LED feed demands

[hayday]

I'm sure I needed more head clearance. I was under 18" at best. Thing is my young uns are on a cabinet built into the flower room so a remodel is a large task.
I have a plan though and Its gonna be implimented sooner rather than later.
Country house build out coming soon

 

[Ichabod Crane]

Yeah that is way to close for little ones.

 

[f-e]

Ok, a bit of a diary entry really.

First days of flower. 2 liters in, 750ml run-off, 3 times a day. Per meter.

That is a 42% run-off, so it should look a lot like what went in.

ec1.7 goes in, ec comes out lower, and dropping each time. Down to 1.4 now

Feeding at 1.7 they have eaten that and started stripping off what's stuck to my coco, in 5 hours. So when I feed, a lot sticks to my coco, giving me a lower run-off than what I fed them. This is not at all acceptable.

roughly 20,000 lux or 300ppfd, which is below anybodies minimum guideline. Sourced from 260w of LM301+660

Growth looks good, but light green. Suspect Mg. No stripes, but I know it's what they are pulling off the coco. I have hard water, mostly Ca. I'm using 0.1g of epsom salts per liter to take my feed from 1% mg to 2% mg to keep it at bay. History is simply repeating itself at this location.

Feed raised to 2.0 and first run-off 1.4 still. I will see if it increases.


Moving to more frequent fertigation has helped address the problem I was having. That I was feeding at almost poisonously high levels, and it wasn't enough food to last until the water ran out. I just can't wait for the water to run out. Air-pots or woven bags might be a real answer for me in the future, to see water consumption better match feed consumption. Looking around, some of the better LED grows I was struggling to match have used such containers. The plants just don't seem to be drinking. Forcing higher temperatures to be used by many. I have logged water consumption under HID though, and it's not a night and day difference. Certainly not a third less water, so 50% more food remains unexplained. At 300ppfd...

 

[Douglas.Curtis]

The plants just don't seem to be drinking. Forcing higher temperatures to be used by many. I have logged water consumption under HID though, and it's not a night and day difference. .

Water usage is a balance between nutrient strength and transpiration.

Your plants draw water through themselves, and evaporate it on the outside of itself for cooling and hydration. They call the movement of this water through the plant "transpiration."

When the plant is too dry it will increase transpiration.
When the plant is too hot it will increase transpiration.

When the feed strength is too high for the transpiration level, the plant suffers. The amount of water the plant needs draws up too much nutrient for the plant to use. At the higher nutrient levels, plant growth and water consumption slow down. At the more extreme levels the plant quickly begins to visibly suffer.

Your feed level, though considered low by industry standards, is pushing close to my personal max feed levels. With a .5conversion ppm pen, most strains don't do 700ppm well, and 750 is the most I've found 'hungry' strains I've run across to eat.

That being said, what are your average temp/RH levels, and do you believe you're pushing 1K HPS levels of light? (My apologies if you've posted these numbers before)

Keep in mind, you can definitely overfeed and still have 'deficiencies' show up. The nutrient needs to be balanced for what the plant is using. Which, fortunately, this thread is hammering out.

The more balanced the nutrient feed and the more complete and regular the root zone pH swing is, the lower the strength of the nutrient solution can go. The lower the nutrient strength needed for full and healthy growth, the higher the possible end quality can go.

Cool, yeah?

 

[Fitzera]

Adding to what DC has written, leds dont cause the leaf temperatures that hid do, so they may not be transpiring properly due to that. I run a small space heater to help keep everything warm, thinking that it is helping with transpiration

 

[Douglas.Curtis]

Adding to what DC has written, leds dont cause the leaf temperatures that hid do, so they may not be transpiring properly due to that. I run a small space heater to help keep everything warm, thinking that it is helping with transpiration

This is a good point. Even in a well cooled grow room, HID still puts out significant infra-red causing leaf temps to rise. I loath increasing temps, so I'm going to be contemplating alternatives.

 

[f-e]

Third day at EC2.1 now, the run-off is still around 1.5 which gives a calculated drop to ec1.2 before fertigation. So the root zone is on a average 1.7 which is keeping them happy, but is concerning me.

Under hid an ec of 1.4 would of been ideal. Not an uncommon number to hear from other people, and just a touch under the 1.5 the bottle recommends. The run-off would be about 1.6 with the rootzone obviously reaching higher.

This doesn't put the average rootzone ec far apart, but the swing with the leds is huge.

My temps are low. I realised it's why they were light coloured, and banging the electric blanket on. I had been seeing 20c night and 23 day, with the pots about 20-21 24/7. With the blanky, only the pots show much change, but almost 23 like the canopy. Water use by the plants increased almost 25% over the 24h period. The signs of cold reduced.

