The problem with maintaining PH in coconut

[hoo]

Hello,
I need advice. The question is written through a translator, so please excuse the quality of the text. I am a beginner and I grow indoor in a 20L pot in a coconut substrate with expanded clay. I measure the PH/EC digitally and use Shogun coconut fertilizer. I water with settled tap water. I have big problems maintaining the PH in the pot. I had PH- from Advanced Hydroponics, but when I watered with water with PH 6, the next day the PH in the drain was 6.5. I watered with a lot of water, about 15 liters, to get the PH in the drain back to 6. However, the next day the PH in the drain was 6.7 again. I had to pour a lot of water to get it to at least 6.3. But the next day the same thing and so on. So I bought crystalline PH- from Terra Aquatica, but the problem is the opposite. I watered with PH 6, but the next day the PH in the drain is 5.6. I had to pour about 20 liters of water with PH 6 to reach this PH in the drain. However, today the drain is flowing again with PH 5.6. Even after 15 liters of water with PH 6.4, the PH of the drain does not change and is still Ph 5.6. Do you know, please, where the problem is? I am already unhappy about it.

 

[OldOneEye]

How do the plants look?

 

[Bobcat.Branch]

Is your coco pre-buffered? If not, did you buffer it? You should not expect to input a specific pH and get the same exact pH in runoff.

What phase of growth are you in? Seedling, veg, flower? Do you have pictures? What is the pH of your tap water?

 

[hoo]

My flowers are showing calcium and magnesium deficiency because my PH is flying out of the range where it is able to take in. I've read that cannabis can only take up calcium in the 6-6.5 range. The new leaves are bright green to yellow. Some of the leaves on the plants had bright green tips, bright green edges and yellowing between the veins. That has disappeared but I am still getting new leaves that are yellow, narrow and sometimes deformed. I am already extending the vegetative phase by 14days because of this. I'm ready to go into bloom.

The coconut I have is Ugro brand, which is supposed to be buffered from the factory.
The ph of my tap water is 7.4-8 / EC 0.5-06

 

[hoo]

I add Calmag to the fertilizer according to the instructions. I keep the EC at 1.8. The temperature in the grow room just below the tops is 26-27 degrees, humidity 60-65%

 

[carlosescobar]

coco holds onto a lot of calcium magnesium so its best to add some now and again, but i think you are looking in the wrong area, check your light is not too close or too bright...plants require a lot less in the veg stage but we (and ive done it twice now) whack our l.e.ds up and this stops the uptake of potassium which will make your leaves go yellow along the edges . you can also combat this by introducing co2

 

[Gmix]

My flowers are showing calcium and magnesium deficiency because my PH is flying out of the range where it is able to take in. I've read that cannabis can only take up calcium in the 6-6.5 range. The new leaves are bright green to yellow. Some of the leaves on the plants had bright green tips, bright green edges and yellowing between the veins. That has disappeared but I am still getting new leaves that are yellow, narrow and sometimes deformed. I am already extending the vegetative phase by 14days because of this. I'm ready to go into bloom.

The coconut I have is Ugro brand, which is supposed to be buffered from the factory.
The ph of my tap water is 7.4-8 / EC 0.5-06

Coir ph should be 5.6-6.2 in veg
In flower it’s slightly higher 5.8-6.3 aiming for 6

 

[Bobcat.Branch]

I add Calmag to the fertilizer according to the instructions. I keep the EC at 1.8. The temperature in the grow room just below the tops is 26-27 degrees, humidity 60-65%

VPD seems a tad low for veg, but that's assuming leaf temp of 4°f less than ambient: Your VPD

Remember, pH requirements are different from soil to hydro, and coco is somewhere in between, but leans towards hydro (in my experience, at least). So, nutrient lockout depends on pH, and therefore growing medium.

 

[OldOneEye]

All this talk of ph of drainage. No description of ailing plants. I think he is overthinking a problem.

