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SOIL pH madness, can't get it down...

kidane

kidane

New member
Hi there I need help once again... I'm struggling with soil pH.

Some of you guys helped me out with a magnesium problem and thanks to you i got that soil pH was too high and caused the deficiency.
Since then, I fed the ladies with ph'd water between 5,5/6 but after 3 weeks run offs are still very high don't seem to go down at all no matter what.
I have 12 plants, 24th day flowering, they've all been fed the same way, same pots, same size, same strain, but 4 of them have a run off around pH 6.7, 4 other around pH 7 and 4 around pH 7.3.

I made sure the pH meter works properly and is calibrated, so that can be ruled out.
I can't figure out why the soil pH doesn't adjust to a more acidic value. And why there is such a difference between all plants run offs.
Even weirder is that when I started giving them pH 5.5 water the magnesium deficiency was under control within a week or so, and run offs were lower, around 6.5 for almost all plants, but now pH is up again.

Might be helpfull to mention that the tapwater has a pH of 7.5 and is hard (300/400ppm) so i'm using quite a lot of pH down (nitric/phosphoric acid) to get to 5.5/6. Could that extra phosphorus has something to do with this? Also having a cold wave around here and temps have dropped a bit in the grow room, around 17°C lights off, 22 °C lights on.

Magnesium deficency didn't strike back yet but something else came up on a few plants, mostly the top and middle leaves, most likely due to incorrect pH, look at the pictures...

Space: L 35 x W 16 x H 43 inches (40*90*110 cm)
Light: 250 W CFL
Soil mix: 80% Plagron Growmix with perlite, 20% Coco
Strain: OG Kush
Pots: 2L (growing Sea of Green)
Organic Nutrients: Green Buzz Grow and Bloom
Water: Tap water pH'd @ 5.5/6
Temps: 17°C-22°C
Extraction: 74 CFM (126 m³/h)
 

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Idk what's in your water that makes it so high but it may lack another nutrient such as copper or zinc. I couldn't tell you but you water company can tell you. Maybe use a different water source.
 
Yes i thought about using different water, but i can't afford much so i've been mixing 1/2 tap water 1/2 distilled water to reduce hardness but doesn't seem to make any difference, run offs still high, there's 1.5 difference between pH in and out!
And what do you think of the pictures??? What does it look like? I would just like to know so i can identify it next time it happens.
 
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Looks to me like a bit of nute lock-out. Cannabis plants can only absorb nutrients between 5.5.- 6.5 pH.
First off I would not use distilled water. It has been boiled and cannot be pHed up or down. Other people would differ on my opinion. I would use rain water before I used distilled.
That being said, get yourself lots of Phed water and flush your plants with three times the pot size. Six litres each pot. Test it of course, but test the last two litres. Then let them dry out.
 
Idk where you live but Wal-Mart sells RO and/or distilled water for 88cents a gallon best water I've found and it comes perfectly balanced which is good for flushes,
 
I reccomend getting that Wal-Mart water I mentioned and just give it a good old flush with that and let it dry out then start the feeds again sounds like you just need a reset button which the flush will do
 
You say soil..like actual dirt..or coco blends?

Ph for "soil" 6.5-6
Ph for coco 6

Soil with bad ph high or low.. Give with ph 6 always it's a nice even manageable number.. Always give 6.. Never waver.. Ph in needs to be a constant unchanged number..always
If you try to give a higher or lower ph in you will be very hard pressed to get it back in line without changing it the other way again.

Ph coming out is not that huge of deal and I never ever worry about it...why you ask..cause my ph going in never changes..ever...i have learned over all my time that a constant ph in will always allow my nutrients to be consumed by the plant when it's called for and correct itself within the pot and root system.. Just water and feed with plenty of run off so the ph cycle circle can eventually correct itself within a point or two..


If you are really in soil..then pick a number between 6 & 6.5 ph and stick with it every time you pour something into the medium..
 
He had problems with pH before to get it to a manageable level with his run off really high. He just got it down to 7.3 so watering with 6 will probably get run off in check. With the water being so high I'm sure if he gets the run off corrected he can begin to water with 6 and should be fine from there. But he had run off over 8 before this.
 
The soil is a mix of 80% dirt (Plagron Grow Mix with perlite) and 20% coco coir.
As Chefbjy said, when I first started checking pH, i had been watering with this tap water for 3 weeks of veg, and the run off was the same as the tap water, pH7.8! . So pH in = pH out = 7.8.
Since then i watered 6 times (twice a week) with ph'd tap water and nutrients every other watering. I kept a record of pH in and out.

Watering 1 (+nuts) pH in = 6.2, pH out = 7
Watering 2 - pH in = 5.8, pH out = 6.8
Watering 3 (+nuts) - pH in = 5.5, pH out = 6.6
Watering 4 - pH in = 5.8, pH out = 6.8
Watering 5 (+nuts) - pH in = 5.8, pH out = 8 plants @6.8 / 4 plants @7.2
Watering 6 - pH in = 5.7, pH out = 4 plants @6.7 / 4plants @7 / 4 plants @7.3

Watering 5 and 6 was mixed 50% tap with 50% distilled water.
All plants get each time the same amount of the same water so i don't understand why they have different values and why it's going up again after it went down.
Out of control!
Let's see after flushing.
 
Does not matter what the different ph levels between the plants are.. The medium inside the pot will always vary from time to time depending on what kind of additives you are giving... Keep the ph in.. a constant always.. When you feed or water... the medium gets soaked.. But before that the medium is dry to damp..more air within the pot the damp medium at bottom or the dry at top will both have different ph levels in the medium.... The ph level of the water or feed will change a few times as it goes through the whole pot and drains out.. keeping a constant ph in is just a simple math must.. Keep your constant..!! It will correct ITSELF.. In time

Always ph anything you give... That's always been number one rule.. in every book... on every bottle

I like to ramble..so take it or leave it
 
I always check my ph run off, so does it really not matter about the run off? I myself am not sure but if it doesn't matter it's something I will stop checking thanks.
 
I think it matters too Deadhead. I don't agree that it will always correct itself didn't happen my first grow any way. I was running really low towards the end of flowering and ran into deficiency. That's a good link shows how nutrients are absorbed at different levels some higher some lower. When using liquid nutes it's a good idea. Though I don't check it every single time either.
 
I think Green and Canuck have gotten to where they don't check their run off because they have gotten their watering process down, and they don't have to check it anymore. Yes, your run off pH matters, but if it's always right, you don't have to check it all the time.

What I think they are suggesting is that if you stabilize your input: meaning adjust the pH your water going in the same way every time, and you water the correct amount, and let her dry off correctly between waterings and feedings, your run off pH will stabilize, and you won't have to chase it around anymore.
 
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