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Root zone PH dropping - help!

Fourtay

Fourtay

Active member
ICMag Donor
Hello,
I grow in amended coco coir, 60% coco coir 40% hydroton.
I use the heads formula General Hydroponics 6/9 micro/bloom per gal water.

I currently water 3 times per day, automated system.
First irrigation is 20 min after lights on, second is 4 hours after lights on, 3rd is 8 hours after lights on

approximately 20% runoff

My starting tap water ranges from 0 PPM to 50 PPM on a Blue Lab meter.
I have seen this problem many times in the past and I do not know how to fix it.
This specific problem seems to happen after about day 30 of bloom.

This particular run I am at day 31 and I just took 3 seperate runoff readings and these were the results: Input pH / ppm = 6.0pH / 650 PPM / 1.3 EC
Cultivar A - 5.0 pH 650 ppm
Cultivar B - 5.3 pH 700 ppm
Cultivar C - 5.4 pH 680 ppm

What typically happens when I have this problem is the ph will continue to fall into the high 4 range, the plants will stop growing, the hairs will turn brown, natural oils / smells will die off and lose their odor.

some advice I have seen in the past has been:

Use calcium carbonate to buffer the water (I dont know how to do this?)

Use citric acid and then potassium hydroxide in concert and quicky feed to the plants to re-establish the lost buffer

Pre-buffer the starting water before adding nutrients via calmag or ph up to approximately 100-150 ppm


What I would like to know if anyone has seen this problem before or has corrected it and any suggestions.
Thank you in advance!
 
T

TanzanianMagic

Well-known member
Veteran
Fourtay said:
Hello,
I grow in amended coco coir, 60% coco coir 40% hydroton.
I use the heads formula General Hydroponics 6/9 micro/bloom per gal water.

I currently water 3 times per day, automated system.
First irrigation is 20 min after lights on, second is 4 hours after lights on, 3rd is 8 hours after lights on

approximately 20% runoff

My starting tap water ranges from 0 PPM to 50 PPM on a Blue Lab meter.
I have seen this problem many times in the past and I do not know how to fix it.
This specific problem seems to happen after about day 30 of bloom.

This particular run I am at day 31 and I just took 3 seperate runoff readings and these were the results: Input pH / ppm = 6.0pH / 650 PPM / 1.3 EC
Cultivar A - 5.0 pH 650 ppm
Cultivar B - 5.3 pH 700 ppm
Cultivar C - 5.4 pH 680 ppm

What typically happens when I have this problem is the ph will continue to fall into the high 4 range, the plants will stop growing, the hairs will turn brown, natural oils / smells will die off and lose their odor.

some advice I have seen in the past has been:

Use calcium carbonate to buffer the water (I dont know how to do this?)

Use citric acid and then potassium hydroxide in concert and quicky feed to the plants to re-establish the lost buffer

Pre-buffer the starting water before adding nutrients via calmag or ph up to approximately 100-150 ppm


What I would like to know if anyone has seen this problem before or has corrected it and any suggestions.
Thank you in advance!
Click to expand...

1. The tapwater is very soft, so it might be best to a) use soft water nutrients, which have extra calcium and magnesium added or b) add calcium, magnesium and trace elements to the water by adding a pinch of Maerl or other magnesium lime to a quart of tapwater for a day, and then mix the clear runoff with 3 parts tapwater.

I grow in amended coco coir, 60% coco coir 40% hydroton.
Click to expand...
2. Why? :)

If you grow in straight up coco coir you:

- don't have to water as often because it just holds water longer
- create a more constant and stable environment for the plant
- coco coir isn't aeroponics - the plants won't die if they don't get watered for a day
- coco coir and hydroton have different pH's - Coco Coir has about 6.0, and hydroton has 7.0, and you end up with a medium with 6.0 pH and lots of 7.0 spots in it
- coco coir has lots of aeration already and doesn't need any amendments, all it needs is to dry out at least a little between feedings
- you can and should use perlite and hydroton as a drainage layer, enough to cover the drainage holes of smaller and bigger pots, respectively. Hydroton should be treated by being put in water for at least a couple of days, so they can uptake more water and don't dry out the plant roots; perlite should also be put in a tub and sprayed with warm water until it floats, stand for 10 minutes and then scoop up whatever floats this takes out the perlite dust and any metal or rocks left, it also allows mixes with perlite to be used multiple times because the dust doesn't turn the medium into cement, so to speak.
 
