LED feed demands

[VerdantGreen]

Hi all, good thread.


I was quite an earlier adopter of LEDs, and the early fixtures i had didn't really make much difference... but i have found over the last couple of years, as LEDs have become more advanced and efficient, that the quantity of useful light that the plants receive can cause deficiencies to show much more quickly... especially in veg when the extra light seems to be 'too much' sometimes



In soil, one factor which is hugely influential is the pot size in relation to plant size. I find in a good soil that the plants will stay happy as long as the roots have plenty of soil to grow into...but as soon as the roots fill the pot and therefore limit the optimum uptake of nutrients, the leaves start to fade very fast.


In flower it is always best to use as much soil and as bigger pots as you can (or even a soil bed) - to remove the risk of rootbinding... and with modern LEDs this is even more important.


the other thing that has been pointed out is that LEDs make your grow run less hot, which can be good or bad depending on where you live... but it is always something to be aware of. eyesdown's post above mine describes this very well.



VG

 

[eyesdownchronic]

Hi all, good thread.


I was quite an earlier adopter of LEDs, and the early fixtures i had didn't really make much difference... but i have found over the last couple of years, as LEDs have become more advanced and efficient, that the quantity of useful light that the plants receive can cause deficiencies to show much more quickly... especially in veg when the extra light seems to be 'too much' sometimes



In soil, one factor which is hugely influential is the pot size in relation to plant size. I find in a good soil that the plants will stay happy as long as the roots have plenty of soil to grow into...but as soon as the roots fill the pot and therefore limit the optimum uptake of nutrients, the leaves start to fade very fast.


In flower it is always best to use as much soil and as bigger pots as you can (or even a soil bed) - to remove the risk of rootbinding... and with modern LEDs this is even more important.


the other thing that has been pointed out is that LEDs make your grow run less hot, which can be good or bad depending on where you live... but it is always something to be aware of. eyesdown's post above mine describes this very well.



VG

to expand on this.

there is a noteworthy plant phenomena where plants will try to balance above ground with below ground resource uptake. ie, in high light environments they will dedicate a higher percentage of energy to below ground growth, and vice versa. and in high water, O2, nutrient environments, they will dedicate more energy to above ground growth.

hydroponics is a vivid example where plants with relatively tiny root systems can create massive plants, as they have been more or less been tricked into thinking they have infinite access to resources. The same concept applies to plants in low light environments stretching and growing excessively to try and access light.

The flip side of this is that in extremely high light environments (high intensity led lighting), plants will dedicate a majority of their energy to root growth.

 

[SuperBadGrower]

A pic from 3 EC coco DTW, 13/11 3000K No IR, no UV no bullshit
A full trash bag of huge shiny deep green leaves after defoliation

 

[saitama]

View attachment 551405

A pic from 3 EC coco DTW, 13/11 3000K No IR, no UV no bullshit
A full trash bag of huge shiny deep green leaves after defoliation

3 EC? You, sir, are a mad man.

 

[SuperBadGrower]

Other plants' leaves would get a little burn on the margins, they get 2.4 . High EC - no problem, but don't let it dry out or you will have 8 EC very quickly . That's really the problem with big feeds I think. keep it in check and it can be OK.
Actually, I wanted to see if high EC would make this plant shorter. It seems to have made it bigger instead.

 

[f-e]

I remember heading for ec3 knowing the runoff 24 hours later would be very low. In my case I decided the coco had been stripped bare and so the new feed was being stripped on it's way through to run-off. It's why I moved to 3 fertigations a day in smaller pots. That exhibits a more typical increase. This run I'm doing two a day and seeing a fairly balanced 16 in and 18 out with 25% to waste.

My plants have really come around to the led's. The massive N demand is more realistic now as they no longer grow ridiculous amounts of foliage. I reckon they did it at first due to something being in short supply from the leds, that they use to judge light levels. Things in the shade still don't stretch to get out of it as they did with HID's but the plants do look a lot like cannabis now, not compact salad greens.

Extra Ca and Mg as expected. P keeps cropping up. I have to use Nitric acid but that and using Nitrate forms of Ca&Mg have the N about covered. Feed is generally about 30% stronger but I can't add K it seems. I'm sorely tempted but must resist as I log another good looking run without it.

