Are we using too much light?

[Hafta]

Lol that's funny! ive Done that to, Dont like to admit but , yeah! For me things like that need to happen so i can learn, a book or a pod cast really doesn't do much for me sometimes except get me in trouble lol!! I like too fuck with shit when things are good but ive gotten better by doing it but that's me

We are all probably the same in that regard.

 

[Delps8]

I have a LUX Meter. Rarely even use it anymore. I just go by the plants leaves these days. If they are praying.... they are good. If they are turning down or cupping or twisting sideways the light is too bright. I personally feel this is the best way to determine how much light the plant needs. I do increase my light strength little by little through the grow. But I'm at 100% by the end of flower which puts me at about 65,000 lux. Not all strains will need the same amount of light so I find that letting the leaves decide does the trick better than a lux meter.

Per my posting, a lot of growers have that approach and, if that works out, that's great.

@Delps8

The wafer in your Avatar looks almost ready for final test.

I must agree with @Delps8, give your plants as much light as they can handle as soon as possible. I do not use gauges (mostly out of stubbornness) but let the plant indicate when I am overdoing it. Too much light will start the edges of the leaf serration to begin to curl. Raise the light a couple of inches.

Something that is often not considered when speaking about DLI and/or PPFD is that the importance of those readings is dependent upon surface area, meaning leaf surface area. If you are counting the photons emitted by the light it does no good if you can't collect them.
More light = more energy = more roots = more vegetation = more transpiration = more nute consumption = more growth. And it starts all over again.

The following plant is 28 days old and seven inches tall. It will soon be allowed to grow vertically. It has received nearly 400 watts of light (six fixtures in a 2' x 3' cabinet) since it was four days old. It has also been fed 130% of recommended nutrient concentration (monitored by the tiny yellow tips of the leaves).

This technique averages 300 grams per plant (more than ten ounces). This is double what most growers on this site achieve per indoor plant, verifying what @Delps8 mentioned above.

A couple of comments…

Heh, you grew a shrubbery! Nice to see. The plant from my last grow looked like that. About 2' tall and 30" around. Beautiful plant but beware of bud rot. :-(

And that res looks very similar to mine. That "nute chute" is a good idea. My takes up almost all of the floor space in my tent and I'd love to get one about ⅔ the size. How big is that res and where did you get it?

"Something that is often not considered when speaking about DLI and/or PPFD is that the importance of those readings is dependent upon surface area, meaning leaf surface area. If you are counting the photons emitted by the light it does no good if you can't collect them."
PPF is the amount of light that a fixture produces. PPFD is the "photosynthetic photon flux density" and it's expressed in µmol/second/square meter.

The best analogy I've heard (strangely enough it's from the guy who teaches this subject in university = Bugbee) is that DLI is how much rain fell in a given day (area not specified) whereas PPFD is akin to how much rain fell on a certain area in a certain time.

 

[Hafta]

Per my posting, a lot of growers have that approach and, if that works out, that's great.

A couple of comments…

Heh, you grew a shrubbery! Nice to see. The plant from my last grow looked like that. About 2' tall and 30" around. Beautiful plant but beware of bud rot. :-(

And that res looks very similar to mine. That "nute chute" is a good idea. My takes up almost all of the floor space in my tent and I'd love to get one about ⅔ the size. How big is that res and where did you get it?

"Something that is often not considered when speaking about DLI and/or PPFD is that the importance of those readings is dependent upon surface area, meaning leaf surface area. If you are counting the photons emitted by the light it does no good if you can't collect them."
PPF is the amount of light that a fixture produces. PPFD is the "photosynthetic photon flux density" and it's expressed in µmol/second/square meter.

The best analogy I've heard (strangely enough it's from the guy who teaches this subject in university = Bugbee) is that DLI is how much rain fell in a given day (area not specified) whereas PPFD is akin to how much rain fell on a certain area in a certain time.

@Delps8

I haven't experienced bud rot. I have twin 200 cfm exhaust fans and can change the cabinet's air ten times per minute. I run three circulating fans collecting warm air from the LED cooling fans and blowing it through the colas. Growing with the Skirted CST method removes most leaves from the canopy so a major source of moisture (transpiration) is not in close proximity to the buds. The cabinet RH is typically between 35% and 50%.

