Coco Coir - Low Rootzone Ph - Stopping Growth

[Fourtay]

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!

 

[newh]

some people add tap water to their ro water for the buffer.

 

[MidwestToker]

You don't need to add cal-carbonate to correct the pH of coir. Natural pH of coir is around 6.4 pH.

As my general rule if the pH is dropping, then you are overfeeding in coir. I do single daily feeds in 9 lt. pots of coir with a max of 550 ppm or 1.1 ec.
Lower you nutrients and pH your feeds to 6.2 for a couple of days and see how they do.

 

[jumpincactus]

I would agree with @MidwestToker .try backing off on frequency of your feeds. How dry is your coco getting between cycles. Of course you don't want it to get bone dry but check your moisture levels right before your next scheduled feed cycle and if the coco/media is still sopping or very wet, you should extend your feed cycles to allow for more drying out of the media before the next feed. You will be fine as long as you don't let the coco get bone dry. If this happens too often you will have root tip dieoff and it will stall out your growth rates.

 

[PharmHand]

Another possibility to consider is you’re over or under watering killing roots which then decompose and acidify your medium. I’d lean more towards overwatering since you have no salt build up. And I would think if it’s strictly over feeding there would be a buildup too of some kind ,but maybe not. If you’re starting water is super clean and you’re in coco you may benefit from a cal/mag nitrate to help balance your anions/cations too. GH has a good amount of ammonium which can drive ph down over time, the nitrate may help counteract

 

[MidwestToker]

Very possible, but he doesn't give container size or run-off ec and I'm just going off my experience running coir many different ways. He is feeding 1.3 ec 3 times a day

 

[PharmHand]

Very possible, but he doesn't give container size or run-off ec and I'm just going off my experience running coir many different ways. He is feeding 1.3 ec 3 times a day

Good point and a good rule of thumb: medium ph dropping=over feeding, rising =under feeding. And if he’s getting runoff it might not even get a chance to build up even if he’s over feeding. You’re probably right just throwing another possibility out there. A link you posted awhile back, a guy was giving a lecture; talked about how medium dropping indicates the plant is actively taking up specific nutrients- nitrogen I believe it was. Been researching nitrogen forms lately and how they affect medium , how and when to cut it out etc. Now I wanna watch that vid again. Maybe it wasnt u that posted it even haha. Peace

 

[Kingkola]

Some times with Coco you are required to water 2 times a day you may have a rootzone drying prob like previously stated just my two cents

 

[Fourtay]

@newh I have done that in the past at other locations but my tap water here is about 0-50 ppm

@MidwestToker I think I might try and reduce the feeding to 500 ppm / 1 EC for a few days with added calimagic

@jumpincactus I am currently feeding 3 times per day, only because they would wilt if I only did two times. They are pretty dry by the time the lights come on again in the morning/lights on right before their first feeding.

They are in 5-gallon tall pots
The environment in the room is 78F / 60RH lights on and 65F / 50 RH lights off with supplemented Co2 in the lights on period

@PharmHand that makes a lot of sense. I really try to watch how much my pots dry down to ensure a bit of dryness to prevent root rot. However, I think I might benefit from adding another watering. The dryness of the plant is most when the lights first turn on, they are the color of dry sand, and are lightweight. They are in 5-gallon pots. However, some of the plants are not that dry and are still wet at lights on. On my growlink moisture sensor it says the pots get to about 15% but I think that number is a bit useless

I have been using gh 6 micro 9 bloom with 3ml canna boost and 5 ml cannazyme all per gallon of water.
Just stopped using the boost a couple days ago. Weekly photo plus for bennies and alliance biologics once a week


I think I will try and do 200 ppm calimagic and then reduce the GH flora to make the final mixture 550 ish ppm and switch from 3 times per day to 4 times per day feeding

 

[m8ty]

over water..

 

[MidwestToker]

@MidwestToker I think I might try and reduce the feeding to 500 ppm / 1 EC for a few days with added calimagic

Your plants must be fairly large to require 3 feedings a day in 5 gal pots. These are in 9 Lt.. pots (2.38 US gallons) being feed once a day.

 

[Fourtay]

I hear ya, they do drink alot. I do 1.5 plants per 1000w

 

[MidwestToker]

I hear ya, they do drink alot. I do 1.5 plants per 1000w

Going over your original post I looked over the fact that your mix was 40% clay balls giving you only 3 gallon total root capacity out of that 5 gallons and 1.5 per 1,000 would be large plants, so no you are not over watering, maybe a little high nutrient strength.
Can you give us a run-off ec?

 

[PharmHand]

Going over your original post I looked over the fact that your mix was 40% clay balls giving you only 3 gallon total root capacity out of that 5 gallons and 1.5 per 1,000 would be large plants, so no you are not over watering, maybe a little high nutrient strength.
Can you give us a run-off ec?

Think he posted numbers in the first post.... @Fourtay id go w the botanicare calmag the gh one is mostly calcium carbonate not a lot of nitrate. Also did you wash the clay balls(hydroton?) beforehand? Most need a good rinse before use or it messes w PH

 

[Fourtay]

@PharmHand Yeah I wash them before mixing with the coco, they come out of the bag very dirty.
I am a firm believer in calmag plus from botanicare, it is a great product. I really like it in veg. I specifically was looking at the calimagic for bloom as it has 1-0-0 opposed to botanicares 2-0-0 nitrogen content, I was hoping to keep the additional nitrogen down if possible.

I just picked some calimagic up last night and it looks like they changed their formulation from what I had read on the internet. The label last night on the bottle was derived from calcium gluconate opposed to their old label which was:

CALiMAGic is derived from magnesium sulfate, calcium carbonate, and iron DTPA.