 

[f-e]

I seem to of homed in on 2-4-4-2-1 as a rough guide.

Just at the end of stacking, 150-250-260-165-~75 (not listed in base)

If I raise either N or K the other suffers. P def if I lower that. The first 10 days Ca was 50% higher by demand. K was 175ppm.

Looking forward, K might accept increasing about week 4. Then Ca 50% in the last 2 weeks for effect, and K if they will take some, but it's unlikely.

Water consumption ~5L per meter, plus run-off. 2 a day. 5L is less than HID. Early on my count passed 8L on 3 a day, but not in the last year. It's consistent and I have a water meter in and measure what comes out.

30-65K lumens. Depends where you measure. I like 40K on the canopy really. About 600ppfd. Capped by the tops reaching 65K/1000ppfd where CO2 deficiencies appear damaging.



Things do change all the time. I have adjusted different feeds based on plant needs and when calculated my PPM's have been the same. Different bottles used to get to the same point. Guided by the plants. Sat in well used coco.

 

[f-e]

This is the 3 week pic to go with my last post


I have logged what they had every day and made notes on why. Mostly I just write how many ml of what, but will get it all in a sharable format when I can bare the agony. There is little point doing so until I get it right though. Which to 3 weeks, I think I'm close enough to offer a baseline

 

[f-e]

Couple of days into the 4th week a stuffy area showed a little soft brown burn to the edges on some leaves. Also a bit of N curl on a second head. Dropped the food and no further progress of the overfeed has been seen

Through to week 4
138-235-292-170-67 still high N
117-235-292-178-65 still not stopped edges
117-175-247-178-65 Been happy a few days.

Development seems slow. I'm not sure.
Ultimately my plants have changed their demands since first going to LED. A shift back to almost what they wanted under HID. In veg where I might of needed ec1.6 I'm back to 1.3 without any need to increase N. It's the biggest change, from needing copious amount, to being happy with the boost from calmag. Which itself seems low in Mg for our needs. I'm mixing something like 1.5:1 in bloom, and just extra Ca for transition and then pulling the Mg for the finish. In veg I just use a bottled 2:1 as I like the N which wasn't toxic until the 2nd week of flower. Having been 165ppm. I need to get it down sooner. It might be why I feel days behind.


At least I'm growing a feed profile, because I'm not growing any buds.

 

[CrustyCruz]

the response is to increase air flow, not add more Ca. Other nutrients such as N or P can be take up via root diffusion so the lack of water uptake has a smaller effect on nutrient uptake of these elements.

Leaf-ambient temp differential will be a cool new term in the led-powered future. Controlling transpiration is key under led.

there is a noteworthy plant phenomena where plants will try to balance above ground with below ground resource uptake.

Roots need phosphorus to expand, which is the only way roots can reach phosphorus, by expanding. Catch 22. Look who's having problems with led.. The biggest clue is in the red stems they have. Why do phosphorus and magnesium move through the phloem? I thought only exudates move through phloem? You only need to understand how and why nutrients move through the plant to replace confusion with knowledge. Day 1 stuff that most growers die never knowing. It's sad, it's embarrassing, it supports every negative stereotype of pot smoking drug dealers.

I think pot growers like being confused. Especially cheap ass growers growing a plant worth 20 dollars a gram. I'll never get it.. You don't even have to know any thing, you just need to donate $20 to a phytologist. Once big grows figure out how to stop over feeding and spraying fungicides you're all out of work. You'd think think there would be motivation associated with that fact.. It's coming. No purple stalks in commercial grows.

Every symptom I've had under led can be solved by the prior thousands of years of non drug cultivation,not by drug growers who embrace confusion and ignorance. These weed forums make you stupider. I've lost 16 IQ points trolling Icmag.com. Grow a few bad plants on purpose and you'll learn more than praying to the weed gods and praising the undercover DEA agents. .

 

[ButterflyEffect]

Leaf-ambient temp differential will be a cool new term in the led-powered future. Controlling transpiration is key under led.



