am pretty sure that is a typo in the paper, I think it should read "12,000", see the graph below that section in the paper, it reads "12,000". I think when the paper was scanned into digital format (PDF) the OCR reader read "12,000" as "120000".
120,000 Lux is a lot of light
Get one that goes up to 50,000. I doubt that study looked at 120,000 Lux; but I could be wrong. I will email the author of the paper if I can find his contact info. That said, the Pnnet found in that paper was highest at 12,000 Lux, but, the researchers noted that Pnnet may continue to increase above 12,000 lux (they didn't test more than 12,000 lux).
The least expensive one i know of is $199 (SpecMater "FieldScout"), so it's even cheaper for you. The one I would suggest, while still being (rather) inexpensive, is $299 (Apogee "MQ-100").
I am probably going to buy the MQ-100 in a week or two, so I can compare it to the Li-cor "Li-190". I could send you the MQ-100 so you can test your lamps and LEDs with it if you wish. I already promised I would let another IC'er use it first though.
Let me know if you want to borrow the MQ-100 once I get it.
Only to a point, too much light is just as bad as not enough light in terms of rate of photosynthesis, etc. In fact, too much light, ex. > 1,600 PPFD, is worse than not enough light in terms of causing various ills due to photoinhibition...
Yup, I am not aware of any cannabis studies that looked at DLI. That is why I did the math legwork that I wrote about, using the natural PPFD bell curve from Hawaii that provides peak PPFD of ~1,500-1,800 (because that PPFD has been studied for cannabis).
I did my best to create a goal DLI from PPFD found ideal for cannabis. But like I wrote, I plan to study DLI and PPFD on cannabis this coming year once I get a good "chlorophyll fluorometer" (~$7,000)...or a full on photosynthesis/chlorophyll fluorometer chamber (but that's around $30-40K so it's not gonna happen next year).
Also, fwiw, you seem to write "DHI" often, it's "DLI". I wasn't sure if "DHL" is a typo or not, so I figured I would point it out. I'm not trying to be a jerk or anything though.
I am pretty sure that is a typo in the paper, I think it should read "12,000", see the graph below that section in the paper, it reads "12,000". I think when the paper was scanned into digital format (PDF) the OCR reader read "12,000" as "120000".
120,000 Lux is a lot of light
yeah it's confusing. the graph in the paper has it up to 12,000 but lists the units as lux x10 to the -1. if 120,000 is classed as 'brightest sunlight' then i wondered if it's correct
Get one that goes up to 50,000. I doubt that study looked at 120,000 Lux; but I could be wrong. I will email the author of the paper if I can find his contact info. That said, the Pnnet found in that paper was highest at 12,000 Lux, but, the researchers noted that Pnnet may continue to increase above 12,000 lux (they didn't test more than 12,000 lux).
The least expensive one i know of is $199 (SpecMater "FieldScout"), so it's even cheaper for you. The one I would suggest, while still being (rather) inexpensive, is $299 (Apogee "MQ-100").
I am probably going to buy the MQ-100 in a week or two, so I can compare it to the Li-cor "Li-190". I could send you the MQ-100 so you can test your lamps and LEDs with it if you wish. I already promised I would let another IC'er use it first though.
Let me know if you want to borrow the MQ-100 once I get it.
hehe just snagged one on auction for about $20 (a lux one), it will have some applications for my work too.
thanks for the offer to borrow yours but that might be complicated as i am in UK. i'll keep a lookout for a good deal on a quantum one though.
cheers
VG
Hummm. Maybe it is. I will look at it again, and try to email the author today...
I already answered it a few times. Look at my post to bobman on last page, and my big post with lots of refs somewhere on page 5-10.
I never said it was "ultimate", I wrote it's a good example to use for natural bell curve of PPFD under sun, and that the PPFD data has a peak of PPFD ~1,800 around noon, which is close to peak PPFD for cannabis. That is why I used it, and the PPFD data was found on a relatively cloudless day. I used it because it's a good example of natural bell curve with high irradiance, and thus good way to find DLI for 'sun loving' plants like cannabis, and it offers very close PPFD to what is saturation point for cannabis...