Last edited:
Creeperpark

Creeperpark

Well-known member
Mentor
Veteran
If you bring your tap up to 150 or 200 ppms with cal-mag that should fix it. You have more free hydrogen than hydroxyl ions. The Cal-mag will buffer the hydrogen. You may have to use more Cal mag, if you have used a lot of acid.
 
Fourtay

Fourtay

Active member
ICMag Donor
Creeperpark said:
If you bring your tap up to 150 or 200 ppms with cal-mag that should fix it. You have more free hydrogen than hydroxyl ions. The Cal-mag will buffer the hydrogen. You may have to use more Cal mag, if you have used a lot of acid.
Click to expand...

Thank you for the advice! I will give this a shot.
How do you mean used alot of acid?
I have only used PH up in the mixture.

The 6/9 fertilizer formula usually comes out to about 5.8 ph and 650 ppm, lately i have added Gen hydro ph up bringing it to 6.3 ph
 
Creeperpark

Creeperpark

Well-known member
Mentor
Veteran
Couldn't You raise your pH with calcium-mag and eliminate the pH up? Couldn't cal-mag buffer your feed without all that pH UP? BTW this is a very helpful thread for me, Thank you for sharing.
 
T

TanzanianMagic

Well-known member
Veteran
The problem isn't pH. The problem is that soft water doesn't have a buffering capacity.

So if you add nutrients with any kind of P in it, it will drag down the pH.

This is what you do: add a pinch of magnesium lime, which has calcium and magnesium in it, let it stand for a day and mix with tapwater at a 1:3 ratio.

Here is why. Hardness of water is determined by the presence of calcium and magnesum atoms in the solution.

See Figure 1.
https://www.canna-uk.com/hard_water_and_soft_water

It is always best to direct the pH through the medium. Coco buffers to a pH of 6.0, while hydroton very persistently buffers to a pH of 7.0. Which is ok in an organic grow.

Also... mixing 40% hydroton into the medium means there is 40% less space for roots. Again, this isn't hydro, where you can just increase the nutrient solution and the plant doesn't need a lot of rootspace. In coco and soil, more roots (at the right time) mean more and bigger flowers.
 
Last edited:
Fourtay

Fourtay

Active member
ICMag Donor
Would it be possible to use calimagic at 5 ml per gal to the tap water first then add my nutrients?

I am unable to let my tank water sit for more than a few hours as the plants dry out too quickly
 
Douglas.Curtis

Douglas.Curtis

Autistic Diplomat in Training
What color are the plants? What shade of green do they have? If your plants are a dark green at day 30, your problem is most likely root rot from too hot of nutrients. If you're running moderate hybrids to heavy feeding indicas, 650ppm is going to be between find and a bit low and I wouldn't expect root rot.

Low calcium can also contribute to weak roots, easier rotting and pH dropping.
 
B

BongFu

Member
Firstly, measuring run off pH isn't an accurate way of monitoring root zone/substrate pH.

Secondly, you should be running coir specific nutrients (a nutrient developed specifically for coir growing) because in coir you need higher levels of Ca and Mg to counter CEC site binding of Ca and Mg.

With your water being so soft and the fact you are running non coir specific nutrients (terrible idea btw) you definitely need to be adding Cal Mag.


To pH buffer soft water predissolve 0.5 gram of citric acid per 10 litres (5 grams to 100 litres) and add to solution. This will drop pH a lot. Then correct the pH to desirable range by adding potassium carbonate. The carbonates and citrates act as an acid and its conjugate base creating a mild pH buffering system.
 
T

TanzanianMagic

Well-known member
Veteran
Fourtay said:
Would it be possible to use calimagic at 5 ml per gal to the tap water first then add my nutrients?

I am unable to let my tank water sit for more than a few hours as the plants dry out too quickly
Click to expand...
You should repot into straight coco with a perlite or hydroton drainage layer.

Mixing coir with 40% hydroton means 40% of the medium is not available for root growth, and hydroton doesn't hold any moisture at all.

Also, what is the Relative Humidity? If it's under 50% you might want to raise that.
 
Fourtay

Fourtay

Active member
ICMag Donor
@douglas.Curtis the plants are picture perfect except for a couple of browning hairs. All a good shade of green, no dark, no light.