Roots need phosphorus to expand, which is the only way roots can reach phosphorus, by expanding. Catch 22. Look who's having problems with led.. The biggest clue is in the red stems they have. Why do phosphorus and magnesium move through the phloem? I thought only exudates move through phloem? You only need to understand how and why nutrients move through the plant to replace confusion with knowledge. Day 1 stuff that most growers die never knowing. It's sad, it's embarrassing, it supports every negative stereotype of pot smoking drug dealers.

I think pot growers like being confused. Especially cheap ass growers growing a plant worth 20 dollars a gram. I'll never get it.. You don't even have to know any thing, you just need to donate $20 to a phytologist. Once big grows figure out how to stop over feeding and spraying fungicides you're all out of work. You'd think think there would be motivation associated with that fact.. It's coming. No purple stalks in commercial grows.

Every symptom I've had under led can be solved by the prior thousands of years of non drug cultivation,not by drug growers who embrace confusion and ignorance. These weed forums make you stupider. I've lost 16 IQ points trolling Icmag.com. Grow a few bad plants on purpose and you'll learn more than praying to the weed gods and praising the undercover DEA agents. .

I came here to learn to be a better grower. The more I learned, the more I realized I had to go to actual Ag or Uni sites for info. Even bought the Hydroponic Food Production book from Resh.

The longer I'm here, the more I learn, the more the disinformation stands out like a neon sign.

I haven't made the transition to LEDs yet, but I'm going to switch one of my flower rooms over this year. I've run CMHs for years now, so the ROI isn't as spectacular as it would be with HPS or MH. I do, however, run into the stem purpling in Veg, as I do have mixed LEDs with my T5 flouros. I'm still working out the reasons for this.

 

[eyesdownchronic]

Leaf-ambient temp differential will be a cool new term in the led-powered future. Controlling transpiration is key under led.



Roots need phosphorus to expand, which is the only way roots can reach phosphorus, by expanding. Catch 22. Look who's having problems with led.. The biggest clue is in the red stems they have. Why do phosphorus and magnesium move through the phloem? I thought only exudates move through phloem? You only need to understand how and why nutrients move through the plant to replace confusion with knowledge. Day 1 stuff that most growers die never knowing. It's sad, it's embarrassing, it supports every negative stereotype of pot smoking drug dealers.

I think pot growers like being confused. Especially cheap ass growers growing a plant worth 20 dollars a gram. I'll never get it.. You don't even have to know any thing, you just need to donate $20 to a phytologist. Once big grows figure out how to stop over feeding and spraying fungicides you're all out of work. You'd think think there would be motivation associated with that fact.. It's coming. No purple stalks in commercial grows.

Every symptom I've had under led can be solved by the prior thousands of years of non drug cultivation,not by drug growers who embrace confusion and ignorance. These weed forums make you stupider. I've lost 16 IQ points trolling Icmag.com. Grow a few bad plants on purpose and you'll learn more than praying to the weed gods and praising the undercover DEA agents. .

Yeah, i think that leaf- ambient temp differential is definitely important. But if anything it would've been more important under HID. its fair to assume that under LED's leaf temps would be closer to ambient levels whereas under HID there would be a significantly larger differential, right? So if anything this will be less important with the implementation of LED's... its just people have gotten used to growing with HID so theyll have to re calibrate so to speak.

I can't really follow the point youre trying to make. That LED's are causing P problems instead of Mg problems? Or that they are linked and the Mg def causes problems with P? so wouldn't the solution be fixing the Mg problem?

**Edit- Hey, I think i got your point. I said that heavy intensity lighting (such as LED's) stimulates below ground growth. And so youre making the point that root growth requires P increasing a plants demand, which can result in a P def. being seen above ground. Interesting! I never thought of that. See, you learn something new on IC everyday.

