What Might Be Causing Ph To Drop In The Rootzone?

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ThcFarmer1

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Plants look healthy besides some minor cupping close to lights. They are almost 4 weeks into flowering.

I've been doing the 1:1.5 extraction analysis for the rootzone 2 times a week and I can't understand why the PH level drops to between 5.1 and 5.5. Measurements are taken before watering and I'm watering every 2 days (1 off 1 on 1 off 1 on...). The thing is that PH of water that goes in with nutrients is 5.8-5.9 and I have always heard that in coco with healthy plants ph swings up in time, not down.

In week 2 readings were 170-280ppm in the rootzone with 1300ppm going in. I've been slightly increasing the ppm of nutrients with every watering and now I'm at 1500ppm going in and rootzone at 450-470ppm. Canna says that target value for EC in the rootzone should be 1.1-1.3 which is 550-650ppm. I'm still not there yet so sounds like a slight deficiency. Trying to dial in with my new sealed co2 environment.

I have heard that too high ppm can lower PH, but I don't think that's the case.
Another thing I've heard it that bad bacterial growth in the rootzone can lower ph, but that too doesn't seem to be the case, because I have 2 different strains in the room and one is 2 times bigger than the other, which means that the bigger ones drink water faster and it's highly unlikely that they are the ones being more bacterial than the smaller ones. And here's that: I have now increased the ph of nutrients going in from 5.9 to 6.4, but still the same drop and the bigger ones show me lower ph than the smaller ones - my last readings were 5.5 vs 5.1 and one week ago it was 5.3 vs 5.5. Do you get it?

What could be the reason?
 
Unit541

Unit541

So... how do the plants look? Do yourself a huge favor, and forget all of these things you have "heard". If you're plants look healthy, make sure the ph of your feed water is dialed, and don't concern yourself with anything else. With coco, going down this road generally leads to real problems for the plant.

If you just can't help yourself, and simply must muck around it, start dropping your feed levels and it'll come up. Want to freak out a little? check the ppm of runoff from the bottom, I bet it's 6-7 times higher than what you're seeing in a slurry test, especially if you're not in absolutely gigantic pots since you're watering every two days. It's much more common to water every two hours in coco.

If the plants are exhibiting problems up top, lets talk about that and see if it leads us to a ph issue in the root zone.
 
1diesel1

1diesel1

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I’ve grown in soil for years and have never checked runoff ph. I’ve never understood why folks do? Always have PHd at 6.0 and have never had an issue.
 
Homesteader

Homesteader

Exudates are the roots leaking acids that will drop the pH just around the roots in an attempt to attract microbes that break down nutrients as well as dissolve and break down on their own. The rhizosphere will typically be slightly lower pH than the rest of the soil because of these exudates that the roots are giving off. It is hard to accurately measure however.
 
T

ThcFarmer1

7
1
So... how do the plants look? Do yourself a huge favor, and forget all of these things you have "heard". If you're plants look healthy, make sure the ph of your feed water is dialed, and don't concern yourself with anything else. With coco, going down this road generally leads to real problems for the plant.

If you just can't help yourself, and simply must muck around it, start dropping your feed levels and it'll come up. Want to freak out a little? check the ppm of runoff from the bottom, I bet it's 6-7 times higher than what you're seeing in a slurry test, especially if you're not in absolutely gigantic pots since you're watering every two days. It's much more common to water every two hours in coco.

If the plants are exhibiting problems up top, lets talk about that and see if it leads us to a ph issue in the root zone.
I think my problem was that I was feeding high PPM and didn't water regularly enough, let the coco dry out too much.
I read a sticky in this forum about healthy roots and discovered I should water more often. Amazing how I have achieved so good results if I've been doing so many mistakes. My last grow was 1.8gpw for example.
Btw I tested runoff too and it was the same what went in. My pots have 18L of coco in them btw.

I think it will be a good idea to start a grow journal. Would be most effective for otther people to help me if I would give as much info as possible about my growroom environment.

Now I'm suddenly dealing with too high ppm in rootzone :) I started watering every day and cut down on nutes aswell.

Here are few pictures of my problematic buds that are getting a bit stressed because of too much radiant heat.

Beginning of 6th week.



 
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