You want a picture? yeah.. of course you do. I have one I can upload. Not be long...

Doing about 4L per meter is reasonable consumption. Peak flower under hids is around 6L so their not refusing to drink. Watching closely though, as you can tell

 

[f-e]

1000 wide that picture.. it looks like a thumbnail. Here's a full pic so big I'm not meant to be able to upload it?

 

[f-e]

So, from the beginning..

6L per day supplied. 2.5L run-off, 3.5L consumption. Canopy 23, pots 20. Food being taken much quicker than the water. 1.7in 1.4out

EC raised, 2in 1.5out

Pots raised to almost canopy temp. 4L of ec2.1 used, 2L of ec1.6 run-off. Meaning, more water was used, so the remainder was more concentrated.

Circulation fans switched on. 4.75L of ec2.1 used, 1.25L of ec1.9 run-off.

Courtesy picture

I'm reporting daily figures, not the 3 readings per day taken, as run-off is pumped out in increments. It's been two days with 20c roots, two days 22-23c roots, then just one day with the fans. Which is a remarkable change, from 2L run-off to just 1.25L which means I must change watering duration now. Along with stronger illumination now I'm happy with my nutrient control. The EC will remain at around 2.1 until I see the run-off equal it, or some food related problem.

For me, this has been a lesson about water use, and how temperature effects it. In order to keep the root zone ec somewhere close to stable. I ignored this last run, and watered when they looked dry enough. By which time the run-off looked ok. But with hindsight the rootzone ec had probably been very very low, until the water was used up, when the water:food ratio would of looked my normal as I got my run-off. Though I was aware from a different system that I had struggled with dropping rootzone ec. Leading me here.

My last run was hard work, and omg it's snowing.. the roofs are white. Deficiencies I couldn't keep on top of.

 

[f-e]

So after a week of pre-flower, where the food demand out stripped water demand(like in grow), things settled down. The run-off rose, so input was lowered, until it balanced as 1.6 in and 1.6 out, with just 20% run to waste. During this time of adjustment the lux level was increased 10% on 3 consecutive days. Each time the food and water use increased a very similar amount. By the end of pre-flower the light was 500-800ppfd (depending where you measure) and the 10L per meter (2.6 US Gallon) of coco was providing the plants with 7L per day, split into 3 fertigations. 7L is a lot of water for a meter to drink. 6L is a book figure I have confirmed in the past using 600w of hid. Peak flower. So to be using 7L at bud onset with an ec of 1.6 is notable. While the food demand in veg and early preflower is just crazy, at a lowly ppfd.

To enable daily (hand) watering of my plantlets, I'm at around 150ppfd and they don't get thirsty, just hungry. With temperature in the mid to upper 20s (77-80f) and some air circulation. Though RH is around 55% which could be higher. But them they would breathe better and eat even more perhaps?

The food I have used for years, was always a little low on Mg but not an issue. Now I'm having to use magnecal? so I have 3 times more in solution (about 3% of my food load, not 1% like Canna/Growth Technologies) Otherwise it's Mg stripped off my coco in hours. Replaced with whatever cation gets there first.

I have too many bottles of mono...This has been hard work and sacrifice. The bathroom looks like the shelves of a grow shop.

 

[f-e]

The change in demand has swung back. Oddly I increased the runoff, and found the value higher instantly. I split a session into 200ml samples and can't relate it to having more runoff. I have a more typical 2.0 going to waste, from the 1.6 input after just a few days. A couple of leaves dropped with N signs. I guess the N was less available because of a K increase, though I can only measure an increase in general.

Looking at some cuttings. They rooted in 2 weeks using a prop with it's own eco system going on. They started with ec1.0 and just rained upon themselves through condensation. Transplanted with their 1" of coco into 15 cell gravel tray, they are taking 1.7 and sending 1.2 to waste on the 4th day. They are really liking it. 100-150ppfd from cobs. That is 50% more food than I would use under discharge lighting, being replaced every day, with a lower figure running to waste. Growing nicely at a low ppdf. The Mg is still raised, or they would be unwell.


I have been having some thoughts beyond my understanding. I see N and Mg issues if I don't treat the LED plants differently. I know N is easily leached, and Mg excess in fields causes water-logging. Also my Mg signs are greatly reduced with 65% humidity, and hard to avoid in dry conditions. If I use 65% and less Mg the N issue seems to increase. I can say with absolute certainty that lower RH increases the Mg requirement and that is under LED or HID. This is a relationship I have never seen discussed though. Maybe lower evaporation causes a xylem that's stronger, and Mg would rather stay with the water in the pot. My xylem tastes the more water like than ever before though. No salt marks on the leaves, not a chance. It's not the usual bitter taste at all. Something is missing, but I don't want to start gargling with mono. But hay... this is just what keeps me awake at night. I can't do anything with this knowledge yet.