 

[OldOneEye]

Oh there it is. I add 3 to 5 ml cal/mag to every feeding growing in coco. Ph to 5.8 to 5.9 in veg , after 21 days lights at 12/12 when I switch to early flower nuts. Ph to 5.9 to 6.0, late flower nutrients ph to 6.2

I water to 20% drainoff. Never do i check my run off. The 20% runoff ensures no toxicity in the media.

I never have problems as long as I do this.

 

[OldOneEye]

I must add....passive hydro. I water by hand when the container is dry.
If you are running active hydro, your problem lies in your water. If so check the PPMs of your water before adding nutrients.

 

[Bobcat.Branch]

Oh there it is. I add 3 to 5 ml cal/mag to every feeding growing in coco. Ph to 5.8 to 5.9 in veg , after 21 days lights at 12/12 when I switch to early flower nuts. Ph to 5.9 to 6.0, late flower nutrients ph to 6.2

I water to 20% drainoff. Never do i check my run off. The 20% runoff ensures no toxicity in the media.

I never have problems as long as I do this.

Solid! Coco is always jonesin for that cal/mg. Those coco pH values are

 

[hoo]

I add calmag exactly according to the shogun calculator, where I set my conditions and it shows me how to dose. I add calmag shogun 0.5ml/L according to the table.

It's not the light. I tried to move the light away, it kept happening. In addition, some new leaves are yellow and others are green, even though they are at the same highest height. In addition, I measure the light intensity and it's normal.

I found another forum on the web where someone is solving the same problem, that the pH in his coconut skyrockets from pH 6 to pH 7-8 within two hours. He has also tried all the acids.

I can't figure out why it fluctuates so much. It's not normal for the pH to change by half a pH in the next day. I understand that the pH fluctuates, but not by that much and so quickly. Not everyone has reverse osmosis, but others use settled water without any problems and this doesn't happen to them.

And that the entire volume of the flowerpot is filled with twenty liters of water with a Ph of 6.3 and the Ph at the drain does not change and remains 5.7.

So 5.7 is okay? I wanted to keep the Ph exactly at 6. Moreover, I am afraid that it will continue to drop and today it will probably be Ph 5.5.

 

[FloridaMike]

In rockwool ideal range is 5.8-6.2 in veg, 5.9-6.3 in flower.
I find it best to let it drift within the range, rather than
trying to maintain a firm number. Imo it's better for the
plants and needs nowhere near as much chemical buffers.
It's also much easier on the stress and aggravation levels
one gets from trying to chase ph numbers around. (I do the
same with my nutrients)

*edit to add photo and say 5.5 won't hurt them

 

[hoo]

Oh, I used to think I had to keep it at 6 or higher because calcium is supposedly absorbed above pH 6... I read that on some websites. That's why I was so stressed that I couldn't get it to 5.9. So hopefully it will improve now if I can keep it. I used to water at pH 6 and the next day the pH came out of the drain at 7.2... I tried measuring it and a few hours after watering it came out at 6.5 even though I used water with pH 6. That was with nitric acid. I read on the websites that it is better to use phosphoric acid for growth, that it keeps the pH and doesn't rise. But it doesn't make sense to me that I'm now using Terra Aquatica, which is supposed to contain nitric, phosphoric and citric acid, and the pH has started to behave the opposite way to before and is actually falling.

Sometimes it happens to me that while pouring water with Ph6, water with Ph6 flows out and then suddenly I measure pH5.7 and after a few liters again Ph 6 and then maybe with Ph 5.6 and then it returns to Ph6. Am I right in thinking that it probably flows irregularly and so there are dead spots that may be washed out later and that is why the differences in measurements?


Thank you all for the advice.

 

[Choppr]

I find it best to let it drift within the range, rather than
trying to maintain a firm number.

This^^^ - is best garden practices!

