Light stress?

I grow in 70/30 coco/perlite in autopot. pH is in check, I set it at 5.7 and let it drift to 6.3. They're under 220W DIY COBs. Light is 30-40cm above plants, I have 6 COBs at 37W. Temperature when lights on is 25-29°C, when lights off it's never under 19°C.

4 hours before lights off they're droopy. Then they go to sleep for 4 hours. After lights on they're still perfect... for next 15 hours instead 19?
I didn't notice that before on previous plants.

Are you sure that the autopot is supplying enough moisture in that heavily aerated medium? Coco/ perlite mix needs couple of watering a day with those ambient temps.

I would check the float valve and wicking properties on the bottom of your pots

Good luck

PSUAGRO. said:

Are you sure that the autopot is supplying enough moisture in that heavily aerated medium? Coco/ perlite mix needs couple of watering a day with those ambient temps.

I would check the float valve and wicking properties on the bottom of your pots

Good luck

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I don't fully understand you... autopot gets bottom feeding. Plants drink when they want. And yes, there is water in tray. I have also couple centimeters perlite at the bottom to cover airdome (air supply).

Auto strain with only 4 hours of night isn't it? 6x37W it's soft, how is it possible to have a light stress in this set up...? I think your prob is not lights.

PilouPilou said:

Auto strain with only 4 hours of night isn't it? 6x37W it's soft, how is it possible to have a light stress in this set up...? I think your prob is not lights.

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Because of higher DLI? I get 35-45.000 LUX at canopy, which should be around 500-650 PPFD.
I don't know what is this, so I am asking you guys if anyone have more knowledge than me...

Your set up & my set up are very similar. There are a few possibilities.
Have they been like that ever since you put the pots in the autopot trays?
Have you successfully grown with autopots before?

KonopCh said:

I don't fully understand you... autopot gets bottom feeding. Plants drink when they want. And yes, there is water in tray. I have also couple centimeters perlite at the bottom to cover airdome (air supply).

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Taking about in a normal setup, coco/ perlite dries out fast, needs water a couple of times a day in warm temps like yours.

Isn't their a float valve to control the water from the res into the tray? They can get stuck

I'm not an autopot guy, but doesn't it need some sort of wicking type medium on the bottom of the pot ? "Couple of cm " Perlite will not help the water travel up to the roots (capillary)......... idk, what's the manual/ website say about recommended medium choices?

Good luck

Again, autopots are working normal. Plants drink normal.

@kushedy they are droopy from week 4 or 5... so 2 weeks let's say.
Yes, I did grow in autopot before, why?

Is it a 2x 2' tent?
To me they look saturated because of too much light(DLI) or thirsty because of too less water.
Rise the lamp 4" up or dimm it a bit down. You could also flush the coco/perlite mix, just to be sure there is no imballance. And make sure there is allways enough fresh air in the chamber.

Had times one, which looked the same. I flushed it thoroughly and reduced the intensity and she has recovered.
If the intensity is high and the smallies getting much light, they can be saturated before the light goes out.

KonopCh said:

Because of higher DLI? I get 35-45.000 LUX at canopy, which should be around 500-650 PPFD.
I don't know what is this, so I am asking you guys if anyone have more knowledge than me...

Click to expand...

Nope, it's more! In a tent 45.000lx is in the 700-750μMol/s range, because of the reflective walls. Conversion factors are calculated without tent. Flush them thoroughly and reduce the intensity and I'm 90% sure she recovers in less than a week.
If they are saturated after they have gotten 14-15h, this would be about 35-38Mol/d with your current setup. You can either shorten the exposure time to 14-15h or reduce the output to about 550μmol/s, or ~35,000lx max.
This should stop it if it's indeed is saturation.

But could also be a lack of nutrients, because the leaf stalks look suspiciously red.
Were they reddish from the beginning, or have they developed it over the time?
I know, for some strains this is normal behavior(eg. PinkKush) but in the most cases it is a sign of a phosphor or nitrogene deficit.