 

[f-e]

The run-off has been creeping up. Quicker as I moved incrementally from grow to flower food. Which I have not yet achieved fully at about 25 days. I need an input ec of 1.7 to keep them happy. At 1.8 they will eat and drink a little less, but show no signs. I read over fed crops loose about 10% in the dry matter stakes. If I feed 1.6 for consecutive days, I see a little N deficiency. I once dropped to 1.4 and leaves jumped off the plant, looking pale and weak in just a 24 hour session. Maybe 15 leaves per meter.

With just 1.6 going in, I have reached 2.2 run-off, which is time for action. I have 30% run-off already. Feeding 6" pots at 80ml per minute, so no run-off until 3.5 minutes. It's not going straight through.

So the kicker. An hour after fertigation, I run the pump again to get another 30%. It comes out at 2.4

This suggests that when fertigating my already wet pot, as normal, something is taking about 5 minutes to dissolve. Or rather, something that was fixed to the coco, is taking a short while to come off into the less saline water. So that it may run off. For a long time I have split 10 minute daily fertigations into 5 on, 5 off, 5 on. Knowing something of this. I just haven't here as they have stayed so wet.

I'm going to break up the 3 5 minute sessions, 4-1.

I realise this isn't quite on topic, but has an impact on my results. I expect this new regime will lead to a better run-off efficiency, lowering rootzone EC and thus expecting a greater supply EC. Leading to more nutrients being purchased, for a better balanced feed at the roots.

3 fertigations per day... we will have a result in before long.

 

[f-e]

Ok, Probably posting too early, but my expected 750ml of run off was 800 in the first 4 mins, and 450 in the last minute. As I stuck in 1.5L between feeds, this extra run-off was expected. Remember my run-off is pumped out to where I get my readings in 200-250ml samples, so the 450ml isn't the full 640ml that went in, there is some left to get pumped out in the next fertigation cycle.

Results:
800ml@2.4 was a surprise.
450ml@2.6 was an eye opener.

I only fed at 1.5 today, and they are asking For N, P and K. So I find it unlikely these are featuring highly in my run off. 1.5 in and 2.6 out is a big gap. One I think Ca and Mg are filling. I'm running 3x too much of both to get the Mg I needed in grow and preflower. I reckon (as I already suspected) that I can drop the magnecal now and replace it with more of my base nutrient. My Mg problem hopefully being history. Mg doesn't really effect yield, while N and K are major contributors.

Yes.. I have talked myself into it.

edit: my magnecal is 7.5% stuff, while my base feed is 6% stuff. The 8-10ml was getting towards 0.3 of my EC 1.7 but even 10-12ml of food doesn't have the same effect on the EC as not all of my 6% stuff is effecting the Electrical Conductivity in the way Calcium and Magnesium will. So dropping the magnecal (a cal/mag product biased towards Mg) has given me a lot of headroom for feeding them more. This look in greater depth also shows the difference in EC people will find, just using different additives. Quite a number of people reach for the cal/mag more with LED's so all there EC values will be effected more than the strength of their feed. You could say my plants are not happy at 1.7 but rather, they like 1.4-1.5 and some Nitrogen containing calmag. Or 1.6-1.7 with some Epson salts. Changed frequently, either way

 

[wvkindbud38]

I've been testing several brands and spectrums of Led grow lights. I feel like one of my strains I underfed a lil. Its hard to say goodbye to the HPS. But this grow I'm doing now is almost finished in flowering and it's been all Leds. I've really lite it up bright. I'm always a more light the better kinda guy. But I'm gonna watch it closer my next grow. It's also the first time I've ran the strain clones so that might be a big reason. But I do like to flush plain water the last 2wks and get some of the leaves to yellow or be close. I'm a soil/soiless guy and like a good flush. The finishing time on this clone has been longer than I was expecting also. Very interesting, it's still a trail and error game though. Ive grew 20yrs + and have a helluva time cloning half the time lol

 

[GOD710]

Always gave them Epsom salt from the first time I saw the deficiency after then I've never had a problem. I add it once during veg and once before the 3rd week of bloom.
And always check the temps with a temp gun, LEDs don't produce infrared heat so its the only way to get the plants, true temp

 

[f-e]

Mostly off topic post:

I have vegged with 3 types of LED, but only flowered with Samsung+660. It's the same story each time. The Mg issue that comes from my feed, usually kept at bay with A high enough RH. Plus a higher N requirement. Both needs can be met by bumping the EC ~40% as others speak of.