I received a Christmas bonus just before I retired so I bought a complete set-up from Supercloset. Then, I modified the hell out of it. The res holds 17 gallons one inch below three inch net cups. I have a 1/2 hp transfer pump that will empty the res into a cart, making res changes much easier (right hand corner of res).

From Wikipedia:
Daily light integral (DLI) describes the number of photosynthetically active photons (individual particles of light in the 400-700 nm range) that are delivered to a specific area over a 24-hour period. This variable is particularly useful to describe the light environment of plants.

I understand that one is a measurement of volume while the other is a measurement of density.

To actually quantify how much light is being utilized by the plant shouldn't the total leaf surface area be calculated? It seems improper or overly aggressive defoliation could nullify the gains of increased PPFD.

My point was not to debate the definitions, it was to re-enforce the need for adequate leaf surface to be exposed to light.

 

[Delps8]

@Delps8

I haven't experienced bud rot. I have twin 200 cfm exhaust fans and can change the cabinet's air ten times per minute. I run three circulating fans collecting warm air from the LED cooling fans and blowing it through the colas. Growing with the Skirted CST method removes most leaves from the canopy so a major source of moisture (transpiration) is not in close proximity to the buds. The cabinet RH is typically between 35% and 50%.

CST - constant stress training? That rings a bell but the details are fuzzy. I'll check out the link in your sig block.

I received a Christmas bonus just before I retired so I bought a complete set-up from Supercloset. Then, I modified the hell out of it. The res holds 17 gallons one inch below three inch net cups. I have a 1/2 hp transfer pump that will empty the res into a cart, making res changes much easier (right hand corner of res).

Congrats on retiring! Leaves you to handle the more important things, like a cannabis garden!

The ridges in the walls of the res looked familiar.cI bought a kit from them in 2017 but went with the 12XL. It's a beast.

17 gallons, eh? That's a nice size. The 12XL takes 28 gallons and it, pretty much, takes up all the floor space in the tent.

I'd be interesting in hearing about the mods that you've made. I only grow one plant at a time now. ATM, I've got two young plants in the tent and they've both beautiful looking so I hate to cull one but I've found that I cannot grow just one plant in that res — they get too big. That was with auto flowers, I'll admit. Autos are just beasts. I switched to photos so I could control flip and try to keep the plant size down. That how I ended up with shrubbery.

In the time I've been on this forum, you're the only other grower I've run into who uses a Superponics res. I'd like to trade tips growing with a large res and, also, about res management. More specifically, I'm interested in how growers modify the res to suit their needs and, on the topic of res management, it would be helpful to understand how other growers approach the issue. For example, I started this thread about res management some time ago and it could stand to be updated.

I'd appreciate any insights you might share but my thinking is that it would be best to do that in another area or a different thread. Something to mull over while I piss off another day of work reading cannabis forums!

From Wikipedia:
Daily light integral (DLI) describes the number of photosynthetically active photons (individual particles of light in the 400-700 nm range) that are delivered to a specific area over a 24-hour period. This variable is particularly useful to describe the light environment of plants.

I understand that one is a measurement of volume while the other is a measurement of density.

To actually quantify how much light is being utilized by the plant shouldn't the total leaf surface area be calculated? It seems improper or overly aggressive defoliation could nullify the gains of increased PPFD.

My point was not to debate the definitions, it was to re-enforce the need for adequate leaf surface to be exposed to light.

Understand completely re not debating the definitions.

Exposure to the light is the key. You raise an interesting point about defoliation. I'm not a fan of removing leaves but isn't defoliating an inherent part of CST?

 

[Hafta]

CST - constant stress training? That rings a bell but the details are fuzzy. I'll check out the link in your sig block.


Congrats on retiring! Leaves you to handle the more important things, like a cannabis garden!

The ridges in the walls of the res looked familiar.cI bought a kit from them in 2017 but went with the 12XL. It's a beast.

17 gallons, eh? That's a nice size. The 12XL takes 28 gallons and it, pretty much, takes up all the floor space in the tent.

I'd be interesting in hearing about the mods that you've made. I only grow one plant at a time now. ATM, I've got two young plants in the tent and they've both beautiful looking so I hate to cull one but I've found that I cannot grow just one plant in that res — they get too big. That was with auto flowers, I'll admit. Autos are just beasts. I switched to photos so I could control flip and try to keep the plant size down. That how I ended up with shrubbery.