Neat side point to this is that ag studies have found in mineral soil that under P def. conditions plants will respond by putting out "hairy" root growth similar to what we associate with plants being associated with myco. The reason being that P is extremely immobile in mineral soils, and plants can only uptake P thats within like nm's of their roots. this creates "P depletion zones" in the immdediate vicinity around their roots, and because of P's immobility in soil, it can't flow from levels of high concentration to lower concentration. this doesnt happen in pure hydropoinic (ie dft or nft) systems. another interesting tid bit is that most growth increases associated with plant-myco relationships is from increase P uptake... just some food for thought...
**endedit

**edit- one thing I 100% agree with you on, is the sentiment I sometimes see of people treating cannabis as a "one of a kind" plant. where like something that wouldnt help a marigold or tomato plant could somehow be beneficial to a cannabis plant. granted, I understand that cannabis is somehow unique in that it is cultivated for specific reasons, ie aesthetics of finished flower, essential oil production, as well as yield. but ultimately, there are plenty of crops that are grown for these reasons as well. herbs for oils, flowers for cut flowers, veggies for yield. so if someone can grow some killer tomoatoes, no reason that can't apply to growing some ganj.

In the same line of thought. Whenever I see a product marketed specifically to cannabis growers, I immediately assume its snake oil, and the seller is trying to profit off of uninformed cannabis growers.
**endedit


And I dont disagree with you about there being a tons of misinformation floating around in the cannabis scene. And it is unfortunate. But have you ever worked at a commercial greenhouse? judging by your comments it sounds like you should have some level of experience with the rest of the horticultural industry. Do you think that education is important there? from what i understand in the hort industry the most important thing is cutting labor costs at the expense of quality of the workforce. Grows are moving towards having one or a couple head growers on top with unskilled labor doing the work. There is a large trend of disinterest in plant physiology and molecular biology in the general hort sphere, and if anything, the cannabis scene is a beacon of light. at least here people give a shit about what they grow and how they grow it. Albeit most people lack any form of formal education, but that can't be attributed to any fault of their own. shit, at least theyre trying.

granted, the corporate cannabis scene is really horrific. I dont know what to say about that . put a lot of money into something and shitty ass people will show up. Those who truly care and grow fine herb will prevail in the end. give it like 15 years.


And about Icmag, with the proper frame of reference one can learn a shit ton here. A lot of the "misinformation" is just anecdotal evidence of something that worked for an individual under their conditions. if one can understand that their experiences are a function of their conditions, and not something that will occur in every instance, one can glean so much from looking through things that went right and wrong for others.



whats the line.
"smart men learn from their mistakes, wise men learn from the mistakes of others." or something like that.


Peace

 

[f-e]

Lets be reasonable. There is lots of bad information in books. Here we have a discussion about growing under LED and are not even using burple. Not that burple is wrong. It's just wrong for our plant.

Who are the DEA agents. Why are they growing weed, and more importantly, is it any good?

 

[Fitzera]

I have noticed my leaf temps are roughly 2 degrees less than ambient, regardless of light source. Hps has raised ambient temperature but the leaf temps are still about 2 degrees below.

 

[eyesdownchronic]

I have noticed my leaf temps are roughly 2 degrees less than ambient, regardless of light source. Hps has raised ambient temperature but the leaf temps are still about 2 degrees below.

Really? im actually kinda surprised to hear that. kinda nice though... what kind of airflow and ventilation you got going?

 

[Fitzera]

Really? im actually kinda surprised to hear that. kinda nice though... what kind of airflow and ventilation you got going?

I have my hps in a cool tube which is plumbed to outside of the tent on both ends. I have 1 large fan blowing down from above the lights and I have a smaller fan on the floor blowing to a wall currently, plan to have it blow up through the girls when they are larger.
I have my exhaust fan connected to the humidity controller so it only kicks on here and there. One vent is open on the tent.

If heat is low in the house, tent sits around 25. When the heat is up, tent is about 28.
I use an infrared thermometer to check leaf temps to keep my vpd in range.

I believe it's the transpiration rate that causes leaf temps to be lower. Like when sweat evaporates, it's cools you. Alcohol evaporating off your skin feels cold.

 

[Horselover Fat]

Leaf-ambient temp differential will be a cool new term in the led-powered future. Controlling transpiration is key under led.