I asked to try & gain your experience level with autopots. No offence meant. In all honesty I am unsure so I am just going to throw all the possibilities at you.

1: Autopot recommend (from memory) a 2 or 3cm layer of clay balls or perlite at the bottom of your pots to prevent direct contact between your coco & the nutrient solution. I personally found that to not be enough.
When I followed their instructions my plants suffered from over watering syndrome as the coco was always soaked. Some people say that you cannot over water in coco. I found out first hand that they were wrong.
In fact your plants look exactly like my plants did when I had that problem.
I would use 2 inches minimum of clay balls or perlite at the bottom of the pots when potting up. I am at the moment using 50% clay balls at the bottom of my pots & a 70/30 coco perlite mix on the top 50% of the pot & it has been working great so that gives you an idea of the flexibility you have when potting up.

2: Your tray ph will differ to your res ph. As your grow progresses you will find the difference gets worse. Not sure why this is but autopot (again from memory suggests that you set your res ph 0.2 below your target ph for your plants. Again I found this to not be a significant enough amendment & used to have ph issues.
I normally set my res ph to 5.3 or 5.4. Thought process is that when the solution sits in the trays it will be initially around the 5.5 mark. As the week progresses my res ph increases slightly as all res ph's will with time. When my res ph hits 5.8 I assume that the tray ph is anything up to 6.2. At that point I reset the res to 5.3/5.4.

3: Could be a nutrient problem but in honesty I doubt it. Since switching to growing with cobs I use 1ml per litre calmag as a minimum otherwise I get deficiencies. If your not using some form of calcium & magnesium additive you will run into problems. That said your plants don't look like they are suffering from a calcium or mag deficiency but I thought I'd throw that in to cover all bases.

Your lights, height, power etc for healthy plant are not an issue the way you are using them. They may be a bit to much though for sick plants. You should probably dim them a tad or move them up a bit until your plants get better.

I think If I were you I would switch the res off for a couple of days. Let your plants suck up all the moisture in the pots & dry out. If they perk up as they dry out you know that the issue was them getting over watered in the system. From that point on you would probably want to switch the res on for say an hour or 2 a day. I.e. let them get enough solution to grow but not enough to over saturate the coco.
then next time you pot up put a more significant layer of clay balls of perlite at the bottom f your pots to avoid this happening again.
I would also suggest you lower your res ph. If you take a ph reading of your res & then at tray level you'll see the difference I'm referring to.

Hope that helps.

no worries your welcome!

Randomblame said:

Nope, it's more! In a tent 45.000lx is in the 700-750μMol/s range, because of the reflective walls. Conversion factors are calculated without tent. Flush them thoroughly and reduce the intensity and I'm 90% sure she recovers in less than a week.
If they are saturated after they have gotten 14-15h, this would be about 35-38Mol/d with your current setup. You can either shorten the exposure time to 14-15h or reduce the output to about 550μmol/s, or ~35,000lx max.
This should stop it if it's indeed is saturation.

But could also be a lack of nutrients, because the leaf stalks look suspiciously red.
Were they reddish from the beginning, or have they developed it over the time?
I know, for some strains this is normal behavior(eg. PinkKush) but in the most cases it is a sign of a phosphor or nitrogene deficit.

Click to expand...

Maybe you have some data how much DLI is recommended for autos?
For photoperiod I think it's up to 60 DLI?

kushedy said:

no worries your welcome!

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Yea, I turn off reservoir for couple hours and plants look better. Pots are dry in couple of hours, not days, as they're quite big. Also dim lights and raise them a little.
Yea, also think that tray pH is higher than reservoir pH, because of airdomes in it. But I read guys uses same pH range as I and didn't get any troubles. Also I didn't read anywhere that pH cause doopy plants so I will keep my pH as it is. As I don't see any imbalances with pH. Also in tray there is around 500-700ml solution and I doubt it changes so much, because plants drink like crazy.

Thank you!

