New Grower My first Auto grow

[Delps8]

So I'm guessing this is the video you meant. It is interesting indeed.
View attachment 1548879
I don't think that's accurate. That curve is very similar to the net photosynthesis curve in the Chandra paper where cannabis is grown under varying temps and CO2 levels. Net photosynthesis is not "growth", and that's not pedantry.

The fact that those are very different is a significant issue in "Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment" which shows that the yield curve has a much more linear slope. Below is a table showing the yield curve that's quoted in that paper with the yield data that they provide. The yield values are quite low but the key point is that % delta. In that study, there was a 16% increase in yield. That's enough to convince me to turn up the lights a little.

That fact is backed up in a couple of places, one of which is by Westmoreland, a Bugbee student, in the video on growing hemp, which is the source for the image below.

Yeh, that was the video. I still haven't watched it all the way through.

 

[Kirka88]

It's nice b/c Bugbee definitely has the experience and has clearly done the research so he's well informed on the subject. Yes it does closely resemble the curve I recall seeing in a Chandra's papers . He has multiple publications and I've yet to read them all. I'll need to look up the paper by Westmoreland b/c Bugbee only labeled his axis as growth rate. His and Chandra's do seem to indicate a more logarithmic growth rate with respect to PPFD.
That aside it's also nice to hear from people who have years and years of first hand experience and knowledge. But it is nice to see data that's been published and peer reviewed!
As an aside I think towards the end of that video Bugbee advocated for increased CO2 levels
And I think your referencing this publication? I give it a read today!
Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment
Victoria Rodriguez-Morrison et al. Front Plant Sci. 2021.

Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment - PubMed

Since the recent legalization of medical and recreational use of cannabis (<i>Cannabis sativa</i>) in many regions worldwide, there has been high demand for research to improve yield and quality. With the paucity of scientific literature on the topic, this study investigated the relationships...

pubmed.ncbi.nlm.nih.gov

 

[Delps8]

It's nice b/c Bugbee definitely has the experience and has clearly done the research so he's well informed on the subject. Yes it does closely resemble the curve I recall seeing in a Chandra's papers . He has multiple publications and I've yet to read them all. I'll need to look up the paper by Westmoreland b/c Bugbee only labeled his axis as growth rate. His and Chandra's do seem to indicate a more logarithmic growth rate with respect to PPFD.
That aside it's also nice to hear from people who have years and years of first hand experience and knowledge. But it is nice to see data that's been published and peer reviewed!
As an aside I think towards the end of that video Bugbee advocated for increased CO2 levels
And I think your referencing this publication? I give it a read today!
Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment
Victoria Rodriguez-Morrison et al. Front Plant Sci. 2021.

Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment - PubMed

Since the recent legalization of medical and recreational use of cannabis (<i>Cannabis sativa</i>) in many regions worldwide, there has been high demand for research to improve yield and quality. With the paucity of scientific literature on the topic, this study investigated the relationships...

pubmed.ncbi.nlm.nih.gov

Bugbee's CV is here. I've never seen his accomplishments compared to others in his field but his CV is quite something.

"logarithmic growth rate" - per my previous posting, they discuss net photosynthesis and that disturbed me a bit because I'm not harvesting net photosynthesis. The paper "Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment" covers a lot of ground, including data re. the internals of plant growth. That's all well and good but the key data for me are the data in the "Yield and Quality" section. The Chandra paper does not discuss yield nor do most of Bugbee's videos and I've had someone argue that there was little value in increasing PPFD because "the curve flattens". Bugbee emphasizes that in his videos so I can understand why some people, erroneously, latch on to that. Even with the Pn curve rolling off, it's still cost effective to increase light levels, some caveats apply, of course, and that would be the completely obvious conclusion with even the most basic consideration of that costs involved.

"But it is nice to see data that's been published and peer reviewed!" - agreed. I'm a 30+ database applications developer so I have a different perspective than a lot of folks re. data. One of my coffee mugs reads "Without data, you're just another person on the internet with an opinion".

"As an aside I think towards the end of that video Bugbee advocated for increased CO2 levels" - unquestionably and, based on the increase in yield, I can see why commercial growers would be using it. It requires additional equipment and different processes than working in ambient CO2 but, again, if you run the numbers, the payoff is significant.

"And I think your referencing this publication? I give it a read today!" - yup, that's the one. Quite a different story from the DLI's that Shane and growlightmeter.com are recommending but, then again, researchers have a different set of motivations and biases than do the people who are trying to sell grow lights.

Aside - there's a body of research available to growers and I've toyed with the idea of starting up series of threads to review and discuss different papers, videos, etc. I haven't really put much thought into it but I think it would be a valuable endeavor.

 

[Kirka88]

Bugbee's CV is here. I've never seen his accomplishments compared to others in his field but his CV is quite something (sayeth the first in his family to not attend an Ivy League school in a few generations).

"logarithmic growth rate" - per my previous posting, they discuss net photosynthesis and that disturbed me a bit because I'm not harvesting net photosynthesis. The paper "Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment" covers a lot of ground, including data re. the internals of plant growth. That's all well and good but the key data for me are the data in the "Yield and Quality" section. The Chandra paper does not discuss yield nor do most of Bugbee's videos and I've had someone argue that there was little value in increasing PPFD because "the curve flattens". Bugbee emphasizes that in his videos so I can understand why some people, erroneously, latch on to that. Even with the Pn curve rolling off, it's still cost effective to increase light levels, some caveats apply, of course, and that would be the completely obvious conclusion with even the most basic consideration of that costs involved.