In the time I've been on this forum, you're the only other grower I've run into who uses a Superponics res. I'd like to trade tips growing with a large res and, also, about res management. More specifically, I'm interested in how growers modify the res to suit their needs and, on the topic of res management, it would be helpful to understand how other growers approach the issue. For example, I started this thread about res management some time ago and it could stand to be updated.

I'd appreciate any insights you might share but my thinking is that it would be best to do that in another area or a different thread. Something to mull over while I piss off another day of work reading cannabis forums!


Understand completely re not debating the definitions.

Exposure to the light is the key. You raise an interesting point about defoliation. I'm not a fan of removing leaves but isn't defoliating an inherent part of CST?

@Delps8

I'll respond to the last part first.

Well you're really going to like this one ............it does have to do with light so this thread should be OK.

Defoliation is a critical part of CST.
In fact, in my current grow the horizontal training with the weights has reached the extremities of the cabinet so it is time to allow the branching to go vertical. Now is the time to add the "healing stress" portion of CST. The root mass will increase as the plant strives to heal and grow simultaneously.

This morning, day 29, I removed 123 leaves. The timing is dependent on horizontal spread.

The plant went from this

To this

Naturally it will recover once it relocates the light.

You will notice that there aren't many large fan leaves in the removal pile but there are quite a few around the base (the skirt).

There will still be some weight training as the different shoots begin to rise above the canopy and need to be redirected.

I will also be removing between 30 and 50 leaves per day through about the third week of flower. Some may think this is aggressive but I leave the majority of the large fan leaves intact. They have propelled the plant to this stage and are a well established source of energy for the plant. It just needs to try harder (CST). Removing the smaller and younger leaves also opens the canopy for better air circulation (no mold issues).

I agree that it is not advisable to try to grow more than one plant at a time, as you have mentioned.

I'll check out your thread about res management. I'm a little off the wall on that one as well.

 

[Delps8]

@Delps8

I'll respond to the last part first.

Well you're really going to like this one ............it does have to do with light so this thread should be OK.

Defoliation is a critical part of CST.
In fact, in my current grow the horizontal training with the weights has reached the extremities of the cabinet so it is time to allow the branching to go vertical. Now is the time to add the "healing stress" portion of CST. The root mass will increase as the plant strives to heal and grow simultaneously.

This morning, day 29, I removed 123 leaves. The timing is dependent on horizontal spread.



The plant went fr

Naturally it will recover once it relocates the light.

You will notice that there aren't many large fan leaves in the removal pile but there are quite a few around the base (the skirt).

There will still be some weight training as the different shoots begin to rise above the canopy and need to be redirected.

I will also be removing between 30 and 50 leaves per day through about the third week of flower. Some may think this is aggressive but I leave the majority of the large fan leaves intact. They have propelled the plant to this stage and are a well established source of energy for the plant. It just needs to try harder (CST). Removing the smaller and younger leaves also opens the canopy for better air circulation (no mold issues).

I agree that it is not advisable to try to grow more than one plant at a time, as you have mentioned.

I'll check out your thread about res management. I'm a little off the wall on that one as well.

Interesting that you're taking out small leaves? In my mind, defoliation is fan leaves but that's just my impression. But you're leaving the fan leaves (good idea) and removing the little ones.

And the result of this is to…control the canopy?

 

[bluter]

that's a salad.

 

[Hafta]

Interesting that you're taking out small leaves? In my mind, defoliation is fan leaves but that's just my impression. But you're leaving the fan leaves (good idea) and removing the little ones.

And the result of this is to…control the canopy?

@Delps8

Most growers consider defoliation as removing fan leaves so you aren't alone. I have not seen anyone else growing this way.

Yes, canopy control is part of it, but there is much more ...

The large fan leaves are what got the plant to this stage, it hasn't relied on the small leaves to this point. By removing the small ones I haven't interrupted its power supply much so it is able to absorb the defoliation stress without much problem. The photo below is less than 24 hours after removing more than 100 leaves.

All of the bright green shoots have located the light and are striving to reach it. These will be the colas. The goal is to have one cola every 3" x 3" square in the canopy. (and completely fill that square with bud)

My reasoning is ..