I know PPFD (or inferior Lux) under HID is a straight line, that's my point. Under sun PPFD is not a straight line, so, if we used very high irradiance that provides peak Pn for cannabis (as instantaneous light) under HID light all day long (i.e. in a straight line), we would most probably be providing too much light, and that's bad. That is why for a good goal of DLI we would use less than peak level of instantaneous irradiance (either PPFD or lux) for cannabis. Using 1,500 PPFD all day, or > 120,000 lux all day, is most likely not a good idea due to photoinhibition of Pn, Pnnet, VPD, etc.
Re-read what I wrote on the last page.
You and VG are probably correct; I was going off of the graph. I don't use lux for lighting, and I have spent very little time looking at lux because it's not a plant light measurement.
yeah lux is based on human vision so definitely will fall short for plants.
the atmosphere is very clean in hawaii afaik - thats why they have some big observatories there.
the atmosphere is very clean in hawaii afaik - thats why they have some big observatories there.
Bob Smith wrote:
FWIW, "dirt" (which is a misnomer) is a "high production" method if the "dirt" is has ideal properties (or near ideal), and is properly watered. I have listed ideal soil and soilless properties in a 20+ page thread elsewhere at ICmag.
Bob Smith wrote:
Bob Smith wrote:
You are going way off-topic, and I doubt you are being sincere. There is a thread about Co2 elsewhere at ICmag that I posted in, and I still have to upload some more papers into...
FWIW, "dirt" (which is a misnomer) is a "high production" method if the "dirt" is has ideal properties (or near ideal), and is properly watered. I have listed ideal soil and soilless properties in a 20+ page thread elsewhere at ICmag.
Bob Smith wrote:
No, it is not.
Bob Smith wrote:
FWIW, lots of far-red light would "get beneath it [the top canopy]". A canopy as you describe, as SOG or SCROG, would negatively effect the red:far-red light ratio intracanopy which makes plants stretch. Again, I wrote a thread on this topic elsewhere at Icmag...
deidree barlow
Member
Why go 24 hours lights on??
My mentor always said "they'll sleep plenty in flower".
My mentor has operated multiple 8k+ grows for many years... But what does he know, right? Haha
Fwiw
My mentor always said "they'll sleep plenty in flower".
My mentor has operated multiple 8k+ grows for many years... But what does he know, right? Haha
Fwiw
QFT. Spurr I think all of us are trying to wrap our heads around these ideas and how to implement them. Lets not get wrapped up in ignoring legitimate questions because the wrong person asked them.
U~know~who
New member
You know the funny thing is that people keep alluding to these drastic things that are going to happen if you don't give them sleep but apparently it doesn't have anything to do with yield. Early on in the thread it was made clear that yield alone meant nothing.
You have in no way offended me. I simply meant that spurr and yourself have disagreed previously and he seems to have discounted your posts as being combative only from them being made by you. I am arguing against this because I think there is a perception that you and bobman are the same person as VG previously said I believe. Maybe adding an avatar would help with this? I don't know. Oh and QFT is Quoted For Truth it is a netspeak way of adding emphasis to something without writing out that you agree with the poster and why and so on and so forth. Short hand...
I know very well whom Bob Smith's pseudonym is, and I have no reason to think he is being sincere, as evidenced from his other posts. In some of which he seemed sincere but to later to be proven otherwise, at least to me. I see no reason to help someone who has so been adversarial to me in the past, and no, I don't consider disagreement to be adversarial, but Bob went far beyond simply disagreeing.
I know Bob couldn't care less what I write, that much as been shown in his previous posts, so I see no reason to write my thoughts, and provide what info I have, for him.
bobman
Member
Bob the jig is up. They know. Spurr in all sincerity I think you have a good hypothesis. The reading has been interesting but I do not think you can say anything for fact until the data comes back. If someone would just pony up the balls and email the guys at ole miss maybe we could cut to the chase. I am sure they have the answer already.