If its always drifting up, mix your solutions to 5.5 - let it drift to the outer range -then repeat. This drifting gives the Plants better nutrient availability along the pH scale. - (5.5-6.8 for Coco)

 

[FloridaMike]

This is from 'GPT, I agree with it and copy/pasting is much easier than one finger typing:


Rapid pH rises in coco coir when using city water can be caused by several factors. Here are the main culprits:

1. High Alkalinity in City Water (Carbonates and Bicarbonates):
   • Many municipal water supplies contain high levels of carbonates and bicarbonates, which act as buffers and cause pH to rise over time. Even if you initially adjust the pH, the buffering capacity of the water can push it back up.
2. Insufficient pH Buffering in Nutrient Solution:
   • If your nutrient solution doesn’t have adequate pH buffers (like phosphoric acid or citric acid), the natural alkalinity of city water can easily raise the pH.
3. Leaching of Calcium from Coco Coir:
   • Coco coir naturally holds calcium. As it releases calcium into the nutrient solution, it can increase pH over time, especially in the early stages of use if it wasn’t properly buffered.
4. Microbial Activity:
   • Beneficial microbes in the root zone can affect pH by metabolizing nutrients, which can cause fluctuations. Some microbes can produce alkaline byproducts, leading to pH rises.
5. Underfeeding:
   • If nutrient levels are too low, the buffering effect from nutrients is reduced, making it easier for the pH to rise due to the water's alkalinity.
6. Poor Quality or Unbuffered Coco:
   • If coco coir is not properly washed and buffered during production, it can contribute to pH instability.

---

Possible Solutions:​

• Use RO (Reverse Osmosis) Water: Removes most of the carbonates and bicarbonates.
• Pre-Buffer Coco: Soak coco in a calcium-magnesium solution before use.
• Add pH Down (Phosphoric Acid): Helps neutralize the alkalinity in the water.
• Monitor and Adjust Regularly: Daily pH checks and adjustments are necessary in coco-based systems.
• Use Silica Supplements Carefully: Silica can raise pH, so be cautious with its use.

 

[hoo]

Yes, I know it's good to keep the Ph throughout the range, but I'm dealing with the fact that either I don't get below Ph 6.3 and within a few hours I have Ph 7 there, or again now I have Ph 5.7 and even after pouring 20 liters of water with Ph 6-6.3 it didn't go up. And when I wrote that I wanted Ph 6 in there, I thought I would take that as the midpoint and move up and down from there, give or take two or three decimal places.

Yes, that's also what I thought I was going to do, I was going to mix it to 5.5 and it would go up to Ph 6.5 by the next day and go all the way through the range, but as I write above, I can't get to a Ph lower than 6.2 even after say 15 liters of water. And I don't want to over pour that amount every day, that's not normal.

 

[FloridaMike]

I don't know if it's been discussed but do
you have a quality meter that you trust
& calibrate? once a week or more til you
know you can trust it, then monthly or
bimonthly, is my recommendation.

 

[hoo]

Florida Mike: Thank you very much for this post GPT!
I noticed that when I let tap water flow through the filter jug with a new filter, the pH was 6.2 and there was no problem with the increase and instability of the Ph. But then, when I filtered about 30 liters of water through the jug, this effect stopped working, because the pH of the filtered water rose to Ph 6.7 even though the filter is supposed to last 120 liters. So it would be pointless to buy new filters after 30 liters. Maybe I will buy a basic model for osmosis, but I can't afford something expensive or professional. My tap water is very hard. The jug is full of limescale in a short time. The pH of tap water is 7.5-8 / EC 5-6. I also wondered if the fluctuations in the PH are caused by some processes in the substrate or if something is trapped there and then it causes fluctuations or an increase in the Ph. But I haven't read anything like that anywhere until now in your post.

Yes, I tried that too and cleaned and calibrated the meter several times to make sure it wasn't bad. I have an Aqua Master Tools P110 PRO PH and EC meter.