HELP!! PH Problems?

[C2L]

Please help with this problem if you can. I’m getting conflicting advice from all angles.
I’m 50/50 coco perlite with temps 75° - 78° and humidity 55% - 65%. Circulation fan with fresh air. I have several symptoms that I have reason to believe is one problem. It began with bronzing spots on the lower leaves then brown spots appeared that didn’t seem to be the same as the bronze colored spots. At the time I was watering perhaps a bit too high at a ph of 6.1 to 6.2. CNS 17 built up over two weeks from 1.0 ml to the liter to 1.7 ml to the liter every two days or so. Additionally, 1.0 ml Cal Mag and 1.0 Rhizotonic were added to 1 ltr. The spots are advancing.
After researching and reading everything I can, I’m more confused. Calcium deficiency?... Magnesium deficiency ?... I have foliar sprayed with 1 teaspoons of Epsom salts in 2 liters and watered with the same solution. I have flushed with straight RO ph’d down to 5.8 No luck… to high still? Additionally I am experiencing drooping leaves on plants that neither over or under watered. I don’t feel that I’m over fertilizing.
But now I have begun to consider this is ph imbalance. I have been bringing the ph down with vinegar and have thought this might not be stable enough. I have checked water that was down to 5.8 and the next day and it was up to 6.3 or 6.4. Do you think my problem is ph? I'm securing ph down in the next few days. Any advice from the coco veterans? Thanks in advance

 

[CannabisTHC]

Vinegar will lower the PH for a short time, get some real PH down like you've stated.

Also lower your PH to 5.6-5.9 preferably on the lower side of that range. It looks as though that is Ca being locked out from too high of PH. The lower PH should fix this problem. Don't go and change everything up, just lower the PH and water for several days, if the problem gets worse then come back to us.

Do you use RO water for your nutrient solution? Because this strips most of the elements from the water mainly being Ca and Mg, nutrient companies design there nutrient lines on the idea that people are using tap water which contain higher amounts of Ca and Mg, which is why you'll need to supplement Ca and Mg.

 

[C2L]

Thanks for the advice THC... Yes, I’m using RO. Only about 25 ppm. The CNS17 has 3.6% Ca and 0.5% Mg., to that I’ve been adding 1.0 ml of Cal Mag per ltr. But I was not wanting to get wrapped up in trying to repair a deficiency that was being created by a ph lock-out. I’ll try lowering the ph and report back. Any other input?

 

[CannabisTHC]

Thanks for the advice THC... Yes, I’m using RO. Only about 25 ppm. The CNS17 has 3.6% Ca and 0.5% Mg., to that I’ve been adding 1.0 ml of Cal Mag per ltr. But I was not wanting to get wrapped up in trying to repair a deficiency that was being created by a ph lock-out. I’ll try lowering the ph and report back. Any other input?

No problem. Well the only reason I stated that is because that could be part of the problem as well. The lower PH will help alleviate that problem but it may still rear its head if Ca is too low. But yeah just see how the lower PH nutrient solution works.

 

[Carl Carlson]

CNS17 - 3.6% has plenty of Ca, even when using with R.O. water.

Maybe your not feeding enough total nutrients? How big are the plants? 1.7 ml / liter = 6.5 ml / gallon

If I remember correctly, 15 ml gallon of CNS17 is around 1.4 EC or 800-900 ppm depending on your meter. So you are at about .7 EC with r.o. water. Do you have a meter, am I close?

I can't tell what the deficiency is, but would lean away from Ca, since it's an immobile nutrient and would most like show up on top growth first.



***

By the way, you're not changing on the fly the pH of the coco or the "coco solution", by making adjustments to the pH of the nutrient solution. Coco is not an inert medium, so even though it is used in hydro systems, it cannot be altered like for example rockwool can. I think this is a source of confusion for a lot growers, both new and old alike. Even some growers that enjoy success think they are changing the pH on the fly in their coco and peat grows, but that just isn't the case. if anyone is curious about that, this might help: http://www.uwm.edu.pl/jelementol/pojedyncze artykuly/13-2-2008/jurnal-04.pdf

If you want to measure the pH of the of the coco solution, the solution that the roots draw nutes from, than use the pour through testing method:

http://www.ces.ncsu.edu/depts/hort/floriculture/crop/crop_PTS.htm


People on icmag like to say all the time, "don't treat coco like soil." But I see there is a groupthink in terms of treating coco like rockwool that comes from the old-timer hydro growers.

 

[BlindDate]

Tell us what ppms you are feeding. Sounds like underfeeding in coco causing that whole cation problem.

 

[CannabisTHC]

I would tend to agree the leaves are a lime green, they do look underfed.

By the way, you're not changing on the fly the pH of the coco or the "coco solution", by making adjustments to the pH of the nutrient solution. Coco is not an inert medium, so even though it is used in hydro systems, it cannot be altered like for example rockwool can. I think this is a source of confusion for a lot growers, both new and old alike. Even some growers that enjoy success think they are changing the pH on the fly in their coco and peat grows, but that just isn't the case. if anyone is curious about that, this might help: http://www.uwm.edu.pl/jelementol/pojedyncze artykuly/13-2-2008/jurnal-04.pdf

Yeah that study just showed that the change wasn't as pronounced in a medium like rockwool so the PH change didn't affect the tomato plants as badly. That doesn't mean that it isn't a good idea to bring his PH down to 5.6-5.9 range, as the study suggests the dynamics will probably take longer to change. Good study though, thanks for the read.

Also coco is an inert medium, it takes numerous grows for the medium to break down after that it will break down into P and K, with a bit more K than P as I recall.

 

[shishkebab]

lower your ph with rainwater. it's ph is around 5

 

[C2L]

Thanks everyone!
Carl C, Blinddate, & THC: 15 ml gallon of CNS17 is the label recommended application but I have been under the impression that application should remain around 50% of recommended. So my 1.7 ml per liter should be about 43%. After Cal Mag and Rhizo it’s 539 ppm with RO. Much lower than label recommendation. And shiskebab; I would love to have rainwater. I would need to think about a collection system.
Ok… so you guys think my application rate is too low and I should up that. I’ve heard some guys having some burn problems with CNS 17 so therefore I’ve been cautious. But I’ll try slowly upping the nutes. What about the drooping? As of this morning, they are still drooping and they had a good drink yesterday. This still gives an impression of a watering related problem that I don’t feel is the issue. So, the ph imbalance comes back to mind. I appreciate everyone’s input!! Thanks!

 

[gaiusmarius]

would be nice to see a pic of the whole plants, but it does sound like some underfeeding might be adding to the problem. also adding the cal mag on such young plants shouldn't be needed and most likely will cause an imbalance.

making sure your nutrient solution is at ph 5.6 to 6.0 will with time cause the coco ph to balance to that level too. but it's not instant no, but still vital to keep ph of tank at that level.

as for the drooping, do you mean the sleep phase kinda drooping? or are they drooping in the middle of the day phase? the plants sometimes let their leaves hang and their times they point straight out or up even.

 

[Carl Carlson]

539 ppms is wicked low