Roots need phosphorus to expand, which is the only way roots can reach phosphorus, by expanding. Catch 22. Look who's having problems with led.. The biggest clue is in the red stems they have. Why do phosphorus and magnesium move through the phloem? I thought only exudates move through phloem? You only need to understand how and why nutrients move through the plant to replace confusion with knowledge. Day 1 stuff that most growers die never knowing. It's sad, it's embarrassing, it supports every negative stereotype of pot smoking drug dealers.

I think pot growers like being confused. Especially cheap ass growers growing a plant worth 20 dollars a gram. I'll never get it.. You don't even have to know any thing, you just need to donate $20 to a phytologist. Once big grows figure out how to stop over feeding and spraying fungicides you're all out of work. You'd think think there would be motivation associated with that fact.. It's coming. No purple stalks in commercial grows.

Every symptom I've had under led can be solved by the prior thousands of years of non drug cultivation,not by drug growers who embrace confusion and ignorance. These weed forums make you stupider. I've lost 16 IQ points trolling Icmag.com. Grow a few bad plants on purpose and you'll learn more than praying to the weed gods and praising the undercover DEA agents. .

Just imagine if you had used that many words to actually educate people. Perhaps that would've made the forum better.

 

[f-e]

Just imagine if you had used that many words to actually educate people. Perhaps that would've made the forum better.

My mind has come back to his post a few times, with the exact same sentiment. I think that there is an element of truth to the P & Mg comment though. It's where I'm looking in books and finding my plants wanting quite a bit more than expected. Mid bloom I should be around 100ppm of P but since dropping from ~250 I just have issues. At 180 it was tips and edges and a few days at 165 had just slightly light green leaves all over the floor. With a growth stall of epic proportion. Most feeds are about 100ppm and Mel offers similar figures. 'pH Imbalance' says about 150ppm. I'm just making a right mess of them approaching those figures though.

I think I'm ready to put out my first recommendation. Mg. I think 80ppm is alright and 100ppm won't hurt, especially later in flower, but not the last week/10 days as it's bad for the smoke.

I know 80-100ppm means nothing to many people. Moderate too Hard tap carries maybe 10ppm. So you are looking for 70-90 from your feed and I guess calmag. I don't know what is in either, but ballpark figures from bottles I have looked over mean 1ml per liter of calmag should be about right. You certainly won't see instant death.

On that tip, if your calmag has 2.5% mag (listed as MgO or Magnesium oxide) then 1ml in 10l is 2.5ppm so my rough 1ml per liter would put 10ml in 10l giving 25ppm. 35ppm with the taps contribution. I'm looking at the feed for 45ppm.

If you struggle with the math, lets look at that again. I have some Mono Calcium liquid that is 12%. For every ml I put in a 10L bucket, it goes up 12ppm. That's not really math. The math is how many times over you have 10L. But times and divide are just moving the decimal point back'n'forth. It's still not really using numbers.

More? Damn your a sadist. You're hurting me now. Okay...
My grow feed is 1.9%N so if I put 1ml in 10L it's 1.9ppm.
My feed says 7ml per Liter.
okay... So if 1ml in 10L is 1.9ppm then 1ml in 1L is 19ppm.
I need 7ml it says.
Arrrgh it's Math!
19 x 7 = idfk about 133ppm

 

[Weird]

https://journals.sagepub.com/doi/10.1177/1477153516642269


The influence of the LED light spectrum on the growth and nutrient uptake of hydroponically grown lettuce

 

[f-e]

https://journals.sagepub.com/doi/10.1177/1477153516642269


The influence of the LED light spectrum on the growth and nutrient uptake of hydroponically grown lettuce

It's interesting that more N wasn't needed to grow the extra leaf. The Mag the cal and iron are there, along with zinc, but not the N.
Lettuce is a little different. Put in the shade it grows bigger leaves, making the far red (730nm perhaps) more effective for lettuce than cannabis. For us, the stretch response helps with plant shape, but while it's intentions are set on stretch, it's not devoted to flowering. So what's good for one, isn't so great for the other.

I can only see the overview unless I pay $41 and as it's for lettuce I will give it a miss.

Thanks for your input. I always like to hear your opinion. You are an important part of this community for me. Though it's taken a while to address one of your posts. As nodding with agreement is just a page filler