I see a lot more growth within the plants structure with multiple points of light. Where a HID plant might of considered under the canopy, the LED plant's will divert power with just the slightest hint of illumination. The effect is a plant full of mid sized buds, where the HID might of grown a sparser plant, with bigger buds on top. I have to wonder how a SOG will grow. I think the plants are trying to grow leaves in places they wouldn't of bothered before. Given a the promise a sniff of light brings, perhaps. The excess N use might be explained as such.

I have found checking the run-off from soil grows to give a lot of information about the soil. I should really be doing this in rockwool but I'm a coco grower this decade so It's all I can share. Coco has it's complications, but soil is increasing it's EC while sat in the shop waiting for you. Run-off measurements are hard to attribute to any particular process. Entire forums exist where talk of run-off measurements will have the holy trinity talking of heresy and finding a reason to remove your unruly self. Likely because many soil growers can make little use of the data. It's still a diagnostic process though. I always get the ec down before doing seeds or cuttings. Even Canna Terra has been seen arriving at 2.2

I take twice as many clones as I need and sometimes that's not enough. I can have bad years, between years where I might not loose any. Things were last going downhill about 2 years ago, when I realised it was my rooting gel getting old and harbouring some cause of dampening off. I remember trying organic gel once, that was a lot worse than using nothing. Like the organic pH down, that after 24 hours has raised the pH. Some things are just crap.

 

[f-e]

Should maybe start another topic for this. I split the 5 minute continuous fertigation into 4 minutes on, 5 minutes off, 1 minute on. My feed was EC1.6 and run-off had climbed to EC2.2
After splitting the duration into two, my run-off went as follows. EC2.6 EC2.4 EC2.1 EC2.0 EC1.9

I had been at 30% run-off and loosing the battle. Now I could probably reduce the run-off. That is a real advance. Who knew?

 

[hayday]

After a few runs with my flower room powered by LED I'm getting what looks like calcium deficencies.

What im wondering is will a cal-mag additive effect my smoke in I use it untill mid flower? I never needed much cal-mag before so rarely used it.

 

[Grapefruitroop]

Hey Hay!
I know everything is relative in this cases but, in the last run i had to use a shitton of Ncalmag till 3rd week of flower and then i switched to a mix of Calcium and magnesium from the Canna Mono nutes like F-e aaaaaand i got some veeeeeeery extra sugary tasting medicine .... many friends told me too that was very sweet and sugary tasting.....
megacrop till 3rd week flo...then maxibloom...last week just RO...


This thread has been very enlightning , Thanks F-e

made me realize that without extras (N cal mg) thers no way to end a LED cycle with no def in my environment..

 

[f-e]

Many feeding schedules, grouped together by MadBuddhaAbuser at the top of this forum, show calmag used until the week before last iirc.

Calcium is going to show, because it's means to move within the plants, is being swept along like driftwood. Caught in the tide of xylem movement, driven by evaporation it the leaves. Something reduced due to the lower levels of radiant heat. Warms roots and rooms, and increasing air circulation can improve the situation. I think the default position for any grower is a need for more Ca though.

I also feel more N is required. I'm using both the extra N of the magnecal and nitric acic to increase mine a third, and any less won't work for me. I'm suffering from K issue's at the moment, which isn't surprising as the balance of N and K is important. The extra Ca also takes up some of my cec, so again effects what K is available. It too early to tell, but I'm using about 4ml of 0-0-16 (canna's mono with 13.5% availability) per 10L just to balance the numbers. The same amount I could normally be adding in the later weeks as an additive.

So I'm nailing through N and Mg like never before, but Mg is a historical issue with my feed. I know Ca is at risk, and I see a K problem that got away from me, but not across all the strains. I have crazy hunger in veg and pre-flower weeks, but by week 3 I saw a return to normality. Week 5 and water consumption is so high, the EC was back to that of a HID grow. But here I veer off, with a stalling in growth from not reducing the food soon enough, letting my run-off get toxic, and browning 20% of my hairs. I have flushed relentlessly and changed direction to this HID like feed level, with the raised N Ca Mg and K. Hoping I now have the recipe. But this isn't anything I can share as yet.


Glad to be of help Grapefruitroop and thinking you for sharing your findings so we can better see what people are going through.

I'm using 600w of decent leds, very low, over a meter. I am literally killing it. Way past the stories of light stress, with a ppfd as high as 1300 in places. Fighting the good fight, in order to see what things are really holding us back. Hopefully, I can drop down to 450w at some point, with a recipe I know lacks nothing. Instead of accelerating from one disaster to another. Which never makes me feel good when I look at them. So It's nice to get a pat on the back. Cheers.