@bongfu I have been told that runoff ph measuring isn't accurate also, I just don't have any other way to spot monitor the plants. I have been told that doing a slurry test is more accurate but I am unable to gather a quantity of medium from the pot as it is all root consumed. I am currently using GH 6/9 Greatfulhead coco formula. I wonder if I could add citric acid before adding nutes then ph adjust after nutes? Or should I ph adjust before nutes? Additionally, it was also recommended to me to use citric acid at 1 gram per gallon then potassium hydroxide to ph to 6.5, feed this to plants immediately, but im not sure which approach to take.

I was thinking about doing 200ppm calimagic then reducing the 6/9 formula to where my final ppm is 1.0 EC
 
Fourtay

Fourtay

Active member
ICMag Donor
Bongfu thank you for this! Do you recommend after I add the citric acid to the tap water, should I then immediately raise the ph back up to the 7.0 tap water start point before adding nutrients? Thank you
 
f-e

f-e

Well-known member
Mentor
Veteran
Well your seeing the numbers on the meter, and the plants telling a story of sadness. Somethings not right. The big hammer answer is simply more run-off, and be sure you have enough drip emitters to distribute the liquid everywhere.

Your waste EC is very close to the supply EC. With just 20% run-off, that seems a little off. 20% higher is more typical. But then your not feeding much compared to what I would be doing. All plants are different, but I run a baseline 1.3 which is bumped up around now, towards maybe 1.6 as they pack the weight on.

A theme here is that your using feed with low ca/mg and people are saying you have signs of it.

I think I would get some proper food and put through about 3x more fluid than normal, to wash away your mistake. EC 1.3 if you like, but what are you growing that wants so little food? I would use some PK to bump that up to 1.4 at least. Tomato's and cucumbers are good with 2.5 while 1.3 is suitable for a lettuce.
 
B

BongFu

Member
Fourtay said:
Bongfu thank you for this! Do you recommend after I add the citric acid to the tap water, should I then immediately raise the ph back up to the 7.0 tap water start point before adding nutrients? Thank you
Click to expand...

Just raise pH to your desired pH for growing. So generally 5.5 to 6.0. Oh and pH buffer after adding nutrients..
 
T

TanzanianMagic

Well-known member
Veteran
Fourtay said:
Hey TanzanianMagic

This is the link, the whole thread is great. Many successful coco guys use it

https://www.icmag.com/ic/showthread.php?t=55683
Click to expand...
I take it this is your first coco grow?

Forget about complicating things, start thinking about simplifying things.

Go with Canna Coco A+B, a flowering food of your choice, epsom salt, pH down, and a pot of magnesium lime or Maerl.

Fill the pots with a drainage layer of perlite or hydrotone. Fill the rest with coco coir and nothing else.

Keep the pH at 6.0 throughout the grow so the medium pH and the nutient pH are the same and nothing challenges the pH buffering capacity of the coco coir.

Start with a bloom food solution of 0.4 EC on top of the water's EC, whenever you've planted a seedling, or repotted or need new roots. When you see the roots, switch to 0.4 EC of Canna Coco A+B, and follow the manufacturer's instructions from there.

If you want to read a book for inspiration, read:

The One Straw Revolution, by Masanobu Fukuoka

His question always is: how much less do I need to do? That really boils down plant growing to it's very essence.

If you want to switch to growing organically, check out:

True Living Organics, by The Rev (latest edition)

I use an adjusted version of that, focusing on feeding and protecting fungi.
 
B

BongFu

Member
Yep if this is your first grow you've started out on the back foot by using the wrong nutrients. Whoever told you to use GH in coir gave you some seriously crap advice. You need a coir specific formula because they contain more Cal-Mag to accommodate for Cal-Mag binding by coir CEC sites.

Good advice by TM - keep it simple. Most importantly focus on environment. Temp, RH, root zone oxygen and moisture. What you may be experiencing is that plants release organic acids through the roots into the substrate (root exudates such as citrates) and if plants are unhappy this may be an outcome.


Definitely soft water may be an issue and even where using a coir nutrient you may need to use additional Cal-Mag at about half strength.


And yep read some books to learn the craft. So the right environment (environment is king) along with the right nutrients for coir will go a long way to fixing your issues.
 
E

Easy7

Active member
Veteran
Organisms acidify soil to break down nutrients. Minerals help mitigate that. The right elements.
 
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