Water them more.

In autopots the plants have constant access to water/nutrients so unless the valve is stuck closed (with he said isn't) it isn't a lack of watering.
Even a big plant in flowering will not dry out a 15lt soaked pot in 2 hours. The tray may empty in 2 hrs, especially if the coco is in constant contact with water, but the pot itself will still be soaked for some time. Lift your pot & you'll know from the weight that its still soaked.
More I look at that picture the more I see my earlier autopot grows where my plants were over saturated & performed badly.
Anyway up to you fella. Best of luck

KonopCh said:

Maybe you have some data how much DLI is recommended for autos?
For photoperiod I think it's up to 60 DLI?

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But 60Mol/d is the upper limit and it's difficult to keep them healthy!

My experience is, the higher the intensity, the faster you get problems with bleaching. When I have two tomato plants in identical soil, one 45cm and the other 70cm away from the lamp, consumes the closer much more nutrients. Even with regularly high doses of fertilizer, leaves are often getting yellow because of too much intensity.

I see this often when the COB's run with 50w or more. The only way to avoid this is to use 10-15w LEDs instead of 50w LED to distribute the light much more evenly. I have a smaller lamp, where many CXB2540 which gets only 350mA (11,7w) and are distributed over a larger area(2,5ft² heatsink over 3ft² area), and with this lamp I have even at 10cm distance no bleaching.

I'd try 30Mol/d spread over 14-18h until she's recovered. Rinse it once and set the lamp 8" higher, then it should quickly look normal again. Then increase intensity again but do not forget to hang the light higher(>24" at this intensity).

The fact that they leave their leaves hanging before the light goes out makes me believe it is a sign that they can not absorb more energy and therefore trying to lower the radiated leaf area.
You could simply turn off the light four hours earlier and increase the distance slightly to at least 20-24" or you can lower/dimm the output by the same amount of light(DLI -4h) and stay with the same day length.
Important is definitely a larger distance to the canopy! My 8 CXB3590's run also at 1050mA(37w) and I need at least 24" at 300w to keep my babes happy(9sft).
Did you use CO² or are you sure there is enough fresh air in the tent "all the time"? It could also be not enough CO²/fresh air in a sealed room and the plants would probably look the same.
You see, from nutrient over light to fresh air, it could have a few reasons. The most likely reason to me is intense(DLI) and distance to the light.

Randomblame said:

The fact that they leave their leaves hanging before the light goes out makes me believe it is a sign that they can not absorb more energy and therefore trying to lower the radiated leaf area.
You could simply turn off the light four hours earlier and increase the distance slightly to at least 20-24" or you can lower/dimm the output by the same amount of light(DLI -4h) and stay with the same day length.
Important is definitely a larger distance to the canopy! My 8 CXB3590's run also at 1050mA(37w) and I need at least 24" at 300w to keep my babes happy(9sft).
Did you use CO² or are you sure there is enough fresh air in the tent "all the time"? It could also be not enough CO²/fresh air in a sealed room and the plants would probably look the same.
You see, from nutrient over light to fresh air, it could have a few reasons. The most likely reason to me is intense(DLI) and distance to the light.

Click to expand...

Yep, I guess it's light stress. Because I dim them and raise them to 45cm. And they look better now.
I am little unsure how much will I yield with that approach, because now one of them receives around 30000-35000 LUX (400 PPFD), and other only around 20000-23000 LUX (300 PPFD). I hope for more than 1.2 GPW, which should be 220W (max. is 280W... ). I can only measure with kill-a-watt meter, so AC side, not actually DC side.

The maximum readings are not so important, more importantly is, what they get on average. If you hold 30-40,000lx over 18h a day, you will be surprised by the results. If one plant is not as tall as the other put them on a stool or a twisted bucket to raise her to the same level.
But it also depends a lot on genetics. If this strain is known for good results, then 1.3g/w should be reachable.
But the most latest generation auto's yields good, only the fisrt few generations were known as less productive.