"But it is nice to see data that's been published and peer reviewed!" - agreed. I'm a 30+ database applications developer so I have a different perspective than a lot of folks re. data. One of my coffee mugs reads "Without data, you're just another person on the internet with an opinion".

"As an aside I think towards the end of that video Bugbee advocated for increased CO2 levels" - unquestionably and, based on the increase in yield, I can see why commercial growers would be using it. It requires additional equipment and different processes than working in ambient CO2 but, again, if you run the numbers, the payoff is significant.

"And I think your referencing this publication? I give it a read today!" - yup, that's the one. Quite a different story from the DLI's that Shane and growlightmeter.com are recommending but, then again, researchers have a different set of motivations and biases than do the people who are trying to sell grow lights.

Aside - there's a body of research available to growers and I've toyed with the idea of starting up series of threads to review and discuss different papers, videos, etc. I haven't really put much thought into it but I think it would be a valuable endeavor.

I think it would be cool to start a thread or blog with that maybe like a paper a week or what ever and then people could hash it out and consider the implications. Videos are easy to watch and papers more effort to read. But a paper will tell you what and how they measured things. What they observed in actual data and if course thier conclusion which I prefer. a quick graph in a video just doesn't give you that level of detail and like you say can be misleading !
Which no doubt you already know but I figured it's worth saying lol

 

[Kirka88]

Dec 22
Just a fast check. Soil looks good not too dry. Plants are growing nicely somewhere around 22" as a ball park average due to height variation.
~650 PPFD 73F, 55% RH

 

[Kirka88]

Dec 25th Merry Christmas!!
Ya lol I'm posting this a day late
So what with the nute burn I figured I'd water my plants with just straight water.
Then next watering I take the nutes backwards 1 step and use Mega Crop 1 part 3/4 tsp/gal (3g, 3/4 strength). Also I'll double check with my new scale to be positive it's really 3g!!.
At this point they're about 24" tall.
650 PPFD, 72F 55%RH

 

[Kirka88]

Jan 1st Happy new year!
Fertilized with MC 1 part (3g/gal 3/4 strength) and Sweet Candy (1g/gal). Plants were a tad light a touch damp to dry at top layer. Averaging around 30" in height. Bought a new smaller scale to weigh out fertilizer. Calibrated it with coins based on the US mints specs for weights and found it was accurate to w/in a few 100th of gram. I did this out of concern that Mega Crop tends to clump and measuring it with a teaspoon may not be that accurate (possibly leading to my having over fertilized the previous time????).
Just starting to see a few yellow leaves, strictly at the very bottom of 3 out of 6 plants (maybe straight water was a mistake last time? Maybe I should have started adding Sweet Candy sooner?). For now I'll take a slow wait and see approach. The yellowing appears to be between the "veins" in the leafs.
~ 650 PPFD (varies due to height that's at the average height, 70F 55% RH.

 

[Bill.de.Cat]

Did you add the .5 gram of epsom salt to the MC 1 part?

 

[Lil Dab]

Jan 1st Happy new year!
Fertilized with MC 1 part (3g/gal 3/4 strength) and Sweet Candy (1g/gal). Plants were a tad light a touch damp to dry at top layer. Averaging around 30" in height. Bought a new smaller scale to weigh out fertilizer. Calibrated it with coins based on the US mints specs for weights and found it was accurate to w/in a few 100th of gram. I did this out of concern that Mega Crop tends to clump and measuring it with a teaspoon may not be that accurate (possibly leading to my having over fertilized the previous time????).
Just starting to see a few yellow leaves, strictly at the very bottom of 3 out of 6 plants (maybe straight water was a mistake last time? Maybe I should have started adding Sweet Candy sooner?). For now I'll take a slow wait and see approach. The yellowing appears to be between the "veins" in the leafs.
~ 650 PPFD (varies due to height that's at the average height, 70F 55% RH.View attachment 1551786View attachment 1551787View attachment 1551788View attachment 1551790

That Burple makes it hard to diagnosis can we get the plant under normal 5000k lighting? But if it were me and I fed then the problem arose I would assume it was the feeding that caused the issue.. I have limited experience with SC added that and BE then I had issues but lots of peeps use it with good results ... I personally was a fan of 3g 1 part with added .5-1g Epsom and little calmag but I was in coco I needed it

 

[Kirka88]

So this might give a better view here's 3 different plants.
Of interest last week there was nothing beyond the burnt leaf tips (over fertilized).
1 So last week I fed no fertilizer (upon seeing the leaf tips) and instead used just water....
2 This week I started seeing the leafs yellowing between the veins , only a few plants and only the lower most leafs
3 today a fed at 3/4 strength MC 1 part which has Cal and Mag in it and today was the very first time I added Sweet Candy. Roughly following another's grow / nutrient schedule but not exact...
4 of interest it's only the 3 plants at the front door of the tent where my air intake hose vent is and these were a fair amount dryer than the back 3 which held more moisture...???
Plant 1

Plant 2

Weird how that leafs growing upside down???
Plant 3

Mega crop 1 part analysis (which I think they claim is all you need??)

So Ive added zero cal mag at this point??