By removing leaves primarily from the canopy I am ...
1. Thinning the area and allowing each top room to access light
2. Allowing light penetration to the lower interior portions of the plant
3. Providing better air circulation through the canopy
4. Concentrating the majority of the transpiration away from the canopy, reducing the amount of moisture being released in the flower area
5. Forcing the plant to "heal" every single branch, sending additional nutrients to that site. Once into flower and defoliation ceases, those "pathways" may be utilized for flower formation.
6. Makes spacing the colas much easier.

Additional "possibilities" are ...

By leaving the fan leaves intact, that portion of the branch is still actively being utilized by the plant. This may help the branch increase in strength and resist sagging and/or bending.

By having a skirt there is more reflected light being captured by the top surfaces of leaves. A reflective res surface is really not needed since not much light can escape the plant.

This is really just the beginning of defoliation. I will be removing 30 - 50 leaves per day for the next few weeks.

 

[Stonecrusher]

Good to see people using a lux meter!

Would you like to increase your crop yield by more than 50%? If so, read on.

When I started growing, I didn't get a lux meter, unfortunately. I tried to use Photone and, after testing it and trading email with the programmer about it, I bought an Apogee*.

The Apogee is a great product but it's $$ so I recommend that growers use a light meter (the Uni-T Bluetooth) and then get their grow to the light saturation point as soon as possible.

One issue with using a light meter is that light meters measure a different part of the spectrum than what plants use. Light meter display results in lux but agriculture measures light as µmol ("micromols").

How to convert from lux to µmols?

"There's an app for that"…called a calculator.

Or you can use a table or do the rough math in your head.

Or you can just run with it that your grow should be at 60,000 lux and you won't have to read the rest of this message.



But, if you're interested in how things work under the hood canopy…

In the PDF on lux that I've attached, the table covers a variety of lights and gives the converted PPFD values vs the lux readings. A standard white LED has a conversion factor of 0.015 vs a really blue light (0.013) vs a dedicated flower light (0.016). It's best to use a factor that matches your light or as close as you can get but close is good enough in this case.

Here's my pitch - your results were great at 30k and that works out to about 450µmols. That's about 50% of the light saturation point for cannabis. You were happy with the results at 30k lux and that's great. If you like how things are turning out, don't touch a thing.

So where's the 50% increase figure coming from?

Read on.

Research tells us that crop yield and quality increase in an almost linear manner as light levels increase, up to the light saturation point (the LSP is 800-1000µmols, depending on the strain). I've attached a paper that discusses this**.

I've created the table below, based on the formula in the paper.

The table was created using the formula for the yield curve and, in the PDF, I started the table at 600µmols because that's the minimum recommended amount for flowering cannabis.

What the table above indicates is that, in the plants that were grown for research, if the increase in yield between crops given 600µmols of light and 900µmols of light was 23.7%. Yup, by turning the lights from 600 to 900µmols, the crop yield would increase by almost 25%.

In the case of the grow that was at 450µmols vs that same grow at 900µmols, the increase in yield was 57±%.

You've taken the step of getting a light meter (I recommend the Uni-T Bluetooth meter or, if you want a PAR meter, I'd go with either an Apogee, a Li-Cor, or the Spot On). The next step is increase your light levels to hit a limit in the range of 800-1000µmols. Assuming that light was your limiting factor, your yield should increase significantly. Per the research, I would expect it to be somewhat more than 50%.


*I've been a software engineer for 30+ years, including three for Apple, so I have some insight into the software and hardware problems that he's dealing with. For a variety of reasons, I don't use Photone and I recommend it under only certain circumstances. I strongly recommend growers use a lux meter and get their grows to the light saturation point as quickly as possible.

**The Chandra paper, which shows that the curve starts to roll off at 500µmols is measuring net photosynthesis. The paper I've cited and attached deal with crop yield and crop quality.

I have to shout out a THANK YOU for providing that Lux vx Par information. It was even more relevant as you provided exact information about the Viparspectra XS-1500 which I own in the form of the XS-2500 (sold as two xs1500's joined with some hardware). I've been overcooking my seedlings a bit and now I can accurately measure the light intensity.
I made a chart that helps me hit the Par values that most growers use.

Lux to Par Conversion Chart
Viparspectra XS-1500
0.0145 conversion factor

Lux in 1000s Par
13.8 200
20.7 300
27.6 400
34.5 500
41.4 600
48.3 700
55.2 800
62.1 900
69.0 1000
75.9 1100